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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Studies of the equilibrium between native and denatured forms of wild-type levansucrase showed that the denatured form was predominant at 37°C and pH 7 in the absence of free metal. The shift to the native form was promoted by metal ions such as Fe3+ or Ca2+. This metal-dependent refolding process was not observed in levansucrase variants bearing the amino acid substitution Gly-366→Asp or Gly-366→Val. These variants were only slightly secreted by Bacillus subtilis although their signal sequences were normally cleaved and their exocellular forms stable. In contrast, the Gly-366→Ser variant was secreted at near-normal levels and shared a part of the in vitro refolding properties of the wild-type protein. These differential properties might be related to the ability of the altered region to form a β-turn structure.We discuss the possible role of metal ions in the coupling of protein folding and secretion.
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  • 2
    ISSN: 1432-1041
    Keywords: Dextromethorphan ; ELISA ; polymorphism ; population study ; French Caucasians
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Simple, sensitive and selective enzyme immunoassays (ELISA) for monitoring urinary dextromethorphan and its major metabolite, dextrorphan, were developed. Dextromethorphan and dextrorphan hemisuccinates were linked to bovine serum albumin and specific antisera against each immunogen were raised in rabbits. The sensitivity of the ELISA was high (limit of detection 740 and 600 pg·ml−1 for dextromethorphan and dextrorphan, respectively). Intra- and interassay variation was 〈10%, and cross-reactivity between the two compounds was 〈1%. The ELISA was employed to phenotype 216 French subjects. The frequency of poor metabolizers was 5.1%.
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  • 3
    ISSN: 1432-1041
    Keywords: Carbamazepine ; Saliva ; Mania ; Carbamazepine epoxide ; drug concentration ; Concentration-response relationship ; therapeutic monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The study was designed to investigate the antimanic profile of carbamazepine as a first-line drug in affective or schizoaffective disorders, to correlate the clinical efficacy with the plasma level of carbamazepine and its 10,11-epoxide metabolite, and to test the potential value of monitoring the salivary level. It was administered alone for 3 weeks to 21 acute manic inpatients. During the first week, the dosage was rapidly increased to 800 mg/day in order to produce steady-state plasma levels of carbamazepine on Day 7. The individual dose was then adjusted to maintain the therapeutic range of 8–12 mg/l. Plasma and saliva levels of the drug and its metabolite, as well as clinical status were assessed weekly. Overall, there was 62% globally improved patients and 77% in affective disorders. The improvement of manic symptoms was significantly lower in schizoaffective than in affective disorders, whereas the dropout rate and the need for antipsychotic medication was higher in the former group. The antimanic response was significantly correlated with the plasma levels both of carbamazepine and its epoxide metabolite, with a time-lag consistent with a delayed drug effect. Drug and metabolite concentrations in saliva were close to their plasma free fraction and were strongly correlated with their plasma levels, suggesting the potential value of salivary drug monitoring.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1432-1068
    Keywords: Cementless ; Hip prosthesis ; Hydroxyapatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Careful analysis of total hip arthroplasty failures including data from biomechanical studies of normal and prosthetic hips, and histological investigation, leads to the conclusion that femoral stem failure is mainly due to inadequate transfer of load from the implant to cortical bone. The long term success of femoral stem implantation requires stable fixation. Primary stability relies on the shape and contour of the implant, - secondary stability relies on the area and type of the surface allowing bony ingrowth into the prosthesis without fibrous interposition and allowing the development of early bony trabecular bridging between implant and cortex. Long term stability is related to the mechanical properties of the metal and shape of the implant allowing optimal transfer of loads between bone and implant. The PRA femoral stem fulfils these requirements: its large proximal part fills the upper femur, avoiding distal migration by its shape and providing excellent resistance to rotational and torsional forces due to its trapezoidal cross-section. Longitudinal grooves and Hydroxyapatite coating of this large surface area allows rapid bony ingrowth. The progressive tapering of the distal part which is not coated, decreases its mechanical influence, so that most of the load transfer occurs at the proximal half of the stem. The excellent clinical and radiological results of the 76 implants performed between October 1988 and January 1992 support the theoretical advantages.
