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PubMed1984

The three-dimensional architecture of the elastic-fiber network in canine hepatic portal system.

The architectural arrangement of the elastic-fiber network in the wall of canine hepatic portal veins was observed with the scanning electron microscope (SEM). Selective NaOH sonication digestion and autoclaving were used to expose and isolate the networks of elastic fibers from six selected regions of the hepatic portal vessels from seven healthy dogs. Elastic stains of adjacent segments prepared for light microscopy demonstrated that the elastic fibers were concentrated in two areas within the intact portal wall. The innermost area corresponded to the internal elastic lamina (IEL) of the tunica intima, the internal muscular layer, and the connective tissue layer of the tunica media. The second area was in the tunica adventitia. SEM specimens revealed two sleeves of elastic fiber networks which corresponded to the above regions. Small scattered bundles of radially oriented elastic fibers spanned the gap between the two sleeves. Each tunica had a different architectural arrangement of elastic fibers. The IEL had circumferentially oriented fibers which branched and anastomosed to form a continuous network on the innermost surface. The architecture of the IEL was the most variable between the different regions. The network of the IEL was the most "open" in the caudal region (splenic vein) and became "denser" toward the liver. The large elastic fibers in the tunica media were oriented at approximately right angles to the primary fibers of the IEL. These longitudinally oriented fibers anastomosed with adjacent longitudinal fibers to form a continuous network. In the tunica adventitia, thick, longitudinally oriented fibers of the continuous network fused together to form incomplete layers of fibers. The architecture of the elastic-fiber network in the canine hepatic portal vein was compared to that previously described in the systemic canine saphenous vein.

Animals↗
PubMed2001

Three-dimensional analysis of nonhuman primate trabecular architecture using micro-computed tomography.

Until recently, detailed analyses of the architecture of nonhuman primate cancellous bone have not been possible due to a combination of methodological constraints, including poor resolution imaging or destructive protocols. The development of micro-computed tomography (microCT) and morphometric methods associated with this imaging modality offers anthropologists a new means to study the comparative architecture of cancellous bone. Specifically, microCT will allow anthropologists to investigate the relationship between locomotor behavior and trabecular structure. We conducted a preliminary study on the trabecular patterns in the proximal humerus and femur of Hylobates lar, Ateles paniscus, Macaca mulatta, and Papio anubis to investigate the quantitative differences in their trabecular architecture and evaluate the potential of microCT in anthropological inquiry. MicroCT allows the researcher to evaluate variables beyond simple two-dimensional orientations and radiographic densities. For example, this methodology facilitates the study of trabecular thickness and bone volume fraction using three-dimensional data. Results suggest that density-related parameters do not reliably differentiate suspensory-climbing species from quadrupedal species. However, preliminary results indicate that measurements of the degree of anisotropy, a measure of trabecular orientation uniformity, do distinguish suspensory-climbing taxa from more quadrupedal species. The microCT method is an advance over conventional radiography and medical CT because it can accurately resolve micron-sized struts that make up cancellous bone, and from these images a wide array of parameters that have been demonstrated to be related to cancellous bone mechanical properties can be measured. Methodological problems pertinent to any comparative microCT study of primate trabecular architecture are discussed.

Animals↗
PubMed2005

Three-dimensional myofiber architecture of the embryonic left ventricle during normal development and altered mechanical loads.

