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Biomedical subjects

M N Khan

Publications and source records attributed to M N Khan.

At least 37 records · Page 2Linked to original sources
PubMed2000

Breast diseases in males--a morphological review of 150 cases.

OBJECTIVE: This study was carried out to observe the prevalence breast diseases of males in our setup. METHOD: All cases of male breast disease diagnosed from 1991-97. RESULTS: One hundred and fifty (150) cases of male breast diseases were diagnosed. Age of the patients ranged from 4 to 90 years, with mean age 38.75 years (median = 33 years). Gynecomastia was the most common pathological abnormality of the male breast (58.66%). Most of the patients presented in the 3rd decade of life. Amongst the malignant conditions, infiltrating ductal carcinoma was most prevalent (82%). Most of the patients with malignancy presented in the 5th and 6th decades of life. CONCLUSION: Gynecomastia was the most prevalent male breast disorder, followed by infiltrating ductal carcinoma. Our findings correspond with that of world literature.

Adolescent↗
PubMed2000

Retinoblastoma tells the story of our health care system.

OBJECTIVE: To review cases of retinoblastoma. SETTING: Department of Pathology Aga Khan University Hospital Karachi. METHOD: Twenty-three specimens from cases of retinoblastoma received over a period of eight years were routinely processes and stained with haematoxylin and Eosin stain. Other stains were used for tuberculoses and melanin. Immunochemistry was resorted to in undifferentiated tumors. RESULTS: Over 60% cases of retinoblastoma were diagnosed after 5 years and nine cases showed involvement of optinerve. CONCLUSION: Late diagnosis of retinoblastoma effects the stage of the tumors and the prognosis.

Child, Preschool↗
PubMed1998

Dental caries in African preschool children: social factors as disease markers.

OBJECTIVE: This study investigated the associations between dental caries prevalence and severity and social factors in 3- to 5-year-old African children. METHODS: Dental caries was diagnosed in natural light using WHO criteria, minors, and explorers. Socioeconomic information was obtained by questionnaire. RESULTS: The percentages of 3-, 4-, and 5-year-olds with any caries experience were 47 percent, 58 percent, and 63 percent, respectively. Mean dmfs scores (SD) were 2.2(3.6), 3.0(3.8), and 3.7(4.1), respectively. Family education was associated with caries prevalence (P = .03) and severity (P = .008) in a multivariable regression model. CONCLUSION: In the indigenous African group studied, family education is a disease marker to target in future caries risk evaluations.

Child, Preschool↗
PubMed1997

Linkage mapping of Thiel-Behnke corneal dystrophy (CDB2) to chromosome 10q23-q24.

Corneal dystrophy of the anterior basement membrane is a heterogeneous set of diseases characterized by painful, recurrent, bilateral erosions of the cornea, which often result in significant visual impairment. There are several similar but clinically distinct forms of anterior basement membrane/Bowman's membrane disease, including two autosomal dominant forms, Reis-Bücklers and Thiel-Behnke corneal dystrophy. Genes causing autosomal, nonsyndromic corneal dystrophy have been mapped to human chromosomes 1p, 5q, 12q, 16q, 17p, and 20p. Using microsatellite markers closely linked to the known corneal dystrophy loci, we excluded linkage between the known sites and the disease locus in a large, four-generation family with Thiel-Behnke corneal dystrophy. A genome-wide search using a panel of microsatellite markers demonstrated a maximum two-point lod score of 4.0 at 0% recombination between the disease locus in this family and the marker D10S1239, which maps to 10q23-q24. Testing with additional microsatellite markers from 10q places the disease locus between D10S677 and D10S1671, a distance of approximately 12.0 cM, with a maximum multipoint lod score of 5.5. Based on this evidence, we have identified another locus (CDB2) for corneal dystrophy of the anterior basement membrane/Bowman's membrane, Thiel-Behnke type, further demonstrating the exceptional genetic and phenotypic heterogeneity of these diseases.

Chromosome Mapping↗
PubMed1997

Steroid metabolism by embryonic tissues of Arctic charr, Salvelinus alpinus.

High-performance liquid chromatography analysis of extracts of Arctic charr (salvelinus alpinus) eggs revealed the presence of several steroids, predominantly progestogens together with testosterone. Yolk sac embryos were incubated with tritiated progesterone ([3H]P4) or 17-hydroxyprogesterone ([3H]17OHP) to examine the ability of the embryos to metabolize progestogens in vitro; both progestogen precursors were converted to various free and conjugated steroids metabolites (sulfates and glucuronides). [3H]P4 was completely metabolized to form steroids that coeluted with standard 11-oxygenated androgens, corticosteroids, progestogens, and some other unidentified metabolites. This report also describes the biosynthesis of 17,20 beta-dihydroxy-4-pregnen-3-one and 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate by embryos of Arctic charr that were incubated with 17OHP.

