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Biomedical subjects

M Islam

Publications and source records attributed to M Islam.

At least 55 records · Page 3Linked to original sources
PubMed1994

Involvement of lysine residues of goat serum albumin in high-affinity binding of bilirubin.

Four maleylated derivatives of goat serum albumin having percent modification as 40%, 46%, 84% and 98% were prepared using varying molar ratio of maleic anhydride over protein. These preparations were found to be pure, both with respect to size and charged as judged by gel filtration and polyacrylamide gel electrophoresis. Maleylation caused significant change in protein conformation as revealed by the change in Stokes radius and frictional ratio of serum albumin, from 3.46 nm and 1.28 to 4.96 nm and 1.79, respectively, upon 98% modification. Immunodiffusion results of native and modified albumins with anti-goat serum albumin antiserum also suggested significant conformational changes in serum albumin upon maleylation. About 88% reduction in bilirubin binding was observed after modification of 98% amino groups of serum albumin as studied by visible difference spectroscopy at pH 8.0, and at 0.15 ionic strength. Increase in ionic strength to 1.0 did not lead to any significant reversal in bilirubin binding. These results prove the involvement of lysine residues in bilirubin-albumin interaction.

Acylation↗
PubMed1994

Alteration in vascular reactivity in isolated aortic rings from portal vein-constricted rats.

It has been suggested that increased production of nitric oxide by an inducible nitric oxide synthase isoenzyme is important in the pathogenesis of the vascular abnormalities seen in human beings and animals with portal hypertension. We investigated this hypothesis by studying the in vitro vascular reactivity of isolated aortic rings from portal vein-constricted and sham-operated rats. Aortic rings from portal vein-constricted rats exhibited significantly impaired contractility to phenylephrine and potassium chloride compared with control rats. Preincubation with the nitric oxide synthase inhibitor nitro-L-arginine methyl ester significantly increased contractility to phenylephrine and potassium chloride in both portal-hypertensive and control tissues, with greater effect in the portal-hypertensive rings. Despite nitro-L-arginine methyl ester, maximal contractions were still significantly smaller in the portal-hypertensive tissues. Vascular relaxation evoked by acetylcholine, but not by the endothelium-independent vasodilator glyceryl trinitrate, was significantly impaired in the portal-hypertensive group. Our results demonstrate significant impairment in vascular function in aortic rings in this model of portal hypertension. The addition of a nitric oxide synthase inhibitor partly corrected these changes, suggesting that although nitric oxide is likely an important mediator, other factors may also be involved in the pathogenesis of these alterations in vascular function.

Acetylcholine↗
PubMed1994

Influence of systemic hypothermia on systolic and diastolic functional recovery after continuous warm antegrade blood cardioplegia.

Experimental observations in our laboratory indicate that myocardial recovery is similar following warm or cold antegrade blood cardioplegia when the core temperature is maintained at 37 degrees C. To determine the effects of hypothermia on myocardial recovery, 15 adult mongrel dogs were randomized to normothermic or hypothermic bypass (28 degrees C) during 60 min of continuous warm antegrade blood cardioplegia. The hypothermic group was rewarmed after releasing the aortic cross-clamp and bypass was discontinued at 30 min in both groups. Myocardial recovery was assessed at 60, 90, and 120 min after the arrest. Core temperature was maintained in the normothermic group but gradually decreased after bypass in the hypothermic group, reaching a low of 33.8 +/- 1 degrees C at 120 min. Myocardial functional recovery was preserved after normothermic bypass. The decrease in core temperature, however, that was observed after systemic hypothermia, was paralleled by significant decreases in the maximum rate of left ventricular pressure rise (dp/dt), the maximum elastance of the left ventricle, and preload recruitable stroke work. Diastolic function decreased slightly, but not significantly, during reperfusion following systemic hypothermia but was unaltered after normothermic bypass. Myocardial oxygen consumption was unchanged in both groups. Myocardial ultrastructure was preserved after normothermic bypass. In contrast, cellular oedema and mild ultrastructural changes were evident after systemic hypothermia. We therefore conclude that the use of systemic hypothermia during bypass is associated with lower core temperatures during early recovery which results in impaired functional recovery.

Animals↗
PubMed1993

Rapid detection of Shigella dysenteriae and Shigella flexneri in faeces by an immunomagnetic assay with monoclonal antibodies.

