Muscle Fiber Contraction and Relaxation

Fiber Connectivity and Cable Management 1 www.adc.com • +1-952-938-8080 • 1-800-366-3891 Pro Patch ™ Optical Normal Through Panel 136 FL2000 System 140 FPL series Fiber Panels 152 Fiber Management Tray 156 FL1000 Fiber Termination Products 162 FiberGuide ® Fiber Management System 167 Fiber Optic Patch Cords 168 3/06 • 102117AE Broadcast Products 2 www.adc.com • +1-952-938-8080 • 1-800-726-4266 Pro Patch ™ Optical Normal Through Panel Introduction ADC’s new Optical Normal Through Panel is the latest addition to its Pro Patch line of broadcast patching products. This new fiber panel is designed to provide patch by exception, normal through functionality, similar to copper-based patch panels. Traditional fiber patch panels require a fiber jumper to be in place at all times. With this newly designed panel, however, all fiber “Source” and “Destination” connections are on the rear of the panel, with a normal through connection between the “Source” and “Destination” ports. For greater convenience and reliability, patch and monitoring capabilities are accessed on the front of the panel. Module Front Module Rear Chassis Open Features Two density options: • 3RU chassis houses 6 modules to provide 24 fiber terminations (12 pairs) using simplex connectors (SC, FC, ST) • 4RU chassis houses 6 modules to provide 48 fiber terminations (24 pairs) using small- form-factor connectors (LC, LX.5) Functionality: • Each module contains pairs of “Source” and “Destination” fibers plus optional monitor ports and a switch for emergency patching. • Accommodates 1310 and 1550 singlemode wavelengths (switch wavelength range is 1290-1330 and 1525-1610) • Connector ports on front and rear may be SC, ST, FC, LC, or LX.5 • IL through module is approximately 0.5 dB (final specifications TBD) • Module port is configurable to 90/10, 95/5 or 99/1 split ratios. Module specifications: • Modules may be added to the chassis as needed. • “Source” and “Destination” terminations may be made by either splicing raw cable to pigtails attached to the modules or by routing connectorized patch cords to the back of the modules. • Manual switch on front of module to change to “Patched” operation. • LED indicators for “Normal” and “Patched” operations. • Modules are available with or without moni- tor ports on the front. Chassis specification: • 19" EIA flush mounting • Hot swappable power supply to power switches inside modules • 110/220 IEC interface 3/06 • 102117AE Broadcast Products 3 www.adc.com • +1-952-938-8080 • 1-800-726-4266 A Source A Destination B Source B Destination 90% Monitor Patched 90% 10% Monitor Source Source Destination Destination Back of Module Front of Module Switch 90/10 Tap 90/10 Tap Switch A Source A Destination B Source B Destination 90/10 Tap 90% 10 % Monitor Normal Switch 90/10 Tap 90% 10% Switch Monitor Source Source Destination Destination Back of Module Front of Module These are preliminary specifications. Call an ADC distributor for more details. To find a distributior near you visit adc.com/partners. The new Pro Patch Optical Normal Through Panel provides patch by exception, normal through functionality. With this newly designed panel, fiber “Source” and “Destination” connections are on the rear of the panel, with a normal through connection between the “Source” and “Destination” ports. To enable patching functionality, a fiber patch cord is plugged into the front of the panel and a switch is flipped. Pro Patch ™ Optical Normal Through Panel Module Schematics Ordering Information Description Catalog Number Empty chassis with power supply 3 RU chassis Muscle Fiber Contraction and Relaxation Muscle Fiber Contraction and Relaxation Bởi: OpenStaxCollege The sequence of events that result in the contraction of an individual muscle fiber begins with a signal—the neurotransmitter, ACh—from the motor neuron innervating that fiber The local membrane of the fiber will depolarize as positively charged sodium ions (Na+) enter, triggering an action potential that spreads to the rest of the membrane will depolarize, including the T-tubules This triggers the release of calcium ions (Ca++) from storage in the sarcoplasmic reticulum (SR) The Ca++ then initiates contraction, which is sustained by ATP ([link]) As long as Ca++ ions remain in the sarcoplasm to bind to troponin, which keeps the actin-binding sites “unshielded,” and as long as ATP is available to drive the cross-bridge cycling and the pulling of actin strands by myosin, the muscle fiber will continue to shorten to an anatomical limit 1/13 Muscle Fiber Contraction and Relaxation Contraction of a Muscle Fiber A cross-bridge forms between actin and the myosin heads