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Biomedical subjects

S Mahmood

Publications and source records attributed to S Mahmood.

At least 73 records · Page 4Linked to original sources
PubMed1993

Clinical high resolution skeletal single photon emission tomography using a triple-headed gamma camera.

Planar skeletal scintigraphy has become established as a standard diagnostic test performed within the nuclear medicine department. Since the 1970s good quality images have been produced using an Anger gamma camera and 99Tcm-labelled diphosphonates. Single photon emission tomography (SPET) has improved the sensitivity of detection and the ability to localize bony pathology, particularly benign bone disease in the spine. Recently multi-detector gamma cameras dedicated to SPET have become available. One such system, the Toshiba GCA-9300A, has been used to perform routine clinical skeletal SPET in 81 patients. Good quality images have been obtained using an 8 min acquisition in the axial skeleton and a 16 min acquisition protocol in the peripheral skeleton. Multiple sites can be tomographed in the same patient during the same examination using two or more 8 min acquisitions. Such a multi-detector gamma camera offers advantages over the standard single-headed rotating camera for skeletal SPET in terms of both imaging time and image quality. A cost analysis was performed which demonstrated that the additional cost of purchasing such a multidector gamma camera was less than 30.00 pounds per SPET study.

Bone Neoplasms↗
PubMed1993

Changes in glycosylation of microvillus membranes in Giardia lamblia infected mice intestine.

Giardia lamblia infection has been shown to modify the glycosylation process of microvillus membranes in mice intestine. Sialic acid content of the membranes was enhanced 3-fold but there was no change in fucose content of infected animals compared to the controls. The binding of 125I-wheat germ agglutinin was augmented and that of Ulex Europeus agglutinin was unaltered to infected membranes. The binding of 125I-peanut agglutinin to brush borders was however, significantly reduced in Giardia infected mice. Kinetic analysis revealed that the observed binding of peanut agglutinin to the membrane was associated with reduced number of the lectin reactive sites (control = 649 and infected 380 nmole/protein) with no change in the affinity constant (Ka = 95.7 nmole/ml) in Giardia infected mice intestine.

Animals↗
PubMed1993

Endoscopic lesions in chronic renal failure.

To determine the frequency and type of upper gastrointestinal lesions in patients with chronic renal failure (CRF), upper G.I. endoscopy was done in 101 cases. Of the various mucosal lesions, inflammatory changes were seen maximally (40), followed by erosions (16) and ulcers (7). Other changes included atrophic gastro-duodenal folds (17), pale mucosa (11) and moniliasis (6) which was only seen in patients with end stage CRF. Lesions were more frequent in those who were in advanced stage of CRF (81%) and those undergoing dialysis (79%), reflecting a positive correlation of upper G.I. lesions with the severity of CRF.

Adolescent↗
PubMed1993

Immunosuppression: tomorrow and beyond.

Balancing the benefits and side effects of immunosuppressive therapy is important in transplant patients. Several new agents appear to be safer, more effective, and more specific than the available standard immunosuppressive drugs. Many of the agents are likely to be used with present drugs.

Forecasting↗
PubMed1992

The use of thallium-201 lung/heart ratios.

This survey gives an overview of the methodology of thallium-201 lung/heart uptake ratios often used as an independent factor in the assessment of patients with coronary artery disease undergoing myocardial perfusion scintigraphy. Different techniques have been used in the past. The most sensitive method is one which calculates a lung/heart ratio from scintigraphy obtained immediately after cessation of exercise. If single photon emission tomography (SPET) is routinely performed the anterior projection of the data set obtained during tomographic acquisition should be used in preference to a separate planar anterior static images recorded before or after the SPET procedure. The lung/heart ratio is useful as a prognostic indicator of outcome as it accurately mimics the degree of left ventricular dysfunction. With the increasing popularity of pharmacological stress testing there is evidence that this ratio still offer valid information. Additional work in this field is nevertheless required to further confirm this observation. In routine clinical practice, the lung/heart ratio should help and enable physicians to prioritise patients for urgent intervention.

