In order to improve the production of acarbose, the fermentation medium of acarbose-producing strain Actinoplanes sp. KCTC 9161 – L14 mutant was optimized in this internship. Fractional factorial design was employ to investigate the influences of glucose, maltose and corn power on acarbose production (by a-glucosidase inhibitory ability). Two significant factors: glucose and maltose have significant and positive effects on acarbose amount. In addition, a model was obtained from the regression results of fractional factorial experiment. Other success, we demonstrated that chromatography by active charcoal column can used to purify acarbose from fermentation broth. Acarbose amount in purification solution was 191.5 g/L and an acarbose - purification process was inducted. / Nhằm mục đích nâng cao khả năng sinh tổng hợp hoạt chất acarbose từ chủng đột biến Actinoplanes sp. KCTC 9161-L14, môi trường lên men của chủng dùng để sản xuất acarbose đã được tối ưu hóa. Một phần mềm thiết kế đã được thiết lập để khảo sát ảnh hưởng của glucose, maltose và bột ngô đến khả năng sản xuất acarbose (thông qua hoạt tính ức chế a-glucosidase). Kết quả đã cho thấy, hai yếu tố glucose và maltose có ý nghĩa quan trọng và ảnh hưởng trực tiếp đến khả năng sinh tổng hợp acarbose. Một phương trình đã được hình thành từ kết quả tối ưu. Bên cạnh đó, chúng tôi đã chứng minh được cột sắc ký sử dụng than hoạt tính có thể tinh sạch acarbose từ dịch lên men. Hàm lượng acarbose trong dung dịch tinh sạch đạt 191,5 g/l và một quy trình tinh sạch acarbose được đề xuất.

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Duration tuning in the mammalian inferior colliculus (IC) is created by the interaction of excitatory and inhibitory synaptic inputs. We used extracellular recording and paired-tone stimulation to measure the strength and time-course of the contralateral inhibition and offset-evoked excitation underlying duration-tuned neurons (DTNs) in the IC of the awake bat. The onset time of a short, best duration (BD), excitatory probe tone was varied relative to the onset of a longer-duration, non-excitatory (NE) suppressor tone. Spikes evoked by the roving BD tone were suppressed or facilitated when the stationary NE tone was varied in frequency or amplitude. When the NE tone frequency was presented away from the cell’s best excitatory frequency (BEF) or at lower SPLs, the onset of inhibition was relatively constant whereas the offset and duration of inhibition decreased. Excitatory and inhibitory frequency response areas were measured and best inhibitory frequencies matched best excitatory frequencies; however, inhibitory bandwidths were broader than excitatory bandwidths. Excitatory rate-level and inhibitory suppression-level functions were also measured and the dynamic ranges and inflection points were similar, which is hypothesized to play a role in the level tolerance of responses measured from DTNs. We compared the latency of offset-locked facilitation to the onset or offset of inhibition as a function of frequency and amplitude; we found that the facilitation was more related to the onset of inhibition. Moreover, facilitation typically preceded the offset of inhibition – suggesting that it is a separate excitatory input to DTNs and not a rebound from inhibition. We conclude that DTNs receive inputs that generate and preserve temporal selectivity. / Dissertation / Doctor of Philosophy (PhD)

Inhibitory control processes have intensively been studied in cognitive science for the past decades. Even though the neural dynamics underlying these processes are increasingly better understood, a critical open question is how the representational dynamics of the inhibitory control processes are modulated when engaging in response inhibition in a relatively automatic or a controlled mode. Against the background of an overarching theory of perception-action integration, we combine temporal and spatial EEG signal decomposition methods with multivariate pattern analysis and source localization to obtain fine-grained insights into the neural dynamics of the representational content of response inhibition. For this purpose, we used a sample of N = 40 healthy adult participants. The behavioural data suggest that response inhibition was better in a more controlled than a more automated response execution mode. Regarding neural dynamics, effects of response inhibition modes relied on a concomitant coding of stimulus-related information and rules of how stimulus information is related to the appropriate motor programme. Crucially, these fractions of information, which are encoded at the same time in the neurophysiological signal, are based on two independent spatial neurophysiological activity patterns, also showing differences in the temporal stability of the representational content. Source localizations revealed that the precuneus and inferior parietal cortex regions are more relevant than prefrontal areas for the representation of stimulus–response selection codes. We provide a blueprint how a concatenation of EEG signal analysis methods, capturing distinct aspects of neural dynamics, can be connected to cognitive science theory on the importance of representations in action control.

