Canine prostaglandin E2 synthase (PGES) and its receptors (EP2 and EP4): expression in the corpus luteum during dioestrus

In the dog CL are the only source of the progesterone in cyclic and pregnant animals. From a high expression of cyclooxygenase 2 (Cox2) at the beginning of the dioestrus and a low one at the end it was suggested that prostanoids may play a role in the formation of the CL. This led to the hypothesis that also in the dog PGE2 of luteal origin might act as paracrine/autocrine factor. Hence, expression of the prostaglandin E2 synthase (PGES) and its receptors (EP2 and EP4) was determined during the course of dioestrus in canine CL from days 5, 15, 25, 35, 45, 65 after ovulation, following cloning of PGES using SMART RACE PCR, which revealed a high homology (82-94%) with other species. Real Time (TaqMan) PCR showed a high PGES and EP2 expression in the early CL-phase with a significant decrease thereafter. EP4 revealed a constant expression pattern throughout the life span of the CL. In situ hybridization co-localized PGES, EP2 and EP4 in the cytoplasm of the luteal cells only. In conclusion, our data suggest that in the dog PGE2 of luteal origin acts by autocrine mechanism as a luteotropic factor through its EP2 and EP4 receptors during the phase of CL-formation.     

Possible Fruit Protein Effects on Primate Communities in Madagascar and the Neotropics

Background

The ecological factors contributing to the evolution of tropical vertebrate communities are still poorly understood. Primate communities of the tropical Americas have fewer folivorous but more frugivorous genera than tropical regions of the Old World and especially many more frugivorous genera than Madagascar. Reasons for this phenomenon are largely unexplored. We developed the hypothesis that Neotropical fruits have higher protein concentrations than fruits from Madagascar and that the higher representation of frugivorous genera in the Neotropics is linked to high protein concentrations in fruits. Low fruit protein concentrations in Madagascar would restrict the evolution of frugivores in Malagasy communities.

Methodology/Principal Findings

We reviewed the literature for nitrogen concentrations in fruits from the Neotropics and from Madagascar, and analyzed fruits from an additional six sites in the Neotropics and six sites in Madagascar. Fruits from the Neotropical sites contain significantly more nitrogen than fruits from the Madagascar sites. Nitrogen concentrations in New World fruits are above the concentrations to satisfy nitrogen requirements of primates, while they are at the lower end or below the concentrations to cover primate protein needs in Madagascar.

Conclusions/Significance

Fruits at most sites in the Neotropics contain enough protein to satisfy the protein needs of primates. Thus, selection pressure to develop new adaptations for foods that are difficult to digest (such as leaves) may have been lower in the Neotropics than in Madagascar. The low nitrogen concentrations in fruits from Madagascar may contribute to the almost complete absence of frugivorous primate species on this island.     

Motional properties of a pentasaccharide containing a 2,6-branched mannose residue as studied by 13C nuclear spin relaxation

Summary ¹³C relaxation data obtained at three different magnetic fields, 9.4, 11.8 and 14.1 T, and at two temperatures, 303 and 318 K, are reported for the pentasaccharide p-trifluoroacetamidophenyl 2,6-di-O-[-d-galactopyranosyl-(14)-O-2-acetamido-2-deoxy--d-glucopyranosyl]-d-mannopyranoside. The pentasaccharide consists of two disaccharide units, attached at position 2 and 6 to the central mannopyranoside residue. The relaxation data were interpreted with the Lipari-Szabo model-free approach. For the central mannose residue in the molecule a high order parameter (S²=0.91) was found and the relaxation data could be interpreted with the truncated form of the Lipari-Szabo model. The motional behavior of the two 2-acetamido-2-deoxy-glucopyranoside residues was found to differ. The one attached at the primary hydroxylic position displayed more extensive local motion (S²=0.75–0.77) than the one attached at the secondary hydroxylic position (S²=0.83–0.85). More extensive local motion for the two outer galactopyranoside residues was found (S²=0.56–0.59), but no significant difference in motional behavior between the two residues could be observed. Analysis of the relaxation data for the exocyclic carbons confirmed the results for the rings. For the mannose C6, the same motional parameters as obtained for the substituting 2-acetamido-2-deoxy-glucopyranoside residue were found. The two exocyclic carbons on the 2-acetamido-2-deoxy-glucopyranoside residues showed more extensive local motion, with lower order parameters (S²=0.59–0.66).To whom correspondence should be addressed.     

