No description available.

The mitochondria are the primary energy providers for most eukaryotic cells. The substrate and products of the mitochondria need to be translocated across the semi-permeable mitochondrial outer membrane (MOM). Mitochondrial porin is an aqueous channel in the MOM thought to provide the primary pathway for metabolite translocation. Porin is a nuclear encoded protein and therefore needs to be transported to the mitochondria, translocated across and assembled within the MOM. Of all the recognition signals required for successful transport, import and assembly, only the β-sorting signal used in assembly is known. In addition, this protein possesses the ability to gate, and in doing so can preferentially allow the passage of anions in the open state and cations in the closed state. However, the precise mechanism by which gating of porin occurs and a complete understanding of porin’s function in vivo remains elusive. The essentiality of porin was examined by constructing a strain of Neurospora crassa deficient for porin. This strain, denoted as WS004, exists as evidence that porin is non-essential for the survival of Neurospora crassa. However, the loss of porin results in a reduction in growth rate due to the dysfunction of the cytochrome mediated respiratory pathway, which was made evident by the reduction of cytochrome b and almost complete lack of cytochrome aa3. WS004 survives by inducing the expression of alternative oxidase, which funnels the electrons from the Q pool directly to oxygen, bypassing the cytochrome b and aa3 containing complexes III and IV respectively. Additional phenotypic differences observed included loss in ability to produce aerial hyphae, reduced amount of conidia produced and strains that were female sterile. It was determined, that additional genetic factors influenced the resulting phenotype due to the loss of porin. LC-MS/MS, in combination with iTRAQ labelling, was utilized to examine changes in the proteome profiles of porin containing and porin lacking mitochondria and showed several different proteins as significantly up- or down-regulated which lend to an explanation to some of the phenotypes observed. Taken together, these results demonstrate the central role of porin in regulating both mitochondrial and cellular processes.

A knowledge of the allometry of algal growth and respiration can be applied to biomass-size distribution models which are in turn used in the prediction of fish yield and ecosystem studies. However, the scaling exponents reported in the literature are variable. This variation may be attributed to differences in the expression of cell size and phylogeny, but could also reflect small sample size which underlie most published regressions. This thesis establishes the allometry of algal growth and respiration based on a larger sample taken from the literature, and evaluates the effects of differences in gross taxonomy and in the expression of cell size on these relations. Allometric relations based on cell carbon appear more consistent with relations from other taxa than those based on cell volume, reflecting the size dependence of algal elemental composition which does not occur in most other taxa. The allometric relation of algal respiration (R in pl O$ rm sb2 cdot cell sp{-1} cdot hr sp{-1})$ was found to be R = 0.030C$ sp{0.93}$ where C is cell carbon content in pg C$ rm cdot cell sp{-1}$. Among the 6 divisions studied (Chlorophyta, Chrysophyta, Cyanophyta, Euglenophyta, Pyrrophyta, Rhodophyta), chlorophytes, euglenophytes and rhodophytes exhibited different respiration-size relation but separate relations were not developed for each of those groups due to patterns in residuals or small sample sizes. The specific rate of algal growth ($ mu$ in divisions$ cdot$day$ sp{-1}$) also depends on size and it is found to be $ mu$ = 3.45C$ sp{-0.21}.$ All taxa studied here (Chlorophyta, Chrysophyta, Pyrrophyta) have similar scaling exponents for growth but Pyrrophyta have significantly lower growth rates than other algae of similar size.

No description available.

Le syndrome de mort subite du nourrisson (SMSN), les malaises graves du nourrisson (ALTE) et les apnées du prématuré sont des pathologies sévères et/ou fréquentes chez le nouveau-né et peuvent être à l'origine d'expériences dramatiques pour les parents. Les observations cliniques et les données actuelles de la littérature nous portent à croire que la laryngite de reflux pourrait être impliquée via son interaction avec la fonction laryngée, incluant les chémoréflexes laryngés, la déglutition et la coordination respiration-déglutition. Notre objectif était d'étudier l'impact d'une laryngite de reflux induite expérimentalement sur la fréquence des déglutitions non nutritives (DNN) et sur la coordination respiration-déglutition dans notre modèle unique d'agneau nouveau-né. Douze agneaux nouveau-nés à terme ont été randomisés dans un groupe contrôle (n=6) et un groupe laryngite (n=6). Après une instrumentation chirurgicale, 2mL d'une solution de pepsine-HCl à pH 2,0 (laryngite) ou de salin 0,9% (contrôle) étaient instillés au niveau de la muqueuse laryngée trois fois par jour pour huit jours. Au dernier jour, une polysomnographie de quatre heures était faite pour enregistrer les DNN et les paramètres cardio-respiratoires. Deux techniques d'analyse complémentaires (qualitative et quantitative) de la coordination respiration-déglutition ont été utilisées sur les données obtenues. Tous les larynx ont été recueillis pour étude histologique et l'application d'un score d'inflammation. Une laryngite de reflux significative d'intensité légère à modérée a été induite dans le groupe laryngite (p= 0,02). Une diminution significative des épisodes de bouffées de DNN en sommeil agité (REM) (p=0,03), ainsi qu'une diminution significative des fréquences cardiaque et respiratoire de base (p < 0,0001) ont été observées dans le groupe laryngite. Aucune altération de la fréquence des DNN isolées (p = 0,9) ou de la coordination respiraton-déglutition (0,3 < p < 1,0) n'a été retrouvée. Nos résultats suggèrent qu'une laryngite de reflux diminue la fréquence des bouffées de DNN en REM, en plus d'augmenter le tonus parasympathique de base dans notre modèle d'ovin nouveau-né.

