Tracking of Mental Workload with a Mobile EEG Sensor

The aim of the present investigation was to assess if a mobile electroencephalography (EEG) setup can be used to track mental workload, which is an important aspect of learning performance and motivation and may thus represent a valuable source of information in the evaluation of cognitive training approaches. Twenty five healthy subjects performed a three-level N-back test using a fully mobile setup including tablet-based presentation of the task and EEG data collection with a self-mounted mobile EEG device at two assessment time points. A two-fold analysis approach was chosen including a standard analysis of variance and an artificial neural network to distinguish the levels of cognitive load. Our findings indicate that the setup is feasible for detecting changes in cognitive load, as reflected by alterations across lobes in different frequency bands. In particular, we observed a decrease of occipital alpha and an increase in frontal, parietal and occipital theta with increasing cognitive load. The most distinct levels of cognitive load could be discriminated by the integrated machine learning models with an accuracy of 86%.

Co-occurrence of patological gambling and alcohol dependence like common behavior

Introduction

Pathological gambling and alcoholism are more common. In recent literature many factors may increase the risk for both conditions (social, cognitive, genetic, psychopharmacological).

Objectives

Experts talk about problematic behavior linking gambling and alcoholism and the terms „disordered gambling behavior“ and „disordered alcoholics behavior“ occurrence like common behaviour. Most gamblers drink alcohol during gambling.

Aim

Our paper show that some kind of disordered or dysfunctional behavior among pathological gambling and alcoholism presented common behavior frame for both of them.

Methods

We observed 25 male inpatients/outpatients, range of age between 20 – 50, for six months period of time who were treated in Department of Alcoholism in Special Hospital On Addictions, Belgrade, Serbia.We used the ICD-X diagnostic criteria for pathological gambling and alcohol dependence (excluded other disorder and co morbidity), data collected by medical history of illnes, psychiatry interview and check list for behavior disorder for both conditions.

Results

All the patients have negative consequences of their pathological gambling and alcoholism like loss the money, loss the job,disfunctonal family and partners relationships, loss of friends, avoid school and other peer activities, improve criminal behavior, sleep disorder, anxiety, depressive mood disorder. Also, occurrences the impulsivity behavior and lack of control as common factor for both behavior.

Conclusion

According the available literature and ICD-X do not meet the diagnostic criteria for common behavior disorder co-occurrence of pathological gambling and alcoholism yet, but determine „event-level“ like co-occurrence of gambling and drinking behavior. Some paper like this shows that exist common behavior linking gambling and alcoholism.

Sleep habits and sleep complaints in Austria: current self-reported data on sleep behaviour, sleep disturbances and their treatment

OBJECTIVES

To acquire current information on sleep habits, disturbances and treatment options in the adult population of Austria and compare results with previously collected data.

MATERIALS AND METHODS

A representative sample of the Austrian population (women: n = 522, men: n = 478).

RESULTS

Seventy-five percent reported daily sleep-duration between 6 and 8 h. In 76%, sleep latency was <30 min, 15% described difficulties in sleep maintenance. Longer sleep on weekends was prevalent in 54%, 23% took a nap. Concerning sleep environment, 31% reported sleeping alone; the rest had a constant or occasional bed partner. Sleep disturbances such as sleep disruption or prolonged sleep latency were reported by 18%. Predominant symptoms included snoring/apneas (22%), nightmares (22%) and restless legs (21%). Daytime tiredness was reported by 17% and sleepiness by 20%. Twenty-four percent did not take treatment. Only 7% asked for medical help: 96% consulted their physician; 47% tried to change their way of living. Sleep promoting drugs were taken by 7%. Sleep improving measures were: sleep promoters (45%), general measures (20%), consultation of general practitioner (20%), psychotherapy (6%), and technical tools (3%). Comparison with a dataset of 1993 revealed only a slight increase in short sleepers and a slight decrease in long sleepers.

CONCLUSIONS

Subjectively reported sleep disorders proved to be relatively stable between 1993 and 2007.

The 10-year follow-up data of the Euro-Lupus Nephritis Trial comparing low-dose and high-dose intravenous cyclophosphamide

OBJECTIVE

To update the follow-up of the Euro-Lupus Nephritis Trial (ELNT), a randomised prospective trial comparing low-dose (LD) and high-dose (HD) intravenous (IV) cyclophosphamide (CY) followed by azathioprine (AZA) as treatment for proliferative lupus nephritis.

PATIENTS AND METHODS

Data for survival and kidney function were prospectively collected during a 10-year period for the 90 patients randomised in the ELNT, except in 6 lost to follow-up.

RESULTS

Death, sustained doubling of serum creatinine and end-stage renal disease rates did not differ between the LD and HD group (5/44 (11%) vs 2/46 (4%), 6/44 (14%) vs 5/46 (11%) and 2/44 (5%) vs 4/46 (9%), respectively) nor did mean serum creatinine, 24 h proteinuria and damage score at last follow-up. Most patients in both groups were still treated with glucocorticoids, other immunosuppressant agents and blood pressure lowering drugs. After 10 years of follow-up, the positive predictive value for a good outcome of an early drop in proteinuria in response to initial immunosuppressive therapy was confirmed.

CONCLUSION

The data confirm that a LD IVCY regimen followed by AZA-the "Euro-Lupus regimen"-achieves good clinical results in the very long term.

