Quantitative evaluation of the response of thalamic neurons to tooth pulp stimulation was made in chronically prepared cats. The latency, duration and intensity of the responses were measured from the post-stimulus time histograms to estimate, from various aspects, the alteration in the responsiveness during different phases of sleep and wakefulness. During slow wave sleep, tooth pulp-evoked impulses tended to be transmitted to the thalamus in a similar or slightly higher intensity compared to wakefulness. In contrast, during paradoxical sleep the signals were often attenuated in many aspects. The results seem to be in favor of the idea that the impairment of signal to noise ratio in a variety of neuronal networks is one of the characteristics of paradoxical sleep.

Animals↗

PubMedDate not supplied

Sliding movement of single actin filaments on one-headed myosin filaments.

The myosin molecule consists of two heads, each of which contains an enzymatic active site and an actin-binding site. The fundamental problem of whether the two heads function independently or cooperatively during muscle contraction has been studied by methods using an actomyosin thread, superprecipitation and chemical modification of muscle fibres. No clear conclusion has yet been reached. We have approached this question using an assay system in which sliding movements of fluorescently labelled single actin filaments along myosin filaments can be observed directly. Here, we report direct measurement of the sliding of single actin filaments along one-headed myosin filaments in which the density of heads was varied over a wide range. Our results show that cooperative interaction between the two heads of myosin is not essential for inducing the sliding movement of actin filaments.

Actins↗

PubMedDate not supplied

cDNA cloning of bovine substance-K receptor through oocyte expression system.

The neuropeptide receptors which are present in very small quantities in the cell and are embedded tightly in the plasma membrane have not been well characterized. Mammals contain three distinct tachykinin neuropeptides, substance P, substance K and neuromedin K, and it has been suggested that there are multiple tachykinin receptors. By electrophysiological measurement, we have previously shown that Xenopus oocytes injected with brain and stomach mRNAs faithfully express mammalian substance-P and substance-K receptors, respectively. Here we report the isolation of the cDNA clone for bovine substance-K receptor (SKR) by extending this method to develop a new cloning strategy. We constructed a stomach cDNA library with a cloning vector that allowed in vitro synthesis of mRNAs and then identified a particular cDNA clone by testing for receptor expression following injection of the mRNAs synthesized in vitro into the oocyte system. Because oocytes injected with exogenous mRNAs can express numerous receptors and channels, our new strategy will be applicable in the general molecular cloning of these proteins. The result provides the first indication that the neuropeptide receptor has sequence similarity with rhodopsin-type receptors (the G-protein-coupled receptor family) and thus possesses multiple membrane-spanning domains.

Amino Acid Sequence↗