Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase

Work and oxygen consumption of isolated right ventricular papillary muscle in experimental pulmonary hypertension

Right-sided myocardial mechanical efficiency (work output/metabolic energy input) in pulmonary hypertension can be severely reduced. We determined the contribution of intrinsic myocardial determinants of efficiency using papillary muscle preparations from monocrotaline-induced pulmonary hypertensive (MCT-PH) rats. The hypothesis tested was that efficiency is reduced by mitochondrial dysfunction in addition to increased activation heat reported previously. Right ventricular muscle preparations were subjected to 5 Hz sinusoidal length changes at 37°C. Work and suprabasal oxygen consumption (V ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ ) were measured before and after cross-bridge inhibition by blebbistatin. Cytosolic cytochrome c concentration, myocyte cross-sectional area, proton permeability of the inner mitochondrial membrane and monoamine oxidase and glucose 6-phosphate dehydrogenase activities and phosphatidylglycerol/cardiolipin contents were determined. Mechanical efficiency ranged from 23% to 11% in control (n = 6) and from 22% to 1% in MCT-PH (n = 15) and correlated with work (r2  = 0.68, P < 0.0001) but not withV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ (r2  = 0.004, P = 0.7919).V ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ for cross-bridge cycling was proportional to work (r2  = 0.56, P = 0.0005). Blebbistatin-resistantV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ (r2  = 0.32, P = 0.0167) and proton permeability of the mitochondrial inner membrane (r2  = 0.36, P = 0.0110) correlated inversely with efficiency. Together, these variables explained the variance of efficiency (coefficient of multiple determination r2  = 0.79, P = 0.0001). Cytosolic cytochrome c correlated inversely with work (r2  = 0.28, P = 0.0391), but not with efficiency (r2  = 0.20, P = 0.0867). Glucose 6-phosphate dehydrogenase, monoamine oxidase and phosphatidylglycerol/cardiolipin increased in the right ventricular wall of MCT-PH but did not correlate with efficiency. Reduced myocardial efficiency in MCT-PH is a result of activation processes and mitochondrial dysfunction. The variance of work and the ratio of activation heat reported previously and blebbistatin-resistantV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ are discussed. KEY POINTS: Mechanical efficiency of right ventricular myocardium is reduced in pulmonary hypertension. Increased energy use for activation processes has been demonstrated previously, but the contribution of mitochondrial dysfunction is unknown. Work and oxygen consumption are determined during work loops. Oxygen consumption for activation and cross-bridge cycling confirm the previous heat measurements. Cytosolic cytochrome c concentration, proton permeability of the mitochondrial inner membrane and phosphatidylglycerol/cardiolipin are increased in experimental pulmonary hypertension. Reduced work and mechanical efficiency are related to mitochondrial dysfunction. Upregulation of the pentose phosphate pathway and a potential gap in the energy balance suggest mitochondrial dysfunction in right ventricular overload is a resiult of the excessive production of reactive oxygen species.

Quantification of Colonic Stem Cell Mutations

The ability to measure stem cell mutations is a powerful tool to quantify in a critical cell population if, and to what extent, a chemical can induce mutations that potentially lead to cancer. The use of an enzymatic assay to quantify stem cell mutations in the X-linked glucose-6-phosphate dehydrogenase gene has been previously reported.(1) This method requires the preparation of frozen sections and incubation of the sectioned tissue with a reaction mixture that yields a blue color if the cells produce functional glucose-6-phosphate dehydrogenase (G6PD) enzyme. If not, the cells appear whitish. We have modified the reaction mixture using Optimal Cutting Temperature Compound (OCT) medium in place of polyvinyl alcohol. This facilitates pH measurement, increases solubilization of the G6PD staining components and restricts diffusion of the G6PD enzyme. To demonstrate that a mutation occurred in a stem cell, the entire crypt must lack G6PD enzymatic activity. Only if a stem cell harbors a phenotypic G6PD mutation will all of the progeny in the crypt lack G6PD enzymatic activity. To identify crypts with a stem cell mutation, four consecutive adjacent frozen sections (a level) were cut at 7 µm thicknesses. This approach of making adjacent cuts provides conformation that a crypt was fully mutated since the same mutated crypt will be observed in adjacent sections. Slides with tissue samples that were more than 50 µm apart were prepared to assess a total of >10(4) crypts per mouse. The mutation frequency is the number of observed mutated (white) crypts÷by the number of wild type (blue) crypts in a treatment group.

Viable tumor tissue adherent to needle applicators after local ablation: a risk factor for local tumor progression

Background

Local tumor progression (LTP) is a serious complication after local ablation of malignant liver tumors, negatively influencing patient survival. LTP may be the result of incomplete ablation of the treated tumor. In this study, we determined whether viable tumor cells attached to the needle applicator after ablation was associated with LTP and disease-free survival.

