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Biomedical subjects

F Khan

Publications and source records attributed to F Khan.

At least 109 records · Page 6Linked to original sources
PubMed1997

Microvascular abnormalities in patients with vibration white finger.

In vivo nailfold capillary microscopy was performed on 10 men with vibration white finger (VWF) and 10 age-matched male controls. The observed nailfold capillaries required adaptation of Maricq's classifications and addition of new morphological scoring systems. These new classifications produced numerical scores for assessing capillary: dropout, tortuosity, elongation, visualization of subpapillary venular plexus, and the degree of disarrangement of nailfold capillary polarity. Application of these new scores showed, for the first time, a complex pattern of abnormal-nailfold capillaries in patients with VWF. Capillary dropout was evident in 7/10 patients, with an associated disarrangement in nailfold capillary polarity in five. All 10 controls had normal capillary morphology. Tortuosity of the capillary loops and elongation of their length was observed in 30% of patients. These significant morphological alterations seen in VWF suggest a local small-vessel vasculitis.

Adult↗
PubMed1997

Sterile abscess formation following plague vaccination.

As part of the immunisation programme of servicemen on OP Granby, deployed in the Gulf, plague vaccine was recommended as a prophylaxis. Out of a total of 524 vaccinations at our location, one sterile abscess formation was noted. The case report is described.

Abscess↗
PubMed1997

Effect of reversible and irreversible ischemia on marker enzymes of BBM from renal cortical PT subpopulations.

The effect of the reversible and relatively irreversible ischemia induced acute renal failure (ARF) in the activities of alkaline phosphatase (AlkPase) and gamma-glutamyltransferase (GGTase) after early (15-30 min) and prolonged (45-60 min) ischemia in the homogenates, and the brush-border membranes (BBM) from rat renal whole, superficial (SC), and juxtamedullary (JMC) cortices were studied. The enzyme activities declined progressively in proportion to the duration of ischemia. Early blood reflow of 15 min to the ischemic rats caused a further decrease in the enzyme activities. However, prolonged reflow (up to 120 min) resulted in partial reversal of the ischemic effect in the early but not in the prolonged ischemic rats. The decrease in the enzyme activities was due to the loss of membrane-bound enzyme components from the damaged BBM into the supernatant fraction as membrane-free enzymes. The activities of AlkPase and GGTase were significantly more decreased by the ischemia in the brush-border membrane vesicles (BBMV)-JMC than in BBMV-SC. The rate of recovery due to reflow for AlkPase was greater in BBMV-SC than apparently for GGTase in BBMV-JMC in early ischemic (15-30 min) rats.

Alkaline Phosphatase↗
PubMed1997

Cutaneous vascular responses to acetylcholine are mediated by a prostanoid-dependent mechanism in man.

Approximately 50% of the forearm vasodilatation to intra-arterial infusions of acetylcholine is mediated by endothelium-derived nitric oxide. These conclusions have been derived from venous occlusion plethysmographic measurements of total forearm blood flow during co-infusions of acetylcholine and NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthase. Since venous occlusion plethysmography measures total limb blood flow, the relative proportion of the measurement from skin cannot be determined precisely. To determine the effects of acetylcholine on skin specifically, we have used laser Doppler flowmetry to measure vascular responses to local iontophoresis of acetylcholine in the forearm of normal male volunteers. To elucidate the possible mechanisms of cutaneous vasodilatation to acetylcholine, vascular responses were measured before and after systemic inhibition of prostanoid production and nitric oxide synthesis by oral aspirin (600 mg daily for 3 days) and intravenous L-NMMA (3 mg/kg for 60 min), respectively. After aspirin administration, dose-dependent vascular responses to acetylcholine were reduced significantly by approximately 53% (p < 0.005, ANOVA). In contrast, intravenous L-NMMA appeared to have no significant effect on cutaneous vascular responses to acetylcholine. While the role of nitric oxide is uncertain, vasodilatation to acetylcholine in the forearm skin is mediated largely by a prostanoid-dependent mechanism. Assessment of cutaneous vascular responses to iontophoresis of acetylcholine may, therefore, be useful in diseases where abnormal endothelium-dependent prostanoid function has been implicated.

Acetylcholine↗
PubMed1997

Body composition and health-related quality of life in patients with obstructive airways disease.

