bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of embryonic anal processes in Girardinichthys viviparus (Cyprinodontiformes, Osteichthyes)
Authors: Schindler Joachim F. , De Vries Uwe 
Published: February 2005

AbstractScanning and transmission electron microscopy were used to examine the morphology of the perianal processes (trophotaeniae) of goodeid embryos (Girardinichthys viviparus) at two stages of gestation. The epithelial surface of trophotaeniae is composed of two cell types, one of which shows distinct features associated with absorptive activity. Such cells are characterized by microvilli, abundant mitochondria, and an agranular tubulolamellar network. Micropinocytosis at the apical surface is relatively rare. The brush border membranes contain high levels of alkaline phosphatase. The cells of the second type are the minor component of the trophotaenial epithelium. Their surface is distinct, due to the presence of microridges rather than microvilli. The reticulate arrangement of the cells gives rise to intercellular spaces which occasionally are very large. These interstices are populated with leukocytes. The histological appearance of these sections indicates that this tissue is involved in gas exchange. Embryos at very early stages of development possess similar epithelia which are differentiated to a lesser extent. The connective tissue in some parts of the processes shows structural modifications. It is densely packed with numerous leukocytes occupying the spaces between the cytyoplasmic ramifications of the stroma cells. Possible roles of the trophotaeniae in absorption, respiration, excretion, and the acquisition of immunity are discussed, and it is concluded that the perianal processes of the Goodeidae are more than just trophic embryonic structures.
Ultrastructural aspects of mouth formation in the starfish Pisaster ochraceus
Authors: Abed M. , Crawford B. J. 
Published: February 2005

AbstractEarly events during mouth formation in embryos of the starfish Pisaster ochraceus have been studied with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Embryos examined by TEM were fixed in glutaraldehyde with Alcian blue, a dye which preserves extracellular materials. Initially, mesenchyme cells migrate off the tip of the archenteron, leaving a defect in the cell layer that is covered by the basal lamina. This region of “naked” basal lamina bulges into the blastocoele and forms a hemispherical blister. At the same time that this is occurring, filamentous and conical processes extend from the inner surface of the presumptive stomodeal ectoderm cells which are located directly opposite the bulge of basal lamina. These processes penetrate the ectodermal basal lamina and project “naked” plasmalemma into the blastocoele. Shortly after this, the blister of endodermal basal lamina becomes irregular in shape, and scattered cells are found both within the blister and between it and the presumptive stomodeal ectoderm cells. Processes of endodermal cells appear to make contact with the filamentous processes of the stomodeal ectoderm cells. In other embryos which appear to be at a slightly later stage, the free basal lamina is conical in shape and is associated with at least one conical ectodermal process. In yet other embryos, the free endodermal basal lamina is either in contact with several other large processes forming a circular region of contact, or the free endodermal and ectodermal basal laminae are fused at the edge of the circle. Degeneration of both the ectodermal and endodermal basal laminae located within the circle, and subsequent invagination of the stomodeal ectoderm, appear to complete this process. The pulsations of stomodeal ectodermal cells seen throughout early stages in mouth formation may be involved in these events.
Ontogeny of cranial ossification in the eastern newt, Notophthalmus viridescens (Caudata: Salamandridae), and its relationship to metamorphosis and neoteny
Authors: Reilly Stephen M. 
Published: February 2005

AbstractThe ontogenetic sequence of cranial osteogenesis through adulthood is described in samples of newts from completely metamorphosing and partially neotenic populations. Cranial ossification proceeds in the same sequence in both samples. Seven stages of cranial development are described on the basis of conspicuous events that occur during ontogeny. These include four larval stages, metamorphs, efts, and adults. Neotenic adults have skulls that are metamorphosed completely and indistinguishable from the skulls of non‐neotenic adults. Neoteny in these newts does not involve the skull and is limited to the postmetamorphic retention of some gill structures and, thus, is termed “limited neoteny.” The evolution of limited neoteny in newts as a correlated response to the inhibition of land‐drive behavior is discussed.
The fibromuscular basket (sporta perimedullaris musculosa) in renculi of kidneys from the ringed seal, Phoca hispida (Pinnipedia)
Authors: Newstead J. D. , Munkacsi I. M. 
Published: February 2005

