bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscopic observations on the vomeronasal sensory epithelium of a crotaline snake, Trimeresurus flavoviridis
Authors: Takami Shigeru , Hirosawa Kazushige 
Published: February 2005

AbstractThe vomeronasal sensory epithelium of a crotaline snake, Trimeresurus flavoviridis, was shown to consist of a superficial supporting cell layer and an underlying sensory cell layer composed of columns of sensory cells. The supporting cell layer consists of both supporting cells and dendrites of the underlying sensory neurons. The apical regions of sensory cell dendrites contain numerous microtubules, many elongated mitochondria, centrioles, and electron‐dense bodies. The dendrites terminate as dendritic knobs from which microvilli project into the vomeronasal lumen. Smooth vesicles are abundant in the dendritic terminals and their vicinity. Supporting cells also bear microvilli, and these cells contain large electron‐opaque granules and dense vesicles near their free surfaces. Cytoplasmic extensions of the supporting cells form a meshwork which separates dendrxites from each other in the vicinity of the luminal surface. The meshwork becomes obliterated in the infranuclear region of each supporting cell. Bipolar‐shaped sensory cells with lightly stained round nuclei contain the characteristic cell organelles of neurons and are thought to be sensory neurons. These cells are especially characterized by well‐developed lamellae of rough endoplasmic reticulum and extensive arrays of smooth endoplasmic reticulum. The perikarya of cells located in the apical region of the cell columns tend to contain larger amounts of smooth endoplasmic reticulum and lipofuscin granules than the perikarya of cells located in lower regions. Undifferentiated cells are found in the basal region of the columns. Satellite cells form the framework of the columns and are also found among neuronal elements.
Morphology of the teeth of the American alligator (Alligator mississippiensis): Fine structure and chemistry of the enamel
Authors: Sato I. , Shimada K. , Yokoi A. , Handal J. C. , Asuwa N. , Ishii T. 
Published: February 2005

AbstractFunctional teeth from young American alligators (120 cm to 260 cm total length) were prepared for scanning electron microscopy (SEM) and electron microprobe analysis (EPMA) of the elements of the enamel layer. On the tip of the tooth, the enamel layer is thick, but over the crown it gradually reduces in thickness until it disappears near the cement‐enamel junction. The enamel layer is distinguished by inner and outer layers. The inner layer is formed of separated, irregularly shaped blocks composed of small crystals. In the outer layer, the enamel crystals are closely packed and oriented perpendicularly to the surface. Radially oriented, lamella‐like structures of the enamel are elongated, crystallized bands which extend from the inner to the outer layer of the enamel as reported by Kvam (Acta Odontol. Scand. 17:745–751, 1959). The highest density of crystals occurs in the enamel layer before complete calcification. Concentrations of iron, copper, and fluoride are located approximately 20 μm below the surface of the enamel in the outer layer where crystals are closely packed. The concentration of trace elements (e.g., Fe, F, Cu) is related to the formation of hydroxyapatite.
Development of caudal structures of a morphogenetic mutant (Da) in the teleost fish, medaka (Oryzias latipes)
Authors: Ishikawa Yuji 
Published: February 2005

AbstractDevelopment of the internal structures of the caudal region (muscles, bones, cartilages, nerves, and blood vessels) of the Da/Da mutant medaka and of wild‐type +/+ fish was compared. Muscles and nerves were immunochemically stained by using an antibody to troponin T and antibodies to neurofilament proteins, respectively. Bones and cartilages were stained with alizarin red and alcian blue. In stages 31–32 of the Da/Da embryo, the rudiments of epurals 1, 2, and 3 differentiated dorsally opposite the sites of the ventral rudiments of the parhypural, the lower hypural plate, and the upper hypural plate, respectively. In the +/+ embryo, the rudiments of epurals 1 and 2 differentiated in the later developmental stages (after stage 34), but the rudiment of epural 3 did not differentiate. In the Da/Da embryo, the deep dorsal flexor passed dorsalwards and ended at the rudiment of epural 2, whereas the muscle passed ventralwards and ended at the rudiment of the upper hypural plate in the +/+ embryo. In the Da/Da fry, the epichordal region of the caudal fin fold grew and the notochord extended straight into the tail without bending, while in the + /+ fry, the epichordal region did not grow and the notochord turned dorsalwards within the tail. In the Da/Da fry, extra skeletal rudiments and musculature differentiated in the epichordal region of the caudal fin, whereas these supernumerary structures did not develop in the +/+ fry. The pattern of the epichordal skeleton and musculature in the caudal region of the adult Da/Da fish was an almost mirror‐image duplication of the hypochordal structures. These observations suggest that the characteristic expansion of the dorsal fin and epichordal lobe in the caudal region of the adult Da/Da fish is due to a process of ventralization, whereby the dorsal skeleton, musculature, and fin fold are stimulated to differentiate in a pattern like that which is restricted to the anal fin and hypochordal lobe of the wild type.
The ultrastructure of the compound eye of Munida rugosa (Crustacea: Anomura) and pigment migration during light and dark adaptation
Authors: Gaten Edward 
Published: February 2005

