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J Ross

Publications and source records attributed to J Ross.

At least 577 records · Page 32Linked to original sources
PubMed1984

Regional myocardial perfusion and wall thickening during ischemia in conscious dogs.

We examined in conscious dogs the effects of reductions in myocardial blood flow (MBF) in three different layers across the wall on regional myocardial contractile function in the ischemic zone, measured as systolic wall thickening (%WT). In 16 dogs, %WT was measured with sonomicrometry and MBF was determined with microspheres (10- to 12-microns diam) during coronary stenosis of the left circumflex coronary artery. The stenoses were categorized into six groups by the effect on %WT (each group representing progressive 20% decrements in %WT from control), and individual and pooled regression analyses were performed on data from six of the dogs having multiple data points to evaluate the shape (linear or curvilinear) of the relationships between MBF and changes in %WT. Transmural contractile function was highly sensitive to acute reductions in MBF, especially reductions in the subendocardium. The shape of the normalized subendocardial MBF-%WT relation was mildly curvilinear by regression analysis (quadratic equation, gamma = -0.75x2 + 2.15x -0.39, r2 = 0.92). Likewise, mean transmural and midmyocardial MBF correlated well and closely with changes in %WT. Subepicardial MBF, however, correlated poorly with changes in %WT, there being no change in subepicardial MBF until %WT had been reduced more than 50%.

Animals↗
PubMed1984

Effects of a calcium-entry blocker (diltiazem) on regional myocardial flow and function during exercise in conscious dogs.

We examined the effects of diltiazem, a calcium-entry blocker, on exercise-induced myocardial ischemia in nine conscious dogs with chronic coronary stenoses. An ameroid constrictor, Doppler flow probe, and hydraulic occluder were placed around the left circumflex coronary artery, and left ventricular pressure was measured (Konigsberg micromanometer). Pairs of ultrasonic crystals were implanted for measuring left ventricular systolic wall thickening (% delta WTh) in control (left ventricular anterior wall) and ischemic (left ventricular posterior wall) regions, and regional myocardial blood flow was measured with the microsphere method. Eighteen days (average) after surgery mean coronary blood flow velocity had decreased and reactive hyperemic flow velocity after 10 sec of coronary occlusion was markedly reduced, but % delta WTh at rest remained normal, indicating collateral development. Control treadmill exercise was performed for 3.7 min (average), and 2 hr later administration of 0.3 mg/kg diltiazem was followed by an identical exercise bout. Control exercise increased % delta WTh in the normal region, while in the ischemic region % delta WTh decreased markedly and ischemia was evident (subendocardial flow, 0.29 +/- 0.12[SD] ml/min/g). After diltiazem hemodynamic and % delta WTh values at rest were not changed; during exercise the heart rate was significantly lower (204 +/- 24 vs 227 +/- 33 beats/min, p less than .01), but values for other hemodynamic measures were similar to those during the control run. % delta WTh in the control region was not changed during exercise after diltiazem, but compared with control exercise in the ischemic zone there was less dysfunction and subendocardial flow was greater. Recovery from exercise-induced dysfunction in the ischemic region occurred within 5 min, compared with over 30 min after control exercise. Thus, in a preparation of chronic coronary stenosis, the calcium-entry blocker improved the relationship between regional myocardial flow and function during exercise and led to more rapid recovery of regional myocardial dysfunction.

Animals↗
PubMed1984

Applications and limitations of end-systolic measures of ventricular performance.

The usefulness of end-systolic measures of left ventricular performance as a load-independent method of assessing of ventricular contractility has been studied in intact, conscious dogs. The end-systolic pressure-chamber diameter (P-D) relation was shown to be linear, unaltered by preload changes, and shifted in a parallel fashion by inotropic stimulation, whereas the end-systolic pressure-volume relation appeared to increase in slope with increased contractility. A simplified measure of end-systolic relations that does not require measurement of chamber volume or diameter, the end-systolic pressure-wall thickness ( WTh ) relation, was also linear and shifted with acute changes in inotropic state. During regional ischemia, the regional end-systolic WTh relation also may provide a relatively load-independent means of detecting regional depression of myocardial contractility. With chronic pressure overload hypertrophy in dogs, the end-systolic P-D relation was markedly shifted upward and to the left, which indicates hyperfunction of the left ventricle; however, end-systolic wall stress-diameter relations were identical before and after the development of hypertrophy, which suggests that myocardial contractility was unaltered. These findings and clinical studies of mitral regurgitation imply that for assessing resting left ventricular contractility in certain chronic conditions, the use of wall stress rather than pressure may be appropriate in the end-systolic framework. Further experimental studies are needed in the intact circulation to better characterize end-systolic relations before their full potential in the clinical setting can be realized.

