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Biomedical subjects

T Ahmad

Publications and source records attributed to T Ahmad.

At least 55 records · Page 3Linked to original sources
PubMed1999

A rational approach to melanoma follow-up in patients with primary cutaneous melanoma. Scottish Melanoma Group.

From the Scottish Melanoma Group database for south-east Scotland we evaluated 5-year follow-up in patients with cutaneous malignant melanoma excised between 1979 and 1994 and devised an 'evidence-based' review protocol. Of the 1568 with stage I melanoma, 293 (19%) developed a recurrence, 32 had a second primary melanoma and 97 had an in-situ melanoma. The disease-free interval shortened progressively with increasing tumour thickness. Overall, 80% of recurrences were within the first 3 years, but a few patients (< 8%) had recurrences 5 or 10 years after the initial surgery. In-situ melanomas did not recur. Almost half (47%) the recurrences were noted first by the patient, and only 26% were detected first at a follow-up clinic. One hundred and thirty-nine patients (89%) were still under review when their recurrences were detected, and 102 (65%) had been seen within the previous 3 months. Questionnaires were completed by 120 patients: sun protection and avoidance, and mole examination were more likely after melanoma excision. We recommend 3-monthly review of patients with invasive lesions for the first 3 years. Thereafter, those with lesions >/= 1.0 mm need two further annual reviews. Patients with in-situ lesions should be reviewed once, to confirm adequate excision (0.5 cm margins) and to give appropriate education. Surveillance beyond 5 years is only justified if there are special risk factors.

Clinical Protocols↗
PubMed1998

Viscosity studies on Mestranol.

The viscosity of 1x10(-4) M to 4x10(-4) M solution of Mestranol (synthetic oestrogenic steroidal hormone) in ethanol was measured at 32 degrees, 40 degrees and 50 degrees C in a viscometric bath. The viscosity rates are maximum at 30 degrees C as compared to 40 degrees and 50 degrees C. The disappearance rate of Mestranol at higher temperature and lower viscosity is due to triplet state of species transitions at higher thermal conditions.

Journal Article↗
PubMed1997

Effect of rotational atherectomy on quality of life.

OBJECTIVE: To evaluate whether percutaneous coronary rotational atherectomy (RA) improves quality of life. DESIGN: Prospective sequential study of the first 20 patients who had RA at St Paul's Hospital, Vancouver from November 1993 to April 1994. SETTING: Tertiary care teaching hospital. PATIENTS: There were nine males and 11 females with a mean age of 68 +/- 9.3 years. All had angina pectoris with type B or C coronary lesions. INTERVENTIONS: RA was performed using the Rotablator device. RESULTS: The procedure was angiographically successful in 20 patients and clinically successful in 18 patients. Two patients who sustained acute myocardial infarctions underwent coronary bypass surgery. Before RA there was one patient in Canadian Cardiovascular Society angina class I, five patients in class II, 12 in class III, and two in class IV. At six months' follow-up there were 11 patients in class I, seven in class II and two in class III. The mean Duke Activity Status Index improved from 21.3 +/- 15.8 (mean +/- SD) before the procedure to 36.9 +/- 15.8 (P < 0.001) at six months' follow-up. The consumption of anti-anginal medications also decreased. CONCLUSIONS: RA was associated with improved functional status and quality of life in patients having angina pectoris with type B or C coronary lesions.

Aged↗
PubMed1996

Multicenter clinical experience with the development of a novel short coronary stent and its prototype device.

Our initial experience with the Micro Stent PL and its prototype intracoronary stent is described. A total of 206 stents were implanted in 84 patients for threatened closure or restenosis following balloon angioplasty. The stenting procedure was successful and uncomplicated in 83 of 84 patients. Potential advantages of this particular stent relate to its short length, low surface area, expandability over a range of diameters, radiopacity, low profile, and ease of delivery.

Angioplasty, Balloon, Coronary↗
PubMed1995

Coronary stenting for acute myocardial infarction.

