Biomedical subjects

R Vince

Publications and source records attributed to R Vince.

At least 37 records · Page 2Linked to original sources

PubMed1989

Comparison of the effect of Carbovir, AZT, and dideoxynucleoside triphosphates on the activity of human immunodeficiency virus reverse transcriptase and selected human polymerases.

Carbocylic 2',3'-didehydro-2',3'-dideoxyguanosine (Carbovir; NSC 614846) is an antiretroviral agent which may be useful in the treatment of AIDS. We have synthesized the 5'-triphosphate of Carbovir and examined its ability to inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (EC 2.7.7.49) and other retroviral reverse transcriptases, as well as human DNA polymerases alpha, beta, gamma (EC 2.7.7.7) and DNA primase (EC 2.7.7.6). Carbovir triphosphate emerges as a highly selective inhibitor of reverse transcriptases with little, if any, effect on the cellular enzymes. 3'-Azido-2',3'-dideoxythymidine (AZT) triphosphate and the two dideoxynucleoside triphosphates, ddTTP and ddGTP, inhibited HIV-1 reverse transcriptase to the same degree as Carbovir triphosphate, but were less selective in that they also inhibited DNA polymerases beta and gamma. We conclude that Carbovir is a highly selective antiretroviral agent.

DNA Primase↗

PubMed1989

Liquid chromatographic assay of carbovir, a carbocyclic nucleoside active against human immunodeficiency virus.

Carbovir is a novel carbocyclic guanosine derivative that has potent in vitro activity against human immunodeficiency virus, the causative agent of acquired immunodeficiency syndrome (AIDS). Two methods of sample preparation were developed for the analysis of carbovir in rat blood. Solid-phase extraction on C18 extraction columns proved to be the most effective. Whole rat blood (200 microliters) was diluted with 0.8 ml of distilled water containing the internal standard. After two freeze-thaw cycles to lyse the red blood cells and subsequent centrifugation at 13,000 g, the supernatant was loaded on the C18 extraction columns. Carbovir and the internal standard were eluted with methanol-water (60:40). The extract was evaporated and reconstituted in mobile phase and the samples were injected onto a high-capacity reversed-phase column. The compounds were detected at 252 nm. Other nucleosides that could be used in the treatment of AIDS such as zidovudine and acyclovir did not interfere. Standard curves were linear over the concentration range 0.156-28.0 micrograms/ml (r2 greater than 0.99). The within-day coefficient of variation was less than 7.6% at all concentrations (n = 4). The between-day coefficient of variation ranged from 16.7 to 2.0% (n = 14). The limit of sensitivity was 0.05 micrograms/ml with a 200-microliters blood sample and the average extraction recovery was 74%. Carbovir was stable in rat blood for at least 4 h at 37 degrees C. The assay was used to determine the blood levels of carbovir in a rat after a 20 mg/kg intravenous dose.

Animals↗

PubMed1989

Pharmacokinetics and bioavailability of carbovir, a carbocyclic nucleoside active against human immunodeficiency virus, in rats.

Carbovir is a novel carbocyclic nucleoside which has been shown to have potent in vitro activity against human immunodeficiency virus, the causative agent of acquired immunodeficiency syndrome. Sprague-Dawley male rats were used to investigate the pharmacokinetics and bioavailability of carbovir. Six rats received carbovir (20 mg/kg of body weight) through the jugular vein, and blood samples were collected through the femoral vein 2, 5, 10, 15, 20, 30, 45, 60, 75, 90, 120, 150, 180, and 240 min after the dose. Four of these rats also received a 60-mg/kg oral dose of carbovir, and a similar blood sampling schedule was followed. Whole-blood samples were prepared by solid-phase extraction, and the carbovir concentration in the samples was analyzed by reversed-phase high-pressure liquid chromatography. The profile of carbovir concentration in blood versus time after the intravenous dose was biexponential, with a very rapid distribution phase. Terminal elimination half-life was 21.4 +/- 4.37 min, and total body clearance was 55.2 +/- 13.8 ml/min per kg, which was within the range of the hepatic blood flow. The volume of distribution at steady state was 1,123 +/- 250 ml/kg. The blood/plasma ratio and the plasma protein binding of carbovir in rat blood were determined in vitro by ultrafiltration. The plasma protein binding of carbovir was only 20% and was not concentration dependent. However, the blood/plasma ratio decreased significantly as concentration increased, indicating saturable binding sites in erythrocytes. After the oral dose, the terminal half-life was 81.0 +/- 67.6 min, indicating that oral carbovir followed "flip-flop" kinetics, with absorption being much slower than elimination of the drug from the body. Oral bioavailability was 0.101 +/- 0.035. Double peaks were present in the concentration-time profile for each rat receiving the oral dose, indicating either a delay in stomach emptying of the drug or slow dissolution of precipitated carbovir in the stomach and upper small intestine.

