Thesis (M.S.)--Ohio University, June, 2004. / Includes bibliographical references (p. 73-84).

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (p. 73-84)

No description available.

The area most widely associated with osmoreception has been the lateral preoptic nucleus. However, Hatton (1976) proposed that the nucleus circularis could be the actual osmoreceptor in the hypothalamus. The present study supported Hatton by using 30 rats which were randomly assigned to sham, lateral preoptic, and nucleus circularis lesion groups. After a 2-week post-operative period, half of each group was injected with isotonic saline while the other half was injected with hypertonic saline. Water consumption was measured at 10-minute intervals for one hour. Following a 4-day recovery period, the injection procedure was reversed. Analysis of difference scores, computed by subtracting the amount of water consumed after isotonic injection from the amount of water consumed after hypertonic injection, revealed a significant difference between the nucleus circularis group and the other two groups.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 98-109).

Thesis (M.S.)--Ohio University, November, 2004. / Includes bibliographical references (p. 83-90)

Thesis (M.S.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 83-90)

Eight endurance~trained cyclists rode as far as possible in 1 h on a stationary cyclesimulator in a moderate environment (20°C, 60% relative humidity, 3 m/s wind speed) while randomly receiving either no fluid (NF) or attempting to replace their ~1.7 l sweat loss measured in a previous 1 h familiarisation performance ride at ~85% of peak oxygen uptake (VO₂ peak) with artificially sweetened, coloured water (F). During F the cyclists drank 1.49 ± 0.14 1 (values are mean± SEM), of which 0.27 ± 0.08 1 remained in the stomach at the end of exercise and 0.20 ± 0.05 1 was urinated after the trial. Thus, only 1.02 ± 0.12 l of the ingested fluid was available to replace sweat losses during the 1 h performance ride. That fluid decreased the average heart rate from 166 ± 3 to 157 ± 5 beats/min (P < 0.0001) and reduced the final serum [Na+] and osmolalities from 143 ± 0.6 to 139 ± 0.6 mEq/1 (P < 0.005) and from 294 ± 1.7 to 290 ± 1.9 mOsm/1 (P = 0.05), respectively. Fluid ingestion did not attenuate rises in plasma anti diuretic hormone and angiotensin concentrations, or decrease the ~-15% falls in estimated plasma volume in the F and NF trials. Nor did fluid ingestion significantly effect the ~1.7 l/h sweat rates, the rises in rectal temperature (~36.6° to 38.3°C) or the ratings of perceived exertion in the two trials. Ingestion of ~1.5 l of fluid produced an uncomfortable stomach fullness and reduced the distance covered in 1 h from 43.1 ± 0. 7 to 42.3 ± 0.6 km (P<0.05). Thus, trying to replace > 1.0 l/h sweat losses during high-intensity, short duration exercise in a moderate environment does not induce beneficial physiological effects, and may impair exercise performance.

Thesis (D.P.H.)--University of Michigan.

Thesis (D.P.H.)--University of Michigan.