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Olfactory receptor neurons (ORNs) project to the rodent main olfactory bulb (MOB) from spatially distinct air channels in the olfactory recesses of the nose. The relatively smooth central channels of the dorsal meatus map onto the dorsal MOB, whereas the highly convoluted peripheral channels of the ethmoid turbinates project to the ventral MOB. Medial and lateral components of each projection stream innervate the medial and lateral MOB, respectively. To ascertain whether such topography entails the disproportionate representation seen in other sensory maps, we used disector-based stereological techniques in hamsters to estimate the number of ORNs associated with each channel in the nose and the number of their targets (glomeruli and mitral and tufted cells) in corresponding divisions of the MOB. Each circumferential half of the MOB (dorsal/ventral, medial/lateral) contained about 50% of the 3,100 glomeruli and about 50% of the 160,000 mitral and tufted cells per bulb. We found equivalent numbers of ORNs with dendritic knobs in the medial and lateral channels (4.5 million each). However, the central channels had only 2 million knobbed ORNs, whereas the peripheral channels had 7 million. Thus, there is a disproportionate mapping of the central-peripheral axis of olfactory airspace onto the dorsal-ventral axis of the MOB, encompassing a greater than threefold variation in the average convergence of ORNs onto MOB secondary neurons. We hypothesize that the disproportionate projections help to optimize chemospecific processing by compensating, with differing sensitivity, for significant variation in the distribution and concentration of odorant molecules along the olfactory air channels during sniffing., (Copyright 2004 Wiley-Liss, Inc.)

The hamster suprachiasmatic nucleus (SCN), site of the circadian clock, has been thought to be equally and completely innervated by each retina. This issue was studied in animals that had received an injection of the tracer cholera toxin subunit B (CTb) conjugated to Alexa 488 into the vitreous of one eye, with CTb-Alexa 594 injected into the other. Retinal projections to the SCN and other nuclei of the circadian system were simultaneously evaluated by using confocal laser microscopy. Each retina provides completely overlapping terminal fields throughout each SCN. Although SCN innervation by the contralateral retina is slightly denser than that from the ipsilateral retina, there are distinct SCN regions where input from one side is predominant, but not exclusive. A dense terminal field from the contralateral retina encompasses, and extends dorsally beyond, the central SCN subnucleus identified by calbindin-immunoreactive neurons. Surrounding the dense terminal field, innervation is largely derived from the ipsilateral retina. The densest terminal field in the intergeniculate leaflet is from the contralateral retina, which completely overlaps the ipsilateral projection. Most nuclei of the pretectum receive innervation largely, but not solely, from the contralateral retina, although the olivary pretectal nucleus has very dense patches of innervation derived exclusively from one retina or the other. Retina-dependent variation in terminal field density within the three closely examined nuclei may indicate areas of specialized function not previously appreciated. This issue is discussed in the context of the melanopsin-containing retinal ganglion cell projections to several nuclei in the circadian visual system., (Copyright 2003 Wiley-Liss, Inc.)

The circadian pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) receives photic information directly via the retinohypothalamic tract (RHT) and indirectly from retinally innervated cells in the thalamic intergeniculate leaflet (IGL) that project to the SCN. Using standard immunohistochemical methods, we examined the presence and distribution of substance P (SP) and the neurokinin-1 receptor (NK-1) in the SCN and IGL of rat and determined whether the patterns of immunostaining generalized to the SCN and IGL of Syrian hamster, Siberian hamster, and mouse. Terminals immunoreactive for SP were sparse within the SCN of Siberian and Syrian hamsters and mouse but were intense in the ventral, retinally innervated portion of the rat SCN. Immunostaining for the NK-1 receptor was mainly absent from the SCN of hamster and mouse. In contrast, a plexus of NK-1-ir cells and processes that was in close proximity to SP-ir terminals was found in the ventral SCN of the rat. Substance P-ir terminals were observed in the IGL of all four species, as were NK-1-ir cells and fibres. Double-labelled IGL sections of hamster or rat revealed SP-ir terminals in close apposition to NK-1-immunostained cells and/or fibres. These data indicate that SP could be a neurotransmitter of the RHT in rat, but not in hamster or in mouse, and they highlight potential species differences in the role of SP within the SCN circadian pacemaker. Such species differences do not appear to exist at the level of the IGL, where SP-ir and NK-1-ir were similar in all species studied., (Copyright 2001 Wiley-Liss, Inc.)

