Histochemical demonstration of enzymes in rat liver during post-natal development

Summary Male and female rat liver were studied during post-natal development. A correlation was found between biochemically determined hydroxylations and enzymhisto-chemically determined NADPH-nitro-BT reductase and Naphthol-AS-D esterase. No correlation was found between glucose-6-phosphate dehydrogenase or iso-citric acid dehydrogenase activity and hydroxylations. The difference in hydroxylating capacity between male and female rats may be caused by the fact that the number of cells with hydroxylating activity in the liver lobule, as judged by the NADPH-nitro-BT reductase and Naphthol-AS-D esterase activity, is higher in male than in female rats.List of Abbreviations NADH reduced nicotinamide adenine dinucleotide - NADPH reduced nicotinamide adenine dinucleotide phosphate - G6PD glucose-6-phosphate dehydrogenase - ICD iso-citric acid dehydrogenase - G6Pase glucose-6-phosphatase - NADPH -nitro-BT red - NADPH Nitro-blue tetrazolium reductase - SDH succinic acid dehydrogenase - TCA trichloracetic acid     

甘蓝型油菜子油分的积累与某些生理变化关系的研究

油菜种子发育过程中,其内部的生理代谢过程发生了规律性的变化。伴随着种子的发育进程,６－磷酸葡萄糖脱氢酶、异柠檬酸裂解酶、异柠檬酸脱氢酶和琥珀酸脱氢酶的活性均有不同程度的增强。在油分旺盛合成期,６－磷酸葡萄糖脱氢酶和异柠檬酸裂解酶的活性均达到了最大值,而此时,异柠檬酸脱氢酶和琥珀酸脱氢酶的活属于匀增加较慢;在种子的不同发育时期,高含油量品系的６－磷酸葡萄糖脱氢酶和异柠檬酸裂解酶的活性均高于低含油量的     

Influence of oxygen tension on the respiratory activity of Mycobacterium phlei

Growth of Mycobacterium phlei under low oxygen tension resulted in specific activities two to twenty times lower for formate dehydrogenase, malate dehydrogenase, beta-hydroxybutyrate dehydrogenase, lactate oxidase and NADH dehydrogenase than when cultures were grown under high aeration. An increase in fumarate reductase and succinate dehydrogenase occurred with M. phlei grown under low oxygen tension. Malate: vitamin K dehydrogenase and glucose-6-phosphate dehydrogenase activity were not significantly affected by the oxygen tension used to grow the bacteria, and neither culture contained a lactate dehydrogenase. With growth of M. phlei in conditions of low oxygen tension, cytochrome a was not detected, but cytochrome b was prominent in membranes and cytochrome c was present in the soluble fraction.     

Histochemical demonstration of enzymes related to NADPH-dependent hydroxylating systems in rat liver after phenobarbital treatment

Summary Male rats were given 100mg phenobarbital for three days intraperitoneally. Biochemically an increase was found in activity of nitro-anisole demethylation and in the content of cytochrome P-450. Enzymhistochemically an increase in activity was noted for NADPH tetr. red., G6PD, ICD, and Naftol AS-D-esterase; a decrease was seen in G6Pase and glycogen, but no difference was found in NADH tetr. red. From these results it has been suggested that NADPH tetr. red. is directly involved in the hydroxylation chain, while G6PD and ICD are more indirectly involved.List of Abbreviations NADH nicotinamide adenine dinucleotide - NADPH nicotinamide adenine dinucleotide phosphate - NADPH tetr. red. NADPH tetrazolium reductase - G6PD glucose-6-phosphate dehydrogenase - ICD iso-citric acid dehydrogenase - G6Pase glucose-6-phosphatase - PAS periodic acid-Schiff method     

Histochemical profiles of motoneurons innervating muscle fibres with different activity patterns in the zebrafish, Brachydanio rerio.

