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Biomedical subjects

S Agarwal

Publications and source records attributed to S Agarwal.

At least 19 recordsLinked to original sources
PubMed1992

Phosphatase inhibitors modulate the growth-regulatory effects of human tumor necrosis factor on tumor and normal cells.

Tumor necrosis factor alpha (TNF-alpha) has been shown to inhibit the growth of tumor cells and stimulate the growth of certain normal cells in vitro. The mechanism by which TNF exerts its cell growth-regulatory effects is not known. In this report, we investigated the effects of phosphatase inhibitors on the cell growth-inhibitory effects of TNF on L-929, a highly sensitive murine connective tissue tumor cell line, and on the growth-stimulatory effects of TNF on normal human fibroblasts. The antiproliferative effects of TNF on L-929 cells were inhibited by orthovanadate, an inhibitor of phosphotyrosine phosphatases, in a dose-dependent manner. Okadaic acid, which is a specific inhibitor of phosphoserine- and phosphothreonine-specific phosphatases, also blocked the growth-inhibitory effects of TNF, suggesting that TNF may function through the activation of certain phosphatases. These inhibitors had no effect on TNF receptors. Addition of phosphatase inhibitor, even 12 h after the treatment of cells with TNF, was sufficient to block the antiproliferative effects of the cytokine, suggesting that the inhibitor is acting at a late event in the pathway of action of TNF. Cells were protected by orthovanadate from the cytotoxic effects of TNF even in the presence of actinomycin D or cycloheximide, thus indicating the lack of a requirement for de novo protein synthesis. Orthovanadate altered the cell morphology from flat spindle shapes to rounded ones. Besides anticellular effects, a phosphatase inhibitor also suppressed the proliferative effects of TNF on human fibroblasts. These results thus suggest that phosphatases may be needed for both proliferative and antiproliferative effects of this cytokine. This is the first report to suggest that phosphatases play a role in the growth-regulatory action of TNF.

Animals↗
PubMed1992

Breakage and binding of DNA by reaction products of hypochlorous acid with aniline, 1-naphthylamine, or 1-naphthol.

Hypochlorous acid (HOCl) is a chemically reactive oxidant and a potent microbicidal agent that is synthesized in phagosomes of inflammatory neutrophils and released into extracellular spaces. Besides reducing pathogenicity by reacting with phagocytized infectious agents, HOCl may damage tissues and yield toxic products upon reaction with various other molecules, including xenobiotics. As model xenobiotics, the substituted aryl compounds aniline, 1-naphthylamine, and 1-naphthol (1-NOH) were investigated herein for their potential to react with HOCl and the transformed into genotoxic products. The compounds were first exposed to HOCl (25-150 microM) in phosphate buffer and afterward used to treat human fibroblasts or purified DNA. DNA single-strand breaks in cells and the binding of HOCl-reacted 1-[14C]NOH to purified DNA were assessed by DNA alkaline elution and scintillation spectrometry, respectively. It was found that neither HOCl nor compounds alone could break cellular DNA. But HOCl-reacted compounds produced up to 400 rad equivalents of DNA breaks. HOCl reaction products of aniline and the model bicyclic aryl compounds differed in their DNA-breaking characteristics. HOCl-reacted 1-[14C]NOH was stable and bound to DNA at up to 124 pmol/mg DNA. Sodium thiosulfate, glutathione, and taurine inhibited the transformation reactions; but only the former two blocked binding of HOCl-reacted 1-NOH to DNA. Ultraviolet spectra showed that HOCl reacted rapidly (less than 1 min) and equally well with 1-NOH at pH 7.2 or at an intraphagosomal pH of 5.0. Reaction concentrations of HOCl in this study were 2- to 11-fold lower than levels generated in vitro by stimulated neutrophils. These results show that certain aryl compounds can react readily with approximated physiological levels of HOCl (-OCl) to form relatively long-lived products that bind DNA and are genotoxic to human cells.

1-Naphthylamine↗
PubMed1992

Isolation of a malondialdehyde-deoxyguanosine adduct from rat liver DNA.

