Responding to health care reform by addressing the institute of medicine report on the future of nursing.

The current health care environment has heightened the importance of achieving positive patient outcomes and excellent customer satisfaction. To remain competitive, health care organizations must adapt quickly to changing regulatory requirements, quality improvement initiatives, and customer expectations. To ensure nursing practice at the Saint Clare's Health System in Northwest New Jersey is at the forefront of leading change, the nursing staff has embraced the Institute of Medicine report The Future of Nursing: Leading Change.

Tensions and stresses of ellipsoidal chambers.

Equations for calculating wall tensions in an ellipsoidal chamber might be useful in analyses of elongated chambers whose transverse sections are not round, and they should be useful for examining the tension distribution associated with such shapes. Considering the forces changing a prolate spheroid (semiaxes a > b = c) into a general ellipsoid (semiaxes a > b > c) led to an equation for tensions at the poles of an ellipsoid. Considering the thickness distribution of a chamber of uniform average stress led to an equation for the average of orthogonal tensions at any point on an ellipsoidal chamber.

Mechanical characteristics of tachycardia-induced left-ventricular failure as evaluated in isolated dog hearts.

Left ventricles of control dog hearts and dog hearts failing due to chronic tachycardia were examined in vivo by echocardiography for systolic function and size, then subsequently studied with an isolated-heart system (artificial perfusion, artificial loading). During 3 weeks of tachycardia (250 bt/min), area ejection fraction fell by 58%, while end-diastolic transverse area increased by 56% (measurements at 120 bt/min). Judging from post-perfusion left-ventricular weights, the dilation occurred with no hypertrophy, raising the question whether the failure model may be associated with anabolic dysfunction.

Characteristics of left-ventricular isovolumic pressure waves in isolated dog hearts.

The peak pressure which a chamber would develop in isovolumic contraction at end-diastolic distention (peak source pressure) is an expression of contractile vigor and a determinant of systolic performance. One can predict source pressure of an ejecting beat by fitting its isovolumic phases with a model isovolumic-wave function. Characteristics of the left-ventricular isovolumic pressure wave (amplitude, duration, shape) were studied in isolated, perfused, artificially loaded dog hearts, where strictly isovolumic conditions could be obtained over a wide range of cavity volumes at constant heart rate and approximately constant contractile state.

Coupling of glucose transport and phosphorylation in Xenopus oocytes and cultured cells: determination of the rate-limiting step.

The initial events in glucose metabolism by all cells are the transport and phosphorylation of glucose. To quantify the relative contributions of these two processes to overall glucose utilization, we have developed an experimental approach for their in situ measurement as parallel processes. The method is based on the use of intracellular [2-3H]glucose as a substrate for both the transporter and hexokinase, and involves simultaneous measurement of [2-3H]glucose efflux and of 3H2O released by phosphorylation.

Characterization of myocardial stress-length relations.

For several decades, some muscle physiologists, cardiac physiologists and cardiologists have normalized systolic load-dimension relations to a positive-strain reference dimension such as the muscle length which is optimal for stress development or the chamber volume resulting in normal end-diastolic stress. Some have viewed isometric stress development at reference length as a contractility index, and some have viewed shortening from reference length in the absence of afterload as an important property (shortening ability or mobility). These intuitive choices together constitute a coherent elastic theory which is more appropriate for activated muscle than is the classical theory, wherein slack length is the reference and slope of the stress-strain relation is the main parameter.

Segmental calculation of left ventricular wall stresses.

A procedure for calculating left ventricular wall stresses segmentally was devised. Rectangular coordinates of the wall surfaces as seen in longitudinal section were plotted with the long axis as the x-axis. For each cavity point, a third-order polynomial (cubic spline) was fitted to the point together with several adjacent points on either side of it; the cavity radius (normal to cavity surface) at the point was found algebraically from the spline's coefficients.

Characteristics of single isovolumic left-ventricular pressure waves of dog hearts in situ.

