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Biomedical subjects

J Buchanan

Publications and source records attributed to J Buchanan.

At least 73 records · Page 4Linked to original sources
PubMed1987

Effect of graded coronary flow reduction on ionic, electrical, and mechanical indexes of ischemia in the pig.

This study was performed to determine the relative sensitivities of ionic, electrical, and mechanical indexes of myocardial ischemia. We used ion-selective and bipolar plunge electrodes, epicardial unipolar electrodes, a suction electrode, and ultrasonic crystals to determine the changes in intramyocardial extracellular potassium ([K+]e) and extracellular pH (pHe), local activation, epicardial TQ-ST segment, monophasic action potential duration (MAPD), and regional contractility during graded coronary flow reduction in open-chest pigs. A carotid-to-coronary shunt was created to perfuse the left anterior descending coronary artery via a roller pump. The shunted coronary flow was reduced in a stepwise fashion at 5-min intervals. In 25 pigs, the approximate myocardial blood flow associated with the initial changes in each variable was as follows: midmyocardial [K+]e, pHe, and TQ-ST segment, 0.7 to 0.8 ml/min/g; subepicardial [K+]e and TQ-ST segment, 0.6 to 0.7 ml/min/g; segmental shortening, 0.5 to 0.6 ml/min/g; local activation and epicardial TQ-ST segment, 0.3 to 0.4 ml/min/g; epicardial MAPD, 0.15 to 0.2 ml/min/g. Our results indicate that changes in [K+]e, pHe, and TQ-ST segment provide the most sensitive means of detecting myocardial ischemia and of determining the effect of interventions capable of influencing the ischemic process.

Action Potentials↗
PubMed1983

Clinical evaluation of a flat-plate membrane plasma exchange system.

A new flat-plate membrane plasma separation system specifically designed for therapeutic plasma exchange (TPE) was clinically evaluated in both research and routine clinical settings. The study included a comparison to a currently available centrifugal cell separation system employed for TPE. A total of 267 membrane procedures were performed on 39 patients over a 14-month period. Both qualitative and quantitative studies showed that membrane plasma exchange procedures were equivalent to centrifugal procedures in the removal of plasma constituents from patients. A notable difference between the two types of procedure was the effect on the peripheral blood platelet count: the plasma filtrate from the membrane system was essentially cell-free and platelet counts fell only 11% during the procedure, compared to a 53% decrease during the centrifugation runs. Patient responses to both types of procedure were similar and the frequency of side-effects was low. A sampling of patient opinion revealed a preference for the membrane system for a variety of reasons. Procedure times were shorter with the membrane system because of higher achievable blood flow rates, and thus higher plasma exchange rates, while the overall nursing time requirement was lower. The results show that this flat-plate membrane TPE system enables rapid and effective plasma exchange therapy, and offered a number of monitoring and control functions that provided a safer, more efficient therapeutic procedure in the majority of patient treatments performed in this study.

Adult↗
PubMed1983

Aorto-atrial fistula in rheumatoid arthritis.

A patient with severe deforming rheumatoid arthritis presented with a short history of chest pain. The clinical signs were of an unusual diastolic murmur and profound shock unresponsive to therapy. Post-mortem examination disclosed the unexpected finding of a large aorto-atrial fistula.

Aged↗
PubMed1981

Ventilation-perfusion lung scanning in patients detected by a screening program for early lung carcinoma.

Ventilation-perfusion (V-P) lung scans obtained in 114 patients in screening program for the early detection of lung cancer were reviewed, and abnormalities were correlated with radiographic and surgical findings. Eighty-seven patients eventually had a tissue diagnosis of carcinoma; 65 (75%) had a perfusion defect and 56 (67%) had a ventilation abnormality at the tumor site. Lobar or segmental perfusion abnormalities were present at the tumor site in two of 13 patients whose lung cancer could not be localized by chest radiographs. However, 12 of these 13 patients and 54% of those with radiographically visible lesions had perfusion abnormalities in other lung regions. Twenty-seven patients with suspected carcinoma who were subsequently proved to have benign lesions had V-P abnormalities similar to those in patients with lung cancer. Thus, no pattern of V-P abnormalities similar to those in patients with lung cancer. Thus, no pattern of V-P abnormalities allowed lung cancer in this screened population to be reliably distinguished from coexisting airway disease or non-malignant pulmonary masses. V-P lung studies have a limited role in the early detection of lung cancer.

Aged↗
PubMed1979

Gamma-aminobutyric-acid deficiency in brain of schizophrenic patients.

Gamma-aminobutyric acid (G.A.B.A.) was measured in the nucleus accumbens and thalamus of brains from patients who had died with schizophrenia or Huntington's chorea (H.C.) and from control subjects. Mean G.A.B.A. content was significantly reduced in both brain areas in schizophrenia and in H.C. Extraneous factors, such as age, interval from death to necropsy, cause of death, and drug use, did not readily explain the observed reduction in brain G.A.B.A. G.A.B.A. deficiency may be a biochemical characteristic of some forms of schizophrenia.

Brain Chemistry↗
PubMed1979

Relation between mammary cancer growth kinetics and the intervals between screenings.

The purpose of this study was to consider the time interval for periodic mammographic screening for breast cancer. One hundred fifteen breast cancers occurring in 10,128 women receiving over 30,000 mammograms over a four year period were reviewed. Tumors were diagnosed at three time intervals: 1) first screening (39/115); 2) annual examination (27/115); and 3) at an examination that occurred less than twelve months from a previous annual examination (10/115). Also, there were tumors that grew to a palpable dimensions and were self-detected between annual examinations (39/115). Our opinion is that screening intervals should be individualized to each patient according to risk factors and suspicious mammographic findings. Further, there is a significant number of breast cancers that grow too fast to be detected effectively by annual mammography. Suspicious mammographic findings did not exist before these cancers reached palpable dimensions. Other risk factors characterizing the hosts who develop these fast growing cancers are yet to be determined.

Biopsy↗
PubMed1979

Improving exposure component and generalization potential of stress inoculation for pain.

Stress inoculation for pain involves education about the psychological dimensions of pain, training in a number of coping skills, and practice in applying these skills during exposure to the noxious stimulus. In a previous study the exposure component (which involved six practice sessions) proved ineffective; moreover the efficacy of the other components was not repeated on the generalization measures. The present study compared three variations in the exposure component and found that training with a single practice session on the cold pressor task proved more helpful than training with no practice at all, which in turn was no worse than training with six practice sessions. Moreover, therapeutic attention to generalization resulted in increased pain tolerance on the pressure algometer task.

Behavior Therapy↗
PubMed1979

Diurnal variation in uterine estrogen receptors in immature female rats--inhibition by arginine vasotocin.

A diurnal variation in uterine estrogen receptors from immature female rats was observed with the peak occurring during the mid-light phase (noon) of the cycle. Although no dose response was noted, all concentrations of arginine vasotocin ranging from 5 x 10(-7) to 5 x 10(-9) significantly inhibited binding of 3H-estradiol to estrogen receptors in the cytosol fraction of uteri obtained from immature female rats either during the light or dark phase of the photoperiod.

Aging↗