Enhanced light microscopic visualization of oxidase activity with the cerium capture method

D-amino acid oxidase: physiological role and applications

D-Amino acids play a key role in regulation of many processes in living cells. FAD-dependent D-amino acid oxidase (DAAO) is one of the most important enzymes responsible for maintenance proper level of D-amino acids. The most interesting and important data for regulation of the nervous system, hormone secretion, and other processes by D-amino acids as well as development of different diseases under changed DAAO activity are presented. The mechanism of regulation is complex and multi-parametric because the same enzyme simultaneously influences the level of different D-amino acids, which can result in opposing effects. Use of DAAO for diagnostic and therapeutic purposes is also considered.

Chelatable Fe (II) is generated in the rat kidneys exposed to ischemia and reperfusion, and a divalent metal chelator, 2, 2'-dipyridyl, attenuates the acute ischemia/reperfusion-injury of the kidneys: a histochemical study by the perfusion-Perls and -Turnbull methods

The perfusion-Perls and -Turnbull methods supplemented by diaminobenzidine intensification demonstrated the generation and localization of chelatable Fe (II) which can catalyze the generation of cytotoxic hydroxyl radicals (OH.) during the Fenton reaction in rat kidneys exposed to 40 min ischemia or 40 min-ischemia followed by 60 min-reperfusion. The kidneys exposed to 40 min-ischemia showed Fe (II)-deposits largely localized in the deeper half of the cortex, where the deposits densely filled the tubular cell nuclei, with a small amount of them in the cytoplasm of the proximal convoluted tubules (PCT). Intraluminally protruded or exfoliated tubular cell nuclei were also filled with the deposits. The kidneys subjected to 40 min-ischemia/ 60 min-reperfusion showed a more extensive distribution of Fe (II)-deposits, including most depths of the cortex. Furthermore, there were numerous exfoliated, Fe (II)-positive nuclei surrounded by a small amount of cytoplasm in the lumen of the PCT. These cells appeared to undergo apoptotic cell death since the lumen of strongly dilated, down-stream, proximal straight tubules were obstructed with numerous apoptotic cells in the kidneys exposed to 40 min-ischemia and 24 h-reperfusion. Pretreatment with a divalent metal chelator, 2, 2'-dipyridyl, effectively inhibited Fe (II)-staining, decreased the number of exfoliated cells in the kidneys with 40 min-ischemia/ 60 m-reperfusion, and decreased the number of apoptotic cells in the kidneys with 40 min-ischemia/24 h-reperfusion. The generation of highly reactive OH. during the Fe2+-catalyzed Fenton reaction was suggested to play a crucial role in ischemia/reperfusion-induced kidney injury.

Visualization of non-heme ferric and ferrous iron by highly sensitive non-heme iron histochemistry in the stress-induced acute gastric lesions in the rat

Redox-active non-heme iron catalyzes hydroxyl radical [Formula: see text] generation through Haber-Weiss reaction. Oxidative tissue damage by OH* has been suggested in the development of stress-induced gastric lesion. Using highly sensitive non-heme iron histochemistry, the perfusion-Perls and -Turnbull methods plus DAB intensification, we studied the distribution of non-heme ferric and ferrous iron (NHF[III] and NHF[II]) in the normal stomach and its changes in the acute gastric lesions induced by restraint water immersion (RWI) stress in the rat. Both NHF[III] and NHF[II] staining increased in the oncotic parietal cells located at the erosive lesion which developed on the gastric mucosal folds after 3 h RWI. It was considered that increase in non-heme iron in these cells catalyzed OH* generation under the presence of O(2)(*-) released from abundant injured mitochondria. This was supported by the increase in H(2)O(2) staining in the erosive region and the obvious reduction of the gastric lesion following administration of deferoxamine before RWI. NHF[II] was stained in the arterial endothelium in the tela submucosa of the normal gastric wall and increase in the entire gastric mucosa after 3 h RWI suggests that the changes in the vascular non-heme iron metabolism were also involved in the response of the stomach to stressful conditions.

