bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality of performance of everyday activities in children with spina bifida: a population‐based study
Authors: Peny‐Dahlstrand M , Åhlander A‐C , Krumlinde‐Sundholm L , Gosman‐Hedström G
Published: July 2009

Aim:  The aim of this study was to evaluate the quality of the performance of everyday activities in children with spina bifida.

Methods:  Fifty children with spina bifida (of 65 children in a geographic cohort), aged 6 to14 years, were evaluated with Assessment of Motor and Process Skills.

Results:  Compared with age‐normative values, 60% of the children with spina bifida were found to have motor ability measures below 2 SD and 48% process ability measures below 2 SD. Most of the children with spina bifida had difficulties performing well‐known everyday activities in an effortless, efficient and independent way, relating to both motor and process skills. The motor skills hardest to accomplish involved motor planning and the process skills hardest to accomplish were adaptation of performance and initiations of new steps, thus actually getting the task done.

Conclusion:  To reach autonomy in life, children with spina bifida may need particular guidance to learn not only how to do things but also how to get things done.
Correlation and Quantitative Trait Loci Analyses of Total Chlorophyll Content and Photosynthetic Rate of Rice (Oryza sativa) under Water Stress and Well‐watered Conditions
Authors: Hu Song‐Ping , Zhou Ying , Zhang Lin , Zhu Xiu‐Dong , Li Lin , Luo Li‐Jun , Liu Guo‐Lan , Zhou Qing‐Ming
Published: July 2009

In order to explore the relevant molecular genetic mechanisms of photosynthetic rate (PR) and chlorophyll content (CC) in rice (Oryza sativa L.), we conducted a series of related experiments using a population of recombinant inbred lines (Zhenshan97B × IRAT109). We found a significant correlation between CC and PR (R= 0.19**) in well‐watered conditions, but no significant correlation during water stress (r= 0.08). We detected 13 main quantitative trait loci (QTLs) located on chromosomes 1, 2, 3, 4, 5, 6, and 10, which were associated with CC, including six QTLs located on chromosomes 1, 2, 3, 4, and 5 during water stress, and seven QTLs located on chromosomes 2, 3, 4, 6, and 10 in well‐watered conditions. These QTLs explained 47.39% of phenotypic variation during water stress and 56.19% in well‐watered conditions. We detected four main QTLs associated with PR; three of them (qPR2, qPR10, qPR11) were located on chromosomes 2, 10, and 11 during water stress, and one (qPR10) was located on chromosome 10 in well‐watered conditions. These QTLs explained 34.37% and 18.41% of the phenotypic variation in water stress and well‐watered conditions, respectively. In total, CC was largely controlled by main QTLs, and PR was mainly controlled by epistatic QTL pairs.
Premature Tapetum Degeneration: a Major Cause of Abortive Pollen Development in Photoperiod Sensitive Genic Male Sterility in Rice
Authors: Shi Yinlian , Zhao Sha , Yao Jialing
Published: July 2009

Photoperiod‐sensitive genic male‐sterile (PSGMS) rice (Oryza sativa L.), a natural mutant found in the rice cultivar Nongken 58, is very useful for the development of hybrid rice cultivars. Despite its widespread use in breeding programs, the initial stage of the abortive development of PSGMS rice and the possible cytological mechanisms of pollen abortion have not been determined. In the present study, a systematic cytological comparison of the anther development of PSGMS rice with its normal fertile counterpart is conducted. The results show that pollen abortion in PSGMS rice first occurs before the pollen mother cell (PMC) stage, and continues during the entire process of pollen development until pollen degradation. The abortive process was closely associated with the abnormal behavior of the tapetum. Although tapetum degeneration in PSGMS rice initiates already at the PMC stage, it proceeds slowly and does not complete until the breakdown of the pollen. Such cytological observations were supported by the results of the TUNEL (TdT‐mediated dUTP Nick End Labeling) assay, which detects DNA fragmentation resulting from programmed cell death (PCD), indicating that the premature tapetum degeneration is in the process of PCD.
Rapid and easy semi‐quantitative evaluation method for diacylglycerol and inositol‐1,4,5‐trisphosphate generation in orexin receptor signalling
Authors: Ekholm M. E. , Johansson L. , Kukkonen J. P.
Published: July 2009

Aim:  Fluorescent protein‐based indicators have enabled measurement of intracellular signals previously nearly inaccessible for studies. However, indicators showing intracellular translocation upon response suffer from serious limitations, especially the very time‐consuming data collection. We therefore set out in this study to evaluate whether fixing and counting cells showing translocation could mend this issue.

Methods:  Altogether three different genetically encoded indicators for diacylglycerol and inositol‐1,4,5‐trisphosphate were transiently expressed in Chinese hamster ovary cells stably expressing human OX1 orexin receptors. Upon stimulation with orexin‐A, the cells were fixed with six different protocols.

Results:  Different protocols showed clear differences in their ability to preserve the indicator’s localization (i.e. translocation after stimulus) and its fluorescence, and the best results for each indicator were obtained with a different protocol. The concentration–response data obtained with cell counting are mostly comparable to the real‐time translocation and biochemical data.

