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Biomedical subjects

S Daikoku

Publications and source records attributed to S Daikoku.

At least 91 records · Page 5Linked to original sources
PubMed1990

Immunohistochemical evidence for synaptic connections between neuropeptide Y-containing axons and periventricular somatostatin neurons in the anterior hypothalamus in rats.

By employing a pre-embedding double immunolabeling technique, we examined light and electron microscopically synaptic associations between neuropeptide Y (NPY)-containing axons and somatostatin (SRIH)-containing neurons in the anterior periventricular area (APV) of the rat hypothalamus. For light microscopy, the immunoreactions for NPY and SRIH were visualized with silver-gold and diaminobenzidine (DAB), respectively, and the reverse labeling was used for electron microscopy. Light microscopy disclosed many brown SRIH perikarya surrounded by several black beads of NPY fibers in the APV. In electron microscopy, immunoreactive SRIH neurons revealed silver-gold particles scattered throughout the cytoplasm and accumulated in the Golgi area and the secretory granules. SRIH perikarya and dendritic processes indicated synaptic associations with DAB-labeled NPY fiber terminals and immunonegative fibers. NPY presynaptic terminals possessed numerous small clear vesicles and a few dense core vesicles; vesicular membranes and cores were labeled with DAB chromogen. Both the pre- and postsynaptic membranes were thickened equally to be a symmetric synapse. These findings suggest that NPY neurons are involved in the regulation of growth hormone secretion from the pituitary by affecting periventricular SRIH neurons.

Animals↗
PubMed1990

Vasopressin-deficient paraventricular magnocellular neurons of homozygous Brattleboro rats synthesize neuropeptide Y.

Immunohistochemical study was carried out to determine whether neuropeptide Y (NPY), which was only found in certain experimental procedures in arginine vasopressin (AVP)-containing neurons of the magnocellular paraventricular nucleus, might also be synthesized in AVP-deficient homozygous Brattleboro (BB) rats. After an intraventricular colchicine administration, NPY was found in many AVP-deficient non-oxytocinergic magnocellular neurons of the paraventricular and supraoptic nuclei in BB rats, but not in suprachiasmatic nucleus neurons. The results suggest that the NPY synthesis is a phenotype of magnocellular non-oxytocinergic neurosecretory neurons and occurs independently from the synthesis of AVP.

Animals↗
PubMed1990

Morphological evidence for neuronal regulation of luteinizing hormone-releasing hormone-containing neurons by neuropeptide Y in the rat septo-preoptic area.

Using a preembedding double immunolabeling technique, synaptic contacts were found between luteinizing hormone-releasing hormone (LHRH)-containing neurons and neuropeptide Y-containing axonal fibers in the rat septo-preoptic area. In demonstrating LHRH neurons, we used mainly an antiserum generated against rat gonadotrophic hormone-releasing hormone-associated peptide. Although many diaminobenzidine-labeled neuropeptide Y-containing fibers were seen around silver-gold-labeled LHRH cell bodies, synapses with synaptic membrane specialization were scarce. The fiber terminals usually contained many small clear vesicles and some large cored vesicles. The synapses were characterized with the presynaptic accumulation of the small clear vesicles and symmetric thickenings of the synaptic membranes.

Animals↗
PubMed1990

Intragranular co-storage of neuropeptide Y and arginine vasopressin in the paraventricular magnocellular neurons of the rat hypothalamus.

Certain populations of arginine vasopressin (AVP) neurons in the magnocellular paraventricular nucleus became immunoreactive for neuropeptide Y (NPY) when rats were treated with colchicine or monosodium glutamate (MSG). The co-storage of these peptides was examined by employing a post-embedding electron-microscopic immunohistochemistry technique using gold-labeled antibodies to the two peptides. In colchicine-treated rats, the neuronal perikarya contained numerous secretory granules showing co-storage of the two peptides. The cells of the MSG-treated rats were characterized by having well-developed Golgi bodies with the granular structures also co-storing the two peptides, although the secretory granules in the perikarya were rather fewer than in the colchicine-treated rats. It is concluded that the destruction of the arcuate nucleus by MSG-treatment may potentiate the synthesis of NPY in AVP neurons, the synthesis of which is latent in intact animals.

Animals↗
PubMed1990

Development of the dorsal pancreatic primordium transplanted into the third ventricle of rats.