17-alpha-Hydroxyprogesterone↗
PubMed1997

Metabolism of estrogens and androgens by embryonic tissues of Arctic charr, Salvelinus alpinus.

This study examines the ability of Arctic charr (Salvelinus alpinus) embryos to metabolize tritiated androstenedione (A4), testosterone (T), 17 beta-estradiol (E2), and estrone (E1) in vitro; the metabolic products were separated by HPLC. A4 was poorly metabolized, with 48 to 64% of the substrate remaining even after 24 hr of incubation. The major metabolites of A4 metabolism are E1 and some other unidentified metabolites. T was mostly converted to A4, along with some reduced steroids, but E2 was a minor metabolite. Further, while E2 was almost exclusively transformed into E1, when E1 was used as the precursor, there was little metabolism; the products of E1 metabolism were small amounts of E1 sulfate, glucuronide, E2, and an unknown metabolite which cochromatographed with reference steroid androstenetrione (also called 11-ketoandrostenedione). It is concluded that in Arctic charr embryos there is preferential expression of a form of 17 beta-hydroxysteroid dehydrogenase resembling the type 2 isozyme of mammals that converts T and E2 to A4 and E1, respectively.

Androgens↗
PubMed1996

The relief of mitral stenosis. An historic step in cardiac surgery.

Significant progress has been achieved in cardiac surgery in the last 50 years. Mitral valve surgery (especially for the relief of mitral stenosis) has paralleled the innovations and trends of cardiac surgery and often has served as the benchmark of the latest procedures and techniques. A chronological survey of mitral valve surgery is presented, with emphasis on parallels to cardiac surgery in general and with highlights of key figures and events that have conclusively altered the surgeon's approach to and success with cardiac dysfunction. A few surgeons promulgated the idea of cardiac surgery in the late 19th century, but mitral valve surgeries were not performed in earnest until Souttar's and Cutler's initial attempts in the 1920s and were not successful on large groups of patients until Bailey and Harken made independent breakthroughs in the 1940s, finally laying to rest the idea of the "inviolable heart." Cardiopulmonary bypass provided cardiac surgeons with the time to implant mechanical and bioprosthetic valves for palliative benefit to patients. The "perfect" valve has yet to be found, but the Starr-Edwards mechanical valve since its inception in 1961 has been one of the most successful and widely used prosthetic valves. Gradual improvement in surgical technique and growing knowledge of valve function enabled the re-emergence of mitral valve repair in the 1980s as the preferred surgical method of treating mitral stenosis. In the last 10 years, mitral valve balloon dilation has provided a nonsurgical technique for relief of stenosis and represents the broader trend towards interventional techniques.

Cardiac Surgical Procedures↗
PubMed1996

Ruptured aneurysm of the sinus of Valsalva.

The objective of the present study was to assess the value of imaging techniques in the diagnosis of ruptured aneurysm of sinus of Valsalva (RASV). 38 patients were included in the study. 30 were male and 8 female. Their age ranged from 7 to 55 years (mean 25.8 years). Echocardiographic and doppler studies were done in all cases and 20 patients underwent catheterization and angiography. Two patients were asymptomatic, 20 (53%) had acute onset of symptoms and in the remaining 16 (42%) patients symptoms developed gradually. Twenty two (58%) patients were in NYHA functional class III or IV when first seen. Predominant symptoms were dyspnea (79%), palpitation (55%) and chest pain (52%). A continuous machinery murmur was detected in all the patients with associated thrill in 34 patients. Right coronary sinus (RCS) was the most common sinus involved (89%) followed by the noncoronary sinus (NCS) which was involved in 11% of patients. None of the patients in our series had aneurysm of the left coronary sinus. Twenty eight of the 34 RCS aneurysms ruptured into the right ventricular outflow tract (RVOT), 4 into right ventricular cavity (RVC), one into right atrium (RA) and one dissected into the ventricular septum and subsequently ruptured into the left ventricle. Of the 4 NCS aneurysms, 2 ruptured into RVC, one into RA and one into both the RA and RVC. Associated ventricular septal defect (VSD) was found in 10 (26%) patients and all of these patients had RCS aneurysm that ruptured into the RVOT. Aortic regurgitation (AR) was detected in 16 (42%) cases. Discrete subaortic stenosis was detected in one patient who also had associated VSD and AR. Vegetation of the aortic valve was detected in one patient who had RCS aneurysm. Twelve patients (11 male and one female) underwent surgical correction, 10 with and 2 without prior catheterization. Localization of the involved sinus, site of rupture and associated cardiac lesions by echocardiography and doppler study were found accurate at surgery and/or angiography in 22 cases of our series. Imaging techniques, thus appeared to be reliable tools for the diagnosis of RASV.

