Search

The fine structure of neuronal perikarya and processes containing VIP-like immunoreactive material in the colon of patients with Hirschsprung's disease was investigated by immunoelectron microscopy. No VIP-like immunoreactive terminals were found in Auerbach's plexus of the ganglionic segment. However, VIP-like immunoreactive preterminal axons were frequently found to make synaptic contact with both immunoreactive and non-immunoreactive elements within Meissner's plexus. Therefore, the function of the VIP neurons in Auerbach's plexus seems to differ from that in Meissner's plexus. In the oligoganglionic segment, there were a few VIP-like immunoreactive processes, but no VIP-like immunoreactive synaptic formations. VIP-like immunoreactive processes were rarely encountered in the aganglionic segment. In both the oligo- and aganglionic segments, bowel relaxation is considered to be disturbed due to the lack of synaptic contacts of VIP-like immunoreactive neurons with other neuronal components.

We demonstrated α-fetoprotein (AFP) -positive cells in the late as well as in the early stage of 3′-methyl-4-dimethylaminoazobenzen (3′-Me-DAB) hepatocarcinogenesis, using immunocytochemical procedures with improved fixation and processing of tissue sections. The superior value of periodate-lysine-4% paraformaldehyde (PLP) as the fixative in the demonstration of AFP-positive cells and the usefulness of cryostat sections in floating immunoreactive processing are discussed. It is suggested that AFP-positive cells are new cell populations in the evolution of hepatocellular carcinoma.

Anatomical mapping of the retinal central projection in albino rats was performed by whole-mount HRP histochemistry, after intraocular injection of HRP. The overall features of the retinal central pathways from the optic chiasma to the superior colliculus as well as the accessory optic systems in normal and monocular rats were clearly visualized, following application of a modified tetramethyl benzidine method on the whole-mounted brain stems including the diencephalon and the mid-brain. When combined with a partial retinal lesion, the whole-mount HRP method made feasible detection of the spatial retinotopy of the collicular projection.

Exogenous horseradish peroxidase (HRP, Type VI, Sigma) was applied as a marker for retrograde neuroanatomical tracing in the nigroneostriatal system and the sciatic nerve of adult rats. The retrograde transport and intraneuronal fate of HRP was examined with light and electron microscopy.In the nigroneostriatal system, the labeled neurons containing many brown granules in their perikarya were observed in the ipsilateral substantia nigra 3-4 hours after an injection of HRP, confirming the existence of a nigroneo-striatal pathway. Ultrastructually, these granules appear as multivesicular and lysosomal bodies in the perinuclear region.The labeled nerve cells of the spinal ganglia were also observed within 12 hours after the application of HRP in the sciatic nerve. The HRP positive brown granules had accumulated in the perinuclear region and were rapidly degraded by the lysosomal system disappearing 2 weeks after the injection.In instances of long periods of survival, characteristic lysosomal bodies which included crystals, crystalloid and laminar structures were found.

The regional distribution of human leumorphin (HL)-like immunoreactivity (HL-LI) in monkey (Macaca fuscata) spinal cord and dorsal root ganglia was investigated by peroxidase-anti-peroxidase immunocytochemistry using specific antiserum. HL-LI-positive fibers and terminals were distributed densely in laminae (Rexed) I and II, and sparsely in laminae III-VII and X, but no immunoreactive elements were observed in the ventral horn, the white matter or the dorsal root ganglia. Many immunoreactive neuronal perikarya were found in laminae I and II. Intrathecal injection of colchicine also revealed the presence of immunoreactive neuronal perikarya in laminae III-VII and X. These results suggest the presence of HL-LI, which represents HL and/or its C-terminal fragment, in the neuronal elements of the monkey spinal cord.

We used transmission electron microscopy to examine a muscle spindle found in serial sections of the arytenoid muscle of the human larynx. Eight intrafusal fibers were observed at the equatorial region and contained two types of muscle fibers, nuclear bag fibers and nuclear chain fibers. The sensory nerve endings found on the nuclear bag fibers were annular or varicose in shape and contained numerous mitochondria. Another small sensory ending was composed of many vesicles and some dense granules. The fusimotor nerve endings found on the nuclear chain fibers had three types of endings with different sizes and complexities.

