The value of enzyme leakage for the prediction of necrosis in liver ischemia

Warburg effect, lactate dehydrogenase, and radio/chemo-therapy efficacy

The anaerobic metabolism of glucose by cancer cells, even under well-oxygenated conditions, has been documented by Otto Warburg as early as 1927. Micro-environmental hypoxia and intracellular pathways activating the hypoxia-related gene response, shift cancer cell metabolism to anaerobic pathways. In the current review, we focus on a major enzyme involved in anaerobic transformation of pyruvate to lactate, namely lactate dehydrogenase 5 (LDH5). The value of LDH5 as a marker of prognosis of cancer patients, as a predictor of response to radiotherapy (RT) and chemotherapy and, finally, as a major target for cancer treatment and radio-sensitization is reported and discussed. Clinical, translational and experimental data supporting the uniqueness of the LDHA gene and its product LDH5 isoenzyme are summarized and future directions for a metabolic treatment of cancer are highlighted.

The addition of protein-bound amino acids in low-protein diets improves the metabolic and immunological characteristics in fifteen- to thirty-five-kg pigs

This study was to evaluate the effects of supplementation of AA form (crystalline vs. protein bound) in low-protein diets on growth, metabolic, and immunological characteristics of pigs. A total of 80 barrows (PIC 327 × 1050; 15.57 ± 0.13 kg BW and 48 ± 2 d of age), housed in 4 pigs per pen with 5 pens per treatment, were assigned to 4 dietary treatments of 17, 15, and 13% CP and 13% CP plus casein for 28 d. The crystalline AA were supplemented to meet the requirement of indispensable AA in pigs. Results showed that pigs fed the 13% CP diet or the 13% CP plus casein diet had lower ( < 0.01) ADG and ADFI and a greater ( < 0.01) feed:gain ratio than pigs fed the 17% CP or 15% CP diets over the 4-wk study period. Compared with other diets, pigs fed the 13% CP diet had decreased concentrations of plasma urea nitrogen, albumin ( < 0.01), and mRNA expressions of Toll-like receptor 4 (), nuclear factor kappa B (; < 0.05), and Toll-interacting protein (; < 0.01) in the ileum and also increased activity of plasma glutamate-pyruvate transaminase ( < 0.05) and concentrations of IL-1β ( < 0.05) and tumor necrosis factor-α ( < 0.01); however, these characteristics were partly normalized by feeding the 13% CP plus casein diet. Furthermore, the plasma concentration of insulin-like growth factor 1 (IGF-1; < 0.01) and mRNA expressions of protein kinase B (), mammalian target of rapamycin (), and ribosomal protein S6 kinase () in longissimus muscle were increased ( < 0.05) in pigs fed the 13% CP plus casein diet relative to pigs fed the 17% CP or 15% CP diets. In summary, reducing dietary CP level from 17% to 15% had no effect on growth, metabolic, and immunological characteristics of 15- to 35-kg pigs. A further reduction of dietary CP level up to 13% would lead to poor growth performance, but metabolic and immunological characteristics were partly normalized using protein-bound AA to replace synthesized AA in the 13% CP diet.

Clinical Pathology Approaches to Hepatic Injury

Testing the blood for evidence of hepatic damage and dysfunction frequently involves measuring several blood constituents simultaneously to screen for disease. While useful, this approach occasionally leads to apparent disparities between the blood test results, and the results of other diagnostic tests such as histology. In part, these perceived discrepancies may stem from a lack of appreciation for tissue, cellular, and molecular factors that affect the appearance of hepatic disease biomarkers in the blood. Further confusing the matter is that in some instances the mechanisms responsible for the appearance of diagnostic compounds in blood are only partially understood. Many of the known factors that affect hepatic biomarkers are similar to those affecting other tissue markers, while others are unique to the liver, such as those involved with cholestasis. Disease conditions can also cause misleading results by affecting tissue concentrations of test compounds, hepatic mass, and the clearance rate of compounds from the blood. Knowledge of the factors affecting the blood concentrations of biomarkers, as well as investigations into the mechanisms behind changes to hepatic biomarker concentrations, may allow for a better interpretation of blood test results and fewer inconsistencies between diagnostic results.

HMGB1 and microparticles as mediators of the immune response to cell death

In a wide variety of diseases, cell death represents both an outcome and an important step in pathogenesis. This duality occurs because cell death leads to the extracellular release of molecules and structures that can potently induce the innate immune system. These mediators include the alarmins which are endogenous cellular constituents that exit activated or dying cells to stimulate toll-like receptors (TLRs) as well as non-TLR receptors. Of alarmins, the nonhistone protein HMGB1 is the prototype. Like DNA and RNA, HMGB1 can translocate from cells as they die. The activity of HMGB1 may reflect its interaction with other molecules such as LPS, DNA, and cytokines. In addition to alarmins, dead and dying cells can release subcellular organelles called microparticles that contain cytoplasmic and nuclear constituents, including DNA and RNA. These particles can impact on many cell types to induce inflammation. The release of HMGB1 and microparticles shows important similarities, occurring with cell death as well as stimulation of certain but not all TLRs. Furthermore, nitric oxide can induce the release of both. These observations suggest that the products of dead cells can serve as important mediators to drive immune responses and promote inflammation and autoreactivity.

Pretreatment with calcitonin gene-related peptide attenuates hepatic ischemia/reperfusion injury in rats

OBJECTIVE

Oxygen free radicals and apoptosis play important roles in liver ischemia/reperfusion (I/R) injury. We sought to investigate the protective effect of calcitonin gene-related peptide (CGRP) to attenuate liver I/R injury due to oxygen free radicals and apoptosis.

MATERIALS AND METHODS

Harvested rat livers were perfused via the portal vein with 60 mL of 4 degrees C histidine-tryptophan-ketoglutarate (HTK) solution alone in the control group, or with the same solution containing CGRP (3 microg/10 g body weight) in the experimental group. After 24 hours of cold storage, hepatic enzyme leakage, portal venous pressure, oxygen consumption, total adenine nucleotides (TAN), bile production, lipoperoxide (LPO) release, apoptosis, and histochemical changes were evaluated upon 45 minutes of isolated reperfusion.

RESULTS

Compared with control livers, CGRP-treated organs showed significantly decreased alanine aminotransferase (ALT) and glutamate-lactate dehydrogenase (GLDH) leakage and portal venous pressure (2.0 +/- 0.3 vs 4.0 +/- 0.4 mmHg; P < .01), with significantly increased bile production (8.56 +/- 0.76 vs 3.34 +/- 0.68 microL/g/45 min; P < .01), oxygen consumption (5.14 +/- 0.4 vs 2.57 +/- 0.2 microL/g/min; P < .01), and total adenine nucleotides (TAN) (11.1 +/- 0.71 vs 7.02 +/- 0.53 micromol/g; P < .01) upon reperfusion as signs of recovered viability. We observed infrequent positive terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) staining, especially in sinusoidal lining cells (SLC). The percentage of TUNEL-positive cells in the CGRP group was significantly decreased compared with the control group: (4.1 +/- 0.67 vs 8.0 +/- 1.27; P < .05). Perfusate levels of low molecular weight (LMW) histone-associated DNA fragments (0.36 +/- 0.04 vs 0.53 +/- 0.06 AU; P < .05) were also decreased, coupled with strong 5'-nucleotidase (5'-NT) and LDH activity staining concentrated on the endothelial cells. LPO release in the perfusate was largely decreased: (0.12 +/- 0.02 vs 0.36 +/- 0.04 nmoL/g, P < .01).

