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  • Analytical Chemistry and Spectroscopy  (2,552)
  • Life and Medical Sciences  (2,260)
  • 1980-1984  (4,696)
  • 1935-1939  (116)
  • 1925-1929
  • 1984  (1,650)
  • 1982  (1,711)
  • 1980  (1,335)
  • 1935  (116)
Collection
Publisher
Years
  • 1980-1984  (4,696)
  • 1935-1939  (116)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 1-29 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two kinds of spermatozoa are formed in the testis of Goniobasis laqueata, typical (eupyrene) and atypical (apyrene); a similar dimorphism is noted in several other related genera. The development of each type of spermatozoon is described in Goniobasis. The apyrene spermatozoa do not appear in the testis until eupyrene spermatogenesis has progressed to the formation of mature eupyrene spermatozoa. After this time apyrene spermatogenesis becomes predominant. It is suggested that this condition is indicative of a modified protandric hermaphroditism, according to a recent theory of spermic dimorphism. The anatomy of the reproductive system of Goniobasis is described briefly, and the behavior and fate of the two types of spermatozoa are noted. Only the eupyrene spermatozoa are inclosed in a spermatophore formed in a special organ of the male, the apyrenes being somehow excluded. Thus the latter do not reach the female in copulation and can have no necessary functional relationship to the ova at the time of fertilization. The delayed formation of the apyrene spermatozoa, and other facts, indicate that they are probably not concerned with the nutrition or transport of the eupyrene spermatozoa.
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  • 2
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 61-89 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Three pairs of thymus primordia are found at 6 to 6.5 mm. on the dorsal lateral ends of the second, third and fourth visceral pouches. Those on each side after fusing by growth and migratin come to lie above the third visceral pouch, whence the thymus migrates upward and backward; growing in size, it stretches above the ends of all the gill pouches. It pushes inward into the mesenchyme at 12 to 13 mm. and becomes perforated and surrounded by blood vessels and connective tissue which separate it almost completely from the epithelium. No septa are found; occasionally the third primordium fails to fuse and forms a separate lobe.The early thymus is a syncytium in which are found lymphoblasts, identified by structure of the cytosome and its behavior during mitosis. Evidence is presented that lymphoblasts migrate into the thymus where they increase in number with corresponding increase in length of cytoplasmic bridges and size of intercellular spaces. At 10 mm. begins a rapid increase in size of the thymus and in number of lymphoblasts and decrease in size of the latter, culminating at 12 to 13 mm. in their transformation into thymocytes. A medulla associated with blood vessels is unmistakable at 30 mm.
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  • 3
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of the development of the sense organs of the larva of Botryllus schlosseri to determine, if possible, any homologies between its sense organs and those of other types of ascidians such as Molgula and Ammaroucium, which have sense organs structurally very different.The statolith appears in the Botryllus embryo as a single club-shaped cell. The lightsensitive organs have their primordia slightly later as five small filaments, each developed from a ganglion cell. A cavity appears in the statolith into which the light-sensitive filaments penetrate. Later development is concerned with pigmentation of the statolith, and a twisting process which orients it into the position in which it is found in the free-swimming larva. The three tactile papillae develop from evaginations of ectoderm at the anterior end of the embryo. The ectodermal cells at the center of a papilla are differentiated into rod-shaped sensory receptors and ganglion-like masses of nerve tissue. Nervous connections are established between these peripheral ganglia and the central nervous system.Results of the investigation indicate that the statoliths of the different ascidian larvae are homologous; the direction eyes probably are not, but have evolved independently from a light-sensitive area in the primitive larva of a common ancestral ascidian. The larvae of Molgula and Ammaroucium possess no structures comparable to the sensory papillae of Botryllus.
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  • 4
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 5
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 335-351 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of the brinchial epithelium in representative specimens of Cyclostomata Elasmobranchii and Teleostei fishes has been made, with special reference to the following: 1) the importance of physiological role of osmotic regulation effected by the gills; 2) the presence or absence of specialized secretory tissue; 3) progressive evolution of the fishes and the possible phylogenetic difference between them. In regard to these topics we find: 1) There is no indication of any specialization in the branchial epithelium of fishes indicating a special role in extrarenal excretion. 2) In the respiratory epithelium of fishes widely separated phylogenetically or in fishes in living in fresh or salt water, the only significant differences are that in general the teleosts have a squamous type of epithelium, whereas, the elasmobranchs have in general a thicker polyhedral investment. 3) Mucous cells appear large and numerous on the filament proper, smaller and less numerous in the interlamellar spaces, and on the free surface of the lamellae. These are the only specialized secretory cells which occur in the gills.
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  • 6
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 461-471 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The exeretory system of Typhlocoelum cucumerinum consists of three pairs of longitudinal channels communicating by a single ventral vessel with the excretory vesicle. Branches subdivide extensively and anastomose forming a dense network of tubules throughout the body. The vessele possess many of the features characteristic of lymph systems as described in amphistome trematodes. They have cuticular walls, come into intimate association with the intestine and contain a granular coagulum and cellular elements suspended in the lumen. The single system of vessels appears to be functioning as a combined lymph and excretory system. Typhlocoelum americanum Manter and Williams ('28) is regarded as a synonym of Typhlocoelum cucumerinum (Rud. 1809).
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  • 7
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 597-615 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the thyroid has been briefly described from an example of each of the four urodele families and comparisons drawn. An attempt has been made toward clarifying previous and conflicting accounts. The thyroid arises as a solid bud from the floor of the pharynx in the region of the first visceral pouches. This bud grows backward until it reaches the pericardium. Division of the primordium into lateral portions is inaugurated and the anterior end of the splitting thyroid loses its connection with the pharynx before the separation of the parts is completed. Some of the undivided anterior portion may persist as an accessory thryroid. After the two lateral thyroid masses are separated the yolk disappears from the cells which then form cell columns and enlarge as a result of the fusion of adjacent vesicles. A thyroid [release] occurs at the time of metamorphosis except in Necturus. After the [release] the follicles refill. Similarities in development and general histological picture are closer between Necturus and Cryptobranchus as a pair than between either of these forms and Amblystoma or Eurycea. Amblystoma and Eurycea also resemble each other in histological picture. It is suggested that Necturus produces the thyroid hormone in sufficient quantity to induce metamorphosis but that some other factor or factors serve to inhibit the response.
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  • 8
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 9
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935), S. 41-85 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Extensive measurements were made on skeletal configurations and muscles of several forms of Hemiptera-Homoptera from the early nymphal instars to the adults, inclusive. It has been shown that several of the muscles actually decrease in length (i.e., contract) as the animal grows as a whole. Such a state of affairs has never before been observed, so far as the writer knows. The most marked increase in length of a skeletal invagination often coincides with the greatest amount of contracture of the muscle which is attached to its extremity. The characteristics of the arthropod skeleton, which consist of invaginations and evaginations are probably, in the forms studied, due to muscular contraction or to the prolonged sustenance of muscular tonicity.The form of muscular contraction described probably belongs to the ‘catch’ type rather than to the metabolic type. The direct cause of these muscular contractions is probably due to changes in physico-chemical constitution of the haemolymph.
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  • 10
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935), S. 173-188 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The tubules vary in number from about 190 to 300. They gather into twelve groups each consisting of an anterior and a posterior division and each emptying into one of twelve ampullae arranged equi-distant from each other about the wall of the posterior mid-gut and in a transverse plane just anterior to the sphincter muscle which marks, externally, the junction of mid- and hind-gut, that is to say, the ‘pyloric valve.’ The lumen of each ampulla is continuous with one of twelve furrows formed by the gathering of the hindgut epithelium into as many folds.The wall of the digestive tube is made up of, (1) an inner epithelium (tall columnar cells), (2) an intermediate connective tissue layer, and (3) an outer muscular coat (inner circular and outer longitudinal layer). The mid-gut epithelium dips down at frequent intervals to form crypts at the bases of which are the ‘regeneration centers.’ This epithelium is covered, on its luminar surface, by a curious striated border. The epithelium of the hind-gut appears to be covered by chitin.A malpighian tubule consists of a single layer of large polygonal cells with indistinct borders. It is covered externally by a thin membrene made up of ‘peritoneal cells’ and internally by a striated border similar to that in the mid-gut. Spiralling about each tubule from origin (free end) to insertion (in the gut) is a slender tracheole.
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  • 11
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The flexures in the flexed-tailed mouse consist of unilateral fusions of adjacent vertebrae. Fusions, if complete, produce straight stiff segments.In normal mouse embryogeny, the precartilage cells surrounding the developing nucleus pulposus of the embryonic intervertebral disk in the proximal tail region begin to elongate and become fiber-like at about 14 days after fertilization. In the flexed mouse, such differentiation fails to take place on one side of an affected disk, and these cells develop through cartilage to bone. At such a point there is frequently a bend in the notochordal axis. Other abnormalities of the notochord have been observed. These are not the cause of the flexures.The gene for flexed tail also produces two effects more general in their expression. First, it slows the growth of the vertebral column as indicated by the shorter vertebrae of the proximal tail region. This is observable 13 days after fertilization. Second, it produces an embryonic anemia which is already in existence at 14 days after fertilization. It is postulated that the flexures are due to the retardation of growth at a time which is critical for the intervertebral disks. Whether this retardation is the primary effect of the gene and produces the anemia, or whether the anemia is primary and produces the retardation, the data do not show.
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  • 12
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935), S. 279-284 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The histological structure of the eye of the monotreme, Echidna hystrix is described with reference to its comparative relationships. The eye is primarily mammalian in character but its choroid contains a definite cartilaginous plate and its retina is anangiotic.
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  • 13
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935), S. 555-571 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Each contractile vacuole system of Paramecium multimicronucleata is made up of a number of components, some temporary and others permanent. The contracting vacuole with its membrane is a temporary structure as are the vesicles which fuse to form it. The vacuole discharges its contents to the exterior leaving a vestige closing the pore. The pore, with its discharging tubule and the feeding canals are permanent cell organelles. The feeding canals end in injection tubules which extend up to the pore. The vesicles, which later fuse to form the vacuole, are formed at the proximal end of the injection canals, leaving a membrane closing the canal, much as a food vacuole is formed at the gullet. The canal-fed contractile vacuole of Paramecium is very similar to the vesicle-fed vacuole of Euplotes both as to its origin and its fate. The Nassonov homology is rejected.
