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Biomedical subjects

A C Ghosh

Publications and source records attributed to A C Ghosh.

At least 19 recordsLinked to original sources
PubMed2002

Growth behaviour and bioproduction of indole acetic acid by a Rhizobium sp. isolated from root nodules of a leguminous tree Dalbergia lanceolaria.

The Rhizobium sp. isolated from healthy and mature root nodules of a leguminous tree, Dalbergia lanceolaria Linn. f., preferred mannitol and KNO3 for growth as carbon and nitrogen sources, respectively. The bacterium produced a high amount (22.3 microg/ml) of indole acetic acid (IAA) from L-tryptophan supplemented basal medium. Growth and IAA production started simultaneously. IAA production was maximum at 20 hr when the bacteria reached the stationary phase of growth. Cultural requirements were optimized for maximum growth and IAA production. The IAA production by the Rhizobium sp. was increased by 270.8% over control when the medium was supplemented with mannitol (1%,w/v), SDS (1 microg/ml), L-asparagine (0.02%,w/v) and biotin (1 microg/ml) in addition to L-tryptophan (2.5 mg/ml). The possible role of IAA production in the symbiosis is discussed.

Fabaceae↗
PubMed2001

Advances in cancer therapy with plant based natural products.

Natural Products have long been a fertile source of cure for cancer, which is projected to become the major causes of death in this century. However, there is a continuing need for development of new anticancer drugs, drug combinations and chemotherapy strategies, by methodical and scientific exploration of enormous pool of synthetic, biological and natural products. There are at least 250,000 species of plants out of which more than one thousand plants have been found to possess significant anticancer properties. While many molecules obtained from nature have shown wonders, there are a huge number of molecules that still either remains to be trapped or studied in details by the medicinal chemists. The article reviews many such structures and their related chemistry along with the recent advances in understanding mechanism of action and structure-function relationships of nature derived anti-cancer agents at the molecular, cellular and physiological levels. Taxol, one of the most outstanding agents, has been found beneficial in treatment of refractory ovarian, breast and other cancers. Another prominent molecule includes Podophyllotoxin. Synthetic modification of this molecule led to the development of Etoposide, known to be effective for small cell cancers of the lungs and testes. Camptothecin isolated from Camptotheca acuminata also have been extensively studied. Other important molecules discussed include Vincristine, Vinblastine, Colchicine, Ellipticine and Lepachol along with Flavopiridol, a semi-synthetic analogue of the chromone alkaloid Rohitukine from India, a pyridoindole alkaloid from leaves of Ochrosia species and many more. The review also deals with the lesser-known plants of sub-Himalayan region.

Humans↗
PubMed2001

Extracellular polysaccharide production by Azorhizobium caulinodans from stem nodules of leguminous emergent hydrophyte Aeschynomene aspera.

The Azorhizobium caulinodans isolated from the stem nodules of a leguminous emergent hydrophyte, Aeschynomene aspera, produced a large amount of extracellular polysaccharides (EPS) in yeast extract basal medium. Maximum EPS production was at the stationary phase of growth. EPS production was increased by 919% over control when the medium was supplemented with sucrose (1.5%), D-biotin (1 microgram/ml) and casamino acid (0.1%). EPS contained rhamnose and arabinose. Possible role of the azorhizobial EPS production in the stem nodule symbiosis is discussed.

Fabaceae↗
PubMed1998

In vitro transformation of ampicillin to cephalexin by free and immobilized cells of Streptomyces sp.

In vitro transformation of ampicillin to cephalexin was studied using calcium alginate-immobilized and free Streptomyces sp. strain DRS-1 packed in glass columns. Tris-HCl buffer containing ampicillin was continuously circulated through the columns for four cycles, each cycle (with fresh ampicillin) being continued for 5 h. The pattern of product formation was identical in both cases, i.e. in each cycle, after reaching a certain concentration, its formation did not increase. Product formation was always higher with immobilized cells. Conversion of ampicillin to cephalexin by the strain was affected by cell and substrate concentration.

