Comparison of formalin- and acetone-fixation for immunohistochemical detection of carcinoembryonic antigen (CEA) and keratin

FoxO3a modulation and promotion of apoptosis by interferon-α2b in rat preneoplastic liver

BACKGROUND

FoxO3a, a member of the FOXO family of transcription factors, is expressed in adult liver and modulates the expression of genes involved in apoptosis. FoxO3a is post-translationally regulated, negatively by PI3K/Akt and MAPK/Erk and positively by oxidative stress/JNK pathways. In previous works, we have demonstrated that interferon-α2b (IFN-α2b) induces apoptosis of hepatic preneoplastic foci through the production of reactive oxygen species (ROS).

AIMS

To investigate the post-translational signal events triggered by the oxidative stress induced by IFN-α2b and the modulation of FoxO3a transcriptional activity during these events in rat preneoplastic liver.

METHODS

Adult male Wistar rats were subjected to a two-phase model of hepatocarcinogenesis. A group of animals received IFN-α2b and another group received IFN-α2b and ascorbic acid (ASC), by intraperitoneal injection. Lipid peroxidation, immunohistochemistry, immunoblotting, co-immunoprecipitation and sqRT-PCR assays were performed to explore the role of ROS, JNK, Akt, Erk, FoxO3a, β-catenin and PUMA in the IFN-α2b-mediated apoptotic mechanism.

RESULTS

In vivo IFN-α2b treatment induced endogenous production of ROS which activated JNK. IFN-α2b blocked the activation of Akt and Erk, avoiding FoxO3a activity repression. Activated JNK was responsible for the nuclear translocation and transcriptional activity of FoxO3a which positively modulated the expression of PUMA, a proapoptotic player. In addition, nuclear FoxO3a competed for the nuclear β-catenin associated to TCF, inhibiting the canonical Wnt signalling pathway.

CONCLUSIONS

The data presented here propose a model in which in vivo IFN-α2b treatment induces nuclear translocation and transcriptional activity of FoxO3a, triggering the mitochondrial apoptotic pathway in hepatic preneoplastic foci.

Involvement of reactive oxygen species on the apoptotic mechanism induced by IFN-alpha2b in rat preneoplastic liver

Interferon-alpha2b (IFN-alpha2b) is an important component in the preventive treatment of patients who have severe hepatic illness such as hepatitis B or C and hepatocarcinomas. In a previous work, using a rat liver preneoplastic model, we have demonstrated that IFN-alpha2b reduces the number and volume of altered hepatic foci (AHF) inducing apoptosis through a mechanism mediated by TGF-beta(1). In this study, the implication of hepatocytes redox status of IFN-alpha2b-treated preneoplastic liver in the TGF-beta(1)-induced apoptotic death was analyzed. Results indicate that IFN-alpha2b induces hepatocytic TGF-beta(1) production and secretion by induction of reactive oxygen species (ROS) formation through the activation of a membrane bound NADPH oxidase complex. TGF-beta(1), in turn, reduces hepatocytes antioxidant defenses and induces programmed cell death. On the other hand, it was also demonstrated that treatment of rats with IFN-alpha2b plus a ROS scavenger such as ascorbic acid, abolishes the apoptotic effect of IFN-alpha2b in rat preneoplastic livers, leading to an increase of the foci volume. In conclusion, these findings strongly suggest that ROS have a fundamental role as signaling and/or regulator molecules in the IFN-alpha2b-induced apoptosis in hepatic preneoplastic cells.

Ultrasound-accelerated formalin fixation of tissue improves morphology, antigen and mRNA preservation

Formalin fixation and paraffin embedding are conventional tissue preservation and processing methods used for histologic diagnosis in over 90% of cases. However, formalin fixation has three disadvantages: (1) slow fixation (16-24 h) hinders intraoperative decision making, (2) slow quenching of enzymatic activity causes RNA degradation, and (3) extensive molecule modification affects protein antigenicity. Applying high-frequency, high-intensity ultrasound to the formalin fixative cuts fixation time to 5-15 min. Fixation of various tissues such as lymph node, brain, breast, and prostate suggests that, compared to the conventional method, implementation of ultrasound retains superior and more uniform tissue morphology preservation. Less protein antigenicity is altered so that rapid immunohistochemical reactions occur with higher sensitivity and intensity, reducing the need for antigen retrieval pretreatment. Better RNA preservation results in stronger signals in in situ hybridization and longer RNA fragments extracted from fixed tissues, probably due to rapid inhibition of endogenous RNase activity. Molecules extracted from ultrasound-fixed tissues are of greater integrity and quantity compared to conventionally fixed tissues, and thus better support downstream molecular analyses. Overall, ultrasound-facilitated tissue preservation can provide rapid and improved morphological and molecular preservation to better accommodate both traditional and molecular diagnoses.

