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The mesonephrogenic cord disintegrates into approximately 35-40 provesicular cell masses which are in close contact with the mesonephric (Wolffian) duct (WD) on their lateral side. Here, the epithelium of the WD is columnar and shares a common basal lamina with the provesicular cell masses. This in turn gives rise to a sickle-shaped pseudostratified epithelium. The concavity of the sickle is filled by spherical cells, the transition of which into the surrounding connective tissue is continuous. The sickle is transformed into a distillation flask and becomes separated from the mesonephric duct while the spherical cells maintain a connection to it by a-for the time being-solid outlet pipe. The columnar epithelium of the mesonephric duct becomes a multilayered cone, whose surface is in contact with the outlet tube. Shortly after, a continuous lumen is formed in the cone and the outlet pipe which is delimited by cells becoming columnar and forming a basal lamina. The epithelial anlage of the nephron is clearly separated from the surrounding mesenchyma by these processes. The flask eventually becomes a corpusculum, the outlet pipe a secretory (proximal) as well as collecting tubule, and the cone of the mesonephric duct a mesoureter. The various sections display differentially differentiated epithelia that are clearly distinct from each other. The mesoureter behaves differently during differentiation of epi- and paragenitale: in the epigenitale, it is short and runs into the collecting tubules of the nephrons at the lateral side of the convolved tubules, whereas a long mesoureter crosses the dorsal side of the convolved tubules and joins the corresponding collecting tubules at the far end of the mesonephros in the paragenitale.

The identification of hereditary variants of cutaneous melanoma and analysis of the role of hereditary factors and syndromes predisposing to cutaneous melanoma were carried out. The involvement of individual nevus phenotypes in the development of this disease was determined. Based on a survey of recent molecular biological data and our studies, the etiological and genetic heterogeneity of cutaneous melanoma is reported. In relatives of patients with cutaneous melanoma and persons with multiple pigmented nevi, the malignant tumors proved to be differentiated in the direction of the neural crist tissues and/or derivatives of cutaneous mesenchyma. Based on the evidence obtained, the approaches have been developed to formation of risk groups for the purpose of early diagnostics of cutaneous melanoma.

Complex 3-dimensional structures with good functions have been obtained under the primary mixcoculture of mouse hepatocytes with mouse liver fibroblasts without serum. Albumin secretion is kept above 10 μg/106 cells and urea synthesis reaches 25 μg/106 on the 7th day of culture. Avoiding serum affection, liver fibroblasts’ effects on hepatocytes’ viability, functions and 3-dimensional structure forming in primary serum-free culture have been studied. Important effects of the mesenchyma, especially the direct adherence of fibroblasts to hepatocytes, are shown.

Mesodermal determinants were investigated by cytoplasmic transfer and blastomere isolation in the eight-cell stage of Bufo arenarum. Their existence was confirmed by assaying the subequatorial cytoplasm's ability to respecify the developmental potency of animal quartets. The gray subequatorial cytoplasm, but not animal cytoplasm, is able to divert the ectodermal fate of animal quartets to several mesodermal components. The source of the transplanted cytoplasm was important in determining the category of the resulting structures. Ventral subequatorial cytoplasm from ventrovegetal blastomeres generated ventral derivatives, namely erythrocytes and mesenchyma. Dorsal subequatorial cytoplasm from dorsovegetal blastomeres produced dorsolateral derivatives, such as notochord, muscle, nephric tubules, and coelomic epithelium, including mesenchyma. On the other hand, transfer of vegetal pole cytoplasm to animal quartets resulted in the formation of groups of endoderm-like cells dispersed among epidermal cells. However, the presence of such cells did not cause any mesodermal induction. The present findings suggest the existence of cytoplasmic information responsible for mesodermal specification. The alternative hypothesis that animal blastomeres become mesoderm due to vegetal induction is questioned.

Based on the findings of their own studies on embryonic histogenesis of human tissues and published reports, the authors determined the time limits of the existence of human embryonic stem cells and type of their determination in divergent development of tissues in different organs. Realization of genetic information of embryonic stem cells during tissue embryogenesis was studied. This information is realized by the cambium. Variability of all tissue processes is possible only within their own embryonic primordium; prospects of the mesenchyma development in an adult body is discussed.

While more and more humoral factors are being implicated in nephrogenesis, there is no detailed knowledge of the morphological structures at the interface of the nephron inducer and the surrounding mesenchyme. Hence we examined this area in the cortex of neonatal rabbit kidneys by scanning and transmission electron microscopy. Our interest was focused on the basal aspect of the collecting duct ampulla and the surrounding competent mesenchyme where morphogenic signals are exchanged during nephron induction. Close contact between these two tissues is assumed during nephrogenesis to allow direct cellular contact or diffusion of soluble factors across a short distance. However, our data show the presence a wide cleft around the collecting duct ampulla spatially separating the inducer and the competent mesenchyme during nephron induction. This cleft is filled with a characteristic fibrillar mesh-work.

