Mind the gap: investigating toddlers' sensitivity to contact relations in predictive events

Toddlers readily learn predictive relations between events (e.g., that event A predicts event B). However, they intervene on A to try to cause B only in a few contexts: When a dispositional agent initiates the event or when the event is described with causal language. The current studies look at whether toddlers' failures are due merely to the difficulty of initiating interventions or to more general constraints on the kinds of events they represent as causal. Toddlers saw a block slide towards a base, but an occluder prevented them from seeing whether the block contacted the base; after the block disappeared behind the occluder, a toy connected to the base did or did not activate. We hypothesized that if toddlers construed the events as causal, they would be sensitive to the contact relations between the participants in the predictive event. In Experiment 1, the block either moved spontaneously (no dispositional agent) or emerged already in motion (a dispositional agent was potentially present). Toddlers were sensitive to the contact relations only when a dispositional agent was potentially present. Experiment 2 confirmed that toddlers inferred a hidden agent was present when the block emerged in motion. In Experiment 3, the block moved spontaneously, but the events were described either with non-causal ("here's my block") or causal ("the block can make it go") language. Toddlers were sensitive to the contact relations only when given causal language. These findings suggest that dispositional agency and causal language facilitate toddlers' ability to represent causal relationships.     

Dose-dependent effects of cholecystokinin-8 on antropyloroduodenal motility, gastrointestinal hormones, appetite, and energy intake in healthy men

CCK mediates the effects of nutrients on gastrointestinal motility and appetite. Intravenously administered CCK stimulates pyloric pressures, increases plasma PYY, and suppresses ghrelin, all of which may be important in the regulation of appetite and energy intake. The dose-related effects of exogenous CCK on gastrointestinal motility and gut hormone release, and the relationships between these effects and those on energy intake, are uncertain. We hypothesized that 1) intravenous CCK-8 would have dose-dependent effects on antropyloroduodenal (APD) pressures, plasma PYY and ghrelin concentrations, appetite, and energy intake and 2) the suppression of energy intake by CCK-8 would be related to the stimulation of pyloric motility. Ten healthy men (age 26 +/- 2 yr) were studied on four separate occasions in double-blind, randomized fashion. APD pressures, plasma PYY and ghrelin, and appetite were measured during 120-min intravenous infusions of 1) saline ("control") or 2) CCK-8 at 0.33 ("CCK0.33"), 3) 0.66 ("CCK0.66"), or 4) 2.0 ("CCK2.0") ng.kg(-1).min(-1). After 90 min, energy intake at a buffet meal was quantified. CCK-8 dose-dependently stimulated phasic and tonic pyloric pressures and plasma PYY concentrations (r > 0.70, P < 0.05) and reduced desire to eat and energy intake (r > -0.60, P < 0.05) without inducing nausea. There were relationships between basal pyloric pressure and isolated pyloric pressure waves (IPPW) with plasma CCK (r > 0.50, P < 0.01) and between energy intake with IPPW (r = -0.70, P < 0.05). Therefore, our study demonstrates that exogenous CCK-8 has dose-related effects on APD motility, plasma PYY, desire to eat, and energy intake and suggests that the suppression of energy intake is related to the stimulation of IPPW.     

Syndecan-4-mediated signalling

The paradigm of cell surface proteoglycan function has been centered on the role of the ectoplasmic heparan sulfate (HS) chains as acceptors of a wide array of ligands, including extracellular matrix (ECM) proteins and soluble growth factors. Within this picture, the core proteins were assigned only a passive role of carrying the glycosaminoglycan (GAG) chains without direct participation in mediating outside-in signals generated by the binding of the above ligands. It appears now, however, that, side by side with the integrins and the tyrosine kinase receptors, the core proteins of the syndecan family of transmembrane proteoglycans are involved in signaling. The highly conserved tails of all the four members of the syndecan family contain a carboxy-terminal PDZ (Postsynaptic density 95, Disk large, Zona occludens-1)-binding motif, capable of forming multimolecular complexes through the binding of PDZ adaptor proteins. The cytoplasmic tail of the ubiquitously expressed syndecan-4 is distinct from the other syndecans in its capacity to bind phosphatidylinositol 4, 5-bisphosphate (PIP₂) and to activate protein kinase C (PKC) . These properties may confer on syndecan-4 specific and unique signaling functions.     

A simplified method for air drill irrigation

A modified No. 20 Foley catheter provides a simple, inexpensive method for intraoperative air drill burr irrigation.     

Response of Microorganisms to an Accidental Gasoline Spillage in an Arctic Freshwater Ecosystem

The response of microorganisms to an accidental spillage of 55,000 gallons of leaded gasoline into an Arctic freshwater lake was studied. Shifts in microbial populations were detected after the spillage, reflecting the migration pattern of the gasoline, enrichment for hydrocarbon utilizers, and selection for leaded-gasoline-tolerant microorganisms. Ratios of gasoline-tolerant/utilizing heterotrophs to “total” heterotrophs were found to be a sensitive indicator of the degree of hydrocarbon contamination. Respiration rates were elevated in the highly contaminated area, but did not reflect differences between moderately and lightly contaminated areas. Hydrocarbon biodegradation potential experiments showed that indigenous microorganisms could extensively convert hydrocarbons to CO₂. In situ measurement of gasoline degradation showed that, if untreated, sediment samples retained significant amounts of gasoline hydrocarbons including “volatile components” at the time the lake froze for the winter. Nutrient addition and bacterial inoculation resulted in enhanced biodegradative losses, significantly reducing the amount of residual hydrocarbons. Enhanced biodegradation, however, resulted in the appearance of compounds not detected in the gasoline. Since the contaminated lake serves as a drinking water supply, treatment to enhance microbial removal of much of the remaining gasoline still may be advisable.     

Differential binding of the fluorescent probe 8-anilinonaphthalene-2-sulfonic acid to rhodanese catalytic intermediates

Studies have been performed to quantitate the binding of the fluorescent probe 8-anilinonaphthalene-2-sulfonic acid (2,8-ANS) to catalytic intermediates of the enzyme rhodanese: the sulfur-substituted form (ES) and the sulfur-free form (E). The molecular 2,8-ANS has not been extensively used for protein studies, and some characterization is presented to demonstrate its usefulness as a probe for apolar binding sites. The molecule 2,8-ANS binds to at least two classes of sites on rhodanese. One class (class 1) is present in the ES form and has a Kd of 1.7 mM. The E form of rhodanese appears to have a second class of sites (class 2) in addition to the class 1 sites. Two independent fluorometric methods of analyzing the class 2 binding of 2,8-ANS to the E form gave an average value for Kd congruent to 179 microM. These fluorometric titrations, together with a Job plot, clearly indicate that 2,8-ANS binds to more than one site on the E form of rhodanese. The apparent apolarity is slightly higher for class 2 sites than for the class 1 sites, but both give Z factors of greater than 85. The substrate thiosulfate is able to displace the probe that is bound to the class 2 sites on the E form of the enzyme. Further, 2,8-ANS is found to be a competitive inhibitor of the catalyzed reaction with an apparent Kd of 170 microM. Circular dichroism measurements detect no significant changes in the average conformation of rhodanese that can be ascribed to the presence of 2,8-ANS.(ABSTRACT TRUNCATED AT 250 WORDS)