CONCLUSION

CGRP ameliorated liver I/R injury due to reactive oxygen species and apoptosis.

Quantification of viability in organotypic multicellular spheroids of human malignant glioma using lactate dehydrogenase activity: a rapid and reliable automated assay

Organotypic spheroids from malignant glioma resemble the biological complexity of the original tumor and are therefore appealing to study anticancer drug responses. Accurate and reproducible quantification of response effect has been lacking to determine drug responses in this three-dimensional tumor model. Lactate dehydrogenase (LDH) activity was demonstrated in cryostat sections of spheroids using the tetrazolium salt method. Calibrated digital image acquisition of the stained cryostat sections enables quantification of LDH activity. Fully automated image cytometry reliably demarcates LDH-active and LDH-inactive tissue areas by thresholding at specific absorbance values. The viability index (VI) was calculated as ratio of LDH-active areas and total spheroid tissue areas. Duplicate staining and processing on the same tissue showed good correlation and therefore reproducibility. Sodium azide incubation of spheroids induced reduction in VI to almost zero. We conclude that quantification of viability in cryostat sections of organotypic multicellular spheroids from malignant glioma can be performed reliably and reproducibly with this approach.

Dimethylethanolamine does not prevent liver failure in phosphatidylethanolamine N-methyltransferase-deficient mice fed a choline-deficient diet

Mice that lack phosphatidylethanolamine-N-methyltransferase (PEMT) and are fed a choline-deficient (CD) diet suffer severe liver damage and do not survive. Since phosphatidyldimethylethanolamine (PDME) has physical properties similar to those of phosphatidylcholine (PC), we hypothesized that dimethylethanolamine (DME) would be converted into PDME that might substitute for PC, and therefore abrogate the liver damage in the Pemt -/- mice fed a CD diet. We fed Pemt -/- mice either a CD diet, a CD diet supplemented with choline, or a CD diet supplemented with DME (CD + DME). Pemt -/- mice fed the CD diet developed severe liver failure by 4 days while CD + DME-fed mice developed severe liver failure by 5 days. The hepatic PC level in choline-supplemented (CS) mice was 67 +/- 4 nmol/mg protein, whereas the PC content was reduced in CD- and CD + DME-fed mice (49 +/- 3 and 30 +/- 3 nmol/mg protein, respectively). Upon supplementation of the CD diet with DME the amount of hepatic PDME was 81 +/- 9 nmol/mg protein so that the hepatic content of PC + PDME combined was 111 nmol/mg protein. Moreover, plasma apolipoprotein B100 and Al levels were markedly lower in mice fed the CD + DME diet compared to mice fed the CS diet, as was the plasma content of PC. Thus, despite replacement of the deficit in hepatic PC with PDME in Pemt -/- mice fed a CD diet, normal liver function was not restored. We conclude that although PC and PDME exhibit similar physical properties, the three methyl groups of choline are required for hepatic function in mice.

Aspectos ultra-estruturais das vilosidades intestinais após o clampeamento do pedículo hepático de ratos

OBJETIVO: Estudar a ultra-estrutura das vilosidades intestinais de ratos após diferentes tempos de clampeamento total do pedículo hepático. MÉTODOS: Foram utilizados 40 ratos, machos, divididos em quatro grupos de 10 animais cada um. O grupo Sham não foi submetido a isquemia. Os grupos E1, E2 e E3 sofreram isquemia de 10, 20 e 30 minutos, respectivamente. Ao final do experimento, fragmentos do intestino delgado (íleo) foram retirados e processados para microscopia eletrônica de transmissão. RESULTADOS: Nos grupos E1 e E2 observou-se infiltração de leucócitos, dilatação vascular e áreas eletrolúcidas na lâmina própria das vilosidades. Já no grupo E3 observou-se desprendimento do revestimento epitelial, desintegração das microvilosidades e núcleos em apoptose. Na lâmina própria notamos áreas hemorrágicas, vasos sangüíneos e linfáticos dilatados e inúmeros leucócitos. CONCLUSÕES: o clampeamento do pedículo hepático hepático provoca congestão esplâncnica, tempo dependente, sendo que aos 30 minutos se nota desprendimento das células epiteliais, apoptose e hemorragia.

Histopathologic and biochemical liver test abnormalities in chronic asymptomatic or oligosymptomatic alcoholics: a review

PURPOSE

To review the medical literature regarding the histopathologic and biochemical liver test abnormalities in chronic asymptomatic or oligosymptomatic alcoholics.

METHODS

Review of articles in the MEDLINE and LILACS databases regarding serum levels and prevalence of alterations in aspartate-aminotransferase, alanine-aminotransferase, alkaline phosphatase, and total bilirubin, in relation to liver histopathology, with or without discrimination of types of histopathologic alteration.

RESULTS

Global mean prevalence rates of aspartate-aminotransferase and alanine-aminotransferase alterations were 86.3% and 51.1%; in cases with steatosis they were 79.1% and 38.5%; and in cases of hepatitis, 90.1% and 58%. In all studies, prevalence rates of aspartate-aminotransferase alterations were significantly higher with lower variability than those of alanine-aminotransferase. Mean aspartate-aminotransferase levels were higher than 2N (N is the upper normal limit of the method employed) in all cases with hepatitis histopathology, while those of alanine-aminotransferase were 1.48N, in the same cases. Prevalence of alkaline phosphatase and total bilirubin abnormalities were 74.5% and 74.9% globally; in cases of steatosis, they were 70.9% and 67.9%; and in cases of hepatitis, 75.9% and 77.7%. Mean alkaline phosphatase levels were above the upper normal limit in all cases, but those of total bilirubin were above normal in 4 of 7 hepatitis studies.

CONCLUSIONS

Prevalence of aspartate-aminotransferase alteration was consistently related to presence of histopathologic abnormalities; an enzyme level higher than 2N suggests the diagnosis of alcoholic hepatitis.

Behavior of cholinesterase and liver mitochondrial function in dogs submitted to normothermic ischemia and reperfusion

PURPOSE: The plasmatic activity of the cholinesterase (CHE) and the liver mitochondrial function, expressed by the ratio of respiratory control (RCR), were studied during normothermic ischemia. METHODS: Sixteen adult mongrels, eight females and eight males were submitted to ischemia by clamping of the hepatic artery, portal vein and infrahepatic inferior vena cava, infra-hepatic, for two h, follwed by reperfusion for 1 h. The CHE and the mitochondrial function were evaluated at 60 and 120 min. of ischemia and at 15 and 60 minutes of reperfusion. RESULTS: The CHE decreased, significantly, during ischemia and in reperfusion. The RCR was decreased at 120 min. of ischemia, returning to the initial values on reperfusion. CONCLUSION: In this study, the CHE was a sensitive indicator of ischemic injury , suggesting irreversibility of ischemia injury. The RCR, by other side, showed a greater sensibility than the CHE in detection sense, during the studied period, the reversibility of the hepatic ischemic injury.

Evaluation of rat liver apoptotic and necrotic cell death after cold storage using UW, HTK, and Celsior

BACKGROUND

The benefit of Celsior in liver graft preservation is controversial. In the isolated perfused rat liver model, we compared the effects of Celsior, University of Wisconsin (UW), and histidine-tryptophan-ketoglutarate (HTK) preservation solutions on liver cell death.

METHODS

Rat livers were stored at 4 degrees C for 0, 8, 16, or 24 hr in either Celsior, UW, or HTK and reperfused for 90 min (37 degrees C). Bile secretion and perfusate levels of liver enzymes and histone-associated DNA fragments were measured. Apoptosis and oncotic necrosis were analyzed in biopsies by DNA gel electrophoresis, hematoxylin and eosin histology, and enzyme histochemistry for lactate dehydrogenase (LDH) and 5'-nucleotidase (5'-NT).