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  • 14
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935), S. 473-499 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The hypoglossal downgrowth is initiated at about the twenty-somite stage, as ventral extensions from the postotic (occipital) myotomes 3 and 4. At thirty somites, occipital myotomes 2, 3 and 4, and cervical 1 have developed ventral processes. These descending processes with contributions from posterior myotomes later form a common condensed area below myotomes 2 to 7, the submyotomic tract. There develops from this a cord of mesoderm, the hypoglossal cord or downgrowth.The anterior postotic myotomes are classed as indirect (numbers 1, 2, 6 and 7) or direct (numbers 3, 4 and 5) contributors to the hypoglossal downgrowth.Mechanical factors associated with this growth process are discussed.The hypoglossal nerve at 75 hours has six roots, four occipital (numbers 1 to 4) and two cervical. The first two occipitai roots fail to keep pace in development and are subsequently lost. A transïtory connection of the third cervical to the hypoglossal nerve is demonstrated at the age of 5 days. At 6 days the first occipital root is reduced to scattered fibers, the remaining occipital roots, numbers 2 to 4, increase in size, cervicals 1 and 2 join the hypoglossa.The correspondence of the myotomes providing the contributions to the hypoglossal cord and the nerves providing the major contributing roots of the hypoglossal nerve is commented on.
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  • 15
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    Journal of Morphology 57 (1935), S. 501-531 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study is presented of the most anterior postotic somites in a series of embryos from the five-somite stage to 16 days. A gradual fading out of the somite forming tendency in this region seems to be indicated both by the formation of a rudimentary somite and by conditions found in the first true somites.There are, in the rabbit, three occipital somites, all of which form myotomes. The fate of the myotomes is traced until their identity is lost in the formation of definitive muscle masses.From the sclerotomes two occipital arches, comparable to those of vertebrae, are formed and can be identified as late as the time of beginning chondrification. There is a marked compression of the tissues in this region, the sclerotomal material being not only relatively but actually shorter in older embryos. This compression results in, 1) the approximation of the hypoglossal roots, and, 2) the fusion of the two occipital arches.The cartilaginous basal plate in rabbits begins development at its caudal end and differentiates anteriorly from this with little evidence of a primitive segmentation except as this posterior first center might be called a segment.
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  • 16
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The female black scale possesses a pair of lateral ocelli. Each develops as a small disc of enlarged hypodermal cells which increases in size and invaginates. The disc finally becomes cut off from the hypodermis to form a vesicle lying between the regular hypodermis and the lateral margin of the brain. The vesicle becomes differentiated into two parts. The outer group of cells forms the vitreous body, the inner group gives rise to the retina. The vitreous body soon begins to secrete the lens which, during embryonic life, becomes biconvex. Pigment granules form only in the retinal cells; at first yellow, later black. The ocellus of the first instar is similar to that of the embryo. During first and second ecdyses the old lens is cast off and a new one secreted by the vitreous body. A large, irregularly shaped crystalline body forms between the vitreous body and the retina. The ocellus is of four parts: lens, vitreous body, crystallin body and retina. Retinal cells are at first nucleated but the nuclei probably pass to the nerve fibers each one of which is connected to a retinal cell. The ocellus does not change in structure throughout the life of the insect but finally disintegrates. The disintegration begins on the inner surface of the lens. Ocelli developed in the embryo remain unchanged throughout the insect's life.
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  • 17
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This article describes the structural features of the mantle and shell, particularly in the tiger snail, Anguispira alternata. The shell and the slime appear to be secreted simultaneously, probably from the same sources, and except for the mucus probably from the same materials, but certainly through very different structures.It is found that all the layers of the shell are secreted in a liquid or semi-liquid state by some part of the mantle. The periostracum is secreted from the supramarginal groove as a liquid which soon toughens as viscosity increases until it forms the organic covering of the shell. The inner layers are derived from epithelia beneath the shell, crystallizing out of a semi-liquid mass into the characteristic patterns, which we recognize as the layers of calcium carbonate. This process is traced from the synthetic viewpoint in the secretion from the mantle, also some of the stages can be detected from the analytic standpoint in the breakdown of shell materials.Some phases of the above structural states can be recognized in living mantles. A chemical analysis of the shell is also given.
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  • 18
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    Journal of Morphology 58 (1935), S. 87-115 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: From the first larval instar until the time of the final transformation into the adult the thoracic muscles are numerically the same. The muscles increase in fiber number with the growth of the larvae. There are two types of larval muscles: a. functional (striated and of considerable diameter) b. non-functional (unstriated and of narrow diameter). The non-functional muscles are mainly the prospective wing muscles of the adult. They grow most in diameter at the time of the final transformation. The positions of attachment of both types of muscles undergo no marked replacements during transformation, although the skeletal parts to which they are attached may become greatly modified. The larva has numerically more muscles than the adult. Extensive obliteration of the trunk leg muscles and of some neck muscles takes place. The intrinsic leg muscles of both the larva and the adult are the same.There are no anlagen of the adult muscles in the larval labium, and myoblasts probably form the adult musculature of this organ.The wing muscles of adult Anisopterid dragonflies insert close to the articulations of the wings on apodemes arising from membranes, or on discs arising as internal invaginations of detached, lateral, tergal plates.During the metamorphosis of its musculature, a dragonfly exhibits every essential phenomenon that a so-called ‘holometabolic’ insect does.
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  • 19
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    Journal of Morphology 163 (1980), S. 99-133 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Study of the visceral anatomy of 41 specimens of amphisbaenians representing 13 genera shows that they share a very distinct structure which differs from that found in either snakes or typical lizards. The left lung is large while the right is rudimentary or absent (unique); the kidneys are freely suspended in the coelom by a mesentery (unique); the spleen is usually embedded in the anterior end of the pancreas (as in snakes); the gall bladder lies in a notch in the liver, and the kidneys lie opposite each other (as in lizards). The distinctness of this pattern supports the recognition of the Amphisbaenia as a separate suborder of the Squamata.
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  • 20
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    Journal of Morphology 163 (1980), S. 175-190 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light and electron microscope studies were made on harvestman oocytes during the course of their origin, differentiation, and vitellogenesis. The germ cells appear to originate from the ovarian epithelium. They subsequently migrate to the outer surface of the epithelium, where they remain attached often by means of stalk cells which suspend them in the hemocoel during oogenesis. The “Balbiani bodies,” “yolk nuclei,” or “nuage” constitute a prominent feature of young, previtellogenic oocytes, and take the form of large, but variable sizes of electron-dense cytoplasmic aggregates with small fibrogranular components. The cytoplasmic aggregates fragment and disperse, and cannot be detected in vitellogenic oocytes. The young oocytes become surrounded by a vitelline envelope that appears to represent a secretory product of the oocyte. The previtellogenic oocytes are impermeable to horseradish peroxidase under both in vivo and in vitro conditions. In addition to mitochondria, dictyosomes, and abundant ribosomes, the ooplasm of the previtellogenic oocyte acquires both vesicular and lamellar forms of the rough-surfaced endoplasmic reticulum. In many areas, a dense homogeneous product appears within the cisternae of the endoplasmic reticulum and represents nascent yolk protein synthesized by the oocyte during early stages of vitellogenesis. Later in vitellogenesis, the oocyte becomes permeable to horseradish peroxidase under both in vivo and in vitro conditions. This change is associated with a massive process of micropinocytosis which is reflected in the presence of large numbers of vesicles of variable form and structure in the cortical ooplasm. Both spherical and tubular vesicles are present, as are coated and uncoated vesicles. Stages in the fusion of the vesicles with each other and with developing yolk platelets are illustrated. In the harvester oocytes, vitellogenesis is a process that involves both autosynthetic and heterosynthetic mechanisms.
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  • 21
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    Journal of Morphology 164 (1980), S. 25-38 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The clitellar epithelium of the freshwater oligochaete, Tubifex hattai, is composed of four types of gland cells (Type I, II, III, and IV), in addition to the cells generally found in the epidermis of this worm. The possible function of these gland cells in cocoon formation was studied with the electron microscope.Type I cells discharge their secretory granules by means of compound exocytosis and provide the materials for the future cocoon membrane. Immediately after completion of the discharge from Type I cells, Type II and III cells simultaneously discharge their secretory granules by means of compound exocytosis. The secretions from Type II cells constitute a colloid in the cocoon lumen and probably cause structural modifications in the future cocoon membrane. The secretory products from Type III cells form the cocoon plug. Although the process of discharge of secretory granules from Type IV cells was not observed, the contribution of these cells to the cocoon formation, producing hoops on the outer surface of the future cocoon membrane and fixing its anterior ends on the clitellum, is inferred from a morphological comparison of the hoop and the structure of the secretory granules.
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  • 22
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    Journal of Morphology 164 (1980), S. 69-81 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution and activity patterns of monoamine oxidase and monoaminergic (formaldehyde-induced) fluorescence in the central nervous system of web-building and hunting spiders have been studied using histochemical methods. Enzyme activity occurred in the neuronal perikarya and in varying intensity in the structures of the neuropile mass, but only when dopamine, adrenaline, and noradrenaline were used as substrates. The optic centres of the spider brain normally exhibited relatively strong enzyme reactions when compared with the staining intensity of the rest of the nervous system.The neuronal cell bodies contained numerous granules of yellow-green fluorescence. Monoaminergic fluorescence of the neuropile was generally a weak green. The optic mases of the hunting spiders, the anterior bridge, several commissures of the ventral cord, and the neural lamellae showed a slightly higher fluorescence intensity and single fluorescing granules.The results obtained indicate the presence of catecholamines in the spider nervous system.
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  • 23
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    Journal of Morphology 164 (1980), S. 107-119 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The tongue of the striped dolphin, Stenella coeruleoalba, shows a V-shaped row of pits on its posterior dorsum. Their development is described on the basis of macroscopic and light microscopic observations on fetal, young, and adult stages. Four to eight pits occur, most often five in the adult. Anlagen of the pits first protrude as round epithelial thickenings which later increase in diameter and become thin. The circular primordia then sink, and grooves oriented both circularly and radially develop in the walls of the shallow pits thus formed. Pits and grooves deepen with development so that older pits become lined with conical projections. As pits grow further, they become elongated anterolaterally, retaining slit-like openings. Each pit in the adult is 2-8 mm long and about 1 mm wide. The pits are not derived from lingual gland ducts but develop independently. Taste buds resembling those of other mammalian tongues can be found in young dolphins but are few in number and limited to the thin epithelium of the pit projections and to that of the side wall of the pits. They first appear in the late prenatal period but degenerate in the adult. A rich nerve supply is observable in the lamina propria below taste buds in the calf. The pits and their projections in the dolphin correspond to the vallate papillae of other mammals, but whether each projection or a whole pit corresponds to a single vallate papilla is undecided.
