Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

The structure of locomotor activity in bilobectomized cockroaches (Blaberus fuscus)

Summary The aperiodic activity patterns of bilobectomized cockroaches can largely be described by simple stochastic regularities: a) there are no correlations between the lengths of successive activity bursts and rest pauses, b) the probabilities for the transition from activity to rest and from rest to activity are time-independent. The activity sequence is strongly influenced by singular temperature steps or temperature cycles.     

Patch clamp technique and biophysical study of membrane channels

The present work describes the patch clamp technique, which first allowed the recording of single channel currents in biological membranes. In particular, it describes procedures for preparation and applications of the four different patch clamp configurations. Briefly, the cell-attached configuration is widely used for investigating channel modulation by transmitters acting via second messengers. The cell-free configurations (inside-out and outside-out), complementary to one another with respect to the orientation of the membrane surface, are particularly indicated for the study of the biophysics (kinetics, conductivity, selectivity, mechanism of permeation and block) of ionic channels. Finally, the whole-cell configuration which, because of the remarkable feature that it allows voltage clamp of very small cells, has given access to a number of physiologically important preparations never studied before.     

Concentration of ‘available’ unesterified cholesterol in human plasma as evaluated from inhibition of hemolysis by lucensomycin

Summary The unesterified cholesterol content of plasma samples can be evaluated from the extent of inhibition of lucensomycin-induced hemolysis. The test measures, however, only the fraction of cholesterol which is available for interaction with lucensomycin, this availability being adversely affected by high phospholipid-cholesterol ratios.     

Peptidergic co-transmission inAplysia: Functional implications for rhythmic behaviors

Despite their ubiquitous presence in the central and peripheral nervous systems, the behavioral functions of peptide co-transmitters remain to be elucidated. The marine molluscAplysia, whose simple nervous system facilitates the study of the neural basis of behavior, was used to investigate the role of peptidergic co-transmission in feeding behavior. Several novel modulatory neuropeptides were purified, and localized to identified cholinergic motorneurons. Physiological and biochemical studies demonstrated that these peptides are released when the motorneourons fire at frequencies that occur during normal behavior, and that the peptides modify the relationship between muscle contraction amplitude and relaxation rate so as to maintain optimal motor output when the intensity and frequency of feeding behavior change.     

Cannflavin A and B,prenylated flavones fromCannabis sativa L.

Summary Two novel prenylat flavones, termed Cannflavin A and B, were isolated from the cannabinoid free ethanolic extract ofCannabis sativa L. Both compounds inhibited prostaglandin E₂ production by human rheumatoid synovial cells in culture.This communication is dedicated to the memory of the late Professor J. W. Fairbairn and the late Dr. J. T. Pickens. We are grateful to the Medical Research Council for a project grant and to Ms J. Elliot of King's College London for NMR spectra.     

Desacetylscalaradial,a cytotoxic metabolite from the spongeCacospongia scalaris

Summary From the marine spongeCacospongia scalaris, scalaradial1, desacetylscalaradial2, and heteronemin3 were isolated. Compound2 showed potent cell growth inhibition. The stereochemistry of3 is briefly discussed.Acknowledgments. The authors are grateful to Prof. T. Hase and Mr R. Nakai for collecting the sponge and to Dr s. Tanida for the sponge identification.