Conclusion:  The counting method, as used here, works at single time point and looses the single‐cell‐quantitative aspect. However, it also has some useful properties. First, it easily allows processing of a 100‐ to 1000‐fold higher cell numbers than real‐time imaging producing statistically consistent population‐quantitative data much faster. Secondly, it does not require expensive real‐time imaging equipment. Fluorescence in fixed cells can also be quantitated, though this analysis would be more time‐consuming than cell counting. Thirdly, in addition to the quantitative data collection, the method could be applied for identifying responsive cells. This might be very useful in identification of e.g. orexin‐responding neurones in a large population of non‐responsive cells in primary cultures.
Cardioprotection of bradykinin at reperfusion involves transactivation of the epidermal growth factor receptor via matrix metalloproteinase‐8
Authors: Methner C. , Donat U. , Felix S. B. , Krieg T.
Published: July 2009

Aim:  The endogenous autacoid bradykinin (BK) reportedly reduces myocardial infarct size when given exogenously at reperfusion. Muscarinic and opioid G‐protein‐coupled receptors are equally protective and have been shown to couple through a matrix metalloproteinase (MMP)‐dependent transactivation of the epidermal growth factor receptor (EGFR). Here we test whether BK protects the rat heart through the EGFR by an MMP‐dependent pathway.

Methods:  Infarct size was measured in isolated perfused rat hearts undergoing 30 min regional ischaemia followed by 120 min reperfusion. In additional studies HL‐1 cardiomyocytes were loaded with tetramethylrhodamine ethyl to measure their mitochondrial membrane potential (Ψm). Adding the calcium ionophore calcimycin, causes Ψm‐collapse presumably due to calcium‐induced mitochondrial permeability transition.

Results:  As expected, BK (100 nmol L−1) started 5 min prior to reperfusion reduced infarct size from 38.9 ± 2.0% of the ischaemic zone in control hearts to 22.2 ± 3.3% (P < 0.001). Co‐infusing the EGFR inhibitor AG1478, the broad‐spectrum MMP‐inhibitor GM6001, or a highly selective MMP‐8 inhibitor abolished BK’s protection, thus suggesting an MMP‐8‐dependent EGFR transactivation in the signalling. Eighty minutes of exposure to calcimycin reduced the mean cell fluorescence to 37.4 ± 1.8% of untreated cells while BK could partly preserve the fluorescence and, hence, protect the cells (50.5 ± 2.3%, P < 0.001). The BK‐induced mitochondrial protection could again be blocked by AG1478, GM6001 and MMP‐8 inhibitor. Finally, Western blotting revealed that BK’s protection was correlated with increased phosphorylation of EGFR and its downstream target Akt.

Conclusion:  These results indicate that BK at reperfusion triggers its protective signalling pathway through MMP‐8‐dependent transactivation of the EGFR.
Functions of glutamate transporters in cerebellar Purkinje cell synapses
Authors: Takayasu Y. , Iino M. , Takatsuru Y. , Tanaka K. , Ozawa S.
Published: July 2009

Glutamate transporters play a critical role in the maintenance of low extracellular concentrations of glutamate, which prevents the overactivation of post‐synaptic glutamate receptors. Four distinct glutamate transporters, GLAST/EAAT1, GLT‐1/EAAT2, EAAC1/EAAT3 and EAAT4, are distributed in the molecular layer of the cerebellum, especially near glutamatergic synapses in Purkinje cells (PCs). This review summarizes the current knowledge about the differential roles of these transporters at excitatory synapses of PCs. Data come predominantly from electrophysiological experiments in mutant mice that are deficient in each of these transporter genes. GLAST expressed in Bergmann glia contributes to the clearing of the majority of glutamate that floods out of the synaptic cleft immediately after transmitter release from the climbing fibre (CF) and parallel fibre (PF) terminals. It is indispensable to maintain a one‐to‐one relationship in synaptic transmission at the CF synapses by preventing transcellular glutamate spillover. GLT‐1 plays a similar but minor role in the uptake of glutamate as GLAST. Although the loss of neither GLAST nor GLT‐1 affects cerebellar morphology, the deletion of both GLAST and GLT‐1 genes causes the death of the mutant animal and hinders the folium formation of the cerebellum. EAAT4 removes the low concentrations of glutamate that escape from uptake by glial transporters, preventing the transmitter from spilling over into neighbouring synapses. It also regulates the activation of metabotropic glutamate receptor 1 (mGluR1) in perisynaptic regions at PF synapses, which in turn affects mGluR1‐mediated events including slow EPSCs and long‐term depression. No change in synaptic function is detected in mice that are deficient in EAAC1.
EPAC signalling pathways are involved in low PO2 chemoreception in carotid body chemoreceptor cells
Authors: Rocher Asuncion , Caceres Ana I. , Almaraz Laura , Gonzalez Constancio
Published: July 2009