Methods

In this prospective study, tissue was collected of 96 consecutive patients who underwent local liver ablations for 130 liver malignancies. Cells and tissue attached to the needle applicators were analyzed for viability using glucose-6-phosphate-dehydrogenase staining and autofluorescence intensity levels of H&E stained sections. Patients were followed-up until disease progression.

Results

Viable tumor cells were found on the needle applicators after local ablation in 26.7% of patients. The type of needle applicator used, an open approach, and the omission of track ablation were significantly correlated with viable tumor tissue adherent to the needle applicator. The presence of viable cells was an independent predictor of LTP. The attachment of viable cells to the needle applicators was associated with a shorter time to LTP.

Conclusions

Viable tumor cells adherent to the needle applicators were found after ablation of 26.7% of patients. An independent risk factor for viable cells adherent to the needle applicators is the omission of track ablation. We recommend using only RFA devices that have track ablation functionality. Adherence of viable tumor cells to the needle applicator after local ablation was an independent risk factor for LTP.

Differential activity of NADPH-producing dehydrogenases renders rodents unsuitable models to study IDH1R132 mutation effects in human glioblastoma

The somatic IDH1(R132) mutation in the isocitrate dehydrogenase 1 gene occurs in high frequency in glioma and in lower frequency in acute myeloid leukemia and thyroid cancer but not in other types of cancer. The mutation causes reduced NADPH production capacity in glioblastoma by 40% and is associated with prolonged patient survival. NADPH is a major reducing compound in cells that is essential for detoxification and may be involved in resistance of glioblastoma to treatment. IDH has never been considered important in NADPH production. Therefore, the authors investigated NADPH-producing dehydrogenases using in silico analysis of human cancer gene expression microarray data sets and metabolic mapping of human and rodent tissues to determine the role of IDH in total NADPH production. Expression of most NADPH-producing dehydrogenase genes was not elevated in 34 cancer data sets except for IDH1 in glioma and thyroid cancer, indicating an association with the IDH1 mutation. IDH activity was the main provider of NADPH in human normal brain and glioblastoma, but its role was modest in NADPH production in rodent brain and other tissues. It is concluded that rodents are a poor model to study consequences of the IDH1(R132) mutation in glioblastoma.

Distribution of lactate dehydrogenase in healthy and degenerative canine stifle joint cartilage

In dogs, degenerative joint diseases (DJD) have been shown to be associated with increased lactate dehydrogenase (LDH) activity in the synovial fluid. The goal of this study was to examine healthy and degenerative stifle joints in order to clarify the origin of LDH in synovial fluid. In order to assess the distribution of LDH, cartilage samples from healthy and degenerative knee joints were investigated by means of light and transmission electron microscopy in conjunction with immunolabeling and enzyme cytochemistry. Morphological analysis confirmed DJD. All techniques used corroborated the presence of LDH in chondrocytes and in the interterritorial matrix of healthy and degenerative stifle joints. Although enzymatic activity of LDH was clearly demonstrated in the territorial matrix by means of the tetrazolium-formazan reaction, immunolabeling for LDH was missing in this region. With respect to the distribution of LDH in the interterritorial matrix, a striking decrease from superficial to deeper layers was present in healthy dogs but was missing in affected joints. These results support the contention that LDH in synovial fluid of degenerative joints originates from cartilage. Therefore, we suggest that (1) LDH is transferred from chondrocytes to ECM in both healthy dogs and dogs with degenerative joint disease and that (2) in degenerative joints, LDH is released from chondrocytes and the ECM into synovial fluid through abrasion of cartilage as well as through enhanced diffusion as a result of increased water content and degradation of collagen.

Biochemical and cytochemical evaluation of heterozygote individuals with glucose-6-phosphate dehydrogenase deficiency

The aim of this study was to diagnose heterozygous glucose-6-phosphate dehydrogenase (G6PD) deficient females by an inexpensive cytochemical G6PD staining method that is easy to perform, allowing diagnosis of G6PD deficiency without cumbersome genetic analysis. Three subject groups were included in the study. The first group consisted of 15 hemizygous deficient males. The second and the third group were composed of 15 heterozygous deficient females and 15 healthy individuals, respectively. Biochemical determination and cytochemical staining of G6PD activity were performed in samples of all subjects. Results obtained with the cytochemical staining method correlated significantly with the biochemical data (p < 0.001), but a only 51-68% of the erythrocytes were stained positively in females with normal biochemical G6PD activity despite their having a G6PD-deficient child. This observation clearly indicates that these individuals are heterozygously deficient. These findings show that the cytochemical staining method to detect G6PD activity in erythrocytes is reliable, sensitive and specific and is superior to the biochemical method. Therefore, this method can be used routinely to detect heterozygous G6PD deficiency.