Comparative histochemical and immunohistochemical study on xanthine oxidoreductase/xanthine oxidase in mammalian corneal epithelium

We have previously found that xanthine oxidase (one form of xanthine oxidoreductase that generates reactive oxygen species, such as superoxide radicals and hydrogen peroxide) is present in corneal epithelium of normal rabbit eye. It was suggested that the reactive oxygen species contribute to additional eye damage related to prolonged continuous contact lens wear and irradiation of the eye with UV-B light. To further explore the potential danger of xanthine oxidase as a source of reactive oxygen species, we have examined in the present paper whether xanthine oxidoreductase and xanthine oxidase are present in corneal epithelium of other mammalian species, employing immunohistochemical and enzyme histochemical methods. In corneal epithelium of normal eyes of ox, pig, guinea-pig, and rat xanthine oxidoreductase activity was detected by the tetrazolium salt reduction method and xanthine oxidase activity was localized by a method based on cerium ions capturing hydrogen peroxide. For the immunohistochemical demonstration of the enzymes, rabbit anti-bovine xanthine oxidase antibody, rabbit anti-human xanthine oxidase antibody and monoclonal mouse anti-human xanthine oxidase/xanthine dehydrogenase/aldehyde oxidase antibody were used. The immunohistochemical and enzyme histochemical results show that xanthine oxidoreductase and xanthine oxidase are present both as proteins and as active enzymes in the corneal epithelium of all animals studied. It is hypothesized that under various pathological states, xanthine oxidase-generated reactive oxygen species might contribute to eye damage.

Ultrastructural localization of xanthine oxidoreductase activity in isolated rat liver cells

Xanthine oxidoreductase (XOR) can exist in a dehydrogenase form (XD) and an oxidase form (XO). The D-form uses NAD as cofactor and the O-form uses oxygen as second substrate and produces oxygen radicals. Both enzymes have a high affinity for hypoxanthine and xanthine as substrate and produce uric acid, a potent antioxidant. In the present study, XOR activity was demonstrated with the ferricyanide method in permeabilized isolated rat liver cells at the electron microscopical level. Moreover, ultrastructural localization of XO activity in these cells was studied with the cerium salt method. Activity of both XOR and XO was found in matrix and core of peroxisomes of rat liver parenchymal cells. Only XOR activity was present as well in the cytoplasm of rat liver parenchymal cells. In Kupffer cells and sinusoidal endothelial cells, XOR activity was demonstrated in vesicles and occasionally on granular endoplasmic reticulum. XO activity was not found in Kupffer cells and sinusoidal endothelial cells. The presence of uric acid oxidase activity in matrix and core of peroxisomes as was found previously suggests further breakdown of purines to allantoin in peroxisomes. It is suggested that the major function of XOR activity in the cytoplasm of rat liver parenchymal cells and in sinusoidal cells is not the production of oxygen radicals, but rather the production of uric acid which can act as a potent antioxidant.

Ebselen suppresses late airway responses and airway inflammation in guinea pigs

Although ebselen, a seleno-organic compound, inhibits inflammation in various animal models, its efficacy as an anti-asthma drug remains to be clarified. In this study, we investigated the inhibitory effect of ebselen on a guinea pig asthma model. Ebselen was orally administered at dosages of 1-20 mg/kg 2 h before an ovalbumin (OA) challenge, and then airway responses, airway inflammation, the generation of superoxide, H(2)O(2), and nitrotyrosine, and the induction of inducible nitric oxide synthase (iNOS) were evaluated. Sensitized animals challenged with OA aerosol showed dual airflow limitations, i.e., immediate and late airway responses (IAR and LAR). Ebselen significantly inhibited LAR at dosages greater than 10 mg/kg, but did not inhibit IAR at any dosage. Bronchoalveolar lavage (BAL) examination showed that airway inflammation was significantly suppressed by ebselen at 10 mg/kg. The generation of superoxide and H(2)O(2) occurred on endothelial cells of LAR bronchi, and was inhibited by 10 mg/kg of ebselen. Superoxide generation was inhibited by diphenyleneiodonium chloride (DPI), a NAD(P)H oxidase inhibitor, but not by allopurinol, a xanthine oxidase inhibitor. Immunoreactivities for iNOS and nitrotyrosine were also observed on endothelial cells of LAR bronchi and were abolished in ebselen-treated animals. The present findings suggest that ebselen can be applied as a new therapeutic agent for asthma. The possible mechanisms by which ebselen inhibits LAR likely involve suppression of oxidant formation and iNOS induction in endothelial cells.

