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1.
Postgrad Med J ; 99(1168): 56-62, 2023 Mar 31.
Artículo en Inglés | MEDLINE | ID: mdl-36828395

RESUMEN

PURPOSE: This work aims to describe patients hospitalized in internal medicine wards in terms of nutrition and sarcopenia. It also seeks to evaluate short- and long-term mortality related to malnutrition and sarcopenia. METHODS: This cross-sectional study collected data on consecutive patients admitted to a single center's internal medicine ward. Patients were recruited in May and October 2021. Malnutrition was determined by the Mini-Nutritional Assessment-Short Form (MNA-SF) and sarcopenia by the Strength, Assistance in walking, Rise from a chair, Climb stairs, and Falls questionnaire (SARC-F scale) and handgrip strength test. Patients who were hospitalized for >48 hours were excluded. RESULTS: The sample included 619 patients with a mean ± SD age of 76.0 ± 14.8 years of which 50.6% were women. Patients were classified into three groups based on malnutrition: group 1 (MNA-SF 12-14 points) (no risk) included 158 patients, group 2 (MNA-SF 8-12 points) (high risk) included 233 patients, and group 3 (MNA-SF 0-7 points) (malnourished) included 228 patients. Malnourished patients had more dysphagia, significantly lower protein and albumin levels, and significantly higher inflammatory marker levels and pressure ulcers. In-hospital mortality was significantly higher in groups 2 and 3 (p < .00001). The worst outcome (mortality and readmissions or mortality) was more common among malnourished patients (p = .0001). Inflammation, comorbidity, and sarcopenia were most closely associated with negative outcomes. CONCLUSION: Malnutrition upon admission is associated with worse short- and long-term outcomes in internal medicine inpatients. Sarcopenia, multimorbidity, and inflammation-measured by albumin, C-reactive protein, or their ratios-are key risk factors. Early identification of malnutrition and sarcopenia through active screening is important in caring for internal medicine patients.


Asunto(s)
Desnutrición , Sarcopenia , Humanos , Femenino , Persona de Mediana Edad , Anciano , Anciano de 80 o más Años , Masculino , Sarcopenia/epidemiología , Pacientes Internos , Fuerza de la Mano , Estudios Transversales , Desnutrición/epidemiología , Desnutrición/diagnóstico , Estado Nutricional , Evaluación Nutricional , Proteína C-Reactiva , Inflamación , Evaluación Geriátrica
2.
Nucleic Acids Res ; 48(14): 7991-8005, 2020 08 20.
Artículo en Inglés | MEDLINE | ID: mdl-32621607

RESUMEN

DNA2 is an essential enzyme involved in DNA replication and repair in eukaryotes. In a search for homologues of this protein, we identified and characterised Geobacillus stearothermophilus Bad, a bacterial DNA helicase-nuclease with similarity to human DNA2. We show that Bad contains an Fe-S cluster and identify four cysteine residues that are likely to co-ordinate the cluster by analogy to DNA2. The purified enzyme specifically recognises ss-dsDNA junctions and possesses ssDNA-dependent ATPase, ssDNA binding, ssDNA endonuclease, 5' to 3' ssDNA translocase and 5' to 3' helicase activity. Single molecule analysis reveals that Bad is a processive DNA motor capable of moving along DNA for distances of >4 kb at a rate of ∼200 bp per second at room temperature. Interestingly, as reported for the homologous human and yeast DNA2 proteins, the DNA unwinding activity of Bad is cryptic and can be unmasked by inactivating the intrinsic nuclease activity. Strikingly, our experiments show that the enzyme loops DNA while translocating, which is an emerging feature of processive DNA unwinding enzymes. The bacterial Bad enzymes will provide an excellent model system for understanding the biochemical properties of DNA2-like helicase-nucleases and DNA looping motor proteins in general.


