bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical properties of the skin of Xenopus laevis (Anura, Amphibia)
Authors: Greven Hartmut , Zanger Klaus , Schwinger Gerhard
Published: February 2005

The skin of the aquatic pipid frog, Xenopus laevis, was examined for specific biomechanical features: (1) thickness, (2) maximal strain at break (εf), (3) tensile strength (σm), (4) modulus of elasticity (E, stiffness), and (5) the area under the stress‐strain curve (W) (breaking energy, toughness). Skin freshly removed from dorsal, ventral, and lateral areas of the body was subjected to uniaxial tension. In both sexes, the dorsal skin is thicker than the ventral. The skin of male frogs was consistently thinner in all body regions than that of females. Most biomechanical parameters showed a considerable range of values in both males (εf = 59–63%, σm = 15–16.5 MPa, E = 33.5–38.4 MPa, W = 3.8–4.5 MJ/m3) and females (εf = 102–126%, σm = 11.5 MPa, E = 10.4–12 MPa, W = 5.2–6.7 MJ/m3). The disparate εf values in males (low) and females (high) might reflect sexual dimorphism. Static stress‐strain curves were typicxally J‐shaped; with the exception of “toe,” the curves rose approximately linearly with increasing strain. The skin of X. laevis, although heterogeneous in structure, possesses features similar to those found in tissues with aligned collagen fibers such as tendons or fish skin. However, in anurans, the skin seems to play a more passive mechanical role during locomotion than in fish. © 1995 Wiley‐Liss, Inc.
Superficial mandibular musculature and vocal sac structure in hemiphractine hylid frogs
Authors: Tyler Michael J. , Duellman William E.
Published: February 2005

Three patterns of superficial mandibular musculature are described in hemiphractine hylid frogs. One of these is unique to the morphologically bizarre Hemiphractus. A second pattern is found in Flectonotus and also occurs in some species of Gastrotheca and Stefania. A third pattern involves a differentiated apical element of the m. intermandibularis and is found in Cryptobatrachus, many species of Gastrotheca, and one species of Stefania. Evidence supports the plesiomorphic state of an undifferentiated m. intermandibularis and two derived states of differentiation of that muscle. One of these is the development of supplementary posterolateral elements characteristic of the Phyllomedusinae, whereas the diferentiation of an apical element has occurred in at least six independent lineages—the entire Pelodryadinae, three unrelated genera of Hylinae, and two genera of Hemiphractinae. Gastrotheca and Stefania are the only anuran genera known to include species possessing, and others lacking, differentiation of the m. intermandibularis. Vocal sacs and apertures are absent in Cryptobatrachus, Hemiphractus, Stefania, and six species of Gastrotheca. © 1995 Wiley‐Liss, Inc.
Presence of interdigitating cells in thymus of the sea bass, Dicentrarchus labrax L. (Teleost)
Authors: Avilés‐Trigueros Marcelino , Quesada Juan A.
Published: February 2005

Interdigitating cells in the thymus of the sea bass, Dicentrarchus labrax, occur principally in the internal zone and in the border with the external zone. Ultrastructurally, the most characteristic cytological features of these cells are their low electron density, complicated labyrinthine membrane‐membrane contacts, scantiness of cytoplasmic organelles, presence of Birbeck‐like granules, juxtanuclear tubulo‐vesicular complex, and phagocytic capacity. © 1995 Wiley‐Liss, Inc.
Morphology of the reflecting superposition eyes of larval oplophorid shrimps
Authors: Gaten Edward , Herring Peter J.
Published: February 2005

The eyes of larval and juvenile oplophorid shrimps are described for the first time. Variations in eye development occur depending on whether the zoeal stages are lecithotrophic or planktotrophic. In those genera where the first free‐living stage is planktonic, the eyes are of the transparent apposition type seen in other decapod zoeas. However, where the eggs hatch after completion of the lecithotrophic zoeal stages, the eyes are laready developing the superposition optics found in the adult. In Oplophorus spinosus the changeover from hexagonal to square facets, indicative of superposition optics, proceeds from anterior to posterior. In Systellaspis debilis the square facets appear first on the lateral face of the eye. Eventually, in both species, only the most dorsal ommatidia retain apposition optics. © 1995 Wiley‐Liss, Inc.
Morphology and ultrastructure of saccular otoliths from five species of the genus Coelorinchus (Gadiformes: Macrouridae) from the Southeast Atlantic
Authors: Lombarte Antoni , Morales‐Nin Beatriz
Published: February 2005

The morphology of the saccular otolith (sagitta) of five species of the genus Coelorinchus (grenadiers) from the southeastern Atlantic (C. coelorinchus, C. fasciatus, C. occa, C. braueri, and C. acanthiger) was analyzed macro‐ and ultrastructurally by digital image processing and scanning electron microscopy (SEM). Interspecies variations have been noted in the morphology and ultrastructure of the sulcus acusticus and are linked to differences in form of the entire otolith. This relationship may indicate a genetic regulation in the growth of the sulcus. Standard canonical analysis of biometric measurements of the otolith and acoustic sulcus has proved to be a good way to distinguish otoliths of the five species of Coelorinchus. © 1995 Wiley‐Liss, Inc.
Marginal tooth‐bearing bones in the lower jaw of the recent australian lungfish, Neoceratodus forsteri (Osteichthyes, Dipnoi)
Authors: Kemp A.
Published: February 2005

