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J Vijg

Publications and source records attributed to J Vijg.

At least 109 records · Page 6Linked to original sources
PubMed1990

mRNA levels and methylation patterns of the tyrosine aminotransferase gene in aging inbred rats.

We have examined the mRNA levels and methylation patterns of the liver-specific tyrosine aminotransferase (TAT) gene in inbred female rats aged 6, 24 and 36 months. Northern hybridization analysis of total RNA showed a 65% decrease in the steady state transcript level of TAT in the liver of 24- and 36-month old rats as compared to 6-month old animals. The TAT gene as studied by Southern hybridization analysis using the isoschizomers Hpa II and Msp I was found to be hypomethylated in the liver as compared to spleen and brain at six CpG sites within the gene. Methylation at these sites remained unchanged during aging.

Aging↗
PubMed1990

Messenger RNA levels and methylation patterns of GAPDH and beta-actin genes in rat liver, spleen and brain in relation to aging.

Messenger RNA levels and methylation patterns of the glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) and beta-actin genes were studied in spleen, liver and brain of 6-, 24- and 36-month old female inbred rats. In the spleen, the mRNA levels of both housekeeping genes significantly increased between 24 and 36 months. No age-related alterations in the expression of GAPDH or beta-actin mRNA were observed in brain or liver. A considerable intertissue and interindividual variation was observed in the mRNA levels of these genes in all age-groups as compared to the level of 28 S rRNA, which was used as an internal control. In this respect the interindividual variation in the level of GAPDH mRNA paralleled the variation observed in the beta-actin mRNA level in the three tissues studied. The methylation pattern of beta-actin was found to be tissue-specific in contrast to that of GAPDH, which was identical in all three tissues. No significant age-related alterations were observed in the GAPDH methylation pattern, whereas beta-actin appeared to become slightly demethylated with age in the spleen at the CpG site for which tissue-specificity was observed.

Actins↗
PubMed1990

Spontaneous DNA breaks in the rat brain during development and aging.

The level of spontaneous DNA breaks in nuclei isolated from the cerebral cortex of rat embryos at 12, 15 and 19 days of gestation, and from cerebral cortex and cerebellum of 24-day-, 6-month- and 36-month-old rats was measured by alkaline elution. A constant low level of DNA breaks was found in brain DNA during development from an embryo at day 12 of gestation to a 24-day-old rat. During aging the level of DNA breaks remained at the same low level, as shown by comparing nuclei from the cerebral cortex and cerebellum of 6- and 36-month-old animals. By contrast, an almost 2-fold increase in the level of DNA breaks was observed in rat liver nuclei between 6 and 36 months of age, confirming our earlier findings on isolated liver cells. Although there were no changes in the level of DNA breaks in rat brain during development or during aging, breaks accumulated rapidly post mortem. The rate of this process was not age-dependent. Our data suggest that the level of spontaneous DNA breaks in the brain is not likely to be of fundamental importance in the complex cellular alterations associated with brain development and aging.

Aging↗
PubMed1990

Denaturing gradient gel electrophoretic analysis of the human cHa-ras1 proto-oncogene.

Activation of ras proto-oncogenes frequently involves point mutations at different sites in the gene. Here we describe the application of denaturing gradient gel electrophoresis to identify and characterize such mutations in the cHa-ras1 proto-oncogene. We calculated a melting map of the cHa-ras1 gene and designed optimal conditions to separate mutant from wild type sequences in the first exon. As an example we examined the T24 guanosine to thymidine point mutation in the first exon which has been found in T24 bladder carcinoma cells. Denaturing gradient gel analysis of both homoduplex as well as heteroduplex molecules resulted in separation of the wild type sequence from the mutant sequence. On the basis of the melting map we present a general scheme for screening the cHa-ras1 proto-oncogene sequence for the occurrence of point mutations.

Chromosome Mapping↗
PubMed1990

[Extension of life: the apotheosis of the molecular biomedical sciences?].

Evolutionary biologists have shown that many of the adverse effects associated with the ageing process are the (by)products of certain genes: the manifestation of the negative effects of these genes only late in life has effectively constrained their elimination from the germ line by natural selection. In addition, during evolution genes have evolved that govern mechanisms for the protection of the body against exogenous and endogenous insults. These two types of genes, in interaction both with themselves and with the environment specify the maximum life span of a species. New scientific developments, especially in molecular biology, allow the careful analysis of the genetic information and its manipulation. On the basis of these developments more insight will be obtained in the causes of ageing and it will be possible to design new therapies for many of the adverse effects associated with ageing. In the long term it may be possible to remove the basic causes of ageing by genetic manipulation. The mission of the biomedical sciences may then be considered as completed.

Aged↗
PubMed1989

The Caenorhabditis elegans genome contains monomorphic minisatellites and simple sequences.

Many species have been shown to contain tandemly repeated short sequence DNA known as minisatellites and simple sequence motifs. Due to allelic variation in the copy number of the repeat unit these loci are usually highly polymorphic. Here we demonstrate the presence of sequences in the genome of the nematode Caenorhabditis elegans which are homologous to two sets of short sequence DNA. However, when two independent strains were compared no polymorphism for these sequences could be detected.

