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Biomedical subjects

Y Sarne

Publications and source records attributed to Y Sarne.

65 records · Page 4Linked to original sources
PubMed1978

Correlation of subjective pain experience with cerebral evoked responses to noxious thermal stimulations.

The relationships between different parameters of the evoked cerebral response to noxious thermal stimulation, stimulus intensity, and subjective pain were investigated in seven normal human volunteers. The evoked response was characterized by late events: a small negative peak at 164--180 ms, followed by a high amplitude positive peak at 372--391 ms. The only correlation found in this study was between the amplitude of the positive component and the qualitative and quantitative aspects of the verbal report of pain. This was manifested by a linear trend of association: an increase in the evoked response amplitude was accompanied by an increase in the magnitude of the subjective sensation. The findings suggest that the evoked response to noxious heat reflects not a mere transduction of the physical parameters of the stimulus, but rather a complex interpretative action at the cerebral level.

Evoked Potentials↗
PubMed1977

Neurophysin biosynthesis: conversion of a putative precursor during axonal transport.

[35S]Cysteine injected adjacent to the supraoptic nucleus of the rat is rapidly incorporated into a 20,000-dalton protein that, in time, is converted to a 12,000-dalton labeled protein, neurophysin. This putative precursor of neurophysin appears to be synthesized in the supraoptic nucleus and transformed to neurophysin and related peptides during axonal transport to the neurohypophysis.

Animals↗
PubMed1977

Biosynthesis and axonal transport of rat neurohypophysial proteins and peptides.

35S-cysteine injected adjacent to the supraoptic nucleus (SON) of the rat is rapidly incorporated into proteins. These 35S-cysteine-labeled proteins in the SON (1-24 h after injection) were separated by polyacrylamide gel electrophoresis, and the distribution of radioactive proteins on the gels was analyzed. 1 h after injection, about 73% of the radioactivity appeared in two peaks (both about 20,000 mol wt). With time, these peaks (putative precursors of neurophysin) decreased, as a 12,000 mol wt peak (containing two distinct neurophysins) increased in radioactivity. Both the 20,000- and 12,000-mol wt proteins are transported into the axonal (median eminence) and nerve terminal (posterior pituitary) regions of the rat hypothalamo-neurohypophysial system. Conversion of the larger precursor protein to the smaller neurophysin appears to occur, in large part, intra-axonally during axonal transport. Six distinct 35S-cysteine-labeled peptides (less than 2500 mol wt), in addition to arginine vasopressin and oxytocin, are also synthesized in the SON and transported to the posterior pituitary where they are released together with labeled neurophysin by potassium depolarization in the presence of extracellular calcium. These data provide support for the hypothesis that the neurohypophysial peptides (vasopressin and oxytocin) and neurophysins are derived from the post-translational clevage of protein precursors synthesized in the SON, and that the conversion process can occur in the neurosecretory granule during axonal transport.

Animals↗
PubMed1976

Protein metabolism in transected peripheral nerves of the crayfish.

The significance of the protein metabolism in crayfish peripheral nerve was studied in relation the ability of crayfish motor axons to survive for over 200 days following axotomy. In contrast to frog peripheral nerves, the crayfish nerves appear to more closely resemble ganglia in their profiles of synthesis expressed on sodium dodecyl sulfate (SDS) gels, and have higher incorporation rates of [3H]leucine into protein than ganglia. Since anisomycin inhibits over 95% of protein synthesis in crayfish peripheral nerve, it was concluded that this local protein synthesis was dependent upon a eukaryotic ribosomal mechanism. Radioautography of isolated nerves reveals newly synthesized proteins in glial sheaths, and also within the axoplasm of large motor fibers. Based upon the data available at present, a hypothesis that the glia surrounding the axons are responsible for the local protein synthesis, and that some of these newly synthesized proteins are transported into the axon, is presented. Transection of crayfish peripheral nerves proximal to the neuron cell bodies produced a more than two-fold increase in [3H]leucine incorporation, but no significant changes in labeling profiles of the proteins on SDS gels. The data suggest that while an active local protein synthesis may be necessary for the maintenance of several crayfish motor axons, it is not a sufficient condition.

Animals↗
PubMed1976

Evidence for the local synthesis of a transmitter enzyme (glutamic acid decarboxylase) in crayfish peripheral nerve.

The activities of three enzymes of neurotransmitter metabolism (choline acetyl-transferase, CAT; acetylcholinesterase, AChE; and glutamic acid decarboxylase, GAD) were studied in normal, transected, and organ cultured crayfish nerves. CAT (to a lesses extent AChE) was dramatically decreased in activity when the nerve was cut proximal to the nerve cell bodies. GAD activity was unaffected by such procedures. In organ cultured nerve, where both motor and sensory axons degenerated, the CAT and AChE activities were virtually absent, whereas GAD activity remained close to normal levels. Inhibition of protein synthesis in cultured nerve caused the GAD activity to decrease rapidly. In view of these data, and the well documented fact that motor axons survive axotomy whereas sensory axons do not, a hypothesis that GAD is synthesized in the peripheral nerve is presented.

Acetylcholinesterase↗
PubMed1976

Desensitization to gamma-aminobutyric acid in crustacean muscle fibres.

1. Desensitization to gamma-aminobutyric acid (GABA) was demonstrated in crab muscle fibres by measurements to conductance changes induced by the drug. 2. In standard solutions (containing 34 mM-Ca2+), complete desensitization occurred in the presence of 5 X 10(-4) M-GABA. In Ca2+-free solutions, however, only partial (70-80%) desensitization was observed after the application of the same concentration of GABA. 3. Complete recovery of the membrane sensitivity to GABA was achieved after less than 60 min of continuous washout with standard solution. Only partial (10%) recovery was observed after 1 hr of washout with Ca2+-free solution. 4. The results support the 'receptor hypothesis' of desensitization which assumes transformation of the receptor from an effective to refractory state, as opposed to the 'ionophore hypothesis' which assumes direct inactivation of the synaptic current. 5. The possible mechanism by which Ca ions effect desensitization is discussed in terms of the 'cyclic model' of Katz & Thesleff (1957).

Aminobutyrates↗