Developmental studies of the Recent Australian lungfish, Neoceratodus forsteri, show that this species has two sets of functional tooth‐bearing bones in the lower jaw of young hatchlings. These coincide with an early stage in the life history when the fish is strictly carnivorous. In N. forsteri, a paired tooth‐bearing dentary and an unpaired symphyseal bone and tooth develop slightly later than the permanent vomerine, prearticular, and pterygopalatine tooth plates, which appear at stage 44 of development, and erupt with the permanent dentition between stages 46 and 48, when the hatchling first starts to feed on small aquatic invertebrates. At these stages of development, all of the teeth are long, sharp, and conical and help to retain prey items in the mouth. Disappearance of the transient dentition coincides with complete eruption of the permanent tooth plates and precedes the change to an omnivorous diet. Existence of a transient marginal dentition in this species of lungfish suggests that the presence of an apparently similar marginal dentition in adults of many species of Palaeozoic dipnoans should be considered in phylogenetic analyses of genera within the group, and when analysing the relationships of dipnoans with other primitive animals. © 1995 Wiley‐Liss, Inc.
Perinatal changes in avian muscle: Implications from ultrastructure for the development of endothermy
Authors: Eppley Zoe A. , Russell Brenda
Published: February 2005

Endothermic heat production and the capacity to shiver develop soon after hatching in birds, permitting chicks to regulate their body temperature. Physiological studies have not clearly identified the developmental events causing this change in function. Here, we use electron microscopy to examine the development of structures involved in muscle activation, contraction, and metabolism coincident with the development of shivering thermogenesis. A stereological study was used to compare the ultrastructure of chicken iliofibularis before endothermic heat production was present (24 h before hatching) and 120 h later, when the iliofibularis had substantial capacity for shivering. Profound increases were found in the t‐tubule system and terminal cisternae, mitochondrial cristae, and lipids. The number of triadic profiles increased 3.8‐fold (7.6 ± 1.31/100 μm2 to 28.5 ± 2.90/100 μm2 fiber area). The surface area of cristae per mitochondrial volume doubled (12.0 ± 1.50 pm2/pm3 to 25.7 ± 1.84 μm2/μm3). Lipid droplets were rare in the iliofibularis of embryos about to hatch, but accounted for 4.4% of the muscle fiber volume in day 4 birds. We suggest that these ultrastructural changes more fully activate the iliofibularis, allow it to produce more heat both from calcium pumping and from contraction, and increase its endurance, thus permitting the muscle to be effective in thermogenesis. © 1995 Wiley‐Liss, Inc.
Sensory receptors on the adult labial and maxillary palpi and galea of Cicindela sexguttata (Coleoptera: Cicindelidae)
Authors: Baker Gerald T. , Monroe William A.
Published: February 2005

Five types of sensilla are situated on the apical area of the labial and maxillary palpi and galea of Cicidela sexguttata. Large, conical, and peg‐like sensilla are in rows on the central region of each palpus. These sensilla have a hollow cuticular peg, with an apical pore and multi‐innervation. This central region of palpal sensilla is surrounded by campaniform sensilla that are disc‐shaped and small conical peg sensilla. A similar type of conical sensillum as the found in the palpal central region is situated around the periphery of the palpal apex and apex of the galea. This conical peg sensillum is located in a shallow depression and is structurally similar to the other peg sensilla, but it has a mechanoreceptor neuron attached to the cuticular base of the sensillum. A long, single, trichoid sensillum is situated in the center of the galea and is hollow, thick‐walled, porous, and multi‐innervated. The apices of the palpi and galea have a large number of dermal gland openings that actively secrete a substance during the feeding process of the tiger beetle. © 1995 Wiley‐Liss, Inc.
Microstructure, evolution, and ontogeny of scale surfaces in cordylid and gerrhosaurid lizards
Authors: Harvey Michael B. , Gutberlet Ronald L.
Published: February 2005

The distal oberhautchen and proximal beta layer of 41 species and every genus of cordylid and gerrhosaurid lizard were examined with a scanning electron microscope. Scale organs in these families are concentrated on the face, and scale organs occur singly or in pairs below the keel on the dorsals of cordylids but not gerrhosaurids. Most species examined possess primitive, lenticular scale organs. Unique and previously unknown, projecting scale organs occur in two species of Cordylus. Scale organs appear to be absent in species of Chamaesaura. The scale surfaces of cordylids are covered in macrohoneycomb. Individual compartments of cordylid macrohoneycomb are not intracellular structures but may be overlain by apparent oberhautchen cells. In some cordylid species, part of each cell is free and projects away from the scale surface as a pointed flap. Gerrhosaurids lack macrohoneycomb. Instead, their scale surfaces are covered in lamellae without dentate borders, 50–100 times as long as wide. The epidermis of Platysaurus is unique among cordylids in possessing lamellae 1–8 times as wide as long that overlap macrohoneycomb in some regions of the body. The scale surfaces of Cordylus cordylus undergo an ontogenetic change similar to that recently described for the xenosaurid genus Shinisaurus. Phylogenetic analysis of scale surface features allows the partitioning of Cordylus into three species groups and Chamaesaura into two species groups. Synapomorphies of the species of Chamaesaura, the species of Platysaurus, and the genera of the gerrhosaurids are also described. © 1995 Wiley‐Liss, Inc.
Spleen of the snake (Elaphe climacophora) and intrasplenic vascular architecture
Authors: Tanaka Yasukazu , Hirahara Yoshihiro
Published: February 2005