Alginates↗
PubMed1998

Indole acetic acid and its metabolism in root nodules of a monocotyledonous tree Roystonea regia.

A monocotyledonous tree, Roystonea regia, was found to bear root nodules. The root nodules contained a high amount (16.9 microg/g fresh mass) of indole acetic acid (IAA). A big tryptophan pool (1555.1 microg/g fresh mass) was found in the root nodules, which might serve as a source of IAA production. The presence of IAA-metabolizing enzymes IAA oxidase and peroxidase indicated metabolism of IAA in the root nodules. The symbiont isolated from the root nodules of R. regia, a Rhizobium sp., produced high amount of IAA in culture when supplemented with tryptophan. The possible role of this IAA production in the monocotyledonous tree-Rhizobium symbiosis is discussed.

Catechol Oxidase↗
PubMed1997

Characterization of Streptomyces sp. strain DRS-1 and its ampicillin transformation product.

Incubation of ampicillin with whole cells of Streptomyces sp. DRS-1 resulted in accumulation of four compounds different from ampicillin. One of them was isolated, purified and partially characterized. On the basis of spectroscopic characteristics, RF value and antibacterial activity the compound was identified as cephalexin. It could also be obtained from ampicillin by using crude protein extract of the strain.

Ampicillin↗
PubMed1997

Extraction and purification of cephalosporin antibiotics.

The biologically active natural and semisynthetic cephalosporin antibiotics require proper methods of extraction and purification for their isolation and subsequent pharmacological studies. This article reviews the various methods useful for extraction and purification of individual compounds as well as the enzymes involved in their biosynthesis. Applicability of the methods for downstream processing of the spent medium has been critically analysed. Adsorption chromatography, particularly with reverse phase materials, in combination with membrane separation is the most successful technique for extraction as well as purification of most of the enzymes and individual compounds. Techniques such as reactive extraction in liquid membrane, non-dispersive extraction in hollow fiber membrane and aqueous two-phase extraction are likely to emerge in new generation processes. Finally, some aspects of process design and scale-up have been discussed, highlighting the research needs of pragmatic importance.

Cell Extracts↗
PubMed1997

Multiple antibiotic resistance (MAR) index and its reversion in Pseudomonas aeruginosa.

The MAR indexes of hospital isolates of Pseudomonas aeruginosa were determined with reference to nine different cephalosporins. The values for all the strains were higher than 0.2 suggesting their origin from a high risk source of contamination where antibiotics are often used. Emergence of MAR pathogenic strains of Ps. aeruginosa indicated possible nosocomial infection in the hospital environment. beta-Lactamases produced by these organisms were tested and their inhibition by clavulanic acid was studied. beta-Lactamase produced by one of these strains (Ps-1) could not be inhibited by clavulanic acid whereas beta-lactamases of three other strains (Ps-2, Ps-3 and Ps-4) could be inhibited by clavulanic acid in the presence of cephalosporins, suggesting a possible use of clavulanic acid in combination with cephalosporins, to combat beta-lactamase induced resistance in Ps. aeruginosa.

Anti-Bacterial Agents↗
PubMed1996

Steroid transformation by mutants of Mycobacterium sp. with altered response to antibiotics.

Mycobacterium sp. NRRLB3683 which is capable to convert beta-sitosterol to 1,4-androstadiene-3,17-dione (ADD) was treated with methyl methane sulfonate and two strains with altered sensitivity to various antibiotics were obtained. One of the strain was steroid 1(2)-dehydrogenase negative and the other positive. Efficiency of utilization of sterols followed the order beta-sitosterol > cholesterol > soluble cholesterol. The steroid 1(2)-dehydrogenase negative strain was capable of producing 17KS (AD) from beta-sitosterol and converting AD to testosterone and ADD to AD suggesting the negative role of 1(2)-dehydrogenase in sterol side chain cleavage and decrease in hydrogenase activity by mutation. But this enzyme can perform the reverse reaction under aerobic condition.

