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  • 1
    ISSN: 1432-0630
    Keywords: 61.10 ; 68.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Single crystals of iodine-intercalated C60 have been examined by transmission electron microscopy. Tilting series of Electron Diffraction Patterns (EDP) confirm that it has a simple hexagonal structure with c/a≈1 in accordance with the results of X-ray diffraction, which allows higher precision c/a=1.0024. Cooling and heating experiments were performed in the vacuum of the microscope to investigate the order — disorder phenomena. High-Resolution Electron Microscopy (HREM) images and electron diffraction patterns reveal that the c/2-displacement along the c-direction plays an important role in the transition from the simple hexagonal structure into the fcc structure when iodine is lost from the specimen or “vice versa”. The orientation relationship between the intercalate and the C60 structure is [01 $$\overline {\text{1}}$$ 10]h∥[1 $$\overline {\text{1}}$$ 10]fcc and (001)h∥(110)fcc. A model is proposed to interpret the features observed in EDP and HREM consistently.
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  • 2
    ISSN: 1432-0738
    Keywords: Aluminum ; Toxicokinetics ; Rat ; Parenterals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The toxicokinetics of aluminum (Al) in male Wistar rats was studied after single intragastric (IG) doses of 1000 and 12000 μg Al/kg and intravenous (IV) doses of 10, 100, 1000, and 12000 μg Al/kg. Serial blood samples, daily samples of urine and feces as well as brain, liver, kidney, spleen, quadriceps muscle, and femur samples were collected. Al was measured by atomic absorption spectrometry. Al blood profiles after IV doses were adequately described by a two-compartment open model. Al toxicokinetics was dose dependent and appeared to plateau at 12000 μg/kg. At IV doses between 10 and 1000 μg/kg the terminal half-life of elimination from whole blood (t1/2β) increased from 29.9±7.8 to 209.3±32.6 min, and the total body clearance (CL) decreased from 2.45±0.64 to 0.28±0.03 ml min−1 kg−1. Following an IV bolus of 10 and 100 μg/kg the administered Al was recovered completely from urine (94.4%±9.9% and 98.5%±3.2%). Twenty-nine days after the IV dose of 1000 μg/kg daily renal excretion decreased to baseline values while only 55.1%±8.0% of the dose was excreted. Nineteen days after the single IV dose of 1000 μg/kg Al accumulated in liver (28.1±7.7 versus 1.7±0.5 μg/g of control rats) and spleen (72.5±21.1 versus 〈0.4 μg/g). After the single 1000 μg/kg IG dose no absorption of Al was detectable. The IG dose of 12000 μg/kg resulted in a maximum blood Al level of 47.9±12.4 μg/l after 50 min. The blood concentration time curve fitted a one-compartment open model with a half-life of absorption of 28.2±3.6 min and a t1/2β of 81.2±20.2 min. Cumulative renal Al excretion was 0.18%±0.10% of the dose and oral bioavailability was 0.02%. Seventeen days after the 12000 μg/kg IG dose the Al content in femur samples was increased (2.7±1.3 versus 0.6±0.4 μg/g). In no case was fecal elimination of incorporated Al observed.
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  • 3
    ISSN: 1432-1106
    Keywords: Electrophysiology ; Medulla oblongata ; Spinal cord ; Interneurons ; Respiratory control ; Intracellular labelling ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Upper cervical inspiratory neurons form a distinct neuronal column located near the lateral edge of the intermediate grey matter in the rostral spinal segments. Previous studies conducted in cats have demonstrated synaptic inputs to these neurons from several respiratory related regions of the medulla, and long descending axonal projections mainly towards the motoneurons supplying the intercostal muscles. The aim of this study was to examine the electrophysiological and morphological properties of this propriospinal system in the rat. Extracellular recordings were made from 127 cervical inspiratory units, mainly in the C1 and C2 segments. Eighty-two percent could be antidromically activated from the C7/C8 border. No evidence of monosynaptic connection was obtained by cross-correlating the activity of some of these units with the discharge of the phrenic nerve. Intracellular recordings were made from seven neurons, three of which were labelled with biotinamide (neurobiotin). Long “survival times” after intracellular injections (up to 23 h) resulted in staining of axons for long distances, at least to the C5 segment. Each of the three labelled axons issued only one short collateral which arborized in the region of the phrenic nucleus. These results demonstrate that upper cervical inspiratory neurons in the rat have features similar to those previously described in the cat, including only a limited projection to the phrenic nucleus. In addition, this study provides the first morphological identification of these neurons.
