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T S Rao

Publications and source records attributed to T S Rao.

At least 19 recordsLinked to original sources
PubMed1995

Azole substituted oligonucleotides promote antiparallel triplex formation at non-homopurine duplex targets.

The ability of certain azole substituted oligodeoxy-ribonucleotides to promote antiparallel triple helix formation with duplex targets having CG or TA interruptions in the otherwise homopurine sequence was examined. 2'-Deoxyribonucleosides of the azoles, which include pyrazole, imidazole, 1,2,4-triazole and 1,2,3,4-tetrazole were synthesized using the stereo-specific sodium salt glycosylation procedure. These nucleosides were successfully incorporated using solid-support, phosphoramidite chemistry, into oligonucleotides designed to interact with the non-homopurine duplex targets. The interaction of these modified oligonucleotides with all four possible base pairs was evaluated and compared to similar data for a series of natural oligonucleotides. The oligonucleotides containing simple azoles enhanced the triplex forming ability considerably at non-homopurine targets. Binding of these modified oligonucleotides to duplex targets containing TA inversion sites was particularly noteworthy, and compare favorably to unmodified oligonucleotides for binding to duplex targets containing CG as well as TA base pairs. The selectivity exhibited by certain azoles is suggestive of base pair specific interactions. Thus, the azoles evaluated during this study show considerable promise for efforts to develop generalized triplex formation at non-homopurine duplex sequences.

Azoles↗
PubMed1995

Triplex formation at the rat neu gene utilizing imidazole and 2'-deoxy-6-thioguanosine base substitutions.

Triplex-forming oligodeoxyribonucleotides (TFOs) can be designed so as to form antiparallel triple helices with duplex DNA by means of GGC and TAT or AAT base triplets, and these have been shown to be useful as sequence-specific DNA binding agents. Using TFOs targeted to the promoter region of the rat neu oncogene, it is shown here that substitution of an imidazole-nucleoside chimera at a single site in a neu specific TFO results in an increase in TFO binding affinity and specificity. This effect is discussed in terms of the stabilizing effect of local imidazole-TA triplet formation. It is also found that site-selective substitution of 2'-deoxy-6-thioguanosine for guanosine (S6-dG) in the TFO results in an increase in triplex formation in the presence of physiological levels of potassium ion. The utility and positioning of S6-dG base substitutions is discussed in the context of an intramolecular tetrad model.

Animals↗
PubMed1995

Incorporation of 2'-deoxy-6-thioguanosine into G-rich oligodeoxyribonucleotides inhibits G-tetrad formation and facilitates triplex formation.

An efficient and expeditious method for the synthesis of S6-(cyanoethyl)-N2-isobutyryl (or trifluoroacetyl)-2'-deoxy-6-thioguanosine (7 and 2) from 2'-deoxyguanosine (G) has been developed. Compound 7 has been incorporated into several G-rich triple-helix-forming oligonucleotides (TFOs) using solid-support, phosphoramidite chemistry. The purified oligonucleotides containing 2'-deoxy-6-thioguanosine (S6-dG) residues in the place of G have been characterized by nucleoside composition analysis. These modified TFOs have been shown to be stable in aqueous, as well as buffered, solutions normally used to assay triple-helix formation. It has also been demonstrated that partial incorporation of S6-dG is effective in inhibiting the formation of G tetrads in G-rich oligodeoxyribonucleotides, thus facilitating triple-helix formation in potassium-containing buffers.

Base Sequence↗
PubMed1994

Binding of T and T analogs to CG base pairs in antiparallel triplexes.

The goal of this study was to address antiparallel triplex formation at duplex targets that do not conform to a strict oligopurine.oligopyrimidine motif. We focused on the ability of natural bases and base analogs incorporated into oligonucleotide third strands to bind to so-called CG inversions. These are sites where a cytosine base is present in an otherwise purine-rich strand of a duplex target. Using a 26-base-triplet test system, we found that of the standard bases, only thymine (T) shows substantial binding to CG inversions. This is quantitatively similar to the report of Beal and Dervan [Science (1991), 251, 1360-1363]. Binding to CG inversions was only slightly weaker than binding to AT base pairs. Binding of T to CG inversions was also evaluated in two other sequences, with qualitatively similar results. Six different analogs of thymine were also tested for binding to CG inversions and AT base pairs. Significant changes in affinity were observed. In particular, 5-fluoro-2'-deoxyuridine was found to increase affinity for CG inversions as well as for AT base pairs. Studies with oligonucleotides containing pyridin-2-one or pyridin-4-one suggest that thymine O4 plays a critical role in the T.CG interaction. Possible models to account for these observations are discussed.