RESULTS

Perfusate flow rate through the liver during perfusion did not significantly differ among preservation solutions. Bile secretion was best preserved in UW livers after 16-hr (versus HTK livers) and 24-hr storage (versus HTK and Celsior livers). Enzyme leakage from UW livers was lower compared with HTK livers after 8-hr storage (serum glutamic oxaloacetic transaminase [SGOT], LDH) and with Celsior and HTK livers after 16-hr (SGOT, LDH) and 24-hr storage (SGOT, serum glutamic pyruvic transaminase, LDH, purine nucleoside phosphorylase). In situ LDH and 5'-NT activities were best preserved in UW livers (up to 24 hr), whereas enzyme activities declined remarkably in HTK livers (after 8 hr) and Celsior livers (after 16 hr of cold storage). Although perfusate DNA fragment levels were repeatedly lowest from Celsior livers, apoptotic DNA laddering and the number of fragmented nuclei in hematoxylin and eosin sections was not different among livers after 8, 16, or 24 hr of storage.

CONCLUSIONS

Celsior and UW are equally effective in preventing rat liver cell death after 0-16 hr of cold preservation as compared with the less effective HTK solution. After 24-hr cold storage, rat livers were best preserved in UW. Furthermore, there was no significant difference in mode of cell death (apoptosis or oncotic necrosis) after storage in any of the three solutions.

Efeitos do clampeamento do pedículo hepático nos intestinos

Foi realizado clampeamento do pedículo hepático de rato por diferentes tempos e estudadas as repercussões nos intestinos. Para tanto foram utilizados 40 ratos, machos, divididos em quatro grupos de 10 animais cada. O grupo S (Sham) não foi submetido a isquemia, já os grupos E1, E2 e E3 sofreram isquemia de 10, 20 e 30 minutos respectivamente. Nossos resultados mostraram alterações macroscópicas quanto a cor dos intestinos nos grupos E2 (20') e E3 (30') e histopatológicas que ocorreram em cada um desses grupos. Observou-se que quanto maior o tempo de clampeamento do pedículo hepático, maior a congestão esplâncnica, sendo que aos 30 minutos ocorreu o despreendimento do revestimento epitelial das vilosidades intestinais e hemorragia.

The protein kinase inhibitor 1-(5-isoquinolinylsulfonyl)-2-methyl-piperzine (H-7) prevents and reverses Ca(2+)-mediated injury in isolated rat hepatocyte couplets

We have recently shown that protein kinase C (PKC) activation induces similar morphological and functional alterations in couplets to that caused by increments of intracellular Ca(2+). Since certain PKC isoforms are activated by Ca(2+), we tested whether the PKC inhibitor H-7 can counteract the alterations induced by this ion in couplets. The Ca(2+) ionophore A23187, which can mobilize Ca(2+) from extracellular and intracellular sources, decreased, in a dose-dependent manner, the percentage of couplets accumulating the fluorescent bile acid analogue cholyl-lysyl-fluorescein (CLF) in their canalicular vacuoles, i.e., in the canalicular vacuolar accumulation test (cVA of CLF), a measure of the overall capability of the couplets to secrete and retain CLF. To a similar extent, A23187 also decreased the percentage of couplets retaining CLF once secreted, i.e., in the canalicular vacuole retention test (cVR of CLF), a measure of tight junctional integrity. ATP (50 microM), another Ca(2+)-elevating compound, altered canalicular function in a similar extent to A23187. All these functional changes were prevented by H-7 in a dose-dependent manner. Canalicular dysfunction was accompanied by bleb formation and extensive redistribution of F-actin from the pericanalicular area to the cell body, which was also fully prevented by H-7; the intracellular Ca(2+) chelator, 1, 2-bis(o-aminophenoxy)-ethene-N,N,N',N'-tetraacetate tetrakis-(acetomethylester), (BAPTA/AM) (20 microM) had virtually the same preventive effects as H-7. Both H-7 and BAPTA/AM not only prevented but also reversed the decrease in cVA of CLF and blebbing induced by A23187. Thus, H-7 can both prevent and reverse Ca(2+)-mediated hepatocellular injury.

The use of hepatocyte extraction fraction to evaluate neonatal cholestasis

PURPOSE

Hepatobiliary scintigraphy is used routinely to evaluate infants with neonatal cholestasis. Hepatobiliary scintigraphy determines biliary patency by detecting radioactivity in the bowel on imaging, in duodenal and gastric aspirates, or all of these. During hepatobiliary scintigraphy, the hepatocyte extraction fraction (HEF) is calculated by deconvolution analysis. Normal values of HEF are more than 90%. It is believed that HEF may predict hepatic dysfunction, because, during hepatobiliary scintigraphy, the radiopharmaceutical used in this test is extracted by the hepatocytes from the blood stream. Therefore, a low value of HEF is seen with more severe hepatocellular disease. The goal of this study was to determine whether HEF has any correlation with synthetic liver function, whether HEF can differentiate obstructive from nonobstructive lesions that cause neonatal cholestasis, and whether HEF can predict the outcome of the different causes of neonatal cholestasis.

METHODS

A retrospective analysis of 68 hepatobiliary scintigraphy results was done in patients with neonatal cholestasis for a period covering 6 years.

RESULTS

The HEF was available in 67 of these 68 patients, with a median value of 25% (range, 3.3% to 100%). The results of synthetic liver function tests (i.e., albumin and prothrombin time) were normal in all infants with neonatal cholestasis. No significant correlation was detected between HEF and the serum levels of total and direct bilirubin, albumin, alkaline phosphatase, and prothrombin time by exploratory data analysis (R = 0.08; small, P > 0.2). The HEF values in different causes of neonatal cholestasis were compared: extrahepatic biliary atresia, neonatal hepatitis, and a miscellaneous category consisting of alpha1-antitrypsin deficiency, ischemic hepatitis, paucity of bile ducts, and others. The outcomes of these diseases were assessed as resolution, continuing disease, transplantation, or death, but no predictive correlation was found with HEF.

CONCLUSIONS

A single determination of HEF is of no value in assessing synthetic liver function (as assessed by albumin and prothrombin time), specific diagnoses, and outcomes in patients with neonatal cholestasis. Therefore, a low isolated value of HEF should not be considered suggestive of poor prognosis and outcome in these patients.

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

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

Indicators of inflammation and cellular damage in chronic asymptomatic or oligosymptomatic alcoholics: correlation with alteration of bilirubin and hepatic and pancreatic enzymes

Biochemical and hematimetric indicators of inflammation and cell damage were correlated with bilirubin and hepatic and pancreatic enzymes in 30 chronic male alcoholics admitted into psychiatric hospital for detoxification and treatment of alcoholism. Aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, and total bilirubin were altered, respectively, in 90%, 63%, 87%, 23% and 23% of the cases. None of the indicators of inflammation (lactic dehydrogenase, altered in 16% of the cases; alpha-1 globulin, 24%; alpha-2 globulin, 88%; leucocyte counts, 28%) was correlated with alterations of bilirubin or liver enzymes. Lactic dehydrogenase was poorly sensitive for detection of hepatocytic or muscular damage. Alterations of alpha-globulins seemed to have been due more to alcohol metabolism-induced increase of lipoproteins than to inflammation. Among indicators of cell damage, serum iron, increased in 40% of the cases, seemed to be related to liver damage while creatine phosphokinase, increased in 84% of the cases, related to muscle damage. Hyperamylasemia was found in 20% of the cases and significantly correlated with levels of bilirubin, alkaline phosphatase and gamma-glutamyltransferase. It was indicated that injuries of liver, pancreas, salivary glands, and muscle occurred in asymptomatic or oligosymptomatic chronic alcoholics.