In summary, our experience suggests that coronary stents may play a useful role in carefully selected patients undergoing angioplasty for myocardial infarction. The potential may exist to increase rates of successful infarct artery reperfusion and increase long-term patency. The use of stents in myocardial infarction should probably be reserved for situations in which balloon angioplasty fails. Newer stent designs and anticoagulant regimens may alleviate some of the current concerns with regard to stenting at the time of acute myocardial infarction.

Aged↗
PubMed1995

alpha-1,4-Glucan lyase, a new class of starch/glycogen degrading enzyme. III. Substrate specificity, mode of action, and cleavage mechanism.

The alpha-1,4-glucan lyase (EC 4.2.2.-), purified from the red alga Gracilariopsis lemaneiformis, is a single polypeptide with a molecular mass of 116,654 Da as determined by matrix-assisted laser-desorption mass spectrometry. It degraded maltose, maltosaccharides, amylose, amylopectin and glycogen, forming 1,5-anhydro-D-fructose from the non-reducing end groups. The substrate specificity, mode of action, and cleavage mechanism of the enzyme were studied by using various naturally occurring and synthesized substrates. This enzyme was highly specific for the alpha-1,4-D-glucosidic bond. When a linear alpha-1,4-glucan was used as substrate, the enzyme split the substrate from the non-reducing end and released 1,5-anhydro-D-fructose successively until only one glucose unit was left. When a branched pentasaccharide of 6(2)-alpha-maltosylmaltotriose, obtained from glycogen by alpha-amylase limitation, was used as substrate, the glucose group in the 4-position of the 4,6-branched residue was not cleaved off. Using maltoheptaose as substrate and following the reaction with HPLC and 1H-NMR spectroscopy, it was found that the action mode of the lyase followed a multichain attack mechanism. 1H- and 13C-NMR spectroscopic studies on unlabelled and labelled amylose (1-2H, 2-2H, 1-13C) as substrates indicated that the lyase cleaved the C-(1')-O(4) bond forming a double bond between C-1' and C-2', thus forming the enol form of 1,5-anhydro-D-fructose. It also indicated that the catalytic process of the lyase involved proton exchanges among C-1, C-2, C-3 and the solvent.

Carbohydrate Sequence↗
PubMed1995

Guide wire extension may not be essential to pass an over-the-wire balloon catheter.

The ability to pass an angioplasty balloon catheter over a regular length free guidewire can be advantageous in certain circumstances. This procedure was performed successfully in 99 consecutive patients without any complications. There was improved tactile sense of the lesion and improved dye delivery without the necessity of resorting to the use of extension wires or magnet exchange device. When performed while observing the required precautions this is a safe procedure.

Angioplasty, Balloon, Coronary↗
PubMed1994

Zinc and barium inhibit the phospholipase A2 from Naja naja atra by different mechanisms.

The mode of inhibition of the phospholipase A2 (PLA2) enzyme from the Chinese cobra (Naja naja atra) by Zn2+ is qualitatively different from inhibition by Ba2+. Inhibition by Ba2+ shows the kinetic characteristics of a conventional competitive inhibitor acting to displace Ca2+ from a single essential site, but Zn2+ has the paradoxical property of being more inhibitory at high than at low Ca2+ concentration. Kinetic analysis of the Ca(2+)-dependence of enzymic activity shows a bimodal response, indicating the presence of two Ca(2+)-binding sites with affinities of 2.7 microM and 125 microM respectively, and we propose that these can be identified with the two Ca(2+)-binding sites revealed by crystallographic analysis [White, Scott, Otwinowski, Gleb and Sigler (1990) Science 250, 1560-1563]. The results are consistent with the model that the enzyme is activated by two Ca2+ ions, one that is essential and can be displaced by Ba2+, and one that modulates the activity by a further 5-10-fold and which can be displaced by Zn2+. An alternative model is also presented in which the modulating Zn(2+)-binding site is a phenomenon of the lipid/water interface.

Barium↗
PubMed1994

Reversible renal failure in renal transplant patients receiving oral acyclovir prophylaxis.

