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  • Life and Medical Sciences  (1,092)
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  • 1980-1984  (1,084)
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  • 1981  (587)
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  • 1927  (34)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1927), S. 521-546 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The literature on the general subject of freezing and survival both in plants and in animals is briefly reviewed and a bibliography given. Insects representing three ecological groups, (1) the oak borers - exposed to temperature extremes normally; (2) stored-products insects representing supposedly a tropical or subtropical group, and, (3) aquatic insects never exposed to temperatures lower than 0°C., were chosen for this study. Determinations of the freezing and undercooling points were made during the yearly cycle.Both the stored-products insects and the aquatic insects studied showed no periodicity in freezing or undercooling. The oak borers showed marked periodicity. The freezing-point varies directly with the moisture content. Cold-hardiness was produced experimentally by, (1) exposure of insects to low temperatures and, (2) by dehydration. Loss of cold-hardiness was produced experimentally by combinations of high temperature, food, and high relative humidity. The freezing-point ordinarily found corresponds with that of the blood. Repeated freezings of the same insect or tissue showed no hysteresis. There exists in certain insects a secondary freezing-point below that ordinarily found. Oak borers in summer condition die at the first freezing-point; in fully hardened condition they die at the secondary freezingpoint.
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  • 2
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 1-20 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ant Formica exsectoides F. builds mounds with some reference to sunlight, and measurements of internal temperatures have shown them higher in upper parts of the mound, but different in different faces of the mound - all higher than the earth outside the mound.Inside temperatures are not constant; they are due to the sunshine. The mound is so fabricated that the internal temperatures are conserved during the night. The ants make use of the differential internal temperatures for rearing broods.Some mounds show bilateral symmetry dependent upon sun exposure.Measurements of rate of running of these ants show a falling off with lower temperatures, and possibly this is one factor in the smaller development of northerly aspects of these mounds.
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  • 3
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 117-125 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the early cleavage stages of Ascaris the homologous chromosomes are of unequal length. Measurements show that these homologues fall into two sharply defined groups suggesting their biparental origin. The shorter are considered to have come from the male.As the age of the embryo increases, these differences between the chromosome mates tend to become less, and it is suggested that at some later period in the history of the animal this difference will entirely disappear in response to the effect of continued existence in a common environment. The length of the chromosomes is very slightly shortened during the early cleavage divisions, while the area of the equatorial cross-section of the cells becomes enormously reduced.
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  • 4
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 313-339 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rates of oxygen consumption of single pupae of blowflies (Phormia terraenovae, Phormia regina, Lucilia sericata), of the flesh fly (Sarcophaga sarracenioides Aldrich), of the Mediterranean flour moth (Ephestia kuehniella), and of the bee moth (Galleria mellonella) during metamorphosis, until emergence, have been determined. The record for each pupa, with the exception of those of blowflies, is practically continuous day and night during the period of pupal development which lasted from 140 to 300 hours, according to the species, at the temperatures used. During pupal development there is first a period of decrease in rate, which is later followed by a steady increase until a short time before emergence, when a sudden decrease occurs.The ‘oxygen curves’ of the blowfly pupae (Diptera) are quite different from those of the flour-moth and bee-moth pupae (Lepidoptera), although all are of the same general U-shaped type. There are strong indications of a specific difference in the curves of the blow-fly pupae. The flour-moth pupae curves differ slightly from those of the bee-moth pupae. During the major part of development the rates of O2 consumption of pupae of both sexes of bee moth and flour moth are about the same, but near the end of metamorphosis the females have higher rates than the males. No such sex difference appears among the dipterous pupae used.
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  • 5
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 363-372 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The history of investigations on the contractile vacuole is reviewed briefly and brought up to date.The study of the contractile vacuole in Amoeba proteus is considered from standpoints of origin, structure, behavior, and function. The results are obtained from a prolonged study of normal organisms and from their reactions when introduced into conductivity water.The origin of vacuoles is studied by means of dark-field illumination which reveals the vacuole to be formed from a fusion and coalescence of extremely minute droplets.The retaining ‘wall’ of the contractile vacuole is not a permanent structure, but is in the nature of a condensation membrane, totally disappearing with each contraction.The loci of the contractile vacuoles are not permanent, but vacuoles are formed more or less at random. It is unlikely that they are supported in gelated areas, for amoebae with a dozen vacuoles are quite active and there is no interference with amoeboid movement.Conductivity water increases the size, number, and rate of contraction of contractile vacuoles, which suggests that they may function in maintaining an osmotic gradient as well as in the elimination of metabolic waste.
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  • 6
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 467-514 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The eggs of Corella develop in the atrial chamber of the parent at a pH below that of normal sea-water (pH 7.4 ±). When removed to normal sea-water in early stages and under certain other experimental conditions, larval development is more or less inhibited, the tail being most inhibited, the dorsal region somewhat less. The free larval stage may be eliminated and later development and metamorphosis may proceed normally to an advanced stage in the chorion and give rise to normal ascidians. The region most inhibited are, in general, those which possess the highest reducing power, as indicated by KMnO4. Experiments made in the attempt to control development all agree in indicating that the early stages are adjusted to a certain CO2 concentration approximately that of the atrial chamber and presumably near that of the body. Solutions of the same pH may or may not inhibit development according to their CO2 content.The tail, the region of highest reducing power in the embryo during its development, is most inhibited; the dorsal region, the next most rapidly reducing region, is next in degree of inhibition. All differences in reducing power disappear when, or soon after, the animals are killed by other agents before treatment with KMnO4.
