bluuebunny/crossref_metadata_2025_split huggingface dataset:
The caudal neurosecretory system of Poecilia sphenops (Poeciliidae)
Authors: Kriebel Richard M. 
Published: February 2005

AbstractThe caudal neurosecretory system of the molly, Poecilia sphenops (Poeciliidae) was studied by light and electron microscopy. In this species the cell bodies form a focal nuclear group in the caudal spinal cord. The neurosecretory cells are in contact with glial elements, axon terminals, and the lumen of the central canal. The axons of the neurosecretory cells form a definitive tract, which leaves the spinal cord proper to penetrate a well defined neurohemal organ, the urophysis. The urophysis contains an abundance of neurosecretory granules within the neurosecretory axonal processes. This study is the first ultrastructural study of the caudal neurosecretory system in this family of fishes, which has been used as a neuroendocrine model. This species acclimates easily to the laboratory aquarium and may be most suitable for further studies on the effects of changes in external salinity on the caudal neurosecretory system.
The origin of protein and fatty yolk in Rana pipiens. V. unusual paracrystalline configurations within the yolk precursor complex
Authors: Ward Robert T. 
Published: February 2005

AbstractThree unusual highly ordered configurations of yolk protein in yolk precursor bodies are described. These differ from the crystalline structure of the main body of mature yolk platelets. One of these is an aggregation of paired membranes with a spacing of about 100 Å between the members of a pair. The paired membranes of such an aggregation may be straight, parallel, and very close together; they may appear as a tight whorl; or they may display an intermediate random arrangement with varying distances between pairs. Another configuration is a tubule with a diameter of about 450 Å, whose wall appears in cross section to consist of particles measuring 50 × 100 Å. A third configuration is a crystalline array of rows of angular‐shaped particles with a spacing of about 160 Å. It is suggested that these may represent intermediates in the transition of vitellogenin to lipovitellin and phosvitin.
Fine structure of the midgut posterior caeca in the crustacean Orchestia in intermolt: Recognition of two distinct segments
Authors: Graf François , Michaut Philippe 
Published: February 2005

AbstractThis study carried out on the posterior caeca of Orchestia in intermolt by means of light and electron microscopy shows that the diverticula of the midgut consist of two segments which are different from an anatomical point of view. The distal segment is in close relationship to the dorsal blood vessel, whereas the proximal segment, twice as long as the distal one, only touches the haemocoel. The cells of the distal segment are characterized by a brush border, some apical extrusions, a great number of ribosomes, rough endoplasmic reticulum, often associated with the mitochondria, the matrix of which is clear, high activity of the Golgi complexes, and a great development of extracellular channels. All these features indicate an activity in synthesizing proteins and transport. In the proximal segment, the cells are characterized by a striated border, reduced intercellular space, and especially by a great development of the smooth endoplasmic reticulum sometimes associated with mitochondria having a dense matrix. These diverse features indicate absorption ion and water transport. From an ultrastructural point of view, the posterior caeca of Orchestia cannot be considered homologous to the Malpighian tubules. Whereas during molting the posterior caeca of Orchestia are sites of calcium storage, during intermolt they are probably involved in the processes of water and mineral regulation and excretion.
Spermatogenic columns, somatic cells, and the microenvironment of germinal cells in the testes of asteroids
Authors: Walker Charles Wayne 
Published: February 2005

