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Biomedical subjects

S F Mahmoud

Publications and source records attributed to S F Mahmoud.

10 recordsLinked to original sources
PubMed2004

Regulation of Slo potassium channel alternative splicing in the pituitary by gonadal testosterone.

Slo gene-encoded BK potassium channels are prominent in both adrenomedullary and pituitary tissues. At one alternative splicing site, both tissues express variants with and without the optional 'STREX' exon. In adrenal chromaffin cells, this splicing choice, which has important ramifications for cell excitability, has been shown to be regulated by steroid hormones, including glucocorticoids and adrenal androgens. Moreover, striking sex differences are seen between male and female tree shrews. Here, we test the hypothesis that gonadal testosterone regulates splicing in these tissues. No significant sex differences were found in rats, in either adrenals or pituitaries. In the adrenal medulla, prepubertal castration in male rats increased the relative abundance of STREX transcripts slightly, but not significantly, as measured several weeks after puberty. However, castration substantially decreased STREX representation in the rat pituitary. Silastic implants of testosterone inserted at castration prevented this STREX decline. In postpubescent males, castration or T implants had less effect. Thus, we report (i) steroidal regulation of Slo splicing in the pituitary and (ii) participation of the male gonads in this regulation.

Adrenal Medulla↗
PubMed2001

Microdomains of high calcium are not required for exocytosis in RBL-2H3 mucosal mast cells.

We have previously shown that store-associated microdomains of high Ca(2+) are not essential for exocytosis in RBL-2H3 mucosal mast cells. We have now examined whether Ca(2+) microdomains near the plasma membrane are required, by comparing the secretory responses seen when Ca(2+) influx was elicited by two very different mechanisms. In the first, antigen was used to activate the Ca(2+) release-activated Ca(2+) (CRAC) current (I(CRAC)) through CRAC channels. In the second, a Ca(2+) ionophore was used to transport Ca(2+) randomly across the plasma membrane. Since store depletion by Ca(2+) ionophore will also activate I(CRAC), different means of inhibiting I(CRAC) before ionophore addition were used. Ca(2+) responses and secretion in individual cells were compared using simultaneous indo-1 microfluorometry and constant potential amperometry. Secretion still takes place when the increase in intracellular Ca(2+) occurs diffusely via the Ca(2+) ionophore, and at an average intracellular Ca(2)+ concentration that is no greater than that observed when Ca(2+) entry via CRAC channels triggers secretion. Our results suggest that microdomains of high Ca(2+) near the plasma membrane, or associated with mitochondria or Ca(2+) stores, are not required for secretion. Therefore, we conclude that modest global increases in intracellular Ca(2+) are sufficient for exocytosis in these nonexcitable cells.

Animals↗
PubMed1997

Correlating Ca2+ responses and secretion in individual RBL-2H3 mucosal mast cells.

The role of Ca2+ in stimulus-response coupling in nonexcitable cells is still not well understood. The Ca2+ responses of individual cells are extremely diverse, often displaying marked oscillations, and almost nothing is known about the specific features of these Ca2+ signals that are important for the functional response of a cell. Using the RBL-2H3 mucosal mast cell as a model, we have studied the temporal relationship between changes in intracellular Ca2+ and serotonin secretion at the single-cell level using simultaneous indo-1 photometry and constant potential amperometry. Secretion in response to antigen never occurs until intracellular Ca2+ is elevated, nor is it seen during the first few oscillations in Ca2+. Exocytotic events tend to be clustered around the peaks of oscillations, but excellent secretion is also seen in cells with sustained elevations in Ca2+. Ca2+ release from stores in the absence of influx fails to elicit secretion. If refilling and continued release of Ca2+ from stores is prevented with thapsigargin, Ca2+ influx can still trigger secretion, suggesting that store-associated microdomains of Ca2+ are not required for exocytosis. Our findings demonstrate the importance of an amplitude-encoded Ca2+ signal and Ca2+ influx for stimulus-secretion coupling in these nonexcitable cells.

Animals↗
PubMed1997

Lawrence-Seip syndrome: report of a case from Egypt.

A case of acquired total lipodystrophy (Lawrence-Seip syndrome) is reported in a 17-year-old Egyptian girl. The patient had generalized lipodystrophy, eruptive xanthomas, diabetes mellitus, and severe osteoporosis.

Adolescent↗
PubMed1996

Basal cell carcinoma in Qatar.

BACKGROUND: There is an increasing incidence of basal cell carcinoma (BCC) and skin cancer in general among various countries, where the sun is implicated as an important causative factor. METHODS: Results of clinical and histopathologic examination and the incidence rate of BCCs were recorded over a period of 5 years at Hamad Medical Corporation, Doha, Qatar. RESULTS: Basal cell carcinoma is the commonest skin cancer in Qatar. The average annual incidence per 100,000 residents of working manpower, standardized to the 1986 census, is 9.9 for both sexes and at all ages. Expatriates formed the highest proportion and of these, Europeans were predominant. The tumor was more frequent in men, on sun-exposed areas, was mostly of the nodular and infiltrative type, and occurred in the 3rd, 4th, and 5th decades. As a whole, persons with relatively heavily pigmented skin constituted 66.7% of the patients. CONCLUSIONS: Intense sunlight exposure during outdoor work and leisure activities in Qatar puts residents at increased risk for nonmelanoma skin cancer, even in persons with relatively pigmented skin.

Adult↗
PubMed1993

Fatal anaphylactic reaction to diclofenac.

A case of apparent anaphylactic reaction to diclofenac sodium (Voltaren) is reported. A 45-year-old man collapsed 15 min after intramuscular injection of diclofenac for treatment of low back pain. Twenty minutes following successful resuscitation, he went into coma from which he never recovered and was pronounced dead on the following day. To our knowledge, this is the first reported case of anaphylactic reaction to diclofenac.

Anaphylaxis↗
PubMed1991

Leprosy in Qatar.

Clinical and histopathologic features of 104 cases of leprosy diagnosed between 1982 and 1989 in the State of Qatar were studied. There were 88 male (84.6%) and 16 (15.4%) female patients aged 18 to 64 years. Eighty-four of the cases were diagnosed during the initial mandatory medical screening on arrival to Qatar. Almost all (103) were expatriates and only one 50-year-old woman was a Qatari. Indians formed the largest group (60.6%), followed by Bangladeshi (6.7%), Pakistani (5.8%), and others. The majority of cases were classified as lepromatous (43.3%) or tuberculoid (43.3%). Although Qatar is a relatively leprosy-free country, the influx of a large number of workers from developing countries seeking employment forms a potential public health hazard.

Adolescent↗
PubMed1988

Klippel-Trenaunay syndrome.

An unusual and extreme case of Klippel-Trenaunay syndrome is presented. The patient has an extensive capillary hemangioma involving the right side of the body, increases in the length and girth of the right lower limb, gross varicosities of the superficial venous system, and complete absence of the deep venous system of the right lower extremity, with suprapubic shunt of the venous blood to the contralateral external iliac vein. Secondary manifestations are increased sweating and compensatory scoliosis.

Adult↗