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Biomedical subjects

F R Butcher

Publications and source records attributed to F R Butcher.

At least 37 records · Page 2Linked to original sources
PubMed1979

Calmodulin resolution of multiple peaks of activity by preparative electrofocusing.

When the supernatant fractions from rat brain homogenates were subjected to preparative electrofocusing in a bed of Sephadex G75, several peaks of calmodulin were resolved. A minor peak representing free calmodulin migrated with a pI of 3.8 --4.4. Other peaks of calmodulin activity were observed with isoelectric points at pH 4.8, 5.2, 6.0 and 6.8. The peak of calmodulin activity at 5.2 co-migrated with phosphodiesterase activity which was stimulated 1.8-fold by calcium. A second peak of phosphodiesterase activity detected at pH 8.0 was stimulated 1.2-fold by calcium and occurred in an area where no calmodulin activity could be detected. If isoelectric focusing was done in the presence of 8 M urea only one peak of calmodulin activity was observed with a pI of 4.0--4.4. It is suggested that the multiple peaks of calmodulin resolved by electrofocusing represent calmodulin associated with various proteins which are subject to modulation by calmodulin and calcium.

Animals↗
PubMed1979

Tetracaine blocks the responses of isolated acinar cells from rat parotid to carbachol but not to substance P.

Carbachol and substance P stimulated 45Ca2+ flux changes, 86Rb+ efflux, and amylase secretion from acinar cells isolated from rat parotid. The local anesthetic tetracaine blocked all of these measured responses to carbachol, but none of the responses to substance P. Tetracaine must act at either the cholinergic receptor or at a subsequent transducing step in the cholinergic stimulus-response sequence. If tetracaine acts at one of the transducing steps between cholinergic receptor occupation and the physiological responses then the action of tetracaine must be at a locus in the cholinergic reaction scheme not shared by substance P, because tetracaine did not block any response of the parotid to substance P.

Amylases↗
PubMed1979

Early effect of progesterone on levels of cyclic adenosine 3':5'-monophosphate in Xenopus oocytes.

Progesterone treatment of Xenopus oocytes in vitro causes progression through meiotic cell division. The role of altered intracellular levels of cAMP on the initiation of meiotic cell division has been studied. Basal levels of cAMP averaged 1.5 pmol in oocytes from eight females, and exposure to progesterone caused a rapid drop in cAMP to about 40 to 60% of basal. Half-maximal decreases occurred within 15 to 60 s, and cAMP returned to near basal values by 20 min after progesterone. Theophylline inhibition of progesterone-induced cell division was characterized by a small increase in basal levels of cAMP and a reduced drop in cAMP due to the hormone. Cholera toxin, an activator of adenylate cyclase, was found to be a potent inhibitor of progesterone-induced meiosis, with half-maximal inhibition at 8 times 10(-12) M. In addition, the purified A subunit of cholera toxin was an effective inhibitor of progesterone action when microinjected into oocytes, with half-maximal inhibition occurring at an approximate internal concentration of 1 X 10(-7) M. Cholera toxin alone increased cAMP levels by 20%, but upon addition of progesterone, the level increased transiently to 200% of basal, indicating that the inhibition was due to elevated levels of cAMP. The results support a model in which the initiation of meiotic cell division is regulated by cAMP and protein phosphorylation.

Animals↗
PubMed1977

3':5'-cyclic AMP: independent induction of amino acid transport by epinephrine in primary cultures of adult rat liver cells.

Liver cells were obtained from adult rats by a collagenase perfusion technique and cultured as monolayers in serum-free media. Epinephrine and isoproterenol both induced large increases in intracellular adenosine 3':5'-monophosphate (cAMP) within 1-2 min whereas epinephrine (but not isoproterenol) induced 2- to 3-fold increases in the rate of alpha-aminoisobutyric acid transport within 2-4 hr after a 1 hr lag. Propranolol abolished the increase in cAMP elicited by epinephrine and isoproterenol, but did not block the induction of alpha-aminoisobutyric acid transport by epinephrine. In contrast, dihydroergotamine abolished and phentolamine diminished the induction of alpha-aminoisobutyric acid transport by epinephrine but did not decrease the stimulation of cAMP levels by epinephrine. Epinephrine dose response curves for cAMP and alpha-aminoisobutyric acid transport were similar. Once exposed to epinephrine, cells became refractory to further stimulation of cAMP levels by epinephrine.

Adrenergic alpha-Antagonists↗
PubMed1977

Effect of electrical stimulation of the autonomic nerves on the levels and synthesis of cyclic nucleotides in the rat salivary glands: relationship to enhanced growth.

