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Biomedical subjects

D G Dyck

Publications and source records attributed to D G Dyck.

18 recordsLinked to original sources
PubMed1992

Aerobic fitness level (VO2max) moderates the increased cardiovascular function and basal thromboxane formation of young healthy Type A males.

The authors evaluated the interaction between physical fitness and Type A behavior on vascular production of prostacyclin and platelet thromboxane in response to a standard vessel injury. Ninety-seven male university students were classified as Type A or B on the basis of the Structured Interview of Rosenman. Reactivity, as measured by changes in systolic blood pressure (SBP), and heart rate (HR), measured before and after a stressful Stroop task 1 week later, showed that Type A individuals were more reactive to the stressor than Type Bs, providing independent confirmation of the behavioral interview assessment procedure. Fitness level was determined by a graded treadmill test and was not different for Type As and Type Bs. Basal thromboxane production, measured as the primary metabolite, thromboxane B2, in blood oozing from the bleeding-time site, was highest among unfit Type A subjects. Fit Type As and Type Bs showed significantly lower thromboxane production. No significant differences in prostacyclin production were seen. This study marks the first time that behavior pattern has been linked to an adverse aspect of a thrombosis-related parameter likely to be involved in the genesis of cardiovascular disease. The present results also indicate that physical fitness may, in some fashion, ameliorate the "toxic" effects of Type A behavior.

Adolescent↗
PubMed1991

Suppression of splenic macrophage interleukin-1 secretion following intracerebroventricular injection of interleukin-1 beta: evidence for pituitary-adrenal and sympathetic control.

Intracerebroventricular (ICV) injections of interleukin-1 beta (IL-1 beta) produced a dose-dependent increase in plasma corticosterone and adrenocorticotropic hormone (ACTH) within 2 hr of injection and then declined over the next 24 hr. Using a potent steroidogenic dose of IL-1 beta (5 ng), ICV injection resulted in suppression of splenic macrophage IL-1 secretion following stimulation by LPS in vitro. Macrophage TGF-beta secretion was not affected, indicating a differential action of ICV IL-1 beta on macrophage cytokine production. Following adrenalectomy (ADX), the suppressive effect of ICV IL-1 beta was reversed and resulted in stimulation of macrophage IL-1 secretion, indicating that the suppression was mediated by adrenocorticol activation. However, surgical interruption of the splenic nerve to eliminate autonomic innervation of the spleen also prevented the macrophage suppressive signal in rats given ICV IL-1 beta. Furthermore, the combination of ADX and splenic nerve section resulted in a potent stimulatory effect of ICV IL-1 beta on splenic macrophage IL-1 secretion which was greater than either ADX or splenic nerve section alone. These results support the concept of a negative feedback on macrophage IL-1 secretion by the central action of IL-1 beta and indicate that both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system mediate this effect.

Adrenalectomy↗
PubMed1991

The interactive effects of Type A behavior and hostility on bleeding time thromboxane and prostacyclin formation.

Sixty-six male university students were classified as Type A or B on the basis of the Structured Interview of Rosenman and as hostile or non-hostile on the basis of the Cook-Medley scale. Vascular production of prostacyclin and platelet thromboxane in response to a standard vessel injury was evaluated. Basal thromboxane production, measured as the primary metabolite, thromboxane B2, in blood oozing from the bleeding-time site, was highest among hostile Type A subjects with significantly lower thromboxane production in hostile Type Bs and all non-hostile groups combined. Following an exercise treadmill test hostile subjects produced more thromboxane than non-hostile ones, and hostile Type As had significantly shorter bleeding times than hostile Type Bs. No significant differences on any measure were observed following a stressful color naming task. The observed interaction of hostility and Type A behavior on bleeding time thromboxane formation links behavior to an adverse aspect of a thrombosis-related parameter thought to be involved in the genesis of cardiovascular disease.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Conditioned taste aversion but not adrenal activity develops to ICV administration of interleukin-1 in rats.

In a previous investigation with mice, the paired presentation of either odor or taste cues with the peripheral (IP) administration of the immunoactive peptide interleukin-1 (IL-1) led to the conditioned enhancement of glucocorticoid production. The present study found that an initial central infusion of IL-1 in the presence of saccharin cues produced a robust taste aversion but not a conditioned elevation of either ACTH or corticosterone production. These results indicate that the glucocorticoid response induced by centrally administered IL-1 in rats is independent of the behaviorally aversive properties of this cytokine which are conditionable. The differential effects of IP versus ICV administration of IL-1 on glucocorticoid conditioning requires a clearer specification of the respective signaling mechanisms and pathways activated by these two routes of administration.

