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Biomedical subjects

E Scherer

Publications and source records attributed to E Scherer.

At least 37 records · Page 2Linked to original sources
PubMed1990

Improved immunocytochemical staining of carcinogen-DNA adducts by a capillary slot block system.

We developed an immunocytochemical protocol in which incubation occurs in a capillary slot instead of the conventional horizontal drop. Slots of constant width were formed by placing slides on top of each other with parafilm spacer layers in between. Cryostat or semi-thin plastic-embedded sections were cut from organs of carcinogen-treated experimental animals. Carcinogen-DNA adducts were visualized in the affected nuclei by a double peroxidase-antiperoxidase method using rabbit antisera specific for certain DNA adducts formed. The staining in capillary slot blocks offered better staining reproducibility than the conventional method. This is particularly important when the staining intensity must be quantified. In addition, handling of the blocks was substantially less laborious than the individual treatment of slides, making this protocol especially suitable for larger series of slides. Other applications for the capillary slot block protocol should be enzyme histochemistry and in situ hybridization.

Animals↗
PubMed1989

Immunocytochemical analysis of O6-alkylguanine shows tissue specific formation in and removal from esophageal and liver DNA in rats treated with methylbenzylnitrosamine, dimethylnitrosamine, diethylnitrosamine and ethylnitrosourea.

The formation and repair of carcinogen-DNA adducts in esophagus and liver of rats treated with a single i.p. dose of methylbenzylnitrosamine (MBN), dimethylnitrosamine (DMN), diethylnitrosamine (DEN) or ethylnitrosourea (ENU) has been studied using peroxidase immunocytochemistry to visualize O6-alkylguanine in DNA of individual cells. After MBN O6-methylguanine (O6-MeG) specific nuclear staining was only present in the target tissue for tumor induction, the esophageal epithelium. Part of the adducts persisted for at least 72 h. No O6-MeG could be detected in liver. DEN, a carcinogen in liver and esophagus, led to DNA modification of esophageal epithelial cells, and liver parenchymal and non-parenchymal (Kupffer and sinusoidal) cells of the centrilobular area. O6-EtG was removed within 72 h from both liver cell populations. A similar distribution of adduct (O6-MeG) formation was observed in liver after the hepatocarcinogen DMN, but this nitrosamine did not detectably modify esophageal cells. O6-MeG persisted in Kupffer and especially sinusoidal lining cells of liver, consistent with the induction of sarcomas by DMN. The relatively unspecific, directly alkylating carcinogen ENU modified DNA of all cell types to a similar extent. A qualitative correlation was obtained between the tissue specific ability to induce tumors and the formation of O6-alkylguanine (O6-alkylG). Our experiments support the hypothesis that DNA modification is necessary for the initiation of carcinogenesis by chemical carcinogens, and that a low capacity to repair promutagenic lesions, like O6-alkylG, potentiates this process.

Animals↗
PubMed1989

Modulation of putative preneoplastic foci in exocrine pancreas of rats and hamsters. Interaction of dietary fat and coffee.

The effects of coffee and dietary fat (alone and in combination) on the development of preneoplastic lesions in exocrine pancreas were investigated in rats and hamsters, treated with azaserine or N-nitrosobis(2-oxopropyl)amine, respectively. The animals were given the respective diets (5% or 25% corn oil) and coffee (instead of drinking water) within one week after the treatment with carcinogen. At four months postinitiation, the pancreata were quantitatively examined for the number and size of preneoplastic foci. In rats, coffee alone inhibited growth of acidophilic foci and, moreover, slightly inhibited the positive modulating effect of fat on growth of these foci, pointing to a negative rather than a positive interaction between these two life-style factors. In hamsters, coffee alone enhanced growth of cystic foci, whereas fat alone enhanced growth of ductular foci. An interaction between fat and coffee on pancreatic carcinogenesis in hamsters could not be demonstrated.

Animals↗
PubMed1989

Modulation of dietary fat-promoted pancreatic carcinogenesis in rats and hamsters by chronic coffee ingestion.

