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Posterior lingual glands consist of two sets of minor salivary glands that serve important functions in oral physiology. To investigate the hypothesis that the hypoglossal nerve provides sympathetic innervation to the posterior lingual glands, we examined ultrastructural changes in the glands following hypoglossal denervation. In the posterior deep lingual glands (of von Ebner), the serous acinar cells showed a decrease in the number of secretory granules and an increase in lipofuscin accumulation. The ratios of cells containing lipofuscin granules were 11.39, 36.49 and 50.46%, respectively, of the control, 3- and 7-day post-axotomy glands (P < 0.001). Intraepithelial phagocytotic activity was increased. The mucous acinar cells in the posterior superficial lingual glands (of Weber) also showed degenerative changes after hypoglossal denervation. One week after nerve transection, marked cytoplasmic vacuolation and fragmentation of organelles were frequently observed. Degenerative changes were also found in unmyelinated axons associated with the glands. We provide the first evidence of the structural and functional connections between the sympathetic component of the hypoglossal nerve and posterior lingual glands.

Previous studies have shown the existence of a sympathetic component in some cranial nerves including the hypoglossal nerve. In this study, the horseradish peroxidase (HRP) tract-tracing retrograde technique and experimental degeneration method were used to elucidate the possible neuroanatomical relationship between the superior cervical ganglion (SCG) and the hypoglossal nerve of hamsters. About 10% of the SCG principal neurons were HRP positive following the tracer application to the trunk of hypoglossal nerve. Most of the HRP-labelled neurons were multipolar and were randomly distributed in the ganglion. When HRP was injected into the medial branch of the hypoglossal nerve, some of the SCG neurons were labelled, but they were not detected when HRP was injected into the lateral branch. The present findings suggest that postganglionic sympathetic fibres from the SCG may travel along the hypoglossal nerve trunk via its medial branch to terminate in visceral targets such as the intralingual glands. By electron microscopy, the HRP reaction product was localised in the neuronal somata and numerous unmyelinated fibres in the SCG. In addition, HRP-labelled axon profiles considered to be the collateral branches of the principal neurons contained numerous clear round and a few dense core vesicles. Besides the above, some HRP-labelled small myelinated fibres, considered to be visceral afferents, were also present. Results of experimental degeneration following the severance of the hypoglossal nerve showed the presence of degenerating neuronal elements both in the hypoglossal nucleus and the SCG. This confirms that the hypoglossal nerve contains sympathetic component from the SCG which may be involved in regulation of the autonomic function of the tongue.

The onset and evolution of the meiotic prophase were assessed by histological and cytological techniques in fetal and neonatal ovaries obtained from day 13 postcoitum to day 11 postpartum in the golden hamster (Mesocricetus auratus). The histological technique based on the Feulgen stain and the cytological technique based on the Giemsa stain of isolated nuclei were judged to be specific for staining chromatin and chromosomal DNA. The results obtained with both techniques were quite similar and confirmed most of the meiotic prophase takes place during the neonatal period. However, at variance with other reports, it was found that the meiotic prophase starts on day 14 postcoitum. This discrepancy is attributed to the greater specificity of techniques and time span covered in the present study.

The ultrastructure of the macula densa of the hamster kidney is, in general, similar to that reported for the few other species which have been studied. Their structure indicates that macula densa cells differ in a number of important respects from those of the rest of the thick ascending limb and the distal convoluted tubule. Among these differences may be mentioned the more widely distributed mitochondria with their circular and elliptical profiles; the extensive subsurface vacuolation and the irregular and shallow folds of the basal plasma membrane. Unlike some reports on other species, however, the Golgi complexes were not restricted to an infranuclear position, but were observed in a variety of situations. It was also observed that T-H glycoprotein characteristically associated with the plasma membranes of the cells of the thick ascending limb and the distal convoluted tubule was invariably absent in the macula densa. The possible physiological implications of this and the other observations are discussed.

The structure of nexuses in the atrioventricular node of the golden hamster was studied with the transmission electron microscope, using thin sections and freeze-fracture replicas, and was compared with that of nexuses in the working myocardium of the right ventricular wall. Whereas ventricular myocardium contained macular nexuses only, nodal tissue contained annular and linear configurations as well as maculae of varying size. The significance of such variations in nexus pattern is not clear although several hypotheses are discussed in the literature. Measurements made on electron micrographs, after allowing for tilt of the specimen, yielded a particle diameter of 10.59 nm for nodal myocardium and 10.95 nm for ventricular myocardium, both measurements being substantially higher than figures generally cited in the literature. In each area the measurements had a normal distribution suggesting a single type of particle. The small but significant difference in particle size between the two areas is more likely to be caused by dissimilarities in packing arrangement rather than by differences in intrinsic structure or in functional state.

