Extending the cardioprotective window using a novel delta-opioid agonist fentanyl isothiocyanate via the PI3-kinase pathway

Selective delta-opioid agonists produce delayed cardioprotection that lasts for 24-48 h in rats; however, the maximum length of the cardioprotective window is unclear. In this study, we attempted to prolong the cardioprotective window using a unique delta-opioid agonist, fentanyl isothiocyanate (FIT), which binds irreversibly to the delta-receptor, and determined the role of the phosphatidylinositol 3-kinase (PI3K) pathway as a trigger or end effector of FIT-induced cardioprotection. Initially, male rats were administered FIT (10 microg/kg) 10 min before hearts were subjected to 30 min of ischemia and 2 h of reperfusion followed by infarct size (IS) assessment. Acute FIT administration reduced IS when given before ischemia, 5 min before reperfusion, or 10 s after reperfusion compared with control. IS reduction also occurred following a single dose of FIT at 48, 72, 96, and 120 h after administration vs. control, with the maximum effect observed at 96 h. FIT-induced IS reduction at 96 h was completely abolished when the irreversible PI3K inhibitor wortmannin (15 microg/kg) was given before FIT during the trigger phase; however, the effect was only partially abrogated when wortmannin was given 96 h later. These data suggest that FIT has a prolonged cardioprotective window greater than that of any previously described cardioprotective agent that requires PI3K primarily in the trigger phase but also partially, as a mediator or end effector.     

The conformational flexibility of the antibiotic virginiamycin M1

The antibiotic virginiamycin is a combination of two molecules, virginiamycin M₁ (VM1) and virginiamycin S₁ (VS1) or analogues, which function synergistically by binding to bacterial ribosomes and inhibiting bacterial protein synthesis. Both VM1 and VS1 dissolve poorly in water and are soluble in more hydrophobic solvents. We have recently reported that the 3D conformation of VM1 in CDCl₃ solution (Aust. J. Chem. 57:415, 2004; Org. Biomol. Chem. 2:2919, 2004) differs markedly from the conformation bound to a VM1 binding enzyme (Sugantino and Roderick in Biochemistry 41:2209, 2002) and to 50S ribosomes (Hansen et al. in J. Mol. Biol. 330:1061, 2003) as found by X-ray crystallographic studies. We now report the results of further NMR studies and subsequent molecular modeling of VM1 dissolved in CD₃CN/H₂O and compare the structure with that in CD₃OD and CDCl₃. The conformations of VM1 in CD₃CN/H₂O, CD₃OD and CDCl₃ differ substantially from one another and from the bound form, with the aqueous form most like the bound structure. We propose that the flexibility of the VM1 molecule in response to environmental conditions contributes to its effectiveness as an antibiotic.     

Coral red fluorescence protein as genetic modified baculovirus tracer

Genetic modified baculovirus (GMBV) are among the most promising alternatives to chemical insecticides. One of the deterrents to the GMBV development is the lack of simple and cost-effective methods for monitoring their efficacy and ecology in fields. Here, we demonstrate the DsRed gene from coral can serve as a convenient GMBV tracer. Insect larvae, including Trichoplusia ni, Spodoptera exigua, and Spodoptera litura, infected the GMBV containing the DsRed gene can emit red fluorescence under sun light without any prosthetic apparatus.     

Determination of triglyceride in the human myocardium by magnetic resonance spectroscopy: reproducibility and sensitivity of the method

The primary aim of this investigation was to determine the reliability and sensitivity of 1H magnetic resonance spectroscopy (1H-MRS) as a method for quantifying myocardial triglyceride (TG) content in humans over time and in response to metabolic perturbations. Three separate experiments were designed to quantify myocardial TG content 1) over a 90-day period, 2) after a high-fat meal, and 3) after a 48-h fast. Proton spectra were collected from a 10 x 20 x 30-mm3 voxel placed within the intraventricular septum, with measurements acquired at end-systole and end-expiration, using cardiac triggering and respiratory gating. Minimal variation was observed between myocardial TG content determined 90 days apart (r = 0.98, CV = 5%), whereas TG values were unaffected by a high-fat meal despite a significant twofold increase (P < 0.05) in serum TG. In contrast, myocardial TG content increased threefold (P < 0.05) after a 48-h fast despite a 25% reduction in serum TG. Body mass index was significantly related to myocardial TG (r = 0.58, P < 0.05) and the change in myocardial TG after a 48-h fast (r2 = 0.60). 1H-MRS is a reliable method for the determination of myocardial TG in humans and is relatively unaffected by the consumption of one high-fat meal but sensitive to changes following a prolonged fast.     