Base Composition↗
PubMed1994

Role of mast cells in calcium ionophore (A23187)-induced peritoneal inflammation in mice.

Several lines of evidence document a critical role for mast cells in immune complex-mediated inflammatory models. However, their role in nonimmune models of acute inflammation is largely unknown. In the present investigation, the role of mast cells was examined in calcium ionophore (A23187)-induced mouse peritoneal inflammation. Intraperitoneal injection of A23187 (20) micrograms/mouse) elicited marked and transient increases in immunoreactive levels of 6-ketoprostaglandin-F2 alpha, leukotrienes B4, C4, D4, E4, and F4. There were no discernible differences in levels of these mediators in male Swiss Webster mice, mast cell-deficient mice (WBB6F1-W/W'), and age-matched controls (WBB6F1-+/+), suggesting a minimal role of mast cells in eicosanoid biosynthesis in this model. However W/W' mice showed smaller increases in levels of myeloperoxidase, a marker for neutrophils, compared to +/+ mice. Both W/W' and +/+ mice have lower constitutive levels of peritoneal N-acetyl-beta-D-glucosaminidase (NAG), a marker for mononuclear cells. Similar to the changes seen in myeloperoxidase, W/W' mice exhibited a blunted NAG response compared to +/+ mice. These results suggest that mast cell products other than eicosanoids may contribute to the changes in cellular trafficking in response to intraperitoneal A23187. These results also suggest that mast cells are required for full expression of inflammatory responses.

Acetylglucosaminidase↗
PubMed1994

Phorbol ester-induced dermal inflammation in mice: evaluation of inhibitors of 5-lipoxygenase and antagonists of leukotriene B4 receptor.

In the present investigation, the effects of selective inhibitors of 5-lipoxygenase (5-LO), zileuton and TZI-41127, E-6080, AA-861 and antagonists of leukotriene B4 (LTB4) receptors, SC-41930, and SC-51146 and a selective cyclooxygenase inhibitor, indomethacin, were examined in TPA-induced acute mouse dermal inflammation. Topical application of all these agents, except indomethacin, resulted in marked attenuation of TPA-induced edema and influx of neutrophils reflected in myeloperoxidase measurements. Topically applied SC-41930 attenuated TPA-induced edema and neutrophil influx in a dose-related manner. Oral administration of LTB4 receptor antagonists either as a pre-treatment or post-treatment attenuated TPA-induced edema and influx of neutrophils. The O-demethyl analog of SC-41930, SC-37920, which was nearly 1000-fold less active than SC-41930 in LTB4 receptor binding assays, was inactive in inflammation assays, suggesting a role for LTB4 in this response. Zileuton and TZI-41127 were more effective as anti-inflammatory agents following oral administration than after i.p. administration. Intraperitoneally administered indomethacin attenuated edema response but not influx of neutrophils. Taken together, these results suggest a role for leukotrienes in acute inflammation induced by TPA and possible utility of this model to test in vivo 5-LO inhibitors and LTB4 receptor antagonists.

Animals↗
PubMed1994

In vivo characterization of zymosan-induced mouse peritoneal inflammation.