Summary Enzyme histochemical profiles of spinal motoneurons in the zebrafish were determined. Five enzymes of glucose metabolism were chosen: glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), phosphofructokinase (PFK), succinate dehydrogenase (SDH) and NADH tetrazolium reductase (NADH-TR). Motoneurons were traced with Fluorogold and classified as those that innervate white muscle fibres (W-MNs) and those that innervate red and intermediate muscle fibres (R/ I-MNs). The average enzyme activities per volume of tissue in the somata of both populations differed at most by 25%. Both the average soma volume and the average number of muscle fibres innervated are three times larger for the W-MNs than for the a/I-MNs. This suggests that the total amount of enzyme activity within a neuron soma matches target size.In the R/I-MNs, the activities of SDH and NADH-TR were closely correlated (correlation coefficient, r=0.99;p<0.05) and HK activity correlated well with G6PDH activity (r=0.94;p<0.05), butnot with PFK (r=0.64;p>0.05). In the W-MNs, there was no correlation between SDH and NADH-TR (r=–0.59;p>0.05) or between HK and G6PDH (r=0.50;p>0.05) and the correlation coefficient between HK and PFK activity was close to zero (r=0.04;p>0.05).It was concluded that in the R/I-MNs gwhich are continuously ctive, firing activity is fuelled by oxidative metabolsm. We suggest that in the W-MNs glucose is stored in the form of glycogen and that, despite high levels of NADH-TR present, the energy for intermittent firing activity is provided by glycolysis.     

Potential biomarkers of dichlorvos induced neuronal injury in rats

The present study was designed to develop suitable biochemical markers of chronic dichlorvos exposure using rat as the animal model. Animals were exposed to dichlorvos (6 mg kg-1 (body weight) day-1) for 8 weeks and the activities of five potential markers were assayed. Acetylcholinesterase, assayed as an index of cholinergic function, was found to decrease in both haemolysate and brain tissue. Cytochrome oxidase, used as a marker of impaired energy metabolism, was also seen to decrease in platelets and brains of dichlorvos-treated animals. However, acid phosphatase, a lysosomal marker of tissue injury, was increased in both serum and brains of experimental animals. Chronic dichlorvos exposure also led to a decrease in the activity of glucose-6-phosphate dehydrogenase, which was assayed in brain as an index of oxidative stress. Dichlorvos administration did not affect 2', 3'-cyclic nucleotide phosphohydrolase. The present study therefore, indicates that apart from acetylcholinesterase, which is probably a non-specific marker of dichlorvos neurotoxicity, the levels of cytochrome oxidase, acid phosphatase and glucose-6-phosphate dehydrogenase may serve as useful determinants of dichlorvosinduced neuronal injury.     

Pathways of glucose catabolism in procyclic Trypanosoma congolense

Studies of respiration on glucose in procyclic Trypanosoma congolense in the presence of rotenone, antimycin, cyanide, salicylhydroxamic acid and malonate have indicated the presence of NADH dehydrogenase, cytochrome b-c1, cytochrome aa3, trypanosome alternate oxidase and NADH fumarate reductase/succinate dehydrogenase pathway that contributes electrons to coenzyme Q of the respiratory chain. The rotenone sensitive NADH dehydrogenase, the trypanosome alternate oxidase, and cytochrome aa3 accounted for 24.5 +/- 6.5, 36.2 +/- 4.2 and 54.1 +/- 5.5% respectively of the total respiration. Activities of lactate dehydrogenase, NAD(+)-linked malic enzyme and pyruvate kinase were less than 6 nanomoles/min/mg protein suggesting that they play a minor role in energy metabolism of the parasite. Phosphoenolpyruvate carboxykinase, pyruvate dehydrogenase, succinate dehydrogenase, NADP(+)-linked malic enzyme, NADH fumarate reductase, malate dehydrogenase, and alpha-ketoglutarate dehydrogenase and glycerol kinase on the other hand had specific activities greater than 60 nanomoles/min/mg protein. These enzyme activities could account for the production of pyruvate, acetate, succinate and glycerol. The results further show that the amount of glycerol produced was 35-48% of the combined total of pyruvate, acetate and succinate produced. It is apparent that some of the glycerol 3-phosphate produced in glycolysis in the presence of salicylhydroxamic acid is dephosphorylated to form glycerol while the rest is oxidised via cytochrome aa3 to form acetate, succinate and pyruvate.     

A tetrazolium technique for the histochemical localization of ATP: Creatine phosphotransferase

Summary A tetrazolium technique is presented that permits the study of ATP: Creatine phosphotransferase, or creatine kinase, in fixed skeletal muscle tissue sections, within the limits imposed by the properties of the chosen ditetrazole, nitro blue tatrazolium. There is a variation in creatine kinase activity between the muscle fibres. Those with high creatine kinase activity also have high succinate dehydrogenase activity.List of Abbreviations ADP Adenosine-5-diphosphate - ATP adenosine-5-triphosphate - CK creatine kinase - G-6-P glucose-6-phosphate - G-6-P-DH glucose-6-phosphate dehydrogenase - HK hexokinase - NADP nicotinamide adenine dinucleotide phosphate - NBT nitro blue tetrazolium - PMS phenazine methosulphate - SDH succinate dehydrogenase     

Metabolic response to treatment with cold, paraquat, or 3-amino-1,2,4-triazole in leaves of winter wheat.