The distributions of gut hormones in the colon of Hirschsprung's disease were investigated by the peroxidase-antiperoxidase (PAP) immunohistochemical method. Three colonic segments (ganglionic, oligoganglionic, and aganglionic) were stained by the unlabeled antibody enzyme method. The immunoreactivity of vasoactive intestinal polypeptide (VIP) was found to be reduced in the oligoganglionic and aganglionic segments. Antisera to substance P and met-enkephalin demonstrated immunoreactive cells and fibers in the ganglionic segment, whereas these cells and fibers were almost completely absent in the oligoganglionic and aganglionic segments. A similar distribution was seen for the mucosal endocrine cells with somatostatin immunoreactivity. Antisera to neurotensin, motilin, bombesin, and cholecystokinin revealed no immunoreactivity in the normal colon or the three segments. The differences in these peptides between normal and impaired colonal segments may be one of the causes of colon constriction in Hirschsprung's disease.

Immunoperoxidase techniques were used to investigate the localization patterns and distribution of hepatitis B virus (HBV)-associated antigens in hepatitis B surface antigen (HBsAg)-positive patients with liver cirrhosis. The membranous type of HBsAg was rarely seen in liver cirrhosis unless there was concomitant evidence of chronic active hepatitis. HBsAg was stained mainly throughout the hepatic cytoplasm or its periphery in liver cirrhosis regardless of the presence of the hepatitis B e antigen (HBeAg) or hepatitis B e antibody (HBeAb) in the serum. In all cases of liver cirrhosis with hepatocellular carcinoma, the inclusion body type of HBsAg was detected in hepatocytes. Simultaneous staining of HBsAg and hepatitis B core antigen (HBcAg) in biopsy tissues of liver cirrhosis revealed that the HBcAg was mainly stained in the nuclei of hepatocytes, and that almost all of the HBcAg-positive hepatocytes contained either cytoplasmic or festoon-like immunoreaction patterns of HBsAg. HBcAg-positive hepatocytes were distributed spottedly, diffusely or in groups in pseudolobules, and clusters of HBcAg-positive hepatocytes were detected in the non-tumor areas adjacent to hepatomas, where liver cell dysplasia was also observed.

The suprachiasmatic nucleus (SCN) of mammals is considered to be a circadian oscillator and it also demonstrates circadian rhythmicity of its multiple unit activity. A number of neuropeptides have been found in the SCN. Vasoactive intestinal peptide (VIP)- and vasopressin-containing neurons comprise large populations of these cells and have a distinct distribution within the nucleus. Therefore we attempted to examine whether the VIP neurons show a diurnal alteration of their immunoreactivity by combined immunocytochemistry and color image analysis. Our results demonstrate that VIP-like immunoreactive neurons show a diurnal change in the amount of immunoreactivity. Immunoreactivity was most intense in the sections from rats maintained in the cyclic photoperiod and sacrificed at 02.00 h and weakest in teh SCN from animals sacrificed at 14.00 h. We considered that VIP-like immunoreactive neurons showed diurnal variation of VIP synthesis depending strongly on the light from the retina.

The origin and the physiological role of an endogenous digitalis-like substance were investigated by measuring both the digoxin-like substance by a digoxin radioimmunoassay (RIA) and the inhibitory activity on the ouabain sensitive Na+,K+-ATPase in rats. The digitalis-like substance was in high concentration in the pituitary, and in decreasing concentration in the hypothalamus, adrenal and the other organs as measured by RIA using an antibody raised from a goat. However, the adrenal showed the highest content of digitalis-like substance as measured by the antibody raised from a rabbit. The plasma level markedly decreased during a 2-week sodium-loading, and the adrenal content decreased markedly on hypophysectomy as measured with the rabbit-antibody. Therefore, the substance measured with the rabbit-antibody must be one of ACTH-dependent adrenal steroids. The inhibitory activity on the Na+,K+-ATPase was high in the pituitary gland, and was decreased in order of the adrenal, hypothalamus and other organs. The 2-week sodium-loading increased both the content in the pituitary gland and the output in the urine, and decreased the hypothalamic content. Immunohistochemical staining of the hypothalamus with the antibody revealed that the immunoreactivity is restricted to the neurons of the paraventricular nucleus, supraoptic nucleus, magnocellular accessory nuclei and extended their fibers reaching to the inner layer of the median eminence. To determine the role of the substance in the brain, the crude extract dissolved in artificial cerebrospinal fluid was injected into the lateral ventricle; vasopressor responses, tachycardia and hyperactivity of the splanchnic nerve lasting for more than 30 min were recorded, which resembled the responses to ouabain injected similarly.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution of substance P (SP) in the rat spinal cord was investigated by peroxidase-anti-peroxidase (PAP) immunocytochemistry. A dense network of SP-immunoreactive fibers and terminals was detected in the ventral column of the rostral lumbar cord with a different density and extent from the other segmental levels. These fibers and terminals were accumulated within and around the centromedial nucleus (CM) of the L1 and L2 segments, with some bundles of immunoreactive fibers between the CM and other areas; i.e. laminae V and X and the contralateral CM. They formed a dense network, such as in arborization of immunoreactive fibers and terminals on the transverse plane and in a comb-shaped structure on the horizontal plane. The origin of the SP in this network was examined. It was determined that neither a total transection of spinal cord at a low thoracic level or mid-lumbar level, nor at an ipsilateral or bilateral section of the 3–5 dorsal roots, containing L1 and L2 roots, induced any visible changes in the SP staining pattern. An intrathecal injection of colchicine revealed the presence of SP-immunoreactive neurons in the dorsal horn and intermediate gray matter at the spinal cord including the rostral lumbar cord. The present findings suggested that the majority of SP immunoreactivities in the above network are derived from local circuit interneurons of the spinal cord.

