bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane production and yolk degradation in the early fly embryo (Calliphora erythrocephala meig.): An ultrastructural analysis
Authors: Lundquist Anders , Emanuelsson Hadar 
Published: February 2005

AbstractFormation of nuclear envelopes during the last cleavage mitosis and the formation of the cell membranes during the cellularization of the blastoderm have been studied ultrastructurally in the blowfly egg. Dense bodies arising from yolk granules by budding could contain membrane material destined to be incorporated into the new membranes of the blastoderm. The presence of transitional structures indicates that these bodies can be converted into dark multivesicular bodies. Large amounts of endoplasmic reticulum are found around the mitotic nuclei. Clusters or branched chains of vesicles associated with this are interpreted as evidence for the formation of endoplasmic reticulum by the breakdown of dark multivesicular bodies. Nuclear envelopes of mitotic daughter nuclei probably originate from endoplasmic reticulum. The egg contains both intranuclear and extranuclear annulate lamellae.The main events of cytokinesis are furrow initiation and cell membrane growth during the slow first phase, but probably only cytokinetic movement during the rapid second phase. On the assumption that cell membrane growth occurs by incorporation of complete membrane pieces, the addition of coated vesicles and/or light multivesicular bodies is definitely most probable. Some intermediate profiles indicate that light and dark multivesicular bodies are related. The membrane needed for second phase cytokinesis could well be provided by the unfolding of surface microvilli and protuberances of the furrow canal.
Studies on the tardigrades. IV. Fine structure of the hindgut of Milnesium tardigradum doyère
Authors: Dewel Ruth Ann , Dewel William C. 
Published: February 2005

AbstractThe hindgut of the semi‐terrestrial tardigrade, Milnesium tardigradum was examined with light and electron microscopy. The hindgut consists of a cloaca and an anterior hindgut. It is delineated anteriorly by the pylorus into which four Malpighian tubules empty and posteriorly, by a broad cloacal slit. A single oviduct enters the hindgut at the junction between the cloaca and the anterior hindgut. Two pairs of muscles insert on the cloaca and anterior hindgut respectively. Electron microscopic observations demonstrate that the anterior hindgut is a specialized transporting epithelium. The luminal surface is covered by a thin layer of cuticle which penetrates into channel‐like invaginations. Numerous mitochondria are concentrated apically. The basal and lateral surfaces are also folded. The cells are joined apically by deep tight junctions and a simple basal lamina lines the entire hindgut. The cloaca which receives the contents of the gut and Malpighian tubules as well as gametes of the reproductive tract is a transitional organ that exhibits several characteristics of the hypodermis and anterior hindgut. The cuticle of the cloaca changes sequentially from the complex structure of the integument to a simple layer of the anterior hindgut. The function of the hindgut is discussed with emphasis on the possible response of the anterior hindgut to a hypoosmotic habitat, evaporative water loss during the induction of anhydrobiosis and low oxygen tension.
Avian scale development. VI. Ultrastructure of the keratinizing cells of reticulate scales
Authors: Sawyer Roger H. , Borg Thomas K. 
Published: February 2005

AbstractReticulate scales develop as radial symmetrical anlagen, in contrast to scuttate scales which appear initially as “epidermal placodes.” Unlike scuttate scales whose outer and inner epidermal surfaces elaborate β‐and α‐type keratins, respectively, reticulate scales elaborate only one type of epidermal surface which has been reported to give an α‐type, X‐ray diffraction pattern. We find that, histologically and ultrastructurally, this surface differs from either epidermal surface of scuttate scales. The keratinizing cells become filled with long interweaving bundles of α‐filaments which aggregate into rather homogeneous α‐fibrils. Keratohyalin granules, which have been shown to be associated with other keratinizing regions in the bird, do not form during the keratinization of reticulate scale epidermis.
Intrinsic organization of snake dorsomedial cortex: An electron microscopic and golgi study
Authors: Ulinski Philip S. 
Published: February 2005

