Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 11 de 11
Filtrar
1.
Adv Exp Med Biol ; 801: 575-81, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24664746

RESUMO

The duration of cell death may allow deducing the underlying degenerative mechanism. To find out how long a photoreceptor takes to die, we used the rd1 mouse model for retinal neurodegeneration, which is characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cGMP levels. Based on cellular data on the progression of cGMP accumulation, cell death, and survival, we created a mathematical model to simulate the temporal development of the degeneration and the clearance of dead cells. Both cellular data and modelling suggested that at the level of the individual cell, the degenerative process was rather slow, taking around 80 h to complete. Organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast, confirmed the surprisingly long duration of an individual photoreceptor cell's death. We briefly discuss the possibility to link different cell death stages and their temporal progression to specific enzymatic activities known to be causally connected to cell death. This in turn opens up new perspectives for the treatment of inherited retinal degeneration, both in terms of therapeutic targets and temporal windows-of-opportunity.


Assuntos
Apoptose/fisiologia , Células Fotorreceptoras de Vertebrados/patologia , Degeneração Retiniana/patologia , Animais , GMP Cíclico/metabolismo , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Canais de Cátion Regulados por Nucleotídeos Cíclicos/metabolismo , Modelos Animais de Doenças , Histona Desacetilases/metabolismo , Camundongos , Camundongos Endogâmicos C3H , Necrose/metabolismo , Células Fotorreceptoras de Vertebrados/metabolismo , Poli(ADP-Ribose) Polimerase-1 , Poli(ADP-Ribose) Polimerases/metabolismo , Degeneração Retiniana/metabolismo
2.
J Biotechnol ; 121(3): 410-7, 2006 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-16125265

RESUMO

In industrial fed-batch cultivations it is often necessary to control substrate concentrations at a low level to prevent the production of overflow metabolites and thus optimize the biomass yield. A new method for on-line monitoring and fed-batch control based on fluorescence measurements has been developed. Via instantaneous in situ measurements and multivariate data analysis a chemometric model has been established, which enables the rapid detection of ethanol production at aerobic Saccharomyces cerevisiae fed-batch cultivations. The glucose feed rate is controlled by predicting the metabolic state directly from the fluorescence intensities. Thus, ethanol production could be avoided completely while increasing the biomass yield accordingly. The robust instrumentation is suitable for industrial applications.


Assuntos
Reatores Biológicos/microbiologia , Microbiologia Industrial/métodos , Saccharomyces cerevisiae/metabolismo , Espectrometria de Fluorescência , Aerobiose , Biomassa , Dióxido de Carbono/metabolismo , Técnicas de Cultura de Células , Etanol/metabolismo , Retroalimentação , Fermentação , Glucose/metabolismo , Cinética , Modelos Lineares , Sistemas On-Line , Oxirredução , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Sensibilidade e Especificidade
3.
J Biotechnol ; 20(1): 95-104, 1991 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-1367539

RESUMO

A flow injection analysis (FIA) system was developed for the determination of cytoplasmic beta-galactosidase activity in recombinant Escherichia coli. The FIA system and its application for on-line monitoring of beta-galactosidase production during cultivation of recombinant E. coli in a 60-l airlift tower loop reactor is described. The results demonstrate that an FIA assay in conjunction with a cell disintegration step can be applied successfully for on-line monitoring of intracellular protein formation.


Assuntos
Escherichia coli/enzimologia , beta-Galactosidase/análise , Colorimetria , Recombinação Genética
4.
Enzyme Microb Technol ; 13(7): 554-64, 1991 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-1367639

RESUMO

E. coli K12 with multicopy plasmid (lambda PR-promoter and temperature-sensitive lambda cI 857 repressor) was cultivated in 60-l bubble column and airlift tower loop reactors. The medium composition, cell concentration, and intracellulary enzyme activity were monitored on-line during batch, fed-batch, and continuous cultivations. The specific growth rates, cell mass yield coefficients, plasmid stabilities, productivities of the amount of active fusion protein (beta-galactosidase activity), concentrations and yields of acetic acid, and volumetric oxygen transfer coefficient were evaluated for different medium compositions and cultivation conditions. The enzyme activity was also monitored during the temperature induction. The results evaluated in the 60-l bubble column and airlift tower loop reactors are compared with those evaluated in a 1-1 stirred-tank reactor.


Assuntos
Proteínas de Bactérias/biossíntese , Técnicas Bacteriológicas/instrumentação , Clonagem Molecular/métodos , Escherichia coli/genética , Engenharia Genética/instrumentação , Proteínas Recombinantes de Fusão/biossíntese , beta-Galactosidase/biossíntese , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Meios de Cultura/farmacologia , Indução Enzimática , Desenho de Equipamento , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Vetores Genéticos , Glicerol/metabolismo , Oxigênio/metabolismo , Desnaturação Proteica , Proteínas Recombinantes de Fusão/isolamento & purificação , Temperatura , beta-Galactosidase/genética , beta-Galactosidase/isolamento & purificação
5.
Cell Death Dis ; 4: e488, 2013 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-23392176

RESUMO

For most neurodegenerative diseases the precise duration of an individual cell's death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.