Adolescent↗
PubMed1995

Kinetics and mechanism of the alkaline hydrolysis of securinine.

The hydroxide ion-catalyzed hydrolysis of securinine involves the ring opening of the lactone moiety. The rate of hydrolysis is insensitive to the ionic strength. The observed pseudo-first-order rate constants reveal a decrease of approximately 4-fold due to the increase in the MeCN content from 4 to 50% (v/v) in mixed aqueous solvent. The temperature dependence of the rate of hydrolysis follows the Eyring equation, which yields delta H* and delta S* as 11.0 kcal mol-1 and -34.5 cal deg-1 mol-1, respectively. The hydroxyl carboxylate product of the alkaline hydrolysis of securinine is shown to undergo cyclization in acidic medium to yield securinine. The observed pseudo-first-order rate constants for cyclization increase linearly with an increase in [H+]. The change in the content of MeCN from 3.8 to 47.2% (v/v) in mixed aqueous solvents does not show an effect on the rate of the cyclization reaction. The most plausible mechanisms for alkaline hydrolysis and acid cyclization reactions are also discussed.

Alkaloids↗
PubMed1995

Kinetics and mechanism of general acid-catalysed thiolytic cleavage of 9-anilinoacridine.

The rates of the reactions of 2-mercaptoethanol (2-ME) with 9-anilinoacridine (9-ANA) have been studied in the buffer solutions of 2-ME, hydroxylamine, phosphate and morpholine. Both ionised and non-ionised forms of 2-ME and free hydroxylamine show nucleophilic reactivity toward protonated 9-ANA. The rate constants for general acid-catalysed thiolytic cleavage of protonated 9-ANA reveal a Brønsted plot of slope (alpha) of 0.93 which indicates that probably the rate-determining step involves proton transfer in a thermodynamically unfavourable direction. A stepwise mechanism for thiolysis has been suggested. General acid catalysis could be detected for thiolysis of non-protonated 9-ANA only in the buffer solutions of phosphate and morpholine. General acid catalysis seems to be unimportant when the nucleophile is non-ionised 2-ME which is attributed to the probable occurrence of intramolecular general acid catalysis.

Acids↗
PubMed1993

Epi-sarsasapogenin and epi-smilagenin: two sapogenins isolated from the rumen content of sheep intoxicated by Brachiaria decumbens.

Spectroscopic examination of purified extracts of the rumen content of sheep intoxicated by Brachiaria decumbens revealed the presence of two spirostanes, identified as epi-sarsasapogenin and epi-smilagenin. Sarsasapogenone was obtained by the oxidation of sarsasapogenin. The reduction of sarsasapogenone using lithium aluminum hydride yielded isomeric products, sarsasapogenin (20%) and epi-sarsasapogenin (80%).

Animals↗
PubMed1993

New saponins from Mangifera indica.

Two new terpenoidal saponins, indicoside A [1] and indicoside B [2], were isolated from Mangifera indica. Their structures were determined as 28-hydroxylupa-12,20(29)-diene-3-O-[beta-glucopyranosyl-(1-->2)] [-beta-glucopyranosyl-(1-->3)]-alpha-L-arabinopyranoside [1] and 28-hydroxylupa-12,20(29)-diene-3-O-[beta-glucopyranosyl-(1-->3)-al pha-L-rhamnopyranosyl-(1-->2)][beta-glucopyranosyl(1-->3)]-alpha-L- arabinopyranoside [2] on the basis of chemical and spectroscopic studies.

Carbohydrate Sequence↗
PubMed1992

Decrease in beta-subunit phosphotyrosine correlates with internalization and activation of the endosomal insulin receptor kinase.

In a previous study, we showed that the rat hepatic insulin receptor (IR) kinase of endosomes (ENs) was transiently activated to levels exceeding those of plasma membrane (PM) receptors following insulin injection. Phosphatase treatment of EN receptors abolished IR kinase activation implicating beta-subunit autophosphorylation as a mediator of the activation process (Khan, M. N., Baquiran, G., Brule, C., Burgess, J., Foster, B., Bergeron, J. J. M., and Posner, B. I. (1989) J. Biol. Chem. 264, 12931-12940). In the present study, the phosphotyrosine (PY) content of the IR beta-subunit in PM and ENs was estimated by two different methods. In one method, direct in vivo labeling with 32Pi followed by receptor immunoprecipitation was carried out. In the second method, immunoblotting with antibodies against the submembrane domain of the IR beta-subunit, encompassing residue 960 (alpha 960), and with antibodies against PY (alpha PY) was used to determine the content of PY/beta-subunit in PM and ENs following injection of insulin. By both methods, it was found that the PY content of PM IR was significantly greater than that of IR in ENs. With doses of 1.5 micrograms of insulin/100 g body weight (50% receptor occupancy) or 15 micrograms/100 g body weight (receptor saturation), the PY/beta-subunit of PM IR attained a level 2.0 to 2.5-fold of that observed for the IR of ENs. Surprisingly, the IR of ENs incorporated 3 to 5 times more PY/beta-subunit than those of PM consequent to autophosphorylation. Exogenous IR kinase activity (poly(Glu:Tyr)) in PM changed only slightly with insulin dose. In contrast, EN receptors exhibited a dose-dependent increase in kinase activity coincident with the decrease in PY/beta-subunit levels. A comparison of the proportion of receptor and kinase activity immunoprecipitated by alpha PY both before and after autophosphorylation indicated that ENs but not PM contained a small population of lightly phosphorylated but highly activated receptors. Since Thr12-Lys (IR kinase residues 1142-1153) efficiently inhibited IR autophosphorylation of both PM and EN receptors, Tris phosphorylation of beta-subunit regulatory tyrosines was unlikely. These results may be explicable by a dephosphorylation-dependent activation of IR kinase, as seen with the src family of tyrosine kinases.