Mechanical load influences embryonic ventricular growth, morphogenesis, and function. To date, little is known regarding how the embryonic left ventricular (LV) myocardium acquires a three-dimensional (3D) fiber architecture distribution or how altered mechanical load influences local myofiber architecture. We tested the hypothesis that altered mechanical load changes the maturation process of local 3D fiber architecture of the developing embryonic LV compact myocardium. We measured transmural myofiber angle distribution in the LV compact myocardium in Hamburger-Hamilton stages 21, 27, 31, and 36 chick embryos during normal development or following either left atrial ligation (LAL; LV hypoplasia model) or conotruncal banding (CTB; LV hyperplasia model). The embryonic LV was stained with f-actin and then z-serial optical sectioning was performed using a laser confocal scanning microscope. We reconstructed local 3D myofiber images and computed local transmural myofiber angle distribution. Transmural myofiber angles in compact myocardium (in LV sagittal sections) were oriented in a circumferential direction until stage 27 (-10 to 10 degrees). Myofibers in the outer side of compact myocardium shifted to a more longitudinal direction by stage 36 (10 to 40 degrees), producing a transmural gradient in myofiber orientation. Developmental changes in transmural myofiber angle distribution were significantly delayed following LAL, while the changes in angle distribution were accelerated following CTB. Results suggest that mechanical load modulates the maturation process of myofiber architecture distribution in the developing LV compact myocardium.

Animals↗
PubMed2006

Three-dimensional fiber architecture of the nonpregnant human uterus determined ex vivo using magnetic resonance diffusion tensor imaging.

The global muscle and collagen fiber orientation in the human uterus has been analyzed hitherto by various standard microscopic techniques. However, no widely accepted model of the fiber architecture of the myometrium could be acquired. The purpose of the present study was to investigate the uterus by magnetic resonance (MR) diffusion tensor imaging (DTI) in a 3D macroscopic approach. Ex vivo MR DTI measurements were performed on five uteri from nonpregnant patients. The main diffusion directions reflecting the orientation of directional structures in the examined tissues were determined from diffusion-weighted spin-echo measurements. A fiber tracking algorithm was used to extrapolate the fiber architecture. The method was validated against histological slides and indirectly through the analysis of leiomyomas, which exhibit less anisotropy than normal myometrium. Significant anisotropy was found in most regions of all examined nonpregnant human uteri. But only two systems of fibers were found running circularly along the intramural part of the uterine tubes. They merged caudally and built a close fitting envelope of circular layers around the uterine cavity. On the cervix, circular fibers were observed in the outer part as well as mostly longitudinal fibers in the inner part. These results confirm the existence of directional structures in the complex fiber architecture of the human uterus. They also indicate that MR DTI is a beneficial and complementary tool to standard microscopic techniques to determine the intrinsic fiber architecture in human organs.

Adult↗
PubMed2006

Number of pericryptal fibroblasts correlates with density of distinct mast cell phenotypes in the crypt lamina propria of human duodenum: implications for the homeostasis of villous architecture.

Pericryptal fibroblasts (PFs), a class of myofibroblasts, have strongly been implicated in the regulation of villous structure because of their location close to crypts and their ability to secrete cytokines affecting intestinal epithelial cell proliferation and differentiation. Recently, mast cells (MCs) have also been involved in the homeostasis of villous architecture. As myofibroblasts arise in a wide variety of settings concurrently with a local increase in the number of tissue MCs, we calculated in this study the density of both PF and distinct pericryptal MC phenotypes in the mucosa of human duodenum showing normal, defective, or atrophic villous profiles. In addition, we evaluated the statistical association between PF-MC densities and each pattern of villous architecture. Finally, we correlated the density of PF with the density of pericryptal MC phenotypes. For this purpose, samples taken by endoscopy from 30 patients complaining of inflammatory bowel disorders were studied by immunohistochemistry. The densities of alpha-smooth muscle actin-positive PFs as well as tryptase-, chymase-, and c-kit-positive MCs were determined in the crypt lamina propria. Villous architecture was found to be significantly associated with the number of PFs and tryptase-, chymase-, c-kit-positive MCs in the lamina propria (ANOVA group effect P < 0.001). High density of both PFs and MCs was found in intestinal samples with normal villous morphology while lower densities were associated with defective or atrophic villous profiles (Tukey's test for multiple comparison P < 0.001). In addition, a significant correlation was found between PF density and the density of each pericryptal MC phenotype (vs. tryptase-positive MCs, r = 0.913; vs. chymase-positive MC, r = 0.905; vs. c-kit-positive MC, r = 0.927; P < 0.001 in all cases). This study provides morphological support for an important cooperation between PFs and MCs in maintaining normal villous architecture.

