bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gut‐associated lymphoid tissue (GALT) of the goldfish, Carassius auratus
Authors: Temkin Robert J. , McMillan Donald B. 
Published: February 2005

AbstractThe head kidney and spleen are major sites of haemopoiesis in fish; a secondary center is found in loose connective tissue of the intestine. In this study we determined the nature of gut‐associated haemopoietic tissue in the goldfish, Carassius auratus, using light and electron microscopy. This tissue is a loose stroma of reticular cells and fibers vascularized by capillaries, venules, and arterioles. The cellular population includes lymphoblasts, small and medium‐sized lymphocytes, plasmocytes, macrophages, and various granulocytes. The most abundant granulocyte is the mast cell, whose large granules stain with Alcian blue and toluidine blue. Heterophils are found in the intestinal connective tissue as well as two other granulocytes: one with ovoid granules having dense parallel lamellae and another with granules containing crystalline inclusions. Immature forms of both granulocytes were also noted. Macrophages containing phagocytosed debris were often located close to the epithelium; they were observed forming clusters with lymphocytes. The epithelium contained a number of migrating leucocytes including lymphocytes and lymphoblasts, macrophages, and heterophils. Although many granulocytes were found in the connective tissue, granulopoiesis does not seem to be a major function. Gut‐associated haemopoietic tissue in goldfish resembles diffuse lymphoid tissue and may be involved in intestinal immune responses.
Comparative morphology of the amphibian opercularis system: I. General design features and functional interpretation
Authors: Hetherington Thomas E. , Jaslow Alan P. , Lombard R. Eric 
Published: February 2005

AbstractThe morphology of the opercularis system of anuran and caudate amphibians suggests that it acts to produce motion of the operculum that in turn produces fluid motion within the inner ear. The operculum and opercularis muscle form a lever system, with a narrow connection between the operculum and otic capsule acting as a fulcrum about which the operculum moves in response to forces applied via the muscle. The opercula of many species possess a muscular process on which the muscle inserts, thereby increasing the moment arm through which the muscle acts. The tonicity of the opercularis muscle allows tensile forces produced by substrate vibration or other mechanical energy applied to the forelimb to be effectively transmitted to the operculum; the elasticity of the connective tissue holding the operculum in place should act to return the operculum to its original position. The opercularis systems of frogs and non‐plethodontid salamanders are similar structurally and functionally; that of plethodontid salamanders is structurally distinct but also functions as a lever system. Fluid motion produced by opercular motion could stimulate various end organs of the inner ear; the saccule, lagena, and amphibian papilla are in close approximation and wave energy could directly affect their otoconial or tectorial structures. In those anurans with a tympanic ear, the stapedial footplate and operculum articulate, but this articulation allows both to move independently. The stapes‐tympanum complex and opercularis system therefore appear to be independent functional systems, and it is unlikely that the opercularis system modulates middle ear responsiveness. The general design of the opercularis system is consistent with a function in reception of substrate vibrations.
Fine structure and development of the sperm of the tickOrnithodoros(Pavlovskyella)erraticus(ixodoidea, argasidae)
Authors: El Shoura Samir M. 
Published: February 2005

