Functional angioarchitectural comparison of the fungiform papillae of rat, rabbit, cat in scanning electron microscopic specimens

The aim of this study was to compare the functional angioarchitectural fungiform papillae (FuP) of three kinds of mammalia, rat, rabbit and cat, with microvascular cast specimens (MVCS) utilizing the corrosive resin cast method in scanning electron microscopy (SEM). FuP distributed geometrically on the dorsal surface of the tongues of the three mammals with different eating habits were of various kinds of form based on their functional and microvascular structure. The basic form of the capillary loop of FuP in the three mammals consisted of the ascending and descending branches of the capillary bed. The basic form of the loop microstructure in rat FuP was a cylindrical or bamboo-basket-like loop structure. In the rabbit, FuPs consisted of a carnation-like structure and in the cat FuP consisted of a half oval fishnet ball-like structure. It can be said conclusively that from this detailed investigation of the intracapillary microvascular architecture of the three mammals, FuP are effective as a sensory organ receiving the taste of foods and liquids by the expansion of the surface area in various functional and microvascular formations in the rat (cylindrical or bamboo-basket-like loop structure), rabbit (carnation-like) and cat (half oval fishnet-ball-like) respectively.

Anatomy of the feeding blood vessels of the cremaster muscle in the rat

Since the early seventies over 300 studies have used the cremaster muscle as a flap model, yet little has been reported on the upstream feeding vessels of this muscle. The purpose of this study was to investigate the anatomy of the cranial feeding vessels of the left and right cremaster muscle in Sprague-Dawley rats. An additional aim was to compare these results with the anatomy of the feeding vessels of the cremaster muscle in another strain (Wistar). To permit identification of the cranial feeding vessels, the pedicle was dissected very carefully and thereafter perfused with green dye, which was administered through a cannula placed in the distal femoral artery. In Sprague-Dawley rats it was found that the cremaster muscle in only 30% of the animals received its total blood supply through the superior external pudendal artery. In Wistar rats the same was true in less than 45%. The cremaster muscle of the rest of the animals appeared to receive its blood either in part or in total from the hypogastric trunk. We suggest that the name pudic-epigastric trunk be abandoned.

Claustrocingulate connections in the rabbit and rat--a stereological study

Unbiased stereological methods were used for estimating the numerical density and the total number of claustral neurones projecting to the cingulate cortex in rabbit and rat. In rat the numerical density of neurones projecting to the retrosplenial granular cortex (RSG) differed significantly from those projecting to the retrosplenial agranular (RSA) and cingulate (Cg) cortices while in rabbit the numerical densities of retrogradely labelled neurones in the claustrum following injections into various areas of the cerebral cortex did not differ significantly. The total number of retrogradely labelled neurones in the claustral limbic zones did not differ significantly in both species. The quantitative analysis of claustral zones projecting to a different cingulate cortex area, both in rabbit and rat, reveals that each of these zones is rather homogeneous.

Intercellular junctions between palisade nerve endings and outer root sheath cells of rat vellus hairs

Hair follicles have a longitudinal set of sensory nerve endings called palisade nerve endings (PN). We examined the junctional structures between the PN and outer root sheath (ORS) cells of hair follicles in the rat external ear. Transmission electron microscopy of serial thin sections showed that the processes of the ORS cells penetrated the basal lamina of the hair follicle, forming intercellular junctions with the PN (PN-ORS junctions). Two types of junctions were found: junctions between nerve endings and ORS cells (N-ORS junctions) and those between Schwann cell processes and ORS cells (S-ORS junctions). The N-ORS junctions had two subtypes: 1) a short process or small eminence of the ORS cell was attached to the nerve ending (type I); or 2) a process of the ORS cell was invaginated into the nerve ending (type II). The S-ORS junctions also had two subtypes: 1) a short process or small eminence of the ORS cell was abutted on the Schwann cell process (type I); or 2) a process of the ORS cell was invaginated into the Schwann cell process (type II). Vesicles, coated pits, coated vesicles, and endosomes were sometimes seen in nerve endings, Schwann cells, and ORS cells near the junctions. Computer-aided reconstruction of the serial thin sections displayed the three-dimensional structure of these junctions. These results suggested that the PN-ORS junctions provided direct relationships between the PN and ORS in at least four different patterns. The discovery of these junctions shows the PN-ORS relationship to be closer than previously realized. We speculate that these junctions may have roles in attachment of the PN to the ORS, contributing to increases in the sensitivity of the PN, and in chemical signaling between the PN and ORS.

