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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d) histochemistry was investigated in the axolotl (Ambystoma tigrinum) inner ear. Hair cells showed an intense NADPH-d reaction; afferent neurones also stained but less intensely than hair cells. Effects of NG-nitro-L-arginine (L-NOARG) on the basal discharge and mechanical responses of semicircular canal afferent neurones recorded extracellularly were also studied. L-NOARG (1 mu M) diminished the basal discharge and the response of afferent neurones to sinusoidal mechanical stimuli to 45 +/- 6.4% and 65 +/- 5.3% (mean +/- SEM) of control value, respectively. These findings suggest that production of nitric oxide (NO) by hair cells and probably also by afferent neurones contributes to the basal discharge and the response of afferent neurones to mechanical stimuli.
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PMID:Histochemistry and role of nitric oxide synthase in the amphibian (Ambystoma tigrinum) inner ear. 890 34

Homogenates of histologically normal human testis from three men were incubated separately with pregnenolone, 16-dehydropregnenolone, 5alpha-pregnane-3,20-dione, 3beta-hydroxy-5alpha-pregnan-20-one and androsta-5,16-dien-3beta-ol (androstadienol) in the presence of NADPH in a study of androst-16-ene and androgen biosynthesis. After the addition of internal standards and initial extraction and purification, metabolites were identified using gas chromatography-mass spectrometry (GC-MS) and monitoring selectively for three principal ions in each case at the appropriate GC retention time. Quantification was achieved by comparison with calibration lines for authentic steroids, together with the appropriate internal standards, prepared by monitoring three ion fragments for each analyte. In all experiments, androstadienol was found to be the major androst-16-ene metabolite of pregnenolone (seven times the control, i.e. endogenous, quantity; 19.8 +/- 3 ng/100 mg homogenate protein, mean +/- SEM, n = 9). Pregnenolone was also converted to androsta-4,16-dien-3-one (androstadienone) with three times the endogenous quantity (44 +/- 10 ng/100 mg homogenate protein, mean +/- SEM, n = 9) being formed. The formation of testosterone occurred only in trace amounts in the incubations of testis taken from one man (a 69-yr-old) but appreciable yields (six times endogenous levels 90 +/- 7 ng/100 mg homogenate protein, mean +/- SEM, n = 9) were found with testes from two younger men. Only traces of 5alpha-dihydrotestosterone were detected. Using androstadienol as the substrate, androstadienone was shown to be the major metabolite (approximately 10 times greater than control incubations) together with 5alpha-androst-16-en-3alpha- and 3beta-ols at approximately twice the endogenous quantities (5 ng/100 mg homogenate protein). In some incubations with androstadienol, 5alpha-androst-16-en-3-one (5alpha-androstenone) was formed (32 +/- 1 ng/100 mg homogenate protein/h; mean +/- SEM, n = 3); surprisingly, no endogenous 5alpha-androstenone could be detected. No evidence was obtained for the production of testosterone or 5alpha-DHT from androstadienol. Using cytosolic fractions of human testis, specific (displaceable) binding of 5alpha-androstenone was determined, with binding sites of approximately 200 fmol/mg tissue and a Ka of approximately 8 nmol/l.
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PMID:Use of gas chromatographic-mass spectrometric techniques in studies of androst-16-ene and androgen biosynthesis in human testis; cytosolic specific binding of 5alpha-androst-16-en-3-one. 918 68