Asunto(s)
Proteínas Bacterianas/metabolismo , ADN Helicasas/metabolismo , ADN de Cadena Simple/metabolismo , Desoxirribonucleasa I/metabolismo , Geobacillus stearothermophilus/enzimología , Adenosina Trifosfatasas/química , Adenosina Trifosfatasas/aislamiento & purificación , Adenosina Trifosfatasas/metabolismo , Adenosina Trifosfato/metabolismo , Proteínas Bacterianas/química , Proteínas Bacterianas/aislamiento & purificación , ADN , ADN Helicasas/química , ADN Helicasas/aislamiento & purificación , Desoxirribonucleasa I/química , Desoxirribonucleasa I/aislamiento & purificación
3.
Nucleic Acids Res ; 48(4): 2013-2025, 2020 02 28.
Artículo en Inglés | MEDLINE | ID: mdl-31930301

RESUMEN

The rolling-circle replication is the most common mechanism for the replication of small plasmids carrying antibiotic resistance genes in Gram-positive bacteria. It is initiated by the binding and nicking of double-stranded origin of replication by a replication initiator protein (Rep). Duplex unwinding is then performed by the PcrA helicase, whose processivity is critically promoted by its interaction with Rep. How Rep and PcrA proteins interact to nick and unwind the duplex is not fully understood. Here, we have used magnetic tweezers to monitor PcrA helicase unwinding and its relationship with the nicking activity of Staphylococcus aureus plasmid pT181 initiator RepC. Our results indicate that PcrA is a highly processive helicase prone to stochastic pausing, resulting in average translocation rates of 30 bp s-1, while a typical velocity of 50 bp s-1 is found in the absence of pausing. Single-strand DNA binding protein did not affect PcrA translocation velocity but slightly increased its processivity. Analysis of the degree of DNA supercoiling required for RepC nicking, and the time between RepC nicking and DNA unwinding, suggests that RepC and PcrA form a protein complex on the DNA binding site before nicking. A comprehensive model that rationalizes these findings is presented.


Asunto(s)
Proteínas Bacterianas/genética , ADN Helicasas/genética , Replicación del ADN/genética , Farmacorresistencia Bacteriana/genética , Roturas del ADN de Cadena Simple/efectos de los fármacos , Proteínas de Unión al ADN/genética , Geobacillus stearothermophilus/efectos de los fármacos , Geobacillus stearothermophilus/genética , Geobacillus stearothermophilus/patogenicidad , Plásmidos/efectos de los fármacos , Plásmidos/genética , Unión Proteica/genética , Dominios y Motivos de Interacción de Proteínas/genética , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidad , Tetraciclina/farmacología , Transactivadores/genética
4.
Nucleic Acids Res ; 46(11): 5704-5716, 2018 06 20.
Artículo en Inglés | MEDLINE | ID: mdl-29762781

RESUMEN

In prokaryotes, the centromere is a specialized segment of DNA that promotes the assembly of the segrosome upon binding of the Centromere Binding Protein (CBP). The segrosome structure exposes a specific surface for the interaction of the CBP with the motor protein that mediates DNA movement during cell division. Additionally, the CBP usually controls the transcriptional regulation of the segregation system as a cell cycle checkpoint. Correct segrosome functioning is therefore indispensable for accurate DNA segregation. Here, we combine biochemical reconstruction and structural and biophysical analysis to bring light to the architecture of the segrosome complex in Type III partition systems. We present the particular features of the centromere site, tubC, of the model system encoded in Clostridium botulinum prophage c-st. We find that the split centromere site contains two different iterons involved in the binding and spreading of the CBP, TubR. The resulting nucleoprotein complex consists of a novel double-ring structure that covers part of the predicted promoter. Single molecule data provides a mechanism for the formation of the segrosome structure based on DNA bending and unwinding upon TubR binding.


Asunto(s)
Centrómero/química , Centrómero/ultraestructura , Proteínas de Unión al ADN/metabolismo , Sitios de Unión , Centrómero/metabolismo , Clostridium botulinum/genética , ADN Bacteriano/química , Operón , Regiones Promotoras Genéticas , Profagos/genética
5.
Exp Parasitol ; 200: 42-47, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-30922888

