The 'nothing dehydrogenase' reaction and the detection of ischaemic damage.

The 'nothing dehyrogenase' reaction is defined as the reduction of tetrazolium salts in media lacking specific substrates for dehydrogenases. In this investigation, the kinetics of the 'nothing dehydrogenase' reaction were studied in cryostat sections of rat heart and liver with the use of various polyvinyl alcohol-containing incubation media. Formazan production was measured at 585 nm with a cytophotometer.

A quantitative histochemical study of 5'-nucleotidase activity in rat liver after ischaemia.

The lead salt method of Wachstein and Meisel15 has been applied using incubation media containing polyvinyl alcohol for the localization and quantification of 5'-nucleotidase (E.C.3.

Ultrastructural changes in the rat liver during Euro-Collins storage, compared with hypothermic in vitro ischemia.

The ultrastructural alterations in liver tissue induced by in vitro ischemia at 4 degrees C under conditions commonly used for transplantation (Euro-Collins perfused and stored liver tissue) have been compared with changes due to hypothermic in vitro ischemia in non-perfused liver. It was found that the process of cell deterioration in non-perfused liver occurred very slowly; signs of irreversible damage appeared in sinusoidal lining cells before hepatocytes (after 24 and 96 h, respectively). Liver perfused with, and stored in Euro-Collins solution showed acceleration of the ischemical damage in both types of cell (irreversible damage to sinusoidal lining cells after 12 h and to hepatocytes after 52 h), compared with non-perfused liver.

A histochemical study of changes in mitochondrial enzyme activities of rat liver after ischemia in vitro.

Changes in the activity of three mitochondrial enzymes in rat liver after in vitro ischemia have been determined by enzyme histochemical methods. The changes were correlated with the appearance in the electron microscope of flocculent densities in the mitochondria indicative of irreversible cell injury. The flocculent densities were observed in rat liver after about 2 h of ischemia in vitro at 37 degrees C.

Quantitative analysis of mitochondrial flocculent densities in rat hepatocytes during normothermic and hypothermic ischemia in vitro.

The development of flocculent densities in mitochondria as a sign of irreversible cell injury in rat hepatocytes has been studied by quantitative electron microscopy during in vitro ischemia under both normothermic (37 degrees C) and hypothermic (4 degrees C) conditions. At 37 degrees C flocculent densities first appear after 1 h ischemia; at this stage they are small in diameter (170 nm) and occur in only 8% of mitochondria. After 1.

Electron microscopic study of the localization of ferric iron in chorionic epithelium of the sheep placenta.

The ferrocyanide method has been used to study, at the ultrastructural level, the maternal-fetal iron transfer in the chorionic epithelium of the haemophagous regions of the sheep placenta during the third trimester of gestation (at the 126th and the 145th day of gestation). No significant differences could be found in the distribution pattern of the ferrocyanide precipitate product with the chorionic epithelium in both stages of gestation. The presence of ferrocyanide reaction product in lysosomal structures, involved in the breakdown of maternal erythrocytes ingested by chorionic epithelial cells, confirmed that trivalent iron is liberated from digested haemoglobin.

Ultrastructural changes in rat liver sinusoids during prolonged normothermic and hypothermic ischemia in vitro.

By means of electron microscopic analysis of liver fragments incubated in an air-tight wrapping (in vitro ischemia), the following facts have been established with regard to the development of signs of irreversible damage in cells from the sinusoidal wall compared with hepatocytes. With normothermic (37 degrees C) in vitro ischemia, signs of irreversible damage appeared in cells of the sinusoidal wall at a a much earlier stage than in hepatocytes (60-90 min and 90 min-2 h respectively). With in vitro ischemia in the cold (4 degrees C), these differences were even more marked; irreversible cell damage was apparent after between 24 and 36 h incubation in endothelial cells, whereas in hepatocytes flocculent densities followed by other signs of irreversible damage were found only after 79 h incubation.

Biochemical and ultrastructural changes in rat liver plasma membranes after temporary ischemia.

In this study we have attempted to correlate reversible and irreversible cell damage induced by in vivo or in vitro ischemia with characteristics of the plasma membranes of liver parenchymal cells, as detected biochemically and ultrastructurally. The effects of in vivo or in vitro ischemia appeared to be similar. It was virtually impossible to isolate a substantial membrane fraction from ischemic livers, probably because of changes in the physical properties of the membranes by ischemia.

The value of enzyme leakage for the prediction of necrosis in liver ischemia.

Following the clamping of the afferent vessels of the left lateral and median lobes in rat liver, a considerable part of these lobes show signs of necrosis 24 h after 90 min of ischemia, whereas no necrotic areas can be detected after 30 min interruption of the blood flow. The purpose of this study was to examine the value of an analysis of the leakage of enzymes from the liver parenchyma in the early phase after restoration of the blood flow after ischemia for a prediction of the occurrence of necrosis. Leakage of the enzymes GPT, GOT and LDH can be detected in the blood plasma with a maximum activity between 1 and 5 h both following 30 and 90 min of ischemia; a considerable difference in clearance is observed, however, in the period afterwards, the normal situation being reached after 24 h with the 30-min ischemic period, but not following the 90-min period.

Final stages of erythrophagocytosis in the sheep placenta.

In trophoblastic epithelial cells of the sheep placenta the final stages of erythrocyte breakdown within the lysosomal apparatus were studied at the ultrastructural level. As a result of hemoglobin digestion lysosomes containing hemoglobin-derived pigments (HDP) were formed. The HDP-lysosomes were acid phosphatase-positive, highly electron-dense bodies of round to irregular shape containing whorled membranous formations.

Lysosomal breakdown of erythrocytes in the sheep placenta. An ultrastructural study.

The breakdown of erythrocytes within the lysosomal apparatus of trophoblastic epithelial cells of the sheep placenta was studied at the ultrastructural level. Acid phosphatase activity could be demonstrated in the interspace between the erythrocyte membrane and the lysosomal membrane, but not inside ingested erythrocytes. The erythrocyte plasma membrane remained observable until the final stage of the breakdown process.

Fusion of erythrolysosomes in epithelial cells of the sheep placenta.

In trophoblastic epithelial cells of the sheep placenta the breakdown of erythrocytes within complex erythrolysosomes was studied at the ultrastructural level. It was found that the formation of complex erythrolysosomes containing from two to several erythrocytes as a result of fusion of erythrolysosomes within the epithelial cells was a common occurrence when the epithelial cells engulfed a large number of erythrocytes. The erythrocytes enclosed in complex erythrolysosomes appear to be either in the same or in different stages of hemolysis.

Erythrophagocytosis by cells of the trophoblastic epithelium in the sheep placenta in different stages of gestation.

Erythrophagocytosis by the trophoblastic epithelial cells of the sheep placenta was studied in different stages of gestation. Light-microscopic observations showed that the erythrophagocytosis became more and more conspicuous with increasing stages of gestation. Electron-microscopically, this process appeared to take place in the same way as described for red cell destruction elsewhere.