Complication and local recurrence rate after endoscopic resection of large high-risk colorectal adenomas of ≥3 cm in size.

PURPOSE: Endoscopic resection is a widely used technique for treatment of large colorectal adenomas, but few data are available including only lesions larger than ≥2 cm. The aim of this study is to evaluate the complication and recurrence rate after endoscopic resection of high-risk colorectal adenomas ≥3 cm in size. METHODS: Retrospective analysis of a prospectively maintained database of patients undergoing polypectomy of large colorectal polyps of ≥3 cm. RESULTS: In 341 patients, 360 colorectal adenomas with a mean size of 3.9 cm were resected endoscopically. In 25 patients, a complication including 22 delayed bleedings (6.5%) and three perforations (0.9%) occurred. Single-variate analysis showed an increasing risk of complications for larger adenomas (3.9 vs. 4.6 cm; p ≤ 0.05). Two hundred twelve patients with 224 adenomas had undergone at least one documented follow-up endoscopy with a medium follow-up period of 16 months. In 95 resected lesions (42.4%), a residual adenoma occurred in the first follow-up colonoscopy (n = 88, 92.6%) or a recurrent adenoma occurred after at least one negative follow-up colonoscopy (n = 7, 7.4%). In multivariate analysis, risk factors were lesion size, sessile growth pattern, and the performing endoscopist. The complication and recurrence rate correlated inversely between endoscopists. CONCLUSIONS: The present study is the largest study showing complication and recurrence rates after colorectal polypectomy of advanced colorectal adenomas of ≥3 cm in size. Polyp size was identified as the most important risk factor for complications. For the first time, this study shows that the complication rate after colorectal polypectomy of large adenomas is correlated inversely with the residual and/or recurrence rate.

High power high voltage bias-T for half wave resonators and radio frequency quadrupole couplers.

High power high voltage bias-T units capable of delivering up to 100 kW CW RF power at 176 MHz and up to 4 kV DC were developed at the Soreq Nuclear Research Center for the Soreq Applied Research Accelerator Facility linac. Two separate bias-T units with different requirements were designed for the radio frequency quadrupole couplers and the half wave resonator couplers. The purpose of this bias-T is to prevent multipacting phenomena by application of a high voltage DC bias to inner conductors of RF couplers. Underlying design principles, indigenous development, and successful off-line and on-line tests results are presented.

Effect of cycloheximide on the cell cycle of the crypts of the small intestine of the rat.

A single injection of 1.5 mg/kg of cycloheximide induces a complete disappearance of mitotic activity in rat intestinal crypts within 1.5-2 hr. No significant necrosis of crypt cells is observed even though this phenomenon is accompanied by a marked decrease in uptake of labeled precursors into protein and DNA. Mitoses reappear 6 hr after injection and recovery then follows a cyclic pattern over a period equivalent to one cell cycle, thereby reflecting at least a partial synchronization of cell division. Concurrent use of colchicine, an agent known to induce metaphase arrest, has demonstrated that cycloheximide, while having no apparent effect on cells already in division, prevents the entrance of new cells into visible mitosis. Analysis of the cell cycle suggests that one block initiated by cycloheximide occurs in G(2), presumably as the result of an interference with the formation of protein(s) required for the normal progression of cells from this phase of the cycle into mitosis.

Reformation of nucleoli after ethione-induced fragmentation in the absence of significant protein synthesis.

The rat liver nucleolus, after fragmentation induced by ethionine treatment, has been found to undergo complete reformation by adenine in the presence of a dose of cycloheximide sufficient to cause inhibition of protein synthesis by 90-95%. In contrast, actinomycin D given along with adenine was followed by the appearance of a small compact mass containing only the fibrillar component with no evident granules. This structure resembled pseudonucleoli seen in the anucleolate mutant of Xenopus laevis or in certain early stages of amphibian oocytes. Actinomycin D administered 2 hr after adenine induced a segregation of the fibrillar and granular components of nucleoli similar to that induced in the normal nucleolus. The implications of these findings in relation to nucleolar organization are briefly discussed.

The disorganization of hepatic cell nucleoli induced by ethionine and its reversal by adenine.

