Leucine reduces the duration of insulin-induced PI 3-kinase activity in rat skeletal muscle

Leucine (Leu) is known to stimulate translation initiation of protein synthesis at mammalian target of rapamycin (mTOR) in the insulin signaling pathway. However, potential feedback from mTOR to upstream aspects of the insulin signaling pathway remains controversial. This study evaluates the impact of a physiological oral dose of Leu and/or carbohydrate (CHO) on upstream elements of the insulin signaling pathway using phosphatidylinositol 3-kinase (PI 3-kinase) activity and glucose uptake as markers for insulin sensitivity and glucose homeostasis. Rats (approximately 200 g) were fasted 12 h and administered oral doses of CHO (1.31 g glucose, 1.31 g sucrose), Leu (270 mg), or CHO plus Leu. Animals were killed at 15, 30, 60, and 90 min after treatment. Plasma and gastrocnemius muscles were collected for analyses. Treatments were designed to produce elevated blood glucose and insulin with basal levels of Leu (CHO); elevated Leu with basal levels of glucose and insulin (Leu); or a combined increase of glucose, insulin, and Leu (CHO + Leu). The CHO treatment stimulated PI 3-kinase activity and glucose uptake with no effect on the downstream translation initiation factor eIF4E. Leu alone stimulated the release of the translation initiation factor eIF4E from 4E-BP1 with no effects on PI 3-kinase activity or glucose uptake. The CHO + Leu treatment reduced the magnitude and duration of the PI 3-kinase response but maintained glucose uptake similar to the CHO treatment and eIF4E levels similar to the Leu treatment. These findings demonstrate that Leu reduces insulin-stimulated PI 3-kinase activity while increasing downstream translation initiation and with no effect on net glucose transport in skeletal muscle.     

Genome informatics: taming the avalanche of genomic data

A report on the fourth Cold Spring Harbor Laboratory/Wellcome Trust Conference on Genome Informatics, Hinxton, UK, 22-26 September 2004.     

Survey for hemoparasites in imperial eagles (Aquila heliaca), steppe eagles (Aquila nipalensis), and white-tailed sea eagles (Haliaeetus albicilla) from Kazakhstan

Prevalence of hemoparasites has been investigated in many avian species throughout Europe and North America. Basic hematologic surveys are the first step toward evaluating whether host-parasite prevalences observed in North America and Europe occur elsewhere in the world. We collected blood smears from 94 nestling imperial eagles (Aquila heliaca), five nestling steppe eagles (Aquila nipalensis), and 14 nestling white-tailed sea eagles (Haliaeetus albicilla) at Naurzum Zapovednik (Naurzum National Nature Reserve) in Kazakhstan during the summers of 1999 and 2000. In 1999, six of 29 imperial eagles were infected with Lencocytozoon toddi. Five of 65 imperial eagles and one of 14 white-tailed sea eagle were infected with L. toddi in 2000. Furthermore, in 2000, one of 65 imperial eagles was infected with Haemoproteus sp. We found no parasites in steppe eagles in either year, and no bird had multiple-species infections. These data are important because few hematologic studies of these eagle species have been conducted.     

Effect of cell physiological state on infection by rat virus

Infection by rat virus has been studied in cultures of rat embryo cells to evaluate the Margolis-Kilham hypothesis that the virus preferentially infects tissues with actively dividing cells. An enhancement of infection was seen in cultures infected 10 hr after fresh medium was added as compared to infection of stationary cultures (infected before addition of fresh medium). Since addition of fresh medium stimulates deoxyribonucleic acid (DNA) synthesis, the number of cells per culture synthesizing DNA at the time of infection was compared with the proportion of cells which synthesized viral protein. Cells were infected before the medium change and 10 or 24 hr after the medium change and were pulse-labeled with ³H-thymidine at the time virus was added. The cells were allowed to initiate viral protein synthesis before they were fixed and stained with fluorescein-conjugated anti-rat virus serum. Fluorescence microscopy permitted both labels to be counted simultaneouly and showed that the greatest proportion of cells synthesizing viral protein were those which had incorporated ³H-thymidine at the time of infection.