Akademisk avhandling--Gothenburg. / Bibliography: p. 69-74.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Includes bibliographical references.

Thesis (MScMedSc)-- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The commercial and military deep diving environment is typically a low visibility environment, where dependence on the visual senses often needs to be replaced by a reliance on tactile senses. This thesis reviewed the current knowledge regarding neuropsychological manifestations of nitrogen narcosis and exposed a number of shortcomings in the current body of knowledge. In particular, the human performance effects of hyperbaric exposure on tactile perception and memory have not been systematically studied. It is further not clear, how exactly psychological factors (e.g. anxiety, mood states) and biographical factors (e.g. age, education, technical exposure, experience) might influence tactile perception and memory performance under conditions of hyperbaric exposure. The correlation between subjective experiences of narcosis, tactile performance, and psychological and biographical variables is also unknown. This study thus set out to investigate certain neuropsychological aspects of nitrogen narcosis, with special reference to tactile perception and memory, and to examine the relationships of tactile performance with other psychological and biographical factors. The effects of experimental hyperbaric exposure (EHE) on tactile (form) perception and tactile shape memory were examined by testing these functions at 6 ATA and 1 ATA, using a cross-over design where two groups completed the same tasks, in opposite sequence. The psychological variables included trait anxiety, transient mood states, and subjective ratings of narcosis, while the biographical variables included age, education, and previous technical exposure. The results demonstrated the detrimental effect of nitrogen narcosis on tactile form perception and manipulation, irrespective of the sequence of testing. It also demonstrated this effect on tactile form memory, although the sequence of testing also played a role here. Higher trait anxiety was associated with poorer recall, and tension was associated with a larger decrement in recall performance, while fatigue was associated with poorer task completion. Subjective experiences also played a role, where feelings of physical anxiety (i.e. increased arousal) were associated with better recall, and feelings of cognitive suppression (decreased arousal) were associated with a larger decrement in recall performance. Lower academic attainment was associated with poorer recall, while higher diving qualification was associated with better recall. Performance on the surface was a good predictor of performance at depth. Qualitative analysis rendered three themes, namely focus vs. distraction, following instructions, and shape memory. Psychometric properties of the subjective narcosis measure were also reported. Theoretical implications include support for the slowed information processing model when completing complex neuropsychological tasks, as well as support for the memory model, thus suggesting that this particular pattern of memory impairment occurs because encoding under narcosis produces a weaker memory trace than normal. Lastly, the study has a number of implications for industry. For example, divers need to compensate for slowed task completion by, firstly, planning more time to complete complex tasks, and secondly, by practicing those tasks prior to the actual deep dive (either on the surface or in shallow water). The need for using additional forms of recording of events or objects at depth, to aid memory encoding and subsequent recall at surface was also emphasised. / AFRIKAANSE OPSOMMING: Kommersieële en militêre duik vind dikwels plaas in ‘n omgewing met swak sig, waar duikers moet staatmaak op taktiele sintuie, eerder as op visuele sintuie. Die tesis begin met ‘n oorsig oor die huidige kennis rakende neurosielkundige verskynsels van stikstof narkose, en het ‘n aantal tekortkominge gevind. Meer spesifiek, die menslike faktor in die effek van hiperbariese druk op taktiese persepsie en geheue is nog nie sistematies bestudeer nie. Dit is verder nie duidelik presies hoe sielkundige faktore (angs, gemoedstoestande) en demografiese faktore (ouderdom, opvoeding, tegniese blootstelling, ondervinding) taktiele persepsie en geheue onder