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  • 7
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    New York, NY : Wiley-Blackwell
    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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  • 8
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    New York, NY : Wiley-Blackwell
    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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  • 9
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    New York, NY : Wiley-Blackwell
    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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  • 10
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    New York, NY : Wiley-Blackwell
    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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  • 11
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    New York, NY : Wiley-Blackwell
    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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  • 12
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    New York, NY : Wiley-Blackwell
    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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  • 13
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 164 (1980), S. 83-88 
    ISSN: 0362-2525
    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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  • 14
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    Journal of Morphology 164 (1980), S. 89-105 
    ISSN: 0362-2525
    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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  • 15
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 164 (1980), S. 161-166 
    ISSN: 0362-2525
    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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  • 16
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 164 (1980), S. 121-138 
    ISSN: 0362-2525
    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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  • 17
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    Journal of Morphology 164 (1980), S. 167-211 
    ISSN: 0362-2525
    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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  • 18
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    Journal of Morphology 164 (1980), S. 311-311 
    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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  • 19
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 20
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    Journal of Morphology 165 (1980), S. 13-29 
    ISSN: 0362-2525
    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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  • 21
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    Journal of Morphology 165 (1980) 
    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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  • 22
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    Journal of Morphology 165 (1980), S. 117-130 
    ISSN: 0362-2525
    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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  • 23
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    Journal of Morphology 165 (1980), S. 131-155 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 24
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    Journal of Morphology 167 (1981), S. 35-42 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vasculogenesis of the bursa cloacalis (bursa of Fabricius) was examined in 10- to 21-day chick embryos and in chicks during the first 5 days post-hatching. The entire circulatory system was injected with India ink, and the bursae were then removed and either cleared for examination in toto or sectioned serially. The bursa was supplied by three pairs of extrinsic blood vessels. At 10 and 11 days of incubation, most intrinsic vessels were arranged in a superficial, hexagonal network. In regions of developing plicae, the hexagonal plexus extended into the core of each plica, forming middle plical vessels. The latter were interconnected across interplical areas by cross-connecting vessels. The middle plical vessels gave rise to small capillary offshoots, which soon increased in complexity, forming delicate loops. Branches extended from these loops through the subepithelial lamina propria to incipient epithelial buds by 12 days of incubation. All epithelial buds were supplied by at least one such branch, and similar branches extended to the basal aspect of the epithelium in areas where epithelial buds had not yet formed. This observation is consistent with the hypothesis that blood vessels induce formation of epithelial buds. At about 15 days of incubation, the cortex and medulla of each developing lymphatic follicle were defined clearly, and an intricate, web-like, capillary network coursed throughout the follicular cortex. The medulla appeared to be devoid of capillaries. The diameters of all intrinsic and extrinsic bursal blood vessels gradually increased throughout development. During post-hatching stages, the diameters of the extrinsic vessels continued to increase, whereas those of the intrinsic vessels were markedly decreased from late pre-hatching stages.
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  • 25
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    Journal of Morphology 167 (1981), S. 103-108 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The use of hormone replacement to support limb regeneration in hypophysectomized newts has been the subject of many investigations. Growth hormone, as well as prolactin (PL) in combination with exogenously supplied thyroxine, have all been shown to he effective. However, the bovine growth hormone used to support limb regeneration was contaminated by prolactin and thyroidstimulating hormone (TSH). The present investigation evaluates the significance of (1) prolactin contamination and (2) endogenous thyroxine synthesis resulting from TSH contamination on limb regeneration in hypophysectomized newts. The effect of supplying exogenous thyroxine was also evaluated. Our studies showed that when hypophysectomized newts were injected with contamination levels of PL and TSH, regeneration occurred, suggesting that the newt's thyroid synthesized sufficient thyroxine to support a prolactin-thyroxine synergism. The endogenous thyroxine was synthesized by thyroid glands that were indistinguishable from those of saline-injected, hypophysectomized controls.
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  • 26
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    Journal of Morphology 167 (1981), S. 109-118 
    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 posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis.
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  • 27
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    Journal of Morphology 167 (1981), S. 167-184 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: There are four major tooth attachment modes in actinopterygians. Type 1 mode is characterized by complete ankylosis of the tooth to the attachment bone; it is the primitive attachment mode for actinopterygians. In Type 2 mode there is a ring of collagen between the tooth base and the bone. In Type 3 mode mineralization extends near or to the bone at the anterior tooth border, and there is a relatively large collagen area on the posterior surface of the tooth; Type 3 teeth are hinged with an anterior axis of rotation. Type 4 teeth also have a relatively large posterior collagen area, but there is no collagenous connection between the anterior basal tooth border and the attachment bone; Type 4 teeth are hinged, with a posterior axis of rotation. Types 2, 3, and 4 attachment modes appear to result from retardation of mineralization and resemble, with some modifications, ontogenetic stages in the development of Type 1 mode; they are considered to be paedomorphic features. Attachment modes 2, 3, and 4 are each associated with a major evolutionary lineage within the Teleostei. The degree to which paedomorphosis has been a factor in teleostean evolution is discussed.
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  • 28
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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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  • 29
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    Journal of Morphology 166 (1980) 
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    Notes: Bolitoglossa occidentalis, a lowland salamander of Mexico and Guatemala, has a highly derived morphology. The features that are derived with respect to the condition in generalized members of the genus include the following: (1) small body size; (2) short tail; (3) fully webbed hands and feet; (4) reduction and loss of certain phalangeal elements; (5) fusion of carpals and tarsals; (6) absence of prefrontal bones; and (7) reduced skull ossification. The ontogeny of this species was analyzed quantitatively and compared with the patterns of growth and differentiation encountered in two morphologically generalized members of the genus, B. rostrata and B. subpalmata. Most of the derived features can be explained by invoking a single heterochronic process: truncation of development at a small size (most likely the product of early maturation). Therefore, B. occidentalis is a paedomorphic species whose morphology has been attained through the process of progenesis. This result supports Alberch's ('80a) prediction, based on functional analysis, that the principle adaptation to arboreality in B. occidentalis is small size; other derived morphological features are associated with the organism's truncated development and may have no adaptive significance. However, patterns of dissociation are found within this overall progenetic process. Some of these include the following: (1) accelerated growth rates of the metatarsals and first phalanges, and retarded growth rates of the second and third phalangeal elements; (2) dissociation between rates of ossification of the skull and the autopodial elements; and (3) dissociation between the timing of termination of the process of shape change during the ontogeny of the foot (the product of differential growth between digital and interdigital areas) and termination of growth in overall foot size (foot surface area). This later result illustrates the independence of morphogenetic phenomena (shape change) from processes of growth (size increase).
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    Notes: A table of development (25 stages) for the period of incubation in the pouch was constructed for Gastrotheca riobambae; it can be used to stage embryos of other egg-brooding hylids. Analysis of embryonic weights during incubation shows that the mother does not contribute nutrients, but gases and other factors are probably exchanged between mother and embryos.According to species, incubation on the back of the mother is carried to the froglet or to the tadpole stages. Development in these hylids is characterized by specialized gills, the bell gills derived from the branchial arches. In some species, the bell gills derive from the first branchial arch and cover less than 50% of the embryo, while in others, the bell gills come from both branchial arches I and II and cover from less than 50% to 100% of the embryo. The most complex bell gills derive from the fusion of the two branchial arches.The majority of egg-brooding hylids live in tropical forests and carry development to the froglet stage. Tadpoles are produced by species of Flectonotus, Fritziana, and Gastrotheca. Tadpole-producing species of Gastrotheca have the most complex reproductive adaptations among egg-brooding hylids Acceleration and retardation in development seem to have played important roles in the evolution of these frogs. The evolutionary trend has been toward direct development, i.e., disappearance of the free-living larval stages through maternal incubation, and later to a recovery of the free-living tadpole stages in species of Gastrotheca with the most complex reproductive adaptations.
