Biomedical subjects

Y Shibayama

Publications and source records attributed to Y Shibayama.

At least 55 records · Page 3Linked to original sources

PubMed1994

Activation of human Hageman factor (factor XII) in the presence of zinc and phosphate ions.

Hageman factor (FXII, HF) is a monomeric plasma zymogen that is capable of autoactivation to the serine protease FXIIa in the presence of negatively charged surfaces such as glass, kaolin, ellagic acid and dextran sulfate. FXIIa activates prekallikrein to kallikrein which in turn digests high molecular weight kininogen (HK) to produce the vasoactive peptide bradykinin (BK). Known natural activators of FXII and the contact system include heparin, sulfatides, phospholipids, endotoxin, and urate crystals. We now present evidence that FXII can undergo activation in the presence of phosphate ions (P(i)) and certain divalent metal ions. FXII (1 microgram/ml) and prekallikrein (1 microgram/ml), in HEPES buffered saline, pH 7.4, were incubated with 0-100 mM sodium phosphate, 0-200 microM zinc chloride, and 0.6 mM Chromozym-PK; absorbance at 405 nm was monitored. Graphic analysis of the data indicated reciprocal activation of the two enzymes within 60 min which was dependent upon Zn(II) and P(i). While Ca(II) did not replace Zn(II) as an activator it significantly enhanced Zn(II)- and P(i)-dependent activation of FXII. Maximum activation occurred at 1-10 mM P(i) and approximately 25 microM Zn(II). Co(II), Cu(II) and Ca(II) were negative while Fe(II) was positive in the presence of 1 mM P(i). Cl-, SO4= and CO3=/HCO3- ions were negative when tested in the presence of 50 microM Zn(II). P(i) and Zn(II) ions promoted activation of FXII alone (but not prekallikrein) and the kinetics of this reaction suggested autoactivation. These data therefore suggest that physiological concentrations of P(i) and Zn(II) may be sufficient for a low-level turnover of the contact system in plasma which in turn may be responsible for the background levels of cleaved HK and BK found in normal plasma.

Chlorides↗

PubMed1993

Human Hageman factor (factor XII) and high molecular weight kininogen compete for the same binding site on human umbilical vein endothelial cells.

Factor XII (FXII, plasma concentration 375 nM) is a critical member of the plasma contact activation system and is the zymogen form of FXIIa, a serine protease involved in intrinsic coagulation, complement activation, activation of factor VII, and generation of the vasoactive peptide bradykinin. As such its interaction with cells involved in inflammatory pathways can be of physiologic and pathologic significance. We have studied the binding of FXII to cultured human umbilical vein endothelial cells (HUVEC). HUVEC were incubated with 125I-FXII, and cell-bound factor FXII was measured. FXII bound to HUVEC saturably in a zinc-dependent manner. The optimal zinc concentration was 50-60 microM. Binding of labeled FXII was drastically reduced when a 200-fold molar excess of unlabeled FXII was included in the incubation mixture at time zero or when added at 60 min during a 150-min time course experiment. Quantitative binding experiments indicated a dissociation constant of 144 nM with 10-12 million binding sites/endothelial cell. Unlabeled high molecular weight kininogen (HK) inhibited the binding of labeled FXII with a Ki of 98 nM, whereas unlabeled FXII inhibited the binding of labeled HK to HUVEC with a Ki of 152 nM. SDS-polyacrylamide gel electrophoresis and autoradiography of cell-bound 125I-FXII showed that factor XII underwent limited proteolysis and the molecular weights of the fragments were similar in size to activated FXII. The cell-bound activated factor XII was also able to activate prekallikrein. These data suggest that (i) FXII binds to HUVEC specifically, saturably, and reversibly in a zinc-dependent manner, (ii) HK and FXII may compete with each other for the same cell-surface receptor/s, and (iii) cell-bound FXII is capable of undergoing activation to FXIIa.

Binding Sites↗

PubMed1993

Human high molecular weight kininogen binds to human umbilical vein endothelial cells via its heavy and light chains.

