Genotoxicity of ptaquiloside, a bracken carcinogen, in the hepatocyte primary culture/DNA-repair test

The genotoxicity of ptaquiloside (PT), recently isolated from bracken fern and shown to be carcinogenic, was examined by means of the hepatocyte primary culture/DNA-repair test. PT elicited clear unscheduled DNA synthesis with a dose-response effect. The result indicates that PT is a genotoxic carcinogen.     

Cross-sectional Area-corrected Compression Modulus of Food Gel

The linearity of the stress-strain relationship for food gel is limited to a very narrow range of the strain (usually less than 0.1 as a Cauchy measure). The reason is thought due to the change in cross-sectional area of the gel upon deformation. In this report, the cross-sectional area was approximately corrected of the compressed gel on the assumption that the gel expanded uniformly without changing its volume upon compression. In cases when the initial Young’s modulus was calculated from the thus-corrected area for some food gels, the linearity was increased for a wider range of strain.     

Fractal property of eye movements in schizophrenia

 On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects (n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was found in normal controls. Received: 21 July 1995/Accepted in revised form: 30 April 1996     

Activation of endogeneous retroviruses in mouse cells by thermal neutrons

The effect of thermal neutrons on the induction of murine endogenous viruses from a mouse fibroblast cell line was investigated. Thermal neutrons were more effective than X-rays in induction of endogenous virus as well as in killing of the cells. However, when measured as a function of cell killing, both radiations had similar efficiency of induction. The RBEs of thermal neutrons alone were calculated on the assumption that the contribution of contaminating gamma-rays was additive. It was 4.2 for the killing effect and 4-5 for virus induction.     

An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis.

The three chromosomal DNAs of S. pombe have been fractionated by pulsed field gel electrophoresis. The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs.     

Spontaneous excretion of D-alanine in urine in mutant mice lacking D-amino-acid oxidase.

Urine from mutant mice lacking D-amino-acid oxidase contained a large amount of alanine compared with that from normal mice. Urinary alanine of the mutant mice was sensitive to D-amino-acid oxidase. H.p.l.c. showed that about 94% of the urinary alanine had the D-configuration. These results suggest that D-amino-acid oxidase functions to decompose D-amino acid(s) in normal mice.     

Characterization of Schizosaccharomyces pombe minichromosome deletion derivatives and a functional allocation of their centromere.

A 530 kb long Schizosaccharomyces pombe linear minichromosome, Ch16, containing a centric region of chromosome III, has previously been made. In the present study, we constructed a number of deletions in the right and/or left arms of Ch16, and compared their structure and behaviour with Ch16. The functional centromere, cen3, is allocated within a 120 kb long region which is covered by the shortest derivative, Ch10, and is comprised mostly of centromeric repeating sequences. The shortest minichromosome is stable in mitosis and the copy number control is apparently precise. In monosomic meiosis it segregates normally. In disomic meioses, however, the frequency of non-disjunction is very high, suggesting that it may not form a pair. The mitotic loss rate of one of the left-arm deletions, ChR32, which lacks a part of the centromeric repeating sequence, is the highest of all the deletions. This deletion also exhibits the highest precocious sister chromatid separation in meiosis I, suggesting that sister chromatid association might become weakened in ChR32. Our results indicate that the proper meiotic segregation of S.pombe minichromosomes is dependent upon the formation of a bivalent. S.pombe may not have the 'distributive segregation' found with Saccharomyces cerevisiae minichromosomes.     

Intestinal bacterial origin of D-alanine in urine of mutant mice lacking D-amino-acid oxidase.

Urine from mutant mice which lack D-amino-acid oxidase contained a large amount of D-alanine. The alanine content was not changed by changes in the dietary composition or by starvation. However, oral administration of an antibiotic, amoxicillin, decreased the urinary alanine to the normal level. These results suggest that the D-alanine is not of dietary origin but of intestinal bacterial origin.     

The genotoxicity of a variety of aniline derivatives in a DNA repair test with primary cultured rat hepatocytes

The genotoxicity of a variety of aniline derivatives was examined by a DNA repair test with rat hepatocytes. Out of 37 aniline derivatives, 6 chemicals, i.e., 2,4,6-trimethylaniline (mesidine), 2,4-xylidine, 3,5-diaminobenzoic acid, 3,4-diaminochlorobenzene, 2-chloro-4-methylaniline and 4-chloro-N-methylaniline, elicited positive DNA repair responses. The results are in agreement with the bacterial mutagenicities with or without norharman of these compounds. Positive compounds of unknown carcinogenicity in the present assay, i.e., 3,5-diaminobenzoic acid, 2-chloro-4-methylaniline and 4-chloro-N-methylaniline are suspected of being potentially carcinogenic.