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Biomedical subjects

M Ahmad

Publications and source records attributed to M Ahmad.

At least 235 records · Page 13Linked to original sources
PubMed1994

Non-Hodgkin's lymphomas with primary manifestation in gonads--a clinicopathological study.

Analysis of 19 cases of Non-Hodgkin's lymphoma (NHL) with primary manifestation in gonads, diagnosed during 1984-1990 at AFIP Rawalpindi is presented. It constituted 10.4% of all extranodal lymphomas during the same period in this institute. Testis were more commonly involved. Mean age at diagnosis was 60.4 years and only 11.4% cases were below 50 years of age. Majority of the patients reported early (mean duration was 4.2 months). The mean tumour size was 3.2 cm. In a significant number of cases (43.5%). NHL was associated with hydrocoele. Diffuse large cell lymphoma was the predominant (73.70%) subtype in testicular lymphoma. One case of Burkitt's lymphoma presenting as ovarian mass was also noted. Most of these cases (56.4%) were in le stage according to Ann Arbor staging. More clinical work-up is required to delineate the course of this entity in Pakistan.

Adult↗
PubMed1994

Biochemical parameters in evaluation of oligospermia.

In Pakistan, male infertility constitutes about 35% of all cases of infertility. The dysfunction can be at the level of the central nervous system or somewhere in the male genital tract. A study was conducted to screen cases of male infertility using various biochemical parameters. A total of 81 cases were screened. Oligospermia was seen in 13 (16%) patients. They were divided into severe and mild to moderate oligospermia. In severe oligospermia, there was an increase in serum FSH level with decrease in seminal transferrin and carnitine suggesting damage to sertoli cells. In mild to moderate oligospermia, serum FSH were normal with levels a slight decrease in the levels of transferrin and carnitine in semen indicating that sertoli cells were not significantly defective and the dysfunction could be somewhere else.

Adult↗
PubMed1994

Demonstration of the site of obstruction in azoospermia by biochemical markers.

This study was carried out on 25 patients with azoospermia and normal serum FSH levels signifying obstruction as its cause. To determine the site of obstruction semen transferrin levels, carnitine and fructose were estimated. Patients with an obstruction at the testis-epididymal junction had low levels of transferrin but normal levels of carnitine and fructose. Patients who had lower levels of transferrin and carnitine, but normal levels of fructose had obstruction at the epididymal level, probably in the tail of the epididymis. Obstruction of the ejaculatory ducts was signified by lower levels of all parameters in the semen. Our study showed that levels of transferrin, carnitine and fructose when used in conjunction with each other could localize the site of obstruction in azoospermia.

Adult↗
PubMed1993

HY4 gene of A. thaliana encodes a protein with characteristics of a blue-light photoreceptor.

Specific responses to blue light are found throughout the biological kingdom. These responses--which in higher plants include phototropism, inhibition of hypocotyl elongation, and stomatal opening--are in many cases thought to be mediated by flavin-type photoreceptors. But no such blue-light photoreceptor has yet been identified or isolated, although blue-light responses in plants were reported by Darwin over a century ago, long before the discovery of the now relatively well characterized red/far-red light photoreceptor, phytochrome. Here we describe the isolation of a gene corresponding to the HY4 locus of Arabidopsis thaliana. The hy4 mutant is one of several mutants that are selectively insensitive to blue light during the blue-light-dependent inhibition of hypocotyl elongation response, which suggests that they lack an essential component of the cryptochrome-associated light-sensing pathway. The HY4 gene, isolated by gene tagging, was shown to encode a protein with significant homology to microbial DNA photolyases. As photolyases are a rare class of flavoprotein that catalyse blue-light-dependent reactions, the protein encoded by HY4 has a structure consistent with that of a flavin-type blue-light photoreceptor.

Amino Acid Sequence↗
PubMed1993

Alopecia universalis as a single abnormality in an inbred Pakistani kindred.

A Pakistani kindred comprising 5 generations contained 9 males and 4 females with alopecia universalis as a single abnormality without any associated defects. The skin biopsy from the scalp showed hair follicles without hair. Analysis of the pedigree is strongly suggestive of autosomal recessive inheritance, and consanguineous loops could account for all affected persons being homozygous for the abnormal allele.

