Milk Fat Content and DGAT1 Genotype Determine Lipid Composition of the Milk Fat Globule Membrane

During secretion of milk fat globules, triacylglycerol (TAG) droplets are enveloped by a phospholipid (PL) trilayer. Globule size has been found to be related to polar lipid composition and fat content, and milk fat content and fatty acid composition have been associated with the diacylglycerol acyltransferase 1 (DGAT1) K232A polymorphism; however, the association between the DGAT1 polymorphism and fat globule size and polar lipid composition has not been studied. The ratio between polar and neutral lipids as well as the composition of the polar lipids in milk has industrial as well as nutritional and health implications. Understanding phenotypic and genotypic factors influencing these parameters could contribute to improving milk lipid composition for dairy products. The focus of the present study was to determine the effect of both fat content and DGAT1 polymorphism on PL/TAG ratio, as a marker for milk fat globule size, and detailed PL composition. Milk samples were selected from 200 cows such that there were equal numbers of samples for the different fat contents as well as per DGAT1 genotype. Samples were analyzed for neutral and polar lipid concentration and composition. PL/TAG ratio was significantly associated with both fat content and DGAT1 genotype. Phosphatidylinositol and phosphatidylserine concentrations were associated with fat content*DGAT1 genotype with a stronger association for the AA than the KK genotype. Sphingomyelin concentration tended to interact with fat content*DGAT1 genotype. Phosphatidylethanolamine (PE) concentration showed a biphasic response to fat content, suggesting that multiple biological processes influence its concentration. These results provide a new direction for controlling polar lipid concentration and composition in milk through selective breeding of cows.     

Is dinitrogen fixation significant in the Levantine Basin,East Mediterranean Sea?

We report N(2) fixation rates measured from two stations monitored monthly off the Mediterranean coast of Israel during 2006 and 2007, and along a transect from Israel to Crete in September 2008. Analyses of time-series data revealed expression of nifH genes from diazotrophs in nifH clusters I and II, including cyanobacterial bloom-formers Trichodesmium and diatom-Richelia intracellularis associations. However, nifH gene abundance and rates of N(2) fixation were very low in all size fractions measured (> 0.7 μm). Volumetric (15) N uptake ranged from below detection (～ 36% of > 300 samples) to a high of 0.3 nmol N l(-1) d(-1) and did not vary distinctly with depth or season. Areal N(2) fixation averaged ～ 1 to 4 μmol N m(-2) d(-1) and contributed only ～ 1% and 2% of new production and ～ 0.25% and 0.5% of primary production for the mixed (winter) and stratified (spring-fall) periods respectively. N(2) fixation rates along the 2008 east-west transect were also extremely low (0-0.04 nmol N l(-1) d(-1), integrated average 2.6 μmol N m(-2) d(-1) ) with 37% of samples below detection and no discernable difference between stations. We demonstrate that diazotrophy and N(2) fixation contribute only a minor amount of new N to the P impoverished eastern Mediterranean Sea.     

Variation in lipid profiles within semen compartments—the bovine model of aging

Semen lipid composition was examined in young and mature bulls. Given the specific roles of various semen compartments (i.e., seminal fluid, sperm head, and sperm tail) during fertilization, we hypothesized that altered fatty acid and cholesterol composition of a specific compartment might impair semen quality and sperm function. Semen samples were collected from five mature and five young Holstein Friesian bulls during the winter (December–January). Semen was evaluated by computerized sperm-quality analyzer for bulls and was centrifuged to separate the sperm from the seminal fluid. The sperm fraction was sonicated to separate its head and tail compartments. Cold extraction of lipids was performed, and fatty acids and cholesterol were identified and quantified by gas chromatography. Semen physiological features (concentration, motility, and progressive motility) did not differ between mature and young bulls. However, lipid composition within fractions varied between groups, with prominent impairments in the head compartment. In particular, the proportions of polyunsaturated fatty acids, omega-3 fatty acids, and docosahexaenoic acid in the intact sperm; seminal fluid; and sperm head were lower in semen collected from mature bulls than in that from young bulls. The finding suggests an age-differential absorption and/or metabolism through spermatogenesis. Reduced proportions of major fatty acids in mature bulls might reduce membrane fluidity, which in turn might affect the ability to undergo cryopreservation and/or oocyte-sperm fusion through fertilization.     

