Eosinophilic Foci Research Articles

Proliferative lesions of the glandular stomach and liver in F344 rats fed diets containing Aroclor 1254.

Aroclor 1254 was fed to groups of 24 male and 24 female F344 rats, from 7 weeks of age, at dietary concentrations of 25, 50 and 100 ppm for up to 105 weeks. There was a dose- related depression of body weight gain for both sexes and decrease in survival for male rats. Histologically, an increased incidence of gastric intestinal metaplasia and adenocarcinoma was found in both sexes. Hepatocellular adenomas, carcinomas, and eosinophilic and vacuolated hepatocellular foci were usually found in dosed rats only. The number of these foci per unit area of liver was significantly increased in dosed rats, although eosinophilic foci were only found in rats exposed to Aroclor 1254. Basophilic hepatocellular foci were found in similar numbers per square centimeter of liver in controls and treated rats. This finding suggested that eosinophilic hepatocellular foci and tumors arose de novo rather than from the naturally occurring basophilic foci. The appearance of unique, potentially preneoplastic lesions and tumors in the liver and stomach in dosed rats which do not usually occur spontaneously in control rats would support the hypothesis that Aroclor 1254 induced or initiated these unique lesions de novo rather than promoted the growth of any naturally occurring lesions. Nonneoplastic hepatic lesions included degenerative hepatocellular changes and aggregates of macrophages with crystalline cytoplasmic structures and pigment granules.

Quantitative evaluation of hepatic foci of cellular alteration occurring spontaneously in Fischer-344 rats

Stereologic procedures were used to quantitate spontaneously occurring liver foci of altered staining in control Fischer-344 rats at 33, 59, 85, and 111 weeks of age. Foci were identified using hematoxylin and eosin stained sections. In both males and females, foci were first observed at 59 weeks. The number of foci per cubic centimeter of liver, as well as mean focal volume, increased significantly with age. Between 85 and 111 weeks, the number of foci per liver increased 3.5 times in females but was unchanged in males. When three groups of 111-week-old animals were evaluated, females consistently had a greater number of foci per cubic centimeter of liver and mean focal volume than males of the same group. For the three groups evaluated at 111 weeks, the mean number of foci per liver ranged from 431 to 1865 in males and from 727 to 1654 in females. The mean volume fraction (% of the liver) occupied by foci ranged from 0.28 to 1.0% in males and from 1.42 to 4.15% in females. When focal staining characteristics were investigated, the majority of foci were basophilic in both sexes at all time points examined. However, males consistently had a higher percentage of eosinophilic foci than females.

Iron exclusion by proliferative foci and neoplastic lesions induced by 7,12-dimethylbenz (a) anthracene in the rat adrenal cortex

Proliferative and neoplastic adrenal cortical lesions were produced in female Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene. These lesions were studied for their ability to store histochemically demonstrable cellular iron compared with normal adrenocortical cells following iron loading by subcutaneous injection of iron-dextran. Stainable iron was excluded, under conditions in which normal cortical cells were heavily loaded with iron, in three histological types of adrenal cortical lesions; eosinophilic and basophilic proliferative foci; adenomas and lesions transitional between foci and tumours. The property of iron exclusion may be useful in studying neoplastic development in the adrenal gland.

Increased incidence of hepatic foci and nodules in rats given one or two doses of 1,2-dibromoethane.

Livers of male Sprague-Dawley rats were evaluated for foci and nodules 90 days and 16 months after one or two oral doses of 1,2-dibromoethane (DBE). Rats (190 g) were given the following oral treatments. Controls received corn oil (2.5 ml/kg) at 0 and 24 hr. DBE X 1 received corn oil at 0 hr and 75 mg DBE/kg at 24 hr. DBE X 2 received 75 mg DBE/kg at 0 and 24 hr. All rats underwent a two-thirds partial hepatectomy at 28-29 hr, a one-third partial hepatectomy at 90 days, and were given 0.05% phenobarbital in drinking water for 4 months beginning at 1 yr. DBE was given to the DBE X 2 group twice within 24 hr because the compound is a hepatocyte mitogen. At 90 days, no appreciable changes were evident in any group. At 16 months, the incidence of nodules in the DBE X 2 group (25 of 41) was double that of the DBE X 1 group (12 of 38) (p less than 0.01) and triple that of the control group (6 of 34) (p less than 0.0001). Both the DBE X 1 and the DBE X 2 groups had higher incidences of eosinophilic foci, and also higher numbers, larger sizes, and larger areas of gamma-glutamyltranspeptidase-positive foci than the control group. These results demonstrate for the first time that hepatocyte foci and nodules are initiated by limited exposure of animals to DBE.

