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Biomedical subjects

A Srinivasan

Publications and source records attributed to A Srinivasan.

At least 253 records · Page 14Linked to original sources
PubMed1988

Pharmacokinetics of pralidoxime chloride and its correlation to therapeutic efficacy against diisopropyl fluorophosphate intoxication in rats.

A two compartment system is used to study the therapeutic efficacy of pralidoxime chloride (1) along with a suitable pretreatment against diisopropyl fluorophosphate (2) intoxication in rats. The data were analyzed by standard techniques. Though thiamine hydrochloride pretreatment prolonged the biological half-life of 1 but it failed to increase the protective efficacy of 1, on the other hand sodium hydrogen carbonate pretreatment augmented the protective action of 1 without altering its biological half-life appreciably, through increased distribution of 1 into tissue compartment.

Animals↗
PubMed1987

Sodium butyrate activates human immunodeficiency virus long terminal repeat--directed expression.

To study the effect of sodium butyrate on human immunodeficiency virus (HIV) long terminal repeat (LTR)--directed expression, we constructed a chimeric plasmid (pLTR-CAT) in which the LTR sequences derived from a molecular clone of HIV were fused to the chloramphenicol acetyltransferase (CAT) gene. We used transient expression assays in transfected tissue culture cells to monitor the activity of the LTR. The expression of the pLTR-CAT plasmid was activated when the cells were exposed to butyrate after transfection. The magnitude of butyrate-induced increase was linear up to an 8 mM concentration and was different with regard to the target promoters used. Recombinant plasmids linked to marker genes may be useful models for studying the effects on HIV of various agents of chemical and biological origin.

Butyrates↗
PubMed1987

Three-dimensional similarity mapping reveals nucleotide sequence relationships among human immunodeficiency virus (HIV) isolates.

A method has been developed to compare and graphically display comparisons between many related nucleotide sequences. Principal coordinate analysis, a multidimensional scaling technique, was used to display DNA homology data in three dimensions. Using these methods, an analysis of the env, gag, and gag/pol overlapping regions of human immunodeficiency virus (AIDS virus) clearly demonstrates a clustering of North American isolates relative to African isolates. Elements of the latter group are dissimilar to one another and to the North America group. For the env region, the North American isolates can be resolved into two distinct groups.

Base Sequence↗
PubMed1987

Molecular characterization of human immunodeficiency virus from Zaire: nucleotide sequence analysis identifies conserved and variable domains in the envelope gene.

To examine the genetic relatedness of human immunodeficiency viruses (HIV) from different geographic locations, we molecularly cloned the genome of HIV isolated from a Zairian AIDS patient. Restriction mapping of the recombinant clone, designated HIV-Zr6, revealed both common (as observed in other HIV isolates) and unique restriction sites. The DNA clone of HIV-Zr6, shown to give rise to infectious cytopathic virus after transfection of cultured lymphoid cells, was sequenced in several regions. The long terminal repeat (LTR), open reading frame 1 (ORF1), C-terminal envelope (env) gene domain, and ORF2 showed less than 6% difference in nucleotide sequence when compared to other HIV isolates including human T-lymphotropic virus-type III (HTLV-III) clone B10, lymphadenopathy-associated virus-1 (LAV-1), and AIDS-associated retrovirus-2 (ARV-2). About 15% difference in nucleotide sequences was noted in the N-terminal env gene domain. Alignments of env gene sequences revealed conserved, moderately variable, and hypervariable stretches in the predicted amino acid sequences. This model provides a basis for assessing the significance of sequence variation on properties controlled by the viral Env glycoproteins such as cell tropism and immunogenicity.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Superinfection of a chimpanzee with a second strain of human immunodeficiency virus.

