Biomedical subjects

D M Thompson

Publications and source records attributed to D M Thompson.

At least 73 records · Page 4Linked to original sources

PubMed1984

Acid phosphatases and seed shriveling in triticale.

Seed shriveling in the man-made intergeneric hybrid, triticale (x Triticosecale Wittmack) appears to be related to increased activity of endosperm acid phosphatases including para-nitrophenyl phosphatase, ATPase, ADPase, phosphatidic phosphatase, and glucose-1-phosphatase that occur specifically at later stages of seed development. These hydrolases may reduce endogenous substrates for starch synthesis, deplete energy supply for maintenance and biosynthesis of tissue growth, and deassemble membrane structures resulting in a partially filled endosperm and localized necrosis. Electrophoretic isozyme patterns of endosperm acid phosphatase exhibited distinctive differences between lines producing plump and shriveled seeds indicating a divergent role of the isozymes in these two different seed conformations.

Journal Article↗

PubMed1984

Effects of opioids on accuracy of a fixed-ratio discrimination in monkeys and rats.

In the presence of a stimulus above the center lever, monkeys and rats were required to complete one of two fixed-ratios (FRs) on the center lever (FR20 or FR40, monkeys; FR8 or FR16, rats). Completion of the ratio turned off the center-lever stimulus and produced a stimulus above each of the two side levers. If the completed ratio was high (e.g., FR40), a response on the left lever produced a food pellet. If the ratio was low (e.g., FR20) a response on the right lever produced food. Errors produced a brief timeout. In monkeys, d-SKF 10,047 either increased slightly or had no effect on response rate on the center lever, whereas increasing errors in a dose-related manner. In rats, both dl-SKF 10,047 and cyclazocine were found to produce a dose-related decrease in response rate and an increase in errors. The putative kappa agonist ethylketocyclazocine produced similar effects in both the monkey and rat. At doses that decreased rate of responding, accuracy was unaffected, except at the highest dose that virtually eliminated responding. Unlike any of the other drugs tested, ethylketocyclazocine decreased rate by producing a dose-related pause at the start of the session rather than by altering the local rates of responding. In monkeys, the mu agonists morphine and methadone produced dose-related decreases in response rate, primarily due to sporadic pausing. Across this same range of doses neither drug affected errors, except at the high doses in which relatively small increases obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Living with an amputation: what it means for patients and their helpers.

The social and emotional problems declared by 134 single-leg amputees are compared with those of 109 people who were their main helpers. The Day Amputee Activity Score, the Goldberg GHQ, Townsend's Social Isolation scale and Forder's concept of Felt Need were used in the study. The majority of patients were elderly males. Most of the carers were women. Peripheral vascular disease was the most frequent reason for the amputation and its persistence postoperatively was predictive of poor rehabilitation outcome. The respondents reported unmet need for information about financial help, employment and social activity. Both groups shared a high level of social isolation, which was associated with risk of psychiatric illness and appeared to inhibit the expression of need. Helpers complained more forcefully than patients about service provision and discussed their emotional reactions more readily. The amputees tended to use denial in confronting the implications of limb ablation. Many respondents had no sources of help with personal or practical problems. Their knowledge of available services was poor. In particular, the role of social workers was not well understood. Neither the social work profession nor the Artificial Limb Centre was used to any appreciable extent as a source of help with psychosocial adjustment to loss of a limb.

Adaptation, Psychological↗

PubMed1983

Effects of heroin, methadone, LAAM and cyclazocine on acquisition and performance of response sequences in monkeys.

In each of three components of a multiple schedule, monkeys were required to emit a different sequence of four responses in a predetermined order on four levels. Sequence completions produced food on a fixed-ratio schedule. Errors produced a brief timeout. One component of the multiple schedule was a repeated-acquisition task where the four-response sequence changed each session (learning). The second component of the multiple schedule was also a repeated-acquisition task, but acquisition was supported through the use of a stimulus fading procedure (faded learning). In a third component of the multiple schedule, the sequence of responses remained the same from session to session (performance). At high doses, each drug tested produced essentially the same effect. In all three components, response rate was substantially decreased and percent errors increased. At lower doses, however, their effects differed. Heroin and methadone produced dose-dependent sporadic periods of pausing, but had little or no effect on the accuracy of responding. LAAM also produced sporadic periods of pausing, but its effects on accuracy were variable. In contrast, cyclazocine produced no such pauses in responding but rather decreased the local rates of correct responding in a dose-related manner. These same doses of cyclazocine increased percent errors in the learning component, but not in the faded learning or performance components. The results are generally consistent with the view that putative mu opioid agonists do not affect the accuracy of a discrimination in monkeys except at those doses which produce a substantial decrease in the overall rate of responding.