RESUMEN

In order to develop a method of identification and discrimination of Echinococcus granulosus sensu stricto from faecal samples of dogs infected with taeniid eggs (Echinococcus spp., Taenia spp.), a combined strategy of Polymerase Chain Reaction (PCR) and Restriction Fragments of Lenght Polymorphisms (RFLP) was proposed. Initially, a pair of primers was designed to amplify a fragment of the 12 Subunit of ribosomal RNA gene (12SrRNA) from mitochondrial DNA. The amplified product was digested by SspI restriction enzyme, which in E. granulosus kept the intact fragment of 160 basis pairs (bp), while in Taenia spp. produced two fragments (62 bp and another of 98 bp). The method was tested using positive controls of DNA, in faecal samples experimentally contaminated with eggs of E. granulosus and Taenia spp. and in dogs naturally infected. In all of them, reproducible results were obtained and the primers were specific to amplify only Taeniidae DNA. The sensitivity of the technique was tested, achieving amplification of DNA extractions with a single egg. In conclusion, the technique developed was optimal and easy to identify patent infections by E. granulosus s.s., constituting a possible alternative for epidemiological studies in dogs, especially in endemic areas where this infection occurs.


Asunto(s)
Enfermedades de los Perros/parasitología , Equinococosis/veterinaria , Echinococcus granulosus/aislamiento & purificación , Heces/parasitología , Taenia/aislamiento & purificación , Teniasis/veterinaria , Animales , Secuencia de Bases , Secuencia de Consenso , ADN de Helmintos/química , Perros , Equinococosis/parasitología , Echinococcus granulosus/genética , Reacción en Cadena de la Polimerasa/veterinaria , Polimorfismo de Longitud del Fragmento de Restricción , Sensibilidad y Especificidad , Alineación de Secuencia/veterinaria , Taenia/genética , Teniasis/parasitología
6.
Nucleic Acids Res ; 44(6): 2727-41, 2016 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-26762979

RESUMEN

In bacteria, the repair of double-stranded DNA breaks is modulated by Chi sequences. These are recognised by helicase-nuclease complexes that process DNA ends for homologous recombination. Chi activates recombination by changing the biochemical properties of the helicase-nuclease, transforming it from a destructive exonuclease into a recombination-promoting repair enzyme. This transition is thought to be controlled by the Chi-dependent opening of a molecular latch, which enables part of the DNA substrate to evade degradation beyond Chi. Here, we show that disruption of the latch improves Chi recognition efficiency and stabilizes the interaction of AddAB with Chi, even in mutants that are impaired for Chi binding. Chi recognition elicits a structural change in AddAB that maps to a region of AddB which resembles a helicase domain, and which harbours both the Chi recognition locus and the latch. Mutation of the latch potentiates the change and moderately reduces the duration of a translocation pause at Chi. However, this mutant displays properties of Chi-modified AddAB even in the complete absence of bona fide hotspot sequences. The results are used to develop a model for AddAB regulation in which allosteric communication between Chi binding and latch opening ensures quality control during recombination hotspot recognition.


Asunto(s)
Bacillus subtilis/enzimología , Proteínas Bacterianas/química , ADN Helicasas/química , ADN Bacteriano/química , Exodesoxirribonucleasas/química , Reparación del ADN por Recombinación , Bacillus subtilis/genética , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Roturas del ADN de Doble Cadena , ADN Helicasas/genética , ADN Helicasas/metabolismo , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Exodesoxirribonucleasas/genética , Exodesoxirribonucleasas/metabolismo , Expresión Génica , Modelos Moleculares , Mutación , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína
7.
Nucleic Acids Res ; 44(18): 8885-8896, 2016 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-27488190

RESUMEN

Many bacterial plasmids replicate by an asymmetric rolling-circle mechanism that requires sequence-specific recognition for initiation, nicking of one of the template DNA strands and unwinding of the duplex prior to subsequent leading strand DNA synthesis. Nicking is performed by a replication-initiation protein (Rep) that directly binds to the plasmid double-stranded origin and remains covalently bound to its substrate 5'-end via a phosphotyrosine linkage. It has been proposed that the inverted DNA sequences at the nick site form a cruciform structure that facilitates DNA cleavage. However, the role of Rep proteins in the formation of this cruciform and the implication for its nicking and religation functions is unclear. Here, we have used magnetic tweezers to directly measure the DNA nicking and religation activities of RepC, the replication initiator protein of plasmid pT181, in plasmid sized and torsionally-constrained linear DNA molecules. Nicking by RepC occurred only in negatively supercoiled DNA and was force- and twist-dependent. Comparison with a type IB topoisomerase in similar experiments highlighted a relatively inefficient religation activity of RepC. Based on the structural modeling of RepC and on our experimental evidence, we propose a model where RepC nicking activity is passive and dependent upon the supercoiling degree of the DNA substrate.