Current cytochemical techniques for the investigation of peroxisomes. A review

The past decade has witnessed unprecedented progress in elucidation of the complex problems of the biogenesis of peroxisomes and related human disorders, with further deepening of our understanding of the metabolic role of this ubiquitous cell organelle. There have been many recent reviews on biochemical and molecular biological aspects of peroxisomes, with the morphology and cytochemistry receiving little attention. This review focuses on the state-of-the-art cytochemical techniques available for investigation of peroxisomes. After a brief introduction into the use of the 3,3'-diaminobenzidine method for localization of catalase, which is still most commonly used for identification of peroxisomes, the cerium technique for detection of peroxisomal oxidases is discussed. The influence of the buffer used in the incubation medium on the ultrastructural pattern obtained in rat liver peroxisomes in conjunction with the localization of urate oxidase in their crystalline cores is discussed, particularly since Tris-maleate buffer inhibits the enzyme activity. In immunocytochemistry, quantitation of immunogold labeling by automatic image analysis enables quantitative assessment of alterations of proteins in the matrix of peroxisomes. This provides a highly sensitive approach for analysis of peroxisomal responses to metabolic alterations or to xenobiotics. The recent evidence suggesting the involvement of ER in the biogenesis of "preperoxisomes" is mentioned and the potential role of preembedding immunocytochemistry for identification of ER-derived early peroxisomes is emphasized. The use of GFP expressed with a peroxisomal targeting signal for the investigation of peroxisomes in living cells is briefly discussed. Finally, the application of in situ hybridization for detection of peroxisomal mRNAs is reviewed, with emphasis on a recent protocol using perfusion-fixation, paraffin embedding, and digoxigenin-labeled cRNA probes, which provides a highly sensitive method for detection of both high- and low-abundance mRNAs encoding peroxisomal proteins. (J Histochem Cytochem 47:1219-1232, 1999)

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.

Development of hydrogen peroxide (H2O2)-generating oxidases in chick organs with special reference to kidneys

The developmental pattern of H2O2-producing oxidases (OX) was studied in chick kidneys (mesonephros, metanephros), intestine, liver, yolk sac and adrenal glands between embryonic days (ED) 5-20 as well as in chick organs after hatching. Sections from snap frozen tissue fixed in cold cacodylate-buffered 2% glutaraldehyde were processed by cerium-DAB-Co-H2O2 methods for benzylamine OX, diamine OX, histamine OX, alpha-hydroxyacid OX, D-amino acid OX (AAOX) and monoamine OX (MAOX). Prenatally, only activities of AAOX and MAOX could be demonstrated. AAOX appeared primarily in the proximal tubular cells of both types of kidneys. In the metanephros the enzyme was also detected in the thick ascending limbs of Henle's loops. The amount of reaction product in tubular cells increased with their maturation. MAOX activity was detected in immature enterocytes, in smooth muscle cells of large systemic arteries (on ED 5-6) as well as in proximal tubular cells of the mesonephros and adrenal gland. Later the enzyme appeared also in smooth muscle cells of the intestinal wall and in endothelial and smooth muscle cells of arterioles of the mesonephros. In the metanephros MAOX was detected at the same locations with a time delay because of a developmental shift of the kidney. Inhibition tests revealed that MAOX differs in epithelial cells from that in smooth muscle cells. Benzylamine OX, diamine OX and histamine OX were detected postnatally in smooth muscle cells of the arterial media and muscularis externa of the intestinal wall with low activities. It is concluded that MAOX and AAOX activities represent useful markers in the development of renal tubules. In addition, MAOX activity can be considered an indicator of maturation of components of the vascular wall.