Two chimpanzees, one (C-499) infected with the acquired immunodeficiency syndrome-associated retrovirus type 2 (ARV-2) strain of human immunodeficiency virus (HIV) and one (C-560) infected with the lymphadenopathy-associated virus type 1 (LAV-1) strain of HIV, were inoculated with approximately 10(4) tissue culture infective doses of the reciprocal strain. At the time of the second inoculation, both chimpanzees had high titers of HIV-specific antibodies, including antibodies that neutralized both virus strains. After inoculation of the second strain of HIV, the antibody titers in both chimpanzees increased 4- to 10-fold, and in one chimpanzee (C-499), the numbers of infectious peripheral blood mononuclear cells (PBMC) increased 1,000-fold to levels that are comparable with those observed after primary HIV infections. By restriction enzyme analysis of virus recovered from PBMC, both ARV-2 and LAV-1 were identified in C-499, thus demonstrating that superinfection had occurred.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Rodent and primate monolayer cells support the expression and assembly of viral particles directed by human immunodeficiency virus (HIV) proviral DNA.

A molecular clone of human immunodeficiency virus (HIV) was transferred to rodent and primate monolayer cells by DNA transfection. Of the cell lines tested, all of them released viral particles as shown by reverse transcriptase assay and dot-blot hybridization. The viruses released from transfected cultures were able to establish infection of human T-cell line HUT 78. These results suggest that factors present in cells of non-lymphoid origin support the expression and assembly of HIV. Thus, transfection with cloned HIV DNA provides an approach to analyse the consequences of viral gene expression in cell types which lack a mechanism for efficient uptake of HIV particles.

Animals↗
PubMed1987

Transactivation of human immunodeficiency virus by herpesviruses.

We examined the interaction of human immunodeficiency virus (HIV) and herpes group viruses. For this purpose, a chimeric plasmid (pLTR-CAT) was constructed in which the long terminal repeat (LTR) sequences derived from a molecular clone of HIV were fused to a bacterial chloramphenicol acetyltransferase gene (CAT). Transient expression assays in transfected tissue culture cells were used to monitor the activity of the LTR. Basal levels of CAT activity were measured in HeLa and human lung fibroblast (HLF) cells transfected with pLTR-CAT. When HeLa or HLF cells transfected with pLTR-CAT were infected with herpesviruses, HIV LTR-directed expression of the CAT gene was detected. An enhancement of the HIV LTR-directed expression of CAT was observed for herpes simplex virus (HSV)-1 and HSV-2, cytomegalovirus and varicella zoster virus. Enhanced CAT expression directed by the LTR was also shown by cotransfection of recombinant plasmids containing two non-overlapping regions of HSV-1, a fragment from HSV-2 which is non-colinear with the regions used from HSV-1, the immediate early gene of pseudorabies virus and the adenovirus early gene EIA. HIV LTR-directed expression may be a useful model for studying the effects on HIV of various infectious agents known to be present in individuals with AIDS or HIV infection.

Cell Line↗
PubMed1987

Transfusion-associated AIDS: donor-recipient human immunodeficiency virus exhibits genetic heterogeneity.

The genetic diversity of the human immunodeficiency virus (HIV) isolated from transfusion-associated AIDS patients has been examined. Restriction enzyme mapping studies of integrated proviral DNA of donor and recipient origin demonstrated genomic variation between isolates. Analysis of the molecularly cloned viral genomes of one donor-recipient pair showed that virus from the recipient had restriction enzyme site differences from the donor, noticeably clustered in the env and orf-2 regions, and also had a greater number of restriction sites in common with the donor as well. These results suggest that HIV may undergo genomic variation in vivo. Comparison of donor-recipient viruses may further the understanding of the molecular basis for AIDS pathogenesis.

Acquired Immunodeficiency Syndrome↗
PubMed1987

DNA and protein heterogeneity in serial isolates of human immunodeficiency virus (HIV-1): indication of change in vivo.

Structural heterogeneity in human immunodeficiency virus (HIV-1) isolates from different sources has been reported. In order to investigate if the virus exhibits heterogeneity in vivo, HIV-1 was isolated over a 3 year period (1983-1985) from a blood donor who progressed from the asymptomatic carrier state to frank AIDS. The HIV-1 specific proteins were characterized and compared by metabolic labelling and immunoprecipitation of infected cells and by Western blot analysis of gradient purified isolates. The data indicate polymorphism in the apparent size of gag gene-encoded p55 and env gene-encoded p41 proteins. The possibility of genomic variations was evaluated by studying the restriction enzyme polymorphism of integrated proviral DNA. Genetic diversity between 1983, 1984 and 1985 isolates was demonstrated by a change in the number and/or size of restriction fragments. In addition, genetic variation was also observed in HIV-1 isolated from the blood transfusion recipient of this donor. Subsequent analysis of the quantitative and qualitative titre of HIV-1 specific antibodies in the donor recipient sera demonstrated a concomitant change with the observed structural variation in the virus. These studies may be useful in elucidating virus or host-related critical events which lead to the onset of AIDS following infection with HIV-1.

