GQ-16, a Novel Peroxisome Proliferator-activated Receptor γ (PPARγ) Ligand, Promotes Insulin Sensitization without Weight Gain

The recent discovery that peroxisome proliferator-activated receptor γ (PPARγ) targeted anti-diabetic drugs function by inhibiting Cdk5-mediated phosphorylation of the receptor has provided a new viewpoint to evaluate and perhaps develop improved insulin-sensitizing agents. Herein we report the development of a novel thiazolidinedione that retains similar anti-diabetic efficacy as rosiglitazone in mice yet does not elicit weight gain or edema, common side effects associated with full PPARγ activation. Further characterization of this compound shows GQ-16 to be an effective inhibitor of Cdk5-mediated phosphorylation of PPARγ. The structure of GQ-16 bound to PPARγ demonstrates that the compound utilizes a binding mode distinct from other reported PPARγ ligands, although it does share some structural features with other partial agonists, such as MRL-24 and PA-082, that have similarly been reported to dissociate insulin sensitization from weight gain. Hydrogen/deuterium exchange studies reveal that GQ-16 strongly stabilizes the β-sheet region of the receptor, presumably explaining the compound's efficacy in inhibiting Cdk5-mediated phosphorylation of Ser-273. Molecular dynamics simulations suggest that the partial agonist activity of GQ-16 results from the compound's weak ability to stabilize helix 12 in its active conformation. Our results suggest that the emerging model, whereby "ideal" PPARγ-based therapeutics stabilize the β-sheet/Ser-273 region and inhibit Cdk5-mediated phosphorylation while minimally invoking adipogenesis and classical agonism, is indeed a valid framework to develop improved PPARγ modulators that retain antidiabetic actions while minimizing untoward effects.     

Fish Farming Effects on Chemical and Microbial Variables of the Water Column: A Spatio-temporal Study Along the Mediterranean Sea

The effects of fish farming on chemical and biological variables of the water column were investigated in three coastal locations along the Mediterranean (Spain, Italy and Greece). Analyses of nutrients, chlorophyll a, particulate organic carbon and nitrogen (POC and PON), heterotrophic bacteria and cyanobacteria (Synechococcus) were carried out on integrated samples (0–30 m depth) taken at various distances from fish farms and the respective reference sites. At one of these sites, water samples were collected by means of Niskin bottles at 09:00, 13:00 and 16:00 h and at three different depths (0 m, 10 m and bottom). Integrated sampling showed no significant changes with distance in any of the variables measured, whereas all variables except PON showed significant changes between the three locations studied. However, changes were found in samples taken by Niskin bottles, with increased concentrations of NH₄⁺, POC, PON and decreased cyanobacteria densities at the surface layer in the immediate vicinity of the cages. Samples taken at the cages in the afternoon showed increased PO₄³⁻ concentrations in comparison to those taken in the morning. Dilution and grazing are probably both responsible for the lack of detectable signs of eutrophication.     

Transformations in flagellar structure of Rhodobacter sphaeroides and possible relationship to changes in swimming speed

Rhodobacter sphaeroides is a photosynthetic bacterium which swims by rotating a single flagellum in one direction, periodically stopping, and reorienting during these stops. Free-swimming R. sphaeroides was examined by both differential interference contrast (DIC) microscopy, which allows the flagella of swimming cells to be seen in vivo, and tracking microscopy, which tracks swimming patterns in three dimensions. DIC microscopy showed that when rotation stopped, the helical flagellum relaxed into a high-amplitude, short-wavelength coiled form, confirming previous observations. However, DIC microscopy also revealed that the coiled filament could rotate slowly, reorienting the cell before a transition back to the functional helix. The time taken to reform a functional helix depended on the rate of rotation of the helix and the length of the filament. In addition to these coiled and helical forms, a third conformation was observed: a rapidly rotating, apparently straight form. This form took shape from the cell body out and was seen to form directly from flagella that were initially in either the coiled or the helical conformation. This form was always significantly longer than the coiled or helical form from which it was derived. The resolution of DIC microscopy made it impossible to identify whether this form was genuinely in a straight conformation or was a low-amplitude, long-wavelength helix. Examination of the three-dimensional swimming pattern showed that R. sphaeroides changed speed while swimming, sometimes doubling the swimming speed between stops. The rate of acceleration out of stops was also variable. The transformations in waveform are assumed to be torsionally driven and may be related to the changes in speed measured in free-swimming cells. The roles of and mechanisms that may be involved in the transformations of filament conformations and changes in swimming speed are discussed.     

