Ciba Foundation symposium最新文献_第7页

Tooth morphogenesis and the differentiation of ameloblasts. 牙齿的形态发生与成釉细胞的分化。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515303.CH2

I. Thesleff, T. Åberg

{"title":"Tooth morphogenesis and the differentiation of ameloblasts.","authors":"I. Thesleff, T. Åberg","doi":"10.1002/9780470515303.CH2","DOIUrl":"https://doi.org/10.1002/9780470515303.CH2","url":null,"abstract":"All vertebrate organs are formed from several cell types, and it is currently believed that interactions between the different components constitute the most important mechanism in the regulation of organ morphogenesis. In developing teeth morphogenetic interactions occur between the epithelium covering the facial processes and the underlying neural crest-derived mesenchyme. Morphogenesis is accompanied by differentiation of the various dental cell types, including the ameloblasts. Although ameloblasts differentiate terminally and start the deposition of enamel matrix only after the completion of crown morphogenesis, there is increasing evidence suggesting that the segregation of the ameloblast cell lineage may start much earlier. For example, the down-regulation of the North receptor, which in some other developmental system is associated with cell fate determination, is already seen in the dental epithelium prior to the bud stage. It is not known to what extent the differentiation of ameloblasts depends on tooth morphogenesis, and whether the same mesenchymal signals regulate morphogenesis and cell differentiation. There is evidence that growth factors act as morphogenetic signals. Bone morphogenetic proteins and fibroblast growth factors appear to regulate the initiation of tooth development, as well as the morphogenesis of the crown shape. However, the molecular nature of the signals regulating the advancing specialization of the cells in the ameloblast cell lineage remains unknown.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"8 1","pages":"3-12; discussion 12-7"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86589799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 27

Determinants and mechanisms of enamel fluorosis. 氟牙釉质中毒的决定因素和机制。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515303.ch16

G M Whitford

{"title":"Determinants and mechanisms of enamel fluorosis.","authors":"G M Whitford","doi":"10.1002/9780470515303.ch16","DOIUrl":"https://doi.org/10.1002/9780470515303.ch16","url":null,"abstract":"Enamel fluorosis occurs when fluoride concentrations in or in the vicinity of the forming enamel are excessive during its pre-eruptive development. Fluoride concentrations in plasma, enamel and other tissues reflect the difference between intake and excretion, i.e. fluoride balance. In addition to the diet, modern sources of ingested fluoride include a variety of dental products, some of which have been identified as risk factors for fluorosis. Fluoride absorption is inversely related to dietary calcium which, at high concentrations, may cause net fluoride secretion into the gastrointestinal tract. The excretion of absorbed fluoride occurs almost exclusively via the kidneys, a process which is directly related to urinary pH. Thus, fluoride balance and tissue concentrations and the risk of fluorosis are increased by factors such as high protein diets, residence at high altitude, and certain metabolic and respiratory disorders that decrease pH. Factors that increase urinary pH and decrease the balance of fluoride include vegetarian diets, certain drugs and some other medical conditions. Although several other fluoride-induced effects might be involved in the aetiology of fluorosis, it now appears that inhibition of enzymatic degradation of amelogenins, which may delay their removal from the developing enamel and impair crystal growth, may be of critical importance. In addition to the effects of fluoride, disturbances in enamel formation that can be confused with fluorosis are caused by chronic acidosis and hypoxia independently of the level of fluoride exposure.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"205 ","pages":"226-41; discussion 241-5"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/9780470515303.ch16","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20134685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 64

Structure, crystal chemistry and density of enamel apatites. 釉质磷灰石的结构、晶体化学和密度。

Ciba Foundation symposium Pub Date : 1997-01-01

J C Elliott

{"title":"Structure, crystal chemistry and density of enamel apatites.","authors":"J C Elliott","doi":"","DOIUrl":"","url":null,"abstract":"The apatitic calcium phosphate crystals in dental enamel are too small for single crystal diffraction studies so the only possible direct structure determination must use whole-pattern-fitting Rietveld analysis of X-ray and neutron powder diffraction patterns. As a result, aspects of the structure are not known in detail. Further structural information can be obtained by consideration of published chemical analyses and infrared studies, taking into account studies of the crystal chemistry of synthetic apatitic analogues of enamel apatite. The apatitic constitutional water and total water content of enamel are particularly important, but there are difficulties in their determination. Making reasonable assumptions, a number of models of the unit cell can be derived. The weight per cent (including constitutional water) and density of the enamel apatite crystals for the most probable model are about 98 wt.% and 3.0 g cm-3, respectively. The apatite volume per cent calculated from these values is about 96%. The weight per cent and volume per cent of enamel apatite are higher than normally accepted values because of inclusion of constitutional water and use of a density for enamel apatite that takes into account its known lattice expansion over hydroxyapatite and probable lattice vacancies.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"205 ","pages":"54-67; discussion 67-72"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20134794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Tuftelin: enamel mineralization and amelogenesis imperfecta. 凝灰质:牙釉质矿化和成釉发育不全。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515303.ch10

