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Fossorial mammals are frequently exposed to hypercapnic and/or hypoxic conditions in their burrows. This research compares ventilatory responses of golden hamsters (<i>Mesocricetus auratus</i>) to different ambient respiratory gas concentrations with those of the white rat (<i>Rattus norvegicus</i>). Total body plethysmography was used to measure tidal volume (V_T), respiratory frequency (R_f), and minute volume (V_E). The respiratory gases had carbon dioxide concentrations ranging from 0 to 790 and oxygen content ranging from 13 to 21%. Both hypercapnic and hypoxic gas mixtures caused hyperventilation in hamsters. The more a gas mixture deviated from normal air, the greater the ventilatory increase. Combining hypercapnic and hypoxic conditions did not potentiate the response. Rats exhibited a greater hyperventilation in response to hypercapnic-hypoxic and hypercapnic gas mixtures than did the hamsters. Hypoxia alone caused a greater response in the hamsters. Greater blood buffering capacity of hamsters offers a possible explanation for the different ventilatory responses observed between these two rodents. / M.S.

The major components of the tracheal system of insects are an extension of the exoskeleton, and the size of the exoskeleton is fixed in the adult stage, so any increase in metabolic demand that may accompany reproduction must be met by a relatively unaltered tracheal system that the female set in place at ecdysis, when entering adulthood. Acute hypoxia tends to elicit an increase in ventilation in insects, and here, I observe increased interburst VCO2 release, and a tendency towards a more continuous gas exchange pattern being preferred over discontinuous gas exchange when Blaptica dubia and Eublaberus posticus are exposed to a descending regime of hypoxia. Additionally, higher temperatures appear to increase sensitivity to hypoxia in these species, an expected result because both species, like most ectothermic animals, display a Q10 effect, increasing metabolic rates as temperature increases. The reproductive mode of B. dubia is considered to be lecithotrophic pseudoviviparity (or type A ovoviviparity), and by the time the embryos are born, they have more than doubles in volume from the time of oviposition. This gain is apparent in the wet mass of the embryo, with no change occurring in dry mass. The egg mass that can be attributed to water begins at 39% at oviposition and increased to nearly 82% at hatching. The metabolic rates of females and embryos increase as embryonic development progresses, but bomb calorimetry reveals that energy content of the embryos does not change. It is possible that these embryos gain some nutrition from the mother during embryonic development, but direct evidence remains to be demonstrated. Blaptica dubia and Eublaberus posticusare both blaberid species that display the same reproductive mode, pseudoviviparity, with incubation occurring in a brood sac. Comparisons between the reproductive traits of B. dubia and E. posticus reveal that the two species have similar reproductive periods, interbirth periods, and clutch sizes to one another, and that both have reproductive cycles and incubation times intermediate to oviparous species and the one species of cockroach that some consider to be truly viviparous (Diploptera punctata). However, whereas adult female E. posticus are larger than female B. dubia (E. posticus non-gravid female mass: 2.91 +/- 0.42 g, 20; B. dubia non-gravid female mass: 2.60 +/- 0.40 g, 20), the offspring of B. dubia are larger than those of E. posticus at the time of birth (B. dubia neonate mass: 24.70 +/- 4.01 mg, 19; E. posticus neonate mass: 22.40 +/- 1.36 mg, 19). Both gravid and non-gravid female B. dubia respond similarly to acute hypoxia exposure, increasing mean total VCO2. However, the reproductive state does not appear to exacerbate, nor dull, the acute response to hypoxia. Gravid and non-gravid female B. dubia were exposed to chronic hypoxia for 30 days and 45 days. Relatively high mortality was observed in nearly all chronic hypoxic treatment groups as compared to controls at 21 kPa O2. Comparing treatment groups to controls maintained at 21 kPa O2, embryo mass was not decreased, nor was embryo VCO2 at day 30. Adult female B. dubia metabolic rates did not show a consistent change in response to chronic hypoxia, but decreased metabolic rate was observed in the non-gravid B. dubia exposed to chronic 4 kPa O2, an observation that is consistent with past studies in insects. Survival rates were lower for both gravid and non-gravid females in 4, 8, and 12 kPa O2, as well as in 15 kPa O2 in gravid females, as compared to 21 kPa O2. Gravid females experiences a decreased survival rate compared with non-gravid females at 12 and 15 kPa O2, but gravid and non-gravid females had similarly low survival rates at 4 and 8 kPa O2. This difference in survival rates suggests there is a cost associated with carrying an ootheca in a brood sac, resulting in an increased sensitivity to hypoxia, at least over a long period of time.

