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Biomedical subjects

S Naik

Publications and source records attributed to S Naik.

At least 73 records · Page 4Linked to original sources
PubMed1997

Characterization of membrane-bound and membrane anchor-less forms of hemagglutinin glycoprotein of Rinderpest virus expressed by baculovirus recombinants.

The Rinderpest virus (RPV) hemagglutinin (H) is a class 2 glycoprotein by means of which the virus attaches to the host cell receptor. A full length cDNA coding for H protein was used to construct a recombinant baculovirus expressing the H protein, recH(M), on the surface of insect cells. The small N terminal cytoplasmic domain was deleted and the transmembrane domain which extends from amino acids 35 to 59 was replaced with a signal peptide derived from the ecdysteroid UDP glycosyl transferase (egt) gene of the baculovirus, AcNPV. The protein recH(sec) expressed by the recombinant baculovirus carrying this engineered gene was secreted into the medium. Both forms of recombinant H protein retained reactivity with conformation-dependent monoclonal antibodies. The recH(M) was recognized by antibodies made in cattle either as the result of vaccination or natural infection. The soluble form of H is a valuable tool for studying the structure and function of the RPV H glycoprotein.

Animals↗
PubMed1997

Functional implications of hepatitis B surface antigen (HBsAg) in the T cells of chronic HBV carriers.

This study was undertaken to investigate the role of T-lymphocyte-derived soluble factors in the maintenance of the hepatitis B virus (HBV) chronic carrier state. Cell-free supernatants from the peripheral blood T lymphocytes of chronic HBV carriers were produced by incubating them for 48 h in tissue culture medium. These supernatants were added to in vitro hepatitis B s antibody (HBsAb)-producing cultures of peripheral blood mononuclear cells from hepatitis B surface antigen (HBsAg) vaccinees stimulated with HBsAg or pokeweed mitogen. T-cell supernatants from chronic carriers suppressed in vitro HBsAb antibody synthesis, whereas those from control subjects did not. This suppression was antigen specific as the supernatants did not suppress synthesis of total IgG or IgM. HBV viral sequences were demonstrable, by Southern and dot-blot hybridization, in the T cells secreting this factor. We also demonstrated the presence of HBsAg in T-cell supernatants derived from these cells. These results show that HBsAg of T-cell origin may have a role in suppressing HBsAb production. Our observations point to the role of HBsAg-specific cellular and humoral responses in favouring persistence of the chronic HBV carrier state.

Adult↗
PubMed1997

First-trimester invasive procedures and congenital abnormalities.

A prospective study was undertaken to determine whether first-trimester amniocentesis or chorion villus sampling was associated with an increased incidence of congenital anomalies. The infants of mothers who had undergone first-trimester amniocentesis (EA) (n = 352), chorion villus sampling (CVS) (n = 348) or no invasive antenatal procedure (controls) (n = 264) were examined at a median age of 5 months. Both the EA and CVS groups had a higher proportion of infants with congenital anomalies (n = 18 and n = 22, respectively) than the control group (n = 4) (p < 0.01). Certain of the abnormalities, however, affected only single infants. Compression abnormalities were more common in the EA group than in the controls (p < 0.05), but not in the CVS group. The isolated limb abnormalities which occurred were minor anomalies affecting the digits and were seen in both the CVS (n = 6) and EA (n = 3) groups. First-trimester invasive procedures are thus associated with an excess of congenital anomalies.

Adolescent↗
PubMed1997

Prospective study of lung volumes in young asthmatic children.

In a 9-y prospective study, the occurrence and duration of lung volume abnormalities in 21 young asthmatic children (median age at recruitment 4 y, range 3-8 y) was determined. The median functional residual capacity (FRC) at recruitment was 135% of that predicted for height (range 79-187%) and 13 children were hyperinflated. The median FRC decreased significantly after 3 y of follow-up and by 9 y only one child remained hyperinflated. We conclude that persistent elevation of lung volume in young asthmatic children appears to be uncommon.

Age Distribution↗
PubMed1997

Perinatal lung function and invasive antenatal procedures.

