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Biomedical subjects

A Bhattacharya

Publications and source records attributed to A Bhattacharya.

At least 19 recordsLinked to original sources
PubMed1992

A major estrogen-regulated protein secreted from the liver of Xenopus laevis is a member of the serpin superfamily. Nucleotide sequence of cDNA and hormonal induction of mRNA.

Estrogen treatment of Xenopus frogs causes four mRNAs to become highly abundant in the liver. Three of these mRNAs have been previously identified as coding for vitellogenin, ferritin, and serum retinol binding protein. We show here that the fourth abundant liver messenger RNA comprises about 1500 nucleotides and codes for a 45-kDa secreted protein, designated Ep45. A clone complementary to Ep45 mRNA was isolated, and its identity was confirmed by hybridization selection of mRNA that translated in vitro into the Ep45 precursor. Nucleotide sequence analysis of the nearly full length cDNA revealed a total length of 1454 base pairs consisting of: 36 nucleotides of the 5' noncoding region, 1308 base pairs encoding an open reading frame of 436 amino acids, and 110 nucleotides of the 3' untranslated region. Ep45 mRNA may originate from as many as four closely spaced transcription start sites, which are 15 to 21 bases upstream of the first nucleotide of the cDNA clone. The Xenopus laevis genome appears to contain a single Ep45 gene. The deduced amino acid sequence indicates that Ep45 has features typical of a secreted protein, including a signal peptide of 16 amino acids and three potential sites for N-linked glycosylation, and is related to the serine protease inhibitors, a large family of proteins with very diverse physiological functions. Ep45 mRNA was absent in the liver of normal male frogs and increased at least 100-fold in response to estradiol-17 beta. Thus, both Ep45 and vitellogenin mRNAs are switched from undetectable to very high levels, a pattern of expression not found for any other mRNAs in Xenopus liver.

Amino Acid Sequence↗
PubMed1992

Immunobiological studies on experimental visceral leishmaniasis. II. Adherent cell-mediated down-regulation of delayed-type hypersensitivity response and up-regulation of B cell activation.

Visceral leishmaniasis or kala-azar is characterized by a variety of immunopathological consequences in man. The most remarkable of these are the depression of cell-mediated immunity and polyclonal B cell activation. The consequences observed in man could be induced in a murine model by inoculating the causative agent, Leishmania donovani. The cell-mediated response was studied in this murine model in terms of the delayed-type hypersensitivity (DTH) response toward leishmania antigen in a progressive infection. BALB/b (H-2b) mice showed progressive enhancement in the DTH response, whereas BALB/c (H-2d) mice showed strong DTH at the onset which gradually disappeared (defined as DTH-negative phase) and reappeared again at the later stage of infection. Adoptive transfer of enriched populations of splenic T cells from infected BALB/c mice together with parasite antigen into the footpad of syngenic normal recipients produced a dramatic enhancement in the DTH response, except at the onset of the DTH-negative phase. These observations indicate that adherent cells have a role in suppression of the cell-mediated immune response and also that another mechanism operates at the onset of the DTH-negative phase. This DTH-negative phase was not caused by depletion of DTH-mediating cells from the repertoire, but rather by suppression mediated by a subset of T cell evolved in the course of infection. Characterization on the basis of lymphokine production of the T cells mediating the DTH response and of T cells mediating suppression of the DTH response showed them to be of Th1 and Th2 type, respectively. Studies also indicated that at the onset and the later stages of infection suppression was mediated by adherent cells, but at the onset of DTH-negative phase, in particular, suppression was mediated by Th2 cells. Furthermore, experiments also showed that adherent cells from infected mice gained another property, that of driving B cells, in a T cell-dependent manner.

Animals↗
PubMed1992

Entamoeba histolytica extrachromosomal circular ribosomal DNA: analysis of clonal variation in a hypervariable region.

The ribosomal RNA genes of the protozoan parasite Entamoeba histolytica are highly repeated and display restriction fragment length polymorphism. Using a set of four DNA probes spanning the coding region and part of the flanking region of the E. histolytica ribosomal RNA genes, an analysis of the DNA bands generated by EcoRI digestion of Entamoeba DNA is presented. This analysis included five strains of E. histolytica, four strains of E. moshkovskii, and one strain each of E. invadens and E. terrapinae. No common bands were observed between E. histolytica and the other Entamoeba. Within E. histolytica, two bands were conserved in all strains while the others were polymorphic. Detailed analysis of DNA from independently isolated clones of the strain HM-1:IMSS of E. histolytica showed two bands to be highly polymorphic. Of these, the 4.4-kb band of clone 6 was further analyzed. Polymorphism in this band could even be demonstrated in cells of the same clone. Restriction enzyme analysis of this DNA band from two clones of HM-1:IMSS showed that the polymorphism may be due to variable numbers of DraI repeat units present in this DNA stretch.

