Search PubMed⌕ Search

Biomedical subjects

G T Gallagher

Publications and source records attributed to G T Gallagher.

36 records · Page 2Linked to original sources
PubMed1990

Use of intracellular H3 messenger RNA as a marker to determine the proliferation pattern of normal and 7,12-dimethylbenz[a]anthracene-transformed hamster oral epithelium.

One of the major goals in cancer research and diagnosis is to identify in a tissue the population of actively dividing cells and their pattern of growth and to differentiate the proliferation patterns of normal and transformed tissues. We now describe a method for determining the proliferation pattern of any tissue (normal, diseased, or transformed), applicable in any mammalian species. This method is based on the fact that the transcription of histone H3 gene in mammalian cells is tightly coupled to DNA synthesis during cellular division. Resting cells or cells that just exited the cell cycle will have no detectable H3 mRNA. The presence of H3 mRNA in a cell is thus a good indicator of its proliferation status. We carried out in situ hybridization of H3 mRNA in hamster oral epithelia exhibiting a variety of altered growth patterns as a consequence of exposure to the chemical carcinogen, 7,12-dimethylbenz[a]anthracene to demonstrate the usefulness of this technique. This application does not require in vitro manipulation of tissues nor does it require the prior administration of a tracer. The proliferation pattern at a single moment in time instead of an accumulated pattern over a period of time is produced. Finally, since the technique of in situ hybridization can be applied to archival tissues, retrospective studies can be done. This application should find usefulness in a wide variety of experimental research settings, particularly cancer research.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Keratinocyte transglutaminase in human skin and oral mucosa: cytoplasmic localization and uncoupling of differentiation markers.

Expression of keratinocyte transglutaminase, a specific differentiation marker, has been examined by immunogold-silver cytochemistry in human epidermis and oral epithelium, and in oral mucosal hyperplasia and neoplasia. Two major findings have been obtained. First, considerable immunoreactivity was evident not only at the plasma membrane (the site of cross-linked envelope formation) but also in the cytoplasm of spinous cells, suggesting a cytoplasmic function for this transglutaminase. Staining at the cell border was seen principally in the granular layer of orthokeratinized epithelium (epidermis, hard palate), the outer spinous cells of ortho- and parakeratinized epithelium and in the suprabasal cells showing squamous differentiation in benign and malignant neoplasms. By contrast, diffuse cytoplasmic staining was observed in the upper spinous layer of the normal epithelium and benign lesions. The cytoplasmic immunoreactivity, which extended nearly to the basal layer in hyperkeratosis of the oral mucosa, was evident in two of three verrucous carcinomas examined. In keeping with their undifferentiated character, invasive nests of squamous cell carcinoma and basaloid epithelium in benign and neoplastic lesions were immunonegative for transglutaminase. The second major finding was that lesions of severe oral epithelial dysplasia, immunonegative for transglutaminase, were capable of expressing involucrin immunoreactivity, indicating an uncoupling of keratinocyte programming. These results suggest that immunogold-silver staining for transglutaminase may be useful in evaluating the degree of differentiation in benign and malignant oral epithelial proliferation.

Cell Differentiation↗
PubMed1990

Production of transforming growth factor alpha by hamster eosinophils.

Previously it was demonstrated that malignant transformation of the Syrian hamster cheek pouch mucosa is associated with the expression of TGF-alpha. Therefore in situ hybridization and immunohistochemistry was used to investigate the cellular sources of TGF-alpha production in this model system. Surprisingly one cell type in the inflammatory infiltrate present in the connective tissue adjacent to the transformed epithelium represented a major source of TGF-alpha mRNA. Detailed analysis of these cells revealed that they were eosinophils. In addition to TGF-alpha mRNA, about 40% of the eosinophils associated with the oral tumors exhibited TGF-alpha product reactive with a monoclonal antibody against the C terminus of the mature TGF-alpha peptide. Normal hamster bone marrow eosinophils also exhibited TGF-alpha mRNA and product by in situ hybridization and immunohistochemistry. These results suggest that the eosinophil represents a biologically significant source of TGF-alpha.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

A rapid method to determine proliferation patterns of normal and malignant tissues by H3 mRNA in situ hybridization.

A general method applicable for the determination of any mammalian tissue's proliferative pattern is described. This method determines the cellular mRNA level of a proliferation-dependent gene, histone H3, by in situ hybridization. The cell-cycle S-phase-specific expression of this highly conserved ubiquitous cellular gene, and the lack of it in resting cells, permits the unambiguous identification of cycling cells in any tissues, normal or diseased. This method can be conveniently coupled with routine biopsy and could be streamlined for a central laboratory with results obtainable in 2 days. Furthermore, this procedure works successfully on formalin-fixed paraffin-embedded sections, thus allowing retrospective studies of biopsies or autopsy materials.