triggering contraction As long as Ca++ ions remain in the sarcoplasm to bind to troponin, and as long as ATP is available, the muscle fiber will continue to shorten Muscle contraction usually stops when signaling from the motor neuron ends, which repolarizes the sarcolemma and T-tubules, and closes the voltage-gated calcium channels in the SR Ca++ ions are then pumped back into the SR, which causes the tropomyosin to reshield (or re-cover) the binding sites on the actin strands A muscle also can stop contracting when it runs out of ATP and becomes fatigued ([link]) 2/13 Muscle Fiber Contraction and Relaxation Relaxation of a Muscle Fiber Ca ions are pumped back into the SR, which causes the tropomyosin to reshield the binding sites on the actin strands A muscle may also stop contracting when it runs out of ATP and becomes fatigued ++ The release of calcium ions initiates muscle contractions Watch this video to learn more about the role of calcium (a) What are “T-tubules” and what is their role? (b) Please describe how actin-binding sites are made available for cross-bridging with myosin heads during contraction The molecular events of muscle fiber shortening occur within the fiber’s sarcomeres (see [link]) The contraction of a striated muscle fiber occurs as the sarcomeres, linearly arranged within myofibrils, shorten as myosin heads pull on the actin filaments 3/13 Muscle Fiber Contraction and Relaxation The region where thick and thin filaments overlap has a dense appearance, as there is little space between the filaments This zone where thin and thick filaments overlap is very important to muscle contraction, as it is the site where filament movement starts Thin filaments, anchored at their ends by the Z-discs, not extend completely into the central region that only contains thick filaments, anchored at their bases at a spot called the M-line A myofibril is composed of many sarcomeres running along its length; thus, myofibrils and muscle cells contract as the sarcomeres contract The Sliding Filament Model of Contraction When signaled by a motor neuron, a skeletal muscle fiber contracts as the thin filaments are pulled and then slide past the thick filaments within the fiber’s sarcomeres This process is known as the sliding filament model of muscle contraction ([link]) The sliding can only occur when myosin-binding sites on the actin filaments are exposed by a series of steps that begins with Ca++ entry into the sarcoplasm The Sliding Filament Model of Muscle Contraction When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller The A band stays the same width At full contraction, the thin and thick filaments overlap Tropomyosin is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin Tropomyosin binds to troponin to form a troponin-tropomyosin complex The troponin-tropomyosin complex prevents the myosin “heads” from binding to the active sites on the actin microfilaments Troponin also has a binding site for Ca++ ions 4/13 Muscle Fiber Contraction and Relaxation To initiate muscle contraction, tropomyosin has to expose the myosin-binding site on an actin filament to allow cross-bridge formation between the actin and myosin microfilaments The first step in the process of contraction is for Ca++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands This allows the myosin heads to bind to these exposed binding sites and form crossbridges The thin filaments are then pulled by the myosin heads to slide past the thick filaments toward the center of the sarcomere But each head can only pull a very short distance before it has reached its limit and must be “re-cocked” before it can pull again, a step that requires ATP ATP and Muscle Contraction For thin filaments to continue to slide past thick ...TrueNet ® Fiber Plug-and-Play Solutions for Data Center Applications Engineered for Uptime ™ Recognizing the need for enterprises to have a dedicated area within a building for connecting servers to internal and external networks, otherwise known as data centers, the Telecommunications Industry Association (TIA) developed and ratified the TIA-942 standard. Data centers operate at very high levels of reliability and demand design flexibility to easily accommodate frequent adds and changes to equipment. Managing the thousands of cables that typically comprise a data center should always be a high priority for the data center or network manager —particularly for maximizing system performance and uptime. ADC’s TrueNet ® Fiber plug-and-play solutions for data center applications are designed to address the reliability, scalability, and thermal needs of today’s mission-critical data centers. The product suite includes plug-and-play MPO solutions