bluuebunny/crossref_metadata_2025_split huggingface dataset:
The development of acellularity of the vertebral bone of the Japanese medaka, Oryzias latipes (Teleostei; Cyprinidontidae)
Authors: Ekanayake Sunetra , Hall Brian K. 
Published: February 2005

AbstractAmong vertebrates, some teleosts are unique in having bone which lacks osteocytes embedded in the matrix. The fate of cells that secrete the matrix of these acellular bones has not been investigated thoroughly. Histological and fluorescent microscopic analysis of the vertebral bone of Oryzias latipes demonstrated that acellularity is not a secondary appearance of an early cellular bone during ontogeny. Vertebral bone is devoid of cells embedded in the matrix throughout development. Cells that secrete bone matrix do not become trapped in their own secretion. Instead, they always remain as a surface layer over the outer surface of the bone. Fluorescent microscopic visualization of tetracycline injected into growing fish demonstrated that bone was only deposited by osteoblasts lining the outer surface of the bone; no deposition of bone took place on the inner surface.
The morphology and vasculature of the lungs and gills of the soldier crab, Mictyris longicarpus
Authors: Farrelly Caroline , Greenaway Peter 
Published: February 2005

AbstractThe five gill pairs of Mictyris longicarpus have the lowest weight specific area reported for any crab. The cuticle of the gill lamellae is lined with epithelial cells which have structural features characteristic of iontransporting cells. Pillar cells are regularly distributed in the epithelium and serve to maintain separation of the two faces of the lamellae. The central hemolymph space is divided into two sheets by a fenestrated septum of connective tissue cells. The dorsal portion of the marginal canal of each lamella receives hemolymph from the afferent branchial vessel and distributes it to the lamella while the ventral portion of the canal collects hemolymph and returns it to the efferent branchial vessel.The lung is formed from the inner lining of the branchiostegite and an outgrowth of this, the epibranchial membrane. Surface area is increased by invagination of the lining which forms branching, blind‐ending pores, giving the lung a spongy appearance. The cuticle lining the lung is thin and the underlyng epithelial cells are extremely attenuated, giving a total hemolymph/gas distance of 90–475 nm. Venous hemolymph is directed close to the gas exchange surface by specialised connective tissue cells and by thin strands of connective tissue which run parallel to the cuticle. Air sacs are anchored in position by paired pillar cells filled with microtubules. Afferent hemolymph is supplied from the eye sinus, dorsal sinus, and ventral sinus. Afferent vessels interdigitate closely with efferent vessels just beneath the respiratory membrane. The two systems are connected by a “perpendicular system” which ramifies between the airways and emerges to form a sinus beneath the carapace and then flows back between the air sacs to the efferent vessels. The afferent side of the perpendicular system is the major site of gas exchange. Efferent vessels return via large pulmonary veins to the pericardial cavity. PaO2 levels were high (95.5 Torr), indicating highly efficient gas exchange.
Changes in femoral robusticity and porosity during the reproductive cycle of the female alligator (Alligator mississippiensis)
Authors: Wink Carole S. , Elsey Ruth M. , Hill Elizabeth M. 
Published: February 2005

AbstractTo help understand the nature of skeletal changes during the reproductive cycle of the female alligator, we compared femoral robusticity (density) and porosity of cross‐sections from the midshafts of femora from the following groups of female alligators: (1) immature; (2) pre‐ovulatory; (3) postovulatory with soft‐shelled oviducal eggs; (4) post‐ovulatory with hard‐shelled oviducal eggs; (5) post‐ovulatory with eggs in the nest; (6) post‐ovulatory with hatched eggs; and (7) mature, quiescent. Femora from alligators with eggs in the nest were significantly less robust (dense) than those of the other groups except those with hard‐shelled oviducal eggs. Cross sections from the midshaft of femora from alligators with eggs in the nest were significantly more porous than those from all the other groups. The results indicated that calcium was mobilized from the femoral shaft shortly before eggs were laid and that femoral density returned to normal levels for mature alligators 1–2 months after egg‐laying.
Transformation of mucocartilage to a definitive cartilage during metamorphosis in the sea lamprey, Petromyzon marinus
Authors: Armstrong L. A. , Wright G. M. , Youson J. H. 
Published: February 2005