We have recently revealed that large multipolar neurons, presumed mossy cells in the hamster dentate gyrus (DG), were calretinin (CR)-immunoreactive (IR) at the ventral level, although these neurons were CR-negative at the dorsal level. In the present study, we confirmed this identification with several methods and analyzed structural features of hamster mossy cells in detail. Golgi impregnationi and intracellular Lucifer yellow labeling studies revealed that mossy cells in the hamster dentate hilus had extraordinarily prominent thorny excrescences on their somata as well as on their proximal dendrites. Mossy cells exhibited dorsoventral differences in their structural features; proximal dendrites of single mossy cells were fewer, and thorny excrescences were larger and more complicated at the dorsal level than at the ventral level. Electron microscopic serial section three-dimensional reconstructions revealed that somatic thorny excrescences consisted of large and complicated spines, which received numerous asymmetrical synapses from mossy fiber terminals. In addition, our confocal laser scanning microscopic observations also revealed many glutamic acid decarboxylase-immunoreactive punctae abutting the mossy cell somata and dendrites. Our present and previous observations revealed the structural features of hamster mossy cells and their differences along the dorsoventral axis and further indicated that mossy cells were prominently different in their chemical and morphological features among species., (Copyright 2001 Wiley-Liss, Inc.)

The number and volume of pulmonary neuroepithelial bodies (NEBs) of 1- and 4-week-old hamsters were estimated using unbiased stereological principles and systematic sampling techniques. For comparative purposes, volume estimations were also made in the carotid body, the parathyroid gland, and the adrenal medulla. A significant decrease was found in the total number of NEBs, immunoreactive for CGRP, between 1 and 4 weeks. Individual as well as cumulative NEB volume also decreased significantly. The cumulative NEB volume in 1-week-old hamsters was in the same range as the volumes of the carotids and parathyroids in the same animals. The postnatal decrease of the NEB number suggests that the NEBs are of primary potential importance in the neonatal stage, when they may complement the chemoreceptor function of the carotid bodies, which are relatively inactive at birth. Since the cumulative NEB volume (at least at the age of 1 week) is equal to that of the carotid bodies and the parathyroids, their physiological function may be of similar importance.

During development, axons of the mammalian cerebral cortex show a high degree of selectivity in their growth into specific regions of the central nervous system (CNS). A number of studies have shown that growing axons are guided by permissive or inhibitory membrane-bound molecules. Cryostat sections of the developing brain provide a useful assay to investigate possible membrane-bound guidance cues because such cues are retained in their normal in situ locations in specific regions of the CNS. Moreover, cryostat sections can also be subjected to various treatments that affect membrane-bound molecules. Therefore, to determine the ability of such cues to regulate the growth and guidance of cortical neurites into specific brain regions at different stages of development, we used an in vitro assay system in which explants from newborn hamster cortex were plated onto various regions of cryostat sections from developing and adult hamster brain. Neurite outgrowth from cortical explants onto the cryostat sections was visualized with a fluorescent vital dye. Results showed first that cortical neurites grew robustly on neonatal cryostat sections but only sparsely on sections from adult hamster. Second, cortical neurites grew preferentially on regions of the neonatal sections such as the cortex, basal ganglia, brainstem, thalamus, and colliculus, which are either pathways or targets for cortical axons in vivo. In contrast, cortical neurites avoided growing on the cerebellum and olfactory bulb, which are neither targets nor pathways for cortical neurites in vivo. Results also showed that cortical neurites extending onto cortical regions of neonatal sections preferred to grow along the radial axis of the cortex. Finally, heat treatment of the neonatal sections drastically reduced cortical neurite outgrowth. Taken together, these results suggest that the growth and guidance of cortical neurites is influenced by substrate-bound, developmentally regulated, heat-sensitive guidance cues preserved in the cryostat sections.

Topographically distinct populations of radial glial cells in the diencephalon and mesencephalon of neonatal rats and hamsters were transcellularly labeled with wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and with the lipophilic tracer DiI. A comparison of the histological distribution of the two tracers is suggestive of two different mechanisms of transcellular labeling. Intraocular injections of WGA-HRP resulted in the uptake of exogenously applied WGA-HRP by retinal ganglion cells, followed by anterograde axonal transport and exocytosis within the optic target nuclei. In addition to the transneuronal labeling, which is typical of such injections, we observed the transcellular labeling of the processes and somata of radial glial cells that were topographically associated with the terminal fields of the labeled axons. Similar transcellular labeling of radial glial cells associated with the axon terminal fields of the colliculogeniculate projection to the medial geniculate nucleus was observed following injections of WGA-HRP in the inferior colliculus. The transcellular labeling within the radial glial cells was discontinuous and somatopetally concentrated, indicating the existence of a retrograde active transport mechanism within the radial glial processes subsequent to its uptake following release of tracer from axons. This type of labeling can be referred to as transcellular retrograde glioplasmic transport. In contrast, DiI was used as a tracer through its capacity to diffuse within the plasmalemma. Topographically distinct populations of radial glial cells were transcellularly labeled following placements of DiI in the retina, inferior colliculus, or dorsal thalamus of fixed brains. The radial processes of labeled radial glial cells consistently extended into regions that also contained labeled axons. It is likely that the transcellular radial glial labeling with DiI occurred via transmembranous diffusion. These data indicate that a close structural and functional relation exists between axons and glial cells in the developing brain.