Antibodies that label paraffin-embedded mouse tissues: a collaborative endeavor

Histology and immunohistochemistry are important tools in the study of human diseases and their respective animal models. The study of mouse models has been hampered by the absence of a large set of mouse-specific antibodies adapted to paraffin-embedded tissues. A total of 196 antibodies were tested on paraffin-embedded mouse tissues preserved in five different fixatives (Fekete's acid-alcohol-formalin, 10% neutral buffered formalin, 4% paraformaldehyde, IHC Zinc Fixative, and Bouin's fixative). The antibodies were targeted to proteins of the cytoplasm (n = 100), plasma membrane (n = 48), nucleus (n = 36), extracellular compartment (n = 5), cytoplasm/cell membrane (n = 4), and viral proteins (n = 3). A total of 83 antibodies provided an adequate signal to noise ratio. Of these, adequate labeling required heat-mediated epitope retrieval or enzymatic digestion for 32 and 8 antibodies, respectively. Epitope recognition was best for tissues fixed with Fekete's acid-alcohol-formalin. However, some proteins could be detected only in IHC Zinc Fixative, confirming that there is no single fixative suitable for the preservation of all epitopes. Four of 13 antibodies that failed to label their cellular targets on tissue sections successfully labeled whole-mount tissues, indicating that tissue processing plays an important role in epitope degradation. Regularly updated information on immunohistochemistry of normal and neoplastic mouse tissues is accessible online at (http://tumor.informatics.jax.org); links to antibody suppliers' web sites are provided.

Interferon alpha-induced apoptosis on rat preneoplastic liver is mediated by hepatocytic transforming growth factor beta(1)

In previous work we showed that interferon alfa-2b (IFN-alpha2b) increases apoptosis on rat hepatic preneoplastic foci. The aim of this study was to determine if transforming growth factor beta1 (TGF-beta1) was involved in the programmed cell death on the foci. Animals were divided into 6 groups: subjected to a 2-phase model (diethylnitrosamine plus 2-acetylaminofluorene) of preneoplasia development (group 1); treated with IFN-alpha2b during the 2 phases (group 2); treated with IFN-alpha2b during initiation with diethylnitrosamine (group 3); treated with IFN-alpha2b during 2-acetylaminofluorene administration (group 4); subjected only to an initiation stage (group 5); and treated with IFN-alpha2b during the initiation period (group 6). Serum TGF-beta1 levels were increased in IFN-alpha2b-treated rats. Immunohistochemical studies showed that IFN-alpha2b significantly increased the quantity of TGF-beta1-positive hepatocytes in groups 2 to 4. Phosphorylated-Smads-2/3 (p-Smads-2/3) proteins in liver nuclear extracts were significantly elevated. To determine the source of TGF-beta1, isolated hepatocytes, Kupffer cells, and peritoneal macrophages from animals in groups 1 and 5 were cultured with or without IFN-alpha2b. IFN-alpha2b stimulus induced several-fold increases of TGF-beta1 secretion from hepatocytes. Neither Kupffer cells nor peritoneal macrophages secreted detectable TGF-beta1 levels when they were treated with IFN-alpha2b. IFN-alpha2b-stimulated cultured hepatocytes from preneoplastic livers showed enhanced apoptosis, measured by fluorescence microscopy and caspase-3 activity. They presented higher nuclear accumulation of p-Smads-2/3, indicating increased TGF-beta1 signaling. When anti-TGF-beta1 was added to the culture media, TGF-beta1 activation and apoptosis induced by IFN-alpha2b were blocked. In conclusion, IFN-alpha2b-induced production of TGF-beta1 by hepatocytes from preneoplastic liver is involved in the apoptotic elimination of altered hepatic foci.

Combined supplementation of vanadium and beta-carotene suppresses placental glutathione S-transferase-positive foci and enhances antioxidant functions during the inhibition of diethylnitrosamine-induced rat liver carcinogenesis

BACKGROUND AND AIM

The present study was designed to investigate the chemopreventive effects of combined vanadium (V; 0.5 p.p.m.) and beta-carotene (BC; 120 mg/kg of basal diet) on diethylnitrosoamine (DEN)-induced and phenobarbital (PB)-promoted rat hepatocarcinogenesis.

METHODS

All rats were subjected to two-thirds partial hepatectomy (PH) at the fourth week. After PH they were administered either trioctanoin alone (groups A', B', C' and D') or a single injection of DEN in trioctanoin at a dose of 10 mg/kg of body weight (groups A, B, C and D). Two weeks after the DEN treatment PB was administered (0.05% in basal diet) to all the DEN-treated rats and continued until the end of the experiment. Supplementation of V (groups B and B'), BC (groups C and C') or both V and BC (groups D and D') at the doses stated previously were started 4 weeks before DEN administration (at week 0) and continued until the 16th week.

RESULTS

It was observed that in the DEN-treated and PB-promoted group (group A) the expression of the numbers and areas of the placental form of glutathione S-transferase (GST-P)-positive altered hepatic foci (AHF) was maximum. Treatment with V (group B) and BC (group C) significantly reduced the expression of GST-P-positive AHF by 29.5% and 42.8%, respectively. An additive protection action (65.7%) was noticed in group D, which received both V and BC for the entire period of the experiment. It was also observed that supplementation of V and BC for the entire period of the experiment significantly reduced the number and size of the hyperplastic nodules, while the combination treatment worked as an additive effect, reducing the number and size of the hyperplastic nodules to 22% from 89%. Moreover, a significantly reduced level of cytosolic glutathione (P < 0.001) and glutathione-S-transferase (P < 0.001) activity and stabilization of aerobic metabolism and hepatic architecture of the cells as compared with carcinogen control were observed in the V + BC-treated group.

CONCLUSION

The present study suggests that V, an essential trace element, may be useful in combination with BC, an antioxidant, in the inhibition of experimentally induced rat hepatocarcinogenesis.

