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Biomedical subjects

A R Khan

Publications and source records attributed to A R Khan.

At least 55 records · Page 3Linked to original sources
PubMed1995

Thyroid malignancy in multinodular goitre and solitary nodule.

This is a retrospective study of 361 thyroid specimens during a 6 1/2-year period with the objective of investigating the prevalence and pattern of thyroid malignancy associated with multinodular goitre (MNG) and solitary nodule (SN). Fourteen of 172 MNG (8%) and 16 of 105 SN (15.2%) were associated with malignancy, a statistically insignificant difference (P = 0.06). Unlike in males, malignancy was significantly commoner in females with SN than those with MNG (P = 0.03) and generally occurred at a significantly older age (P < 0.05). On analysing thyroid carcinoma and lymphoma separately, patients with SN had a higher incidence of carcinoma compared with those with MNG (P = 0.01). It is concluded that surgical intervention may be the appropriate method of treating male patients presenting with MNG. However, in females, conservative management of MNG should be adopted unless surgery is indicated depending on clinical judgement and, if feasible, the result of fine needle aspiration biopsy.

Adolescent↗
PubMed1994

Beta-human chorionic gonadotropin, progesterone, and aqueous dynamics during pregnancy.

OBJECTIVE: To determine whether the altered hormonal milieu of pregnancy is associated with changes in the dynamics of aqueous humor formation and drainage. DESIGN: Nineteen women were studied during each trimester of a single pregnancy and post partum. Measures of aqueous dynamics included intraocular pressure, aqueous flow, facility of outflow, aqueous flare, and corneal thickness. RESULTS: Pregnancy was associated with relatively lower intraocular pressure, reduced aqueous flare, increased corneal thickness, and increased aqueous outflow facility. Aqueous flow was unchanged. The progesterone level increased during pregnancy and decreased during the postpartum period. The beta-human chorionic gonadotropin level was highest during the first trimester. The progesterone level, but not the beta-human chorionic gonadotropin level, was correlated with intraocular pressure, aqueous flare, and corneal thickness. The change in aqueous outflow facility that accompanied pregnancy could not be correlated directly to changes in beta-human chorionic gonadotropin or progesterone concentrations. CONCLUSIONS: Aqueous flow remains constant during and after pregnancy, but intraocular pressure decreases during pregnancy due to an increase in the outflow facility. The changes in aqueous dynamics are consistent with the hypothesis that excess progesterone during pregnancy blocks the ocular hypertensive effect of endogenous corticosteroids. However, we were unable to find a statistically significant correlation when a direct comparison between the observed changes in outflow facility and the observed changes in the progesterone level was made, perhaps because of intersubject variability of these changes. The changes in intraocular pressure and outflow facility could have been due to one of many other changes in pregnancy that were not measured.

Adult↗
PubMed1994

Blood pressure and glycemic status in relation to body mass index in a rural population of Bangladesh.

A cluster sampling of five villages in Dohar thana were selected for screening of hypertension and diabetes in relation to age structure and body habitus. All the subjects over 15 years of age were enlisted for investigation. The response rate was more than 70%. Height, weight, blood pressure (BP) and capillary blood glucose (fasting and 2-hPG) were measured. Diagnostic criteria of international standard were used for hypertension and diabetes. Out of 1005 participants 106 subjects (10.5%) had systolic blood pressure (sBP) more than 140 mmHg and 9% of them had diastolic blood pressure (dBP) more than 90 mmHg. The prevalence of non-insulin-dependent diabetes mellitus (NIDDM) was 2.1% and impaired glucose tolerance (IGT) was 13.3%. The mean body mass index (BMI) of men was 20.39 (SD = 2.91) and that of women was 20.11 (SD = 2.92), having no significant difference between them. Increased age (> or = 50 yr), high BMI (> or = 23.0) and hyperglycemia (2-hPG > 7.8 mmol/L) were the risk factors for both systolic (sBP > 140 mmHg) and diastolic (dBP > 90 mmHg) hypertension. Likewise, increased age, high BMI and hypertension showed significant association with glucose intolerance. Moreover, significant correlations were observed between age and BP (sBP, r = 0.328 p < 0.001; dBP, r = 0.187 p < 0.001) BMI and BP (sBP, r = 0.193 p < 0.001; dBP, r = 0.192 p < 0.001) and 2-hPG and BP (sBP, r = 0.188 p < 0.001; dBP, r = 0.134 p < 0.001).

