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Biomedical subjects

S Kume

Publications and source records attributed to S Kume.

At least 109 records · Page 6Linked to original sources
PubMed1989

Stimulative effects of TMB-8 and trifluoperazine on pancreatic hormone release.

The effects of 8-N-N-diethylamino octyl 3,4,5-trimethoxybenzoate (TMB-8) and trifluoperazine (TFP) on the early phase (10 min) of the release of pancreatic hormones from isolated rat islets were investigated. TMB-8 and TFP stimulated insulin, glucagon, and somatostatin release in a dose-dependent manner at a low glucose concentration (2.5 mM). The levels of glucagon and somatostatin release were also stimulated by these two agents at a high glucose concentration (10 mM). Their effects were independent of external calcium ion level. These two agents did not modify insulin release at the high glucose concentration. The stimulative effects of the two agents on the release of these hormones were partially suppressed when the islets were pretreated with 6-hydroxydopamine (6-OHDA), a chemical adrenergic denervator that acts at nerve endings. In this situation, the norepinephrine (NE) released from pancreatic islets decreased to 44% of that of non-treated islets (P less than 0.01). The addition of NE (10(-9) M) to the incubation medium increased insulin, glucagon, and somatostatin secretion by 20-30% over control levels (P less than 0.05). In conclusion, the early phase of pancreatic hormone release was stimulated by TMB-8 and TFP. Our results strongly suggest that these two drugs could be mediated by the NE released from nerve endings in the islets.

Animals↗
PubMed1989

Anion channels contribute to the regulation of intracellular pH in human platelets.

The presence of extracellular bicarbonate potentiated platelet intracellular pH rises induced by thrombin. The effect was most remarkable in sodium-depleted buffers. This effect of bicarbonate was dose-dependent and was inhibited by anion channel blockers. Bicarbonate also potentiated the pHi recovery after acid loading, but had no effect on alkali loading. It was suggested that anion exchange, most probably that of bicarbonate/chloride, contributes to the regulation of intracellular pH in human platelets.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Exacerbation of toxic effects by endotoxin contamination of recombinant human tumor necrosis factor.

The toxic effects of endotoxin-free human recombinant tumor necrosis factor (rH-TNF), shown to contain less than 50 pg endotoxin/mg rH-TNF, were investigated and compared with those of rH-TNF and endotoxin coadministered at 4-400 ng endotoxin/mg rH-TNF in female Sprague-Dawley rats. The mean lethal dose of 5.9 mg/kg rH-TNF found for the endotoxin-free rH-TNF was far higher than that attributed to rH-TNF by other investigators. Coadministration with endotoxin derived from E. Coli. Salmonella abortus equi, or Serratia marcescens reduced the apparent mean lethal dose of rH-TNF in correspondence to the endotoxin concentration, with a value of 0.7 mg/kg rH-TNF observed at 1600 ng, 757 ng, and 5260 ng endotoxin/mg rH-TNF, respectively. Coadministration also resulted in more severe histopathologic and physicochemical effects than rH-TNF alone. Histopathologic abnormalities observed only in coadministration included interlobular edema and hemorrhage of the pancreas and, most remarkably, splenomegaly, which was not observed with rH-TNF alone even at lethal doses. The results indicate that particular care in determining endotoxin contamination is essential in any consideration of TNF toxicity.

Animals↗
PubMed1989

Localization of granular components in ADP- and/or teleocidin-stimulated human blood platelets as revealed by immunocytochemical methods.

