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Biomedical subjects

S Khalifa

Publications and source records attributed to S Khalifa.

At least 19 recordsLinked to original sources
PubMed1993

Myocardial infarction in Qatar: the first 2515 patients.

The data registry of all patients admitted between 1982 and 1990 to the Coronary Care Unit at Hamad General Hospital with the diagnosis of documented acute myocardial infarction is reviewed. We report a total of 2,515 patients (86.6% men and 13.4% women) with a mean age of 51 years (range 18-99). Of these, 62% were smokers, 29% had diabetes, and 20% had hypertension. The hospital mortality rate was 10%. The most significant factors associated with higher mortality were older age, female gender, and anteroseptal infarction. The age of 23% of the patients was 40 years or younger. Comparison between these younger patients (Group I) and those over 40 years (Group II) demonstrated that Group I had lower mortality (3.6%) than Group II (12%) (p < 0.001). Group I patients were predominantly men (96.8%), of Asian nationalities (71%), and usually smokers (78%). The observation that myocardial infarction occurs frequently in young Asian men needs further evaluation to identify specific risk factors.

Adult↗
PubMed1983

Stimulation of calcium uptake by parathyroid hormone in renal brush-border membrane vesicles. Relationship to membrane phosphorylation.

The effect of parathyroid hormone (PTH) on Ca2+ uptake was studied in brush-border membrane vesicles (BBMV) prepared from the kidneys of dogs administered 4-5 micrograms/kg of bovine PTH 1-84 in vivo. PTH stimulated Ca2+ uptake at 20 s of incubation from control values of 231 +/- 21 to 306 +/- 30 pmol/mg of protein, p less than 0.001. The stimulation of Ca2+ uptake by PTH was not reversed by incubation of the BBMV with the Ca2+ ionophore, despite the fact that Ca2+ uptake was several times greater than the expected uptake at equilibrium, indicating that most of the uptake represented Ca2+ binding to the BBMV. In BBMV from kidneys exposed to PTH, hypotonic lysis or increasing the osmolality of the solution external to the BBMV did not affect Ca2+ uptake. These data also indicated that the largest fraction of Ca2+ uptake in the presence of a chemical potential represented binding of Ca2+ to BBMV. Ca2+ binding was initially to the exterior of the BBMV, then translocated within the membrane and to the interior vesicular face as assessed by chelation of Ca2+ bound to the BBMV by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Incubation of BBMV from kidneys exposed to PTH with gentamicin, which competes with Ca2+ for anionic phospholipid-binding sites, reversed the stimulatory effects of PTH on Ca2+ uptake. Phosphorylation of BBMV and PTH treatment in vivo had similar effects on BBMV phospholipid composition increasing the levels of anionic phospholipids. Phosphorylation of the BBMV also produced gentamicin-inhibitable increases in membrane Ca2+ binding. Phosphorylation of BBMV from kidneys exposed to PTH was inhibited suggesting a higher state of phosphorylation in vivo. The data demonstrate that PTH administered in vivo stimulated Ca2+ binding in BBMV that was gentamicin inhibitable and associated with an increase in the membrane content of anionic phospholipids.

Animals↗
PubMed1975

Retinoblastoma. A model of hereditary fragile chromosomal regions.

Direct karyotyping of tumour cells from three familial and two sporadic cases of retinoblastoma revealed the existence of a Dq- marker chromosome. The hypothesis is launched that a specific region on the long arm of one of the D chromosomes is the site of a locus which is essential for the sustained differentiation of specialized retinal tissue and may be the site of other loci essential for the maturation of other embryonic tissues. Fragility of this region and its potentiality for breakage under the influence of various environmental insults could be the basic cytological event leading to the development of sporadic retinoblastoma. Mutants at these loci, including those of sustained differentiation, could be a less common operational event whereby some variants could enhance the fragility of their respective chromosomal region and thereby explain the genetic transmission of retinoblastoma in certain families. It is common for the critical functional disruption of the locus to precede the deletion which may then be considered the terminal event in the fragile region.

Child, Preschool↗
PubMed1974

Toxaphene insecticide: a complex biodegradable mixture.

Adsorption and gas-liquid chromatography separate toxaphene into at least 175 polychlorinated 10-carbon compounds including Cl(6), Cl(7), Cl(8), Cl(9), and Cl(10) derivatives. One toxic component is 2,2,5-endo,6-exo,8,9,10-heptachlorobornane. Rats metabolically dechlorinate toxaphene, removing about half of the chlorine from the technical insecticide and from each of seven subfractions of varying composition and toxicity.

Animals↗