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Biomedical subjects

T Nagata

Publications and source records attributed to T Nagata.

At least 451 records · Page 25Linked to original sources
PubMed1991

Electron microscopic radioautographic study on the incorporation of 3H-proline by mouse decidual cells.

A qualitative radioautographic analysis showed that mature decidual cells of the mouse are able to incorporate 3H-proline. After 1 hour silver grains are concentrated mainly over these cells although some of them can be found over collagen fibrils. After 2,6 and 24 hours there is a progressive increase of silver grains on the extracellular space most of them concentrated over thick collagen fibrils. These results strongly indicate that mature decidual cells of the mouse produce collagen and that they conserve a behavior of the fibroblast from which they originated.

Animals↗
PubMed1990

zeta-Related protein kinase C in nuclei of nerve cells.

To determine whether or not PKC is present in the nuclei of nerve tissue we made use of biochemical and immunocytochemical techniques. A 219-fold purification of rabbit brain nuclear protein kinase C was achieved by sequential steps of Triton X-100 extraction of isolated nuclei, DEAE-cellulose, Butyl-toyopearl and hydroxylapatite chromatography. The major peak of protein kinase C activity was eluted from the hydroxylapatite column at the KPO4 concentration of 0.3 M. Both Ca2+ and Ptd Ser were required for stimulation of the enzyme. Immunoblot analysis revealed that the kinase fraction was immunoreactive with a polyclonal antibody, PC-zeta, that had been raised against a peptide synthesized according to the deduced sequence of rat zeta protein kinase C. Light-microscopy revealed strong immunoreactivity in the nuclei of Purkinje cells in cerebellum and pyramidal cells in the rat cerebral cortex. These observations suggest that a zeta-related protein kinase C is present in the nuclei of nerve cells.

Animals↗
PubMed1990

Inhibition of cell growth and stable DNA replication by overexpression of the bla gene of plasmid pBR322 in Escherichia coli.

A composite plasmid comprising the mini-F and pBR322 replicons was found to inhibit cell growth of a host with conditional mutations in dnaA and rnh under restrictive conditions, where the normal initiation of replication from oriC was inactivated, but the alternative replication initiation from oriK was active. It was further shown that the composite plasmid inhibited stable DNA replication (SDR) which occurs constitutively in cells mutant for rnh. Neither pBR322 nor mini-F alone produced these inhibitory effects. Deletion analyses revealed that the mini-F segment responsible for the inhibition of both processes was the promoter region of the sopA gene which had been cloned into a site upstream of the bla gene on pBR322 in such an orientation as to cause overexpression of bla. Inserting the promoter of the Escherichia coli lac gene into the same site had the same effect. Introduction of a deletion and a frameshift mutation into bla abolished the inhibition. Thus, the inhibition of growth and SDR appear to be due to overproduction of the bla gene product, beta-lactamase.

Chloramphenicol Resistance↗
PubMed1990

Discrepancy of protein kinase C translocation and platelet aggregation--immunocytobiochemical evidence.

We searched for possible relationships between platelet aggregation induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA) or thrombin and the translocation of protein kinase C. Using monoclonal antibodies against subspecies of protein kinase C, we noted a predominant expression of the isozyme, type II, in human platelets (M. Watanabe, M. Hagiwara, K. Onoda, and H. Hidaka, 1988, Biochem. Biophys. Res. Commun. 152, 642). Analysis of the subcellular distribution of protein kinase C revealed that 65% of the kinase activity was present in the cytosolic fraction in unstimulated platelets, with the remaining activity in the membrane fraction. Treatment of platelets with 100 nM TPA resulted in a greater than 60% decrease in protein kinase C activity in the cytosolic fraction and a greater than 200% increase in the activity in the membrane fraction, within 10 min after treatment. Translocation of the enzyme was also found after treatment of platelets with thrombin, although the response was of lower magnitude than that induced by TPA. Similar results were obtained by immunoblotting using MC-2a, an anti-type II protein kinase C monoclonal antibody. We also examined localization of the enzyme, by electron microscopic immunocytochemistry. The presence of type II protein kinase C seemed to be localized mostly in hyaluromeres and not in granulomeres. When platelets were fixed just after the addition of TPA (within 1 min), protein kinase C was localized at the submembranal region with no remarkable change in shape but there was a decrease in the number of granules in the cytoplasma and the open canalicular system was dilated. We then investigated the effects of cytochalasin B, W-7, ML-9, and H-7 on TPA-induced platelet aggregation and the translocation of protein kinase C. W-7 and ML-9 potently inhibited platelet aggregation but none of these compounds hampered the translocation. Thus, activation of protein kinase C may not be a complete requirement for the initiation of platelet aggregation.