Rapid Chlorophyll a Fluorescence Transients of Lemna minor Leaves as Indication of Light and Exogenous Electron Carriers Effect on Photosystem II Activity

By using saturating flash, we investigated the change in the rapid fluorescence rise when Lemna minor leaf was exposed to different light conditions and treated with exogenous electron acceptors (methyl viologen and duroquinone) and electron donor (hydroxylamine). Investigation was carried out by using combined pulse amplitude modulated fluorometer and plant efficiency analyzer system, which were employed simultaneously to provide different light conditions and to induce rapid fluorescence rise respectively. We have shown that when leaf of L. minor was exposed to different conditions of illumination, rapid fluorescence rise was greatly influenced by the electron transport functions beyond quinone A-plastoquinone reduction. This was indicated by the change in both fluorescence yield and appearance time of the different transients. When exogenous electron donor (hydroxylamine) and acceptors (methyl viologen and duroquinone) were applied in in vivo condition, we showed that rapid fluorescence rise represented a reliable indicator of PSII-PSI electron transport state and energy dissipation process.

Systemic lupus erythematosus in Europe at the change of the millennium: lessons from the "Euro-Lupus Project"

The "Euro-Lupus Cohort" is composed by 1000 patients with systemic lupus erythematosus (SLE) that have been followed prospectively since 1991. These patients have been gathered by a European consortium--the "Euro-Lupus Project Group". This consortium was originated as part of the network promoted by the "European Working Party on SLE", a working group created in 1990 in order to promote research in Europe on the different problems related to this disease. The "Euro-Lupus Cohort" provides an updated information on the SLE morbidity and mortality characteristics in the present decade as well as defines several clinical and immunological prognostic factors.

Effects of socio-demographic variables on health-related quality of life determined by the quality of life index--German version

STUDY OBJECTIVE

The purpose of this study was to determine subjective health-related quality of life (HRQoL) in a sample of the Austrian population over 14 years of age in order to evaluate the effect of socio-demographic variables on HRQoL.

DESIGN/SETTING

HRQoL was determined by means of the quality of life index-German version (QLI-Ge). The influence of socio-demographic variables on HRQoL was assessed by statistical analysis using the Kruskal-Wallis test and an analysis of variance.

PARTICIPANTS

A random-quota procedure was used to get balanced representation from regions and demographic groups of the Austrian population. The sample consisted of 1049 participants, 493 men and 556 women.

MAIN RESULTS

Age was found to influence the QLI-Ge total score (index score) and most individual items, with increasing age resulting in a decrease in HRQoL. Differences between the sexes were observed in three dimensions: males scored higher in 'physical well-being', 'psychological well-being' and 'occupational functioning'. Marital status impacted most items with married persons showing better values than divorced persons or singles. Profession had only a minor effect on HRQoL, the level of education showed no influence at all.

CONCLUSIONS

The socio-demographic variables age, sex and objective living conditions had a major influence on subjectively rated HRQoL, whereas profession and education were found to play a minor role in this context. It is recommended that in the interpretation of studies assessing HRQoL the above-mentioned objective factors be considered. This will be of particular importance when determining the effect of a pharmacotherapy on HRQoL in patients.

Oxyfluorfen toxic effect on S. obliquus evaluated by different photosynthetic and enzymatic biomarkers

The effect of oxyfluorfen was investigated when alga Scenedesmus obliquus has been exposed to different concentrations (7.5, 15, and 22.5 microg x L(-1)) at 12, 24, and 48 hours of exposure. Toxicity test was done by using 13 biomarkers concerning growth rate, chlorophyll content and indicators of photosynthetic and antioxidant enzyme activities. The change of the 13 parameters showed a great variation of sensitivity indicating differences in parameters' suitability to be used as biomarkers when alga culture was exposed to oxyfluorfen toxicity. The order of sensitivity between those biomarkers was: Antenna size (ABS/RC) > Chlorophyll content > Catalase (CAT) > Operational PSII quantum yield (phiS(PSII)) > Glutathione S-transferase (GST) > Functional plastoquinone pool (Q(PQ)) > Glutathione reductase (GR) > Growth rate > Nonphotochemical quenching (QN) > Proton gradient quenching (Q(Emax)) > Ascorbate peroxidase (APX) > Photochemical quenching (Q(p)) > Maximum PSII quantum yield (Phi(PSII)). The effect of oxyfluorfen on the changes of those parameters was interpreted as a result of herbicide mode of action at molecular level of alga cellular system. This study indicated for some photosynthetic and enzymatic biomarkers to be useful indicators of toxicity effect induced in non-target alga species. Determination of biomarkers' sensitivity order may facilitate their selection to be used in environmental risk assessment of polluted water.

Lessons from the "Euro-Lupus Cohort"

The "Euro-Lupus Cohort" is composed by 1,000 patients with systemic lupus erythematosus (SLE) that have been followed prospectively since 1991. These patients have been gathered by a European consortium - the "Euro-Lupus Project Group". This consortium was originated as part of the network promoted by the "European Working Party on SLE", a working group created in 1990 in order to promote research in Europe on the different problems related to this disease. The "Euro-Lupus Cohort" provides an updated information on the SLE morbidity and mortality characteristics in the present decade as well as defines several clinical and immunological prognostic factors.

