Architectural and histochemical analysis of the semitendinousus muscle in mice,rats, guinea pigs,and rabbits

The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series—a destal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.     

Split flexor carpi radialis muscle

A detailed anatomic and intramuscular neural staining study in 22 human and 5 monkey upper limbs revealed that the flexor carpi radialis can be raised on its proximal neurovascular pedicle and that the muscle can be split along its tendon into two independently functioning neuromuscular compartments, each with its own nerve and blood supply. A study of the muscle architecture in the human specimens found the radial compartment to have significantly longer fiber length and a larger physiologic cross-sectional area than the ulnar compartment. Independence of function of each compartment was demonstrated in electrical stimulation studies in six monkeys (Macaca fascicularis), but no significant difference was noted in the peak isometric load between the two compartments (p = 0.68) in the monkey. The extra functioning muscle units become important in local transfers for restoring function in multiple nerve palsies as in Hansen's disease, severe traumatic loss of muscle in crush injuries and compartment syndromes, and after wide resection in infective and neoplastic conditions in the forearm and hand.     

Morphometric properties and innervation of muscle compartments in rat medial gastrocnemius

The rat medial gastrocnemius (MG) muscle is composed of the proximal and distal compartments. In this study, morphometric properties of the compartments and their muscle fibres at five levels of the muscle length and the innervation pattern of these compartments from lumbar segments were investigated. The size and number of muscle fibres in the compartments were different. The proximal compartment at the largest cross section (25% of the muscle length) had 34% smaller cross-sectional area but contained a slightly higher number of muscle fibres (max. 5521 vs. 5360) in comparison to data for the distal compartment which had the largest cross-sectional area at 40% of the muscle length. The muscle fibre diameters revealed a clear tendency within both compartments to increase along the muscle (from the knee to the Achilles tendon) up to 46.9?μm in the proximal compartment and 58.4?μm in the distal one. The maximal tetanic and single twitch force evoked by stimulation of L4, L5, and L6 ventral roots in whole muscle and compartments were measured. The MG was innervated from L4 and L5, only L5, or L5 and L6 segments. The proximal compartment was innervated by axons from L5 or L5 and L4, and the distal one from L5, L5 and L6, or L5 and L4 segments. The forces produced by the compartments summed non-linearly. The tetanic forces of the proximal and distal compartments amounted to 2.24 and 4.86?N, respectively, and their algebraic sums were 11% higher than the whole muscle force (6.37?N).     

Changes in muscle activity in response to different impact forces affect soft tissue compartment mechanical properties

Electromyographic (EMG) activity is associated with several tasks prior to landing in walking and running including positioning the leg, developing joint stiffness and possibly control of soft tissue compartment vibrations. The concept of muscle tuning suggests one reason for changes in muscle activity pattern in response to small changes in impact conditions, if the frequency content of the impact is close to the natural frequency of the soft tissue compartments, is to minimize the magnitude of soft tissue compartment vibrations. The mechanical properties of the soft tissue compartments depend in part on muscle activations and thus it was hypothesized that changes in the muscle activation pattern associated with different impact conditions would result in a change in the acceleration transmissibility to the soft tissue compartments. A pendulum apparatus was used to systematically administer impacts to the heel of shod male participants. Wall reaction forces, EMG of selected leg muscles, soft tissue compartment and shoe heel cup accelerations were quantified for two different impact conditions. The transmissibility of the impact acceleration to the soft tissue compartments was determined for each subject/soft tissue compartment/shoe combination. For this controlled impact situation it was shown that changes in the damping properties of the soft tissue compartments were related to changes in the EMG intensity and/or mean frequency of related muscles in response to a change in the impact interface conditions. These results provide support for the muscle tuning idea--that one reason for the changes in muscle activity in response to small changes in the impact conditions may be to minimize vibrations of the soft tissue compartments that are initiated at heel-strike.     

