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Biomedical subjects

R E Butcher

Publications and source records attributed to R E Butcher.

At least 37 records · Page 2Linked to original sources
PubMed1977

Induced PKU in rats: effects of age and melatonin treatment.

Newborn rats injected on Days 1-8 of life with L-phenylalanine (2 g/kg) and p-chlorophenylalanine (80 mg/kg) displayed biochemical symptoms analogous to human phenylketonuria (PKU) and maze learning impairments. The behavioral effects were less evident in rats treated on Days 9-16 or 7-24. None of the symptoms observed were alleviated by simultaneous administration of melatonin (10 mg/kg/day).

Aging↗
PubMed1976

Behavioral testing as a method for assessing risk.

Behavioral effects have been found to result from the prenatal administration of substances known to be teratogenic to the CNS. These effects occur at dose levels lower than those producing gross malformations and when the agent is administered at times other than that optimal for CNS relevant technique for detecting adverse consequences of prenatal exposure to drugs and chemicals. Behavioral testing, however, also appears to have attributes that dictate a thoughtful approach to its role as a method for assessing risk, and additional research is needed to obtain usable techniques. The need for such research is intensified by the present inability to identify potential behavioral teratogens by means other than laboratory investigation.

Animals↗
PubMed1975

Biochemical effects of induced phenylketonuria in rats.

Phenylketonuria (PKU) was induced in rats by the combined feeding of 3 per cent excess phenylalanine and 0.12 per cent of p-chlorophenylalanine, an inhibitor of phenylalanine and tryptophan hydroxylases. Increased concentrations of phenylalanine and increased ratio of phenylalanine to tyrosine were demonstrated in blood from pregnant rats fed the experimental PKU diet from day 10 to 20 of pregnancy, in fetal blood and amniotic fluid of fetal animals from mothers fed the PKU diet, and in blood of rats fed the PKU diet for 28-30 days beginning at 20-21 days of age. Both phenylpyruvic acid and orthohydroxyphenylacetic acid were excreted by rats fed the PKU diet, but neither were detected in urine in animals fed either excess phenylalanine or excess inhibitor alone. Reduced serotonin concentrations were found in brains of rats fed p-chlorophenylalanine, either alone or in combination with excess phenylalanine in the PKU diet. These biochemical changes in rats with induced PKU and the behavioral changes described earlier are similar to those of the human condition. The animal model should prove useful in searching for the mechanism of the disease.

Amino Acids↗
PubMed1969

Stimulus properties of reinforcing brain shock.

Rats easily discriminate between two types of subcortical brain shock which differ in reinforcing properties. When both stimuli are either neutral or positively reinforcing subjects have difficulty in responding differentially to the two types of electrical stimulation of the brain. Possible implications for a theory concerning a generalized or diffuse reinforcement system are discussed.

Analysis of Variance↗
PubMedDate not supplied

Workshop on the qualitative and quantitative comparability of human and animal developmental neurotoxicity, Work Group IV report: triggers for developmental neurotoxicity testing.

A Work Group was formed to evaluate the criteria considered important in determining when to require developmental neurotoxicity testing in animal studies (i.e., triggers for testing). The primary objective of the Work Group was to determine whether there is sufficient scientific evidence to support the triggers identified by the Environmental Protection Agency and determine whether there is sufficient evidence to use structure activity relationships (SAR) to trigger automatic testing of certain classes of chemicals. A weight of evidence (WOE) approach was recommended by the Work Group in order to assist in determining which agents should undergo developmental neurotoxicity testing and to what level of testing. Evaluation of biological effects, length and duration of exposure, and quality and quantity of data available on an agent should be used in the WOE approach. Agents that are teratogenic to the central nervous system (CNS) were considered of highest priority for developmental neurotoxicity testing, especially if there is the potential for a high degree of exposure. Neuropathic and neuroactive compounds, chemicals with hormone-like activity, and developmental toxicants (with effects other than structural abnormalities of the CNS) were also considered likely candidates for such testing. Although reluctant to recommend testing based solely on SAR or chemical class, the Work Group recognized the importance of considering SAR along with other toxicity data, pharmacokinetic data and potential human exposure in making final requirements or recommendations for further testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