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At least 379 records · Page 21Linked to original sources
PubMed2001

The response of shoot accumulation of trace elements in Chinese cabbage to microclimate modification.

In three consecutive years of field experiments (1994-96), three different environmental conditions for the growth of Chinese cabbage (Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50) were established by using two cover treatments (T1 and T2) and a control uncovered cultivation (T0). The T1 [50 microm polyethylene cover; 20 degrees C air temperature; 61.9% relative moisture; 207 Wm(-2) irradiance] and T2 [a 17 gm(-2) non-woven fleece; 18 degrees C; 63.4%; 205 Wm(-2) gave rise to differences in environmental conditions with respect to T0 [14 degrees C; 57.5%; 237 Wm(-2)]. We analysed chloride (Cl), barium (Ba). rubidium (Rb) and tin (Sn) in the whole tops of experimental plants. Chloride removal was high for Brassica pekinensis but considerably lower for Rb, giving intermediate values for Ba and Sn. The influence of environmental factors under T1 increased trace-element removal and enhanced the usefulness for phytoremedation.

Air Conditioning↗
PubMed1978

An ATPase dependent, radiosensitive acidic microclimate essential for intestinal folate absorption.

1. 5-Methyltetrahydrofolic acid transport was studied across everted sacs of rat jejunal segments from control and whole body X-irradiated (700 rad) rats at 10(-5)M concentrations (at which optimum transport occurs) at various pHs.2. The folate transport from mucosal to serosal compartment was inhibited by about 55% in irradiated rat at the pH of the intestinal chyme (6.5). Extraneous ATP in the incubation system could restore the defective transport of the irradiated intestine.3. The maximum folate transport which occurred at pH 4.0 was not adversely affected by whole body irradiation. An acidic, pH dependent, passive uptake of 5-methyltetrahydrofolic acid was observed.4. The normal absorption barrier of the small bowel was not disrupted by the acidification process as practically no uptake was observed with irradiated segments pretreated at pH 4.0 except in the presence of ATP.5. Leucine and serine transport at a zero concentration gradient indicated active transport mechanisms which were not affected by acidification. Their uptake was additively increased in the presence of glucose and ATP, further indicating that the normal physiology of the intestines was not affected by the acidification process.6. An intestinal mucosal cell surface ATPase was observed which was Mg(2+) dependent. It could hydrolyse solution phase ATP and thus generate the protons necessary for the acidification of a microenvironment where passive uptake of the neutral folate species could occur.7. The ATPase activity was inhibited about 90% by 50 mM-Na azide at pH 6.5. Below this concentration folate transport was also inhibited.8. Na azide did not inhibit folate transport at pH 4.0, suggesting that its inhibition of folate uptake at pH 6.5 is related to its inhibitory effect on ATPase, rather than on folate transport per se. ATPase activity was therefore essential for folate transport at the pH of the intestinal chyme.

Adenosine Triphosphatases↗
PubMed1978

Acid microclimate in coeliac and Crohn's disease: a model for folate malabsorption.

The surface pH of human proximal jejunum was measured in biopsy samples and found to be more acid than the phosphate buffer in which they were incubated. The in vitro jejunal surface pH was 5.93 +/- 0.05 in control subjects and 6.19 +/- 0.09 in treated coeliac patients. A group of untreated coeliac patients with a surface pH of 6.56 +/- 0.14 had a significantly less acid surface pH compared to controls, as did a group of Crohn's patients with a surface pH of 6.21 +/- 0.04. These two groups with a significantly raised surface pH were subdivisible into 'high' and 'low'groups. Surface pH was found to remain low in the treated coeliac and control groups but became more acid over the incubation period reaching almost normal values in the Crohn's group and the untreated coelic initial surface pH. The raised surface pH in untreated coeliac disease and Crohn's disease would alter the amount of a weak acid available for non-ionic diffusion. Therefore the present results may help to explain the folate malabsorption known to occur in untreated coeliac disease and the frequently seen low serum folate levels in Crohn's disease.

Adolescent↗
PubMed1988

Acidic colonic microclimate--possible reason for false negative hydrogen breath tests.

About 5% of normal subjects fail to produce increased hydrogen breath concentration after ingestion of the non-digestible carbohydrate lactulose (low hydrogen producers). The existence of low hydrogen producers limits the diagnostic use of hydrogen (H2) breath tests. We studied the effects of lactulose and of magnesium sulphate (MgSO4) pretreatment on stool-pH and on hydrogen exhalation after oral loading with lactulose or lactose in 17 hydrogen producers and 12 low hydrogen producers. In seven hydrogen producers acidification of stool pH by lactulose pretreatment (20 g tid) decreased hydrogen exhalation and three of seven (43%) became low hydrogen producers. In contrast, after pretreatment of eight low hydrogen producers with magnesium sulphate (5 g twice daily) all eight produced hydrogen after a lactulose load. Similarly four lactose intolerant low hydrogen producers had abnormal lactose hydrogen breath tests after MgSO4 pretreatment. MgSO4 pretreatment neither resulted in false positive lactose hydrogen breath tests in five lactose tolerant hydrogen producers, nor increased the hydrogen exhalation in five additional hydrogen producing controls after ingestion of lactulose. The results of these studies confirm that hydrogen production from lactulose decreases when the colonic pH is lower (lactulose pretreatment), and increases when colonic pH is higher (MgSO4 pretreatment). In low hydrogen producers the lacking increase of H2 exhalation after ingestion of non-digestible carbohydrates can be overcome by MgSO4 pretreatment, thus increasing the sensitivity of the test by avoiding false negative hydrogen breath tests in low hydrogen producers with disaccharide malabsorption or maldigestion. The underlying mechanism of this remarkable effect of MgSO4 pretreatment warrants further investigation.

Breath Tests↗
PubMed1999

Electro-ionic microclimate and materials used in the indoor environment.

In 170 experiments relationships between 31 different materials used in indoor premises and ionization of the air in their proximity were assessed. The influence of temperature and relative humidity on ionization of air was studied. It was observed that the materials tested could be divided into four groups according to their behaviour towards ambient light negative ions. From the results obtained it follows that the more humid and thus more conductive the material in question, the greater is its influence on the ionization of the air. The most important criterion influencing the relationship of the material and ambient air ionization is the magnitude of the contacting surface of the material that is given by its ruggedness and structure. In natural materials considerable porosity may be expected. In contrast smooth surfaces without pores can be expected in materials produced by melting. Other physico-chemical properties of the materials are manifested in a more discrete way.

Air Ionization↗
PubMed1999

[Ecology of Lymnaea truncatula Müller, intermediate host of Fasciola hepatica Linné in the microclimate of Tozeur (southeast of Tunisia)].

Systematic visits were carried out in the traditional Tozeur' oasis (Tunisia), in 1997/1998 in order to study the ecology of Lymnaea truncatula as well as its density in relation to habitat characteristics in the hydrographical networks of the oases. Lymnaea truncatula was enumerated on 1 m2 surface by habitat, according to the quadrat method. Samples of soil, irrigation and draining water were also analysed. The density of Lymnaea truncatula detected in autumn was constantly higher. It depends on the nature of the habitat: 54.8% in the secondary irrigation canals, 34.8% in those of draining, 7.6% in the seguia and 2.9% in the principal draining canal. Ecological factors--permanent dampness, suitable luminosity, basic pH of soil and water, temperature between 10 and 28 degrees C--contribute to the multiplicity of snails.

Animals↗