Effect of Dietary Lipid on the Acyl Group Composition of Glycerophospholipids of Brain Endothelial Cells in the Developing Rat

Abstract: The effects of dietary lipid on the acyl group composition of glycerophospholipids of isolated brain endothelial cell fractions have been determined in the developing rat. Rats were fed high-protein diets containing differing dietary linoleic/linolenic acid ratios but having a similar caloric percentage, or were fed a fat-free diet. With a diet supplemented with corn oil (linoleic/linolenic ratio, 47:1), the proportion of acyl groups of the linolenic acid series (n-3) declines in all glycerophospholipid fractions compared with the controls (linoleic/linolenic ratio, 8.5:1), but the proportion of linoleic acid series (n-6) tends to rise. Consequently, the n-6/n-3 ratio of these glycerophospholipids is markedly higher with corn oil than the control diet. N-9 groups (oleic acid series) are consistently lower in proportion. With fat-free diet, the proportion of n-9 groups is higher in these glycerophospholipids than in the controls, but there is no change in the n-6/n-3 ratio. Comparing the changes produced in the adult and the developing cell fraction, the developing cell fraction is more responsive to dietary influence than that of the adult.     

Environmental effects on primary radical formation in guanine: solid-state ESR and ENDOR of guanine hydrobromide monohydrate.

Single crystals of guanine hydrobromide monohydrate, in which the guanine base is protonated at N7, were X-irradiated at 8 and 65 K. Using K-band ESR, ENDOR, and field-swept-ENDOR (FSE) techniques, the crystals were studied between 8 K and room temperature. There was evidence for five different radicals, RI-RV, immediately following irradiation at 8 or 65 K. RI was identified as the O6-protonated anion. It decayed near room temperature with no detectable successor. RII was identified as the N7-deprotonated cation, and decayed near 130 K. RIII is thought to be a ring-opened product formed by C8-N9 bond rupture; upon warming, it decayed at 150 K. RIV is the well-known C8 H-addition radical. These four radicals have been observed previously in the hydrochloride salt of guanine monohydrate. RV is novel, however, with magnetic characteristics consistent with those of the product formed by net OH addition to C5 of the unsaturated C4-C5 bond. It is characterized by four alpha-proton couplings indicating pi-electron spin as follows: 13% at C8; 11% at N7; and 12% at N10. RV decayed between 240 and 255 K with no detectable successor. Upon further warming, very weak resonance lines due to additional, unidentified radicals were observed. A comparison of these results with those obtained from other systems containing N7-protonated guanine bases demonstrates the effect of the environment on the primary radical formation.     

The Pattern of Activation in the Sartorius Muscle of the Frog

The development of isometric twitch tension has been compared with the redevelopment of isometric tension in the fully active frog sartorius muscle following release. At 0°C the rate of rise of isometric twitch tension is the same as that for the muscle in the fully active state at the same tension but not until about 40 msec. after the stimulus and then only for a few milliseconds. The rates of rise of tension in the twitch and in the redevelopment of tension in the fully active muscle appear to be nearly the same at low tensions. Substitution of nitrate for chloride in the Ringer's solution bathing the muscle retards the development of tension during the early part of the contraction phase of the twitch and the effect reaches a maximum within 3 minutes after changing the solutions. These observations have been discussed in connection with some possible patterns of activation and the hypothesis has been advanced that the rate of activation of a sarcomere is determined mainly by the rate at which the transverse component of the link between excitation and contraction is propagated inwards from the periphery to the center of the fiber. This hypothesis has been discussed in relation to others concerning the nature of excitation-contraction coupling.     

A newly identified barley gene, Dhn12, encoding a YSK2 DHN, is located on chromosome 6H and has embryo-specific expression

Dehydrins are water-soluble lipid-associating proteins that accumulate during low-temperature or water-deficit conditions, and are thought to play a role in freezing- and drought-tolerance in plants. Dhn genes exist as multi-gene families in plants. Previously, we screened lambda genomic libraries of two barley cultivars in an effort to isolate all of the barley Dhn genes. We identified 11 unique Dhn genes and estimated a total of 13 Dhn genes in the barley genome. To extend the collection, we used an alternative source of clones, a 1.5×Morex barley BAC library. In this library, we found nine Dhn genes that we described previously and one new Dhn gene, Dhn12. The Dhn12 gene encodes an acidic YSK₂ dehydrin. The Dhn12 gene is located on chromosome 6H, and shows a different expression pattern from all other Dhn genes identified previously. RT-PCR results show that Dhn12 expression is embryo-specific. Dhn12 is not expressed in seedling shoots under any of the conditions tested, including non-stressed as well as dehydrated, or cold-, ABA- or NaCl-treated seedlings. Received: 6 June 1999 / Accepted: 3 November 1999