Tumor-promoting phorbol esters stimulate hematopoietic colony formation in vitro

Tumor-promoting phorbol esters stimulated mouse bone marrow cells to form myeloid colonies in agar cultures without added colony-stimulating factors. The colony-stimulating ability of various phorbol esters correlated well with their ability to promote skin tumors in vivo. These results suggest that phorbol esters mimic the action of specific colony-stimulating factors that regulate growth.     

The illusion of control: industrialized agriculture,nature, and food safety

I explore the role of nature in the agrifood system and how attempts to fit food production into a large-scale manufacturing model has lead to widespread outbreaks of food borne illness. I illustrate how industrial processing of leafy greens is related to the outbreak of E. coli 0157:H7 associated with spinach in the fall of 2006. I also use this example to show how industry attempts to create the illusion of control while failing to address weaknesses in current processing systems. The leafy greens industry has focused efforts on sterilizing the growing environment and adopting new technologies, while neglecting to change the concentrated structure of processing systems. Repeated breakdowns in these systems illustrate a widening fault line between attempted and failed control of nature in industrial food production.

Reversal of neurological defects in a mouse model of Rett syndrome

Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.     

A bond-fluctuation mechanism for stochastic switching in wired molecules

Stochastic on-off conductivity switching observed in phenylene-ethynylene oligomers has been explained in terms of changes in ring conformations, or electron localization, or both. We report the observation of stochastic on-off switching in the simplest of wired molecules: octanedithiol, decanedithiol, and dodecanedithiol bonded on an Au(111) surface. Stochastic switching was observed even when a top gold contact was pressed on by a conducting atomic force microscope tip at constant force. The rate of switching increased substantially at 60 degrees C, a temperature at which these films are commonly annealed. Because such switching in alkanethiols is unlikely to be caused by internal molecular electronic changes and cannot be fully accounted for by breaking of the top contact, we argue that the cause is the well-known mobility of molecules tethered to gold via a thiol linkage.     

Alarm, defense, and construction behavior relationships in termites (Isoptera)

Evidence indicates that building behavior in termites is a direct consequence of low-level alarm stimuli and that its immediate function is defense. As in other forms of termite defense behavior, recruitment of nymphs and workers is accomplished by trail laying in conjuction with transmission of the alarm. The number recruited is related to the intensity of the input stimulus. Primary construction ceases when the original causal stimulus is eliminated by the effects of the actual building.     

Magnetospheric effects of power line radiation

Radiation from electrical power lines leaks into the magnetosphere and stimulates strong very-low-frequency wave activity out to many earth radii. Observations in Antarctica show that wave activity induced by power lines tends to occur during the daytime when power consumption is high in the source region in eastern Canada. The wave frequency ranges from 1 to 8 kilohertz. This man-made wave activity may have significant effects on energetic electrons trapped in the earth's radiation belts.     

Dependence of EPSP efficacy on synapse location in neocortical pyramidal neurons

Neurons receive thousands of synaptic inputs throughout elaborate dendritic trees. Here we determine the somatic impact of excitatory postsynaptic potentials (EPSPs) generated at known dendritic sites in neocortical pyramidal neurons. As inputs became more distal, somatic EPSP amplitude decreased, whereas use-dependent depression increased. Despite marked attenuation (>40-fold), when coactivated within a narrow time window (approximately 10 milliseconds), distal EPSPs could directly influence action potential output following dendritic spike generation. These findings reveal that distal EPSPs are ineffective sources of background somatic excitation, but through coincidence detection have a powerful transient signaling role.     

The catalytic cross-coupling of unactivated arenes

The industrially important coupling of aromatic compounds has generally required differential prefunctionalization of the arene coupling partners with a halide and an electropositive group. Here we report that palladium, in conjunction with a copper oxidant, can catalyze the cross-coupling of N-acetylindoles and benzenes in high yield and high regioselectivity across a range of indoles without recourse to activating groups. These reactions are completely selective for arene cross-coupling, with no products arising from indole or benzene homo-coupling detected by spectroscopic analysis. This efficient reactivity should be useful in the design of other oxidative arene cross-couplings as well.     

Strain-softening instability model for the san fernando earthquake

Changes in the ground elevation observed before and immediately after the 1971 San Fernando, California, earthquake are consistent with a theoretical model in which fault zone rocks are strain-softening after peak stress. The model implies that the slip rate of the fault increased to aboul 0.1 meter per year near the focus before the earthquake.