Synthesis of 2'-C-methyl-beta-D-ribofuranosylimidazo [4,5-d]-pyridazine derivatives (2-aza-3-deazapurine nucleoside analogues)

In order to evaluate their antiviral properties, two imidazo[4,5-d]pyridazine 2'-C-methyl-beta-D-ribofuranonucleoside derivatives have been synthesized.     

Scar myofibroblasts of the infarcted rat heart express natriuretic peptides

The present study examined whether natriuretic peptide expression in the scar of post-myocardial infarcted (MI) rats was derived at least in part by residing myofibroblasts. ANP and BNP mRNA levels were significantly increased in the non-infarcted left ventricle and scar of 1-week post-MI male rats, as compared to the left ventricle of normal rats. The infarct region contained myofibroblasts and contracted cardiac myocytes residing predominantly in the epicardial border zone. In primary passage scar-derived myofibroblasts, alpha-myosin heavy chain mRNA was undetectable, whereas ANP, BNP, as well as adrenomedullin and corin mRNA expression persisted. In 1-3 day cultured primary passage myofibroblasts, prepro-ANP, mature ANP, and BNP staining was observed in the cytoplasm/perinuclear region co-incident with unorganized alpha-smooth muscle actin. Following 4-7 days in culture, myofibroblasts expressed organized alpha-smooth muscle actin filaments. However, natriuretic peptides were predominantly detected in the nucleus and cytoplasm, and thin filaments occupying the perinuclear region were positive for prepro-ANP and BNP. Isoproterenol treatment of first passage scar myofibroblasts increased protein synthesis and induced BNP mRNA expression, whereas ANP mRNA levels remained unchanged. By contrast, neither ANP nor BNP mRNAs were induced following exposure to AII despite increased protein synthesis. These data highlight the novel observation that scar myofibroblasts synthesized ANP, BNP, adrenomedullin, and expressed the pro-convertase corin. Constitutive and sympathetic-driven natriuretic peptide synthesis by myofibroblasts may in part influence reparative fibrosis.     

Measuring internal representations from behavioral and brain data

The study of internal knowledge representations is a cornerstone of the research agenda in the interdisciplinary study of cognition. An influential proposal assumes that the brain uses its internal knowledge of the external world to constrain, in a top-down manner, high-dimensional sensory data into a lower-dimensional representation that enables perceptual decisions and other higher-level cognitive functions [1-9]. This proposal relies on a precise formulation of the observer-specific internal knowledge (i.e., the internal representations, or models) that guides reduction of the high-dimensional retinal input onto a low-dimensional code. Here, we directly revealed the content of subjective internal representations by instructing five observers to detect a face in the presence of only white noise, to force a pure top-down, knowledge-based task. We used reverse correlation methods to visualize each observer's internal representation that supports detection of an illusory face. Using reverse correlation again, this time applied to observers' electroencephalogram activity, we established where and when in the brain specific internal knowledge conceptually interprets the input white noise as a face. We show that internal representations can be reconstructed experimentally from behavioral and brain data, and that their content drives neural activity first over frontal and then over occipitotemporal cortex.     

Effect of the power Balance® band on static balance, hamstring flexibility, and arm strength in adults

The purpose of this study was to determine the effect of Power Balance? bands on strength, flexibility, and balance. Strength and flexibility were measured using the MicroFit system. Strength was measured via a bicep curl and flexibility via the sit-and-reach method. Balance was measured by the BIODEX System SD. There were 4 different conditions for the balance test: eyes open on a firm surface (EOFS), eyes closed on a firm surface (ECFS), eyes open on a foam surface (EOFoS), and eyes closed on a foam surface (ECFoS). There were 24 subjects in the study (10 men and 14 women). A counterbalance, double-blind, placebo, controlled within-subject design was used. Each of the subjects participated in 3 treatment sessions, consisting of Power Balance?, placebo band, and no band. An alpha level of p ≤ 0.05 was set a priori. There were no significant differences in strength, flexibility, or balance with regard to the treatments used. There was a significant difference between the conditions in the balance test (p = 0.000): EOFS (0.51), ECFS (0.68), EOFoS (0.99), and ECFoS (2.18); however, these were independent of the treatment conditions. The results indicate that the Power Balance? bands did not have an effect on strength, flexibility, or balance.     

Dexamethasone treatment of post-MI rats attenuates sympathetic innervation of the infarct region.