We treated leaves of winter wheat (Triticum aestivum L.) with cold, paraquat, or 3-amino-1,2,4-triazole and compared the responses. We assayed the activities of glucose-6-phosphate dehydrogenase, catalase, dehydroascorbate reductase and ascorbate free radical reductase and levels of hydrogen peroxide, glucose-6-phosphate, fructose-6-phosphate, ascorbate, dehydroascorbate, reduced and oxidized glutathione. With any of the three treatments, contents of cellular peroxides and hexose phosphates were raised. The content of ascorbate was lowered markedly by paraquat treatment, which produces active oxygen species, whereas such a decrease did not occur in other two treatments. When the plants were treated with 3-amino-1,2,4-triazole, which is a specific inhibitor of catalase, the content of oxidized glutathione increased severalfold. The glucose-6-phosphate dehydrogenase activity increased with all three treatments, but it decreased after glyphosate treatment, which does not stimulate the formation of peroxides. The activities of catalase and dehydroascorbate reductase were increased by the treatment of cold and paraquat, while 3-amino-1,2,4-triazole did not affect the dehydroascorbate reductase activity. The activity of ascorbate free radical reductase increased after treatment by paraquat only.     

Enzyme reaction rate studies in electromotor neurons of the weakly electric fish Apteronotus leptorhynchus

A histochemical analysis of reaction rates of a series of enzymes was performed in electromotor neurons of the weakly electric fish Apteronotus leptorhynchus. These neurons were selected because of their functional homogeneity. The high metabolic activity of these cells as well as their large size facilitate cytophotometric analysis in cryostat sections. Sections were incubated for the activity of hexokinase, glucose-6-phosphate dehydrogenase, succinate dehydrogenase, NADPH dehydrogenase, NADPH ferrihaemoprotein reductase and beta-hydroxybutyrate dehydrogenase. All media contained polyvinyl alcohol as tissue stabilizer and Nitro BT as final electron acceptor. Measurements were performed with a Vickers M85a cytophotometer. Linear relationships between the specific formation of formazan (test minus control reaction) and incubation time were obtained for all enzymes although some reactions showed an initial lag phase or an intercept with the ordinate. The relatively high activities of hexokinase, succinate dehydrogenase and the extremely low activity of hydroxybutyrate dehydrogenase indicate that energy is mainly supplied by glycolysis. Glucose-6-phosphate dehydrogenase showed a high activity whereas NADPH reductase and dehydrogenase activity were low in electromotor neurons, indicating that the NADPH generated is largely used for biosynthesis. Despite their synchronous firing pattern activity, electromotor neurons showed a considerable heterogeneity with respect to their metabolic activity.     

Localization of several rhodopsin regeneration enzymes in retinal rods]

The distribution of NAD kinase and glucose-6-phosphate dehydrogenase within membranes of both outer and inner retina rod segments was studied by the sucrose gradient centrifugation of crude outer segment preparations. Rhodopsin and retinoldehydrogenase served as markers for outer segment membranes, whereas succinate dehydrogenase was a marker for inner ones. It is shown that NAD kinase and glucose-6-phosphate dehydrogenase are localized within inner segment membranes of the photoreception cell and that the activity of these enzymes in the crude preparations is due to contamination of the inner segments.     

Differential inactivation of Escherichia coli membrane dehydrogenases by a myeloperoxidase-mediated antimicrobial system.

