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Biomedical subjects

M Ghosh

Publications and source records attributed to M Ghosh.

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

CYP3A gene expression in human gut epithelium.

CYP3A4, a major Phase I xenobiotic metabolizing enzyme present in liver, is also present in human small bowel epithelium where it appears to catalyse significant 'first pass' metabolism of some drugs. To determine whether CYP3A4 or the related enzymes CYP3A3, CYP3A5, and CYP3A7 are present in other regions of the digestive tract, we used CYP3A-specific antibodies to examine histological sections and epithelial microsomes obtained from a human organ donor. CYP3A-related proteins were detected in epithelia throughout the digestive tract and in gastric parietal cells, in pericentral hepatocytes, and in ductular cells of the pancreas. Immunoblot analysis suggested that the major CYP3A protein present in liver, jejunum, colon, and pancreas was CYP3A4 or CYP3A3, whereas CYP3A5 was the major protein present in stomach. Both CYP3A4 and CYP3A5 mRNA were detectable in all regions of the digestive tract using the polymerase chain reaction (PCR); however, only CYP3A4 could be detected by Northern blot analysis. CYP3A7 mRNA was consistently detected only in the liver by PCR and CYP3A3 mRNA was not detected in any of the tissues. We conclude that CYP3A4 and CYP3A5 are present throughout the human digestive tract and that differences in the expression of these enzymes may account for inter-organ differences in the metabolism of CYP3A substrates.

Adult↗
PubMed1994

Purification and some properties of a xylanase from Aspergillus sydowii MG49.

Aspergillus sydowii MG49 produces a 30-kDa exosplitting xylobiohydrolase during growth on xylan. A specific chemical modification and substrate protection analysis of purified xylanase provided evidence that tryptophan and carboxy and amino groups are present at the catalytic site of this enzyme. Thermal inactivation of the xylanase occurs because of irreversible polymolecular aggregation, which is slower in the presence of glycerol.

Aspergillus↗
PubMed1994

Embryonic fat-cell lineage in Drosophila melanogaster.

The Drosophila adipose tissue, or fat body, and the bodywall muscle are two major tissues derived from the mesoderm. Although much is known about the lineage of muscle cells, little is known about the development of the fat body. Using known genes and an enhancer trap (29D), we have begun to trace the lineage of the cells comprising the fat body. The genes Adh (alcohol dehydrogenase) and DCg1 (type IV collagen) code for gene products involved in fat-cell metabolism and therefore serve as terminal fat-cell differentiation markers. The expression of these genes was used to identify the fat body at stage 17 and to identify the start of terminal fat-cell differentiation at stage 15. We found that the steroid-hormone receptor gene, svp (seven-up), was expressed transiently within the fat-cell lineage from stages 12 to 14. We suggest that stage 12 marks the beginning of early fat-cell differentiation and that the svp-positive cells within the mesoderm are early precursor fat cells. To confirm the identity of these cells and to establish the role of svp in the developing fat cell, we examined svp mutant embryos for alterations in the expression of the two terminal fat-cell differentiation markers, Adh and DCg1. Loss of svp function resulted in the loss of Adh transcript and a reduction of DCg1 expression specifically in the fat body. Thus, svp plays a role in fat-body-specific expression of at least two terminal fat-cell differentiation genes. In contrast to svp, we found no evidence that the steroid receptor HNF-4(D) gene was expressed in the fat body nor that it was involved in the development of this tissue. Using an enhancer-trap line (29D), we further traced the fat-cell lineage to nine bilateral clusters of cells within the mesoderm at germ-band extension. We suggest these 29D-positive cells represent the progenitor fat cells. In stage-12 embryos, the 29D-positive cell clusters can be identified within the mesoderm internal to nautilus-expressing cells. These data suggest that the precursor fat cells may be derived from the inner mesoderm, or spanchnopleura. Embryos deficient for the DNA region surrounding the site of the 29D enhancer trap lack most, if not all, of the cells in the fat-cell lineage. These embryos exhibit the loss of svp-positive precursor fat cells and concomitant loss of fat-body-specific expression of Adh and DCg1.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1994

Some hitherto unreported findings on the extragenital effects of progesterone in human females--a clinical study.

