bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructurally different muscle cell types in Eisenia foetida (Annelida, Oligochaeta)
Authors: Royuela Mar , Fraile Benito , García‐Anchuelo Rosa , Paniagua Ricardo
Published: February 2005

Muscles in the body wall, intestinal wall, and contractile hemolymphatic vessels (pseudohearts) of an oligochaete anelid (Eisenia foetida) were studied by electron microscopy. The muscle cells in all locations, except for the outer layer of the pseudohearts, are variants of obliquely striated muscle cells. Cells comprising the circular layer of the body wall possess single, peripherally located myofibrils that occupy most of the cytoplasm and surround other cytoplasmic organelles. The nuclei of the cells lie peripherally to the myofibrils. The sarcomeres consist of thin and thick myofilaments that are arranged in parallel arrays. In one plane of view, the filaments appear to be oriented obliquely to Z bands. Thin myofilaments measure 5–6 nm in diameter. Thick myofilaments are fusiform in shape and their width decreases from their centers (40–45 nm) to their tips (23–25 nm). The thin/thick filament ratio in the A bands is 10. The Z bands consist of Z bars alternating with tubules of the sarcoplasmic reticulum. Subsarcolemmal electron‐dense plaques are found frequently. The cells forming the longitudinal layer of the body wall musculature are smaller than the cells in the circular layer and their thick filaments are smaller (31–33 nm centrally and 21–23 nm at the tips). Subsarcolemmal plaques are less numerous. The cells forming the heart wall inner layer, the large hemolymphatic vessels, and the intestinal wall are characterized by their large thick myofilaments (50–52 nm centrally and 27–28 nm at the tips) and abundance of mitochondria. The cells forming the outer muscular layer of the pseudohearts are smooth muscle cells. These cells are richer in thick filaments than vertebrate smooth muscle cells. They differ from obliquely striated muscle cells by possessing irregularly distributed electron‐dense bodies for filament anchorage rather than sarcomeres and Z bands and by displaying tubules of smooth endoplasmic reticulum among the bundles of myofilaments. © 1995 Wiley‐Liss, Inc.
Early embryonic development, including germ‐disk stage, in the theridiid spider Achaearanea japonica (Bös. et Str.)
Authors: Suzuki Hirohumi , Kondo Akio
Published: February 2005

Early embryonic development, from the first cleavage to the germ‐disk stage, in the theridiid spider Achaearanea japonica was examined by light and electron microscopy. The eggs are syncytial during the first four cleavages, and then invaginations of cell membranes fuse to generate the blastomeres at the sixteen‐nucleus stage. The cleavage pattern is a modified type of total cleavage. It appears that radial bundles of microtubules that radiate from the perinuclear cytoplasm may participate in the migration of cleavage nuclei for the formation of the blastoderm. The large yolk granules are sequestered by cell membranes from the blastomeres or blastoderm cells into the interior of the embryo together with various organelles and glycogen granules. Most of the blastoderm cells converge in the upper hemisphere to form the germ disk, whereas a few cells remain in the lower hemisphere. The embryo at the germ‐disk stage contains many spherical germ‐disk cells. Almost no large yolk granules are found in these cells, but the flat remaining cells each contain several large yolk granules. These remaining cells may preserve a flat shape to cover the surface of the embryo that does not include the germ disk. © 1995 Wiley‐Liss, Inc.
Incubation temperature and gonadal sex affect growth and physiology in the leopard gecko (Eublepharis macularius), a lizard with temperature‐dependent sex determination
Authors: Tousignant Alan , Crews David
Published: February 2005

Temperature‐dependent sex determination (TSD), in which the temperature at which an egg incubates determines the sex of the individual, occurs in egg‐laying reptiles of three separate orders. Previous studies have shown that the embryonic environment can have effects lasting beyond the period of sex determination. We investigated the relative roles of incubation temperature, exogenous estradiol, and gonadal sex (testis vs. ovary) in the differentiation of adult morphological and physiological traits of the leopard gecko, Eublepharis macularius. The results indicate that incubation temperature, steroid hormones, and gonads interact in the development of morphological and physiological characters with incubation temperature resulting in the greatest differences in adult phenotype. Incubation temperature did not affect reproductive success directly, but may influence offspring survival in natural situations through effects on adult female body size. Postnatal hormones seem to be more influential in the formation of adult phenotypes than prenatal hormones. These results demonstrate that TSD species can be used to investigate the effects of the physical environment on development in individuals without a predetermined genetic sex and thus provide further insight into the roles of gonadal sex and the embryonic environment in sexual differentiation. © 1995 Wiley‐Liss, Inc.
Comparative embryology of teleostean fishes. I. Development and staging of the american shad, Alosa sapidissima (Wilson, 1811)
Authors: Shardo Judith D.
Published: February 2005

