RESUMEN
BACKGROUND: Brain function in schizophrenia has been probed using saccade paradigms and functional magnetic resonance imaging, but little information exists about how changing task context impacts saccade related brain activation and behavioral performance. We recruited schizophrenia and comparison subjects to perform saccade tasks in differing contexts: (1) two single task runs (anti- or pro-saccades alternating with fixation) and (2) one dual task run (antisaccades alternating with prosaccades). RESULTS: Context-dependent differences in saccade circuitry were evaluated using ROI analyses. Distinction between anti- and pro-saccade activation across contexts (single versus dual task) suggests that the schizophrenia group did not respond to context in the same way as the comparison group. CONCLUSIONS: Further investigation of context processing effects on brain activation and saccade performance measures informs models of cognitive deficits in the disorder and enhances understanding of antisaccades as a potential endophenotype for schizophrenia.
Asunto(s)
Encéfalo/fisiopatología , Esquizofrenia/fisiopatología , Adulto , Encéfalo/metabolismo , Mapeo Encefálico , Movimientos Oculares/fisiología , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Estimulación Luminosa , Tiempo de Reacción/fisiología , Movimientos Sacádicos/fisiología , Esquizofrenia/metabolismoRESUMEN
Children with low aerobic fitness have altered brain function compared to higher-fit children. This study examined the effect of an 8-month exercise intervention on resting state synchrony. Twenty-two sedentary, overweight (body mass index ≥85th percentile) children 8-11 years old were randomly assigned to one of two after-school programs: aerobic exercise (n=13) or sedentary attention control (n=9). Before and after the 8-month programs, all subjects participated in resting state functional magnetic resonance imaging scans. Independent components analysis identified several networks, with four chosen for between-group analysis: salience, default mode, cognitive control, and motor networks. The default mode, cognitive control, and motor networks showed more spatial refinement over time in the exercise group compared to controls. The motor network showed increased synchrony in the exercise group with the right medial frontal gyrus compared to controls. Exercise behavior may enhance brain development in children.
Asunto(s)
Encéfalo/fisiología , Terapia por Ejercicio/métodos , Sobrepeso/rehabilitación , Descanso , Análisis de Varianza , Atención/fisiología , Encéfalo/irrigación sanguínea , Niño , Cognición , Ejercicio Físico/fisiología , Femenino , Estudios de Seguimiento , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Pruebas Neuropsicológicas , OxígenoRESUMEN
Removal of radioactive cobalt at trace levels (approximately nM) in the presence of large excess (10(6)-fold) of corrosion product ions of complexed Fe, Cr, and Ni in spent chemical decontamination formulations (simulated effluent) of nuclear reactors is currently done by using synthetic organic ion exchangers. A large volume of solid waste is generated due to the nonspecific nature of ion sorption. Our earlier work using various fungi and bacteria, with the aim of nuclear waste volume reduction, realized up to 30% of Co removal with specific capacities calculated up to 1 microg/g in 6-24 h. In the present study using engineered Escherichia coli expressing NiCoT genes from Rhodopseudomonas palustris CGA009 (RP) and Novosphingobium aromaticivorans F-199 (NA), we report a significant increase in the specific capacity for Co removal (12 microg/g) in 1-h exposure to simulated effluent. About 85% of Co removal was achieved in a two-cycle treatment with the cloned bacteria. Expression of NiCoT genes in the E. coli knockout mutant of NiCoT efflux gene (rcnA) was more efficient as compared to expression in wild-type E. coli MC4100, JM109 and BL21 (DE3) hosts. The viability of the E. coli strains in the formulation as well as at different doses of gamma rays exposure and the effect of gamma dose on their cobalt removal capacity are determined. The potential application scheme of the above process of bioremediation of cobalt from nuclear power reactor chemical decontamination effluents is discussed.
Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas de Transporte de Catión/metabolismo , Radioisótopos de Cobalto/metabolismo , Descontaminación/métodos , Escherichia coli/metabolismo , Ingeniería Genética , Reactores Nucleares , Proteínas Bacterianas/genética , Biodegradación Ambiental , Proteínas de Transporte de Catión/genética , Escherichia coli/genética , Escherichia coli/efectos de la radiación , Rayos gamma , Expresión Génica , Residuos Radiactivos , Rhodopseudomonas/metabolismoRESUMEN
NikR proteins are bacterial metallo-regulatory transcription factors that control the expression of the nickel uptake system and/or nickel containing enzymes such as urease, and are involved in the acid stress response. Here, a comparative study is reported on NikR from Helicobacter pylori (HpNikR) and Escherichia coli (EcNikR), as well as the Q2E mutant of EcNikR. Most attention was focused on the Ni(II) binding properties of these proteins, as a function of pH. The influence of the pH on the Ni(II) binding and aggregation properties was studied using gel filtration analysis and UV-visible absorption spectroscopy in the presence of an increasing concentration of nickel. Q2E and wt EcNikR are identical in Ni(II) binding but the Q2E mutant is impaired to some extent in DNA-binding. For EcNikR it is shown that between pH 6 and 8, addition of Ni(II) above 1 equiv. induces mass aggregation and precipitation, concomitant with binding of Ni(II) up to a maximum of 5-8 Ni(II) ions per monomer. The Ni(II) site with highest affinity is the well-described square planar site with three histidines and one cysteine ligands. Aggregation is complete in the presence of less than 1 extra equiv. of Ni(II) and aggregation is fully reversible and precipitates are rapidly solubilized by addition of EDTA. The sensitivity of EcNikR to aggregation decreases with decreasing pH, concurrent with histidines being the main ligands of the site responsible for aggregation. HpNikR does not display aggregation except at alkaline pH, where 3 Ni(II) equiv. are needed. The participation of a cluster consisting of surface-exposed histidines present in EcNikR but not in HpNikR, is proposed to be involved in aggregation. Our results on HpNikR are compatible with the crystallographic data and with the ability of this protein to bind more than one nickel.
Asunto(s)
Proteínas de Escherichia coli/metabolismo , Helicobacter pylori/metabolismo , Níquel/metabolismo , Proteínas Represoras/metabolismo , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Cromatografía en Gel , Cartilla de ADN , Proteínas de Escherichia coli/genética , Concentración de Iones de Hidrógeno , Cinética , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Conformación Proteica , Proteínas Recombinantes/metabolismo , Proteínas Represoras/genéticaRESUMEN
Analysis of a Brucella suis 1330 gene fused to a gfp reporter, and identified as being induced in J774 murine macrophage-like cells, allowed the isolation of a gene homologous to nikA, the first gene of the Escherichia coli operon encoding the specific transport system for nickel. DNA sequence analysis of the corresponding B. suis nik locus showed that it was highly similar to that of E. coli except for localization of the nikR regulatory gene, which lies upstream from the structural nikABCDE genes and in the opposite orientation. Protein sequence comparisons suggested that the deduced nikABCDE gene products belong to a periplasmic binding protein-dependent transport system. The nikA promoter-gfp fusion was activated in vitro by low oxygen tension and metal ion deficiency and was repressed by NiCl(2) excess. Insertional inactivation of nikA strongly reduced the activity of the nickel metalloenzyme urease, which was restored by addition of a nickel excess. Moreover, the nikA mutant of B. suis was functionally complemented with the E. coli nik gene cluster, leading to the recovery of urease activity. Reciprocally, an E. coli strain harboring a deleted nik operon recovered hydrogenase activity by heterologous complementation with the B. suis nik locus. Taking into account these results, we propose that the nik locus of B. suis encodes a nickel transport system. The results further suggest that nickel could enter B. suis via other transport systems. Intracellular growth rates of the B. suis wild-type and nikA mutant strains in human monocytes were similar, indicating that nikA was not essential for this step of infection. We discuss a possible role of nickel transport in maintaining enzymatic activities which could be crucial for survival of the bacteria under the environmental conditions encountered within the host.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Proteínas Bacterianas/genética , Brucella/genética , Proteínas Portadoras/genética , Proteínas de Escherichia coli , Familia de Multigenes , Níquel/metabolismo , Proteínas Represoras/genética , Ureasa/metabolismo , Transporte Biológico , Brucella/enzimología , Clonación Molecular , Regulación Bacteriana de la Expresión Génica , Metaloproteínas/metabolismo , Datos de Secuencia Molecular , Mutagénesis Insercional , Periplasma/metabolismo , Regiones Promotoras Genéticas , Análisis de Secuencia de ADN , Homología de SecuenciaRESUMEN
Screening the Pseudomonas aeruginosa genome has led to the identification of the highest number of putative genes encoding two-component regulatory systems of all bacterial genomes sequenced to date (64 and 63 encoding response regulators and histidine kinases, respectively). Sixteen atypical kinases, among them 11 devoid of an Hpt domain, and three independent Hpt modules were retrieved. These data suggest that P. aeruginosa possesses complex control strategies with which to respond to environmental challenges.