Despite extensive study of corticospinal connections in a variety of species, little is known about the detailed morphology of corticospinal axon arbors. Results in previous studies of primates based on intra-axonal filling with horseradish peroxidase (HRP) staining of a limited sample of fibers suggest that corticospinal arbors branch widely to multiple motoneuronal pools. To determine whether this pattern of corticospinal connectivity is present in nonprimate species as well, we studied the branching patterns of corticospinal axon arbors in a rodent species, the golden hamster. The axons were labeled by iontophoretic injection of Phaseolus vulgaris-leucoagglutinin (PHA-L) into small regions of the forelimb and hindlimb sensorimotor cortex, and immunohistochemistry with the peroxidase-antiperoxidase (PAP) method was used to reveal fine details of terminal arbors within the cervical and lumbar enlargements of the spinal cord. As in higher mammals, corticospinal connections are topographically organized. Moreover, corticospinal axons arising from somatosensory cortex project primarily to the dorsal horn, whereas those from motor cortex terminate most heavily in the ventral horn. This differential projection pattern, not previously demonstrated in rodents, implies functional differences between somatosensory and motor components of the corticospinal pathway. Reconstruction of corticospinal arbors in the ventral horn showed that in both cervical and lumbar spinal cord segments, axons branch widely into interneuronal regions. A surprising number appear to extend into motoneuron cell groups, and some of these axons branch into multiple motoneuronal pools. Widely divergent corticospinal axons that branch to multiple motoneuron pools have been shown to mediate activity in functionally related muscle groups of the primate forearm. The present results suggest that in other species, such as the rodent, a similar divergence of corticospinal arbors may also function to facilitate activity in subsets of muscles.

Immunocytochemistry using antisera directed against dopamine-beta-hydroxylase (DBH) was used to determine the organization of the noradrenergic (NE) input to the hamster's superior colliculus (SC). Immunocytochemistry for DBH was combined with retrograde transport of fluorogold (FG) to determine the sources of NE input to SC. Microiontophoretic techniques were used together with extracellular single unit recording and receptive field mapping techniques to determine the manner in which NE influenced the responses of individual SC neurons. The hamster's SC contained numerous DBH-positive fibers but no immunopositive cells. These fibers formed a plexus that was most dense in the lower stratum griseum superficiale (SGS). The density of DBH-positive fibers was very low in the stratum opticum (SO) and increased in density in the stratum griseum intermediale (SGI) and the other deep layers. When FG injections into the SC were combined with immunocytochemical detection of DBH, double-labeled cells were observed in the contralateral locus ceruleus. DBH-positive neurons were observed in several other portions of the mesencephalon and pons, but none of these were labelled with FG. The effects of NE iontophoresis were assessed for a total of 135 SC neurons. In 74% (N = 100), NE reduced spontaneous and/or stimulus evoked activity. In 3% (N = 4 cells), NE increased activity, and in 23% (N = 31 cells) it had no effect. These percentages were essentially the same for superficial layer visual cells and somatosensory neurons in the deep laminae. The effect of NE iontophoresis upon signal to noise ratios was assessed for 46 visual and 56 somatosensory neurons. For 54% (N = 25) of the visual cells and 16% (N = 9) of the somatosensory cells, NE iontophoresis decreased signal to noise ratios. For 13% (N = 6) of the visual cells and 21% (N = 12) of the somatosensory cells, NE iontophoresis increased signal to noise ratios. The effects of NE on the responsivity of SC neurons were antagonized by propranolol (86% of the 21 cells tested), sotalol (67% of the six cells tested), and atenolol (effective in the single cell tested). All these agents are beta-adrenergic antagonists. The single alpha-adrenergic antagonist that we evaluated, corynanthine, potentiated the effects of NE on the responsivity of the two SC neurons that we tested.