A new approach to devising embryological staging systems allows improved phylogenetic comparisons of developmental patterns. As in traditional approaches, morphological features provide the defining criteria for stages, but unlike traditional normal tables, each stage is defined by no more than one or two morphological criteria that are fundamental developmental features of all teleosts. Additional developmental features that occur concurrently with the defining criteria of a stage are treated as variables potentially uncoupled from the defining criteria for that stage. This system is well suited to detect phylogenetic heterochrony and promises to increase our understanding of conserved vs. labile features in teleostean embryology. In this study, I explain the defining criteria for American shad and then make comparisons with other clupeoids. The development of American shad includes 35 stages extending from fertilization to metamorphosis. Comparisons with other clupeoids indicate that the developmental pattern of shad is representative of the early ontogeny of many clupeoids during the embryonic and yolk sac periods and may be conservative for the group. However, several concurrent features, particularly hatching, formation of neuromasts, and opercular development, vary in developmental timing among clupeoids. Comparisons indicate that shad embryos delay the development of these concurrent features relative to other clupeoids. Modifications of the developmental pattern for different species of clupeoids are heterochronic but their phylogenetic and adaptive significance is unknown. © 1995 Wiley‐Liss, Inc.
Histological, histochemical, and ultrastructural investigations on the gastrointestinal system of antarctic seals: Weddell seal (Leptonychotes weddellii) and crabeater seal (Lobodon carcinophagus)
Authors: Schumacher Udo , Klein Peter , Plötz Joachim , Welsch Ulrich
Published: February 2005

The morphology of the principal sections of the gastrointestinal system of two Antarctic seals with different dietary habits, namely, the Weddell seal (Leptonychotes weddellii) and the crabeater seal (Lobodon carcinophagus), has been investigated. Histologically examined by light microscopy, the tissue layers of the gastrointestinal tract of both seals are almost identical to those observed in most other mammals and no major differences in principle organization could be found between the two seal species. The ultrastructure of the gastric and intestinal epithelial cells has been examined and is also closely comparable to that of these cells in other mammals; however, Paneth cells have not been found in our material. In general, therefore, adaptations of the gastrointestinal tract to the aquatic environment or the diet are not obvious at the morphological levels of organization studied.

Histochemical differences are found between the two closely related species; mucins of the surface epithelium in the stomach of Weddell seals are highly sulfated, while those in the crabeater seal are not. Mucous neck cells in Weddell seals contain acid mucosubstances, while those of crabeater seals contain neutral ones. Goblet cells in the small and large intestine in Weddell seals contain both neutral and acid mucosubstances. Both mucin types are detected in the crabeater seal; however, the mucins of the colon in the crabeater seal are more highly sulfated than those in the Weddell seal. The ratio of globet cells to enterocytes in the large intestine of crabeater seals is higher than that in Weddell seals. © 1995 Wiley‐Liss, Inc.
Effects of caffeine treatment on the fine structure, silica secretion, and shell morphology of the testate amoeba Assulina muscorum
Authors: Anderson O. Roger
Published: February 2005

Assulina muscorum secretes morphologically altered shells when cultured in a medium with 5 mM caffeine. The siliceous scales, normally distributed in a regular overlapping pattern, are disorganized, thicker and wider than normal, and occasionally have incompletely silicified surfaces that appear irregular in profile in transmission electron microscopic ultrathin sections. The shape of the silica deposition vesicles (SDVs) in the cytoplasm is altered and they are less regularly arranged. The swollen appearances of the SDVs, and of nearby Golgi tubules, give additional evidence that caffeine affects the fine structural morphology of membranous secretory organelles and can disrupt their normal depositional activity. In addition to the greater thickness and width of the siliceous scales in caffeine‐treated cells, the length and width of the shell are larger compared to controls, but the aspect ratio (length / width) is smaller. The latter is attributed to a larger increase in width relative to the increase in length of the caffeine‐reated cells. Since some of the scales are deposited with the long axis laterally on the shell surface, in addition to being greater in width, this raises the interesting question of whether the morphology of the SDVs and the siliceous products influences the size and morphogenesis of the shell. Further research is needed to clarify the interaction of the SDVs with the cytoplasmic cytoskeletal system during shell morphogenesis. © 1995 Wiley‐Liss, Inc.
Testis morphology and spermatozeugma formation in three genera of viviparous halfbeaks: Nomorhamphus, dermogenys, and Hemirhamphodon (Teleostei: Hemiramphidae)
Authors: Downing Amy L. , Burns John R.
Published: February 2005

The testes of 19 species of viviparous halfbeaks from three genera, Nomorhamphus, Dermogenys, and Hemirhamphodon, are examined histologically. The testes are unfused, paired organs running laterally along the body wall on either side of the gut. In all genera, primary spermatogonia are restricted to the distal termini of the testicular lobules just beneath the tunica albuginea, conforming to the typical atherinomorph testis type. The short efferent ducts empty into a single longitudinal main duct in each testis. All species package sperm in the form of unencapsulated sperm bundles, which are referred to as spermatozeugmata. The mechanism of packet formation and the resulting spermatozeugmata are similar in all five species of Nomorhamphus and in four species of Dermogenys, with each spermatocyst releasing several small spermatozeugmata. In the other four species of Dermogenys, the mechanism of packet formation is similar, and each spermatocyst releases a single, large spermatozeugma. The spermatozeugmata of six species of Hemirhamphodon are unlike those seen in the other two genera, with five different sperm bundle types described herein. The unique sperm bundles of the viviparous halfbeaks are compared with those of the internally fertilizing but oviparous halfbeak genus, Zenarchopterus, discussed within a phylogenetic framework, and hypothesized to be independently derived within the Atherinomorpha. © 1995 Wiley‐Liss, Inc.
Ultrastructure and function of cellular components of the intercentral joint in the percoid vertebral column
Authors: Schmitz Robert J.
Published: February 2005

