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Biomedical subjects

K K Rao

Publications and source records attributed to K K Rao.

At least 19 recordsLinked to original sources
PubMed2002

Hydrogen production by cyanobacteria in an automated outdoor photobioreactor under aerobic conditions.

The possibility of hydrogen production by a hydrogenase impaired mutant strain of Anabaena variabilis in outdoor culture was studied. A computer-controlled rooftop (outdoor) tubular photobioreactor (4.35 L) was assembled. H(2) production rates by A. variabilis PK84 grown in CO(2) + air in the photobioreactor were measured together with other parameters such as temperature, irradiance, pH, dry biomass weight, and pO(2), and Chl a concentrations during summer months of 1998 and 1999. Efficiencies of light energy bioconversion to H(2) energy and energy accumulated in biomass were calculated. The influence of irradiance, temperature, and mode of cultivation on H(2) production and efficiency of light energy bioconversion were evaluated. The culture produced up to 1.1 L H(2) day(-1) PhBR(-1). The efficiency of light energy to H(2) energy bioconversion on some days was 0.094%. However, the conditions for maximum H(2) photoproduction and for maximum efficiency of light energy to H(2) energy bioconversion were not the same. A. variabilis PK84 could produce hydrogen for prolonged periods (up to 40 days) without injection of fresh inoculum. During this period photobioreactor produced 24.5 L of H(2). Possibilities for increasing the efficiency of light energy conversion are discussed.

Aerobiosis↗
PubMed2002

DNA markers and marker-assisted breeding for durable resistance to bacterial blight disease in rice.

Bacterial leaf blight caused by the bacterial pathogen Xanthomonas oryzae pv oryzae (Xoo) limits rice yield in all major rice-growing regions of the world, especially in irrigated lowland and rainfed conditions where predisposition factors favor disease development to epidemic proportions. Since bacterial pathogens are difficult to manage, development of host plant resistance is the most effective means of disease management. As many as 24 major genes conferring resistance to various races of the pathogen have been identified and utilized in rice breeding programs. However, large-scale and long-term cultivation of varieties carrying a single gene for resistance resulted in a significant shift in pathogen race frequency with consequent breakdown of resistance in these cultivars. To combat the problem of resistance breakdown, pyramiding of resistance genes into different cultivars is being carried out. Pyramiding of resistance genes is now possible with molecular markers that are developed for individual genes. This review discusses the various bacterial blight resistance genes identified and their corresponding molecular markers developed for breeding durable resistance into modern rice cultivars.

Journal Article↗
PubMed2001

Aminopeptidase-N from the Helicoverpa armigera (Hubner) brush border membrane vesicles as a receptor of Bacillus thuringiensis crylac delta-endotoxin.

Brush border membrane vesicles (BBMVs) were prepared from the 2nd instar larvae of Helicoverpa armigera. Binding of the activated Cry1Ac of Bacillus thuringiensis (Bt) toxin was shown by immunoblot. A 120-kDa protein was identified as a receptor for the Cry1Ac type delta-endotoxin. The aminopeptidase-N activity of BBMVs was measured as the hydrolysis of L-leucine p-nitroanilide. The specific activity was 35 units/mg protein. The BBMV preparation also showed low level of alkaline phosphatase activity. Zn++ chelating agents 2,2'-dipyridyl and 1,10-phenanthroline inhibited aminopeptidase activity at 10 mM concentration, indicating the presence of zinc-dependent aminopeptidase in the brush border of H. armigera. The aminopeptidase activity was increased with increasing concentration of delta-endotoxin. The purified 120-kDa binding protein was N-terminally sequenced. The first 10-amino-acid sequence showed 60-77% similarity with human cysteine-rich secretory protein-1 precursor, inhibin alpha chain precursor. Salmonella flagellar hook protein and yeast carboxypeptidase S.

Amino Acid Sequence↗
PubMed2000

Hydrogen production by Anabaena variabilis PK84 under simulated outdoor conditions.

