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Biomedical subjects

A Chandra

Publications and source records attributed to A Chandra.

At least 19 recordsLinked to original sources
PubMed1992

Antimicrobial screening of essential oils and extracts of some Humulus lupulus L. cultivars.

The essential oils as well as solvent extracts of 11 hop cultivars, 1 hop variety and a wild type of hop were screened for their antimicrobial activities using the agar overlay technique. The oils were isolated from the cones of the various hop plants by hydrodistillation, the extracts were obtained by soaking the hop cones in chloroform. The oils and the extracts showed activity against the Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and the fungus (Trichophyton mentagrophytes var. interdigitale), but almost no activity against the Gram-negative bacterium (Escherichia coli) and the yeast (Candida albicans) used in the screening. The peak area percentages of the main volatile components and the contents of the bitter acids of the extracts were determined for all cultivars using chromatographic methods.

Bacteria↗
PubMed1991

Epidemiology of infertility.

Recent infertility literature has focused on the epidemiologic evaluation of diagnostic and therapeutic measures. The predictive value of the postcoital test and the sperm penetration assays has been called into question, particularly for female factor infertility. Several studies have sought better prognostic guidelines for assisted reproductive technologies such as artificial insemination by donor and in vitro fertilization and embryo transfer, as well as more cost-effective screening measures for evaluating infertile couples. Recent epidemiologic investigations have found no adverse effects of infertility therapy on the health of mothers or their babies.

Female↗
PubMed1990

Novel features of retroviruses associated with human diseases.

The last decade has witnessed a new chapter in the history of retrovirology. As of now, four human retroviruses have been identified and molecularly characterized. They are associated with a wide spectrum of human diseases including cancer, immunodeficiency and neurological disorders. By virtue of their clinical relevance, their novel genes and regulatory mechanisms these viruses have become the focal point of research in retrovirology. The study of these viruses is of fundamental importance in understanding the mechanisms leading to transformation of human cells and distortion of the immunological state.

Genes, Viral↗
PubMed1990

Retroviral expression in mononuclear blood cells isolated from a patient with osteopetrosis (Albers-Schönberg disease).

We report the presence of reverse transcriptase activity in the supernatant of long-term culture of mononuclear blood cells (monocytes and lymphocytes) isolated from a 27-year-old patient suffering from benign osteopetrosis. The enzyme was purified to homogeneity according to the technique of Chandra and Steel, by chromatography, first on DEAE-cellulose (DE 52) and then on phosphocellulose (P11). After purification, the enzyme was characterized biochemically for its template specificity and ionic requirements. The purified enzyme was able to transcribe poly(rA).(dT)12-18 and poly(rC).(dG)12-18 very efficiently and had a marked preference for Mg2+ ions over Mn2+ ions. The pattern of ionic dependency for this enzyme is similar to that of reverse transcriptases purified from human lymphotropic viruses. The patient was tested and found sero-negative for HIV-1, HIV-2, and HTLV-I and seropositive (immunoglobulin G) for cytomegalovirus. Epstein-Barr virus nuclear antigens (EBNA) were detected in the patient's B lymphocytes. Since reverse transcriptase is the hallmark of retroviruses, we suggest that a retrovirus may be involved in the etiology of osteopetrosis.

Adult↗
PubMed1990

A host-mediated in vivo/in vitro assay with peritoneal murine macrophages for the detection of carcinogenic chemicals.

We have developed a host-mediated assay system for the detection of the transforming action of chemical carcinogens on peritoneal macrophages. Directly as well as indirectly acting carcinogenic substances administered intraperitoneally to NMRI mice could be examined in this way. Resident macrophages were recovered by peritoneal lavage from treated and untreated mice and were cultured in soft agar. After 5-6 days normal and transformed cells could be distinguished. Statistical analysis comparing cells, for example, from alpha-naphthylamine or diphenylhydantoin-treated animals with those from control mice proved that the test is positive at least on a significance level of 5% using the t-test. Further substances revealing a cell-transformation potential were benzene, benz(a)pyrene, 2,3,7,8-tetrachlorodibenzodioxin, N-nitrosodimethylamine, ethidium bromide, aflatoxin B1,N-methyl-N-nitrosourea, 1-methyl-3-nitro-1-nitrosoguanidine, 2-naphthylamine, dieldrin, suramin and trichloroethylene. A weak transforming potential was found for chlorambucil as well as for tetrachloroethylene. With toluene or azidothymidine no cell transformation could be observed. Several immortal cell lines could be established form NMRI mice treated with alpha-naphthylamine or N-methyl-N-nitrosourea. Athymic nu/nu mice injected subcutaneously with these cells developed tumors, establishing the oncogenic potential of these cell lines.

