RESUMO
Our research group has been investigating the effect of cyclic deformations on the evolution of fibroblast populated collagen gels (FPCG). Since existing traction machines are not designed for such an application, we had to design a cyclic traction machine adapted to tissue culture inside an incubator over an extended period of time. Biocompatible materials were used for fabrication to allow for easy sterilization and to prevent any adverse reaction from the tissue. The traction machine is based on a computer-controlled stepping motor system for easy adjustment of the deformation amplitude and frequency. The maximum stretching speed achieved is around 1 mm/s. The traction machine can measure FPCG mechanical properties and perform rupture tests to determine its ultimate strength. Several FPCGs have been successfully cultured with the machine for up to four weeks without any adverse reaction.
Assuntos
Técnicas de Cultura de Células/instrumentação , Colágeno , Fibroblastos/citologia , Materiais Biocompatíveis , Géis , Fatores de TempoRESUMO
The crystal structure of the tetrameric enzyme, fumarase C from Escherichia coli, has been determined to a resolution of 2.0 A. A tungstate derivative used in the X-ray analysis is a competitive inhibitor and places the active site of fumarase in a region which includes atoms from three of the four subunits. The polypeptide conformation is similar to that of delta-crystallin and is comprised of three domains. The central domain, D2, is a unique five-helix bundle. The association of the D2 domains results in a tetramer which has a core of 20 alpha-helices. The other two domains, D1 and D3, cap the helical bundle on opposite ends giving both the single subunit and the tetramer a dumbbell-like appearance. Fumarase C has sequence homology to the eukaryotic fumarases, aspartase, arginosuccinate lyase, adenylosuccinate lyase and delta-crystallin.
Assuntos
Escherichia coli/enzimologia , Fumarato Hidratase/química , Estrutura Secundária de Proteína , Adenilossuccinato Liase/química , Sequência de Aminoácidos , Argininossuccinato Liase/química , Aspartato Amônia-Liase/química , Sequência de Bases , Sítios de Ligação , Simulação por Computador , Cristalinas/química , Cristalografia por Raios X , Primers do DNA , Escherichia coli/genética , Fumarato Hidratase/metabolismo , Genes Bacterianos , Cinética , Substâncias Macromoleculares , Modelos Moleculares , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Homologia de Sequência de AminoácidosRESUMO
Between 16 July and 1 October 1984, prospectively monitored corridor air samples from a bone marrow transplant station revealed a marked increase in airborne thermotolerant Penicillium spores. Simultaneous cultures of outside air showed lower spore counts, which were unchanged before, during, and after the corridor outburst, establishing that the source was within the hospital. Although the corridor was equipped with recirculating high-efficiency particulate air filtration units which provided 16 air changes per h, the mean corridor air count rose to 64.4 thermotolerant Penicillium CFU/m3 during the outburst period. The in-hospital source was ultimately traced to rotting cabinet wood enclosing a sink with leaking pipes in the medication room. It produced approximately 5.5 X 10(5) thermotolerant Penicillium CFU/h. In a patient room supplied by corridor air, an in-room recirculating high-efficiency particulate air filter reduced the mean thermotolerant Penicillium count to 2.2 CFU/m3. No patient illness or colonization occurred as a result of this event, although the cabinet wood, after sterilization, was shown to sustain abundant growth of Aspergillus fumigatus and Aspergillus flavus. Wet organic substrates should be avoided in hospital areas with immunosuppressed patients.
