Rheological analysis and measurement of neutrophil indentation

Aspects of neutrophil mechanical behavior relevant to the formation of adhesive contacts were assessed by measuring the dependence of the contact area between the cell and a spherical substrate under controlled loading. Micropipettes were used to bring neutrophils into contact with spherical beads under known forces, and the corresponding contact area was measured over time. The neutrophil was modeled as a viscous liquid drop with a constant cortical tension. Both the equilibrium state and the dynamics of the approach to equilibrium were examined. The equilibrium contact area increased monotonically with force in a manner consistent with a cell cortical tension of 16-24 pN/microm. The dynamic response matched predictions based on a model of the cell as a growing drop using published values for the effective viscosity of the cell. The contact pressure between the cell and substrate at equilibrium is predicted to depend on the curvature of the contacting substrate, but to be independent of the impingement force. The approach to equilibrium was rapid, such that the time-averaged stress for a two-second impingement was within 20% of the equilibrium value. These results have implications for the role of mechanical force in the formation of adhesive contacts.

[The dynamic changes in the tissue components of the myocardial layers under compensatory heart hypertrophy in exposure to a peptide hydra morphogen]

Morphometric analysis of the left ventricle myocardial layers under heart hypertrophy was carried out. Values of tissue parameters on the 3rd, 10th and 24th days after 50% coarctation of the abdominal aorta were received. Is shown the heart functioning under conditions of myocardial compensatory hypertrophy development is characterized by expressed zones and different directions of changes of quantitative parameters of tissue components. The single injection of HMP (Hydra morphogen peptide) made the development of myocardial hypertrophy easy at early stages, decreasing depth of manifestations morphologic changes and perhaps affected the time of their development.

[Effect of peptide hydra morphogen on the structure of tissue components of rat myocardial layers in the early period of heart hypertrophy development]

The morphological study showed that the single injection of HMP (Hydra Morphogen Peptide) facilitated the development of the myocardium hypertrophy. This effect is expressed in the subendocardial layer most of all, where the normalization of the relative volume and diameter of the cardiomyocytes and the decrease of the connective tissue oedema are noted. These parameters are normalized in the intramural and subepicardial layers in less degree. The decrease of the connective tissue oedema is noted in the intramural layer. The normal correlation recovery between the relative volumes of the cardiomyocytes and the connective tissue is shown in the subepicardial layer, the diameters of the myocytes are essentially increased. The influence of HMP is manifested not only on the muscular and connective tissue components of the myocardium, but touches on also the system of the myocardial wall vessels, causing the redistribution of the intramural blood circulation.

[Morphological characteristics of tissue components of various layers of the rat myocardium in the early period of development of myocardial hypertrophy]

The tissue components of the subendocardial, intramural and subepicardial layers of the myocardium of rats were examined by morphometry on the 10 day after 50% subphrenic coarctation of the abdominal aorta. The decrease of the relative volume of cardiomyocytes in the subendocardial layer and the increase of this index in the other layers of myocardium were discovered. The decrease of the surface of cardiomyocytes was maximal in the intramural layer and in the other examined layers the decrease was less. Some increase of the average diameters of cardiomyocytes in subepicardial and intramural layers was shown. The cardiomyocytes diameter practically did not change in the subendocardial layer. The increase of the relative volume and surface of the capillaries was revealed in the subendocardial layer. These indexes were decreased in a different degree in the subepicardial and intramural layers.