The spleen of the blue‐green snake (Elaphe climacophora) lies at the head of the pancreas and is separated from it by a fibrous capsule. A hilus is not clearly distinguished. Arteries and veins enter or leave the spleen through the capsule, but no collateral relationship is observed between these vessels. Histologically, the spleen consists of the capsule‐septal tissue, lymphoid tissue (the white pulp), and a fibrous zone (the perilymphoid fibrous zone: PLFZ) around the lymphoid tissue that includes many small veins. The PLFZ probably represents the involuted red pulp. The border between the white pulp and PLFZ is unclear in routine histological sections due to diffuse infiltration of lymphocytes into the latter region, but the border could be distinguished clearly in silver‐impregnated specimens.

Arteries enter the spleen, run within the septa, and divide into terminal arteries in the lymphoid tissue that form end branches. There are no ellipsoids around the terminal arteries. The end branches communicate with veins of the PLFZ through transitional vessels within the lymphoid tissue (closed circulation). The veins of the PLFZ anastomose with drainage veins in the capsule.

The snake spleen retains the basic histological characteristics of a spleen and is morphologically distinguishable from a lymph node. It may represent an extreme example of a spleen modified by the remodelling of the intrasplenic vasculatures during evolution. © 1995 Wiley‐Liss, Inc.
Contrast bone cement
Authors: Bargar William L. , Heiple Kingsbury G. , Weber Stephen , Brown Stanley A. , Brown Richard H. , Kotzar Geoff
Published: February 2005

The effects of adding 1.0 cc of aqueous methylene blue dye as a visual contrast agent to a standard 40 g pack of acrylic bone cement are determined. These cements are evaluated: Simplex P (Radiopaque), Zimmer Bone Cement, and Zimmer LVC Bone Cement. Seven tests were performed. Leach out is less than 2.0% and was undetectable after day 8. Biocompatibility using a rabbit model shows contrast and white cement to be equivalent. Tension, compression, and 3‐ and 4‐point bending strengths are not significantly altered except for a slight increase in 4‐point bending strength for contrast Zimmer (regular) bone cement. Dough, set, and working times are decreased by 30–150 s. The ASTM F451 intrusion standards are met for all three contrast cements. Viscosity increases more rapidly for contrast cement, but remains sufficiently low (less than 100 N‐s/m2) early after mixing to allow good penetration into bone. Ease of removal and visualization of contrast cement are shown by revision of cemented femoral total hip components in synthetic and cadaver femurs and by debriding cement particles from a soft tissue background coated with blood. The use of contrast bone cement appears to be both safe and efficacious for use in initial and revision total joint replacements. Because of the decreased working times, its use is recommended only by experienced surgeons.
Long‐term measurement of muscle function in the dog hindlimb using a new apparatus
Authors: Hargens Alan R. , Mortensen Wayne W. , Gershuni David H. , Crenshaw Albert G. , Lieber Richard L. , Akeson Wayne H.
Published: February 2005

The objective of this study was to develop an apparatus for reliable, reproducible, and minimally invasive measurements of long‐term, myoneural function. Twenty conditioned dogs were anesthetized and placed supine with one hindlimb secured in a boot apparatus. The hindpaw was attached to a force transducer that was connected to a recorder for continuous monitoring of torque. Muscles within the anterolateral compartment were stimulated by percutaneous electrodes over the peroneal nerve near the fibular head. This elicited isometric dorsiflexion of the hindpaw. Twitch and tetanic torques correlated positively with dog weight whereas other skeletal‐muscle function parameters (time to peak tension, one‐half relaxation time, and endurance) were independent of dog weight. Muscle function results were consistent with an overall compartmental composition of 30% Type I and 70% Type II fibers. Repetitive testing of twitch and tetanic torques in the dog legs yielded coefficients of variance of 3–4% (intraday) and 7% (interday). Thus, about onehalf of the interday variability may be accounted for by diet, exercise, and other physiological conditions that change daily. The apparatus was also used to detect myoneural degeneration following tourniquet ischemia. The results indicate that this procedure for evaluating muscle function yields reliable and quantitative results noninvasively, and thus allows long‐term testing of muscle function in normal and diseased hindlimbs of dogs.
Age‐related changes in bone in the dog: Calcium homeostasis
Authors: Williams E. Alan , Kelly Patrick J.
Published: February 2005

