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Biomedical subjects

S Kito

Publications and source records attributed to S Kito.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of calcium antagonists on muscarinic receptor subtypes in the rat brain.

The effects of several calcium antagonists, including nicardipine, nifedipine, verapamil, and diltiazem, on muscarinic acetylcholine antagonist binding were studied in the P2 fraction of the rat cerebral cortex using either [3H]quinuclidinyl benzilate ([3H]QNB) or [3H]pirenzipine as the radioactive ligand. (1) The potency of [3H]QNB binding inhibition was in the order nicardipine greater than verapamil greater than diltiazem greater than nifedipine. The IC50 values of nicardipine, verapamil, and diltiazem were 2.56 X 10(-6) M, 1.28 X 10(-5) M, and 6.00 X 10(-5) M, respectively. (2) The inhibition of [3H]QNB binding by nicardipine was significantly decreased in the presence of Ca ions. (3) In saturation experiments of [3H]QNB binding in the presence of nicardipine, the Kd value appeared to be significantly affected, but the Bmax value was unchanged. This indicated that nicardipine probably inhibited [3H]QNB binding allosterically. On the other hand, (4) nicardipine inhibited [3H]pirenzipine binding completely with an IC50 value of 7.87 X 10(-7) M. It was concluded that nicardipine had an inhibitory effect on M1-receptor binding.

Animals↗
PubMed1987

Ontogeny of muscarinic receptors in the rat brain with emphasis on the differentiation of M1- and M2-subtypes--semi-quantitative in vitro autoradiography.

The ontogeny of muscarinic acetylcholine receptors (mAChR) in the rat brain was studied with emphasis on the differentiation of M1- and M2-receptor subtypes through semi-quantitative in vitro autoradiography. [3H]Quinuclidinyl benzilate (QNB) and [3H]pirenzepine (PZ) were used for labeling total mAChR and M1-receptors, respectively. In the cerebral cortex of adult rats, [3H]QNB binding sites were more richly present in the superficial and deeper layers than in the middle layer, while M1-receptors were diffusely observed in all the layers. This means that M2-receptors are highly concentrated in the superficial and deeper layers. The ontogenetical differentiation of the laminar distribution between M1- and M2-receptors first appeared at 14 days of postnatal age. In the hippocampus and striatum whose mAChR were predominantly of the M1-type in the adult rat brain, ontogenic patterns of M1-receptors were almost identical to those of total mAChR. On the other hand, mAChR in the cerebellar cortex and lower brainstem of the adult rat were mainly of the M2-subtype. In these areas, the ontogeny of total mAChR was apparently observed. However, M1-receptors were not observed at any stage of the ontogeny. The above-mentioned results indicate that M1- and M2-receptors show distinct developmental behaviors in the rat brain.

Age Factors↗
PubMed1987

Transient appearance of calcitonin gene-related peptide-like immunoreactive fibers in the developing cerebellum of the rat.

A plexus of calcitonin gene-related peptide (CGRP)-containing fibers were transiently found in the developing cerebellum of the rat by means of the indirect immunofluorescent method. CGRP-like immunoreactive fibers appeared in the cerebellum by embryonic day 22. Immunoreactive fibers rapidly increased and these made a dense plexus in the Purkinje cell layer by postnatal day 2. However, only a few if any immunoreactive fibers were seen in the Purkinje cell layer or molecular layer of adult rats.

Animals↗
PubMed1987

Neostriatal cholinergic neurons receive direct synaptic inputs from dopaminergic axons.

We used an electron microscopic 'mirror technique' to determine whether cholinergic neurons are in direct synaptic contact with dopaminergic axons in the rat neostriatum. Tyrosine hydroxylase-immunoreactive axons make synaptic contacts with the somata and proximal dendrites of large choline acetyltransferase-immunoreactive striatal neurons which are thought to be interneurons. This provides morphological evidence that nigrostriatal dopaminergic neurons can influence monosynaptically the striatal cholinergic neurons.

Adrenergic Fibers↗
PubMed1987

Dopaminergic axons directly make synapses with GABAergic neurons in the rat neostriatum.

