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F Marx

Publications and source records attributed to F Marx.

62 records · Page 4Linked to original sources
PubMedDate not supplied

Histochemical detection of glycogen phosphorylase activity as parameter for early ischemic damage in rat heart.

In the present study we have investigated whether enzyme histochemical parameters can be applied to detect early ischemic damage in rat heart after ischemia without restoration of the blood flow. Ischemia was induced by incubating heart fragments for 0, 10, 20, 30, 60, 120 and 240 min at 37 degrees C. The activity and localization of the following enzymes was studied in unfixed cryostat sections using quantitative histochemical methods: lactate dehydrogenase, creatine kinase, succinate dehydrogenase, phosphofructokinase, acid phosphatase, 5'-nucleotidase and glycogen phosphorylase. Moreover, the ultrastructure of the tissue was studied with special attention to the appearance of flocculent densities in mitochondria, which can be seen as a sign of irreversible cell damage. It was shown that glycogen phosphorylase activity in rat heart decreased after short periods (30 min) of in vitro ischemia, whereas all other enzymes studied were not decreased up to 240 min, with the exception of lactate dehydrogenase and phosphofructokinase activities which were diminished only at 240 and 120 min of ischemia, respectively. Some reaction product was found after incubating for 5'-nucleotidase activity in the absence of substrate, indicating the presence of endogenous substrate(s). This endogenous substrate disappeared from the myocytes after 20 min of ischemia. It is assumed that AMP and/or other phosphate-containing compounds play an essential role in the activation of glycogen phosphorylase. Significant reduction of glycogen phosphorylase activity is correlated with the irreversible stage of damage of myocytes as judged from the ultrastructure.

5'-Nucleotidase↗
PubMedDate not supplied

Histochemical demonstration of creatine kinase activity using polyvinyl alcohol and auxiliary enzymes.

Creatine kinase activity (EC 2.7.3.2.) has been demonstrated in myocardium and skeletal muscle from rats by a method based on the incubation of cryostat sections with a polyvinyl alcohol-containing medium and the use of auxiliary enzymes. Hexokinase and glucose-6-phosphate dehydrogenase were spread on object glasses before mounting the sections to be incubated. In this way, the auxiliary enzymes were interposed between glass slide and section thus preventing loss of formazan generated within the sections. Creatine kinase activity was found to be localized in finely dispersed form along the myofibrils and as large granules in the sarcoplasm of myocardium and skeletal muscle. The formazan produced specifically by creatine kinase (test minus control), as measured cytophotometrically at 585 nm, was completely inhibited by 2 mM 2,4-dinitrofluorobenzene, a specific inhibitor of creatine kinase activity. The control reaction was unaffected by the inhibitor. The results obtained with the present method are similar to results obtained with the far more complicated semipermeable membrane technique. The introduction of auxiliary enzymes in the polyvinyl alcohol method enables the development of histochemical methods for many enzymes by linking the reactions to a dehydrogenase reaction.

Animals↗
PubMedDate not supplied

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. The 'nothing dehydrogenase' reaction was substantially lower in the heart than in the liver which was due to low levels of endogenous lactate and the absence of proteins containing thiol groups, such as albumin, in the heart. In vitro ischaemia resulted in a reduced 'nothing dehydrogenase' reaction due to loss of NAD+, possibly as a consequence of its breakdown by glycohydrolase activity. One hour reperfusion following one hour ischaemia caused a decreased 'nothing dehydrogenase' reaction in certain areas of the liver. This reduction was a result of leakage of lactate dehydrogenase and thiol-containing molecules. It appeared at the ultrastructural level that parenchymal and endothelial cells were heavily damaged in the areas containing a low 'nothing dehydrogenase' activity. In conclusion, early ischaemic damage in liver can be detected with the 'nothing dehydrogenase' reaction.

Animals↗
PubMedDate not supplied

The possible role of the immune system in Alzheimer's disease.

Currently, there is little doubt that the immune system plays a role in the neurodegenerative process in Alzheimer's disease (AD). Inflammatory proteins such as complement components, enzymes, eicosanoids, and cytokines are found in association with cerebral amyloid plaques and may exacerbate the fundamental pathology of AD, by stimulating Amyloid beta (A beta) production, supporting its aggregation and increasing its cytotoxicity. Activated microglia and astrocytes are the main source of these proteins, and A beta may trigger their release. Interestingly, there are also indications that the immune system may play a protective role against the development of AD. Microglial cells have been shown to degrade A beta, and recent evidence suggests that autoreactive A beta-specific T cells may be relevant to the elimination of the peptide. This mechanism seems, however, impaired in the majority of patients with AD. The immune system seems thus to represent a natural line of defense against the accumulation of dangerous amyloidogenic substances. Impairment of this specific immunological defense mechanism and the failure to eliminate a toxic metabolite can be the basis for a chronic nonspecific inflammatory process in the brain, as described above. AD is a good example how an immune response initially aiming at maintaining the integrity of the body may fail and consequently lead to tissue destruction and neuronal loss.

Alzheimer Disease↗