EEG changes induced by meditative practices: State and trait effects in healthy subjects and in patients with epilepsy

The effect of meditation on brain activity has been the topic of many studies in healthy subjects and in patients suffering from chronic diseases. These effects are either explored during meditation practice (state effects) or as a longer-term result of meditation training during the resting-state (trait). The topic of this article is to first review these findings by focusing on electroencephalography (EEG) changes in healthy subjects with or without experience in meditation. Modifications in EEG baseline rhythms, functional connectivity and advanced nonlinear parameters are discussed in regard to feasibility in clinical applications. Secondly, we provide a state-of-the-art of studies that proposed meditative practices as a complementary therapy in patients with epilepsy, in whom anxiety and depressive symptoms are prevalent. In these studies, the effects of standardized meditation programs including elements of traditional meditation practices such as mindfulness, loving-kindness and compassion are explored both at the level of psychological functioning and on the occurrence of seizures. Lastly, preliminary results are given regarding our ongoing study, the aim of which is to quantify the effects of a mindfulness self-compassion (MSC) practice on interictal and ictal epileptic activity. Feasibility, difficulties, and prospects of this study are discussed.

Schizophrenia and epileptic comorbidity

Epileptic seizures have been widely considered as a complication of external or iatrogenic factors in schizophrenia. However, epidemiologic, neurodevelopmental and genetic data have changed regards on this topic considering the complexity of the bidirectional link between epilepsy and schizophrenia. We will examine these data constituting the pathophysiological aspects of this particular association and detail the particular impact of antipsychotics on the occurence of epileptic seizure in schizophrenia as well as the management strategies.

Apathy in depression: An arterial spin labeling perfusion MRI study

INTRODUCTION

Apathy, as defined as a deficit in goal-directed behaviors, is a critical clinical dimension in depression associated with chronic impairment. Little is known about its cerebral perfusion specificities in depression. To explore neurovascular mechanisms underpinning apathy in depression by pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI).

METHODS

Perfusion imaging analysis was performed on 90 depressed patients included in a prospective study between November 2014 and February 2017. Imaging data included anatomical 3D T1-weighted and perfusion pCASL sequences. A multiple regression analysis relating the quantified cerebral blood flow (CBF) in different regions of interest defined from the FreeSurfer atlas, to the Apathy Evaluation Scale (AES) total score was conducted.

RESULTS

After confound adjustment (demographics, disease and clinical characteristics) and correction for multiple comparisons, we observed a strong negative relationship between the CBF in the left anterior cingulate cortex (ACC) and the AES score (standardized beta = -0.74, corrected p value = 0.0008).

CONCLUSION

Our results emphasized the left ACC as a key region involved in apathy severity in a population of depressed participants. Perfusion correlates of apathy in depression evidenced in this study may contribute to characterize different phenotypes of depression.

Multimodal MRI cerebral correlates of verbal fluency switching and its impairment in women with depression

BACKGROUND

The search of biomarkers in the field of depression requires easy implementable tests that are biologically rooted. Qualitative analysis of verbal fluency tests (VFT) are good candidates, but its cerebral correlates are unknown.

METHODS

We collected qualitative semantic and phonemic VFT scores along with grey and white matter anatomical MRI of depressed (n = 26) and healthy controls (HC, n = 25) women. Qualitative VFT variables are the "clustering score" (i.e. the ability to produce words within subcategories) and the "switching score" (i.e. the ability to switch between clusters). The clustering and switching scores were automatically calculated using a data-driven approach. Brain measures were cortical thickness (CT) and fractional anisotropy (FA). We tested for associations between CT, FA and qualitative VFT variables within each group.

RESULTS

Patients had reduced switching VFT scores compared to HC. Thicker cortex was associated with better switching score in semantic VFT bilaterally in the frontal (superior, rostral middle and inferior gyri), parietal (inferior parietal lobule including the supramarginal gyri), temporal (transverse and fusiform gyri) and occipital (lingual gyri) lobes in the depressed group. Positive association between FA and the switching score in semantic VFT was retrieved in depressed patients within the corpus callosum, right inferior fronto-occipital fasciculus, right superior longitudinal fasciculus extending to the anterior thalamic radiation (all p < 0.05, corrected).

CONCLUSION

Together, these results suggest that automatic qualitative VFT scores are associated with brain anatomy and reinforce its potential use as a surrogate for depression cerebral bases.

[Anticholinergic scales: Use in psychiatry and update of the anticholinergic impregnation scale]

Anticholinergic properties are well known to prescribers, notably in mental health, as a therapeutic strategy for i.e. extrapyramidal syndrome but also as a source of numerous adverse side effects. Herein, we propose a narrative literature review describing: (i) cholinergic pharmacology and anticholinergic properties; (ii) the importance of anticholinergic therapeutic properties in psychiatry; (iii) the existing anticholinergic drug scales and their usage limitations in Psychiatry and; last (iv) an update to the anticholinergic drug impregnation scale, designed for the French psychiatry practice. The anticholinergic side effects can appear both in the peripheral level (dry mouth, constipation, etc.) and in the central level (especially as cognitive deficits). Many of the so called « anticholinergic » drugs are in fact entirely or mostly antimuscarinic and act essentially as parasympathetic system antagonists. Overall, anticholinergic/antimuscarinic side effects are usually attributed to psychotropic medications: to certain antipsychotics, notably classical neuroleptics such as phenothiazine and also to tricyclic antidepressants. In practice, the impact of anticholinergic toxicity treatments is often highlighted due to their excessively prolonged use in patients on antipsychotics. Interestingly, these antipsychotic treatments are better known for their anticholinergic side effects, especially cognitive ones, with an early onset specially in elder patients and/or in the case of polymedication. In order to evaluate anticholinergic side effects, metrics known as anticholinergic burden scales were created in the last few decades. Nowadays, 13 different scales are documented and accepted by the international academic community, but only three of them are commonly used: the Anticholinergic Drug Scale (ADS), the Anticholinergic Risk Scale (ARS) and the Anticholinergic Burden Scale (ACB). All of them are based on a similar principle, consisting of grading treatments individually, and they are normally scored from 0 - no presence of side effects - to 3 - anticholinergic effects considered to be strong or very strong. Using these scales enables the calculation of the so-called "anticholinergic burden", which corresponds to the cumulative effect of using multiple medications with anticholinergic properties simultaneously. The application of anticholinergic scales to patients with psychiatric disorders has revealed that schizophrenic patients seem to be especially sensitive to anticholinergic cognitive side effects, while elder and depressed patients were more likely to show symptoms of dementia when exposed to higher anticholinergic burden. Unfortunately, these tools appear to have a low parallel reliability, and so they might induce large differences when assessing side effects predictability. In addition, the capacity of these scales to predict central adverse effects is limited due to the fact they poorly or do not differentiate, the ability of treatments to cross the blood-brain barrier. Finally, one last limitation on the validity of these scales is prescription posology is not accounted for side effects considered to be dose dependent. Recently, the MARANTE (Muscarinic Acetylcholine Receptor ANTagonist Exposure) scale has incorporated an anticholinergic burden weighting by posology. Nevertheless, this new model can be criticized, due to the limited number of medications included and due to testing a limited number of potency ranges and dosages for each treatment. Herein, we propose an update to the Anticholinergic Impregnation Scale, developed specifically for the French Psychiatry practice. The scale validation was based on an evaluation of the prescriptions correcting anticholinergic peripheral side effects (constipation, xerostomia and xeropthalmia). This indirect evaluation allowed us to show patients with an anticholinergic impregnation score higher than 5 received significantly more treatments for constipation and xerostomia. This strategy bypasses the bias of a cognitive evaluation in patients with severe mental health disorders. Moreover, the relevance of a tool developed specifically for French psychiatry is justified by the fact that some highly prescribed treatments for mental illness in France (cyamemazine and tropatemine) are strong anticholinergics, and also by the fact they are rarely included in the existing anticholinergic scales. This update of the original scale, published in 2017, includes information whether prescribed drugs cross the blood-brain barrier and thus makes possible a more accurate assessment when evaluating anticholinergic central side effects. Finally, the anticholinergic impregnation scale will soon be integrated into a prescription help software, which is currently being developed to take into consideration dose dependent adverse effects.

