We have purified the yeast U5 and U6 pre-mRNA splicing small nuclear ribonucleoproteins (snRNPs) by affinity chromatography and analyzed the associated polypeptides by mass spectrometry. The yeast U5 snRNP is composed of the two variants of U5 snRNA, six U5-specific proteins and the 7 proteins of the canonical Sm core. The U6 snRNP is composed of the U6 snRNA, Prp24, and the 7 Sm-Like (LSM) proteins. Surprisingly, the yeast DEAD-box helicase-like protein Prp28 is stably associated with the U5 snRNP, yet is absent from the purified U4/U6[bull ]U5 snRNP. A novel yeast U5 and four novel yeast U4/U6[bull ]U5 snRNP polypeptides were characterized by genetic and biochemical means to demonstrate their involvement in the pre-mRNA splicing reaction. We also show that, unlike the human tri-snRNP, the yeast tri-snRNP dissociated upon addition of ATP or dATP.

Habitat selection by translocated black howler monkeys (Alouatta pigra) was studied in Belize, Central America. Ranging patterns of two recently translocated groups were contrasted with those of two groups in the same area with established home ranges, on a yearly and monthly basis. All groups concentrated their activities along stream beds at elevations below 200 m. Newly translocated groups increased the percentage of their monthly ranges in riverine areas (within 100 m of a water source) over the year of the study (with the exception of the last month) while established groups did not. Areas used more than five times by the monkeys contained larger trees and a greater relative coverage of major food species than low-use areas even though they had a lower overall species richness and diversity. These monkeys may be selecting habitat within the forest based upon vegetative differences and ranging patterns may be affected by patterns of food availability.

Nine 5-month-old lambs were randomly allocated to two groups and were fed on either a Co-deficient whole-barley diet (n 5), or the same diet supplemented with Co (n 4). The lambs were fed on their respective diets for 28 weeks. Plasma vitamin B12 concentrations fell below the lower limit of normality after 6 weeks, and plasma methylmalonic acid (MMA) concentrations rose above the upper limit of normality after 10 weeks. However, plasma MMA concentrations fell to near normal levels towards the end of the experiment suggesting that diagnosis of more severe Co deficiency based on determination of plasma MMA concentrations may be of limited value. Analysis of tissue samples collected at slaughter revealed a marked reduction in the vitamin B12 concentration and the activity of methylmalonyl-CoA mutase (EC 5.4.99.2) in the tissues taken from the Co-deficient sheep, by comparison with the controls. Although tissue concentrations of MMA in the Co-deficient animals were not significantly different from those of the controls, we did detect increased concentrations of branched-chain fatty acids. This suggested that misincorporation of MMA, but not propionic acid, into fatty acids had occurred. The Co-deficient lambs did not develop any neurological signs, suggesting that accumulation of branched-chain fatty acids may not be involved in the development of neurological lesions.