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Biomedical subjects

A I Ahmed

Publications and source records attributed to A I Ahmed.

At least 19 recordsLinked to original sources
PubMed1998

Review of 3,530 referrals for bone density measurements of spine and femur: evidence that radiographic osteopenia predicts low bone mass.

PURPOSE: To determine the relationship between bone mineral density (BMD) measurements and the initial reason for referral to a BMD screening service. MATERIALS AND METHODS: Referral letters for 3,479 of the 3,530 women referred for BMD screening were classified according to the indication for screening. Mean age-matched standard deviation scores (Z scores) were derived for each of the 10 most common indications. Mean BMD between each group was compared with the age-matched value from the local normal range by means of a one-sample Student t test. Mean young normal standard deviation scores (T scores) were derived, and the percentages of women with osteopenia or osteoporosis from each referral group were calculated on the basis of the World Health Organization criteria. RESULTS: The most common reason for referral was to aid in a decision regarding hormone replacement therapy (n = 700). The highest proportion of women with osteoporosis in any group was in the radiographic osteopenia group (n = 269). CONCLUSION: Radiographic evidence of osteopenia is a strong predictor of osteoporosis. Screening for osteopenia appears justified in this and other high-risk groups and those seeking a rationale for preventive therapy.

Adolescent↗
PubMed1997

Screening for osteopenia and osteoporosis: do the accepted normal ranges lead to overdiagnosis?

Osteoporosis is a common disease which causes significant morbidity and mortality and in many cases may be preventable. In the absence of fragility fractures the accepted method of identifying those at high risk is based upon bone mineral density (BMD) measurements with defined cut-off points. To correctly delineate normal from abnormal, reliable reference ranges appropriate to the observed population are required. We have studied the age-dependent changes in mean BMD and standard deviation at the lumbar spine and femoral neck in a normal population extracted from 4280 women screened for osteopenia and compared our findings with the manufacturer's normal range (MNR). The recent World Health Organization criteria for the diagnosis of osteopenia and osteoporosis using the 'manufacturer's young normal' (MYN) values and our 'study young normal' (SYN) values have been applied. The study normal population (SNP) included 2068 women (mixed social class; mean age 53 years, range 30-79 years). The distribution of mean lumbar spine BMD with age in SNP was generally similar to the MNR. In contrast mean femoral neck bone density from SNP was significantly different from the MNR, ranging from 3% to 12% lower in each 5-year group analysed (p < 0.05). Comparison of standard deviations in spine BMD in SNP against the fixed MNR standard deviation showed a statistically significant increase commencing at 45 years of age. The magnitude of this increase appeared to rise with age and remained significant in the 75- to 79-year age group (p < 0.05). In contrast, standard deviation in femoral neck BMD in SNP appeared relatively constant with age except in the group of women at and around the time of the menopause. The SYN value for mean lumbar spine BMD was 0.994 g/cm2 (cf. MYN value 1.047, p < 0.0001) with a standard deviation of 0.122 g/cm2 (cf. MYN 0.11, p = 0.0005). Similarly our SYN value for femoral neck BMD was 0.787 (cf. MYN value 0.895, p < 0.0001) with a standard deviation of 0.109 (cf. MYN value 0.10, p = 0.0027). Using SYN values 36% (748) for the spine and 33% (675) for the hip of our normal population are classified as osteopenic or osteoporotic. Using MYN values increases the proportion of women classified as osteopenic or osteoporotic to 52% (1078) for the spine and 68% (1409) for the femur. If both sites of measurement are considered simultaneously SYN classifies 46% (952) as either osteopenic or osteoporotic at one or other site, which is increased to 73% (1513) when the MYN values are used. We observe that manufacturer's reference ranges may not be appropriate for the local population and may lead to an erroneously high diagnosis of osteopenia and osteoporosis, which would lead to unnecessary patient anxiety and perhaps errors regarding treatment.

Adult↗
PubMed1995

Hormone replacement therapy and serum angiotensin-converting-enzyme activity in postmenopausal women.