Cytochemically detectable glucose-6-phosphate dehydrogenase is present in human fetal membrane chorion laeve trophoblasts

We examined the ultrastructural localization of glucose-6-phosphate dehydrogenase (G6PD), a NADPH-generating enzyme, in human fetal membranes at various gestational ages, using newly developed enzyme histochemistry (copper-ferrocyanide method). Electron-dense deposits indicative of G6PD activity were clearly visible in the cytoplasm and on the cytosolic side of the endoplasmic reticulum of chorion laeve cytotrophoblasts at various gestational ages. Positive and negative cytochemical controls ensured specific detection of enzyme activity. These observations indicated that chorion laeve trophoblasts were the site of NADPH production. Chorion laeve trophoblast G6PD may play a significant role in fetal membrane physiology, by delivering NADPH to NADPH-dependent oxidoreductases which these cells possess.

Evaluation of a tetrazolium salt test to determine absence of live mycobacteria in tuberculin purified protein derivative

Current methodology to determine absence of live mycobacteria in tuberculin purified protein derivative (PPD) takes up to 8 weeks to perform and may also involve testing on animals. In this paper we describe an in vitro test utilising the tetrazolium salt, 2,3-bis-(2-methoxy-4-nitro-5-sulphenyl)-(2H)-tetrazolium-5-carboxanilide (XTT) to monitor the absence of live Mycobacterium tuberculosis (Mtb) in PPD. In the presence of live cells XTT is converted to a coloured formazan product that can be measured spectrophotometrically. Live mycobacteria present in spiked PPD were detected by a marked change in optical density above background levels. This test is easy to perform and is complete in just 48 hr.

Glucose-6-phosphate dehydrogenase is present in normal and pre-eclamptic placental trophoblasts: ultrastructural enzyme-histochemical evidence

The present study investigated the localization of glucose-6-phosphate dehydrogenase (G6PD) activity in the human placenta at various gestational ages. Placentae from patients with severe pre-eclampsia were also studied. Ultrastructural enzyme-histochemical analysis was performed by newly developed G6PD histochemistry using copper ferrocyanide as a capturing agent. Precipitates indicative of G6PD activity were markedly visible in the cytotrophoblastic cytoplasm and faintly in the syncytiotrophoblastic cytoplasm of placentae at various gestational ages, as well as those from pre-eclampsia. Frequently, precipitations were localized on the cytosolic side of the endoplasmic reticular membranes of the cytotrophoblasts. Stringent cytochemical control experiments performed also ensured the specific detection of G6PD activity. The results indicated that cytochemically detectable G6PD was localized in cytotrophoblastic cytoplasm. This enzyme may play significant roles in the carbohydrate metabolism of the human placenta, and further maintenance of villous tree architecture. Combining the previous data, the human placenta has many carbohydrate metabolizing-enzymes, similar to the adult liver.

Effects of ischaemia and reperfusion on NADH coenzyme Q reductase activity in rat liver

NADH coenzyme Q reductase (EC 1.6.5.3) has been suggested in the literature to be inactivated by ischaemia. In the present study, NADH coenzyme Q reductase activity was localized in unfixed cryostat sections of ischaemic rat livers and quantified using image analysis. In vitro ischaemia was induced by storage of rat liver fragments for 30, 60, and 120 min at 37 degrees C. In vivo ischaemia was provoked by clamping the afferent vessels of median and left lateral liver lobes for 60 min followed by 30, 60 and 180 min of reperfusion. NADH coenzyme Q reductase activity was demonstrated with the tetrazolium salt method in the presence of polyvinyl alcohol. Final reaction product was found in liver parenchymal cells and its distribution was homogeneous within liver lobules. Only low amounts of final reaction product were formed when the incubation was performed in the absence of the substrate NADH. A non-linear relation was found between the absorbance and incubation time when the reaction was performed in the presence of NADH. Therefore, the initial velocity was taken as the true rate of enzyme activity. A linear relationship was found for the initial velocity and section thickness up to 6 microm followed by a levelling off. Electron microscopically, NADH coenzyme Q reductase activity was localized at the outer and inner membranes of mitochondria. In vitro ischaemia up to 120 min did not affect NADH coenzyme Q reductase activity. At 30 min reperfusion after in vivo ischaemia for 60 min enzyme activity was slightly decreased in certain foci which also showed diminished lactate dehydrogenase activity. A further decrease of enzyme activities in foci was observed at 180 min reperfusion after ischaemia. It is concluded that NADH coenzyme Q reductase activity is not sensitive to ischaemia. Furthermore, it is likely that the enzyme leaks from liver parenchymal cells into the circulation during reperfusion after ischaemia.

