Biomedical subjects

T Shimazu

Publications and source records attributed to T Shimazu.

At least 19 recordsLinked to original sources

PubMed1992

Three-dimensional crystal structure of recombinant murine interferon-beta.

The crystal structure of recombinant murine interferon-beta (IFN-beta) has been solved by the multiple isomorphous replacement method and refined to an R-factor of 20.5% against 2.6 A X-ray diffraction data. The structure shows a variant of the alpha-helix bundle with a new chain-folding topology, which seems to represent a basic structural framework of all the IFN-alpha and IFN-beta molecules belonging to the type I family. Functionally important segments of the polypeptide chain, as implied through numerous gene manipulation studies carried out so far, are spatially clustered indicating the binding site(s) to the receptor(s). Comparison of the present structure with those of other alpha-helical cytokine proteins, including porcine growth hormone, interleukin 2 and interferon gamma, indicated either a topological similarity in chain folding or a similar spatial arrangement of the alpha-helices.

Amino Acid Sequence↗

PubMed1992

Alteration in sympathetic nerve activity during liver regeneration in rats after partial hepatectomy.

To determine if the sympathetic nerve has a role in liver regeneration, the alterations of tissue norepinephrine (NE) content and its turnover were measured in rats after partial hepatectomy. NE content per unit liver mass decreased progressively to about one-fourth of controls by the ninth day after partial hepatectomy. Since the total amount of NE in the whole liver did not change during nine days of liver regeneration, it was supposed that sympathetic innervation could make slower progress than proliferation of hepatocytes. Fractional turnover rate of NE was reduced transiently in regenerating liver 24-48 h after partial hepatectomy and recovered to normal 8-9 days after the operation. Such a transient reduction of NE turnover was observed specifically in the liver. These results suggest that sympathetic nerve activity of the liver is suppressed at the early stage of regeneration.

Animals↗

PubMed1992

Vanadate stimulates D-glucose transport into sarcolemmal vesicles from rat skeletal muscles.

Vanadate is known to have various insulin-like actions including activation of D-glucose uptake into the skeletal muscle and adipose tissue. In this study, we examined the effect of orthovanadate on D-glucose uptake into sarcolemmal vesicles prepared from rat hind limb skeletal muscles. In the presence of 10 mM vanadate, the initial rate of D-glucose uptake into sarcolemmal vesicles was enhanced 4-5 times above the basal value. Half-maximal concentration for this effect of vanadate was 3 mM. The D-glucose uptake was also stimulated by metavanadate, but not by selenite, selenate, or molybdate. When vanadate was removed from the vesicles by dilution and centrifugation, D-glucose uptake into the vesicles returned to the basal level, indicating that the effect of vanadate was reversible. Saturation curves showed that the Vmax value for the D-glucose uptake was enhanced more than 4-fold by 10 mM vanadate. Therefore, the activation of D-glucose uptake was due, at least in part, to a large increase in the Vmax value. These results suggest that vanadate increases the intrinsic activity (turnover number) of skeletal muscle glucose transporters in a reversible manner.

Animals↗

PubMed1992

Effects of ventromedial hypothalamic stimulation on glucose transport system in rat tissues.

Electrical stimulation of the ventromedial hypothalamus (VMH) increased the rate constant of glucose uptake in rat heart and brown adipose tissue (BAT), as measured in vivo by the 2-deoxy-D-[3H]glucose method. The increase in glucose uptake in BAT was abolished by local sympathetic denervation. To analyze the mechanism of this hypothalamic modulation, the effects of VMH stimulation and insulin treatment on the number and dissociation constant (Kd) of glucose transporters in the plasma and microsomal membranes were examined by means of [3H]cytochalasin B binding. VMH stimulation did not alter either the number or Kd value of glucose transporters in plasma and microsomal membranes prepared from heart and BAT, whereas insulin treatment increased the number of glucose transporters in the plasma membranes and decreased those in the microsomal membranes. D-Glucose transport activity was also measured with the same plasma membrane vesicles. An apparent functional activity of transporters was detected to be increased in the heart and BAT plasma membranes after VMH stimulation but not after insulin treatment. These results suggest that VMH stimulation enhances glucose utilization in heart and BAT via sympathetic innervation and that the mechanism by which VMH stimulation increases tissue glucose uptake is different from that of insulin, possibly causing an activation of glucose transporters present in the plasma membrane.