AbstractThe medulla of renculi from kidneys of Ringed seals (Phoca hispida) is completely enclosed by cortex except at the hilum. Within the renculus, the fibromuscular coat of the calyx separates from the transitional epithelium at the level of the corticomedullary junction, where the intrarencular arteries also diverge into the parenchyma. Flat ribbons of this stromal tissue form an arborized framework near the medullary side of the intrarencular arteries and the larger of the arcuate arteries derived from them. The ribbons, which are clearly distinct from periarterial connective tissue, are composed of coarse collagenous fibers, elastic fibers, and smooth muscle cells, all oriented in the direction of the long axes of the ribbons, and myofibroblasts. The proportion of smooth muscle cells decreases and that of myofibroblasts increases with increasing distance from the calyx. At the base of the medullary pyramid, the elements of the framework diminish in width and ultimately blend with the surrounding interstitial tissue. The stromal framework, or basket, is homologous with the Sporta perimedullaris musculosa of cetacean kidneys.
Morphology of the green livers in upstream migrants of Petromyzon marinus L.
Authors: Youson J. H. , Sargent P. A. , Ogilvie D. , Shivers R. R. 
Published: February 2005

AbstractA morphological comparison was made of the green livers of male and female lampreys (Petromyzon marinus L.) collected during the upstream (prespawning) migration. Light and electron microscope histochemistry for iron, and both thin sections and freeze‐fracture replicas in the electron microscope, revealed some sexual dimorphism in these livers. Ferric iron is much more abundant in the liver of females and is present in the cytoplasmic matrix, in dense bodies, and in vacuoles of hepatocytes. The numerous vacuoles of females may be the deposition site of biliverdin and other bile components that would account for the darker green coloration of the liver compared to males. Hepatocytes in females are also characterized by prominent rough endoplasmic reticulum and Golgi apparatus that reflect the involvement of the cells in vitellogenesis. The presence of numerous lipid droplets in the hepatocytes of males indicates that the liver is an important storage site for fat. The lipid droplets are associated with electron‐dense deposits of unknown nature. Large gap junctions typify the parenchymal cells of both male and female livers. Perisinusoidal and sinusoidal cells are similar to those in the nonparenchymal region in other vertebrate livers, namely, endothelial and Kupffer cells, lipocytes (Ito), and some granulated cells. The relationship of lipocytes to fibrous tissue and fibrogenesis is discussed.
The morphology of Idiocranium russeli (amphibia: Gymnophiona), with comments on miniaturization through heterochrony
Authors: Wake Marvalee H. 
Published: February 2005

AbstractIdiocranium russeli is among the smallest species of caecilians. The morphology of the skull (e.g., small, widely spaced dermal elements, retention of cartilaginous remnants) and of the posterior vertebrae (incomplete development, retention of a postvertebral notochord) indicate that heterochrony, or change in timing of development, has resulted in the miniaturization of the species. The pattern is apparently a progenetic one, characterized by early offset of development (see Alberch et al., 1979). Other unique features of osteology (e.g., extensive sphenethmoid development) correlate with the burrowing habit of the species and may have arisen to compensate for progenetic effects. Several features of the myology, neurology, and visceral morphology are correlated with miniaturization as well. Reproductive maturity occurs at approximately 75 mm total length; gonads are proportionately small, but other aspects of reproductive morphology are typical of direct‐developing caecilians.
Fine structure of the hemocytes and nephrocytes of Argas (Persicargas) arboreus (Ixodoidea: Argasidae)
Authors: Shoura Samir M. El 
Published: February 2005

