Biomedical subjects

Y Hashimoto

Publications and source records attributed to Y Hashimoto.

At least 1,297 records · Page 72Linked to original sources

PubMed1987

Simple separation of tritiated water and [3H]deoxyuridine from [5-3H]deoxyuridine 5'-monophosphate in the thymidylate synthase assay.

A simple micromethod was developed for the accurate measurement of the activity of dTMP synthase in rat liver crude extracts. The reaction product of dTMP synthase activity assay, i.e., tritiated water, generated by the release of tritium from carbon-5 of [5-3H]deoxyuridine 5'-monophosphate (dUMP), was separated simply by 100% KOH absorption from [5-3H]deoxyuridine (dUrd), which is the side-product by dephosphorylation of [5-3H]deoxyuridine (dUrd), which is the side-product by dephosphorylation of [5-3H]dUMP during the enzyme reaction. Tritiated water was trapped in three droplets of 100% KOH deposited on the underside of the vessels' lids, while [3H]dUrd remained in the bottom of vessels after absorption of the substrate, [5-3H]dUMP, from the reaction mixture by charcoal treatment. Under standard assay conditions in the crude extract of rat liver, the specific activities of dTMP synthase and dUMP phosphatase were 0.092 +/- 0.002 and 0.351 +/- 0.013 nmol/h/mg protein, respectively. This method was also adapted for dTMP synthase assay in crude extracts of rat hepatoma 3924A. The major advantages of this procedure are the elimination of the phosphatase activity which interferes with the estimation of dTMP synthase activity in crude extracts, one-step separation of 3H2O, high sensitivity (with a limit of detection of 10 pmol of 3H2O production), high reproducibility (less than +/- 4.3%), and capability to measure activity in small amounts of sample (30-45 micrograms protein).

Animals↗

PubMed1987

The role of lymphokine-activated cell-associated antigen. II. Distribution and correlation with cell cycle.

It has previously been shown that killer-blocking monoclonal antibody (KBA MAb) recognizes lymphokine-activated cell-associated antigen (LAA) involved in broad-reactive killer. (BRK) cell-mediated cytotoxicity. We now report that LAA is expressed on all lymphoid cells, though the amount of LAA on unstimulated lymphocytes is low. In contrast, lymphocytes activated in vitro with either concanavalin A, alloantigens, lipopolysaccharide, or recombinant interleukin 2 express high levels of LAA. In addition, in vivo activated lymphocytes, such as OK-432-activated lymphocytes and tumor-infiltrating lymphocytes express higher levels of LAA than unstimulated lymphocytes. We also demonstrate that the expression of LAA is restricted in T-cell lymphomas and a M phi cell line, while myelomas, fibrosarcomas, and carcinomas do not express LAA. Cell cycle analysis using propidium iodide and KBA MAb showed that LAA expression was closely correlated with the transition of cells from G1a to G1b phase.

Animals↗

PubMed1987

The role of lymphokine-activated cell-associated antigen. III. Inhibition of T-cell activation by monoclonal killer-blocking antibody.

The addition of monoclonal killer blocking antibodies (KBA MAb) to cultured T cells resulted in significant inhibition of T-cell responses to concanavalin A (Con A), class I antigen and class II antigen, whereas T-cell responses to phytohemagglutinin are insensitive to KBA MAb. The inhibitory effect of KBA MAb is observed only when KBA MAb is added to the culture at an early time. This indicates that the lymphokine-activated cell-associated antigen (LAA) defined by KBA MAb plays an important role in the early stages of T-cell activation. Con A-induced interleukin 2 (IL-2) receptor acquisition and IL-2 production, both of which are required for the early steps of T-cell activation, were greatly inhibited by KBA MAb. However, KBA MAb did not inhibit the action of IL-2, which is required for later stages of T-cell activation.

Animals↗

PubMed1987

Newly synthesized analogues of the spider toxin block the crustacean glutamate receptor.

Effects of synthetic compounds similar to the structure of a spider toxin were studied on the glutamate receptors in crustacean neuromuscular synapses. Two kinds of analogues, 2,4-dihydroxyphenylacetyl-asparaginyl cadaverine (C-1) and 2,4-dihydroxyphenylacetyl-asparaginyl spermine (C-2), suppressed the excitatory postsynaptic potentials in a manner similar to natural spider toxin (JSTX). The dose-response relationship showed that the relative potency of the compounds is C-1 less than C-2 less than JSTX. While the effect of JSTX was irreversible, those of C-1 and C-2 were reversible. These synthetic compounds may serve as important tools in studying the structure and function of glutamate receptors.

Animals↗

PubMed1987

A rapid and simplified extraction of haloperidol from plasma or serum with bond elut C18 cartridge for analysis by high performance liquid chromatography.

This method for the determination of haloperidol (HAL) in plasma is based on high-performance liquid chromatography (HPLC) with a reversed-phase column, ODS-C18. HAL is rapidly extracted from human plasma by using Bond Elut C18 cartridge and its recovery is over 90%. The mobile phase is a mixture of 1% acetate/acetonitrile/tetrahydrofuran/triethylamine (69.5: 28.2:1.9:0.4, by vol.). The method is rapid, simple and free from intereferences and gives good precision.

