Search results for "Hamster"
showing 10 items of 141 documents
Ribonuclease H levels in herpes simplex virus-infected cells.
1980
Two forms of ribonuclease H (RNase H) have been identified both in uninfected and Herpes Simplex virus (HSV-)infected BHK cells. Identical RNase H species were detected in control- as well as in infected cells. RNase H I and II have not been found to be associated both with host cell DNA polymerase alpha and beta and HSV-induced DNA polymerase. Infection of BHK cells with HSV type 1 does not lead to a pronounced alteration of RNase H II activity but to an increase (3-fold) of the extractable RNase H I activity. RNase H I activity increases to a maximum between 8-10 hours p.i.; the bulk of HSV-DNA synthesis occurs between 6-8 hours p.i. From these experiments we draw the preliminary conclusi…
Metabolic activation of dibenzo[a,l]pyrene by human cytochrome P450 1A1 and P450 1B1 expressed in V79 Chinese hamster cells.
1999
Metabolic activation of the strongly carcinogenic polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P) and its trans-8,9-dihydrodiol (trans-8,9-diol) catalyzed by human cytochromes P450 (P450) 1A1 and 1B1 was investigated. DNA binding of DB[a,l]P in mammalian cell lines has previously been shown to be preferentially mediated by fjord region DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (DB[a,l]PDE). In order to elucidate different capabilities of both P450 enzymes for metabolic activation of DB[a, l]P V79 Chinese hamster cells, stably expressing human P450s 1A1 or 1B1 have been exposed to the parent PAH or its racemic trans-8, 9-diol. For this purpose, synthesis and spectroscopic…
Day-night differences in the sensitivity of adrenoceptors in the Syrian hamster pineal gland: an in vivo iontophoretic study.
1989
Abstract Investigations on the regulation of pineal melatonin synthesis in the Syrian hamster revealed distinct differences compared to this well-understood mechanism in rat. E.g., a circadian profile of pineal norepinephrine (NE) is absent, there is no β-adrenoceptor sensitivity during daytime and adrenergic receptor supersensitivity is not easily achieved. To elucidate the action of NE on pineal receptor sites, the effects of iontophoretic application of adrenergic compounds on spontaneous electrical discharge rates of pinealocytes were investigated during day- and nighttime. Following application of either NE, isoproterenol or clonidine, cells were activated, inhibited or not affected. W…
Epigenetic Status of an Adenovirus Type 12 Transgenome upon Long-Term Cultivation in Hamster Cells
2007
ABSTRACT The epigenetic status of integrated adenovirus type 12 (Ad12) DNA in hamster cells cultivated for about 4 decades has been investigated. Cell line TR12, a fibroblastic revertant of the Ad12-transformed epitheloid hamster cell line T637 with 15 copies of integrated Ad12 DNA, carries one Ad12 DNA copy plus a 3.9-kbp fragment from a second copy. The cellular insertion site for the Ad12 integrate, identical in both cell lines, is a >5.2-kbp inverted DNA repeat. The Ad12 transgenome is packaged around nucleosomes. The cellular junction is more sensitive to micrococcal nuclease at Ad12-occupied sites than at unoccupied sites. Bisulfite sequencing reveals complete de novo methylation i…
DNA strand break induction, mutagenicity, and cytotoxicity of the mycotoxins 11-β-hydroxy-7-deoxy-rosenonolactone, rosenonolactone, and trichothecin.