Adolescent↗
PubMed1993

Val-->Ala mutations selectively alter helix-helix packing in the transmembrane segment of phage M13 coat protein.

Val-->Ala mutations within the effective transmembrane segment of a model single-spanning membrane protein, the 50-residue major coat (gene VIII) protein of bacteriophage M13, are shown to have sequence-dependent impacts on stabilization of membrane-embedded helical dimeric structures. Randomized mutagenesis performed on the coat protein hydrophobic segment 21-39 (YIGYAWAMV-VVIVGATIGI) produced a library of viable mutants which included those in which each of the four valine residues was replaced by an alanine residue. Significant variations found among these Val-->Ala mutants in the relative populations and thermal stabilities of monomeric and dimeric helical species observed on SDS/PAGE, and in the range of their alpha-helix-->beta-sheet transition temperatures confirmed that intramembranous valine residues are not simply universal contributors to membrane anchoring. Additional analyses of (i) nonmutatable sites in the mutant protein library, (ii) the properties of the double mutant V29A-V31A obtained by recycling mutant V31A DNA through mutagenesis procedures, and (iii) energy-minimized helical dimer structures of wild-type and mutant V31A transmembrane regions indicated that the transmembrane hydrophobic core helix of the M13 coat protein can be partitioned into alternating pairs of potential protein-interactive residues (V30, V31; G34, A35; G38, I39) and membrane-interactive residues (M28, V29; I32, V33; T36, I37). The overall results consitute an experimental approach to categorizing the distinctive contributions to structure of the residues comprising a protein-protein packing interface vs. those facing lipid and confirm the sequence-dependent capacity of specific residues within the transmembrane domain to modulate protein-protein interactions which underlie regulatory events in membrane proteins.

Alanine↗
PubMed1993

Visceral leishmaniasis: II. Histiocyte ultrastructure in bone marrow associated with low level of parasitaemia and mimicking malignant histiocytosis.

The ultrastructural features of histiocytes in the bone marrow (BM) were studied in a febrile, splenomegalic and pancytopenic Sudanese patient who was diagnosed by one of us as visceral leishmaniasis (VL) associated with low level of parasitaemia and mimicking malignant histiocytosis (MH). Serial thick (STS) and ultrathin (SUT) sections showed that the BM was hypercellular and markedly infiltrated by large histiocytes with prominent phagocytosis. A thorough examination of various ST and UT section revealed only a single, typical Leishman-Donovan body. At transmission electron microscopy (TEM) level, two principal types of histiocytic cells were identified: Type I, subdivided into two subtypes, were actively phagocytic histiocytes (PH) with large digestive vacuoles and primary lysosomes; type II were nonphagocytic histiocytes (nPH) with primary lysosomes only. The rate of PH to nPH ws 7:2 in plastic STS. The interaction between the PH and ingested cells is described. Both types of cell were morphologically similar to previously described malignant histiocytic cells. However, this study showed a better characterization of PH during VL.

Adult↗
PubMed1993

Aqueous humor flow and flare in patients with myotonic dystrophy.