Regulation of the neurotensin (NT)-producing neurons by ascending catecholamine fibers in the paraventricular nucleus of the rat hypothalamus was examined using fluorescence histochemistry and immunohistochemistry after the destruction of the ascending catecholamine pathway by 6-hydroxydopamine. On the ipsilaterally operated side, the fluorescence of the catecholamine terminals decreased remarkably in the paraventricular nucleus whereas an accumulation of catecholamine fluorescence was observed in the caudal mesencephalon rostral to the locus coeruleus. In addition, the number of neural perikarya with NT-like immunoreactivity was greatly decreased in the paraventricular nucleus on the operated side compared with the intact side as determined by peroxidase-antiperoxidase immunohistochemistry. This decrease in the NT-like immunoreactive neural perikarya may be due to the disappearence of noradrenergic input to the NT-like immunoreactive neurons through axo-somatic or axo-dendritic synapses.

The distribution of neurotensin-like immunoreactive (NT-LI) neurons was examined in the thalamus and hypothalamus of the Japanese monkey (Macaca fuscata) by using the peroxidase-antiperoxidase immunocytochemistry technique. In the thalamus, NT-LI neuronal perikarya were distributed mainly in the midline nuclear group and the dorsomedial nucleus, and partially in the intralaminar nucleus: Immunoreactive fibers were mainly distributed in the midline nucleus, particularly in the nucleus rhomboidalis. Numerous immunoreactive fibers were also detected in the regions that contain the pathways to extrathalamic areas such as the stratum zonale and inferior thalamic peduncle. In the hypothalamus, many immunoreactive neuronal perikarya were distributed in the lateral hypothalamic area and in the arcuate nucleus. Immunoreactive fibers were disseminated throughout the hypothalamus, but they were dense in the preoptic area and sparse in the ventromedial nucleus. An accumulation of dense immunoreactive endings was also observed in the external layer of the median eminence. NT-LI fibers in the external layer of the median eminence were considered to represent nerve endings near portal vessels. Functional roles of neurotensin in the thalamus and hypothalamus are discussed from the anatomical point of view.

Horseradish peroxidase (HRP)-filled neurons and their processes were consistently detected in the ventral portion of the dog hypothalamus after intraocular injection of HRP. The number of HRP-filled neurons decreased in parallel with extent of the resection of the optic nerve. HRP-filled neurons were never detected in specimens with a complete resection of the optic nerve. These findings strongly indicate that these HRP-filled neurons in the ventral hypothalamus are the source of centrifugal fibers to the retina.