Androstenedione↗
PubMed1996

Lipid and fatty acid composition of muga silkworm, Antheraea assama, host plants in relation to silkworm growth.

The lipid and fatty acid composition of the leaves (tender, medium and mature) of muga host plants, Machilus bombycina, Litsaea monopetala (primary food plants) and L. cubeba and L. salicifolia (family: Lauraceae) (secondary food plants) was investigated by standard procedures, gas chromatography after saponification and esterification. The total lipid content of M. bombycina and L. monopetala leaves was recorded to be higher (16 and 18 g%), respectively, than that of L. cubeba (10 g%) and L. salicifolia (12 g%). GC analysis identified the presence of eight fatty acids (C14 to C22) and the concentration varied from 0.0297 to 8.1572 g% dry leaf powder. Among the fatty acids, (C14 to C22), polyunsaturated fatty acids were recorded to be highest in concentration in mature leaves of the primary host plants. The concentrations of saturated and polyunsatuated fatty acids were found to be at a minimum level in all the types of leaves of secondary muga host plants.

Animals↗
PubMed1996

Developments in liquid membrane separation of beta-lactam antibiotics.

This paper presents an overview on the developments in liquid membrane separation and purification of commercially important beta-lactam antibiotics. Reactive extraction via liquid-liquid ion exchange or ion-pair extraction mechanism can be exploited to develop liquid membrane processes for separation and concentration of penicillins and cephalosporins. Because of high selectivity and flux, liquid membrane processes can be adopted for direct extraction of beta-lactams from fermentation broth. Other advantages of liquid membrane technologies are low capital and operating costs, compact unit installation in commercial plants, low material inventory, etc. Both emulsion liquid membrane and supported liquid membrane techniques can be effective under the reactive extraction conditions. However, the stability problems of liquid membrane should be resolved before commercial application can be established. Alternately, reactive extraction in non-dispersive mode with hollow fiber membranes can be an attractive and viable strategy for practical application. Applicability of the liquid membrane processes has been discussed from process engineering and design considerations.

Amines↗
PubMed1980

Laboratory induced variations in a standardized Salmonella isolation method.

Four microbiologists from four European laboratories came together to a single laboratory for two weeks and during that period examined 100 samples of minced meat artificially contaminated with salmonellae and 100 naturally contaminated samples using a standardized technique. No significant differences were found between the results obtained by the different analysts with 92 to 97 of the artificially contaminated and 30 to 42 of the naturally contaminated samples being found positive. Over a further period of eight weeks, these analysts examined the same number of samples in their own laboratories again using an identical procedure. There were no significant containing approximately 100 salmonellae per gram but significant differences (43 to 93) were found in isolation rates from the artificially contaminated samples copntaining approximately 1 salmonella per gram. The differences in findings between the first and the second part of the experiments may have been caused fairly by variations in media preparation, temperature of incubators, storage conditions of media and thawing conditions of samples etc., and secondly by differences in working conditions such as performing only one task during two weeks in contrast to examining the samples as part of the daily routine. At high levels of contamination, these factors do not appear to have an important influence on the performance of a laboratory.

Animals↗
PubMed1979

Mass spectrometric peptide sequencing: cyclochlorotine.

A potent toxin isolated from Penicillium islandicum Sopp was found to have the composition C24H31N5O7Cl2. Mass spectrometric investigation of a partial acid hydrolyzate showed that it has the structure of cyclochlorotine. The mass spectral characteristics of polyamino alcohol-related derivatives of peptides containing beta-phenylalanine, alpha-amino butyric acid and dichloroproline were determined in the course of this work.

Amino Acid Sequence↗
PubMed1978

Infant botulism in England.

A 24-week-old girl presented with an acute illness characterised by constipation at 22 weeks, followed a week later by the sudden onset of generalised weakness, poor feeding, and a weak cry. Laboratory examination of her stools confirmed the clinical diagnosis of infant botulism.

Acute Disease↗