Possible mechanism of pesticide toxicity-related oxidative stress leading to airway narrowing

Abstract

The study was conducted to assess the magnitude of oxidative stress and lung function abnormalities in 34 male pesticide sprayers on exposure to pesticides in mango plantations. Biochemical studies on blood antioxidant enzymes revealed an unchanged glutathione level and increased level of malondialdehyde (P < 0.001), which indicates that pesticide sprayers may have suffered from oxidative stress. Decreased acetyl-cholinesterase levels (P < 0.001) in sprayers compared to the controls suggest inhibition of cholinesterase activity. The present study shows that pesticide toxicity might lead to oxidative stress and airway narrowing resulting in decreased peak expiratory flow rate.     

Fluid pressure induces osteoclast differentiation comparably to titanium particles but through a molecular pathway only partly involving TNFα

In contrast to the well-understood inflammatory pathway driven by TNFα, by which implant-derived particles induce bone resorption, little is known about the process in which loosening is generated as a result of force-induced mechanical stimulus at the bone-implant interface. Specifically, there is no knowledge as to what cells or signaling pathways couple mechanical stimuli to bone resorption in context of loosening. We hypothesized that different stimuli, i.e., fluid flow versus wear particles, act through different cytokine networks for activation and localization of osteoclasts. By using an animal model in which osteoclasts and bone resorption were induced by fluid pressure or particles, we were able to detect distinct differences in osteoclast localization and inflammatory gene expression between fluid pressure and titanium particles. Fluid pressure recruits and activates osteoclasts with bone marrow contact away from the fluid pressure exposure zone, whereas titanium particles recruit and activate osteoclasts in areas in direct contact to particles. Fluid pressure induced weaker expression of the selected inflammatory related genes, although the eventual degree of osteoclast induction was similar in both models. Using TNFαRa (4 mg/kg) (Enbrel) and dexamethasone (2 mg/kg) as specific and more general suppressors of inflammation we showed that the TNFαRa failed to generate statistically impaired osteoclast generation while dexamethasone was much more potent. These results demonstrate that fluid pressure induces osteoclasts at a different localization than titanium particles by a molecular pathway less associated with TNFα and the innate system, which open up for other pathways controlling pressure induced osteoclastogenesis.     

The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river

The proposed construction of a second hydroelectric power-generating dam on the Cunene (Kunene) River on the Namibia-Angola border, more than 100km downstream of the Ruacana hydroelectric power plant, will have a major influence on the aquatic biota of this river. In order to assess the potential impact of this impoundment a more detailed inventory of the biota in the river prior to this development was needed. Unfortunately the river presently does not represent an entirely undisturbed system as the operation of the Ruacana hydroelectric power station since 1970 has had a long-term effect on its biota. In the low-flow mid-summer season in particular, large areas of the river become irregularly inundated and exposed, sometimes on a daily basis, making them unsuitable for macroinvertebrate colonisation. There are six impoundments along the Cunene River upstream of the Ruacana Falls in Angola. These, however, do not have any major disruptive effects on daily flow variation in the Cunene River in Namibia although whole system biological consequences could be considerable but are unstudied. The Cunene River has a diverse freshwater fish fauna but, prior to the surveys reported here, the aquatic macroinvertebrates had been poorly studied. Surveys conducted by staff of the Department of Water Affairs (DWA) of Namibia and the Albany Museum, Grahamstown, in 1997 and 1998 have resulted in 216 aquatic macroinvertebrate species being recorded from Ruacana to the river mouth. The lower Cunene River, flowing through a very arid region, is biogeographically isolated and therefore highly vulnerable to change. The biota recorded reflects a fauna of widespread species and several elements of tropical origin. Several undescribed species may reflect some endemics but because of limited knowledge of the tropical rivers, this cannot be ascertained with certainty. From the aspect of conservation, the river contains a diversity of species with an abundance of filter-feeding species. Further surveys conducted during different seasons will undoubtedly record more taxa.     

Calypogeia Meylanii Buch,new to Britain

Abstract

A comparison was made between the rapid fluorescence induction characteristics of bryophytes (mosses, liverworts and hornworts), vascular plants and a microalga under actinic irradiation. The bryophytes studied showed similar induction characteristics to microalgae, with a fast decline from an initial peak (P) to a quasi-stationary fluorescence yield (S). Dark relaxation characteristics of the bryophytes were also comparable with those of algae, showing a rapid decline in fluorescence to the F_o value when actinic light was switched off. The degree and duration of the P/S decline was related to the intensity of actinic irradiation, although with increasing irradiance the ratio of P/S remained constant for most species. When actinic light was supplied with no prior dark relaxation, the initial peak (P) was suppressed after registration of the first I–P–S cycle, indicating a dependence of the induction characteristics on the oxygen status of the organism. The implication of these observations of oxygen-dependent electron flow in furthering our understanding of bryophyte photosynthetic physiology is discussed.     

