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Biomedical subjects

S A Ali

Publications and source records attributed to S A Ali.

At least 91 records · Page 5Linked to original sources
PubMed1995

The VEX-test for myocardial scintigraphy with thallium-201 and sestamibi: effect on abdominal background activity.

UNLABELLED: High abdominal background activity of 99mTc-sestamibi may interfere with the diagnosis in studies in which a coronary vasodilator is used; supplemental dynamic exercise might reduce this problem. METHODS: Clinical and angiographic determinants of subdiaphragmatic-to-myocardial activity ratios were measured on immediate poststress left anterior oblique images and on corresponding tomographic studies 1 hr after injection in 600 sestamibi studies. Similar measurements were made in 550 historic controls with planar 201Tl imaging. Patients performed symptom-limited ergometry when there were no limiting factors, dipyridamole-handgrip in which ergometry was not possible and VEX (vasodilator followed by symptom-limited ergometry) in which exercise capacity was reduced. RESULTS: Abdominal activity was higher with sestamibi than with 201Tl, in women versus men, and with dipyridamole-based tests compared to exercise alone. Compared to the dipyridamole-handgrip, 3 min of ergometry as part of VEX decreased abdominal background (p < or = 0.02) by 18% on immediate 201Tl images, by 13% on immediate sestamibi images and by 12% on 1-hr delayed sestamibi tomoacquisitions. CONCLUSIONS: Poststress abdominal background activity is influenced by similar factors with both agents. Supplemental exercise following dipyridamole reduces potentially interfering abdominal activity but perhaps not as efficiently with sestamibi as with 201Tl.

Abdomen↗
PubMed1995

Role of cholinergic receptors in melanophore responses of amphibians.

Responses of isolated skin melanophores of Rana tigerina and Bufo melanostictus to cholinergic drugs were studied using the Mean Melanophore Size Index assay to explore the nature and role of cellular receptors in melanophore regulation activity. Acetylcholine (Ach) in a concentration of 10(-7) to 6.4 x 10(-6) g/ml caused dispersion of the skin melanophores of R. tigerina and B. melanostictus. These effects were blocked by both atropine and hyoscine in a concentration of 8 x 10(-6) g/ml each. Eserine augmented the melanophore dispersal effects of Ach. This potentiation of the dispersal effect of Ach by eserine was also antagonised by hyoscine. Carbachol another specific cholinergic agonist significantly caused dispersion of the melanophores of both the amphibian species. The effects were also blocked by atropine and hyoscine. These data indicate that cholinergic receptors of muscarinic type are present on the melanophores of R. tigerina and B. melanostictus which mediate dispersion of integumental melanophores leading to darkening of the skin.

Acetylcholine↗
PubMed1994

Molecular biointeractions of biomedical polymers with extracellular exudate and inflammatory cells and their effects on the biocompatibility, in vivo.

The stability of biomedical polymers in physiological environments is crucial for the normal operation of devices, as well as determining their effect on the tissue response. Degradation is an important factor in polymer biocompatibility, since the environment of the human body can be aggressive to polymers. Most implanted polymers suffer degradation to some extent, and the kinetics and mechanisms of the processes can be affected significantly by various biologically active species, especially enzymes, lipids, peroxides, free radicals and phagocytic cells. The degradation of poly(caprolactone) and poly(DL-lactic acid) under controlled in vivo conditions was studied using a poly(methyl methacrylate) chamber designed to control the exposure of polymers to physiological environments. In particular they may be designed to allow access of extracellular exudate only or access to cells as well as the fluid. The chambers, sealed with filters of pore size either 0.45 micron (impervious to cells) or 3.0 microns (allowing cells to enter the chamber), were implanted subcutaneously into experimental animals for 10, 20 and 30 wk periods. Degradation and molecular interactions of the polymers were characterized by gel permeation chromatography and scanning electron microscopy. The extracellular exudate formed within the implanted chamber is active in promoting the degradation of some biomedical polymers. Inflammatory cells are involved in the biodegradation of implanted polymers by releasing biologically active species such as free radicals into the area surrounding the implant. The data have demonstrated that the hydroxyl radical is likely to be one of the main causes of polymer degradation.

