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T Toyota

Publications and source records attributed to T Toyota.

At least 325 records · Page 18Linked to original sources
PubMed1987

An immunohistochemical study of methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactivity-containing neurons in the parasympathetic preganglionic regions of the rat spinal cord.

The localization of the methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu)-like immunoreactivity-containing neurons in the rat lumbosacral spinal cord was immunohistochemically examined by an antiserum very specific to Met-Enk-Arg-Gly-Leu. The immunoreactive neurons occupied the positions corresponding to the parasympathetic preganglionic nuclei determined by the previous horseradish peroxidase (HRP)-tracing experiments. The present study suggests that the parasympathetic preganglionic neurons in the rat lumbosacral spinal cord produce preproenkephalin A and its related peptides.

Animals↗
PubMed1987

ATP-Mn2+ stimulates the generation of a putative mediator of insulin action.

Substantial evidence suggests that insulin receptor-associated protein kinase may play a pivotal role in the expression of the intracellular effects of insulin. This study was undertaken to determine whether insulin receptor kinase contributes to the generation of putative insulin mediators. The effect of ATP and divalent cation addition on the production of insulin mediators from liver plasma membranes was investigated. ATP (1 mM) added to liver plasma membranes in the absence of divalent cations enhanced insulin-stimulated release/generation of mediator slightly (approximately 3-fold). ATP in the presence of Mn2+ further increased release/generation of mediator markedly (approximately 100-fold). In contrast, ATP in the presence of Mg2+ had no stimulatory effect. Mn2+ and Mg2+ alone were ineffective. Addition of EDTA completely diminished the stimulatory effects of insulin, ATP, and Mn2+. The stimulation was ATP-specific since other nucleotides and nonhydrolyzable analogues of ATP had no or very weak activity. ATP-Mn2+ stimulated insulin-dependent mediator release/generation in a dose-dependent manner. These results suggest that insulin mediator release/generation is markedly stimulated by an ATP-Mn2+-dependent phosphorylation reaction, similar to insulin-stimulated receptor tyrosine kinase phosphorylation.

Adenosine Triphosphate↗
PubMed1987

Ultrastructural alterations in cardiac muscle of diabetic BB Wistar rats.

The cardiac muscle of BB Wistar rats suffering from diabetes for 8 and 16 weeks (8-Wk and 16-Wk of DM) were examined by light and electron microscopy. The diabetic rats were kept alive by injections of small doses of insulin and exhibited severe hyperglycaemia, glycosuria and weight loss. The heart/body weight ratio of all diabetic groups was greater than that of age matched controls. Over the experimental period, the left ventricular myocardium of the diabetic BB rats sustained damage that was progressively more serious with the duration of the diabetic state. In BB rats after 8-wk of diabetes the myocardium contained large numbers of lipid droplets and glycogen granules around mitochondria which showed patchy swelling, and slight loss of myofilaments. Disruption of mitochondrial membranes and extensive loss of myofilaments were seen in rats diabetic for 16 wk. In addition, dilatation of the sarcoplasmic reticulum-transverse tubular system, formation of a contraction band and myelin bodies and widening of the intercellular space at the fasciae adherens of the intercalated disc were characteristically observed in BB rats after 16-wk of diabetes. However, there were no evident alterations in the capillaries of any diabetic BB rats. Morphometric analyses showed the volume percentage of myofibrils in diabetic rats to be significantly decreased when compared with controls. The loss of myofibrillar elements may be a primary damage induced by insulin deficiency. The formation of contraction bands suggests Ca2+ overload caused by diabetic metabolic disturbances.

Actin Cytoskeleton↗
PubMed1987

Characterization of the insulin receptor kinase from human erythrocytes.

