Biomedical subjects

G R Reddy

Publications and source records attributed to G R Reddy.

At least 55 records · Page 3Linked to original sources

PubMed1994

Anti-inflammatory activity of substituted 1,3,4-oxadiazoles.

Various 5-[[(acetamidophen-4-yl)oxy]methyl]-2-(p-substituted phenylamino)-1,3,4-oxadiazoles (4a-4d) were synthesized by cyclization of the corresponding N1-[[(acetamidophen-4-yl)oxy]acetyl]- N4-(p-substituted phenylamino)-3-thiosemicarbazides (3a-3d). All four of the thiosemicarbazides [250 mg/kg, orally (p.o.)] and the corresponding oxadiazoles (250 mg, p.o.) possessed anti-inflammatory activity. In the Carrageenan-induced edema test in rat paw, the activity ranged from 28 to 47% for 3a-3d and 44 to 63% for 4a-4d, with indomethacin (10 mg/kg, p.o.), used as the standard reference drug, showing 88.5% protection. The compounds (1 mM) were also tested for the inhibition of bovine serum albumin denaturation, and this activity ranged from 27 to 68%. No correlation was seen between the anti-inflammatory activity of 3a-4d and the inhibition of denaturation of bovine serum albumin. The low toxicity of these compounds was reflected by their high approximate 50% lethal dose (LD50) values, ranging from 2000 to 2500 mg/kg.

Animals↗

PubMed1994

Sequence, expression and modeled structure of an aspartic proteinase from the human malaria parasite Plasmodium falciparum.

A clone encoding the aspartic proteinase (PFAPD) from Plasmodium falciparum strain HB3 was obtained during the course of a project designed to sequence and identify the protein coding regions of the parasite's genome. The protein encoded by the clone contains a sequence identical to the N-terminal sequence determined for an aspartic proteinase isolated from the digestive vacuole of P. falciparum and demonstrated to participate in the hemoglobin digestive pathway (D. Goldberg, personal communication). The translated polypeptide sequence encompasses a number of features characteristic of aspartic proteinases, having > 30% identity and > 50% similarity overall to human cathepsin D, cathepsin E and renin. A model of the three-dimensional structure of PFAPD was constructed using rule-based procedures. This confirms that the primary sequence may be folded as a single chain into a three dimensional structure closely resembling those of other known aspartic proteinases. It includes a lengthy prosegment, two typical-hydrophobic-hydrophobic-Asp-Thr/Ser-Gly motifs and a tyrosine residue positioned in a beta-hairpin loop. The distribution of hydrophobic residues throughout the active site cleft is indicative of a likely preference for hydrophobic polypeptide substrates. The recombinant form of this enzyme expressed using the pGEX2T vector in Escherichia coli is active in digesting hemoglobin at acidic pH and in hydrolyzing a synthetic peptide corresponding to the putative initial cleavage site in hemoglobin. Activity is inhibited completely by pepstatin, confirming the identity of PFAPD as a member of the aspartic proteinase family. Specific mRNA for PFAPD is expressed in the erythrocytic stages of the life cycle.

Amino Acid Sequence↗

PubMed1994

Analysis of expressed sequence tags from Plasmodium falciparum.

An initiative was undertaken to sequence all genes of the human malaria parasite Plasmodium falciparum in an effort to gain a better understanding at the molecular level of the parasite that inflicts much suffering in the developing world. 550 random complimentary DNA clones were partially sequenced from the intraerythrocytic form of the parasite as one of the approaches to analyze the transcribed sequences of its genome. The sequences, after editing, generated 389 expressed sequence tag sites and over 105 kb of DNA sequences. About 32% of these clones showed significant homology with other genes in the database. These clones represent 340 new Plasmodium falciparum expressed sequence tags.

Animals↗

PubMed1993

Gene sequence tags from Plasmodium falciparum genomic DNA fragments prepared by the "genease" activity of mung bean nuclease.

A genes-first approach to genome sequencing is described which efficiently generates gene sequence tags from genomic DNA. Mung bean nuclease (EC 3.1.30.1) cleaves the genomic DNA of many organisms before and after genes and within some introns. Analysis of gene sequence tags prepared from mung bean nuclease-digested Plasmodium falciparum DNA demonstrates that this method has several advantages over the popular cDNA expressed sequence tag approach. To date, 673 sequence tags containing over 215 kb of sequence have been generated from 400 clones. Sixty clones (15%) have significant similarity to sequences in the protein and translated nucleic acid data bases. These represent 51 unique genes, of which only 5 encode previously known P. falciparum proteins. The identified proteins include those expressed in erythrocytic, exoerythrocytic, and gametocytic stages of the parasite. Thirty percent of clones identified appear to carry complete coding regions. The spacer DNA separating genes is rarely cloned. These gene sequence tags will form a useful data base from which to initiate projects to develop new therapeutics, vaccines, and strategies to control human malaria.