Actins↗
PubMed2006

Regional differences in architecture and mineralization of developing mandibular bone.

The goal of this study was to investigate the mutual relationship between architecture and mineralization during early development of the pig mandible. These factors are considered to define the balance between the requirements for bone growth on the one hand and for load bearing on the other. Architecture and mineralization were examined using micro-CT, whereas the mineral composition was assessed spectrophotometrically in groups of fetal and newborn pigs. The development of the condyle coincided with a reorganization of bone elements without an increase in bone volume fraction, but with an increase in mineralization and a change in mineral composition. In the corpus, the bone volume fraction and mineralization increased simultaneously with a restructuring of the bone elements and a change in mineral composition. The growth of the condyle was reflected by regional differences in architecture and mineralization. The anterior and inferior regions were characterized by a more dense bone structure and a higher mineralization as compared to posterior and superior regions, respectively. In the corpus, growth was mainly indicated by differences between buccal and lingual plates as well as between anterior, middle, and posterior regions characterized by a more compact structure and higher mineralization in the lingual and middle regions. In conclusion, the architecture and mineralization in the condyle and corpus started to deviate early during development toward their destiny as trabecular and cortical bone, respectively. These results were compatible with those obtained with mineral composition analysis. Regional differences within condyle and corpus reflected known developmental growth directions.

Animals↗
PubMed2006

Dietary consistency and plasticity of masseter fiber architecture in postweaning rabbits.

Dietary consistency has been shown to influence cross-sectional area and fiber type composition of the masticatory muscles. However, little is known about the effects of dietary consistency on masticatory muscle fiber architecture. In this study, we explore the effects of dietary consistency on the internal architecture of rabbit masseter muscle. Because activity patterns of the rabbit chewing muscles show inter- and intramuscular heterogeneity, we evaluate if alterations in fiber architecture are homogeneous across various portions of the superficial masseter muscle. We compared masseter muscle fiber architecture between two groups of weanling rabbits raised on different diets for 105 days. One group was raised on a diet of ground rabbit pellets to model underuse of the masticatory complex, while the other group was fed a diet of intact pellets and hay blocks to model an overuse diet. In all portions of the superficial masseter, physiological cross-sectional areas (PCSAs) are greater in the overuse compared to underuse diet rabbits. Thus, the mechanical demands for larger muscle and bite forces associated with early and prolonged exposure to a tough diet are met by an increase in PCSA of the superficial masseter. The larger PCSA is due entirely to increased muscle mass, as the two rabbit groups show no differences in either fiber length or angle of pinnation. Thus, increasing pinnation angle is not a necessary biomechanical solution to improving muscle and bite force during growth. The change in PCSA but not fiber length suggests that variation in dietary consistency has an impact on maximum force production but not necessarily on excursion or contraction velocity.

Adaptation, Physiological↗
PubMed2007

Two-component supramolecular helical architectures: creation of tunable dissymmetric cavities for the inclusion and chiral recognition of the third components.

The inclusion and chiral recognition of racemic arylalkanols by supramolecular helical architectures consisting of enantiopure primary amines and achiral carboxylic acids were thoroughly studied. Among the architectures examined, a supramolecular helical architecture composed of the salt of enantiopure erythro-2-amino-1,2-diphenylethanol (1 b) and benzoic acid (2 a) was found to include a wide variety of racemic arylalkanols with recognition of their chirality. The helical architecture gave a dissymmetric 1D groove in the salt crystal, and the arylalkanols were enantioselectively included in the groove. The size and shape of the groove were tunable by proper selection of the achiral carboxylic acid component. The origin of the chiral recognition with the combination 1 b/2 a is discussed on the basis of X-ray crystallographic analyses.