Neurotensin-like immunoreactive neuronal perikarya, fibers and terminals in the rat hypothalamus, particularly in the arcuate nucleus, the paraventricular nucleus and the median eminence, were investigated by light and electron microscopic immunocytochemistry. The main distributional areas of immunoreactive neuronal perikarya were found to be the arcuate nucleus, the periventricular nucleus and the paraventricular nucleus by light microscopic immunocytochemistry. Immunoreactive neuronal perikarya showed a characteristic distributional pattern in the arcuate nucleus. In the paraventricular nucleus they were distributed in both the magnocellular and parvocellular portions. A large number of immunoreactive terminals were observed throughout the external layer of the median eminence, particularly its lateral portion. A moderate number of immunoreactive terminals were also observed in the internal layer of the median eminence. By electron microscopic immunocytochemistry immunoreactive neuronal perikarya both in the arcuate and paraventricular nuclei showed generally well-developed cell organelles such as mitochondria, r-ER, and Golgi complex. In addition, immunoreactive dense granules were dispersed throughout the perikarya. A large number of immunoreactive terminals containing immunoreactive dense granules, clear vesicles and mitochondria were observed in the vicinity of pericapillary spaces of the external layer of the median eminence. This observation strongly suggests that neurotensin-like immunoreactive substance is released into the portal capillaries.

We examined retinal projections to the hypothalamus in albino rats at early postnatal stages by means of injecting horseradish peroxidase (HRP) into the eye and observing the anterograde transport. On the 1st postnatal day, HRP-filled retinal fibers reached the suprachiasmatic nucleus (SCN) on the bilateral sides to the eye injection of HRP, and made synaptic connections with dendrites of the SCN neurons. The retinal projection to the lateral hypothalamic area (LHA) on the contralateral side to the eye injection of HRP was also noted at the 1st and 3rd postnatal days, but not on the 7th and 10th postnatal days or in the adults.

The distribution of the Substance P (SP) immunoreactive nerve fibres in the canine larynx and laryngeal nerves was studied by PAP immunohistochemistry. Many individual SP immunoreactive nerve fibres with varicosities were observed within the epithelial layer and in the connective tissue below the epithelium of the laryngeal mucosa. Small numbers of SP immunoreactive nerve fibres were also found in the submucosal gland region and some of them appeared to terminate in glandular cells. These findings are consistent with the view that SP might be involved in the laryngeal sensory innervation system and the laryngeal glandular secretion. No SP immunoreactive nerve fibres were found in any intrinsic laryngeal muscles. The recurrent laryngeal nerve and the superior laryngeal nerve contained SP immunoreactive nerve fibres and were considered to lie in the pathway of the SP nerve fibres to the larynx.

Clonal culture of muscle cells from thigh muscles of the term fetus of the mouse was undertaken. Myoblasts were spherical or spindle-shaped, and proliferated exponentially until day 4 in culture. The generation time of the muscle cells from 2 to 4 days' culture was 9.1 to 13.4 hr. The fusion of myoblasts began on day 4 in culture; many myotubes had been formed by day 6 and spontaneous contraction was observed on day 7. Clonal efficiency was 30%, and the proportion of muscle colonies in all the colonies was 72%.

The projection from the medial preoptic area to the median eminence of the cat was clarified by electron microscopy. After placing the electrolytic lesion in the preoptic area several kinds of degenerating neuronal processes and terminals were observed in the external layer of the median eminence. The one was dark shrunk terminals containing dense cored vesicles, the other was the dark ones containing myeline figure-like structure. The relationship between catecholamine-containing nerve endings and RH/IH-containing endings in the external layer of the median eminence was discussed.

PH-8P (dynorphin[1-8])-like immunoreactive neuronal perikarya, processes, and terminals located within the human hypothalamus were investigated by the avidin-biotin peroxidase complex (ABC) immunocytochemical procedure. Immunopositive neurons were distributed throughout the hypothalamus. The distributional pattern was found to be similar to that in other mammalian species by the use of antisera against dynorphin. A large number of immunoreactive neuronal perikarya were detected in the supraoptic nucleus (SON) and the magnocellular portion of the paraventricular nucleus (PVN). Their processes appeared to project to the posterior pituitary via the internal layer of the median eminence and their distribution seemed to be less dense than in other mammalian species. PH-8P and vasopressin were colocalized in the neuronal perikarya in the human SON unlike the colocalization of these peptides in the rat SON and PVN. There were a few immunoreactive terminals in the external layer of the median eminence; their immunoreactive substances may be released into the portal veins to act on anterior pituitary cells. In addition, PH-8P-like immunoreactive neurons in the human hypothalamus may project to the extrahypothalamic area.