Neutrophil myeloperoxidase, hydrogen peroxide, and chloride constitute a potent antimicrobial system with multiple effects on microbial cytoplasmic membranes. Among these is inhibition of succinate-dependent respiration mediated, principally, through inactivation of succinate dehydrogenase. Succinate-dependent respiration is inhibited at rates that correlate with loss of microbial viability, suggesting that loss of respiration might contribute to the microbicidal event. Because respiration in Escherichia coli can be mediated by dehydrogenases other than succinate dehydrogenase, the effects of the myeloperoxidase system on other membrane dehydrogenases were evaluated by histochemical activity stains of electrophoretically separated membrane proteins. Two bands of succinate dehydrogenase activity proved the most susceptible to inactivation with complete loss of staining activity within 20 min, under the conditions employed. A group with intermediate susceptibility, consisting of lactate, malate, glycerol-3-phosphate, and dihydroorotate dehydrogenases as well as three bands of glucose-6-phosphate dehydrogenase, was almost completely inactivated within 30 min. The relatively resistant group, including the dehydrogenases for glutamate, NADH, and NADPH and the remaining bands of glucose-6-phosphate dehydrogenase, retained substantial amounts of diaphorase activity for up to 60 min of incubation with the myeloperoxidase system. The differential effects of myeloperoxidase on dehydrogenase inactivation could not be correlated with published enzyme contents of flavin or iron-sulfur centers, potential targets of myeloperoxidase-derived oxidants. Despite the relative resistance of NADH dehydrogenase/diaphorase activity to myeloperoxidase-mediated inactivation, electron transport particles prepared from E. coli incubated for 20 min with the myeloperoxidase system lost 55% of their NADH oxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Schistosoma haematobium: oxidoreductase histochemistry and ultrastructure of niridazole-treated females

Administration of niridazole to Saccostomus campestris produced changes in enzyme activity in Schislosoma haematobium females as indicated histochemically by a decrease in the activity of cytochrome oxidase (EC 1.9.3.1), malate (NAD) dehydrogenase (EC 1.1.1.37), malate (NADP) dehydrogenase (EC 1.1.1.40), succinate dehydrogenase (EC 1.3.99.11), isocitrate (NAD) dehydrogenase (EC 1.1.1.41), isocitrate (NADP) dehydrogenase (EC 1.1.1.42), lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), NADH: tetrazolium oxidoreductase, NADPH: tetrazolium oxidoreductase, and a disappearance of both the activity of phenolase (EC 1.10.3.1) and the reactivity of vitelline phenols. These changes were associated with the following alterations in the ultrastructure of the parasites: a decrease in number of immature vitelline cells of gonial type, a disruption of the tegument surface, a swelling of mitochondria in vitelline cells, a disappearance of the regular structure of the endoplasmic reticulum and a vaeuolization of the cytoplasm in vitelline cells, an appearance of areas of focal cytoplasmic degradation in vitelline cells, and a disruption of shell globules. The degree of changes in enzyme activity and ultrastructure increased both with increase in the dose of niridazole administered to the hosts, and with length of time after treatment.Preincubation of control sectioned material in a buffered niridazole-sucrose solution produced total inhibition of succinate dehydrogenase activity, whereas the activity of other enzymes examined remained unchanged.     

Glucose-6-phosphate dehydrogenase from a tetracycline producing strain of Streptomyces aureofaciens: some properties and regulatory aspects of the enzyme

Glucose-6-phosphate dehydrogenase from Streptomyces aureofaciens exhibited activity with both NAD and NADP, the maximum reaction rate being 1.6 times higher for NAD-linked activity than for the NADP-linked one. The KM values for NAD-linked activity were 2.5 mM for glucose-6-phosphate and 0.27 mM for NAD, and for NADP-linked activity 0.8 mM for glucose-6-phosphate and 0.08 mM for NADP. NAD- and NADP-linked activities were inhibited by both NADH and NADPH. (2'-phospho-)adenosinediphospho-ribose inhibited only NAD-linked activity. The inhibition was competitive with respect to NAD and noncompetitive with respect to glucose-6-phosphate.     

Glucose-6-phosphate dehydrogenase activity and NADPH/NADP+ ratio in liver and pancreas are dependent on the severity of hyperglycemia in rat

