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Isolated myocytes were prepared from Sprague Dawley rats, golden Syrian hamsters, and Hartley guinea pigs to investigate regional variations in myocyte size. Cell volume (V) was measured with a Coulter Channelyzer, cell length (L) was measured directly, and cross-sectional area (CSA) was calculated from V/L. Compared to values from the left ventricle (LV), right ventricular L was shorter in the rat (P less than .01) and hamster (P less than .05) and longer in the guinea pig (P less than .01). Guinea pig atrial L was shorter (P less than .01) than L in the right ventricle (RV) but did not differ from L in the LV. No significant differences in L existed between endomyocardium, middle myocardium, and epimyocardium of the LV in all three species. In rats and hamsters, myocytes from the RV had smaller V and CSA values (P less than .01) compared to any region of the LV. A transmural gradient of cellular dimensions existed in the LV of the rat, but not in hamster, with V and CSA of endomyocardium being largest and epimyocardium smallest (P less than .01). Endomyocardial V and CSA were larger (P less than .01) than all other regions in the hamster, but the difference was not significant compared to epimyocardial V. In the guinea pig, no significant differences in V existed between RV and LV or between the three LV regions. No pattern of regional differences was seen between ventricular CSA values in the guinea pig. Guinea pig atrial V and CSA values were smaller (P less than .01) than those for ventricular myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

The formation and cytochemical characterization of cortical granules in the ovarian oocytes of the golden hamster have been investigated by use of light and electron microscopical techniques. Particular emphasis is given to the changing population of organelles associated with cortical granule formation. Our observations indicate that cortical granules are produced by the participation of both the Golgi complex and the rough endoplasmic reticulum. Ultrastructural cytochemistry reveals that the cortical granules are composed of glycoprotein. The cortical granules are released at fertilization by a merocrine-type of secretory process.

Linear regression analysis was used to determine the correlation between testicular volume (calculated from measurements of length and width) and weights of paired testes. Line equations that can be used to predict weights of paired testes from the volume of one or both testes are given for three species of hamster (Mesocricetus auratus, Mesocricetus brandti, and Phodopus sungorus sungorus). Because these parameters are highly correlated (r greater than or equal to 0.97), the line equations provide a highly reliable means of estimating weights of paired testes from in situ surgical measurements. Weights of testes predicted in this manner are highly correlated with actual weights of paired testes (r greater than or equal to 0.96). The surgical method for measurement of the gonads is also described. This technique for estimating paired testicular weight allows considerable reduction in the number of animals required for long-term experiments and also permits longitudinal studies of individual animals.

Conspicuous cytological differences are found between specific secretory cells of the hypophysial pars tuberalis of Djungarian hamsters exposed to long and short photoperiods. The cells differ with respect to the shapes of perikarya and nuclei and show diverse amounts of secretory granules, lysosome-like bodies and glycogen.

The amygdaloid neurons of origin and the trajectory of amygdaloid fibers to the medial preoptic area of the adult male Syrian hamster were identified by using horseradish peroxidase (HRP) histochemistry. After iontophoresis of HRP into the medial preoptic area, retrogradely labeled amygdaloid neurons were located in the dorsal and caudal parts of the medial amygdaloid nucleus and throughout the amygdalohippocampal area. No amygdaloid neurons were labeled after HRP applications confined to the most rostral portion of the medial preoptic area (anterior to the body of the anterior commissure). Following more caudal medial preoptic area injections (body of the anterior commissure to the suprachiasmatic nucleus) the distribution of retrogradely labeled cells in the medial amygdaloid nucleus and the amygdalohippocampal area revealed no topographic organization of the amygdalopreoptic connections. When amygdaloid neurons were labeled, the amygdalohippocampal area contained two to five times as many HRP-filled cells as the medial amygdaloid nucleus. Retrogradely transported HRP could be followed from the medial preoptic area to the amygdala through fibers in the dorsomedial quadrant of the stria terminalis. In addition, electrolytic lesions of the stria terminalis prior to iontophoresis of HRP into the medial preoptic area prevented retrograde transport to neurons in both the dorsocaudal medial amygdaloid nucleus and the amygdalohippocampal area. These results confirm earlier observations describing the location of autoradiographically labeled efferents from the medial amygdaloid nucleus to the medial preoptic area and provide new information about the restricted region within the medial amygdaloid nucleus from which these projections arise. They also suggest that, unlike the projections from the medial amygdaloid nucleus to the bed nucleus of the stria terminalis, the efferents to the medial preoptic area travel entirely in the stria terminalis.

A subpopulation of basal epithelial cells which retains tritiated thymidine label for extended periods was previously demonstrated in skin and oral mucosae of mice. The present study examined the presence of similar cells in hamsters. Five-day-old hamsters were labeled with tritiated thymidine and the rate at which label was diluted from the basal cells observed. A small percentage of basal cells was found to retain label for up to 69 days. The location of such label-retaining cells ( LRCs ) in the palatal epithelium and in tongue papillae was examined. Thirty and 69 days after labeling, approximately 80% of LRCs in palate were located in the proximal halves of papillae and 80% of LRCs in tongue were positioned basally with approximately 30% of such LRCs occupying positions previously suggested to be stem cell locations. The finding that slowly cycling keratinocytes are related to patterns of tissue architecture is compatible with a function of these cells as epithelial stem cells.

