Biomedical subjects

Gerda Mitteregger

Publications and source records attributed to Gerda Mitteregger.

8 recordsLinked to original sources

PubMed2006

Cell-free formation of misfolded prion protein with authentic prion infectivity.

Prion propagation has been modeled in vitro; however, the low infectious titer of PrP(Sc) thus generated has cast doubt on the "protein-only" hypothesis. Here we show that prion delivery on suitable nitrocellulose carrier particles abrogates the apparent dissociation of PrP(Sc) and infectivity. Misfolded prion protein generated by protein misfolding cyclic amplification is as infectious as authentic brain-derived PrP(Sc) provided that confounding effects related to differences in the size distribution of prion protein aggregates generated in vitro and consecutive differences in regard to biological clearance are abolished.

Animals↗

PubMed2006

Synapse formation and function is modulated by the amyloid precursor protein.

The amyloid precursor protein (APP) is critical in the pathogenesis of Alzheimer's disease. The question of its normal biological function in neurons, in which it is predominantly located at synapses, is still unclear. Using autaptic cultures of hippocampal neurons, we demonstrate that hippocampal neurons lacking APP show significantly enhanced amplitudes of evoked AMPA- and NMDA-receptor-mediated EPSCs. The size of the readily releasable synaptic vesicle pool was also increased in neurons lacking APP, whereas the release probability was not affected. In addition, the analysis of spontaneous miniature synaptic currents revealed an augmented frequency in neurons lacking APP, whereas the amplitude of miniature synaptic currents was not found to be altered. Together, these findings strongly indicate that lack of APP increases the number of functional synapses. This hypothesis is further supported by morphometric immunohistochemical analysis revealing an increase of synaptophysin-positive puncta per cultured APP knock-out neuron. In conclusion, lack of APP affects synapse formation and transmission in cultured hippocampal neurons.

Action Potentials↗

PubMed2006

Unaltered prion protein cleavage in plasminogen-deficient mice.

In normal brains and cultured cells, cellular prion protein (PrP) is partially found as N-terminally truncated fragments, designated C1 and C2. The cleavage of recombinant PrP to a fragment corresponding to C1 can be mediated by the protease plasmin (Pln) in vitro, suggesting that plasmin might be responsible for the generation of the C1 fragment in vivo as well. The cleavage pattern of PrP found in both brain lysates and other tissues of plasminogen knock-out mice, however, is unaltered. The presence of C1 fragment in homogenates from plasminogen-deficient mice in a comparable ratio with full-length PrP as can be found in wild-type animals indicates that other proteases in addition to plasmin are responsible for PrP cleavage in vivo.

Animals↗

PubMed2006

Loss of the cellular prion protein affects the Ca2+ homeostasis in hippocampal CA1 neurons.

Previous neurophysiological studies on prion protein deficient (Prnp(-/-)) mice have revealed a significant reduction of slow afterhyperpolarization currents (sI(AHP)) in hippocampal CA1 pyramidal cells. Here we aim to determine whether loss of PrP(C.) directly affects the potassium channels underlying sI(AHP) or if sI(AHP) is indirectly disturbed by altered intracellular Ca(2+) fluxes. Patch-clamp measurements and confocal Ca(2+) imaging in acute hippocampal slice preparations of Prnp(-/-) mice compared to littermate control mice revealed a reduced Ca(2+) rise in CA1 neurons lacking PrP(C) following a depolarization protocol known to induce sI(AHP). Moreover, we observed a reduced Ca(2+) influx via l-type voltage gated calcium channels (VGCCs). No differences were observed in the protein expression of the pore forming alpha1 subunit of VGCCs Prnp(-/-) mice. Surprisingly, the beta2 subunit, critically involved in the transport of the alpha1 subunit to the plasma membrane, was found to be up-regulated in knock out hippocampal tissue. On mRNA level however, no differences could be detected for the alpha1C, D and beta2-4 subunits. In conclusion our data support the notion that lack of PrP(C.) does not directly affect the potassium channels underlying sI(AHP), but modulates these channels due to its effect on the intracellular free Ca(2+) concentration via a reduced Ca(2+) influx through l-type VGCCs.