Prognostic estimation of survival of colorectal cancer patients with the quantitative histochemical assay of G6PDH activity and the multiparameter classification program CLASSIF1

Prognosis of colorectal cancer patients that show similar histopathology may vary substantially. An attempt was made to improve prognosis by the self-learning classification program CLASSIF1, based on automated multiparameter analysis of quantitative histochemical and clinical parameters of 64 colorectal carcinomas and adjacent normal mucosae. The histochemical parameters applied were the oxygen-insensitivity assay of glucose-6-phosphate dehydrogenase (G6PDH) activity, a valid discriminator between normal and cancerous mucosae, and related parameters CuZn- and Mn-superoxide dismutase (SOD) levels, and lipid peroxidation (LPO) capacity. Data were processed on the basis of a postoperative follow-up of minimally 32 and maximally 56 months. CLASSIF1 selected the parameters oxygen insensitivity of G6PDH activity, CuZn-SOD and Mn-SOD levels, LPO capacity, lymph node metastasis, Dukes' stage, and age for the highest prognostic value. On the basis of these selected parameters, CLASSIF1 correctly predicted favorable outcome in 100% of the surviving patients and fatal outcome in 64% of the deceased patients. G6PDH activity appeared to be the major information carrier for CLASSIF1. On the basis of G6PDH activity parameters alone, 96% of the surviving patients and 55% of the deceased patients were correctly classified. In comparison, estimation of prognosis on the basis of Dukes' stage alone resulted in 71% correctly classified surviving patients and 61% of patients who died. It is concluded that the self-learning classification program CLASSIF1, on the basis of quantitative histochemical and clinical parameters, is the best prognostic estimator for colon cancer patients yet available.

Reactive oxygen species (ROS) generated by xanthine oxidase in the corneal epithelium and their potential participation in the damage of the corneal epithelium after prolonged use of contact lenses in rabbits

Prolonged use of contact lenses (for 14 days) evoked an imbalance between the activity of xanthine oxidase (an enzyme belonging to reactive oxygen species-generating oxidases) and catalase (an enzyme belonging to reactive oxygen species-scavenging oxidases) in the corneal epithelium of rabbits. The activity of catalase decreased, while xanthine oxidase activity was very high. Of other enzymes studied in the corneal epithelium, the activities of xanthine oxidoreductase, glucoso-6-phosphate dehydrogenase and succinate dehydrogenase were decreased. In contrast, the activities of lactate dehydrogenase and lysosomal hydrolases (acid beta-galactosidase, dipeptidyl peptidase II) were increased and appeared in animals sacrificed immediately after contact lens removal. In rabbits sacrificed later (after 1 h), an additional increase of lactate dehydrogenase and lysosomal hydrolase activities developed in the superficial layers of the corneal epithelium. Catalase supplementation during use of contact lenses prevented both the significant decrease of catalase activity in the corneal epithelium and the development of additional epithelial damage. In contrast, topical treatment with 3-aminotriazole (an inhibitor of catalase) resulted in the nearly complete loss of catalase activity in the corneal epithelium and the appearance of more serious epithelial damage. We conclude that ROS generated by xanthine oxidase induce additional damage of the corneal epithelium related to the use of contact lenses.

The use of intermediate electron acceptors to enhance MTT bioreduction in a microculture tetrazolium assay for human growth hormone

We contrast the effects of three intermediate electron acceptors (IEAs) on the highly quantitative ESTA bioassay for human growth hormone. This is a microculture tetrazolium assay based upon the in vitro reduction of the tetrazolium salt MTT, by Nb2 cells which have been activated with hGH. Each of the IEAs influenced MTT-formazan production in a distinctive manner. The two quinonoids, namely menadione and co-enzyme Q0 markedly increased the MTT-formazan produced by hormone activated Nb2 cells and thereby amplified the response of our bioassay for human growth hormone (hGH). The exceptionally low bioassay baseline which is characteristic of the unstimulated Nb2 cells when only MTT is added was retained in the presence of CoQ0, but was greatly increased by menadione. Phenazine methosulphate, which is the most widely used redox intermediary in microculture tetrazolium assays, also increased the baseline, but had only a minimal additional effect on MTT reduction by activated Nb2 cells. We conclude that CoQ0 is the preferred IEA for this ESTA bioassay for hGH.

