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Biomedical subjects

R Yui

Publications and source records attributed to R Yui.

At least 19 recordsLinked to original sources
PubMed1991

Inhibition of intracellular topoisomerase II by antitumor bis(2,6-dioxopiperazine) derivatives: mode of cell growth inhibition distinct from that of cleavable complex-forming type inhibitors.

In the accompanying paper (K. Tanabe, Y. Ikegami, R. Ishida, and T. Andoh, Cancer Res., 51: 4903-4908, 1991), we showed that ICRF-154 and -193, dioxopiperazine derivatives, inhibited the activity of purified topoisomerase II, without formation of a cleavable DNA-protein complex. In order to see whether ICRF-154 and ICRF-193 affect cellular topoisomerase II in situ or not, we examined the effect of these drugs on etoposide (VP-16)-induced, topoisomerase II-mediated DNA breaks in RPMI 8402 cells by alkaline sedimentation analysis. When RPMI 8402 cells were exposed to VP-16 in the presence of ICRF-154 or ICRF-193 for 1 h, VP-16-induced DNA strand breaks were greatly inhibited by both ICRF compounds. In parallel with this observation, VP-16-induced growth inhibition was also reversed by ICRF-193. Exposure of cells to ICRF-154 resulted in a progressive accumulation of cells with 4C DNA content. Although mitotic index did not significantly increase, mitotic abnormalities were seen in cells exposed to ICRF-193 or ICRF-154: all mitotic cells exhibited early mitotic figures with fewer condensed and entangled chromosomes. The most sensitive phase of the cell cycle to ICRF-154 was the G2-M. ICRF-154 did not affect the spindle formation. However, abnormally oriented spindles were observed in drug-treated cells in parallel with the appearance of multinucleated cells. The results suggest that ICRF-154 and -193 inhibit topoisomerase II activity in RPMI 8402 cells, and this effect resulted in the appearance of cells in G2 and early M phase with fewer condensed and entangled chromosomes and of cells with multilobed nuclei.

Cell Cycle↗
PubMed1990

Maintenance of embedded pig pancreatic pseudo-islets in a collagen gel matrix: study of the effect of hydrocortisone, a collagenase inhibitor, and nicotinamide on collagenolysis and the morphogenesis of pancreatic islet-cells in collagen gel matrix.

We describe a method for maintaining neonatal pig pancreatic isletlike cell clusters (as pseudo-islets) embedded in a collagen gel matrix for long periods. The pseudo-islets were formed from single cells of pig pancreas maintained in a suspension culture and then embedded in pepsin-solubilized type I collagen. When the pseudo-islets were cultured in the collagen matrix, the amount of collagen in the culture decreased gradually during the culture period as soluble hydroxyproline-containing material accumulated in the medium. A low concentration of collagen (0.16%) degraded the collagen gels more rapidly than did high concentrations of collagen (0.64%). The degradation of collagen depended both on the number of pseudo-islets embedded in the gel matrix and on the culture conditions used to maintain them. With added nicotinamide, the accumulation of hydroxyproline decreased in the medium and the structure of the gel matrix was well maintained. Hydrocortisone or a specific inhibitor of collagenase did not decrease the solubilization of embedded pseudo-islet cultures and did not help to maintain their structure. These observations indicate the possible utility of long-term maintenance of pseudo-islets in collagen gel matrix in the presence of nicotinamide.

Animals↗
PubMed1988

Immunocytochemical studies on the islet and the gut of the arctic lamprey, Lampetra japonica.

