Automated tracking of muscle fascicle orientation in B-mode ultrasound images

B-mode ultrasound can be used to non-invasively image muscle fascicles during both static and dynamic contractions. Digitizing these muscle fascicles can be a timely and subjective process, and usually studies have used the images to determine the linear fascicle lengths. However, fascicle orientations can vary along each fascicle (curvature) and between fascicles. The purpose of this study was to develop and test two methods for automatically tracking fascicle orientation. Images were initially filtered using a multiscale vessel enhancement (a technique used to enhance tube-like structures), and then fascicle orientations quantified using either the Radon transform or wavelet analysis. Tests on synthetic images showed that these methods could identify fascicular orientation with errors of less than 0.06°. Manual digitization of muscle fascicles during a dynamic contraction resulted in a standard deviation of angle estimates of 1.41° across ten researchers. The Radon transform predicted fascicle orientations that were not significantly different from the manually digitized values, whilst the wavelet analysis resulted in angles that were 1.35° less, and reasons for these differences are discussed. The Radon transform can be used to identify the dominant fascicular orientation within an image, and thus used to estimate muscle fascicle lengths. The wavelet analysis additionally provides information on the local fascicle orientations and can be used to quantify fascicle curvatures and regional differences with fascicle orientation across an image.     

Observation of flagellation of spermatozoa by depolarized laser light scattering.

Depolarized laser light-scattering theory was applied to derive the autocorrelation function of laser light scattered by motile spermatozoa, assuming that each spermatozoon is a chain of rotatable rigid ellipsoids of revolution and also that the rotational velocity about an axis perpendicular to the symmetry axis of the ellipsoid is constant for times of the order of the characteristic decay time of the autocorrelation function. The rotations are produced by flagellar movements of the spermatozoa. The correlation function thus obtained was related to the second-order coefficient of a Legendre polynomial expansion of the rotation of the direction angle of the ellipsoidal axis. The experimental fact that the correlation function for dead spermatozoa of sea urchin resembled that for flagella mechanically separated from spermatozoa indicated to us that the depolarized light was scattered mainly by flagella. The rotational velocity distribution of the flagella was determined by comparing the theoretical analysis with the experimentally obtained correlation functions for the motile and dead spermatozoa. The value of the average velocity caused by the flagellation, 230 rad/s, was in good agreement with that measured under an optical microscope.     

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

In leech, the central annulus of each midbody segment possesses seven pairs of sensilla, which are mixed clusters of primary peripheral sensory neurons that extend their axons into the CNS where they segregate into distinct fascicles. Pathway selection by individual afferent growth cones of sensillar neurons was examined by double labeling using intracellular dye-filling with anitobody labeling in early Hirudo medicinalis embryos. The monoclonal antibody Lan3–2 was used because sensillar neuronal tracts are specifically labeled by this antibody. Examining 68 individually filled neurons we found that sensillar neuron growth cones bifurcate within the CNS, that they project long filopodia capable to sampling the local environment, and that all of them appeared to choose a single particular CNS fascicle without apparent retraction or realignment of growth cones. Furthermore, each side of the bifurcating afferent growth cones always chose the same fascicle, implying a specific choice of a distinct labeled pathway. By dye-filling individual central neurons (P-cells), we show that there are centrally projecting axons present at the time sensillar afferents enter the ganglionic primordia and select a particular fascicle, and we confirm that at least the dorsal peripheral nerve is likely to be pioneered by central neurons, not by the peripheral afferent. In the sensillum studied here, we sound examples of sensory neurons extending axons into one of all the avilable fascicles. Thus, an individual embryonic sensillum possesses a heterogeneous population of afferents with respect to the central fascicle chosen. This is consistent with the idea that segregation into distinct axon fascicles may be based upon functional differences between individual afferent neurons. Our findings argue strongly in favor of specific pathway selection by afferents in this system and are consistent with previous suggestions that there exists a hierarchy of cues, including surface glycoconjugates that mediate navigation of the sensillar growth cones and the fasciculation of their axons. 1994 John Wiley & Sons, Inc.     