Hydrogen production by autotrophic, vanadium-grown cells of Anabaena variabilis PK84, a cyanobacterial mutant impaired in the utilization of molecular hydrogen, has been studied under simulated outdoor conditions. The cyanobacterium was cultivated in an automated helical tubular photobioreactor (4.35 L) under air containing 2% CO(2), with alternating 12-h light (36 degrees C) and 12-h dark (14 degrees to 30 degrees C) periods. A. variabilis steadily produced H(2) directly in the photobioreactor during continuous cultivation for 2.5 months. The maximum H(2) production by the continuously aerated culture under light of 332 microE. s(-1). m(-2) was 230 mL per 12-h light period per photobioreactor and was observed at a growth density corresponding to 3.6 to 4.6 microgram Chl a. mL(-1) (1.2 to 1.6 mg dry weight. mL(-1)). Replacement of air with an argon atmosphere enhanced H(2) evolution by a factor of 2. This stimulatory effect was caused mainly by N(2) deprivation in the cell suspension. A short-term decrease of the CO(2) concentration in the air suppressed H(2) evolution. Anoxygenic conditions over the dark periods had a negative effect on H(2) production. The peculiarity of hydrogen production and some physiological characteristics of A. variabilis PK84 during cultivation in the photobioreactor under a light-dark regime are investigated.

Air↗
PubMed1999

H(2) photoproduction by batch culture of Anabaena variabilis ATCC 29413 and its mutant PK84 in a photobioreactor.

Hydrogen production by Anabaena variabilis ATCC 29413 and of its mutant PK84, grown in batch cultures, was studied in a photobioreactor. The highest volumetric H(2) production rates of native and mutant strains were found in cultures grown at gradually increased irradiation. The native strain evolved H(2) only under an argon atmosphere with the actual rate as high as the potential rate (measured in small vials under optimal conditions). In this case 61% of oxygenic photosynthesis was used for H(2) production. In contrast the mutant PK84 produced H(2) during growth under CO(2)-enriched air. Under these conditions at the maximum rate of H(2) production (10 mL h(-1) L(-1)), 13% of oxygenic photosynthesis was used for H(2) production and the actual H(2) production was only 33% of the potential. Under an atmosphere of 98% argon + 2% CO(2) actual H(2) production by mutant PK84 was 85% of the potential rate and 66% of oxygenic photosynthesis was used for H(2) production. Hydrogen production under argon + CO(2) by the mutant was strictly light-dependent with saturation at about 300 microE m(-2) s(-1). However, the rate of photosynthesis was not saturated at this irradiation. At limiting light intensities (below 250 microE m(-2) s(-1)) 33-58% of photosynthesis was used for H(2) production. Hydrogen evolution by PK84 under air + 2% CO(2) was also stimulated by light; but was not saturated at 332 microE m(-2) s(-1) and did not cease completely in darkness. The rate of oxygen photoevolution was also not saturated. A mechanism for increasing cyanobacterial hydrogen production is proposed.

Anabaena↗
PubMed1998

Possible role of glutathione in predicting radiotherapy response of cervix cancer.

PURPOSE: To see if changes in tumor/blood glutathione (GSH) levels after one fraction of radiotherapy can be correlated with the treatment response in patients with carcinoma of the uterine cervix. METHODS AND MATERIALS: The study was done on 45 patients with squamous cell carcinoma of the uterine cervix, FIGO Stages IIB (17 patients) and IIIB (28 patients). Stage IIB patients received 35 Gy of cobalt-60 external radiotherapy (RT) in 16 fractions over 4 weeks with a concurrent high-dose-rate intracavitary dose of 8.5 Gy to point A once a week. Stage IIIB patients were given 45 Gy of RT in 20 fractions over 5 weeks, followed by two doses of intracavitary therapy once a week. Blood and tumor samples were collected before and after one dose of RT and GSH was estimated. Tumor response was assessed clinically at 1 month after treatment. RESULTS: Glutathione levels in both blood and tumor showed a significant decrease after one fraction of RT, but the degree of decrease varied among patients. There was a good correlation between the extent of GSH decrease and the tumor response. All patients who had complete response (CR) (seven Stage IIB and eight Stage IIIB) showed > or =70% decrease in both tumor and blood GSH, while those who had <50% regression (NR) (five Stage IIB and 13 Stage IIIB) showed <50% decrease in GSH. The partial responders recorded an intermediate level (50-70%) of depletion in blood and tumor GSH. CONCLUSIONS: The results indicate that the changes in tumor/blood GSH levels after one fraction of RT could serve as an index of tumor response to therapy and may help in identifying radioresistant tumors, at least in the case of cervix carcinoma.

Biomarkers↗
PubMed1998

Prognostic factors for spinal cord myelitis--an analysis of compiled literature data.