Animals↗

PubMed1983

Drug effects on repeated acquisition: comparison of cumulative and non-cumulative dosing.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of a sequence of four colors. The response chain was maintained by food presentation under a fixed-ratio schedule. Errors produced a brief timeout but did not reset the chain. Each day there were four 15-minute sessions, with a 10-minute inter-session interval. Cumulative dose-effect curves for phencyclidine, pentobarbital, and d-amphetamine were obtained by giving an injection before each of the four sessions; successive injections increased the cumulative dose in equally spaced logarithmic steps. For comparison, non-cumulative doses of each drug (i.e., doses not preceded by other doses on the same day) were also tested. As the cumulative dose of each drug increased, the overall response rate decreased, the percent errors increased, and there was less within-session error reduction (acquisition). With phencyclidine and pentobarbital, the rate-decreasing and error-increasing effects tended to be greater with a non-cumulative dose than with the corresponding cumulative dose. In contrast, with d-amphetamine, the effects were considerably greater with the cumulative doses. The results indicate that although the cumulative-dosing procedure saved a substantial amount of time in determining dose-effect curves, there were quantitative differences in effects between cumulative and non-cumulative doses.

Animals↗

PubMed1983

Living with an amputation: the patient.

The findings of a study of 134 single-leg amputees are presented, comparing those who had recently lost a leg with others who had worn prostheses for 1-2 years. Social isolation, psychological risk and felt need were the principal indicators of level of adjustment selected. On none of these measures did experienced prosthesis-wearers show any appreciable improvement over amputees in the early stages of prosthetic rehabilitation. Severe social isolation was present in both groups, and seemed to inhibit the declaration of needs. The persistence of peripheral vascular disease was predictive of poor rehabilitation outcome.

Activities of Daily Living↗

PubMed1983

Differential effects of prototype opioid agonists on the acquisition of conditional discriminations in monkeys.

In each of two components of a multiple schedule, patas monkeys were required to respond on a right or left lever depending upon the stimulus combination (a color and a geometric form) presented. Reinforcement of a response in the presence of one stimulus (the form) was conditional upon the other stimulus (the color). The completion of a two-member chain of discriminations produced a food pellet. Errors produced a brief time-out. One component of the multiple schedule was a repeated-acquisition task where the discriminative stimuli for left- and right-lever responses changed each session (learning). In the other component, the discriminative stimuli were the same each session (performance). Morphine, ketocyclazocine and SKF 10,047 each produced dose-related decreases in overall rate of responding in both components of the multiple schedule. However, each drug affected the patterning of responding in a different manner. Across a range of doses which decreased response rate, neither morphine nor ketocyclazocine affected accuracy of the discriminations. In contrast, SKF 10,047 and its enantiomers produced a dose-dependent disruption of accuracy; errors were increased in the acquisition component at doses lower than those required to disrupt the discrimination in the performance component. The effects of the l-isomer of SKF 10,047 were generally comparable to those of the racemate. In comparison to the racemate, the d-isomer of SKF 10,047 was found to produce greater error-increasing effects in the acquisition component and smaller rate-decreasing effects in both components of the multiple schedule. In general, the effects of cyclazocine and pentazocine on both accuracy and rate of responding were comparable to those obtained with SKF 10,047. The results suggest that in patas monkeys, opioids with activity at the putative sigma receptor such as SKF 10,047, cyclazocine and pentazocine exert a dose-dependent disruptive effect on the accuracy of discriminations, an action not shared by prototypical mu and kappa opioid agonists, at doses which produce approximately equivalent rate-decreasing effects.

Animals↗

PubMed1982

Phencyclidine in combination with pentobarbital: supra-additive effects on complex operant behavior in patas monkeys.

In one component of a multiple schedule, patas monkeys acquired a different four-response chain each session by responding sequentially on three keys in the presence of four geometric forms (learning). In the other component, the four-response chain was the same each session (performance). The response chain in each component was maintained by food presentation under a fixed-ratio schedule. Errors produced a brief timeout but did not reset the chain. When administered alone, phencyclidine and pentobarbital, at the higher doses, generally decreased the overall response rate and increased the percent errors in both components. The performance component tended to be less sensitive than the learning component to the drug effects. When phencyclidine was administered in combination with pentobarbital, the phencyclidine dose-effect curves for both rate and accuracy generally shifted progressively to the left as the dose of pentobarbital was increased. In two of three monkeys, combinations of phencyclidine with a high dose of pentobarbital consistently produced greater rate-decreasing and error-increasing effects than expected from simple addition of the effects of each drug given alone. In other words, the phencyclidine-pentobarbital combinations produced supra-additive effects on responding under the multiple schedule.

