Stabilized Magnesium/Perfluoropolyether Nanocomposite Films by Helium Droplet Cluster Assembly

The production of stable, pre‐reactive, nanocomposite mixtures of magnesium and a perfluoropolyether (PFPE) has been achieved through the application of helium droplet cluster assembly. The nanocomposite films presented in this work demonstrated clear thermal desorption features that indicate the formation of an MgF₂ passivation layer between unreacted magnesium cores and PFPE shells upon heating. Additional heating resulted in the later rupture of the MgF₂ layer and release of trapped magnesium. The passivation behavior occurred only after deposition with the input of thermal energy, demonstrating the ability of helium droplets to assemble and deposit clusters in a pre‐reactive state.     

Classroom peer acceptance, friendship, and victimization: distinct relational systems that contribute uniquely to children's school adjustment?

The proposition that relationships make differential (i.e., unique, redundant, contingent) contributions to adjustment was examined by investigating the linkages between children's participation in different types of peer relationships (i.e., friendship, peer acceptance, peer victimization) and their adjustment to school. Relationship measures were gathered for 5- to 6-year-old children (105 males, 95 females) twice during kindergarten (i.e., fall and spring) and were correlated with adjustment indicators at each time of assessment and used to predict changes in school adjustment over time. Examination of the relative associations between the relationship measures and children's adjustment revealed evidence of both unshared (i.e., unique) and shared (i.e., redundant) linkages, depending on the form of adjustment examined. These findings suggest that adjustment may be influenced by the diverse experiences (i.e., provisions) that children encounter in different forms of relationship, and that certain types of relationships may have greater or lesser adaptive significance depending on the adjustment outcome examined.     

Diffusion coefficients in the lateral intercellular spaces of Madin-Darby canine kidney cell epithelium determined with caged compounds

The diffusion coefficients of two caged fluorescent dyes were measured in free solution and in the lateral intercellular spaces (LIS) of cultured Madin-Darby canine kidney (MDCK) cells after photoactivation by illumination with a continuous or pulsed UV laser. Both quantitative video imaging and a new photometric method were utilized to determine the rates of diffusion of the caged fluorescent dyes: 8-((4,5-dimethoxy-2-nitrobenzyl)oxy)pyrene-1,3,6-trisulfonic acid (DMNB-HPTS) and (4,5-dimethoxy-2-nitrobenzyl) fluorescein dextran (10,000 MW) (DMNB-caged fluorescein dextran). The diffusion coefficients at 37 degrees C in free solution were 3.3 x 10(-6) cm2/s (HPTS) and 0.98 x 10(-6) cm2/s (10,000 MW dextran). Diffusion of HPTS within nominally linear stretches of the LIS of MDCK cells grown on glass coverslips was indistinguishable from that in free solution, whereas dextran showed a 1.6 +/- 0.5-fold reduction in diffusivity. Measurements of HPTS diffusion within the LIS of multicellular regions also exhibited a diffusivity comparable to the free solution value. The restriction to diffusion of the dextran within the LIS may be due to molecular hindrance.     

Preservation of global cardiac function in the rabbit following protracted ischemia/reperfusion using monophosphoryl lipid A (MLA)

Monophosphoryl lipid A (MLA), a derivative of the minimal substructure of lipopolysaccharide (lipid A) possesses immunomodulatory activity of the parent lipid A yet enjoys reduced toxicity. It has previously been reported that pretreatment with MLA reduces myocardial infarct size and stunning in dogs following ischemia and reperfusion. The aim of this study was to evaluate the ability of monophosphoryl lipid A (MLA) to preserve global cardiac function and peripheral hemodynamics in a rabbit model of prolonged regional ischemia (90 min), and reperfusion (6 h). An evaluation of potential mechanisms by which MLA may preserve cardiac function was also undertaken. Single dose pretreatment with MLA (35 micrograms/kg i.v.) 24 h prior to ischemia resulted in significant improvement in left ventricular developed pressure, dP/dt, rate-pressure product and mean arterial pressure during reperfusion (P < 0.05 v control). Although in this model of prolonged ischemia MLA pretreatment did not reduce infarct size (54.5 +/- 11.4% in control v 63.3 +/- 8.3% in MLA, P = N.S.), evaluation of myocardial adenylate and adenosine catabolite pools at the end of ischemia indicated a preservation of ATP and ADP and a decreased production of downstream adenosine catabolites including inosine, xanthine and uric acid. Adenosine kinase, but not 5'-nucleotidase (5'-NTase) or adenosine deaminase activity determined following reperfusion was 76% and 60% higher (P < 0.05) in non-risk and post-ischemic myocardium of MLA pretreated rabbits compared with controls. Although there was a trend toward lower tissue myeloperoxidase activity in post-ischemic myocardium from treated rabbits, the results were not significantly different from control animals. These results suggest that a 24-h pretreatment with MLA, without further treatment during ischemia or reperfusion was associated with: (1) preservation of global myocardial function during reperfusion; (2) preservation of myocardial high energy adenylates and reduced formation of adenosine catabolites during ischemia; (3) elevated myocardial adenosine kinase activity. Increased recycling of adenosine to phosphorylated nucleotides may result from MLA's affect on adenosine kinase, which could explain the drugs effect on adenylate and adenosine metabolite pools.