Directional errors of movement and their correction in a discrete tracking task.

Many studies have shown that subjects can correct their own errors of movement more quickly than they can react to external stimuli. In the control of movements, three general categories of feedback have been defined as follows: (a) knowledge of results, primarily visually mediated, (b) proprioceptive or kinesthetic, such as from muscle spindles and joint receptors, and (c) corollary discharge or efference copy within the central nervous system. Experiments were conducted on eight normal human subjects to study the effects of these feedbacks on simple RT, choice RT, and error correction time.

Fluctuations in prey availability and food limitation for a terrestrial salamander.

A Virginia population of the forest-dwelling salamander Plethodon cinereus was repeatedly sampled over four years to determine volume and number of prey ingested under varying conditions of moisture and temperature. The proportion of the population on a daily negative energy budget was estimated by comparing actual foraging success with laboratory determined values of energetic requirements at various temperatures.Prey became "limited" in availability during rainless periods, apparently because salamanders were not able to forage in dry leaf litter.

Population screening for beta-thalassemia minor. Report of cooperative trials based on two approaches.

In a cooperative intrastate program based upon experience with sickle-cell anemia screening, the authors explored the feasibility of applying hemoglobin electrophoresis for detection of beta-thalassemia gene carriers. Initially, blood samples collected in capillary tubes were analyzed by cellulose acetate electrophoresis with densitometric quantitation of hemoglobin A2 (Hb A2), followed by selective spectrophotometric quantitation. This approach proved insufficiently specific or reproducible.

Phototactic responses of anuran amphibians to monochromatic stimuli of equal quantum intensity.

The phototactic responses of anuran amphibians to narrow-band monochromatic stimuli of equal quantum intensity were measured for the first time in eight new experiments. The unimodal spectral response, obtained from dark-adapted American toads (Bufo americanus), peaks near 626 THz of frequency (480 nm wavelength). The bimodal, U-shaped spectral response, obtained from dark-adapted tailed frogs (Ascaphus truei), has the anti-mode at about 589 THz (510 nm) and is not merely the spectral mirror-image of the unimodal response.

1,1-Dichloroethylene hepatotoxicity: proposed mechanism of action and distribution and binding of 14C radioactivity following inhalation exposure in rats.

1,1-Dichloroethylene is reported to produce renal tumors in male mice. It is an hepatotoxin in fasted rats after inhalation. We found that trichloropropane epoxide, an inhibitor of epoxide hydrase, enhances hepatic injury as measured by serum sorbitol dehydrogenase elevation.

Acute hepatotoxicity of ethylene and halogenated ethylenes after PCB pretreatment.

Previous studies from our laboratory have shown that ethylene, vinyl fluoride monomer (VFM), vinyl chloride monomer (VCM), and vinyl bromide monomer (VBM) are all acutely hepatotoxic in rats pretreated with polychlorinated biphenyl (PCB). The time course of hepatic injury development after exposure and several parameters, environmental and chemical, affecting this toxicity were evaluated in the work reported here. Liver injury, as measured by serum alanine-alpha-ketoglutarate transaminase (SAKT) or sorbitol dehydrogenase (SDH), develops progressively over a 24-hr period following a 4-hr inhalation exposure of PCB-pretreated rats to ethylene or VCM.

Protracted radiation-stressed primate performance.

An experimental investigation has been made of the effects of nuclear radiation on the behavior of four trained primates (rhesus monkeys) proficient in control of the primate equilibrium platform during a hypothetical 72-h aircraft mission. The radiation exposure was assumed to result from a radioactive cloud penetration at the start of the mission, with subsequent low dose rate exposure resulting from radioactive debris in and on the aircraft. Minor performance changes were detected in three of four subjects; all experienced emesis.

[Electron microscopic presentation of immune reactions on Candida cells: asteroid bodies in Candida albicans from the urine of nephritis patients].

Candida albicans cells from the urine of two nephritis patients were concentrated and incubated with ferritin-labeled antihuman grammaglobulin (either anti-IgA, anti-IgG, or anti-IgM). Electron microscopy showed the electron-transparent yeast cell wall to be surrounded by an electron-dense capsule-like substance of remarkable volume. This must be regarded as an antigen-antibody precipitate corresponding to the "asteroid body" of previous authors.

Ontogenetic shift of spectral phototactic preferences in anuran tadpoles.

Tadpoles of three species of anurans initially had a midspectrum ("green") preference in laboratory phototactic tests, which was shown experimentally to involve a form of true color vision in one species and probably in the other two as well. During development, the preference shifted to shorter wave-lengths (higher frequencies) until a short-wavelength ("blue") preference predominated in the pre- and postmetamorphic stages and in the adults of six species tested; color vision was involved in all of these stages. The green preference of young tadpoles is ecologically adaptive, in that it directs larvae to green plants that provide food or shelter.