Endotoxin-induced mortality in bile duct-ligated rats after administration of reconstituted high-density lipoprotein

Cholestatic patients have substantial morbidity because of increased susceptibility to endotoxin (lipopolysaccharide [LPS]). Although reconstituted high-density lipoprotein (rHDL) can bind and neutralize LPS, cholestasis is associated with a near complete absence of HDL. Effects of rHDL infusion on the outcome of LPS-induced inflammatory responses in cholestatic rats were determined. Bile duct-ligated (BDL) and sham rats were treated with rHDL or saline and challenged with LPS. Distribution of cholesterol over the lipoprotein subclasses changed by ligation: levels in low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) were increased 2-fold and 5-fold, respectively, and were decreased in HDL 2-fold. rHDL treatment did not affect cholesterol distribution. LPS was mainly found in the HDL fraction, and ligation affected only levels of HDL-bound LPS (50% decrease; P<.05). Although rHDL infusion effectively normalized the lipoprotein-bound LPS distribution, it resulted in increased sensitivity (mortality: 88% in the ligation + rHDL group versus 44% in the ligation + saline group, 25% in the sham + saline group, and 0% in the sham + rHDL group, P <.05). In accordance with these results, plasma tumor necrosis factor (TNF) was significantly highest in the BDL + rHDL group at several hours after LPS challenge as well as the accumulation of LPS in the liver (P<.05). rHDL infusion leads to increased LPS-induced mortality in cholestatic rats. These results sharply contrast with the protective effects of rHDL suppletion in experimental endotoxemia in animals and human volunteers without biliary obstruction and suggest that there may be danger in administration of rHDL to cholestatic patients.

Organ blood flow after partial hepatectomy in rats: modification by endotoxin-neutralizing bactericidal/permeability-increasing protein (rBPI23)

BACKGROUND/AIM

Both maintenance of adequate perfusion and regeneration of the remnant liver are important in the recovery of liver function after partial hepatectomy. In previous experiments, we have shown that profound hypotension and liver injury can be attenuated by neutralizing endotoxins. The relative contribution of endotoxemia to changes in liver blood flow and blood flow to other major organs after partial hepatectomy is not known. The aim of this study was to examine the effect of endotoxin neutralization on individual organ blood flows including hepatic artery and splanchnic blood flow after experimental partial hepatectomy and its relation to liver cell proliferation.

METHODS

Male Wistar rats underwent either two-thirds partial hepatectomy or sham operation. Treatment consisted of continuous infusion of recombinant N-terminal bactericidal/permeability-increasing protein (rBPI23) or control protein. At 4 h after surgery, organ blood flows were measured using the radiolabeled microsphere technique, and at 24 h, proliferation index in liver tissue was calculated.

RESULTS

After partial hepatectomy, blood flows to virtually all organs were significantly lower as compared to values obtained in sham-operated rats. rBPI23 greatly improved hepatic artery flow (p<0.001) but not portal venous flow. These effects of rBPI23 on liver flow preceded an equally enhanced liver cell proliferation (p<0.01). Endotoxin neutralization led to significantly higher flows to some but not all splanchnic organs. Lung perfusion was significantly improved by rBPI23.

CONCLUSIONS

Neutralization of endogenous endotoxins improves liver blood flow after partial hepatectomy and also periportal and pericentral liver cell proliferation. This proliferation effect may result from an increased hepatic artery flow. Lung, colon, spleen and pancreas flow but not kidney flow was greatly enhanced by rBPI23.

Molecular basis and enzymatic properties of glucose 6-phosphate dehydrogenase volendam, leading to chronic nonspherocytic anemia, granulocyte dysfunction, and increased susceptibility to infections

We have investigated the blood cells from a woman with a low degree of chronic nonspherocytic hemolytic anemia and frequent bacterial infections accompanied by icterus and anemia. The activity of glucose 6-phosphate dehydrogenase (G6PD) in her red blood cells (RBCs) was below detection level, and in her leukocytes less than 3% of normal. In cultured skin fibroblasts, G6PD activity was approximately 15% of normal, with 4- to 5-fold increased Michaelis constant (Km) for NADP and for glucose 6-phosphate. Activated neutrophils showed a decreased respiratory burst. Family studies showed normal G6PD activity in the RBCs from all family members, including both parents and the 2 daughters of the patient. Sequencing of polymerase chain reaction (PCR)-amplified genomic DNA showed a novel, heterozygous 514C-->T mutation, predicting a Pro172-->Ser replacement. Analysis of G6PD RNA from the patient's leukocytes and fibroblasts showed only transcripts with the 514C-->T mutation. This was explained by the pattern of X-chromosome inactivation, studied by means of the human androgen receptor (HUMARA) assay, which proved to be skewed in the patient, her mother, and one of the patient's daughters. Thus, the patient has inherited a de novo mutation in G6PD from her father and an X-chromosome inactivation determinant from her mother, causing exclusive expression of the mutated G6PD allele. Purified mutant protein from an Escherichia coli expression system showed strongly decreased specific activity, increased Km for NADP and for glucose 6-phosphate, and increased heat lability, which indicates that the defective phenotype is due to 2 synergistic molecular dysfunctions: decreased catalytic efficiency and protein instability.