The endocrine cells and nerves in the islet and the gut of the arctic lamprey Lampetra japonica were examined immunocytochemically by using antisera against brain-gut peptides and amine. The cellular composition of the islets as reported by previous researchers in European species of the lamprey was confirmed in the present study. The islet consisted exclusively of insulin immunoreactive cells in the larvae (ammocoetes), whereas in the adult somatostatin immunoreactive cells were added to the insulin immunoreactive cells; the gut epithelium in the adult was now devoid of somatostatin cells. In the gut of the lamprey, the endocrine cells--which were flask-shaped with a cytoplasmic process extended to the lumen--were classified into three types in the larvae, but were represented by a single type in the adult. In the larval lamprey, the first type was immunoreactive for somatostatin, the second one for gastrin/cholecystokinin (CCK) and the third cell type was immunoreactive for glucagon, pancreatic polypeptide and FMRFamide, simultaneously. In the gut of the adult lamprey, the single type of endocrine cell reacted simultaneously to C-terminal specific anti-glucagon serum, N-terminal specific anti-glucagon serum, anti-bovine PP serum, anti-neuropeptide Y serum and anti-FMRFamide serum. These cells occurred most frequently in the upper intestine, their distribution decreasing from the middle to the lower intestine. Two types of peptide containing nerves were identified in the islet and the gut of the larval and adult lamprey. The first type of neurons (perikarya and fibers) was immunoreactive for serotonin and calcitonin gene-related peptide (CGRP), and was located in the mucous and muscular layer of the intestine and in the islet. The second type of neurons contained both serotonin- and gastrin releasing peptide (GRP)-like immunoreactivities and was scattered exclusively in the muscular layer of the gut. In larval and adult lampreys, a few serotonin/CGRP immunoreactive nerve cell bodies and beaded fibers were found in the connective tissue around the islet cell cords. These nerve fibers were sometimes closely apposed to the blood capillaries and to the islet cells. These findings indicate that a neuroendocrine correlation comparable with that in mammals may have been established in the islet of this most primitive vertebrate.

Aging↗
PubMed1987

Serotonergic efferent nerve fibers in the retinal plexiform layer of the abalone.

Serotonin (5-HT)-immunohistochemistries at light- and electron-microscopic levels, using rabbit anti-5-HT serum (#1234), were applied to the whole head and only to the eye of the abalone, respectively. Peroxidase-antiperoxidase and fluorescein isothiocyanate methods were used for the light-microscopic immunohistochemistries. Many immunoreactive nerve fibers were demonstrated in the outer zone of the retinal plexiform layer, small optic nerve fiber bundles, the optic nerve trunk and the cerebral ganglion. Immunoreactive somata were observed only in the cerebral ganglion. Accordingly the immunoreactive fibers in the retinal plexiform layer are considered to be efferent. Cored vesicles in the retinal plexiform layer demonstrated by both conventional chemofixation and a rapid-freeze-substitution method showed strong immunoreactivities localized within their limiting membrane. The same fibers also contained small clear vesicles. They are considered to be different from larger clear vesicles in non-immunoreactive fibers reportedly containing acetylcholine. The function of the efferent fibers remains to be elucidated.

Animals↗
PubMed1987

Monolayer-forming islet cell culture from neonatal pig pancreas: using sequential treatment with EDTA-dispase and monoiodoacetic acid for preparation and purification.

A new method for the preparation and purification of a monolayer-forming islet cell culture from the neonatal pig pancreas is described. Single cell preparations of the pig pancreas were obtained by gently stirring the chopped pancreases in a medium containing sequential EDTA-dipase. Exposure of the cells to monoiodoacetic acid (10 micron) and BSA-gradient resulted in improved preparation, highly enriched in the endocrine cells. The cells were maintained in tissue culture medium 199 containing 5.5 mM D-glucose, with or without 0.1 mM 3-isobutyl-1-methylxanthine, or 16.7 mM D-glucose and 20% fetal calf serum. During a 6-day culture period, many small cell aggregates appeared in the media. The cell clusters attached to the bottom of the dish and formed monolayers. Provocative stimulation and radioimmunoassay for insulin showed the existence of numerous and viable B cells in the cell clusters. The other three types of islet cells were also demonstrated immunohistochemically in the cell cluster. It is concluded that this improved culture technique provides a useful tool for morphological and biochemical studies of islet cells and a potential source of material for transplantation of B-cells from the pancreas.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Glucagon-related peptides in the rat hypothalamus.

Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism.

Animals↗
PubMed1986

Immunocytochemical studies on the pancreatic islets of the ratfish Chimaera monstrosa.

The islet cells and nerves in the pancreas of the ratfish Chimaera monstrosa were examined immunocytochemically by using antisera against mammalian brain-gut peptides. Five types of islet cells were recognized. The B and D cells reacted to anti-insulin and anti-somatostatin sera, respectively. The A and X cells exhibited glucagon-like immunoreactivities. The N-terminal anti-glucagon serum reacted both to the A and the X cells, while the C-terminal anti-glucagon serum bound specifically to the X cells. These results suggested that the X cells contained pancreatic-type glucagon, whereas the A cells, an enteroglucagon (glicentin)-like substance. A fifth type of endocrine cell was scattered in the islets and contained serotonin-like immunoreactivity. Two kinds of peptide nerves were identified. Vasoactive intestinal polypeptide (VIP)-immunoreactive neuronal somata were located in the intrapancreatic ganglia. Nerve fibers and terminals containing VIP-like immunoreactivities occurred in the pericapillary space surrounding the islets. Gastrin releasing peptide (GRP)-immunoreactive nerve somata and fibers were scattered along the margins of the islets. The pericapillary arrangement of these nerve terminals suggests a hemocrine release of the peptides.

Animals↗
PubMed1985

Neuropeptide immunocytochemistry in protostomian invertebrates, with special reference to insects and molluscs.

In some molluscs (Aplysia and Fusitriton) and insects (silkworm and cricket), occurrence and distribution of neuropeptides in the nervous system and gut were studied with following results: in these invertebrates and also in planaria, PP-like immunoreactivity is extensively distributed in neurons and (in insects) in gut endocrine paraneurons. These cells are negative for NPY, the mammalian neuropeptide related to PP in molecular structure. PHI-like immunoreactivity is widely distributed in the neurons of those invertebrates; it occurs also in gut endocrine paraneurons in insects. The PHI-immunopositive cells are immunonegative for VIP and the coexistence of both peptides due to the common precursor in mammals cannot be recognized in these invertebrates. Immunoreactivity for urotensin I, the neuropeptide derived from teleostean urophysial neurons, is widely distributed in the neurons of the invertebrates. In insects (cricket) it occurs in gut endocrine cells.

Animals↗
PubMed1985

PHI-like immunoreactivity in the nervous system of the cockroach (insect) and Aplysia (mollusc) with special reference to its relationship to VIP-like immunoreactivity.

Studies in mammals have indicated that PHI (peptide histidine isoleucine) and VIP (vasoactive intestinal polypeptide) share a prepropeptide, and that both peptides are contained in the same neurons. The present study proposes that this relationship may not hold true in protostomian invertebrates. In the nervous system of the cockroach (Insecta, Arthropoda) and Aplysia (Gastropoda, Mollusca) distribution of PHI and VIP was examined by immunocytochemistry. In both animals neurons containing PHI-like immunoreactivity were numerously found and only a small part of them in the cockroach contained VIP-like immunoreactivity. These findings suggest that in these invertebrates, PHI may play a more important regulatory role than VIP. Possible reasons for the difference in the distribution of immunoreactivities for PHI and VIP are discussed.

Animals↗
PubMed1984

Co-existence of enkephalin and adrenalin in the frog adrenal gland.

By means of immunohistochemistry combined with formaldehyde-induced fluorescence microscopy, met-enkephalin-like immunoreactivity was found to occur in the adrenalin -cells of frog adrenal glands. Immunoelectron microscopy demonstrated that the immunoreactive material is confined to the secretory granules. These findings suggest the concomitant release of enkephalin and adrenalin by exocytosis.

Adrenal Glands↗
PubMed1982

An electron microscopic study on enkephalin-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs.

