Lignocellulolytic Enzyme Production by Aquatic Hyphomycetes Species Isolated from the Nile's Delta Region

Twenty-six species of aquatic hyphomycetes were isolated from woody sources (unidentified wood segments, leaf skeletons and neck of leaves and bark) in the North River Nile (Delta region). Alatospora acuminata, Anguillospora crassa, Flagellaspora penicillioides, Lunulospra curvula, Tetracladium marchalianum and Triscelophorus monosporus were the most common species. Temperature was the highest physico-chemical parameter affecting the aquatic hyphomycetes occurrence. Twelve species of hyphomycetes, isolated from woody substrates, were screened for their ability to produce extracellular lignocellulolytic enzymes on solid media. The enzymes tested included: endoglucanase, endoxylanase, beta-glucosidase, laccase, peroxidase, polyphenoloxidase, tyrosinase and beta-xylosidase. Three species, A. acuminata, F. penicillioides, T. monosporus, were positive for all tested enzymes. Also, A. longissima was positive for all enzymes except lignin-peroxidase. The ability to produce cellulase was 100% for all species while only, four species were positive for lignin-peroxidase. The ability of the species to produce other lignocellulotic enzyme ranged from 50% to 83%. Freshwater hyphomycetes have been shown to produce a rich array of enzymes able to degrade the polysaccharides of plant debris.     

Mitochondrial requirement for endothelial responses to cyclic strain: implications for mechanotransduction

Mechanical strain triggers a variety of cellular responses, but the underlying mechanotransduction process has not been established. Endothelial cells (EC) respond to mechanical strain by upregulating adhesion molecule expression through a signaling process involving reactive oxygen species (ROS), but the site of their generation is unknown. Mitochondria anchor to the cytoskeleton and could function as mechanotransducers by releasing ROS during cytoskeletal strain. In human umbilical vein EC (HUVEC), ROS production increased 221 +/- 17% during 6 h of cyclic strain vs. unstrained controls. Mitochondrial inhibitors diphenylene iodonium or rotenone abrogated this response, whereas inhibitors of nitric oxide (NO) synthase (L-nitroarginine), xanthine oxidase (allopurinol), or NAD(P)H oxidase (apocynin) had no effect. The antioxidants ebselen and diethyldithiocarbamate inhibited the increase in ROS, but the NO scavenger Hb had no effect. Thus strain induces ROS release from mitochondria. In other studies, HUVEC were rendered mitochondria deficient (rho0 EC) to determine the requirement for electron transport in the response to strain. Strain-induced 2'7'-dichlorofluorescein fluorescence was attenuated by >80% in rho0 EC compared with HUVEC (43 +/- 7 vs. 221 +/- 17%). Treatment with cytochalasin D abrogated strain-induced ROS production, indicating a requirement for the actin cytoskeleton. Cyclic strain (6 h) increased VCAM-1 expression in wild-type but not rho0 EC. Increases in NF-kappaB activation and VCAM-1 mRNA expression during strain were prevented by antioxidants. These findings demonstrate that mitochondria function as mechanotransducers in endothelium by increasing ROS signaling, which is required for strain-induced increase in VCAM-1 expression via NF-kappaB.     

Modelling the behaviour of ligaments: a technical note

Experimental observations suggest that during a ligament tensile strain test, water and glycosaminoglycans are exuded. Many attempts have been tried to model this behaviour using continuum mechanics. We have investigated this unique behaviour and have established three mechanisms which may contribute to the experimental observations: the slackness of the fibres before stretching can lead to a decrease in volume upon straightening; a Poisson's ratio higher than 0.5 from the axial to the lateral direction (as recorded in the literature [Hewitt, J., Guilak, F., Glisson, R. and Parker Vail, T. (2001) "Regional material properties of the human hip joint capsule ligaments", Journal of Orthopaedic Research 19(3), 359-364]) due to the very high level of anisotropy of the tissue; and an osmotic pressure, with a certain level of anisotropy, that causes the swelling of the tissue before loading [Thornton, G.M., Shrive, N.G. and Frank, C.B. (2001) "Altering ligament water content affects ligament pre-stress and creep behaviour", Journal of Orthopaedic Research 19(5), 845-851]. There may be other mechanisms that also contribute in the observed fluid exudation on tensile loading.     

