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Biomedical subjects

J R Mason

Publications and source records attributed to J R Mason.

At least 73 records · Page 4Linked to original sources
PubMed1985

Avfail in color avoidance learning by starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus).

Certain unconditioned stimuli (UCS) in flavor avoidance learning sometimes become ineffective after pairings with relatively stronger UCS. This failure of avoidance learning (avfail) has been demonstrated only with rodents. The present investigations were conducted to determine whether avfail might also occur with avian species, the food selection of which is guided primarily by visual cues. In Experiment 1, starlings were given pairings of methiocarb (a relatively weak UCS) and LiCl (a relatively strong UCS). In Experiment 2, red-winged blackbirds were given pairings of two concentrations of methiocarb (relatively weak and relatively strong UCS, respectively). Pairings were followed by a conditioning trial (UCS gavage in the presence of a color cue) and two-choice tests. Conditioned avoidance was always observed except when methiocarb preceded LiCl and when the low preceded the high methiocarb dose in preconditioning pairings. Experiment 3 demonstrated that UCS habituation could not account for the results of Experiments 1 and 2. The data reflect avfail in the visual modality, and a biological implication of the results is that birds may not learn strong avoidance of aposematic prey containing varied levels of toxicant.

Animals↗
PubMed1984

Thallium scintigraphy during dobutamine infusion: nonexercise-dependent screening test for coronary disease.

Exercise thallium scintigraphy has proven to be a sensitive method for detecting coronary artery disease (CAD). However, early redistribution of thallium and inadequate exercise can reduce its sensitivity. In this study, dobutamine was infused in incremental doses (5, 10, 15, and 20 micrograms/kg/min) in 24 patients being evaluated for chest pain. Thallium scintigraphy was completed during the maximum dose of dobutamine tolerated and repeated 4 hours later. Significant CAD was present in 16 patients; the remaining eight had normal coronaries. Exercise ECG was obtained in 23 patients. During dobutamine thallium scintigraphy, reversible perfusion defects occurred in 15 of 16 CAD and in one of eight non-CAD patients, resulting in a sensitivity of 94% and a specificity of 87%. Exercise ECG had a sensitivity of 60% and a specificity of 63%. We conclude that: (1) dobutamine thallium scintigraphy appears to be a sensitive method for detecting significant CAD and provided a more sensitive screening test than exercise ECG; (2) dobutamine thallium scintigraphy is especially useful in patients who cannot exercise; and (3) because imaging occurs during dobutamine infusion, the problem of early redistribution may be mitigated.

Catecholamines↗
PubMed1983

Characterization of a Chinese hamster ovary cell line resistant to uncouplers.

The chemiosmotic theory of oxidative phosphorylation and the action of uncouplers was examined by characterizing a clone, UH5, of Chinese hamster ovary (CHO TK-) cells resistant to 5-chloro-3-tert-butyl-2'-chloro-4'-nitrosalicylanilide (S-13), a potent uncoupler of oxidative phosphorylation. About 9-times and 4-times more S-13 was required to effect growth and respiration respectively of UH5 cells compared to the parental CHO TK- cells. UH5 cells were cross-resistant to the uncouplers SF-6847 (3,5-di-tert-butyl-4-hydroxy-benzylidenemalononitrile), carbonylcyanide p-trifluoromethoxyphenylhydrazone and 2,4-dinitrophenol but not to oligomycin, venturicidin or Tevenel. Size, chromosome number and DNA content indicated that the UH5 cell line was probably pseudotetraploid compared to the parental pseudodiploid CHO TK- cells. Hybrid and cybrid cells formed from crosses of UH5 cells and cytoplasts, respectively, with an uncoupler-sensitive cell line were sensitive to S-13 indicating that resistance is probably nuclear-determined. UH5 cell mitochondria had increased cytochrome oxidase and decreased H+-ATPase activities. A fivefold resistance of oxidative phosphorylation to uncouplers was found at the mitochondrial level with respiration driven by either succinate or ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine. In contrast, no difference in sensitivity was found to valinomycin between mitochondria from UH5 and CHO TK- cells. The oligomycin-sensitive H+-ATPase activity of UH5 and CHO TK- cell mitochondria was equally stimulated by the uncoupler S-13. Uncoupler-resistant mitochondria would not be expected on the basis of the chemiosmotic theory, and the relation of the results to other modes of coupling is considered.

Adenosine Triphosphatases↗
PubMed1983

Trigeminally mediated odor aversions in starlings.

Electrophysiological and psychophysical evidence has demonstrated that trigeminal receptors in the nasal cavity respond to odorants. Despite these demonstrations of trigeminal chemoreception, it is not clear whether naso-trigeminal stimulation can be used to mediate learned behaviors in contexts such as feeding. Here, we report that starlings will learn aversions to odorant volatiles in a feeding context and that these aversions can be mediated by trigeminal cues.

Animals↗
PubMed1983

Conditioned aversions to an intravascular odorant.

The odorant allyl sulfide (essence of garlic) dissolved in a corn oil vehicle was injected into rats to induce a conditioned aversion. In subsequent two-choice drinking tests, rats injected with odorant and lithium chloride, and rats injected with odorant and saline avoided drinking from a water bottle paired with the odorant. Because allyl sulfide and saline injections produced symptoms of malaise, we suspect that the odorant served as its own unconditioned stimulus. Rats injected with vehicle and saline showed no differential behavior. In a second experiment, gas chromatography indicated that allyl sulfide was present on the rat's breath within 3 minutes of injection, and was detectable for up to 5 hours post-injection. We conclude that conditioned aversions can be obtained to an intravascular odorant and that one route by which such odorants reach the nose is the breath.