Animals↗

PubMed1982

Phencyclidine in combination with pentobarbital: supra-additive effects on complex operant behavior in pigeons.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. The response chain was maintained by food presentation under a fixed-ratio schedule. Errors produced a brief timeout but did not reset the chain. When phencyclidine was administered alone, the overall response rate decreased and the percent errors increased with increasing doses. Similar effects were found with a high dose of pentobarbital alone. When phencyclidine was administered in combination with pentobarbital, the phencyclidine dose-effect curves for rate and accuracy shifted to the left as the dose of pentobarbital was increased. Combinations of phencyclidine with a high dose of pentobarbital produced supra-additive effects; i.e., the effects on rate and accuracy were greater than expected from simple addition of the effects of each drug given alone. These results extend the generality of previous findings in patas monkeys in a similar repeated-acquisition task.

Animals↗

PubMed1982

Effects of chronic phencyclidine on fixed-ratio responding: no relation to neurotransmitter receptor binding in rat cerebral cortex.

The effects of chronic phencyclidine (3.2 mg/kg for 25 days) on responding maintained under a fixed-ratio 30 schedule of food presentation were studied in rats. Initially phencyclidine produced large decreases in the overall rate of responding. This decrease was due primarily to long pauses in responding and secondarily to a decrease in local rates of responding. Although tolerance developed to the rate-decreasing effects of phencyclidine in each subject, the extent and pattern of its development differed among the subjects. After the chronic drug regimen, the rats were sacrificed. Ligand binding to muscarinic cholinergic, opiate, adrenergic, and serotonergic receptors in cortex was then compared to that in rats which received saline with operant training, phencyclidine alone, or saline alone. Neither operant behavior alone, phencyclidine alone, nor the interaction of phencyclidine and operant behavior was found to alter binding to these receptors. These results indicate that behavioral tolerance develops to phencyclidine, but it is not accompanied by changes in binding to the receptors studied.

Animals↗

PubMed1982

Intravenous diazepam in humans: effects on acquisition and performance of response chains.

A technique based upon an individual-subject design was used to investigate the effects of intravenous diazepam on the acquisition and performance of response chains in humans. In each of two conditions subjects were required to emit a different sequence of ten responses in a predetermined order on three levers. The conditions alternated within each session under a multiple schedule. In the performance condition the sequence of responses was the same each session. The second condition was a repeated-acquisition task. In this condition subjects were required to learn a different sequence of responses each session. Diazepam produced dose-dependent decreases in the overall rate of responding in each subject under both conditions. In two of the three subjects tested, errors were increased in the learning condition at doses lower than those required to disrupt accuracy in the performance condition. In one subject, accuracy in both the learning and performance conditions was equisensitive to the disruptive effects of diazepam. These data are consistent with the effects of the benzodiazepines in analogous animal procedures. Furthermore, the data suggest that the behavioral effects of intravenous diazepam may exhibit marked variations across subjects at clinically relevant doses (5-10 mg).

Adult↗

PubMed1982

Toxic shock syndrome in the postoperative patient.

Toxic shock syndrome occurred in two patients within seven days of operation in women in whom Staphylococcus aureus was isolated from the wound incisions. Both patients had negative vaginal cultures. One patient was menstruating at the time of onset of the disease and the other was seven days' postpartum. Although toxic shock syndrome mainly occurs in menstruating women who use tampons and have positive vaginal cultures for Staphylococcus aureus, wound infection may also be a source for toxin production and adsorption.

Adult↗

PubMed1981

Effects of phencyclidine, d-amphetamine and pentobarbital on schedule-controlled behavior in rats.

The effects of phencyclidine, d-amphetamine, and pentobarbital on responding maintained under a multiple fixed-interval (FI) 3-min fixed-ratio (FR) 30 schedule of food presentation were studied in rats. Phencyclidine (0.32-7.5 mg/kg) had a biphasic effect on overall response rate in both components; response rate increased and then decreased as the dose was increased. The FR was slightly more sensitive to the rate-decreasing effects of phencyclidine than the FI. The effects of d-amphetamine (0.1-7.5 mg/kg) on overall response rate were qualitatively similar to those of phencyclidine. The FI tended to be slightly more sensitive than the FR to the rate-increasing effects of d-amphetamine. Pentobarbital (1-18 mg/kg) produced little or no rate-increasing effects in the FR at low doses and decreased FR response rate at higher doses. In the FI, pentobarbital produced small increases in overall rate at intermediate doses while decreasing response rate at higher doses. The FR tended to be more sensitive than the FI to the rate-decreasing effects of pentobarbital. Unlike d-amphetamine and pentobarbital, phencyclidine produced smaller rate-increasing effects when the dose-effect curves were redetermined. Within the FI, the effects of phencyclidine and d-amphetamine on response rate were generally independent of the control rate of responding.