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    Journal of Morphology 164 (1980), S. 139-159 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two morphologically distinct structures occur on the surfaces of the oral papillae in several loricariid catfish species; namely, (1) typical vertebrate taste buds composed of receptor and sustentacular cells and (2) brushlike projections, termed epidermal brushes, that represent specialized epidermal cells containing keratin. Both of these structures were studied with the combined use of light microscopy and scanning and transmission electron microscopy. The general body surface, fins, and rostral cutaneous processes of some loricariid catfishes are covered with taste or terminal buds but lack the epidermal brushes. It is suggested that the epidermal brushes found on the oral papillae serve as protective devices for the taste buds and as abrasive surfaces for substrate scraping during feeding. The taste buds on the oral papillae may detect any gustatory stimuli from the resulting substrate disturbance. Comparative studies reveal many differences in the number and spatial arrangement of these two structures on the oral papillae among the several species of the Loricariidae examined. These differences may represent functional adaptations to the various modes of life in the Loricariidae.
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  • 25
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    Journal of Morphology 164 (1980), S. 83-88 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Y-organ has been histologically identified in all six larval stages of the crab, Cancer anthonyi. The paired glands are located anterior to the branchial chamber and ventral to the base of the antennules. In the first zoeal stage the gland consists of a cord of 6 to 10 epidermal cells with dark staining nuclei, sparse cytoplasm, and indistinct cell boundaries. As development progresses the glands become more complex through extensive folding and intertwining of the cellular cords. The glands in all larval stages show cyclical activity which corresponds to the molt cycle. Immediately following a molt the gland is dense and compact with little cytoplasm. At approximately day four in the molt cycle, the glands become greatly hyperthropied due to an increase in the number and size of the cytoplasmic vacuoles. These histological changes suggests a cyclical production and presumably the release of some product most likely ecdysone.
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  • 26
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    Journal of Morphology 164 (1980), S. 89-105 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The digestive tract of a harpacticoid copepod, Tigriopus californicus (Baker), was studied by using techniques of light and electron microscopy. Four cell types could be distinguished: type 1, an embryonic cell which will replace cells worn away or lost during secretion; type 2, a cell which synthesizes and secretes proteins and also plays a role in lipid absorption; and types 3 and 4, two cell types which absorb lipids. From the abundance of each cell type, the length of microvilli, the development of basal plasma membrane (PM), and luminal projections, the following conclusions were made. (1) The midgut caecum absorbs digested nutrients. (2) The anterior midgut absorbs nutrients and more importantly functions in merocrine and exocrine secretion. The presence of concretions in cell types 2 and 3 in the anterior midgut suggests that these tissues contribute in excretion, and in water and/or ion regulation. (3) The posterior midgut absorbs nutrients and contributes some holocrine secretion.
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  • 27
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    Journal of Morphology 164 (1980), S. 161-166 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tactile hairs are present on all three subsegments of the antennal flagellum of the human louse. There is, in addition, a single chemoreceptor (tuft organ) on subsegment 2 and 12 or 13 chemoreceptors (one tuft organ, two pore organs and nine or ten pegs) on subsegment 3. The cuticle surrounding the bases of the pegs at the tip of the antenna is unusual in that parts of it are perforated by many fine pores. This cuticle is underlain by a thin layer of dendrites. This region may also have a chemoreceptor function.
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  • 28
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    Journal of Morphology 164 (1980), S. 121-138 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The heart-body of the marine worm Amphitrite, located within the supraesophageal dorsal vessel, is in the form of a cylinder the thin wall of which is deeply corrugated by luminal projections and folds along its entire length. It is anchored in places to the luminal surface of the dorsal vessel by an extracellular matrix containing collagen fibers. The luminal surfaces of both the heart-body and the dorsal vessel are covered by a basement membrane-like vascular lamina which in turn supports a discontinuous pseudoendothelium of littoral hemocytes.The cells of the heart-body constitute a pseudostratified, high columnar epithelium. They possess extensive rough endoplasmic reticulum (RER), a well developed Golgi zone, ferritin particles and granules, and several types of membrane-bound inclusions. Hemoglobin molecules identical to those in the circulation lie within cytoplasmic, membrane-bound vesicles. Analysis of our electron micrographs suggests the following sequence of hemoglobin production and secretion: Large quantities of a moderately dense flocculent material, probably globin, are synthesized in RER and move to the Golgi zone within partly rough- and partly smooth-surfaced transitional cisternae; small transport vesicles, formed from Golgi cisternae that have fused with transitional cisternae, convey the flocculent material from the convex to the concave face of the Golgi complex; a similar flocculent material and an amorphous, highly dense material are processed in the Golgi complex and are transferred to condensing vacuoles in which clearly identifiable hemoglobin molecules are first observed. Mature secretory vesicles containing only hemoglobin migrate to the cell periphery and discharge their contents by exocytosis. Hemoglobin molecules then cross the vascular lamina to reach the circulation.
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  • 29
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    Journal of Morphology 164 (1980), S. 167-211 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The dermopteran basicranium combines a primitively constructed and oriented auditory bulla formed by ectotympanic, rostral entotympanic, and tubal cartilage with derived features of the middle ear transformer and internal carotid circulation. Living dermopterans possess a primitive eutherian auditory region that has been structurally modified to perceive a lower frequency sound spectrum than probably was utilized by ancestral Mesozoic therians. Perception of the low to midfrequency range is enhanced in Dermoptera by reducing stiffness in the mechanical transformer while maintaining low mass of the component parts. Stiffness has been reduced by (1) development of an epitympanic sinus about four times the volume of the middle ear cavity proper, (2) detachment of the anterior process of the malleus from the ectotympanic, and (3) by delicate suspension of the ear ossicles within the middle ear.We apply to dermopterans a measure of hearing efficiency derived from recent functional studies of the mammalian middle ear that regards the middle ear mechanism as an impedance matching transformer. Calculation of the impedance transformer ratio for Dermoptera suggests that these mammals are relatively efficient in comparison to other eutherians in their ability to match the impedance of cochlear fluids to that of air at the eardrum. Dermopterans theoretically are capable of using over 90% of incident sound energy striking the eardrum at the resonant or natural frequency. Mechanical impedance of the middle ear transformer exerts a minimal influence on hearing efficiency due to low mass, little stiffness, and little frictional resistance.Analysis of measurements of the middle ear transformer published by Gerald Fleischer and integration of these data with current theory on the peripheral hearing mechanism in mammals allow us to propose a model that describes the structural and functional evolution of the mammalian middle ear transformer. Structural changes appear to be correlated with alteration in function from primitive small mammals with stiff middle ear transformers and high frequency dominated hearing to mammals with a wider range in body size with more mobile middle ear transformers and a greater range of frequency perception, often including improved sensitivity to lower frequencies.Mammals employ different anatomical strategies in attainment of increased hearing efficiency and sensitivity. Efficiency is improved by adjustment of lever and areal ratios of the middle ear transformer to achieve an optimum impedance match of external air and cochlear fluids. Sensitivity over a broad frequency spectrum is attained by minimizing mass, stiffness, and frictional resistance of the transformer. The morphology of the auditory region of both living and fossil mammals seems explicable in terms of selection pressure directed toward these ends.
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    Journal of Morphology 164 (1980), S. 311-311 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Analysis based on telemetered electromyography from the quadriceps femoris of Lemur fulvus, a Malagasy prosimian, during walking, galloping, leaping, and a variety of postural behaviors partially confirms and partially contradicts earlier hypothesized functions of this musculoskeletal complex. As predicted on the basis of morphological criteria (large physiological cross-section and long parallel fibers), the vastus lateralis is of special functional significance in leaping. This relatively large muscle consistently initiates the leap and frequently undergoes a very long period of force enhancement via active stretch. By contrast, the vastus intermedius fails to exhibit increased electrical activity and undergoes little or no active stretch during jumps. The myological details of vastus intermedius (short fibers, no fusion with other components), therefore, cannot be accounted for as adaptations to leaping. Rather, a primary postural role is indicated for the vastus intermedius, because in normal resting postures, with the knee quite flexed, it alone is continuously active. The existence of a fibrocartilaginous superior patella in the tendon of vastus intermedius, however, is most plausibly related to the complex tensile and compressive stresses generated in the tendon during the completely hyperflexed phase of leaping.The phasic patterning of the quadriceps femoris of Lemur fulvus does not point to any special role of the vastus lateralis or vastus intermedius during walking and galloping; it does indicate very different patterns of muscle recruitment in comparison to those in nonprimate mammals and some anthropoid primates. The forward cross walk (diagonal sequence, diagonal couplets) of primates versus the backward cross gait (lateral sequence) of most other mammals probably accounts for some of these differences. Lemur fulvus lacks the degree of elastic storage and release of kinetic energy in the quadriceps femoris that characterizes the gallop of dogs, cats, and Erythrocebus patas.
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  • 32
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    Journal of Morphology 165 (1980), S. 13-29 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The active motility of the cells of the yolk sac of the living Fundulus embryo was studied by time-lapse cinemicrography with phase contrast optics. In the teleost, the yolk sac lies peripheral to the body of the embryo proper and consists of a fluid-filled space bounded above by a superficial epithelium, the enveloping layer (EVL), and below by the yolk syncytial layer (YSL). The cell types treated in the present study are the enveloping layer epithelial cell, the stellate cell which lies in a layer flattened on the inner surface of the EVL, the epithelioid deep cell, the yolk sac amoebocyte, the yolk sac endothelial cell and the yolk sac melanoblast. The most actively motile cells examined in the present study are the yolk sac amebocyte and the melanoblast, which emigrates from the embryo proper at stages 19-21. The amoebocytes are compact rounded cells that move very rapidly by the extension of lamellipods with scalloped margins. The amoebocytes wander over the yolk sac in an apparently undirected fashion and invade the embryo proper when they happen to encounter it, moving between cells of the lateral mesoderm. The melanoblasts migrate by the gradual extension of elongated branching processes. Cells are sometimes monopodial, with movement being parallel to the long axis of the cell. Alternatively, movement may be perpendicular to the predominant long axis, with processes being extended alternatively from opposite ends of the cell obliquely forward, so the path described is a zig-zag to either side of the overall direction of movement. Although the melanoblasts show irregularity in their movement, the predominant direction of initial movement is away from the embryo proper. The major yolk sac blood vessels form in situ by the collective activities of presumptive endothelial cells that enclose volumes of the yolk sac space with sheet-like processes from the cell body and from the extensions that connect cells into networks.
