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

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

SinR is a mutational target for fine-tuning biofilm formation in laboratory-evolved strains of Bacillus subtilis

Background: Bacteria often form multicellular, organized communities known as biofilms, which protect cells from a variety of environmental stresses. During biofilm formation, bacteria secrete a species-specific matrix; in Bacillus subtilis biofilms, the matrix consists of protein polymers and exopolysaccharide. Many domesticated strains of B. subtilis have a reduced ability to form biofilms, and we conducted a two-month evolution experiment to test whether laboratory culturing provides selective pressure against biofilm formation in B. subtilis. Results: Bacteria grown in two-month-long batch culture rapidly diversified their biofilm-forming characteristics, exhibiting highly diverse colony morphologies on LB plates in the initial ten days of culture. Generally, this diversity decreased over time; however, multiple types of colony morphology remained in our final two-month-old populations, both under shaking and static conditions. Notably, while our final populations featured cells that produce less biofilm matrix than did the ancestor, cells overproducing biofilm matrix were present as well. We took a candidate-gene approach to identify mutations in the strains that overproduced matrix and found point mutations in the biofilm-regulatory gene sinR. Introducing these mutations into the ancestral strain phenocopied or partially phenocopied the evolved biofilm phenotypes. Conclusions: Our data suggest that standard laboratory culturing conditions do not rapidly select against biofilm formation. Although biofilm matrix production is often reduced in domesticated bacterial strains, we found that matrix production may still have a fitness benefit in the laboratory. We suggest that adaptive specialization of biofilm-forming species can occur through mutations that modulate biofilm formation as in B. subtilis. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0301-8) contains supplementary material, which is available to authorized users

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

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

A High School Comes to Scarborough

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

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

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

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

Phosphorylated DegU Manipulates Cell Fate Differentiation in the <i>Bacillus subtilis</i> Biofilm<em/>

Cell differentiation is ubiquitous and facilitates division of labor and development. Bacteria are capable of multicellular behaviors that benefit the bacterial community as a whole. A striking example of bacterial differentiation occurs throughout the formation of a biofilm. During Bacillus subtilis biofilm formation, a subpopulation of cells differentiates into a specialized population that synthesizes the exopolysaccharide and the TasA amyloid components of the extracellular matrix. The differentiation process is indirectly controlled by the transcription factor Spo0A that facilitates transcription of the eps and tapA (tasA) operons. DegU is a transcription factor involved in regulating biofilm formation. Here, using a combination of genetics and live single-cell cytological techniques, we define the mechanism of biofilm inhibition at high levels of phosphorylated DegU (DegU∼P) by showing that transcription from the eps and tapA promoter regions is inhibited. Data demonstrating that this is not a direct regulatory event are presented. We demonstrate that DegU∼P controls the frequency with which cells activate transcription from the operons needed for matrix biosynthesis in favor of an off state. Subsequent experimental analysis led us to conclude that DegU∼P functions to increase the level of Spo0A∼P, driving cell fate differentiation toward the terminal developmental process of sporulation

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

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

Social behaviours by Bacillus subtilis: quorum sensing, kin discrimination and beyond

Here we review the multiple mechanisms that the Gram‐positive bacterium Bacillus subtilis uses to allow it to communicate between cells and establish community structures. The modes of action that are used are highly varied and include routes that sense pheromone levels during quorum sensing and control gene regulation, the intimate coupling of cells via nanotubes to share cytoplasmic contents, and long range electrical signalling to couple metabolic processes both within and between biofilms. We explore the ability of B. subtilis to detect “kin” (and “cheater cells”) by looking at the mechanisms used to potentially ensure beneficial sharing (or limit exploitation) of extracellular “public goods”. Finally reflecting on the array of methods that a single bacterium has at its disposal to ensure maximal benefit for its progeny, we highlight that a large future challenge will be integrating how these systems interact in mixed species communities