Brassinosteroids and analogs as neuroprotectors: synthesis and structure-activity relationships

We have demonstrated previously that the brassinosteroid (BR) 24-epibrassinolide exerts neuroprotective effects deriving from its antioxidative properties. In this study, we synthesized 2 natural BRs and 5 synthetic analogs and analyzed their neuroprotective actions in neuronal PC12 cells, against 1-methyl-4-phenylpyridinium (MPP(+)), a neurotoxin known to induce oxidative stress and degenerescence of dopaminergic neurons characteristic of Parkinsonian brains. We also tested the neuroprotective potential of 2 commercially available BRs. Our results disclosed that 6 of the 9 BRs and analogs tested protected neuronal PC12 cells against MPP(+) toxicity. In addition, our structure-activity study suggests that the steroid B-ring and lateral chain play an important role for their neuroprotective action.     

Competition in vitro among fungi acquired from the exoskeleton of the giant Madagascar hissing-cockroach,Gromphadorhina portentosa,and its relevance to human health

Few insects have received as much public attention as the Madagascar hissing-cockroach, Gromphadorhina portentosa, coveted by children as a household pet. Recently, this insect has been linked to allergies and asthma triggered by an antagonistic external mycoflora, and some of these fungi are known to cause serious illnesses, namely Aspergillus spp., Mucor spp. and Rhizopus spp. Other cockroach species serve as carriers of medically important fungi, but G. portentosa is of special concern because it is deliberately reared in captivity. The aim of this study was to ascertain why certain types of fungi dominate the exoskeleton’s mycoflora whereas others do not. Six ascomycetes (Alternaria alternata, Aspergillus flavus, Aspergillus niger, Cladosporium cladosporioides, Penicillium glabrum, Trichoderma viride), and two zygomycetes (Mucor racemosus, Rhizopus stolonifer) initially acquired from the exoskeleton of G. portentosa, were tested for their competitive ability to inhibit one another in vitro, using the cockroach as the primary substratum. R. stolonifer, M. racemosus, and mycoparasitic T. viride grew at a significantly faster rate compared to the other taxa, and growth rates correlated positively with conidia output. Slower colony growth rates were noted prior to physical contact, suggesting that the fungi engaged in chemical antagonism. Three genera emerged that best fit the profile of exploitative competitors – Rhizopus, Mucor, Trichoderma. The latter two genera completely inhibited the growth of all fungal taxa tested and also had some capacity to grow over the mycelium of another fungus. We conclude that M. racemosus and T. viride in particular, are successful agents of G. portentosa’s mycoflora because they utilize both exploitation and interference competition to their advantage. Eliminating or reducing the simple sugar load entering the cockroach colony may be one way to tilt the composition of the mycoflora to favour strains that are less medically significant. Thus, we emphasize reduction of the antagonistic fungi at the colony (food entry) level and less so on the exoskeleton level.     

The complete phylogeny of Pseudobulweria, the most endangered seabird genus: systematics, species status and conservation implications

Pseudobulweria is one of the least known and most endangered of all seabird genera. It comprises six taxa, of which two are extinct, three are critically endangered and one is near threatened. Phylogenetic relationships between these taxa and position of the genus in the Order Procellariiformes have never been studied, and the taxonomic status of several taxa remains unsettled. Conservation management of Pseudobulweria taxa will be enhanced if these uncertainties are resolved. We used a multilocus gene tree approach with two mitochondrial DNA markers (cytochrome oxidase subunit 1 and cytochrome b gene) and one nuclear intron (β Fibrinogen intron 7) to investigate phylogenetic relationships within the genus using sequences from all taxa. We combined gene trees to estimate a phylogeny of the genus using a multispecies coalescent methodology. We confirmed the link between Pseudobulweria and a clade comprising Puffinus and Bulweria genera. The Fiji petrel’s status, as belonging to the genus, is confirmed, as is the specific status of newly rediscovered Beck’s petrel. Maintenance of the two sub-species of Tahiti petrel as currently described is not supported. Discovering the breeding grounds of all taxa is the key for their conservation, which is vital to both the marine and fragile insular tropical ecosystems where Pseudobulweria are apical predators.     