PURPOSE: Myotonic dystrophy is an autosomal dominant form of muscular dystrophy associated with a mutation that affects a gene on chromosome 19. Extremely low intraocular pressure is one of a constellation of clinical signs that sometimes accompany this disorder. This study was performed to determine if the ocular hypotony can be explained by aqueous humor hyposecretion. METHODS: Seventeen persons with myotonic dystrophy and seventeen age-matched controls were studied. Intraocular pressure, light scattering (flare), fluorescein clearance at various times of day, and the response of the eye to the topical timolol were measured. RESULTS: Intraocular pressure was 40% lower in the persons with myotonic dystrophy (8.4 mm Hg vs 14.0 mm Hg) and flare was 50% higher (55.8 mg/dl albumin equivalent vs 37.1 mg/dl albumin equivalent). Fluorescein clearance in persons with myotonic dystrophy was indistinguishable from normal at all times of day. Myotonic eyes responded normally to topical timolol. The physiological data of this study are most consistent with the conclusion that the rate of aqueous humor flow is reduced approximately 9%, and the rate of inward leakage of light scattering proteins is increased approximately 37% in well-established myotonic dystrophy with ocular hypotony. CONCLUSIONS: The reduced aqueous humor flow alone is insufficient to explain the ocular hypotony. We hypothesize that the hypotony is due primarily to atrophy of the ciliary muscle that increases fluid exchange between the anterior chamber and the anterior uvea with consequent enhancement of uveoscleral outflow.

Administration, Topical↗
PubMed1992

Integrity of the alveolar-capillary barrier and alveolar surfactant system in smokers.

BACKGROUND: The permeability of the alveolar-capillary barrier to technetium-99m labelled diethylenetriamine pentaacetate (99mTc DTPA) is known to be greatly increased in smokers, but the underlying mechanism is poorly understood. Abnormal permeability of the alveolar epithelium as well as impaired surfactant function has been suggested. The purpose of this study was to examine transudation of urea and albumin into the alveoli and alveolar surfactant function in smokers and non-smokers and to relate these variables to the rate of alveolar-capillary transfer of 99mTc DTPA. METHODS: Standardised bronchoalveolar lavage was performed and the yield of urea and albumin measured in the lavage fluid. The integrity of the alveolar surfactant system was assessed by measurement of the surface activity and of the yield of phospholipids in alveolar lavage fluid. RESULTS: The mean decay constant for the pulmonary clearance of 99mTc DTPA was 0.028/min in the smokers and 0.009/min in the non-smokers. The recovery of albumin and urea in alveolar lavage fluid was very similar in the two groups. The surface activity of alveolar lavage fluid was lower in smokers than in non-smokers (minimum surface tension 37.9 versus 28.6 mN/m) and the yield of phospholipids was reduced (2.08 versus 3.86 mg). The rate constant for the pulmonary clearance of 99mTc DTPA correlated with the yield of phospholipids at bronchoalveolar lavage. CONCLUSIONS: The study shows that increased alveolar-capillary transfer of 99mTc DTPA in smokers is not accompanied by increased transudation of small or large molecules into the alveoli. The findings support the hypothesis that increased clearance of 99mTc DTPA in smokers is related to surfactant dysfunction.

Adult↗
PubMed1992

Impact of schistosomiasis on urinary bladder cancer in the southern province of Saudi Arabia: review of 60 cases.

The histopathologic findings reported in 254 consecutive urinary bladder biopsies were reviewed. Evidence of urinary schistosomiasis was identified in 88 biopsies (35%) and malignant neoplasms were diagnosed in 60 cases (24%). Nine out of 60 (15%) cases of bladder cancer had urinary bladder schistosomiasis and the remaining 51 cases (85%) had no clinical evidence of schistosomiasis. Transitional cell carcinoma was the commonest type of urinary bladder cancer (70%) followed by squamous cell carcinoma (20%) adenocarcinoma (8%) and rhabdomyosarcoma (2%). The mean age of the patients included was 60 +/- 15 years and the male:female ratio was 9:1. Comparison of our findings to those reported from other provinces of Saudi Arabia and from other countries, including those with known high incidence of schistosomiasis, is included.

