In vitro determination of the pressure-diameter relationship and velocity profiles by ultrasonic technics. In vivo application

A good knowledge of arterial flow mechanics and of the phenomena associated with fluid-boundary interactions is necessary for the determination of some fundamental parameters such as velocity, pressure and pressure-diameter relationship during a cardiac cycle. Ultrasonic techniques were developed on a test bench and directly applied to animals without major modification. On such a test bench allowing a good simulation of physiological type flows, velocity field and pressure-diameter relationship were determined. In vivo application of these techniques allowed a systematic analysis of velocity profiles in the rabbit abdominal aorta and a precise approach of rheological properties of the vascular wall.     

In vivo estimation of the short-range stiffness of cross-bridges from joint rotation

Short-range stiffness (SRS) is a mechanical property of muscles that is characterized by a disproportionally high stiffness within a short length range during both lengthening and shortening movements. SRS is attributed to the cross-bridges and is beneficial for stabilizing a joint during, e.g., postural conditions. Thus far, SRS has been estimated mainly on isolated mammalian muscles. In this study we presented a method to estimate SRS in vivo in the human wrist joint.SRS was estimated at joint level in the angular domain (N m/rad) for both flexion and extension rotations of the human wrist in nine healthy subjects. Wrist rotations of 0.15 rad at 3 rad/s were imposed at eight levels of voluntary contraction ranging from 0 to 2.1 N m by means of a single axis manipulator.Flexion and extension SRS of the wrist joint was estimated consistently and accurately using a dynamic nonlinear model that was fitted onto the recorded wrist torque. SRS increased monotonically with torque in a way consistent with previous studies on isolated muscles.It is concluded that in vivo measurement of joint SRS represents the population of coupled cross-bridges in wrist flexor and extensor muscles. In its current form, the presented technique can be used for clinical applications in many neurological and muscular diseases where altered joint torque and (dissociated) joint stiffness are important clinical parameters.     

In vivo glucose metabolism in individual tissues of the rat. Interaction between epinephrine and insulin

The interaction between epinephrine and insulin in modulating in vivo glucose metabolism within individual tissues of the body has not previously been examined. This was investigated using the euglycemic hyperinsulinemic (120 milliunits/liter) clamp combined with administration of [3H]2-deoxyglucose and D-[U-14C]glucose. Epinephrine produced whole body insulin resistance due to increased hepatic glucose output and reduced peripheral glucose disposal. Despite elevated insulin levels liver glycogen content was reduced by 50% during epinephrine infusion (5 nM). However, this effect was transient, occurring predominantly during the initial 60 min of study. These effects were prevented during beta-adrenergic blockade with propranolol and potentiated during alpha 1-adrenergic blockade with prazosin. The most significant effect of epinephrine in peripheral tissues was increased glycogenolysis in both oxidative and glycolytic skeletal muscle. A significant reduction in insulin-mediated [3H]2-deoxyglucose uptake (30%) was evident in 5 of 9 muscles tested during epinephrine infusion. This effect was most pronounced in the more insulin-sensitive oxidative muscles. The latter effect was probably indirectly mediated via increased glycogenolysis--increased accumulation of metabolites--inhibition of hexokinase. In addition, it is evident that insulin-mediated glycogen synthesis occurred during epinephrine infusion. All effects of epinephrine on muscle glucose metabolism were prevented by propranolol but not prazosin. Similar effects to that observed in muscle were not evident in adipose tissue. It is concluded that epinephrine may override many of the actions of insulin in vivo, and most of these effects are mediated via the beta-adrenergic receptor. In the intact rat there may be a complex interaction between alpha- and beta-adrenergic effects in regulating hepatic glucose output.     

In vivo muscular force analysis during the isometric flexion on a monkey's elbow

An experimental method has been developed to analyse muscular forces and torques in vivo during isometric flexion of the elbow in small monkeys (Macaca fascicularis). A mini-transducer was built with a view to measure forces in situ, without cutting tendons. The positions of tendon insertions were measured on anatomical parts, then integrated in a series of calculations aiming of deducing the lever arms of forces to be included in a torque equilibrium relationship. Muscle activity of the three main flexors was measured for five angles of isometric flexion between 70 degrees and 110 degrees, 0 degrees corresponding to the full extended forearm. The analysed signals were selected using physiological and biomechanical criteria. Then, results corresponding to force participation, and torque participations, were worked out; they are presented and discussed in the present paper.     