AbstractThe fine structure of the hemocytes and nephrocytes in Argas (Persicargas) arboreus is described and compared with that of similar cells in other tick species and insects. The hemocytes are of three types: prohemocytes, with a relatively undifferentiated cytoplasm lacking granular inclusions and probably serving as progenitors of the other hemolymph cell types; plasmatocytes, containing abundant mitochondria, cisternae of rough endoplasmic reticulum (RER), and free ribosomes, as well as some small granular inclusions; granulocytes, the predominant cell type in the hemolymph, containing numerous granules of variable electron density and maturity, and pseudopodia‐like processes on the cell surface. Plasmatocytes and granulocytes are phagocytic and possibly also have other functions in the tick body. Cells with intermediate features appear to be in a stage of transition from plasmatocyte to granulocyte.Nephrocytes contain vacuoles enclosing fibrillar material, some electrondense granules, and moderate amounts of the active organelles—mitochondria, RER, and ribosomes. The nephrocyte is surrounded by a basal lamina and its plasma membrane infolds to form many deep invaginations coated by a fine fibrillar material. Openings to these invaginations are closed by membranous diaphragms. Coated tubular elements connect the surface invaginations with large coated vesicles, which appear to be specialized for internalization of proteins from the hemolymph. The dense granules may represent an advanced stage of condensation of ingested protein and thus may be lysosomal residual bodies, or they may develop by accumulation of secretory products.
Mastication in the musk shrew, Suncus murinus (mammalia, Soricidae)
Authors: Dötsch Christel 
Published: February 2005

AbstractHigh‐speed cinematography shows that Suncus murinus (Crocidurinae) masticates fast (mean 5.5, 5–10 masticatory cycles per sec). Their grasping behavior is not stereotyped. The unilateral mandibular movements combine vertical, anteroposterior, and lateral displacements; and any masticatory sequence may include crushing, repositioning, shearing, and grinding components. Size and consistency of food influence the duration of individual chewing cycles. As food is transferred to the new working side, the chewing direction reverses, either near maximum closure or near maximum opening. An unfused mandibular symphysis permits tilting movements of the two halves of the mandible. Food may be squeezed between the lower incisors. The working side tilts outward during closing; this may improve shearing or grinding action. The closing phase is posteriorly directed. Thus, the masticatory movements of these shrews differ from those that have been described in many other mammals.
Adrenergic innervation of the gills, pulmonary arterial plexus, and dorsal aorta in the neotenic salamander, Ambystoma tigrinum
Authors: Malvin Gary M. , Dail William G. 
Published: February 2005

AbstractThe presence of adrenergic innervation was investigated in four different vascular segments of the neotenic tiger salamander, Ambystoma tigrinum, by histofluorescent staining for catecholamines. The segments were the respiratory section of the gill, the branchial shunt vessels, a vascular plexus in the pulmonary artery, and the dorsal aorta. No adrenergic fibers were detected in the respiratory section of the gill or the pulmonary arterial plexus. In contrast, the branchial shunt vessels contained both adrenergic varicosities and catecholamine‐containing cell bodies. These cells resemble Type I cells of the mammalian carotid body and amphibian carotid labyrinth. Adrenergic innervation of the dorsal aorta was sparse and restricted to the adventitia. The results suggest that adrenergic nerves may directly regulate blood flow in the gill, and thus gas exchange, by controlling vascular resistance of the branchial shunts. The contractile state of the dorsal aorta may also be under adrenergic control. In addition, it is suggested that the adrenergic cells of the branchial shunts may serve a receptor function in being sensitive to arterial blood gases.
Fine structure of the doliolaria larva of the feather star Florometra serratissima (Echinodermata: Crinoidea), with special emphasis on the nervous system
Authors: Chia Fu‐Shiang , Burke Robert D. , Koss Ron , Mladenov Philip V. , Rumrill Steven S. 
Published: February 2005