Vanadium inhibits placental glutathione S-transferase (GST-P) positive foci in 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Vanadium (V) has recently been found to possess potent anti-neoplastic activity in rat colon carcinogenesis. In the present study attempts have been made to investigate the expression of the number and area of aberrant crypt foci positive for placental glutathione S-transferase (GST-P) during 1,2-dimethyl hydrazine (DMH)-induced rat colon carcinogenesis. Male Sprague Dawley rats were randomly divided into four groups. Rats in group A were designed as normal controls. Group B animals received DMH once a week (20 mg/kg body wt.) intraperitoneally for 16 weeks. Group C rats received the same treatment of DMH as in group B, along with 0.5-ppm vanadium as ammonium monovanadate ad libitum in drinking water throughout the experiment. Vanadium alone was given to Group D rats without any DMH injection. The expression of the number and the area of aberrant crypt foci (ACF) positive for GST-P was maximum in DMH-treated group. Vanadium-treated rats significantly reduced (P < 0.001) the expression of GST-P positive ACF cells (by 71.13%) for the entire period of the study. Moreover the histopathological examination also showed that vanadium action could minimize the aberrant crypt foci (P < 0.001). Furthermore, vanadium supplementation also elevated SOD activities in both liver and colon (P < 0.01, P < 0.02 and P < 0.01, P < 0.02 respectively) when compared to their carcinogen counterparts. Our results confirm that vanadium is particularly effective in limiting the action of the carcinogen, thereby establishing its anticarcinogenicity in chemically induced rat colon carcinogenesis.

The in vivo apoptotic effect of interferon alfa-2b on rat preneoplastic liver involves Bax protein

To determine whether interferon alfa (IFN-alpha) prevents in vivo oncogenesis in very-early-stage cancer cells, we evaluated the action of IFN-alpha2b over preneoplastic foci in rats. Animals were divided into 6 groups: subjected to a 2-phase model (diethylnitrosamine [DEN] plus 2-acetylaminofluorene [2-AAF]) of preneoplasia development (group 1), treated with IFN-alpha2b during the 2 phases (group 2), only during initiation with DEN (group 3), only during administration of 2-AAF (group 4), subjected only to an initiation stage (group 5), and treated with IFN-alpha2b during this period (group 6). The numbers of placental form of rat glutathione S-transferase (rGST-P)-positive foci per liver and the foci as percentage of liver were significantly reduced in groups 2, 3, and 6 but not in group 4. Rats treated with IFN-alpha2b showed a higher apoptotic index (AI) in altered hepatic foci (AHF). Levels of p53 and Bax protein in liver lysates were significantly increased in those animals. Similarly, levels of antiapoptotic proteins Bcl-2 and Bcl-x(L) in mitochondrial fraction were decreased. Finally, increased levels of Bax protein were localized in the mitochondria of rats that received IFN-alpha2b, at least during the DEN phase (groups 2, 3, and 6), whereas mitochondrial Bax expression was not increased in group 4. In conclusion, the preneoplastic hepatocytes in rats that received IFN-alpha2b during the initiation stage undergo programmed cell death as a primary result of a significant increase in the amount and translocation to the mitochondria of Bax protein.

Involvement of mu class glutathione S-transferase subunit M2 (rGST M2) levels in the initiation and promotion of hepatocellular carcinogenesis in old rats

Age-associated differences in the response of the initiation and promotion of hepatocellular carcinogenesis in the rat were analyzed. Male Wistar rats 5 and 18 months-old were used throughout. They underwent an experimental design of multistage model of hepatocarcinogenesis: hepatic cells were initiated with the complete carcinogen Aflatoxin B1 (0.5mg/Kg b.w.) and the promotion was performed through a combined treatment of proliferation (partial hepatectomy, 65%) and administration of the tumorigenic promoter phenobarbital (0.1% in drinking water for 21 days). After the treatment, rats were sacrificed and the following parameters were determined: activity and subunit composition of the glutathione S-transferase enzyme system, the number of liver preneoplastic foci and the proliferation cell index. The combined treatment (initiation + promotion) lowered the expression of the mu class GST (rGST M1, rGST M2). The inhibition in rGST M2 in old animals (which in basal conditions had already been lower) was significant. On the other hand, the treatment increased the alpha class GST (rGST A, rGST A3). The number of preneoplastic foci was higher in old rats (number of foci/cm(2): 6.9+/-0.3 vs 3.9+/-0.3 in young rats, p< 0.05). The proliferation cell index did not show age-related differences. Because rGST M2 deficiency coexisted with induced expression of alpha class, the livers would be resistant to some toxic insults, being selectively sensitive to potentially genotoxic substances for which M2 is an essential detoxification pathway. The transition to a rGST M2-deficient phenotype during aging could induce higher responsiveness to genotoxic effects, and might favor the likelihood of further progression, indicating a higher susceptibility of aged animals to the development of carcinogenesis.

Determination of optimal conditions for the immobilization of cells in a cell capture enzyme immunoassay (CC-EIA) by a simple Geimsa assay

To determine the optimal conditions for the immobilization of cells in a cell capture enzyme immunoassay (CC-EIA), the most suitable diluent, and the optimal pH, temperature and period of incubation were examined using WI-38, a human embryonic lung fibroblast cell line. For the evaluation, we devised a simple Giemsa assay method, in which immobilized cells on a microplate were stained with Giemsa solution, the stained dye was eluted with ethanol after washing the plate, and the optimal density (O.D.) was measured at wavelength 620 nm. The optimal conditions for the immobilization were determined to be treatment with 5% formalin in phosphate-buffered saline (PBS) (pH 7.2) for 15 minutes at room temperature, which were confirmed to be suitable for the measurement of cell associated collagen by CC-EIA. Additionally, we found that the simple Giemsa staining method was also useful for evaluating the number of immobilized cells on the microplate after CC-EIA.

