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We previously observed that the serum testosterone level was greatly reduced in the course of diethylnitrosamine-nodularin–induced hepatocarcinogenesis in Fischer 344 male rats (Lim et al., Gastroenterological Carcinogenesis, 1999). As an extension of this observation, this study was undertaken to investigate the molecular mechanism of downregulation of testosterone and its effect on target organs in Fischer 344 male rats treated with the hepatotoxin nodularin. After treating the rats with nodularin, a marked reduction of the testosterone level was noted in both serum and testis, with an accompanying accumulation of cholesterol in serum. Reduction of serum testosterone was not due to increased degradation of testosterone in the liver but to impaired biosynthesis in the testes, reduced activities of the cholesterol side chain cleavage enzyme and 17α-hydroxylase, and decreased expression of the steroidogenic acute regulatory protein gene, all of which constitute rate-limiting steps for testosterone biosynthesis in the testes. Intraperitoneal injection of nodularin into rats induced cuboidal changes of glandular epithelium in ventral prostates and apoptotic changes of spermatogonium, for example, nuclear chromatin condensation, shrinkage, and detachment from Sertoli cells, which included many lysosomal granules. Leydig cells also showed evidence of chromatin condensation and significant induction of peroxisome proliferation. In conclusion, the potential causes of impaired testosterone biosynthesis might have been apoptosis of Leydig cells induced by direct toxicity of the hepatotoxin on testes or hypothalamopituitary dysfunction. © 2002 Wiley-Liss, Inc.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:43:52Z No. of bitstreams: 1 S0073-47212001000200025.pdf: 408215 bytes, checksum: 653ef987ea24b6ba95a65beca64ec0fc (MD5) Made available in DSpace on 2013-08-22T18:43:52Z (GMT). No. of bitstreams: 1 S0073-47212001000200025.pdf: 408215 bytes, checksum: 653ef987ea24b6ba95a65beca64ec0fc (MD5) Previous issue date: 2001-11-27 Made available in DSpace on 2013-09-30T19:31:49Z (GMT). No. of bitstreams: 2 S0073-47212001000200025.pdf: 408215 bytes, checksum: 653ef987ea24b6ba95a65beca64ec0fc (MD5) S0073-47212001000200025.pdf.txt: 15928 bytes, checksum: 742c7050ebb5b738c9fd79a97fc441bc (MD5) Previous issue date: 2001-11-27 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:08:41Z No. of bitstreams: 2 S0073-47212001000200025.pdf: 408215 bytes, checksum: 653ef987ea24b6ba95a65beca64ec0fc (MD5) S0073-47212001000200025.pdf.txt: 15928 bytes, checksum: 742c7050ebb5b738c9fd79a97fc441bc (MD5) Made available in DSpace on 2014-05-20T15:08:41Z (GMT). No. of bitstreams: 2 S0073-47212001000200025.pdf: 408215 bytes, checksum: 653ef987ea24b6ba95a65beca64ec0fc (MD5) S0073-47212001000200025.pdf.txt: 15928 bytes, checksum: 742c7050ebb5b738c9fd79a97fc441bc (MD5) Previous issue date: 2001-11-27 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The morphology of the cyst cells in Apis mellifera Linné, 1758, Scaptotrigona postica Latreille, 1804, and Melipona bicolor bicolor Lepeletier, 1836 testis, as well as the average number of spermatic cells are reported. The data indicates a supporting and nourrishing role of the cyst cells to the developing cystocytes. The counts of immature spermatozoa in the cysts show an average of 202.8 ± 21.2 spermatozoa for A. mellifera, 117.4 ± 8.68 for S. postica and 88.8 ± 15.57 for M. bicolor, which predict the occurrence of 8 mitotic cycles in the cystocytes of A. mellifera and 7 in the meliponines, considering that only one spermatozoom originates of each final spermatogonium. Universidade Estadual Paulista Instituto de Biociências Departamento de Biologia Universidade Estadual Paulista Instituto de Biociências Departamento de Biologia

Spermatogenesis was investigated in seminiferous tubules of 100 males with nonobstructive azoospermia. Forty-four (44%) cases had Sertoli-cell-only syndrome, 23 (23%) had spermatogonium in the tubules, 17 (17%) had primary spermatocyte in the tubules, and 16 (16%) had round or late spermatid in the tubules. No cases showed secondary spermatocyte present in the tubules. The mean serum follicle-stimulating hormone (FSH) in males with nonobstructive azoospermia was significantly higher than that in males with obstructive azoospermia (p.001). The mean concentrations of serum FSH in cases with Sertoli-cell-only syndrome and spermatogonium in the tubules were significantly higher than those in cases with primary spermatocyte and spermatid in the tubules (p.05-.001). The results indicate that the evaluation of testicular histology using the type of germ cells present in seminiferous tubules is available for assisted reproductive technology.

Expression of bcl-w, a close relative of bcl-2 is essential for male fertility in mice. Although the initial wave of spermatogenesis in bcl-w −/− mice proceeds normally until 3–4 weeks of age, adults fail to produce sperm. To clarify why bcl-w is essential for adult but not juvenile spermatogenesis, we investigated the expression pattern of eight bcl-2 family members. We found that both the level and pattern of expression varied in different cell types during juvenile and adult spermatogenesis. Anti-apoptotic genes bcl-w, bcl-2 and bcl-xL were all expressed in spermatogonia during juvenile spermatogenesis, but only bcl-w was detected in spermatogonia of adult mice. A similar shift was evident in Sertoli cells. This developmental regulation may co-ordinate physiological germ cell apoptosis in wild type mice and account for the time of onset for pathological germ cell apoptosis in bcl-w −/− animals. Cell Death and Differentiation (2001) 8, 225–233

We isolated DEAD-box genes from three ascidian species (Ciona intestinalis, Ciona savignyi, and Halocynthia roretzi) by polymerase chain reaction methods. We obtained two types from each of C. intestinalis and C. savignyi, and four types from H. roretzi. The first type (DEAD1) belonged to the vasa subfamily, the second type (DEAD2) to the PL10 subfamily, the third type (DEAD3) to the p68 subfamily, and the forth type (DEAD4) did not belong to any of the subfamilies. We further analyzed in detail the expression pattern of C. intestinalis vasa-type gene (Ci-DEAD1) by in situ hybridization. In sections of the ovary and testis, the Ci-DEAD1-specific probe reacted intensely to small germ cells, oogonium, and/or oocyte and spermatogonium and/or spermatocyte, respectively. In whole-mount specimens of juveniles this probe specifically reacted to the primordial germ cells in the gonad rudiment. These gonad-specific expressions were confirmed by reverse transcriptase polymerase chain reaction of RNA from various tissues. The transcript was present in unfertilized eggs and in the central cytoplasm of blastomeres until the two-cell stage. During the second cleavage a part of the transcripts moved to the posterior region of embryos and, during early embryogenesis, was localized in the posterior-most blastomeres. In the tailbud, one or two hybridization signals were detected in the caudal endodermal strand. Based on these observations, we propose precursors of primordial germ cells in ascidians.

