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Biomedical subjects

S Helmi

Publications and source records attributed to S Helmi.

9 recordsLinked to original sources
PubMed1996

A sensitive sperm-motility test for the assessment of cytotoxic effect of pesticides.

A sensitive sperm-motility test for the evaluation of cytotoxic effects of carbofuran and glyphosate in a defined protein-free culture medium is described. The sperm motility was compared to that obtained with a protein-containing medium. The use of protein-free medium considerably increased the sensitivity of sperm cells from rabbit and human to the toxic effects of the pesticide. The respective IC50 values (the concentration needed to cause 50% inhibition of sperm motility) in protein-free medium of carbofuran and glyphosate were 321 and 48.2 microM with human sperm, and 116 and 23.5 microM with rabbit sperm. Whereas, the corresponding values in protein-containing medium were 920 and 740 microM, and 910 and 500 microM with human and rabbit sperm, respectively. Our results show that testing human and rabbit sperm in protein-free medium proves to be a more sensitive method than that in protein-containing medium. Additionally, the use of rabbit sperm is a more sensitive test system than human sperm. This study suggests that the rabbit sperm test appears to have a potential for the assessment of toxicity on human reproduction.

Animals↗
PubMed1995

Toxic effects of carbofuran and glyphosate on semen characteristics in rabbits.

The present study was undertaken to investigate the effect of chronic treatment with two sublethal doses of Carbofuran (carbamate insecticide) and Glyphosate (organophosphorus herbicide) on body weight and semen characteristics in mature male New Zealand white rabbits. Pesticide treatment resulted in a decline in body weight, libido, ejaculate volume, sperm concentration, semen initial fructose and semen osmolality. This was accompanied with increases in the abnormal and dead sperm and semen methylene blue reduction time. The hazardous effect of these pesticides on semen quality continued during the recovery period, and was dose-dependent. These effects on sperm quality may be due to the direct cytotoxic effects of these pesticides on spermatogenesis and/or indirectly via hypothalami-pituitary-testis axis which control the reproductive efficiency.

Animals↗
PubMed1994

Nitrate, nitrite and volatile N-nitroso compounds in the urine of Schistosoma haematobium and Schistosoma mansoni infected patients.

The present study presents, for the first time, the amounts of nitrate, nitrite and volatile N-nitroso compounds in saliva and urine samples of Schistosoma haematobium and Schistosoma mansoni infected patients. Mid-morning saliva and 24 h urine samples were collected from male patients infected with S.haematobium (n = 129 saliva and 79 urine samples) and S.mansoni (n = 64 saliva and 65 urine samples) and in a comparative control group of healthy individuals (n = 27) from the Nile Delta region of Egypt. Saliva samples were analyzed for the presence of nitrate and nitrite; while urine samples were analyzed for the presence of nitrate, nitrite and volatile N-nitroso compounds. In the control group, N-nitroso-dimethylamine (NDMA) was detected at concentrations (mean +/- SD) of 0.27 +/- 0.47 microgram/day. N-Nitrosopiperidine (NPIP; 0.6 microgram/day) and N-nitrosopyrrolidine (NPYR; 0.4 microgram/day) were also present in one sample. S.mansoni infected subjects showed significantly (P < 0.001) higher levels of 2.9 +/- 2.9 micrograms/day NDMA and a higher frequency of NPIP (in 40/65 samples; 0.4 +/- 0.3 microgram/day) and NPYR occurrence (in 59/65 samples; 0.9 +/- 0.9 microgram/day). Significant further increases in the excretion of volatile N-nitroso compounds were found in S.haematobium-infected patients with mean daily excretion of 19.2 +/- 21 micrograms/day NDMA (in all samples; P < 0.001), 1.6 +/- 2.3 micrograms/day NPIP (in 56/79 samples; P < 0.001) and 1.3 +/- 1.9 micrograms/day NPYR (in 58/79 samples; P < 0.1). The differences either in salivary nitrite/nitrate or in urinary nitrite between the three distinct groups were not significant. However, the urinary excretion of nitrate was elevated from 139 +/- 82 mg/day in the control group to 249 +/- 126 mg/day in S.mansoni infected patients (P < 0.001) and to 174 +/- 176 mg/day in S.haematobium infected subjects (P < 0.005 in comparison to S.mansoni infected group). These results suggest a possible role of N-nitroso compounds in the etiology of schistosome-associated bladder cancer and imply a partial participation of S.mansoni in the multistage process of urinary schistosomiasis-associated bladder carcinogenesis.

Adult↗
PubMed1989

The effects of gene conversion control factors on conversion-induced changes in allele frequencies in populations and on linkage disequilibrium.

Conversion control factors (ccfs) are widespread. They control conversion properties at their target loci, affecting the conversion frequency and the amount and even the direction of gene conversion disparity. Three major types of ccf can be recognised. Experimental studies of the effects of ccfs have been combined with theoretical studies and modelling to examine the effects of ccfs on the evolutionary population genetics of alleles at the target locus. The ccf alleles present can greatly affect the rate and the direction of conversion-induced changes in target locus allele frequencies. Gene conversion can both cause and remedy linkage disequilibrium, with causation being related to polymorphism for ccfs. Disparity in conversion direction does not by itself necessarily cause linkage disequilibrium.

Alleles↗