Electrical stimulation of either the parasympathetic or the sympathetic nerve supply to the parotid and submaxillary glands increases the intracellular level of cyclic GMP and the rate of DNA synthesis and cell division while only sympathetic stimulation raises cyclic AMP levels. The periods of electrical stimulation inducing hyperplasia also raise the cyclic GMP concentration but there is no similar correlation with changes in cyclic AMP levels. However, the extent of hyperplasia induced by parasympathetic and sympathetic stimulation is not directly related to the size of the increase in cyclic GMP concentration that these treatments produce. Changes in cyclic AMP levels are reflected in altered in vitro adenylate cyclase activity. This activity is raised after 2 min sympathetic stimulation and markedly decreased with 30 min sympathetic or parasympathetic stimulation. Guanylate cyclase activity shows no such changes with nerve stimulation.

Adenylyl Cyclases↗
PubMed1976

Effect of substance P and eledoisin on K+ efflux, amylase release and cyclic nucleotide levels in slices of rat parotid gland.

The undecapeptides, substance P and eledoisin, caused a rapid, concentration-dependent increase in K+ efflux and amylase release from parotid tissue slices. The effects were not blocked by beta-adrenergic, alpha-adrenergic, or cholinergic antagonists. Incubation buffer calcium was required for stimulation of K efflux and amylase release. The action of the undecapepides was independent of any effects on parotid cyclic AMP or cyclic GMP levels. Since the actions of the undecapeptides were Ca2+ dependent and no effects on cyclic nucleotide levels were discerned it was concluded that Ca2+ plays a primary role in agonist regulation of K+ efflux from the parotid.

Amylases↗
PubMed1976

Induction of amino acid transport in primary cultures of adult rat liver parenchymal cells by insulin.

Amino acid transport was studied in primary cultures of parenchymal cells isolated from adult rat liver by a collagenase perfusion technique and maintained as a monolayer in a serum-free culture medium. Amino acid transport was assayed by measuring the uptake of the nonmetabolizable amino acid, alpha-aminoisobutyric acid. Rat liver parenchymal cells transported alpha-aminoisobutyric acid by an energy-dependent Na+-requiring system which displayed Michaelis-Menten kinetics. Addition of insulin to cultured rat liver parenchymal cells resulted in an increased influx of alpha-aminoisobutyric acid which was reflected in a higher initial rate of alpha-aminoisobutyric acid transport as well as an increased accumulation of alpha-aminoisobutyric acid at later time points. Cycloheximide effectively blocked the increase while results with actinomycin D were equivocal. Insulin at concentrations as low as 50 pM was effective in stimulating alpha-aminoisobutyric acid transport while the maximal response was observed at 80 nM.

Aminoisobutyric Acids↗
PubMed1976

Studies on the role of cyclic guanosine 3':5'-monophosphate and extracellular Ca2+ in the regulation of glycogenolysis in rat liver cells.

Catecholamines increased guanosine 3':5'-monophosphate (cyclic GMP) accumulation by isolated rat liver cells. The increases in cyclic GMP due to 1.5 muM epinephrine, isoproterenol, or phenylephrine were blocked by phenoxybenzamine but not by propranolol. The possibility that cyclic GMP is involved in the glycogenolytic action of catecholamines seems unlikely since cyclic GMP accumulation is also elevated by carbachol, insulin, A23187, and to a lesser extent by glucagon. Furthermore, carbachol had little effect on glycogenolysis while insulin actually inhibited hepatic glycogenolysis. The rise in cyclic GMP due to carbachol was abolished by atropine and that due to all agents was markedly reduced by the omission of extracellular calcium. However, the glycogenolytic action of glucagon and catecholamines was only slightly inhibited by the omission of calcium. The only agent which was unable to stimulate glycogenolysis in calcium-free buffer was the divalent cation ionophore A23187. There was a drop in ATP content of liver cells during incubation in calcium-free buffer which was accompanied by an inhibition of glucagon-activated adenosine 3':5'-monophosphate (cyclic AMP) accumulation. The presence of calcium inhibited the rise in adenylate cyclase activity of lysed rat liver cells due to glucagon or isoproterenol but not that due to fluoride. These results suggest that the stimulation by catecholamines and glucagon of glycogenolysis is not mediated through cyclic GMP nor does it depend on the presence of extracellular calcium. Cyclic GMP accumulation was increased in liver cells by agents which either inhibit, have little affect, or accelerate glycogenolysis. The significance of elevations of cyclic GMP in rat liver cells remains to be established.

Adenosine Triphosphate↗