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  • Blackwell Publishing Ltd  (10)
  • Springer  (10)
  • American Association for the Advancement of Science  (8)
  • Blackwell Science, Ltd  (3)
  • 2000-2004  (24)
  • 1960-1964  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Spontaneous Astomy: Loss of Oral Areas in Glaucoma chattoni (1961)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 8 (1961), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Specimens of Glaucoma chattoni lacking in oral areas and unable to divide were observed in both axenic and bacterized cultures. The frequency of incidence of astomy rose in the course of continued cultivation of G. chattoni A, which was the strain most extensively studied.Observations on silver impregnated animals from mass cultures, and studies of individually isolated living ciliates, have both led to the conclusion that all cells destined to become astomous pass through a certain definite sequence of events. These axe: 1. Initial damage, not microscopically detectable, predisposes the cell in such a way that within a few generattons all of its progeny become astomous. 2. The ability to complete normal stomatogenesis is lost; the cell cannot maintain normal posterior oral anlagen and also cannot regenerate following damage to the existing oral area. At this stage the cell can still divide, so that astomous opisthes are produced. 3. The existing oral area disappears shortly after the ability to produce new oral areas is lost. Loss of ability to divide occurs simultaneously with loss of oral areas. 4. Finally, there is increasing disorganization of the kineties, gradually decreasing activity and death.The incidence of astomy was compared in several different strains of G. chattoni, including two newly isolated from nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1961.tb01211.x
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  • 2
    Electronic Resource
    Electronic Resource
    Morphogenesis in Glaucoma chattoni (1960)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 7 (1960), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The techniques of silver impregnation and of digitonin solubilization have been applied to an investigation of aspects of cortical morphogenesis in Glaucoma chattoni. The typical stages of the formation of new oral areas (stomato-genesis), as well as of other related surface events, are described in detail. Estimates were made of the relative and absolute durations of these stages; these estimates indicate that for animals growing at 25°C. in bacterized culture, stomatogenesis and cell division together occupy about one third of the division cycle.Certain atypical morphogenetic phenomena have been encountered and are briefly described. These include three cases of stomatogenesis along a kinety other than kinety 1, several instances of anterior stomatogenesis leading to replacement of existing oral areas, and numerous cases of spontaneous loss of oral areas.Finally, the process of increase in number of kinetosomes along certain kineties has been submitted to intensive study. It has been found that comparatively little increase takes place during stomatogenesis and cell division; the bulk of kinetosomal increase along the kineties takes place during the first two-thirds of the division cycle. Data relevant to this increase have been analyzed according to the method of Scherbaum & Rasch; this analysis reveals that the probable phases of most rapid kinetosomal increase, along kinety l at least, occur just after division, and just before the beginning of stomatogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1960.tb05983.x
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  • 3
    Electronic Resource
    Electronic Resource
    Morphogenesis and Division in Chains of Tetrahymena pyriformis GL (1964)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 11 (1964), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. The formation of chains was induced both in exponentially growing and in synchronized cultures of Tetrahymena Pyriformis GL, by application of one or two hr 34°C shocks. An arrest in constriction along the division furrow is brought about as a result of prolonged exposure to 34° during an early phase of cell division.After return to optimal temperatures, the chains remain in their original tandem configuration. They possess two sets of cortical structures, and generally also two macronuclei.Subsequently, two new oral primordia appear, one in each component. These primordia develop in synchrony with each other. The later development of the chains is correlated with the placement of the oral primordia. In some situations, these primordia form immediately posterior to the pre-existing oral areas and replace them; in these cases, the original division furrow is obliterated, and irregular and probably unstable homopolar doublets form. More frequently, one or both of the oral primordia are normal division primordia. In these cases, the original oral area of the anterior component persists, while that of the posterior component is resorbed. The original fission line persists, and two new fission lines are formed anterior to each of the new oral primordia. When constriction takes place along the new fission lines, the original arrested fission line is occasionally reactivated, and the chain then divides into four cells. More often, the original furrow is not reactivated (or only incompletely reactivated), and the chain divides into two or three cells, depending on how close the two new division furrows are to each other.The chains ultimately give rise to normal clones of singlet cells. No clones of doublets were observed.In the Discussion, the synchronization of developmental events in the two components of the chain is emphasized. The cases of reactivation of the original fission line in synchrony with constriction along the newly formed fission lines seem to indicate that furrowing results from an interaction of a preformed cortical site (fission line) with a pervasive substance which acts to trigger constriction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1964.tb01791.x
