The relationships between muscle length, fractional change in length (strain) and work output during cyclic contraction were examined in scaphognathite levator muscle L2B of the green crab Carcinus maenas (L.). The muscle was subjected to sinusoidal strain at 2 Hz and to phasic stimulation in the strain cycle. At an average length and stimulus phase which are optimum for net work output, the wo...

Hypothesis: excessive bronchoconstriction in asthma is due to decreased airway elastance. A.M. Bramley, R.J. Thomson, C.R. Roberts, R.R. Schellenberg. ERS Journals Ltd 1994. ABSTRACT: Based on the strikingly different mechanical properties of airway smooth muscle preparations of different species, we hypothesized that a decrease in the elastance of nonmuscle elements within airway walls of ast...

A mathematical model was analyzed to obtain a quantitative and testable representation of the long-standing hypothesis that the respiratory muscles drive the chest wall along the trajectory for which the work of breathing is minimal. The respiratory system was modeled as a linear elastic system that can be expanded either by pressure applied at the airway opening (passive inflation) or by activ...

Transgenic mice that overexpress human type 1 angiotensin II receptor (AT(1)R) in the heart develop cardiac hypertrophy. Previously, we have shown that in 6-mo AT(1)R mice, which exhibit significant cardiac remodeling, fractional shortening is decreased. However, it is not clear whether altered contractility is attributable to AT(1)R overexpression or is secondary to cardiac hypertrophy/remodel...

OBJECTIVES Myocardial cell injury may contribute to cardiac dysfunction in septic shock. Troponin I is a biochemical marker of myocardial cell injury and death. We hypothesized that troponin I is increased in pediatric patients with septic shock and correlates with cardiac dysfunction and disease severity. DESIGN Prospective, observational study. SETTING Children's medical center. PATIENT...

BACKGROUND Until now, many investigators have focused on describing right ventricular (RV) dysfunction in groups of patients with pulmonary arterial hypertension (PAH), but very few have addressed the deterioration of RV function over time. The aim of this study was to investigate time courses of RV geometric changes during the progression of RV failure. METHODS Forty-two patients with PAH we...

Although cell shortening in patch-clamped cells (current-clamp mode) is triggered by an ordinary action potential, the trigger mechanism in field-stimulated cells is not so obvious. The contraction characteristics of the two methods differ, and we, therefore, examined the triggering sequence in field-stimulated cells. Isolated rat cardiomyocytes were plated on laminin-coated coverslips that wer...

Aortic pulse wave velocity (PWV), generally considered an intrinsic marker of arterial stiffness, might depend in part on the velocity of myocardial fiber shortening, but the relation between PWV and myocardial function in humans has been understudied. A total of 237 untreated hypertensive subjects over a wide age range (18 to 88 years) underwent aortic PWV determination and echocardiography, f...

Global and regional systolic function during exercise were studied at cardiac catheterization with biplane cineangiography and micromanometer pressures in three groups of patients: an ischemia group (n = 22) with exercise-induced asynergy from coronary artery disease, a control group with no or minimal cardiovascular disease (n = 5) and a "scar" group (n = 5) with prior infarction and no new as...