bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oogenesis in the terrestrial hermit crab Coenobita clypeatus (decapoda, anomura). I. Previtellogenic oocytes
Authors: Komm Barry S. , Hinsch Gertrude W. 
Published: February 2005

AbstractUltrastructural study of previtellogenic oocytes found in cystlike clusters scattered throughout the length of the bilobed ovary of the hermit crab Coenobita clypeatus shows a high nuclear:cytoplasm ratio. Large, round nuclei containing synaptinemal complexes serve as good temporal markers for identification of previtellogenic oocytes. The cytoplasm contains many smooth‐membraned vesicles filled with granules and probably of nuclear origin. In addition to its complement of Golgi complexes, endoplasmic reticulum, mitochondria, and free ribosomes, the cytoplasm also contains stacks of annulate lamellae, a feature not previously described for decapod oocytes. Typically, the previtellogenic oocyte with its accumulation of ribosomes has the appearance of a nonsynthetic cell preparing to go through a metabolic transition.
The ontogeny of shell secretion in Terebratalia transversa (brachiopoda, articulata) I. Development of the mantle
Authors: Stricker Stephen A. , Reed Christopher G. 
Published: February 2005

AbstractThe morphology of the mantle in free‐swimming and metamorphosing larvae of the articulate brachipod Terebratalia transversa has been examined by scanning and transmission electron microscopy. The mantle begins to form approximately 2 days after fertilization and subsequently develops into a skirtlike lobe that encircles the middle region of the larval body. A simple epithelium covers both the outer surface of the mantle lobe and the inner side situated next to the pedicle lobe of the larva. During metamorphosis, the mantle lobe is everted over the anterior end of the larva. Thus, the epithelium covering the outer part of the mantle lobe in the larva subsequently becomes the inner epithelium of the juvenile mantle. Similarly, the inner epithelium of the larval mantle lobe represents the future outer epithelium of the juvenile mantle. In free‐swimming larvae, the prospective outer mantle epithelium contains two types of cells, called “lobate” and “vesicular” cells. Lobate cells initially deposit a thin layer of amorphous material, and vesicular cells produce ovoid multigranular bodies. Following settlement at about 5 days postfertilization, the vesicular cells secrete an electron‐dense sheet that constitutes the basal layer of the developing periostracum. Within several hours to a day thereafter, reversal of the mantle lobe is rapidly effected, apparently by contractions of the pedicle adjustor muscles.
The mechanism of frill erection in the bearded dragon Amphibolurus barbatus with comments on the jacky lizard A. muricatus (Agamidae)
Authors: Throckmorton Gaylord S. , De Bavay John , Chaffey Wayne , Merrotsy Bruce , Noske Susan , Noske Richard 
Published: February 2005

AbstractAmphibolurus barbatus has a threat display which includes the erection of the gular regions as a frill and may also include wide opening of the mouth to display a yellow mouth lining. Frill erection involves protraction, depression, and lateral expansion of the hyoid apparatus. Electrical stimulation of the hyoid muscles and dissection of the hyoid apparatus were used to examine specializations for producing frill erection. Specializations of the hyoid skeleton include the absence of a ceratobranchial II, presence of a synovial joint between the ceratohyal and body of the hyoid, and combined shortening of the entoglossal process and lengthening of the posterior arches. The only apparent specialization of the hyoid musculature is the anterior displacement of the origin of m. hyomandibularis. All of the hyoid muscles are involved in some way in frill erection and the actions of each muscle is described. The characteristic frill erection in the threat display of Amphibolurus barbatus is possible because of the 1:2 ratio of the anterior and posterior parts of the apparatus and the absence of the ceratobrnchial II.
External features of the developing embryo of the stonefly, Kamimuria tibialis (pictet) (plecoptera, perlidae)
Authors: Kishimoto Tohru , Ando Hiroshi 
Published: February 2005

