Fungal products. Part XVII. Microbiological hydroxylation of gibberellin A9 and its methyl ester

Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels."     

Differential Performance of a Specialist and Two Generalist Herbivores and Their Parasitoids on <Emphasis Type="Italic">Plantago lanceolata</Emphasis>

The ability to cope with plant defense chemicals differs between specialist and generalist species. In this study, we examined the effects of the concentration of the two main iridoid glycosides (IGs) in Plantago lanceolata, aucubin and catalpol, on the performance of a specialist and two generalist herbivores and their respective endoparasitoids. Development of the specialist herbivore Melitaea cinxia was unaffected by the total leaf IG concentration in its host plant. By contrast, the generalist herbivores Spodoptera exigua and Chrysodeixis chalcites showed delayed larval and pupal development on plant genotypes with high leaf IG concentrations, respectively. This result is in line with the idea that specialist herbivores are better adapted to allelochemicals in host plants on which they are specialized. Melitaea cinxia experienced less post-diapause larval and pupal mortality on its local Finnish P. lanceolata than on Dutch genotypes. This could not be explained by differences in IG profiles, suggesting that M. cinxia has adapted in response to attributes of its local host plants other than to IG chemistry. Development of the specialist parasitoid Cotesia melitaearum was unaffected by IG variation in the diet of its host M. cinxia, a response that was concordant with that of its host. By contrast, the development time responses of the generalist parasitoids Hyposoter didymator and Cotesia marginiventris differed from those of their generalist hosts, S. exigua and C. chalcites. While their hosts developed slowly on high-IG genotypes, development time of H. didymator was unaffected. Cotesia marginiventris actually developed faster on hosts fed high-IG genotypes, although they then had short adult longevity. The faster development of C. marginiventris on hosts that ate high-IG genotypes is in line with the “immunocompromized host” hypothesis, emphasizing the potential negative effects of toxic allelochemicals on the host’s immune response.     

Variation in host fruit volatiles attractive to apple maggot fly,Rhagoletis pomonella

We conducted a comparative study of volatiles produced by wholeCrataegus hawthorn fruit and four cultivars of apple (Royal Red Delicious, Red Astrachan, McIntosh, and Wealthy) and determined quantitative and qualitative changes of volatiles associated with fruit ripening. Within the approximate range of the GLC fraction known to elicit behavioral activity in the apple maggot fly,Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), 52 esters were identified.     

Corrosion Testing of Ni Alloy HVOF Coatings in High Temperature Environments for Biomass Applications

This paper reports the corrosion behavior of Ni alloy coatings deposited by high velocity oxyfuel spraying, and representative boiler substrate alloys in simulated high temperature biomass combustion conditions. Four commercially available oxidation resistant Ni alloy coating materials were selected: NiCrBSiFe, alloy 718, alloy 625, and alloy C-276. These were sprayed onto P91 substrates using a JP5000 spray system. The corrosion performance of the coatings varied when tested at ~525, 625, and 725 °C in K₂SO₄-KCl mixture and gaseous HCl-H₂O-O₂ containing environments. Alloy 625, NiCrBSiFe, and alloy 718 coatings performed better than alloy C-276 coating at 725 °C, which had very little corrosion resistance resulting in degradation similar to uncoated P91. Alloy 625 coatings provided good protection from corrosion at 725 °C, with the performance being comparable to wrought alloy 625, with significantly less attack of the substrate than uncoated P91. Alloy 625 performs best of these coating materials, with an overall ranking at 725 °C as follows: alloy 625 > NiCrBSiFe > alloy 718 ? alloy C-276. Although alloy C-276 coatings performed poorly in the corrosion test environment at 725 °C, at lower temperatures (i.e., below the eutectic temperature of the salt mixture) it outperformed the other coating types studied.     

