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Biomedical subjects

R A Allen

Publications and source records attributed to R A Allen.

At least 55 records · Page 3Linked to original sources
PubMed1983

Behaviour and quantitation of extrinsic (tissue-type) plasminogen activator in human blood.

Functional assay of extrinsic (tissue-type) plasminogen activator (EPA) in plasma on fibrin plates was evaluated. Using specific quenching antibodies, we demonstrated the method to be specific for EPA under all conditions tested. Contributions of urokinases and intrinsic activators were excluded. The quantity of EPA in blood samples, as compared with purified uterine tissue activator, shows 1 blood activator unit (BAU) to be comparable to 0.93 ng. The median values for EPA activity for healthy volunteers were: baseline, 1.9 BAU/ml (n = 123); diurnal, 5.5 BAU/ml (n = 12); DDAVP administration, 11.7 BAU/ml (n = 39); exhaustive exercise, 25 BAU/ml (n = 24); venous occlusion (15 min), 35 BAU/ml (n = 61). A large inter-individual variation in EPA activity was found, while individual baseline values tended to be constant for periods of weeks. In vitro in blood EPA activity shows a disappearance of 50% in about 90 min at 37 degrees C; EPA activity in euglobulin fractions is stable for less than or equal to 2 hr at 37 degrees C. A rapid decrease in EPA activity occurs in vivo, as noted after extracorporal circulation and exercise stimulation (t1/2 decay, 2-5 min).

Adult↗
PubMed1982

The use of desmopressin acetate (DDAVP) as a test of the fibrinolytic capacity of patients--analysis of responders and non-responders.

Intravenous infusion of desmopressin (DDAVP, 0.4 micrograms/kg b.w. in 12') causes an increase in the level of extrinsic plasminogen activator, measured in plasma euglobulin fractions with added C1-inactivator on fibrin plates. A poor response or no response at all was elicited in two out of 21 patients with spontaneous thrombosis, 18/38 with hyperlipoproteinaemia and 10/14 with terminal renal insufficiency requiring haemodialysis. Haemodilution during the first 30' after starting the DDAVP-infusion occurred both in responders and in non-responders; so did haemodynamic reactions: increase in heart rate, drop in diastolic blood pressure, facial flushing. The rise of fibrinolytic activity was shown not to be associated with decreased hepatic blood flow. Normal factor VIII-rises in "non-responders" indicate the responsiveness of the receptive organs, including the hypothalamus, to DDAVP. Despite a normal baseline level of fibrinolytic activity in the blood, as occurs for instance in terminal renal insufficiency, the vascular endothelium may be refractory to stimulation. In some patients especially in type IV hyperlipoproteinaemia, a selective defect of the release of plasminogen activator is postulated. In subjects with low fibrinolytic activity at rest, as observed in spontaneous thromboembolism and in hypertriglyceridaemia, the failure to release plasminogen activator upon stimulation with DDAVP might be a consequence of an impairment of synthesis as well.

Antigens↗
PubMed1982

An enhancing effect of poly-lysine on the activation of plasminogen.

This study demonstrates that poly-lysine mimics the cofactor (enhancing) function of fibrin that is seen in tissue activator-induced plasminogen activation. Additionally, and in contrast to fibrin, poly-lysine exhibited an enhancing effect on low molecular weight (and not high molecular weight) urokinase-induced plasminogen activation. A mechanism is proposed for this enhancement that involves the rendezvous and local concentration of plasminogen and plasminogen activator molecules on the lysine polymer. All components were able to bind to immobilized poly-lysine making the proposed mechanism feasible. It was possible to elute the activators and mini-plasminogen and plasmin which required 1 M lysine for elution, suggesting specific binding involving lysine binding sites. The enhancing effect was specific for poly-D- and L-lysine and poly-L-ornithine, which has a similar structure. The use of poly-lysine can lead to a better standardization and increased sensitivity of indirect two-step assays for plasminogen activators employing synthetic chromogenic substrates.

Binding Sites↗
PubMed1982

The effects of unilateral plethysmographic feedback of temporal artery activity during migraine head pain.

Eight classic migraine sufferers were trained to self-regulate blood volume pulse amplitude (BVPA) using photoelectric plethysmograph feedback. Using a within-subject design, subjects learned to increase and decrease BVPA at superficial temporal artery (STA) and finger locations. They were then assessed while experiencing a migraine headache in the training laboratory during which pain measurements were obtained. Results showed a significant relationship between voluntary pulse amplitude changes in the STA and pain reports during migraine consistent with expectations from Wolff's theory. Further, pain did not change as a result of pulse amplitude changes in the finger location. A two-stage biofeedback treatment model for migraine is proposed.

Biofeedback, Psychology↗
PubMed1982

The mcGill-Melzack Pain Questionnaire in the diagnosis of headache.

The McGill-Melzack Pain Questionnaire (MMPQ), comprised primarily of adjectives descriptive of pain, was administered to 100 patients seeking treatment for headache. Diagnostic classification of patients into migraine or muscle contraction headache groups was conducted by a screening neurologist using information other than pain description. Reliability determinations were made following independent diagnosis by two other neurologists using a headache pain history and symptom form (HPHSF) devoid of pain adjectives. Comparison of 30 subjects HPHSF's revealed that the screening neurologist's diagnosis and that of two other neurologists, (tau = .87, rho < .01) and (tau = .48, rho < .05), indicate high agreement between three physicians in headache diagnosis devoid of pain description. Results show that migraine headache patients report significantly more affective words (t 99 = 3.89, rho < .001) than do muscle contraction headache sufferers; however, no significant differences existed between the groups' use of sensory or evaluative works. Migraine sufferers, while not reporting their headache as more severe "generally," did report more intense pain when recalling headache at its "worst" (t99 = 2.69, rho < .01) and at its "least" (t99 = 1.74, rho < .05) compared to the muscle contraction headache 'group. Discriminant analyses were conducted on one-half of the sample to determine diagnostic group membership on the basis of pain description alone. Findings revealed that group membership could be predicted at a 90% rate (chi2 145 = 33.06, rho < .001). A cross validation on the second half of the sample confirmed these findings (chi2 1.48 = 13.08, rho < .05) suggesting that the MMPQ is of value in headache diagnosis. Differences between electromyographic studies and headache pain report are discussed as well as suggestions concerning modification of the MMPQ for headache assessment.

Adolescent↗
PubMed1980

Relaxation training, twenty-four-hour blood pressure reductions.

If the demonstrated effects of relaxation training on blood pressure (BP) occur only during relaxation practice, then little effect on the morbidity and mortality of exssential hypertensives would be expected. This question was addressed by inpatient monitoring of five hypertensive patients' BP for 24 hours during six experimental days, including a no-treatment baseline, three days of relaxation training, and one day of recovery. Lowering of both systolic and diastolic pressures persisted beyond the end of the training sessions. Moreover, systolic BP was significantly lower during relaxation training days than during either baseline or recovery days, a difference particularly noticeable at night when patients were sleeping. The BPs of the three patients showing the largest initial effects of training averaged 12.5/7.3 mm Hg less during nights following relaxation sessions than during nights following no treatment.

Blood Pressure↗