Electron microscope studies of glutamic oxalacetic transaminase in rat liver cell

Liver tissue of the rat, fixed in glutaraldehyde and formaldehyde, was incubated in a medium which consisted of 20 mML-aspartic acid, 2 mM alpha-ketoglutaric acid, 50 mM imidazole and 6 mM lead nitrate at pH 7.2-7.4. The electron-opaque precipitates, due to glutamic oxalacetic transaminase activity in liver cells, were found to be localized to the cristae and surface membranes of the mitochondria, the limiting membrane of the microbodies, and the nuclear membrane. Sucrose storage and trauma resulted in altered morphology and diminished final product intensity in mitochondria, but the microbody enzyme activity disappeared completely under these conditions. These distinctive responses of enzymatic activity are considered to indicate a difference in either the enzyme protein or its membrane attachment to these two sites. The use of a buffered dehydrating ethanol series to prepare tissue blocks for electron microscopy appeared to result in more precise intracellular localization of enzymatic reaction product.

A biochemical and histochemical study of glutamic oxalacetic transaminase activity of rat hepatic mitochondria fixed in situ and in vitro

Rat liver perfused in situ briefly with a glutaraldehyde-formaldehyde mixture was homogenized in isotonic sucrose. The mitochondria, isolated from a homogenate of the perfused liver by differential centrifugation, assumed a slender and compact appearance similar to those often seen in an intact cell. The glutamic oxalacetic transaminase (GOT) activity of this mitochondrial fraction survived an additional formaldehyde fixation and was studied by biochemical and histochemical methods. The biochemical assay of the enzyme activity revealed that the activity was only slightly less than that of an unfixed mitochondrial fraction. The reaction product due to mitochondrial GOT activity was found to be localized to the cristae, as had been demonstrated in an intact liver cell. GOT activity of the mitochondrial fraction isolated from fresh liver tissue homogenate in 0.25 M sucrose was inactivated readily by either glutaraldehyde or formaldehyde and was no longer demonstrable by biochemical and histochemical methods after fixation.

The effects of lead and fixatives on activity of glutamic oxalacetic transaminase

Lead oxalacetate, a primary reaction product precipitate for the visualization of the activity of glutamic oxalacetic transaminase in tissue sections, is stable at a slightly alkaline pH. At concentrations which are used for tissue fixation a slight inhibitory effect on glutamic oxalacetic transaminase activity is produced by acetone while a glutaraldehyde-formaldehyde mixture results in marked reduction of activity. The concentration of lead which is used to form the primary reaction product does not significantly inhibit this enzyme activity.

Vaccinia gangrenosa and 1-methylisatin 3-thiosemicarbazone (methisazone)

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In vitro autolysis of plant cell walls

Primary cell walls of Zea mays prepared in a glycerol medium are capable of autolysis in vitro. Autolysis results in solubilization of about 10% of the wall substance during an 8 hour incubation period. Approximately 10% of the solubilized material is glucose and the remainder consists of an unidentified polymer which yields only glucose upon hydrolysis. Cell wall autolysis is a linear function of time of incubation and of wall concentration. The autolytic process occurs optimally over the pH range of 5.5 to 6.5. The possible relationship between autolytic capacity and capacity for elongation is discussed.

Fatal primary Epstein-Barr virus infection masquerading as histiocytic medullary reticulosis in young children in Taiwan

We reported 3 fatal cases of primary Epstein-Barr virus (EBV) infection resembling histiocytic medullary reticulosis (HMR) in young children in Taiwan, where an HMR-like illness has been previously found to be prevalent. The disease ran a fulminant course, manifesting as fever, anemia, jaundice, skin rash, pulmonary infiltration, and/or hepatosplenomegaly lasting for only 1-3 weeks. Laboratory tests revealed no hemolytic anemia and Coombs test was negative. Sepsis or HMR was the main clinical differential. At autopsy, the spleen, liver, lymph node, lung, and bone marrow showed infiltration of atypical "histiocytes" or blasts, lymphocytes, and mature histiocytes with hemophagocytosis. Immunophenotype and gene rearrangement studies of the lymphoid tissues revealed that these atypical "histiocytes" were actually polyclonal B immunoblasts in one case and transformed T lymphocytes in the remaining 2 cases, representing two different types of virus-host interaction. Southern blot and in situ hybridization studies on frozen lymphoid tissues demonstrated the presence of EBV DNA in all 3 patients; the study for cytomegalovirus was negative. The young age of these patients, closely correlated with the prevalent age of primary EBV infection in the general populations in Taiwan, strongly suggest that these childhood cases of previously diagnosed HMR-like disease may actually represent a lethal form of primary EBV infection or fatal infectious mononucleosis.