High molecular weight kininogen (HK) is a multifunctional plasma glycoprotein that occupies a critical position in pathways that link inflammation and coagulation. Excision of the vasoactive peptide bradykinin by plasma kallikrein results in kinin-free HK that consists of a 65-Kd N-terminal heavy chain (HK-HC) linked to the C-terminal 45-Kd light chain (HK-LC) by a disulfide bridge. HK-HC is an inhibitor of SH-proteases and HK-LC contains the binding sites for coagulation cofactors prekallikrein and factor XI. HK has previously been shown to bind specifically to human umbilical vein endothelial cells (HUVEC) in a zinc(2+)-dependent manner by a single class of high-affinity binding sites. We have further characterized that interaction in order to determine the cell-binding regions of HK. Competition binding experiments have indicated that either HK-LC or HK-HC was able to inhibit the binding of labeled HK with a 50% inhibitory concentration (IC50) of 77 nmol/L and 89 nmol/L, respectively. Cleaved two-chain HK (HKa) had an IC50 of 73 nmol/L, whereas uncleaved HK had an IC50 of 335 nmol/L. Direct binding experiments have indicated that HUVEC bind both purified [125I]HK-HC and [125I]HK-LC in a zinc(2+)-dependent manner and that HK-LC did not displace bound HK-HC. The light chain of low molecular weight kininogen or prekallikrein-binding region of HK did not inhibit the binding of HK to HUVEC. Our results, therefore, indicate that (1) HK is capable of binding to endothelial cells via both heavy and light chain moieties, (2) HKa has a higher affinity to HUVEC, and (3) purified heavy and light chains are capable of directly binding to HUVEC. The data are consistent with the presence of a single high-affinity site for HK on endothelial cells within which are subsites that bind to heavy and light chains.

Binding Sites↗

PubMed1993

Hepatic failure after partial hepatectomy due to synergism between endotoxaemia and congestion of the liver.

To determine whether hepatic failure after partial hepatectomy is due to synergism between endotoxaemia and congestion of the liver, we examined endotoxin hepatotoxicity in partially hepatectomized rats with and without congestion of the liver. In partially hepatectomized rats without congestion of the liver, endotoxin administration induced slight elevation of the serum transaminase activity and mild or moderate hepatocellular necrosis in a few rats: these findings were not significantly different from those in sham operated rats treated with endotoxin. On the other hand, in partially hepatectomized rats with congestion of the liver, endotoxin administration induced marked elevation of serum transaminase activity and moderate or severe hepatocellular necrosis in almost all rats: these findings were significantly different from those in endotoxin-treated partially hepatectomized rats without congestion of the liver. These experimental data suggest that synergism between endotoxaemia and congestion of the liver may be a cause of hepatic failure after partial hepatectomy.

Animals↗

PubMed1993

Effect of exogenous antioxidant enzymes and antioxidants on the development of endotoxin-induced hepatocellular necrosis in rats.

To determine whether released oxidants in endotoxemia contribute to the development of hepatocellular necrosis, we examined the effects of antioxidants and antioxidant enzymes on endotoxin hepatotoxicity in rats. In rats given endotoxin, focal and random hepatocellular coagulative necrotic areas with infiltration of polymorphonuclear leukocytes and mononuclear cells and an elevation of serum transaminase activities were found. The extent of hepatocellular necrosis and the level of serum transaminase activities were not significantly decreased by treatment with superoxide dismutase, catalase, alpha-tocopherol or allopurinol. These experimental data indicate that even if endotoxin is related to a release of oxidants, the oxidants do not appear to play an important role in the development of hepatocellular necrosis.

Allopurinol↗

PubMed1993

Augmentation of endotoxin hepatotoxicity by zinc.

The present study was undertaken in rats to determine whether zinc protects against endotoxin hepatotoxicity and mortality. Treatment with zinc (50-200 mumol/kg body weight) alone or endotoxin (lipopolysaccharide B, Escherichia coli 026:B6, Difco, 2 mg/kg body weight) alone did not induce significant morphological changes in the liver parenchyma or any abnormalities in liver function tests. The mortality rate was 0%. In the rats pretreated with 100 mumol of zinc and then injected with endotoxin, the mortality rate, the incidence of focal hepatocellular coagulative necrosis and serum transaminase activity increased markedly. Eleven of the 12 rats pretreated with 200 mumol of zinc died within 4 h after endotoxin injection. In the rats pretreated with 50 mumol of zinc and then injected with endotoxin, there was no conspicuous change, in the mortality rate, liver function tests or morphology of the liver. These experimental data indicate that zinc increases the mortality rate in endotoxemic rats and augments biochemical and morphological evidence of endotoxin hepatotoxicity.