Asunto(s)
Roturas del ADN de Cadena Simple , ADN Helicasas/metabolismo , Replicación del ADN , Transactivadores/metabolismo , ADN Helicasas/química , Modelos Biológicos , Plásmidos/genética , Unión Proteica , Multimerización de Proteína , Proteínas Recombinantes , Transactivadores/química
8.
J Biol Phys ; 44(2): 225-235, 2018 06.
Artículo en Inglés | MEDLINE | ID: mdl-29654426

RESUMEN

We use the nano-dissection capabilities of atomic force microscopy to induce structural alterations on individual virus capsids in liquid milieu. We fracture the protein shells either with single nanoindentations or by increasing the tip-sample interaction force in amplitude modulation dynamic mode. The normal behavior is that these cracks persist in time. However, in very rare occasions they self-recuperate to retrieve apparently unaltered virus particles. In this work, we show the topographical evolution of three of these exceptional events occurring in T7 bacteriophage capsids. Our data show that single nanoindentation produces a local recoverable fracture that corresponds to the deepening of a capsomer. In contrast, imaging in dynamic mode induced cracks that separate the virus morphological subunits. In both cases, the breakage patterns follow intratrimeric loci.


Asunto(s)
Bacteriófago T7/metabolismo , Microscopía de Fuerza Atómica , Bacteriófago T7/fisiología , Fenómenos Biomecánicos , Cápside/química , Cápside/metabolismo , Factores de Tiempo , Virión/química , Virión/metabolismo
9.
Proc Natl Acad Sci U S A ; 110(28): E2562-71, 2013 Jul 09.
Artículo en Inglés | MEDLINE | ID: mdl-23798400

RESUMEN

Double-stranded DNA break repair by homologous recombination is initiated by resection of free DNA ends to produce a 3'-ssDNA overhang. In bacteria, this reaction is catalyzed by helicase-nuclease complexes such as AddAB in a manner regulated by specific recombination hotspot sequences called Crossover hotspot instigator (Chi). We have used magnetic tweezers to investigate the dynamics of AddAB translocation and hotspot scanning during double-stranded DNA break resection. AddAB was prone to stochastic pausing due to transient recognition of Chi-like sequences, unveiling an antagonistic relationship between DNA translocation and sequence-specific DNA recognition. Pauses at bona fide Chi sequences were longer, were nonexponentially distributed, and resulted in an altered velocity upon restart of translocation downstream of Chi. We propose a model for the recognition of Chi sequences to explain the origin of pausing during failed and successful hotspot recognition.


Asunto(s)
Daño del ADN , ADN/genética , Recombinación Genética
10.
Small ; 11(11): 1273-84, 2015 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-25400244

RESUMEN

Motor protein functions like adenosine triphosphate (ATP) hydrolysis or translocation along molecular substrates take place at nanometric scales and consequently depend on the amount of available thermal energy. The associated rates can hence be investigated by actively varying the temperature conditions. In this article, a thermally controlled magnetic tweezers (MT) system for single-molecule experiments at up to 40 °C is presented. Its compact thermostat module yields a precision of 0.1 °C and can in principle be tailored to any other surface-coupled microscopy technique, such as tethered particle motion (TPM), nanopore-based sensing of biomolecules, or super-resolution fluorescence imaging. The instrument is used to examine the temperature dependence of translocation along double-stranded (ds)DNA by individual copies of the protein complex AddAB, a helicase-nuclease motor involved in dsDNA break repair. Despite moderately lower mean velocities measured at sub-saturating ATP concentrations, almost identical estimates of the enzymatic reaction barrier (around 21-24 k(B)T) are obtained by comparing results from MT and stopped-flow bulk assays. Single-molecule rates approach ensemble values at optimized chemical energy conditions near the motor, which can withstand opposing loads of up to 14 piconewtons (pN). Having proven its reliability, the temperature-controlled MT described herein will eventually represent a routinely applied method within the toolbox for nano-biotechnology.


