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Biomedical subjects

M A Mohamed

Publications and source records attributed to M A Mohamed.

At least 19 recordsLinked to original sources
PubMed1991

Effect of some arsenic antagonists on the toxicity, distribution and excretion of arsenite and arsenate in rats.

1. Arsenite and arsenate poisoned rats were treated with either BAL (2,3-dimercapto-1-propanol), penicillamine (PA) (beta-beta dimethyl cystein) or selenium (Se) (as sodium selenite). 2. The minimal dose of each antagonist that treated arsenic-induced lethality (causing 100% survival) was the same for both arsenite and arsenate. 3. Arsenic mobilization from the tissues (blood, kidney, liver, lungs, spleen, muscles, brain, heart) and its excretion in urine and feces were higher in arsenite-intoxicated animals than in arsenate-intoxicated ones. 4. The effect of each antagonist, when injected alone, on the urinary and fecal excretion of endogenous metals (Cu, Zn, Fe, Ca and Mg) was also examined. 5. The results indicated marked differences in the relative ability of BAL, PA and Se to increase the excretion of the metals.

Animals↗
PubMed1991

Purification and characterization of purine nucleoside phosphorylase from developing embryos of Hyalomma dromedarii.

Purine nucleoside phosphorylase from Hyalomma dromedarii, the camel tick, was purified to apparent homogeneity. A molecular weight of 56,000 - 58,000 was estimated for both the native and denatured enzyme, suggesting that the enzyme is monomeric. Unlike purine nucleoside phosphorylase preparations from other tissues, the H. dromedarii enzyme was unstable in the presence of beta-mercaptoethanol. The enzyme had a sharp pH optimum at pH 6.5. It catalyzed the phosphorolysis and arsenolysis of ribo- and deoxyribo-nucleosides of hypoxanthine and guanine, but not of adenine or pyrimidine nucleosides. The Km values of the enzyme at the optimal pH for inosine, deoxyinosine, guanosine, and deoxyguanosine were 0.31, 0.67, 0.55, and 0.33 mM, respectively. Inactivation and kinetic studies suggested that histidine and cysteine residues were essential for activity. The pKa values determined for catalytic ionizable groups were 6-7 and 8-9. The enzyme was completely inactivated by thiol reagents and reactivated by excess beta-mercaptoethanol. The enzyme was also susceptible to pH-dependent photooxidation in the presence of methylene blue, implicating histidine. Initial velocity studies showed an intersecting pattern of double-reciprocal plots of the data, consistent with a sequential mechanism.

Amino Acids↗
PubMed1989

Polyacrylamide gel miniaturization improves protein visualization and autoradiographic detection.

Polyacrylamide gels shrink to one-quarter of their original area when soaked in a 50% (w/v) solution of polyethylene glycol. Gel miniaturization improves the contrast of protein bands, with four valuable consequences. (i) A 5- to 10-fold increase in sensitivity for Coomassie blue is observed. (ii) Gels are more durable; i.e., they resist tearing when wet and they do not crack during drying under vacuum. (iii) Shrunken gels give sharper photographic images and provide better interlane protein band comparisons. (iv) Condensed protein bands lead to an increased sensitivity for detecting low-abundance, radioactively-labeled proteins by fluorography.

Affinity Labels↗
PubMed1985

The effect of aflatoxin B1 on the utilization of serum calcium.

The mathematical analysis for plasma disappearance curve of aflatoxicosed animals, subsequently injected with 45Ca was determined. The analysis showed that the three main compartments of the calcium pool (plasma, bone and the labile calcium pool on the surface of bone and soft tissues) had been affected. Specifically, the fractional rate constant for migration of 45Ca from plasma pool to the labile pool had been diminished to its third value. This led to a corresponding reduction in the calcium content of the bone ash. The probable mechanism by which aflatoxin B1 affects calcium dynamics may be interpreted by the inhibitory effect of aflatoxin in the hydroxylation mechanism of vitamin D3 into an active intermediate. During aflatoxicosis (induction of 15 days) the animals entered a state of calcium deficiency, secondary to intestinal absorption inhibition. This was followed by bone resorption and disturbance of the fractional removal rate constant among different calcium compartments.

Aflatoxin B1↗
PubMed1984

Effect of oral contraception on serum bile acid.

Eighteen normal women, 20 with active urinary schistosomiasis, and 25 with past histories of viral hepatitis were given a contraceptive pill containing 0.05 mg ethinyl estradiol and 0.5 mg levonorgestrel for six consecutive cycles. Serum bile acid levels were measured by enzyme immunoassay method before and after 3 and 6 months of use. Simultaneously, conventional liver function tests (serum bilirubin, transaminases, alkaline phosphatase and albumin) were done. Serum bile acid concentration was not significantly changed by the contraceptive use in any group. The concentration of cholylglycine (the main bile acid measured) did not correlate with the values of any of the other tests. Pretreatment values of serum cholylglycine were significantly lower in the past-hepatitis group. The difference was maintained during treatment.

Alanine Transaminase↗
PubMed1972

Siderosis bulbi.

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Adult↗