toestande van hiperbariese druk sou beïnvloed nie. The korrelasie tussen die subjektiewe ervaring van narkose, taktiele taakverigting, en sielkundige en biografiese veranderlikes is ook nie bekend nie. Die studie het verskeie neurosielkundige aspekte van stikstof narkose, met spesifieke verwysing na taktiele persepsie en geheue, sowel as die verhouding tussen taktiele prestasie en sielkundige en biografiese faktore ondersoek. Die effek van hiperbariese druk op taktiele persepsie en geheue is ondersoek deur hierdie funksies te toets by 6 en 1 ATA, deur middel van ‘n oorkruis studie ontwerp, waar twee groepe die take voltooi het, in teenoorgestelde volgorde. Die sielkundige veranderlikes het bestaan uit trek-angs, tydelike gemoedstoestande, en die subjektiewe evaluering van narkose, terwyl die biografiese veranderlikes ouderdom, opvoeding, en vorige tegniese blootstelling ingesluit het. Die resultate het die nadelige effek van stikstof narkose op taktiele vorm persepsie en manipulasie gedemonstreer, ongeag die rigting van toetsing. Dit het ook hierdie effek op taktiele vorm geheue gedemonstreer, hoewel die rigting van toetsing wel hier ‘n rol gespeel het. Hoër trek-angs was geassosieër met swakker herroeping, en spanning met ‘n groter agteruitgang in herroeping, terwyl matheid geassosieer was met swakker taakvoltooiing. Subjektiewe ervarings het ook ‘n rol gespeel, met ervarings van fisiese spanning (verhoogde opwekking) geassosieer met beter herroeping, en ervarings van kognitiewe onderdrukking (verlaagde opwekking) met groter agteruitgang in herroeping. Laer akademiese kwalifikasie was geassosieer met swakker herroeping, terwyl hoër duik kwalifikasie geassosieer was met beter herroeping. Taakverrigting op die oppervlak was ‘n goeie voorspeller van prestasie op diepte. Kwalitatiewe analiese het drie temas geidentifiseer, naamlik fokus vs. afleibaarheid, die volg van instruksies, en vorm geheue. Die psigometriese eienskappe van die subjektiewe narkose meetinstrument is ook gerapporteer. Teoretiese implikasies van die studie sluit in ondersteuning vir die vertraagde prosesseringsmodel, wanneer komplekse neurosielkundige take voltooi word, sowel as ondersteuning vir die model vir hierdie spesifieke herroepingspatroon wat ‘n swakker geheuespoor laat wanneer enkodering plaasvind onder toestande van narkose. Die studie het ook praktiese implikasies vir industrie. Dit is byvoorbeeld nodig om te kompenseer vir vertraagde taakvoltooïng deur, eerstens, die beplanning vir meer tyd om komplekse take te voltooi, en tweedens, deur daardie take te oefen voor die diep duik plaasvind. Die noodsaaklikheid vir additionele maniere om gebeure of voorwerpe op diepte vas te lê is ook beklemtoon.

A aquicultura no Brasil encontra-se numa fase de crescimento, principalmente com o cultivo intensivo de espécies de interesse comercial. Os peixes são abatidos por imersão em gelo e água, ou por asfixia em gelo, métodos que comprovadamente não causam a imediata perda de função cerebral e podem ter consequências prejudiciais à qualidade da carne. Desta forma, tornam-se necessários estudos que identifiquem a melhor forma de insensibilização para peixes, que proporcionem ao mesmo tempo menor sofrimento e maior qualidade da carne. Assim, o objetivo deste trabalho foi avaliar influência da insensibilização pré abate por eletronarcose, narcose por CO2 e hipotermia sobre a qualidade da carne de bijupirá e estudar a estabilidade da carne sob o resfriamento e congelamento, mensurando as principais variáveis físico-químicas e sensoriais utilizadas tanto na indústria e na pesquisa. Para isso foram realizados dois experimentos, onde no primeiro noventa exemplares foram submetidos aos três tratamentos. Após a insensibilização os peixes foram abatidos por sangria e mantidos resfriados a 4ºC durante 21 dias. As amostras foram coletadas após a determinação da morte do animal (hora 0), 5 horas e aos 1, 7, 14 e 21 dias de armazenamento. Os dados foram submetidos à ANOVA e constatada diferença significativa (P<0,05), as médias foram comparadas pelo teste de Tukey. Foram avaliados o índice de rigor, pH muscular, bases nitrogenadas voláteis (BNV), propriedades dielétricas, análise sensorial, degradação do ATP muscular. O tempo decorrido para a insensibilização dos animais foi bastante diferente (eletronarcose: 2 segundos; narcose CO2: 31 minutos; hipotermia: 17,5 minutos). A coloração das brânquias apresentou