AbstractExternal features of the egg, developing embryo, and first instar nymph of Kamimuria tibialis are described. The embryonic development from the germ disc to the full‐grown embryo is divided into 12 stages. The saclike embryonic rudiment is formed by the bending and folding of the germ disc. The embryo first elongates at the egg surface and then sinks into the yolk due to caudal flexure. In the head, four paired protocerebral lobes differentiate and the fourth lobes are thought to be the rudiments of preantennal ganglia. The columnar serosal cells appear at the posterior pole of the egg and they disappear before katatrepsis. The coniform chloride cells occur at the hind margins of the first nine abdominal segments in the full‐grown embryo and first instar nymph. Amnion formation in K. tibialis is very similar to that of Allonarcys proteus and the Isoptera. It is proposed that the immersed type of growth pattern of embryos is divided into two subtypes in hemimetabolous insects; one is in the Palaeoptera and Paraneoptera, and the other is in the Plecoptera, Orthoptera, Notoptera, Isoptera, Embioptera, and the blattarian, Periplaneta americana.
Scanning electron microscope studies on blastodisc formation in the zebrafish, Brachydanio rerio
Authors: Beams H. W. , Kessel R. G. , Shih C. Y. , Tung H. N. 
Published: February 2005

AbstractUpon fertilization, the zebrafish egg undergoes marked physiological and structural changes, one of which involves blastodisc formation. Before fertilization, yolk globules are rounded and the endoplasm extends throughout the oocyte. During blastodisc formation, the yolk globules become angular and the endoplasm is restricted to streamers among the yolk globules. The streamers are oriented in an anterior‐posterior axis of the egg. During blastodisc formation the cytoskeleton consists of an extensive array of filamentous structures of variable width in both the cortex as well as within elongate endoplasmic streamers. Although the filamentous components in the cortex and endoplasmic streamers probably include both microfilaments and microtubules, frequently they are somewhat wider than the usual dimensions, and possible reasons for this are suggested. From their arrangement in both the cortex and endoplasm, it seems likely that the components of the cytoskeleton (e.g., microfilaments and microtubules) may provide, through contraction, the major force responsible for the streaming of the endoplasm into the forming blastodisc. It is assumed that the surface tension of the vegetal hemisphere exceeds that of the animal hemisphere, thus forcing, through differential contraction, the endoplasm to flow in the direction of the forming blastodisc. No distinct barrier between the yolk and forming blastodisc was observed. The compressed condition of the larger and many‐sided yolk globules could prevent their movement into the blastodisc. Scanning electron microscopy is limited in the resolution with which it can depict the cytoskeleton, but nonetheless it provides useful information about structural interrelationships.
Synaptic organization of dorsal area of the turtle, Pseudemys scripta elegans
Authors: Weiss Jonathan C. , Ulinski Philip S. 
Published: February 2005

AbstractThe dorsal ventricular ridge is a subcortical structure receiving sensory information from the thalamus in reptiles. In the red‐eared turtle, Pseudemys scripta elegans, it contains four cytoarchitectonic areas each characterized by distinct thalamic projections. This is an electron microscopic study of one of these, the dorsal area, which receives its thalamic input from the tectorecipient nucleus rotundus. It contains four concentric zones, internal to the ependymal zone, each of which is distinguished by the distribution of spiny and aspiny neurons.The ependymal zone of dorsal area contains tanycytes whose tails extend into zones 2 and 4. Synapses, usually with asymmetric junctional complexes and round synaptic vesicles, occur on these processes. Zone 1 neurons have fusiform somata and dendrites that parallel the ventricular surface. Their cytoplasm contains rough endoplasmic reticulum located primarily in Nissl bodies, lipofuchsin granules, multivesicular bodies, extensive arrays of Golgi apparatus, and large numbers of mitochondria. Synapses occur mainly on dendritic spines and shafts of zone 1 neurons and less frequently on somata. The majority have round vesicles and asymmetric junctional complexes. In contrast to those in zone 1, neurons in zones 2 and 4 have large amounts of rough endoplasmic reticulum, giving their cytoplasm an electron‐dense quality. Synapses occur mainly on spines and shafts of zone 2 and 4 neurons. As in zone 1, the majority have round synaptic vesicles and contain asymmetric junctional complexes. Zones 2 and 4 contain clusters of neurons distributed among isolated neurons. The clusters are larger and less frequent in zone 2. Protoplasmic and fibrous glial processes, axon boutons, dendrites, and axon fascicles surround the neuron clusters. Though less numerous, the same structures also occur inside the clusters. Most synapses inside the clusters have round synaptic vesicles, asymmetric junctional complexes, and occur mainly on spines. Some neurons in clusters have somata whose plasma membranes are in direct apposition. In contrast to dorsal ventricular ridge in snakes, no specialized intercellular contacts were seen between somata in clusters.
Fine structure of oviducal epithelium of Xenopus laevis in relation to its role in secreting egg envelopes
Authors: Yoshizaki Norio 
Published: February 2005

