Search PubMed⌕ Search

Biomedical subjects

J Axelrod

Publications and source records attributed to J Axelrod.

At least 271 records · Page 15Linked to original sources
PubMed1970

Phase difference in the induction of tyrosine hydroxylase in cell body and nerve terminals of sympathetic neurones.

The induction of tyrosine hydroxylase in the nerve terminals of the rat heart by reserpine lags behind that in the stellate ganglion by two to three days. Cycloheximide given three days after reserpine blocks the further rise of the enzyme in the nerve terminals. The increase in tyrosine hydroxylase activity of the lumbar ganglion is as marked as that in the stellate ganglion. The increase of enzyme activity in the sciatic nerve after reserpine administration resembles that found in the heart nerve terminals. Determination of enzyme activity in segments of sciatic nerves indicates a two-day lag and then a proximal-distal transport of enzyme, but the apparent rate is not sufficient to account for the increase in enzyme in the nerve terminals. These findings are compatible with the local synthesis of induced tyrosine hydroxylase in the nerve terminals rather than the peripheral movement of the completed enzyme.

Animals↗
PubMed1970

Neurally mediated increase in dopamine-beta-hydroxylase activity.

The development of a sensitive and specific enzymatic assay for dopamine-beta-hydroxylase has enabled us to measure the activity of this enzyme in several tissues where it has previously been measured. The administration of reserpine leads to an increase in dopamine-beta-hydroxylase activity in the rat adrenal, heart, salivary gland, and in sympathetic ganglia. The increase in the heart is preceded by a small but significant fall. We have confirmed the increase in tyrosine hydroxylase which follows the administration of reserpine and have found that the activity of phenylethanolamine-N-methyltransferase also increases after administration of this drug. The activities of two enzymes not involved in the synthesis of catecholamines, monoamine oxidase and lactate dehydrogenase, are not affected by reserpine treatment. The rise of dopamine-beta-hydroxylase activity in the sympathetic ganglia is blocked by surgical decentralization.

Adrenal Glands↗
PubMed1969

Stimulation of C14-melatonin synthesis from C14-tryptophan by noradrenaline in rat pineal in organ culture.

Previous work has shown that the activity of the melatonin-forming enzyme in the rat pineal gland is elevated in rats kept in continuous darkness as compared to those kept in continuous light. Information about environmental lighting reaches the pineal gland via nerves that liberate noradrenaline. Rat pineal glands in organ culture can form C(14)-melatonin from C(14)-tryptophan as follows: tryptophan --> 5-hydroxytryptophan --> serotonin --> melatonin. Noradrenaline was found to stimulate the synthesis of C(14)-melatonin from C(14)-tryptophan in rat pineals in organ culture. Other compounds related in structure to noradrenaline increase melatonin and serotonin synthesis and inhibit the formation of the deaminated product of serotonin, 5-hydroxyindole acetic acid. Cycloheximide, a compound that inhibits protein synthesis, also prevents the formation of serotonin, melatonin, and 5-hydroxyindole acetic acid from tryptophan in pineal organ culture. These observations suggest that noradrenaline liberated from sympathetic nerves stimulates the formation of melatonin either by increasing the formation of new melatonin-forming enzyme, by increasing transport of tryptophan into the pineal cell, or by inhibiting the metabolism of serotonin by the alternate deaminating pathway.

Animals↗
PubMed1969

Incorporation of 14C-tryptophan into 14C-protein by cultured rat pineals: stimulation by l-norepinephrine.

Organ cultures of individual rat pineals incorporate (14)C-tryptophan into proteins at a nearly constant rate for at least 48 hours. Previous studies have shown that these cultures also convert (14)C-tryptophan to serotonin, melatonin, and 5-hydroxyindoleacetic acid, and release these indoles into the media. The formation of (14)C-protein from (14)C-tryptophan is accelerated by the addition to the culture medium of l-norepinephrine or related catecholamines but is not modified by serotonin, melatonin, or 5-hydroxyindoleacetic acid. One mechanism by which norepinephrine stimulates the synthesis of (14)C-protein from (14)C-tryptophan involves increasing the uptake of the (14)C-tryptophan into pineal parenchymal cells, inasmuch as (1) norepinephrine increases the intracellular content of (14)C-tryptophan as well as its conversion to its major products, (14)C-protein and (14)C-indoles; (2) norepinephrine does not stimulate (14)C-protein synthesis in pineal organs which contain a previously fixed amount of (14)C-tryptophan; and (3) norepinephrine does not stimulate (14)C-protein synthesis from (14)C-methionine or (14)C-leucine. The finding that norepinephrine, but not serotonin, can stimulate the incorporation of (14)C-tryptophan into pineal proteins is consistent with the hypothesis that norepinephrine is the neurotransmitter substance utilized by pineal sympathetic nerve endings.

Aminoisobutyric Acids↗