Electromyography of trunk muscles in isometric graded axial rotation.

This study was conducted to determine the pattern, magnitude, and phasic inter-relationship of the trunk muscles in maximal isometric and graded isometric axial rotational contractions and compare them with those previously observed from the same subjects in the same experimental session in dynamic conditions. In 50 normal young healthy subjects (27 male and 23 female), after a suitable skin preparation, bipolar silver-silver chloride recessed pregelled surface electrodes were placed on external oblique, internal oblique, rectus abdominis, pectoralis major, latissimus dorsi, erector spinae at T(10) and L(3) levels bilaterally with 2 cm interelectrode distance. EMG signals from grounded subjects were suitably preamplified and amplified by a fully isolated system. These subjects were stabilized in an upright-seated posture in the Axial Rotation Tester (AROT), which was placed in isometric mode for force and rotation output from the AROT. The 14 channels of EMG, the force and the rotation were sampled at 1 kHz. The subjects initially registered their isometric maximal voluntary contraction (MVC) on both sides which was used for reference and then performed their 25%, 50% and 75% of MVC bilaterally in an isometric mode in a random order. The EMG magnitude, the slope of the rise of the EMG, and the phasic interrelationship of muscles were analyzed. The results showed that female sample generated only 65% of torque of their male counterparts. There were no significant differences between the male and the female samples in the EMG variables. Exertions to the left and to the right were not significantly different from each other for the measured variables. However, the magnitude contribution of the muscles and the slope of rise of EMG were significantly different in two directions (p<0.001). The phasic interrelationship of the external obliques, the latissimus dorsi and the erector spinae were different from other muscles (p<0.01). With the increasing grades of contraction the latissimus dorsi and the external obliques increased their magnitude significantly whereas that of the erectores spinae underwent a decrease in proportionate terms (but not in absolute magnitude) suggesting their role as stabilizers but not as rotators.     

The isometric functional capacity of muscles that cross the elbow

We hypothesized that muscles crossing the elbow have fundamental differences in their capacity for excursion, force generation, and moment generation due to differences in their architecture, moment arm, and the combination of their architecture and moment arm. Muscle fascicle length, sarcomere length, pennation angle, mass, and tendon displacement with elbow flexion were measured for the major elbow muscles in 10 upper extremity specimens. Optimal fascicle length, physiological cross-sectional area (PCSA), moment arm, operating range on the force-length curve, and moment-generating capacity were estimated from these data. Brachioradialis and pronator teres had the longest (17.7cm) and shortest (5.5cm) fascicles, respectively. Triceps brachii (combined heads) and brachioradialis had the greatest (14.9cm(2)) and smallest (1.2cm(2)) PCSAs, respectively. Despite a comparable fascicle length, long head of biceps brachii operates over a broader range of the force-length curve (length change=56% of optimal length, 12.8cm) than the long head of triceps brachii (length change=28% of optimal length, 12. 7cm) because of its larger moment arm (4.7cm vs. 2.3cm). Although brachioradialis has a small PCSA, it has a relatively large moment-generating capacity (6.8cm(3)) due to its large moment arm (average peak=7.7cm). These results emphasize the need to consider the interplay of architecture and moment arm when evaluating the functional capabilities of a muscle.     

A predictive model of moment-angle characteristics in human skeletal muscle: application and validation in muscles across the ankle joint

In the present work, a generic model for the prediction of moment-angle characteristics in individual human skeletal muscles is presented. The model's prediction is based on the equation M = V x Lo(-1)sigma c cos phi x d, where M, V, and Lo are the moment-generating potential of the muscle, the muscle volume and the optimal muscle fibre length, respectively, and sigma, phi and d are the stress-generating potential of the muscle fibres, their pennation angle and the tendon moment arm length, respectively, at any given joint angle. The input parameters V, Lo, sigma, phi and d can be measured or derived mechanistically. This eliminates the common problem of the necessity to estimate one or more of the input parameters in the model by fitting its outcome to experimental results often inappropriate for the function modelled. The model's output was validated by comparisons with the moment-angle characteristics of the gastrocnemius (GS) and tibialis anterior (TA) muscles in six men, determined experimentally using voluntary contractions at several combinations of ankle and knee joint angles for the GS muscle and electrical stimulation for the TA muscle. Although the model predicted realistically the pattern of moment-angle relationship in both muscles, it consistently overestimated the GS muscle M and consistently underestimated the TA muscle M, with the difference gradually increasing from dorsiflexion to plantarflexion in both cases. The average difference between predicted and measured M was 14% for the GS muscle and 10% for the TA muscle. Approximating the muscle fibres as a single sarcomere in both muscles and failing to achieve complete TA muscle activation by electrical stimulation may largely explain the differences between theory and experiment.     

