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Biomedical subjects

K Sakai

Publications and source records attributed to K Sakai.

At least 1,027 records · Page 57Linked to original sources
PubMed1988

Importance of fibrinogen and platelet membrane glycoprotein IIb/IIIa in shear-induced platelet aggregation.

The mechanism of shear-induced platelet aggregation was investigated using a polycarbonate cone and plate viscometer. After exposed to shear stress of 54-90 dyne/cm2 for 2 min. at 37 degrees C, platelets aggregated without a significant amount of serotonin release and lactic dehydrogenase leakage from platelets. Under this conditions, platelets from 2 patients with thrombasthenia and a patient with congenital afibrinogenemia failed to aggregate. When fibrinogen was added to platelet rich plasma from a patient with afibrinogenemia, shear-induced platelet aggregation occurred at the same extent of aggregation as observed in normal platelets. Shear-induced platelet aggregation was inhibited by monoclonal antibody to GPIIb/IIIa (1 microgram/ml) and synthetic peptide, Arg-Gly-Asp-Ser (RGDS) (1 mM). Apyrase and hirudin showed no effect on this aggregation. Indomethacin (100 microM) and thromboxane A2 synthetase inhibitor, OKY-046 (100 microM) markedly inhibited aggregation, while thromboxane A2 competitive inhibitor, ONO-3708 (100 microM) exhibited only partial inhibition. These results indicate that fibrinogen and GPIIb/IIIa are important for shear-induced platelet aggregation and that the induction of fibrinogen receptor on GPIIb/IIIa may partially depend upon thromboxane A2 synthesis in platelets.

Afibrinogenemia↗
PubMed1988

Inhibitory effect of salicylate on 2,4-dinitrophenol and diethyl maleate in isolated rat intestinal epithelial cells.

Studies on the mechanism of chemically induced intestinal epithelial injury were carried out using isolated, rat small intestinal epithelial cells. Compounds such as 2,4-dinitrophenol (DNP) and diethyl maleate (DEM), caused NADH loss, an increase in cytosolic Ca2+ concentration and protein thiol loss. Further, these compounds accelerated cell aggregation and decreased cell viability. Calmodulin antagonists inhibited protein thiol loss induced by either of the compound, inhibited cell aggregation and prolonged cell viability, but did not influence NADH loss. It has been reported that the calmodulin-binding protein may regulate cytoskeletal activity. Therefore, the inhibition of protein thiol loss by calmodulin antagonist may be due to a dissociation of calmodulin-binding proteins from cytoskeletal elements. Salicylate also inhibited protein thiol loss induced by DNP and DEM, and inhibited cell aggregation. However, salicylate may have a direct effect in reducing the cytosolic free Ca2+ concentration by complexation and subsequent facilitated release of Ca2+ from cells. Further, in the present study, the induction of cell aggregation may be caused by the appearance of specific sites on the cell membrane surface to which arsenazo III could adsorb, since adsorption of arsenazo III to the isolated epithelial cells seemed to correlate with increased cell aggregation.

Animals↗
PubMed1988

Characterization of partially purified cytosolic protein-tyrosine kinase from porcine spleen.

Biochemical properties of a cytosolic protein-tyrosine kinase (CPTK-40) partially purified from porcine spleen were characterized and compared with p40 kinase, a cytosolic protein-tyrosine kinase from bovine thymus. When CPTK-40 was incubated with MnCl2 and (gamma-32P)ATP, only a phosphoprotein with a molecular weight of 40 kilodalton was observed. CPTK-40 efficiently phosphorylated tubulin with the rate of 0.5 nmol/min/mg. Unlike p40 kinase, casein was also a substrate for CPTK-40. Among various divalent cations tested, Co2+, Mn2+ and Mg2+ were effective metal ions for the enzyme activity. Ca2+ could also serve as a divalent cation for the activity although the rate was low. These results suggest that CPTK-40 is similar but not identical to p40 kinase.

Animals↗
PubMed1988

Predominant expression of a T cell receptor V beta gene subfamily in autoimmune encephalomyelitis.