Alopecia↗
PubMed1993

Mapping of the gene for X-chromosomal split-hand/split-foot anomaly to Xq26-q26.1.

A large inbred kindred from Pakistan in which an isolated type of split-hand/split-foot anomaly is transmitted as an X-chromosomal trait has previously been described. An X/autosomal translocation and an X-chromosomal rearrangement have been excluded by cytogenetic studies. In order to map the gene responsible for this disorder, linkage analysis has been performed by using 14 highly polymorphic DNA markers distributed over the whole X chromosome. Two-point linkage analysis between the disease locus and X-chromosomal marker loci gives maximal lod scores at theta = 0.00 with the loci DXS294 (Zmax = 5.13) and HPRT (Zmax = 4.43), respectively, suggesting that the gene for the X-chromosomal split-hand/split-foot anomaly is localized at Xq26-q26.1.

Chromosome Mapping↗
PubMed1993

The ontogeny of the gut mucosal immune system and the susceptibility to infections in infants of developing countries.

In this review we summarize data on the human gut mucosa associated lymphatic tissues as part of the common mucosal immune system. Its embryonal-fetal and post-natal ontogeny becomes severely distorted and compromised by mal-/undernutrition which is so prevalent in developing countries. Pathogenetic interdependencies exist between maternal-fetal undernutrition, the ontogeny of the immune system, constant antigenic stimulation of the mucosal immune system post-natally, and the 14 million deaths annually from infections in children below the age of 5 years in developing countries. A detailed knowledge of these interdependencies is required for effective prevention and treatment in an attempt to reduce the high morbidity and mortality rates of children in developing countries.

Animals↗
PubMed1993

Subcutaneous phaeohyphomycosis.

We report the case of a 13-year-old boy who presented with multiple swellings all over the body. His condition remained undiagnosed for over 3 years. Exophiala spinifera was recovered from pus drained from the swellings. We discuss the difficulties in the initial diagnosis and the ease of correct diagnosis once we had used special fungal stains.

Adolescent↗
PubMed1993

The vibratory pattern of ultrasonic files driven piezoelectrically.

The pattern of oscillation of a Piezon-Master 400 ultrasonic file driven by a piezoelectric transducer was studied in air and on water. In addition, the displacement amplitudes of the files were measured. The findings were compared with those observed with the Cavi-Endo unit reported in another study (Ahmad 1969). It was observed that the file vibrated such that a standing wave was formed on the file and it exhibited points of maximum deflection (antinode) and points of minimum deflection (node) with the largest deflection occurring at the apical end. This pattern of oscillation was similar to that exhibited by the Cavi-Endo file which employed a magnetostrictive transducer. However, the displacement amplitudes were very much higher than those exhibited by the Cavi-Endo. It is considered that the 120 degrees angle of the file holder inherent in the Piezon-Master 400 unit and the more effective power transmission with the piezoelectric transducer may have contributed to the large amplitudes.

Dental Cavity Preparation↗
PubMed1993

Imaging the ovine heparin-protamine interaction with 111In-protamine.

Protamine reversal of heparin anticoagulation occasionally induces the release of thromboxane into plasma with catastrophic pulmonary hypertension. To examine the site of neutralization, we labeled protamine sulfate with 111In and compared activity scans after administration of labeled protamine in unheparinized and heparin-anticoagulated sheep. Protamine administration in sheep without prior heparinization did not cause thromboxane release, pulmonary hypertension, or significant leukopenia, and 111In-protamine was rapidly cleared from the lungs (half time 0.48 +/- 0.08 min). Neutralization of heparin anticoagulation by labeled protamine produced elevated plasma thromboxane, pulmonary vasoconstriction, leukopenia, and prolonged pulmonary clearance of 111In-protamine (half time 3.32 +/- 0.43 min). In rats, protamine reversal of heparin anticoagulation did not induce either thromboxane synthesis or pulmonary hypertension, and 111In-protamine cleared rapidly from the lungs. Thus the ovine heparin-protamine reaction produces concomitant pulmonary sequestration of heparin-protamine complexes, thromboxane release, and pulmonary vasoconstriction; this did not occur in the rat. The lung specificity of the reaction and interspecies differences suggest that ovine pulmonary intravascular macrophages may be activated by heparin-protamine complexes to release thromboxane and provoke acute pulmonary vasoconstriction.