Antibodies, Monoclonal↗
PubMed1987

Retinal toxicity of combination antiviral drugs in an animal model.

We investigated the retinal toxicity of various combinations of four antiviral agents in intravitreal injection and vitrectomy infusion solutions in the rabbit. The nontoxic concentration of each individual agent for intravitreal injection and for vitrectomy infusion has previously been described. Our results support the concept that concentrations of 200 micrograms/0.1 mL of trifluridine, 400 micrograms/0.1 mL of hydroxyacyclovir, 200 micrograms/0.1 mL of acyclovir and 30 micrograms/0.1 mL of vidarabine can be combined for intravitreal injection without toxic retinal effects. Moreover, 60 micrograms/mL of trifluridine, 20 micrograms/mL of hydroxyacyclovir, 40 micrograms/mL of acyclovir and 8 micrograms/mL of vidarabine can be combined in vitrectomy infusion solutions without retinal damage. Further study is needed to determine the full potential of such combinations.

Acyclovir↗
PubMed1986

Isolation of a T-lymphotropic retrovirus from naturally infected sooty mangabey monkeys (Cercocebus atys).

Healthy mangabey monkeys in a colony at the Yerkes Regional Primate Research Center were found to be infected with a retrovirus related to human immunodeficiency virus (HIV). Virus was isolated from peripheral blood cells of 14 of 15 randomly selected mangabeys. All virus-positive animals had antibodies to the mangabey virus at the time of virus isolation and, in a retrospective study, 82% of mangabey serum samples obtained in 1981 had antibodies to the virus. The newly isolated retrovirus is (i) morphologically identical to HIV by electron microscopy; (ii) serologically related to the human virus by enzyme immunoassay, immunoblotting experiments, radioimmunoprecipitation, and neutralization; and (iii) cytopathic for human OKT4+ cells. The mangabey virus also shares these properties with the simian T-lymphotropic virus type III (STLV-III) recently isolated from diseased macaques and from healthy African green monkeys (STLV-IIIAGM). However, the mangabey virus, like STLV-IIIAGM, differs from both HIV and STLV-III in that it apparently does not cause clinical immunodeficiency or disease following natural infection of the host from which it was isolated. Comparison of the virus-host interactions of these isolates may be valuable in defining determinants of pathogenicity for cytopathic retroviruses.

Animals↗
PubMed1986

Genomic diversity of the acquired immunodeficiency syndrome retroviruses is reflected in alteration of its translational products.

We have isolated retroviruses from six acquired immunodeficiency syndrome (AIDS) and three lymphadenopathy syndrome (LAS) patients by cocultivation of patients' lymphocytes with phytohemagglutinin-stimulated normal T cells. In an effort to address the extent to which these viruses have identical genetic information or there is divergence in their genomic sequences, we have compared the nine retrovirus isolates by the following criteria: (i) antigenic cross-reactivity by highly specific and sensitive competition radioimmunoassay for the major internal antigen; (ii) restriction site mapping analysis; and (iii) immunoblot analysis and metabolic labeling of viral structural proteins and their analysis by polyacrylamide gel electrophoresis. The data indicate that individual retroviruses have significant restriction site polymorphism in their genome even though they were isolated from patients residing at one geographic location. Furthermore, this polymorphism is reflected in the variation of the apparent size of the gag and env gene-encoded structural proteins. The heterogeneity in AIDS retrovirus-encoded proteins may be due to either substitutions in the primary amino acid sequence of the protein or deletions or additions in the coding regions of proteins. The alterations in viral structural proteins among various AIDS retroviruses could have important implications in antigenic properties and/or pathogenicity in development of the disease, its detection, and ultimately its eradication.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Molecular cloning and primary nucleotide sequence analysis of a distinct human immunodeficiency virus isolate reveal significant divergence in its genomic sequences.