for TrueNet Fiber products for placement in the main distribution area (MDA), backbone, and horizontal and equipment distribution areas (HDA and EDA). These solutions are included in the TrueNet Zero Bit-Error Warranty, and promote increased reliability of the data center through properly managed and scalable cable density, which encourages proper airflow and reduces overall installation and maintenance costs. Fiber Plug-and-Play Solutions: Managing reliability, scalability, and thermal needs of the data center Equipment Distribution Area Horizontal Distribution Area Main Distribution Area Backbone Cabling TrueNet Fiber Panels w/MPO Cassettes Data Center Optical Distribution Frame w/MPO Solution TrueNet MPO Microcable Trunk Assemblies TracerLight ® TrueNet Fiber Panel (5RU) One of the most common questions regarding MPO deployments is how the system design addresses the polarity issue of the fiber. ADC’s TrueNet system employs the recommendations made in TIA standard TIA-568.b.1-7 TrueNet plug-and-play trunks use a key up/key down fiber array as noted in TIA-568.b.1-7. The TrueNet plug-and-play cassettes are wired straight through. In addition, TrueNet duplex jumpers have a duplex clip that is easily removed for polarity changes in the field. Polarity Made Simple TIA-568-B.1-7 4 Figure 1: Connectivity Method A for Duplex Signals NOTE 1. For ease of illustration the Type-A cable is shown with a twist. This is the same cable construction shown in Figure 6. Example Optical Path A-to-B Patch Cord Type-A Array Connector Cable A-to-A Patch Cord Figure 1 Connectivity method A for duplex signals Main Distribution Area TIA-942 presents the cross-connect architecture as the best practice for Main Distribution Area (MDA). In the past, Local Area Network (LAN) cabling was based on an interconnect architecture. While interconnects are prevalent in LANS and can work in smaller data centers, in larger data centers, an interconnect architecture limits growth and manageability by requiring routine maintenance to occur on cables directly attached to active equipment. Utilizing a centralized cross-connect frame allows maintenance to be performed without disrupting the cables attached to active equipment. All moves, adds and changes can be performed on the passive cross-connect frame. The benefits of deploying a cross-connect architecture in the MDA include: lower operating costs, enhanced reliability, and a reduced risk of downtime due to poor fiber jumper management. Data Center Optical Distribution Frame With an MPO Solution ADC’s Data Center Optical Distribution Frame (ODF) is the highest density fiber Supramolecular calsequestrin complex Protein–protein interactions in chronic low-frequency stimulated muscle, postnatal development and ageing Louise Glover 1 , Sandra Quinn 1 , Michelle Ryan 1 , Dirk Pette 2 and Kay Ohlendieck 3 1 Department of Pharmacology, University College Dublin, Belfield, Ireland; 2 Fachbereich Biologie, Universita ¨ t Konstanz, Germany; 3 Department of Biology, National University of Ireland, Maynooth, Co. Kildare, Ireland As recently demonstrated by overlay assays using calseque- strin-peroxidase conjugates, the major 63 kDa Ca 2+ -bind- ing protein of the sarcoplasmic reticulum forms complexes with itself, and with junctin (26 kDa), triadin (94 kDa) and the ryanodine receptor (560 kDa) [Glover, L., Culligan, K., Cala, S., Mulvey, C. & Ohlendieck, K. (2001) Biochim. Biophys. Acta 1515, 120–132]. Here, we show that variations in the relative abundance of these four central elements of excitation–contraction coupling in different fiber types, and during chronic electrostimulation-induced fiber type transi- tions, are reflected by distinct alterations in the calsequestrin overlay binding patterns. Comparative immunoblotting with antibodies to markers of the junctional sarcoplasmic reticulum, in combination with the calsequestrin overlay binding patterns, confirmed a lower ryanodine receptor expression in slow soleus muscle compared to fast fibers, and revealed a drastic reduction of the RyR1 isoform in chronic low-frequency stimulated tibialis anterior muscle. The fast- to-slow transition process included a distinct reduction in fast calsequestrin and triadin and a concomitant reduction in calsequestrin binding to these sarcoplasmic reticulum ele- ments. The calsequestrin-binding protein junctin was not affected by the muscle transformation process. The increase in calsequestrin and decrease in junctin expression during postnatal development resulted in similar changes in the intensity of binding of the calsequestrin conjugate to these sarcoplasmic reticulum components. Aged skeletal muscle fibers tended towards reduced protein