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T Watabe

Publications and source records attributed to T Watabe.

At least 145 records · Page 8Linked to original sources
PubMed1985

Sulfate esters of hydroxymethyl-methyl-benz[a]anthracenes as active metabolites of 7,12-dimethylbenz[a]anthracene.

7-Hydroxymethyl-12-methylbenz[a]anthracene (7-HMBA) and 12-hydroxymethyl-7-methylbenz[a]anthracene (12-HMBA), carcinogenic major metabolites of 7,12-dimethylbenz[a]anthracene (DMBA) in untreated rat liver, showed high mutagenic activities toward Salmonella typhimurium TA 98 after preincubation with a sulfotransferase-PAPS system consisting of ATP, sodium sulfate, and a post-mitochondrial fraction (S-9) or a soluble supernatant fraction (S-105) from untreated rat liver. The 7- and 12-HMBAs themselves induced His+ mutation in TA 98 only slightly after preincubation with S-9 in the presence of an NADPH-generating system. Mutagenicity of DMBA toward TA 98 after preincubation with S-9 in the presence of the NADPH-generating system was remarkably enhanced by the addition of ATP and sodium sulfate. The active metabolites, 7-HMBA sulfate and 12-HMBA sulfate, were isolated from these preincubation systems and identified by comparison with the corresponding synthetic specimens. The sulfuric acid ester conjugates were potent mutagens toward TA 98 in the absence of rat liver subcellular fractions. The conjugates bound covalently at significant rates to calf-thymus DNA as well as to S-105 proteins at 37 degrees and pH 7.4 through the 7- or 12-methylene carbon with concomitant loss of their sulfate group. In the presence of S-105, glutathione inhibited the mutagenicity of the metabolically formed or exogenously added 7- and 12-HMBA sulfates. The non-mutagenic glutathione conjugates were isolated from the incubation mixtures and identified as S-(12-methylbenz[a]anthracen-7-yl)methylglutathione from 7-HMBA or its sulfate and S-(7-methylbenz[a]anthracen-12-yl)methylglutathione from 12-HMBA or its sulfate.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Regiospecific and diastereoselective inactivation of mutagenic 9,10-dihydrobenzo[a]-pyrene 7,8-oxide by hepatic cytosolic glutathione S-transferase.

Racemic, (7R,8S)-(+)-, and (7S,8R)-(-)-9,10-dihydrobenzo[a]pyrene 7,8-oxides (DBPOs) showed markedly different mutagenicity towards Salmonella typhimurium TA 98 in the order of (7R,8S)-(+)- greater than racemic greater than (7S,8R)-(-)-DBPOs. The enantiomeric epoxides were inactivated at significantly different rates by preincubating with rat liver cytosol fortified with glutathione (GSH) in the order of (7S,8R)-(-)- greater than racemic greater than (7R,8S)-(+)-DBPOs. Two non-mutagenic water-soluble metabolites were isolated from the preincubation mixture containing racemic DBPO as a substrate, separated by hplc, and identified by 13C nmr and uv absorption spectroscopy as diastereoisomers of S-(8-hydroxy-7,8,9,10-tetrahydrobenzo[a]pyren-7-yl)glutathione (conjugates I and II). Conjugates I and II were specifically yielded from (7R,8S)-(+)- and (7S,8R)-(-)-DBPOs, respectively, at different rates by rat liver cytosol; apparent values of Km were 20.1 and 15.6 microM and of Vmax 17.2 and 26.7 nmole/mg protein/min for (7R,8S)-(+)- and (7S,8R)-(-)-DBPOs, respectively. Conjugates I and II, therefore, were reasonably assigned to have (7S,8S)- and (7R,8R)-configurations, respectively. Conjugate II was yielded preferentially to conjugate I from racemic DBPO at an early stage of the enzyme reaction.

Animals↗
PubMed1984

A mechanism for epoxidation of cholesterol by hepatic microsomal lipid hydroperoxides.

Evidence was obtained, using cis-stilbene as a model substrate, for the participation of peroxy and/or oxy radicals in epoxidation of cholesterol by rat liver microsomal phospholipid hydroperoxides and a ferrous ion-ADP complex. Under the conditions used, cholesterol was epoxidised to the alpha- and beta-epoxides in the ratio 1:2-4, and cis-stilbene to trans-stilbene oxide without concomitant formation of the cis-oxide. Microsomal phospholipid hydroperoxides could be replaced with methyllinoleate monohydroperoxide for the epoxidation of both substrates. The hydroperoxide-mediated epoxidations were completely inhibited by alpha-tocopherol and t-butylhydroxyanisole. A GLC study suggested that highly polyunsaturated fatty acyl constituents of the microsomal phospholipids might play an important role in epoxidation of the olefinic substrates.