Localization of superoxide dismutase activity in rat tissues

Superoxide anion radicals have been implicated in a variety of pathological processes. Under physiological conditions, superoxide dismutase (SOD) is effectively able to disproportionate superoxide anions into hydrogen peroxide and dioxygen. Until now, no techniques have been available to localize SOD activity within tissues. In the present study, SOD activity was detected in different rat tissues using a thin film of xanthine oxidase between the glass slide and the unfixed cryostat section and a medium containing hypoxanthine as a source of electrons for the production of superoxide anions. The incubation medium also contained cerium ions to precipitate the hydrogen peroxide product and polyvinyl alcohol to prevent leakage of soluble and/or loosely bound enzymes from the sections into the incubation medium. The cerium perhydroxides that are formed were visualized for the light microscope in a second step using an incubation medium consisting of 3,3'-diaminobenzidine, cobalt ions, and hydrogen peroxide, which results in oxidation of the diaminobenzidine to the final insoluble blue reaction product. By this methodology, high enzyme activity was found not only in endothelial cells of liver and kidney but also in hepatocytes of liver, myocytes of heart, smooth and striated cells of muscle, acinar cells of pancreas, epithelial cells of kidney ducts, and epithelial cells of the small intestine and colon. These findings were largely in agreement with immunohistochemical data obtained using antibodies against the Cu/Zn- and Mn-SODs. However, high activity was also detected extra-cellularly at the surface of epithelia of trachea, esophagus, small intestine, and colon and at the extracellular matrices, cartilage, and connective tissues. We conclude from these latter data that the activity of the extracellular form of the dismutase is localized. The present method allows the analysis of all three types of known SOD activity (Cu/Zn, Mn, and extracellular) in different tissues and cell compartments.

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.

Reflectance enzyme histochemistry (REH): visualization of cerium-based and DAB primary reaction products of phosphatases and oxidases in cryostat sections by confocal laser scanning microscopy

In the present study the reflectance mode of confocal laser scanning microscopy was adapted to detect and to assess semiquantitatively cerium-based primary reaction products of oxidases [Ce(IV) perhydroxide] and phosphatases [Ce(III) hydroxyphosphate converted into Ce(IV) perhydroxyphosphate] as well as of the 3,3'-diaminobenzidine (DAB)-based primary reaction product of cytochrome c oxidase in cryostat sections. Confocal laser scanning microscopy offers a unique way of making visible histochemical reaction products which are weakly absorbant but sufficiently reflective. It was easily possible to record simultaneously the reflectance signals at the wavelength of the exciting laser (preferentially 488 nm) and the autofluorescence signals ( > 580 nm in our set-up) of glutaraldehyde-fixed tissue. The results of an imbibition study of cerium-containing model precipitates indicate that the cerium, generally, should be oxidized prior to observation because the index of refraction of Ce(IV) compounds is considerably higher than that of the corresponding Ce(III) compounds. An attempt at comparative numerical assessment of reflection intensities from reflectant parts in morphologically similar sections is presented. The proposed technique may open new possibilities in enzyme- and immunohistochemistry.

Histochemical study on xanthine oxidase activity in the normal rabbit cornea and lens and after repeated irradiation of the eye with UVB rays

In the normal rabbit cornea and lens the activity of xanthine oxidase, an enzyme belonging to oxidases generating reactive oxygen species (ROS), is present in the corneal epithelium as well as endothelium and lens epithelium. Repeated irradiation of the eyes with UVB rays (5 min 1 x daily, for 1 to 4 days) caused a gradual increase of xanthine oxidase activity, particularly in the corneal epithelium. Application of catalase, a scavenger of hydrogen peroxide, to the eye surface during the irradiation diminished the increase of xanthine oxidase activity. On the contrary, the pretreatment of the rabbit eyes with 3-aminotriazole, an inhibitor of catalase, for 3 days before the irradiation enhanced the increase of xanthine oxidase activity. In comparison to untreated eyes, protracted irradiation of the eyes with UVB rays (up to 10 days) caused a decrease of xanthine oxidase activity in the same cell layers of the cornea and lens. It is suggested that xanthine oxidase is involved in the generation of ROS in the anterior eye segment during early irradiation of the eyes with UVB rays and participates in its damage. Prolonged repeated irradiation of the eye (5 min 1 x daily for 5 to 10 days) caused a decrease of xanthine oxidase activity in the cornea and lens which is attributed to profound damage of the whole anterior eye segment.

