bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractTemperature‐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

AbstractA 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

AbstractThe 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

AbstractAssulina 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

AbstractThe 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

AbstractThe 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

AbstractAnalysis 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

AbstractEctoplacental 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThere 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

AbstractAn 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

AbstractThe 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

AbstractThe 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.