Upregulation of plasma insulin-like growth factor binding protein 2 levels after biliopancreatic diversion in humans

The biliopancreatic diversion surgery with duodenal switch (BPD-DS) is a surgical procedure that not only induces significant weight loss, but also promotes remission of diabetes. However, the mechanism responsible for this insulin-potentiating effect (both on sensitivity and production) is not yet clearly understood. The insulin-like growth factor (IGF) binding protein 2 (IGFBP-2) is a 36 kDa circulating protein that has been recently suggested to modulate insulin sensitization and fat accumulation. In humans, a low-circulating concentration of IGFBP-2 has been associated with obesity and insulin resistance. We thus tested the hypothesis that BPD-DS would trigger an increase in IGFBP-2 levels. Plasma IGFBP-2 was quantified by enzyme-linked immunosorbent assay in 77 severely obese men and women before and up to 1 year after BPD-DS surgery. Baseline IGFBP-2 levels were 159 ± 17 ng/ml. Plasma IGFBP-2 levels increased significantly as soon as 24 h after BPD-DS surgery and were further augmented at both 6 months and 1 year after the surgery, reaching 748 ± 65 ng/ml. Changes in IGFBP-2 concentrations were significantly and negatively associated with blood glucose, insulin, triglycerides, and total cholesterol levels. The present findings suggest that the rise in IGFBP-2 levels is associated with the improvements in glucose and lipid metabolism in the short- and long-term after BPD-DS. The mechanisms for the augmentation in IGFBP-2 after BPD-DS and its contribution to insulin sensitization remain to be elucidated.     

Metabolic control by S6 kinases depends on dietary lipids

Targeted deletion of S6 kinase (S6K) 1 in mice leads to higher energy expenditure and improved glucose metabolism. However, the molecular mechanisms controlling these effects remain to be fully elucidated. Here, we analyze the potential role of dietary lipids in regulating the mTORC1/S6K system. Analysis of S6K phosphorylation in vivo and in vitro showed that dietary lipids activate S6K, and this effect is not dependent upon amino acids. Comparison of male mice lacking S6K1 and 2 (S6K-dko) with wt controls showed that S6K-dko mice are protected against obesity and glucose intolerance induced by a high-fat diet. S6K-dko mice fed a high-fat diet had increased energy expenditure, improved glucose tolerance, lower fat mass gain, and changes in markers of lipid metabolism. Importantly, however, these metabolic phenotypes were dependent upon dietary lipids, with no such effects observed in S6K-dko mice fed a fat-free diet. These changes appear to be mediated via modulation of cellular metabolism in skeletal muscle, as shown by the expression of genes involved in energy metabolism. Taken together, our results suggest that the metabolic functions of S6K in vivo play a key role as a molecular interface connecting dietary lipids to the endogenous control of energy metabolism.     

Interaction of surfactant protein A with the intermediate filaments desmin and vimentin

Surfactant protein A (SP-A), a member of the collectin family that modulates innate immunity, has recently been involved in the physiology of reproduction. Consistent with the activation of ERK-1/2 and COX-2 induced by SP-A in myometrial cells, we reported previously the presence of two major proteins recognized by SP-A in these cells. Here we identify by mass spectrometry one of these SP-A targets as the intermediate filament (IF) desmin. In myometrial preparations derived from desmin-deficient mice, the absence of binding of SP-A to any 50 kDa protein confirmed the identity of this SP-A-binding site as desmin. Our data based on partial chymotrypsin digestion of pure desmin suggested that SP-A recognizes especially its rod domain, which is known to play an important role during the assembly of desmin into filaments. In line with that, electron microscopy experiments showed that SP-A inhibits in vitro the polymerization of desmin filaments. SP-A also recognized in vitro polymerized filaments in a calcium-dependent manner at a physiological ionic strength but not the C1q receptor gC1qR. Furthermore, Texas Red-labeled SP-A colocalized with desmin filaments in myometrial cells. Interestingly, vimentin, the IF characteristic of leukocytes, is one of the major proteins recognized by SP-A in protein extracts of U937 cells after PMA-induced differentiation of this monocytic cell line. Interaction of SP-A with vimentin was further confirmed using recombinant vimentin in solid-phase binding assays. The ability of SP-A to interact with desmin and vimentin, and to prevent polymerization of desmin monomers, shed light on unexpected and wider biological roles of this collectin.     

Effect of body length and temperature on the crawling speed of Protophormia terraenovae larvae (Robineau-Desvoidy) (Diptera Calliphoridae)

This work investigates variation in the crawling speed of Protophormia terraenovae larvae (Robineau-Desvoidy) (Diptera Calliphoridae) as a function of body length and ambient temperature. A video-tracking system was used to follow the movement of larvae in an experimental arena, and to estimate their average crawling speed. Recordings were carried out at various temperatures using larvae of different developmental stages. As temperature increased, the larvae crawled at a faster speed. Furthermore, speed increased as a function of body length. We present a general allometric relationship to express the average crawling speed of larvae as a combined function of temperature and body length, expressed in the following equation: speed (cm/min)=5.45 x log[length (mm)]+0.66 x temperature (degrees C)-12.8. These results are particularly useful in forensic entomology for estimating the time that elapsed following the larva's departure from the corpse. This information can provide more accuracy for post-mortem interval estimations and a better comprehension of larvae behaviour and displacement.