Salmonella typhimurium fliG and fliN mutations causing defects in assembly, rotation, and switching of the flagellar motor.

FliG, FliM, and FliN are three proteins of Salmonella typhimurium that affect the rotation and switching of direction of the flagellar motor. An analysis of mutant alleles of FliM has been described recently (H. Sockett, S. Yamaguchi, M. Kihara, V. M. Irikura, and R. M. Macnab, J. Bacteriol. 174:793-806, 1992). We have now analyzed a large number of mutations in the fliG and fliN genes that are responsible for four different types of defects: failure to assembly flagella (nonflagellate phenotype), failure to rotate flagella (paralyzed phenotype), and failure to display normal chemotaxis as a result of an abnormally high bias to clockwise (CW) or counterclockwise (CCW) rotation (CW-bias and CCW-bias phenotypes, respectively). The null phenotype for fliG, caused by nonsense or frameshift mutations, was nonflagellate. However, a considerable part of the FliG amino acid sequence was not needed for flagellation, with several substantial in-frame deletions preventing motor rotation but not flagellar assembly. Missense mutations in fliG causing paralysis or abnormal switching occurred at a number of positions, almost all within the middle one-third of the gene. CW-bias and CCW-bias mutations tended to segregate into separate subclusters. The null phenotype of fliN is uncertain, since frameshift and nonsense mutations gave in some cases the nonflagellate phenotype and in other cases the paralyzed phenotype; in none of these cases was the phenotype a consequence of polar effects on downstream flagellar genes. Few positions in FliN were found to affect switching: only one gave rise to the CW mutant bias and only four gave rise to the CCW mutant bias. The different properties of the FliM, FliG, and FliN proteins with respect to the processes of assembly, rotation, and switching are discussed.     

A biphasic and transversely isotropic mechanical model for tendon: application to mouse tail fascicles in uniaxial tension

A transversely isotropic biphasic mixture model was applied to tendon in uniaxial tension. Parametric analyses were performed and the sensitivity in predicting material parameters was evaluated. Our results provide quantitative evidence for fluid flow as a mechanism that contributes to tendon viscoelasticity. Transversely isotropic material properties were calculated for mouse tail tendon fascicles. The average transverse modulus (E(1)) was 0.046 MPa, the fiber-aligned Poisson's ratio (v(31)) was 2.73, and the transverse Poisson's ratio [(v(21)) was 0.96; these properties were not strain-dependent. The fiber-aligned modulus (E(s)) was strain-dependent and was 20.7 MPa in the toe region and 86.1 MPa in the linear region. These solid matrix properties were consistent with previously published tendon tissue and fascicle data. The fascicle permeability was strain-dependent and was 5.5 x 10(-18)m(4)/Ns in the toe region and 0.32 x 10(-18)m(4)/Ns in the linear region, similar to previously reported meniscus permeability in tension. The similar permeabilities of both fascicle and tissue-level samples suggest that fluid flow from individual fascicles, not the packing of multiple fascicles together, may be the primary barrier to fluid flow in tendon and thus the primary mechanism for viscoelasticity.     

Heterogeneous fascicle behavior within the biceps femoris long head at different muscle activation levels

Magnetic resonance and ultrasound imaging have shown hamstring strain injuries occur most often in the biceps femoris long head (BFLH), and particularly in the proximal vs. distal region of this muscle. Animal research and musculoskeletal modeling (MSK) have detected heterogeneous fascicle behavior within muscle regions, and within fascicles. Understanding architectural behavior differences during muscle contractions may help to discern possible mechanisms behind proximal BFLH injuries. The purpose of our study was to assess the magnitude of shortening of the proximal and distal fascicles of the BFLH under a range of muscle activation levels under isometric conditions using ultrasound imaging (US). Thirteen healthy adults performed targeted sustained isometric contractions while US were taken of the entire BFLH. Measurements of fascicle lengths in both muscle regions were compared at 20%, 30%, 50%, and 67% MVIC. The results showed that while both regions shortened significantly with activation, the proximal fascicles were significantly longer, regardless of activation level (~38%), and shortened significantly more than the distal fascicles overall (~40%), and cumulatively at higher activation levels (30% and above). No significant strain differences were found between the two regions. These data suggest heterogeneous fascicle behavior exists in an absolute sense; however, differences in behavior are eliminated when normalized (strain). Coupled with MSK literature, the absence of regional fascicle strain differences in this study may indicate strain heterogeneity is not detectable at the whole fascicle level. Further knowledge of this commonly strained muscle?s regional behavior during dynamic movements could provide evidence of proximal hamstring strain predisposition.     