The ventilatory threshold (VT) is measured frequently during graded exercise tests (GXT) for exercise prescription purposes. The computerized V-slope method for VT determination has been reported to be valid yet little data exists concerning the reliability of the measure. The purpose of this study was to determine the reliability of the VT using the computerized V-slope method. Sixteen healthy volunteers, (eight men and eight women) ages 21-27 (23.6 ± 1.7yrs), performed three maximal GXT on an electronically-braked cycle using an individualized ramp protocol. A minimum of 48 hours separated each test; all three tests were completed within two weeks. Breath-by-breath analysis of gas exchange was performed using a SensorMedics 2900 cart. The VT, expressed as L • min1, was selected by a computerized V-slope method. There were no differences in V02 max between the 3 trials, (overall mean 3.18 ± 0.87 L - min-1). No significant differences were observed for V02 at VT (L - min-1) for tests 1, 2, and 3 (1.62 ± 0.44, 1.58 ± 0.49, and 1.49 ± 0.48) respectively. The VT was determined to be 49.7 ± 7.9% of V02 max. Correlations between the VT in trials 1-2, 1-3, and 2-3 were 0.829, 0.791, and 0.925, respectively. The overall coefficient of variation (C.V.) of the VT measures was 10.61 ± 5.1%. The overall (male and female) variability in VT was 1.28 ± 0.63 METS. Due to high variability and a wide range in correlations, the results failed to support the reliability in the computerized V-slope method. / School of Physical Education

The mitochondria are the primary energy providers for most eukaryotic cells. The substrate and products of the mitochondria need to be translocated across the semi-permeable mitochondrial outer membrane (MOM). Mitochondrial porin is an aqueous channel in the MOM thought to provide the primary pathway for metabolite translocation. Porin is a nuclear encoded protein and therefore needs to be transported to the mitochondria, translocated across and assembled within the MOM. Of all the recognition signals required for successful transport, import and assembly, only the β-sorting signal used in assembly is known. In addition, this protein possesses the ability to gate, and in doing so can preferentially allow the passage of anions in the open state and cations in the closed state. However, the precise mechanism by which gating of porin occurs and a complete understanding of porin’s function in vivo remains elusive. The essentiality of porin was examined by constructing a strain of Neurospora crassa deficient for porin. This strain, denoted as WS004, exists as evidence that porin is non-essential for the survival of Neurospora crassa. However, the loss of porin results in a reduction in growth rate due to the dysfunction of the cytochrome mediated respiratory pathway, which was made evident by the reduction of cytochrome b and almost complete lack of cytochrome aa3. WS004 survives by inducing the expression of alternative oxidase, which funnels the electrons from the Q pool directly to oxygen, bypassing the cytochrome b and aa3 containing complexes III and IV respectively. Additional phenotypic differences observed included loss in ability to produce aerial hyphae, reduced amount of conidia produced and strains that were female sterile. It was determined, that additional genetic factors influenced the resulting phenotype due to the loss of porin. LC-MS/MS, in combination with iTRAQ labelling, was utilized to examine changes in the proteome profiles of porin containing and porin lacking mitochondria and showed several different proteins as significantly up- or down-regulated which lend to an explanation to some of the phenotypes observed. Taken together, these results demonstrate the central role of porin in regulating both mitochondrial and cellular processes.