Asunto(s)
ADN Helicasas/química , ADN/química , Magnetismo/instrumentación , Micromanipulación/instrumentación , Microscopía/instrumentación , Técnicas de Sonda Molecular/instrumentación , ADN/ultraestructura , ADN Helicasas/ultraestructura , Diseño de Equipo , Análisis de Falla de Equipo , Calefacción/instrumentación , Unión Proteica , Estrés Mecánico , Temperatura
11.
Proc Natl Acad Sci U S A ; 109(30): 12028-33, 2012 Jul 24.
Artículo en Inglés | MEDLINE | ID: mdl-22797893

RESUMEN

In this study we test the hypothesis that mechanically elastic regions in a virus particle (or large biomolecular complex) must coincide with conformationally dynamic regions, because both properties are intrinsically correlated. Hypothesis-derived predictions were subjected to verification by using 19 variants of the minute virus of mice capsid. The structural modifications in these variants reduced, preserved, or restored the conformational dynamism of regions surrounding capsid pores that are involved in molecular translocation events required for virus infectivity. The mechanical elasticity of the modified capsids was analyzed by atomic force microscopy, and the results corroborated every prediction tested: Any mutation (or chemical cross-linking) that impaired a conformational rearrangement of the pore regions increased their mechanical stiffness. On the contrary, any mutation that preserved the dynamics of the pore regions also preserved their elasticity. Moreover, any pseudo-reversion that restored the dynamics of the pore regions (lost through previous mutation) also restored their elasticity. Finally, no correlation was observed between dynamics of the pore regions and mechanical elasticity of other capsid regions. This study (i) corroborates the hypothesis that local mechanical elasticity and conformational dynamics in a viral particle are intrinsically correlated; (ii) proposes that determination by atomic force microscopy of local mechanical elasticity, combined with mutational analysis, may be used to identify and study conformationally dynamic regions in virus particles and large biomolecular complexes; (iii) supports a connection between mechanical properties and biological function in a virus; (iv) shows that viral capsids can be greatly stiffened by protein engineering for nanotechnological applications.


Asunto(s)
Proteínas de la Cápside/química , Elasticidad , Virus Diminuto del Ratón , Modelos Moleculares , Conformación Proteica , Virión/química , Proteínas de la Cápside/ultraestructura , Microscopía de Fuerza Atómica , Microscopía de Sonda de Barrido , Mutagénesis Sitio-Dirigida , Nanotecnología/métodos , Plásmidos/genética , Ingeniería de Proteínas/métodos , Espectrometría de Fluorescencia , Termodinámica , Virión/ultraestructura
12.
J Am Chem Soc ; 135(1): 122-31, 2013 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-23214411

RESUMEN

Double-stranded (ds) RNA is the genetic material of a variety of viruses and has been recently recognized as a relevant molecule in cells for its regulatory role. Despite that the elastic response of dsDNA has been thoroughly characterized in recent years in single-molecule stretching experiments, an equivalent study with dsRNA is still lacking. Here, we have engineered long dsRNA molecules for their individual characterization contrasting information with dsDNA molecules of the same sequence. It is known that dsRNA is an A-form molecule unlike dsDNA, which exhibits B-form in physiological conditions. These structural types are distinguished at the single-molecule level with atomic force microscopy (AFM) and are the basis to understand their different elastic response. Force-extension curves of dsRNA with optical and magnetic tweezers manifest two main regimes of elasticity, an entropic regime whose end is marked by the A-form contour-length and an intrinsic regime that ends in a low-cooperative overstretching transition in which the molecule extends to 1.7 times its A-form contour-length. DsRNA does not switch between the A and B conformations in the presence of force. Finally, dsRNA presents both a lower stretch modulus and overstretching transition force than dsDNA, whereas the electrostatic and intrinsic contributions to the persistence length are larger.


