Investigation of the potential of yeast strains for phytase biosynthesis in a two-step screening procedure.

Research into phytase production is useful for improving the efficiency of animal production, reducing environmental impact, and contributing to the development of sustainable and efficient animal production systems. This study aims to investigate the potential of yeast strains for phytase biosynthesis in nutrient media. Phytase is a phosphomonoesterase (E.C 3.1.3.8) catalyzing in a ladder-like manner the dephosphorylation of phytic acid and its salts, with various resulting myo-inositol phosphates and phosphoric acid. Yeasts of the genera Saccharomyces, Zygosaccharomyces, Candida, and Pichia were evaluated in a two-step screening procedure for phytase production. One hundred and eighteen strains were screened in the first stage, which was conducted on four types of solid culture media containing calcium phytate as the selected background. On PSM medium, many strains were found to form halos as early as the 24th hour of development. Several strains with significant potential for enzyme production were evaluated in the second step of the screening. It was conducted in a liquid culture medium. In conclusion, the strain C. melibiosica 2491 was selected for further studies when cultured in a YPglu culture medium. Further research will focus on finding suitable conditions that increase the biosynthesis of the enzyme, which is of significant technological and practical interest for animal nutrition.

Unveiling the need of interactions for social N400s and supporting the N400 inhibition hypothesis.

When participants (Pps) are presented with stimuli in the presence of another person, they may consider that person's perspective. Indeed, five recent ERP studies show that the amplitudes of their N400s are increased. The two most recent ones reveal that these social-N400 increases occur even when instructions do not require a focus on the other's perspective. These increases also happen when Pps know that this other person has the same stimulus information as they have. However, in all these works, Pps could see the other person. Here, we tested whether the interaction occurring with this sight is important or whether these social N400 increases also occur when the other person is seated a bit behind Pps, who are aware of it. All had to decide whether the word ending short stories was coherent, incoherent, or equivocal. No social N400 increase was observed: N400s elicited by those words in Pps who were with a confederate (n = 50) were similar to those of Pps who were alone (n = 51). On the other hand, equivocal endings did not elicit larger N400s than coherent ones but triggered larger late posterior positivities (LPPs), like in previous studies. The discussion focuses on the circumstances in which perspective-taking occurs and on the functional significance of the N400 and the LPP.

Health and Social Case Management for the Inclusion of People Living with a Schizophrenic Disorder: The PASSVers Experience.

The way the social protection system in France is organized frequently leads to coordination difficulties between the social and healthcare sectors. A health and social program has been implemented in a French medical-psychological center to optimize the coherence of the pathway for people living with schizophrenia. This study evaluated the way users and professionals perceive this program so as to assess the relevance of double case management. Semi-structured interviews were conducted with users (N = 21) and professionals (N = 11) of this program and then analyzed with Alceste software. The results highlight the overall satisfaction of the participants with the program, and the double case management was shown to be beneficial in supporting people living with schizophrenia in their life project. These results indicate that this program enabled the emergence of a collective empowerment, which could assist with the recovery process of schizophrenia.

Study on Galanthus species in the Bulgarian flora.

Genus Galanthus (Amaryllidaceae) includes 19 species in Europe and the Middle East. The Flora of Bulgaria recognizes two species: G. nivalis L. and G. elwesii Hook. Galanthus elwesii is characterized by relatively high morphological variability, leading some authors to identify some populations as G. gracilis Celak. However, the occurrence of G. gracilis in the Bulgarian flora is disputed. The hypothesis was that populations previously identified as G. gracilis belong indeed to a separate species. Therefore, the objective of this study was to compare G. nivalis and G. elwesii with plants from populations previously identified as G. gracilis. Morphological, DNA, embryological and anatomical analyzes were conducted to meet the objective. The morphological characteristics and DNA dendrogram revealed that G. gracilis and G. elwesii were situated in the same cluster and had significant morphological similarity, whereas plants from populations identified as G. nivalis were dissimilar in morphology and situated in a separate cluster. The revealed features of the generative sphere showed similarities across the species. Scanning electron microscopy (SEM) analyses of the surface revealed that the anticillinal walls of G. elwesii and G. gracilis were straight, while those of G. nivalis were wavy. This research demonstrated that the plants of G. elwesii and those from populations identified as G. gracilis are morphologically, embryologically and genetically similar, thus refuting the hypothesis. This study did not provide sufficient evidence to support the claim of the existence of G. gracilis in the Bulgarian flora; the populations identified as G. gracilis in Bulgaria may be forms of G. elwesii.