The effectiveness of radiotherapy in the treatment of malignant tumors in the head and neck, thorasic and upper abdominal regions is frequently limited by the tolerance of the spinal cord. Therefore knowledge of the factors that influence the tolerance of the spinal cord to radiation is of the upmost important. Safe limits for irradiation of the spinal cord determined in a number of clinical studies is on the conservative side from the point of view of tumor control probability. The bioeffect of a physical dose takes into account the treatment variables and the radiobiological characteristics of the relevant tissue; hence deciding spinal cord tolerance on the basis of bioeffect models would be better approach. The aim of the present study was to analyze the relationship of the prognostic factors with percentage incidence of spinal cord myelitis and to arrive at a spinal cord tolerance bioeffect dose TDF and ERD for optimum incidence of radiation myelitis.

Dose Fractionation, Radiation↗
PubMed1996

Synthesis, characterization, cytotoxic, and DNA binding studies of some platinum (II) complexes of 1,2-diamine and alpha-diimine with 2-pyridinecarboxylate anion.

Seven new water-soluble cationic complexes of general formula [Pt(2-pyc)(N-N)]+ (where N-N is 2NH3, ethylenediamine (en), 1,2-diaminopropane (1,2-dap), 1,3-diaminopropane (1,3-dap), (+/-) trans-1,2-diaminocyclohaxane (dach), 2,2'-dipyridylamine (dpa) or 1,10-phenanthroline (phen), and 2-pyridinecarboxylate anion) have been prepared. These complexes have been characterized by conductance measurements, and by ultraviolet-visible, infrared (IR), and 1H nuclear magnetic resonance (NMR) spectroscopy. The COSY (correlated spectroscopy) spectra of [Pt(2-pyc)(dpa)]+ and [Pt(2-pys)(dpa)]+ further support the structures of the above complexes with three nitrogen and one oxygen donor atoms in the first coordination sphere of platinum(II) with 1,2-diamine or alpha-diimine and 2-pyridinecarboxylate anion behaving as bidentate ligands. One of the compounds, [Pt(2-pyc)(dpa)]Cl, also shows a birefringence property in water. These compounds inhibit the growth of P388 lymphocytic leukemia cells. [Pt(2-pyc)(dpa)]+ shows I.D.50 value comparable to cisplatin. However, six other complexes show higher I.D.50 values than cisplatin. In addition, the inhibition studies also suggest that their target is DNA. Therefore, the interactions of four of the above complexes with calf thymus DNA have been studied by ultraviolet and fluorescence spectral methods. These studies suggest that [Pt(2-pyc)(NH3)2]+ and [Pt(2-pyc)(1,2-dap)+ bind to DNA by noncovalent interactions. On the other hand, [Pt(2-pyc)(dpa)]+ and [Pt(2-pyc)(phen)]+ bind to DNA by covalent monofunctional binding. The latter two complexes have also been interacted with PUC19 DNA. The gel electrophoresis studies of these interactions suggest that these complexes bind to DNA, and this binding leads to a conformational change in DNA.

Anions↗
PubMed1996

Salinity and osmotic stress-regulated proteins in cowpea Rhizobium 4a (peanut isolate).

The effect of salinity and osmotic stress on protein synthesis was studied in cowpea Rhizobium 4a. Osmotic component of salinity stress has been shown to induce ten proteins in a salt tolerant/osmosensitive cowpea Rhizobium. 4a (groundnut isolate). Of these seven polypeptides were induced only by salt/osmotic stress while two were induced by heat shock. The results demonstrate a commonality as well as stress specificity of protein synthesis regulation.

Arachis↗
PubMed1995

Production of beta-glucosidase by Aspergillus terreus.

The production of beta-glucosidase by Aspergillus terreus was investigated in liquid shake cultures. Enzyme production was maximum on the 7th day of growth (2.18 U/ml) with the initial pH of the medium in the range of 4.0-5.5. Cellulose (Sigmacell Type 100) at 1.0% (wt/vol) gave maximum beta-glucosidase activity among the various soluble and insoluble carbon sources tested. Potassium nitrate was a suitable nitrogen source for enzyme production. Triton X-100 at 0.15% (vol/vol) increased the enzyme levels of A. terreus. The test fungal strain showed an ability to ferment glucose to ethanol.

Aspergillus↗
PubMed1992

Activity staining of endoglucanases in polyacrylamide gels.

The endoglucanases of Penicillium funiculosum were analyzed for the presence of multiple forms using a modified version of the Congo red method. Postelectrophoretic slab gels were directly incubated in a solution of carboxymethylcellulose for a period as short as 15 min and then the activities were visualized by staining with Congo red. Ten distinct bands of clearances were obtained indicating the presence of at least as many multiple forms.

Acrylic Resins↗
PubMed1991

Clinico-pathological profile of lymphomas in south India: a prospective rural referral hospital study of 103 cases.

