Gail Galasko

Studies on the insulin mediator. II. Separation of two antagonistic biologically active materials from fraction II.

SUMMARY Insulin treatment significantly altered the elution profile of deproteinized muscle extracts chromato-graphed on Sephadex G-25 columns, particularly in fraction II, which contains the insulin mediator. Further purification of fraction II by high-voltage paper electrophoresis at pH 1.9 and 3.5 resulted in two active fractions. Fraction 1 → 4 stimulated the cyclic AMP-dependent protein kinase and inhibited glycogen synthase phosphoprotein phosphatase, and may be a novel substance. Fractions 1 → > 6 and 3 → 6 inhibited the cyclic AMP-dependent protein kinase and stimulated glycogen synthase phosphatase. It is proposed that the insulin mediator is present in fractions 1 → 6 and 3 → 6.

Insulin Mediators and Their Control of Metabolism through Protein Phosphorylation

Publisher Summary This chapter presents insulin mediators and their control of metabolism through protein phosphorylation. Insulin initiates three types of actions: (1)a rapid set of actions at the cell membrane which increases hexose transport, ion transport, and the transport of other monomeric metabolites including amino acids, fatty acids, and nucleosides, (2) a slower direction of metabolism into an anabolic mode both by enhancing anabolic pathways and by decreasing catabolic pathways including lipolysis, proteolysis, glycogenolysis, and gluconeogenesis, and (3) a still slower stimulation of cell growth. Two general biochemical mechanisms can be devised to understand the interaction of the insulin molecule with its receptor. In the first, there is a separation of the binding domain from the biological activity domain; in the second, there is no separation and these functions coexist in the same portions of the molecule.

Chemical mechanism of insulin action via proteolytic formation of mediator peptides

In 1972 (1) we proposed a novel chemical mediator of insulin action. We next announced the discovery of an insulin-generated substance which inhibited the cyclic AMP-dependent protein kinase in 1976 (2). In 1979 (3) we demonstrated the existence of a chemical mediator of insulin action which had intracellular effects: it Specifically inhibited cyclic AMP-dependent protein kinase, stimulated glycogen synthase phosphoprotein phosphatase, and, in collaboration with Jarett and Seals (4), activated mitochondrial pyruvate dehydrogenase. This latter effect has been shown to result from a stimulation of the pyruvate dehydrogenase phosphatase (5). In our 1979 paper we identified insulin mediator as a peptide or peptide-like substance with a molecular weight of I000-1500 daltons. In 1980 (6) we announced the separation of two peptides in the mediator fraction which had opposing effects on phosphorylation, with the mediator promoting dephosphorylation and the additional peptide promoting phosphorylation. In this paper we will consider further the nature of insulin mediator, propose its site of origin, suggest mechanisms for its generation by limited proteolysis and rapid intracellular internalization, and discuss its possible involvement in the pleotypic actions of insulin, including cellular growth promotion. The effects of trypsin and other proteolytic enzymes, as well as proteolytic enzyme inhibitors, have become extremely important tools for analyzing insulin action (7, 8). Proteolytic enzymes have been shown to act in intact rat adipocytes via mediator formation (8, 9) (see Tables 1,2). In isolated adipocyte cell membranes proteolytic enzymes (7), lectins, and anti-insulin receptor antibodies (10) also enhance mediator formation. This constellation of active agents suggests that aggregation or cross linking of insulin receptors, especially by the latter two classes of agents, initiates the proteolytic events leading to mediator formation.

Optical rotatory dispersion of carotenoids

The o.r.d. curves of ca. 40 carotenoids have been measured, chiefly in dioxan, over the range 400–200 nm. The chromophore in all cases is a conjugated polyene system which is perturbed by one or two chiral end-groups. The curves are analysed in terms of the simple additivity of the effects of end-groups, and the absolute configurations of several compounds have been provisionally assigned.

The caffeine contents of non alcoholic beverages

The caffeine content of a number of non-alcoholic beverages was determined using HPLC. It was found that Diet Coke had a greater caffeine content than Coke (4.15 compared with 3.13 mg/fl oz), Tab is virtually caffeine free, and Lucozade, sold as a tonic, contains more caffeine than any of the other carbonated beverages tested (5.17 mg/fl oz). The pure instant coffee tested contained much more caffeine than the coffee/chicory mixtures (12.61 compared with 3.18 mg/fl oz). The caffeine content of Ceylon tea blends increases with the time the tea is allowed to draw (from about 8 mg/fl oz after 1 min to about 12 mg/fl oz after 20 min). Tea that has been allowed to draw for 20 min has a caffeine content similar to that of pure coffee.

Carotenoids and related compounds. Part XXII. Allenic carotenoids in sea urchins

Three pigments from sea urchins have been identified as fucoxanthin (II), fucoxanthinol (I), and a novel allenic ketone (V), ‘paracentrone.’

Carotenoids and related compounds. Part XXI. Structure of neoxanthin (foliaxanthin)

Neoxanthin, a universal pigment in green leaves, has been shown to have the allenic structure 5,6-epoxy-3,3′,5′-trihydroxy-6′,7′-didehydro-5,6,5′,6′-tetrahydro-β-carotene (IVa).Samples of lutein (XI), and of zeaxanthin (III), from various natural sources have been compared and their structures have been confirmed.Attempts to isolate taraxanthin, which Curl has suggested may be identical with neoxanthin, yielded the well known epoxide (XIV) of lutein but no carotenoid possessing the O4 formulation proposed for taraxanthin.

Insulin action in intact mouse diaphragm II.

SummaryThe incubation of intact mouse diaphragms with insulin caused a dose and time dependent increase in the independent activity of glycogen synthase in tissue extracts. 2-deoxyglucose (2–10 mm) alone markedly stimulated the conversion of glycogen synthase to the independent activity under conditions in which tissue ATP concentrations were not affected. The incubation of diaphragms with both insulin and 2-deoxyglucose resulted in a greater than additive effect. Insulin stimulated the uptake of 2-deoxyglucose into mouse diaphragms, accumulating as 2-deoxyglucose-6-phosphate. The accumulation of 2-deoxyglucose-6-phosphate correlated well with the increase in the independent activity of glycogen synthase and with the activation of glycogen synthase phosphatase in tissue extracts. The uptake of 3-0-methyl glucose was also markedly stimulated by insulin, without affecting the activity of glycogen synthase. Both glucose-6-phosphate and 2-deoxyglucose-6-phosphate stimulated the activation of endogenous glycogen synthase phosphatase activity in muscle homogenates. We conclude that insulin, in addition to its effects in the absence of exogenous sugars, increases the independent activity of glycogen synthase through increased sugar transport resulting in increased concentrations of sugar-phosphates which promote the activity of glycogen synthase phosphatase.

Locally released small (non‐protein) ninhydrin‐reacting molecules underlie developmental differences of cultured medullary versus spinal dorsal horn neurons

J. Neurochem. (2012) 122, 605–618.

Cushing's Disease

Cushings syndrome is an endocrine disease characterized by prolonged exposure to high levels of glucocorticosteroids. Cushings syndrome may be due to the systemic administration of exogenous glucocorticosteroids (the most common cause), overproduction of cortisol by the …