TCR beta chain gene expression of individual T cell clones that share the same MHC class II restriction and similar fine specificity for the encephalitogenic NH2 terminus of the autoantigen myelin basic protein (MBP) has been examined. TCR V beta expression was examined by FACS analysis with mAbs specific for the V beta 8 subfamily of TCR beta chain genes. 14 of 18 (78%) NH2-terminal MBP-specific clones examined express a member of the TCR V beta 8 subfamily. Southern analysis was used to identify which member(s) of the TCR V beta 8 subfamily is expressed by these clones. Each of four clones examined uses V beta 8.2, though two different V beta 8.2-J beta 2 combinations were identified. Our findings indicate that there is restricted TCR V beta usage in the autoimmune T cell response to the dominant encephalitogenic NH2-terminal epitope of the MBP. The use of an mAb to the antigen-specific TCR in the prevention of T cell-mediated autoimmune disease has been investigated. Our results demonstrate that in vivo administration of a TCR V beta 8-specific mAb prevents induction of autoimmune encephalomyelitis.

Animals↗
PubMed1988

Topography of neurophysin-immunoreactive neurons projecting to the neurohypophysis: direct evidence as revealed by a double staining method.

The topographic distribution of neurophysin-immunoreactive (NP-IR) cells projecting to the posterior pituitary gland has been studied in the cat using a double staining method: immunohistochemistry of neurophysin in conjunction with horseradish peroxidase (HRP) retrograde tracer technique. We found that almost all the hypothalamic NP-IR cells project directly to the neurohypophysis except those localized in the suprachiasmatic nucleus and in the caudal part of the paraventricular nucleus.

Animals↗
PubMed1988

Inactivation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase by koningic acid.

Koningic acid, a sesquiterpene antibiotic, is a specific inhibitor of the enzyme glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12). In the presence of 3 mM of NAD+, koningic acid irreversibly inactivated the enzyme in a time-dependent manner. The pseudo-first-order rate constant for inactivation (kapp) was dependent on koningic acid concentration in saturate manner, indicating koningic acid and enzyme formed a reversible complex prior to the formation of an inactive, irreversible complex; the inactivation rate (k 3) was 5.5.10(-2) s-1, with a dissociation constant for inactivation (Kinact) of 1.6 microM. The inhibition was competitive against glyceraldehyde 3-phosphate with a Ki of 1.1 microM, where the Km for glyceraldehyde 3-phosphate was 90 microM. Koningic acid inhibition was uncompetitive with respect to NAD+. The presence of NAD+ accelerated the inactivation. In its absence, the charcoal-treated NAD+-free enzyme showed a 220-fold decrease in apparent rate constant for inactivation, indicating that koningic acid sequentially binds to the enzyme next to NAD+. The enzyme, a tetramer, was inactivated when maximum two sulfhydryl groups, possibly cysteine residues at the active sites of the enzyme, were modified by the binding of koningic acid. These observations demonstrate that koningic acid is an active-site-directed inhibitor which reacts predominantly with the NAD+-enzyme complex.

Animals↗
PubMed1988

Asbestos fibers in human pulmonary and extrapulmonary tissues.

The association between asbestos fibers in human lung tissues and those in other extrapulmonary organs was studied by analysing three autopsied cases, one of whom had a high pulmonary asbestos burden, one an intermediate burden, and one a low burden. The amount, types and sizes of asbestos fibers in the tissues of lung, liver, spleen, pancreas, kidney, and gastrointestinal tract were identified and measured by transmission electron microscopy equipped with an energy dispersive X-ray analyser. The following results were obtained: 1) The concentrations of asbestos fibers in extrapulmonary organs tended to increase with that in lung tissues. 2) The types of fibers identified in lungs were approximately consistent with those in other organs. 3) A relatively large range of fiber length was observed in both lungs and other organs. The findings extend and support previous light microscopic studies comparing asbestos bodies in various organs, and may imply that persons with high levels of asbestos in their lungs are also likely to have the same types and high levels of asbestos in their other tissues.