An Event Related Potentials Study of Semantic Coherence Effect during Episodic Encoding in Schizophrenia Patients.

The objective of this electrophysiological study was to investigate the processing of semantic coherence during encoding in relation to episodic memory processes promoted at test, in schizophrenia patients, by using the N400 paradigm. Eighteen schizophrenia patients and 15 healthy participants undertook a recognition memory task. The stimuli consisted of pairs of words either semantically related or unrelated to a given category name (context). During encoding, both groups exhibited an N400 external semantic coherence effect. Healthy controls also showed an N400 internal semantic coherence effect, but this effect was not present in patients. At test, related stimuli were accompanied by an FN400 old/new effect in both groups and by a parietal old/new effect in the control group alone. In the patient group, external semantic coherence effect was associated with FN400, while, in the control group, it was correlated to the parietal old/new effect. Our results indicate that schizophrenia patients can process the contextual information at encoding to enhance familiarity process for related stimuli at test. Therefore, cognitive rehabilitation therapies targeting the implementation of semantic encoding strategies can mobilize familiarity which in turn can overcome the recollection deficit, promoting successful episodic memory performance in schizophrenia patients.

Impaired context processing during irony comprehension in schizotypy: An ERPs study.

Mentalizing deficits are a core manifestation of schizophrenia spectrum disorders. They contribute to the social handicap associated with the pathology, leading to disruption in autonomy, professional achievement, and interpersonal relationships. However, the underlying mechanisms of these deficits remain poorly understood. The aim of the present study was to test the hypothesis that context processing deficits would be responsible for mentalizing difficulties in schizotypy (personality traits considered as attenuated manifestations of schizophrenic symptoms) by using an irony comprehension task. Irony processing is a mentalizing exercise that requires the ability to take into account the semantic context to understand the literal meaning of the utterance, and to integrate the pragmatic context to infer the speaker's intention. These two steps of processing can be indexed by the N400 and P600 components, respectively, of event-related brain potentials (ERPs). Forty participants were assigned to high or low schizotypy groups according to their Schizotypal Personality Questionnaire (SPQ) score, and ERPs were recorded while they read short stories ending with a literal, ironic, or incompatible statement. In the low-SPQ group, there was a significant N400 semantic context effect (literal targets elicited less negative N400 amplitudes compared to incompatible targets) followed by a P600 pragmatic context effect (ironic targets evoked greater positive P600 amplitudes than literal targets). In contrast, there was neither a N400 nor P600 effect in the high-SPQ group. These abnormalities were associated with high interpersonal SPQ factor scores. These results show a strong association between context processing, mentalizing abilities, and interpersonal functioning in schizophrenia spectrum.

Effect of semantic coherence on episodic memory processes in schizophrenia.

Schizophrenia is associated with severe episodic retrieval impairment. The aim of this study was to investigate the possibility that schizophrenia patients could improve their familiarity and/or recollection processes by manipulating the semantic coherence of to-be-learned stimuli and using deep encoding. Twelve schizophrenia patients and 12 healthy controls of comparable age, gender, and educational level undertook an associative recognition memory task. The stimuli consisted of pairs of words that were either related or unrelated to a given semantic category. The process dissociation procedure was used to calculate the estimates of familiarity and recollection processes. Both groups showed enhanced memory performances for semantically related words. However, in healthy controls, semantic relatedness led to enhanced recollection, while in schizophrenia patients, it induced enhanced familiarity. The familiarity estimates for related words were comparable in both groups, indicating that familiarity could be used as a compensatory mechanism in schizophrenia patients.

