Lors de variations de PO2 et PCO2, différents mécanismes se mettent en place afin demaintenir l’oxygénation des tissus, notamment au niveau du métabolisme et de la ventilation. En casde stimulation hypoxique ou hypercapnique, on observe alors une réponse ventilatoire, caractériséepar une augmentation progressive de la ventilation. Parmi les facteurs qui influencent la réponse àl’hypoxie, on trouve l’érythropoïétine (Epo) qui, en plus de son rôle dans l’érythropoïèse, possèded’autres rôles, notamment au sein du système nerveux central. Cette thèse présente l’étude del’implication de l’Epo et de différents systèmes de neurotransmission dans les réponses ventilatoiresà l’hypoxie (RVH) et à l’hypercapnie (RVHc).Nous avons alors pu mettre en évidence l’implication du NO, du glutamate et de la sérotonine dansla RVH et dans l’acclimatation ventilatoire à une hypoxie prolongée (VAH) chez un modèle de sourisanémique déficient en Epo (Epo-TAgh) et un animal adapté à la vie en altitude, la plateau Pika. Nousavons ensuite étudié l’impact de la déficience en Epo sur la RVHc, et nous avons confirmé que l’Epon’était pas nécessaire à l’obtention de la RVHc, tout en mettant en évidence un rôle de l’Epo sur lepatron ventilatoire et sur l’implication de certaines structures du système nerveux central dans lamise en place de cette réponse. Une étude en parallèle sur les femelles a permis de mettre enévidence que le cycle oestral n’était pas impliqué dans les réponses ventilatoires mais qu’il semble yavoir une interaction entre l’Epo et les hormones sexuelles femelles dans la RVH et la RVHc. Enfin,différentes expériences réalisées lors de collaborations (Chili, Canada) ont permis d’étudier les effetsde l’Epo sur les chémorécepteurs centraux et périphériques dans la mise en place des réponsesventilatoires.In fine, ces différentes expériences ont permis de préciser les différents facteurs impliqués dans lamise en place des réponses ventilatoires à l’hypoxie et à l’hypercapnie, ce qui pourrait aider par lasuite à mieux comprendre les modifications respiratoires induites par des pathologiques liées àl’anémie ou l’exposition prolongée à l’altitude. / When PO2 and PCO2 are modified, various mechanisms are being established to maintaintissue oxygenation, such as ventilation and metabolism adaptations. In case of hypoxia orhypercapnia stimulation, we observed a ventilatory response, characterized by an increase in minuteventilation. Among the factors involved in the hypoxic response, Epo plays a key role. In addition toits role in erythropoiesis, Epo has other functions, especially in the central nervous system. Thisthesis presents the study of Epo involvement in the ventilatory responses to hypoxia (HVR) andhypercapnia (HcVR).We demonstrate the involvement of NO, glutamate and serotonin in the HVR and in acclimatizationto sustained hypoxia (VAH) in Epo deficient mice (Epo-TAgh) and in an animal adapted to highaltitude, the plateau Pika. Then we studied the impact of Epo-deficiency on HcVR and confirmed thatEpo is not mandatory to obtained HcVR but we demonstrate that Epo can modulate the ventilatorypattern and central nervous system structures involvement in this response. During this study, wealso demonstrate that in female mice, estrous cycle is not involved in HVR or HcVR but it seems thatthere is an interaction between Epo and female sexual hormones in these responses. Finally, someexperiments in collaboration with different countries (Chile, Canada) allowed us to study the effectsof Epo on peripheral and central chemoreceptors during HVR and HcVR.In fine, these experiments allows us to specify the factors involved in ventilatory responses tohypoxia and hypercapnia, which could be helpful to better understand respiratory pathologies suchas anemia or pathologies associated with high altitude.

Master of Science (Medicine) / Clinical studies have demonstrated an arousal deficit in infants suffering Obstructive Sleep Apnoea (OSA), and that treatment to alleviate the symptoms of OSA appears to reverse the deficit in arousability. Some sudden infant deaths are thought to be contingent upon such an arousal deficit. This research utilised young piglets during early postnatal development, and exposed them to intermittent hypercapnic hypoxia (IHH) as a model of clinical respiratory diseases. Arousal responses of control animals were compared to the animals exposed to IHH. Comparisons were also made between successive exposures on the first and the fourth consecutive days of IHH. Time to arouse after the onset of the respiratory stimulus, and frequency of arousals during recovery, demonstrated that arousal deficits arose after successive exposures and that these were further exacerbated on the fourth study day. After an overnight recovery period, the arousal deficit was apparently dormant, and only triggered by HH exposure. These studies confirm that both acute and chronic deficits can be induced on a background of otherwise normal postnatal development, suggesting that deficits observed in the clinical setting may be a secondary phenomenon.