diferença significativa (P<0,05). Peixes insensibilizados por hipotermia apresentaram maior velocidade de degradação de adenosina trifosfato e maior velocidade de formação de hipoxantina, animais insensibilizados por eletronarcose apresentaram maior velocidade aumento de valor de K. No segundo experimento os peixes foram submetidos a cada um dos tratamentos, e quando constatado o estado de insensibilização aparente, precedia-se com o corte dos arcos branquiais, filetagem, congelamento ultrarrápido, embalagem e manutenção em freezer -18ºC por 180 dias. A cada 60 dias amostras foram coletadas para avaliação de perda de água por gotejamento, perda de água por cocção, oxidação lipídica, desnaturação proteica, pH muscular, contração do filé, cor e alteração dos ácidos graxos durante o congelamento. A intensidade de vermelho foi maior nos peixes insensibilizado por eletronarcose (P>0,05). Foi constatado que o congelamento ultrarrápido é capaz de mascarar as perdas de qualidade decorrentes do estresse pré-abate. Nenhum dos tratamentos foi capaz de interferir significativamente (P>0,05) na degradação destes ácidos. Para os índices de saudabilidade estudados, houve diferença significativa entre os tratamentos tanto na relação n6/n3, peixes insensibilizados por eletronarcose apresentam melhores médias para índices trombogênico e aterogênico. Conclui-se que a eletronarcose pode ser uma boa opção para o abate de bijupirás, por causar insensibilização aparente rápida e com mínimo de sofrimento sem perda de qualidade da carne. / Aquaculture in Brazil is growing phase, particularly with the intensive cultivation of commercial species. The fish are killed by immersion in ice and water, or by asphyxiation in ice, proven methods that do not cause immediate loss of brain function and may have adverse consequences on meat quality. Thus it becomes necessary studies to identify the best way to fish stunning, which provide the same, less pain and better quality of the meat. The objective of this study was to evaluate the influence of pre slaughter by electro stunning, CO2 narcosis and hypothermia on the quality of cobia meat and study the stability of the meat in cooling and freezing, measuring the main physical and chemical variables and sensory used both in industry and research. For this two experiments were conducted, where the first ninety copies were submitted to three treatments. After stunning the fish were slaughtered by bleeding and kept refrigerated at 4°C for 21 days. Samples were collected after determination of the death of the animal (time 0), 5 hours and 1, 7, 14 and 21 days of storage. The data were submitted to ANOVA and found significant differences (P <0.05), means were compared by Tukey test. We evaluated the accuracy index, muscle pH, volatile nitrogenous bases (VBN), dielectric properties, sensory evaluation, muscle ATP degradation. The elapsed time for the stunning of animals was quite different (electronarcosis: 2 seconds; CO2 narcosis: 31 minutes; hypothermia: 17.5 minutes). The color of the gills showed a significant difference (P <0.05). Fish were stunned by hypothermia showed greater speed of adenosine triphosphate degradation of hypoxanthine and higher speed of training, animals were stunned by electro showed greater speed increasing value K. In the second experiment, fish were subjected to each treatment, and when the verified state of apparent stunning if preceded with cutting the gill arches, filleting, ultra-fast freezing, packaging and maintenance in freezer -18 ° C for 180 days. Every 60 days samples were collected for assessment of loss of water drip water loss by cooking, lipid oxidation, protein denaturation, muscle pH, fillet contraction, color and alteration of fatty acids during freezing. The red intensity was higher in fish numb by electro (P> 0.05). It was found that the ultrafast freezing is able to mask the quality losses associated with the pre-slaughter stress. none of the treatments were able to interfere significantly (P> 0.05) in the degradation of these acids. For the healthiness indices studied, there was a significant difference between treatments in both the relationship n6/n3, fish stunned by electro have better averages for thrombogenic and atherogenic index. It concludes that electro can be a good option for slaughtering bijupirás, to cause rapid apparent stunning and with minimal suffering no loss of meat quality.