The insulin receptor from human erythrocytes was studied for receptor-associated tyrosine kinase activity. Receptor phosphorylation was performed by incubation of the receptor with [gamma-32P]ATP and Mn2+ in the presence or absence of insulin, and the phosphorylated receptor was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In Triton X-100-solubilized, and partially purified, receptor preparations, insulin stimulated the phosphorylation of a 95,000 dalton protein in a dose-dependent fashion. Immunoprecipitation with antiinsulin receptor antibodies indicates that this 95,000 dalton protein corresponds to the beta-subunit of the insulin receptor. Phosphoaminoacid analysis revealed that 32P incorporation occurred predominantly on tyrosine residues of the beta-subunit. In addition, the insulin receptor kinase catalyzed the phosphorylation of Histone H2b. Dose response curves for insulin-stimulated phosphorylation of the beta-subunit and Histone H2b were sigmoidal. Both half-maximal effects were observed at 3 X 10(-9) M insulin with maximal effects at 10(-6) M. When insulin binding was examined under the same conditions as phosphorylation, the dose-response curves for receptor occupancy and the kinase activation were nearly superimposable, indicating few or no spare receptors for this response to insulin. Insulin-stimulated receptor phosphorylation was diminished by treatment with N-ethylmaleimide, indicating that the receptor possesses sulfhydryl groups, which are important for its enzyme activity. This study demonstrates that insulin receptor kinase from human erythrocytes shares characteristics which are similar to those found in other classical insulin target cells and tissues.

Adenine Nucleotides↗
PubMed1987

[The effect of cisapride on gastric emptying time and release of gastrointestinal hormones].

Cisapride is a novel gastrointestinal prokinetic drug. The aim of the present study was to investigate gastric emptying time and secretion of gastrointestinal hormones (Gastrin, Motilin, Glucagon) after single oral intake of 5 mg or 10 mg cisapride. The healthy men aged 23-55 years participated the study. The gastric emptying time and gastrointestinal hormones were measured by gamma-camera radioisotopic technique and radioimmunoassay, respectively. The half time of emptying phase was reduced from 31.78 min to 29.88 min, and emptying rate increased in 10 mg cisapride group. There was a tendency that cisapride accelerated a stimulation of Motilin secretion.

Adult↗
PubMed1986

An immunohistochemical study of methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactivity-containing liquor-contacting neurons (LCNs) in the rat spinal cord.

The localization of methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu)-like immunoreactivity in the medullospinal liquor-contacting neurons (LCNs) of the rat was immunohistochemically investigated using a modified Sternberger's PAP method. In this study, we also examined the distribution of Met-Enk-Arg-Gly-Leu-like immunoreactive LCNs in the entire length of the medulla oblongata and spinal cord. The immunoreactive LCN possessed an oval, polygonal or rod-shaped perikaryon which protruded an axon-like process and a CSF-contacting process. In the entire length of the medulla oblongata and spinal cord, 60-70 immunoreactive LCNs were observed. They were sparsely distributed along the central canal. The ratio of the number of immunoreactive LCNs in each segment/total number of immunoreactive LCNs in the medulla oblongata and whole spinal cord was as follows: medulla oblongata, 0%; cervical segments, 28.1%; thoracic segments, 56.8%; lumbar segments, 12.0%; sacral segments, 3.0%; and coccygeal segments, 0%. When the immunoreactivity of perikarya of LCNs was weak, a few nerve terminals with a strong Met-Enk-Arg-Gly-Leu-like immunoreactivity were noticed on them. These findings suggest that preproenkephalin A-related opioid peptides including Met-Enk-Arg-Gly-Leu may be secreted into the cerebrospinal fluid (CSF) through the terminal portions of axon-like processes and/or CSF-contacting processes of LCNs. Enkephalin-containing nerve terminals on the LCNs may represent modulating afferents aiding the receptive and/or secretory functions of the neurons.

Animals↗
PubMed1986

A culture method for the isolation of pancreatic islet cells from young rats.

Following digestion of a single pancreas from 30- to 50-day-old Sprague Dawley rats, many single cells and small cell clusters were obtained. Over a succeeding 5-day interval in tissue culture, many islet-like cell clusters were noted. They were smaller than isolated intact rat islets and appeared to develop from selective aggregation of islet cells. More than 1,000 of these islet-like clusters were obtained from a single pancreas. The physiologic characteristics of these cells indicated preservation of insulin secretory responses to glucose (30, 50, 100, 150, 200, and 300 mg/dl), theophylline (1.5 mM), and arginine (10 mM). This appears to be a useful method to follow when large quantities of islet cells are required, as for transplantation.

Animals↗
PubMed1986

Quantitative evaluation of diabetic autonomic neuropathy by using heart rate variations: relationship between cardiac parasympathetic or sympathetic damage and clinical conditions.

