bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of the pronephros and pronephric duct rudiment in the Mexican axolotl
Authors: Gillespie Laura L. , Armstrong John B. 
Published: February 2005

AbstractIn the Mexican axolotl (Ambystoma mexicanum), the pronephros begins to form at the four‐somite stage. It is initially continuous with the posterior‐lateral region of somite 2 and the lateral margin of somites 3 and 4. By the seven‐somite stage, the pronephros has become compacted, and the cells are now morphologically distinct from the somitic cells. At this stage, a mass of loosely connected cells, apparently originating from the lateral mesoderm, is seen below somites 4 and 5. By the eight‐somite stage, these presumptive duct cells have migrated dorsally to the duct path and are found below somites 5–7. By the nine‐somite stage they have begun to migrate caudally.
Functional morphology of the feeding mechanism in aquatic ambystomatid salamanders
Authors: Lauder George V. , Shaffer H. Bradley 
Published: February 2005

AbstractThis study addresses four questions in vertebrate functional morphology through a study of aquatic prey capture in ambystomatid salamanders: (1) How does the feeding mechanism of aquatic salamanders function as a biomechanical system? (2) How similar are the biomechanics of suction feeding in aquatic salamanders and ray‐finned fishes? (3) What quantitative relationship does information extracted from electromyograms of striated muscles bear to kinematic patterns and animal performance? and (4) What are the major structural and functional patterns in the evolution of the lower vertebrate skull?During prey capture, larval ambystomatid salamanders display a kinematic pattern similar to that of other lower vertebrates, with peak gape occurring prior to both peak hyoid depression and peak cranial elevation. The depressor mandibulae, rectus cervicis, epaxialis, hypaxialis, and branchiohyoideus muscles are all active for 40–60 msec during the strike and overlap considerably in activity. The two divisions of the adductor mandibulae are active in a continuous burst for 110–130 msec, and the intermandibularis posterior and coracomandibularis are active in a double burst pattern. The antagonistic depressor mandibulae and adductor mandibulae internus become active within 0.2 msec of each other, but the two muscles show very different spike and amplitude patterns during their respective activity periods. Coefficients of variation for kinematic and most electromyographic recordings reach a minimum within a 10 msec time period, just after the mouth starts to open.Pressure within the buccal cavity during the strike reaches a minimum of −25 mmHg, and minimum pressure occurs synchronously with maximum gill bar adduction. The gill bars (bearing gill rakers that interlock with rakers of adjacent arches) clearly function as a resistance within the oral cavity and restrict posterior water influx during mouth opening, creating a unidirectional flow during feeding.Durations of electromyographic activity alone are poor predictors of kinematic patterns. Analyses of spike amplitude explain an additional fraction of the variance in jaw kinematics, whereas the product of spike number and amplitude is the best statistical predictor of kinematic response variables.Larval ambystomatid salamanders retain the two primitive biomechanical systems for opening and closing the mouth present in nontetrapod vertebrates: elevation of the head by the epaxialis and depression of the mandible by the hyoid apparatus.
Calcitonin cell population and distribution in the thyroid gland of the rat
Authors: Monsour P. A. , Kruger B. J. , Barnes A. 
Published: February 2005

AbstractCalcitonin‐containing cells (C cells) were identified in male Wistar white rats using an immunoperoxidase technique. They occupied a central position within the thyroid; very few were found peripherally, inferiorly, and superiorly; and none were present in the isthmus. The number of calcitonin‐containing cells present per gram of body weight increased with age up to 70 days and had declined by 100 days. Determining the true total C‐cell count through the entire thyroid is a very laborious procedure. However, a simple estimate of this total count can be made; the total number of C cells in every tenth section (6 μm) of thyroid was found to be highly correlated with the weight of the animal expressed as an allometric function. A better estimate can be derived from counts of just three sections: the tenth, twentieth, and thirtieth after the section of greatest cross sectional area.
The innervation of some proboscis structures involved in feeding behavior of the blowfly (Calliphora vicina)
Authors: van Mier P. , van der Molen L. , van der Starre H. 
Published: February 2005