The intervertebral joint of the teleost, Perca flavescens, is formed by opposing amphicoelus centra whose rims are connected by external ligaments. The tissue, located within the space formed by these structures, is derived from the notochord and consists of the elastic externa, the fibrous sheath, and the notochordal cells. The cellular tissue within the joint has many characteristics of a stratified epithelium, and when examined with the transmission electron microscope, at least three morphologically distinct regions can be recognized. First, a peripheral single layer of columnar to squamous‐shaped cells lies on a basement membrane immediately deep to the fibrous sheath. Second, several layers of cells, each containing a large central vacuole, occur. Third, in the deepest part of the joint, several layers of attenuated cells surround intracentral fluid‐filled lacunae and form a transverse septum across the joint. All cells in this tissue are interconnected by numerous desmosomes. Further, an extensive intermediate filament network exists in all three types of cells. The intermediate filament network in the vacuolated cells is arranged cortically around a membrane‐bound vacuole, and suggests that these cells may act as passive cellular hydrostats. The squamous cells surrounding the joint lacunae are structurally similar to mammalian epidermal cells, and the intermediate filament network within them is layered parallel to the surface of the lacunae. The organization of these cells suggests that they are the tensile component of extracellular hydrostats within the intercentral joint. These cellular and extracellular hydrostats within the intercentral joint would function to resist the compressive and tensile stresses encountered during undulatory swimming. © 1995 Wiley‐Liss, Inc.
Incisal biting in the mountain beaver (Aplodontia rufa) and woodchuck (Marmota monax)
Authors: Druzinsky Robert E.
Published: February 2005

Analysis of synchronously recorded cine‐radiographs and electromyograms in two rodents (Aplodontia rufa and Marmota monax) demonstrates that jaw movements and muscle activiteis during incisal functions are distinctly different from those found during mastication. Movements during incisal biting are primarily along the midline, accompanied by symmetrical activity of the jaw adductor muscles. Most biting cycles do not end in contact between upper and lower incisors. When contact does occur, the lower incisors are dragged along the lingual surfaces of the upper incisors. Cropping, or tip‐to‐tip occlusion of upper and lower incisors, was not observed.

Sharpening of the lower incisors, a behavior which may be unique to the Rodentia, was recorded in both A. rufa and M. monax. During sharpening, the lingual surface of the lower incisor is dragged across the tip of the upper incisor producing a lingual wear facet. Like incisal biting, sharpening movements are primarily confined to the midline, although there may be lateral movements in some sharpening cycles. Sharpening cycles are among the most rapid cyclic movements recorded in mammals, as the mean frequencies of sharpening are 11 cycles/s in A. rufa and 8 cycles/s in M. monax. © 1995 Wiley‐Liss, Inc.
Cytological aspects of vascular invasion by the trophoblast of Calomys callosus in hepatic tissues
Authors: Faria Miriam , Bevilacqua Estela
Published: February 2005

Ectoplacental cones isolated from embryos on the seventh day of pregnancy wer transplanted beneath the hepatic capsule of recipeint adult animals to document the morphological patterns of vascular invasion by the trophoblast in the absence of the maternal environment and the influence of its peculiar vasculature. Females, and females and males of Calomys collosus, a cricetid rodent, were used, respectively, as embryo donors and recipient animals. Three to 5 days later, the grafted regions were excised and processed for light and electron microscopy. Invasion of the liver parenchyma by the trophoblast progressed along the vascular beds, associated with gradual phagocytosis of hepatic cells, greatly favoring the morphological characterization of invasive steps exhibited by the trophoblast to access the different kinds of vessels, to trespass the various vascular components and the different levels of the surrounding hepatic parenchyma. It is possible that either in utero during the establishment of embryomaternal circulation in early pregnancy or ex utero under experimental conditions, the trophblast exhibits similar vascular invasion behavior. In view of this, our findings may contribute to a better understanding of trophoblast cell migration to the maternal blood supply as well as the role of the trophoblast in the establishment of the placental circulation during pregnancy. © 1995 Wiley‐Liss, Inc.
The juxtatesticular body of jawfishes (Teleostei, Opistognathidae): Comparative morphology and fine structure
Authors: Rasotto Maria B. , Manni Lucia
Published: February 2005