Psychotropics and COVID-19: An analysis of safety and prophylaxis

The use of psychotropics during the COVID-19 pandemic has raised two questions, in order of importance: first, what changes should be made to pharmacological treatments prescribed to mental health patients? Secondly, are there any positive side effects of these substances against SARS-CoV-2? Our aim was to analyze usage safety of psychotropics during COVID-19; therefore, herein, we have studied: (i) the risk of symptomatic complications of COVID-19 associated with the use of these drugs, notably central nervous system activity depression, QTc interval enlargement and infectious and thromboembolic complications; (ii) the risk of mistaking the iatrogenic impact of psychotropics with COVID-19 symptoms, causing diagnostic error. Moreover, we provided a summary of the different information available today for these risks, categorized by mental health disorder, for the following: schizophrenia, bipolar disorder, anxiety disorder, ADHD, sleep disorders and suicidal risk. The matter of psychoactive substance use during the pandemic is also analyzed in this paper, and guideline websites and publications for psychotropic treatments in the context of COVID-19 are referenced during the text, so that changes on those guidelines and eventual interaction between psychotropics and COVID-19 treatment medication can be reported and studied. Finally, we also provide a literature review of the latest known antiviral properties of psychotropics against SARS-CoV-2 as complementary information.

Structural abnormalities associated with poor outcome of a major depressive episode: The role of thalamus

An identification of precise biomarkers contributing to poor outcome of a major depressive episode (MDE) has the potential to improve therapeutic strategies by reducing time to symptomatic relief. In a cross-sectional volumetric study with a 6 month clinical follow-up, we performed baseline brain grey matter volume analysis between 2 groups based on illness improvement: 27 MDD patients in the "responder" (R) group (Clinical Global Impression- Improvement (CGI-I) score ≤ 2) and 30 in the "non-responder" (NR) group (CGI-I > 2), using a Voxel Based-Morphometry analysis. NR had significantly smaller Grey Matter (GM) volume in the bilateral thalami, in precentral gyrus, middle temporal gyrus, precuneus and middle cingulum compared to R at baseline. Additionally, they exhibited significant greater GM volume increase in the left anterior lobe of cerebellum and posterior cingulate cortex. The latter result was not significant when participants with bipolar disorder were excluded from the analysis. NR group had higher baseline anxiety scores. Our study has pointed out the role of thalamus in prognosis of MDE. These findings highlight the involvement of emotion regulation in the outcome of MDE. The present study provides a step towards the understanding of neurobiological processes of treatment resistant depression.

[Informations on psychotropics and their adaptations for patients suffering from mental disorders in France during the SARS-CoV-2 epidemic]

The 2019-20 coronavirus pandemic (SARS-CoV-2; severe acute respiratory syndrome coronavirus 2) has dramatic consequences on populations in terms of morbidity and mortality and in social terms, the general confinement of almost half of the world's population being a situation unprecedented in history, which is difficult today to measure the impact at the individual and collective levels. More specifically, it affects people with various risk factors, which are more frequent in patients suffering from psychiatric disorders. Psychiatrists need to know: (i) how to identify, the risks associated with the prescription of psychotropic drugs and which can prove to be counterproductive in their association with COVID-19 (coronavirus disease 2019), (ii) how to assess in terms of benefit/risk ratio, the implication of any hasty and brutal modification on psychotropic drugs that can induce confusion for a differential diagnosis with the evolution of COVID-19. We carried out a review of the literature aimed at assessing the specific benefit/risk ratio of psychotropic treatments in patients suffering from COVID-19. Clinically, symptoms suggestive of COVID-19 (fever, cough, dyspnea, digestive signs) can be caused by various psychotropic drugs and require vigilance to avoid false negatives and false positives. In infected patients, psychotropic drugs should be used with caution, especially in the elderly, considering the pulmonary risk. Lithium and Clozapine, which are the reference drugs in bipolar disorder and resistant schizophrenia, warrant specific attention. For these two treatments the possibility of a reduction in the dosage - in case of minimal infectious signs and in a situation, which does not allow rapid control - should ideally be considered taking into account the clinical response (even biological; plasma concentrations) observed in the face of previous dose reductions. Tobacco is well identified for its effects as an inducer of CYP1A2 enzyme. In a COVID+ patient, the consequences of an abrupt cessation of smoking, particularly related with the appearance of respiratory symptoms (cough, dyspnea), must therefore be anticipated for patients receiving psychotropics metabolized by CYP1A2. Plasma concentrations of these drugs are expected to decrease and can be related to an increase risk of relapse. The symptomatic treatments used in COVID-19 have frequent interactions with the most used psychotropics. If there is no curative treatment for infection to SARS-CoV-2, the interactions of the various molecules currently tested with several classes of psychotropic drugs (antidepressants, antipsychotics) are important to consider because of the risk of changes in cardiac conduction. Specific knowledge on COVID-19 remains poor today, but we must recommend rigor in this context in the use of psychotropic drugs, to avoid adding, in patients suffering from psychiatric disorders, potentially vulnerable in the epidemic context, an iatrogenic risk or loss of efficiency.

