Arterial smooth muscle cells (SMCs) from the systemic and pulmonary circulations experience a broad range of oxygen concentrations under physiological conditions. The hypoxic response, however, has been inconsistent, with both enhanced proliferation and growth arrest being reported. This variability precludes a definitive conclusion regarding the role of oxygen tension in arterial disease. In the first part of this study, we determined if hypoxia elicits different proliferative and apoptotic responses in human aortic SMCs (HASMCs) incubated under conditions which do or do not result in cellular ATP depletion and whether these effects are relevant to vascular remodeling in vivo. Gene expression profiling was used to identify potential regulatory pathways. In HASMCs incubated at 3% O2, proliferation and progression through G1/S interphase are enhanced. Incubation at 1% O2 reduced proliferation, delayed G1/S transition, increased apoptosis and cellular ATP levels were reduced. In aorta and mesenteric artery from hypoxia exposed rats, both proliferation and apoptosis are increased after 48hrs. p53 and p21expression is differentially affected in HASMCs incubated at 1% and 3% O2. Hypoxia induces a state of enhanced cell turnover, conferring the ability to remodel the vasculature in response to changing tissue metabolic needs while avoiding the accumulation of mutations that may lead to malignant transformation or abnormal vascular structure formation. A unifying hypothesis in which events at the G1/S transition and apoptosis activation are coordinated by effects on p53, p21, their downstream effector genes and regulatory factors is proposed. Differences in the contractile responses of systemic and pulmonary arterial smooth muscle cells to hypoxia are well studied. Differences in proliferation and survival are anticipated because of differences in embryonal cell origin, oxygen concentrations within their respective microenvironments and in cellular energetics but these responses have not been directly compared. In the second part of the study, human pulmonary arterial SMCs (HPASMCs) proliferated at oxygen concentrations which inhibited cell growth in HASMCs. HPASMCs survived and maintained their intracellular ATP levels at levels of hypoxia sufficient to deplete ATP and induce apoptosis in HASMCs. In vivo studies in rats show proliferation and apoptosis in main or branch PASMCs only after 7 days of hypoxia. VSMCs are able to proliferate under hypoxic conditions as long as cellular ATP levels are maintained. HPASMCs have an enhanced capacity to maintain cellular energy status compared to HASMCs and hence their viability is preserved and the proliferative response predominates at lower oxygen concentrations.

Solid tumours are a hostile tissue environment in which the cells are exposed to many stresses including hypoxia. One consequence of hypoxic conditions is an increase in extracellular levels of the purine nucleoside adenosine, which enhances tumour cell migration. This is achieved in part through an increase in the levels of the chemokine receptor CXCR4, which along with its ligand CXCL12, is a key player in breast cancer metastasis. The cellular response to stress is mediated by a family of proteins known as heat-shock proteins (HSPs). The small heat shock protein 27 (HSP27) has been implicated in changes in cancer cell migration. I have therefore studied the regulation of HSP27 in human breast cancer cells by conditions that normally exist in the stressful tumor environment. My project specifically aimed to establish whether changes in HSP27 are linked to hypoxia, adenosine levels and alterations in the CXCL12-CXCR4 migratory pathway.

In early rainbow trout development, a switch from high-affinity embryonic hemoglobin to lower-affinity adult hemoglobin occurs along with a turnover of round, embryonic erythrocytes to oval, adult erythrocytes. The objective of my thesis was to determine how the ontogeny of blood oxygen transport was affected by chronic hypoxia (30% of saturation) in rainbow trout. Hemoglobin-oxygen affinity, cooperativity, and the Bohr and Root effects were unaffected by hypoxia treatments, whereas hemoglobin content, erythrocyte counts, and hematocrit were significantly reduced. In hypoxia, larvae had higher concentrations of embryonic hemoglobin mRNA and embryonic erythrocytes than stage-matched normoxia-reared larvae. Overall, these results indicate that chronic hypoxia suppresses erythrocyte development prior to complete yolk absorption. Ultimately, this suggests that in early ontogeny rainbow trout conform to low oxygen conditions, rather than mounting the hypoxia response observed in oxygen-regulating adult trout.

In most organisms the cellular response to hypoxia is mediated by the master regulator hypoxia-inducible factor-1 (HIF-1). Zebrafish embryos can also arrest development (suspended animation) to tolerate low oxygen. I tested the hypothesis that induction of HIF-1 and associated target genes (eg. erythropoietin) during embryonic development would alter the hypoxia tolerance phenotype of larval and adult fish. I exposed zebrafish embryos at 3 developmental stages to acute (4 h) bouts of hypoxia (5% dissolved oxygen, DO) or anoxia (<0.5% DO). I found that embryos that mount a HIF-1 response have a greater hypoxia tolerance as larvae. Additionally, populations that experienced embryonic HIF-1 induction show an increase in the proportion of males (~70% male), that are more hypoxia tolerant than female fish, compared to control populations (~45% male). Overall, induction of HIF-1 during ontogeny alters the larval and adult zebrafish phenotype to better tolerate future hypoxic bouts. / NSERC

