Search

The purpose of this study was to advance our knowledge of the histogenesis of spontaneous mammary tumours in laboratory mice. Normal mammary tissue and 19 spontaneous mammary tumours from adult female mice were examined using monoclonal and polyclonal antibodies differing in their recognition of various cytokeratin intermediate filament proteins (CKs). All neoplasms were intraductal and were invasive carcinomas with a tubular, papillary, cystic or solid growth pattern. CK8-positive reactions were detected in the normal alveolar and ductal epithelia and CK5- and CK14-positive reactions were seen in myoepithelial cells of nonlactating mammary glands. Positive staining for CK5 and CK8 was detected in all tumours and CK14 was expressed in those with a papillary pattern. Comparisons between non-lactating glands and tumours indicated that the neoplasms were well or moderately differentiated, there was no squamoid differentiation and that they arose from the alveoli and duct system, not the myoepithelial cells.

The status of DNA methylation, as measured by the 5-methylcytosine content of nuclear DNA, was examined in normal livers and in chemically induced or spontaneous primary hepatocellular carcinoma (PHC) arising in three strains of mice. The DNA from spontaneous tumors of genetic origin in C3H mice and also from acetylaminofluorene, chlordane, or 3'-methyl-4-dimethylaminoazobenzene-induced tumors in C57Bl and B6C3 mice was undermethylated compared to the levels in background and normal liver samples. The DNA methylase activities from normal liver, background liver, and PHC were assayed in C3H mice to determine whether the observed genomic undermethylation is related to a dysfunction of this enzyme and were compared to the rates of DNA synthesis in these tissues. Since DNA methylase levels from tumor nuclei were elevated compared to background, it is concluded that the undermethylation found in the tumor genomes of this system is not due to inactivation nor a significant deficiency of the activity of this enzyme relative to the demand in tumors for methylation of de novo synthesized DNA.

The components and variations of glycosaminoglycan (GAG) in the growth of transplantable tumors derived from a spontaneous mouse mammary tumor were investigated. A 45-week-old ddY female mouse, obtained from Shizuoka Laboratory Animal Center, was found to have a bean-sized mass at the third mammary gland of the left side. The tumor mass was surgically excised and used for transplantation in the present study. This mammary tumor was histologically found to be Type B-adenocarcinoma. Transplantable mammary tumors consisted of the fibrous or edematous interstitium contained a large amount of GAG components, which was mainly hyaluronic acid (HA), dermatan sulfate (DS) and chondroitin sulfate A/C (ChS). In the analysis of GAG components, HA content was present in a large amount in logarithmic growth phase of transplanted mammary tumors, but it was markedly decreased in stationary phase. On the other hand, the contents of DS and ChS increased in stationary phase of the tumor growth, and these increases corresponded, histologically, with the propagation of the fibrous interstitial tissues.

Gastric hyperplasia occurred more frequently among densely housed mice than mice housed singly, and crowding stress may have been implicated in this increased prevalence. Affected stomachs had striking increases in sulfomucin secretion when compared with unaffected gastric mucosa. The mucin changes suggested incomplete maturation of mucous cells in this condition and were similar to those reported in association with early neoplastic or pre-neoplastic lesions in the stomach of both man and rodents.

A remarkably severe spontaneous amyloidosis involving multiple organs has characterized the inbred PS mouse strain since the 25th generation. The amyloid substance was extracted with H2O and purified by successive gel filtrations on Sephadex G100, Sephadex G10 and Biogel P4. It was submitted to biochemical, immunochemical and histochemical analysis in order to determine its origin. Potassium permanganate resistance of the affinity for Congo Red dye, aminoacid composition, cross-reactivity with anti-mouse light chains antisera suggested an amyloidogenic process comparable to that described for the AL substance in man. However, even if abnormal lymphoid infiltrates were present in several organs, the presence of M component could not be demonstrated in serum or urine of these mice. This indicated either a limited tumoral mass or a tumor poorly secreting a precursor that would be strongly amyloidogenic. Alternatively, the existence of a so far unidentified precursor could not be excluded.

Myocardial lesions were noticed in BALBc/Cr mice during experiments with Moloney sarcoma virus (MSV). A study was initiated using unifected BALBc/Cr mice to determine whether these lesions were the result of a viral infection. Sixty percent of the females and 30% of the males used were found to have macroscopic lesions (mainly white spots on the right ventricle). The reported lesions were studied both histologically and histochemically. The animals were also examined for parasites such as Toxoplasma and tapeworm larvae, and were found negative. The investigation, which is still in progress, demonstrates the spontaneity of myocardial lesions in BALBc/Cr mice.

Morphologically abnormal lysosomes demonstrated in individuals with the Chediak-Higashi syndrome (CHS) suggested a defect in the function of these abnormal lysosomes. To gain direct experimental evidence of such a defect, horseradish peroxidase (HRP) was injected intravenously into CHS and control mice, the mice killed at varying intervals and the kidneys studied by ultrastructural cytochemistry. No morophologic difference was observed in the absorption and uptake of HRP by proximal convoluted tubules in the two groups of mice. In CHS mice, however, some of the HRP fused with enlarged lysosomes. By 48 hours after injection, the lysosomes of normal mice had digested all but trace amounts of HRP, whereas large amounts were still present in CHS mice at this time. In CHS mice, moderate amounts were still present at 72 hours and trace amounts 96 hours post injection. This slowed rate of digestion of HRP by lysosomes of the proximal convoluted tubule cells of CHS mice suggests a similar defect in all cells in CHS individuals in which there is a lysosomal degradation of protein or other matter obtained by endocytosis. Such a defect may explain some manifestations of impaired host defense observed in CHS.