In previous studies, an adduct of malondialdehyde (MDA) with guanine was identified in rat and human urine. Subsequent detection of an adduct with deoxyguanosine (dG) in urine prompted an investigation of its possible occurrence in DNA. Rat liver DNA was hydrolyzed using nuclease P1 and alkaline P-ase and subjected to deoxyribonucleoside analysis using reverse phase high-pressure liquid chromatography (HPLC) with fluorescence detection. A compound was isolated that could not be separated from a synthetic pyrimidinopurine adduct of MDA and dG (dG-MDA). Partial hydrolysis released guanine (Gua), Gua-MDA, and dG in amounts that, in aggregate, were the molar equivalent of the starting material calculated by fluorescence analysis as dG-MDA. Complete acid hydrolysis of the isolate yielded an equimolar amount of MDA. Analysis of liver DNA isolated from growing rats yielded a value for dG-MDA content of 9.0 +/- 1.6 pmol/100 micrograms DNA (mean +/- SEM, N = 5). This value is approximately 7 times those reported for the 8-hydroxy deoxyguanosine content of rat liver nuclear DNA. This study demonstrates that DNA is modified in vivo by reactions of its guanylate moiety with MDA, and indicates that, at least in the case of rat liver DNA, the prevalence of such modifications is greater than those caused by reactions with hydroxyl radicals.

Animals↗
PubMed1992

High-efficiency gene transfer mediated by adenovirus coupled to DNA-polylysine complexes.

Employment of recombinant viruses as gene transfer vectors is limited by constraints on the size and functional design of the genetic material to be transferred as well as potential safety hazards deriving from obligatory co-transfer of viral genetic elements. As an alternative strategy that capitalizes on the efficient cellular entry mechanisms of viruses, we have derived adenovirus-polylysine-DNA complexes whereby foreign DNA is transferred bound to the exterior of the virion. This linkage was accomplished utilizing an antibody bridge in which a monoclonal antibody was rendered competent to carry DNA by the attachment of a polylysine residue. Attachment of the antibody-polylysine to the virus was by virtue of the antibody's specificity for the virion. The resulting vector system mediates high-efficiency gene transfer to target cells in vitro. In addition, this vector design allows greatly enhanced flexibility in terms of the size and design of heterologous sequences that can be transferred. Since this strategy selectively exploits viral entry functions, which are independent of viral gene expression, the potential exists to derive vectors that avoid the hazards deriving from transfer of parent virus genome.

Adenoviridae↗
PubMed1992

Gene transfer to respiratory epithelial cells via the receptor-mediated endocytosis pathway.

Gene-based therapies for a variety of inherited and acquired pulmonary diseases will require the development of vectors capable of safe and efficient transfer of DNA to the respiratory epithelium. The present study examined the feasibility of delivering DNA to respiratory epithelial cells by the receptor-mediated endocytosis pathway. This strategy employs molecular conjugates consisting of a cognate moiety, in this case human transferrin, covalently linked to a DNA-binding moiety, such as a cationic polyamine. Complexes were formed between transferrin-polylysine conjugates (hTfpL) and plasmid DNA carrying the firefly luciferase reporter gene (pRSVL). The conjugate-DNA complexes were added directly to cells in tissue culture and incubated for 24 h, after which cell lysates were analyzed for luciferase enzyme activity by luminometry. An immortalized human respiratory epithelial cell line (HBE1) treated with the transferrin-polylysine-DNA complexes exhibited luciferase enzyme activity significantly augmented over background levels. This respiratory epithelial cell line exhibited greater susceptibility to gene transfer by the transferrin-polylysine conjugates than did non-respiratory epithelial cell lines known to possess high levels of transferrin receptors. Effective gene transfer was shown to require both the DNA-binding moiety and cognate moiety for the cell surface receptor. Specific internalization of the conjugates by the transferrin pathway was verified by competition for the transferrin receptor. In addition, treatment with agents that either increased transferrin receptor number or decreased lysosomal degradation markedly augmented gene expression mediated by the conjugates. Thus, respiratory epithelial cells possess receptors for transferrin that can be exploited to accomplish gene transfer by the receptor-mediated endocytosis pathway.

