Evaluation of thermal acclimation capacity in corals with different thermal histories based on catalase concentrations and antioxidant potentials

Colonies of Pocillopora damicornis from Kaneohe Bay and colonies of Pocillopora meandrina from a thermal outfall site and a control site at Kahe were exposed to three different temperatures (29, 32 and 33 degrees C) in outdoor aquaria on running water tables for five days. Samples (n=3) were taken from each treatment at 0800, 1200 and 1600 h. ELISAs using catalase antibodies and ferric reducing/antioxidant potential (FRAP) assays were run on the samples to determine how antioxidant levels changed throughout the experiment. Light levels during the experiment were highest in the morning ( approximately 1000-1500 micromol quanta m(-2) s(-1)) and decreased to 25-60 micromol quanta m(-2) s(-1) by 1100 h and remained low until sunset. Antioxidant concentrations were highest in the morning for P. damicornis from Kaneohe and P. meandrina outfall samples. There was no significant change through the day for P. meandrina samples from the control site. The difference in response between the outfall samples and the control samples suggests that P. meandrina has acclimated to elevated temperatures found at the outfall site.     

Emerging role of protein kinase B/Akt signaling in pancreatic beta-cell mass and function

The serine-threonine kinase Akt also known as protein kinase B is one of the most studied molecules. In addition to the important role in carcinogenesis, Akt is a major regulator of carbohydrate metabolism. Akt mediates insulin-dependent glucose uptake in insulin-sensitive tissues. Recent evidence underscores the importance of Akt for regulation of beta-cell mass and function. This review summarizes current findings concerning the molecular mechanisms, downstream signaling pathways, and critical components involved in regulation of beta-cell mass and function by Akt. The results of these observations suggest that elucidation of critical downstream effectors of this signaling pathway could generate promising molecules as a potential target to induce proliferation and survival of beta-cells.     

Role of the methylcitrate cycle in Mycobacterium tuberculosis metabolism, intracellular growth, and virulence

Growth of bacteria and fungi on fatty acid substrates requires the catabolic beta-oxidation cycle and the anaplerotic glyoxylate cycle. Propionyl-CoA generated by beta-oxidation of odd-chain fatty acids is metabolized via the methylcitrate cycle. Mycobacterium tuberculosis possesses homologues of methylcitrate synthase (MCS) and methylcitrate dehydratase (MCD) but not 2-methylisocitrate lyase (MCL). Although MCLs share limited homology with isocitrate lyases (ICLs) of the glyoxylate cycle, these enzymes are thought to be functionally non-overlapping. Previously we reported that the M. tuberculosis ICL isoforms 1 and 2 are jointly required for growth on fatty acids, in macrophages, and in mice. ICL-deficient bacteria could not grow on propionate, suggesting that in M. tuberculosis ICL1 and ICL2 might function as ICLs in the glyoxylate cycle and as MCLs in the methylcitrate cycle. Here we provide biochemical and genetic evidence supporting this interpretation. The role of the methylcitrate cycle in M. tuberculosis metabolism was further evaluated by constructing a mutant strain in which prpC (encoding MCS) and prpD (encoding MCD) were deleted. The DeltaprpDC strain could not grow on propionate media in vitro or in murine bone marrow-derived macrophages infected ex vivo; growth under these conditions was restored by complementation with a plasmid containing prpDC. Paradoxically, bacterial growth and persistence, and tissue pathology, were indistinguishable in mice infected with wild-type or DeltaprpDC bacteria.     

The native-state ensemble of proteins provides clues for folding, misfolding and function

The predominant equilibrium in proteins is not between native and unfolded states, it is between the native and multiple partially unfolded forms. Some of these partially unfolded forms can be energetically close to the native state and, therefore, have the potential to become appreciably populated. This could have an important role in protein function or misfolding diseases. The recent identification and characterization of the partially unfolded forms of apoflavodoxin furthers our understanding of their formation.     

Bis-imidazoles as molecular probes for peripheral sites of the zinc endopeptidase of botulinum neurotoxin serotype A

Botulinum neurotoxin serotype A (BoNTA) is highly toxic, and its antidote is currently unavailable. The essential light-chain subunit of BoNTA is a zinc endopeptidase that can be used as a target for developing antidotes. However, the development of high-affinity, small-molecule inhibitors of the endopeptidase is as challenging as the development of small-molecule inhibitors of protein-protein complexation. This is because the polypeptide substrate wraps around the circumference of the endopeptidase upon binding, thereby constituting an unusually large substrate-enzyme interface of 4840 angstroms2. To overcome the large-interface problem, we propose using the zinc-coordination and bivalence approaches to design inhibitors of BoNTA. Here we report the development of alkylene-linked bis-imidazoles that inhibit the endopeptidase in a two-site binding mode. The bis-imidazole tethered with 13 methylene groups, the most potent of the alkylene-linked dimers, showed 61% inhibition of the zinc endopeptidase of BoNTA at a concentration of 100 microM. The results demonstrate the presence of a peripheral binding site for an imidazolium group at the rim of the BoNTA active-site cleft. This peripheral site enables the use of the bivalence approach to improve our previously reported small-molecule inhibitors that were developed according to the zinc-coordination approach.     