In situ heterogeneity of peroxisomal oxidase activities: an update

Oxidases are a widespread group of enzymes. They are present in numerous organisms and organs and in various tissues, cells, and subcellular compartments, such as mitochondria. An important source of oxidases, which is investigated and discussed in this study, are the (micro)peroxisomes. Oxidases share the ability to reduce molecular oxygen during oxidation of their substrate, yielding an oxidized product and hydrogen peroxide. Besides the hydrogen peroxide-catabolizing enzyme catalase, peroxisomes contain one or more hydrogen peroxide-generating oxidases, which participate in different metabolic pathways. During the last four decades, various methods have been developed and elaborated for the histochemical localization of the activities of these oxidases. These methods are based either on the reduction of soluble electron acceptors by oxidase activity or on the capture of hydrogen peroxide. Both methods yield a coloured and/or electron dense precipitate. The most reliable technique in peroxisomal oxidase histochemistry is the cerium salt capture method. This method is based on the direct capture of hydrogen peroxide by cerium ions to form a fine crystalline, insoluble, electron dense reaction product, cerium perhydroxide, which can be visualized for light microscopy with diaminobenzidine. With the use of this technique, it became clear that oxidase activities not only vary between different organisms, organs, and tissues, but that heterogeneity also exists between different cells and within cells, i.e. between individual peroxisomes. A literature review, and recent studies performed in our laboratory, show that peroxisomes are highly differentiated organelles with respect to the presence of active enzymes. This study gives an overview of the in situ distribution and heterogeneity of peroxisomal enzyme activities as detected by histochemical assays of the activities of catalase, and the peroxisomal oxidases D-amino acid oxidase, L-alpha-hydroxy acid oxidase, polyamine oxidase and uric acid oxidase.

Microculture tetrazolium assays: a comparison between two new tetrazolium salts, XTT and MTS

Microculture tetrazolium assays are being widely exploited to investigate the mechanisms of both cell activation and cell damage. They are colorimetric assays which are based upon the bioreduction of a tetrazolium salt to an intensely coloured formazan. We contrast the responses obtainable with two new tetrazolium salts, MTS and XTT, when used on the rat lymphoma cell line (Nb2 cells), which has been activated by human growth hormone. These tetrazolium salts, unlike the more commonly used MTT, form soluble formazans upon bioreduction by the activated cells. This has the advantage that it eliminates the error-prone solubilisation step which is required for the microculture tetrazolium assays which employ MTT. Bioreduction of XTT and MTS usually requires addition of an intermediate electron acceptor, phenazine methosulphate (PMS). We found that the XTT/PMS, but not the MTS/PMS, reagent mixture was unstable. Nucleation and crystal formation in the XTT/PMS reagent mixture, prepared in DPBS, could occur within 1-3 min. This resulted in a decline in XTT-formazan production and manifested itself in the microculture tetrazolium assay as both poor within-assay precision and serious assay drift. Several features of the system suggested that the formation of charge-transfer complexes between XTT and PMS accounted for this instability. No such instability was encountered when MTS and PMS were mixed. We demonstrate that MTS/PMS provides microculture tetrazolium assays for hGH which are free from these serious artefacts and which are uniquely precise. In conclusion we therefore advocate the use of MTS in preference to XTT for the new generation of microculture tetrazolium assays.

Adaptive sex-dependent changes in the zonation of carbohydrate and lipid metabolism in rat liver lobules after partial hepatectomy

To evaluate changes in metabolic heterogeneity in rat liver lobules after partial hepatectomy, we measured parameters of carbohydrate and lipid metabolism cytophotometrically in periportal and pericentral zones of livers of mature female and male rats. Glycogen content was shown to be always higher in pericentral zones than in periportal zones. After a rapid depletion of glycogen stores during the first 8 hr after partial hepatectomy, the levels were restored to normal after 24 hr, but a significant depletion was found again at 48 hr after operation. These fluctuations were similar in female and male rat livers. The lipid content in control rat livers was low and was mainly localized in periportal zones. Partial hepatectomy caused a significant increase in lipid content after 24 to 48 hr in periportal zones only, which was distinctly higher in female than in male rat livers. Activity of NADPH-producing glucose-6-phosphate dehydrogenase was heterogeneously distributed in lobules of female control rats with highest activity in pericentral zones, whereas a lower but evenly distributed activity was found in lobules of control male rats. The activity was not affected by partial hepatectomy in male rats, whereas the activity in female rat livers decreased to levels found in male rats at 24 to 48 hr after operation. Another NADPH-producing enzyme, malate dehydrogenase, showed the highest activity pericentrally in female rats, and a low activity was evenly distributed in male rats. The activity did not change significantly after partial hepatectomy. The ketogenic enzyme beta-hydroxybutyrate dehydrogenase showed the highest activity in pericentral zones of control livers. The activity in male rat livers was almost twice as high as in female rat livers in both zones. Partial hepatectomy caused a distinct reduction in activity in both zones and both sexes, but the strongest reduction was found periportally. Alkaline phosphatase activity, which is linked with bile acid secretion by hepatocytes, was low in control male and female rats and was mainly found periportally. The activity was increased dramatically at 24 to 48 hr after partial hepatectomy in both zones and particularly in male rat livers. The index for the Krebs cycle, succinate dehydrogenase activity, was highest in periportal zones. At 24 to 48 hr after partial hepatectomy, this preferential zonation was lost, and the activity was slightly higher in pericentral zones. This reversal of zonation was found in all livers of female and male rats investigated.(ABSTRACT TRUNCATED AT 400 WORDS)