To explore the changes in the relationship between skeletal and Ca2+ homeostasis with age, we studied 50 dogs divided into four age groups. The skeletal uptake of 85Sr decreased markedly with age, and the immunoreactive parathyroid hormone (iPTH) level increased. There was a significant correlation between iPTH value and the calculated short‐term exchange of Ca in bone (r = −0.55; p < 0.001). Bone formation and bone resorption decreased with age except that in the oldest group of dogs the resorption increased (p < 0.001). We suggest that in aging dogs the skeletal exchange of Ca falls to a very low level that decreases the immediate effect of PTH and thus leads to a chronic net increase in circulating PTH. Concomitant with this is an increase in osteoclastic bone resorption and, over a long time, loss of skeletal mass.
In vitro growth of bovine articular cartilage chondrocytes in various capacitively coupled electrical fields
Authors: Brighton Carl T. , Unger Anthony S. , Stambough Jeffery L.
Published: February 2005

Isolated articular cartilage chondrocytes from 1‐ to 3‐week‐old male Holstein calf knee joints were formed into pellets containing 4 × 106 isolated cells and were grown in tissue culture medium (minimum essential medium/NCTC 135) containing either 1 or 10% newborn calf serum (NBCS) in plastic Petri dishes in 5% CO2 and air at 37°C in saturation humidity. On the 4th postisolation day either [35S]sulfate or [3H]thymidine was added to the medium, and the pellets were exposed for 24 h to capacitively coupled electrical fields (10, 100, 250, and 1,000 V peak‐to‐peak, 60 kHz, sine wave signals). The pellets were then harvested, dialyzed, hydrolyzed, and assayed for DNA, protein, [35S]sulfate incorporation, and [3H]thymidine incorporation. Results indicated that at 250 V peak‐to‐peak there was a statistically significant increase in [35S]sulfate in 1% NBCS and a statistically significant increase in [3H]thymidine in 10% NBCS. At potentials above or below 250 V no changes were noted. Thus, articular cartilage chondrocytes grown in pellet form can be stimulated to increase glycosaminoglycan synthesis or to increase cell proliferation by an appropriate capacitively coupled electrical field. The importance of the serum concentration in the medium in evaluation of biosynthesis in vitro is noted.
The apparent elastic modulus of the juxtaricular subchondral bone of the femoral head
Authors: Brown Thomas D. , Vrahas Mark S.
Published: February 2005

An experiment was undertaken to obtain approximate values for the intrinsic elastic modulus of subchondral bone. Shallow spherical caps, with uniform and incrementally controlled thickness, were machined from subchondral bone in the weight‐bearing regions of 11 fresh‐frozen normal femoral head autopsy specimens. Under application of polar point loads, the measured deflections were compared with a corresponding analytical shell solution, thus allowing back‐calculation of the apparent modulus. Analogous tests were performed on similarly shaped specimens of stock Plexiglas® of known modulus in order to estimate the precision of the testing method. The aggregate results for subchondral bone showed that its intrinsic stiffness correlated inversely with nominal shell thickness, but even the thinnest (1.0 mm thick) of these shells had an apparent modulus (mean = 1.372 GN/m2, SD = 414 MN/m2) well below that generally accepted for “pure” cortical bone (about 14 GN/m2). This stiffness deficit was very likely due to the presence of histologically evident marrow spaces. However, the low apparent modulus values measured in this study may not be fully representative of complex in vivo behavior, because in the testing of excised shells there is no radial compressive stress transfer to underlying cancellous bone.
An epidemiologic study of lifting and twisting on the job and risk for acute prolapsed lumbar intervertebral disc
Authors: Kelsey Jennifer L. , Githens Penny B. , White Augustus A. , Holford Theodore R. , Walter Stephen D. , O'Connor Theresa , Ostfeld Adrian M. , Weil Ulrich , Southwick Wayne O. , Calogero John A.
Published: February 2005

An epidemiologic case‐control study undertaken in Connecticut during 1979–1981 indicated that persons with jobs requiring lifting objects of more than 11.3 kg (25 lb) an average of more than 25 times per day had over three times the risk for acute prolapsed lumbar intervertebral disc as people whose jobs did not involve lifting objects of this weight. If the body was usually twisted while the lifting was done, this elevation in risk was apparent with less frequent lifting. An especially high risk for prolapsed lumbar disc was associated with jobs involving lifting objects of more than 11.3 kg with the body usually twisted and the knees not bent while the lifting was done. Neither lifting objects of less than 11.3 kg nor twisting without lifting was associated with an increase in risk.
A system to measure the forces and moments at the knee and hip during level walking
Authors: Gilbert Jerome A. , Maxwell G. Maret , McElhaney James H. , Clippinger Frank W.
Published: February 2005

The forces and moments in the sagittal plane at the knee and hip were calculated using gait data collected during level walking. Accelerations were measured by accelerometers attached to the legs, and the force reactions at the foot were measured by a force plate. The recorded accelerations and the foot forces were used to determine the joint reactions through a Newtonian formulation modeling the leg as articulated, rigid links. Twelve normal subjects were included in this study along with nine lower limb amputees. Obvious differences were observed when comparing amputee data to normal data both at the knee and hip. Gait data obtained by this system can be readily used to form criteria for objective gait analysis and improved prosthesis design.
Relation of intramuscular pressure to the force output and myoelectric signal of skeletal muscle
Authors: Körner L. , Parker P. , Almström C. , Andersson G. B. J. , Herberts P. , Kadefors R. , Palmerud G. , Zetterberg C.
Published: February 2005