Tezosentan increases nitric oxide signaling via enhanced hydrogen peroxide generation in lambs with surgically induced acute increases in pulmonary blood flow

We have previously shown that acute increases in pulmonary blood flow (PBF) are limited by a compensatory increase in pulmonary vascular resistance (PVR) via an endothelin‐1 (ET‐1) dependent decrease in nitric oxide synthase (NOS) activity. The mechanisms underlying the reduction in NO signaling are unresolved. Thus, the purpose of this study was to elucidate mechanisms of this ET‐1–NO interaction. Pulmonary arterial endothelial cells were acutely exposed to shear stress in the presence or absence of tezosentan, a combined ET_A/ET_B receptor antagonist. Shear increased NO_x, eNOS phospho‐Ser1177, and H₂O₂ and decreased catalase activity; tezosentan enhanced, while ET‐1 attenuated all of these changes. In addition, ET‐1 increased eNOS phospho‐Thr495 levels. In lambs, 4 h of increased PBF decreased H₂O₂, eNOS phospho‐Ser1177, and NO_X levels, and increased eNOS phospho‐Thr495, phospho‐catalase, and catalase activity. These changes were reversed by tezosentan. PEG‐catalase reversed the positive effects of tezosentan on NO signaling. In all groups, opening the shunt resulted in a rapid increase in PBF by 30 min. In vehicle‐ and tezosentan/PEG‐catalase lambs, PBF did not change further over the 4 h study period. PVR fell by 30 min in vehicle‐ and tezosentan‐treated lambs, and by 60 min in tezosentan/PEG‐catalase‐treated lambs. In vehicle‐ and tezosentan/PEG‐catalase lambs, PVR did not change further over the 4 h study period. In tezosentan‐treated lambs, PBF continued to increase and LPVR to decrease over the 4 h study period. We conclude that acute increases in PBF are limited by an ET‐1 dependent decrease in NO production via alterations in catalase activity, H₂O₂ levels, and eNOS phosphorylation. J. Cell. Biochem. 114: 435–447, 2013. © 2012 Wiley Periodicals, Inc.     

The IFR process: beyond the specialist workshop

The process of determining Instream Flow Requirements (IFRs) has been well developed to the point at which an IFR table which quantifies the temporal distribution of discharge, upon which the modified flow regime is based, is produced. During the last three years, the process has been further developed by linking the IFRs (using the IFR model) to an historical time series and a natural flow trigger. It has become imperative that the liaison between IFR specialists and developers of the methodology should not end here, as some of the most important requirements for supplying the IFR include the determination of the yield of a system as well as the design and ultimate operation of storage structures. On the basis of some case studies this paper considers how the liaison should take place after the specialist workshop and summarises the areas where further development is required.     

Estimation of preferred water flow parameters for four species of Simulium (Diptera: Simuliidae) in small clear streams in South Africa

Blackfly larvae typically occur in fast-flowing riffle sections of rivers, with different blackfly species showing preferences for different hydraulic conditions. Very little quantitative data exist on hydraulic conditions linked to the blackfly species occurring in South African streams. Stones-in-current biotopes (i.e. fast riffle flows over cobbles) were sampled from four sites in three small clear streams in the Eastern and Western Cape provinces of South Africa. Mean water column velocities at each sampled stone were measured using a mini current meter, while flow velocities closer to the boundary layer where blackfly larvae occurred were estimated using indirect techniques (standard hemispheres and aerating tablets). Standard hemispheres were also used to calculate more complex hydraulic parameters such as Froude and Reynolds numbers. Four species of Simuliid were sampled in sufficient numbers to show trends in flow velocity preferences. Simulium impukane and S. rutherfoordi both occurred at their highest densities at velocities of 0.3m s^?1, while S. merops preferred velocities of 0.7m s^?1. Simulium nigritarse SL attained the highest densities of all the blackfly species sampled, and its relative abundances were greatest at velocities of 0.8–0.9m s^?1. Within the streams surveyed, all blackfly species occurred in subcritical-turbulent flows — based on a classification using Froude and Reynolds numbers — although two of the species were also found in high densities in supercritical flows where these existed at the sites. Local hydraulics within the stones-in-current biotope are complex, but in the absence of fine-scale equipment for measuring micro-velocities, standard hemispheres are a useful, cost-effective technique for the initial quantification of hydraulic parameters in small, clear streams. Such an approach facilitates further understanding of links between hydraulics and aquatic invertebrates in South African streams.     

Some aspects of the ecology of the Groot Letaba River in the Northern Province,South Africa

The aim of this pilot study was to evaluate the current ecological status of the Groot Letaba River and to compare this information with historical data. The objective was to determine the effects of various impacts on the fish populations of the river. This was done by analysing the water quality and by considering the effect of weirs and dams, as well as various illegal angling activities, on the fish community.

The Groot Letaba River is not highly polluted and the decline in its flow seems to be the greatest threat to the system. During a preliminary study to develop the river's resource potential, it was stated that the annual water allocation from Tzaneen Dam was 103.9 million m³/annum for irrigation, 8.4 million m³/annum for domestic and industrial use and 14.7 million m³/annum for environmental purposes. However, the yield from Tzaneen Dam was only 98 million m³/annum, suggesting that more water had been allocated than was available. As a result only 20% of the simulated natural flow is observed at Letaba Ranch Weir at the lower end of the river.

Over the past few years many weirs and dams, none of which have fishways, have been constructed in the Groot Letaba River, impacting on the flow regime and on the migration potential of many fish species. Tiger fish (Hydrocynus vittatus) and the largescale yellowfish (Barbus marequensis) are two of the more prominent species influenced negatively by these barriers. This problem is aggravated by the illegal netting of fish stranded below these barriers during their spawning migrations.