Further Than the Eye Can See: Psychological Distance and Perception of Environmental Threats

The deteriorating state of the environment and global warming pose a serious and unprecedented threat to humanity. Yet, public response and personal behavior do not reflect the proportions of such a threat. In the present research we explored possible reasons for this discrepancy. Past research has shown that people perceive events as more threatening based on their immediacy, certainty, or personal implications. Liberman and Trope (2008) developed the concept of “psychological distance” (PD), according to which more immediate events are seen as “closer in time,” more certain events as “closer in probability,” and events with greater potential for personal harm as “socially closer.” Adopting this concept, we examined how distant, in terms of PD, people perceive environmental threats to be. Using a structural equations model, we measured how PD influences environmental threat perception. In a sample of 305 Israeli students who completed a computerized questionnaire, we found that environmental threats were perceived as psychologically distant in all of the PD dimensions, and that PD strongly affected perceived severity of environmental threats and willingness to engage in pro-environmental behavior. The reasons for the psychological remoteness of environmental threats and possible approaches to cope with its implications are discussed.     

Plasminogen activator and protease inhibitor activities in isolated rat thymocytes

Summary Plasminogen Activator (PA) and its response to glucocorticoids and androgens was studied in viable rat thymocytes in suspension. PA was measured by its ability to convert plasminogen to plasmin, and the formed plasmin determined by cleavage of ¹⁴C-labeled globin. Using this functional assay, PA was found to be associated with the outer surface of thymic cells, and only negligible activity recovered from the incubation medium. Rat thymocytes also contain cytoplasmic and nuclear inhibitor(s) of the serine proteases plasmin, trypsin, chymotrypsin and thymic PA. Release of these inhibitors prevented determination of thymic PA activity in presence of lysed cells.The specific activity of PA in thymocytes isolated from adrenalectomized-castrated rats did not differ significantly from the specific activity associated with cells from intact animals. Furthermore, treatment of adrenalectomized-castrated rats with 0.1 mg of dexamethasone/ kg for 2 days induced thymic involution without affecting thymic PA activity. These observations suggest that PA activity of thymocytes is not involved in glucocorticoid-mediated thymic involution.     

Seasonal Characteristics of the Daily Fluctuation in Nitrate Reductase Activity

The daily fluctuation of nitrate reductase activity in leaves of tobacco may be controlled by the relative amounts of endogenous cytokinin and gibberellin. While plants growing during the summer exhibit maximum nitrate reductase activity at midday, winter-grown plants show minimum activity at that time. One reason for this phenomenon seems to be a relatively higher level of endogenous kinin in winter-grown plants. Salt-stress treatment of these plants changes the fluctuation pattern of nitrate reductase activity from a winter to a summer type. Kinetin addition to summer-grown plants changes their fluctuation pattern from a summer to a winter type.     

Effect of mating on UV-induced DNA degradation in an Hfr recA strain of Escherichia coli

Summary Degradation of DNA occurs in a mated UV irradiated Hfr recA strain but at a rate less than when not mated. The difference in the amount of DNA degradation between mated and unmated UV irradiated Hfr recA can be accounted for by the net synthesis of DNA previously observed in the mated males.     

Antiganglioside Antibodies Inhibit Neuritic Outgrowth from Regenerating Goldfish Retinal Explants

Abstract: Antibodies elicited in rabbits against bovine brain gangliosides were applied to regenerating retinal explants to examine the role of gangliosides in the trophic effect responsible for the induction of outgrowth. The results indicate that antibodies specific to gangliosides block the neuritic outgrowth from the regenerating retinal explants. It is inferred that gangliosides function as receptors on the cell surface of the retinal explants that interact with the trophic substances inducing the outgrowth. The relevance of gangliosides to the mechanism of regeneration and development induced by trophic factors is discussed.