New Insights into Leaf Physiological Responses to Ozone for Use in Crop Modelling.

Estimating food production under future air pollution and climate conditions in scenario analysis depends on accurately modelling ozone (O3) effects on yield. This study tests several assumptions that form part of published approaches for modelling O3 effects on photosynthesis and leaf duration against experimental data. In 2015 and 2016, two wheat cultivars were exposed in eight hemispherical glasshouses to O3 ranging from 22 to 57 ppb (24 h mean), with profiles ranging from raised background to high peak treatments. The stomatal O3 flux (Phytotoxic Ozone Dose, POD) to leaves was simulated using a multiplicative stomatal conductance model. Leaf senescence occurred earlier as average POD increased according to a linear relationship, and the two cultivars showed very different senescence responses. Negative effects of O3 on photosynthesis were only observed alongside O3-induced leaf senescence, suggesting that O3 does not impair photosynthesis in un-senesced flag leaves at the realistic O3 concentrations applied here. Accelerated senescence is therefore likely to be the dominant O3 effect influencing yield in most agricultural environments. POD was better than 24 h mean concentration and AOT40 (accumulated O3 exceeding 40 ppb, daylight hours) at predicting physiological response to O3, and flux also accounted for the difference in exposure resulting from peak and high background treatments.

Homocysteine as a risk factor for cognitive impairment in stroke patients.

BACKGROUND: Elevated total homocysteine (tHcy) levels are associated with an increased risk of cerebrovascular disease. It is uncertain whether tHcy is also an independent risk factor for cognitive impairment. METHODS: We examined 95 stroke subjects 3 months after their strokes, and 55 healthy comparison subjects, with a detailed neuropsychological assessment, and MRI brain scans in a proportion (n = 97). Baseline measurements of tHcy, serum folate and B(12), creatinine and plasma fibrinogen levels were obtained. RESULTS: tHcy levels were higher in the stroke subjects by a mean 34%. These levels were significantly correlated with the first factor of a principal component analysis of the neuropsychological data, after controlling for age, folate, B(12) and creatinine levels. The correlation of Hcy levels was particularly significant with frontal-executive functioning and attention. tHcy levels were significantly correlated with number of infarcts and total stroke volume in the stroke group, but not with T(2)-weighted deep white matter hyperintensity scores, after correction for age. In the control group, tHcy levels were significantly correlated with ventricle-to-brain ratios as measures of brain atrophy. CONCLUSION: This study provides evidence that high tHcy levels are associated with cognitive impairment, in particular that of frontal-executive function. The major component of this association is accounted for by small and large strokes, but non-vascular neurotoxic effects of tHcy also appear to play a role. tHcy must receive greater attention as a risk factor for cognitive impairment.

[The merits of comprehensive therapy for acute stroke].

OBJECTIVE: To evaluate the advantages of comprehensive therapy for acute stroke in a stroke unit. METHODS: The data of 207 acute stroke patients treated in a stroke unit in Australia (group A) were compared with those of 326 acute stroke patients treated in our neurological ward (group B). They were diagnosed by CT or MRI and found to have hemiplegia in 48 hours. RESULTS: There were significant differences between group A and group B in mortality within 14 days (5.3% vs 10.4%), rate of non-cerebral causes of death (27.3% vs 64.7%) and rate of infection (17.9% vs 47.9%), P < 0.01. Moreover the scores of Europe Stroke Scale at 21 days and Modified Rankin Scale at 90 days were significantly different between the two groups (P < 0.01). CONCLUSION: Prognosis of acute stroke patients managed by comprehensive therapy in stroke unit was superior to that treated conventionally in neurological ward.