Relationship of ATP turnover, polyphosphoinositide metabolism, and protein phosphorylation in sciatic nerve and derived peripheral myelin subfractions from normal and streptozotocin diabetic rats

Sciatic nerve from streptozotocin-induced diabetic rats has previously been shown to incorporate more 32P into phosphatidylinositol-4,5-bisphosphate (PIP2) and the principal myelin proteins than normal nerve. In the present study, labeling of ATP and PIP2 was compared. Using nerve segments, [gamma-32P]ATP specific activity reached a plateau after incubation for 4 h with [32P]orthophosphate, whereas the specific activity of [32P]PIP2 rose much more slowly and was still increasing after 8 h. The rate of disappearance of radioactivity from prelabeled ATP was biphasic, with 75% being lost within 30 min and the remainder declining much more slowly for several hours thereafter. In contrast, no decrease in prelabeled PIP2 radioactivity could be detected for up to 4 h. The kinetics of ATP metabolism were not appreciably different for normal and diabetic nerve. However, after incubation with [32P]orthophosphate for 2 h, the specific activity of PIP2 was 50-120% higher in diabetic nerve. This phenomenon, therefore, cannot be ascribed to altered specific activity of the ATP precursor pool. Greater labeling of PIP2 in 32P-labeled diabetic nerve was present in purified myelin isolated using a simple discontinuous sucrose density gradient, but not in a "nonmyelin" fraction. When nerve homogenate was fractionated on a more complex gradient, three myelin-enriched subfractions were obtained which were heterogeneous as judged by morphological appearance, protein profile, and lipid metabolic activity. The proportion of total lipid radioactivity accounted for by PIP2 was elevated in all the subfractions relative to the homogenate. As compared to myelin subfractions from normal nerve, an increased percentage of 32P in PIP2 was obtained only in the major myelin subfraction from diabetic nerve. The phosphorylation of P0 relative to the other myelin proteins was also enhanced in this subfraction in nerve from diabetic animals.

Enhanced mode locking of color-center lasers

A significant enhancement in the mode locking of a KCl:Tl color-center laser has been observed when a length of optical fiber having positive group-velocity dispersion was incorporated within an external control cavity. Pulse durations of ~260 fsec were obtained by this method, representing a compression factor ~60x that with the colorcenter laser alone. Similar results have also been observed with an InGaAsP semiconductor diode amplifier as the nonlinear element within the control cavity.

Characterization of ion-exchanged planar microlenses by ray tracing

For the design and optimization of the fabrication condition of distributed-index planar microlenses, it is necessary to evaluate the N. A., focal length, focused spot, and aberration of a fabricated lens. In this paper, a ray tracing method is improved for this purpose, and properties of planar microlenses aie evaluated. An ion concentration matrix is proposed to simplify lens design.

A signal-processing research facility and its application to the processing of fetal phonocardiographic signals for heart rate estimation

Part 1 of this paper describes a real-time medical signal-processing research facility which is being developed at Edinburgh University. Part 2 describes the application of this facility to the estimation of fetal heart rate from phonocardiographic signals using a new frequency-domain estimation algorithm.