PubMed Health⌕ Search

Biomedical subjects

R Lal

Publications and source records attributed to R Lal.

At least 19 recordsLinked to original sources
PubMed1998

Amyloid beta protein-(1-42) forms calcium-permeable, Zn2+-sensitive channel.

Amyloid beta protein (AbetaP) forms senile plaques in the brain of the patients with Alzheimer's disease. The early-onset AD has been correlated with an increased level of 42-residue AbetaP (AbetaP1-42). However, very little is known about the role of AbetaP1-42 in such pathology. We have examined the activity of AbetaP1-42 reconstituted in phospholipid vesicles. Vesicles reconstituted with AbetaP show strong immunofluorescence labeling with an antibody raised against an extracellular domain of AbetaP suggesting the incorporation of AbetaP peptide in the vesicular membrane. Vesicles reconstituted with AbetaP showed a significant level of 45Ca2+ uptake. The 45Ca2+ uptake was inhibited by (i) a monoclonal antibody raised against the N-terminal region of AbetaP, (ii) Tris, and (iii) Zn2+. However, reducing agents Trolox and dithiothreitol did not inhibit the 45Ca2+ uptake, indicating that the oxidation of AbetaP or its surrounding lipid molecules is not directly involved in the AbetaP-mediated Ca2+ uptake. An atomic force microscope was used to image the structure and physical properties of these vesicles. Vesicles ranged from 0.5 to 1 microm in diameter. The stiffness of the AbetaP-containing vesicles was significantly higher in the presence of calcium. The stiffness change was prevented in the presence of zinc, Tris, and anti-AbetaP antibody but not in the presence of Trolox and dithiothreitol. Thus the stiffness change is consistent with the vesicular uptake of Ca2+. These findings provide biochemical and structural evidence that AbetaP1-42 forms calcium-permeable channels and thus may induce cellular toxicity by regulating the calcium homeostasis in Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1998

Upper-tract changes after treatment of posterior urethral valves.

This paper discusses the long-term sequelae in the upper urinary tract with respect to hydroureteronephrosis (HUN), vesicoureteral reflux (VUR), renal parenchymal disease, and their correlation with renal function in 84 boys with posterior urethral valves followed for 1 to 21 years. Thirty-one boys (39.3%) were adolescents or older at the time of review. The incidence of high-grade VUR (grade III or more) was 47.6% at presentation, and resolution following decompression of the lower urinary tract occurred in 38.7% of refluxing units. VUR was associated with a high incidence of chronic renal failure (CRF) (30%) on long-term follow up; however, 16% of non-refluxing patients also progressed to CRF. The incidences of renal parenchymal disease and persistent upper-tract dilatation in the non-refluxing group were 25% and 50% of renal units respectively. Gross HUN persisted in 12.3% of patients despite decompression and reconstructive surgery, with vesicoureteral junction (VUJ) obstruction being documented in 1 patient only. Moderate and mild upper-tract dilatation persisted in 31.6% and 43.9% of patients, respectively. Persistent gross HUN was associated with a very high incidence of CRF (92.3%), while 88.4% of those with persistent mild/moderate dilatation maintained normal renal function over a follow-up period ranging from 1 to 21 years. This study emphasizes the need for systematic evaluation to exclude VUJ obstruction and abnormal urodynamics as a cause of persistent HUN so that effective therapy can be instituted early to relieve back-pressure and to provide a low-pressure reservoir with effective emptying. In the absence of either of these causes, persistent ureterectasis after treatment is presumably due to secondary peristaltic failure as a consequence of ureteral fibrosis, ureteral tortuosity, or developmental dysplasia.

Adolescent↗
PubMed1998

Urethral strictures after fulguration of posterior urethral valves.