Animals↗
PubMed1992

Identification and partial characterization of a lipophosphoglycan from a pathogenic strain of Entamoeba histolytica.

An acidic glycoconjugate could be extracted from a delipidated residue fraction of [3H]galactose, [3H]mannose or [32P]orthophosphate metabolically labeled Entamoeba histolytica with water/ethanol/diethylether/pyridine/NH4OH (15:15:5:1:0.017). The radioactively labeled glycoconjugate comprised 50-55% of the total [3H]galactose label incorporated into macromolecules. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the radiolabeled glycoconjugate showed two diffuse smears centering around 110 kDa and 45 kDa. Similar profiles were observed for both [3H]galactose- and [32P]orthophosphate-labeled glycoconjugate. No such bands were visible in [35S]methionine-labeled material. The hydrophobic nature of this glycoconjugate was inferred from its chromatographic behavior on phenyl-Sepharose. The molecule was rendered hydrophilic after digestion with phosphatidylinositol-specific phospholipase C. It was also sensitive to deamination by nitrous acid. Mild acid hydrolysis led to its fragmentation into smaller molecules as revealed by Sepharose 4B chromatography. Paper chromatographic analysis of the depolymerized [3H]galactose- and [3H]mannose-labeled fragments revealed that each was sensitive to alkaline phosphatase. The major dephosphorylated fragment migrated as an apparent galactose and mannose containing disaccharide which migrated identically to the Gal beta 1-4Man disaccharide derived from the lipophosphoglycan of Leishmania donovani. The above data support the existence of a major acidic glycoconjugate in E. histolytica bearing striking structural similarities to the lipophosphoglycan of Leishmania.

Alkaline Phosphatase↗
PubMed1992

Recognition of Entamoeba histolytica lipophosphoglycan by a strain-specific monoclonal antibody and human immune sera.

Western blot analysis showed that the monoclonal antibody 2D7.10 recognized lipophosphoglycan (LPG) from Entamoeba histolytica HM-1:IMSS. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern of [3H]galactose-labeled LPG and Western blot analysis of total lysate of E. histolytica with 2D7.10 revealed patterns similar to that of LPG with 2D7.10. This antibody could also immunoprecipitate purified LPG from the strain HM-1:IMSS after biosynthetically labeling with [3H]galactose and [32P]orthophosphate. However, no immunoprecipitation was observed when 2D7.10 was incubated with [32P]orthophosphate-labeled purified LPG from strain 200:NIH. Sera from patients suffering from invasive amoebiasis also immunoprecipitated 32P-labeled, purified LPG and could immunostain this molecule in Western blots. The human immune sera recognized carbohydrate epitopes but not the associated polypeptides of LPG, as evidenced by sensitivity to periodate digestion, mild acid hydrolysis but not to pronase treatment. It was earlier shown that 2D7.10 binds a carbohydrate epitope in a subset of axenized pathogenic strains of E. histolytica and that this epitope undergoes changes when cultured along with bacteria. These observations suggest that the E. histolytica LPG contains a strain-specific, variable epitope and that LPG is immunogenic in human.

Animals↗
PubMed1992

Acute isoniazid poisoning.

We present two cases of acute isoniazid poisoning in patients who ingested 7.5 g and 5.0 g of isoniazid respectively, with the intention of committing suicide. Both were admitted unconscious, with ventilatory insufficiency and convulsions. Hepatic dysfunction and peripheral neuropathy were notable complications.

Acute Disease↗
PubMed1992

Oral clonidine premedication for elderly patients undergoing intraocular surgery.

