LIPIDAT: a database of lipid phase transition temperatures and enthalpy changes. DMPC data subset analysis.

The systematic study of the mesomorphic phase properties of synthetic and biologically derived lipids began some 30 years ago. In the past decade, interest in this area has grown enormously. As a result, there exists a wealth of information on lipid phase behavior, but unfortunately these data have until now been scattered throughout the literature in a variety of books, proceedings and journals. The data have recently been compiled in a centralized database, LIPIDAT, with a view to providing ready access to the data and to the appropriate literature. LIPIDAT consists of a tabulation of all known mesomorphic and polymorphic phase transition temperatures and enthalpy changes for synthetic and biologically-derived lipids in the dry and in the partially and fully hydrated states. Also included is the effect of pH, and of salt and metal ion concentration and other additives such as proteins, drugs, etc., on the thermodynamic values. The methods used in making the measurements and the experimental conditions are reported. Bibliographic information includes comprehensive literature referencing and list of authors, but does not at the present time include article titles. As of this writing, the database is current through June, 1990 and is approaching 10,000 records in length. Each record contains 28 fields. In this paper we report the contents and present an analysis of LIPIDAT as it refers to fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). This database subset represents about 7% of all LIPIDAT records. It includes data collected over a 23-year period from 1967 to 1989 and consists of 702 records obtained from 336 articles in 55 different journals. The number of records per year rises steadily beginning in 1971, reaches a maximum of 89 records/year in 1977 and remains relatively constant at 60-70 records/year in the succeeding period. Journals making the greatest contribution to the DMPC subset include Biochimica et Biophysica Acta, Biochemistry, Chemistry and Physics of Lipids and the Biophysical Journal. These four journals account for 71% of the total records in the database subset. The analysis shows that differential scanning calorimetry, electron spin resonance, fluorescence, nuclear magnetic resonance and Raman spectroscopy are the methods most commonly used for DMPC transition temperature determination. An interesting pattern emerges as to the place in time the different methods assume or loose popularity.(ABSTRACT TRUNCATED AT 400 WORDS)     

Prevalence and intensity of Thelazia spp. (Nematoda: Thelazioidea) in a Musca autumnalis (Diptera: Muscidae) population from Central Alberta

A face fly (Musca autumnalis) population near Wetaskiwin, central Alberta, Canada, was sampled 9 times from 26 July to 29 September 1988 for the early larval stages of Thelazia spp. Of 426 female flies examined, 159 (37%) contained Thelazia spp. (almost exclusively T. skrjabini), with an average worm burden of 4.2 larvae per infected fly. Prevalence ranged from 17 to 56% over 9 collections. This is the first report of Thelazia skrjabini in flies from western North America and the highest Thelazia prevalence in face flies yet reported in North America. The face fly population was also parasitized by Heterotylenchus autumnalis, with a prevalence of 5.5%.     

T Cell Factor-1 Controls the Lifetime of CD4+ CD8+ Thymocytes In Vivo and Distal T Cell Receptor α-Chain Rearrangement Required for NKT Cell Development

Natural killer T (NKT) cells are a component of innate and adaptive immune systems implicated in immune, autoimmune responses and in the control of obesity and cancer. NKT cells develop from common CD4+ CD8+ double positive (DP) thymocyte precursors after the rearrangement and expression of T cell receptor (TCR) Vα14-Jα18 gene. Temporal regulation and late appearance of Vα14-Jα18 rearrangement in immature DP thymocytes has been demonstrated. However, the precise control of lifetime of DP thymocytes in vivo that enables distal rearrangements remains incompletely defined. Here we demonstrate that T cell factor (TCF)-1, encoded by the Tcf7 gene, is critical for the extended lifetime of DP thymocytes. TCF-1-deficient DP thymocytes fail to undergo TCR Vα14-Jα18 rearrangement and produce significantly fewer NKT cells. Ectopic expression of Bcl-x_L permits Vα14-Jα18 rearrangement and rescues NKT cell development. We report that TCF-1 regulates expression of RORγt, which regulates DP thymocyte survival by controlling expression of Bcl-x_L. We posit that TCF-1 along with its cofactors controls the lifetime of DP thymocytes in vivo.