Animals↗

PubMed1993

Arachidonate 12-lipoxygenase of platelet-type in human epidermal cells.

A homogenate of epidermal cells isolated from human skin converted arachidonic acid to 12S-hydroxy-5, 8,10,14-eicosatetraenoic acid and 15-hydroxy-5, 8,11,13-eicosatetraenoic acid as the main lipoxygenase products. The production of these hydroxy acids was not stimulated by the addition of 1 mM NADPH required for cytochrome P-450 reaction, but inhibited by 65-75% with 40 microM nordihydroguaiaretic acid, a nonspecific lipoxygenase inhibitor. In addition to these lipoxygenase products, the epidermal cell homogenate converted arachidonic acid to prostaglandin E2 together with minor amounts of prostaglandins D2 and F2a and 12-hydroxy-5,8,10-heptadecatrienoic acid. Thromboxane B2 was not detected. This finding rules out the possible contamination of platelet 12-lipoxygenase in the epidermal cells. After subcellular fractionation of the epidermal cell homogenate, the 12-lipoxygenase activity was found in the 164,000 x g supernatant, the 164,000 x g pellet, and the 10,000 x g pellet. The cytosolic enzyme and the enzymes solubilized from the two pellets produced 12S-hydroperoxy-5,8,10,14-eicosatetraenoic acid as the primary product in contrast to cytochrome P-450 which produces primarily hydroxy acids. The 12-lipoxygenase in the 164,000 x g supernatant and the solubilized enzymes from the 164,000 x g pellet and 10,000 x g pellet were precipitable by antibodies raised against human platelet 12-lipoxygenase, but not by antibodies against porcine leukocyte 12-lipoxygenase. The immunoprecipitated 12-lipoxygenase from each fraction was almost inactive with linoleic acid as substrate, characteristic of 12-lipoxygenase of platelet-type. Furthermore, 12-lipoxygenase mRNA in the epidermal cells could be reverse-transcribed and amplified by polymerase chain reaction with the primers specific for human platelet 12-lipoxygenase cDNA, but not with those for porcine leukocyte 12-lipoxygenase cDNA. Thus, the 12-lipoxygenase of human epidermal cells is similar to human platelet 12-lipoxygenase in terms of immunogenicity, catalytic property, and primary structure, and distinct from leukocyte 12-lipoxygenase.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

11-hydroperoxyeicosatetraenoic acid is the major dioxygenation product of lipoxygenase isolated from hairy root cultures of Solanum tuberosum.

The profile of primary dioxygenation products of arachidonic acid catalyzed by lipoxygenase isolated from hairy root cultures of Solanum tuberosum treated with a fungal elicitor was compared to that obtained for the enzyme from potato tubers. 11-Hydroperoxyeicosatetraenoic acid (11-HPETE) was the most abundant dioxygenation product formed followed by 8- and 5-HPETEs in the decreasing order of abundance. In contrast, 5-HPETE is the predominant oxidation product of lipoxygenase from potato tubers. Differences in the defense requirements of storage tuber as compared to roots may be the basis of the differences in regio-specificity demonstrated in this work.

Arachidonic Acid↗

PubMed1992

Prostaglandin H synthase-dependent genotoxicity of 2,4-diaminotoluene.

2,4-Diaminotoluene (2,4-DAT), a high volume synthetic compound, is moderately carcinogenic to rodents. We report here that 2,4-DAT is a substrate for the peroxidase activity of prostaglandin H synthase (PHS). In contrast to many aromatic amines which are activated as mutagens by PHS, we find that 2,4-DAT is not mutagenic to six S. typhimurium strains with this activation system. The strains tested include YG1006, YG1024, and YG1029, which are far more sensitive to the mutagenicity of aromatic amines and nitroarenes than are the standard tester strains. Although not mutagenic itself, 2,4-DAT does enhance the mutagenicity of 2-aminofluorene (2-AF) in the PHS-catalyzed system in strains TA98, YG1006, and YG1024, with maximal enhancement of 140%, 1831%, and 1216%, respectively. Half-maximal enhancement of 2-AF mutagenicity is observed at 15-20 microM 2,4-DAT for strains YG1006 and YG1024, and about 80 microM for TA98. Studies with compounds structurally related to 2,4-DAT revealed enhancement of 2-AF mutagenicity with 2,5-DAT and o-phenylenediamine (o-PD) but not for other DAT isomers, toluidines, and phenylenediamines. Maximal enhancement of 2-AF mutagenicity observed in TA98 with PHS-catalyzed activation was 110% for o-PD and 60% for 2,5-DAT. This comutagenic effect of 2,4-DAT appears quite specific for 2-AF, as it fails to enhance either the PHS-dependent mutagenicity of the aromatic amines benzidine and 2-naphtylamine, or the direct mutagenicity of N-acetoxy-acetylaminofluorene,2-nitrofluorene,4- nitroquinoline-N-oxide and 1,1,1-trichloropropene-2,3-oxide. Enhancement of 2-AF mutagenicity by 2,4-DAT is also observed with cytochrome P-450-dependent activation, however the half-maximal 2,4-DAT concentration was 400 microM, and the maximal enhancement was only 50%. The ability of 2,4-DAT, under conditions where it is not itself mutagenic, to enhance the genotoxicity of the potent carcinogen 2-AF comprises an intriguing toxicological interaction, and underscores the inherent difficulties in assessing the genotoxic risks posed by mixtures of compounds.

