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Biomedical subjects

H Kaur

Publications and source records attributed to H Kaur.

At least 37 records · Page 2Linked to original sources
PubMed2001

A cohort study of health care workers to assess nosocomial transmissibility of Nipah virus, Malaysia, 1999.

During 1998-1999, an outbreak of Nipah virus encephalitis occurred in Malaysia. To assess the possibility of nosocomial transmission, 338 health care workers (HCWs) exposed and 288 HCWs unexposed to outbreak-related patients were surveyed, and their serum samples were tested for anti-Nipah virus antibody. Needlestick injuries were reported by 12 (3%) HCWs, mucosal surface exposure to body fluids by 39 (11%), and skin exposure to body fluids by 89 (25%). No encephalitis occurred in either group. Three exposed and no unexposed HCWs tested positive by EIA for IgG antibodies. It is likely that these 3 were false positives; no IgM response occurred, and the serum samples were negative for anti-Nipah virus neutralizing antibodies. The risk of nosocomial transmission of Nipah virus appears to be low; however, given the high case-fatality rate and the presence of virus in respiratory secretions and urine of some patients, standard and droplet infection-control practices should be maintained with these patients.

Antibodies, Viral↗
PubMed2001

Identification and characterization of an excretory-secretory product from Giardia lamblia.

A 58 kDa excretory-secretory product (ESP) of Giardia lamblia has been characterized. The ESP was purified over 508-fold by a combination of ammonium sulphate precipitation and sequential chromatography on affinity matrix and a gel filtration column. The homogeneity of the purified protein was established by sodium dodecyl sulphate polyacrylamide gel electrophoresis (Mr, 58 kDa) and analytical isoelectrophoresis (pI 4.75). The purified protein was recognized by the pooled sera of G. lamblia-positive patients as well as an antiserum raised against crude Giardia extract, thus indicating it to be an immunodominant parasite product. The ESP was found to agglutinate rabbit erythrocytes. The haemagglutinating activity of this protein was inhibited strongly by thyroglobulin, fetuin, asialofetuin and monosialoganglioside but not by simple sugars. The purified protein was characterized immunochemically and was found to be heat stable as well as protease sensitive. Lectin-binding studies of the purified ESP and its sensitivity to periodic-acid silver staining as well as to metaperiodate treatment clearly indicated its glycoprotein nature. The major localization site of the ESP was found to be on the surface of the parasite as revealed by flow cytometric analysis. Further, this glycoprotein induced fluid accumulation in ligated rabbit ileal loops and revealed a positive skin permeability reaction in the rabbit.

Animals↗
PubMed2001

Cloning and partial characterization of the putative rifamycin biosynthetic gene cluster from the actinomycete Amycolatopsis mediterranei DSM 46095.

The actinomycete Amycolatopsis mediterranei produces the commercially and medically important polyketide antibiotic rifamycin, which is widely used against mycobacterial infections. The rifamycin biosynthetic (rif) gene cluster has been isolated, cloned and characterized from A. mediterranei S699 and A. mediterranei LBGA 3136. However, there are several other strains of A. mediterranei which also produce rifamycins. In order to detect the variability in the rif gene cluster among these strains, several strains were screened by PCR amplification using oligonucleotide primers based on the published DNA sequence of the rif gene cluster and by using dEBS II (second component of deoxy-erythronolide biosynthase gene) as a gene probe. Out of eight strains of A. mediterranei selected for the study, seven of them showed the expected amplification of the DNA fragments whereas the amplified DNA pattern was different in strain A. mediterranei DSM 46095. This strain also showed striking differences in the banding pattern obtained after hybridization of its genomic DNA against the dEBS II probe. Initial cloning and characterization of the 4-kb DNA fragment from the strain DSM 46095, representing a part of the putative rifamycin biosynthetic cluster, revealed nearly 10% and 8% differences in the DNA and amino acid sequence, respectively, as compared to that of A. mediterranei S699 and A. mediterranei LBGA 3136. The entire rif gene cluster was later cloned on two cosmids from A. mediterranei DSM 46095. Based on the partial sequence analysis of the cluster and sequence comparison with the published sequence, it was deduced that among eight strains of A. mediterranei, only A. mediterranei DSM 46095 carries a novel rifamycin biosynthetic gene cluster.

