Spelling suggestions: "subject:"hypoxic"" "subject:"hipoxic""
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The pharmacological effect of alpha-tocopherol on hypoxia-induced changes in isolated portal vein of the guinea-pigRichardson, W. January 1984 (has links)
No description available.
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Some factors affecting respiration in manBascom, Daphne Ayn January 1991 (has links)
No description available.
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Hypoxia and the pulmonary circulationJones, Richard David January 1998 (has links)
No description available.
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The Morphological and Molecular Basis of Hypoxic Chemotransduction and Transmission in Neuroepithelial Cells of Zebrafish (Danio rerio)Pan, Wen 13 September 2021 (has links)
O2 is essential to many animals. Vertebrate species rely on specialized chemoreceptive cells to “sense” O2 changes in order to make appropriate physiological adjustments to maintain homeostasis. Aquatic vertebrates are especially prone to fluctuations in environmental O2 availability and have adapted respiratory and cardiovascular responses to cope with hypoxia, a condition characterized by a low level of O2. In teleost fish, such as zebrafish (Danio rerio), neuroepithelial cells (NECs) present in the gill epithelium are the putative O2 chemoreceptors that mediate hypoxic signals to facilitate such responses. NECs contain the neurotransmitter serotonin (5-HT) and exhibit extensive neural innervation. They are sensitive to hypoxia, as isolated NECs undergo membrane depolarization and vesicular recycling when exposed to acute hypoxia. Other neurotransmitters, such as dopamine (DA), acetylcholine (ACh) and adenosine triphosphate (ATP), have also been suggested to regulate the ventilatory responses to hypoxia. However, the presence of these neurotransmitters or targeted receptors in gills are not well explored. In my PhD studies, I identified cellular and molecular components involved in chemotransduction and transmission for hypoxic signals in NECs of zebrafish through various experimental approaches. First, using the existing transgenic zebrafish line, ETvmat2:GFP, I established a method to reliably identify gill NECs. I showed that these cells could be distinguished based on their high expressions of the reporter gene GFP in vitro, in situ and in cytometric analyses. GFP-labeled NECs also displayed increases in cell size and population in response to chronic hypoxia. Second, using immunohistochemistry and confocal microscopy, I localized cholinergic cells and dopaminergic cells, sources of DA and ACh secretion respectively, in the gills. These cells present distinct populations from serotonergic NECs. In addition, I found purinergic P2X3 receptors, targets of ATP, to be present in gill NECs and other iv neurons. These findings offered different avenues in which hypoxic signals could be regulated. Lastly, using the single cell RNA sequencing approach, I determined the transcriptomic profile of NECs. NECs showed high expressions of G protein regulators, similar to those found in the mammalian O2 chemoreceptors, and they expressed high levels of genes likely to be involved in O2 signal transduction and transmission. Within the gill cell atlas generated using the single cell sequencing data, I localized a number of 5-HT, ACh and DA receptors in various gill cell populations, providing evidence for the 5-HT fast synaptic excitatory neurotransmission, paracrine and endocrine regulation of the signal. The studies overall provide compelling evidence to support a role for NECs as the primary O2 chemoreceptor in zebrafish, and further our understanding of signal modulation in the hypoxic response.
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A familial comparison of hypoxic sensitivity in two South-African populationsTerblanche, Jonathan Steed 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Chapter 1 presents a general literature review on the acute isocapnic hypoxic ventilatory
response (HVR).
The main findings from Chapter 2 indicate that our modified breathing circuit effectively
measured the HVR while maintaining isocapnia. The measured ventilatory variables
changed significantly with repeated short-term exposure to hypoxia over a 30-minute
period, and the within- and between-day variability did not differ significantly.
Furthermore, the variability in the HVR response (as measured by the coefficient of
variation, (CV» amounted to approximately 27% between tests in both parameters.
Repeated measures are recommended in future determinations of the HVR.
In Chapter 3 the main findings were that hypoxic sensitivity does not differ between
Caucasian and Xhosa sea-level populations in South Africa, and that ventilatory
components in both normoxia and hypoxia differed between these two populations. Two
distinct patterns of breathing were evident: shallow, rapid breathing among Xhosa
subjects, and deeper, slower breathing among Caucasians. Moreover, lower arterial
oxygen saturation levels during hypoxia among Xhosa subjects suggest that these two
patterns of breathing differ in the effectiveness with which they oxygenate the blood.