AbstractThe galatheid squat lobster, Munida rugosa, has compound eyes of the reflecting superposition type in which a distal cone cell layer and a proximal rhabdom layer are separated by an extensive clear zone. The eye is shown to have certain unique features. In all other reflecting superposition eyes, the clear zone is traversed by crystalline tracts formed by the cone cells. In M. rugosa a thin distal rhabdom thread, formed by the eighth retinula cell, connects the cones to the proximal fusiform rhabdoms. The cytoplasm of the other retinula cells also crosses the clear zone in a complex pattern. Fully light‐adapted ommatidia are optically isolated by limited migrations of distal shielding pigments. A reflecting pigment multilayer lines each cone to facilitate the formation of a superposition image. This also shows a light‐induced change which may limit the acceptance angle of the eye during light adaptation.
Desmosome‐like junctions between sertoli‐sertoli and sertoli‐germ cells in the ovotestis of Arion hortensis (Mollusca: Pulmonata)
Authors: Hou S. T. , Maxwell W. L. 
Published: February 2005

AbstractThe ovotestis of Arion hortensis was investigated by electron microscopy, using serial ultrathin sections and freeze‐fracture. Desmosome‐like junctions between Sertoli‐Sertoli and Sertoli‐germ cells (spermatogonia, spermatocytes, spermatids, and spermatids just prior to spermiation) were studied. Desmosome‐like junctions were circular when viewed en face and 90‐‐180 nm in diameter. The intercellular space at the junctional site was 15–25 nm in width. An intermediate dense line was absent.Freeze‐fracture replicas showed that these junctions formed groups, with one to ten junctions within each group. Groups of junctions were scattered over the Sertoli cell surface. The most prominent feature of this junction was an electron‐dense plaque on the cytoplasmic face of the plasmalemma. We describe variation in the development of the electron‐dense plaque on the germ cell side at different stages in the development of the germ cell. In the spermatogonium and spermatocyte stages, desmosome‐like junctions had equally developed electron‐dense plaques. The plaques are pronounced in junctions between Sertoli cells and spermatocytes/spermatids and less developed in relation to late spermatids where nuclear condensation is complete, and appear to be lost at spermiation. Finger‐like processes arise from the Sertoli cell as desmosome‐like junctions are lost at spermiation.Hypertonic fixative solutions containing dextrose were applied to the ovotestis resulting in cell shrinkage. The intercellular space between Sertoli cells and germ cells was increased except where the desmosome‐like junctions were present. We suggest that desmosome‐like junctions provide strong adhesive sites between Sertoli and germ cells.
Morphology and morphometry of motor endings on macaque intrafusal fibers
Authors: Sahgal Vinod , Subramani Venka , Sahgal Sudarshan 
Published: February 2005

