Luteinizing hormone-releasing hormone in cerebrospinal fluid of women

The concentration of luteinizing hormone-releasing hormone (LH-RH) in both cerebrospinal fluid (CSF) and plasma in 36 women with various conditions were determined, and the correlation of LH-RH concentrations between plasma and CSF was studied. Paired samples of plasma and CSF were obtained just before operation and were extracted with methanol for LH-RH radioimmunoassay. LH and FSH were also measured by radioimmunoassay. The mean plasma LH-RH levels were 3.79 pg/ml in the follicular phase, 4.15 pg/ml in the luteal phase, 12.73 pg/ml in postmenopausal women and 2.31 pg/ml in pregnant women at term. No immunoreactive LH-RH in the CSF was found in 29 out of 36 subjects, and the remaining 7 subjects showed very low levels (less than 0.95 pg/ml). The LH-RH levels in the CSF of post-menopausal women were not higher their those in the remaining 3 groups, although their plasma levels of LH-RH were significantly (p less than 0.001) elevated. The mean plasma levels of LH and FSH in post-menopausal women were significantly higher than those in normal cyclic women and in pregnant women. The present results suggest that little or no LH-RH is present in the CSF, and it is not clear that there is any correlation between the LH-RH level of plasma and those of CSF.

Dynamic characteristics of F-actin and thin filaments in vivo and in vitro

Measurements of birefringence, ultraviolet dichorism and quasielastic light scattering were carried out on F-actin in solution and on the thin filaments of glycerinated myofibrils. The birefringence of the I-bands of myofibrils was of the same order of magnitude as that of F-actin or the F-actin-tropomyosin-troponin complex oriented in vitro at the same concentration. The ultraviolet dichroism spectrum of the I-bands was very similar to that of F-actin or the F-actin complex in vitro, which is due to orientation of bound ADP and tryptophan residues in F-actin. Quasielastic light scattering measurements, electronmicroscopic observations and the analyses of the electro-optic effect of the I-bands suggested approximately the same flexibility for F-actin in vitro and for the thin filaments in vivo. These optical measurements which were made under various conditions provide evidence for a conformational change induced by calcium ions in F-actin both in vivo and in vitro. This conformational change was found to be amplified by the interaction of F-actin with myosin. This is a brief review of our investigation on the dynamics of F-actin and the thin filament in vivo and in vitro by optical methods.

Birefringence of glycerinated crab muscle fiber under various conditions

By using glycerinated single fibers of crab muscle (Sesarma haematocheir) which has long sarcomeres, the birefringence of the I band, H band and the overlapping region between thin and thick filaments was measured separately, under various environmental conditions. At the resting length, the birefringence of the fiber was decreased by the addition of Ca2+ in the absence of ATP, by about 0.35%. This birefringence decrease was found to take place in the overlapping region. The decrease corresponded to about 2% of the birefringence of thin filaments in this region. The birefringence of the fiber was increased by the addition of ATP in the absence of Ca2+, by about 6%. This birefringence increase also took place mostly in the overlapping region. The increase of birefringence by pyrophosphate was about half of that by ATP. The birefringence of the fiber was decreased by the increase of the ionic strength from 0.12 to 0.20. The origin of the observed changes of birefringence is discussed.

Effect of myosin on conformational changes of F-actin in thin filament in vivo induced by calcium ions

The measurements of ultraviolet linear dichroism has been carried out on glycerinated muscle fibers of rabbit psoas and crab leg having various sarcomere lengths and the effect of interaction of the thin filament with myosin on the dichroism has been investigated under various conditions. The dichroism spectrum of the muscle fiber has a large positive peak at 285 nm (smaller absorption of light polarized perpendicular to the fiber axis) and a small negative peak at 297.5 nm. The negative peak at 297.5 nm, which comes from the dichroism of F-actin in the thin filament, became smaller in the presence of Ca2+ than in its absence. The positive peak at 285 nm, where the thick filament has main contribution, showed no appreciable change by Ca2+. The dichroism at 292.5 nm, where the thin filament has no contribution, showed no change either. Thus, the decrease of negative dichroism at 297.5 nm by Ca2+ indicates a conformational change in F-actin in the thin filament. With decreasing sarcomere length or increasing overlapping between thin and thick filaments, the dichroism decrease at 297.5 nm by Ca2+ increased, and attained a maximum at maximum overlapping. That is the conformational change of F-actin by Ca2+ was amplified by interaction with myosin. With further decrease of the sarcomere length, the dichroism decrease by Ca2+ decreased. In the absence of Ca2+, the addition of ATP or pyrophosphate induced a large change of transmittance and transmittance anisotropy, and also a large increase of birefringence at long wavelengths.