Extinction coefficient of polymerized diaminobenzidine complexed with cobalt as final reaction product of histochemical oxidase reactions

The extinction coefficient is essential for the conversion of cytophotometric (mean integrated) absorbance values into absolute units of enzyme activity, for instance expressed in terms of moles of substrate converted per unit time and per unit wet weight of tissue. The extinction coefficient of polymerized diaminobenzidine (polyDAB) complexed with cobalt as the final reaction product of oxidase reactions was estimated at 575 nm by comparison of the amounts of final reaction products formed after incubation of serial unfixed cryostat sections of rat kidney to demonstrate D-amino acid oxidase activity with either the tetrazolium salt method or the cerium-DAB-cobalt-hydrogen peroxide method. Both procedures resulted in similar localization patterns of final reaction product in a granular form in epithelial cells of proximal tubules in rat kidney. The granules were peroxisomes. Linear relationships were found for both methods between the specific amounts of final reaction product generated by D-amino acid oxidase activity and incubation time. The cerium salt method gave rise to 7.4 times higher absorbance values of final reaction product generated per unit time and per unit wet weight of tissue than the tetrazolium salt procedure. The extinction coefficient of tetranitro BT-formazan is 19,000 at 557 nm. Therefore, the cytophotometric extinction coefficient of the polyDAB-cobalt complex as final reaction product of oxidase reactions was established to be 140,000.

Visualization of hydrogen peroxide (H2O2)-production from histamine

The cellular and intracellular metabolization sites of the tissue hormone and paracrine compound histamine as a source for the indirect and potentially toxic or physiological mediator molecule H2O2 are not yet known. Therefore, in the present study, histamine was used as the substrate in a cerium-diaminobenzidine-H2O2-Co procedure to visualize for the first time the oxidative deamination and H2O2-production sites of this amine in various laboratory animals. Diamine oxidase (DAOX) was shown to be the responsible enzyme. With the exception of marmosets, all species could deaminate histamine oxidatively and form H2O2. In most species, H2O2 was produced by DAOX from histamine in small intestinal enterocytes; in rats H2O2 was generated in all vascular and non-vascular smooth muscle cells; in guinea-pigs only smooth muscle cells in the digestive tract and uterus and in addition the cardiac and gastric capillary endothelium and hepatic sinusoidal endothelium produced H2O2. Furthermore, in some species H2O2 was generated by DAOX with histamine as the substrate in certain renal, adrenal and splenic cell types. While H2O2-production in enterocytes may derive from luminal-borne histamine, i.e., from histamine of foreign origin, the formation of H2O2 in the other cells suggests endogenous (mast cell, basophilborne) histamine as the substrate and H2O2 source.

A re-evaluation of the tissue distribution and physiology of xanthine oxidoreductase

Xanthine oxidoreductase is an enzyme which has the unusual property that it can exist in a dehydrogenase form which uses NAD+ and an oxidase form which uses oxygen as electron acceptor. Both forms have a high affinity for hypoxanthine and xanthine as substrates. In addition, conversion of one form to the other may occur under different conditions. The exact function of the enzyme is still unknown but it seems to play a role in purine catabolism, detoxification of xenobiotics and antioxidant capacity by producing urate. The oxidase form produces reactive oxygen species and, therefore, the enzyme is thought to be involved in various pathological processes such as tissue injury due to ischaemia followed by reperfusion, but its role is still a matter of debate. The present review summarizes information that has become available about the enzyme. Interpretations of contradictory findings are presented in order to reduce confusion that still exists with respect to the role of this enzyme in physiology and pathology.

Light microscopic visualization of monoamine oxidase using a cerium method

H2O2-generating monoamine oxidase can be visualized in the light microscope with tetrazolium, metal salt (ferricyanide) and coupled peroxidatic oxidation methods. Due to methodological draw-backs these procedures do no allow satisfactory results. In search for an alternative method a light microscopic cerium procedure was designed in which the primary reaction product, cerium perhydroxide, serves for the generation of amplified and intensified diaminobenzidine brown. With this cerium-diaminobenzidine-H2O2-Co method monoamine oxidase was visualized more easily and reliably and with higher sensitivity and more precise localization than with the other techniques. At present this method is considered to be the procedure of choice and was used to re-investigate and investigate the distribution of monoamine oxidase in rats, mice, gerbils, guinea-pigs, marmosets, monkeys and man. In these species many cells and tissues showed monoamine oxidase activity where the enzyme has not yet been found before and the structures with already known monoamine oxidase activity showed an improved localization.