Asunto(s)
ADN/química , ARN/química , Microscopía de Fuerza Atómica
13.
Brain ; 134(Pt 1): 119-36, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-20929960

RESUMEN

Endocannabinoids act as neuromodulatory and neuroprotective cues by engaging type 1 cannabinoid receptors. These receptors are highly abundant in the basal ganglia and play a pivotal role in the control of motor behaviour. An early downregulation of type 1 cannabinoid receptors has been documented in the basal ganglia of patients with Huntington's disease and animal models. However, the pathophysiological impact of this loss of receptors in Huntington's disease is as yet unknown. Here, we generated a double-mutant mouse model that expresses human mutant huntingtin exon 1 in a type 1 cannabinoid receptor-null background, and found that receptor deletion aggravates the symptoms, neuropathology and molecular pathology of the disease. Moreover, pharmacological administration of the cannabinoid Δ(9)-tetrahydrocannabinol to mice expressing human mutant huntingtin exon 1 exerted a therapeutic effect and ameliorated those parameters. Experiments conducted in striatal cells show that the mutant huntingtin-dependent downregulation of the receptors involves the control of the type 1 cannabinoid receptor gene promoter by repressor element 1 silencing transcription factor and sensitizes cells to excitotoxic damage. We also provide in vitro and in vivo evidence that supports type 1 cannabinoid receptor control of striatal brain-derived neurotrophic factor expression and the decrease in brain-derived neurotrophic factor levels concomitant with type 1 cannabinoid receptor loss, which may contribute significantly to striatal damage in Huntington's disease. Altogether, these results support the notion that downregulation of type 1 cannabinoid receptors is a key pathogenic event in Huntington's disease, and suggest that activation of these receptors in patients with Huntington's disease may attenuate disease progression.


Asunto(s)
Cuerpo Estriado/metabolismo , Enfermedad de Huntington/genética , Neuronas/metabolismo , Receptor Cannabinoide CB1/genética , Análisis de Varianza , Animales , Western Blotting , Supervivencia Celular , Dronabinol/farmacología , Hormona Liberadora de Hormona del Crecimiento/análogos & derivados , Enfermedad de Huntington/metabolismo , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Transgénicos , Actividad Motora/efectos de los fármacos , Receptor Cannabinoide CB1/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Prueba de Desempeño de Rotación con Aceleración Constante
14.
Proc Natl Acad Sci U S A ; 106(33): 13655-60, 2009 Aug 18.
Artículo en Inglés | MEDLINE | ID: mdl-19666560

RESUMEN

We study the physical origins of phase contrast in dynamic atomic force microscopy (dAFM) in liquids where low-stiffness microcantilever probes are often used for nanoscale imaging of soft biological samples with gentle forces. Under these conditions, we show that the phase contrast derives primarily from a unique energy flow channel that opens up in liquids due to the momentary excitation of higher eigenmodes. Contrary to the common assumption, phase-contrast images in liquids using soft microcantilevers are often maps of short-range conservative interactions, such as local elastic response, rather than tip-sample dissipation. The theory is used to demonstrate variations in local elasticity of purple membrane and bacteriophage 29 virions in buffer solutions using the phase-contrast images.


Asunto(s)
Microscopía de Fuerza Atómica/métodos , Microscopía de Contraste de Fase/métodos , Algoritmos , Fagos de Bacillus/química , Tampones (Química) , Calibración , Microscopía por Crioelectrón/métodos , Citoplasma/metabolismo , Elasticidad , Cinética , Modelos Estadísticos , Modelos Teóricos , Oscilometría , Membrana Púrpura/metabolismo , Estrés Mecánico
15.
Biophys J ; 100(10): 2450-6, 2011 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-21575579

RESUMEN

Motor proteins of the kinesin family move actively along microtubules to transport cargo within cells. How exactly a single motor proceeds on the 13 narrow lanes or protofilaments of a microtubule has not been visualized directly, and there persists controversy on the relative position of the two kinesin heads in different nucleotide states. We have succeeded in imaging Kinesin-1 dimers immobilized on microtubules with single-head resolution by atomic force microscopy. Moreover, we could catch glimpses of single Kinesin-1 dimers in their motion along microtubules with nanometer resolution. We find in our experiments that frequently both heads of one dimer are microtubule-bound at submicromolar ATP concentrations. Furthermore, we could unambiguously resolve that both heads bind to the same protofilament, instead of straddling two, and remain on this track during processive movement.


