Motor and Hippocampal Dependent Spatial Learning and Reference Memory Assessment in a Transgenic Rat Model of Alzheimer\u27s Disease with Stroke

Alzheimer\u27s disease (AD) is a debilitating neurodegenerative disease that results in neurodegeneration and memory loss. While age is a major risk factor for AD, stroke has also been implicated as a risk factor and an exacerbating factor. The co-morbidity of stroke and AD results in worsened stroke-related motor control and AD-related cognitive deficits when compared to each condition alone. To model the combined condition of stroke and AD, a novel transgenic rat model of AD, with a mutated form of amyloid precursor protein (a key protein involved in the development of AD) incorporated into its DNA, is given a small unilateral striatal stroke. For a model with the combination of both stroke and AD, behavioral tests that assess stroke-related motor control, locomotion and AD-related cognitive function must be implemented. The cylinder task involves a cost-efficient, multipurpose apparatus that assesses spontaneous forelimb motor use. In this task, a rat is placed in a cylindrical apparatus, where the rat will spontaneously rear and contact the wall of the cylinder with its forelimbs. These contacts are considered forelimb motor use and quantified during video analysis after testing. Another cost-efficient motor task implemented is the beam-walk task, which assesses forelimb control, hindlimb control and locomotion. This task involves a rat walking across a wooden beam allowing for the assessment of limb motor control through analysis of forelimb slips, hindlimb slips and falls. Assessment of learning and memory is completed with Morris water maze for this behavioral paradigm. The protocol starts with spatial learning, whereby the rat locates a stationary hidden platform. After spatial learning, the platform is removed and both short-term and long-term spatial reference memory is assessed. All three of these tasks are sensitive to behavioral differences and completed within 28 days for this model, making this paradigm time-efficient and cost-efficient

APP21 transgenic rats develop age-dependent cognitive impairment and microglia accumulation within white matter tracts.

Background Most of the animal models commonly used for preclinical research into Alzheimer\u27s disease (AD) largely fail to address the pathophysiology, including the impact of known risk factors, of the widely diagnosed sporadic form of the disease. Here, we use a transgenic rat (APP21) that does not develop AD-like pathology spontaneously with age, but does develop pathology following vascular stress. To further the potential of this novel rat model as a much-needed pre-clinical animal model of sporadic AD, we characterize APP21 transgenic rats behaviorally and histologically up to 19 months of age. Methods The open field test was used as a measure of activity; and the Morris water maze was used to assess learning, memory, and strategy shift. Neuronal loss and microglia activation were also assessed throughout the brain. Results APP21 transgenic rats showed deficits in working memory from an early age, yet memory recall performance after 24 and 72 h was equal to that of wildtype rats and did not deteriorate with age. A deficit in strategy shift was observed at 19 months of age in APP21 transgenic rats compared to Fischer wildtype rats. Histologically, APP21 transgenic rats demonstrated accelerated white matter inflammation compared to wildtype rats, but interestingly no differences in neuron loss were observed. Conclusions The combined presence of white matter pathology and executive function deficits mirrored what is often found in patients with mild cognitive impairment or early dementia, and suggests that this rat model will be useful for translationally meaningful studies into the development and prevention of sporadic AD. The presence of widespread white matter inflammation as the only observed pathological correlate for cognitive deficits raises new questions as to the role of neuroinflammation in cognitive decline

The effects of different saddle pads on the pressure exerted on the equine back by correctly fitting dressage saddles

In order to improve saddle fit and comfort for the horse, many equestrians use a saddle pad in addition to an ordinary saddle cloth or blanket. To date, only a few scientific studies have investigated if such pads lower the magnitude of pressure exerted on the horse’s back. The results of these studies are highly variable, presumably due to the different materials of the examined pads. The present study investigated the effect of five different, commercially available saddle pads on the mean pressure, the highest mean pressure, and the loaded area below the saddle, as well as the range of motion (ROM) of the centre of pressure (COP) on the horse’s back. Electronic saddle pressure measurements were carried out with eight horses ridden by the same person, using five different pads and a thin saddle cloth as control. Saddle pressure measurements were carried out at all gaits and on both reins, using the Pliance®-S system (Novel). The results revealed that all tested pads except for the gel pad significantly lowered mean pressure below the saddle (range in reduction: 0.8 to 1.8 kPA) as well as in areas with the highest mean pressure, representing pressure points (range: 2.1 to 5.8 kPA). None of the pads increased pressure. The loaded area below the saddle was decreased slightly, but not significantly, when pads were used. The effect of the pads on the ROM of the COP was inconsistent; certain pads significantly increased this variable, but only at certain gaits. This may indicate a loss of stability in the horse-rider system, but if the magnitude of the observed changes is relevant needs further investigation. The results indicate that none of the investigated pads affected mean pressure in an unfavourable way and that the thicker pads may help to reduce the pressure acting on the horse’s back