By fitting isovolumic phases of an ejecting beat with a model-wave function, one can predict source pressure of the ejecting beat (Sunagawa et al. Trans Biomed Eng 1980; 27:299-305), this being a major determinant of systolic performance. Prior applications of this principle have involved two assumptions: (1) that the isovolumic pressure wave is shaped like an inverted cosine wave, and (2) that duration of an isovolumic beat is the same as that of an ejecting beat.

Transport and metabolism of glucose in an insulin-secreting cell line, beta TC-1.

Kinetic characteristics of glucose transport and glucose phosphorylation were studied in the islet cell line beta TC-1 to explore the roles of these processes in determining the dependence of glucose metabolism and insulin secretion on external glucose. The predominant glucose transporter present was the rat brain/erythrocyte type (Glut1), as determined by RNA and immunoblot analysis. The liver/islet glucose transporter (Glut2) RNA was not detected.

Increase in membrane uptake of long-chain fatty acids early during preadipocyte differentiation.

An increase in early rates of oleate uptake, which reflected fatty acid (FA) entry into the cells, was apparent 2-3 days after confluence of differentiating BFC-1 preadipocytes. The increase was measured in cells kept without glucose and with arsenate, where greater than 95% of intracellular radioactivity was recovered as free unesterified oleate. Uptake of retinoic acid, a molecule structurally similar to long-chain FA, remained unaltered during cell differentiation.

Metabolism of oleic acid in differentiating BFC-1 preadipose cells.

Incorporation of [3H]oleate and [14C]glucose into cellular lipids was studied in the preadipose cell line BFC-1 to determine flux changes that accompany the adipose conversion process. Dilution of oleate by intracellular fatty acids (FA) was estimated from the 3H/14C incorporation ratios and from relating steady-state radioactivity in diglycerides to their measured cellular levels. The data indicated that exogenous FA mixed with less than 1% of endogenous FA on its pathway to esterification.

Evidence that downregulation of hexose transport limits intracellular glucose in 3T3-L1 fibroblasts.

Measurements of initial glucose entry rate and intracellular glucose concentration in cultured cells are difficult because of rapid transport relative to intracellular volume and a substantial extracellular space from which glucose cannot be completely removed by quick exchanges of medium. In 3T3-L1 cells, we obtained good estimates of initial entry of [14C]methylglucose and D-[14C]glucose with 1) L-[3H]glucose as an extracellular marker together with the [14C]glucose or [14C]methylglucose in the substrate mixture, 2) sampling times as short as 2 s, 3) ice-cold phloretin-containing medium to stop uptake and rinse away the extracellular label, and 4) nonlinear regression of time courses. Methylglucose equilibrated in two phases--the first with a half-time of 1.

Calculation of left ventricular wall stress.

Chamber-stress equations relate wall stresses to pressure and wall dimensions. Such equations play a central role in the analysis and understanding of heart-chamber function. Over the past three decades, several stress equations giving radically different results have been derived, used, and/or espoused.

Estimation of left-ventricular systolic performance and its determinants in man from pressures and dimensions of one beat: effects of aortic valve stenosis and replacement.

Within a thick heart-chamber wall, there is a midwall element or layer whose displacements best express systolic performance. The volume enclosed by that midwall element (Vm) and the average stress in that element (sigma m) can be calculated accurately by simple formulae. From simultaneous left-side pressure tracings and contrast cine-ventriculograms, Vm and sigma m were calculated at 20-ms intervals for an entire cardiac cycle in five normal subjects and in eight patients before and one year after replacement of stenotic aortic valves.

Evaluation of systolic effectiveness and its determinants: pressure/midwall-volume relations.

It is generally agreed that systolic performance of a heart chamber is the fractional inward displacement of its wall during contraction and that this depends on preload, afterload, and characteristics of the relation between afterload and end-ejection dimensions. However, there is no consensus on the details of this statement. How can one define and identify the wall element, the displacement of which best expresses performance? What is preload? What parameters best characterize the relation between afterload and end-ejection dimensions? Dividing a thick-wall compliance equation by a thick-wall pressure equation reveals the midwall element, the normalized displacements of which depend consistently on normalized pressure changes according to wall properties regardless of wall-to-cavity ratio.