Diploid and triploid specimens of Japanese and Korean Fasciola sp. showed abnormality in their spermatogenesis. Live germ cells obtained from the testes were observed under a differential interference contrast microscope. In the stages from spermatogonium to spermatid, the cells combined together at the central cytoplasmic bridge during a series of divisions. One spermatogonium becomes a cell group of 8 primary spermatocytes through 3 mitoses. Until the primary spermatocyte stage, cells are divided in a uniform manner. In most of the diploid specimens, the primary spermatocytes are irregularly divided into non-uniform secondary spermatocytes, however, some specimens perform a regular division. In the majority of triploid flukes, the primary spermatocytes are divided in a regular pattern, but some of the specimens perform an irregular division. The non-uniform spermatids do not perform a spermiogenesis. In the diploid specimens, no spermatozoa were found that were produced by spermiogenesis. Whereas in the triploid specimens, some spermatids distributed uniformly on the surface went through a spermiogenesis. We observed some moving spermatozoa in one triploid specimen. The spermatozoa possibly retain their normal reproductive function.

Spermatogenesis is the process by which stem cell spermatogonia form sperm. In theory, one stem cell spermatogonium of the rat can produce 4096 sperm (1). The theoretical limit is never achieved in normal spermatogenesis because cells degenerate along the way. Numerous genetic, environmental, and toxicological factors can negatively influence the yield of cells. Although several papers and reviews have been written on this topic (2–5), the relatively recent description of apoptosis has prompted this author to revisit the topic.

To determine the duration of 1 spermatogenic cycle, a single pulse of tritiated thymidine was infused into a branch of the spermatic artery in each of 3 chimpanzees (Pan troglodytes). Samples were recovered surgically prior to infusion, at 1 h, and at 3, 8, 14, 16, 17, 28, 30, 33, 40, 44, and 48 days postinfusion. Tissues were fixed in Bouin's solution, dehydrated, paraffin-embedded, sectioned at 5 micrometers, and stained. Pre-infusion samples were used in morphometric studies to estimate the percentage frequency of area occupied by each of the 6 cellular associations (stages I-VI) characteristic of chimpanzee spermatogenesis, and thus, to estimate the days duration of each stage. To estimate the duration of 1 spermatogenic cycle, pre- and post-infusion, tissue sections were coated with undiluted Kodak NTB2 liquid autoradiographic emulsion and incubated at 4 +/- 1 degree C. At optimum exposure times, slides were processed with Kodak D-19 and Fixer; light microscopic analyses were conducted to determine the most mature labeled cell in stage III for each of the sample times. The duration of the 6 stages (I-VI) are 4.2, 2.0, 4.3, 1.5, 1.3 and 0.6 days, respectively, and the duration of 1 spermatogenic cycle is approximately 14 days. Thus, the duration of spermatogenesis from the Ap spermatogonium to mature Sd2 spermatid is approximately 62.5 +/- 1.5 days or 4.46 spermatogenic cycles.

Spermatogenesis appears to be a fairly conserved process throughout the vertebrate series. Thus, spermatogonia develop into spermatocytes that undergo meiosis to produce spermatids which enter spermiogenesis where they undergo a morphological transformation into spermatozoa. There is, however, variation amongst the vertebrates in how germ cell development and maturation is accomplished. This difference can be broadly divided into two distinct patterns, one present in anamniotes (fish, amphibia) and the other in amniotes (reptiles, birds, mammals). For anamniotes, spermatogenesis occurs in spermatocysts (cysts) which for most species develop within seminiferous lobules. Cysts are produced when a Sertoli cell becomes associated with a primary spermatogonium. Mitotic divisions of the primary spermatogonium produce a cohort of secondary spermatogonia that are enclosed by the Sertoli cell which forms the wall of the cyst. With spermatogenic progression a clone of isogeneic spermatozoa is produced which are released, by rupture of the cyst, into the lumen of the seminiferous lobule. Following spermiation, the Sertoli cell degenerates. For anamniotes, therefore, there is no permanent germinal epithelium since spermatocysts have to be replaced during successive breeding seasons. By contrast, spermatogenesis in amniotes does not occur in cysts but in seminiferous tubules that possess a permanent population of Sertoli cells and spermatogonia which act as a germ cell reservoir for succeeding bouts of spermatogenic activity. There is, in general, a greater variation in the organization of the testis and pattern of spermatogenesis in the anamniotes compared to amniotes. This is primarily due to the fact there is more reproductive diversity in anamniotes ranging from a relatively unspecialized condition where gametes are simply released into the aqueous environment to highly specialized strategies involving internal fertilization. These differences are obviously reflected in the mode of spermatogenesis and this is particularly true of the stage of spermiogenesis where the morphology of the species-specific spermatozoon is determined. Moreover, unlike amniotes, many anamniotes display a spermatogenic wave manifest, depending upon the species, either at the level of the cyst or seminiferous lobule. This variation in the organization of the testis makes certain anamniotes perfect models for investigating germ cell development and maturation. For instance, the presence of a spermatogenic wave provides an opportunity to manually isolate discrete germ cell stages for analysis of specific Sertoli/germ cell interactions. Furthermore, for many anamniotes, germ cells mature in association with a morphologically poorly developed Sertoli cell. This seeming independence of Sertoli cell regulation allows the in vitro culture of isolated germ cells of some species of anamniotes through several developmental stages. Thus, due either to the anatomical organization of the testis, or structural simplicity of the germinal units, nonmammalian vertebrates can provide excellent experimental animal models for investigating many basic problems of male reproduction.

In many groups of insects with holokinetic chromosomes the meiotic process is, without doubt, either pre‐reductional or post‐reductional. In Odonata, however, the mode of orientation (axial or equatorial) and type of meiosis (pre‐ or post‐reductional) of bivalents is still controversial. Copyright © 1995, Wiley Blackwell. All rights reserved Fil:Mola, L.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Publisher Summary This chapter provides an overview of differential gene expression from a single transcription unit during spermatogenesis. Spermatogenesis is a unique and continual process in mammals whereby stem cells divide mitotically to become cells that either remain quiescent or give rise to those that undergo a series of mitotic and meiotic divisions, culminating in the onset of a remarkably complicated differentiation pathway. It is this differentiation process, called spermiogenesis, that results in formation of immature spermatozoa. The frequency of stem cell division is tightly controlled in rodents. Because of the incredibly intractable nature of the process, virtually nothing is known about the molecular mechanisms that control spermatogenic stem cell renewal. Several events that occur during the life of a spermatogonium are quite unusual and are undoubtedly programmed to ensure survival of several genetically identical germ cells. The administration of exogenous follicle-stimulating hormone to immature rats decreases degenerative process, presumably due to the stimulation of production of as yet uncharacterized factors from Sertoli cells. The developing germ cells that can no longer divide mitotically, thus, become protected from the environment because of the blood–testis barrier that separates the two compartments. It is known that germ cell-specific expression is controlled by a germ cell-specific promoter/enhancer, that this regulatory DNA is sufficient to target germ cell-specific expression of a heterologous gene in transgenic mice, and that the mRNA is stored in the cells that express it to be translated at a later stage of development.