In vivo treatment of rats with unfractionated heparin (UFH) or low molecular weight heparin (LMWH) does not affect experimentally induced colon carcinoma metastasis

Recent randomized trials have suggested that treatment with low molecular weight heparin (LMWH) improves survival of cancer patients with venous thromboembolism, as compared to treatment with unfractionated heparin (UFH). Experimental studies have shown that UFH has activities besides its anticoagulant function which may affect progression of malignancy, including stimulation of new blood vessel formation. In contrast, LMWH has been suggested to inhibit angiogenesis. In the present study, we compared quantitatively the effects of treatment with UFH, LMWH or placebo on the development of experimentally induced colon carcinoma metastases in rat liver and on tumor-associated angiogenesis. It is shown that UFH and LMWH in therapeutic dosages neither affect development of metastases nor tumor blood vessel formation in this animal model. These results indicate that heparins do not affect colon cancer metastasis in liver. Further studies in other animal models are required to establish the mechanisms by which heparins potentially affect cancer.

Short periods of oscillating fluid pressure directed at a titanium-bone interface in rabbits lead to bone lysis

Fluctuating high fluid pressures have been reported in pseudojoints after total hip arthroplasty, and may be present throughout the effective joint space. When the pressure extends locally to the bone implant interface, we hypothesized that it might have led to bone resorption. We developed an experimental implant model to study whether oscillating fluid pressure, applied during 2 hours a day, can lead to osteolysis at the bone implant interface. 12 mature rabbits received a titanium implant, which was allowed to osseointegrate. Thereafter, fluid pressure was applied to a specific area of the titanium bone interface at the periosteal side of the cortex in 6 of the rabbits. The pressure, applied during 2 hours a day for 14 days, oscillated between 70 and 150 mm Hg, with a frequency of 0.1 Hz. Bone resorption was not found in any of the control animals, but it occurred under 4 implants exposed to fluid pressure (p = 0.03; Fisher's exact test). Localized osteolytic lesions had developed, with evidence of osteocyte death in the surrounding cortical bone. In 1 of the 2 specimens without osteolysis, there was evidence of fluid leakage into the soft tissues. In 4 specimens (3 with and 1 without osteolysis), bone formation was observed at the endosteal side opposite to the pressure zone. This did not occur in the controls. No signs of infection were observed. Our findings indicate that oscillating fluid pressure, even when present only during short periods, can lead to osteolysis and may be a cause of prosthetic loosening. Endosteal bone apposition may be a result of the interstitial flow that was created, giving false signals of mechanical load to the osteocytes.

Three-dimensional reconstruction of colon carcinoma metastases in liver

Resection of liver metastases in patients with colon cancer increases survival but success depends on removal of all tumour tissue. For this purpose, understanding of spatial relationships between metastases and liver architecture is essential. Because metastatic cancer growth is essentially a three-dimensional (3D) event, we decided to apply 3D reconstruction techniques to study these spatial relationships between metastases and liver structures such as blood vessels, stroma and the liver capsule (Glisson's capsule). Colon carcinoma metastases were experimentally induced in rat liver by injection of colon cancer cells (CC531) into the portal vein. Three weeks later, livers from these animals and control livers were removed and immediately frozen in liquid nitrogen. Thirty-seven to 110 consecutive sections were used for each 3D reconstruction of 26 metastases in eight livers. Contours of different structures were stained by (immuno)histochemical means, traced in each section and stored in a database. From the contour model, a volume model was generated. Among the 26 metastases, seven were found to grow distantly from the liver capsule. They were small and consisted of well-differentiated cancer cells that were totally surrounded by a basement membrane and stroma which was always connected with adjacent blood vessels of a portal tract. The remaining 19 metastases showed a more advanced pattern of development. Infiltration of poorly differentiated colon cancer cells progressed through the stroma at various sites and areas of direct contact between cancer cells and hepatocytes were frequently found. This type of outgrowth of cancer cells was only found when metastases had made contact with the liver capsule. However, some areas in sections of these advanced stages still resembled small metastases. On the basis of these findings, we conclude that stroma-affects the differentiation pattern of cancer cells and has at least a dual role in tumour growth. On the one hand it limits invasion of cancer cells in the surrounding host tissue. On the other hand, stroma formation at the capsule, which consists mainly of granulation tissue, facilitates outgrowth of the tumours. Furthermore, our 3D reconstructions demonstrate the spatial heterogeneity of larger metastases and the importance of a 3D approach to understand growth and development of metastases in general and colon cancer metastases in the liver in particular.

