PubMed Health⌕ Search

Biomedical subjects

J B Mays

Publications and source records attributed to J B Mays.

At least 19 recordsLinked to original sources
PubMed1993

Elevated lipoprotein (a) blood levels as the single treatable atherosclerotic risk factor in patients with coronary artery disease.

An elevated blood level of lipoprotein (a) [Lp(a)] has been studied as an independent risk factor for coronary artery disease. We report a series of nine consecutive patients with clinical onset or recurrence of coronary artery disease who presented without treatable atherosclerosis risk factors, five of whom had elevated Lp (a) blood levels. Indications for measuring Lp (a) levels and usefulness of niacin therapy are reviewed.

Aged↗
PubMed1992

Inhibition of mouse glutathione transferases and glutathione peroxidase II by dicumarol and other ligands.

Dicumarol, often used as a specific inhibitor of DT diaphorase (NAD(P)H:(quinone-acceptor) oxidoreductase; EC 1.6.99.2), was found to potently inhibit GSH transferases (EC 2.5.1.18). Dicumarol exhibited an IC50 of 11 microM in inhibiting the conjugation of 1-chloro-2,4-dinitrobenzene (50 microM) by GSH transferase GT-8.7, the major hepatic class mu isoenzyme of CD-1 mice. The activities of GT-8.7 and of the class pi isoenzyme, GT-9.0, toward a carcinogenic substrate, 4-nitroquinoline 1-oxide (100 microM), were inhibited by dicumarol with IC50 values of 14 and 9 microM, respectively. Dicumarol also affected GSH peroxidase II activity, inhibiting the reduction of cumene hydroperoxide by GT-10.6, the predominant class alpha GSH transferase of mouse liver, with an IC50 of 14 microM. GSH peroxidase I (EC 1.11.1.9) and GSH peroxidase II activities were resolved by chromatography of liver and testis cytosols. While inhibiting GSH peroxidase II with IC50 of 9-10 microM, dicumarol did not affect the activity of the selenoenzyme, GSH peroxidase I. Whereas several other non-substrate ligands were more potent inhibitors of 1-chloro-2,4-dinitrobenzene conjugation, dicumarol effectively inhibited GSH transferase and GSH peroxidase II activities in the range of dicumarol concentrations frequently used for detection of DT diaphorase action. These results indicate that physiological consequences resulting from the use of supramicromolar concentrations of dicumarol should not be interpreted in terms of DT diaphorase inhibition alone.

4-Nitroquinoline-1-oxide↗
PubMed1990

Cardiorespiratory interactions in patients with an artificial heart.

A retrospective analysis of the influence of respiration was carried out in three patients with artificial hearts. During spontaneous ventilation, large swings in intrathoracic pressure can produce a pattern reminiscent of pulsus paradoxus in the systemic arterial pressure. A decrease in intrathoracic pressure decreased biventricular filling and enhanced biventricular emptying. An increase in intrathoracic pressure increased biventricular filling, but acting as an increased afterload, impeded biventricular emptying. The influence of respiration on the artificial heart can be considered the result of the artificial ventricles' functioning effectively as extrathoracic pumps, such that changes in intrathoracic pressure produce gradients for biventricular filling and ejection relative to atmospheric pressure (which serves as the reference pressure for the artificial ventricles). Respiratory-induced variation in ventricular performance is clearly present with the artificial heart, but the mechanisms producing these changes appear to be markedly different from normal conditions, in which the ventricles are functionally within the thorax and have a compliant common septum allowing ventricular interaction.

Atrial Function↗
PubMed1986

Covalent binding of the phenacetin metabolite p-nitrosophenetole to protein.

Addition of p-[3H]nitrosophenetole to protein incubations resulted in quantitative binding of radiolabel to protein. Preincubation of protein with N-methylmaleimide to derivatize sulfhydryl groups followed by addition of p-[3H]nitrosophenetole resulted in a 90% decrease in covalent binding. Treatment of the p-[3H]nitrosophenetole protein-bound residue, after extensive solvent washing, with HCl decreased binding by 72% and the corresponding amine, p-phenetidine was detected in the aqueous phase. Inasmuch as incubation of the bound residue with reduced glutathione did not alter protein binding appreciably the involvement of a sulfinanilide S-oxide is suggested. Incubation of p-[3H]phenetidine with microsomal incubation mixtures resulted in NADPH-dependent covalent binding to protein. Treatment of the p-[3H]phenetidine protein-bound residue after extensive solvent washing with HCl decreased binding by 64%. Administration of either p-[3H]phenetidine (500 mg/kg i.p.) or [14C]phenacetin (500 mg/kg i.p.) to mice resulted in covalent binding of radiolabel to protein of liver, lung, kidney, small intestine and blood. Incubation of solvent-washed protein with acid resulted in an approximately 35% decrease in protein binding in lung and blood of both treatment groups.

