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B V Reddy

Publications and source records attributed to B V Reddy.

At least 37 records · Page 2Linked to original sources
PubMed1997

Forskolin delays the ethanol-induced desensitization of hypothalamic beta-endorphin neurons in primary cultures.

Ethanol and its metabolite acetaldehyde have been shown to stimulate immunoreactive beta-endorphin (IR-beta-EP) secretion from hypothalamic neurons in primary cultures. Also, chronic ethanol and acetal-dehyde have been shown to cause the development of tolerance and desensitization of these neurons. In this study, we determined some of the cellular events leading to desensitization of the function of beta-endorphin (beta-EP) secretory neurons. The fetal hypothalamic cells were treated with various doses of ethanol (25 and 50 mM) or acetaldehyde (6.25, 12.5, and 25 mM) for 6 hr or treated with these drugs at 12 hr intervals for 72 hr. Determination of IR-beta-EP concentrations in the media revealed that ethanol increased IR-beta-EP secretion from these cultures for 12 hr, after this period, the cultured cells did not respond to ethanol. Acetaldehyde stimulated IR-beta-EP secretion from this culture for a period of 48 hr, but the IR-beta-EP secretory response to acetaldehyde reduced gradually with time during the first 48-hr period and reached the basal level at 72 hr. The desensitization of beta-EP neurons 12 hr after treatment with alcohol did not seem to be related to the loss of viable cells, because chronic ethanol exposures did not produce any effect on cell viability. However, reduced IR- beta-EP secretory response to acetaldehyde with time was associated with the time-dependent increase in cell death. Pretreatment of cultures with a cAMP analog, forskolin, increased the activity of functional beta-EP neurons and delayed the ethanol desensitization effects on these neurons. Pretreatment of forskolin did not delay the acetaldehyde desensitization of beta-EP neurons, but protected these cells from acetaldehyde toxicity. These results suggest that (i) chronic treatment with ethanol desensitizes beta-EP-secreting neurons due to reduced cellular functions and (ii) chronic acetaldehyde reduces beta-EP neurotransmission due to cell death. Furthermore, data suggest for the first time that cAMP pretreatments delay the ethanol-induced desensitization of opioid neurons and partly protect against the neurotoxic action of acetaldehyde on opioid neurons.

Animals↗
PubMed1996

Modification of the sialic acid residues of choriogonadotropin affects signal transduction.

Human choriogonadotropin (hCG) is a glycoprotein hormone that activates adenylyl cyclase. The carbohydrate moieties of hCG are required for biological activity, but not for binding to the gonadotropin receptors. We modified N-acetylneuraminic acid (NeuAc) on the oligosaccharide moieties of hCG, and determined the effect on its biological activity by measuring hormone-stimulated adenylyl cyclase. Treating hCG with sodium periodate to remove two carbon atoms from NeuAc or quantitatively removing NeuAc from hCG reduced its biological activity by 36% and 50%, respectively. The galactose residues of asialo-hCG were reacted with NeuAc-hydrazone or a hydrazone of the oligosaccharide from the ganglioside GM1 (Gal(beta 1-3)GalNAc(beta 1-4) [NeuAc(alpha 2-3)]Gal(beta 1-4)Glc). The gonadotropin receptor had high affinity for both derivatives, but their biological activity was less than that of hCG. These results suggest that several structural aspects of NeuAc including carbon side chain, an intact ring structure, and the position of NeuAc relative to other carbohydrate residues are important for full biological activity of hCG.

Adenylyl Cyclases↗
PubMed1996

Structural distribution of dipeptides that are identified to be determinants of intracellular protein stability.