Cytology, synaptology and immunocytochemistry of commissural neurons and their putative axonal terminals in the dorsal cochlear nucleus of the rat

The first binaural integration within the auditory system responsible for sound localization depends upon commissural neurons that connect the two symmetrical cochlear nuclei. These cells in the deep polymorphic layer of the rat dorsal cochlear nucleus were identified with the electron microscope after injection of the retrograde tracer, Wheat Germ Agglutinin conjugated to Horseradish Peroxydase, into the contralateral cochlear nucleus. Commissural neurons are multipolar or bipolar with an oval to fusiform shape. Few commissural neurons, most inhibitory but also excitatory, connect most of the divisions of the rat cochlear nuclei. The most common type is a glycinergic, sometimes GABAergic, moderately large cell. Its ergastoplasm is organized into peripheral stacks of cisternae, and few axo-somatic synaptic boutons are present. Another type of commissural neuron is a medium-sized, spindle-shaped cell, glycine and GABA-negative, with sparse ergastoplasm and synaptic coverage. A giant, rare type of commissural neuron is glycine-positive and GABA-negative, with short peripheral stacks of ergastoplasmic cisternae. It is covered with synaptic boutons, many of which contain round synaptic vesicles. Another rare type of commissural neuron is a moderately large cell, oval to fusiform in shape, immunonegative for both glycine and GABA, and contacted by many axo-somatic boutons. It contains large dense mitochondria and numerous dense core vesicles of peptidergic type. Some labelled boutons, mostly inhibitory and probably derived from commissural neurons, contact pyramidal, cartwheel, giant and tuberculo-ventral neurons. The prevalent inhibition of electrical activity in a cochlear nucleus observed after stimulation of the contralateral cochlear nucleus may be due to commissural inhibitory terminals which contact excitatory neurons such as pyramidal and giant cells. Other inhibitory commissural terminals which contact inhibitory neurons such as cartwheel and tuberculo-ventral neurons, may explain the stimulation of electrical activity in the DCN after contralateral stimulation.

Decussations of the descending paraventricular pathways to the brainstem and spinal cord autonomic centers

Decussations of descending fibers of the hypothalamic paraventricular nucleus (PVN) were investigated by using Phaseolus vulgaris-leucoagglutinin (PHA-L) in intact and brainstem-operated rats. Fibers descend ipsilaterally along the brainstem and spinal cord and decussate at four levels: 1) Supramamillary decussations (SM). PVN fibers reach this area through the lateral hypothalamus and along the third ventricle in the dorsal hypothalamus. In the posterior hypothalamus some fibers crossover in the SM and terminate in the supramamillary region bilaterally. 2) Pontine tegmentum. PVN fibers run in the lateral part of the tegmentum arching to the basis of the pons. Some fibers crossover under the fourth ventricle. The locus ceruleus and the Barrington's nucleus receive bilateral innervation with ipsilateral dominance. 3) Commissural part of the nucleus of the solitary tract (NTS). The major crossover of PVN fibers is found here. The decussated fibers form a dense network here, and loop rostralward to innervate the entire NTS. A midsagittal knife-cut through the NTS eliminated paraventricular-fibers on the contralateral side. Synaptic contacts between PHA-L-labeled boutons and tyrozine hydroxilase-positive neurons were verified in the NTS. The caudal ventrolateral medulla also receives bilateral innervation. 4) Lamina X of the thoracic spinal cord. Paraventricular fibers enter the lateral funiculus ipsilaterally and innervate the intermediolateral cell column (IML). Some fibers cross the midline ventral and dorsal to the central canal running to the contralateral IML, at the level of the decussation. Our results demonstrated that paraventricular projections form a continuous descending pathway on their side of origin, and provide crossover fibers which may terminate segmentally without forming long tracts after crossover.