Intraperitoneal administration of zymosan to mice resulted in marked biosynthesis of eicosanoids and influx of neutrophils with distinct time course profiles. 6-Keto-prostaglandin-F1 alpha (6-KPA) increased between 30 and 60 min and rapidly decreased thereafter. Leukotriene (LT)C4 levels showed similar patterns, but were sustained for several hours. LTB4 increased in a biphasic manner with peak increases between 2 to 3 hr. Repeated injections with zymosan suggested that incoming neutrophils generate most of the LTB4. Myeloperoxidase (MPO), an enzyme marker for neutrophils, continued to increase throughout the time course. Mast cells regulate LTB4 biosynthesis and neutrophil trafficking, whereas resident macrophages contribute to 6-KPA and LTC4 biosynthesis. The complement fragment C5a has a minimal role in zymosan-induced inflammation. Selective 5-lipoxygenase (5-LO) inhibitors, zileuton [N-(1-benzo[b]thienyl-2yl-ethyl)-N-hydroxyurea], TZI-41127 [2-(4-hydroxy-3,5-dimethylphenyl)-5-methoxy-3-methylindole] and cyclooxygenase (CO) inhibitors selectively modulated eicosanoid biosynthesis. Both 5-LO and CO inhibitors attenuated influx of neutrophils to varying degrees. A LTB4 receptor antagonist, SC-41930 [7-(3-(4-acetyl-3-methoxy-2-propylphenoxy)-propoxy]-3,4-dihydro-8- propyl-2H-1-benzopyran-2-carboxylic acid) and an LTD4 receptor antagonist, LY-171883 [1-(2-hydroxy-3-propyl-4-(4-1H-tetrazol-5-yl)butoxy-phenyl) ethanone)] (i.v.) attenuated influx of neutrophils and associated LTB4 biosynthesis. These results suggest that both 5-LO and CO metabolites regulate neutrophil influx in this model. Marked eicosanoid biosynthesis and cellular influx in response to zymosan provides an attractive experimental paradigm to evaluate anti-inflammatory effects of inhibitors of arachidonate CO or 5-LO pathways.

Acetophenones↗
PubMed1993

Comparative evaluation of arachidonic acid (AA)- and tetradecanoylphorbol acetate (TPA)-induced dermal inflammation.

The effects of topical application of arachidonic acid (AA) or phorbol ester, tetradecanoylphorbol 13-acetate (TPA), on edema response, vascular permeability, MPO, NAG, and generation of eicosanoids were studied in two murine models of cutaneous inflammation. AA produced a short-lived edema response with a rapid onset that was associated with marked increases in levels of prostaglandins (PGE2, 6-keto-PGF1 alpha, PGF2 alpha), thromboxane B2 (TxB2) and leukotriene B4 (LTB4), with smaller increases in levels of LTC4. TPA produced a longer-lasting edema that was associated with marked influx of neutrophils and predominant formation of LTB4 along with significant changes in levels of TxB2. Circulating T lymphocytes have no apparent role in the acute inflammatory responses induced by either agent. Arachidonic acid-induced vascular permeability preceded the edema response and neutrophil influx, whereas TPA-induced vascular permeability paralleled the edema response and influx of neutrophils. Mast cells appear to be important in the complete expression of inflammatory response, i.e., edema, cellular influx, and vascular permeability induced by either AA or TPA, as these responses were blunted in mast cell-deficient mice. Inhibitors of CO or 5-LO attenuated inflammatory responses in both models. The LTB4 receptor antagonist, SC-41930, inhibited the inflammatory response to TPA but had little effect on that initiated by AA. This suggests that LTB4 is an important mediator in the phorbol ester-induced inflammatory response, whereas peptidoleukotrienes and prostaglandins regulate vascular permeability responses in the arachidonate model.

Acetylglucosaminidase↗
PubMed1993

Evaluation of 5-lipoxygenase inhibitors, zileuton, A-78773 and ICI-D-2138 in an ionophore (A-23187)-induced pleural inflammation model in the rat.

Intrapleural injection of A-23187 (10 micrograms), a calcium ionophore, elicited rapid increase in biosynthesis of prostaglandins and leukotrienes in a time-dependent manner. 6-Keto-prostaglandin-F1 alpha (6-KPA) was the principal cyclooxygenase product with modest increases in levels of thromboxane B2 and prostaglandin-E2. Orally administered indomethacin, a selective cyclooxygenase inhibitor, and three selective 5-lipoxygenase inhibitors, zileuton, A-78773 and ICI-D-2138 markedly attenuated respective arachidonate pathways with projected ED50 values of < 1-2 mg/kg. Furthermore, a single oral administration of either ICI-D-2138 or A-78773 (each 20 mg/kg, po) resulted in persistent inhibition of 5-lipoxygenase pathway for up to 24 hr. These results indicate zileuton, A-78773 and ICI-D-2138 to be potent and selective inhibitors of 5-LO and document the utility of A-23187-induced pleural inflammation in evaluating efficacy of inhibitors of arachidonic acid metabolism in vivo.