AbstractSixty‐seven specimens of the common North Atlantic asteroid, Asterias vulgaris, were collected at seasonal intervals over a 2‐year period and their testes observed with both light and electron microscopy. In the germinal epithelium, a predictable series of interactions between versatile somatic cells and germinal cells is repeated annually in relation to sequential events in spermatogenesis. For example, massive proliferation and differentiation of spermatogenic cells depend on the elaboration of thousands of spermatogenic columns, which are distinct cellular subdivisions of the germinal epithelium. Each fully developed column is composed of at least one somatic cell surrounded by ≈︁ 400 germinal cells. Such columns form only after intensive spermatogonial mitosis begins in the germinal epithelium. Single annual periods of spermatogenic proliferation and differentiation are initiated from 1 to 3 months out of phase in different individuals and overlap incompletely. Therefore, it is possible to observe testes that are entirely in the proliferative phase, entirely in the differentiative phase, or in both phases simultaneously. Detailed ultrastructural observations and preliminary autoradiographic data demonstrate that columns maintain their height for a variable period of time as germinal cells are generated near their bases, pass along their lengths, and differentiate near their tips; therefore, simultaneous proliferation and differentiation of more than one generation of germinal cells occur in the same column. Finally, formation of primary spermatocytes ceases basally, (terminating proliferation), and remaining columns degrade completely as germinal cells composing them differentiate or are phagocytized (terminating differentiation and spermatogenesis); resulting spermatozoa ultimately accumulate in the expandable lumen. It is proposed that spermatogenic columns provide the structural basis for organization of the microenvironment of small groups of spermatogenic cells (≈︁ 400 at a time) during proliferation and differentiation. Preliminary evidence from A. vulgaris and other species also suggests that somatic cells are temporally pluripotent and are variously involved in the formation, structure, and activities of columns, in extensive phagocytosis, and probably in contributing intrinsic (e.g., 1‐methyl adenine and steroids) and mediating extrinsic (e.g., gamete shedding substance and nutrients) microenvironmental factors influential during spermatogenesis in asteroids. The prodigious spermatogenic capabilities of asteroids apparently depend on the generation of spermatogenic columns, on the progressive interaction of germinal and somatic cells before, during, and after columns form, and on the predictable effects of microenvironmental factors received and interpreted at the structural level of the spermatogenic column.
The trunk musculature of caecilians (Amphibia: Gymnophiona)
Authors: Naylor Bruce G. , Nussbaum Ronald A. 
Published: February 2005

AbstractDescriptions of the trunk musculature of six species representing sex genera and five families of caecilians reveal considerable variation, which may be useful in future systematic studies. The muscle units of the external muscular sheath (M. dorsalis trunci, M. subvertebralis) of caecilians are homologous with, and closely similar in position to, those of salamanders. The major difference in trunk musculature is the presence in caecilians of an additional muscle layer ventral to the M. subvertebralis. This muscle may be a neomorphic derivative from either the M. subvertebralis or the M. transversus. Unlike burrowing reptiles, which have ball‐and‐socket intervertebral joints, caecilians have retained the primitive amphicoelous centrum and compensate for stresses associated with burrowing by the presence of intercentral ligaments and interlocking basapophyses and subcentral keels. Association of Uraeotyphlus with the Ichthyophiidae and the validity of the Rhinatrematidae are supported by data from the trunk musculature.
Surface ultrastructure of the cornea and adjacent epidermis during metamorphosis of Rana pipiens A scanning electron microscopic study
Authors: Kaltenbach Jane C. , Harding Clifford V. , Susan Stanley 
Published: February 2005

AbstractThe external surface of the cornea and adjacent epidermis of larvae in representative developmental stages and of adult frogs, Rana pipiens, was studied by scanning electron microscopy. Surface cells are polygonal, usually hexagonal, in outline and covered with microprojections. During larval development prior to metamorphic stages, neither eyelids nor Harderian glands have developed; microprojections on the corneal surface are high and branched, and cell boundaries are elevated. On the anterior portion of the cornea and on the epidermis near the eye, the surface pattern is less dense, and ciliated cells are present. During metamorphic stages, corneal cell boundaries become less prominent and the pattern of microprojections more variable and markedly different from that of larvae of earlier stages. Corneal cells have a spongy appearance, are covered by a coating material, or are characterized as light or dark based on their brightness and surface texture. As eyelids develop in metamorphic stages XX–XXI, the numbers of ciliated cells increase dramatically, both on the corneal surface and on the edges of the developing lids. In later metamorphic stages XXII–XXV, lids and Harderian glands become well‐developed, and cilia are no longer observed. The adjacent epidermal surface becomes devoid of cilia but perforated by openings of cutaneous glands. Its spongy appearance is similar to that of both the cornea and neighboring epidermis of the mature frog. Changes in corneal surface features are probably metamorphic events associated with development of lids and Harderian glands and a shift from an aqueous to an air environment.
The kidney of Leptonychotes weddelli (Pinnipedia: Phocidae) with some observations on the kidneys of two other southern phocid seals
Authors: Vardy P. H. , Bryden M. M. 
Published: February 2005