Made available in DSpace on 2014-06-11T19:30:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-31Bitstream added on 2014-06-13T20:01:10Z : No. of bitstreams: 1 berger_b_dr_rcla.pdf: 1800024 bytes, checksum: b803c12973aa74cd00fe939959c8d1f1 (MD5) / Os ovários das rainhas diferem dos de operárias de Apis mellifera quanto ao número e comprimento dos ovaríolos. Tanto o número, como o comprimento destes, é muito maior na rainha que nas operárias. No entanto, em ambos os casos os ovários são funcionais, isto é, capazes de produzir óvulos maduros. Apesar disso, operárias e rainhas diferem muito quanto à fertilidade e aos mecanismos controladores/estimuladores da vitelogênese, ou seja, da maturação dos óvulos. Em condições normais da colônia, nas rainhas a vitelogênese é desencadeada pelo acasalamento e nas operárias, pela ausência da rainha ou do recebimento de informações sobre sua presença na colônia. Passada a ocasião própria para o acasalamento no caso da rainha, e em idade avançada das operárias, os ovários entram em degeneração. O objetivo do presente trabalho foi o de avaliar como se comporta o desenvolvimento do ovário em rainhas e operárias mantidas fora dos condicionamentos da colônia e o efeito do tratamento destas com CO2, prática corrente na apicultura. Para tanto, operárias e rainhas foram mantidas aprisionadas em caixas com candy e água durante 15 dias e seguida a seqüência de desenvolvimento de seus ovários. O efeito do não acasalamento na época própria e do tratamento com CO2 foi feito estudando a morfologia do desenvolvimento da ovogênese, usando TUNEL e reação de fosfatase acida para caracterizar possíveis alterações celulares. As células do filamento terminal apresentaram-se empilhadas em fila única. Na transição para o germário as células tornam-se piramidais com a base apoiada sobre a lâmina própria e o ápice voltado para o centro do ovaríolo. São encontradas células esféricas, provavelmente ovogônias. No germário estão presentes células somáticas e germinativas, sendo da linhagem germinativa, os cistoblastos, os cistócitos, os ovócitos e as futuras... / The ovaries of queens and workers of Apis mellifera differs in number and length of the ovarioles. Length and number of ovarioles are larger in queen than in workers. However, in both cases, the ovaries are functional, i.e., it is able of produce mature eggs. Despite of that, workers and queens differ very in fertility and mechanisms of controlling/inducing vitellogenesis. In colony conditions, queen’s vitellogenesis is triggered by the matting and in workers by the absence of the queen or of the receipt of information about its presence in the colony. After the age proper to mate or in workers advanced age, the ovaries enter in degeneration. The objective of the present work was the evaluating of the ovary development in queens and workers maintained caged outside of the colony conditionings and the effect of the narcosis with CO2, practice current in the beekeeping. Newly emerged queens and workers were caged with candy and water during 15 days. For the queens the effect of the mate delay and CO2 narcosis were studied using TUNEL and acid fosfatase reaction to evaluate cell damages. The cells of the terminal filament appear as rows of one single cell, with a rectangular shape, poor in organelles and with a big central nucleus. In the transition for the germarium the cells present a pyramidal form with their base widened resting on tunica propria and the apex directed to center of the ovariole. Below the region of transition to the germarium are spherical cells, probably the oogonia. In the germarium are found somatic (pre-follicular cells) and germinative (cystoblasts, the cystocists, the oocytes and the future nurse cells) cells. The queen’s ovaries develop normally until the mating age, 5 days old queens. About the 10 days, the virgin queen beginning to presents an ovariolar disorganization with big incidence of injured cells with characteristics of apoptosis and autofagic death... (Complete abstract click electronic access below)