Imagerie cérébrale en psychiatrie : applications cliniques actuelles et défis à venir

Ce symposium a pour objectif de faire la lumière sur trois axes de développement de l’imagerie cérébrale en psychiatrie. La première communication porte sur l’imagerie de cohorte. Celle-ci permet l’étude des variations des caractéristiques (ou phénotypes) d’imagerie cérébrale dans le temps et du rôle des facteurs endogènes (ex. : rechutes de la maladie, observance & facteurs génétiques) et exogènes (ex. : stress & prises de toxiques). La maîtrise des techniques d’imagerie longitudinale se heurte cependant à des défis méthodologiques tels que la maîtrise des outils nécessaires pour équilibrer les pré-traitements sur l’ensemble des données [1], le développement d’outils statistiques permettant d’obtenir suffisamment de puissance mais également capables de s’adapter aux aléas du suivi de cohorte (perdu de vue notamment) [2]) et enfin la question de l’intégration d’une approche multimodale et d’un suivi longitudinal en imagerie. Dans la continuité avec cette dernière question, la seconde communication traite de l’emploi de l’approche multimodale en imagerie cérébrale afin d’explorer la connectivité anatomique (au moyen de l’imagerie par tenseur de diffusion) et fonctionnelle (à l’aide de l’imagerie fonctionnelle de repos). Sur le socle de l’état hallucinatoire chronique et des différentes modalités sensorielles (auditives et visuelles), l’approche multimodale permet de revisiter les premières descriptions cliniques des hallucinations [3]. Plus sensibles que leurs homologues cliniques, les phénotypes d’imagerie permettent un gain de puissance considérable des lors qu’il s’agit d’évaluer un pronostic. À cette fin, les traitements statistiques multivariés des phénotypes d’imagerie marquent une rupture avec l’approche univariée (i.e. voxel par voxel) jusqu’ici dominante dans le champ de l’imagerie fonctionnelle [4]. C’est dans ce cadre conceptuel que s’inscrit la troisième communication qui décrira la valeur prédictive des phénotypes d’imagerie et comment l’imagerie peut affiner le pronostic des sujets à très haut risque de transition psychotique [5]. Chacun des orateurs fera l’état des connaissances actuelles dans le domaine, en évoquant les applications cliniques possibles, mais aussi les perspectives futures en termes de recherche et d’applications aux soins.

[Cost-effectiveness study of olanzapine pamoate: Mirror-image analysis after one year]

INTRODUCTION

Olanzapine pamoate has a higher cost of treatment than the oral form and requires administration in a hospital setting (unlike other long-acting antipsychotics), and the cost-effectiveness of this treatment may be questioned. Many scientific societies and national health systems are increasingly interested in the pharmacoeconomic impact of health products. The search for efficacy of a treatment can be done in two ways: medico-economic modeling studies or observational studies i.e. randomized controlled trials or mirror studies. The models are based on theoretical models from published clinical data simulating the course and evolution of patient health conditions, which benefit from a particular therapeutic strategy. Even if the design of observational mirror studies makes it possible to get closer to the clinical reality by observing the patient before and after the initiation of the treatment, the majority of the pharmacoeconomic studies published on olanzapine pamoate are modeling works that do not reflect actual conditions of care. The Guillaume Régnier Hospital Center in Rennes has a large cohort of patients treated with olanzapine pamoate: 121 instauration treatments are recorded from April 1, 2010 to Mars 1, 2015. The objective of this study is to evaluate the cost-effectiveness of olanzapine pamoate in actual clinical practice.

METHODS

This is a one-year cost-effectiveness retrospective observational mirror-image study of a cohort of 52 patients with schizophrenia who were treated for at least three months with olanzapine pamoate. The primary efficacy endpoint is the differential in the number of full-time hospitalizations before and after the introduction of olanzapine pamoate versus the hospital cost differential. The secondary criteria are the difference of the number of the days spent in hospital and the number of outpatient consultations between the year preceding the injection and the year following it. The results were calculated on the general cohort and within 2 subgroups: patients treated for more than one year and those receiving less than one year of treatment with olanzapine pamoate.

RESULTS

Fifty-two patients were included (median age=35 years, sex ratio H/F=2.7) and only 38.5% discontinued treatment. For patients who maintained long-acting treatment, they received a dosage of 25mg oral olanzapine (min=7.5mg, max=60mg), 5mg more medially than the group having stopped the olanzapine pamoate (20mg; min=10mg, max=40mg). The majority of these patients were receiving off-label authorized marketing doses of oral olanzapine, whereas 22% of them had off-label dosages of olanzapine pamoate. The main causes of discontinuation were symptom persistence, loss of vision and the occurrence of adverse effects (including weight gain and sedation). Olanzapine pamoate significantly reduced the number of hospitalizations compared to the previous management strategy (1 less hospitalization, P<0.001 in patients treated more than one year and in the general cohort). As a logical consequence the number of hospitalization days in day care increased after the establishment of this long-acting antipsychotic with hospital reserve status (18 in median; min=0, max=159). We observed a non-statistically significant tendency of decrease in the number of days of full-time hospitalization and an increase in the number of ambulatory procedures, particularly in patients who have maintained the treatment for one year. This efficiency had a non-significant additional cost of €3361 per year. There was an average multiplication by 8,5 of the drug cost a year later in the general cohort (5.5 in the group of patients treated less than one year and 10.4 in the group of patients who maintained it a year). There was a 23,2% average increase in the cost of hospitalization in the general cohort (3.75 % in patients who maintained treatment compared to 48.9% in patients who discontinued treatment).

CONCLUSION

By its mirror design, the study was placed in real conditions of care of the patient with schizophrenia. A total of 61.5% of patients maintained treatment with olanzapine pamoate for a minimum of one year. This APAP is more effective without significantly increasing the cost compared to the previous therapeutic strategy (including oral olanzapine). The additional cost is partly due to the administration restriction in a hospital setting in relation to risk of Post-Injection Delirium/Sedation Syndrom (PDSS). There is currently no acceptable efficiency limit. The results of this cost-effectiveness analysis cannot be extrapolated to the other long-acting antipsychotics since it is the only one with hospital reserve status. The current limitations of medico-economics in psychiatry derive from the heterogeneity of clinical forms and the management of mental pathologies.

Apathy in depression: An arterial spin labeling study

Introduction

Apathy is usually defined as a lack of goal-directed behavior. Although it is observed in about 30% of depressed patients, neurovascular mechanisms underpinning apathy remain little-known.

Objectives

The main objective of this study was to compare the cerebral perfusion of apathetic depressed patients with non-apathetic depressed patients by arterial spin labeling (ASL), a quantitative and non-invasive perfusion magnetic resonance imaging (MRI) technique. The secondary objectives were to study their clinical profile and their correlation with cerebral perfusion data.