Chemoreceptor cells of the carotid bodies (CB) are activated by hypoxia and acidosis, responding with an increase in their rate of neurotransmitter release, which in turn increases the electrical activity in the carotid sinus nerve and evokes a homeostatic hyperventilation. Studies in isolated chemoreceptor cells have shown that moderate hypoxias (≈ 46 mmHg) produces smaller depolarisations and comparable Ca2+ transients but a much higher catecholamine (CA) release response in intact CBs than intense acidic/hypercapnic stimuli (20% CO2, pH 6.6). Similarly, intense hypoxia (≈ 20 mmHg) produces smaller depolarizations and Ca2+ transients in isolated chemoreceptor cells but a higher CA release response in intact CBs than a pure depolarizing stimulus (30–35 mm external K+). Studying the mechanisms responsible for these differences we have found the following. (1) Acidic hypercapnia inhibited ICa (∼60%; whole cell) and CA release (∼45%; intact CB) elicited by ionomycin and high K+. (2) Adenylate cyclase inhibition (SQ‐22536; 80 μm) inhibited the hypoxic release response (>50%) and did not affect acidic/hypercapnic release, evidencing that the high gain of hypoxia to elicit neurotransmitter release is cAMP dependent. (3) The last effect was independent of PKA activation, as three kinase inhibitors (H‐89, KT 5720 and Rp‐cAMP; ≥ 10 × IC50) did not alter the hypoxic release response. (4) The Epac (exchange protein activated by cAMP) activator (8‐pCPT‐2′‐O‐Me‐cAMP, 100 μm) reversed the effects of the cyclase inhibitor. (5) The Epac inhibitor brefeldin A (100 μm) inhibited (54%) hypoxic induced release. Our findings show for the first time that an Epac‐mediated pathway mediates O2 sensing/transduction in chemoreceptor cells.
Excitability of paraventricular nucleus neurones that project to the rostral ventrolateral medulla is regulated by small‐conductance Ca2+‐activated K+ channels
Authors: Chen Qing‐Hui , Toney Glenn M.
Published: July 2009

Whole cell patch‐clamp recordings were performed in brain slices to investigate mechanisms regulating the excitability of paraventricular nucleus (PVN) neurones that project directly to the rostral ventrolateral medulla (RVLM) (PVN–RVLM neurones) of rats. In voltage‐clamp recordings, step depolarization elicited a calcium‐dependent outward tail current that reversed near EK. The current was nearly abolished by apamin and by UCL1684, suggesting mediation by small‐conductance Ca2+‐activated K+ (SK) channels. In current‐clamp recordings, depolarizing step current injections evoked action potentials that underwent spike‐frequency adaptation (SFA). SK channel blockade with apamin or UCL1684 increased the spike frequency without changing the rate of SFA. Upon termination of step current injection, a prominent medium after‐hyperpolarization potential (mAHP) was observed. SK channel blockade abolished the mAHP and revealed an after‐depolarization potential (ADP). In response to ramp current injections, the rate of sub‐threshold depolarization was increased during SK channel blockade, indicating that depolarizing input resistance was increased. Miniature EPSC frequency, amplitude, and decay kinetics were unaltered by bath application of apamin, suggesting that SK channel blockade likely increased excitability by a postsynaptic action. We conclude that although SK channels play little role in generating SFA in PVN–RVLM neurones, their activation nevertheless does dampen excitability. The mechanism appears to involve activation of a mAHP that opposes a prominent ADP that would otherwise facilitate firing.
The kinaesthetic senses
Authors: Proske Uwe , Gandevia Simon C.
Published: July 2009

This review of kinaesthesia, the senses of limb position and limb movement, has been prompted by recent new observations on the role of motor commands in position sense. They make it necessary to reassess the present‐day views of the underlying neural mechanisms. Peripheral receptors which contribute to kinaesthesia are muscle spindles and skin stretch receptors. Joint receptors do not appear to play a major role at most joints. The evidence supports the existence of two separate senses, the sense of limb position and the sense of limb movement. Receptors such as muscle spindle primary endings are able to contribute to both senses. While limb position and movement can be signalled by both skin and muscle receptors, new evidence has shown that if limb muscles are contracting, an additional cue is provided by centrally generated motor command signals. Observations using neuroimaging techniques indicate the involvement of both the cerebellum and parietal cortex in a multi‐sensory comparison, involving operation of a forward model between the feedback during a movement and its expected profile, based on past experience. Involvement of motor command signals in kinaesthesia has implications for interpretations of certain clinical conditions.
The Effects of Contact Lens Deformation on Tear Film Pressure and Thickness During Motion of the Lens Towards the Eye
Authors: Conway H. D. , Richman M. W.
Published: July 2009

An analysis is made of the motion of a contact lens normal to the eye through a tear film. The eye is modeled as a rigid sphere and the lens as a deformable spherical cap. Graphs of pressure distribution and tear film thickness variations are obtained. It is found that the pressures are very markedly reduced and film thicknesses increased by decreasing the modulus of the lens materials.
Response of an Advanced Head-Neck Model to Transient Loading
Authors: Winters J. M. , Goldsmith W.
Published: July 2009