Genome-wide loss of heterozygosity analysis of chemically induced rat hepatocellular carcinomas reveals elevated frequency of allelic imbalances on chromosomes 1, 6, 8, 11, 15, 17, and 20

Neoplastic development is a multistep process that involves the stochastic accumulation of heritable genetic alterations in proto-oncogenes, DNA repair genes, and tumor suppressor genes. Loss of heterozygosity (LOH) analysis has been used successfully to identify the genetic determinants of neoplastic development, including tumor suppressor genes, in several species and organs but not in the rat liver. We report the results of a sensitive genome-wide LOH analysis of rat hepatocellular carcinomas (HCCs). Heterozygous rats (Wistar-Furth x Fisher 344) were subjected to an Initiation-Promotion-Progression (IPP) protocol of hepatocarcinogenesis. Two weeks after initiation (by partial hepatectomy, 10 mg/kg diethylnitrosamine), the rats were placed on a diet containing 0.05% phenobarbital (PB). After 24 wk of PB promotion, the rats received either 100 or 1 50 mg/kg ethylnitrosourea. Hepatocellular tumors were resected after a total of 76wk of PB promotion. LOH analysis was completed on 26 HCCs by using 60 microsatellite markers covering all 20 rat autosomes and chromosome X. While 85% of the HCCs had one or more allelic imbalances, the average HCC had 3.3 allelic imbalances (range 0-9). A conditional hypothesis-testing method called the Hot-Cold model was used to determine the location of statistically significant elevations in the frequency of allelic imbalances. Elevated allelic imbalances were observed on chromosomes 1q, 6, 8, 11, 15, 17, and 20p. Together, these allelic imbalances suggest that the retinoblastoma and insulin-like growth factor genes as well as the resistance to chemical carcinogenesis (rcc) locus may be involved in HCC development in the rat but that LOH of the p53 gene is not. The elevated rate of allelic imbalances on chromosomes 8,11, and 17 may indicate the location of undiscovered tumor suppressor genes important to neoplastic development in rat liver. Microdissection-based LOH analysis of HCC revealed that contamination of non-neoplastic and nonhepatocellular tissue was not masking LOH in the whole-tumor analysis. There were no statistically significant differences in the frequency of allelic imbalances between HCC of any differentiation state (histological grade). To the degree that it does not reflect differences in etiological factors, the absence of allelic imbalances in chromosomal regions containing the p53 and mamose-6-phosphate/insulin-like growth factor II receptor tumor suppressor genes and the generally low frequency of allelic imbalances in these tumors, suggests that LOH and allelic imbalances play a less significant role in the molecular pathogenesis of HCC in rats than humans.

The slow induction of resistant hepatocytes during initiation of hepatocarcinogenesis by the nongenotoxic carcinogen clofibrate

This study was designed to explore whether a well-known nongenotoxic liver carcinogen, clofibrate, would induce rare resistant hepatocytes similar to those seen during initiation of hepatocarcinogenesis with many genotoxic carcinogens. Male young adult F344 rats were exposed to a control diet containing 0.5% (w/w) clofibrate for 3, 6, or 10 months. After 1 month on a diet free of clofibrate, the animals were assayed for resistant hepatocytes by a standardized selection procedure using 2-acetylaminofluorene as the inhibitor and partial hepatectomy as a strong stimulus for cell proliferation. No resistant hepatocytes were found in the animals exposed to clofibrate for 3 months or in any of a series of control animals. However, animals on the clofibrate for 6 and 10 months contained resistant hepatocytes that were clonally expanded to produce hepatocyte nodules. These nodules were indistinguishable on gross and microscopic examination from hepatocyte nodules seen in animals in which nodules are induced with one of many different genotoxic carcinogens. Also, like those nodules, the nodules seen in the animals exposed to clofibrate stained positively for glutathione S-transferase 1-1 and gamma-glutamyl transpeptidase and negatively for ATPase. The evidence from this study indicates that the nongenotoxic carcinogen, clofibrate, induces early cellular changes in the liver that are very similar to those induced by many different genotoxic carcinogens. These changes are manifest as a resistance phenotype in a few scattered hepatocytes that now can be clonally expanded selectively to form hepatocyte nodules. However, the resistant hepatocytes are induced by clofibrate much more slowly. Whether this basic similarity pertains to the later steps in the hepatocarcinogenic process remains to be studied.

The quantitation of altered hepatic foci during multistage hepatocarcinogenesis in the rat: transforming growth factor alpha expression as a marker for the stage of progression

The experimental three-stage hepatocarcinogenesis protocol of initiation, promotion, and progression, coupled with the analytical technique of stereology, permits quantitative analysis of the carcinogenic process, including the derivation of biologically based risk assessment models. The aberrant expression of the placental isozyme of glutathione S-transferase (PGST) is an efficient marker for initiated, preneoplastic, and neoplastic hepatocytes. Putatively initiated cells and their clonal progeny can be identified, enumerated, and their growth characteristics determined on the basis of their aberrant expression of this protein. A lack of suitable markers has made the identification and quantitation of hepatocytes in the early stage of progression more difficult. One characteristic of cells in the stage of progression is the evolution of relatively autonomous growth. The alteration of growth factor signalling pathways may provide one mechanism for this observation. The expression of transforming growth factor alpha (TGF alpha) is seen in many malignancies. The initiation-promotion-progression protocol has been used to induce progression in the rat liver. The focal expression of TGF alpha was found to correlate with areas of progression in rats subjected to this protocol. The ability to identify and quantitate cells in the stage of progression should facilitate application of the Moolgavkar-Venzon-Knudson model for assessing human risk from carcinogens active at each of these three stages. Validation of this model will require determination of the number and growth characteristics of hepatocytes in the stage of progression.

