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  • 1
    Electronic Resource
    Electronic Resource
    No effects of DC and 60-Hz AC magnetic fields on the first mitosis of two species of sea urchin embryos (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 19 (1998), S. 494-497 
    Details
    ISSN: 0197-8462
    Keywords: sea urchin egg ; static and sinusoidal magnetic fields ; first division ; effect of temperature ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The early divisions of sea urchin eggs was used as a model to study the effects of static and of 60 Hz sinusoidal magnetic fields. Two species were used (Sphaerechinus granularis and Paracentrotus lividus). Eggs were fertilized and exposed in two separate coils to the fields (up to 8 mT). Great care was taken to control the temperature of each sample. No difference was found in the time of the first division that could not be attributed to a temperature difference between samples. Comparison is made with other published data on various species. Bioelectromagnetics 19:494-497, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Production of chimaeric bovine embryos and calves by aggregation of inner cell masses with morulae (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 295-304 
    Details
    ISSN: 1040-452X
    Keywords: Chimaera ; Stem cells ; Cell marker ; Interspecies ; Transfer ; Freemartin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Bovine inner cell masses (ICMs) were isolated by immunosurgery at day 8 or 10, or by dissection at day 14, and combined with day-5.5 morulae. Aggregation was obtained between 89%, 62%, and 0% of the day-5:day-8, day-5:day-10, day-5:day-14 composites, respectively. Chromosome analysis of composites potentially carrying the 1/29 translocation as a chromosome marker and temporarily transferred to the bovine uterus for 8 days showed that chimaeric day-14 embryos can be obtained from day-5:day-8 aggregation. The definitive transfer of eight day-5:day-8 and 11 day-5:day-10 composites resulted in the birth of six and four calves, respectively; five of the six, but none of the four, were chimaeric. The five chimaeras showed mostly the ICM phenotype. The morphological differences between ICMs at different stages of development were examined by electron microscopy and related to the success of the aggregation technique. It is concluded that bovine embryonic cells can regulate for at least 3 days difference in development but not 5 days even though aggregation is still possible.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080270404
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cement gland of Xenopus laevis (1976)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 148 (1976), S. 193-207 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To establish a morphological baseline for experimental studies of differentiation using the cement gland as a model, the following observations are added to those on record. The elongated cells of Xenopus laevis cement glands have an internal organization displaying five distinct zones differing in structure and specialized function. The apical zone contains packed secretion vesicles apparently belonging to two different types. The transit zone appears to be devoid of major biosynthetic activity and contains secretion vesicles migrating toward the surface. The zone of biosynthesis is typically organized in concentric regions. The very elongated nucleus lies in the next zone. Finally, the storage zone is characterized by lipid droplets and yolk platelets.Only quantitative differences are observed between cells of young and mature cement glands. Though all cells have the same general organization they may probably be divided into two subtypes according to the structure of their cytoplasm. The epithelial cells surrounding the gland differ according to their position along lateral or basal borders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051480206
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  • 4
    Electronic Resource
    Electronic Resource
    Stimulation of large proteoglycan synthesis in cultured smooth muscle cells from pig aorta by endothelial cell-conditioned medium (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 149 (1991), S. 436-443 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have previously shown (Berrou et al., J. Cell. Phys., 137:430-438, 1988) that porcine endothelial cell-conditioned medium (ECCM) stimulates proteoglycan synthesis by smooth muscle cells from pig aorta. ECCM stimulation requires protein cores for glycosaminoglycan chain initiation and is accompanied by an increase in the hydrodynamic size of proteoglycans secreted into the medium. This work investigates the mechanisms involved in the ECCM effect. (1) Control and ECCM stimulated proteoglycan synthesis (measured by a 20 min [35S]-sulfate labeling assay) was not inhibited by cycloheximide, indicating that the proteoglycans were composed of preexisting protein cores and that ECCM stimulates glycosylation of these protein cores. (2) Whereas ECCM stimulation of [35S]-methionine incorporation into secreted proteins only occurred after a 6 h incubation, the