Animals↗
PubMed1992

A study of the formation of the neural network in the lungs of Perdicula asiatica, as revealed by the cholinesterase technique.

The investigation was undertaken to investigate the formation and association of neural network and their fibres with nerve cells and ganglia in the parenchyma. The staining of the neural network was done by the cholinesterase technique under the maintained pH 5.2, temperature 40 degrees C and incubation period 30 hrs. The neural network was formed by a good number of tortuous thick nerves and was related either with nerve cells or ganglia. At times, it was formed by a good number of thick nerves and a few thin nerves in the connective tissue space.

Acetylcholinesterase↗
PubMed1992

Immunoreactivity with S100 protein as an indicator of pregnancy.

The usefulness as a pregnancy marker, of immunoreactivity with S100 protein antiserum in endometrial curettings and fallopian tubes during pregnancy was assessed. Twenty six placental tissues of various gestational age, two hydatidiform moles and four fallopian tubes removed for ectopic pregnancy were stained with S100 protein polyclonal antiserum by immunoperoxidase technique. Strong immunostaining was found in glands within the decidua and epithelial cells of fallopian tubes during early pregnancy. However, no S100 protein could be demonstrated in the endometrium in various phases, endometrial carcinomas, decidual glands beyond 12 wk of gestation and normal fallopian tubes. The results indicate a relationship between S100 protein and early pregnancy. Positive immunoreactivity with S100 protein antiserum in the decidual glands and fallopian tube epithelium may help in confirmation of doubtful cases of pregnancy.

Biomarkers↗
PubMed1992

Hydatid bone disease of the pelvis. A report of two cases and review of the literature.

Hydatid disease is caused by a parasitic tapeworm Echinococcus. This parasite in larval stage can thrive in many parts of the body, most frequently in the liver. Hydatid disease in bone is rare, but in areas where hydatid disease is endemic, it must always be considered in the differential diagnosis. Two cases of hydatid bone disease of the pelvis are reported. The treatment of choice is a combination of chemotherapy and surgery.

Aged↗
PubMed1992

Gene therapy: a status report.

Gene therapy is a way to treat disease by transfer of genetic material into the cells of a diseased organism. Generally it is transferred in the form of one or few genes. There is a tremendous potential for application of this technique to the treatment of human hereditary diseases, particularly single gene disorders. Due to ethical and practical reasons, it is currently being used only as somatic cell therapy but it could be achieved by germline also. The major problem in gene therapy is achieving an efficient gene transfer and a persistent gene expression in appropriate somatic cells.

Animals↗
PubMed1991

Adenovirus enhancement of transferrin-polylysine-mediated gene delivery.

Gene transfer may be accomplished by the receptor-mediated endocytosis pathway using transferrin-polylysine conjugates. For some target cells, however, gene transfer by this vector is extremely limited, despite the presence of the appropriate surface receptors, a phenomenon attributed to lysosomal degradation of endosome-internalized conjugate-DNA complexes. To enhance DNA escape from the cell vesicle system and thus augment gene transfer by this route, we have used the capacity of adenoviruses to disrupt endosomes as part of their entry mechanism. Adenoviral infection augmented levels of gene transfer by transferrin-polylysine conjugates in a dose-dependent manner: levels of gene transfer of greater than 2000-fold above baseline were achieved. Use of the adenovirus in this context allowed enhanced levels of gene transfer in a variety of target cells, including cell lines otherwise refractory to gene transfer by transferrin-polylysine conjugates. This augmentation was based on adenoviral-mediated vesicle disruption, a process independent of viral gene expression. Thus, the development of specific mechanisms to effect release from the endosome in combination with gene transfer by the receptor-mediated endocytosis pathway will increase the utility of this delivery system by allowing high levels of gene expression in target cells.

Adenoviridae↗
PubMed1991

Susceptibility of glucose-6-phosphate dehydrogenase deficient red cells to primaquine, primaquine enantiomers, and its two putative metabolites. II. Effect on red blood cell membrane, lipid peroxidation, MC-540 staining, and scanning electron microscopic studies.