An immunohistochemical study on the cytogenetic origin of pulmonary multinucleate giant cells in porcine dermatosis vegetans

The origin of pulmonary multinucleate giant cells (MGC) in porcine dermatosis vegetans was studied in six Norwegian Landrace pigs ages 4 (male), 5 (female), 6 (female), 10 (female), and 12 (one male, one female) weeks, using an avidin biotin peroxidase and alkaline phosphatase complex immunohistochemical method on sections of formalin- and ethanol-fixed and frozen tissue specimens. Well-characterized, commercially available antisera/monoclonal antibodies to keratin, vimentin, lysozyme, a monocytic antigen, and a myelomonocytic antigen were used. The immunoreactivity to intermediate-sized filaments in MGC was negative for keratins and positive for vimentin. In addition, a positive reaction was found in alveolar macrophages, chondrocytes, fibrocytes, alveolar lymphocytes, and granulocytes in ethanol-fixed tissue. Marked masking was observed in formalin-fixed tissue. Antilysozyme antiserum gave a positive cytoplasmic reaction in alveolar macrophages and MGC, although the reaction was variable in ethanol-fixed tissue. In trypsinized formalin-fixed tissue, a moderate and more consistent cytoplasmic reaction was observed in alveolar macrophages and MGC. Two monoclonal antibodies that identify human cells of the MMS, EMB 11 and Mac 387, were negative for EMB 11 in ethanol-fixed and frozen sections, whereas Mac 387 showed a positive and specific cytoplasmic immunoreaction in alveolar macrophages and small MGC in ethanol- and formalin-fixed tissue. Pulmonary MGC in dermatosis vegetans are derived from mesenchymal cells, and substantial evidence is provided in support of a monocyte/macrophage origin based on a positive reaction for lysozyme and a myelomonocytic antigen. The importance of adequate fixatives for immunohistochemical demonstration of cell-specific markers is clearly shown.

Hepatocellular cancer development in spleen of syngenic rats after transfer of potential precursor hepatocytes

An in vitro-in vivo approach was used to examine the effect of selected cell proliferation on the progression to cancer. Liver cells isolated from rat donors with nodular livers were kept for 3 h in vitro, transferred to spleens and livers of syngeneic recipients and assessed at 4 and 10 months for evidence of cancer. Ten months after transfer of one million nodular liver cells (40% were GST-P + hepatocytes) to each of 50 recipients, 13 rats developed 21 hepatocellular cancers in their spleens (11 cancers) and livers. The latency to cancer was shortened by exposure to 2-acetylaminofluorene of the recipient rats at the time of hepatocyte transfer.

Immunohistochemistry of solid tumors. Brief review of selected problems

The immunohistochemical approach to tumor typing has dramatically improved our possibilities in the objective diagnosis of neoplasms. Use of optimal material and careful techniques will help to maintain good sensitivity, specificity, and reproducibility of immunohistochemistry. However, the complexity of antigen patterns in tumors, and lack of comprehensive knowledge about them requires caution in the interpretation of results, and may prohibit the simple use of diagnostic algorithms. Especially it is not certain whether the results obtained from typical representatives of various tumor entities will pertain to borderline cases and to undifferentiated variants of the same entities. Use of panels of antibodies rather than the use of single "diagnostic" tests will help to avoid these diagnostic pitfalls. However, all tumor types do not have immunohistochemically distinctive features. This emphasizes the need to use other techniques in such cases, and also suggests that some entities, such as malignant fibrous histiocytoma, are from the point of view of immunohistochemistry diagnoses only made by exclusion rather than being specifically diagnosable entities. All diagnostic immunohistochemistry has to be interpreted in the context of standard histological examination.

Cycle- and function-related changes in lectin binding to human endometrium: a histochemical study with pronase treatment

Forty-eight endometrial biopsy specimens were obtained during a normal menstrual cycle, during pregnancy and from patients with dysfunctional bleeding. The specimens were examined for Peanut (PNA), Soybean (SBA), Vicia villosa (VVA), Phytohem- (PHA), Lens culinaris (LCA) and Concanavalin (succ. Con A) agglutinin binding. The study was performed on paraffin sections using the pronase digestion and either the peroxidase-antiperoxidase or the avidin-biotin-peroxidase method. Cycle-related changes of the PNA, SBA, VVA, and to some degree PHA binding, were based on the transfer of the cytoplasmic reaction toward the glandular lumena. PNA + and SBA + material moved to the cell surface at the transition of the follicular and luteal phase and before the basal vacuolization appeared. Functional disturbances mainly influenced the intensity of the reaction. It was true only for those lectins, whose binding pattern showed cycle-related changes. In curettings from patients with a prolonged menstrual cycle the lectin binding seen in normal late secretory endometrium was absent or significantly diminished. Lectin binding to the endometrial surface epithelium was variable; PHA was the only lectin, the binding pattern of which followed cyclic changes in the glycocalyx, detected previously by means of PAS and alcian blue methods.