Leung, Kin Ling. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 133-162). / Abstracts in English and Chinese. / CONTENTS --- p.i / ACKNOWLEDGEMENTS --- p.ii / ABBREVIATIONS --- p.iii / ABSTRACT --- p.vi / 論文摘要 --- p.ix / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Obstructive sleep apnea syndrome --- p.1 / Chapter 1.1.1 --- Symptoms of OSA --- p.2 / Chapter 1.1.2 --- Causes of OSA --- p.5 / Chapter 1.1.3 --- Complications of OSA --- p.6 / Chapter 1.1.4 --- Episodic hypoxia profile --- p.9 / Chapter 1.2 --- Hippocampus --- p.12 / Chapter 1.2.1 --- General structure of hippocampus --- p.12 / Chapter 1.2.2 --- The neuronal circuitry of hippocampus --- p.17 / Chapter 1.2.3 --- Cell types of hippocampus --- p.21 / Chapter 1.2.4 --- Functions of hippocampus --- p.24 / Chapter 1.3 --- Memory Formation and long term potentiation --- p.27 / Chapter 1.4 --- Neurotrophins --- p.33 / Chapter 1.5 --- Brain-derived neurotrophic factor (BDNF) --- p.38 / Chapter 1.5.1 --- Molecular characteristics of BDNF --- p.38 / Chapter 1.5.3 --- Functions of BDNF --- p.46 / Chapter 1.5.4 --- BDNF and neuronal plasticity --- p.46 / Chapter 1.6 --- Tissue plasminogen activator - plasmin system --- p.51 / Chapter 1.6.1 --- Molecular characteristics of tissue plasminogen activator - plasmin system --- p.51 / Chapter 1.6.2 --- Functions of tissue plasminogen activator - plasmin system --- p.54 / Chapter 1.7 --- Aim of the study --- p.59 / Chapter CHAPTER 2 --- MATERIALS AND METHODS --- p.61 / Chapter 2.1 --- Animal model of obstructive sleep apnea --- p.61 / Chapter 2.1.1 --- Intermittent hypoxia --- p.61 / Chapter 2.2 --- Electrophysiological recordings --- p.65 / Chapter 2.2.1 --- Preparation of brain slices --- p.65 / Chapter 2.2.1 --- Visualization of hippocampus CA1 Neurons --- p.66 / Chapter 2.2.3 --- Patch-clamp recordings --- p.66 / Chapter 2.3 --- Protein analysis - ELISA --- p.71 / Chapter 2.3.1 --- Isolation of mouse hippocampus total protein --- p.71 / Chapter 2.3.2 --- ELISA --- p.72 / Chapter 2.3 --- Protein analysis (II) - Western blot --- p.74 / Chapter 2.4.1 --- Isolation of mouse hippocampus total protein --- p.74 / Chapter 2.4.2 --- Western blot analysis --- p.75 / Chapter 2.5 --- Data analysis --- p.78 / Chapter CHAPTER 3 --- RESULTS --- p.79 / Chapter 3.1 --- Effect of intermittent hypoxia on passive and active properties of hippocampal CA1 neurons --- p.79 / Chapter 3.1.1 --- Passive properties --- p.79 / Chapter 3.1.2 --- Membrane excitability --- p.83 / Chapter 3.1.3 --- Action potential characteristics --- p.93 / Chapter 3.2 --- Effect of intermittent hypoxia on the expression of BDNF and related proteins --- p.104 / Chapter 3.2.1 --- "Levels of total BDNF, NGF, NT-3 and NT-4/5" --- p.104 / Chapter 3.2.2 --- Recovery study of the expression of BDNF after IH treatment --- p.110 / Chapter 3.2.3 --- Differential effect of IH on pro-BDNF and mature BDNF --- p.114 / Chapter 3.2.4 --- "Expressions of tissue plasminogen activator, plasmin and plasminogen" --- p.117 / Chapter Chapter 4 --- Discussion --- p.121 / Chapter 4.1 --- Changes in neuronal excitability of CA1 neurons under intermittent hypoxia --- p.121 / Chapter 4.2 --- Intermittent hypoxia-induced changes in BDNF level --- p.127 / Chapter 4.3 --- Conclusion --- p.130 / REFERENCES --- p.133