Four different types of spermatogonia were identified in the seminiferous tubules of the Japanese quail: a dark type A (Ad), 2 pale A types (Ap1 and Ap2), and a type B. A model is proposed describing the process of spermatogonial development in the quail. The Ad spermatogonia are considered to be the stem cells. Each divides to produce a new Ad spermatogonium and a Ap1 spermatogonium during Stage IX of the cycle of the seminiferous epithelium. An Ap1 spermatogonium produces two Ap2 spermatogonia during Stage II of the cycle, Ap2 spermatogonia produce four type B spermatogonia during Stage VI of the cycle, and type B spermatogonia produce eight primary spermatocytes during Stage III of the cycle. Consequently, 32 spermatids can result from each division of an Ad spermatogonium. Spermatogonial development in the quail differs from the process described in mammals in that there are fewer mitotic divisions and they are all synchronized with the cycle of the seminiferous epithelium. It is suggested that the fewer mitotic divisions explain why a smaller area of the seminiferous tubule is occupied by a cellular association in the quail than in mammals like the rat, ram and bull. The duration of spermatogenesis from the division of the Ad spermatogonia to sperm release from the seminiferous epithelium was estimated to be 12.77 days.

Minute elements detected in Megaselia scalaris (Phoridae, Diptera) lack chromosome arms but carry centromeres and possess kinetochore microtubules in mitosis as well as in meiosis. These centromere-like elements (CLEs) were present in two geographically independent strains of the fly. This indicates that their origin is not a recent event in the karyotype evolution of M. scalaris and that they are rather stable constituents of the karyotype. Most often, two CLEs were found in gonial and somatic mitosis. Spermatocytes contained one CLE. Two individuals examined deviated from this rule in that a metaphase spermatogonium showed three and an anaphase spermatogonium eight CLEs. These animals are believed to have been aneuploid relative to the CLEs. An analysis of spermatogonial division revealed that the CLEs behave like the centromeres of the regular chromosomes but seem to separate precociously, since they were closer to the spindle poles in late anaphase cells. Whereas the size of the CLEs was not significantly different between mitotic cells and secondary spermatocytes, the CLEs in primary spermatocytes were larger in volume by a factor of about 4.5 than those in mitosis and meiosis II. The additional material is interpreted as a glue that holds two CLEs together. This, in turn, is a prerequisite for orderly segregation. The function of the CLEs is not known. They are considered as B chromosomes reduced to the minimum required for segregation, the centromere.

The distribution of actin filaments in the spermatogenic cells of Fasciola hepatica was determined using a fluorescent derivative of phalloidin. Actin was localised primarily in the region of separation of a secondary spermatogonium from a primary spermatogonium, in the inner faces at the centre of four-cell clusters of tertiary spermatogonia and in the cytophore region of spermatocyte and spermatid rosettes. The effect of the microfilament inhibitor cytochalasin B (100 micrograms/ml) on the ultrastructure of the spermatogenic cells was determined in vitro by transmission electron microscopy using tissue-slice material. Cytochalasin B treatment led to the formation of bi- and multinucleate cells, whose frequency increased with progressively longer incubation periods. Few typical rosettes of spermatocyte and spermatid cells were evident from 6 h onwards, being replaced by syncytial masses of cells. Spermatozoon formation became abnormal in the longer treatment periods, the spermatozoa containing variable numbers of axonemes and an altered distribution of cortical microtubules. Multiple axonemes were observed in the cytoplasm of spermatid cells. The results are discussed in relation to the established role of actin in the cytokinesis phase of cell division and to the effects of cytochalasin B on other tissues and organ systems within the fluke.

A triple synaptomal complex was observed between 3 small-sized chromosomes in 4 spermatocytes closely connected by intercellular bridges, of the common vole (Microtus arvalis L.). Other spermatocytes from the same and from 2 other males had a normal chromosome complement and pairing patterns. This finding was interpreted as the result of a single act of non-disjunction taking place in a spermatogonium. These data suggest that chromosome non-disjunction in premeiotic germ cells can be considered one of the causes of aneuploidy in mammals.

Currently, swine biotechnologies related to reproduction increase considerably. Investments are made in order to improve the reproductive rates and performance of breeding stock. Understanding the physiology of spermatogenesis will help increase sperm production and improve boar efficiency. Sertoli cells are the only somatic cells present in the seminiferous tubules. Their function is to guarantee proper sperm formation and maturation. Each Sertoli cell is responsible for nursing a finite number of spermatogonia. At puberty, Sertoli cell maturation and lumen formation have occurred within the seminiferous tubules and germ cells have proliferated rapidly followed by the onset of spermatogenesis. At least two hormones are known to play a role in Sertoli cell proliferation and maturation: follicle-stimulating hormone (FSH) and thyroid hormone. FSH secretion has been assumed to be the stimulus for proliferation. The thyroid hormone is responsible for normal postnatal growth and development. Alterations in thyroid activity have frequently been associated with changes in male reproductive functions, since hypothyroidism, induced with 6-N-propyl-2-thiouracil (PTU) soon after birth, is associated with a marked delay in sexual maturation and development. The goal of this study was to report the effect of FSH and PTU on the stages of sperm cell development of young pigs. Six piglets of 1, 7, 14, 25, and 55 days of age were castrated and their testes were sectioned to grafts of 5 mm3. The grafts were then transplanted subcutaneously into the dorsum of 12 castrated nude mice per age group. Two days post-surgery mice were randomly assigned to one of four treatment groups: control, FSH (5 IU rFSH), PTU (0.015% solution), and FSH + PTU. Following 14 days of treatment, testicular tissue pieces were allowed to grow for 2 additional weeks. Tissues were then harvested, immersion-fixed in neutral buffered formalin, and embedded in paraffin. Five-micron-thick sections were stained using hematoxylin and eosin. Slides were evaluated under light microscopy and the oldest germ cell type present in each section was recorded. Germ cell types were recorded as spermatogonium, spermatocyte, early spermatid, and late spermatid. Statistical differences between all groups were detected using paired Student t-tests. There were no differences noted between control groups and those treated with PTU or FSH alone. No effect concerning age of castration on grafts development was observed. There was a slightly significant increase (P = 0.05) in the number of spermatocytes observed in the groups treated with FSH+PTU. These data suggest that there is a potential synergistic effect of FSH and PTU on sperm cell development. Based on these results, further studies need to be performed to completely understand the effect of these two hormones on Sertoli cells.