AbstractThe microtopology of the motoneurons involved in protraction and retraction of the proboscis of the blowfly (Calliphora vicina) has been studied. In addition, taste input from the labellar hairs was investigated. As a result of this study it appears that protraction movements are controlled by two while retraction movements are guided by three motoneurons on each side. The neurons in each group apear to be in ipsicontralateral communication with each other. The musculi protractores fulcri (MPF) probably contain a proprioceptive cell group which projects to the MPF motoneurons. It is proposed that the proboscis motor system can be modulated by proprioception as well as by chemosensory labellar input. Neurosecretory cells may be involved in adjusting muscle power.
Morphology and histochemistry of the ambiens muscle of the red‐eared turtle Pseudemys scripta
Authors: Hermanson John W. , Lennard Paul R. , Takamoto Richard L. 
Published: February 2005

AbstractSix fiber types have been described in the ambiens muscle of red‐eared turtles. These include one slow oxidative type, two fast oxidative types, two fast oxidative and glycolytic types, and one fast glycolytic type. Fiber types are non‐randomly distributed throughout cross sections of the muscle. There is a decreasing gradient of oxidative staining and an increasing gradient of glycolytic staining along an axis from the superficial to deep regions of the muscle. The slow oxidative fibers are predominantly located within one or two fascicles of the superficial surface of the muscle. The fast glycolytic fibers are predominant in deep fascicles.In contrast to previous reports of histochemically monotypic intrafusal fibers in turtle muscle, ambiens muscle spindles have been observed containing one to eleven intrafusal fibers, including two fiber types. Fiber diameter and area are consistently smaller than observed in most extrafusal fibers. Spindles are predominantly located in superficial and cranial fascicles of the ambiens muscle and are located in regions characterized by extrafusal fibers with high oxidative activity.
The fine structure of the nephronic tubule of the mudskipper Periophthalmus koelreuteri (Pallas)
Authors: Safer A. M. A. , El‐Sayed N. K. 
Published: February 2005

AbstractUltrastructural examination of the head kidney of Periophthalmus koelreuteri (Pallas) (Teleostei, Gobiidae) revealed that the nephronic tubule cells are bound by tight junctions and desmosomes with little intercellular space. The first proximal segment (PI) consists of low columnar cells with well developed brush borders, indented nuclei, and numerous apical endocytic vesicles and lysosomes. A second cell type possessing clusters of apical cilia and lacking brush border and lysosomes is occasionally found between PI cells. The second proximal segment (PII) is formed of high columnar cells with brush border, regular spherical nuclei and numerous mitochondria located between well developed infoldings of the basal membrane. Single ciliary structures protrude into the lumen from PI and PII cells. The distal segment is lined by low columnar epithelium with few microvilli, regular spherical nuclei, numerous scattered mitochondria, and microbodies. The collecting tubule cells are cuboidal with few euchromatic nuclei, some mitochondria, and secondary lysosomes.
The pharyngeal jaw apparatus of labrid fishes: A functional morphological perspective
Authors: Liem Karel F. , Sanderson S. Laurie 
Published: February 2005

AbstractAmong the acanthopterygian fishes, the Labridae possess the most highly integrated and specialized pharyngeal jaw apparatus. The integrated feature involves many osteological components and aspects of muscle form, architecture, composition, and function. The upper jaw articulates by means of a true diarthrosis with the pharyngeal process of the parasphenoid, whereas the lower jaw has established physical contact with the cleithrum. Complex muscle fusions have contributed significantly in the development of a double muscle sling operating the lower jaw. The original levator externus 4 fuses with the central head of the obliquus posterior, whereas the original levator posterior combines with the lateral head of the obliquus posterior as well as with the adductor branchialis 5.During the masticatory cycle, both upper and lower jaws undergo complex movement orbits resulting in shearing and crushing functions. Shearing occurs as the forward moving upper jaw collides with the dorsally held lower jaw. Crushing is effected by an extreme posterodorsal movement of the lower jaw against the retracted upper jaw, thereby establishing full occlusion of the teeth.The specialized morphological and functional design of the labrid pharyngeal jaw apparatus is similar to that found in cichlids. In sharp contrast to primitive acanthopterygian fishes, the Labridae and Cichlidae exhibit a spectacular morphological diversity that parallels their ecological diversification. Our combined functional and historical analysis has established a correlation between the complex integration of the pharyngeal jaw apparatus and morphological and ecological diversity in the Labridae and Cichlidae.
Ultrastructure of the dental epithelium and odontoblasts during enameloid matrix deposition in cichlid teeth
Authors: Prostak Kenneth , Skobe Ziedonis 
Published: February 2005