This report discusses the incidence and predisposing factors for postfulguration urethral strictures in 82 boys with posterior urethral valves treated over 20 years and followed up for a period ranging from 1 to 21 years. A urethral stricture developed in three of the 82 patients (3.6%). All newborns and infants with small urethral caliber at presentation were treated on a temporary tubeless diversion, and fulguration of the valves was deferred until 9 to 12 months of age. A 9F resectoscope with a loop electrode was used to fulgurate at 5, 7, and 12 o'clock positions. A definite technical factor leading to a stricture could be identified in one of these three patients. Comparison of the "stricture" group with the "no stricture" group suggested that although dry fulguration did not have a definite correlation with stricture formation, it is best avoided. Refulguration and properly managed preoperative catheterization did not predispose to stricture formation. Meticulous surgical technique and avoiding oversized instrumentation were the most important factors for preventing this complication.

Adolescent↗
PubMed1998

Development of an improved cloning vector and transformation system in Amycolatopsis mediterranei (Nocardia mediterranei).

A versatile plasmid cloning vector pRL60 carrying kanamycin/neomycin resistance (km/neo), erythromycin resistance (ermE) and alpha-amylase (alpha-amy) marker genes that replicates in various Amycolatopsis mediterranei strains and Escherichia coli has been constructed. This cloning vector has been derived from a hybrid plasmid pRL50, which was developed by cloning ermE from pIJ4026 into a pRL1 derivative pULAM2. While cloning ermE into the BamHI site of pULAM2, only a hybrid plasmid pRL50 with an additional copy of pULAM2 was selected. Thus pRL50 (18.7 kb) contained two copies each of the km/neo, alpha-amy, and one copy of ermE. When pRL50 was transformed into A. mediterranei DSM 40773 through electroporation and selected under erythromycin resistance, the plasmid underwent a spontaneous deletion of 8.5 kb fragment resulting in the formation of plasmid pRL60. pRL60 (10.2 kb) is a shuttle vector between A. mediterranei and E. coli with three marker genes: km/neo, ermE and alpha-amy. ermE is expressed in A. mediterranei thus allowing good selection of transformants. The alpha-amy gene of pRL60 is also expressed in A. mediterranei DSM 40773 and its activity can be easily detected on starch containing medium after iodine staining. Most critical parameters evaluated for electrotransformation using pRL60 in A. mediterranei were growth phase, electrical field strength, pulse length, pretreatment of mycelia with lysozyme and use of salt free water. At optimized parameters, a transformation efficiency of 4.0 x 10(4) transformants/microg DNA was reproducibly achieved for A. mediterranei DSM 40773. pRL60 could also be transformed into A. mediterranei DSM 43304, DSM 46095, MTCC-17 and in mutants F1/24 and T-195, (derived from an industrial strain of A. mediterranei N813). The alpha-amy of pRL60 conferred an amylolytic phenotype to all these strains. With the development of pRL60 and a reproducible transformation protocol, the application of recombinant DNA techniques to these industrial microorganisms has now become feasible.

Actinobacteria↗
PubMed1997

Atomic force microscopy of arthropod gap junctions.

Atomic force microscopy has been used to characterize gap junctions isolated from the hepatopancreas of Nephrops norvegicus. The major polypeptide of these gap junctions is ductin, a highly conserved 16- to 18-kDa protein. The hydrated gap junctions, imaged in phosphate-buffered saline, appeared as membrane plaques with a thickness of 14 nm, consistent with their being a pair of apposing membranes. The upper membrane was removed by force dissection using an increased imaging force. The thickness of the lower membrane was 6 nm, giving a separation or gap between the two membranes of 2 nm. High-resolution images show fine details of the force-dissected extracellular surfaces, as previously reported for vertebrate and heart gap junctions. In addition high-resolution AFM images show for the first time detailed substructure on the cytoplasmic face of hydrated gap junctions of either vertebrate or invertebrate. The plaques had particles on their exposed and force-dissected faces. These particles were packed in a hexagonal lattice (a = b = 8.9 nm on both faces) and had a diameter of approximately 6.5 nm, with a central, pore-like depression. Fourier maps calculated from the AFM data suggested that each particle was composed of six subunits. These images show a marked similarity to the widely accepted structure of the connexon channel of vertebrate gap junctions.

Animals↗
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↗