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Biomedical subjects

M Ahmad

Publications and source records attributed to M Ahmad.

At least 289 records · Page 16Linked to original sources
PubMed1991

In vitro studies on mild alkali induced lesions in DNA.

S1 nuclease hydrolysis, benzoylated naphthoylated DEAE cellulose (BND-cellulose) chromatography as well as certain immunological and genetic techniques have been used to evaluate the effect of mild alkali (pH10.0) on the DNA molecule. Native calf thymus DNA after exposure to alkaline pH10.0 when subjected to S1 nuclease hydrolysis released significant amount of acid soluble nucleotides as compared to the untreated control. With pBR322 DNA, the population of linear DNA species increased on S1 digestion with concomitant reduction in the supercoiled form. BND cellulose chromatographic studies also suggested the formation of single strandedness and/or distortions in the alkali treated DNA molecule. Antisera raised against the alkali treated DNA exhibited high cross-reactivity with both single stranded and Z DNA. Moreover, a significant reduction in transformation frequency of the treated DNA molecule compared with the untreated control further ascertained the structural alterations in DNA as a result of exposure to mild alkali.

Animals↗
PubMed1991

Comparison of enzymatic semisyntheses of peptide amides: human growth hormone releasing factor and analogs.

Enzymatic semisyntheses of growth hormone releasing factor (GRF), a 44-residue peptide amide hormone, from C-terminal acid precursors, are compared. A recombinant alpha-amidating enzyme was used to convert the glycine-extended precursor, GRF(1-44)-Gly-OH, to GRF(1-44)-NH2 in an essentially quantitative fashion. Trypsin was used to convert the precursors, GRF(1-43)-OH and GRF(1-44)-OH, to GRF(1-44)-NH2 (60 and 15% conversion, respectively) in a 75% v:v N,N'-dimethylacetamide solution containing a large excess of leucine amide. Carboxypeptidase Y catalyzed transpeptidations of the precursors, GRF(1-44)-OH and [Ala44]-GRF(1-44)-OH, to GRF(1-44)-NH2 in aqueous leucine amide solutions were also attempted. The trypsin catalyzed direct amidation of [Ala15]-GRF(1-29)-OH in concentrated ammonium acetate/ammonia buffer (95% 1,4-butanediol cosolvent) to form the superactive analog, [Ala15]-GRF(1-29)-NH2 (ca. 25% conversion at equilibrium), is also described.

Amino Acid Sequence↗
PubMed1991

Cardiac blood-pool scintigraphy in rats and hamsters: comparison of five radiopharmaceuticals and three pinhole collimator apertures.

Preclinical evaluation of cardiac drugs may require evaluation of cardiac function in intact animals. To optimize the quality of radionuclide measurements of ventricular function in small animals, a comparison was made of gated blood-pool scans recorded with five blood-pool radiopharmaceuticals (99mTc-labeled human polyclonal IgG, 99mTc-human serum albumin labeled by two methods, and red blood cells radiolabeled with 99mTc via in vivo and in vitro methods) in rats and three pinhole apertures in hamsters. The quality of the radiopharmaceuticals was evaluated by comparing count density ratios (LV/BACKGROUND and LV/LIVER) and ejection fractions recorded with each agent. The edge definition of the left ventricle and count rate performance of the 1-, 2-, and 3-mm apertures was evaluated in hamsters. In general, the images obtained with the radiolabeled cells were superior to those obtained with the labeled proteins and no significant differences between the protein preparations were detected. Left ventricular ejection fractions calculated with all five radiopharmaceuticals were not significantly different. The best quality images were obtained with the 1-mm pinhole collimator. Ejection fraction and acquisition time were inversely related to aperture size. A good compromise between resolution and sensitivity was obtained with the 2-mm pinhole collimator.

Animals↗
PubMed1991

Histiocytic necrotizing lymphadenitis. A clinicopathological study.

Seven cases of Histiocytic necrotizing Lymphadenitis (HNL) were studied. They constituted 0.56% of all lymph nodes biopsies. The condition primarily affects young women causing cervical lymph node enlargement and leukopenia. The basic lesion is characterized by proliferation of lymphocytes and histiocytes with nuclear debris in the para cortex and cortex. This study examined various bacterial, viral and immunological factors which could possibly be responsible for this condition. However, it failed to find positive association with any of them. The existence of this disease in Pakistan is documented.

Adolescent↗
PubMed1990

Fibular hypoplasia and complex brachydactyly (Du Pan syndrome) in an inbred Pakistani kindred.

A Pakistani kindred comprising 7 generations contained 7 men and 2 women with fibular hypoplasia and complex brachydactyly (syn: Du Pan syndrome). Analysis of the pedigree is strongly suggestive of autosomal recessive inheritance. The average inbreeding coefficient (F) for the affected persons was found to be significantly greater than that for unaffected persons in the pedigree and consanguineous loops could account for all affected persons being homozygous for the abnormal allele.

Consanguinity↗
PubMed1990

Reliability of radionuclide scintigraphy for detection of testicular torsion: an animal study.