Subretinal macrophages in the developing eye of eutherian mammals and marsupials

Blood-borne mononuclear cells invade the developing retina via the hyaloid vasculature at the optic nerve head. Following removal of apoptotic cell debris they give rise to the network of resident microglia. The population of cells recently described in the peripheral subretinal space of developing human eyes may represent a further population of macrophages destined to become microglia. The aim of the present study was to confirm the presence of subretinal macrophages in the developing eye in other mammalian species and perform preliminary immunophenotypic analysis in rat tissues. The range of species chosen included eutherian mammals (rat and rabbit) and marsupials (wallaby and opossum). Ocular tissues from a range of developmental stages were studied by scanning electron microscopy and transmission electron microscopy. Distinctive networks of dendriform and pleomorphic macrophages were observed by scanning electron microscopy in the peripheral subretinal space of D2 rabbits, newborn and D2 rats and D75 wallaby. Transmission electron microscopic studies of D2 rabbit, newborn and D2 rat and all ages of North American opossum revealed cells with the ultrastructural features of macrophages in the peripheral subretinal space, cilio-retinal junction and between ciliary epithelial cells. Preliminary immunoperoxidase studies using a panel of anti-leukocyte monoclonal antibodies on frozen sections of rat ocular tissues (newborn, D2 and D4) revealed ED1(+) Ox42(+) ED2(+) but Ox6(-) cells in the peripheral subretinal space, peripheral retina and ciliary body epithelia. The data confirms that subretinal macrophages are a feature of the developing eye in a broad range of mammalian species and immunophenotypic evidence leads the author to postulate that these cells arise from the ciliary body vasculature and may migrate into peripheral neural retina and mature into resident microglia.

Quantitative changes of lung tissue components during perinatal period in rats

Quantitative changes of lung tissue components (air spaces lined by PAS-positive and PAS-negative epithelium, blood vessels and interstitium) were investigated in developing rats from fetal day 18 through neonatal day 1. The volume of the left lung increased significantly from fetal day 18 through neonatal day 1. The percentage and volume of the air spaces increased strikingly between fetal days 20 and 21. However, the percentage of the air spaces lined by PAS-positive epithelium decreased significantly from fetal days 20 to 21, and that of the spaces lined by PAS-negative epithelium increased between the two days. The proliferating cell nuclear antigen (PCNA)-positive cells were rich in the interstitium and epithelium of the air spaces on fetal days 18 and 19. The percentage of the interstitium decreased significantly from fetal day 18 through neonatal day 1, showing remarkable decrease between fetal days 20 and 21. From fetal day 20 onward, the PCNA-positive cells decreased in number and located in the epithelium of the conducting air ways and interstitium. Based upon these findings, the present study suggests that the period from fetal days 20 to 21 is a critical time for the development of fetal lung: the period before fetal day 20 is that for proliferation and the period after fetal day 21, functional differentiation of the lung.

Differences in adrenal morphology in male Dark Agouti, Sprague-Dawley and Wistar rats

There is little published information describing the differences in adrenal structure between strains of a single species despite quite well known functional differences. In this paper we report morphological differences in the adrenal glands between three strains of laboratory rat; Dark Agouti (DA), Sprague-Dawley (SD) and Wistar (W). Significant differences in adrenal weights (as a percentage of body weight) were not detected between any of the groups. While there were no significant differences in the volume of medullary or zonae glomerulosa or fasciculata tissue, the volume fraction for the zona reticularis was significantly smaller in DAs compared to the other strains. The functional significance of these differences is unknown. However, it is suggested that the reduced volume of zona reticularis tissue may contribute to a reduced capacity for glucocorticoid synthesis or storage.

Bilateral dimorphism of Loewenthal's gland in young male albino rats: an ultrastructural investigation

This study represents a further contribution to our knowledge about the structure of Loewenthal's gland. There are several divergences in the available literature on the topic, concerning both the histological and ultrastructural findings. However, in these studies, the authors did not take into account the potential influence of a putative side-dependent dimorphism previously reported by us. We therefore carried out histological and electronmicroscopic observations specifically aimed at evaluating the importance of the gland shape for its structure. In particular, in male albino rats aged 70-120 days, we compared the structure of the left and right glands. Depending on the side undergoing morphological investigation, we observed differences in the acini, cells, nuclei, endoplasmic reticulum, Golgi apparatus and granular content. Apart from slight individual differences, we found that structural variations were most frequently observed in glands displaying a more evident macroscopic side-specific dimorphism. Our findings demonstrate that several conflicting data in the literature dealing with the structure of Loewenthal's glands might be explained by the morphofunctional side-dependent dimorphism of the organ.

