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M-O Krebs

Publications and source records attributed to M-O Krebs.

10 recordsLinked to original sources
PubMed2006

Peri-pubertal maturation after developmental disturbance: a model for psychosis onset in the rat.

Schizophrenia is thought to be associated with abnormalities during neurodevelopment although those disturbances usually remain silent until puberty; suggesting that postnatal brain maturation precipitates the emergence of psychosis. In an attempt to model neurodevelopmental defects in the rat, brain cellular proliferation was briefly interrupted with methylazoxymethanol (MAM) during late gestation at embryonic day 17 (E17). The litters were explored at pre- and post-puberty and compared with E17 saline-injected rats. We measured spontaneous and provoked locomotion, working memory test, social interaction, and prepulse inhibition (PPI). As compared with the saline-exposed rats, the E17 MAM-exposed rats exhibited spontaneous hyperactivity that emerged only after puberty. At adulthood, they also exhibited hypersensitivity to the locomotor activating effects of a mild stress and a glutamatergic N-methyl-D-aspartate receptor antagonist (MK-801), as well as PPI deficits whereas before puberty no perturbations were observed. In addition, spatial working memory did not undergo the normal peri-pubertal maturation seen in the sham rats. Social interaction deficits were observed in MAM rats, at both pre- and post-puberty. Our study further confirms that transient prenatal disruption of neurogenesis by MAM at E17 is a valid behavioral model for schizophrenia as it is able to reproduce some fundamental features of schizophrenia with respect to both phenomenology and temporal pattern of the onset of symptoms and deficits.

Age Factors↗
PubMed2004

Working memory deficits in adult rats after prenatal disruption of neurogenesis.

We investigated the cognitive consequences of a prenatal injection of the mitotic inhibitor methylazoxymethanol (MAM) into pregnant rats at embryonic day 15 (E15) or 17 (E17). The male offspring were tested when adult on a version of the radial-arm maze task that assesses spatial working memory with an extended delay, where performance is dependent, in part, on the hippocampal-prefrontal circuit. A major impairment of spatial learning was observed in E15 MAM rats. However, the E17 MAM rats did learn the rule but were impaired selectively in the 30-min delay-interposed task. Morphologically, the E15 MAM rats exhibited dramatic gross brain abnormalities, whereas the E17 MAM animals displayed aberrant cell migration in the hippocampus and a disrupted laminar pattern in the neocortex. These results suggest that late gestational MAM injection (E17) causes a cognitive impairment in a prefrontal cortex-hippocampus-dependent working memory task. This approach could provide a new developmental model of disorders associated with working memory deficits, such as schizophrenia.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

[Neurodevelopmental hypothesis in schizophrenia].