On the mechanism of the multistep reduction of tetrazolium salts with special reference to the involvement of tetrazolium radicals

Thin layer chromatography (TLC) was performed to analyze which products are formed when unstable tetrazolinyl radicals are generated during the reduction of tetrazolium salts under physiological conditions of biochemical and histochemical assays. It was found in aqueous media that irrespective the assay conditions, reduction of 2,3-di(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (p-DNTTC) or 2,3-di(4-nitrophenyl)-5-t-butyl-2H-tetrazolium chloride (t-butyl-DNTC) always lead to production of formazan and never to generation of the corresponding 2(4-nitrophenyl)-5-phenyl- (respectively t-butyl-) tetrazoles by splitting off a nitrophenyl side chain from the tetrazolium ring as a cation. This reaction is known to occur in non-aqueous media (Neugebauer, 1973). Because p-DNTTC is analogous to tetrazolium salts that are used in biochemical and histochemical assays, it is concluded that reduction of tetrazolium salts leads to formation of formazans only under these conditions.

Glucose-6-phosphate dehydrogenase is enriched in oligodendrocytes of the rat spinal cord. Enzyme histochemical and immunocytochemical studies

Glucose-6-phosphate dehydrogenase (G6PD) was localized in rat spinal cord by catalytic enzyme histochemistry and immunocytochemistry. G6PD detected by either method was shown to be strongly enriched in cell bodies and processes of oligodendrocytes, whereas in the compact myelin G6PD was not detected. The enzyme histochemical procedure for the demonstration of G6PD was also adapted for microphotometric measurements of G6PD activity in the spinal cord white matter. There was a linear relationship between G6PD activity and section thickness up to 14 microns and between G6PD activity and reaction time up to 5-6 min as demonstrated by kinetic and end-point measurements. Significantly lower activities were measured in end-point measurements than in kinetic measurements because of formazan loss during rinsing. Methoxyphenazine methosulphate as an exogenous electron carrier and sodium azide as a blocker of the respiratory chain significantly increased the demonstrable G6PD activity. The Km was 0.62 mM and the Vmax 3 mumol glucose-6-phosphate/cm3 wet tissue and per min at 25 degrees C. It is concluded that G6PD in oligodendrocytes may be important for the generation of NADPH required for lipid biosynthesis related to myelogenesis, and reduction of glutathione required for protection of membrane sulphydryl groups.

Metabolic profiles of white and red-intermediate spinal motoneurons in the zebrafish

To study the interactions between the citrate cycle and amino acid metabolism in zebrafish spinal motoneurons, we composed enzyme histochemical profiles from the activities of NAD-linked isocitrate dehydrogenase (NAD-ICDH), glutamate dehydrogenase (GDH), succinate dehydrogenase (SDH) and glucose 6-phosphate dehydrogenase (G6PDH). The enzyme assays were performed on serially-sectioned motoneuron somata. The motoneurons were identified by retrograde tracing from the trunk muscle and classified, on the basis of their location in the motor column, as those innervating the white, fast glycolytic fibers (WMNs) or those innervating the red and intermediate slow oxidative fibers (RIMNs). We found the following relationships between enzyme activities in WMNs: GDH correlates with G6PDH activity (r = 0.31; p = 0.02) and NAD-ICDH correlates with GDH activity (r = 0.37; p < 0.01); correlations between NAD-ICDH and SDH and between SDH and GDH are not significant. In RIMNs we found correlations between NAD-ICDH and SDH (r = 0.34; p = 0.03), between NAD-ICDH and GDH (r = 0.41; p < 0.01) and between GDH and SDH (r = 0.50; p < 0.01); the correlation between GDH and G6PDH is not significant. The differences in metabolic profiles between WMNs and RIMNs can be explained in the following way: in WMNs, alpha-ketoglutarate is drawn off from the citrate cycle and is used in amino acid metabolism whereas in RIMNs the removal of alpha-ketoglutarate from the cycle is balanced by formation of alpha-ketoglutarate. The data suggest that the functional role of the citrate cycle differs in the two motoneuron populations: in RIMNs energy generation predominates but in WMNs a role in biosyntheses seems most important.

