The role of leptin in striped hamsters subjected to food restriction and refeeding

Food restriction(FR) and refeeding(Re) have been suggested to impair body mass regulation and thereby making it easier to regain the lost weight and develop over-weight when FR ends. However, it is unclear if this is the case in small mammals showing seasonal forging behaviors. In the present study, energy budget, body fat and serum leptin level were measured in striped hamsters that were exposed to FR-Re. The effects of leptin on food intake, body fat and genes expressions of several hypothalamus neuropeptides were determined. Body mass, fat content and serum leptin level decreased during FR and then increased during Re. Leptin supplement significantly attenuated the increase in food intake during Re, decreased genes expressions of neuropepetide Y(NPY) and agouti-related protein(AgRP) of hypothalamus and leptin of white adipose tissue(WAT). Hormone-sensitive lipase(HSL) gene expression of WAT increased in leptin-treated hamsters that were fed ad libitum, but decreased in FR-Re hamsters. This indicates that the adaptive regulation of WAT HSL gene expression may be involved in the mobilization of fat storage during Re, which partly contributes to the resistance to FR-Re-induced overweight. Leptin may be involved in the down regulations of hypothalamus orexigenic peptides gene expression and consequently plays a crucial role in controlling food intake when FR ends.

Light-controlled pulsed x-ray tube with photocathode

Unstable mechanical structure,low energy efficiency,and cooling requirements limit the application of conventional x-ray tubes based on filament as cathode in several academic areas.In this paper,we demonstrate a light-controlled pulsed x-ray tube using multialkali cathode as electron generator.The photocathode active area of the light controlled x-ray tube is 13.2 cm^(2)(41 mm in diameter),which provides high photoelectron-emitting efficiency up to 0.288 mA/lm in 460-nm LED and 2.37-mA maximum tube current.Furthermore,the modulation ability from 1 kHz to 100 kHz of the x-ray tube is tested.The results suggest that the light-controlled pulsed x-ray tube has easy modulation and short x-ray pulse properties and is promising to be the next generation x-ray tube with wide applications in medical radiation therapy as well as the calibration for detectors and scintillators.