Two different charge-separation pathways in photosystem II

Charge separation is an essential step in the conversion of solar energy into chemical energy in photosynthesis. To investigate this process, we performed transient absorption experiments at 77 K with various excitation conditions on the isolated Photosystem II reaction center preparations from spinach. The results have been analyzed by global and target analysis and demonstrate that at least two different excited states, (Ch

Photoacclimation in Dunaliella tertiolecta reveals a unique NPQ pattern upon exposure to irradiance

Highly time-resolved photoacclimation patterns of the chlorophyte microalga Dunaliella tertiolecta during exposure to an off–on–off (block) light pattern of saturating photon flux, and to a regime of consecutive increasing light intensities are presented. Non-photochemical quenching (NPQ) mechanisms unexpectedly responded with an initial decrease during dark–light transitions. NPQ values started to rise after light exposure of approximately 4 min. State-transitions, measured as a change of PSII:PSI fluorescence emission at 77 K, did not contribute to early NPQ oscillations. Addition of the uncoupler CCCP, however, caused a rapid increase in fluorescence and showed the significance of qE for NPQ. Partitioning of the quantum efficiencies showed that constitutive NPQ was (a) higher than qE-driven NPQ and (b) responded to light treatment within seconds, suggesting an active role of constitutive NPQ in variable energy dissipation, although it is thought to contribute statically to NPQ. The PSII connectivity parameter p correlated well with F′, Fm′ and NPQ during the early phase of the dark–light transients in sub-saturating light, suggesting a plastic energy distribution pattern within energetically connected PSII centres. In consecutive increasing photon flux experiments, correlations were weaker during the second light increment. Changes in connectivity can present an early photoresponse that are reflected in fluorescence signals and NPQ and might be responsive to the short-term acclimation state, and/or to the actinic photon flux

Assessment of combined treatment with vigabatrin and antihypertensive drugs against electroconvulsions in mice

Introduction and objective: It is likely that cardiovascular drugs will be used in epileptic patients because heart failure and hypertension are common comorbid conditions with epilepsy. Experimental studies show that some cardiovascular drugs can affect the protective activity of antiepileptics. The aim of this study was to examine the effects in mice of angiotensin-converting enzyme (ACE) inhibitors (captopril and perindopril), angiotensin AT1 receptor antagonists (losartan and candesartan) and diuretics (hydrochlorothiazide and ethacrynic acid) on the anticonvulsant activity of vigabatrin (VGB), a second generation antiepileptic drug. Material and Methods: Adult Swiss mice were used in the study. The anticonvulsant action of VGB was assessed in the maximal electroshock seizure threshold test. Combined treatment with VGB and antihypertensive drugs was also tested for adverse effects in the passive avoidance task and chimney test. All drugs were administered intraperitoneally. Results: Captopril (50 mg/kg), perindopril (10 mg/kg), losartan (50 mg/kg), candesartan (8 mg/kg), hydrochlorothiazide (100 mg/kg) and ethacrynic acid (100 mg/kg) did not influence the protective action of VGB. The combined treatment with VGB (700 mg/kg) and antihypertensive drugs showed a strong tendency towards impaired retention in the passive avoidance task, and in the case of the combination of VGB with ethacrynic acid it reached statistical significance (P < 0.05). Mice were not disturbed in the chimney test following applied treatment. Conclusions: From the preclinical point of view, the use of the tested antihypertensive drugs in patients treated with VGB seems neutral regarding its anticonvulsant activity

Homocysteine, antioxidant vitamins and lipids as biomarkers of neurodegeneration in Alzheimer’s disease versus non-Alzheimer’s dementia

Introduction and objective Evidence for the benefit of antioxidants’ based therapeutic intervention in dementia are inconsistent. Parallel studies in disease forms of dementia different than Alzheimer’s are even less conclusive. In this study, the role of serum levels of homocysteine (tHcy), lipids and antioxidants in predicting the risk of cognitive decline in Alzheimer’s disease (AD) versus non-Alzheimer’s dementias (n-AD). The objective was to add to the ongoing cumulative research to establish the biochemical baseline for potential nutri-therapeutic intervention in different forms of dementia. Material and Methods 65 participants with dementia (DP-s) were divided into two groups: ADP – patients with Alzheimer’s disease and n-ADP – patients with dementia of a different etiology than primary neurodegenerative dementia in the course of Alzheimer’s disease. Cognitive function was assessed by Mini-Mental State Examination (MMSE) and related to plasma levels of tHcy, folate, vitamins B-6, B-12, lipids and vitamins A and E for both groups. Also examined were associations between cognitive impairment and several variables (age, education, duration of dementia) that might confound nutrition-cognition associations. Results A significant reduction in serum vitamin A levels and elevation of total cholesterol levels were shown for the DP-s group compared to those in the control group. Moreover, significant differences were found in MMSE data and serum vitamin E and tHcy levels between patients with ADP and n-ADP. The scores for MMSE showed a correlation with the vitamin E levels and duration of dementia in the ADP group and/or correlation with tHcy, levels of vitamins A and/or E, and duration of dementia in the n-ADP group. Conclusions The results obtained suggest that elevated serum tHcy and decreased levels of vitamins A and E are associated with an increased risk of non-Alzheimer’s dementias, although further studies involving a larger cohort are now needed to verify these results