Two children who developed acute renal failure in the immediate post-renal transplantation period are presented. Each was immunosuppressed with cyclosporin and was also receiving oral acyclovir for prophylaxis against cytomegalovirus infection. Renal biopsy findings suggested drug toxicity. Discontinuation of acyclovir coincided with reversal of renal impairment. As cyclosporin levels were at the lower end of the therapeutic range, we believe acyclovir to be the likely causative agent.

Acute Kidney Injury↗
PubMed1994

Prognostic significance of left ventricular aneurysm in the Cardiac Arrhythmia Suppression Trial (CAST) population.

Left ventricular aneurysm has been associated with increased mortality rates. The Cardiac Arrhythmia Suppression Trial (CAST) database was used prospectively to assess (1) the prognostic significance of left ventricular (LV) aneurysm after myocardial infarction on mortality rates and (2) the relation of LV aneurysm to ventricular arrhythmias and their suppressibility. All patients in the CAST study were enrolled after myocardial infarction. They had > or = 6 ventricular premature depolarizations (VPDs) per hour and ejection fraction < or = 55%; they were enrolled in the study an average of 96 days after the index myocardial infarction. Of 2494 patients with wall motion data, 164 had LV aneurysm, 600 had only dyskinesis, 913 had only akinesis, and 817 had none of these. Radionuclide scan was used in 39%, two-dimensional echocardiography in 30%, and LV angiogram in 31%. Baseline VPDs and nonsustained ventricular tachycardia were similar in all groups. LV aneurysm patients were more frequently eliminated during open-label titration. The incidence of sustained VT during follow-up was only 2.8% for aneurysm patients, a rate that was similar to the other groups. Patients with LV aneurysm had significantly lower survival rates (82% vs 91%) at 16 months after study entry than those without these wall motion abnormalities (p < 0.005). When survival rates were adjusted for ejection fraction there was still a moderately large hazard ratio (1.34) of LV aneurysm that was not statistically significant (p = 0.18). We conclude that (1) the presence of LV aneurysm does not independently worsen prognosis, and (2) older concepts of LV aneurysm and ventricular arrhythmias must be reevaluated.

Arrhythmias, Cardiac↗
PubMed1994

Insulin sensitivity and metabolic clearance rate of insulin in cystic fibrosis.

We have evaluated the metabolic clearance rate (MCR) of insulin and insulin sensitivity in 12 older patients with cystic fibrosis (CF) using the hyperinsulinemic euglycemic clamp method. Compared with a control group matched accurately for age and body mass index (BMI), the MCR of insulin was significantly enhanced in CF CF = 21.85 +/- 1.17 v controls = 16.01 +/- 0.92 mL/kg/min, P < .005), and this difference persisted after correction for lean body mass ([LBM] CF = 26.32 +/- 1.28 v controls = 19.09 +/- 1.09 mL/kg LBM/min, P < .005). Glucose disposal rates (M) were similar in the two groups during the clamp (CF = 7.28 +/- 0.41 v controls = 6.83 +/- 0.60 mg/kg/min, P > .5), but the insulin sensitivity index, M/I x 100 (I = steady-state insulin concentration), was markedly increased in the CF group (CF = 17.62 +/- 1.30 v controls = 11.75 +/- 0.71, P < .005). In conclusion, the MCR of insulin is enhanced in CF, which is in keeping with previous observations on drug metabolism in this disorder. Second, insulin sensitivity is increased in CF, and this points to a compensatory mechanism to counteract the insulinopenia.

Adolescent↗
PubMed1994

High-resolution two-part basic urea gels for analysis of venom phospholipase A2 isoforms.

