Interpretation of small-angle scattering of block copolymer/nanoparticle blends using random phase approximation.

The scattering characteristics of block copolymer (BCP)/nanoparticle (NP) blend systems are analyzed in the weak segregation limit using random phase approximation (RPA). The scattering function is established and shown to adequately capture reported data of small-angle neutron scattering in poly(norbornene-b -d-norbornene dicarboxylic acid)/ Fe3O4 nanoparticle blend systems over the entire small-angle range for a variety of BCP and NP compositions. Besides predicting the relevant length scales of microstructure formation, the RPA analysis reveals the increase of segregation in the BCP system upon NP addition. The insight into the thermodynamics of microstructure formation in BCP/NP blend systems that is provided by the RPA analysis should be a valuable asset for the design of BCP-based microstructured hybrid materials with predetermined structure and properties.

Use of bed rest and head-down tilt to simulate spaceflight-induce immune system changes.

Bed rest, both with and without head-down tilt, has been extensively used as an earth-bound analog to study physiologic effects mimicking those occurring in weightlessness during spaceflight. We have been able to show in six subjects that 4 weeks of head-down tilt bed rest induces a significant decrease in interleukin-2 secretion by PHA-stimulated T lymphocytes. Another study, lasting 113 days, with two subjects showed a decreased interleukin-2 receptor expression in PHA-stimulated peripheral blood mononuclear cells but a decreased interleukin-2 production in one subject only. Under the same conditions, interleukin-1 production was largely increased in both subjects. Several other immune parameters were also analyzed. Increased interleukin-1 production could contribute to bone mineral loss encountered during bed rest and decreased interleukin-2 secretion could play a role in the appearance of infectious diseases often observed during bed red.

Chronic methanesulfonyl fluoride enhances one-trial per day reward learning in aged rats.

Aged (24-month-old) rats were treated chronically with methanesulfonyl fluoride (MSF), an acetylcholinesterase (AChE) inhibitor with selectivity for central nervous system AChE, or with injection vehicle alone. Twelve 0.22 mg/kg IP injections were given over 4 weeks. MSF rats showed significantly greater speed and accuracy on a 1 trial/day discriminative reward learning task. The chronic MSF treatment resulted in a 56% decrease in brain AChE activity but no discernable locomotor side effects and no liver damage as indicated by aspartate transferase activity.

Cerebrospinal fluid from morphine-dependent rats precipitates opiate abstinence syndrome.

Cerebrospinal fluid (CSF) was withdrawn from opiate-dependent rats following six hours of abstinence. It was infused into the third ventricle of opiate-dependent rats, precipitating immediate abstinence signs. The effect was similar to that of infusing the opiate antagonist naloxone, suggesting that opiate-dependent organisms may secrete an endogenous opiate antagonist substance. CSF withdrawn from non-dependent rats failed to precipitate an abstinence syndrome in morphine-dependent recipients. Conversely, CSF withdrawn from opiate-dependent rats following six hours of abstinence failed to precipitate an abstinence syndrome in non-dependent recipients. The active factor in the CSF is probably a peptide since it is filterable through a 10,000 MW filter and its activity is destroyed by three different proteolytic enzymes.