Exact trajectory and pattern of branching of individual regenerating retinal axons derived from different retinal quadrants was detected within the tectum by labeling selected retinal axons with horseradish peroxidase (HRP) at the 4th, 6th, and 10th weeks after transection of the optic nerve in adult newt Cynops pyrrhogaster . In the early phase of regeneration, each regenerating retinal axon sprouted several branches, in random directions within the tectum. As the regeneration proceeded, only branches directed toward the site of normal innervation were maintained, while the sproutings toward the ectopic part of the tectum were retracted or became atrophic. The surviving branches then sprouted several new branches. Sprouting of new branches and the disappearance of old branches occurred simultaneously throughout the process of regeneration. At the 10th week of regeneration, most regenerating retinal axons possessed branches only at the distal part within the site of normal innervation. These observations strongly suggest that the retinotopic central connection of regenerating retinal axons may be reestablished by means of a stepwise selection of widespread axonal branches.

The present study, using a combination of catecholamine (CA) histofluorescence and peptide immunocytochemistry in the same tissue sections, investigated the coexistence of neuropeptide Y (NPY) and methionine-enkephalin-Arg6-Gly7-Leu8 (MEAGL)-like immunoreactivity (LI) in catecholaminergic neurons of colchicine-treated rat brain stems. Of the total number of catecholaminergic neurons in the A1/C1, A2/C2, A3, A4, and A6 regions approximately 83, 28, 98, 76, and 36%, respectively, contained both NPY-LI and CA. Of the total number of catecholaminergic neurons in A1/C1, A2/C2, A3, and A5 regions, approximately 47, 4, 8, and 17%, respectively, contained both MEAGL-LI and CA. Moreover, about 24% of the catecholaminergic neurons in the A1/C1 region contained both NPY- and MEAGL-LI. Neither the noradrenergic neurons (A7) in the pons nor any of the dopaminergic neurons in the midbrain (A8, A9, A10) contained NPY- or MEAGL-LI. Neurons containing both NPY- and MEAGL-like immunoreactive peptides without CA were not found in the rat brain stem. These findings indicate that catecholaminergic neurons in the brain stem of the rat can be subdivided into distinct subgroups on the basis of the coexistence of specific peptides.

Fine structures of neuropeptide Y (NPY)-like immunoreactive neuronal perikarya in the lateral geniculate nucleus and their terminals in the suprachiasmatic nucleus were investigated by peroxidase-antiperoxidase immunocytochemistry using male Wistar rats. NPY-like immunoreactive preterminal axons from both axo-somatic and axo-dendritic synapses on the neurons mainly located in the ventral portion of the suprachiasmatic nucleus. Almost all of them appeared as symmetrical synapses. Immunoreactive neuronal perikarya in the lateral geniculate nucleus show good development of cell organelles such as rough-surfaced endoplasmic reticulum and mitochondria. NPY-like immunoreactivity was distributed throughout the perikarya. The functional role of NPY-like immunoreactive terminals in the suprachiasmatic nucleus were briefly discussed.

The ontogenic development of vasoactive intestinal polypeptide (VIP)-immunoreactive amacrine cells in the rat retina was studied using peroxidase-antiperoxidase (PAP) immunohistochemistry. In the rat retina, VIP immunoreactivity appeared entirely in postnatal stage. On the 12th postnatal day, VIP-immunoreactive amacrine cells could be first detected. However, VIP immunoreactivity was very weak and VIP-immunoreactive amacrine cell processes could not be observed at this stage. On the 21st postnatal day, VIP-immunoreactive amacrine cell bodies became more mature and their processes were distinctly observed, resembling their appearance in adult rat retinas. VIP immunoreactivity could be detected in both stratified and diffuse amacrine cells at this stage. The relationship between the first appearance of VIP-immunoreactive amacrine cells and the synaptic formation in the inner plexiform layer is briefly discussed.

The existence of the adrenergic terminals of the canine laryngeal glands has been revealed by electron microscopy and fluorescence histochemistry. Adrenergic fibres with fluorescent varicosities were observed around the base of th acini in the submucosa. In dogs treated with 5-OHDA, varicosities containing both small and large, dense-cored vesicles containing both small and large, dense-cored vesicles, believed to be adrenergic terminals, were found near blood vessels, gland cells and myoepithelial cells in the submucosal gland region. The role of these adrenergic terminals is briefly discussed.