Methods

This study was conducted from a cohort of depressed patients in Rennes, France. Eighty-three depressed patients were included, of whom 22 were apathetic (AES≥42), 61 non-apathetic (AES < 42). Everyone got a clinical evaluation with scale screenings, especially for apathy (AES), anxiety (STAI) and anhedonia (SHAPS) as well as a cerebral MRI, including a pseudo-continuous ASL sequence.

Results

Apathetic depressed patients were significantly less anxious and less anhedonic. Apathetic perfused better than non-apathetic in the inferior frontal gyrus (P = 0.022). We found a significant positive relationship between apathy and perfusion of the left frontal inferior gyrus (P = 0.05, r = 0.21). State-anxiety was positively correlated with perfusion of the cingulate cortex, the insula and the left amygdala. Anhedonia was positively correlated with the perfusion of the ventromedial prefrontal cortex, the cingulate cortex and the insula.

Conclusions

We have shown that the clinical and perfusional profiles of apathetic depressed and non-apathetic differ. This study suggests the existence of two distinct neurobiological networks for depressed patients; one involving motivational networks for apathetic patients, and another one involving emotional networks for more anhedonic patients.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Manic switches induced by antidepressants: an umbrella review comparing randomized controlled trials and observational studies

OBJECTIVE

We aimed to explore whether the prevalence of manic switch was underestimated in randomized controlled trials (RCTs) compared to observational studies (OSs).

METHOD

Meta-analyses and simple and systematic reviews were identified by two reviewers in a blinded, standardized manner. All relevant references were extracted to include RCTs and OSs that provided data about manic switch prevalence after antidepressant treatment for a major depressive episode. The primary outcome was manic switch prevalence in the different arms of each study. A meta-regression was conducted to quantify the impact of certain variables on manic switch prevalence.

RESULTS

A total of 57 papers (35 RCTs and 22 OSs) were included in the main analysis. RCTs underestimated the rate of manic switch [0.53 (0.32-0.87)]. Overestimated prevalence was related to imipraminics [1.85 (1.22-2.79)]; to serotonin-norepinephrine reuptake inhibitors [1.74 (1.06-2.86)]; and to other classes of drugs [1.58 (1.08-2.31)], compared to placebo treatment. The prevalence of manic switch was lower among adults than among children [0.2 (0.07-0.59)]; and higher [20.58 (8.41-50.31)] in case of bipolar disorder.

CONCLUSION

Our results highlight an underestimation of the rates of manic switch under antidepressants in RCTs compared to the rates observed in observational studies.

Recognition Of Emotional Prosody In Anorexia Nervosa

Deficits in emotional processes are often observed by clinicians in anorexia nervosa and may have an impact on social functioning. Recognition of emotion was mostly investigated using visual stimuli as faces of emotional scenes. Only one study (Kucharska-Pietura et al., 2004) demonstrated impairments in emotional prosody using positive and negative valenced stimuli. However, this study did not provide a highlight for the identification of emotional bias (for example, to recognize an intense fear in a friendly voice). The aim of this study is to better understand the recognition of emotional prosody in anorexia nervosa using a wide range of positive, negative and neutral stimuli (Belin et al., 2008).

In order to test emotion recognition biases in emotional prosody, we exposed 15 patients with anorexia nervosa and 15 healthy controls (HCs) to emotional vocal tasks asking them to rate emotional intensity on visual analog scales. In addition, we assessed clinical symptomatology and cognitive functioning for all participants.

We showed that patients with anorexia nervosa provided higher intensity ratings on the non-target scales (e.g., surprise scale for fear stimuli) than HCs for sadness, fear and neutral voices. Furthermore, with the exception of neutral vocal stimuli, they provided the same intensity ratings on the target scales as the HCs.

These findings suggested a bias in the processing of emotional prosody and may impact the social functioning of patients with anorexia nervosa. The bias may result from a sensorial deficit or a high-order cognitive dysfunction and have to be investigated in future studies.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

[Impulsivity: What are the consequences on compliance to rehabilitation?]

INTRODUCTION

Impulsivity is a transnosographical dimension with major consequences on medical care with which psychiatrists are frequently confronted. Furthermore, compliance is a major variable that can affect the efficiency of therapeutics and hospitalizations in psychiatry. A study was carried out in three drug and alcohol rehabilitation hospitalization units to find out if impulsivity can have consequences on compliance.

METHOD

The studied population was composed of 85 patients aged from 18 to 70, hospitalized for one or more addiction disorders in a psychometric hospital in Vannes (France). Impulsivity was measured for all patients with the BIS-11 at the beginning of the rehabilitation program. Because no tool to evaluate a total rehab program compliance existed, a scale, used at the end of the hospitalization, was created to measure patient compliance. This score was composed of two simple numeric scales (one used by the nurses and one used by the patient's psychiatrist) and a coefficient of hospitalization duration that was the ratio of completed to planned days of hospitalization. Correlations were made between the different dimensions: impulsivity and compliance, impulsivity and hospitalization conditions, compliance and hospitalization conditions (voluntary or involuntary, planned by a psychiatrist or not, etc.).

RESULTS

The main statistically significant result of the study was a negative correlation existing between the motor dimension of impulsivity and compliance (r=-0.37 and P=0.001). The other dimensions of impulsivity showed no significant correlation with compliance score. The study revealed that the different hospitalization conditions showed no link with compliance or impulsivity.

CONCLUSION

These original results show that motor impulsive patients need an adaptation of the rehabilitation programs. Shorter programs might be more efficient.

Recognition of emotional prosody in anorexia nervosa

Deficits in emotional processes are often observed by clinicians in anorexia nervosa and may have an impact on social functioning. Recognition of emotion was mostly investigated using visual stimuli as faces of emotional scenes. Only one study (Kucharska-Pietura et al., 2004) demonstrated impairments in emotional prosody using positive and negative valenced stimuli. However, this study did not provide a highlight for the identification of emotional bias (for example, to recognize an intense fear in a friendly voice). The aim of this study is to better understand the recognition of emotional prosody in anorexia nervosa using a wide range of positive, negative and neutral stimuli (Belin et al., 2008). In order to test emotion recognition biases in emotional prosody, we exposed 15 patients with anorexia nervosa and 15 healthy controls (HCs) to emotional vocal tasks asking them to rate emotional intensity on visual analog scales. In addition, we assessed clinical symptomatology and cognitive functioning for all participants. We showed that patients with anorexia nervosa provided higher intensity ratings on the non-target scales (e.g., surprise scale for fear stimuli) than HCs for sadness, fear and neutral voices. Furthermore, with the exception of neutral vocal stimuli, they provided the same intensity ratings on the target scales as the HCs. These findings suggested a bias in the processing of emotional prosody and may impact the social functioning of patients with anorexia nervosa. The bias may result from a sensorial deficit or a high-order cognitive dysfunction and have to be investigated in future studies.