Comparative analysis of the zeta-crystallin/quinone reductase gene in guinea pig and mouse

zeta-Crystallin is a novel nicotinamide adenine dinucleotide phosphate:quinone reductase, present at enzymatic levels in various tissues of different species, which is highly expressed in the lens of some hystricomorph rodents and camelids. We report here the complementary DNA (cDNA) cloning of zeta-crystallin from liver libraries in guinea pig (Cavia porcellus), where zeta-crystallin is highly expressed in the lens, and in the laboratory mouse (Mus musculus), where expression in the lens occurs only at enzymatic levels. A 5' untranslated sequence different from the one previously reported for the guinea pig lens cDNA was found in these clones. We also report the isolation of genomic clones including the complete guinea pig zeta-crystallin gene and the 5' region of this gene in mouse. These results show the presence of two promoters in the guinea pig zeta-crystallin gene, one responsible for expression at enzymatic levels and the other responsible for the high expression in the lens. The guinea pig lens promoter is not present in the mouse gene. This is the first example in which the recruitment of an enzyme as a lens crystallin can be explained by the acquisition of an alternative lens- specific promoter.      

The vascular endothelial growth factor (VEGF) family: angiogenic factors in health and disease

Vascular endothelial growth factors (VEGFs) are a family of secreted polypeptides with a highly conserved receptor-binding cystine-knot structure similar to that of the platelet-derived growth factors. VEGF-A, the founding member of the family, is highly conserved between animals as evolutionarily distant as fish and mammals. In vertebrates, VEGFs act through a family of cognate receptor kinases in endothelial cells to stimulate blood-vessel formation. VEGF-A has important roles in mammalian vascular development and in diseases involving abnormal growth of blood vessels; other VEGFs are also involved in the development of lymphatic vessels and disease-related angiogenesis. Invertebrate homologs of VEGFs and VEGF receptors have been identified in fly, nematode and jellyfish, where they function in developmental cell migration and neurogenesis. The existence of VEGF-like molecules and their receptors in simple invertebrates without a vascular system indicates that this family of growth factors emerged at a very early stage in the evolution of multicellular organisms to mediate primordial developmental functions.     

Calcium is required for swimming by the nonflagellated cyanobacterium Synechococcus strain WH8113.

The marine cyanobacterium Synechococcus strain WH8113 swims in the absence of any recognizable organelles of locomotion. We have found that calcium is required for this motility. Cells deprived of calcium stopped swimming, while addition of calcium completely restored motility. No other divalent ions tested could replace calcium. Terbium, a lanthanide ion, blocked motility even when calcium was present at 10(5)-fold-higher concentrations, presumably by occupying calcium binding sites. Calcium chelators, EGTA or EDTA, blocked motility, even when calcium was present at 25-fold-higher concentrations, presumably by acting as calcium ionophores. Finally, motility was blocked by verapamil and nitrendipine, molecules known to block voltage-gated calcium channels of eukaryotic cells by an allosteric mechanism. These results suggest that a calcium potential is involved in the mechanism of motility.     

Antischistosomal action of thioxo-imidazolidine compounds: an ultrastructural and cytotoxicity study

Schistosomiasis is a disease caused by helminthes of the genus Schistosoma, which threatens approximately 207 million people worldwide. Recently, strains of Schistosoma mansoni appear to be developing tolerance and resistance against Praziquantel, the most commonly available drug on the market used in the treatment of disease. This worrisome development justifies studies that seek alternatives for the prevention, treatment and cure of this disease. This study aimed to evaluate the in vitro activity of new imidazolidine compounds 1-benzyl-4-[(4-chloro-phenyl)-hydrazono]-5-thioxo-imidazolidin-2-one (LPSF/PT-5) and 1-(4-chloro-benzyl)-4-[(4-fluoro-phenyl)-hydrazono]-5-thioxo-imidazolidin-2-one (LPSF/PT-11) against adult worms of S. mansoni. LPSF/PT-5 and LPSF/PT-11 imidazolidine derivatives showed relevant schistosomicidal activity in vitro and induced significant ultrastructural alterations in worms and cell death: results similar to praziquantel. Thus, it is possible that these imidazolidine derivatives can be future candidates as schistosomotic drugs, but further studies are needed to elucidate the induced mechanisms behind this response.     

Courtship Behavior of Zaprionus indianus (Gupta) (Diptera: Drosophilidae) from Populations Colonizing South America

We describe for the first time the sexual behavior and the courtship song of males of the African fly Zaprionus indianus (Gupta), a recent invader of South America. The male courtship song is formed by monocyclic pulses and the courtship behavior is simple when compared to that of species of Drosophila. Two interpulse interval (IPI) distributions were observed: pre-mounting and mounting. No significant difference was observed between the pre-mounting IPIs of males that descended from three geographical populations from South America. We also observed the songs produced by females and the homosexual behavior exhibited by males. A sequence of bursts is produced by females as a refusal signal against males, while males emit a characteristic song that identifies sex genus, which differs from the courtship song. The short courtship and mating latencies recorded reveal vigorous males and receptive females, respectively.