The effect of chronic coffee ingestion on dietary fat-promoted pancreatic carcinogenesis was investigated in rats and hamsters. Rats were given a single i.p. injection of 30 mg azaserine per kg body weight at 19 days of age. Hamsters were injected s.c. with 20 mg N-nitrosobis(2-oxopropyl)amine (BOP) per kg body weight at 6 and 7 weeks of age. The animals were fed a semi-purified diet high in unsaturated fat (25% corn oil) either in combination with coffee or not. Coffee was provided instead of drinking water. A separate group maintained on a diet low in unsaturated fat (5% corn oil) was included as extra controls. The rats and hamsters were given their diets and coffee after treatment with carcinogen. Terminal autopsy of rats was 15 months after azaserine treatment and of hamsters 12 months after the last injection with BOP. In rat pancreas, the numbers of adenomas and carcinomas were significantly lower in the group maintained on the combination of a high-fat diet and coffee than in the high-fat group without coffee, while in the latter group the number of adenomas and carcinomas had significantly increased as compared to the low-fat controls. In hamsters, the number of ductal/ductular adenocarcinomas had significantly increased in the high-fat group as compared to the low-fat controls. The inhibitory effect of coffee on dietary fat-promoted pancreatic carcinogenesis was also noticed in this species but was less pronounced than in rats. It was concluded that chronic coffee consumption has an inhibitory effect on dietary fat-promoted pancreatic carcinogenesis in rats and hamsters. More research is needed to elucidate the mechanism by which coffee (constituents) modulates carcinogenesis.

Adenocarcinoma↗
PubMed1989

Modulation of dietary fat-promoted pancreatic carcinogenesis in rats and hamsters by chronic ethanol ingestion.

The effect of chronic ethanol ingestion on dietary fat-promoted pancreatic carcinogenesis was investigated in rats and hamsters. Rats were given a single i.p. injection of 30 mg azaserine per kg body wt at 19 days of age. Hamsters were injected s.c. with 20 mg N-nitrosobis(2-oxopropyl)amine (BOP) per kg body wt at 6 and 7 weeks of age. The animals were fed a semi-purified diet high in unsaturated fat (25% corn oil) either separately or in combination with ethanol. Ethanol was provided in drinking water at a concentration of 10% (w/v). A separate group maintained on a diet low in unsaturated fat (5% corn oil) was included as extra controls. The rats and hamsters were given their diets and received ethanol via their drinking water after treatment with carcinogen. Terminal autopsy of rats was 15 months after azaserine treatment and of hamsters 12 months after the last injection with BOP. Dietary fat was found to enhance pancreatic carcinogenesis in both rats and hamsters. In rats, ethanol slightly enhanced the multiplicity but not the incidence of malignant tumours, while in hamsters ethanol did not show any modulating effect on dietary fat-promoted carcinogenesis. It was concluded that dietary fat-promoted pancreatic carcinogenesis as observed in the animal models applied is not significantly modulated by chronic ethanol ingestion.

Animals↗
PubMed1989

Single cell analysis of DNA modifications induced by chemical carcinogens and cytostatic drugs.

Antibodies recognizing specific DNA modifications allow the immunocytochemical visualization and quantification of these modifications at the level of the individual cell. Thus, the formation and repair of DNA adducts induced by chemical mutagens and carcinogens and by cytostatic drugs can be studied in very small samples in relation to e.g. cell type and tissue localization. A number of existing and potential applications in the fields of chemical carcinogenesis, chemical mutagenesis, experimental chemotherapy and molecular epidemiology are illustrated.

Animals↗
PubMed1988

[The role of postoperative radiotherapy in the treatment of hypernephroid carcinoma].

The following results can be derived from the clinical and radiobiological literature as well as from the authors's own experiences with 91 patients analyzed retrospectively and evaluated with respect to their risk factors. 1. A postoperative irradiation is very probably sensible in patients with tumor perforation through the renal capsule (T3/T4) and with venous or lymph node manifestations. 2. The operation method is essential, above all the transabdominal technique and the quality of lymph dissection. 3. Prospective studies are necessary in order to clear up the role of radiotherapy in patients with lymph node manifestations and the other two risk factors mentioned in item 1. 4. Further studies on the tumor biology of the hypernephroid carcinoma are necessary in order to gain prognostic criteria allowing a pretherapeutic sensitivity recognition. 5. The effect of a supplementary radiotherapy can be only that of local recurrence prevention in case of a locally advanced tumor and the absence of demonstrable remote metastases. This seems justified, because the local recurrence rate in our own patients was only 3.3%.