AbstractThe cellular populations present in dorsomedial cortex in the snakes Constrictor constrictor, Natrix sipendon and Thamnophis sirtalis are described at the light microscopic level using Nissl and Golgi preparations as well as at the ultrastructural level. This area plays a central role in cortical organization in snakes by participating in major commissural and association projections.Systematic analyses of Golgi preparations indicate that five populations of neurons are present in dorsomedial area and have a preferential laminar distribution. Layer 1 stellate cells have somata positioned in the center of the outermost cortical layer, layer 1. Their dendrites are confined to this layer. Double pyramidal cells have their somata loosely packed in layer 2. Their dendrites bear a moderate population of spines, ascending through layer 1 to the pial surface and descending partially through layer 3. Some double pyramidal cells have somata displaced downwards into the upper third of layer 3. These neurons closely resemble the layer 2 double pryamidal cells. Layer 3 stellate cells have somata positioned in the middle third of layer 3. Their dendrites extend in all directions throughout layer 3 and through layer 2 into layer 1. Finally, horizontal cells have their somata positioned deep in layer 3, near the ventricle, and dendrites aligned concentric with the ventricle.Comparison of the organization of the known afferents to dorsomedial area with the distribution of the five cell types suggests that the laminations of both afferent fibers and dorsomedial neurons places specific neuronal populations in synaptic contact with specific sets of afferents.
Nucleolar reorganization in liver cells of the aging rat
Authors: Adamstone F. B. , Taylor A. B. 
Published: February 2005

AbstractThe nucleoli of rat liver cells duplicate in great detail the lifelong series of reorganizational changes encountered in kidney and intestinal epithelial cells. The ultrastructural components of the large, loosely organized polymorphous nucleoli, which are dominant in the rapidly multiplying stem cells of embryos, are readily accessible for chemical activities. Smaller, more compact amphinucleoli are dominant in more mature cells, which were characterized by Smetana ('70) as “idling” cells, showing slowly continuing ribosome formation and RNP synthesis. In older cells bipartite nucleoli become dominant and are reorganized in increasing numbers from the younger amphinucleoli. These, however, are not replaced in equal numbers from the shrinking pool of polymorphs of young cells which have greatly reduced mitotic potential. Paralleling the shifts in dominant nucleolar types, the high level of protein synthesis declines in older cells not only in the quantity of proteins synthesized but also in kinds of enzymes produced. These fail to meet the structural and functional requirements of aging cells leading ultimately to the onset of age‐related degenerative changes. Again it is noted that separation of the karyosomal DNA from the plasmosomal RNA‐protein complex of the nucleolus may lead to possible breakdown of the DNA‐dependent RNA‐protein transcription system ultimately bringing protein synthesis to a very low level in the senescent animal.
Microanatomy of the lung parenchyma of a tegu lizard Tupinambis nigropunctatus
Authors: Klemm Robert D. , Gatz Randall N. , Westfall Jane A. , Fedde M. Roger 
Published: February 2005

AbstractThe combined techniques of light microscopy, scanning (SEM) and transmission (TEM) electron microscopy were used for the first time to study the structure of unicameral lungs of a Tegu lizard (Tupinambis nigropunctatus). The lungs are prolate spheroid bags with blood supplied by superficial branches of a dorsal pulmonary artery and returned by diffuse, more deeply located veins. The primary bronchus enters the medial aspect near the apex of the lung. The lung wall is composed of trabeculae: (1) arranged in a faviform pattern, (2) forming individual faveoli (gas exchange chambers) which appear deepest in the cranial one‐half of the lung, (3) all of which have a smooth muscle core overlain by either a ciliated or nonciliated epithelium. A ciliated epithelium lines the luminal surfaces of the large primary trabeculae and parts of smaller secondary trabeculae; it is composed of cone‐shaped cells with ciliated‐microvillous surfaces, and of columnar serous secreting cells. Nonciliated epithelium covers the luminal surface of portions of some secondary trabeculae, abluminal surfaces of primary and secondary trabeculae and all surfaces of the small tertiary trabeculae forming the faveoli. The nonciliated epithelium overlies an extensive superficial capillary network. The blood‐gas barrier (0.7‐1.0 μm thick) is composed of a thin cytoplasmic flange of Type I pneumonocytes, a thick homogeneous basal lamina and an attenuated endothelial cytoplasm. Numerous surfactant‐producing Type II pneumonocytes are closely associated with the Type I pneumonocytes. The nonrespiratory ciliated epithelium may function in humidification of air and clearing of the lungs.
The blood supply of muscle spindles in some mammals and the pigeon
Authors: Maier Alfred 
Published: February 2005

