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  • Life and Medical Sciences  (5)
  • Organic Chemistry  (4)
  • Hydroxyapatite  (3)
  • 1
    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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1068
    Keywords: Hydroxyapatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hydroxyapatite (HA), which constitutes 65% of the mineral component of human bone, is a crystalline structure whose synthesis was achieved at the beginning of the century. The development of the technology of coating metals with a ceramic material stimulated extensive research throughout the world leading to the use of implants coated with HA in maxillofacial surgery. The application to ostearticular implants was preceded by rigorous and prolonged experimentation, which demonstrated that implants of titanium coated with HA were devoid of risk and made it possible to secure excellent bony fixation. With a follow-up well in excess of 10 years the published results are evidence of considerable improvement and confirm that articular implants coated with HA represent a major advance. However, HA is only involved in bony fixation and cannot compensate for inadequate design of the implants as regards their shape or surface state.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0897-3806
    Keywords: myocardium ; transcoronary ablation ; anterior interventricular artery ; Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The aim of this study is to determine the anatomical explanation for the greater or lesser vulnerabilities of the left ventricular segments in the event of occlusion of each of the main coronary arteries. To this end, we analyzed the arterial perfusion of 1,080 left ventricular segments from 90 human hearts obtained at autopsy. Post-mortem angiography, dissection, and constriction of an arterial map using the classification of Selvester et al. (1982) were applied. By careful monitoring of the arterial perfusion of each segment we conclude that (1) obstruction of the anterior interventricular artery (AIV) especially affects the superomesial, superoapical, and anteroapical segments; (2) obstruction of the circumflex artery (CX) especially affects the posterobasal and posteromesial segments; and (3) obstruction of the right coronary artery (RC) especially affects the inferobasal and inferomesial segments. Vulnerability of the myocardially segments decreases in those segments which have collateral supply, i.e., those which are only relatively dependent upon a particular coronary artery. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2161
    Keywords: Key words Osteosclerotic lesion ; Calcification ; Hydroxyapatite ; Humerus ; Disappearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report on the spontaneous disappearance of a dense round lesion from within the greater tuberosity of the humerus. The patient was treated with oral non-steroidal anti-inflammatory agents for symptoms of subacromial bursitis. Symptoms resolved in 10 days and the lesion had vanished when radiographed 3 months later. We surmise the lesion to represent intraosseous crystal deposition.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0730-2312
    Keywords: monoclonal antibody DWP ; activated ras protein reactive antibody ; anti-ras antibodies ; anti-ras monoclonal antibody ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Activated ras transforming genes have been described in a variety of neoplasms and encode 21,000-Dalton (p21) proteins with amino acid substitutions at positions 12, 13, and 61. In this report we describe a monoclonal antibody designated DWP that reacts. Specifically with synthetic dodecapeptides containing valine at position 12, to a lesser extent with peptides containing cysteine at position 12 and not with peptides containing glycine, arginine, serine, aspartic acid, glutamic acid or alanine at the same position. Western blot and immunoperoxidase studies showed that DWP specifically reacts with activated rasH or rasK proteins in NIH cells transformed by DNA from the human carcinoma cells that encode valine at position 12. DWP did not react with normal p21s encoding glycine at position 12, nor with activated p21s encoding aspartic acid, glutamic acid, arginine, serine, or cysteine at position 12. A survey of human tumor cell lines demonstrated that DWP reacted with the human bladder carcinoma cell line T24 but not with human tumor cell lines previously shown td contain other activating mutations at positions 12 or 61. DWP and perhaps additional antibodies that specifically react with alterations at positions 12 or 61 of the ras protein may be valuable in determining the presence and frequency of activated ras proteins in human malignancy.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Development of ciliated (CC) in the fetal human trachea was studied by light and electron microscopy in specimens obtained from 45 embryos or fetuses aged from 9 to 27 weeks of gestation (menstrual age). Four stages could be recognized during tracheal development. Up to 11 weeks (stage I), the trachea was covered with a columnar undifferentiated epithelium with abundant glycogen, apical microvilli, and primary cilia. From 12 to 18-19 weeks (stage II), centriolo-genesis and secondary ciliogenesis were very active, and the percentage of CC and secretory cells (SC) progressively increased. From 20 to 22-23 weeks, the density of CC was higher but, in parallel, the percentage of SC decreased (stage III). Throughout this period, the different steps of ciliogenesis could be identified in the same field, and the ciliated borders consisted of ciliary shafts with a disorderly arrangement. Megacilia were identified. Some of the preciliated cells had both cilia and secretory granules in their apical cytoplasm. After 24 weeks (stage IV), the ciliated border was apparently mature, the rootlets lengthened, and the cilia were correctly orientated. Whatever the fetal age, the density of CC was significantly higher (P 〈 .01) in the dorsal trachea compared to the ventral trachea. There are many similarities between animal and human ciliogenesis, but in human fetuses, most of the ciliary differentiation occurs early, during the first half of gestation. As demonstrated in experimental models, SC likely play a major role in genesis of CC during the fetal development of the human trachea.