Mechanistic studies on effervescent-induced permeability enhancement

PURPOSE

To determine the mechanism(s) by which effervescence induces penetration enhancement of a broad range of compounds ranging in size, structure, and other physiocochemical properties across rat and rabbit small intestinal epithelium.

METHODS

Effervescent induced penetration enhancement was investigated in vitro by utilization of a modified Ussing chamber diffusion cell apparatus and in vivo by single-pass intestinal perfusion.

RESULTS

Carbon dioxide (CO2) bubbling directly onto rabbit ileum epithelium induced an increase in drug permeability. Mechanistic studies indicated that effects due to CO2 bubble evolution, such as increased drug dissolution rates, mucus thinning/stripping, and pH buffer effects did not contribute to increases in drug flux. Cellular enzyme (5'-ND and LDH) and total protein release assays did not indicate cell membrane perturbation and/or damage. CO2 bubbling induced a reduction in transepithelial electrical resistance (TEER) indicating epithelial disruption due to a structural change of the paracellular pathway. This was further substantiated by a MW dependence on paracellular marker flux. In addition, tissue recovery was relatively rapid, approximately 20 min.

CONCLUSIONS

CO2 bubbling directly onto the intestinal epithelium induced enhanced drug permeability due to an alteration of the paracellular pathway. This, in addition to fluid flow and membrane hydrophobicity concepts, may account for observed increases in drug flux.

Hepatic protein synthesis rate of liver specimens as a predictor of viability in rat cold ischemia liver transplantation model

BACKGROUND/AIMS

We have previously reported that the hepatic protein synthesis rate, calculated as the uptake rate of L-[4.5 3H] leucine by the protein fraction during a 10-min incubation of a 16-G needle biopsy specimen of liver tissue, represents a high level of liver function and is therefore useful for evaluating liver function. We investigated the hepatic protein synthesis rate level in a pre-transplant liver to learn if it might predict the outcome in a rat orthotopic liver transplantation model.

METHODS

Grafts were stored, liver specimens were obtained using a 21-G Chiba type II skinny needle, and the hepatic protein synthesis rate was calculated. Subsequently, liver transplantation was performed, and the hepatic protein synthesis rate level of revascularized liver, tissue blood flow rate, serum alanine aminotransferase, lactate dehydrogenase, hyaluronic acid, ketone body rate, and 2-week survival were examined.

RESULTS

The hepatic protein synthesis rate of pretransplant liver was correlated with parameters of post-transplant liver function: hepatic protein synthesis rate of the revascularized liver (r=0.92, p<0.0001), tissue blood flow rate (r=0.77, p<0.004), serum alanine aminotransferase (r=-0.69, p<0.003), lactate dehydrogenase (r=-0.54, p<0.03), hyaluronic acid (r=-0.86, p<0.0002), and ketone body rate (r=0.57, p<0.02). Pretransplant hepatic protein synthesis rate in survivors was 263.6+/-54.2 nmol/mg protein/10 min, while that in nonsurvivors was significantly lower at 162.0+/-39.0 (p<0.0001). When evaluation was made using a logistic regression model, the accuracy predicted using the value of hepatic protein synthesis rate was 95% (19/20).

CONCLUSIONS

These results suggest that measuring the hepatic protein synthesis rate of the grafts with a 21-G Chiba type II skinny needle may be a predictive criterion in the assessment of graft viability.

No attenuation of ischemic and reperfusion injury in Kupffer cell-depleted, cold-preserved rat livers

Activated Kupffer cells (KC) have been implicated in the damage sustained by preserved liver grafts during ischemia and reperfusion. The aim of this study was to compare ischemia/reperfusion injury in preserved, KC-depleted rat livers and preserved control livers, with special regard to sinusoidal endothelial cell (SEC) injury. Wistar rats were injected with liposome-encapsulated dichloromethylene diphosphonate, 48 hr before hepatectomy, to eliminate KC, or were withheld this pretreatment (controls). Livers were flushed with cold University of Wisconsin solution and after 0, 8, 16, or 24 hr of storage at 4 degrees C, were reperfused in a recirculation system with 200 ml of oxygenated Krebs-Henseleit solution at 37 degrees C for 90 min. Damage to SEC was measured by the uptake of hyaluronic acid (HA) from the perfusate and release of purine nucleoside phosphorylase (PNP). Perfusate samples were, furthermore, analyzed for aspartate aminotransferase (AST) and tumor necrosis factor-alpha. Carbon particles were infused in the perfusate to determine the phagocytotic capacity of KC. Biopsies were taken for histological examination and sections were stained with ED2 monoclonal antibodies to confirm the absence of KC. After 90 min of reperfusion, immediately after cold flush (t0), the uptake of HA was 72.2+/-2.3% and 69.3+/-1.3% in KC-depleted livers and in control livers, respectively (n.s.). After 8 hr of storage, HA uptake was 21.6+/-4.5% and 34.6+/-8.0%, respectively (n.s.). After 16 and 24 hr of storage and reperfusion, no uptake of HA was found in either KC-depleted or control livers, indicating abolished SEC function. PNP activities in the perfusate were higher in control livers (after 8 and 24 hr of storage), presumably due to release from damaged KC. No difference was found in AST and no tumor necrosis factor-alpha was measured in the perfusates of normal and KC-depleted livers. Electron microscopic studies showed that after 8 and 24 hr of storage and reperfusion, KC were activated and were able to phagocytose colloidal carbon. Our conclusion was that the elimination of Kupffer cells did not result in reduction of ischemic and reperfusion damage in livers preserved up to 24 hr, as assessed in vitro by SEC uptake of HA, PNP release, and AST release.

Hyaluronic acid uptake in the assessment of sinusoidal endothelial cell damage after cold storage and normothermic reperfusion of rat livers

The uptake of hyaluronic acid (HA) was used to assess preservation damage to sinusoidal endothelial cells (SEC) during cold storage and subsequent normothermic reperfusion of rat livers. After 8, 16, 24, and 48 h storage in University of Wisconsin (UW) solution, livers were gravity-flushed via the portal vein with a standard volume of cold UW solution containing 50 micrograms/l HA. The effluent was collected for analysis of HA, aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). The mean uptake of HA at 0 h was 59.1% +/- 4.6% (mean +/- SEM). After 8 h of storage, HA uptake was similar (55.5% +/- 7.3%), whereas after 16 h of storage it was reduced to 34.7% +/- 5.8%. At 24 and 48 h of storage, no uptake of HA was found. In a second series of experiments, livers were stored in UW solution and subsequently reperfused for 90 min with a Krebs-Henseleit solution (37 degrees C) in a recirculating system containing 150 micrograms/l HA. Following 8 h of storage, 34.6% +/- 8.0% of the initial HA concentration was taken up from the perfusate. After 16 and 24 h of storage, no uptake of HA was found. The results of this study indicate that damage to SEC occurs progressively during storage, leading to zero uptake of HA by the rat livers at 24 h of cold ischemia time. Additional reperfusion injury to the SEC was demonstrated by the reduced ability of the SEC to take up HA following normothermic reperfusion. The uptake of exogenous HA in preserved livers, used as a tool to assess SEC injury, enables the detection of early preservation damage.