Cerium methods for light and electron microscopical histochemistry

Methods based on the use of cerium to detect the activity of oxidases and phosphatases are rapidly expanding. Both classes of enzymes can be demonstrated with cerium at the electron and light microscopical level. The in situ detection of H2O2 production with cerium is another application that has great potential, particularly in experimental pathological research. The fine precipitate of the cerium-containing final reaction product, cerium perhydroxide or cerium phosphate, enables a very precise localization. With such techniques, important advances have been made in cell biology, such as the discovery of new organelles, functional subcompartmentization of peroxisomes, tubular lysosomes and the elucidation of the function of extracellular ATPases. At the light microscopical level, the activity of enzymes can be quantified in situ because the production of final reaction product in the cerium methods is proportional to enzyme activity in tissue sections or cells. Cerium precipitates have strong reflectance properties and this enables their use in confocal scanning laser microscopy. In the present review, the principles of cerium methods are outlined and applications in cell biology and pathology are discussed.

Enzyme histochemistry of the regressing rat decidua and metrial gland

In order to understand more about participation of the basal placental zones in processes of regression and degradation as well as separation on the cellular level, the cell metabolism of the rat decidua and metrial gland was investigated enzyme histochemically in cryosections for activities of oxyradical-forming enzymes and hydrolyzing enzymes. Additionally, plastic sections were studied to facilitate the recognition of cell types. Decidual stromal cells and fibroblasts formed the vast majority amongst many cell types in the decidua and metrial gland. High activities of enzymes involved in purine degradation and oxyradical generation were demonstrated in decidual stromal cells and fibroblasts. Microsomal alanyl aminopeptidase and various acid hydrolases were shown to be extremely active in decidual stromal cells. The abundance of these enzyme activities in the decidua and metrial gland in contrast to other placental areas suggests, that these enzymes may have specialized functions in connection with regression and degradation processes finally contributing to placental separation.

Histochemistry of peroxisomal enzyme activities: a tool in the diagnosis of Zellweger syndrome

The localization of the activity of the peroxisomal enzymes D-amino acid oxidase and hydroxyacid oxidase was studied at the light-microscopical level in livers and kidneys of control subjects and patients with Zellweger syndrome, an inherited disease characterized by a lack of intact peroxisomes. D-Amino acid oxidase and hydroxyacid oxidase activities were demonstrated in unfixed cryostat sections with the cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure, in which cerium ions capture hydrogen peroxide, the product of both enzymes. In a second step reaction decomposition of cerium perhydroxide gives rise to a diaminobenzidine polymer complexed with cobalt ions. D-Amino acid oxidase and hydroxyacid oxidase activities were found in peroxisomes of liver parenchymal cells, and only D-amino acid oxidase in peroxisomes of proximal tubular cells of kidneys of control humans. The activities of these enzymes were not detectable in livers and kidneys of Zellweger patients. It is concluded that the cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure enables the demonstration of peroxisomal enzyme activities in human tissues at the light-microscopical level and is an important tool in detecting patients with Zellweger syndrome.

A new staining method for the detection of activities of H2O2-producing oxidases on gels and blots using cerium and 3,3'-diaminobenzidine

Cerium chloride (CeCl3) was used to trap the hydrogen peroxide generated by several oxidases on native gels and blots. The pale yellow color of cerium perhydroxide formed is converted to a brown-black precipitate by the subsequent reaction with 3,3'-diaminobenzidine. The suitability of this method for the detection of the activity of several oxidases on gels and on blots under nondenaturing conditions, employing different electrophoretic systems and resolving techniques, is demonstrated. Moreover, this method has proven to be highly suitable for the assessment of the substrate and stereospecificity of oxidases, the determination of their molecular weights, and the isoelectric points of isoforms.