Biotransformation↗

PubMed1992

rRNA-based method for sensitive detection of Babesia bigemina in bovine blood.

Three synthetic oligonucleotide probes complementary to unique regions of Babesia bigemina small-subunit rRNA were developed for detecting the parasite in bovine blood. These probes specifically detected a parasitemia of 2 x 10(-5)% by autoradiography in less than 24 h by using a 200-microliters sample of bovine blood. These probes did not bind to total RNA or genomic DNA isolated from another closely related species, Babesia bovis, or to bovine leukocyte RNA. This method detected B. bigemina infections in calves inoculated with as few as 1,000 infected erythrocytes from the second day onward for 16 days.

Animals↗

PubMed1991

Sequence microheterogeneity of the three small subunit ribosomal RNA genes of Babesia bigemina: expression in erythrocyte culture.

Three distinct ribosomal RNA (rRNA) transcription units (rDNA units), designated A, B and C, were identified in the intraerythrocytic protozoan parasite, Babesia bigemina. These rDNA units were cloned, and restriction maps were constructed showing the approximate location of the small and large rRNA coding regions. The arrangement of the genes in the genome and copy number analysis suggests the presence of a single copy of each rDNA unit per haploid genome. The complete nucleotide sequence of the small subunit rRNA coding region (1693 bp) and parts of the 5' and 3' flanking regions were determined for all three units. Units A and B have identical sequences, but unit C differs from units A and B at ten nucleotide positions, two in the small subunit rRNA coding region and four each in the adjacent 5' and 3' flanking regions. The differences in the coding region are confirmed in genomic DNA and RNA from two different isolates of B.bigemina. The RNA of both sequence types is transcribed in parasites from erythrocyte culture, however, the products of gene units A + B accumulate at a ratio of approximately 4:1 compared with the product of unit C.

Animals↗

PubMed1991

A prenylflavone, artonin E, as arachidonate 5-lipoxygenase inhibitor.

Several naturally occurring prenylflavones were tested for their inhibitory actions on arachidonate 5-lipoxygenase purified from porcine leukocytes. Of the compounds tested, artonin E (5'-hydroxymorusin) exhibited the most potent inhibition on arachidonate 5-lipoxygenase (IC50 = 0.36 microM). Arachidonate 12-lipoxygenase purified from porcine leukocytes and human platelets, 15-lipoxygenase from rabbit reticulocytes and fatty acid cyclooxygenase from bovine vesicular glands were inhibited by the compound only at higher concentrations (IC50 = 2.3, 11, 5.2 and 2.5 microM, respectively).

Animals↗

PubMed1991

Cercal sensory regulation of ganglionic protein metabolism in the field cricket, Gryllotalpa africana.

The effect of cercal deafferentation (cercectomy) on the ganglionic protein metabolism of the cricket, Gryllotalpa africana was studied. Significant changes in the activities of the enzymes acetylcholinesterase, glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase were observed in the terminal ganglion following unilateral and bilateral cercectomy.

Acetylcholinesterase↗

PubMed1991

Cercal sensory regulation of acetylcholinesterase in nervous system of the cockroach, Periplaneta americana.

Cercal ablation caused a significant loss in acetylcholinesterase (AChE) activity of the cercal nerves and terminal ganglion within 12 hr while a similar reduction in enzyme activity of connectives was noticed at least one day after cercectomy. The decrease in AChE activity of the nervous tissues showed a recovery toward control levels from 20 days of unilateral cercectomy whereas the bilateral cercectomy produced a continuous and irreversible decline in enzyme activity. These localized changes in AChE activity of the abdominal nervous system of the cockroach were attributed to be regulated by the cercal sensory innervation.

Acetylcholinesterase↗

PubMed1990

Phenylhydrazine mediated degradation of bovine serum albumin and membrane proteins of human erythrocytes.

