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Biomedical subjects

R Misra

Publications and source records attributed to R Misra.

At least 109 records · Page 6Linked to original sources
PubMed1994

Platelet serotonin uptake in duodenal ulcer patients.

Platelet serotonin uptake was measured in 10 duodenal ulcer patients and 10 controls by determining the concentration of radioactivity in platelets after incubation with tritium-labelled serotonin binoxalate. Platelet 5-HT uptake in ulcer patients (312.0 +/- 125.0 CPM/10(7) platelets) was significantly higher than that in the control group (186.0 +/- 53.0 CPM/10(7) platelets; p < 0.01). Since the kinetics of 5-HT uptake by platelets may be a reflector of enhanced serotonergic activity, this finding may have implications in future therapeutic strategies for this disease.

Adult↗
PubMed1993

A novel ompC mutation of Escherichia coli K-12 that reduces OmpC and OmpF levels in the outer membrane.

A novel ompC mutation was isolated that not only lowered the amount of its own product, OmpC27, but also reduced the level of OmpF present in the outer membrane. ompC27 codes for a mutant OmpC protein that contains two non-native cysteine residues. The ompC27 allele confers phage resistance by lowering the level of OmpC present in the outer membrane. This effect on OmpC27 was manifested at the level of assembly as a result of disulphide bond formation between the two cysteine residues. This disulphide bonding in OmpC27 also produced a novel phenotype by specifically influencing OmpF levels. The effect of OmpC27 on OmpF was partly a result of a lowering of ompF transcription, and partly a result of an effect at the post-transcription level. The transcriptional effect is likely to be brought about by a defective membrane as a result of the insertion of the disulphide bond containing OmpC27. The post-transcriptional effect of OmpC27 on OmpF could be due to interference at the assembly level. In a dsbA::kan1 background where the in vivo disulphide bonding ability was dramatically reduced, the OmpC27-mediated effects were also curtailed.

Bacterial Outer Membrane Proteins↗
PubMed1993

OmpF assembly mutants of Escherichia coli K-12: isolation, characterization, and suppressor analysis.

This paper describes a novel genetic method used to isolate mutations that alter proper assembly of OmpF in the outer membrane. The thermolabile nature of assembly intermediates allowed selection of temperature-sensitive mutations within the ompF gene. A variant allele of ompF (ompF-Dex) was used because it provided a convenient selectable phenotype (Dex+). Assembly mutants were isolated in two steps. First, amber mutations were obtained that mapped in ompF-Dex. This resulted in a Dex- phenotype. Starting with these Dex- strains, Dex+ revertants were isolated. Mutants that displayed a temperature-sensitive Dex+ phenotype were further characterized. Three such mutants possessed a single substitution within ompF that reverted the nonsense codon to a sense codon which replaced W214 with either an E or Q and Y231 with a Q residue in the mature OmpF protein. All three mutant OmpF proteins showed an assembly defect. This defect led to a substantial reduction in the amount of stable OmpF trimers with the concomitant increase of a high-molecular-weight form of OmpF which migrated at the top of the gel. Suppressor mutations were sought that corrected the assembly defect of OmpF. These extragenic suppressor mutations were mapped at 45 min on the Escherichia coli chromosome. The suppressor mutations displayed no allele specificity and were recessive to the wild-type allele. In the presence of a suppressor, mutant stable trimers appeared in an almost normal manner. The appearance of stable trimers concurred with a substantial loss of the high-molecular-weight OmpF species. At this stage, it is not clear whether the high-molecular-weight species of OmpF is a normal assembly intermediate or a dead-end assembly product. The results presented in this study raise the intriguing possibility of a chaperone-like activity for the wild-type suppressor gene product.

Alleles↗
PubMed1992

Arabidopsis Acetohydroxyacid Synthase Expressed in Escherichia coli Is Insensitive to the Feedback Inhibitors.

Acetohydroxyacid synthase (AHAS), the first enzyme unique to the biosynthesis of isoleucine, leucine, and valine, is the target enzyme for several classes of herbicides. The AHAS gene from Arabidopsis thaliana, including the chloroplast transit peptide, was cloned into the bacterial expression plasmid pKK233-2. The resulting plasmid was used to transform an AHAS-deficient Escherichia coli strain MF2000. The growth of the MF2000 strain of E. coli was complemented by the functional expression of the Arabidopsis AHAS. The AHAS protein was processed to a molecular mass of 65 kilodaltons that was similar to the mature protein isolated from Arabidopsis seedlings. The AHAS activity extracted from the transformed E. coli cells was inhibited by imidazolinone and sulfonylurea herbicides. AHAS activity extracted from Arabidopsis is inhibited by valine and leucine; however, this activity was insensitive to these feedback inhibitors when extracted from the transformed E. coli.

