Di(2-ethylhexyl)phthalate induces hepatocellular adenoma in transgenic mice carrying a human prototype c-Ha-ras gene in a 26-week carcinogenicity study

To evaluate the transgenic mouse carrying a human prototype c-Ha-ras gene (rasH2 mouse) as a model for 26-week carcinogenicity tests, Di(2-ethylhexyl)phthalate (DEHP), a peroxisome proliferator, was administered to 15 rasH2 mice/sex/group at concentrations of 1,500, 3,000 or 6,000 ppm, and to 15 wild-type (non-Tg) mice/sex/group at a concentration of 6,000 ppm in their diets for 26 weeks. Survival rates and food consumption in the groups treated with DEHP and in the control group were similar. Body weight gain in rasH2 and non-Tg mice at 6,000 ppm in the terminal week decreased about 10% as compared to the control group. Common findings related to treatment with DEHP in rasH2 and non-Tg mice included hypertrophy with coarse granules and deposit of pigment in the liver, hydronephrosis and tubular regeneration in the kidney, focal atrophy in the testis, and increased eosinophilic body in the nasal cavity. Hepatocellular adenoma was induced by treatment with DEHP, and was confined to male rasH2; mice the incidence being 7%(1/15), 13%(2/15), and 27%(4/15) in the 1,500-, 3,000-, and 6,000-ppm group, respectively. Point mutation was not detected in codon 12 and 61 of human c-Ha-ras transgene upon DNA analyses on frozen samples taken from these hepatocellular adenomas. From the results obtained in this 26-week carcinogenicity study, it is concluded that DEHP is a hepato-carcinogen for transgenic mouse carrying a human prototype c-Ha-ras gene.

A novel "Nihon" rat model of a Mendelian dominantly inherited renal cell carcinoma

A novel rat model of hereditary renal cell carcinoma (RC) was found in a rat colony of the Sprague-Dawley strain in Japan, and named the rising "Nihon" rat. In this strain, RCs develop from early preneoplastic lesions, which begin to appear at 4 weeks of age, forming adenomas by the age of 16 weeks. The RCs are predominantly of clear cell type. Southern blot, northern blot and SSCP analyses revealed no change in the Tsc1, Tsc2, VHL, and c-Met genes. Thus, the Nihon rat should be a valuable experimental model for understanding renal carcinogenesis, especially clear cell type, which is common among human RCs.

Choriocarcinoma and teratoma in the ovary of a cynomolgus monkey

An ovarian choriocarcinoma was found in a 13-year-old cynomolgus monkey (Macaca fascicularis). The tumor was accompanied by a mature teratoma in the contralateral ovary. Histologically, the choriocarcinoma was characterized by nests of cells where cytotrophoblasts occupied the periphery with syncytiotrophoblasts at the center. Immunohistochemical staining for anti-human chorionic gonadotropin was positive in the syncytiotrophoblasts. The teratoma consisted of well-differentiated epidermal cells, sebaceous glands, hair follicles, cartilage, bone, and teeth. Choriocarcinoma metastases were in multiple organs. The concomitant development of choriocarcinoma and teratoma in the ovary is a consistent finding with the human counterparts of these lesions.

Autosomal dominant cone-rod dystrophy associated with mutations in codon 244 (Asn244His) and codon 184 (Tyr184Ser) of the peripherin/RDS gene

OBJECTIVE

To characterize clinical findings associated with mutations in codon 244 (Asn244His) and codon 184 (Tyr184Ser) of the peripherin/RDS gene.

DESIGN

Case reports with clinical features and results of fluorescein angiography, electroretinography, kinetic visual field testing, and DNA analysis.

SETTING

University medical center.

PATIENTS

Four affected members of two Japanese families with autosomal dominant cone-rod dystrophy associated with transversion mutations in codon 244 (Asn244His) and codon (Tyr184Ser) of the peripherin/RDS gene.

RESULTS

Characteristic features included the initial symptoms of decreased visual acuity, macular degeneration, central or paracentral scotoma, cone-mediated electroretinographic responses that were more impaired than rod-mediated responses, and pigmentary degeneration in the midperipheral retina in the late stage. These phenotypic features corresponded to cone-rod dystrophy type 2a by the classification of Szlyk and associates.

CONCLUSIONS

The Asn244His and Tyr184Ser mutations in the peripherin/RDS gene cause con-rod dystrophy type 2a. These findings imply that a mutation in codon 244 or codon 184 of the peripherin/RDS gene affects the functions and/or structural stability of cones and rods.

Ocular findings in patients with autosomal dominant retinitis pigmentosa and transversion mutation in codon 244 (Asn244Lys) of the peripherin/RDS gene

OBJECTIVE

To identify phenotypic characteristics of a certain mutation in the peripherin/RDS gene.

DESIGN

Case reports with clinical features and results of fluorescein angiography, electroretinography, kinetic visual field testing, dark adaptometry, and DNA analysis.

SETTING

University medical center.

PATIENTS

We studied the ocular findings in eight members of a Japanese family with autosomal dominant retinitis pigmentosa and cytosine-to-adenine transversion at the third nucleotide in codon 244 of the peripherin/RDS gene. This mutation resulted in a substitution of lysine for asparagine in amino acid 244 of peripherin/RDS, a photoreceptor-specific glycoprotein.

RESULTS

Clinical findings of each affected member in this family showed a marked intrafamilial similarity, which may provide the natural course of the phenotype produced by the Asn244Lys mutation. Characteristic features include diffuse pigmentary retinal degeneration in the midperipheral and peripheral fundi associated with macular degeneration in the later stage, starting with bull's-eye maculopathy, and severely deteriorated electroretinographic findings in both rods and cones, even in the early stage.

CONCLUSION

The mutation at codon 244 of the peripherin/RDS gene causes both rod and cone degeneration, although the precise mechanism of retinal degeneration is currently unknown.

Contribution of Oceanic Gabbros to Sea-Floor Spreading Magnetic Anomalies

The contribution of oceanic gabbros, representative rocks for layer 3 of the oceanic crust, to sea-floor spreading magnetic anomalies has been controversial because of the large variation in magnetic properties. Ocean Drilling Program (ODP) Leg 118 contains a continuous 500.7-meter section of oceanic gabbro that allows the relations between magnetization and petrologic characteristics, such as the degree of metamorphism and the magmatic evolution, to be clarified. The data suggest that oceanic gabbros, together with the effects of metamorphism and of magmatic evolution, account for a significant part of the marine magnetic anomalies.