Just-in-time connectivity for large spiking networks

The scale of large neuronal network simulations is memory limited due to the need to store connectivity information: connectivity storage grows as the square of neuron number up to anatomically relevant limits. Using the NEURON simulator as a discrete-event simulator (no integration), we explored the consequences of avoiding the space costs of connectivity through regenerating connectivity parameters when needed: just in time after a presynaptic cell fires. We explored various strategies for automated generation of one or more of the basic static connectivity parameters: delays, postsynaptic cell identities, and weights, as well as run-time connectivity state: the event queue. Comparison of the JitCon implementation to NEURON's standard NetCon connectivity method showed substantial space savings, with associated run-time penalty. Although JitCon saved space by eliminating connectivity parameters, larger simulations were still memory limited due to growth of the synaptic event queue. We therefore designed a JitEvent algorithm that added items to the queue only when required: instead of alerting multiple postsynaptic cells, a spiking presynaptic cell posted a callback event at the shortest synaptic delay time. At the time of the callback, this same presynaptic cell directly notified the first postsynaptic cell and generated another self-callback for the next delay time. The JitEvent implementation yielded substantial additional time and space savings. We conclude that just-in-time strategies are necessary for very large network simulations but that a variety of alternative strategies should be considered whose optimality will depend on the characteristics of the simulation to be run.     

Ca2+ in the dense tubules: a model of platelet Ca2+ load

In this work, we explored the relationship between the freely exchangeable Ca2+ (FECa2+) in the dense tubules (DT) and the sarco(endo)plasmic reticulum (SER) Ca2+-ATPase (SERCA) in circulating human platelets and examined the relationship between blood pressure (BP) and these platelet parameters. Studying platelets from 32 healthy men, we showed that the maximal reaction velocity (Vmax) of the SERCA significantly correlated with FECa2+ in the DT and with the protein expressions of SERCA 2 and 3. BP positively correlated with both the Vmax of the SERCA (r=.462, P=.010) and the FECa2+ sequestered in the DT (r=.492, P=.005). The relationships between these platelet Ca2+ parameters and BP were in part confounded by increased levels of serum triglycerides and diminished HDL cholesterol with a higher BP. No correlation was observed between the resting cytosolic Ca2+ and BP. Collectively, these findings indicate that (1) an increase in the cellular Ca2+ load in platelets is expressed by a higher activity of the SERCA and an increase in the expressions of SERCA 2 and 3 proteins, coupled with an increase in the FECa2+ in the DT, and (2) a higher BP is associated with an increase in platelet Ca2+ load in human beings, expressed by a rise in the FECa2+ in the DT and the upregulation of SERCA activity.     

Child and parent effects in boys' conduct disorder: A reinterpretation.

The importance of parent and child influences on the development of conduct disorder (CD) in boys is evaluated. The research approaches reviewed include studies of interactions between unrelated mothers and children, reaction to punishment, autonomic reactivity, biochemical factors, and drug treatment and longitudinal studies of delinquency. Evidence from this research and from research on parental influences, reviewed in detail elsewhere, is interpreted as demonstrating the primacy of the child's own contribution to CD within a reciprocal parent–child interactive system, thus corroborating control systems theory (R. Q. Bell, 1977). Demonstrated parental influences are interpreted as actions that are elicited by or that exacerbate the child's tendencies and that may represent genetic continuities. The heuristic utility and consequences of this model are outlined. It is emphasized that child effects do not imply immutability of behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Renal cortical blood flow distribution in obstructive nephropathy in rats

To examine the role of intrarenal hemodynamics in in obstructive nephropathy, we determined cortical blood flow distribution (CBFD) in rats with bilateral ureteral occlusion (BUO) and unilateral ureteral occlusion (UUO) during and after release of obstruction. Prior to release of obstruction of 24 hours' duration, we found that outer cortical perfusion decreased by 20+/-5% in both BUO and UUO rats. Furthermore, one hour after release of BUO, there was rapid normalization of CBFD associated with a modest return of glomerular filtration rate (GFR), an almost complete return of renal blood flow (RBF), and a marked postobstructive diuresis. In contrast, after release of UUO, we observed that outer cortical perfusion remained decreased by 21+/-31%, both GFR and RBF remained markedly depressed, and no diuresis occurred. These data demonstrate (1) marked ischemia of the outer cortex in both BUO and UUO during obstruction, (2) a rapid return of CBFD to a normal pattern after release of BUO, but (3) persistent outer cortical ischemia following release of UUO.     

Correlates of compliance and the rudiments of conscience in two-year-old boys.

Studied compliance in the context of parent–child interaction in 90 2?-yr-old boys by means of naturalistic home observation and interviews. 46 Ss were twins (17 monozygotic and 29 dizygotic). Compliance criteria, including a rating for internalized standards, correlated positively with independence and maturity of speech. Multiple regression analyses of the criteria with parent variables showed that consistently enforced discipline, encouragement of independence, psychological rewards, and maternal play made important contributions to the positive prediction of compliance, whereas physical punishment and use of material rewards were negatively associated with it. A reciprocity system existed between child and parent compliance. Findings underline the importance of cognitive structure and positive social reinforcement as well as of a parental authority role for moral development. (French summary) (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning electron microscope localization of zinc granules in the oyster ostrea angasi by backscattered electron imaging

A method for rapid localization of the zinc granules in oyster tissue using SEM has been developed. The results are discussed in terms of electron backscattering coefficients η for tissue, carbon support and embedding medium. Also, the application of the presented method for marine environment pollution detection and monitoring is recommended.