1992
11-β-hydroxy-7-deoxy-rosenonolactone (TSS1), a mycotoxin of the rosenane class, was tested on cytotoxicity, induction of DNA single strand breaks and muta-genicity. Its effects were compared to those of rosenonolactone and trichothecin. TSS1 had stronger antibiotic activity againstEscherichia coli (EC 50: 10μg/mL) than rosenonolactone (EC 50: >200μg/mL) but weaker activity than trichothecin (EC 50: 3μg/mL). The same order of activity was found for the inhibition of yeast fermentation (EC 50 of TSS1: 45μg/mL; EC 50 of rosenonolactone: > 120μg/mL; EC 50 of trichothecin: 3.4μg/mL). In the trypan blue exclusion test using V79 Chinese hamster cells, TSS1 proved to be cytotoxic (EC50: 30μg/mL) at…
Endometrial Adenocarcinoma in Syrian Hamsters Treated with Diethylstilbestrol, Tamoxifen and N-Ethyl-Nitrosourea
2006
The synthetic estrogen diethylstilbestrol (DES) causes marked abnormalities in the female hamster genital tract, after either prenatal or postnatal exposure, leading to endometrial hyperplasia and carcinoma. Acting as an initiating event, DES altering uterine development may facilitate the abnormal response of promoting agents. Tamoxifen (TAM) is an antiestrogen that competes for central and peripheral estrogen receptor (ERα). TAM exerts agonistic effects on E-dependent endometrial proliferation. N-ethyl-N-nitrosourea (ENU), a potent mutagenic agent, induces tumors in a variety of organs, predominantly in the peripheral nervous system. To test whether ENU and TAM treatment in a model of hyp…
Independent Generation of Aβ42 and Aβ38 Peptide Species by γ-Secretase
2008
Proteolytic processing of the amyloid precursor protein by beta- and gamma-secretase generates the amyloid-beta (Abeta) peptides, which are principal drug targets in Alzheimer disease therapeutics. gamma-Secretase has imprecise cleavage specificity and generates the most abundant Abeta40 and Abeta42 species together with longer and shorter peptides such as Abeta38. Several mechanisms could explain the production of multiple Abeta peptides by gamma-secretase, including sequential processing of longer into shorter Abeta peptides. A novel class of gamma-secretase modulators (GSMs) that includes some non-steroidal anti-inflammatory drugs has been shown to selectively lower Abeta42 levels withou…
Stable Expression of Heterologous Sulfotransferase in V79 Cells: Activation of Primary and Secondary Benzylic Alcohols
1994
Abstract A sulfotransferase (ST) capable of activating 1-hydroxymethylpyrene (HMP) and 9-hydroxymethylanthracene (HMA) to mutagens was purified from rat liver. This enzyme appeared to be identical with hydroxysteroid STa, whose cDNA was cloned and stably expressed in Chinese hamster V79 cells. Several primary and secondary benzylic alcohols derived from polycyclic aromatic hydrocarbons induced gene mutations, sister chromatid exchanges (SCE) and/or cytotoxicity in these cells.
Microcirculatory Dysfunction Induced by Cigarette Smoking
2000
This review deals with the deleterious effects of cigarette smoking on the microcirculation, both in terms of morphological (i.e., vessel wall injury, capillary loss) and functional aspects. The latter concerns predominantly changes in tissue perfusion and its regulatory mechanisms (i.e., reactive hyperemia, sequestration of blood cells in the microcirculation). The mechanisms of action of cigarette smoking on the microcirculation include compromised endothelial-dependent vasorelaxation, platelet aggregation, endothelial cell dysfunction, and the activation of circulating leukocytes. Through these mechanisms, cigarette smoking elicits the aggregation and adhesion of leukocytes and/or platel…
Genetically engineered V79 Chinese hamster cells metabolically activate the cytostatic drugs cyclophosphamide and ifosfamide.
1990
V79 cells, genetically engineered to express active cytochromes P450IIB1 and P450IA1, were used to study the cytotoxicity and mutagenicity of cyclophosphamide and ifosfamide. Cyclophosphamide, tested up to a concentration of 2 mM, was not cytotoxic in V79 nor in the P450IA1-expressing V79-derived cell line XEM2. Pronounced cytotoxicity was, however, observed in the P450IIB1-expressing V79-derived cell line SD1. Induction of gene mutations (acquisition of 6-thioguanine resistance) was observed in SD1 cells as well, but the effects were weak. Ifosfamide was inactive in V79 cells, but was cytotoxic in SD1 cells. Ifosfamide mustard, an active metabolite of ifosfamide, was equally cytotoxic and …