A second-generation mechanical head-neck model was constructed, instrumented and subjected to pendulum impact tests against both the head and torso and directed from the front, rear and side. The response history of the system was measured by thirty channels of instrumentation including disk pressure transducers and muscle displacement gages in the neck, and a central accelerometer, intracranial pressure transducers and skull strain gages for the cranium and its contents. The kinematics of the unit was observed by an intermediate speed framing camera and the input was determined by a calibrated force transducer located at the contact point. It was found that peak head linear acceleration and velocity occur either during or immediately after the impact, with corresponding peak rotational values manifested somewhat later, but well before maximum head displacement. Head accelerations were similar, albeit slightly lower than in corresponding cases for an earlier model and displacement values were also similar until large extensions were reached. For rear head or frontal base impact, the head experienced a significant period of translation without rotation immediately after loading, and the system appears to respond more violently to side than to corresponding front or rear impact. The muscle beahvior, which support the findings from the head kinematics, is analyzed in detail and shows its strong influence on limiting head excursions, with strain values up to 40 percent. Disk pressure histories were similar to those found in tests on an earlier model with the highest values between T2 and C4, while the intercranial pressure exhibited more realistic values, about an order of larger magnitude.
Impulse and Moment of Impulse in the Leg Joints by Impact From Kicking
Authors: Lindbeck L.
Published: July 2009

In a previous paper we have given a theoretical analysis of the impulsive motion of the leg, modeled as a double pendulum. This analysis made it possible to estimate the impulsive reactions in the knee joint as a function of the measured initial and final velocities of the leg, when an impact was given to the lower leg, e.g., by means of a kick. This estimation was made under the assumption that no impulsive moments occur in the hip and the knee joints, i.e., that no muscles were stretched during the time of impact. In the present paper it is shown how such impulsive moments, should they occur, can be determined by means of an additional measurement, i.e., of the velocity of the ball after the impact. The results from a series of experiments are reported, showing that such impulsive moments in the joints occur in an appreciable number of the kicks, especially in the hip joint, indicating that muscles, acting on this joint, are prestressed during the impact.
Pulsatile Flow in Tapered Tubes: A Model of Blood Flow With Large Disturbances
Authors: Kimmel E. , Dinnar U.
Published: July 2009

Blood flow-through segments of large arteries of man, between adjacent bifurcations, can be modeled as pulsatile flow in tapered converging tubes, of small angle of convergence, up to 2 deg. Assuming linearity, rigid tube and homogeneous Newtonian fluid, the physiological flow field is governed by the Navier-Stokes equation with dominant nonlinear and unsteady terms. Analytical solution of this problem is presented based on an integral method technique. The solution shows that even for small tapering the flow pattern is markedly different from the flow obtained for a uniform tube. The periodic shear stresses at the wall and pressure gradients increase both in their mean value and amplitude with increased distance downstream. These results are highly significant in the process of atherogenesis.
Error Analysis of a System for Measuring Three-Dimensional Joint Motion
Authors: Suntay W. J. , Grood E. S. , Hefzy M. S. , Butler D. L. , Noyes F. R.
Published: July 2009

In the past ten years there has been increased use of six-degree-of-freedom instrumented spatial linkages for the measurement of biological joint motions. In spite of the increased popularity, little information has been reported on the accuracy of these devices. In this paper, we present a two-part investigation of the accuracy of the instrumented spatial linkage when used to measure knee joint kinematics. In the first part, we present the results of a theoretical analysis and an experimental determination of the errors associated with spatial linkage systems. In the second part, we describe the errors associated with a bi-planar X-ray system used to obtain the coordinate transformation between the linkage ends and coordinate systems located in the bones comprising the joint. We found that the theoretical error analysis consistently overestimated the actual measurement error, thus providing an unreliable estimate of errors. The experimental study of both the linkage system and the bi-planar X-ray system demonstrated that the accuracy of displacement measurement is insensitive to large systematic errors in position measurement.
Tension-Torsion Characteristics of the Canine Anterior Cruciate Ligament—Part I: Theoretical Framework
Authors: Stouffer D. C. , Butler D. L. , Kim H.
Published: July 2009

It has been observed that the fascicles in the canine anterior cruciate ligament do not follow a straight line path between the tibial and femoral attachment sites, but rather their path is approximately helical about the ligament axis. Thus, a mathematical model for the mechanical response of a ligament was developed from the observed geometrical configuration of the fascicle. The principal result of the model indicated that a torque must always accompany the force during elongation of a ligament. The relationships between the ligament and fascicle variables are also examined in detail.
Cycle-Dependent and Time-Dependent Bone Fracture With Repeated Loading
Authors: Carter D. R. , Caler W. E.
Published: July 2009

Fatigue tests of human cortical bone (up to 1.74 × 106 cycles) were conducted under tension-compression (T-C) and zero-tension (O-T) modes with a 2Hz, stress controlled, sinusoidal loading history. Tensile creep-fracture tests at constant stress levels were also performed. The relationship between the initial cyclic strain range and cycles to failure with the T-C specimens were consistent with that derived previously in low-cycle fatigue under strain control. Using a time-dependent failure model, the creep-fracture data was found to be consistent with previous studies of the influence of strain rate on the monotonic tensile strength of bone. The model also predicted quite well the time to failure for the O-T fatigue specimens, suggesting that creep damage plays an important role in O-T fatigue specimens.
Measurement of Turbulence Intensity in the Center of the Canine Ascending Aorta With a Hot-Film Anemometer
Authors: Yamaguchi T. , Kikkawa S. , Yoshikawa T. , Tanishita K. , Sugawara M.
Published: July 2009