The hypothesis for a neurodevelopmental basis to the underlying physiopathological disorder leading to schizophrenia has been proposed by many investigators for more than two decades. This hypothesis is supported by -several lines of evidence. Pregnancy and delivery complications, particularly those with known or presumed impact on fetal neurologic development, result in increased risk for psychotic disorders. Other possible etiologic candidates include viral infections. Minor physical anomalies, manifesting as slight anatomical defects of the head, hair, eyes, mouth, hands and feet, as dematoglyphic fluctuating asymmetries, are due to some injury occurring during the first or second trimester of fetal life, and are more common among patients with schizophrenia and in their unaffected siblings than in the general population. But a major Issue in a such neurodevelopmental model theory is the delayed onset of the schizophrenic disorder. Although early signs and prodromal symptoms can be defined retrospectively in patients who have developed schizophrenia, they do have to be confirmed as early predictors in prospective and longitudinal studies. Abnormalities in brain development and maturation seem to begin prenatally, but may continue throughout childhood and the observed changes during these periods must have -consequences for the neuronal circuitry and connectivity. Advances in brain imaging have now led to the identification of a great number of brain abnormalities in schizophrenia. The most consistently replicated structural anomaly present in the brains of patients with chronic schizophrenia is ventricular enlargement. These findings also include medial temporal lobe structures (which include the amygdala, hippocampus, and parahippocampal gyrus), and neocortical temporal lobe regions (superior temporal gyrus). There is also some evidence for frontal lobe abnormalities, particularly prefrontal gray matter and orbitofrontal regions. Similarly, there are findings for parietal lobe abnormalities (particularly of the inferior parietal lobule which includes both supramarginal and angular gyri) and subcortical abnormalities (basal ganglia, corpus callosum, and thalamus) but more equivocal evidence for cerebellar abnormalities. However, it is possible that the brain structural abnormalities observed in schizophrenia are not only due to neurodevelopmental anomalies, but also to an alteration in cortical plasticity and maturation processes that occurs over the long course of the disease. The genetic predisposition for schizophrenia has been confirmed in many studies. It is utterly disappointing that molecular genetic approaches have so far not yielded conclusive evidence for vulnerability or protection genes in schizophrenia. Future studies will likely benefit from: 1) studying more homogeneous patient groups, 2) studying high risk populations such as biological relatives of patients with schizophrenia, 3) using longitudinal and prospective methodological design in order to confirm the predictive validity of neurodevelopmental clues found in patients with schizophrenia, 4) applying newer strategies such as composite phenotypes of developmental origin, in combination with new genetic methods.

Amygdala↗
PubMedDate not supplied

[Schizophrenia and amphetamine dependence. A case report].

UNLABELLED: Whereas observations of psychotic disorders induced by amphetamines are common, few observations described the impact of chronic amphetamine abuse on schizophrenic patients. We report the case of a schizophrenic patient who presented with amphetamine dependence for several years, without other accompanying addiction. CASE REPORT: During his adolescence, Mr. X. gradually developed delusional beliefs of persecution and telepathy. He believed that the other pupils and teachers spoke about him in malicious terms. At the age of 23, Mr. X began to consume 60-100 mg/week of amphetamines orally. He consumed amphetamines during 7 years. The delusions, in particular the auditory hallucinations worsened after the use of amphetamines. Subsequently, he married and was declared unfit for national service due to the psychotic disorders. Mr. X received neuroleptic treatment with moderate effects on the psychotic symptoms. Between the age of 24 and 30, the patient presented persecutory, megalomanic and physical transformation beliefs, delusions of being controlled as well as auditory, somatic-tactile and visual hallucinations. At the age of 30, while he had stopped his consumption of amphetamines for 9 months, the patient, overwhelmed with the delusions, murdered his wife. He was sent in jail for 13 months, and subsequently hospitalized for one year in a high security psychiatric department and 7 years in our psychiatric department. The neuroleptic treatment was effective, particularly against the hallucinations. Following stabilisation, the symptomatology of the patient was marked by a disorganization syndrome, including prominent thought disorder, disorganized speech, associative loosening, frequent derailments and negative signs of schizophrenia, in particular affective flattening and blunting of emotional expression. When the patient was 43, a trial discharge was authorized owing to improvement of his condition. The neuroleptic treatment was switched with single-drug olanzapine therapy, 10 mg/day which improved the negative symptoms. Mr. X. resumed part-time professional activities and remarried. DISCUSSION: The patient fulfilled the DSM IV criteria for schizophrenia and for amphetamine dependence assessed using the Composite International Diagnostic Interview (CIDI). He presented, in particular, withdrawal syndrome when amphetamines were discontinued. The amphetamine consumption was followed by a marked deterioration in the delusions, particularly the hallucinations. Worsening of the positive symptoms in schizophrenic patients by amphetamines has been established in single dose studies, in particular characterized by persecutory delusions and hallucinations. On the other hand, amphetamines tend to transiently and moderately reduce the negative symptoms. Some stu-dies have shown that amphetamine consumption promoted violent acting out in non-schizophrenic subjects. In our observation, the acting out may be not related to the acute effects of these substances, since it occurred 9 months after stated discontinuation of amphetamine consumption. However, the cerebral toxicity and psycho-behavioural disturbances related to amphetamines might be prolonged after withdrawal. In non-schizophrenic patients, the existence of prolonged neurotoxicity of amphetamines and related psycho-behavioral disturbances has been suggested. The prolonged administration of amphetamines to animals produces neuro-axonal degeneration in the striatum, the frontal cortex, the nucleus accumbens and the amygdala. In human, there are some evidence of persistant deteriorations of the serotoninergic and dopaminergic systems in the caudate nucleus, the putamen and the nucleus accumbens following amphetamine consumption. CONCLUSION: The neurobiological and psycho-behavioural effects of amphetamines may be prolonged following withdrawal in both schizophrenic and non-schizophrenic patients.