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  • 33
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    Journal of Morphology 165 (1980) 
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  • 34
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    Journal of Morphology 165 (1980), S. 117-130 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Morphometric analysis of vertebral structure in caecilians (Amphibia: Gymnophiona) is presented. Ontogenetic variation in Dermophis mexicanus is analyzed through the 100+ vertebrae composing the column. Vertebral structure in adult D. mexicanus is compared with that in Ichthyophis glutinosus and Typhlonectes compressicauda. Centra of the atlas, second, tenth, 20th, and 50th vertebrae grow at allometrically different rates in D. mexicanus, though the 20th and 50th are not significantly different, Growth appears significantly slower in several dimensions of anterior and posterior vertebrae relative to midtrunk vertebrae in all three species. Mensural patterns throughout the entire column are similar in the terrestrial burrowers D. mexicanus and I. glutinosus; patterns in the aquatic T. compressicauda differ substantially from those of the burrowing species and are strongly influenced by allometry. Of the 112 D. mexicanus examined, 13.4% had vertebral anomalies, usually fusions.
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  • 35
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    Journal of Morphology 165 (1980), S. 131-155 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Statoblasts of five higher phylactolaemates were compared morphologically. As a result, they were divided into two groups: Group I comprising Lophopus crystallinus, Lophopodella carteri, and Pectinatella gelatinosa, and Group II comprising Pectinatella magnifica and Cristatella mucedo. These two groups are thought to represent independent evolutionary series. In Group I and in P. magnifica, the statoblasts are curved to varying degrees after the manner of a saddle. When the dorsal and ventral valves are flattened, therefore, the contour is different between the two. In Group I, the outermost layer of a mature statoblast is hard-gelatinous and basophilic; it remains intact after the statoblast is set free. The statoblast does not float until it is dry, and the float is similar in size on both valves. In Group II, a mature statoblast is covered by a softgelatinous basophilic layer, which decays after the statoblast is released. The statoblast floats without drying, and the float is better developed on the dorsal valve than on the ventral. Moreover, in the members of Group II, large yolk granules are first formed, followed by much smaller yolk granules. When their statoblasts are treated with KOH, the shell is separated completely into two valves. These characters are common to many lower phylactolaemates. By contrast, in L. carteri and P. gelatinosa, the yolk granules are uniformly small and the capsule proper resists KOH treatment. On these points, L. crystallinus is somewhat different from these two species, suggesting its primitive nature.
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  • 36
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    Journal of Morphology 166 (1980), S. 203-216 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Teeth of fetuses of a caecilian, Dermophis mexicanus (Amphibia: Gymnophiona), show ontogenetic variation in crown structure from small, multidenticulate, and non-pedicellate to larger, spoon-shaped, pedicellate teeth with a single apical spike. Number of denticles decreases as enamel-secreting cells mature. Numbers of teeth and of tooth rows increase ontogenetically. A fetal vomeropalatine set of teeth is present in D. mexicanus but absent in species previously examined. Teeth transitional to the adult shape and arrangement appear shortly before birth. The transition is correlated with birth, not fetal size. There is relatively little increase in numbers of teeth during the juvenile period. The pattern of development does not fully agree with either morphogenetic field theory or with clone theory, both as defined by Osborn ('78). Sequence of initiation is appropriate to either. Tooth shape changes agree with aspects of clone theory. Multiple rows of fetal teeth and the transition to adult follow field theory. Clone theory holds that patterns of development and shape are self-regulated, field theory that they are controlled extrinsically. I suggest that substances regulating differentiation mediate early development, and hormones later development, including inception of adult teeth, and are comparable to “field substances” influencing primordia that originate according to clone theory. Components of both theories are appropriate to analyzing tooth development phenomena.
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    Journal of Morphology 166 (1980) 
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  • 38
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    Journal of Morphology 171 (1982) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 39
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    Journal of Morphology 173 (1982), S. 87-100 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an attempt to determine the role in the immune responses of the typhlosole, a hematopoietic tissue along the ventral wall of the larval lamprey Lampetra reissneri, scanning and transmission electron microscopic observations were made on ammocoetes hyperimmunized with sheep red blood cells. Besides including the cells of the erythrocyte series, this tissue also contained the following leucocytes forming an amorphous parenchyma: the cells of the granulocyte series, the most predominant cell type, possessing a markedly lobed nucleus and membrane-bounded granules of various sizes; the macrophages possessing primary and secondary lysosomes and long lamellipodia on the cell surface; the lymphocytes of a large nucleocytoplasmic ratio with a number of long, spiky microvilli, constituting a major type of rosette-forming (antigen-binding) cells; and the plasma cells possessing highly extended cisternae of rough endoplasmic reticula that are characteristic of the higher vertebrates. The immunoperoxidase technique, which employs rabbit antibodies against lamprey immunoglobulin, proved that these plasma cells do contain immunoglobulin. These results strongly indicate that the typhlosole of the larval lamprey, besides functioning as a hematopoietic tissue, is actively involved in the antibody responses. It is also stressed that the plasma cell occurs in the most primitive vertebrates as an immunologically competent cell.
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    Journal of Morphology 173 (1982), S. 129-135 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The regenerative capacity of limbs was investigated by amputation of limbs at the zeugopodium in postmetamorphic froglets and adults of various sizes in four species of Japanese frogs, all of which showed some regeneration at these ages. In Hyla arborea japonica and Rana brevipoda porosa most young froglets regenerated their limbs well; however, the rate of regeneration decreased with the age of amputation, and the limb became nonregenerative in adults. Limbs of adults in Rana rugosa and R. japonica, on the other hand, exhibited good regeneration. All of the regenerates in the four species were heteromorphic, consisting histologically of well-developed cartilaginous rods surronded by connective tissue and skin. Limited development of muscle was appartment in regenerates of the three ranid species. The relations between body size, innervation of limbs, and regenerative capacity are discussed.
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  • 41
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    Journal of Morphology 174 (1982), S. 283-312 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structure and mechanism involved in jaw movements are described for an inertial high-speed suction feeding fish, Chaetodon miliaris. Jaw biomechanics were studied by (1) manipulation of live and fresh-killed specimens, (2) electrical muscle stimulation of anesthetized live specimens, (3) connective tissue severance experiments of fresh-killed and live anesthetized specimens, and (4) cine photography of live unimpaired and surgically impaired specimens.Three couplings appear to be involved in jaw opening: a levator operculi-opercular-interopercular-mandible coupling; and epaxial complex and/or hypaxial/sternohyoideus complex-hyoid apparatus-uncontracted protractor hyoideus-mandible coupling. Jaw opening, protrusion, closing of the protruded mouth, and jaw retraction occur in 60-110 msec. Jaw protrusion coincides with mandible depression during opening of the mouth. Closure of the protruded mouth is apparently the result of contractions of pars A1 and A2 of the adductor mandibulae muscle. Pars A3 and Aw may induce retraction of the jaws in the closed-protruded state. Jaw closure in the retracted, nonprotruded state may involve all branches of the adductor mandibulae.The importance of these findings is discussed in light of previous studies as are some proposed functions of jaw protrusion in this species.
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  • 42
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    Journal of Morphology 174 (1982), S. 41-56 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: We have studied the comparative anatomy of arterial plexuses (retia mirabilia) related to supply of the central nervous system in two closely related species of toothed whales - narwhal (Monodon monoceros) and beluga Delphinaterus leucas). In both species, retia originate from major vessels in the neck, thorax, and lumbar regions, then extend into the neural canal and cranium to supply the spinal cord and brain. The system generally consists of arteries embedded in á matrix of fatty connective tissue. Constituent vessels are only occasionally reated to veins or venous sinuses. Though retial anatomy is similar in the two species, there are two related features that appear species specific: (1) amount of retia originating from the supreme intercostal arteries and (2) thoracic retial size. Both are larger in the narwhal, as are values for hematocrit and hemoglobin concentration, which, in this study, we use as indices of diving ability. Our data are consistent with the hypothesis that the retia are in some way linked to diving ability. The nature of this link is not known; however, we discuss our results in the context of the most popular hyotheses of retial function.
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    Journal of Morphology 174 (1982), S. 141-147 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The reduced bone resorption characteristic of osteopetrosis is accompanied in the incisors-absent (ia) rat mutation by a significant increase in osteoclasts of inactive (mutant) phenotype. Restoration of bone resorption in ia rats by transfer of spleen cells from normal littermates is preceded by a transformation of osteoclasts from mutant to normal phenotype.In this investigation the proportions of osteoclasts of normal phenotype have been determined by light microscopy in untreated ia and normal rats and in ia rats treated with various cell populations from normal rats. Significant increases in numbers of osteoclasts of normal phenotype were seen in the mutant skeleton soon after cell treatments that eventually restored bone resorption and cured the disease. No changes in osteoclast phenotype were seen after cell transfers that did not cure the disease.These data establish transformation of osteoclast phenotype as an early event in the recovery from osteopetrosis and suggest that determination of osteoclast phenotype is a reliable predictor of the success of normal cell populations to restore bone resorption in this mutation.
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  • 44
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    Journal of Morphology 174 (1982), S. 169-184 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The gross morphology, histology, and ultrastructure of Liolaemus gravenhorsti gonads prior to and after differntiation are described. Special emphasis has been given to characterization and changes of the germ cell line throughout intrauterine development and 3 days postpartum.During the pregonadal stage, the primordial germ cell migrates toward gonadal rudiments by way of the mesenchyme. These cells can easily be identified by their great size, voluminous and lobulated nucleus, great quantities of yolk platelets, microtubules, and numerous lipid inclusions. In the undifferentiated gonad, the germ cells (type 1 gonocytes) have an ovoid or spherical shape and autodigestion of yolk platelets, great development of Golgi complex, and mitochondrial aggregation, though fewer liposomes, pseudopodes, and microtubules were noted. Concomitantly with the beginning of mitosis, a third type of germ cell appears, the type 2 gonocytes, which are smaller, with poorly defined membranous systems in various degrees of involution. The seminiferous cords are organized when somatic cells of the medullar portion of the gonad surround type 1 gonocytes. Germinal cells are centrally localized in the cords. Near birth many gonocytes migrate toward the basal lamina of cords and differentiate into spherical prespermatogonia, with few organoids. Sertoli cells eparate them from the basal lamina. In advanced pregnancy, Leyding cells become numerous with morphology typical of androgen-producing cells.
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    Journal of Morphology 174 (1982), S. 217-236 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: A forebrain atlas and stereotaxic neurosurgical techniques were developed for use in anatomical and behavioral experiments on the green anolis lizard (Anolis carolinensis). Green anoles are convenient and robust experimental subjects with a rich behavioral repertoire, the social components of which are partly under hormonal control.The technique and atlas were devised to conduct neuroethological investigations of the effect of lesions on species-typical display behavior. The atlas consists of 12 transverse sections from an average size adult male. The figures (4-15) are based on Nissl material and supplemented with fiber-stained material from adjacent sections. They appear at the end of the article. Limitations on the accuracy of stereotaxic coordinates are discussed and tables of correlative nomenclature for principal telencephalic and diencephalic nuclei are provided.