The force output of the biceps brachii muscle during static isometric contractions was studied in 26 arms of 23 subjects in relation to the simultaneously recorded level of the electromyogram (EMG) and the intramuscular pressure (IMP). The EMG was picked up with wire electrodes and the IMP recorded through wick catheters or by infusion technique. The load at the wrist was monitored using a force transducer. A near linear relationship with correlation coefficients exceeding 0.96 was shown between the load on the wrist on the one hand and IMP and EMG on the other. The regression coefficients of the relation between the load and IMP or EMG varied considerably between individuals and between different measuring points in the same individual. In cases where the correlation between the wrist load on one hand and the IMP and EMG on the other was poor because of varying synergistic interaction between the flexor muscles, the EMG and IMP were always well correlated. This means that they change in the same way when the mechanical output of the muscle varies. This was also the case in three experiments where the IMP and EMG from all three elbow flexors were recorded while the subjects changed from a supinated to a pronated position supporting a constant load on the wrist. Considering these observations we present indirect evidence that IMP and the level of the EMG signal both are good estimators of isolated muscular force under isometric static conditions and over limited time.
Medullary osteogenesis with platinum cathodes
Authors: Dymecki S. M. , Black J. , Nord D. S. , Jones S. B. , Baranowski T. J. , Brighton C. T.
Published: February 2005

Studies of electrical stimulation of osteogenesis with stainless steel electrodes have previously established a dose‐response relationship between current and bone growth. Examination of the effect of different geometric current densities resulted in the conclusion that very little electrode surface area was involved in stimulation and led to the design of a multiport “distributive” cathode. A series of experiments were performed to extend these results to wire and multiport platinum electrodes. As before, a current‐bone growth dose‐response relationship was found. Peak bone growth was greater than for stainless steel. However, peak bone growth occurred at 2.0 μA (versus 20 μA for stainless steel). Correlation studies suggest that small changes in cathodic potential affect bone growth more than similar size changes in current. Finally, the generally benign local host response to platinum suggests that platinum may be a suitable materials for chronic indwelling anodes for stimulation of osteogenesis.
Sequential technetium‐99m/gallium‐67 scintigraphic evaluation of subclinical osteomyelitis complicating fracture nonunion
Authors: Esterhai John , Alavi Abass , Mandell Gerald A. , Brown Jamie
Published: February 2005

Twenty‐four patients with a history of post‐traumatic fracture nonunion underwent sequential 99mTc and 67Ga citrate scintigraphy in an attempt to differentiate between posttraumatic fracture nonunion and nonunion complicated by subclinical osteomyelitis. Neither technetium nor gallium studies alone nor in combination, with or without clinical correlation, could help delineate between fracture nonunion and nonunion complicated by subclinical osteomyelitis because of the increased technetium and gallium radioisotope uptake associated with the nonunion site.
Effect of freezing on histologic and biomechanical failure patterns in the rabbit capital femoral growth plate
Authors: Lee Kendrick E. , Pelker Richard R.
Published: February 2005

Ten pairs of proximal femora were harvested from 8‐week‐old New Zealand white rabbits. Experimental shear fractures were then created in vitro, and load‐displacement curves were recorded. One specimen from each animal was tested within 4 h of death, whereas the contralateral specimen was frozen for 10 to 20 days and thawed prior to testing. Histologic sections of the fractured specimens were studied. No statistically significant differences could be demonstrated between the fresh and the frozen/thawed specimens in either the histologic patterns or the shear load or stress to failure.
Guidelines for external fixation frame rigidity and stresses
Authors: Huiskes R. , Chao E. Y. S.
Published: February 2005

Using results from FEM analyses and experiments as references, analytical methods are applied to develop simple approximate formulas to relate frame rigidity, maximal pin stresses, and peak pin–bone stresses in external fracture fixation (EFF) configurations in axial loading to the most important frame, pin, and bone parameters. It is found that, in a realistic range, the parameters can be adapted to vary the frame rigidity from about 13 N/mm to 17,000 N/mm, thereby reducing the maximal stresses in the pins and at the pin–bone interface by a factor of 140. In particular, when compromises have to be established in the frame characteristics in order to ensure a flexible configuration and limit the stress values at the same time, the formulas presented can provide useful guidelines. The side‐bar separation and the pin modulus, in particular, can be adapted to decrease the rigidity, while only moderately increasing the stresses, thereby reducing chances for pin failure, pin–bone loosening, and pin‐tract infection. A nomogram is presented for a quick reference to estimated relations between frame characteristics, rigidity, and stresses. It is believed that this material may be of use in EFF design and applications in clinical and animal experimental trials.
Effect of fatigue on joint position sense of the knee
Authors: Skinner H. B. , Wyatt M. P. , Hodgdon J. A. , Conard D. W. , Barrack R. L.
Published: February 2005

