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T E Bunton

Publications and source records attributed to T E Bunton.

At least 19 recordsLinked to original sources
PubMed2001

Phenotypic alteration of vascular smooth muscle cells precedes elastolysis in a mouse model of Marfan syndrome.

Marfan syndrome is associated with early death due to aortic aneurysm. The condition is caused by mutations in the gene (FBN1) encoding fibrillin-1, a major constituent of extracellular microfibrils. Prior observations suggested that a deficiency of microfibrils causes failure of elastic fiber assembly during late fetal development. Mice homozygous for a targeted hypomorphic allele (mgR) of Fbn1 revealed a predictable sequence of abnormalities in the vessel wall including elastic fiber calcification, excessive deposition of matrix elements, elastolysis, and intimal hyperplasia. Here we describe previously unrecognized concordant findings in elastic vessels from patients with Marfan syndrome. Furthermore, ultrastructural analysis of mgR mice revealed cellular events that initiate destructive changes. The first detectable abnormality was an unusually smooth surface of elastic laminae, manifesting the loss of cell attachments that are normally mediated by fibrillin-1. Adjacent cells adopted alteration in their expression profile accompanied by morphological changes but retained expression of vascular smooth muscle cell markers. The abnormal synthetic repertoire of these morphologically abnormal smooth muscle cells in early vascular lesions included elastin, among other matrix elements, and matrix metalloproteinase 9, a known mediator of elastolysis. Ultimately, cell processes associated with zones of elastic fiber thinning and fragmentation. These data suggest that the loss of cell attachments signals a nonproductive program to synthesize and remodel an elastic matrix. This refined understanding of the pathogenesis of vascular disease in Marfan syndrome will facilitate the development of therapeutic strategies.

Actins↗
PubMed2000

The oncogenic properties of the HMG-I gene family.

The HMG-I gene family encodes high mobility group proteins originally identified as nonhistone chromosomal binding proteins. HMG-I and -Y proteins are alternatively spliced products of the same mRNA; HMG-C is encoded by a separate gene. The HMG-I proteins function as architectural chromatin-binding proteins that bind to the narrow groove of AT-rich regions in double-stranded DNA. Recent studies indicate an important role for HMG-I proteins in regulating gene expression. Moreover, increased expression of the HMG-I, -Y, and -C proteins correlates with cellular proliferation and neoplastic transformation in several cell types and human cancers. Previous work from our laboratory has shown that HMG-I is a direct c-Myc target gene that is involved in Myc-mediated neoplastic transformation. In this report, we show that increased expression of HMG-Y or -C leads to transformation with anchorage-independent cell growth in two experimental cell lines in a manner similar to that of HMG-I or c-Myc. Moreover, Rat la cells overexpressing HMG-Y or -C form tumors in nude mice analogous to Rat 1a cells overexpressing HMG-I or c-Myc. Distant metastases developed in animals injected with cells overexpressing HMG-I or -C. Our findings suggest that the HMG-I gene family is involved in neoplastic transformation and may represent a new family of oncogenes important in the pathogenesis of several human cancers.

Animals↗
PubMed2000

Brown bullhead (Ameiurus nebulosus) skin carcinogenesis.

Alternative models using fish species have been tested in liver toxicity and carcinogenesis bioassays. Similar models have not been developed for skin. The brown bullhead (Ameiurus nebulosus) has shown potential as a model for skin carcinogenesis studies due to its sensitivity to environmental chemical pollutants. The present study is an initial morphologic and biochemical characterization of the normal and neoplastic brown bullhead skin to assess its suitability as a model of skin carcinogenesis. Brown bullhead were removed from Back River in the Chesapeake Bay region, an area historically polluted with heavy metals and polycyclic aromatic hydrocarbons. Histology, histochemistry, and electron microscopy were used to stage the morphologic development and progression of neoplasia in skin. The distribution of keratin, a family of structural proteins with altered expression in mammalian tumorigenesis, was analyzed with one and two dimensional gel electrophoresis and nitrocellulose blots of extracts from normal skin. Keratin expression in skin and other organs was also assessed with immunohistochemistry using AE1, AE3, and PCK 26 antibodies, and the proliferation index in skin and neoplasms with PCNA antibody. Skin lesions appeared to progress from hyperplasia through carcinoma, and the proliferation index was increased in papilloma. Also in papilloma, intercellular interdigitations appeared increased and desmosomes decreased which may in future studies correlate with changes in expression of other molecular markers of neoplastic progression. Both Type I and Type II keratin subfamilies were detected in skin using gel electrophoresis with the complimentary keratin blot-binding assay. For further development of the brown bullhead model, future studies can compare and relate these baseline data to alterations in expression of keratin and other markers in fish neoplasms and to molecular events which occur in man.

