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S Das

Publications and source records attributed to S Das.

At least 487 records · Page 27Linked to original sources
PubMed1991

Chitin synthase in encysting Entamoeba invadens.

Although the cyst wall of Entamoeba invadens contains chitin, synthesis of this structural polymer during encystation has not been described before. Here we report that conditions which stimulate encystation of the parasite lead to increased chitin synthase (ChS) activity, measured by incorporation of [3H]GlcNAc ([3H]N-acetylglucosamine) from UDP-GlcNAc. The radiolabelled product was precipitable by trichloroacetic acid or ethanol and identified as chitin because it was digested by purified chitinase to radioactive chitobiose and GlcNAc. Cell fractionation indicated that approx. 60% of the enzyme is in the high-speed supernatant. pH-activity profiles showed that soluble ChS has an optimum at 6.0, whereas particulate ChS has a peak at pH 7.0-7.5. Both the activities were dependent on bivalent metal ions, especially Mn2+ and Mn2+ plus Co2+. In contrast with the ChS of other organisms, neither the particulate nor the soluble ChS of E. invadens was activated by trypsin treatment. Soluble and particulate ChS were also stimulated by digitonin and phosphatidylserine, whereas phosphatidylethanolamine stimulated only the soluble ChS. The enzyme activities were inhibited by UDP, UDP-glucose and UDP-GalNAc, but not by the analogues Polyoxin-D or Nikkomycin. This is the first report of an enzyme which is developmentally regulated during encystation of the primitive eukaryotic genus Entamoeba.

Animals↗
PubMed1991

A surface antigen of Giardia lamblia with a glycosylphosphatidylinositol anchor.

Since Giardia lamblia trophozoites are exposed to high concentrations of fatty acids in their human small intestinal milieu, we determined the pattern of incorporation of [3H]palmitic acid and myristic acid into G. lamblia proteins. The pattern of fatty acylation was unusually simple since greater than 90% of the Giardia protein biosynthetically labeled with either [3H]palmitate or myristate migrated at approximately 49 kDa (GP49) in reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis during both growth and differentiation. GP49, which partitions into the Triton X-114 detergent phase, is localized on the cell surface since it is 125I-surface-labeled. GP49 was also biosynthetically labeled with [14C]ethanolamine and [3H]myoinositol, suggesting that it has a glycosylphosphatidylinositol (GPI) anchor. Moreover, phospholipase A2 (PLA2) or mild alkaline treatment released free fatty acids, indicating a diacylglycerol moiety with ester linkages. Finally, a 3H- and 14C-labeled species was released by nitrous acid deamination from [14C]palmitate- and [3H]myoinositol-labeled GP49. The GPI anchor of GP49 is unusual, however, because purified GP49 was cleaved by Bacillus cereus phosphatidylinositol (PI)-specific PLC, but not by Staphylococcus aureus PI-PLC, or plasma PLD, and did not react with antibody against the variant surface glycoprotein cross-reactive determinant. Moreover, the double-labeled deaminated GP49 anchor migrated faster than authentic PI in TLC and produced [3H]glycerophosphoinositol after deacylation. In contrast to the variable cysteine-rich G. lamblia surface antigens described previously, GP49 was identified in Western blots of every isolate tested, as well as in subclones of a single isolate which differ in expression of a major cysteine-rich 85/66-kDa surface antigen, which does not appear to be GPI-anchored. These observations suggest that GP49, the first common surface antigen to be described in G. lamblia, may play an important role in the interaction of this parasite with its environment.

Acylation↗
PubMed1991

CD3G is within 200 kb of the leukemic t(4;11) translocation breakpoint.

The t(4;11)(q21;q23) has been associated with acute lymphocytic leukemia (ALL) especially in infants. The t(4;11) breakpoint on chromosome 11 is cytogenetically indistinguishable from breakpoints for other leukemia-associated translocations affecting 11q23. The molecular basis of the t(4;11) is unknown although a number of genes have been mapped to 11q23. The CD3D, G, and E genes have been positioned proximal to the 11q23 breakpoint of the 4;11 translocation while the THY1 and ETS1 genes have been mapped distal to this breakpoint. We report evidence that CD3G is within 200 kb of the 4;11 breakpoint as observed by pulsed field gel analysis. A rearrangement of the CD3G gene has been observed in a cell line derived from a patient with the t(4;11) translocation and in a hybrid cell line containing the derivative 11q chromosome derived from this cell line, using the restriction enzymes SacII and ClaI. Similar rearrangements using SacII were observed in 2 further patients with ALL and the t(4;11) translocation. No rearrangements in the same DNA were observed using ETS1, THY1, and D11S29 and a range of rare cutter restriction enzymes. CD3G thus provides a tool for the cloning and analysis of the 4;11 translocation, and poses a question of its possible involvement at long range with this translocation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

Human tuberculosis sera show prominent antibody responses to particulate fractions of Mycobacterium tuberculosis.

