Absence of mutagenic and antimutagenic activities of fluoride in Ames salmonella assays

The mutagenicity of fluoride (as sodium fluoride, NaF) was investigated with Ames Salmonella/microsome assays in strains of TA97a, TA98, TA100, TA102 and TA1535. The concentrations of NaF tested ranged from 0.44 to 4421 micrograms/plate (0.1 to 1000 ppm F), both with and without microsome activation. In addition, the suggested antimutagenic effect of fluoride was evaluated with known mutagens at various concentrations of NaF (0.44-442.2 micrograms/plate, 0.1-100 ppm F). The data showed that NaF, in amounts from 0.44 to 442.2 micrograms/plate (0.1-100 ppm F), failed to significantly increase the number of the revertants over the number observed in the solvent (distilled deionized water) controls. Increases of NaF to, and beyond, 1100 micrograms/plate (250 ppm F) resulted in a toxic effect and a reduction of the revertants to various degrees among the strains. NaF in the presence of known mutagens did not significantly decrease the number of the revertants. The results of this study indicate that NaF does not have mutagenic or antimutagenic effects in the strains tested with Ames Salmonella assays.

Disease specificity of nondefective Friend and Moloney murine leukemia viruses is controlled by a small number of nucleotides

Moloney murine leukemia virus induces T cell lymphomas after injection into NFS mice, whereas the nondefective Friend virus induces erythroleukemias. Previous studies showed that sequences encompassing the viral transcriptional signals in U3 are the primary determinant of this phenotype in recombinants between these two viruses. To more precisely identify the sequences responsible, we constructed additional recombinants, within U3, between Friend and Moloney viruses and assayed these recombinants for for their disease specificity. We found that a fragment 191 bases long that included the direct repeat (enhancer) region plus 22 nucleotides to its 3' side from Friend virus was sufficient to convert Moloney virus to a virus that induced only erythroleukemias. A 171-base-long fragment of Moloney virus, including just the direct repeat, converted Friend virus to a virus that induced primarily lymphomas (about 85% of mice injected). We also constructed Moloney and Friend virus variants with one rather than two copies of the enhancer element. These viruses retained their disease specificity, although they exhibited a marked increase in the latent period of disease induction. Together the results suggest that 25 or fewer nucleotide differences, lying within and also just 3' of the direct repeat, are the primary determinant of the distinct disease specificities of nondefective Friend and Moloney viruses.

A new procedure for the purification of monodisperse highly active cytochrome c oxidase from bovine heart

A simple and rapid method for the isolation of a large quantity of cytochrome c oxidase from bovine heart mitochondria was developed, based on selective solubilization of mitochondrial protein with first Triton and then lauryl maltoside. Gel filtration shows that the lauryl maltoside-solubilized oxidase preparation is in a hydrodynamically homogeneous state with a Stokes radius of 7.5 +/- 0.2 nm. It contains 8.0 mumol of haem (with an a/a3 ratio of 1)/g of protein. The catalytic constant (maximum turnover number) with respect to cytochrome c approaches 600 S-1. After further purification of the solubilized enzyme on a sucrose-gradient centrifugation, the purified enzyme has a haem content of 10.3 mumol/g of protein and eight major polypeptide bands shown on SDS/polyacrylamide-gel electrophoresis.

Effect of exercise training on resting blood pressure and heart rate in adult and aged rats

To test the hypothesis that advancing age may have an effect on cardiovascular adaptation (resting blood pressure and heart rate) in response to exercise training, we compared adult (4.5 months at start of training) and aged (21.5 months at start of training) male Fischer 344 rats exercised on a rodent treadmill 5 days/week for 9 weeks. Two additional age-matched control groups were similarly handled and placed on the nonmoving treadmill for the same duration. Chronic exercise did not alter blood pressure in the adult group but lowered resting blood pressure in the aged rats during the midportion of the training period. On the other hand, the adult group demonstrated a significant decrease in the resting heart rate from Weeks 3 through 7 during training, whereas the aged group showed no change in resting heart rate during the entire study. These findings suggest that there may exist an age-related difference in the effect of exercise training on basal cardiovascular homeostasis, which is cardioinhibitory in the adult and vasodepressant in the aged.

Multipass counterrotating wave-plate frequency shifters for heterodyne interferometry

A multipass counterrotating wave-plate frequency shifter for heterodyne interferometry is proposed. By using this method, with a fixed optical system, it is possible to generate wide, tunable-frequency-shifted signals.

Age-related differences in effect of exercise training on cardiac muscle function in rats

To test the hypothesis that age may alter the effect of exercise training on myocardial function, we trained young adult (4-5 mo at study initiation) and old (21 mo at initiation) male Fischer 344 rats to run on a rodent treadmill 5 days/wk for 4.5 mo and compared their myocardial function with that of age-matched sedentary controls. Right ventricular papillary muscles were isolated from the young adult and aged animals and stimulated at the length at which developed isometric tension was maximal to contract isometrically at 12/min, bathed in oxygenated modified Krebs solution, and studied at 28 degrees, 32 degrees, 35 degrees, and 38 degrees C. In the absence of cardiac hypertrophy, exercise training significantly reversed the age-related prolongation of isometric contraction duration in the senescent rat (P less than 0.001). However, exercise training prolonged contraction duration in the young adult rat (P less than 0.05). The relaxation phase was more sensitive than the contraction phase to changes in temperature, especially in the aged rat (P less than 0.02). The ratio of developed tension to time-to-peak tension of the isometric twitch was not affected by exercise training. Because exercise training affects cardiac function in opposite directions from young adulthood to senescence, caution is advised in extrapolating results from exercise studies in young adult rats to populations of older animals.