Animals↗
PubMed1993

Mechanisms of polymer degradation in implantable devices. 2. Poly(DL-lactic acid).

The hydrolytic degradation of poly(DL-lactic acid) in an aqueous environment in which hydroxyl radicals have been generated has been investigated. Different methods (gel permeation chromatography, differential scanning calorimetry, and scanning electron microscopy) were employed to study the mechanisms of degradation of this amorphous physiologically absorbable polymer. The data indicated that the hydroxyl radical is likely to be a significant factor in the degradation of this polymer.

Biodegradation, Environmental↗
PubMed1993

Sexual aggression and love styles: an exploratory study.

The relationship between sexual aggression and theoretical love styles was studied. Based on self-reported sexual history, 63 college men were grouped as having either consensual sexual experience only (n = 33) or having verbally coercive sexual experience (n = 30). Analyses were conducted using six love style scales, likelihood to rape, likelihood to use sexual force, masculinity, and sociopathy to predict sexual coercive group membership. Logistic regression indicated that the Ludus love style, a manipulative, game-playing orientation towards intimate relationships, was the best predictor of sexual coercion among the six love styles. Additionally, logistic regression indicated that the Ludus love style was as effective in classifying men as coercive or noncoercive as other dispositions related to sexual aggression. These results suggest that the Ludus love style may serve as a unifying construct for dispositions related to sexual aggression. This study constitutes an initial attempt to link sexually coercive behaviors to a theoretical model of intimate relationships. Results are discussed in the context of a situational model of sexual coercion.

Adult↗
PubMed1993

Mechanisms of polymer degradation in implantable devices. I. Poly(caprolactone).

Poly(caprolactone) is a biodegradable aliphatic (poly(alpha-hydroxy acid), with important applications in the field of human therapy, due to its biocompatibility and bioresorbability. The degradation of poly(alpha-hydroxy acids) depends on chemical hydrolysis, but there is much interest in the precise mechanisms, including the role of free radicals, especially oxygen free radicals and their role in human disease. The hydrolytic degradation of poly(caprolactone) in aqueous environments was used as the control in a study of the effects of hydroxyl radicals in aqueous solutions. Different methods (GPC, DSC, SEM) were employed to investigate the mechanism of degradation of this semicrystalline physiologically absorbable polymer. The data indicate that hydroxyl radical is likely to be a major factor in the degradation of this polymer.

Biocompatible Materials↗
PubMed1993

The characteristics and performance of dentine bonding agents.

Several attempts have been made to synthesise dentine bonding systems, but low bonding strength, increased variance, toxicity and poor hydrolytic stability were some of the disadvantages excluding them from being widely approved. However, many dentine bonding systems are considered to be biocompatible and have become commercially available. These adhesives are thought to have one or two bifunctional agents where one part of the molecule is intended to bond to the inorganic part of the dentine (calcium ions of the apatite), or to the organic part of the dentine (amino and hydroxy groups of the collagen), and the methacrylate part of the molecule is intended to copolymerise with the restorative resin. This review demonstrates that further work is needed to achieve the synthesis of novel dentine bonding agents which bond chemically to dentine by strong covalent bonds, and which are hydrolytically durable and non-toxic to the oral environment.

Dental Bonding↗
PubMed1993

Psychiatric morbidity: prevalence, associated factors and significance.

A cross-sectional observational systematic study was carried out on ambulatory patients at a tertiary care hospital to determine the probable prevalence, associated factors and significance of psychiatric morbidity by using an Urdu translation of the hospital anxiety and depression (HAD) scale over a period of 6 days in a week. Results showed a prevalence of 38.4% which is slightly higher than what has been generally reported (30%). Two variables, i.e., female sex and being a housewife were significantly related with the outcome. An attempt has been made to identify the probable reasons for this and some suggestions laid down for further work.

Adult↗
PubMed1993

Effect of histaminergic drugs on tail melanophores of tadpole, Bufo melanostictus.

The H1 and H2 receptor agonist histamine caused a powerful aggregation of B. melanostictus tail melanophores, which was completely blocked by metiamide, a specific H2 receptor antagonist, while mepyramine an H1 receptor blocker partially blocked the aggregating response. The strong melanin aggregating effect of 4-methyl histamine a specific H2 receptor agonist and its complete blockade by metiamide further supports the conclusion that there exists a dominant population of H2 type of histamine receptors along with sparse population of H1 receptor on the tail melanophores of the toad, which mediate centripetal movement of melanin granules within the pigment cells leading to blanching of the animal.

