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  • 1995-1999  (147)
  • 1965-1969  (23)
  • 1935-1939  (1)
  • 1
    ISSN: 1432-0983
    Keywords: Key words Mitochondrial DNA ; Mitochondrial transcription ; Heteroplasmy ; Drosophila subobscura
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eighty percent of DNA molecules are deleted in the mitochondrial population of an adult mutant strain of D. subobscura. Both intact and deleted genomes are autonomous monomers. The heteroplasmy level, which is lower in germ tissue, increases from the oocytes (60%) to the third larval instar (83%), and is then maintained throughout the life of the fly. The mtDNA/nuclear DNA ratio is on average two-times greater in the heteroplasmic strain than in the wild-type strain, irrespective of the stage, but the cellular content of mitochondria is elevated only in the embryos and pupae of the mutant strain. The steady state concentrations (SSCs) of the transcripts affected by the deletion are greatly reduced at the larval and adult stages, and less so at the pupal stage of the mutant strain compared with the wild-type. The SSCs of these transcripts are identical in the two strains at the embryonic stage. The fusion transcript, indicating that the deleted genome is expressed, was detected at all stages. The mechanisms involved in the changes in the heteroplasmy level during the course of development and in its maintenance from the third larval instar onwards are discussed.
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Omnipause neurons ; OPN ; Saccade ; Gaze shift ; Tracking ; Perisaccadic drifts ; Moving target ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Pontine omnipause neurons (OPNs) have so far been considered as forming a homogeneous group of neurons whose tonic firing stops during the duration of saccades, when the head is immobilized. In cats, they pause for the total duration of gaze shifts, when the head is free to move. In the present study, carried out on alert cats with fixed heads, we present observations made during self-initiated saccades and during tracking of a moving target which show that the OPN population is not homogeneous. Of the 76 OPNs we identified, 39 were found to have characteristics similar to those of previously described neurons, ”saccade” (S-) OPNs: (1) the durations of their pauses were significantly correlated with the durations of saccades; (2) the discharge ceased shortly before saccade onset and resumed before saccade end; (3) visual responses to target motion were excitatory; and (4) during tracking, S-OPNs interrupted the discharge for the duration of saccades and resumed firing during perisaccadic ”drifts”. However, the characteristics of 37 neurons (”complex” (C-) OPNs) were different: (1) the pause duration was not correlated with the duration of self-initiated saccades; (2) time lead of pause onsets relative to saccades was, on average, longer than in the group of S-OPNs, and firing resumed after the saccade end; (3) visual target motion suppressed tonic discharges; and (4) during tracking, firing was interrupted for the total duration of gaze shifts, including not only saccades but also perisaccadic ”drifts”. We conclude that cat OPNs can be subdivided into two main groups. The first comprises neurons whose firing patterns are compatible with gating individual saccades (”saccade” OPNs). The second group consists of ”complex” OPNs whose firing characteristics are appropriate to gate total gaze displacements rather than individual saccades. The function of these neurons may be to disinhibit pontobulbar circuits participating in the generation of saccade sequences and associated perisaccadic drifts.
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  • 3
    ISSN: 1432-1238
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 4
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of cadmium in different samples such as coal fly ashes, soils and sediments by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) was studied. The best analytical conditions and instrumental parameters were deduced. Different types of matrix modifiers were tested and an optimization of several conditions (pyrolysis and atomization temperatures, heating rate, use of L’vov platform, etc.) was carried out. A mixture of 2% NH4H2PO4 + 0.4% Mg(NO3)2 in 0.5 mol L–1 HNO3 as matrix modifier provided the highest sensitivity and an efficient behaviour for the three types of samples. A detection limit of 26 ng g–1 was achieved and other figures of merit are shown. Analytical results obtained by direct calibration using standard samples prepared in the laboratory and by standard addition method were comparable.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Usher syndrome (USH) is an autosomal-recessive disease characterized by neurosensory deafness and progressive retinitis pigmentosa. So far, three clinical types of Usher syndrome have been defined, and are caused by defects at more than eight loci. We report the linkage analysis of seven Lebanese families with Usher syndrome, two with type I (USH1) and five with type II (USH2). We demonstrate that one family is linked to the USH1C locus, a rare form of USH1 only reported in the French Acadian population. Linkage analysis of the five USH2 families with recently mapped loci allowed us to reduce the USH2A candidate region to a very small interval flanked by D1S2646/D1S2629 and D1S2827. Furthermore, haplotype comparison between the different families suggests a founder effect for the USH2A mutation among the different Lebanese ethnic groups, while a genetic heterogeneity is noted for Usher syndrome type I.
