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R Cameron

Publications and source records attributed to R Cameron.

At least 109 records · Page 6Linked to original sources
PubMed1981

Some conclusions derived from a liver model for carcinogenesis.

A new model of liver cancer development with chemicals is described. This model was based on the hypothesis that chemical carcinogens induced as a first step altered hepatocytes that are resistant to the inhibitory effect of a carcinogen, such as N-2-fluorenylacetamide, on cell proliferation. After the administration of a single initiating dose of a carcinogen, the rare resistant hepatocyte is selected by the creation of a special selection pressure, consisting of a stimulus for cell proliferation in the presence of an environment that inhibits normal hepatocyte proliferation. The latter is created by brief exposure to dietary N-2-fluorenylacetamide. With this approach, initiated hepatocytes and large hyperplastic liver nodules can be rapidly induced in a synchronized fashion. A direct material continuity between resistant hepatocytes, foci, and nodules of such cells (hyperplastic nodules) and hepatocellular carcinoma was established with diethylnitrosamine as the initiating carcinogen. The use of the resistant cell model has shown that initiation consisted of at least two steps, the second of which is a compulsory round of cell proliferation. With this model, three mechanisms of promotion in the liver are suggested: differential inhibition, differential stimulation, and differential recovery. The relationship of these early changes to liver cancer development is discussed.

Animals↗
PubMed1980

Polyamine metabolism in mouse kidney after administration of mercuric chloride.

Testosterone administration to gonadectomized male mice, besides giving rise to a distinct hypertrophy of the kidneys, results in a large increase in renal ornithine decarboxylase activity and accumulation of polyamines. Experiments were performed to examine the effects of localized renal injury caused by mercuric chloride administration on the polyamine metabolism in the testosterone stimulated mouse kidney. A single injection of mercuric chloride resulted in severe damage of tubular epithelium primarily in the proximal convolutions situated in the cortex and outer medullary stripe. Although the injection of mercuric chloride to testosterone treated mice decreased the stimulation of ornithine decarboxylase activity it did not prevent the increase in the concentration of putrescine. The levels of spermidine as well as of RNA were elevated. These results may indicate early reperative growth following mercuric chloride administration. The observations are discussed in relation to the effects of 1,3-diaminopropane, another nephrotoxic agent on renal growth and polyamine metabolism.

Animals↗
PubMed1980

Anatomy of the pancreatic veins. A post mortem and clinical phlebographic investigation.

The venous anatomy of 22 autopsy specimens of human pancreas was examined by dissection and radiography after injection of gelatin agent. The most constant findings were the posterior superior pancreaticoduodenal vein draining to the portal vein and the anterior superior pancreaticoduodenal vein draining to the gastrocolic trunk and superior mesenteric vein. Both veins were identified in 21 and 20 of 22 cases, respectively. All other pancreatic veins varied considerably in their course. The normal findings in clinical selective pancreatic phlebography based on 148 examinations are described.

Adult↗
PubMed1980

Cognition and behaviour change.

For the past decade we have been attempting to understand the role of cognition in psychopathology and behaviour modification. The purpose of the present paper is to highlight and discuss what we consider to be some of the most important findings and issues that have emerged. While many other investigators are conducting related research, we have limited our review and discussion to work conducted by Meichenbaum and his colleagues. The research program and the field in general have been reviewed in more detail by Meichenbaum (1977). See an annual newsletter on cognitive-behaviour modificaiton for further detailed reviews (Meichenbaum, 1975-1979). Initially, we were interested in developing and evaluating treatment procedures that blended cognitive and behavioural components. While this work continued, we have become interested in attempting to formulate an integrative model of behaviour change (Meichenbaum, 1977). The following review and discussion will describe the research program that led us to highlight the role of cognition in behaviour change.

Adaptation, Psychological↗
PubMed1979

Effects of 1,3-diaminopropane on testosterone induced hypertrophy and polyamine synthesis in mouse kidney.

The effects of prolonged treatment with 1,3-diaminopropane, a structural analogue of putrescine, on polyamine metabolism and growth in kidney tissue, were studied in mice in which renal hypertrophy was induced by testosterone treatment. Injections of 1,3-diaminopropane resulted in an almost total suppression of the testosterone induced stimulation of ornithine decarboxylase activity and prevented the accumulation of putrescine and spermidine in the kidneys. Renal spermine concentration was even lowered. Administration of 1,3-diaminopropane effectively prevented the testosterone induced increase in renal weight and RNA. In mice receiving 1,3-diaminopropane proteinuria was observed and histological examination revealed renal damage. Due to the nephrotoxic action of 1,3-diaminopropane caution is essential in relating the prevention of renal hypertrophy and the inhibition of polyamine synthesis.

Adenosylmethionine Decarboxylase↗
PubMed1978

Gamma-glutamyltransferase in putative premalignant liver cell populations during hepatocarcinogenesis.