Antibodies, Monoclonal↗
PubMed1990

A complement-dependent neutralizing monoclonal antibody against glycoprotein II of pseudorabies virus.

A monoclonal antibody (MAb), 1.21, was produced against pseudorabies virus (PRV). It exhibited virus neutralization activity only in the presence of complement. Immunoblot analysis after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of virions revealed that MAb 1.21 bound with the 230 kilodalton (kD) virus protein only under non-reducing conditions. This protein was purified by immuno-affinity chromatography using MAb 1.21 and was found to be composed of three subunits, 60, 70 and 120 kD polypeptides when analyzed by SDS-PAGE under reducing conditions. This protein is probably glycoprotein II of PRV.

Animals↗
PubMed1990

Methamphetamine and amphetamine concentrations in postmortem rabbit tissues.

The feasibility of detecting methamphetamine and its major metabolite, amphetamine, in postmortem tissues over a 2-year period was examined. It is important to determine if the abuse and toxic effects of drugs can be proved from evidence found in decayed, submerged, or stained tissue materials. The blood, urine, liver, skeletal muscle, skin and extremity bones from rabbits given methamphetamine intravenously were kept at room temperature, under 4 different conditions: sealed in a test tube, dried in the open air, submerged in tap water and stained on gauze. Methamphetamine was present in all the samples, with slight change in concentration in case of sealed and air dried tissues. Changes varied in bones kept in water. There were considerable decreases in methamphetamine in blood and urine stains. Despite long term storage, drug abuse and/or toxicity could be determined, in all tissues examined.

Amphetamine↗
PubMed1990

Location of the cis-acting auxin-responsive region in the promoter of the par gene from tobacco mesophyll protoplasts.

We have isolated a genomic clone of an auxin-regulated par gene, which is expressed during the transition from G0 phase to S phase in the early stage of tobacco mesophyll protoplasts cultured in vitro, from a tobacco genomic library using the par cDNA as a probe. When a chimeric gene, in which a reporter gene for bacterial beta-glucuronidase (GUS) was placed downstream of the 5' flanking sequences of the par gene, was introduced into tobacco mesophyll protoplasts by electroporation, the chimeric gene elicited auxin-regulated expression of GUS activity. Because deletion of a 111-base-pair (bp) direct repeat in the 5' flanking sequences of the par gene abolished the auxin-induced GUS activity, it is deduced that in the 111-bp direct repeat of the par gene promoter is localized an auxin-responsive region, which regulates auxin-mediated activation of transcription.

Amino Acid Sequence↗
PubMed1990

Ventricular enlargement in normal weight bulimia.

Cranial computed tomography (CT) scans of 17 patients with bulimia were compared with those of 21 age- and sex-matched controls. The ventricular brain ratio (VBR) of the bulimics was 7.29, which was significantly greater than the 4.55 seen in controls. However, no correlation was found between VBRs and clinical variables, endocrine or metabolic parameters.

Adolescent↗
PubMed1990

Insulin sensitivity in patients with anorexia nervosa and bulimia.