Stereological studies on the adrenal cortex of unilaterally adrenalectomised hamsters have revealed differences in adrenal compensatory hypertrophy in male and female animals. The operation evokes an increase in the average volume of the zona fasciculata cells in the male and of the zona reticularis cells in the female.

Clustered cells with steroid-secreting morphology (SH), located within the paraaortic lymph node (PLN) capsules of normal and pregnant female golden hamsters, were examined by light and electron microscopy. Hydroxysteroid dehydrogenase (HD) activity of the SH cell cluster also was examined by histochemical techniques. The cluster was composed of mostly packed SH cells and surrounding mesenchymal cells. Individual SH cells possessed prominent smooth endoplasmic reticulum, well-developed Golgi complexes, some lipid droplets, and numerous mitochondria containing tubulovesicular cristae common to mammalian SH cells. Intermediate-type junctions were often observed between SH cells. The same SH cells were rarely detected in the subcapsular sinus and in the cortical parenchyma of the PLN. Early oophorectomy of the hamster resulted in cytoplasmic degeneration of the SH cell at day 5 after the operation. On the other hand, normal adult male hamsters possessed similar PLNs, but no SH cells were recognized in the nodes. The present histochemical preparation of normal female PLNs revealed moderate-to-strong HD activity, probably associated with SH cell clusters, in the limited regions of the capsules. Based on the present ultrastructural and histochemical findings, it is proposed that the SH cell cluster consists of steroid hormone producing cells.

The golden hamster has a compartmentalized stomach consisting of a forestomach and a glandular stomach. The forestomach is lined with keratinized epithelium and contains an active microbiol population capable of significant cellulolytic activity. This organ is not essential for life and is the first entrance point for swallowed feed. The hamster, while having a protein requirement like that of the rat, utilizes protein much differently. It ranks soybean meal above a fish protein concentrate and does not utilize added crystalline essential amino acids as such. Acceptance of the hamster as a nutritional surrogate of the rat seems unwarranted.

The influence of long (LD 16:8) and short (LD 8:16) photoperiods on the autonomic innervation of the ductus epididymidis and ductus deferens of Phodopus sungorus was studied using the glyoxylic acid-induced catecholamine fluorescence and acetylcholinesterase (ACHE) histochemical methods. ACHE-positive nerve fibres could be demonstrated in the smooth muscle layer along the whole sperm transporting duct, in the lamina propria and within the epithelium of the ductus deferens. The extent and intensity of enzymatic reaction did not change between LD 16:8 and LD 8:16 conditions. An adrenergic nerve plexus was found in the smooth muscle layer of the sperm transporting duct. Especially in the ductus deferens, the intensity of fluorescence and the number of adrenergic nerves decreased in animals kept at short photoperiods. The influence of androgens on the sympathetic innervation of the ductus epididymidis and ductus deferens was discussed.

The transformation of fibroblasts into decidual cells was studied ultrastructurally in golden hamsters pregnant for 3, 3 1/2, 4, 4 1/2, 5, or 5 1/2 days (post-ovulation). Cells within the endometrial stroma were generally separated from one another and spindle-shapted before blastocyst contact with the uterine epithelium. Once the epithelium enclosed the blastocyst (3 1/2 days), stromal cells adjacent to the blastocyst antimesometrially began to exhibit more extensive Golgi complexes with increased secretory activity. As differentiation proceeded the amount of cellular contact increased and various types of junctions formed between the cells. Throughout the period examined, intercellular space progressively decreased, while the cisternal width of the granular endoplasmic reticulum continually increased. Special organelles, whose functions remain unknown, first appeared in differentiating cells at 4 days (fibrils) and 5 1/2 days (crystalloid and 'dumb-bell' structures).

Paired cisternae of rough endoplasmic reticulum linked together by two parallel structures exhibiting periodic striations have been observed in the cytoplasm of small pre-antrum oocytes in the golden hamster. They are present only in oocytes from animals older than 3 weeks of age. Two or more such pairs may be associated with one another, and similar structures have been observed in contact with the nuclear envelope. The peak incidence of the paired membranes coincides with a sharp increase in rough endoplasmic reticulum as the oocyte commences rapid growth. A suggested role for the paired membranes in production of new endoplasmic reticulum is discussed.