AbstractThe epidermis of the doliolaria larva of the Florometra serratissima is differentiated into distinct structures including an apical organ, adhesive pit, ganglion, ciliary bands, nerve plexus, and vestibular invagination. All these structures possess unique cell‐types, suggesting that they are functionally specialized in the larva, except the vestibular invagination that becomes the postmetamorphic stomodeum. The epidermis also contains yellow cells, amoeboid‐like cells, and secretory cells. The enteric sac, hydrocoel, axocoel, and somatocoels have differentiated but are probably not functional in the doliolaria stage. Mesenchymal cells, around the enteric sac and coeloms, appear to be actively secreting the endoskeleton and connective tissue fibers.The nervous system is composed of a nerve plexus, ganglion, and sensory receptor cells in the apical organ. The apical organ is a larval specialization of the anterior end; the ganglion is located in the base of the epidermis at the anterior dorsal end of the larva. The nerve plexus underlies most of the epidermis, although it is more prominent in the anterior region. Here, processes from sensory receptor cells of the apical organ, as well as those from nerve cells, contribute to the plexus. These processes contain one or a combination of organelles including vesicles, vacuoles, microtubules, and mitochondria. The configuration of glyoxylic acid‐induced fluorescence, revealing catecholamine activity, correlates to the apical organ, nerve cells, and nerve plexus. Morphological evidence suggests that the nervous system may function in initiation and control of settlement, attachment, and metamorphosis. The crinoid larval nervous system is discussed and compared to that found in other larval echinoderms.
Mechanical factors in the evolution of the mammalian secondary palate: A theoretical analysis
Authors: Thomason J. J. , Russell A. P. 
Published: February 2005

AbstractThe secondary palate of mammals is a bony shelf that closes the ventral aspect of the rostrum. The rostrum, therefore, approximates to a tapered semicylindrical tube that is theoretically a mechanically efficient structure for resisting the forces of biting, including the more prolonged bouts of mastication typical of mammals. Certain mammal‐like reptiles illustrate stages in the development of the palate in which the shelves projecting medially from each premaxilla and maxilla do not meet in the midline. We evaluate several geometric properties of sections through the rostrum of the American opossum (Didelphis virginiana). For loading at the incisors and canines, these properties indicate the structural strength and stiffness in both bending and torsion of the rostrum and of single maxillae. We then repeat the analysis but progressively omit segments of the palatal shelf, a procedure which simulates, in reverse, the evolutionary development of the structure. The results demonstrate that the secondary palate contributes significantly to the torsional strength and stiffness of the rostrum of Didelphis and to the strength of each maxilla in lateromedial bending. The major evolutionary implications of the results are that the rapid increase in rostral strength with small increments of the palatal shelves may have been a significant factor in the development of the complete structure. The results indicate that there was a marked jump in torsional strength and stiffness when the shelves met in the midline, which is likely to have been important in the subsequent development of the diverse masticatory mechanisms of cynodonts and mammals. On the basis of this analysis the mammalian secondary palate may be interpreted as one of a number of methods, seen in the mammal‐like reptiles, for strengthening the rostrum.
A morphological analysis of the ampullae of Lorenzini in selected skates (Pisces, Rajoidei)
Authors: Raschi William 
Published: February 2005

AbstractA comparison of the ampullae of Lorenzini among 40 species of skates (Rajoidei) demonstrates a close relationship between inferred electroreceptive capabilities and feeding mechanisms. Three general lines of morphological modifications are noted. (1) Whereas the majority of ampullary pores are located on the ventral surface of the dorsoventrally flattened body, the relative proportion of ventral pores is significantly lower on species inhabiting aphotic waters. (2) The ventral pores on more piscivorous species are distributed over a larger portion of body surface than they are on those species that feed primarily on invertebrates. Ventral pores in this latter group are more noticeably concentrated around the mouth and their densities on the adult are inversely related to the overall mobility of preferred prey species. (3) The size of each ampulla and the number of alveoli associated with it are directly related to the habitat depth occupied by each species. Shallow‐water species have smaller ampullae with fewer alveoli than deeper‐dwelling (> 1,000 m) species.The general distribution of ampullary pores on deep dwelling rajoids appears to compensate for reduced visual input, whereas their relative densities are a measure of the system's resolution and reflect major differences in feeding strategies. The increased ampullary size and complexity observed in deep‐sea rajoids provides mechanisms to increase both the sensitivity and signal‐to‐noise ratios.
Evolutionary trends in adrenal gland of anurans and urodeles
Authors: Milano Elena Grassi , Accordi Fiorenza 
Published: February 2005