Carcinoma, Renal Cell↗
PubMed1988

Immunocytochemical analysis of DNA adducts in single cells: a new tool for experimental carcinogenesis, chemotherapy and molecular epidemiology.

The immunocytochemical staining of carcinogen-DNA adducts by a double peroxidase-anti-peroxidase (PAP) method is critically described. It is a powerful new tool for the investigation of the initial processes of chemical carcinogenesis--such as metabolic activation of carcinogens, and modification/repair of DNA--at the level of individual, putative target cell types. It is the method of choice if the cell populations are too small for determination of adducts in isolated DNA, or if information on the tissue distribution of DNA damage is needed. Advantages of the peroxidase staining endpoint over immunofluorescence are its stability on storage of slides and the possibility of evaluation by a conventional microscope. First attempts to quantify staining intensity by microdensitometric equipment are described.

Carcinogens↗
PubMed1988

Immunocytochemical localization of DNA adducts in rat tissues following treatment with N-nitrosomethylbenzylamine.

Immunocytochemical visualization of O6-methylguanosine (meGua) and 7-meGua shows that DNA methylation by N-nitrosomethylbenzylamine(NMBzA) occurs not only in the target organs for tumour induction by this nitrosamine, the oesophagus and (occasionally) the tongue, but also in other tissues (liver, lung, trachea, tracheal glands and nasal cavity) for which no tumour induction by NMBzA has been reported. Thus, the organotropic carcinogenic action of NMBzA cannot be exclusively ascribed to differences in levels of DNA methylation. Additional determinants of the cancer risk in extra-oesophageal tissues could be the small size of the NMBzA-activating target cell population and a low proliferative activity.

Animals↗
PubMed1988

Application of antibody methods to the detection of aflatoxin in human body fluids.

Four different approaches to the quantification of human exposure to aflatoxins (AF) are presented: (i) analysis of urinary AF metabolites and DNA adducts, (ii) assay of AF bound to blood proteins and to lymphocyte DNA, (iii) immunocytochemical localization of AF in individual cells, and (iv) detection of AF in human breast milk. The potential applications of these approaches for assessing the role of both AF and hepatitis B virus (HBV) in primary hepatocellular carcinoma (HCC) are presented. The advantages and limitations of the methods for use in large-scale epidemiological studies are discussed, with particular attention to sensitivity.

Aflatoxins↗
PubMed1987

Immunocytochemical detection of interaction products of cis-diamminedichloroplatinum(II) and cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) with DNA in rodent tissue sections.

Calf thymus DNA was modified in vitro by cis-diamminedichloroplatinum(II) (cisDDP), complexed with methylated bovine serum albumin and used to immunize rabbits. The anti-cisDDP-DNA antiserum obtained was applied in a double peroxidase-antiperoxidase staining procedure to localize cisDDP-DNA and cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA)-DNA interaction products in cryostat tissue sections of mice and rats. Rats received cisDDP (0-10 mg/kg) and were killed after 24 h. Mice received cisDDP (0-15 mg/kg) or CBDCA (200 mg/kg), and were killed after 2 h-162 days. For each time-dose combination two mice or one rat were used; agents were given i.p. Specific nuclear staining was observed in all tissues examined from cisDDP- or CBDCA-treated animals. No significant nuclear staining could be observed in tissue sections from control rats and mice. The extent of staining after cisDDP was dose and time dependent. The lowest dose of cisDDP after which specific nuclear staining could be detected varied from tissue to tissue [e.g., 0.1 mg/kg, pancreas (mouse); 0.5 mg/kg, liver, kidney (mouse, rat)]. The longest time interval after a single dose of 6 mg/kg cisDDP in which adducts could be visualized also depended on the tissue and varied between 9 days (spleen, testis) and 162 days (kidney). The staining intensity in liver and kidney, measured microdensitometrically, decreased relatively fast in the first days after treatment, but much slower thereafter. In the kidney, cisDDP-induced DNA modification showed regional variation: inner cortex greater than outer cortex greater than medulla (rat) and cortex greater than medulla (mouse). In the mouse kidney, a small subpopulation of tubular cells in close association with the renal corpuscles showed a remarkably high staining intensity after both cisDDP and CBDCA administration. Tissues that showed clear cisDDP-induced histological alterations (kidney, pancreas, testis, and duodenum) also showed moderate to high levels of cisDDP-DNA interaction products. A correlation between cell damage (measured histologically) and cisDDP-DNA binding within one tissue type was demonstrated in the rat inner renal cortex, the murine renal cortex, and in duodenal epithelial cells of both mice and rats.