Cytotoxic activity of (S)-goniothalamin and analogues against human cancer cells

(R)- and (S)-Goniothalamin (1) and analogues 2-9 were efficiently prepared in high overall yield and enantiomeric purity, and their cytotoxic activities were evaluated against eight human cancer cell lines. A structure-activity relationship study (SAR) allowed us to establish the relevant structural features for the cytotoxic activity of goniothalamin analogues. In addition, we have identified non-natural form of goniothalamin (S)-1 and analogue 5 as the highest and more selective cytotoxic compounds against kidney cancer cell growth (786-0) with IC50 = 4 and 5 nM, respectively, and compound 8 (IC50 = 4 nM) as the more potent against breast cancer cells with resistance phenotype for adryamycin (NCI.ADR).     

A chemoenzymatic scalable route to optically active (R)-1-(pyridin-3-yl)-2-aminoethanol, valuable moiety of beta3-adrenergic receptor agonists

Enantiomerically pure (R)-2-chloro-1-(pyridin-3-yl)ethanol has been prepared by kinetic resolution performed in the presence of Candida antarctica SP435-L lipase immobilized on a macroporous polyacrylate resin (Novozym 435). It was converted into (R)-1-(pyridin-3-yl)-2-aminoethanol, left-hand side of beta(3)-adrenergic receptor ligands.     

Molecular characterization of the 18S rDNA gene of an avian Hepatozoon reveals that it is closely related to Lankesterella

As a part of intensive study of blood parasite infections in a population of the passerine bird blue tit (Cyanistes caeruleus, Paridae), we detected a parasite species that, based on its morphological similarity, was tentatively identified as Hepatozoon parus, the only species of this parasite genus described from birds of this family. However, morphological measurements show that H. parus is slightly larger than the parasite detected in our population. A molecular characterization of the parasite species was conducted by amplification of the 18S rDNA gene, using primers that were reported previously to amplify in Hepatozoon sp. of water pythons. Additional primers were developed based on the new sequence obtained. The 1,484-bp fragment amplified reveals that the parasite from our bird population is more closely related to Lankesterella minima than to Hepatozoon species from other vertebrates according to analysis using the BLAST comparison method (93% identity). In addition, phylogenetic analyses using parsimony and Kimura procedures unequivocally related the parasite species detected by PCR with L. minima. The bootstrap values obtained were 97% and 100%, respectively. These results imply that this parasite is a species of a lankesterellid instead of Hepatozoon.     

A biomechanical model for size, speed and anatomical variations of the energetic costs of running mammals

Here we propose a model of energetic costs and the muscle-tendon unit function on running mammals. The main goal is to set a simple theoretical framework which gives an understanding of the biomechanical principles behind the size, speed and anatomical variations of the energetic costs of running mammals. The model is a point-like mass withstood by a two-segment leg with an extensor muscle serially attached to a tendon. We considered withstanding body weight during the stance phase as the main role of the muscle-tendon unit during fast locomotion. The ground reaction force dependence on speed and the time of stance phase as well as other biomechanical characteristics were taken from previous empirical studies of running. At the same time, the morphological variations with body mass were taken from empirically well-established allometric equations for mammals. The metabolic cost was estimated from an empirical equation relating metabolic power with muscular force and speed in shortening and stretching. Our model predicts the pattern of mass specific metabolic rate variations with both speed and body mass. It also gives an explanation of the experimentally reported linear inverse relationship between the rate of energy used for running and the time of application of force by the foot to the ground during each stride. It also suggests an explanation of the unusual energy saving adaptations of large macropodids. It provides some predictions on the relationship, between energy costs and muscle-tendon unit characteristics, testable on further experiments.     

Positive interactions between alpine plant species and the nurse cushion plant Laretia acaulis do not increase with elevation in the Andes of central Chile

In alpine habitats, positive interactions among plants tend to increase with elevation as a result of altitudinal increase in environmental harshness. However, in mountains located in arid zones, lower elevations are also stressful because of scarce availability of water, suggesting that positive interactions may not necessarily increase with elevation. Here we analysed the spatial association of plant species with the nurse cushion plant Laretia acaulis at two contrasting elevations, and monitored the survival of seedlings of two species experimentally planted within and outside cushions in the semiarid Andes of central Chile. Positive spatial associations with cushions were more frequent at lower elevations. Species growing at the two elevations changed the nature of their association with cushions from neutral or negative at higher elevations to positive at lower elevations. Survival of seedlings was higher within cushions, particularly at lower elevations. The increased facilitation by cushions at lower elevations seems to be related to provision of moisture. This result suggests that cushion plants play a critical role in structuring alpine plant communities at lower elevations, and that climatic changes in rainfall could be very relevant for persistence of plant communities.