This study evaluated the effects of body weight and lean mass abnormalities on health-related quality of life (HRQL) in obstructive airways disease. Body weight, lean mass (using dual-energy X-ray absorptiometry), and HRQL (using the St George's Respiratory Questionnaire (SGRQ)) were measured in 50 patients. Low lean mass was defined as a lean mass index (lean mass/height2) below the fifth percentile of a control population. Dyspnoea was measured by the baseline dyspnoea index. The mean (SD) age was 69+/-9 yrs; the forced expiratory volume in one second (FEV1) was 39+/-19% of predicted. Patients had 2.4+/-4.1 kg less lean mass than predicted. Increased dyspnoea was the most influential predictor of poor HRQL. Compared to normal-weight patients, those who were underweight had significantly greater impairment in activity, impact, and total SGRQ scores, while those who were overweight had greater impairment in impact and total SGRQ scores. Low lean mass was associated with greater impairment in symptoms, activity and impact subscores and the total SGRQ score. When dyspnoea was added to the model as a covariate, neither weight nor lean mass remained significantly related to HRQL. Thus, although body weight and lean mass abnormalities influence health-related quality of life, their effects appear to be mediated through increased levels of dyspnoea.

Absorptiometry, Photon↗
PubMed1997

Rates of formation of anhydronucleosides and comparison with their corresponding oxy analogues.

Anhydronucleosides are reactive intermediates in the synthesis of modified nucleosides. Their rates of cyclization of 2,2'; 2,3' and 2,5'-anhydro 2-thiouridine were studied and compared with their oxy analogues. The order of displacement of the leaving group is as follows: 2' > 5' > 3'. It was also observed that the rates of cyclization onto the 5' or 3'-position was about 70 times faster in 2-thiouridine series as compared with the uridine series. Similarly the rate of formation of 2, 2'-anhydronucleoside is nearly 2 orders of the magnitude faster in the case of thionucleosides.

Journal Article↗
PubMed1997

Prevalence of hepatitis B surface antigen (HBsAg) in Viqarunnessa noon girls' school children in Dhaka, Bangladesh.

Screening of serum samples from 836 apparently healthy school girls with sound socioeconomical background from Viqarunnessa Noon Girls' School in Dhaka, was done for hepatitis B surface antigen (HBsAg) by Latex quick test and all Latex quick test positive samples were rechecked by enzyme-linked immunosorbent assay. Thus the prevalence of HBsAg among healthy female school age children was 2.3% by the former method and 0.8% by the latter. Hepatitis B virus (HBV) infection is more common in Bangladesh but HBsAg prevalence rate in normal school age children of the present study was much lower than reported from many other parts of the world. The reason of this fact presumably was that in this study serum specimens were collected from apparently healthy female children belonging to high socioeconomic status in Bangladesh. Further studies are appreciated to determine the prevalence of HBsAg among healthy low socioeconomic school age children and to investigate HBsAg subtypes and possible main mode of transmission of HBV in Bangladeshi population.

Adolescent↗
PubMed1996

Biosynthesis in vitro of neolactotetraosylceramide by a galactosyltransferase from mouse T-lymphoma: purification and kinetic studies; synthesis of neolacto and polylactosamine core.

The galactosyltransferase, GalT-4, which catalyses the biosynthesis in vitro of neolactotetraosylceramide, nLcOse4Cer (Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer) from lactotriaosylceramide, LcOse3Cer (Glc NAc beta 1-3Gal beta 1-4Glc-Cer), and UDP-galactose has been purified 107 500-fold from a mineral oil induced mouse T-lyphoma P-1798, using affinity columns. The purified enzyme is partially stabilized in the presence of phospholipid liposomes. Two closely migrating protein bands of apparent molecular weights 56 kDa and 63 kDa were observed after sodium dodecyl sulfate polyacrylamide gel electrophoresis of highly purified mouse GalT-4. These two protein bands, when subjected to limited proteolysis, resulted in three peptides with identical mobilities indicating amino acid sequence identity between the proteins. Both protein bands from P-1798 gave a positive immunostain when tested with polyclonal antibody against bovine lactose synthetase (UDP-Gal:Glc beta 4-galactosyltransferase) following Western blot analysis on nitrocellulose paper. The enzyme has a pH optimum between 6.5 and 7.0 and like all other galactosyltransferases, GalT-4 has absolute requirements for divalent cation (Mn2+). The K(m) values for the substrate LcOse3Cer and donor UDP-galactose are 110 and 250 microM, respectively. Substrate competition studies with LcOse3Cer and either asialo-agalacto-alpha 1-acid glycoprotein or N-acetylglucosamine revealed that these reactions might be catalysed by the same protein. The only other glycolipid which showed acceptor activity toward the purified GalT-4 was iLcOse5Cer (GlcNAc beta 1-1-3Gal beta 1-4Lc3), the precursor for polylactosamine antigens. However, competition studies with these two active substrates using the most purified enzyme fraction, revealed that these two reactions might be catalysed by two different proteins since the experimental values were closer to the theoretical values calculated for two enzymes. Interestingly however, it seems that the GalT-4 from P-1798 has an absolute requirement for an N-acetylglucosamine residue in the substrate since the lyso-derivative (GlcNH2 beta 1-3Gal beta 1-4Glc-sphingosine) of the acceptor glycolipid LcOse3Cer is completely inactive as substrate while the K(m) and Vmax of the reacetylated substrate (GlcNAc beta 1-3Gal beta 1-4Glc-acetylsphingosine) was comparable with LcOse3Cer. Autoradiography of the radioactive product formed by purified P-1798 GalT-4 confirmed the presence of nLcOse4Cer, as the product cochromatographed with authentic glycolipid. The monoclonal antibody IB-2, specific for nLcOse4Cer, also produced a positive immunostained band on TLC as well as giving a positive ELISA when tested with radioactive product obtained using a highly purified enzyme from mouse P-1798 T-lymphoma.