AbstractSperm development inOrnithodoros (Pavlovskyella) erraticusincludes the formation of subsurface cisternae in the primary spermatocytes, which divide meiotically to secondary spermatocytes and ultimately to spermatids. During spermiogenesis the spermatid undergo morphological transformation including polarization of the nucleus and subsurface cisternae, formation of a cisternal tube, and modification of the subsurface cisternae to cellular processes surrounded by cisternal vesicles. Further transformation occurs after spermatids are introduced into the female. The spermatid cisternal tube now invaginates to form an inner cord surrounded by an outer sheath. The invaginated inner cord elongates anteriorly as the outer sheath continues to invaginate posteriorly during spermiogenesis. With further elongation, the spermatid membrane ruptures anteriorly, leaving the inner cord exposed as the outer surface of the maturing sperm. Posteriorly, the original plasma membrane invaginates to form an acrosomal canal which becomes surrounded by an acrosome. The hemispherical anterior end of the mature sperm is covered with rows of projections separated from the remainder of the sperm by a row of fringed processes. Except for the posterior end, the rest of the sperm is covered by longitudinally distributed electron‐dense cellular processes and an outer mat of more electron‐lucent tubular elements. Mitochondria and bundles of microfibrils are found beneath the cellular processes. Microfibrils are suggested to be the principal contractile organelles responsible for sperm motility. Cellular processes appear to be the main external motile structures, while movements of tubular elements and fringed processes may also contribute to sperm motility.
On the allometry of long bones in dogs (Canis familiaris)
Authors: Casinos A. , Bou J. , Castiella M. J. , Viladiu C. 
Published: February 2005

AbstractThe allometric relations of diameter and length of humerus, ulna, femur, and tibia of 108 specimens, from 63 different breeds of dogs and 12 specimens of wolves, were calculated by means of model II of regression or major axis method. Only for the tibia were the values of wolves included in the cluster formed for dog breeds. Consequently, separate lines of regression were calculated for the other bones.Results agree in general with the exponents predicted by the theory of geometric similarity; however, the slope obtained for femur (0.865) differed significantly from this. Morphology of the long bones of the legs does not differentiate dogs and wolves; this probably reflects secondary convergence among wolves with relatively modern breeds of dogs.
Embryogenesis of a springtail, Tomocerus ishibashii (Collembola, tomoceridae): External morphology
Authors: Uemiya Hideyuki , Ando Hiroshi 
Published: February 2005

AbstractThe external features of the developing embryos of the springtail, Tomocerus ishibashii, are described. The clypeolabral anlage arises as a single, unpaired swelling. The entognathy is completed by the ventral growth of the tergal anlagen of mandibular, maxillary, and labial segments. These anlagen also form the posterior part of the cranium. The palpi of maxilla and labium are homologous with the telopodites, and proximal parts of these head appendages are homologous with the coxopodites. The sternal element of the labial segment does not participate in the postmentum formation. The anlagen of abdominal appendages appear in the first to the fourth abdominal segments. The first, third, and fourth appendage anlagen form the ventral tube, tenaculum, and furcula, respectively. The fused proximal parts of the first, third, and fourth appendage anlagen are homologous with the coxopodites, and the distal parts which do not fuse are homologous with the telopodites. The anlagen of the second abdominal appendages become flattened and spread over the ventral side of this segment. The ventral structures of the first four abdominal segments are appendicular in origin.
Ontogeny of the hyobranchial apparatus in the salamanders Ambystoma talpoideum (Ambystomatidae) and Notophthalmus viridescens (Salamandridae): The ecological morphology of two neotenic strategies
Authors: Reilly Stephen M. 
Published: February 2005

AbstractComparison of metamorphosis of skull and hyobranchial system in two species of neotenic salamanders reveals two different types of neoteny. Ambystoma talpoideum is completely neotenic owing to delayed metamorphosis. Notophthalmus viridescens exhibits limited neoteny as a result of incomplete metamorphosis. Morphological details of neoteny are compared to life history in both species in order to discuss the ecological morphology of the two neotenic strategies. Comparisons to Taricha granulosa, Triturus vulgaris, and Ambystoma gracile indicate that these two strategies are widely employed and may represent familial patterns.
Ultrastructure of the venous ampulla in the interradicular microvascular bed of the mandibular molars ofMus musculus
Authors: Sims M. R. 
Published: February 2005