Animals↗

PubMed1988

Potent and selective activity of a new carbocyclic nucleoside analog (carbovir: NSC 614846) against human immunodeficiency virus in vitro.

Carbocyclic 2',3'-didehydro-2',3'-dideoxyguanosine (Carbovir: NSC 614846), a novel nucleoside analog, emerged as a potent and selective anti-HIV agent from a large screening program conducted by the National Cancer Institute and its contractors. Its hydrolytic stability and its ability to inhibit the infectivity and replication of HIV in T-cells at concentrations of approximately 200- to 400-fold below toxic concentrations make carbovir a top-priority candidate for development as a potential antiretroviral agent in the treatment of AIDS patients.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Synthesis and biological evaluation of acyclic neplanocin analogues.

Acyclic neplanocin analogues were prepared by condensation of adenine or N2-acetylguanine with (E)-1,4-dichlorobut-2-ene and subsequent hydrolysis. The N-9-substituted product 9-[(E)-4-hydroxybut-2-enyl]adenine was obtained when adenine was employed as the starting purine, while N2-acetylguanine yielded both the N-7 and N-9 isomers. Cell-culture studies revealed that only the chloro-substituted intermediate 9-[(E)-4-chlorobut-2-enyl]adenine exhibited significant cytotoxicity against P-388 mouse lymphoid leukemia cells, while the N-9-substituted guanine analogue 9-[(E)-4-hydroxybut-2-enyl]guanine inhibited replication of herpes simplex viruses type 1 and type 2.

Adenine↗

PubMed1987

Synthesis and antiviral activity of carbocyclic analogues of xylofuranosides of 2-amino-6-substituted-purines and 2-amino-6-substituted-8-azapurines.

(+/-)-(1 alpha,2 beta,3 alpha,5 alpha)-3-[(2,5-Diamino-6-chloro-4- pyrimidinyl)amino]-5-(hydroxymethyl)-1,2-cyclopentanediol (7) was synthesized from 2-amino-4,6-dichloropyrimidine and the carbocyclic xylofuranosylamine (+/-)-(1 alpha,2 beta,3 alpha,5 alpha)-3-amino-5-(hydroxymethyl)-1,2-cyclopentanediol (2) by subsequent preparation of the 5-[(4-chlorophenyl)azo] derivative of the resulting pyrimidine and reduction of the azo moiety with zinc and acetic acid. The carbocyclic analogue of 2-amino-4-chloropurine xylofuranoside (8) and the corresponding 8-azapurine 11 were prepared from 7. The carbocyclic analogues xylofuranosylguanine (9), xylofuranosyl-2,6-diaminopurine (10), xylofuranosyl-8-azaguanine (13), and xylofuranosyl-8-aza-2,6-diaminopurine (14) were prepared from 8 and 11. Compounds 9 and 13 were active against herpes simplex virus (types 1 and 2), with 9 being the more potent against both viruses. Analogue 9 also exhibited potent activity against human cytomegalovirus and varicella-zoster virus.

Animals↗

PubMed1986

Carbocyclic puromycin: synthesis and inhibition of protein biosynthesis.

The carbocyclic analogue of puromycin was prepared by the coupling of N-(benzyloxycarbonyl)-p-methoxy-L-phenylalanine to the racemic aminonucleoside (+/-)-9-[3 beta-amino-2 beta-hydroxy-4 alpha-(hydroxymethyl)cyclopent-1 alpha-yl]-6-(dimethylamino)purine, followed by separation of the diastereomers and subsequent removal of the Cbz blocking group. Kinetic studies indicate that carbocyclic puromycin is an excellent substrate for the peptidyltransferase reaction with both prokaryotic and eukaryotic ribosomes. A comparison of carbocyclic puromycin with previously synthesized analogues indicate that the furanosyl ring oxygen and the hydroxymethyl group of puromycin do not contribute to ribosomal binding, but both moieties contribute to the rate of product formation from the enzyme-substrate complex. Carbocyclic puromycin was equal to puromycin when evaluated for cytotoxicity using P-388 mouse lymphoid leukemia cells in culture.