Insulin sensitivity was studied using the euglycemic insulin clamp technique in 5 female patients with anorexia nervosa and 4 females with bulimia. The results were compared with those of 15 male patients with non-insulin-dependent diabetes mellitus. Euglycemic insulin clamp is performed for 2 h using the Biostator, during which time insulin was infused at a rate of 0.77 mU kg-1 min-1. Fasting plasma glucose and immunoreactive insulin tended to be lower in patients with anorexia nervosa than in those with bulimia (69.8 +/- 6.7 vs 75.9 +/- 7.7 mg/dl, and 5.9 +/- 2.0 vs 9.8 +/- 3.4 U/ml). The mean metabolic clearance rate (MCR) was 9.2 +/- 3.9 ml kg-1 min-1 for patients with anorexia nervosa, 5.1 +/- 2.2 ml kg-1 min-1 for patients with bulimia, and 3.8 +/- 0.3 ml kg-1 min-1 for patients with diabetes mellitus. However, one anorectic had a significantly high MCR. One anorectic and 3 bulimics had a significantly low MCR. These results suggest that insulin sensitivity varied in patients with anorexia nervosa, whereas it tended to decrease in some patients with bulimia but not to the same degree as in patients with diabetes mellitus.

Adult↗
PubMed1990

Carbon- and Nitrogen-to-Volume Ratios of Bacterioplankton Grown under Different Nutritional Conditions.

Carbon- and nitrogen-to-volume (C/V and N/V) ratios were determined for freshwater bacterial assemblages grown in lake water filtrate or in water enriched with nutrients (aqueous extract of lake seston, glucose, arginine, phosphate, or ammonium). Biovolume was measured by epifluorescence microphotography, and carbon and nitrogen biomasses were measured with a CHN analyzer. Despite large variations of nutritional conditions (i.e., the composition and concentration of the dissolved organic carbon) and different mean cell sizes of the bacterial assemblage (0.17 to 1.8 mum per cell), the C/V, N/V, and carbon-to-nitrogen weight ratios varied little (C/V ratio, 0.14 pg of C per mum [standard deviation, 0.057; n = 15]; N/V ratio, 0.027 pg of N per mum [standard deviation; 0.011, n = 15]; carbon-to-nitrogen weight ratio, 5.6 [standard deviation, 2.2, n = 15]). An average C/V ratio of 0.12 pg of C per mum that was derived from natural and cultured bacterial assemblages is proposed as an appropriate conversion factor for estimation of the biomass of freshwater bacteria.

Journal Article↗
PubMed1990

Radical scavengers of indapamide in prostacyclin synthesis in rat smooth muscle cell.

Indapamide, a nonthiazide diuretic, exhibits direct vasodilator action as well as natriuretic and diuretic effects. Although calcium antagonist-like activity has been addressed so far, the mechanisms for vasodilator effect are still uncertain. To understand the wide range of indapamide actions, we examined the effects of indapamide on the vascular eicosanoid generation and investigated its mechanisms by using rat vascular smooth muscle cells in culture. Indapamide uniquely increased the prostacyclin generation in the vascular smooth muscle cells in a dose-dependent manner, whereas it did not affect the vasoconstrictor thromboxane A2. Thiazide diuretics lowered the prostacyclin generation, while nonthiazide derivatives did not affect the biosynthesis. Enzymatic analysis revealed that indapamide affected neither [14C]arachidonate liberation nor prostacyclin synthase of the smooth muscle cells. Indapamide eliminated a stable free radical in a cell-free system, lowered the formation of malondialdehyde from lipid peroxides in rat brain homogenate, and reduced lipid peroxidation by the free radical generating system of xanthine-xanthine oxidase. Indeed, the scavenging action of indapamide significantly attenuated the inhibitory activity of 15-hydroperoxy-arachidonate to prostacyclin synthase activity. These results indicate that indapamide diuretic increases prostacyclin generation in the vascular smooth muscle cells possibly through antioxidant effects and that the enhanced prostacyclin generation is partly responsible for its direct vasodilator action.