Adenocarcinoma↗
PubMed1991

Lipoid pneumonia in children following aspiration of animal fat (ghee).

Exogenous lipoid pneumonia induced by modified animal fat (ghee) in 10 children is described. The initial presentation was of an acute or chronic pneumonia which proved refractory to anti-microbial chemotherapy. The radiological presentation varied from mild perihilar consolidation to diffuse and extensive bilateral involvement, particularly of the posterior lung segments. A history of administration of ghee provided the initial clue to the diagnosis, which was confirmed by demonstration of fat by bronchoalveolar lavage or by open lung biopsy. Eight of the 10 patients improved with either steroid therapy alone or steroids with resection of the most involved lung segments. One patient, who had extensive superinfection with Mycobacterium fortuitum, died. Lipoid pneumonia should be considered in the differential diagnosis of 'non-resolving' pneumonias in communities where the cultural practice of infant feeding with ghee is prevalent. Public awareness through health education about the potential hazards of this practice to infants and children can contribute to reduce the incidence of the problem.

Animals↗
PubMed1991

Recoveries of phosphatidylcholine and alveolar macrophages in lung lavage from healthy light smokers.

Twenty-one healthy volunteers, 11 light smokers and 10 non-smokers, were studied by broncho-alveolar lavage. The levels of the phosphatidylcholine (PC) in broncho-alveolar lavage were measured and used as an index of surfactant. The PC levels in broncho-alveolar lavage obtained from the smokers were significantly lower than in lavage fluid from the non-smokers. There was an inverse correlation between PC levels and cumulated tobacco smoke exposure, as estimated by the number of pack-years, and to current smoking habits as estimated by the number of cigarettes smoked per day. The number of alveolar macrophages was significantly higher in broncho-alveolar lavage obtained from smokers, and there was a significant inverse correlation between PC levels and numbers of alveolar macrophages in the lavage fluids. The potential role of alveolar macrophages in the elimination of surfactant lipids is discussed.

Adult↗
PubMed1989

Inflammatory cell infiltrate in distal ureteral segments from patients with reflux.

A total of 110 reimplanted ureters from 61 patients were examined by light microscopy. Twenty-four distal segments from nonrefluxing ureters were used as control group. Overall, 55 of 110 specimens (50%) had inflammatory cell infiltrates (ICI) consisting of lymphocytes and plasma cells in the submucosa and adjacent muscularis. Forty-five ureters (82%) had mild ICI, and 10 ureters (18%) had moderate or severe ICI only in patients with history of infection. ICI increased with grade of reflux in both infected and noninfected groups. Of 75 ureters (68%) from patients with history of infection, 45 (60%) had ICI. Ten of 35 ureters (29%) from patients without history of infection had ICI. A causal relationship between reflux and ICI remains speculative and needs further study.

Adolescent↗
PubMed1989

Diagnostic value of longterm ambulatory ECG in patients with syncope, dizziness or palpitations.

The diagnostic value of longterm ambulatory ECG recording (LTER) was determined in 63 patients referred for investigation of syncope, in 32 with dizziness and in 89 with palpitations. Among patients referred for syncope, dizziness or palpitations 8, 13 and 54%, respectively, had typical symptoms during the recording with concomitant arrhythmia explaining the symptom, and 6, 50 and 11% had a typical symptom without concomitant arrhythmia. In 12 and 3% of the patients referred for syncope or dizziness, respectively, arrhythmia was observed and probably explained their previous complaint, but no symptoms occurred during LTER. LTER was found to be of diagnostic value in 24% of the patients with syncope, in 66% of those with dizziness and in 65% of those with palpitations. In the latter two groups the presence of symptoms the week before the start of these recordings predicted the occurrence of symptoms during LTER. Only occasionally was there a higher yield of typical symptoms beyond 48 h of recording.

Aged↗
PubMed1988

Functional properties of neoplastic T cells in helper T cell prolymphocytic leukaemia with IgM hypergammaglobulinaemia.