Adipose Tissue, Brown↗

PubMed1992

Effects of concentration reduction and partial replacement of paraquat by diquat on human toxicity: a clinical survey.

Paraquat poisoning was studied in 174 patients over a 12-month period when a new, low concentration paraquat product (4.5% w/v paraquat ion mixed with 4.5% w/v diquat ion; 63 cases) replaced the original high concentration paraquat product (20% w/v paraquat ion only; 111 cases). In both groups approximately 60% of the patients died from circulatory failure accompanied by multiple organ failure within a week of ingesting the products. However, a remarkable reduction in late deaths from respiratory failure was noted in the new product group (17.1% vs 6.3%). This was reflected in this group's improved survival (23.4% vs 34.9%). The improvement in survival seems to be attributable to the dilution of paraquat with diquat which seems to have a different toxicological profile to paraquat.

Blood Urea Nitrogen↗

PubMed1992

Importance of sympathetic nerves for the stimulatory effect of cold exposure on glucose utilization in brown adipose tissue.

The effects of cold exposure on glucose transport system in brown adipose tissue (BAT) and the role of sympathetic nerves in this response were studied in rats. The rate constant of glucose uptake in BAT increased 10-, 13-, and 14-fold after 6 h, 1 d, and 2 d of cold exposure, respectively, as compared with controls. After 2 d of cold exposure, the number of glucose transporters in the plasma membranes increased from 10.2 +/- 1.1 to 16.7 +/- 1.4 pmol/mg protein and the transporter number in the microsomal membranes decreased from 15.1 +/- 1.0 to 9.0 +/- 1.1 pmol/mg protein, as measured by cytochalasin B binding. However, the increase in glucose utilization in BAT preceded the recruitment of glucose transporters to the plasma membranes. Thus, the glucose utilization markedly increased 6 h after cold exposure without significant increase in the glucose transporter number. The apparent dissociation constant (Kd) for cytochalasin B was unchanged. The stimulatory effect of cold exposure on glucose utilization in BAT was prevented by sympathetic denervation. In denervated BAT, cold exposure conversely decreased the number of glucose transporters in the plasma membranes. These results indicate that: (1) cold exposure increases glucose utilization in BAT and promotes translocation of glucose transporters from the microsomes to plasma membranes; (2) the effects of cold exposure depend entirely upon sympathetic innervation of BAT; (3) the recruitment or redistribution of glucose transporters accounts only partly for the large increase in glucose utilization in BAT after acute cold exposure.

Adipose Tissue, Brown↗

PubMed1991

Inhibition of glucose production during hepatic nerve stimulation in regenerating rat liver perfused in situ. Possible involvement of gap junctions in the action of sympathetic nerves.

To explore the possible role of gap junctions in neural regulation of hepatic glucose metabolism, the effects of hepatic nerve stimulation on metabolic and hemodynamic changes were examined in normal and regenerating rat liver which was perfused in situ at constant pressure via the portal vein with a medium containing 5 mM glucose, 2 mM lactate and 0.2 mM pyruvate. 1. The content of connexin 32, a major component of gap junctions in rat liver, decreased transiently to about 25% of the control level in regenerating liver 48-72 h after partial hepatectomy and recovered to normal by the 11th day after the operation. 2. In normal liver, electrical stimulation of the hepatic nerves (10 Hz, 20 V, 2 ms) and infusion of noradrenaline (1 microM) both increased glucose and lactate output and reduced perfusion flow. 3. In early stage of regenerating liver 48 h and 72 h after partial hepatectomy, the increase in glucose output in response to nerve stimulation was almost completely inhibited, whereas the change in lactate balance was partially suppressed and the reduction of flow rate was retained. The response of glucose output to nerve stimulation recovered by the 11th day after partial hepatectomy. In contrast, exogenous application of noradrenaline increased glucose output even in the early stage of regenerating liver. 4. The increase in noradrenaline overflow during hepatic nerve stimulation in the early stage of regenerating liver was approximately the same as in normal liver. Liver glycogen was sufficiently preserved in the early stage of regenerating liver. However, noradrenaline infusion could no more increase glucose output both in normal and in regenerating livers after 24 h of fasting that depleted liver glycogen. These results suggest that the impaired effects of sympathetic nerve stimulation on glucose metabolism observed in regenerating liver are derived neither from reduced release of noradrenaline nor from depletion of liver glycogen, but rather from transient reduction of gap junctions which assist signal propagation of the nerve action through intercellular communication in rat liver.