Nitric oxide synthase (NOS) is responsible for the biological production of nitric oxide (NO) in several organs, including those of the reproductive tract. We investigated potential changes in NADPH-diaphorase (NADPH-d) activity (marker for NOS activity) and the presence and distribution of NOS in the porcine oviduct. Tissues were obtained from gilts (n=16) on different days of the estrous cycle. One fallopian tube was used for histo- and immunohistochemistry and the other for Western blotting analysis. NADPH-d activity was much higher in the epithelium of the mucosa than in the myosalpinx. The highest activity of NADPH-d was always found in the epithelium of the isthmus. The intensity of the reaction (arbitrary units +/- SEM) in isthmus epithelium increased from the postovulatory period until early proestrus (96.2 +/- 11.2) and then gradually decreased. The lowest intensity of NADPH-d reaction in the epithelium of the isthmus was seen at estrus (58.4 +/- 7.7). The most intense NADPH-d activity in myosalpinx of all parts of the oviduct was observed at the postovulatory stage of the estrous cycle (isthmus 38.3 +/- 2.5; ampulla 35.6 +/- 4.2; infundibulum 24.7 +/- 0.8) and then decreased during the remaining stages of the estrous cycle (p< 0.001). The presence of endothelial NOS (eNOS) was detected in epithelial cells of mucosa and in endothelium of vascular tissues and myosalpinx during all studied days of the estrous cycle. The positive reaction for inducible NOS (iNOS) was restricted only to the endothelium of lymph vessels and some blood vessels. Because our Western blotting analysis revealed that porcine oviduct contains eNOS but not iNOS, we suggest that eNOS is the main isoform of NOS expressed in the porcine oviduct. We concluded that the different activity of NADPH-d in the various regions of the oviduct, accompanied by changes in its activity during the course of the estrous cycle, could indicate an important role of NO in regulation of tubal function.
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PMID:Distribution of NADPH-diaphorase and nitric oxide synthase (NOS) in different regions of porcine oviduct during the estrous cycle. 1082 Jan 60

Red wine concentrate has been reported to inhibit the catalytic activity of human recombinant cytochrome P450 (CYP) 3A4. Wine contains many polyphenolic compounds, including trans-resveratrol, which is also available commercially as a nutraceutical product. In the present study, we examined the in vitro effect of trans-resveratrol on human CYP3A catalytic activity by employing recombinant CYP3A4 and CYP3A5 as model enzymes and 7-benzyloxy-4-trifluoromethylcoumarin (BFC) as a CYP3A substrate. Trans-resveratrol inhibited BFC O-dealkylation catalyzed by CYP3A4 and CYP3A5 in a concentration-dependent manner. In each case, the inhibition was noncompetitive, as determined by Lineweaver-Burk and Dixon plots of the enzyme kinetic data. The apparent Ki values (mean +/- SEM) for the inhibition by trans-resveratrol of BFC O-dealkylation catalyzed by CYP3A4 and CYP3A5 were 10.2+/-1.1 microM and 14.7+/-0.3 microM, respectively. Preincubation of trans-resveratrol with NADPH and CYP3A4 or CYP3A5 for 10 or 15 min prior to initiation of substrate oxidation did not enhance the inhibitory effect, suggesting that this compound was not a mechanism-based inactivator of CYP3A4 or CYP3A5 when BFC was used as the substrate. Overall, our study provides the first demonstration that trans-resveratrol inhibits, in vitro, a substrate oxidation reaction catalyzed by human recombinant CYP3A4 and CYP3A5.
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PMID:Effect of trans-resveratrol on 7-benzyloxy-4-trifluoromethylcoumarin O-dealkylation catalyzed by human recombinant CYP3A4 and CYP3A5. 1129 98