PAM fluorometry in the determination of the sensitivity of Chlorella vulgaris, Selenastrum capricornutum, and Chlamydomonas reinhardtii to copper

The pulse-amplitude-modulation (PAM) fluorometric method was used in the past as a sensitive and rapid method for assessing toxic effect of pollutants in plants. Here, we used the advantages of this method to evaluate the difference in sensitivity of Chlorella vulgaris, Selenastrum capricornutum, and Chlamydomonas reinhardtii to copper toxicity. We found by using the PAM-fluorescence parameters (phiM, phi'M, QP, and QN), that C. reinhardtii is the most sensitive species, followed by S. capricornutum and C. vulgaris. Indeed, the copper 5-, 48-, and 96-h EC50 for phiM, phi'M, and QP vary between 11 and 34 microg/L for C. reinhardtii, while for S. capricornutum this value is between 25 and 50 microg/L. However, the same parameters obtained from C. vulgaris did not show susceptibility to copper, even at very high concentrations (100 microg/L). In this study, the estimated 5-h EC50 for C. reinhardtii and S. capricornutum are lower than the 24-h EC50 reported earlier for these species with other bioassays, indicating that the use of PAM fluorometry in copper bioassay provides a more sensitive method than the other biotests in aquatic toxicology.

Sleeping habits in the Austrian population

OBJECTIVES

To gain reliable data on sleeping habits and sleep disturbances of the Austrian population.

BACKGROUND

Exact data on sleeping habits are of interest in relation to assessment of sleep disturbance-related illnesses and general social processes.

METHODS

A prospective, cross-sectional study was performed with recruitment of a representative sample of 1049 Austrians (aged 15-82 years), according to the Federal Statistics population characteristics. Interviews were conducted in the households of the participants by specially trained interviewers of an institute for empirical research.

RESULTS

Men consider their quality of sleep to be significantly better than women (P=0.00234), and younger persons consider their quality of sleep to be significantly better than older persons (P=0.00001). In comparison, women and people over the age of 50 report worse subjective sleep quality, worse sleep efficiency, more difficulty in falling asleep and sleep maintenance, more apneic events, more pathologic limb movements, more daytime dysfunction, and more intake of sleeping medication. Other sociodemographic factors influence sleep reports to a lesser extent.

CONCLUSIONS

Subjectively disturbed sleep (prevalence in the total population 24.9%), excessive hypnotic drug intake (prevalence 13.0%), and daytime dysfunction (prevalence 17.4%) are a widespread problem, especially in women and older people. With increasing life expectancy in Western societies, the prevalence of sleep disturbances will increase.

Evaluation of different algal species sensitivity to mercury and metolachlor by PAM-fluorometry

In this study, the pulse-amplitude-modulation (PAM)-fluorometric method was used to evaluate the difference in the sensitivity to mercury (Hg) and metolachlor of six algal species: Ankistrodesmus falcatus, Selenastrum capricornutum, Chlorella vulgaris, Nannoplankton (PLS), Microcystis aeruginosa and Pediastrum biwae. We found that the fluorescence parameters (phiM, the maximal photosystem II (PSII) quantum yield, phi'M, the operational PSII quantum yield at steady state of electron transport, Q(P), the photochemical quenching value, and Q(N), the non-photochemical quenching value) were appropriate indicators for inhibitory effects of mercury but only phi'M and Q(N) were useful for metolachlor. The examined algal species showed very different levels of sensitivity to the effect of Hg and of metolachlor. The most sensitive species to Hg and metolachlor were respectively M. aeruginosa and A. falcatus, while the least sensitive were C. vulgaris and P. biwae. We interpreted these differences by the action mode of pollutants and by the different metabolism properties and morphological characteristics between algal species. These results related to fluorescence parameters may offer useful tool to be used in bioassay for different pollutants. Heterogeneous algal sensitivity to the same pollutant suggests the need to use a battery of species to evaluate the effects of mixtures of pollutants in aquatic systems.

Spectroscopic analysis of desiccation-induced alterations of the chlorophyllide transformation pathway in etiolated barley leaves

Effects of water deficit on the chlorophyllide (Chlide) transformation pathway were studied in etiolated barley (Hordeum vulgare) leaves by analyzing absorption spectra and 77-K fluorescence spectra deconvoluted in components. Chlide transformations were examined in dehydrated leaves exposed to a 35-ms saturating flash triggering protochlorophyllide (Pchlide) and Chlide transformation processes. During the 90 min following the flash, we found that dehydration induced modifications of Chlide transformations, but no effect on Pchlide phototransformation into Chlide was observed. During this time, content of NADPH-Pchlide oxydoreductase in leaves did not change. Chlide transformation process in dehydrated leaves was characterized by the alteration of the Shibata shift process, by the appearance of a new Chlide species emitting at 692 nm, and by the favored formation of Chl(ide) A(668)F(676). The formation of Chl(ide) A(668)F(676), so-called "free Chlide," was probably induced by disaggregation of highly aggregated Chlide complexes. Here, we offer evidence for the alteration of photoactive Pchlide regeneration process, which may be caused by the desiccation-induced inhibition of Pchlide synthesis.