AbstractDuring passage through the oviduct, the egg of Xenopus laevis acquires the following substances or envelopes: electron‐dense particles in the vitelline coat, the prefertilization layer in and around the vitelline coat, and four layers of jelly. Both gross anatomical observation and light and scanning or transmission electron microscopic observations of various levels of oviduct revealed that the first two are produced in the pars recta 1 and 2 portions, and that jelly layers 1–4 are added in the pars convoluta 1–4 respectively. The relative lengths of these portions were 0–0.044, 0.044–0,055, 0.055–0.52, 0.52–0.70, 0.70–0.87 and 0.87–1.00 from anterior to posterior. Along the whole length of the oviduct, the epithelium was comprised of ciliated cells and various types of secretory cells. Except for the pars recta 1 portion, there were two or three types of secretory cells in each portion of the oviduct, indicating that the structure of each stratum of the egg envelope is formed by an interaction of products from the specific types of secretory cells in each portion of the oviduct.
Light and electron microscopic localization of a monoclonal antibody in neurons in situ in the head region of Hydra
Authors: Yu Shang‐Ming , Westfall Jane A. , Dunne John F. 
Published: February 2005

AbstractA mouse monoclonal antibody to Hydra attenuata was used to demonstrate immunoreactive product in neurons in situ, in both whole mount and sectioned hypostomes and tentacles of H. oligactis and H. littoralis. Immunoreactive cells were concentrated around the mouth and scattered along the length of the tentacles. In the hypostome, nerve cells sent one or more processes orally and the others aborally but the processes were more distinctly stained in H. oligactis. A thin strand of five to six perihypostomal neurons was present close to the hypostome‐tentacle junction. In the tentacles, neurons with long processes contacted up to five different batteries of nematocysts. Neural processes were associated with nematocyst batteries in three ways: (1) forming a perikaryal loop to encircle a centrally located stenotele, (2) branching at a distance from the perikaryon to contact a variety of nematocysts, and (3) terminal branching by one or more neurons with contacts on one to several nematocysts within a battery. Immunocytochemical localization of neurons in Hydra by light microscopy was correlated for the first time with electron microscopy. Peroxidase‐antiperoxidase (PAP)‐positive sensory cells were concentrated around the mouth opening. PAP‐positive ganglion cells were predominant in the tentacles. Sensory cells were elongate or spindle‐shaped (unipolar), triangular with two oppositely directed processes (bipolar), and multipolar (tripolar or tetrapolar) with one of the processes extending to the epidermal surface. Ganglion cells were either unipolar or bipolar or multipolar, with neurites paralleling the mesoglea and occasionally having processes abut on it.
Scanning electron microscope study of cat and dog enamel structure
Authors: Skobe Ziedonis , Prostak Kenneth S. , Trombly Paul L. 
Published: February 2005

AbstractScanning electron microscopy revealed several similarities as well as significant differences in the enamel structure between cat and dog teeth. Three enamel layers were present in both species; a surface rodless (aprismatic) layer, an outer layer of parallel rods (only at some sites), and an inner layer with prominent Hunter‐Schreger bands. In the inner layer of both carnivores, the diameter of individual rods varied significantly and frequently their course changed abruptly with respect to neighboring rods. In dog teeth the cross‐sectional shape of inner enamel rods was pleomorphic, but hexagonal in outer enamel. In contrast, cat enamel rods were rounded in both inner and outer enamel layers. Hunter‐Schreger bands of cats circumscribed the teeth in relatively straight segments, but these bands showed pronounced waviness in dog teeth. In cats and dogs the surface rodless layer was structurally continuous with subjacent interrod enamel and covered all tooth surfaces with the exception of the cervical areas.The data show that the structure of inner and outer enamel layers differ between these two carnivore species and that the enamel structure of the cat was most similar to that described in humans. One principal difference between carnivore and human teeth is that the growth lines of carnivores do not terminate at perikymata on the tooth surface.
The morphology and histology of the endocrine pancreas of the Southern Hemisphere lamprey, Geotria australis gray
Authors: Hilliard R. W. , Epple A. , Potter I. C. 
Published: February 2005