This study was designed to test position sense of the knee joint before and after fatigue in order to determine whether muscle or capsular receptors are the primary sensors for joint position sense. Reproduction of passive positioning and detection of the onset of motion (kinesthesia) were employed to measure joint position sense. Eleven subjects underwent joint position sense measurement before and after a fatigue protocol. A significant worsening of reproduction of knee joint angle after fatigue was noted (p < 0.05). Threshold (kinesthesia) showed no statistically significant change after fatigue. A significant correlation of reproduction measurements and threshold measurements prior to fatigue (p < 0.01) demonstrated that the same neural mechanism is applicable in the rested state, but these variables did not correlate significantly after fatigue. There was a significant correlation between reproduction measurements before and after fatigue (p = 0.018), while no correlation was seen for the pre‐ and postfatigue threshold measurements, suggesting a change in the neural path after fatigue. Since both tests of joint position sense are affected by fatigue, we conclude that muscle receptors are a prominent, if not primary, determinant of joint position sense, and capsular receptors may have a secondary role. Reproduction ability is decreased, presumably through the loss of efficiency of muscle receptors. The threshold data suggest a change in the mechanism of appreciation after fatigue, possibly due to increased sensitivity of capsular receptors from muscle‐fatigue‐induced laxity.
The phenomenon of “Ligamentization”: Anterior cruciate ligament reconstruction with autogenous patellar tendon
Authors: Amiel David , Kleiner Jeffrey B. , Roux Richard D. , Harwood Frederick L. , Akeson Wayne H.
Published: February 2005

Reconstruction of the anterior cruciate ligament (ACL) with patellar tendon (PT) is a common procedure for the symptomatic ACL‐deficient knee. Questions regarding graft incorporation, viability, and nutrition of the transplanted tissue are of concern. This relates to the graft's response to its new intrasynovial milieu and new physical forces. These factors were studied in a rabbit model of ACL reconstruction using PT and were evaluated with histological and biochemical parameters with respect to time. A histological and biochemical metamorphosis of the grafted PT occurred in this study. Autografts demonstrated a gradual assumption of the microscopic properties of normal ACL; by 30 weeks postoperatively, cell morphology was ligamentous in appearance. Normally, type III collagen is not observed in PT, however, a gradual increase in its concentration was seen in the grafts; by 30 weeks its concentration (10%) was the same as in normal ACL. Similarly, glycosaminoglycans content increased from its normally low level in PT to that found in native ACL. Collagen‐reducible crosslink analysis demonstrated that grafted tissue changed from the normal PT pattern of low dihydroxylysinonorleucine (DHLNL) and high histidinohydroxymerodesmosine (HHMD) to the pattern seen in normal ACL (high DHLNL and low HHMD) by 30 weeks. These data suggest that when PT is placed in the anatomic and environmental milieu of the ACL, a “ligamentization” of the grafted tissue results; also the autograft initially depends on synovial fluid nutrition, as revascularization occurs after 6 weeks.
Electrical stimulation of human muscle studied using 31P‐nuclear magnetic resonance spectroscopy
Authors: Shenton David W. , Heppenstall R. Bruce , Chance Britton , Glasgow Steven G. , Schnall Mitchell D. , Sapega Alexander A.
Published: February 2005

This study used phosphorous nuclear magnetic resonance (31P‐NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with 31P‐NMR during both maximum voluntary and 6‐s EMS‐induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p < 0.025) depletion of phosphocreatine (36%) than did tetanic 70‐Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by 31P‐NMR spectroscopy.
Patellar surface strain
Authors: Goldstein Steven A. , Coale Edward , Weiss Arnold‐Peter C. , Grossnickle Mark , Meller Bruce , Matthews Larry S.
Published: February 2005

We measured longitudinal surface strains on the anterior patella at controlled simulated quadriceps loads, quadriceps angles, and knee flexion angles. We studied both the natural patella and patellas resurfaced with domed, bifaceted, and metal backed polyethylene components. Twelve matched pairs of fresh human cadaver knee specimens were tested. Midanterior longitudinal patellar strains were greatest at knee flexion angles at 45 to 60° of knee flexion. Alterations in quadriceps angle medially and laterally did not decrease recorded strain values significantly. Polyethylene patellar prostheses increased patellar strains but a bifaceted component or “total contact” design minimized this effect. Metal support for the prosthetic patella decreased the recorded surface strains. This study of patellar surface strain at the three midline locations provides experimental results that may prove useful for design and validation of analytic models of the patella. The study also suggests that patellar surface strain measures may provide a method for evaluating the effects of patellar prosthesis design and resurfacing procedures.
Clonal analysis of the population of chondrocytes from the swarm rat chondrosarcoma in agarose culture
Authors: Sun Deqing , Aydelotte M. B. , Maldonado B. , Kuettner K. E. , Kimura J. H.
Published: February 2005

Chondrocytes from the Swarm chondrosarcoma, a transplantable rat tumor, have been difficult to maintain in tissue culture for extended periods due to a time‐dependent alteration of the culture to a more fibroblastic pheno‐type. This feature precluded the use of these cultures to examine chronic conditions that may affect cell metabolism, and the homogeneity or heterogeneity of the tumor cells within the culture population could not be examined. Use of suspension culture in agarose stabilized the chondrocyte phenotype, permitting long‐term culture. Clones of tumor chondrocytes were established in agarose and were examined over 2–3 weeks for evidence that the cells were accumulating a proteoglycan‐rich extracellular matrix, as determined by positive staining by Alcian blue, and were undergoing cell division. Nearly 90% of the cloned cells exhibited a prominent extracellular matrix by day 7 of culture and greater than 99% did so by day 14. Cell division did not occur to any great extent until days 6–7 of culture. After this lag, the cells appeared to undergo logarithmic growth, with a cell generation time of about 12 days. By 20 days of culture, between 80 and 90% of the initial clones contained multiple cells, indicating that nearly all the cells were in, or had entered, the cell cycle. These results suggest that the chondrocytes from the rat chondrosarcoma form a homogeneous cell population with respect to their ability to synthesize an extracellular matrix and divide.
Augmentation of anterior cruciate ligament reconstruction in dogs with prostheses of different stiffnesses
Authors: Yoshiya Shinichi , Andrish Jack T. , Manley Michael T. , Kurosaka Masahiro
Published: February 2005