Cell Cycle↗
PubMed1989

Detection of transforming growth factor-alpha messenger RNA in normal and chemically transformed hamster oral epithelium by in situ hybridization.

We have recently demonstrated the consistent detection of transforming growth factor alpha (TGF-alpha) in chemically transformed hamster oral tumors. By Northern blot analysis, no TGF-alpha mRNA can be detected in normal cheek pouch mucosa. The consistent expression of TGF-alpha associated with the malignant transformation in the well-defined hamster oral cancer model prompted us to hypothesize that the aberrant expression of this important cellular gene could be related to a specific stage of epithelial alteration. In situ hybridization was used to test this hypothesis. We now report that by in situ hybridization we can detect TGF-alpha mRNA in normal hamster oral epithelium and also at all stages of transformation. In all epithelium, labeling of TGF-alpha mRNA in the basal layer is more pronounced than that observed in the spinous and squamous layers. There is a significant increase of TGF-alpha mRNA labeling early in 7,12-dimethylbenz(a)anathracene-induced oral carcinogenesis. This increase is associated with morphological changes of epithelial hyperplasia or dysplasia. Although lesions exhibiting full-thickness epithelial dysplasia (carcinoma in situ) showed more labeling of TGF-alpha mRNA than do areas of lesser dysplasia, the transition to full-fledged papillary or invasive squamous cell carcinoma is not associated with further elevations of TGF-alpha expression.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

TGF-alpha and EGF-receptor mRNAs in human oral cancers.

Transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) have been shown to be present in most squamous cell carcinomas. Using the Syrian hamster oral cancer model, we have recently demonstrated the consistent presence of TGF-alpha and EGFR mRNAs in chemically transformed hamster oral keratinocytes. We now present evidence that in human oral cancer (in vivo and in vitro), TGF-alpha and EGFR mRNAs can also be consistently detected. No TGF-alpha mRNA can be detected in normal human oral epithelium by Northern blot analysis. These findings reinforce the use of the hamster cheek pouch as an experimental model for the study of oral cancer development, at least in reference to the possible participation of TGF-alpha in the malignant transformation process.

Animals↗
PubMed1988

Transforming growth factor alpha in chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent tissue for the experimental induction of oral cancer by carcinogenic chemicals. Lysate prepared from a cell line (HCPC-1) derived from one of these hamster oral tumors greatly increased the growth of these oral tumor cells in vitro. We now show that the mitogenic substance, transforming growth factor alpha (TGF-alpha), is present in all of the chemically transformed hamster oral tumors examined (in vitro and in vivo). In no adult normal tissue of the Syrian hamster can we detect expression of TGF-alpha. TGF-alpha could be partly or wholly responsible for the mitogenic activity detected in the lysate of the chemically transformed hamster oral keratinocytes. Both normal and chemically transformed hamster oral keratinocytes express the receptor to epidermal growth factor. The consistent detection of TGF-alpha and epidermal growth factor receptor mRNAs in these hamster oral tumor cells suggests that an autocrine growth mechanism might be operative. This hamster cheek pouch oral cancer model can be used for the molecular analysis of how TGF-alpha and epidermal growth factor receptor might be involved in the malignant transformation of epithelial tissues.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

Cysteamine induces duodenal ulcer in the mouse.

A new model of duodenal ulcer disease has been developed in the mouse. The ulcers were produced after either oral or subcutaneous administration of cysteamine which has been shown to cause duodenal ulcer in the rat. Cysteamine induced duodenal ulcers in a time- and dose-dependent manner after oral administration. The new mouse model shares many similarities with both the rat model and human ulcer disease. Cysteamine caused a significant increase in gastric acidity and pepsin activity. The mouse can be protected against the cysteamine-induced duodenal ulcer by either the dopamine agonist lergotrile or histamine H2 receptor antagonist cimetidine. This new model of duodenal ulcer disease in the mouse may represent a simple and inexpensive way to screen for new antiulcerogenic drugs.

Administration, Oral↗
PubMed1985

Biliary and pancreatic secretions influence experimental duodenal ulcer without affecting gastric secretion in the rat.

