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Several established models in human and veterinary medicine exist to evaluate an individual health or disease status. Many of these seem unsuitable for further epidemiological research aimed at discovering underlying influential factors. As a case example for score development and choice, the present study analyses different approaches to scoring the foot health of Asian elephants (Elephas maximus) living in European facilities. Sum scores with varying degree of detail, and without or with a weighting method, were compared using descriptive statistics, ie kurtosis, skewness, Shannon entropy, total redundancy, their maximum and their actual ranges. With increasing score complexity, a higher level of differentiation was reached. In parallel, the distribution of score frequencies in the population shifted systematically: with the least complex scoring model the pattern indicated a severely unhealthy population with an opposite skew to a hypothetically healthy population, whereas the most complex scoring model indicated a mildly affected population with a skew corresponding to that expected for a healthy population. We propose the latter, in the form of the Particularised Severity Score (ParSev), which accounts for every nail and pad individually and weights the sub-scores by squaring, as the most relevant score for further investigations, either in assessing changes within an elephant population over time, or correlating foot health in epidemiological studies to potentially influencing factors. Our results emphasise the relevance of choosing appropriate scoring models for welfare-associated evaluations, due to implications for the applicability as well as the perceived welfare status of the test population.
In the juvenile trkB knockout
(trkB−/−) mouse, retina synaptic
communication from rods to bipolar cells is severely compromised as
evidenced by a complete absence of electroretinogram (ERG)
b-wave, even though the inner retina appears anatomically
normal (Rohrer et al., 1999). Since it is
well known that the b-wave reflects light-dependent synaptic
activation of ON bipolar cells via their metabotropic
glutamate receptor, mGluR6, we sought to analyze the anatomical and
functional integrity of the glutamatergic synapses at these and other
bipolar cells in the trkB−/− mouse.
Although rod bipolar cells from wild-type juvenile mice were determined
to be immunopositive for trkB, postsynaptic metabotropic and ionotropic
glutamate receptor-mediated pathways in ON and OFF bipolar cells were
found to be functionally intact, based on patch electrode recordings,
using brief applications (“puffs”) of glutamate or its
analog, 2-amino-4-phosphonobutyric acid (APB), a selective agonist for
mGluR6 receptors. Ionotropic glutamate receptor function was assayed in
OFF-cone bipolar and horizontal cells by applying exogenous
glutamatergic agonists in the presence of the channel-permeant
guanidinium analogue, 1-amino-4-guanidobutane (AGB).
Electron-microscopic analysis revealed that the ribbon synapses between
rods and postsynaptic rod bipolar and horizontal cells were formed at
the appropriate age and appear to be structurally intact, and
immunohistochemical analysis did not detect profound defects in the
expression of excitatory amino acid transporters involved in glutamate
clearance from the synaptic cleft. These data indicate that there does
not appear to be evidence for postsynaptic deficits in glutamatergic
signaling in the ON and OFF bipolar cells of mice lacking trkB.
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