interactions within the calsequestrin complex. This agrees with the physiological concept that the key regulators of Ca 2+ homeostasis exist in a supramolecular membrane assembly and that protein– protein interactions are affected by isoform shifting under- lying the finely tuned adaptation of muscle fibers to changed functional demands. Keywords: calsequestrin; calcium homeostasis; chronic low- frequency stimulation; excitation–contraction coupling; ryanodine receptor. The physiological importance of direct protein–protein interactions being involved in Ca 2+ -regulatory processes is exemplified by a supramolecular triad membrane complex mediating between sarcolemmal excitation and muscular contraction [1]. It is well established that physical coupling between the voltage-sensing dihydropyridine receptor and the Ca 2+ -release channel provides the signal transduction mechanism between the transverse tubules and the junc- tional sarcoplasmic reticulum (SR) in mature skeletal muscle fibers [2]. Conversely, it has not yet been determined how many SR elements are involved in the regulation of the contraction-inducing efflux of Ca 2+ -ions from the SR lumen through the ryanodine receptor (RyR) complex, and which components prevent passive disintegration of these large heterogeneous SR membrane assemblies. Previous studies on excitation–contraction coupling have established that the RyR1 isoform of the Ca 2+ -release channel exists in a close neighborhood relationship with various potential regulators, such as triadin (TRI), junctin (JUN), JP-45, JP-90, the histidine-rich Ca 2+ -binding protein, calsequestrin (CSQ) and Endogenous mono-ADP-ribosylation mediates smooth muscle cell proliferation and migration via protein kinase N-dependent induction of c- fos expression Lorraine Yau 1,2 , Brenda Litchie 1 , Shawn Thomas 1 , Benjamin Storie 1 , Natalia Yurkova 1 and Peter Zahradka 1,2 1 Institute of Cardiovascular Sciences, St. Boniface Research Centre and 2 Department of Physiology, University of Manitoba, Winnipeg, MB, Canada ADP-ribosylation has been coupled to intracellular events associated with smooth muscle cell vasoreactivity, cytoskel- etal integrity and free radical damage. Additionally, there is evidence that ADP-ribosylation is required for smooth muscle cell proliferation. Our investigation employed selective inhibitors to establish that mono-ADP-ribosylation and not poly(ADP-ribosyl)ation was necessary for the sti- mulation of DNA synthesis by mitogens. Mitogen treatment increased concomitantly the activity of both soluble and particulate mono-ADP-ribosyltransferase, as well as the number of modified proteins. Inclusion of meta-iodo- benzylguanidine (MIBG), a selective decoy substrate of arginine-dependent mono-ADP-ribosylation, prevented the modification of these proteins. MIBG also blocked the stimulation of DNA and RNA synthesis, prevented smooth muscle cell migration and suppressed the induction of c-fos and c-myc gene expression. An examination of relevant signal transduction pathways showed that MIBG did not interfere with MAP kinase and phosphatidylinositol 3-kin- ase stimulation; however, it did inhibit phosphorylation of the Rho effector, PRK1/2. This novel observation sug- gests that mono-ADP-ribosylation participates in a Rho- dependent signalling pathway that is required for immediate early gene expression. Keywords: ADP-ribosylation; smooth muscle; DNA syn- thesis; c-fos; MAP kinase. Post-translational modification by ADP-ribosylation, the enzymatic transfer of ADP-ribose from NAD + to an acceptor protein, has been grouped into two distinct classes that are distinguished by their reaction mechanisms [1]. O-linked ADP-ribosylation of glutamate residues is catalyzed by poly(ADP-ribose) polymerase (PARP-1), as is the subsequent formation of polymers containing 10–100 ADP-ribose units. This process occurs primarily in the nucleus, and is responsible for modulating DNA– protein interactions [2]. It has been established that poly(ADP-ribosyl)ation participates in DNA-base excision repair [3], while PARP-1 degradation is a marker for apoptosis [4]. PARP-1 has also been linked to differen- tiation of neutrophilic cells [5], and may be important for chromatin condensation [6], centromere function [7] and transcription [8,9]. Unlike poly(ADP-ribosyl)ation, mono-ADP-ribosyla- tion reactions involve the transfer of a single ADP-ribose to various amino acid (arginine, histidine, diphthamide, cysteine, asparagine) residues by mono-ADP-ribosyltrans- ferases (mART) [10]. Investigations of bacterial toxins (e.g. clostridia, cholera, pertussis, diphtheria) that exhi- bited mART activity foreshadowed the identification of endogenous