Interface corrective force measurements in Boston brace treatment.

Brace application has been reported to be effective in treating idiopathic adolescent scoliosis. The exact working mechanism of a thoracolumbo spinal orthosis is a result of different mechanisms and is not completely understood. One of the supposed working mechanisms is a direct compressive force working through the brace upon the body and thereby correcting the scoliotic deformity, achieving optimal fit of the individual orthosis. In this study we measured these direct forces exerted by the pads in a Boston brace in 16 patients with idiopathic adolescent scoliosis, using the electronic PEDAR measuring device (Novel, Munich, Germany). This is designed as an in-shoe measuring system consisting of two shoe insoles (size 8 1/2), wired to a computer, recording static and dynamic pressure distribution under the plantar surface of the foot. After positioning the inserts between the lumbar and thoracic pads and the body, we measured the forces acting upon the body in eight different postures. In all positions the mean corrective force through the lumbar brace pad was larger than the mean corrective force over the thoracic brace pad. Some changes in body posture resulted in statistically significant alterations in the exerted forces. There was no significant correlation between the magnitude of the compressive force over the lumbar and thoracic brace-pad and the degree of correction of the major curve. Comparing the corrective forces in a relatively new (<6 months) and old (>6 months) brace, there was no statistically relevant difference, although the corrective force was slightly larger in the new braces. We think that the use of this pressure measurement device is practicable and of value for studies of the working mechanism of brace treatment, and in the future it might be of help in achieving optimal fit of the individual orthosis.

In situ detection of spontaneous superoxide anion and singlet oxygen production by mitochondria in rat liver and small intestine.

In the present study, the endogenous formation of reactive oxygen species was localized in rat liver and small intestine. The 3,3'-diaminobenzidine (DAB)-Mn2+ technique in which cobalt ions were included in the incubation medium was applied to unfixed cryostat sections of intact tissues. Addition of manganese ions to the DAB-Co(2+)-containing medium greatly increased the amounts of final reaction product formed compared with incubations with only DAB and cobalt ions. In liver, a blue final reaction product was deposited, particularly in hepatocytes surrounding portal tracts. In the small intestine, the DAB-cobalt complex was mainly found at the basal side of enterocytes. Goblet cells remained unstained. Electron microscopical images revealed that an electron-dense reaction product was exclusively present at both inner and outer membranes and at the intermembrane space in mitochondria of liver parenchymal cells and duodenal enterocytes. It was shown that the spontaneous formation of final reaction product was enzymatic and dependent on the presence of oxygen in the medium. Sulphide decreased the reaction, which may indicate that cytochrome c oxidase was partially involved. Benzoquinone and histidine, which are scavengers of superoxide anions and singlet oxygen respectively, reduced the amount of final reaction product considerably. Furthermore, the formation of final reaction product was sensitive to specific inhibitors of NADH:coenzyme Q reductase and aldehyde oxidase, indicating that these enzymes were at least partly responsible for the generation of superoxide anions and singlet oxygen and for the formation of the DAB-cobalt complex.

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.

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.

In situ substrate specificity and ultrastructural localization of polyamine oxidase activity in unfixed rat tissues.

Data concerning the substrate specificity and the exact intracellular localization of the polyamine-catabolizing enzyme polyamine oxidase are conflicting. Biochemical studies have shown that N1-acetylation of spermine and spermidine dramatically increases the specificity of these compounds for peroxisomal polyamine oxidase to produce spermidine and putrescine, respectively. On the other hand, polyamine oxidase activity was demonstrated histochemically both in peroxisomes and in cytoplasm of several tissues, using spermidine and/or spermine as substrate. To elucidate the in situ substrate specificity of polyamine oxidase and the localization of its activity, enzyme activity was detected in rat liver, kidney, and duodenum at the light and electron microscopic levels. For this purpose, unfixed cryostat sections were applied to avoid changes in enzyme activity owing to chemical fixation. Spermine, spermidine, their N1-acetylated forms, and putrescine were used as substrates, and cerium ions as capturing agent for H2O2. Control reactions were performed in the absence of substrate or in the presence of substrate and specific oxidase inhibitors. At the light microscopic level, final reaction product specifically generated by polyamine oxidase activity was found exclusively in a granular form in hepatocytes, epithelial cells of proximal tubules of the kidney, and epithelial cells of duodenal villi with N1-acetylspermidine or N1-acetylspermine as substrates. Final reaction product was not observed in any of the tissues after incubation in the presence of putrescine, spermidine, or spermine. Formation of specific final reaction product was prevented by incubation in the presence of a specific polyamine oxidase inhibitor, but it was not affected by a diamine oxidase inhibitor. Ultrastructural studies revealed that polyamine oxidase activity is localized exclusively to the matrix of peroxisomes of kidney and liver and to microperoxisomes of the duodenum. The localization patterns obtained with unfixed tissues are in agreement with biochemical data. Strong intraperoxisomal, interperoxisomal, and intercellular heterogeneity in polyamine oxidase activity was found in all tissues investigated.