Hamsters of three types designated as inbred cream (Epp/e/e), linebred white (EPP/cdcd/RB/A), and linebred albino (EPP/cdcde/e) were thoroughly examined histopathologically for spontaneous diseases. All hamsters were maintained simultaneously for life under identical standard laboratory conditions. Marked differences were found in longevity of the animals and in incidence, sites, patterns, and types of spontaneous diseases. In cream hamsters (CH), survival time was shorter than in white hamsters (WH) and albino hamsters (AH). More tumors and malignant lesions unrelated to survival were found in AH compared to CH and WH; also, the multiplicity of neoplasms were more pronounced in AH. The predominating tumor types differed in each line: Pancreatic islet cell neoplasms were most common in CH, adrenal gland tumors predominated in WH, and thyroid gland tumors in AH. Also, the relative incidence of spontaneous tumors varied among the lines. Some tumors seemed strain-specific and were not seen in other lines; malignant melanomas, for example, occurred only in CH and WH. Certain neoplasms, e.g., those of the thyroid and adrenal glands, were found more often in one sex than the other. The three hamster groups differed also in nonneoplastic diseases. Detailed histopathologic findings are presented and compared with data on the Syrian golden hamster, the ancestral line of these three groups.

The origin and renewal of the argentaffin cells in the pyloric glands of hamsters were studied by flash, cumulative and pulse labelling autoradiography with 3H-thymidine. The argentaffin cells were identified by the Diazo Method using Fast Red B Salt. By flash labelling autoradiography, it was shown that the argentaffin cells located from the middle to the lower level of the pyloric mucosa were not labelled with 3H-thymidine, indicating that this cell type has no proliferative activity. On the 10th and the 20th day of cumulative labelling, 31% and 63% of the argentaffin cells in the gland were found to be labelled, respectively. The labelled argentaffin cells were concentrated in the upper part of the gland (around the region of the isthmus), and no label was found over nuclei of the cells at the lowermost level of the gland. These labelled cells were shown to undergo a downward migration in the days following pulse labelling. They were replaced by unlabelled (and weakly or very weakly labelled) cells which arose at the region of the isthmus. The argentaffin cells in the pyloric gland are thought to arise from epithelial precursor cells at the region of the isthmus. The labelled argentaffin cells in the gland were found to decrease in number almost exponentially after pulse labelling. This indicates that the life span of argentaffin cells is not fixed, but their renewal conforms to the "random loss system". The half time of turnover of this cell population was 15 days on average.

The mandibular gland of the Djungarian hamster was examined by light microscopy, and transmission and scanning electron microscopies. Its acinar cells reacted with periodic acid-Schiff (PAS) and were weakly stained with alcian blue (AB). There were intercellular canaliculi between the acinar cells. These cells therefore appeared to be seromucous. The acinar epithelium was composed of light cells containing various spherical secretory granules. The granular cells of the mandibular gland possessed many acidophilic granules exhibiting a positive reaction to PAS stain. They were frequently observed at the junction of the acini and intercalated ducts in all mandibular glands examined. All of these cells were light and contained secretory granules of varying size and density. The intercalated ducts consisted exclusively of light cells possessing a few round granules of high density in the apical region. The striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion consisted of light, dark and specifically light epithelial cells containing acidophilic granules, which exhibited a strongly positive PAS reaction. The epithelium of typically striated portions was composed of light and dark cells containing fine vacuoles in the apical region. The mandibular gland of the Djungarian hamster revealed no histological differences between sexes.

The subcommissural organ (SCO) of the golden hamster (Mesocricetus auratus) was studied by conventional electron microscopy, freeze-fracture technique, zinc-iodide-osmium (ZIO) and acid phosphatase cytochemical reactions. The ultrastructure of hamster SCO cells shows a few flattened cisternae of rough endoplasmic reticulum (ER) without dilated ones in the cytoplasm. The Golgi apparatus is very well developed. Freeze-fracture studies also indicate only short profiles of flattened ER in the cytoplasm endorsing the absence of dilated ER cisternae. After the treatment with ZIO mixture, reaction products were observed over flattened cisternae of the ER and the nuclear envelope. The Golgi apparatus was also reactive toward the ZIO mixture. Acid phosphatase activities are localized in the inner one or two saccules of the Golgi apparatus and dense bodies. From these results we suggest that (1) hamster SCO cells do not accumulate secretory material in the cytoplasm in the form of discrete secretory granules or dilated cisternae of ER, and (2) hamster SCO cells may possess extremely high secretory activity or may not be actively involved in secretory function at all as in rats or other rodents.

The fine structure of the testicular interstitium was studied in normal adult golden hamsters sacrificed in the reproductive season (spring and summer) and in the winter. The Leydig cells in the reproductively active testes contain abundant endoplasmic reticulum (ER) and numerous mitochondria. The ER occurs in the form of flattened cisternae and tubules, the former prevailing. The cisternae are extremely extensive and are partly granular and partly agranular, their ends being continuous with the tubluar reticulum. Mitochondria intervening between the cisternae are closely associated with the agranular portions of the latter. Adjacent to the Golgi complex and continuous with the centrosome a unique filamentous body with a dense laminar core is often observed. In the regressive testes, the Leydig cells show a great reduction of cytoplasmic volume and a remarkable decline of the organelles, especially agranular tubules. The possible functional significance of the tubular and cisternal ER with the associated mitochondria is discussed in relation to the biosynthesis of androgens. Macrophages appear to constitute another important population of the interstitial cell clusters.