Animals↗

PubMed1986

Hypotensive and renal vasodilator effects of carbocyclic adenosine (aristeromycin) in anesthetized spontaneously hypertensive rats.

Systemic arterial pressure and renal blood flow were measured in pentobarbital-anesthetized spontaneously hypertensive rats to assess the influence and mechanism of action of metabolically stable adenosine analogs on renal hemodynamics. (-)-Aristeromycin (carbocyclic adenosine; CA), a model carbocyclic nucleoside, was characterized with respect to adenosine receptor pharmacology by comparison to the effects elicited by the prototypic adenosine analogs 5'-N-ethylcarboxamide adenosine (NECA; an adenosine A1 and A2 receptor agonist) and N6-cyclohexyl adenosine (an adenosine A1 agonist). Intravenous bolus injections of CA and NECA caused dose-dependent hypotension and renal vasodilatation. Although CA and NECA were equally efficacious hypotensive agents, NECA was approximately 100-fold more potent than CA. CA was a more efficacious renal vasodilator than NECA. In contrast, at doses which had minimal effects on systemic arterial pressure, N6-cyclohexyl adenosine decreased renal blood flow. The hypotensive and renovascular effects of the adenosine analogs but not those of a control vasodilator, methacholine, were attenuated by i.v. administration of the xanthines aminophylline and 8-phenyltheophylline; thus, the effects of the nucleosides on renal blood flow in vivo appear to be attributable in part to activation of adenosine receptors. The profile of cardiovascular effects caused by CA suggests that this agent acts primarily as an adenosine A2 receptor agonist.

Adenosine↗

PubMed1984

Inhibition of peptidyltransferase and possible mode of action of a dipeptidyl chloramphenicol analog.

A dipeptidyl chloramphenicol analog, D-threo-2-(L-phenylalanylglycyl)amino-3-p-nitrophenyl-1,3- propanediol, has been prepared and examined as an inhibitor of ribosomal peptidyltransferase. The analog is a more effective inhibitor of poly (U,C) directed protein biosynthesis in an Escherichia coli cell-free system than chloramphenicol and shows inhibitory activity equal to the parent antibiotic in the transpeptidation reaction. These results and the common structural features of puromycin and this compound suggest a model for the binding modes of chloramphenicol and chloramphenicol analogs. This proposal invokes four major binding pockets at the A-site of the peptidyltransferase center.

Acyltransferases↗

PubMed1984

Carbocyclic analogues of xylofuranosylpurine nucleosides. Synthesis and antitumor activity.

(+/-)-4 alpha-Amino-2 alpha,3 beta-dihydroxy-1 alpha-cyclopentanemethanol (6), the carbocyclic analogue of xylofuranosylamine, was synthesized from the previously reported 4 alpha-acetamido-2 alpha,3 alpha-epoxycyclopentane-1 alpha-methanol. Amine 6 was converted to (+/-)-4 alpha-[(5-amino-6-chloro-4-pyrimidinyl)amino]-2 alpha,3 beta-dihydroxy-1 alpha-cyclopentanemethanol (7) by condensation with 5-amino-4,6-dichloropyrimidine. From 7, the carbocyclic analogues of xylofuranosyladenine and xylofuranosyl-8-azaadenine were prepared. In contrast to 9-beta-D-xylofuranosyladenine and its 8-aza analogue, the corresponding carbocyclic nucleosides were resistant to deamination by adenosine deaminase. The carbocyclic 8-aza derivative 10 exhibited significant in vivo antitumor activity which varied according to treatment schedule.

Adenosine Deaminase↗

PubMed1983

Carbocyclic arabinofuranosyladenine (cyclaradine): efficacy against genital herpes in guinea pigs.

Carbocyclic arabinofuranosyladenine (cyclaradine), a novel nucleoside analog with such desired features as hydrolytic and enzymatic stability, adenosine deaminase resistance, and low systemic toxicity, inhibited the replication of herpes simplex virus types 1 and 2. The 5'-methoxyacetate prodrug form exhibited significant efficacy in the topical treatment of genital infections by herpes simplex virus type 2.

Acyclovir↗

PubMed1983

Comparison of the efficacy of vidarabine, its carbocyclic analog (cyclaradine), and cyclaradine-5'-methoxyacetate in the treatment of herpes simplex virus type 1 encephalitis in mice.

