Search PubMed⌕ Search

Biomedical subjects

R Roth

Publications and source records attributed to R Roth.

At least 55 records · Page 3Linked to original sources
PubMed1978

Binding of benzo[a]pyrene at the 1,3,6 positions to nucleic acids in vivo on mouse skin and in vitro with rat liver microsomes and nuclei.

Loss of tritium from specific positions in [3H,14C] aromatic hydrocarbons can elucidate their binding site(s) to DNA and RNA and indicate the mechanism of activation. Studies of tritium loss from [6-3H,14C]benzo[a]pyrene (B[a]P), [1,3-3H,14C]B[a]P, [1,3,6-3H,14C]B[a]P, [6,7-3H,14C]B[a]P, and [7-3H,14C]B[a]P were conducted in vitro using liver nuclei and microsomes from 3-methylcholanthrene-induced Sprague-Dawley rats and in vivo on the skin of Charles River CD-1 mice. The relative loss of tritium from [3H, 14C]B[a]P was measured after binding to skin DNA and RNA, to nuclear DNA, and to native and denatured calf thymus and rat liver DNA's and poly(G) by microsomal activation. In skin, nuclei, and microsomes plus native DNA, virtually all B[a]P binding occurred at positions 1,3 and 6; while with microsomes plus denatured DNA or poly(G), B[a]P showed no binding at the 6 position and a small amount at the 1 and 3 positions. In vivo and with nuclei, binding at the 6 position predominated. Little loss of tritium from the 7 position was seen; this was expected because binding at this position is not thought to occur. This confirms the interpretation of loss of tritium as an indication of binding at a given position. These results demonstrate that the use of microsomes to activate B[a]P is not a valid model system for delineating the in vivo mechanism of B[a]P activation, and support previous evidence for one-electron oxidation as the mechanism of activation of hydrocarbons in binding to nucleic acids.

Animals↗
PubMed1978

Carcinogenicity and metabolic profiles of 6-substituted benzo[a]pyrene derivatives on mouse skin.

The ability was tested of appropriate substituents of benzo[a]pyrene (BP) at C-6 to decrease or suppress the carcinogenic activity for these BP derivatives relative to the parent compound. 8-week-old female Swiss mice in 9 groups of 30 were treated on the back with 0.2 mumol of compound in acetone 4 times weekly for 20 weeks. The following compounds were administered: BP, 6-methylbenzo[a]pyrene (BP-6-CH3), 6-hydroxymethylbenzo[a]pyrene (BP-6-CH2OH), benzo[a]pyrene-6-carboxaldehyde (BP-6-CHO), benzo[a]pyrene-6-carboxylic acid, 6-methoxybenzo[a]pyrene, 6-acetoxybenzo[a]pyrene, 6-bromobenzo[a]pyrene, and 6-iodobenzo[a]pyrene. Two additional groups received BP or BP-6-CH3 twice weekly for 20 weeks at a total dose 25% of that above. In addition, the metabolism of selected 6-substituted BP derivatives was studied, using mouse skin homogenates in vitro and mouse skin in vivo. Only four compounds were carcinogenic; the order of potency was BP greater than BP-6-CH3 greater than BP-6-CH2OH and BP-6-CHO. The difference in carcinogenicity between BP-6-CH2OH and BP-6-CHO could not be assessed by this experiment. In a further tumorigenesis experiment the carcinogenicity of BP-6-CH2OH was compared to that of BP-6 CHO, BP-6-CH3 and 6-hydroxymethylbenzo[a]pyrere sulfate ester (BP-6-CH2OSO3Na) on mouse skin. 9-week-old female Swiss mice in groups of 28 were treated at three dose levels with 0.8, 0.2 and 0.05 mumol of compounds in dioxane--dimethyl sulfoxide (75 : 25) twice weekly for 40 weeks. After 40 experimental weeks BP-6-CH2OSO3Na proved to be a more potent carcinogen than BP-6-CH2OH, which, in turn was more active than BP-6-CHO. The greater carcinogenicity of BP-6-CH3 relative to BP-6-CH2OH and BP-6-CHO is confirmed, suggesting that BP-6-CH2OH is not a proximate carcinogenic metabolite for BP-6-CH3. Since BP-6-CHO is a weaker carcinogen than BP-6-CH2OH and is efficiently reduced metabolically to BP-6-CH2OH, the latter compound may be a common proximal carcinogenic metabolite. The stronger potency of BP-6-CH2OSO3Na, compared to its alcohol, suggests that an ester of BP-6-CH2OH might be the ultimate alkylating compound reacting with cellular nucleophiles.

Animals↗
PubMed1978

Carcinogenicity and metabolic profiles of 3-methylcholanthrene oxygenated derivatives at the 1 and 2 positions.