Animals↗
PubMed1987

Relationship among histochemically distinguishable early lesions in multistep-multistage hepatocarcinogenesis.

The evolution of liver cancer is discussed on the basis of the multistep-multistage hypothesis. In rat liver the sequential generation of the tumor cell via intermediate precancerous cell populations is strongly supported by histopathological evidence (focus-in-focus lesions) indicating precursor-product relationships, inducibility of progression in an initiation-promotion-initiation type of experiment, and by the kinetics of focus and tumor induction. The formation of mouse liver tumors, either spontaneously in susceptible strains, or induced by a short initiating dose of carcinogen, may follow the same general pathway. The frequent observation of focus-in-focus patterns in mouse and the kinetic characteristics of that process favour the sequential development of cancer cell formation. The kinetic analysis suggested that (large) basophilic foci in mouse liver may be the result of spontaneous progression from an initiated cell population which is represented by either the small basophilic foci or by a cell population generally not recognized due to the lack of a suitable marker reaction. Furthermore, the basophilic foci may represent the precursor cell population leading by another step of spontaneous progression to hepatocellular carcinoma.

Animals↗
PubMed1987

Immunocytochemical studies on the formation and repair of O6-alkylguanine in rat tissues.

The immunocytochemical visualization of the carcinogen-DNA adducts O6-ethylguanine (O6-etGua) and O6-methylguanine (O6-meGua) in histological sections of a large series of rat tissues, including liver, pancreas, testis and oesophagus, is described. In the liver of rats treated with N-ethyl-N-nitrosourea (ENU), N-nitrosodiethylamine (NDEA) or N-nitrosodimethylamine (NDMA), large differences were found in the formation and/or repair of O6-alkylGua between different cell types, between hepatocytes of different localization, and also between normal and precancerous hepatocytes. Heterogeneity of O6-etGua formation and repair was also found in pancreatic tissue of rats treated with ENU. O6-etGua was relatively persistent in nonparenchymal liver cells, pancreatic islet cells, spermatogonia, renal glomeruli and smooth-muscle cells. Our aim is to extend the immunocytochemical analysis to other DNA adducts, and ultimately to human tissues.

Animals↗
PubMed1986

Adenosine triphosphatase, a new marker for the differentiation of putative precancerous foci induced in rat pancreas by azaserine.

Enzyme-histochemical investigation of pancreatic carcinogenesis in male Wistar rats treated at the age of 19 days by a single dose of 30 mg azaserine/kg body wt led to the detection of a new 'marker' for the recognition of foci of atypical acinar cells: the Mg2+-dependent ATPase. The two well-known populations of pancreatic atypical acinar cell foci, classified histologically as basophilic and acidophilic foci, showed a decreased and strongly increased ATPase reaction, respectively. The enhanced enzyme activity of the acidophilic foci has been characterized as unspecific nucleoside polyphosphatase. To validate the new marker, comparative quantitative evaluation was performed on haematoxylin and eosin-stained paraffin sections and ATPase-stained cryostat sections of the same pancreata of 25 azaserine-treated rats. Evaluation of basophilic ATPase-deficient foci of small diameter was more reproducible in haematoxylin and eosin-stained sections, while small acidophilic strongly ATPase-positive foci could be detected more reliably by the ATPase staining technique. The number of foci/cm3 pancreas was similar for both staining techniques above a focus diameter of about 100 microns for basophilic foci and 200 micronfor acidophilic foci. There were more acidophilic than basophilic foci/cm3 pancreas, and the acidophilic foci had significantly larger mean focal diameters than the basophilic foci. Together with the strong acidophilic staining of the latter emerging adenoma, this suggests that the acidophilic foci represent a neoplastic cell population progressing eventually to pancreatic carcinoma. The new 'marker' enzyme ATPase may greatly facilitate further investigations into the role of these putative preneoplastic lesions in pancreatic carcinogenesis.