Coronary Disease↗
PubMed1992

Assessment of myocardial viability with 201Tl SPET and reinjection technique: a quantitative approach.

The definition of viable myocardium after an acute myocardial infarction (MI) is important as it will determine which therapeutic option will be best for the patient. In 201Tl scintigraphy it has been shown that late redistribution (8-24 h) or reinjection may help to identify viable myocardium which does not appear to reperfuse on the 4 h redistribution image. In a prospective study 20 patients with a persistent defect seen on both stress and redistribution images were imaged after reinjection of 201Tl. On visual analysis a total of 180 segments were studied, 85 were normal, 18 reperfused at redistribution and a further nine (in six patients) after reinjection. Bull's-eye analysis at stress demonstrated a mean defect size of 279 pixels, S.D. +/- 74. After redistribution, there was no significant change in mean defect size (227 +/- 96 pixels). At reinjection, there was a significant reduction in mean defect size (189 +/- 107 pixels) (P < 0.05, paired 't'-test). Quantification shows a significant reduction in defect size between stress and reinjection. The use of the 201Tl reinjection technique in patients with a fixed perfusion deficit on stress and redistribution images improves the detection of viable myocardium and is to be preferred to a method of redistribution analysis alone.

Adult↗
PubMed1992

Comparative elasticity tests for elastomeric (non putty) impression materials.

This study was conducted to evaluate the methods used for measuring the elastic recovery of various elastomeric impression materials. One brand from each chemical group was selected to allow relative ranking of the results from each deforming test mode. For compression tests, the polysulphide and silicone specimens made in metal moulds gave significantly less set than those made in acrylic moulds; this was not so for the polysiloxane and polyether specimens. For polysulphide and polyether materials, the set in compression was greater using the BSI balanced beam method than for an optical method without inertia or load effects; this was not so for silicone or polysiloxane materials. The elastic recovery of the materials did not alter significantly after ten minutes of strain release, except in tensile tests, where the elastic recovery continued to change for twenty minutes. The rank ordering of the deformation set showed a relative correlation for the compression test, a new tensile test method, and bend and torsion testing methods. Thus only one method is needed to determine set per cent.

Dental Impression Materials↗
PubMed1992

Some parameters for testing deformation of elastomeric impression materials.

Because of conflicting published data, the temperature rise in four elastomeric materials was measured with a thermistor during setting in the oral cavity and in metal and plastic moulds of varying shapes and volumes for 'elastic set' specimens. The clinical temperature rise was 2-3 degrees C higher in the molar region than anteriorly, except for the polysiloxane. The temperature range attained in the set materials varied from 29 degrees C to nearly 35 degrees C for clinical and in vitro specimens. The average time taken by a group of operators to remove this type of impression from the mouth was five seconds. In a custom tray with light and heavy viscosity materials, the syringe material layer was only 0-0.15 mm thick and, essentially, the heavy viscosity material provided the elastic components for the impression.

Dental Impression Materials↗
PubMed1991

The rat H+/K(+)-ATPase beta subunit gene and recognition of its control region by gastric DNA binding protein.

The rat gastric H+/K(+)-ATPase beta subunit gene was cloned, and its nucleotide sequence was determined. The coding region is separated by 6 introns, whereas the related human Na+/K(+)-ATPase beta subunit gene was shown to have 5 introns (Lane, L.K., Shull, M.M., Whitmer, K.R., and Lingrel, J.B. (1989) Genomics 5, 445-453). The positions of introns 1, 2, and 5 of the two genes were the same. The similarities in intron/exon organizations and primary structures (30-40% identical residues) suggest that the beta subunit genes for H+/K(+)-ATPases were derived from a common ancestor. The upstream region of the rat H+/K(+)-ATPase beta subunit gene contains direct repeat sequences and palindromes, potential binding sites for RNA polymerase II and E4TF1, and CACCC box sequences. Gel retardation assay demonstrated that the stomach, but not other tissues (liver, brain, kidney, spleen, and lung), has a nuclear protein(s) capable of binding to the regions upstream of the potential RNA polymerase II binding sites (TATA box). The nuclear protein(s) are suggested to recognize three tandem GATAGC sequences and may be important for controlled transcription of the H+/K(+)-ATPase beta subunit gene in gastric parietal cells.

