Neoplastic transformation and angiogenesis in the thymus of transgenic mice expressing SV40 T and t antigen under an L-pyruvate kinase promoter (SV12 mice).

Using several techniques, we have assessed morphological characteristics of a malignant thymic tumour in SV12 transgenic (Tg) mice expressing SV40 T and t antigens under control of an L-PK promoter. We describe the development of a carcinoma originating from thymic hyperplasia and followed by the formation of a benign tumour composed chiefly of medullary epithelial cells expressing the transgene and of lymphocytes, a pathology very rarely reported in mice. Our study of the SV12 Tg mice represents the first description of a model of a pure malignant thymic tumour associated with extensive angiogenesis maintained in numerous descendants.

Early steps of a thymic tumor in SV40 transgenic mice: hyperplasia of medullary epithelial cells and increased mature thymocyte numbers disturb thymic export.

Bone marrow progenitors migrate to the thymus, where they proliferate and differentiate into immunologically competent T cells. In this report we show that mice transgenic for SV40 T and t antigens under the control of the L-pyruvate kinase promoter develop, in a first step, thymic hyperplasia of both thymocytes and epithelial cells. Morphological studies (histology, immunohistolabeling and electron microscopy) revealed modifications of the thymic microenvironment and gradual expansion of medullary epithelial cells in 1 month-old mice, taking over the cortical region.

Unusual IgM fibrillar deposits in glomerulonephritis: ultrastructural and diffraction studies in a case report.

Morphological examination of 2 renal biopsy specimens obtained from a 69-year-old woman with a nephrotic syndrome, high blood pressure, and a reduced glomerular filtration rate revealed, in ultrastructural study, a type of a glomerulonephritis with fibrillar deposits in a subendothelial position which were unusual in their immunoglobulin components (mainly IgM). The fibrillar components were of irregular size, 13 to 18 nm in diameter and presented a very particular "barbed wire" morphological aspect, not hitherto described. Diffraction studies and image analysis, revealed spiraled fibrils with regular alternating elements that we suggest may correspond to IgM molecules.

Mesangial IgG glomerulonephritis: a distinct type of primary glomerulonephritis.

Fourteen cases of mesangial IgG glomerulonephritis characterized by exclusive or predominant mesangial IgG deposits are reported. The median age at onset was 19 yr (range, 13 to 47 yr). No patient exhibited evidence of systemic lupus erythematous or other systemic diseases.