PubMed · 13629549
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G WRIGHT. 1959. Medullary nailing.. https://pubmed.ncbi.nlm.nih.gov/13629549/
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Recently, we reported that intracerebroventricularly (i.c.v.) administered arginine-vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by brain thromboxane A2-mediated mechanisms in rats. These results suggest the involvement of brain arachidonic acid in the vasopressin-induced activation of the central adrenomedullary outflow. Arachidonic acid is released mainly by two pathways: phospholipase A2 (PLA2)-dependent pathway; phospholipase C (PLC)- and diacylglycerol lipase-dependent pathway. In the present study, therefore, we attempted to identify which pathway is involved in the vasopressin-induced release of both catecholamines from adrenal medulla using urethane-anesthetized rats. Vasopressin (0.2 nmol/animal, i.c.v.)-induced elevation of plasma noradrenaline and adrenaline was dose-dependently reduced by neomycin [0.28 and 0.55 micromol (250 and 500 microg)/animal, i.c.v.] and 1-[6-[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) [5 and 10 nmol (2.3 and 4.6 microg)/animal, i.c.v.] (inhibitors of PLC), and also by 1,6-bis(cyclohexyloximinocarbonylamino)hexane (RHC-80267) [1.3 and 2.6 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of diacylglycerol lipase). On the other hand, mepacrine [1.1 and 2.2 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of PLA2) was largely ineffective on the vasopressin-induced elevation of plasma catecholamines. These results suggest that vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by the brain PLC- and diacylglycerol lipase-dependent mechanisms in rats.
We identified the previously unknown structures of ribosylated imidazoleacetic acids in rat, bovine, and human tissues to be imidazole-4-acetic acid-ribotide (IAA-RP) and its metabolite, imidazole-4-acetic acid-riboside. We also found that IAA-RP has physicochemical properties similar to those of an unidentified substance(s) extracted from mammalian tissues that interacts with imidazol(in)e receptors (I-Rs). ["Imidazoline," by consensus (International Union of Pharmacology), includes imidazole, imidazoline, and related compounds. We demonstrate that the imidazole IAA-RP acts at I-Rs, and because few (if any) imidazolines exist in vivo, we have adopted the term "imidazol(in)e-Rs."] The latter regulate multiple functions in the CNS and periphery. We now show that IAA-RP (i) is present in brain and tissue extracts that exhibit I-R activity; (ii) is present in neurons of brainstem areas, including the rostroventrolateral medulla, a region where drugs active at I-Rs are known to modulate blood pressure; (iii) is present within synaptosome-enriched fractions of brain where its release is Ca(2+)-dependent, consistent with transmitter function; (iv) produces I-R-linked effects in vitro (e.g., arachidonic acid and insulin release) that are blocked by relevant antagonists; and (v) produces hypertension when microinjected into the rostroventrolateral medulla. Our data also suggest that IAA-RP may interact with a novel imidazol(in)e-like receptor at this site. We propose that IAA-RP is a neuroregulator acting via I-Rs.
A simple and efficient procedure has been developed to enzymatically dissociate aggregates of bovine adrenal chromaffin cells in suspension culture into viable, responsive single cells. For dissociation, the neutral protease dispase is added directly to the culture medium for a minimum of 3 h, followed by incubation of the cells in Hank's calcium-magnesium-free balanced salt solution at 37 degrees C with intermittent trituration to facilitate dispersion. This procedure generates a population of phase-bright single cells that are round in morphology, take up the dye neutral red, exclude the dye trypan blue and readily attach to tissue culture dishes coated with collagen, fibronectin or polylysine, thereby permitting applications that require plated-down conditions. When transferred to culture medium, the cells begin to reaggregate. By altering the length of time the cells are incubated in culture medium prior to attachment, the degree of reaggregation can be controlled to obtain plate-down profiles that consist of both isolated cells and cells in aggregates of varying sizes. Returning dissociated cells to suspension culture results in the reformation of large cell aggregates. Several measures of chromaffin cell function were indistinguishable for dissociated cells placed either in monolayer culture or suspension culture versus non-dissociated cells, implying that the dissociation procedure does not alter cellular responses or cause cellular damage.