GABA increases electrical excitability in a subset of human unmyelinated peripheral axons

A proportion of small diameter primary sensory neurones innervating human skin are chemosensitive. They respond in a receptor dependent manner to chemical mediators of inflammation as well as naturally occurring algogens, thermogens and pruritogens. The neurotransmitter GABA is interesting in this respect because in animal models of neuropathic pain GABA pre-synaptically regulates nociceptive input to the spinal cord. However, the effect of GABA on human peripheral unmyelinated axons has not been established

The Effects of Polarizing Current on Nerve Terminal Impulses Recorded from Polymodal and Cold Receptors in the Guinea-pig Cornea

It was reported recently that action potentials actively invade the sensory nerve terminals of corneal polymodal receptors, whereas corneal cold receptor nerve terminals are passively invaded (Brock, J.A., S. Pianova, and C. Belmonte. 2001. J. Physiol. 533:493–501). The present study investigated whether this functional difference between these two types of receptor was due to an absence of voltage-activated Na+ conductances in cold receptor nerve terminals. To address this question, the study examined the effects of polarizing current on the configuration of nerve terminal impulses recorded extracellularly from single polymodal and cold receptors in guinea-pig cornea isolated in vitro. Polarizing currents were applied through the recording electrode. In both receptor types, hyperpolarizing current (+ve) increased the negative amplitude of nerve terminal impulses. In contrast, depolarizing current (−ve) was without effect on polymodal receptor nerve terminal impulses but increased the positive amplitude of cold receptor nerve terminal impulses. The hyperpolarization-induced increase in the negative amplitude of nerve terminal impulses represents a net increase in inward current. In both types of receptor, this increase in inward current was reduced by local application of low Na+ solution and blocked by lidocaine (10 mM). In addition, tetrodotoxin (1 μM) slowed but did not reduce the hyperpolarization-induced increase in the negative amplitude of polymodal and cold nerve terminal impulses. The depolarization-induced increase in the positive amplitude of cold receptor nerve terminal impulses represents a net increase in outward current. This change was reduced both by lidocaine (10 mM) and the combined application of tetraethylammomium (20 mM) and 4-aminopyridine (1 mM). The interpretation is that both polymodal and cold receptor nerve terminals possess high densities of tetrodotoxin-resistant Na+ channels. This finding suggests that in cold receptors, under normal conditions, the Na+ conductances are rendered inactive because the nerve terminal region is relatively depolarized

Supporting Cancer Knowledge Needs Using Online Information

Information is exploding at an exponential rate. Because there is a flood of medical information on the Internet, it can be difficult to wade through the many resources to determine what information is best to use in practice. The intent of this chapter in Cancer Concepts: A Guidebook for the Non-Oncologist is to help the health care provider find reliable online cancer information. To help inform clinical decision making, health science librarians continue to address this rapidly growing body of literature by analyzing resources and identifying the highest quality information available on the Internet. The concept of Evidence-Based Medicine (EBM) is important to understand, as well as the process needed to find literature supporting EBM. Why EBM? EBM is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. Making evidence-based clinical decisions is not about intuition, but finding reliable, up-to-date literature and using it in combination with clinical expertise and patient choice. Once a source for free online quality literature is located, a health care provider can consider the best current evidence to thoroughly answer clinical questions.https://escholarship.umassmed.edu/cancer_concepts/1026/thumbnail.jp

Effects of Heating and Cooling on Nerve Terminal Impulses Recorded from Cold-sensitive Receptors in the Guinea-pig Cornea

An in vitro preparation of the guinea-pig cornea was used to study the effects of changing temperature on nerve terminal impulses recorded extracellularly from cold-sensitive receptors. At a stable holding temperature (31–32.5°C), cold receptors had an ongoing periodic discharge of nerve terminal impulses. This activity decreased or ceased with heating and increased with cooling. Reducing the rate of temperature change reduced the respective effects of heating and cooling on nerve terminal impulse frequency. In addition to changes in the frequency of activity, nerve terminal impulse shape also changed with heating and cooling. At the same ambient temperature, nerve terminal impulses were larger in amplitude and faster in time course during heating than those recorded during cooling. The magnitude of these effects of heating and cooling on nerve terminal impulse shape was reduced if the rate of temperature change was slowed. At 29, 31.5, and 35°C, a train of 50 electrical stimuli delivered to the ciliary nerves at 10–40 Hz produced a progressive increase in the amplitude of successive nerve terminal impulses evoked during the train. Therefore, it is unlikely that the reduction in nerve terminal impulse amplitude observed during cooling is due to the activity-dependent changes in the nerve terminal produced by the concomitant increase in impulse frequency. Instead, the differences in nerve terminal impulse shape observed at the same ambient temperature during heating and cooling may reflect changes in the membrane potential of the nerve terminal associated with thermal transduction

