Cross-linking of DNA in liver and testes of rats fed 1,3-propanediol

1,3-Propanediol (PAD) was fed to rats for 15 weeks, and its effects on hepatic and testicular DNA were studied. The control rats were fed a casein-based diet that contained 10% tocopherol-stripped corn oil with 30 IU of d,l-α-tocopherol acetate/kg; the experimental rats were fed the same diet with 500 ppm of PAD. Homogenates prepared from the livers of each group of rats converted 1,3-propanediol to malondialdehyde (MDA) with equal efficacy, but homogenates of testes did not catalyze this conversion. After 10–15 weeks of feeding the diets, the hepatic DNA of the rats fed PAD had less template activity, more bound tryptophan and more DNA-protein and interstrand DNA cross-links than that of the control rats. As measured by template activity and bound tryptophan, testicular DNA of the experimental rats was not different from that of the control rats; however, there was slightly more cross-linking in the testicular DNA of experimental rats than in that of control rats. Testes of the experimental rats contained more lipid-soluble fluorophores than did those of the control rats. The results are consistent with the conclusion that PAD was converted to MDA in vivo and that MDA is the reactive species that caused the observed biological damage.     

A note on antibiotic-resistant Escherichia coli in adult man, raw sewage and sewage-polluted River Tigris in Mosul, Nineva

A total of 600 isolates of Escherichia coli were isolated, over a 9 month period during 1984, from healthy human adults, raw sewage and the sewage-polluted River Tigris in Nineva. Over 90% of these organisms were E. coli type 1, but only 8.3% could be serogrouped as enteropathogenic E. coli . Resistance of these organisms to 11 antimicrobial drugs was assessed. Over 40% were antibiotic-resistant and of these 77.1% were resistant to more than one antibiotic. The minimal inhibitory concentration of ampicillin for 193 selected strains from the various sources was determined and ranged from <0.625- > 160 μg/ml. The high incidence of antibiotic-resistant E. coli in this locality and the possible implications to human health are discussed.     

Neuromuscular, anaerobic, and aerobic performance characteristics of elite power athletes

Various aspects of neuromuscular, anaerobic, and aerobic performance capacity were investigated in four powerlifters, seven bodybuilders, and three wrestlers with a history of specific training for several years. The data (means +/- SD) showed that the three subject groups possessed similar values for maximal isometric force per unit bodyweight (50.7 +/- 9.6, 49.3 +/- 4.1, and 49.3 +/- 10.9 N/kg, respectively). However, significant (P less than 0.05) differences were observed in the times for isometric force production, so that e.g., times to produce a 30% force level were shorter for the wrestlers and bodybuilders (28.3 +/- 3.1 and 26.4 +/- 6.6 ms) than that (53.3 +/- 23.7 ms) for the powerlifters. Utilization of elastic energy by the wrestlers was significantly (P less than 0.05) better than that of the other two subject groups, as judged from differences between the counter-movement and squat jumps at 0, 40, and 100 kg's loads. No differences were observed between the groups in anaerobic power in a 1-min maximal test, but the values for VO2 max were higher (P less than 0.05) among the wrestlers and bodybuilders (57.8 +/- 6.6 and 50.8 +/- 6.8 ml X kg-1 X min-1) as compared to the powerlifters (41.9 +/- 7.2 ml X kg-1 X min-1). Within the limitations of the subject sample, no differences of a statistical significancy were observed between the groups in fibre distribution, fibre areas, or the area ratio of fast (FT) and slow (ST) twitch fibres in vastus lateralis.(ABSTRACT TRUNCATED AT 250 WORDS)     

How are sticky chromosomes formed?

Blood lymphocytes in culture were irradiated by gamma-rays 3 h to 30 mn before harvesting. The various induced lesions were analysed, with a particular attention on sticky chromosomes, i.e. radial figures in which chromosomes are not obviously broken, but are linked by a tiny filament. Such anomalies are preferentially induced in mid to late G2-phase. They result from recombinations occurring at nonrandom chromosome regions: junction between hetero- and euchromatin, and telomeric regions. It is proposed that they are formed when double strand breaks are induced while intrachromatidic links have started to be formed in the course of chromosome condensation. If this interpretation is correct, the apparent lack of induced breakage of premitotic chromosomes is artifactual.     

Siblings with chromosome mosaicism,microcephaly, and growth retardation: the phenotypic expression of a human mitotic mutant?

Summary We report male and female siblings with extreme microcephaly and mental retardation, growth retardation, and multiple chromosome mosaicism. Mental retardation associated with chromosome mosaicism does not always carry a low recurrence risk.     