A case of T cell prolymphocytic leukaemia of helper/inducer T cell phenotype with IgM hypergammaglobulinaemia in a 65-year-old Saudi man is presented. The neoplastic T cells in the patient had an OKT3+, OKT4+, OKT8-, OKT11+, OKCLL+, OKIa1+, OKDR+, Tac+ phenotype. The presence of OKIa1+, OKDR+, and Tac+ antigens indicates that the leukaemic T cells were in an activated state. The cells responded to phytohaemagglutinin, but showed a diminished response to concanavalin A. The reduced interleukin 2 receptor expression and interleukin 2 production were associated with defective concanavalin A-induced proliferation. There was suppression of mixed lymphocyte culture reaction between the patient and two healthy donors in response to concanavalin A. In vitro immunoglobulin production experiments demonstrate that the leukaemic T cells provided an enhanced helper cell function to produce IgM, and suppressor cell function to produce IgG immunoglobulins by pokeweed mitogen-induced normal B lymphocyte differentiation. In this study we also found that the patient's T cells proliferate in response to lipopolysaccharides, thus providing the first evidence that leukaemic (OKT4+) T cells from a prolymphocytic leukaemia patient can be stimulated by lipopolysaccharides.

Aged↗
PubMed1988

An ultrastructural analysis of plasma membrane in the U18666A cataract.

Because the cholesterol concentration of lens fiber cell membrane in general and lens intercellular junctions in particular is comparatively high, it is likely that it plays a major role in maintaining these structures. In addition, the high concentration of cholesterol in fiber cell membrane is also likely to influence membrane fluidity. Subcutaneous injections of U18666A (3 beta-(2-diethylaminoethoxy) androst-5-en-17-one HCl) into rats effects: (1) a blockade of sterolgenesis in the lens; (2) a depletion of lens fiber cell membrane cholesterol; and (3) the development of irreversible nuclear cataracts. In the present study we have analyzed the ultrastructure of lens fiber cell membrane in adult rats, these by the freeze-etch technique. Whereas it has been previously demonstrated that intercellular junctions comprise approximately one-third of the intermediate cortical fiber cell membrane in adult rats, these junctions were completely absent between comparable fiber cells taken from opaque regions of the U18666A cataractous lenses. There was also a concomitant increase in the extracellular space between the opaque fiber cells and a substantial redistribution of intramembrane proteins in the exoplasmic and protoplasmic faces of these cells. These findings support a "hypothesis" that inhibition of endogenous lens cholesterol production leads to damage and/or degeneration of lens fiber cell membrane in general and in intercellular junctions in particular, resulting in the production of an irreversible nuclear cataract.

Androstenes↗
PubMed1987

Analysis of the inotropic effect of prenalterol in papillary muscles from guinea-pig hearts.

The inotropic effects of prenalterol were studied in papillary muscles isolated from the right ventricle of guinea-pig hearts. Force production and action potential were recorded. The preparations were paced at 0.4 Hz (at 31-32 degrees C) under isometric conditions. Prenalterol, in concentration 0.1 microM did not change the action potential duration whereas the peak force and the maximum rate of force development increased by 40.3 and 36.3%, respectively. Time to peak force was slightly shortened (-3.0%) and so was the time from peak force to half relaxation (-5.2%). A predetermined stimulus protocol was used for assessment of the recirculation fraction of activator calcium. At selected times an extra contraction was introduced in order to obtain contractile potentiation. Force of the subsequent two test contractions (after fixed intervals) was analysed. Prenalterol slightly reduced the decay of the postextrasystolic potentiation measured in the two test contractions. It is suggested that the inotropic effect of prenalterol is due to an intensified calcium influx during the action potential, and to some extent to more efficient re-utilization of released calcium. There seems to be a more rapid release of calcium from troponin C giving rise to a shortened time to peak force and an enhanced relaxation.

Action Potentials↗