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    Journal of Morphology 167 (1981), S. 313-331 
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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 ectodermal eyes, 45-55 μm in diameter, of the cnidarian hydrozoan Cladonema radiatum Dujardin possess a lens approximately 15 μm in diameter enveloped by an eyecup (retina). An overlying layer of intensely vacuolated distal process of the adjoining epithelial cells forms a transparent cornea. The eyecup is composed of three cell types: basal cells, melanin-containing pigment cells, and photoreceptor cells. The last two cell types occur in the ratio of approximately 2:1. Histogenesis of the eye both during ontogeny and regeneration is described from light and electron microscopic investigations. During ontogeny the cell types forming the retina are derived from a compact group of morphologically undifferentiated cells, but during regeneration a primordium is formed by regeneration cells. In both cases the lens is built from distal nonnucleated cytoplasmic portions pinched off from the pigment cells. The cornea is formed by distal lamellar processes of the ocellus adjoining the epithelial cells. Through EM-histochemical methods (silver impregnation and DOPA-oxidase reaction) the pigment of the chromatophores of the retina was identified as melanin.
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    Journal of Morphology 168 (1981), S. 247-247 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 34
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    Journal of Morphology 168 (1981) 
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  • 35
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    Journal of Morphology 168 (1981), S. 189-227 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The neural organization of the olfactory system in the desert iguana, Dipsosaurus dorsalis, has been investigated by using the Fink-Heimer technique to trace the efferents of the main and accessory olfactory bulbs, and Golgi preparations to determine the spatial relations between olfactory afferents and neurons in the primary olfactory centers.The accessory olfactory bulb projects to the ipsilateral nucleus sphericus via the accessory olfactory tract. The main olfactory bulb projects to the ipsilateral telen-cephalon via four tracts. The medial olfactory tract projects to the rostral continuation of medial cortex and to the septum. The intermediate olfactory tract projects to the olfactory tubercle and retrobulbar formation. The lateral olfactory tract projects to the rostral part of lateral cortex. The intermediate and lateral olfactory tracts also merge caudally to form the stria medullaris, which crosses the midline in the habenular commissure and distributes fibers to the contralateral hemisphere via two tracts. The lateral corticohabenular tract terminates in the contralateral lateral cortex. The anterior olfactohabenular tract terminates in the contralateral olfactory tubercle, retrobulbar formation and septum.The relation of olfactory afferents to neurons in the medial cortex, lateral cortex, nucleus sphericus, and septum corresponds to a pattern of organization that is typical of many olfactorecipient structures. Such structures are trilaminar, with neurons whose somata are situated in the intermediate layer (layer 2) sending spine-laden dendrites into an outer, molecular layer (layer 1). Olfactory afferents intersect the distal segments of these dendrites. By contrast, other olfactorecipient structures in Dipsoaurus deviate from the familiar pattern. Olfactory afferents intersect somata lying in layer 2 of the retrobulbar formation. Olfactory afferents include some fibers which course perpendicularly to the surface of the olfactory tubercle and extend deep to layer 2.
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    Journal of Morphology 168 (1981), S. 281-288 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microscopic examination of adipocytes isolated from adult rat epididymal adipose tissue revealed numerous small cells (〈 10 μm) morphologically similar to larger adipocytes. These small adipocytes appear identical to a new classification of adipose cells termed preadipocytes. Electron micrographs of these preadipocytes revealed examples of cells 〈 10 μm in diameter in various stages of maturation and lipid accumulation. The percent distribution pattern of these small adipocytes was not significantly altered by exercise although exercise shifted the distribution patterns of the larger cells (〉 30 μm) toward a smaller mean cell size. The quantitative significance of preadipocytes is not established but these preliminary observations indicate that adipocytes 〈 10 μm in diameter may account for a numerically greater proportion of the total adipocytes observed in collagenase isolated preparations than heretofore recognized, although their contribution to total adipose mass is probably negligible.
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  • 37
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    Notes: When a newt is hypophysectomized prior to or at the time of forelimb amputation a dermal barrier eventually forms between the apical cap of epithelium and the underlying mesenchymal tissues, and the typical regeneration response is transformed to a wound-healing morphology. When hypophysectomized newts are injected on continuous alternate days beginning either at the time of amputation or following a fifteen-day delay, with either growth hormone (GH) or prolactin in combination with thyroxine (PLT4), normal regeneration occurs. Our experiment was designed to examine critically the early changes occurring in apical connective tissue that had been allowed to form as a consequence of hypophysectomy prior to forelimb amputation. Adult newts were hypophysectomized and five days later both forelimbs were amputated distal to the elbow. Following a delay of eight days, to permit the formation of connective tissue beneath the apical epithelium, they were injected intraperitoneally on successive alternate days with GH or with PL in combination with T4 in the aquarium water. The apical connective tissue of the limb stumps underwent a progressive erosion and became discontinuous by day 4. The limb morphology of hypophysectomized newts receiving ACTH or PL or maintained in thyroxine was virtually identical to sham-injected hypophysectomized controls. It appears that an initial effect of GH or PLT4 therapy is to establish the epithelial-mesenchymal interface that previously has been suggested to be a requisite for the regenerative event.
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  • 38
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    Notes: The external features of the embryo and the first instar larva of Pedetontus unimaculatus are described. Blastokinesis of P. unimaculatus is very similar to that of Petrobius brevistylis (Larink, '69), but differs from that of Machilis alternata (Heymons and Heymons, '05). The superficial structures of three pairs of protocerebral lobes are present. The terga of the mandibular, maxillary, and labial segments take part in the formation of the head capsule. In the maxilla and labium, the palpi are homologous with the telopodites of the legs; the other parts proximal to the palpi are homologous with the coxopodites. No sternal element contributes to the postmentum. Both glossa and paraglossa consist of two lobes. The pleuropodium, stylus and ventral sac are derived from distal parts of appendage anlagen. The pleuropodium of the first abdominal segment is homologous with the styli of the successive abdominal segments; the ventral sacs of succeeding segments are serially homologous. The basal parts of appendage anlagen cover each sternum in the first to ninth abdominal segments to form coxites, which are therefore appendicular in origin. The basal part of the cercus also covers the ventral and lateral surfaces of the eleventh abdominal segment.
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  • 39
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    Notes: The micropterygid moth Neomicropteryx nipponensis belongs to the most primitive suborder Zeugloptera of the Lepidoptera. During embryogenesis the small circular germ disk formed on the ventral egg surface invaginates deeply into the yolk. It finally separates from the egg periphery or rudimentary serosa, and becomes a sac-shaped germ rudiment. Its anterior part later develops into the germ band, while its posterior part is the future amnion. Just before revolution of the embryo, the embryo assumes a completely superficial position beneath the yolk. Neither amnion nor serosa rupture during revolution; by completion of dorsal closure they have been incorporated into the yolk to form the secondary dorsal organ.The formation of the germ rudiment and embryonic membranes in N. nipponensis resembles those of swift moths, Endoclyta (suborder Monotrysia) and of the caddisflies, Stenopsyche (Trichoptera), but differs from those of ditrysian Lepidoptera. The secondary dorsal organ has never been found in any other lepidopteran embryos; however, it is formed in N. nipponensis and in the Trichoptera. The results of the present study strongly support the general phylogenetic views that the Zeugloptera have a close affinity to the Trichoptera.