Hyperglycemia is associated with metabolic disturbances affecting cell redox potential, particularly the NADPH/NADP+ ratio and reduced glutathione levels. Under oxidative stress, the NADPH supply for reduced glutathione regeneration is dependent on glucose-6-phosphate dehydrogenase. We assessed the effect of different hyperglycemic conditions on enzymatic activities involved in glutathione regeneration (glucose-6-phosphate dehydrogenase and glutathione reductase), NADP(H) and reduced glutathione concentrations in order to analyze the relative role of these enzymes in the control of glutathione restoration. Male Sprague-Dawley rats with mild, moderate and severe hyperglycemia were obtained using different regimens of streptozotocin and nicotinamide. Fifteen days after treatment, rats were killed and enzymatic activities, NADP(H) and reduced glutathione were measured in liver and pancreas. Severe hyperglycemia was associated with decreased body weight, plasma insulin, glucose-6-phosphate dehydrogenase activity, NADPH/NADP+ ratio and glutathione levels in the liver and pancreas, and enhanced NADP+ and glutathione reductase activity in the liver. Moderate hyperglycemia caused similar changes, although body weight and liver NADP+ concentration were not affected and pancreatic glutathione reductase activity decreased. Mild hyperglycemia was associated with a reduction in pancreatic glucose-6-phosphate dehydrogenase activity. Glucose-6-phosphate dehydrogenase, NADPH/NADP+ ratio and glutathione level, vary inversely in relation to blood glucose concentrations, whereas liver glutathione reductase was enhanced during severe hyperglycemia. We conclude that glucose-6-phosphate dehydrogenase and NADPH/NADP+ were highly sensitive to low levels of hyperglycemia. NADPH/NADP+ is regulated by glucose-6-phosphate dehydrogenase in the liver and pancreas, whereas levels of reduced glutathione are mainly dependent on the NADPH supply.     

Nitrite reduction in barley-root plastids: Dependence on NADPH coupled with glucose-6-phosphate and 6-phosphogluconate dehydrogenases,and possible involvement of an electron carrier and a diaphorase

Plastids from roots of barley (Hordeum vulgare L.) seedlings were isolated by discontinuous Percoll-gradient centrifugation. Coinciding with the peak of nitrite reductase (NiR; EC 1.7.7.1, a marker enzyme for plastids) in the gradients was a peak of a glucose-6-phosphate (Glc6P) and NADP⁺-linked nitrite-reductase system. High activities of phosphohexose isomerase (EC 5.3.1.9) and phosphoglucomutase (EC 2.7.5.1) as well as glucose-6-phosphate dehydrogenase (Glc6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) were also present in the isolated plastids. Thus, the plastids contained an overall electron-transport system from NADPH coupled with Glc6PDH and 6PGDH to nitrite, from which ammonium is formed stoichiometrically. However, NADPH alone did not serve as an electron donor for nitrite reduction, although NADPH with Glc6P added was effective. Benzyl and methyl viologens were enzymatically reduced by plastid extract in the presence of Glc6P+ NADP⁺. When the plastids were incubated with dithionite, nitrite reduction took place, and ammonium was formed stoichiometrically. The results indicate that both an electron carrier and a diaphorase having ferredoxin-NADP⁺ reductase activity are involved in the electron-transport system of root plastids from NADPH, coupled with Glc6PDH and 6PGDH, to nitrite.Abbreviations Cyt cytochrome - Glc6P glucose-6-phosphate - Glc6PDH glucose-6-phosphate dehydrogenase - MVH reduced methyl viologen - NiR nitrite reductase - 6PG 6-phosphogluconate - 6PGDH 6-phosphogluconate dehydrogenase     

Nitrate assimilation in Crotalaria juncea (Linn.) pollen suspension culture

In vivo and in vitro activities of nitrate reductase were assayedin Crotalaria juncea pollen suspension cultures. This enzymewas found to be substrate-inducible and enhanced activity wasobserved when it was extracted with cysteine buffer or incubatedwith NADH (0.6 mM) at 25?C or when the germinated pollen grainswere treated with red light for 10 min. Enzymes of ammonia assimilation,glutamate dehydrogenase and glutamate synthetase, and also thepentose phosphate-shunt enzyme, glucose-6-phosphate dehydrogenase,which catalyzes the step that provides reducing power to thesystem, are described. (Received October 20, 1977; )     

Identification and localization of enzymes of the fumarate reductase and nitrate respiration systems of escherichia coli by crossed immunoelectrophoresis

Crossed immunoelectrophoresis was used to analyze the components of membrane vesicles of anaerobically grown Escherichia coli. The number of precipitation lines in the crossed immunoelectrophoresis patterns of membrane vesicles isolated from E. coli grown anaerobically on glucose plus nitrate and on glycerol plus fumarate were 83 and 70, respectively. Zymogram staining techniques were used to identify immunoprecipitates corresponding to nitrate reductase, formate dehydrogenase, fumarate reductase, and glycerol-3-phosphate dehydrogenase in crossed immunoelectrophoresis reference patterns. The identification of fumarate reductase by its succinate oxidizing activity was confirmed with purified enzyme and with mutants lacking or overproducing this enzyme. In addition, precipitation lines were found for hydrogenase, cytochrome oxidase, the membrane-bound ATPase, and the dehydrogenases for succinate, malate, dihydroorotate, D-lactate, 6-phosphogluconate, and NADH. Adsorption experiments with intact and solubilized membrane vesicles showed that fumarate reductase, hydrogenase, glycerol-3-phosphate dehydrogenase, nitrate reductase, and ATPase are located at the inner surface of the cytoplasmic membrane; on the other hand, the results suggest that formate dehydrogenase is a transmembrane protein.     