Animals↗
PubMed1983

Adenocarcinoma of the endometrium. Analysis of 256 cases with disease limited to the uterine corpus: treatment comparisons.

Between 1959 and 1975, 256 patients with pathologic Stage I uterine adenocarcinoma were treated at Stanford University Hospital, Stanford, California. One hundred ninety-three patients were initially treated with surgery, and 63 received preoperative radium, reflecting different treatment philosophies of physicians operating at Stanford. Relapse rates for the two treatment groups were 9% (17 of 193) and 14% (9 of 63), respectively (P = 0.24). In both groups of patients, relapse rates were correlated with grade, although for those treated with initial surgery myometrial invasion was a much better predictor of relapse. Only one of the 127 patients without demonstrable myometrial invasion suffered a possible relapse. Sixteen of 66 patients with myometrial invasion (24%) relapsed after treatment. A review of the histologic material revealed 26 of 256 cases with a special histologic variant termed uterine papillary serous carcinoma, which was associated with a high relapse rate (50%) and a marked tendency for upper abdominal spread. It was found that the use of preoperative intracavitary radium was not demonstrated to be of value. Histologic information obtained from the hysterectomy specimen can be used to determine patients at high risk for relapse who may benefit from adjuvant treatment based on our understanding of the natural history of endometrial carcinoma.

Adenocarcinoma↗
PubMed1983

Human beta and delta globin messenger RNAs turn over at different rates.

We have tested the hypothesis of Winslow & Ingram (1966) that the steady-state levels of human beta and delta globin proteins are determined, in part, by the stabilities of their respective messenger RNAs. Nucleated bone marrow cells were cultured under different RNA "chase" conditions, and samples were harvested at intervals thereafter. The quantities of beta and delta globin mRNA sequences in total RNA from these cells were measured by solution hybridization with specific 32P-labeled DNA probes. The average half-lives of beta and delta globin mRNAs are 16.5 and 4.5 hours, respectively. Both mRNAs are polyadenylated. The rapid turnover of delta globin mRNA accounts, at least in part, for the low level of delta globin mRNA in non-nucleated peripheral blood reticulocytes. The possibility that the rate of mRNA decay is determined by nucleotide sequence signals located in the 3' untranslated region is discussed.

Adult↗
PubMed1983

The role of the pericardium in interactions between the cardiac chambers.

Distension of one side of the heart involves both the atrium and the ventricle, and such atrioventricular enlargement encroaches more on pericardial volume than would ventricular distension alone. The influence of distension of the entire right side of the heart on the pressure-volume relationship of the entire left heart was studied in six postmortem canine hearts with intact pericardium. The pressure-volume relation of the left heart was determined when the right heart was empty and when it was filled with saline. The pressure-volume curve of the left heart became steeper when the volume of the right heart was increased. However, after subtracting pericardial pressure from the left heart pressure, the pressure-volume curves were unaffected by increased volume of the right heart. Selective distension of the entire right heart has a considerable effect on the filling characteristics of the left heart when the pericardium is intact, although this is less than that observed in experiments in which the more compliant atria have been excluded. This effect becomes negligible after subtracting pericardial pressure.

Animals↗
PubMed1983

Influence of the pericardium on left ventricular diastolic pressure-volume curves in dogs with sustained volume overload.

The pericardium is largely responsible for displacement of the left ventricular diastolic pressure-volume curve observed after acute volume loading in dogs. Likewise the pericardium has been considered likely to play a role in displacement of the curve in patients with acute cardiac failure and in shifts following manipulation of afterload. This study was designed to examine the influence of the pericardium on the diastolic pressure-volume relation of the left ventricle when volume load is more sustained, a setting relevant to observations made in patients with heart failure. We measured left ventricular pressure and volume in six conscious dogs with sustained volume overload (mean left ventricular end-diastolic pressure 21 mm Hg, left ventricular end-diastolic volume 149% of the upper limit of normal for our laboratory) produced by aortocaval shunt created 7 to 29 days earlier. Simultaneous left ventriculograms and pressures were obtained before and during nitroprusside infusion with the pericardium intact and in four dogs the studies were repeated 7 to 15 days after pericardiectomy. In all six dogs with intact pericardium, nitroprusside displaced the entire pressure-volume curve downward whereas after pericardiectomy, the pressure-volume data points obtained before and during nitroprusside infusion fell on a single curve. These results were similar to those previously reported for acute volume overload. Nitroprusside did not alter the time course of left ventricular pressure fall during the isovolumic period of diastole either before pericardiectomy (28.8 +/- 10.2 sec,-1, 28.4 +/- 11.9 sec-1) or after (28.8 +/- 6.7 sec-1, 26.1 +/- 7.2 sec-1). These data indicate that in dogs subjected to volume overload sustained for periods of up to 29 days, the pericardium affects the left ventricular diastolic pressure-volume curve and contributes to the elevation of left ventricular filling pressure through upward displacement of this curve.

Animals↗
PubMed1983

Periods of differing mortality distribution during the first year after acute myocardial infarction.

The mortality rate after acute myocardial infarction (AMI) has generally been modeled by a single exponential function. The present study was undertaken to determine, in 3 different populations, whether or not periods exist during the first year after AMI which have mortality distributions that differ from this pattern. The 3 patient populations included San Diego (346 patients, 71 deaths), Vancouver (704 patients, 146 deaths), and Copenhagen (1,140 patients, 262 deaths). Hospital admission was within 24 hours of the onset of symptoms, and patients dying within the first 24 hours after hospital admission or of noncardiac or unknown causes were not analyzed. The mortality between 2 and 21 days in the combined data base was 11.4% (range 10.9 to 11.7) and from 3 weeks to 1 year 10.5% (range 9.0 to 11.3). A high degree of similarity was noted among the shapes of the 3 survival curves. The hypothesis of an exponential mortality rate during the entire first year was rejected. Using a special statistic, changepoints at days 17, 23, and 24 in the 3 populations (21 days for the combined data base) were identified and used thereafter to divide the year into 2 separate periods of mortality within which exponentiality for the mortality rate was not rejected. The point by which exactly 50% of deaths had occurred was day 19, with 75% of deaths occurring by day 100. These data further define the natural history after AMI and indicate optimal follow-up periods for short- and longer-term management strategies based on risk assessment or trials of risk reduction after AMI.

Aged↗
PubMed1983

End-systolic dimension-wall thickness relations during myocardial ischemia in conscious dogs. A new approach for defining regional function.

Overall and regional left ventricular (LV) function was studied during progressive coronary stenosis in conscious dogs by determining the relations at end-systole between LV pressure, chamber dimensions, and regional LV wall thickness. An index of regional wall stress was also analyzed. Using ultrasonic dimension gauges, measurements were made of LV wall thickness in control and ischemic regions, and the external long- and short-axis LV diameters were determined; an implanted micromanometer measured LV pressure. Internal LV diameters were obtained from the external diameters by subtraction of wall thickness, and the index of regional wall stress employed a thick-walled ellipsoidal model. During regional ischemia, the LV long axis at end-systole did not change, whereas the short-axis diameter progressively increased (from 24 +/- 7 mm [standard deviation] to 30 +/- 9 mm, p less than 0.001, indicating a more spherical LV shape during ischemia). The end-systolic pressure did not change, and therefore the end-systolic pressure-diameter relation shifted progressively, suggesting a global decrease in LV contactility. The end-systolic points relating LV wall thickness in the ischemic region to the end-systolic LV pressure revealed the regional nature of the abnormality, showing a progressive displacement to the left, whereas there was no significant displacement of this relation in the control region. The application of this index over a range of loading conditions during partial vena caval occlusion was illustrated. Thus, the regional end-systolic wall thickness-pressure relation provides a new index for defining the regional contractile state of the LV myocardium which is potentially load-independent and offers the possibility for echocardiographic application.