Animals↗
PubMed1991

Onset and regulation of anti-lamin B autoantibody production is independent of the level of polyclonal activation.

Anti-lamin B autoantibodies are associated with both systemic lupus erythematosus (SLE) and autoimmune liver disease. We examined the possibility that the underlying clinical feature in patients with anti-lamin B autoantibodies might be chronic autoimmune liver disease, and whether the hypergammaglobulinemia present in both disorders is involved in generating anti-lamin B autoantibodies. A lamin B fusion protein (MLB1), consisting of amino acids 77-533 of lamin B fused to TrpE, was used to screen sera from 84 patients with SLE for anti-lamin B autoantibodies. 3/4 prototype human lamin B antisera, 5/84 SLE sera (6%), and 0/30 sera from healthy individuals reacted with MLB1 on immunoblots at a 1:500 dilution. Of the 9 anti-lamin B autoantibody positive patients studied, all but 1 fulfilled at least four ARA criteria for SLE. None of the patients displayed evidence of chronic autoimmune liver disease, suggesting that autoimmune liver disease is not strongly associated with anti-lamin B antibodies in SLE. In SLE, as in "lupoid hepatitis", anti-lamin B autoantibodies are often produced transiently during periods of increased disease activity. Although polyclonal hypergammaglobulinemia is also associated with increased activity of both diseases, anti-lamin B autoantibody production in 2 patients was independent of total immunoglobulin levels, antibodies to irrelevant proteins, and production of some other autoantibodies. Thus, polyclonal activation is insufficient to explain either the initiation or regulation of anti-lamin B autoantibody production, supporting the hypothesis that antinuclear antibodies are antigen-selective.

Adult↗
PubMed1990

Improving the tumor retention of radioiodinated antibody: aryl carbohydrate adducts.

Improved methods for attaching radioiodine to monoclonal antibodies have been developed. Ten aryl carbohydrate adducts were synthesized by the reductive amination of a carbohydrate with an aryl amine, using sodium cyanoborohydride as a reducing agent. After purification by chromatography and characterization by nuclear magnetic resonance they were iodinated using the chloramine-T method. Iodinated adducts were activated with cyanuric chloride and incubated with protein at room temperature. The immunoreactivity and avidity of radioiodinated tyramine cellobiose (TCB) labeled antibody were fully preserved when compared to electrophilically radioiodinated antibody. Radioiodinated TCB-and tyramine glucose-labeled monoclonal antibodies showed much greater intracellular retention of radioiodine when compared to electrophilically radioiodinated monoclonal antibodies. Neither radioiodinated tyramine nor radioiodinated TCB had any specific tissue uptake or retention. In mice the retention of radioiodinated TCB labeled anti-Thy-1.1 antibody (1A14) by Thy-1.1-bearing lymphoma cells was 2 times greater than that of chloramine-T labeled 1A14 antibody, whereas the plasma clearance curve and uptake in normal tissues was not changed. This method of radioiodinating monoclonal antibodies increases the retention time of radioiodine in tumor and thus may obviate the problem of intracellular deiodination, a perceived disadvantage of electrophilically iodinated antibodies, with respect to tumor retention of radioactivity.

Animals↗
PubMed1989

Preferential use of lambda L chain in lamin B autoantibodies.

The generation of lamin B autoantibodies was examined in a patient with SLE. Lamin B autoantibodies in this individual's serum were almost entirely IgG1 lambda at the onset of the autoimmune response. There was no evidence of IgM to IgG class switching, and no apparent diversification of the autoantibody response over the next 2 yr. The kappa/lambda L chain ratio of the lamin B autoantibodies was 0.13 by ELISA, with a kappa/lambda ratio of 0.70 for the patient's total IgG. In contrast, anti-histone autoantibodies in the patient's serum contained primarily kappa L chain. The kappa/lambda L chain ratios of lamin B autoantibodies from sera of four other patients with SLE were also consistent with restricted heterogeneity of lamin autoantibodies. In two, lambda L chain predominated, and in two others, the lamin B autoantibodies contained predominantly kappa L chains. The restricted heterogeneity of lamin B autoantibodies could be related to targeting of a single immunodominant autoepitope, to the existence of a particular L chain gene or genes that preferentially undergo somatic mutation, leading to the production of lamin B reactive clones, or to a combination of both mechanisms.