This thesis is concerned with modelling the properties of human ventilation during steady-state conditions and during acute and sustained isocapnic hypoxia. <strong>Chapter 1</strong> reviews some of the relevant studies in animals and humans. <strong>Chapter 2</strong> describes the origins of the data studied in this thesis. In particular, it describes the experimental apparatus and the technique of dynamic end-tidal forcing used to gather the data, as well as the particular protocols employed. <strong>Chapter 3</strong> studies the breath-to-breath variations in ventilation during steady breathing in both rest and during light exercise with the end-tidal gases controlled. The results suggest that: 1) both simple ARMA models and a simple state-space model can describe the autocorrelation present in the data; 2) variations in spectral power were present in the data which cannot be described by these models; and 3) these variations were often due to a uniform modulation and did not significantly affect the coefficients of the models. For these kinds of data, a heteroscedastic form of state-space model provides an attractive theoretical structure for the noise processes. <strong>Chapter 4</strong> studies human ventilation during sustained isocapnic hypoxia. Two models are used. The first, developed by Painter et al. (J. Appl. Physiol. 74:2007-2015, 1993) describes hypoxic ventilatory decline (HVD) as a decline in peripheral chemoreflex sensitivity. The second is an extended model which incorporates a component of HVD that is independent of peripheral chemoreflex sensitivity. The models incorporate a parallel noise structure. It is concluded that, in some subjects but not others, there is a component of HVD which is independent of peripheral chemoreflex sensitivity. <strong>Chapter 5</strong> studies the human ventilatory response to cyclic isocapnic hypoxia. Both a simple proportional dynamic model suggested by Clement and Robbins (Respir. Physiol. 92:253-175, 1993), and an extended model with an additional non-linear rate-sensitive component are studied. The models incorporate a parallel noise structure. The results show that, although the extended model improves the fit to the data for some subjects, both models failed to explain the data fully, especially the occasional large breaths, which were shown to occur more frequently in some parts of the hypoxic cycle than other parts.

The work contained in this thesis was concerned with rebreathing methods of measuring lung volume. In particular, one novel rebreathing technique which uses oxygen as the indicator gas was assessed. This technique appeared methodologically simple and readily applicable in a clinical environment. In essence, it relied on a graphical extrapolation of the time related changes in oxygen concentration to allow for oxygen uptake. This technique has been tested using a mass spectrometer which enabled nitrogen and argon as well as oxygen to be simultaneously used as indicator gases. Although the lung volumes as measured by the different indicator gases should have been the same, these were found to be different. These discrepancies were related to the concentration of the indicator gas which existed in the bag and lung prior to rebreathing. A hypothesis explaining these inconsistancies was formulated. This was based on an initial but non-sustained output of carbon dioxide into the bag-plus-lung system. A numerical model of idealised rebreathing showed that the hypothesis was sufficient to explain the discrepancies observed. A correction procedure was devised which performed successfully in the model. This correction was incorporated into an on-line computing procedure for calculating real lung volume. When tested in normal subjects this gave consistent results for lung volume, irrespective of indicator gas employed. The corrected lung volumes were unaffected by the initial gas compositions in the bag and lung, and were also independent of non-sustained gas exchange, whether this was due to carbon dioxide and/or nitrous oxide. This technique could, therefore, be use under anaesthetic conditions, since the uptake or output of nitrous oxide no longer upsets the calculation of lung volume. The use of more than one indicator gas, within the same manoeuvre, was shown to provide a valuable indication of the presence of errors in the system. When this approach was applied to more conventional rebreathing techniques of lung volume measurement, it also highlighted the presence of inaccuracies.

Aspects of the resting respiration rate, specific dynamic action (SDA) and components of the total energy budget of 55 - 80g common carp were studied in the laboratory. The resting respiratory rate was monitored in computer operated metabolic chambers under different photoperiods. Common carp showed a crepuscular respiratory rhythm with peaks at dawn and dusk during a 12L : 12D photoperiod, with a mean oxygen consumption of 152 mg/kg/h. When acclimated to longer or shorter photoperiods respiration was also cyclic but with a lower mean respiratory rate. In continuous light or darkness respiratory rhythm was suppressed with no significant peakings. In carp fed with three diets containing 20,35 and 50% protein at a ration level of 0.40 to 1.00% body weight per day, SDA coefficient varied from 8.99 to 15.94% and was dependent on dietary protein but not on ration levels. SDA magnitude and post-feeding peak oxygen consumption varied significantly with both dietary protein content and total daily ration level. SDA duration was only related to ration size. The pattern of food energy allocation between the major components of the energy budget varied with dietary protein content and ration levels. The energy lost as heat of metabolism was found to increase with dietary protein level and total ration. Energy lost as faeces 'F' varied from 19 - 24% of 'C' and did not appear to be related to either protein content or ration levels. Nitrogenous excretion increased with an increase of dietary protein but decreased with an increase of ration level in the diet. Regression equations were developed from the data to allow prediction of respiratory energy loss 'R', faecal energy loss 'F' and energy lost through excretion 'U' from the food ingested V. Complete energy budget models compiled from experiments conducted over a 17 days period and using different diets did not successfully predict the actual growth. The energy budget balance was between 66.04% and 81.96%. Observed growth was less than predicted growth in every trial and it is suggested that this difference might have been due to short-term cyclic growth regulation and other minor experimental features. The data presented form the basis for the first reported study of total energy budgets in Cyprinus carpio.