The endoendothelial fibrin lining, fibrinogen gel clotting, and the endothelium-blood interface

Modeling of the cerebral blood circulation in a capillary network accounting for the influence of the endothelial surface layer

BACKGROUND AND OBJECTIVE

The paper describes a mathematical model of blood flow in capillaries with accounting for the endothelial surface layer (ESL).

METHOD

The influence of ESL is modeled by a boundary layer with zero flow velocity. Finite element modeling and an analytical approach based on the homogenization of the core region of blood flow occupied by erythrocytes are developed to describe the resistance of a capillary. The reliability of the results obtained is verified for different values of the discharge hematocrit and vessel diameter using known in vivo data.

RESULTS

The proposed approach is applied to the numerical simulation of blood circulation in a capillary network of the germinal matrix of infants born at 25 gestational weeks. The influence of the hematocrit level and effective thickness of ESL on the resistance of the capillary network of the germinal matrix of preterm infants is studied. It was found that a decrease in the effective thickness of ESL in the capillary network (and/or a decrease in the hematocrit) leads to reducing the resistance of the capillary network.

CONCLUSION

A decrease in the effective thickness of ESL in the capillary network leads to an increase in the pressure drop in arterioles, which may be considered as an additional risk factor for hemorrhages in fragile blood vessels within the germinal matrix.

Fibrinogen in rat gastrointestinal lymph before, during and after intraduodenal administration of emulsified triglyceride: fibrinogen bound to chylomicrons in gastrointestinal lymph is functional

Samples of gastrointestinal lymph were collected from fasted, male, Sprague-Dawley rats before, during and after intraduodenal administration of either a phospholipid-stabilized, triglyceride-rich emulsion or the dextrose-saline diluent of the emulsion. In lipid-treated rats, the triglyceride, total protein, and functional fibrinogen contents of lymph increased significantly during the 4 h of continuous lipid infusion, with all analytes returning to near baseline values by 20 h later. Levels of the same analytes changed little, if at all, in control animals. As assessed using immunoblotting, chylomicrons in gastrointestinal lymph are coated with fibrinogen. Fibrinogen-coated chylomicrons readily incorporate into solution phase clots and, in the presence of thrombin, adhere in heparin-preventable fashion to each other and to other fibrinogen-coated surfaces. Taken together, these data indicate that lipid feeding creates in gastrointestinal lymph a condition that is conducive temporally to the physical association of fibrinogen with newly ingested lipids before they reach the circulatory system.