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R M Judd

Publications and source records attributed to R M Judd.

40 records · Page 3Linked to original sources
PubMed1991

Effects of barium-induced cardiac contraction on large- and small-vessel intramyocardial blood volume.

We have measured the effects of barium-induced cardiac contraction on the intramyocardial blood volume content of all vessels and have independently measured the blood volume content of vessels with a diameter greater than 100 microns in rat myocardium. Measurements of total intramyocardial blood volume were made by using [125I]albumin as a plasma marker and technetium-99m as a red blood cell marker. In one group of rats (n = 8), diastolic arrest was induced by an intravenous injection of KCl; in a second group (n = 8), systolic arrest was induced by an intravenous injection of BaCl2. In both groups, the hearts were frozen in situ immediately after heart arrest while aortic pressure was decaying from its former physiological level. The left ventricular free wall was sectioned transmurally in a cryomicrotome, and the blood volume within each tissue sample was calculated from its radioactivity. The volume of blood in vessels larger than 100 microns was independently estimated from the exposed cross-sectional area of these vessels in photographs of the frozen tissue taken during tissue sectioning in the cryomicrotome. Total intramyocardial blood volume was found to decrease by about 42% from 8.6 +/- 1.3 ml/100 g (mean +/- SEM) in the KCl group to 5.0 +/- 0.7 ml/100 g in the BaCl2 group (p less than 0.01). Total volume was greater in the epicardial than in the endocardial layers of both groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Tone-dependent waterfall behavior during venous pressure elevation in isolated canine hearts.

We examined the "vascular waterfall" hypothesis, which proposes that coronary flow is unaffected by elevations in outflow pressure until the latter reaches a critical threshold level, in 29 isolated canine hearts. In fibrillating hearts vasodilated with adenosine or carbocromen, coronary flow and the coronary pressure-flow relation were not affected by changes in great cardiac vein pressure (PGCV) below a threshold value of 11 +/- 0.9 (mean +/- SEM) mm Hg. Further elevations of PGCV reduced flow and shifted the pressure-flow relation to the right, increasing its pressure-axis intercept (Pf=0). When vasomotor tone was augmented with vasopressin, threshold PGCV increased to 25 +/- 2.7 mm Hg (p less than 0.001). Once again, the pressure-flow relation was unaffected by changes in PGCV below the threshold value and shifted to the right when this value was exceeded. The amount by which spontaneous values of Pf=0 exceeded threshold values of PGCV was greater when vasomotor tone was augmented than during vasodilation. Pf=0 continued to exceed PGCV when the latter was raised above the threshold level. Both Pf=0 and threshold values of PGCV were less during a long diastole than during ventricular fibrillation. We reached the following conclusions. 1) During changes in PGCV below a threshold value, the coronary circulation exhibits traditional waterfall behavior. 2) The threshold pressure for altering waterfall behavior is affected by vascular tone and mechanical activity. 3) Pf=0 remains above PGCV when the latter is increased above the threshold value needed to alter flow.

Animals↗
PubMed1976

Placental amino acid uptake. III. Transport systems for neutral amino acids.

The human placenta is known to concentrate nearly all amino acids intracellularly for transfer to the fetus. To clarify the mechanism and regulation of this process we have determined the specificity of the principal placental transport systems for neutral amino acids. With the use of competitive inhibition techniques, three transport systems of overlapping specificity have been elucidated. These correspond approximately to the "A", "L", and "ASC" systems of Christensen and associates. In the placenta the specificity of these systems is as follows: A system - alpha aminoisobutyric acid (AIB), glycine, proline, N-methylalanine, alanine, serine, threonine, and glutamine; L system - isoleucine, valine, phenylalanine, BCH, alanine, serine, threonine, and glutamine; and ASC system - alanine, serine, threonine, and glutamine. Placental AIB uptake previously has been shown to increase with preincubation of tissue in vitro. This increase has now been found to be limited to the A system. Activity of the other two systems is essentially unaffected, demonstrating that the transport pathways are separately regulated.

Amino Acids↗