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  • 4
    Electronic Resource
    Electronic Resource
    Human intestinal tissue tropism of intimin epsilon O103 Escherichia coli (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 218 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Human intestinal in vitro organ culture was used to assess the tissue tropism of human isolates of Escherichia coli O103:H2 and O103:H- that express intimin ɛ. Both strains showed tropism for follicle associated epithelium and limited adhesion to other regions of the small and large intestine. This is similar to the tissue tropism shown by intimin γ enterohaemorrhagic (EHEC) O157:H7, but distinct from that of intimin α enteropathogenic (EPEC) O127:H6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(02)01182-5
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  • 5
    Electronic Resource
    Electronic Resource
    ATOC AND OTHER FACTORS AFFECTING THE DISTRIBUTION AND ABUNDANCE OF HUMPBACK WHALES (MEGAPTERA NOVAEANGLIAE) OFF THE NORTH SHORE OF KAUAI (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 18 (2002), S. 0 
    Details
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Humpback whale diving behavior changes subtly when exposed to signals transmitted from the Acoustic Thermometry of Ocean Climate (ATOC) sound projector located 14 km offshore the island of Kauai. This study considered whether such responses would lead to changes in distribution and abundance. A land-based shore station measured humpback whale locations (scan samples) for both nearshore (〈5 km) and offshore (5–10 km) areas. Control observations were made in 1994 and 1998. In 1998 multipleday blocks with ATOC transmissions were interspersed with multiple-day control blocks without transmissions. Sighting rates were higher in 1998 (ATOC) than in 1994 (control year), probably due to better sighting conditions, but may reflect increased population size. Sighting rates did not differ between control and ATOC conditions in 1998. A seasonal sighting peak was observed in both years. No vessel effect on sighting rate was detected in 1998.There was no effect of ATOC on the distance from the shore station to whales, or the depth of water where pods were located. However, the distribution of whales shifted slightly eastward during the ATOC blocks and the mean distance between the ATOC source and pods was greater during transmissions. Nonetheless, more whales were found close to the source when it was on, suggesting a more variable response rather than simple avoidance, with whales found both closer to, and farther away from, the source during transmissions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1748-7692.2002.tb01064.x
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  • 6
    Electronic Resource
    Electronic Resource
    Site-directed mutagenesis of intimin α modulates intimin-mediated tissue tropism and host specificity (2001)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 40 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The hallmark of enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherchia coli adhesion to host cells is intimate attachment leading to the formation of distinctive ‘attaching and effacing’ lesions. This event is mediated, in part, by binding of the bacterial adhesion molecule intimin to a second bacterial protein, Tir, delivered by a type III secretion system into the host cell plasma membrane. The receptor-binding activity of intimin is localized to the C-terminal 280 amino acids (Int280) and at least five distinct intimin types (α, β, γ, δ and ε) have been identified thus far. In addition to binding to Tir, intimin can also bind to a component encoded by the host. The consequence of latter intimin-binding activity may determine tissue tropism and host specificity. In this study we selected three amino acids in intimin, which are implicated in Tir binding, for site-directed mutagenesis. We used the yeast two-hybrid system and gel overlays to study intimin–Tir protein interaction. In addition, the biological consequences of the mutagenesis was tested using a number of infection models (cultured epithelial cells, human intestinal explants and a mouse model). We report that while an I237/897A substitution (positions numbered according to Int280α/whole intimin α) in intimin α did not have any affect on its biological activity, a T255/914A substitution attenuated intimin activity in vivo. In contrast, the mutation V252/911A affected tissue targeting in the human intestinal explant model and attenuated the biological activity of intimin in the mouse model. This study provides the first clues of the molecular basis of how intimin mediates tissue tropism and host specificity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02371.x
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  • 7
    Electronic Resource
    Electronic Resource
    Activation of enteropathogenic Escherichia coli (EPEC) LEE2 and LEE3 operons by Ler (2000)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 38 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enteropathogenic Escherichia coli (EPEC) produces attaching and effacing lesions (AE) on epithelial cells. The genes involved in the formation of the AE lesions are contained within a pathogenicity island named the locus of enterocyte effacement (LEE). The LEE comprises 41 open reading frames organized in five major operons: LEE1, LEE2, LEE3, LEE4 and tir. The first gene of the LEE1 operon encodes a transcription activator of the other LEE operons that is called the LEE-encoded regulator (Ler). The LEE2 and LEE3 operons are divergently transcribed with overlapping −10 promoter regions, and gene fusion studies have shown that they are both activated by Ler. Deletion analysis, using lacZ reporter