AbstractAn ultrastructural analysis of the development of adult piston (tongue) cartilage in the ventromedial longitudinal bar (VMLB), an area of larval mucocartilage, was undertaken in the lamprey, Petromyzon marinus, in order to clarify the relationship between these two unique larval and adult connective tissues. At the onset of metamorphosis, the mucocartilage fibroblasts dedifferentiate into a “mesenchymal” cell type. Migration of unspecialized cells from surrounding tissues plays an important role in the development of a cellular “embryonic” tissue in the VMLB. Degradation of the mucocartilage extracellular matrix (ECM) by the unspecialized cells seems to occur prior to cartilage differentiation. This event is followed by the appearance of a blastema of undifferentiated cells, which expands by proliferation of cells in the core of the VMLB. The cells of the blastema subsequently differentiate into chondroblasts, which secrete adult ECM components consisting of 20‐nm nonbanded fibrils, electron‐dense branched lamprin fibrils, and proteoglycan. The present study suggests that mucocartilage, as a primitive or embryonic connective tissue, temporarily specializes to act as a skeletal support during larval life. Once metamorphosis is initiated, this tissue resumes an embryonic character (mesenchymal) and cartilage histogenesis takes place. The mechanism of cartilage development within the lamprey VMLB is similar to that observed in the chondrogenic system of higher vertebrates.
Development and evolution of avian racket plumes: Fine structure and serial homology of the wire
Authors: Bleiweiss Robert 
Published: February 2005

AbstractAvian racket plumes, characterized by a vaned paddle‐shaped tip borne on a wirelike segment, are among the most spectacular pennaceous contour feathers. This is the first detailed description of the fine structure of the wirelike segment in several racket plumes that acquire their shape exclusively during development, for the parrot Prioniturus discurus, the hummingbirds Ocreatus underwoodii and Loddigesia mirabilis, the kingfisher Tanysiptera carolinae, and the bird of paradise Parotia carolae. Scanning electron microscopy reveals that the wirelike segments are comprised of small, structurally simplified barbs located along a central rachis, indicating that racket plumes retain the basic structural organization of pennaceous contour feathers. The diverse structures provide evidence of several alterations to normal developmental processes, including arrested and disrupted development of the barbs. Many of the major differences among the five species in the fine structure of the wire apparently result from differences in the morphogenesis of barb ridges on the epidermal collar of the developing plume. The structure and morphogenesis of the racket plumes described herein are distinct from those described in motmots (Momotidae), indicating that racket plumes can evolve through convergence.
The ultrastructure and innervation of the ear of the gar, Lepisosteus osseus
Authors: Mathiesen Carsten , Popper Arthur N. 
Published: February 2005

AbstractThe endorgans of the inner ear of the gar were examined using transmission and scanning electron microscopy as well as nerve staining. The ultrastructure of the sensory hair cells and supporting cells of the gar ear are similar to cells in other bony fishes, whereas there are significant differences between the gar and other bony fishes in the orientations patterns of the sensory hair cells on the saccular and lagenar sensory epithelia.The saccular sensory epithelium has two regions, a main region and a secondary region ventral to the main region. The ciliary bundles on the main region are divided into two groups, one oriented dorsally and the other ventrally. Furthermore, as a result of curvature of the saccular sensory epithelium, the dorsal and ventral ciliary bundles on the rostral portion of the epithelium are rotated ninety degrees and are thus oriented on the animal's rostro‐caudal axis. Hair cells on the secondary region are generally oriented ventrally.The lagenar epithelium has three groups of sensory hair cells. The groups on the rostral and caudal ends of the macula are oriented dorsally, whereas the middle group is oriented ventrally. Hair cell orientations on the utricular epithelium and macula neglecta are similar to those in other bony fishes.Nerve fiber diameters can be divided into three size classes, 1–8 μm, 9–13 μm, and 14 μm or more, with the smallest size class containing the majority of fibers. The distribution of the various classes of fiber diameters is not the same in nerve branches to each of the end organs. Similarly, the ratio of hair cells to axons differs in each end organ. The highest hair cell to axon ratio is in the utricle (23:1) and the smallest is in the macula neglecta (7:1). The number of sensory hair cells far exceed the number of eighth nerve axons in all sensory epithelia.
Intrinsic organization of the medial cerebral cortex of the lizard Lacerta pityusensis: A golgi study
Authors: Berbel P. J. , Martínez‐Guijarro F. J. , López‐García C. 
Published: February 2005