Development and evaluation of a system of microencapsulation of primary rat hepatocytes

To determine the in vitro function of microencapsulated hepatocytes, viable hepatocytes were isolated from rats and encapsulated within biocompatible alginate-polylysine membranes for in vitro studies. Urea formation, prothrombin and cholinesterase activity, the incorporation of tritiated leucine into intracellular proteins and the immunolocation of synthesized albumin were monitored in culture. Despite a decrease in some of these activities, the cultured hepatocytes continued to function throughout the 5-week observation period, producing and excreting urea, prothrombin and cholinesterase activity into the medium. In addition, albumin could be demonstrated within encapsulated hepatocytes for up to 5 weeks. Scanning and transmission electron microscopy showed the cells to be embedded within the alginate matrix and to retain a globular shape.

The effects of progressive formaldehyde fixation on the preservation of tissue antigens

A wide variety of fresh post-mortem tissues was fixed in 4% formaldehyde for 6 hours, 1, 3, 7, 14 and 30 days to simulate possible fixation schedules in the diagnostic laboratory, before processing through alcohol and chloroform. The immunoreactivity of paraffin-embedded sections to 25 monoclonal and polyclonal antibodies commonly used in tissue diagnosis was tested employing an avidin-biotin-peroxidase technique. There was a distinct fall-off in the staining of many antigens including the lymphocyte antigens LN1, LN2, LN3 and UCHL1 after 3 days of fixation and the intermediate filament proteins vimentin, desmin and neurofilaments failed to be labelled by monoclonal antibodies after 1 day and only variable staining for the cytokeratins was retained. S100 protein, prostate specific antigen, thyroglobulin and carcinoembryonic antigen were more resilient and showed weak staining after 14 days exposure to formaldehyde. Trypsinization improved the staining for cytokeratins, neurofilaments, desmin and Factor VIII-related protein, but for other antigens, the immunoreaction was weaker and background staining was increased. For the effective application of immunohistochemical staining as a diagnostic tool, the duration of formaldehyde fixation should be kept to a minimum and enzyme digestion should only be judiciously employed for selected antigens.

Identification of the putative first cellular step of chemical hepatocarcinogenesis

A first cellular step of chemical hepatocarcinogenesis is characterized by identifying hepatocytes with preneoplastic properties: positivity for glutathione transferase-P or GST-P+, cell proliferation marked by bromodeoxyuridine or BUDR+, resistance to hepatotoxins and persistence. Hepatocellular doublets, both GST-P+ and BUDR+, are located immunohistochemically 4 days after a single dose of diethylnitrosamine, 25 mg/kg, using antibodies bound to different chromogens. GST-P+ hepatocytes proliferate after selection for resistance to 2-acetylaminofluorene, and persist in the absence of selection for 6 weeks. The actual probability of the same cell being GST-P+ and BUDR+ is 200 times the expected value implying close links between cell proliferation and GST-P expression at initiation.

Immunostaining of intermediate filament proteins in paraffin sections. Evaluation of optimal protease treatment to improve the immunoreactivity

Different protocols of protease (pepsin) treatment were compared in the immunostaining for intermediate filament (IF) proteins in formaldehyde-fixed and paraffin-embedded tissues. Without protease treatment, the immunoreactivity for all IF proteins was poor in such material. Appropriate pepsin pretreatment improved the immunoreactivity of formaldehyde-fixed tissues for all types of IF proteins, except for the 68 K neurofilament protein, which could not be immunostained with the antibody used. The optimal time for the pepsin treatment was varying in different tissues, and too long treatment caused progressive loss of immunostaining. Thus, for instance when demonstrating cytokeratins, renal adenocarcinomas were more sensitive to protease and needed a shorter treatment than other carcinomas. Therefore, a nonoptimal protease treatment protocol may cause false negative results and false cell type selective IF immunostaining. Prolonged fixation made it necessary to prolong the protease treatment. In tissues fixed up to four years in formalin, cytokeratin immunoreactivity could still be restored by a long pepsin treatment (up to 2-3 hours). For most tissues fixed for 24 hours in formaldehyde, an optimal protocol was the following: 0.05% pepsin (2 U/ml) in HCl, pH 1.8, at +37 degrees C for 20-30 minutes. The protease treatment did not produce false positive results. Alcohol-fixed material was good for IF immunostaining without any protease treatment, but such tissue blocks mostly lost the immunoreactivity during long term storage.

A comparative study of PAS-phosphotungstic acid-Diamine Supra Blue FGL and immunological reactions for type I collagen

Immunohistochemical techniques proved valuable in histological studies of various types of collagens. However drawbacks include non-specific reactions of antibodies, masking of antigens, and the high cost of antibodies. This study was undertaken to ascertain the specificity of the PAS-phosphotungstic acid-Diamine Supra Blue FGL (PAS-PTA-DSB-FGL) reaction for type I collagen, differentiating it from other collagens. Duplicate series of methacarn-fixed sections of various tissues were treated with the PAS-PTA-DSB FGL reaction and the peroxidase-antiperoxidase (PAP) technique for type I collagen and the staining patterns were compared. Fibers binding the blue dye were found only at sites reacting with antibodies against type I collagen. These observations indicate that the PAS-PTA-DSB FGL procedure is suitable for visualization of type I collagen, e.g. in screening of large series of sections and in the practice of surgical and autopsy pathology.

Antigen preservation in microwave-irradiated tissues: a comparison with formaldehyde fixation

A wide range of immunoreactive antigens commonly investigated in diagnostic pathology were evaluated in tissues subjected to fixation by microwave irradiation in normal saline to 63 degrees C. All of the 23 antigens studied were well preserved and compared with corresponding tissues conventionally fixed by formaldehyde for periods of 16 and 18 h, respectively, immunostaining in microwave-irradiated tissues was clearly superior, being more intense and also more extensive. Proteolytic digestion was not necessary for irradiated tissues except for the staining of cytokeratins and desmin. It was also possible to stain for Leu-14 (CD22) and Leu-1 (CD5), whereas these lymphocyte antigens were lost during formaldehyde fixation. Cytomorphological details were well preserved in the rapidly-fixed irradiated tissues.

