Evaluation of nucleolus organizer regions (NORs) by automatic image analysis: a contribution to standardization.

This study summarizes our experiences with the silver staining of nucleolus organizer regions (AgNORs) in a total of 580 tumours from ten different tissues. In contrast to other investigators, we made use of automatic image analysis for the evaluation of AgNORs. This provided good reproducibility as determined by the standard cumulative means technique and intra-observer (r1) and inter-observer (r2) agreement in 30 benign (r1 = 0.83-0.95, r2 = 0.76-0.92) and 50 malignant tissue samples (r1 = 0.72-0.85, r2 = 0.51-0.78). By using a series of staining times on sections from 30 tissue blocks taken from the ten types of tissue investigated, considerable variation in the argyrophilic staining of NORs in different tissues and in different blocks from one tumour was shown. The mean AgNOR area of resting lymphocytes or connective tissue cells within tissue blocks of the same organ system varied up to four-fold, even though identical staining times had been used. The most suitable silver reaction time which rendered a good diagnostic difference in the AgNOR content of benign and malignant tissue ranged, for example, in the breast cancer specimens, from 23 to 35 min. We therefore conclude that the staining time has to be adjusted to the individual silver-binding characteristics of each tissue block or even each section. The use of internal staining standards like lymphocytes or connective tissue cells in the same tissue section is mandatory. This, in turn, is most precisely controlled by morphometry.     

Mechanisms of angiogenesis in the brain

Brain angiogenesis is a tightly controlled process that is regulated by neuroectodermal derived growth factors that bind to tyrosine kinase receptors expressed on endothelial cells. In the rat brain, angiogenesis is complete around postnatal day 20, but endothelial cells can proliferate in the adult brain under pathological conditions such as hypoxia/ischemia and brain tumor growth. Current evidence suggests that physiological angiogenesis in the brain is regulated by similar mechanisms as pathological angiogenesis induced by tumors or by hypoxia/ischemia. The hypoxia-inducible endothelial cell mitogen and vascular permeability factor, vascular endothelial growth factor (VEGF) appears to play a pivotal role in most of these processes. VEGF is expressed when angiogenesis is high, as in embryonic neuroectoderm, in glioblastomas and around infarcts, but is expressed at low levels when angiogenesis is absent, as in adult neuroectoderm. Since growth factors such as VEGF and angiopoietins and their receptors appear to be necessary for angiogenesis, targeting of growth factor/receptor pathways for angiogenesis-dependent diseases such as glioblastoma might be useful for therapy. Several compounds, including anti-VEGF antibodies and VEGFR-2 inhibitors are currently in clinical trial. On the other hand, induction of angiogenesis by growth factors (pro-angiogenesis) might prove to be a rational therapy for patients with stroke.     

Vascularization of human glioma spheroids implanted into rat cortex is conferred by two distinct mechanisms

Aim of this study was to develop and characterize an applicable in vivo model to investigate angiogenesis of human gliomas. An established glioblastoma spheroid model was used to investigate the neovascularization of a standardized avascular solid tumor mass. Spheroids of two human glioma cell lines were labeled with an in vivo fluorescent dye. Single spheroids were implanted into the cortex of athymic rats. After 1, 3, 7, 14, and 21 days, brain sections containing the spheroid were immunostained for endothelial cells or vascular endothelial growth factor (VEGF). The dye-stained glioma spheroid and the endothelial cells were visualized by confocal microscopy. Two distinct mechanisms of tumor vascularization could be observed. (1) "Classical" angiogenesis with new vessels sprouting from existing host vessels into the spheroid was seen. (2) Individual endothelial cells were found to migrate towards and into the center of the spheroid where they coalesced to form new vessels. This process occurred as early as 24 hr after spheroid implantation. Spheroid vascularization was accompanied by an increase of VEGF expression, which peaked 7 days after implantation and returned to normal patterns by 14-21 days. Besides the "classical" angiogenesis by angiogenic blood vessels, the recruitment of individual endothelial cells seems to be an additional mechanism in early glioma vascularization. Our model proves to be a reliable, reproducible system to study in vivo angiogenesis of human gliomas.     

Negative effect of lockdown on juvenile idiopathic arthritis patients

Clinical Rheumatology - The aim of this study is to evaluate a possible negative action of lockdown, during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, in the...