Aged↗
PubMed1988

Resection of hepatocellular carcinoma with obstructive jaundice caused by compression of the common hepatic duct.

We treated a patient with hepatocellular carcinoma in whom jaundice was caused by obstruction of the common hepatic duct because of compression by the tumor. Percutaneous transhepatic cholangiodrainage was performed preoperatively. The tumor was entirely in the medial segment of the liver, without invasion of the hepatic ducts, and medial segmentectomy was performed. As of the end of 1985, 58 cases of hepatocellular carcinoma complicated by extrahepatic obstructive jaundice have been reported in Japan. In only four was obstructive jaundice caused by extraluminal biliary compression. We review ten patients treated by liver resection.

Aged↗
PubMed1988

Ventricular septal perforation following acute myocardial infarction in a patient with hypothyroidism--a case report.

A 61-year-old woman with profound hypothyroidism underwent surgery for a ventricular septal perforation 15 days following an acute myocardial infarction, with no preoperative thyroid replacement. Her immediate postoperative course was complicated by a low cardiac output, respiratory suppression and high output renal failure, requiring prolonged hemodynamic and respiratory support. Thyroid replacement (50 micrograms of thyronine and 100 micrograms of thyroxine daily) was given in two installments on the 2nd day after the operation. The effect of the inotropic agents increased gradually and the patient was weaned off intra-aortic balloon pumping. A large quantity of diuretics, hydration and hyperalimentation also successfully reduced her elevated BUN and serum creatinine. After full thyroid replacement, she was discharged in good health on the 40th postoperative day.

Female↗
PubMed1988

Evidence for histaminergic arousal mechanisms in the hypothalamus of cat.

Polygraphic 23-hr recordings were carried out in 25 adult cats in order to examine the effects of both systemic and local injections of various histaminergic and antihistaminergic drugs on sleep-waking cycles. alpha-Fluoromethylhistidine (alpha-FMH), a specific inhibitor of histidine decarboxylase, when injected intraperitoneally at a dose of 20 mg/kg, induced a significant increase in deep slow wave sleep (S2) and a decrease in wakefulness (W), without modifying light slow wave sleep (S1) and paradoxical sleep (PS). Intraperitoneal injections of mepyramine (1 mg and 5 mg/kg), a well-known histamine H1-receptor antagonist, increased deep slow wave sleep and decreased wakefulness, as well as paradoxical sleep. Bilateral injections of alpha-FMH (50 micrograms/1 microliter) into the ventrolateral posterior hypothalamus, where histamine immunoreactive neurones have been recently identified, resulted in a significant decrease in wakefulness and increase in deep slow wave sleep. Similarly, injections of mepyramine (120 micrograms/1 microliter) in the same structures caused a significant decrease in wakefulness and an increase in deep slow wave and paradoxical sleep as well. In contrast, local injections of SKF-91488 (50 micrograms/1 microliter), a specific inhibitor of histamine-N-methyltransferase, led to a significant increase in wakefulness and decrease in both slow wave sleep (SWS) and paradoxical sleep. Injections of histamine, at doses of 5, 30 and 60 micrograms/1 microliter, also increased wakefulness and decreased slow wave sleep dose dependently, while these effects were completely blocked by pretreatment with mepyramine. The results suggest that histaminergic systems in the hypothalamus play an important role in arousal mechanisms and their actions are mediated through H1-receptors.

Animals↗
PubMed1988

Establishment of human glial cell lines chronically infected with the human immunodeficiency virus.

Human malignant glioma cells were cotransfected with an infectious molecular clone of the human immunodeficiency virus (HIV) and a selectable drug resistance gene (neo). HIV/neo-positive cell clones were maintained in continuous culture for over 5 months and showed the following characteristics: (i) expression of HIV antigens as detected by indirect immunofluorescence staining in 80-90% of cells; (ii) efficient production of HIV RNA and infectious progeny virus; (iii) minimal cytopathic effects (notably in cell morphology), in contrast to HIV-infected T lymphocytes. These results demonstrate that certain glial cells originating from human brain can support a chronic infection with HIV comparable to that observed in T lymphoid cell lines. The cell lines provide an in vitro model system for studies on the mechanism and biological effects of HIV infection in glial cells, and offer an alternative source of the virus that has not been Adapted to lymphocytes or macrophages.