Animals↗

PubMed1993

Influence of chronic alcohol consumption on the development of altered hepatocellular foci in rats.

The effect of chronic alcohol consumption on the development of altered hepatocellular foci was examined in 150 male Slc:Wistar rats fed an ethanol solution (0, 5 or 20%, w/v) ad libitum instead of drinking water. In the 120th week of the treatment period, the liver was examined histopathologically. There was no significant difference in the incidence, number and volume fractions of altered hepatocellular foci between the 0% and the 5% ethanol groups. In the 20% ethanol group, the incidence of altered hepatocellular foci was significantly higher than in the 0% ethanol group, and the number and the volume fraction of altered hepatocellular foci were significantly greater than in the 0% and the 5% ethanol groups. These results indicate that chronic consumption of a large amount of alcohol promotes the development of altered hepatocellular foci. However, there was no statistically significant difference in the incidence of benign liver cell tumours and hepatocellular carcinoma among the three groups.

Alcohol Drinking↗

PubMed1993

Role of microenvironmental deterioration of the bone marrow in the development of bone atrophy in magnesium silicate-treated rats.

The role of microenvironmental deterioration of the bone marrow in the development of bone atrophy was examined in rats with bone atrophy induced by magnesium silicate. In the tibial metaphyses, proliferation of myelocytic elements of haematopoietic tissue was prominent and caused narrowing of sinusoids, increased distance between sinusoids and trabecular bone and atrophy of trabecular bone. There was a significant correlation in volume percentage between haematopoietic cells and trabecular bone, between haematopoietic cells and sinusoids and between sinusoids and trabecular bone. These results imply that atrophy of trabecular bone is related to microenvironmental deterioration of the bone marrow, that is, a decrease in efficiency of exchange of nutrients and waste products between sinusoids and trabecular bone due to the proliferation of haematopoietic cells and a deficiency of nutrient supply to the bone marrow due to the narrowing of sinusoids.

Animals↗

PubMed1993

Microvascular events in bone marrow related to development of and recovery from bone atrophy in thiotepa-treated rats.

To clarify the relationship of microvascular events in the bone marrow to the development of and the recovery from bone atrophy, we examined quantitatively and qualitatively trabecular bone, sinusoids and haematopoietic tissue in the metaphysis of the tibia of rats given thiotepa, an antitumour drug derived from nitrogen mustards. The administration of thiotepa rapidly reduced the number of haematopoietic cells causing significant dilatation of the sinusoids and atrophy of the trabecular bone 1 day after the injection. However, these changes were transient; regeneration of haematopoietic cells and normalization of the dilated sinusoids started 3 days after the injection, and the atrophied trabecular bone gradually returned to normal starting 6 days after the injection. These results imply that an extreme decrease in velocity and margination of sinusoidal blood flow following marked dilatation due to a decrease in haematopoietic cells cause atrophy of the trabecular bone, and that normalization of the sinusoidal blood flow following regeneration of haematopoietic cells leads to recovery from atrophy of trabecular bone.

Animals↗

PubMed1992

Generation of vasoactive peptide bradykinin from human umbilical vein endothelium-bound high molecular weight kininogen by plasma kallikrein.

High molecular weight kininogen (HK) is a multifunctional plasma glycoprotein that occupies a critical position in pathways that link inflammation and coagulation. It is an inhibitor of sulfhydryl proteases and has procoagulant properties. It is also a source of the vasoactive peptide bradykinin (BK). It has been previously shown that HK binds to human umbilical vein endothelial cells (HUVEC) in culture. We have further characterized that interaction herein. Immunohistochemical experiments have indicated that when freshly obtained umbilical vein segments were treated with HK, washed, and probed with anti-HK antibodies, HK was localized on the endothelium. We next determined whether HUVEC-bound HK can be cleaved by plasma kallikrein to release BK. Cultured HUVEC were incubated with unlabeled HK for varying times, washed, and the kinetics of BK release by plasma kallikrein were assayed by radioimmunoassay. Results indicated that kallikrein released BK from HUVEC in proportion to the initial amount of bound HK. No release of BK occurred in the absence of kallikrein. Also, there was no BK release upon kallikrein treatment of the HUVEC not treated with exogenous HK. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of HUVEC-bound 125I-HK indicated that addition of kallikrein resulted in cleavage of HK, thus corroborating the BK release experiments. Comparison of cleavage patterns has also indicated that cell-bound HK is slightly less susceptible to digestion by kallikrein than free HK. Therefore, our data suggest that human HK can bind to vascular endothelium in situ and that plasma kallikrein can recognize endothelial-bound HK as a substrate and liberate the vasoactive peptide BK.