A rapid and sensitive method for the detection of Shigella dysenteriae type 1 and Shigella flexneri serotypes in faeces based on capture of the bacteria with immunomagnetic particles is described. The particles were coated with either of two different monoclonal antibodies specific for the O-antigens of Shigella dysenteriae type 1 and Shigella flexneri serotypes. Captured bacteria were detected by an enzyme immunoassay with O-antigen specific rabbit antiserum. The whole assay required 2 to 3 hours to perform and the sensitivity limit was 10(3) cfu/ml as determined by viable cell counting. One hundred and fifty enterobacteria strains, including 100 Shigella strains from a strain collection, and 302 fresh faecal samples were used for the study. All Shigella dysenteriae type 1 and Shigella flexneri culture-positive faecal samples were positive in the immunomagnetic assay. In addition 18 of 252 culture-negative faecal samples were positive. The immunomagnetic assay was compared with latex agglutination and indirect immunofluorescence using culture as the reference method. The immunomagnetic assay had a sensitivity of 100%, latex agglutination a sensitivity of 72% with 28% false-negative results, and indirect immunofluorescence a sensitivity of 95%. The immunomagnetic assay was superior in sensitivity since it also detected Shigella in faecal samples up to two days after antibiotic therapy had been started, which both latex agglutination and indirect immunofluorescence failed to do. The high sensitivity in detecting live and dead bacteria, and the ease of performance of the immunomagnetic assay render it an attractive method for detection of Shigella.

Animals↗
PubMed1993

Probing the determinants of protein solubility with amino acid modification.

Chemical modification was used as a probe to study the effect of structural features of serum albumin (charge, conformation, surface hydrophobicity, etc.) on its solubility behavior in concentrated ammonium sulfate solutions. Four different acetylated derivatives of goat serum albumin namely 18% acetylated, 40% acetylated, 53% acetylated, and 93% acetylated albumins were prepared. The homogeneity of these preparations was established by gel chromatography and polyacrylamide gel electrophoresis. Hydrodynamic data on the Stokes radius of native and acetylated albumins suggested gradual change in conformation on increasing modification. Solubility experiments performed in concentrated ammonium sulfate solutions at pH 7.0 and at 30 degrees C showed a slight decrease in salting-out parameter, Ks, up to 40% modification, whereas a significant decrease was obtained at higher modification. However, the salting-out parameter, beta, decreased monotonously. Similar decrease in these parameters was also observed with different modified albumins at other pH values viz. pH 5.5, 4.5, and 3.6. From these results we conclude that the decrease in solubility of serum albumin on increasing modification was primarily due to change in conformation.

Acetylation↗
PubMed1991

Hafnia alvei, a probable cause of diarrhea in humans.

Hafnia alvei, a member of the family Enterobacteriaceae, was the only species of bacteria cultured from the stool of a 9-month-old child who was admitted with a 3-day history of watery diarrhea. The isolated strain of H. alvei failed to produce heat-labile or heat-stable enterotoxins or Shiga-like toxin I or II and did not invade HeLa cells, nor did it cause keratoconjunctivitis (determined by the Sereny test) in a guinea pig's eye. The strain, however, induced diarrhea in 8 of 12 adult rabbits with removable intestinal ties (removable intestinal tie-adult rabbit diarrhea [RITARD] assay) and in 1 of 2 orally fed animals. No diarrhea could be induced with Escherichia coli K-12 in eight RITARD assay rabbits and three orally fed rabbits, respectively. Microscopic examination of affected animals revealed moderate inflammatory cellular infiltration of the intestinal mucosa, in which bacterial attachment to the surface epithelium and loss of the microvillus border were evident in the ileum and colon. Electron microscopy demonstrated cellular modifications of the apical surface, with cupping or pedestal formation and increased terminal web density at sites of bacterial "attachment-effacement," a well-known characteristic and mechanism of diarrhea of enteropathogenic E. coli. Identical lesions were also induced by H. alvei in rabbit ileal loops, which ruled out naturally occurring rabbit enteropathogenic E. coli strains, which are known to produce similar lesions. It is concluded that at least some strains of H. alvei have the potential to cause diarrhea and that attachment-effacement is a virulence characteristic shared by bacteria other than E. coli.

Animals↗
PubMed1991

Localized adherence and attaching-effacing properties of nonenteropathogenic serotypes of Escherichia coli.