It was previously suggested that respiratory heart rate (HR) variations were predominantly affected by the parasympathetic nerve and HR increase to standing was predominantly affected by the sympathetic nerve. To compare parasympathetic and sympathetic nerve function in diabetics, these two tests were performed in 95 diabetics and 38 controls by use of an instantaneous-HR-change continuous recorder. All subjects were between 40 and 59 years-old. As indices of autonomic nerve function, the mean difference between maximal and minimal HR during deep breathing (delta I-E) and the HR increase on standing (delta HR) were determined. The mean delta I-E and delta HR in the diabetics were 9.4 beats/min and 15.1 beats/min, respectively. These values were significantly lower than those in the controls (delta I-E 14.4, delta HR 20.5 beats/min). delta I-E correlated negatively to duration of diabetes and mean fasting blood glucose during the last 6 months in the diabetics, but delta HR did not correlate to them at all. Diminished delta I-E was found in the patients with insulin treatment, retinopathy or persistent proteinuria. Diminished delta HR, however, was found only in the patients with long-standing complicated diabetes. Thus, both cardiac parasympathetic and sympathetic nerve function were significantly impaired in the diabetics as compared with the controls and that parasympathetic nerve damage occurred early whereas sympathetic innervation was preserved.

Adult↗
PubMed1986

Inhibitory effects of rimorphin and dynorphin on insulin secretion from the isolated, perfused rat pancreas.

In order to settle the question about whether or not opioid peptides stimulate or inhibit insulin secretion, we studied effects of rimorphin and dynorphin, two members of the preproenkephalin B group, on glucose-induced insulin secretion in the isolated, perfused rat pancreas. These peptides (3.95 X 10(-8) M), like morphine (3.95 X 10(-8) M), significantly inhibited the glucose-induced insulin secretion. The inhibitory effect of rimorphin was attenuated by naloxone (1.2 X 10(-6) M) and phentolamine (10(-6) M), suggesting an involvement of adrenergic alpha receptors in the inhibition of glucose-induced insulin secretion mediated through specific opiate receptors. Rimorphin also inhibited glucose-induced insulin secretion even in the cysteamine-treated rat pancreas from which somatostatin had been depleted. Thus, somatostatin does not appear to play a major regulatory role in the insulin secretion in the pancreas.

Animals↗
PubMed1986

Streptococcal preparation (OK-432) inhibits development of type I diabetes in NOD mice.

OK-432 (a streptococcal preparation) has been widely used for cancer immunotherapy in Japan. It is the most potent immunomodulator in activating both macrophages and killer T cells and in increasing interleukin 2 production. Two K.E. (Klinische Einheit, clinical unit) of OK-432 were given intraperitoneally to each of 17 female nonobese diabetic (NOD) mice every week from 4-24 wk of age. NOD mice as well as BB rats spontaneously develop type I diabetes. During administration of OK-432, the development of diabetes was inhibited in 17 of 17 mice over the 24-wk observation period, whereas 14 of 17 female NOD mice given physiological saline had developed diabetes by 24 wk of age. At the onset of diabetes, nonfasting blood glucose was 511 +/- 82 mg/dl. Histologic examination showed that in the OK-432-treated NOD mice, 98% of total islets were intact or mildly infiltrated with mononuclear cells, whereas in saline-treated NOD mice, 79% of total islets exhibited severe insulitis. In OK-432-treated NOD mice, both the number of the mononuclear spleen cells and their natural killer cell activity was significantly increased.

Animals↗
PubMed1985

[Met-enkephalin-Arg-Gly-Leu-like immunoreactivity-containing nerve elements in the guinea-pig intestine. An immunohistochemical study using whole mount preparations].