African Americans (AA) are at an increased risk for cardio and cerebral vascular disease relative to Caucasians (CA) and the underlying impairments manifest as early as the second generation prior to overt signs of risk. The mechanisms of this increased risk are multifactorial; however, evidence suggests that microvascular dysfunction is a primary contributor. This study tested the hypothesis that microvascular function, indexed by the skin vascular conductance (SkVC) response to local heating, is impaired in young otherwise healthy AAs. Furthermore, we hypothesized that AAs have an attenuated cerebral vasodilator response to hypercapnia. Nineteen healthy young individuals were participated in this study (9 AAs, 10 CAs). SkVC was assessed while the skin was clamped at 34 °C and 40 °C and values were normalized to a maximal value obtained during heating at 43 °C for 30 min. Cerebral vasomotor reactivity (CVMR) was assessed by increases in cerebral vascular conductance (CVC) during a rebreathing protocol. SkVC was lower in the AA group at 34 °C (AA: 10±3 % max vs. CA: 16±7 % max; P < 0.01) In addition, SkVC was reduced in AAs at 40 °C (AA: 56±15 % max vs. CA: 68±12 % max; P=0.03). CVMR was significantly attenuated during hypercapnic rebreathing in AAs relative to CAs (AA: 2.8 ± 1.2 %CVC/Torr vs. CA: 5.7 ±0.9 %CVC/Torr; P < 0.001). Our findings suggest that microvascular function is impaired in young otherwise healthy AAs. / text

Mechanically ventilated patients are at risk of developing Ventilator-Associated Lung Injury (VALI). Improved ventilation strategies by lung-protective settings may cause hypercapnia. This study investigated whether attenuation of VALI is attributed to protective ventilation with low tidal volume (VT) or hypercapnia. Lung injury was induced in rats by instillation of 1.25M HCl. Ten rats each were ventilated for 4 hours with: Conventional Normocapnia (highVT), Lung-Protective Ventilation (VT¬ 8mL/Kg), Injurious Normocapnia (highVT, added dead space), Conventional Hypercapnia (highVT, inhaled CO2), Protective Hypercapnia (VT 8mL/Kg, inhaled CO2) and Permissive Hypercapnia (VT 8mL/Kg, hypoventilation). Lung-Protective Ventilation reduced pulmonary edema compared to Conventional and Injurious Normocapnia. Therapeutic hypercapnia reduced alveolar damage and inflammation by reducing IL-6 and MCP-1 in the lung, and IL-1? and TNF-? systemically. Therapeutic hypercapnia may be more effective in attenuating some of the biomarkers of VALI and protecting the lung than protective ventilation alone.