Microencapsulated hepatocytes for bioartificial liver support

Free hepatocytes, harvested from normal rat livers by portal vein collagenase perfusion, were encapsulated within alginate-polylysine membranes and served as a liver support system. The encapsulated hepatocytes remained viable and were able to synthesize protein for up to 3 weeks in culture. Allografts of encapsulated hepatocytes replaced the function of a damaged liver and reduced the mortality rate among rats with galactosamine-induced fulminant hepatic failure.

Significance of keratosis and dyskeratosis for classifying hyperplastic aberrations of laryngeal mucosa

Retrospective study of 325 tissue samples of hyperplastic aberrations of the laryngeal mucosa by means of light and electron microscopy and immunohistochemical methods has demonstrated that superficial keratinization is not important for determining changes into precancerosis or "risky epithelium" or even for the progress from hyperplastic aberrations to carcinoma. The degree of keratinization of the epithelial surface in all three forms of hyperplastic aberrations is almost the same. In grouping the hyperplastic aberrations into "precanceroses" or "risky epithelium," the following morphologic changes have to be considered as extremely important factors: the occurrence of dyskeratotic cells, the basalification of the epithelium, and the response of the organism in the form of infiltration of immunocompetent cells in the subepithelial stroma.

Lectin binding patterns in salivary glands treated with amylase

Lectin binding patterns of ConA (Glc, Man), PNA and SBA (Gal, GalNAc), RCA-I (Gal) DBA (GalNAc), WGA (GlcNAc), and UEA-I (Fuc) in the major salivary glands of mice, rats, hamsters, and guinea pigs were reported using paraffin sections subjected to alpha-amylase treatment at 1, 3, and 6 h digestions. Lectin staining following treatment with amylase was generally enhanced in acinar, duct, and GCT cells. However, increasingly different reactions were obtained depending upon the lectins used, the various salivary glands from different specimens treated, and the different properties of the serous, mucous, and sero-mucous cells in the histologic sections. The lectins that demonstrated rather markedly increased staining were ConA, PNA, SBA, WGA, and UEA-I, whereas RCA-I and DBA increased little in comparison, or actually decreased. It appears from these findings that complex carbohydrates within murine salivary glands contained large amount of glucose, mannose, galactose, and N-acetyl galactosamine residues. The basement membranes of glandular cells in salivary glands demonstrated markedly positive ConA staining following alpha-amylase digestion.

Distribution difference of lectin binding in salivary gland treated with sialidase and trypsin

Histochemical evaluation of complex carbohydrates in the salivary glands from rodents following sialidase and trypsin treatment were reported by the use of lectins binding technique which specifically link to corresponding sugar residues in macromolecules. Lectin staining in salivary gland generally increased following 1 h sialidase treatment, particularly in guinea-pig specimens. Lectin staining followed by treatment of trypsin (30 min) showed in increase in staining which is characteristic of UEA-I lectin. In long duration treated sections, by either sialidase or trypsin, lectin staining usually decreased in salivary glands. In the present study, complex carbohydrates of salivary glands may be hydrolyzed and degraded by sialidase and trypsin treatments, and lectin binding affinity is then also enhanced due to exposed sugar residues in complex carbohydrates.

Different bindings to lectin in human submandibular gland after enzymatic digestion

Lectin binding affinities were described in human submandibular gland (SMG) in the paraffin sections following alpha-amylase, sialidase, and trypsin digestions. Lectins in the present study were used Con A (Glc, Man binding lectins), PNA, and SBA(Gal, GalNAc), RCA-1(Gal), DBA(GalNAc), WGA(GlcNAc), and UEA-1(Fuc). Lectin stainings in serous and mucous acinar cells and ductal epithelia were reported to compare enzyme treated and nontreated sections. Amylase treatment showed increasing Con A staining in connective tissue fibers and no marked changes in SMG to lectin bindings. Sialidase digestion was characteristically intense in PNA and SBA bindings in SMG cells, and also enhanced staining to UEA-1 in serous and duct cells and to WGA in mucous and duct cells were noted. Trypsin digestion indicated a slight increase to Con A binding, and was relatively strong to UEA-1 in serous and duct cells and a little strong to WGA. The results suggested that SMG serous cells contain higher amounts of Gal, GalNAc, and Fuc residues; and mucous cells were also abundant in Gal, GalNAc, and GlcNAc residues.

A comparative study of myosins and prekeratin in epithelial cells of methacarn-fixed tissues