The possibility of retinotopic organization of pathways of retinal fibers within the optic tract and the tectum of the frog was studied by selective labeling of the retinal fibers with horseradish peroxidase. Within the optic tract the pathways of the ventral, temporal and dorsal retinal fibers were ordered from the dorsal to ventral edges of the optic tract. The nasal retinal fibers ran along both the dorsal and ventral edges of the optic tract. The dorsal retinal fibers and the nasal retinal fibers which were located along the ventral edge of the optic tract entered the ventrolateral perimeter of the tectum and formed the lateral tract. The ventral retinal fibers and the nasal retinal fibers which were located along the dorsal edge of the optic tract entered the dorsomedial perimeter of the tectum and formed the dorsomedial tract. The temporal retinal fibers invaded the tectum directly at the diencephalo-tectal junction. The topography of fiber pathway observed for the frog was exactly the same as that seen in the newt, and seemed to be common to all amphibian species.

We used the method of thiamine pyrophosphatase (TPPase) enzyme histochemistry and flat-mounted and transverse-sectioned retinas to identify microglial cells. Light microscopically, TPPase activity was demonstrated on the outer surfaces of glial cells located in the inner plexiform layer (IPL) and the ganglion cell layer (GCL) of the entire retinal regions, and also on the outer surfaces of blood vessels. Electron microscopically, TPPase activity was observed on the plasma membranes of the glial cells, the endothelial cells of microvessels and the pericytes. The TPPase-positive glial cells had a dark nucleus with large clumps of chromatin beneath the nuclear envelope. These findings strongly suggest that the glial cells with TPPase activity observed in the IPL and the GCL of the rat retina were microglial cells.

The morphological distribution of the nerve terminals containing LH-RH in the hypothalamus especially in the median eminence of the proestrus female rat was demonstrated by immunohistochemistry, using FITC and peroxidase antibody. The terminals containing LH-RH were classified into four groups on the topographic relationship. LH-RH nerve processes terminated mainly in the infurdibular radix within an elliptical zone surrounding the bases of the infundibular recessus. The heaviest concentration of LH-RH terminals immunohistochemically demonstrated lay on each side of the region extending from the dorsal part of tuberoinfundibular sulcus to the lateral part of the external layer of the superior labium of the infundibulum. We were unable to detect any neuronal soma with the immunoreactivity to LH-RH in the hypothalamic gray matter. The distributional patterns of LH-RH, GH-RIH and monoamine in the median eminence as well as their relationships were briefly discussed.

The distribution of substance P (SP) in the rat spinal cord was investigated by peroxidase-anti-peroxidase immunocytochemistry combined with retrograde horseradish peroxidase (HRP) labeling via the cremaster muscle. In the male rats, a dense network of SP immunoreactive (SP-IR) fibers and terminals was detected in the ventral column of the L1 and L2 segments (Vent L1-2) with a different density and extent from the other segmental levels. These fibers and terminals were accumulated within and around the nucleus centromedialis lumbaris (CM) of the L1 and L2 segments. However, in the female rats, SP-IR fibers and terminals were sparse in the Vent L1-2 without particular segmental differences. HRP-positive motoneurons were located in the CM and surrounded by SP-IR fibers and terminals. These results indicate that the Vent L1-2 of the rat spinal cord shows sexual dimorphism with respect to the regional distribution of SP-IR fibers and terminals, and that motoneurons that innervate the cremaster muscle are innervated by dense SP-IR fibers and terminals.

Immunohistochemical topographic localization of the vasoactive intestinal polypeptide (VIP)-like immunoreactive neurons in the cat brain was investigated using a peroxidase anti-peroxidase technique. VIP-like immunoreactive neurons were mainly localized in the cerebral cortex, limbic cortex, hypothalamic nuclei; suprachiasmatic nucleus, supraoptic nucleus, paraventricular nucleus, periventricular nucleus and arcuate nucleus, and in the midbrain; such as the central grey and the raphe nucleus. It was demonstrated that VIP-like immunoreactive neurons were widely distributed in the cat brain, particularly in the hypothalamus, compared with those of the rat and mouse; though whether these differences were species-related or due to differences in the physiological conditions remains to be determined. This is the first report of VIP neuronal perikarya in the arcuate nucleus of mammalian species, although these cells are present in the arcuate nucleus of birds.

