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Biomedical subjects

L Macdonald

Publications and source records attributed to L Macdonald.

26 records · Page 2Linked to original sources
PubMed1986

Cause of death in 1144 patients with diabetes mellitus: an autopsy study.

The pathological reports for all patients over 13 years of age who had had an autopsy at one of three university-affiliated hospitals between 1967 and 1976 were reviewed to determine the principal cause of death. The clinical records of the patients with diabetes were reviewed to verify the diagnosis and to determine the known duration of diabetes. There were 1144 patients with diabetes mellitus and 5674 without. The sex distribution was similar in the two groups. The patients with diabetes were slightly older, males by 2.2 years and females by 3.2 years. Disease of the circulatory system was the principal cause of death in males (53.7%) and females (58.9%) with diabetes. The rates in the corresponding patients without diabetes were 37.6% and 35.2%. Neoplasms accounted for 18.9% of deaths in males with diabetes, compared with 35.7% in males without diabetes; the corresponding figures in females were 16.0% and 39.4%. Renal disease accounted for 5.9% of deaths in patients with diabetes.

Adolescent↗
PubMed1973

A rate measure of the relative aversiveness of signalled vs unsignalled shock.

Five rats were trained on a two-component multiple schedule with each component consisting of a two-link chain schedule. Differential response suppression in the initial links of the chain schedules was used as a measure of the relative aversiveness of events introduced into the subsequent terminal links. When unsignalled shock was scheduled in one terminal link and signalled shock in the other (in addition to equal numbers of food reinforcers), responding was suppressed to a greater degree in the initial link preceding the unsignalled-shock condition. Reversing the terminal-link positions of unsignalled shock and signalled shock led to a reversal of the differential response suppression in the initial links. These results confirm previous findings that signalled shock is less aversive than unsignalled shock and extend the generality of this phenomenon from choice measures to rate measures of aversiveness.

Journal Article↗
PubMed1973

The relative aversiveness of signalled versus unsignalled shock-punishment.

Six rats were trained on a two-component multiple schedule with each component consisting of a two-link chain schedule. Differential response suppression in the two initial links, as well as in the two terminal links of the chain schedules, was used as a measure of the relative aversiveness of stimulus events in the two terminal links. When signalled and unsignalled shock-punishment (in addition to equal numbers of food reinforcers) were scheduled in the separate terminal links, subjects responded at lower rates in the initial link preceding unsignalled shock-punishment than in the initial link preceding signalled shock-punishment. Similarly, subjects responded at lower rates in the terminal link containing unsignalled shock-punishment than in the terminal link containing signalled shock-punishment. Reversing the terminal-link positions of signalled and unsignalled shock-punishment led to a reversal of the differential response suppression in the two initial and the two terminal links of the chain schedules. These results indicate that signalled punishment is relatively less aversive than unsignalled punishment and support an "information hypothesis", which assumes that a condition in which information is provided about the onset of environmental events, even negative events such as shock punishment, is more reinforcing than a condition in which such information is absent.

Journal Article↗
PubMedDate not supplied

The effect of amantadine on levodopa-induced dyskinesias in Parkinson's disease: a double-blind, placebo-controlled study.

We performed a double-blind, placebo-controlled, crossover study to assess the effect of amantadine versus placebo on levodopa-induced dyskinesias in Parkinson's disease. We found a 24% reduction in the total dyskinesia score after amantadine administration (p = 0.004). This improvement was achieved without any influence on the severity of "on" period parkinsonism. The results confirm that amantadine reduces levodopa dyskinesias and support the hypothesis that dyskinesias can be reduced by blockade of excitatory pathways in the basal ganglia.

Aged↗