Obstructive sleep apnoea (OSA) is a common condition characterized by recurrent complete and partial upper airway obstruction. OSA sufferers have been shown to have a significantly smaller upper airway lumen compared to non-OSA sufferers. However, non-anatomical factors of sleep stage, arousability and neuromechanical responses to airway occlusion and chemosensitivity are likely to play a significant part in influencing OSA severity across the night. An exploration of these non-anatomical factors forms the basis for the experiments in this thesis. In the first experimental chapter presented in this thesis, a detailed retrospective epoch by epoch analysis of nocturnal polysomnography in 253 patients referred to a clinical sleep service was performed to examine differences in sleep apnoea severity and arousal indices across the different stages of sleep, while controlling for posture. Both patients with and without OSA demonstrated significant reductions in respiratory and arousal event frequencies from stage 1 to 4 with intermediate frequencies in REM sleep. Lateral posture was also associated with significant improvements in OSA and arousal frequencies, with an effect size comparable to that of sleep stage. The majority of patients showed significant reductions in OSA severity during slow wave sleep. In non-REM sleep, there was a strong correlation between OSA severity and arousal frequency. These results confirm in a large group of patients, a strong sleep stage dependence of both OSA and arousal frequencies. The second study in this thesis explores the development of a CO2 stabilising or ‘clamp’ device to enable the provision of positive airway pressure, and by proportional rebreathing, the maintenance of relatively constant end-tidal CO2 despite significant hyperventilation. Healthy volunteers performed brief periods of significant voluntary hyperventilation at 2 levels of CPAP with the rebreathing function off and with active CO2 clamping in randomized order. Compared to CPAP alone, the device substantially attenuated hypocapnia associated with hyperventilation. The third study of the thesis was designed to investigate if increasing and stabilizing end-tidal CO2 could improve obstructive breathing patterns during sleep. 10 patients with severe OSA underwent rapid CPAP dialdown from therapeutic to a sub-therapeutic level to experimentally induce acute, partial upper airway obstruction over 2 minute periods repeated throughout the night. The CO2 clamp device developed and validated in Study 2 was used to determine whether during periods of partial upper airway obstruction with severe flow limitation, (1) increased end-tidal CO2 resulted in improved airflow and ventilation and (2) clamping end-tidal CO2 lessened post-arousal ventilatory undershoot. Three conditions were studied in random order: no clamping of CO2, clamping of end-tidal CO2 3-4 mmHg above eucapnic levels during the pre-dialdown baseline period only, and clamping of CO2 above eucapnia during both baseline and dialdown periods. Elevated CO2 in the baseline period alone or in the baseline and dialdown periods together resulted in significantly higher peak inspiratory flows and ventilation compared to the no clamp condition. Breath-by-breath analysis immediately pre- and post-arousal showed higher end-tidal CO2 despite hyperventilation immediately post-arousal and attenuation of ventilatory undershoot in CO2 versus non-CO2 clamped conditions. These results support that modulation of ventilatory drive by changes in pre- and post-arousal CO2 are likely to importantly influence upper airway and ventilatory stability in OSA. The fourth study was designed to explore several possible pathophysiological mechanisms whereby obstructive sleep apnoea is improved in stages 3 & 4 (slow wave) versus stage 2 sleep. 10 patients with severe OSA who demonstrated significant reductions in OSA frequency during slow wave sleep on diagnostic investigation were studied. Patients underwent rapid dialdowns from therapeutic CPAP to 3 different pre-determined sub-therapeutic pressures to induce partial airway obstruction and complete airway occlusions in a randomised sequence during the night in both stage 2 and slow wave sleep. Partial airway obstructions and complete occlusions were maintained until arousal occurred or until 2 minutes had elapsed, whichever came first. After airway occlusions, time to arousal, peak pre-arousal negative epiglottic pressure and the rate of ventilatory drive augmentation were significantly greater, suggesting a higher arousal threshold and ventilatory responsiveness to respiratory stimuli during slow wave compared to stage 2 sleep. Post dialdowns, the likelihood of arousal was lower with less severe dialdowns and in slow wave compared to stage 2 sleep. Respiratory drive measured by epiglottic pressure progressively increased post-dialdown, but did not translate into increases in peak flow or ventilation pre-arousal and was not different between sleep stages. These data suggest that while arousal time and propensity following respiratory challenge are altered by sleep depth, there is little evidence to support that upper airway and ventilatory compensation responses to respiratory load are fundamentally improved in slow wave compared to stage 2 sleep. In summary, sleep stage, arousal threshold and chemical drive appear to strongly influence upper airway and ventilatory stability in OSA and are suggestive of important non-anatomical pathogenic mechanisms in OSA.

Master of Science (Medicine) / Clinical studies have demonstrated an arousal deficit in infants suffering Obstructive Sleep Apnoea (OSA), and that treatment to alleviate the symptoms of OSA appears to reverse the deficit in arousability. Some sudden infant deaths are thought to be contingent upon such an arousal deficit. This research utilised young piglets during early postnatal development, and exposed them to intermittent hypercapnic hypoxia (IHH) as a model of clinical respiratory diseases. Arousal responses of control animals were compared to the animals exposed to IHH. Comparisons were also made between successive exposures on the first and the fourth consecutive days of IHH. Time to arouse after the onset of the respiratory stimulus, and frequency of arousals during recovery, demonstrated that arousal deficits arose after successive exposures and that these were further exacerbated on the fourth study day. After an overnight recovery period, the arousal deficit was apparently dormant, and only triggered by HH exposure. These studies confirm that both acute and chronic deficits can be induced on a background of otherwise normal postnatal development, suggesting that deficits observed in the clinical setting may be a secondary phenomenon.