Ultrastructural localization of xanthine oxidase activity in the digestive tract of the rat.

Precise localization of xanthine oxidase activity might elucidate physiological functions of the enzyme, which have not been established so far. Because xanthine oxidase is sensitive to chemical (aldehyde) fixation, we have localized its activity in unfixed cryostat sections of rat duodenum, oesophagus and tongue mounted on a semipermeable membrane. Previous studies had shown that this procedure enables the exact localization of activities of peroxisomal oxidases with maintenance of acceptable ultrastructure. Moreover, leakage and/or diffusion of enzyme molecules was prevented with this method. The incubation medium to detect xanthine oxidase activity contained hypoxanthine as substrate and cerium ions as capturing agent for hydrogen peroxide. After incubation, reaction product in the sections was either visualized for light microscopy or sections were fixed immediately and processed for electron microscopy. At the ultrastructural level, crystalline reaction product specifically formed by xanthine oxidase activity was found to be present in the cytoplasmic matrix of enterocytes and goblet cells and in mucus duodenum. Moderate activity was found in the cytoplasm of apical cell layers of epithelia of oesophagus and tongue, with highest activity in the cornified layer. Moreover, large amounts of reaction product were found to surround bacteria present between cell remnants of the cornified layer of the oesophagus. Many bacteria surrounded by the enzyme showed signs of destruction and/or cell death. The intracellular localization of xanthine oxidase activity in the cytoplasm of epithelial cells as well as the extracellular localization suggest that the enzyme plays a role in the lumen of the digestive tract, for instance in the defence against microorganisms.

Demonstration of 5'-nucleotidase activity in unfixed cryostat sections of rat liver using a combined light- and electron-microscope procedure.

In the present study a technique was developed to demonstrate 5'-nucleotidase activity in unfixed cryostat sections of rat liver at the light- and electron-microscope level using a semipermeable membrane. In order to retain the ultrastructure of the unfixed material as much as possible, incubations were also performed at 4 degrees C rather than at 37 degrees C. The optimized incubation medium contained 300 mM Tris-maleate buffer, pH 7.2, 5 mM adenosine monophosphate as substrate, 30 mM cerium chloride as capturing agent for liberated phosphate, 10 mM magnesium chloride as activator and 1.5% agar. At the light-microscope level, similar localizations of 5'-nucleotidase activity were obtained when incubations were performed at 37 degrees C and 4 degrees C. Enzyme activity was present mainly at bile canalicular membranes and at sinusoidal membranes of hepatocytes; total activity was higher in pericentral than in periportal areas. Cytophotometric analyses revealed that specific formation of final reaction product (FRP) (test minus control reaction) at 37 degrees C followed a hyperbolic curve with time. A linear relationship was found between specific amounts of FRP and section thickness up to 8 micrograms. 5'-Nucleotidase activity was about three-fold higher after incubation for 30 min at 37 degrees C than at 4 degrees C. At the electron-microscope level, it was demonstrated that the ultrastructure of rat liver was rather well-preserved after incubating unfixed cryostat sections attached to a semipermeable membrane and electron-dense FRP was found at bile canalicular and sinusoidal plasma membrane of hepatocytes. The most distinct changes in ultrastructure after incubation at 37 degrees C, in comparison with that at 4 degrees C, were the appearance of multi-lamellar structures at bile canaliculi at 37 degrees C. We conclude that the present method is valid for the demonstration of 5'-nucleotidase activity in unfixed cryostat sections of rat liver at both the light- and electron-microscope levels and that hypothermic incubations improve ultrastructural morphology substantially.