Actinomycetales↗
PubMed2001

Preparation of monoclonal antibodies against human telomerase.

Telomerase, a ribonucleoprotein enzyme that extends telomeres of eukaryotic chromosomes, consists of the catalytic protein submit telomerase reverse transcriptase (TERT) and a telomerase RNA subunit. Nearly 85% of human tumors have tested positive for high telomerase activity. Telomerase activity is very low or not present in normal cells, whereas it is up-regulated in immortalized cells. Telomerase, partially purified from the breast tumor cell line MCF-7, was used to immunize Balb/C mice. Monoclonal antibodies (MAbs) were prepared by conventional hybridoma technology and screened by enzyme-linked immunoadsorbent assay (ELISA), followed by a polymerase chain reaction (PCR) based telomeric amplification repeat protocol (TRAP) assay to detect binding to or inhibition of telomerase activity. Reactive MAbs were found to be of IgM type by mu specific ELISA. Two MAbs were characterized, one that neutralizes telomerase activity in TRAP assay and the other non-neutralizing. In Western blotting, crude telomerase extract and HIV-1 virus lysate (control) were blotted on nitrocellulose membranes and the strips were treated with both MAbs and a nonrelated HIV polymerase-specific MAb, also IgM type. A band of approx. 65-kDa was detected in extracts of 293 cells with both the MAbs, but no reaction occurred with the HIV polymerase-specific MAb used as control. Similarly, when HIV-1 virus lysate strips were treated with HIV polymerase-specific MAb, a 65-kDa band was detected and no band was observed with either of the hybridoma supernatants. These antibodies may be useful for studying regulatory mechanism of telomerase and inhibition of its activity in vitro and in vivo.

Antibodies, Monoclonal↗
PubMed2001

The watermelon rectum.

This is the first reported case of rectal vascular ectasia in association with gastric antral vascular ectasia (watermelon stomach). The patient, a 39-year-old woman with systemic sclerosis, reported chronic gastrointestinal blood loss and iron deficiency anemia. She had aperistalsis of the distal esophagus, decreased lower esophageal sphincter pressure leading to severe gastroesophageal reflux, and dysmotility of the small intestine. Diagnosis was made by endoscopic appearance of visible linear watermelon-like vascular stripes in the gastric antrum and rectum. Histology confirmed the vascular nature of this disorder, showing dilated and thrombosed capillaries in the lamina propria. Gastric biopsy showed associated fibromuscular hyperplasia in the lamina propria. However, the colonic biopsy showed only focal hyalinization in the lamina propria. The patient was successfully treated using endoscopic bipolar electrocautery. Watermelon stomach has previously been described in association with systemic sclerosis. Based on the histopathologic similarity between rectal vascular ectasia, gastric antral vascular ectasia, and systemic sclerosis, we suggest that the rectal vascular lesion may represent a component of the gastrointestinal manifestations of systemic sclerosis.

Adult↗
PubMed2001

Radio-frequency ablation of liver tumors: assessment of therapeutic response and complications.

An alternative to surgical resection of liver tumors, radio-frequency ablation induces in situ thermal coagulation necrosis through the delivery of high-frequency alternating current to the tissues. Imaging helps to detect treatable lesions, guide the placement of the probe, and assess the effect of therapy. Computed tomography (CT) is used most frequently to determine whether the ablation is complete and to screen for early recurrences that may benefit from reablation. Complete ablation creates an area of necrosis that, at CT, is of low attenuation compared with the surrounding liver tissue, is often homogeneous, and has smooth margins. The most important features are the size of the necrotic defect, which, immediately after treatment, should be larger than that of the pretreatment tumor, and the sharpness of the margins, which indicates an abrupt change in attenuation between the necrotic tissue and surrounding liver tissue. Enhancement, when present, is due to perfusion abnormality or granulation tissue and forms a regular rim or a homogeneous zone at the margin of the defect. It is seen immediately after ablation but may be prolonged. Enhancement is affected by the scanning technique. Over time, the size of the defect remains stable or decreases. Any variation from this general pattern is suggestive of incomplete ablation or recurrence.