Thesis (Ph. D.)--University of Sydney, 2003. / Title from title screen (viewed 7 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Dept. of Medicine, Faculty of Medicine. Includes bibliographical references. Also available in print form.

As one of the most successful invasive species in the marine environment around the globe, the green crab Carcinus maenas possesses efficient regulatory mechanisms to quickly acclimate to environmental changes. The most important organs in this process are the nine pairs of gills that not only allow for osmoregulation, but have been shown to be involved in ammonia excretion and respiratory gas exchange. To date, however, little is known about the gills’ contribution to acid-base regulation that might become increasingly important in a “future ocean scenario” whereby surface ocean pH is predicted to drop by up to 0.5 units by the year 2100. The present thesis aims to characterize the green crab gills’ role in acid-base regulation and how it is linked to ammonia excretion. After exposure to hypercapnia (0.4 kPa pCO2 for 7 days), osmoregulating green crabs were capable of fully compensating for the resulting extracellular respiratory acidosis, while osmoconforming green crabs only partially buffered the accompanying drop in hemolymph pH after acclimation to 1% CO2 for 48 hours. Perfusion experiments on isolated green crab gills showed that different gills contributed to the excretion of H+ in an individual pattern and indicated that NH4+ is an important component of branchial acid excretion. Experiments on gill mRNA expression and pharmaceutical effects on isolated gills identified distinct epithelial transporters to play significant roles in branchial acid base regulation: Rhesus-like protein, basolateral bicarbonate transporter(s), cytoplasmic V-(H+)-ATPase, Na+/H+-exchanger, basolateral Na+/K+-ATPase, cytoplasmic and membrane bound carbonic anhydrase, and basolateral K+ channels. Regarding the latter, the present work provides the first sequence-based evidence for a potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel (CmHCN) capable of promoting NH4+ transport in the green crabs’ gill epithelium, and further demonstrates its direct involvement in branchial acid-base regulation. This highly conserved protein is a potentially important novel key-player in acid-base regulation in all animals. Interestingly, the observed principles linking acid-base to ammonia regulation in the decapod crustacean gill epithelium resemble many observations previously made in vertebrates. The data of the present thesis therefore provides valuable information for general acid-base regulation, while contributing substantially to our understanding of acid-base regulation in invertebrates. / February 2016

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第12970号 / 論医博第2103号 / 新制||医||1012(附属図書館) / 32408 / 新制||医||1012 / 京都大学大学院医学研究科医学専攻 / (主査)教授 小池 薫, 教授 三嶋 理晃, 教授 中山 健夫 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DGAM

Despite dramatic morphological differences between animals from different taxa, several important features in organization and sensory system processing are similar across animals. Because of this similarity, a number of different organisms including mammals, insects, and decapod crustaceans serve as valuable model systems for understanding general principles of environmental effects. This research examines intrinsic and extrinsic factors by behaviorally and physiologically means to identify the impact of environmental conditions on two distinct crayfish species- Procambarus clarkii (surface) and Orconectes australis packardi (cave). The research identified behavioral and physiological responses in these two morphological and genetically distinct species. The studies also examined multiple levels of complexity including social behavior, an autonomic response, chemosensory capabilities and neuronal communication, identified comparative similarities/differences, addressed learning and environmental influences on learning and examined behavioral and cellular responses to high levels of carbon dioxide. I found environmental factors directly influence crayfish behavior of social interactions. Interactions were more aggressive, more intense and more likely to end with a physical confrontation when they took place 'in water' than 'out of water'. The modified social interaction resulted in a altered fighting strategy. A study on motor task learning was undertaken which showed similar learning trends among these crayfish species despite their reliance on different sensory modalities. I also demonstrated learning was dependent on perceived stress by the organism. Previously trained crayfish inhibited from completing a task showed significant increase in an autonomic stress response. Studies on the behavioral and physiological responses to CO2 revealed that high [CO2] is a repellent in a concentration dependent manner. The autonomic responses in heart rate and an escape tailflip reflex shows complete cessation with high [CO2]. A mechanistic effect of CO2 is by blocking glutamate receptors at the neuromuscular junction and through inhibition of the motor nerve within the CNS.