The purpose of the present investigation was to study the ultrastructure of the arcuate nucleus (ARC) and median eminence of hamsters on days 1-15 of the neonatal period. From days 1-6, the neurons of the ARC had large nuclei and a small amount of cytoplasm which contained polysomes, mitochondria, RER, lysosomes and Golgi complexes. From days 7-15 there was an increase in the amount of cytoplasm as well as more extensive Golgi complexes and RER. Astrocytes were the predominant glial component in both the ARC and median eminence. Astrocytic processes were in juxtaposition to unmyelinated axons, dendrites, and synapses. Axodendritic and axosomatic synapses containing clear vesicles were observed in the neuropil on day 1. There was an increase in the number of dense-core vesicles in the axonal endings beginning on day 4. Concomitantly, there were increasing numbers of clear and dense-core vesicles (64-70 nm) in terminals of the external layer of the median eminence, whereas larger dense-core vesicles (105-140 nm) were distinguishable by day 10 immediately dorsal to the external layer. The capillaries of the median eminence were composed of nonfenestrated endothelium from days 1-9. Fenestrae began to appear about day 10. Ependymal cells lining the third ventricle had pinocytotic vesicles, microvilli, and bleb-like protrusions on their apical surfaces. Ependymal processes were adjacent to nerve processes in the neuropil of the ARC and in the external layer of the median eminence, where they contacted the perivascular space. Two types of supraependymal cells were seen in animals throughout the neonatal period. One resembled a neuron which sent processes along the ependymal surface and often between cells. The second type was similar to a macrophage. The results of this study demonstrate the maturation of the neural elements in the ARC/median eminence area of the neonatal hamster.

Morphometric analysis of the superficial pineal gland of intact and blinded golden hamsters was conducted at both the light and electron microscopic level. The volume of the superficial gland was estimated to be 151 X 10(6) micron 3, comprising 90-94% of the total pineal parenchymal tissue. Analysis of structural rhythms in animals maintained under a 14:10 L:D cycle showed significant 24-hr variations in values for pinealocyte nuclei, nucleoli, rough and smooth endoplasmic reticulum, Golgi bodies, dense bodies, and dense-cored vesicles. Peak values for these structures generally occurred at the light:dark interface. These results provide morphological correlates for known rhythmic variations in the synthesis of pineal-gland products. Superficial pineals examined 8 weeks following optic enucleation exhibited a decrease in the volume of pinealocyte nuclei and cytoplasm, while nucleolar size and the amounts of smooth and rough endoplasmic reticulum, Golgi bodies, dense bodies and dense-cored vesicles were enhanced. The latter changes are interpreted as indications of increased synthetic activity by the superficial pineal gland in response to light deprivation.

Ganglion cell swere counted and measured in whole mounts of the hamster's retina, stained with methylene blue. Their density varies between about 1,000/mm2 at the edge of the retina to about 5-6,000/mm2 in a broad area centralis centred about 1.9 mm(39 deg) directly temporal to the optic disk. Maps of cell density show a long horizontal extension of the dense area in the nasal direction. The sizes of ganglion cell somata fall into two main groups--small cells (5-11 mum diameter) and large cells (greater than 11 mum), the latter including a small proportion of giant cells (greater than 17 mum). All three classes of cells are maximal in density in the area centralis, although the small cells are relatively more numerous there. The total number of cells is about 114,000 with about 63,000 small cells and about 51,000 large. The optic nerve contains about 69,000 unmyelinated axons and about 50,000 myelinated axons, suggesting that the latter are the fibres of the larger ganglion cells. It is likely that the projections of the centres of the areae centrales of the two eyes are normally divergent in space; they are therefore not on "corresponding retinal points."

The normal ventral and dorsal prostatic lobes of the young adult Syrian hamster were examined at the light and electron microscopic levels. Each lobe is composed of branched tubular secretory units separated from each other by loose interacinar connective tissue and draining into the urethra. The lumen of each acinus is lined by a simple epithelium composed of columnar secretory cells with occasional small basal cells. The epithelial layer, with the thin underlying lamina propria, forms a mucosa that is often highly folded. The whole acinus is bounded by a thick muscular stroma. In each of the ventral lobes, there are three main ducts, each one formed of tubular branched tributary secretory units. The walls of the secretory acini are moderately folded. Microvilli dominate the lumenal surface of the secretory epithelial cells. The Golgi complex is very extensive and shows dilated cisternae and secretory vesicles and vacuoles of various sizes. Membrane-bounded secretory granules populate the Golgi and apical areas and are released into the acinar lumen by exocytosis. The rough endoplasmic reticulum is dispersed throughout the cytoplasm, except in the region of the Golgi apparatus. In each of the dorsal lobes, there are several main tubular ducts that open into the urethra. Both proximal (ductal) and distal portions of the glandular tree are secretory in nature. Microvilli and cytoplasmic bulges and blebs dominate the lumenal surface of the secretory cells. The cells are also characterized by highly dilated cisternae of rough endoplasmic reticulum. The secretory cells show heterogeneity in the degree of dilation and distribution of rough endoplasmic reticulum, and this heterogeneity may reflect location in the glandular tree.(ABSTRACT TRUNCATED AT 250 WORDS)