Endotoxin and interleukin-1 related hepatic inflammatory response promotes liver failure after partial hepatectomy

Impairment of various functions of the liver and concomitantly increased levels of parameters of liver damage, a clinical entity termed liver failure, is commonly seen after partial hepatectomy. We investigated in a rat model whether damage of the remnant liver was due to local inflammatory responses, and related to endotoxin or interleukin-1 (IL-1). To address this question, the effects of partial hepatectomy on infiltration of immunocompetent cells and expression of major histocompatibility complex (MHC) class II antigen of macrophages in the remnant liver was studied using immunohistochemical techniques. Specific intervention with recombinant N-terminal bactericidal/permeability-increasing protein (rBPI23) to neutralize endotoxin and with IL-1 receptor antagonist (IL-1ra) to block IL-1 activity was used to examine the respective roles of endotoxin and IL-1. After partial hepatectomy, we found an influx of neutrophils, an increased expression of MHC class II antigens, and morphologic changes of Kupffer cells consistent with activation. These inflammatory events coincided with increased serum levels of markers of liver damage (aspartate aminotransferase, alanine aminotransferase, ammonia). Both neutralization of endotoxin and blocking of IL-1 activity reduced hepatic inflammation and reduced serum levels of aminotransferases and ammonia. In addition, liver cell proliferation as assessed by staining for proliferating cell nuclear antigen (PCNA) expression was significantly enhanced when either endotoxin or IL-1 effects were blocked. Thus, our results suggest that local hepatic inflammatory responses inhibit liver cell proliferation and promote liver failure, presumably by affecting the functional capacity of the remnant liver.

Effects of partial hepatectomy, phenobarbital and 3-methylcholanthrene on kinetic parameters of glucose-6-phosphate and phosphogluconate dehydrogenase in situ in periportal, intermediate and pericentral zones of rat liver lobules

Glucose-6-phosphate dehydrogenase (G6PDH) and phosphogluconate dehydrogenase (PGDH) are heterogeneously distributed in liver lobules of female rats. The maximum activity of both enzymes is approximately twice higher in intermediate and pericentral zones than in periportal zones. Enzyme activities and their distribution patterns were manipulated by partial hepatectomy and treatment with phenobarbital (PB) or 3-methylcholanthrene (3-MC). Vmax values of G6PDH for glucose-6-phosphate decreased mainly in intermediate and pericentral zones after partial hepatectomy, whereas they increased after PB treatment. Vmax values of PGDH for phosphogluconate decreased after partial hepatectomy in both zones, whereas other treatments did not have any effect. The affinity of G6PDH for glucose-6-phosphate was similar in all zones and it was decreased 2-3 fold by PB and 3-MC treatment. The affinity of PGDH for phosphogluconate was 1.4-2.3 times lower in intermediate and pericentral zones than in periportal zones of all livers tested and was not affected by treatment. From these data it can be concluded that not only the maximum activity of enzymes may differ in periportal, intermediate and pericentral zones of the liver lobule but also the affinity of enzymes for their substrates. The implication of these findings is that metabolic flux rates as they occur in vivo in these different metabolic compartments may be significantly different from predictions on the basis of maximum enzyme activities as detected immunohistochemically, microchemically or cytophotometrically.

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.