Animals↗
PubMed1993

Vascular cell adhesion molecule-1 (VCAM-1) gene transcription and expression are regulated through an antioxidant-sensitive mechanism in human vascular endothelial cells.

Oxidative stress and expression of the vascular cell adhesion molecule-1 (VCAM-1) on vascular endothelial cells are early features in the pathogenesis of atherosclerosis and other inflammatory diseases. Regulation of VCAM-1 gene expression may be coupled to oxidative stress through specific reduction-oxidation (redox) sensitive transcriptional or posttranscriptional regulatory factors. In cultured human umbilical vein endothelial (HUVE) cells, the cytokine interleukin 1 beta (IL-1 beta) activated VCAM-1 gene expression through a mechanism that was repressed approximately 90% by the antioxidants pyrrolidine dithiocarbamate (PDTC) and N-acetylcysteine (NAC). Furthermore, PDTC selectively inhibited the induction of VCAM-1, but not intercellular adhesion molecule-1 (ICAM-1), mRNA and protein accumulation by the cytokine tumor necrosis factor-alpha (TNF alpha) as well as the noncytokines bacterial endotoxin lipopolysaccharide (LPS) and double-stranded RNA, poly(I:C) (PIC). PDTC also markedly attenuated TNF alpha induction of VCAM-1-mediated cellular adhesion. In a distinct pattern, PDTC partially inhibited E-selectin gene expression in response to TNF alpha but not to LPS, IL-1 beta, or PIC. TNF alpha and LPS-mediated transcriptional activation of the human VCAM-1 promoter through NF-kappa B-like DNA enhancer elements and associated NF-kappa B-like DNA binding proteins was inhibited by PDTC. These studies suggest a molecular linkage between an antioxidant sensitive transcriptional regulatory mechanism and VCAM-1 gene expression that expands on the notion of oxidative stress as an important regulatory signal in the pathogenesis of atherosclerosis.

Antioxidants↗
PubMed1993

Lipid components of caralluma edulis (edgew.) hook.

Eighteen fatty acids (A-R), four hydrocarbons (S-V) and sterol (W) have been isolated from the ethyl acetate fraction of the vegetative part of the medicinal herb Carallurna edulis. Chemical and spectroscopic methods were used for the characterization of compounds as fatty acids, hydrocarbons and sterol.

Journal Article↗
PubMed1993

Local anesthesia in cataract surgery--a comparison of different methods.

Seven groups of thirty patients undergoing cataract extraction under local anesthesia were each given different combinations of local anesthesia. These varied from a maximum approach using supra-orbital, infra-orbital and facial blocks with Hyalase, orbital compression and pre-operative Acetazolamide down to a minimum group receiving purely an infra-orbital and supra-orbital block with a Lignocaine/Bupivacaine mixture. There was no significant difference in local analgesia or in the complication rates between the seven groups. The benefits of Acetazolamide and orbital compression remain doubtful. The use of Hyalase and of a facial block resulted in fewer complications and in better akinesia.

Aged↗
PubMed1993

Serial course of left ventricular function, perfusion and fatty acid uptake in the cardiomyopathic hamster.