AbstractThe location and arrangement of the pancreatic endocrine tissue in larval and adult Geotria australis (Geotriidae) differ markedly from those exhibited by the comparable stages of Northern Hemisphere lampreys (Petromyzontidae). In larval Geotria australis, the main zones of islet proliferation are located laterally between the oesophagus and the inner edge of the two large intestinal diverticula unique to this species rather than dorsal and ventral to the oesophagus. In adult Geotria australis, the islet follicles are closely packed into a single discrete capsule which could be easily removed surgically, rather than into cranial, intermediate, and caudal cords. The differences in the adult can be related to a lack of involvement of the bile duct in islet formation during metamorphosis. While B cells were found in both larval and adult islet follicles, the PI acidophilic cells and argyrophilic cells, which appeared respectively at stages 3 and 4 in metamorphosis, were present in all adult stages.
Fine structure of the micropylar cell and its change during oocyte maturation in the chum salmon, Oncorhynchus keta
Authors: Kobayashi Wataru , Yamamoto Tadashi S. 
Published: February 2005

AbstractIn the ovarian follicle, the micropylar cell (MPC) is distinguished from neighboring granulosa cells by its larger cell size and its thick cytoplasmic process. The micropylar cell body fits into a shallow depression (micropylar vestibule) on the outer surface of the egg envelope; its process extends through the micropylar canal, which extends from the bottom of the vestibule through the full thickness of the zona pellucida interna. At its distal end, the cell process expands into a bulb which fits into an indentation of the ooplasmic surface immediately beneath the inner opening of the micropylar canal. Intermediate and desmosomelike junctions establish an intimate association between MPC process and oocyte. Various kinds of organelles and inclusions in the MPC show a characteristic pattern of cytoplasmic distribution; rough endoplasmic reticulum with markedly dilated cisternae is found exclusively in the main cell body, while microtubules and thin filaments are observed in the cytoplasmic process.Immediately before or during the breakdown of the germinal vesicle in the intrafollicular oocyte, the cytoplasmic process of the MPC gradually decreases in length and begins to withdraw from the micropylar canal. At the same time, the ooplasmic surface protrudes outward to form a papilla in the canal. The intimate MPC‐oocyte association disappears during formation of the ooplasmic papilla. Hydration of the oocyte apparently occurs at the final stage of maturation and probably participates in papilla formation. Although the MPC undergoes degenerative changes as ovulation draws near, it remains attached to the inner surface of the granulosa cell layer even after its association with the oocyte has completely disappeared.We speculate that the micropyle develops during fish oogenesis through the combined activity of the MPC and neighboring granulosa cells. It appears that the cell body of the micropylar cell and nearby granulosa cells exert mechanical pressure on the external surface of the growing oocyte and thus participate in formation of the micropylar vestibule. The cytoplasmic process of the MPC evidently forms a passive barrier to deposition of material for the egg envelope in the animal pole, thereby resulting in formation of the micropylar canal.
Development and rudimentation of the peripheral olfactory system in the harbor porpoise Phocoena phocoena (Mammalia: Cetacea)
Authors: Oelschläger Helmut A. , Buhl Eberhard H. 
Published: February 2005

AbstractSerial sections of 13 embryos and fetuses of the harbor porpoise from 10 mm crown‐rump length up to 167 mm total length were studied. Unlike the adult animals, ontogenetic stages of 18–27 mm crown‐rump length still show a typical mammalian olfactory bulb. The olfactory bulb primordium is penetrated by olfactory nerve fibers, the latter passing through the cribriform plate. However, the olfactory bulb anlage is gradually reduced in later stages, its placodal component being largely uncoupled from the telencephalon. As a ganglionlike structure, the remains of the placodal component stay in contact with the nasal septum and mucosa via thin bundles of nerve fibers. The ganglion and plexus can be traced within the meninges until the adult stage of the porpoise. There is strong evidence that they represent the material of the terminalis system, which cannot be distinguished from the olfactory system in earlier stages. A vomeronasal organ could not be detected in the embryonal and fetal material investigated.
The intrarenal and pericapsular venous systems of kidneys of the ringed seal, Phoca hispida
Authors: Munkacsi I. M. , Newstead J. D. 
Published: February 2005