Journal Article↗
PubMed1992

Design and control of the head retractor muscle in a turtle, Pseudemys (Trachemys) scripta: I. Architecture and histochemistry of single muscle fibers.

We are using the head retractor muscle (RCCQ) of a turtle, Pseudemys scripta, to analyze the neuromuscular mechanisms by which organisms vary the force and timing of muscle contraction. Previously we demonstrated that RCCQ comprises three histochemically defined fiber types: fast glycolytic (Fg), fast oxidative glycolytic (FOG), and slow oxidative (SO). In the present paper we report the 1) architectural features of single muscle fibers in RCCQ, including their lengths, diameters, and taper characteristics, 2) histochemical profiles of single muscle fibers, and 3) quantitative relations between our architectural and histochemical variables. Single fibers in RCCQ exhibit an order of magnitude variation in length (4-60 mm). Approximately 40% span the full muscle. The remaining fibers generally attach to bone or tendon at one end, and the other end tapers intramuscularly; rarely a fiber may taper at both ends. The maximum (untapering) diameters of single fibers are bimodally distributed, forming two diameter classes. Fibers also vary in the percentage of their total length that tapers and in the shape of the tapering region. Large diameter muscle fibers generally are longer and have shorter, more blunted tapers than small diameter fibers. The large diameter fibers are almost all Fg types; these fibers have a median diameter of 59.3 microns, and they account for approximately 60% of total fibers in RCCQ. FOG and SO fibers generally have small diameters (median: 32.5 microns and 35.8 microns), and they typically account for 30% and 10% of total fibers. We use these relations to draw inferences about the attachments and architecture of glycolytic (Fg) and oxidative (FOG, SO) fiber types. Taken together, our data suggest that single muscle fibers in RCCQ may be architecturally as well as histochemically specialized to perform different roles in head retraction. In the accompanying paper we report the efferent innervation of these fibers and consider some of the neural control problems posed by these diverse fiber types.

Animals↗
PubMed2003

Engineered cellular response to scaffold architecture in a rabbit trephine defect.

Tight control of pore architecture in porous scaffolds for bone repair is critical for a fully elucidated tissue response. Solid freeform fabrication (SFF) enables construction of scaffolds with tightly controlled pore architecture. Four types of porous scaffolds were constructed using SFF and evaluated in an 8-mm rabbit trephine defect at 8 and 16 weeks (n = 6): a lactide/glycolide (50:50) copolymer scaffold with 20% w/w tri-calcium phosphate and random porous architecture (Group 1); another identical design made from poly(desaminotyrosyl-tyrosine ethyl ester carbonate) [poly(DTE carbonate)], a tyrosine-derived pseudo-polyamino acid (Group 2); and two poly(DTE carbonate) scaffolds containing 500 microm pores separated by 500-microm thick walls, one type with solid walls (Group 3), and one type with microporous walls (Group 4). A commercially available coralline scaffold (Interpore) with a 486-microm average pore size and empty defects were used as controls. There was no significant difference in the overall amount of bone ingrowth in any of the devices, as found by radiographic analysis, but patterns of bone formation matched the morphology of the scaffold. These results suggest that controlled scaffold architecture can be superimposed on biomaterial composition to design and construct scaffolds with improved fill time.

Animals↗
PubMed1992

Control of bone architecture by functional load bearing.