BACKGROUND: Second trimester amniocentesis has been associated with an excess of perinatal lung function abnormalities. Early amniocentesis might have a similar adverse effect, as could other invasive investigations carried out in the first trimester. METHODS: Plethysmographic measurements of thoracic gas volume (TGV) and airway resistance (Raw), from which specific conductance (sGaw) was calculated, were made in the perinatal period in non-sedated infants. In addition, functional residual capacity (FRC) was measured using a helium gas dilution technique. Measurements were made in 47 infants whose mothers had undergone early amniocentesis, 19 whose mothers had undergone chorion villus sampling, and 25 controls whose mothers had undergone no invasive antenatal procedures. RESULTS: The infants of mothers who had undergone early amniocentesis had higher TGV (95% CI -6.3 to 1.1 ml/kg) and Raw values (95% CI -10.68 to -5.23 cm H2O/l/s) and lower sGaw (0.11 to 0.84 l/cm H2O.s) and FRC (-5.17 to - 0.87 ml/kg) values than the controls. Infants whose mothers had undergone chorion villus sampling also differed significantly from the controls with higher Raw (-7.59 to -1.99 cm H2O/l/s) and lower sGaw values (0.11 to 0.24 l/cm H2O.s), and had lower Raw values than those in the early amniocentesis group (not significant). Logistic regression analysis, taking into account possible risk factors for abnormal lung function, showed that the procedures performed in the first trimester were independently associated with a high airways resistance. CONCLUSION: These results suggest that invasive procedures performed in the first trimester of pregnancy have an adverse effect on perinatal lung function.

Adult↗
PubMed1997

The effect of in vitro bacterial association on virulence of Entamoeba histolytica.

When trophozoites of axenic E. histolytica strains NIH : 200 were associated in vitro with Escherichia coli K12 for three hours at 37 degrees C, the virulence was enhanced as shown by increased cytopathogenicity to baby hamster kidney (BHK) cell monolayer. Further, the trophozoites were observed to adhere to the polystyrene surface, a hitherto unreported phenomenon. The co-association of E. histolytica trophozoites with Bacteroides fragilis and Clostridium perfringens for three hours duration at 37 degrees C neither led to increase in cytotoxicity potential nor to adherence phenomenon; in contrast significant inhibition of cytotoxicity was observed. We have thus shown that while co-association of E. histolytica (NIH : 200) with E. coli K12 leads to enhanced amoebic virulence, that with anaerobic bacteric leads to its inhibition.

Animals↗
PubMed1997

Does Entamoeba histolytica cause irritable bowel syndrome?

BACKGROUND: Symptoms of patients with irritable bowel syndrome (IBS) closely mimic those of patients with non-dysenteric amebic colitis. AIM: To examine the clinical relevance of presence and types of Entamoeba histolytica in stools of patients with IBS. METHODS: IBS was diagnosed by Manning's criteria. Stool examination was done 4-weekly for 48 weeks to detect E. histolytica cysts or trophozoites. Patients underwent initial sigmoidoscopy. Sera of 22 IBS patients, 23 asymptomatic cyst passers and 36 healthy volunteers whose stools were also examined were tested for presence of antiamebic antibodies. Stools were cultured for amebae; positive cultures were subjected to polyacrylamide-gel electrophoresis (PAGE) using hexokinase (HK) isoenzyme to distinguish between pathogenic (fast-moving band) E. histolytica infection and nonpathogenic (slow band) species of Entamoeba dispar. RESULTS: E. histolytica cultured from stool samples of four IBS patients had slow-moving band of HK on PAGE. All patients spontaneously eradicated the infection during the next eight to 24 weeks; all had negative serology for antiamebic antibodies, and normal rectal mucosa on sigmoidoscopy. No change in symptom score occurred on follow up in IBS patients, although all of them cleared the infection. Three additional E. histolytica isolates from IBS patients obtained from another laboratory also showed nonpathogenic isoenzyme pattern. CONCLUSION: Bowel symptoms in IBS patients were not related to E. histolytica infection. The term non-dysenteric amebic colitis thus appears to be inappropriate, since it may be used erroneously for patients with IBS with nonpathogenic ameba, leading to injudicious treatment with antiamebic drugs.