AbstractThe morphology of cells and the organization of axons were studied in Golgi‐Colonnier and toluidine blue stained preparations from the medial cerebral cortex of the lizard Lacerta pityusensis. In the medial cortex, six strata were distinguished between the superficial glial membrane and the ependyma. Strata I and II formed the outer plexiform layer, stratum III formed the cellular layer, and strata IV go VI the inner plexiform layer. The outer plexiform layer contained smooth bipolar neurons; their dendrites were oriented anteroposteriorly and their axons were directed towards the posterior zone of the brain. Five neuronal types were observed in the cellular layer. The spinous pyramidal neurons had well‐developed apical dendrites and poorly developed basal ones. Their axons entered the inner plexiform layer and gave off collaterals oriented anteroposteriorly. The small, sparsely spinous pyramidal neurons had poorly developed dendrites and their axons entered the inner plexiform layer. The spinous bitufted neurons had well‐developed apical and basal dendritic tufts. Their axons gave off collaterals that reached the outer and inner plexiform layers of both the dorsomedial and dorsal cortices. The sparsely spinous horizontal neurons had dendrites restricted to the outer plexiform layer. Their axons entered the inner plexiform layer. The sparsely spinous, multipolar neurons had their soma close to stratum IV and their axons entered the outer plexiform layer. In stratum V of the inner plexiform layer were large, spiny polymorphic neurons; they had dendrites with long spines, and their axons reached the cellular layer. On the basis of these results, we have subdivided the medial cortex into two subregions: the superficial region, which contains the neurons of the cellular layer and their dendritic domains, and the deep region, strata V and VI, which contains the large, spiny polymorphic neurons. The neurons in the medial cortex of these lizards resembles those in the area dentata of mammals. On this basis, the superficial region may be compared to the dentate gyrus and the deep region to the hilar region of the hippocampus of mammals.
Development of an avascular region (the stigma) in ovarian follicles of lizards (Anolis)
Authors: Jones Richard E. , Lopez Kristin H. , Summers Cliff H. , Austin Harriet B. , Rand Matt S. 
Published: February 2005

AbstractThe architecture of follicular blood vessels in the ovary of lizards (Anolis equestris and Anolis carolinensis) was studied by standard histology and also after vascular perfusion with an orange silicone‐rubber compound or with India ink. The theca of the follicular wall contains a netlike arrangement of anastomosing sinusoids, which increase in size as a follicle grows. An avascular stigma forms in very small, growing follicles when a portion of the follicular wall contacts the ovarian surface epithelium. Blood vessels then invade the theca except in the zone of contact. The diameter of the stigma is about 50% of follicular diameter, regardless of follicular size. Although the stigma of smaller follicles is avascular, that of vitellogenic follicles is hypovascular, i.e., a few vessels radiate into the stigma region. The antiangiogenic process involved in stigma formation may continue as the stigma enlarges. The development pattern of stigma formation found in Anolis is displayed by many other vertebrates.
Fine structure of the fungiform papilla in a ranid frog (Rana esculenta)
Authors: Gioglio Luciana , Rapuzzi G. , Dell'orbo C. 
Published: February 2005

AbstractThe freetop of the fungiform papilla shows a sensorial area about 100 μm in diameter, surrounded by a ring of ciliated cells. Externally to the ciliated cells, i.e., in the lateral wall, numerous large goblet cells can be seen devoid of their mucous content. The sensorial area is composed by three types of cells: mucous, supporting, and neuroepithelial cells. Mucous cells form the most superficial layer, while the cell bodies of the other two are deep, and from them basal and apical processes arise. The above mentioned cells are connected by desmosomes preferentially located between the mucous and the supporting cells, rather than between the supporting and the neuroepithelial cells. The lateral wall of the papilla is made up of a multilayered epithelium that comprises two types of cells: the first type contains electron‐dense granules and an abundant rough endoplasmic reticulum, the others are ciliated cells. In the connective axis of the papilla, numerous fenestrated capillaries with endothelial vesiculated cells and nerve fibers are found.
Arrangement of accessory cells and nematocytes bearing mastigophores in the tentacles of the cubozoan Chironex fleckeri
Authors: Rifkin J. F. , Endean R. 
Published: February 2005

