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Biomedical subjects

K Venkateswarlu

Publications and source records attributed to K Venkateswarlu.

At least 19 recordsLinked to original sources
PubMed1995

Resistance to fluconazole in Candida albicans from AIDS patients correlated with reduced intracellular accumulation of drug.

Mucosal candidosis is an almost inevitable consequence of AIDS. Resistance to fluconazole therapy associated with enhanced tolerance, detectable in microbiological estimation of sensitivity, occurs in up to 10% of cases with late-stage AIDS. We report here our biochemical analysis of the basis of resistance in a study of two susceptible and two resistant isolates. Resistance was not associated with a change in the target enzyme sterol 14 alpha-demethylase, as indicated by equivalent levels of fluconazole inhibition of activity in extracts from all four isolates, or by mutations in sterol delta desaturase as previously observed in Saccharomyces cerevisiae and Ustilago maydis. Reduced cellular content of fluconazole in the resistant isolates of between six to ten-fold was observed which could account for their resistant phenotype.

AIDS-Related Opportunistic Infections↗
PubMed1992

Interactions of monocrotophos and quinalphos with Anabaena torulosa isolated from rice soil.

The interaction of insecticide combinations of monocrotophos and quinalphos on Anabaena torulosa, by the criteria of absorbance (OD) and packed cell volume (PCV) of the culture, content of chlorophyll a, phycocyanin, carotenoids, total protein, DNA and RNA, heterocyst differentiation and nitrogen fixation, were assessed. In general, monocrotophos and quinalphos, in combination, interacted significantly yielding three different responses viz., additive, antagonistic or synergistic. The nature of the interaction found with OD and PCV was nearly the same for a particular concentration of the insecticides. However, no consistent interaction was observed with respect to carotenoids and phycocyanin. The three types of interaction were noticed for total protein, DNA and RNA. Interestingly, the insecticide combinations at lower concentrations yielded all interaction responses for heterocyst frequency and nitrogenase activity. But, higher concentrations, in combination, resulted in synergism for heterocyst differentiation and nitrogen fixation.

Anabaena↗
PubMed1991

Conserved upstream sequence elements in plant 5S ribosomal RNA-encoding genes.

As a basis for further comparative studies, nuclear 5S rRNA gene repeats from two plants of the Solanaceae family, tobacco (Nicotiana rustica) and tomato (Lycopersicon esculentum), were isolated and sequenced. The more abundant 5S rRNA gene repeat in tobacco is 430 bp long, while a second less common variant is 521 bp long. In contrast, the 5S rRNA gene repeat from tomato is only 355 bp long. The spacer sequences from these gene repeats, as well as from other published plant nuclear 5S rRNA genes, were compared for repeating or conserved sequence elements. The results indicate that often observed, but non-conserved, repeating sequence elements probably arise spontaneously by unequal crossover with no functional significance. However, three conserved sequence elements immediately upstream of the coding sequence; a C residue at -1, a G + C-rich element centered at -13, and an A + T-rich element centered at -26 resemble regulatory features which have been identified in other types of genes.

Base Sequence↗
PubMed1991

A conserved core structure in the 18-25S rRNA intergenic region from tobacco, Nicotiana rustica.

To identify conserved and functionally important features in the intergenic sequences of ribosomal DNAs, the nucleotide sequence of the 18-25S rRNA intergene region in tobacco rDNA was determined and compared to that of other higher plants. Unlike previous comparisons of more diverse organisms, sufficient sequence homology is retained in the higher plants to examine the evolutionary changes which make these regions diverse. Estimates of the secondary structure permit the identification of a 'core-like' structure which appears to maintain the processed sites in close proximity and can be identified in the more divergent sequences.

Base Sequence↗
PubMed1991

Evidence for T-DNA mediated gene targeting to tobacco chloroplasts.

The integration of foreign DNA into plant cells by Agrobacterium mediated transformation is random and normally directed at the nucleus. Here we present evidence that such transformation can be used to introduce foreign genes into higher plant chloroplasts by site-specific homologous recombination. A binary vector was made in vitro that included chloroplast ribosomal DNA (rDNA) within T-DNA borders, and transgenic tobacco plants obtained using this construct were analyzed for the targeted recombination by hybridization, polymerase chain reaction (PCR) and DNA sequencing.

Base Sequence↗
PubMed1990

Stimulation of ammonification and nitrification in soils by the insecticides monocrotophos and quinalphos.