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Social learning has given us insight into how children learn actions from others across different domains (e.g., actions on objects, pretend play, and tool use). However, little research exists to confirm whether young children can generate their own novel actions. Three different settings were chosen to offer a varied investigation of children’s ability to generate novel actions: generating multiple actions with novel objects; generating iconic gestures in order to communicate; and generating pretend actions using object substitution. Generating multiple actions with novel objects: The Unusual Box test was developed to investigate children’s ability to generate multiple actions with novel objects (Chapter 2). The Unusual Box test involves children playing with a wooden box that contains many different features (e.g., rings, stairs, strings), and five novel objects. The number of different actions performed on the box and with the objects (i.e., fluency) was used as a measure of their individual learning. Positive correlations between the fluency scores of 24 3- and 4-year-olds on the Unusual Box test and two existing measures of divergent thinking were found. Divergent thinking relates to the ability to think of multiple answers based on one premise. Furthermore, a large range of fluency scores indicated individual differences in children’s ability to generate multiple actions with novel objects. In addition, 16 2-year-olds were assessed on the Unusual Box test, twice two weeks apart, to investigate test-retest reliability and the possibility that the Unusual Box test could be used with children younger than 3 years. A strong positive correlation between the scores on the two assessments showed high test-retest reliability, while individual differences in fluency scores and the absence of a floor effect indicated that the Unusual Box test was usable in children from 2 years of age. Generating iconic gestures in order to communicate: Children’s ability to generate iconic gestures in order to communicate was assessed using a game to request stickers from an experimenter (N = 20, Chapter 3). In order to get a sticker children had to communicate to the experimenter which out of two objects they wanted (only one object had a sticker attached to it). Children’s use of speech or pointing was ineffective; therefore only generating an iconic gesture was sufficient to retrieve the sticker. Children generated a correct iconic gesture on 71% of the trials. These findings indicate that children generate their own iconic gestures in order to communicate; and that they understand the representational nature of iconic gestures, and use this in their own generation of iconic gestures. Generating pretend actions using object substitution: In order to determine whether children are able to generate their own object substitution actions and understand the representational nature of these actions, 45 3- and 4-year-olds were familiarized with the goal of a task through modelling actions. Children distinguished between the intentions of an experimenter to pretend, or try and perform a correct action. Children mainly imitated the pretend actions, while correcting the trying actions. Next, children were presented with objects for which they had to generate their own object substitution actions without being shown a model. When children had previously been shown pretend actions, children generated their own object substitution actions. This indicates that children generate their own object substitution actions, and that they understand the representational nature of these actions. An additional study with 34 3-year-olds, revealed no significant correlations between divergent thinking, inhibitory control, or children’s object substitution in a free play setting, and children’s ability to generate object substitution actions in the experimental setting.

Les modèles kainate et pentylènetétrazole représentent deux modèles d’épilepsie du lobe temporal dont les conséquences à long terme sont différentes. Le premier est un modèle classique d’épileptogénèse avec crises récurrentes spontanées tandis que le second se limite aux crises aigües. Nous avons d’abord caractérisé les différents changements survenant dans les circuits excitateurs et inhibiteurs de l’hippocampe adulte de rats ayant subi des crises à l’âge immature. Ensuite, ayant observé dans le modèle fébrile une différence du pronostic lié au genre, nous avons voulu savoir si cette différence était aussi présente dans des modèles utilisant des neurotoxines. L’étude électrophysiologique a démontré que les rats KA et PTZ, mâles comme femelles, présentaient une hyperactivité des récepteurs NMDA au niveau des cellules pyramidales du CA1, CA3 et DG. Les modifications anatomiques sous-tendant cette hyperexcitabilité ont été étudiées et les résultats ont montré une perte sélective des interneurones GABAergiques contenant la parvalbumine dans les couches O/A du CA1 des mâles KA et PTZ. Chez les femelles, seul le DG était légèrement affecté pour les PTZ tandis que les KA présentaient, en plus du DG, des pertes importantes au niveau de la couche O/A. Les évaluations cognitives ont démontré que seuls les rats PTZ accusaient un déficit spatial puisque les rats KA présentaient un apprentissage comparable aux rats normaux. Cependant, encore une fois, cette différence n’était présente que chez les mâles. Ainsi, nos résultats confirment qu’il y a des différences liées au genre dans les conséquences des convulsions lorsqu’elles surviennent chez l’animal immature. / Kainate and pentylenetetrazole models represent two animal models of temporal lobe epilepsy in which long-term consequences differ. The first model is a classical model of epileptogenesis with spontaneous recurrent seizures while the second one is limited to acute seizures. We wanted to characterize the difference in changes which occur in excitatory and inhibitory systems of the hippocampus of adult males and females having suffered an episode of status epilepticus during the immature stage of life. Besides having noticed a difference between genders in the febrile model, our second objective was to see if this difference was also present in models using neurotoxins. Electrophysiology recordings indicated that KA and PTZ rats (both male and female) showed a hyperactivity of NMDA receptors in CA1, CA3 and DG pyramidal cells. Anatomical modifications causing hyperactivity were studied and results show a selective loss of specific GABA interneurons PV in the O/A layer of CA1 region of the hippocampus in KA and PTZ male rats. However in female rats, only the DG layer was slightly affected in PTZ while female KA presented losses in both DG and O/A layers. Cognitive evaluation indicated that only PTZ rats showed a spatial impairment since KA rats had a similar learning pattern as controls. However, once again, that difference was observed only in males and not in females. In summary, our results confirmed that there is a difference between genders regarding brain damages after having suffered an episode of status epilepticus during the immature stage.