The visual cortex of the golden hamster was studied by means of multi-unit and single unit recording, which revealed three separate retinotopic maps of the visual field in the posterior cortex. V1, corresponding to cyto-architectonic area 17, has the contralateral temporal field represented medially, the central visual field (extending about 10 deg ipsilateral) represented laterally and the lower field anteriorly. The borders of the map, especially for the upper field, seem to be more restricted than the whole visual field available to the contralateral hemiretina: V1 probably does not represent the extreme periphery of the field. A large fraction of V1 has binocular input, for up to about 50 deg lateral to the vertical midline. There is a retinotopic reversal near the representation of the vertical midline where V1 meets V2 (corresponding to the more lateral "area 18a"). There is another retinotopic reversal at the extremity of the contralateral field representation, where V1 meets Vm (the medial visual area, corresponding to "area 18"). V2 and Vm each contain a reduced mirror image version of the map in V1. Almost all isolated single units in V1 have receptive fields that can be classified as radially symmetrical (60%) or asymmetrical (35%). Symmetrical fields have ON (13%), OFF (4%), ON-OFF (30%) or "SILENT" (12%) central areas when plotted with flashing spots. There are minor but not striking differences between these groups in their field sizes, velocity preferences and so on. They almost invariably prefer moving to stationary stimuli but are not selective for orientation or direction of movement. Asymmetrical fields are of four types, three of which (type 1, 11%; type 2, 17%; and type 3, 2%) are orientation selective and resemble simple, complex and hypercomplex cells in the cat cortex. Some of these have direction as well as orientation preference. Axial movement detectors (5%) have a selectivity for one axis of motion, and thus prefer one orientation of edge, but respond equally well to movement of a spot. Vertical and horizontal orientation preferences, especially the latter, are much the most common. There is some evidence of clustering of cells according to receptive field type and, possibly, preferred orientation. Asymmetrical cells are, relatively somewhat rarer in the deeper cortical layers. Within the binocular segment, fully 89% of cells are binocularly driven and the receptive fields are similar in the two eyes. Receptive fields tend to increase in size away from the area centralis representation and, in a complementary fashion, the magnification factor decreases from up to 0.1 mm/deg at the area centralis representation to about 0.02 mm/deg for the peripheral field.

The somal shapes, dendritic features, and orientations of the neurons within the gustatory zone of the nucleus of the solitary tract were studied with the rapid Golgi method in the adult hamster. These Golgi studies complement previous quantitative morphometric analyses of the distributions of large and small neurons within the gustatory zone. Class 1 neurons are usually fusiform and possess long, relatively unbranched dendrites that often extend beyond the cytoarchitectonic boundaries of the gustatory zone. Class II neurons are multipolar and possess more dendrites that are significantly shorter than those of class I neurons. Both classes of neurons are spine poor. Computer-generated three-dimensional rotational analyses demonstrate that the dendritic arborizations of neurons of the gustatory zone are oriented preferentially in the horizontal plane. Dendrites extend in parallel or perpendicular to the solitary tract, the source of peripheral gustatory inputs, and appear to be positioned spatially to maximize synaptic interactions with these peripheral fibers. These Golgi studies also suggest that individual gustatory neurons may be influenced by incoming gustatory fibers that innervate separate populations of taste buds, a finding that is not predictable from the topographical organization of the gustatory zone.

The morphological relationships between the superficial and deep pineal glands of neonatal Syrian hamsters are described at both light and electron microscopic levels. In addition, melatonin contents in the two glandular masses are compared throughout a 14 hr light:10 hr dark photoperiod in 20-day-old hamsters. It has been found that the pineal anlage begins to separate into deep and superficial components between the first and third postnatal days of life. Separation is usually complete by day 12. The fine structure of the deep gland is similar to that of the superficial gland throughout development. By the time of weaning (20 days of age), the young hamsters exhibit distinct nighttime elevations of melatonin in both the superficial and deep glands, the quantities in the deep gland being approximately 5% those of the superficial pineal. Like that of the superficial pineal, the rise in deep pineal melatonin content can be abolished by exposure of hamsters to light.