The effects of primaquine (PQ), its enantiomers [(+)PQ,(-)PQ] and hydroxy metabolites [5-hydroxyprimaquine (5HPQ) and 6-desmethyl-5-hydroxyprimaquine (6D5HPQ)] on cell membranes of glucose-6-phosphate dehydrogenase (G-6-PD) deficient red cells were studied in vitro. There was no significant effect of PQ on the malonyldialdehyde (MDA) content of normal and heterozygous red cells, but it caused a significant increase in MDA in G-6-PD deficient red cells (P less than 0.05). There was no noticeable difference between the effects of the two enantiomers on this variable (P greater than 0.05). Compared to PQ, the hydroxy metabolites produced a significantly greater increase in MDA in all the groups studied (P less than 0.001). Of the two hydroxy metabolites, 6D5HPQ was more toxic than 5HPQ. Staining with MC540 showed that exposure to PQ, its enantiomers and two putative metabolites produced significant fluorescence, indicating that the drug produces marked alterations in membrane fluidity. Although the fluorescence was seen both in normal and heterozygous cells, the effect was marked in hemizygous deficient red cells (P less than 0.001). Scanning electron microscopic (SEM) studies revealed that PQ enantiomers had a stomatocytic effect on red cells of normal, heterozygous and hemizygous G-6-PD deficient red cells, whereas the putative metabolites had an echinocytic effect. The effects were most pronounced in G-6-PD deficient red cells.

Erythrocyte Membrane↗
PubMed1991

The effect of sanguinarine on human peripheral blood neutrophil viability and functions.

Human polymorphonuclear cell (PMN) viability, morphology, adherence, chemotaxis, oxidative metabolism, degranulation and phagocytosis were evaluated following treatment with sanguinarine (SANG). SANG was noncytotoxic to PMNs at all concentrations tested (0.31-200 microM). SANG entered the PMNs rapidly without altering the membrane fluidity and localized in the nuclear matrix. SANG (1.56-6.21 microM) inhibited chemotaxis, chemokinesis and adhesion in a dose-dependent manner, with a complete inhibition at 6.2 microM concentration. Concentrations of SANG up to 1.56 microM did not affect PMN oxidative burst; however, higher concentrations were found to inhibit basal as well as PMA-induced superoxide anion generation. The effect of SANG was time- and dose-dependent, and could be reversed if the PMNs were exposed to 12.5 microM or lower concentrations of SANG for less than 5 min. Autologous serum increased the tolerance of PMNs to SANG. Exogenous Ca2+ or Mg2+ did not alter the SANG-mediated inhibition of PMN functions. Treatment of PMNs with 3.12 microM or higher concentrations of SANG also resulted in inhibition of PMN degranulation and phagocytosis. The results suggest that SANG-mediated inhibition of PMN functions, without cytolysis or resultant release of inflammatory mediators, may have clinical implications.

Alkaloids↗
PubMed1991

Certain mutations observed in the 5' sequences of the G gamma- and A gamma-globin genes of beta S chromosomes are specific for chromosomes with major haplotypes.

In this paper we describe the distribution of some specific sequence differences in the 5' flanking regions of the A gamma- and G gamma-globin genes from 100 Black adult and 57 newborn SS patients from the southeastern United States, from 76 individuals with AS, S-beta-thal, SC, AC, or A-beta-thal, and from 31 normal individuals. Haplotypes for all adult individuals have been previously determined using various restriction endonucleases. The DNA samples were amplified, dot blotted, and hybridized with 32P-labeled specific oligonucleotide probes. All 134 chromosomes with haplotype 19 were positive for the G----T substitution at position -657 (A gamma), while 132 were also positive for the C----G mutation at -369 (G gamma). The three specific changes for the chromosome with haplotype 20 were found on all 54 chromosomes with this haplotype. The C----T mutation at -158 5' to G gamma was present on all 41 chromosomes with haplotype 3, and on two chromosomes with a related atypical haplotype. Normal and beta-thal chromosomes with each of these substitutions had the same 5' subhaplotype as beta S haplotypes 19 or 20, respectively. The close relationship between the occurrence of specific mutations and the haplotype of beta S chromosomes makes the determination of these haplotypes with specific oligonucleotide probes attractive with respect to time and expense.

Adult↗