The movement of spermatozoa with helical head: theoretical analysis and experimental results.

The present work is concerned with the study of the swimming of flagellated microscopic organisms with a helical head and a helical pattern of flagellar beating, such as Xenopus sperms. The theoretical approach is similar to that taken by Chang and Wu (1971) in the study of helical flagellar movement. The model used in the present study allows us to determine the velocity of propulsion (U) and the frequency of rotation of the sperm head (fh) as a function of the frequency of the wave of motion (ft) traveling along the tail. The results relative to the case of helical and planar flagellar waves are compared. Our main finding is that the helical shape of the head seems to increase the efficiency of propulsion of the spermatozoon when compared with the more commonly shaped spherical head. Experimentally measured values of fh versus U may be fitted by a linear plot whose slope is much higher than that corresponding to the case of planar flagellar beating. This fact is consistent with an effectively three-dimensional (nonplanar) movement of the flagellar tail. However, the results do not fit those predicted from a circular helix, suggesting that a different shape of the flagellar beating should be considered.     

Magnetic resonance and diffusion tensor imaging analyses indicate heterogeneous strains along human medial gastrocnemius fascicles caused by submaximal plantar-flexion activity

Sarcomere length changes are central to force production and excursion of skeletal muscle. Previous modeling indicates non-uniformity of that if mechanical interaction of muscle with its surrounding muscular and connective tissues is taken into account. Hence, quantifying length changes along the fascicles of activated human muscle in vivo is crucial, but this is lacking due to technical complexities. Combining magnetic resonance imaging deformation analyses and diffusion tensor imaging tractography, the aim was to test the hypothesis that submaximal plantar flexion activity at 15% MVC causes heterogeneous length changes along the fascicles of human medial gastrocnemius (GM) muscle. A general fascicle strain distribution pattern shown for all subjects indicates that proximal track segments are shortened, whereas distal ones are lengthened (e.g., by 13% and 29%, respectively). Mean fiber direction strains of different tracts also shows heterogeneity (for up to 57.5% of the fascicles). Inter-subject variability of amplitude and distribution of fascicle strains is notable. These findings confirm the hypothesis and are solid indicators for the functionally dependent mechanics of human muscle, in vivo. Heterogeneity of fascicle strains can be explained by epimuscular myofascial force transmission. To the best of our knowledge, this is the first study, which quantified local deformations along human skeletal muscle fascicles caused by sustained submaximal activation. The present approach and indicated fascicle strain heterogeneity has numerous implications for muscle function in health and disease to estimate the muscle’s contribution to the joint moment and excursion and to evaluate mechanisms of muscle injury and several treatment techniques.     

Spatial and numerical regulation of flagellar biosynthesis in polarly flagellated bacteria

Control of surface organelle number and placement is a crucial aspect of the cell biology of many Gram‐positive and Gram‐negative bacteria, yet mechanistic insights into how bacteria spatially and numerically organize organelles are lacking. Many surface structures and internal complexes are spatially restricted in the bacterial cell (e.g. type IV pili, holdfasts, chemoreceptors), but perhaps none show so many distinct patterns in terms of number and localization as the flagellum. In this review, we discuss two proteins, FlhF and FlhG (also annotated FleN/YlxH), which control aspects of flagellar assembly, placement and number in polar flagellates, and may influence flagellation in some bacteria that produce peritrichous flagella. Experimental data obtained in a number of bacterial species suggest that these proteins may have acquired distinct attributes influencing flagellar assembly that reflect the diversity of flagellation patterns seen in different polar flagellates. Recent findings also suggest FlhF and FlhG are involved in other processes, such as influencing the rotation of flagella and proper cell division. Continued examination of these proteins in polar flagellates is expected to reveal how different bacteria have adapted FlhF or FlhG with specific activities to tailor flagellar biosynthesis and motility to fit the needs of each species.     