AbstractTeleost enameloid matrix has been proposed to be an ectodermal, mesodermal, or joint ectodermal‐mesodermal product. To determine its origin we examined the ultrastructure of the inner dental epithelium (IDE), odontoblasts, enameloid, and dentin matrices of cichlid tooth buds at the stage of enameloid formation. © Alan R. Liss, Inc.Columnar IDE cells had apical and basal terminal webs and contained organelles associated with protein synthesis, including elongated secretory granules containing fibrillar material having cross‐striations with 60‐nm periodicity. The morphology of IDE secretory granules was typical of procollagen granules observed in a large variety of ectodermal and mesodermal cells synthesizing collagen. In contrast, the paucity of secretory granules within three odontoblast types indicates that these cells probably do not synthesize enameloid matrix. These observations are consistent with the idea that the bulk of the enameloid matrix is itself an ectodermal collagen synthesized and secreted by IDE cells.
Morphological and fine structural features of the basilar papilla in ambystomatid salamanders (amphibia; caudata)
Authors: White James S. 
Published: February 2005

AbstractThe morphology and fine structure of the basilar recess and basilar papilla were investigated in four species of salamanders from the family Ambystomatidae. The otic relationships of the recess and papilla to the proximal part of the lagena and saccule are described, and new terminology is suggested for the periotic relationships of the basilar recess to a diverticulum of an intracapsular periotic sac. The basilar papilla consists of supporting cells united laterally by gap junctions, capped by microvilli uniformly arranged around a short, central cilium, and hair cells that typically show several synapses with a single afferent nerve fiber, each marked by a rounded synaptic body surrounded by vesicles. In contrast to anuran basilar papillae, efferent nerve terminals were observed in synapse with hair cells and, rarely, upon afferent fibers. The distal half of the ambystomatid papilla contained hair cells capped by tall ciliary bundles, with kinocilia that show swellings near their tips with delicate attachments to adjacent tall stereocilia. A tectorial body covers only this region of the papilla. Hair cells with shorter stereocilia, situated in the proximal half and at the papillar margins, are related only to filamentous extensions of the tectorial body. The ambystomatid basilar recess and papilla are compared to auditory end‐organs in other vertebrates, and it is suggested that a basic distinction can be made between aural neuroepithelia in amniotes versus that in nonamniotic vertebrate ears.
Limb morphology of domestic and wild canids: The influence of development on morphologic change
Authors: Wayne Robert K. 
Published: February 2005

AbstractBiomechanical hypotheses are often invoked to explain the characteristic scaling of limb proportions. Patterns of static allometry and morphologic diversity, however, may also reflect the developmental mechanisms underlying morphologic change. In this study I document the importance of such developmental influences on the evolution of limb morphology in the extremely polymorphic domestic dog and in wild canid species. I use bivariate and discriminant function analyses to compare the limb morphology of adult dogs and wild canid species. I then compare ontogenetic allometry of four dog breeds with static allometry of domestic and wild canids.Results reveal, first, that there is considerable similarity between dogs and wild canid species; many wolf‐like canids cannot be distinguished from domestic dogs of equivalent size. However, all dogs are consistently separated from fox‐sized, wild canids by subtle but evolutionarily significant differences in olecranon, metapodial, and scapula morphology. Second, in domestic dogs the pattern of static allometry is nearly identical to that of ontogenetic allometry. This finding can be attributed to simple heterochronic alterations of postnatal growth rates. Apparently the diversity of limb proportions among adult domestic dogs and the observed difference between dogs and wild canids are somewhat predetermined, as they directly reflect the diversity of limb proportions evident during development of the domestic dog.
Egg capsules of a parasitic turbellarian flatworm: Ultrastructure of hatching sutures
Authors: Shinn George L. , Cloney Richard A. 
Published: February 2005