Sera from smear-positive pulmonary tuberculosis patients and normal control subjects in Madras were analyzed by Western blotting for their reactivity with soluble and particulate (membrane-rich and cell wall-rich) antigen fractions extracted by sonication from Mycobacterium tuberculosis H37Rv. Discrimination between patient and control sera was best with particulate antigen fractions: 60% of patient sera reacted with a 38-kD antigen band and 90% reacted with a 55-kD band. Reactions of control sera with the 38- and 55-kD bands were infrequent and faint. The results suggest that a serodiagnostic test might be based on quantitation of responses to these two antigens.

Adolescent↗
PubMed1991

Laparoscopic evaluation of nonpalpable testes.

Laparoscopy was utilized in the evaluation of 27 nonpalpable testes in 21 patients prior to exploration and necessary definitive surgery. Laparoscopic prediction of the location of the nonpalpable testes was accurate in all cases. Laparoscopic findings can help in determining the appropriate technique of orchiopexy expected to yield better testicular salvage. It can also prevent unnecessary exploration of children with anorchia as evidenced by blind-ending vas deferens and spermatic vessels.

Adolescent↗
PubMed1991

Traumatic stricture of prostatic urethra in ten-year-old boy.

Stricture of the midprostatic urethra resulted from a pelvic fracture injury in a ten-year-old boy. The stricture was successfully managed by core-through urethrotomy and transurethral resection of the scarred area in the prostate. The possible mechanism of traumatic stricture formation at such a rare anatomic location and the therapeutic options are reviewed.

Child↗
PubMed1991

Therapeutic dilemmas in management of cystine calculi.

The appropriate management of patients with cystine calculi necessitates a fundamental understanding of the pathophysiology of cystinuria and a working knowledge of the available therapeutic modalities. The following case reports and review of the literature serve to illustrate that successful treatment involves a multidimensional approach to eradication of calculi with long-term follow-up aimed at prevention.

Adult↗
PubMed1991

The generation of DNA probes to chromosome 11q23 by Alu PCR on small numbers of flow-sorted 22q- derivative chromosomes.

A strategy for the isolation of DNA probes from small numbers of flow-sorted human chromosomes has been developed. A lymphoblastoid cell line carrying the 22q- derivative chromosome product of the constitutional t(11;22) translocation was used as the source of chromosomes. Synthetic oligonucleotide primers, based on the consensus Alu sequence, were used to amplify inter-Alu sequence from 500 flow-sorted 22q- derivative chromosomes. The amplified sequences were cloned into a plasmid vector by blunt-end ligation, yielding clones with inserts in the range of 400 to 1000 bp. Approximately 70% of these clones hybridized to human DNA as single-copy probes. To identify clones derived from chromosome 11, the library was screened with a heterogeneous probe prepared by Alu-PCR amplification from the DNA of a somatic cell hybrid containing one homology of chromosome 11. All the positive clones found were mapped to within the q23-q25 region of chromosome 11 known to be translocated onto the 22q- derivative chromosome. Further mapping studies showed that most of these probes (7/8) lay between the breakpoints for the t(4;11) translocation of acute lymphocytic leukemia and the t(11;22) of Ewing sarcoma. Thus, the use of Alu-PCR on the small derivative chromosome 22q- has provided a greatly enriched source of probes to region 11q23, a part of the genome that is currently of great interest. This approach will be particularly appropriate to small numbers of chromosomes when high specificity rather than total representation is required.

Animals↗
PubMed1991

Photophysics and photochemistry of new verdin compounds.

Five different verdins, including one zinc metal chelate, were examined by laser flash techniques. Triplet molar absorption coefficients, triplet and singlet oxygen quantum yields and triplet lifetimes were determined. Zinc methyl pyroverdin (ZNMPV), copro II verdin trimethyl ester (CVTME) and deuteroverdin methyl ester (DVME) have the highest triplet and singlet oxygen quantum yields. ZNMPV and CVTME have the longest triplet lifetimes. Our data are consistent with singlet oxygen as the primary modality for phototherapy and it is suggested that DVME and CVTME may be useful agents.

Lasers↗
PubMed1991

Evidence for translational control of beta-tubulin synthesis during differentiation of Leishmania donovani.