Three-dimensional analysis of the arrangement and length distribution of fascicles in the triceps muscle of Galea musteloides (Rodentia, Cavimorpha)

Non-uniformity of fascicle parameters (fascicle lengths and orientation) within one skeletal muscle is well known. These parameters have an effect on the physiological cross-sectional area and lengthening rate of the skeletal muscle. Using a binocular microscope with a table driver (q- and p-axes) and vertical drive (v-axis) as a tool for reconstruction of the spatial orientation of single muscle fascicles, we developed an approach for three-dimensional analysis of the arrangement and length distribution in the skeletal muscle of small mammals. Two subunits of the triceps brachii muscle of the Galea musteloides forelimb, triceps longum and triceps laterale, were quantified and compared. Our data show that in the triceps laterale the fascicles are significantly longer (10.23 mm, SD=1.19, n=41) than those in the triceps longum (6.58 mm, SD=2.88, n=39). In the triceps laterale, the fascicle orientation is more or less uniform, whereas, in the triceps longum, there are two areas with different orientation of fascicles: anterior and posterior ones. Different inner architecture of the subunits can be interpreted as an adaptation to the main locomotory function of the triceps muscle, namely production of propulsive force during limb transfer phase and keeping dynamic stability during stance phase. Comparison of our data on the fascicle length and geometry with our previous histochemical results on G. musteloides, shows that the anterior region of the triceps longum, which differs in the fascicle orientation, also contains a significantly larger percent of slow muscle fibres. It is hypothesised here that this small region is involved in keeping posture. Accepted: 16 May 2000     

一种简易小鼠尾部皮肤移植教学实验改良方法的建立

目的 为本校生物工程系实验动物学课程小鼠尾部皮肤移植实验课提供一种合适的操作方法.方法 分别用0.7%、1%、1.5%戊巴比妥钠和10%水合氯醛对小鼠进行麻醉试验,选出合适的麻醉方法;再进行小鼠尾部皮肤移植,对比玻璃套管法和创可贴法2种包扎方法的效果,以选出合适的手术方法.结果 0.7%和1%戊巴比妥钠麻醉持续时间过短,1.5%戊巴比妥钠和10%水合氯醛能维持足够手术操作所需的时间,但1.5%戊巴比妥钠易导致动物死亡,故采用10%水合氯醛麻醉小鼠较合适;玻璃套管法包扎的效果较创可贴法为好且更简便.结论 10%水合氯醛麻醉结合玻璃套管法包扎进行小鼠尾部皮肤移植是一种有效、简便、经济的小鼠尾部皮肤移植手术实验方法;此方法技术失败率低,适合学生实验课采用.     

Dynamic measurement of pennation angle of gastrocnemius muscles during contractions based on ultrasound imaging

ABSTRACT: BACKGROUND: Muscle fascicle pennation angle (PA) is an important parameter related to musculoskeletal functions, and ultrasound imaging has been widely used for measuring PA, but manually and frame by frame in most cases. We have earlier reported an automatic method to estimate aponeurosis orientation based on Gabor transform and Revoting Hough Transform (RVHT). METHODS: In this paper, we proposed a method to estimate the overall orientation of muscle fascicles in a region of interest, in order to complete computing the orientation of the other side of the pennation angle, but the side found by RVHT. The measurements for orientations of both fascicles and aponeurosis were conducted in each frame of ultrasound images, and then the dynamic change of pennation angle during muscle contraction was obtained automatically. The method for fascicle orientation estimation was evaluated using synthetic images with different noise levels and later on 500 ultrasound images of human gastrocnemius muscles during isometric plantarflexion. RESULTS: The muscle fascicle orientations were also estimated manually by two operators. From the results it's found that the proposed automatic method demonstrated a comparable performance to the manual method. CONCLUSIONS: With the proposed methods, ultrasound measurement for muscle pennation angles can be more widely used for functional assessment of muscles.     