Amino Acid Sequence↗

PubMed1992

Pathogenesis of pancreatic perilobular necrosis in patients with liver disease.

We often see perilobular necrosis of the pancreas in patients with liver disease at autopsy. This study was undertaken to determine the frequency and the mechanism of development of pancreatic perilobular necrosis in patients with liver disease. Pancreatic perilobular necrosis was seen in 21 per cent of 261 autopsied patients: in 41 per cent of 73 autopsied patients with liver disease and in 13 per cent of 188 autopsied patients without liver disease. Moreover, splanchnic congestion was present in 90 per cent of 30 pancreatic perilobular necrosis patients with liver disease. These data indicate that patients with liver disease develop perilobular necrosis of the pancreas more often than patients without liver disease, and that the high frequency may be a sequela of splanchnic congestion; that is, congestion of the pancreas and endotoxaemia due to congestion of the gut.

Adolescent↗

PubMed1992

Changes in hepatic lymph vessels in endotoxaemia.

This study was undertaken into rats to investigate changes in the hepatic lymph vessels and the space of Disse in endotoxaemia and to examine their relationship with the development of endotoxin-induced hepatic injury. Lymph stasis, namely dilatation of the lymph vessels and oedema, developed rapidly in the medium-sized portal canals, the large portal canals, and the liver hilum after endotoxin injection, but not in the small portal canals. Such changes reached their maximum 4-8 h after endotoxin injection and had recovered markedly by 16 h after the injection. The space of Disse remained within normal limits during this period. These findings suggest that the intrahepatic lymph stasis in endotoxaemia may be caused by a reduction in the pumping activity of the extrahepatic and the intrahepatic large lymph vessels rather than by an increase of lymph formation in the liver lobules. There was no evidence suggesting a direct relationship between the disturbance of hepatic lymph flow and the development of hepatic injury in endotoxaemia.

Alanine Transaminase↗

PubMed1992

A study of endotoxin-associated hepatotoxicity on proliferating hepatocytes.

It is thought that regeneration of the liver provides a state of preparedness for the Shwartzman reaction and contributes to the development of endotoxin-associated massive hepatic necrosis following partial hepatectomy. Therefore we examined endotoxin hepatotoxicity in rats with hepatic regeneration after 35% hepatectomy and in rats with liver cell proliferation induced by lead nitrate. Biochemical and histopathological studies showed no enhanced endotoxin hepatotoxicity in either partially hepatectomized rats or in rats with lead nitrate-induced liver cell proliferation. These results indicate that the development of endotoxin-associated hepatic damage after partial hepatectomy may not relate to regeneration and proliferation of the liver.

Animals↗

PubMed1992

Hepatic haemodynamics and microvascular architecture after portal venular embolization in the rat.

To clarify the relationship between hepatic damage and alterations of hepatic microvascular architecture and haemodynamics following portal venule occlusion, the present study was performed in rats which had been injected into the portal vein with 700,000 plastic beads (30-35 microns in diameter). When the occluded segment of the portal venule was short, infarction did not occur because of the prompt development of vascular channels bypassing the obstructed venules. On the other hand, when the occluded segment was long, infarction usually occurred. In this case, formation of collateral vascular channels began as dilatation of the sinusoids in the vicinity of the occluded portal venules and increased in diameter and developed into new portal venules in 5 days. Increased portal vascular resistance after embolization was normalized after 5 days in parallel with the progression of reconstruction of vascular channels. Reduced bile production returned to a normal level 3 days after embolization. Necrotic tissue was resorbed completely and replaced by fibroblasts 5 days after embolization. These findings indicate that the development of infarct following portal venule occlusion depends on the length of the occluded segment, and that hepatic microvasculature has a great capacity for adaptation and rapid reconstruction of vascular channels which leads to speedy recovery from hepatic circulatory disturbances and resulting hepatic damage.

Animals↗

PubMed1992

Role of lipid peroxidation in enhancement of endotoxin hepatotoxicity.