Coupled pacing improves cardiac efficiency during acute atrial fibrillation with or without cardiac dysfunction

Coupled pacing (CP), a method for controlling ventricular rate during atrial fibrillation (AF), consists of a single electrical stimulation applied to the ventricles after each spontaneous activation. CP results in a mechanical contraction rate approximately one-half the rate during AF. Paired stimulation in which two electrical stimuli are delivered to the ventricles has also been proposed as a therapy for heart failure. Although paired stimulation enhances contractility, it greatly increases energy consumption. The primary hypothesis of the present study is that CP improves cardiac function during acute AF without a similar increase in energy consumption because of the reduced rate of ventricular contractions. In a canine model, CP was applied during four stages: sinus rhythm (SR), acute AF, cardiac dysfunction (CD), and AF in the presence of cardiac dysfunction. The rate of ventricular contraction decreased in all four stages as the result of CP. In addition, we determined the changes in external cardiac work, myocardial oxygen consumption, and myocardial efficiency in the each of four stages. CP partially reversed the effects of AF and CD on external cardiac work, whereas myocardial oxygen consumption increased only moderately. In all stages but SR, CP increased myocardial efficiency because of the marked increases in cardiac work compared with the moderate increases in total energy consumed. Thus this pacing therapy may be a viable therapy for patients with concurrent atrial fibrillation and heart failure.     

Methylglyoxal-induced glycation affects protein topography

Methylglyoxal is a metabolic byproduct that is elevated in diabetic tissue. We examined the effects of methylglyoxal on cytosolic aspartate aminotransferase (cAAT), which is an enzyme previously shown to be modified by glyceraldehyde, acrolein, and ribose 5-phosphate. In the present study we observed that methylglyoxal caused real-time changes in tryptophan (intrinsic) fluorescence. Millimolar concentrations of methylglyoxal predominately decreased the fluorescence emission at 388 nm. While micromolar concentrations also decreased emission at 388 nm, low levels of methylglyoxal caused a prominent redshift in the wavelength of maximal emission. The changes in intrinsic fluorescence reflect definable changes in protein topography. These observations are consistent with a change in conformation that is more compact than that of native cAAT, suggesting that intramolecular cross-links (i.e., lysine-lysine) or hydrophobic pockets (i.e., carboxyethyl-lysines) were formed. Methylglyoxal also inhibited activity, and the inhibition correlated with the methylglyoxal-induced change in protein conformation.     

Acrolein modifies and inhibits cytosolic aspartate aminotransferase

Acrolein is a reactive lipid peroxidation byproduct, which is found in ischemic tissue. We examined the effects of acrolein on cytosolic aspartate aminotransferase (cAAT), which is an enzyme that was previously shown to be inhibited by glycating agents. cAAT is thought to protect against ischemic injury. We observed that acrolein cross-linked cAAT subunits as evidenced by the presence of high molecular weight bands following SDS-PAGE. Acrolein-modified cAAT resisted thermal denaturation when compared with native cAAT. We also observed a decrease in intrinsic fluorescence (290 nm, ex; 380 nm, em). These observations are consistent with an acrolein-induced change in conformation that is more rigid and compact than native cAAT, suggesting that intramolecular cross-links occurred. Acrolein also inhibited activity, and the inhibition of enzyme activity correlated with the acrolein-induced formation of cAAT cross-links.     

Environmental and scale-dependent evolutionary trends in the body size of crustaceans

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum, mean and median body size increased, but no increase in minimum size was observed. This increase is not expressed within lineages, but is rather a product of the appearance and/or diversification of new clades of larger, primarily burrowing to shelter-seeking decapods. This argues against directional selective pressures within lineages. Rather, the trend is a macroevolutionary consequence of species sorting: preferential origination of new decapod clades with intrinsically larger body sizes. Furthermore, body size evolution appears to have been habitat-controlled. In the Cretaceous, reef-associated crabs became markedly smaller than those in other habitats, a pattern that persists today. The long-term increase in body size of crabs and lobsters, coupled with their increased diversity and abundance, suggests that their ecological impact may have increased over evolutionary time.