40 women suffering from 'dysfunctional uterine bleeding' (DUB) were treated by progesterone (P) and signs and symptoms of 'extragenital effects' of P were noted. In addition to the previous ones reported from this laboratory, a new crop of effects, which, as far as we are aware of, have never been reported in the literature, were found and included: (i) Changes in the frequency of EEG waves, (ii) changes in the ECG (iii) changes in psychoanalytical scoring. Further (iv) with most of the parametres, the intensity of the changes showed considerable waning with passage time, despite the fact that the subjects were still receiving P. Blood P levels similarly fell considerably in the initial phase of the therapy, but recovered to some extent afterwards, despite the continuance of P therapy.

Administration, Oral↗
PubMed1993

Thermostability of beta-xylosidase from Aspergillus sydowii MG49.

Heating of Aspergillus beta-xylosidase at 85 degrees C +/- 1 degree C and pH 5.5-6.0 (optimum for activity), causes irreversible, covalent thermoinactivation of the enzyme, involving oxidation of the thiol groups that are required for catalysis. Exogenous addition of cysteine, DTT, GSH and mercaptoethanol stabilizes the enzyme by extending its half-life. A similar effect is also exhibited by bivalent cations like Mg2+, Mn2+, Co2+, Ca2+ and Zn2+ while, on the other hand Cu2+ accelerates thermoinactivation. Chemical modification of crude beta-xylosidase with cross-linking agents like glutaraldehyde or covalent immobilization to a nonspecific protein like gelatin and BSA also enhances enzyme thermostability. These results suggest that addition of thiols and bivalent metal ions to a crude beta-xylosidase preparation or immobilization/chemical modification enhances its thermal stability, thus preventing loss of catalytic activity at elevated temperatures.

Aspergillus↗
PubMed1993

Sequence of the algL gene of Pseudomonas aeruginosa and purification of its alginate lyase product.

The alginate lyase-encoding gene (algL) of Pseudomonas aeruginosa was localized to a 1.7-kb EcoRI-XbaI fragment within the alginate biosynthetic gene cluster at 34 minutes on the chromosome. The nucleotide sequence of this DNA fragment revealed an ORF encoding a protein of M(r) 40,885 which is transcribed in the same orientation as the other alg genes within the biosynthetic gene cluster. The predicted protein has a potential N-terminal signal peptide which is consistent with its proposed periplasmic location. The AlgL protein was overproduced in Escherichia coli and purified. The purified protein was shown to have alginate lyase activity. In addition, an algL insertion mutant of the mucoid P. aeruginosa 8830 was constructed. This mutant (alm1) had a nonmucoid phenotype due to a polar effect on the transcription of an essential alg gene, algA. Thus, the algL gene is located within a region of the alginate biosynthetic gene cluster that appears to be non-essential for alginate production.

Alginates↗
PubMed1993

Cultured adult rat jejunal explants as a model for studying regulation of CYP3A.

Enzymes within the CYP3A subfamily are major Phase I drug-metabolizing enzymes present in hepatocytes and small bowel enterocytes. These enzymes are highly inducible in the liver by many structurally diverse compounds, including a number of commonly used medications. Studies indicate that CYP3A enzymes present in small bowel enterocytes are also inducible. However, the regulation of CYP3A enzymes in this tissue has not been well characterized, in part because in vivo studies are difficult, especially in humans. Our goals was to develop an in vitro model to study the regulation of CYP3A in enterocytes. To this end, we defined culture conditions under which adult rat jejunal explants maintained viable appearing villi for 21 hr. When dexamethasone, the prototypical inducer of CYP3A1 in rat hepatocytes, was added to the culture medium, there was a time-dependent induction of CYP3A1 mRNA and CYP3A protein in explant enterocytes which was essentially indistinguishable from the time course of induction of CYP3A1 mRNA and protein in enterocytes in vivo. This effect of dexamethasone appeared to be specific since dexamethasone had no consistent effect on the explant concentration of another enterocyte specific mRNA, intestinal fatty acid binding protein. Using this explant culture model, we found that CYP3A1 mRNA was also inducible by clotrimazole but we were unable to detect induction by rifampicin or troleandomycin. Our observations suggest that jejunal explants may provide an appropriate model for the study of the regulation of CYP3A and other drug-metabolizing enzymes.