Abstract not available

[Truncated abstract] Cardiovascular reflex control of the vasculature is important in maintaining adequate tissue oxygenation in the face of disturbances in physiological homeostasis. Alterations in blood oxygen levels and blood distribution evoke integrated neural, mechanical and humoral responses which modulate peripheral vasomotor tone to maintain systemic cardiovascular integrity. The balance between the local effects of hypoxia and changes in chemoreflex control of vascular tone during hypoxia determine whether net vasoconstriction or vasodilatation is evident in the peripheral vasculature. The mechanisms contributing to hypoxic vasodilatation per se have not previously been defined in healthy humans. Study 1 of this thesis (Chapter 3) investigated the mechanisms contributing to vasomotor responses to chemoreflex activation in the human forearm ... Study 2 (Chapter 4a) investigated the mechanisms controlling vasomotor responses to isocapnic hypoxia in subjects with type 2 diabetes ... Study 3 (Chapter 5) compared the vascular responses to decreased venous return in individuals with and without right atrial afferent innervation ... The results of this thesis indicate that in healthy humans isocapnic hypoxia induces sympathetic vasoconstriction, which masks underlying β-adrenoceptor mediated vasodilatation. The normal vasomotor response to isocapnic hypoxia is impaired in subjects with type 2 diabetes. Despite intact vasoconstrictor responses, subjects with type 2 diabetes exhibited attenuated adrenaline-mediated vasodilatation compared to healthy control subjects, suggesting that the chemoreflex in these subjects is ill-equipped to respond to hypoxic stress. In clinical terms, impaired reflex vasomotor

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 5 uppsatser.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 200-217). Also available in electronic format on the Internet.

Thesis (Au.D.)--James Madison University, 2010. / Includes bibliographical references.

Phosphorescent transition metal complexes make up an important group of compounds that continues to attract intense research owing to their intrinsic bioimaging applications that arise from bright emissions, relatively long excited state lifetimes, and large stokes shifts. Now for biomaging assay a model organism is required which must meet certain criteria for practical applications. The organism needs to be small, with a high turn-over of progeny (high fecundity), a short lifecycle, and low maintenance and assay costs. Our model organism C. elegans met all the criteria. The ideal phosphor has low toxicity in the model organism. In this work the strongly phosphorescent platinum (II) pyrophosphito-complex was tested for biological applications as a potential in vivo hypoxia sensor. The suitability of the phosphor was derived from its water solubility, bright phosphorescence at room temperature, and long excited state lifetime (~ 10 µs). The applications branched off to include testing of C. elegans survival when treated with the phosphor, which included lifespan and fecundity assays, toxicity assays including the determination of the LC50, and recovery after paraquat poisoning. Quenching experiments were performed using some well knows oxygen derivatives, and the quenching mechanisms were derived from Stern-Volmer plots. Reaction stoichiometries were derived from Job plots, while percent scavenging (or antioxidant) activities were determined graphically. The high photochemical reactivity of the complex was clearly manifested in these reactions.