Animals↗
PubMed1989

Age-related induction and disappearance of carcinogen-DNA-adducts in livers of rats exposed to low levels of 2-acetylaminofluorene.

It was investigated whether in vivo aging of rat liver is associated with changes in the induction and rate of disappearance of DNA damage. For this purpose 6- and 36-month-old rats were intraperitoneally injected with a single, low dose (5 mg/kg body wt.) of the model liver carcinogen 2-acetylaminofluorene (AAF). Using the 32P-postlabeling assay we found that N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) was the major DNA-adduct formed. The minor adduct N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-C8-AAF) could only be detected after doses of 20 mg/kg or more. Quantitation of adduct levels at various time points after treatment indicated a rapid induction of AF-adducts, which were already present at 6 h after treatment. The subsequent loss of AF-adducts was relatively slow, as was indicated by the presence of a substantial amount of AF-adducts as late as 21 days after treatment. Slight age-related differences in the pattern of induction and disappearance of AF-adducts and a somewhat higher level of persisting lesions in old than in young rats were observed.

2-Acetylaminofluorene↗
PubMed1989

Quiescent human peripheral blood lymphocytes do not contain a sizable amount of preexistent DNA single-strand breaks.

Sedimentation of nucleoids through neutral sucrose density gradients has shown that nucleoids isolated from phytohemagglutinin (PHA)-stimulated human peripheral blood lymphocytes (PBL) sediment faster than nucleoids derived from quiescent lymphocytes, which was attributed to rejoining of DNA single-strand breaks (SSB) present in the resting cells (A.P. Johnstone, and G.T. Williams (1982) Nature (London) 300, 368). We isolated PBL from donors and determined the amount of SSB in nonradiolabeled, untreated resting and PHA-stimulated cells by applying the alkaline filter elution technique. Calibration was based on dose-dependent induction of SSB by 60Co-gamma-radiation. Quiescent cells did not contain a sizable amount of SSB. Mitogen-stimulated cells showed equally low amounts of SSB per cell. The present study indicates that the interpretation of the results obtained with the nucleoid sedimentation technique concerning the supposed rejoining of SSB in PHA-stimulated human lymphocytes is incorrect. Other, equally sensitive, techniques such as alkaline filter elution appear to be preferable for studies on DNA damage and repair.

DNA Damage↗
PubMed1989

Effects of lethal exposure to hyperoxia and to hydrogen peroxide on NAD(H) and ATP pools in Chinese hamster ovary cells.

Cell death by oxidative stress has been proposed to be based on suicidal NAD depletion, typically followed by ATP depletion, caused by the NAD-consuming enzyme poly(ADP)ribose polymerase, which becomes activated by the presence of excessive DNA-strand breaks. In this study NAD+, NADH and ATP levels as well as DNA-strand breaks (assayed by alkaline elution) were determined in Chinese hamster ovary (CHO) cells treated with either H2O2 or hyperoxia to a level of more than 80% clonogenic cell killing. With H2O2 extensive DNA damage and NAD depletion were observed, while at a higher H2O2 dosage ATP also became depleted. In agreement with results of others, the poly(ADP)ribose polymerase inhibitor 3-aminobenzamide completely prevented NAD depletion. However, both H2O2-induced ATP depletion and cell killing were unaffected by the inhibitor, suggesting that ATP depletion may be a more critical factor than NAD depletion in H2O2-induced killing of CHO cells. With hyperoxia, only moderate DNA damage (2 X background) and no NAD depletion were observed, whereas ATP became largely (70%) depleted. We conclude that (1) there is no direct relation between ATP and NAD depletion in CHO cells subjected to toxic doses of H2O2 or hyperoxia; (2) H2O2-induced NAD depletion is not by itself sufficient to kill CHO cells; (3) killing of CHO cells by hyperoxia is not due to NAD depletion, but may be due to depletion of ATP.

Adenosine Triphosphate↗
PubMed1989

The removal of UV-induced pyrimidine dimers from DNA of rat skin cells in vitro and in vivo in relation to aging.

Young and old rats were compared with respect to the capacity of their skin fibroblasts and epidermal keratinocytes to remove low levels of ultraviolet light (UV) induced UV-endonuclease sensitive sites (pyrimidime dimers) from their DNA, in vitro and in vivo, respectively. In vitro, over a 24-h time period, fibroblasts from both young and old rats were found to remove about 20% of the pyrimidine dimers originally induced by 4.6 J/m2 of UV-C. In vivo, after 2.6 kJ/m2 of UV-B hardly any UV lesions were found to be present in fibroblasts, as demonstrated by immunohistochemistry using an anti-thymine dimer antibody. As reported earlier (Mullaart et al., J. Invest. Dermatol., 90 (1988) 346-349) cultured epidermal keratinocytes do not differ from cultured fibroblasts in UV repair kinetics, whereas in vivo they remove at least 50% of the pyrimidine dimers induced by 4 kJ/m2 of UV-B within 3 h. We now show that epidermal keratinocytes from old rats are not deficient in their in vivo repair characteristics upon this low UV-B dose. However, since a considerable fraction of the pyrimidine dimers appeared to be persistent in fibroblasts and keratinocytes, demonstrated by both enzymatic and immunochemical assays, the possibility is discussed that long-term exposure of skin cells to UV may lead to an accumulation of DNA damage with age.

Aging↗