The effect of the absence of biliary and/or pancreatic secretions in the duodenum or the enhanced presence of bile at the proximal duodenum on the incidence, severity, number, and location of cysteamine-induced duodenal ulcers was investigated in the rat. Cysteamine produced ulcers on the anterior wall of the duodenum in 75% and on the posterior wall ("kissing ulcers") in 50% of the animals. Diversion of biliary and/or pancreatic secretions from the duodenum increased both the severity and the incidence of the posterior duodenal ulcers. Diversion of bile to the proximal duodenum, on the other hand, decreased the severity as well as the incidence of the anterior duodenal ulcers. Mortality in rats receiving cysteamine correlated with the severity of ulcers. Taurocholic acid at nontoxic doses given subcutaneously or orally to nonoperated rats and rats which had bile diverted to the proximal duodenum aggravated the cysteamine-caused duodenal ulcers. Neither proximal nor distal diversion of bile had a major effect on gastric secretion of acid and pepsin in normal or cysteamine-treated rats. We conclude that both bile and pancreatic secretions may directly influence the development of cysteamine-induced duodenal ulcers in the rat.

Animals↗
PubMed1984

Subacute and chronic action of acrylonitrile on adrenals and gastrointestinal tract: biochemical, functional and ultrastructural studies in the rat.

A single dose of acrylonitrile can produce fatal adrenal apoplexy within approximately 2 h. Our previous studies also indicate that multiple injections of the chemical cause acute hemorrhagic and occasional nonperforating duodenal ulcers. Other authors have reported increase in gut and lung neoplasia after chronic exposure. The present study was designed to elucidate the subacute and chronic actions of acrylonitrile on the adrenals, stomach and duodenum by correlating biochemical, functional and morphologic investigations, as well as to gain insight into the mechanisms of action of acrylonitrile. Rats were exposed to 0, 0.0001% (1 ppm), 0.002%, 0.01%, 0.05% or 0.2% acrylonitrile in drinking water, or to the same amount of the chemical given through daily gavage, for 7, 21 or 60 days. Acrylonitrile caused a time- and dose-dependent decrease in plasma corticosterone levels; aldosterone was affected only by the 'high' dose and prolonged time of exposure. Young rats were more susceptible than adults to this action of acrylonitrile. The adrenal cortex, especially the zona fasciculata, was atrophic in rats that had ingested the nitrile through drinking water. At 0.05% and 0.2%, it also caused decreased food intake and body weight gain. The adrenals were enlarged with a hyperplastic zona fasciculata after daily doses of a bolus of acrylonitrile. Ingestion of the chemical did not interfere with compensatory enlargement of the adrenal gland following unilateral adrenalectomy. On the other hand, the ACTH-induced elevation of corticosterone plasma concentration was significantly attenuated by acrylonitrile in drinking water. Electron microscopy of the adrenal glands revealed no consistent changes in the steroid-producing cells. We thus postulate that accelerated turnover of circulating corticoids and/or interference with the secretion or action of ACTH may primarily be responsible for the decreased plasma levels of corticosterone and aldosterone in rats that ingest acrylonitrile. The mucosa in the stomach at the junction of the forestomach and glandular region of animals that had ingested acrylonitrile was hyperplastic. The corpus also showed regional mucosal hyperplasia with the appearance of 'cobble-stoning'. These changes were preceded and associated with an elevated concentration of non-protein sulfhydryls mostly in the mucosa of the glandular stomach. A similar, less prominent elevation also occurred in the proximal duodenum. These alterations may resemble the preneoplastic combination of elevated glutathione and focal hyperplasia described in the liver with hepatocarcinogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Acrylonitrile↗
PubMed1984

Direct measurement of duodenal acid-pepsin exposure at site of ulceration in rats.

A new technique for the preparation of a chronic duodenal fistula in the rat is described. The effect of cysteamine and propionitrile on the acidity of duodenal contents was studied, and the degree of acidity correlated with the respective duodenal ulcerogenicity of these two compounds. After subcutaneous administration of cysteamine, reduced duodenal acid was seen for 2-4 h, followed by large increases continuing up to 12 h and declining thereafter. Oral cysteamine administration produced acid increases of rapid onset and shorter duration, accompanied by increased pepsin activity. The weak duodenal ulcerogen propionitrile did not affect duodenal acidity. Cimetidine markedly reduced the duodenal acidification induced by cysteamine, whereas the dopamine agonist bromocriptine did not affect acid delivery to the duodenum but reduced the pepsin activity in the duodenal contents by 50%. The duodenal fistula rat provides a new model system for studies on the pathogenesis of experimental duodenal ulcer.

Animals↗
PubMed1984

Secretory changes associated with chemically-induced duodenal ulceration: simultaneous measurements of acid, pepsin, base and pancreatic enzymes in rats with chronic gastric fistula.

Rats with chronic gastric fistula were used to study gastric and duodenal/pancreatic secretory changes evoked by chemical duodenal ulcerogens. Although the data demonstrate stimulation of gastric output of acid and pepsin by certain doses of cysteamine or propionitrile, cysteamine produced dose-response increases in acid secretion only during the 1st hour following administration. The base output was also elevated at most of the time intervals after cysteamine. Decreased alkaline secretion was only seen following propionitrile injection. Although hyperacidity at the ulcer site may occur during duodenal ulcerogenesis, these results suggest that direct stimulation of acid-pepsin secretion or depression of pancreatic alkaline output are not the primary mechanisms explaining the ulcerogenic action of cysteamine and propionitrile.

