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  • 1
    Electronic Resource
    Electronic Resource
    NaCl-sensitive mutant of Staphylococcus aureus has a Tn917-lacZ insertion in its ars operon (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 222 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Staphylococcus aureus is a Gram-positive bacterium that is extremely halotolerant. To investigate the molecular mechanisms by which S. aureus can cope with osmotic stress, Tn917-lacZ-induced NaCl-sensitive mutants were isolated. An NaCl-sensitive mutant showed a longer lag period, slower growth rate, and lower final culture turbidity than the parent strain in liquid medium containing 1.5 M NaCl. Electron microscopic observation of the NaCl-sensitive mutant under NaCl stress conditions revealed large, pseudo-multicellular cells. Addition of exogenous osmoprotectants, such as glycine betaine, choline, l-proline, and proline betaine, did not relieve the NaCl sensitivity of the mutant. The region flanking the transposon insertion site in the NaCl-sensitive S. aureus chromosome was sequenced. The mutated gene was 99% identical to arsR, the arsenic operon regulatory protein present on the pI258 plasmid of S. aureus. The ars operon from pI258 was subcloned into the shuttle vector pLI50 and transferred into the NaCl-sensitive mutant. The ars operon in trans restored NaCl tolerance in the mutant, suggesting that NaCl sensitivity is due to the mutation in arsR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00312-4
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  • 2
    Electronic Resource
    Electronic Resource
    Unique morphogenesis in Saccharomyces cerevisiae strain GS1731 (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 166 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During the lag and early exponential phase of growth, 50–60% of budded cells of Saccharomyces cerevisiae strain GS1731 were multiply budded. During subsequent culture growth, the frequency of multiply budded cells decreased until by stationary phase multiply budded cells were rare. Data from renewed growth of a culture after hydroxyurea treatment indicated that GS1731 mother cells could assemble up to three pre-bud sites and begin bud growth and development in each. Light and scanning electron microscopy showed two or three very small buds emerging simultaneously on a mother cell and either reaching full size at the same time or enlarging sequentially. Immunofluorescence studies revealed that these multiply budded cells had multiple bundles of cytoplasmic microtubules. DAPI staining of nuclei revealed that some of the unbudded mother cells were multinucleate and completed cytokinesis giving rise to normal daughter cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb13188.x
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  • 3
    Electronic Resource
    Electronic Resource
    An ultrastructural survey of the genus Prototheca with special reference to plastids (1977)
    Springer
    Mycopathologia 61 (1977), S. 117-119 
    Details
    ISSN: 1573-0832
    Keywords: Prototheca ; Colorless alga ; Plastids ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract An ultrastructural investigation of six different species of Prototheca showed that all of them contained starch grains enclosed in double-membrane-bounded structures recognized as plastids. It is concluded that these unicellular species of Prototheca must be considered as non-photosynthetic algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443840
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructural features of the pineal gland from cold-exposed golden hamsters (1973)
    Springer
    Journal of neurocytology 2 (1973), S. 237-247 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Golden hamsters exposed to various temperatures (5 and 25 °C) and photoperiods (8∶16 L∶D and 12∶10 L∶D), were killed at the end of 4, 8 and 12 weeks of exposure. The pineal glands were examined electron microscopically. Ultrastructural differences in the pineal gland were observed between the cold-exposed animals and the corresponding controls. The most striking difference was the occurrence of membranous whorls in pinealocytes of cold-exposed hamsters. These membranous whorls were of varying sizes and degree of complexity suggesting possible developmental stages of the membranous whorls. An apparent increase in ribosomal density and nuclear polymorphism were observed in the pinealocytes of cold-exposed hamsters. Short photoperiod appeared to augment the formation of membranous whorls in animals exposed to cold. It is suggested that the membranous whorls are focal sites of membrane reorganization that may be requisite for cellular activity under these environmental conditions. It is also suggested that gonadal involution owing to cold exposure may be mediated by the pineal gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01104028
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of cell surface material removed by water and NaCl washing ofParacoccus denitrificans grown under conditions of divalent cation deficiency and sufficiency (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 35-39 
    Details
    ISSN: 1572-9699
    Keywords: Paracoccus denitrificans ; water and NaCl washing ; outer membrane ; ornithine-containing lipid ; cell surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paracoccus denitrificans grown on complex medium deficient in Mg2+ and Ca2+ are rendered lysozyme susceptible by washing with NaCl, whereas cells grown in a succinate-salts medium (Mg2+ and Ca2+ sufficient) or complex medium supplemented with Mg2++Ca2+ are not. The material released by water washing of cells grown on complex medium and complex medium supplemented with Mg2+ and Ca2+ was characterized by a high protein content. There was a high lipid: protein ratio and an appreciable amount of 3-deoxyoctulosonic acid in the material released by NaCl washing of cells grown under all conditions, indicating release of outer membrane material. The lipid ornithine: lipid phosphorous ratios of NaCl wash from cells grown on complex medium and complex medium supplemented with Mg2+ and Ca2+ were 0.54 and 0.34, respectively. Although NaCl washing removed outer membrane material from cells grown under all conditions, only divalent cation deficient cells were rendered lysozyme susceptible. This might be explained by the increased outer membrane ornithine-containing lipid to phospholipid ratio in these cells yielding a more permeable outer membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878277