In a randomized double-blind study, the effects of clonidine premedication as a sedative, anxiolytic, analgesic and oculohypotensive agent were studied in 100 elderly patients (62 to 65 +/- 10 years, ASA grade I-II) undergoing elective intraocular surgery under local anaesthesia. The control group (Group A, n = 50) received oral diazepam 0.15 mg/kg 120 min before surgery and Group B (n = 50) received oral clonidine 300 micrograms 120 min before surgery. Two hours after the premedication, there was significantly more sedation (P less than 0.05) and less subjective anxiety (P less than 0.05) in the clonidine group than in the control group. There was a significant fall in intraocular pressure (IOP) from 20 +/- 0.5 to 13 +/- 0.5 mmHg (P less than 0.05) and significant reduction in systolic and diastolic blood pressure (BP) and heart rate (HR) (P less than 0.05) in the clonidine group as compared to the control group. Perioperatively, significantly more supplementation with i.v. diazepam was given in the control group than in the clonidine group (P less than 0.01). The incidence of intra-operative hypertension (P less than 0.01) and tachycardia (P less than 0.05) was significantly greater in the control group than in the clonidine group. A significantly larger number of patients in the clonidine group scored a Post-Anaesthesia Recovery (PAR) score of 10 as compared to the control group (P less than 0.01). There was no statistical difference in the postoperative Visual Analogue Scale (VAS) scores for pain, number of analgesic requests and emesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Modulation of a surface antigen of Entamoeba histolytica in response to bacteria.

Changes in the cell surface of Entamoeba histolytica, a human intestinal parasite and the causative agent of amebic dysentery, were examined with a monoclonal antibody, 2D7.10, which selectively recognizes carbohydrate epitopes in some axenic amebic strains. While high-level expression of this epitope was observed in axenic amebae, it was either absent or present only in small amounts in xenic amebae. Furthermore, reassociation of the axenic amebae with intestinal flora resulted in loss of the 2D7.10 epitope. Our data suggest that surface antigens of E. histolytica can be modulated in response to bacteria and may provide an explanation for the observed influence of bacteria on amebic virulence.

Animals↗
PubMed1992

Can pulse oximetry be used to measure systolic blood pressure?

This study evaluates the use of pulse oximetry to accurately monitor systolic arterial blood pressure in 100 healthy volunteers. Determination of arterial blood pressure using oximetry was made at the disappearance of visual display upon blood pressure cuff inflation, at the reappearance of visual display upon cuff deflation, and by averaging the two. The blood pressures obtained by pulse oximetry were compared with the arterial blood pressures obtained by Korotokoff sounds and noninvasive blood pressure equipment. Good agreement was obtained when the average of oximetry-based systolic blood pressure estimates at the disappearance and reappearance of the waveform were compared with Korotokoff sound pressures and noninvasive equipment pressures. Thus pulse oximetry can be used to measure systolic arterial blood pressure. This technique is specifically important for patients with Takayasu's syndrome (pulseless disease) where conventional techniques often fail to monitor systolic arterial blood pressure.

Adult↗
PubMed1992

Organization of repeated sequences in the region downstream to rRNA genes in the rDNA episome of Entamoeba histolytica.

The E. histolytica rDNA episome consists of a 3.7 kb HindIII fragment located downstream of the rDNA inverted repeats. We have determined the complete nucleotide sequence of this fragment and have shown that it is comprised of two families of short tandem repeats, the 170 bp DraI repeat and the 144 bp ScaI repeat. Each DraI repeat unit consists of 12-mer sequences with near complete homology to yeast consensus autonomously replicating sequence. In addition, a 21-mer subrepeat structure is also present in each unit. The sequence of the ScaI repeat is about 90% homologous with the sequence of another family of 145 bp tandem repeats, the PvuI repeats reported to be present upstream of the rRNA genes (3). Compared with most other parts of the rDNA episome, the downstream region showed frequent restriction fragment length polymorphism. This was due to changes in the number of tandem DraI repeat units. The loss of these repeats might explain how rDNA length heterogeneity observed in the clones of HM1:IMSS could have arisen. On the other hand, the number of ScaI repeat units in these clones remained unchanged. The repeat units found in the 3.7 kb HindIII fragment show superficial resemblance to equivalent regions of the intergenic spacers of higher eukaryotes. Moreover, these repeated sequences seem to be specific for the pathogenic strain of E. histolytica.

Animals↗
PubMed1992

The directional reflectance of the retinal nerve fiber layer of the toad.