AbstractThe interradicular periodontal ligament of mandibular molars contains an apparently unique dilated vessel straddling the interradicular alveolar bone. This structure is designated a venous ampulla. The vessel possesses a luminal length and width of approximately 200 × 100 μm, respectively. Ultrastructurally, the endothelium has an average thickness of 0.35μm, a continuous basement membrane, and an incomplete layer of pericytes. Open endothelial junctions are not present. The anatomy of the vessel wall differs markedly on the dental‐ and bone‐related aspects. Calculated ratios for the luminal diameter to wall thickness vary from 1:80 to 1:150. Postcapillary‐sized limbs from this vessel drain into the interradicular septum of bone and the ligament microvascular bed. Arterial supply to the ampulla is provided via arteriovenous anastomoses characterized by their association with myelinated and unmyelinated nerve groups.Oxytalan fibers are present throughout the wall of the venous ampulla, penetrating to the abluminal side of the endothelium where they are associated with unmyelinated axons and free nerve endings. Elsewhere, oxytalan fibers are related to the arteriovenous anastomoses and their accompanying myelinated and unmyelinated nerves located adjacent to the endothelium. Pericytes form membranous contacts with the endothelium of the arteriovenous anastomoses and have processes penetrating the endothelium basement membrane.
Ultrastructural and quantitative dynamics of the granulosa of ovarian follicles of the lizard gerrhonotus coeruleus (family anguidae)
Authors: Klosterman Lorrie L. 
Published: February 2005

AbstractThe progression of ovarian follicular development in the Northern Alligator Lizard has been documented ultrastructurally and by enumeration of cells, with a focus on changes in the granulosa component of the follicle. The pattern of cellular differentiation of the granulosa entails, as in other lizards, the transformation of a simple, cuboidal epithelium in small follicles into a complex layer consisting of three types of cells. Marked differences in size and ultrastructure of the cell types indicate different functional states: the smallest cells are little differentiated and serve primarily as stem cells to other granulosa cells throughout follicular growth, whereas the larger “intermediate” and “pyriform” cells do not divide and show ultrastructural features indicative of synthetic activity. Contrary to some views that this latter cell type is the final step in cellular differentiation and provides organelles and cytoplasm to the oocyte through an intercellular bridge, the results of this study suggest that only relatively small molecules such as ribosomal RNA might pass between cells. Further, these observations support the interpretation that a heterogeneous granulosa results from the fusion in early follicular stages of some cells that are in surface contact with the oocyte. Several of the cytological features of the larger granulosa cell types are seen in the oocyte and in germ‐line cells generally, such as highly dispersed chromatin, large nucleoli, abundant nuclear pores, mitochondrial “rosettes,” annulate lamellae, “ribosome bodies,” and surface microvilli. This strongly suggests that the cytology of large granulosa cells is induced by the oocyte. The heterogeneous granulosa persists only through previtellogenesis and at the onset of exogenous yolk uptake by the oocyte it becomes a secondarily homogeneous layer. The appearance of the granulosa at this stage is similar to that of reptiles whose granulosa remains a single‐cell layer throughout folliculogenesis (e.g., turtles and crocodilians). Thus, although follicular development has been scrutinized in only a few representative genera of reptiles to date, the course of follicular development among lizards is similar in detail and involves the transitory development of a heterogeneous population of cells. This feature appears to be exclusive to the squamate reptiles.
Spicule formation in the solitary ascidian, herdmania momus
Authors: Lambert Gretchen , Lambert Charles C. 
Published: February 2005

