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Biomedical subjects

M I Khan

Publications and source records attributed to M I Khan.

At least 19 recordsLinked to original sources
PubMed1992

Risk factors associated with hydropericardium syndrome in broiler flocks.

A prospective study was undertaken to identify the epidemiological factors associated with the development and spread of the hydropericardium syndrome in broiler flocks. Data were collected between July 1989 and April 1990 from 131 flocks in 105 broiler production units pertaining to their demography, management practices, prophylactic procedures and concurrent diseases. The incidence rate of the syndrome in the whole population was 46.6 per cent. There were significant associations between the incidence in a flock and visits by a poultry vaccination crew (P = 0.014), the number of flocks raised (P = 0.004) and the source of light and heat (P = 0.007). Flocks that had one or more visits by a poultry crew were 15 times more likely to be affected by the syndrome than flocks that had no such visits. Premises where one flock was raised were nearly three times more likely to be affected than premises where two flocks were raised, and the use of electricity as a source of light and heat entailed a much lower risk of hydropericardium syndrome than kerosene oil.

Animals↗
PubMed1992

Effect of long-term captopril therapy on left ventricular remodeling and function during healing of canine myocardial infarction.

To determine whether the long-term reduction of preload and afterload by captopril during healing after acute anterior myocardial infarction might attenuate left ventricular remodeling and improve function, 30 chronically instrumented dogs with infarction produced by left anterior descending coronary artery ligation were randomized 2 days later to oral therapy with placebo (n = 15) or captopril, 50 mg twice daily (n = 15), for 6 weeks. Serial hemodynamic as well as topographic and functional variables (two-dimensional echocardiography) were measured over 6 weeks. Scar topography (planimetry), occluded bed size (coronary arteriography) and collagen (hydroxyproline) content were measured at 6 weeks. Between 2 days and 6 weeks, captopril decreased (p less than 0.001) mean arterial pressure and mean left atrial pressure more than did placebo, but it did not influence heart rate. Infarct scar mass, transmurality and collagen content at 6 weeks were similar in the two groups but scars showed less (p less than 0.001) thinning and expansion with captopril than with placebo. Echocardiograms showed similar infarct expansion and thinning in the two groups at 2 days but less aneurysm with captopril at 6 weeks. Between 2 days and 6 weeks, expansion index (infarct-/noninfarct-containing segment length) decreased (p less than 0.001) with captopril but increased (p less than 0.001) with placebo. Also, thinning ratio (infarct/normal wall thickness) decreased (p less than 0.001) with placebo but did not change (p = NS) with captopril. By 6 weeks, left ventricular asynergy and volumes showed a greater decrease (p less than 0.01) and global ejection fraction a greater increase (p less than 0.05) with captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Functional impact of remodeling during healing after non-Q wave versus Q wave anterior myocardial infarction in the dog.

OBJECTIVES: This study was undertaken to compare changes in left ventricular remodeling and function during healing after a first anterior non-Q wave versus a Q wave myocardial infarction in the dog. BACKGROUND: Whether ventricular remodeling is more severe after anterior Q wave than after anterior non-Q wave infarction has not been studied systematically. METHODS: Serial remodeling and functional variables (two-dimensional echocardiography), electrocardiography and hemodynamic data were recorded over 6 weeks in 58 instrumented dogs subjected to left anterior descending coronary artery ligation or ligation plus collateral obliteration. Postmortem topography and transmurality (by planimetry) and infarct collagen (hydroxyproline) were measured at 6 weeks. RESULTS: At 6 weeks, infarct collagen was similarly increased in both groups, but the Q wave group had greater infarct size (7.2% vs. 4.5%, p less than 0.025) and greater transmurality (88% vs. 58%, p less than 0.001), higher left atrial pressures, more infarct expansion (expansion index 2.62 vs. 2.31, p less than 0.001), more thinning (thinning ratio 0.62 vs. 0.72, p less than 0.001), greater cavity dilation (diastolic volume 88 vs. 72 ml, p less than 0.001), more regional bulging in the short-axis view (depth 4.9 vs. 1.9 mm, p less than 0.001), more regional asynergy (18% vs. 7%, p less than 0.001), lower global ejection fraction (40% vs. 48%, p less than 0.001), more endocardial and epicardial bulging in the long-axis view and greater incidence of aneurysm (82% vs. 36%, p less than 0.005), left ventricular thrombus (64% vs. 0%, p less than 0.0005) and ventricular arrhythmias. Echocardiograms obtained during a 6-week period indicated that left ventricular topographic deterioration and dysfunction were present in the earliest postinfarction study at 2 days in both groups but were more frequent in the Q wave group. Regional myocardial blood flow (24 dogs) was lower in the Q wave than in the non-Q wave group. Scanning electron microscopy (10 dogs) revealed preservation of the epicardial collagen matrix in the non-Q wave but not the Q wave group. CONCLUSIONS: Anterior Q wave infarction is associated with greater transmurality and more postinfarction left ventricular remodeling and dysfunction than is non-Q wave infarction.

Animals↗
PubMed1992

Impact of increased infarct transmurality on remodeling and function during healing after anterior myocardial infarction in the dog.

To determine the impact of greater infarct transmurality on changes in left ventricular remodeling and function after acute anterior myocardial infarction, serial topographic and functional parameters (two-dimensional echocardiograms) and hemodynamics over 6 weeks, and postmortem topography (planimetry) at 6 weeks, were measured in chronically instrumented dogs randomized to standard coronary artery ligation (group 1) or a modified lower ligation plus collateral obliteration to decrease collateral inflow and increase transmurality (group 2). At 6 weeks, postmortem scar size and collagen were similar in the two groups, but group 2 had greater transmurality associated with more necrosis relative to area at risk, Q waves, infarct expansion, thinning, regional bulging, and cavity dilatation. Over the 6 weeks, group 2 showed more early expansion, late thinning and regional bulging in the short axis, larger diastolic and systolic volumes, and more apical aneurysmal bulging in the long-axis, reflecting more topographic deterioration. More important, group 2 showed greater regional and global left ventricular dysfunction over 6 weeks, lower ejection fraction at 2 days with further decrease over 6 weeks, and more left ventricular thrombus, ventricular arrhythmias, and deaths. In addition, transmurality correlated with the severity of remodeling and dysfunction. The findings indicate that transmurality is a major determinant of remodeling and left ventricular dysfunction during healing after anterior infarction.

Animals↗
PubMed1992

Effect of left ventricular unloading with captopril on remodelling and function during healing of anterior transmural myocardial infarction in the dog.

OBJECTIVE: To determine whether left ventricular (LV) unloading with captopril between two days and six weeks during healing after transmural anterior acute myocardial infarction might prevent further LV remodelling and preserve function in the canine model. DESIGN: Serial LV topographic and functional parameters (two-dimensional echocardiograms) and hemodynamics over six weeks and scar topography (planimetry) and collagen (hydroxyproline) at six weeks were measured in 34 chronically instrumented dogs; 24 with anterior transmural acute myocardial infarction (coronary artery ligation and collateral obliteration) that had been randomized at two days post infarction to therapy with oral 50 mg bid placebo (n = 12) or captopril (n = 12) for six weeks, and 10 with sham infarction. MAIN RESULTS: At six weeks, captopril and placebo groups had similar scar mass (7.7 versus 8.1% LV), infarct hydroxyproline and transmurality but the captopril group showed significantly less (P less than or equal to 0.05) infarct expansion and thinning, cavity dilation, epicardial and endocardial bulge. Between two days and six weeks, captopril decreased mean left atrial and arterial pressures compared to placebo or sham. Echocardiograms at two days showed similar LV asynergy, ejection fraction, infarct expansion and thinning with placebo and captopril. In contrast, echocardiograms between two days and six weeks showed that: further expansion and thinning occurred with placebo but not captopril; LV volumes increased with placebo but decreased with captopril; total LV asynergy was unchanged with placebo but decreased with captopril; and LV ejection fraction was unchanged with placebo but increased with captopril. At six weeks, LV ejection fraction was 10% higher (45 versus 35%, P less than 0.001) and LV aneurysm was less frequent (33 versus 100%, P less than 0.005) with captopril compared to placebo. CONCLUSIONS: Chronic LV unloading with captopril therapy during healing after canine transmural anterior acute myocardial infarction limits further remodelling, decreases aneurysm formation and improves function.

Animals↗
PubMed1991

Interactions of concanavalin A with glycoproteins. A quantitative precipitation study of concanavalin A with the soybean agglutinin.

Certain oligomannose-type glycopeptides have been previously shown to be bivalent for binding to concanavalin A and capable of precipitating the lectin by forming homogeneous cross-linked lattices [L. Bhattacharyya, M. I. Khan, and C.F. Brewer, Biochemistry, 27 (1988) 8762-8767]. In the present study, the effect of protein environment on the binding properties of an oligomannose-type oligosaccharide has been examined through quantitative precipitation analysis of the interactions of concanavalin A (Con A) with the soybean (Glycine max) agglutinin (SBA), which is a tetrameric glycoprotein possessing a single Man9-oligomannose chain per monomer. The results showed that SBA forms two different types of cross-linked complexes with tetrameric Con A, depending on the relative ratio of the two molecules in solution. At a concentration of one equivalent or less, SBA forms a 1:1 complex with Con A. At concentrations exceeding one equivalent, SBA forms a 2:1 complex with Con A. However, SBA forms only 1:1 cross-linked complexes with dimeric forms of Con A, such as acetyl- and succinyl-Con A. The results demonstrated that the total valency of the carbohydrate of SBA is a function of both the quaternary structure of Con A, as well as the relative ratio of SBA to Con A. In addition, the individual Man9-oligosaccharide, which as a glycopeptide is bivalent for binding to Con A, expresses univalency when present on the protein matrix of SBA.