Orientador: Carminda da Cruz-Landim / Banca: Karina Patrício / Banca: José Lino Neto / Banca: José Chaud Netto / Banca: Daniela Carvalho dos Santos / Resumo: Os ovários das rainhas diferem dos de operárias de Apis mellifera quanto ao número e comprimento dos ovaríolos. Tanto o número, como o comprimento destes, é muito maior na rainha que nas operárias. No entanto, em ambos os casos os ovários são funcionais, isto é, capazes de produzir óvulos maduros. Apesar disso, operárias e rainhas diferem muito quanto à fertilidade e aos mecanismos controladores/estimuladores da vitelogênese, ou seja, da maturação dos óvulos. Em condições normais da colônia, nas rainhas a vitelogênese é desencadeada pelo acasalamento e nas operárias, pela ausência da rainha ou do recebimento de informações sobre sua presença na colônia. Passada a ocasião própria para o acasalamento no caso da rainha, e em idade avançada das operárias, os ovários entram em degeneração. O objetivo do presente trabalho foi o de avaliar como se comporta o desenvolvimento do ovário em rainhas e operárias mantidas fora dos condicionamentos da colônia e o efeito do tratamento destas com CO2, prática corrente na apicultura. Para tanto, operárias e rainhas foram mantidas aprisionadas em caixas com candy e água durante 15 dias e seguida a seqüência de desenvolvimento de seus ovários. O efeito do não acasalamento na época própria e do tratamento com CO2 foi feito estudando a morfologia do desenvolvimento da ovogênese, usando TUNEL e reação de fosfatase acida para caracterizar possíveis alterações celulares. As células do filamento terminal apresentaram-se empilhadas em fila única. Na transição para o germário as células tornam-se piramidais com a base apoiada sobre a lâmina própria e o ápice voltado para o centro do ovaríolo. São encontradas células esféricas, provavelmente ovogônias. No germário estão presentes células somáticas e germinativas, sendo da linhagem germinativa, os cistoblastos, os cistócitos, os ovócitos e as futuras... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The ovaries of queens and workers of Apis mellifera differs in number and length of the ovarioles. Length and number of ovarioles are larger in queen than in workers. However, in both cases, the ovaries are functional, i.e., it is able of produce mature eggs. Despite of that, workers and queens differ very in fertility and mechanisms of controlling/inducing vitellogenesis. In colony conditions, queen's vitellogenesis is triggered by the matting and in workers by the absence of the queen or of the receipt of information about its presence in the colony. After the age proper to mate or in workers advanced age, the ovaries enter in degeneration. The objective of the present work was the evaluating of the ovary development in queens and workers maintained caged outside of the colony conditionings and the effect of the narcosis with CO2, practice current in the beekeeping. Newly emerged queens and workers were caged with candy and water during 15 days. For the queens the effect of the mate delay and CO2 narcosis were studied using TUNEL and acid fosfatase reaction to evaluate cell damages. The cells of the terminal filament appear as rows of one single cell, with a rectangular shape, poor in organelles and with a big central nucleus. In the transition for the germarium the cells present a pyramidal form with their base widened resting on tunica propria and the apex directed to center of the ovariole. Below the region of transition to the germarium are spherical cells, probably the oogonia. In the germarium are found somatic (pre-follicular cells) and germinative (cystoblasts, the cystocists, the oocytes and the future nurse cells) cells. The queen's ovaries develop normally until the mating age, 5 days old queens. About the 10 days, the virgin queen beginning to presents an ovariolar disorganization with big incidence of injured cells with characteristics of apoptosis and autofagic death... (Complete abstract click electronic access below) / Doutor

A aquicultura no Brasil encontra-se numa fase de crescimento, principalmente com o cultivo intensivo de espécies de interesse comercial. Os peixes são abatidos por imersão em gelo e água, ou por asfixia em gelo, métodos que comprovadamente não causam a imediata perda de função cerebral e podem ter consequências prejudiciais à qualidade da carne. Desta forma, tornam-se necessários estudos que identifiquem a melhor forma de insensibilização para peixes, que proporcionem ao mesmo tempo menor sofrimento e maior qualidade da carne. Assim, o objetivo deste trabalho foi avaliar influência da insensibilização pré abate por eletronarcose, narcose por CO2 e hipotermia sobre a qualidade da carne de bijupirá e estudar a estabilidade da carne sob o resfriamento e congelamento, mensurando as principais variáveis físico-químicas e sensoriais utilizadas tanto na indústria e na pesquisa. Para isso foram realizados dois experimentos, onde no primeiro noventa exemplares foram submetidos aos três tratamentos. Após a insensibilização os peixes foram abatidos por sangria e mantidos resfriados a 4ºC durante 21 dias. As amostras foram coletadas após a determinação da morte do animal (hora 0), 5 horas e aos 1, 7, 14 e 21 dias de armazenamento. Os dados foram submetidos à ANOVA e constatada diferença significativa (P<0,05), as médias foram comparadas pelo teste de Tukey. Foram avaliados o índice