A prospective clinical and histopathological study of 103 patients with lymphomas is reported. Of these, 72 (69.9%) had non-Hodgkin's lymphoma (NHL) and 31 (30.1%) had Hodgkin's lymphoma (HL). The median age at presentation was 34 and 43 years for Hodgkin's and non-Hodgkin's lymphoma respectively, which is lower than that seen in the West. Fever and superficial lymphadenopathy were the commonest presenting features and 'B' symptoms were present in over 60% of both groups. Seventy-five per cent of NHL and 64.5% of HL presented in stages III and IV of the disease.

Adolescent↗
PubMed1988

Deletional analysis of the promoter region of the human transferrin receptor gene.

Fragments of human genomic DNA corresponding to the promoter region of the gene for the transferrin receptor have been cloned upstream of the bacterial gene for chloramphenicol acetyltransferase and these constructs used to assess promoter activity following transfection into a human rhabdomyosarcoma cell line. Progressive 5' deletions as well as internal linker-substitution constructs support a critical role in gene expression of a sequence element approximately 70 bp upstream of the mRNA start site. In this region, the receptor gene was found to contain 11bp that are identical to a segment of the enhancers of polyoma virus and adenovirus. A fragment encompassing this element was shown to increase gene expression when the fragment was placed in either orientation upstream of the remainder of the transferrin receptor promoter but the same fragment did not activate an enhancer-less SV40 promoter. Removal from within the receptor promoter of three potential binding sites for the transcription factor Sp1 did not decrease the promoter's activity.

Acetyltransferases↗
PubMed1986

Activation and deactivation of the membrane-bound hydrogenase from Desulfovibrio desulfuricans, Norway strain.

The hydrogenase from D. desulfuricans, when isolated in air, had a low activity in the hydrogen-methyl viologen reductase assay, and no activity in the hydrogen-methylene blue reductase assay. The activity increased markedly during incubation under hydrogen. This process is interpreted in terms of conversion of the enzyme from a relatively inactive Unready state to the Active state. Oxidation by dichloro-indophenol caused conversion to a state in which the hydrogen-uptake activity to methyl viologen was preserved, but hydrogen-methylene blue activity was not. This form is termed the Ready state. This behaviour resembles that of the hydrogenase of Desulfovibrio gigas and thus may be a widespread property of this class of hydrogenases. The electron-spin-resonance spectra of the D. desulfuricans enzyme showed the presence of [3Fe-xS] and [4Fe-4S] clusters. Spectra were also observed in the various states of activation of the enzyme. In these respects, the hydrogenase of D. desulfuricans resembles that from D. gigas, although the latter may have an additional iron-sulphur cluster.

2,6-Dichloroindophenol↗
PubMed1986

The redox properties of the iron-sulphur cluster in hydrogenase from Chromatium vinosum, strain D.

The midpoint potentials of the changes in the electron spin resonance (ESR) spectra in the region of g = 2 in hydrogenase II from Chromatium vinosum were estimated by redox titrations. As the enzyme was progressively reduced, the g = 2.02 signal increased, while the satellite lines at g = 1.98 etc. decreased. At still lower potentials the signal at g = 2.02 decreased. The midpoint potentials of the two processes were estimated to be + 100 mV and - 20 mV, respectively, at pH 8.5. The first potential showed significant pH-dependence. The titration data fitted to n = 1 curves with reasonable reversibility. The enzyme activity showed no significant changes in this potential range. The results are discussed in relation to the interaction of the iron-sulphur cluster with nickel.

Chromatium↗
PubMed1986

Light induced H2 evolution in a hydrogenase-TiO2 particle system by direct electron transfer or via rhodium complexes.

Three different hydrogenases (isolated from Clostridium pasteurianum, Desulfovibrio desulfuricans strain Norway 4 and D. baculatus 9974) added to a suspension of TiO2 (anatase) powder are able to catalyze H2 evolution under band gap illumination of the semiconducting particles, and in the presence of EDTA or methanol as electron donor. This H2 production can be obtained by the direct electron transfer from the conduction band of the TiO2 particles to the active site of the enzyme at pHs higher than 7. This mediator-independent charge transfer is more efficient with C. pasteurianum and D. baculatus 9974 hydrogenases, and in the presence of methanol. Rhodium tris- and bis-bipyridyl complexes can act efficiently as electron carriers from the supporting particles to the adsorbed enzyme molecules in cases where the direct transfer is inefficient.

Clostridium↗