Biophysical properties of resuscitation fluids.

The preliminary results of this study indicate that the biophysical characteristics of stroma-free hemoglobin solution (SFH) make it an extremely suitable blood substitute. At the concentration that is currently being considered as an infusing solution (70 g/L), it is a Newtonian fluid having a viscosity very similar to that of plasma. At this concentration, SFH also has very favorable hemodilution properties, as well as potential oxygen transport ability, which most expanders lack. There seems to be little interaction between the plasma proteins and SFH, as indicated from viscosity measurements. The osmotic behavior of SFH indicates that it approaches an ideal polymer-solvent system as illustrated by the small value of the second virial coefficient, especially when compared to other plasma substitutes. In mixtures with whole blood at a series of hematocrits, SFH seems to be hyperosmotic. This biophysical property could certainly have significance in patients with severe shock. SFH maintains the integrity of whole blood and does not initiate erythrocyte aggregation. The investigations of the erythrocyte sedimentation rate (ESR) in this study with SFH indicate the potential usefulness of SFH in maintaining stability of these systems, particularly during the treatment of shock. The transport properties of the red cell membrane are apparently not effectively altered by the presence of SFH. This has been illustrated in the hemolytic malonamide kinetic and osmotic fragility studies. Although the results are preliminary, it should be stressed that SFH may offer protection against hemolysis when used as a transfusion solution.

The logistic curve for the fitting of sigmoidal data.

In 1838 a differential equation was developed by Verhulst to explain what is currently termed the S-shaped curve. Reviewed here are his application of the equation to population data and significant later applications by various workers to problems in physics, chemistry, and biology. The usefulness, versatility, and convenience of this integrated equation are illustrated by examples from our own work, including superimposition of data by use of reduced variables.

Population screening for beta-thalassemia minor. Report of cooperative trials based on two approaches.

In a cooperative intrastate program based upon experience with sickle-cell anemia screening, the authors explored the feasibility of applying hemoglobin electrophoresis for detection of beta-thalassemia gene carriers. Initially, blood samples collected in capillary tubes were analyzed by cellulose acetate electrophoresis with densitometric quantitation of hemoglobin A2 (Hb A2), followed by selective spectrophotometric quantitation. This approach proved insufficiently specific or reproducible. Follow-up hematologic and family studies of presumptive beta-thalassemia gene carriers indicated that coordinate measurement of erythrocytic indices and Hb A2 values would have discriminated a subpopulation with a high incidence of beta-thalassemia trait more specifically. This approach was tested prospectively by the use of 731 venous blood samples collected in a county with a large population of Mediterranean ancestry. Of 31 individuals (4.2%) with presumptive thalassemia trait, 13 returned for a repeat testing, and the initial results for 11 were confirmed. These findings lend support to an empirical screening sequence suggested by Pearson (erythrocytic indices followed by Hb A2 quantitation), but they also indicate that a significant subpopulation of beta-thalassemia gene carriers with limited phenotypic expression may elude detection in any single-pass approach.

Quantitative osmotic fragility and disease states: a preliminary study.

The Kalmedic D-3 Fragiligraph was used to obtain both cumulative and derivative osmotic fragility data. Several instrumental modifications and several procedural changes combined to make the data more reproducible and more easily obtained. An analytical expression employing but two parameters was found to give excellent fits for the cumulative data, and when differentiated, reproduced the experimental derivative data equally well. The curve fitting procedure used is given in detail. Data obtained on a limited number of subjects with beta-thalassemia or multiple sclerosis are presented. The interpretation of these data by techniques common to the literature is compared with the procedure developed in this paper.