AbstractTwo types of calcareous spicules occur abundantly in Herdmania momus, a solitary pyurid ascidian with a worldwide warm water distribution. The large spindle‐shaped body spicules are 1.5–2.5‐mm long and are located primarily in the mantle, siphons, and branchial basket. Each body spicule possesses 100 or more rows of overlapping, unidirectional fringing spines. Numerous body spicules occur regularly spaced within a long common sheath of complex structure, and there are many sheaths per animal. Between neighboring body spicules and overlying the fringing spines are the tightly connected pseudopodial sclerocytes. Spine formation is hypothesized to occur within these cells. The body spicules apparently continue to increase in size throughout the animal's life.The tunic spicules are about one tenth the length of the body spicules. They have 20–40 rows of unidirectional nonoverlapping fringing spines and a mace‐shaped spiny base that anchors them at the tunic surface. They form quickly in individual spicular envelopes inside the tunic blood vessels over a 4–5‐day period. Each tunic spicule then leaves its surrounding envelope and blood vessel, passes into the tunic, and ultimately protrudes through the outer surface of the tunic. An organic covering inside the envelope closely adheres to the tunic spicules and stains with toluidine blue. Dissolution of the CaCO3 mineral phase by EDTA or EDTA‐cetylpyridinium chloride‐formaldehyde reveals an intricately patterned organic matrix within or upon which the spicules develop.
Formation of the septate junction in regenerating planarian gastrodermis
Authors: Hori Isao 
Published: February 2005

AbstractSeptate junctions develop initially just basad from apical junctional complexes at the apical ends of regenerating gastrodermal cells. The first morphological indication of differentiation of the junction is the appearance of gentle undulations of the plasma membranes of apposing cells. Subsequently dense dots develop at fairly regular intervals at the cytoplasmic surface of one cell, while SER cisternae become localized opposite them near the surface of the apposing cell. The dense dots are associated with bulges which narrow the intercellular space. Later the dense dots are replaced by filaments aligned along the inner leaflet of the parent cell. Strands of amorphous deposits form connections between SER cisternae and the sister membrane on the opposite side of the junction. Ruthenium red staining provides information on precursors which occupy the intercellular space between the apposed plasma membranes. As development of the junction progresses, ruthenium red stains only the newly formed septa but not the interseptal matrix. Regular arrangement of individual septa seems to be completed under the control of V‐projections from both of their surfaces. Precursors for the structural material of the septa may be a secretory product derived from the SER. Dense dots and their derived filaments probably serve as reinforcing material for strengthening the cell membrane of the junction.
Ultrastructural investigations on the labral glands of Daphnia obtusa (Crustacea, Cladocera)
Authors: Zaffagnini F. , Zeni C. 
Published: February 2005

AbstractThe labral glands of Daphnia consist of three distinct functional units on each side: (1) several cells at the base of the head, (2) two large cells at the base of the labrum and one large cell (cell A) in the median part of the labrum and (3) one large cell (cell B) in the median part of the labrum. These gland cells do not form a syncytium, contrary to reports by previous investigators. With the exception of cell B, they have a well‐developed rough endoplasmic reticulum and many active Golgi complexes. The Golgi activity changes during the molt cycle. The Golgi activity of the cells of the head base is different from that of the large cells of the labrum. Since clear exocytotic phenomena were not observed, the secretion can be assumed to flow into the hemolymph after accumulation in the enlarged intercellular spaces. Cell B has a distinctive cytoplasmic ultrastructure the function of which is not yet understood.The four large cells of the labrum are in contact with a duct cell (or several duct cells) characterized by a deep infolding of the plasma membrane. This delimits a narrow lumen, which contains no secretion. No passage of substance is visible from the gland cells to the duct cell(s).
Morphology of the nervous and muscular systems in the heads of pedicellariae from the sea urchin Echinus esculentus L
Authors: Peters Brian H. , Campbell Andrew C. 
Published: February 2005

AbstractLight and electron microscopy reveal that simple receptor cells in the jaw epithelium of sea urchin pedicellariae are connected by nerve tracts to the neuropile that coordinates jaw movements. The muscles responsible for jaw opening and closure and for flexion of the stem are all innervated in this neuropile. At least two types of vesicles occur at the simple synapses between neurone profiles and at neuromuscular junctions. The muscles include both striated and smooth fibres; however, their distribution varies according to pedicellaria type, and an unexpected arrangement exists in trifoliate pedicellariae.
Model of jaw depression during feeding in Astatotilapia elegans (Teleostei: Cichlidae): Mechanisms for energy storage and triggering
Authors: Aerts Peter , Osse J. W. M. , Verraes W. 
Published: February 2005

