Co-expression of the proto-oncogene fos (c-fos) and an embryonic interferon (ovine trophoblastin) by sheep conceptuses during implantation.

Expression of the c-fos proto-oncogene by ovine conceptuses was analyzed by Northern and slot blots and indirect immunohistofluorescence in relation to the expression of the embryonic interferon-alpha (oTP) during implantation. c-fos was expressed initially in the trophoblast, and then in the allantois, when this tissue began to develop (day 17). In the embryonic tissues, the c-fos proto-oncogene was weakly expressed up to day 22 and increased thereafter. In the trophoblast, the expression of c-fos proto-oncogene was transient, occurring when the oTP gene was transcribed at a maximal level at the beginning of implantation (days 14-15), and decreased thereafter, following the pattern of oTP gene expression. This decline is due essentially to the arrest of c-fos and oTP gene expression by the trophoblastic cells which established cellular contacts with the uterine epithelium during the implantation process.     

Characterization of a frequent polymorphism in the coding sequence of the Tp53 gene in colonic cancer patients and a control population

Summary We describe a simple method for characterizing a frequent polymorphism (that subsitutes an arginine for a proline) in the coding sequence of the Tp53 gene in patients with colonic cancer and in a control population. We could find no evidence that this polymorphism is associated with a marked predisposition to colorectal cancer.     

Binding of spin-labeled clofibrate to lipoproteins

The binding of spin-labeled clofibrate to native and partially delipidated lipoproteins is a rapid, linear and non-saturable process observed up to the critical micellar concentration of the drug. Low-density lipoproteins (LDL) display a lower affinity for the drug than very-low-density lipoproteins (VLDL) and high-density lipoproteins (HDL) relative to their respective specific volume. Unlike various lipophilic drugs, uptake of spin-labeled clofibrate does not correlate with lipoprotein lipid volume. Spin-labeled clofibrate binding to LDL is enhanced when the temperature increases above 25 degrees C. The binding to HDL and VLDL is less temperature-sensitive. The simulation of the ESR spectra has shown that two types of motion should be superimposed for the spin-labeled clofibrate in HDL, in LDL or in partially delipidated LDL. From 40 down to 25 degrees C for HDL and LDL, a fast anisotropic motion is observed. From 25 degrees C down to 5 degrees C, a two-component motion takes place, including a slow isotropic motion of the probe tumbling in a highly hydrophobic environment. Interactions of spin-labeled clofibrate with the apolipoproteins in HDL and LDL are assumed from the emergence of this strongly immobilized component observed when the temperature decreases. In contrast, for spin-labeled clofibrate inserted in the apolar core of VLDL, ESR shows only one component in the whole temperature range (5-40 degrees C). The location of the spin-labeled drug inside the various lipoprotein particles is discussed as a function of temperature.     

Low-spin sulfite reductases: a new homologous group of non-heme iron-siroheme proteins in anaerobic bacteria

Two new low molecular weight proteins with sulfite reductase activity, isolated from Methanosarcina barkeri (DSM 800) and Desulfuromonas acetoxidans (strain 5071), were studied by EPR and optical spectroscopic techniques. Both proteins have visible spectra similar to that of the low-spin sulfite reductase of Desulfovibrio vulgaris strain Hildenborough and no band at 715 nm, characteristic of high-spin Fe3+ complexes in isobacteriochlorins is observed. EPR shows that as isolated the siroheme is in a low-spin ferric state (S = 1/2) with g-values at 2.40, 2.30 and 1.88 for the Methanosarcina barkeri enzyme and g-values at 2.44, 2.33 and 1.81 for the Desulfuromonas acetoxidans enzyme. Chemical analysis shows that both proteins contain one siroheme and one [Fe4S4] center per polypeptidic chain. These results suggest that the low molecular weight, low-spin non-heme iron siroheme proteins represent a new homologous class of sulfite reductases common to anaerobic microorganisms.