AbstractEgg capsules of Syndisyrinx franciscanus, an intestinal parasite of sea urchins (Strongylocentrotus spp.), consist of a bulb, which contains the embryos, and a stalk‐like filament. The wall of the bulb is about 12 μm thick and is composed of sclerotized proteins. The end of the bulb opposite the attachment of the filament bears a reticulum of hatching sutures. Transmission electron microscopy discloses that hatching sutures traverse the entire thickness of the capsule wall. The inner 9‐10 μm of sutures are a uniform 20 nm in width and contain a trilaminar cementum. The outer 2‐3 μm of sutures are 15 nm to more than 500 nm in width and contain an electron‐lucent cementum. The latter may contain an irregular, median, electron‐dense layer or, more commonly, electron‐dense granules. The outside of some capsules is partially covered by a thin, electron‐dense material.A previous study showed that sutures in intact capsules of Syndisyrinx franciscanus are not affected by host digestive fluids, but are severely weakened immediately prior to hatching owing to activities of the embryos. The hypothesis that the embryos secrete a hatching enzyme is supported by findings that sutures of intact capsules are not affected by externally applied trypsin, but become weakened when capsules are cut open and then incubated in trypsin. Scanning electron microscopy reveals that the outer parts of sutures often remain intact after hatching. We hypothesize that the ability of sutures to resist enzymatic attack from the outside, but not the inside, results from differences in the chemical properties of the cementums in outer and inner parts of sutures.
Electron microscopy of the dorsomedial cortex in the lizard Psammodromus algirus
Authors: Guirado S. , Dávila J. C. , De La Calle A. , Marín‐Girón F. 
Published: February 2005

AbstractThe cellular populations and the plexiform layers of the dorsomedial cortex of Psammodromus algirus are described at the ultrastructural level. Solitary globous cells are located in the outermost layer of the cortex, the superficial plexiform layer. Double pyramidal cells of the cellular layer show uniform ultrastructural characteristics. Displaced double pyramidal cells, vertical fusiform cells, and globous cells are found in the deep plexiform layer. Two types of dendritic spines are described. Large spines may contain membranous sacs and mitchondira and are located at the upper third of the superifical plexiform layer; small spines do not contain organelles and are located throughout the entire cortex. Two types of axon terminals are widely distributed in both plexiform layers: terminals with only clear vesicles and terminals with both dense‐core and clear vesicles. Terminals with large dense‐core vesicles may be related to peptidergic synapses and are more frequent at the upper levels of the superficial plexiform layer. The neuroglia described in the dorsomedial cortex of Psammodromus are protoplasmatic astrocytes and oligodendrocytes.
Use of a monoclonal antibody to classify neurons isolated from the head region of Hydra
Authors: Yu Shang‐Ming , Westfall Jane A. , Dunne John F. 
Published: February 2005