Abdominal Pain↗
PubMed1996

Takayasu's arteritis: role of Mycobacterium tuberculosis and its 65 kDa heat shock protein.

BACKGROUND: Mycobacterium tuberculosis has been implicated in the pathogenesis of Takayasu's arteritis (TA). Recently, its 65 kDa heat shock protein (HSP) has been implicated in the pathogenesis of other autoimmune diseases. We thus decided to study humoral immune response to Mycobacterium tuberculosis antigens in patients with TA. AIM: To study humoral immune response to Mycobacterium tuberculosis and its 65 kDa HSP, a putative autoantigen, in patients with TA. METHODS: Antibodies to sonicated Mycobacterium tuberculosis extract (MBA) and its recombinant 54 kDa protein were measured using ELISA in 36 patients with TA and 35 healthy controls. Levels exceeding mean +2 S.D. of the controls were taken as positive responses. RESULTS: Abnormally elevated levels of IgG, IgM and IgA antibodies against MBA were present in 6, 20 and 7 patients respectively whereas those against r65 kDa protein were present in 6, 7 and 33 patients, respectively. Though the levels of IgG antibodies were also elevated, those of IgM and IgA antibodies were elevated to a greater extent. CONCLUSIONS: Patients with TA have heightened immune response to Mycobacterium tuberculosis antigens, in particular to its 65 kDa HSP, suggesting that this organism may have a role in the immunopathogenesis of this disease.

Adolescent↗
PubMed1996

Tissue-specific expression of the human pyruvate dehydrogenase alpha (Pdha-1)/chloramphenicol acetyltransferase fusion gene in transgenic mice.

A chimeric gene (-763/+33Pdha-1/CAT) containing -763/+33 nucleotides o f the human pyruvate dehydrogenase gene (Pdha-1) and the structural gene of chloramphenicol acetyltransferase (CAT) was used to generate transgenic mice. CAT activity was detected predominantly in the brain followed in decreasing order by adipose tissue, spleen, heart, kidney and liver. Developmental expression of CAT activity in the testes was similar to that of the endogenous Pdha-1 subunit expression in the testes. Dietary regulation of the transgene was comparable to the expression of endogenous pyruvate dehydrogenase complex in kidney and adipose tissue. Thus, the -763/+33 bp segment of the human Pdha-1 gene is transcriptionally active in vivo and can direct the expression of CAT in several tissues.

Adipose Tissue↗
PubMed1996

Prediction of morbidity during infancy after repair of congenital diaphragmatic hernia.

Recent studies have suggested there may be a high incidence of pulmonary and extrapulmonary sequelae among infants who have undergone repair of congenital diaphragmatic hernia (CDH). The aim of this study was to identify factors that predict high-risk cases to facilitate counseling of parents. Morbidity, defined as conditions requiring treatment and/or hospitalization during follow-up, was documented. Only five of 15 cases that had been diagnosed antenatally (at 16 to 26 weeks' gestation) and underwent surgical repair after preoperative stabilization were without morbidity at the time of follow-up. Respiratory problems were identified in seven (chylothorax in 3, recurrent infections in 4) and failure to thrive in four; three infants required further gastrointestinal surgery. A comparison of infants with and without morbidity showed that the only significant difference between the groups was in the duration of respiratory support. A requirement for respiratory support for more than 10 days had 90% sensitivity, 100% specificity, and a positive predictive value for morbidity at follow-up of 100%.

Follow-Up Studies↗
PubMed1996

Post-transfusion hepatitis type B following multiple transfusions of HBsAg-negative blood.

