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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 169 (1981), S. 185-190 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Seventy-nine chick embryos were examined by light microscopy and scanning electron microscopy to determine the mechanism of primary palatal development. Fusion between two discrete processes, the medial nasal and maxillary prominences, was found to be necessary for formation of a complete primary palate. This was one component of a three-stage process that included: (1) invagination of the nasal pit prior to the appearance of the facial prominences; (2) fusion between the medial nasal and inaxillary processes caudal to the nasal groove; (3) rupture of the bucconasal membrane. The lateral nasal and maxillary prominences were found to be part of the same tissue mass. Mergence was proposed as a mechanism for the obliteration of the groove between these two localized prominences. These results were compared with those obtained by other authors for primary palate formation in rodents and man.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The surfaces of palatal shelves from carefully staged A/Jax mouse embryos were examined with the scanning electron microscope prior to and during palatal fusion. No change was observed in the appearance of cells covering the oral and nasal surfaces of the shelves. A change was observed, however, in the region of presumptive fusion, and was detectable on vertical shelves just prior to transposition. This change initially involved surface cells along the future medial edge of the shelf at the level of the second to third rugae. It was characterized by a loss of distinct cellular boundaries, the appearance of intercellular gaps caused by apparent retraction of adjacent cells, and a progressive accumulation of filamentous material at the surface. These alterations spread posteriorly along the medial edge of the shelf during transposition and fusion. While it was impossible to determine the precise nature of the surface change from S.E.M. data alone, the fact that it both preceded closure and was restricted to the region of subsequent contact and fusion between the shelves suggests it may be a prerequisite for normal palatal fusion and may represent an expression of the acquisition of a potential to fuse similar to that proposed for palatal fusion in vitro.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 190 (1978), S. 223-231 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The prefusion epithelium of human palatal processes was examined for evidence of specialization which might facilitate epithelial adherence with the opposing palatal process. A surface coat stained with ruthenium red (RR) was found on all apical aspects of the palatal epithelium. In the prefusion regions, RR staining was also observed in the spaces between the superficial cells of the epithelium and in necrotic cells. Adjacent oral and nasal epithelium excluded the RR below the level of the apical junctional complex. In the absence of RR, a dense material was observed in the most superficial intercellular spaces of the prefusion region. Many superficial cells in the area were in various stages of necrosis. The combination of degenerating surface cells and an accumulation of a poly-anionic substance such as glycoprotein may facilitate epithelial adherence between opposing human palatal processes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 193 (1979), S. 831-855 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Various stages of embryonic human secondary palatal development were examined for the presence of epithelial glycogen. Utilizing periodic acid-Schiff's reagent staining of thich plastic sections and osmium ferrocyanide enhancement of thin sections, dramatic changes in epithelial glycogen distribution were noted during palatogenesis. Prior to fusion, the epithelium destined to adhere in the midline exhibited a marked diminution of glycogen in the superficial cell layer. This cell layer was composed of slender dense cells and cuboidal cells undergoing lysis. Adjacent nonfusing epithelium was markedly different and contained large glycogen reserves in its superficial cell layer. Glycogen may play a role either as precursor for specific adhesive macromolecules or as a physical agent capable under the influence of appropriate enzymes of causing cell lysis.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 198 (1980), S. 229-244 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Examination of surface topography in prefusion stages of secondary palatal development in rabbit embryos reveals a sequence of alterations in the surface cells of the epithelium along the medial margins of the palatal processes. A progressive increase in cellular protrusions resembling lamellipodia and filopodia, as well as cellular necrosis, is observed in those areas that undergo fusion. The changes precede fusion and are restricted to fusion sites. Prior to and at the time of epithelial contact between palatal processes, many long slender cellular protrusions are seen bridging the gap between the approximating tissues. The localization of the epithelial alterations and the appearance of similar cellular morphology in other embryonic epithelial fusion events strongly suggest: either an active role of the epithelial cells in the fusion of the secondary palate, or some common fundamental biochemical events that may facilitate or are responsible for the initial adhesion of such tissues.
    Additional Material: 32 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 180 (1974), S. 111-135 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The surface topography of palatal shelves was examined by scanning electron microscopy prior to and during secondary palate formation in 72 therapeutically aborted human embryos and fetuses ranging in age from 37 days to 12 weeks (post-fertilization). Alterations in epithelial surface appearance were observed in the prospective region of fusion prior to contact between the shelves. First seen as an elliptical area along the anterior portion of the presumptive medial edge, a zone of alteration spread progressively along the anterior four-fifths of the medial edge prior to shelf contact, and continued along the posterior one-fifth of the shelf as fusion proceeded. The altered zone eventually extended onto the oral surface in the middle of the shelf but was restricted to a narrow zone along the medial edge posteriorly. Initially characterized by elongation and “intertwining” of superficial cells, alterations later included cell death, desquamation and possible active migration of surface cells. The shelf epithelium subjacent to the zone of alteration exhibited increased irregularity in thickness and numerous “invaginations” into the underlying mesenchyme. These alterations are thought to reflect intrinsic changes within the shelf and may play a role in the fusion process. Evidence for surface remodeling following fusion was also observed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Embryonic and adult rodent tissues were fixed and prepared for scanning electron microscopy by dehydration in ethanol followed by critical point drying with liquid carbon dioxide or Freon 13 (E. I. du Pont de Nemours, Inc.). After coating the dried specimens with evaporated metal, the tissues were studied by scanning microscopy. The same tissues were subsequently embedded in Epon-Araldite, thin sectioned and examined by transmission electron microscopy. The cytological details in these specimens were comparable to tissues embedded directly, without drying or metal-coating. With this technique it is possible to identify with greater certainty the structures responsible for surface contours revealed by the scanning electron microscope.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Specimens, representative of each of the major taxa of mosquitoes, were fixed in copula and the external genitalia examined by scanning electron microscopy. The periphery of the basin-like everted aedeagus of Aedus aegypti precisely matches that of the everted atrial membrane of the female. These structures are appressed during coitus and sealed by pressure of the paraprocts, aedeagal pouch and proctiger. When everted, the aedeagus of male Culex pipiens reveals a ridged dome that surrounds the genital opening. This dome seals itself laterally into a gutter formed by pad-like extensions of the female's genital lips and is sealed dorsally by pressure of the aedeagal apodeme. The aedeagus of another culicine species, Wyeomyia smithii, bears the gonopore at the apex of a spined tube. This tube is inserted between the female's genital lips and is sealed within the genital atrium. The aedeagus of the toxorhynchitine species Toxorhynchitis brevipalpus is immobile and is inserted deep within the genital atrium of the female where it is sealed by pressure of the atrial walls. Males of each of these mosquitoes deliver a mixture of semen and sperm to the copulatory bursa of the female. After withdrawal of the aedeagus, sperm is transferred to the spermathecae.In contrast, sperm of Anopheles quadrimaculatus are delivered directly to the spermathecal duct. The tube-like aedeagus is positioned by its leaflets during sperm transfer and is driven deep into the atrium, where a mixture of semen and sperm is ejaculated.The significance of mechanical barriers to mating between species is discussed.
    Type of Medium: Electronic Resource
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