Animals↗
PubMed1990

Immunoelectron microscopy of tissues processed by rapid freezing and freeze-substitution fixation without chemical fixatives: application to catalase in rat liver hepatocytes.

We report on the immunohistochemical demonstration of an enzyme at the electron microscopic level using specimens processed by rapid freezing and the freeze-substitution technique without the use of any chemical fixatives. Fresh rat liver tissue blocks were rapidly frozen by the metal contact method using liquid nitrogen, and were freeze-substituted with acetone without any chemical fixatives at -80 degrees C. Some of the freeze-substituted tissues were embedded in Lowicryl K4M at -20 degrees C; the others were returned to room temperature and embedded in Epok 812 at 60 degrees C. Ultra-thin sections were stained using anti-peroxisomal catalase antibody by the protein A-gold technique. The ultrastructure of the hepatocytes was very well preserved compared with that of conventionally processed tissues. The labeling for catalase was confined to peroxisomes. When the labeling density was compared among freeze-substituted tissues and conventionally processed tissues, that of freeze-substituted and Lowicryl K4M-embedded tissues was the most intense. These results show the usefulness of freeze-substituted tissues for immunohistochemical analysis of cell organelles.

Animals↗
PubMed1990

Different expression of protein kinase C isozymes in pancreatic islet cells.

To elucidate differential roles of protein kinase C isozymes in pancreatic islet cells, the precise localization of the isozymes in rabbit and rat islet endocrine cells was investigated using monoclonal antibodies specific for three types of the enzyme. We detected strong immunoreactivity for the type III protein kinase C in B cells. Immunoreactivity for the type II enzyme was seen in A cells, and no apparent immunoreactivity for type I was observed in the islet cells. The expression of the type III protein kinase C in B cells was confirmed using rat insulinoma cells. The predominant expression of the type III enzyme in these cells was shown by immunoblotting. Moreover, on the basis of an enzyme-linked sandwich immunoassay, the levels of protein kinase C isozymes were determined in these cells. The significant amounts of the type III enzyme was detected, but the contents of the type I and II enzyme were under detectable level. These results suggest that the type III protein kinase C is involved in the regulation of insulin release in pancreatic B cells.

Adenoma, Islet Cell↗
PubMed1990

Electron microscopic radioautographic study of the localization of an anti-allergic agent, Tranilast, in rat mast cells.

We have previously reported that Tranilast, an anti-allergic agent, was rapidly taken into the cytoplasm of rat mast cells in vitro by means of light microscopic radioautography. The present study was performed at the electron microscopic level to elucidate the fine localization of this agent in the mast cells. The results revealed that the number of radioautographic silver grains in the cells increased by the incubation with 3H-labelled Tranilast for 0 to 60 min. and that many silver grains were localized on the specific granules, especially on the perigranular membranes. These results suggest that the mode of inhibitory action of mast cell degranulation by Tranilast is related to the specific localization of this agent on the perigranular membranes.

Animals↗
PubMed1990

Localization of the anti-allergic agent tranilast in the urinary bladder of rats as demonstrated by light microscopic radioautography.

Tranilast (N-(3,4-dimethoxycinnamoyl)anthranilic acid), an anti-allergic drug, has been developed and used for the treatment of anaphylactic hypersensitivity such as bronchial asthma in Japan. Recently, many cases with eosinophilic cystitis associated with administration of this drug have been reported. In a series of studies to elucidate the pathoetiology of this unusual cystitis, the distribution of tranilast in urinary bladder of rats was investigated. Light microscopic radioautography using tritiated tranilast showed that this drug was localized specifically in the transitional epithelial cells of the mucosa and the endothelial cells of venous vessels for a fairly long time after an oral administration. These results should be taken into consideration in further studies of this drug-associated cystitis.

Animals↗