Effects of inter- and extramuscular myofascial force transmission on adjacent synergistic muscles: assessment by experiments and finite-element modeling

The effects of inter- and extramuscular myofascial force transmission on muscle length force characteristics were studied in rat. Connective tissues at the bellies of the experimental synergistic muscles of the anterior crural compartment were left intact. Extensor digitorium longus (EDL) muscle was lengthened distally whereas tibialis anterior (TA) and extensor hallucis longus (EHL) were kept at constant muscle–tendon complex length. Substantial differences were found in EDL force measured at the proximal and distal tendons (maximally 46% of the proximal force). EDL with intact inter- as well as extramuscular connections had an increased length range between active slack and optimum length compared to EDL with extramuscular connections exclusively: optimum muscle length was shifted by more than 2 mm. Distal EDL lengthening caused the distal force exerted by TA+EHL complex to decrease (approximately 17% of the initial force). This indicates increased intermuscular myofascial force transmission from TA+EHL muscle complex to EDL muscle.

Finite-element modeling showed that: (1) Inter- and extramuscular myofascial force transmission leads to a substantial distribution of the lengths of the sarcomeres arranged in series within muscle fibers. Distribution of stress within the muscle fibers showed that the muscle fiber cannot be considered as a unit exerting equal forces at both ends. (2) Increased heterogeneity of mean fiber sarcomere lengths (i.e., a “parallel” distribution of length of sarcomeres among different muscle fibers) is found, particularly at high muscle lengths. This also explains the shift in muscle optimum length to higher lengths.

It is concluded that inter- and extramuscular myofascial force transmission has substantial effects on muscle length–force characteristics.     

The neuromuscular compartments of the flexor carpi ulnaris

Learning Objectives: After studying this article, the participant should be able to: 1. Report on the vascular supply and innervation pattern of the flexor carpi ulnaris. 2. Describe the muscle architecture of the flexor carpi ulnaris, including the physiological cross-sectional area and fiber length. 3. State the uses of the flexor carpi ulnaris both for resurfacing defects in the vicinity of the elbow and in local functional tendon transfers. 4. Understand the principles of splitting skeletal muscles based on neurovascular supply to enhance its utilization in reconstructive procedures. The aim of this study was to describe the intramuscular innervation and vascular supply of the human flexor carpi ulnaris, with confirmation of findings by a similar study in the primate. Two distinct intramuscular nerve branches running parallel to each other, on either side of a central tendon, from the proximal quarter of the muscle belly to its insertion were found. The muscle could then be split into a humeral and an ulnar compartment, each with its own primary nerve branch. Perfusion studies confirmed the adequacy of circulation to the two compartments. In the primate flexor carpi ulnaris, electrical stimulation of the respective branches revealed independent contraction of each compartment. This study provides useful information for enabling the local transfer of the muscle as a whole, both for resurfacing in the vicinity of the elbow and for functional tendon transfers. It will also enable the transfer of the muscle as one or two separate compartments (for resurfacing, in tendon transfers for muscle paralysis, congenital defects, and muscle defects resulting from trauma, and after resections for neoplasm and infection).     

A novel multi-coaxial hollow fiber bioreactor for adherent cell types. Part 1: hydrodynamic studies.

A novel multi-coaxial bioreactor for three-dimensional cultures of adherent cell types, such as liver, is described. It is composed of four tubes of increasing diameter placed one inside the other, creating four spatially isolated compartments. Liver acinar structure and physiological parameters are mimicked by sandwiching cells in the space between the two innermost semi-permeable tubes, or hollows fibers, and creating a radial flow of media from an outer compartment (ECC), through the cell mass compartment, and to an inner compartment (ICC). The outermost compartment is created by gas-permeable tubing, and the housing is used to oxygenate the perfusion media to periportal levels in the ECC. Experiments were performed using distilled water to correlate the radial flow rate (Q(r)) with (1) the pressure drop (DeltaP) between the media compartments that sandwich the cell compartment and (2) the pressure in the cell compartment (P(c)). These results were compared with the theoretical profile calculated based on the hydraulic permeability of the two innermost fibers. Phase-contrast velocity-encoded magnetic resonance imaging was used to visualize directly the axial velocities inside the bioreactor and confirm the assumptions of laminar flow and zero axial velocity at the boundaries of each compartment in the bioreactor. Axial flow rates were calculated from the magnetic resonance imaging results and were similar to the measured axial flow rates for the previously described experiments.     