Animals↗

PubMed1991

Single administration of hepatotoxic chemicals transiently decreases the gap-junction-protein levels of connexin 32 in rat liver.

Effects of a single administration of hepatotoxic chemicals on the major gap-junction protein of liver (connexin 32) were studied in rats. The connexin-32 content was analyzed by immunoblotting and immunohistochemistry using an affinity-purified monoclonal antibody against connexin 32. The connexin-32 content decreased dramatically to less than 10% of the control value 24 h after injection of 25 mg/kg dimethylnitrosamine and returned to the normal level 240 h later. Injection of CCl4 at a dose of 1 ml/kg also caused a transient reduction of connexin-32 content in the liver, as seen after the dimethylnitrosamine injection. The decrease in hepatic connexin-32 content was inversely correlated to the increase in plasmic alanine-aminotransferase activity which has been used as an index of acute liver injury. The changes in connexin 32 were essentially similar to those observed in regenerating liver after partial hepatectomy. However, incorporation of [3H]thymidine into liver DNA after dimethylnitrosamine injection was significantly less than that obtained after partial hepatectomy. The 5'-nucleotidase activity of the plasma-membrane fraction of the liver was not significantly altered by the injection of dimethylnitrosamine. These results suggest that liver gap-junction protein is specifically reduced by acute liver injury and that this kind of decrease in connexin 32 is not simply related to cell proliferation, unlike the decrease after partial hepatectomy.

Alanine Transaminase↗

PubMed1991

Increased neuropeptide Y content in the arcuato-paraventricular hypothalamic neuronal system in both insulin-dependent and non-insulin-dependent diabetic rats.

Neuropeptide Y (NPY) concentration was determined by radioimmunoassay in selected hypothalamic regions microdissected from fresh brain slices of different types of diabetic rats. In spontaneously diabetic (BB) rats and streptozotocin (STZ)-induced diabetic rats, models of insulin-dependent diabetes mellitus, an elevated concentration of NPY was detected in the paraventricular nucleus (PVN) and arcuate nucleus (ARH) of the hypothalamus. In Wistar fatty rats, a model of non-insulin-dependent diabetes mellitus, NPY concentration was also high in the PVN as compared to controls. When STZ-induced diabetic rats were treated with insulin, elevated NPY content in the PVN returned to the normal level. These findings, together with our previous finding of increased secretion of insulin after microinjection of NPY into the PVN, suggest a crucial role of NPYergic neuronal system in the ARH-PVN area in controlling endocrine pancreas and glucose homeostasis.

Adipose Tissue↗

PubMed1991

Studies on the venom components of the long-glanded coral snake, Maticora bivirgata.

The venom of the Asian long-glanded coral snake, Maticora bivirgata, was fractionated into five fractions, S1-S5, by passing through a Sephadex G-50 column. Fraction S2 contains two phospholipases A2, PLA2 I and PLA2 II, fraction S3 contains four cytotoxin homologues, maticotoxins A, C, D1 and D2, and fractions S4 and S5 contain a large amount (about 1 mg/specimen) of adenosine accompanied with smaller amounts of inosine and guanosine. The amino-terminal amino acid sequences of PLA2, I, PLA2 II and maticotoxin A suggest that Maticora bivirgata is closely related to Bungarinae, especially to genera Hemachatus and Naja.

Amino Acid Sequence↗

PubMed1991

Pulmonary contusion causes long-term respiratory dysfunction with decreased functional residual capacity.