The continuing ability of the skeleton to withstand functional loads without damage requires that bone mass and architecture are adjusted according to the loads experienced. Load bearing is the only functional influence that requires a particular bone architecture, and functionally engendered strains within the bone tissue provide the only feedback containing the necessary information on the relationship between current architecture and prevailing load history. The specific strain-related objectives of the adaptive modeling and remodeling response to load bearing have not been adequately defined. They appear to be different for cortical and cancellous bone and vary according to cortical location. Experiments suggest that adaptive modeling and remodeling is sensitive to dynamic but not static strain change and that the osteogenic response to a period of dynamic strain is quickly saturated but is higher when the rate of change in strain is high and the distribution of strain unusual. Presumably it is the cumulative effect of this osteogenic response to load bearing that normally maintains bone mass above that seen in disuse situations. Through their independent effects on bone cell behavior, nutritional and hormonal factors can enable, enhance, limit, or frustrate full expression of the osteogenic response to strain change. However, such systemic factors do not appear to be able to engender or successfully imitate the sustained cumulative local response to load bearing that normally maintains functionally appropriate bone mass and architecture. Experiments in vivo and in vitro suggest that in osteocytes and surface osteoblasts the almost immediate response to strain change is increased production of prostacyclin. Surface osteoblasts also produce prostaglandin E.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Altered trabecular architecture induced by corticosteroids: a bone histomorphometric study.

Prolonged corticosteroid (CS) therapy induces osteoporosis and fractures. Osteoporosis is characterized at the histomorphometric level by reduced bone volume (BV/TV) and disruption of the three-dimensional (3D) trabecular architecture. Several stereological methods have been proposed to characterize these alterations: measurements of trabecular thickness and trabecular number, star volumes, interconnectivity index (ICI) of the bone marrow spaces, and trabecular bone pattern factor (TBP(f)). These methods were computerized with a single program running on an image analyzer to evaluate the bone changes in a series of iliac biopsies performed on 31 male patients. All of them were asthmatic and had received CS for a long period of time. BV/TV was reduced when compared with age-matched controls. In the CS-treated population, exponential relationships were obtained between bone volume and the different connectivity parameters. The various methods used to measure connectivity were well correlated. When the population was divided into two groups (BV/TV greater or less than an 11% threshold), the architectural disturbances were found to imply two mechanisms. A progressive decline in trabecular thickness was noted in both groups versus controls. Trabecular perforations were not established in the group with BV/TV> 11% with the star volume or ICI, although some alterations were detected by trabecular bone pattern factor measurement. However, perforations were revealed in the group with BV/TV < 11% by all the different methods. Perforations seemed to occur when the trabecular thickness was below 70 mu m. This strongly suggests that bone histomorphometry should take into consideration bone volume in combination with detailed 3D descriptors of the trabecular architecture. Several histological methods need to be used in combination to appreciate the 3D architecture of trabecular bone.

Adrenal Cortex Hormones↗
PubMed2003

Architectural properties of distal forelimb muscles in horses, Equus caballus.

Articular injuries in athletic horses are associated with large forces from ground impact and from muscular contraction. To accurately and noninvasively predict muscle and joint contact forces, a detailed model of musculoskeletal geometry and muscle architecture is required. Moreover, muscle architectural data can increase our understanding of the relationship between muscle structure and function in the equine distal forelimb. Muscle architectural data were collected from seven limbs obtained from five thoroughbred and thoroughbred-cross horses. Muscle belly rest length, tendon rest length, muscle volume, muscle fiber length, and pennation angle were measured for nine distal forelimb muscles. Physiological cross-sectional area (PCSA) was determined from muscle volume and muscle fiber length. The superficial and deep digital flexor muscles displayed markedly different muscle volumes (227 and 656 cm3, respectively), but their PCSAs were very similar due to a significant difference in muscle fiber length (i.e., the superficial digital flexor muscle had very short fibers, while those of the deep digital flexor muscle were relatively long). The ulnaris lateralis and flexor carpi ulnaris muscles had short fibers (17.4 and 18.3 mm, respectively). These actuators were strong (peak isometric force, Fmax=5,814 and 4,017 N, respectively) and stiff (tendon rest length to muscle fiber length, LT:LMF=5.3 and 2.1, respectively), and are probably well adapted to stabilizing the carpus during the stance phase of gait. In contrast, the flexor carpi radialis muscle displayed long fibers (89.7 mm), low peak isometric force (Fmax=555 N), and high stiffness (LT:LMF=1.6). Due to its long fibers and low Fmax, flexor carpi radialis appears to be better adapted to flexion and extension of the limb during the swing phase of gait than to stabilization of the carpus during stance. Including muscle architectural parameters in a musculoskeletal model of the equine distal forelimb may lead to more realistic estimates not only of the magnitudes of muscle forces, but also of the distribution of forces among the muscles crossing any given joint.