The relative therapeutic effects of vidarabine (9-beta-D-arabinofuranosyladenine), cyclaradine (the adenosine deaminase-resistant carbocyclic analog of vidarabine), and cyclaradine-5'-methoxyacetate in the parenteral treatment of systemic herpes simplex virus type 1 infections in Swiss mice were determined. Among control mice inoculated intraperitoneally with virus, a mortality rate of 95% was observed. The intraperitoneal administration of nontoxic doses of vidarabine (125 to 250 mg/kg per day) or cyclaradine (113 to 450 mg/kg per day), by daily injections for 7 days beginning 4 h after virus inoculation, reduced mortality to 0 to 10%. Among control animals inoculated intracerebrally with 32 50% lethal doses of virus, 100% mortality was observed, with a mean survival time of 4.6 days. Treatment with either drug at equimolar dose levels ranging from ca. 32 to 750 mg/kg per day produced significant (P less than 0.0005), dose-dependent increases in the mean survival time of animals dying of herpesvirus encephalitis. Mice inoculated intracerebrally with 10 50% lethal doses of virus exhibited 97% mortality and a mean survival time of 5.5 to 6.4 days. Treatment with vidarabine, cyclaradine, or cyclaradine-5'-methoxyacetate significantly increased the mean survival time of dying animals and, at doses ranging from 250 to 750 mg/kg per day, produced significant increases in survival. The three drugs displayed equivalent antiviral efficacy in vivo. Drug toxicity (measured by weight loss) was not detected in mice treated with cyclaradine or cyclaradine-5'-methoxyacetate at 750 mg/kg per day, whereas severe toxicity (weight loss of greater than or equal to 3 g) was observed in mice treated with vidarabine at an equivalent dose level. Thus, cyclaradine or its 5'-methoxyacetic acid ester may possess some advantage over vidarabine in the treatment of severe herpesvirus infections and should therefore be considered for clinical trials in humans.

Animals↗

PubMed1981

Puromycin analogues. Effect of aryl-substituted puromycin analogues on the ribosomal peptidyltransferase reaction.

A series of ortho- and para-substituted L-phenylalanylpuromycin analogues were synthesized and evaluated as substrates for the peptidyltransferase reaction of Escherichia coli ribosomes. Kinetic results reveal that substitution of the p-methoxy group of the puromycin molecule alters the peptidyltransferase activity of the molecule with the following decreasing order of substrate efficiencies: p-NH2 greater than p-NHCOCH3 greater than p-NO2 = p-NHCO(CH2)2CH3 greater than p-NHCOCH2Br. However, the inability of the ribosome to tolerate a nitro group at the ortho position of the phenylalanine ring precluded the use of the photosensitive puromycin analogue, 2-nitro-4-azidophenylalanylpuromycin aminonucleoside (7a), as a photoaffinity label for the peptidyltransferase site.

Acyltransferases↗

PubMed1981

5'Chloropuromycin. Inhibition of protein synthesis and antitrypanosomal activity.

A facile, two-step conversion of puromycin aminonucleoside (PAN) into 5'-deoxy-PAN (5) via 5'-chloro-5'-deoxy-PAN (1) was accomplished. Replacement of the 5'-OH group of PAN with H or Cl resulted in the elimination of kidney toxicity associated with the administration of PAN. The corresponding puromycin derivatives, 5'-chloro-5'-deoxypuromycin (4) and 5'-deoxypuromycin (6), derived from 1 and 5, respectively, were compared in a ribosomal peptidyltransferase assay. Both compounds were excellent substrates for the transpeptidation reaction, confirming our previous observations with 6 that the 5'-OH of puromycin is not essential for activity at the ribosomal level. Thus, 4 represents a new puromycin derivative that retains puromycin-like activity at the ribosomal site but is capable of releasing only a nonnephrotoxic aminonucleoside upon enzymatic release of the p-methoxyphenylalanyl side chain. The chloro derivative 4 exhibited significant antitrypanosomal activity in mice infected with Trypanosoma rhodesiense. The 5'-deoxy derivative 6 was inactive against trypanosomes.

Animals↗

PubMed1980

Carbocyclic analogs of arabinosylpurine nucleosides.