Antigens, Viral↗
PubMed1988

12-Hydroperoxyeicosatetraenoic acid (12-HPETE) and 15-HPETE stimulate melatonin synthesis in rat pineals.

The role of arachidonic acid metabolites in norepinephrine (NE)-induced N-acetyltransferase (NAT) activity and melatonin release was examined from 6 h-incubations of rat pineal glands. A cyclooxygenase inhibitor, indomethacin (5 x 10(-8) - 5 x 10(-6) M) was ineffective on melatonin release, in the presence of absence of NE (5 x 10(-6) M) while a lipoxygenase inhibitor, nordihydroguaiaretic acid (5 x 10(-7) -5 x 10(-5) M) had an inhibitory effect. Among the lipoxygenase metabolites, 12-hydroperoxyeicosatetraenoic acid (12-HPETE) and 15-HPETE stimulated both NAT activity and melatonin release in a dose-dependent manner, with a maximal effect occurring at 10(-6) M, while 5-HPETE or hydroxy derivatives of these compounds (12-HETE, 15-HETE and 5-HETE) were ineffective. These results indicate that 12-HPETE and 15-HPETE can be involved in NE-induced melatonin release.

Animals↗
PubMed1988

Increase in copy number of N-myc in retinoblastomas in comparison with chromosome abnormality.

N-myc oncogene amplification was studied in tumor tissue DNA from Japanese retinoblastoma patients, taking into consideration their uni- or bilateral disease form, their family history, and any chromosome abnormalities. Of the 23 cases examined, seven (30%) showed a 1.9- to 2.3-fold amplification of N-myc. No correlation was found between N-myc amplification and either tumor form or family history. Two of three cases having double minute bodies in their tumors showed N-myc amplification. In two tumors with 13q deletions, one produced in the host with constitutional 13q--abnormality showed no N-myc amplification, and the other one produced in the host with normal karyotype showed an N-myc amplification. These results indicate N-myc amplification is independent of the known genetic background in retinoblastoma patients.

Child↗
PubMed1988

Characterization of a major encephalitogenic T cell epitope in SJL/J mice with synthetic oligopeptides of myelin basic protein.

The C-terminal 89-169 amino acid fragment of myelin basic protein (MBP) causes experimental allergic encephalomyelitis (EAE) in SJL/J mice. In order to identify the encephalitogenic T cell epitope, we have examined the fine specificity of encephalitogenic SJL/J T cell clones with synthetic peptides derived from the C-terminal 89-169 amino acids of MBP. These peptides were examined for their immunogenic and encephalitogenic activity in the SJL/J mouse. The SJL/J-derived, encephalitogenic T cell clone, 4b.14a, was shown to be responsive to rat myelin basic protein synthetic peptides pR89-101 (VHFFKNIVTPRTP) as well as to intact MBP. Its response was effectively blocked by mAb 10-2.16 (anti-I-As) as was the response to intact MBP. Furthermore, pR89-101 was revealed to be highly immunogenic for the (PLSJ)F1 mouse in terms of lymphocyte proliferation, but not for the PL/J mouse, in spite of the fact that there exists a strong bias to H-2u restricted responses in the (PLSJ)F1 mouse at the T cell level. By using pR89-101, T cells of (PLSJ)F1 origin were revealed to recognize the peptide in association with the I-As molecule on (PLSJ)F1 antigen presenting cells (APC). When examined for encephalitogenicity for the SJL/J mouse, pR89-101 was found to be as encephalitogenic as intact rat MBP. These results demonstrated that MBP peptide pR89-101 is a major encephalitogenic determinant for the SJL/J mouse.

Amino Acid Sequence↗
PubMed1988

Effects of dithiothreitol and ascorbate on the penetration of diclofenac across excised rat dorsal skin.

