[Effect of tyrosine on progesterone and hCG production by human trophoblast cells in vitro]

The purpose of the present study was to investigate the effect of tyrosine on progesterone and hCG production by human placental cells in vitro. The results showed that the three concentrations (0.02 mmol/L, 0.2 mmol/L and 2mmol/L) of tyrosine inhibited progesterone secretion by trophoblast cells in vitro. While progesterone secretion was suppressed by tyrosine, hCG secretion was unchanged. Thus, it seems unlikely that the suppression of progesterone production by tyrosine was due to a decrease in hCG production. It was further demonstrated that tyrosine inhibited 3 beta-HSD activity of trophoblast cells, indicating that the progesterone production inhibition by them might be due to the decreased 3 beta-HSD activity of trophoblast cells.

UV photoelectron spectroscopy and ab initio characterization of valence orbital structures and conformations of neutral phosphate esters

The HeI UV photoelectron spectrum of trimethyl phosphate (TMP) has been measured and interpreted with the aid of SCF molecular orbital calculations carried out with STO-3G, STO-3G* and 4-31G basis functions. The photoelectron spectrum of TMP is more accurately reproduced by results from 4-31G calculations than by results from STO-3G or STO-3G* calculations. However, all three basis sets yield results which predict the same assignment of the photoelectron spectrum. Results at the 4-31G level indicate that whether calculations are based on crystallographic bond angles and bond lengths or on STO-3G optimized geometries has little effect on the energetic ordering of the upper occupied orbitals. The energetic ordering of orbitals is also found to be only weakly dependent upon the torsional angle phi, describing rotation of ester groups about P-O bonds and upon the torsional angle psi, describing rotation of methyl groups about C-O bonds. For trimethyl phosphate, with C3 symmetry, the vertical ionization potentials of the upper occupied orbitals are 10.81 eV (8e), 11.4 eV (9a), 11.93 eV (7e), 12.6-12.9 eV (8a and 6e), 14.4 eV (7a) and 15.0-16.0 eV (5e and 6a). Calculations at the 4-31G level indicate that many of the highest occupied orbitals in neutral dimethyl phosphate and methyl phosphate have energies and electron distributions similar to orbitals in TMP. For TMP, a search for optimized values of phi and psi has been carried out at the STO-3G*level. In agreement with previous NMR studies and with classical potential calculations, the STO-3G* results indicate that both the gauche (phi = 53.1 degrees) and anticlinal (phi = 141.9 degrees) conformations are thermally accessible. Also in agreement with the classical potential calculations, the STO-3G* results predict that in the all gauche conformation energy is minimized when the methyl groups assume a staggered geometry (psi = 60 degrees to 80 degrees) and that an energy maximum occurs for an eclipsed geometry (phi = 0 degrees to 20 degrees). A study of the dependence of optimized values of O-P-O ester bond angles on the torsional angles, phi, was carried out at the STO-3G, STO-3G* and 4-31G levels. The results demonstrate that for C3 symmetry, the coupling of O-P-O angles to phi is influence by repulsive steric interactions.

Triple-in double-out optical parallel logic processing system

A triple-in double-out optical logic operating system based on shadow-casting processing is described. All the 256 logic operations of three inputs can be performed, and the optical adder can be easily implemented. A real-time encoding method for the input patterns is also presented.

Depolarizing responses of L-type external horizontal cells in the goldfish retina under intense chromatic background

The external horizontal cells (EHCs) in the goldfish retina are known to respond with hyperpolarization to monochromatic flashes of all wavelengths. From their spectral responses they are referred to as "monophasic" horizontal cells. However, when the retina is exposed to an intense red background, EHCs showed a depolarizing response to flashes of intermediate and short wavelength of moderate intensity. The depolarizing component is presumably driven by the input from green-sensitive cones.