Sodium pertechnetate Tc99m scintigraphy is a valuable technique for the evaluation of acute testicular torsion in postpubescent males. However, in neonates and children with small testicles, the method is less reliable. Since the testicles of adult rats and young children are of similar size, the reliability of testicular imaging for detecting torsion was evaluated in this species. The utility of the radionuclide angiogram (RA) and static images were determined in 17 anesthetized animals before, 2 h after and 20 h after ligation of the left spermatic cord. The preligation RA was asymmetric in 27% of animals, while the static images were abnormal in 18%. Postligation flow and static images were abnormal in 57% and 82% of the animals (localized to the correct side, 38% and 36%), respectively. The animals with vascular occlusion failed to show any statistically significant greater incidence of decreased radionuclide accumulation on the ligated side. To determine the influence of relative perfusion and extracellular fluid space of the scrotum and testicles on the images, additional studies were performed with 201Tl (representing perfusion) and 99mTcO4- (representing ECF space). Perfusion was approximately equal in the testis and epididymis but significantly higher in the scrotum. These results suggest that scrotal scintigraphy is unreliable for detecting acute torsion of small testicles.

Animals↗
PubMed1990

Biochemical variations in Gigantocotyle explanatum and Gastrothylax crumenifer with respect to their seasonal reproduction.

Biochemical components, glycogen, protein, nucleic acids and lipid fractions were analysed every month from January to December 1986, in the liver and rumen amphistomes Gigantocotyle explanatum and Gastrothylax crumenifer, respectively. The results reveal a considerable seasonal variation. In the rumen amphistome the components reach their maximum level only once a year, whereas in the liver amphistome, more than one peak is observed in a year. In G. crumenifer the content of glycogen and nucleic acids increases before the onset of egg production while protein and lipids reach their maximum level during the egg production phase. The variations in biochemical components were associated with the reproductive cycles and gonad recrudescence of these parasites.

Animals↗
PubMed1990

Effectiveness of ultrasonic files in the disruption of root canal bacteria.

The physical mechanisms of ultrasound, namely cavitation and acoustic streaming, generated by the Enac-Osada ultrasonic unit were investigated for effectiveness in disrupting Streptococcus mitis. In addition, the bactericidal effect of ultrasound in the presence of 2.5% sodium hypochlorite was examined. Bacterial suspensions were irradiated directly with ultrasound in simulated root canals, and the viability of bacteria was examined after growth on a blood agar medium under anaerobic conditions at 37 degrees C for 5 days. The results indicated that ultrasound per se failed to disrupt bacteria but resulted in increases in the viable counts; the former was considered to be because of the lack of cavitation and the latter because of the dispersal effects of acoustic streaming. The 2.5% sodium hypochlorite solution demonstrated powerful bactericidal activity.

Colony Count, Microbial↗
PubMed1990

Left ventricular response to exercise in regular runners and controls. A radionuclide evaluation.

Radionuclide angiography was performed during upright exercise to compare left ventricular function in nine regular runners to nine age-matched, healthy controls. Heart rate, blood pressure, left ventricular ejection fraction (LVEF), end diastolic volume index (EDVI), end systolic volume index (ESVI), and stroke volume index (SVI) were measured at rest and at 40%, 60%, 80%, and 100% of maximum work capacity (mean maximal workload [KPM +/- SD] was 1,773 +/- 157 in runners and 1,260 +/- 324 in controls). The resting data of runners and controls were similar. There were no significant differences in heart rate, systolic blood pressure, and LVEF between runners and controls during exercise. SVI and EDVI were higher in runners during exercise (P less than 0.05). ESVI was lower in controls at a 60% level of exercise (P less than 0.05). The data indicate that an early and sustained increase in the diastolic volume of the left ventricle is important for enhanced cardiac performance of regular runners during exercise.

Adult↗
PubMed1990

Some observations on the mechanics of oscillation of ultrasonic files.

The resonant characteristics of ultrasonic files driven by the Cavi-Endo unit were examined. The investigation was carried out by evaluating the pattern of oscillation and the power emitted by the ultrasonic files. It was observed that the files oscillated in a sinusoidal fashion, exhibiting a standing wave pattern along the file. The power emitted was found to be directly proportional to the flexibility of the file. Such behaviour is typical of a system that exhibits resonance.

Dental High-Speed Equipment↗
PubMed1990

Measurements of temperature generated by ultrasonic file in vitro.

The temperature rise of the irrigant in the root canal during free vibration of the ultrasonic file was studied in vitro in 10 human teeth. The mean temperature rise was found to be 0.6 degrees C. The minimal temperature increase may not significantly contribute to the effectiveness of ultrasonic root canal instrumentation.

Hot Temperature↗
PubMed1990

Redistribution of regional and organ blood volume and effect on cardiac function in relation to upright exercise intensity in healthy human subjects.