Inter-individual variation in HVR within each population is of the same high magnitude
as that reported in the literature (Beall et al., 1997), further supporting the use of repeated
measures in future studies.
As previously reported (Sahn et al., 1977, Reeves et al., 1993), in Chapter 3 I document a
significant correlation between HVR and partial pressure of end-tidal CO2 (PETCO).
Future studies of HVR should consider PETCO2 as a covariate, despite the fact that my
analyses of covariance (ANCOV A) showed no inter-population differences in HVR.
In Chapter 4 I report that regression analysis shows that the HVR of parents is not a
predictor of that of their offspring. No significant heritability was evident for any of the
additional key variables of hypoxic VE ,hypoxic Sa02, and the CV for HVR, but a priori
analyses showed that I tested too few subjects to be able to demonstrate heritability (or
the lack thereof) conclusively by means of regression analyses. Importantly, repeatability
estimates within populations (86 %) revealed that despite its high variability, the HVR is
highly repeatable, and therefore remains a useful comparative research tool for studies of
human adaptation to hypoxia. / AFRIKAANSE OPSOMMING: Hoofstuk 1 gee 'n algemene literatuuroorsig van die akute isokapniese hipoksiese
ventilatoriese reaksie (HVR).
Die hoofbevindinge uit Hoofstuk 2 dui aan dat ons gemodifiseerde asemhalingsbaan
HVR effektief meet terwyl isokapniese toestande gehantaaf word. Die ventilatoriese
veranderlikes gemeet, het betekenisvol verskil met herhaalde korttermyn blootstelling aan
hipoksie in a 30-minuut periode, en die binne- en tussen-daagse afwykbaarheid het nie
betekenisvol verskil nie. Verder het die afwykbaarheid van die HVR reaksie (soos bepaal
deur die koëffisiënt van variasie (KV)) ongeveer 27 % beloop tussen toetse van beide
parameters. Herhaalde metings word vir toekomstige bepalings van die HVR voorgestel.
In Hoofstuk 3 was die hoofbevindinge dat hipoksiese sensitiwiteit nie verskil tussen
Kaukasiese- en Xhosa- seevlak populasies in Suid-Afrika nie, en dat ventilatoriese
komponente in beide normoksie en hipoksie verskillend was tussen hierdie twee
populasies. Twee definitiewe asemhalingspatrone was duidelik merkbaar: vlak, vinnige
asemhaling in Xhosa proefpersone, en dieper, stadiger asemhaling in Kaukasiërs. Verder
het laer arteriële suurstof versadigingsvlakke gedurende hipoksie in Xhosa proefpersone
daarop gedui dat hierdie twee asemhalingspatrone moontlik verskil in hul effektiwiteit
om die bloed met suurstof te verryk.
Inter-individuele variasie in HVR binne elke populasie was van dieselfde groot omvang
as wat in die literatuur gerapporteer word (Beall et al., 1997), wat die gebruik van
herhaalde metings in toekomstige studies verder ondersteun.
Soos voorheen gerapporteer (Sahn et al., 1977, Reeves et al., 1993), dokumenteer ek in
Hoofstuk 3 'n merkbare korrelasie tussen HVR en parsiële druk van eind-tidale CO2
(PET CO2
). Verdere HVR studies behoort PET CO2 as a kovariant te beskou, ten spyte van
die feit dat my analise van kovariansie (ANCOV A) geen inter-populasie verskille in
HVR getoon het nie.
In Hoofstuk 4 rapporteer ek dat regressie analise bewys dat die HVR van ouers nie 'n
voorspeller van dié van hul kinders is nie. Geen betekenisvolle oorerflikheid was duidelik
vir enige van die addisionele sleutelveranderlikes van hipoksiese VE ,hipoksiese Sa02, of
die KV van HVR nie, maar 'n vorige analise het getoon dat ek te min proefpersone
getoets het om oorerflikheid (of die gebrek daaraan) m.b.v. regressie analises te kan
demonstreer. Dit is belangrik dat intra-populasie herhaalbaarheidsskattings (86 %) getoon
het dat ten spyte van sy hoë afwykbaarheid, die HVR hoogs herhaalbaar is, en daarom 'n
nuttige vergelykende navorsingshulpmiddel is vir studies rakende menslike aanpassing by
hipoksie.