Biotin carboxylases in mitochondria and the cytosol from skeletal and cardiac muscle as detected by avidin binding

Biotin carboxylases in mammalian cells are regulatory enzymes in lipogenesis and gluconeogenesis. In this study, endogenous biotin in skeletal and cardiac muscle was detected using avidin conjugated with alkaline phosphatase and applied in high concentrations to muscle sections. The avidin binding was subsequently visualized by histochemical demonstration of the alkaline phosphatase activity. All cardiac muscle cells showed high affinity for avidin with only the nuclei and the intercalated discs remaining unstained. In skeletal muscle a diffuse reaction could be detected in the sarcoplasm of the muscle fibres. A granular reaction was noted in the same fibres that showed activity for succinic dehydrogenase. The specificity of the coloured reaction product in the muscle sections was investigated and is suggested to be caused by avidin binding to biotin moieties in mitochondria and the cytosol. Mitochondrial and cytosolic preparations of skeletal muscle were electrophoresed in sodium dodecyl sulphate gels. After blotting and incubation with conjugated avidin, two bands with molecular weights of 75 kDa and 130 kDa respectively were evident in the mitochondrial preparation. It is suggested that the 75-kDa band represents comigration of the biotin-containing subunits of propionyl-CoA carboxylase and methylcrotonyl-CoA carboxylase. The 130-kDa band may represent the biotin-containing pyruvate carboxylase. In the cytosolic preparation a 270-kDa band was stained in blots that had been incubated with conjugated avidin; this band is suggested to represent acetyl-CoA carboxylase. A 190-kDa cytosolic band might be a cleavage product of acetyl-CoA carboxylase. We propose that using alkaline phosphatase-conjugated avidin it is possible to detect the mitochondrial and cytosolic biotin-dependent carboxylases in striated muscle.

Effects of dietary fatty acid composition on tumor growth and metastasis

Unsaturated fatty acids of the n-6 and n-3 class have been shown to affect tumor growth and metastasis. The very long chain polyunsaturated fatty acids of the n-3 family, e.g. eicosapentaenoic acids (C20:5n-3) and docosahexaenoic acids (C22:5n-3), have an inhibiting effect on tumor growth. Metastasis is promoted by n-6 polyunsaturated fatty acids, e.g. linoleic acid (C18:2n-6) and gamma-linolenic acid (C18:3n-6). The mechanisms of promotion and inhibition are described in the present review. The mechanisms of lipid peroxidation, which appears to be an important factor in the inhibition of tumor growth, are discussed. Lipid peroxidation is induced by polyunsaturated fatty acids involving autoperoxidation a.o. and the enzymes cytochrome P450, cyclooxygenase and lipoxygenase. In tumor cells these enzymes are decreased in activity but at present the reason for this reduction is not known. Lipid peroxidation products such as hydroxyeicosatetraenoic acids (HETES), hydroperoxy eicosatetraenoic acids (HPETES) and malondialdehyde may have a regulating effect on DNA duplication enzymes (e.g. polymerases). Prostaglandin synthesis in tumor cells and macrophages is also affected by polyunsaturated fatty acids. The fish oil fatty acids are known to reduce prostaglandin synthesis by competing with arachidonic acid for the enzyme cyclooxygenase. However, fish oil fatty acids have an antagonistic effect on cyclooxygenase. Polyunsaturated fatty acids also have an effect on the immune system and particularly on macrophages. Macrophages, but also T-cells and B-cells, are inhibited by prostaglandins such as PGE2, while immunosuppressor cells are stimulated by PGE2.

Detection of extracellular neutrophil elastase in hamster lungs after intratracheal instillation of E. coli lipopolysaccharide using a fluorogenic, elastase-specific, synthetic substrate

Repeated intratracheal instillations of E. coli lipopolysaccharide (LPS) in hamster lungs cause an influx of polymorphonuclear leukocytes (PMNs) into the alveolar walls, with concomitant development of severe emphysema. It has been suggested that elastase, released by these PMNs, is involved in the development of emphysema. This study demonstrates the release of elastase from recruited PMNs in cryostat sections of hamster lungs, after being treated once, twice, or thrice with LPS, intratracheally. Elastase activity was visualized using two elastase-specific synthetic substrates, to which a methoxynaphthylamine (MNA) group had been bound covalently. Liberated MNA, when made insoluble by coupling with 5-nitrosalicylaldehyde, fluoresces strongly. The authors observed that the interval between start of incubation and appearance of fluorescence and the intensity of fluorescence correlated with the number of LPS administrations. Fluorescence was observed to be located in or in close vicinity to alveolar walls. No fluorescence was observed in sections of untreated hamsters. Liberation of MNA from synthetic substrates was delayed strongly by the addition of a recombinant secretory leukocyte proteinase inhibitor or a substituted cephalosporin neutrophil elastase inhibitor. The authors conclude that LPS-mediated PMN influx into the lung is accompanied by release of elastase from these cells and speculate that this PMN-elastase is involved in the development of LPS-mediated emphysema.