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Proteínas Bacterianas/genética , Regulación Bacteriana de la Expresión Génica , Proteínas Quinasas/genética , Pseudomonas aeruginosa/genética , Transducción de Señal , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Genoma Bacteriano , Histidina Quinasa , Humanos , Datos de Secuencia Molecular , Proteínas Quinasas/metabolismo , Pseudomonas aeruginosa/fisiologíaRESUMEN
Periplasmic or membrane-bound bacterial hydrogenases are generally composed of a small subunit and a large subunit. The small subunit contains a peculiar N-terminal twin-arginine signal peptide, whereas the large subunit lacks any known targeting signal for export. Genetic and biochemistry data support the assumption that the large subunit is cotranslocated with the small subunit across the cytoplasmic membrane. Indeed, the signal peptide carried by the small subunit directs both the small and the large subunits to the recently identified Mtt/Tat pathway, independently of the Sec machinery. In addition, the twin-arginine signal peptide of hydrogenase is capable of directing protein import into the thylakoidal lumen of chloroplasts via the homologous deltapH-driven pathway, which is independent of the Sec machinery. Therefore, the translocation of hydrogenase shares characteristics with the deltapH-driven import pathway in terms of Sec-independence and requirement for the twin-arginine signal peptide, and with protein import into peroxisomes in a "piggyback" fashion.
Asunto(s)
Membrana Celular/enzimología , Escherichia coli/enzimología , Hidrogenasas/metabolismo , Escherichia coli/genética , Señales de Clasificación de Proteína , Transporte de ProteínasRESUMEN
Bacterial periplasmic nickel-containing hydrogenases are composed of a small subunit containing a twin-arginine signal sequence and a large subunit devoid of an export signal. To understand how the large subunit is translocated into the periplasm, we cloned the hyb operon encoding the hydrogenase 2 of Escherichia coli, constructed a deletion mutant, and studied the mechanism of translocation of hydrogenase 2. The small subunit (HybO) or the large subunit (HybC) accumulated in the cytoplasm as a precursor when either of them was expressed in the absence of the other subunit. Therefore, contrary to most classical secretory proteins, the signal sequence of the small subunit itself is not sufficient for membrane targeting and translocation if the large subunit is missing. On the other hand, the small subunit was required not only for membrane targeting of the large subunit, but also for the acquisition of nickel by the large subunit. Most interestingly, the signal sequence of the small subunit determines whether the large subunit follows the Sec or the twin-arginine translocation pathway. Taken together, these results provide for the first time compelling evidence for a naturally occurring hitchhiker co-translocation mechanism in bacteria.
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Escherichia coli/metabolismo , Productos del Gen tat/metabolismo , Hidrogenasas/metabolismo , Periplasma/enzimología , Transporte Biológico , Clonación Molecular , Dimerización , Escherichia coli/enzimología , Hidrogenasas/química , Hidrogenasas/genética , Mutagénesis , Operón , Señales de Clasificación de Proteína/metabolismoRESUMEN
We analyzed the involvement of chaperonins GroES and GroEL in the biosynthesis of the three hydrogenase isoenzymes, HYD1, HYD2, and HYD3, of Escherichia coli. These hydrogenases are NiFe-containing, membrane-bound enzymes composed of small and large subunits, each of which is proteolytically processed during biosynthesis. Total hydrogenase activity was found to be reduced by up to 60% in groES and groEL thermosensitive mutant strains. This effect was specific because it was not seen for another oligomeric, membrane-bound metalloenzyme, i.e., nitrate reductase. Analyses of the single hydrogenase isoenzymes revealed that a temperature shift during the growth of groE mutants led to an absence of HYD1 activity and to an accumulation of the precursor of the large subunit of HYD3, whereas only marginal effects on the processing of HYD2 and its activity were observed under these conditions. A decrease in total hydrogenase activity, together with accumulation of the precursors of the large subunits of HYD2 and HYD3, was also found to occur in a nickel uptake mutant (nik). The phenotype of this nik mutant was suppressed by supplementation of the growth medium with nickel ions. On the contrary, Ni2+ no longer restored hydrogenase activity and processing of the large subunit of HYD3 when the nik and groE mutations were combined in one strain. This finding suggests the involvement of these chaperonins in the biosynthesis of a functional HYD3 isoenzyme via the incorporation of nickel. In agreement with these in vivo results, we demonstrated a specific binding of GroEL to the precursor of the large subunit of HYD3 in vitro. Collectively, our results are consistent with chaperonin-dependent incorporation of nickel into the precursor of the large subunit of HYD3 as a prerequisite of its proteolytic processing and the acquisition of enzymatic activity.