Arteries of the carotid body in rats

The arterial blood supply of 40 carotid bodies in 20 Wistar rats of both sexes, aged 10-12 weeks (250-350 g), was examined by light microscopy. The carotid bodies of all rats were supplied by only one carotid body artery. The average diameter of the carotid body arteries was 40 microns. This artery arose either from the external carotid artery (97.5%) or the occipital artery (2.5%). There was an intimal cushion at the origin of the carotid body artery. The carotid body artery, after reaching the caudal pole of the carotid body, divided into the first-order branch. In the carotid body, the paranchyma was divided into the second-order branch. The carotid body artery was of the muscular type.

Laminar boundaries persist in the hippocampal dentate molecular layer of the mutant Shaking Rat Kawasaki despite aberrant granule cell migration

The present report provides the first detailed description of the hippocampus in the Shaking Rat Kawasaki (SRK) mutant by using a panel of antibody markers to delineate its laminar organization. The mutant was characterised at postnatal day 21 by severe malformations of both neuronal position and orientation, the most striking of which was the presence of a rounded central granule cell mass in the dentate gyrus rather than the normal V-shaped granule cell layer. Despite this finding, the SRK dentate gyrus not only retained a cell-sparse molecular layer (thinner but similar in gross appearance to that of control littermates), but the sharp laminar boundary between its inner and outer parts was as clearly marked by IM1 and OM4 antibody staining as it was in the normal dentate gyrus. These immunocytochemical data suggest that the entorhinal terminal field of the dentate gyrus may be relatively normal in the mutant, despite entorhinal afferents appearing to take an abnormal trajectory after they fail to cross the hippocampal fissure. Laminar malformations included disruption of the SRK pyramidal cell layer, with spreading of the CA3 mossy fibre projection to an ectopic infrapyramidal position, radial displacement of CA1 pyramids, and transposition of a hitherto unremarked longitudinal fibre bundle immunoreactive for calretinin from its normal position in the stratum lacunosum-moleculare of field CA2 to an alvear position in SRK. The SRK malformations were very like but not identical to those seen in the mouse reeler mutant, suggesting similar underlying developmental mechanisms.

Rat eustachian tube and its musculature

The objective of this study was to evaluate the anatomy of the eustachian tube (ET) of the rat and the paratubal musculature. Microdissection and serial sections were used. The ET consists of collapsible membranous and membranocartilaginous segments and a noncollapsible bony segment. Tubal muscles are attached to the collapsible part; the salpingopharyngeus muscle (SPM) is well developed and consists of 3 distinct groups of muscle fibers; the tensor veli palatini muscle (TVPM) consists of 2 functionally different groups of fibers, but only 1 group assists in opening the ET. Attachment of the fibers of the SPM and TVPM that are involved in tubal opening is confined to the dorsal portion of the ET. This finding, together with the earlier observation that this part is mainly lined by squamous epithelium, strongly suggests that the dorsal part has a ventilatory function. The ventral portion of the ET, which is lined by ciliated-secretory epithelium and lacks the attachment of muscle fibers that can dilate the lumen, is assumed to serve clearance. The anatomic position of the levator veli palatini muscle suggests that this muscle contributes to the protective function of the ET. These findings are discussed with regard to the ET in humans.

Calretinin immunoreactive nerve endings in the trachea and bronchi of the rat

Nerve endings showing calretinin immunoreactivity were examined in the lower respiratory tract of the adult rat. Tree-like nerve endings were immunostained in the tracheal and bronchial smooth muscle layer. The endings that arose from thick nerve fibers and formed corpuscles composed of many arborized nerve terminals. A few of the nerve endings were also observed in the lamina propria of the tracheal mucosa, close to the epithelial layer. Immunoelectron microscopy revealed that the immunoreactive terminals were filled with mitochondria and scattered among the intermuscular collagen fibrils. Schwann cell sheath and collagen fibrils were intercalated between the smooth muscle cells and nerve endings. The calretinin immunoreactive nerve endings observed in the present study seem to be slowly adapting stretch receptors.