Hyaluronic acid uptake in the assessment of sinusoidal endothelial cell damage after cold storage and normothermic reperfusion of rat livers

The uptake of hyaluronic acid (HA) was used to assess preservation damage to sinusoidal endothelial cells (SEC) during cold storage and subsequent normothermic reperfusion of rat livers. After 8, 16, 24, and 48 h storage in University of Wisconsin (UW) solution, livers were gravity-flushed via the portal vein with a standard volume of cold UW solution containing 50 micrograms/l HA. The effluent was collected for analysis of HA, aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). The mean uptake of HA at 0 h was 59.1% +/- 4.6% (mean +/- SEM). After 8 h of storage, HA uptake was similar (55.5% +/- 7.3%), whereas after 16 h of storage it was reduced to 34.7% +/- 5.8%. At 24 and 48 h of storage, no uptake of HA was found. In a second series of experiments, livers were stored in UW solution and subsequently reperfused for 90 min with a Krebs-Henseleit solution (37 degrees C) in a recirculating system containing 150 micrograms/l HA. Following 8 h of storage, 34.6% +/- 8.0% of the initial HA concentration was taken up from the perfusate. After 16 and 24 h of storage, no uptake of HA was found. The results of this study indicate that damage to SEC occurs progressively during storage, leading to zero uptake of HA by the rat livers at 24 h of cold ischemia time. Additional reperfusion injury to the SEC was demonstrated by the reduced ability of the SEC to take up HA following normothermic reperfusion. The uptake of exogenous HA in preserved livers, used as a tool to assess SEC injury, enables the detection of early preservation damage.

Early effects of high doses of retinol (vitamin A) on the in situ cellular metabolism in rat liver

Understanding of the possible toxicity associated with hypervitaminosis A becomes increasingly important in view of the popularity of vitamin A supplementation. Hypervitaminosis A for many years may eventually lead to hepatocellular damage. In the present study, rats were treated for 7 days with high doses of retinol to study the early effects on the metabolism of different types of liver cells using (enzyme) histochemistry, immunohistochemistry and electron microscopy. Excessive intake of vitamin A activates Kupffer cells and induces accumulation of lipid droplets in fat-storing cells as well as proliferation of these cells. Moreover, it affects the metabolic heterogeneity in the liver lobules, but does not lead to apparent cell damage. Based on the changes in marker enzymes for different metabolic processes, it is concluded that the capacity for breakdown of purines, the antioxidant capacity, the potential for phagocytosis and the regulation of ammonia levels were largely decreased. Increased alkaline phosphatase activity in hepatocytes pointed to an activated process of transport of retinol esters over the bile canalicular membrane. The possible causes of these metabolic changes have been described in the discussion.

Electrical properties of extracted rat liver tissue

We attempted to investigate the process of ischemia-induced disturbances in the rat liver, employing the electrical bio-impedance technique. The electrical bio-impedance was measured continuously over 6 h by the 4-electrode method, at various incubation temperatures, in six liver samples extracted from male Wistar rats. The electrical properties of biological tissues can be expressed in terms of three parameters: extracellular resistance (Re), intracellular resistance (Ri) and cell membrane capacitance (Cm). These three parameters were calculated from the measured values of the electrical impedance by the curve-fitting technique, using a computer program. The Re value increased rapidly after the rat livers were extracted, and then decreased slowly. The Re value reached a peak after about 13 min at 36 degrees C, and then decreased slowly, becoming constant after 3 h. There was a negative correlation between the Tmax of Re (the time when Re reached a maximum) and the incubation temperature (R = -0.973, P < 0.001). The Ri value decreased once in the early stage after extraction, followed by almost no change and then an increase after 4 h at 36 degrees C. The Cm showed a similar pattern of change to the Re value, and a negative correlation was also found between the Tmax of Cm and the incubation temperature (R = -0.969, P < 0.001). The increase in the Re and Cm values, and the decrease in the Ri value for quite long periods after the blood flow has stopped, suggest an increase in the resistance of extracellular fluid due to a decrease in its volume, an increase in cell membrane capacitance due to cell swelling, and a decrease in cellular fluid resistance due to an increase in its volume. The time when the Cm value decreases rapidly after an initial gradual decrease after the peak corresponds well with the time when the Ri value begins to increase, from which it is estimated that cell lysis proceeds and that the flow of extracellular fluid into the cell begins at this time. The findings of this study suggest the possibility of estimating the changes in liver tissue or the tissue structure due to ischemia.

Rat peripheral mononuclear cell thymidine kinase activity increases during liver regenerative processes after partial hepatectomy

Deoxythymidine kinase (TK; EC 2.7.1.21) activity in the liver has been used as a marker of liver regeneration after partial hepatectomy. In this study we examined TK activity of various organs, plasma and peripheral blood mononuclear cells (PMNC) in 70% partially hepatectomized rats. TK activity of lymph nodes, small intestine, heart, lung, kidney and thymus did not increase significantly during the course of the study, except for spleen at 72 h. On the other hand, PMNC-TK and liver cystosolic TK activity increased in a parallel fashion at all times after partial hepatectomy; they began to increase 12 h after surgery and peaked 48 h post-surgery. Fractionation of PMNC into T cells and B cells revealed that both populations increased and peaked 48 h post-surgery. Plasma TK peaked 12-24 h after surgery, then declined at 36, 48 and 72 h after partial hepatectomy. This change paralleled plasma levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). PMNC-TK activity correlated significantly with liver cystosolic TK activity 24 h (r = 0.743; P < 0.05) and 48 h (r = 0.708; P < 0.05) after partial hepatectomy. However, it did not correlate with plasma levels of TK, AST and ALT. The results indicate that in the early stage of liver regeneration PMNC-TK may provide a marker of liver regenerative processes.

Ultrastructure of the liver of reindeer calves under different nutritional conditions

A total of 12 reindeer calves were divided into two groups and the volume densities of liver cytoplasmic structures were counted using TEM. The six animals in group 1 were allowed to graze freely while those in group 2 were kept in pens and fed with lichens. All of them had a negative energy balance and lost weight from November to April, group 1 by 14.9% and group 2 by 24.8%. In spite of the weight losses, no significant changes in volume densities occurred during the winter. Glycogen remained fairly steady and there was no fatty infiltration into the hepatocytes. The very low incidence of Golgi apparatus in the hepatocytes may have been due to the inhibition of protein and lipid synthesis during the winter. These results point to substantial adaptation to extreme environmental conditions. The animals in group 1 apparently moved about more, which may have caused a greater breakdown of glycogen, resulting in turn in a lower volume density of glycogen in January and March.

Combined enzyme histochemical and ultrastructural study on cryostat sections of pig heart to detect early reperfusion damage after ischaemia

In cardiac surgery, recognition of peroperative myocardial infarction may improve patient selection for prolonged circulatory support. The value of enzyme histochemistry to discriminate between reversible and irreversible myocardial damage at short periods of reperfusion was studied in an in vivo model of regional ischaemia in pig hearts. The left anterior descending coronary artery (LADCA) was clamped for 45 min followed by 2 h reperfusion (group 1, n = 3). Post-mortem heart tissue showed markedly decreased activities of lactate dehydrogenase (LDH) and beta-hydroxybutyrate dehydrogenase (BDH) as demonstrated in cryostat sections, accompanied by massive leakage of LDH in the venous effluent. The depleted areas showed irreversible cell damage based on the presence of flocculent densities in mitochondria. In group 2 (n = 6), LADCA flow was reduced to 40 per cent of the base-line value followed by 2 h reperfusion. Heart tissue showed normal LDH and BDH activities, except for some cells surrounding blood vessels, which activity was minimally decreased. Flocculent densities in mitochondria were never observed. We conclude that enzyme histochemistry of LDH and BDH activity on cryostat sections is a useful tool for detecting irreversible myocardial cell damage as early as 2 h reperfusion after ischaemia of the pig heart. The technique has potential applications in the detection of peroperative infarction in human biopsies.