The localization and distribution of Met-enkephalin-Arg-Gly-Leu (Met-Enk-Arg-Gly-Leu)-like immunoreactivity in whole mount preparations of different layers of guinea-pig gut (duodenum, jejunum, ileum and proximal colon) were studied by Sternberger's indirect immunocytochemistry. Anti-Met-Enk-Arg-Gly-Leu serum used as the primary antiserum was raised in a rabbit against synthetic Met-Enk-Arg-Gly-Leu coupled to ascaris protein by the glutaraldehyde method. The results obtained were summarized as follows: In the intestinal wall of the guinea-pig, Met-Enk-Arg-Gly-Leu-like immunoreactivity was localized only in nerve elements of the enteric nervous system. In the myenteric plexus, many perikarya showed Met-Enk-Arg-Gly-Leu-like immunoreactivity. Immuno-positive nerve fibers showing varicose appearance were demonstrated not only in the myenteric plexus but also in the longitudinal muscle layer, in the circular muscle layer, in the deep muscular plexus, in the submucous plexus and in the muscularis mucosae. No immuno-positive perikarya were found in the submucous plexus. Met-Enk-Arg-Gly-Leu-like immunoreactivity was not shown in the perivascular plexus and in the mucosa. Compared to those of the duodenum, jejunum or ileum, immuno-positive perikarya in the myenteric plexus of the proximal colon were apparently few in number. The density of a network in the deep muscular plexus formed by immunoreactive fibers was looser in the proximal colon than that in the duodenum, jejunum or ileum. Since Met-Enk-Arg-Gly-Leu-like immunoreactivity-containing nerve elements were densely distributed in the muscular layers of the intestinal wall, it is possible for this nervous system to regulate the contractility of the smooth muscles of the gut.

Animals↗
PubMed1985

Methionine-enkephalin-Arg6-Gly7-Leu8-immunoreactive nerve fibers and cell bodies in lumbar paravertebral ganglia and the celiac-superior mesenteric ganglion complex of the rat: an immunohistochemical study.

Lumbar paravertebral ganglia and prevertebral ganglia of the rat were immunohistochemically examined using an antiserum against Methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu). Colchicine (5 mg/kg body wt., i.p. injection) was employed as an axonal transport blocker to intensify the immunoreactivity in the nerve cell bodies. In the lumbar paravertebral ganglia of the colchicine-treated rats, about 55% of nerve cell bodies showed a positive immunoreactivity. In the celiac-superior mesenteric ganglion complex, a dense network of positively immunostained nerve fiber varicosities surrounded immunonegative nerve cell bodies. The Met-Enk-Arg-Gly-Leu-like immunoreactivity demonstrated in this study suggests the occurrence of preproenkephalin A and related opioid peptides.

Animals↗
PubMed1985

[Met-enkephalin-Arg-Gly-Leu-like immunoreactivity-containing nerve fibers and cell bodies in the abdominal sympathetic ganglia of the rat--an immunohistochemical study].

The occurrence and localization of Met-enkephalin-Arg-Gly-Leu (Met-Enk-Arg-Gly-Leu)-like immunoreactivity in the lumbar paravertebral ganglion and the superior mesenteric ganglion in the rat were investigated by immunocytochemistry. Colchicine was employed as an axonal flow blocker to accumulate Met-Enk-Arg-Gly-Leu in the nerve cell bodies. The Met-Enk-Arg-Gly-Leu serum (R 0171) was produced by immunizing a mixed breed female rabbit with synthetic Met-Enk-Arg-Gly-Leu conjugated to ascaris protein by the glutaraldehyde method. Sections, 7 micron in thickness, of Bouin-fixed and paraffin-embedded tissues were immunostained by the peroxidase-antiperoxidase (PAP) method. Results obtained were summarized as follows: Colchicine-untreated rats possessed no strongly-immunoreactive nerve cell bodies for Met-Enk-Arg-Gly-Leu in the lumbar paravertebral ganglion, though a few of them were weakly immunopositive. Met-Enk-Arg-Gly-Leu-like immunoreactivity showing nerve fibers were occasionally seen in nerve fiber bundles of the lumbar paravertebral ganglion. In the superior mesenteric ganglion, a dense network of positively immunostained nerve fibers with a beaded appearance were seen around nerve cell bodies which were immunonegative for Met-Enk-Arg-Gly-Leu. In colchicine-treated rats, 55 percent of nerve cell bodies of the lumbar paravertebral ganglion showed various degrees of positive immunoreactivities for Met-Enk-Arg-Gly-Leu. Many strongly immunostained nerve terminals were seen in the lumbar paravertebral ganglion of colchicine-treated rats. In the superior mesenteric ganglion, the immunoreactivity for Met-Enk-Arg-Gly-Leu in the beaded nerve fibers around nerve cell bodies was intensified by the colchicine treatment, whereas the nerve cell bodies themselves remained immunonegative for Met-Enk-Arg-Gly-Leu.

Animals↗