Adult↗
PubMedDate not supplied

[Visuospatial context processing in untreated schizophrenic patients and relation to disorganization syndrome].

AIM: Previous studies on schizophrenia have suggested that context-processing disturbances were one of the core cognitive deficits present in schizophrenia. Schizophrenic patients have a failure either of inhibition strategy and maintenance of visuospatial information (25) in condition of contextual interference. In the present study, we explored the performances of untreated schizophrenic patients with 2 tasks exploring detection and long term retention of complex visual features and field dependence-independence tasks were selected. These abilities involve temporary maintenance of visuospatial information and executive functioning of visual working memory system. Several studies have shown that cognitive deficit may depend on schizophrenic symptomatology. However results remain controversial in determining the specific influence of negative and positive symptomatologies as well as clinical disorganization. Our goal was to explore the processing of spatial context and its relation to disorganized syndrome. This study was approved by the local ethic committee. METHODOLOGY: Thirty-six schizophrenic patients were included according to DSM IV criteria (19 neuroleptic naïve, 17 unmedicated patients during more than 3 months). Thirty-six healthy controls were matched to patients for age, gender and level of education. Absence of axis 1 pathology was attested for controls with SCID-NP. Current symptomatology was evaluated by the Positive and Negative Syndrome Scale (PANSS) (14). Clinical disorganisation was evaluated with the disorganisation score established upon a factorial analysis of PANSS by Lepine and Lançon. Items selected to distinguish the disorganised group were abstraction, disorganization, orientation, and attention. PROCEDURE: Two tasks of embedded figures were administered individually to patients and controls. The Faverge task (Research of Figures-RF) (10) evaluates the ability to recognize the target from spatial complex geometrical figures. The Group Embedded Figure Task (GEFT - Oltman) assesses the detection and maintenance of visual target and its recognition within a complex figure. Performance between patients and controls were compared with the Student T test. The comparison of two clinical subgroups of disorganized and low disorganized patients and control group was performed with an ANOVA. Tuckey test was used for pairwise comparisons. RESULTS: We defined two subgroups of patients, disorganized patients (subscore 12, n=17) and low disorganized patients (subscore<12, n=19). Theses 2 subgroups were similar for age and level of education. Concerning the two tasks, there was no significant difference between schizophrenic patients and normal controls. The comparison between subgroups of disorganized and low disorganized patients, for RF task, showed a decrease of correct answers with disorganized patients (p<0.05). For GEFT task, disorganized patients had a decrease of correct answers p<0.01) and more errors (p<0.01) and omissions (p<0.05). The low disorganized patients exhibited for the two tests comparable performance to controls. The disorganized patients had a decrease of right answers (p<0.05) and more errors (p<0.05) than controls for GEFT task and no significant difference for RF. However, with IQ (evaluated with an abstract reasoning test) introduced as covariate, only correct answers for GEFT task remain significant (p<0.05). DISCUSSION: The weak performance of disorganized schizophrenic patients for two tasks RF and GEFT showed that treatment of visuospatial information was impaired in the first perceptive phase of selection and in the organization of information (RF), especially with the maintenance of visual information in memory (GEFT). By contrast, low disorganized patients demonstrated a correct analytic treatment of elementary processing and visuospatial working memory. CONCLUSION: The severity of disorganization influences the visuospatial context processing and visuospatial working memory. These results show the heterogeneity of cognitive functioning regarding to schizophrenic symptomatologies. This difficulty could be related to a problem of central executive functioning in the visuospatial component of working memory, possibly mediated by the dysfunction of dorsolateral prefrontal cortex.