Amino Acid Sequence↗
PubMed1991

The differential regulation by glucagon and growth hormone of insulin-like growth factor (IGF)-I and IGF binding proteins in cultured rat hepatocytes.

The liver is a major site of production of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGF-BPs). GH decisively influences IGF-I production. To study the role of GH and glucagon in the regulation of IGF-I and IGF-BP production, we examined IGF-I and IGF-BPs secreted by primary rat hepatocytes cultured in a serum-free medium. Glucagon (1 x 10(-8) M) stimulated IGF-I secretion and IGF-BP secretion. Bovine GH (bGH, 300 ng/ml) stimulated IGF-I secretion but suppressed IGF-BP secretion. Combining bGH and glucagon significantly augmented IGF-I secretion above the level seen with each individual agent. The inhibitory effect of bGH on IGF-BP secretion was reversed by glucagon. The major species of IGF-BPs secreted by hepatocytes were found, on Western ligand blotting, to be 24K and 30-34K. All species of secreted IGF-BPs appeared to be comparably affected by glucagon, bGH, and their combination. Northern analysis of IGF-I mRNA revealed three transcripts of 0.7-1.1 kilobases (kb), 1.8 kb, and 7.0 kb. Glucagon stimulated IGF-I mRNA levels 1.8- to 2.0-fold, whereas bGH stimulated IGF-I mRNA levels 2.0- to 2.5-fold. When hepatocytes were incubated with glucagon and bGH for 6 h, IGF-I mRNA levels were augmented 10-fold. Glucagon, in the presence of 50 ng/ml bGH, had a dose-dependent effect on IGF-I mRNA accumulation from a 6-fold level of stimulation at 50 ng/ml of glucagon to a 9-fold level of stimulation at 1000 ng/ml glucagon to a 9-fold level of stimulation at 1000 ng/ml glucagon. This study has demonstrated that glucagon, as well as GH, has significant effects on the production of both IGF-I and IGF-BPs. Of particular interest was the marked augmentation of hepatic IGF-I messenger RNA levels and the reversal of the low levels of IGF-BP production seen on adding glucagon to bGH.

Animals↗
PubMed1991

Assessment of low attendance at primary health care centre.

The study was conducted at 11 (eleven) randomly selected villages of Rupganj Upazila in order to find out the way to promote Primary Health Care. 1186 household heads and 11 physicians interviewed for the purpose. The study revealed that more than 54.14 percent of the study population were suffering from various diseases and only 4 percent of the patients attended Primary Health Care Centre/Complex. 52% of the patients were not satisfied by the service of Primary Health Care Centre/Complex. Want of medicine, lack of good physicians and doctors, carelessness about the patients constituted the principal causes of unsatisfactory treatment. The comparative distribution of opinion of household heads and physicians about non-attendance to Primary Health Care Centres by patients is statistically insignificant (P less than 0.05) which implies that the opinions are more or less the same. Both household heads and physicians opined that supply of sufficient medicine, equipment, improvement of health education and more budget allocations are essential to make the Primary Health Care service effective.

Bangladesh↗
PubMed1990

Comparison of temperatures at different sites in term and pre-term neonates.

Temperatures of 30 term and 20 preterm neonates were recorded by mercury-in-glass thermometer at 4 measurement sites; rectum (2 cm beyond anus), external auditory canal, axilla and between skin and mattress. Whereas, the mean rectal and aural temperatures in term infants were significantly higher than their preterm counterparts (p less than 0.01), axillary and skin mattress temperatures did not differ significantly in the two groups. The variation between stabilized temperature at four measurement sites was less marked in preterm as compared to term infants. The skin mattress temperature measurement is a simpler technique and it closely approximates the rectal temperature in preterm infants. Temperatures at all the measurement sites stabilized by 5 minutes both in term and preterm infants.

Body Temperature↗