Adaptation, Physiological↗
PubMed1983

Behavioral and physiological effects of capsaicin in red-winged blackbirds.

We injected red-winged blackbirds (Agelaius phoeniceus) subcutaneously with capsaicin, and assessed (a) changes in basal body temperature, (b) ability to discriminate warm from cool drinking water, and (c) sensitivity to oral and topical applications of capsaicin, a trigeminal irritant. As predicted from studies of mammals, the injections seemed to disrupt thermoregulation when the ambient temperature increased, and eliminated discrimination between warm and cool drinking water (Figs. 1 and 2). In contrast to effects on mammals, injections failed to observably diminish oral or topical sensitivity to capsaicin and apparently induced a capsaicin preference in two-bottle drinking tests between capsaicin and its vehicle (Fig. 3). Such preferences were context-dependent, however, since water was reliably preferred to capsaicin or vehicle in three-bottle tests. To our knowledge, the present work is the first to report physiological and behavioral effects of capsaicin on birds, and the first to suggest that the substance may have different behavioral and physiological effects on different classes of animals.

Administration, Oral↗
PubMed1982

Temporary and selective anosmia in tiger salamanders (Ambystoma tigrinum) caused by chemical treatment of the olfactory epithelium.

Tiger salamanders (Ambystoma tigrinum) were trained to respond to two dissimilar odorants (i.e., cyclohexanone, dimethyl disulfide) but not to a third odorant (n-butanol). When the training criterion was met, the animals were anesthetized and given nasal lavages of saline or odorants in saline. Lavage with cyclohexanone decreased responding to cyclohexanone but not dimethyl disulfide, and vice-versa, in later behavioral tests. Likewise, ethyl acetoacetate lavage produced selective response decrements to cyclohexanone. Lavage with n-butanol had no effect on responding to presentations of either cyclohexanone or dimethyl disulfide. The effects of lavage increased with increasing odorant concentration. Thus, lavage with 0.05 M cyclohexanone or ethyl acetoacetate produced more persistent response decrements than lavage with 0.01 M concentrations of either odorant. Such results are consistent with several testable interpretations, including the possibility the response decrements could reflect the nature of odorant-receptor interactions.

1-Butanol↗
PubMed1982

The relative importance of reinforced versus nonreinforced stimuli in visual discrimination learning by redwinged blackbirds (Agelaius phoeniceus).

Redwinged blackbirds were trained to locate and peck apple slices in two discrimination problems with four times more training on one problem than on the other. The birds were then given transfer tests with the stimuli re-paired. Nonreinforced (S-) stimuli exerted greater control over behavior than did reinforced (S+) stimuli. We inferred that the blackbirds learned more about what to avoid than what to approach when searching for food in the two-choice situation. That inference is contrary to the notion that, by being alert to the visual cues which signal foods (i.e., S+ stimuli), birds can more successfully cope with irrelevant visual information encountered during foraging. Rather, being alert to cues which signal the absence of food (i.e., S- stimuli) may be relatively more important.

Animals↗
PubMed1981

Cybrid formation with recipient cell lines containing dominant phenotypes.

A clone of Chinese hamster ovary (CHO) cells, BT3, resistant to Tevenel, the sulfamoyl analog of chloramphenicol has been isolated. Resistance was found to be at the mitochondrial level and was shown to be cytoplasmically inherited. This marker was then used to develop a method by which a cell line possessing a dominant nuclear mutation (resistance to 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, DRB) could be used as the recipient in cybrid formation. The unique feature in this procedure was the removal of nucleated cells from the cytoplasts by passage through unipore filters. The dominant character of the DRB- and Tevenel-resistant phenotypes permitted the selection of cybrids immediately after fusion. This initially increased the frequency of cybrid clones 16-fold as compared to a recipient cell line possessing a recessive marker. The possibility of extending the method to recipient cells lacking a selectable drug-resistance marker is discussed.

Animals↗
PubMed1975

Transmission and recombination of extranuclear genes during sexual crosses in Aspergillus nidulans.

Three extranuclear mitochondrial mutations in Aspergillus nidulans, (oliA1), (camA1) and (cs67), were used as markers in sexual crosses to provide information on the frequencies of transmission and recombination of the mitochondrial genome. Any individual perithecium contained ascospores of only one extranuclear genotype. Using mono-, bi- and trifactorial crosses it was found that all three markers could be recovered from the progeny, although the transmission frequencies were different for each marker. This bias was present irrespective of the nuclear background or the presence of selective agents in the medium on which the cross was established. These findings enable a series of "transmission strength" to be established, as shown below:-- (camA1) greater than (cs67, camA1) greater than (+) = (cs67) greater than (oliA1, cs67) greater than (oliA1) greater than (oliA1, camA1). However, the numbers of recombinants isolated were so variable as to make this form of analysis unsuitable for mapping the mitochondrial genome.

Aspergillus nidulans↗
PubMed1975

Certificate of need: the Massachusetts experience.

Certificate of Need legislation is one of several regulatory programs designed to control the allocation of health care delivery resources. This paper examines the Massachusetts experience with Certificate of Need, focusing on two major administrative law controversies--the extent of the regulatory agency's power to participate actively in the planning process, and the scope of review of agency decisions permitted under a non-judicial appeals mechanism. The study concludes that any Certificate of Need program may be strengthened by accurately defining the roles of the participants and by providing for safeguards within the system itself.

Decision Making↗