A peculiar gland, the juxtatesticular body (JTB), ductless and consisting of follicles, had previously been discovered in males of two Opistognathus species (Teleostei, Opistognathidae). In this paper, we describe (1) the general morphology of the JTB in an additional two Opistognathus species, O. aurifrons and O. macrognathus, comparing it with that of the previously described species, and (2) the fine structure of the JTB of Opistognathus whitehurstii and O. maxillosus. Interspecific variability occurs both in the general organization of this gland and in the number of follicular cells. Fine structural analysis of the JTB, both in O. whitehurstii and O. maxillosus, reveals strong similarities with thyroid follicular cells, suggesting a similar pattern of synthesis and secretion. JTB follicular cells are arranged as a monolayered epithelium that surrounds a follicular lumen; they show a polarity in organelle distribution and membrane specialization typical of secreting cells. On the basis of their cytological and histochemical characteristics we propose that JTB follicular cells perform two major types of secretory activities: the secretion of a glycoprotein from the apical part of the cells into the follicular lumen and the endocrine, or paracrine, secretion of a still unknown substance(s) from the basal part of the cell either into the extrafollicular space or the blood or both. A hypothesis concerning the functional cycle of JTB follicle is also discussed. © 1995 Wiley‐Liss, Inc.
Effects of photoperiod on structure of lamina propria of the testis of Octodon degus
Authors: Rojas M. A. , Morales B. , Esponda P.
Published: February 2005

The changes occurring in the testicular lamina propria (LP) of the seasonal breeder Octodon degus were analyzed. Four groups of animals were studied using electron microscopic procedures. The animals in group I were reproductively active, whereas those in groups II, III, and IV were in periods of recrudescence, regression, and resting, respectively. These changes, observed in animals maintained under laboratory lighting conditions, resembled those known to be elicited in feral populations by natural photoperiods. Testicular changes in each group were monitored by calculating the gonadosomatic and spermatogenetic indexes, and by obtaining averages of the diameter of the seminiferous tubules and the height of the seminiferous epithelium. The LP of group I animals consisted of a basal membrane formed by two to four lamellae, inner and outer acellular layers containing moderate numbers of collagenous fibrils, and single or double layers of smoothly contoured myoid cells encircled by a discontinuous lymphatic epithelium. The LP of group IV animals differed considerably from the LP of group I animals: The inner acellular layer was enlarged, and the basal membrane appeared composed of a variable number of lamellae with numerous folds and indentations. Myoid cells were very irregular in contour and enveloped by a well‐developed surface coating. The LPs of animals in groups II and III possessed relatively similar characteristics, which appeared to be intermediate between those of groups I and IV. The significance of these morphological changes in the LP are discussed in relation to testicular changes induced by photoperiod and other normal or pathological processes. © 1995 Wiley‐Liss, Inc.
Guerin versus malgaigne: A precedent for the free criticism of scientific papers
Authors: Peltier Leonard F.
Published: February 2005

The right to publish data and opinions which are critical of the theories and practices of our colleagues is taken for granted. This right was not gained without a struggle, both moral and legal. The case of Guerin versus Malgaigne established a significant precedent in this regard. Since the protagonists were both orthopaedic pioneers and the case involved the first surgical approach to the treatment of scoliosis, it is of great interest.
Intrinsic tendon fibroplasia: Documentation by In vitro studies
Authors: Graham Martin F. , Becker Hilton , Cohen I. Kelman , Merritt Wyndell , Diegelmann Robert F.
Published: February 2005

There has been considerable controversy concerning the capacity of tendons to heal intrinsically without adhesion formation. To help clarify this issue, a tissue culture model was developed to study the potential of tendon fibroblasts to proliferate and migrate. Avian flexor tendons, isolated free of sheath and all synovial components, were maintained in sterile culture plates with Dulbecco's Modified Eagle Medium. After 5 days in culture, the 2 mm tendon biopsies were analyzed for DNA synthesis ([125I]iododeoxyuridine incorporation) and migration of fibroblasts out of the explant (planimeter analysis). DNA synthesis was maximal on day 5 in culture, and tendon fibroblasts were observed migrating from the biopsy within 48 h. Addition of cells from plasma resulted in a significant increase in fibroblast migration, and the presence of fibrin in the plasma clot was an absolute requirement for the migratory process. These findings further support the hypothesis that injured tendons can heal by an intrinsic healing process in addition to healing by adhesion formation.
Isolation of a plasma membrane‐enriched fraction from collagenase‐suspended rachitic rat growth plate chondrocytes
Authors: Bohn William W. , Stein Ross M. , Hsu Howard H. T. , Morris David C. , Anderson H. Clarke
Published: February 2005

An attempt was made to concentrate plasma membranes of homogenized chondrocytes isolated by collagenase digestion of rachitic rat epiphyseal growth plate cartilage. This study reports the characterization of enzymes in the plasma membrane of isolated chondrocytes and their comparison with extracellular matrix vesicle components. The plasma membraneenriched fractions that were obtained showed a sevenfold increase in 5′‐nucleotidase and a 15‐fold increase in alkaline phosphatase, both of which are regarded as plasma membrane markers. SDS‐polyacrylamide gel electrophoretic profiles of proteins extracted from membrane fractions contained several major protein bands also seen in isolated matrix vesicles. These studies indicate the usefulness of concentrating plasma membrane components from isolated chondrocytes, after the chondrocytes have been enzymatically freed from investing matrix and other stromal components by collagenase.
Electromyographic analysis of shoulder muscle load
Authors: Sigholm Göran , Herberts Peter , Almström Christian , Kadefors Roland
Published: February 2005