AbstractThe kidneys of Phoca hispida are comprised of many closely adherent renculi, each of which is a small kidney, functionally independent of its neighbours except with respect to venous drainage. Venous blood from the rencular parenchyma drains to the periphery through interlobular veins. These interlobular veins empty into a perirencular plexus comprised of subcapsular veins on the free surface of the renculus, interrencular veins on adjoined surfaces, and marginal subcapsular veins lying in the furrows between adjoined renculi. A pericapsular plexus of large veins overlies the marginal subcapsular veins and has frequent connections with them. Blood drains from the pericapsular plexus into large superficial collecting veins that converge over the surface of the kidney toward the divided hilum and connect directly to the paired trunks of the posterior vena cava. There are also connections to other major venous systems of the region.There is no arcuate venous system, no major vein at the rencular hilum, and no vein of consequence emerging from the renal hilum. Venous outflow is virtually entirely directed to the peripheral plexuses. The venous pattern differs from that of most mammals in which blood drains from the renal parenchyma to arcuate veins and leaves the kidney through a renal vein, or veins, emerging from the hilum.The walls of veins in the kidney are remarkably thin in comparison to their size. Subcapsular veins up to 0.5 mm wide have walls on the parenchymal side that in places consist only of a thin, fenestrated endothelium and a basal lamina.
The follicle cell‐oocyte interaction in ovarian follicles of the stick insect Bacillus rossius (Rossi): (Insecta: Phasmatodea)
Authors: Mazzini Massimo , Giorgi Franco 
Published: February 2005

AbstractDeveloping ovarian follicles of Bacillus rossius have been examined ultrastructurally in an attempt to understand how inception of vitel‐logenesis is controlled. Early vitellogenic follicles are characterized by a thick cuboidal epithelium that is highly interlocked with the oocyte plasma membrane. Gap junctional contacts are present both at the follicle cell/oocyte interface and in between adjacent follicle cells. In addition, microvilli of follicle cells protrude deeply into the cortical ooplasm of these early vitellogenic oocytes. With the onset of vitellogenesis, wide intercellular spaces appear in the follicle cell epithelium and at the follicle cell/oocyte interface. Gap junctions become progressively reduced both on the follicle cell surface and on the oocyte plasma membrane. Microvilli from the two cell types no longer interlock.From a theoretical standpoint each of the two structural differentiations present at the follicle cell/oocyte interface—gap junctions and follicle cell microvilli—could potentially trigger inception of vitellogenesis. Gap junctions might permit the passage of a regulatory molecule, transferring from follicle cells to oocyte, which would control the assembly of coated pits on the oocyte plasma membrane. Alternatively cell interaction via microvilli might induce the appearance of coated pits, thus creating a membrane focus for vitellogenin receptors. Both possibilities are discussed in relation to current literature.
Development of gap junctions in normal and mutant ovaries of Drosophila melanogaster
Authors: Giorgi F. , Postlethwait J. H. 
Published: February 2005

AbstractAn ovarian follicle of Drosophila consists of an oocyte, 15 nurse cells, and hundreds of follicular epithelial cells. A freeze‐fracture analysis of the surfaces between glutaraldehyde‐fixed ovarian cells showed that all three cell types were interconnected by gap junctions. This is the first report of gap junctions between adjacent nurse cells, between nurse cells and oocytes, and between follicle cells and oocytes in Drosophila. Since we did not observe intramembranous particle clumping into crystalline patterns and since structurally different gap junctions occurred at different times in development and at different cell‐cell interfaces, it is unlikely that fixation artifacts influenced particle distribution in our experiments. A computer‐assisted morphometric analysis showed that the extent, size, and morphology of gap junctions varied with development and that these junctions can cover up to 9% of the cell surfaces. To test the role of gap junctions in follicular maturation, we studied ovaries from flies homozygous for the female sterile mutation fs(2)A17, in which follicles develop normally until yolk deposition commences. During the development of mutant follicles, gap junctions became abnormal before any other morphological aspect of the follicle. These studies show that gap junctions are available to play an important role in coordinating intercellular activities between all three cell types in ovarian follicles of Drosophila.