Browsing by Author "Hansen, J."

The type and intensity of forest management directly influences regional catchment hydrology. Future forest management must optimise the effects of its practices to achieve sustainable management. With scenario analysis of forestry practices, the effects of different forest utilisation strategies on the hydrology of forested catchments can be temporally and spatially quantified. The approach adopted in this study necessitated the development of an interactive system for the spatially distributed modelling of hydrology in relation to forest stand development. Consequently, a forest growth model was used to simulate stand development assuming various forest management activities. Selected simulated forest growth parameters were entered into the hydrological model to simulate water fluxes under different conditions of forest structure. The approach enables the spatially differentiated quantification of changes in the water regime (e.g. increased evapotranspiration). The results of hydrological simulations in the study area, the Oker catchment (northern Harz Mountains), show that forests contribute to the protection of water systems because they have a balancing effect on the hydrological regime. As scenario simulations also suggest, however, forestry practices can also lead to substantial changes in water budgets of forested catchments. The preservation of the hydrological services of forests requires a sustainable and long-term forest conversion on the basis of current management directives for near natural silviculture. Management strategies on basis of moderate harvesting regimes are preferred because of their limited impact on the water budget.

Tumour-induced hem- and lymph-angiogenesis are frequently associated with tumour progression. Vascular endothelial growth factor-C (VEGF-C) is a potent inducer of lymphangiogenesis, while the endogenous soluble splice-variant of VEGF receptor-2, esVEGFR-2, acts as a natural inhibitor. Previously we have shown down-regulation of esVEGFR-2 mRNA in progressed stages of neuro-blastoma (NB), a tumour derived from sympatho-adrenal precursor cells. Here we studied the immunolocalization of esVEGFR-2 in human embryos, infantile adrenal gland and primary NB. We also quantified esVEGFR-2 mRNA in NB cell lines after differentiation-induction by all-trans retinoic acid (ATRA). By immunoperoxidase staining we observed expression of esVEGFR-2 in both the sympathetic trunk and the adrenal medulla. Additionally, esVEGFR-2 was found in spinal ganglia, floor plate of the neural tube, choroid plexus, notochord, arterial endothelium, skeletal muscle, epidermis and gut epithelium. Developing and circulating leukocytes showed the strongest signal. In NB, esVEGFR-2 was considerably stronger in differentiating low grade tumours with neuronal phenotype than in undifferentiated lesions. Differentiation-induction of the NB cell line SMS-Kan with 5-10 µM ATRA resulted in a significant increase of esVEGFR-2 mRNA after 6, 9 and 12 days. We show that esVEGFR-2 is widely expressed in embryonic tissues. Especially, the adrenal medulla and circulating leukocytes seem to be potent inhibitors of lymphangiogenesis. We provide additional evidence for a role of esVEGFR-2 in NB. Thereby, high levels of esVEGFR-2 correlate with a more differentiated phenotype, and may inhibit tumour progression by inhibition of lymphangiogenesis.