Connective-tissue macromolecules in Golgi chicken tendon organs and at their interface with muscle fibers and adjoining tendinous structures.

Tendon organs from leg and forearm muscles of white leghorn chickens were examined with a library of monoclonal antibodies to determine the composition of their connective-tissue framework and the types of connective-tissue macromolecules that occur at the sites where muscle fibers attach to the receptors. The capsules of the tendon organs were positive for connective-tissue macromolecules typical of basal lamina (collagen type IV, laminin, and heparin sulfate proteoglycan) and for tenascin, collagen types III and VI, and fibronectin. Connective-tissue bundles in the lumen of a receptor reacted primarily with antibodies against collagen type I and 4-chondroitin sulfate. The narrow partitions that divide each lumen into compartments stained for collagen type III. Toward its tendinous end, a receptor made few contacts with muscle fibers. Instead, the capsule and the collagenous bundles blended gradually with the intermuscular portions of tendons. At the muscular end, the connections were more complex. Muscle fibers that attached in series to tendon organs split to produce basal lamina-covered, finger-like extensions, which were separated from each other by fissures. Tongues of connective tissue containing tenascin, collagen types I and VI, and fibronectin extended into the fissures. Distally the tongues were continuous with the tenascin in the capsule and just internal to the capsule, fibronectin and basal lamina macromolecules in the capsule, and collagen type I in the collagenous bundles. The uninterrupted presence of these macromolecules around terminating muscle fibers and in the capsule and/or the intraluminal collagen bundles suggests that muscle fibers that attach in series at the muscular end exert a force during muscular contraction on the intraluminal collagen bundles and on the receptor capsule.     

Water Permeability of Isolated Muscle Fibers of a Marine Crab

This report deals with the diffusional and nondiffusional water fluxes of muscle fibers of the crab, Chionoecetes bairdi. Graphical analysis of the deuterium exchange indicates that two fiber compartments exist for water. The first, comprising about 60–70% of the fiber water, probably represents the sarcoplasm which is bounded externally by the plasma membrane. The second compartment might represent intracellular organelles. The ratio between the nondiffusional and diffusional fluxes is very much larger than that found earlier for erythrocytes and for the giant axon of the squid. A ratio of such size is unlikely to be caused by unstirred layers and more accurate determinations of the water flux must include study of the influence of the complex morphology of these muscle fibers.     

Strain energy descriptions of biological swelling. II: Multiple fluid compartment models

A series of multicompartmental, biphasic elastic tissue models is developed. In its most general form, the models consist of multiple tubular networks, each with an internal spring network. In addition, another spring network occupies the extratubular compartment. Strain energy functions are derived for the models, as well as expressions for the fluid pressures in each compartment arising from volume expansion or swelling. Calculations also show that the distribution of fluid among compartments is a significant determinant of tissue elasticity.     

The composite structure of quail pectoralis muscle.

The twitch fibers of the quail pectoralis muscle were found to have one neuromuscular junction each, located in the middle third of the fiber. The length of isolated fibers varied between 8.8 and 33.2 mm, with mean and median values of 16 and 15.6 mm, respectively. The lengths of the fascicles from which the fibers were isolated varied between 30 and 51 mm. The muscle fibers taper at both ends. The neuromuscular junctions, revealed after histochemically reacting the intact muscle for acetyl cholinesterase activity, were arranged in discrete bands, separated by intervals of between 0.94 and 6.70 mm, with a mean value of 3.14 mm. The quail pectoralis muscle is thus composed of discontinuous, tapered muscle fibers, arranged in an overlapping series. It is therefore a muscle in which tension is transmitted laterally between muscle fibers.     