Effects of neuroprotective cocktails on hippocampal neuron death in an in vitro model of cerebral ischemia

Cocktails of neuroprotectants acting at different parts of the ischemic injury cascade may have advantages over single agents. This study investigated, singly and in combination, the neuroprotective efficacy of an energy substrate (3.5 mM fructose 1,6-bisphosphate, FBP), an antagonist of NMDA receptors (1 and 10 microM MK-801), a free-radical scavenger (100 microM ascorbate), an adenosine A1 receptor agonist (10 microM 2-chloroadenosine), and an inhibitor of neurotransmission (2% isoflurane). These agents were evaluated for their ability to prevent loss and morphologic damage of CA1 neurons in rat hippocampal slices when these agents were administered during 30 minutes in vitro ischemia (combined oxygen/glucose deprivation at 37 degrees C) followed by 5 hours of recovery. Ten microM MK-801, alone or in combination with the other compounds, prevented loss of CA1 neurons and preserved their histologic appearance. Isoflurane, which prevents glutamate receptor-dependent cell death in this model, was also protective. Protection against neuron loss was also found when a subtherapeutic concentration of MK-801 (1 microM) was combined with 2-chloroadenosine (which indirectly causes NMDA receptor suppression), but not FBP or ascorbate. The authors conclude that in this model, the strategy of antagonizing NMDA receptors appears more protective than fructose-1,6-bisphosphate, 2-chloroadenosine or ascorbate.

Sleep and quality of life in the Austrian population

PURPOSE

To compare the self-reported estimation of sleep quality evaluated by the Pittsburgh Sleep Quality Index (PSQI) and life quality assessed by the Quality of Life Index (QLI).

BACKGROUND

The PSQI comprised 19 questions and assessed a wide variety of factors relating to sleep quality. The QLI consisted of 10 items for self assessment of different dimensions of life quality.

SUBJECTS

A representative Austrian sample (n = 1049) aged above 15 years.

PROCEDURE

Interviews in the homes of the participants.

RESULTS

32.1% could be classified as poor sleepers (37% females, 26.5% males). Sleep quality decreased with increasing age, especially in women. Overall quality of life was highest in younger (15-29 years) and lowest in elderly subjects (over 50 years). Life quality decreased with increasing age. Between subjective sleep quality and quality of life a moderate, significant correlation was found (r2= 0.6721).

CONCLUSIONS

Complaints about a bad quality of sleep could be used as a screening method in the exploration of patients' quality of life (QoL).

Upper airway findings in patients with nocturnal breathing disorders

This prospective open study was performed to examine the relation between pathologic findings of the upper respiratory tract and the types of noncentral sleep disorders (rhonchopathy, obstructive sleep apnea). 312 men and 274 women aged between 35-75 years attended our outpatient department for relief of their nocturnal breathing disorder. About 1/3 of the patients suffered only of habitual rhonchopathy and 2/3 were obstructive. No findings of the head and neck examination could predict the degree of oxygen desaturation, although pathologies of the nose (73.68%), the soft palate (94.1%) and narrowing of the oro- and hypopharynx (74.19%) were very common in patients with sleep disorder. At least one pathology could be found in every patients. The more pathologies were found the higher was the risk of obstructive sleep apnoea with desaturation below 70%. Unrelated tonsillectomy (51.36%) did not prevent nocturnal breathing disorders.

Excessive daytime sleepiness in patients suffering from different levels of obstructive sleep apnoea syndrome

Excessive daytime sleepiness (EDS) is a frequent symptom of patients with obstructive sleep apnoea (OSA). EDS is a high-risk factor for accidents at work and on the road. Thirty untreated patients with different levels of severity of OSA were studied concerning night sleep and EDS. The criterion for severity was the respiratory disturbance index (RDI): 15 patients were classified as 'moderately' apnoeic (RDI < 40), 15 as 'severely' apnoeic (RDI > 40). Following night-time polysomnography, objective and subjective aspects of EDS were studied. To assess objective EDS the Maintenance of Wakefulness Test (MWT) and a computer-based vigilance performance test were used. Subjective EDS was determined using the Stanford Sleepiness Scale (SSS), the Epworth Sleepiness Scale (ESS) and the Visual Analogue Scales for Performance (VAS-P) and Tiredness (VAS-T). Well-being was assessed using the Scale of Well-Being by von Zerssen (Bf-S/Bf-S'). Severe apnoea patients spent more time in stage 1 and less in slow-wave sleep. MWT latencies tended to be shorter in the severe apnoea group. Vigilance testing revealed no group differences. Patients with moderate apnoea described themselves as more impaired in all subjective scales, but only SSS scores reached statistical significance. Our results suggest that there is no simple correlation between polysomnographic and respiratory sleep variables at night on the one hand, and the extent of EDS on the other hand. Furthermore, subjective and objective evaluation of EDS does not yield the same results. New approaches which allow a more detailed analysis of night sleep and daytime function are required to identify high-risked patients.

Evidence of chlorophyll synthesis pathway alteration in desiccated barley leaves

In etiolated leaves, saturating flash of 200 ms induces phototransformation of protochlorophyllide (Pchlide) F655 into chlorophyllide (Chlide), then into Chl through reactions which do not need light sensibilisation. The synthesis of Chl is known to be slowed down in etiolated leaves exposed to desiccation stress. In order to analyse the intensity and time-course of Chlide transformation into Chl, we used the fluorescence emission of etiolated leaves previously exposed to a 200 ms saturating flash. We used low-temperature fluorescence spectroscopy to reveal the inhibition site of Chl synthesis in etiolated barley leaves exposed to water stress. Shibata shift appears as the main target point of the water deficit. It was found that water deficit inhibits partially active Pchlide F655 regeneration. Also, esterification of Chlide into Chl is impaired. It appears that these inhibitory effects alter the appearance of PSII active reaction centres.