Semirelativistic stability of N-boson systems bound by 1/r pair potentials

We analyze a system of self-gravitating identical bosons by means of a semirelativistic Hamiltonian comprising the relativistic kinetic energies of the involved particles and added (instantaneous) Newtonian gravitational pair potentials. With the help of an improved lower bound to the bottom of the spectrum of this Hamiltonian, we are able to enlarge the known region for relativistic stability for such boson systems against gravitational collapse and to sharpen the predictions for their maximum stable mass.Comment: 11 pages, considerably enlarged introduction and motivation, remainder of the paper unchange

How spiking neurons give rise to a temporal-feature map

A temporal-feature map is a topographic neuronal representation of temporal attributes of phenomena or objects that occur in the outside world. We explain the evolution of such maps by means of a spike-based Hebbian learning rule in conjunction with a presynaptically unspecific contribution in that, if a synapse changes, then all other synapses connected to the same axon change by a small fraction as well. The learning equation is solved for the case of an array of Poisson neurons. We discuss the evolution of a temporal-feature map and the synchronization of the single cells’ synaptic structures, in dependence upon the strength of presynaptic unspecific learning. We also give an upper bound for the magnitude of the presynaptic interaction by estimating its impact on the noise level of synaptic growth. Finally, we compare the results with those obtained from a learning equation for nonlinear neurons and show that synaptic structure formation may profit from the nonlinearity

Low-Resolution Imaging Spectrometer for the Keck Telescope

The Low Resolution Imaging Spectrometer is designed for use at the Cassegrain focus of the Keck 10-m telescope. It provides the capability of acquiring low resolution (R equals 1000 to 5000) digital spectra, as well as 6 X 8 arc-minute moderately high spatial resolution (4.65 pixels/arc-second) direct images. Spectroscopy can be carried out with single slits which are 3 arc-minutes long. In addition punched multi-slits can also be employed which allow for the acquisition of at least forty spectra simultaneously. Since the instrument is designed to be as efficient as possible, it is a double spectrograph, with a dichroic splitting the blue and red light into separate optical paths after the collimator. Only the red side has been constructed thus far. With a 2048 by 2048 thinned Tektronix CCD as the detector the total efficiency of the red side at the peak of the grating blaze is predicted to be nearly 40%. Results of the commissioning observing runs will be described

Spallation-Fission Competition in Heaviest Elements; Helium IonInduced Reactions in Plutonium Isotopes

Excitation functions have been determined for the spallation and fission reactions induced in plutonium isotopes by 20 to 50 Mev helium ions. The method employed consisted of cyclotron bombardments of plutonium oxide followed by the chemical isolation and alpha or beta counting of radioactive reaction products. Formation cross sections are given where possible for the curium and americium spallation products corresponding to ({alpha},n), ({alpha},2n), ({alpha},3n), ({alpha},4n), ({alpha}5n), ({alpha},p), ({alpha},pn or d), ({alpha},p2n or t), and ({alpha},p3n) reactions in Pu{sup 238} , Pu{sup 239}, and Pu{sup 242}. Fission yield curves and fission cross sections for Pu{sup 238} and Pu{sup 239} serve to define the characteristics of the ({alpha},f) reaction for plutonium isotopes. Chemical procedures are outlined for the separation of both spallation and fission product elements in a sequence of operations performed on the entire dissolved target

Differential gene expression in the nucleus accumbens with ethanol self-administration in inbred alcohol-preferring rats

The current study examined the effects of operant ethanol (EtOH) self-administration on gene expression in the nucleus accumbens (ACB) and amygdala (AMYG) of inbred alcohol-preferring (iP) rats. Rats self-trained on a standard two-lever operant paradigm to administer either water-water, EtOH (15% v/v)-water, or saccharin (SAC; 0.0125% g/v)-water. Animals were killed 24 hr after the last operant session, and the ACB and AMYG dissected; RNA was extracted and purified for microarray analysis. For the ACB, there were 513 significant differences at the p < 0.01 level in named genes: 55 between SAC and water; 215 between EtOH and water, and 243 between EtOH and SAC. In the case of the AMYG (p < 0.01), there were 48 between SAC and water, 23 between EtOH and water, and 63 between EtOH and SAC group. Gene Ontology (GO) analysis indicated that differences in the ACB between the EtOH and SAC groups could be grouped into 15 significant (p < 0.05) categories, which included major categories such as synaptic transmission, cell and ion homeostasis, and neurogenesis, whereas differences between the EtOH and water groups had only 4 categories, which also included homeostasis and synaptic transmission. Several genes were in common between the EtOH and both the SAC and water groups in the synaptic transmission (e.g., Cav2, Nrxn, Gabrb2, Gad1, Homer1) and homeostasis (S100b, Prkca, Ftl1) categories. Overall, the results suggest that changes in gene expression in the ACB of iP rats are associated with the reinforcing effects of EtOH