AbstractThe blood supply of muscle spindles was studied in serial cross sections in macaque, cat, rabbit, guinea pig, mouse and pigeon muscles which had been incubated in a medium containing 3,3′ diaminobenzidine. Lumina of blood vessels were recognized by the reaction product that was localized within erythrocytes. The outer capsule was well vascularized, but few or no capillaries were seen in the periaxial space. The inner spindle capsule, which closely invests the axial bundle, was rarely contacted by periaxial capillaries at the equator and juxtequator. Capillaries occurred more frequently adjacent to intrafusal fibers at the polar region and beyond the end of the outer capsule. Shorter diffusion distances and, usually, higher capillary densities were found at the polar region than at the spindle midsection. This suggests that transcapillary exchange at the polar segment is nearer to conditions prevalent in extrafusal muscle than elsewhere in the spindle, provided the inner and outer capsules are not less permeable at the poles than at the midsection. Differences in blood supply among mammalian species appear to be related to receptor size.
Interactions between Tectal Radial Cells in the Red‐Eared Turtle, Pseudemys scripta elegans: An Analysis of Tectal Modules
Authors: Schechter P. B. , Ulinski P. S. 
Published: February 2005

AbstractThe optic tectum is a major subdivision of the visual system in reptiles. Previous studies have characterized the laminar pattern, the neuronal populations, and the afferent and efferent connections of the optic tectum in a variety of reptiles. However, little is known about the interactions that occur between neurons within the tectum. This study describes two kinds of interactions that occur between one major class of neurons, the radial cells, in the optic tectum of Pseudemys using Nissl, Golgi and electron microscopic preparations.Radial cells have somata which bear long, radially oriented apical dendrites from their upper poles and short, basal dendrites from their lower poles. They are divided into two populations on the basis of the distribution of their somata in the tectum. Deep radial cells have somata densely packed in the stratum griseum periventriculare. Their plasma membranes form casual appositions. Middle radial cells have somata scattered throughout the stratum griseum centrale and stratum fibrosum et griseum superficiale and do not contact each other. The apical dendrites of both populations of radial cells participate in vertically oriented, dendritic bundles. The plasma membranes of the dendrites in these bundles form casual appositions in the deeper tectal layers and chemical, dendrodenritic synapses within the stratum fibrosum et griseum superficiale. The synapses have clear, round synaptic vesicles and slightly asymmetric membrane densities. Thus, radial cells interact via both casual appositions and chemical synapses.These interactions suggest that radial cells may form a basic framework in the tectum. Because both populations of radial cells extend into the stratum fibrosum et griseum superficiale and stratum opticum, they may receive input from some of the same tectal afferent systems. Because the deep radial cells alone have somata and dendrites in the deep tectal layers, they may receive additional inputs that the middle radial cells do not. Neurons in the two populations interact via chemical dendrodendritic synapses, thereby forming vertically oriented modules in the tectum.
Sense organs on the antennal flagellum of the mimosa webworm, Homadaula anisocentra (Lepidoptera, Glyphipterygidae)
Authors: Slifer Eleanor H. 
Published: February 2005

AbstractFive different types of sense organs were found on the antennal flagellum of Homadaula anisocentra. These were (1) tactile hairs; (2) thick‐walled chemoreceptors; (3) thin‐walled chemoreceptors of several kinds; (4) styloconic chemoreceptors and (5) small chemoreceptor pegs in shallow depressions. No coeloconic sense organs were seen.
Structure and carbohydrate histochemistry of the intestine in ten teleostean species
Authors: Reifel Conrad W. , Travill Anthony A. 
Published: February 2005