Animals↗

PubMed1981

Selective antagonism of the error-increasing effect of morphine by naloxone in a repeated-acquisition task.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. The response chain was maintained by food presentation under a fixed-ratio schedule. Errors produced a brief timeout but did not reset the chain. When either morphine or naloxone was administered alone, the overall response rate decreased with increasing doses. The rate-decreasing effect was accompanied by an increase in percent errors with morphine but not with naloxone. Both effects of morphine were antagonized by doses of naloxone that were ineffective when given alone. The antagonism was selective in that naloxone (3 mg/kg) completely blocked the error-increasing effect but not the rate-decreasing effect of the higher doses of morphine. The view that naloxone is a specific narcotic antagonist was supported by the finding that naloxone failed to antagonize the rate-decreasing and error-increasing effects of d-amphetamine, pentobarbital, and phencyclidine.

Animals↗

PubMed1980

Cardiac valve replacement in elderly patients.

Cardiac valve replacement in 65 consecutive elderly patients (aged 65 years and older) revealed that the indications for cardiac valve replacement in the elderly should be the same as those in the general population. These 65 patients represented 16% of the patients undergoing valve replacement. The mortality in the first 30 days after operation was 4.6% in the elderly group, compared with 0.9% in the group under 65 years of age. There were 26 significant but nonfatal early complications in the elderly patients, but their long-term functional status was excellent, most of the survivors ending up in either class I or class II of the New York Heart Association functional classification. The late mortality was 3.9% per patient year for aortic valve replacement and 15.1% for mitral with or without aortic valve replacement. The actuarial survival rates were 88% at 24 months and 55% at 54 months for the total elderly group, 86% at 36 months for those with aortic valve replacement, 85% at 24 months and 64% at 36 months for those with mitral valve replacement, 90% at 24 months and 77% at 42 months for the men, and 82% at 24 months and 68% at 42 months for the women. Aortic valve replacement was more common in the elderly than in the younger group because of the higher prevalence of congenital calcific aortic stenosis in the former, and this operation provided more gratifying results than mitral valve replacement in the elderly patients.

Age Factors↗

PubMed1980

Combination chemotherapy in invasive thymoma role of COPP.

Combination chemotherapy consisting of cyclophosphamide, vincristine, prednisone, and procarbazine (COPP) was administered to 5 patients with invasive lymphoepithelial thymoma. Objective evidence of tumor regression was seen in 4 patients. Given prior to preoperative radiation therapy, COPP produced partial remissions in 2 patients, making possible smaller radiation treatment fields. Two patients with pleural involvement when first seen, achieved tumor regression when COPP was given prior to radical radiation therapy. One of these patients remains disease-free at 34 months; the other succumbed to pneumonitis. One patient, presenting with pleural metastasis three years after undergoing incomplete resection of thymoma, failed to respond to treatment. Combination chemotherapy with COPP can produce objective regression of invasive lymphoepithelial thymomas which may be useful in the preoperative management of selected cases, as well as in the management of unresectable or metastatic disease.

Adult↗

PubMed1980

Effects of phencyclidine, pentobarbital, and d-amphetamine on the acquisition and performance of conditional discriminations in monkeys.

In each of two components of a multiple schedule, monkeys were required to respond on a right or left lever depending upon the stimulus combination (a color and a geometric form) presented. Reinforcement of a response in the presence of one stimulus (the form) was therefore conditioned upon the other stimulus (the color). The completion of a two-member chain of discriminations produced a food pellet. Errors produced a brief timeout. One composition of the multiple schedule was a repeated-acquisition task where the discriminative stimuli for left- or right-lever responses changed each session (learning). In the other component, the discriminative stimuli for left- or right-lever responses were the same each session (performance). Phencyclidine, pentobarbital, and d-amphetamine each produced dose-related decreases in the overall rate of responding in both components of the multiple schedule. At high doses each drug increased the percent errors in each component. At lower doses, however, the three drugs produced selective effects on accuracy. Errors were increased in the learning component at lower doses than those required to disrupt the discrimination in the performance component. A signal detection analysis of the data revealed that none of the drugs tested increased errors by selectively affecting either discriminability or bias.

Animals↗

PubMed1980

Effects of d-amphetamine and cocaine on strained ratio behavior in a repeated-acquisition task.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. When the fixed-ratio requirement for food presentation was five completions of the chain, d-amphetamine and cocaine disrupted the behavior. As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i,e., percent errors increased), and there was less within-session error reduction (acquisition). In contrast, when the fixed-ratio requirement was either 20 or 50 completions of the chain, certain doses of both drugs produced large increases in the overall response rate by eliminating the extended pausing (ratio strain) that was characteristic of the control sessions. These rate-increasing effects were accompanied by error-decreasing effects, both during acquisition and after the response chain had been acquired. Taken together, the results show that the effects of d-amphetamine and cocaine on behavior in a repeated-acquisition task can be modulated by manipulating the value of the fixed-ratio schedule maintaining the behavior.

Animals↗