The dorsal pancreatic primordia of 12.5-day-old rat embryos transplanted into the third ventricle of adult female rats were immunohistochemically examined 10, 20 and 40 days after transplantation. On day 10, the grafts grew into an epithelial sacculus (S) with a thick subepithelial tissue (ST). Tubular and vesicular structures with a single cuboidal epithelium were found within the wall of the S, but they underwent thereafter a regression without allowing the primordia to differentiate into the exocrine acinar tissues. In contrast with this, pancreatic hormone-containing cells existed in the ST, and were arranged like the islands of a mature animal. The tissue also has smooth muscle fibers and neurons. When the primordium was grafted along with its root connected to the duodenum, gut-like tubular structures differentiated, showing mucosa with villi and crypts, submucous mesenchymal tissue and muscle layers. The mucosa possesses epithelial cells immunoreactive for the pancreatic hormones, and the muscle layers have the myenteric plexuses. These findings seem to provide further evidence that in the rat pancreas, pancreatic-hormone-containing cells differ from the acinar cells in origin.

Animals↗
PubMed1990

Appearance of neurons with glucocorticoid receptors and neurovascular links in the embryonal rat hypothalamus grafted in the third ventricle.

We have investigated the appearance of the transmitter phenotypes of hypothalamic neurons in grafts transplanted into the third ventricle of adult female rats. The grafts were the mediobasal hypothalamus and the preoptic area of 12.5-day-old rat embryos, and were examined 40-100 days later. Wheat germ agglutinin (WGA) was injected into the jugular vein of several animals for the examination of the existence of neurovascular associations. Three days after the injection, WGA appeared to have been incorporated into the neurons in the paraventricular, periventricular, and arcuate nuclei of the host animals. In the grafts, WGA was also seen incorporated in certain neurons which were found immunoreactive for tyrosine hydroxylase (TH), rat corticotropin-releasing factor (rCRF), substance P (SP), or somatostatin (SRIH). Neurons immunoreactive for neuropeptide Y (NPY) and ACTH did not seem to incorporate WGA. These findings suggest that the neurons containing TH, rCRF, SP, or SRIH link with fenestrated capillaries developed in the grafts. The immunoreactivity for glucocorticoid receptor (GR) was detected mainly in the nucleus of certain neurons and glial cells in the grafts as well as in the host hypothalamic neurons. In the grafts, strong GR immunoreactivity was detected in the cells immunoreactive for TH, NPY, and rCRF as in the host animals. It is concluded that the undifferentiated hypothalamic neurons differentiate to synthesize GR as well as definitive peptides and TH in the grafts.

Animals↗
PubMed1990

Development of the hypothalamic luteinizing hormone-releasing hormone-containing neuron system in the rat: in vivo and in transplantation studies.

The development of the hypothalamic LHRH-containing neuron system was immunohistochemically investigated in vivo and in tissue transplantation using rat embryos aged from 12.5 to 17.5 days of gestation. The sera used were generated against rat gonadotropic hormone-releasing hormone-associated peptide (28-56) (rGAP) and LHRH. Immunoreaction for rGAP was first found in cells migrated from and in the vomeronasal organ on Days 13.5 and 14.5 of gestation. Immunoreactive cells seem to ascend along the terminal nerves, reaching the medial surface of the forebrain vesicles. Subsequently the cells occurred in the septum and further into their final position in the septopreoptic-diagonal band area on Days 16.5-17.5 of gestation; during this traverse the cells become secretory neurons after changes in morphology and in behavior. Intraventricular transplantation revealed that nasal epithelia of Day 12.5 embryos raised only a few cells immunoreactive both for LHRH and rGAP, but a great number of immunoreactive cells and fibers in the presence of the medial basal hypothalamus (MBH). The fibers formed a median eminence-like structure together with dense capillary plexus that had grown in the cografted MBH. The same phenomenon was apparently observed in the grafts obtained from older embryos of gestation, but not in the combined grafts of the anterior septum and the nasal epithelium or the MBH. We conclude that hypothalamic LHRH neurons originate from the nasal placode and acquire secretory behavior in the presence of the MBH.

Animals↗
PubMed1990

[Paradoxical response of blood pressure to salt loading in renovascular hypertension].