To determine the relationship of metabolic and perfusion changes to alterations in ventricular function in the course of cardiomyopathy, we performed serial measurements of ejection fraction, myocardial perfusion, fatty acid uptake of 3-methyl-p[123I]-phenyl-pentadecanoic acid ([123I]3MPDA) and myocardial histology in Syrian hamsters genetically predisposed to the development of congestive cardiomyopathy (Bio T0-2) (n = 30) and normal age-matched control animals (Bio F1B) (n = 13). To obtain high-resolution information about the myocardium at the time of onset of the first noticeable decrease in ventricular function, a multitracer autoradiographic study using 99mTc-pyrophosphate, 201Tl and [14C]3MPDA was obtained at 90 days of age. Baseline ejection fraction recorded at 60 days averaged 60.3%; by 90 days, it decreased to 54.3% (p < 0.05), falling to 41.3% at 180 days (p < 0.01) and declining to 30% at the end of the study. A progressive increase in the extent of myocytolysis, fibrosis and calcification was seen in the histologic studies as the animals aged. The ratio of fatty acid-to-thallium uptake dropped from 0.51 +/- 0.09 to 0.45 +/- 0.11 (p < 0.01), which is in parallel with the reduction in ejection fraction. The thallium lung-to-heart ratio increased from 0.51 at 90 days to 0.59 at 270 days (p < 0.05), which corresponds to the worsening of cardiac function. The macroautoradiographic studies demonstrated slight uptake of pyrophosphate in the myopathic hamster hearts and minimal changes in the regional distribution of fatty acid compared to that of perfusion. We conclude that the decrease in ventricular function parallels the severity of myocytolysis and fibrosis. Although decreased fatty acid uptake was apparent at an early stage, the extent of the change is modest and is difficult to detect from external images.

Animals↗
PubMed1993

Steroid induced single strand breaks in DNA mediated by active oxygen species and its biological consequences.

A mutagenic steroidal derivative (3 beta-Acetoxy-5 alpha-Cholestano[6 alpha,5-d']1'-3'oxathiolane-2' thione) structurally related to cholesterol caused strand scission and induced nicks in calf thymus, supercoiled pBR322 and single stranded M13 mp8 phage DNAs. S1 nuclease hydrolysis, reaction with pBR322 and M13 phage DNA as well as treatment of E. coil mutant strains and phage was used to evaluate the effect of test steroid on the DNA molecule. The strand scission/nicking of DNA by the test steroid was enhanced by some metal ions, especially the Cu(II). Scavengers of active oxygen radical species significantly inhibited the S1 nuclease hydrolysis by the test steroid indicating the major role of active oxygen species in DNA strand scission and nicking. The steroid brought about the DNA degradation even in the absence of S1 nuclease. There was an appreciable reduction in the survival of steroid treated polA and lig mutants of E. coli K12 compared to the wild type strain. Phage on steroid treatment also lost its plaque forming units (P.F.U.) which was more pronounced in the polA and rec A background.

Animals↗
PubMed1992

Enzymatic semisynthesis of a superpotent analog of human growth hormone-releasing factor.

A superpotent analog of human growth hormone-releasing factor, [desNH2Tyr1,D-Ala2,Ala15]-GRF(1-29)-NH2 (4), was prepared from the precursor, [Ala15,29]-GRF(4-29)-OH (1), by a two-step enzymatic semisynthesis. The amidated C-terminus, essential for high biological potency, was obtained via a carboxypeptidase Y-catalyzed exchange of Ala29-OH for Arg29-NH2 to produce [Ala15]-GRF(4-29)-NH2 (2). The N-terminal desNH2Tyr-D-Ala moiety, which greatly increases in vivo duration of action, was then incorporated by V8 protease-catalyzed condensation of segment 2 with desNH2Tyr-D-Ala-Asp(OH)-OR [R = CH3CH2- (3a) or 4-NO2C6H4CH2-(3b)]. The main focus of this report was to develop conditions to use the V8 protease-catalyzed coupling while avoiding a competing cleavage of the proteolytically-sensitive Asp25-Ile26 bond in GRF. Conversion of 2 to 4 in couplings employing the alpha-ethyl ester of the acyl component 3a was limited to about 60% by competing proteolysis at Asp25-Ile26. This system was adequate for preparing, isolating, and fully characterizing the target analog 4 and identifying the side products. The 4-nitrobenzyl ester 3b proved to be a superior substrate, resulting in 90% conversion of 2 to 4 with no detectable loss to proteolysis and requiring significantly lesser amounts of catalyst. These results demonstrate that enzymatic semisynthesis of a biologically-active peptide amide which contains unnatural amino acids at the N-terminus can be achieved from a biosynthetic precursor in good yield and purity.

Amino Acid Sequence↗