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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 35 (1988), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Serotonin and catecholamines affect the regeneration of cilia in Tetrahymena thermophila in a dose-dependent manner: micromolar concentrations are stimulatory, whereas millimolar concentrations have little or no effect. This conclusion is based on motility measurements in regenerating cells and on ciliary counts in scanning electron micrographs. In addition, the recognition mechanism for each hormone appears to be specific and independent. Our results suggest an evolutionary link with hormonal mechanisms in multicellular eukaryotes.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6164-6166 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mathematical modeling of the dynamics of ultrathin perfluoropolyalkylether (PFPE) films, taking into consideration both the disk carbon surface composition and lubricant endgroup functionality, is described. Theoretical development based on the Monte Carlo method was employed to emulate experimental spreading data. In this model, we construct a system Hamiltonian based on a lattice-gas model by explicitly incorporating four classes of interactions: molecule/molecule, molecule/surface, endgroup/endgroup, and endgroup/surface, where a molecule is denoted as a backbone in the absence of endgroups. Spreading properties are investigated by tuning the lubricant interactions to model PFPE Z (without polar endgroups) and PFPE Zdol (with polar endgroups) on several surfaces. The simulations qualitatively describe the spreading profiles for molecules with and without polar endgroups. Acquired from N-frame animations, L-t plots are constructed and provide a qualitative comparison with the experimental data obtained from scanning microellipsometry. © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 383 (1982), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 513 (1987), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Perspectives in drug discovery and design 5 (1996), S. 213-224 
    ISSN: 1573-9023
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The term ‘microbicide’ denotes a vaginal product which could be used to protect an individual from infection by HIV and other sexually transmitted pathogens. This manuscript describes an in vitro model which is based on the mechanism of sexual transmission of HIV, and can be used to screen compounds for anti-HIV activity. An in vitro model forChlamydia is also described. Sulfated polysaccharides are exceedingly effective in blocking infection in both of these in vitro systems. Nevertheless, a formidable amount of animal and clinical work will need to be conducted before it will be clear whether this group of compounds will be efficacious in a product for human use.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 261 (1990), S. 249-259 
    ISSN: 1432-0878
    Keywords: Cumulus oophorus ; Mucus ; Fertilization ; Rat ; Syrian hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural and morphometric techniques were employed to examine the ovulated cumulus oophorus of hamsters and rats. Observations on cumuli prepared in a variety of ways including different chemical fixation techniques and cryofixation freeze substitution were compared. It was concluded that the cumulus mucus is not arranged in lamellae or granules as has previously been suggested but is composed of molecules which form very fine filaments when properly fixed. Morphometric analysis of cumuli fixed either in situ or after being explanted into medium revealed that the distance between neighboring cumulus cells was greater with increasing distance from the oocyte. Morphometry revealed that, when placed into medium, the cumulus expands possibly due to hydration. Thus physiological experiments carried out on cumuli should be performed very shortly after cumuli are isolated. From their ultrastructure cumulus cells appear to be actively involved in protein synthesis and secretion as well as steroid production.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 9 (1984), S. 1-19 
    ISSN: 0148-7280
    Keywords: spermatozoa ; acrosome ; fertilization ; hamster ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Adult female golden hamsters were induced to superovulate. When they were mated several hours prior to ovulation or artificially inseminated about the time of ovulation, nearly 100% of their eggs were subsequently fertilized monospermically. During the progression of fertilization when the eggs were still surrounded by compact cumulus oophorus, the contents of the ampullary region of the oviducts were collected and spermatozoa moving in the ampullary fluid, within the cumulus and on/in the zonae pellucidae of unfertilized eggs, were examined by light and electron microscopy to evaluate the status of their acrosomal caps.Most spermatozoa swimming in the ampullary fluid had apparently intact acrosomal caps, while the vast majority moving within the cumulus had distinctly modified acrosomal caps. Most spermatozoa that had passed through the cumulus and reached the zona surfaces had remnants of their acrosomal caps (“acrosomal ghosts”). When the ghosts were present around the sperm heads on the zona, the heads pivoted about a point roughly corresponding to the places where the ghosts were located. The ghosts seemed to firmly attach to the zona surfaces, then were split open by the sperm heads and left behind as the sperm heads advanced into the zona. A few spermatozoa on the zona surfaces had no acrosomal ghosts (at least not detectable by light microscopy). In this case, the sperm head pivoted about either the inner acrosomal membrane or the equatorial segment of the acrosome. In no instance were spermatozoa with intact acrosomal caps found on zona surfaces.We infer from these observations that most spermatozoa in vivo initiate their acrosome reactions while they are advancing through the cumulus. When they arrive at the zona surfaces, acrosomal ghosts are generally present on the sperm heads. These ghosts appear to hold sperm heads to zona surfaces as well as to restrict the direction of advancement of sperm head through the zona. In a minority of cases, ghostless spermatozoa reach the zona surfaces. As these spermatozoa appear to be able to penetrate the zona successfully, structures other than the acrosomal ghost (ie, the inner acrosomal membrane and the plasma membrane over the equatorial segment of the acrosome) may also attach to zona surfaces before spermatozoa penetrate into the zona.