AbstractNematocytes containing microbasic mastigophores are intimately associated with accessory cells in the epidermis of Chironex fleckeri. Large microbasic mastigophores may be surrounded by seven to nine such cells. Each accessory cell possesses an apical portion containing secretory droplets and a basal portion which carries a radially oriented fibre linking the cell to the underlying mesogloea. The fibre is capable of projecting and retracting the accessory cell. Junctional complexes occur between accessory cells and the apical regions of neighbouring mastigophores. Each nematocyte bearing a mastigophore contains a triggering apparatus consisting of a cnidocil surrounded by microvilli. This apparatus protrudes from an invagination in the apical region of the nematocyte and is exposed when the mastigophore is in the fire‐ready position. A basket of filaments which make contact with microvilli surrounds the apical end of the nematocyst like a collar. The basket is linked via fibrous bundles which envelop the mastigophore to radially oriented fibres basally. These fibres are capable of projecting and retracting the mastigophore and its associated triggering apparatus. Up to nine such fibres were observed to be associated with a single large microbasic mastigophore. Microtubules averaging 25 nm in diameter and linked via cross bridges to electrondense material were detected in the radial fibres of both nematocytes and accessory cells. Retraction of the accessory cells and projection of nematocytes result in mastigophores being brought to the firing line and in the exposure of the cnidocil apparatus.
Some aspects of segment formation and post‐placental development in Peripatus acacioi marcus and marcus (Onychophora)
Authors: Walker Muriel , Campiglia Sylvia 
Published: February 2005

AbstractThe surface morphology of the anterior‐to‐posterior sequence of segment formation in embryos of a viviparous neotropical onychophoran and aspects of post‐placental development seen using scanning electron microscopy are described. When all the segments have formed and the walking legs have completed their elongation, the body surface becomes covered with an embryonic cuticle that does not exhibit the hydrofuge properties seen in the adult cuticle. As soon as the walking legs have reached their full length, barbed projections are formed at their distal extremities. These projections are extensions of single cells and are covered by the embryonic cuticle. Transmission electron microscopy reveals that the cells at the distal ends of the legs and their projections have many pinocytotic vesicles at their surfaces. The cytoplasm of these cells and their projections is rich in mitochondria, rough endoplasmic reticulum, glycogen, and granules of storage material. There are minor differences in the surface morphology of the projections found at the ends of the walking legs in embryos of Peripatus acacioi and those of Peripatus biolleyi. The projections and the embryonic cuticle persist thoughout postplacental development. The role of the projections in the uptake of material by the embryo from the uterus is discussed and the possible phylogenetic significance of these projections is suggested.
Ultrastructure and silver‐staining analysis of spermatogenesis in the sea urchin Paracentrotus lividus (Echinodermata, Echinoidea)
Authors: Sousa Mario , Azevedo Carlos 
Published: February 2005

AbstractSpermatogenesis of the sea urchin Paracentrotus lividus has been studied at the ultrastructural level after conventional staining of thin sections and after en bloc silver staining. Cytoplasmic dense bodies are present in all steps of spermatogenesis except in late spermatids and spermatozoa. These bodies are closely associated with the development of centrioles and of the acrosomal vesicle during spermiogenesis. After it first appears, acrosomal vesicle is linked to the nuclear envelope by electron‐dense material and subsequently acquires a dense core. Later the acrosomal vesicle moves to the apical pole of the cell while maintaining its connection to the nucleus. Although chromatin was highly condensed in the head of spermatozoa, one or more nuclear vacuoles within the nucleus were found to contain uncondensed chromatin fibers. Silver nitrate stains several nuclear and cytoplasmic structures. In the nucleus it stains the nucleolus, specific regions at the periphery of the chromatin, the synaptonemal complexes, the nuclear basal fossa, and the nuclear vacuoles of spermatozoa. In the cytoplasm, silver stains the cytoplasmic dense bodies, the material that connects the acrosomal vesicle to the spermatid nucleus, the spermatozoan subacrosomal and periacrosomal materials, the intercellular bridges of spermatids, and the centrioles. Silver staining is abolished by pretreatment with pronase E, suggesting that silver staining is due to protein.
Atavisms and the homology of hyobranchial elements in lower vertebrates
Authors: Reilly Stephen M. , Lauder George V. 
Published: February 2005