Liver cell necrosis: cellular mechanisms and clinical implications

Based on our current understanding, we have developed a provisional model for hepatocyte necrosis that may be applicable to cell necrosis in general (Figure 6). Damage to mitochondria appears to be a key early event in the progression to necrosis. At least two pathways may be involved. In the first, inhibition of oxidative phosphorylation in the absence of the MMPT leads to ATP depletion, ion dysregulation, and enhanced degradative hydrolase activity. If oxygen is present, toxic oxygen species may be generated and lipid peroxidation can occur. Subsequent cytoskeleton and plasma membrane damage result in plasma membrane bleb formation. These steps are reversible if the insult to the cell is removed. However, if injury continues, bleb rupture and cell lysis occur. In the second pathway, mitochondrial damage results in an MMPT. This step is irreversible and leads to cell death by as yet uncertain mechanisms. It is important to note that MMPT may occur secondary to changes in the first pathway (e.g. oxidative stress, increased Cai2+, and ATP depletion) and that all the "downstream events" occurring in the first pathway may result from MMPT (e.g., ATP depletion, ion dysregulation, or hydrolase activation). Proof of this model's applicability to cell necrosis in general awaits further validation. In this review, we have attempted to highlight the advances in our understanding of the cellular mechanisms of necrotic injury. Recent advances in this understanding have allowed scientists and clinicians a better comprehension of liver pathophysiology. This knowledge has provided new avenues of therapy and played a key role in the practice of hepatology as evidenced by advances in organ preservation. Understanding the early reversible events leading to cellular and subcellular damage will be key to prevention and treatment of liver disease. Hopefully, disease and injury specific preventive or pharmacological strategies can be developed based on this expanding data base.

Expression of cytokine-dependent adhesion molecules in postreperfusion biopsy specimens of liver allografts

BACKGROUND/AIMS

Allogeneic recognition of donor cells by host T lymphocytes requires the expression of cytokine-dependent molecules, such as class II major histocompatibility antigens, intracellular adhesion molecule 1 (ICAM-1), and lymphocyte function-associated antigen 3 (LFA-3). In the liver, activation of Kupffer cells after ischemic injury during the transplantation procedure may result in an early induction of cytokine-dependent molecules.

METHODS

The pattern of induction of ICAM-1, HLA-DR, HLA-DQ, and LFA-3 was investigated in 30 postreperfusion surgical biopsy specimens of liver allografts by an immunohistochemical technique.

RESULTS

Two patterns of induction were observed: focal or diffuse. On hepatocytes, ICAM-1 was induced in 22 cases (11 focal, 11 diffuse), HLA-DR in 18 cases (13 focal, 5 diffuse), HLA-DQ in 13 cases (3 focal, 10 diffuse), and LFA-3 in 1 case (focal). On bile duct cells, HLA-DR was expressed in 19 cases, associated with HLA-DQ in 7 cases. No induction of ICAM-1 and LFA-3 was detected. Compared with the other patients, the group of patients with diffuse postoperative hepatocellular induction of ICAM-1 was characterized by higher preharvesting serum transaminase levels in the donor (P < or = 0.001), suggestive of preoperative ischemic injury, and increased incidence of acute graft rejection (P = 0.04).

CONCLUSIONS

Preoperative warm ischemia may modify the immunogenicity of liver allografts.

Quantitative comparison between the gel-film and polyvinyl alcohol methods for dehydrogenase histochemistry reveals different intercellular distribution patterns of glucose-6-phosphate and lactate dehydrogenases in mouse liver

The precise histochemical localization and quantification of the activity of soluble dehydrogenases in unfixed cryostat sections requires the use of tissue protectants. In this study, two protectants, polyvinyl alcohol (PVA) and agarose gel, were compared for assaying the activity of lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6PDH) in normal female mouse liver. Quantification of enzyme activity was determined cytophotometrically in periportal (PP), pericentral (PC) and midzonal (MZ) areas. No coloured reaction product was present in PVA media after the incubation period. In contrast, the agarose gels appeared to be highly coloured after incubation. As a consequence, sections incubated with gel media were less intensely stained than those incubated in PVA-containing media. The specific G6PDH reaction (test minus control) yielded approximately 75% less formazan in sections incubated by the agarose gel method than with the PVA method. Further, the amount of formazan deposits attributable to G6PDH activity was highest in the midzonal and pericentral zones of the liver lobule with PVA media, and Kupffer cells could be discriminated easily because of their high G6PDH activity. Significant zonal differences or Kupffer cells could not be observed when agarose gel films were used for the detection of G6PDH activity. The LDH localization patterns appeared to be more uniform after incubation with both methods: no significant differences in specific test minus control reactions were seen between PP, PC and MZ. However, less formazan production (33%) was detected in sections incubated with agarose gels when compared with those incubated with PVA media.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of diclofenac, a non-steroidal anti-inflammatory drug, on lipid peroxidation caused by ischemia-reperfusion in rat liver

The present study investigated the effects of diclofenac sodium (Dic Na) on lipid peroxidation (LPO) and liver injury in ischemia-reperfused rat. LPO was estimated from the levels of phosphatidylcholine hydroperoxide (PCOOH), a primary peroxidative product of phosphatidylcholine. Hepatic ischemia-reperfusion induced significant elevation of plasma PCOOH and caused liver injury in rats. Rats were treated daily with Dic Na or alpha-tocopherol (alpha-toc.), p.o., for 5 days and once at 1 hr prior to induction of ischemia. Both substances prevented LPO from decreasing the plasma PCOOH level, and they significantly suppressed the elevation of serum GOT and LDH, in a dose-dependent manner. Dic Na was able to scavenge the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), but did not show radical-trapping ability for superoxide anion (O2-) or hydroxyl radicals (.OH), nor a suppressive ability for the NADPH-dependent LPO of microsomes. In contrast, alpha-toc. trapped both DPPH and O2-, but not .OH, and it inhibited the NADPH dependent LPO in vitro. These results suggest that Dic Na may suppress liver injury caused by ischemia-reperfusion through stable radical scavenging and the inhibition of superoxide production in activated phagocytes, both of which may restrain the induction and progression of oxidative stress.

Protective effect of silymarin on rat liver injury induced by ischemia

The effect of silymarin on liver cell damage induced by ischemia was studied in rats fasted for 24 h. In the first series of experiments in vitro ischemia was induced by storing tissue blocks in closed vials at 37 degrees C for 15, 30, 45 and 60 min. Cell injury was detected by the cytophotometrical measurement of glycogen phosphorylase activity in unfixed cryostat sections demonstrated by a modified histochemical procedure. In the second series of experiments in vivo ischemia was provoked by clamping the afferent vessels to the median and left lateral lobes of the liver for 60 min, followed by removal of the clamp and reperfusion. The extent of cell damage was determined by measuring the ALAT and ASAT activities in serum at 1, 3, 6 and 24 h after ischemia and by quantifying the extent of necrosis in the liver after 24 h reperfusion by measuring the unstained areas in cryostat sections incubated for lactate dehydrogenase activity. Silymarin (100 mg/kg b.w.) was administered intravenously at 5 min before both the induction of ischemia and the restoration of blood flow (in vivo ischemia) and at 1 h and at 5 min before sacrifice (in vitro ischemia). Controls received an equal amount of saline. The serum amino-transferase activities after 24 h reperfusion were significantly reduced in the silymarin-treated group (n = 10); ALAT 293 +/- 193 U/L, ASAT 343 +/- 229 U/L compared with the control group (n = 7): ALAT 1238 +/- 743 U/L, ASAT 948 +/- 541 U/L (p < 0.03), and the extent of necrosis decreased from 25.6 +/- 16.0% ( n = 7) to 7.8 +/- 8.3% (n = 10) (p < 0.01) after treatment with silymarin.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of xanthine oxidoreductase activity in human tissues — a histochemical and biochemical study

