Maskulinisasi Ikan Nila Melalui Perendaman Larva pada Suhu 36 °c dan Kadar Residu 17a-metiltestosteron dalam Tubuh Ikan

The residue of 17a-methyltestosterone (MT) in fish has been a concern related to food and the environment safety. This study aimed to determine sex ratio of Nile tilapia treated by MT immersion at 36 °C water temperature, and measure the level of testosterone in fish body. Three hundreds of ten-day-old post hatched larvae was immersed in one liter of water containing 2 mg MT, at 26 °C and 36 °C. Immersion was performed for 2 and 4 hours. The results showed that immersion at 36 °C and increasing immersion time increased male percentage. Higher male percentage was obtained in treatment 4 hours immersion at 36 °C (92.5% male) and the effective treatmen 4 hours immersion at room temperature. By ELISA method, testosterone level in MT treated fish decreased sharply to 88.2% at one month after immersion, and being the same as control without MT immersion. Thus, masculization in tilapia could be performed by MT immersion at 36 °C water temperature for 4 hours, and it is most likely that no MT residual in fish after one month post immersion. Keywords: Nile tilapia, sex reversal, temperature, 17a-methyltestosterone

Effect of Genetic Obesity on Thermoregulatory Activity Responses to Inversion of the Light/Dark Cycle

In this pilot work, the authors compared the circadian rhythm responses of 3-month-old female fatty Zucker rats with those of lean Zucker rats and Sprague-Dawley rats to reversal of the light/dark (LD) cycle. Core temperature and spontaneous cage activity were continuously monitored by implanted microtelemetry devices prior to and for 5 days following complete LD cycle reversal. By the 5th day after LD reversal, temperature rhythm nadir had phase-advanced 10.5 hours in the lean Zucker rats, 10.8 hours in the Sprague-Dawley rats, and only 3.8 hours in the fatty Zucker rats. Similarly, total activity increased in lean Zucker rats and Sprague-Dawley rats after LD reversal but declined in the fatty Zucker rat during the same time. Results of this study show that obese Zucker rats displayed an impaired ability to reentrain circadian rhythms for temperature and activity when compared to lean Zucker rats and Sprague-Dawley rats. These findings suggest that dysfunction in the circadian pacemaker previously shown to manifest itself by 43 weeks of age in fatty Zucker rats may already be present at 3 months of age and suggest that altered thermoregulation may play a role in the development of obesity in this animal model of genetic obesity.

Electromigration in metals

In bulk and thin film metal samples, a net migration of material may take place when electrical current is passed through the sample at an elevated temperature. The migration is due to the passage of electron (or hole) current, the electrostatic force on the metal ions, and the temperature gradient in the sample. The extent and the direction of net migration has not been predicted satisfactorily by existing theories, leaving many unexplained anomalous experimental results. The present work is the development of a generalized theory that contains the main features of previous theories. It can explain all major experimental observations. Its main features include predictions on the temperature and time dependence of migration, its direction, its reversal temperature, and the approximate sample position that is affected most. The theory has been used to interpret available experimental data on a number of electron- and hole-type metals.