Animals↗

PubMed2006

Lentivector-mediated RNAi efficiently suppresses prion protein and prolongs survival of scrapie-infected mice.

Prion diseases are fatal neurodegenerative diseases characterized by the accumulation of PrP(Sc), the infectious and protease-resistant form of the cellular prion protein (PrP(C)). We generated lentivectors expressing PrP(C)-specific short hairpin RNAs (shRNAs) that efficiently silenced expression of the prion protein gene (Prnp) in primary neuronal cells. Treatment of scrapie-infected neuronal cells with these lentivectors resulted in an efficient and stable suppression of PrP(Sc) accumulation. After intracranial injection, lentiviral shRNA reduced PrP(C) expression in transgenic mice carrying multiple copies of Prnp. To test the therapeutic potential of lentiviral shRNA, we used what we believe to be a novel approach in which the clinical situation was mimicked. We generated chimeric mice derived from lentivector-transduced embryonic stem cells. Depending on the degree of chimerism, these animals carried the lentiviral shRNAs in a certain percentage of brain cells and expressed reduced levels of PrP(C). Importantly, in highly chimeric mice, survival after scrapie infection was significantly extended. Taken together, these data suggest that lentivector-mediated RNA interference could be an approach for the treatment of prion disease.

Animals↗

PubMed2004

In vitro metabolism of dehydroepiandrosterone and testosterone by canine hair follicle cells.

The metabolism of radioactive dehydroepiandrosterone (DHEA) and testosterone was studied in dermal papilla cells (DPC) and dermal fibroblasts (DFB) derived from hair follicles from two different body sites (head, flank) of four male, castrated beagle dogs. Thin layer chromatography was used for separation, and autoradiography for identification of the radioactive metabolites. DHEA was metabolized mainly to 11 alpha-OH-testosterone and only to a minor extent to 11 alpha-OH-androstenedione and another unidentified metabolite. The highest percentage of metabolization of DHEA was found in DFB of the head. Testosterone was metabolized only to a minor extent (less than 10%) to 5 alpha-dihydrotestosterone and epiandrosterone and there was no significant difference between either the two cell types or the two locations. These results clearly show that the metabolization of androgens in canine DPC and DFB is different from that observed in cells from the human hair follicle.

Animals↗

PubMed2002

Primary cell culture and morphological characterization of canine dermal papilla cells and dermal fibroblasts.

Skin biopsies were taken from female dogs, the primary hair follicles isolated and the dermal papilla dissected. After incubation in supplemented Amniomax complete C100 medium in 24-well culture plates, the dermal papilla cells (DPC) grew to confluence within 3 weeks. Thereafter, they were subcultivated every 7 days. Dermal fibroblast (DFB) cultures were established by explant culture of interfollicular dermis in serum-free medium, where they reached confluence in 10 days. They were subcultivated every 5 days. For immunohistochemistry, cells were grown on cover slips for 24 h, fixed and stained with antibodies against collagen IV and laminin. DPC showed an aggregative growth pattern and formation of pseudopapillae. Intensive staining for collagen IV and laminin could be observed until the sixth passage. DFB grew as branching, parallel lines and showed only weak staining for collagen IV and laminin.

Animals↗

PubMed2002

Immunohistochemical localization of androgen and oestrogen receptors in canine hair follicles.

Skin biopsies from seven different body sites were obtained from 21 dogs of different breeds (short, normal, long hair), which were presented for euthanasia. Commercially available polyclonal antibodies were used for the immunohistochemical detection of androgen and oestrogen receptors. Both receptors showed a similar distribution in canine skin, with specific intranuclear staining. In the epidermis, the percentage of androgen receptor (AR)-positive cells, but not that of oestrogen receptor (ER)-positive cells, was significantly higher in samples from the thorax and the flank. In the dermal papilla, the percentage of ER-positive (but not AR-positive) cells was significantly lower in biopsies from the flank. No significant difference was found for both receptors between the locations in the outer root sheath, among the three different hair types, between sex and between intact and castrated dogs.

Animals↗