In an effort to evaluate data on genomic relatedness among the various human immunodeficiency viruses (HIVs), we have molecularly cloned a virus isolate designated HIV (CDC-451). Preliminary characterization of the HIV (CDC-451) clone indicated that the restriction enzyme map was distinct from those of other known HIV isolates. Analysis of the primary nucleotide sequence of the regions encoding the structural proteins and comparison with sequences known for other HIV isolates indicated substantial differences for HIV (CDC-451). The sequences encoding the group-specific antigen gene, although they showed some variation, were conserved to a greater extent than were those encoding envelope proteins. In the envelope gene sequences, most of the changes (up to 24.5% divergence) were located in the amino-terminal region encoding a glycoprotein with a Mr of 120,000. The carboxyl-terminal region, encoding a protein of Mr 41,000, was more highly conserved. The variation in the sequences encoding envelope proteins may have important implications for the antigenic properties and/or pathogenicity of the disease and for its detection and ultimate eradication.

Adolescent↗
PubMed1984

Molecular dissection of transcriptional control elements within the long terminal repeat of the retrovirus.

The retroviral long terminal repeat (LTR) contains transcriptional control elements that affect viral gene expression. By deletion mutagenesis of the genome of the cloned Abelson murine leukemia virus, regulatory signals could be mapped to at least three domains within the LTR. A defective 5' LTR that did not sustain transforming gene function was complemented by an intact LTR positioned at the 3' end of the genome. This versatility of the retroviral genome with respect to its transcriptional control elements appears to provide a strong selective advantage for viral gene expression.

Abelson murine leukemia virus↗
PubMed1984

Sequences in the long terminal repeats of the Moloney murine sarcoma virus-124 genome which control transforming gene function.

The role of long terminal repeat (LTR) sequences in the efficient expression of Moloney murine sarcoma virus (MSV-124) transforming gene function was investigated. Recombinant plasmids containing a single LTR positioned 3' of v-mos were subjected to sequential deletions, and the relative transforming efficiency of these recombinants was analyzed in the NIH/3T3 transfection assay. Recombinants lacking CAAT, TATA, and poly(A) signals within the LTR were able to transform with an efficiency comparable to that of the wild-type MSV-124 genome. Deletion of one of the two 74-bp tandem repeat units within the LTR did not abolish v-mos gene function, whereas removal of both 74-bp repeat units completely eliminated transforming activity. The addition of a fragment containing only a single 74-bp unit and 29-bp downstream sequences derived from the LTR to a position 3' of v-mos led to efficient activation of v-mos transforming function. Residual potentiating activity for v-mos expression was retained even when the distance between v-mos and the 3' LTR was increased by several kilobase pairs. All these findings are consistent with the concept that the potentiating action of the LTR in its 3' position is due to activator/enhancer sequences localized to one of its 74-bp repeats. A permuted MSV-124 molecule, whose single LTR was localized 5' of v-mos, was very inefficient at transformation. However, its transforming activity could be increased by approximately 1000-fold by tandemization of the molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Expression of the normal human sis/PDGF-2 coding sequence induces cellular transformation.

The human sis proto-oncogene contains the coding sequence for one of two polypeptide chains present in preparations of biologically active human platelet-derived growth factor (PDGF). A human clone, c-sis clone 8, which contains all of the v-sis-related sequences present in human DNA, was transcriptionally inactive when transfected into NIH/3T3 cells. When placed under the control of a retrovirus LTR, the clone was transcribed at levels comparable to that observed in cells transformed by SSV DNA. However, c-sis clone 8 DNA did not express detectable sis/PDGF-2 proteins and lacked biologic activity. A putative upstream exon was identified by its ability to detect the 4.2 kb sis-related transcript in certain human cells. When this sequence was inserted in the proper orientation between the LTR and c-sis clone 8, the chimeric molecule acquired high titered transforming activity, comparable to that of SSV DNA. Transformants containing this construct expressed human sis/PDGF-2 translational products. Thus the normal coding sequence for a human growth factor has transforming activity when expressed in an appropriate assay cell.

Amino Acid Sequence↗