Adenosine Triphosphatases↗
PubMed1986

Modulation of putative preneoplastic foci in exocrine pancreas of rats and hamsters. I. Interaction of dietary fat and ethanol.

The effect of dietary fat and ethanol and their interactions on the development of putative, preneoplastic foci in exocrine pancreas was investigated in rats and hamsters. Rats were given a single i.p. injection of 30 mg azaserine per kg body wt at 19 days of age. Hamsters were injected s.c., with 20 mg N-nitrosobis(2-oxopropyl)amine (BOP)/kg body wt at 6 and 7 weeks of age. The animals were fed a low fat (LF) control diet (5% corn oil) or a high fat (HF) diet (25% corn oil). Ethanol was provided in drinking water at a 15% (w/v) concentration. The animals were given the respective diets and ethanol after the treatment with carcinogen. At 4 months post-initiation, the pancreata were quantitatively examined for the number and size of preneoplastic foci. In rats, acidophilic as well as basophilic foci were subject to modulation by HF and ethanol. The results point to a specific promoting effect of unsaturated fat on the growth potential of azaserine-induced acidophilic acinar cell foci in rat pancreas. There was no evidence of an interaction between HF and ethanol as far as acidophilic foci are concerned. Evaluation of the number and size of the basophilic foci demonstrated an enhancing effect of ethanol on the modulation of pancreatic carcinogenesis by fat, pointing to a possible interaction between these two lifestyle factors. This suggestion was supported by the finding that six out of 20 rats in the HF with ethanol group exhibited a carcinoma in situ, whereas in the HF and in the ethanol group such an advanced lesion was found in one animal only. Unlike in rats, ethanol had no modulating effect on number and growth of putative, preneoplastic lesions in hamsters, either in combination with LF or in combination with HF. A HF diet, however, caused a significant increase in number as well as an increase in percentage of pancreatic tissue occupied by early lesions induced in hamster pancreas by BOP.

Adenosine Triphosphatases↗
PubMed1986

[Esophageal carcinoma: the final results of a multicenter and controlled German study with misonidazole and radiation].

A prospective, randomized clinical study on 91 patients with squamous cell carcinoma of the oesophagus was undertaken in order to investigate the radiosensitizing effect of misonidazole. After histologic verification and extensive diagnosis, the greater tumor region was at first irradiated during 2.5 weeks with ten fractions of 3 Gy each up to a target volume dose of 30 Gy. Prior to each fraction, patients received randomly misonidazole or a placebo in a dose of 1 g/m2 body surface. Then they were presented to the oncologic surgeon in order to decide whether a surgical resection should be performed or not. Following to this operation no further radiotherapy was performed. However, if a surgical intervention did not take place, radiotherapy was continued without administration of misonidazole or placebo up to a target volume dose of 60 to 70 Gy. There was no evidence of neurotoxic side effects or modifications of the blood count and some laboratory parameters caused by misonidazole. As to recurrence-free interval and survival time, no significant differences were found between the different therapy groups, so that a radiosensitizing effect of misonidazole was not demonstrated in this study. Regarding several positive phase II studies with misonidazole, some hopes had been placed in this study because at present the therapeutic situation in oesophagus carcinoma is extremely unsatisfactory. Even the combination of a most sophisticated operation technique prior or following to irradiation could not essentially improve the poor healing rates.

Adolescent↗