Increased Stress Sensitivity Research Articles

Expression of Arabidopsis CAX1 in tobacco: altered calcium homeostasis and increased stress sensitivity.

Calcium (Ca(2)+) efflux from the cytosol modulates Ca(2+) concentrations in the cytosol, loads Ca(2+) into intracellular compartments, and supplies Ca(2+) to organelles to support biochemical functions. The Ca(2+)/H(+) antiporter CAX1 (for CALCIUM EXCHANGER 1) of Arabidopsis is thought to be a key mediator of these processes. To clarify the regulation of CAX1, we examined CAX1 RNA expression in response to various stimuli. CAX1 was highly expressed in response to exogenous Ca(2+). Transgenic tobacco plants expressing CAX1 displayed symptoms of Ca(2+) deficiencies, including hypersensitivity to ion imbalances, such as increased magnesium and potassium concentrations, and to cold shock, but increasing the Ca(2+) in the media abrogated these sensitivities. Tobacco plants expressing CAX1 also demonstrated increased Ca(2+) accumulation and altered activity of the tonoplast-enriched Ca(2+)/H(+) antiporter. These results emphasize that regulated expression of Ca(2+)/H(+) antiport activity is critical for normal growth and adaptation to certain stresses.

Audiogenic seizure sensitivity in mouse lines genetically selected for high versus low blood magnesium levels.

The MGH and MGL mouse lines, genetically selected for high and low blood magnesium (Mg) levels, respectively, exhibit marked differences for characteristics expected to be related to blood Mg levels, such as increased stress sensitivity and stress-induced aggressivity in MGL mice. However, although Mg deficiency experimentally induced by low oral Mg intake has been shown previously to increase susceptibility to audiogenic seizures, MGL were less sensitive to audiogenic seizures than MGH mice. The MGH-MGL lines may, therefore, provide a beneficial and complementary model for the study of the relationships between audiogenic seizures and blood Mg levels.

Inactivation by gene disruption of 2‐cysteine‐peroxiredoxin in Synechocystis sp. PCC 6803 leads to increased stress sensitivity

2‐Cysteine‐peroxiredoxins (2‐CP) constitute a ubiquitous group of enzymes which reduce toxic alkyl hydroperoxides. In higher plants it was shown that the nuclear encoded 2‐CPs are posttranslationally imported into the chloroplasts, the site of most active oxidative metabolism in plants (Baier and Dietz 1997, Plant J. 12; 179‐190). The genome of the bluegreen alga Synechocystis (EMBL acc. # D64000) encodes a 2‐CP which shares 60% homology to higher plant 2‐CPs on the gene level and about 70% on the level of the mature protein. In order to elucidate the physiological significance of 2‐CPs for photosynthetic organisms, the 2‐CP gene was mutated in Synechocystis sp. PCC 6803 by insertion of a kanamycin gene cartridge. Following complete segregation mutant lines were analyzed for growth and photosynthetic parameters. The mutants revealed decreased growth rates as compared to the wild type. Growth inhibition was relieved after lowering the concentration of Fe or trace elements in the growth medium. Chlorophyll a fluorescence transients as induced by saturating light pulses were used as indicator for the state of photosynthesis. The effective quantum yield decreased at lower light intensities in the mutants as compared to the wild type Synechocystis. Simultaneously, electron transport rates saturated at lower light intensities in the mutants. These data provide the first evidence that 2‐CPs play a pivotal protective role in photosynthesis.

Investigation of the Personality Structure in Patients with Vitiligo and a Possible Association with Impaired Catecholamine Metabolism

Patients with vitiligo show an increased beta 2-adrenoceptor density in differentiating vitiliginous keratinocytes correlating with a defective extracellular calcium uptake. Thirty-one percent of the patients present increased norepinephrine levels in their urine and 98% in their plasma. The aim of this study was to find out whether these patients may: (a) have a characteristic personality structure and/or (b) show an increased stress sensitivity towards physical/environmental/hormonal changes in association with a defective catecholamine metabolism. The investigation included a randomized group of 117 patients with vitiligo (89 female, 28 male). Catecholamines were determined in plasma in a random sample of the total group (n = 30, M/F = 10/20). Norepinephrine levels in plasma were significantly higher compared to controls, whereas epinephrine was within the normal range. No specific personality pattern was found although divergencies from the normal healthy control were observed in 5 out of 12 personality dimensions. Moderate to intolerable disfigurement and psychological disturbance were stated by 75% of the patients. Evaluation of the educational status revealed that 26.5% of the patients graduated successfully from university compared to 8.4% in the normal population. The results of this study suggest a possible link between catecholamine-based stress and a genetic susceptibility to the onset/progression of this depigmentation disorder.

Influence of NH3and (NH4)2SO4on heathland vegetation

Heathland is currently being threatened by nitrogenous atmospheric deposition, mainly NHy (NH3 and NH+4). Deschampsia flexuosa and Calluna vulgaris in monocultures were well able to use NHy for biomass production, although in the case of C. vulgaris only shoot growth was stimulated and C. vulgaris increased its sensitivity to drought and the heather beetle (Lochmaea suturalis). In a mixed culture of C. vulgaris and D. flexuosa, the latter species was the better competitor for NHy. The relation between stimulated biomass production and increased stress sensitivity also applied to several other heathland species. A general effect threshold for adverse effects of NH3 on plants has been established with a toxicological model: 270 and 8 μg m−3 for a daily and annual mean, respectively. Heathland species are relatively sensitive to NHy.

The Comparative Morphology of the Muscle Tissues and Changes of Constituents in the Pig Types

The authors have revealed the main value characteristics of pork production by testing in five different types of pig the volume of contractile and collagen proteins, that of proteoglycans, the constituents of blood and the enzymes of the blood plasma. The contractile proteins of the muscle tissues basically determine the quality of pork. The same applies to the water retention capacity, colloidal characteristics and glycogen content of meat. The amount of contractile proteins has decreased in the best meat producing types of pig. Parallel with the decrease of white meat, and with the increase in the volume of ham, chop and chuck the contractile protein content of muscles decreased. The scientific fact according to which there is a certain correlation among the changes in the volume of contractile proteins, blood sugar level, blood serum CPK and the intensity of activity of the LDH enzymes promotes the qualifying of live animals and the work of the geneticists aiming at the increasing of the contractile protein content of the muscle tissues of pigs by selection. According to tests carried out by us the primary cause of PSE changes is a decreased volume of contractile proteins. Increased stress sensitivity and all the other factors have but a secondary importance and are all consequential. The decrease in the quantity of contractile proteins or--it is better to put it this way--the lack of the proper amount of such proteins characterizing a fully developed pig's organism is caused by the nowadays usual breeding technologies and can be well explained by those selection activities which aim at a one-sided kind of pork production.