Traditional enteropathogenic Escherichia coli serotypes demonstrate a plasmid-mediated localized adherence in cultured HeLa or HEp-2 cells and induce an attaching-effacing intestinal lesion, both of which are considered pathognomonic and causes of diarrhea. This study describes three E. coli strains from infantile diarrhea which share these properties but belong to serotypes (O2:H2, O2:H25 and O15:H2) not considered enteropathogenic.

Animals↗
PubMed1989

Causes of death and the histopathologic findings in fatal shigellosis.

Thirty-seven children (median age, 2 years) with shigellosis in Bangladesh were subjected to postmortem examination to determine causes of death and the spectrum of intestinal histopathology. Infecting species were: Shigella dysenteriae 1, 7 cases; S. dysenteriae 2, 2 cases; Shigella flexneri, 23 cases; Shigella boydii, 4 cases; and mixed infection with Shigella boydii and Shigella sonnei, 1 case. Complicating conditions detected before death included malnutrition in 25 cases, pneumonia in 11 cases and septicemia in 8 cases. In all 37 cases the colon showed gross colitis, consisting of mucosal erythema and edema; superficial ulcerations were visible in 15 cases. Microscopically in the colon the lamina propria showed inflammatory cellular infiltration in 27 cases and crypt abscesses were present in 22 cases. In 9 cases each there were colonic glands in the submucosa and branching of colonic crypts, indicating increased regenerative activity of crypt cells. Severe lesions were mucosal denudation and deep ulceration in 15 cases with a pseudomembrane in 7 and pseudopolyposis in 2 of these patients. The most common underlying cause of death was colitis, whereas the most common immediate and associated causes were, respectively, septicemia and pneumonia. These results indicated that fatal childhood shigellosis results from severe colitis, often complicated by septicemia and concomitant malnutrition and pneumonia.

Bangladesh↗
PubMed1989

Characterization by enzyme-linked immunosorbent assay using subgroup- and serotype-specific monoclonal antibodies of human rotavirus obtained from diarrheic patients in Bangladesh.

By enzyme-linked immunosorbent assay with group A-, subgroup-, and serotype-specific monoclonal antibodies (MAbs), we tested 414 stool specimens collected from pediatric and adult patients hospitalized with acute gastroenteritis between January and June 1988. Of 414 specimens tested, 124 (30%) were positive for group A rotavirus. The subgroup was determined in 110 specimens (88.7%); 16.1% were subgroup I, and 72.6% were subgroup II. Two specimens reacted with both subgroup I- and subgroup II-specific MAbs. Serotype determinations showed that serotype 1 (38.4%) was predominant over serotypes 2 (28.2%), 3 (2.5%), and 4 (23%). Three specimens reacted with more than one serotype-specific MAb. While the frequency of serotype 1 was highest in the two hospitals in Mymensingh, serotype 2 was most prevalent in one hospital in Dhaka. All human rotavirus strains with subgroup I and serotype 2 specificities showed a short electropherotype, and all but one strain with subgroup II and serotype 1, 3, or 4 specificities exhibited a long electropherotype.

Acute Disease↗
PubMed1989

Histopathology and etiology of childhood pneumonia: an autopsy study of 93 patients in Bangladesh.

The causes and pathogenesis of severe childhood pneumonia in a developing country were studied in lungs removed at autopsy from 119 Bangladeshi children who presented with pneumonia and/or diarrhea. Pneumonia was observed in 93 patients. Morphologic features included acute alveolar exudate in 51% (of the 93 patients), necrotizing pneumonia in 31%, interstitial pneumonia in 22%, and caseating granulomas in 4%, while a mixed pattern occurred in 16% of patients. Causes of pneumonia were Gram-negative bacteria in 27%, pneumococcus in 8%, cytomegalovirus (CMV) in 8%, Pneumocystis carinii (PC) in 4%, mycobacteria in 3%, aspergillus in 3%, mixed anaerobes in 3%, viral (not CMV) in 2%, Staphylococcus aureus in 1% and ascaris in 1%. Two causative agents were identified in 7% of patients. In 46% of the cases, no etiologic agent was identified. Our data suggest that most pneumonias had a bacterial etiology; however, viruses, including CMV, and other opportunistic organisms such as PC, were also important pathogens. Gram-negative pneumonia was partially attributed to concomitant intestinal infections. Opportunistic infections resulted from malnutrition and debilitated host defenses during prolonged fatal illnesses.

Adolescent↗