Animals↗
PubMed1990

Effects of growth on architecture and functional characteristics of adult rat gastrocnemius muscle.

Changes of architecture of adult rat gastrocnemius medialis muscle (GM) due to growth were studied in relation to length-force characteristics. Myofilament lengths were unchanged, indicating constant sarcomere length-force characteristics. Number of sarcomeres within fibers was unchanged as a consequence of growth, allowing persistence of differences between proximal and distal fibers in all age groups. Distal fiber length at muscle optimum length was shorter for the 14- than for the 10- and 16-week age groups despite a lack of difference of number of sarcomeres. This is indicative of a shift of optimum length. Some evidence for the occurrence of distribution of fiber optimum lengths with respect to muscle optimum length was found in other age groups as well, albeit of a smaller magnitude. Muscle and aponeurosis length increased substantially with growth. Functional effects of increased aponeurosis lengths were increased contributions to muscle length changes by the aponeurosis, allowing smaller fiber contributions in older animals. Fiber angle increased approximately 5 degrees with growth. Despite the differences of architecture indicated above, muscle length range between optimum length and active slack length was constant. This was probably caused by widening of this length range in the youngest age group by variations of architecture within the muscle. It is concluded that adaptation of aspects of muscle architecture is an important mechanism for adult muscle growth in rat GM. Of these aspects regulation of muscle length seems a dominant factor.

Aging↗
PubMed1994

Relationship between muscle fiber types and sizes and muscle architectural properties in the mouse hindlimb.

Skeletal muscle fiber and architectural properties both contribute to the functional behavior of a muscle. This study uses discriminant analysis and mathematical modeling to identify the structurally and functionally significant properties. The architectural properties of fiber length, muscle length, and pennation angle are found to be the most structurally significant parameters, whereas fiber length, muscle length, and fiber type distribution are found to be most functionally determining. Architectural speed and fiber type do not appear to be complimentary (i.e., the architectural determinant of speed, fiber length, is not associated with fibers of high intrinsic velocity). However, there does seem to be a synergistic relation between the two property classes and force production. Muscles with large physiological cross sectional areas (PCSAs) tend to contain a greater proportion of larger, faster fibers. Structurally or morphologically significant parameters are not always found to have a large functional effect. Pennation angle, though one of the most structurally significant variables, was found to have very little functional effect.

Animals↗
PubMed2001

Occurrence of two architectural types of hexagonal bilayer hemoglobin in annelids: comparison of 3D reconstruction volumes of Arenicola marina and Lumbricus terrestris hemoglobins.