Morphological aspects of the platelet release reaction induced by adenosine 5'-diphosphate (ADP) and/or teleocidin (a tumor promoter) in the presence of aspirin were studied by transmission electron microscopy. Human platelet-rich plasma treated with reagents at 37 degrees C for 1-5 min was fixed with aldehyde and embedded in Epon or Lowicryl K4M. Addition of ADP (10 microM) resulted in the centralization of granules without granule release, while teleocidin (100 ng/ml) induced the swelling of the open canalicular system (OCS) and the release of alpha-granules without centralization of these granules. When both ADP and teleocidin were added successively, a synergistic effect was predominant; and both alpha- and dense-granules were discharged from the cytoplasm. Postembedding immunocytochemical studies employing specific antibodies against various granular components in combination with protein A gold as a label revealed that, following the administration of teleocidin, several components of alpha-granules such as beta-thromboglobulin and platelet factor 4 moved into the swollen OCS, while the dense-granule component, serotonin, did not. When both teleocidin and ADP were administered, both alpha-granular and dense-granular components moved into the swollen OCS.

Adenosine Diphosphate↗
PubMed1989

Acetyltransferase activity and production of platelet-activating factor by human neutrophils activated with various stimuli.

The acetyltransferase activity and biosynthesis of platelet-activating factor (PAF) were assessed in human neutrophils activated by 4 microM A23187, 20 ng/ml phorbol myristate acetate (PMA), and 10(-6) M n-formyl-methionyl-leucyl-phenylalanine (fMLP). All three agents elevated the acetyltransferase activity dose-dependently. There were no significant differences in the Km values for acetyl CoA between non-stimulated and stimulated cells. All three stimuli gave a similar Vmax value of acetyltransferase determined 10 min after stimulation, being more than twice as high as the control value. By contrast, the amount of PAF produced by the neutrophils differed with the stimuli, A23187 being by far the most potent. The time course of PAF synthesis, particularly when activated by PMA, did not parallel that of acetyltransferase activity; PMA-induced PAF production was negligible for the first 20 min and gradually increased to reach its plateau 60 min after stimulation, while enzyme activity was at its highest level 5 min after stimulation. These results suggest that the different stimuli activated the same acetyltransferase, and that there was an increase in the number of the enzyme molecules in the activated state. It is unlikely that a change in the biological activity of a preexisting enzyme without a change in the number of active enzyme molecules could be the cause. Certain factors other than acetyltransferase may also regulate the PAF biosynthesis induced by these stimuli.

Acetyltransferases↗
PubMed1989

The role of intracellular pH and Ca++ on arachidonic acid metabolism in human platelets.

High concentrations of ionomycin induced arachidonic acid metabolism, while its magnitude appeared to be poorly correlated with the increase in intracellular Ca++ induced by ionomycin. Intracellular pH elevation had no direct effect on arachidonic acid release. On the other hand, the elevation in intracellular pH potentiated arachidonic acid release induced by low concentrations of ionomycin, and appeared to increase the sensitivity to Ca++ of the arachidonic acid releasing mechanism. pHi fixed at low values suppressed the formation of the product of the cyclooxygenase pathway more severely than that of 12-lipoxygenase in platelet activation induced by receptor-mediated agonists. Inhibition of the Na+/H+ exchanger, which participates in intracellular pH elevation, reduced the production of arachidonic acid metabolites, with a more profound effect on the product of the cyclooxygenase pathway. The findings suggest that intracellular Ca++ and pH act synergistically to activate the arachidonic acid releasing mechanism in platelets, and that pH also regulates the activity of the cyclooxygenase pathway.

Arachidonic Acid↗
PubMed1989

Functional activity of protein S determined with use of protein C activated by venom activator.

A new screening procedure, an easy and specific assay for determining functional Protein S activity, has been developed, with use of Protein C activated by venom activator (Protac). Purified Protein C (100% amidolytic activity) was activated by venom activator (6 units/mL). To a mixture of 100 microL of Protein S-deficient plasma, 20 microL of sample plasma, 100 microL of cephalin (Actin), and 20 microL of activated Protein C we added 100 microL of 25 mmol/L CaCl2 solution and measured the clotting time with a KC 10 coagulometer. The functional Protein S activity correlated well with the concentrations of Protein S antigen measured by enzyme immunoassay and the Laurell rocket technique (r = 0.810 and 0.850, respectively) in normal subjects, patients with myocardial infarction undergoing warfarin therapy, and patients with liver cirrhosis.