de rigor, pH muscular, bases nitrogenadas voláteis (BNV), propriedades dielétricas, análise sensorial, degradação do ATP muscular. O tempo decorrido para a insensibilização dos animais foi bastante diferente (eletronarcose: 2 segundos; narcose CO2: 31 minutos; hipotermia: 17,5 minutos). A coloração das brânquias apresentou diferença significativa (P<0,05). Peixes insensibilizados por hipotermia apresentaram maior velocidade de degradação de adenosina trifosfato e maior velocidade de formação de hipoxantina, animais insensibilizados por eletronarcose apresentaram maior velocidade aumento de valor de K. No segundo experimento os peixes foram submetidos a cada um dos tratamentos, e quando constatado o estado de insensibilização aparente, precedia-se com o corte dos arcos branquiais, filetagem, congelamento ultrarrápido, embalagem e manutenção em freezer -18ºC por 180 dias. A cada 60 dias amostras foram coletadas para avaliação de perda de água por gotejamento, perda de água por cocção, oxidação lipídica, desnaturação proteica, pH muscular, contração do filé, cor e alteração dos ácidos graxos durante o congelamento. A intensidade de vermelho foi maior nos peixes insensibilizado por eletronarcose (P>0,05). Foi constatado que o congelamento ultrarrápido é capaz de mascarar as perdas de qualidade decorrentes do estresse pré-abate. Nenhum dos tratamentos foi capaz de interferir significativamente (P>0,05) na degradação destes ácidos. Para os índices de saudabilidade estudados, houve diferença significativa entre os tratamentos tanto na relação n6/n3, peixes insensibilizados por eletronarcose apresentam melhores médias para índices trombogênico e aterogênico. Conclui-se que a eletronarcose pode ser uma boa opção para o abate de bijupirás, por causar insensibilização aparente rápida e com mínimo de sofrimento sem perda de qualidade da carne. / Aquaculture in Brazil is growing phase, particularly with the intensive cultivation of commercial species. The fish are killed by immersion in ice and water, or by asphyxiation in ice, proven methods that do not cause immediate loss of brain function and may have adverse consequences on meat quality. Thus it becomes necessary studies to identify the best way to fish stunning, which provide the same, less pain and better quality of the meat. The objective of this study was to evaluate the influence of pre slaughter by electro stunning, CO2 narcosis and hypothermia on the quality of cobia meat and study the stability of the meat in cooling and freezing, measuring the main physical and chemical variables and sensory used both in industry and research. For this two experiments were conducted, where the first ninety copies were submitted to three treatments. After stunning the fish were slaughtered by bleeding and kept refrigerated at 4°C for 21 days. Samples were collected after determination of the death of the animal (time 0), 5 hours and 1, 7, 14 and 21 days of storage. The data were submitted to ANOVA and found significant differences (P <0.05), means were compared by Tukey test. We evaluated the accuracy index, muscle pH, volatile nitrogenous bases (VBN), dielectric properties, sensory evaluation, muscle ATP degradation. The elapsed time for the stunning of animals was quite different (electronarcosis: 2 seconds; CO2 narcosis: 31 minutes; hypothermia: 17.5 minutes). The color of the gills showed a significant difference (P <0.05). Fish were stunned by hypothermia showed greater speed of adenosine triphosphate degradation of hypoxanthine and higher speed of training, animals were stunned by electro showed greater speed increasing value K. In the second experiment, fish were subjected to each treatment, and when the verified state of apparent stunning if preceded with cutting the gill arches, filleting, ultra-fast freezing, packaging and maintenance in freezer -18 ° C for 180 days. Every 60 days samples were collected for assessment of loss of water drip water loss by cooking, lipid oxidation, protein denaturation, muscle pH, fillet contraction, color and alteration of fatty acids during freezing. The red intensity was higher in fish numb by electro (P> 0.05). It was found that the ultrafast freezing is able to mask the quality losses associated with the pre-slaughter stress. none of the treatments were able to interfere significantly (P> 0.05) in the degradation of these acids. For the healthiness indices studied, there was a significant difference between treatments in both the relationship n6/n3, fish stunned by electro have better averages for thrombogenic and atherogenic index. It concludes that electro can be a good option for slaughtering bijupirás, to cause rapid apparent stunning and with minimal suffering no loss of meat quality.