Adrenocorticotropic Hormone↗
PubMed1991

Predicting postpartum depressive symptoms: a structural modelling analysis.

In this prospective, longitudinal study, 42 first-time mothers, recruited through prenatal classes, were assessed on variables predictive of postpartum depressive symptoms. Using a causal modelling structural analysis, it was found that prenatal depression, partners' support, and infant-related factors all contributed to the development of depression following childbirth.

Adult↗
PubMed1991

The structured interview elicits a differential prostacyclin response in A and B behaviour types.

OBJECTIVE: To determine whether individuals exhibiting the type A behaviour pattern have a different extent of prostacyclin or thromboxane production after relaxation or after a structured interview compared to individuals exhibiting the type B behaviour pattern. DESIGN: Subjects were randomized to receive prospectively either a relaxation session or a mildly stressful interview first. Each then received the alternate treatment second. SETTING: Students attending an introductory psychology course at the University of Manitoba received a relaxation session (20 mins lying down listening to a tape) and an interview session (the structured interview of Rosenman). OUTCOME MEASURES: Type A/B behaviour pattern was rated using the structured interview of Rosenman. Production of 6-keto prostaglandin F1-alpha and thromboxane B2, metabolites of prostacyclin and thromboxane A2, respectively, were measured in response to a standardized vascular injury-bleeding time. MAIN RESULTS: No significant differences were observed in the length of bleeding time, in bleeding time thromboxane production or in prostacyclin production after relaxation between individuals exhibiting type A and B behaviour patterns. Prostacyclin production after the interview was lower in type A individuals (3.29 +/- 0.29 pg/min) than in individuals exhibiting type B behaviour (4.76 +/- 0.63 pg/min) (P = 0.04). No significant post interview differences in bleeding time or in thromboxane production were seen. CONCLUSION: After relaxation, type A and B subjects are similar in their prostacyclin and thromboxane responses to vascular injury. However, type A individuals show a less favorable prostacyclin response than type B when confronted with the structured interview; type A individuals responded in an aggressive or hostile fashion, while the type B individuals exhibited a more relaxed response.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

The Pavlovian conditioning of IL-1-induced glucocorticoid secretion.

Recombinant IL-1-beta, which is capable of stimulating the pituitary-adrenal axis to secrete corticosterone, was paired with environmental cues in either a taste aversion or odor conditioning procedure. Among mice receiving paired delivery of cues and IL-1, subsequent re-exposure to cues elicited corticosterone production. This response was significantly greater than in animals that were conditioned but not re-exposed to the cues or were exposed to the cues alone. These results indicate that the IL-1 activation of adrenal cortical secretion can be conditioned to environmental stimuli.

Animals↗
PubMed1989

Cognitive appraisal and attributional correlates of depressive symptoms in children.

This study examined differences in cognitive appraisal and causal attributions in response to a task among schoolchildren reporting high and low depressive symptomatology. From a sample of 361 fifth- and sixth-grade students, 72 children were classified as depressed or nondepressed on the basis of their scores on the Children's Depression Inventory. They were then presented with modified Picture Arrangement problems from the WISC-R and questioned about their performance. Pretask expectations, evaluations, and future expectations of performance for the self and that of same-aged peers were assessed, as well as causal explanations for solvable and unsolvable problems. Despite similar performance, the depressed group of children provided lower evaluations for themselves than for others on all three measures of self-appraisal, whereas the nondepressed group did not show this tendency. Further, the attribution results indicated that the two groups differed in their explanations for failure, with the depressed group emphasizing the importance of ability in failure and the nondepressed group emphasizing factors other than ability. Overall, the results provide support for the presence of negative cognitions and self-defeating attributional style among depressed relative to nondepressed children, as well as pointing to the importance of social comparison processes in depression.

Achievement↗
PubMed1987

Conditioned tolerance to drug-induced (poly I:C) natural killer cell activation: effects of drug-dosage and context-specificity parameters.

