Kir2.2 inward rectifier potassium channels are inhibited by an endogenous factor in Xenopus oocytes independently from the action of a mitochondrial uncoupler.

We previously showed inhibition of Kir2 inward rectifier K+ channels expressed in Xenopus oocytes by the mitochondrial agents carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and sodium azide. Mutagenesis studies suggested that FCCP may act via phosphatidylinositol 4,5-bisphosphate (PIP2) depletion. This mechanism could be reversible in intact cells but not in excised membrane patches which preclude PIP2 regeneration. This prediction was tested by investigating the reversibility of the inhibition of Kir2.2 by FCCP in intact cells and excised patches. We also investigated the effect of FCCP on Kir2.2 expressed in human embryonic kidney (HEK) cells. Kir2.2 current, expressed in Xenopus oocytes, increased in inside-out patches from FCCP-treated and untreated oocytes. The fraction of total current that increased was 0.79?±?0.05 in control and 0.89?±?0.03 in 10 µM FCCP-treated (P?>?.05). Following “run-up,” Kir2.2 current was re-inhibited by “cramming” inside-out patches into oocytes. Therefore, run-up reflected not reversal of inhibition by FCCP, but washout of an endogenous inhibitor. Kir2.2 current recovered in intact oocytes within 26.5 h of FCCP removal. Injection of oocytes with 0.1 U apyrase completely depleted ATP (P?<?.001) but did not inhibit Kir2.2 and inhibited Kir2.1 by 35% (P?<?.05). FCCP only partially reduced [ATP] (P?<?.001), despite inhibiting Kir2.2 by 75% (P?<?.01) but not Kir2.1. FCCP inhibited Kir2.2 expressed in HEK cells. The recovery of Kir2.2 from inhibition by FCCP requires intracellular components, but direct depletion of ATP does not reproduce the differential inhibitory effect of FCCP. Inhibition of Kir2.2 by FCCP is not unique to Xenopus oocytes. J. Cell. Physiol. 219: 8–13, 2009. © 2008 Wiley-Liss, Inc.

Evidence That Interspecies Polymorphism in the Human and Rat Cholecystokinin Receptor-2 Affects Structure of the Binding Site for the Endogenous Agonist Cholecystokinin

The cholecystokinin (CCK) receptor-2 exerts very important central and peripheral functions by binding the neuropeptides cholecystokinin or gastrin. Because this receptor is a potential therapeutic target, great interest has been devoted to the identification of efficient antagonists. However, interspecies genetic polymorphism that does not alter cholecystokinin-induced signaling was shown to markedly affect activity of synthetic ligands. In this context, precise structural study of the agonist binding site on the human cholecystokinin receptor-2 is a prerequisite to elucidating the molecular basis for its activation and to optimizing properties of synthetic ligands. In this study, using site-directed mutagenesis and molecular modeling, we delineated the binding site for CCK on the human cholecystokinin receptor-2 by mutating amino acids corresponding to that of the rat homolog. By doing so, we demonstrated that, although resembling that of rat homolog, the human cholecystokinin receptor-2 binding site also displays important distinct structural features that were demonstrated by susceptibility to several point mutations (F120A, Y189A, H207A). Furthermore, docking of CCK in the human and rat cholecystokinin receptor-2, followed by dynamic simulations, allowed us to propose a plausible structural explanation of the experimentally observed difference between rat and human cholecystokinin-2 receptors.

Endogenous Two-Sided Markets with Repeated Transactions

We consider homogeneous two-sided markets, in which connected buyer-seller pairs bargain and trade repeatedly. In this infinite market game with exogenous matching probabilities and a common discount factor, we prove the existence of equilibria in stationary strategies. The equilibrium payoffs are given implicitly as a solution to a system of linear equations. Then, we endogenize the matching mechanism in a link formation stage that precedes the market game. When agents are sufficiently patient and link costs are low, we provide an algorithm to construct minimally connected networks that are pairwise stable with respect to the expected payoffs in the trading stage. The constructed networks are essentially efficient and consist of components with a constant buyer-seller ratio. The latter ratio increases (decreases) for a buyer (seller) that deletes one of her links in a pairwise stable component.