1-Naphthylamine↗
PubMed1990

Postviral syndrome.

Explore the source record for details and available documents.

Fatigue Syndrome, Chronic↗
PubMed1990

Epitope mapping of the low-molecular-mass subunits of reverse transcriptase in human immunodeficiency virus type 1 by monoclonal antibodies.

With the aid of monoclonal antibodies to the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1), low-molecular-mass subunits (p29, p32, and p40) were identified in HIV-1 RT purified from HIV (HTLV-IIIB) virions by isoelectric focusing. Epitope mapping with synthetic polypeptides from various regions of the pol gene suggests that the low-molecular-mass subunits result from N-terminal cleavage of the p51 subunit. The subunits could be separated only by SDS-polyacrylamide gel electrophoresis and detected by immunoblotting. They could not be separated on chromatographic columns, suggesting that the subunits are complexed or conformationally arranged in such a way that their separation on the basis of molecular mass is not possible. The molecular mass of the active enzyme eluted from a chromatographic column (Sephacryl S-300) loaded with a mixture of the subunits was estimated to be 100 kDa.

Animals↗
PubMed1988

D-penicillamine inhibits transactivation of human immunodeficiency virus type-1 (HIV-1) LTR by transactivator protein.

D-Penicillamine, an amino acid analogue of cysteine, has been shown to inhibit the transactivation of HIV-1 LTR by the transactivator protein, tat protein. The transactivation was studied in Jurkat cells co-transfected with plasmids containing HIV-LTR sequences fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and HIV tat gene. The expression of CAT activity was a measure of transactivation of LTR by the tat protein. Incubation of transfected Jurkat cells with D-penicillamine led to inhibition of CAT activity. This inhibition was found to be concentration-dependent; more than 90% inhibition of chloramphenicol acetylation was seen in extracts prepared from cultures incubated with 40 micrograms/ml of D-penicillamine. Earlier experiments have shown that D-penicillamine at 40 micrograms/ml can completely inhibit HIV-1 (HTLV-III B) replication in H9 cells [(1986) Drug Res. 36, 184-186]. These results suggest that inhibition of transactivation may be the molecular mechanism involved in the inhibition of HIV-1 replication by D-penicillamine.

Cell Line↗
PubMed1986

Serological relationship between reverse transcriptases from human T-cell lymphotropic viruses defined by monoclonal antibodies. Evidence for two forms of reverse transcriptases in the AIDS-associated virus, HTLV-III/LAV.

The immunological relationship between reverse transcriptases purified from human T-cell lymphotropic viruses (HTLV-I, HTLV-II, HTLV-III) was defined using monoclonal antibodies specific for HTLV-III reverse transcriptase, secreted by a mouse/mouse hybridoma clone (4F8) developed in our laboratory. The viral proteins from HTLV-I and HTLV-II do not bear any cross-reactive epitope to antibodies secreted by this clone. These antibodies specifically cross-react with HTLV-III reverse transcriptase. The antibodies failed to neutralize the catalytic activity of reverse transcriptase; however, after immunoprecipitation with a magnetic conjugate of goat anti-mouse IgG, the residual activity was completely inhibited. This shows that the antibodies are not directed towards the catalytic active center of the enzyme. Using an immunoblotting technique (Western blotting), we have found two cross-reactive proteins with HTLV-III lysate with molecular masses of 53 and 66 kDa. This suggests that HTLV-III possesses two reverse transcriptase activities with a common determinant recognized by the same epitope.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Biochemical heterogeneity of reverse transcriptase purified from the AIDS virus, HTLV-III.