Animals↗
PubMed1983

Human beta-globin promoter and coding sequences transcribed by RNA polymerase III.

We have investigated low abundance RNAs transcribed in vitro and in vivo from the human beta-globin gene. These RNAs contain globin mRNA sequences covalently linked to sequences transcribed from the 5' flanking region between -235 and the mRNA cap site (+1). Their synthesis in vitro is sensitive to high (100 micrograms/ml) levels of alpha-amanitin but not to low (2 micrograms/ml) levels, and one region of the DNA template bordering their 5' termini is similar to a small segment of Alu repetitive DNA and to the RNA polymerase III promoter consensus sequence. Therefore, these RNAs are transcribed by RNA polymerase III but extend into the mRNA-coding region that is usually transcribed by polymerase II. The polymerase III transcripts are polyadenylated and are probably spliced. Their presence in bone marrow cells and peripheral blood reticulocytes implies that they play some role in the erythroid cell.

Base Sequence↗
PubMed1983

Two-dimensional echocardiographic estimation of right ventricular ejection fraction in patients with coronary artery disease.

Two-dimensional echocardiographic determination of right ventricular ejection fraction was compared with right ventricular ejection fraction obtained by first pass radionuclide angiography in 39 patients with coronary artery disease. Apical four chamber and two chamber right ventricular views were obtained in 34 (87%) of the 39 patients, while a subcostal four chamber view was obtained in 31 patients (80%). Right ventricular ejection fraction by two-dimensional echocardiography was calculated by the biplane area-length and Simpson's rule methods using two paired orthogonal views and utilizing a computerized light-pen method for tracing the right ventricular endocardium. A good correlation (r = 0.74 to 0.78) was found between radionuclide angiographic and two-dimensional echocardiographic right ventricular ejection fraction for each method used. Patients with acute inferior myocardial infarction had the lowest right ventricular ejection fraction by radionuclide angiography and two-dimensional echocardiography (p less than 0.05 compared with patients with right coronary artery obstruction and no infarction). There were no differences in right ventricular ejection fraction between patients with acute and old inferior myocardial infarction by both techniques. No correlation was found between left and right ventricular ejection fraction by radionuclide angiography (r = 0.16). It is concluded that 1) right ventricular ejection fraction by two-dimensional echocardiography correlates well with radionuclide angiographic measurements and can reliably evaluate right ventricular function in coronary artery disease, 2) patients with inferior myocardial infarction have reduced right ventricular ejection fraction, and 3) changes in left ventricular ejection fraction do not directly influence right ventricular function.

Adult↗
PubMed1983

Two-dimensional echocardiographic determination of left atrial emptying volume: a noninvasive index in quantifying the degree of nonrheumatic mitral regurgitation.

Several noninvasive techniques, including radionuclide angiography and Doppler echocardiography, have attempted to measure the regurgitant volume in patients with mitral regurgitation; however, none of these techniques are entirely satisfactory. Utilizing a computerized light pen method for tracing the left atrial endocardial border during systole and diastole in two orthogonal planes (apical four and two chamber views), biplane volume determinations were calculated in 12 normal subjects and 30 patients with nonrheumatic mitral regurgitation. Left atrial emptying volume determinations were performed by subtracting the left atrial end-diastolic volume from the left atrial end-systolic volume. The degree of mitral regurgitation was visually assessed as normal (0, trivial, Group I, 12 patients), mild (1+, Group II, 4 patients), moderate (2+, Group III, 8 patients), moderately severe (3+, Group IV, 12 patients) and severe (4+, Group V, 6 patients) by contrast left ventricular angiography and also quantitatively by regurgitant fraction at cardiac catheterization. All 18 patients with moderately severe (Group IV) and severe (Group V) mitral regurgitation had a left atrial emptying volume greater than 40 ml compared with none of the normal subjects and patients with mild (Group II) or moderate (Group III) mitral regurgitation. There was good correlation between left atrial emptying volume and mitral regurgitant fraction (r = 0.85, p less than 0.01). Thus, in patients with nonrheumatic mitral regurgitation, left atrial emptying volume is useful in separating mild from severe mitral regurgitation.

Adult↗