D Deutsch, L Dafni, A Palmon, M Hekmati, M F Young, L W Fisher

{"title":"Tuftelin: enamel mineralization and amelogenesis imperfecta.","authors":"D Deutsch, L Dafni, A Palmon, M Hekmati, M F Young, L W Fisher","doi":"10.1002/9780470515303.ch10","DOIUrl":"https://doi.org/10.1002/9780470515303.ch10","url":null,"abstract":"Tuftelin is a novel acidic enamel protein thought to play a major role in enamel mineralization. Its identity and localization has been confirmed by amino acid composition, enzyme-linked immunosorbant assay, Western blots, indirect immunohistochemistry and high resolution protein-A gold immunocytochemistry. The deduced tuftelin protein (pI 5.2) contains 389 amino acids and has a calculated peptide molecular mass of 43,814 Da. Immunological studies suggest conservation of tuftelin structure between species throughout vertebrate evolution. The cDNA sequence encodes for several putative post-translation sites including one N-glycosylation consensus site, seven O-glycosylation sites and seven phosphorylation sites, as well as an EF-hand calcium-binding domain (with mismatch), localized towards the N-terminal region. At the C-terminal region (residues 252-345) tuftelin contains structurally relevant determinants for self assembly. We recently cloned and partially sequenced the human tuftelin gene (four exons have now been sequenced). These sequences include exon 1 and over 1000 bases of the putative promoter region. Employing fluorescent in situ hybridization, we mapped the human tuftelin gene to chromosome 1q 21-31. Localization of the human tuftelin gene to a well-defined cytogenetic region may be important in understanding the aetiology of autosomally inherited amelogenesis imperfecta, the most common enamel hereditary disease.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"205 ","pages":"135-47; discussion 147-155"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/9780470515303.ch10","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20134799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 20

The antibiotic selective process: concentration-specific amplification of low-level resistant populations. 抗生素选择过程:低水平耐药群体的浓度特异性扩增。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515358.ch7

F Baquero, M C Negri, M I Morosini, J Blázquez

{"title":"The antibiotic selective process: concentration-specific amplification of low-level resistant populations.","authors":"F Baquero, M C Negri, M I Morosini, J Blázquez","doi":"10.1002/9780470515358.ch7","DOIUrl":"https://doi.org/10.1002/9780470515358.ch7","url":null,"abstract":"The biochemistry and genetics of antibiotic resistance are far better known than the equally important events underlying the selection of resistant populations. The hidden selection of low-level resistant variants may be a key process in the emergence of high-level antibiotic resistance. Different low-level resistant bacterial subpopulations may be specifically selected by different low antibiotic concentrations. The space in the environment (human body) where a given selective concentration exists represents the selective compartment. For pharmacokinetic reasons, low antibiotic concentrations occur in a larger selective compartment and persist longer than high antibiotic concentrations. The specific selection of low-level variants by low concentrations of antibiotic can be reproduced in experimental in vitro models using mixtures of susceptible and low-level resistant populations. We demonstrated this in Escherichia coli strains harbouring TEM-1, TEM-12 and TEM-10 beta-lactamases challenged by cefotaxime, and also Streptococcus pneumoniae strains with various levels of penicillin resistance challenged by amoxicillin or cefotaxime. In both cases, four hours of antibiotic challenge produced selective peaks of low-level resistant variant populations at low-level antibiotic concentrations. We conclude that variants with small decreases in antibiotic susceptibility may be fully selectable under in vivo circumstances; on the other hand, low-level antibiotic concentrations may have a considerable selective effect on the emergence of antibiotic resistance.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"207 ","pages":"93-105; discussion 105-11"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20135905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 65