The influence of hand tool weight and arm position on shoulder muscle load was studied by electromyography. The investigation was made to facilitate recommendations on work place design. The aim is to reduce the occurrence of occupational shoulder disorders in industry. Nine volunteers held 21 different arm positions with the hand over waist level. In each position, the hand was loaded with 0, 1, and 2 kg. Each load was maintained for 15 s. The myoelectric activity in six shoulder muscles was recorded and analyzed automatically with respect to the amplitude. The results indicate that the degree of upper arm elevation is the most important parameter influencing shoulder muscle load. Short rotator muscles stabilizing the shoulder joint were found to be more hand‐load dependent than the deltoid muscle. The ergonomic implications of this study are that work situations should be designed so that the arm can be kept close to the body and the hand load minimized.
Thoracic spine centers of rotation in the sagittal plane
Authors: Panjabi M. M. , Krag M. H. , Dimnet J. C. , Walter S. D. , Brand R. A.
Published: February 2005

The purpose of this study was to determine in vitro the centers of rotation of thoracic functional spinal units in the sagittal plane. The center of rotation is a convenient concept and part of a precise method of documenting the kinematics of a joint moving in a plane. Fresh cadaver functional spinal units from the thoracic region were utilized. Six load types were used that produced motions only in the sagittal plane, namely anterior and posterior shear forces, flexion and extension moments, and compression and distraction forces. The resulting motion with three degrees of freedom was measured with dial gauges. Statistical methods were used to analyze data from the viewpoint of vertebral level, load magnitude, and load type. Only the load type was found to be significantly related to the location of the centers of rotation. Although there was significant variability in the centers of rotation, there were definite locations related to each load type. The average center of rotation was 15–45 mm directly below the geometric center of the moving vertebra. The results of the present study may be helpful in the clinical interpretation of spinal kinematic studies.
Less rigid internal fixation plates: Historical perspectives and new concepts
Authors: Woo S. L‐Y. , Lothringer K. S. , Akeson W. H. , Coutts R. D. , Woo Y. K. , Simon B. R. , Gomez M. A.
Published: February 2005

In the application of “rigid” plates for diaphyseal fractures, lack of callus healing and overprotection of the underlying bone are viewed by many investigators as undesirable consequences. Potential solutions offered to overcome these deficiencies include modification of the timing of plate removal, use of biologically degradable materials for plates so that stressshielding can be minimized, and use of less rigid plate fixation systems. This study emphasizes the selection of appropriate design criteria for less rigid plate‐fixation systems. To accomplish this goal, the axial, bending, and torsional stiffness parameters are considered in place of the oversimplified terms such as “flexible plate” or “elastic fixation.” With the aid of finite element modeling and simplified bench experiments, we performed parametric studies and singled out the plate axial stiffness as the dominant factor in altering the bone stresses. As a result, we designed two experimental plates, one a thin Ti‐6Al‐4V (titanium with 6% aluminum and 4% vanadium) alloy plate with low stiffness in axial and bending directions, and the other a tubular stainless steel plate with low stiffness in the axial direction but moderate stiffness in bending and torsional directions. The low‐stiffness Ti‐6Al‐4V alloy plate was first tested in a demanding bilateral canine midshalt osteotomy, and proved to be inadequate. Both experimental plates were successful in the unilateral osteotomies, with the tubular plate yielding the best results. After 6 months of plating, the bones beneath the tubular plate had superior mechanical and structural properties as compared to those of the control “rigid” stainless steel and the Ti‐6Al‐4V alloy plates. Application of this plate prolonged for 9 months did not cause reduction in bone properties and strength. The success of the tubular plate is due to its moderate bending and torsional stiffnesses, which provide adequate fixation to achieve callus union, while its low axial stiffness permits the underlying bone to share the physiological stresses needed for bone remodeling. These drastic changes in mechanical demands on the internal fixation plate during the early healing phase and the postunion remodeling phase are discussed.
Age‐related changes in bone in the dog: Fluid spaces and their potassium content
Authors: Pinto Manuel R. , Kelly Patrick J.
Published: February 2005

We measured erythrocyte, plasma, osteocyte, extravascular extracellular, and total water fluid spaces and calculated their K content in cortical bone of dogs of various age. Total and exchangeable K were measured by atomic absorption spectroscopy and by volume of distribution techniques, respectively. All fluid spaces in bone decreased with increasing age of the dogs. The total and exchangeable K contents of cortical bone and the K content calculated from the fluid spaces were within the same range in each age group. These values all fell with increasing age.
Fatigue crack propagation behavior of ultrahigh molecular weight polyethylene
Authors: Connelly G. M. , Rimnac C. M. , Wright T. M. , Hertzberg R. W. , Manson J. A.
Published: February 2005