Event-related brain potential study of expectancy and semantic matching in schizotypy.

Priming studies have revealed semantic processing abnormalities in subjects that display high schizotypal traits. The objective of the present study was to further elucidate the contribution of predictive (expectancy) and integrative (semantic matching) context processing to the semantic deficit described in schizotypy. Thirty-six participants were assigned into high or low schizotypy groups according to their score on the Schizotypal Personality Questionnaire (SPQ), and event-related brain potentials were recorded while these individuals performed semantic judgments based on asymmetrically associated word pairs. Viewed in one direction (forward), the target was highly predictable from the prime, whereas in the backward direction, the prime-to-target association was weak. It was assumed that the forward condition would be dependent on expectancy generation, while the backward condition would rely on semantic matching. In the low-SPQ group, forward and backward related words evoked a reduced (less negative) N400 amplitude compared to unrelated words, resulting in a significant forward and backward N400 priming effect, respectively. By contrast, only forward related words were facilitated in the high-SPQ group, resulting in significant forward priming and a lack of backward priming. Furthermore, the N400 amplitude for forward related words was less negative within the high-SPQ group in comparison to the low-SPQ group, which indicated easier semantic access to predictable words for high-SPQ individuals. Therefore, schizotypy may be associated with an imbalance in the use of predictive and integrative context processing strategies, namely preserved, if not over allocated, expectancy generation along with altered integration of unpredictable words due to semantic matching deficit.

An event-related potential study of predictive and integrative semantic context processing in subjects with schizotypal traits.

Context processing abnormalities may explain thought disorder in schizophrenia/schizotypy. This study aimed to assess predictive and integrative context processing in subjects with high or low scores on the Schizotypal Personality Questionnaire (SPQ). The N400 amplitude was recorded during semantic judgment of sentence pairs ending with a lateralized expected or unexpected word from the same or a different category (related and unrelated violation). In both groups, the N400 amplitude was less negative for expected words versus unrelated violations, regardless of which hemisphere received the stimulus, and for related versus unrelated violations, but only for left-hemisphere stimuli. The N400 amplitude for unrelated violations was less negative in subjects with high SPQ scores for both hemispheres. These results indicate that subjects with schizotypal traits use context to predict or integrate congruent words, but fail to inhibit incongruent words.

ERP evidence of a meaningfulness impact on visual global/local processing: when meaning captures attention.

Event-related potentials (ERPs) were recorded to investigate whether the meaningfulness of experimental stimuli impacted performances during global/local visual tasks. Participants were presented with compound stimuli, based on either meaningful letters, meaningful objects, or meaningless non-objects. The ERP recordings displayed typical early components, P1 and N1, evoked by task-related processes that affected global and local processes differently according to the meaningfulness of the stimuli. The effect of meaningfulness of the stimuli during global processing showed that P1 amplitudes were larger in response to objects and non-objects compared to letters, while letters and objects elicited larger N1 amplitudes than non-objects. Second, during local processing, the mean amplitudes of the ERPs recorded for object and letter stimuli were systematically smaller than the amplitudes recorded for non-object stimuli for both P1 and N1 components. In addition, object and letter stimuli elicited comparable mean ERP responses during local processing. These results are discussed in terms of the influences of both attentional and top-down identification processes. Taken together, these findings suggested that looking for meaning is crucial in the perception of visual scenes and that the meaningfulness nature of the stimuli should be taken into account in future studies.

Left but not right hemisphere semantic processing abnormalities in language comprehension in subjects with schizotypy traits.