The blood flow velocity near the central axis of the canine ascending aorta was measured with a hot-film anemometer. The cardiac output and the heart rate were controlled at will by means of an extracorporeal circulation and by atrial pacing. The turbulent component of the blood flow velocity was calculated using an ensemble average technique. Ensemble average turbulent intensity was also calculated to show the time course of turbulence in the aorta. The ratio of the mean turbulence intensity to the time mean sectional average velocity in the aorta was constant in most animals regardless of the changes in fluid mechanical parameters. The correlation between the frequency parameter and the relative mean turbulence intensity was weakly positive. The power spectrum of the turbulence was also calculated.
On Nonlinear Viscoelastic Properties of Arterial Tissue
Authors: Wu S. G. , Lee G. C.
Published: July 2009

Nonlinear viscoelasticity is important in a variety of studies in biomechanics. One of the subject areas is the necessity to characterize the dynamic properties of blood vessels. This study concerns a theoretical formulation to examine the higher order nonlinear viscoelastic relaxation functions for arterial tissue based on the assumption of transversely isotropic material properties. Simple numerical results for the first-order theory are compared with those available in the literature.
Effect of Mild Atherosclerosis on Flow Resistance in a Coronary Artery Casting of Man
Authors: Back L. H. , Cho Y. I. , Crawford D. W. , Cuffel R. F.
Published: July 2009

An in-vitro flow study was conducted in a mildly atherosclerotic main coronary artery casting of man using sugar-water solutions simulating blood viscosity. Steady flow results indicated substantial increases in pressure drop, and thus flow resistance at the same Reynolds number, above those for Poiseuille flow by 30 to 100 percent in the physiological Reynolds number range from about 100 to 400. Time-averaged pulsatile flow data showed additional 5 percent increases in flow resistance above the steady flow results. Both pulsatile and steady flow data from the casting were found to be nearly equal to those from a straight, axisymmetric model of the casting up to a Reynolds number of about 200, above which the flow resistance of the casting became gradually larger than the corresponding values from the axisymmetric model.
The Distribution of Pressure Behind a Soft Contact Lens
Authors: Jenkins J. T. , Shimbo M.
Published: July 2009

We determine the pressure distribution behind a soft contact lens that is necessary to keep the lens in conformity with an axisymmetric substrate. The substrate consists of two regions: a central portion, the cornea, supposed to be an ellipsoid; and a peripheral region, the sclera, taken to be a sphere. The pressure is obtained as part of a numerical solution of the axisymmetric equilibrium equations for an initially curved, linearly elastic membrane. The relaxed shape of the lens is assumed to be an axisymmetric ellipsoid with a central curvature and a shape factor different from those of the cornea. The variation in the thickness of the lens from its center to edge is approximated by a polynomial. Pressure distributions are obtained for several typical soft contact lens fittings.
Comparative Study of the Amount of Backflow Produced by Four Types of Aortic Valve Prostheses
Authors: Sabbah H. N. , Stein P. D.
Published: July 2009

To determine the extent of backflow encountered with currently used prosthetic valves, four types of aortic valves with comparable orifice diameters were tested in a pulse duplicating system. These were a Hancock porcine valve, a Lillehei-Kaster pivoting disk valve, a St. Jude bileaflet valve and a Bjo¨rk-Shiley tilting disk valve. Mean aortic pressure was sequentially increased from 83 to 147 mmHg, keeping the pump rate essentially constant (69–73 strokes/min). The porcine valve produced the least amount of total backflow (backflow due to closure plus leakage backflow) (1.6 to 2.4 mL/stroke). Among the mechanical valves the Bjo¨rk-Shiley valve showed the least amount of total backflow (5.0 to 6.0 mL/stroke). At a mean aortic pressure of 100 mmHg and a low cardiac output of 2 L/min, the total backflow with the porcine valve was only 6 percent of forward flow; whereas it was 19 percent with the Lillehei-Kaster valve, 22 percent with the St. Jude valve and 18 percent with the Bjo¨rk-Shiley valve. Leakage backflow at a given level of mean aortic pressure was, as expected, directly related to the annular clearance area. It is concluded that the Hancock valve showed the least amount of backward flow, which would be particularly beneficial in low output states. In the presence of normal hemodynamics, the amount of backflow with the three mechanical valves appeared to be well below the level of backflow considered to be clinically significant.
Modeling Technique of Prosthetic Heart Valves
Authors: Kitamura T. , Kijima T. , Akashi H.
Published: July 2009

This paper demonstrates a modeling technique of prosthetic heart valves. In the modeling, a pumping cycle is divided into four phases, in which the state of the valve and flow is different. The pressure-flow relation across the valve is formulated separately in each phase. This technique is developed to build a mathematical model used in the real time estimation of the hemodynamic state under artificial heart pumping. The model built by this technique is simple enough for saving the computational time in the real time estimation. The model is described by the first-order ordinary differential equation with 12 parameters. These parameters can be uniquely determined beforehand from in-vitro experimental data. It is shown that the model can adapt, with sufficient accuracy, to a change in the practical pumping condition and the viscosity of the fluid in their practical range, and is also demonstrated that the estimated backflow volume by model agrees closely with the actual one.
Thermal Modeling of the Normal Woman’s Breast
Authors: Osman M. M. , Afify E. M.
Published: July 2009

