Ursachen der Frostresistenz bei Winterweizen

Ohne ZusammenfassungMit 15 Textabbildungen     

Apoplastic Ascorbate Does not Prevent the Oxidation of Fluorescent Amphiphilic Dyes by Ambient and Elevated Concentrations of Ozone in Leavesl

Cut leaves of spinach were infiltrated with solutions containingoxidation-sensitive fluorescent dyes. Excess solution was removedfrom the intercellular space by centrifugation. Fluorescenceof the dyes D494 and D283 started to decrease immediately afterthe onset of fumigation with ozone at concentrations similarto or not much higher than ambient concentrations in air onsunny days. Only part of ozone entering the leaves was interceptedby the dye. The major part was degraded by unspecified reactions.Photosynthesis was not inhibited while the introduced dye wasoxidized by ozone, showing that open stomata facilitated gasexchange after the introduction of dye into the leaf interior.Feeding of ascorbate to the leaves via the petiole failed toaffect the ozone-dependent decrease in fluorescence emissionfrom the dye. Likewise, infiltration of leaves by solutionscontaining dye and 10 mM ascorbate did not produce significantprotection of the dye against oxidation by ozone. However, suchprotection was observed in vitro, when solutions of dye andascorbate were bubbled with air containing ozone. Although thereis little doubt that apoplastic ascorbate occupies a centralposition in the antioxi-dative defense of leaf tissue, we aresurprised to find that it is much less effective than expectedto decrease the oxidation of fluorescent lipophilic probes whichhad been introduced into the leaf interior. The data suggestthat ascorbate is not a primary reductant of ozone in the apoplast.With a microscope-mounted CCD-camera connected to the gas exchangeequipment we obtained spatial information on the fluorescencesignal and present first results on an heterogeneous distributionof ozone action. (Received June 20, 1997; Accepted December 26, 1997)     

Confort térmico y el riesgo de infecciones respiratorias en los adultos mayores en la sierra rural del Perú

The objective is to evaluate thermal comfort in the rural highlands of Peru and determine if thermal conditions influence the risk of respiratory infections. The probit regression model is used for this, with the unit of analysis being adults over 60 years of age. The information source is the data from the National Household Survey and the National Service of Meteorology and Hydrology of Peru. In addition, it was possible to monitor the temperature and the interior relative humidity of 4 types of bedrooms with a thermo-hygrometer and compared it with the desired thermal comfort index criterion. The results show that if the air temperature drops on average by one degree (1° C) in the area of residence, the probability of risk of respiratory infections in older adults increases by 0.18, although the relative humidity and the wind speed were not statistically significant at 1% significance level. Finally, the 4 types of bedrooms evaluated lacked the desired thermal comfort and increased the risk of acquiring respiratory infections.     

Pituitary receptor binding activity of active, inactive, superactive and inhibitory analogs of gonadotropin-releasing hormone.

We have previously described the binding of biologically active ¹²⁵I gonadotropin-releasing hormone to the 10,800 × g membrane fraction prepared from 7-day castrate adult female rat anterior pituitary glands. Specific binding with two equilibrium association constants (10⁹ liters per mole and 10⁵ liters per mole) was found and an equilibrium competitive binding radio-receptor assay established. In order to further characterize the gonadotropin-releasing hormone receptor, 20 synthetic analogs with known bioactivity were tested in the radioreceptor assay. In vivo biological activity correlated with high affinity receptor binding but not with low affinity binding. Inhibitory analogs with no in vivo biological activity and weak antagonistic properties did not bind, while in vivo active or superactive analogs bound to high affinity receptors. These findings suggest that the high affinity gonadotropin-releasing hormone receptor binds only biologically active gonadotropin-releasing hormone like peptides and that this binding may be the initial step in gonadotropin-releasing hormone actions at the pituitary level.