Journal Article↗
PubMed1992

Scleromyxoedema with features of systemic sclerosis.

The case is described of a patient with scleromyxoedema with features typical of systemic sclerosis. The features were so characteristic that the disease was misdiagnosed as systemic sclerosis. A brief review of the association of the two diseases is given.

Adult↗
PubMed1991

A genetic approach for analyzing the pathway of LamB assembly into the outer membrane of Escherichia coli.

Results presented in this study demonstrate that a mutation which inserts an additional tyrosine between the 2 tyrosines at residues 118 and 119 of mature LamB protein results in a temperature-dependent assembly defect. This defect leads to the accumulation of an intermediate at the restrictive temperature that is most likely an assembly-defective monomer. These monomers are rapidly degraded in the wild type (htrA+) strain, and the biphasic kinetics of this degradation indicate that the mutation affects the assembly process and not the final product, i.e. stable trimers. In addition, our data show that the temperature-dependent assembly defect in the mutant strain is reversible, and therefore the accumulated monomers represent a true assembly intermediate. Fractionation studies show that the monomers, which can be accumulated in htrA (degP) mutants at the restrictive temperature, are associated with the outer membrane, indicating that trimerization of LamB is not a prerequisite for localization.

ATP-Binding Cassette Transporters↗
PubMed1991

Overexpression of Acetohydroxyacid Synthase from Arabidopsis as an Inducible Fusion Protein in Escherichia coli: Production of Polyclonal Antibodies, and Immunological Characterization of the Enzyme.

Acetohydroxyacid synthase (AHAS, EC 4.1.3.18) is the first enzyme unique to the biosynthesis of valine, leucine, and isoleucine. This enzyme is the target site of several classes of structurally unrelated herbicides. The conventional method of antibody production using purified protein has not been successful with this enzyme. Two separate fragments of a gene encoding a portion of the mature region of AHAS from Arabidopsis were fused with the trpE gene from Escherichia coli using the pATH1 vector. E. coli cells transformed with each respective plasmid expressed a fusion protein at levels greater than 10% of the total cell protein. The fusion protein was purified and used to immunize rabbits. Antisera obtained from the immunized rabbits immunoprecipitated AHAS activity from Arabidopsis cell free extracts. The anti-AHAS antisera reacted with a 65 kilodalton protein band in electrophoretically resolved extracts of Arabidopsis. In cross-reactivity tests, this antibody was able to immunoprecipitate AHAS activity from various plant species. Furthermore, a protein band with a molecular mass of 65 kilodaltons was detected in the crude extracts of all plant species tested on a Western blot. These results indicate that the 65 kilodalton protein represents AHAS in various plant species. The wide spectrum of cross-reactivity for the antisera supports the view that the AHAS enzyme is highly conserved across all plant species.

Journal Article↗
PubMed1991

Nur77 is differentially modified in PC12 cells upon membrane depolarization and growth factor treatment.

The rat pheochromocytoma cell line PC12 can be induced by growth factors to undergo proliferation and neuronal differentiation. These cells also have excitable membranes that can be depolarized by neurotransmitters or elevated levels of extracellular KCl. Treatment of PC12 cells with growth factors or membrane-depolarizing agents rapidly activates the expression of specific genes whose products are thought to mediate the subsequent biological responses. One such gene, nur77, is a member of the steroid and thyroid hormone receptor gene superfamily. We have identified the Nur77 protein and shown that it is synthesized rapidly and transiently in PC12 cells following stimulation, has a short half-life of 30 to 40 min, and is located in both the nucleus and the cytoplasm. Nur77 is posttranslationally modified, primarily by phosphorylation on serine residues. Phosphopeptide analysis reveals that Nur77 is modified differently upon membrane depolarization than after treatment with growth factors. We hypothesize that the activity of Nur77 is regulated by both differential gene expression and posttranslational modification and that these modes of regulation contribute to distinct downstream responses specific to membrane depolarization and growth factor treatment.

Adrenal Gland Neoplasms↗
PubMed1991

Occurrence of systemic autoimmune disorders & autoantibodies in house-hold contacts of patients with systemic lupus erythematosus.