Adult↗
PubMed2001

Conformational study of peptides containing dehydrophenylalanine: helical structures without hydrogen bond.

The conformational behaviour of deltaZPhe has been investigated in the model dipeptide Ac-deltaZPhe-NHMe and in the model tripeptides Ac-X-deltaZPhe-NHMe with X=Gly,Ala,Val,Leu,Abu,Aib and Phe and is found to be quite different. In the model tripeptides with X=Ala,Val,Leu,Abu,Phe the most stable structure corresponds to phi1=-30 degrees, psi1=120 degrees and phi2=psi2=30 degrees. This structure is stabilized by the hydrogen bond formation between C=O of acetyl group and the NH of the amide group, resulting in the formation of a 10-membered ring but not a 3(10) helical structure. In the peptides Ac-Aib-deltaZPhe-NHMe and Ac-(Aib-deltaZPhe)3-NHMe, the helical conformers with phi = +/-30 degrees, psi = +/-60 degrees for Aib residue and phi=psi= +/-30 degrees for deltaZPhe are predicted to be most stable. The computational studies for the positional preferences of deltaZPhe residue in the peptide containing one deltaZPhe and nine Ala residues reveal the formation of a 3(10) helical structure in all the cases with terminal preferences for deltaZPhe. The conformational behaviour of Ac-(deltaZPhe)n-NHMe with n< or =4 is predicted to be very labile. With n > 4, degenerate conformational states with phi,psi values of 0 degrees +/- 90 degrees adopt helical structures which are stabilized by carbonyl-carbonyl interactions and the N-H-pi interactions between the amino group of every deltaZPhe residue with one C-C edge of its own phenyl ring. The results are in agreement with the experimental finding that screw sense of helix for peptides containing deltaZPhe residues is ambiguous in solution. The helical structures stabilized by hydrogen bond formation are found to be at least 3kCalmol(-1) less stable. Conformational studies have also been carried out for the peptide Ac-(deltaEPhe)6-NHMe and the peptide Ac-deltaAla-(deltaZPhe)6-NHMe containing deltaAla residue at the N-terminal. The N-H-pi interactions are absent in peptide Ac-(deltaEPhe)6-NHMe.

Hydrogen Bonding↗
PubMed2000

Case-control study of risk factors for human infection with a new zoonotic paramyxovirus, Nipah virus, during a 1998-1999 outbreak of severe encephalitis in Malaysia.

An outbreak of encephalitis affecting 265 patients (105 fatally) occurred during 1998-1999 in Malaysia and was linked to a new paramyxovirus, Nipah, that infected pigs, humans, dogs, and cats. Most patients were pig farmers. Clinically undetected Nipah infection was noted in 10 (6%) of 166 community-farm controls (persons from farms without reported encephalitis patients) and 20 (11%) of 178 case-farm controls (persons from farms with encephalitis patients). Case patients (persons with Nipah infection) were more likely than community-farm controls to report increased numbers of sick/dying pigs on the farm (59% vs. 24%, P=.001) and were more likely than case-farm controls to perform activities requiring direct contact with pigs (86% vs. 50%, P=.005). Only 8% of case patients reported no contact with pigs. The outbreak stopped after pigs in the affected areas were slaughtered and buried. Direct, close contact with pigs was the primary source of human Nipah infection, but other sources, such as infected dogs and cats, cannot be excluded.

Agricultural Workers' Diseases↗
PubMed2000

The importance of homologous recombination in the generation of large deletions in hybrid plasmids in Amycolatopsis mediterranei.