AbstractThe morphology and carbohydrate histochemistry of ten teleostean intestines are compared. Although there is an absence of regional differentiation seen in higher vertebrates, specializations in some species occur in the form of intestinal swellings, pyloric ceca and recta, the latter separated by a valve. The intestinal lumen is lined by a simple columnar epithelium interspersed with goblet cells; multicellular intestinal glands are absent. Thick basement membranes seen in centrarchids and Perca flavescens closely resemble the stratum compactum found in the lamina propria of esocids. Granular cells, which vary in number from species to species, are often seen in the mucosa and submucosa but less frequently in the muscularis. In species with intestino‐rectal valves, a rectum is easily defined by the abrupt appearance of lower mucosal folds, more goblet cells and a thicker muscularis. In the remaining species the above features appear gradually in the distal intestine. Goblet cells show species variations in localization of epithelial mucosubstances, which in broad terms are recognized as sulfomucins, sialomucins and neutral mucosubstances. In both proximal and distal intestines the majority of goblet cells contain sialomucin although small amounts of sulfomucin are also often present. In species without intestino‐rectal valves, no changes in carbohydrates occur between proximal and distal intestines. The possible significance of the heterogeneous character of digestive tract mucosubstances is discussed.
The structure of the canary's incubation patch
Authors: Kern Michael D. , Coruzzi Laura 
Published: February 2005

AbstractThe gross morphology, histology and ultrastructure of the canary's incubation patch and the ventral apterium from which it arises are described. The apterium is vascularized by pectoral, external mammary, incubation, and prepubic arteries. It is innervated by cutaneous branches of spinal nerves. It has a surface area of 6 cm2.Its epidermis is a stratified squamous epithelium with basal, intermediate, transitional and cornified layers. Cells in the stratum germinativum contain a normal array of organelles, but are characterized by tonofilaments, desmosomes and interdigitating surfaces. Cellular organelles disappear in the stratum transitivum and are replaced by large vacuoles and keratohyalin bands. Nonmyelinated nerve fibers are abundant in the stratum germinativum.The dermis consists of (1) an avascular layer of dense collagen subjacent to the epidermis and containing many nonmyelinated nerves, and (2) an underlying layer of areolar connective tissue containing blood vessels, lamellar corpuscles and nerves. A layer of coarse elastic fibers, reinforced by collagen and smooth muscle, separates the dermis from subcutaneous tissue.In contrast to the ventral apterium, the incubation patch is featherless and visibly hypervascular and edematous. Its epidermis is both hypertrophic and hyperplastic. Large spaces separate cells in the stratum germinativum. The visible hypervascularity is due to hyperemia and increased number and size of blood vessels in the dermis. Visible edema is due to the accumulation of fluid interstitially. Although no histological differences exist among various regions of the ventral apterium, such differences are present in the incubation patch.
The timing of the onset of osteogenesis in the tibia of the embryonic chick
Authors: Scott‐Savage Peter , Hall Brian K. 
Published: February 2005

AbstractHaematoxylin, Alcian Blue‐Chlorantine Fast Red (ABCR) and the Ralis osteoid‐specific stain were employed to closely follow the histogenesis of the tibia of the embryonic chick so as to provide an accurate description of the onset of ossification.An overview of the major cytological events preceding osteogenesis in the tibia was obtained from hindlimbs of embryos of H. H. (Hamburger and Hamilton, '51) stages 16‐26 (2.5‐5 days of incubation) stained with ABCR. A description of the cytological changes in the periosteum as it develops from the perichondrium and an analysis of the timing of the onset of osteoid deposition was obtained from the tibiae of accurately aged and staged embryos of H. H. stages 28‐32 (5.5‐8 days). These tibiae were stained specifically for the detection of osteoid:the freshly‐secreted, unmineralized product of fully‐differentiated osteoblasts. The perichondrium transformed into a bi‐layered periosteum at H. H. late stage 29 (6.5 days) while osteoid was first detected adjacent to the hypertrophic cartilage of H. H. stage 30 (6.5‐7 days) tibial diaphyses.These results, correlated with the immunoflourescent studies of Von der Mark et al. ('76a,b), which revealed the presence of Type I (bone‐type) collagen‐synthesizing cells in the perichondria of tibiae from embryos of H. H. stage 28 (5.5‐6 days), demonstrated that the onset of determination of cells for osteogenesis and the cytodifferentiation of the periosteum are not temporally coupled.
Pheromone glands of microcaddisflies, (Trichoptera: Hydroptilidae)
Authors: Roemhild George 
Published: February 2005

