Mutations in the CDP-choline pathway for phospholipid biosynthesis bypass the requirement for an essential phospholipid transfer protein.

SEC14p is the yeast phosphatidylinositol (PI)/phosphatidylcholine (PC) transfer protein, and it effects an essential stimulation of yeast Golgi secretory function. We now report that the SEC14p localizes to the yeast Golgi and that the SEC14p requirement can be specifically and efficiently bypassed by mutations in any one of at least six genes. One of these suppressor genes was the structural gene for yeast choline kinase (CKI), disruption of which rendered the cell independent of the normally essential SEC14p requirement. The antagonistic action of the CKI gene product on SEC14p function revealed a previously unsuspected influence of biosynthetic activities of the CDP-choline pathway for PC biosynthesis on yeast Golgi function and indicated that SEC14p controls the phospholipid content of yeast Golgi membranes in vivo.

An essential role for a phospholipid transfer protein in yeast Golgi function.

Progression of proteins through the secretory pathway of eukaryotic cells involves a continuous rearrangement of macromolecular structures made up of proteins and phospholipids. The protein SEC14p is essential for transport of proteins from the yeast Golgi complex. Independent characterization of the SEC14 gene and the PIT1 gene, which encodes a phosphatidylinositol/phosphatidylcholine transfer protein in yeast, indicated that these two genes are identical. Phospholipid transfer proteins are a class of cytosolic proteins that are ubiquitous among eukaryotic cells and are distinguished by their ability to catalyse the exchange of phospholipids between membranes in vitro. We show here that the SEC14 and PIT1 genes are indeed identical and that the growth phenotype of a sec14-1ts mutant extends to the inability of its transfer protein to effect phospholipid transfer in vitro. These results therefore establish for the first time an in vivo function for a phospholipid transfer protein, namely a role in the compartment-specific stimulation of protein secretion.

Hydrogen peroxide levels in mouse oocytes and early cleavage stage embryos developed in vitro or in vivo.

We describe a fluorimetric method for measuring the level of H2O2 in individual mouse oocytes and early embryos. Levels of H2O2 are low but detectable in unfertilized oocytes recovered freshly from the female reproductive tract. The levels in early cleaving embryos (1-cell to 8-cell stages) immediately after recovery from the female tract seem to be slightly higher the later the stage examined. However, when embryos are cultured in vitro from the 1-cell or early 2-cell stage, H2O2 levels rise when the embryos reach the mid-2-cell stage and remain elevated until they enter the early 4-cell stage. No equivalent elevation of H2O2 is seen during the transition from 1-cell to 2-cell or from 4-cell to 8-cell stages. Embryos that are able to develop successfully in vitro, as well as those that show a developmental block at the 2-cell stage on culture in vitro, both show this rise in H2O2 levels after in vitro culture. The relationship between the rise in H2O2 and the '2-cell block' to development is discussed.

Psychological differences noted in aircrewmembers undergoing systematic desensitization and their subsequent functioning.

This study presents the results of a 3-year follow-up of patients treated for flight anxiety via relaxation/desensitization. Noted differences between successfully and unsuccessfully treated patients are discussed as well as the long-range effectiveness of relaxation/desensitization. Significant differences were noted on MMPI (Minnesota Multiphase Personality Inventory) scale elevations and major presenting symptoms. There was a significant relationship between specific MMPI profiles and failure to successfully treat flight anxiety. Individuals most likely to benefit from therapy were those subjects who exhibited normal MMPI profiles and manifested airsickness as their major presenting symptom.

The use of relaxation/densensitization in treating anxiety associated with flying.

This study describes the use of relaxation/densensitization therapy in treating anxiety associated with flying. Treated were 46 male and 1 female flight students who attended 3-6 sessions lasting 1 h each. This therapy uses a behavioral approach in treating anxiety associated with flying. Relaxation/densensitization incorporates the use of relaxation exercises and in-depth mental imagery. Six months after completion of therapy, all subjects were followed up to determine the therapy's effectiveness. There was a high success rate (79%) of subjects successfully completing training.