Cervical tissue and plasma concentrations of alpha-carotene and beta-carotene in women are correlated.

Results from epidemiologic studies suggest that a carotenoid-rich diet may reduce risk for cervical cancer, possibly by inhibiting the progression of cervical intraepithelial neoplasia, a preneoplastic lesion of the cervical tissue. Laboratory studies suggest that the mechanism may be linked to the metabolism of carotenoids to retinoic acid or retinoic acid-like compounds, which has been hypothesized to occur in the cervical tissue. The purpose of this study was to demonstrate the presence of provitamin A carotenoids in biopsied samples of this peripheral tissue in human subjects and to examine the relationship between baseline concentrations of these carotenoids in plasma and normal cervical tissue in subjects who were being evaluated for possible participation in a diet intervention trial. Subjects were 13 women aged 19-41 y. With the use of HPLC methodology, plasma concentrations of alpha-carotene, beta-carotene and beta-cryptoxanthin were determined with UV/visible light detection for plasma and electrochemical detection for cervical tissue. Relationships between plasma and cervical tissue were evaluated with Pearson correlation analysis. Adjusted for plasma cholesterol concentration, plasma alpha-carotene and beta-carotene were correlated with cervical tissue concentrations (r = 0.91, P < 0.001; r = 0.90, P < 0.001; respectively). Adjusted for plasma cholesterol concentration, plasma beta-cryptoxanthin tended to be correlated with cervical tissue concentrations (r = 0.62, P = 0.058). These findings suggest that plasma concentrations of alpha-carotene and beta-carotene are good predictors of cervical tissue concentrations of these compounds in human subjects and describe a first step toward demonstrating a biological link between provitamin A carotenoids and cervical cancer in vivo.

Evidence for cell surface and internal phospholipase activity in ascidian eggs.

Upon fertilization, ascidian eggs release a cell surface glycosidase used in the block to polyspermy and undergo cortical contractions resulting from increased intracellular calcium levels. The glycosidase is released by fertilization, calcium ionophores or added phospholipase C (PLC) activity. The PLC inhibitor D609 blocks glycosidase release. Intact Ascidia ceratodes eggs cleave 4-methylumbelliferyl-phospho-choline when it is added to seawater. This yields highly fluorescent 4-methylumbelliferone. Authentic phospholipase C but not phospholipase D can cleave this substrate. Thus, the authors believe that cleavage of the substrate is specific for PLC activity. Eggs incubated in the fluorogenic substrate after having been washed and detergent extracted were not fluorescent. Therefore the substrate failed to enter intact cells. Glycosidase release and PLC activity were stimulated by ionomycin. Octylglucoside or Triton X-100 extracts of ascidian eggs had two forms of phospholipase activity as shown by ion affinity chromatography: PL1 eluting at 0.25 mol/L NaCl and PL2 eluting at 0.6 mol/L NaCl. The PL1 appeared to be isolated as a single protein. When surface proteins were labeled with non-penetrating biotin and were subsequently reacted with streptavidin, half of the PLC activity bound. This demonstrates that half the ascidian egg PLC activity is located on the surface of either the egg or follicle cell, and half is located within the egg.

The genomic structure of the rat corticotropin releasing factor receptor. A member of the class II G protein-coupled receptors.

Isolation and structural characterization of the rat corticotropin releasing factor receptor (CRFR) gene was performed to determine the exon/intron organization of the coding region and the potential for splice variants. The CRFR gene contains 13 exons and 12 introns, and the positions of the exon/intron junctions are similar to those of other Class II G protein-coupled receptor genes including the parathyroid hormone and glucagon receptors. The promoter resides within 593 base pairs of the initiation codon and the major transcriptional start site at nucleotide -238. This domain does not possess a TATA box but contains multiple Sp1 and AP-2 sites upstream and downstream of the major transcriptional start site. Intron junctions were identified in the extracellular, transmembrane (TM), and cytoplasmic (C) domains of the CRFR, giving the potential for differential signal transduction by splice variants. CRFR cDNAs derived from rat Leydig cell mRNA included the pituitary Form A, which spans exons 1-13, and two splice variants with deletion of exon 3 or exons 7, 11, and 12. An evolutionary link between the intronless TM/C module of the glycoprotein hormone receptors and the intron-containing TM/C module of the CRFR is suggested by the common position of the luteinizing hormone receptor Form D alternate acceptor splice site and the CRFR intron 12.