The relative fatigue crack propagation resistance of plain and carbon fiber‐reinforced ultrahigh molecular weight polyethylene (UHMWPE) was determined from cyclic loading tests performed on compact tension specimens machined from the tibial components of total knee prostheses. Both materials were characterized by dynamic mechanical spectroscopy, X‐ray diffraction, and differential scanning calorimetry. The cyclic tests used loading in laboratory air at 5 Hz using a sinusoidal wave form. Dynamic mechanical spectroscopy showed that the reinforced UHMWPE had a higher elastic storage modulus than the plain UHMWPE, whereas X‐ray diffraction and differential scanning calorimetry showed that the percent crystallinity and degree of order in the crystalline regions were similar for the two materials. Fatigue crack propagation in both materials proved to be very sensitive to small changes in the applied cyclic stress intensity range. A 10% increase in stress intensity resulted in approximately an order of magnitude increase in fatigue crack growth rate. The fatigue crack propagation resistance of the reinforced UHMWPE was found to be significantly worse than that of the plain UHMWPE. This result was attributed to poor bonding between the carbon fibers and the UHMWPE matrix and the ductile nature of the matrix itself.
Demonstration of increased proteoglycan turnover in cartilage explants from dogs with experimental osteoarthritis
Authors: Carney Stephen L. , Billingham Michael E. J. , Muir Helen , Sandy John D.
Published: February 2005

The turnover of proteoglycans (assessed by the release into the medium of newly synthesised [35S]‐proteoglycan) in explant cultures of articular cartilage from various anatomical sites of the knee joints (stifle) of mature beagles with experimental osteoarthritis has been studied with the following findings: (a) The proportion of newly synthesised proteoglycans released from cartilage explants maintained in vitro was generally increased for cartilage from operated compared with nonoperated control joints. (b) At 3 weeks after surgery there was a significant increase in the release of [35S]‐proteoglycans from explants of the lateral and medial tibial plateaux of operated joints compared with sham‐operated joints but not from other sites. On the other hand, when this comparison was made at 3 to 6 months after surgery, significant increases in the release of [35S]‐proteoglycans were observed from cartilage of all anatomical areas except the patellar groove. (c) The release of [35S]‐proteoglycan from cartilage explant cultures was dependent on live chondrocytes, since freeze‐thawing the tissue immediately after labelling markedly reduced the release from both normal and osteoarthritic cartilage.
Bone density in women: College athletes and older athletic women
Authors: Jacobson P. C. , Beaver W. , Grubb S. A. , Taft T. N. , Talmage R. V.
Published: February 2005

Bone density was studied in intercollegiate athletes and older athletic women. Single‐photon densitometry was used to assess bone density parameters at a new distal radial site, the midradius, and the first metatarsus. Dual‐photon densitometry assessed bone density of the lumbar spine. Eleven intercollegiate tennis players, 23 swimmers, and 86 older “athletic” women from 23 to 75 years of age were compared with age‐matched nonathletic controls. “Athletic” describes adult women who exercised at least three times per week, 8 or more months of the year, for a minimum of 3 years. The radius and metatarsus bone content of intercollegiate athletes was significantly above control values. Lumbar spine density was significantly higher only in tennis players. Mean bone density values for adult “athletic” women were also significantly greater than in age‐matched controls. In the oldest athletic group (55–75 years of age) bone measurement values in radius and lumbar spine were in the same range as for younger “athletic” women. In contrast, after 50 years of age, these values in the control population decreased by 0.7%/year. Therefore the largest variance (increase) from age‐matched controls occurred in the oldest “athletic” group. Also, we have established a distal radial density value (using our modified site) below which we consider women “at risk” and recommend further bone health evaluation. Only two adult athletic women > 55 years of age fell into this category. It is concluded from this cross‐sectional study that a regularly maintained athletic program for adult women may reduce the rate of “normal” bone mass loss accompanying age, particularly postmenopausally. Whether this will also decrease the risk of nontraumatic fractures in later life has yet to be determined.
Intervertebral disc degeneration in adult mice with hereditary kyphoscoliosis
Authors: Mason R. M. , Palfrey A. J.
Published: February 2005

Breeding experiments confirmed that a hereditary form of kyphoscoliosis in the BDL strain mouse was due to an autosomal recessive gene (ky). Sagittal sections of whole vertebral columns from adult homozygous recessive mice (ky/ky) were examined histologically. All mice showed varying degrees of degenerative change in one or more intervertebral discs between the fifth cervical and the second thoracic vertebrae. The changes comprised loss of cells, loss of distinction between nucleus pulposus and annulus fibrosus, loss of characteristic ring‐like structure in the annulus, and development of wedge‐shaped discs. In most animals, degenerative disc substance protruded from the disc space, usually posteriorly, sometimes anteriorly, and occasionally through the vertebral end plate cartilage. Posterior protrusions impinged on the spinal cord.
Abnormality of cartilage collagen in a patient with unclassified chondrodystrophy
Authors: Sussman Michael D. , Kelly Thaddeus , Rosenbaum Kenneth N. , Balian Gary
Published: February 2005