Three experiments were conducted to evaluate the role of drug-dosage and stimulus-specificity parameters on the tolerance of drug-induced (poly I:C) natural killer (NK) cell activity. In the first experiment a protocol which provided mice with four weekly 20 micrograms/mouse ip injections of the immunostimulatory synthetic polynucleotide (poly I:C) following exposure to either a simple odor cue or a complex cue resulted in tolerance of NK cell activity. The identical protocol with a higher drug dose (50 micrograms/mouse) did not produce tolerance. In a second experiment, the stimulus specificity of tolerance was assessed by giving two groups of mice repeated signaled drug injections. For one of these groups the final poly I:C injection of the series was signaled, while for the other group it was not. Although both groups were tolerant relative to controls not previously exposed to the drug, indirect evidence of conditioning was obtained. Specifically, it was found that tolerance among mice receiving the signal on the test was such that they were not different from undrugged controls, while uncued mice had significantly higher levels of NK cell activity. The third experiment evaluated the role of stimulus specificity within an extinction paradigm. It was found that tolerance was reversed in mice provided with repeated nonreinforced reexposure to drug-signaling cues, while mice exposed to novel cues remained tolerant. These results further support the hypothesis that associative factors contribute to the tolerance of a drug-induced immune response.

Animals↗
PubMed1986

Tolerance to drug-induced (poly I:C) natural killer cell activation: congruence with a Pavlovian conditioning model.

Two experiments were conducted to assess the role of conditioning factors on the tolerance of drug-induced natural killer (NK) cell activity. A protocol in which mice were given four weekly injections of the immunostimulatory synthetic polynucleotide (poly I:C) paired with a complex environmental stimulus produced a reliable tolerance effect. The sensitivity of the observed tolerance to known decremental conditioning procedures--extinction (Experiment 1) and preexposure to the conditioning stimulus (latent inhibition, Experiment 2)--was investigated. The results indicated that posttreatment exposure to drug-signaling cues (i.e., extinction) significantly reversed tolerance such that NK cell activity was at a level comparable to that for controls receiving the drug for the first time (Experiment 1). In a similar fashion, pretreatment exposure to the drug-signaling cues (CS preexposure) inhibited the development of tolerance (Experiment 2). These results provide initial evidence that nonpharmacological manipulations of drug-signaling environmental cues can affect tolerance to the immunostimulatory effect of poly I:C, as would be expected with a conditioning analysis of such tolerance.

Animals↗
PubMed1984

Type A behavior, heart rate and pupillary response: effects of cold pressor and ego threat.

The present study tested the hypothesis that Type A individuals would respond to a relevant stressor (ego-threat), but not an irrelevant one (cold pressor), with higher heart rate (HR) and larger pupil size than Type B's. These measures of physiological arousal were taken during baseline and during exposure to each of two sequentially presented, but counterbalanced stress conditions: ego threat and cold pressor. The physiological measures of sympathetic arousal were supplemented with repeated measures of self-reported anxiety. Three distinct findings emerged. First, Type A subjects had higher levels of HR in response to ego threat, but lower levels in response to cold pressor stress, compared to non-stressed baseline levels. Type B's on the other hand had slight, but nondifferential increased HR to the two different stress regimens. Second, the pupillary response to light did not produce results wholly parallel to those obtained with HR, or with the hypothesis that A's are more physiologically responsive than B's. Finally the Type A subjects in all conditions reported less anxiety than did Type B's. The present results generally indicate that A/B differences in cardiovascular arousal do not generalize readily across situations or to all autonomic indices.

Adolescent↗
PubMed1984

Neurohormonal modulation of natural resistance to a murine lymphoma.

The hypothesis that neuroendocrine stimulation after aversive handling can alter natural resistance was examined in the tail electroshock (TES) model, a procedure that can activate pituitary neuropeptide secretion. Immediately after a brief TES session, the resistance of DBA/2J mice was suppressed in proportion to the intensity of the shock. Initial suppression of the natural resistance was rapidly reversed in longer treatment protocols, and repeated aversive stimulation augmented the antitumor response, leaving the mice more resistant to lymphoma than unhandled animals. Corticosterone was released into the serum after all acute handling procedures, and hydrocortisone inoculation suppressed antitumor responses. However, serum corticosterone levels did not quantitatively correlate with the alterations in natural resistance. The observation that TES-induced suppression of natural resistance could be reversed by the opiate receptor antagonist naltrexone suggested that endogenous opiated released after TES stimulation were immunosuppressive.

Animals↗