The reverse transcriptase from AIDS virus, HTLV-III, was purified and characterized. The purified enzyme has a very high affinity for template primers (rC)n X (dG)12 and (rCm)n X (dG)12 compared to that for (rA)n X (dT)12. In addition, the HTLV-III reverse transcriptase was able to transcribe (rAm)n X (dT)12 very efficiently. The ionic requirements are unique in the sense that HTLV-III reverse transcriptase prefers Mg2+ as divalent ions to transcribe (rC)n X (dG)12 and (rA)n X (dT)12. The Mr of the enzyme is 95 000-98 000. Unlike the HTLV-I reverse transcriptase, the HTLV-III enzyme is highly stable and has a much higher activity in the presence of (rC)n X (dG)12; the Vmax for HTLV-III reverse transcriptase is several-fold higher than that for HTLV-I enzyme. The enzyme activity of the purified reverse transcriptase from HTLV-III was resolved into two peaks on a preparative isoelectric column, one at pH 5.75 and the other at pH 6.25. This leads us to conclude that the reverse transcriptase of HTLV-III is biochemically heterogeneous.

Cations, Divalent↗
PubMed1986

The effect of 17-alpha-estradiol, a possible endogenous opiate antagonist, on D-ala2-met5-enkephalinamide-induced blood pressure responses in conscious, unrestrained rats.

D-ala2-met5-enkephalinamide (DAME) produced a dose-related increase in the mean arterial blood pressure of conscious, unrestrained rats. Intravenous injection of DAME (0.5, 1, 2, and 4 mg/kg) resulted in mean systemic arterial blood pressures of 138 +/- 2, 146 +/- 5, 141 +/- 4, 156 +/- 5 mmHg, respectively. 17-alpha-estradiol and its derivatives are known to be inactive in target tissues responsive to estrogenic hormones such as 17-beta-estradiol. However, LaBella et al. (1978) found after testing a large number of steroid hormones and their metabolites that only 17-alpha-estradiol significantly inhibited binding of 3H-naloxone, an opiate antagonist, in rat-brain homogenates. The present study was designed to determine whether 17-alpha-estradiol could antagonize the cardiovascular responses elicited by intravenous injections of DAME. Intravenous infusion of 17-alpha-estradiol (1.5 mg/kg) every 2 hours for 24 hours (total infusion time was 2 minutes for each infusion) did not change the mean systemic arterial blood pressure (94 +/- 5 mmHg) compared to the blood pressure prior to infusion of 17-alpha-estradiol (99 +/- 7 mmHg). Intravenous infusion of 17-alpha-estradiol (1.5 mg/kg) 10 minutes prior to DAME (1 mg/kg, i.v.) resulted in a blood pressure of 106 +/- 9 mmHg, which is significantly less than the blood pressure of 146 +/- 5 mmHg seen with DAME (1 mg/kg, i.v.) alone. Intravenous injection of DAME (1 mg/kg) 8 hours after the last infusion of 17-alpha-estradiol produced an increase in mean systemic arterial blood pressure of 136 +/- 8 mmHg. These results indicate that 17-alpha-estradiol may function as an opiate antagonist.

Animals↗
PubMed1979

Effects of gamma-hydroxybutyric acid on metabolic, respiratory and vasomotor activities and body temperature in rats.

The effects of gamma-hydroxybutyric acid (GHBA) on metabolic, respiratory and vasomotor activities and body temperature were assessed in unanesthetized rats at three different ambient temperatures (Ta) of 8, 22 and 30 degrees C. Intraperitoneal administration of GHBA produced dose-dependent hypothermia in rats at both 8 and 22 degrees C Ta. At Ta = 8 degrees C the hypothermia was brought about solely by a decrease in metabolic heat production, while at Ta = 22 degrees C the hypothermia was due to both a decrease in metabolic heat production and an increase in cutaneous circulation (as indicated by changes in tail and foot skin temperatures). However, at Ta = 30 degrees C GHBA administration produced no changes in rectal temperature or other thermoregulatory parameters. Respiratory evaporative heat loss was not affected by GHBA application. Furthermore, it was found that the GHBA-induced hypothermia was antagonized by haloperidol (a selective blocker of dopamine receptors), but not by p-chlorophenylalanine (an inhibitor of serotonin synthesis). The data suggest that GHBA elicits a central dopamine receptor activation mainly via release of endogenous dopamine and leads to a hypothermia.

Animals↗