Le plongeur subit de nombreuses contraintes issues du milieu dans lequel il évolue. La narcose à l’azote par ses effets sur la performance cognitive en fait partie. Elle est impliquée dans de nombreux accidents de plongée sous-marine. Il est donc nécessaire de développer un outil fiable pour évaluer la performance cognitive sous l’eau de manière quantitative, reproductible et indépendante de la subjectivité du plongeur. Ensuite, après validation de cet outil (fréquence critique de fusion du scintillement - CFFF) préciser le rôle des facteurs modulateurs de la narcose en particulier celui de l’oxygène. Nos investigations sont réalisées chez des volontaires sains sélectionnés spécifiquement pour obtenir une population homogène (genre, âge, BMI, condition physique et expérience en plongée). L’analyse de la performance cérébrale est réalisée au moyen de tests psychométriques, d’échelles visuelles analogique et de la CFFF dans différentes conditions (normobarie, plongées simulées et réelles à 30 mètres de profondeur pendant 20 minutes) et avec différents gaz (air et Nitrox 40%). L’effet propre de l’oxygène est appréhendé par l’utilisation de la spectroscopie proche de l’infrarouge (NIRS).Nos mesures confirment d’une part la dégradation progressive de la performance cognitive tant par les tests psychométriques que par la CFFF avec un bon degré de corrélation (Pearson de 0,86 à 0,93) entre eux et d’autre part l’incapacité du plongeur à s’auto- évaluer. L’évolution de la performance cognitive est caractérisée par une amélioration lors de l’arrivée en profondeur d’autant plus marquée que la quantité d’oxygène dans le mélange respiré est importante, suivie par une dégradation qui persiste au moins jusqu’à 30 minutes après le retour en surface, surtout en respiration d’air. L’utilisation de l’imagerie fonctionnelle cérébrale (NIRS) permet d’associer l’amélioration des performances cognitives à une activation cérébrale dépendante de l’oxygène. L’oxygène semble donc être un élément important de la modulation des symptômes de la narcose à l’azote. De manière très cohérente avec la théorie neurochimique de la narcose nous suggérons que l’effet net sur la performance cérébrale dépend d’une balance entre les effets activateurs de l’oxygène et les effets inhibiteurs de l’azote. / During a dive subjects undergo many environmental stressors. Nitrogen narcosis through its effects on cognitive performance is one of them. Narcosis is indeed involved in many scuba diving accidents. It is therefore mandatory to develop a quantitative, reliable, reproducible tool to evaluate underwater diver’s cognitive performance. This tool should not be dependent on diver’s subjectivity. Once this tool (critical flicker fusion frequency - CFFF) is validated, we could then clarify the role of narcosis modulating factors in particular that of oxygen.Our investigations were performed in healthy volunteers specifically selected in a large group of recreational diver to obtain a standard population (gender, age, BMI, fitness and experience in diving). Cerebral performance analysis is carried out using psychometric tests, visual analogic scale and CFFF in different conditions (normobaria, simulated and open-water dives to a depth of 30 meters of fresh or salt water for 20 minutes) and with different gases (air and EANx 40%). The specific effect of oxygen is apprehended by use of near infrared spectroscopy (NIRS).On one hand, our measurements confirm the gradual deterioration of cognitive performance by both psychometric tests and CFFF, which share a good degree of correlation (Pearson from 0.86 to 0.93) and on the other hand diver’s inability to assess themselves.The evolution of cognitive performance is characterized by an improvement when arriving at depth followed by a progressive impairment that persists for at least 30 minutes after surfacing.The more oxygen in the breathing mixture, the better improvement in the early part of the dive and the less impairment in the following measurements are observed. Brain functional imaging (NIRS) allows us to pair the observed cognitive performance improvement with oxygen-dependent brain activation.It seems that Oxygen is an important modulator of the symptoms of nitrogen narcosis. In accordance with the neurochemical theory of narcosis we suggest that the net effect on cerebral performance depends on a balance between the activating effects of oxygen and the inhibitory effects of nitrogen.