Adult↗
PubMedDate not supplied

[Cannabis and schizophrenia: demographic and clinical correlates].

UNLABELLED: The high prevalence of psychoactive substance abuse or dependence among schizophrenic patients has now been well established. Mueser et al. stressed the need to assess the abuse of specific classes of substances and analyse the data accordingly. The objective of this study was to compare the socio-demographic correlates and the clinical features in a group of schizophrenic patients with a lifetime cannabis abuse or dependence according to the DSM III-R with a group of schizophrenic patients who had never presented any abuse or dependence. SUBJECTS AND METHODS: The study included 124 subjects with diagnoses of schizophrenia or schizoaffective disorders according to the DSM III-R. Inclusion criteria for participation in the study were age 18 years or older and willingness to provide consent to participate in the study. The inpatients were evaluated when their condition was stabilised. Assessment tools were the psychoactive substance use disorder section of the Composite International Diagnostic Interview (CIDI), the Positive and Negative Syndrome Scale (PANSS), the Global Assessment of Functioning Scale (GAF). Subjects with cannabis abuse or dependence during their lifetime were compared with subjects without abuse or dependence, using chi(2) test for categorical variables and analyses of covariance (ANCOVA) for quantitative variables. RESULTS: Forty-nine subjects (42,6%) presented lifetime abuse or dependence on one or more substances. Since 19 patients with alcohol, stimulant, sedative or opiate abuse or dependence were excluded, the study finally included 96 subjects including a first group of schizophrenic patients with cannabis abuse (n=6) or dependence (n=24) and a second group without any psychoactive substance abuse (n=66). Thirteen (11.3%) patients presented cannabis abuse or dependence within the 6 months prior to the assessment. The mean SD age of onset of cannabis abuse or dependence was 19.6 +/- 3.0 years. Cannabis abuse/dependence preceded the first psychiatric treatment in 70% of the subjects (n=21). 83.3% of the schizophrenic patients with cannabis abuse or dependence were male (n=25) compared to 62.1% in the group without substance abuse (n=41) (chi(2)=4.32, df=1, p=0.04). Schizophrenic patients with cannabis abuse were significantly younger (mean age: 28.9 +/- 6.3 vs 37.0 +/- 12.7, ANCOVA, F=7.2, df=1,96 p=0.009). There was no significant difference between the two groups for marital status, (chi(2)=5.34, df=2, p=0.07), level of education, (chi(2)=0.93, df=2, p=0.62) professional status, (chi(2)=8.7, df=5, p=0.11), on PANSS total score (ANCOVA, F=0.42, df=1,93, p=0.52), GAF score (ANCOVA, F=0.06, df=1,92, p=0.80), mean number of hospitalizations (ANCOVA, F=3.25, df=1,85, p=0.08), mean age of first psychiatric contact (ANCOVA, F=0.74, df=1,93, p=0.39), and neuroleptic dosages (ANCOVA, F=0.03, df=1,90, p=0.87). In contrast, the total duration of hospitalization was significantly longer for the group with cannabis abuse. Patients with cannabis abuse were more likely to have an history of suicide attempts than subjects without substance abuse (chi(2)=11.52, df=1, p=0.0007). DISCUSSION: The prevalence rates for substance abuse and the socio-demographic characteristics of the population of our study are consistent with findings of previous studies. Male gender and age were significantly related to history of cannabis abuse or dependence. Cannabis abuse frequently preceded the onset of psychiatric treatment. However, both schizophrenia and substance abuse tend to develop gradually, with no clear demarcation for the onset of schizophrenia. The absence of any link between the scores for the subscales of the PANSS and cannabis abuse, both in our study and in some retrospective previous studies, is not suggestive of cannabis abuse as a self-medication of positive or negative symptoms of schizophrenia. Self-medication could concern other symptoms, such as cognitive deficits. In addition, the hypothesis of self-medication has especially been suggested in cocaine abuse or dependence. Some limitations to this study can be discussed. First, although the recruitment was systematic and done in a public mental health service, the patients of our study are not necessarily representative of all schizophrenic patients. Secondly, as in any retrospective study, the prevalence of lifetime substance abuse may have been under-estimated. Urinary toxicology tests may have been able to improve the sensitivity of the diagnosis of recent substance abuse, but structured interviews are more appropriate for the diagnosis of lifetime substance abuse in schizophrenic patients than urinary toxicology tests. CONCLUSION: The socio-demographic characteristics of cannabis abuse or dependence in schizophrenia are similar to those found in general population. Cannabis using schizophrenic patients were more likely to be younger and male than non users. The duration of hospitalization was significantly longer for the group with cannabis abuse. Prevalence of suicide attempts in schizophrenia is closely correlated to cannabis abuse.