Light diffraction study of single skeletal muscle fibres.

Light diffraction patterns from isolated frog semitendinosus muscle fibers were examined. When transilluminated by laser light, the muscle striations produce a diffraction pattern consisting of a series of lines that are projected as points onto an optical detector by a lens system. Diffraction data may be sequentially stored every 18 ms for later processing by digital computer systems. First- and second-order diffraction line intensities were examined from intact, chemically skinned, and glycerinated single fibers. The diffraction line intensities demonstrated a strong length dependence upon passive stretch from reference length to 3.6 micrometer. The first-order intensity linearly increased an average of 15-fold over the range examined. The magnitude of the second order intensity was less than the first order and showed an exponential rise with increasing length. Both first- and second-order intensities decreased upon muscle activation. Data from chemically skinned and glycerinated single fibers were not significantly different from intact fibers, indicating that the membrane structure has little effect upon the diffraction phenomenon in muscle. Theoretical model systems are examined in an attempt to find the basis of these results. Neither an analysis based on a diffraction grating with variable spacing nor the unit cell model of Fujime provides an explanation for the observed length dependency of intensity. Though the origin of the intensity decrease upon stimulation is not known, we have suggested that it could result from lateral misalignment of myofibrils and can occur upon activation.     

Chromatophore Organs, Reflector Cells, Iridocytes and Leucophores in Cephalopods

The chromatophore organs of Lohgo are each composed of fivetypes of cells: a central pigment cell: radially arranged, obliquelystriated muscle fibers: neuronal processes; glial cells: andan investment of sheath cells. Sheath cells are absent in Octopuschromatophore organs. The cycle of expansion and retractionof a chromatophore organ may occur within the order of a second.It is clear that the muscle fibers expand the pigment cell andspread out the pigment granules. The pigment is contained withinan unusual, filamentous, cytoplasmic compartment called thecytoelastic sacculus. This compartment has elastic properties. Reflector cells and iridocytes produce structural colors eventhough their components are colorless. Reflector cells in Octopusbear peripheral sets of leaf-like reflecting lamellae calledreflectosomes: these contain proteinaceous platelets with ahigh refractive index (1.42). In each reflectosome the reflectinglamellae are separated by gaps that are about equal to the thicknessof the lamellae, but have a lower refractive index (1.33). Reflectosomesare believed to reflect light and to function as thin-film interferencedevices. Iridocytes in squid and cuttlefish contain iridosomes that arealso composed of sets of ribbon-like platelets but these arelocated centrally within the cell body. The platelets are usuallyoriented on edge with respect to the surface of the skin. Thepossibility that dermal iridocytes may act as diffraction gratingsis discussed. Leucophores have thousands of processes that containglobules of protein with a high refractive index. These cellsscatter light of all wave lengths and appear white in whitelight.     

Task-related differences in peroneus longus muscle fiber conduction velocity

It has been identified that the peroneus longus presents a regional activity. Specifically, a greater activation of the anterior and posterior compartments has been observed during eversion, whereas a lower activation of the posterior compartment has been reported during plantarflexion. In addition to myoelectrical amplitude, motor unit recruitment can be inferred indirectly from muscle fiber conduction velocity (MFCV). However, there are few reports of MFCV of the regions that make up a muscle, and even less, MFCV of the peroneus longus compartments. This study aimed to analyze the MFCV of peroneus longus compartments during eversion and plantarflexion. Twenty-one healthy individuals were assessed. High-density surface electromyography was recorded from the peroneus longus during eversion and plantarflexion at 10%, 30%, 50%, and 70% of maximal voluntary isometric contraction. The posterior compartment presented a lower MFCV than the anterior compartment during plantarflexion, and both compartments did not show differences in MFCV during eversion; however, the posterior compartment showed an increase in MFCV during eversion compared to plantarflexion. Differences observed in the MFCV of the peroneus longus compartments could support a regional activation strategy and, to some extent, explain different motor unit recruitment strategies of the peroneus longus during ankle movements.     