The purpose of this study was to investigate the biological and bio‐mechanical properties of anterior cruciate ligament (ACL) reconstruction augmented with Dacron prostheses of three different stiffnesses. The ACLs of 36 adult mongrel dogs were removed and the ligament was reconstructed. In 18 dogs, one knee was reconstructed with patellar tendon alone, and the contralateral knee with Dacron augmented patellar tendon. In the remaining 18 dogs, reconstruction was with Dacron augmented patellar tendon with Dacron alone being used for the contralateral control knee. Death was 3 months after surgery, and the reconstructions were examined biologically and biomechanically. The mechanical data were compared with immediate postoperative data obtained from 45 reconstructed fresh cadaveric knees. Tensile testing demonstrated that an increase in failure load was found when the implanted patellar tendon graft was compared with the cadaveric reconstruction. The strength of the Dacron augmented reconstruction showed little change while the Dacron alone graft decreased in strength during the period of implantation. No clear difference was found between the performance of augmentation devices of different stiffnesses. Microangiography showed that grafts were totally revascularized in patellar tendon alone, but not well revascularized in Dacron augmented patellar tendon and Dacron alone reconstruction. The presence of the Dacron appeared to have an adverse effect on revascularization.
Three‐dimensional spinal curvature in idiopathic scoliosis
Authors: Stokes Ian A. F. , Bigalow Llynda C. , Moreland Morey S.
Published: February 2005

Scoliosis is usually considered as a deformity of the spine in the frontal plane, without reference to curvatures in other planes. In this study, the three‐dimensional shape of the spine of 104 patients with untreated idiopathic scoliosis (5–55° Cobb) was studied by means of stereo radiographs to determine relationships between curvature of the spine in the frontal plane view, in the lateral view, and in the intermediate views. There was a weak but statistically significant correlation (r = 0.2) relating greater scoliosis with lesser kyphosis or greater lordosis. In the thoracic region, the sagittal plane spinal curvature was less than that measured in a population without scoliosis (mean difference, 7.72 ° 9.9°). Seventy‐four of 76 scolioses in the upper region of the spine with lateral curvature greater than 5° Cobb were kyphotic. Sixty‐four of 84 curves greater than 5° Cobb in the lower region were lordotic. Measuring curvatures in the plane of symmetry of the rotated apical vertebra altered these ratios to 69 of 76 kyphotic in the upper region and 68 of 84 lordotic in the lower region. The plane of maximum curvature of sections of the spine with scoliosis was not related to the plane of symmetry of the rotated apical vertebra, for in kyphotic regions of the spine the rotations of these two planes were in opposite directions. In all cases, the magnitudes of the rotations were quite different, i.e., by a factor of −0.22 for curves in thoracic region and by a factor of 0.24 for curves in the lumbar region. This implies that mechanical measures to correct this spinal deformity or to prevent progression should apply different rotations to the apex from those applied to the curve as a whole and, in opposite senses, in curves in kyphotic regions. There was no evidence of an abnormality of sagittal curvature of a magnitude to implicate it in the etiology or in the treatment.
Tensile properties of human knee joint cartilage. II. Correlations between weight bearing and tissue pathology and the kinetics of swelling
Authors: Akizuki Shaw , Mow Van C. , Muller Francisco , Pita Julio C. , Howell David S.
Published: February 2005

The nonequilibrium or kinetic swelling behavior of normal, fibrillated, and osteoarthritic (OA) (removed from total knee joint replacements) human knee joint cartilage has been measured using our isometric tensile apparatus (ITA). We found that large local variation exist in the manner with which human knee joint cartilage swells, including anisotropic effects, inhomogeneities, and dependence on local biochemical composition and pathological condition. The ITA provides three convenient biomechanical parameters—peak stress (s̀P), stress relaxation (s̀R), and diffusion coefficient (D)—to quantify the kinetics of swelling. We used these parameters to quantify and differentiate the kinetic swelling behavior of normal, fibrillated, and osteoarthritic cartilage, as well as the swelling behavior of cartilage from high and low weight‐bearing areas. Also, these kinetic swelling parameters correlated very well, though by varying degrees, with such biochemical measures as collagen/proteoglycan ratio, hexosamine content/wet weight, and hydroxyproline content/dry weight, providing important insight into the mechanisms and processes involved during the course of swelling. Hence, the kinetic swelling behavior of cartilage should be used to provide important information not obtainable from equilibrium swelling studies.
Accuracy and reproducibility of instrumented knee‐drawer tests
Authors: Edixhoven Ph. , Huiskes R. , De Graaf R. , Van Rens Th. J. G. , Slooff T. J.
Published: February 2005