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    Journal of Morphology 169 (1981) 
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  • 41
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    Journal of Morphology 169 (1981), S. 29-47 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning and transmission electron microscopic observations were made on the rattlesnake lung, which has the form of a cigar-shaped bag enclosing a large axial air chamber. The lungs were fixed by tracheal instillation of fixative to preserve the structural features of inflated lungs. An open tracheal groove along the ventral aspect of the lung is the only structural “airway” present. The wall of the lung has two histologically distinct regions: anteriorly, a respiratory portion, where up to three generations of septa subdivide the wall into cup-shaped gas-exchange chambers, termed faveoli; and posteriorly, a simple, thin-walled saccular portion. The epithelium lining the internal surface of the lung is composed of several cell types: (1) ciliated cells; (2) type I pneumonocytes; (3) type II pneumonocytes, secretory cells characterized by the presence of lamellar bodies; and (4) serous epithelial cells, secretory cells characterized by the presence of homogeneous, densely staining secretory granules. However, the distinctiveness of the secretory cell types in the snake lung is blurred because intermediate-appearing cells have both the lamellar body and homogenous type of secretory granule. The nonepithelial components of the pulmonary wall and septa consist of blood vessels and lymphatics, smooth muscle cells and fibroblasts, embedded in a matrix of extracellular connective tissue fibers. Tubular myelin figures were observed in the faveolar lining layer.
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    Journal of Morphology 169 (1981), S. 91-111 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Autoradiographic, HRP, and Fink-Heimer techniques define olfactory bulb efferents in the channel catfish. The olfactory bulb projects bilaterally to eight targets in the area ventralis telencephali including the preoptic area, five targets in area dorsalis telencephali, and the posterior tuber of the diencephalon. There is additional input to the peripheral margin of the internal cell layer of the contralateral olfactory bulb. Fibers cross in rostral (nervus terminalis and commissure of Goldstein) and caudal components of the anterior commissure and the habenular commissure. HRP techniques reveal the origin of bulb efferents from the internal and mitral cell layers of the olfactory bulb. The olfactory tract is divided into five major components, each with a unique subset of ipsilateral and commissural pathways.
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    Journal of Morphology 169 (1981), S. 149-159 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anuran (Rana) and urodele (Ambystoma) amphibian eggs were subjected to prolonged unnatural orientations in relation to gravity. In some cases eggs were rotated 90°, while in other instances eggs were rotated 180° (complete inversion). Alterations in the pigmentation pattern, cleavage pattern, and site of involution were observed. Despite these unnatural orientations to gravity, the morphogenesis of axial structures was frequently normal. Reorganization of the egg cytoplasm apparently takes place after the unnatural orientation. Rather than being localized in a fixed position in the egg (e.g., the egg cortex), the determinants for the pattern of early embryogenesis are probably located in that portion of the cytoplasm (e.g., “internal” cytoplasm) that orients to gravity.
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    Journal of Morphology 169 (1981), S. 207-223 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoarchitecture and neuronal morphology of the torus semicircularis in the red-eared turtle, Chrysemys scripta elegans, were examined in Nissl-stained and Golgi-impregnated material. The torus semicircularis begins in the caudodorsal mesencephalon and extends rostrally and laterally to end ventrally to the tectal ventricle. The torus semicircularis consists of a central nucleus and a laminar nucleus, which is interposed between the central nucleus and the ventricle.The central nucleus can be divided into two regions, a small, large-celled area, located dorsally, and a larger area of small spherical (6-17 μm), large spherical (18-25 μm), triangular (15-27 μm) and fusiform (10-26 μm) neurons. The small spherical cells have two dendritic patterns: “radiate” and “single.” The radiate pattern has a dorsoventral orientation, several secondary branches and few dendritic spines. These cells are usually located in the center of the central nucleus. The single pattern is oriented mediolaterally. This cell type is most often observed at the periphery of the central nucleus. These neurons have few secondary branches and dendritic spines. The large spherical neurons display two dendritic orientations: dorsoventral and mediolateral. All dendritic trees have numerous secondary branches and few dendritic spines. The triangular neurons exhibit primary dendrites projecting from the corners of the somata and have few secondary branches and dendritic spines.The fusiform neurons have a majority of their dendrites oriented mediolaterally, few secondary branches and a small number of dendritic spines.The laminar nucleus consists of several layers and three cell types: ovoid (9-15 μm), triangular (20-40 μm), and fusiform (20-40 μm). All neurons have few secondary dendritic branches and few dendritic spines. The dendrites of many neurons course perpendicularly to the long axis of the brainstem and encapsulate the central nucleus. Some ovoid and fusiform neurons display dendrites that enter the central nucleus.
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    Journal of Morphology 170 (1981), S. 113-131 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the foregut muscles of five spider families (Theraphosidae, Agelenidae, Araneidae, Lycosidae, Salticidae) was described, and the individual fibre numbers and fibre cross diameters of the muscles were determined. The nomenclature of these muscles was reviewed and modified if necessary.Oxidative enzyme and myosin-ATPase histochemistry revealed eight dilatatory muscles of the foregut to consist of slow (type I) fibres, while fast fibres (type IIB), and intermediate fibres, were only to be found in the two other muscles of the foregut, and in the remaining prosomal muscles (type IIA fibres around the poison gland).The eight sucking muscles proper of the foregut also showed stronger activities of transmitter metabolizing enzymes [monoamine oxidase, glutamate dehydrogenase(NAD)], and comparatively distinct amounts of glycogen and lipids.
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  • 46
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    Journal of Morphology 169 (1981), S. 325-336 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper reports observations on the innervation of gill filaments of the lamprey, Lampetra japonica. Nerve fibers run on each side of the afferent filament artery (AFA nerve) and in the connective tissue compartment along the efferent filament artery (EFA nerve). The AFA nerve supplies vasomotor fibers to the afferent filament artery and arteriovenous anastomoses and special visceral motor fibers to branchial muscle fibers (musculus compressor branchialis circularis). Nerve endings of the vasomotor fibers contain large, cored vesicles (60-180 nm in diameter) with a variable number of small, clear vesicles (30-70 μm in diameter), whereas those of the visceral motor fibers have many small, clear vesicles with few large, cored vesicles. The EFA nerve supplies vasomotor fibers to the efferent filament artery. Their endings, containing mixtures of predominantly large, cored vesicles and small, clear vesicles make close synaptic contacts with reticular cells. The latter in turn are connected with each other or with smooth muscle cells in the wall of the efferent filament artery by nexuses. No nerves are found in the axial plate between the afferent and efferent filament arteries nor in the secondary lamellae of individual gill filaments. No afferent nerve supply to the gill filament has been found.
