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INTRODUCTION: The role of CD44 protein in astrocytes in physiological and pathological conditions in the brain remains largely unknown. To study its function the transgenic animal models were used. The CD44 knock-out mice are commercially available, however the compensatory effect of ICAM‑1 molecule forthe CD44 deficiency has been previously described. For that reason, we decided to create conditional knockout mice where we can control the time of gene silencing during animal development by tamoxifen (TAM) administration. Moreover, we generated a conditional overexpression mouse line in which the transgene overexpression is also initiated by TAM. By using CreERT2 fusion protein driven by GFAP (glial fibrillary acidic protein) promoter, we can achieve inducible astrocyte‑specific CD44 knock‑out/overexpression line in which CD44 gene becomes altered in astrocytes of the adult brain upon the tamoxifen-driven activation of Cre recombinase, at the chosen time point. This gives us an ability to change the CD44 expression after the mice reach adulthood. AIM(S): The aim of our work is to validate two conditional double transgenic mouse lines created with the use of Cre/lox system to study the function of CD44 protein in astrocytes. METHOD(S): For the comparison of Cre/lox activation efficacy, mice were injected with TAM either every 12 hours (10 mg/ml) or every 24 hours (20 mg/ml) for the duration of 5 constitutive days. Then, the effect of the transgene activation was validated using western blot and immunohistochemistry techniques. RESULTS: Validation studies confirm CD44 overexpression model works. CD44 overexpression can be seen in all hippocampus, cerebral cortex and cerebellum. Immunohistochemistry staining shows increased level of CD44 in astrocytes of cerebral cortex and hippocampus, especially in the molecular layer of dentate gyrus. CONCLUSIONS: Described inducible CD44 transgenic mouse lines are the first animal models that can help scientists study the yet undiscovered function of CD44 protein in astrocytes.
The study focused on the effects of deforestation by heavy winds and tree stand damage produced by bark beetle invasion on water chemistry of mountainous catchment of Kościeliski Stream in the Tatra National Park (southern Poland). 200 samples of stream and spring water were collected in three series: in July, August and October 2015. Water samples obtained from areas characterized by tree stand damage caused by heavy winds were found to have much higher mean concentration of nitrate (15.44 mg/L) as well as a much higher overall mean nitrate content (3.44% mval/L) than samples obtained from non−deforested areas (3.26 mg/L and 0.78% mval/L). The increase in nitrate concentration and its share in overall water chemistry was high enough that the anion sequence for the deforested areas became altered from HCO3>SO4>NO3>Cl to HCO3>NO3>SO4>Cl. The mean change in water nitrate concentration in areas with tree stands damaged by the bark beetle was smaller (6.17 mg/L; 1.60% mval/L) than that for areas deforested by wind. The concentration of NO3– in stream water in deforested areas varied more than that in stream water in non−deforested areas.
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