The dipeptides that had been previously implicated as determinants of in vivo protein stability (Guruprasad, K., Reddy, B.V.B. and Pandit, M.W., 1990. Protein Eng. 4, 155-161) have been reassessed on a latest data set and about 25% dipeptide combinations (102 dipeptides) were found to play significant role in determining the intracellular protein stability. These were classified as stabilizing dipeptides (Stb), destabilizing dipeptides (Dst) and normal dipeptides (Nor). By different theoretical approaches we have investigated the global localization of these dipeptides in a set of 303 best resolved (< or = 2.0A) non-homologous X-ray defined protein structures. The Dst dipeptides are found to be more of hydrophilic combinations where as Stb dipeptides are more of hydrophobic combinations. We observed a significant difference in overall frequency of occurrence of Stb and Dst dipeptides in different secondary structural regions. The sensitive dipeptides (Stb + Dst) are less in beta-strands and more in coils. A high frequency of occurrence of Stb are observed in the regions closer to the molecular surface compared to the Dst and Nor dipeptides. A significantly high dipole interactions are observed in the Dst dipeptides. The studies indicate that though the Dst dipeptides are more of hydrophilic nature they are localized significantly more in the buried regions of protein structures, on the other hand Stb are more of hydrophobic nature but relatively more accessible to the solvent. These dipeptides therefore increasing sensitivity of the protein to external environment, any alteration in their occurrence in the sequence could increase or decrease intracellular stability of the protein. These observations are useful to select mutations to alter intracellular stability of a given protein and therefore have implications in protein engineering.

Binding Sites↗
PubMed1995

A statistical analytical approach to decipher information from biological sequences: application to murine splice-site analysis and prediction.

A simple statistical approach for the analysis of biological sequences, such as splice-sites, promoter regions, helices and extended structure forming regions or any other sequence dependent functional entities in proteins, is presented. The approach has been proved useful to develop a method for prediction of such entities in newly available sequences. We first search for invariant sequence features of each functional entity from the experimentally available sequences and identify a set of 'like' sequences with similar sequence features. In the next step, concrete features of sequence entities in terms of occurrences of smaller subsequences are identified at various positions which are used as a knowledge base to select potential functional entities from the identified 'like' sequences. The third step consists of refinement of this pattern learning, statistical improvements of the knowledge base weight matrices, and finally its application to predict functional entities in newly available sequences. Such an analysis is operationally described for murine splice-site predictions. Regions comprising -30 to +30 nucleotides from the splice-junction at the murine splice-sites (donors and acceptors), reported earlier, were analyzed. Invariant sequence-specific features in terms of monomer frequency average were used to identify splice-site-like sequences in the EMBL murine DNA sequence data base. The frequencies of occurrence of mono-, di-, tri- and tetranucleotides in the known splice-sites were studied in comparison with the splice-site-like sequences; the significant differences in their occurrences were extracted as statistical knowledge coded in weight matrices for computer to identify potential splice-sites. The algorithm was refined and a method was developed to predict potential splice-sites in a given murine DNA; the analysis was also extended to human DNA. The success rate of the method to predict correct splice-sites in these species is found to be 80% and 85%, respectively. The major strength of this method lies in reducing significantly the number of false positives which are normally picked up in such analysis.

Algorithms↗
PubMed1995

Effect of ethanol, propanol, butanol, and catalase enzyme blockers on beta-endorphin secretion from primary cultures of hypothalamic neurons: evidence for a mediatory role of acetaldehyde in ethanol stimulation of beta-endorphin release.

