Impairment of Spike-Timing-Dependent Plasticity at Schaffer Collateral-CA1 Synapses in Adult APP/PS1 Mice Depends on Proximity of Aβ Plaques

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder characterized by progressive and irreversible cognitive decline, with no disease-modifying therapy until today. Spike timing-dependent plasticity (STDP) is a Hebbian form of synaptic plasticity, and a strong candidate to underlie learning and memory at the single neuron level. Although several studies reported impaired long-term potentiation (LTP) in the hippocampus in AD mouse models, the impact of amyloid-β (Aβ) pathology on STDP in the hippocampus is not known. Using whole cell patch clamp recordings in CA1 pyramidal neurons of acute transversal hippocampal slices, we investigated timing-dependent (t-) LTP induced by STDP paradigms at Schaffer collateral (SC)-CA1 synapses in slices of 6-month-old adult APP/PS1 AD model mice. Our results show that t-LTP can be induced even in fully developed adult mice with different and even low repeat STDP paradigms. Further, adult APP/PS1 mice displayed intact t-LTP induced by 1 presynaptic EPSP paired with 4 postsynaptic APs (6× 1:4) or 1 presynaptic EPSP paired with 1 postsynaptic AP (100× 1:1) STDP paradigms when the position of Aβ plaques relative to recorded CA1 neurons in the slice were not considered. However, when Aβ plaques were live stained with the fluorescent dye methoxy-X04, we observed that in CA1 neurons with their somata <200 µm away from the border of the nearest Aβ plaque, t-LTP induced by 6× 1:4 stimulation was significantly impaired, while t-LTP was unaltered in CA1 neurons >200 µm away from plaques. Treatment of APP/PS1 mice with the anti-inflammatory drug fingolimod that we previously showed to alleviate synaptic deficits in this AD mouse model did not rescue the impaired t-LTP. Our data reveal that overexpression of APP and PS1 mutations in AD model mice disrupts t-LTP in an Aβ plaque distance-dependent manner, but cannot be improved by fingolimod (FTY720) that has been shown to rescue conventional LTP in CA1 of APP/PS1 mice.

Mesenchymal Stem Cells Application in Wound Tissue Healing in Old Animals

Purpose

An assessment of the effectiveness of progenitor mesenchymal stem cell as injections and as part of a polymer hydrogel for the wounds treatment.

Materials and Methods

Fixed-size wounds (average area of 135.8 mm²) were modeled on the back of white Wistar rats, aged 9 months. Mesenchymal stem cells (MSC) isolated from a human umbilical cord were injected into the wounds once on the modeling day (SC group). In other animals, MSC were periodically applied externally as one of the components in the polymer hydrogel (Polymer_sc group). The systemic effect of the cells was assessed via the analysis of intact contralateral wounds located on the opposite side of the same animal’s back (groups Control_sc and Control_Psc, respectively). The reference intact wounds belonged to the Control_0 group. The wound area was studied in dynamics. Descriptive microscopy was supplemented by an assessment of the collagen fibers’ maturity, the epidermal layers, and the number of fibroblasts and leukocytes in different parts of the wounds.

Results

Both the local and systemic application of MSC led to an improvement in wound regeneration. During the acute inflammatory phase (up to 3 days), the method and place of application did not affect the dynamics of wound healing. The use of Polymer_sc ultimately demonstrated the best effectiveness. The anti-inflammatory effect of MSC was confirmed by a decrease in leukocyte infiltration in the wound centers (Polymer_sc and SC groups) and edges (all groups, with the greatest extent in the Polymer_sc group). The proliferative phase that expresses itself via accelerated growth in fibroblast number and collagen production was affected in the Control_Psc group and mostly in the Polymer_sc group.

Conclusion

The applications of MSC in various ways improve and accelerate wound healing even in old animals. The best performance was achieved in the Polymer_sc group.

Corynebacterium pseudotuberculosis infection in goats. III. The influence of age

Serological examinations for Gorynebacterium pseudotuberculosis in-fection were carried out in 14 known positive herds and in 1 herd that had beeni recently established through purchase of animals from different herds. Serum samples were collected sequentially on up to 4 occasions from animals during their first year of life. In most herds, these animals were examined clinically for superficial swellings once or twice during the same period.

The adult goats in 8 infected herds were examined both clinically and serologically. Age distribution was similar in each of these herds. All serum samples were examined for antibodies against Gorynebac-terium pseudotuberculosis in both the bacterial agglutination test (BAT) and the hemolysis inhibition test (HIT).

The proportion of kids which were seropositive in both tests de-creased to zero at 4 months of age. At the age of 11–12 months, the proportion of seropositive animals was about 50 % in the BAT and 30 % in the HIT.

When examined when housed for the winter at the age of about 8 months (mean age), the prevalence of animals with superficial swellings was 7 %. At the age of about 1 year (mean age), 29 % of the examined animals had such lesions. In the recently established herd, only a few of the yearlings were seropositive.

Titre values in BAT and HIT increased until 6 years of age. Anti-body titre values were significantly lower in yearlings than in older goats in both tests, P < 0.005. No significant difference in the propor-tion of goats with superficial swellings was seen at the different ages.