The effects of annual fertilization and complete competition control on fascicle morphology of different aged loblolly pine stands

The goal of this study was to determine how increased nutrient availability affects foliage morphology of loblolly pine (Pinus taeda L.) without introducing the confounding influence of light availability. Morphology of fascicles from the terminal leader (radius, length, specific needle area, density, and needles per fascicle) and terminal leader traits (length, foliated length, total leaf area, and total fascicles) were measured for different aged (ranged from 5-year-old to 12-year-old) loblolly pine stands growing on the Piedmont and lower Coastal Plain of Georgia, USA. A factorial combination of annual fertilization and complete interspecific competition control was applied as stand level treatments. Competition control and stand age generally did not affect fascicle morphology. In contrast, annual fertilization significantly increased fascicle length (5%), needles per fascicle (4%), and total leaf area of the terminal (18%), while decreasing specific needle area (4%). Fertilization also increased terminal leader growth (5%) and total number of fascicles (6%). Therefore, loblolly pine foliage morphology does have plasticity to respond to increased nutrient availability. However, the magnitude of these morphological changes is small compared to changes in total canopy leaf area.     

Muscle fiber and tendon length changes in the human vastus lateralis during slow pedaling.

Muscle fascicle lengths of vastus lateralis (VL) muscle were measured in five healthy men during slow pedaling to investigate the interaction between muscle fibers and tendon. Subjects cycled at a pedaling rate of 40 rpm (98 W). During exercise, fascicle lengths changed from 91 +/- 7 (SE) to 127 +/- 5 mm. It was suggested that fascicles were on the descending limb of their force-length relationship. The average shortening velocity of fascicle was greater than that of muscle-tendon complex in the first half of the knee extension phase and was less in the second half. The maximum shortening velocity of fascicle in the knee extension phase was less than that of muscle-tendon complex by 22 +/- 9%. These discrepancies in velocities were mainly caused by the elongation of the tendinous tissue. It was suggested that the elasticity of VL tendinous tissue enabled VL fascicles to develop force at closer length to their optimal length and kept the maximum shortening velocity of VL fascicles low during slow pedaling.     

Motility and flagellum synthesis in Halobacillus halophilus are chloride dependent

The motility of Halobacillus halophilus as observed on swarm agar plates was strictly dependent on the chloride concentration. Cl(-) was apparently not used as the coupling ion for flagellar rotation. Cells grown in the absence of chloride were devoid of flagella, but flagellation was restored upon the addition of chloride. These experiments indicate that chloride is involved in synthesis of flagella in H. halophilus.     

Minimum Requirements of Flagellation and Motility for Infection of Agrobacterium sp. Strain H13-3 by Flagellotropic Bacteriophage 7-7-1

The flagellotropic phage 7-7-1 specifically adsorbs to Agrobacterium sp. strain H13-3 (formerly Rhizobium lupini H13-3) flagella for efficient host infection. The Agrobacterium sp. H13-3 flagellum is complex and consists of three flagellin proteins: the primary flagellin FlaA, which is essential for motility, and the secondary flagellins FlaB and FlaD, which have minor functions in motility. Using quantitative infectivity assays, we showed that absence of FlaD had no effect on phage infection, while absence of FlaB resulted in a 2.5-fold increase in infectivity. A flaA deletion strain, which produces straight and severely truncated flagella, experienced a significantly reduced infectivity, similar to that of a flaB flaD strain, which produces a low number of straight flagella. A strain lacking all three flagellin genes is phage resistant. In addition to flagellation, flagellar rotation is required for infection. A strain that is nonmotile due to an in-frame deletion in the gene encoding the motor component MotA is resistant to phage infection. We also generated two strains with point mutations in the motA gene resulting in replacement of the conserved charged residue Glu98, which is important for modulation of rotary speed. A change to the neutral Gln caused the flagellar motor to rotate at a constant high speed, allowing a 2.2-fold-enhanced infectivity. A change to the positively charged Lys caused a jiggly motility phenotype with very slow flagellar rotation, which significantly reduced the efficiency of infection. In conclusion, flagellar number and length, as well as speed of flagellar rotation, are important determinants for infection by phage 7-7-1.     