AbstractThe ultrastructural studies have shown three types of motor endings in the macaque intrafusal fibers: (1) unindented axon terminals with smooth or shallowly folded postsynaptic membrane; (2) indented terminals with few postsynaptic folds; and (3) indented terminals with heavily folded postsynaptic membrane. The terminals on bag 1 and chain fibers were generally more indented than those on the bag 2 fibers. Deeply indented terminals with highly folded postsynaptic membranes were noticed on the bag 1 and chain endings in spindles from lumbrical but not the biceps muscle. In the individual intrafusal fibers from the biceps and lumbrical spindles, the degree of indentation did not correlate with the extent of postsynaptic folding (P>.01). Endings on bag 1 and chain fibers in the lumbrical spindles showed a positive correlation between indentation of terminals and their distance from the primary sensory endings (P<.01), whereas the lumbrical bag 2 endings and the biceps intrafusal endings did not (P>.01). The shape of the intrafusal motor endings thus is independent of their location but dependent on the type of intrafusal fibers.
Cellular basis of an avian countercurrent multiplier system
Authors: Post Marc , Greenwald Lewis , Stetson David 
Published: February 2005

AbstractA kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian‐type nephrons (without loops of Henle) and mammalian‐type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian‐type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+, K+‐ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+, K+‐ATPase activity. The structure of the avian mammalian‐type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.
Structure of the scales of Dermophis and Microcaecilia (Amphibia: Gymnophiona), and a comparison to dermal ossifications of other vertebrates
Authors: Zylberberg Louise , Wake Marvalee H. 
Published: February 2005

AbstractThe structures of the dermal scales and the cells surrounding the scales in two species of gymnophione amphibians were studied using histochemistry and light, scanning and transmission electron microscopy. Scales are composed of a basal platt of several layers of unmineralized collagenous fibers topped with mineralized squamulae. Squamulae are composed of numerous mineralized globules and mineralized, thick collagen fibers. Mineralization is therefore both spheritic and inotropic. Isolated flattened cells lie on the outer surface of the squamulae and seem to be involved in mineral deposition. Cells that line the basal plate synthesize the collagenous stroma of the plate. Each scale lies in a thin connective tissue pocket, and a large connective tissue pouch includes several scales in each annulus.The similarities of gymnophione scales to elasmoid scales of osteichthyans are largely superficial. Aspects of mineralization and of pocket development differ considerably. There are also similarities, as well as differences, in the gymnophione scales and osteoderms of amphibians and of reptiles. We consider that such dermal structures have arisen many times in diverse lineages of vertebrates, and that these are expressions of properties of dermal collagen to support mineralization by specialized dermal cells. However, we recommend that the term “dermal scale” be used for the mineralized dermal units of osteichthyans and gymnophiones, and “osteoderm” for the dermal structures of frogs and squamates, with the understanding that the terminology recognizes certain convergent attributes of shape and structure, but not of process.
Paralysis and growth of the musculoskeletal system in the embryonic chick
Authors: Hall Brian K. , Herring S. W. 
Published: February 2005

AbstractAvian embryos can be completely paralyzed by injection of neuromuscular‐blocking agents. We used a single injection of decamethonium iodide to paralyze embryos at 7, 8, or 10 days of incubation and analyzed the growth of individual bones (clavicle, mandible, ulna, femur, tibia, humerus) and of individual muscles that act upon some of those bones (clavicular and sternal heads of m. pectoralis, and mm. biceps brachii, depressor mandibulae, pseudotemporalis, and adductor externus). Growth of the bones is not equally affected by paralysis. Only 27% of clavicular growth (by mass) but 77% of mandibular growth occurred in paralyzed embryos, whereas the four long bones exhibited 52–63% of their normal growth. Analysis of muscle weight, fiber length and physiological cross‐sectional area (weight/fiber length) indicate that there was greater reduction of the muscles acting on the limbs than of those acting on the mandible, i.e., diminished growth of the skeleton is correlated with reduced muscular activity. Specific retardation of clavicular growth is due to fusion of sternal rudiments and collapse of the thorax, as well as virtual absence of the musculature that normally attaches to the clavicle. We discuss these results in the light of intrinsic and extrinsic factors governing growth of tne embryonic skeleton. Paralysis reduces skeletal growth by reducing both the movements taking place in ovo, and the loads imposed on the bones by muscle contraction, changes that represent alterations in the mechanical environment of the skeleton.
Some ultrastructural observations of leydig and sertoli cells in the testis of Tilapia rendalli following induced testicular recrudescence
Authors: Van Vuren J. H. J. , Soley J. T. 
Published: February 2005