A comprehensive thermal model of the normal woman’s breast is presented. The model is developed taking into consideration metabolic heat production, tissue perfusion with capillary blood, arterial and venous blood thermal interaction and change of arterial blood temperature with position. A series of computer programs are written using a 3-dimensional finite-element technique to evaluate the surface temperature distribution of the breast. Comparison between the results obtained for the model and those from thermograms of a woman’s breast are in good agreement.
Mechanical Properties of Human Tendon and Their Age Dependence
Authors: Hubbard R. P. , Soutas-Little R. W.
Published: July 2009

There are no previously published data on changes in the mechanical behaviors of human tendon from maturation in the second decade to senectitude in the seventh decade or thereafter. In this study, 44 tendons from individuals ranging in age from 16 to 88 yr were subjected to an extensive series of mechanical tests which included preconditioning, extensions at strain rates of 100 percent/s, 1 percent/s, and 0.01 percent/s, and stress relaxation with cyclic and constant extensions. Pairs of extensions at 1 percent/s were run throughout the protocol to evaluate the repeatability of tissue response. It was found that these responses changed little for any single sample within a pair of such tests; however, throughout the protocol, the peak stresses and moduli decreased. Extensions at different rates revealed a definite rate dependency of tendon responses with sample modulus being directly related to extension rate and slightly less hysteresis at 1 percent/s than at 100 percent/s or 0.01 percent/s. The load relaxation in samples subjected to either cyclic or constant extensions was generally best described by a linear function of the logarithm of time. The rate of relaxation with constant extension varied little with extension magnitude. The rate of relaxation in the cyclic tests was greater at 10 Hz than at 0.1 Hz. The results indicate that subject age has no effect on tendon modulus and a very small effect on hysteresis and relaxation. Extensive information on subject history was not available in this study for correlation with mechanical responses so that an age effect may have been masked by other variables, possibly health, diet, disease, or exercise.
A Continuum Theory and an Experiment for the Ion-Induced Swelling Behavior of Articular Cartilage
Authors: Myers E. R. , Lai W. M. , Mow V. C.
Published: July 2009

Swelling of normal bovine articular cartilage equilibrated in NaCl solutions was dimensionally measured in thin strips of tissue. The ion-induced strains show that free swelling of articular cartilage is anisotropic and inhomogeneous. For the molar concentrations used, contraction increased linearly with concentration, defining a “coefficient of chemical contraction” (αc). Isometrically constrained specimens registered a rise in tensile force followed by stress relaxation. An extension of the biphasic theory incorporating this ion-induced strain is proposed. This theory can describe the equilibrium anisotropic swelling behavior of cartilage and explain the transient force history observed in the isometric experiment.
Relaxation and Creep Quasilinear Viscoelastic Models for Normal Articular Cartilage
Authors: Simon B. R. , Coats R. S. , Woo S. L.-Y.
Published: July 2009

A quasilinear viscoelastic model was used to develop relaxation and creep forms for a constitutive law for soft tissues. Combined relaxation and cyclic test data as well as preconditioned and nonpreconditioned creep data were used to demonstrate the approach for normal bovine articular cartilage. Values for mechanical parameters in the analytical models were determined using a generalized least squares method.
An Analysis of the Unconfined Compression of Articular Cartilage
Authors: Armstrong C. G. , Lai W. M. , Mow V. C.
Published: July 2009

Analytical solutions have been obtained for the internal deformation and fluid-flow fields and the externally observable creep, stress relaxation, and constant strain-rate behaviors which occur during the unconfined compression of a cylindrical specimen of a fluid-filled, porous, elastic solid, such as articular cartilage, between smooth, impermeable plates. Instantaneously, the “biphasic” continuum deforms without change in volume and behaves like an incompressible elastic solid of the same shear modulus. Radial fluid flow then allows the internal fluid pressure to equilibrate with the external environment. The equilibrium response is controlled by the Young’s modulus and Poisson’s ratio of the solid matrix.
A Technical Survey: A Review of Biomechanical Models
Authors: King A. I.
Published: July 2009

This paper surveys biomechanical models of the nonimpact type, involving the musculo-skeletal system. Models of bones, joints and body segments, including human gait and motion of the whole body are discussed. In particular, stress analysis of bone, calculation of ligament and muscle forces across joints and the kinetics and kinematics of locomotion are discussed. The models are described in terms of the method of formulation, the method of solution and the realism of the results obtained. There is a need for more data on material properties of various body tissues and more experimental research to develop techniques for validating many of the models. Further work on the selection of appropriate objective functions for indeterminate problems is also required.
The Simultaneous Measurement of Thermal Conductivity, Thermal Diffusivity, and Perfusion in Small Volumes of Tissue
Authors: Valvano J. W. , Allen J. T. , Bowman H. F.
Published: July 2009

An improved technique is presented for the “in-vivo” determination of thermal conductivity, thermal diffusivity, and perfusion using a self-heated spherical thermistor probe. In the presence of flow, solution of the time-dependent, probe-tissue coupled thermal model allows the measurement of “effective” thermal conductivity and “effective” thermal diffusivity, which represent the thermal properties of the perfused tissue. Perfusion can be quantified from both “effective” thermal properties. In the presence of flow, it has been shown that the transient power response does not follow t−1/2 as has been previously assumed. An isolated rat liver preparation has been developed to validate the measurement technique. Radioactive microspheres are used to determine the true perfusion from the total collected hepatic vein flow. Experimental data demonstrates the ability to quantify perfusion in small volumes of tissue.
Kinematic and Force Data Collection in Biomechanics by Means of Sonic Emitters—II: Force Data Collection and Application to the Human Shoulder Complex
Authors: Engin A. E. , Peindl R. D. , Berme N. , Kaleps I.
Published: July 2009

