Stable isotope analysis of local avian diets

Stable Isotope Analysis (SIA) quantifies the proportion of 13C and 15N within an organism’s tissue and may be used in trophic and nutrient assimilation analysis (Hobson and Sealy 1991). Birds were mist-netted at the North Maple River MAPS site between July 17 and August 1, 2008. Birds were identified and banded according to MAPS protocol and blood samples of 100 μl were taken. Food items were also collected at site and sorted into three groups: berries, aquatic insects, and terrestrial insects. Blood and diet samples were dried and analyzed for δ 13C and δ 15N. Bird isotope signatures were adjusted with discrimination factors and plotted within a mixing model. Proportions for species within model were calculated using IsoSource (interval=1.0, tolerance=0.05). All species, excluding Yellow Warblers, Black-capped Chickadees, and Gray Catbirds, assimilated at least 50% of nutrients from the terrestrial food group. SIA is a new tool for diet analysis and more research is necessary to determine more accurate discrimination factors for North American avifauna.http://deepblue.lib.umich.edu/bitstream/2027.42/61426/1/Bakhurin_Burtch_Latta_2008.pd

Gain Modulation by Corticostriatal and Thalamostriatal Input Signals during Reward-Conditioned Behavior.

The cortex and thalamus send excitatory projections to the striatum, but little is known about how these inputs, either individually or collectively, regulate striatal dynamics during behavior. The lateral striatum receives overlapping input from the secondary motor cortex (M2), an area involved in licking, and the parafascicular thalamic nucleus (PF). Using neural recordings, together with optogenetic terminal inhibition, we examine the contribution of M2 and PF projections on medium spiny projection neuron (MSN) activity as mice performed an anticipatory licking task. Each input has a similar contribution to striatal activity. By comparing how suppressing single or multiple projections altered striatal activity, we find that cortical and thalamic input signals modulate MSN gain and that this effect is more pronounced in a temporally specific period of the task following the cue presentation. These results demonstrate that cortical and thalamic inputs synergistically regulate striatal output during reward-conditioned behavior

Haploinsufficiency of myostatin protects against aging‐related declines in muscle function and enhances the longevity of mice

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112228/1/acel12339-sup-0003-TableS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112228/2/acel12339.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112228/3/acel12339-sup-0004-TableS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112228/4/acel12339-sup-0002-FigureS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112228/5/acel12339-sup-0001-DataS1.pd

Physiological loading of tendons induces scleraxis expression in epitenon fibroblasts

Scleraxis is a basic helix–loop–helix transcription factor that plays a central role in promoting fibroblast proliferation and matrix synthesis during the embryonic development of tendons. Mice with a targeted inactivation of scleraxis ( Scx −/− ) fail to properly form limb tendons, but the role that scleraxis has in regulating the growth and adaptation of tendons of adult organisms is unknown. To determine if scleraxis expression changes in response to a physiological growth stimulus to tendons, we subjected adult mice that express green fluorescent protein (GFP) under the control of the scleraxis promoter ( ScxGFP ) to a 6‐week‐treadmill training program designed to induce adaptive growth in Achilles tendons. Age matched sedentary ScxGFP mice were used as controls. Scleraxis expression was sparsely observed in the epitenon region of sedentary mice, but in response to treadmill training, scleraxis was robustly expressed in fibroblasts that appeared to be emerging from the epitenon and migrating into the superficial regions of tendon fascicles. Treadmill training also led to an increase in scleraxis, tenomodulin, and type I collagen gene expression as measured by qPCR. These results suggest that in addition to regulating the embryonic formation of limb tendons, scleraxis also appears to play an important role in the adaptation of adult tendons to physiological loading. © 2011 Orthopaedic Research Society. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:606–612, 2012Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90076/1/21550_ftp.pd

Haploinsufficiency of myostatin protects against aging-related declines in muscle function and enhances the longevity of mice

Summary The molecular mechanisms behind aging-related declines in muscle function are not well understood, but the growth factor myostatin (MSTN) appears to play an important role in this process. Additionally, epidemiological studies have identified a positive correlation between skeletal muscle mass and longevity. Given the role of myostatin in regulating muscle size, and the correlation between muscle mass and longevity, we tested the hypotheses that the deficiency of myostatin would protect oldest-old mice (28-30 months old) from an aging-related loss in muscle size and contractility, and would extend the maximum lifespan of mice. We found that MSTN +/À and MSTN À/À mice were protected from aging-related declines in muscle mass and contractility. While no differences were detected between MSTN +/+ and MSTN À/À mice, MSTN +/À mice had an approximately 15% increase in maximal lifespan. These results suggest that targeting myostatin may protect against aging-related changes in skeletal muscle and contribute to enhanced longevity

Temporally restricted dopaminergic control of reward-conditioned movements.

Midbrain dopamine (DA) neurons encode both reward- and movement-related events and are implicated in disorders of reward processing as well as movement. Consequently, disentangling the contribution of DA neurons in reinforcing versus generating movements is challenging and has led to lasting controversy. In this study, we dissociated these functions by parametrically varying the timing of optogenetic manipulations in a Pavlovian conditioning task and examining the influence on anticipatory licking before reward delivery. Inhibiting both ventral tegmental area and substantia nigra pars compacta DA neurons in the post-reward period had a significantly greater behavioral effect than inhibition in the pre-reward period of the task. Furthermore, the contribution of DA neurons to behavior decreased linearly as a function of elapsed time after reward. Together, the results indicate a temporally restricted role of DA neurons primarily related to reinforcing stimulus-reward associations and suggest that directly generating movements is a comparatively less important function

Temporally restricted dopaminergic control of reward-conditioned movements.

Midbrain dopamine (DA) neurons encode both reward- and movement-related events and are implicated in disorders of reward processing as well as movement. Consequently, disentangling the contribution of DA neurons in reinforcing versus generating movements is challenging and has led to lasting controversy. In this study, we dissociated these functions by parametrically varying the timing of optogenetic manipulations in a Pavlovian conditioning task and examining the influence on anticipatory licking before reward delivery. Inhibiting both ventral tegmental area and substantia nigra pars compacta DA neurons in the post-reward period had a significantly greater behavioral effect than inhibition in the pre-reward period of the task. Furthermore, the contribution of DA neurons to behavior decreased linearly as a function of elapsed time after reward. Together, the results indicate a temporally restricted role of DA neurons primarily related to reinforcing stimulus-reward associations and suggest that directly generating movements is a comparatively less important function

Gain Modulation by Corticostriatal and Thalamostriatal Input Signals during Reward-Conditioned Behavior.

The cortex and thalamus send excitatory projections to the striatum, but little is known about how these inputs, either individually or collectively, regulate striatal dynamics during behavior. The lateral striatum receives overlapping input from the secondary motor cortex (M2), an area involved in licking, and the parafascicular thalamic nucleus (PF). Using neural recordings, together with optogenetic terminal inhibition, we examine the contribution of M2 and PF projections on medium spiny projection neuron (MSN) activity as mice performed an anticipatory licking task. Each input has a similar contribution to striatal activity. By comparing how suppressing single or multiple projections altered striatal activity, we find that cortical and thalamic input signals modulate MSN gain and that this effect is more pronounced in a temporally specific period of the task following the cue presentation. These results demonstrate that cortical and thalamic inputs synergistically regulate striatal output during reward-conditioned behavior