Animals↗
PubMed1993

Indole-2-carboxylates, novel antagonists of the N-methyl-D-aspartate (NMDA)-associated glycine recognition sites: in vivo characterization.

Recent in vitro receptor binding studies have indicated that indole-2-carboxylates with halogen substitutions at the position 5 or 6 are potent competitive antagonists of the NMDA (N-methyl-D-aspartate)-associated strychnine-insensitive glycine receptor (Gray N. M., Dappen M. S., Cheng B. K., Cordi A. A., Biesterfeldt J. P., Hood W. F. and Monahan J. B. (1992) J. med. Chem. 34: 1283-1292; Hood W. F., Gray N. M., Dappen M. S., Watson G. B., Compton R. P., Cordi A. A., Larthorn T. H. and Monahan J. B. (1992) J. Pharmac. exp. Ther. 262: 654-660). In the present investigation, a series of indole-2-carboxylates and two putative antagonists of glycine receptor HA-966 (3-amino-l-hydroxypyrrolidin-2-one) and 7-chlorokynurenic acid were examined for their effects on cGMP responses, mediated by the NMDA receptor complex, in vivo. Both SC-49648 (6-chloro-2-carboxyindole-3-acetic acid, intracerebellar injection, i.c.b.) and HA-966 (i.c.b. or intraperitoneal, i.p.) antagonized increases in levels of cyclic GMP in the cerebellum of the mouse, induced by the intracerebellar administration of NMDA and D-serine, agonists of the NMDA and the NMDA-associated glycine recognition sites, respectively. The drugs SC-49648 and 7-chlorokynurenic acid (i.p.) did not affect cGMP responses, suggesting poor bioavailability in brain. Following direct intracerebellar injection, SC-49648 was eliminated with a half-life of 12 min from the brain. Following intraperitoneal administration, SC-50132, the 3-ethylester analog of SC-49648, was eliminated from the brain with a half-life of 35 min and was found to be metabolized to SC-49648, in vivo. Some lipophilic analogs of SC-49648, designed as its prodrugs, were minimally active as glycine antagonists, in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Potential prodrug derivatives of 2',3'-didehydro-2',3'-dideoxynucleosides. Preparations and antiviral activities.

The preparations and antiviral activities of a series (4-17) of potential prodrug forms of the antivirals 2',3'-didehydro-2',3'-dideoxyadenosine (D4A) and 2',3'-didehydro-2',3'-dideoxycytosine (D4C) are reported. The 5'-phenyl- and 5'-methylphosphonates (4, 6, 8, and 10) and their phosphonothionate congeners (5, 7, 9, and 11), with the exception of 10, were inactive in vitro against HIV-1 and HIV-2. However, the 5'-phenyl, 5'-methyl, and 5'-(3'-thymidyl) phosphate diesters (12-17) demonstrated inhibition of the cytopathic effect of HIV-1 and HIV-2 (EC50 approximately 1-60 microM) and cytotoxicities (CC50 approximately 35-200 microM) at concentration levels comparable to those of their parent compounds, D4A and D4C. This strongly suggests that the diesters are hydrolyzed to the nucleosides D4A and D4C and/or their 5'-monophosphates. The facile hydrolysis of 12 and 13 to these products was demonstrated in a medium containing 10% fetal calf serum. The molecules can serve as ready prodrug sources of the free nucleosides and their 5'-monophosphates. Evidently, the phosphonates and phosphonothionates are not similarly cleaved, nor are they phosphorylated to form antivirally active or cytotoxic products. The importance of intracellular formation of these products in the activation of 12-17 is less clear. Potential prodrugs 4-17 are all stable in aqueous solution for hours with the exception of 14. Conjugates 4-17 showed no activity against a series of DNA and RNA viruses.