Repopulating spermatogenic colonies, found in the seminiferous epithelium after irradiation with fast-fission neutrons, were studied to determine the cha nce that a stem cellAsingle (As spermatogonium would complete a self-renewing division (P). Mathematical formulas originally derived for such studies in haemopoietic colonies were employed, and a method specifically aimed at spermatogenic colonies was developed. The results showed that during the first division after irradiation, P is close to 1 -0. P decreases in later generations, but remains 0-7 or higher up to the 4th or 5th divisions. The mean value for P was over 0-8, which is higher than the value of 0-6-0-7 found for stem cells in haemopoietic colonies.

An ultrastructural study of male germ cells in the testes of Haliotis ovina revealed that spermatogenesis could be classified into 13 stages, based on the pattern of chromatin condensation and distribution of organelles, as follows: the spermatogonium; five stages of the primary spermatocyte; the secondary spermatocyte; five stages of the spermatid; and the spermatozoa. Each spermatogonium was round or oval, with a euchromatic nucleus and prominent nucleolus. The primary spermatocytes were divided into five stages: leptotene (LSc); zygotene (ZSc); pachytene (PSc); diplotene (DSc); and metaphase (MSc). The nucleus of the LSc contained scattered small heterochromatin blocks that were increasingly thickened in the ZSc. The PSc was characterised by a bouquet pattern of heterochromatin fibres. The DSc decreased in size, resulting in close clumping of chromatin blocks, whereas in the MSc, long and large blocks of chromosomes were formed and then moved to be aligned along the equatorial region. Secondary spermatocyte showed thick chromatin blocks that appeared reticulate. The spermatid could be divided into five stages (St1–5). The St1 was a large round cell and its nucleus contained homogeneous chromatin granules. In St2, the nuclear chromatin started to condense into patches. The St3 was smaller with a round nucleus containing dark blocks of heterochromatin. The St4 became smaller still, with a round opaque nucleus. The St5 was the smallest round cell, with almost completely condensed chromatin. The spermatozoon had a round to barrel-shaped head that contained completely condensed chromatin covered by a conical acrosome. The posterior border of the nucleus was flanked by five large spherical mitochondria and the tail consisted of axonemal microtubules surrounded by the plasma membrane.

The fine structure of the spermatogonium, spermatocyte and spermatid of a marine snail, Littorina sitkana is described. The ring centriole (annulus) is formed from the distal centriole and it migrates to the base of the mitochondrial region where it lies in a joint-like structure which is formed by an area of invaginated plasma membrane. The distal and proximal centrioles are at first perpendicular to each other but the proximal centriole rotates to a position coaxial with the distal centriole and fuses with it. The peripheral doublet fibers are continuous between the two centrioles but the central fibers originate only in the distal centriole. The acrosome differentiates from the proacrosomal granule which is derived from a Golgi body. Microtubules, present at this stage, may assist acrosomal formation. Chromatin condensation begins with the formation of fibrous strands, then to lamellar plates which become folded and later twisted around the flagellar shaft. In the final stages the lamellae appear in cross section as concentric rings which eventually fuse to form a homogeneously dense nuclear tube.

Nuclear cytoplasmic exchange is conspicuous during spermatogenesis in the pseudoscorption Diplotemnus sp. The incidence of structural components demonstrating this phenomenon, though variable, can unmistakably be followed from the spermatogonium to the late spermatid stage. In conjunction with this feature it is noticed that the nuclear envelope exhibits changes in the number and distribution of its pores. One of the most interesting findings is that direct connection can be visualized between the nuclear RNA and a specific cytoplasmic structure. In late spermatid stage a certain amount of RNA still retained in the nucleus separates from the DNA and in turn becomes associated with the vesiculated area of the nuclear envelope. The latter is transformed into a “cisternal convolution” which contributes to the makeup of the flagellar sheath. Besides detailing nuclear changes, observations embodying an overall view of sperm morphogenesis, including the formation of transitory central vacuole, are reported herein.

We have developed genetic tests for estimating the proportion of small deletions among chemically induced point mutations in Drosophila. The criteria used allow the detection of deletions that are large enough to include a viable visible mutation as well as a lethal, or a sex-linked lethal as well as a gene that is required for the development of a spermatogonium into a spermatozoon. On these criteria, we have concluded that DEB produces a high proportion of deletions among point mutations; that HA produces no deletions; and that DEN produces either no deletions or only very small ones that cannot be detected by our methods.

This review aims at giving the up-to-date results in studies of proteins in spermatozoa and seminal fluids, mainly in domestic animals. Attention was given to protein and antigenic substances appearing during spermatogenesis and spermiogenesis in the testes. The problem of proteosynthesis of haploid testicular cells was also noted. Peptide hormones in the testes have an important role for the function of the testicle and the synthesis of sperm and testicular fluid proteins. Epididymal proteins are very important for the fertility and motility of spermatozoa in all mammalian species, but only some of them have been isolated and chemically and functionally characterized. It looks as though the specific accessory sex gland proteins are not necessary for actual fertilizing capacity, but this is probably not the case. Many proteins have been isolated from seminal plasma and studied. Some of them are important because they enable spermatozoa to survive in the female genital tract. The physiological function of a series of other proteins/enzymes is still unknown, however, although their significance is demonstrated by studies showing that many of them are bound to the sperm cells. The sperm cell proteins are of both primary and secondary origin. From the primitive spermatogonium to union of the spermatozoon with the egg, the male germ cell undergoes continual metabolic, protein synthetic, protein destructive and, of course, morphological changes. The primary spermatozoa-specific proteins are mainly formed during meiotic processes and during spermiogenesis in the Sertoli cells. There are experimental and clinical results which show that specific sperm cell and seminal plasma proteins can induce immune processes in males and in females.

Ripe male specimens of the nemertean worm Tetrastemma phyllospadicola (Nemertea, Hoplonemertea) measure about 7 mm long and characteristically possess 100–200 saccular testes. Each testis connects to a short gonoduct which is lined by myofilament-containing cells. The testicular sac is also lined by cells packed with myofilaments and typically contains scattered clusters of spermatogenic cells and bundles of sperm. During spermatogenesis, a spermatogonium divides mitotically several times and ultimately forms a cluster of primary spermatocytes that remain interconnected by narrow cellular bridges. Spermatocytes undergo meiotic divisions to produce syncytial clones of spermatids. As spermiogenesis proceeds, each spermatid differentiates into a modified spermatozoon with a wavy head measuring about 40 μm long. The head contains a well-developed acrosomal complex situated lateral to the anterior end of the nucleus and a long mitochondrion that lies within a groove in the posterior part of the nucleus. A discrete midpiece is lacking. The centriolar anchoring apparatus comprises nine unbranched spokes, and the tail exhibits a 9 × 2 + 2 arrangement of microtubules. Somatic cells that possess ramifying processes are intimately associated with the spermatogenic clones in each testis. Peculiar attributes of the testes and spermatozoa of this species are discussed with reference to previous accounts of spermatogenesis in nemerteans.