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  • 47
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    Journal of Morphology 169 (1981), S. 351-355 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study, using the cobalt chloride technique, clarifies the origin of the giant axons in the cockroach, Periplaneta. Each giant axon in the ventral nerve cord arises from a single cell body located in the sixth abdominal ganglion. The position of the soma is always contralateral to the giant axon; it projects anteriorly. In six giant neurons, the axonic and dendritic branches are ipsilateral while the somata are contralateral. In two neurons, both the soma and the dendritic branches are ipsilateral while the axons are contralateral. The dendritic arborizations of the giant neurons form a dense and compact mass of neuropile in each half of the posterior and middorsal part of the ganglion where sensory fibers, primarily from the cercal nerves terminate. The relation of these findings to earlier electrophysiological studies is discussed.
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  • 48
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    Journal of Morphology 170 (1981) 
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  • 49
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    Journal of Morphology 168 (1981), S. 309-319 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Untreated adult newts do not undergo normal limb regeneration following hypohysectomy. A fibrocellular dermal barrier (cicatrix) atypically forms between the apical epithelium and the underlying mesenchymal tissues. Historically, continuous administration of growth hormone or of prolactin in combination with thyroxine restored regenerative capacity to these newts. In a previous investigation, we demonstrated that the initial effect of these two hormone treatments, when administered on alternate days to hypophysectomized newts beginning eight days post-amputation, was to facilitate the erosion of the fibrocellular barrier and establish the epithelial mesenchymal interface that is observed in a regenerating limb.The present investigation was designed to evaluate the necessity of continuous hormone therapy to maintain limb regeneration in hypophysectomized newts. One, two, or three injections of growth hormone or of prolactin in combination with thyroxine was administered on successive alternate days to hypophysectomized newts either immediately following limb amputation (ID) or beginning eight days post-amputation (DD). The ID and DD newts receiving one, two, or three injections of growth hormone showed evidence of regeneration to the digitiform stage by day 30 post-amputation, while those receiving prolactin and thyroxine underwent wound healing. While both hormone treatments initially promoted a dermis-free apical epithelium, only hypophysectomized newts that had received growth hormone were able to continue regenerating.We have, therefore, concluded that discontinuous growth hormone therapy is sufficient to initiate and maintain the conducive environment for limb regeneration to advanced stages in the hypophysectomized newt. While initiating this process, prolactin and thyroxine therapy on a discontinuous regime does not maintain regeneration. The direct and indirect role of growth hormone in supporting limb regeneration in normal and hypophysectomized newts is discussed.
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  • 50
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    Journal of Morphology 170 (1981) 
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  • 51
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    Journal of Morphology 163 (1980), S. 9-12 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 52
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    Journal of Morphology 163 (1980), S. 37-44 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 53
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    Journal of Morphology 163 (1980) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 54
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    Journal of Morphology 163 (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: 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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  • 55
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    Journal of Morphology 163 (1980) 
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  • 56
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    Journal of Morphology 163 (1980), S. 219-230 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 57
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    Journal of Morphology 169 (1981), S. 71-90 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.
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  • 58
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    Journal of Morphology 169 (1981), S. 61-70 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The morphology of the newly hatched larva of Carcinonemertes epialti Coe has been examined by light and electron microscopy. The newly hatched larva is covered with cilia and measures about 110 μm in length. Four types of epidermal cells are recognizable: (1) Multiciliated cells, (2) vacuolated cells, (3) mucous cells, and (4) “knob cells”. The knob cells protrude from the posterior end of the larva and contain granules and bundles of microfilaments. The gut is incomplete and is located ventral to the bipartite proboscis. A bilobed brain and two subepidermal ocelli are found in the anterior end of the larva. The anterior and posterior cirri are composed of long, tightly appressed cilia that arise from an invagination of the epidermis at each end of the larva. The anterior cirrus is surrounded by two types of glandular cells. It is proposed that the knob cells have a role in larval attachment, combining the functions of the adhesive cells and anchor cells described in the duo-gland system of turbellarians. The cirri are believed to be larval sensory structures that function in substrate selection. Histological and ultrastructural observations suggest that the larvae of Carcinonemertes are relatively long lived and develop into juveniles without a drastic metamorphosis.
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  • 59
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    Journal of Morphology 169 (1981), S. 141-148 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Glycoproteins are present in the web of the orb-weaving spiders Argiope trifasciata and Argiope aurantia. Periodic acid-Schriff reactive glyco-proteins are confined in large part, to the sticky spiral and sticky spiral-radial junctions. Glycoproteins containing amino sugars appear associated with all fibers, especially the radial fibers. Enzymes may be used to remove glycoproteins selectively from the sticky spiral and stabilimentum.
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  • 60
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    Journal of Morphology 169 (1981), S. 191-206 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The pineal organ of Ensatina eschscholtzi, a terrestrial and secretive species of salamander of the family Plethodontidae, is a photoreceptive structure lying on the dorsal surface of the diencephalon. The pineal is flattened with a broad lumen and consists of three cell types: photoreceptors, supportive cells, and neurons. Pineal photoreceptors are typical vertebrate photoreceptors and possess outer segment formations which, however, are frequently contorted and disorganized. Sloughing of apical portions of outer segments and vesiculation along the lateral edges of outer segment membrane disks are consistently observed and presumed to represent mechanisms of outer segment membrane recycling. Photoreceptors have basal processes which synapse with neural dendrites. Synapses between photoreceptor basal processes are occasionally observed. All synapses are characterized by synaptic ribbon structures of variable number, size, and configuration. Dense-core vesicles are occasionally observed mingled with clear synaptic vesicles within photoreceptor basal processes. Supportive cells within the pineal function in phagocytosis and recycling of shed outer segment membrane material, and neurons are localized at the lateral margins of the organ. The latter send axons into the ipsilateral side of the dorsal diencephalon. The pineal organ of Ensatina shows marked variation in overall size (cell total), cell type proportions, absolute neuron number, and ratio of photoreceptor number to neuron number for individual pineals. None of these morphological parameters is correlated with body size, sex, or season, and it is assumed that such variability represents significant variation in photosensory capabilities. It is suggested that the pineal organ of Ensatina is a partially degenerate photoreceptive structure.