The cloning vector pRL60 was developed previously as a tool for genetic manipulations in Amycolatopsis mediterranei, which produces the commercially and medicinally important antibiotic rifamycin. Here, a method based on intraplasmid recombinations is described for the construction of smaller plasmids in A. mediterranei, which also helped in delimiting the origin of replication (pA-rep) of the parent plasmid. The strategy involved the cloning of a selectable marker, erythromycin resistance gene (ermE), onto plasmids pULAM2 and pULVK2A (derivatives of pRL1), followed by selection of the hybrid or concatemeric plasmids pRL50 and pRL80 (with large homologous repeats) in Escherichia coli GM2163. These hybrid plasmids were then transferred to A. mediterranei DSM 40773 by electroporation, with selection in the presence of different antibiotics. During the process of transformation and selection in A. mediterranei, pRL50 and pRL80 underwent intraplasmid recombinations, yielding derivatives that retained a common region essential for maintenance and replication, as well as the selected resistance genes. This approach produced several smaller plasmids designated pRL51, pRL52, pRL53, pRL60, pRL81, and pRL82. These plasmids, isolated from A. mediterranei DSM 40773, could be transferred to different Amycolatopsis strains at transformation efficiencies ranging from 0.7 x 10(2) to 4 x 10(4) transformants/microg DNA. The electroporation parameters under which maximum transformation efficiencies were obtained varied from strain to strain. Since the isolation of plasmid DNA from Amycolatopsis strains were extremely difficult, a convenient and rapid method of direct transfer of plasmid DNA, i.e., electroduction, was also developed in which the above-described shuttle plasmids were transferred directly from A. mediterranei to E. coli. In addition, the sequence of the minimal (pA-rep, approximately 1.0 kb) of plasmid pRL51 was determined. The nucleotide base sequence of the pA-rep region did not have any clear similarity to the DNA or amino acid sequences in various databases, suggesting that it is unique.

Actinomycetales↗
PubMed2000

Regulation and manipulation of the gene clusters encoding type-I PKSs.

Modular polyketide synthases are large, multifunctional enzyme complexes that are involved in the biosynthesis of important polyketides. Recent studies have revolutionized our understanding of the linear organization of polyketide-synthase-gene clusters. They have provided crucial information on the initiation, elongation and termination of polyketide chains, and thus a rational basis for the generation of novel compounds. Combinatorial libraries have helped this field to move from a random approach to a more empirical phase. The large number of diverse analogs of antibiotics that are presently produced demonstrate the enormous potential of combinatorial biosynthesis.

Combinatorial Chemistry Techniques↗
PubMed2000

Membrane surface of Mycobacterium microti-infected macrophages antigenically differs from that of uninfected macrophages.

Identification of the antigenic changes in mycobacteria-infected macrophage may be important in understanding the mechanisms responsible for the intracellular survival of the bacteria. In the present study, Mycobacterium microti-infected macrophages were utilized to investigate the possibility of differentiating the infected cells from normal cells, based on the antigenic changes occurring in the membranes. Antisera were generated against bacterial extract, heat-killed bacteria and crude preparation of M. microti-infected homologous macrophage membrane. The reactivity of these antisera, towards in vitro infected macrophages, was compared by flow cytometry. Unlike anti-bacterial extract antiserum or anti-heat-killed bacterial antiserum, anti-infected macrophage membrane antiserum reacted with infected macrophage surface. This reactivity increased with the increase in post-infection time. However, it was not observed with uninfected macrophages, PMA- or lipopolysaccharide-activated macrophages and those harboring Mycobacterium tuberculosis H37Ra, heat-killed M. microti and Leishmania donovani. Interestingly, anti-infected macrophage membrane antiserum identified a 63-kDa antigen in M. microti-infected macrophage membranes which was not present in the membranes of normal macrophages, activated macrophages and of those infected with M. tuberculosis H37Ra, heat-killed M. microti and L. donovani. Thus, membranes of M. microti-infected macrophages differ antigenically from those of the normal macrophages and infected homologous macrophage membrane antiserum provides a useful tool in studying such changes.

Animals↗
PubMed2000

Heme oxygenase-1-derived bilirubin ameliorates postischemic myocardial dysfunction.