Antibody Specificity↗
PubMed1988

Synthesis and radioiodination of tyramine cellobiose for labeling monoclonal antibodies.

A tyramine cellobiose (TCB) adduct was synthesized by the reductive amination of cellobiose by tyramine with a product yield of 78%. The TCB adduct was purified by chromatography and then iodinated using the chloramine-T method. After iodination, the adduct was activated with cyanuric chloride and linked to protein by incubation at room temperature for 2 h. Immunoreactivity and avidity were well maintained compared to electrophilically radioiodinated 1A14 whole antibody. The tumor uptake and retention were strikingly greater with iodinated TCB-antibody compared to that of the conventionally iodinated antibody; whereas, the plasma clearance curve and uptake in other organs were not changed. This method of labeling increases the retention time of radioiodine in tumors and thus extends to iodinated antibodies one of the advantages of indium labels, namely that the isotope is not readily washed out of the tumor after it becomes localized.

Animals↗
PubMed1988

Peptidic uraemic toxins.

A systematic investigation concerning uraemic toxicology has been made using modern analytical methods. The interest is especially focused on substances which are present in uraemic subjects in high concentrations, the so called "uraemic toxins". The samples from biological fluids have been screened with special regards to the presence of peptides and low molecular proteins. These peptidic uraemic toxins are thought to be responsible for certain physiological disturbances when present in uraemic subjects.

Journal Article↗
PubMed1988

[Non-invasive evaluation of cardiac output by Doppler echocardiography].

In order to evaluate Doppler echocardiography (DEC) used for cardiac output (CO) measurement, 22 patients (7 with coronary heart disease, 6 with dilatation cardiomyopathy, 5 with primary pulmonary hypertension and 4 with rheumatic heart disease) were studied. In all patients, invasive CO determination was performed by right heart catheterization, using thermodilution (T). In DEC, CO was calculated as CO = IV.S.HR, where IV was integral velocity, estimated on the basis of flow areas under planimetric curves, S was aortic root cross-section area, and HR was heart rate. A close correlation was demonstrated between DEC and T results (r-0.74). Only in one case with severe aortic atherosclerosis was there a significant difference between the data. This case excluded, the correlation becomes even closer (r-0.86). It is concluded that: 1) DEC is a valuable and precise method of CO assessment, 2) DEC may be used to monitor treatment efficacy, and 3) its limitation is aortic lesions.

Adult↗
PubMed1987

Hepatic phosphoribosyl pyrophosphate concentration. Regulation by the oxidative pentose phosphate pathway and cellular energy status.

Measurements have been made of the tissue content of phosphoribosyl pyrophosphate (PPRibP) and of a range of metabolic intermediates involved in the energy charge of the cell, the glycolytic and pentose phosphate pathways, and of the activity of the enzymes of the pentose phosphate pathway and of PPRibP synthetase (EC 2.7.6.1) in the livers of normal, diabetic, insulin-treated diabetic and starved rats and in livers of rats previously starved and then re-fed with high-fat or high-carbohydrate diets. Diabetes, starvation and high-fat diet all caused a fall in the hepatic PPRibP content, whereas insulin treatment and high-carbohydrate diet raised the tissue content. A positive correlation was shown between the PPRibP content and ATP, energy charge and the cytosolic [NAD+]/[NADH] quotient. A positive association between the PPRibP content and the flux of glucose through the pentose phosphate pathway and the synthesis of ribose 5-phosphate via the oxidative enzymes of that pathway, including ribose-5-phosphate isomerase (EC 5.3.1.6), was also observed. A negative correlation was found between the ADP, AMP and Pi contents, and no correlation existed between PPRibP content and the enzymes of the non-oxidative branch of the pentose phosphate pathway. There was no correlation between hepatic PPRibP content and the activity of PPRibP synthetase measured in vitro. These results are considered in relation to the control of PPRibP synthetase in the liver in vivo.

Adenine Nucleotides↗