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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 31 (1993), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: During the time over which the data for a regional hydrogeocheimical survey are collected, the physical and chemical attributes of the ground-water flow regime may exhibit appreciable temporal variation. A case study is presented in which the temporal variance of many physical and chemical attributes of ground water at single locations was close to or even exceeded the spatial variance of concentrations measured over the region at a single point in time. Thus, the results of a multivariate analysis of the spatial variability could have led to incorrect inferences had the regional sampling not been done within a period of time that was short enough so that no appreciable temporal variation occurred. A methodology using both spectral and multi variate analyses was used in determining: (a) the window of time allowable in collecting the water samples so that the temporal variability of the attributes did not affect the spatial analyses, and (b) the dominant factors that explain the spatial variability of physical and chemical attributes at that particular period in time.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Entamoeba histolytica is an intestinal parasite and the causative agent of amoebiasis, which is a significant source of morbidity and mortality in developing countries. Here we present the genome of E. histolytica, which reveals a variety of metabolic adaptations shared with two other ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 56 (2002), S. 39-64 
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Entamoeba histolytica, as its name suggests, is an enteric parasite with a remarkable ability to lyse host tissues. However, the interaction of the parasite with the host is more complex than solely destruction and invasion. It is at the host-parasite interface that cell-signaling events commit the parasite to (a) commensal, noninvasive infection, (b) developmental change from trophozoite to cyst, or (c) invasion and potential death of the human host. The molecule central to these processes is an amebic cell surface protein that recognizes the sugars galactose (Gal) and N-acetylgalactosamine (GalNAc) on the surface of host cells. Engagement of the Gal/GalNAc lectin to the host results in cytoskeletal reorganization in the parasite. The parasite cytoskeleton regulates the extracellular adhesive activity of the lectin and recruits to the host-parasite interface factors required for parasite survival within its host. If the parasite lectin attaches to the host mucin glycoproteins lining the intestine, the result is commensal infection. In contrast, attachment of the lectin to a host cell surface glycoprotein leads to lectin-induced host cell calcium transients, caspase activation, and destruction via apoptosis. Finally, trophozoite quorum sensing via the lectin initiates the developmental pathway resulting in encystment. The structure and function of the lectin that controls these divergent cell biologic processes are the subject of this review.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Attachment of Entamoeba histolytica to colonic epithelium and a variety of other target cells is mediated by a galactosc/N-acetyl D-galactosamine (Gal/GalNAc) inhibitable adhesin. Seven monoclonal antibodies specific for nonoverlapping epitopes of the 170 kDa subunit have been shown to have distinct effects on adherence. Four of these monoclonal antibodies inhibit or have no effect on amebic adherence while two others enhance amebic adherence. The epitopes recognized by these seven monoclonal antibodies have been mapped to the extracellular cysteine rich region of the 170 kDa subunit. The conformational nature of the epitopes was examined by testing monoclonal antibody reactivity with isolated regions of the 170 kDa subunit expressed as fusion proteins in E. coli and also with denatured native adhesin. These analyses suggested that three of monoclonal antibodies recognized conformational epitopes while the remaining four recognized linear epitopes. The mapping of these monoclonal antibodies have identified functionally important regions of the Gal/GalNAc adhesin and have also shown that recombinant Gal/GalNAc adhesin, when expressed in E. coli, retained at least some of its native conformation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Health & social care in the community 9 (2001), S. 0 
    ISSN: 1365-2524
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: An understanding of perceived barriers to health-care is critical to improving healthcare access for all Americans. To determine perceived barriers to health-care in an urban poor population in Dayton, Ohio, a face-to-face door-to-door survey of individuals identified through targeted, stratified, area probability sampling was done. A sample of 413 non-elderly poor adults, including 19% without telephones, reported personal relevance of various barriers to healthcare access. Most frequently endorsed barriers were lack of information about free or reduced-cost health-care, anticipated cost, and difficulty accessing child-care. Seventy-four per cent of respondents reported more than one barrier. Individuals without telephones and those without health insurance reported more barriers to health-care. Reported barriers were similar for working and non-working poor, except for transportation problems, more frequently reported by non-working respondents. This study provides important data on what poor people in a medically underserved community perceive to be barriers to accessing health-care and underscores the importance of including people without telephones in the study design. Respondents who did not have telephones were more likely to report multiple barriers, particularly problems with lack of information about free or discounted medical care, child-care, and transportation. These findings suggest the importance of door-to-door surveys rather than telephone surveys for getting accurate data on the poor.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 33 (1986), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The tonB gene product is necessary for the energy-dependent transport of ferric chelates and vitamin B12 across the Escherichia coli outer membrane. When carried on multicopy plasmids, the cloned tonB gene complemented tonB hosts, restoring transport of ferri-siderophone complexes and vitamin B12, and susceptibility to the group B colicins and phage ф80. The levels of these activities were all markedly lower than when the tonB+ gene was present in single copy. This depression of TonB function occurred even when the chromosome carried the normal tonB+ allele, but plasmids carrying only a portion of the tonB gene, including the 5′-regulatory region, were not inhibitory.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Adherence of the enteric protozoan parasite Entamoeba histolytica is mediated by an N-acetyl d-galactosamine (GaINAc)-specific lectin, a heterodimer of heavy (170 kDa) and light (35/31 kDa) subunits. The gene families encoding the lectin subunits were characterized using clamped homogeneous electric field (CHEF) gel electrophoresis in the strain HM1:IMSS. The heavy sub-unit was shown to be encoded by a family of five hgl genes, which were physically mapped to five distinct Hindlll restriction fragments. The light subunit was shown to be encoded by a family of lgl genes located at six loci in the genome. Heavy and light subunit genes did not appear to be linked. Partial sequences of new members of the hgl and lgl gene families were obtained. Several different strains of E histolytica were found to contain multiple hgl loci in their genomes. Expression of hgl and lgl genes in HM1: IMSS trophozoites was examined under different growth conditions using the reverse transcription-polymerase chain reaction (RT-PCR). mRNA transcripts were detected from three hgl genes and three lgl genes, with no significant differences between cultured amoebae and amoebae from liver abscesses. The complexity of GaINAc lectin gene expression observed suggests distinct biological functions for the products of the individual genes during pathogenesis.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1617-4623
    Keywords: E. coli ; Vitamin B12 ; btuB ; Repression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Synthesis of the btuB-encoded outer membrane receptor for vitamin B12 and the metE-encoded homocysteine methyltransferase is repressed by growth of Escherichia coli in the presence of vitamin B12. The regulation by vitamin B12 of the production of β-galactosidase in strains carrying btuB-lac or metE-lac operon fusions indicated that repression of both genes operates at the transcriptional level. Selection for expression of these fusions under repressive conditions allowed isolation of second-site mutations in which repressibility by vitamin B12 had been lost. Mutations in metH and metF prevented vitamin B12-dependent regulation of metE, but not that of btuB. Mutations in btuB and other genes involved in uptake of the vitamin eliminated or reduced repression. Mutations in the newly identified gene, btuR, controlled the repressibility of btuB, but had no effect on metE regulation. The btuR gene resides at 27.9 min on the genetic map in the gene order cysB-topA-btuR-trp; it acts in a trans-dominant manner and appears to encode a repressor of btuB transcription.
    Type of Medium: Electronic Resource
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