A Sequential Study of Methapyrilene Hydrochloride-Induced Liver Carcinogenesis in Male F344 Rats2

Methapyrilene hydrochloride [2-[2-(dimethylamino)-ethyl)-2-thenylamino)pyridine monohydrochloride (CAS: 135-23-9)]-induced hepatocarcinogenesis was studied in male F344/NCr rats by sequential histologic, histochemical, and biologic methods. Methapyrilene hydrochloride was administered in the feed to rats at a concentration of 1,000 ppm for periods up to 89 weeks. Groups of rats were killed after 5, 10, 15, 29, 40, or 73 weeks of ingesting the carcinogen. Another group was allowed to live out their life-span. Hepatocellular eosinophilic foci and adenomas were seen after 10 and 15 weeks, respectively. Basophilic foci and adenomas were found after 29 and 40 weeks, respectively. Hepatocellular carcinomas developed in 5 of 10 rats at week 40, in 3 of 5 rats at week 73, and in 19 of 19 rats that lived out their life-span. Carcinomas arose within adenomas or as small in situ carcinomas. The histologic types included trabecular, adenocarcinoma, mixed, and solid poorly differentiated hepatocellular carcinomas. Eleven of the mixed and solid poorly differentiated carcinomas metastasized to the lung. Solid poorly differentiated hepatocellular carcinomas grew upon transplantation to the mammary fat pad of weanling F344 rats. Cholangiocarcinomas were found in 7 of 19 rats only in the life-span group. Mucous cholangiofibrosis was seen in all rats after 15 weeks. With the use of Regaud's mitochondrial stain, an increased cellular density of mitochondria was seen in some hepatocytes of peripheral and central lobular areas and in some hepatocellular carcinoma cells, but not in cells in many of the adenomas and foci. Cellular alpha-fetoprotein was found by immunoperoxidase staining in portions of hepatocellular carcinomas, but not in foci, adenomas, and nonneoplastic areas. The majority of hepatocytes in foci, adenomas, and hepatocellular carcinomas contained gamma-glutamyl transpeptidase. The findings suggest that multiple pathways may be followed in the development of methapyrilene-induced liver cancer that are similar to those found in rats exposed to many other hepatic carcinogens.

Sequential Morphologic Changes During Methapyrilene-Induced Hepatocellular Carcinogenesis in Rats<xref ref-type="fn" rid="FN2">2</xref><xref ref-type="fn" rid="FN3">3</xref><xref ref-type="fn" rid="FN4">4</xref>

The pathogenesis of hepatocellular tumors induced in F344 rats by the antihistaminic methapyrilene was investigated by light and electron microscopy in a serial sacrifice study. Eosinophilic foci of altered hepatocytes were found in portal areas after 1 week of treatment, the eosinophilia being caused by proliferation of mitochondria. Eosinophilic neoplastic nodules developed from such lesions after 16 weeks of treatment. Hepatocellular carcinomas developed after 26 weeks of treatment. Mitochondrial proliferation, which had been found as a marker for hepatocytes altered by this compound at 1 week of treatment, was still present in the hepatocellular carcinomas, which therefore met the morphologic criteria of oncocytomas.

Increased Susceptibility of Livers of Aged F344/NCr Rats to the Effects of Phenobarbital on the Incidence, Morphology, and Histochemistry of Hepatocellular Foci and Neoplasms<xref ref-type="fn" rid="FN2">2</xref><xref ref-type="fn" rid="FN3">3</xref>

Aged (875 days old) and young 42 days old) male F344/NCr rats were given sodium phenobarbital (PB) in drinking water for periods up to 233 days. Groups of aged rats were killed at 30 or 60 days or allowed to live their normal life-span, and the cause of death was determined. Young rats killed after 30, 60, and 150 days of PB exposure. Hepatocellular foci were classified into basophilic, eosinophilic, or vacuolated types according to morphologic appearance of the hepatocyte cytoplasm and were characterized by histochemical methods for the presence of gamma-glutamyl transpeptidase (GGT). The most common contributing causes of death for rats in both groups were large granular lymphocyte (LGL) leukemia and pituitary tumors. PB decreased the incidence of LGL leukemia but increased the incidence and multiplicity of hepatocellular GGT-positive foci, eosinophilic foci, and eosinophilic hepatocellular adenomas. GGT-positive eosinophilic foci increased in diameter and volume, but not in number, after appearing early in the experiment. Hepatocellular basophilic foci and neoplasms in aged control rats were usually GGT-negative and did not appear to respond to dietary PB. GGT-positive foci were seen in aged control rat livers and were composed of vacuolated amphophilic hepatocytes that differed morphologically from hepatocytes in naturally occurring liver tumors. Young rats given PB had few GGT-positive foci by 150 days on test. Aged rat livers were thus more sensitive to the effects of PB than were livers of young rats.

