Differences in the long chain (sphingoid) base composition of sphingomyelin from rats bearing Morris hepatoma 7777

The long chain bases of sphingomyelin from Morris hepatoma 7777 and host and control livers were analyzed by capillary gas liquid chromatography. Sphingosine (18∶1) was the major long chain base of control livers (66.5%) and hepatomas (65.6%), but hepatomas also had a high percentage (9.3 vs 4.4) of the 16∶1 homolog. Host liver had the most unusual long chain base composition, with ca. equal 16∶1 (24.4%) and 18∶1 (21.4%) and high amounts of 20-carbon bases (9.2% 20∶0 and 15.3% 20∶1). These differences may be related to the aberrant fatty acid metabolism known to occur in tumor-bearing animals. Such large perturbations in the long chain base composition of hepatic sphingomyelin are unprecedented and could have a major impact on the properties of host membranes.     

Irradiation-modification of starch-containing thermoplastic blends. I. Modification of properties and microstructure

Irradiation-modification of the blends of various starches with a synthetic polymer [poly(ethylene-co-vinyl alcohol)] was carried out using an electron beam. The effect of irradiation on neat starches was studies using gel permeation chromatography. Changes in the thermal and mechanical properties of the blends, as well as in their microstructures, were also evaluated. The data indicate, consistent with other reports in literature, that starch molecules fragment under the effect of ionizing radiation, while the EVOH is relatively unaffected. These substantial (mainly physical) modifications to the starch molecules manifest themselves in changes in the thermal behavior of the blends. Furthermore, the mechanical properties of filaments obtained from molten irradiated pellets were quite different from those of control filaments, at least for some starches. Micrographic examination of some blends indicated a correspondence between a modification in the microstructure of the filaments and a change in their mechanical properties. It seems likely that the enhanced mobility of the fragmented starch molecules in the melt is responsible for these changes in the microstructure and concomitantly, the mechanical properties of the blend. Such an irradiation-based physical modification of starch may be of use in tailoring the properties of commercial blends of starches with synthetic thermoplastics. © 1996 John Wiley & Sons, Inc.     

Family life stress and insomnia symptoms in a prospective evaluation of young adults.

The present study prospectively investigated the association between family life stress and insomnia symptoms among 115 undergraduates, ages 17-22 years. Participants completed the following questionnaires at 2 study time points, spaced 3 weeks apart: the Insomnia Severity Index, the Negative Life Events Questionnaire (NLEQ), and the Beck Depression Inventory. First, family life stress at baseline was hypothesized to predict elevated insomnia symptoms 3 weeks later, above and beyond depressive symptoms. Second, compared with academic stressors, negative family and social life events were expected to best predict increased insomnia. Regression analyses were conducted to test study predictions. Hypotheses were partially supported. Family life stress was significantly associated with increased insomnia symptomatology, even after controlling for depression. Results also revealed that negative family life events, together with academic stress, predicted the highest levels of insomnia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Regulation of phosphatidate phosphatase activity from the yeast Saccharomyces cerevisiae by sphingoid bases

The regulation of Saccharomyces cerevisiae membrane-associated phosphatidate phosphatase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) activity by sphingoid bases was examined using Triton X-100/lipid-mixed micelles. Sphingosine, phytosphingosine, and sphinganine inhibited purified preparations of the 104- and 45-kDa forms of phosphatidate phosphatase in a dose-dependent manner. The structural requirements for the sphingoid base inhibition of phosphatidate phosphatase activity were a free amino group and a long chain hydrocarbon. A detailed kinetic analysis was performed to determine the mechanism of phosphatidate phosphatase inhibition by sphingoid bases. The phosphatidate phosphatase dependence on phosphatidate was cooperative (Hill numbers of approximately 2) in the absence and presence of sphingoid bases. Sphingosine, phytosphingosine, and sphinganine were parabolic competitive inhibitors of phosphatidate phosphatase activity. This indicated that more than one inhibitor molecule contributed to the exclusion of phosphatidate from the enzyme. The aKi values (inhibitor constants) for sphingosine, phytosphingosine, and sphinganine were 1.5, 0.4, and 0.2 mol %, respectively, and the Km value for phosphatidate was 2.2 mol %. The cellular concentrations of free phytosphingosine and sphinganine were 0.16 and 0.53 mol %, respectively, relative to the total phospholipids in S. cerevisiae. The cellular concentrations of phytosphingosine and sphinganine were in the range of the aKi values for these sphingoid bases. These results raised the suggestion that phosphatidate phosphatase activity may be regulated in vivo by sphingoid bases.     

Parsing Non-LR(k) grammars with yacc

Of the parser generating tools currently in use, yacc (or one of its several variants) is perhaps the most frequently employed. However, because of inherent ambiguities there are some languages (such as C++) that a yacc-generated parser cannot successfully compile. This paper describes a set of minor modifications to yacc-like tools that allows them to be used in a straightforward way to parse ambiguities and, more generally, grammars that require an indefinite amount of lookahead. Required changes to the lexical analyzer are also discussed, and the application of these techniques is illustrated within the context of specific examples.     

Kinetic analysis of respiratory tract proteins recovered during a sequential lavage protocol

Although bronchoalveolar lavage (BAL) has been used as a research tool for over a decade, the technique of lavage has varied markedly between laboratories. For example, lavage instillate volumes from 50 to 300 ml have been used, and yet the influence of the variable of total lavage volume on subsequent protein recovery is uncertain. We performed sequential BAL (50 ml/aliquot; total volume, 300 ml) of the right middle lobe of 14 normal volunteers and separately processed and analyzed recovered aliquots for the absolute and relative concentrations of several protein substances. These proteins include free secretory component and secretory IgA, which emanate from airway secretions, and IgG, which is thought to transude from more distal alveolar sites. Analysis of these data showed a marked decrease in the absolute concentration of all proteins measured in serial aliquots. Analysis of protein ratios in sequential aliquots, however, revealed no significant change from the first to the fifth recovered aliquot. Finally, we analyzed the influence of the size of the first recovered aliquot on absolute and relative concentrations of proteins. Here there seemed to be a trend indicating preferential recovery of airway proteins in smaller aliquots. This was significant for the ratio of free secretory component to albumin (p less than 0.05). We conclude that lung proteins are efficiently and homogeneously sampled with 100 ml of lavage instillate. Larger volumes will add more protein but not alter protein ratios. Lavage with smaller volumes may preferentially sample airway proteins.     

Molten poly(methyl methacrylate) under electron irradiation: Studies of depropagation and chain scission

The degradation rates of free radical polymerized and syn-diotactic poly(methyl methacrylate) (PMMA) under electron radiation were explored at temperatures ranging from 225 to 325°C and at electron dose rates from 10,000 rads/min to 100,000 rads/min. Scission of bonds between main-chain atoms resulted in pairs of radical chain ends, of which some disportionated, thereby reducing polymer molecular weight without loss of volatile, while others proceeded to depropagate via the usual radical transfer, causing complete volatilization of the chain without significant change of molecular weight of the residual polymer. Electron irradiation at a dose rate of 100,000 rads/min produced a significant enhancement in the reaction, rate, and reduced the overall activation energy from 140 KJ/g-mole observed for thermally induced depropagation to a value of 75 KJ/g-mole observed during simultaneous irradiation and/thermal depropagation.