Spatial and Ontogenetic Variability of Sea Lamprey Diets in Lake Superior

Invasive sea lamprey (Petromyzon marinus) remain an important source of fish mortality in the Laurentian Great Lakes, yet assessing their impact is hindered by lack of quantitative diet information. We examined nitrogen and carbon stable isotope ratios (δ¹⁵N and δ¹³C) of sea lamprey and host species in six ecoregions of Lake Superior, mainly in 2002–2004. Data implied that most sea lamprey fed primarily on upper trophic level species, including forms of lake trout (Salvelinus namaycush). However, in Ontario waters, particularly semi-enclosed Black Bay, sea lamprey relied heavily on lower trophic levels, such as coregonines (Coregonus spp.) and suckers (Catostomus spp.). Sea lamprey δ¹⁵N and δ¹³C generally increased with sea lamprey size, implying dependence on higher trophic levels later in life. Most parasitic sea lamprey that we captured were attached to either lean lake trout (35% of observed attachments), lake whitefish (Coregonus clupeaformis; 25%), or cisco (C. artedii; 25%); the latter sea lamprey were typically < 15 g. Survey- and fishery-dependent wounding rate data compiled from 1986–2005 suggest that lean and siscowet lake trout were selectively parasitized by sea lamprey, which is consistent with our stable isotope data. Our results largely support the notion that lake trout are the principal host species in Lake Superior. However, stable isotope evidence that sea lamprey feed at lower trophic levels in some regions argues for comprehensive monitoring of sea lamprey impacts throughout the fish community in systems that sea lamprey have invaded.     

The effects of creatine ethyl ester supplementation combined with heavy resistance training on body composition, muscle performance, and serum and muscle creatine levels

Numerous creatine formulations have been developed primarily to maximize creatine absorption. Creatine ethyl ester is alleged to increase creatine bio-availability. This study examined how a seven-week supplementation regimen combined with resistance training affected body composition, muscle mass, muscle strength and power, serum and muscle creatine levels, and serum creatinine levels in 30 non-resistance-trained males. In a double-blind manner, participants were randomly assigned to a maltodextrose placebo (PLA), creatine monohydrate (CRT), or creatine ethyl ester (CEE) group. The supplements were orally ingested at a dose of 0.30 g/kg fat-free body mass (approximately 20 g/day) for five days followed by ingestion at 0.075 g/kg fat free mass (approximately 5 g/day) for 42 days. Results showed significantly higher serum creatine concentrations in PLA (p = 0.007) and CRT (p = 0.005) compared to CEE. Serum creatinine was greater in CEE compared to the PLA (p = 0.001) and CRT (p = 0.001) and increased at days 6, 27, and 48. Total muscle creatine content was significantly higher in CRT (p = 0.026) and CEE (p = 0.041) compared to PLA, with no differences between CRT and CEE. Significant changes over time were observed for body composition, body water, muscle strength and power variables, but no significant differences were observed between groups. In conclusion, when compared to creatine monohydrate, creatine ethyl ester was not as effective at increasing serum and muscle creatine levels or in improving body composition, muscle mass, strength, and power. Therefore, the improvements in these variables can most likely be attributed to the training protocol itself, rather than the supplementation regimen.     

PML absorbing boundary conditions for the characterization of openmicrowave circuit components using multiresolution time-domaintechniques (MRTD)

The multiresolution time domain technique (MRTD) is applied to the modeling of open microwave circuit problems. Open boundaries are simulated by the use of a novel formulation of the perfect matching layer (PML) absorber. The PML is modeled both in split and nonsplit forms and can be brought right on the surface of the planar components. The applicability of the MRTD technique to complex geometries with high efficiency and accuracy in computing the fields at discontinuities is demonstrated through extensive comparisons to conventional finite difference time domain (FDTD). In addition, the numerical reflectivity of the PML absorber is investigated for a variety of cell sizes, some of which are very close to the Nyquist limit (λ/2)     

Investigating teacher stress when using technology

In this study we use a model which we refer to as the ‘teacher–technology environment interaction model’ to explore the issue of the stress experienced by teachers whilst using ICT in the classroom. The methodology we used involved a comparison of three datasets obtained from: direct observation and video-logging of the teachers in the classroom; recordings of their galvanic skin response (GSR) taken whilst teaching; and interviews. Data were obtained from nine teachers, and in total, approximately 32 h of teaching activities were observed. The main results of this study were (a) the demonstration that teachers do suffer stress associated with the use of technology in the classroom (i.e. technostress) (b) the identification of causes, symptoms and coping strategies associated with technostress in the classroom. This study, therefore, points to an alternative way of thinking about the problems of implementing e-learning by conceptualizing some of these implementation problems in terms of technostress (and in particular of teacher–technology environment fit).