Hyalomma (Hyalommina) arabica: nymphal and larval identity and spiny mouse hosts in Saudi Arabia (Acarina: Ixodoidea: Ixodidae)

Nymphal and larval Hyalomma (Hyalommina) arabica Pegram, Hoogstraal, and Wassef, 1982, described herein, closely resemble those of Hyalomma (Hyalommina) rhipicephaloides Neumann, differing chiefly in body size (both stages), nymphal basis capituli and scutal proportional dimensions, and distinctness of larval coxal spurs. Females of these species are also structurally similar but males differ in major critical characters. Nymphs and larvae of both species parasitize the spiny mouse (Acomys spp.), but immatures of the third African- Arabian species of this subgenus, Hyalomma (Hyalommina) punt Hoogstraal, Kaiser, and Pedersen, are unknown. Hyalomma (Hyalommina) arabica occurs in valleys and hills of western Saudi Arabia and western Yemen; H. (H.) rhipicephaloides in the Red Sea and Dead Sea areas; and H. (H.) punt in northeastern Somalia and eastern Ethiopia. The ibex (Capra ibex nubiana Cuvier) is probably the original host of adult H. (H.) arabica and H. (H.) rhipicephaloides; the related domestic goat is an important host of adults of the 3 species, which also parasitize domestic sheep. Gazelles are recorded hosts of adults of H. (H.) rhipicephaloides and H. (H.) punt and the latter is also recorded from goats, sheep, camels and cattle.     

Substitution of selenocysteine for cysteine in a reticulocyte lysate protein synthesis system

Selenocysteine occurs in the peptide backbone of several selenoenzymes. The mechanism, of selenocysteine incorporation has not been well characterized. The incorporation of selenocysteine into protein in a rabbit reticulocyte lysate (RRL) was studied at high levels of selenocysteine. [⁷⁵Se]Selenocysteine incorporation was inhibited by cycloheximide and by nuclease treatment. Random RNA copolymers were tested for protein synthesis activity in the messenger RNA-dependent RRL system. Of the active polymers, poly CIU and GU most strongly stimulated the incorporation of selenocysteine. In a series of four polymers with different ratios of U to G, incorporation of selenocysteine and cysteine increased with increasing percentages of U, suggesting that selenocysteine and cysteine responded to the same codon, presumably UGU. Of the 20 protein amino acids, only cysteine and cystine competed with selenocysteine incorporation. Selenocysteine was charged to cysteine-accepting tRNA in RRL. These results show that at supraphysiological concentrations selenocysteine can substitute for cysteine in RRL protein synthesis. Misincorporation of selenocysteine could be important when animal tissues contain high levels of selenium.     

Cloning of genes controlling alginate biosynthesis from a mucoid cystic fibrosis isolate of Pseudomonas aeruginosa.

Mucoid strains of Pseudomonas aeruginosa isolated from the sputum of cystic fibrosis patients produce copious quantities of an exopolysaccharide known as alginic acid. Since clinical isolates of the mucoid variants are unstable with respect to alginate synthesis and revert spontaneously to the more typical nonmucoid phenotype, it has been difficult to isolate individual structural gene mutants defective in alginate synthesis. The cloning of the genes controlling alginate synthesis has been facilitated by the isolation of a stable alginate-producing strain, 8830. The stable mucoid strain was mutagenized with ethyl methanesulfonate to obtain various mutants defective in alginate biosynthesis. Several nonmucoid (Alg-) mutants were isolated. A mucoid P. aeruginosa gene library was then constructed, using a cosmid cloning vector. DNA isolated from the stable mucoid strain 8830 was partially digested with the restriction endonuclease HindIII and ligated to the HindIII site of the broad host range cosmid vector, pCP13. After packaging in lambda particles, the recombinant DNA was introduced via transfection into Escherichia coli AC80. The clone bank was mated (en masse) from E. coli into various P. aeruginosa 8830 nonmucoid mutants with the help of pRK2013, which provided donor functions in trans, and tetracycline-resistant exconjugants were screened for the ability to form mucoid colonies. Three recombinant plasmids, pAD1, pAD2, and pAD3, containing DNA inserts of 20, 9.5, and 6.2 kilobases, respectively, were isolated based on their ability to restore alginate synthesis in various strain 8830 nonmucoid (Alg-) mutants. Mutants have been assigned to at least four complementation groups, based on complementation by pAD1, pAD2, or pAD3 or by none of them. Introduction of pAD1 into the spontaneous nonmucoid strain 8822, as well as into other nonmucoid laboratory strains of P. aeruginosa such as PAO and SB1, was found to slowly induce alginate synthesis. This alginate-inducing ability was found to reside on a 7.5-kilobase EcoRI fragment that complemented the alg-22 mutation of strain 8852. The pAD1 chromosomal insert which complements the alg-22 mutation was subsequently mapped at ca. 19 min of the P. aeruginosa PAO chromosome.