    Additional Material: 12 Ill.
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  • 7
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A study of the isthmus and ligament in unionid mussels was undertaken employing methods specifically designed to preserve the in vivo relationships of these interrelated structures. Serial sections of the hard and soft tissues were used for two-dimensional analysis. From these, a tridimensional computerized reconstruction was developed. Special dissections of the undisturbed isthmus were also utilized. By using such methodologies, a new description of the ligament has been developed employing such terminology as the foliated ligament and the posterior folding laminae. Similarly, for the isthmus, an anterior lyre, a pallial crest, a pallial peduncle, and a posterior lyre are described. Such entities are both morphologically and physiologically related to the shell and ligament.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0749-503X
    Keywords: Heterologous gene expression ; levansucrase precursor ; Bacillus subtilis ; yeast ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Levansucrase, a Bacillus subtilis extracellular enzyme, was not secreted in the culture medium when produced in yeast. The protein accumulated inside the cell in its precursor form which represented 0·3% of total proteins. The absence of any post-translational modifications, such as signal sequence cleavage or addition of N-linked sugars, indicated that this protein did not enter the reticulum secretion pathway.Direct observation of the cells by confocal laser scanning microscopy showed that levansucrase was associated with the cytoplasmic membrane. Subcellular fractionation experiments revealed that levansucrase precursor form is associated with membranes through weak ionic interactions. The purified precursor displayed the same catalytic properties as levansucrase secreted by B. subtilis. Thus yeast could be used as a source of levansucrase precursor allowing its isolation as a pure form on a milligram scale.
    Additional Material: 8 Ill.
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  • 9
    ISSN: 0899-0042
    Keywords: solvent ; basic medium ; competitive solubilities ; optimization ; optical resolution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several preparative resolutions of 5,5-disubstituted hydantoins have been achieved via fractional crystallization of diastereoisomeric salts. The process can be extended by making use of the difference between the variation of solubilities of the hydantoins and their salts with α-methylbenzylamine as a function of the alkalinity of the medium. Optimization for each resolution procedure involves a refinement of the excess amount of base needed. © 1992 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Phenyldiazomethane with 1,3-Thiazole-5(4H)-thiones: Base-Catalyzed Ring Opening of the Primary AdductReaction of 1,3-thiazole-5(4H)-thiones 1 and phenyldiazomethane (2a) in toluene at room temperature yields the thiiranes trans- and cis-1,4-dithia-6-azaspiro[2.4]hept-5-enes (trans- and cis-4; Scheme 2). With Ph3P in THF at 70°, these thiiranes are transformed stereospecifically into (E)- and (Z)-5-benzylidene-4,5-dihydro-1,3-thiazoles 5, respectively. In the presence of DBU, 1 and 2a react to give 1,3,4-thiadiazole derivatives 6 or 7 via base-catalyzed ring opening of the primary cycloadduct (Scheme 3). In the case of 2-(alkylthio)-substituted 1,3-thiazole-5(4H)-thiones 1c and 1d, this ring opening proceeds by elimination of the corresponding alkylthiolate, yielding isothiocyanate 7. The structures of (Z)-5c and 6b have been established by X-ray crystallography.
    Additional Material: 1 Ill.
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