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    Journal of Morphology 169 (1981) 
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  • 62
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    Notes: In order to investigate quantitatively and objectively the influence of the normal microbial flora on the ultrastructure of the alveolar macrophage, three groups of mice were studied stereologically: germ-free (GF), conventionally reared under non sterile isolation conditions (IC), and conventionally reared in an open environment (OC). The alveolar macrophages of GF mice possess a smaller mitochondrial compartment, possibly with fewer organelles, than the macrophages of conventional mice. Other influences of the normal microflora on alveolar macrophage substructure are obscured by the effects of nonmicrobial stimuli such as droplets of lung surfactant.No previous comparison exists of alveolar and peritoneal macrophage ultrastructure. Lung macrophages are larger than the phagocytes of the peritoneum, but the difference in size is much less than is commonly believed. Alveolar macrophages are rounder than peritoneal macrophages, and exhibit much less rough endoplasmic reticulum (RER) as well as differences in mitochondrial morphometry. No difference in mitochondrial volume fraction exists between the two types of macrophage even though alveolar macrophages represent the extreme of aerobic adaptation in the mononuclear phagocyte system. Phagosomes occupy a significant fraction of cellular volume only in the alveolar macrophages. Moreover alveolar phagocytes contain fewer but larger lysosome-like granules than are found in peritoneal macrophages. The results represent the first objective, quantitative structural evidence confirming the common belief that alveolar macrophages experience greater physiological stimulation than peritoneal macrophages. The normal microflora accounts for only a small proportion of the differing degree of stimulation exerted on the two types of macrophage.
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  • 63
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    Notes: In this work, we have completed a study of the development of the ovoviviparous lizard Liolaemus tenuis tenuis. Ovoviviparity in this lizard is a condition in which eggs are retained within the reproductive duct for about 60 days. During this period the phases of segmentation, gastrulation, neurulation, presomitic, and somitic embryos transpire. During the months of December and January the eggs are laid, and at this time the embryos are comparable to stage 27 Liolaemus gravenhorsti lizard embryos, or to stage 29 Calotes versicolor lizard embryos. Differentiation of the facial region occurs between Days 12 and 42 after egg laying. Limbs develop rapidly between the 8th and 23rd days. By 53 days the appendicular skeleton is completely formed. After 36 days the mesonephros begins to degenerate, and its function is gradually taken over by the developing metanephros. Newborn lizards do not possess an egg caruncle. During the period up to hatching, there is a great increase of liquid within the egg, presumably amniotic fluid. Cracks develop in the leathery shell shortly before hatching and are, perhaps, the first sign of the onset of hatching. Increase of liquid in the egg during postlaying development accounts for its increase in weight and change in shape. Weight of the embryo at hatching does not exceed 32% of the total weight of the egg.
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  • 64
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    Journal of Morphology 170 (1981), S. 1-27 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The coronary arterial supply and associated structures have been examined and described for 29 species covering 11 reptilian families, with supplementary observations on other species. Variation in the origin, number, and configuration of coronary arterial vessels is mainly interfamilial and the same is true regarding the presence or absence of a gubernaculum cordis. It is suggested that the presence of a hitherto unrecognized intertruncal branch of the coronary artery has been responsible for much of the alleged intrafamilial variation reported in earlier literature. A general review of the cardiac blood supply and coronary arterial supply of other lower vertebrates is presented and used as a basis for interpreting phyletic and functional aspects of the reptilian conditions.
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  • 65
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    Notes: The enameloid and dentine of Squalus acanthius have been compared histochemically with those of Bos taurus. Squalus enameloid is much less reactive to a variety of stains or reagents than dentine or bovine immature enamel but it does have positive reactions with picromethyl blue, Mallory's and Van Gieson's stains, and Alcian blue. It stains faintly with Biebrich scarlet, indicating some anionic groups. Specific reactions for tyrosine, tryptophane, lysine, histidine, arginine, and cysteine are negative. Bos immature enamel is positive for cationic, anionic, and aromatic reactive groups by all test procedures, and dentine was positive for the anionic components. Bovine maturing enamel, however, is more similar in terms of lack of reactivity to Squalus enameloid but differed because the bovine enamel was moderately positive for tyrosine; tryptophane, and anionic groups and negative with Mallory's picromethyl blue and Van Gieson's stains. A fibrous transitional area between Squalus dentine and enameloid has staining reactions characteristic of both collagen and keratins.
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  • 66
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    Journal of Morphology 170 (1981), S. 181-194 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Five concentrations of nitrogen mustard (methyl-bis-chlorethylamine) have been administrated to different stages of development of trout embryos (Salmo gairdneri), in order to study their effect on the formation of both pelvic fins soft tissue and skeleton. Sensitivity of epidermis and mesoderm toward this cytotoxic agent has been assessed histologically. Although both components are sensitive to nitrogen mustard, mesoderm is more sensitive than epidermis. These results are compared with the results of similar studies on tetrapod limb buds. The pelvic fin skeleton of some treated animals was doubly stained in toto for cartilage and bone by Alcian blue and alizarin, followed by clearing. Other specimens were processed for histological serial sections. Analysis included comparison of the following parameters: (1) dose of nitrogen mustard, (2) stage of fin bud development at the time of treatment, (3) importance of necrosis in the fin bud, and (4) abnormalities of the endoskeleton of the fin (pelvic girdle and radials) and of the dermal skeleton (lepidotrichia and actinotrichia) one month after the hatching of control animals. Results suggest (1) that material of endoskeleton and lepidotrichia are laid down simultaneously, and (2) that differentiation of actinotrichia is independent of differentiation in endoskeleton and lepidotrichia.
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  • 67
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    Journal of Morphology 44 (1927), S. 89-115 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The investigation is based upon hemal nodes of dog, man, and sheep. The material can be arranged in a regressive series leading from a typical lymph node, except for the occurrence of blood in parenchyma and sinuses, to a lymphoid structure at a late stage of involution. These structures uniformly lack lymphatics. There is no evidence of direct luminal connection between the blood-vascular supply and the sinuses. The observation that certain cervical and subcutaneous lymph nodes of the rabbit undergo a myeloid metaplasia following atrophy and disjunction of their lymphatics is used as an explanatory key of hemal nodes. According to our view, hemal nodes represent stages in the involution of transient lymph nodes. Disjunction of the lymphatics leaves the sinuses filled with entrapped lymphocytes. These differentiate into erythrocytes. These red blood cells may disintegrate and pass into solution or be removed either by giant cells or mononuclear phagocytes. Late stages in this process are represented by small irregular masses of lymphocytes, with wide sinuses practically free of blood.
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    Journal of Morphology 44 (1927), S. 217-264 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A description is given of the cytoplasmic alterations in the ovarian egg of Limulus polyphemus leading to the formation of yolk. The nucleolus is found to arise by the confluence of substance which passes from the cytosome into the nucleus, and it is suggested that the chondriosomes, and possibly also the dictyosomes, are derived from an excess of this substance which accumulates in the cytosome. Chondriosomes and dictyosomes are not present in the oogonia, but appear first in oocytes after the formation of the nucleolus is completed.During oogenesis the nucleolus is very active and the greater part of its substance is passed back to the cytosome. By the application of the method of Bell and Doisy for the determination of phosphate in body fluids, the nucleolus is found to be richer in phosphorus than are the other constituents of the cell. The nucleolar emissions effect the transport of phosphorus from the nucleus to the cytosome, where it is used in the synthesis of yolk. The definitive yolk arises by the interaction of nucleolar emissions, chondriosomes, dictyosomes, and ground cytoplasm.