    Additional Material: 19 Ill.
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  • 8
    ISSN: 0148-7280
    Keywords: oocyte ; cumulus oophorus ; corona radiata ; zona pellucida ; hyaluronidase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Cumulus-oocyte complexes were isolated from the follicles of proestrous rats or from the oviducal ampullae of estrous rats. The zona pellucida of some complexes was dissolved before fixation. The follicular cumulus cells were seen to be held together mainly by long processes, which often extended over a distance of several cells. Large numbers of straight processes from the corona radiata cells, passing to the oocyte, surface, were seen in the space formerly occupied by the zona pellucida. Oocyte microvilli were uniformly short; none traversed the zona.The postovulatory complexes were covered by amorphous extracellular material which also filled the spaces between the cells. By lysis of this material with hyaluronidase the cumulus cells were detached. The surfaces of these cells were covered with blebs.By testing the ability of hyaluronidase to remove the corona cells from the zona pellucida of complexes isolated around the time of ovulation, it was found that the completion of retraction of the corona cells processes occurred in the oviduct, immediately after ovulation. It is suggested that the oviducal environment may influence the final step of the withdrawal of the corona cells' projections from the zona pellucida.
    Additional Material: 8 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 22 (1989), S. 1-13 
    ISSN: 0148-7280
    Keywords: fertilization ; spermatozoa ; acrosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Over the past 40 years evidence from many sources has indicated that the mammalian acrosome reaction occurs within or near the cumulus oophorus. Recently, however, workers investigating in vitro fertilization in the mouse have concluded that in this system the acrosome reaction takes place on the surface of the zona pellucida. We have investigated the interaction of rat spermatozoa and the zona pellucida by using the scanning electron microscope (SEM) and two monoclonal antibodies which are directed to antigens of the rat sperm acrosome.When in vitro inseminated eggs from which the cumulus has been removed are viewed with the SEM some sperm heads on the surface of the zona pellucida appear unaltered whereas others appear to be undergoing changes. In vivo, all displayed altered head morphology. Using immunogold labeling we found that the two antibodies employed, 2C4 and 5B1, were directed to acrosomal content and vesiculating acrosomal membranes. Immunofluoresence staining of zonae pellucidae in in vitro fertilization studies revealed numerous small positive regions. These were presumably acrosomal content and membranes which had been left on the zona surface by spermatozoa which had been associated with the zona surface. Our results suggest that the rat acrosome interacts with the zona pellucida. During this interaction some acrosomal content and membranes detach from the spermatozoon and remain on the surface of the zona pellucida.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 1 (1978), S. 27-37 
    ISSN: 0148-7280
    Keywords: oocyte ; fertilization ; incorporation cone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: At the time of in vivo sperm-egg fusion in the rat, a small region of the oolemma under the head of the fertilizing sperm is observed to be free of microvilli. The microvilli-free region increases in area, and by one hour after sperm-egg contact extends over an area 20-30 μ in circumference and bulges out to form an “incorporation cone” visible by light microscopy. The microvilli-free incorporation cone reaches its maximum size at about two hours after sperm-egg interaction. It soon becomes smaller and has disappeared three to four hours after sperm-oocyte fusion. The cone cytoplasm is characterized by a 0.1 μ zone of thin filaments below the plasma membrane. Cytochalasin-B, 2.5 μg/ml, prevents formation of the cone or destroys the intact cone. It is suggested that micro filaments may be involved in the formation of the incorporation cone.
    Additional Material: 15 Ill.
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