Seasonal variation in number of spermatogonia and germ cell degeneration was evaluated to determine which mechanism might explain seasonal differences in daily sperm production per testis (DSP/testis) or per g parenchyma (DSP/g) in stallions. Comparing 28 adult stallions (4 to 20 yr old) in each of the nonbreeding (December-January) and breeding (June-July) seasons, the population of type A spermatogonia was more than two times greater (P less than 0.01) in the breeding season. While the number of type B spermatogonia also was elevated (P less than 0.01) in the breeding season, the number of type B spermatogonia/type A spermatogonium was similar (P greater than 0.05) between seasons. Daily sperm production/testis based on each cell type from type B spermatogonia to spermatids with elongated nuclei was lower (P less than 0.01) in the nonbreeding season. Based on DSP/g, there was significant degeneration during the meiotic divisions in the nonbreeding season. However, this reduction in potential spermatozoan production was not significant (P greater than 0.05) when considering DSP/testis. Significant germ cell degeneration also occurred in the breeding season between type B spermatogonia and primary spermatocytes. However, the type A spermatogonial population was sufficiently elevated to override this degeneration and to explain elevated production of sperm in the breeding season of stallions.

The cycle of the seminiferous epithelium of the nine-banded armadillo can be divided into ten stages. As in most mammals, only one stage is observed per tubular cross-section. The process of spermiogenesis can be divided into thirteen steps according to the development of the acrosomal system and the flagellum. Four generations of spermatogonia are observed in the germinal epithelium: 1) stem cells, 2) type “A”, 3) intermediate, and 4) type “B” spermatogonia. The stem cell is characterized by a highly irregular nucleus and the presence of glycogen in its cytoplasm. The type “A” spermatogonium contains an oblong nucleus with one or two shallow infoldings of the nuclear membrane. The intermediate spermatogonium contains an ovoid nucleus characterized by one or two nuclei and heterochromatin scattered in the nucleoplasm. The nucleus of the type “B” spermatogonium is more spherically shaped with a centrally placed nucleolus and heterochromatin associated with the nuclear envelope.

Testes from 37 Holstein bulls, 38-99 mo of age, were used to investigate the relationship of Sertoli cell number, Sertoli cell-germ cell ratios and other related factors to daily sperm production (DSP). DSP was assessed by enumeration of spermatids in testicular homogenates, whereas Sertoli cell and germ cell ratios were based on direct counts in 20 round Stage VIII seminiferous tubular cross sections per bull. Numbers of Sertoli cells were calculated as (total homogenization resistant spermatids:spermatid:Sertoli cell ratio)/0.394; the factor of 0.394 adjusted for the presence of homogenization resistant spermatids during only 39.4% of the spermatogenic cycle. Data were subjected to simple linear and second-order regression analyses. Positive linear relationships were observed between DSP and testicular parenchymal weight (p less than 0.005, R = +0.71), DSP per gram (p less than 0.005, R = +0.79), total Sertoli cells (p less than 0.005, R = +0.83), Sertoli cells per gram (p less than 0.01, R = +0.47) and the yield of Step 8 spermatids per Type A spermatogonium (p less than 0.05, R = +0.34). DSP was not related (p greater than 0.10) to the number of germ cells supported per Sertoli cell. Testicular parenchymal weight and DSP per gram were unrelated to each other (p greater than 0.10), but both were related (p less than 0.005) to the total Sertoli cell number (R = +0.61 and +0.62, respectively). Total number of Sertoli cells accounted for more of the variation in DSP between bulls (R2 = 68.2%) than did any other factor examined. It was suggested that total Sertoli cell number may be an important determinant of a bull's spermatogenic potential.

The histological, cytological and cytogenetic effects of nogalamycin were studied in rats, mice and cultured human leukocytes. Four standard test systems were used in the cytological studies: (1) analysis of spermatogonial cells, (2) cytological evaluation of bone marrow metaphase plates, (3) micronucleus test in polychromatic erythrocytes, and (4) determination of chromosomal aberrations in cultured human leukocytes. The results of the studies indicated that the types and frequencies of cytological errors induced by the drug were not significantly different from the concurrent control. The reduced incidence of fertile matings from 22 to 35 days after treatment is attributed to the cytostatic effect of nogalamycin (NM) on spermatogonia and spermatocytes. Subsidence of NM-induced inhibition of spermatogonium differentiation and spermatocyte maturation occured 37 days post-treatment. Accordingly, fertile matings, which had reached a zero level by the 23rd day, occurred 35 days after treatment, and reached the control level between 47 and 49 days post-treatment.

The efficiency of spermatogenesis and degenerations of different spermatogenic cells under normal conditions of the environment have been investigated in rams. The meiotic divisions and the position of first-generation spermatids in haematoxylin-eosin stained testicular preparations were used to identify eight stages of the seminiferous epithelial cycle (SEC). The stages of relatively long duration (i.e., 1,2,3,4,8) were sub-divided. The percent-ages of frequency for the 14 stages reported were also studied. Three generations of type A (A 1 , A 2 , A 3 ), one generation of type intermediate (In) and two generations of type B (B 1 , B 2 ) spermatogonia were recognized. A 2 and B 2 spermatogonia as well as primary and secondary spermatocytes did not degenerate. Contrarily, A 1 , A 2 , A 3 , In and B 1 spermatogonia showed 25, 13.7, 27.3 and 21.2% degenerations respectively. We concluded that compared with the previously used eight-stage classification, subdividing stages with long durations as done in this study facilitates investigating the degenerations of spermatogenic cells. The efficiency of spermatogenesis in rams was 47.58% since one A 3 spermatogonium produces 30.45 spermatids/spermatozoa against the expected number of 64.

Seasonal changes in the Leydig, Sertoli and stem cells (undifferentiated A0 and cyclic A1) spermatogonia and the daily spermatid production were analysed in the testes of adult Soay rams exposed to short days (8L:16D) or long days (16L:8D) for 12 weeks. The total numbers of Leydig, Sertoli and stem cells (A0 + A1) were not affected by the treatments, but the size of the Leydig and the Sertoli cells, the efficiency of spermatogenesis (i.e. the number of male gametes produced by an A1 spermatogonium) and the daily sperm production were all significantly reduced in the rams exposed to long days. There was a positive correlation between the concentration of FSH and testosterone and many of the cytological changes consistent with a causal role for these hormones in mediating the effects of photoperiod on the testicular function in the ram.