    Notes: Résumé Les échecs des implants fémoraux relèvent en très grande majorité de causes mécaniques. La conception de l'implant fémoral PRA exploite l'analyse des échecs observés et publiés, les études biomécaniques, les données histologiques pour satisfaire aux trois impératifs de la stabilité: Stabilité Primaire liée à la forme et aux reliefs de l'implant, Stabilité Secondaire liée à l'état et à l'étendue de sa surface, Stabilité Définitive, garantie par le transfert harmonieux des contraintes entre la tige prothétique et l'os. Implant en alliage de titane (Ti6Al4V), réalisant un bon remplissage et une surface développée maximale de contact os-implant dans la région métaphysaire, la tige PRA est progressivement réduite dans sa portion diaphysaire. Le revêtement de la portion métaphysaire la plus significative sur le plan mécanique par l'hydroxyapatite de calcium entraîne sa fixation rapide par adaptation osseuse sans interposition fibreuse, et le développement précoce d'un pontage trabéculaire osseux entre l'implant et la corticale. La qualité des résultats cliniques et radiologiques obtenus au cours des trois premières années d'implantation confirme le bien-fondé des principes biomécaniques et biologiques retenus dans sa conception.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a four-generation family, chondrodysplasia punctata was found in a boy and one of his maternal uncles. These two patients also have short stature, as do all female members of the family. DNA molecular analysis of the pseudoautosomal and Xp22.3-specific loci revealed the presence of an interstitial deletion that cosegregates with the phenotypic abnormalities. The proximal breakpoint of this deletion was located distal to the DXS31 locus and the distal breakpoint in the pseudoautosomal region between DXYS59 and DXYS17. This maps the recessive X-linked form of chondrodysplasia punctata between the proximal boundary of the pseudoautosomal region and DXS31, and an Xp gene controlling growth between DXYS59 and DXS31.
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  • 6
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A case of X-linked recessive chondrodysplasia punctata (CP) is described. The finding of a reciprocal X-Y translocation involving the region distal to Xp22.3 and the presence of fluorescent Yp11.23 regions confirms the localization of X-linked recessive CP at p22.3. No gross peroxisomal abnormalities were present in the propositus.
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Type XI collagen was localized with polyclonal antibodies specific for α1(XI) and α2(XI) chains in the resting zone of epiphyseal cartilage from calf fetuses. The immunofluorescence technique was used on sections of cartilage, and the immunogold labelling technique for electron microscopy on fibrils isolated from cartilage and, for the fist time, in situ on blocks of cartilage fractured in liquid nitrogen. Immunofluorescence showed that without pepsin treatment the staining of type XI collagen was restricted to the pericellular zones; after pepsin treatment, the staining was co-distributed with that of type II collagen. Immunoelectron microscopy performed on isolated fibrils and on cartilage blocks showed that after disruption of fibrils with pepsin, type XI collagen was labelled on small filaments on the fibrils. When the fibrils were not disrupted, labelling was observed in situ only at the ends of the fibrils or on cross-sections of some fibrils. These results indicate that type XI collagen is located inside type II collagen fibrils in fetal bovine epiphyseal cartilage, as already postulated for embryonic chicken sterna.
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  • 8
    ISSN: 1432-1068
    Keywords: Hydroxyapatite de calcium ; Prothèse totale de genou ; Stabilisation des implants prothétiques ; Calcium hydroxyapatite coating ; Total knee arthroplasty ; Bone implant stabilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Calcium hydroxyapatite produced by chemical industry is very similar to the mineral structure of bone. Calcium hydroxyapatite implants in bone show a rapid bone ingrowth, without fibrous tissue interposition, provided that the implant be stable. Advanced plasma spraying techniques provide strong bonding of hydroxyapatite to titanium, and allowed the development of successful hip prostheses. Histological studies of retrieved hydroxyapatite coated stems show that the formation of new bone starts ten days after operation, and that thereafter osseous trabeculae develop, and by physiological remodelling the periimplant bone shows dynamic adaptation to its functional requirements. Knee prostheses, though submitted to different forces, would presumably benefit from the early dynamic bone adaptation.
    Notes: Résumé La synthèse chimique de l'hydroxyapatite de calcium donne un cristal de composition très voisine de l'hydroxyapatite naturelle, trame minérale de toute structure osseuse. La poudre ainsi obtenue est fixée par le procédé de la torche à plasma sur les implants en titane, en particulier, avec une excellente stabilité compatible avec l'utilisation clinique. Ce revêtement ostéo-conducteur accélère remarquablement la reconstruction osseuse au contact du métal et entraîne une stabilisation rapide des implants, démontrée par l'étude histologique des prothèses explantées post-mortem. La qualité des résultats obtenus par les prothèses de hanches revêtues d'hydroxyapatite de calcium avec un recul significatif justifie d'exploiter ces propriétés dans l'arthroplastie du genou, dans l'espoir de remplacer le matériel bio-inerte qu'est le ciment acrylique par un matériel bio-actif efficace.
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  • 9
    ISSN: 1432-1068
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1432-1068
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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