Previously, we have shown that low doses of ethanol (12.5-100 mM) and acetaldehyde (12.5-50 microM), but not salsolinol, enhanced immunoreactive beta-endorphin (IR-beta-EP) secretion from fetal hypothalamic neurons in primary culture. In this study, the effects of ethanol, propanol, and butanol, as well as the effect of catalase inhibitors on IR-beta-EP secretion were studied in vitro to determine the role of membrane fluidization and ethanol metabolism on ethanol-induced IR-beta-EP secretion. The primary cultures of fetal hypothalamic neurons were maintained for 8-9 days in chemically defined medium and treated for 5 hr with ethanol (50 mM), propanol (25 and 50 mM), and butanol (25 and 50 mM). Determination of hourly secretion of IR-beta-EP from the cultures revealed that only 50 mM ethanol caused stimulation of IR-beta-EP secretion, whereas propanol and butanol did not alter IR-beta-EP response at any given concentration. Pretreatment of these cultures with the catalase inhibitors, 3-amino-1,2,4-triazole (3-AT; 1, 5, and 10 mM), caused a dose-dependent inhibition of ethanol-stimulated IR-beta-EP secretion, but did not inhibit dibutyryl cAMP (dcAMP)-stimulated IR-beta-EP secretion. Another catalase inhibitor, sodium azide (5 mM), also inhibited ethanol-stimulated IR-beta-EP secretion. Measurement of acetaldehyde production in cultured cells and media after ethanol or dcAMP treatments revealed that cultured cells produce acetaldehyde only after ethanol treatment and at levels of acetaldehyde (8-24 microM) that are known to evoke IR-beta-EP release. The catalase inhibitor 3-AT (10 mM) treatment reduced ethanol-evoked acetaldehyde production.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Butanol↗
PubMed1995

Contextual constraints in the choice of synonymous codons.

From EMBL Nucleotide Sequence Database, protein coding sequences of all E. coli and its DNA phages, were extracted using our computer programme. Same programme has been used to form a database of sequence of oligonucleotides of length 18 nucleotides on both sides of each of the 61 codons. From analysis of this database and study of variations in twist parameter (Tw) values, as an indicator of sequence dependent variations in B-DNA helix, a method is developed to fix the codon among the set of synonymous codons. The accuracy of the method was checked on enlarged data set by adding data from more prokaryotes. Our method assign the codon 85-90% times correctly if the selection has to be made between codons having different sequence in terms of R and Y. The accuracy of the method is somewhat lower when choice of the codon has to be made between codons having same codes in terms of R and Y. This study points out that the major factors which decide the choice of a codon from a set of synonymous codons are contextual constraints arising from flanking regions.

Base Sequence↗
PubMed1994

Cyclic AMP and ethanol interact to control apoptosis and differentiation in hypothalamic beta-endorphin neurons.

In this study we have determined the role of cyclic AMP on the function and differentiation of beta-endorphin (beta-EP) neurons in rat fetal hypothalamic cell cultures. Addition of Bt2cAMP or the cAMP elevating agent, forskolin, in cultures, dose and time dependently increased beta-endorphin secretion. The increased beta-EP secretion after Bt2cAMP or forskolin treatment was associated with proopiomelanocortin gene expression, enhanced neurite growth, and increased neuronal viability. Determination of internucleosomal cleavage of DNA by agarose gel electrophoresis revealed that apoptosis occurred in hypothalamic neurons during the first 6-8 days in culture. Addition of Bt2cAMP during this developmental period inhibited DNA degradation in hypothalamic neurons. Furthermore, incubation with various doses of ethanol, which is known to reduce intracellular levels of Bt2cAMP, increased DNA degradation in these cells. Ethanol-induced DNA degradation was blocked by concomitant incubation with Bt2cAMP. Histochemical identification of apoptotic cells following ethanol and Bt2cAMP treatments further revealed that apoptosis occurred in beta-EP neurons during the developmental period, and that ethanol increased and Bt2cAMP reduced apoptotic beta-EP cell numbers. These results suggest that ethanol neurotoxicity on beta-EP neurons during early neuronal differentiation involves an apoptotic process and that the cAMP signaling system plays an important role in controlling apoptosis and differentiation of the beta-EP neuronal system.

Animals↗
PubMed1994

Proline-protein interactions: protection of structural and functional integrity of M4 lactate dehydrogenase.