We examined with an electron microscopic 'mirror technique' whether glutamic acid decarboxylase-immunoreactive (GAD-IR) neurons are in direct synaptic contact with tyrosine hydroxylase-immunoreactive (TH-IR) axons in the rat neostriatum. Three types of GAD-IR neurons were identified in the nucleus caudatus putamen based upon their size and ultrastructural characteristics. These were medium spiny, medium aspiny and large cells. All types of GAD-IR neurons made synaptic contact with TH-IR axonal boutons at least on perikarya and proximal dendrites. This provides ultrastructural evidence for catecholaminergic, presumably, nigrostriatal dopaminergic inputs to both long- and short-axon neurons most probably containing GABA.

Animals↗
PubMed1987

Ontogeny of [3H]neurotensin binding sites in the rat cerebral cortex: autoradiographic study.

The ontogeny of the neurotensin binding sites in the rat caudal cortex such as the retrosplenial cortex, the visual area containing area 17 and 18, the caudal somatosensory area and temporal area was examined by autoradiography. During the early postnatal period (from birth to day 10), very-high-density [3H]neurotensin binding sites were observed in the caudal cortical area, but the number of binding sites decreased markedly with age. On the other hand, the ventral tegmental area and substantia nigra pars compacta had a low density of binding sites at birth, but the density increased until about day 15 and remained even in the adult rat. These findings were confirmed by the biochemical binding analysis.

Animals↗
PubMed1987

Glutamate decarboxylase-like immunoreactive neurons in the rat caudate putamen.

GAD-IR neurons were roughly divided into those with medium sized perikarya and large perikarya. The medium-sized GAD-IR neurons accounted for about 85% of the GAD-IR neurons. The medium-sized perikarya were further divided into two, those with a smooth nuclear membrane and those with an indented nucleus. The former were very similar to medium-sized spiny neurons and the latter corresponded to medium-sized aspiny neurons. The GAD-IR large cells that were identified by light microscopy, had nuclear indentations and were divided into two classes based on their ultrastructural features, type 1 large cells received few synaptic inputs and type 2 large cells received many synaptic contacts from non-immunoreactive or immunoreactive boutons. The former resembles Type I large cells and the latter Type II large cells identified recently by Chang and Kitai; the latter are also similar to the second type of projecting neurons identified by Bolam et al.

Animals↗
PubMed1986

Enkephalinergic projection from the ventromedial hypothalamic nucleus to the midbrain central gray matter in the rat: an immunocytochemical analysis.

The projection of enkephalin-like immunoreactive (EnkI) neurons in the ventromedial hypothalamic nucleus (VMH) in the rat was investigated using immunocytochemistry. These neurons project to the dorsal portion of the midbrain central gray matter (DCG), because the destruction of the VMH resulted in a marked ipsilateral reduction of EnkI fibers there. Destruction of the dorsomedial portion of the VMH caused the appearance of fibers accumulating EnkI ventrolateral to the lesion and these fibers could be traced to the ventrolateral portion of the VMH where many EnkI neurons were concentrated. Transection of the brain at the level of the premammillary nucleus, mammillary body and superior colliculus caused the appearance of fibers accumulating EnkI in the posterior hypothalamic nucleus (PH), central gray matter medial to the fasciculus retroflexus Mynert and in the DCG, respectively. We concluded that the axons from these neurons first project dorsomedially to situate in the PH. These fibers ran caudodorsally and entered into the dorsal longitudinal fasciculus in the DCG at the midbrain.

Animals↗
PubMed1986

Ultrastructural evidence of enkephalinergic input to glucoreceptor neurons in ventromedial hypothalamic nucleus.

A combination of intracellular injection of horseradish peroxidase into the ventromedial hypothalamic nucleus glucoreceptor neurons and immunohistochemical staining for enkephalin allowed ultrastructural visualization of interrelations between these electrophysiologically identified neurons and enkephalin-like immunoreactive (ENK-IR) terminals. The results show that glucoreceptor neurons receive direct inputs from ENK-IR neurons. This is the first evidence that glucoreceptor neurons, identified electrophysiologically, can be affected monosynaptically by endogenous enkephalin, probably released from ENK-IR terminals.

Animals↗
PubMed1986

Is the effect of somatostatin on muscarinic receptors selective to M1 type?