We have described a previously unrecognized chondrodystrophy characterized by short‐limbed dwarfism, blue sclera, severe cardiopulmonary problems, and failure of postnatal growth. The first of two siblings thus affected died at age 6 months following attempted correction of an atrial septal defect. Growth plate cartilage from multiple sites obtained at autopsy showed a marked abnormality of architecture on the light microscopic level. Biochemical studies demonstrated an absence of normal α 1(II) collagen in costochondral junction growth plate cartilage and an appearance of the major collagen in a band which comigrates on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis with 3α collagen. Cartilage extracted from structural rib appeared to be normal.
Effects of low‐modulus coatings on pin–bone contact stresses in external fixation
Authors: Manley M. T. , Hurst L. , Hindes R. , Dee R. , Chiang F. P.
Published: February 2005

The intent of this study was to investigate the stress distribution in cortical bone around fracture fixation pins and around pins coated with various polymeric and elastomeric materials. Since these interface stresses cannot be measured directly, a photoelastic technique was employed and stresses were measured in two‐dimensional bone models fabricated from sheets of epoxy resin. Our results showed that when a fixation pin was loaded in compression, the compressive stress measured in the model was greatest at the pin–model interface. The magnitude of the compressive stress was found to diminish steeply away from the hole in a log decrement distribution which was asymptotic to the value of the average stress in the model. When polymeric and elastomeric materials were applied as pin coatings and the performance of the coated pins was compared to that of uncoated pins of the same overall diameter, a reduction of the maximum stress in the bone model was demonstrated. Among the coatings tested, we found that of the polymeric materials ultrahigh molecular weight polyethylene (UHMWPE) was most effective at reducing the peak cortical stress magnitude. The most effective coating material overall was found to be silicon elastomer. Computation of stress values in models loaded through stainless‐steel pins and through pins coated with 1‐mm silicon elastomer showed that the presence of the elastomer layer caused a reduction of about 50% in the maximum compressive stress in the model.
In vivo strain patterns in the four major canine knee ligaments
Authors: Monahan John J. , Grigg Peter , Pappas Arthur M. , Leclair Walter J. , Marks Thomas , Fowler David P. , Sullivan Thomas J.
Published: February 2005

Using mercury gauges, we measured strains in vivo in the four major ligaments of the canine knee joint as the tibia was loaded in valgus or varus at fixed angles of knee flexion. Free axial rotation of the tibia on the femur was allowed. Forces up to 78.4 N were applied to the tibia, producing moments of approximately 9 N‐m. We found that with valgus loading, significant strains were observed in the medial collateral ligament at extension. At 45° of flexion, the medial collateral, posterior cruciate, and anterior cruciate were strained. At 90° of flexion, all four ligaments were strained. With varus loading, significant strains were found in the lateral collateral and anterior cruciate at extension. The lateral collateral and anterior cruciate ligaments were strained at 45° of flexion. At 90° of flexion, the lateral collateral, anterior cruciate, and posterior cruciate ligaments were strained. With valgus loading, the tibia rotated internally and the degree of axial rotation increased with flexion. External rotation of the tibia resulted from varus loading, and was relatively constant through the range of flexion. Thus when axial rotation is allowed, stability of the knee in response to valgus and varus loads is maintained by the cruciates as well as the collaterals, and the role of the cruciates increases with flexion and axial rotation.
Characterization of arthroplasty tissue after 14 years post‐cup arthroplasty: A morphological and biochemical assessment
Authors: Coutts Richard D. , Amiel David , Harwood Frederick L. , Bradley Gary , Akeson Wayne H.
Published: February 2005

The cup arthroplasty has been reported to cause the formation of a fibrocartilaginous joint surface, which may result in a painless, functional joint. The joint surface of a 38‐year‐old man with a failed cup arthroplasty implanted for 14 years was examined histologically and biochemically. The joint surface tissue of this patient resembled fibrous connective tissue, with major types of collagen being Type I and Type III. No evidence of cartilaginous transformation in the healing scar was demonstrated, despite several years of successful functioning of the cup arthroplasty.
The organization of collagen in cryofractured rabbit articular cartilage: A scanning electron microscopic study
Authors: Clark John M.
Published: February 2005

Adult rabbit articular cartilage was prepared for scanning electron microscopy using, in order, glutaraldehyde fixation, enzymatic removal of proteoglycan, dehydration in ethanol, cryofracture in liquid nitrogen, and criticalpoint drying. Enzymes were effective in fixed material. Fixation, cryofracture, alignment of fracture surfaces with “split lines,” and retention of subchondral bone were found to be necessary steps for the preservation of collagen detail. The fibrous framework was found to be similar to that proposed by Benninghoff and favored by more recent phase‐contrast microscopic studies. Vertical fibers extending from subchondral bone and a network of tangentially oriented superficial fibrils converge in the transitional zone. No random layer is seen. Pericellular capsules interdigitate with the vertical fibers. When cartilage is prepared in a manner that minimizes tissue damage, scanning electron microscopy provides useful, unique information.
Induction of heat‐shock protein synthesis in chondrocytes at physiological temperatures
Authors: Madreperla Steven A. , Louwerenburg Binno , Mann Robert W. , Towle Christine A. , Mankin Henry J. , Treadwell Benjamin V.
Published: February 2005