Adenosine Diphosphate↗
PubMed1984

7-Glycidoxycoumarin (GOC): a fluorophotometric epoxide substrate for the assay of glutathione S-transferase activity.

7- Glycidoxycoumarin ( GOC ), a new fluorophotometric epoxide substrate for glutathione S-transferase (GSH TFase ), was conjugated regiospecifically with GSH at pH 6.5 in rat liver cytosol to yield S-(2-hydroxy-3-(7'- coumaroxy )-1-propyl)glutathione which was isolated by HPLC and identified with an authentic specimen by 13C NMR spectroscopy. The conjugation product formed in the incubation media consisting of GOC , GSH, and 9000 g supernatant fractions from various tissues of the rat, was directly determined by photometry of fluorescence emission at 388 nm at an excitation wavelength of 328 nm after removal of the unreacted substrate and its enzymic hydrolysis product, 7-(1',2'-dihydroxy-3'-propoxy)coumarin, by simple extraction with isobutyl alcohol in the presence of a saturating amount of sodium chloride. Stability of GOC at pH 6.5 markedly retarded its autoconjugation with GSH and made the fluorophotometric method sensitive enough to assay small GSH TFase activities in gel column chromatographic fractions as well as in various tissues of the animals. Apparent Km and Vmax for GOC in rat liver cytosol were 55 microM and 7.41 nmole/mg protein/min, respectively. GSH conjugation of GOC was catalyzed by at least two isozymes, E and AA, of hepatic GSH TFases .

Animals↗
PubMed1984

Studies on relationship between cysts and granulomas in murine cryptococcosis.

The histopathology of murine cryptococcosis was observed until the 55th day and particular attention was paid to whether or not cysts, which had been formed in the brain, could change to granulomas. Cryptococcus neoformans RIB-12M was used in this experiment. As experimental animals, five-week-old male BALB/c mice, weighing 20-22 g, were used. An infective inoculum was prepared by adjusting the number of cryptococci to 10(6) or 5 X 10(6)/0.2 ml. Each mouse was inoculated intravenously with 0.2 ml of the cell suspension, and the colony forming unit of the brain and liver, and the histopathological findings in various visceral organs were investigated. 40 X 10(4) colonies grew from 100 mg of the brain tissue of the eighth day. Thereafter, the number increased gradually. It reached 500 X 10(4) on the 20th day. The colony forming unit from the liver reached a peak on the 12th day (250 X 10(4] and thereafter the number decreased gradually. Histopathologically, the brain and liver were severely affected with the fungus. In the brain cysts with cryptococci continued to increase until the end of the experiment. On the other hand, in the liver several purulent foci appeared on the second day. On the eighth day numerous mononuclear cells accumulated at the foci and their lesions changed to granulomatous ones with cryptococci. The number of granulomatous lesions reached a peak on the 16th day in the mice inoculated with 5 X 10(6) cryptococci, and thereafter showed a tendency to decrease gradually.

Animals↗
PubMed1984

Immunologic characterization of plasma glucagon components in a patient with malignant glucagonoma.

Plasma immunoreactive glucagon (IRG) components were analyzed by gel filtration on either a Bio-Gel P-30 or a Sephadex G-150 column (1.0 X 68 cm) in a 47-year-old male with biopsy-proven malignant glucagonoma. Plasma samples were obtained before and after 20 courses of streptozotocin treatment as well as after administration of a somatostatin-derivative (SRIF-D, 0.38 mg, subcutaneous), regular insulin (0.2 U/kg, intravenous), and secretin (2 U/kg, intravenous). The fractions from the columns were assayed for IRG by simultaneous radioimmunoassay with C-terminal (Unger 30 K) and N-terminal (OAL 196) antibodies to glucagon. Four IRG components were observed. The largest had a molecular weight of approximately 150,000 daltons and cross-reacted much more strongly with the N-terminal antibody than with the C-terminal. The second IRG component appeared to be about 9000 daltons and cross-reacted more strongly with the N-terminal antibody. The third and major IRG component comprised 51.8% to 88.1% of the total IRG as measured with C-terminal antibody, corresponded in molecular weight to synthetic 3500 dalton glucagon, and reacted roughly equally with each of the two antibodies. The fourth IRG component cross-reacted only with N-terminal antibody and appeared to be smaller than 3500 daltons. The plasma IRG level decreased from 8829 pg/mL to 1421 pg/mL (averages of five consecutive determinations) after 20 courses of treatment with streptozotocin with significant clinical improvement. A marked (74%) but transient decrease in plasma IRG was observed after the SRIF-D injection, whereas secretion and insulin caused increases in plasma IRG level of 53% and 22%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Islet Cell↗
PubMed1984

Existence of multiple forms of microsomal epoxide hydrolases with radically different substrate specificities.