Carbohydrate Sequence↗
PubMed1991

Characteristics of an unusual mycoplasma isolated from a case of caprine mastitis and arthritis with possible systemic manifestations.

A mycoplasma designated strain GM790A was isolated from milk and internal organs of 2 lactating goats showing mastitis and arthritis. The isolate was not related serologically to any of the currently known ovine-caprine mycoplasmas, except an isolate designated Mycoplasma sp. G, first recorded from the external ear canal of clinically normal goats in Australia. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and restriction enzyme DNA studies of strain GM790A and Mycoplasma sp. G revealed similar but not identical patterns. The inoculation of strain GM790A into the teat canal of 2 lactating goats resulted in an abrupt diminution of lactation leading to mastitis and agalactia in about 3 days. A maximum of 1 x 10(7) colony-forming units (CFU) of the mycoplasma were shed per ml of mammary secretion. Milk production partially resumed at a low level 3 weeks postinoculation, the longest period tested, but the milk still contained 1 x 10(2) CFU of the agent. The results of this study indicate that strain GM790A possesses pathogenic potential for the goat and most probably represents a new species of the genus Mycoplasma.

Animals↗
PubMed1991

Predicting recovery of facial nerve function following injury from a basilar skull fracture.

Twenty-five patients with posttraumatic facial nerve palsy were studied. Partial recovery of function had occurred in 95% of these patients by 18 months after injury. At 5 months posttrauma, there was some recovery in 92.5% of those with a partial lesion compared with 10% of those with a complete lesion. This difference attains statistical significance. Complete recovery of nerve function had occurred by 10.5 months in 53.5% of the patients; in 62% of patients with a partial lesion, complete recovery had occurred by 4 months compared with 0% in those with a complete lesion. This difference also attains statistical significance. There was no statistically significant difference in recovery of function between patients with an immediate as opposed to a delayed onset of facial nerve palsy. It was determined that the degree of palsy had a statistically significant influence on recovery of facial nerve function, whereas the time of onset did not. The data presented support a conservative approach to these injuries and it is recommended that the possibility of surgical treatment should be entertained in patients with complete facial palsy persisting for 12 to 18 months after injury.

Adolescent↗
PubMed1990

Effectiveness of multiple bolus administration of tissue-type plasminogen activator in acute myocardial infarction.

The feasibility and possible advantages of intravenous bolus administration of recombinant tissue-type plasminogen activator (rt-PA) were investigated in 26 consecutive patients with early (less than 6 hours) evolving acute myocardial infarction. Either an intravenous infusion of 40 clot-lysis megaunits (cIMU) double-chain rt-PA over 1.5 hours followed by 20 cIMU over 5 hours (infusion group, n = 12) or 4 intravenous bolus injections of 10 cIMU at 20 minute intervals (bolus group, n = 14) were randomly administered. Coronary arteriography was performed before and at regular predefined intervals up to 90 minutes from the start of rt-PA administration, and at 24 hours. Acute recanalization of the infarct-related coronary artery was demonstrated in 7 of 12 patients (58%; 95% confidence interval 28 to 85%) in the infusion group and 11 of 14 patients (79%; 95% confidence interval 49 to 95%) in the bolus group (difference not significant). Two patients in the bolus group had reoccluded by 24 hours. Mean time from the start of rt-PA to patency of the infarct-related coronary artery was 39 +/- 6 (standard error of the mean) minutes in the infusion group and 28 +/- 6 minutes in the bolus group (p = 0.2). There were no significant differences in the minimum infarct-related coronary artery luminal diameter measured by computerized quantitative arteriography between the infusion group and the bolus group at 90 minutes or at 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Early coronary reperfusion blunts the procoagulant response of plasminogen activator inhibitor-1 and von Willebrand factor in acute myocardial infarction.