Glycoproteins↗
PubMed1988

Functional responses of aequorin-loaded human neutrophils. Comparison with fura-2-loaded cells.

Aequorin-loaded human neutrophils in response to chemotactic peptides and ionomycin showed a sharp rise in their intracellular Ca2+ concentration which decayed within 2 min. Depletion of extracellular Ca2+ suppressed only the ionomycin-induced increase. Fura-2-loaded cells also showed a sharp rise in the intracellular Ca2+ concentration in response to each stimulator, while the decline was extremely slow in the ionomycin-induced Ca2+ increase. Depletion of extracellular Ca2+ reduced the duration of ionomycin-induced Ca2+ increase. Cytochalasin B almost equally potentiated the rise in the intracellular Ca2+ concentration induced by each stimulator. Aequorin-loaded cells showed impaired phagocytotic activity, while degranulation and oxygen radical production were not affected.

Aequorin↗
PubMed1988

Effect of recombinant DNA-produced tumor necrosis factor on various parameters of neutrophil function.

The effect of recombinant DNA-produced human tumor necrosis factor (TNF) on various parameters of neutrophil function was evaluated. TNF was a weak direct activator of oxygen radical production. It released the specific granule contents to a limited extent, but the azurophilic granule contents were retained even in the presence of cytochalasin B. It had a chemotactic activity for neutrophils, as determined by the use of a modified Boyden's chamber. Pretreatment of neutrophils with TNF increased phagocytosis of opsonized particles and markedly potentiated in a dose-dependent manner oxygen radical production induced by opsonized zymosan. The inhibitors of lipoxygenase, but not those of cyclooxygenase, reduced the potentiating effect of TNF on phagocytosis, suggesting that the products of lipoxygenase play an important role in mediating the effect of TNF on neutrophils.

Arachidonate 5-Lipoxygenase↗
PubMed1988

Amidolytic kinetic assay of protein C by selective spectrophotometry in a centrifugal analyzer.

This rapid, simple amidolytic assay of protein C activity in whole plasma involves activation by protein C activator from the venom of Agkistrodon contortrix contortrix (Protac) and use of a Cobas Fara spectrophotometer programmed for kinetic assay. Plasma is incubated with activator venom in the presence or absence of antibody to human protein C in the instrument, chromogenic substrate (S-2366) is added, and the absorbance is measured at 405 nm. The difference between the absorbance of the sample plasma with and without antibody to human protein C correlated well with protein C antigen as assayed by enzyme-linked immunosorbent assay (ELISA) and the Laurell rocket technique in normal subjects, patients being treated with warfarin, and patients with liver cirrhosis or disseminated intravascular coagulation. Our mean value for protein C in normal subjects is 115.9 (SD 16.7)% for amidolytic activity, 103.0 (SD 17.4)% for ELISA, and 97.2 (SD 18.1)% for the rocket technique. The high value for normal subjects presumably includes some nonspecific amidolytic activity activated by the activator venom, as indicated by measurable activity in immuno-depleted protein C-deficient plasma. Within-run and between-run CVs were less than 5% at low, normal, and high concentrations of protein C amidolytic activity.

Centrifugation↗
PubMed1987

Synergism between subthreshold concentrations of thrombin and 12-O-tetradecanoylphorbol 13-acetate in platelet activation.

A comparison was made between the time courses and interdependence of platelet aggregation, serotonin release, and cytosolic free Ca2+ concentration in the same sample of platelets loaded with [14C]-serotonin and Ca2+-sensitive photoprotein aequorin. In 100 micrograms/ml aspirin-treated platelets, neither 0.01 U/ml thrombin nor 50nM TPA, an active phorbol ester, induced significant aggregation, serotonin release, or a rise in the intracellular calcium concentration. However, when these two agents were added together, marked aggregation and release were observed without a change in the cytosolic free Ca2+ concentration. No correlation was observed between the extent of the synergistic effects and time of preincubation with TPA. Potentiatory effects of protein kinase C on receptor-mediated agonists need to be considered in platelet activation.