The structure of nuclei and nucleoli of hepatic cells after short-term ethionine administration was investigated with the electron microscope. By 1(1/2) hr after the injection, a distinct alteration occurred in the nucleoli which was characterized by the appearance of electron-opaque masses in the nucleolonema. After 6-8 hr, the nucleoli showed partial fragmentation into small, dense masses. Large aggregates of interchromatinic granules appeared in the nucleoplasm. Condensation of chromatin became prominent in the nucleoplasm particularly along the nuclear membrane. By 12 hr almost complete fragmentation of nucleoli had occurred. The administration of adenine or methionine at 4 hr prevented the development of nucleolar changes. Also, adenine administration at 8 hr after ethionine completely reversed the nucleolar lesion by 12 hr. After methionine administration at 8 hr, many nucleoli showed incomplete reconstruction with many twisted ropelike structures when viewed 4 hr later. Identical structures were found when adenine was given at 8 hr, and animals were sacrificed 2 hr later. On the basis of this observation, the simplified structures of nucleoli found 2 hr after adenine or 4 hr after methionine appeared to be precursors of the nucleolonema. It is suggested that nucleoli show at least two basic reaction patterns to inhibitors of RNA synthesis, one typified by actinomycin D and one by ethionine.

Unusually high mitochondrial alpha glycerophosphate dehydrogenase activity in rat brown adipose tissue.

Brown adipose tissue of the rat has been found to have an unusually high activity of mitohondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) when assayed both by a histochemical staining procedure and by a quantitative biochemical method with isolated mitochondria. In contrast to succinic, glutamic, and beta-hydroxybutyrate dehydrogenases, all mitochondrial enzymes, the activity of alpha-GPD in brown fat was 10 times that in liver, more than 20 times that in white adipose tissue, and 9 times that in kidney. The soluble NAD-linked alpha-GPD was also higher in brown adipose tissue than in white adipose tissue, liver, or kidney, but the differences were much less marked. The possible importance of the high activity of mitochondrial alpha-GPD in the regulation of synthesis of esterified lipid and in thermogenesis in brown fat is discussed.

Reformation of functional liver polyribosomes from ribosome monomers in the absence of RNA synthesis.

The administration to rats of the ethyl analog of methionine, ethionine, results in the rapid decrease in the hepatic concentration of adenosine triphosphate followed by an extensive disaggregation of polysomes to ribosome monomers and a concomitant inhibition of protein synthesis. These effects are readily reversed by the injection of methionine or precursors of adenine nucleotides such as adenine. The reformation of liver polyribosomes in such animals following the administration of adenine plus methionine was found to occur under conditions in which new RNA synthesis was markedly inhibited. Free messenger RNA without attached ribosomes must be capable of remaining functionally active in the liver cytoplasm for many hours.

Chemical carcinogenesis: persistence of bound forms of 2-fluorenylacetamide.

The persistent binding of metabolites of hepatic carcinogen, 2-fluorenylacetamide, to glycogen and to DNA in a new population of liver cells, hyperplastic nodules, and to glycogen in liver cancer cells weeks to months after the carcinogen was removed from the animals' diet is indicated by spectrophotometric, chromatographic, and mass spectrographic data. This persistence of binding does not appear to occur in the nonhyperplastic or nonneoplastic liver surrounding the nodules or the cancer.

Growth in vitro of cells from hyperplastic nodules of liver induced by 2-fluorenylacetamide or aflatoxin B1.

Cell suspensions obtained from hyperplastic nodules induced in rat liver by either of the two hepatic carcinogens, 2-fluorenylacetamide or aflatoxin B(1), show growth when cultured in vitro. No growth of cells from liver adjacent to the hyperplastic nodules or from liver of control rats has been obtained so far under comparable conditions. Hepatocarcinoma cells induced by 2-fluorenylacetamide grow readily in vitro but behave differently. These findings suggest that some nonmalignant cells capable of growth in vitro arise during liver carcinogenesis prior to the appearance of unequivocal cancer. Cultures of such cells may offer new avenues for the study of liver carcinogenesis.

Polymorphisms in the STAT6 gene and their association with carcass traits in feedlot cattle.

Identification of the genes and polymorphisms underlying quantitative traits, and understanding how these genes and polymorphisms affect economic traits, are important for successful marker-assisted selection and more efficient management strategies in commercial cattle populations. Signal transducer and activator of transcription 6 (STAT6) gene is tightly connected to IL-4 and IL-13 signalling and plays a key role in T(H)2 polarization of the immune system. In addition, STAT6 acts as a mediator of leptin signalling and has been associated with body weight regulation. The objective of this study was to determine if SNPs within the bovine STAT6 gene are associated with economically important traits in feedlot cattle. The approach consisted of resequencing STAT6 using a panel of DNA from unrelated animals of different beef breeds. Specifically, 16 kb of STAT6 was resequenced in 47 animals and the process revealed 39 SNPs. From the 39 SNPs, a panel of 15 tag SNPs was genotyped in 1500 beef cattle samples with phenotypes to perform a marker-trait association analysis. Among the 15 tag SNPs, five and six were polymorphic in Bos taurus and Bos indicus respectively. An association analysis was performed between the 15 tag SNPs and 14 performance and production traits. SNP ss115492459:C > A, ss115492461:A > G and ss115492458:G > C were significantly associated with back fat, calculated yield grade, cutability, hot carcass weight, dry matter intake, days on feed, back fat rate and average daily gain. These three SNPs were present in all Bos taurus beef breeds examined. Our results provide evidence that polymorphisms in STAT6 are associated with carcass and growth efficiency traits, and may be used for marker-assisted selection and management in feedlot cattle.