1. The metabolism of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) to 7-hydroxy-4-trifluoromethylcoumarin (HFC) was studied in human liver microsomal preparations and in cDNA-expressed human cytochrome P450 (CYP) isoforms. 2. Kinetic analysis of the NADPH-dependent metabolism of BFC to HFC in four preparations of pooled human liver microsomes revealed mean (+/- SEM) Km and Vmax of 8.3 +/- 1.3 microM and 454 +/- 98 pmol/min/mg protein respectively. 3. The metabolism of BFC to HFC was determined in a characterized bank of 24 individual human liver microsomal preparations employing BFC substrate concentrations of 20 and 50 microM (i.e. about two and six times Km respectively). With 20 microM BFC the highest correlations were observed between BFC metabolism and markers of CYP1A2 (r2 = 0.784-0.797) and then with CYP3A (r2 = 0.434-0.547) isoforms, whereas with 50 microM BFC the highest correlations were observed between BFC metabolism and markers of CYP3A (r2 = 0.679-0.837) and then with CYP1A2 (r2 = 0.421-0.427) isoforms. At both BFC substrate concentrations, lower correlations were observed between BFC metabolism and enzymatic markers for CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP4A9/11. 4. Using human beta-lymphoblastoid cell microsomes containing cDNA-expressed CYP isoforms, 20 microM BFC was metabolized by CYP1A2 and CYP3A4, with lower rates of metabolism being observed with CYP2C9 and CYP2C19. Kinetic studies with the CYP1A2 and CYP3A4 preparations demonstrated a lower Km with the CYP1A2 preparation, but a higher Vmax with the CYP3A4 preparation. 5. The metabolism of 20 microM BFC in human liver microsomes was inhibited to 37-48% of control by 5-100 microM of the mechanism-based CYP1A2 inhibitor furafylline and to 64-69% of control by 5-100 microM of the mechanism-based CYP3A4 inhibitor troleandomycin. While some inhibition of BFC metabolism was observed in the presence of 100 and 200 microM diethyldithiocarbamate, the addition of 2-50 microM sulphaphenazole, 50-500 microm S-mephenytoin and 2-50 microM quinidine had little effect. 6. The metabolism of 20 microM BFC to HFC in human liver microsomes was also inhibited by an antibody to CYP3A4, whereas antibodies to CYP2C8/9 and CYP2D6 had no effect. 7. In summary, by correlation analysis, use of cDNA-expressed CYP isoforms, chemical inhibition and inhibitory antibodies, BFC appears metabolized by a number of CYP isoforms in human liver. BFC metabolism appears to be primarily catalysed by CYP1A2 and CYP3A4, with possibly some contribution by CYP2C9, CYP2C19 and perhaps other CYP isoforms. 8. The results also demonstrate the importance of the selection of an appropriate substrate concentration when conducting reaction phenotyping studies with human hepatic CYP isoforms.
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PMID:Metabolism of 7-benzyloxy-4-trifluoromethyl-coumarin by human hepatic cytochrome P450 isoforms. 1131 4

Thiols like glutathione may serve as reducing cofactors in the production of nitric oxide (NO) and protect NO from inactivation by radical oxygen species. Depletion of thiol compounds reduces NO-mediated vascular effects in vitro and in vivo. The mechanisms underlying these actions are not clear, but may involve decreased synthesis of NO and/or increased degradation of NO. This study investigates the effect of glutathione depletion on the response to NO-mediated vasodilation induced by acetylcholine (Ach, 10 micrograms/kg), endothelial NO synthase (eNOS) activity and potential markers of vascular superoxide anion (O2.-) production in conscious chronically catheterized rats. Thiol depletion induced by buthionine sulfoximine (BSO, 1 g i.p. within 24 h) decreased the hypotensive effect of Ach by 30% (MAP reduction before BSO 27 +/- 3 mmHg, 19 +/- 3 mmHg after BSO, (mean +/- SEM), p < .05, n = 8). The impaired effect of Ach was associated with a significant reduction in eNOS activity (control: 7.7 +/- 0.8, BSO: 3.9 +/- 0.4 pmol/min/mg protein (p < .05), n = 6). In contrast, neither NADH/NADPH driven membrane-associated oxidases nor lucigenin reductase activity were significantly (p < .05) affected by BSO (BSO: 4415 +/- 123, control: 4105 +/- 455 counts/mg; n = 6) in rat aorta. It is concluded that in vivo thiol depletion results in endothelial dysfunction and a reduced receptor-mediated vascular relaxation. This effect is caused by reduced endothelial NO formation.
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PMID:Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels: role of endothelial nitric oxide synthase. 1169 35