To determine the effect of relative exercise intensity on organ blood volume and its relation to cardiac function, changes in relative blood volume and cardiac function were monitored with radionuclide techniques in 14 healthy volunteers. After labeling the subject's red cells with technetium 99m, we acquired data at rest, zero-load cycling, and at 50%, 75%, and 100% of maximal oxygen uptake. From rest to zero-load cycling, leg blood volume decreased 32 +/- 2% (mean +/- SEM), whereas relative end-diastolic blood volume increased 9.6 +/- 1.2%, and lung blood volume increased 18 +/- 2%, suggesting that the lungs may act as a blood volume buffer during periods of acutely increased venous return. With relative increasing exercise, leg blood volume stabilized, and then the blood volume in the abdominal organs decreased, further augmenting cardiopulmonary blood volume; leg blood volume and abdominal blood volume decreased by 23 +/- 2% and 19 +/- 2% from baseline, respectively, whereas thoracic blood volume increased 38 +/- 4%. In the abdomen, large decreases in blood volume were observed in the spleen (46 +/- 2%), kidney (24 +/- 4%), and liver (18 +/- 4%). In contrast, lung blood volume increased 50 +/- 4%, with the upper lung fields increasing more than the lower. Blood sampling revealed an increase in the hematocrit level by 4.3 +/- 0.4 units at peak exercise that paralleled the decrease in splenic blood volume (r2 = -0.64, p less than 0.001), suggesting a role for the spleen in augmenting cardiovascular performance by the release of concentrated red blood cells into general circulation. We conclude that upright exercise results in marked blood volume shifts from the legs and abdominal organs to the heart and lungs in a dynamic process correlating closely with oxygen consumption.

Adult↗
PubMed1990

Immunologic studies of alveolar macrophages from patients with metastatic renal cell carcinoma.

Alveolar macrophage function in patients with renal carcinoma, a disease characterized by frequent pulmonary metastases, has not been examined. The purpose of this study was to evaluate tumoricidal responses of alveolar macrophages in renal carcinoma to determine if such activity is compromised. Alveolar macrophages and/or blood monocytes were obtained from 26 normal volunteers and 16 patients with renal carcinoma. Tumoricidal activity of alveolar macrophages and monocytes was assessed against 3H-thymidine-labeled tumor target cells. Patient alveolar macrophages and monocytes exposed to lipopolysaccharide (LPS) or recombinant interferon-gamma expressed tumoricidal activity comparable to those in normal subjects. Activated alveolar macrophages recognized and lysed neoplastic cells (including allogenic renal carcinoma cells), but not nonneoplastic cells. Alveolar macrophage and monocyte tumoricidal responses of patients with pulmonary metastases were not different from those of patients with metastases to other sites. These results indicate that alveolar macrophages from patients with renal carcinoma with or without pulmonary metastases are not compromised in vitro, but respond to immunomodulators with enhanced tumoricidal activity in the same fashion as do alveolar macrophages from normal volunteers.

Adult↗
PubMed1990

Amyloidosis and pleural disease.

Pleural involvement with systemic amyloidosis has been reported rarely in the literature. Diagnosis of this entity by percutaneous needle biopsy of the pleura has been described only in two prior case reports. We describe five patients in whom the diagnosis of pleural amyloidosis was established by Cope needle biopsy during evaluation of pleural effusions of indeterminate cause. Three patients presented with a history suggestive of multiorgan disease and a pleural biopsy performed despite a transudative effusion demonstrated amyloid infiltration of the pleura, obviating the need for other organ biopsies. We conclude that in patients with pleural effusions, if history suggests multiorgan involvement and there is suspicion for amyloidosis, then a closed pleural biopsy with special stains for amyloid should be performed even if the effusions are transudative. This may be the diagnostic procedure of choice in such patients.

Aged↗
PubMed1990

Lymphocytic alveolitis in primary HIV infection.

Primary infection with the human immunodeficiency virus (HIV-1) has been associated with a self-limited illness resembling acute infectious mononucleosis. Pulmonary manifestations have been notably absent in published reports. The authors describe a 28-year-old homosexual male who presented with primary HIV-1 infection associated with CD8+ lymphocytic alveolitis. Diagnosis was delayed because HIV antibody was not detected by the Abbott ELISA, although the same and subsequent specimens were later found to be positive by Genetic Systems' ELISA and Western blot analysis. Lymphocytic alveolitis must be added to the expanding clinical spectrum of acute HIV-1 infection. The time to detection of seroconversion may vary with different immunoassays.

Adult↗
PubMed1990

The effects of steroid therapy on pulmonary hypertension secondary to fibrosing mediastinitis.

Mediastinal fibrosis, a rare cause of pulmonary hypertension, may produce cough, dyspnea, and hemoptysis. Steroid therapy has been suggested for individuals with progressive symptoms, but data demonstrating the efficacy of such therapy are lacking. We present a case of pulmonary hypertension secondary to fibrosing mediastinitis. Hemodynamic and scintigraphic studies performed before and after a trial of corticosteroid therapy were unable to demonstrate any therapeutic benefit from the corticosteroids. In order to achieve better use of steroids for the treatment of this disease, we suggest that similar determinations be made on other patients with mediastinal fibrosis who receive such treatment.

Adult↗