Phenylhydrazine in solution has been shown to produce hydroxyl radicals, as measured by 2-deoxyribose degradation assay. In vitro incubation of bovine serum albumin with phenylhydrazine leads to extensive degradation of the former which, however, is not inhibited by hydroxyl-radical scavengers like mannitol, Tris or n-butanol. Metal chelators like EDTA, however, inhibits the breakdown of BSA. Erythrocyte ghosts incubated in vitro with phenylhydrazine also show extensive loss of membrane cytoskeletal proteins, inhibited by 5 mM EDTA but not by mannitol. In both the occasions a hydroxyl-radical mediated damage to protein takes place by a 'site-specific mechanism'. Further, such a damage to erythrocyte membrane proteins by phenylhydrazine may be related to well known action of this compound in producing accelerated aging of erythrocytes.

Cytoskeletal Proteins↗

PubMed1990

Alternative splicing of the transcript encoding the human muscle isoenzyme of phosphofructokinase.

The genomic DNA encoding human muscle phosphofructokinase (HPFK-M) exons VII to X has been cloned and the coding regions have been sequenced. The intron/exon boundaries are located at the same positions as those identified for the rabbit phosphofructokinase-M gene (Lee, C. -P., Kao, M. -C., French, B. A., Putney, S. D., and Chang, S. H. (1987) J. Biol. Chem. 262, 4195-4199). A HPFK-M cDNA clone lacking the sequences corresponding to exon IX was isolated from a human fibroblast (IMR-90) library, suggesting that the HPFK-M transcript may be alternatively spliced. Exon IX is 93 nucleotides in length, and the absence of this sequence from the HPFK-M transcript would generate an RNA coding for a HPFK-M-related polypeptide lacking 31 amino acids compared with the HPFK-M polypeptide. HPFK-M transcripts approximately 3.0 kilobases in length are expressed in a tissue-specific manner with high levels in cell lines and skeltal muscle tissue and very low levels in peripheral blood mononuclear cells and liver tissue. Characterization of the structure of these HPFK-M transcripts by nuclease S1 and polymerase chain reaction analysis demonstrated that all the cell lines and tissues examined expressed the alternatively spliced transcript in addition to the transcript coding for the enzymatically functional HPFK-M polypeptide.

Amino Acid Sequence↗

PubMed1990

Ionic imbalances in the CNS of neonate rat during induced benthiocarb stress.

The effect of benthiocarb, an organocarbamate herbicide, on the ionic profiles of the developing central nervous system of rat has been studied. The ionic profiles altered by benthiocarb toxicity indicate possible perturbations in the electric activity of neurons, in oxygen consumption, and in the ATPase system, as well as disruption in the movement of ions across ionic pumps and impairment of synaptic transmission.

Animals↗

PubMed1990

Effect in vitro of propoxur on kinetics of K+ stimulated PNPPase and protection by thiol reagents.

Kinetics analysis of K+ stimulated PNPPase was studied in the rat brain synaptosomes in the presence of propoxur. Non-competitive inhibition with respect to activation by PNPP was seen by the decreased maximal velocity (Vmax) without change in Michaelis-Menten Constant (Km). Activation energy values (delta E) were increased suggesting the decreased catalytic potential of the enzyme. It is also observed that dithiothrietol (DTT) (76 microM), cysteine (82 microM) and glutathione (120 microM) neutralized the inhibition of K(+)-PNPPase by propoxur to different extents.

4-Nitrophenylphosphatase↗

PubMed1990

Modulations in ionic composition and ATPase system in the brain of albino rat under induced propoxur toxicity.

Modulations in ionic composition were seen in the rat brain during propoxur treatment indicating an impairment in the electric activity of neurons, oxygen consumption, ATPase system, disruption in the movement of ions across ionic pumps and synaptic transmission. The specific activity levels of ATPases were also altered confirming that the impairment in the ATPase system might be due to the ionic imbalances under propoxur stress.

Adenosine Triphosphatases↗

PubMed1990

Biosynthesis of prostaglandins in ovarian follicles and corpus luteum of sheep ovary.

The biosynthetic potential of prostaglandins (PGs) was measured in ovarian follicles and corpus luteum of sheep ovary. The total prostaglandins formed under non-enzymatic conditions were much lower in comparison to that formed using native GSTs. When the GSTs of ovarian follicles were employed, the major prostaglandin formed was PGE2 (81.22%) followed by PGD2 (16.9%) and PGF2 alpha (1.87%). In case of corpus luteum, prostaglandin formed was PGF2 alpha (59.01%). Since PGF2 alpha was demonstrated to be the luteolytic factor, the present study indicates the formation of luteolytic factor in the ovarian tissue itself.

Animals↗