Molecular extinction coefficients of lead sulfide and polymerized diaminobenzidine as final reaction products of histochemical phosphatase reactions

Molar extinction coefficients of precipitated lead sulfide (PbS) and polymerized diaminobenzidine (polyDAB) have been determined at wavelengths of 450 nm and 480 nm, respectively, for quantitative histochemical analysis of phosphatase reactions. These values are essential for the conversion of cytophotometric (mean integrated) absorbance values to absolute units of substrate converted per unit time and volume of tissue. This conversion allows direct comparison of histochemical and biochemical data. The molar extinction coefficient of PbS at 450 nm was found to be 3,800 and therefore, per mole phosphate liberated, the molar extinction coefficient is 5,700 because 3 moles phosphate are captured by 2 moles lead at neutral or alkaline pH. Parallel experiments with the cerium-DAB method revealed that the molar extinction coefficient of polyDAB at 480 nm is 5,500 with respect to liberated phosphate. The molar extinction coefficients were applied for comparison of data from biochemical and histochemical assays of glucose-6-phosphatase activity in rat livers. A significant correlation was found between both sets of data. The values were in the same order of magnitude with histochemical values approximately 1.4 times higher than biochemical values.

Assessment of lysosomal function by quantitative histochemical and cytochemical methods

Quantitative histochemistry and cytochemistry enables a direct link to be made between metabolic functions such as the activity of lysosomal enzymes and the morphology of a tissue or a type of cell. Several approaches exist such as microchemistry based on (bio)chemical analysis of a single cell or a small piece of tissue dissected from a freeze-dried section. This technique has been routinely used for prenatal diagnosis of inherited enzyme defects and especially of lysosomal storage diseases. Other approaches are cytofluorometry or cytophotometry, which are based on the principle that a fluorescent or coloured final reaction product is precipitated at the site of the enzyme. The amount of final reaction product is analysed per cell or per unit volume of tissue using either a microscope cytofluorometer or flow cytometer for fluorescence measurements or an image analysing system or scanning and integrating cytophotometer for absorbance measurements. In principle, fluorescence methods are to be preferred over chromogenic methods because they are more sensitive and enable multiparameter analysis. However, only a limited number of fluorogenic methods are at hand that give a final reaction product which is sufficiently water-insoluble to guarantee good localisation. The best results have been obtained with methods based on naphthol AS-TR derivatives and with methods for the demonstration of protease activity using methoxynaphthylamine derivatives as substrates and 5'-nitrosalicylaldehyde as coupling reagent. Chromogenic methods are far better with respect to localisation properties and, therefore, most commonly used for quantitative histochemical analysis of lysosomal enzyme activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Homogeneous distribution of phosphofructokinase in the rat liver acinus: a quantitative histochemical study

A quantitative histochemical method was developed for the demonstration in rat liver of the activity of phosphofructokinase, one of the enzymes assumed to be rate-limiting for glycolysis. The procedure was based on the reduction of a tetrazolium salt as final electron acceptor and a multistep reaction using the exogenous or endogenous auxiliary enzymes aldolase, triosephosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase. The highest activity was found in unfixed cryostat sections of rat liver when the incubation medium contained 17% (wt/vol) polyvinyl alcohol, 100 mmol/L Tris-maleate buffer (pH 8.4), 20 mmol/L fructose-6-phosphate, 2 mmol/L ATP, 2 mmol/L MgCl2, 5.9 mmol/L NAD+, 0.47 mmol/L 1-methoxyphenazine methosulfate, 5 mmol/L sodium azide and 5 mmol/L Nitro BT. The addition of auxiliary enzymes was not necessary to demonstrate maximum activity in rat liver. The specificity of the reaction was proven by the absence of any specific (test minus control) reaction when the incubation was performed in the presence of 25 mmol/L phosphoenolpyruvate, a competitive inhibitor of phosphofructokinase. Cytophotometric analysis revealed that linear relationships exist between the amount of specific reaction product formed and incubation time and the section thickness. The Km values for fructose-6-phosphate and the Vmax values were not significantly different in periportal and pericentral areas of livers from either normally fed or 24-hr-fasted rats. The homogeneous distribution of phosphofructokinase activity in the liver acinus is in line with biochemical findings using hepatocytes isolated from the two different areas showing that these cells contained similar amounts of enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective inhibition of cysteine proteinases by Z-Phe-AlaCH2F suppresses digestion of collagen by fibroblasts and osteoclasts