The renal pelvis of the hamster has been studied by light microscopy (epoxy resin sections), transmission electron microscopy, and morphometric analysis of electron micrographs. Three morphologically distinct epithelia line the pelvis, and each covers a different zone of the kidney. A thin epithelium covering the outer medulla (OM) consists of two cell types: (1) granular cells are most numerous and have apically positioned granules which stain intensely with toluidine blue, are membrane-bound, and contain a fine particulate matter that stains light grey to black in electron micrographs. (2) Basal cells do not have granules, are confined to the basal lamina region, and do not reach the mucosal epithelial surface. The inner medulla (IM) is covered by a pelvic epithelium morphologically similar to collecting duct epithelium of IM. Some cells in this portion of the pelvic epithelium (IM) stain intensely dark with toluidine blue, osmium tetroxide, lead, and uranyl acetate. Transitional epithelium, which separates cortex (C) from pelvic urine, has an asymmetric luminal plasma membrane and discoid vesicles, each of which is similar to those previously observed in mammalian ureter and urinary bladder epithelia. Based on morphological comparisons with other epithelia, the IM and OM pelvic epithelia would appear permeable to solutes and/or water, while the transitional epithelium covering the C appears relatively impermeable. It would also appear that the exchange of solutes and water between pelvic urine and OM would involve capillaries, primarily, since morphometric analysis showed that both fenestrated and continuous capillaries of the OM were extremely abundant (greater than 60% of OM pelvic surface area) just under the thin pelvic epithelium.

A cytoarchitectonic analysis is presented of a configuration of cells which extends through the medial preoptic and rostral part of the anterior hypothalamus of the guinea pig, rat, hamster, and mouse. Within that configuration, called here the sexually dimorphic nuclear complex of the medial preoptic-anterior hypothalamic area (SDNC-MPAH), there is nearly continuous variation in cellular distribution or packing density as one proceeds rostrocaudally, as well as variations between females and males at corresponding levels. The major cell groups comprising SDNC-MPAH are the medial preoptic nucleus (MP) and the preventricular portion of the periventricular nucleus (Pep) rostrally, and the anterior hypothalamic nucleus (AH), anterior portion of periventricular nucleus, (Pea), and bed nucleus of stria terminalis (ST) caudally. The most striking cytoarchitectonic dimorphisms usually involve MP and AH. In all four species examined, MP is larger and, except for the mouse, appears to be more densely cellular in the female than in the male. Most prominently in the rat and guinea pig, AH is densely cellular throughout in the female, including the subependymal zone, whereas in the male AH lies at a distance from the third ventricle, separated from the ependyma by a cell-poor zone. The significance of these findings may lie in the fact that the region exhibiting the sexual dimorphisms has been shown to be involved in the regulation of reproductive functions which are sexually differentiated and developmentally influenced by the fetal or perinatal hormonal milieu in some species.

Anterograde tracing with Phaseolus vulgaris leucoagglutinin (PHA-L) was employed to describe the projection from the superficial to the deep layers of the hamster's superior colliculus (SC). Deposits of PHA-L in the stratum griseum superficiale (SGS) resulted in labelled terminal swellings in the stratum opticum and all of the deep laminae (the stratum griseum intermediate [SGI], stratum albumin intermedium [SAI], stratum griseum profundum [SGP], and stratum albumin profundum [SAP]). Labelled terminals were also visible in the periaqueductal gray (PAG). Reconstructions of individual axons showed that many collateral in the deep laminae arose from axons that projected to targets outside the colliculus. The projection from the superficial to the deep laminae had a loose topographic organization, and the trajectories of interlaminar axons were generally deflected laterally from "projection" lines that were orthogonal to the SC surface. Physiological recording and receptive field mapping were used to determine actual projection lines, which connect neurons in the superficial and deep layers that have receptive fields with the same elevation. These projection lines closely matched the trajectory of the pathway from the superficial to the deep laminae.

The deep pineal gland of golden hamsters was morphometrically analyzed and quantitatively compared with the superficial pineal under a 14:10 lighting regime and following blinding. The deep pineal comprised 6-10% of the total pineal parenchymal tissue. Pinealocytes of the deep gland were smaller than the cells of the superficial pineal and showed a greater percent volume of Golgi bodies, rough endoplasmic reticulum, and dense-cored vesicles. Twenty-four-hour rhythms in nucleoli and Golgi bodies were found in deep pinealocytes. These rhythms were out of phase with comparable rhythms in the superficial pineal gland, suggesting that distinct subpopulations of pinealocytes are present within the respective parts. Blinding resulted in decreased nuclear and nucleolar volume, while the amount of smooth endoplasmic reticulum, Golgi bodies, dense bodies, and dense-cored vesicles increased significantly. Marginal increases were seen in mitochondria and lipid droplets. The greater abundance of those organelles involved in synthesis and secretion suggests enhanced cellular activity after blinding. Many of the morphological responses are similar to alterations in the pinealocytes of the superficial pineal following optic enucleation.