Localization of the activity of both the dehydrogenase and oxidase forms of xanthine oxidoreductase were studied in biopsy and postmortem specimens of various human tissues with a recently developed histochemical method using unfixed cryostat sections, poly-(vinyl alcohol) as tissue stabilizator, 1-methoxyphenazine methosulphate as intermediate electron acceptor and Tetranitro BT as final electron acceptor. High enzyme activity was found only in the liver and jejunum, whereas all the other organs studied showed no activity. In the liver, enzyme activity was found in sinusoidal cells and both in periportal and pericentral hepatocytes. In the jejunum, enterocytes and goblet cells, as well as the lamina propria beneath the basement membrane showed activity. The oxidase activity and total dehydrogenase and oxidase activity of xanthine oxidoreductase, as determined biochemically, were found in the liver and jejunum, but not in the kidney and spleen. This confirmed the histochemical results for these organs. Autolytic rat livers several hours after death were studied to exclude artefacts due to postmortem changes in the human material. These showed loss of activity both histochemically and biochemically. However, the percentage activity of xanthine oxidase did not change significantly in these livers compared with controls. The findings are discussed with respect to the possible function of the enzyme. Furthermore, the low conversion rate of xanthine dehydrogenase into xanthine oxidase during autolysis is discussed in relation to ischemia-reperfusion injury.

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

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

Experimentally induced colon cancer metastases in rat liver increase the proliferation rate and capacity for purine catabolism in liver cells

Metastases in rat liver were generated experimentally by intraportal injection of colon cancer cells to investigate the effects of cancerous growth on the metabolism of surrounding liver tissue. Maximum activities (capacity) of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, lactate dehydrogenase, succinate dehydrogenase, alkaline phosphatase, 5'-nucleotidase, xanthine oxidoreductase, purine nucleoside phosphorylase and adenosine triphosphatase have been determined. Two types of metastases were found, a small type surrounded by stroma and a larger type in direct contact with hepatocytes. Both types affected the adjacent tissue in a similar way suggesting that the interactions were not mediated by stroma. High capacity of the degradation pathway of extracellular purines released from dead cells of either tumours or host tissue was found in stroma and sinusoidal cells. Metastases induced both an increase in the number of Kupffer cells and proliferation of hepatocytes. The distribution pattern in the liver lobulus of most enzymes investigated did not change distinctly. However, activity of alkaline phosphatase, succinate dehydrogenase and phosphogluconate dehydrogenase was increased in hepatocytes directly surrounding metastases. These data imply that the overall metabolic zonation in liver lobuli is not dramatically disturbed by the presence of cancer cells despite the fact that various metabolic processes in liver cells are affected.

Reversibility of cholestatic changes following experimental common bile duct obstruction: fact or fantasy?

In 36 male Wistar rats extrahepatic cholestasis was induced by ligation and transsection of the common bile duct. After 1, 2 and 3 weeks of cholestasis the bile flow was restored by means of a Roux-en-Y choledochojejunostomy. Plasma levels of bilirubin, alkaline phosphatase, GOT and clotting factor X were measured weekly. Liver biopsies were taken at the time of restored bile flow as well as 3 and 8 weeks thereafter. Histochemical reaction for lactate dehydrogenase activity and Sirius Red F3BA staining were used as measure for functional liver parenchyma and collagen, respectively. Acid phosphatase, alkaline phosphatase and 5'-nucleotidase activities as well as the glycogen content were demonstrated in cryostat sections of the same biopsies. After 1, 2 and 3 weeks of common bile duct obstruction, levels of bilirubin, alkaline phosphatase and GOT significantly increased, whereas levels of clotting factor X decreased. RBF resulted in normalization of all these levels to control range. The volume density of functional parenchyma was found to be reduced to 90%, 73% and 64% of the control values following 1, 2 and 3 weeks of common bile duct obstruction respectively, returning to 96%, 94% and 88% at 8 weeks, respectively, after restored bile flow. The collagen content increased significantly during cholestasis up to 5-fold after 3 weeks of common bile duct obstruction. After restored bile flow, a slight decrease of collagen was measured in some animals but in none of the three groups a return to normal values appeared. Cholestasis induced an alteration in localization and/or activity of the three enzymes analyzed as well as a depletion of glycogen stores. All changes in activity and distribution pattern of the three enzymes, as well as the glycogen depletion during common bile duct obstruction normalised after restored bile flow was performed. However, the longer common bile duct obstruction had existed, the longer period was needed for full recovery. In conclusion, even after 3 weeks of common bile duct obstruction the parenchyma/stroma relationship grossly normalized after restored bile flow with an almost complete restoration of the parenchyma and a concomitant recovery of liver function. However, collagen once formed, did not disappear but remained as more condensed septa, which apparently did not interfere with normal function.

Histochemical detection of glycogen phosphorylase activity as parameter for early ischemic damage in rat heart

In the present study we have investigated whether enzyme histochemical parameters can be applied to detect early ischemic damage in rat heart after ischemia without restoration of the blood flow. Ischemia was induced by incubating heart fragments for 0, 10, 20, 30, 60, 120 and 240 min at 37 degrees C. The activity and localization of the following enzymes was studied in unfixed cryostat sections using quantitative histochemical methods: lactate dehydrogenase, creatine kinase, succinate dehydrogenase, phosphofructokinase, acid phosphatase, 5'-nucleotidase and glycogen phosphorylase. Moreover, the ultrastructure of the tissue was studied with special attention to the appearance of flocculent densities in mitochondria, which can be seen as a sign of irreversible cell damage. It was shown that glycogen phosphorylase activity in rat heart decreased after short periods (30 min) of in vitro ischemia, whereas all other enzymes studied were not decreased up to 240 min, with the exception of lactate dehydrogenase and phosphofructokinase activities which were diminished only at 240 and 120 min of ischemia, respectively. Some reaction product was found after incubating for 5'-nucleotidase activity in the absence of substrate, indicating the presence of endogenous substrate(s). This endogenous substrate disappeared from the myocytes after 20 min of ischemia. It is assumed that AMP and/or other phosphate-containing compounds play an essential role in the activation of glycogen phosphorylase. Significant reduction of glycogen phosphorylase activity is correlated with the irreversible stage of damage of myocytes as judged from the ultrastructure.

Elevated serum thymidine kinase activity in patients with acute viral hepatitis

To evaluate the clinical applications of serum thymidine kinase (TK) activity, we compared the results obtained with this parameter with those of other liver function tests in 27 patients with acute viral hepatitis and 16 normal controls. In those in the acute stage, the serum TK activity increased significantly to 55.5 +/- 66.5 U/L. There was no significant correlation between serum TK activity and findings for serum albumin, bilirubin, alkaline phosphatase or r-glutamyl transpeptidase. However, it did correlate significantly well with the serum activity of aspartate aminotransferase (AST) (r = 0.621, P < 0.01), alanine aminotransferase (ALT) (r = 0.551, P < 0.01), and lactate dehydrogenase (LDH) (r = 0.620, P < 0.01). Serum TK activity reached higher than 70 U/L in 8 of 11 patients with hepatitis A; however, no patients with the other types of hepatitis reached such a high level. During the recovery stage, the serum TK activity decreased significantly to 5.9 +/- 1.7 U/L (P < 0.01), and did not correlate with AST, ALT, LDH or other conventional liver function parameters. The data suggest that an elevation of serum TK in patients with acute viral hepatitis results from hepatocellular damage. A marked elevation of serum TK activity may thus provide a marker for acute hepatitis A infection.