Induction of heat‐shock protein (HSP) synthesis is demonstrated in cultured calf‐chondrocytes at temperatures shown to occur in normal human cartilage during experiments subjecting intact cadaverous hip joints to the parameters of level walking. A 70,000 MW heat‐shock protein (HSP‐70) is synthesized by chondrocytes at temperatures above 39°C, while induction of synthesis of a 110,000 MW HSP only occurs at temperatures of 45°C or greater. These differences in critical temperatures for induction, and data showing differences in kinetics of induction and repression of synthesis, suggest that there are differences in the mechanism of induction of the two HSPs. The duration of HSP synthesis and inhibition of synthesis of normal cellular proteins is directly proportional to the duration and magnitude of the temperature rise. Possible relationships between these new findings and the initiation and progression of degenerative joint disease are discussed.
Bone ingrowth into three different porous ceramics implanted into the tibia of rats and rabbits
Authors: Uchida Atsumasa , Nade Sydney , McCartney Eric , Ching William
Published: February 2005

Three different porous ceramics—calcium aluminate, calcium hydroxyapatite, and tricalcium phosphate—were implanted into the proximal tibia in rats and rabbits to study the interactions between these ceramics and a bony site that is abundant in bone marrow. New bone was consistently formed within the bone marrow surrounding and adjacent to all three types of ceramics. Calcium hydroxyapatite and tricalcium phosphate ceramics permitted bone ingrowth into their pores. The newly formed bone was found only in the part of the ceramic intruding into the bone, not in the portion protruding in the soft tissues outside the tibia. Partial replacement of the new bone opposite the medullary portion by new hemopoietic marrow occurred with longer implantation times. In contrast, no bone was seen within the pores of any of the calcium aluminate implants.
A cumulative damage model for bone fracture
Authors: Carter D. R. , Caler W. E.
Published: February 2005

A mathematical model is presented to describe the combined time‐dependent and cycle‐dependent fracture characteristics of devitalized cortical bone. Failure is interpreted based on a linear‐life fraction rule, which accounts for cumulative creep and fatigue damage under arbitrary loading histories. The model is successful in describing the influence of loading rate on monotonic tensile strength, the time to failure in constant stress creep‐fracture tests, and bone fracture in zero‐tension and tension‐compression cyclic loading. The possible implications of the model to in vivo bone fracture, deformity, and remodelling in response to various loading histories are considered.
Effects of short‐term Cyclosporin‐A on biomechanical properties of intact and fractured bone in the rat
Authors: Warren Steven B. , Pelker Richard R. , Friedlaender Gary E.
Published: February 2005

Cyclosporin‐A is a new immunosuppressant drug being used widely for solid organ transplantation. The systemic effects of Cyclosporin‐A on the skeletal system have not previously been defined. This study examined the effects of Cyclosporin‐A on biomechanical properties of intact bone and fracture repair in a rat model. Closed midshaft femoral fractures were produced over a preplaced intramedullary pin. Cyclosporin‐A, dissolved in olive oil and administered by gavage, was begun the day following surgery and continued for 14 consecutive days at a dose known to prolong solid organ allograft survival in rats (7 mg/kg/day), and a second group of control animals received comparable volumes of plain olive oil under identical circumstances. Groups of both experimental and control animals were killed at 4, 8, 12, or 16 weeks following fracture, after which both intact and fractured femurs were tested to failure in torsion. As judged by torque, angular deformation, stiffness, and energy absorption, Cyclosporin‐A did not significantly alter the biomechanical properties of fracture repair or intact bone turnover. Based on current biomechanical data, we can find no reason to discourage the short‐term clinical use of Cyclosporin‐A in patients with or without fractures. Histomorphometric studies are required to accurately assess the biologic effects of this drug on bone biology and to complete the analysis of skeletal toxicity.
Temporal course of bone formation in response to constant direct current stimulation
Authors: Esterhai J. L. , Friedenberg Z. B. , Brighton C. T. , Black J.
Published: February 2005

Reactive, post‐traumatic bone formation in response to intramedullary insertion of a polytetrafluorethylene‐coated, 28 gauge stainless steel wire was compared with the sequential bone formation seen in response to an indentical intramedullary stainless steel cathode delivering 20 μA constant direct current. Animals were studied at days 1, 2, 3, 4, 5, 7, 9, 11, 14, 17, and 21 after wire insertion. Point count analysis revealed progressive bone formation beginning as early as day 3 on the constant direct current‐stimulated side, progressing steadily through day 21. Control tibia, however, began to show bone formation on day 5 with peaking at day 9 and subsequent bone resorption. The osteogenic response at the 20 μA cathode was statistically elevated above that seen at the control on days 11, 17, and 21.