532 research outputs found

    A High School Comes to Scarborough

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    https://digitalmaine.com/scarborough_books/1149/thumbnail.jp

    C57BL/6 life span study: age-related declines in muscle power production and contractile velocity

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    Quantification of key outcome measures in animal models of aging is an important step preceding intervention testing. One such measurement, skeletal muscle power generation (force * velocity), is critical for dynamic movement. Prior research focused on maximum power (P max), which occurs around 30-40 % of maximum load. However, movement occurs over the entire load range. Thus, the primary purpose of this study was to determine the effect of age on power generation during concentric contractions in the extensor digitorum longus (EDL) and soleus muscles over the load range from 10 to 90 % of peak isometric tetanic force (P 0). Adult, old, and elderly male C57BL/6 mice were examined for contractile function (6-7 months old, 100 % survival; ~24 months, 75 %; and ~28 months, 50 % P 0). The shape of the force-velocity curve also changed with age (a/P 0 increased). In addition, there were prolonged contraction times to maximum force and shifts in the distribution of the myosin light and heavy chain isoforms in the EDL. The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.R01 AG017768 - NIA NIH HHS; F31 AG044108 - NIA NIH HHS; T32 AG029796 - NIA NIH HHS; R01 EY15313 - NEI NIH HHS; R01 EY015313 - NEI NIH HH

    Regional Differences in the Subacute Response of Rabbit Orbicularis Oculi to Bupivacaine-Induced Myotoxicity as Quantified With a Neural Cell Adhesion Molecule Immunohistochemical Marker

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    Purpose. This study examined the subacute myotoxic effects of injection of the local anesthetic bupivacaine on the orbicularis oculi muscle in the rabbit eyelid. In contrast to other muscles, the orbicularis oculi was resistant to injury by the usual anesthetic doses of bupivacaine when local infiltration is used. An attempt was made to assess the sensitivity of orbicularis oculi muscle to bupivacaine using a variety of increased bupivacaine concentrations and in combination with hyaluronidase. Methods. Bupivacaine was injected into rabbit lower eyelids at a variety of doses with and without the injection of hyaluronidase before bupivacaine treatment. Muscle injury was assessed immunohistochemically using an antibody to an isoform of neural cell adhesion molecule, anti-leu-19, a molecule shown to localize on the surface of regenerating muscle fibers. The number of neural cell adhesion molecule-positive muscle fibers was assessed 4 and 7 days after bupivacaine injection to determine the number of fibers that were injured. Results. When bupivacaine was injected into the lower eyelid at a dose of 1.5 mg, only 10% of the orbicularis oculi muscle was injured. The most effective injury involved either multiple injections of 3 mg bupivacaine or of hyaluronidase 20 minutes before the injection of 3 mg bupivacaine, resulting in injury of up to 58% of the muscle fibers. In all cases, the preseptal region of the orbicularis oculi showed a greater percentage of injury than the pretarsal portions of the muscle. Conclusions. Although multiple injections of bupivacaine and bupivacaine combined with hyaluronidase significantly increased the percentage of muscle cells injured, total destruction of the orbicularis oculi muscle was never seen. Neural cell adhesion molecule was a good marker for the quantification of the regenerating muscle fibers. It is proposed that the tight fasciculation of the orbicularis oculi muscle may play a role in preventing access of the local anesthetic to the individual muscle fibers. This demonstrates the relative clinical safety of local anesthetic injection into the eyelid. Invest Ophthalmol Vis Sci. 1993;34:3450-3458. skeletal muscle is susceptible to injury by a number of agents and methods that result in rapid degeneration of the muscle fibers. Some muscle toxic agents cause permanent muscle loss. These include x-ray irradiation 1 and doxorubicin. 2 " 4 Other agents cause muscle injury followed by regeneration. These include physi

    Antinociception Following Implantation of AtT-20 and Genetically Modified AtT-20/hENK Cells in Rat Spinal Cord

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    AtT-20 cells, which produce β-endorphin, and AtT-20/hENK cells, which are AtT-20 cells transfected with a proenkephalin gene, were implanted in the rat spinal subarachnoid space in an effort to produce an antinociceptive effect. Host rats were tested for antinociceptive activity by standard nociceptive tests, tail flick and hot plate. Although cell implants had minimal effect on the basal response to thermal nociceptive stimuli, administration of the β2-adrenergic agonist isoproterenol produced antinociception in the cell-implanted group but not in the control group. The antinociceptive effect of isoproterenol was dose-related and could be blocked by the opioid antagonist naloxone. Immunohistochemical analysis of spinal cords revealed the presence of enkephalin-negative cells surrounding the spinal cord of rats receiving AtT-20 cell implants, and enkephalinpositive cells surrounding the spinal cord of rats. receiving AtT-20/hENK cell implants. These results suggest that opioid-releasing cells implanted around rat spinal cord can produce antinociception and may provide an alternative therapy for chronic pain

    Improvement of Eye Alignment in Adult Strabismic Monkeys by Sustained IGF-1 Treatment