Anesthetics and mild hypothermia similarly prevent hippocampal neuron death in an in vitro model of cerebral ischemia

BACKGROUND

General anesthetics reduce neuron loss following focal cerebral ischemia in rodents. The relative efficacy of this action among different anesthetics clinically used for neuroprotection is uncertain. In addition, it remains unclear how anesthetics compare to neuroprotection afforded by mild hypothermia. This study was performed to evaluate the comparative effects of isoflurane, sodium pentothal, and mild hypothermia in a hippocampal slice model of cerebral ischemia and to determine if the mechanism of neuroprotection of isoflurane involves inhibition of glutamate excitotoxicity.

METHODS

Survival and morphology of CA1, CA3, and dentate gyrus neurons in rat hippocampal slices were examined after 10 or 20 min of combined oxygen-glucose deprivation (in vitro ischemia) followed by a 5-h recovery period.

RESULTS

10 or 20 min in vitro ischemia at 37 degrees C killed 35-40% of neurons in CA1 (P < 0.001), 6% in CA3 (not significant) and 18% in dentate (P < 0.05). Isoflurane (0.7 and 2.0%, approximately 0.45 and 1.5 minimum alveolar concentration), pentothal (50 microm, approximately 1 minimum alveolar concentration equivalent) and mild hypothermia (34 degrees C) all reduced CA1 cell loss and morphologic damage to similar degrees in 10- and 20-min periods of ischemia (P < 0.001). The noncompetitive N-methyl-D-aspartate antagonist MK-801 prevented cell damage, showing that N-methyl-D-aspartate receptor activation is an important mechanism of injury in this model. Glutamate (1 mm) produced cell loss similar to in vitro ischemia. Isoflurane (2%) prevented cell damage from glutamate exposure.

CONCLUSIONS

In hippocampal slices, neuron death from simulated ischemia was predominately due to activation of glutamate receptors. Isoflurane, sodium pentothal, an N-methyl-D-aspartate receptor antagonist, and mild hypothermia prevented cell death to similar degrees. For isoflurane, the mechanism appears to involve attenuation of glutamate excitotoxicity.

[Daytime tiredness correlated with nocturnal respiratory and arousal variables in patients with sleep apnea: polysomnographic and EEG mapping studies]

There is evidence that daytime tiredness is caused by apnea/hypopnea with oxygen desaturation and/or by sleep fragmentation due to arousals. The aim of this study was to investigate objective and subjective sleep and awakening quality and daytime vigilance--objectified by midmorning mapping of vigilance-controlled EEG (V-EEG)--in sleep apnea patients (N: 18), as compared with age- and sex-matched normal controls (N: 18) as well as to correlate nocturnal respiratory distress and arousals to daytime brain function. Statistical analyses demonstrated a deterioration in subjective and objective sleep and awakening quality in apnea patients. Midmorning V-EEG mapping in apnea patients exhibited less total power, more delta and theta, less alpha and beta activity, as well as a slower dominant frequency and centroid of the total activity compared to controls, which suggests a vigilance decrement. The Spearman rank correlation between 6 polysomnographically registered respiratory variables and 36 diurnal quantitative EEG measures demonstrated the following: the higher the apnea, apnea-hypopnea, snoring and desaturation indices and the lower the minimum and average low oxygen saturation, the more pronounced was diurnal tiredness. Eleven arousal measures based on ASDA criteria showed the following significant correlations: the higher the nocturnal arousal index and the more arousals due to hypopneas, the greater was daytime tiredness. On the other hand, the greater the average frequency change during arousals and the more spontaneous arousals, the better was daytime vigilance. Our findings show that, in contrast to the lengthy Multiple Sleep Latency (MSLT) and Maintenance of Wakefulness (MWT) tests which evaluate sleep pressure under resting conditions conducive to sleep, V-EEG mapping provides a brief objective measure of a sleep apnea patient's daytime tiredness under conditions of wakefulness more appropriate to reflect the patient's everyday life.

Electron donation to photosystem II by diphenylcarbazide is inhibited both by the endogenous manganese complex and by exogenous manganese ions

Diphenylcarbazide (DPC) is an efficient electron donor to the inactive oxygen-evolving complex of photosystem II (PSII). We investigated the role of manganese on the rate of electron donation from DPC to PSII in both Mn-depleted (Tris washed) and Mn-retaining (NaCl washed) PSII preparations. The rate of electron donation from DPC to PSII was significantly higher in Mn-depleted than in Mn-retaining preparations, indicating a negative role of native Mn complex on DPC electron donation. The apparent Km values for DPC were found to be 0.11 and 0.17 mM for Mn-depleted and Mn-retaining PSII preparations, respectively. This difference in the Km values also indicates an antagonistic effect of endogenous Mn cluster on electron donation from DPC, which was markedly inhibited by exogenous Mn2+. However, the magnitude of inhibition was greater in Mn-depleted than in Mn-retaining PSII preparations. This indicates a higher accessibility to DPC to PSII in the absence of native Mn complex. Our results suggest (i) that Mn, either endogenous or added, acts as an accessibility barrier for DPC to donate electrons to PSII and (ii) that the native Mn complex not only functions as an accumulator of oxidizing equivalents but may also protect PSII from exogenous reductants.