Evidence for the existence in rat and rabbit liver of two microsomal epoxide hydrolases with radically different substrate specificities was obtained, one with a broad specificity (EHb), whilst the other catalyzed the hydrolysis of cholesterol 5 alpha,6 alpha-oxide (EHch), a reaction taken as diagnostic since it was not observed with pure fractions of EHb. The two enzymes were physically separated by immunoprecipitation using antibodies which had been raised against EHb purified to apparent homogeneity. The substrate specificity of the two enzymes is radically different and mutually complementary. Cholesterol 5 alpha,6 alpha-oxide has a trisubstituted oxirane ring. All epoxides of this nature tested to date were not, or very poor, substrates of EHb. The two enzymes can also effectively be discriminated by inhibitors, in that 5 alpha,6 alpha-imino-5 alpha-cholestane-3 beta-ol potently inhibits EHch but not EHb whilst 1,1,1-trichloropropene oxide has the opposite specificity. The cytosolic EH did not significantly contribute to the catalysis of the hydrolysis of cholesterol 5 alpha,6 alpha-oxide.

Animals↗
PubMed1984

Effect of synthetic ovine corticotropin-releasing factor on growth hormone secretion in patients with acromegaly.

In a significant proportion of patients with acromegaly, a non-specific increase in plasma growth hormone (GH) has been recognized following administration of thyrotropin-releasing hormone (TRH) or luteinizing hormone-releasing hormone (LH-RH), probably due to the lack of the specificity of the receptor in their tumor cells. In this study, the effects of corticotropin-releasing factor (CRF), a newly isolated hypothalamic hormone, in addition to TRH and LH-RH, on plasma levels of GH and the other anterior pituitary hormones were evaluated in 6 patients with acromegaly. Synthetic ovine CRF (1.0 microgram/kg), TRH (500 micrograms) or LH-RH (100 micrograms) was given as an iv bolus injection, in the morning after an overnight fast. Blood specimens were taken before and after injection at intervals up to 120 min, and plasma GH, adrenocorticotropin (ACTH), thyrotropin, prolactin, luteinizing hormone, follicle-stimulating hormone and cortisol were assayed by radioimmunoassays. A non-specific rise in plasma GH was demonstrated following injection of TRH and LH-RH, in 5 of 6 and 2 of 5 patients, respectively. In all subjects, rapid rises were observed in both plasma ACTH (34.3 +/- 6.2 pg/ml at 0 min to 79.5 +/- 9.5 pg/ml at 30 min, mean +/- SEM) and cortisol level (9.1 +/- 1.3 micrograms/dl at 0 min to 23.4 +/- 1.2 micrograms/dl at 90 min). However, plasma levels of GH and the other anterior pituitary hormones did not change significantly after CRF injection. These results indicate that CRF specifically stimulates ACTH secretion and any non-specific response of GH to CRF appears to be an infrequent phenomenon in this disorder.

Acromegaly↗
PubMed1983

Studies on metabolism and toxicity of styrene--VI. Regioselectivity in glutathione S-conjugation and hydrolysis of racemic, R- and S-phenyloxiranes in rat liver.

Rat liver cytosol converted phenyloxirane enantiomers regioselectively to glutathione S-conjugates. R-(+)-Phenyloxirane was converted to S-(1-phenyl-2-hydroxyethyl)glutathione (conjugate 1) and S-(2-phenyl-2-hydroxyethyl)glutathione (conjugate 2) (ratio 6.1:1), and S-(-)-phenyloxirane to conjugates 1 and 2 (ratio 1:32). Racemic phenyloxirane was converted to conjugates 1 and 2 (ratio 1.8:1). The conjugates were separated by HPLC on an octadecylsilicone column and identified with synthetic specimens whose structures were assigned by 13C NMR spectrometry. R-(+)-, S-(-)- and racemic phenyloxiranes were hydrolyzed to R-(-)-, S-(+)- and racemic phenylethanediols by microsomal epoxide hydrolase without inversion of absolute configurations of their benzylic carbons. R-(+)-Phenyloxirane had much smaller Km and Vmax than the S-(-)-oxirane did. The R-(+)-oxirane potentially inhibited the microsomal hydrolysis of the S-(-)-oxirane and was preferentially hydrolyzed when the racemic oxirane was used as the substrate. Microsomal monooxygenase oxidized styrene to R-(+)- and S-(-)-phenyloxiranes (ratio 1.3:1), and the ratio was little changed by the pretreatment of the animal with phenobarbital, 3-methylcholanthrene and polychlorinated biphenyls.

Animals↗