Animals↗
PubMed2000

HMG-I/Y, a new c-Myc target gene and potential oncogene.

The HMG-I/Y gene encodes the HMG-I and HMG-Y proteins, which function as architectural chromatin binding proteins important in the transcriptional regulation of several genes. Although increased expression of the HMG-I/Y proteins is associated with cellular proliferation, neoplastic transformation, and several human cancers, the role of these proteins in the pathogenesis of malignancy remains unclear. To better understand the role of these proteins in cell growth and transformation, we have been studying the regulation and function of HMG-I/Y. The HMG-I/Y promoter was cloned, sequenced, and subjected to mutagenesis analysis. A c-Myc-Max consensus DNA binding site was identified as an element important in the serum stimulation of HMG-I/Y. The oncoprotein c-Myc and its protein partner Max bind to this site in vitro and activate transcription in transfection experiments. HMG-I/Y expression is stimulated by c-Myc in a Myc-estradiol receptor cell line in the presence of the protein synthesis inhibitor cycloheximide, indicating that HMG-I/Y is a direct c-Myc target gene. HMG-I/Y induction is decreased in Myc-deficient fibroblasts. HMG-I/Y protein expression is also increased in Burkitt's lymphoma cell lines, which are known to have increased c-Myc protein. Like Myc, increased expression of HMG-I protein leads to the neoplastic transformation of both Rat 1a fibroblasts and CB33 cells. In addition, Rat 1a cells overexpressing HMG-I protein form tumors in nude mice. Decreasing HMG-I/Y proteins using an antisense construct abrogates transformation in Burkitt's lymphoma cells. These findings indicate that HMG-I/Y is a c-Myc target gene involved in neoplastic transformation and a member of a new class of potential oncogenes.

Animals↗
PubMed2000

Oxygen-independent upregulation of vascular endothelial growth factor and vascular barrier dysfunction during ventilated pulmonary ischemia in isolated ferret lungs.

Vascular endothelial growth factor (VEGF) is a potent mediator of endothelial barrier dysfunction, and is upregulated during ischemia in many organs. Because ventilated pulmonary ischemia causes a marked increase in pulmonary vascular permeability, we hypothesized that VEGF would increase during ischemic lung injury. To test this hypothesis, we measured VEGF expression by Northern and Western blot analysis in isolated ferret lungs after 45 (n = 12) or 180 (n = 12) min of ventilated (95% or 0% O(2)) ischemia. Pulmonary vascular permeability, assessed by measurement of osmotic reflection coefficient for albumin (sigma(alb)), was evaluated in the same lungs, as was expression of the transcription factor, hypoxia-inducible factor (HIF)-1alpha. Distribution of VEGF as a function of ischemic time and oxygen tension was also evaluated by immunohistochemical staining in separate groups of lungs (n = 3). VEGF messenger RNA (mRNA) increased 3-fold by 180 min of ventilated ischemia, independent of oxygen tension. VEGF protein increased in parallel to mRNA. Immunohistochemical staining demonstrated the appearance of VEGF protein along alveolar septae after 180 min of hyperoxic ischemia, and after 45 or 180 min of hypoxic ischemia. sigma(alb) was not altered by 45 min of hyperoxic ischemia (0.69+/-0.09 versus 0.50+/-0.12, respectively), but decreased significantly after 180 min of hyperoxic ischemia and after 45 and 180 min of hypoxic ischemia (0.20+/-0.03, 0.26+/-0.08, and 0.23+/-0.03, respectively; P<0.05). HIF-1alpha mRNA increased during both hyperoxic and hypoxic ischemia, but HIF-1alpha protein increased only during hypoxic ischemia. These results implicate VEGF as a potential mediator of increased pulmonary vascular permeability in this model of acute lung injury.

Animals↗
PubMed2000

Targeted disruption of the Kvlqt1 gene causes deafness and gastric hyperplasia in mice.