Use of very-high-dose olanzapine in treatment-resistant schizophrenia

Schizophrenia is a chronic illness with a progressive course that can be marked by resistance to antipsychotic treatment. This can make therapeutic support challenging for the practitioner, with results that are partial and unsatisfactory. In the literature, treatment with high-dose olanzapine (>20mg/day) appears to be a good alternative to clozapine, the gold standard for treatment-resistant schizophrenia. In the present observational prospective study, we studied the clinical and biological profiles of patients treated with olanzapine doses up to 100mg/day. In total, 50 patients were clinically and biologically assessed. We found a linear relationship between oral dose and serum concentration (Pearson's r=0.83, p<0.001) with effects of tobacco (p<0.05) and of coffee and tea consumption (p<0.01). Tolerance seemed to be good regardless of dose. No link was found between concentration and efficiency. Despite a nonexhaustive assessment of pharmacokinetic parameters, not least pharmacogenetic data (e.g., genotyping of cytochrome P450-1A2 or glycoprotein P Abcb1a), pharmacokinetic aspects alone cannot account for why the disease may sometimes be resistant to 20mg of olanzapine but respond to higher doses. A nuclear imaging study exploring brain occupancy by high-dose olanzapine, coupled with the abovementioned pharmacokinetic assessment, may prove a relevant experimental paradigm for studying the pathophysiological mechanisms of resistant schizophrenia.

Repetitive transcranial magnetic stimulation over the orbitofrontal cortex for obsessive-compulsive disorder: a double-blind, crossover study

This pilot study was designed to assess the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right orbitofrontal cortex (OFC) by means of a double-cone coil in patients suffering from obsessive-compulsive disorder. We hypothesized that low-frequency stimulation of the OFC would lead to a reduction in clinical symptoms, as measured on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). A randomized, double-blind, crossover design was implemented with two 1-week treatment periods (active stimulation versus sham stimulation) separated by a 1-month washout period. Concomitantly, a subgroup of patients underwent a positron emission tomography (PET) scan after each stimulation sequence. Statistical analyses compared the Y-BOCS scores at the end of each period. At day 7, we observed a significant decrease from baseline in the Y-BOCS scores, after both active (P<0.01) and sham stimulation (P=0.02). This decrease tended to be larger after active stimulation than after sham stimulation: -6 (-29, 0) points versus -2 (-20, 4) points (P=0.07). Active versus sham PET scan contrasts showed that stimulation was related to a bilateral decrease in the metabolism of the OFC. The OFC should definitely be regarded as a key neuroanatomical target for rTMS, as it is easier to reach than either the striatum or the subthalamic nucleus, structures favored in neurosurgical approaches.

Étude des anomalies morphométriques et de perfusion dans la dépression chronique et résistante

La dépression est une pathologie invalidante et récurrente. En effet, après un premier épisode dépressif caractérisé, le risque de rechute est estimé à 50 %. À l’heure actuelle, les processus physiopathologiques impliqués dans cette pathologie restent encore mal compris [2]. L’Arterial Spin Labeling (ASL) est une technique d’imagerie de perfusion innovante, non invasive, permettant une quantification du débit sanguin cérébral [1]. Elle a été utilisée dans l’étude de la perfusion cérébrale dans le trouble dépressif récurrent et résistant [3,4] avec des résultats divergents. Aucune étude n’a encore combiné des données morphométriques et de perfusion (ASL). L’objectif de ce travail est d’étudier les anomalies de perfusion et morphométriques impliquées chez des patients souffrant d’un état dépressif caractérisé et stratifiés en deux populations, les patients résistants et répondeurs aux thérapeutiques usuelles. Une hyper-perfusion de l’amygdale droite (p = 0,02) et de l’hippocampe droit (p = 0,02) chez les patients résistants a été décrite. Il a également été retrouvée une atrophie de régions corticales telles que le cortex orbito-frontal (p < 0,001), le cortex cingulaire antérieur (p = 0,002) chez les patients déprimés, ainsi qu’une hypertrophie des hippocampes droit et gauche (p = 0,004, p < 0,001) des patients résistants en comparaison des répondeurs. Notre étude a pu mettre en exergue que la combinaison des informations à la fois morphométriques et de perfusion permettrait d’améliorer la stratification des patients déprimés et notamment en ce qui concerne la notion de résistance thérapeutique.

[Apathy neural bases in neurodegenerative disorders]

Apathy is widely recognized as a lack of motivation, which expresses through the cognitive, behavioral and emotional dimensions of living. It is described within several neuropsychiatric syndromes such as degenerative disorder and is associated with poorer outcomes. In order to better understand the underpinnings of apathy and to develop specific treatment strategies, much research has been conducted to define its neural bases. In the present review, perfusion, metabolic, pathologic and functional results of apathy neural bases in Alzheimer's and Parkinson's diseases are displayed. Methods and strategies to control for confounding factors such as depression, cognitive impairments and other behavioral disorders are described. Results are not strictly identical between disorders and even within disorders. Variation of methods employed on assessment tools and control for confounding factors such as cognitive disorders, depression, other behavioral disorders and medical treatment is thought to be the main reason for this discrepancy. However, it seems that the inferior prefrontal cortex, especially the orbitofrontal cortex, the lateral prefrontal cortex and the anterior cingulate are of particular interest. The second part of the review discusses the literature in these three areas in conditional learning essentially via the reward characteristic encoding, auto-initiated and perseverance behaviors and emotional experience and its regulation.

[Apathy and deep brain stimulation in Parkinson's disease]

Apathy was defined by Marin as diminished motivation not attributable to diminished level of consciousness, cognitive impairment, or emotional distress. Up to 42% of Parkinson's disease patients could be concerned. It has a pejorative impact on quality of life and could be predictive of cognitive decline. It has been shown that deep brain stimulation in Parkinson's disease may induce apathy. It seems directly related to the stimulation target, i.e. the subthalamic nucleus, since such an effect has not been observed so far in thalamic and pallidal stimulation. It should certainly not make us question the remarkable effectiveness of subthalamic stimulation in Parkinson's disease patients, but encourages us to be very careful about operability criteria. We must, in this sense, improve identification of at risk patients, seeking a thoroughly diminished motivation, loss of interest or blunting affects.