enzymes capable of catalyzing similar reac- tions [1]. The majority of vertebrate mARTs studied to date have been found to modify either cysteine or arginine. The cellular location of these enzymes has been shown to vary, with enzymes detected in the cytosol, microsomal and nuclear fractions [11]. Many membrane- bound mARTs belong to the family of glycosylphospha- tidylinositol (GPI)-anchored proteins present on the extracellular surface. It has been proposed that the GPI- anchored mARTs modulate transmembrane signalling events, as integrin a7 is one target molecule that Muscle Contraction and Locomotion Muscle Contraction and Locomotion Bởi: OpenStaxCollege Muscle cells are specialized for contraction Muscles allow for motions such as walking, and they also facilitate bodily processes such as respiration and digestion The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle ([link]) The body contains three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle, visualized here using light microscopy Smooth muscle cells are short, tapered at each end, and have only one plump nucleus in each Cardiac muscle cells are branched and striated, but short The cytoplasm may branch, and they have one nucleus in the center of the cell (credit: modification of work by NCI, NIH; scale-bar data from Matt Russell) Skeletal muscle tissue forms skeletal muscles, which attach to bones or skin and control locomotion and any movement that can be consciously controlled Because it can be controlled by thought, skeletal muscle is also called voluntary muscle Skeletal muscles are long and cylindrical in appearance; when viewed under a microscope, skeletal muscle tissue has a striped or striated appearance The striations are caused by the regular arrangement of contractile proteins (actin and myosin) Actin is a globular contractile protein that interacts with myosin for muscle contraction Skeletal muscle also has multiple nuclei present in a single cell Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels Smooth muscle has no striations, is not under voluntary control, has only one nucleus per cell, is tapered at both ends, and is called involuntary muscle 1/14 Muscle Contraction and Locomotion Cardiac muscle tissue is only found in the heart, and cardiac contractions pump blood throughout the body and maintain blood pressure Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle It has one nucleus per cell, is branched, and is distinguished by the presence of intercalated disks Skeletal Muscle Fiber Structure Each skeletal muscle fiber is a skeletal muscle cell These cells are incredibly large, with diameters of up to 100 µm and lengths of up to 30 cm The plasma membrane of a skeletal muscle fiber is called the sarcolemma The sarcolemma is the site of action potential conduction, which triggers muscle contraction Within each muscle fiber are myofibrils—long cylindrical structures that lie parallel to the muscle fiber Myofibrils run the entire length of the muscle fiber, and because they are only approximately 1.2 µm in diameter, hundreds to thousands can be found inside one muscle fiber They attach to the sarcolemma at their ends, so that as myofibrils shorten, the entire muscle cell contracts ([link]) A skeletal muscle cell is surrounded by a plasma membrane called the sarcolemma with a cytoplasm called the sarcoplasm A muscle fiber is composed of many fibrils, packaged into orderly units The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along the length of myofibrils Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes the entire cell to appear striated or banded Each I band has a dense line running vertically through the middle called a Z disc or Z line The Z discs mark the border of units called sarcomeres, which are the functional units of skeletal muscle One sarcomere is the space between two consecutive Z discs and contains one entire A band and two halves of an I band, one on either side of the A 2/14 Muscle Contraction and Locomotion band A myofibril is composed of many sarcomeres running along its length, and as the sarcomeres individually contract, the myofibrils and muscle cells .. .Muscle Fiber Contraction and Relaxation Contraction of a Muscle Fiber A cross-bridge forms between actin and the myosin heads triggering contraction As long as Ca++... the actin strands A muscle also can stop contracting when it runs out of ATP and becomes fatigued ([link]) 2/13 Muscle Fiber Contraction and Relaxation Relaxation of a Muscle Fiber Ca ions are... thin and thick filaments, the muscle fiber loses its tension and relaxes Muscle Strength The number of skeletal muscle fibers in a given muscle is genetically determined and does not change Muscle