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Biomedical subjects

S Chaudhuri

Publications and source records attributed to S Chaudhuri.

At least 55 records · Page 3Linked to original sources
PubMed1998

Why relapse occurs in PB leprosy patients after adequate MDT despite they are Mitsuda reactive: lessons form Convit's experiment on bacteria-clearing capacity of lepromin-induced granuloma.

It is amazing how after years of scientific research and therapeutic progress many simple and basic questions about protective immunity against Mycobacterium leprae remain unanswered. Although the World Health Organization (WHO) has recommended short-term multidrug therapy (WHO/MDT) for the treatment of paucibacillary (PB) leprosy patients, from time to time several workers from different parts of the globe have reported inadequate clinical responses in a few tuberculoid and indeterminate leprosy patients following adequate WHO/MDT despite the fact that they are Mitsuda responsive. A few borderline tuberculoid patients harbor acid-fast bacilli (AFB) in their nerves for many years even though they become clinically inactive following MDT, a fact which has been ignored by many leprosy field workers. Keeping these patients in mind, we have attempted to investigate the cause of the persistence of AFB in PB cases and have looked into the question of why Mitsuda positivity in tuberculoid and indeterminate leprosy patients, as well as in healthy contacts, is not invariably a guarantee for protectivity against the leprosy bacilli. We have: a) analyzed the histological features of lepromin-induced granulomas, b) studied the bacteria-clearing capacity of the macrophages within such granulomas, and c) studied the in vitro leukocyte migration inhibition factor released by the blood leukocytes of these subjects when M. leprae sonicates have been used as an elicitor. The results of these three tests in the three groups of subjects have been compared and led us to conclude that the bacteria-clearing capacity of the macrophages within lepromin-induced granuloma (positive CCB test) may be taken as an indicator of the capability of elimination of leprosy bacilli and protective immunity against the disease. This important macrophage function is not invariably present in all tuberculoid and indeterminate leprosy patients or in all contacts even though they are Mitsuda responsive and are able to show a positive leukocyte migration inhibition (LMI) test. It is likely but not certain that this deficit of the macrophage is genetically predetermined and persists after completion of short-term WHO/MDT. Thus, after discontinuation of treatment slow-growing, persisting M. leprae multiply within macrophages leading to relapse.

Adolescent↗
PubMed1998

Effects of gonadotropins and prolactin on ovarian activity of a wild avian species, the tree pie Dendrocitta vagabunda.

Ovine FSH (40: g per bird daily for 10 days) increased ovarian weight, follicular size, phosphatase activities, and RNA and protein levels in tree pie (Dendrocitta vagabunda), but exogenous ovine LH (40 micrograms per bird daily for 10 days) with the same dose and duration caused depletion of ovarian cholesterol and ascorbic acid concentrations with a rise in sialic acid and glycogen levels of the ovary. In contrast, prolactin (LTH: 5 I.U. per bird daily for 10 days) administration showed reverse biochemical changes to those of FSH. The findings suggest that FSH induces mainly ovarian follicular growth and LH stimulates ovarian steroidogenesis, but LTH is antigonadal in this wild avian species.

Animals↗
PubMed1997

On the dynamics of synaptic vesicles: effects on the rate of neurotransmitter release.

Release of transmitter substances during synaptic communication in a biological process of great importance, and it is worthwhile to ascertain the basic molecular events underlying this process. We present a minimal model of synaptic vesicle (SV) dynamics, with which most of the major experimentally observed features of evoked neurotransmitter release can be reproduced. The effect of different parameters on the time course of evoked release as well as the effect of repetitive stimulation on this model system has been examined.

Animals↗
PubMed1996

Sequences directing C to U editing of the plastid psbL mRNA are located within a 22 nucleotide segment spanning the editing site.

In plastids, editing of an ACG codon to an AUG codon creates the translation initiation codon for the psbL and ndhD transcripts in tobacco. To identify the RNA segment required for psbL editing, chimeric kanamycin resistance genes were constructed containing psbL deletion derivatives, and tested in vivo for editing in transgenic plants. We report here that a 22 nucleotide segment is sufficient to direct efficient psbL editing, including 16 nucleotides upstream and five nucleotides downstream of the editing site. Mutation of the A nucleotide to a C upstream of the editing site completely abolished editing, while mutation of the downstream G to a C only reduced the editing efficiency. Out of the 22 nucleotide editing target sequence, the 16 upstream nucleotides were found to compete with the endogenous psbL transcript for a depletable trans-factor. To test whether editing of initiation codons involves a common trans-factor, a chimeric gene containing the ndhD editing site was expressed in tobacco plastids. As for psbL, editing of the ndhD site requires a depletable trans-factor. However, the ndhD trans-factor is distinct from that required for psbL editing. Distinct cissequences and trans-factor requirements for the psbL and ndhD editing sites indicate an individual recognition mechanism for the editing of plastid initiation codons.

Amino Acid Sequence↗
PubMed1996

Changes in thyroid activity during the annual sexual cycle of a wild avian species, the tree pie Dendrocitta vagabunda.

Thyroid activity was studied during the annual gonadal cycle in both sexes of the tree pie (Dendrocitta vagabunda). The study was conducted once a month throughout the year by evaluating thyroid weight, epithelial height and peroxidase activity. The values of these parameters moderately increased during the progressive phase, maximally increased during breeding, decreased in the regression phase and decreased further during the non-breeding phase in both sexes of birds. The findings indicate that thyroid activity, probably including thyroxine synthesis, varies annually, being highest during breeding compared to other phases of the gonadal cycle and that, there may be a progonadal relationship of the thyroid gland in both sexes of the tree pie.

Animals↗
PubMed1996

Unilateral Fontan operation for tricuspid atresia.