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Cellular mechanisms of acute hypoxic pulmonary vasoconstriction in intrapulmonary veinsDospinescu, Ciprian January 2009 (has links)
In the pulmonary circulation, alveolar hypoxia contributes to blood flow regulation. Hypoxic pulmonary vasoconstriction (HPV) involves both pulmonary arteries and veins, but little is known of the contractile mechanisms specific to the veins. The aim of these studies was to examine the hypoxic response in small porcine intrapulmonary veins in relation to the arterial response, and investigate the effects of hypoxia on ion conductances in single myocytes from intrapulmonary veins. In wire myography experiments, intrapulmonary veins contracted more than sizematched arteries in response to hypoxia and agonists KCl and PGF2α. Venous contractions were inhibited by removal of extracellular Ca2+ or in the presence of Clchannel blocker NFA, effects not seen in the arteries. To examine the mechanisms of venous contraction at cellular level, single pulmonary vein smooth muscle cells (PVSMC) were freshly isolated and characterised morphologically and electrophysiologically for the first time. In patch-clamp studies, hypoxia reversibly inhibited a whole-cell outward current in the presence of BKCa channel antagonist Penitrem A. By subtracting currents recorded in normoxia and hypoxia, a novel hypoxia-sensitive K+ current (IK(H)) was revealed in PVSMC. IK(H) was a rapidly activating, partially inactivating current and was sensitive to KV channel blocker 4-AP. The biophysical properties of IK(H) revealed the voltage window of current availability with a peak near the resting membrane potential of PVSMC. In conclusion, these findings highlight differences between the contractile properties of veins and arteries and reveal a significant contribution of Ca2+ influx and an NFA-sensitive conductance during venous contraction to agonists and hypoxia. Furthermore, the results suggest that a novel hypoxia-sensitive KV current contributes to membrane potential under resting conditions in PVSMC and its inhibition by hypoxia may contribute to the initiation of HPV in porcine intrapulmonary veins.
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Novel use of oxygen-regulated bacterial transcription factors to target gene expression to solid tumoursSumner, Stephanie Gillian January 2001 (has links)
No description available.
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Effects of oxygen tension on articular chondrocytesGrimshaw, Matthew John January 1999 (has links)
No description available.
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Description of the Dynamic Responses to Hypoxia:Ventilation, Cerebral Blood Flow (CBF), Blood Pressure (BP), and Heart Rate (HR)Battisti, Anne Marie Gabrielle 04 September 2012 (has links)
This thesis describes experiments to measure the ventilatory response to hypoxia at a constant (isocapnic) level of CO2 (HVR) in 18 subjects. So as to provide a complete picture of the autonomic responses, middle cerebral artery velocity, a surrogate for cerebral blood flow (CBF), as well as finger plethysmography blood pressure (BP) were also measured. Ventilatory responses have been previously described only in terms of an acute peak followed by a decline. However, rather than a single type of response, I found four types categorized as: Decline, Double, Plateau, or No response. The Double pattern, characterized by a second peak of response was the most common, yet is described here for the first time. These patterns are also characteristic of the CBF and BP responses. Furthermore the temporal correlations between these brainstem-controlled responses are also reported here for the first time.
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Description of the Dynamic Responses to Hypoxia:Ventilation, Cerebral Blood Flow (CBF), Blood Pressure (BP), and Heart Rate (HR)Battisti, Anne Marie Gabrielle 04 September 2012 (has links)
This thesis describes experiments to measure the ventilatory response to hypoxia at a constant (isocapnic) level of CO2 (HVR) in 18 subjects. So as to provide a complete picture of the autonomic responses, middle cerebral artery velocity, a surrogate for cerebral blood flow (CBF), as well as finger plethysmography blood pressure (BP) were also measured. Ventilatory responses have been previously described only in terms of an acute peak followed by a decline. However, rather than a single type of response, I found four types categorized as: Decline, Double, Plateau, or No response. The Double pattern, characterized by a second peak of response was the most common, yet is described here for the first time. These patterns are also characteristic of the CBF and BP responses. Furthermore the temporal correlations between these brainstem-controlled responses are also reported here for the first time.
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