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  • 1
    Electronic Resource
    Electronic Resource
    Differentiation of the female reproductive body in the colonial hydroidCampanularia flexuosa (1975)
    Springer
    Development genes and evolution 177 (1975), S. 163-181 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A comparison of two genetic stocks ofCampanularia flexuosa revealed consistent differences with respect to (1) the number of eggs present in the maturefemale reproductive body (gonangium), (2) the level on each upright stem at which the first gonangium forms, and (3) their preference for the formation of reproductive versusvegetative (side-branch) structures. Alterations in food intake established the optimum feeding level for maximal production of structurally normal gonangia and also showed differences between stocks in the effects of reduced food intake on gonangial versus vegetative growth. A staging series for gonangiogenesis was developed from observations of filling of the gonangium with primordial egg cells (PEC), gonangial elongation, funnel maturation and oogenesis. When upright segments bearing immature gonangia are isolated from the stolon the gonangia frequently resorb, transform into vegetative outgrowths, or form structurally abnormal gonangia bearing fewer germ cells than normal. These responses, and the observed accumulation of PEC at sites of presumptive gonangial outgrowth, support a stolonic origin hypothesis for PEC and implicate PEC and oocytes in the initiation, maintenance and maturation of structurally normal gonangia. In addition, continued differentiation of the gonangial structure appears to be necessary for oocyte maturation. Possible mechanisms for somatic and gametic cell recruitment, and the theoretical importance of cellular proliferation, aging, cell-shape changes, cell movement and cellular interactions in normal gonangial differentiation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848078
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  • 2
    Electronic Resource
    Electronic Resource
    Teratogenic effects of the organophosphate insecticide dicrotophos (Bidrin): Histological characterization of defects (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 213 (1985), S. 464-472 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: White Leghorn chicken eggs, specific pathogen free, were treated with the organophosphate insecticide dicrotophos and the early defects thus induced were characterized histologically. Eggs were incubated for 24, 48, 72, or 96 hr, injected with doses of dicrotophos ranging from 250 μg to 2.0 mg per egg, and observed after an additional 48 hr of incubation. Treated embryos displayed general developmental retardation as well as unilateral retardation of the cranial sense organs, the youngest embryos being most severely affected. Many embryos injected with insecticide at 24 hr, and all but one injected at 48 or 72 hr, displayed notochordal folding, usually restricted to the cervical region; most of these also showed deformities of the adjacent spinal cord. Other defects, seen on a less consistent basis, included branching of the neural canal in the lumbar region, bifurcation of the neural epiphysis, deformation of the lens vesicle, and distention of the major blood vessels. The incidence and severity of epiphyseal, lens, and vascular defects were greatest among embryos treated at 24 hr, whereas notochordal and both types of neural defects were greatest among those treated at 48 hr. The incidence and severity of the abnormalities diminished with increasing age such that by 96 hr the only defect noted was a weak notochordal folding in one embryo. To a lesser extent, incidence and severity were dose-related also. Histological similarities between embryos displaying vascular distention and recently dead treated embryos suggested that this abnormality is a precursor to death. All defects were associated with the presence of the insecticide at the time the affected structures were undergoing initial or early morphogenesis or else the deposition of a supportive sheath, suggesting these activities as targets of the teratogen.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092130312
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  • 3
    Electronic Resource
    Electronic Resource
    Variations in the mode of stolon growth among different genera of colonial hydroids, and their evolutionary implicationsSupported by National Science Foundation grant GB-6245 and National Institutes of Health grant GM 11555. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 363-375 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Stolonic growth has been compared among several genera of calyptoblastic (Campanularia flexuosa, C. calceolifera, Gonothyraea and Sertularia) and gymnoblastic (Pennaria, Bougainvillia, Eudendrium and Cordylophora) hydroids with respect to such features as the (1) complexity and uniformity of the tip movements, (2) constancy of growth cycle duration, (3) variability in growth among cycles, (4) growth rate, and (5) variability of retractions among cycles.The “growth cycle,” previously described in C. flexuosa, is the basis for elongation in all species observed. Its pattern is indistinguishable between the Campanularia species; however, at the generic level the tip movements show peculiarities which delineate each genus from all others. In addition, the movements in all calyptoblasts are uniform from cycle to cycle and comparatively simple, whereas those of the gymnoblasts are complicated by the variable appearance of one or more secondary forward thrusts between crests.A dichotomy is seen between the calyptoblasts and most gymnoblasts in other respects as well. Cycle time is very predictable and cycle-to-cycle variability in growth is relatively narrow in all calyptoblasts. However, in most gymnoblasts both features are much more loosely regulated: only Pennaria shows some degree of control to its timing mechanism, and only in Bougainvillia and Eudendrium does the uniformity of growth per cycle reach the calyptoblast level.On the premise that calyptoblasts are evolutionarily the more advanced group, simplicity and regularity of growth movements are concluded to be the evolved, and complexity and variability the primitive, conditions. On this basis the evolutionary relations among the four gymnoblasts, as deduced from their stolonic growth behavior alone, are consistent in many but not all respects with those interpreted from morphological considerations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051390306
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of the organophosphate insecticide malathion on very young chick embryos: Malformations detected by histological examination (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 174 (1985), S. 187-202 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This histological study sought to determine the nature and incidence of developmental abnormalities induced by one of the reportedly least teratogenic of insecticides injected into very young chick embryos. Using techniques to assure rapid contact between injectant and embryo, eggs incubated for 24, 48, or 72 hr were injected with corn oil or 125 μg-4.0 mg malathion. The embryos were recovered 48 hr later, paraffin-embedded, serially cross-sectioned, and examined in detail. Structures affected (and the nature of the defects) were as follows: (1) wing level notochord and spinal cord (folded or undulated); (2) trunk/leg level spinal cord (variously, neural folds unfused, roof infolded, canal partitioned, etc.); (3) eye (lens misshapen or severely thinned, optic cup incompletely invaginated); (4) diencephalon (epiphysis bifurcated or off-center, supernumerary outgrowths); (5) cardiovascular structures (atrium and major blood vessels enlarged); and (6) tailbud (curled into hindgut: ourentery). Overall incidence was both dose- and age-related, doubling for each doubling of dose and tripling for each 24 hr less age at exposure. For most (not all) individual structures, incidence was greatest when exposed at 24 hr and nil at 72 hr. Severity of effect was not consistently doseor age-dependent. We conclude that (1) contrary to previous reports, 24- to 72- hr embryos are highly vulnerable to insecticide exposure, with the youngest the most vulnerable, and (2) many of the defects detected may be attributed to either of two mechanisms: failure in formation of the supportive sheath, or factors that cause epithelial morphogenesis (e.g., microtubules, microfilaments, extracellular material, cell-to-cell adhesion mechanisms). Previous observations that 1- to 3-day embryos are relatively unresponsive to insecticides are probably artifactual owing to imprecise techniques.
    Additional Material: 39 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001740208
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