Bilirubin is a potent antioxidant generated intracellularly during the degradation of heme by the enzyme heme oxygenase. The purpose of this study was to determine the role of increased cardiac bilirubin in protection against postischemic myocardial dysfunction. Rat hearts were isolated and perfused according to the Langendorff technique to evaluate the recovery of myocardial function after 30 min of global ischemia and 60 min of reperfusion. We found that upregulation of the inducible isoform of heme oxygenase (HO-1) by treatment of animals with hemin 24 h before ischemia ameliorated myocardial function and reduced infarct size (tetrazolium staining) on reperfusion of isolated hearts. Tin protoporphyrin IX, an inhibitor of heme oxygenase activity, completely abolished the improved postischemic myocardial performance observed after hemin-mediated HO-1 induction. Likewise, cardiac tissue injury was exacerbated by treatment with tin protoporphyrin IX. Increased cardiac HO-1 expression and heme oxygenase activity were associated with enhanced tissue bilirubin content and an increased rate of bilirubin release into the perfusion buffer. Furthermore, exogenously administered bilirubin at concentrations as low as 100 nanomolar significantly restored myocardial function and minimized both infarct size and mitochondrial damage on reperfusion. Our data provide strong evidence for a primary role of HO-1-derived bilirubin in cardioprotection against reperfusion injury.

Animals↗
PubMed2000

Mycobacterium w vaccine, a useful adjuvant to multidrug therapy in multibacillary leprosy: a report on hospital based immunotherapeutic clinical trials with a follow-up of 1-7 years after treatment.

A vaccine based on autoclaved Mycobacterium w was administered, in addition to standard multidrug therapy (MDT), to 156 bacteriologically positive, lepromin negative multibacillary leprosy patients compared to a well matched control group of 145 patients with a similar type of disease who received a placebo injection in addition to MDT. The MDT was given for a minimum period of 2 years and continued until skin smear negativity, while the vaccine was given at 3-month intervals up to a maximum of eight doses. The fall in clinical scores and bacteriological indices was significantly more rapid in vaccinated patients, from 6 months onward until years 2 or 3 of therapy. However, no difference was observed in the fall in bacteriological index in the two groups from year 4 onwards. The number of LL and BL patients released from therapy (RFT) following attainment of skin smear negativity, after 24-29 months of treatment was 84/133 (63.1%) in vaccinated and 30/120 (25.0%) in the placebo group; the difference was highly statistically significant (P < 0.0001). In all, 90.2% patients (146/162) converted from lepromin negativity to positivity in the vaccine group, as against 37.9% (56/148) in the placebo group. The average duration of lepromin positivity maintained following eight doses of vaccine administered over 2 years was 3.016 years in the vaccine and 0.920 years in the placebo group. Histological upgrading after 2 years of treatment in the LL type was observed in 34/84 (40.5%) cases in the vaccine and 5/85 (5.9%) cases in the placebo group, the difference being statistically significant (P < 0.001). The incidence of type 1 reactions was significantly higher (30.5%) in the vaccine group than (19.7%) in the placebo group (P = 0.0413); the difference was mainly observed in LL type (P = 0.009). The incidence of type 2 reactions was similar (31.8 and 34.6%) in vaccine and placebo groups. The vaccine did not precipitate neuritis or impairments over and above that encountered with MDT alone. After 5 years of follow-up following RFT, no incidence of bacteriological or clinical relapses was observed in both groups.

Bacterial Vaccines↗
PubMed2000

Reactional states and neuritis in multibacillary leprosy patients following MDT with/without immunotherapy with Mycobacterium w antileprosy vaccine.