Adult↗
PubMedDate not supplied

[Prodromal symptoms of schizophrenia].

The concept of prodromal symptoms of schizophrenia has frequently been subject to debate. Authors widely admit the existence of early specific and non-specific signs preceding the first psychotic episode; however, they have yet to clearly demonstrate their ability to predict and specify the outbreak of a psychosis. These prodromal symptoms consist of behavioral abnormalities, pseudo-neurotic signs, subtle cognitive and affective changes. All these symptoms vary from patient to patient. In general, it is widely believed that future patients go through a variety of abnormal, subjective experiences that progressively develop during their pre-puberty and puberty periods. However, the limit of this assessment is that an individual could present the same prodromal symptoms without necessarily developing a psychotic illness, as a result of toxic intake, a situational crisis, etc. Furthermore, while the prodrome is a retrospective concept, its value and specificity can only be prospective, given that patients' descriptions of pre-morbid changes may be corrupted by inefficient memory reconstruction. DSM III-R included prodromal symptoms; individual presenting such symptoms would potentially present psychopathological vulnerability to psychosis regardless of associated genetic risk. Several investigations have shed doubts on their measurement's reliability; therefore, this classification is no longer present in the latest version (DSM IV). Moreover, recent neurodevelopemental hypothesis on schizophrenia have paved the way for possible early intervention, especially because early treatments could well improve illness prognosis. This viewpoint is reinforced by the improved tolerance of new anti-psychotic treatment. In this report, we review the key Articles published over the last 15 Years on this matter. We distinguish two schools of thought: on one hand, the German school referring to the validity of particular neuro-psychological symptoms: attention, perception, proprioperception which can be assessed with many evaluation tools: PAS, TDI, BSABS, SPI-A. The German school points to the fact that patients experimenting such changes could potentially be aware of their state. On the other hand, the Anglo-Saxon school refers to the detection of an "at risk" population. The Anglo-Saxons no longer refer to "prodromal symptoms" but rather to a "prodromal period" that extends to about one Year. This period would begin with the patient's first behavioral changes and extend until the first psychotic episode. Both schools agree that, at this stage, neither the recognition nor the description of the period preceding psychosis allows to effectively predict it. As a result, some Authors continue to refer to psychological changes forming a risk factor for the development of subsequent psychosis, rather than clear predictors of inevitable illness. As for relapses, prodromal signs and symptoms found in schizophrenic patients are both specific and non-specific. In most cases, patients experiment perceptions and behavioral changes before psychosis exacerbation. It is not uncommon for a substantial increase in prodromal symptoms to be followed by degradation in psychotic symptoms. On the other hand, many such increases in psychotic symptoms were not preceded by increases in possible prodromal symptoms; hence their importance in identifying the timing of an intervention, but many relapses will occur regardless of the detection of said symptoms.

Diagnosis, Differential↗