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    Journal of Morphology 44 (1927), S. 341-361 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Conjugating individuals of Metopus sigmoides fuse at the anterior end, the pair presenting the appearance of an inverted letter U. The micronucleus of each conjugant by two successive divisions forms four micronuclei. Three of each four degenerate and the fourth by division forms the pronuclei. Cytoplasm and pronuclei from one conjugant pass over into the other, leaving the old macronucleus and a minimum of cytoplasm behind in the shrunken pellicle of the smaller conjugant, which then separates from the larger one. In the larger exconjugant two pronuclei fuse, forming the functional synkaryon; the two residual pronuclei degenerate and disappear. The synkaryon divides. One of the daughter nuclei condenses into the new micronucleus, the other grows into the new macronucleus. The old macronucleus liquefies and is absorbed. The larger exconjugant, after losing its cilia, secretes a cyst wall about itself and becomes dormant. The whole process requires at least six days for its consummation.
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    Notes: In conjugation fusion occurs along the entire oral surfaces of the proboscides of Dileptus gigas. Two size-reducing divisions occur in rapid succession immediately preceding conjugation. Only one of the many micronuclei takes part in the process of nuclear reorganization. All other chromatic material is massed at this time in the posterior portions of the conjugants. The pronuclei are derived from the single active micronucleus, and interchange occurs immediately preceding the separation of the mating individuals. The fertilization nucleus divides to form two nuclei of diverse size. The smaller one produces thirty-two or sixty-four micronuclei, while the larger one divides to produce a like number of macronuclei, each of which finally breaks up into many chromatic granules which form the numerous densely staining nuclear derivatives which are characteristic of the vegetative stage of Dileptus gigas.In the early stages of this reorganization process specimens are frequently found with from two to eight distinct nuclei often arranged in a series as in a beaded nucleus. This condition probably explains the frequent references in literature regarding such a nuclear condition in Dileptus.Dileptus gigas has, accordingly, in the vegetative stage, a multinucleate condition with reference to the micronucleus and a fragmented or distributed condition with reference to the macronucleus.
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  • 71
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: By the use of a satisfactory technique, excellently preserved spermatogenetic tissue was had both for Rattus rattus and Rattus norvegicus. The careful examination of twelve spermatogonial cells of the former species and of twenty in the latter species shows that R. rattus has forty diploid chromosomes and R. norvegicus, forty-two. A careful examination of the haploid cells of both species, both in the first and in the second spermatocyte divisions, confirms the diploid determinations.Both species have an unequal pair in the spermatogonial divisions and the finding of a similar unequal pair in the first spermatocyte division constitutes the evidence for an X-Y mechanism in each. A comparison of the morphology of the first spermatocyte tetrads in the two species reveals the presence of a large K-shaped chromosome in R. norvegicus which is not present in R. rattus. Furthermore, a comparison of the X-Y complex in both the spermatogonial and first spermatocyte divisions shows that these are morphologically different in the two species, the Y in particular being markedly dissimilar in size. A short discussion as to the bearing of these findings on the questions of the origins of the two species and their known intersterility is presented. The marked similarity of the tetrads of the black rat to those described for the mouse is noted.
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  • 72
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    Journal of Morphology 44 (1927) 
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  • 73
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    Journal of Morphology 44 (1927), S. 29-87 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The anlage of the abducens musculature appears first at 24-25 somites as a condensation situated dorsal to the mandibular arch.The anlage of the superior oblique grows forward from a mesodermal condensation situated in the maxillomandibular region, termed for convenience the maxillomandibular condensation. This last consists of three parts: (1) the anlage of the superior oblique: (2) the anlage of the abducens musculature, and, (3) an intermediate region.The intermediate portion of the maxillomandibular mass forms a condensation with which the anlage of the abducens musculature fuses. Its fate is, therefore, similar to that of the so-called ‘muscle E’ of elasmobranchs, which has been described as fusing with the lateral rectus. How much muscle is formed from the intermediate condensation in the chick has not been determined.The development of the pyramidalis and quadratus nictitans muscles, derivatives of the abducens complex, is described.The premandibular head cavities are replaced by solid mesodermal condensations, on the surface of which the anlagen of the oculomotor muscles appear. The premandibular mass expands laterally and anteriorly over the bulbus, carrying the oculomotor muscles to their respective positions on the bulbus.Portions of the premandibular and maxillomandibular condensations not involved in eye-muscle formation take part in the formation of choroid and sclera.The growth shiftings of the eye muscles are analyzed. The order of their appearance is commented upon.
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  • 74
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    Journal of Morphology 44 (1927), S. 127-216 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This study represents the first critical investigation on the development of the embryonic skull of the porcupine. A complete series of stages makes it possible to trace the developing chondrocranium from its first formation in precartilage to its later transformation into cartilage bone. Concurrent with this growth is the investment of the cartilaginous cranium by membrane bone.The very primitive nature of the chondrocranium offers an excellent opportunity to discuss the existing problems of the embryonic skull from a new angle. Evidence is presented in support of the assumption that the ala temporalis is the homologue of the cynodont epipterygoid. The lamina parietalis develops from a single chondrifying center, thus producing a different arrangement of parietal elements from that found in most mammals. New evidence as to the relationship of the dens epistrophei and basal plate is presented. The position of the internal carotid artery on entering the cranium is different from the condition found in most mammals and throws new light on the interpretation of surrounding structures. The presence of a structure comparable with the crista longitudinalis of Lacerta shows close affinity to the solum nasi of more primitive forms.The great specialization of the face is seen in the early and rapid growth of the membrane bones. The chondrocranium is long persistent and cartilage bone appears late in embryonic life.
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  • 75
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    Journal of Morphology 44 (1927) 
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  • 76
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    Journal of Morphology 44 (1927), S. 417-465 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Observations indicate that this Balantidium from the guinea-pig is Balantidium coli, the form found in the pig and man. The lengths and breadths of this Balantidium and the ratios of length to breadth are very close to the measurements and ratios given by McDonald for B. coli. When plotted, the body lengths of the guinea-pig parasites appear in two groups, the smaller individuals being the exconjugants. Many of these exconjugants resemble Neiva's B. caviae. The structure of the Balantidium from the guinea-pig is essentially identical with that of B. coli as given by McDonald.Fission and conjugation of this ciliate follow the general course found in a number of other ciliates. During fission the micronucleus divides and the daughter micronuclei migrate to each end of the macronucleus before the latter divides. In conjugation there are two divisions of the micronucleus, one of these nuclei dividing to form the pronuclei. Pronuclear exchange and fusion are followed by a heteropolar division of the synkaryon, resulting in the formation of the new macronuclear and micronuclear anlagen.The parasite was found in the intestinal tissue of the host. No reproductive stages were found in the cysts. New hosts are invaded through contamination of the food and drink with the cysts.
