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Biomedical subjects

R L Clarke

Publications and source records attributed to R L Clarke.

At least 109 records · Page 6Linked to original sources
PubMed1980

Failure of rats to escape from a potentially lethal microwave field.

Ocularly pigmented rats, all mature females of the Long-Evans strain, were repeatedly presented an opportunity to escape from an intense 918-MHz field (whole-body dose rate = 60 mW/g) to a field of lower intensity (40, 30, 20, or 2 mW/g) by performing a simple locomotor response. Other rats could escape 800-microamperemeter faradic shock to the feet and tail by performing the same response in the same milieu, a multimode cavity. None of 20 irradiated rats learned to associate entry into a visually well-demarcated area of the cavity with immediate reduction of dose rate, in spite of field-induced elevations of body temperature to levels that exceeded 41 degrees C and would have been lethal but for a limit on durations of irradiation. In contrast, all of ten rats motivated by faradic shock rapidly learned to escape. The failure of escape learning by irradiated animals probably arose from deficiencies of motivation and, especially, sensory feedback. Whole-body hyperthermia induced by a multipath field may lack the painful or directional sensory properties that optimally promote the motive to escape. Moreover, a decline of body temperature after an escape-response-contingent reduction of field strength will be relatively slow because of the large thermal time constants of mammalian tissues. Without timely sensory feedback, which is an essential element of negative reinforcement, stimulus-response associability would be imparied, which could retard or preclude learning of an escape response.

Animals↗
PubMed1978

(2-exo-3-endo)-2-Aryltropane-3-carboxylic esters, a new class of narcotic antagonists.

Tropanes 4 bearing an exo aromatic group on carbon-2, an endo-carbomethoxy group on carbon-3, and either a methyl group or a hydrogen on the nitrogen were found to be narcotic antagonists which were devoid of demonstrable analgesic activity. The activity resided in the 1S enantiomer. Compound 4 (R = m-hydroxyphenyl) showed an AD50 of 0.37 mg/kg sc and 1.8 mg/kg po (rats) as an antagonist in the Harris-Pierson modification of the D'Amour-Smith test. The tropane esters for this study were prepared by a Grignard reaction which gave essentially complete 1,4-addition in the absence of copper salts. Nearly equal quantities of esters epimeric at carbon-3 were formed.

Acetylcholine↗
PubMed1978

(exo, exo)-2-Aryltropane-3-carboxylic esters, hypoglycemic agents with accompanying analgesic activity.

(exo, exo)-2-Aryltropane-3-carboxylic esters of types 6, 7, and 10 lower circulating blood glucose levels by 60--80%. This activity is accompanied by an analgesic activity roughly equal to that of codeine. Both of these activities reside in the 1R enantiomer and extensive structure-activity studies failed to separate them. The specific opioid antagonist nalorphine blocks the analgesic activity but does not diminish the hypoglycemic action. Conformational integrity afforded by the ethylene bridge is neccessary for the observed activities.

Administration, Oral↗
PubMed1975

Perianal Paget's disease: report of two cases.

A patient with extensive perianal extra-mammary Paget's disease was treated by wide local excision of the perianal skin. No underlying associated adenocarcinoma was identified, and the patient is clinically free of disease five years after treatment. A second patient had a small focus of Paget's disease confined to a hemorrhoid. The necessity for histologic evaluation of all anal lesions is emphasized.

Adult↗
PubMed1975

Beta-cocaine.

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Anesthetics, Local↗
PubMed1975

Analgesic activity of the epimeric tropane analogs of meperidine. A physical and pharmacological study.

Condensation of cis-N-benzyl-2,5-bis(chloromethyl)pyrrolidine (6) and phenylacetonitrile afforded a mixture of epimers 7 and 8. Compound 8 was readily converted to the meperidine analog 1 prepared earlier by Bell and Archer. Compound 7 was converted to a new tropane analog of meperidine, compound 3. The ED50 of 1 and 3 in the D'Amour-Smith "tail flick" test for narcotic type analgesia, which differs by a factor of only 3 or 4 potency, supports the accumulated data that suggest that the analgesic activity of the meperidine type is not very sensitive to the conformation of the phenyl group in 4-phenylpiperidines. A proton and 13C magnetic resonance spectral comparison of 1 and 3, as well as a reevaluation of the conformational requirements of 17-19, leads to the conclusion that the differences in conformation of 1,3,17, and 18 are due to the varying degrees of flattening of piperidine ring. The 1H NMR and 13C NMR data are not consistent with the boat conformation suggested earlier for compound 17.

Analgesics↗
PubMed1971

Behavioral sensitivity to microwave irradiation.

Rats assayed by the technique of conditional suppression were able to detect the presence of 12.25-centimeter microwaves at doses of power approximating 0.5 to 6.4 milliwatts per gram. The assay, which controlled for sensitization, for pseudo and temporal conditioning, and for several possible sources of artifactual cueing, revealed that irradiation by microwaves, although lacking the saliency of an auditory stimulus, can function as a highly reliable cue. Efficiency of detection was strongly and positively related to the amount of microwave energy to which the rats were exposed.

Animals↗