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Biomedical subjects

V R Rao

Publications and source records attributed to V R Rao.

At least 19 recordsLinked to original sources
PubMed2007

Dynamics of changes in methanogenesis and associated microflora in a flooded alluvial soil following repeated application of dicyandiamide, a nitrification inhibitor.

Influence of repeated application of the nitrification inhibitor dicyandiamide (DCD), on CH(4) production and associated microflora in a flooded alluvial soil, was investigated in a laboratory incubation study. Application of DCD at the time of soil incubation resulted in a substantial reduction in CH(4) production (31% over that of untreated control). Second repeat application of DCD, on the contrary, annulled the inhibitory effect on CH(4) production, restoring it to the level of unamended soil. Application of the third dose of DCD maintained CH(4) production almost to the same extent as that of second application. The alleviation of the initial inhibitory effect of DCD on CH(4) production was linked to the enhanced degradation of DCD following its repeated application to the flooded soil. Admittedly, abatement of the initial inhibitory effect of DCD on CH(4) production in soil repeatedly amended with DCD was also related to the inhibition of CH(4)-oxidizing bacterial population and noticeable stimulation of heterotrophic bacterial population. Results suggest that repeat application of DCD with fertilizer-N to flooded rice soils might not be effective in controlling CH(4) production under field condition.

Anaerobiosis↗
PubMed2000

Influence of heavy metals on methane oxidation in tropical rice soils.

In a laboratory incubation study, the effect of select heavy metals on methane (CH4) oxidation in two rice soils was investigated under two moisture regimes. Heavy metals differed in their effect on CH4 oxidation in both soils under the two water regimes. Cr significantly inhibited CH4 oxidation in the alluvial soil at 60% moisture holding capacity, while Cu stimulated the process. On the contrary, Zn inhibited CH4 oxidation in both alluvial and laterite soils only under flooded conditions. Application of rice straw alleviated the inhibitory effect of heavy metals on CH4 oxidation and CO2 production. Inhibition of CH4 oxidation in the alluvial soil was related to the methanotrophic bacterial population in Cr- and Zn-amended alluvial soil.

Metals, Heavy↗
PubMed2000

On speed and aerodynamic forces of mosquito.

In the present investigation, speed of mosquitoes A. aegyptii (Linnè) and Culex quinquefasciatus (Say) is measured by designing and constructing a low speed wind tunnel in the laboratory. The velocity of mosquitoes is less than the other myogenic and neurogenic insects. Lift, one of the important aerodynamic forces that a flier has to develop for its efficient flight, is studied in mosquitoes by developing a simple technique using digital single pan balance. Lift, drag and their coefficients of hovering mosquito are calculated from the knowledge of body parameters by considering the wings of mosquito as harmonic oscillator. The calculated value of lift is verified with the experimental. The study throws light on morphophysiological adaptation of mosquitoes for the generation of aerodynamic forces in hovering, tethered and forward flights.

Aedes↗
PubMed1999

Expression cloning of protein targets for 3-phosphorylated phosphoinositides.

The phosphatidylinositol 3-kinase (PI 3'-K) family of lipid kinases play a critical role in cell proliferation, survival, vesicle trafficking, motility, cytoskeletal rearrangements, and oncogenesis. To identify downstream effectors of PI 3'-K, we developed a novel screen to isolate proteins that bind to the major products of PI 3'-K: phosphatidylinositol-3,4-bisphosphate (PtdIns-3,4-P(2)) and PtdIns-3,4,5-trisphosphate (PtdIns-3,4,5-P(3)). This screen uses synthetic biotinylated analogs of these lipids in conjunction with libraries of radiolabeled proteins that are produced by coupled in vitro transcription/translation reactions. The feasibility of the screen was initially demonstrated using avidin-coated beads prebound to biotinylated PtdIns-3,4-P(2) and PtdIns-3,4,5-P(3) to specifically isolate the pleckstrin homology domain of the serine/threonine kinase Akt. We then demonstrated the utility of this technique in isolating novel 3'-phosphorylated phosphatidylinositol (3'-PPI)-binding proteins through the preliminary screening of in vitro transcribed/translated cDNAs from a small pool expression library derived from mouse spleen. Three proteins were isolated that bound specifically to 3'PPIs. Two of these proteins have been previously characterized as PIP3BP/p42(IP4) and the PtdIns-3,4,5-P(3)-dependent serine/threonine kinase phosphoinositide-dependent kinase 1. The third protein is a novel protein that contains only a Src homology 2 domain and a pleckstrin homology domain; this protein has a higher specificity for both PtdIns-3,4,5-P(3) and PtdIns-3,4-P(2) than for PtdIns-4, 5-bisphosphate. Transcripts of this novel gene are present in every tissue analyzed but are most prominently expressed in spleen. We have renamed this new protein PHISH for 3'-phosphoinositide-interacting Src homology-containing protein. This report demonstrates the utility of this technique for isolating and characterizing 3'-PPI-binding proteins and has broad applicability for the isolation of binding domains for other lipid products.