Trapping of 3-methylcholanthrene (MC) radical cation by nucleophilic compounds occurs specifically at the 1-carbon atom. With the purpose of providing more evidence for the hypothesis that the critical mechanism of activation of MC is one-electron oxidation, the carcinogenicity of MC was compared to that of 1-hydroxy-3-methylcholanthrene (MC-1-OH), 3-methylcholanthrene-1-one (MC-1-one), 2-hydroxy-3-methylcholanthrene (MC-2-OH), 3-methylcholanthrene-2-one (MC-2-one) and 3-methylcholanthrylene (MCL) by repeated application on mouse skin. Seven-week-old female Swiss mice in 6 groups of 30 were treated on the back with 0.2 mumol of compound in acetone twice weekly for 20 weeks. In addition, the metabolism of MC and its derivatives was studied using mouse skin homogenates. The compounds tested were classified according to carcinogenicity in 4 groups: MC and MC-2-OH, the strongest carcinogens; MC-2-one and MCL, weaker than MC and MC-2-OH; MC-1-OH, the weakest carcinogen; and MC-1-one, non-carcinogenic. These results support the hypothesis that one-electron oxidation for MC, MC-2-OH and MC-1-one might be the critical mechanism of carcinogenic activation, with C-1 the binding site to cellular nucleophiles. The carcinogenic effect of MC-1-OH is speculated to be the formation of an ester bearing a good leaving group, which might be the ultimate alkylating compound in the in vivo reaction. The lack of carcinogenic activity for MC-1-one may be attributed to absence of nucleophilic trapping at C-1 via the radical cation pathway as well as the inability of mouse skin to reduce MC-1-one to the carcinogenic MC-1-OH.

Animals↗
PubMed1977

[Lysozyme and beta2-microglobulin in cerebrospinal fluids from healthy children and in children with diseases of the central nervous system (author's transl)].

Lysozyme is absent from normal cerebrospinal fluid (C.S.F.) and in C.S.F. from children with viral meningitis. Appreciable amounts of lysozyme were noted in C.S.F. from children with bacterial meningitis (0.23 +/- 0.14 mg/100 ml) and cerebral convulsions (0-0.82 mg/100 ml). The C.S.F.-lysozyme content is a sensitive indicator for bacterial meningitis and important in the differential diagnosis between viral and bacterial meningitis. The beta2-microglobulin content of C.S.F. in healthy children was 0.11 +/- 0.05 mg/100 ml; in children with viral meningitis 0.20 +/- 0.06 mg/100 ml and in children with bacterial meningitis 0.44 +/- 0.17 mg/100 ml. Children with cerebral convulsions had also a rise in C.S.F. beta2-microglobulin.

Adolescent↗
PubMed1977

Role of mitotic replication genes in chromosome duplication during meiosis.

In the yeast Saccharomyces cerevisiae, DNA synthesis preceding meiosis requires the expression of replication genes used during mitosis. Diploids carrying either a temperature-sensitive lesion in cdc4 (a gene required for initiation of mitotic DNA synthesis) or a lesion in cdc8 (a gene controlling mitotic polymerization) completed premeiotic DNA synthesis at a permissive but not at a restrictive temperature. The roles of cdc4 and cdc8 were evaluated by characterizing the kinetics of premeiotic DNA synthesis after a shift to a restrictive temperature. In the cdc8 diploid, DNA synthesis was immediately inhibited, consistent with a role in polymerization. In contrast, cdc4 exhibited residual DNA synthesis characteristic of an initiation function. The cdc4 gene function was completed much earlier in the meiotic cycle than the cdc8-mediated step.

Chromosomes↗
PubMed1976

Temperature-sensitive yeast mutants defective in meiotic recombination and replication.

A system is described for isolating temperature-sensitive mutants of Saccharomyces cerevisiae with defects in early meiotic events. We used an otherwise haploid strain disomic (n+1) for chromosome III, and heteroallelic at the leucine-2 locus. Meiotic development was initiated by exposure of the strain to acetate sporulation medium, and monitored by the appearance of leucine-independent intragenic recombinants. Mutant isolation was based on the recovery of thermally induced defects in recombination. The temperature-sensitive characteristic was included to allow eventual characterizations of the temporal period during meiosis when each gene performs its essential function. Following mutagenesis with either ethyl methane sulfonate or nitrosoguanidine individual clones were tested at 34 degrees and 24 degrees for acetate-induced recombination. Starting with 2700 clones, derived from cells that survived mutagenic treatment, we isolated 48 strains with thermally induced lesions in recombination. In the majority of mutants premeiotic replication occurred normally, or nearly normally, at the restrictive temperature, indicating that the meiotic cycle was initiated and that there was a defect in an event required for intragenic recombination. We also detected mutants where the thermally induced lesion in recombination resulted from temperature-sensitive premeiotic DNA synthesis.

