Biomedical subjects

A Zayed

Publications and source records attributed to A Zayed.

At least 19 recordsLinked to original sources

PubMed2004

Effective population size in Hymenoptera with complementary sex determination.

Complementary sex determination in the haplodiploid Hymenoptera leads to the production of inviable or effectively sterile diploid males when diploid progeny are homozygous at the sex-determining locus. The production of diploid males reduces the number of females in a population and biases the effective breeding sex ratio in favor of haploid males. This in turn will reduce the effective population size (Ne) of hymenopteran populations with complementary sex determination relative to the expected reductions due to haplodiploidy alone. The effects of diploid male production on Ne in hymenopterans with complementary sex determination when diploid males are either inviable or effectively sterile are assessed theoretically. In both models, low allelic diversity at the sex locus reduces the Ne of hymenopteran populations, and this effect is largest when diploid males are effectively sterile.

Animals↗

PubMed2002

Managing selenium-contaminated agricultural drainage water by the integrated on-farm drainage management system: role of selenium volatilization.

The Integrated on-Farm Drainage Management (IFDM) system was designed to dispose of selenium (Se)-contaminated agricultural irrigation drainage water through the sequential reuse of saline drainage water to grow crops having different salt tolerance. This study quantified the extent of biological volatilization in Se removal from the IFDM system located in the western San Joaquin Valley, California. Selenium volatilization from selected treatment areas, including pickleweed (Salicornia bigelovii Torr.), saltgrass (Distichlis spicata L.), bare soil, and the solar evaporator, was monitored biweekly using an open-flow sampling chamber system during the pickleweed growing season from February to September 1997, and monthly from September 1997 to January 1998. Biological volatilization from the pickleweed section removed 62.0 +/- 3.6 mg Se m(-2) y(-1) to the atmosphere, which was 5.5-fold greater than the Se accumulated in pickleweed tissues (i.e., phytoextraction). The total Se removed by volatilization from the bare soil, saltgrass, and the solar evaporator was 16.7 +/- 1.1, 4.8 +/- 0.3, and 4.3 +/- 0.9mg Se m(-2) y(-1), respectively. Selenium removal by volatilization accounted for 6.5% of the annual total Se input (957.7mg Sem(-2) y(-1)) in the pickleweed field, and about 1% of the total Se input (432.7 mg Se m(-2) y(-1)) in the solar evaporator. We concluded that Se volatilization under naturally occurring field conditions represented a relatively minor, but environmentally important pathway of Se removal from the IFDM system.

Agriculture↗

PubMed2001

High levels of diploid male production in a primitively eusocial bee (Hymenoptera: Halictidae).

Under single locus complementary sex determination (sl-CSD), diploid males are produced from fertilized eggs that are homozygous at the sex-determining locus. Diploid males are effectively sterile, and thus their production generates a costly genetic load. Using allozyme electrophoresis, a large number of diploid males were detected in natural populations of the primitively eusocial bee, Halictus poeyi Lepeletier collected in southern and central Florida during May 2000. Estimates for the proportion of diploids that are male ranged from 9.1% to 50%, while the frequency of matched matings ranged from 18.2% to 100%. The effective number of alleles at the sex-determining locus ranged from two to 11, with an average of five alleles. The effective population size of Halictus poeyi was estimated to be 19.6 +/- 2.5 SE. These data are interpreted in the light of the biogeographic history of Florida and the social biology/population dynamics of H. poeyi.

Animals↗

PubMed1994

Feminization as a result of both peripheral conversion of androgens and direct estrogen production from an adrenocortical carcinoma.

A 45-year-old man presented with gynecomastia, hypertension and a large left adrenal mass. Further evaluation revealed elevated serum concentrations of estrogen, estrone sulfate, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, deoxycorticosterone, and aldosterone and increased 24-hour urinary 17-ketosteroid and free cortisol excretion. Removal of a 10 kg adrenocortical carcinoma led to normalization of the hormone concentrations and partial resolution of the gynecomastia. There was no clinical evidence of metastases. Incubation of tumor slices demonstrated that the tumor had an active aromatase and sulfotransferase. We estimated that about half the serum estrone arose from peripheral conversion of androstenedione. Feminizing adrenocortical carcinomas are rare and this case is unusual given the lack of clinical metastases and the probable dual source of estrogen from tumor as well as from the peripheral conversion of tumor-derived androgens.

Adrenal Cortex Neoplasms↗

PubMed1979

Synthesis and antibacterial activity of some nitrobenzimidazoles and 2(3H)-benzimidazolones.

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Anti-Bacterial Agents↗

PubMed1978

Synthesis of benzo-benzothiopyranoquinolines (pyridobenzothioxanthones) as possible schistosomicidal and antitumor agents.

The synthesis of a new class of compounds structurally related to cyclohexenothiaxanthones and benzothiaxanthones including a pyridine ring is described in an attempt to find compounds that may have schistosomicidal and carcinostatic activity. Synthesis was achieved through the condensation of amino-cyclohexenothiaxanthones and amino-benzothiaxanthones with ethyl acetoacetate by the Knorr and Conrad-Limpach methods.

Animals↗

PubMed1978