Histochemical study on the distribution of some enzyme activities in the vagal and facial lobes of the goldfish, Carassius auratus.

The histochemical localization of six enzymic activities (acetylcholinesterase, pseudocholinesterase, monoamine oxidase, lactate dehydrogenase, succinate dehydrogenase and glucose-6-phosphate dehydrogenase) has been studied in the vagal and facial lobes of the goldfish, Carassius auratus. These encephalic centers are hypertrophic in Cyprinidae, corresponding to the dominance of gustatory function. Acetylcholinesterase shows a complex laminar distribution in the vagal lobes and a peculiar cellular localization in vagal motor neurons. Monoamine oxidase activity is mainly evident in fibrous tracts coming to or leaving from the lobes. Among oxidative enzymes examined, lactate dehydrogenase and succinate dehydrogenase exhibit distribution patterns respectively similar to those observed for acetylcholinesterase and monoamine oxidase. Some features on enzymes distribution in the gustatory centers of Carassius are in agreement with the enzymatic patterns well known in higher vertebrates.     

Enzymatic organization of the subcommissural organ.

In the subcommissural organ (SCO) of the guinea pig, rat, golden hamster, and mouse the activity and distribution of enzymes related to the energy-supplying metabolism and of some marker enzymes of different cell organelles have been investigated by means of mostly modified histochemical methods. The results were compared with findings in the ciliated ependyma of the ventricular wall and with those in the ependyma of the choroid plexus of the third ventricle. In the ependymal part of the SCO only a moderate activity of hexokinase is observed in its specialized columnar cells whereas a high activity is present both in the ciliated ependyma and the choroid plexus. - The staining pattern of glucose-6-phosphatase is similar to that of hexokinase but this enzyme is found is the SCO only. - Likewise hexokinase, glycogen granules and enzymes related to glycogen metabolism (phosphoglucomutase, uridine-diphosphoglucose pyrophosphorylase, glycogen synthetase and phosphorylase) are regularly found most numerous and active in the nuclear and supra-nuclear area of the ependymal part. These enzymes are less active in both the other ependymal regions. - Uridine-diphosphoglucose dehydrogenase could not be demonstrated in the SCO. The NADP-linked enzymes of the pentose phosphate shunt, glucose-6-phosphate and 6-phosphogluconate dehydrogenase, show a moderate activity which decreases also from the nuclear towards the apical area of the ependymal cells of the SCO. Enzymes of the glycolytic pathway, such as glucosephosphate isomerase, fructose-6-phosphate kinase, fructose-I,6-diphosphate aldolase, glyceraldehyde-3-phosphate and lactate dehydrogenase, are highly active in the SCO and are located mainly in the supranuclear area, too. Fructose-1,6-diphosphatase could not be demonstrated thus indicating that in the SCO the pathway is most probably only glycolytic but not gluconeogenetic. Compared to the ependyma of the ventricular wall and of the choroid plexus, in the SCO the M type subunits of lactate dehydrogenase predominate. Glycolytic enzymes are also very active in the choroid plexus but less in the ciliated ependyma. Compared to the ciliated ependyma and especially to the ependyma of the choroid plexus, the activities of enzymes which are only present in mitochondria (NAD-linked isocitrate dehydrogenase, succinate dehydrogenase, NAD-linked malate dehydrogenase after preextraction, cytochrome oxidase, 3-hydroxybutyrate and glycerolphosphate and glutamate dehydrogenase) are relatively low. Mitochondria are accumulated near the superior pole of the nuclei as well as in the most apical part of the ependymal cells. - The staining pattern of NADP-linked isocitrate and malate dehydrogenase as well as of NADH dehydrogenase suggests that these enzymes are localized both in and out of mitochondria. The extramitochondrial activity of the first two enzymes might be localized in the cytosol. The extramitochondrial activity of NADH dehydrogenase might be localized in the endoplasmic reticulum...