Around the turn of the century, tonofibrils and contractile myofibrils were observed within the same cells. These findings have been largely forgotten. To clarify the topical relations of these proteins in epithelial cells, duplicate sections of methacarn-fixed human and canine tissues were treated with the tannic acid-phosphomolybdic acid (TP)-Levanol Fast Cyanine 5RN reaction for myosins and the PAP technic for prekeratin, respectively. In bronchi, lingual and sweat glands, liver and pancreas, myosin was confined to the terminal bar-terminal web system, including pericanalicular layers. Prekeratin occurred throughout the epithelium of bronchi and ducts; secretory cells showed little or no reaction. Observations on myosin in kidney confirmed data by Harper et al. (1970). The PAP technic colored transitional epithelium and collecting tubules intensely; convoluted tubules did not react. Staining of segments of Henle's loops varied from case to case. Both reactions colored thymic epithelial cells. In myoid cells of Hassall's corpuscles myosin was gradually replaced by prekeratin and keratin. Basal cells of epididymis reacted strongly with the PAP technic, but did not contain myosin. Prekeratin is apparently identical with epidermin, whose composition and structure were well known in the 1950's. Epidermin undergoes chemical changes as cells move from the stratum basale to the stratum corneum. According to DAKO, the antibodies used in this study were prepared with prekeratin extracted from stratum corneum. Data in the literature and observations in this investigation indicate that some samples of antibodies do not react with all tonofilaments.(ABSTRACT TRUNCATED AT 250 WORDS)

On the chemistry of formaldehyde fixation and its effects on immunohistochemical reactions

Formalin has been recommended as an innocuous fixative for immunohistochemistry. However, several studies demonstrated impairment or blocking of antigenic activity of certain proteins. Formalin fixation was discovered accidentally by F. Blum in 1893 and its deleterious effects on various tissue structures were discussed extensively during the following decades. More recently, some authors assumed that formaldehyde bound to tissues can be largely or completely removed by washing and dehydration. According to chemical data, formaldehyde forms highly reactive methylols with uncharged amino groups. Such methylol groups yield methylene bridges with suitably spaced amides, arginine and aromatic amino acid sidechains. Only loosely bound formaldehyde is removed by washing for several hours. Residual bound formaldehyde cannot be dislodged by washing for weeks, but some formaldehyde is gradually removed when tissues are stored in water for an extended number of years. Methylene crosslinks resist treatment with high concentrations of urea, and can be broken only by drastic hydrolysis. It appears unlikely that such firmly bound formaldehyde is removed by conventional washing and dehydration procedures used in histochemistry. The superiority of methacarn, alcohol or acetone over formaldehyde fixation for immunohistochemical demonstration of prekeratin, myosin, type I and type IV collagen, laminin and fibronectin can be ascribed to the irreversible alterations of tissue proteins by formaldehyde.

Lectin-binding patterns in the developing tooth

The lectin-binding patterns of the cells involved in amelogenesis and dentinogenesis in developing teeth of rats were studied. Undifferentiated odontogenic epithelia exhibited very slight staining with almost all of the lectins examined. The lectin-staining affinities of secretory ameloblasts could be divided into two categories: Concanavalin-A (Con-A), Wheat germ agglutinin (WGA) and Soybean agglutinin (SBA) binding occurred from the middle to apical cytoplasm, whereas Ricinus communis agglutinin-I (RCA-I) and Ulex europeus I (UEA-I) binding predominated in the basal regions. The cells of the stratum intermedium exhibited relatively strange lectin staining, which appeared to be dependent on ameloblastic maturation. The basement membranes in undifferentiated epithelia were markedly positive for lectin binding. Odontoblasts showed moderate Con-A staining on the apical side of the cells, as well as slight-to-moderate reactions with WGA and SBA. Pulp cells and dental papillae showed slight-to-moderate lectin staining, and predentin and dentin were also moderately positive for Con-A and RCA-I binding and slightly so for WGA and SBA. The lectin-binding affinities were enhanced during the formation of enamel and dentin, and appeared to be dependent on the degree of cellular differentiation in ameloblasts and odontoblasts.

Evaluation of nine different fixatives. 2. Preservation of IgG, IgA and secretory component in an artificial immunohistochemical test substrate

An artificial substrate was developed for quantitative testing of the ability of various fixatives to preserve the reactivity of IgG and IgA isotypes (gamma and alpha chains) and the secretory component (SC) of secretory IgA as model antigens. Polymerized normal rabbit serum was used as matrix and defined amounts (10-0.1 g/l) of antigen were incorporated into it by diffusion before fixation and paraffin embedding. The various fixatives comprised alcohol, routine formalin, glutaraldehyde(1%)-formalin, Baker's formol calcium, formol sublimate, acetic acid(2%)-formol saline, Bouin's fluid, Susa fixative, and carbodiimide. The detection sensitivity afforded by these fixatives was defined as the immunofluorescence staining end point. Compared to the reference value obtained with alcohol (gamma and alpha chains, 0.06 g/l of IgG and IgA; SC, 0.12 g/l of colostral IgA), an antigen concentration at least 8 times higher was necessary for detection with most of the cross-linking fixatives. Bouin's and Susa fixatives were peculiar in that they required more than 150 times higher antigen concentration for detection of IgG but only 3-8 times higher for IgA. The determined sensitivities were compared with the immunofluorescence performance results obtained on human tissues prepared with the same fixatives; excepting carbodiimide (which produced unacceptable autofluorescence of the substrate matrix) a remarkably good correlation was found with regard to IgG- and IgA-producing cells (especially of the former isotype) and secretory epithelium (IgA and SC). However, the latter result depended on pronase treatment of the tissue sections to unmask epithelial antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to intermediate filament proteins in the diagnosis and classification of human tumors

Immunohistochemistry of intermediate filaments (IF) is a new and important way to evaluate the epithelial, mesenchymal, muscular, glial, or neural differentiation in tumors. This is based on the stable cell-type-specific expression of IF proteins in normal and neoplastic tissues. Immunohistochemical studies with antibodies to intermediate filaments have also given new perspectives in the histogenesis and biologic nature of many tumors. This article reviews both the recent findings and the authors' experience in the use of intermediate filament antibodies in tumor diagnosis and classification.