Les patients atteints d'épilepsie du lobe temporal (TLE) ainsi que les rats injectés à l'acide kaïnique (KA) exhibent des patrons pathophysiologiques similaires de crises, de sclérose de l'hippocampe et de perte de certains types neuronaux. Parmi les cellules atteintes dans le modèle KA du TLE on retrouve certains interneurones inhibiteurs du CA1. En effet, certains interneurones des couches oriens et alveus (O/A-IN) meurent suite à une injection de KA chez le rat, contrairement aux interneurones à la bordure des couches radiatum et lacunosum/moleculare (R/LM-IN) de la même région. Bien que cette perte soit empêchée par des antagonistes des récepteurs glutamatergiques métabotropes de groupe I (mGluR1/5), la cause de cette perte sélective des O/A-INs reste à être précisée. Au cours des travaux de cette thèse, nous avons effectué des enregistrements de patch-clamp en configuration cellule-entière en modes courant- et voltage-imposé couplés à l'imagerie calcique pour étudier les causes de la vulnérabilité sélective des O/A-INs dans ce modèle. Dans un premier temps, nous avons évalué les effets d'une application aiguë de KA sur les propriétés membranaires et calciques pour voir s'il y avait des différences entre les O/A-INs et R/LM-INs qui pourraient expliquer la vulnérabilité. Nos résultats montrent que les dépolarisations et variations de résistance d'entrée ainsi que les augmentations de calcium intracellulaire, dépendantes principalement des récepteurs -amino-3-hydroxy-5-methyl-4-isoxasole propionic acid (AMPA), sont similaires entre les deux types d'interneurones suite à des applications aigües de KA. Ceci indique que l'effet aigu du KA sur les interneurones ne serait pas la cause de la vulnérabilité des O/A-INs. Dans un second temps nous avons comparé l'implication des sous-types de récepteurs mGluR1 et 5 dans l'activité épileptiforme des deux types d'interneurones évoquée dans un modèle de tranche désinhibée. Dans ce cas, nos données montrent un rôle important des mGluR1 et 5 activés synaptiquement lors des décharges épileptiformes et ce, de manière spécifique aux O/A-INs. Les courants synaptiques sous-tendant ces décharges impliquent des récepteurs ionotropes et métabotropes du glutamate. En présence d'antagonistes des récepteurs ionotropes glutamatergiques, les courants synaptiques sont biphasiques et formés de composantes rapide et lente. Les récepteurs mGluR1 et 5 sont différemment impliqués dans ces composantes: les mGluR5 étant impliqués dans les composantes rapide et lente, et les mGluR1 que dans la composante lente. Ces résultats indiquent que les mGluR1 et 5 contribuent différemment à l'activité épileptiforme, et spécifiquement dans les O/A-INs, et pourraient donc être impliqués dans la vulnérabilité sélective de ces interneurones dans le modèle KA. / Temporal lobe epilepsy (TLE) patients, as well as kainic acid (KA)-treated rodents, display similar pathophysiological patterns of behavioural seizures, hippocampal sclerosis and loss of certain neuronal types in the hippocampus. Among the cell types selectively vulnerable in the experimental KA model of TLE are certain inhibitory interneurons of the CA1 hippocampal region. Specifically, interneurons located in the oriens and alveus layers (O/A-IN) are lost following KA injections, whereas interneurons found in the radiatum/lacunosum-moleculare layers (R/LM-IN) are resistant. Although it has been shown that the group I metabotropic glutamate receptor (mGluR1/5) inhibitors can block this cell loss seen in the KA model, the precise cause of the selective O/A-IN vulnerability remains to be clarified. In this thesis, we have performed whole-cell patch-clamp recordings with simultaneous calcium imaging in an effort to elucidate the cause of the selective vulnerability of O/A-INs. We first determined the effects of acute KA applications on membrane properties and intracellular calcium rises in hippocampal slices to see if they might be different between O/A-INs and R/LM-INs. Our results reveal similar -amino-3-hydroxy-5-methyl-4-isoxasole propionic acid (AMPA) receptor dependent membrane depolarizations, input resistance variations and calcium reponses in these cells following KA applications, suggesting that acute KA actions may not cause the selective vulnerability of O/A-INs. Furthermore, we evaluated the contribution of mGluR1/5 to epileptiform discharges evoked in a disinhibited slice model, comparing responses between O/A-INs and R/LM-INs. Our data show an important role of synaptically activated mGluR1/5 during epileptiform discharges specifically in O/A-INs. In addition we show that the synaptic currents underlying these discharges involve ionotropic and metabotropic glutamate receptors. In the presence of antagonists of ionotropic glutamate receptors, synaptic currents are biphasic and composed of fast and slow components. mGluR1 and mGluR5 are involved differently in these components with mGluR5 implicated in fast and slow components and mGluR1 in the slow component only. Our findings therefore suggest that mGluR1 and 5 contribute differently to epileptiform discharges, and do so specifically in O/A-INs, suggesting that their activation may contribute to the selective vulnerability of these interneurons in the KA model of TLE.