The application (up to 5 kg ha-1) of monocrotophos or quinalphos to four types of agricultural soils significantly stimulated the mineralization of peptone-nitrogen and the oxidation of ammonium-nitrogen. In soils treated with 2.5 kg ha-1 of either insecticide, the rate of ammonification and nitrification was fairly rapid after 2 and 4 weeks of incubation. The enhancement of both transformations, mediated by microorganisms, was significantly more in the quinalphostreated soils. The results suggest that a balance between the effect of insecticides on insect pests and their impact on beneficial microbial activities in soil must be determined.

Ammonia↗
PubMed1989

Effect of monocrotophos and quinalphos on soil population and nitrogen-fixing activity of Azospirillum sp.

The effects of monocrotophos and quinalphos on population and nitrogen-fixing activity of Azospirillum sp. in four agricultural soils were determined in a laboratory study. Concentrations of the two insecticides up to a 5 kg ha-1 level were either stimulatory or innocuous to the population of Azospirillum in the soils. Four successive applications of the insecticides to soils resulted in a significant increase in the population density. Cultures of Azospirillum sp., isolated from insecticide-treated soils, exhibited greater nitrogen-fixing activity. Three consecutive subculturings of the isolates from insecticide-treated soils had no effect on their nitrogen-fixing activity.

Bacteria↗
PubMed1988

Influence of glucose amendment on the toxicity of two nitrophenols to Chlorella vulgaris.

Glucose amendment (0.5%) to the culture medium of Chlorella vulgaris reversed the algal toxicity caused by p-nitrophenol (PNP) and m-nitrophenol (MNP), only at their algistatic levels. Algistatic and algicidal concentrations of PNP and MNP, in the absence of glucose, led to the liberation of more nitrite in the culture medium. However, addition of glucose inhibited nitrite formation.

Cell Count↗
PubMed1988

Keratoplasty in children.

One hundred sixty-two eyes of children less than 14 years of age with corneal disease underwent keratoplasty over a period of eight years. The cases were divided into two groups and different subgroups, and the results were compared. The results of the recent group of cases after introduction of microsurgery were definitely better. However, being a referral center, the cases came to us at a late stage with complications and required larger grafts. Interestingly, graft transparency has a direct correlation with the size of the graft and type of corneal disease. Lastly, there was a marked reduction in frequency of therapeutic keratoplasty later, a result of the availability of various drugs.

Adolescent↗
PubMed1988

Keratomycosis--a retrospective histopathologic and microbiologic analysis.

In this retrospective study, the results of concurrent histopathologic and microbiologic examinations of 61 corneal buttons were evaluated. These revealed histologic fungus identification in 77.04% of cases compared with culture examination which yielded fungal growth in 75.4% of cases. Mixed fungal and bacterial infection caused difficulty not only in isolation but also in demonstrating fungus in the tissue sections. Staphylococcus epidermidis was the most common isolate in cases of mixed infection. Aspergillus was the most prevalent nondematiaceous fungus. Dematiaceous fungi were isolated in culture in only 10.8% of our cases, and in none of them was the histopathology positive, indicating that they might have been contaminants.

Abscess↗
PubMed1987

Influence of cypermethrin and fenvalerate on a green alga and three cyanobacteria isolated from soil.

The effects of two pyrethroid insecticides, cypermethrin and fenvalerate, on a green alga (Scenedesmus bijugatus) and three species of cyanobacteria (Synechococcus elongatus, Nostoc linckia, and Phormidium tenue), all isolated from a black cotton soil, were studied using either cell number or chlorophyll a as toxicity criterion. All the four species were either unaffected or stimulated at 5 micrograms ml-1. Of the two insecticides, cypermethrin, at 10 to 50 micrograms ml-1, inhibited S. bijugatus while these concentrations stimulated or only slightly inhibited the growth of S. elongatus. There was a significant inhibition in the growth of S. bijugatus and stimulation in S. elongatus with 10 to 50 micrograms ml-1 fenvalerate. The growth of N. linckia was enhanced by both insecticides while P. tenue was significantly affected.

Chlorophyll↗
PubMed1987

Hydatid disease of spleen treated by cyst enucleation and splenic salvage.

A 4-year-old boy with unilocular hydatid cysts of spleen and liver was successfully treated by enucleation of both the cysts and salvage of the spleen. The conventional surgical treatment of choice for hydatid cyst of the spleen is splenectomy. The authors demonstrate that preservation of a spleen afflicted by hydatid disease is technically feasible and is recommended as the choice of treatment to obviate the well-recognized postsplenectomy complications especially in children.

Child, Preschool↗