We studied the effect of high salt intake on blood pressure in two cases with renovascular hypertension. They had hypertension with hyperreninemia and marked difference in plasma renin activity between both renal veins. Blood pressure significantly decreased after single oral administration of captopril. Renal arteriogram revealed significant stenosis in the main artery to the left (case 1) and right (case 2) kidney. Blood pressure response was evaluated after seven (case 1) and five (case 2) days of low salt and seven days (both cases) of high salt intake. Mean blood pressure in two patients was significantly decreased (case 1; 118 +/- 5.5 to 108 +/- 6.1 mmHg and case 2; 150 +/- 3.8 to 138 +/- 3.1 mmHg). Plasma renin activity was also decreased (case 1; 6.25 to 0.77 ng/ml/hr and case 2; 22.8 to 6.3 ng/ml/hr). In case 2, blood pressure elevated markedly during low salt intake, compared with blood pressure level during normal salt intake. The results suggest that excessive salt intake in patients with unilateral renovascular hypertension produces blood pressure reduction because of suppression of renin-angiotensin system. We concluded that in patients with unilateral renovascular hypertension dietary sodium depletion may be harmful, whereas salt supplement may have a beneficial effect.

Adult↗
PubMed1989

Topographic relations between tyrosine hydroxylase- and luteinizing hormone-releasing hormone-immunoreactive fibers in the median eminence of adult rats.

Employing electron microscopic double immunolabeling, we determined a close apposition of tyrosine hydroxylase (TH) and luteinizing hormone-releasing hormone (LHRH) nerve fibers in the rat median eminence (ME). These axo-axonic contacts occurred frequently in the internal and palisade zones, i.e. at the level of the fiber preterminals. In the superficial area of the ME, major TH fibers abutted on the basal lamina and some were projected into the pericapillary space of the portal vessels. Conversely, LHRH fibers were arrested by the endfeet of tanycytes in reaching the basal lamina.

Animals↗
PubMed1989

Differentiation between late potentials of right ventricular and of left ventricular origin.

The aim of this study was to determine whether late potentials of right and left ventricular origin could be differentiated with the use of a signal-averaging technique. Nineteen patients with both late potentials and recurrent sustained ventricular tachycardia were divided into 2 groups according to the origin of their late potentials. Group I consisted of 10 patients with late potentials that originated from the right ventricle. Group II consisted of 9 patients with late potentials originating from the left ventricle. Signal-averaged electrocardiograms (Marquette Electronics MAC I unit) were recorded using 3 bipolar and 3 augmented unipolar leads (the electrode positions were V1, V5 and V6R) with a band-pass filter of 100 to 300 Hz. The augmented unipolar V5 lead (aV5) was used for left-side recording and the augmented unipolar V1 lead (aV1) was used for right-side recording. In group I, the mean maximal late potential amplitude was larger in lead aV1 than in lead aV5 (5.1 +/- 2.5 vs 3.7 +/- 1.8 microV, p less than 0.005) and the maximal late potential amplitude was larger in lead aV1 in all except 1 patient. In group II, however, the mean maximal late potential amplitude was smaller in lead aV1 than in lead aV5 (4.0 +/- 3.0 vs 5.7 +/- 3.2 microV, p less than 0.005) and the maximal late potential amplitude was smaller in lead aV1 in all patients. Thus, the origin of late potentials (right ventricular vs left ventricular origin) can be determined by comparing the maximal amplitudes of late potentials in the right- and left-sided leads. This method might be useful in determining ventricular tachycardia origins.

Electrocardiography↗
PubMed1989

Synaptic regulation of paraventricular arginine vasopressin-containing neurons by neuropeptide Y-containing monoaminergic neurons in rats. Electron-microscopic triple labeling.

Synaptic regulation of arginine vasopressin (AVP)-containing neurons by neuropeptide Y (NPY)-containing monoaminergic neurons was demonstrated in the paraventricular nucleus of the rat hypothalamus. NPY and AVP were immunolabeled in the pre- and the post-embedding procedures, respectively, and monoaminergic fibers were marked by incorporating 5-hydroxydopamine (5-OHDA), a false neurotransmitter. The immunoreaction for NPY was expressed by diaminobenzidine (DAB) chromogen, and that for AVP by gold particles. The DAB chromogen was localized on the surface of the membrane structures, such as vesicles or mitochondria, and on the core of large cored vesicles. Gold particles were located on the core of the secretory granules within the AVP cell bodies and processes. The incorporated 5-OHDA was found as dense cores within small or large vesicular structures. From these data, three types of nerve terminals were discernible: NPY-containing monoaminergic, NPY-containing non-aminergic, and monoaminergic fibers. The AVP cell bodies appeared to have synaptic junctions formed by these nerve terminals as well as by the unlabeled nerve terminals which have small clear vesicles and large cored vesicles. These different types of nerve terminals were frequently observed in a closely apposed position on the same AVP cell bodies. The functional relationships of these three types of neuronal terminals are discussed.