Amylases↗
PubMed1984

Role of local secretory and motility changes in the pathogenesis of experimental duodenal ulcer.

Changes in gastric acid and pepsin secretions do not fully account for the duodenal ulcerogenic effect of cysteamine or propionitrile in the rat. We investigated the role of pancreatic and biliary secretions as well as motility changes in the duodenum. Bypass of bile to the jejunum and/or ablation of pancreatic secretion or drainage of these secretions through chronic duodenal fistula aggravated the cysteamine-induced duodenal ulcers. Biliary bypass to the proximal duodenum, on the other hand, decreased the incidence and intensity of experimental duodenal ulcers. An increased and dopamine-sensitive myoelectric activity caused by cysteamine or propionitrile was recorded in the proximal duodenum, indicating a state of hypermotility. Indeed, a decreased quantity of bilirubin was recovered through the chronic fistula in the proximal duodenum, suggesting an impaired delivery of bile to the ulcer area after cysteamine administration. Thus, duodenal hypermotility probably prevents the proper mix and neutralization of gastric acid and duodenal (mucosal, biliary and pancreatic) secretions, predisposing to ulceration in the proximal duodenum.

Animals↗
PubMed1983

Duodenal ulcerogens cysteamine and propionitrile decrease duodenal neutralization of acid in the rat.

Neutralization of acid was evaluated in rat proximal duodenal segments isolated from biliary and pancreatic secretions. Duodenal ulcerogenic doses of cysteamine produced a significant decrease in acid disposal 0.5-2 hr after treatment. Oral or subcutaneous administration of the duodenal ulcerogen was effective. The potent ulcerogen cysteamine produced a more pronounced decrease than propionitrile (a weak duodenal ulcerogen). The failure of ethanolamine, a nonulcerogenic structural analog of cysteamine to significantly alter acid disposal suggests that the effect is not due to the toxic properties of the duodenal ulcerogen. The results reinforce the concept that the duodenum is able to dispose of significant quantities of acid. The decrease in acid-handling may contribute to duodenal susceptibility to acid after treatment with ulcerogens and possibly reflects pathophysiologic changes early in duodenal ulceration.

Animals↗
PubMed1983

Potentiation of duodenal ulcerogenic action of acrylonitrile by PCB or phenobarbital in the rat.

Pretreatment of rats with the polychlorinated biphenyl (PCB) Aroclor 1254 or phenobarbital markedly increased the duodenal ulcerogenic action of acrylonitrile. The extent of forestomach and hepatic lesions in these rats, on the other hand, was not modified. The duodenal ulcers produced by Aroclor 1254 and acrylonitrile morphologically resembled the ulcers induced in other animal models of the human duodenal ulcer disease. The possible mechanisms of this potentiation of acrylonitrile action are discussed.

Acrylonitrile↗
PubMed1983

Role of the adrenal cortex in gastric mucosal protection by prostaglandins, sulfhydryls, and cimetidine in the rat.

To investigate the possible role of hormones in gastric mucosal protection, the effect of prostaglandin F2 beta, dimercaprol, or cysteamine on ethanol-induced gastric erosions, and of cimetidine on gastric erosions caused by aspirin was studied in intact, adrenalectomized, medullectomized, ovariectomized, or thyroidectomized rats. Cimetidine was administered at a low dose that did not inhibit hydrogen ion secretion. Adrenalectomized animals failed to exhibit the usual mucosal protective response to prostaglandin F2 beta, sulfhydryls, or cimetidine. Ovariectomy or thyroidectomy did not influence mucosal protection with these agents. The inhibition by total adrenalectomy of mucosal protection was not reversed by large intragastric doses or by parenteral administration of prostaglandin F2 beta. Adrenal medullectomy alone significantly diminished (by approximately one-third) ethanol-induced gastric mucosal injury; prostaglandin F2 beta or sulfhydryl drugs produced significant additional protection. Replacement therapy with glucocorticoids (triamcinolone, corticosterone) but not with mineralocorticoids (deoxycorticosterone, 9 alpha-fluorocortisol) restored the cytoprotective effect of prostaglandin F2 beta and sulfhydryls in adrenalectomized rats. The generation of prostaglandin E2- and prostaglandin I2-like activity in the gastric mucosa was unaltered by adrenalectomy. These studies suggest a permissive role for glucocorticoids in gastric mucosal protection induced by prostaglandins, sulfhydryls, and cimetidine.

Adrenal Cortex↗