The effects of storage on the retention of enzyme activity in cryostat sections. A quantitative histochemical study on rat liver

The effect of storage of unfixed cryostat sections from rat liver for 4 h, 24 h, 3 days and 7 days at -25 degrees C was studied on the activities of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, xanthine oxidoreductase, glutamate dehydrogenase, succinate dehydrogenase (all demonstrated with tetrazolium salt procedures), glucose-6-phosphatase (cerium-diaminobenzidine method), 5'-nucleotidase (lead salt method), dipeptidyl peptidase II, acid phosphatase (both simultaneous azo coupling methods), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure) and catalase (diaminobenzidine method). The effect of drying of the cryostat sections at room temperature for 5 and 60 min was investigated as well. The enzyme activities were quantified by cytophotometric measurements of test and control reactions. The test minus control reaction was taken as a measure for specific enzyme activity. It was found that the activities of all the enzymes investigated, with one exception, were affected neither by storage of the cryostat sections at -25 degrees C for up to 7 days, nor by drying of the sections at room temperature for up to 60 min. The exception was xanthine oxidoreductase, whose activity was reduced by 20% after 5 min drying of sections or after 4 h storage. Therefore, only incubations for xanthine oxidoreductase activity have to be performed immediately after cutting cryostat sections, whereas for the other enzymes a considerable margin appears to exist.

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.

Ischemic injury in liver transplantation: difference in injury sites between warm and cold ischemia in rats

Using liver allografts with warm or cold ischemia, we evaluated functional and morphological alterations in hepatocytes, sinusoidal endothelial cells and Kupffer cells in a rat transplantation model. All recipients of allografts with either 4 hr of cold or 30 min of warm ischemia lived more than 22 days and were judged viable. On the other hand, all recipients of grafts with 6 hr of cold or 60 min of warm ischemia died within 2 days and were therefore judged to be nonviable. With these viable and nonviable allograft models, hepatocyte function was evaluated by the bile output and serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminase and serum lactate dehydrogenase levels; endothelial cell function was judged by the serum hyaluronic acid level, and Kupffer cell function was measured by an intravenous colloidal carbon clearance test. Hepatocyte injury was the prominent feature in warm ischemic grafts, especially in the nonviable ones. On the other hand, serum hyaluronic acid values were significantly higher in the nonviable cold ischemic group, compared with the viable counterpart, suggesting that the functional depression of endothelial cells was predominant in cold, nonviable livers. Histological examinations coincided with the above findings. The phagocytic activity of Kupffer cells was depressed by warm or cold ischemia, whereas the number of Kupffer cells was reduced in the warm ischemia group. We conclude that in liver allografts the main site of injury in warm ischemia is the hepatocytes and suggest that cold ischemia is associated with endothelial cell damage.

Cytoskeleton as a target in menadione-induced oxidative stress in cultured mammalian cells: alterations underlying surface bleb formation

Several in vitro and in vivo studies have suggested that surface bleb formation during oxidative cell injury is related to alteration in cytoskeleton organization. Various cell lines different in origin and growth characteristics were exposed to 2-methyl-1,4-naphthoquinone (menadione) which is known to induce bleb formation and cytotoxicity by generating considerable amounts of oxygen-reactive species. Treated cells were analyzed by means of immunocytochemistry and electron microscopy in order to investigate the morphological and molecular features underlying bleb generation. The results obtained indicate that menadione-induced bleb formation is a widely observed phenomenon present mainly in round or mitotic cells. Surface blebs appear free of organelles and contain only few ribosomes and amorphous material. Occasionally, they undergo detachment from the cell surface as large cytoplasmic vesicles. Bleb surfaces with protein clusters as well as bald blisters with an almost exclusive localization of intramembrane particles on their narrow base were detected using freeze-fracture techniques. Immunocytochemical investigations performed on menadione-exposed cells revealed that some surface proteins (collagen IV, sialo-proteins, beta 2 microglobulin and fibronectin) and adhesion molecules (vinculin) underwent changes in their expression over the bleb surface. Moreover, different behavioural characteristics of actin microfilaments, vimentin and keratin intermediate filaments and microtubules was observed. Alpha-actinin, vimentin and microtubular proteins (tubulin, MAPs and tau) were detected within the blebs. On the other hand, actin and keratin filaments appeared to be absent. The results presented here demonstrate that cytoskeletal structures and the microfilament system in particular, represent important targets in menadione-induced morphological changes in cultured cells. These changes appear to lead to the redistribution of several cytoskeletal and membrane proteins as well as dissociation of the cytoskeleton network from its anchoring domains in the plasma membrane thus generating sites of structural weakness where blebs would arise and progressively grow. Experimental evidence supporting a crucial role of thiol oxidation and elevation of cytoplasmic calcium concentration in bleb formation is also provided.

Different patterns of leakage of cytosolic and mitochondrial enzymes

The mechanisms of leakage of intracellular enzymes, and especially the cytosolic and mitochondrial isozymes of aspartate aminotransferase (AST), in ischemic rat liver were studied. On recirculation of ischemic liver, cytosolic AST (cAST) promptly appeared in the blood. Release of cytosolic enzymes, including cAST and lactic dehydrogenase, resulted from disruption of blebs that protruded from parenchymal cells into the sinusoidal space. When these blebs were formed in ischemic liver, mitochondria still remained in core regions of the injured cells and were not found in the blebs. Consistent with this fact, mitochondrial AST (mAST) did not leak into the circulation from ischemic liver until most of the cAST had leaked out. This delayed leakage of mitochondrial enzymes was also consistent with the fact that the mitochondrial membranes maintained a diffusion barrier against matrix enzymes even after anoxia for 2 h, when their oxidative phosphorylation capacity had been lost. These results indicate that mitochondrial enzymes are liberated into the blood only after appreciable disintegration of the cells, probably necrosis, and that the cumulative activity of mAST in the blood should reflect the extent of necrosis in ischemic organs better than that of cAST.

Changes in acid phosphatase activity in rat liver after ischemia

The effect of ischemia on the stability, i.e. the permeability of the lysosomal membrane of rat liver has been studied using quantitative histochemical analysis of acid phosphatase activity. Ischemia in vitro was performed for 0-240 min at 37 degrees C and ischemia in vivo for 60 min was followed by 1, 5, 24 and 48 h of reperfusion. Acid phosphatase activity was demonstrated in cryostat sections using naphthol AS-BI phosphoric acid as substrate and polyvinyl alcohol was added to the incubation medium to counteract diffusion phenomena. Ischemia in vitro up to 240 min did not affect the localization nor the total activity of acid phosphatase activity. After 60-min ischemia in vivo followed by 1-h reperfusion distinct areas showed decreased acid phosphatase activity. A further decrease in activity was observed after 5 h reperfusion. Final reaction product generated by acid phosphatase activity was rather diffusely distributed in border zones between normal and damaged tissue after 24 and 48 h of reperfusion following 60 min ischemia in vivo. It is concluded that not ischemia itself but rather reperfusion affects the stability of the lysosomal membrane due to the occurrence of oxygen-derived free radicals and/or imbalanced Ca2+ concentration. Restoration of the blood flow causes leakage of acid phosphatase from the lysosomes into the cytoplasm of liver parenchymal cells and from there to the blood.