Temperature dependence of chaperone-like activity and oligomeric state of alphaB-crystallin

The chaperone-like activity and the oligomeric state of alphaB-crystallin were studied at different temperatures and in the presence of urea and thiocyanate. The activity, assessed measuring the ability of alphaB-crystallin to prevent the aggregation of denatured insulin, strongly depends on temperature. While a significant activity increase was detected at 42 degrees C, the presence of urea and thiocyanate does not affect the protein activity in an irreversible way. In-solution SAXS measurements performed in the same experimental conditions showed that alphaB-crystallin forms near-spherical, hollowed, polydisperse oligomers, whose dimensions change above 42 degrees C. Moreover, in the presence of urea and thiocyanate, a global fit analysis confirms the high stability of alphaB-crystallin assemblies in relationship with their variable quaternary structure. In particular, the changes in the inner radius as well as the thickness and dispersion of the protein shell, account for the preservation of the chaperone-like activity.     

Novel Angiotensin I-converting enzyme inhibitory peptides found in a thermolysin-treated elastin with antihypertensive activity

Angiotensin I-converting enzyme (ACE) inhibitory activity was generated from elastin and collagen by hydrolyzing with thermolysin. The IC50 value of 531.6 μg/mL for ACE inhibition by the elastin hydrolysate was five times less than 2885.1 μg/mL by the collagen hydrolysate. We confirmed the antihypertensive activity of the elastin hydrolysate in vivo by feeding spontaneously hypertensive rats (male) on a diet containing 1% of the elastin hydrolysate for 9 weeks. About 4 week later, the systolic blood pressure of the rats in the elastin hydrolysate group had become significantly lower than that of the control group. We identified novel ACE inhibitory peptides, VGHyp, VVPG and VYPGG, in the elastin hydrolysate by using a protein sequencer and quadrupole linear ion trap (QIT)-LC/MS/MS. VYPGG had the highest IC50 value of 244 μM against ACE and may have potential use as a functional food.     

Morphological Changes in the Midgut of Aedes aegypti L. (Diptera: Culicidae) Larvae Following Exposure to an Annona coriacea (Magnoliales: Annonaceae) Extract

Bioinsecticides are important in the control of disease vectors, but data regarding their physiological effects on target insects are incomplete. This study describes morphological changes that occur in the midgut of third instar Aedes aegypti L. (Diptera: Culicidae) following treatment with a methanolic extract of Annona coriacea (Magnoliales: Annonaceae). Dissected midguts were subdivided into anterior and posterior regions and analyzed by light and scanning electron microscopy. Insects exposed to the extract displayed intense, destructive cytoplasmic vacuolization in columnar and regenerative midgut cells. The apical surfaces of columnar cells exhibited cytoplasmic protrusions oriented toward the lumen, suggesting that these cells could be involved in apocrine secretory processes and/or apoptosis. We report that A. coriacea extracts induced morphological alterations in the midgut of A. aegypti midgut larvae, supporting the use of plant extracts for control of the dengue vector.     

Studies on purine turnover in the camel (Camelus dromedarius) and zebu (Bos indicus)

Significantly higher hypoxanthine over uric acid ratios were found in camel plasma and urine, with respect to those of zebu. Enzyme levels of purine catabolism were markedly lower in camel than in zebu liver. Oxidation of hypoxanthine appears to be the limiting step of purine metabolism in camel liver. Any hepatic hypoxanthine appears to be actively converted into IMP in camel liver, rather than oxidized to uric acid.     

Evidence for diet partitioning among three coexisting native freshwater fishes in South Africa's Cape Fold Ecoregion

The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems.     

Age-associated increase in PGE2 synthesis and COX activity in murine macrophages is reversed by vitamin E

We previouslyshowed that increased macrophage andPGE₂ production with age is due toenhanced cyclooxygenase (COX) activity and COX-2 expression. This studydetermined the effect of vitamin E supplementation on macrophagePGE₂ synthesis in young and old mice and its underlying mechanism. Mice were fed 30 or 500 parts permillion vitamin E for 30 days. Lipopolysaccharide (LPS)-stimulated macrophages from old mice produced significantly morePGE₂ than those from young mice.Vitamin E supplementation reversed the increasedPGE₂ production in old mice buthad no effect on macrophage PGE₂production in young mice. In both LPS-stimulated and unstimulated macrophages, COX activity was significantly higher in old than in youngmice at all intervals. Vitamin E supplementation completely reversedthe increased COX activity in old mice to levels comparable to those ofyoung mice but had no effect on macrophage COX activity of young miceor on COX-1 and COX-2 protein or COX-2 mRNA expression in young or oldmice. Thus vitamin E reverses the age-associated increase in macrophagePGE₂ production and COX activity.Vitamin E exerts its effect posttranslationally, by inhibiting COXactivity.