Transfer of viable putative preneoplastic hepatocytes to the livers of syngeneic host rats.

A new approach was developed by which freshly isolated, chemical carcinogen-altered hepatocytes with the positive marker gamma-glutamyl transpeptidase (gamma-GT) could be transferred from adult donor F344 rats to the livers of syngeneic, adult host rats. Selective proliferation of gamma-GT-positive hepatocytes was induced in host rat livers, such that large, macroscopic colonies of altered hepatocytes could be generated within 10 days of the cell transfer operation. Quantitation of the number of gamma-GT-positive hepatocyte colonies (foci) appearing per square centimeter of host liver section area on day 10 following cell transfer revealed that prior treatment of host rats with a low dose of 2-acetylaminofluorene was essential for the appearance of large numbers of foci. In addition, the appearance of foci on day 10 depended on the presence of intact, gamma-GT-positive hepatocytes in the infused (transferred) cell suspensions.

A new common marker for premalignant and malignant hepatocytes induced in the rat by chemical carcinogens.

A new common antigen, preneoplastic (PN), was found in every early and late hyperplastic nodule and in every primary hepatoma induced by N-2-fluorenylacetamide, ethionine, 3-methyl-4-dimethylaminoazobenzene, dimethylnitrosamine, or diethylnitrosamine in three strains of rats (CFN, F344, and BUF). It so far has not been found in normal adult rat liver, liver surrounding nodules or cancer, fetal liver, amniotic fluid, adult rat serum, sera from rats with hyperplastic nodules or primary hepatomas, or various normal rat tissues. Immunofluorescent staining indicated the PN antigen was present in the cytoplasm of hepatocytes in hyperplastic nodules and in primary hepatomas.

Nature of early appearing, carcinogen-induced liver lesions to iron accumulation.

A technique for induction of iron accumulation in hepatocytes of rats was used to identify early carcinogen-induced lesions by their histochemical absence of iron. Foci of iron-free altered hepatocytes produced by the feeding of N-2-fluorenylacetamide (FAA) for 3 weeks were composed of cells that were replicating when surrounding iron-containing hepatocytes were not, and that responded to a mitotic stimulus when surrounding hepatocytes were inhibited or showed a delayed response. Thus these lesions represented focal hyperplastic overgrowths. The iron-free hyperplastic foci developed into hyperplastic areas that progressed with longer feeding of FAA to form hyperplastic nodules. The lack of iron was a sensitive and reliable marker for hyperplastic lesions, which also permitted their identification in the fresh state. Both early hyperplastic lesions and nodules were often resistant to the necrogenic effects of dimethylnitrosamine, as well as to the antireplicative effect of FAA. The selection of such cells resistant to the toxic effects of carcinogens may be important in the pathogenesis of liver neoplasia.

Influences of different polychlorinated biphenyls on cytocidal, mitoinhibitory, and nodule-selecting activities of N-2-fluorenylacetamide in rat liver.