Effects of the selective inhibitor of cathepsins B and L, Z-Phe-AlaCH2F were studied on the degradation of fibrillar collagen by fibroblasts and osteoclasts in cultured rabbit calvariae at the electron microscopic level. Periosteal fibroblasts from inhibitor-treated explants showed a dose-dependent increase of the volume fraction of vacuoles containing cross-banded collagen fibrils. This was a 7-fold increase over control fibroblasts and the ratio of intracellular and extracellular collagen increased from 2 to 43. The presence of collagen-containing vacuoles was also found in some osteoclasts from inhibitor-treated explants (1 microM or more). The inhibitor appeared to have cytotoxic effects at a concentration of 100 microM. It was concluded that this selective inhibitor exerts its effects intralysosomally in living cells, indicating possibilities for in vivo inhibition of protein degradation.

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.

Immunocytochemical determination of ploidy class-dependent bromodeoxyuridine incorporation in rat liver parenchymal cells after partial hepatectomy

Immunocytochemistry of bromodeoxyuridine (BrdU) incorporated in DNA was performed on cryostat sections of rat liver and on isolated hepatocytes after partial hepatectomy using a two-step labeling technique. The method enabled the detection of S-phase nuclei in both tissue preparations. Quantification of the number of labeled nuclei in sections showed that the number of nuclei in S-phase increased from 0.3% in control liver to about 36% at 24 h after partial hepatectomy. The detection of BrdU in isolated hepatocytes showed the same labeling index of binuclear diploid, mononuclear tetraploid and binuclear tetraploid cells. A special role for mononuclear diploid cells in proliferation did not seem to occur.

Hepatic enzymic zonation: a reevaluation of the concept of the liver acinus

The distribution pattern of a periportal enzyme (carbamoylphosphate synthetase) and a pericentral enzyme (glutamine synthetase) in human and rat liver has provided an objective parameter to delineate the zonal boundaries of the liver acinus. On sections, the pericental zone (zone 3) is circular and discrete rather than star-like and reticular, as predicted by the acinar concept, whereas the periportal zone (zone 1) is reticular, i.e. contiguous between adjacent acini rather than discrete. Three-dimensionally, the composite of pericentral zones (the pericentral compartment) follows the branching pattern of the terminal hepatic (central) vein, whereas the composite of periportal zones (the periportal compartment) envelops the pericentral compartment as a three-dimensional network (reticulum). This modified concept that is based upon the three-dimensional distribution of hepatocyte-specific enzymes is supported by data from the literature regarding the three-dimensional angioarchitecture of the liver, the perfusion pattern of the liver and the three-dimensional pattern of tissue oxygenation. Hence, a unified concept of the liver architecture that is based upon the observed distribution pattern of blood flow, of gene expression and of metabolism can be established.

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

Visualization methods for the light microscopic detection of the activity of oxidases after being localized with cerium ions as reported by Angermüller and Fahimi (1988a, b) are not suitable for the demonstration of H2O2-genrating oxidases at sites with low activity. Therefore, the cerium-diaminobenzidine (DAB) visualization procedure of these authors was modified. Nickel or cobalt ions were added to the DAB solution together with small amounts of H2O2. Visualization was performed in a one-step-method. This modified visualization technique enables light microscopic detection of amino acid oxidase activity in kidney and liver cells where it was found with the original method but the amounts of final reaction product were considerably higher. Moreover, the DAB-nickel-H2O2 and DAB-cobalt-H2O2 procedures were more sensitive than the cerium-lead method of Angermüller and Fahimi (1988a, b). The method appeared to be specific, because final reaction product was not found after control incubation. Especially the DAB-nickel-H2O2 procedure can also be used for immunohistochemistry when glucose oxidase serves as the enzyme label.