3,3'-Diaminobenzidine↗
PubMed1989

Axons containing neuropeptide Y innervate arginine vasopressin-containing neurons in the rat paraventricular nucleus. Dual electron microscopic immunolabeling.

Synaptic connections between neurons immunoreactive for arginine vasopressin (AVP) and axon terminals immunoreactive for neuropeptide Y (NPY) were found in the magnocellular part of the paraventricular nucleus (PVN) in the rat hypothalamus. In pre-embedding double immunolabeling, NPY axon terminals labeled with diaminobenzidine (DAB) reaction product established synaptic junctions on the perikarya and neuronal processes of AVP neurons labeled with silver-gold particles. Ultrastructural morphology of the neurons was more suitably preserved by a combination of pre- and post-embedding procedures. The presynaptic NPY terminals contained many small clear vesicles and a few cored vesicles, and DAB chromogen (immunoreaction product) was located on the surface of the vesicular profiles and on the core. The postsynaptic AVP neurons possessed many large secretory granules labeled with gold particles. At the synaptic junctions, small clear vesicles were accumulated at the presynaptic membrane, and the postsynaptic membrane was coated with a dense accumulation of fine electron dense particles. The perikarya also received synapses made by immuno-negative axon terminals containing many small clear vesicles and a few cored vesicles. These terminals were found more frequently than those containing NPY.

Animals↗
PubMed1989

Development of the neuronal system containing neuropeptide Y in the rat hypothalamus.

In the rat hypothalamus, neuropeptide Y-containing neurons first appeared on day 14.5 of gestation in the arcuate nucleus and in the dorsolateral hypothalamic area. Until birth neuropeptide Y-containing cell bodies increased in number in the arcuate, dorsomedial-lateral and paraventricular nuclei, but disappeared thereafter, but some cells remaining in the arcuate nucleus. In animals treated neonatally with monosodium L-glutamate to destroy the arcuate nucleus, neuropeptide Y-immunoreactivity became evident in many cells scattered in the magnocellular paraventricular and dorsomedial-lateral hypothalamic nuclei on day 16 but not on days 60 and 12. These neuropeptide Y-immunoreactive neurons which appeared in the paraventricular nucleus were also vasopressin-positive. Neuropeptide Y fibers, on the contrary, remarkably diminished in number on day 16, particularly in the paraventricular and dorsomedial-lateral nuclei, and the medial preoptic area, but made a considerable recovery on days 60 and 120. Hence it is probable that, in normal ontogenetic progress, the development of the neuropeptide Y fibers in these areas is inhibitorily affected by that of arcuate neuropeptide Y neurons.

Aging↗
PubMed1989

Immunohistochemical approach to the functional morphology of the hypothalamic-hypophysial system.

Immunohistochemical studies at the light and electron microscopic levels have provided much information on functional morphology in the hypothalamic-hypophysial system. The present paper describes the immunohistochemical techniques available at present and their use to determine the localizations of neurons containing hypophysiotrophic substances, the co-storage of plural signals in these neurons, and the synaptic regulation of these neurons in rats.

Animals↗
PubMed1989

Hypothalamic neurons from a developmental aspect.

The development of hypothalamic neurons was examined in vivo and in transplanted grafts in rats. The neurons appeared in vivo in distinctive chronotopical schedules showing such morphological characteristics as synaptocrine or hemocrine neurons. These phenotypical properties seemed to be primed already by day 12.5 of gestation in rats, because the grafted hypothalamic primordia from 12.5-day-old embryonal rats differentiated neurons, which express these neuronal properties in the third ventricle of adult female rats. The synaptocrine neurons projected to other neurons, suggesting the establishment of synaptic contacts, and the hemocrine neurons projected to vasculatures developed in the grafts, suggesting the accomplishment of neurovascular associations.

Animals↗