Carbocyclic analogs of arabinofuranosylguanine (VII) and 2,6-diamino-9-beta-arabinofuranosylpurine (VIII) and the corresponding 8-azapurine analogs, 5-amino-7-hydroxy-3-[2 alpha,3 beta-dihydroxy-4 alpha-(hydroxymethyl)cyclopent-1 alpha-yl]-v-triazolo[4,5-d]pyrimidine (X) and 5,7-diamino-3-[2 alpha,3 beta-dihydroxy-4 alpha-(hydroxymethyl)cyclopent-1 alpha-yl]-v-triazolo[4,5-d]pyrimidine (XI), were prepared. Carbocyclic nucleoside analogs VII and X exhibited significant cytotoxicity against P-388 mouse leukemia cells in culture. In vitro testing against herpes simplex type 1 (strain HF) indicated that only VIII exhibited significant antiviral activity.

Animals↗

PubMed1979

Ribosomal protein alterations in thiostrepton- and Micrococcin-resistant mutants of Bacillus subtilis.

Ribosomal proteins of parental thiostrepton- and micrococcin-sensitive Bacillus subtilis cysA14 and thiostrepton-and micrococcin-resistant mutants were compared. Several electrophoretic and immunochemical techniques showed unambiguously that BS-L11 was not present on 50 S ribosomal subunits from the six thiostrepton-resistant mutants. Protein BS-L11 reappeared in all six revertants from thiostrepton resistance to thiostrepton sensitivity. No definitive protein alteration could be ascribed to the mutation from micrococcin sensitivity to resistance. It was also demonstrated that B. subtilis protein BS-L11 is homologous to Escherichia coli ribosomal protein L11. The finding that ribosomes from thiostrepton-resistant mutants do not contain protein L11 suggests that L11 not only is involved in binding of thiostrepton, but also, when mutationally altered, confers resistance to this antibiotic. Although the ribosomes of these strains do not contain protein L11, all thiostrepton-resistant mutants showed the same viability as the parental strain. Thus protein L11 cannot be obligatory for the structure and function of the ribosome.

Anti-Bacterial Agents↗

PubMed1979

Poly(2-fluoroadenylic acid). The role of basicity in the stabilization of complementary helices.

The polymerization of 2-fluoroadenosine 5'-diphosphate by polynucleotide phosphorylase to give high molecular weight poly(2-fluoroadenylic acid), poly(fl2A), is described. Both the single-stranded and double-stranded (acid) forms of poly(fl2A) exhibit strikingly similar ultraviolet and circular dichroism spectra to those of poly(A), and the enzymatic polymerization rates and thermal hyperchromicities of the two polymers are also very similar. However, the pKa of poly(fl2A) for protonation at N-1 is 2.9 compared to 5.9 for poly(A) under similar conditions. Poly(fl2A) forms a triple-stranded helix with poly(U) which has ultraviolet and cd spectra very reminiscent of poly(A) . 2 poly(U), but no conditions could be found which permitted the formation of a double helix. In the Escherichia coli ribosome system poly(fl2A) codes for the synthesis of polylysine, as does poly(A), although the rate and extent of incorporation were less in the former case. The role of basicity of adenine N-1 in these interactions is discussed.

Drug Stability↗

PubMed1979

In vitro biosynthesis of juvenile hormone by the larval corpora allata of Manduca sexta: quantificationby radioimmunoassay.

An in vitro method has been developed for the investigation of the regulation of juvenile hormone biosynthesis by insect corpora allata. Glands were maintained in Marks medium 19AB and JH synthesis quantified by a modified radioimmunoassay for juvenile hormone I. The radioimmunoassay is specific for JH I and exhibits approximately 12.6% cross reactivity with JH II and no cross reactivity with JH III. The assay directly measures the JH present in culture medium and has a maximum sensitivity of 50 pg JH I equivalents. Corpora allata from day 5 last instar Manduca sexta larvae were used to define the kinetics parameters of the in vitro system, including a demonstration that small groups of right and left glands synthesize equivalent amounts of juvenile hormone. The juvenile hormones synthesized were identified as juvenile hormones I and II in a ratio of 1:4, respectively. Juvenile hormone III could not be excluded as a product of the corpora allata owing to the low cross reactivity of this homolog (1.7%) in the radioimmunoassay. Corpora allata from different developmental stages exhibited synthesis rates generally consistent with predicted activity based on in vivo hormone titers with the exception of day 5 of the last instar. The variation in gland activity relative to the control of juvenile hormone titer in vivo is discussed.

Aging↗