The superior colliculus of the golden hamster was investigated by means of multi-unit and single unit recording. The retinotopic map, which probably embraces a projection from the entire retina of the contralateral eye, is organized as in other vertebrates, with the central field represented in the anterior colliculus, the upper field medially. Magnification factor is fairly uniform and is about 0.02 mm/deg. There is a small binocular segment (where almost half of all neurones have input from the ipsilateral eye) in the anterior colliculus, representing the area of field around the area centralis and the anterior pole of the field. In the more superficial layers, units have small (about 10 deg diameter) receptive fields, which can be classified as symmetrical, responding to slow movement (80%), very fast movement detectors (6%), directional movement detectors (13%) and axial movement detectors (1%). In the deeper layers, below the stratum opticum, receptive field size increases dramatically and many cells habituate rapidly, making them sensitive only to new events. Receptive fields can be classified as movement detectors (89%), directional movement detectors (10%) and axial movement detectors (2%). All directional receptive fields, at least in the upper visual field, have an upward component in their directional preferences. About 42% of deeper layer cells have somatic sensory input, responding to light touch on the fur or whiskers of the contralateral half of the body. Some 5% of cells respond to complex sounds on the contralateral side of the animal. Many of these somatic and auditory cells also have visual receptive fields and, throughout the colliculus, there is general correspondence between the maps of visual space, auditory space and the body surface. This correlation may be important in the regulation of orienting behaviour towards novel peripheral stimuli.

Alignment of the flattened keratinizing cells of the upper strata of mammalian epidermis leads to the formation of columnar units of structure. In mouse epidermis, mitoses have been found to occur relatively infrequently in the region beneath the center of each cell column where a non-keratinocyte dendritic cell, usually with freatures typical of an epidermal Langerhans cell, is situated. The observed pattern of mitosis could therefore be due either to displacement of central keratinocytes by Langerhans cells or indicate some control of keratinocyte proliferation related either to the Langerhans cells or to the over-lying cell columns. No relationship exists between the position of Langerhans cells and epidermal cell columns in hamster epidermis but measurement of the position of mitosis has shown a reduced frequency of occurrence of mitosis beneath the central region. This pattern of mitosis is therefore unrelated to Langerhans cells and appears to reflect differences in the mitotic potential of basal keratinocytes which could be associated with feedback from the overlying cell columns or with an intrinsic pattern of basal cell activity.

This histochemical study was undertaken to determine whether sexual differences existed in the duodenal glands of hamster. Alcian blue staining and atomic absorption spectrophotometry (for copper content of the bound Alcian blue) showed the duodenal glands of males to contain about double the acid mucosubstance of the female glands. Periodic acid Schiff staining was stronger in the females over a larger portion of the gland than in males. It was concluded that sexual differences were evident in duodenal glands of hamster.

The hamster renal pelvis has been studied by means of low-power light microscopy, scanning electron microscopy and morphometric analyses. The results of this study are highly suggestive that the contact of pelvic urine with the other medulla as well as with the inner medulla may be an important aspect of final urine formation. The outer medulla constituted nearly 50% of the total pelvic surface area, with the inner stripe of the outer medulla more than twice the pelvic surface area of the outer stripe of the outer medulla. The large outer medullary pelvic surface area was accounted for by the elaboration of the upper pelvic walls into peripelvic columns, opercula ("secondary pyramids"), fornices and secondary pouches. A thin simple-squamous to low cuboidal pelvic epithelium separated pelvic urine from outer medullary parenchyma. The inner medulla which constituted about one quarter of the total pelvic surface area was covered by a cuboidal to columnar pelvic epithelium which appeared morphologically similar to the papillary collecting duct epithelium. Tubules and capillaries of the inner medulla did not appear as closely juxtaposed to the pelvic epithelium as did those of the outer medulla. Cortical tissue comprised only 11.7% of the total pelvic surface area and was covered by transitional epithelium similar to that of ureter and bladder. The previously reported impermeability of this epithelium suggests that pelvic urine contact with the cortex is unimportant in final urine formation. The rich layer of smooth muscle under the transitional epithelium probably functions to move urine into and out of the pelvis during pelvic peristalsis, which has been observed in vivo.