Thought and language disorders in schizophrenia and schizotypy are thought to result from hemispheric dysfunction during semantic processing. Left hemisphere (LH) abnormalities are well established, but little is known about right hemisphere (RH) semantic processes. We explored hemispheric processing in 50 healthy volunteers assigned to high (h-SZT) or low schizotypy (l-SZT) group using the Schizotypal Personality Questionnaire (SPQ). Subjects were asked to make semantic judgments on sentence pair ending with a target that was either expected word (EW) or an unexpected word from the same (related violation, RV) or a different category (unrelated violation, URV). Targets were presented in a dichotic manner to the left or right ear. Analyses of reaction times in the l-SZT group showed semantic compatibility effect (URV-EW) in the LH and semantic memory activation effect (RV-URV) as well as semantic compatibility effect in the RH. The h-SZT group showed semantic memory activation but no semantic compatibility effect in the LH, the RH pattern resembling that of the l-SZT group. The magnitude of the LH semantic compatibility effect was inversely correlated with SPQ total scores and SPQ Cognitive-perceptual factor. Thus, RH semantic processes are effective and there is a deficit in LH focused activation in schizotypy.

N400 and P300 modulation as functions of processing level in schizophrenia patients exhibiting formal thought disorder.

In a semantic priming paradigm, the effects of different levels of processing on N400 were assessed by changing task demands in 10 schizophrenics and 10 matched controls. In the lexical decision task subjects had to discriminate between words and nonwords, and in the physical task subjects had to discriminate between cyan and blue ink letters. A lexicality test of reaction times demonstrated that the physical task was performed non-lexically in both groups. Moreover, a semantic priming reaction time effect was obtained only in the lexical decision task for the control group. The level of processing clearly affected event-related potentials. An N400 priming effect was only observed for the control group in the lexical decision task. By contrast, in the physical task a P300 effect was observed for either related or unrelated targets in both groups. Taken together, these results indicate that FTD schizophrenics are impaired specifically when task performance induces the semantic aspects of words as indexed by reduction of the N400 priming effect.

N400 anomalies in schizophrenia are correlated with the severity of formal thought disorder.

We explored the link between N400 anomalies and clinical profile in schizophrenia patients. N400 was recorded in 50 schizophrenia patients and 40 healthy controls during a lexical decision task with semantic priming. Comparison between controls and schizophrenia patients showed the classical anomalies reported for N400 in schizophrenia patients: greater amplitude for related words and lack of N400 effect. Analyses of the correlations between N400 effect and various symptoms of schizophrenia (formal thought disorder, positive symptoms, negative symptoms, overall symptoms, mean neuroleptic dose) or socioeducational data (age, vocabulary level, number of years of study) revealed that only the correlation with formal thought disorder was significant: the higher the scores for formal thought disorder, the lower the N400 effect observed.

An electrophysiologic study: can semantic context processes be mobilized in patients with thought-disordered schizophrenia?

OBJECTIVE: The aim of this study was to test the hypothesis that reinforcing the structuring of verbal material may bring about an improvement in contextualization processes in patients with formal thought-disordered schizophrenia. METHOD: A total of 38 schizophrenia patients with formal thought disorders and 24 matched healthy control subjects performed 2 lexical decision tasks, involving 2 levels of contextual structuring (with 16.7% and 33% of related words, respectively). The event-related potentials, N400 and late positive component (LPC), and behavioural variables (reaction times and error percentages) were analyzed. RESULTS: A context-structuring effect was observed on LPC, but not on N400. In subjects with schizophrenia, the N400 anomalies (that is, increase in amplitude for the related words and reduction of the N400 effect) persisted in both context-structuring conditions. Similarly, a reduction in LPC amplitude for the unrelated word category, as well as a decrease in the LPC effect, was observed in these patients. CONCLUSIONS: The schizophrenia patients with formal thought disorders did not benefit from the structuring of the context to implement context integration strategies. This deficit appears to be stable. The results are discussed within the framework of a previously published model of language comprehension.