Transcript profiling and lipidomic analysis of ceramide subspecies in mouse embryonic stem cells and embryoid bodies

Ceramides (Cers) are important in embryogenesis, but no comprehensive analysis of gene expression for Cer metabolism nor the Cer amounts and subspecies has been conducted with an often used model: mouse embryonic stem cells (mESCs) versus embroid bodies (EBs). Measuring the mRNA levels by quantitative RT-PCR and the amounts of the respective metabolites by LC-ESI/MS/MS, notable differences between R1 mESCs and EBs were: EBs have higher mRNAs for CerS1 and CerS3, which synthesize C18- and C≥24-carbons dihydroceramides (DH)Cer, respectively; EBs have higher CerS2 (for C24:0- and C24:1-); and EBs have lower CerS5 + CerS6 (for C16-). In agreement with these findings, EBs have (DH)Cer with higher proportions of C18-, C24- and C26- and less C16-fatty acids, and longer (DH)Cer are also seen in monohexosylCers and sphingomyelins. EBs had higher mRNAs for fatty acyl-CoA elongases that produce C18-, C24-, and C26-fatty acyl-CoAs (Elovl3 and Elovl6), and higher amounts of these cosubstrates for CerS. Thus, these studies have found generally good agreement between genomic and metabolomic data in defining that conversion of mESCs to EBs is accompanied by a large number of changes in gene expression and subspecies distributions for both sphingolipids and fatty acyl-CoAs.     

Autoimmune disease and the nervous system. Biochemical,molecular, and clinical update.

Autoimmunity in the central and peripheral nervous system can manifest as the result of cellular or humoral immune responses to autoantigens. There is evidence that multiple sclerosis is a cell-mediated autoimmune disease of the central nervous system in which both myelin and the cell that produces the myelin are destroyed. Diseases such as acute inflammatory demyelinating polyneuropathy (also called Guillain-Barré syndrome) and myasthenia gravis are considered antibody-mediated diseases of the peripheral nervous system and neuromuscular junctions, respectively. We review these diseases and explore mechanisms of immune-mediated destruction of these nervous system components. We specifically focus on one effective therapy aimed at countering the immune attack, that of thymectomy in patients with myasthenia gravis.     

Functional differences in human neutrophils isolated pre- and post-prandially.

Activated polymorphonuclear leukocytes have been associated with neoplasia, atherogenesis and reperfusion injury. Since some of these conditions are also correlated with dietary fat, we examined the functional characteristics of leukocytes isolated from subjects before and after consumption of a lipid-rich meal. There was up to 2-fold greater superoxide generation in response to agonists in leukocytes obtained post-prandially; the maximum increase was observed about 4 h after eating and followed the peak (2-4 h) in serum triglycerides. Neutrophils isolated post-prandially also exhibited impaired chemotaxis and defective bacterial killing, but normal phagocytosis. These findings provide a new variable that should be considered in studies of leukocytes.     

THE INFLUENCE OF INTRASPECIFIC VARIATION IN DISPERSAL STRATEGIES ON THE GENETIC STRUCTURE OF PLANTHOPPER POPULATIONS

The hypothesis that levels of gene flow among populations are correlated with dispersal ability has typically been tested by comparing gene flow among species that differ in dispersal abilities, an approach that potentially confounds dispersal ability with other species-specific differences. In this study, we take advantage of geographic variation in the dispersal strategies of two wing-dimorphic planthopper species, Prokelisia marginata and P. dolus, to examine for the first time whether levels of gene flow among populations are correlated with intraspecific variation in dispersal ability. We found that in both of these coastal salt marsh–inhabiting species, population-genetic subdivision, as assessed using allozyme electrophoresis, parallels geographic variation in the proportion of flight-capable adults (macropters) in a population; in regions where levels of macroptery are high, population genetic subdivision is less than in regions where levels of macroptery are low. We found no evidence that geographic variation in dispersal capability influences the degree to which gene flow declines with distance in either species. Thus, both species provided evidence that intraspecific variation in dispersal strategies influences the genetic structure of populations, and that this effect is manifested in population-genetic structure at the scale of large, coastal regions, rather than in genetic isolation by distance within a region. This conclusion was supported by interspecific comparisons revealing that: (1) population-genetic structure (G_ST) of the two Prokelisia species correlated negatively with the mean proportion of flight-capable adults within a region; and (2) there was no evidence that the degree of isolation by distance increased with decreasing dispersal capability. Populations of the relatively sedentary P. dolus clustered by geographic region (using Nei's distances), but this was not the case for the more mobile P. marginata. Furthermore, gene flow among the two major regions we surveyed (Atlantic and Gulf Coasts) has been substantial in P. marginata, but relatively less in P. dolus. The results for P. marginata suggest that differences in the dispersal strategies of Atlantic and Gulf Coast populations occur despite extensive gene flow. We argue that gene flow is biased from Atlantic to Gulf Coast populations, indicating that selection favoring a reduction in flight capability must be intense along the Gulf. Together, the results of this study provide the first rigorous evidence of a negative relationship within a species between dispersal ability and the genetic structure of populations. Furthermore, regional variation in dispersal ability is apparently maintained by selective differences that outweigh high levels of gene flow among regions.     

Sesquiterpene lactones from Centaurea solstitialis

Eight sesquiterpene lactones were isolated from Centaurea solstitialis (yellow starthistle). They are solstitialin A, repin, subluteolide, acroptilin, janerin, cynaropicrin, and the new lactones solstitiolide and episolstitiolide.     

Do Birds Alter Levels of Parental Investment Based on Nest‐Site Habitat Features?

Many habitats have undergone rapid changes over the past century as a result of anthropogenic activities. Organisms can respond to changes in their environment in many ways, including how much they invest in a given reproductive bout. Optimality theory and life history theory together have provided a framework for understanding how individuals make decisions about the risks and rewards of investing high levels of resources into their offspring within the context of current vs. future reproduction. Shrubland birds in the United States often breed in habitat that has been impacted by humans to varying degrees and provide an ideal system for examining whether organisms alter their levels of parental investment based on the habitat around the nest site. In this study, we assessed levels of nest‐defense behavior during a simulated nest predation event in four shrubland birds: American robins (Turdus migratorius), gray catbirds (Dumetella carolinensis), brown thrashers (Toxostoma rufum), and northern cardinals (Cardinalis cardinalis). We found that thrashers and catbirds exhibited significantly higher levels of nest defense compared to robins and cardinals and that birds with larger broods acted more aggressively in defending them. We also found that thrashers acted less aggressively as the proportion of shrubland around the nest increased and as the proportion of developed land around the nest decreased and that cardinals acted less aggressively as the proportion of developed land around the nest increased. These patterns suggest that nest‐defense behavior can covary with features of the landscape surrounding the nest, but that the factors shaping that behavior can differ by species.