AbstractThe structure of the kidney of Leptonychotes weddelli was examined using corrosion casts, India ink injection, and histological methods. Some observations were made on the kidney of the crabeater seal (Lobodon carcinophagus) and the elephant seal (Mirounga leonina). The kidneys in all three species are reniculate, as in many other marine mammalian species. Features that have not been described previously in a phocid seal are a peripyramidal muscle, and venous drainage characterized by a large extrinsic system and a small intrinsic system.Examination of specialized fornices, relative medullary thickness, and the volumes of juxtamedullary relative to peripheral glomeruli (all of which relate to urine concentrating ability) revealed that each reniculus of Leptonychotes is similar to the unilobar kidney of a small mammal that produces only moderately concentrated urine. The high glomerular volume to cortical volume ratio may be related to high glomerular filtration rates after feeding observed in marine mammals.It is concluded that reniculation is more likely to be related to the large size of most marine mammals than to some factor related directly to the marine environment.
Vasculogenesis of the bursa cloacalis (bursa of Fabricius) of the chick embryo
Authors: Schoenwolf Gary C. , Bell Laird A. , Watterson Ray L. 
Published: February 2005

AbstractVasculogenesis of the bursa cloacalis (bursa of Fabricius) was examined in 10‐ to 21‐day chick embryos and in chicks during the first 5 days post‐hatching. The entire circulatory system was injected with India ink, and the bursae were then removed and either cleared for examination in toto or sectioned serially. The bursa was supplied by three pairs of extrinsic blood vessels. At 10 and 11 days of incubation, most intrinsic vessels were arranged in a superficial, hexagonal network. In regions of developing plicae, the hexagonal plexus extended into the core of each plica, forming middle plical vessels. The latter were interconnected across interplical areas by cross‐connecting vessels. The middle plical vessels gave rise to small capillary offshoots, which soon increased in complexity, forming delicate loops. Branches extended from these loops through the subepithelial lamina propria to incipient epithelial buds by 12 days of incubation. All epithelial buds were supplied by at least one such branch, and similar branches extended to the basal aspect of the epithelium in areas where epithelial buds had not yet formed. This observation is consistent with the hypothesis that blood vessels induce formation of epithelial buds. At about 15 days of incubation, the cortex and medulla of each developing lymphatic follicle were defined clearly, and an intricate, web‐like, capillary network coursed throughout the follicular cortex. The medulla appeared to be devoid of capillaries. The diameters of all intrinsic and extrinsic bursal blood vessels gradually increased throughout development. During post‐hatching stages, the diameters of the extrinsic vessels continued to increase, whereas those of the intrinsic vessels were markedly decreased from late pre‐hatching stages.
The effects of androgens on the β‐glands of the tokay (Gekko gecko): Modification of an hypothesis
Authors: Maderson P. F. A. , Chiu K. W. 
Published: February 2005

AbstractStudy of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β‐gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot‐pad, shows a pattern of histogenesis directly comparable to that of β‐glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis.
The cranial nerves of the teleost Trichiurus lepturus
Authors: Harrison George 
Published: February 2005