The KvLQT1 gene encodes a voltage-gated potassium channel. Mutations in KvLQT1 underlie the dominantly transmitted Ward-Romano long QT syndrome, which causes cardiac arrhythmia, and the recessively transmitted Jervell and Lange-Nielsen syndrome, which causes both cardiac arrhythmia and congenital deafness. KvLQT1 is also disrupted by balanced germline chromosomal rearrangements in patients with Beckwith-Wiedemann syndrome (BWS), which causes prenatal overgrowth and cancer. Because of the diverse human disorders and organ systems affected by this gene, we developed an animal model by inactivating the murine Kvlqt1. No electrocardiographic abnormalities were observed. However, homozygous mice exhibited complete deafness, as well as circular movement and repetitive falling, suggesting imbalance. Histochemical study revealed severe anatomic disruption of the cochlear and vestibular end organs, suggesting that Kvlqt1 is essential for normal development of the inner ear. Surprisingly, homozygous mice also displayed threefold enlargement by weight of the stomach resulting from mucous neck cell hyperplasia. Finally, there were no features of BWS, suggesting that Kvlqt1 is not responsible for BWS.

Animals↗
PubMed1999

Use of non-mammalian species in bioassays for carcinogenicity.

The high costs of bioassays for carcinogenicity in rodents have sparked interest in the use of non-mammalian species as possible alternatives. Invertebrate and lower vertebrate species have been used for many years in bioassays for teratogenicity, toxicity and carcinogenicity involving exposure to a range of genotoxic compounds. Carcinogenicity tests have shown that the development of neoplasia in non-mammalian species is predictable and reproducible and that the results are affected by species, age, chemical class and dose. One disadvantage of using these species in cancer bioassays is the absence of tissues of critical importance in human cancer, such as prostate, lung and breast; however, the similarities between mammals and lower species in basic cellular responses to carcinogens allow reliable correlation of many mechanisms of cancer development down the phylogenetic tree.

Animals↗
PubMed1997

Cytochrome P450 isoenzyme activities in cultured rat and mouse liver slices.

1. The objective of this study was to determine the basal and inducible activities of several cytochrome P450 (CYP) isozymes and monitor the acinar and hepatocyte morphology in precision cut, cultured rat and mouse liver slices. 2. The slices were cultured up to 96 h in Chee's essential medium supplemented with insulin, transferrin, selenium, DMSO, dexamethasone and epidermal growth factor. A dynamic roller system was used to incubate the slices at 37 degrees C in an atmosphere of 95% O2:5% CO2. 3. Histopathology of the liver slices revealed maintenance of normal hepatic lobular architecture with time in culture. 4. CYP isozyme activities were measured at various times of culture. In rat liver slices, at 72 h, CYP1A1/1A2 activity was induced 4-fold by beta NF and 37-fold by dioxin (TCDD) whereas in mouse liver slices, 1A1/1A2 activity was not inducible by beta NF but was induced 19-fold by TCDD. At 72 h, CYP2A5 (coumarin-7-hydroxylase) activity was not detected in rat liver slices but in mouse liver slices, 2A5 was induced 2-fold by beta NF, 11-fold by phenobarbital (PB) and 3-fold by TCDD. 5. Hydroxylation of testosterone at specific positions was used as an indication of the activities of various P450 isoforms. Testosterone was added to the cultures at 0 and 72 h and the metabolites were measured at 24 and 96 h respectively by hplc analysis. Depending upon the species, the treatment and the time in culture, CYP1A, 2A, 3A, 2B and 2C activities were detectable. 3A activity was highly induced by PB in both rat and mouse liver slices. These results demonstrate that this culture system can be used to assess and compare xenobiotic metabolism in liver slices from rodent species.

Animals↗
PubMed1995

Expression of actin and desmin in experimentally induced hepatic lesions and neoplasms from medaka (Oryzias latipes).

