Retinoids regulate tight junctional resistance of cultured human cervical cells

The objective ofthe study was to determine the effect of retinoids on paracellularresistance across the cervical epithelium and the mechanisms involved.The experimental model was cultures of human CaSki cells on filters,which retain phenotypic characteristics of the endocervical epithelium.End points for paracellular resistance were measurements oftransepithelial electrical resistance and fluxes of pyranine (atrisulfonic acid that traverses the epithelium via the intercellularspace). Paracellular resistance was significantly increased in cellsgrown in retinoid-free medium; the effect could be blocked and reversedwith all-trans-retinoic acid (tRA) and with agonists of RAR and RXR receptors but only partially with retinol.The effect of tRA was dose dependent and saturable, with a 50%effective concentration of 0.8 nM. The increases in paracellular resistance induced by vitamin A deficiency required longer incubation in retinoid-free medium than decreases in resistance induced by retinoic acid. tRA had only a minimal effect on paracellular resistance in cells maintained in regular medium. Retinoid-free medium increased and tRA decreased the relative cation mobility across CaSki cultures. Also the effects of tRA were nonadditive to those of cytochalasin D(which decreases tight junctional resistance) and additive to those ofionomycin (which decreases the resistance of the lateral intercellularspace), suggesting that tRA modulates tight junctional resistance. Itis concluded that vitamin A determines the degree of paracellularresistance across cervical cells by a mechanism that involvesmodulation of tight junctional resistance.

     

RADIATION AND CONVECTION IN CONIFERS

The transfer of energy to and from a conifer branch involves solar radiation, thermal radiation from the ground, atmosphere, and surroundings, thermal emission by the branch, and free convection in still air and forced convection in wind. It is necessary to know the actual surface area of the branch, the effective area for absorbing sunlight, the effective area for absorbing long wave thermal radiation and for emission, and the free and forced convection coefficients. These parameters are determined using silver castings of blue spruce and white fir branches suspended in an evacuated radiation chamber and in a wind tunnel. The actual surface area of a branch is determined by means of an electrolytic technique. Numerical examples are given for energy transfer in a natural environment for conifers and comparison is made to a broad deciduous type of leaf. The role of transpiration in the energy transfer process is discussed.     

Prostate--a novel target for evaluation of FSH modulating peptides

Effects of prostatic inhibin peptide and its synthetic fragments on FSH biosynthesis by the human pituitary and prostate, were examined in vitro. The results showed that FSH biosynthesis by prostatic tissue is modulated by these peptides in a similar fashion to that observed at the pituitary level.     

Electron microscopic evidence of an immobilized living cell system

Whole cells of Rhodopseudomonas capsulata were immobilized by entrapment in Ca²⁺ alginate gel. The cell growth inside the matrix was observed by transmission electron microscopy. Colonies enlarged upon incubation, giving some evidence of an immobilized living cell system. This observation was correlated by measurements of bacteriochlorophyll, nitrogen, and protein content.     

Plasma-derived serum as a selective agent to obtain endothelial cultures from swine aorta

Summary Endothelial cell and smooth muscle cell cultures from artery wall provide a potential model system for studying cellular processes involved in atherogenesis. To prepare serial subcultures of swine arterial endothelial cells that are free of smooth muscle cells without either selecting a small population or subjecting the cells to cytotoxic conditions, we used swine plasma-derived serum (SPDS) to establish conditions in which endothelial cells have a growth advantage. Endothelial cells were collected by collagenase digestion and smooth muscle cell cultures were prepared by outgrowth from explants of arterial medial segments. Growth rates were compared when each cell type was maintained on SPDS, or fetal bovine serum (FBS), or swine whole serum (SWS). When 20% FBS or SWS were used the doubling times were <30 h for both endothelial cells and smooth muscle cells. On 20% SPDS the doubling time for endothelial cells was 32 h, but for smooth muscle cells it was at least 168 h. Using SPDS, we prepare endothelial subcultures from swine aorta that express principally polygonal morphology at confluence. Endothelial cell cultures grown on SPDS have higher angiotensin-converting enzyme than those grown on FBS. This work was supported by grants HL 22486 and HL 24660 from the National Institutes of Health, Bethesda, Maryland. Dr. Slakey is an Established Investigator of the American Heart Association. Portions of this work were presented at the 31st Annual Meeting of the Tissue Culture Association in St. Louis, Missouri.     

Growth factors which affect bone

The coupled processes of bone resorption and bone formation occur throughout life. New research suggests that some well-characterized growth factors affect bone and that transforming growth factors and tumor-derived growth factors may also influence bone growth and remodeling.     

Oral estrogen treatment induces a decrease in expression of sialyl Lewis x on {alpha}1 glycoprotein in females and male-to-female transsexuals

The effect of estrogen on the glycosylation of