Various optical methods for assessing the retinal nerve fiber layer (RNFL) depend on reflected light, but little is known about the characteristics of the RNFL as a reflecting structure. The authors investigated the angular dependence of light reflected by the unmyelinated nerve fibers of the toad eyecup using a small 500-nm light source that could illuminate the retina from various directions and a movable low-power microscope that imaged the retina onto a cooled charge-coupled device in a digital camera system. Measured areas had nerve fiber bundles separated by gaps. Therefore, the reflectance of a bundle alone could be determined from the difference in intensity between the bundle and an adjacent gap. The RNFL reflectance showed striking directional dependence; nerve fiber bundles seen when illuminated from one direction disappeared completely when illuminated from another. Light reflected by a bundle was confined to a conical sheet concentric with the axis of the bundle. The apex angle of the cone was twice the angle between the incident light and the bundle axis, and the orientation of the cone changed with the orientation of the RNFL. This behavior was consistent with the theory of light scattering by cylinders. Therefore, it was concluded that the RNFL reflectance arises from cylindric structures. These results have clinical significance for imaging the RNFL in the human eye because the apparent intensity of the RNFL will depend, not just on its thickness, but also on its orientation relative to the imaging system.

Animals↗
PubMed1991

Biochemical and immunological characterization of exometabolites from an Indian strain of Leishmania donovani promastigotes grown in a chemically defined medium.

Exometabolites (EXOM) of an Indian strain of Leishmania donovani promastigotes isolated from a chemically defined medium by ultrafiltration consisted of proteins, glycoproteins, lipid and lipophosphopolysaccharide (LPPS). LPPS of Mr 40-28 kDa in SDS-PAGE could be labelled metabolically with [32P]-phosphate and recovered in the aqueous phase of hot-phenol-water extraction of EXOM (PE-Aq) along with a glycoprotein of Mr 150-130 kDa (GP150-130). These two molecules could be eluted from DE-52 column with 200 mM NaCl (D2). The 300 mM NaCl (D3) and 400 mM NaCl (D4) eluates from DE-52 column contained one unsaturated polar lipid component. The LPPS had Rf value of 0.65-0.75 in Thin Layer Chromatography (TLC) using saturated phenol water solvent system. EXOM revealed 15 bands in SDS-PAGE of which proteins of Mr 84, 66, 56, 50 and 29 kDa were prominent. When EXOM were fractionated through Con A-Sepharose column, the fraction eluted with alpha-methyl-D-mannoside (Con A-E) had seven bands as revealed by SDS-PAGE of which 25, 16, 13 and 12 kDa glycoproteins were prominent. The antigens present in EXOM can be classified as slower anodic migrating and faster anodic migrating antigens as revealed by immunoelectrophoresis (IEP). The slower anodic migrating antigens, LPPS and GP150-130 recovered in PE-Aq and D2 did not cross-react with kala-azar patients' sera but cross-reacted with homologous anti-promastigote sera. Two faster anodic migrating antigens which could be recovered in organic phase of hot phenol extraction of EXOM (PE-O) and eluted in D3 and D4 and Con A-E, cross-reacted with kala-azar patients' sera. The antigens of both the classes were sensitive to periodic acid oxidation.

Animals↗
PubMed1991

Xenopus liver ferritin H subunit: cDNA sequence and mRNA production in the liver following estrogen treatment.

In vitro translation of liver mRNA from estrogen-treated Xenopus frogs yields two abundant polypeptides in the range of 20 kDa. DNA clones for one of these translation products were isolated and shown to be complementary to mRNA for the heavy subunit of ferritin. The predicted Xenopus amino acid sequence shares about 86% identity with the ferritin heavy chain from bullfrogs and about 70% identity with the comparable mammalian and avian proteins. Clone identity was confirmed by hybridization selection followed by in vitro translation into translation products of 19.5-20 kDa. The nearly full-length cDNA clone, termed XlferH1, comprises 868 nucleotides plus 22 adenosines of the poly(A) tail, including 134 nucleotides of the 5'-untranslated region, a 528-base coding region for 176 amino acids, and a 206-nucleotide 3'-untranslated region. The clone lacks 22 nucleotides from the 5' end of the mRNA. The level of ferritin mRNA in the liver of estrogen-treated frogs was determined over time. The amount of this mRNA relative to total RNA decreased about 3-fold 14 days after estradiol-17 beta was administered. However, the hormone also elevated total RNA in the liver about 24-fold. Hence, the total ferritin mRNA content of the liver increased to about 8 times its initial amount. This pattern of gene expression was very similar to that for serum retinol binding protein. The estrogen induction of these two mRNAs appeared to parallel the overall stimulation of hepatic RNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