The mechanisms by which hormone replacement therapy (HRT) reduces the risk of coronary heart disease (CHD) are incompletely understood, but may include direct arterial effects. We examined the effect of oestrogen/progestagen HRT on serum angiotensin-converting-enzyme (ACE) activity in postmenopausal women. After 6 months, ACE activity was reduced by 20% (p < 0.001) on average in 28 treated women but remained unchanged in 16 controls. Serum ACE activity is modifiable by gonadal steroids and changes in serum ACE may represent a novel mechanism by which HRT reduces CHD risk in women.

Coronary Disease↗
PubMed1993

Prolonged pregnancy.

The perceived risks to the fetus of the postmature syndrome have led to the obstetrician's dilemma of whether to await spontaneous parturition or to artificially bring forward the onset of labor to an arbitrarily defined gestation. A prolonged or post-term pregnancy relates to a gestation of greater than 42 weeks and should not be regarded as synonymous with postmaturity. The latter describes a clinical syndrome thought to be a consequence of failing placental function. It is the difficulty in identifying the 'at risk' fetus which has led to routine induction policies. But is such a policy justified in terms of fetal outcome, and if so, is the mother put at increased risk? This review puts into perspective the most recent publications and points out areas requiring further study.

Algorithms↗
PubMed1989

Trypanosome infection rate of Glossina morsitans submorsitans in Bahr El Arab, South Darfur Province, Sudan.

Trypanosome infection rate of Glossina morsitans submorsitans in Bahr El Arab fly belt, Sudan was investigated in four areas using fly rounds with screen and bait animals together with traps during the dry season February to May 1985. The overall infection rate of tests flies captured in the four areas was 5.1%. The infection rate of vivax group trypanosomes comprised 64.7% of total infections, congolense group 31.2% and brucei group trypanosomes 3.9%: 27.3% of the vivax and 31.3% of the congolense were immature trypanosome infections. Mixed trypanosome infections were encountered in a few flies. Trypanosome infection rate of flies differed with the sampling technique employed. A linear positive correlation existed between the physiological age of males and their trypanosome infection rates.

Age Factors↗
PubMed1986

Ocular toxicity of desferrioxamine: light microscopic histochemical and ultrastructural findings.

This study documents for the first time light and electron microscopical changes in the retinal pigment epithelium (RPE) following treatment with high dose desferrioxamine for systemic iron overload. The changes include loss of microvilli from the apical surface, patchy depigmentation, vacuolation of the cytoplasm, swelling and calcification of mitochondria, and disorganisation of the plasma membrane. In addition, Bruch's membrane overlying degenerate RPE cells appeared abnormally thickened owing to the accumulation of large amounts of mature elastic fibres, pre-elastic oxytalan, and long spacing collagen. The specificity of these changes and the mechanism of toxicity are discussed.

Adult↗
PubMed1985

Physiological and pathobiological significance of ocular glycoproteins. I. Studies using fluorescein labelled glycine max.

Cell surface carbohydrates play an important role in several biological, immunological, and neoplastic phenomena including development, growth regulation, cellular locomotion, receptor activation, and tumour metastasis. Fluorescein labelled lectins which bind to specific carbohydrate residues in glycoproteins and glycolipids are being increasingly used as chemical probes to study cell components. Several different preparations of ocular tissues from human, rabbit, and rat were examined for the distribution of N-acetyl-D-galactosamine (D-gal NAc) by means of fluorescein-labelled lectin from soybean (glycine max). A very strong fluorescence was observed in the corneal epithelium; Descemet's membrane and corneal endothelium were also strongly fluorescent. The conjunctival epithelium similarly showed a strong reaction, as did the goblet cells. The iris epithelium and the dilator pupillae were only weakly fluorescent, but the ciliary body showed strong fluorescence, as did the blood vessels. As compared with lens fibres the lens epithelium was strongly fluorescent. The outer retina, that is, the photoreceptors, the pigment epithelium, and Bruch's membrane, showed a very strong reactivity. The optic nerve showed moderate fluorescence, but reaction with extraocular muscles was variable. The skin of the upper and lower eyelids, hair follicles, and blood vessels showed strong lectin binding. Sections of retinoblastoma and malignant melanoma showed no reaction. The physiological and pathological significance of these findings is discussed.