Assuntos
Apoptose/efeitos dos fármacos , Neurônios/metabolismo , Inibidores de Fosfodiesterase/farmacologia , Purinonas/farmacologia , Animais , Células Cultivadas , GMP Cíclico/metabolismo , Nucleotídeo Cíclico Fosfodiesterase do Tipo 6/antagonistas & inibidores , Nucleotídeo Cíclico Fosfodiesterase do Tipo 6/genética , Nucleotídeo Cíclico Fosfodiesterase do Tipo 6/metabolismo , Camundongos , Modelos Biológicos , Mutação , Neurônios/patologia , Células Fotorreceptoras de Vertebrados/citologia , Células Fotorreceptoras de Vertebrados/efeitos dos fármacos , Células Fotorreceptoras de Vertebrados/metabolismo , Retina/citologia , Retina/metabolismo , Retinose Pigmentar/metabolismo , Retinose Pigmentar/patologia
8.
Biotechnol Bioeng ; 39(1): 33-43, 1992 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-18600884

RESUMO

For the control of bioprocesses, a priori knowledge exists which cannot be readily incorporated as a mathematical model but which can be represented by language-based rules, such as "IF/THEN" conditions. This knowledge is usually implemented via a process operator for the automation of the fermentation. A knowledge-based system has been developed which can use this kind of knowledge and which is complemented by algorithmic systems, such as statistical analyses and mathematical modeling, for the supervision and control of a bioprocess. In this article, a description of this system is presented. Furthermore, the following features of the system are discussed in detail which are especially important for the development of real-time, on-line, knowledge-based systems: the representation of time-dependent knowledge; processing of imprecise, uncertain, and incomplete knowledge; the combination of shallow reasoning with model-based reasoning; informing the bioprocess operator about the inferences and decisions; the demands of the diversity of the knowledge handling; performance; and maintenance and extension of the system.

9.
Adv Biochem Eng Biotechnol ; 74: 21-38, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-11991181

RESUMO

Optical sensors appear to be very promising for different applications in modern biotechnology. They offer the possibility to interface all the well known optical analysis techniques to bioprocesses via fiber optical cables. Thus, high sophisticated and sensitive optical analysis techniques can be coupled to a bioprocess via these light signal transporting fibers. A wide variety of sensor types for application in biotechnology has been described. Normally these sensors are non-invasive and the response times are nearly instantaneous. In particular, the use of glass fiber technology makes these sensors small, robust and reduces their costs.


Assuntos
Corantes Fluorescentes/química , Espectrometria de Fluorescência/métodos , Biomassa , Técnicas Biossensoriais
10.
Appl Microbiol Biotechnol ; 61(5-6): 456-62, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12764560

RESUMO

The extracellular production of Escherichia coli phytase was studied in fed-batch fermentations. Two different feeding strategies were compared: control by keeping the glucose concentration constant, and control by keeping a low constant oxygen level in the medium. For the feeding control based on glucose concentration, a recently developed rapid glucose controlling system was tested for the first time in bacterial cultivations and used to establish the fermentative production of extracellular phytase with E. coli. High activity levels (120 U ml(-1)) at short cultivation times (14 h) were obtained. Even higher activity levels - albeit at longer cultivation times - were reached by applying a feeding control, the main characteristic of which was a constant low oxygen concentration. The optimum oxygen level for the production of phytase was in the range of 5-10% saturation.


Assuntos
6-Fitase/biossíntese , Escherichia coli/enzimologia , 6-Fitase/genética , Reatores Biológicos , Meios de Cultura , Escherichia coli/genética , Fermentação , Expressão Gênica , Genes Bacterianos , Glucose/metabolismo , Cinética , Oxigênio/metabolismo
11.
Bioinformatics ; 19(2): 173-7, 2003 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-12538236

RESUMO

MOTIVATION: 2D fluorescence spectra provide information from intracellular compounds. Fluorophores like trytophan, tyrosine and phenylalanin as well as NADH and flavins make the corresponding measurement systems very important for bioprocess supervision and control. The evaluation is usually based on chemometric modelling using for their calibration procedure off-line measurements of the desired process variables. Due to the data driven approach lots of off-line measurements are required. Here a methodology is presented, which enables to perform a calibration procedure of chemometric models without any further measurement. RESULTS: The necessary information for the calibration procedure is provided by means of the a priori knowledge about the process, i.e. a mathematical model, whose model parameters are estimated during the calibration procedure, as well as the fact that the substrate should be consumed at the end of the process run. The new methodology for chemometric calibration is applied for a batch cultivation of aerobically grown S. cerevisiae on the glucose Schatzmann medium. As will be presented the chemometric models, which are determined by this method, can be used for prediction during new process runs. AVAILABILITY: The MATHLAB routine is free available on request from the authors.


Assuntos
Algoritmos , Calibragem , Saccharomyces cerevisiae/fisiologia , Espectrometria de Fluorescência/instrumentação , Espectrometria de Fluorescência/métodos , Simulação por Computador , Etanol/química , Etanol/metabolismo , Glucose/química , Glucose/metabolismo , Modelos Biológicos , Modelos Químicos , Controle de Qualidade , Reprodutibilidade dos Testes , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/metabolismo , Sensibilidade e Especificidade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA