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- Muscle conduction velocity, surface electromyography variables, and echo intensity during concentric and eccentric fatigue. [Journal Article, Randomized Controlled Trial]
- Muscle Nerve 2014 Mar; 49(3):389-97.
Concentric (CON) and eccentric (ECC) contractions may involve different mechanisms related to changes in sarcolemma status and the consequent alteration of action potential transmission along muscle fibers.Muscle conduction velocity (CV), surface electromyography signal (sEMG), muscle quality, and blood lactate concentrations were analyzed during CON and ECC actions.Compared with ECC, the CON protocol resulted in greater muscle force losses, blood lactate concentrations, and changes in sEMG parameters. Similar reductions in CV were detected in both protocols. Higher echo intensity values were observed 2 days after ECC due to greater muscle damage.The effects of the muscle damage produced by ECC exercise on the transmission of action potentials along muscle fibers (measured as the CV) may be comparable with the effects of hydrogen accumulation produced by CON exercise (related to greater lactate concentrations), which causes greater force loss and change in other sEMG variables during CON than during ECC actions.
- The potential of irradiation as a postharvest disinfestation treatment against Phlyctinus callosus (Coleoptera: Curculionidae). [Evaluation Studies, Journal Article, Research Support, Non-U.S. Gov't]
- J Econ Entomol 2014 Feb; 107(1):154-60.
Phlyctinus callosus (Boheman) (Coleoptera: Curculionidae) is a pest of major phytosanitary concern for some of South Africa's biggest export markets such as the United States and Europe because this pest does not occur there. At present, fumigation with methyl bromide is the only postharvest disinfestation treatment against this pest; therefore, sustainable alternatives are needed. One such alternative is irradiation treatment of whole pallets of packed fruit to sterilize insects that may be present within the cartons. Wild adult P. callosus weevils were treated with 5, 10, 20, 40, and 80 Gy of gamma-irradiation and then cross mated to breed with either treated or nontreated adults of the opposite sex. Fecundity and fertility were monitored and recorded. Trials were conducted during the 2009-2010 and 2010-2011 fruit harvesting seasons. The results from both seasons indicated that irradiation did not affect fecundity but fertility was significantly affected, decreasing as irradiation doses increased. Egg hatch was zero for mating crosses that involved females weevils treated with a dose of 80 Gy gamma-irradiation. Probit analysis indicated that in the first season, the estimated LD95 for crosses involving treated males and treated females was 30 Gy, while in the second season it was 49.5 Gy. Respective estimated LD99S were 47.9 and 169.4 Gy. Ultimately, a dose lower than the current generic dose of 400 Gy, approved for irradiation disinfestation treatments, would control P. callosus should they occur in packed export fruit.
- [Calculation of radiation loads in a space station compartment with a secondary shielding]. [English Abstract, Journal Article]
- Aviakosm Ekolog Med 2013 Nov-Dec; 47(6):61-6.
Doses from space ionizing radiation were estimated using a model of ISS cosmonaut's quarters (CQ) outfitted with secondary shielding ("Protective shutter" (PS) as part of experiment MATRYOSHKA-R). Protective shutter is a "blanket" of water-containing material with mass thickness of - 6 g/cm2 covering the CQ exterior wall. Calculation was performed specifically for locations of experimental dosimetry assemblies. Agreement of calculations and experimental data reaching accuracy - 15% proves model applicability to estimating protective effectiveness of secondary shielding in the present-day and future space vehicles. This shielding may reduce radiation loading onto crewmembers as an equivalent dose by more than 40% within a broad range of orbit altitudes equally during the solar minimum and maximum.
- [Effects of exposure to high-energy protons on rat's behavior and underlying neurochemical mechanisms]. [English Abstract, Journal Article]
- Aviakosm Ekolog Med 2013 Nov-Dec; 47(6):54-60.
Effects of 1.5 and 3 Gy from high-energy protons (165 MeV) on rat's motor and oriented trying activities, rate of the Y-labyrinth learning with electric pain stimulation, and levels of monoamines and their metabolites in different brain structures were studied. The experimental results showed that irradiation with these proton doses caused considerable inhibition of the motor and oriented trying activities, and strengthening of passive defense reactions in the open field test; however, no significant change was induced in the learning rate or monoamines turnover. Apparently, emotional and motivational systems were affected to a greater degree than cognitive functions.
- [Effects of small ionizing radiation doses on hemato-encephalic barrier permeability]. [English Abstract, Journal Article]
- Aviakosm Ekolog Med 2013 Nov-Dec; 47(6):46-9.
Goal and objectives of the study was comparative description and establishment of dose-time dependence of changes in permeability of the hemato-encephalic barrier (HEB) in phylogenetically different parts of the brain cortex, i.e. new (Fr2 and Cg3), old (hippocampal fields CA1-CA4 and dentate fascia) and paleocortex (piriform cortex) following exposure to 0.1; 0.2; 0.5 and 1 Gy of ionizing radiation (dose rate = 50 cGy). Dependence of microvessels permeability on dose, post-exposure time and cortex phylogenetic age was established. Changes in brain microvessels, in the phylogenetically young cortex in particular, produced by 0.5 Gy and 1 Gy remained uncompensated till the end of investigation. Pronounced changes persisted over the period of one year after radiation exposure; complete recovery was not observed even in the phylogenetically old cortex.