To elucidate the mechanism of persistent dyspnea after blunt chest trauma, we prospectively studied the pulmonary function of 18 patients with blunt chest trauma for 6 months. Nine of the patients had flail chest and 12 had pulmonary contusion (PC). Pulmonary function was evaluated using spirometry, arterial blood gas analysis, chest x-ray studies and CT scans. Functional residual capacity (FRC) remained significantly reduced throughout the 6 months in patients with PC. Such patients experienced a fall in Pao2 when changed from a sitting position to a supine position and they had fibrous changes in the contused lung as demonstrated by CT scans at 6 months after injury. These findings were supported in an additional study of another 20 patients who had suffered PC 1 to 4 years previously. This study demonstrated that pulmonary function recovered within 6 months in patients without PC even with a residual deformity of the thoracic wall caused by flail chest, while patients with PC had decreased FRC and a fall in Pao2 when moved to the supine position even several years after injury. This might be related to the persistent dyspnea seen after blunt chest trauma.

Adult↗

PubMed1991

The morphology of smoke inhalation injury in sheep.

Pulmonary injury resulting from inhalation of chemical and particulate products of incomplete combustion is one of the principal determinants of mortality following burn injury. In this study, the histopathology of inhalation injury was examined in sheep. Mild, moderate, or severe smoke injury was produced in anesthetized sheep by insufflation with various doses of ambient temperature smoke, generated by burning polyethylene, wood pulp, and nonwoven cellulose pads. A total of 64 sheep were exposed and evaluated at times ranging from 15 minutes to 4 weeks after exposure. Morphologic changes in the lungs were studied using light microscopy and both transmission and scanning electron microscopy. The primary, dose-responsive injury observed was acute cell membrane damage in the trachea and bronchi leading to edema, progressive necrotic tracheobronchitis with pseudomembrane formation, and airway obstruction. These inflammatory and occlusive effects were followed by congestion, alveolar space edema, atelectasis, and bronchopneumonia. Morphologic changes occurring in the alveolar epithelium following high smoke dosage included intracellular edema in type-I cells, changes in the membrane-bound vacuoles of type-II cells, and septal thickening caused by interstitial edema. No capillary endothelial changes were observed.

Animals↗

PubMed1991

Ventromedial hypothalamic stimulation enhances peripheral glucose uptake in anesthetized rats.

Effects of electrical and chemical stimulation of the ventromedial (VMH) and lateral hypothalamic (LH) nuclei on glucose uptake in peripheral tissues were studied by the 2-deoxy-D-[3H]glucose (2-[3H]DG) method in anesthetized rats. Electrical stimulation of the VMH increased the rate constant of glucose uptake in brown adipose tissue (BAT; 8 times), heart (3 times), and skeletal muscles (1.5 times) but not in white adipose tissue, diaphragm, and brain, without detectable changes in plasma insulin levels. Chemical stimulation of the VMH by microinjection of L-glutamate also enhanced the rate constant of glucose uptake in BAT, heart, and skeletal muscles preferentially, which indicates that the enhancement of glucose uptake in these tissues is derived from activation of VMH neurons. The increased rate of glucose uptake in BAT in response to VMH stimulation was effectively suppressed by surgical sympathetic denervation, suggesting a mediation of the sympathetic nerve in this effect. On the other hand, electrical stimulation of the LH had no appreciable effect on 2-[3H]DG uptake in any tissues. It is concluded that glucose uptake in certain peripheral tissues is accelerated selectively by activation of VMH neurons, the action of which is independent of plasma insulin but which is probably via the sympathetic nervous system.

Adipose Tissue, Brown↗

PubMed1991

Purification and primary structure of C-1027-AG, a selective antagonist of antitumor antibiotic C-1027, from Streptomyces globisporus.

C-1027-AG, a selective antagonist of antitumor antibiotic C-1027, was isolated by column chromatography on DEAE-cellulose, butyl-Toyopearl and Sephadex G-50 from a culture filtrate of Streptomyces globisporus. The amino acid sequence of purified C-1027-AG was determined with a protein sequencer on the basis of fragment peptides obtained by enzymatic hydrolysis with lysylendopeptidase, V8 protease, endopeptidase AspN and chymotrypsin, after performic acid oxidation. C-1027-AG is shown to consist of a single polypeptide chain cross-linked by two disulfide bonds, and to contain a total of 110 amino acid residues with alanine and glycine as its amino- and carboxyl-termini, respectively; its molecular weight was calculated to be 10,500 daltons. The primary structure of C-1027-AG is indicated to be identical to the protein moiety of C-1027, and is highly homologous to the sequences of antitumor proteins obtained from other Streptomyces species.

