Mutagenic activity of tryptophan metabolites produced by rat intestinal microflora

The catabolism of tryptophan by rat intestinal microflora was studied for the production of mutagenic metabolites that might be involved in the etiology of colon cancer. Various tryptophan metabolites were assayed for mutagenic and comutagenic activity in the Ames bacterial test system. These included metabolites that were identified by thin-layer chromatography in cultures of rat fecal bacteria, other compounds structurally related to tryptophan, whole unfractionated mixed fecal bacteria culture filtrates, and concentrated solvent extracts. A total of 27 materials were tested with 5 Salmonella strains in the mutagenesis assay. Most substances were inactive, and only one compound, o-aminoacetophenone, which was unlikely to be produced in the intestine, showed weak comutagenic activity. Our results did not support the hypothesis that tryptophan metabolites produced by intestinal microflora are major etiologic factors in cancer of the colon.     

Dose-rate dependence of heat radiosensitization

The dose rate dependence of heat radiosensitization was studied using rat astrocytoma cells in culture and a clinically relevant protocol of heat dose and heat radiation sequence. Cells were treated with a minimally toxic heat dose of 43 degrees C for 30 minutes, after which they were irradiated with varying doses of radiation at dose rates ranging from 0.567 to 300 cGy/min. This heat dose substantially reduced the extrapolation number (n), but had little effect on Do of the radiation survival curve at dose rates of 50 cGy/min or greater. At dose rates less than 10 cGy/min, 43 degrees C for 30 min had little effect on n and only for the lowest dose rate studied (0.567 cGy/min) was there a significant reduction in Do (60%). The thermal enhancement ratio did not vary inversely with radiation dose rate over the dose rate range studied but, instead, was maximal at the two dose rate extremes (0.567 and 300 cGy/min). These data demonstrate that a clinically relevant heat dose enhances very low dose rate, as well as high dose rate, ionizing radiation, but suggest that little benefit is to be gained from using dose rates intermediate between conventional radiotherapeutic high dose rates or dose rates representative of interstitial implants.     

Electric Regulation: Has Retail Choice Delivered for Natural Gas Residential Customers?

The nationwide participation of residential customers in natural gas retail choice programs has grown from less than 0.5 percent of total US residential customers in 1997 to over 10 percent in 2012. Seventy percent of the 2012 total comes from three states: Georgia, New York, and Ohio. Add Illinois, Maryland, Michigan, New Jersey, and Pennsylvania, and the eight states constitute nearly 95 percent of the total residential retail choice market participation.     

Syntenic organization of the mouse distal chromosome 7 imprinting cluster and the Beckwith-Wiedemann syndrome region in chromosome 11p15.5

In human and mouse, most imprinted genes are arranged in chromosomal clusters. Their linked organization suggests co-ordinated mechanisms controlling imprinting and gene expression. The identification of local and regional elements responsible for the epigenetic control of imprinted gene expression will be important in understanding the molecular basis of diseases associated with imprinting such as Beckwith-Wiedemann syndrome. We have established a complete contig of clones along the murine imprinting cluster on distal chromosome 7 syntenic with the human imprinting region at 11p15.5 associated with Beckwith-Wiedemann syndrome. The cluster comprises approximately 1 Mb of DNA, contains at least eight imprinted genes and is demarcated by the two maternally expressed genes Tssc3 (Ipl) and H19 which are directly flanked by the non-imprinted genes Nap1l4 (Nap2) and Rpl23l (L23mrp), respectively. We also localized Kcnq1 (Kvlqt1) and Cd81 (Tapa-1) between Cdkn1c (p57(Kip2)) and Mash2. The mouse Kcnq1 gene is maternally expressed in most fetal but biallelically transcribed in most neonatal tissues, suggesting relaxation of imprinting during development. Our findings indicate conserved control mechanisms between mouse and human, but also reveal some structural and functional differences. Our study opens the way for a systematic analysis of the cluster by genetic manipulation in the mouse which will lead to animal models of Beckwith-Wiedemann syndrome and childhood tumours.     

Age-related invariance of abilities measured with the Wechsler Adult Intelligence Scale-III.

Examination of measurement invariance tests the assumption that the model underlying a set of test scores is directly comparable across groups. The observation of measurement invariance provides fundamental evidence for the inference that scores on a test afford equivalent measurement of the same psychological traits among diverse groups. Groups may be derived from different psychosocial backgrounds or different clinical presentations. In the Wechsler Adult Intelligence Scale-III (WAIS-III)/Wechsler Memory Scale-III (WMS-III) Technical Manual (Psychological Corporation, 2002), there appears to be a breakdown in factor structure among the standardization cases in older adults. In this study, the authors evaluated the invariance of the measurement model of the WAIS-III across 5 age bands. All components of the measurement model were examined. Overall, the evidence pointed to invariance across age of a modified 4-factor model that included cross-loadings for the Similarities and Arithmetic subtests. These results support the utility of the WAIS-III as a measure of stable intelligence traits across a wide age range. (PsycINFO Database Record (c) 2010 APA, all rights reserved)