Animals↗
PubMed1993

Evaluation of 'cypenhymustine', a new anticancer compound, in murine tumour models.

'Cypenhymustine', 3-[2-[bis(2'-chloroethyl)-amino] ethyl]-5,5- tetramethylenehydantoin, has been synthesised as a potential analog of spiromustine (NSC 172112). The LD50 value was determined in Swiss male mice and found to be 65.0 mg/kg by single i.p. injection. In in vivo screening experiments, three parameters, namely, ascites cell count, ascites fluid measurement and increase in life span (ILS) of drug-treated over control Swiss mice were studied in three murine ascites tumours namely Ehrlich ascites carcinoma (EAC), sarcoma-180 (S-180) and Dalton's lymphoma (DL). Cypenhymustine exhibited a very high percentage of inhibition of both the ascites cell and fluid in these models and also displayed excellent reproducible ILS activity (ILS values of 151 in EAC, 157 in S-180 and 181 in DL at the optimum dose of 3 mg/kg for days 1-7 treatment following tumour transplant on day 0) having a 'curative' effect (1-2 animals: 6 having > 60 days survival rate). The chemical alkylating activity has been compared with spiromustine and another antitumour agent namely nor-HN2.

Animals↗
PubMed1993

Targeting of antisense DNA: comparison of activity of anti-rabbit beta-globin oligodeoxyribonucleoside phosphorothioates with computer predictions of mRNA folding.

To assess the usefulness of computer-assisted modeling of mRNA as an aid in design of antisense DNA, the efficiency of inhibition of translation of rabbit beta-globin mRNA by various antisense sequences was compared with calculated structures of the mRNA. The model obtained by consideration of 30 lowest-energy computer-simulated structures is consistent with the high accessibility of the AUG initiation codon region known from digestion with nucleases and with previous antisense inhibition studies reported in the literature. Additional antisense inhibition data were obtained with 20-mer phosphorothioate oligonucleotides, targeted to regions of beta-globin mRNA differing moderately in their degree of participation in intramolecular folding. The efficiency of translation arrest by the oligonucleotides in cell-free expression systems (wheat germ extract and rabbit reticulocyte lysate) was obtained by measuring incorporation of [35S]methionine into total protein, and corrected for sequence-nonspecific inhibition using brome mosaic virus mRNA. In the presence of RNase H (wheat germ system), the inhibitory activity of the oligonucleotides showed correlation with the calculated secondary structure of mRNA, in particular at low oligonucleotide-to-mRNA ratios (correlation coefficient, 0.95). No correlation was observed in the reticulocyte lysate system, in which the inhibition is mediated by translational arrest.

Animals↗
PubMed1993

Nucleotide sequence and expression of the Pseudomonas aeruginosa algF gene controlling acetylation of alginate.

Colonization of the cystic fibrosis lung by Pseudomonas aeruginosa is greatly facilitated by the production of an exopolysaccharide called alginate. In this study we determined the nucleotide sequence of an alginate modification gene, algF, which controls the addition of acetyl groups to alginate. Expression of algF using a T7 promoter-expression system showed that algF codes for a 24.5 kDa polypeptide (predicted size 22,832 Da) that is processed to 19.5 kDa. The N-terminus of the processed polypeptide matched the predicted amino acid sequence of AlgF starting at Asp-29. An algF mutant failed to produce alginate owing to a polar effect on the downstream algA gene. Although the algA gene, provided in trans, restored synthesis of alginate, the alginate was non-acetylated. We show that a plasmid containing both the algF and algA gene complements the alginate acetylation defect of the algF mutant strain.