Impact of aging on myocardial metabolic response to dobutamine

In humans, under resting conditions there is an age-related decrease in myocardial fatty acid utilization (MFAU) and oxidation (MFAO) and a relative increase in myocardial glucose utilization (MGU). The impact of age on an individual's myocardial metabolic response to catecholamines is not well defined. Sixteen younger (mean age, 26 +/- 5 yr) and 14 older (mean age, 69 +/- 4 yr) volunteers underwent positron emission tomography to measure myocardial blood flow, myocardial oxygen consumption (M.VO2), MFAU, MFAO, and MGU both under resting conditions and during dobutamine infusion. In response to dobutamine administration, the rate-pressure product, myocardial blood flow, and M.VO2 measurements increased by similar amounts in both groups. No age-related differences were noted in the responses of plasma insulin, glucose, fatty acid, or lactate levels to dobutamine. With dobutamine infusion, MFAU and MFAO increased by a similar extent in both younger and older volunteers (age/dobutamine interactions, P = 0.62 and 0.75, respectively). In contrast, MGU increased with dobutamine administration in the younger (from 149 +/- 71 to 209 +/- 78 nmol.g(-1).min(-1); P = 0.04) but not in the older (from 235 +/- 147 to 176 +/- 84 nmol.g(-1).min(-1); P = 0.23; age/dobutamine interaction, P = 0.03) group. With dobutamine infusion, hearts in both younger and older volunteers responded by increasing their MFAU and MFAO values. Whereas younger hearts also responded with an increase in MGU, older hearts did not. Although the clinical significance of these findings awaits further study, these results may partially explain the impaired contractile reserve and the increased incidence of cardiovascular disease in older individuals.     

Solid-phase synthesis and biochemical evaluation of conformationally constrained analogues of deglycobleomycin A5

Deglycobleomycin binds to and degrades the self-complementary oligonucleotide d(CGCTAGCG)(2) in a sequence selective fashion. A previous modeling study [J. Am. Chem. Soc. 120, (1998), 7450] had shown that, during binding to double stranded DNA, the conformation of the methylvalerate domain of deglycoBLM approximated that of S-proline. In the belief that an analogue of deglycoBLM structurally constrained to mimic the DNA-bound conformation might exhibit facilitated DNA binding and cleavage, an analogue of deglycoBLM was prepared in which the methylvalerate moiety was replaced by S-proline. This deglycoBLM analogue, as well as the related analogue containing R-proline, was synthesized on a TentaGel resin. Both of the analogues were found to be capable of binding Fe(2+) and activating O(2) for transfer to styrene. However, both deglycoBLM analogues exhibited diminished abilities to effect the relaxation of supercoiled plasmid DNA, and neither mediated sequence selective DNA cleavage.     

Evaluation of three concentrations of tebufenpyrad for the control of Varroa destructor (Acari: Varroidae)

We evaluated three concentrations of tebufenpyrad (17.5, 15 and 12.5%) in strip formulations for controlling varroa mites, Varroa destructor Anderson and Trueman (2000), in honey bee colonies. We also included colonies treated with Apistan, CheckMite+, and untreated colonies in our evaluation. The three concentrations we evaluated reduced varroa populations but also reduced the amount of brood and adult bees when compared with untreated colonies and colonies treated with Apistan or CheckMite+. Alternative delivery methods, lower concentrations of tebufenpyrad, and the evaluation of related compounds are logical next steps in evaluating the varroacidal potential of tebufenpyrad and related compounds.