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    Notes: Dissection and a variety of absorption and fluorescent cytochemical methods have demonstrated that Antrodiaetus unicolor females have only one type of silk gland and spigot and, consequently, the simplest silk production system of any spider yet investigated histochemically. The small spherical to pear-shaped glands are grouped into four clusters, each cluster serving one of the four spinnerets. The spigots are long, slender, and slightly bent distally. Although all gland cells are structurally similar, each gland simultaneously produces two different secretory products, the secretion of the distal hemisphere being rich in basic protein and sulfhydryl groups, and the proximal hemisphere secretion being an acidic protein containing a high concentration of histochemically demonstrable C-terminal carboxyl groups. The two products remain segregated as they pass through the duct, where the acidic protein forms a thin outer layer around a core of basic protein. It is suggested that this segregation may persist in the silk strand after it exits from the spigot and that the outer acidic protein may be an adhesive agent.
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  • 47
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    Journal of Morphology 174 (1982), S. 335-348 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The organization of the vestibulolateral lobe of the cerebellum is described in electroreceptive and closely related nonelectroreceptive teleost fishes. The vestibulolateral lobe includes an eminentia granularis and a lobus caudalis. The eminentia granularis is a lateral line-recipient, granule cell zone which in weakly electric fish (i.e., electroreceptive fish with an electric organ) has anterior and posterior divisions associated respectively with a mechanoreceptive medial medullary nucles and an electroreceptive lateral line lobe. A lobus caudalis includes a separate granule cell zone - the pars medialis, a molecular layer, and large Purkinje-like cells. Compared with weakly electric mormyrids, the pars medialis is hypertrophied in weakly electric gymnotoids and electroreceptive silurids. However, the pars medialis is also hypertrophied in nonelectroreceptive teleosts, suggesting it is a granule cell zone not associated with electroreception and perhaps the lateral line system.
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  • 48
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    Journal of Morphology 163 (1980), S. 9-12 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Previously 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.
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  • 49
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    Journal of Morphology 163 (1980), S. 37-44 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The 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.
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    Journal of Morphology 163 (1980) 
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  • 51
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    Journal of Morphology 163 (1980), S. 157-165 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Electron microscopy of the cerebral ganglionic commissure of the leech Macrobdella decora (Say, 1824) revealed numerous neurosecretory axons terminating in the neural lamella of both the inner and outer capsules, and in the neural lamella deep within the neuropile. The proximal protions of the terminals, with an investment of glial tissue, contain either numerous large homogeneously electron dense granules, or numerous large granules of varying electron density. The distal portions, often devoid of glia, display numerous infoldings, omega profiles, and electron dense focal sites, and contain numerous neurosecretory granules, small lucent vesicles, and, occasionally, acanthosomes. Statistical analysis of the size distribution and morphology of the neurosecretory granules showed that in many individual terminals the granules are not significantly different from those seen within four groups of neurosecretory cells found in the cerebral ganglion. These terminals, because of their diffuse nature, probably represent a neurohemal complex of a primitive nature. The term “intralamellar complexes” is proposed to describe the form and location of these neurosecretory terminals.
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  • 52
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    Journal of Morphology 163 (1980) 
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  • 53
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    Journal of Morphology 163 (1980), S. 219-230 
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    Notes: Rat submandibular gland was dissociated by enzymatic digestion with collagenase and hyaluronidase, followed by mild mechanical shearing and filtration through a nylon mesh. The dissociated cell populations contained predominantly groups of acinar cells which maintained their acinar arrangement. The morphological and functional viability of the cells was confirmed by electron microscopic examination and a normal secretory response to β-adrenergic or cholinergic stimulation was observed. Both isoproterenol (IPR) and carbachol caused the fusion of secretory granules into large vacuoles which were also continuous with the lumen, and into which the secretory product was released. Secretion was assessed quantitatively from the incorporation of 14C-glucosamine into the acinar cells and its subsequent release into the culture medium as labelled glycoprotein. IPR stimulated secretion to 125% of untreated controls in the concentration range 5 × 10-5 to 5 × 10-7 M, and to 110% of controls at 5 × 10-8 M, after 40 min incubation. Carbachol stimulated secretion to 131% of controls at 5 × 10-5 M and to 115% at 5 × 10-6 M but had no effect at 5 × 10-7 or 5 × 10-8 M. The secretory response was blocked by the respective β-adrenergic and cholinergic antagonists, propranolol and atropine. These findings show that dissociated rat submandibular acinar cells provide a useful in vitro model for the study of mucus synthesis and secretion.
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    Journal of Morphology 179 (1984), S. 229-242 
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    Notes: Wild-collected adults of Bombina orientalis are bright green dorsally and red to red-orange ventrally. As a prelude to an analysis of the differentiation of pigment cells in developing B. orientalis, we describe structural and chemical aspects of the fully differentiated pigment pattern of the “normal” adult.Structurally, differences between dorsal green and ventral red skin are summarized as follows: (1) Dorsal green skin contains a “typical” dermal chromatophore unit comprised of melanophores, iridophores, and xanthophores. Red skin contains predominantly carotenoid-containing xanthophores (erythrophores), and skin from black spot areas contains only melanophores. (2) In ventral red skin, there is also a thin layer of deep-lying iridophores that presumably are not involved in the observed color pattern. (3) Xanthophores of red and green skin are morphologically distinguishable from each other. Dorsal skin xanthophores contain both pterinosomes and carotenoid vesicles; ventral skin xanthophores contain only carotenoid vesicles. Carotenoid vesicles in dorsal xanthophores are much larger but less electron dense than comparable structures in ventral xanthophores.The presence of carotenes in ventral skin accounts for the bright red-orange color of the belly of this frog. Similar pigments are also present in green skin, but in smaller quantities and in conjunction with both colored (yellow) and colorless pteridines. From spectral data obtained for xanthophore pigments and structural data obtained from the size and arrangement of reflecting platelets in the iridophore layer, we attempt to explain the phenomenon of observed green color in B. orientalis.
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    Journal of Morphology 180 (1984) 
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    Journal of Morphology 180 (1984), S. 29-35 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: This study describes intercellular bridges in the ovaries of neonatal gerbils. Electron microscopy has revealed the presence of true intercellular bridges, connecting oogonia or oocytes, in ovaries of newborn gerbils. The cytoplasm of the intercellular channels is similar to that of the connected cells, with mitochondria, smooth and rough endoplasmic reticulum, and free ribosomes present. Lysosomes are also occasionally present in the intercellular bridges and they may be involved in early waves of oocyte atresia. An electrondense substance, 350-500 Å thick, is located immediately beneath the unit membrane of the intercellular bridges. Accumulation of electron-dense material increases the thickness of the walls of the intercellular bridges, supporting and maintaining the patency of the channels. It is suggested that the intercellular channels probably allow the interchange of nutrients, organelles, and possibly regulatory materials as well.
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    Journal of Morphology 180 (1984), S. 55-68 
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    Notes: A comparative study of the forelimbs of the semifossorial prairie dog, Cynomys gunnisoni, and the scansorial tree squirrel, Sciurus niger, was focused on the musculoskeletal design for digging in the former and climbing in the latter. Based on lever arm mechanics, it was expected that the forelimb of the prairie dog would show features appropriate to the production of relatively large forces and that of the fox squirrel to relatively great velocity. Force and lever arm measurements were made of select forelimb muscles at the shoulder, elbow, and wrist joints for a series of angles in both species. Contraction time and fatigue indexes were determined for the same forelimb muscles. Contrary to expectation, in the few cases in which significant (P 〈 .05) differences were found, the forces, lever arms, and torques (force times its lever arm) were greater in the smaller fox squirrel. The observed variation in the torques produced fits the demands on the forelimb during climbing and digging as estimated from films. Several forelimb muscles of the fox squirrel show significantly higher mean contraction times than do the homologous muscles of the prairie dog. There were no significant differences between the two species in the fatigability of the selected forelimb muscles, although the mean fatigue index was always higher (less fatigable muscle) in the prairie dog. Similarities in the forelimbs of these two sciurids suggest that only minor modifications may have been required of the ancestral forelimb in order for descendent forms to operate successfully as climbers and diggers.
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    Journal of Morphology 180 (1984), S. 105-124 
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    Notes: The anatomy of neurons of the stomatogastric nervous system of Ascheta domesticus was studied using heavy metal iontophoresis through cut nerve ends followed by silver intensification. Nineteen categories of neuron are described and compared with neurons known from the stomatogastric nervous system of other insects. Possible functions for the neurons are suggested. Motor neuron candidates are suggested for all parts of the gut served by the stomatogastric nervous system, and axons of sensory neurons of the anterior pharynx are located. There are four neuron types that cannot readily be assigned motor, sensory, or interneuron functions: large dorsal cells of the frontal ganglion; the two neurons of the nervus connectivus, and two categories of neurons in the median neurosecretory cell group of the pars intercerebralis, the axons of which are contained in the stomatogastric nerves.
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    Journal of Morphology 180 (1984), S. 159-169 
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    Notes: In the pedicellar segment of the fly antenna there is a large campaniform sensillum. The central projection of the sensory cell (LCC) of this large campaniform sensillum is described from labeling with horseradish peroxidase (HRP) and cobalt. The LCC projects bilaterally to several regions of the brain and subesophageal and thoracic ganglia. The LCC processes in these termination areas were analyzed in relation to other neural processes, including the remaining antennal sensory and motor projection. This analysis was aided by combining HRP labeling with Golgi silver impregnation. Based on earlier findings and the present data we suggest that the LCC, with its various outputs in, e.g., antennal and leg motor centers, serves as a multifunctional sensory path involved in control functions necessary in flight.
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    Journal of Morphology 180 (1984) 
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  • 61
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    Journal of Morphology 180 (1984), S. 173-180 
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    Notes: During the long starvation period (November to June) of the lizard (Varanus exanthematicus), pancreatic B cells undergo profound modification. The degeneration of β granules observed in electron microscopy appears correlated with the diminution of the immunoreactive insulin-like content of the pancreas. The analogy between the phenomena observed here and those reported in animals treated with alloxan is discussed.