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    Purpose: The goal of this study was to determine if continuous application of insulin-like growth factor-1 (IGF-1) could improve eye alignment of adult strabismic nonhuman primates and to assess possible mechanisms of effect. Methods: A continuous release pellet of IGF-1 was placed on one medial rectus muscle in two adult nonhuman primates (M1, M2) rendered exotropic by the alternating monocular occlusion method during the first months of life. Eye alignment and eye movements were recorded for 3 months, after which M1 was euthanized, and the lateral and medial rectus muscles were removed for morphometric analysis of fiber size, nerve, and neuromuscular density. Results: Monkey 1 showed a 40% reduction in strabismus angle, a reduction of exotropia of approximately 11° to 14° after 3 months. Monkey 2 showed a 15% improvement, with a reduction of its exotropia by approximately 3°. The treated medial rectus muscle of M1 showed increased mean myofiber cross-sectional areas. Increases in myofiber size also were seen in the contralateral medial rectus and lateral rectus muscles. Similarly, nerve density increased in the contralateral medial rectus and yoked lateral rectus. Conclusions: This study demonstrates that in adult nonhuman primates with a sensory-induced exotropia in infancy, continuous IGF-1 treatment improves eye alignment, resulting in muscle fiber enlargement and altered innervational density that includes the untreated muscles. This supports the view that there is sufficient plasticity in the adult ocular motor system to allow continuous IGF-1 treatment over months to produce improvement in eye alignment in early-onset strabismus

    Molecular mechanisms separating two axonal pathways during embryonic development of the avian optic tectum

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    During embryonic development of the avian optic tectum, retinal and tectobulbar axons form an orthogonal array of nerve processes. Growing axons of both tracts are transiently very closely apposed to each other. Despite this spatial proximity, axons from the two pathways do not intermix, but instead restrict their growth to defined areas, thus forming two separate plexiform layers, the stratum opticum and the stratum album centrale. In this study we present experimental evidence indicating that the following three mechanisms might play a role in segregating both axonal populations: Retinal and tectobulbar axons differ in their ability to use the extracellular matrix protein laminin as a substrate for axonal elongation; the environment in the optic tectum is generally permissive for retinal axons, but is specifically nonpermissive for tectobulbar axons, resulting in a strong fasciculation of the latter; and growth cones of temporal retinal axons are reversibly inhibited in their motility by direct contact with the tectobulbar axon's membrane

    Transplantation of Photoreceptor and Total Neural Retina Preserves Cone Function in P23H Rhodopsin Transgenic Rat

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    Background: Transplantation as a therapeutic strategy for inherited retinal degeneration has been historically viewed to restore vision as a method by replacing the lost retinal cells and attempting to reconstruct the neural circuitry with stem cells, progenitor cells and mature neural retinal cells. Methods and Findings: We present evidence for an alternative strategy aimed at preventing the secondary loss of cones, the most crucial photoreceptors for vision, by transplanting normal photoreceptors cells into the eye of the P23H rat, a model of dominant retinitis pigmentosa. We carried out transplantation of photoreceptors or total neural retina in 3-monthold P23H rats and evaluated the function and cell counts 6 months after surgery. In both groups, cone loss was significantly reduced (10%) in the transplanted eyes where the cone outer segments were found to be considerably longer. This morphological effect correlated with maintenance of the visual function of cones as scored by photopic ERG recording, but more precisely with an increase in the photopic b-wave amplitudes by 100 % and 78 % for photoreceptor transplantation and whole retinal transplantation respectively. Conclusions: We demonstrate here that the transplanted tissue prevents the loss of cone function, which is furthe

    A comparison of the normal and regenerated retinotectal pathways of goldfish

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    This is a light and electron microscopic study of the retinotectal pathway: intact and after regeneration of the optic nerve. The spatiotemporal pattern of axonal outgrowth and termination was studied with the methods of proline autoradiography, horseradish peroxidase (HRP) labeling, and fiber degeneration. The spatial order of optic fibers in the normal and regenerated pathways was assessed by labeling small groups intraretinally with HRP and then tracing them to the tectum. The labeled fibers occupied a greater fraction of the cross section of the regenerated than the normal optic tract. At the brachial bifurcation, roughly 20% of the regenerated fibers chose the incorrect brachium vs. less than 1% of the normals. In tectum, the regenerated optic fibers reestablished fascicles in stratum opticum , but they were less orderly than in the normals. The retinal origins of the fibers in the fascicles were established by labeling individual fascicles with HRP and then, following retrograde transport, finding labeled ganglion cells in whole-mounted retinas. Labeled cells were more widely scattered over the previously axotomized retinas than over the normal ones. A similar result was obtained when HRP was applied in the tectal synaptic layer. All of these results indicate that the pathway of the regenerated optic fibers is less well ordered than the intact pathway. Both autoradiography and HRP showed that the regenerating optic fibers invaded the tectum from the rostral end, and advanced from rostral to caudal and from peripheral to central tectum, along a front roughly perpendicular to the tectal fascicles. Synapses of retinal origin were noted electron microscopically in the tectum at the same sites where autoradiography indicated that the fibers had arrived. No retinal terminals were seen where grain densities were at background levels. Fiber ingrowth and synaptogenesis apparently occurred simultaneously. The synapses were initially smaller and sparser than in normals, but were in the normal tectal strata and contacted the same classes of post synaptic elements as in normals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50021/1/902230106_ftp.pd
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