Influence of Pretreatment on Interstitial and Intracellular Space of Canine Left-Ventricular Myocardium

Abstract

In this study, the interstitial space and myocytes were investigated qualitatively and morphometrically in samples from beating, fibrillating as well as from cardioplegically HTK-arrested hearts fixed by immersion or perfusion. The size of tissue clefts separating bundles of myocytes and that of the interstitial space within bundles of myocytes depend on the functional state and on the kind of fixation. Cellular preservation is significantly better in HTK-arrested hearts compared to beating or fibrillating hearts. Thus, for the structural evaluation of myocytes and interstitium, the pretreatment constitutes a highly significant factor.

Morphometric evaluation of volume shifts between intra‐ and extra‐cellular space before and during global ischemia

“…Whereas the use of extracellular tracers leads to a remarkable variability of values (Polimeni, 1974;Reil et al, 1987), the size of the interstitial space should be defined morphometrically as discussed earlier . For morphometry, it was useful to separate the myocardial interstitial space into two types of reaction spaces, which were evaluated at different magnifications using a light microscope (Schmiedl et al, 1990a;Haasis et al, 1991). The first type, known as a tissue cleft (Henle, 1876), serves as a disposal sink during relaxation-contraction cycles (Feneis, 1944).…”

Morphometric Evaluation of the Myocardial Interstitial Space after Physical and Chemical Fixation

“…The results show that the technique of fixation does not significantly influence VVis ( fig.4) and confirm that the slightly hyperosmolar fixation solution [4] as well as the iso-osmolar postfixation prevent artificial shrinkage or swelling of the compact tissue [2,11]. There are volume changes of the whole tissue block during the following steps, because after postfixation with osmium tetroxide the cells show no osmotic reactions [ 12.…”

“…therefore, an overestimation of the volume of the tissue clefts. Perfusion fixation following cardioplcgic coronary perfusion resulting in the lowest values for VVrc (2.62 ±0.54% ) [3,4] leads to a more rapid fixation of ves sels and a withdrawal of water [20] and a diminution of the tissue clefts [2] and therefore to an underestimation of the interstitial volume. After cryofixation, there are no signif icant artificial fluid shifts compared to chemical fixation.…”

“…FRG). The volume densities of tissue clefts (Vvic) were determined at a magnification of 100. the volume densities of the interstitium within bundles of myocytes (Vvl<), of the capillaries (Vv< n) and of connective tissue (VVo) were deter mined at a magnification of 1.000 [2][3][4].…”

“…The size of the tissue clefts between the bundles of myo cytes depends on the method of chemical fixation (immer sion fixation, perfusion fixation) following identical pre treatment [2][3][4] as well as on the site from which samples are taken [2. 7],…”