A simpler way of comparing the labelling densities of cellular compartments illustrated using data from VPARP and LAMP-1 immunogold labelling experiments

Quantitative immunoelectron microscopy of gold label in intracellular compartments often involves calculating labelling densities (LDs). These are related to antigen concentrations and usually refer gold particle counts to the sizes of compartments on sections (for example, golds per microm(2) of organelle profile area or per microm of membrane trace length). Here, we show how LD values can be estimated more simply (without estimating areas or lengths) and also how observed and expected LD values can be used to calculate a relative labelling index (RLI) for each compartment and then test statistically for preferential (non-random) labelling. For random labelling, RLI=1. Compartment size is estimated stereologically by superimposing random test points (which hit organelle profiles in proportion to their area) or test lines (which intersect membrane traces in proportion to their length). By this means, the observed LD of a compartment (LD(obs)) can be expressed simply as golds per test point (organelles) or per intersection (membranes). Furthermore, the LD obtained by dividing total golds (on all compartments) by total points or intersections (on all compartments) is the value to be expected (LD(exp)) when compartments label randomly. For each compartment, RLI=LD(obs)/LD(exp). Statistical analysis is undertaken by comparing observed distributions of golds with predicted random distributions (calculated from point or intersection counts). A compartment is preferentially labelled if two criteria are met: (1) its RLI>1 (i.e. LD(obs) is greater than LD(exp)) and (2) its partial chi-squared value makes a substantial contribution to total chi-squared value. This approach provides a simple and efficient way of comparing LDs in different compartments. Its utility is illustrated using data from VPARP and LAMP-1 labelling experiments.     

A multicompartment model of carboxyhemoglobin and carboxymyoglobin responses to inhalation of carbon monoxide.

We have developed a model that predicts the distribution of carbon monoxide (CO) in the body resulting from acute inhalation exposures to CO. The model includes a lung compartment, arterial and venous blood compartments, and muscle and nonmuscle soft tissues with both vascular and nonvascular subcompartments. In the model, CO is allowed to diffuse between the vascular and nonvascular subcompartments of the tissues and to combine with myoglobin in the nonvascular subcompartment of muscle tissue. The oxyhemoglobin dissociation curve is represented by a modified Hill equation whose parameters are functions of the carboxyhemoglobin (HbCO) level. Values for skeletal muscle mass and cardiac output are calculated from prediction formulas based on age, weight, and height of individual subjects. We demonstrate that the model fits data from CO rebreathing studies when diffusion of CO into the muscle compartment is considered. The model also fits responses of HbCO to single or multiple exposures to CO lasting for a few minutes each. In addition, the model reproduces reported differences between arterial and venous HbCO levels and replicates predictions from the Coburn-Forster-Kane equation for CO exposures of a 1- to 83-h duration. In contrast to approaches based on the Coburn-Forster-Kane equation, the present model predicts uptake and distribution of CO in both vascular and tissue compartments during inhalation of either constant or variable levels of CO.     

Distribution and innervation of short, interdigitated muscle fibers in parallel-fibered muscles of the cat hindlimb

The cat hindlimb contains several long, biarticular strap muscles composed of parallel muscle fascicles that attach to short tendons. Three of these muscles--sartorius, tenuissimus, and semitendinosus--were studied by dissecting individual gold-stained fibers and determining the surface distribution of acetylcholinesterase-stained end-plate zones. In each muscle, fascicles were composed of muscle fibers that ran only part of the fascicle length and tapered to end as fine strands that interdigitated with other tapering fibers within the muscle mass. Most muscle fibers measured 2-3 cm in length. Fascicles of muscle fibers were crossed by short transverse bands of endplates (1 mm wide by 1-5 mm long) that were spaced at fairly regular intervals from the origin to the insertion of the muscle. The endplate pattern suggested that the fiber fascicles were organized into multiple longitudinal strips. In the sartorius, the temporospatial distribution of electromyographic (EMG) activity evoked by stimulating fine, longitudinal branches of the parent nerve confirmed that each strip was selectively innervated by a small subset of the motor axons. These axons appeared to distribute their endings throughout the entire length of the fascicles, providing for synchronous activation of their in-series fibers.     