A 12-year-old child with tricuspid atresia and acquired hypoplasia of the left pulmonary artery was successfully treated with unilateral Fontan operation. Angiography at age 2 months had shown a normal left pulmonary artery, and a modified Potts shunt was performed. An emergency central shunt was required a year later. Reinvestigation 5 years after the initial operation revealed severe hypoplasia of the left pulmonary artery.

Anastomosis, Surgical↗
PubMed1995

X-ray crystallographic studies on hexameric insulins in the presence of helix-stabilizing agents, thiocyanate, methylparaben, and phenol.

Three X-ray crystallographic studies have been carried out on pig insulin in the presence of three ligands, thiocyanate, methylparaben (methyl p-hydroxybenzoate), and phenol. In each case, rhombohedral crystals were obtained, which diffracted to 1.8, 1.9, and 2.3 A, respectively. Each crystal structure was very similar to that of 4-zinc pig insulin, which was used as a starting model for PROLSQ refinement (Collaborative Computational Project, Number 4, 1994). The R factors for the refined structures of thiocyanate insulin, methylparaben insulin, and phenol insulin were 19.6, 18.4, and 19.1, respectively. Each crystal structure consists of T3R3f insulin hexamers with two zinc ions per hexamer. In the R3f trimer of the thiocyanate insulin hexamer, one thiocyanate ion is coordinated to the zinc on the hexamer 3-fold axis, but there is no evidence of zinc ion binding in the off-axis zinc ion sites seen in the 4-zinc pig insulin structure. In the methylparaben insulin and phenol insulin hexamers, the phenolic ligands are bound at the dimer-dimer interfaces in the R3f trimers in a manner similar to that of phenol in R6 phenol insulin. The binding of methylparaben appears to make the hexamer more compact by drawing the A and the B chains closer together in the binding site. In all three structures presented herein, the conformations of the first three residues of the B chain in the R3f trimer are extended rather than alpha-helical, as is seen in R6 phenol insulin. The energetics of ligand binding in the insulin hexamer are discussed.

Animals↗
PubMed1995

Site-specific factor involved in the editing of the psbL mRNA in tobacco plastids.

In tobacco plastids, functional psbL mRNA is created by editing an ACG codon to an AUG translation initiation codon. To determine if editing may occur in a chimeric mRNA, the N-terminal part of psbL containing the editing site was translationally fused with the aadA and kan bacterial genes. The chimeric constructs were introduced into the tobacco plastid genome by targeted gene insertion. Editing of the chimeric mRNAs indicated that the 98 nt fragment spanning the psbL editing site contains all cis information required for editing. Expression of the chimeric gene transcripts led to a significant decrease in the editing efficiency of the endogenous psbL mRNA. However, the efficiency of editing in the transplastomic lines was unchanged for four sites in the rpoB and ndhB mRNAs. Reduced efficiency of psbL editing, but not of the other four sites, in the transplastomic lines indicates depletion of psbL-specific editing factor(s). This finding implicates the involvement of site-specific factors in editing of plastid mRNAs in higher plants.

Amino Acid Sequence↗
PubMed1995

RFLP mapping of the maize dzr1 locus, which regulates methionine-rich 10 kDa zein accumulation.

The dzrl locus in maize posttranscriptionally regulates the accumulation of methionine-rich 10 kDa zein in the endosperm. An allele of this locus present in the inbred line BSSS53, dzrl + BSSS53, conditions several-fold higher accumulation of the 10 kDa zein in comparison with standard inbred lines, leading to enrichment of methionine content in BSSS53 by 30%. In a population segregating for high and low 10 kDa zein, dzr1 + BSSS53 was found tightly to cosegregate with a 22 kDa zein gene cluster, belonging to the Z1C subfamily of alpha-zeins that is located on chromosome 4S. One member of this gene cluster, azs22/6, was estimated to be located less than 0.4 cM from dzr1 + BSSS53, while three other 22 kDa zein genes mapped 3.4 cM away. Restriction fragment length polymorphism (RFLP) mapping of dzr1 was conducted using additional maize DNA markers and orthologous rice DNA markers. One maize marker, php20725, was identified that mapped 1.1 cM from dzr1, proximal to the centromere. Another marker derived from rice, rz329, mapped 6.6 cM distal to dzr1. Pulsed-field gel electrophoresis (PFGE) of the 22 kDa zein cluster showed that probably all copies of the 22 kDa zein genes are present within a 200 kb SalI fragment. The recombination frequency within this cluster was estimated to be 20-fold higher than that predicted for the maize genome.

Amino Acid Sequence↗
PubMed1995

Determinants of the high-methionine trait in wild and exotic germplasm may have escaped selection during early cultivation of maize.

The 18 kDa high-methionine delta-class zein gene from maize has been cloned, and its regulation, structure, and map position studied. These studies have shown that (i) zein genes may also contain tryptophan and lysine codons, (ii) the 18 kDa and the related 10 kDa zein gene are coordinately regulated, but their products accumulate to different levels in a genotype-dependent manner, (iii) the duplication of delta-zein genes probably involved unequal crossing over, (iv) no copy correction in either direction has occurred from teosinte to modern corn, and (v) the duplication of of the 18 kDa zein gene probably occurred before the tetraploidization of a progenitor chromosome. The work shows that important nutritional quality determinants like the high-methionine seed proteins are abundant in several exotic and wild corn varieties and low in most of the inbreds screened. The lack of a selectable phenotype for such quality traits during initial domestication and breeding of corn would have eliminated cis and trans regulatory determinants from the germplasm used in modern corn breeding. Examples of the high-methionine delta-class zeins shown here may be generally applicable in explaining the low nutritional quality of most present-day corn grown.

Amino Acid Sequence↗