Chromatography, High Pressure Liquid↗

PubMed1987

HIV-infection in forensic autopsy cases.

Sudden and unexpected death and violent death of persons with a high risk of acquiring HIV-infections, especially homosexual males and intravenous drug abusers, have to be investigated by forensic autopsies. Therefore every forensic pathologist has to be aware of this infection and should try to make the proper diagnosis. Three typical cases are described: (1) suicide by hanging, (2) homicide by cutting the throat and (3) intravenous heroin overdose. Merely retrospectively it could be cleared up that the deceased were homosexual but did not manifestly suffer from AIDS. The morphological findings in the lymph nodes and the postmortem serological findings are described in detail.

Acquired Immunodeficiency Syndrome↗

PubMed1987

T-cell receptor genes in autoimmune mice: T-cell subsets have unexpected T-cell receptor gene programs.

Two unique cell subsets have been identified in the autoimmune-prone MRL/MP lpr/lpr and C3H/HeJ gld/gld murine strains that have the Lyt-2-,L3T4-,Thy-1+, and Lyt-2-,L3T4-,Ia-,Thy-1- phenotypes, respectively. We have now found that these cells express T-cell receptor proteins on their surface. Our observations further indicate that the expression of the Thy-1 antigen does not correlate with the expression of alpha-chain and beta-chain T-cell receptor polypeptides. Interestingly, T-cell receptor gamma-chain RNA expression may be influenced or correlate with Thy-1 molecular expression. These studies indicate unusual relationships of different cell-surface structures that may reflect unexpected developmental programs.

Animals↗

PubMed1987

Species, sex and organ differences in induction of a cytochrome P-450 isozyme responsible for carcinogen activation: effects of dietary hepatocarcinogenic tryptophan pyrolysate components in mice and rats.

Both sexes of BALB/c X DBA/2 F1 mice and F344 rats were treated for 1 week with a diet containing 0.02% of hepatocarcinogenic tryptophan pyrolysate component (Trp P-1 or Trp P-2), and changes in the carcinogen activation enzyme activity in various organs were examined comparatively using a mutation test with Salmonella typhimurium TA98 as a tester bacterium. Hepatic enzymes from untreated mice and rats showed a definite catalytic activity for mutagenic activations of Trp P-1 and Trp P-2, whereas the activities of other organs--such as lung, kidney, small intestine and colon--were undetectable or very low. In both mice and rats either the Trp P-1 or Trp P-2 feeding resulted in induction of cytochrome P-450 isozyme(s), which could mediate in the liver but not in other organs the mutagenic activation of the carcinogen itself. As to the sex difference, the induction of the activation enzyme(s) was greater in the female animals than in the males. Species difference in the activity of hepatic enzymes catalyzing the Trp P-1 and Trp P-2 mutageneses was also observed in animals treated with the basal diet; the activity was higher in mice than in the sex-matched rats (Trp P-1, approximately 1.5-fold; Trp P-2, approximately 7-fold). When diet containing Trp P-1 or Trp P-2 was fed for 1 week, the activity of the rat liver for Trp P-1 mutagenesis was of a level similar to that of the sex-matched mice, but for Trp P-2 mutagenesis it was less than half that in the mice. The induced hepatic enzymes in mice and rats were suggested to be 3-methylcholanthrene-inducible cytochrome P-448 isozymes as determined by mutation tests with Trp P-1, Trp P-2 and two other substrates and by immunochemical analyses of rat hepatic cytochrome P-450 using monoclonal antibodies against rat cytochrome P-448 isozymes. These results indicate that a form of cytochrome P-450 responsible for activation of Trp P-1 and Trp P-2 is inducible by dietary treatment of mice or rats with these carcinogens and that the amount of the cytochrome P-450, including resident and induced forms, is related to the species, sex and organ differences in their carcinogenic susceptibility to these chemicals.

Animals↗

PubMed1987

Organ selective induction of cytochrome P-448 isozymes in the rat by 2-methoxy-4-aminoazobenzene and 3-methylcholanthrene.

Male Sprague Dawley rats were injected intraperitoneally with 2-methoxy-4-amino-azobenzene (2-MeO-AAB) or 3-methylcholanthrene (MC), and then the expression of microsomal cytochrome P-450 isozymes in liver and extrahepatic tissues was investigated by means of immunological methods and a bacterial mutation test. The results of protein A-enzyme-linked immunosorbent assaying and immunoblotting using anti-rat cytochrome P-448 monoclonal antibodies showed that MC induced at least two microsomal cytochrome P-448 isozymes, a high spin form (cytochrome P-448H) and a low spin form (cytochrome P-448L), in liver, but that it induced only cytochrome P-448L in extrahepatic tissues such as lung, kidney, small intestine, and colon. The results also indicated that, in contrast to MC, 2-MeO-AAB selectively induced microsomal cytochrome P-448H in liver but did not induce any cytochrome P-448 isozymes in extrahepatic tissues. The activities of 9,000 X g supernatants from the individual organs, as to the mutagenic conversion of 3 aromatic amines (3-amino-1-methyl-5H-pyrido(4,3-b)indole, 2-amino-6-methyldipyrido(1,2-a: 3',2'-d)-imidazole and 3-methoxy-4-aminoazobenzene), toward Salmonella typhimurium TA 98 bacteria were dependent upon the quantity and/or quality of the microsomal cytochrome P-448 isozymes in the organs.