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  • 77
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    Journal of Morphology 43 (1927), S. 347-385 
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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 development of the thigh musculature in a series of chick embryos is described and figured. In the earliest the muscular tissue is in the form of two distinct masses lying on opposite surfaces of the limb. Later, both divide into proximal and distal portions at the knee. The proximal portions, by a series of divisions, gradually attain the condition found in the adult thigh.The embryological findings tend to support the theory of the derivation of tetrapod limb musculature from the two opposed (dorsal and ventral) muscle masses of the paired fins of bony fish.The reptilian homologies of the ilio-trochanterici cannot be definitely ascertained from embryological evidence.The ischio-femoralis (= ischio-trochantericus), Previously regarded as dorsal, and the coccygeo-femorales, previously classed as incertae sedis, are in reality members of the ventral group.The distinction between ‘intrinsic’ and ‘extrinsic’ muscles inserting on the free limb appears to have no embryological or phylogenetic basis in fact.Double innervation (motor) is a primitive condition in tetrapods.Rotation of the avian pubis is correlated with an improved functioning of the obturator in the rotated position coupled with a lack of interference with the other musculature concerned.
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  • 78
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    Journal of Morphology 43 (1927), S. 547-555 
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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 diploid number of chromosomes obtained from counts of anaphases of the first somatic mitosis is found to be forty-four. Of these, seven have terminal, thirty-seven non-terminal attachment, giving a distribution of seven rods, thirteen V's, and twenty-four J's. The number is constant in all the fertilized eggs counted, indicating an XX-XY arrangement of the sex chromosomes.
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  • 79
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    Journal of Morphology 163 (1980), S. 27-35 
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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 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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  • 80
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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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  • 81
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    Journal of Morphology 164 (1980) 
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  • 82
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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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  • 83
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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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  • 84
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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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    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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  • 85
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    Journal of Morphology 165 (1980), S. 67-83 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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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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  • 86
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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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  • 87
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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.
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  • 88
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    Journal of Morphology 165 (1980), S. 167-174 
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    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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  • 89
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    Journal of Morphology 165 (1980), S. 223-223 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 90
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    Journal of Morphology 165 (1980), S. 261-284 
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    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.
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  • 91
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    Journal of Morphology 166 (1980), S. 1-25 
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    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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  • 92
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    Journal of Morphology 166 (1980), S. 65-80 
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    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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    Journal of Morphology 165 (1980), S. 205-222 
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    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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    Journal of Morphology 165 (1980) 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 95
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the bean-shaped accessory glands (BAGs) of males of Tenebrio molitor is described. All cells in the secretory epithelium are long and narrow (300-400 mμ × 5 mμ). The seven types of secretory cells are distinguished from one another by the morphology of their secretory granules. Granule substructure varies from simple spheres with homogeneous electrondense contents to complex forms with thickened exterior walls or with crystalline and membranous contents. Individual cell types were mapped by staining whole glands with Oil Red O, and the cell distributions were confirmed by wax histology and ultramicroscopy. The secretions of all seven cell types form a secretory plug composed of seven layers. During mating, the secretory plug from each BAG is forced into the ejaculatory duct by contractions of a sheath of circular muscle. The mirror image plugs from symmetrical BAGs fuse and are transformed into the wall of the spermatophore.
    Additional Material: 69 Ill.
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  • 96
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 166 (1980), S. 387-387 
    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 168 (1981) 
    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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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981), S. 121-135 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper describes the regeneration of the caudal axial skeleton after amputation of the tail, including about 20 vertebrae, in the gymnotoid fish Eigenmannia virescens. Seven days after amputation, a regeneration blastema developed and soft tissues degenerated. A cylinder of cartilage developed at the end of the notochord. When this cartilage was about 10 mm long (21 days), perichondral ossification began. The cartilage continued to elongate and ossification increased while osteoclasts began to destroy the cartilage ventrally. Finally, a bony rod formed and at its tip the cartilage persisted as a rod, 2 to 3 mm long. The anal fin also regenerated: Endoskeletal cartilage developed first, following by differentiation of the lepidotrichia, and finally ossification of the endoskeleton.
    Additional Material: 20 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 91-102 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The endemic Antarctic teleosts of the suborder Notothenioidei are bottom dwellers. They lack swim bladders, are heavier than seawater, and feed on or near the bottom. The midwaters surrounding the Antarctic continent are productive and underutilized by fishes. There is an evolutionary trend toward pelagism in some notothenioids. We discovered that the largest Antarctic fish, Dissostichus mawsoni, was neutrally buoyant. Attainment of neutral buoyancy was associated with specializations of the skeletal, integumentary, muscular, and digestive systems. The skeleton had a low mineral content and contained considerable cartilage. Scales were also incompletely mineralized. Static lift was obtained from extensive lipid (mostly triglyceride) deposits. A 2-8 mm subcutaneous lipid layer accounted for 4.7% of the body weight. White muscle also contained much lipid-23% on a dry weight basis, or 4.8% of the body weight. Microscopic examination suggested that the liver was active in lipid metabolism, although it was not an organ of buoyancy. Stellate (perisinusoidal) cells with many lipid droplets were a very prominent cytological component of the liver. These specializations made Dissostichus neutrally buoyant and capable of inhabiting the food-rich Antarctic midwaters.
    Additional Material: 7 Ill.
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  • 100
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spongillid freshwater sponges asexually produce an encapsulated dormant stage, the gemmule. With release from dormancy, internal, yolk-laden, binucleate thesocytes differentiate into histoblasts or archeocytes. The histoblasts emerging first from the gemmule form the initial pinacoderm of the hatching sponge. Immunohistochemistry was employed to examine the distribution of cyclic GMP (cGMP) and cyclic AMP (cAMP) following dormancy release and during gemmule germination and hatching in the freshwater sponge, Spongilla lacustris L. Cyclic nucleotide fluorescence patterns were analyzed in relation to the distribution of cytochemically demonstrable macromolecular constituents and intracellular organelles. Twenty-four hours following temperature-activated release from dormancy, cGMP fluorescence levels are elevated in thesocytes at the gemmule periphery prior to histoblast formation. The cAMP fluorescence in the gemmule also occurs first in those thesocytes differentiating into histoblasts. Cytochemical patterns in germinating gemmules are comparable with those described by Ruthmann ('65) and Tessenow ('69). However, cytochemically demonstrable events of cytodifferentiation follow the earlier appearance of cGMP and cAMP in the histoblast precursors by approximately 12 hours. In addition, cGMP appears to be associated with the membranes of cytoplasmic organelles, possibly lysosomes or lipid inclusions, in the region of vitelline platelets and with symbiotic algae. cAMP is located primarily on the membranes of the vitelline platelets and on membranes of vacuoles involved in forming the spicular skeleton These observations suggest that cGMP and cAMP are involved in the mobilization of nutrient reserves and in ion transport during dormancy release and development from gemmules in freshwater sponges.
    Additional Material: 13 Ill.
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