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  • 6
    Electronic Resource
    Electronic Resource
    Prototheca filamenta: A fungus not an alga (1975)
    Springer
    Mycopathologia 57 (1975), S. 89-91 
    Details
    ISSN: 1573-0832
    Keywords: Fungus ; Light Microscopy ; Prototheca filamenta ; Scanning Electron Microscopy ; Transmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The genusPrototheca is composed of colorless algae. Plastids, a characteristic feature of colorless algae, are absent fromP. filamenta cells. The growth pattern seen with light and scanning electron microscopes, and the ultrastructure observed with the transmission electron microscope suggest thatP. filamenta is a fungus. Consequently we recommend the removal ofP. filamenta from the genusPrototheca and subsequent investigation of this organism to determine its correct taxonomic placement among the fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01365709
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  • 7
    Electronic Resource
    Electronic Resource
    Prevention by pinealectomy of short-photoperiod-induced ultrastructural changes in the hamster harderian gland (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 449-452 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Harderian gland ultrastructure was examined at biweeky intervals for 16 weeks after either pinealectomy or sham-operation of male and female hamsters kept in 1L:23D and 14L:10D photoperiods. Female characteristics such as membrane formations and extensive smooth endoplasmic reticulum appeared in the males kept under short photoperiod conditions. Similarly, male characteristics such as the tubular clusters appeared in the glands of females kept in the short photoperiod. When male and female hamsters were pinealectomized and exposed to the short photoperiod, the glands in each sex retained the characteristics typical of that sex. Atrophy of the testes and uteri was also observed in the sham-operated hamsters maintained under short photoperiods, but not in the pinealectomized animals. The changes observed in the Harderian glands and reproductive organs of hamsters kept in the short photoperiod were not observed in the hamsters maintained in the long photoperiod. The photoperiod-induced ultrastructural changes in the hamster Harderian glands are most likely due to changes in hormonal levels brought about by the regression of reproductive organs and can be prevented by pinealectomy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100305
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructural investigation of the postnatal development of the hamster harderian gland (1972)
    Springer
    Cell & tissue research 135 (1972), S. 149-153 
    Details
    ISSN: 1432-0878
    Keywords: Harderian gland ; Hamster ; Mitosis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The glandular cells of the Harderian gland of the very young hamsters are loosely arranged in lobules. Large nuclei are present in such cells. Mitosis is observed in the alveolar cells of hamsters of both sexes from the first day to the 3rd week of development. Cell division was not observed after 3 weeks of age. The alveolar cells increase considerably in size after this period. Although sexual dimorphism of the Harderian gland was evident by 3 weeks, the dividing cells from both sexes of this age are ultrastructurally alike.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315122
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  • 9
    Electronic Resource
    Electronic Resource
    The androgenic effect on the fine structure of the harderian gland in the male hamster (1979)
    Springer
    Cell & tissue research 198 (1979), S. 119-127 
    Details
    ISSN: 1432-0878
    Keywords: Male hamster ; Harderian gland ; Castration ; Sexual dimorphism ; Porphyrin ; Testosterone ; Tubular clusters ; Membranous structures ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A sexual dimorphism of the hamster Harderian gland at the ultrastructural level has been reported. The effect of testosterone on the fine structure of the gland from castrated male golden hamsters is reported here. Harderian glands from the following three groups of animals were examined at regular intervals up to 60 days after castration: (1) castrated; (2) castratedsham-injected, receiving 0.1 ml sesame oil per day; (3) castrated-testosterone injected, receiving 2mg testosterone propionate in 0.1 ml sesame oil per day. In groups 1 and 2, clusters of cylindrical tubules, typical of the male gland, decreased in number and disappeared almost completely 2 weeks after castration. Membranous structures, typical of the female gland, prevailed in these two groups throughout the remaining period of experiment. On the other hand, these changes were prevented in the group of castrated animals maintained on testosterone propionate. It is concluded that castration modified the ultrastructure of the male hamster Harderian gland toward the female type and that daily administration of testosterone propionate prevented this change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234839
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of ingested gossypol on the ultrastructure of rat ovarian follicles (1987)
    Springer
    Cell & tissue research 250 (1987), S. 215-220 
    Details
    ISSN: 1432-0878
    Keywords: Gossypol ; Ovarian follicle ; Granulosa cells ; Lysosomes ; Smooth endoplasmic reticulum ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural changes were observed in the oocytes and granulosa cells of the ovarian follicles of sexually mature female rats treated daily for 60 days with gossypol acetic acid at a dosage known to induce sterility in male rats (20 mg/kg body weight, orally). The changes included an increased lysosomal population in the ooplasm and a reduced, poorly developed smooth endoplasmic reticulum in the granulosa cells. The latter changes suggest a suppression of the secretory activity of the granulosa cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214674
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