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Thesis (M.P.H.)--University of Western Australia, 2006.

Thesis (M.F.A.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references (leaf 44).

Plasma catecholamines have been measured in chronically adrenalectomised (ADX) ducks, in chronically adrenal denervated ducks (DNX), in their respective sham-operated controls (SH-adx, SH-dnx) as well as in intact ducks after 3 minutes forced submergence. The results showed that 100% of the plasma Epinephrine (EP) and 40 to 80% of plasma Norepinephrine (NE) released during the dive came from the adrenal glands. 20 to 60% of plasma NE came from endings of the autonomic vascular sympathetic nerves which are strongly stimulated during diving. Adrenal catecholamines were released by nerve activation only; non neural mechanisms did not play any role in their release. Maximum dive times (MDT) in chronically adrenalectomised ducks (ADX: 5 min. 19 ± 20 sec.) and in chronically adrenal denervated ducks (DNX: 7 min. 10 ± 13 sec.) were significantly lower than in sham-operated controls (respectively SH-adx: 9 min. 58 ± 45 sec., SH-dnx: 12 min. 10 ± 28 sec). Venous infusion of catecholamines in ADX and DNX during the dive increased MDT: MDT of DNX ducks perfused with catecholamines (9 min. 46 ± 20 sec.) were significantly higher than in DNX perfused with saline (7 min. 21 ± 17 sec.), but did not reach the MDT observed in the SH-dnx: other adrenal products must be involved. Diving heart rates of ADX and DNX (at 4 min. dive respectively: 62 ± 16 and 31 ± 2 beats/min.) were significantly higher than in their sham-operated controls (23 ± 3 and 17 ± 2 beats/min.) . Blood pressure during the dive was signifi- cantly lower in ADX and DNX (at 4 min. dive respectively: 93 ± 8 and 98 ± 4 mmHg) compared with their sham-operated controls (131 ± 12 and 118 ± 6 mmHg). Infusion of catecholamines in DNX raised blood pressure towards SH-dnx values, but there was no change in heart rate. PaO₂, CaO₂, pHa and lactate levels in DNX (respectively: 42 ± 2 mmHg, 4.5 ± 0.8 ml 02 /100ml blood, 7.233 ± 0.016, 3.1 + 0.3 mM) were significantly lower than in SH-dnx after 5 minutes submergence (53 ± 1 mmHg, 6.8 ± 0.4 ml 02 /100 ml blood, 7.301 ± 0.007, 4.8 + 0.4 mM). There was also a significant increase of plasma N⁺ (+ 5.4 ± 1.7 mEq/L) in SH-dnx after 5 minutes submergence, but this was not the case in DNX where it was K⁺ (+ 1.1 ± 0.4 mEq/L) which increased. This suggested that adrenal catecholamines increase tolerance to underwater submersion by enhancing peripheral vasoconstriction, thus preserving the O₂ stores for the heart and brain. Moreover, they may affect the acid-base equilibrium during diving by increasing the activity of the Na⁺K⁺ pump and may also have a direct effect on the rate of glycogenolysis. Preventing the actions of catecholamines on the heart by injecting beta-blocker during forced submersion did not decrease MDT; however the cardiovascular response was markedly affected. During beta-blockade, diving heart rate rose steadily from 24 ± 6 beats/minute after 2 minutes to 52 ± 8 beats/minute after 6 minutes diving. In contrast, heart rates remained close to the levels reached at 2 minutes (17 ± 3 and 19 ± 4 beats/minute) throughout the control dives. Perfusion pressure and blood flow have been recorded simultaneously in both hind limbs of ducks. One leg was perfused with different blood mixtures devoid of catecholamines (Test leg) and compared with the other, perfused with the ducks'own blood (autoperfused leg). This showed that hyper-capnia has a depressant effect on the neural component of the peripheral vasoconstriction. Perfusion of test legs with hypoxic-hypercapnic blood to which catecholamines were added, showed that circulating catecholamines are needed to increase peripheral vasoconstriction during diving. In summary, during forced submergence circulating catecholamines, released mainly by the adrenal glands, compensate for the depressant action of hypercapnia on the neural component of peripheral vasoconstriction. Maintenance of this peripheral vasoconstriction during forced diving ensures that O₂ stores are not wasted on peripheral tissues, and this explains how MDT is prolonged. / Science, Faculty of / Zoology, Department of / Graduate

