The effect of antibiotics on the electrical polarisability of aqueous suspensions of bacteria.

The orientation of washed Escherichia coli bacteria in suspension induced by applied a.c. electric fields has been monitored by observing the accompanying changes in the intensity of light scattered by the suspension. The data enable the anisotropy of electrical polarisability deltaalpha to be determined. Changes in deltaalpha due to the addition of various antibiotics to the suspension have been measured as a function of both the antibiotic concentration and the temperature of the suspension. The results are taken to indicate that there is an accumulation of the antibiotic molecules at the bacterial surface.     

Occupational Toxic Factor in Mortality from Coronary Heart Disease

Between 1933 and 1962 42% of 223 deaths of male workers exposed to carbon disulphide in three viscose rayon factories in England and Wales were certified to coronary heart disease—compared with 24% of the deaths in the other workers of the same age, 17% of the deaths in other local men, and 14% in the Registrar General''s Tables. Of men with more than 10 years in the rayon industry employed in one of the factories, those exposed to carbon disulphide had death rates from coronary heart disease between 1950 and 1964 two and a half times that of the other workers.This evidence of an occupational risk of coronary heart disease from long-term exposure to low concentrations of CS₂ was strongest in the 1940s and slight in 1958–62, and it may relate to wartime plant conditions. Current and prospective biochemical and morbidity surveys of exposed workers are now needed. These may also throw light on general issues of atherosclerosis and coronary heart disease.     

Physical mapping and a new variant of Puroindoline b-2 genes in wheat

Puroindoline a and b proteins soften the endosperm of wheat kernels. When the underlying puroindoline genes are altered by mutation or are deleted, kernels become harder. Thus, puroindoline a and b (Pina and Pinb) play an important role in wheat quality and utilization. Recently, additional Pinb genes have been reported. In the present report, we provide corroborating coding and additional 5′ and 3′ flanking sequence for three Pinb variants: Pinb-2v1, Pinb-2v2, and Pinb-2v3. Additionally, a new Pinb variant, Pinb-2v4, is reported. All four variants were physically mapped using Chinese Spring (CS) diteolosomics, nullisomic–tetrasomics, and CS-Cheyenne disomic substitution lines. Results place Pinb-2v1 on 7DL, Pinb-2v2 on 7BL, Pinb-2v3 on 7B, and Pinb-2v4 on 7AL. Pinb-2v1 and Pinb-2v4 were present in all cvs. examined: CS, Cheyenne, Recital, Wichita and Winsome. Pinb-2v2 was present in CS and Recital; Pinb-2v3 was present in Cheyenne, Wichita, and Winsome. These results are not wholly consistent with prior research and additional studies will be required to reconcile discrepancies. The discovery of Pinb-2v4 and the mapping of all four variants will contribute to a better understanding of gene duplication events in wheat and their bearing on wheat kernel texture and grain utilization.     

Ca2+ and pH responses to sequential additions of mitogens in single 3T3 fibroblasts: correlations with DNA synthesis

The progression of Swiss 3T3 fibroblasts from the quiescent state (G0) through G1 to DNA synthesis in S phase generally requires the synergistic action of two mitogens. The main aim of this study was to compare systematically the early Ca2+ and pH responses in quiescent cells to all of the pair combinations of eight mitogens (bombesin, platelet-derived growth factor, vasopressin, prostaglandin F2 alpha, epidermal growth factor, 12-O-tetradecanoyl phorbol-13-acetate, insulin, 8-bromo-cAMP) with their subsequent effects on DNA synthesis. Each of the mitogens which caused inositol phosphate accumulation (bombesin, platelet-derived growth factor, vasopressin, prostaglandin F2 alpha) also activated Ca2+- and phospholipid-dependent protein kinase (protein kinase C) and generated both the Ca2+ and pH responses, although epidermal growth factor also generated the ionic responses without causing release of inositol phosphates or activation of protein kinase C. For sequential mitogen additions the ionic signals were measured in single cells as well as in cell populations to avoid ambiguities due to heterogeneity in the responses of the cells to the various mitogens. The modulating effects of the mitogens on the [Ca2+]i responses to subsequent mitogen additions varied widely, but detailed comparisons showed that the pattern of blocking effects could not be attributed solely to the effect of the first mitogen causing either maximal breakdown of phosphatidylinositol 4,5-bisphosphate or complete depletion of the intracellular Ca2+ pool or activation of protein kinase C. From these analyses it was concluded that the requirement for two mitogens for effective DNA synthesis could not be attributed to the summation to a critical threshold of either the ionic signals or phosphatidylinositol 4,5-bisphosphate breakdown, and that these responses are insufficient by themselves to cause the cells to progress to DNA synthesis in S phase.