Tubulin biosynthesis was rapidly induced during transformation of the mammalian (amastigote) stage of the kinetoplastid parasite Leishmania donovani to flagellated promastigotes. However, transcription of beta-tubulin genes occurred constitutively, as judged by nascent RNA synthesis in isolated nuclei and Northern blotting of steady-state mRNA. Two mRNA species of 2.2 and 2.4 kb were shared by the two cell-types, while a third 2.6 kb species, constituting about 20% of the total, was present in large amounts in promastigotes. RNase protection experiments demonstrated sequence microheterogeneity in the 5'-untranslated region, the pattern of which was identical in promastigotes and amastigotes. By primer extension assays, heterogeneity in the 5'-terminal cap structure of amastigote beta-tubulin mRNA and differential pausing of reverse transcriptase within the mini-exon leader region were detected. These differences correlated with enhanced translational efficiency of tubulin mRNA from promastigotes in a rabbit reticulocyte lysate system. The results indicate that translational control plays a major role in tubulin induction during L. donovani differentiation.

Animals↗
PubMed1991

Stimulation by cGMP of apical Na channels and cation channels in toad urinary bladder.

The effects of 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) on apical membrane cation conductances in the toad urinary bladder were investigated. 8-BrcGMP (1 mM) added to the serosal solution increased the amiloride-sensitive short-circuit current (INa) after a delay of 5 min to a steady-state value 1.8 times that of controls achieved after 30 min. Similar effects were seen when the bladders were bathed on the serosal side with a normal NaCl Ringer solution and with a high-K sucrose solution to depolarize the basolateral membrane. Under the latter conditions, the amiloride-sensitive transepithelial conductance increased in parallel with the short-circuit current, indicating stimulation of apical membrane Na channels. The threshold concentration for observing the stimulation of INa was 100 microM, 10-100 times larger than the concentration of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) required to elicit an increase in INa. Currents through an outwardly rectifying Ca-sensitive cation conductance (Iout) were also increased by 1.8-fold relative to controls. This stimulatory effect occurred after a delay of 15 min and reached maximal levels 90-120 min after addition of the nucleotide. The effects of cGMP on INa were not additive with those of 8-BrcAMP or with antidiuretic hormone, an agent known to act by increasing cAMP within the cell. Addition of 1 mM 3-isobutyl-1-methylxanthine to the serosal side of the bladders stimulated INa by 1.3-fold and Iout by 2.4-fold. In both cases, subsequent addition of cGMP produced no further activation of either conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1991

Mosquito fauna of certain areas of deltaic West Bengal--a preliminary report.

Survey of mosquito fauna in certain areas of deltaic Bengal was conducted between September 1989 to February 1990. Anopheles vagus predominated in Canning study area and Anopheles hyrcanus in Budge Budge. Comparatively low densities of Anopheles annularis were recorded from Canning (6.05% of the total anophelines) and Budge Budge (7.36% of the total anophelines), respectively. C. vishnui, C. pseudovishnui and C. tritaeniorhynchus were collected from both Canning and Budge Budge study areas. C. pseudovishnui predominated in Canning and C. vishnui in Budge Budge. Amongst the three species of C. vishnui complex, C. triateniorhynchus ranked third in order of preponderance at both the study areas.

Animals↗
PubMed1991

A clinico-pathological study of cervical carcinoma through histopathology, SEM and tumour marker expression.

Carcinoma of the uterine cervix is the commonest tumour in India. Our study on the biological behaviour of cervical carcinoma was made with respect to oncofetoprotein expression, histopathology and scanning electron microscopy. A clinical picture was compared with the above three parameters to note the embryonic degeneration of the tumour. The objective of this study was to establish a new grading system of tumour pathology which might be an adjunct to clinical staging. This should be helpful for the formulation of different treatment protocols.

Adult↗
PubMed1991

Extraperitoneal closure of colostomy in children.

In 12 children colostomy wound closure was undertaken with liberal extraperitoneal mobilisation of the bowel. In all the cases adequate length of the colonic loops could be achieved for resection of the colostomy and end to end anastomosis. There was only minor wound infection in 3 cases. There was no faecal fistula nor any postoperative intestinal obstruction.

Anal Canal↗
PubMed1991

Mortality events amongst non insulin dependent diabetes mellitus patients in Orissa.

In a study over one year, it was observed that mortality amongst hospitalised patients with non insulin dependent diabetes mellitus (NIBDM) was nearly 20%. Those dying within 24 hr were classified as group A, between one day and one week as B, between one week and one month as C, and those after one month as D. There were 31 patients each in groups A and B, 14 in C, and 4 in D. The mean age at death was 61 years in the first three groups. The prevalence of cerebro-vascular accident as a terminal event was similar i.e. 32.2, 35.5 and 35.7 per cent in groups A, B and C respectively; 48% of patients in group A suffered from ischaemic heart disease. Diabetic ketoacidosis was equally prevalent amongst groups A, B and C. Infection was significantly more common in group B (45.2%) than A (P less than 0.05). Nephropathy was observed in 57% of patients in group C as compared to 22.5% in A (P less than 0.02). Cerebrovascular accident and infection were the major causes of mortality in groups B and C (80.7% and 71.4%), whereas ischaemic heart disease and cerebrovascular accident accounted for 80% of deaths in group A.

Cause of Death↗