Amino Acid Sequence↗

PubMed1990

Neural control of biosynthesis and secretion of serum transferrin in perfused rat liver.

The effects of sympathetic- and parasympathetic-nerve stimulation on the synthesis of transferrin and other serum proteins from [14C]leucine and their secretion were studied in rat liver perfused in situ. The radioactivities incorporated into perfusate transferrin, albumin and total protein increased with time during 90 min perfusion after an initial lag period of 15-30 min. The increases in the radioactivities of the perfusate proteins were inhibited by electrical stimulation of the hepatic nerve, whereas the increases were enhanced by vagal-nerve stimulation. Measurement of the incorporation of [14C]leucine into transferrin in the microsomal and cytosol fractions of the liver after 90 min perfusion revealed that the synthesis of this serum protein was suppressed by hepatic-nerve stimulation and increased by vagal-nerve stimulation. The results indicate that the biosynthesis and secretion of transferrin, and possibly other serum proteins, are inhibited by sympathetic-nerve stimulation and enhanced by parasympathetic-nerve stimulation.

Animals↗

PubMed1990

A sensitive and specific assay for granulocyte elastase in inflammatory tissue fluid using L-pyroglutamyl-L-prolyl-L-valine-p-nitroanilide.

Granulocyte elastase (GE, EC 3.4.21.37) is a key enzyme in tissue injury. To elucidate the role of GE in tissue injury, a new method of measuring GE activity in various inflammatory tissue fluids was developed using diazotization and the chromogenic synthetic substrate, L-pyroglutamyl-L-prolyl-L-valine-p-nitroanilide (S-2482). GE activity demonstrated first order kinetics in the range from 1.9 to 30 U/l. Other proteases, such as pancreatic elastase, trypsin, and chymotrypsin did not hydrolyze S-2484. This assay permits the determination of GE activity with a coefficient of variance less than 7.8% and 95.6 to 105.4% recovery. With this method, hydrolytic GE activity was found to be increased in bronchoalveolar lavage fluid from patients with ARDS or pneumonia, synovial fluid from patients with rheumatoid arthritis, and blister fluid from burn patients.

Blister↗

PubMed1990

Adrenergic blockade paradoxically increases lipogenic response of brown adipose tissue to sympathetic nerve stimulation.

Intermittent electrical stimulation of sympathetic nerves entering the interscapular brown adipose tissue (BAT) in rats increased the rate of glyceride glycerol synthesis in BAT but the fatty acid synthesis did not change. Simultaneous administration of phenoxybenzamine and propranolol paradoxically increased the fatty acid synthesis in response to the nerve stimulation whereas the glyceride glycerol synthesis was inhibited. Propranolol alone was also effective in mimicking the effects of adrenergic blockade, but guanethidine selectively eliminated the lipogenic response to the nerve stimulation. These results indicate that synthesis of glyceride glycerol induced by sympathetic nerve stimulation is largely due to beta-adrenergic action of noradrenaline, whereas synthesis of fatty acids may be mediated by non-adrenergic transmission of the sympathetic nerves.

Adipose Tissue, Brown↗

PubMed1990

Neuropeptide Y in the specific hypothalamic nuclei of rats treated neonatally with monosodium glutamate.

Neuropeptide Y (NPY) concentration was determined by radioimmunoassay in selected hypothalamic regions microdissected from fresh brain slices of rats treated neonatally with monosodium glutamate (MSG). Fourteen weeks after MSG treatment, significant decreases in NPY concentration were found in the paraventricular nucleus (PVN) and arcuate nucleus (ARH), while there was no appreciable change in the ventromedial nucleus (VMH) and lateral area (LH). The decrease in NPY in the ARH-PVN system may contribute to the endocrine and metabolic disturbances seen in MSG-treated animals.

Animals↗