[Repetitive transcranial magnetic stimulation in the treatment of obsessive-compulsive disorder]

Obsessive-compulsive disorder (OCD) is a chronic, often resistant neuropsychiatric disorder leading to severe social impairment. Neurophysiological theories suggest an imbalance between the frontal-striatal circuits involved in goal directed behavior. Repetitive transcranial magnetic stimulation (rTMS) has been suggested as a therapeutic option. Various targets of stimulation have been tested based on neurophysiological theories. The first studies, stimulating the dorsolateral prefrontal cortex, did not show an efficacy but the more recent ones, stimulating the supplementary motor area or the orbitofrontal cortex, seem to be promising. Further studies with larger sample should be conducted in order to propose rTMS as a therapeutic tool for OCD.

Prevalence, characteristics and comorbidities of anxiety disorders in France: results from the "Mental Health in General Population" survey (MHGP)

PURPOSE

Only a few European countries have carried out large, community-based, national surveys about psychiatric morbidity. Here is presented the first national French survey, aiming to estimate the prevalence of anxiety disorders and associated comorbidities according to sociodemographic characteristics.

MATERIALS AND METHODS

The Mental Health in General Population (MHGP) database is derived from a representative national survey of the French adult population (n=36,105), conducted between 1999 and 2003. Data collection was done using an anonymous face-to-face interview. The presence of anxiety disorders (generalized anxiety disorder, panic disorder, agoraphobia, social phobia and post-traumatic stress disorder) was assessed using the Mini International Neuropsychiatric Interview.

RESULTS

The overall prevalence of anxiety disorders was estimated to be 21.6%, generalized anxiety disorder being the most prevalent one (12.8%). Women, young people, and people earning low income were identified as the more at risk. Major depressive episode, alcohol abuse and drug addiction frequently co-occur with anxiety disorders (28.3, 4.4 and 2.8% respectively).

CONCLUSION

The MHGP study showed that anxiety disorders are highly prevalent in France with a high frequency of comorbidities. Our results highlight the need for considering anxiety disorders as a public health priority in France as well as in other European countries.

Subthalamic nucleus stimulation in Parkinson disease induces apathy: a PET study

OBJECTIVE

Apathy may be induced by subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson disease (PD). We therefore wished to test the hypothesis that apathy induced by STN-DBS correlates with changes in glucose metabolism, using (18)FDG-PET.

METHODS

Twelve patients with PD were assessed 3 months before (M-3) and 3 months after (M+3) STN-DBS with (18)FDG-PET and the Apathy Evaluation Scale.

RESULTS

Apathy had significantly worsened at M+3 after STN-DBS. Positive correlations were observed between this variation in apathy scores and changes in glucose metabolism, especially in the right frontal middle gyrus (Brodmann area [BA] 10) and right inferior frontal gyrus (BA 46 and BA 47). Negative correlations between the two were observed in the right posterior cingulate gyrus (BA 31) and left medial frontal lobe (BA 9).

CONCLUSION

These preliminary results confirm the role of the subthalamic nucleus in associative and limbic circuitry in humans and suggest that it is a key basal ganglia structure in motivation circuitry.

Neural markers of symptomatic improvement during antidepressant therapy in severe depression: subgenual cingulate and visual cortical responses to sad, but not happy, facial stimuli are correlated with changes in symptom score

Resting state activity in the ventral cingulate may be an important neural marker of symptomatic improvement in depression. The number of task related functional magnetic resonance imaging (fMRI) studies correlating blood oxygenation level dependent (BOLD) response with symptomatic improvement is limited and methodologies are still evolving. We measured BOLD responses to sad and happy facial stimuli in 12 severely depressed individuals in the early stages of antidepressant treatment (Time 1) and 12 weeks later (Time 2) using event-related fMRI. We calculated correlations between temporal changes in BOLD response and changes in symptom scores. Most subjects improved markedly by Time 2. At Time 1, depression severity correlated positively with responses to sad stimuli in the right visual cortex, subgenual cingulate, anterior temporal pole and hippocampus and correlated negatively with responses to happy stimuli in left visual cortex and right caudate. Decreases in individual effect sizes of right subgenual cingulate and right visual cortical responses to sad, but not happy, facial stimuli were correlated with decreases in symptom scores. There are contrasting cortical and subcortical responses to sad and happy stimuli in severe depression. Responses to sad stimuli show the strongest correlates of clinical improvement, particularly in the subgenual cingulate.

Proposed diagnostic criteria for apathy in Alzheimer's disease and other neuropsychiatric disorders

There is wide acknowledgement that apathy is an important behavioural syndrome in Alzheimer's disease and in various neuropsychiatric disorders. In light of recent research and the renewed interest in the correlates and impacts of apathy, and in its treatments, it is important to develop criteria for apathy that will be widely accepted, have clear operational steps, and that will be easily applied in practice and research settings. Meeting these needs is the focus of the task force work reported here. The task force includes members of the Association Française de Psychiatrie Biologique, the European Psychiatric Association, the European Alzheimer's Disease Consortium and experts from Europe, Australia and North America. An advanced draft was discussed at the consensus meeting (during the EPA conference in April 7th 2008) and a final agreement reached concerning operational definitions and hierarchy of the criteria. Apathy is defined as a disorder of motivation that persists over time and should meet the following requirements. Firstly, the core feature of apathy, diminished motivation, must be present for at least four weeks; secondly two of the three dimensions of apathy (reduced goal-directed behaviour, goal-directed cognitive activity, and emotions) must also be present; thirdly there should be identifiable functional impairments attributable to the apathy. Finally, exclusion criteria are specified to exclude symptoms and states that mimic apathy.

Subthalamic nucleus stimulation affects orbitofrontal cortex in facial emotion recognition: a PET study

Deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN) in Parkinson's disease is thought to produce adverse events such as emotional disorders, and in a recent study, we found fear recognition to be impaired as a result. These changes have been attributed to disturbance of the STN's limbic territory and would appear to confirm that the negative emotion recognition network passes through the STN. In addition, it is now widely acknowledged that damage to the orbitofrontal cortex (OFC), especially the right side, can result in impaired recognition of facial emotions (RFE). In this context, we hypothesized that this reduced recognition of fear is correlated with modifications in the cerebral glucose metabolism of the right OFC. The objective of the present study was first, to reinforce our previous results by demonstrating reduced fear recognition in our Parkinson's disease patient group following STN DBS and, second, to correlate these emotional performances with glucose metabolism using ¹⁸FDG-PET. The ¹⁸FDG-PET and RFE tasks were both performed by a cohort of 13 Parkinson's disease patients 3 months before and 3 months after surgery for STN DBS. As predicted, we observed a significant reduction in fear recognition following surgery and obtained a positive correlation between these neuropsychological results and changes in glucose metabolism, especially in the right OFC. These results confirm the role of the STN as a key basal ganglia structure in limbic circuits.

Aripiprazole : à propos de cas cliniques chez des patients souffrant de schizophrénie ou d’un trouble schizo-affectif

INTRODUCTION

In this study, we present seven case reports concerning patients suffering from schizophrenia or schizo-affective disorders, treated by aripiprazole.