AbstractMorphological, histological, ultrastructural, and developmental research on the adrenal gland of several species of anurans and urodeles belonging to different families is presented. Urodeles show a large variability in adrenal glandular structure without a clear taxonomic pattern, although increased compactness of the gland and mingling of steroidogenic and chromaffin cells are found only in some neourodeles. In anurans the glandular pattern may be divided into two subtypes: one more medial and diffuse, which is observed in frogs of the more primitive families; the other more lateral and aggregated, as seen in the more advanced families. The adrenal gland therefore increases in its compactness and aggregation of chromaffin and steroidogenic tissues in the transition from primitive to advanced families, both in urodeles and anurans. Until the end of metamorphosis, morphogenesis of the gland is similar in all amphibians studied. This process is extended after metamorphosis in the advanced anurans, in order that the gland may reach its definitive position.
Composition and ultrastructure of the byssus of Mytilus edulis
Authors: Benedict Christine V. , Waite J. Herbert 
Published: February 2005

AbstractThree regions of the byssus of the marine mussel Mytilus edulis L. are distinct in structural organization at the macroscopic and microscopic level and in amino acid composition. The threads that emanate from the stem at the base of the foot are divided into two regions. The proximal, elastic region has a crimped, densely staining cortex enclosing an interior matrix of spiral fibers, and its amino acid composition reflects protein heterogeneity. The more distal, rigid region has a straight, tubular cortex surrounding an inner matrix of linearly arranged bundles of fibrils and has a composition approximating pure collagen. The plaque, or disc‐shaped portion, which mediates attachment to various substrates, is distinguished by a surface matrix of collagen‐like fibers similar to those of the thread region and anchored on an inner spongy matrix. Compositional evidence exists for a collagenous component, a catechol‐rich protein, and at least one other accessory protein in the plaque.
Synthesis of the mesoglea by ectoderm and endoderm in reassembled hydra
Authors: Epp Leonard , Smid Iris , Tardent Pierre 
Published: February 2005

AbstractThe structure and synthesis of the mesoglea was investigated in “reassembled” hydra—hydra regenerating from ectoderm and endoderm previously isolated from each other and then recombined. During tissue isolation and reassembly the mesoglea remains attached to the endoderm. It is observed to be quite elastic and resilient. The mesoglea disappears by 6–8 hr after reassembly, having apparently been digested by endoderm. “New” mesoglea is undergoing synthesis by 12 hr after reassembly. It trilaminar appearance at this time suggests an origin from both epithelia. Interepithelial contact, by cell processes of epithelial cells, is reestablished within the mesoglea between 24 and 48 hr after reassembly. Mesoglea appears normal 48 hr after reassembly. Autoradiographic experiments, performed during the reassembly manipulations, conclusively demonstrate that the mesoglea originates from both epithelia. Mesoglea precursors, amino acids, are incorporated within the mesoglea about 5–6 hr after initial acquisition by epithelia, but subsequent turnover of these amino acids is slow.
Differentiation of worker‐derived intercastes and precocious imagoes after queen removal in the Neo‐Guinean termite Nasutitermes princeps (Desneux)
Authors: Roisin Yves , Pasteels Jacques M. 
Published: February 2005

AbstractNumerous female workers underwent a beginning of sexualization in an experimentally orphaned colony of the Neo‐Guinean termite N. princeps (Desneux). This led to the development of intercastes, displaying variable mosaics of worker, nymph, and soldier characteristics. The developmental pathways of these intercastes were studied with the help of multivariate techniques that revealed two main lines, one ending in a new “giant soldier” morph, the other proceeding toward the differentiation of nymphal characters, i.e., wing pads and compound eyes. It is not known whether these individuals might ultimately have become functional. Precocious adults resulting from a shortened nymphal course were also present, and one young replacement queen had already begun laying eggs.