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    Journal of Morphology 180 (1984), S. 195-211 
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    Notes: The structure and crystallography of the internal shell of the pulmonate gastropod slug Limax maximus were studied at the levels of light and scanning electron microscopy, revealing patterns of shell ontogeny and morphogenesis. The calcified portion of the slightly convex ovoid shell is composed of a single palisade layer of calcitic crystals. Numerous projections, 100 μm in width at the dorsal tip, are found on the dorsal surface of the shell and coincide with local nucleation sites of primordial calcium salt deposition onto the periostracum. With continued calcification these projections coalesce ventrally, forming the single crystalline shell layer. The organic portion of the shell includes the periostracum and an extensive PAS-staining conchiolin. In EDTA-etched preparations, conchiolin appears as a spongy network of fibers throughout the shell. Both horizontal and vertical components of the conchiolin are present, the former of variable thickness and occurring in an intercrystalline manner, the latter always occurring normal to the horizontal set. Macromorphogenic growth is characterized by three distinct temporal stages. Primary growth occurs radially from the umbonal region. Secondary growth is synonymous with shell thickening. Tertiary growth is characterized by both a lateral component, in which the shell extends beyond the primary growth boundaries, and a ventral component, in which the shell continues to grow in thickness. SEM of the ventral shell surface reveals a pattern of growth at the crystalmatrix interface. Proteinaceous fibers of the conchiolin occur unidirectionally in horizontal rows. Zones of incipient calcitic crystallization onto these hypostracal fiber bundles are contrasted by zones of increasing crystallization until the fibrous template (reduced hypostracum) is completely covered by crystals.
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    Journal of Morphology 180 (1984), S. 271-296 
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    Notes: Electron microscopy shows that the pharyngeal lining of the larval lamprey Petromyzon marinus is a structurally complex epithelial system that can be separated into eight epithelial types: gill lamellar, gill interlamellar, goblet cell, protective, terminal (taste) bud, preciliated, ciliated in tracts, and ciliated in grooves. Furthermore, these epithelial types encompass at least sixteen different cell types based on ultrastructure and, in some cases, correlative histochemistry (PAS, Alcian blue). Common to nearly all the epithelial types are basal cells and intermediate cells. These two cell types are seen as undifferentiated. Among mature cells, structural specialization as proceeded in three directions: (1) elaboration of mitochondria, probably related to molecular transport (ion-uptake cells, chloride cells); (2) ciliogenesis (preciliated and ciliated cell types); and (3) production of mucous secretory granules (mucous-platelet cells, goblet cells, superficial protective cells, columnar mucous cells, “cobblestone” cells, and marginal and dark cells in the terminal buds). Many of the functions of the cell types relate to the process of suspension feeding in this animal.
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    Journal of Morphology 180 (1984), S. 243-252 
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    Notes: A small short muscle frequently acts across a joint in parallel with a vastly larger and longer muscle; therefore it should play a minimal role in the mechanical control of that joint. This study provides evidence suggesting that the small member of such a “parallel muscle combination” (PMC) may serve an important sensory feedback role. The spindle densities of large and small members of PMCs in man and the dog were determined and compared. Epaxial PMCs controlling canine intervertebral joints were dissected and tissue samples were embedded in paraffin, sectioned transversely to the muscles' long axis and, stained with hematoxylin-periodic acid-Schiff (PAS). Representative tissue sections were projected on to stereological grids and the percentage volume of spindles was determined. Data existing in the literature were used to ascertain spindle densities in human PMCs controlling joints in the cervico-occipital region and the extremities. The spindle density for each muscle in a group of PMCs controlling a particular motion was listed, and the mean spindle densities were determined for both the large and the small members of the group. Student's unpaired t test was used to determine the significance of the differences between mean spindle densities. Linear regression was calculated and the data were plotted graphically.In all PMCs examined, the spindle density of the small muscles was significantly higher than that of their large counterparts. It is therefore proposed that the small muscles of PMCs may function as “kinesiological monitors” generating important proprioceptive feedback to the central nervous system.
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    Journal of Morphology 181 (1984), S. 1-8 
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    Notes: The internal reproductive apparatus of female Platynotus punctatipennis is composed of the paired ovaries, paired lateral oviducts, common oviduct, spermatheca associated with its accessory gland, and a bursa copulatrix. The accessory (colleterial) glands are absent. The ovary is made up of a large number of telotrophic ovarioles which are covered by a double-layered peritoneal sheath. The terminal filament is separated from the germarium by the basement membrane of the latter and consists of a syncytial core surrounded by the peritoneal sheath. Nutritive cords are absent. The pedicel shows highly eosinophilic and PAS-positive secretion of obscure origin. The spermatheca reveals a number of interesting features. It is composed of a pair of sperm-storing tubules, enclosed in a very thin muscle layer. A winecup-like structure, provided with a thick coat of circular muscles, connects the spermathecal gland with thespermathecal duct. Four types of intimal linings occur in the spermatheca and its associated structures. The wine-cup-like connection and four types of intima are entirely new features observed. Histology of the various parts of the reproductive apparatus is described.
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    Journal of Morphology 181 (1984), S. 29-47 
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    Notes: The formation of somites, coelomic sacs, splanchnic mesoderm, fat bodies, circular system, gonads, and musculature in the embryo of the primitive moth, Neomicropteryx nipponensis Issiki, is described. The following paired somites are formed: the labral, antennal, intercalary, mandibular, maxillary, labial, three thoracic, and 11 abdominal. Small but distinct coelomic cavities appear in all these somites. Labral somites differentiate into the labral muscles, stomodaeal muscles, and dorsal dilator muscles of the pharynx. Antennal somites differentiate into the antennal muscles, aorta, and the ventral dilator muscles of the pharynx. Intercalary somites are short-lived, disintegrating to liberate many free cells into the yolk. The suboesophageal body is not formed. Mandibular somites differentiate into the mandibular flexor and extensor muscles. Maxillary and labial somites differentiate into the splanchnic mesoderm, fat bodies, and into muscles of the maxillolabial region. Three pairs of thoracic and ten pairs of abdominal somites split into the splanchric and somatic mesoderm. The 11th abdominal somites merge into the proctodaeal mesoderm, and differentiate into the musculature of the hindgut. The heart is formed by the fusion of the cardioblasts derived from the first thoracic to the tenth abdominal segment. The aorta arises from the antennal median mesoderm. Blood cells are derived from the median mesodermal cells of the maxillary to the tenth abdominal segment. Germ cells appear at the mediodorsal corner of each somite in the fifth abdominal segment. They become enclosed with a mesodermal sheath to form a pair of rudimentary gonads in this segment. Major muscles in the head, thorax, and abdomen of the fully grown embryo are described.
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    Journal of Morphology 181 (1984), S. 155-160 
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    Notes: The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series - a destal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.
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    Journal of Morphology 181 (1984), S. 97-131 
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    Notes: The three-dimensional structure of the organ of Bellonci in the marine amphipod Gammarus setosus and the relationship between its sensory cells and concretion are described using light, transmission, and scanning electron microscopy, with chemical treatment for cell lysis, calcium chelation, glycogen staining, and lanthanum labelling. The organ is encapsulated and has three units called fuselli. Each is enclosed by two fusellar cells which generate and release calcium granule strands into the cores of the fusellar concretions, which are united in the center of the organ. The surface of each fusellus is traversed by spiral dendrites entering dorsally and ending ventrally. The spiral dendrites arise from sensory neurons contained in a palm-shaped ganglion in the center of the capsule, beyond which they are twisted like a rope before reaching the concretion. The spiral dendrites are linked in pairs by gap and tight junctions and each gives origin to two pairs of 9+0 sensory cilia 30 μm apart. The ciliary distal segments give rise to long tubules which are in contact with the calcium granule strands. The ciliary proximal segments are expanded by many long mitochondria which interdigitate with the branched striated ciliary rootlets. The concretion is suspended in the capsule cavity by axons originating from four neurons of a remote mechanoreceptor. The structure of the organ suggests that it is a sensory organ involved in the reception and integration of a variety of stimuli.
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    Notes: The fine structure of the kidney and the bladder of the bullfrog (Rana catesbeiana), the bullfrog tadpole, and the mudpuppy (Necturus maculosus) were studied with special attention to the innervation of renal tubule cells and bladder epithelial cells. In the bullfrog kidney, nerve terminals and varicosities were frequently associated with the tubule cells, apparently in an increasing order from the proximal tubule to the connecting tubule. Although these terminals and varicosities did not directly contact the tubular cell membrane, an aggregation of synaptic vesicles on the side facing the tubule was considered as morphological evidence that neurotransmitter can be released here and can affect the transport activity of the tubule cells. The association of nerve varicosities with canaliculi cells in the connecting tubule was also demonstrated. In the bullfrog tadpoles, renal tubule cells were occasionally innervated. In the mudpuppy, renal tubule cells were only poorly innervated. The epithelium of the bullfrog bladder was commonly innervated. Nerve terminals with synaptic vesicles were located very near basal cells and even contacted them directly on rare occasions. In the mudpuppy, the innervation of the bladder epithelium was observed infrequently. The bullfrog tadpoles did not possess an apparent bladder. In all materials studied, renal arterioles and bladder smooth muscle cells were innervated.
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  • 71
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    Journal of Morphology 181 (1984) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 72
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    Journal of Morphology 172 (1982), S. 313-322 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The fine structure of the fat body of the higher termite king and queen has been studied both in species with (Macrotermes bellicosus, M. subhyalinus) and without (Cubitermes fungifaber) tracheal rosettes. There is a very pronounced sexual dimorphism. The adipocytes of the queen are highly specialized for protein synthesis and secretion; they store only a small quantity of reserves. The adipocytes of the king are not specialized in protein synthesis, but accumulate large amounts of reserve substances. The previously proposed different functions of the termite queen's fat body are discussed; it appears to be mainly concerned with vitellogenesis.
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  • 73
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    Journal of Morphology 173 (1982), S. 1-16 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Scanning and transmission electron microscopy, together with dissection and light microscopy, have produced heretofore unavailable structural detail of the ovary of Fundulus heteroclitus. Structural and functional interrelationships among developing follicles and other histological elements, particularly as they might relate to vascularization of follicles, oocyte development, and ovulation, are described and discussed. Mature eggs, ovulated into the ovarian lumen, accumulate in the posterior “ovisac” region of the ovary prior to oviposition. This “ovisac” region is thin-walled and apparently nongerminal. The temporary retention of ovulated eggs permits cyclical oviposition even though oogenesis and ovulation are asynchronous. The histological differences between the ovisac and the anterior ovigerous of the ovary are described. The lumenal epithelium of the ovisac displays a localized population of unusual cells with long cytoplasmic extensions. The ultrastructure of these cells suggests that they might function in the transport of ovulated eggs into the oviduct and/or in secreting the substance (“jelly”) which forms the surface coat of extruded eggs.