Amines↗

PubMed1987

Reduced renal reabsorption of 1,5-anhydro-D-glucitol in diabetic rats and mice.

A stable amount, approximately 60 micrograms, of 1,5-anhydro-D-glucitol (AG) was detected in the 24-h-urine of normal young rats fed ad libitum. Upon administration of streptozotocin (STZ), this amount was temporarily elevated to as much as 1.1 mg and AG was concomitantly removed from the circulation. The plasma AG level stayed almost null thereafter while the acutely elevated urinary AG excretion declined within 24 h to another stable excretion level that was three times as high as that of the untreated rats. In contrast, glucosuria developed much more slowly in the drug-treated rats. Normal rats and mice retained exogenous [14C]AG to a considerable extent and the radioactivity was distributed all over the body. Only a marginal fraction of the radioactivity was excreted as expired CO2. The radio-activities retained in the body and excreted into the urine were mostly attributed to unmetabolized AG. The observations of AG's metabolic stability and its relatively low level of leakage into urine suggested the concept of effective renal AG reabsorption. On the other hand, the rats with STZ-induced diabetes and NOD-mice with spontaneously developed diabetes retained little of the radioactive AG in their bodies; most of the injected radioactivity was recovered in the urine within 24 h. This observation was interpreted as due to reduced renal AG reabsorption in these animals. The concept of reduction in renal AG reabsorption in diabetes could account for the reduced plasma AG level generally observed in human diabetic cases.

Absorption↗

PubMed1987

Direct effects of H2-receptor antagonists on airway smooth muscle and on responses mediated by H1- and H2-receptors.

Because it has been suggested that histamine H2-receptor antagonists may worsen airway constriction in asthmatic patients, we investigated the comparative effects of three histamine H2-receptor antagonists on guinea pig tracheal smooth muscle in vitro. When tested against resting tone, cimetidine, ranitidine and famotidine produced dose-related relaxation with pD2 values (negative log of ED50 for relaxation) (+/- SE, n; eq 5) of 3.20 +/- 0.04, 2.95 +/- 0.16 and 2.97 +/- 0.14, respectively. Concentrations that were below threshold for relaxation, did not elicit contraction. However, when the preparations were precontracted with histamine (10(-5)M), dose-response curves for relaxation were shifted to the right, and low-concentrations of all three histamine H2-antagonists augmented histamine-induced tone. When preparations were pretreated with cimetidine (10(-6) to 10(-4) M) and then tested for sensitivity to histamine, dose-response curves for histamine-induced contraction were shifted to the left (potentiated). These results provide further evidence for a modulatory effect of airway H2-receptors on the contractile response to histamine. In addition, since the concentrations associated with potentiation of histamine-induced contraction were about the same for all three H2-receptor antagonists (greater than or equal to 10(-5) M), our studies suggest a greater likelihood of airway constriction for the less potent H2-receptor antagonists that must be administered in higher clinical doses.

Animals↗

PubMed1987

Effect of dietary cholesterol on production of lipoproteins and apolipoproteins by perfused livers from Japanese monkeys (Macaca fuscata).

Isolated livers from Japanese monkeys were perfused for the purpose of characterizing low density lipoprotein (LDL) secreted directly by the liver, and for determining whether cholesterol feeding affects the hepatic production of LDL. Perfusate containing [3H]leucine was recirculated for 60 min, followed by perfusion with fresh perfusate for two additional 2-h periods. Radiolabelled lipoproteins, which are isolated by ultracentrifugation as very low density lipoprotein (VLDL), LDL, and high density lipoprotein were 0.87 +/- 0.74, 1.83 +/- 1.47, and 0.44 +/- 0.33%, respectively, of total radiolabelled protein in the medium of the last 2-h period. Subfractionation of perfusate LDL by high performance liquid chromatography, and by concanavalin A sepharose chromatography, revealed that the newly synthesized LDL were secreted as apo E-rich particles. Cholesterol feeding resulted in a four-fold increase in hepatic secretion of newly synthesized VLDL, but not of the LDL. The distribution of radioactivity among VLDL apolipoproteins was not affected by cholesterol feeding. Incorporation of radioactivity into apo B100 of LDL decreased significantly, but that into apo E did not change. These results suggested that (i) the elevation of serum LDL in cholesterol-fed monkeys is not due to enhanced hepatic production of LDL, but probably results from intravascular metabolism of VLDL, which is of hepatic origin, and (ii) cholesterol feeding affects the hepatic apo B100 synthesis and/or release but not apo E.

Animals↗

PubMed1987