Antiviral Agents↗
PubMed1992

Characterization of 3-carboxy-5-phosphono-1,2,3,4-tetrahydroisoquinoline (SC-48981), a potent competitive N-methy-D-aspartate (NMDA) receptor antagonist, in vitro and in vivo.

(+/-)-3-Carboxy-5-phosphono-1,2,3,4-tetrahydroisoquinoline (SC-48981), a conformationally restricted analog of the potent competitive N-methyl-D-aspartate (NMDA) antagonist, 2-amino-5-phosphonopentanoate (AP-5), potently inhibited the binding of [3H]glutamate to the N-methyl-D-aspartate (NMDA) receptors with a Ki of 1.6 mcM, but with minimal affinity for kaininate and quisqualate receptors (Ki greater than 50 mcM), in vitro. Consistent with its ability to antagonize the NMDA receptor, SC-48981 decreased the binding of [3H]glycine and [3H]TCP [1-(2-thienyl)cyclohexylpiperidine] to the NMDA-associated glycine and phencyclidine (PCP) recognition sites, in vitro. SC-48981 attenuated levels of basal cGMP and harmaline-induced increases in levels of cGMP in the mouse cerebellum, in vivo, in a competitive manner, with ED50 values of 5.5 and 8.7 mg/kg, i.p. Direct intracerebellar injection of SC-48981 (0.5 microgram) attenuated increases in levels of cGMP induced by central injection of the NMDA-associated glycine receptor agonist, D-serine and by NMDA itself. Parenteral administration of SC-48981 (25 mg/kg, s.c.) decreased basal levels of cGMP for up to 3 h. These results indicate that SC-48981 represents a novel bioavailable competitive NMDA antagonist with a long duration of action.

Animals↗
PubMed1991

Effects of sigma ligands on mouse cerebellar cyclic guanosine monophosphate (cGMP) levels in vivo: further evidence for a functional modulation of N-methyl-D-aspartate (NMDA) receptor complex-mediated events by sigma ligands.

In the present investigation, the effects of sigma ligands [WY-47384 [8-fluoro-2,3,4,5-tetrahydro-2[3-(3-pyridinyl)propyl)1H- pyrido(4,3b)indole], (+)-pentazocine, (+)-SFK 10,047 (N-allylnormetazocine), mafoprazine, opipramol, dextromethorphan, dextrorphan, (+)-3-PPP [3-(3-hydroxyphenyl)-N-propylpiperidine], (-)-butaclamol, DTG [1,3-di(2-tolyl)guanidine], rimcazole, ifenprodil and BMY-14802 [alpha-(fluorophenyl)-4-(5-fluoropyrimidinyl)-1-piperazine butanol]] on harmaline-, pentylenetetrazol (PTZ)-, methamphetamine (MA)- and D-serine-induced increases in mouse cerebellar levels of cGMP were determined. Ifenprodil, BMY-14802, dextromethorphan, dextrorphan, (+)-SKF 10,047, opipramol and mafoprazine reversed harmaline-, PTZ-, MA- and D-serine-induced increases in levels of cGMP. Rimcazole reversed only the harmaline-induced response. WY-47384 reversed harmaline-, MA-, D-serine-, but not PTZ- or quisqualate-induced increases in levels of cGMP. (+)-Pentazocine attenuated harmaline- and D-serine-, but not PTZ- and MA-induced cGMP responses. Haloperidol did not affect harmaline- and D-serine-induced cGMP responses. (+)-3-PPP and (-)-butaclamol did not affect any of the responses studied. Furthermore, (+)-3-PPP-induced increases in levels of cGMP were reversed by the competitive N-methyl-D-aspartate (NMDA) antagonist, CPP]3-(2-carboxypiperazin-4-yl)propyl- 1-phosphonic acid, the non-competitive NMDA antagonist, (+)-MK-801 (dizocilipine maleate), the NMDA-associated glycine receptor antagonist, HA-966 (3-amino-1-hydroxypyrrolidin-2-one), the partial glycine agonist, DCS (D-cycloserine) as well as by the sigma ligands, ifenprodil, WY-47384, (+)-pentazocine, (+)-SKF 10,047, dextromethorphan and dextrorphan but not by rimcazole.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Morphine stimulation of mesolimbic and mesocortical but not nigrostriatal dopamine release in the rat as reflected by changes in 3-methoxytyramine levels.