Evidence for functionally distinct glucose transporters in basal and insulin-stimulated adipocytes.

The activity and Km of glucose transport of rat adipocytes are quite variable in the basal state. This could be due to differing levels of highly saturable transport against a background of less saturable transport. Such heterogeneity could lead to differing conclusions as to the Km of basal cells compared to insulin-stimulated cells depending on the choice of substrate, the range of concentrations tested, and the rigor of data analysis.

Activation energy of the slowest step in the glucose carrier cycle: break at 23 degrees C and correlation with membrane lipid fluidity.

Glucose transport in the rat erythrocyte is subject to feedback regulation by sugar metabolism at high but not at low temperatures [Abumrad et al. (1988) Biochim. Biophys.

Independent determinants of systolic effectiveness: growth ability, contractility and mobility.

The left ventricle of the heart is a thick-walled chamber. In such a chamber, cavity dimensions do not express overall wall stretch, so fractional cavity-surface displacements are not ideal performance expressions, and the intercepts and slopes of relations between intensive variables (pressure, stress, resistance, viscosity) and cavity dimensions do not express wall properties. By contrast, there is a midwall isobar whose enclosed volume (Vm) does express distension and stretch, so fractional midwall-volume displacement is an ideal expression of systolic performance, and characteristics of P-Vm and sigma-Vm relations do relate consistently to wall properties.

Effects of chamber shape and fiber orientation on relations between fiber dynamics and chamber dynamics.

The function of a chamber depends on its hydrodynamic properties: isometric pressures it can exert in the operating range of distensions, compliances in the operating range of distensions, and wall-displacement resistances in the operating range of distensions. Wall-displacement resistance is the departure of pressure from isometric pressure relative to rate of cavity-volume change. The dependence of pressure on average stress and wall/cavity volume ratio is indifferent to chamber shape, which suggests that the volume-based compliance-elastance and resistance-viscosity equations would be only moderately shape dependent.

Relations between hydrodynamic and mechanical properties of a sphere.

Important hydrodynamic characteristics of a heart chamber are isometric pressures at operating distensions, compliances at operating distensions, and wall-displacement resistances at operating distensions. Wall-displacement resistance is the pressure change relative to the rate of cavity-volume change causing the pressure change. Another chamber characteristic is the dependence of wall-displacement resistance on distension.

Left-ventricular cavity dimensions in children with normal and dilated hearts.

Studies were carried out to find how left-ventricular length and length/diameter ratio relate to body size and degree of dilation. By use of M-mode and two-dimensional echocardiography, diastolic cavity long axis (Led), diastolic cavity diameter (Ded), systolic cavity long axis (Les), systolic cavity diameter (Des), fractional L shortening (SFL), and fractional D shortening (SFD) were measured in children, adolescents, and young adults between two and 23 years of age, with body-surface area (BSA) between 0.5 and 2.

Evaluation of myocardial properties from image/pressure data: chronic conditions.

Since the wall/cavity ratio of a heart chamber is not a biological constant, fractional cavity-surface motion is not a valid performance index and the stresses most commonly used in the myocardial-mechanics literature are not valid expressions of pulling action or contractility. We have developed a system for analyzing and expressing left-ventricular performance and abilities which avoids these problems. It allows one to estimate the following quantities from left-ventricular image data and arterial pressures: "Fractional midwall excursion", the fractional change in a weighted average of inner- and outer-surface dimensions, which is a valid but preload-dependent expression of performance regardless of wall/cavity ratio.

Dependence of heart chamber dimensions and dynamics on chamber demands and myocardial properties.

A heart chamber undergoes eccentric hypertrophy in response to a chronic elevation of stroke-displacement demand, and it undergoes concentric hypertrophy in response to a chronic elevation of systolic-pressure demand. Both of these adaptations, which occur in various combinations, involve two myocardial plastic properties, "stretch normalization" and "stress normalization". We have developed a model which predicts dimensions and dynamics of the left ventricle as functions of myocardial properties and of the loads to which the chamber is adapted.