In this study, the responses of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and neuronal nitric oxide synthase (nNOS) activities were quantitatively analyzed at different times in both ipsilateral and contralateral sides of trigeminal nuclei, after unilateral trigeminal muscle nerve transection, in Sprague Dawley rats. In the control animals, both NADPH-d- and nNOS-positive neurons were constitutively distributed in the rostrolateral solitary tract nucleus, dorsomedial part of trigeminal nucleus oralis (Vo/Sn), and superficial layers (VcI/II) of the trigeminal nucleus caudalis (Vc). NADPH-d-positive neurons appeared in the trigeminal mesencephalic nucleus ipsilaterally at 5 days (mean +/- SEM: 30.5 +/- 5.6) and were maintained until 8 weeks (33 +/- 10.6) after the denervation. In the trigeminal motor nucleus, NADPH-d-positive neurons appeared transiently and bilaterally, peaking at 1 week (663.5 +/- 156.2, ipsilateral side; 687.5 +/- 118.6, contralateral side) after unilateral denervation of the masseteric nerve. In both Vo/Sn and Vc, the number of NADPH-d-positive neurons in the control animals showed a decrease at 3 days but significantly increased from 5 days to 1 week and gradually fell to the control values by 8 weeks after the denervation. There were no significant differences observed between the two sides in either Vo/Sn or Vc. nNOS-positive neurons were similarly distributed and the numbers of labeled neurons were similar to those of NADPH-d-positive neurons after the denervation, although the changes were delayed by approximately 1 week. In conclusion, after unilateral nerve transection, the peak NADPH-d activity occurs 1 week prior to nNOS activity.
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PMID:Nitric oxide synthase/nicotinamide adenine dinucleotide phosphate-diaphorase in the brainstem trigeminal nuclei after transection of the masseteric nerve in rats. 1174 60

1. The effect of cimetidine on the metabolism of zaleplon (ZAL) in human liver subcellular fractions and precision-cut liver slices was investigated. 2. ZAL was metabolized to a number of products including 5-oxo-ZAL (M2), which is known to be formed by aldehyde oxidase, N-desethyl-ZAL (DZAL), which is known to be formed by CYP3A forms, and N-desethyl-5-oxo-ZAL (M1). 3. Human liver microsomes catalysed the NADPH-dependent metabolism of ZAL to DZAL. Kinetic analysis of three microsomal preparations revealed mean (+/-SEM) S(50) and V(max) of 310 +/- 24 micro M and 920 +/- 274 pmol/min/mg protein, respectively. 4. Human liver cytosol preparations catalysed the metabolism of ZAL to M2. Kinetic analysis of three cytosol preparations revealed mean (+/-SEM), K(m) and V(max) of 124 +/- 14 micro M and 564 +/- 143 pmol/min/mg protein, respectively. 5. Cimetidine inhibited ZAL metabolism to DZAL in liver microsomes and to M2 in the liver cytosol. With a ZAL substrate concentration of 62 micro M, the calculated mean (+/-SEM, n = 3) IC50 were 596 +/- 103 and 231 +/- 23 micro M for DZAL and M2 formation, respectively. Kinetic analysis revealed that cimetidine was a competitive inhibitor of M2 formation in liver cytosol with a mean (+/-SEM, n = 3) K(i) of 155 +/- 16 micro M. 6. Freshly cut human liver slices metabolized ZAL to a number of products including 1, M2 and DZAL. 7. Cimetidine inhibited ZAL metabolism in liver slices to M1 and M2, but not to DZAL. Kinetic analysis revealed that cimetidine was a competitive inhibitor of M2 formation in liver slices with an average (n = 2 preparations) K(i) of 506 micro M. 8. The results demonstrate that cimetidine can inhibit both the CYP3A and aldehyde oxidase pathways of ZAL metabolism in the human liver. Cimetidine appears to be a more potent inhibitor of aldehyde oxidase than of CYP3A forms and hence in vivo is likely to have a more marked effect on ZAL metabolism to M2 than on DZAL formation. 9. The results also demonstrate that precision-cut liver slices may be a useful model system for in vitro drug-interaction studies.
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PMID:Inhibition of zaleplon metabolism by cimetidine in the human liver: in vitro studies with subcellular fractions and precision-cut liver slices. 1241 15