A time-course study on production of vasopressin neurons (VP-neurons) in the mouse hypothalamus was carried out by application of [3H]thymidine autoradiography and PAP-immunocytochemistry simultaneously on the same tissue sections. In the paraventricular nucleus (PVN) and the supraoptic nucleus (SON), heavily [3H]thymidine-labeled VP-neurons were detected only in the specimens of the animals exposed to the isotope on the gestational day 12. While in the suprachiasmatic nucleus (SCN), heavily isotope-labeled VP-neurons were observed in the specimens of the animals exposed to the isotope on the gestational day 12 or day 14. Therefore, the production of the VP-neurons in the SCN is prolonged and slightly more delayed than that in the SON or PVN.

The fine structures of the VIP-like immunoreactive neurons in the suprachiasmatic nucleus (SCN) and the arcuate nucleus ( ARN ) of the cat hypothalamus were investigated by electron microscopic immunocytochemistry. The VIP-like immunoreactive soma and fibers could be successfully visualized by a modified PAP method. VIP-like immunoreactive neurons in both nuclei contained immunoreactive rER, Golgi complexes and many immunoreactive granules, as well as well developed mitochondria. VIP-like immunoreactive synaptic endings with synaptic membrane specialization of Gray's type I and II were found in the SCN. Moreover VIP-like immunoreactive preterminal elements that made synaptic contact with VIP-like immunoreactive neuronal soma were also detected. On the other hand, it was difficult to detect typical preterminal endings with immunoreactivity in the ARN ; however, VIP-like immunoreactive processes in contact with the basement membrane of the capillaries were observed. These observations indicate that VIP-like immunoreactive neurons in the SCN act as intrinsic neurons and are involved in neuroendocrine function in ARN .

The influence of ascending noradrenergic neuronal input on the neurotensin (NT)-like immunoreactive neuronal perikarya located in the dorsal part of the central nucleus of the amygdala (CNA) was examined using fluorescence histochemistry and peroxidase-antiperoxidase (PAP) immunocytochemistry. Unilateral hemitransection of the ascending noradrenergic pathway by injection of 6-hydroxydopamine into the caudal mesencephalon just rostral to the locus coeruleus caused a marked depletion of immunoreactivity in NT-like immunoreactive neuronal perikarya in the CNA. Ascending noradrenergic neuronal input, therefore, is considered to facilitate production of NT-like immunoreactive substances in neuronal perikarya and to influence on the functional role of the amygdaloid complex. In addition, we obtained evidence of unilateral direct ascending projections of NT-like immunoreactive neurons into the CNA since the disappearance of NT-like immunoreactive processes occurred mainly in the ventral part of the CNA after surgical hemitransection of the ascending neuronal pathway that interrupts the ascending NT-like immunoreactive pathway arising from the neurons in the brain stem.

The toxic effect on area CA3 of the hippocampus of the rat of small doses of kainic acid (KA) injected into the lateral ventericles was examined by electron microscopy. The most characteristic feature revealed was degeneration in the pyramidal cell somata and in their dendrites from as early as 3hr after injection. We found four types of degenerating pyramidal cells probably corresponding to their susceptibility to KA intoxication. We also detected degenerating preterminal axons and terminals in addition to degenerating pyramidal cells and dendrites. Temporary structural alterations of the mossy fiber endings and intimate adhesional contacts between the mossy fiber endings were also observed. The response of the glia to the damage area CA3 was an increase in the number of astroglia and macrophages in the early stage followed later by mobilization of microglia and astroglia for the formation of scar tissue.

The localization of motoneurons innervating the canine intrinsic laryngeal muscles was investigated by the fluorescent labeling technique. Labeled cells were found in the ipsilateral nucleus ambiguus. The most rostral labeled neurons for the cricothyroid muscle, the posterior cricoarytenoid muscle, the thyroarytenoid muscle, and the lateral cricoarytenoid muscle were found at progressively more caudal levels, respectively, within the nucleus ambiguus. The rostral tip of the arytenoid muscle cell column was at the same level as the lateral cricoarytenoid muscle cell column. The cells labeled from the cricothyroid muscle occupied the ventral part of the nucleus at the rostral level of the nucleus. At the middle level of the nucleus, the cells from the posterior cricoarytenoid muscle occupied the ventral part of the nucleus and the cells from the thyroarytenoid muscle, the lateral cricoarytenoid muscle and the arytenoid muscle occupied the dorsal part of the nucleus. The existence of double-labeled cells which innervated both thyroarytenoid muscle and lateral cricoarytenoid muscle was detected.