A vaccine based on autoclaved Mycobacterium w was administered, in addition to standard multidrug therapy (MDT), to 157 untreated, bacteriologically positive, lepromin negative multibacillary leprosy patients, supported by a well matched control group of 147 patients with similar type of disease, who received a placebo injection in addition to MDT. The MDT was given for a minimum period of 2 years and continued until skin smear negativity, while the vaccine/placebo was given at 3-monthly intervals up to a maximum of eight doses. The incidence of type 2 reaction and neuritis during treatment and follow-up showed no statistically significant difference in the vaccine and placebo groups. The incidence of type 1 reaction (mild in most cases), however, was higher in the vaccine group (P = 0.041, relative risk ratio 1.79), considering LL, BL and BB leprosy types together, and considerably higher (P = 0.009) in LL type, probably because of confounding due to higher number of patients with previous history of reaction in this group. The occurrence of reactions and neuritis in terms of single or multiple episodes was similar in the vaccine and placebo groups. The association of neuritis and reactions, as well as their timing of occurrence (during MDT or follow-up), was also similar in the two groups, with more than 90% of occurrences taking place during MDT. The incidence of reversal reaction was significantly higher among the males in the vaccine group (34.5% versus 8.3%, P = 0.019). Patients with high initial BI (4.1-6.0) showed higher incidence of reactions (70.3%) as compared to those with medium (2.1-4.0) and low (0.3-2.0) BI where the reactions were observed with a frequency of 56.1% and 38.8%, respectively. However, unlike reactions, neuritis incidence did not seem to be affected by initial BI to the same extent in the vaccine group, with frequencies of 35.3%, 36.3% and 25.9% in the three mentioned BI ranges. Overall, the vaccine did not precipitate reactional states and neuritis over and above that observed with MDT alone.

Bacterial Vaccines↗
PubMed2000

Induction of lepromin positivity and immunoprophylaxis in household contacts of multibacillary leprosy patients: a pilot study with a candidate vaccine, Mycobacterium w.

We screened 487 household contacts of multibacillary (MB) patients for evidence of disease and their lepromin status. From the 444 results available, 302 (68.02%) were lepromin positive and 142 (31.98%) were lepromin negative on initial testing. The initial lepromin status as assessed in the group of 54 contacts having disease at the outset showed 24 out of 46 (52.2%) to be lepromin positive and 22 of 46 (47.8%) to be lepromin negative. In the same group, among 24 lepromin positives, 22 (91.7%) had paucibacillary (PB) and 2 (8.3%) had multibacillary (MB) disease; among the lepromin negatives, 12 (54.5%) had PB and 10 (45.5%) had MB disease. Out of 72 initially lepromin-negative contacts administered Mycobacterium w vaccine and followed up, the cumulative percentages show that 53 (73.6%) converted to positivity after a single dose, 10 (87.5%) after a second dose and 67 (93.1%) after the third dose. The incidence of new cases with leprosy was 8 out of 231 (3.46%) among lepromin-positive contacts and 5 out of 93 (5.38%) among lepromin-negative contacts administered Mycobacterium w vaccine. Among 231 lepromin-positive contacts, the new cases occurred in those with a 1+ and 2+ lepromin response only, and no case occurred among 51 contacts with a 3+ lepromin response. The incidence among lepromin-positive contacts in this study (3.46%) was similar to the observations in two other studies: 3.2% by Dharmendra, et al. and 6.9% by Chaudhary, et al. However, the incidence among lepromin-negative contacts administered Mycobacterium w vaccine was significantly lower than that observed among lepromin-negative contacts not administered any vaccination in the other two studies (14.1% by Dharmendra, et al. and 29.0% by Chaudhary, et al.). To conclude, although a study of small sample size, the preliminary evaluation indicates that administration of Mycobacterium w vaccine seems to have the potential to reduce the incidence of leprosy among household contacts of leprosy patients. More explicit results about the vaccine will be available from the ongoing field trials in Kanpur Dehat in the near future.

Bacterial Vaccines↗
PubMed1999

Inhibition of peroxynitrite dependent DNA base modification and tyrosine nitration by the extra virgin olive oil-derived antioxidant hydroxytyrosol.

Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been suggested to be a potent antioxidant. The superoxide radical (O2*-) and nitric oxide (NO*) can react very rapidly to form peroxynitrite (ONOO ), a reactive tissue damaging species thought to be involved in the pathology of several chronic diseases. Hydroxytyrosol was highly protective against the peroxynitrite-dependent nitration of tyrosine and DNA damage by peroxynitrite in vitro. Given that extra virgin olive oil is consumed daily by many humans, hydroxytyrosol derived from this diet could conceivably provide a defense against damage by oxidants in vivo. The biological activity of hydroxytyrosol in vivo will depend on its intake, uptake and access to cellular compartments.

Animals↗