The effect of somatostatin on muscarinic receptors (mAchR) was investigated through saturation experiments of [3H]oxotremorine-M-acetate and oxotremorine/[3H]N-methyl-scopolamine competition experiments. Somatostatin converted oxotremorine high affinity binding sites to low affinity sites in the hippocampus and cerebral cortex whose mAchR were dominantly of M1 type. Somatostatin did not alter agonist binding in the medulla-pons where M2 receptors were abundant. Therefore, the effect of somatostatin on mAchR seems to be selective to high affinity binding sites of M1 receptors.

Animals↗
PubMed1986

Innervation of substance P neurons by catecholaminergic terminals in the neostriatum.

In this study we tried to establish by the electron microscopic 'mirror technique' whether substance P-like immunoreactive neurons in the neostriatum receive synaptic inputs from catecholaminergic, presumably dopaminergic, nigrostriatal axons. Tyrosine hydroxylase-immunoreactive (TH-IR) axonal boutons were in synaptic contact with the somas and proximal dendrites of SP-IR neostriatal neurons, which are medium in size and have unindented nuclei. This suggests that nigrostriatal dopaminergic neurons monosynaptically influence the strionigral substance P neurons.

Animals↗
PubMed1986

Autoradiographic localization of calcitonin gene-related peptide binding sites in human and rat brains.

125I-calcitonin gene-related peptide (CGRP) binding sites were mapped in the human brain and rat brains by in vitro macroautoradiography, and compared to each other. Binding experiments were made to characterize 125I-CGRP binding on the human and rat brains. Scatchard analysis of saturation experiments from slide-mounted sections of the human and rat cerebellum displayed 125I-CGRP binding sites with a dissociation constant (Kd) of 0.17 nM and 0.11 nM, respectively, and a maximal number of binding sites (Bmax) of 96.8 fmol/mg and 23.0 fmol/mg protein. 125I-CGRP binding was time-dependent, reversible and saturable with high affinity in the brains. Autoradiograms showed a discrete distribution of 125I-CGRP binding sites throughout the brains of human and rat with patterns similar to each other. In the human brain, the highest binding was seen in the cerebellum, inferior olivary nuclear complex, certain parts of the central gray matter, arcuate nuclei of the medulla oblongata and dorsal motor nucleus of the vagus, and densities of CGRP-binding sites were high in the nucleus accumbens, amygdala, tail of the nucleus caudatus, substantia nigra, ventral tegmental area, medial portion of the inferior colliculus, medial pontine nuclei, locus coeruleus, inferior vestibular nucleus, substantia gelatinosa of the spinal trigeminal nucleus, nucleus of the solitary tract and nucleus cuneatus lateralis. In the rat, high densities were found in the hippocampus pars anterior, nucleus accumbens, ventral and caudal portions of the nucleus caudatus-putamen, central and basolateral nuclei of the amygdala, caudal portion of the insular cortex, medial geniculate body, superior and inferior colliculi, certain portions of the central gray matter, locus coeruleus, inferior olivary nuclei, vagal complex, nucleus cuneatus lateralis and cerebellum. In contrast, in both species, most of the cortical areas including the hippocampus, most of the thalamus, and hypothalamus exhibited few binding sites. In addition, high quantities of the binding sites were seen on the pia mater and on walls of blood vessels in the brain and subarachnoidea. These results revealed essentially homologous locations of CGRP binding sites in the human and rat central nervous systems and well corresponding distributions of binding sites and endogenous CGRP-like immunoreactivity.

Aged↗
PubMed1986

Ultrastructural evidence of dopaminergic input to enkephalinergic neurons in rat neostriatum.

The synaptic relationship between neuronal structures reacting with antibodies to tyrosine hydroxylase (TH) and Leu- or Met-enkephalin (ENK) was studied by the 'mirror technique' in adjacent sections of rat neostriatum. TH-immunoreactive (TH-IR) axonal boutons surrounding the neural perikarya and proximal dendrites of ENK-immunoreactive (ENK-IR) neurons were very thin (0.1-0.4 micrograms). They contained many small clear vesicles and sometimes had symmetrical membrane specializations. This provides morphological evidence for catecholaminergic, presumably dopaminergic inputs to rat striatal enkephalin neurons.

Animals↗
PubMed1986

Ultrastructural localization of enkephalin immunoreactivity in the substantia nigra of the monkey.