Projections from the lateral, basal, and accessory basal nuclei of the amygdala to the hippocampal formation in rat

The amygdaloid complex and hippocampal formation mediate functions involving emotion and memory. To investigate the connections that regulate the interactions between these regions, we injected the anterograde tracer Phaseolus vulgaris-leucoagglutinin into various divisions of the lateral, basal, and accessory basal nuclei of the rat amygdala. The heaviest projection to the entorhinal cortex originates in the medial division of the lateral nucleus which innervates layer III of the ventral intermediate and dorsal intermediate subfields. In the basal nucleus, the heaviest projection arises in the parvicellular division and terminates in layer III of the amygdalo-entorhinal transitional subfield. In the accessory basal nucleus, the parvicellular division heavily innervates layer V of the ventral intermediate subfield. The most substantial projection to the hippocampus originates in the basal nucleus. The caudomedial portion of the parvicellular division projects heavily to the stratum oriens and stratum radiatum of CA3 and CA1. The accessory basal nucleus projects to the stratum lacunosum-moleculare of CA1. The subiculum receives a substantial input from the caudomedial parvicellular division. The parasubiculum receives dense projections from the caudal portion of the medial division of the lateral nucleus, the caudomedial parvicellular division of the basal nucleus, and the parvicellular division of the accessory basal nucleus. Our data show that select nuclear divisions of the amygdala project to the entorhinal cortex, hippocampus, subiculum, and parasubiculum in segregated rather than overlapping terminal fields. These data suggest that the amygdaloid complex is in a position to modulate different stages of information processing within the hippocampal formation.

Efferent and collateral organization of paratrigeminal nucleus projections: an anterograde and retrograde fluorescent tracer study in the rat

The paratrigeminal nucleus (PTN) receives primary visceral afferent projections through cranial nerves IX and X and somatic afferent projections through cranial nerve V and dorsal roots as far caudally as C7. Pressure injections of the anterograde tracer tetramethylrhodamine dextran into the PTN in the rat resulted in bilateral labeling in the nucleus of the tractus solitarius, dorsal motor nucleus of the vagus nerve, and parabrachial nucleus. Anterograde labeling in the parabrachial nucleus was strongest in the external medial, external lateral, and ventral lateral subnuclei. Anterograde labeling was also found in the contralateral paratrigeminal nucleus, lamina I of the spinal trigeminal nucleus subnucleus caudalis, and ventroposteromedial nucleus of the thalamus. The collateral organization of PTN neurons was demonstrated by injecting different fluorescent retrograde tracers into the terminal fields of PTN projections as determined by the anterograde tracing experiments. Double-labeled neurons were found in the paratrigeminal nucleus following all combinations of injection sites. The most prominent PTN efferent projections and the most highly collateralized were to the nucleus of the tractus solitarius and parabrachial nucleus. The efferent and collateral connections of the paratrigeminal nucleus may provide a neuroanatomical substrate for integrating convergent visceral and somatic afferent information used to modulate autonomic function and behavior related to thermoregulation, nociception, and gustation.

Three-dimensional angioarchitecture of tongue corrosion casts from normal young rats

The three-dimensional architecture of the vascular network of the rat's lingual papillae has been studied employing the corrosive resin cast technique. The casts of the microvasculature of these types of papillae (the small conical filiform, true filiform, fungiform and vallate papillae) have been observed under scanning electron microscopy (SEM). The microvascular arrangements of the filiform papillae consist of well-defined simple or twisted capillary loops. The fungiform papillae have a cylindrical form with a central hole, and the capillary network gives shape to the whole papilla. Finally, the capillary bed of the oval-shaped vallate papilla with its characteristic network and small hairpin-like loops was also examined.

Morphology of the abdominal hemolymph nodes in the Wistar rats

In 26 Wistar rats the morphology of 30 renal and 20 splenic lymph nodes were investigated. The left renal nodes are usually singular as compared to multiple right renal nodes. Microscopically they present segmental structure with erythroidal elements located mainly in the medullary cords. The splenic nodes, 1 to 5 in number do not show segmental structure but have uniformly dispersed erythroidal elements.