Adaptation strategies of horses with induced forelimb lameness walking on a treadmill

Background There is a paucity of research describing the gait pattern of lame horses at the walk. Objectives To describe the changes in motion pattern and vertical ground reaction forces (GRFz) in horses with induced forelimb lameness at the walk and compare those changes with the changes observed at the trot. Study design Experimental study. Methods In 10 clinically sound Warmblood horses, moderate forelimb lameness was induced using a sole pressure model followed by trot and walk on a treadmill. Kinematic data were collected using 3D optical motion capture (OMC), and GRFz by an instrumented treadmill. Mixed models were used to compare sound baseline versus forelimb lameness (significance was set atP < .05). Results Lameness induction significantly reduced peak GRFz on the second force peak, and vertical impulse in the lame limb. Stride and stance duration in all limbs were reduced. Lameness significantly affected the vertical movement symmetry of the head and withers. Maximum limb retraction angle, fetlock extension and protraction speed were reduced in the lame limb. Body centre of mass (COM) translation was reduced in the side-to-side direction and increased in the vertical and fore-aft directions. Several compensatory kinetic and kinematic changes were observed in the nonlame limbs. The observed changes in both kinetics and kinematics were generally smaller at walk with fewer variables being affected, compared to the trot. Main limitations Only one degree and type of orthopaedic pain (sole pressure) was studied. Conclusions Compensatory strategies of forelimb lameness at the walk include alteration of several kinetic and kinematic parameters and have some specific patterns and inter-individual differences that are not seen at the trot. However, much like at the trot, head movement and forelimb vertical force symmetry seem to be the most useful parameters to detect forelimb lameness at walk

Zielsteuerung in der Arbeitsverwaltung - ein europäischer Vergleich

"Verschiedene Industrieländer steuern ihre Arbeitsmarktverwaltungen inzwischen über Ziele. Vorliegend wird die Ausgestaltung zentraler Zielsteuerungssysteme im Jahr 2010 in sieben westeuropäischen Ländern vorgestellt. Außerdem werden insbesondere auf Basis leitfadengestützter Experteninterviews in den sieben Ländern bisherige Erfahrungen mit der Zielsteuerung ausgewertet. In die vergleichende Untersuchung sind Deutschland, Frankreich, Großbritannien, die Niederlande, Österreich, Schweden und die Schweiz einbezogen." (Autorenreferat

Passive dynamics explain quadrupedal walking, trotting, and tölting

This paper presents a simplistic passive dynamic model that is able to create realistic quadrupedal walking, tölting, and trotting motions. The model is inspired by the bipedal spring loaded inverted pendulum (SLIP) model and consists of a distributed mass on four massless legs. Each of the legs is either in ground contact, retracted for swing, or is ready for touch down with a predefined angle of attack. Different gaits, that is, periodic motions differing in interlimb coordination patterns, are generated by choosing different initial model states. Contact patterns and ground reaction forces (GRFs) evolve solely from these initial conditions. By identifying appropriate system parameters in an optimization framework, the model is able to closely match experimentally recorded vertical GRFs of walking and trotting of Warmblood horses, and of tölting of Icelandic horses. In a detailed study, we investigated the sensitivity of the obtained solutions with respect to all states and parameters and quantified the improvement in fitting GRF by including an additional head and neck segment. Our work suggests that quadrupedal gaits are merely different dynamic modes of the same structural system and that we can interpret different gaits as different nonlinear elastic oscillations that propel an animal forward

Kinetische Auswertung des Schrittes von Jungrindern und Kühen auf einem instrumentierten Laufband