Proliferation of stromal cells is a common occurrence in experimentally induced hepatocarcinogenesis in fish. However, the role of these cells in fish hepatic injury and neoplasia is unknown. To better understand the biology of the cells comprising the hepatic stroma, livers from medaka (Oryzias latipes) experimentally induced by diethylnitrosamine or methylazoxymethanol acetate were labeled with keratin, actin, and desmin antibodies. The distribution of these proteins in hepatocellular carcinoma, cholangiocarcinoma, spindle cell proliferative lesions, and spongiosis hepatis was assessed, including three peritoneal sarcomas for comparison. Ductular epithelial cells in cholangiocarcinoma were positive for keratin, with desmin and actin positive ductular walls. Presumptive perisinusoidal cells in primarily trabecular and schirrous hepatocellular carcinoma were also actin positive. Only one spindle cell proliferative lesion was positive for any of the antibodies (desmin), and this lesion was morphologically distinct from others in the same category. Spongiosis hepatis, the peritoneal sarcomas, and normal perisinusoidal and other stromal cells were negative for these proteins. Since actin and desmin can be alternatively or coexpressed by mammalian perisinusoidal cells in association with hepatic fibrosis and neoplasia, the present studies suggest these proteins may serve as functional markers of hepatic stromal cells in fish as well.

Actins↗
PubMed1995

Exclusion of copper from altered hepatocytes in white perch (Morone americana) with hepatic copper storage.

Iron is excluded from foci of hepatocellular alteration in carcinogenesis of rodents and some fish. Among white perch (Morone americana), there is a condition of hepatic copper storage in which copper-loaded livers are produced naturally. In a group of fish collected from the Chesapeake Bay, Maryland (USA), from September to December 1990, we observed hepatic lesions which excluded copper similar to the phenomenon of iron exclusion, in a white perch with over 3,600 micrograms/g wet weight hepatic copper. The lesions were of two types: one with cells morphologically different from normal hepatocytes and which had diminished to absolute exclusion of copper with the copper specific histochemical stain rubeinic acid, and a second with cells morphologically similar to normal hepatocytes which had only a partial exclusion of copper. Although the exact cause and nature of the lesions was not determined, intrinsic copper toxicity, environmental pollution, or a combination of these factors may have contributed to their development.

Animals↗
PubMed1994

Intermediate filament reactivity in hyperplastic and neoplastic lesions from medaka (Oryzias latipes).

To determine if hyperplastic and neoplastic lesions from medaka showed similar immunoreactivity to intermediate filament antibodies as the tissues of origin, two week old medaka were exposed to 10 or 20 mg/L of methylazoxymethanol acetate for two hours and transferred to clean water for up to six months. Using a streptavidin peroxidase method, paraffin embedded Bouins fixed neoplasms were incubated with cytokeratin, vimentin, or neurofilament antibodies. Like their nonneoplastic cellular counterparts, hepatocellular carcinoma, pancreatic acinar carcinoma and mesenchymal neoplasms including hemangioma and hemangiopericytoma reacted negatively to cytokeratin antibodies. Cholangiocarcinoma, mesothelioma, and proliferative lesions containing biliary epithelial cells reacted positively to cytokeratin antibodies. All neoplasms and proliferative lesions were negative with vimentin and neurofilament antibodies. These data indicate that while some epithelial neoplasms showed cytokeratin reactivity similar to the parent tissues, additional markers are needed to identify mesenchymal tissues and neoplasms.

Adenoma, Liver Cell↗
PubMed1993

The immunocytochemistry of cytokeratin in fish tissues.

An increasing interest in fish species as sentinels of environmental pollution and in carcinogenesis research has led to the identification of diagnostically challenging neoplasms of uncertain cellular origin and the need for additional diagnostic methods. To determine the potential of using commercially available antibodies to intermediate filament proteins on paraffin-embedded fish tissues for immunocytochemistry in tumor diagnosis, the application of three antikeratin antibodies to normal adult tissues from two fish species was assessed. Multiple tissues from 12-14-in. striped bass (Morone saxatilis) and 6-month-old medaka (Oryzias latipes) of both sexes were fixed in Bouin's or formalin fixatives. Formalin-fixed neoplasms from several mammalian species, including cat, dog, hedgehog (Atelerix albiventris, Erinaceus europaeus), rhesus macaque (Macaca mulatta), and sloth bear (Melursus ursinus), were also used as positive controls. Using a strepavidin horseradish peroxidase method on paraffin-embedded tissues, the broad spectrum antibodies AE1/AE3 (Boehringer Mannheim, Indianapolis, IN) and MAK-6 (Triton Biosciences, Alameda, CA), which recognize most of the 19 human cytokeratins, and CAM 5.2 (Becton Dickinson, Mountain View, CA), which recognizes cytokeratins present in human liver, were used as primary antibodies. Epithelia from skin, gills, cornea, bile ducts, renal tubules, gastrointestinal tract, and thymus were strongly positive with AE1/AE3 and MAK-6 in striped bass, but nonepithelial tissues such as bone and muscle were negative. Skin, gills, cornea, and portions of the gastrointestinal tract were strongly positive in medaka with the same antibodies, whereas bile duct, renal, and intestinal epithelia were less so. Tissue digestion improved the intensity of staining, and fixation with Bouin's fixative improved results somewhat compared with formalin fixation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ultrastructure of hepatic hemangiopericytoma in the medaka (Oryzias latipes).