DNA Replication↗
PubMed1976

Adenosine utilization in cordycepin-sensitive mutants of Saccharomyces cerevisiae.

A purine-requiring, wild-type yeast strain was cordycepin resistant and failed to grow in medium containing adenosine; in contrast, a cordycepin-sensitive mutant (also purine requiring) grew well in medium containing adenosine. The cordycepin-sensitive mutant incorporated [8-14C]adenosine at nine times the wild-type rate, and adenosine completely fulfilled the purine requirement of the cells. Exogenous adenosine rapidly entered the mutant cells, apparently as free nucleoside, and was phosphorylated; uptake displayed concentration-dependent saturation kinetics (Km, 6 mM). Within 10 min 14C radioactivity was being incorporated into nucleic acids.

Adenine↗
PubMed1976

Oxygen-dependent circulation of sickle erythrocytes.

The effects of in vivo hyperoxia and hypoxia on the intravascular survival of 51Cr-labeled human sickle erythrocytes (SS RBS's) were studied after transfusion into rats and guinea pigs. The function of these animals' reticuloendothelial and complement systems had been previously inhibited by ethyl palmitate and cobra venom factor, thus allowing extension of the survival of the heterologous human RBC's. In the blood of rats breathing ambient air the 51Cr half-life survival of RBC's from 11 patients with sickle-cell anemia (mean, 7.1 hours; range, 2.0 to 16.5 hours) was significantly shorter (p less than 0.001) than that of five control subjects (mean, 17.5 hours; range, 12.0 to 26.5 hours). When rats transfused with sickle RBC's were exposed to 100 per cent O2, a mean increment of 16.5 per cent blood 51Cr activity was observed within the first 15 to 60 minutes of hyperoxia. Subsequent oxygen deprivation (7 to 8 per cent O2) resulted in an equally rapid decrease (mean, 35.6 per cent) in blood 51Cr activity. Continuation of hypoxia for up to 17 hours did not cause further acceleration of 51Cr activity. Continuation of hypoxia for up to 17 hours did not cause further acceleration of 51 Cr RBC clearance. Under these conditions the slope of the sickle RBC survival curve was similar to that in animals kept in ambient air. After hypoxic rats were allowed to breate room air again, mean 51Cr blood activity increased by 41.7 per cent. Sickle RBC's transfused to guinea pigs exhibited similar oxygen-dependent survival characteristics. The survival of 51Cr RBC's from four adult control subjects and of unlabeled fetal RBC's from three human cord blood samples was unaffected by oxygen changes. When rats that had been transfused with sickle reticulocytes labeled in vitro with 59Fe were made hypoxic, a decrease in blood 59Fe activity was observed. The extent of this decrease was comparable to that in rats transfused with 51Cr labeled RBC's from the same patients. There was increased liver and spleen 51Cr activity in animals transfused with 51Cr SS RBC's and killed during hypoxia when compared to that of hyperoxic animals. These studies suggest that a minor population of sickle cells is removed from circulation during hypoxia and circulates again upon reoxygenation of the animals. Erythrocyte aging does not appear to be responsible for this phenomenon. The oxygen-depdendent circulation of a population of SS RBC's in this animal system is probably due to reversible sickling and trapping of sickled cells in the microcirculation.

Adolescent↗
PubMed1974

Carbohydrate metabolism during ascospore development in yeast.

Carbohydrate metabolism, under sporulation conditions, was compared in sporulating and non-sporulating diploids of Saccharomyces cerevisiae. Total carbohydrate was fractionated into trehalose, glycogen, mannan, and an alkali-insoluble fraction composed of glucan and insoluble glycogen. The behavior of three fractions was essentially the same in both sporulating and non-sporulating strains; trehalose, mannan, and the insoluble fraction were all synthesized to about the same extent regardless of a strain's ability to undergo meiosis or sporulation. In contrast, aspects of soluble glycogen metabolism depended on sporulation. Although glycogen synthesis took place in both sporulating and non-sporulating strains, only sporulating strains exhibited a period of glycogen degradation, which coincided with the final maturation of ascospores. We also determined the carbohydrate composition of spores isolated from mature asci. Spores contained all components present in vegetative cells, but in different proportions. In cells, the most abundant carbohydrate was mannan, followed by glycogen, then trehalose, and finally the alkali-insoluble fraction; in spores, trehalose was most abundant, followed by the alkali-insoluble fraction, glycogen, and mannan in that order.

Carbohydrate Metabolism↗