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Biomedical subjects

R Lal

Publications and source records attributed to R Lal.

At least 73 records · Page 4Linked to original sources
PubMed1997

Antifungal attributes of lactic acid bacteria--a review.

Molds constitute a very important contaminating flora of dairy products. Contamination with undesirable molds has been a serious and frequently disturbing problem in the dairy industry that results in huge losses due to spoilage of cheese and other fermented foods incriminated by a variety of mycoflora such as Aspergillus, Penicillium, Fusarium, Rhizopus, and Mucor. The considerable drop in pH caused by the growth of lactic acid bacteria (LAB) in fermented milk makes such foods a breeding ground for the highly opportunistic fungi to proliferate and thrive, spoiling the products and effecting cost and its commensurate accessories. The major antimicrobial substances isolated from the LAB are found effective against bacteria only and their inhibition toward the growth of contaminating bacteria has been explored in detail. However, studies on the fungistatic properties of LAB are relatively rare. This article reviews the investigative studies on the antifungal aspects of different lactic acid bacteria and the prospects of this exceptional trait as a potential food biopreservative.

Animals↗
PubMed1997

Interaction of synthetic pyrethroids with micro-organisms: a review.

Pyrethroids are widely used insecticides in agriculture and public health. They are photostable with high insecticidal activity and low toxicity to birds and mammals. At lower concentrations, they are less toxic, but have significant effects on micro-organisms at high concentrations. Pyrethroids constitute about 25% of the total pesticides used in the world and due to the restricted use of organochlorine insecticides, the application of pyrethroids is expected to increase. The present review deals with the interaction of pyrethroids with micro-organisms.

Bacteria↗
PubMed1996

Male-to-female transmission of human T-cell lymphotropic virus types I and II: association with viral load. The Retrovirus Epidemiology Donor Study Group.

SUMMARY: Risk factors for male-to-female sexual transmission of human T-lymphotropic virus types I and II (HTLV-I/II) were investigated among HTLV-seropositive volunteer blood donors and their long-term (> or = 6 month) sex partners. Direction of transmission in concordantly seropositive pairs was assessed by analyzing risk factors for HTLV infection. Donors and their partners were also questioned regarding sexual behaviors during their relationships; HTLV antibody titers and viral load were determined for specimens from male partners. Among 31 couples in whom HTLV-infected men likely transmitted infection to their partners (11 HTLV-I and 20 HTLV-II) and 25 male-positive, female-negative couples (8 HTLV-I and 17 HTLV-II), HTLV transmitter men had been in their relationships longer (mean 225 months vs. 122 months) and had higher viral loads (geometric mean 257,549 vs. 2,945 copies/300,000 cells for HTLV-I; 5,541 vs. 118 copies/300,000 cells for HTLV-II) than non-transmitters (P = 0.018 and P = 0.001 for duration of relationship and viral load, respectively, logistic regression analysis). Transmitter men also tended to have higher antibody titers against various env and whole virus proteins than non-transmitters. The identification of high viral load and duration of relationship as risk factors provides a biologically plausible framework in which to assess risk of sexual transmission of the HTLVs.

Adult↗
PubMed1996

Imaging the internal and external pore structure of membranes in fluid: TappingMode scanning ion conductance microscopy.

We have constructed a combined TappingMode atomic force microscope and scanning ion conductance microscope. The design is based on a bent glass pipette that acts as both the force sensor and conductance probe. Measuring the pipette deflection allows more stable feedback than possible with previous versions of the scanning ion conductance microscope. Using this microscope, we have imaged synthetic membranes in both contact and tapping modes under fluid. Although contact mode operation is possible, we found that our microscope provided higher contrast and less apparent sample damage in the topographic and ionic conductance images in the tapping mode.

Ions↗
PubMed1996

Genetic manipulations of microorganisms for the degradation of hexachlorocyclohexane.

Hexachlorocyclohexane (HCH) is an organochlorine insecticide which has been banned in technologically advanced countries. However, it is still in use in tropical countries for mosquito control and thus new areas continue to be contaminated. Anaerobic degradation of HCH isomers have been well documented but until recently there have been only a few reports on aerobic microbial degradation of HCH isomers. The isolation of these microbes made it possible to design experiments for the cloning of the catabolic genes responsible for degradation. We review the microbial degradation of HCH isomers coupled with the genetic manipulations of the catabolic genes. The first part discusses the persistence of residues in the environment and microbial degradation while the second part gives an account of the genetic manipulations of catabolic genes involved in the degradation.

Bacteria↗
PubMed1996

Engineering antibiotic producers to overcome the limitations of classical strain improvement programs.

Improvement of the antibiotic yield of industrial strains is invariably the main target of industry-oriented research. The approaches used in the past were rational selection, extensive mutagenesis, and biochemical screening. These approaches have their limitations, which are likely to be overcome by the judicious application of recombinant DNA techniques. Efficient cloning vectors and transformation systems have now become available even for antibiotic producers that were previously difficult to manipulate genetically. The genes responsible for antibiotic biosynthesis can now be easily isolated and manipulated. In the first half of this review article, the limitations of classical strain improvement programs and the development of recombinant DNA techniques for cloning and analyzing genes responsible for antibiotic biosynthesis are discussed. The second half of this article addresses some of the major achievements, including the development of genetically engineered microbes, especially with reference to beta-lactams, anthracyclines, and rifamycins.

