The deposition of bacterial cells from laminar flows onto solid surfaces

In a previous article, the authors proposed a simple model for the rate of removal of bacterial cells from solid surfaces by fluid shear. This Model has been extended to include the deposition of cells from a flowing suspension. The theory is compared to experimentally obtained data for the deposition of Bacillus cereus cells onto the surface of glass capillaries. The effect of a hydrophobic surface, siliconized glass, and the addition of an antifoam agent to the suspension is also investigated.     

Gammaphotography

The Anger scintillation camera greatly broadens the range of studies performed by radioisotope imaging devices. Its ability to view in any direction, to make an image simultaneously of an entire field of view, and to obtain images rapidly, all serve to make scintiphotography analogous to fluoroscopy. Illustrations of its uses in static and dynamic gammaphotography and in numerical data processing are described.     

Translational capacity of sheep oocytes microinjected with messenger RNA

Sheep oocytes were microinjected with tobacco mosaic virus RNA (TMV-RNA) and isotopically labelled with L-[35S]methionine. Total incorporation of labelled methionine was similar in TMV-RNA-injected and in carrier-injected control oocytes, whether injections were performed during the period of high protein synthesis at maturation or during the period of reduced synthesis at a time equivalent to the mid-cleavage transition (48 h after germinal vesicle breakdown). Varying the amount of TMV-RNA injected from 2.5 to 10 pg had little effect on the overall level of amino acid incorporation. Furthermore TMV-RNA appeared to be very stable in oocytes and eggs; the proportion of total polypeptide synthesis directed by TMV-RNA did not diminish during the first 48 h after injection. Synthesis of most endogenous proteins was uniformly reduced to compensate for the synthesis of TMV-polypeptides. Our results suggest, therefore, that the translational capacity of sheep oocytes is fully saturated during maturation.     

Application of Deuterated A-Tocopherols to the Biokinetics and Bioavailability of Vitamin E

-Tocopherol, a superior chain-breaking, peroxyl radical-trapping antioxidant and the most active component of vitamin E, is elevated in liver tumor cells, contributing to their greater resistance towards lipid peroxidation compared to cells from normal tissues. Also, in regenerating rat liver the level of vitamin E has been found to fluctuate in phase with the rate of cell division. In order to study the biokinetcis and mechanisms of the distribution of vitamin E in organs and within tissues of animals, deuterated forms of -tocopherol have been synthesized and their uptake into blood and tissues has been measured by gas chromatography-mass spectrometry. Measurement of the competitive uptake from a mixture of the RRR-and SRR--tocopherol stereoisomers labelled with different amounts of deuterium shows that the liver exerts a strong preference for secretion of the natural (RRR) stereoisomer into the plasma. It is suggested that a tocopherol-binding protein plays a key role in this process.     

Habitat choice in natural populations of Drosophila

Summary Mark-release-recapture experiments performed with natural populations of Drosophila at Mather, California show that flies tend to return to their area of original capture or an area ecologically similar to it. Such habitat choice explains the microgeographic genetic differentiation we observed in the population. This behavioral difference between the flies may have a genetic component or may be environmentally induced. Either way, the results help explain how high levels of genetic variation are maintained by natural selection in these species.     

Factors affecting the termination of cardiovascular actions of 10, 10-difluoro, 13-dehydroprostacyclin

Experiments were conducted to determine why 10,10-difluoro, 13-dehydroprostacyclin (DF₂-PGI₂) has a long vascular relexant activity but like PGI₂ hads a short duration of effect . DF₂-PGI₂ produced depressor responses in anesthetized dogs which were not affected by nephrectomy suggesting that the kidney was not responsible for the termination of action. DF₂-PGI₂ given intravenously or into the ascending oarta produced depressor responses of a similar magnitude but injection of the same doses into the hepatic portal circulation resulted in a large attenuation of responses. The data suggest hepatitic, but not pulmonary, metabolism of DF₂-PGI₂. Injection or infusion of PGI₂ and DF₂-PGI₂ into the hindlimb circulation caused vasodilation of a similar duration suggesting diffusion from tissue sites as another mechanims of termination of action.     

Cloning and characterization of the cDNA encoding human adenylosuccinate synthetase.

Adenylosuccinate synthetase (AS) catalyzes the first committed step in the conversion of IMP to AMP. A cDNA was isolated from a human liver library which encodes a protein of 455 amino acids (M(r) of 49,925). Alignments of human, mouse, Dictyostelium discoideum and E. coli AS sequences identify a number of invariant residues which are likely to be important for structure and/or catalysis. The human AS sequence was also 19% identical to the human urea cycle enzyme, argininosuccinate synthetase (ASS), which catalyzes a chemically similar reaction. Both human liver and HeLa AS mRNA showed signals of 2.3 and 2.8 kb. An unmodified N-terminus is required for function of the human AS enzyme in E. coli mutants lacking the bacterial enzyme. The human cDNA provides a means to assess the possible role of AS abnormalities in unclassified, idiopathic cases of gout.     

Peopling of the Americas: paleobiological evidence.

A subjective and bivariate analysis of 8500-10,000-year-old human fossil remains from North America substantiates that the fossils' closest affinities are with Asian populations. Within North American prehistoric Indian populations, increasing brachycephalization and the possible development of a larger, broader face are two structural trends that can be identified. In those respects where Paleo-Indian specimens differ from modern northern Asians and North American Indians, they tend to resemble southern Asian and European populations. These assessments generally support the inference that populations entered the New World relatively recently but before the modern northern Asian and North American features were fully developed. Based on the data examined, no date can be specified for time of entrance of the first populations, nor can the number of founding populations be discerned.