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  • 4
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wird über Ergebnisse einer numerischen Studie berichtet, welche die Ermittlung des Gleichgewichtszustandes bei Konvektion von Wasser in Gegenwart von Eis in einem geneigten, rechteckigen, mit porösem Medium befüllten Behälter zum Ziele hatte. Eine Seite des Behälters wird über Schmelztemperatur, die andere darunter gehalten, während die übrigen zwei Seiten wärmedicht sind. Die Auswertung der Resultate erfolgt hinsichtlich des Dichteinversionsparameters, des Neigungswinkels und der Kühlplattentemperatur. Unterhalb einer Heiztemperatur von 25°C wird der Gleichgewichtszustand des Eis/Wasser-Systems entscheidend durch das Phänomen der Dichteanomalie beeinflußt. In einem Vertikalbehälter verursacht letztere die Ausbildung von zwei gegensinnig drehenden Walzen, was zu einer Verbreiterung der Wasserzone am Boden gegenüber der im oberen Bereich führt. Bei geneigtem Behälter existieren zwei Lösungszweige, welche die Boden-bzw. die Seitenheizungscharakteristik repräsentieren (Bénard- und Seitenheizungszweig). Aufgrund der Dichteinversion kann die Lösung auf dem Bénardzweig bei kleinen Neigungswinkeln oszillatorisches Verhalten anstatt Konvergenz liefern. Auf dem anderen Zweig ergibt sich bei 70° Neigungswinkel ein Maximum des Wärmestroms. Das Volumen der Wasserzone zeigt nur schwache Abhängigkeit vom Neigungswinkel. Bei Berücksichtigung des Unterkühlungseffektes führt die Wechselwirkung zwischen Leitung in der festen und Konvektion in der flüssigen Phase zu einer Gleichgewichtsstruktur der Eis/Wasser-Grenzfläche, welche bei einigen intermediären Kühlungsplattentemperaturen äußerst starke Unregelmäßigkeiten aufweist.
    Notes: Abstract This paper reports on the results of a numerical study on the equilibrium state of the convection of water in the presence of ice in an inclined rectangular cavity filled with a porous medium. One side of the cavity is maintained at a temperature higher than the fusion temperature while the opposite side is cooled to a temperature lower than the fusion temperature. The two remaining sides are insulated. Results are analysed in terms of the density inversion parameter, the tilt angle, and the cooling temperature. It appears that the phenomenon of density inversion plays an important role in the equilibrium of an ice-water system when the heating temperature is below 20°. In a vertical cavity, the density inversion causes the formation of two counterrotating vortices leading to a water volume which is wider at the bottom than at the top. When the cavity is inclined, there exist two branches of solutions which exhibit the bottom heating and the side heating characteristics, respectively (the Bénard and side heating branches). Due to the inversion of density, the solution on the Bénard branch may fail to converge to a steady state at small tilt angles and exhibits an oscillating behavior. On the side heating branch, a maximum heat transfer rate is obtained at a tilt angle of about 70° but the water volume was found to depend very weakly on the inclination of the cavity. Under the effect of subcooling, the interplay between conduction in the solid phase and convection in the liquid leads to an equilibrium ice-water interface which is most distorted at some intermediate cooling temperature.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A polymorphic BamHI site was located in the coding region of the human T cell receptor delta gene TCRDV2. Two alleles defined by the absence or the presence of the BamHI site were detected by the polymerase chain reaction.