Arterial blood supply of the thoracic and lumbosacral parts of the spinal cord in Wistar rats

The thoracic and lumbosacral parts of the rat's spinal cord are supplied by 1) ventral and dorsal radicular arteries which contribute to vascular trunk passing along the spinal cord, and 2) ventral and 2) dorsolateral spinal arteries. The dorsal radicular arteries in the thoracic part arise bilaterally at the same level and are more numerous and of lesser diameter than corresponding ventral radicular arteries. In the lumbar part the dorsal radicular arteries are also more numerous than ventral ones which were mainly found at the levels of L1, L2 and L3. The sacral radicular arteries are present sporadically at the S1.

Topographical organization of group II afferent input in the rat spinal cord

The organization of neurons in the lumbar enlargement of the rat spinal cord processing information conveyed by group II afferents of hind-limb muscle nerves has been investigated by using cord dorsum and intraspinal field potential recording. Group II afferents of different muscle nerves were found to evoke their strongest synaptic actions in specific segments of the lumbar cord. Group II afferents of quadriceps and deep peroneal nerves evoked potentials mainly at the rostral end of the lumbar enlargement (L1-rostral L3), whereas group II afferents of gastrocnemius-soleus and hamstring nerves evoked their main synaptic actions at the caudal end of the lumbar enlargement (L5). In the central lumbar segments (caudal L3-L4), the largest group II potentials were produced by afferents of tibialis posterior and, to a lesser degree, flexor digitorum longus. Field potentials evoked by group II afferents of quadriceps, tibialis posterior, and flexor digitorum longus were largest in the dorsal horn (up to 600 microV), but also occurred in the ventral horn where they were sometimes preceded by group I field potentials. In contrast, field potentials evoked by group II afferents of gastrocnemius-soleus and hamstring nerves were restricted to the dorsal horn. These results indicate that neurons in different segments of the rat lumbar spinal cord process information from group II afferents of different hind-limb muscles. Furthermore, the topographical organization of group II neuronal systems in the rat is similar in several respects to that in the cat and may therefore represent a general organizational feature of the mammalian spinal cord.

Single Purkinje cell can innervate multiple classes of projection neurons in the cerebellar nuclei of the rat: a light microscopic and ultrastructural triple-tracer study in the rat

Two different populations of projection neurons are intermingled in the cerebellar nuclei. One group consists of small, gamma-aminobutyric acid-containing (GABAergic) neurons that project to the inferior olive, and the other group consists of larger, non-GABAergic neurons that provide an input to one or more, usually premotor, centers in the brainstem, such as the red nucleus, the thalamus, and the superior colliculus. All cerebellar nuclear neurons are innervated by GABAergic Purkinje cells. In this study, we investigated whether individual Purkinje cells of the C1 zone of the paramedian lobe of the rat innervate both groups of projection neurons in the anterior interposed nucleus. Two different, retrogradely transported tracers, either cholera toxin beta subunit (CTb) or wheat germ agglutinin coupled to horseradish peroxidase (WGA-HRP) and a gold lectin tracer were injected into the red nucleus and the inferior olive, respectively, whereas Purkinje cell axons were anterogradely labeled with biotinylated dextran amine (BDA) injected into the paramedian lobule. Cerebellar nuclear sections studied with the light microscope demonstrated a close relation of varicosities from BDA-labeled Purkinje cell axons with both gold lectin- and CTb-labeled neurons. Branches of individual axons could be traced to both retrogradely labeled cell populations. At the ultrastructural level, synapses of labeled Purkinje cell terminals with profiles of WGA-HRP-labeled projection neurons predominated over contacts with gold lectin-containing neurons. Nine out of 367 investigated BDA-labeled terminals were observed to be presynaptic to a WGA-HRP-labeled profile as well as to a gold lectin-labeled profile. This indicates that nuclear cells that project to the inferior olive as well as those that project to premotor centers are under the influence of the same Purkinje cells. Such an arrangement would suggest an in-phase cortical modulation of the activation patterns of the inhibitory cells that project to the inferior olive and excitatory cells that project to premotor nuclei, which could explain why olivary neurons, especially those of the rostral part of the dorsal accessory olive, appear to be unresponsive to stimuli generated during active movement.

Bioelectrical impedance analysis for the estimation of body composition in rats

Bioelectrical impedance analysis (BIA) was used to assess body composition in rats fed on either standard laboratory diet or on high-fat diet designed to induce obesity. Bioelectrical impedance analysis predictions of total body water and thus fat-free mass (FFM) for the group mean values were generally within 5% of the measured values by tritiated water (3H2O) dilution. The limits of agreement for the procedure were, however, large, approximately +/- 25%, limiting the applicability of the technique for measurement of body composition in individual animals.