Cytophotometric analysis of alkaline phosphatase and 5'-nucleotidase activity in regenerating rat liver after partial hepatectomy

Alkaline phosphatase and 5'-nucleotidase activities were analysed cytophotometrically in cryostat sections of female rat liver after partial hepatectomy. Alkaline phosphatase activity increased rapidly after operation up to a maximum seven-fold rise at 24 h in comparison with sham operated or control rats. There was no indication of preferential localization of alkaline phosphatase activity in either periportal or pericentral areas at any time point in control rats, sham operated rats or hepatectomized rats. Microscopical observation revealed that (a) all alkaline phosphatase activity was present at the bile canalicular surface of hepatocytes and (b) hepatocytes in mitosis did not show any increase in activity. These findings indicate that the high alkaline phosphatase activity after partial hepatectomy is not involved primarily in proliferation processes because cell division mainly takes place periportally. It may be needed for enhanced bile secretion by conversion of intracellular phosphorylcholine into choline which can be transported into the bile. The intracellular phosphorylcholine level is high after operation due to changes in phospholipid metabolism. 5'-Nucleotidase appeared to be three times higher pericentrally than periportally under normal conditions. Partial hepatectomy caused a 40 per cent decrease in activity in pericentral areas and only a small decrease periportally. It has been suggested that 5'-nucleotidase plays a role in breakdown of messenger RNA and its activity in control liver could be considerably lower periportally because plasma protein synthesis mainly takes place in this area.(ABSTRACT TRUNCATED AT 250 WORDS)

Linearity in dehydrogenase reaction rate studies in tissue sections is affected by loss of endogenous substrates during the reaction

We studied the effect of section thickness on the reaction rate of glucose-6-phosphate dehydrogenase (G6PD) activity in unfixed sections of rat liver by use of continuous monitoring by microdensitometry of the reaction product as it formed in the section during incubation. Tetranitro BT or nitro BT was used as final electron acceptor and polyvinyl alcohol as tissue stabilizer. Each test minus control reaction curve deviated from linearity during the first 2 min of incubation. This was mainly due to loss of low molecular weight endogenous dehydrogenase substrates from the surface of the section. For any given reaction, the same absolute amount of endogenous substrate was lost from each section, and hence a much greater proportion was lost from the thinner sections. Such losses lead to a deficit in (nonspecific) formazan production. There was a greater loss from, and hence a greater deficit in, formazan production in sections incubated at 30 degrees C than at 37 degrees C and when nitro BT was used instead of tetranitro BT, but the greatest loss of endogenous substrates occurred in sections incubated in control media. Therefore, greater losses seemed to occur when the reactions were slower because of failure to overcome the critical supersaturation level of the formazan. A consequence of this was a non-linear test minus control response during the first minutes of the incubation.

Detection of glucose-6-phosphate dehydrogenase deficiency in erythrocytes: a spectrophotometric assay and a fluorescent spot test compared with a cytochemical method

The results of a quantitative spectrophotometric enzyme assay, a fluorescent spot test and a cytochemical assay for glucose-6-phosphate dehydrogenase deficiency were compared systematically. The high sensitivity of the spectrophotometric assay and the fluorescent spot test in the detection of severely deficient individuals was confirmed. For the detection of heterozygote females, however both tests were unreliable; the sensitivities of the fluorescent spot test and the spectrophotometric assay being 32% and 11% respectively. Specificities for both tests were high (99%). Introduction of the ratio of glucose-6-phosphate dehydrogenase and pyruvate kinase (G-6-PD/PK ratio) activities increased the sensitivity of the spectrophotometric assay to nearly 100%. It is concluded that the fluorescent spot test should be used for the diagnosis of G-6-PD deficiency in developing countries; whereas if spectrophotometric enzyme assays are available, the G-6-PD/PK ratio should always be performed. In cases where the ratio is less than 0.70, cytochemical analysis is indicated.

Age-related changes of glucose-6-phosphate dehydrogenase activity in mouse oocytes

Glucose-6-phosphate dehydrogenase (G6PDH) activity was measured in follicular oocytes and in ovulated eggs of prepubertal, adult and aged mice. G6PDH activity in ovulated eggs was 60% of the activity in follicular oocytes in all age groups. The mean G6PDH activity was significantly higher in follicular oocytes of adult mice than in oocytes of both prepubertal and aged mice. In aged mice, the decreased mean activity in follicular oocytes as well as in ovulated eggs was mainly due to a high percentage of cells with extremely low activity (25 and 18%, respectively). The percentage of preovulatory oocytes with low activity in prepubertal mice was 9% and in adult mice 0.3%. For ovulated eggs these percentages were 0% for both prepubertal and adult mice. In every age group, all ovulated eggs showed a normal morphology. When ovulated eggs with extremely low G6PDH activity can still be fertilized, it can be questioned whether this loss of activity could cause disturbances in development of (preimplantation) embryos. Our findings emphasize the potentialities of investigating intact singly oocytes for changes in enzyme activities, which could be applied as parameters for 'quality control' of these cells.