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Chaperonina 10/metabolismo , Chaperonina 60/metabolismo , Escherichia coli/metabolismo , Hidrogenasas/biosíntesis , Isoenzimas/biosíntesis , Níquel/metabolismo , Secuencia de Aminoácidos , Anaerobiosis , Sitios de Unión , Chaperonina 10/genética , Chaperonina 60/genética , Precursores Enzimáticos/metabolismo , Escherichia coli/genética , Isoenzimas/genética , Datos de Secuencia Molecular , Mutación , Fenotipo , Unión Proteica , Procesamiento Proteico-PostraduccionalRESUMEN
The cellular location of membrane-bound NiFe-hydrogenase 2 (HYD2) from Escherichia coli was studied by immunoblot analysis and by activity staining. Treatment of spheroplasts with trypsin was able to release active HYD2 into the soluble fraction, indicating that HYD2 is attached to the periplasmic side of the cytoplasmic membrane and that HYD2 undergoes a trans-membrane translocation during its biosynthesis. By using a nik mutant deficient in the high affinity specific nickel transport system, we show that the intracellular availability of nickel is essential for the processing of the large subunit and for the transmembrane translocation of HYD2. We also demonstrate that the processing of the precursor, which is related with nickel incorporation, can occur in the membrane-depleted soluble fraction and that it is associated with the increase in resistance to proteolysis of the processed form of the large subunit. The mechanism of the transmembrane translocation of HYD2 is discussed.
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Escherichia coli/enzimología , Hidrogenasas/metabolismo , Níquel/metabolismo , Secuencia de Aminoácidos , Transporte Biológico , Membrana Celular/enzimología , Datos de Secuencia Molecular , Procesamiento Proteico-PostraduccionalRESUMEN
Intravenous administration sets continue to become more sophisticated in response to advances in medical therapy. A number of design options are available to meet specialized needs. It behooves the pharmacist to become familiar with them in order to insure that sets compatible with and optimal for their intended application are selected in his or her institution. Doing so will fully execute his or her increasing responsibilities in I.V. therapy.
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Infusiones Parenterales/instrumentaciónRESUMEN
The effect of temperature, pH, salinity and ultraviolet irradiation on the infectivity of Herpes Channel Catfish Virus (HCCV) has been determined. It has been shown that the pH and the culture medium is an important factor in maintaining virus infectivity. The temperatures higher than 4 degrees C rapidly inactivate the virus while this one can be grown successfully after several months of storage at -75 degrees C and at -20 degrees C. In common with other herpesviruses, HCCV is quickly inactivated by UV irradiation. The signification of these findings on the mode of viral infection and of viral harvesting, disinfection measures and marine farming of Ictalurids is important.
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Herpesviridae/fisiología , Animales , Peces , Herpesviridae/efectos de la radiación , Concentración de Iones de Hidrógeno , Concentración Osmolar , Temperatura , Rayos UltravioletaRESUMEN
The DNA of Channel Catfish virus (CCV) was selectively extracted from infected cells with a 5% solution of sodium deoxycholate, deproteinized using sodium sarcosinate and pronase, and purified by phenol extraction followed by equilibrium density gradient centrifugation in a cesium chloride solution. CCV DNA displays a buoyant density of 1.715 g/cm3 in such a solution, as would be expected from a duplex DNA containing 56.1% of guanine plus cytosine. As estimated from both its sedimentation coefficient and length in the electron microscope, CCV DNA is a linear duplex molecule of approximately 85 x 10(6) daltons.
Asunto(s)
ADN Viral/aislamiento & purificación , Herpesviridae/análisis , Animales , Células Cultivadas , Centrifugación Isopicnica , Peces/microbiología , Herpesviridae/crecimiento & desarrollo , Microscopía Electrónica , Peso MolecularRESUMEN
Channel Catfish virus was highly purified from host cells by precipitation with PEG-6000 and isopycnic centrifugation in a metrizamide gradient. As calculated from reconstruction experiments, only 0.09 and 0.05% respectively of the host DNA and the host proteins were recovered at the position of the viral band. The final recovery of infectivity was about 30%. Electron microscopy showed mostly intact viral particles.
Asunto(s)
Herpesviridae/aislamiento & purificación , Animales , Línea Celular , Centrifugación por Gradiente de Densidad/métodos , Peces , Herpesviridae/crecimiento & desarrollo , Herpesviridae/ultraestructura , MetrizamidaRESUMEN
32P-labeled Egtved virus RNA was released from highly purified virus by phenol-SDS extraction. The single-stranded nature of the RNA was demonstrated by (1) its buoyant density of 1.69 g/cm3 in Cs2-SO4, (2) its susceptibility to digestion by pancreatic ribonuclease in either 1 X SSC or 0.01 X SSC (standard saline citrate), (3) its base composition (29.3% C, 23.6% A, 14.5% U. 32.6% G). This Egtved virus is different from the other rhabdoviruses since the base composition of its genomic RNA is lower in its composition of A + U. Such a result could have possible taxonomic implications concerning the orignin and evolution of Egtved Virus relative to the other known rhabdoviruses.