Changes In Cellular Integrity Research Articles

Enhanced electroporation in plant tissues via low frequency pulsed electric fields: Influence of cytoplasmic streaming

Pulsed electric fields (PEF) are known to be effective at permeabilizing plant tissues. Prior research has demonstrated that lower pulse frequencies induce higher rates of permeabilization, but the underlying reason for this response is unclear. Intriguingly, recent microscopic observations with onion tissues have also revealed a correlation between PEF frequency and the subsequent speed of intracellular convective motion, i.e., cytoplasmic streaming. In this paper, we investigate the effect of cytoplasmic streaming on the efficacy of plant tissue permeabilization via PEF. Onion tissue samples were treated with Cytochalasin B, a known inhibitor of cytoplasmic streaming, and changes in cellular integrity and viability were measured over a wide range of frequencies and field strengths. We find that at low frequencies (f < 1 Hz), the absence of cytoplasmic streaming results in a 19% decrease in the conductivity disintegration index compared with control samples. Qualitatively, similar results were observed using a microscopic cell viability assay. The results suggest that at low frequencies convection plays a statistically significant role in distributing more conductive fluid throughout the tissue, making subsequent pulses more efficacious. The key practical implication is that PEF pretreatment at low frequency can increase the rate of tissue permeabilization in dehydration or extraction processes, and that the treatment will be most effective when cytoplasmic streaming is most active, i.e., with freshly prepared plant tissues.

Effect of selective PKC isoform activation and inhibition on TNF-alpha-induced injury and apoptosis in human intestinal epithelial cells.

(1) We have investigated the effects of specific PKC isoforms in TNF-alpha mediated cellular damage using a human intestinal cell line (SCBN). (2) TNF-alpha treatment induced a decrease in the extent of intestinal cellular viability as determined by a formazan-based assay and an increase in the apoptotic index as assessed by immunohistology. These changes in cellular integrity were found to be related to the degradation of I-kappaBalpha, mobilization of NF-kappaB and release of mitochondrial cytochrome c. (3) TNF-alpha treatment also induced the activation of selective PKC isoforms which were associated with the decrease in cellular viability and an increase of cellular apoptosis. (4) Nonselective PKC antagonists, such as GF109203X and Gö6976 as well as isoform-selective PKC-inhibiting peptides would reverse the cellular injury as well as reduce the degradation of I-kappaBalpha and mitochondrial cytochrome c release. These effects were most highly correlated with changes in PKCdelta and epsilon primarily. (5) Intestinal cellular injury could be induced by treating cells with agonists selective for PKCdelta and epsilon mainly. (6) In conclusion, this study has shown that TNF-alpha treatment can induce the activation of PKCdelta and epsilon in the human intestinal cell line, SCBN, and this response is closely associated with an increase in cellular damage and apoptosis. PKCdelta and epsilon primarily mediate the release of mitochondrial cytochrome c and degradation of I-kappaBalpha and hence mobilization of NF-kappaB, which are responsible for the pathway leading to cell injury.

Cellular changes and physiological responses to tuber pressure-bruising

Tubers located at lower depths in bins of stored potatoes suffer from pressure-bruising which often develops into an internal grayish or blackspot-like defect. However, little is known about key physiological and cellular changes that constitute pressure-bruising and resulting defects that degrade potato marketability and profits. We determined the changes in periderm water vapor permeability and some of the changes in cellular integrity that may occur in pressure-bruised areas compared to non-pressure-bruised areas of tubers after eight months of storage. Porometric measurements of pressure-bruised areas revealed elevated water vapor loss, which is conducive to blackspot formation, even though there were no apparent breaks in the periderm of pressure-bruised areas. Pressurebruised areas did not appear to readily wound-heal, because the elevated water vapor loss was shown to continue, without decline, when the tubers were porometrically measured again 4 days after removal from the pressure-bruising environment. Analysis of changes in cellular integrity of pressure-bruised regions showed that the tough, rigid cells of the suberized phellem could be damaged or completely flattened by this form of stress. A layer of what appeared to be crushed cells was often detected beneath the pressure-bruised, but partially intact, phellem. Autofluorescence of the crushed layer appeared to be derived from cell walls of collapsed phelloderm cells, starch granules of neighboring cells and material accumulated as a physiological response to the cellular damage incurred from pressure-bruising. These results help explain why the blackspot-like defect sometimes occurs at pressure-bruise sites.