Quantitative aspects of enzyme histochemistry on sections of freeze-substituted glycol methacrylate-embedded rat liver

Freeze-substituted rat liver embedded in glycol methacrylate (GMA) has been used to demonstrate the activities of several enzymes. The following enzymes could be detected in GMA-sections by the indicated histochemical procedure(s): 5'-nucleotidase (lead salt, cerium-diaminobenzidine), alkaline phosphatase (indoxyl-tetrazolium salt), catalase (diaminobenzidine), acid phosphatase (diazonium salt), lactate dehydrogenase (tetrazolium salt) and glutamate dehydrogenase (tetrazolium salt). The activities of all these enzymes were dramatically decreased compared with the activities demonstrated in unfixed cryostat sections, with the exception of catalase. The activities of the following enzymes could not be detected in GMA-sections: glucose-6-phosphate dehydrogenase (tetrazolium salt), xanthine oxidoreductase (tetrazolium salt), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide) and glucose-6-phosphatase (cerium-diaminobenzidine). The possible role of restricted penetration of reagents into the resin was studied by measuring cytophotometrically the enzyme activities in GMA-sections of 3 and 6 microns in thickness. For all the enzymes that could be detected, the 6 microns:3 microns ratio varied from 1.4 to 2.7. An eventual retarded penetration of reagents into the resin was investigated by measuring cytophotometrically the amount of final reaction product during incubation for acid phosphatase and glutamate dehydrogenase activities. In both cases linear relationships without a lag phase were found for the specific enzyme activities with incubation time. Chemical denaturation of proteins or masking of active sites in proteins due to embedding in the resin monomer may be considered to be the main cause of decreased enzyme activities.

Enzyme activities of six different dehydrogenases in Ehrlich ascites cells measured by flow cytometry

Flow cytometric measurements of the activities of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, glycerol-3-phosphate dehydrogenase, succinate dehydrogenase and glutamate dehydrogenase in single Ehrlich ascites tumour cells are described using a tetrazolium salt/fluorescent formazan reaction. Applying cyano-ditolyl-tetrazolium chloride (CTC) as redox dye indicating enzyme reaction, and DAPI as a fluorochrome for nuclear DNA staining, the bivariate flow cytometric assay of enzyme activity and cell cycle analysis was established. Furthermore, adopting the calibration procedure reported formerly, consisting of biochemical determination and flow cytometry of the same sample performed parallelly, the enzyme activities were expressed in biochemical units. The dehydrogenase activities found in Ehrlich ascites cells were 97.5 fmol H2 per average positive cell during 5 min for lactate dehydrogenase, 69.0, 10.6, 25.3, 29.7, and 19.0 fmol H2 per average positive cell during 20 min for glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, glycerol-3-phosphate dehydrogenase, succinate dehydrogenase and glutamate dehydrogenase, respectively. This quantitative procedure can offer an alternative analytic tool for enzyme cytology.

The tetrazolium-formazan system: design and histochemistry

Our increasing knowledge about the chemistry and the correlations between chemical structure and histochemical properties of the tetrazolium/formazan system is resulting in: a better understanding of existing histochemical tetrazolium techniques; the selection of optimal tetrazolium salts for qualified use in histochemistry, cytochemistry and biochemistry; both qualitative and quantitative improvements in histochemical techniques for purposes demonstrating the activities of various dehydrogenating enzymes; an extended insight into the "state" of the tested biological object by means of tetrazolium indicators with special properties; and the combination of histochemical enzyme determination with further morphological techniques. This article has attempted to illustrate the progress in the use of the tetrazolium/formazan-system for histochemical purposes.

Enzyme histochemical profiles of fish spinal motoneurons after cordotomy and axotomy of motor nerves

Histochemical profiles were made of identified spinal motoneurons from normal adult zebrafish and from animals subjected to cordotomy or unilateral axotomy of the motor nerves. The lesions caused an increase of the myotomal area with oxidative muscle fibers. We studied the question: do changes in the myotomal muscle configuration concur with changes in the enzyme histochemical profiles of innervating motoneurons? Based on the location and size of cell somata, two categories of motoneurons are distinguished: large white (W) motoneurons that innervate the deep fast, glycolytic muscle fibers, and smaller red and intermediate (RI) motoneurons that innervate the superficial slow oxidative and intermediate muscle fibers. In normal animals, glucose-6-phosphate dehydrogenase activity is high in the large W motoneurons and relatively low in the small RI motoneurons. The reverse holds for succinate dehydrogenase activity is high in the large W motoneurons and relatively low in the small RI motoneurons. The reverse holds for succinate dehydrogenase activity. W and RI motoneurons show similar nicotinamide adenine dinucleotide diaphorase activity. Short- (2 weeks) and long- (8 weeks) term effects of lesions were studied. The results show that: (1) the 3 types of lesions lead to prolonged changes in the enzyme histochemical profiles of spinal motoneurons. The type of change depends on the type of lesion and on the type of motoneuron; (2) unilateral axotomy of the motor nerves affects the histochemical characteristics of spinal motoneurons and the myotomal muscle fiber type configuration on the ipsi- and contralateral side. The contralateral effects are conceived as adaptations to maintain a left-right symmetry in the motor output.