Animals↗
PubMed1996

Routine use of the piggyback technique in pediatric orthotopic liver transplantation.

The theoretical advantages of the piggyback technique over conventional orthotopic liver transplantation are as follows. (1) Continuous venous decompression during the anhepatic phase is provided without venovenous bypass. (2) Warm ischemia time can be shortened because there is no need for the infrahepatic vena cava anastomosis. The following report is a review of the authors' experience with this method in children during the past year at their institution. Analyses of intraoperative hemodynamics and blood loss, postoperative renal function, patient and graft survival, and length of hospital stay have shown excellent results. There were no intraoperative deaths, and causes of death and graft loss were not related to the technique. The authors conclude that children who undergo liver transplantation can be very satisfactorily managed with the piggyback operation, and this technique may be more advantageous than the conventional method.

Adolescent↗
PubMed1996

Vasodilator responses in the forearm skin of patients with insulin-dependent diabetes mellitus.

The integrity of endothelium-dependent vasodilation in the skin of patients with insulin-dependent diabetes mellitus (IDDM) is unclear, especially with respect to the role of nitric oxide. To examine this, forearm skin blood flow by laser Doppler flowmetry and total blood flow by venous occlusion plethysmography was measured in response to brachial artery infusions of an endothelium-dependent (methacholine) and -independent (sodium nitroprusside) vasodilator. Peak hyperemic forearm blood flow, following 5 min of arterial occlusion, was also determined. Responses were compared in 11 control subjects and 16 patients with insulin-dependent diabetes mellitus. In ten normal subjects, co-infusion of NG-monomethyl-L-arginine with methacholine produced a significant reduction in total forearm blood flow response to methacholine (p < 0.002), measured by venous occlusion plethysmography, as well as vascular conductance (p < 0.001), confirming that nitric oxide contributes to this response. In contrast, NG-monomethyl-L-arginine had no significant effect on the methacholine-induced increase in forearm skin blood flow measured by laser Doppler flowmetry indicating that factors other than nitric oxide may be involved. Increases in forearm skin blood flow in response to methacholine, sodium nitroprusside and to an ischemic stimulus were not significantly different between the normal subjects and patients with IDDM. Dose-related increases in total forearm blood flow and vascular conductance were not significantly different between control subjects and diabetic patients during infusions of methacholine. The increases in these parameters during infusions of sodium nitroprusside, however, were significantly less in the diabetic group than in the control group (p < 0.05) as was the peak reactive hyperemic blood flow (p < 0.05). Since skin blood flow was not affected, the reduced vasodilator responses to sodium nitroprusside and an ischemic stimulus in the diabetic group are in forearm skeletal muscle. The reduced muscle blood flow does not reflect a decreased vasodilatory capacity, but rather a functional impairment in response to nitric oxide and ischemia since the methacholine dilation was normal. The normal vasodilator responses in the forearm skin, which is predominantly capillary as opposed to arteriovenous anastomatic blood flow, indicate that the response to nitric oxide and an ischemic stimulus in this vascular bed is intact in patients with IDDM. This is, therefore, an unlikely cause of diabetic skin, complications in these areas.

Adult↗