Adaptor Proteins, Signal Transducing↗
PubMed1999

A chemically synthesized version of the insect antibacterial glycopeptide, diptericin, disrupts bacterial membrane integrity.

Insects protect themselves against bacterial infection by secreting a battery of antimicrobial peptides into the hemolymph. Despite recent progress, important mechanistic questions, such as the precise bacterial targets, the nature of any cooperation that occurs between peptides, and the purpose of multiple peptide isoforms, remain largely unanswered. We report herein the chemical synthesis and preliminary mechanistic investigation of diptericin, an 82 residue glycopeptide that contains regions similar to two different types of antibacterial peptides. A revised, highly practical synthesis of the precursor N(alpha)-Fmoc-Thr(Ac(3)-alpha-D-GalNAc) allowed us to produce sufficient quantities of the glycopeptide for mechanistic assays. The synthetic, full-length polypeptide proved to be active in growth inhibition assays with an IC(50) of approximately 250 nM, a concentration similar to that found in the insect hemolymph. Biological analysis of diptericin fragments indicated that the main determinant of antibacterial activity lay in the C-terminal region that is similar to the attacin peptides, although the N-terminal segment, related to the proline-rich family of antibacterial peptides, augmented that activity by 100-fold. In all assays, activity appeared glycosylation independent. Circular dichroism of unglycosylated diptericin indicated that the peptide lacked structure both in plain buffer and in the presence of liposomes. Diptericin increased the permeability of the outer and inner membranes of Escherichia coli D22 cells, suggesting possible mechanisms of action. The ability to access glycopeptides of this type through chemical synthesis will facilitate further mechanistic studies.

Amino Acid Sequence↗
PubMed1998

Circulating levels in serum of total sialic acid, lipid-associated sialic acid, and fucose in precancerous lesion and cancer of the oral cavity.

Total sialic acid (TSA), lipid-associated sialic acid (LASA), and fucose were estimated in sera of 35 patients with precancerous lesion of the oral cavity, 68 patients with cancer of the oral cavity, and 25 age- and sex-matched non-chewers of both tobacco and betal nut and nonsmokers as controls. Significant elevation in the serum levels of TSA and LASA were observed in patients with the precancerous and cancer lesions when compared with the controls. Serum TSA levels were elevated significantly in patients with cancer when compared with those with precancerous lesions. Circulating TSA and LASA levels were found to reflect tumor burden and correlated well with stage of the disease. However, serum fucose levels did not show an increase corresponding to stage of the disease. The results suggests that combined evaluation of these markers may be useful in predicting early malignant change and also in assessing the spread and invasiveness of the disease in cancer of the oral cavity.

Biomarkers, Tumor↗
PubMed1996

Distribution of contaminants in aquatic organisms from East Fork Popular Creek.

The ecological risk assessment of East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee, investigated the nature and magnitude of the observed or expected adverse effects of the site's organic and inorganic contaminants on the ecosystem structure and function. Aquatic biota such as benthic macroinvertebrates, crayfish (Astacidae), redbreast sunfish (Lepomis auritus), and stonerollers (Campostoma anomalum), representative of various habitats, were sampled for whole-body contaminant analysis. The whole-body residue analysis of the representative aquatic organisms revealed the presence of over 50 contaminants in varying proportions. The relative whole-body distribution of organic contaminants such as mixtures of polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides was comparable among the indicator organisms. The relative whole-body distribution of inorganic contaminants was, however, less consistent. Physicochemical variables characteristic of organic contaminants--such as long octanol/water partition coefficient (log KOW), log aqueous solubility, and log bioconcentration factors (log BCF), and chemical uptake efficiency (E) unique for the organisms sampled for chemical analysis--were used to explain the observed whole-body distribution of contaminants in the aquatic organisms from EFPC.

Animals↗
PubMed1996

Serum vitamins' status in oral leucoplakias--a preliminary study.

Vitamins, such as A, beta carotene, C, E, B12 and folate, are the micronutrients with the strongest evidence of having a link to cancer prevention and control. Deficiency of these vitamins at the dietary, systemic or mucosal level will interact with tobacco use and increase the risk of oral precancerous lesions. The objective of this study was to (1) establish the baseline circulating levels of these vitamins in our normal population with and without tobacco use and (2) compare these levels with the values obtained in cases of oral leucoplakias. 50 normal controls with 25 each in chewers and non-chewers, matched for age and sex, were selected. 50 cases of oral leucoplakias (clinically detectable white patches) from the field constituted the study group. Simultaneous measurement of serum vitamin B12 and folate were carried out by radioassay. The other serum vitamins were estimated spectrophotometrically. Except for serum vitamin E, all the other serum vitamin levels were significantly decreased in oral leucoplakias compared to the controls. Cancer chemopreventive agents acting as inhibitors of both initiation and promotion, as analysed in our population, is promising for further intervention trials.