After a long hibernation, snails Helix aspersa were reactivated and maintained under either long (LD 18:6) or short (LD 8:16) photoperiods. Twenty days after activation, they were injected with (")thymidine in order to estimate the duration of spermatogenic stages under both conditions. Whereas the spermatogonium and spermatocyte I stages prove to have the same duration under both short and long photoperiods, the male cells stay longer at spermatocyte I1 stage in short-day snails. In these animals, spermiogenesis proceeds normally and its duration is similar to that in long-day snails. Therefore, in the course of Helix aspersa spermatogenesis, two phases are particularly sensitive to the photoperiod: spermatogonial proliferation and transition from spermatocyte I1 to spermatid. Gradual decrease of the levels of (3H)thymidine in the gonad of long-day snails from the 6th week may be interpreted as being due to release of labeled sperm; in short-day snails, these levels remain nearly unchanged to the end of the experiment, which indicates that the temporary blockade of spermatogenesis at the completion of spermatocyte I1 results in a delay in spermiation. As in many gastropod species (Henderson and Pel- luet, '60; Sokolove and McCrone, '78; McCrone and Sokolove, '79; Bohlken and Joosse, '821, in HeZix as- persa the photoperiod is an environmental factor that much affects the gonadal activity and reproductive rate. Thus, at 15"C, egg-laying occurs only under long photoperiods (Enee et al., '82). At temperatures alternating between 17°C (during the day) and 12°C (during the night), short photoperiods inhibit sper- matogonial proliferation and cause a delay in sper- matogenesis (Gomot and Gomot, '85; Gomot and Griffond, '87). We have recently shown by autora- diography that the step from spermatocyte I1 to sper- matid is particularly sensitive to external conditions (Medina et al., '88), but it is still unknown whether spermiogenesis is also affected by the photoperiod. Since the blockade of spermatogenesis at the sper- matocyte I1 stage is not a definitive one (Gomot and Gomot, '85; Gomot and Griffond, '87), we undertook the present investigation in an attempt to estimate the duration of the transition from spermatocyte I1 to spermatid and the manner in which spermioge- nesis and spermiation proceeds in snails kept under short-day conditions.

A quantitative evaluation of spermatogenesis in the guinea pig was made at the light microscope level following improved methods of fixation and plastic embedding. The pattern of germ cell differentiation was studied by counting the average number of germ cell nuclei per Sertoli cell nucleus during the seminiferous epithelial cycle. Appreciable cell loss occurred during spermatogenesis. As a result, only 20.8% of the theoretically possible number of spermatozoa were produced from each spermatogonium. A slightly better yield of germ cells was obtained from Epon sections in comparison to paraffin sections. Epon sections can be effectively used for quantitative analyses of various cell populations in small biopsy specimens of testis tissue.

Adult Long-Evans male rats were treated with various dosages of pure or technical grade 1,2-dibromo-3-chloropropane (DBCP), epichlorohydrin (Epi), or allyl chloride (AC) for 1, 3, or 6 months on a daily basis. AC, which is the substrate for the production of DBCP, and Epi, which is a contaminant and/or metabolite of DBCP, had no effect on any of the parameters of the male reproductive system studied. The deleterious effects on male reproduction are therefore attributable specifically to DBCP. The effects of DBCP were dose and duration dependent. At the lowest dose (1 mg/kg) DBCP did not have any discernible effects on the male reproductive system. By 3 months of treatment at the intermediate dose of 5 mg/kg, the morphology of the testis ranged from normally appearing seminiferous tubules to ones which contained Sertoli cells only. At 6 months of treatment there was a reduction in the weights of the testes and sexual accessory glands. At the highest dose, the majority of the rats showed advanced testicular regression by 1 month of treatment. The most extreme testicular regression was observed in the 6-month treatment group. Almost all of the seminiferous tubules of all of the rats were composed of Sertoli cells only. In some of the animals, a few isolated seminiferous tubules contained an occasional spermatogonium or primary spermatocyte. Some of the Leydig cells of the rats in this group showed morphological evidence of atrophy as evidenced by the clumping of chromatin and paucity of stainable cytoplasm. This was confirmed by lower levels of intratesticular testosterone, a significant reduction in the number of luteinizing hormone (LH) receptors and increased serum levels of LH and follicle-stimulating hormone (FSH). From these results we conclude that DBCP is a specific male gonadotoxin and that the effects are not a result of contamination or metabolism. The effects appear to be a direct action at the testicular level because feedback inhibition to the pituitary gland was adversely affected.

Testes weights, sperm motility and enzyme activities in single sperm were compared with respect to their ability to detect either developmental or mutational damage to germ cells. Male mice were injected i.p. with 2.5 mg/kg mitomycin C (MC) or 50 or 100 mg/kg ethylnitrosourea (ENU) or saline and were then killed at times such that sperm derived from treated vas sperm (SZ), spermatids (ST), preleptotene-late-spermatogonial cells (PLSG), spermatogonial cells (SG), or spermatogonial stem cells (SGS) could be evaluated. Testis weights decreased significantly as early as 1 wk after treatment, with the greatest decrease reached 3-4 wk after treatment, followed by recovery to normal levels 10-15 wk after treatment. We conclude that testis weight, which is easily obtained, is a sensitive indicator of germ cell damage by these agents. Sperm from each animal were evaluated for sperm motility, acrosin activity, succinic dehydrogenase (SDH) activity with or without the competitive inhibitor malonate or after exposure to 60 degrees C for 10 min. The latter two assays were to detect sperm enzymes resistant to the inhibitor or heat. The presence of the acrosin protein was also detected immunologically. Sperm motility decreased most from treatment of PLSG and SG. After MC or ENU treatment, the greatest loss of acrosin activity and of the acrosin protein was also noted in sperm derived from treated PLSG and SG. MC and ENU failed to induce SDH activity in single sperm resistant to 60 degrees C heat inhibition or to inhibition by malonate. Of the sperm assays, acrosin activity proved to be the most sensitive indicator of germ cell damage and was the simplest to measure.

The modal number of chromosomes in Eptatretus burgeri was 36 in 297 (81.8%) of 363 somatic cells, 52 in 13 (30.2%) of 43 spermatogonia, and 25 (46.8%) or 26 (40.3%) in 162 of 186 first spermatocytes. The relative amount of DNA in a somatic cell to that in a spermatogonium averaged 79.2%. C-band-positive chromatin was observed along almost the entire length of the associated dumbbell-shaped bivalents and part of two other bivalents in the metaphases of first spermatocytes, but was rarely observed in somatic cells. These results indicate that, in E. burgeri, chromosome elimination takes place during the early stages of cleavage, except for the ancestral germ-line cells.