A 3D reconstruction at 25 A resolution of native hemoglobin of the polychaete worm Arenicola marina was carried out from frozen-hydrated specimens examined in the electron microscope. The reconstruction volume of this large extracellular multimeric respiratory pigment appears as a hexagonal bilayer structure with eclipsed vertices in its upper and lower hexagonal layers. Conversely, in hemoglobins of oligochaetes, achaetes, and vestimentiferans and in chlorocruorins of the Sabellidae (polychaete) family, the vertices of the upper layer are 16 degrees clockwise rotated with respect to those of the lower layer. The fact that two other polychaete hemoglobins (Alvinella pompejana and Tylorrhynchus heterochaetus) have the same architecture as Arenicola led us to define two types of hexagonal bilayer hemoglobins/chlorocruorins: (i) type-I present in oligochaete, achaete, and vestimentiferan hemoglobins and in Sabellidae chlorocruorins; and (ii) type-II present in polychaete hemoglobins. A comparative study of the hemoglobins of Lumbricus terrestris (type-I) and Arenicola marina (type-II) showed that only two small differences located in the c4 and c5 linking units are responsible of the important architectural difference present in oligomers. A likely scheme proposed to explain the phylogenic distribution of the two types suggests that Clitellata, Sabellida (polychaete), and vestimentiferan hemoglobins and chlorocruorins derive from a type-I ancestral molecule, while Terebellida (Alvinella), Phyllodocida (Tylorrhynchus), and Scolecida (Arenicola) and possibly other polychaetes derive from an ancestor molecule with type-II hemoglobin. The architectures of the hollow globular substructures are highly similar in Arenicola and Lumbricus hemoglobins, with 12 globin chains and three linking units (c3a, c3b, and c4). The central piece of Arenicola hemoglobin is an ellipsoid while that of Lumbricus is a toroid. No phylogenic correlation could be found between the structure of the central pieces and the architecture type.

Animals↗
PubMed2000

Failure of laser Doppler signal to correlate with total flow in muscle: is this a question of vessel architecture?

The signal strength from LDF probes positioned in perfused muscle can be altered by vasoconstrictors despite total flow being maintained constant. Apart from redistribution of flow via collateral channels outside the region of measurement, the change in LDF signal may arise because the vasoconstrictors have switched flow to vessels of different architecture or altered the architecture of the blood vessels being perfused. Thus we have examined the effect of tube architecture on LDF signal using polymer tubes of 250, 100, and 50 microm internal diameter. At 3% hematocrit the LDF signal was linear for each of the three tube sizes from 10 to 80 microl/h. The signal strength was greatest from the smallest tube and least from the largest tube. For a single tube (100 microm) that doubled back on itself twice to cross the field of measurement three times, the LDF signal at any flow (10-80 microl/h, hematocrit 3%) was approx threefold greater than that for the same tube crossing the field of measurement once. The effect of progressively switching flow (constant at 120 microl/h, hematocrit 9%) from five to one tube in a manifold of five tubes (100 microm) gave rise to a progressive increase in signal. It is concluded that LDF signal derives predominantly from nonvectorial cell speed and less from cell number. Thus any agent that alters the architecture has the potential to alter the LDF signal.

Animals↗
PubMed1983

Influence of muscle architecture on the length-force diagram of mammalian muscle.

The functions and geometrical characteristics of a pennate and a parallel-fibered muscle in rats are quantified and compared to each other. The pennate medial gastrocnemius and the more parallel fibered semimembranosus are investigated in fourteen male Wistar rats. The length force diagram, twitch time characteristics and muscle architecture are quantified. In the parallel fibered semimembranosus the length of the muscle fibres is about 70% of the muscle optimum length (the length at which the muscle performs maximal active force), while in the pennate fibered gastrocnemius the length of the muscle fibres is 36% of the muscle optimum length. The active length force diagrams normalized with respect to the muscle optimum length show considerable differences between semimembranosus and gastrocnemius: The normalized active length force diagram runs from about 71%-129% of the muscle optimum length for the semimembranosus and from about 82-118% for the gastrocnemius. The latter muscle also has a steeper normalized passive length force curve and produces more active tetanic force per gram muscle (877 g/g for gastrocnemius versus 379 g/g for semimembranosus). No differences between the semimembranosus and gastrocnemius are found with respect to the passive tension at twitch optimum length (38 g/cm2 versus 32 g/cm2), the maximal active tension (1.27 kg/cm2 versus 1.18 kg/cm2) and the twitch contraction time at twitch optimum length (43.8 ms versus 48.4 ms). It is concluded that several functional characteristics show a linear relationship with the index of architecture, a measure for the muscle architecture, while others (especially time and tension characteristics) are independent of muscle architecture.

Animals↗