Morphometry of Macaca mulatta forelimb. I. Shoulder and elbow muscles and segment inertial parameters

The present study examined the morphometric properties of the forelimb, including the inertial properties of the body segments and the morphometric parameters of 21 muscles spanning the shoulder and/or elbow joints of six Macaca mulatta and three M. fascicularis. Five muscle parameters are presented: optimal fascicle length (L(0)(M)), tendon slack length (L(S)(T)), physiological cross-sectional area (PCSA), pennation angle (alpha(0)), and muscle mass (m). Linear regressions indicate that muscle mass, and to a lesser extent PCSA, correlated with total body weight. Segment mass, center-of-mass, and the moment of inertia of the upper arm, forearm, and hand are also presented. Our data indicate that for some segments, radius of gyration (rho) predicts segment moment of inertia better than linear regressions based on total body weight. Key differences between the monkey and human forelimb are highlighted.     

Environment and individual: a dialectic relationship.

The role of development in current neo-Darwinian evolutionary theory is still underestimated. Only a few experimental and theoretical efforts have been made to bridge the gap, among which the theories of genetic assimilation, stabilising selection and autopoiesis. The relationship between the organism and its environment is a focal point for understanding development. The organism itself determines which environmental features are relevant to it, what represents a stimulus that would trigger its behaviour, and continuously affects the environment through its activities, in a dialectic relationship. Such a relationship is unique and diachronic, changing with time and defining the individual. Development in the broad sense and behavioural plasticity refer to the individual unlike evolution, which refers to populations.     

In vivo determination of cell cycle kinetics of non-Hodgkin's lymphomas using iododeoxyuridine and bromodeoxyuridine.

Using sequential infusions of two S-phase-specific drugs, iododeoxyuridine and bromodeoxyuridine, we have developed an in vivo method for determining the labeling index (LI), the S-phase duration (Ts), and total cell cycle times (Tc) of non-Hodgkin's lymphomas. In nine non-Hodgkin's lymphomas studied, the LI ranged from 1.5% in a follicular small cleaved-cell lymphoma to 29.6% in a diffuse large-cell lymphoma. The Ts ranged from 16 hr in a large-cell lymphoma (immunoblastic type) to 117 hr in a follicular small cleaved-cell lymphoma. The Tc varied from 69 hr in a large-cell lymphoma (immunoblastic type) to over 1000 hr in all low-grade lymphomas studied. Immunohistochemical methods using anti-BrdU antibodies were used to detect cell incorporation of the two S-phase-specific drugs. In this manner, cell cycle times could be calculated while the architecture of the tumor specimen was preserved. Difficulties in using this methodology, specifically in the calculation of the growth fraction and total cell cycle times, are pointed out. This in vivo method does, however, allow for Ts calculations independent of growth fraction considerations. Correlations of cell cycle data with various biological and clinical factors await further patient follow-up.     

In vivo prediction of the nutrient status of individual microalgal cells using Raman microspectroscopy

An in vivo method for predicting the nutrient status of individual algal cells using Raman microspectroscopy is described. Raman spectra of cells using 780 nm laser excitation show enhanced bands mainly attributable to chlorophyll a and beta-carotene. The relative intensities of chlorophyll a and beta-carotene bands changed under nitrogen limitation, with chlorophyll a bands becoming less intense and beta-carotene bands more prominent. Although spectra from N-replete and N-starved cell populations varied, each distribution was distinct enough such that multivariate classification methods, such as partial least squares discriminant analysis, could accurately predict the nutrient status of the cells from the Raman spectral data.     

Helical phasing between DNA bends and the determination of bend direction.