Gegenstand und Ziel: Daten über die Schrittcharakteristika oder die Bodenreaktionskräfte von Milchkühen gewinnen zunehmend an Bedeutung. Deshalb wurden kinetische Variablen von gesunden Jungrindern und Kühen, die auf einem Laufband im Schritt gingen, dokumentiert und ausgewertet. Material und Methodik: Neun Jungrinder und 10 Kühe wurden an das Gehen auf dem Laufband gewöhnt. Mit dem mit Kraftaufnehmern versehenen Laufband konnten Bodenreaktionskräfte, Schrittlängen und zeitliche Variablen der Stütz- und Hangbeinphasen für alle Gliedmaßen gleichzeitig aufgezeichnet werden. Ergebnisse: Die Kühe gingen bei einer durchschnittlichen Geschwindigkeit von 1,2 ± 0,05 m/s (Mittelwert ± Standardabweichung) mit einer Doppelschrittkadenz von 43,0 ± 1,9/min und einer Doppelschrittlänge von 1,68 ± 0,1 m. Bei den Jungrindern ergaben sich für die entsprechenden Parameter 1,3 ± 0,04 m/s, 53,7 ± 2,2/min und 1,49 ± 0,05 m. Der zeitliche Anteil der Stützbeinphase relativ zur Dauer eines Doppelschritts war bei Kühen an den Schultergliedmaßen (67%) signifikant größer als an den Beckengliedmaßen (64%). Die Kraft-Zeit-Kurven aller Gliedmaßen waren zweigipflig mit einem Gipfel (FP1) kurz nach dem Auffußen und einem Gipfel (FP2) in der Abstoßphase. Die vertikale Bodenreaktionskraft war an den Beckengliedmaßen bei FP1 am höchsten, an den Schultergliedmaßen bei FP2. Das zwischen den beiden Gipfeln befindliche Minimum lag mit 45–49% der Stützbeinphase kurz vor deren Mitte. Der Anteil beider Schultergliedmaßen am Gesamtimpuls betrug 53,7% bei Kühen und 55,0% bei Jungrindern. Die Lage des Körperschwerpunkts variierte während der einzelnen Bewegungsphasen, war jedoch immer mehr zu den Schultergliedmaßen hin lokalisiert. Schlussfolgerungen: Gesunde Kühe und Jungrinder zeigten einen symmetrischen Gang mit minimalen intraindividuellen Abweichungen. Die Hinterbeine wurden vorwiegend beim Auffußen, die Vorderbeine beim Abstoßen vermehrt belastet. Die Vorderbeine hatten einen größeren Anteil am Gesamtimpuls. Die Untersuchung liefert kinetische Daten für die Ganganalyse von gesunden Kühen und Jungrindern, die bei der automatisierten Erkennung lahmer Rinder nützlich sein können

Comparison of limb loading and movement of Icelandic horses while tölting and trotting at equal speeds

OBJECTIVE: To compare gait mechanics and limb loading in Icelandic horses tölting and trotting at equal speeds and estimate their impact on orthopedic health. ANIMALS: 12 orthopedically normal Icelandic horses. PROCEDURES: Kinetic and kinematic gait variables were simultaneously recorded as each horse was ridden at a tölt and trot on an instrumented treadmill at 3.4 m/s and 3.9 m/s. Differences between gaits were tested via 1-factor repeated-measures ANOVA. RESULTS: Horses had a higher stride rate and lower stride impulses at a tölt than at a trot. For forelimbs at a tölt, shorter relative stance duration resulted in higher peak vertical force (Fzpeak). Conversely, for hind limbs, longer relative stance duration resulted in lower Fzpeak. The higher head-neck position at a tölt versus trot caused no weight shift to the hind limbs, but a higher forehoof flight arc and lower proretraction movement were identified. Stance durations for forelimbs were briefer than for hind limbs at a tölt, and the inverse was observed at a trot. Minimal height of the horse's trunk at the point of Fzpeak of the respective limb suggested a spring-like mechanism for all limbs at a tölt. Hind limb measurements revealed no evidence of increased collection. Stride-to-stride limb timing varied more at a tölt than at a trot. At a trot, horses had brief or no suspension phases and a slightly 4-beated footfall rhythm was common. Post hoc energetic estimations revealed that tölting at the measured speeds was less advantageous than trotting. CONCLUSIONS AND CLINICAL RELEVANCE: High forelimb action in Icelandic horses and higher head-neck position at a tölt were associated with more restricted limb proretraction, higher Fzpeak, and faster force onset than at a trot. The impact of these differences on orthopedic health needs to be investigated more in detail