Enhanced Survival and Absence of Progressive Growth of Transplanted Rat Liver Altered Eosinophilic Foci and Neoplastic Nodules in Phenobarbital-Treated Rats<xref ref-type="fn" rid="FN2">2</xref>

Hepatocellular altered eosinophilic cell foci and neoplastic nodules induced in inbred F344 male albino rats by the feeding of N-2-fluorenylacetamide were transplanted into the inguinal mammary fat pads of syngeneic animals to assess their ability to produce neoplasms. Treatment of one-half of the recipients with the neoplasm promoter phenobarbital sodium enhanced survival of both types of transplants. However, at the end of 6 or 12 months of maintenance of recipients of altered foci and 6 months of maintenance of recipients of early and late nodules, no neoplasms occurred, in spite of persistence of abnormal cells at the transplant sites. Therefore, the conclusion was that these carcinogen-induced liver lesions possess limited growth capacity in this ectopic site and that transition to carcinoma under these conditions did not occur in high frequency.

DNA Content of Liver Cell Nuclei of N-2-Fluorenylacetamide-Induced Altered Foci and Neoplasms in Rats and Human Hyperplastic Foci2

The DNA content of cell nuclei of liver lesions induced in inbred male ACI rats by administration of 0.02% N-2-fluorenylacetamide (2-FAA) diet was measured with a microspectrophotometer in Feulgen-stained specimens. Altered liver foci of the eosinophilic, clear, and simple basophilic (toluidine blue weakly positive or negative) types had modal DNA values with a wider deviation (2C-10C) than the euploid pattern of normal hepatocytes (2C-6C). However, the DNA histograms of cells in hyperbasophilic (intensely toluidine blue-positive) foci were aneuploid (2C-18C) and resembled those of cells in hepatocellular carcinomas (2C-23C). Conversely, the modal DNA values of neoplastic nodules showed a narrower range (2C-12C). These results confirm that the hyperbasophilic foci may be a population similar to carcinoma in situ or may be a direct precursor lesion of hepatocellular carcinoma. In the livers from 4 humans, 3 of whom had a history of long-term use of some drugs, multiple hyperplastic foci resembling eosinophilic or clear cell foci in rats were identified. The modal DNA values of the cell nuclei in these foci showed a wider deviation (2C-10C) than in surrounding hepatocytes (2C-6C). In 2 patients, the lesions contained neoplasms and, therefore, hyperplastic foci in humans may be related to tumor development.

Light and electron microscopy of prednisolone-induced nephropathy in rabbits.

Three adult rabbits given 1 mg. prednisolone intramuscularly four times weekly for twelve weeks developed glycosuria and albuminuria, and became weak and flaccid. Light and electron microscopy reveals a variety of changes in the kidneys of the treated rabbits. By light microscopy, the glomerular tufts show congestion, capillary aneurysms, eosinophilic foci and cellular loss; Bowman's space may contain blood and other elements; the cells lining Bowman's capsule are sometimes degenerated or necrotic; and the tubules may exhibit fatty infiltration, intracytoplasmic hyaline droplets, an increase of acidophile cells in the collecting segments, cellular necrobiosis and necrosis and, like Bowman's space, a content of blood and other substances. By electron microscopy, the glomerular tufts show two types of abnormal foci; one apparently results from proteinous occlusion of one or more degenerated capillaries such as may be normal in size and shape or dilated and locally collapsed, and the other consists in an axially located intermingling of basement membrane-like material and unusually osmiophilic endothelial cytoplasm; apart from such foci the podocytes may exhibit hyaline droplets, vacuolation, intense osmiophilia or loss of substance, while the endothelial cells are sometimes abnormally electron dense and vacuolated; the cells lining Bowman's capsule may also be unusually osmiophilic and deposits of plasma-like material are occasionally noted in Bowman's space; the tubular changes include intracytoplasmic hyaline droplets, luminal debris and dilatation of the collecting tubules, but these are overshadowed by necrosis of the tubular cells, particularly in the collecting series. The experimental renal findings are considered in relation to human diabetic glomerulopathy.