Household contacts of 22 randomly selected patients with systemic lupus erythematosus (SLE) were screened for autoimmune diseases and autoantibodies. Thirty nine consanguineous and 17 nonconsanguineous household contacts were studied. In the first group symptomatic SLE was seen in 5 per cent, rheumatoid arthritis in 2.5 per cent, antinuclear antibody (ANA) in 10 per cent and rheumatoid factor (RF) in 5 per cent while anti-dsDNA, anti-nRNP and anti-Sm antibodies were not detected in any individual. The second group showed total absence of any marker of autoimmunity. In normal controls only RF was detected in 3 per cent. The occurrence of markers of autoimmunity only in consanguineous household contacts of patients with SLE further confirms the recognised role of genetic factors in the etiology of SLE.

Aged↗
PubMed1990

Effects of commonly used NSAID's on gastric mucosa. A clinico-endoscopic and histopathological study.

Non steroidal anti-inflammatory drugs (NSAID's) are one of the most commonly used agents in clinical practice today. All these drugs are known to produce gastro-intestinal lesions. In the present study we found that aspirin, indomethacin and phenylbutazone caused gastric mucosal damage in 90.9%, 100%, respectively while ibuprofen and paracetamol caused gastric mucosal damage in 33.3% and 37.5% respectively. Thus latter two drugs were safer NSAID's. Further more we have demonstrated that endoscopic monitoring of the patients on NSAID's is a sensitive method of early detection of gastric mucosal damage. This monitoring may be particularly valuable in high risk subjects on NSAID's.

Acetaminophen↗
PubMed1990

Effects of commonly used non steroidal anti-inflammatory drugs on gastric mucosa. A clinical, endoscopic and histopathological study.

Non steroidal anti-inflammatory drugs (NSAIDS) are known to produce gastro-intestinal lesions. In the present work we found that aspirin, indomethacin and oxyphenbutazone caused gastric mucosal damage in 90.9%, 100% and 100% respectively, while ibuprofen and paracetamol caused damage in 33.3% and 37.5% of cases respectively. Thus the latter two drugs were much safer NSAIDs. Furthermore we demonstrated that endoscopic monitoring of patients on NSAIDs is a sensitive method for early detection of gastric mucosal damage. This monitoring may be particularly valuable in high risk subjects on NSAIDs.

Adolescent↗
PubMed1990

Brainstem auditory evoked potentials (BAEPs) in pregnant women.

The electrophysiological correlate of change in sensory function during pregnancy has not been reported. The brain stem auditory evoked potentials were recorded in eight pregnant women during third trimester from CZ-A1 and CZ-A2 position, with alternating 90 dB sound pressure click stimuli delivered at 10/sec and -40 dB (white noise) masking of contralateral ear. Two thousand and forty eight responses were analysed and replicated. The noise and other artefacts were rejected with filter bandpass setting 150 to 3000 Hz. The evoked responses in pregnant women were compared with ten age matched normal subjects using Student's 't' test. The threshold for eliciting wave V of the brainstem auditory response was higher in pregnant women (28.1 +/- 2.1 dB). The absolute peak latencies of waves I to V were similar in both groups. However, Inter peak latencies (IPLs) I-III, III-V were on higher side in the pregnant women, and I-V, in particular (3.9 +/- 0.14) was significantly higher when compared with controls (3.73 +/- 0.16). These findings suggest that besides an increase in evoking wave V threshold, neural conduction process in brainstem auditory pathways during pregnancy is also delayed within + 2SD of the mean central conduction time in nonpregnant state.

Adult↗
PubMed1990

Platelet ionic calcium and serum total calcium in essential hypertension.

A total of 44 cases comprising hypertensive (31) and normotensive group (13) were studied. Serum total calcium concentrations remained unaltered in hypertensives. Platelet cytosolic calcium in hypertensive group was significantly higher as compared to the normotensive controls. Platelet cytosolic calcium correlated with systolic and diastolic blood pressure and mean arterial pressure significantly.

Blood Platelets↗
PubMed1989

Recombination mediates production of an extrachromosomal circular DNA containing a transposon-like human element, THE-1.

An abundant class of HeLa extrachromosomal circular DNA containing the transposon-like element, THE-1, is shown to arise via site specific recombination. The chromosomal locus from which these circles are derived, however, is single-copy. Northern blot analysis detects homology to two polyadenylated RNAs in HeLa cells. The possible presence of an origin of replication and its role in generating these small polydisperse circles is discussed.

Base Sequence↗