Acetylation↗
PubMed1993

Antifilarial effect of two triterpenoid saponins isolated from Acacia auriculiformis.

The active principle, isolated from the funicles of A. auriculiformis, consisted of two triterpenoid saponins, acaciaside A and acaciaside B which killed in vitro 97% microfilaria of Setaria cervi in 100 min at 4mg/ml concentration and 100% of adults in 35 min. The drug, when administered orally at 100 mg/kg on rats, in which S. cervi adults were implanted intra-peritoneally, increased the blood mf count by 1.5-fold after the first phase of treatment for 10 days. Following the third phase of treatment and thereafter, the mf density was reduced by more than 80%. No toxic effect of the saponins was observed in rats. The rise in mf count indicated that the drug induced a very high physiological stress on the adult worms which increased the rate of discharge of the mf before impending death. The treated rats on autopsy did not show any adult worms.

Acacia↗
PubMed1993

Utilization of maternal services in west Bengal.

A study was conducted in selected blocks of West Bengal to assess the utilization of available maternal health services specially immunization, antenatal care and other services. Coverage with two doses of tetanus toxoid levels varied between 58.6 to 86.7% but it fell far short of Universal Immunization Programme target of 100%. Drop out rates were slightly higher in the rural areas. It was observed that in 5 out of 7 blocks more than 55% of the deliveries were conducted either at hospital or Primary Health Centre by health personnel. However, untrained dais predominated over the trained dais in conducting deliveries in most of the areas. This indicates the poor availability or utilization of the latter.

Female↗
PubMed1992

Crystallization and preliminary crystallographic investigation of methanol dehydrogenase from Methylobacterium extorquens AM1.

Single crystals of methanol dehydrogenase (MDH) from Methylobacterium extorquens AM1 have been grown by the vapour diffusion method. These crystals diffract to beyond 2 A resolution and are suitable for X-ray crystallography. They belong to the orthorhombic space group P2(1)2(1)2(1) and have the following unit cell parameters: a = 66.79 A, b = 108.9 A, c = 188.9 A. One asymmetric unit contains an alpha 2 beta 2 tetramer of MDH and the location of the non-crystallographic 2-fold symmetry axis of this tetramer is defined by the paired positions of the binding sites of heavy atoms in four MDH-derivatives.

Alcohol Oxidoreductases↗
PubMed1991

Crystallization and preliminary crystallographic study of cathepsin D inhibitor from potatoes.

Single crystals of the glycosylated inhibitor of cathepsin D and trypsin isolated from potato tubers were obtained using the hanging drop vapor diffusion method and ammonium nitrate as precipitant. The crystals exhibit strong F222 pseudo symmetry but belong to the orthorhombic space group C222 or C222(1), with cell parameters a = 73.8 A, b = 119.9 A and c = 133.2 A with two molecules per asymmetric unit. The crystals diffract to a resolution of 2.4 A.

Cathepsin D↗
PubMed1991

Oligodeoxynucleotide analogs as informational drugs to regulate translation.

Of the chemically modified backbone analogs of oligodeoxynucleotides that have been developed for antisense applications, the phosphorothioate (PS) analog has perhaps the best properties. Nevertheless, it also has certain disadvantages, notably reduced hybridization and increased non-selective inhibition of translation, compared to the natural phosphodiester (PO) compounds. We have therefore synthesized and characterized a series of co-polymers, with the same antisense beta-globin sequence, but with different repeated sequences of PO and PS and tested them for their comparative properties. The results indicate that a PO-PS co-polymer is the best backbone modification for an antisense compound.

Animals↗
PubMed1991

Serum sialic acid, fucose, sialic acid/fucose ratio as tumor markers in oral cancer.

To our knowledge, no study has been undertaken before by any researcher as to the direction of content of the components of serum glycoproteins simultaneously as well as their ratios in oral cancer patients. The aim of the present paper is to establish the direct relationship between fucose and sialic acid levels in the sera of such patients. The biochemical levels were studied among 37 oral cancer patients and were compared with 15 controls.

Biomarkers, Tumor↗