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  • 74
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    Journal of Morphology 173 (1982), S. 43-72 
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    Notes: A scanning electron microscopy study was made of the male setiferous sex patches and analogous structures in 11 families of Coleoptera (Anthribidae, Bruchidae, Ciidae, Cleridae, Coccinellidae, Dermestidae, Leiodidae, Ptinidae, Staphylinidae, Tenebrionidae, and Ostomatidae). These secondary sexual characters appear to have several features in common including relatively long, often ridged, setae, cuticular ducts (frequently cribriform pore plates), and the production of a secretion. It is suggested that these structures may all be concerned with the production, release, and dissemination of pheromones.
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  • 75
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    Journal of Morphology 173 (1982) 
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  • 76
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    Journal of Morphology 173 (1982), S. 159-177 
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    Notes: Single esophageal and paired cheliceral, palpal, pedal (I-IV), and opisthosomal nerves enter the synganglion and form specific neuropilar ganglia. The ganglia are integrated by a complex series of commissures and connectives. Eighteen paraldehyde-fuchsin-positive neurosecretory regions, which vary greatly in size and amount of granular neurosecretory material, are each associated (one or more) with neuropilar ganglia. Presumably transport of neurosecretory materials to target tissues occurs through axonal pathways, perineurial-neural lamella associations, and the neurohemal retrocerebral organ complex.
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  • 77
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    Journal of Morphology 57 (1935), S. 275-302 
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    Notes: The sexual dimorphism of Chinese cobitids consists of peculiar structures of the pectoral fins and of variations in the lengths of these as well as of the ventral fins. In all groups the paired fins are, as a rule, longer in the male sex, and the female has no lamina circularis, enlargement of pectoral rays or dilation of lateral muscles.In males of Cobitis and Misgurnus, the second rays of the pectorals are enlarged and possess at their base a bony plate (lamina circularis). In other Chinese genera the lamina circularis is absent. Males of the Misgurnus group are easily recognized by the dilation of the lateral muscles in the region of the dorsal fin. Males of Barbatula have several enlarged inner rays in the pectoral fin and numerous nuptial tubercles on the head, arranged in prepercular and preorbital groups. In the European, B. barbatula, however, tubercles on the head are wanting.In males of the Leptobotia and probably Botia groups, the first pectoral ray is enlarged, and the membrane between several of the inner rays is covered with nuptial tubercles.In general, in the Chinese cobitids the differences in sexual dimorphism are correlated with the differences between genera, i.e., each genus possesses a quite different sexual dimorphism; thus the secondary sexual characters can be used for taxonomic purposes.
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  • 78
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    Journal of Morphology 57 (1935), S. 533-545 
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    Notes: The thyroid primordium is a solid median outgrowth from the pharynx which is attached to the truncus arteriosus at its bifuracation. The thyroid is soon detached from the pharynx and migrates to its definitive position ventral to the aorta between the bases of the third visceral pouches. After detachment the primary follicle appears in the lower part of the primordium; during migration and early growth it is divided apparently by stress and pressure to form secondary follicles. Independent follicles are formed also by secretion of colloid between solid masses of thyroid cells. Other secondary follicles are formed by pinching off evaginations from large follicles. Colloid appears soon after the primary follicle is divided. The adult thyroid is a group of follicles scatterd in a venous plexus in the ventral pharyngeal region, around the aorta.
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  • 79
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    Journal of Morphology 57 (1935), S. 617-653 
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    Notes: Three to 5 minutes after implantation of a spermatophore in Placobdella parasitica there is a pronounced granulation of the tissues in the immediate region of the capsule. During the following 20 minutes a path 81 to 120 μ across communicating with the sinuses of the body cavity is established. By a mechanical shrinkage of the distended spermatophore the spermatozoa are injected through this path into the coelomic sinuses. They are dispersed through the body by the haemolymph and possibly by muscular contractions of the recipient. Fifty to 75 hours after their introduction into the body some of them arrive in the ventral sinus. From here they penetrate the walls of the ovisacs and take up a position in the lumina in preparation for fertilization. Two to 30 hours after implantation a plug of cells composed of migrating cellular elements of the recipient's body and of cells introduced along with the spermatozoan bundles forms in the subhypodermal region of the sperm path. Twenty to 45 hours later the wound is entirely repaired. Hypodermal epithelium is replaced by a migration into the affected region of similar reserve cells. The parenchymatous tissue is restored by a differentiation and growth of some of the cellular elements making up the plug.
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  • 80
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    Journal of Morphology 58 (1935), S. 1-39 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Flatfishes lying on one side and that blind and colorless, but having the upper side two-eyed and colored are abnormal fishes which in their own group are perfectly normal. Some normally lie right side up (dextral) others point left (sinistral). Any departure from these normal conditions constitutes such a specimen an abnormal flatfish. The simplest departure is reversal-i.e., a normal dextral fish lies on its right side and points left and vice-versa. Sixteen reversed fishes have been described, but in various species from 3 to 100 per cent reversals have been noted.Reversal might be thought dependent on the structure of the optic chiasma. The Psettodidae (lowest family) have a dimorphic chiasma (right or left nerve dorsal) and are indifferently dextral or sinistral. But the dextral Soleidae and the sinistral Cynoglossidae (highest families) have dimorphic chiasmas with only five recorded reversals. In between, the monomorphic sinistral Bothidae have the right nerve dorsal even in the five indifferent species. And the monomorphic dextral Pleuronectidae include three indifferent species (one having up to 100 per cent reversed) with the left nerve dorsal even in reversed fish. The explanation of reversal must be found in genetics.
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  • 81
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    Journal of Morphology 58 (1935), S. 157-172 
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    Notes: This study reveals the existence of four distinct but genetically related types of upper jaw mechanisms:1. The non-protractile, with no mechanism for the protrusion of the pre-maxillae. The maxillaries form part of the upper margin of the mouth, as in Isospondyli, Apodes and Haplomi.2. The crossed ligaments in the snout as in Acanthopteri, Heterosomata and Anacanthini.3. The twisting action type in which the internal hook of the maxilla drives out the pre-maxilla as found in Cyprinodontes and Percesoces.4. The rostral or sigmoid ligament attached to the pre-maxilla as in Cyprinidae and Catostomidae.The three protractile types all possess an enlarged pre-maxilla with a medium dorsal process, suggesting a common origin of all from a single non-protractile form of upper jaw.
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  • 82
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    Journal of Morphology 58 (1935), S. 211-220 
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    Notes: The shell of Cardium corbis is composed of three layers, an outer periostracum of conchyolin and two layers of aragonite. The outer aragonitic layer presents a laminated appearance, but in reality is made up of fibers which extend across several of the curved lamellar lines. Each fiber is enclosed in an organic sheath which can be dissolved in potassium hydroxide. The inner aragonitic layer is composed of vertical prisms which are made up of two sets of fibers inclined to each other at an angle of 55 to 60°. The outer layer of aragonite is secreted by glands on the mantle edge outside the pallial line; the inner layer is secreted by glands on the mantle area within the pallial line. The dentition is formed of the same material as the inner aragonitic layer.The ligament is composed of two layers, the outer being less impregnated with calcium carbonate than the inner. Both layers are continuous with the organic matrix of the shell.
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  • 83
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    Journal of Morphology 58 (1935) 
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  • 84
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    Journal of Morphology 58 (1935), S. 355-383 
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    Notes: New dissections of the caudal and short posterior thigh muscles of the reptiles Iguana, Varanus, Crocodilus and Testudo, and the mammals Sciurus, Galago and Herpestes were made, and the findings correlated with those described in the literature. The condition in the lizards, Sphenodon and crocodiles is very constant; in each case there is a puboischiofemoralis externus and an ischiotrochantericus passing from the pelvis to the femur, a deep caudal mass passing from the tail to the femur, and a superficial caudal sheet attached to the ilium and ischium. In the Chelonia, with the specialization of the gait, the deep caudal musculature has lost its attachment to the femur, and has migrated onto the vertebral column and the inner surface of the pelvis, while the other muscles occupy their typical position. In the Mammalia the deep caudal musculature has undergone a change similar to that in the Chelonia, forming the pubo-, ilio-, sacro- and ischiococcygeus muscles, while the superficial caudal musculature has disappeared except for a part which forms a sphincter cloacae. The posterior part of the puboischiofemoralis externus has formed the quadratus femoris, and the ischiotrochantericus the obturator internus and the two gemelli. In specialized mammals with reduced tails the caudal musculature has taken over new functions and become respecialized in different ways.
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  • 85
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    Journal of Morphology 58 (1935), S. 419-437 
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    Notes: A histological study has been made of the developing mid-gut or mesenteron of Melanoplus differentialis from diapause until after hatching. The primitive mid-gut consists at first of a single laver os squamous epithelium surrounding the yolk; to this is added later an outer layer. These two layers give rise to the muscular and connective tissue elements of the definitivo mid-gut. Near the of hateching, vitellophanges which have been present in the yolk since earlier stages migrate peripherally to form a lining upon the inner surface of the primitive mid-gut. The vitellophage nuclei divide to form the smaller nuclei of the definitive epithelium of the mid-gut. The vitellophage nuclei divede to form the smaller nuclei of the definitive epithelium of the mid-gut. The development of the definitive mesenteron fron the primitive mid-gut takes place rapidly and occurs near the time of hatching.
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  • 86
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    Journal of Morphology 163 (1980), S. 27-35 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The presence of scolopophorous organs in aquatic Heteroptera has been reported in a number of species. This study presents a morphological investigation of these sensory structures of Lethocerus (Belostomatidae) as observed with the scanning electron microscope (SEM). Paired mesothoracic and metathoracic organs are present. Externally, each sensory structure consists of a raised sensory membrane. The distal-most portion consists of thickenings of this sensory membrane (sclerite). The receptor neurons of the mesothoracic organ are of two types - one discolopidial sensillum and 12 monoscolopidial sensilla. The former is attached to the internal wall and distal thickening of the sensory membrane, while the latter are dispersed throughout the interior and attached to the internal wall of the sensory membrane. The structure of the organs suggest that an effective stimulus could be a compression of the membrane. A discussion of possible functions (pressure reception and hearing) is included.
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  • 87
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    Notes: Scanning electron microscopy (SEM) of the surface tubercles of a specialized mechanoreceptor found within the head of Elaphe obsoleta lindheimeri indicates that the tubercle consists of a craterlike structure with a peg emerging from its center. After removal of the outer keratinized layers of the epidermis, the SEM discloses a replicate tubercle on the underlying alpha keratin layer. Over 6000 tubercles were found within a single snake. The mechanoreceptors were more densely concentrated on anterior scales, and their number appears to be species specific so that they are more concentrated in snakes with smaller heads than in those with larger ones.