The intercollicular pathway of the hamster was studied by means of a combination of horseradish peroxidase (HRP), autoradiographic, and double-labeling (nuclear yellow-HRP) techniques. Small deposits of HRP marked significant numbers of cells in the contralateral colliculus only when the injection site included the laminae ventral to the stratum opticum. Anterior deposits labeled many more neurons than injections into the caudal part of the tectum. Of the cells labeled by our injections, 18.2% were located in the superficial collicular laminae (stratum griseum superficiale and stratum opticum), and the remainder (81.8%) were in the deep layers. A wide variety of morphological cell types contributed axons to the intercollicular projection, and in a given animal the loci of the labeled neurons were generally symmetrical with the injection site. Small deposits of [3H]-leucine resulted in contralateral labeling only when the injection included the deep collicular laminae. The transported label was most dense in the stratum griseum intermediale and stratum griseum profundum, and its location was generally homotopic with the injection site. Experiments in which collicular HRP deposits were combined with large cervical spinal or pontine reticular injections of Nuclear Yellow indicated that intertectal neurons did not, in most cases, contribute axon branches to the spinal or pontine reticular projections of the colliculus. Receptive field data obtained at the time of the HRP and/or [3H]-leucine deposits demonstrated that the collicular representations of the ipsilateral and at least 45 degrees of the contralateral hemifields were encompassed by intercollicular connections. This was also true for the somatosensory representation of the entire head and a portion of the neck.

Intra-axonal recording and horseradish peroxidase (HRP) injection techniques were employed to define the response characteristics of low-threshold, rapidly conducting trigeminal primary afferents and the morphological features of their axon arbors in subnucleus interpolaris and subnucleus caudalis (or the medullary dorsal horn; these last two terms are used synonomously throughout the paper). A total of 61 such afferents were characterized and recovered. Of these, ten gave rapidly adapting (RA) and 17 slowly adapting (SA type I) responses to vibrissa deflection. Twenty were sensitive to guard hair deflection and 14 were responsive to indentation of the hairy skin. The vibrissa-sensitive primary afferents were all quite similar morphologically. Primary collaterals proceeded directly, in a radial fashion, to their zone of termination and gave rise to dense and compact arbors. These tended to be larger in the medullary dorsal horn (MDH) than in interpolaris and they also gave rise to more boutons in the former nucleus. Guard hair afferents generally had smaller arbors and gave rise to fewer boutons than vibrissa-sensitive axons. Like vibrissa afferents, their arbor were generally circumscribed in both interpolaris and MDH, but they were larger in the latter nucleus. Skin-sensitive afferents had arbors that tended to be somewhat larger than those of vibrissa- or guard-hair-related fibers. Unlike the other fiber types, the arbors of skin-sensitive afferents were on average larger in interpolaris than MDH. Quantitative analysis of the morphological data from well-filled examples from each of these four functional types verified our qualitative impressions regarding differences between interpolaris and MDH collaterals of a given fiber-type. Statistical comparison of data from different functional classes indicated trends that supported our qualitative impressions, but none of these was statistically significant. The topography of the trigeminal primary afferent input to interpolaris was organized such that the head was inverted and fibers with caudal receptive fields terminated in the lateral portion of the nucleus. This was true for all of the functional afferent types that we examined. Vibrissa-related fibers differed from nonvibrissa afferents in that they tended to avoid the most rostral portion of interpolaris. In the MDH, the primary afferent representation of the head was also inverted, but fibers with caudal facial receptive fields tended to terminate medially rather than laterally.(ABSTRACT TRUNCATED AT 400 WORDS)

This study provides a scheme for subdividing the nucleus of the solitary tract of the hamster on the basis of cytoarchitectonic criteria, cell measurements, and neuronal cell types identified with the Golgi method. Reduced silver-stained sections revealed the feltlike neuropil that characterizes the nucleus of the solitary tract and were used to define the boundaries of the nuclear complex. Adjacent sections stained for Nissl substance revealed ten subdivisions, each with a characteristic neuronal architecture based on cell sizes, shapes, and packing density. Some subdivisions, e.g., the ventral and medial subnuclei, were identified at all rostrocaudal levels of the nuclear complex, while other subdivisions, e.g., the caudally located dorsolateral and ventrolateral subnuclei, were restricted to particular levels. Golgi preparations were counterstained for Nissl substance, thus allowing dendro- and cytoarchitecture to be compared directly. This material permitted the identification of a number of functionally relevant features of the neuronal constituents of the subdivisions. This approach, employing three cytological methods, has permitted the assembly of a detailed atlas of the nucleus of the solitary tract. The subdivisions of the present atlas have been compared with their likely counterparts identified in previous investigations of the mammalian nucleus of the solitary tract. In order to relate cytoarchitecture with primary afferent termination sites and to define the gustatory-recipient subdivisions, the differential relationships of the subdivisions with lingual afferent projections in the hamster are also described. The present parcellation scheme is intended to facilitate anatomical and physiological investigations of the types of circuits that compose the medullary gustatory and general visceral sensory systems.

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.