Some animals have adapted to hypoxia by increasing their haemoglobin affinity for oxygen, but in vitro studies have not shown any change of haemoglobin affinity for oxygen in human high altitude natives or lowlanders acutely acclimatized to high altitude. We conducted the first in vivo study of the oxyhaemoglobin dissociation curve by progressively reducing arterial PO2 while maintaining normocapnia in lowlanders at sea level, lowlanders sojourning at 3600m for two weeks and native Andeans at the same altitude. We found that the in vivo PO2 at which haemoglobin is half-saturated (P50) is higher in lowlanders at sea level (32 mmHg) than that measured in vitro (27 mmHg) and that lowlanders and highlanders do significantly increase the in vivo affinity of their haemoglobin for oxygen with exposure to high altitude. These results indicate the value of an in vivo approach for studying the oxyhaemoglobin dissociation curve.

Some animals have adapted to hypoxia by increasing their haemoglobin affinity for oxygen, but in vitro studies have not shown any change of haemoglobin affinity for oxygen in human high altitude natives or lowlanders acutely acclimatized to high altitude. We conducted the first in vivo study of the oxyhaemoglobin dissociation curve by progressively reducing arterial PO2 while maintaining normocapnia in lowlanders at sea level, lowlanders sojourning at 3600m for two weeks and native Andeans at the same altitude. We found that the in vivo PO2 at which haemoglobin is half-saturated (P50) is higher in lowlanders at sea level (32 mmHg) than that measured in vitro (27 mmHg) and that lowlanders and highlanders do significantly increase the in vivo affinity of their haemoglobin for oxygen with exposure to high altitude. These results indicate the value of an in vivo approach for studying the oxyhaemoglobin dissociation curve.

Most advice for improving physiological strain in the heat includes maintaining hydration using long-term acclimation protocols (>10 days). Therefore, the major aims of this thesis were to examine; (i) effectiveness of short term (5-day) heat acclimation (STHA) with moderately and highly trained athletes; (ii) fluid regulatory strain has a thermally-independent role in heat adaptation; and, (iii) impact of STHA on a marker of thermotolerancè (inducible heat shock protein 70; HSP70). Ten moderately trained males completed heat acclimation (Acc) under controlled hyperthermia (rectal temperature 38.5�C) for 90-min on five consecutive days (T[a] = 40�C, 60% RH), on two occasions separated by a five-week washout, in a cross-over design. One Acc was undertaken with euhydration (fluid replenishment; EUH) and one with dehydration (no fluid intake; DEH) during daily Acc bouts. Participants completed an exercising heat stress test (HST) one week before, then on the 2nd day after Acc for both regimes. HST involved cycling at 40% PPO for 90 min (T[a] = 35�C, 60% RH), 10 min rest and a ramp protocol (2% PPO each 30 s) to volitional fatigue. HSTs were further completed 1, 2, and 3 wks after Acc to track the acclimation decay. On a later occasion eight highly trained male rowers were heat acclimated under the same protocol but with DEH acclimation only and a rowing-specific HST (2000 m rowing performance test). Plasma volume (PV) at rest and cardiac output (Q̇) during HSTs were measured using CO and CO₂ rebreathing, respectively. A number of plasma constituents were measured: PV, AVP, aldosterone, HSP70, total protein, albumin, Na⁺, K⁺, Cl⁻ and osmolality. Short term heat acclimation resulted in physiological adaptation and enhanced exercise capacity for moderately trained participants. Compared to EUH permissive DEH during Acc bouts conferred larger acclimation-induced increases in resting PV by 4.1% (95%CI: -1.5 to 9.8%; p=0.06), Q̇[F]. (4.2: 0.7 to 7.8 mlmin⁻� 100 ml⁻�; p0.009), FVC (0.06: 0.02 to 0.10 ml 100ml Tissue⁻�mmHg⁻�; p=0.006), end-exercise V[s] (45.9: 3.6 to 84.4 mL; p=0.02) and decreased end-exercise f[c] by 17% (19: -29 to 9 b�min⁻�; p=0.08). Cardiovascular adaptations except PV persisted for one wk, but not two wks after Acc indicating that cardiovascular-related benefits from STHA may not be mediated by hypervolaemic responses per se. The highly trained athletes had functional heat adaptations of similar magnitude to lesser fitness-adapted participants across DEH acclimation, including resting PV expansion (4.5: 0.7 to 8.3%) and increased performance (-4.0: -6.3 to 0.6[s]; p=0.02). Plasma total protein-corrected HSP70 concentration increased from rest to end-exercise across acclimation (p=0.001). There was a greater change from rest to end-exercise on day one versus day five Acc (p=0.05), indicating a reduced stress-induced increase and a protective adaptive change. There were weak to moderate relationships between hydration indices in dynamic circumstances indicating that there is no single measure to accurately assess hydration status. In conclusion, short-term (5-day) heat acclimation was effective with adaptations more pronounced after fluid regulatory strain from a dehydration acclimation regime. Similar findings were found using highly trained and lesser- fitness adapted participants. Thermotolerance was increased by dehydration acclimation.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (leaves 107-118). Also available via the World Wide Web.