Ascorbic Acid↗
PubMed1996

Activating mutations of rhodopsin and other G protein-coupled receptors.

Rhodopsin, the visual pigment of rod photoreceptors cells, is a member of the large family of G protein-coupled receptors. Rhodopsin is composed of two parts: a polypeptide chain called opsin and an 11-cis-retinal chromophore covalently bound to the protein by means of a protonated Schiff base linkage to Lys296 located in the seventh transmembrane segment of the protein. Several mutations have been described that constitutively activate the apoprotein opsin. These mutations appear to activate the protein by a common mechanism of action. They disrupt a salt-bridge between Lys296 and the couterion Glu113 that helps constrain the protein to an inactive conformation. Four of the mutations have been shown to cause two different diseases of the retina, retinitis pigmentosa and congenital night blindness. Recently, several other human diseases have been shown to be caused by constitutively activating mutations of G protein-coupled receptors.

GTP-Binding Proteins↗
PubMed1996

Reversible non enhancing lesions without focal neurological deficits in eclampsia.

Nine patients with eclampsia, were subjected to computerized tomographic scan (CT scan) of the head to ascertain the changes in the brain that accompany seizures and encephalopathy of eclampsia. Only those patients who had a seizure within the past 24 h were included in this study. None of the patients had any focal neurological deficit. Six of the nine patients had abnormal findings on CT scan consisting of multiple non enhancing hypodensities in the cerebral white matter. One patient also had subependymal haemorrhage over the lateral ventricle. These changes were found to have disappeared when the CT scan was repeated on the seventh day. There was no correlation between the mean arterial blood pressure or the number of seizures and the presence of hypodensities in the brain. These findings suggest that subclinical changes in the form of reversible hypodensities and rarely bleeding can occur in eclampsia even when patients have no focal neurological deficits. It appears that these lesions represent focal areas of cerebral oedema, secondary to failure of autoregulation of cerebral blood flow.

Adult↗
PubMed1995

A novel application of a competitive binding model in dioxin risk assessment.

The EPA-recommended toxicity equivalence factor (TEF) approach to estimating the lifetime incremental cancer risks for dioxins does not address (a) differences in the severity of toxicity according to the composition of chemical mixture and (b) potentials for modification of tissue-level doses of congeners in mixtures and consequently the cancer risk estimates. Our earlier efforts to model the binding of congeners to the Ah receptor in the low-dose range and to develop quantitative estimates for the formation of fractions of Ah receptor-congener complexes resulted in the definition of a unique parameter, defined as competitive binding ratio (CBR), to adjust tissue-level doses for mixture exposure. We made an effort to incorporate CBR values in the dose-response analysis and risk characterization of congeners in two distinct exposure scenarios. The modified approach to estimating tissue-level doses of congeners in mixtures by the use of a competitive binding model indicated that (a) the Ah receptor affinity is an important criterion in the determination of tissue-level dose of congeners, (b) the TEF doses calculated by using the model algorithms modified the tissue-level doses for congeners in mixture exposures, and (c) the combined lifetime incremental cancer risks for all congeners were generally lower when model algorithms were used in the dose-response analysis. However, the percentage contribution of toxic congeners was significantly higher when model algorithms were used. The percentage contribution of higher congeners with low toxicity was considerably reduced when model algorithms were used.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1995

Effect of herbicides on nitrogen fixation (C2H2 reduction) associated with rice rhizosphere.

In a field study nitrogenase activity associated with rice rhizosphere was differently influenced by the applied herbicides. Pretilachlor at two application levels had no effect on nitrogenase activity while butachlor and benthiocarb exerted marginal stimulation. Cinmethylin consistently stimulated nitrogenase activity throughout the plant growth period. Anilofos when applied singly had no substantial effect on nitrogenase activity but in combination with 2,4-D the activity was enhanced. Populations of anaerobic nitrogen-fixing bacteria and Azospirillum sp. and Azotobacter sp. were stimulated in such a combination.

Azospirillum↗
PubMed1994

Rhodopsin mutation G90D and a molecular mechanism for congenital night blindness.