Detection of metabolic changes in hepatocytes by quantitative cytochemistry

Studies by means of quantitative histochemistry and cytochemistry have greatly contributed to the knowledge of metabolic changes in liver parenchymal cells. In the present paper recent work along this line is reviewed with emphasis on three topics, polyploidy as a source of metabolic heterogeneity, proteolysis in the regulation of hepatocyte cell mass and ischemic injury of hepatocytes. In all three fields, accuracy and precision of information obtained by quantitative histochemical means has been greatly enhanced by a thorough knowledge of the mechanisms of histochemical reactions obtained by fundamental work on matrix chemistry, and well-considered application of optical measuring tools and conditions of measurement. These are the principles put forward by van Duijn since the pioneer period of histochemistry and to whom this review is dedicated.

Enzyme cytochemical staining of individual cells with the use of a polyacrylamide carrier. Studies on the synthetizing reaction technique, the indigogenic method, the metal salt method, the post-azo-coupling technique, and the tetrazolium salt technique

A recently developed method for the (quantitative) demonstration of glucose-6-phosphate dehydrogenase activity in individual cells with the use of a polyacrylamide carrier has been extended for other enzyme cytochemical techniques. Isolated hepatocytes have been incorporated in the matrix of a thin transparent polyacrylamide gel prior to incubation in a cytochemical medium. The techniques which have been applied are the synthetizing reaction technique for glycogen phosphorylase, the indigogenic method for nonspecific esterase, the metal salt method for glucose-6-phosphatase, the post-azo-coupling technique for acid phosphatase, and the tetrazolium salt technique for succinate and lactate dehydrogenase activities. In all cases a few major problems which occur in the cytochemistry on single cells seem to be solved. The morphology is very well preserved, the final reaction product seems to be precipitated at the expected site of enzyme activity and the coloured end-product is highly specific for the enzyme activity to be studied, as has been demonstrated well with control experiments. The conclusion is reached, therefore, that this relatively simple device can be used routinely for the optimalization of enzyme cytochemistry of single cells.

A sensitive cytochemical staining method for glucose-6-phosphate dehydrogenase activity in individual erythrocytes. I. Optimalization of the staining procedure

A sensitive cytochemical staining method for glucose-6-phosphate dehydrogenase activity in individual human erythrocytes is described. This staining method can be used for the rapid routine discrimination of patients with a deficiency of the enzyme in its homozygote or heterozygote form, but also for quantitative localization of its activity in individual erythrocytes. The staining procedure in its optimal form consists of a treatment of the erythrocytes with sodium nitrite, then a "fixation" in 0.025% glutaraldehyde (under NADP+ protection of the active site of the enzyme), followed by incubation of the cells in suspension in the presence of tetranitro BT, 1-methoxyphenazine methosulphate and polyvinyl alcohol. Using this new technique, a sharp localization is obtained of the glucose-6-phosphate dehydrogenase activity, which enables discrimination between red cells with different levels of enzyme activity, as a consequence of enzyme deficiencies or age changes.

A new method for the enzyme cytochemical staining of individual cells with the use of a polyacrylamide carrier

A new method for enzyme cytochemical studies on individual cells is developed. Cells are incorporated in the matrix of a thin film of transparent polyacrylamide prior to incubation in a cytochemical medium. Five different kinds of individual cells, i.e. isolated rat hepatocytes, isolated mouse oocytes, cultivated human fibroblasts, rat thymocytes and human blood cells are used for testing the applicability of this method for the cytochemical demonstration of glucose-6-phosphate dehydrogenase with tetranitro BT. The incorporation technique solves at least some of the problems occurring with enzyme cytochemistry on single cells. The morphology of the cell is very well preserved, the formazan precipitation due to enzyme activity occurs entirely within the cell cytoplasm, the nothing dehydrogenase activity can be kept very low and the loss of cells is completely prevented with all cell types used.

Propranolol inhibits the in vitro conversion of thyroxine into triiodothyronine by isolated rat liver parenchymal cells

A model for the in vitro study of the conversion of thyroxine into triiodothyronine using isolated rat liver parenchymal cells is described. Isolated liver cells (mean protein content 18 mg/ml) convert approximately 0.8% of 1.3 microM exogenously added T4 into T3 during thirty minutes incubation. Carbimazole (50 microM) has no effect on the conversion process, whereas propylthiouracil (50 microM) inhibits the conversion. The beta-adrenoceptor blocking agent propranolol lowers the conversion ratio when added in concentrations of 580 and 1160 microM, but has no inhibitory effect when 290 microM is added.