The caudal solitary complex (cSC) is a cardiorespiratory integrative center in the dorsal medulla oblongata that plays a vital role in the central CO2-chemoreceptive network. Neurons in this area respond to hypercapnic acidosis (HA) by a depolarization of the membrane potential and increase in firing rate, however a definitive mechanism for this response remains unknown. Likewise, CO2-chemoreceptive neurons in the cSC respond to hyperoxia in a similar fashion, but via a free radical mediated mechanism. It remains unknown if the response to increased pO2 is merely an increase in redox signaling, or if it’s the result of a pathological state of redox stress. Importantly, free radical production is known to be stimulated by increasing pO2, and can be exacerbated downstream by the addition of CO2 and its subsequent acidosis. Conditions of hyperoxia in combination with HA can therefore become detrimental in several scenarios, including O2 toxicity seizures in divers and stranded submariners, as well as in cases of ischemia-reperfusion injury and sleep apneas. As such, we sought to not only determine how O2 and CO2 interact to affect cellular excitability in the cSC, but also if these cells exhibited increases in redox signaling and/or stress. We employed sharp-electrode intracellular electrophysiology to study whole-cell electrical responses to varied combinations of hyperoxia (0.4 0.95/1.95 ATA O2) and HA (0.05 0.1 ATA CO2). Additionally, we used fluorescence microscopy under similar conditions to study changes in the production rates of various free radicals, including superoxide (˙O2-), nitric oxide (˙NO), and a downstream aggregate pool of CO2/H+-dependent reactive oxygen and nitrogen species (RONS). Finally, we used several colorimetric assays to measure markers of oxidative and nitrosative stress, including malondialdehyde, 3-nitrotyrosine, and protein carbonyls. Our hypothesis for these experiments was that hyperoxia and HA alone could produce effects, but would be more pronounced when used together. As such, we saw that ~89% of cells tested that were sensitive to both hyperoxia and HA showed larger firing rate responses to HA during an increased background O2 (0.9 and/or 1.9 ATA) after showing a smaller response or no response to HA during control levels O2 (0.4 ATA). Additionally, we noted that the rate of ˙O2- fluorescence increased in response to hyperoxia, but only during pharmacological inhibition of its reactions with ˙NO and SOD. Likewise, the rate of ˙NO fluorescence increased during hyperoxia compared to control O2, but only during pharmacological scavenging of ˙O2-. Downstream, our aggregate pool of RONS showed increased rates of fluorescence during both hyperoxia alone and HA in control O2, however the most prominent increases were seen during hypercapnic hyperoxia. Finally, no significant effects were seen when probing for markers of redox stress in response to hyperoxia and hypercapnic hyperoxia. Overall, these results suggest that the increased excitability seen in cSC neurons during hypercapnic hyperoxia is the result of physiological redox signaling rather than pathological redox stress. Further research needs to be done to determine how this redox mechanism is specifically resulting in increased cellular excitability.