The production of normal sperm in numbers adequate for conception is imperative for reproduction. The process by which sperm are produced is termed spermatogenesis. Thus, a general understanding of spermatogenesis and of certain details of this process is essential for a stud manager or veterinarian to effectively utilize the reproductive capactiy of a stallion. Only with such a background can an individual working with stallions understand the possible origin for alterations in sperm production, the dangers inherent in certain practices, or the rationale behind recommendations for maximizing the reproductive capacity of a stallion. Spermatogenesis is the sum of the transformations that result in formation of spermatozoa from spermatogonia while maintaining spermatogonial numbers. This review of spermatogenesis is based on all published data for the stallion, but the explanation of many details of the process integrates studies with other species. Spermatozoa are produced within the germinal epithelium of the seminiferous tubules. The germinal epithelium of a mature stallion is composed of somatic cells termed Sertoli cells and different types of germ cells, namely the spermatogonia, primary spermatocytes, secondary sperrnatocytes, and spermatids (Figure 1). In a cross section through a normal seminiferous tubule, four or five generations of developing germ cells are arranged in well defined cellular associations. 4,6,8,19,20,21 In the stallion, each succeeding layer or generation of germ cells within a cellular association is 12.2 days more advanced.P-" The time required to "produce a spermatozoon from a differentiated spermatogonium is not influenced by season or other factors6,16,17 and averages about 55 days in stallions. 1,3 Consequently, the interval between occurrence of an event deleterious to spermatogenesis and the resulting decline in semen quality might be as long as two months. A similarly long, or even longer, interval may be required for restoration of normal spermatogenesis after the agent acting on the reproductive system (e.g., an anabolic steroid) has been eliminated.

It has been observed that conspicuous characteristic changes occur in mitochondrial number, size, shape, disposition, and ultrastructural organization during spermatogenesis of a pseudoscorpion, Diplotemnus sp. Mitochondria are drastically reduced in number in the spermatids as compared with the spermatocytes. In the spermatogonium, mitochondria are minute, later they proliferate and become irregular, and in the primary spermatocyte they tend to gather precisely as a “rosette” around the “idiosome” of R. H. Bowen ((1922/1923) Anat. Rec. 24, 159–180). In the secondary spermatocyte, mitochondria become spherical cricket-ball like and just prior to the completion of second meiotic division they appear as biconcave discs or cup shaped; the latter often are stacked one inside another. Soon these disc-like, cup-like mitochondria in the spermatid are transformed into cylindrical entities of indeterminate length. As soon as the vacuole formation begins in the spermatid, mitochondria (assumed to be not more than 30 per section) tend to coil circularly in the cortical cytoplasm of the cell. In doing so they lie close together without fusing with each other. The coiling of the mitochondria gets accentuated with progressive shrinkage of the spermatid. Mitochondria occupy the major portion of the mature spermatozoon. In Diplotemnus sp., unlike most of the animal spermatozoa, mitochondria are not at all associated with the axonemal complex; rather, the two organelles stand separated from each other with the interposition of two electron-dense sheaths which surround the axoneme. Last, in the spermatid an unusual association of the mitochondria with a unique body, “cisternal convolution,” has been observed.

We investigated stem cell renewal and differentiation in 10- and 15-days-old spermatogonial clones developing in mouse seminiferous epithelium after an extremely large cell loss, inflicted by high doses of the alkylating agent Myleran. The spermatogonial clones arise from cells that resemble the Ais spermatogonia but have a larger nuclear diameter. In spite of their mitotic activity these ‘re-populating stem cells’ lie mainly isolated or in pairs. This is explained by migration and differentiation. Migration appeared to occur at random in all directions along the basement membrane of the seminiferous tubule. After one or more divisions of the stem cells, a second type of cell appears, which is called the ‘differentiating spermatogonium’. The time elapsing before this type of cell appears, depends on the dose of Myleran: the larger the dose the later differentiation starts. A relation could be demonstrated between the stage of the cycle of the seminiferous epithelium and the start of differentiation. Differentiating cells were found isolated or in groups of two, four, eight or sixteen cells. Hence we concluded that at least up to their fourth division differentiating cells divide synchronously without degenerations. Three types of division of repopulating stem cells were distinguished, producing (1) two repopulating stem cells, (2) one repopulating stem cell and one cell starting spermatogonial differentiation, or (3) two differentiating cells. Type 1 divisions were found most frequently.

Hydroxyurea, a chemotherapeutic agent that prevents mitosis by inhibiting DNA synthesis, was administered to adult male rats for 70 days. Plasma FSH and LH showed no systematic trend although severe germinal cell depletion was produced. These data suggest that the cell(s) of the seminiferous tubule involved in FSH regulation must be either the type A spermatogonium or the Sertoli cell. (Endocrinology 96: 564, 1975)

Spermatogenesis in Rana esculenta is initiated during metamorphic climax and mature spermatozoa are present in froglets 45 days old. Cytological analysis of cell populations shows that some of the primary spermatogonia may lie dormant for brief intervals of time. Timing analysis of the process of spermatogenesis, in adults and in developing Frog larvae maintained at approximately 18°C, was investigated by different methods. The results are remarkably similar. Although perfect synchrony of the developing cells within a single germinal cyst is not the rule, a uniform rate of advancement of germinal cysts of the same stage of development, in most of the seminiferous tubules of a testis is evident. The duration of the secondary spermatogonial divisions is five to six days, involving five or six mitotic cycles, each cycle lasting approximately 24 h. The premeiotic S-phase, and phases of leptotene, zygotene, pachytene, diplotene+secondary spermatocytes, and spermiogenesis each have a duration, respectively, of six, two, six, twelve, two and seven days. The duration of spermatogenesis, from a “committed” primary spermatogonium to the formation of spermatozoa is 41 days.

Spermatogenesis is studied in rats after 5, 50, and 200 mu c. injections of Cs/sup 137/, for times up to 10 weeks after irradiation. The concentrations of spermatogonium, spermatocytes, spermatids, ard sperm cells in the seminiferous tubules are given as functions of dose and time. (T.F.H.)

The sexual reproduction and auxospore formation of Centrales had been misinterpreted for a long time. It was believed until recently that auxospore formation had no connection with sexual reproduction. More recently, however, STOSCH2) demonstrated oogamy clearly in Melosira varians for the first time, and since then STOSCH4-8) and GEITLER9, 10) studied the sexual reproduction in many marine Centrales. In this work, the author observed the sexual reproduction of Skeletonema costatum in axenic culture, and the following results were obtained. 1. When the narrow filamentous colonies of Skeletonema less than 5-6μ in breadth were cultured at the temperature of 17-23°C, formation of spermatogonia and oogonia was observed. 2. The spermatogonia are produced after 1 or 2 cell-divisions of vegetative cells, and four spermatozoa are formed in each spermatogonium. The spermatozoa are globular in shape, 3-3.5μ in diameter, poor in plastids, and they each have one flagellum being 7-10μ in length. 3. The oogonia are produced from vegetative cells by extension of the cells, and one egg cell is formed in each oogonium. 4. After fertilization, a zygote develops into an auxospore without any resting stage. The fully grown auxospore is generally about three times as large in diameter as the mother cell. 5. The spermatogonia and oogonia are produced in the same clone, and accordingly this species is monoecious. 6. The auxospore formation is found more abundantly at the temperature of 20°C than 15 or 25°C. The sex determination in this species is influenced by light intensity. Clones of vegetative cells produce female cells under strong light, but they produce only male cells under weak light.