The histologic and ultrastructural features of hepatic hemangiopericytoma from a medaka (Oryzias latipes) exposed for 48 hr to 400 mg/liter of diethylnitrosamine at 14 days of age are described. The predominant histologic pattern was of spindle-shaped cells forming numerous whorls around central capillaries, vacuolated areas, or necrotic debris. The predominant cell type was a spindle-shaped cell with oval nuclei, elongated cell processes, and abundant organelles converging upon normal appearing capillaries. Occasionally, however, they converged upon cells swollen with cytoplasmic filaments and/or containing large fenestrated or debris-filled cytoplasmic vacuoles. These features were reminiscent of endothelial cells undergoing intracellular canalization seen in angiogenesis or neovascularization. Individual capillaries were also seen in the mass independent of whorls. It was not clear, as is the case in man, if capillary formation was an integral part of the neoplastic process or a reactive response. Although the liver is an unusual location for hemangiopericytoma in man, many of the cellular features in the fish tumor were similar to the human tumor. The ultrastructural characterization of tumor cells in fish carcinogenesis correlated with histologic patterns of growth will expand our understanding of how fish cells respond when transformed, and augment the development and use of aquatic bioassays for carcinogenesis research.

Actin Cytoskeleton↗
PubMed1990

Comparison of three histochemical staining methods for the detection of copper in white perch (Morone americana) with abnormal hepatic copper storage.

A comparison of orcein, rubeanic acid and rhodanine histochemical stains in serial sections of liver from white perch (Morone americana) with abnormal hepatic copper storage is described. Staining reactions correlated well with hepatic copper concentrations although the threshold was the most problematic for rhodanine and rubeanic acid. Orcein was positive at a lower concentration than the two other stains. Hepatocellular granules and macrophage centres increased in size and number with copper concentration and could be related to increased lysosomes, as described for other species.

Animals↗
PubMed1990

Hepatopathology of diethylnitrosamine in the medaka (Oryzias latipes) following short-term exposure.

The effect of short-term exposure (48 hr) of 14-day-old medaka (Oryzias latipes) to diethylnitrosamine (DEN) was tested on 4 groups of fish at 0, 100, 200, and 400 mg/L, with interim sacrifices of up to 6 months post exposure. Many of the lesions seen were similar to those seen in other fish DEN carcinogenicity studies using longer term, adult exposures, including a cytotoxic phase with cystic degeneration of the hepatic parenchyma, cellular vacuolation, globular acidophilic cytoplasmic inclusions, spongiosis hepatis, foci of cellular alteration, adenomas, and cholangiomas. There were also several proliferative lesions of uncertain origin which occurred throughout the study. There appeared to be a direct relationship between exposure level and the incidence and severity of the lesions seen, including aggressiveness and invasiveness of the neoplasms seen. However, there was a possible difference from other studies in the types of neoplasms seen with this protocol, which may be related to age at exposure, exposure level, duration of exposure, or a combination of these factors. Similarities in lesions seen in this study and in rodent and other fish studies is an indication of promise for the use of this model in carcinogenicity testing. Differences indicate the variety of ways the fish liver can respond to toxic injury, and lend flexibility to the model.

Animals↗
PubMed1988

Cholangioma in white perch (Morone americana) from the Chesapeake Bay.

Cholangiomas found in two of 21 wild-caught white perch (Morone americana) from the Chesapeake Bay are described. The two fish were part of a study investigating a condition of abnormal hepatic copper storage in this species. The tumors were superficial, solitary masses consisting of cuboidal to columnar cells in tubuloglandular arrangement. Mild to marked peribiliary inflammation and fibrosis was seen also. Environmental pollution, the condition of abnormal copper storage, peribiliary fibrosis, and/or parasites may have contributed to the development of these tumors.

Adenoma, Bile Duct↗