Morphine was shown to enhance dopamine release in the rat olfactory tubercle, nucleus accumbens, prefrontal cortex and pyriform cortex, as assessed by increased 3-methoxytyramine (3-MT) levels and 3-MT accumulation after pargyline treatment. In contrast, both 3-MT levels and accumulation after pargyline were unaffected by morphine in the rat striatum. These data suggest that the mesolimbic and mesocortical dopaminergic projections in the rat can be activated by opiates and lead to changes in cortical function which may be involved in some of the complex behavioral actions of opiates and opioid peptides.

Animals↗
PubMed1991

Clozapine attenuates N-methyl-D-aspartate receptor complex-mediated responses in vivo: tentative evidence for a functional modulation by a noradrenergic mechanism.

Recent studies revealed a role for dopamine and noradrenaline in the etiology of ischemia-induced neuronal cell death. In the present investigation, the modulation by clozapine, an atypical antipsychotic agent that interacts with adrenergic receptors, of N-methyl-D-aspartate (NMDA) receptor complex-mediated events were studied by examining its effects on levels of cGMP in the cerebellum. Clozapine decreased basal levels of cGMP in the cerebellum and antagonized harmaline-, methamphetamine-, pentylenetetrazol- and D-serine-induced increases in levels of cGMP with ED50 values of 3.9, 2.36, 2.13 and 2.1 mg/kg (i.p.). However, clozapine (1.25-25 mg/kg) did not attenuate the quisqualate-induced increases in levels of cGMP, indicating a specific modulation of events modulated by the NMDA receptor complex. Antagonists of dopamine (D2), serotonin (5-HT)-5-HT1, 5-HT2 and 5-HT3 [haloperidol, propranolol, ritanserin, ICS 205-930 [(3-tropanyl-indole-3-carboxylate methiodide)] respectively], did not reverse the response to harmaline. However, WB-4101 [(2,6-dimethoxy-phenoxyethyl)aminomethyl-1,4-benzodioxane HCl], and alpha 1-adrenergic antagonist, reversed harmaline-, D-serine-, PTZ- and MA-induced increases in levels of cGMP, indicating an adrenergic modulation of the events mediated by the NMDA receptor complex. Intracerebellar and intracerebroventricular administration of clozapine and intracerebellar administration of WB-4101 reversed the D-serine-induced response, indicating a central locus of action. These results indicated that clozapine modulates levels of cGMP predominantly through its interactions with central adrenergic receptors.

Adrenergic alpha-Antagonists↗
PubMed1991

Polyamines modulate events mediated by the N-methyl-D-aspartate (NMDA) receptor complex through an ifenprodil-insensitive pathway: in vivo measurements of cyclic GMP in the cerebellum.

In the present investigation, the effects of polyamines, spermidine and spermine on events mediated by the N-methyl-D-aspartate (NMDA) receptor complex were examined. Spermine and spermidine did not alter basal levels of cyclic GMP (cGMP) in the cerebellum of the mouse, over a wide range of concentrations. However, exogenously added spermine, spermidine, D- and L-ornithine and putrescine attenuated the increases in cGMP seen after the administration of D-serine, an agonist of the NMDA receptor-associated glycine recognition sites. Spermine and/or spermidine also antagonized harmaline-, methamphetamine- and pentylenetetrazol-induced increases in the levels of cGMP. Spermidine also potentiated (+)-MK-801 (dizocilipine)-induced attenuation of basal levels of cGMP. Intracerebroventricular administration of ifenprodil, a suggested polyamine antagonist, did not antagonize spermine- and spermidine-induced attenuation of the response to D-serine. These data suggest that exogenously added polyamines attenuate events mediated by the NMDA receptor complex, in an ifenprodil-insensitive manner.

Animals↗