STUDY DESIGN

Through these patient case reports, we have attempted to highlight the specificities of aripiprazole's action on schizophrenic symptoms, especially in the cognitive dimension. In acting as a regulator more than as a brake on the translation messages between neurons, aripiprazole does not increase cognitive disorders, but may have a procognitive affect.

RESULTS

We particularly noticed an improvement in attention abilities, both in selective attention - in order to take into account the context of the situation - and in sustained attention allowing patients to maintain a stable and appropriate level of efficiency while performing an activity. Case reports (n 2, n 3 and n 5) also seem to show the ability of aripiprazole to improve working memory: indeed, abilities of patients to maintain and recall information regarding different cognitive activities required in rehabilitation psychiatric care were noticed with aripiprazole while they were not with previous antipsychotic drugs used in the same patients.

DISCUSSION

Our sample, although too small for global consideration, suggests that aripiprazole provides stimulating properties for schizophrenic patients including those with primary deficient syndrome. This action, probably through cognitive improvement, needs some clarification in more precisely defining deficit features as juxtaposed by the classical criteria used on the SANS-SAPS and PANSS scales. Finally, we should stress aripiprazole's rapidity of effect. In half the cases, the reported improvement in our patients occurred during the first week of treatment. Hence, the patient should be informed of the short time-span effect for aripiprazole, in order to prevent the emergence of symptoms due to the rapid switch of medication and eventual side effects.

CONCLUSION

Aripiprazole acts as a partial agonist of D2 receptors as well as a partial agonist of 5HT1A and an antagonist of 5HT2A. This drug constitutes the first that permits regulation of both the dopamine and serotonine systems: dopamine activity is blocked when D2 receptors are over-stimulated and increased when D2 receptors require stimulation; on the other hand, in the cortical region, the inactivation of 5HT2A allows for a release of dopamine firing, whereas in the striatum where the 5HT2A receptors density is increased, their blockage inhibits dopamine release and limits extrapyramidal symptoms. In addition, the synergy between 5HT1A antagonism and 5HT2A antagonism seems to provide aripiprazole with both anxiolytic and affective properties. Finally, the absence of an affinity for histamine, muscarinic and adrenergic alpha-1 receptors limits the side effects compared to other antipsychotic drugs.

Does subthalamic nucleus stimulation induce apathy in Parkinson's disease?

BACKGROUND

Subthalamic Nucleus Deep Brain Stimulation (STN-DBS) has been shown to significantly improve motor symptoms in advanced Parkinson's disease (PD). Only few studies, however, have focused on the non-motor effects of DBS.

METHODS

A consecutive series of 15 patients was assessed three months before (M-3), then three months (M3) and six months (M6) after surgery. Mean (+/- SD) age at surgery was 59.7 (7.6). Mean disease duration at surgery was 12.2 (2.8) years. The Mini International Neuropsychiatric Inventory was used to assess psychiatric disorders three months before surgery. Depression was evaluated using Montgomery and Asberg Rating Scale (MADRS). Anxiety was evaluated using the AMDP system (Association for Methodology and Documentation in Psychiatry). Apathy was particularly evaluated using the Apathy Evaluation Scale (AES) and the Starkstein Scale. All these scales were performed at every evaluation.

RESULTS

Apathy worsened at M3 and M6 after STN-DBS in comparison with the preoperative evaluation: the AES mean score was significantly impaired between the preoperative (38.4+/-7.1) and both the postoperative M3 (44.6+/-9.5, p = 0.003) and M6 scores (46.0+/-10.9, p = 0.013). Significant worsening of apathy was confirmed using the Starkstein scale. There was no evidence of depression: the mean MADRS score did not differ before surgery (9.1+/-7.4) and at both M3 (8.6+/-8.2) and M6 (9.9+/-7.7) after STN-DBS. The anxiety level did not change between preoperative (9.4+/-9.2) and both M3 (5.5+/-4.5) and M6 (6.6+/-4.6) postoperative states.

CONCLUSION

Although STN-DBS constitutes a therapeutic advance for severely disabled patients with Parkinson's disease, we should keep in mind that this surgical procedure may contribute to the inducing of apathy. Our observation raises the issue of the direct influence of STN- DBS on the limbic system by diffusion of stimulus to the medial limbic compartment of STN.

Assembly-controlled regulation of chloroplast gene translation

Studies of the biogenesis of the photosynthetic protein complexes in the unicellular green alga Chlamydomonas reinhardtii have pointed to the importance of the concerted expression of nuclear and chloroplast genomes. The accumulation of chloroplast- and nuclear-encoded subunits is concerted, most often as a result of the rapid proteolytic disposal of unassembled subunits, but the rate of synthesis of some chloroplast-encoded subunits from photosynthetic protein complexes, designed as CES proteins (Controlled by Epistasy of Synthesis), is regulated by the availability of their assembly partners from the same complex. Cytochrome f, a major subunit of the cytochrome b(6)f complex is a model protein for the study of the CES process. In the absence of subunit IV, another subunit of the cytochrome b(6)f complex, its synthesis is decreased by 90%. This results from a negative autoregulation of cytochrome f translation initiation, mediated by a regulatory motif carried by the C-terminal domain of the unassembled protein [Choquet, Stern, Wostrikoff, Kuras, Girard-Bascou and Wollman (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 4380-4385]. Using site-directed mutagenesis, we have characterized this regulatory motif. We discuss the possible implications regarding the mechanism of the CES process for cytochrome f expression. We have studied the possible generalization of this mechanism to other CES proteins.

The light sensitivity of ATP synthase mutants of Chlamydomonas reinhardtii

Chlamydomonas reinhardtii mutants defective in the chloroplast ATP synthase are highly sensitive to light. The ac46 mutant is affected in the MDH1 gene, required for production or stability of the monocistronic atpH mRNA encoding CF(O)-III. In this and other ATP synthase mutants, we show that short-term exposure to moderate light intensities-a few minutes-induces an inhibition of electron transfer after the primary quinone acceptor of photosystem II (PSII), whereas longer exposure-several hours-leads to a progressive loss of PSII cores. An extensive swelling of thylakoids accompanies the initial inhibition of electron flow. Thylakoids deflate as PSII cores are lost. The slow process of PSII degradation involves the participation of ClpP, a chloroplast-encoded peptidase that is part of a major stromal protease Clp. In the light of the above findings, we discuss the photosensitivity of ATP synthase mutants with respect to the regular photoinhibition process that affects photosynthetic competent strains at much higher light intensities.