fusions, of the LEE2 and LEE3 promoters demonstrated that deletions extending closer to the LEE2 transcription start site than −247 bp lead to loss of activation by Ler, whereas only 70 bp upstream of the LEE3 transcription start site is required for Ler-mediated activation. We have purified Ler as a His-tagged protein and used it to perform DNA-binding assays with LEE2 and LEE3. We observed that Ler bound to a DNA fragment containing the −300 to +1 region of LEE2; however, it failed to bind to a DNA fragment containing the −300 to +1 region of LEE3, suggesting that Ler activates both operons by only binding to the regulatory region upstream of LEE2. The Ler-activatable LEE3::lacZ fusions extended to what would be −246 bp of the LEE2 operon. A lacZ fusion from the −300 to +1 region of LEE3 failed to be activated by Ler, consistent with our hypothesis that Ler activates the expression of LEE2 and LEE3 by binding to a region located downstream of the LEE3 transcription start site. DNase I footprinting revealed that Ler protected a region of 121 bp upstream of LEE2. Purified Ler mutated in the coiled-coil domain was unable to activate transcription and to bind to the LEE2 regulatory region. These data indicate that Ler may bind as a multimer to LEE2 and activate both divergent operons by a novel mechanism potentially involving changes in the DNA structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02168.x
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  • 8
    Electronic Resource
    Electronic Resource
    Coiled-coil proteins associated with type III secretion systems: a versatile domain revisited (2002)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Summary The pathogenic potential of many Gram-negative bacteria is indicated by the possession of a specialized type III secretion system that is used to deliver virulence effector proteins directly into the cellular environment of the eukaryotic host. Extracellular assemblies of secreted proteins contrive a physical link between the pathogen and host cytosol and enable the translocated effectors to bypass the bacterial and host membranes in a single step. Subsequent interactions of some effector proteins with host cytoskeletal and signalling proteins result in modulation of the cytoskeletal architecture of the aggressed cell and facilitate entry, survival and dissemination of the pathogen. Although the secreted components of type III secretion systems are diverse, many are predicted to share a common coiled-coil structural feature. Coiled-coils are ubiquitous and highly versatile assembly motifs found in a wide range of structural and regulatory proteins. The prevalence of these domains in secreted virulence effector proteins suggests a fundamental contribution to multiple aspects of their function, and evidence accumulating from functional studies suggests an intrinsic involvement of coiled-coils in subunit assembly, translocation and flexible interactions with multiple bacterial and host proteins. The known functional flexibility that coiled-coil domains confer upon proteins provides insights into some of the pathogenic mechanisms used during interaction with the host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03083.x
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  • 9
    Electronic Resource
    Electronic Resource
    Inheritance of caudal peduncle banding in the spike-tailed paradisefish (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 59 (2001), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Segregation patterns observed in the progenies from 13 different crosses of the spike-tailed paradisefish Pseudosphromenus cupanus support the hypothesis that caudal peduncle banding is controlled by a major effect gene exhibiting the classical monohybrid Mendelian pattern of inheritance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb00175.x
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  • 10
    Electronic Resource
    Electronic Resource
    Identification of a novel type IV pilus gene cluster required for gastrointestinal colonization of Citrobacter rodentium (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Citrobacter rodentium is used as an in vivo model system for clinically significant enteric pathogens such as enterohaemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC). These pathogens all colonize the lumen side of the host gastrointestinal tract via attaching and effacing (A/E) lesion formation. In order to identify genes required for the colonization of A/E-forming pathogens, a library of signature-tagged transposon mutants of C. rodentium was constructed and screened in mice. Of the 576 mutants tested, 14 were attenuated in their ability to colonize the descending colon. Of these, eight mapped to the locus of enterocyte effacement (LEE), which is required for the formation of A/E lesions, underlying the importance of this mechanism for pathogenesis. Another mutant, P5H2, was found to have a transposon insertion in an open reading frame that has strong similarity to type IV pilus nucleotide-binding proteins. The region flanking the transposon insertion was sequenced, identifying a cluster of 12 genes that encode the first described pilus of C. rodentium (named colonization factor Citrobacter, CFC). The proteins encoded by cfc genes have identity to proteins of the type IV COF pilus of enterotoxigenic E. coli (ETEC), the toxin co-regulated pilus of Vibrio cholerae and the bundle-forming pilus of EPEC. A non-polar mutation in cfcI, complementation of this strain with wild-type cfcI and complementation of strain P5H2 with wild-type cfcH confirmed that these genes are required for colonization of the gastrointestinal tract by C. rodentium. Thus, CFC provides a convenient model to study type IV pilus-mediated pathogen–host interactions under physiological conditions in the natural colonic environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03470.x
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