The myogenic potential of chick limb mesenchyme from stages 18-25 was assessed by micromass culture under conditions conductive to myogenesis, and was measured as the proportion of differentiated (muscle myosin-positive) mononucleated cells detected. It was found that similar myogenic potentials existed in mesenchyme from whole limbs between stages 18 and 19, but this potential was halved by stage 20. At stage 21, proximal mesenchyme showed significantly more myogenesis than distal mesenchyme, but this difference was abolished by stage 22. Thereafter, myogenesis was increasingly restricted from the distal mesenchyme, whilst the potential in more proximal regions did not significantly increase after stage 23. When the ratio between total limb myoblasts which differentiated on days 1 and 4 of culture was analysed, it was found that two distinct peaks existed at stages 20 and 23. The significance of these ratio peaks is unclear, but may be related to different proliferative potentials of the pre-myoblasts at these stages.

In order to analyze the influence of the orientation of the wing bud mesenchyme on the proximodistal direction of the migration of myoblasts in the avian embryonic wing bud, blocks of wing-bud mesenchyme were cut out and rotated around a dorso-palmar axis through 90 degrees or 180 degrees. Tissues originating from the quail wing bud and containing myoblasts were grafted into the space between the wing mesenchyme and the rotated blocks of mesenchyme proximal to the latter. In all experiments the donor-embryos were older than the acceptor-embryos. From HH stage 24 on, the rotation of the block of mesenchyme inhibited the migration of the myoblasts in a distal direction. We therefore propose that the orientation of the wing bud mesenchyme has an influence on the migratory behavior of myoblasts. This influence could provide "directional information" for the migrating myoblasts, allowing the migration of myoblasts in a distal direction only.

We studied the effects of synthetic peptides from the pituitary gland and brain cortex on differentiation of polypotent ectodermal tissue of the early gastrula of Xenopus laevis. It was shown that the pituitary gland peptide stimulates differentiation of polypotent tissue into epidermis and nerve tissue, while brain cortex peptide induces the development of mesenchyma and epidermis. Differentiation of polypotent tissue under the effect of the peptide is a mechanism of their geroprotective effect and suggests that they are promising as preparations for the treatment of neurodegenerative diseases.

A case of mesenchymal hamartoma of the liver in a 30-year-old female is reported. Ultra-sonography, computed tomography, and hepatic angiography demonstrated the presence of a large, mixed cystic and solid mass within the liver, suggesting the diagnosis of a mesenchymal hamartoma. At surgery, the tumor proved to be unresectable.

With the aim of expanding knowledge on the pathogenesis of nephroblastomata, an embryological organ culture system (Grobstein, 1956) was tested for its applicability to in vitro carcinogenesis experiments by using murine sarcoma virus (MSV-M) and 3-methylcholanthrene (MCA). Treatment of CBA/H-T6 mouse metanephrogenic mesenchyma with MSV-M at the pretubular stage neither disturbed the glomerulogenesis nor induced rapid malignant transformation. Treatment of the same tissues with MCA considerably inhibited the glomerulogenesis but failed to also reduce rapid malignant transformation. However, one MSV-M, one MCA and two untreated cultures showed malignant transformation after prolonged survival in vitro and produced different histological types of tumours upon transplantation into newborn CBA/H-T6 mice.

Im ausgespannten vitalen Mesenterium der narkotisierten Maus last sich innerhalb der „Taches laiteuses“ (Ranvier) bei unterschiedlichster Gewebereizung (Atzstoffe, Bakterien) das Auftreten einer mesenchymalen ortsstandigen Zellform beobachten, die sich durch einen ringformigen Kern und das Fehlen cytoplasmatischer Granula auszeichnet. Diese Zellen werdenCricokaryocyten genannt. Durch weitere Transformation der Kernfigur offenbar zum Zwecke der Oberflachenvergroserung gegenuber dem Cytoplasma entstehen gelapptkernige Zellen, die in ihrerMorphe nicht ohne weiteres von segmentierten Blutleukocyten zu unterscheiden sind. Auch im Hautchenpraparat des Omentem majus vom Menschen kann eine autochthone Aktivierung der „Taches laiteuses‘ mit dem Auftreten von ringkernhaltigen Zellen gesehen werden und dies besonders dann, wenn vom Netz als Organ spezielle Leistungen der Abwehr einer Schadlichkeit gefordert werden.

The ossification of the otic capsule is studied by means of TEM in the rat and compared to that of man. The cells of the globuli ossei which line the interglobular spaces derive from the perivascular mesenchyma during osteogenesis in the endochondral layer. They are not a result of a “metaplasia” of embryonic cartilage cells to osteocytes which has been discussed by many authors. The onset of the ossification of the otic capsule is independent from the vascularization of the cartilage.

IN the course of development the optic cup induces formation of the normal lens in overlying ectoderm and, later on, the pupil provokes formation of the cornea from ectoderm and mesenchyma. This regular scheme was described by Mangold1 in his classical review of the determination of the vertebrate eye. This scheme was also included in a more recent article by Lopashov and Stroeva2 dealing with the same question without any considerable alterations.

In Fortfuhrung fruherer Versuche uber die experimentelle Beeinflussung der Epidermolyse wird gezeigt, das Isonicotinsaurehydrazid in einer Konzentration von 50 mg-% die durch Hyaluronidase fermentativ ausgeloste Epidermolyse inhibiert. Die in destilliertem Wasser und in physiologischer Kochsalzlosung vor sich gehende Epidermisablosung wird dagegen durch Isonicotinsaurehydrazid nicht beeinflust.