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V J Hruby

Publications and source records attributed to V J Hruby.

At least 469 records · Page 26Linked to original sources
PubMed1975

Structure-function relationships in glucagon: properties of highly purified des-His-1-, monoiodo-, and (des-Asn-28, Thr-29)(homoserine lactone-27)-glucagon.

We have compared the ability of glucagon and three highly purified derivatives of the hormone to activate hepatic adenylate cyclase (an expression of biological activity of the hormone) and to compete with [125]glucagon for binding to sites specific for glucagon in hepatic plasma membranes. Relative to that of glucagon, biological activity and affinity of [des-Asn-28,Thr-29](homoserine lactone-27)-glucagon, prepared by CNBr treatment of glucagon, were reduced equally by 40- to 50-fold. By contrast, des-His-1-glucagon, prepared by an insoluble Edman reagent and highly purified (less than 0.5% contamination with native glucagon), displayed a 15-fold decrease in affinity but a 50-fold decrease in biological activity relative to that of the native hormone. At maximal stimulating concentrations, des-His-1-glucagon yielded 70% of the activity given by saturating concentrations of glucagon. Thus, des-His-1-glucagon can be classified as a partial weak agonist. Highly purified monoiodoglucagon and native glucagon displayed identical biological activity and affinity for the binding sites. Our findings suggest that the hydrophilic residues at the terminus of the carboxy region of glucagon are involved in the process of recognition at the glucagon receptor but do not participate in the sequence of events leading to activation of adenylate cyclase. The amino-terminal histidyl residue in glucagon plays an important but not obligatory role in the expression of hormone action and contributes to a significant extent in the recognition process.

Adenylyl Cyclases↗
PubMed1974

Biogenic amines and control of melanophore stimulating hormone release.

Release of melanophore stimulating hormone (MSH) from the vertebrate pars intermedia is under inhibitory control by the hypothalamus. Removal of the rat pituitary or the neurointermediate lobe of the frog (Rana pipiens) to in vitro incubation medium results in rapid uninhibited release of MSH. This secretion is inhibited by norepinephrine, epinephrine, phenylephrine, and dopamine, and the inhibition is antagonized by alpha-adrenergic receptor blocking agents. Isoproterenol stimulation of MSH secretion from isolated glands is blocked by pro-pranolol, a beta-adrenergic receptor antagonist. These results implicate dopaminergic or classical alpha-adrenergic receptors (or both) in inhibition of MSH release by catecholamines, and implicate beta-adrenergic receptors in stimulation of MSH release by the bioamines.

Animals↗
PubMed1973

300-MHz nuclear magnetic resonance study of oxytocin aqueous solution: conformational implications.

The 300-MHz nuclear magnetic resonance spectrum of the peptide hormone, oxytocin, in water, was obtained. Extensive nuclear magnetic resonance spindecoupling experiments, including those involving irradiation of the alpha-proton resonance under the water peak, studies using partially deuterated hormone derivatives, and nuclear magnetic resonance studies of some precursor peptides to oxytocin, permitted us to assign most of the proton resonance of the hormone unambiguously. The JNalpha values and temperature dependence of the chemical shift of the peptide amide and carboxamide protons of oxytocin were also obtained. These studies indicate that, in aqueous solution, oxytocin is a flexible molecule possessing several different conformations. Corresponding studies of [4-leucine]oxytocin were also made, with similar results and conclusions.

Magnetic Resonance Spectroscopy↗