BACKGROUND/AIMS: Post-transfusion hepatitis continues to occur, though with decreasing frequency, even after screening donor blood for HBsAg, anti-HBc, anti-HCV and alanine aminotransferase activity. Data from developing countries on the frequency and type of post-transfusion hepatitis are scarce. We undertook this prospective study to determine the incidence and type of post-transfusion hepatitis at our center after transfusion of blood negative for HBsAg by ELISA. METHODS: Forty-one patients undergoing open-heart surgery, who had received 3 or more units of HBsAg-negative blood, were followed up. Serum samples of donor units transfused to recipients who developed post-transfusion hepatitis-B were subjected to HBV DNA amplification by the polymerase chain reaction, using two sets of X-gene specific primers which amplified a 250-bp fragment of the HBV DNA. RESULTS: We found that six of the 41 patients (14.6%) developed post-transfusion hepatitis; four of them (66.6%) developed icteric post-transfusion hepatitis B, whereas two (33.3%) developed anicteric post-transfusion hepatitis C. These six recipients received a total of 48 units of blood and 30 of these 48 units could be subjected to HBV DNA amplification by polymerase chain reaction. Eleven donor samples were polymerase chain reaction positive and had been transfused to three of the four patients who had developed post-transfusion hepatitis B. CONCLUSIONS: We conclude that post-transfusion hepatitis B continues to be the most common cause of post-transfusion hepatitis in India. Screening of donor units for HBsAg by ELISA does not exclude all blood units infectious for hepatitis B virus. Additional measures to ensure safety of blood supply should be sought.

Cardiopulmonary Bypass↗
PubMed1996

The Hering-Breuer reflex in ventilated children.

The authors tested the hypothesis that, in the paediatric population, the Hering-Breuer reflex would be provoked by the positive pressure inflation of mechanical ventilation (IPPV), and that the strength of the reflex would relate to the child's age and compliance of the respiratory system (CRS). During IPPV, changes in air flow, volume and airway pressure were recorded simultaneously. From the traces, expiratory times and CRS were calculated. The mean expiratory time (Te1) prior to each inflation and the mean expiratory time (Te2) immediately following an inflation were determined. The presence of the reflex was indicated by Te2 being longer than Te1, and the strength of the reflex was calculated as the difference between Te2 and Te1 expressed as a percentage of Te1. Twenty children were studied who had a mean age of 0.7 years (range 0.1-9.8 years). The reflex was provoked in 19 of the 20 patients and was not seen in the oldest patient. The strength of the reflex varied from 22 to 144% and was inversely related to postnatal age significantly (r = -0.73) but not CRS or inflation volume. It is concluded that the Hering-Breuer reflex is provoked during IPPV in young children; whether, as in neonates, this influences the efficacy of ventilation deserves investigation.

Aging↗
PubMed1996

Urinary excretion of adrenocortical steroid metabolites by pre-term human infants: trends from birth until 3 months post term.

We report trends in urinary steroid excretion in serial 24 hour collections made using a novel method based on "Supersorb" type disposable nappies. Using capillary column gas chromatography, we quantified nine cortisol metabolites (FM) and 11 steroid sulphates (SM) in 6 infants born at 29-31 weeks gestation on 9 occasions until 24 weeks post delivery. In all infants, SM excretion increased progressively until 33-39 weeks (mean 36.8) post conception to maxima of (all values mg/24 h) 2.6-11.7 and then declined to 5-15% of peak values at the end of the study period in 4 infants born after a period of labour but to only 54 and 71% in 2 infants born without labour. FM levels showed a wide range which was not correlated with body weight, eg: on week 1, 0.06-0.20 and on week 24, 0.15-0.72. progression over this period was essentially linear. The ratio (mean (SD)) of 11-oxo/11-hydroxy metabolites decreased from 10.0 (8.2) to 2.3 (0.4) in the same period, p = < 0.10, while that of 20-oxo/20-hydroxy metabolites increased from 0.18 (0.07) to 1.08 (0.42), p = < 0.04. The ratio of metabolites with 5 oxygen functions relative to 6 increased from 0.38 (0.16) to 1.36 (0.43), p = < 0.04. Excretion of 5 alpha-tetrahydrocortisol began to rise at 44-47 wk post conception, but, unexpectedly, that of the 5 beta epimer began to rise sooner, at 39-41 wk, reaching a peak at 44-51 wk and then declining. The ratio of 5 beta/5 alpha epimers was 11.71 (11.1) at the peak and 1.14 (0.87) at 24 weeks, p = < 0.07. We conclude that, using a collection method which is reliable, non-stressful and repeatable at frequent intervals, new information on the evolution of steroid secretion and metabolism postpartum is emerging.