Above- and below-ground growth of white spruce seedlings with roots divided into different substrates with or without controlled-release fertilizer

Thirty-two one-year-old white spruce (Picea glauca (Moench) Voss) seedlings were grown outdoors for one season in 35 L pots buried in the soil. The pots were vertically split in half. One compartment (mineral) was filled with loamy sand. The bottom of the other compartment (organic) was filled with 10 cm sand topped with 15 cm of organic substrates. Two seedling types (16 seedlings each), (i) polystyroblock-grown and (ii) peat-board grown with mechanical root pruning had their root systems split approximately in half into each of the vertical compartments. Controlled-release (26-12-6 N-P-K) fertilizer was added to one or to none (control) of the compartments. Above-ground growth was positively affected by fertilizer placed in either soil compartmnent. Nutrient content of the foliage was greater in fertilized than in unfertilized seedlings; N and P concentrations were significantly increased. Bud reflushing occurred frequently in fertilized seedlings. Unfertilized container-grown seedlings had the fewest roots in either soil compartment. Unfertilized mechanically-pruned seedlings had significantly greater root length, root surface area, and more root tips in mineral than in organic compartments. They also had more P in current-year leaves than did unfertilized container-grown seedlings. Fertilizer added to mineral compartments significantly affected root growth in these compartments only, whereas when added to organic compartments it affected root growth in both compartments. Root systems of the two seedling types were differently affected by fertilizer: in mechanically-pruned seedlings, the number of roots was reduced but their length and diameter increased; in container-grown seedlings, root proliferation was stimulated and this increased total root length and root surface area. Five ectomycorrhizal morphotypes were identified. E-strain was the most abundant. Except for Cenococcum, all morphotypes were present in nursery stock prior to planting. Changes in distribution of morphotypes after planting appeared related to root health condition rather than to applied fertilizer. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecular Analysis of Bacterial Communities in a Three-Compartment Granular Activated Sludge System Indicates Community-Level Control by Incompatible Nitrification Processes

Bacterial community structure and the predominant nitrifying activities and populations in each compartment of a three-compartment activated sludge system were determined. Each compartment was originally inoculated with the same activated sludge community entrapped in polyethylene glycol gel granules, and ammonium nitrogen was supplied to the system in an inorganic salts solution at a rate of 5.0 g of N liter of granular activated sludge⁻¹ day⁻¹. After 150 days of operation, the system was found to comprise a series of sequential nitrifying reactions (K. Noto, T. Ogasawara, Y. Suwa, and T. Sumino, Water Res. 32:769–773, 1998), presumably mediated by different bacterial populations. Activity data showed that all NH₄-N was completely oxidized in compartments one and two (approximately half in each), but no significant nitrite oxidation was observed in these compartments. In contrast, all available nitrite was oxidized to nitrate in compartment three. To study the microbial populations and communities in this system, total bacterial DNA isolated from each compartment was analyzed for community structure based on the G+C contents of the component populations. Compartment one showed dominant populations having 50 and 67% G+C contents. Compartment two was similar in structure to compartment one. The bacterial community in compartment three had dominant populations with 62 and 67% G+C contents and retained the 50% G+C content population only at a greatly diminished level. The 50% G+C content population from compartment one hybridized strongly with amo (ammonia monooxygenase) and hao (hydroxylamine oxidoreductase) gene probes from Nitrosomonas europaea. However, the 50% G+C content population from compartment two hybridized strongly with the hao probe but only weakly with the amo probe, suggesting that the predominant ammonia-oxidizing populations in compartments one and two might be different. Since different activities and populations come to dominate in each compartment from an identical inoculum, it appears that the nitrification processes may be somewhat incompatible, resulting in a series of sequential reactions and different communities in this three-compartment system.