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Arterial smooth muscle cells (SMCs) from the systemic and pulmonary circulations experience a broad range of oxygen concentrations under physiological conditions. The hypoxic response, however, has been inconsistent, with both enhanced proliferation and growth arrest being reported. This variability precludes a definitive conclusion regarding the role of oxygen tension in arterial disease. In the first part of this study, we determined if hypoxia elicits different proliferative and apoptotic responses in human aortic SMCs (HASMCs) incubated under conditions which do or do not result in cellular ATP depletion and whether these effects are relevant to vascular remodeling in vivo. Gene expression profiling was used to identify potential regulatory pathways. In HASMCs incubated at 3% O2, proliferation and progression through G1/S interphase are enhanced. Incubation at 1% O2 reduced proliferation, delayed G1/S transition, increased apoptosis and cellular ATP levels were reduced. In aorta and mesenteric artery from hypoxia exposed rats, both proliferation and apoptosis are increased after 48hrs. p53 and p21expression is differentially affected in HASMCs incubated at 1% and 3% O2. Hypoxia induces a state of enhanced cell turnover, conferring the ability to remodel the vasculature in response to changing tissue metabolic needs while avoiding the accumulation of mutations that may lead to malignant transformation or abnormal vascular structure formation. A unifying hypothesis in which events at the G1/S transition and apoptosis activation are coordinated by effects on p53, p21, their downstream effector genes and regulatory factors is proposed. Differences in the contractile responses of systemic and pulmonary arterial smooth muscle cells to hypoxia are well studied. Differences in proliferation and survival are anticipated because of differences in embryonal cell origin, oxygen concentrations within their respective microenvironments and in cellular energetics but these responses have not been directly compared. In the second part of the study, human pulmonary arterial SMCs (HPASMCs) proliferated at oxygen concentrations which inhibited cell growth in HASMCs. HPASMCs survived and maintained their intracellular ATP levels at levels of hypoxia sufficient to deplete ATP and induce apoptosis in HASMCs. In vivo studies in rats show proliferation and apoptosis in main or branch PASMCs only after 7 days of hypoxia. VSMCs are able to proliferate under hypoxic conditions as long as cellular ATP levels are maintained. HPASMCs have an enhanced capacity to maintain cellular energy status compared to HASMCs and hence their viability is preserved and the proliferative response predominates at lower oxygen concentrations.

Although there has been considerable work on the role of nutrient-derived (mostly nitrate) primary production in fueling hypoxia in northern Gulf of Mexico, very little is known about the relative importance of autochthonous versus allochthonous sources of dissolved organic matter (DOM). Moreover, even less is known about the importance of dissolved organic nitrogen (DON), a critical component of DOM (along with DOC) in supporting hypoxia in this region. Most nitrogen in marine organisms exists in the form of amino acids. Changes in the spatial and temporal distribution of amino acids in the Mississippi River Plume have been shown to be important in the dynamic microbial cycling in the plume. In this study, concentrations of amino acids, DON and DOC were linked with hydrography data (e.g., DO, salinity, temperature, fluorescence) to determine how these sources of DOM are related to seasonal and diurnal changes in hypoxia on the inner Louisiana shelf. The general working hypothesis of this work was that allochthonous and autochthonous sources of DOM on the Louisiana shelf have been largely underestimated in their role in fueling hypoxia in northern Gulf of Mexico. A positive correlation between DOC, DON and fluorescence demonstrated that the main source of both DOC and DON was likely to be in situ phytoplankton production. Surface waters in the near-field showed this relationship more than at stations to the west where a sub-surface chlorophyll peak near the pycnocline may also provide a source of DOC and DON in bottom waters. DFAA always had relatively low concentrations at all water depths, which further supports prior work which has shown rapid cycling and high consumption rate of DFAA by heterotrophic bacteria. In addition to biotic controls, selective adsorption of DFAA likely contributed to the dominance of aspartic and glutamic acids at our stations. Hypoxia was generally observed in bottom waters in both spring and summer 2010. Dissolved oxygen generally revealed a negative correlation with nitrate+nitrite concentrations. Based on other work, one possible reason for such linkages may be from NH4+ released from dissimilatory nitrate reduction to ammonium (DNRA). Another possible reason may be the high degradation of labile DOM (such as DFAA) as shown by high respiration in bottom waters in prior work by Amon and Benner (1998).

Syftet med denna studie var att undersöka om vistelse på hög höjd påverkar den anaeroba arbetsförmågan. Sex aktiva universitetsstudenter, fyra män och två kvinnor, deltog frivilligt i studien. Expeditionen till Nepal varade i 40 dagar och under den perioden sov och vandrade försökspersonerna mellan 1400 och 5100 meter över havet. Före och efter expeditionen genomförde försökspersonerna ett anaerobt wingatetest där peak power, average power, minimum power and power drop uppmättes. Resultatet visade en signifikant sänkning av average power efter den genomförda expeditionen på hög höjd, med ett medelvärde på 8.44 ± 0,84 w/kg före expeditionen och 7.81 ± 0,87 w/kg efter expeditionen. Inga signifikanta förändringar sågs hos övriga uppmätta parametrar. Konklusionen är att average power försämras efter 40 dagars vistelse på hög höjd.

Throughout history, cancer has been severely plaguing mankind; the search for a cure to cancer had long been sought by scientists and still poses as one of the greatest challenges scientists have yet to overcome. Hypoxia in cells is a condition where there is little to no oxygen availability in its environment. In general, this event is detrimental since this can lead to cell necrosis or reoxygenation injuries. However, hypoxia, a prominent property of most solid tumors, activates the hypoxia-inducible factor (HIF-1) family of transcription factors that promotes angiogenesis. In this study, we describe the design and synthesis of small-molecule inhibitors of the HIF-1 pathway.