Animals↗
PubMed1984

Acetaminophen-induced alterations in blood glucose and blood insulin levels in mice.

Three hours following administration of a toxic dose of the analgesic acetaminophen (500 mg/kg) to mice, blood glucose levels increased to 225 per cent. By six hours blood glucose levels decreased to approximately control values and by 24 hours glucose levels were 45 percent saline-treated control values. Immunoprecipitable blood insulin levels increased dramatically following acetaminophen treatment and were 300 per cent at 3 hours, 1100 per cent at 8 hours and 800 per cent at 24 hours. Saline treatment did not appreciably alter blood insulin levels. These observations indicate that acetaminophen may selectively alter pancreatic beta cells.

Acetaminophen↗
PubMed1984

Reaction of mutagenic phenacetin metabolites with glutathione and DNA. Possible implications for toxicity.

The direct-acting mutagens, N-hydroxy-p-phenetidine and p-nitrosophenetole, are known to be metabolites of the analgesic phenacetin and may be responsible for its carcinogenic activity. In this study, the potential detoxification of these metabolites by glutathione was examined. Glutathione reacted rapidly with p-nitrosophenetole, which was quantitatively converted to a single product as determined by high-pressure liquid chromatography. The analysis of the product by fast atom bombardment mass spectrometry and 500-MHz 1H-NMR spectroscopy established its structure as N-(glutathion-S-yl)-p-phenetidine. The same glutathione conjugate was also formed when N-hydroxy-p-phenetidine was incubated with glutathione. However, since conjugate formation from N-hydroxy-p-phenetidine occurred slowly and was decreased in the presence of an argon atmosphere as well as by higher levels of glutathione, it was concluded that the conjugate resulted from oxidation of the N-hydroxy arylamine to the nitrosoarene, which subsequently reacted with glutathione. N-(Glutathion-S-yl)-p-phenetidine was semistable in water (half-life, 6-7 hr) and very unstable in the presence of nucleophiles such as 10 mM glutathione (half-life, 7 min), quantitatively decomposing to p-phenetidine. The conjugate was also very unstable in acidic buffers (half-life, 17 min, pH 5). Radiolabeled N-hydroxy-p-phenetidine, but not p-nitrosophenetole, was shown to bind covalently to calf thymus DNA in vitro, and 4 times more binding was detected at pH 5 than at pH 7. Glutathione did not significantly decrease binding of the N-hydroxy derivative at either pH, nor did purified ring-radiolabeled N-(glutathion-S-yl)-p-phenetidine significantly bind to DNA at either pH. Thus, we hypothesize that an important detoxification pathway for phenacetin in vivo could involve the facile oxidation of N-hydroxy-p-phenetidine to p-nitrosophenetole, which then reacts rapidly with glutathione to form an excretable conjugate.

Aminophenols↗
PubMed1983

Acetaminophen-induced hepatic glycogen depletion and hyperglycemia in mice.

Two hours following administration of a hepatotoxic dose of acetaminophen (500 mg/kg, i.p.) to mice, liver sections stained with periodic acid Schiff reagent showed centrilobular hepatic glycogen depletion. A chemical assay revealed that following acetaminophen administration (500 mg/kg) hepatic glycogen was depleted by 65% at 1 hr and 80% at 2 hr, whereas glutathione was depleted by 65% at 0.5 hr and 80% at 1.5 hr. Maximal glycogen depletion (85% at 2.5 hr correlated with maximal hyperglycemia (267 mg/100 ml at 2.5 hr). At 4.0 hr following acetaminophen administration, blood glucose levels were not significantly different from saline-treated animals; however, glycogen levels were still maximally depleted. A comparison of the dose-response curves for hepatic glycogen depletion and glutathione depletion showed that acetaminophen (50-500 mg/kg at 2.5 hr) depleted both glycogen and glutathione by similar percentages at each dose. Since acetaminophen (100 mg/kg at 2.5 hr) depleted glutathione and glycogen by approximately 30%, evidence for hepatotoxicity was examined at this dose to determine the potential importance of hepatic necrosis in glycogen depletion. Twenty-four hours following administration of acetaminophen (100 mg/kg) to mice, histological evidence of hepatic necrosis was not detected and serum glutamate pyruvate transaminase (SGPT) levels were not significantly different from saline-treated mice. The potential role of glycogen depletion in altering the acetaminophen-induced hepatotoxicity was examined subsequently. When mice were fasted overnight, hepatic glutathione and glycogen were decreased by 40 and 75%, respectively, and fasted animals showed a dramatic increase in susceptibility to acetaminophen-induced hepatotoxicity as measured by increased SGPT levels. Availability of glucose in the drinking water (5%) overnight resulted in glycogen levels similar to those in fed animals, whereas hepatic glutathione levels were not significantly different from those of fasted animals. Fasted animals and animals given glucose water overnight were equally susceptible to acetaminophen-induced hepatotoxicity, as quantitated by increases in SGPT levels 24 hr after drug administration. The potential role of a reactive metabolite in glycogen depletion was investigated by treating mice with N-acetylcysteine to increase detoxification of the reactive metabolite. N-Acetylcysteine treatment of mice prevented acetaminophen-induced glycogen depletion.