The present study was undertaken in the rats to examine whether endotoxin hepatotoxicity is enhanced by increased lipid peroxidation. The rats were given 10 ml of water, corn oil or heated and oxygenated corn oil per kg body weight by stomach tube twice a day for 14 days, and then they were injected physiological saline solution or endotoxin (2 or 2.5 mg per kg body weight) into the tail vein. In the rats pretreated with water or corn oil, the activity of serum glutamic pyruvic transaminase was within the normal limit, and there was no conspicuous morphological change in the liver, except for accumulation of fine fat droplets in few liver cells. On the other hand, in the rats pretreated with heated and oxygenated corn oil, containing a large amount of lipid peroxides, accumulation of small fat droplets in the liver cells and a slight elevation of serum transaminase activity were induced. The challenge with endotoxin (2.5 mg per kg body weight) caused focal hepatocellular coagulative necrosis and a marked elevation of serum transaminase activity, irrespective of the sorts of pretreatment, and there was no significant difference in the biochemical change and the histopathological damage between the rats pretreated with water, corn oil and heated and oxygenated corn oil. These results suggest that increased lipid peroxidation does not contribute to the enhancement of endotoxin hepatotoxicity, although it is thought that carbon tetrachloride and ethanol enhance endotoxin hepatotoxicity by synergism between endotoxin and the chemicals through lipid peroxidation.

Alanine Transaminase↗

PubMed1992

Hepatotoxicity of heated and oxygenated corn oil.

The present study was undertaken in rats to examine the hepatotoxicity of ingested heated and oxygenated corn oil. Activities of serum glutamic pyruvic transaminase markedly increased in the rats given heated and oxygenated corn oil for two weeks as compared with that of the control group. In the rats given heated and oxygenated corn oil, small fat droplets were found in the liver cells, but liver cell necrosis was not seen. Ultrastructurally, there was no conspicuous change in the liver cells, except for depletion of glycogen and dilatation of cisternae of rough and smooth surfaced endoplasmic reticulum. These experimental data show that ingestion of heated and oxygenated corn oil induces hepatic injury, and that the development of hepatic injury may relate to liver cell membrane damage due to active oxygen radicals contained in heated and oxygenated corn oil.

Alanine Transaminase↗

PubMed1992

Significance of septal fibrosis for disturbance of hepatic circulation.

To examine the significance of fibrous septa of the liver for hepatic circulatory disturbance, haemodynamic changes were investigated in rats with septal fibrosis induced with horse serum injections. The fibrotic liver showed thin fibrous bands originating in the vicinity of the peripheral branches of the hepatic vein connected with each other and partly with the portal triads, without conspicuous periportal, pericentral or perisinusoidal fibrosis. There was no evidence of hepatic cell enlargement, disarrangement of hepatic cell plates or narrowing of the sinusoids in the fibrotic livers. Portal vascular resistance, bile production and hepatic oxygen consumption, which were measured by an isolated liver perfusion method, were much the same in the normal and the fibrotic livers. Moreover, there was no significant difference in in vivo blood pressures of the portal vein, the terminal portal venule, the terminal hepatic venule and the inferior vena cava between the normal and the fibrotic rats. These data suggest that septal fibrosis in itself does not disturb hepatic circulation.

Animals↗

PubMed1992

Role of septal fibrosis in development of hepatic circulatory disturbance in the presence of liver cell enlargement.

The effect of septal fibrosis on hepatic circulation was examined in rats with enlarged liver cells. Septal fibrosis was produced by horse serum injections and liver cell enlargement by a choline-deficient diet. Septal fibrosis alone did not induce any disturbance of hepatic circulation. In fatty livers, a slight increase in sinusoidal vascular resistance and a slight elevation of portal vein pressure were found. However, in fatty livers with septal fibrosis, portal hypertension and sinusoidal vascular resistance were higher than in fatty livers without septal fibrosis. These experimental data clearly demonstrate that septal fibrosis alone has no effect on hepatic circulation, but septal fibrosis in the presence of liver cell enlargement markedly affects sinusoidal circulation and induces portal hypertension. The augmentation of sinusoidal vascular resistance by septal fibrosis in the presence of liver cell enlargement might be due to the severe deformation of the sinusoids by enlarged liver cells in the limited spaces surrounded by septal fibrous bands.

Animals↗