Mercury inhibition at the donor side of photosystem II is reversed by chloride

Mercury is an environmental contaminant that strongly inhibits photosynthetic electron transport, photosystem II being the most sensitive target. We investigated in greater detail the effect of mercury using photosystem II submembrane fractions of higher plants. Oxygen evolution was strongly inhibited and variable chlorophyll fluorescence was severely quenched by mercury. Chloride, an inorganic cofactor known to be essential for the optimal function of photosystem II, significantly reversed the inhibitory effect of mercury. However, calcium, another essential cofactor, showed no reversal capacity. It is concluded that on the donor side of PSII, mercury exerts its action by perturbing chloride binding and/or function. Considering the exceptional affinity of mercury for sulfhydryl groups of proteins, the results suggest the implication of cystein residue(s) in maintaining structural and functional integrity of photosystem II.

Atrial natriuretic peptide release in response to different positive end-expiratory pressure levels

OBJECTIVE

To assess the influence of different positive end-expiratory pressure (PEEP) levels on plasma atrial natriuretic peptide concentrations.

DESIGN

Prospective, randomized study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

Twenty-seven patients who were mechanically ventilated due to acute respiratory failure.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The patients were randomized into three groups: in each group, a defined PEEP level (5, 10, or 15 cm H2O, respectively) was applied, alternating with zero PEEP (0 cm H2O) in consecutive order (reversal experiment). Blood samples for the determination of atrial natriuretic peptide concentrations were drawn from the pulmonary artery and the radial artery catheters. There were no decreases in atrial natriuretic peptide concentrations with a PEEP of 5 cm H2O, but significant decreases could be shown for PEEP values of 10 and 15 cm H2O. The patients of all groups were subjected to PEEP levels of 5, 10, 15, and 20 cm H2O in randomized order (step experiment). The data demonstrated a significant inverse correlation between changes in PEEP levels and changes in plasma atrial natriuretic peptide concentrations.

CONCLUSION

The data suggest that the release of atrial natriuretic peptide is influenced by a PEEP of > or = 10 cm H2O, while a PEEP of < or = 5 cm H2O does not disturb this cardiac endocrine function.

Improvement of four sigma analysis for the investigation of oxygen evolution by Photosystem II

We present here an improvement to the analysis of oxygen evolution with four sigma coefficients (4-S) by computing z, the sum of the S-state probabilities, which was introduced earlier (Delrieu and Rosengard 1987, Biochim Biophys Acta 892: 163-171). We demonstrate that z is equal to the ratio of two consecutive Mean Y (the estimation of the steady state oxygen production based on local properties) found by three sigma analysis. The quantity z is useful for computing double-hits, and for showing the inactivation/activation processes of PS II complexes. Three sigma analysis assumes z=1 exactly; since this is not verified, it is argued that four sigma analysis is closer to the real workings of the water oxidizing complex. Oxygen evolution can then be interpreted in the frame of a modified Kok's model where the sum of the probabilities equals z. We therefore suggest that the closer fitting of four sigma analysis to oxygen production data is not simply due to an extra, unnecessary variable, but to the fact that PS II complexes can be inactivated and reactivated under flashing light. Finally, in order to facilitate the use of four sigma analysis, a computer program is made available upon request.

[DEXA (dual-energy x-ray absorptiometry) and DPA (dual photon absorptiometry) in densitometry of the femoral neck: correlation of the measurements of three commercially available instruments]

The bone mineral density measurements of three different instruments at the femoral head were compared using 12 cadaver specimens. Two of these instruments were operated by x-rays (dual energy x-ray absorptiometry = DEXA), whereas one system was based on a gadolinium source (dual photon absorptiometry = DPA). Although excellent correlation between the measurements was obtained (r greater than 0,9), the measurements of one of the DEXA-instruments were significantly higher than the measurements of the two other systems. We conclude that a comparison of bone mineral density measurements obtained on different densitometry instruments may pose problems. Follow-up examinations should be done on one single densitometry unit.

The time for oxygen release in photosynthesis: reconciliation of flash polarography with other measurement techniques

The time for oxygen release in photosynthesis has been reported to be 30-130 ms when measured by flash polarography under low polarization voltages (Plijter et al. 1988), in opposition to 1-3 ms with light modulated oxygen polarography (Jolio et al. 1966), with the detection of produced oxygen in a flowing sample (Etienne 1968) or with photoacoustic detection of oxygen evolution (Canaani et al. 1988). However, we show here that flash polarographic measurements require properly cleaned electrodes, a precise polarization voltage, as well as a short polarization time of the electrodes. When these criteria were met, an oxygen release in less than 2 ms could be measured by flash polarography under low polarization voltages, in accordance with the other techniques. But under high polarization voltages, the interpretation of the polarographic response to oxygen production must take into account the diffusion of oxygen, the capacitance of the platinum electrode and the oxygen release time. We present a model of the electrode response taking into account these factors; by interpreting the response of the electrodes with this model, we found an oxygen release time of 1.7 ms. These evidences support strongly a short oxygen release time of 1-3 ms.

Protective role of CaCl2 against Pb2+ inhibition in Photosystem II

The Pb2+ treatment of Photosystem II (PS II) membrane fragments, either intact or depleted in 17 and 23 kDa extrinsic polypeptides, inhibits PS II activity. When CaCl2 was present in the assay, the Pb2+ inhibition was significantly reduced in both types of PS II membranes, suggesting a protective role of CaCl2 against Pb2+ inhibition. However, in either case, the degree of PS II inhibition by Pb2+ was higher in the protein depleted than in intact PS II. It showed that the loss of endogenous Ca2+ induced by polypeptide depletion causes the PS II to be more susceptible to Pb2+. The interaction of Pb2+ with CaCl2 in protein-depleted PS II was competitive. Our results suggest that Pb2+ competes for binding to the Ca2(+)- and Cl- active sites in the water-splitting complex. Since Pb2+ inhibition of PS II activity cannot be reversed by CaCl2 but can be reversed by diphenylcarbazide, we conclude that Pb2+ induced inhibition of PS II activity was mediated via the water-splitting system.

Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

The way misses happen in oxygen evolution is subject to debate (Govindjee et al. 1985). We recently observed a linear lowering of the miss probability with the flash number (Meunier and Popovic 1989). Therefore, we investigated in Dunaliella tertiolecta the link between the average miss probability and the redox state of plastoquinone after n flashes. The effect of flashes was to oxidize the plastoquinone pool; we found that the oxidation of plastoquinone highly correlated (linear regression: R (2)=0.996) with the lowering of the miss probability. The flash frequency was found to affect both the miss probability and the redox state of plastoquinone. When pre-flashes were given using a high flash frequency (10 Hz), the plastoquinone pool was oxidized and misses were low; however, if long dark intervals between flashes were used, the oxidizing effect of flashes was lost and the misses were high. We could not explain our results by assuming equal misses over all S-states; but unequal misses, caused by deactivations, were coherent with our results. We deduced that chlororespiration was responsible for the reduction of plastoquinone in the dark interval between flashes. We compared oxygen evolution with and without benzoquinone, using a low flash frequency (0.5 Hz) for maximum misses. Benzoquinone lowered the misses from 34% to 3%, and raised the amplitude of oxygen evolution by more than a factor of two (2). From this we deduced that the charge carrier "C" postulated to explain misses (Lavorel and Maison-Peteri 1983) did not account for more than 3% of miss probability in Dunaliella tertiolecta. These results indicate that the misses in oxygen evolution are controlled by the redox state of plastoquinone, through deactivations.

Determination of four apparent mercury interaction sites in photosystem II by using a new modification of the Stern-Volmer analysis

We used the Stern-Volmer method to analyze the mercury fluorescence quenching effect in the green alga Dunaliella tertiolecta. To this end, we introduced a new modification of the Stern-Volmer equation on the basis of the Lineweaver-Burk analysis used to characterize allosteric enzyme activity. This modification was useful to determine the Stern-Volmer constant, the parameter indicating the fraction of PSII fluorescence susceptible to the mercury quenching effect (Fs), and to estimate the apparent number of mercury binding sites (Napp = 3.72) on PSII which affect the variable fluorescence. This value of Napp indicates the possibility of four mercury binding sites in the PSII complex. We suggested that this may be related to the mercury inhibition of the oxygen-evolving complex containing four Mn active sites.

Evidence for a linear variation of the miss and single hit S-state probabilities with the flash number, measured by oxygen evolution in Dunaliella tertiolecta

Oxygen evolution in Dunaliella tertiolecta under flashing light was measured with a bare electrode, at a 10 Hz frquency. The 'sigma coefficients' of the oxygen evolution recurrence law (Thibault (1978) J Theor Biol 73, 271) were determined using groups of nine consecutive points. The S-state transition probabilities were computed from the sigma coefficients and plotted as a function of the flash number of the first of the points used. Low standard deviations over the sigma coefficients resulted from the use of our system (Meunier & Popovic (1988) Rev Sci Instr 59, 486). We observed a linear lowering of the miss probability with time, and a linear rise of the single-hit probability with the same absolute value of the slope. The hypothesis that the slopes were zero was statistically tested and was rejected with a 99.9% confidence interval. Our work demonstrates that, to be accurate, an oxygen evolution model has to take the variations in the properties of S-states into account.

Removal of the 33, 23 and 18 kDa extrinsic proteins of photosystem II by sulfite treatment at alkaline pH

We found that sulfite incubation of photosystem II submembrane fractions can induce selective depletion of the 18, 23 and 33 kDa polypeptides of the PSII oxygen evolving complex. When the sulfite treatment was done at pH 8.0, the 18 and 23 kDa proteins were removed efficiently from the PSII oxygen evolving complex. Under the same conditions, the 33 kDa subunit remained bound (even when 2 M sodium sulfite was used). However, in more alkaline conditions (pH 9.8), we show extensive removal of the 33 kDa in the presence of a low sulfite concentration (50 mM). The different extraction affinity for the 18, 23 and 33 kDa of the photosystem II complex was interpreted to mean that the 33 kDa polypeptides are bound to photosystem II by both electrostatic and hydrogen bonding forces.

Optimization of the bare platinum electrode as an oxygen measurement system in photosynthesis

This paper is concerned with the definition of the standard conditions required for optimum operation of the bare platinum electrode with photosynthetic samples. Experimental evidence shows the following: 1) Polarization circuits should have zero resistance; 2) The electrolyte layer between the electrodes should have a conductance higher than 54×10(-6) Ω(-1) per mm(2) of platinum electrode area; 3) The electrodes should be polarized just before taking the measurements. All these facts can be interpreted in terms of phenomena occurring on the electrode: The adsorption of hydrogen on the electrode imposes the need for low resistances in the system, and oxygen consumption by the electrode is minimized by polarizing the electrodes as late as possible. This investigation increases the reliability of the bare platinum electrode and gives a basis for a comparison of the results from different experiments. Demonstrations of the pertinence of these conditions are made in our lab with the algae Dunaliella Tertiolecta.

