Preventing tobacco use in young people: strategies for the nurse practitioner

The use of tobacco is considered to be one of the most serious public health issues in America today. Each day thousands of young people start smoking or begin to use smokeless tobacco, both of which are known to increase the rate of illness, particularly heart disease and cancer. This article provides important and useful information in educating in health promotion strategies for the nurse practitioner working with families and communities to reduce tobacco use by young people.

Low density lipoprotein cholesterol and whole blood viscosity

Whole blood viscosity (WBV) was measured in a normal population and was analyzed in relation to packed cell volume, (hematocrit, PCV), fibrinogen, white blood cell count (WBC), platelet count, and plasma lipids, including total cholesterol, triglycerides, high density lipoprotein cholesterol (HDLc) and low density lipoprotein cholesterol (LDLc). Conventional assays were used for all blood and lipid measurements. Whole blood viscosity was measured under disaggregating conditions with a disposable, porous bed viscometer. As expected, the strongest correlation was seen between WBV and PCV (r = 0.78, p < 0.001). Significant positive correlations also were demonstrated between WBV and cholesterol (r = 0.22, p < 0.001), triglycerides (r = 0.14, p < 0.001) and LDLc (r = 0.21, p < 0.001). A significant negative correlation was found between HDLc and WBV (r = -0.20, p < 0.001). Correlation analysis by sex showed only the correlation of LDLc was significant for both men and women. A stepwise multiple regression analysis of WBV indicated that LDLc, fibrinogen (Fbg) and platelet (Plt) counts correlated independently of PCV to WBV. The equation derived from multiple regression and partial correlation analysis was: WBV (mPa.sec) = -9.317 + 0.0047 (LDLc) + 0.381 (PCV) + 0.00152 (Plt) + 0.0021 (Fbg). The calculated mean specific contribution of PCV was 90.8 percent, LDLc 3.5 percent, and fibrinogen 3.3 percent to observed mean WBV. This study shows that LDLc is the principal lipoprotein independently influencing whole blood viscosity and its effect is similar in magnitude to fibrinogen. Further studies to elucidate the mechanism and clinical significance of the effects of LDLc on WBV are indicated.

The estimation of whole blood viscosity by a porous bed method

A significant impediment in determining the relative contribution of whole blood viscosity to the pathogenesis of cardiovascular and cerebrovascular disease has been the lack of an uncomplicated method to measure whole blood viscosity. To address this problem, a simplified porous bed viscometer has been developed to measure whole blood viscosity. Whole blood is passed through a porous bed of branching channels with a mean pore diameter of 69.6 +/- 20.2 microns and an estimated mean shear rate of 19.6 seconds-1. The effects of sample collection, sample storage, and temperature are described. The mean whole blood viscosity of 242 healthy persons was 22.7 +/- 5.3 seconds, which, when corrected to centipoise using Darcy's equation, corresponds to an apparent viscosity of 5.7 +/- 1.3 cp. There was a significant difference in the whole blood viscosity of normal men and women related to their different packed cell volumes. Platelets and granulocytes influenced whole blood viscosity in proportion to their contribution to the total packed cell volume. Fibrinogen levels did not significantly influence measured whole blood viscosity, which is consistent with the disaggregating conditions and the mean shear rate of the instrument. The porous bed viscometer is a convenient means to measure whole blood viscosity and it should be useful as a screening test for clinical and epidemiologic studies.

An analysis of the importance of the "labile" fraction of glycosylated hemoglobin as determined by a minicolumn method

The authors have studied the contribution of the labile fraction of glycosylated hemoglobin to the total glycosylated hemoglobin (GH) in hospitalized, poorly controlled diabetic patients, and in a large group of outpatient diabetics using a conventional minicolumn method. A 5-hour saline incubation of erythrocytes or extensive dialysis of hemoglobin against a glucose-free buffer were used to remove the labile glycohemoglobin fraction. Equivalent results were obtained with either method. The change in GH after dialysis in a group of poorly controlled diabetics averaged 1.1%, but only 0.2% in a group of outpatients whose glycohemoglobin levels were being determined on a routine basis. In both groups, the size of the dialyzable fraction increased in proportion to the total GH level, and outpatients with a dialyzable fraction greater than or equal to 2.0% always had GH levels greater than or equal to 12.0%. In most cases where the total glycohemoglobin was less than 12%, the size of the dialyzable fraction approached the limits of the analytical variability of the minicolumn method (SD = approximately 0.3). The authors conclude that while saline incubation of erythrocytes is a practical procedure for removal of labile glycohemoglobin in a routine clinical laboratory, the use of this procedure is probably only necessary for patients with a high level of total glycosylated hemoglobin.

Heparin-Coated Surfaces that bind Antithrombin have Reduced Platelet Reactivity

Surfaces with heparin bound by covalent linkage react with platelets but are passivated by prior exposure to platelet free plasma (PFP), provided they are capable of adsorbing antithrombin III (AT). For example, heparin-agarose beads induce platelet adhesion and aggregation, which are reduced by preincubation of the beads with PFP, but PFP depleted of AT is not effective. The degree of passivation of the beads parallels their removal of AT from PFP. The beads are also passivated by a solution of purified AT.

Furthermore heparin-polymethyl acrylate copolymers made by radical polymerization initiated by Ce4+ bind AT, as demonstrated by measurement of AT remaining in solution after adsorption or eluted from the surface after plasma incubation. On such a surface, AT is activated just as by heparin in solution, measured by the ability of heparinized beads to inactivate thrombin (S-2160 chromogenic tripeptide substrate assay) in the presence of AT and by lack of inactivation of thrombin with AT-poor plasma and return of inactivating effect when AT is added back.

Aggregation of platelets by specific heparin fractions in solution appears to be an analogous phenomenon, which is inhibited by antithrombin.

In vitro assessment of interaction of blood with model surfaces

An in vitro system for the assessment of blood compatibility of artificial surfaces is described. Anticoagulated human whole blood was pumped through columns of beads and then analyzed for evidence of platelet retention and the release of platelet constitutents. Platelets were retained on the columns by adhesion to the beads and by aggregation. Experiments were conducted with PVAc, PC, PMA and PS beads to provide data on the reproducibility of the system and the effects of anticoagulants and RBC concentration on platelet adhesion and release. The system is versatile, inexpensive, reproducibile, and also suitable for studies of the effects of pharmacologic agents and other aspects of platelet-artificial surface interaction.

Interaction of human platelets with heparinized agarose gel

Platelet interaction with surfaces to which heparin had been covalently bonded was investigated with a chromatographic technique employing agarose gel beads heparinized via a cyanogen bromide reaction. Heparinization significantly increased platelet retention by the gel. Platelet retention was unchanged after pretreatment of the heparinized gel with albumin but increased after pretreatment with fibrinogen. Pretreatment with plasma or purified AT III decreased platelet retention. Reduction in platelet retention was correlated with the amount of AT III removed from plasma. Plasma with decreased levels of AT III was less effective in surface passivation. Pretreatment of heparinized gel with PF4 or protamine sulfate did not decrease platelet retention, but subsequent exposure to plasma did. The results suggest that a surface with covalently bonded heparin is reactive toward platelets but can be passivated by formation of a heparin/AT III complex.