Influence of riffle characteristics,surficial geology,and natural barriers on the distribution of the channel darter, <Emphasis Type="Italic">Percina copelandi,</Emphasis> in the Lake Ontario basin

Synopsis The channel darter, Percina copelandi, is a small benthic fish with a wide but disjunct distribution across central North America. The development of conservation and recovery strategies for Canadian populations is limited by a lack of knowledge regarding ecology, population size and other factors that affect its distribution and abundance. We sampled five rivers in the Lake Ontario basin to test whether the distribution of P. copelandi reflected riffle habitat characteristics or landscape-scale factors such as surficial geology and natural barriers (waterfalls). At most sites yielding P. copelandi, riffles flowed into deep sand bottomed run or pool habitats. Despite a lack of association with local surficial geology or riffle habitat characteristics, both the upstream limits of P. copelandi occurrence and distribution of suitable habitats reflected the distribution of waterfalls, chutes and bedrock outcroppings. In contrast to P. copelandi, distributions of Etheostoma flabellare, P. caprodes and Rhinichthys cataractae reflected among site differences in riffle habitat.     

Predictability of littoral-zone fish communities through ontogeny in Lake Texoma,Oklahoma-Texas,USA

Synopsis We sampled larval, juvenile and adult fishes from littoral-zone areas of a large reservoir (Lake Texoma, Oklahoma-Texas) (1) to characterize environmental factors that influenced fish community structure, (2) to examine how consistent fish–environment relationships were through ontogeny (i.e., larval vs. juvenile and adult), and (3) to measure the concordance of larval communities sampled during spring to juvenile and adult communities sampled at the same sites later in the year. Larval, juvenile and adult fish communities were dominated by Atherinidae (mainly inland silverside, Menidia beryllina) and Moronidae (mainly juvenile striped bass, Morone saxatilis) and were consistently structured along a gradient of site exposure to prevailing winds and waves. Larval, juvenile and adult communities along this gradient varied from atherinids and moronids at highly exposed sites to mostly centrarchids (primarily Lepomis and Micropterus spp.) at protected sites. Secondarily, zooplankton densities, water clarity, and land-use characteristics were related to fish community structure. Rank correlation analyses and Mantel tests indicated that the spatial consistency and predictability of fish communities was high as larval fishes sampled during spring were concordant with juvenile and adult fishes sampled at the same sites during summer and fall in terms of abundance, richness, and community structure. We propose that the high predictability and spatial consistency of littoral-zone fishes in Lake Texoma was a function of relatively simple communities (dominated by 1–2 species) that were structured by factors, such as site exposure to winds and waves, that varied little through time.     

Resource use by salmonids in riverine,lacustrine and marine environments: Evidence from stable isotope analysis

Synopsis We measured stable isotope ratios (δ¹³C and δ¹⁵N) of invertebrates, Atlantic salmon, Salmo salar, and brook trout, Salvelinus fontinalis, in three distinct freshwater environments (headwater tributary, ultra-oligotrophic lake, and main-stem river) in the Western Brook system, Newfoundland, Canada. Large differences in the stable carbon signatures of invertebrates allowed the identification of organic matter assimilation from each environment by resident parr and migrating smolts. Brook trout captured in the headwater tributary in June had a carbon signature characteristic of the tributary, while those collected in August had enriched ¹³C (maximum = −15.6‰) and ¹⁵N (maximum = 12.8‰) values. These enriched carbon and nitrogen signatures were indicative of foraging at sea. There was a low correlation between δ¹³C and δ¹⁵N (r² = 0.198) for individual fish that was likely due to the confounding influence of trout feeding in the lake and the lower main-stem of the river, where δ¹³C of food sources was high but δ¹⁵N was low. Smolts emigrating from Western Brook Pond where they had been foraging (based on lacustrine carbon signatures) were significantly larger than those emigrating from a nursery brook and the main river in the same basin, despite having the same median age. These results suggest better growth opportunities in the lake environment. Trout fork length was positively correlated with δ¹³C and δ¹⁵N, demonstrating that larger individuals had been feeding outside the brook. These results support previous studies that found increased growth potential for salmonids in lacustrine and marine environments, and further, indicate possible adaptive advantages for salmonid movement away from natal brooks.     

Differential phospholipase C activation by phenylalkylamine serotonin 5-HT 2A receptor agonists

Experiments compared a series of phenethylamine hallucinogens with their phenylisopropylamine analogues for binding affinity and ability to stimulate serotonin 5-HT 2A receptor-mediated hydrolysis of phosphatidyl inositol in cells expressing cloned rat and human 5-HT 2A receptors. The (+/-)phenylisopropylamine analogues had significantly higher intrinsic activities for 5-HT 2A receptor-mediated hydrolysis of phosphatidyl inositol compared to their phenethylamine analogues. With respect to the effects of the stereochemistry of the phenylisopropylamines, those with the (R) absolute configuration at the alpha carbon had higher intrinsic activities for hydrolysis of phosphatidyl inositol in a cell line expressing the human 5-HT 2A receptor compared to those with the (S) absolute configuration. In virtual docking studies comparing the (R)- and (S)-phenylisopropylamines with their phenethylamine analogues, there were distinct differences in the orientations of key ligand binding domain residues that have been identified as important by previous mutagenesis studies. In conclusion, our data support the hypothesis that phenylisopropylamines have higher hallucinogenic potency than their phenethylamine analogues primarily because they have higher intrinsic activities at 5-HT 2A receptors. Although virtual ligand binding led to significant perturbations of certain key residues, our results emphasize the conclusion reached by others that overall three-dimensional structural microdomains within the receptor must be considered.