Effect of Deutectomy, Fasting and Environmental Temperature on Free Fatty Acid Concentration in the Blood Plasma of Chickens in the First Week after Hatching

Effects of food intake, fasting, environmental temperature and deutectomy on plasma free fatty acids (FFA) were investigated in 210 sexed Shaver Starcross cockerels in the first week after hatching. At the end of hatching the FFA concentration in plasma of chickens was 1.0 ± 0.2 mmoh l-". During the 2-hour long transport it increased. On the other hand, upon I-hour long exposure to 18°C a decrease was noted in plasma FFA concentration in chicks exposed to cold both before and after transport as against the values found at 35°C. The intact fed birds aged 2,3 and 4 days showed no changes, whereas a substantial increase in plasma FFA to values exceeding those of the first day were found in birds aged 5 days. Chickens deprived of food and held at 35°C and those exposed to 18 "C showed higher plasma FFA concentrations than fed birds. It is suggested that fasting results in mobilization of lipid stores shortly after hatching whereas upon exposure to cold thermoregulation mechanisms operative in adults seem not to operate till the end of the first week after hatching

Chemical shift extremum of ¹²⁹Xe(aq) reveals details of hydrophobic solvation

Abstract The ¹²⁹Xe chemical shift in an aqueous solution exhibits a non-monotonic temperature dependence, featuring a maximum at 311 K. This is in contrast to most liquids, where the monotonic decrease of the shift follows that of liquid density. In particular, the shift maximum in water occurs at a higher temperature than that of the maximum density. We replicate this behaviour qualitatively via a molecular dynamics simulation and computing the ¹²⁹Xe chemical shift for snapshots of the simulation trajectory. We also construct a semianalytical model, in which the Xe atom occupies a cavity constituted by a spherical water shell, consisting of an even distribution of solvent molecules. The temperature dependence of the shift is seen to result from a product of the decreasing local water density and an increasing term corresponding to the energetics of the Xe-H₂O collisions. The latter moves the chemical shift maximum up in temperature, as compared to the density maximum. In water, the computed temperature of the shift maximum is found to be sensitive to both the details of the binary chemical shift function and the coordination number. This work suggests that, material parameters allowing, the maximum should be exhibited by other liquids, too