The influences of different polychlorinated biphenyl (PCB) isomers and congeners on distinct hepatotoxic responses to the hepatocarcinogen N-2-fluorenylacetamide [(2-FAA) CAS: 53-96-3] were examined in F344 rats. Cytocidal toxicity of 2-FAA (25-400 microM), determined by lactate dehydrogenase release during 20 hours in primary monolayer cultures of isolated rat hepatocytes, was reduced by in vivo pretreatment with either phenobarbitone [(PB) CAS: 50-06-6] or 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP), a PB-type PCB inducer. However, cytocidal toxicity of 2-FAA was substantially potentiated by either 3-methylcholanthrene [(MCA) CAS: 56-49-5] or 3,3',4,4'-tetrachlorobiphenyl [(TCBP) CAS: 32598-13-3], an MCA-type PCB. In the same cell culture assays, all four pretreatments similarly reduced cytocidal toxicity of N-hydroxy-N-2-fluorenylacetamide (0.32-32 microM; CAS: 53-95-2). By comparison, pretreatments with either the PB-type or MCA-type PCB's (50-200 mumol/kg) diminished mitoinhibitory toxicity of 2-FAA in vivo, as measured by hepatic regenerative growth and hepatocyte labeling indices 7 days after partial hepatectomy (PH) in rats given 3 consecutive daily doses of 2-FAA (20/mg/kg/day) before PH. This regimen of 2-FAA and PH promoted rapid selective growth of gamma-glutamyltranspeptidase-positive (gamma-GT+) nodules at 2 and 4 weeks after PH in rats previously given an initiating hepatocarcinogen, diethylnitrosamine [(DENA) CAS: 55-18-5]. However, various PCB's, including 2,2',4,4',5,5'-HCBP, 3,3',4,4'-TCBP, 2,2',4,4'-TCBP, 2,2',5,5'-TCBP, and the commercial mixture Aroclor 1254, each given as a single dose of 50 mumol/kg by gavage 10 days after DENA and 7 days before 2-FAA, all reduced the size of 2-FAA-selected gamma-GT+ nodules during the 4-week period after PH. These results indicate that, in spite of predictable inducer-specific opposite influences of different types of PCB's on cytocidal toxicity of 2-FAA, all PCB's similarly reduce nodule selection by 2-FAA in initiated livers. Reduced growth of 2-FAA-selected nodules correlated with the consistent ability of all PCB's to enhance regeneration of liver mass after 2-FAA and PH.

Cellular biochemistry of the stepwise development of cancer with chemicals: G. H. A. Clowes memorial lecture.

The sequence of possible cellular, tissue, biochemical, and molecular changes that are important during the development of experimental liver cancer with chemicals is reviewed from the viewpoint of the author's experience in carcinogenesis over the past 25 years. The development of a new model for the analysis of liver carcinogenesis, the resistant hepatocyte model, is briefly described, as are the known steps between exposure to an initiating dose of a chemical carcinogen to the appearance of hepatocellular carcinoma. These steps include: (a) the interactions with DNA; (b) the dependence on a round of cell proliferation for initiation; (c) one type of initiated hepatocyte, a resistant hepatocyte; (d) the selection of these new hepatocytes, probably by clonal expansion, to form synchronously the first type of hepatocyte nodules, early nodules; (e) the election of the majority of these nodules to undergo remodeling to normal-appearing liver by differentiation ("redifferentiation"); (f) the election of a minority of early nodules to persist; (g) the slow growth of the few persistent nodules; and (h) the precursor role of persistent nodules in the development of hepatocellular carcinoma. The evidence for such a precursor role includes: (a) the common occurrence in persistent nodules of a subsequent precancerous step, "nodules in nodules"; (b) the occurrence of metastasizing cancer inside nodules without cancer elsewhere in the liver; and (c) the high rate of evolution to cancer of persistent nodules, but not of early nodules, when transplanted to the spleen. Based on the common architecture, organization, blood supply, and biochemical pattern of properties relating to the metabolism of xenobiotics in hepatocyte nodules in six different models of liver carcinogenesis and on the common occurrence of a highly programmed redifferentiation pattern of carcinogen-induced hepatocyte nodules, it is concluded that heterogeneity and diversity seen in many phenotypic properties of cancers, including liver cancers, is preceded by a precursor population that is unusually homogeneous and uniform in phenotype. Thus, the heterogeneity and diversity of cancers are probably late manifestations in carcinogenesis. The available evidence is very suggestive that the hepatocyte nodules are an expression of physiological adaptation to exposure to hazardous xenobiotics and not a form of aberration or mutation. The data also suggest that hepatocyte nodules are an additional pattern of liver differentiation and that liver cancer, to be understood, should be compared with this precursor new state rather than the conventional adult, fetal, or embryonic states.(ABSTRACT TRUNCATED AT 400 WORDS)

Kinetics of phenotypic maturation of remodeling of hyperplastic nodules during liver carcinogenesis.

Hyperplastic nodules appearing during the preneoplastic phase of liver carcinogenesis were divided into two types, persistent and remodeling, according to the pattern of staining for gamma-glutamyltransferase. In the resistant cell model of liver carcinogenesis used in this study, hyperplastic nodules, uniformly staining for gamma-glutamyltransferase, rapidly emerge by 4 weeks after a single injection of diethylnitrosamine and brief selection by dietary 2-acetylaminofluorene plus partial hepatectomy. By 6 weeks, a majority of nodules (about 75%) show an obvious irregularity and loss of uniformity in staining for gamma-glutamyltransferase while the remaining nodules continue to be uniformly stained. The number of irregularly stained nodules increases over the next 18 weeks until over 95% of nodules show the nonuniform loss of enzyme activity. The progressive loss of enzyme activity is accompanied by architectural remodeling to normal-appearing liver. This is associated with the increasing disappearance of many obvious nodules from the liver as the remodeling ones blend imperceptibly with the surrounding liver. The uniformly stained nodules show the persistence of hepatocyte arrangements in plates two or more cells thick and in acini and of cytoplasmic hypertrophy characteristic of persistent hyperplastic nodules. Labeling indices are much higher in hepatocytes of the persistent uniformly stained nodules than in the remodeling ones. The possibility of exploiting this phase of the model further for in-depth analysis of the nodule-to-carcinoma sequence is discussed.