Enkephalin-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs were characterized by a high population of large granular vesicles mixed with small clear vesicles. The immunoreactive material is confined to the large granular vesicles. The immunoreactive nerve fibers formed many axo-dendritic as well as axo-somatic synapses and also formed a few synapses with presumed preganglionic axons containing numerous vesicles. The immunoreactive fibers were regarded as presynaptic at these synapses. These findings suggest that enkephalin might play a role as a neurotransmitter or neuromodulator in the ganglionic transmission of this prevertebral ganglion.

Animals↗
PubMed1982

On the occurrence and physiological effect of somatostatin in the ciliary ganglion of cats.

Somatostatin-like immunoreactive nerve fibers occurred among and around ganglion cells in the form of punctate structures or varicose processes in the cat ciliary ganglion. The density of the fibers varied greatly from region to region and approximately 25% of the whole population of neuronal soma that appeared in a single section were surrounded by immunoreactive fibers. No somatostatin-positive cell bodies were observed. Application of somatostatin to this ganglion in vitro by superfusion induced membrane hyperpolarization in approximately 60% of the neurons examined. The hyperpolarization was preserved in a low Ca/high Mg medium. This response was associated with a decrease in input membrane resistance and was reversed in polarity at nearly --90 mV. The present findings suggest that somatostatin may play a role as a neurotransmitter or modulator in this parasympathetic ganglion.

Animals↗
PubMed1982

An electron microscopic study on VIP-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs.

An immuno-electron microscopic study revealed that VIP-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs were characterized by a conspicuously numerous large granular vesicles mixed with small clear vesicles. The immunoreactive materials were localized in the core of the large granular vesicles and a distinct halo was recognized between the core and the limiting membrane of the vesicles. These fibers made numerous axo-dendritic and a few axo-somatic synapses with the post-ganglionic principal neurons and also formed some synapses with vesicle-containing neuronal profiles which are presumably preganglionic axons. The immunoreactive fibers were presynaptic at all these synaptic sites. In addition, some synaptic contacts were found between two adjacent immunoreactive nerve fibers. These findings strongly suggests that VIP might be involved in the ganglionic transmission of the prevertebral ganglia.

Animals↗
PubMed1981

An electron microscopic study on substance P-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs.

Substance P-immunoreactive nerve fibers in the celiac ganglion of guinea pigs were revealed with the PAP procedures to contain abundant small clear vesicles mixed with a few large granular vesicles. The immunoreactive materials were localized around cytoplasmic components including vesicles and on the inside of the plasma membrane. The immunoreactive fibers directly apposed to unlabelled dendrites of postganglionic neurons and also to preganglionic axons. Morphological features of synapses could be identified at sites of apposition to unlabelled dendrites: clusters of vesicles in the immunoreactive fibers, intercellular spaces of about 20 nm, and an intermediate density on the postjunctional membrane of unlabelled dendrites. On the other hand, no distinct electron density together with accumulations of vesicles was seen underneath the apposed membrane of unlabelled axons. These findings indicate at the ultrastructural level that substance P-fibers form axo-dendritic synapses on the postganglionic neurons and also suggest the presence of the presynaptic interaction between substance P-fibers and some preganglionic axons in this ganglion.

Animals↗
PubMed1981

Evolutionary aspects of "brain-gut peptides": an immunohistochemical study.

Phylogeny of biogenic peptides and their source cells was studied by immunohistochemistry and electron microscopy. The distribution of the peptide containing neurons and paraneurons in the brain and in the gastroenteropancreatic endocrine system was depicted, especially in the bullfrog as the representative of deuterostomia and in the cockroach and some other insects as the representatives of protostomia. Stress was given to: (1) calcitonin-immunoreactive neurons in bullfrog hypothalamus and PP-reactive neurons in the cockroach protocerebrum as instances of transmissional-hormonal partition of a neuropeptide, (2) open-type endocrine cells in the gut structurally and functionally common to the protostomia and deuterostomia, and (3) phylogeny of the prohormones with special reference to big gastrin and proglucagon (glicentin).

Animals↗