ADP ribose is an endogenous ligand for the purinergic P2Y1 receptor

The mechanism by which extracellular ADP ribose (ADPr) increases intracellular free Ca2+ concentration ([Ca2+](i)) remains unknown. We measured [Ca2+](i) changes in fura-2 loaded rat insulinoma INS-1E cells, and in primary beta-cells from rat and human. A phosphonate analogue of ADPr (PADPr) and 8-Bromo-ADPr (8Br-ADPr) were synthesized. ADPr increased [Ca2+](i) in the form of a peak followed by a plateau dependent on extracellular Ca2+. NAD(+), cADPr, PADPr, 8Br-ADPr or breakdown products of ADPr did not increase [Ca2+](i). The ADPr-induced [Ca2+](i) increase was not affected by inhibitors of TRPM2, but was abolished by thapsigargin and inhibited when phospholipase C and IP3 receptors were inhibited. MRS 2179 and MRS 2279, specific inhibitors of the purinergic receptor P2Y1, completely blocked the ADPrinduced [Ca2+](i) increase. ADPr increased [Ca2+](i) in transfected human astrocytoma cells (1321N1) that express human P2Y1 receptors, but not in untransfected astrocytoma cells. We conclude that ADPr is a specific agonist of P2Y1 receptors. (c) 2010 Elsevier Ireland Ltd. All rights reserved.

Diagnosis and treatment of endogenous fungal endophthalmitis

Endogenous infectious endophthalmitis is rare, and a primary source is usually identified. A case of primary fungal endophthalmitis successfully treated with vitrectomy and systemic antifungal therapy is presented. The aetiology and treatment of the condition are discussed.

Reasons for the variability in growth hormone (GH) responses to GHRH challenge:the endogenous hypothalamic-somatotroph rhythm (HSR)

The aims of this study were: (1) to test the possibility that pre-GHRH plasma GH values could reflect the functional status of the hypothalamic-somatotroph rhythm (HSR) at testing, and thus explain if it is responsible for the marked variability in GH responsiveness to GHRH challenge and (2) to see if exogenous somatostatin (SS) could disrupt this endogenous HSR and thus make the GH responses homogeneous. (1) Two to 14 GHRH acute tests (GRF-29, 1 µg/kg, i.v. bolus) were performed in 12 normal men and 10 normal women at the same time (0830 h) at random intervals (2 to 60 days). Blood samples to measure plasma GH were drawn at 15 min intervals before and after GHRH challenge. Given that the increments in pre-GHRH plasma GH values (I = value at 0 min minus value at -15 min) were highly correlated with either GHRH-elicited peaks of GH (men, r = 0.81; women, r = 0.69; P

ivlewbel: Uses heteroscedasticity to estimate mismeasured and endogenous regressor models

GMM estimation of triangular systems using heteroscedasticity based instrumental variables as in Lewbel (2012).

Market Economies with an Endogenous Social Division of Labour

This paper considers a general equilibrium theory of a competitive market economy with an endogenous social division of labour. The theory is founded on the notion of a “consumer- producer”, who consumes as well as produces commodities. In this approach, the emergence of a meaningful social division of labour is guided by the property of increasing returns to specialisation and the process of trade among fully specialised individuals. All decisions of individual consumer-producers are based on a set of perfectly competitive market prices of the commodities in the economy.
We show that a perfectly competitive price mechanism supports a dichotomy of production and consumption at the level of the individual consumer-producer. In this context we show existence of competitive equilibria and characterise these equilibria under increasing returns to specialisation: Under certain well-described conditions, markets are equilibrated through adjustment of the social division of labour; therefore prices are fully determined by the supply side of the economy.