A new method for the separation of the constant and the variable fluorescence of chlorophyll a in in vivo

The constant fluorescence of chlorophyll a in alga Dunaliella tertiolecta was estimated by a method of the least square regression applied to the linearized form of the equation y = axb. The value of the constant fluorescence obtained by this method was compared by the values estimated with simple linear extrapolation. Constant fluorescence, evaluated by the simple linear extrapolation of 10 ms of the initial variable fluorescence, was 50% higher than the value obtained by the method of the least square regression. We demonstrated that the estimation of constant fluorescence by the least square regression is a more correct method and provides a better comparison of results from different laboratories. This method offers a simple way to determine and separate constant fluorescence from variable fluorescence in the total yield of chlorophyll a fluorescence in "in vivo" conditions. Furthermore it facilitates the interpretation of the variable fluorescence phenomena in "in vivo".

Mechanical ventilation with the esophageal tracheal combitube (ETC) in the intensive care unit

Mechanical ventilation in critically ill patients is usually performed with the conventional endotracheal airway. The esophageal tracheal combitube (ETC) is a new device for cardiopulmonary resuscitation, conceived to bridge the gap between hospital and prehospital phases. The ETC may be used in esophageal and endotracheal positions. The authors report six patients who were ventilated with the ETC in the esophageal obturator position for 2-8 h after emergency ventilation. Blood gas data showed adequate ventilation with the ETC during the observation period. Data suggest that mechanical ventilation with the ETC is possible for several hours after cardiopulmonary resuscitation. This might be helpful during the initial post-arrest period, when replacement of the ETC by a conventional endotracheal airway might destabilize a vulnerable patient.

A new medium improves sampling for determination of platelet factor 4 in human plasma

The determination of alpha-granule specific platelet proteins in human plasma is a valuable indicator of in-vivo release and platelet activation provided that an artificial in-vitro release during sampling can be avoided. A new sampling medium (M) has been compared with the commercially available ones for the sampling and the subsequent determination of platelet factor 4 and beta-thromboglobulin. M allows blood withdrawal at room temperature (22 degrees C) (3.49 +/- 0.7 ng/ml) without any difference to 4 degrees C (3.47 ng/ml) up to a 30 minutes sedimentation period. However, after 40 minutes there is a significant (p less than 0.01) increase, amounting at 22 degrees C (13.30 ng/ml) and at 4 degrees C 6.68 ng/ml. The addition of prostacyclin (PGI2) in-vitro as well as blood withdrawal from volunteers infused with PGI2 at a rate of 5 ng/kg/min did not alter the values of M-preserved samples, whereas in the commercially available ones, PGI2 caused a decrease. A comparison of radioimmunoassay and enzyme immunoassay exhibited no significant difference in the absolute values. Beta-thromboglobulin was assayed as control. The findings indicate M being optimal for the sampling of platelet factor 4, but not for other alpha-granule release products. Thus, there is again evidence, that the alpha-granule products are not released to an equal extent upon a certain stimulus. Furthermore, it seems likely, that various substances inhibit their liberation from the platelet to a differing extent.

Study of Energy Storage Processes in Bundle Sheath Cells of Zea mays

Photochemical energy storage in isolated bundle sheath cells from Zea mays was examined. Photoacoustic spectroscopy was used in this study to monitor energy storage processes. The presence of methyl viologen or addition of substrates which activated carbon fixation, prevented energy storage processes through the electron transport system. The energy storage was inhibited completely by dibromothymoquinone (DBMIB) and DCMU, inhibitors of noncyclic electron flow. However, the reductants such as dithiothreitol and ascorbate increased the energy storage. It was concluded that photosystem (PS) I may be reduced by some electron donor(s) other than water and that PSII only partially participates in PSI reduction. It is postulated that the role of PSII is to regulate PSI electron transport and prevent its overoxidation. In the presence of high level of malate, photoacoustic spectroscopy indicated a low energy storage which may be due to induction of energy utilization in carbon assimilation.

Photosynthetic action spectra of the energy storage in bundle sheath cells of Zea mays

Photosynthetic action spectra (Formula: see text), (Carpentier, R., Larue, B. and Leblanc, R. (1984) Arch. Biochem. Biophys. 228, 534-543.), from 400 to 750 nm were studied in bundle sheath cells of maize. Photosynthetic action spectra in the presence of 10 mM ascorbate or 4 mM ribose-5-phosphate were increased and shifted through all the spectra. After the addition of 10 microM DCMU photosynthetic action spectra were remarkably diminished. On the basis of these results we suggest that the role of PSII in BS chloroplasts will be to prevent the overoxidation of PSI. It appears that in addition to PSII some endogen electron donor may regulate the PSI activity in bundle sheath cells.

Artificial inhibitory effects of sulfite on photosystem II activity measured by oxygen evolution in chloroplasts

In this report we demonstrate sulfite interaction with oxygen and PSII electron acceptors (ferricyanide and para-benzoquinone) during measurement of oxygen evolution in chloroplasts. Redox potentials of oxygen, ferricyanide and para-benzoquinone allow them to compete for sulfite. Without taking this into account, sulfite inhibition of oxygen evolution can be overestimated, since sulfite consumes oxygen and reduces ferricyanide or para-benzoquinone during the measurement. In order to correctly measure the rate of oxygen evolution in chloroplasts, it is necessary to avoid presence of sulfite during the measurement. After overcoming the artifact, mentioned above, we confirm the sulfite inhibition of oxygen evolution in chloroplasts but at a lesser extent than earlier reported. This, however, is a pretreatment effect.