increase in [35S] methionine-labeled proteoglycans was observed after 1 h, and the increase was stable for at least 16 h. (3) As analysed by electrophoresis in SDS, chondroitinase digestion generated from [14C] serine-labeled proteoglycans 7 protein cores of high apparent molecular mass (550-200 kDa) and one of 47 kDa. The two protein cores of highest apparent molecular masses (550 and 460 kDa), but not the 47 kDa protein cores, showed increased [14C]-serine incorporation in response to ECCM (51%, as measured by Sepharose CL-6B chromatography). (4) Finally, incorporation of [35S]-sulfate into chondroitinase-generated glycosaminoglycan linkage stubs on protein cores was determined by Sepharose CL-6B chromatography: ECCM did not modify the ratio [35S]/[14C] in stimulated protein cores, indicating that ECCM did not affect the number of glycosaminoglycan chains. The results of these studies reveal that (1) endothelial cells secrete factor(s) that preferentially stimulate synthesis of the largest smooth muscle cell proteoglycans without structural modifications and (2) the stimulation proceeds via increased glycosylation of protein core through enhancement of xylosylated protein core, followed by enhanced protein synthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041490312
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of endothelial-cell-conditioned medium on proteoglycan synthesis in cultured smooth muscle cells from pig aorta (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 137 (1988), S. 430-438 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of porcine endothelial-cell-conditioned medium on proteoglycan synthesis by pig aorta smooth muscle cells was studied under serum-free conditions. Maximal stimulation of [35S]-sulfate incorporation (50%) into medium-secreted and cell layer proteoglycans was observed after 20 min and 4 h incubation, respectively. This stimulation can be explained neither by increased secretion nor by oversulfation of medium-secreted [35S]-labeled proteoglycans. Those [35S]-proteoglycans secreted (for 24 h) in the presence of endothelial cell-conditioned medium were characterized by a higher hydrodynamic size than those secreted in the presence of control medium, without modification of glycosaminoglycan chain length. Agreement between the stimulation of incorporation of [35S]-sulfate into glycanic chains (50.1%) and [14C]-serine residues associated with glycosaminoglycans (49.9%) involved an increase in the number of glycanic chains linked to protein cores. The lesser stimulation of [14C]-serine incorporation into secreted proteins (18%) suggested that stimulation of glycosaminoglycan synthesis was not the direct consequence of enhanced protein synthesis. Proteoglycan synthesis was studied in the presence of para-nitrophenyl-b̃-D-xyloside. Fractionation of medium-secreted [35S]-proteoglycans and xyloside-initiated glycosaminoglycans revealed that stimulation of [35S]-glycosaminoglycan synthesis by endothelial-cell-conditioned medium required a protein core acceptor for glycanic chain initiation. Our results suggest that the factor(s) secreted by endothelial cells are able to modify smooth muscle cell proteoglycan synthesis by stimulating the first step of protein core glycosylation. This stimulation was accompanied by an increase in proteoglycan hydrodynamic size.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041370306
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  • 6
    Electronic Resource
    Electronic Resource
    Development of the nucleolus in early goat embryos (1987)
    New York, NY : Wiley-Blackwell
    Gamete Research 18 (1987), S. 201-213 
    Details
    ISSN: 0148-7280
    Keywords: goat ; embryo ; ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In vivo nucleologenesis was studied in goat embryos from the pronuclear stage to the blastocyst stage by light and electron microscopy. Ultrastructural changes of the nucleoli were characterized by the following progression: homogeneous electron-dense fibrillar primary nucleoli in the pronucleus; small, dense fibrillar masses dispersed in clusters of chromatin at the two-cell stage; ring-shaped nucleoli made up of a fibrillar center surrounded by a layer of dense fibrillar components at the four-cell stage; reticulated nucleoli composed of a three-dimensional network of fibrillar components surrounded by small amounts of granular components at the eight-cell stage; fully developed compact-type nucleoli consisting of several fibrillar centers each surrounded by a layer of fibrillar componenets and abundant granular components in morulae and blastocysts. Moreover, it was concluded that activation of rRNA transcription, as evidenced by specific silver nitrate staining of the nucleolus organizer regions of metaphase chromosomes, occurs at the two-to four-cell stage and that the morphological changes accompanied a substantial increase in nucleolar transcriptional activity up to the blastocyst stage. This study provides evidence that a structure-function relationship exists during nucleologenesis in goat embryos.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120180302
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