Protection against salicylate-induced hepatic injury by zinc. A histochemical and biochemical study

Female Wistar rats received an oral dose of 700 mg salicylic acid/kg body wt., given as sodium salicylate. Some of the salicylate-treated rats received two subcutaneous injections of 100 mumol kg-1 ZnCl2 (24 h before and simultaneously with the salicylate administration). Other animals were given one subcutaneous injection of 100 mumol kg-1 ZnCl2 simultaneously with the salicylate treatment. Control rats were similarly injected with ZnCl2. Twenty four hours after salicylate treatment, serum and livers were taken for histochemical and biochemical analysis. The most remarkable effects of the treatment were enrichment of lipid droplets and iron and a reduction of glycogen, particularly in the periportal hepatocytes. The effects of salicylate were partially prevented by two ZnCl2 injections. The protective effects of ZnCl2 may be due to lower iron uptake into hepatocytes and by the induction of zinc metallothionein, which can serve as a scavenger for oxygen radicals.

Light microscopical detection of H2O2-generating oxidases using cerium ions and aqueous incubation media

Light microscopical procedures were optimized and tested for specificity for the histochemical demonstration of D-amino acid oxidase, alpha-hydroxy acid oxidase, monoamine oxidase, and xanthine oxidase using cerium ions and a visualization step originally described by Angermüller and Fahimi (1988a, b), and modified for D-amino acid oxidase by Gossrau et al. (1989). The visualization medium contained diaminobenzidine, cobalt ions, and small amounts of hydrogen peroxide. Procedures of pretreatment of cryostat sections, types of substrate, concentrations of substrates, and cerium ions were varied. Optimum procedures are reported for the detection of these oxidases in different rat tissues. The results are compared with those obtained with other methods described for the demonstration of hydrogen peroxide-generating oxidases such as the tetrazolium, Hatchett Brown, and coupled peroxidatic methods.

Histochemistry of reactive oxygen-species (ROS)-generating oxidases in cutaneous and mucous epithelia of laboratory rodents with special reference to xanthine oxidase

Cutaneous and mucous epithelia of various organs of laboratory rodents were analysed histochemically for reactive oxygen species (ROS)-generating oxidases using cerium methods. High activities of xanthine oxidase and also superoxide dismutase were present in orthokeratotic stratified squamous epithelia of skin, lips, esophagus and forestomach and parakeratotic keratinizing stratified epithelia of vagina, tongue and penis. Moreover, activity was found in simple epithelium of the uterus and intestine of rats, mice and guinea-pigs. Moderate activities of monoamine oxidase and D-amino acid oxidase were only seen in enterocytes of large and small intestine, whereas alpha-hydroxy acid oxidase could not be detected at all. With the use of specific inhibitors for superoxide anions-producing xanthine oxidase and H2O2-generating superoxide dismutase it was shown that epithelial cells of all studied external and internal surface epithelia contain a highly effective xanthine oxidase-superoxide dismutase system. It is hypothesized that this system might have a general microbicidal function and might play a special role in tumor promotion of the skin.

Pitfalls in the light microscopical detection of NADH oxidase

NADH oxidase activity has been detected at the ultrastructural level using cerium ions to trap H2O2 generated by the enzyme (via intermediate reactive oxygen species). In an attempt to localize NADH oxidase activity at the light microscope level using the cerium-diaminobenzidine (DAB)-nickel-H2O2, the cerium-DAB-cobalt-H2O2 or the cerium-alkaline lead procedures, the distribution patterns of the revealed enzyme were found to be identical to those for non-specific alkaline phosphatase and especially 5'-nucleotidase activity. With the cerium-DAB-cobalt-H2O2 visualization procedure, the distribution pattern of the final reaction product was similar to that obtained with the other two techniques but much less final reaction product was formed. Incubations for NADH oxidase activity performed in the presence of exogenous catalase or in the absence of catalase or peroxidase inhibitors did not affect the staining intensity, whereas inhibitors of 5'-nucleotidase (EDTA) and non-specific alkaline phosphatase (levamisole) always did. Therefore, phosphatases contribute to the formation of the final reaction product. Since NADH initially cannot be hydrolysed by either of these two phosphatases, then presumably nucleotide pyrophosphatase (E.C.3.6.1.9) cleaves NADH into 5'-AMP and nicotinamide mononucleotide in a first step. Both nucleotides can be hydrolysed further by the two monophosphatases. These then generate cerium phosphate which is detected by the DAB-nickel-H2O2, DAB-cobalt-H2O2 or lead visualization methods.