Observations at venus encounter by the plasma science experiment on mariner 10

Preliminary results from the rearward-looking electrostatic analyzer of the plasma science experiment during the Mariner 10 encounter with Venus are described. They show that the solar-wind interaction with the planet probably involves a bow shock rather than an extended exosphere, but that this is not a thin boundary at the point where it was crossed by Mariner 10. An observed reduction in the flux of electrons with energies greater than 100 electron volts is interpreted as evidence for somne direct interaction with the exosphere. Unusual intermittent features observed downstream of the planet indicate the presence of a comet-like tail hundreds of scale lengths in length.     

Refractoriness in female lizard reproduction: a probable circannual clock

Postreproductive Cnemidophorus uniparens maintained under free-running conditions of constant darkness for 7 months became reproductive at the same time as controls exposed to a long photoperiod. This lizard exhibits a pause in reproductive activity (refractory period) commencing in late summer in nature and terminating in mid-December in captivity. Both groups terminated refractoriness and started reproducing simultaneously in December despite maintenance of the experimental group in darkness since September. These results confirm the hypothesis that the refractory period in this lizard is under endogenous control.     

Quantitative autoradiography of [3H]muscimol binding in rat brain

A simple quantitative autoradiographic technique for the study of neurotransmitter receptors that includes the use of a tritium-sensitive film permits saturation, kinetic, and competition studies of brain samples as small as 0.01 cubic millimeter. This technique was used to study [3H]muscimol binding in rat brain. Unilateral gamma-aminobutyric acid receptor supersensitivity was observed in the substantia nigra pars reticulata after production of localized lesions of the ipsilateral corpus striatum.     

Demyelinating encephalomyelopathy associated with lead poisoning in nonhuman primates

Lead poisoning was diagnosed in four primates by the finding of toxic amounts of lead in tissues. Abnormalities in the brain and spinal cord were characterized by vascular lesions and demyelination. These findings suggest a new animal model for the study of demyelination and strengthen the supposition that lead may be a factor in some idiopathic demyelinating diseases.