Growth cones stall and collapse during axon outgrowth in Caenorhabditis elegans.

During nervous system development, neurons form synaptic contacts with distant target cells. These connections are formed by the extension of axonal processes along predetermined pathways. Axon outgrowth is directed by growth cones located at the tips of these neuronal processes. Although the behavior of growth cones has been well-characterized in vitro, it is difficult to observe growth cones in vivo. We have observed motor neuron growth cones migrating in living Caenorhabditis elegans larvae using time-lapse confocal microscopy. Specifically, we observed the VD motor neurons extend axons from the ventral to dorsal nerve cord during the L2 stage. The growth cones of these neurons are round and migrate rapidly across the epidermis if they are unobstructed. When they contact axons of the lateral nerve fascicles, growth cones stall and spread out along the fascicle to form anvil-shaped structures. After pausing for a few minutes, they extend lamellipodia beyond the fascicle and resume migration toward the dorsal nerve cord. Growth cones stall again when they contact the body wall muscles. These muscles are tightly attached to the epidermis by narrowly spaced circumferential attachment structures. Stalled growth cones extend fingers dorsally between these hypodermal attachment structures. When a single finger has projected through the body wall muscle quadrant, the growth cone located on the ventral side of the muscle collapses and a new growth cone forms at the dorsal tip of the predominating finger. Thus, we observe that complete growth cone collapse occurs in vivo and not just in culture assays. In contrast to studies indicating that collapse occurs upon contact with repulsive substrata, collapse of the VD growth cones may result from an intrinsic signal that serves to maintain growth cone primacy and conserve cellular material.     

A quantitative investigation of structure-function relationships in a tendon fascicle model

These studies sought to investigate quantitative relationships between the complex composite structure and mechanical properties of tendon. The isolated mouse tail tendon fascicle was chosen as an appropriate model for these so-called "structure-function" investigations. Specifically, collagen fibril diameters and mechanical properties were measured in fascicles from immature (3 week) control, adult (8 week) control, and adult (8 week) MovI3 transgenic mice. Results demonstrated a moderate correlation between mean fibril diameter and fascicle stiffness (r = 0.73, p = 0.001) and maximum load (r = 0.75, p < 0.001), whereas a weak correlation with fascicle modulus (r = 0.39, p = 0.11) and maximum stress (r = 0.48, p = 0.04). An analysis of pooled within-group correlations revealed no strong structure-function trends evidenced at the local or group level, indicating that correlations observed in the general structure-function analyses were due primarily to having three different experimental groups, rather than significant correlations of parameters within the groups.     

Region-specific mechanical properties of the human patella tendon.

The present study investigated the mechanical properties of tendon fascicles from the anterior and posterior human patellar tendon. Collagen fascicles from the anterior and posterior human patellar tendon in healthy young men (mean +/- SD, 29.0 +/- 4.6 yr, n = 6) were tested in a mechanical rig. A stereoscopic microscope equipped with a digital camera recorded elongation. The fascicles were preconditioned five cycles before the failure test based on pilot data on rat tendon fascicle. Human fascicle length increased with repeated cycles (P < 0.05); cycle 5 differed from cycle 1 (P < 0.05), but not cycles 2-4. Peak stress and yield stress were greater for anterior (76.0 +/- 9.5 and 56.6 +/- 10.4 MPa, respectively) than posterior fascicles (38.5 +/- 3.9 and 31.6 +/- 2.9 MPa, respectively), P < 0.05, while yield strain was similar (anterior 6.8 +/- 1.0%, posterior 8.7 +/- 1.4%). Tangent modulus was greater for the anterior (1,231 +/- 188 MPa) than the posterior (583 +/- 122 MPa) fascicles, P < 0.05. In conclusion, tendon fascicles from the anterior portion of the human patellar tendon in young men displayed considerably greater peak and yield stress and tangent modulus compared with the posterior portion of the tendon, indicating region-specific material properties.