The tendency for sickle cells to adhere to each other is increased in oxygenated sickle blood in parallel with cell density. The increased adherence of these cells occurred despite their reduced deformability and diminished ability to form rouleaux. Using a method developed in our laboratory, we measured the yield stress: a sensitive index of cell-cell adhesion of deoxygenated suspensions of si...

RATIONALE Skeletal muscle blood flow is coupled with the oxygenation state of hemoglobin in young adults, whereby the erythrocyte functions as an oxygen sensor and releases ATP during deoxygenation to evoke vasodilation. Whether this function is impaired in humans of advanced age is unknown. OBJECTIVE To test the hypothesis that older adults demonstrate impaired muscle blood flow and lower in...

Macromolecules such as hemoglobin exert both kinetic and matrix effects on osmotic pressure. The kinetic osmotic pressure of sickle-cell hemoglobin is lost upon deoxygenation at physiological erythrocyte concentrations. The non-kinetic or matrix component of osmotic pressure remains relatively unchanged. Loss of thermal-osmotic activity during deoxygenation occurs throughout a hemoglobin concen...

The purpose of this study was to determine whether acute hypoxia alters the deoxygenation level in vastus lateralis muscle during a 30 s Wingate test, and to compare the muscle deoxygenation level between sprint athletes and untrained men. Nine male track sprinters (athletic group, VO2max 62.5 ± 4.1 ml/kg/min) and 9 healthy untrained men (untrained group, VO2max 49.9 ± 5.2 ml·kg(-1)·min(-1)) pe...

PURPOSE This study evaluated heterogeneity of muscle O2 dynamics in a single muscle during bicycle exercise using an eight-channel near-infrared continuous wave spectroscopy (NIRcws) mapping system. METHODS Nine healthy subjects performed bicycle exercise at fixed workloads of 20, 40, 60, 80, and 100% maximal workload for 5 min at each level. Muscle oxygenation in the vastus lateralis (VL) du...

1. The kinetics of oxygen transfer across the water-blood barrier in fish gills were studied by measuring oxygenation and deoxygenation of single red blood cells contained within isolated secondary lamellae using a microphotometric technique. 2. Recordings of the overall time courses show that both oxygenation and deoxygenation are more rapid in the carp than in the eel. In both species the hal...

Phosphatidylserine exposure occurs in red blood cells (RBCs) from sickle cell disease (SCD) patients and is increased by deoxygenation. The mechanisms responsible remain unclear. RBCs from SCD patients also have elevated cation permeability, and, in particular, a deoxygenation-induced cation conductance which mediates Ca(2+) entry, providing an obvious link with phosphatidylserine exposure. The...

Between 1930 and 1975 biochemical and structural analysis of enzymes led to a clear set of ideas that might form a basis for detailed understanding of enzyme action. Further development required energetic and thermodynamic analysis of enzymes in an aqueous medium, beyond the computational power then available. Structural enzymology advanced in other directions, but the fundamental questions of ...