AbstractPreviously unreported structures found on the head and thorax of several species of microcaddisflies (Trichoptera: Hydroptilidae) are described. Depending on the species, these presumptive pheromone‐producing glands are found either (1) on the basal segment of the antenna, (2) on movable and immovable occipital sclerites, (3) as eversible organs from the occipital area of the head, or (4) on structures which are attached near the bases of the front wings.
Structural modulation of the surface and cytoplasm of oocytes during vitellogenesis in the lobster, Homarus americanus. An electron microscope‐protein tracer study
Authors: Schade Martha Louise , Shivers Richard R. 
Published: February 2005

AbstractThe present investigation describes the ultrastructural changes which occur at the surface and in the cytoplasm of developing oocytes of the lobster, Homarus americanus, during vitellogenesis. The immature oocytes showed no surface specializations of the oolemma and no pinocytotic activity was observed. Horseradish peroxidase (HRP) tracer studies showed penetration of the tracer into the perivitelline space, but no uptake by the oocytes. The surfaces of oocytes examined during vitellogenesis, when yolk protein accumulation was maximal, exhibited numerous microvilli that projected into the perivitelline space, often appearing to be embedded in the follicular cell mass. In addition, the plasma membrane of vitellogenic oocytes contained many pinocytotic pits frequently situated at the bases of microvilli. The perivitelline space was engorged with electrondense material which appeared similar to that contained in pinocytotic structures of the oocytes. Vitellogenic oocytes incubated in HRP showed uptake of tracer reaction product by the coated pits and vesicles of the oolemma. Aggregation and subsequent fusion of these vesicles into large multivesicular bodies of ingested material were also observed in vitellogenic oocytes. Animals artificially induced to undergo vitellogenesis exhibited modulations of oocyte ultrastructure similar to those of normal vitellogenesis, notably, pinocytotic incorporation of extra‐oocytic material and hypertrophy of oocyte surface microvilli. This study supports the hypothesis for a dual source of yolk protein in the American lobster.
The morphology of dermal chromatophores in the infrared‐reflecting glass‐frog Centrolenella fleischmanni
Authors: Schwalm Patricia A. , McNulty John A. 
Published: February 2005

AbstractThe morphology and organization of chromatophores in the neotropical glass‐frog, Centrolenella fleischmanni (family Centrolenidae), were studied with both light and electron microscopes. Four types of pigment cells are described in the dorsal skin. The fine structure of two chromatophores corresponds to the typical amphibian xanthophore and iridophore; one is similar to the unusual melanophore found in phyllomedusine hylids; the fourth cell type is unlike any chromatophore previously described. Pigment granules in the unusual chromatophore are moderately electron‐dense and have an irregular shape, suggesting a fluid composition. This pigment appears to be laid down in organelles similar in appearance to pterinosomes. The organization of pigment cells in this species differs from that of other green, leaf‐sitting frogs in that there are few discrete groups resembling “dermal chromatophore units.” It is suggested that the unusual new pigment cell contributes significantly to the overall green color of C. fleischmanni.
An ultrastructural study of the craniocaudal continuation of the glycogen body
Authors: Sansone Frances M. 
Published: February 2005

AbstractAn ultrastructural analysis of the chicken glycogen body and its craniocaudal continuation areas shows a continuum of astroglial cell types. Characteristic glycogen body astroglia are confined to the classically defined body located in the chicken lumbosacral spinal cord. These are large cells which have an eccentric dark nucleus surrounded by a rim of dense cytoplasm which contains the usual complement of organelles. The remainder of the cell volume is occupied by alpha and beta glycogen particles interspersed with a flocculo‐granular material continuous with the main cytoplasmic mass. Astroglial cells of continuation areas usually have a light cytoplasm and a centrally placed nucleus. They contain beta glycogen particles of varying sizes, but like the glycogen body cells, may have beta particles as large as 45 nm. Such particles, which resemble four leaf clovers in shape, are suggestive of an ordered substructure. Gliofilaments are not always conspicuous in astroglial perikarya, but large numbers of them are present in the processes. Although the continuation areas are mostly confined to gray matter regions, the contained astroglial processes exhibit circular, triangular, or cylindrical shapes and form an unpatterned mosaic. Astrocytic processes forming the glia limitans on the anterior and posterior margins of the cord often contain conspicuous amounts of glycogen. The ultrastructural identification of such large amounts of glycogen within the chicken nervous system suggests that it plays a major role in avian neural metabolism.