Thesis (M.S.P.H.)--University of Michigan, 1939.

Thesis (M.S.P.H.)--University of Michigan, 1939.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 58-66). Also available via the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 113-118).

Abstract Winter energy management in small passerines living year-round in boreal or alpine areas presumably results in strong selective pressure since they need to find food, at a time when natural resources diminish and become less available, and energy requirements increase dramatically. In this thesis energy management during the non-breeding season was studied in three species of tits (Parus spp.), from three different populations: Coll de Pal (Spanish Pyrenees), Lund (Southern Sweden) and Oulu (Northern Finland). Energy management strategies vary significantly between species and among populations and individuals of the same species. Such differences may depend on several environmental factors, food predictability and individual characteristics. Birds from the studied populations appear to react to energetic challenges on a short-term basis and in a highly flexible way. The coal tit (Parus ater) in Coll de Pal and the willow tit (Parus montanus) in Oulu, both hoarding species, relied mostly on short-term management of energy for winter survival. Social and residence status appeared to be the most important factors in determining the level of energy reserves, underlining the importance of food predictability for energy management in wintering tits. Further studies were carried out on two distinct populations of great tit (Parus major) exposed to different winter hardiness. Birds from both populations increased their resting metabolic rate (MR) with experimentally decreasing ambient temperatures. Birds from Oulu maintained higher expenditures than birds from Lund in all cases, but also experienced higher energetic cost of thermoregulation at the lowest temperatures. The differences probably did not arise from a differential insulation capacity between populations, despite the differences in plumage structure found, but from a differential metabolic acclimatization. Birds from Lund probably became hypothermic at the lowest temperatures, which may have exceeded the levels they were acclimatized for. The observed differences in basal MR in laboratory conditions were consistent in wild birds throughout the non-breeding season. Birds from both populations experienced similar patterns of variation in basal MR, with expenditures increasing with mass but decreasing with day length, size and age. Great tits modulate their energy expenditure in a flexible way as a means for surviving the non-breeding season. Further, despite such flexibility, populations appear to be locally adapted for such metabolic acclimatization. These results may have important implications on their life-history and distribution. Winter acclimatization appears to be a complex set of entangled strategies that are based on a metabolic adjustment to cope with changing energy requirements. Other mechanisms that apparently play a secondary role, for example the long term management of reserves through fattening or hoarding, or conserving heat through hypothermia and by developing a better insulative plumage, are certainly important emergency strategies that in natural conditions may explain how some populations can endure winter conditions.

Thesis (M. Sc. (Microbiology)) --University of Limpopo, 2017 / The recent oil crisis and environmental concerns over fossil fuels has led to the development of biofuels from lignocellulosic materials. Two main sugars from lignocellulose that can be used for bioethanol production are glucose and xylose. Xylose is problematic, because there are few yeasts that can utilise and ferment it. Xylose fermentation is not as efficient compared to glucose fermentation. Some of the factors that affect xylose fermentation include rate of xylose consumption, aeration, temperature and inhibitors. To improve ethanol production and fermentations and to make the process economically viable at industrial scale, there is a need to find a robust microorganism that can ferment efficiently in harsh industrial conditions. Therefore, the aim of this study was to investigate by means of evolutionary engineering (adaptation), the adaptability of seven locally isolated yeasts in terms of growth on high xylose concentration, in the presence of acetic acid as well as at elevated temperatures. Seven yeast strains (Candida guilliermondii MBI2, Candida sp. Kp6.2ey, Candida tropicalis Kp21ey, Candida tropicalis Kp42ey, Candida tropicalis Kp43ey, Ogatea methanolica Kp2ey and Pichia kudriavzevii Kp34ey) were adapted to ferment 60 g/L xylose as sole carbon source in the presence of 3 g/L acetic acid at 37°C. P. kudriavzevii Kp34ey was the only yeast to adapt to these conditions. The adapted P. kudriavzevii Kp34ey was compared with the parental strain (unadapted) and a reference strain, Scheffersomyces stipitis NRRLY-7124, using different volumetric oxygen transfer coefficient (KLa) rates. P. kudriavzevii Kp34ey (adapted and parental strain) and S. stipitis NRRLY-7124 produced the highest ethanol concentrations at a KLa value of 3.3. Overall, for all KLa values tested, the adapted strain performed better than the parental strain and S. stipitis NRRLY-7124. The adapted P. kudriavzevii Kp34ey yielded 4.03 g/L ethanol on 60 g/L xylose with 3 g/l acetic acid at 37°C at a KLa value of 3.3 and was the only yeast tested to grow under these conditions.