Adrenal Cortex Hormones↗
PubMed1996

Flow cytometric characterization of isolated porcine hepatocyte suspensions for liver support.

The high yield hepatocyte isolation necessary for hybrid liver assist devices (LAD) unavoidably increases contamination by nonparenchymal cells and depresses hepatocyte viability and functions. We have developed a flow cytometric procedure that improves quality control of the isolations. Cells present in these preparations were labeled by immunofluorescent antibody staining against cytokeratin 8, 18 as well as vimentin to identify hepatocytes, fibroblasts, and endothelial cells. Antibody staining against albumin and carbamoylphosphate synthetase allowed assessment of levels of albumin and carbamoylphosphate synthetase based on the hepatocyte relative fluorescence intensity. Hepatocyte P450 enzyme activity was measured by its ability to convert 5,6-methoxycarbonylfluorescein, a nonfluorescent substrate, to an intracellular fluorescent product. Flow cytometric methods of cell type identification and cell function assessment are fast and accurate and can be applied to commercial cell production. They may also provide an avenue for the enrichment of otherwise heterogeneous hepatocyte suspensions with cells presenting the specific functions desired for an hybrid liver assist devices.

Animals↗
PubMed1996

Infective endocarditis of the tricuspid valve in an orthotopic heart transplant recipient.

A 43-year-old orthotopic heart transplant recipient had coagulase-negative staphylococcus endocarditis 26 weeks after the operation. A diagnosis of endocarditis was confirmed and followed up by serial transoesophageal echocardiography. Treatment with intravenous gentamycin and vancomycin cured her endocarditis, and a 2.5 cm vegetation regressed significantly. She has been well since and, at 14 months after transplantation, was back to her normal activities. Although repeated blood culture yielded only intermittent light growths of coagulase-negative staphylococci, there were several positive samples. In a setting of infective features, light growths of coagulase-negative staphylococcus should be taken seriously if repeatedly positive in heart transplant recipients or other immunocompromised patients. Transesophageal echocardiography offers significant advantages over the transthoracic modality in suspected endocarditis.

Adult↗
PubMed1996

Immunoproliferative small intestinal disease: a frequently missed diagnosis.

Immunoproliferative small intestinal disease (IPSID) is a poorly recognized cause of malabsorption syndrome in India. Clinicopathological features of five patients with IPSID seen over a two-year period are described. Our data suggest that IPSID is commonly misdiagnosed as intestinal tuberculosis due to lack of awareness and reluctance to obtain small bowel biopsies. Empirical institution of anti-tubercular chemotherapy not only leads to delayed diagnosis but also possibly alters the natural history of the disease, resulting in an intermediate phase of amelioration followed by a terminal phase of lymphomatous transformation. The disease is therefore usually diagnosed at an advanced stage and hence is associated with a relatively poor outcome.

Adult↗
PubMed1996

The prevalence of transfusion transmitted diseases in renal transplant recipients.

Majority of renal transplant patients have history of blood transfusion. Out of a total of 120 renal transplant patients, 20 (16.6%) patients showed raised alanine aminotransferase (ALT) levels (> 45 IU) on 2 or more occasions at 2 weeks interval. This study was undertaken to estimate the risk of transfusion transmitted diseases (TTD) in these 20 renal transplant patients. Another 200 voluntary blood donors were also included as control. Both subject groups were screened by ELISA for HBsAg, anti HBc (IgG & IgM), anti HCV, anti CMV (IgM), anti HIV and VDRL tests for syphilis. A total of 11 (55%) patients and 3 (1.5%) blood donors showed the evidence of HBsAg positivity (p < 0.01). Anti HBc antibody was present in 12 (60%) patients and 39 (19.5%) donors which was significantly (p < 0.01) different. Anti HCV antibody was detected in 5 patients and in one blood donor (p < 0.01). However, anti CMV antibody was present in 4 (20%) patients and 3 (1.5%) donors, respectively. There was no evidence of HIV and syphilis infection in both these groups. High incidence of hepatitis markers were observed in renal transplant patients.

Biomarkers↗