A well defined labile isozyme, rabbit muscle M4-lactate dehydrogenase was denatured under freeze-thaw, heat and GuHCl treatment in the presence and absence of proline, and the corresponding structural changes of the enzyme were monitored through fluorescence and CD spectral studies. The data reveal that proline confers protection to the structural integrity of the enzyme, thereby protecting its activity. This was attributed to its property of forming hydrophilic colloids in aqueous media with a hydrophobic backbone interacting with protein. Unlike other osmolytes, proline is proposed to act on the enzyme stability not only by inducing preferential hydration of proteins but also through the interactions of its multimeric hydrophobic backbone with the solvent-accessible hydrophobic regions of the enzyme.

Animals↗
PubMed1993

Packing of secondary structural elements in proteins. Analysis and prediction of inter-helix distances.

Interacting helix pairs were defined as those in which each member has one residue which undergoes a fractional loss of 0.10 solvent accessible contact area on association. Analysis of 1095 such pairs of helices, selected from the Brookhaven Data Bank, confirms that helix pairs in proteins can pack interactively at all angles with preferential packing observed in the angle intervals (omega), -160 degrees to -140 degrees, -100 degrees to -20 degrees, 10 degrees to 40 degrees, and 50 degrees to 160 degrees. The distance (d) between the helix axes in the contact region of two interactively packed helices is linearly correlated with the volume-dependent function, log(V/nda), of the residues in this region. The correlation is used to predict inter-helix distances in equivalent helix pairs of homologous proteins and is therefore of value in comparative modelling of protein three-dimensional structures.

Amino Acid Sequence↗
PubMed1993

Effect of alcohol, acetaldehyde, and salsolinol on beta-endorphin secretion from the hypothalamic neurons in primary cultures.

The effect of ethanol, acetaldehyde, and salsolinol on hypothalamic beta-endorphin secreting neurons is studied by using rat fetal hypothalamic neurons in primary culture. Exposure of these neuronal cells to different concentrations of ethanol (12.5-50 mM) and acetaldehyde (12.5-50 microM) caused a concentration-dependent increase in the secretion of beta-endorphin. Salsolinol (12.5-50 microM) did not cause any significant change in the secretion of beta-endorphin. Ethanol's effect was short-lasting (2 hr). Acetaldehyde's effect on beta-endorphin secretion was greater and longer lasting, as compared with ethanol. Ethanol and salsolinol do not have any effect on cell viability, whereas higher concentrations of acetaldehyde appear to reduce the number of viable cells after 6 hr of treatment. None of the above treatments has any effect on cellular DNA content. These results suggest that ethanol is a potent stimulator of hypothalamic beta-endorphin. These results also show for the first time that ethanol's metabolite acetaldehyde is more potent in stimulating beta-endorphin secretion and may be significant in the ethanol regulated beta-endorphin secretion.

Acetaldehyde↗
PubMed1992

Impact of chronic phosalone toxicity on Bohr factor and oxygen equilibrium curves of rat.

The multiple sublethal doses of phosalone induced changes in haemodynamics, maximum absorption spectra, oxygen equilibrium curves (OEC), half saturation tension (P50), degree of interaction (n), pH of blood, Bohr factor and circulatory gases of blood in rat, Rattus norvegicus. The results have obviously shown that increase the activation of pyridoxal phosphate, shift of OEC to right and decrease in the affinity of haemoglobin for oxygen at tissue level.

Animals↗
PubMed1992

Effect of chronic insecticide, phosalone, toxicity on haem synthesis and blood gas composition in the rat.

The influence of multiple sublethal concentrations of phosalone on whole animal and kidney oxygen consumption, haem synthesis and blood gases of rat, were carried out over a 90 day dosed period. The results indicate the existence of hypoventilation and a hypoxic condition in the animals which lead to the disruption of neuromuscular transmission in respiratory muscles and increase of erythropoiesis and haemoglobin synthesis. The changes were most pronounced when animals were exposed for the 90 day dosed period.

Animals↗
PubMed1991

Impact of chronic phosalone toxicity on erythropoietic activity of fish, Oreochromis mossambicus.