Levels of components of the cytochrome P450 (CYP)-dependent monooxygenase system were characterised in microsomes of major biotransformation tissues, or whole bodies, of 33 species from six phyla of aquatic invertebrates. The phylogenetic distribution of benzo[a]pyrene hydroxylase (BPH) activity in the absence of added NADPH (so-called 'NADPH-independent BPH activity') and presence of NADPH was also examined. Microsomal protein yield was higher in individual tissues than whole tissues. The main components (total CYP and cytochrome b5; NADPH-dependent cytochrome c (CYP) reductase, NADH-dependent cytochrome c reductase and NADH-dependent ferricyanide (b5) reductase activities) were found in most species of the Porifera, Cnidaria, Mollusca, Polychaeta, Crustacea and Echinodermata examined. The so-called '418-peak' of the carbon-monoxide difference spectrum of reduced microsomes was found in all species, indicating the wide distribution of this protein. Total CYP levels (pmol mg(-1) protein; mean+/-SEM) were similar in molluscs (50+/-7), crustaceans (61+/-11) and echinoderms (56+/-9), with the exception of high levels (223-266) in two crustacean species. NADPH-dependent BPH activity (pmol min(-1) mg(-1) protein) was found in 32 species, being lowest in Porifera and Cnidaria (3-4), intermediate in Mollusca (7.8+/-1.3), and highest in Crustacea (25+/-4) and Echinodermata (15+/-4). NADPH-independent BPH activity was evident in 13 out of 15 molluscan species examined, with the addition of NADPH either stimulating (8 species) or inhibiting (5 species) the activity. NADPH-independent BPH activity was also seen in two poriferan species and indicated in three crustacean species, suggesting that the phenomenon is not solely restricted to the Mollusca.
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PMID:Components of the cytochrome P450-dependent monooxygenase system and 'NADPH-independent benzo[a]pyrene hydroxylase' activity in a wide range of marine invertebrate species. 1597 46

The elimination of tetryl was studied using ring-labeled 14C-tetryl. Tetryl was given subcutaneously to male Sprague-Dawley rats at doses of 25, 100, and 300 mg kg(-1), and urine and feces were collected 24 h post-injection. Percent urinary elimination was observed to be 10.02 +/- 2.48, 11.2 +/- 1.66, and 13.24 +/- 5.79 (mean +/- SEM) respectively. Percent fecal elimination was 15.68 +/- 6.13, 9.41 +/- 1.52, and 8.45 +/- 1.81 respectively. At 24 h post-injection, tissues from male Sprague-Dawley rats were collected from animals that received 100 mg kg(-1) 14C-tetryl. Tetryl was found to be poorly absorbed with approximately 65% of the administered dose remaining at the site of subcutaneous injection. Blood was found to be the principal depot of radioactivity, followed by muscle, liver, and kidney. Analysis of the tissue to blood radioactivity ratio revealed that the liver had the highest ratio (1.2), followed by brain (0.45), kidney (0.38), and testes (0.35). All other tissues analyzed had ratios less than 0.30. Urine of animals receiving 14C-tetryl (100 mg kg(-1)) was analyzed using HPLC coupled with UV detection (200-600 nm; 1.2 nm resolution). During HPLC analysis, 1 min fractions were collected and radioactivity measured. Two major peaks of radioactivity were identified at approximately 5 and 14 min retention times, respectively. The 14 min peak had the same retention time and UV spectrum as picric acid and 5 min peak had the same retention time and UV profile as picramic acid. The data presented demonstrates that that there is little retention of tetryl in specific tissue depots and that tetryl is eliminated in roughly equal amounts in both urine and feces. The major urinary metabolites identified picric acid and picramic acid (a known urinary metabolite observed in rabbits). From microsomal fraction studies, a major metabolite, NMPA, was identified. The formation of this metabolite was found to be dependent on at least two enzymes. One enzyme is dependent on NAD+ for NMPA formation and is likely to be NADP(H):quinone oxidoreductase. The second metabolite is NADP+ dependent and is probably related to NADPH:cytochrome-P450 reductase.
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PMID:Tissue distribution and elimination of N-methyl-N-2,4,6-tetranitroaniline (tetryl) in rats. 1768 Feb 34


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