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1 v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (M.D.)--University of Adelaide, Dept. of Human Physiology and Pharmacology, 1972

Scuba diver impacts on coral reefs are causing many threats to reefs. One solution is to change divers’ behaviors through on-site environmental education. The Flower Garden Banks National Marine Sanctuary developed an education program in an effort to achieve this goal. The purpose of this study was to describe the education program, understand how it affected divers’ knowledge of and value orientation toward coral reefs, and examine two teaching approaches conducted in a recreation/tourism setting. Two theories were tested in this study. Orams’ model was used to develop the “Naturalist Onboard” program and describe how the model played out in a diver education situation. The work Bransford’s team did was tested to see how their teaching approach works in a recreation/tourism setting. Evaluating this program was achieved through pre- and post-questionnaires, participant observation and semi-structured interviews. They were used in the first article to provide a description of how Orams’ model played out in the real world. In the second article they were used to determine: 1) the value orientation of the divers, 2) how much knowledge divers gained via participation in this program, 3) the relationship between value orientation and knowledge gained, and 4) the degree their value orientations affect knowledge acquisition. In the final article they were used to see how two teaching approaches affected divers’ knowledge and value orientations about coral reefs, and how the divers responded to the two approaches. The program aroused divers’ curiosity, engaged their emotions, and motivated them to minimize their impacts while visiting the coral reef. However, suggestions for making changes in their behavior at home were not received well. Most divers had a “biocentric” value orientation and gained a significant amount of knowledge. These divers were also more open to learning and changing their behaviors. There was no significant difference between the two approaches regarding the divers’ knowledge and value orientation. This may be due to validity threats. Due to time constraints and divers’ lack of interest in actively acquiring knowledge, the constructivist teaching approach did not work well in this setting.

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This purpose of this investigation was to develop a methods for the determination of trace level VOCs present in offshore hyperbaric diving environments using Thermal Desorption Gas Chromatography-Mass Spectrometry. As the hyperbaric chambers would usually be onboard a ship, the sampling and transportation of samples would be in cylinders rather than canisters or sorbent tubes.  The sensitivity of the method had to be greater than methods for normobaric occupational exposure, as a chamber pressure was typically ten times normal atmospheric pressure and the divers were continuously exposed to all the VOCs present in the atmosphere. To reduce background contamination, cleaning procedures were put in place for both Tenax tubes and sampling cylinders.  The performance of the Tenax tubes, the recovery from cylinders and GC-MS were investigated systematically using standards, CRM and environmental samples. This ensured that results determined were both qualitative and quantitative. The cylinder sampling experiments had shown that electropolished cylinders were quantitative for all types of trace VOC gas mixtures, while the Teflon lined and sand-blasted cyclinders showed reasonable recoveries for humid samples, like those of hyperbaric but low recoveries for dry gas mixtures. The VOC concentrations present in hyperbaric atmospheres were typically ten times those found in normobaric work environments, in the range of 50 - 300 <span style='font-family:Symbol'>mg/m³ for living chambers. Many compounds had been detected, including benzene, toluene, substituted aromatics, alkanes, chloroform, trichloroethylene and even compounds like pinene or limonene.  In general all locations showed levels well below their HOELs or OELs. The method was also adapted to determine VOCs present in atmospheres by Tenax tube diffusive sampling. These experiments showed clearly that the method could be used for detection of VOCs in occupational environments and also urban air environments if required.