Mutations in the gene for the visual pigment rhodopsin cause retinitis pigmentosa (RP) and congenital night blindness. Inheritance of the diseases is generally autosomal dominant and about 40 different rhodopsin mutations have been documented. Although the cell death and retinal degeneration associated with RP have been suggested to result from improper folding and accumulation of the mutant proteins in rod photoreceptor cells, this may not account for the disease in all cases. For example, RP mutations at Lys 296, site of Schiff base linkage to the retinal chromophore, result in constitutive activation of the protein in vitro; that is, the mutants can catalytically activate the G protein transducin in the absence of chromophore and in the absence of light. Similarly, mutation of Ala 292-->Glu activates opsin in vitro and causes night blindness. We show here that the mutation Gly 90-->Asp (G90D) in the second transmembrane segment of rhodopsin, which causes congenital night blindness, also constitutively activates opsin. Furthermore, we show that Asp 90 can substitute for the Schiff base counterion, Glu 113, which is located in the third transmembrane segment of the protein. This demonstrates the proximity of Asp 90 and Lys 296 in the three-dimensional structure of rhodopsin and suggests that the constitutively activating mutations operate by a common molecular mechanism, disrupting a salt bridge between Lys 296 and the Schiff base counterion, Glu 113.

Cell Line↗
PubMed1994

Natural history of aortoarteritis: an angiographic study in 26 survivors.

The natural history of aortoarteritis was angiographically studied in 26 surviving patients (19 female; 7 male). The interval between the initial and current angiographic study was 38-228 months (mean -84.46 months). All patients underwent panaortography during both studies and one patient also underwent pulmonary angiography. The lesions were extensive involving the ascending, arch and the descending thoracic and/or the abdominal aorta (Type III) in 15 patients; localized to the arch alone (Type I) in five patients and to the descending thoracic and/or abdominal aorta in five patients (Type II). Pulmonary angiography in the solitary patient with clinical features of pulmonary hypertension showed occlusion of the lower lobe branch of the right pulmonary artery. The lesions were occlusive in 19 patients, aneurysmal in one patient and mixed in six patients. While four patients developed fresh lesions in the follow-up period, two showed progression of existing lesions and one revealed partial thrombosis of an aneurysm. Persistently elevated erythrocytic sedimentation rate (> 40 mm) was identified as a reliable indicator for activity of inflammatory process and disease progression. The stable nature of the lesions in 20 out of 26 patients in this study indicates a non-progressive course in the healed stage of aortoarteritis and suggests a conservative approach to the management of this disease in all patients except those with severe, life-threatening manifestations.

Adolescent↗
PubMed1994

Self-expandable stents for tracheal stenosis: experience in two patients.

Two patients with cervical tracheal stenosis, following prolonged ventilatory support, underwent balloon dilatation and expandable stainless steel stent placement across the stenoses. Following the successful release of the stent, there was gradual widening of the stenosed trachea in one patient, while in the other re-stenosis occurred due to columns of tracheal tissue projecting between the limbs of the stent. In the chronically ill and debilitated, use of expandable stents provides a good alternative to complex reconstructive surgery.

Adult↗
PubMed1994

Influence of ammonium and 2,4-dichlorophenoxy acetic acid on nitrogenase activity in Azospirillum species from rice rhizosphere.

The influence of 2,4-dichlorophenoxy acetic acid (2,4-D) and ammonium on the nitrogenase activity of Azospirillum sp. under normal fixing and low-fixing conditions was evaluated. Nitrogenase activity was substantially stimulated following exposure to 2,4-D at various concentrations up to 5 ppm under normal fixing conditions. A pronounced enhancement in activity occurred with incubation. Significant reduction of the nitrogenase activity occurred in the presence of NH(4+)-N at almost all concentrations of 2,4-D. With incubation the toxic effects of combined nitrogen were alleviated in the presence of higher levels of 2,4-D. Results indicated that the toxic effects of a combination of agrochemicals on nitrogenase in Azospirillum sp. could be mitigated following a long exposure.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1994

Focal occlusive disease of the common femoral artery: a report of 20 cases.

Occlusive disease localized to the common femoral artery without contiguous involvement of the external iliac and superficial femoral arteries is distinctly uncommon in vascular surgical practice. Twenty patients with focal occlusive disease in 21 common femoral arteries are featured in this report. All except one had severe disabling symptoms: Fontaine classification was stage I in one patient, stage IIb in 13, and stage III in six patients. The probable aetiology, based on clinical features and angiographic observations, was identified as atherosclerosis (nine cases), thromboangiitis obliterans (three) and Takayasu's arteritis (two). Histological features of mucoid vasculopathy, a novel disorder, was seen in one patient while no specific aetiology was evident in five patients. Associated lesions were seen in fourteen patients: aortoiliac in one, femoropopliteal in seven (without any continuity to the common femoral lesion), internal iliac in three and tibial in three. Balloon angioplasty of the common femoral artery lesions was attempted in 14 patients with successful outcome in nine. Three patients (including two with failed balloon angioplasty), underwent thromboendarterectomy and two bypass procedures (iliofemoral, one; femoropopliteal, one). Late reocclusion occurred in one patient each in the angioplasty and surgical groups. There were no procedure-related complications in either group.

Adolescent↗