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  • 88
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    Journal of Morphology 164 (1980) 
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  • 89
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    Journal of Morphology 164 (1980), S. 265-285 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The interstitial nematode Theristus caudasaliens n. sp. normally locomotes by hopping on the left side of its tail tip, a mode of locomotion that is unique among nematodes. The animal uses its caudal glands and caudal musculature to perform the hops, attaching itself momentarily between hops with the glands and executing the hops by straightening and curling the posterior part of its body.The caudal gland apparatus can be seen by electron microscopy to consist of five gland cells of two different types. Three of these cells, termed viscid glands, are involved in adhesion of the animal to substrates and produce ovoid granules with a central dense band. The other two cells are characterized by smaller, lessdense granules and presumably function in releasing the animal from substrates. The ducts of both gland types extend to the tail tip where they terminate in a common crescent-shaped space. Their secretions are released to the outside through two pores on the left side of the tail tip. There is no spinneret valve in this nematode. The muscles of the tail and of the mid-body region are developed to the same extent.The caudal gland apparatus can be compared with the duo-gland adhesive organs of other interstitial animals, but its homology with either these organs or the caudal glands of other nematodes is uncertain. Theristus caudasaliens is described as a new species.
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  • 90
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    Notes: The ventral surface of the most proximal tarsomere of each mesothoracic leg of the female black fly, Simulium venustum Say, bears approximately 60 bifurcate sensilla. Externally, a sensillum appears as a hair set into an asymmetric socket and with the distal tip flattened into two flared lobes. A single pore opens into a short groove at the base of the lobes. The hair shaft is divided into two lumina, one of which contains the dendrites. Each sensillum is innervated by four neurons, the dendrites of which extend unbranched to the pore. Sensillum liquor bathes the dendritic tips and extends through the pore into the adjacent groove and across part of the lobes. A sieve-like structure exists in the pore region of many if not all sensilla. At least two sheath cells are associated with each sensillum.It is suggested that, although the bifurcate sensilla have the internal structure associated with known contact chemosensilla, they have secondarily acquired an olfactory function which is facilitated by the flattened lobes which increase the adsorptive surface area.Along each side of the bifurcate sensilla is a row of sturdy spines, each innervated by a neuron with a tubular body, a characteristic of cuticular mechanoreceptors. These spines are likely tactile sensilla.
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  • 91
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    Journal of Morphology 165 (1980), S. 41-54 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Histology and cytology of dermal scales of the gymnophionans Ichthyophis kohtaoensis and Hypogeophis rostratus reveal their structure and the nature of their mineralization.Dermal scales are small flat disks set in pockets in the transverse ridges of the skin. Each pocket contains several scales of various sizes. A ring of “hypomineralization” of varying diameter may occur on scales of a particular dermal pocket but bears no relation to the diameter of these scales.Three different layers form the scales and are seen on sections perpendicular to the surface. The cells of the basal layer lie deepest. Each of the two or three more superficial fibrous layers is composed of bundles of fibres that are oriented in parallel. The orientation varies among layers. The striation of the fiber scales has a periodicity comparable to that of the surrounding dermal fibers. Squamulae form a discontinuous layer on the scale surface and are the only mineralized part of the scale. The minerals are deposited both on the collagen fibers passing from the fibrous layers into the squamulae, and in the interfibrillar spaces. Spherical concretions, either isolated or coalescent, reaching up to 1 μm, are found on the surface of the squamulae.The dermal scales of Gymnophiona present some analogies with those of evolved bony fishes. Their characteristics could make them an original model for the study of mineralization.
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  • 92
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    Journal of Morphology 165 (1980), S. 67-83 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Using light and electron microscopy, three hemocyte types are described in the hemolymph of the crayfish. The coagulocyte comprises 65% of the total hemocyte number and contains medium-sized cytoplasmic granules, abundant dilated rough endoplasmic reticulum, and a highly developed Golgi complex. It rapidly undergoes cytolysis in vitro and participates in coagulation by releasing the contents of its granules to the hemolymph. The granulocyte comprises 31% of the total hemocyte number and is capable of phagocytosis. It contains large, irregularly shaped cytoplasmic granules, a moderately developed Golgi complex, and moderate amounts of non-dilated rough endoplasmic reticulum. During coagulation in vitro, the cell attaches and spreads onto the substratum; this is followed by a slow intracellular granule breakdown and cytolysis. The amebocyte comprises 4% of the total hemocyte number and it is also capable of phagocytosis. It possesses small cytoplasmic granules, many vacuoles, a moderately developed Golgi complex, and large amounts of smooth endoplasmic reticulum. It is distinguished from the other two cell types by being stable and motile in vitro.
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  • 93
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    Journal of Morphology 165 (1980), S. 85-116 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Lateral cortex is the most laterally placed of the four cortical areas in snakes. Earlier studies suggest that it is composed of several subdivisions but provide no information on their organization. This paper first investigates the structure of lateral cortex in boa constrictors (Constrictor constrictor), garter snakes (Thamnophis sirtalis), and banded water snakes (Natrix sipedon) using Nissl and Golgi preparations; and secondly examines the relation of main olfactory bulb projections to the subdivisions of lateral cortex using Fink-Heimer and electron microscopic preparations.Lateral cortex is divided on cytoarchitectonic grounds into two major parts called rostral and caudal lateral cortex. Each part is further divided into dorsal and ventral subdivisions so that lateral cortex has a total of four subdivisions: dorsal rostral lateral cortex (drL), ventral rostral lateral cortex (vrL), dorsal caudal lateral cortex (dcL) and ventral caudal lateral cortex (vcL). Systematic analyses of Golgi preparations indicate that the rostral and caudal parts each contain distinct populations of neurons. Rostral lateral cortex contains bowl cells whose dendrites arborize widely in the outer cortical layer (layer 1). The axons of some bowl cells can be traced medially into dorsal cortex, dorsomedial cortex and medial cortex. Caudal lateral cortex contains pyramidal cells whose somata occur in layers 2 and 3 and whose dendrites extend radially up to the pial surface. In addition, three populations of neurons occur in both rostral and caudal lateral cortex. Stellate cells occur in all three layers and have dendrites which arborize in all directions. Double pyramidal cells occur primarily in layer 2 and have dendrites which form two conical fields whose long axes are oriented radially. Horizontal cells occur in layer 3 and have dendrites oriented concentric with the ependyma. Fink-Heimer preparations of snakes which underwent lesions of the main olfactory bulb show that the primary olfactory projections to cortex are bilateral and restricted precisely to rostral lateral cortex. Electron microscopic degeneration experiments indicate that the olfactory bulb fibers end as terminals which have clear, spherical vesicles and asymmetric active zones. The majority are presynaptic to dendritic spines in outer layer 1.These studies establish that lateral cortex in snakes is heterogeneous and contains two major parts, each containing two subdivisions. The rostral and caudal parts have characteristic neuronal populations. Primary olfactory input is restricted to rostral lateral cortex and seems to terminate heavily on the distal dendrites of bowl cells. Axons of some of these cells leave lateral cortex, so that the rostral lateral cortex forms a direct route by which olfactory information reaches other cortical areas. The functional role of caudal lateral cortex is not clear.
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    Journal of Morphology 165 (1980), S. 157-165 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The 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.
    Additional Material: 11 Ill.
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  • 95
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 165 (1980), S. 167-174 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The relationships between dimensions of book lung subunits were measured and analyzed as a function of body size in diverse spiders over a body mass range of 3.4 to 3,190 mg. Book lungs are the characteristic respiratory gas exchange organs in these arachnids. Actual gas exchange occurs across numerous air-filled cuticular plates, which invaginate hemolymph sinuses within the abdomens of these animals. Characteristic linear dimensions of these air-filled compartments reflecting diffusion paths scaled to the 0.2 power of body mass and showed only a fourfold increase over the size range in the sample. This deviation from isometric scaling in the direction obtained and its numerical similarity to scaling of alveolar dimensions to body size in vertebrates was interpreted as an adaptation to reduce diffusion distances between these compartments and vascular fluids. Conversely, lengths and widths of these plates scaled to the one-third power of body mass, isometric scaling, and increased between six-and eightfold over the size range. This result is consistent with the hypothesis that respiratory gas distribution within spider lungs is achieved by convective mixing as has been recently hypothesized.
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  • 96
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 165 (1980), S. 223-223 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 165 (1980), S. 261-284 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This 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.
    Additional Material: 22 Ill.
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  • 98
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 166 (1980), S. 1-25 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The paired spermathecae of Rhodnius are simple tubular out-pocketings of the common oviduct. Each consists of a short muscular proximal duct and the distal glandular region with a blind tapering end. The spermathecal wall has a cuticular intima, slender columnar epithelial cells and ensheathing longitudinal striated muscle, connective tissue, tracheoles, and nerves. Glandular epithelial cells possess an elaborate apical secretion-filled tubular inpocketing with an extensively folded plasma membrane. Laterally, cells interact by desmosomes, septate desmosomes, and extensive interdigitations. The cytoplasm is rich in longitudinally oriented microtubules associating with membrane densities along the invagination, lateral, and basal plasmalemmae. Apical concentration of mitochondria suggests their role in secretion or ion transport. The possible role of the spermathecae in maintaining the stored luminal sperm and its role in transmitting the mating stimulus is considered in light of the epithelial ultrastructure. The ultrastructure of the spermathecae of Rhodnius differs significantly from that of other insects.
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  • 99
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 166 (1980), S. 65-80 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anatomical studies were conducted to characterize the source, type, and distribution of parathyroid gland innervation in European starlings. Denervation experiments demonstrated that the parathyroid glands and adjacent carotid bodies are innervated by nerve fibers originating in the nodose ganglion of the vagus nerve. In the parathyroid parenchyma, these fibers terminate adjacent to chief cells or near vascular smooth muscle. Vagal fibers also form synapses with catecholamine-containing glomus cells of the carotid body. Blood that first perfuses the carotid body subsequently perfuses the parathyroid parenchyma. These observations suggest that vagal innervation may influence parathyroid function in starlings either through direct chief cell innervation or through alteration of vascular perfusion. A neurohemal relationship also may exist between the carotid body and parathyroids.
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 165 (1980), S. 205-222 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Voles and lemmings are the most successful group of graminivorous rodents, but the adaptations allowing them to enter this niche are not fully known. Dissections of the masticatory musculature of the 12 genera and subgenera of North American microtines show an increase in the potential anterior vector component and in the potential vertical vector component of these muscles relative to the molar tooth row. The result is a separation of the compressive and propulsive functions of the masticatory muscles during the power stroke of mastication. This has led to the formulation of a propalinal “swing” hypothesis which is supported by vector analyses of the musculature.
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