Electron microscopical study of a cytosolic enzyme in unfixed cryostat sections: demonstration of glycogen phosphorylase activity in rat liver and heart tissue.

Glycogen phosphorylase activity has been demonstrated at the ultrastructural level in liver and heart tissue of fasted rats. Unfixed cryostat sections were incubated by mounting them on a semipermeable membrane stretched over a gelled incubation medium. The medium contained a high concentration of glucose 1-phosphate which enables indirect detection of glycogen phosphorylase activity on the basis of the synthesis of glycogen. Tissue fixation, dehydration and embedding for electron microscopical study were performed after the incubation had been completed. The ultrastructure of both liver and heart tissue was rather well preserved. Glycogen granules resulting from glycogen phosphorylase activity were found in the cytoplasmic matrix of both hepatocytes and cardiomyocytes; no relationship with membranous structures could be detected. It is concluded that the semipermeable membrane method is well suited for localizing cytosolic enzyme activities at the ultrastructural level without prior tissue fixation; this opens further perspectives for correlations between histochemical and biochemical data.

A quantitative histochemical study of xanthine oxidase activity in rat liver using the cerium capture method in the presence of polyvinyl alcohol.

A recently developed histochemical technique to demonstrate xanthine oxidase activity in milk globules of bovine mammary gland and in epithelial cells of rat small intestine using cerium ions and a semipermeable membrane was slightly modified. The semipermeable membrane method was replaced by the addition of 10% (w/v) polyvinyl alcohol to the incubation medium. This technically more simple procedure enabled detection of xanthine oxidase activity in unfixed cryostat sections of rat liver. Both methods gave qualitatively and quantitatively similar results. Activity was found in sinusoidal cells and in liver parenchymal cells, with 50% higher activity in pericentral than in periportal areas. The specificity of the reaction was proven by the generation of only small amounts of final reaction product on incubation either in the absence of the substrates hypoxanthine or oxygen or in the presence of hypoxanthine and allopurinol. Allopurinol is a specific inhibitor of xanthine oxidase activity. The amount of final reaction product, as measured cytophotometrically in rat liver, increased linearly with incubation time (15-90 min) and with section thickness (up to 12 microns). By varying the hypoxanthine concentrations, a Km value of 0.05 mM was found. Addition of dithiothreitol to the incubation medium reduced the amount of final reaction product by 85%, which was caused by conversion of reversible xanthine oxidase into xanthine dehydrogenase. This histochemical method can be used for quantitative analysis of in situ xanthine oxidase activity.

Localization of uric acid oxidase activity in core and matrix of peroxisomes as detected in unfixed cryostat sections of rat liver.

Because of controversial data in the literature, we studied the localization of uric acid oxidase (UAOX) activity in rat liver by light microscopy (LM) and electron microscopy (EM). UAOX is partially inactivated by aldehyde fixation and therefore we developed a technique that permits the use of unfixed cryostat sections for both LM and EM studies. Sections of rat liver were mounted on a semipermeable membrane stretched over a gelled incubation medium containing urate as specific substrate for UAOX and cerium ions to capture H2O2 produced by oxidase activity. The specificity of the reaction was checked by comparing incubations in the presence of substrate with incubations either in the absence of substrate or in the presence of substrate and 2,6,8-trichloropurine, a competitive inhibitor of UAOX. After incubation the sections were either fixed immediately for EM or visualized for LM with a second-step incubation. At the LM level, final reaction product was found in a granular form, homogeneously distributed throughout the hepatocytes. EM revealed excellent subcellular morphology and electron-dense reaction product in both the core and the matrix of peroxisomes, but not in other organelles or the cytoplasmic matrix. After incubations without substrate or with substrate and inhibitor, hardly any reaction product was found. We conclude that, because of the use of unfixed tissue, UAOX is not inactivated, which results in localization of UAOX activity not only in the core of peroxisomes but also in the peroxisomal matrix.