The inaccuracy in our estimates could also be due to the mixing models employed. We chose linear mixing models, but more complex models that incorporate the concentration of macronutrients in the various diets may yield different results (). However, both artificial diets contained 5% of the limiting nutrient (viz. protein), so adjusting for concentration dependence seems unlikely to improve our estimates. In contrast, isotopic routing might have a strong effect on our estimates. Isotopic routing refers to the fact that dietary amino acids tend to be sent directly to the consumer’s tissues as amino acids, instead of being broken down and then reassembled randomly by the consumer, as linear models assume (, ). Because, we fed grasshoppers a high-protein artificial diet and low-protein lettuce, it is possible that the amino acids in the artificial diets were preferentially allocated to the grasshoppers’ tissues for growth and egg production.
This study lays the groundwork for further experiments on nutrient allocation in long-lived ovariectomized grasshoppers. We have confirmed that we have diets that are functionally similar, and we can track ingested nutrients to multiple tissues and simultaneously measure anti-oxidant activities in those tissues. To our knowledge, this is the first report of concurrent nutrient tracking and quantification of cellular maintenance in a long-lived phenotype, and we have done it in multiple tissues. Measuring nutrient allocation and cellular maintenance in old ovariectomized females will allow us to further test the physiological predictions of the disposable soma hypothesis beyond the first clutch, the point in the lifecycle when mechanisms underlying extension of life span in ovariectomized females are likely to diverge from those of intact females.
Liver: nature’s most potent superfood - Chris Kresser
Stable isotopes are useful for long-term tracking of nutrients in individual animals because the isotopes do not decay, are nontoxic, and occur naturally in the environment (including in animals’ diets). This avoids many of the potential pitfalls of radioisotopes, which have historically been used to trace nutrients (; , ; ; ). Hence, we used stable isotopes to track the allocation of nutrients to reproduction and to multiple somatic tissues of animals after ovariectomy. Diets with distinct stable isotope signatures are typically offered in reciprocal switches in diet (e.g., one group is started on a low-13C diet and switched to a high-13C diet, whereas the second group is started on the high-13C diet and switched to the low-13C diet). This approach helps control for differences in composition between the diets, which may result in different rates of development between the two groups. A goal of this project was to develop two diets that have distinct signatures of stable isotopes yet allow similar rates of reproductive development, thereby minimizing problems due to different developmental rates on different diets. Such diets are ideal for studies of allocation of nutrients.
Antioxidants and Health Benefits: Free Radicals & …
L-selenomethionine is a highly bioavailable form of selenium, a nutrient essential for the functioning of glutathione peroxidase, one of the bodys main antioxidants. This is the form of selenium increasingly used in cancer treatment and studies and is believed to be protective against cancer. Since selenium content of fruits and vegetables is determined by the selenium content of the soil in which they are grown, its hard to know that you are getting enough selenium from what you eat. But if you eat Brazil nuts regularly, you probably get plenty of selenium.