The effects of early coronary recanalization on the plasma levels of two procoagulant acute phase proteins, the fastacting plasminogen activator inhibitor and von Willebrand factor, were investigated in 24 patients with myocardial infarction receiving intravenous recombinant tissue-type plasminogen activator (rt-PA) within 6 h of the onset of symptoms. Coronary angiography was performed before and 90 min after the start of rt-PA infusion. Continuous electrocardiographic recordings and 4 h plasma creatine kinase MB isoenzyme (CK MB) were performed over the first 24 h. Plasma plasminogen activator inhibitor activity, von Willebrand factor and C-reactive protein were measured before rt-PA infusion, daily for the first 3 days and after 90 days. In the entire group, plasminogen activator inhibitor activity peaked at 24 h (day 1), representing a significant increase over values at all other times (p = 0.03). von Willebrand factor was higher in the first 2 days of infarction compared with after 90 days (p = 0.001). C-reactive protein peaked on day 2, with an eightfold increase over values on admission (p = 0.001). In the 16 patients with a patent infarct-related artery at 90 min, infarct size estimated by integrated 24 h CK MB, time for ST segment elevation to decrease to half-maximum and peak C-reactive protein were reduced significantly by more than twofold compared with values in the 8 patients with an occluded artery at 90 min. The patients with early recanalization also had lower plasminogen activator inhibitor activity on day 2 (p = 0.05) and day 3 (p = 0.02) and lower 0 to 72 h averaged von Willebrand factor (p = 0.01). Thus, early coronary recanalization curtails the response of plasminogen activator inhibitor activity and von Willebrand factor to myocardial infarction, most likely by reducing the extent of ischemia and necrosis and the consequent acute phase reaction. By blunting the early postinfarction procoagulant state, prompt recanalization may reduce the risk of thromboembolic complications in the first days after myocardial infarction.

C-Reactive Protein↗
PubMed1990

Effect of reactor retention on the spread of brucellosis in Jersey cattle and buffalo herds.

The rate of spread of bovine brucellosis was investigated in buffalo and Jersey cattle herds maintained at a Livestock Research station in Pakistan. Reactor animals (identified by conventional serological tests) were either retained or culled because of advanced age or poor productivity. Reactors were housed, managed and fed separately from the rest of the herds. The initial seroprevalence of brucellosis among both the Jersey cattle and the buffalo tested was 21.4%, the difference being statistically insignificant (p = 0.218). For 34 months, the spread of brucellosis was limited to 25 new reactors in the 334 cows and 33 in the 442 buffaloes. The mean attack rate was 7.5% for both herds during the test intervals. Trend analysis of proportions positive at each testing revealed a significant decrease in the percentages observed at the first testing. The management practice of segregation offered some advantage in reducing the spread of brucellosis to negative animals. However, an epidemiological study covering a large number of herds would be required to identify risk factors responsible for perpetuating the disease.

Animals↗
PubMed1989

Formation of highly ordered cross-linked lattices between asparagine-linked oligosaccharides and lectins observed by electron microscopy.

The interaction of asparagine-linked carbohydrates (N-linked) with carbohydrate binding proteins called lectins has been demonstrated to be involved in a variety of cellular recognition processes. Certain N-linked carbohydrates have been shown to be multivalent and capable of binding, cross-linking, and precipitating lectins (Bhattacharyya, L., Ceccarini, C., Lorenzoni, P., and Brewer, C. F. (1987) J. Biol. Chem. 262, 1288-1293; Bhattacharyya, L., Haraldsson, M., and Brewer, C. F. (1987) J. Biol. Chem. 262, 1294-1299; Bhattacharyya, L., Haraldsson, M., and Brewer, C. F. (1988) Biochemistry 27, 1034-1041). Recent data have further suggested that certain oligomannose and bisected hybrid-type N-linked glycopeptides form homogeneous cross-linked lattices with concanavalin A (Bhattacharyya, L., Khan, M. I., and Brewer, C. F. (1988) Biochemistry 27, 8762-8767). In the present study, evidence has been obtained from electron microscopy for the formation of highly ordered and distinct lattices for two bivalent complex type oligosaccharides cross-linked with soybean lectin (Glycine max) and isolectin A from Lotus tetragonolobus, respectively. The results indicate a new source of specificity for interactions of N-linked carbohydrates with lectins, namely their ability to form highly ordered homogeneous aggregates.

Asparagine↗
PubMed1989

Differentiation of the vaccine F-strain from other strains of Mycoplasma gallisepticum by restriction endonuclease analysis.

The electrophoretic patterns of the nucleic acids (DNA) of Mycoplasma gallisepticum strains digested with the restriction enzymes Bam HI, Eco RI and Hind III were useful for differentiating the vaccine F-strain from other strains of M. gallisepticum. The procedure was more sensitive than the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) technique. The vaccine F-strain, represented by cultures designated F-K810 and F-F2F10 was clearly differentiated from other strains of M. gallisepticum. This procedure may be useful in field studies to determine if the vaccine strain will replace wild-type M. gallisepticum in commercial layers.

Bacterial Vaccines↗