Acetylgalactosamine↗
PubMed1985

Lipid keratopathy and atheromatosis in an SPF laboratory rabbit colony attributable to diet.

Sporadic cases of corneal opacity occurred in an SPF rabbit colony fed on a diet containing 10% white fish-meal. Routine histological monitoring also revealed atheromatous lesions involving the intima of the aorta, coronary arteries and the arteries of other organs in 29 rabbits examined. Serum cholesterol levels above 10 mmol/l were found in 7 rabbits, including 4 affected with corneal lesions, which proved to be lipid keratopathy on histochemical and electron microscopical examination. The serum cholesterol level was found to be within normal range (below 2.27 mmol/l) in 10 rabbits reared entirely on a modified version of the diet, where the 10% fish-meal content was replaced with 10% grass-meal. No more ocular or atheromatous lesions have been found since the adoption of the new diet for the colony.

Age Factors↗
PubMed1983

Intake and digestibility of berseem (Medicago sativa) and Sorghum Abu 70 (Sorghum vulgare) forages by Sudan zebu cattle and desert sheep.

Two experiments were carried out with Sudan zebu cattle and desert sheep to study the voluntary intake and digestibility of berseem (Medicago sativa) and Abu 70 (Sorghum vulgare) forages when offered ad lib. alone and with supplements of molasses to the cattle and dura grain to the sheep. In both experiments the intake of berseem was significantly higher than Abu 70. Supplementation increased Abu 70 intake and while molasses significantly increased berseem intake by cattle, dura decreased its intake by sheep. On the basis of metabolic body size sheep showed a higher intake of these forages than cattle. There was no significant difference in DM digestibility between berseem and Abu 70 by cattle. Sheep digested berseem significantly better than Abu 70. Molasses and dura significantly increased the digestibility of Abu 70 by cattle and sheep but had no significant effect on the DM digestibility of berseem.

Animals↗
PubMed1976

Antifreeze glycoproteins from Antarctic fish. Inactivation by borate.

Antifreeze glycoprotein, which has previously been shown to be inactive in the presence of borate, migrates electrophoretically as the borate complex, presumably through formation of borate complexes with hydroxyl groups on the sugar side chains. Antifreeze glycoprotein (5 mg/ml) has been found to be completely active in the presence of 0.1 M borate at pH 7, but inactive at pH 9. A titration curve of pH versus the antifreeze activity of glycoprotein (5 mg/ml) in 0.1 M borate showed a progressive decrease in antifreeze activity as the pH was increased. Concomitant with decreases in activity were increases in binding of borate. At pH 9.0, nearly 2 mol of borate were complexed per glycotripeptide. Ultracentrifuge analyses showed similar molecular weights and laser quasi-elastic light scattering showed similar diffusions at pH 7.0 and 9.0 in borate and in the absence of borate. The binding of borate, rather than a change in conformation, is thus directly related to the loss of antifreeze activity. Alkaline borate also decreased hemagglutinating activity of Osage orange lectin and decreased the inhibition of the activity by the antifreeze glycoproteins.

Aldehydes↗
PubMed1975

Antifreeze glycoproteins from an Antarctic fish. Quasi-elastic light scattering studies of the hydrodynamic conformations of antifreeze glycoproteins.

A quasi-elastic light-scattering technique was used to study the hydrodynamic conformations of antifreeze glycoproteins from an Antarctic fish. Antifreeze glycoprotein is composed of repeating units of Ala-Ala-Thr, with each threonine O-linked to a disaccharide, and it exists as several polymers of different numbers of this repeating unit. Molecular weights of the two major active polymers are 10,500 and 17,500 by such methods as centrifugation and osmotic pressure, but smaller than 20 by freezing-point depression. Translational diffusion coefficients at 20 degrees were 8.35 times 10-7 cm2 s-1 and 6.15 times 10-7 cm2 s-1 for the M-r-10,500 and 17,500 polymers, respectively. Measurements at -0.2 degrees in the presence of ice crystals did not indicate any conformational changes that might be related to the lowering of the freezing temperature. Lowering the temperature of these glycoprotein solutions close to temperatures of freezing caused a decrease in the effective hydrodynamic radius of both active and inactive glycoprotein components.

Animals↗