Periphery of ethylnitrosourea-induced spinal gliomas in rats with special reference to the vascular structure

VEGF immunopositivity related to malignancy degree, proliferative activity and angiogenesis in ENU-induced gliomas

Growth of solid tumors is highly dependent on angiogenesis. During tumor development, neoplastic cells switch to an angiogenic phenotype, playing a significant role in the expression of the vascular endothelial growth factor (VEGF). Seventy-two brain gliomas were induced in Sprague Dawley rats by prenatal exposure to ethylnitrosourea (ENU). Screening and location of tumors was carried out using magnetic resonance imaging (MRI). Conventional histology and immunocytochemistry for antibodies against glial fibrillary acidic protein (GFAP), S-100, NF, oligodendrocyte Ab-2, Ki-67, and VEGF165 were performed. The proliferation index (PI) was calculated from the Ki-67 labeling index, and the concentration of VEGF165 was quantified by enzyme-linked immunosorbent assay (ELISA). In vivo identification of macro- and microtumor appears to be useful to lead morphological and biochemical studies. Histopathology allows us to identify microtumors as classic oligodendrogliomas (CO; mean PI of 6.01 +/- 2.8%) and macrotumors as anaplastic oligodendrogliomas (AO; mean PI of 14.06 +/- 5%). Classic oligodendrogliomas show scarce VEGF165 expression whereas anaplastic ones display VEGF165 protein level 100-fold increased respect to CO. Astrocytes, neoplastic, and endothelial cells show differential immunostaining patterns from the border to the core of neoplasm. Positive structures for VEGF and their distribution vary according to PI increase. Anaplastic gliomas displaying VEGF-positive intratumor capillaries correspond to the highest PI values. To identify the "angiogenic switch," we propose the glioma stage characterized by VEGF immunopositive neoplastic cells inside the tumor and positive endothelial cells surrounding it.

Lectin histochemistry of ethylnitrosourea-induced oligodendrogliomas in the rat

Oligodendrogliomas (n = 26) induced by ethylnitrosourea (ENU) in wistar rats were examined to assess the lectin specificity to oligodendroglial membranes. Two different types of oligodendrogliomas were found in our material: an isomorphous type (n = 12), and a polymorphous type (n = 14). The first one, with two variants according to its size, macro- (n = 9) and microtumors (n = 3), had predominantly a honey-comb pattern with 'clear halos' around the nuclei without anaplasia. The second type, composed mostly by macrotumours, was anaplastic, with high cellular density, necrosis and intratumoral hemorrhages. Peanut agglutinin (PNA) labelled plasma membranes of well-differentiated cellular components of the first group. The tumoral oligodendrocytes lost the property to bind PNA in the second group of tumours, while Concanavalin A (Con A) showed affinity to intracytoplasmic structures of these tumours. PNA is a reliable marker of oligodendroglial plasma membrane of well-differentiated ENU-induced oligodendrogliomas. This experimental model, using PNA and Con A, may have important clinical applications regarding the biological behaviour of this type of neoplasm.

Experimental CNS tumors in rats. Testing field for a computerized classification and tumor grading

The purpose of this study was to verify the efficiency of a previously described method for the computerized histological diagnosis of experimental brain tumors (Kroh et al. 1988). 117 tumors (astrocytomas, glioblastomas, meningosarcomas, neurinomas, oligoastrocytomas and oligodendrogliomas), experimentally induced in rats, were studied. In every case the same 50 histological characteristics used for the elaboration of a computerized system for the diagnosis of experimental brain tumors in mice were analyzed. Our results demonstrate the efficiency of this diagnostic method for experimental brain tumors. Furthermore, the grade of malignancy of these tumors was also determined by using a previously described computer program.

Establishment and characterization of an intracerebrally transplanted tumor line, induced experimentally in the spinal cord

Transplanted tumor lines are useful to study open questions in human pathology and clinical research, particularly with the evaluation of therapeutic measures. Transplantation tumor lines derived from neoplasms in the nervous system originally induced with resorptive carcinogens are considered to be useful for these purposes. In this study observations on the histological pattern of original and intracerebrally transplanted new induced spinal cord tumors, mainly in early passages, has been investigated with the aim to improve the usefulness of the experimental model.