AbstractTransmission electron microscopical studies performed on the testis of Tilapia rendalli confirmed the presence of Leydig and Sertoli cells. These cells displayed characteristic morphological features and were positively identified in the interstitial tissue and lobules, respectively. Based on cytoplasmic features it appeared that Leydig cells were responsible for male sex steroid synthesis. Although no clear evidence of steroidogenesis was found in the Sertoli cells, they perform a phagocytic function in the seminiferous lobules.
Scalariform junctions in the malpighian tubules of the insects Rhodnius prolixus (Hemiptera: Reduviidae) and Aedes taeniorhynchus (Diptera: Culicidae)
Authors: Bradley Timothy J. 
Published: February 2005

AbstractThe ultrastructure of scalariform junctions in the Malpighian tubules of the hemipteran Rhodnius prolixus and the dipteran Aedes taeniorhynchus is described. Both autocellular and intercellular scalariform junctions are illustrated. This is the first report of scalariform junctions in the Malpighian tubules of a dipteran. When combined with previous observations by other authors, the presence of scalariform junctions has now been reported in the Malpighian tubules of insects from five orders, including ametabolous, hemimetabolous, and holometabolous forms. The cell types in which scalariform junctions were found in R. prolixus and A. taeniorhynchus differ in the direction of ion and fluid transport. The cells share the capacity to transport KCl. These same cells also possess morphological features promoting close associations of mitochondria and plasma membranes in the apical region of the cell. The possible role of scalariform junctions is discussed in light of these observations.
Morphology and innervation of the buccal glands of the southern hemisphere lamprey, Geotria australis
Authors: Cook R. D. , Potter I. C. , Hilliard R. W. 
Published: February 2005

AbstractThe buccal glands of adults of the Southern Hemisphere lamprey Geotria australis consist of a pair of small, bean‐shaped, hollow sacs, embedded within the basilaris muscle in the region below the eyes and to either side of the piston cartilage. Each gland, which is lined by a simple columnar epithelium and surrounded by an incomplete layer of skeletal muscle, discharges its contents into the oral cavity via a long, narrow duct. In downstream migrating young adults, the epithelial cells are low columnar, intermediate in electron density, and contain dark‐staining inclusions and numerous lipid‐like droplets. After saltwater acclimation, the epithelial cells become taller and the numbers of dark‐staining inclusions increase whereas those of lipid‐like droplets decline. By the end of the marine phase, the epithelium is more folded and now also contains dark and light cells. The ultrastructure of the epithelium shows the characteristics of both apocrine and merocrine secretion. Although intra‐epithelial nerve endings were not observed, axons and occasional neurons are present in the lamina propria. Since the skeletal muscle capsule is also well innervated and contains neurons, a local feed‐back mechanism may regulate the release of buccal gland fluid by monitoring the luminal pressure. Contractions of the skeletal muscle capsule and movements of the basilaris muscle during feeding would presumably assist the movement of secretion along the duct. The secretion possesses anticoagulating and haemolytic properties.
Functional morphology of dewlap extension in the lizard Anolis equestris (Iguanidae)
Authors: Font Enrique , Rome Lawrence C. 
Published: February 2005

AbstractThe dewlap is an extendible flap of skin ordinarily folded under the throat. Lizards, particularly those in the genus Anolis, extend their dewlaps during interactions with conspecifics, other lizards, and potential predators. Dewlap extension is effected by movements of elements of the hyoid apparatus. This paper describes the anatomy of the hyoid and associated musculature in Anolis equestris, a large arboreal lizard with a prominent dewlap. A mechanism for dewlap extension is proposed based on results of morphological and experimental techniques.Specializations of the hyoid skeleton for dewlap extension include elongated second ceratobranchials and highly movable joints between the ceratohyals and the hypohyals and between the first ceratobranchials and the body of the hyoid. A well developed M. ceratohyoideus extends between the ceratohyals and the first ceratobranchials of the hyoid apparatus. During dewlap extension, the hyoid apparatus acts as a first order lever. Contraction of M. ceratohyoideus pulls the ceratohyals posterorly causing the hypohyals and the body of the hyoid to rotate dorsally around the first ceratobranchial/body joints. This movement results in the second ceratobranchials swinging forward and down, unfolding the dewlap. The relative immobility of the first ceratobranchials provides stability to the hyoid apparatus during dewlap extension. A comparison is made of dewlap extension and other hyoid displays.
Structure of the spleen of the sea bass (Dicentrarchus labrax): A light and electron microscopic study
Authors: Quesada J. , Viilena M. I. , Agulleiro B. 
Published: February 2005