Premorphological metabolic changes in human breast carcinogenesis

Malignant breast tissue is characterized by morphological and metabolic changes when compared with normal breast tissue. In this study, the cytochemical measurement of glucose-6-phosphate dehydrogenase (G6PD) activity was used to detect abnormal metabolism in breast tissue and to determine whether abnormal metabolic activity precedes morphological change during human breast carcinogenesis. Normal and benign breast tissue, morphologically normal tissue from cancer-containing breasts, and malignant breast tissue were studied. In malignant tissue, mean(s.e.m.) G6PD activity was significantly increased when compared with normal and benign tissue (9.69(2.3) versus 27.02(1.7) mean integrated extinction (MIE) x 100, P less than 0.01). G6PD activity was increased in morphologically normal tissue from cancer-containing breasts when compared with normal and benign breast tissue from breasts with no known cancer (27.02(1.7) versus 18.42(2.6) MIE x 100, P less than 0.05). These findings suggest that metabolic abnormalities precede morphological changes in breast carcinogenesis. Abnormal metabolism can be detected widely within a cancer-containing breast. The detection of such abnormality may prove helpful in identifying patients at high risk of developing breast cancer.

Enzyme cytochemistry of unfixed leukocytes and bone marrow cells using polyvinyl alcohol for the diagnosis of leukemia

Cytochemical methods for the demonstration of enzyme activities in blood and bone marrow cells were systematically improved by the addition of an inert polymer, polyvinyl alcohol (PVA), to the incubation medium and by using optimized reaction media. The methods investigated were tetrazolium salt methods for lactate, glucose-6-phosphate, succinate and glutamate dehydrogenase, the indoxyl-tetrazolium salt method for alkaline phosphatase, the diaminobenzidine method for peroxidase, and diazonium salt methods for chloroacetate esterase, beta-glucosaminidase, beta-glucuronidase, acid phosphatase, and dipeptidylpeptidase II and IV. PVA in the media preserved the morphology of cells very well and prevented leakage of large molecules such as enzymes from the cells. Therefore, fixation or long periods of air-drying prior to incubation leading to substantial loss of enzyme activity could be avoided. A brief period of drying (2 min at 37 degrees C) of the cell preparations just before the incubation was sufficient for making the cells permeable. Localization of enzyme activities was very precise and precipitation of the final reaction product was confined to sites which are known to contain the enzyme under study (granules, mitochondria, lysosomes). These advantages advocate the use of PVA in haematological enzyme cytochemistry and especially for diagnosis of leukemia.

Dehydrogenase enzyme histochemistry on freeze-dried or fixed resin-embedded tissue

A method has been developed for the histochemical demonstration of a variety of dehydrogenases in freeze-dried or fixed resin-embedded tissue. Seven dehydrogenases were studied. Lactate dehydrogenase, NADH dehydrogenase and NADPH tetrazolium reductase were all demonstrable in sections of paraformaldehyde-fixed resin-embedded tissue. Freeze-dried specimens were embedded, without fixation, in glycol methacrylate resin or LR Gold resin at either 4 degrees C or -20 degrees C. All the dehydrogenases except succinate dehydrogenase retained their activity in freeze-dried, resin-embedded tissue. Enzyme activity was maximally preserved by embedding the freeze-dried tissue specimens in glycol methacrylate resin at -20 degrees C. The dehydrogenases were accurately localized without any diffusion when the tissue sections were incubated in aqueous media. Addition of a colloid stabilizer to the incubating medium was not required. Freeze-drying combined with low-temperature resin embedding permits accurate enzyme localization without diffusion, maintenance of enzyme activity and excellent tissue morphology.

Regulation of glucose-6-phosphate dehydrogenase activity in sea urchin eggs by reversible association with cell structural elements

In unfertilized eggs of the sea urchin, Strongylocentrotus purpuratus, glucose-6-phosphate dehydrogenase (G6PDH) associates with the particulate elements remaining either after homogenization or extraction of eggs with non-ionic detergent in low ionic-strength media. At physiological ionic strength, the extent of G6PDH binding to these particulate elements is proportional to the total protein concentration in the extracts. In fertilized eggs this association is prevented by one or more low molecular weight solutes. The dissociation is reversible, and there are no permanent modifications of either G6PDH or its particulate binding site that affect binding. After fertilization, the time course of dissociation of G6PDH from particulate elements is too fast to be caused by a change in intracellular pH, but it could be triggered, but not maintained, by an increase in the intracellular calcium concentration. Binding of G6PDH to the particulate fraction lowers its catalytic activity at all substrate concentrations. Therefore, release of the enzyme into the cytoplasm may be an important part of the suite of events causing metabolic activation of the egg at fertilization.