Scanning tunnelling microscopy of Z-DNA

Scanning tunnelling microscopy (STM) has been used to map the surface topography of inorganic materials at the atomic level, and is potentially one of the most powerful techniques for probing biomolecular structure. Recent STM studies of calf thymus DNA and poly(rA).poly(rU) have shown that the helical pitch and periodic alternation of major and minor grooves can be visualized and reliably measured. Here we present the first STM images of poly(dG-me5dC).poly(dG-me5dC) in the Z-form. Both the general appearance of the fibres and measurements of helical parameters are in good agreement with models derived from X-ray diffraction.     

Maternal involvement in the development of cardiovascular phenotype

Over the past 20 years, laboratory studies of genetically defined animal models of human essential hypertension have provided valuable information on the pathophysiology of this disturbance in cardiovascular regulation. Relatively fewer studies have examined the impact of preweaning factors on the developing cardiovascular system of hypertensive animals. In our laboratory studies, we have utilized two inbred genetically hypertensive models: the spontaneously hypertensive (SHR) rat and its Wistar/Kyoto (WKY) normotensive control strain as well as the Dahl hypertension-sensitive (SS/Jr) and hypertension-resistant (SR/Jr) strains. To manipulate the preweaning maternal environment, we have employed the technique of reciprocal cross-fostering of litters between hypertensive and matched normotensive mothers. Our findings to date point to the maternal environment as a powerful influence on the development of high blood pressure in genetically hypertensive rats. In general, hypertensive rats reared by normotensive foster mothers have significant reductions in arterial blood pressure in adulthood. Thus, the progression of hypertinsive disease is not strictly predtermined by genotypic factors. Rather, a genetic predisposition to hypertension interacts with preweaning environmental factors to determine an animal's cardiovascular phenotype in adulthood.     

Effect of p-nitrophenylglycerol on motility of rat epididymal spermatozoa

Summary Using a convenient capillary tube assay, the antiswarming agent acting onProteus, p-nitrophenylglycerol (PNPG), was found to have produced an antimotility effect in sperms from rat cauda epididymides.Acknowledgment. The authors are grateful to K. C. Tsui and Y. F. Lam of the Hong Kong Agriculture and Fisheries Department for valuable discussion.     

High K+-induced release of somatostatin from the cortical preparation of rat brain

Summary Release of endogenous somatostatin (SRIF) from the rat cerebral cortical slices incubated in Krebs-bicarbonate buffer was increased from the basal rate of 3.4±0.6% of the total SRIF content in 15 min at [K⁺]_o=5.6 mM, to 13.1±1.6% upon raising the [K⁺]_o to 56.6 mM. The high-K⁺ evoked SRIF release was absent when Ca⁺⁺ in the medium was replaced by Mn⁺⁺. The isolated synaptosomes from rat cerebral cortex contain 13.2±3.1 ng SRIF/mg protein compared to 0.33±0.01 ng/mg protein in the cortical tissue as a whole, suggesting that nerve terminals are the main source of the peptide released upon membrane depolarization.The study was supported by a grant from the Medical Research Council of Canada. Results of this work have been published in part as abstracts: Can. Physiol.9, 45 (1978), and Fedn Proc.37, 665 (1978).The authors are greatly indebted to Dr M. Gotz and the Ayerst Research Laboratories for the most generous supply of the synthetic somatostatin.