The performance of acidic and basic urea polyacrylamide gels has been improved by adopting a two-part gel system with a concentration discontinuity to act as a stacking boundary and by increasing the urea concentration to 8 M. The contributions of primary amino-group and guanidino-group ionizations to mobility have been evaluated by acetylation and phenyl glyoxal treatment respectively. The chromogenic PLA2 detection method of Shier and Trotter (Analyt. Biochem. 87, 604, 1978) has been modified for use with basic urea PAGE. The results have confirmed the major findings of other workers, but have demonstrated the presence of many hitherto uncharacterised isoforms of PLA2 in a variety of whole snake venoms. The basic urea PAGE (BG) method is proposed as the basis of a simple and rapid method for the classification of PLA2 isoforms which should allow unambiguous identification of isoforms by referring bands for purified material to the isoform content of whole venoms.

Acetylation↗
PubMed1994

Addition-order dependent modulation of the sensitivity of rabbit erythrocyte membrane to bee venom phospholipase A2 by oleic acid, lysophosphatidyl choline and albumin.

The addition of exogenous oleic acid to erythrocyte membranes induces a characteristic membrane crenation and sensitises the cells to the lytic action of phospholipase A2 enzymes. Both effects are extremely sensitive to inhibition by endogenous lysophosphatidyl choline (LPC), but the strength of inhibition depends of the order in which the reagents are added to the cells. These responses are further enhanced when the reagents are extracted from the cell membranes by treatment with albumin. Thus the inhibitory action of LPC added before oleic acid increases when the reagents have been extracted but that of LPC added after oleic acid decreases after extraction. The results are discussed in terms of the stimulation of PLA2 activity by enhanced membrane curvature.

Albumins↗
PubMed1994

Into the dangerous world: an in vivo study of information processing in agoraphobics.

The differential processing of threatening information in anxious patients is now well established, but there has been little attention to situational variation in information processing. A review of the experimental literature suggests that agoraphobics should show interference in the performance of the modified Stroop task for threat words and that this interference should increase in phobic situations. In the present study, agoraphobics and normal controls carried out the Stroop task either in a safe setting or a public place. Agoraphobics showed greater interference with threat words but this interference was not affected by setting. The implications of this result are considered.

Adult↗
PubMed1993

Purification and activation of phospholipase A2 isoforms from Naja mossambica mossambica (spitting cobra) venom.

Isoforms of phospholipase A2 (PLA2) from the venom of Naja mossambica mossambica (the spitting cobra) were purified by a combination of gel filtration on Bio-gel P-30 and ion exchange chromatography on DE-52 Cellulose and the purification followed by three types of polyacrylamide gel electrophoresis. SDS PAGE failed to resolve the active band into separate isoforms. Acid/urea PAGE, resolved the peptides and major protein components of the venom and was able to separate two PLA2 bands in the whole venom. Alkali/urea PAGE resolved four PLA2 bands in whole venom, but could resolve six distinct purified PLA2 species. Of the known isoforms, the acidic form (CM-1) was purified to homogeneity. The basic non-toxic isoform (CM-II) was shown to migrate as a close doublet of PLA2 isoforms. A novel minor purified isoform was identified with mobility intermediate between CM-I and the basic non-toxic isoform CM-II. CM-III was shown to contain a minor PLA2 contaminant. The analysis was facilitated by the fact that all of the isoforms could be eluted from the gels with > 60% recovery of activity. The venom therefore contains at least six isoforms of PLA2 which differ largely by their content of acidic acids. Oleoyl imidazolide treatment increased the haemolytic activity of all but the toxic PLA2 isoform in Naja mossambica mossambica, but partially inhibited the catalytic activity of acidic, toxic and newly purified isoforms whilst partially activating the non-toxic isoform.

Amino Acid Sequence↗
PubMed1993

A study of the photostability of ergocalciferol (vitamin d(2)) in organic solvents.

The photolysis of ergocalciferol (vitamin D(2)) in several organic solvents has been studied to determine the influence of solvent dielectric constant and viscosity on the rate of reaction. Ergocalciferol degrades by zero-order kinetics and the rate constants vary from 0.74x10(-5) mol 1(-1) (methanol) to 1.56x10(-5) mol 1(-1) (chloroform). The rates appear to be a linear function of the reciprocal of dielectric constant and viscosity of the medium in the range studied.

Journal Article↗