Topographical distribution of neurons containing endothelin type A receptor in the rat brain

Endothelin (ET) was originally identified as a vasoactive peptide biosynthesized in vascular endothelial cells. Because ET has also been found in the brain as a neuropeptide, it has been thought to belong to the group of brain-vascular peptide hormones. To date, type A and type B receptors for ET have been found. To elucidate the topographic distribution of type A receptor (ET-AR) in the brain, we raised a specific antibody to the C-terminal (64 amino acids) peptide of rat ET-AR and immunostained rat brain sections with this antibody. Immunoreactivity for ET-AR was detected in neuronal cell bodies and also in the many proximal and some distal parts of their fibers. Nerve cell bodies containing strong ET-AR-immunoreactivity were distributed in the lateral part of the reticular formation, the nucleus of the solitary tract and its surrounding area, the dorsal midline area and medial longitudinal fasciculus, the subependymal layer of the fourth ventricular roof, the caudolateral area of the pontine tegmentum, the locus coeruleus, the rostral pontine area of the lateral reticular formation, the retrorubral area, the substantia nigra, the ventral tegmental area, the periventricular region lateral to the rostral mesencephalic aqueduct and caudal third ventricle, the arcuate hypothalamic nucleus, the caudomedial area of the zona incerta, the periventricular hypothalamic nucleus, the parvocellular portion of the paraventricular hypothalamic nucleus, and the periglomerular region of the olfactory bulb. In addition, the Purkinje cells of the cerebellar cortex, the nerve cells in the mesencephalic trigeminal nucleus, and the magnocellular neurons of the supraoptic and paraventricular hypothalamic nuclei showed weak immunoreactivity. The distribution of highly ET-AR-immunoreactive neurons is quite similar to that ofcatecholamine neurons.

Structure and function of the hemolymph node in rats

Hemolymph nodes (HLs) are unique lymph nodes, in that their lymphatic sinuses contain numerous erythrocytes. In this study, we compared the internal structure and immunologic function of HLs with those of ordinary lymph nodes (OLs) and the spleen. Electron microscopy revealed erythrocytes passing through the walls of blood vessels in the intermediate sinus area (IMSA) of a HL between expanded endothelial cell junctions. However, no direct communication was found between lymphatic sinuses and blood vessels. Numerous carbon particles appeared in the IMSA of HLs on 5 days after intravenous carbon particle injection, while OLs lacked particle deposition. Immunohistochemical studies showed that lipopolysaccharide (LPS) reached the IMSA of HLs and extravasated into medullary cords 4 hours after intravenous LPS injection, resulting in the appearance of more IgM-stained lymphocytes in the IMSA of HLs than in that of OLs on day 5. The ability of organs to produce antibodies was determined by counting the number of plaque forming colonies after intravenous injection of sheep red blood cells (SRBC). The HLs antibody-producing ability was between that of OLs and the spleen. These results suggest that HLs possess functionally open blood vessels in the IMSA and their immunologic capability is between that of OLs and the spleen. These findings suggests that HLs are lymphoid organs that have characteristics between those of the OLs and the spleen, both ultrastructurally and functionally.

Angioarchitectural structure of the fungiform papillae on the anterodorsal surface of the rat tongue

To ascertain whether the microvascular morphological differences of fungiform papillae (FuP) on the anterodorsal surface of the rat tongue are locationally and functionally related, this study aimed at examining and comparing, in greater detail, the comparative morphological characteristics of FuP. FuP were sporadically and consistently scattered among numerous filiform papillae (FiP) in three parts: the apical, central and in front of the intermolar eminence on the anterodorsal surface. We studied these by means of the microvascular cast specimen (MVCS) of FuP using scanning electron microscopy (SEM). The results obtained in this study showed that in all three parts on the anterodorsal region, the capillary bed of FuP presented as a netbasket-like and cylindrical figure with a central hole consisting of 4-5 horizontal rings of several ascending and descending roots. FuP in the central part on the anterodorsal region were relatively larger in size and more cylindrical in shape than those of both the other parts, and they play the leading part as sensory organs for the taste sense and were regarded as taste receptive organs.