[Combination of radiation, chemotherapy and surgery in rectal cancer--an analysis of 128 patients]

The results of 128 patients with rectal cancer treated by the combination of surgery, preoperative radiotherapy and chemotherapy from June 1975 to December 1979 are reported and compared with those by operation alone. The 5 year survival rates of the different groups were: 69.5% (16/23) for radical surgery plus preoperative radiotherapy and chemotherapy (RRCG), 56% (14/25) for radical surgery plus preoperative radiotherapy, 53.8% (7/13) for radical surgery plus chemotherapy and 40% (10/25) for radical surgery alone. The 5 year survival rate of RRCG was significantly higher than that of the radical surgery alone group (P less than 0.05). The authors believe that the combination of preoperative radiotherapy, chemotherapy plus radical surgery improves the 5 year survival rate and is worthy of further study.

Theory and modeling of stereoselective organic reactions

Theoretical investigations of the transition structures of additions and cycloadditions reveal details about the geometries of bond-forming processes that are not directly accessible by experiment. The conformational analysis of transition states has been developed from theoretical generalizations about the preferred angle of attack by reagents on multiple bonds and predictions of conformations with respect to partially formed bonds. Qualitative rules for the prediction of the stereochemistries of organic reactions have been devised, and semi-empirical computational models have also been developed to predict the stereoselectivities of reactions of large organic molecules, such as nucleophilic additions to carbonyls, electrophilic hydroborations and cycloadditions, and intramolecular radical additions and cycloadditions.

Transforming Sloan-Kettering viruses generated from the cloned v-ski oncogene by in vitro and in vivo recombinations

The Sloan-Kettering viruses (SKVs) are replication-defective retroviruses that transform avian cells in vitro. Each of the three SKV isolates is a mixture of viruses with genomes ranging in size from 4.1 to 8.9 kilobases (kb) with a predominant genome of 5.7 kb. Using a cDNA representing a sequence, v-ski, that is SKV specific and held in common by the multiple SKV genomes, we generated a restriction map of the 5.7-kb SKV genome and molecularly cloned a ski-containing fragment from SKV proviral DNA. Southern hybridization and sequence analysis showed that the cloned DNA fragment consisted of the 1.3-kb ski sequence embedded in the p19gag sequence and followed by the remaining 5' half of the gag gene and small portions of both the pol and env genes. A large deletion encompassing the 3' half of gag and the 5' 80% of pol was mapped to a position about 1 kb downstream from the 3' ski-gag junction. To determine whether the cloned ski sequence had transforming activity, the ski-containing fragment and a cloned Rous-associated virus 1 (RAV-1) genome were used to construct an analog of the 5.7-kb SKV genome, RAV-SKV. Cotransfection of chicken embryo cells with RAV-SKV and RAV-1 yielded foci of transformed cells whose morphology was identical to that induced by the natural SKVs. The transformed transfected cells produced transforming virus with a 5.7-kb ski-containing genome and synthesized a gag-containing polyprotein of 110 kilodaltons (kDa). Several nonproducer clones of RAV-SKV-transformed cells were analyzed, and most were found to synthesize a 5.7-kb SKV RNA and a 110-kDa polyprotein. One clone was found to contain an 8.9-kb SKV RNA, and this clone synthesized a 125-kDa polyprotein. Since both the 5.7- and 8.9-kb genomes and the 110- and 125-kDa polyproteins had been identified in studies on the natural SKVs, the present results not only demonstrate the transforming activity of these individual SKVs but also suggest mechanisms for their generation.

Unique sequence, ski, in Sloan-Kettering avian retroviruses with properties of a new cell-derived oncogene

The Sloan-Kettering viruses (SKVs) are a group of transforming retroviruses that were isolated from chicken embryo cells which had been infected with the avian leukosis virus transformation-defective Bratislava 77 (tdB77). Each of the SKV isolates was shown to contain multiple genomes of different sizes indicating the presence of several viruses in addition to tdB77. To identify and characterize the putative transforming gene(s) of the SKVs, we used hybridization selection to isolate the fraction of a representative cDNA which was SKV specific. Both solution and blot hybridization studies with viral RNAs showed that the specific probe contained a sequence, ski, that was at least partially held in common by the multiple SKV genomes. This conclusion was confirmed by the observation that a molecularly cloned ski probe also hybridized to each of the multiple SKV genomes. Southern blots of chicken DNA revealed homologs of ski (c-ski) which were not associated with endogenous viral loci. Results showing that c-ski was expressed in polyadenylated cytoplasmic RNA of uninfected chicken cells indicated that it is a functional gene. Other data showed that c-ski was conserved in avian and mammalian evolution, suggesting a functional role for the gene in species other than chickens. Using ski cDNA in solution hybridizations with viral RNAs and in Southern blot hybridization with cloned retroviral oncogenes, we did not detect any relationship between ski and any of 15 previously identified oncogenes.