AbstractA mouse monoclonal antibody (JD1) to Hydra attenuata using the peroxidase‐antiperoxidase (PAP) method revealed unipolar, bipolar, and multipolar sensory and ganglion cells in the head region of H. littoralis. Neurons isolated from macerated hypostomes and tentacles were classified according to the number of their cytoplasmic processes and the position of the cilium, when present, relative to the perikaryon. PAP‐stained sensory cells had an apical ciliary cone, whereas ganglion cells did not. Neurons with cytoplasmic processes longer than 50 μm stained faintly, whereas those with processes shorter than 50μm in length stained mainly dense brown. Unipolar neurons had an oval, crescent, round, or elliptic perikaryon with a single short axon. The perikaryal shape of bipolar neurons varied from round to tall triangular, short triangular, crescent, oval, or elliptic with two oppositely directed symmetric or asymmetric processes. Asymmetric processes were present in a bipolar sensory cell with a long apical cilium typical of gastrodermal sensory cells. One type of bipolar ganglion cell had a short perikaryal cilium. Another type had neurites longer than 50 μm. We found seven morphological variations of multipolar neurons, including one with an apical knob, two with a short perikaryal cilium, two with cytoplasmic loops near the perikaryon, one with perpendicular processes projecting from the major neurites, and one with a branched process longer than 50 μm opposite a tangled mass of neurites.
Ultrastructure and role of the lobster vas deferens in spermatophore formation: The proximal segment
Authors: Kooda‐Cisco M. , Talbot P. 
Published: February 2005

AbstractWe have examined the anatomy of the vas deferens of the lobster Homarus americanus and have described the structure of the proximal vas deferens (segments one and two). The two tubes of segment one descend from the testes and gradually merge into segment two. The epithelium of segment one has synthetic activity and appears to contribute to the sperm‐supporting matrix by exocytotic release of granules through its apical surface. The epithelium of segment two is also highly synthetic and secretes the primary spermatophore layer and part of the intermediate layer that surround the sperm mass. The trifoil shape of the extruded spermatophore is established through a change in height of some of the cells lining the lumen in segment two. Connective tissue and circular bands of striated muscle surround the epithelium of both segments.
Tympanohyal bone in toothed whales and the formation of the tympano‐periotic complex (Mammalia: Cetacea)
Authors: Oelschläger Helmut A. 
Published: February 2005

AbstractA tympanohyal bone is reported in dolphins for the first time. The exceptional occurrence of this element in the bottlenose dolphin (Tursiops truncatus) and its location in a furrow of the tympanic can be taken as a vestige of an ancestral conformation indicating that, in cetacean ancestry, uncoupling of the periotic from the mastoid must have taken place laterally and dorsally to attachment of the hyoid arch and the stylomastoid foramen. There is a good correspondence between morphology and topographical relations of structures surrounding the facial canal in toothed whales and terres‐trial mammals (especially perissodactyls and artiodactyls).During early cetacean evolution, the tympanic had to undergo strong modification because of its functional correlation with the periotic. In precetaceans, the tympanic was probably loosely attached to neighboring skull bones, while at the same time it was suspended from the periotic via the tympanohyal. The earliest known cetaceans obviously lost this indirect osseous suspension but retained the peripheral attachments of the tympanic. In advanced archeocetes, two of these attachments are maintained but have shifted onto the periotic. In modern dolphins, the tympanic is in firm osseous contact exclusively with the periotic (tympano‐periotic complex). Both elements are isolated from the skull acoustically and form a separate mechanical unit specialized for high‐frequency underwater sound perception.
Chiton integument: Development of sensory organs in juvenile Mopalia muscosa
Authors: Leise Esther M. 
Published: February 2005

AbstractThe girdle epidermis of adult Mopalia muscosa secretes several types of structures, including calcareous spicules and innervated hairs. Newly metamorphosed chitons superficially resemble adult animals, but they lack the adult girdle ornaments, shell sculpture, and coloration. The morphogenesis of the adult girdle structures has not been described previously for any species. Juvenile Mopalia muscosa secrete hairs at metamorphosis, but it was not known if these hairs were sensory or if they were retained as the animals grew. I discovered that the hairs of juveniles become the tips of adult hairs. When juvenile hairs are detectable by light microscopy the sensory components already exist, suggesting that they are functional receptor organs. The other girdle ornaments of young juveniles, the primary calcareous spicules, are lost as the animal grows. I also demonstrated that the hairs are not uniquely innervated; the same sensory structures are produced in conjunction with other girdle ornaments on the marginal and ventral faces.