Home About us Contact
|
Home About us Contact | ||
|
|
||
Membrane Breakdown (membrane + breakdown)
Selected AbstractsConduction block and glial injury induced in developing central white matter by glycine, GABA, noradrenalin, or nicotine, studied in isolated neonatal rat optic nerveGLIA, Issue 11 2009Stavros Constantinou Abstract The damaging effects of excessive glutamate receptor activation have been highlighted recently during injury in developing central white matter. We have examined the effects of acute exposure to four other neurotransmitters that have known actions on white matter. Eighty minutes of Glycine or GABA-A receptor activation produced a significant fall in the compound action potential recorded from isolated post-natal day 10 rat optic nerve. This effect was largely reversed upon washout. Nicotinic acetylcholine receptor (nAChR) or adrenoreceptor activation with noradrenalin resulted in an ,35% block of the action potential that did not reverse during a 30-min washout period. While the effect of nAChR activation was blocked by a nAChR antagonist, the effect of noradrenalin was not ablated by ,- or ,-adrenoreceptor blockers applied alone or in combination. In the absence of noradrenalin, co-perfusion with ,- and ,-adrenoreceptor blockers resulted in nonreversible nerve failure indicating that tonic adrenoreceptor activation is required for nerve viability, while overactivation of these receptors is also damaging. Nerves exposed to nAChR + adrenoreceptor activation showed no axon pathology but had extensive glial injury revealed by ultrastructural analysis. Oligodendroglia exhibited regions of membrane vacuolization while profound changes were evident in astrocytes and included the presence of swollen and expanded mitochondria, vacuolization, cell processes disintegration, and membrane breakdown. Blinded assessment revealed higher levels of astrocyte injury than oligodendroglial injury. The findings show that overactivation of neurotransmitter receptors other than those for glutamate can produce extensive injury to developing white matter, a phenomenon that may be clinically significant. © 2009 Wiley-Liss, Inc. [source] Critical Electric Field Strengths of Onion Tissues Treated by Pulsed Electric FieldsJOURNAL OF FOOD SCIENCE, Issue 7 2010Suvaluk Asavasanti Abstract:, The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (Ec) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-,s pulses indicate that breakdown of the plasma membrane occurs above Ec= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either Ec= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n,10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses. [source] Salmonella Enteritidis Risk Assessment: A Kinetic AnalysisJOURNAL OF FOOD SCIENCE, Issue 3 2002S. Almonacid ABSTRACT: Egg and egg preparations are important vehicles for Salmonella enteritidis infections. The influence of time-temperature becomes important when the presence of this microorganism is found in commercial shell eggs, particularly in countries where refrigeration is not mandatory as in Chile. The objective of this research was to develop a mathematical model to analyze the Salmonella enteritidis risk under variable ambient temperatures. Breakdown of vitelline egg membrane was assumed to be required for initiation of bacterial growth. When the critical factor concerning safety is the vitelline membrane breakdown, 15 °C was found to be the storage threshold temperature for a 30-d shelf life. This computer based tool can be used as a contribution in current regulation adjustments or modifications. [source] Effect of minimal processing on the textural and structural properties of fresh-cut pearsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2002Robert C Soliva-Fortuny Abstract The feasibility of minimal processing and modified atmosphere packaging to preserve the original textural quality of fresh-cut pears was evaluated throughout storage under refrigeration. Fresh-cut pear firmness could be extended up to several weeks with low-O2 atmospheres. A packaging atmosphere of 100% N2 combined with the use of plastic bags with an O2 permeability of 15,cm3,m,2 bar,1,day,1 maintained cell structure and partially avoided membrane breakdown and exudate accumulation in intercellular spaces. Under the other conditions studied, pear texture underwent dramatic deterioration, which could be related to complete inundation of the extracellular environment. Firmness decreased linearly throughout the storage period studied, with rate constants ranging from 0.0097 to 0.040 day,1. The consideration of other textural variables also gave valuable information, similar to that provided by firmness data. © 2002 Society of Chemical Industry [source] Unaliasing lipid contamination for MR spectroscopic imaging of gliomas at 3T using sensitivity encoding (SENSE),MAGNETIC RESONANCE IN MEDICINE, Issue 5 2006Esin Ozturk-Isik Abstract 3D magnetic resonance spectroscopic imaging (MRSI) has been successfully employed to extract information about brain tumor metabolism, such as cell membrane breakdown, cellular energetics, and neuronal integrity, through its ability to differentiate signals coming from choline (Cho), creatine (Cr), and N-acetyl aspartate (NAA) molecules. The additional presence of lipids within subregions of the tumor may indicate cellular membrane breakdown due to cell death. Another potential source of lipids is subcutaneous fat, which may be excited with point-resolved spectroscopy (PRESS) volume selection and aliased into the spectral field of view (FOV) due to the chemical shift artifact and the low bandwidth of the selection pulses. The purpose of our study was to employ a postprocessing method for unaliasing lipid resonances originating from in-slice subcutaneous lipids from the 3D MRSI of gliomas at 3T, using an eight-channel phased-array coil and sensitivity encoding (SENSE). Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Oocyte-selective expression of MT transposon-like element, clone MTi7 and its role in oocyte maturation and embryo developmentMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2004Chang-Eun Park Abstract Previously, we found MT transposon-like element, clone MTi7 (MTi7) is highly expressed in the mouse ovary. Here, we show that the MTi7 is expressed in the oocyte from the primordial to the preovulatory follicles. For RNA interference (RNAi), double stranded RNAs (dsRNAs) were prepared for MTi7 and c-mos, a control gene with known functions. Each dsRNA was microinjected into germinal vesicle (GV) stage oocytes or zygotes with pronuclei (PN), after which developmental changes, mRNA expression, and nuclear and microtubular organization were analyzed. We found a 43.4,53% GV arrest in the microinjected oocytes with a concomitant decrease in targeted mRNA expression. In MTi7 dsRNA-injected early and late PN zygotes, a 92.9% 1-cell arrest and 76.9% 2-cell arrest were observed, respectively. This is the first report of an oocyte-selective expression of MTi7 mRNA, and our results strongly suggest that MTi7 involved in the nuclear membrane breakdown during oocyte maturation and embryo development. Mol. Reprod. Dev. 69: 365,374, 2004. © 2004 Wiley-Liss, Inc. [source] | |||||||||||||