The activity of gamma-glutamyltransferase, as measured quantitatively and by histochemical staining, was studied in different cell populations during the induction of liver cancer with 2-acetylaminofluorene (2-AAF) or diethylnitrosamine and compared with findings in fetal and in intact and regenerating adult liver. The enzyme activity is 20-fold higher in 12-week nodules than in control livers and 30-fold higher in 20-week nodules than in controls. A similar 30-fold increase in activity relative to control is present in hepatomas, induced by either 2-AAF or diethylnitrosamine, and in fetal hepatocytes. The enzyme shows increases in activity in foci of very early putative preneoplastic hepatocytes induced by a single dose of diethylnitrosamine and selected by low doses of 2-AAF plus partial hepatectomy. By 7 days, the foci show a 4-fold increase in enzyme activity, and by 3 weeks they are 40-fold higher than in the control liver. Histochemically, the foci are strongly positive for gamma-glutamyltransferase, especially in the bile canaliculi. By 21 days, the ductular (oval) cells induced by 2-AAF have disappeared. When stained for the enzyme activity, the foci stand out clearly against the negative background of the liver, allowing easy quantitation. It appears that gamma-glutamyltransferase is a useful marker for preneoplastic hepatocytes.

2-Acetylaminofluorene↗
PubMed1977

Newer insights into the pathogenesis of liver cancer.

A new hypothesis leading to a new model of liver carcinogenesis is described; it is based on the acquisition by carcinogen-altered hepatocytes during initiation of a new functional handle--resistance to the cytotoxicity of a carcinogen--and on the ability of such cells to proliferate in an environment that prevents proliferation of normal hepatocytes. The creation of such a differential environment now enables a quantitative analysis for initiation, the beginning synchronization of the putative premalignant hepatocytes for about 15 cell cycles, the study of the pattern of growth of such resistant cells to form nodules that have some resemblance to the organizational pattern of fetal liver, the analysis of the appearance of distinctive positive and negative markers for these cells, and the further investigation of the development of liver cancer from such cells. The remarkable similarity in overall pattern betweeen the development of cancer in the skin and in the liver with chemicals and the possible role of both somatic mutation and neodifferentiation in carcinogenesis are briefly discussed.

Aflatoxins↗
PubMed1976

A relative deficiency of cytochrome P-450 and aryl hydrocarbon [benzo(a)pyrene] hydroxylase in hyperplastic nodules induced by 2-acetylaminofluorene in rat liver.

The concentrations of cytochrome P-450 and the activities of aryl hydrocarbon [benzo(a)pyrene] hydroxylase (AHH) and reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase were measured in early (gray-white) and remodeled (brown) hyperplastic nodules induced in the livers of rats with 2-acetylaminofluorene and were compared to the values in control livers and in the liver surrounding the nodules. Cytochrome P-450 content of early (14 weeks) hyperplastic nodules is 30% of the activity of untreated control livers and 48% of the activity of the surrounding liver. AHH activity of the early nodules is 10% of the control activity and 33% of the activity in the surrounding nonnodular liver. Nicotinamide adenine dinucleotide phosphate-cytochrome c reductase activity in the microsomes of early nodules is 76% of the control activity and 78% of the activity in the surrounding liver. In the late remodeled nodules, (22 and 25 weeks), the cytochrome P-450 content is 40% of that of controls and AHH activity is 15% of the control activity. In primary hepatomas induced by 2-acetylaminofluorene, cytochrome P-450 content is 21% of that of controls, AHH activity is 11% of the activity of controls, and reductase is 50% of the control activity. These results, indicating a relative nodule deficiency in some of the cellular components believed to be important in the activation of hepatocarcinogens and hepatotoxins, offer one possible explanation for the relative resistance to carcinogen cytotoxicity of hyperplastic liver nodules.

2-Acetylaminofluorene↗
PubMed1969

Brooke Moore.

Explore the source record for details and available documents.

Australia↗
PubMedDate not supplied

Free jejunal interposition graft for reconstruction of the esophagus.

Forty-seven patients underwent pharyngoesophageal reconstruction using a free jejunal interposition graft (FJIG) at Duke University Medical Center from 1978 through 1987. There were 30 men and 17 women with ages ranging from 38 to 87 years old (mean age, 64 years). Twenty-one patients (group A) had no prior surgical procedures, 20 (group B) were reconstructed following radiation and/or surgical failure, with 6 patients (group C) having benign strictures of the upper alimentary tract. Follow-up ranged up to 122 months (mean, 23 months), with 3 patients lost to follow-up, and 4 perioperative deaths (within 3 months of surgery). There were a total of 9 initial graft failures, 4 patients undergoing successful re-implantation, resulting in an overall success rate of 89% (42 of 47). Excluding patients with graft failures, perioperative deaths, and patients lost to follow-up, 33 of 36 patients with a viable FJIG were able to maintain adequate swallowing function yielding a physiologic success rate of 86%. All of the 21 patients dying of recurrent disease had excellent palliation with the FJIG. Of the 7 patients who are alive, only 1 has dysphagia secondary to stricture. In conclusion, it is felt that the FJIG is a sophisticated method of reconstructing large surgical defects of the pharyngoesophagus with a high technical and physiologic success rate.

Adult↗