AbstractThe cranial nerves of the cutlassfish, Trichiurus lepturus, were described from their external brain origin to their most distal points. The nervus olfactorius, nervus opticus, nervus oculomotorius, nervus trochlearis, nervus abducens, nervus glossopharyngeus, and nervus vagus of Trichiurus are characteristic of teleosts. The cephalic autonomic nervous system also follows the general scheme for teleosts.Atypical patterns are exhibited by portions of the ramus mandibularis facialis, ramus mandibularis trigemini, nervus stato‐acusticus, and nervus lineae later‐alis. A cutaneous ramus mandibularis externus facialis arises from the ramus mandibularis; this cutaneous nerve has been recorded specifically in only certain siluroid catfish. A connection from the ramus mandibularis trigemini to the cutaneous ramus mandibularis externus facialis is present; an equivalent of this connection has been reported only in the silversides, Menidia, and the siluroid catfish Parasilurus. This nerve pattern probably represents an archaic arrangement. The nervus stato‐acusticus of Trichiurus is typical for teleosts, except for a branch extending from the posterior part of the nerve; this branch sends connections to the nervus lineae lateralis and then exits the cranium via the vagus foramen. Connections between the nervus lineae lateralis and the nervus stato‐acusticus have previously been reported in only the hatchetfish, Argyropelecus, and the bristle‐mouth, Cyclothone. This condition may represent a specialized adaptation of certain mesopelagic teleosts having extreme vertical‐migration capabilities.
Evidence for the holocrine nature of lipoid secretion by avian epidermal cells: A histochemical and fine structural study of rictus and the uropygial gland
Authors: Menon G. K. , Aggarwal S. K. , Lucas A. M. 
Published: February 2005

AbstractCells of the avian epidermis (rictus of the chicken), when examined under the light microscope following suitable fat staining, show similarities to epithelial cells of the uropygial gland of chicken and pigeon, an organ which is recognized both morphologically and functionally as a holocrine gland. Evidence thus far from electron microscopic studies strongly suggests that the skin of the bird is also a holocrine gland, although details of cytogenesis and secretion differ somewhat in the two organs.
Morphogenesis of the hereditary microphthalmia in a new strain of rat
Authors: Kobayashi Kenji , Otani Katsumi 
Published: February 2005

AbstractMorphogenesis of the eye was studied in a new strain of micro‐phthalmic rat. Abnormalities were noted immediately after the formation of the optic cup. The inner layer in the central part of the optic cup was relatively thick and contained many mitotic figures, whereas that of the marginal part was thin and contained only a few. The transitional point in the inner layer between the central and the marginal parts was well marked. This is evidently due to the extreme growth inhibition of the inner layer at the marginal part.At the early developmental stage, an area of the inner layer corresponding to the transitional point protruded toward the lens because the central part of the inner layer continued to differentiate.The differentiation and the protrusion of the inner layer proceeded variably at the later stages depending on the degree of the growth inhibition. The eyes were classified into three groups: Group A–the retina was recognized as a cyst consisting of the pigment layer and the pigment‐layerlike structure which originated from the inner layer; group B‐the neural retina and its layered structure were inverted; group C‐abnormalities, such as the destruction of the lens, were observed.Although previous authors who studied eye mutants suggested the vascular abnormality as the primary cause of the production of abnormal eyes, we feel that this is not the case in our animals.
Characteristics of gonads and oviducts in hatchlings and young of Chelydra serpentina resulting from three incubation temperatures
Authors: Yntema C. L. 
Published: February 2005

AbstractEggs of Chelydra serpentina were incubated at 30°C and 26°C. In addition, incubation was done at 20°C during the temperature‐sensitive period for sex determination. Incubation at 20°C and 30°C resulted in females; incubation at 26°C resulted in males in 99% of the cases. The average gonadal length was less in the males. The average length of the 20°C ovaries did not vary significantly from that of the 30°C ovaries.The condition of the oviducts was correlated with histology of the gonads in hatchlings and in 3‐month‐old animals. When at least one of the oviducts was obvious and intact, ovaries were present. If the oviducts were absent or interrupted, testes were present. Histological characteristics of the gonads resulting from the three incubation temperatures are described. In the 26°C testes, cellular infiltrations occurred frequently. The ovaries of 20°C hatchlings tended to have a less developed germinal epithelium than that of the 30°C animals. Also, epithelial cysts occurred frequently in the 20°C ovaries. The incidence of follicles at 3 months was not differential.
Johnston's organ in Neodiprion sertifer (Insecta: Hymenoptera)
Authors: Hallberg Eric 
Published: February 2005