Adenosine Triphosphatases↗
PubMed1991

Control region and gastric specific transcription of the rat H+,K(+)-ATPase alpha subunit gene.

The rat gastric H+,K(+)-ATPase alpha subunit gene was cloned and the nucleotide sequence of its 5'-upstream region was determined. Sequence comparison with the corresponding part of the human gene indicated the presence of highly conserved regions which may be important for specific transcription of the alpha subunit in gastric parietal cells. The amino-terminal sequence (Met-Gly-Lys-Ala-Glu-) of the rat enzyme was similar to those of the pig and human enzymes. The gene organization of the rat enzyme was also similar to that of the human gene: introns 1, 2 and 9 were located in exactly the same positions as those in the human gene, and, as in the latter, exon 6 was not separated by an intron. The sequences of introns 1 and 2 were highly conserved among the rat, human and pig genes, but were entirely different from those of Na+,K(+)-ATPase catalytic subunit genes. Northern blot hybridization indicated that the gene was transcribed only in gastric mucosa.

Adenosine Triphosphatases↗
PubMed1990

Bacillus thuringiensis insecticidal delta-endotoxin: diversity of crystal proteins and its relatedness to the toxicity spectrum.

Bacillus thuringiensis strains produce crystal delta-endotoxins which exhibit a diverse toxicity spectrum. In order to explore the basis of toxin specificity, a comparison of the activity of 13 strains belonging to seven serotypes was made against three insect species. The delta-endotoxin crystals were purified and their polypeptide composition analyzed by SDS-PAGE. Among the strains studied, the delta-endotoxins consist of a variety of crystal proteins in the 60-144 KDa size range. On the basis of molecular mass, endotoxins maybe grouped into two classes; one contained both high (125-144 KDa, P1) and medium sized (60-66 KDa, P2) proteins and a second class consisting of only the high Mr polypeptides. Immunoblotting with B. aizawai P1 antiserum revealed antigenic cross-reaction with one or more of the polypeptides in 125-144 KDa range in all the strains studied. When the crystal proteins from different strains were immunoblotted with kurstaki P2 antiserum, none of the P1 protein crossreacted suggesting that the P1 and P2 proteins are not structurally related. However, the B. kurstaki P2 antiserum crossreacted with 66 KDa proteins in some other strains which underlines a structural homology in this class of the toxic polypeptides. Toxicity studies revealed that the high Mr P1 proteins of all the strains in this study were active against lepidopteran (Pieris brassicae and Diacrisia obliqua) larvae. B. thuringiensis aizawai strains exhibit a dual toxicity associated with the high Mr (130-135 KDa; P1) proteins. The P2 crystal proteins (60-66 KDa) also showed dual toxicity against the lepidopteran and dipteran larvae but were found to be structurally and immunologically distinct.

Animals↗
PubMed1990

Stimulation of the absorption of macromolecules in Giardia lamblia infected mice intestine.

The absorption of 125I-labelled bovine serum albumin, gamma-globulin and alpha-lactalbumin was considerably enhanced in G. lamblia infected Swiss mice intestine compared to uninfected controls. The binding of 125I-proteins to brush border membrane was however, significantly (P less than 0.01) low in infected animals. Kinetic studies with gamma-globulin binding to brush borders revealed a decrease in the number of binding sites in infected animals (1.52) compared to controls (2.86 micrograms/mg protein) with no change in the affinity constant (47.60 micrograms/ml) under these conditions. These findings suggest that G. lamblia infection in mice leads to enhanced macromolecular absorption which seems unrelated to the binding of proteins to epithelial cell surface.

Animals↗