Sympathetic fiber innervation of the damaged region following injury represents a conserved event of wound healing. The present study tested the hypothesis that impaired scar healing in post-myocardial infarction (post-MI) rats was associated with a reduction of sympathetic fibers innervating the infarct region. In 1-wk post-MI rats, neurofilament-M-immunoreactive fibers (1,116 +/- 250 microm(2)/mm(2)) were detected innervating the infarct region and observed in close proximity to a modest number of endothelial nitric oxide synthase-immunoreactive scar-residing vessels. Dexamethasone (Dex) treatment (6 days) of post-MI rats led to a significant reduction of scar weight (Dex + MI 38 +/- 4 mg vs. MI 63 +/- 2 mg) and a disproportionate nonsignificant decrease of scar surface area (Dex + MI 0.54 +/- 0.06 cm(2) vs. MI 0.68 +/- 0.06 cm(2)). In Dex-treated post-MI rats, the density of neurofilament-M-immunoreactive fibers (125 +/- 47 microm(2)/mm(2)) innervating the infarct region was significantly reduced and associated with a decreased expression of nerve growth factor (NGF) mRNA (Dex + MI 0.80 +/- 0.07 vs. MI 1.11 +/- 0.08; P < 0.05 vs. MI). Previous studies have demonstrated that scar myofibroblasts synthesize NGF and may represent a cellular target of Dex. The exposure of 1st passage scar myofibroblasts to Dex led to a dose-dependent suppression of [(3)H]thymidine uptake and a concomitant attenuation of NGF mRNA expression (untreated 3.47 +/- 0.35 vs. Dex treated 2.28 +/- 0.40; P < 0.05 vs. untreated). Thus the present study has demonstrated that impaired scar healing in Dex-treated post-MI rats was associated with a reduction of neurofilament-M-immunoreactive fibers innervating the infarct region. The attenuation of scar myofibroblast proliferation and NGF mRNA expression may represent underlying mechanisms contributing to the diminished neural response in the infarct region of Dex-treated post-MI rats.     

Hepatitis C virus NS3 NTPase/helicase: different stereoselectivity in nucleoside triphosphate utilisation suggests that NTPase and helicase activities are coupled by a nucleotide-dependent rate limiting step.

Hepatitis C virus (HCV) NS3 protein is a multifunctional enzyme, possessing protease, NTPase and helicase activities within a single polypeptide of 625 amino acid residues. These activities are essential for the virus life cycle and are considered attractive targets for anti-HCV chemotherapy. Beside ATP, the NS3 protein has the ability to utilise deoxynucleoside triphosphates (dNTPs) as the energy source for nucleic acid unwinding. We have performed an extensive analysis of the substrate specificities of both NS3 NTPase and helicase activities with respect to all four dNTPs as well as with dideoxynucleoside triphoshate (ddNTP) analogs, including both d-(beta) and l-(beta)-deoxy and dideoxy-nucleoside triphosphates. Our results show that almost all dNTPs and ddNTPs tested were able to inhibit hydrolysis of ATP by the NTPase activity, albeit with different efficiencies. Moreover, this activity showed almost no stereoselectivity, being able to recognise both d-(beta), l-(beta)-deoxy and ddNTPs. On the contrary, the helicase activity had more strict substrate selectivity, since, among d-(beta)-nucleotides, only ddTTP and its analog 2',3'-didehydro-thymidine triphosphate could be used as substrates with an efficiency comparable to ATP, whereas among l-(beta)-nucleotides, only l-(beta)-dATP was utilised. Comparison of the steady-state kinetic parameters for both reactions, suggested that dATP, l-(beta)-dCTP and l-(beta)-dTTP, specifically reduced a rate limiting step present in the helicase, but not in the NTPase, reaction pathway. These results suggest that NS3-associated NTPase and helicase activities have different sensitivities towards different classes of deoxy and dideoxy-nucleoside analogs, depending on a specific step in the reaction, as well as show different enantioselectivity for the d-(beta) and l-(beta)-conformations of the sugar ring. These observations provide an essential mechanistic background for the development of specific nucleotide analogs targeting either activity as potential anti-HCV agents.     

Pathways of carbon cycling in marine surface waters: the fate of small-sized phytoplankton in the Northeast Water Polynya

The fate of small-sized phytoplankton (<5 µm) and pathwaysof carbon cycling in surface waters, i.e. recycling within orexport out of the mixed layer, were investigated in the NortheastWater (NEW) Polynya (77–81°N) from 23 May to 22 July1993. The sampling covered a wide range of ice, hydrographicand nutrient conditions. Chlorophyll a concentrations, phytoplanktonproduction rates and zooplankton abundances were determinedin the field, and potential rates of grazing by protozoa, copepodsand appendicularians were calculated from abundances, usingassumptions from the literature. To our knowledge, this is thefirst published attempt to assess concurrently the grazing ofthese three plankton groups in the Arctic. The production rateof small-sized phytoplankton was significantly higher in ice-freecompared with ice-covered areas, but the biomasses of small-sizedphytoplankton and zooplankton were not. Potential recycling,downward export and horizontal advection of phytoplankton werecalculated by resolving carbon budgets for the mixed layer.A large fraction of the small-sized phytoplankton produced insidethe polynya was advected horizontally to the ice-covered partof the NEW, where these algae were necessary to sustain theheterotrophic community. We conclude that the fate of small-sizedphytoplankton production was mostly recycling (>70%). Downwardexport would have occurred infrequently, as a result of intensegrazing by appendicularians. Size-differential pathways of carboncycling in planktonic food webs are discussed.