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  • 6
    ISSN: 1432-1068
    Keywords: Greffe ; Substitut osseux ; Graft ; Bone substitute
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs ont revu leurs arthroplasties it#x00E9;ratives de hanche avec utilisation d'allogreffes pour combler une perte de substance cotyloidienne stade II ou III. 51 dossiers ont pû être retenus (27 greffes lyophilis#x00E9;es et 24 cryo-conservées). Le recul moyen est de 4 ans. Le motif de réintervention a été 2 fois sur 4 un descellement aseptique bipolaire ; 14 % des descellements #x00E9;taient septiques. Dans 75 % des cas a été utilisé un anneau de soutien. 3 fois sur 4 les greffons ont été volumineux, vissés ou encastrés; une fois sur 4, il s'agissait de greffons de petite taille. L'étude clinique a été faite selon la classification de Merle d'Aubigné. L'étude radiologique est bas#x00E9;e sur les critères définis par Gross et par De Lee. Il n'y a aucune différence significative entre les greffes lyophilisées et les cryoconservées. Sur le plan clinique, 55 % des cas sont classés excellents, et 11 % mauvais ; le reste est classé moyen ou bon ; le résultat #x00E9;tant plus péjoré par la stabilité que par la douleur. Sur le plan radiologique, dans 53 % des cas existe une fusion entre le greffon et l'hôte mais dans 41 % des cas persiste un liseré partiel. 14 fois sur 20, nous avons noté la résorption partielle du greffon, dans la partie débordant la zone mécaniquement utile. Cinq dossiers sont des échecs radiologiques complets, dont 4 qui ont été repris rapidement pour sepsis, avec séquestration complète des greffons. Dans l'attente d'un bon substitut osseux, l'allogreffe cryo-conservée ou lyophilisée semble une bonne solution pour les pertes de substance importante du cotyle, dans la mesure où le montage est solide. L'infection est une mauvaise indication pour ce type de reprise. Cette technique nous amène dans plus de 8o % des cas, de bons et d'excellents résultats sur le plan clinique, bien que dans plus de 4 cas sur io, persiste sur le plan radiologique une non-intégration totale du greffon au délai de révision de ces dossiers.
    Notes: Summary 51 cases of repeat hip replacement have been reviewed, using allografts for acetabular bone loss, stages 2 and 3 (27 lyophilised and 24 deep-frozen). Mean follow-up was 4 years. Loosening was the reason for intervention; 14% of cases were septic. Massive grafts were used in 75% of cases and smaller grafts in 25% of cases. In addition a reinforcement ring was necessary in 75% of cases. Merle d'Aubigné's rating scale was used to assess results. The radiologic assessment score was that of Gross and De Lee. There was no difference between lyophilised and deep-frozen grafts. Clinical scores found 55% of excellent results; 11% were poor, the rest were good or fair. Stability was more troublesome than pain. Radiologic screening showed union between graft and host in 53% of cases but in 41% there was incomplete fusion. In the non-weight-bearing area bone lysis appeared in 14 cases out of 20. Five cases were complete failures; four of these were infected and were reoperated, the bone-graft acting as a foreign body. To date, we have no better bone replacement material than allografts. Fixation of the graft must be secure. An infected hip is not a good indication for this type of operation. Clinical results are satisfactory in more than 80% of cases, although 40% of grafts seem to be incompletely integrated.
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  • 7
    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.
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  • 8
    ISSN: 1432-1068
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Implants coated with hydroxyapatite (HA) are of very special importance in revisions of total hip prostheses. As far as the fernur is concerned, the rapid bony reconstruction due to the osteoconductive properties which ensure in particular the filling of defects of bony contact guarantee excellent secondary stabilization of the implants, provided that the mechanical assembly secured at operation be stable. The results of a personal series of 46 patients confirm the efficacity of the HA coating by demonstrating the quality of bony reconstruction and the long-term stability of the implants with satisfactory clinical results.
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  • 9
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The occurrence of more than two small accessory chromosomes (SACs) in a single individual is extremely rare. Here, we characterize six SACs found in the cells of two different tissues of a moderately mentally retarded male. Microdissection combined with regular FISH demonstrates that the SACs are ring chromosomes derived from the centromeres of different chromosomes. The SACs are often associated with the centromeres of other chromosomes. Immunofluorescence with an anti-CENP-C antibody demonstrates that the SACs contain an active centromere. A possible mechanism by which the SACs originated and their clinical relevance are discussed.
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  • 10
    ISSN: 1432-1084
    Keywords: Key words: Nasopharynx ; neoplasma ; Angiofibroma ; Angiofibroma ; postoperative ; CT ; MR imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this study was to assess the radiological findings after surgical removal of juvenile nasopharyngeal angiofibromas (JNA). The postoperative CT and MRI scans of ten patients were reviewed. The cured group included six patients. The non-controlled group included six patients with eight recurrences. Two patients belonged to both groups as they were also followed and cured after surgery for relapse. Four recurrences were asymptomatic and diagnosed by imaging. The imaging patterns were matched to the patients clinical status and endoscopic findings. In the cured group, non-enhanced residual soft tissue masses were seen in all cases. In the non-controlled group, recurrence was always demonstrated on early postoperative CT or MR as a dramatically enhanced mass. The recurrence was located in the lateral or superior aspect of the nasopharynx (n = 3), deep to the fossa of Rosenmuller (n = 4) or out of the nasopharynx (n = 1). In two cases a remaining enhanced mass disappeared spontaneously on iterated examinations. Because of numerous asymptomatic relapses, a radiological workup is recommended four months after surgery, even in patients with normal endoscopy, to rule out posterolateral or extranasopharyngeal recurrences. Spontaneous evolution of residual masses must be appreciated on iterated imaging examinations.
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