The presence and location of bends in DNA can be inferred from the anomalous mobility of DNA fragments or protein-DNA complexes during electrophoresis in polyacrylamide gels. Direction of bending is not so easily determined. We show here that a protein-induced bend, when linked to a protein-independent DNA bend by a segment of variable length, exhibits an electrophoretic mobility that varies in a sinusoidal manner with the length of the linker. Mobility minima occur once for each addition to the linker of one helical turn of DNA. Since minima should occur when two bends reinforce one another, the direction of one bend relative to the other can be determined from the distances between the two centers of bending at which minima occur. Our results strongly support the idea that the A5-6 tracts in kinetoplast DNA bend towards the minor groove while the bend at the recombination site of the gamma delta resolvase (binding site I of the gamma delta res site) bends towards the major groove.     

In vivo determination of normal and anterior cruciate ligament-deficient knee kinematics

The objective of the current study was to use fluoroscopy to accurately determine the three-dimensional (3D), in vivo, weight-bearing kinematics of 10 normal and five anterior cruciate ligament deficient (ACLD) knees. Patient-specific bone models were derived from computed tomography (CT) data. 3D computer bone models of each subject's femur, tibia, and fibula were recreated from the CT 3D bone density data. Using a model-based 3D-to-2D imaging technique registered CT images were precisely fit onto fluoroscopic images, the full six degrees of freedom motion of the bones was measured from the images. The computer-generated 3D models of each subject's femur and tibia were precisely registered to the 2D digital fluoroscopic images using an optimization algorithm that automatically adjusts the pose of the model at various flexion/extension angles. Each subject performed a weight-bearing deep knee bend while under dynamic fluoroscopic surveillance. All 10 normal knees experienced posterior femoral translation of the lateral condyle and minimal change in position of the medial condyle with progressive knee flexion. The average amount of posterior femoral translation of the lateral condyle was 21.07 mm, whereas the average medial condyle translation was 1.94 mm, in the posterior direction. In contrast, all five ACLD knees experienced considerable change in the position of the medial condyle. The average amount of posterior femoral translation of the lateral condyle was 17.00 mm, while the medial condyle translation was 4.65 mm, in the posterior direction. In addition, the helical axis of motion was determined between maximum flexion and extension. A considerable difference was found between the center of rotation locations of the normal and ACLD subjects, with ACLD subjects exhibiting substantially higher variance in kinematic patterns.     

In vivo behavior of muscle fascicles and tendinous tissues of human gastrocnemius and soleus muscles during twitch contraction.

The present study investigated the differences between the human medial gastrocnemius (MG) and soleus (SOL) muscles in length changes of muscle fascicles and tendinous tissues during twitch contraction induced by an electrical nerve stimulus. Also, the time-course characteristics of twitch torque were related with changes in the length of muscle fascicles and tendinous tissues. No significant difference was observed between MG and SOL in contraction and half relaxation times of the changes in lengths and velocities of both muscle fascicles and tendinous tissues. The time-course of changes in twitch torque was nearly identical to that of the length of muscle fascicles and tendinous tissues. It was suggested that the behavior of MG and SOL during twitch contraction is practically similar in spite of their known physiological and architectural differences, and that the time-course of twitch torque is greatly influenced by the changes in the length of muscle fascicles and tendinous tissues.     

In vivo microdialysis for determination of nasal liquid ion composition

Airway surface liquid (ASL) contains substances important in mucociliary clearance and airway defense. Little is known about substance concentrations in ASL because of its small volume and sampling difficulties. We used in vivo microdialysis (IVMD) to sample liquid lining the nasal cavity without net volume removal and incorporated into IVMD a potential difference (PD) electrode to assess airway integrity. The cystic fibrosis (CF) mouse nasal epithelia exhibit ion transport defects identical to those in CF human airways and, thus, are a good model for CF disease. We determined that nasal liquid [Na+] (107 +/- 4 mM normal; 111 +/- 9 mM CF) and [Cl-] (120 +/- 6 mM normal; 122 +/- 4 mM CF) did not differ between genotypes. The nasal liquid [K+] (8.7 +/- 0.4 mM) was significantly less in normal than in CF mice (16.6 +/- 4 mM). IVMD accurately samples nasal liquid for ionic composition. The ionic composition of nasal liquid in the normal and CF mice is similar.