T cells as orchestrators of the asthmatic response. T细胞作为哮喘反应的协调者。

Ciba Foundation symposium Pub Date : 1997-01-01

A B Kay

{"title":"T cells as orchestrators of the asthmatic response.","authors":"A B Kay","doi":"","DOIUrl":"","url":null,"abstract":"The T cell hypothesis of asthma, particularly chronic asthma, is based around the concept that the disease is driven and maintained by the persistence of a specialized subset of chronically activated T memory cells sensitized against an array of allergenic, occupational or viral antigens which home to the lung after appropriate antigen exposure or viral infection. Allergens induce a CD4+ T helper (Th) cell response, whereas viruses recognize CD8+ T cytotoxic (Tc) cells. In the asthmatic airway there appears to be both CD4+ and CD8+ cells with a type 2 cytokine phenotype (i.e. Th2 and Tc2 type). These cells produce: interleukin (IL)-5, IL-3 and granulocyte macrophage colony-stimulating factor, which recruit, mobilize and activate eosinophils for subsequent mucosal tissue damage; and IL-4, an essential co-factor for local or generalized IgE production. This in turn leads to eosinophilic desquamative bronchitis, with epithelial shedding, mucus hypersecretion and bronchial smooth muscle contraction. Thus, although the eosinophil is largely responsible for airway symptoms, its function appears to be under T cell control. Support for this hypothesis includes: the observations that activated T cells and their products can be identified in biopsies from the major variants of the disease (atopic, nonatopic [intrinsic] and occupational asthma); the co-localization of mRNA for type 2 cytokines to CD4+ and CD8+ cells in atopic and non-atopic asthma; the presence of chronically activated cytokine-producing T cells in corticosteroid-resistant asthma; the association of disease severity with type 2 cytokines, especially IL-5; and the efficacy of cyclosporin A in chronic steroid-dependent disease. Inhibitors and/or antagonists directed against more precise T cell-associated molecular targets hold promise for the future treatment of chronic asthma.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"206 ","pages":"56-67; discussion 67-70, 106-10"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20198527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Health impacts of large releases of radionuclides. The fate and impact of radiocontaminants in urban areas. 放射性核素大量释放对健康的影响。放射性污染物在城市地区的命运和影响。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515006.ch8

J Roed, K G Andersson, C Lange

引用次数: 1

Health impacts of large releases of radionuclides. Cytogenetic effects as quantitative indicators of radiation exposure. 放射性核素大量释放对健康的影响。作为辐射照射定量指标的细胞遗传学效应。

Ciba Foundation symposium Pub Date : 1997-01-01

M Bauchinger

{"title":"Health impacts of large releases of radionuclides. Cytogenetic effects as quantitative indicators of radiation exposure.","authors":"M Bauchinger","doi":"","DOIUrl":"","url":null,"abstract":"Scoring of dicentrics in metaphase preparations of human T lymphocytes is the method of choice for estimating individual whole-body doses of radiation exposure. A quantification of partial-body exposures or non-uniform distribution of the dose is more complicated but it can be achieved by using specific mathematical approaches. For retrospective biodosimetry, conventional scoring of dicentrics is less precise because these unstable aberrations are eliminated with time post-exposure. Symmetrical translocations are not selected against during mitotic division in the haematopoietic cell reproductive centres, so the frequencies of these stable aberrations are generally assumed to remain constant even for decades. They can now be analysed precisely by fluorescence in situ hybridization using whole chromosome-specific DNA probes (chromosome painting) with an alpha-satellite DNA probe for centromere detection. Based on in vitro calibration curves established with single or multicolour paints covering 4-22% of the total human genomic DNA content, scoring of translocations has been applied for dose reconstruction in smaller groups of atomic bomb survivors and victims of the Chernobyl and Goiania radiation accidents. However, prior to routine use, the method requires further validation. Such work includes the precise evaluation of the unexpectedly high frequency of complex exchanges (> or = 3 breaks in > or = 2 chromosomes) found both at > 2 Gy doses of low linear energy transfer (LET) radiation and generally for high LET alpha-particles. Data on the long-term stability of translocations and the appearance of clonal abberrations, as well as improved measurements of the linear coefficient of standard calibration curves, are also required.","PeriodicalId":10218,"journal":{"name":"Ciba Foundation symposium","volume":"203 ","pages":"188-99; discussion 199-204, 232-4"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20272098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Evolutionary conflicts and adapted psychologies. 进化冲突和适应心理。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515372.ch4

A P Møller

引用次数: 0

Cross-species comparisons. 跨物种的比较。

Ciba Foundation symposium Pub Date : 1997-01-01 DOI: 10.1002/9780470515372.ch10

D F Sherry

引用次数: 29