The number and behavior of the chromosomes have been investigated in the spermatogenesis of Cryptobranchus allegheniensis. The spermatogonium contains sixty-two chromosomes, which are composed of twelve atelomitic V-shaped ones, and eighteen long and thirty-two short telomitic ones. The haploid number of chromosomes is ascertained to be thirty-one in both of the primary and secondary spermatocytes. The chromosomal relation between the present species and Megalobatrachus japonicus, a closely related form, has been discussed.

During spermatogonial stages in Xiphophorus and Platypoecilus maculatus and Platypoecilus couchiana and in the hybrid, two distinct types of cells are observed, a large lightly staining primary spermatogonium and a smaller deeply staining secondary spermatogonium. Chromosomes of primary spermatogonia of Platypoecilus maculatus and Platypoecilus couchiana differ somewhat from those of Xiphophorus helleri and Xiphophorus jalapa, but are very similar to those of the hybrid at this stage. Chromosomes of Xiphophorus at this stage are long and thin, while those of Platypoecilus and of the hybrid are somewhat short and thick. Visible chromosome differences appear only during the primary spermatogonial stages. The haploid group of chromosomes, numbering twenty-four in the hybrid, so resembles that of Xiphophorus and of these two species of Platypoecilus in both number and morphological characteristics during the primary spermatocyte division as to be practically indistinguishable from either. Persistent lagging of one large chromosome as it comes upon the equatorial plate during the primary spermatocyte division is very noticeable. Precocious division of this chromosome and the advancing of its two daughter components to the poles of the spindle in advance of other chromosomes indicates that this chromosome may be a sex chromosome. The fact that two daughter components are identical morphologically and that each secondary spermatocyte receives one of them suggests that the male in Xiphophorus and in Platypoecilus is homogametic.

In this paper, sixth in the series ‘Studies on Insect Spermatogenesis’ observations on the cytoplasmic inclusions in the living male germ cells of Pyrilla sp. and Dysdercus cingulatus have been presented.The mitochondria appear as granules and delicate fibrils in the spermatogonium of Pyrilla sp. and Dysdercus cingulatus respectively. Some of the mitochondrial granules align to form filaments of low phase-change in the spermatocyte of Pyrilla sp. Some of the filamentous mitochondria bend to form ovals or rings or vesicles during meiotic stages.The mitochondrial nebenkern, to start with, is ‘vacuolar’ in Pyrilla sp. and later reveals an ‘onion like’ pattern lacking in Dysdercus cingulatus. The ‘central substance’ is conspicuous by its absence in both the species.‘Chondriokinesis’ without fragmentation of the individual mitochondria has been recorded in Pyrilla sp., and D. cingulatus.During spermateleosis the fusion of the Golgi bodies result in the formation of the acroblast to which is later on associated the acrosomal vesicle. This vesicle condenses to form the acrosome, there being no acrosomal granule in both the species.

In both round (Heterodera s.g. Globodera Skarbilovich) and lemon-shaped (H. s.g. Heterodera Skarbilovich) species of cyst nematodes studied, the early stages of spermatogenesis were completed in the 4th-stage larva and no further cell divisions took place after the last moult. Only spermatids and spermatozoa were present in adult males; in old males the whole gonad was occupied by mature sperm. Evidently the sperm output of the non-feeding, adult male is limited, possibly conserving reserves of energy for mate-finding, Resources are also conserved when, during maturation of the spermatozoa, the discarded cytoplasm and organelles of the so-called 'residual bodies' are engulfed by cells of the testis wall. Heterodera sperm resemble other described nematode sperm in being aflagellate and amoeboid, in lacking a nuclear membrane during all stages except the spermatogonium and in having a fibrillar storage product in the spermatids which in H. rostochiensis disperses during the transition to sperm but in H. schachtii is retained. They differ from other nematode sperm in lacking the polarity, the secretory granules and the so-called 'membrane specialisations' found in one or other of the four main types of nematode sperm, and in possessing a layer of cortical microtubules lining the whole surface of the sperm, including the pseudopodia. In round-cyst nematodes the state of condensation of the sperm nucleus changes several times during spermiogenesis and insemination, the chromatin passing through a compact homogeneous, a finely stranded, another compact and finally a coarsely stranded phase. These changes have not been recorded in other nematode sperm. The sperm nucleus in lemon-shaped cyst nematodes does not pass through the finely stranded phase in the testis, a further difference distinguishing the two main groups of cyst nematodes.

(1) The length of the mitotic spindle, i. e. the distance between the two centrosomes, at the stage of the metaphase when the chromosomes are undergoing constriction in the equatorial plane, appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 6.9, 10.2 and 7.8 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively. (2) The length of the mitotic spindle at the conclusion of the metaphase when the daughter-chromosomes are ready to move apart appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 7.1, 10.4 and 8.1 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively. (3) The length of the mitotic spindle in the earliest anaphase, i. e. at the moment when the daughter-chromosomes have begun to move apart, appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 7.3, 10.7 and 8.3 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively. (4) The ratio between the lengths of the mitotic spindle at the conclusion of the primary and secondary spermatocyte metaphases is almost identical with the ratio between the radii of two spheres of which the volume of one is equal to twice that of the other ; and the volume of the primary spermatocyte cell must be equal to twice that of the secondary spermatocyte at this stage, because no growth or resting stage intervenes. (5) The ratio between the lengths of the mitotic spindle at the conclusion of the primary spermatocyte and secondary spermatogonial metaphases is almost identical with the ratio between the radii of two spheres of which the volume of one is equal to three times that of the other. The initial volume of the primary spermatocyte cell must be half that of the secondary spermatogonium, because the latter divides to form two daughter primary spermatocytes; but the large size of the last-named, observed at the close of the growth period, does not refute the suggestion that the initial volume is increased six-fold during this period. (6) If coincidence is not responsible for the apparent connection between the ratios mentioned above, correction is established between the cell volume and length of spindle in the spermatogeiietic metaphases of this species.

The DNA content was studied histographically in the nuclei of the cells of certain mitorically dividing tissues (spermatogonium, fibroblasts of albino mice, liver cells and those of the pancreas in young albino rats). The authors came to a conclusion, that the process of DNA reduplication is nonuniform. Each subsequent stage of the DNA synthesis is more intense than the preceeding one; the rate of synthesis increases during the second half of the process, reaching the maximum near the end of reduplication.