Identification of the initiation codon for the atpB gene in Chlamydomonas chloroplasts excludes translation of a precursor form of the beta subunit of the ATP synthase

The chloroplast atpB gene of Chlamydomonas reinhardtii, which encodes the beta subunit of the ATP synthase, contains three in-frame ATGs that are candidate translation initiation codons. An earlier study revealed that the N terminus of the assembled beta subunit maps at the +2 position with respect to the second in-frame methionine codon (Fiedler et al. 1995). Using chloroplast transformation, we have examined the possibility that either of the two additional in-frame ATG codons is competent for translation initiation. We provide evidence that translation of atpB is initiated exclusively at the second ATG codon. We conclude that the beta subunit is not synthesized with an N-terminal leader before its assembly into a functional ATP synthase complex.

The chloroplast atpA gene cluster in Chlamydomonas reinhardtii. Functional analysis of a polycistronic transcription unit

Most chloroplast genes in vascular plants are organized into polycistronic transcription units, which generate a complex pattern of mono-, di-, and polycistronic transcripts. In contrast, most Chlamydomonas reinhardtii chloroplast transcripts characterized to date have been monocistronic. This paper describes the atpA gene cluster in the C. reinhardtii chloroplast genome, which includes the atpA, psbI, cemA, and atpH genes, encoding the alpha-subunit of the coupling-factor-1 (CF1) ATP synthase, a small photosystem II polypeptide, a chloroplast envelope membrane protein, and subunit III of the CF0 ATP synthase, respectively. We show that promoters precede the atpA, psbI, and atpH genes, but not the cemA gene, and that cemA mRNA is present only as part of di-, tri-, or tetracistronic transcripts. Deletions introduced into the gene cluster reveal, first, that CF1-alpha can be translated from di- or polycistronic transcripts, and, second, that substantial reductions in mRNA quantity have minimal effects on protein synthesis rates. We suggest that posttranscriptional mRNA processing is common in C. reinhardtii chloroplasts, permitting the expression of multiple genes from a single promoter.

Chloroplasts can accommodate inclusion bodies. Evidence from a mutant of Chlamydomonas reinhardtii defective in the assembly of the chloroplast ATP synthase

We identified two neighboring missense mutations in the chloroplast atpA gene which are responsible for the defect of ATP synthase assembly in the FUD16 mutant from Chlamydomonas reinhardtii. The two corresponding amino acid substitutions, Ile184-->Asn and Asn186-->Tyr, occurred at strictly conserved sites among the alpha and beta subunits of (C)F1 complexes from bacteria, mitochondria, and chloroplasts. The altered region in the alpha polypeptide chain is located 7 amino acids downstream of the P-loop, which forms most of the conserved nucleotide binding site. Although the resulting chloroplast mutant fails to accumulate most of the ATP synthase subunits, it displays an increased intracellular content in both the alpha and beta subunits. We demonstrate that the two subunits do not bind to the thylakoid membranes but associate and overaccumulate in the chloroplast stroma as inclusion bodies. Increased rates of synthesis of the two subunits in the mutant point to an early interaction between the two subunits during their biogenesis.

A nuclear mutation affects the synthesis of the chloroplast psbA gene production Chlamydomonas reinhardtii

The effect of the nuclear mutation F34 on the synthesis of chloroplast-encoded photosystem II (PSII) polypeptides has been controversial. While we had concluded that the synthesis of the psbC gene product (P6) was specifically deficient in this mutant, another laboratory has found that the synthesis of the psbA gene product, the herbicide-binding protein D1, was primarily affected. These conflicting results were re-analyzed through genetic and biochemical characterization of the different strains used by the two laboratories in question. While the strain used in our laboratory carries the single F34 mutation responsible for the deficiency of P6, the other strain contains three nuclear mutations: the original F34 mutation, a suppressor mutation of F34 and a second PSII mutation, F35. Mutation F35 does not affect P6 synthesis but is responsible for the deficiency in the synthesis of the herbicide-binding protein D1. Furthermore, since both F34 and F35 mutant strains accumulate wild-type levels of psbC and psbA transcripts, we show that these nuclear mutations affect nuclear genes whose products are involved in the expression of psbC or psbA at a post-transcriptional level.

Evidence for Nuclear Control of the Expression of the atpA and atpB Chloroplast Genes in Chlamydomonas

We analyzed three nuclear mutants of Chlamydomonas reinhardtii altered in the expression of the chloroplast genes atpA or atpB coding for the [alpha] or [beta] subunit of the chloroplast ATP synthase. These mutants revealed the existence of three nuclear products controlling the expression of the two chloroplast genes: the first one acts on the translation of the atpA transcript, and the two others act specifically on the stability of either the atpB or the atpA mRNAs. The nuclear mutation responsible for the decreased stability of the atpB mRNA prevented translation of the corresponding polypeptide. In contrast, the mutation responsible for the decreased stability of the atpA mRNA had limited effect on the translation of the [alpha] subunit, thereby allowing its accumulation and assembly in an active ATP synthase. Although acting originally on the expression of only one of the two main coupling factor 1 subunits, the three mutations caused a change in the translation rate of the other subunit, as viewed in 5-min pulse labeling experiments. This is indicative of a concerted expression of the [alpha] and [beta] subunits at an early post-translational step, or during translation, that may be critical for the assembly of the chloroplast ATP synthase.

Posttranslational events leading to the assembly of photosystem II protein complex: a study using photosynthesis mutants from Chlamydomonas reinhardtii

We studied the assembly of photosystem II (PSII) in several mutants from Chlamydomonas reinhardtii which were unable to synthesize either one PSII core subunit (P6 [43 kD], D1, or D2) or one oxygen-evolving enhancer (OEE1 or OEE2) subunit. Synthesis of the PSII subunits was analyzed on electrophoretograms of cells pulse labeled with [14C]acetate. Their accumulation in thylakoid membranes was studied on immunoblots, their chlorophyll-binding ability on nondenaturating gels, their assembly by detergent fractionation, their stability by pulse-chase experiments and determination of in vitro protease sensitivity, and their localization by immunocytochemistry. In Chlamydomonas, the PSII core subunits P5 (47 kD), D1, and D2 are synthesized in a concerted manner while P6 synthesis is independent. P5 and P6 accumulate independently of each other in the stacked membranes. They bind chlorophyll soon after, or concomitantly with, their synthesis and independently of the presence of the other PSII subunits. Resistance to degradation increases step by step: beginning with assembly of P5, D1, and D2, then with binding of P6, and, finally, with binding of the OEE subunits on two independent high affinity sites (one for OEE1 and another for OEE2 to which OEE3 binds). In the absence of PSII cores, the OEE subunits accumulate independently in the thylakoid lumen and bind loosely to the membranes; OEE1 was found on stacked membranes, but OEE2 was found on either stacked or unstacked membranes depending on whether or not P6 was synthesized.