The penetration of diclofenac through excised rat dorsal skin was found to be poor. Treatment of the skin with a reductant such as dithiothreitol or ascorbate increased the permeability of the skin to diclofenac, along with an increase in the protein thiol content of the stripped skin surface tissue. An increase in protein thiol content may increase the hydration capability of the stratum corneum.

Animals↗
PubMed1988

Involvement of distinct murine T-cell receptors in the autoimmune encephalitogenic response to nested epitopes of myelin basic protein.

The peptide p89-101 (Val-His-Phe-Phe-Lys-Asn-Ile-Val-Thr-Pro-Arg-Thr-Pro) of myelin basic protein is encephalitogenic in mice expressing H-2q and H-2s antigens. Six of 13 encephalitogen-specific T-cell clones were shown to express the variable beta-chain (V beta) 17a gene product (KJ23a+), whereas seven clones were KJ23a-. Both KJ23a+ and KJ23a- subpopulations were encephalitogenic in SJL/J mice when adoptively transferred. Depletion of KJ23a+ cells in vivo with the administration of the antibody KJ23a suppresses experimental allergic encephalomyelitis induced with KJ23a+ T-cell lines. However, experimental allergic encephalomyelitis induced with either (i) encephalitogenic peptide p89-101, (ii) intact myelin basic protein, or (iii) KJ23a- T cells reactive to p89-101 cannot be prevented with monoclonal antibody KJ23a. These data indicate that in spite of the V beta 17a gene expression in a relatively large proportion of p89-101-specific T cells, such V beta gene use is not essential for the induction of experimental allergic encephalomyelitis in SJL/J mice. These results contrast with the predominance of V beta gene use (V beta 8.2) in T cells reactive to the encephalitogenic fragment (pR1-11) in PL/J mice. One reason for this lack of dominant use of a particular T-cell receptor V beta gene family in the autoimmune response to myelin basic protein in SJL/J mice stems from the observation that two encephalitogenic epitopes exist in p89-101. KJ23a- T cells are stimulated by the deleted peptide p89-100, whereas KJ23a+ T cells are not. Thus, in the response to an encephalitogenic fragment of myelin basic protein containing two nested epitopes, at least two distinct T-cell receptor V beta genes are expressed. These distinct T-cell subpopulations can each trigger experimental allergic encephalomyelitis. These findings have implications for therapy of autoimmune disease with antibodies to the T-cell receptor gene products.

Animals↗
PubMed1988

p-nitrophenyl penta-N-acetyl-beta-chitopentaoside as a novel synthetic substrate for the colorimetric assay of lysozyme.

p-Nitrophenyl beta-glycosides of N-acetylchitooligosaccharides (PNP-(GlcNAc)n n = 3-5) were examined as substrates for lysozyme [EC 3.2.1.17]. The enzyme released predominantly p-nitrophenyl N-acetyl-beta-D-glucosaminide (PNP-GlcNAc) from each substrate. Furthermore, the initial rate of PNP-GlcNAc formation in lysozyme-catalyzed hydrolysis of p-nitrophenyl penta-N-acetyl-beta-chitopentaoside (PNP-(GlcNAc)5) was about 350 and 25 times faster than those of p-nitrophenyl tri-N-acetyl-beta-chitotrioside (PNP-(GlcNAc)3) and p-nitrophenyl tetra-N-acetyl-beta-chitotetraoside (PNP-(GlcNAc)4), respectively. From these results, a new colorimetric assay method of lysozyme using PNP-(GlcNAc)5 as a substrate was developed on the basis of the determination of p-nitrophenol liberated from the substrate by lysozyme through a coupled reaction involving beta-N-acetylhexosaminidase (NAHase). The assay system gave a linear dose-response curve in the range of 2-120 micrograms of lysozyme in a 15-60 min incubation. The present assay was not significantly influenced by the ionic strength of the medium and was reproducible. This method using PNP-(GlcNAc)5 as a substrate was shown to be useful for lysozyme assay.

Animals↗