Patterns of ligand binding to normal, regenerating, preneoplastic, and neoplastic rat hepatocytes.

The binding of epidermal growth factor, asialoorosomucoid, and apoprotein E-rich lipoproteins to isolated hepatocytes was investigated at various time intervals during the step-by-step development of liver cancer in rats. The degree of binding of the three ligands showed a progressive reduction in early persistent and late persistent putative preneoplastic hepatocyte nodules. This was further decreased in hepatocytes isolated from unequivocal hepatocellular carcinomas. Regenerating liver hepatocytes bound lesser amounts of epidermal growth factor and asialoorosomucoid than did hepatocytes from control resting liver but increased amounts of apoprotein E-rich lipoproteins. The progressive decrease in ligand binding during the precancerous phase of hepatocarcinogenesis, the nodule-to-cancer sequence, may render nodules less responsive to the influences of their external environments.

The resistance of putative premalignant liver cell populations, hyperplastic nodules, to the acute cytotoxic effects of some hepatocarcinogens.

The hypothesis that liver carcinogenesis may have as an important facet the early selection of carcinogen-resistant cells was tested in animals in which putative premalignant hepatocyte populations, hyperplastic nodules, were induced by 2-acetylaminofluorene or by ethionine. Hyperplastic nodules were observed to be resistant to the acute necrogenic effects of 2 hepatotoxins, CCl4 and dimethylnitrosamine, under conditions in which liver cell necrosis occurred in the liver surrounding the nodules. In addition, although [methyl-3H]dimethylnitrosamine was taken up to an equal degree in nodules and normal liver, the interactions with DNA, RNA, and protein in hyperplastic nodules were found to be about 50% less than in control liver. Hyperplastic nodules showed a marked decrease in uptake of [9-14C]-2-acetylaminofluorene, a finding that could account for the large decrease in labeling of DNA, RNA, and protein by [9-14C]-2acetylaminofluorene observed in the nodules. The results are consistent with and support the hypothesis that new hepatocyte populations that appear prior to cancer, during liver carcinogenesis, have as an important biological property a resistance to the cytotoxic effect of hepatocarcinogens. The basis for this resistance might be a decrease in uptake and/or a reduction in the level of activation of carcinogens.

Induction of resistant hepatocytes as a new principle for a possible short-term in vivo test for carcinogens.

The induction of resistant hepatocytes in vivo in the rat has been observed with 21 different chemical carcinogens. The resistance was measured by the ability of the cells to proliferate as focal lesions in the presence of an environment that inhibits the original or surrounding hepatocytes from proliferation. This was created by a dietary 2-acetylaminofluorene plus a stimulus for cell proliferation, a single necrogenic dose of CCl4. The foci were readily visualized by staining for gamma-glutamyl transpeptidase activity. With most of the chemicals, a single administration at an appropriate time after partial hepatectomy is efficacious. However, with safrole and dieldrin, three doses over a 36-hr period were required to induce a significant number of foci of resistant hepatocytes. The presumptive preneoplastic nature of the resistant hepatocytes and the possible usefulness of this approach for the development of a new in vivo short-term test system for carcinogens are discussed.

Redifferentiation as a basis for remodeling of carcinogen-induced hepatocyte nodules to normal appearing liver.

A system is described for the detailed study of the remodeling of hepatic nodules that appear regularly during liver carcinogenesis with chemicals. With the use of the resistant hepatocyte model and by focusing on the caudate lobe, it has been possible to label with [3H]thymidine all the hepatocytes in hepatocyte nodules without any significant degree of labeling of the surrounding hepatocytes. Through such a model, the persistence of the label, in relation to the organization and appearance of the hepatocytes in the nodules, has been followed for 26 weeks. Nodules do not "disappear" to any significant degree by regression or by replacement with hepatocytes from the surrounding liver. Rather, nodule hepatocytes undergo differentiation to an adult liver phenotype. Thus, differentiation ("redifferentiation") of a carcinogen-induced altered hepatocyte population is seen regularly during carcinogenesis despite the irreversible nature of some of the changes induced by a chemical carcinogen during initiation.