In multisegmented mathematical models of the human body the most difficult and the least successful modeling of a major articulating joint has been the shoulder complex because of the lack of appropriate biomechanical data as well as the anatomical complexity of the region. In this paper, quantitative results on the variability of the stiffness of the shoulder complex dependent upon orientation of the upper arm are presented by applying the principles and theory developed in Part I. The paper starts with a descripition of a multiple-axis force and moment transducer and its utilization with sonic emitters in determining direction as well as location of the general force and moment vectors applied on a body segment. The numerical results which are presented for three subjects are in the form of plots showing the passive resistance of the shoulder complex as functions of drawer displacements of the upper arm along its long bone axis. Exponential and power curve fitting of the numerical results are also provided to establish intra-subject variations and similarities of the behavioral patterns of the axial stiffness characteristics of the human shoulder complex.
A Crack Model of a Bone Cement Interface
Authors: Clech J. P. , Keer L. M. , Lewis J. L.
Published: July 2009

This paper is concerned with the fracture mechanics of a bone-cement interface that includes a cohesive zone effect on the crack faces. This accounts for the experimentally observed strengthening mechanism due to the mechanical interlock between the crack faces. Edge crack models are developed where the cohesive zone is simulated by a continuous or a discrete distribution of linear or nonlinear springs. It is shown that the solution obtained by assuming a homogeneous material is fairly close to the exact solution for the bimaterial interface edge crack problem. On the basis of that approximation, the analysis is conducted for the problem of two interacting edge cracks, one at the interface, and the other one in the cement. The small crack that was observed to initiate in the cement, close to the bone-cement interface, does not affect much the mode I stress-intensity factor at the tip of the interface crack. However it may grow, leading to a catastrophic breakdown of the cement. The analysis and following discussion point out an interdependency between bone-cement interface strength and cement strength not previously appreciated. The suggested crack models provide a framework for quantifying the fracture mechanisms at the bone-cement interface.
Electro-Mechanical Behavior of Wet Bone—Part II: Wave Propagation
Authors: Guzelsu N. , Saha S.
Published: July 2009

In this study, a general mixture model, which was developed for wet bone, has been used to analyze the flexural wave propagation in long bones. The electrical conduction is taken into account as well as the piezo-electric properties of bone tissue. The general formulation is simplified and certain assumptions made to yield a particular set of equations. The solution of the magnetic induction vector outside the bone due to the mechanical wave propagation is obtained. The results are compared with a similar problem using dry bone. The results indicate that the electro-mechanical properties of bone tissue could be used for monitoring the rate of fracture healing in long bones.
Determination of Muscle Orientations and Moment Arms
Authors: An K. N. , Takahashi K. , Harrigan T. P. , Chao E. Y.
Published: July 2009

In muscle force analysis, orientations and moment arms of the muscles about a joint provide essential coefficients in the equilibrium equations. For the determination of these parameters, several experimental techniques, including geometric measurement, tendon-joint displacement measurement and direct load measurement, are available. Advantages and disadvantages associated with each of the techniques are reviewed and compared based on our extensive experience.
Torsion and Bending Imposed on a New Anterior Cruciate Ligament Prosthesis During Knee Flexion: An Evaluation Method
Authors: Gely P. , Drouin G. , Thiry P. S. , Tremblay G. R.
Published: July 2009

A new composite prosthesis was recently proposed for the anterior cruciate ligament. It is implanted in the femur and the tibia through two anchoring channels. Its intra-articular portion, composed of a fiber mesh sheath wrapped around a silicons rubber cylindrical core, reproduces satisfactorily the ligament response in tension. However, the prosthesis does not only undergo elongation. In addition, it is submitted to torsion in its intra-articular portion and bending at its ends. This paper presents a new method to evaluate these two types of deformations throughout a knee flexion by means of a geometric model of the implanted prosthesis. Input data originate from two sources: (i) a three-dimensional anatomic topology of the knee joint in full extension, providing the localization of the prosthesis anchoring channels, and ii) a kinematic model of the knee describing the motion of these anchoring channels during a physiological flexion of the knee joint. The evaluation method is independent of the way input data are obtained. This method, applied to a right cadaveric knee, shows that the orientation of the anchoring channels has a large effect on the extent of torsion and bending applied to the implanted prosthesis throughout a knee flexion, especially on the femoral side. The study suggests also the best choice for the anchoring channel axes orientation.
Three-Dimensional Finite Element Analysis of a Simplified Compression Plate Fixation System
Authors: Cheal E. J. , Hayes W. C. , White A. A. , Perren S. M.
Published: July 2009