AbstractThe homology of branchial arch segments in salamanders has been a matter of controversy since the last century. Many investigators term the most medial paired elements of salamander branchial arches “ceratobranchials” and the next distal paired elements “epibranchials.” This suggests that the first two segmental elements of the salamander branchial arch are not homologous with elements occupying the same position in ray‐finned fishes, Latimeria, “rhipidistians,” and lungfishes, in which these bones are called hypobranchials and ceratobranchials, respectively. Three lines of evidence suggest that it is more parsimonious to interpret urodele branchial arch segments as being homologous with those of other vertebrate clades−(1) comparative osteology, (2) comparative myology, and (3) the discovery of cartilaginous structures forming a third segmental unit that we interpret as atavistic epibranchials of the branchial arch in one population of the salamander Notophthalmus viridescens. These structures possess all the defining attributes of atavisms, and illustrate the special role that atavistic features play in resolving questions of homology recognition.
Ultrastructure of early cleavage and yolk extrusion in the marsupial Antechinus stuartii
Authors: Selwood Lynne , Sathananthan A. H. 
Published: February 2005

AbstractThe fertilized egg and the two‐cell stage and four‐cell stage of the marsupial Antechinus stuartii were studied by transmission electron microscopy. The features that make the fertilized egg of Antechinus stuartii different from those of any eutherian mammal are (1) the presence of a shell and (2) the relatively large quantity and polarized distribution of cytoplasmic inclusions, including lipid, protein yolk bodies, and protein fibers. Mitochondria and vesicles of smooth endoplasmic reticulum are also polarized in distribution. Early cleavage differs from that of eutherians in several ways: (1) it occurs in the uterus; (2) there is extrusion of a large, single, membrane‐bound yolk mass at first cleavage; and (3) blastomeres become separated after the second cleavage division and thus do not adhere by cell‐to‐cell contacts. Prior to the second division, blastomeres are connected to each other by remnants of the midbody and to the yolk mass by remnants of a cytoplasmic bridge. The yolk mass after extrusion is surrounded by plasma membrane and contains inclusions of lipid, protein yolk bodies, and fibers, as well as mitochondria and smooth endoplasmic reticulum. The blastomeres of the two‐cell and four‐cell stages also show intracellular polarization in the distribution of retained inclusions and organelles. Vesicles developing at the periphery of blastomeres and discharging their contents extracellularly increase in size and number from the fertilized egg to the four‐cell stage. The discharged contents may be implicated in early development of the blastula cavity.
Chondrocranium and ossification sequence of Hyla lanciformis
Authors: De Sa Rafael O. 
Published: February 2005

AbstractTadpoles of Hyla lanciformis live in midwater and have a normal, beaked, anteroventral, subterminal mouth. Overall, they are generalized pond‐type anuran larvae that show no specific modification for a particular habitat. The chondrocranium and ossification sequences of this hylid frog were studied, utilizing cleared and Alcian blue‐alizarin red‐stained tadpoles. The chondrocranium is similar to that of other unspecialized tadpoles. No larval otic process was found and a large process projecting from the otic capsule is considered homologous with the larval crista parotica described for other anurans. The pattern of cranial and postcranial ossification is reported. The sequence of cranial ossification is explained in the framework of functional changes of the skull through metamorphosis. Comparison with the available information for other hylid frogs shows clear differences in the ossification sequences. The sequence of postcranial ossification is described for the first time for any species of hylid frog.