Because, in previous investigations on the rat pineal gland, karyometric studies of pinealocytes from cortical and medullary regions had yielded contradictory results, experiments were carried out to resolve this problem. In immersion-fixed, paraffin-embedded pineal glands, nuclear size of cortical regions was invariably larger than that in the medulla, the nuclear size clearly depending on the plane of sectioning. The differences between cortex and medulla were abolished in (a) pineal glands sagittally bisected prior to immersion fixation and (b) perfusion-fixed, epoxy resin-embedded pineal tissue, suggesting that unequal pinealocyte nuclear size in cortex and medulla is artefactual. In the hamster pineal gland, cortical and medullary regions are separated by a narrow band of interstitial cells, indicating that different structural features account for this subdivision in different species.

Hamster lung morphometry and histology have been studied in an attempt to determine differences between hamster and human lungs which may have relevance for lung carcinogenesis studies. Morphometric measurements were made on fresh lungs, lung casts, and histological sections. Cell type and frequency measurements were determined from frozen, paraffin, 1 micron plastic (glycol methacrylate) and electron microscopic sections. A standard terminology for hamster lung histology is established, and differences between hamster and human lung morphometry and histology are discussed.

Electron microscope studies of the myocardium of the golden hamster revealed that the primary T-tubules in ventricular and atrial myocytes are substantially wider than their counterparts in most other mammalian species. Another feature is the presence of numerous lipid bodies but these are not as closely apposed to mitochondria as in seal myocardial cells. General atrial myocardial cells in the hamster contain numerous electron-dense spherical granules but these are absent from cells of the nodal and conducting system; in regard to these latter features in hamster resembles most other mammals.

The dorsal motor nucleus of the vagus nerve of the hamster was studied electron microscopically. Two types of neuron distinguished by their ultrastructural features were identified. Type I cells, which had an average dimension of 20 X 12 microns, were rich in cytoplasmic organelles. The smaller Type II cells (15 X 9 microns) had scanty cytoplasm and a deeply indented nucleus. Type I cells were labelled by horseradish peroxidase (HRP) following its injection into the vagus nerve, whereas Type II cells were not. Seven days after cervical vagotomy, Type I neurons underwent typical retrograde degeneration. By the fourteenth postoperative day, the density of the cells was greatly enhanced, an early sign of cell death. Type II cells were not affected by vagotomy. With the electron microscope, three types of axon terminals were identified in the neuropil of the DMN: (1) boutons containing round agranular vesicles, (2) boutons containing round and elongated dense-cored vesicles, and (3) boutons containing pleomorphic agranular vesicles, a few of which were dense-cored. All of them showed synaptic contacts with HRP-labelled dendrites. Occasional boutons containing pleomorphic vesicles showed degenerative changes after vagotomy. Moreover, a few of them were seen to contain HRP granules. The observations made in the present study strongly suggest that the Type I neurons send efferent fibres to the vagus nerve. The Type II cells which are not labelled by HRP nor affected by vagotomy, probably serve as interneurons, or they may be cells projecting to other areas of the brain.

The membrane systems of hamster general atrial and ventricular myocytes were studied and their reactivity with the sterol probes, filipin and tomatine, compared with that of atrioventricular nodal myocytes. The sarcolemma of atrial and atrioventricular nodal myocytes was considerably more reactive to sterol probes than the sarcolemma of general ventricular myocytes. Atrial myocyte sarcolemma was also more reactive than previously reported in rat atrial myocytes. Particle-free regions of annular nexuses were consistently unreactive with all combinations of sterol probes whereas much smaller particle-free regions of macular nexuses and desmosomes were reactive with the same probes. Intracellular membrane systems of all three types of cardiac myocyte reacted in a similar manner with sterol probes. These results indicate variation in comparable sarcolemma composition of cardiac myocytes between the rat and hamster and between cardiac regions within the same species.

The fine structure of the filiform papillae on the hamster tongue is described level by level from the basal layer to the surface. We did not observe two distinct types of cells with different morphology or components which could be held responsible for the production of two different types of keratin as have been described in other animals, but rather a uniformity of cell structures in each layer and only the so-called "smooth" type of keratin. However, keratin granules were more abundant in the anterior part of the papilla.

Cell abutments in the ovarian bursal epithelium of the golden hamster included tight junctions, desmosome-like junctions, gap junctions and zonulae adhaerentes. The plasma membranes of adjacent epithelial cells were often closely apposed forming a zonula adherens at the apex of the intercellular space, but these did not fuse along the entire length of the intercellular space. Gap junctions and other intercellular junctions did not allow diffusion of ferritin into the junctional areas, but failed to prevent ferritin from filling the intercellular space basal to the junction. This suggested that these junctions were not continuous around the entire circumference of the cell. In general, intercellular connections in the bursal epithelium may be labile and this lability, as well as periodic distention of the bursa, may give rise to separation of epithelial cells. Ferritin injected into the bursal cavity reached lymphatics via three routes: (1) via stomata; (2) via gaps and pores; (3) via intercellular spaces. Transcellular transport did not make a major contribution to permeation of ferritin across the bursal epithelium, and ferritin particles did not enter fenestrated blood vessels within 30 minutes after injection. The variety of routes may facilitate rapid and complete drainage of fluid and cellular components from the bursal cavity.

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.

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).