AbstractThe spleen of sea bass (Dicentrarchus labrax) is composed mainly of red pulp, whereas the white pulp is poorly developed. The red pulp consists of clear reticular cells intermingled with blood cells, sinusoids, and melanomacrophage centers (MMCs). The MMCs are enclosed by an interrupted connective tissue capsule and show some areas in continuity with the adjacent pulp. The MMCs are formed by the association of free macrophages that have phagocytosed some blood cells. Sparse white pulp is diffuse, forming a cuff around the pulp arteries and MMCs, or occurring in small groups between the splenic cords. A longitudinal artery and vein, lying side by side, extend the length of the spleen. Frequently the capillaries are surrounded by a sheath of macrophages or ellipsoids. These macrophages may contain erythrocytes in varying degrees of degradation. Lymphopoiesis and plasmapoiesis occur in the sparse lymphold areas. Abundant plasma cell groups may indicate the presence of antibody production.
Comparative ultrastructure of ant spermatozoa (formicidae: Hymenoptera)
Authors: Wheeler Diana E. , Crichton Elizabeth G. , Krutzsch Philip H. 
Published: February 2005

AbstractMature spermatozoa from spermathecae of founding queens were obtained from 5 species of ants, representing the major subfamilies Myrmicinae (Acromyrmex versicolor, Crematogaster sp.) and Dolichoderinae (Tapinoma sessile, Conomyrma insana, Conomyrma wheeleri). The ultrastructure of ant spermatozoa has many features in common with that of higher insects and is similar to that of other Hymenoptera. Structural similarities to spermatozoa of other Hymenoptera include an acrosome containing an internal rod that extends into the nucleus, two elongate mitochondrial derivatives, a centriolar adjunct, and an axonemal arrangement of 9 + 9 + 2 that includes well‐developed coarse, or accessory, tubules. Spermatozoa obtained from A. versicolor, a species that is known to store and utilize viable sperm from this supply for over 10 years, show greater development of the mitochondrial derivatives than do the other species. The most distinctive feature of ant spermatozoa in comparison to other Hymenoptera is the large size of the centriolar adjunct relative to the other organelles. The centriolar adjunct is located posterior to the nucleus, anterior to the mitochondrial derivatives, and opposite the axoneme.
Histochemistry of acetylcholine receptors and acetylcholinesterase during the formation of neuromuscular junctions in the urodele Hynobius nigrescens
Authors: Tabuchi Masahiro , Fujikura Keiko , Inoue Sakae 
Published: February 2005

AbstractThe development and structure of neuromuscular junctions (n‐m‐js) in stylopodia of forelimbs of larvae and adults of Hynobius nigrescens were histochemically investigated for acetylcholine receptors (AChRs) and acetylcholinesterase (AChE) activity. In larvae, the tetramethyl rhodamine‐labelled α‐bungarotoxin (TMR‐αBT) positive areas appeared either as small fluorescent spots or fluorescent plates of various sizes. The mature fluorescent plate was found to be formed by the successive addition of spots, and the plates thus established were arranged linearly parallel to the axes of muscle fibers. AChE activity occurred almost exactly at TMR‐αBT‐positive sites. In adults, plate assemblies were often seen as a single dotted line (type A form) for both AChR binding and AChE reaction, in contrast to larval n‐m‐js in which AChE activity appeared as a continuous line. By applying the TMR‐αBT method, two other forms of adult n‐m‐js were observed: type B, a long dotted line several plates wide; and type C, with a cluster of plates randomly dispersed over the whole width of the muscle fiber. It seems that protoforms of the latter two forms of n‐m‐js appear in the muscles just before and after metamorphosis.