Instrumented devices for knee‐drawer tests have become popular in orthopaedics relatively recently. The objective of the present study was to document the effects of several parameters on the accuracy and reproducibility of anterior‐posterior (AP) drawer measurements. An instrumented knee‐drawer tester for AP laxity evaluations was constructed, based on the differential displacement method, measuring shifts of the tuberosity relative to the patella. The accuracy of the AP‐shift was determined with the parallel use of a highly accurate roentgen stereo photogrammetric (RSP) measurement system on two postmortem leg specimens. The effects of relative motion between patella and femur were negligible. In addition to AP shifts, significant knee flexion and tibial rotations occurred, although the foot and the thigh were fixed as well as possible. The differential displacement method was effective in circumventing this problem. The accuracy of the AP shift was >10%. The reproducibility of the AP drawer parameters (shifts and compliances) was determined in normal subjects and patients. Tests were made to evaluate the effects of different observers, time sequences, and different days. In addition, effects of muscle relaxation were studied. Overall, the shift parameters at different forces were found to be reproducible to between 5 and 15%. The slopes (compliances) of the laxity curves, at different forces, were found to be reproducible to between 20 and 40%. The reproducibility was principally affected by deviations in the subject positioning procedure.
Mechanical behavior of the human lumbar spine. I. Creep analysis during static compressive loading
Authors: Keller T. S. , Spengler D. M. , Hansson T. H.
Published: February 2005

The in vitro viscoelastic “creep” behavior was examined in 18 cadaveric human lumbar motion segments subjected to static axial compressive loads. Axial deformation was followed for 30 min under constant applied load. Compressive material constants (moduli and viscosity coefficients) were then determined for each intervertebral disc using a linerization method based on a Taylor series expansion of experimental data for the “three parameter” viscoelastic creep model. The degree of disc degeneration and bone mineral content (BMC) were also assessed. Good correlation between the experimentally determined and model predicted strain values were found, with the average error <1%. We found that motion segments from older and more degenerated lumbar discs were less stable and had lower material constants than segments from younger and less degenerated discs. Material constants and BMC correlated closely, suggesting that an interdependency of disc and vertebral body properties exists. No correlation between the creep characteristics and disc height, disc area, segment level, or sex were noted.
Tendon synovial cells secrete fibronectin in vivo and in vitro
Authors: Banes Albert J. , Link G. William , Bevin A. G. , Peterson Hugh D. , Gillespie Yancy , Bynum Donald , Watts Susan , Dahners Lawrence
Published: February 2005

The chemistry and cell biology of the tendon have been largely overlooked due to the emphasis on collagen, the principle structural component of the tendon. The tendon must not only transmit the force of muscle contraction to bone to effect movement, but it must also glide simultaneously over extratendonous tissues. Fibronectin is classified as a cell attachment molecule that induces cell spreading and adhesion to substratum. The external surface of intact avian flexor tendon stained positively with antibody to cellular fibronectin. However, if the surface synovial cells were first removed with collagenase, no positive reaction with antifibronectin antibody was detected. Analysis of immunologically stained frozen sections of tendon also revealed fibronectin at the tendon synovium, but little was associated with cells internal in tendon. The staining pattern with isolated, cultured synovial cells and fibroblasts from the tendon interior substantiated the histological observations. Analysis of polyacrylamide gel profiles of 35S‐methionine‐labeled proteins synthesized by synovial cells and internal fibroblasts indicated that fibronectin was synthesized principally by synovial cells. Fibronectin at the tendon surface may play a role in cell attachment to prevent cell removal by the friction of gliding. Alternatively, fibronectin, with its binding sites for hyaluronic acid and collagen, may act as a complex for boundary lubrication.
Kinetics of osmotic water movement in chondrocytes isolated from articular cartilage and applications to cryopreservation
Authors: McGann L. E. , Stevenson M. , Muldrew K. , Schachar N.
Published: February 2005

The ability of chondrocytes to survive conditions encountered during cryopreservation depends on the responses of the cells to the physiochemical changes that result when water is removed from the environment of the cells in the form of ice. Cellular responses are therefore closely related to the osmotic permeability properties of the plasma membrane. In order to optimize the conditions for cryopreservation of chondrocytes, osmotic properties of the chondrocyte membrane were determined from the kinetics of volume change in hypertonic solutions at different temperatures. The hydraulic conductivity of the plasma membrane was 0.305 ± 0.025 μm3/μm2/min/atmosphere at 24°C, with an Arrhenius activation energy of 8.06 kcal/mol. These values are similar to those reported for other cell types, but the osmotically inactive volume of the chondrocytes (0.41 ± 0.04) was significantly higher than for other cells, implying that chondrocytes have a higher dry weight ratio or that they contain a higher proportion of osmotically inactive or bound water. These results were used to calculate the osmotic responses of chondrocytes at low temperatures and to predict that the least damaging cooling rate for isolated chondrocytes in the absence of cryoprotective compounds is 10°C/min. The ultimate goal of this study is the development of an analytical model applicable to the optimization of techniques for cryopreservation of intact cartilage and other tissues.