AbstractSuction feeding in Astatotilapia elegans occurs by a series of rapid, coupled movements of various head parts. The lower jaw rotates with respect to the neurocranium through an angle of 62° in less than 15 ms. The power requirements for jaw depression are calculated from a mathematical model and may reach a peak of ±4 watt in a 12‐cm‐long specimen. Data from the literature on mechanical output of fish muscle suggest that a muscular volume equal to 44% of the volume of the fish (= 45 cm3) should be required, if it is premised that movement and muscle shortening are directly coupled. Therefore, we assumed that storage and release of strain energy must be considered. The work demands for depression equal 0.014 J. The amount of energy storable in only three pairs of head ligaments can be estimated between 0.008 J and 0.05 J. The use of strain energy implies initial blocking and subsequent triggering of the movement. The position of the hyalomandibular connection, dorsal to the mandibular‐suspensorial articulation, appears to be of crucial importance in balancing the forces of sternohyoideus and the body muscles. Triggering at the onset of jaw depression occurs by the contraction of the levator operculi. The line of action of the hyalomandibular connection is lowered beneath the jaw suspension, which raises the equilibrium of forces. Elastic recoil can occur thereafter.
Location of the rostral end of the longitudinal brain axis: Review of an old topic in the light of marking experiments on the closing rostral neuropore
Authors: Puelles L. , Domenech‐Ratio G. , Martinez‐De‐La‐Torre M. 
Published: February 2005

AbstractThe rostral end of the forebrain was classically defined on the basis of descriptive data. Different assumptions on the mode of closure of the rostral neuropore caused three different theories of the rostral end of the forebrain to be formulated (His 1893a; von Kupffer, '06; Johnston, '09). Some recent descriptive and experimental data have put these theories into question.A piece of black nylon thread was inserted through the rostral neuropore of chick embryos and was fixed to its ventral lip. These operations were done at all intermediate stages during the process of closure of the rostral neuropore. The embryos were sacrificed at a later stage, by which time the neuropore had disappeared.In the cleared specimens the threads always lay at the same site, namely the upper border of lamina terminalis, irrespective of the stage at which the marker was inserted. These results stand against His's conception ((1893a, b) of a sutura terminalis and support the single mechanism of sutura dorsalis during closure of the rostral neuropore. The marking data therefore imply that the topologic rostral end of the forebrain lies at the upper limit of lamina terminalis, as proposed by von Kupffer, '06).
Skull development during anuran metamorphosis: I. Early development of the first three bones to form—the exoccipital, the parasphenoid, and the frontoparietal
Authors: Hanken James , Hall Brian K. 
Published: February 2005

AbstractIn anuran amphibians, cranial bones typically first form at metamorphosis when they rapidly invest or replace the cartilaginous larval skull. We describe early development of the first three bones to form in the Oriental fire‐bellied toad, Bombina orientalis—the parasphenoid, the frontoparietal, and the exoccipital—based on examination of serial sections. Each of these bones is fully differentiated by Gosner stage 31 (hindlimb in paddle stage) during premetamorphosis. This is at least six Gosner developmental stages before they are first visible in whole‐mount preparations at the beginning of prometamorphosis. Thus, developmental events that precede and mediate the initial differentiation of these cranial osteogenic sites occur very early in metamorphosis—a period generally considered to lack significant morphological change. Subsequent development of these centers at later stages primarily reflects cell proliferation and calcified matrix deposition, possibly in response to increased circulating levels of thyroid hormone which are characteristic of later metamorphic stages. Interspecific differences in the timing of cranial ossification may reflect one or both of these phases of bone development. These results may qualify the use of whole‐mount preparations for inferring the sequence and absolute timing of cranial ossification in amphibians.