Effect of multiple sublethal concentrations of Phosalone on whole animal and kidney oxygen consumption, haematological indices and serum enzymes of freshwater fish, Oreochromis mossambicus, were carried out over a 90 day exposure period. Significant changes were observed which have been indicating that the presence of hypoxic condition in the biosystem, gradual increase in the rate of synthesis of haemoglobin and disruption of liver function during the toxicity of phosalone.

Animals↗
PubMed1990

Correlation between stability of a protein and its dipeptide composition: a novel approach for predicting in vivo stability of a protein from its primary sequence.

Statistical analysis of 12 unstable and 32 stable proteins revealed that there are certain dipeptides, the occurrence of which is significantly different in the unstable proteins compared with those in the stable ones. Based on the impact of these dipeptides on the unstable proteins over the stable ones, a weight value of instability is assigned to each of the dipeptides. For a given protein the summation of these weight values normalized to the length of its sequence helps to distinguish between unstable and stable proteins. Results suggest that the in vivo instability of proteins is possibly determined by the order of certain amino acids in its sequence. An attempt is made to correlate metabolic stability of proteins with features of their primary sequence where weight values of instability for a protein of known sequence could thus be used as an index for predicting its stability characteristics.

Amino Acid Sequence↗
PubMed1989

Testosterone response in arginine vasopressin desensitized immature rat testis.

Direct injection of arginine vasopressin into immature rat testis inhibited basal testosterone synthesis. Simultaneous injection of arginine vasopressin with luteinizing hormone, norepinephrine or cholera toxin inhibited these agonists - induced testosterone response. In arginine vasopressin - desensitized testis, cAMP response to luteinizing hormone, norepinephrine and cholera toxin was not disturbed. However, testosterone response to luteinizing hormone, norepinephrine or cholera toxin was drastically reduced in arginine vasopressin-desensitized testis. This shows that the increased cAMP generated by luteinizing hormone, norepinephrine or cholera toxin in arginine vasopressin desensitized testis did not cause increase in steroidogenesis. This could be due to a lesion in steroidogenic pathway beyond cAMP generation caused by arginine vasopressin.

Animals↗
PubMed1989

Effects of vanadyl sulphate on ornithine decarboxylase and progesterone levels in the ovary of rat.

The effects of vanadyl sulphate in vitro on the levels of ODC activity and progesterone synthesis in ovaries were studied. The levels of ODC in the ovaries were stimulated with high concentration of vanadyl sulphate and at low concentrations there was no change in the levels of ODC activity. On the contrary progesterone levels were stimulated with low concentrations of vanadyl sulphate and were inhibited at higher concentrations. Vanadyl sulphate showed additional stimulation of ODC activity, when it was added with hCG and caused inhibition of hCG induced progesterone biosynthesis. These results show that the effects of vanadyl sulphate on ODC and progesterone are different.

Animals↗
PubMed1987

Desensitization of immature rat testicular ornithine decarboxylase to arginine vasopressin.

Prior exposure of immature rat testis to arginine vasopressin caused the testis refractory at 24 h in terms of ornithine decarboxylase activity. Arginine vasopressin caused desensitization both in Leydig cells and seminiferous tubules. Arginine vasopressin induced desensitization was found to be both time and dose-dependent. Arginine vasopressin desensitized testis was refractory to luteinizing hormone, follicle stimulating hormone, norepinephrine, dibutyryl cAMP, phorbol-myristate acetate and cholera toxin at 24 h. Arginine vasopressin desensitized testis showed recovery of response to norepinephrine at 48 h after the first injection. On the contrary arginine vasopressin could stimulate ornithine decarboxylase in luteinizing hormone desensitized testis. These results indicate that in arginine vasopressin desensitized testis the block is at post cAMP step which is common to both cAMP dependent and protein kinase C-diacylglycerol system in stimulating testicular ornithine decarboxylase.

Animals↗