- Iron and lead ion adsorption by microbial flocculants in synthetic wastewater and their related carbonate formation. [Evaluation Studies, Journal Article, Research Support, Non-U.S. Gov't]
- J Environ Sci (China) 2013 Dec 1; 25(12):2422-8.
Although microbial treatments of heavy metal ions in wastewater have been studied, the removal of these metals through incorporation into carbonate minerals has rarely been reported. To investigate the removal of Fe3+ and Pb2+, two representative metals in wastewater, through the precipitation of carbonate minerals by a microbial flocculant (MBF) produced by Bacillus mucilaginosus. MBF was added to synthetic wastewater containing different Fe3+ and Pb2+ concentrations, and the extent of flocculation was analyzed. CO2 was bubbled into the mixture of MBF and Fe3+/Pb2+ to initiate the reaction. The solid substrates were analyzed via X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy. The results showed that the removal efficiency decreased and the MBF adsorption capacity for metals increased with increasing heavy metal concentration. In the system containing MBF, metals (Fe3+ and Pb2+), and CO2, the concentrated metals adsorbed onto the MBF combined with the dissolved CO2, resulting in oversaturation of metal carbonate minerals to form iron carbonate and lead carbonates. These results may be used in designing a method in which microbes can be utilized to combine CO2 with wastewater heavy metals to form carbonates, with the aim of mitigating environmental problems.
- Cr(VI) and azo dye removal using a hollow-fibre membrane system functionalized with a biogenic Pd-magnetite catalyst. [Journal Article, Research Support, Non-U.S. Gov't]
- Environ Technol 2014 Mar-Apr; 35(5-8):1046-54.
This study investigates the application of a hybrid system combining hollow-fibre membrane technology with the reductive abilities of magnetic nanoparticles for the remediation of toxic Cr(VI) and the azo dye, Remazol Black B. Nano-scale biogenic magnetite (Fe3O4), formed by microbial reduction of the mineral ferrihydrite, has a high reductive capacity due to the presence of Fe(II) in the mineral structure. The magnetic nanoparticles (approximately 20 nm) can be arrayed with Pd0 nanoparticles (approximately 5 nm) making a catalytically active nanomaterial. Membrane units, with and without nanoparticles, were challenged with either Cr(VI) or azo dye and some were supplemented with sodium formate, as an electron donor for contaminant reduction promoted by the Pd. The combination of Pd-magnetite with formate resulted in the most effective remediation strategy for both contaminants and the lifetime of the membrane unit was also increased, with 55% (19 days) and 70% (23 days) removal of the azo dye and Cr(VI), respectively. Low flow rates of 0.1 ml/min resulted in improved efficiencies due to increased contact time with the membrane/nanoparticle unit, with 70-75% removal of each contaminant. Chemical analyses of the nanoparticles post-exposure to Cr(VI) in the membrane modules indicated Pd to be more oxidized when Cr removal was maximized, and that the Cr was partially reduced to Cr(III) at the surface of the magnetite. These results have demonstrated that hollow-fibre membrane units can be enhanced for the removal of soluble, redox sensitive contaminants by incorporation of a layer of palladized biogenic nanoparticulate magnetite.
- Determination of a safe and effective ultraviolet B radiant dose in budgerigars (Melopsittacus undulatus): a pilot study. [Journal Article, Randomized Controlled Trial]
- J Avian Med Surg 2013 Dec; 27(4):269-79.
The object of this study was to establish a minimum dose of ultraviolet B (UVB) radiation capable of producing an erythemal reaction in budgerigars (Melopsittacus undulatus), to determine a threshold dose of UVB for vitamin D photoconversion, and to investigate the use of safer UVB wavelengths. In each of 5 experiments of this study, 20 birds were divided into a control group (n = 10) and a UVB irradiated group (n = 10). Light sources that provide broadband UVB wavelengths (280-315 nm) and narrowband UVB (310-320 nm) were used. Varied doses of UVB radiation were administered to budgerigars by altering exposure time and irradiance. Safety was determined by observing body weight and incidence of photokeratitis and photodermatitis. Efficacy was evaluated by measuring changes in serum 25-hydroxycholecalciferol levels. Serum corticosterone was measured in 1 experiment to monitor stress levels. The results demonstrated that exposure to 180 mJ/cm2 broadband UVB induced vitamin D photoconversion, decreased body weights, and increased serum corticosterone levels. At these wavelengths, UVB-induced lesions were observed. A broadband UVB of 150 to 300 mJ/cm2 was determined as the minimum erythema dose, and the threshold dose for vitamin D photoconversion was calculated to be in the range of 113-225 mJ/cm2. No erythemal lesions or vitamin D photoconversion took place after exposure to up to 1730 mJ/cm2 narrowband UVB radiation. A minimum erythema dose and a threshold dose for vitamin D conversion need to be determined for each species if phototherapy is to be considered as a safe and effective therapeutic or husbandry tool.