Blood Platelets↗
PubMed1987

Fibrinogen-induced erythrocyte aggregation: erythrocyte-binding site in the fibrinogen molecule.

The effect of fibrinogen and fibrinogen-derived products on the velocity of rouleau formation of human erythrocytes was quantitatively examined with a rheoscope combined with a video-camera, an image analyzer and a computer. (i) The velocity of rouleau formation by naturally occurring low-molecular-weight fibrinogen of 305 kDa and by desialylated fibrinogen was the same as that by native fibrinogen of 340 kDa. (ii) Concerning fibrinogen degradation products by plasmin, the velocity of rouleau formation decreased upon going from fibrinogen greater than fragment X greater than fragment Y (the ratio of molar concentration of fibrinogen, fragment X and fragment Y for giving a certain velocity of rouleau formation was approx. 1:2:5). The effect of fragments X and Y on the fibrinogen-induced rouleau formation was additive. (iii) Fragments D and E could not induce rouleau formation and did not affect the fibrinogen-, fragment X- and fragment Y-induced rouleau formation. (iv) Fibrinopeptides A and B and artificial tetrapeptides (Gly-Pro-Arg-Pro and Gly-His-Arg-Pro) did not affect the fibrinogen-induced rouleau formation. (v) The possible erythrocyte-binding site in fibrinogen molecule for leading to rouleaux was proposed to be in A alpha-chain (probably, around residues No. 207-303) near the terminal domain of the trinodular structure of fibrinogen.

Binding Sites↗
PubMed1987

Potentiation of neutrophil function by recombinant DNA-produced interleukin 1a.

The effect of interleukin 1a (IL-1a) produced by E. coli-derived recombinant DNA was evaluated on various parameters of human neutrophil function. IL-1a alone stimulated neutrophil hydrogen peroxide production in a dose-dependent manner, but the rate was much lower than that of opsonized zymosan. IL-1a induced release of specific granule contents, but not azurophilic granule contents. Cytochalasin B did not augment the rate of release. IL-1a was chemotactic for neutrophils at the optimal concentrations of 0.1-10 ng/ml. Pretreatment of the neutrophils with IL-1a augmented neutrophil oxygen radical production induced by opsonized zymosan, and this synergistic effect was evident as early as 10 min after IL-1a was added to the neutrophil culture. Phagocytosis of opsonized particles by neutrophils, and degranulation induced by opsonized zymosan were also enhanced by IL-1a in a dose-dependent manner. The present results suggest that IL-1a is weak as a direct activator of neutrophil function and that IL-1a in vivo may augment the response of neutrophils to other stimulators such as foreign bodies.

Chemotaxis, Leukocyte↗
PubMed1987

Vascularizing the ischemic jejunum by intra-seromuscular implantation of a gastroepiploic vascular pedicle--an application of experimental esophageal reconstruction.

Many experimental studies have been done in an attempt to feed various ischemic organs. Of these, both direct intraorganic vascular implantation, and vascular anastomosis, appear to show promise for vascularizing the ischemic gastrointestinal tracts. Preliminary experiments were done in 24 Mongrel dogs to establish the blood flow of the jejunum by direct epiploic vascular pedicle implantation. Morphological development of the communicating vascular system, newly formed between the implanted epiploic vessel and the indigenous vascular network of the jejunum, was clarified by microangiography and histology. In 20 dogs, esophageal reconstruction was successfully accomplished, using the jejunal loop vascularized as described above. The total length of the jejunal segment, and the esophagojejunal anastomotic portion, had neither signs of circulatory disturbance nor necrosis, one, three and twelve months post-operatively. Our experimental findings suggest that direct vascular implantation is the simplest way to vascularize the ischemic intestinal tract and may also be applicable widely in the field of abdominal surgery.

Animals↗