Search PubMed⌕ Search

Biomedical subjects

N MacDonald

Publications and source records attributed to N MacDonald.

At least 109 records · Page 6Linked to original sources
PubMed1986

Study of cardiovascular autonomic insufficiency in advanced cancer patients.

To determine the incidence of cardiovascular autonomic insufficiency (CAI), 43 patients with advanced breast cancer and 20 normal controls were evaluated using electrocardiographic tests (heart rate variation during deep breathing and Valsalva maneuver and upon standing) and clinical tests (blood pressure variation during hand grip tests and upon standing). Nutritional status, tumor mass, Karnofsky performance status (PS) score (0-100), and peripheral reflexes were also determined. Tests for CAI were abnormal in 43 patients (52%), versus seven of 100 in 20 controls (7%, P less than 0.001). In cancer patients, tests for CAI were more frequently abnormal in patients with PS less than 60 (P less than 0.01), basal heart rate greater than 100 (P = 0.05), and malnutrition (P less than 0.01). We conclude that CAI is a frequent finding in patients with advanced breast cancer and should be suspected mainly in patients with a low PS, tachycardia, or malnutrition. It is probably a multifactorial syndrome, and malnutrition, drugs, decreased activity, or paraneoplastic syndromes are all possible causes for CAI.

Autonomic Nervous System↗
PubMed1985

Quantitative measurement of myocardial blood flow with oxygen-15 water and positron computed tomography: an assessment of potential and problems.

An in vivo measurement technique using 15O water and positron CT for quantitation of myocardial blood flow (MBF) was investigated. A closed-chest dog model and NeuroECAT scanner were used in the study. The in vivo technique involves i.v. infusion of 15O water for a duration of 2-3 min. Oxygen-15 water radioactivity in myocardium was imaged with a NeuroECAT scanner for 10 min, starting at the time of tracer infusion. A separate scan following inhalation of 15O CO was obtained to label the blood pool and to help remove the contribution of radioactivity in the blood pool during the 15O water scans. The integrated projection technique was used for calculating MBF. The quantitative microsphere technique for measurement of MBF was performed along with the 15O water study to provide reference values, with which the MBF values by the in vivo technique was compared. Results of 12 experimental runs (in seven animals) show the in vivo technique with 15O water and positron CT can give quantitative flow images of myocardium. The in vivo positron CT measurement was found to correlate well (r = 0.93) with the in vitro values (by microspheres) over the flow range of 40 to 150 ml/min/100 g.

Animals↗
PubMed1983

Antepartum chronic fetal vesicoamniotic shunts for obstructive uropathy: A report of two cases.

Two fetuses with obstructive uropathy characterized by striking oligohydramnios and dilatation of the urinary collecting system were identified by ultrasound and treated by percutaneous insertion of a long-term vesicoamniotic silicone rubber shunt. Both fetuses were less than 16 weeks' gestation at diagnosis and less than 18 weeks at treatment. One fetus was delivered at 35 weeks and is alive and well; the other died early in the neonatal period at 31 weeks with pulmonary hypoplasia.

Adult↗
PubMed1983

Short- and long-term effects of cromolyn sodium on the airway reactivity of asthmatics.

To study the effects of cromolyn sodium on the airway reactivity of asthmatics, we performed a randomized, double-blind, crossover study in which 11 atopic asthmatics inhaled 20 mg of cromolyn sodium or a matching placebo four times daily for 4 wk each, while in their allergy season. Bronchial challenges consisting of either eucapnic hyperventilation with frigid air or methacholine were performed before, in the middle, and at the end of each treatment period. Stimulus-response relationships were assessed with the forced expiratory volume in I sec (FEV1). The level of ventilation (VE) and the provocative dose of methacholine (meth) required to reduce the FEV1 20% from control were recorded as the PD20VE and PD20meth, respectively. There were no significant differences in the baseline FEV1 on any study day. The short-term administration of cromolyn brought about a significant increase In PD20VE prior to both the placebo and active phases of the study. Placebo had no effect on airway reactivity. After 2 wk of cromolyn, PD20VE rose significantly and stayed elevated during the course of the study. Neither the short- nor long-term administration of cromolyn had any effect on the responsiveness to methacholine. These results demonstrated that long-term therapy can attenuate the responsiveness to naturally occurring asthmogenic stimuli even when nonspecific reactivity is unchanged.

Adult↗
PubMed1983

Quantitative measurement of local cerebral blood flow in humans by positron computed tomography and 15O-water.

A noninvasive method that employs 15O-water and positron-computed tomography (PCT) was used to measure quantitative local cerebral blood flow (lCBF) in man. 15O-Water (about 30-50 mCi) was introduced through a single-breath inhalation of 15O-carbon dioxide or through an intravenous bolus injection of 15O-water. A sequence of five 2-min PCT scans was initiated at the time of tracer administration. A series of 15-20 blood samples (1 ml each) was withdrawn from the radial artery of the subject over a period of 10 min. Oxygen-15 radioactivities in the blood samples were immediately counted in a well counter to give an input function, which together with the projection data collected by PCT were processed to provide images of 1CBF and local water distribution volume. The method was found to be convenient to use and gave good-quality images of 1CBF. Quantitative values of 1CBF in images were 59 +/- 11 and 20 +/- 4 ml/min/100 g for gray and white matter, respectively, with a gray-to-white matter ratio of 2.93 and a global flow value of 42 +/- 8 ml/min/100 g. Distribution volume of water was 0.85 +/- 0.03, 0.76 +/- 0.03, and 0.81 +/- 0.02 ml/g respectively, for gray matter, white matter, and whole brain.

Adult↗
PubMed1981

Review of coccidioidomycosis in immunocompromised children.

Only 13 cases of coccidioidomycosis in immunocompromised children have been previously reported. Of the reported cases, seven children had extrapulmonary involvement and died, while the six children with disease limited to the lungs survived the infection. A leukemic child who was treated for disseminated coccidioidomycosis and survived is described. Reviews of immunocompromised adult patients with coccidioidomycosis suggest factors that might be related to dissemination. Similar factors for immunocompromised children could not be defined, thus suggesting the need for more information regarding coccidioidomycosis.

Child, Preschool↗
PubMed1976

Time delay in simple chemostat models.

The models of Monod and Williams, for the growth of unicellular organisms in chemostats, give strongly damped transients in the biomass and cell number when the flow rate of the chemostat is changed. A simple trick is used to incorporate time delay in these models while still allowing a conventional stability analysis. For long enough time delays the equilibrium point is unstable and limit cycles can be compared. Results obtained using Williams' model, with weakly damped transients as a result of using moderately long time delay, are compared with his data in which cell numbers show weak damping but biomass shows strong damping.

Cells, Cultured↗