Anthracyclines↗
PubMed1996

Molecular aspects of pesticide degradation by microorganisms.

Microorganisms are able to degrade a large variety of compounds, including pesticides under laboratory conditions. However, methods have yet to be developed to decontaminate the environment from residues of pesticides. Pesticidal degradative genes in microbes have been found to be located on plasmids, transposons, and/or on chromosomes. Recent studies have provided clues to the evolution of degradative pathways and the organization of catabolic genes, thus making it much easier to develop genetically engineered microbes for the purpose of decontamination. Genetic manipulation offers a way of engineering microorganisms to deal with a pollutant, including pesticides that may be present in the contaminated sites. The simplest approach is to extend the degradative capabilities of existing metabolic pathways within an organism either by introducing additional enzymes from other organisms or by modifying the specificity of the catabolic genes already present. Continuous efforts are required in this direction, and at present several bacteria capable of degrading pesticides have been isolated from the natural environment. Catabolic genes responsible for the degradation of several xenobiotics, including pesticides, have been identified, isolated, and cloned into various other organisms such as Streptomyces, algae, fungi, etc. In addition, recombinant DNA studies have made it possible to develop DNA probes that are being used to identify microbes from diverse environmental communities with an unique ability to degrade pesticides.

Ascomycota↗
PubMed1996

Spread of lymphatic filariasis, re-emergence of leishmaniasis & threat of babesiosis in India.

The impact of unabated population growth and consequent ecological changes is felt in the spread of vector-borne diseases also. Filariasis, once considered to be more associated with urban areas and urbanization, is rapidly emerging as a major problem in rural areas. The need to delimit the endemic areas through a new rapid assessment procedure and the possible control methods of rural filariasis are discussed. Leishmaniasis has re-emerged with a vengeance in some parts of the country and the reasons for this are analyzed. Babesiosis, though zoonotic, has the potential to invade the domain of man in India.

Animals↗
PubMed1996

Experience with roxithromycin in visceral leishmaniasis in north Bihar.

In search of an oral drug for Visceral Leishmaniasis, 54 cases of Kala-azar were treated with roxithromycin, an orally administrable drug at a dose of 300 mg twice daily for 21 days. Thirty-nine (86.7%) were responsive (cured), 11 (28.2%) relapsed. The results appeared equally or even more effective when compared to the sodium antimony gluconate in two recent trials in Kala-azar in almost same demographic pattern. A possible synergistic action of roxithromycin and SAG was explored. Toxicities of SAG and roxithromycin are compared and discussed. Further controlled trials are needed before it can be widely used as first line drug for Indian Kala-azar in the present epidemic.

Administration, Oral↗
PubMed1996

Imaging molecular structure of channels and receptors with an atomic force microscope.

Biological membranes contain specialized protein macromolecules such as channels, pumps and receptors. Physiologically, membranes and their constituent macromolecules are the interface surfaces toward which most of the regulatory biochemical and other signals are directed. Yet very little is known about these surfaces. The structure of biological membranes has been analyzed primarily using imaging techniques that are limited in their resolution of surface topology. An atomic force microscope (AFM) developed by Binnig, Quate and Gerber, can image molecular structures on specimen surfaces with subnanometer resolution, under diverse environmental conditions. Also, AFM can manipulate surfaces with molecular precision: it can nanodissect, translocate, and reorganize molecules on surface. The surface topology has been imaged for several hydrated channels, pumps and receptors which were a) present in isolated native membranes, b) reconstituted in artificial membrane or, c) expressed in an appropriate expression system. These images, at molecular resolution, reveal exciting new findings about their architecture. AFM induced "force dissection" reveals surfaces which are commonly inaccessible. In whole cell studies, in addition to the molecular structure of membrane receptors and channels, correlative electrical and biochemical activities have been examined. Such study suggests a "single cell" experiment where the structure-function correlation of many cloned channels and receptors can be understood.

Animals↗
PubMed1995

The application of atomic force microscopy for the detection of microcrystals in synovial fluid from patients with recurrent synovitis.

Synovial fluid from 33 patients with inflammatory arthritis was examined with a polarized light microscope (PLM) and an atomic force microscope (AFM). Two samples were imaged with a transmission electron microscope (TEM) to determine calcium/phosphate ratios and identify microcrystals of calcium pyrophosphate dihydrate and octacalcium phosphate. Additional correlative x-ray diffraction studies were performed on several samples including purified hydroxyapatite and sodium chloride crystals. Monosodium urate, calcium pyrophosphate dihydrate, hydroxyapatite, octacalcium phosphate, and cholesterol crystals were identified with AFM. AFM images of these microcrystals revealed detailed surface topology, including lattice parameters and structural irregularities at the crystals' surface. These features were consistent with those obtained by TEM and x-ray diffraction studies. In addition, AFM images revealed that some specimens contained microcrystals that were undetected by PLM and/or TEM. These results suggest that AFM may provide a simple yet powerful technique for the detection of microcrystals in synovial fluid taken from patients with crystal-induced arthritis.

Arthritis↗