AbstractThe fine structure of Johnston's organ in the pine sawfly, Neodiprion sertifer, was studied by electron microscopy to determine if there exists a dimorphism in this organ corresponding to the sexual dimorphism in antennal shape and surface area.The organ is made up of scolopidia that are ultrastructurally similar to those of other insects. The scolopidia, identical in both sexes, comprise three sensory cells bearing two types of sensory processes: Two are shorter and smaller in diameter than the third, which extends into the cuticle of the membrane connecting pedicel and flagellum and terminates at an epicuticular invagination. The dendrites and sensory processes are surrounded by two types of enveloping (glial) cells‐a scolopale cell and an attachment cell. Other enveloping cells occur at different levels of the scolopidium.Sexual dimorphism is evident only in the numbers of scolopidial groups: Males have more groups with fewer scolopidia, but both sexes possess about the same total number of scolopidia.
A stereological analysis of developing egg chambers in Ephestia kuhniella
Authors: Torres Joseph 
Published: February 2005

AbstractA polytrophic ovariole of the flour moth, Ephestia kuhniella, is composed of a linear series of increasingly mature egg chambers, each consisting of an oocyte, an interconnected cluster of seven nurse cells, and a covering layer of follicle cells. This study describes changes in the volume of each component as a function of the position of the egg chamber in the ovariole. Analysis of the growth curve of the Ephestia oocyte yields two possible correlations between accelerated oocyte growth and ultrastructural events enhancing the supply of yolk materials to the oocyte: the first is the initiation of yolk synthesis by the follicle cell layer and its transfer to the oocyte, and the second is the formation of channels between the follicle cells allowing hemolymph to gain access to the oocyte. An Ephestia oocyte increases in volume from approximately 2.5 × 103 μm3 to approximately 2.0 × 107 μm3 over an average series of 58 egg chambers.
Allometric analysis of the morphometric pulmonary diffusing capacity in dogs
Authors: Gehr Peter , Siegwart Benno , Weibel Ewald R. 
Published: February 2005

AbstractThe lung volume, the morphometrically determined alveolar and capillary surface area, and the capillary volume of 27 dogs (weight 2.65–57 kg) all were linearly correlated with body weight. The thickness of the air‐blood barrier increased only slightly with increasing body size. The structural diffusing capacity, containing these parameters, was used to estimate the gas exchange capabilities of the lung and was also found to scale in direct proportion to body size. This coincides with reports on physiologically estimated diffusing capacity but is obviously different from the interspecies slope for metabolism which scales to the 3/4 power of body weight.
Experimental regeneration of the caudal skeleton of the glass knifefish, Eigenmannia virescens (Rhamphichthydae, Gymnotoidei)
Authors: Kirschbaum Frank , Meunier Francois Jean 
Published: February 2005

AbstractThis paper describes the regeneration of the caudal axial skeleton after amputation of the tail, including about 20 vertebrae, in the gymnotoid fish Eigenmannia virescens. Seven days after amputation, a regeneration blastema developed and soft tissues degenerated. A cylinder of cartilage developed at the end of the notochord. When this cartilage was about 10 mm long (21 days), perichondral ossification began. The cartilage continued to elongate and ossification increased while osteoclasts began to destroy the cartilage ventrally. Finally, a bony rod formed and at its tip the cartilage persisted as a rod, 2 to 3 mm long. The anal fin also regenerated: Endoskeletal cartilage developed first, following by differentiation of the lepidotrichia, and finally ossification of the endoskeleton.