Acetaminophen↗
PubMed1982

Cytochrome P-450- and flavin-containing monooxygenase-catalyzed formation of the carcinogen N-hydroxy-2-aminofluorene and its covalent binding to nuclear DNA.

The metabolic N-oxidation of the carcinogen 2-aminofluorene was examined in vitro using fortified hepatic microsomes from a variety of species. Rat, dog, human, and pig liver microsomes catalyzed the formation of N-hydroxy-2-aminofluorene (N-OH-AF) from AF at rates of 1.6, 1.0, 1.2, and 3.5 nmol/min/mg protein, respectively. The involvement of both cytochrome P-450 and the flavin-containing monooxygenase was demonstrated with hepatic microsomes and with purified enzymes by using specific enzyme inhibitors. 2-[(2,4-Dichloro-6-phenyl)phenoxy]ethylamine, a potent cytochrome P-450 inhibitor, decreased microsomal N-OH-AF formation by 96, 83, 70, and 46% in the rat, dog, human, and pig, respectively; and further addition of methimazole, a high-affinity flavin-containing monooxygenase substrate, abolished the residual N-hydroxylating activity. Using the purified porcine flavin-containing monooxygenase, metabolic formation of N-OH-AF occurred at a rate of 4.9 nmol/min/nmol flavin adenine nucleotide and was insensitive to 2-[(2,4-dichloro-6-phenyl)phenoxy]ethylamine inhibitor. In addition, purified rat liver cytochrome P-450 (isolated from 5,6-naphthoflavone-induced animals) N-hydroxylated AF (1.1 nmol/min/nmol P-450) and was completely inhibited by 2-[(2,4-dichloro-6-phenyl)-phenoxy]ethylamine, but the reaction was insensitive for methimazole. To determine whether or not the metabolic formation of N-OH-AF could lead directly to covalently bound adduct(s) with DNA under these incubation conditions (30 min, pH 7.5), the binding of synthetic and metabolically formed [3H]-N-OH-AF to added calf thymus DNA and to DNA in isolated rat liver nuclei was investigated. In all cases, the amount of DNA-bound carcinogen accounted for 0.08 to 0.15% of the N-OH-AF present in the incubation mixtures. These data, when compared to the levels of AF bound to hepatic nuclear DNA reported in vivo, suggest that the nonenzymatic reaction of N-OH-AF with nuclear DNA may be sufficient to account for a substantial portion of the observed in vivo binding of this carcinogen.

Animals↗
PubMedDate not supplied

Indexes of hemolysis in human recipients of the Jarvik-7 total artificial heart: a cooperative report of fifteen patients.

The degree of red cell destruction in human recipients of the total artificial heart has not previously been described. Fifteen patients implanted with a Jarvik-7 total artificial heart for either temporary or permanent heart replacement were reviewed. Clinically significant elevations of plasma free hemoglobin and serum lactate dehydrogenase were demonstrated in patients receiving the standard (100 ml) Jarvik-7 containing Medtronic-Hall valves and powered by pulses of compressed air delivered at a dP/dT of 6000 mm Hg/sec to 8000 mm Hg/sec. Reduction of the dP/dT by drive unit modification greatly reduced the plasma free hemoglobin and lactate dehydrogenase in subsequent patients. Introduction of the smaller (70 ml) total artificial heart was not associated with greater hemolysis once dP/dT had been reduced. With the current driver delivering systolic pulses at less than 4500 mm Hg/sec, both size hearts are free of clinically relevant hemolysis. In addition, it appears that attempts to eliminate hemolysis completely by lowering heart rates, cardiac outputs, or driving pressures are potentially dangerous. The eventual development of embolic cerebrovascular accidents is associated statistically with heart rates below 80 beats/min. These data reassure implanting physicians that the updated Jarvik-7 total artificial heart system does not induce worrisome hemolysis. In addition, this study has uncovered a link between eventual cerebrovascular accident and low heart rate, implying that purposeful application of heart rates around 100 beats/min may provide a significant margin of protection against cerebrovascular accident during implantation.

Adult↗