A three-dimensional, linear finite element model was generated for an intact plexiglass tube with an attached six-hole stainless steel compression plate. We examined external forces representing axial, off-center axial, and four-point bending, along with superimposed plate and screw pretension. Strain gage experiments were conducted to test model validity and the finite element results were contrasted to a composite beam theory solution. Excellent correspondence was observed between finite element and strain gage data for the most significant strain components. Composite beam theory tended to overestimate the neutral axis shift which results from plate application. The model also demonstrated fracture site distraction due to plate pretension, and the tendency for outer screw failure for the combination of bending-closed with a preload in the plate and screws.
Entry Flow in a Circular Tube of Aortic Arch Dimensions
Authors: Lim K. O. , Kennedy J. S. , Rodkiewicz C. M.
Published: July 2009

Steady flow within a uniform circular curved tube formed by two 90-deg elbows was studied as a function of ψ, the angle between the planes of curvature of the two elbows. Boundary layer separation was found at two locations. The sites of these separation zones were observed to be essentially independent of ψ while the Reynolds number at which separation was first detected was found to decrease as ψ increased. The relation between separation and the pathogenesis of atherosclerosis is discussed. Secondary flow pattern was found to depend on ψ and in some instances on Reynolds number as well.
Determination of Muscle and Joint Forces: A New Technique to Solve the Indeterminate Problem
Authors: An K. N. , Kwak B. M. , Chao E. Y. , Morrey B. F.
Published: July 2009

Analytic determination of muscle force across human joints encounters an indeterminate problem. A new optimization approach, based on minimizing the upper bound of muscle stress, is introduced to obtain a unique solution. Mathematical and physiological justification of this new approach distinguishes it from previously described methods. A complex joint, the elbow, was studied. The results of muscle forces in resisting the elbow flexion moment were obtained and compared with electromyographic observation, as well as with solution from other optimizing techniques. The resultant humero-ulnar joint forces at various elbow joint positions are calculated. In normal daily activities, resultant joint forces of 0.3–0.5 times body weight are commonly encountered.
Control of Sliding and Rolling at Natural Joints
Authors: Wongchaisuwat C. , Hemami H. , Buchner H. J.
Published: July 2009

The planar motion of the human knee joint is modeled, involving the relative motion of the geometry of the contacting surface between the tibia and the femur. The pure gliding motion and the pure rolling motion are formulated including the holonomic and nonholonomic constraints that must be satisfied. A control strategy with two classes of inputs: muscle forces that stabilize and bring about the motion and the ligament forces that maintain the constraints is presented. Finally, the effectiveness of this control structure is demonstrated via digital computer simulations in the pure gliding motion and the pure rolling motion of the knee.
Measurement of the Water Permeability of Single Human Granulocytes on a Microscopic Stopped-Flow Mixing System
Authors: Diller K. R. , Bradley D. A.
Published: July 2009

The water permeability (Lp) of human granulocytes was measured for individual isolated cells with a novel, microscopic stopped-flow mixing system. Changes in volume were monitored as a cell was introduced suddently into an osmotically active solution. Permeability values were determined as a function of solution osmolality from the volume versus time curves for mixing into both hypotonic and hypertonic solutions within the range of 145 to 833 mOsm. The calculated reference permeability at 25°C was 1.15 μm/atm·min with an osmotic coefficient of 0.46 Osm/kg.
Dynamic Capacitance of Epicardial Coronary Arteries In Vivo
Authors: Reneman R. S. , Arts T.
Published: July 2009

The dynamic capacitance of epicardial coronary arteries (i.d. ≥ 0.4 mm) in vivo was assessed from the volume stiffness and volume of these arteries. The volume stiffness was derived from the pressure wave front velocity as determined in dogs by measuring the delay time between the pressure pulses recorded proximal and distal to a segment of the anterior descending branch of the left coronary artery. The pressure pulse was generated elsewhere in the arterial system during diastole. The volume of the epicardial coronary arteries was calculated from the lengths and diameters as measured in araldite casts, making corrections for in-vitro/in-vivo differences in dimensions. The dynamic capacitance of the right coronary artery, and the anterior descending and circumflex branches of the left coronary artery at an arterial pressure of 13.3 kPa and a frequency between 7 and 30 Hz was found to be 0.0024 ± 0.0013, 0.0062 ± 0.0028 and 0.0079 ± 0.0035 mL/kPa (mean ± SD), respectively. The total capacitance of the epicardial coronary arteries was calculated to be (0.007 mL/kPa)/100 g, which is small as compared to the total capacitance of the coronary vasculature, including the intramyocardial compartment, which is in the order of (0.5 mL/kPa)/100g [1].
Intramyocardial Pressure and Coronary Extravascular Resistance
Authors: Stein P. D. , Sabbah H. N. , Marzilli M.
Published: July 2009

Intramyocardial pressure is an indicator of coronary extravascular resistance. During systole, pressure in the subendocardium exceeds left ventricular intracavitary pressure; whereas pressure in the subepicardium is lower than left ventricular intracavitary pressure. Conversely, during diastole, subepicardial pressure exceeds both subendocardial pressure and left ventricular pressure. These observations suggest that coronary flow during systole is possible only in the subepicardial layers. During diastole, however, a greater driving pressure is available for perfusion of the subendocardial layers relative to the subepicardial layers. On this basis, measurements of intramyocardial pressure contribute to an understanding of the mechanisms of regulation of the phasic and transmural distribution of coronary blood flow.