Localization of enkephalin-like immunoreactivity in the substantia nigra of the Japanese red-faced monkey was investigated by light and electron microscopy using the peroxidase-anti-peroxidase method. Immunoreactive precipitates were predominantly distributed in the nerve fibers of the substantia nigra pars reticulata but not in the perikarya, and a low density of immunoreactive enkephalin was found in the pars compacta of this nucleus. Electron microscopic observations showed that enkephalin-immunoreactive precipitates were located in axon terminals containing numerous small clear vesicles either with or without labeled large granular vesicles and formed predominantly axo-dendritic synapses.

Animals↗
PubMed1986

Ontogeny of calcitonin gene-related peptide and calcitonin in the rat thyroid.

In this immunohistochemical study, the ontogenic development of calcitonin-gene-related peptide (CGRP) in the rat thyroid was investigated and compared with that of calcitonin using the indirect-immunofluorescence method. Parafollicular cells with immunoreactivity to both CGRP and calcitonin first appeared at an early stage of gestation (days 17 and 18) in the central portion of the thyroid. Cells immunoreactive to CGRP and calcitonin had became numerous by gestational day 22. After postnatal day 7, CGRP- and calcitonin-immunoreactive (C-IR) cells increased rapidly both in number and in the intensity of their fluorescence. In 14- to 90-day old rats, many intensely immunoreactive cells were distributed in the central portion of the thyroid. The cells immunoreactive to CGRP and to calcitonin had an almost identical ontogenic appearance. In 14-day-old and adult rats, C-IR cells also exhibited CGRP immunostaining, suggesting that these cells simultaneously produce and store CGRP during ontogeny.

Aging↗
PubMed1986

Study on the appearance of the cavity in the corpus luteum of cows by using ultrasonic scanning.

A transrectal real-time B mode linear scanner was used to learn if the appearance of a cavity in the corpus luteum (CL) in cows causes infertility. Sixty-one cows that were confirmed to have ovulated after artificial insemination (AI) were used. Some of the cows that returned to estrus were examined two or three times; thus, a total of 78 observations were made. The rate of cavity appearance was 37.2% (29 78 ). In relation to the size of cavity, the rates of appearance were 30.8% of CL with cavities of 7 mm or greater and 24.4% with cavities of 10 mm or greater in diameter. It took more than 21 days for the cavity more than 10 mm to disappear. In the cows that were observed two or three times, the cavity did not tend to reappear. The mean period for return to estrus, mean serum progesterone concentration and mean pregnancy rate were not significantly different (P>0.05) for cows that had CL with or without a cavity. Our results suggest that the cavity mentioned above does not cause infertility.

Journal Article↗
PubMed1986

Immunoreactive atrial natriuretic polypeptides in the adrenal medulla and sympathetic ganglia.

Atrial natriuretic polypeptide (ANP)-like immunoreactivity was found in the rat adrenal gland by using indirect immunofluorescence and peroxidase-antiperoxidase techniques. ANP-like immunostaining was present in most of chromaffin cells with varying degrees of immunoreactivity. The majority of medullary cells displayed very intense immunostaining, and several clusters revealed weaker immunostaining. No staining was found in the adrenal cortex or in the nerve fibers in this organ. In the consecutive sections treated for dopamine-beta-hydroxylase (DBH), apparently all medullary cells had intense immunofluorescence for DBH and its distribution pattern was very similar to that for ANP-like immunoreactivity. While phenylethanolamine N-methyltransferase (PNMT) immunoreactive cells largely corresponded to the intensely stained ANP-like immunoreactive cells, suggesting that adrenaline cells contained a large amount of ANP-like substance, noradrenaline cells contained a smaller amount of this substance than adrenaline cells. Ultrastructural study showed that end-products due to the immunoreaction with the ANP antiserum were primarily associating with chromaffin granules. In addition, the presence of ANP-like immunoreactivity was investigated in several sympathetic ganglia of the rat. No principal ganglion cells were ANP-positive, whereas a few small intensely fluorescent (SIF) cells were ANP-immunoreactive. The present findings suggest that catecholamines coexist with ANP which has a natriuretic and vasodilating effect, in adrenal medullary cells and SIF cells in several rat sympathetic ganglia, but not in principal ganglion cells.

Adrenal Medulla↗