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  • 6
    ISSN: 1432-1106
    Keywords: Plasticity ; Enkephalin ; Vasoactive intestinal polypeptide ; Somatostatin ; Neuropeptide tyrosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The extent to which the plasticity in peptide expression observed in developing spinal motoneurons occurs following proximal peripheral axotomy in the adult rat was examined using in situ hybridization and immunohistochemical techniques to visualize the changes. Transient upregulation of galanin, vasoactive intestinal polypeptide (VIP) and substance P messenger ribonucleic acids (mRNAs) was observed within subpopulations of motoneurons ipsilateral to lesion for periods lasting 2–3 weeks after injury. In contrast, the axotomy-induced heterogenous increases in somatostatin and neuropeptide tyrosine mRNA expression in ipsilateral motoneurons remained elevated, or, in the case of somatostatin, continued to increase for the time period studied (1 month). Immunohistochemical analysis agreed with the in situ hybridization results, showing some motoneurons within the injured ventral horn to contain galanin-, VIP-or somatostatin-like immunoreactivity. In some instances, galanin-immunoreactive motoneurons colocalized with calcitonin gene-related peptide immunoreactivity. Most of the neurons expressing the injury-induced peptides appeared large, presumably alpha-motoneurons, but there were also many small neurons expressing galanin in the ventral horn ipsilateral to lesion. This may represent evidence for peptide synthesis in gamma-motoneurons. The only peptide mRNA studied to be downregulated in response to axotomy was enkephalin. The results show that peptide expression in injured motoneurons is dramatically altered, the significance of which remains to be determined.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The human T-cell receptor gamma gene region spans 160 kb genomic DNA. Restriction fragment length polymorphisms (RFLPs) have been previously documented for the constant region (TRGC) genes, the joining (TRGJ) segments and the variable (TRGV) genes. We have recently defined the alleles of the T-cell receptor gamma V, J and C genes and we have described seven haplotypes of the V gamma subgroup I genes characterized either by RFLPs or by deletion or insertion of V gamma genes. The number of VγI genes may vary from 7 to 10 per haploid genome, the 9-gene haplotype being the most frequent. Allelic fragments can unambiguously characterize the TRGC2 gene with duplication or triplication of the exon 2. These alleles and haplotypes have been analyzed in four different populations (French, Lebanese, Tunisian and Black African). In this paper, we compare these allele and haplotype frequencies with those found in a Chinese population and we describe new TRGV allelic restriction fragments found only in the Chinese samples. These results and the previous data demonstrate the flexibility of the human T cell receptor gamma locus and the importance of unequal crossing-overs in the evolution of that locus. Moreover, they underline the importance of studying these polymorphisms in population genetics.
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  • 8
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A rare HindIII restriction fragment variant of the human T cell receptor gamma joining segment TRGJ1 has been identified, in addition to two previously described alleles.
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  • 9
    ISSN: 1432-1246
    Keywords: Toluene ; Xylene ; Human blood lymphocytes ; Cytogenetic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was undertaken to investigate, both in vitro and in vivo, the genotoxic potential of short-term low-level exposure to toluene, xylene, and their mixture, for which information is limited at the present time. Five adult healthy white men were exposed for 7 consecutive hours per day over 3 consecutive days to 50 ppm toluene and 40 ppm xylene either alone or in combination in a controlled exposure chamber. Such an exposure was repeated three times at intervals of 2 weeks. Blood samples were taken before and after the termination of such exposure. Three different cytogenetic end-points were evaluated using peripheral blood lymphocytes: number of sister chromatid exchanges (SCEs), cell cycle delay, and cell mortality. No significant effects on SCEs, cell cycle delay, and cell mortality were observed following such exposure to toluene or xylene or their mixture. Similarly, exposure of human blood lymphocytes in vitro to either toluene (0–2.5 mM) or xylene (0–2 mM) or their mixture for 72 h did not result in any significant cytogenetic effects at lower concentrations, while at higher concentrations, only cell mortality was found to be significantly affected. Thus our present study indicates that simultaneous exposure to low levels (within the admissible limits) of toluene, xylene, or their mixture for a short period does not pose any potential mutagenic threat to humans.
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  • 10
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The nucleotide sequence of the S gene of the bovine respiratory coronavirus (BRCV) strain G95, which was isolated from nasal swabs of a calf suffering from respiratory disorders, was determined and compared with the S gene of the enteropathogenic bovine coronavirus (BECV) strain LY138. Sequence analysis revealed 98.7% nucleotide and 98.3% deduced amino acid identities between the S genes of BRCV-G95 and BECV-LY138 without any deletions or insertions. Nucleotide substitutions were distributed randomly throughout the gene. Five monoclonal antibodies specific for the S protein distinguished BRCV-G95 from BECV-L9, but failed to differentiate it from BECV-LY138 in Western blots under denatured and native conditions. BRCV-G95 induced cytopathic changes in cell cultures that were similar to BECV-LY138 but different from BECV-L9. These results suggest that strain BRCV-G95 is more closely related to the virulent strain BECV-LY138 than to the avirulent, cell culture-adapted strain BECV-L9.
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