New essential trace elements for the life sciences

The possible importance of some new essential trace elements in nutrition is discussed. Most likely, insufficient intake of a specific trace element becomes obvious only when the body is stressed in some way that enhances the need for that element; this has been supported by recent findings with selenium. The trace elements boron and copper may be of nutritional significance in a manner similar to selenium. When the diets of animals and humans are manipulated to cause possible changes in cellular integrity or in hormone responsiveness, a large number of responses to dietary boron occur. The findings indicate that boron is important for optimal calcium and, thus, bone metabolism. High dietary cystine and fructose exacerbate the signs of copper deficiency in rats; this indicates that the response to copper deficiency by humans would vary with the amino acid and carbohydrate composition of the diet. There is some evidence that chromium, molybdenum, nickel, arsenic, and vanadium may also be of nutritional significance under stress conditions. In other words, an increasing number of studies have been performed that have examined the importance of trace element nutriture in various forms of nutritional, metabolic, hormonal, or physiologic stress in animals and humans. These studies indicate that situations will be found in which a trace element is of nutritional significance. It is likely that some of the trace elements are more important in human nutrition than is now generally acknowledged.

Does of the local myocardial release of prostaglandin E 2 or F 2α contribute to the early consequences of acute myocardial ischaemia?

The possible role of prostaglandins in acute myocardial ischaemia was investigated in anaesthetized greyhounds which were subjected to either short (3 min) occlusions or permanent ligation of the left anterior descending coronary artery. Plasma PGE 2 and PGF 2α concentrations were measured by radioimmunoassay in blood from the aorta, the coronary sinus (draining the essentially normal myocardium) and from a local coronaryvein (draining the area rendered ischaemic by coronary artery ligation). In the permanent ligation studies PGE 2 and PGF 2α were measured before, and 2, 10 and 30 min post-ligation. At 2 and 10 min post ligation there were no significant changes in the concentrations of either prostaglandin in blood from the essentially normal myocardium or from the acutely ischaemic myocardium. After 30 min of coronary artery ligation there was a significant increase in PGE 2 in the local coronary vein. This release of PGE 2 from the ischaemic myocardium was not related to the occurrence of cardiac dysrhythmias but may reflect the onset of changes in cellular integrity in the developing area of infarction. Despite electrocardiographic and metabolic evidence of acute myocardial ischaemia there was no increase in PGE 2 or PGF 2α values in either the coronary sinus or the local coronary vein following the release of a 3-min coronary artery occlusion. Since neither PGE 2 nor PGF 2α is released from the acutely ischaemic myocardium during the first 10 min post-ligation or during reperfusion following 3-min occlusions, it is unlikely that either of these prostaglandins is involved in the early consequence of coronary artery ligation.

SOME PHYSIOLOGICAL DIFFERENCES IN VIBRIO MARINUS GROWN AT ENVIRONMENTAL AND OPTIMAL TEMPERATURES1

Cells of an obligately psychrophilic marine bacterium, Vibrio marinus, were grown at environmental (4C) and optimal (15C) temperatures and tested for physiological differences. Sugar fermentation patterns and temperature‐shift growth studies showed no differences, but membrane stability and glucose utilization were affected. The cells grown at 15C were more heat stable and utilized glucose at a faster rate than the cells grown at 4C. These differences were attributed to changes in cellular integrity or membrane integrity, or both. The results indicated that for correlation of in vitro results with in situ conditions, marine microorganisms should be grown at the temperature and under the nutrient conditions of their natural habitat.