Asunto(s)
Cinesinas/metabolismo , Microscopía de Fuerza Atómica/métodos , Neurospora crassa/metabolismo , Citoesqueleto de Actina/efectos de los fármacos , Citoesqueleto de Actina/metabolismo , Adenosina Trifosfato/farmacología , Adenilil Imidodifosfato/farmacología , Simulación por Computador , Humanos , Proteínas Inmovilizadas/metabolismo , Cinesinas/química , Microtúbulos/efectos de los fármacos , Microtúbulos/metabolismo , Neurospora crassa/efectos de los fármacos , Unión Proteica/efectos de los fármacos , Multimerización de Proteína/efectos de los fármacos , Transporte de Proteínas/efectos de los fármacos
16.
Proc Natl Acad Sci U S A ; 105(11): 4150-5, 2008 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-18334651

RESUMEN

In a previous study, we showed that the DNA molecule within a spherical virus (the minute virus of mice) plays an architectural role by anisotropically increasing the mechanical stiffness of the virus. A finite element model predicted that this mechanical reinforcement is a consequence of the interaction between crystallographically visible, short DNA patches and the inner capsid wall. We have now tested this model by using protein engineering. Selected amino acid side chains have been truncated to specifically remove major interactions between the capsid and the visible DNA patches, and the effect of the mutations on the stiffness of virus particles has been measured using atomic force microscopy. The mutations do not affect the stiffness of the empty capsid; however, they significantly reduce the difference in stiffness between the DNA-filled virion and the empty capsid. The results (i) reveal that intermolecular interactions between individual chemical groups contribute to the mechanical properties of a supramolecular assembly and (ii) identify specific protein-DNA interactions as the origin of the anisotropic increase in the rigidity of a virus. This study also demonstrates that it is possible to control the mechanical properties of a protein nanoparticle by the rational application of protein engineering based on a mechanical model.


Asunto(s)
Ingeniería de Proteínas , Proteínas Virales/química , Proteínas Virales/metabolismo , Microscopía de Fuerza Atómica , Virus Diminuto del Ratón/química , Virus Diminuto del Ratón/genética , Virus Diminuto del Ratón/metabolismo , Modelos Moleculares , Mutación/genética , Proteínas Virales/genética , Proteínas Virales/ultraestructura , Virión/química , Virión/metabolismo , Virión/ultraestructura
17.
Andes Pediatr ; 92(1): 104-109, 2021 Feb.
Artículo en Inglés, Español | MEDLINE | ID: mdl-34106190

RESUMEN

INTRODUCTION: Meckel's diverticulum (MD) is the remnant of the vitelline duct (VD) also called omphalomesente ric duct and it is considered the most frequent gastrointestinal malformation. Most of the cases are asymptomatic and the diagnosis of this type is always a challenge. OBJECTIVE: To describe 3 sympto matic presentations of MD and to discuss its symptoms, signs, and possible diagnostic-therapeutic tools. CLINICAL CASES: Case 1: A six-month-old patient with obstructive bowel syndrome. In explo ratory laparotomy, an MD was identified with a mesodiverticular band causing an internal hernia. Case 2: A three-year-old patient presenting with digestive hemorrhage and severe anemia requiring blood transfusion. Upper gastrointestinal endoscopy did not show bleeding origin. Due to persis tent melena, the patient required a new blood transfusion. An Abdomen/pelvis tomography scan was performed, showing a suspicious image of MD which was confirmed by laparotomy. Case 3: A newborn with prenatal anencephaly and omphalocele diagnosis. In immediate care of the newborn, meconium evacuation from the umbilical defect was noticed. It was managed as ruptured omphalo cele, installing a bowel silo bag. In primary closure, the permeability of the omphalomesenteric duct was confirmed. An intestinal en bloc resection and anastomosis were performed in all 3 cases. The last one developed an anastomosis leakage resulting in a terminal ileostomy. CONCLUSION: MD, frequently asymptomatic, is often overlooked as a differential diagnosis of abdominal emergencies in children. When suspecting DM with gastric ectopic mucosa, Tc-99m pertechnetate scintigraphy should be performed as a diagnostic procedure of choice, according to each case.


Asunto(s)
Divertículo Ileal/diagnóstico , Transfusión Sanguínea , Preescolar , Diagnóstico Diferencial , Hemorragia Gastrointestinal/diagnóstico , Hemorragia Gastrointestinal/terapia , Hernia Umbilical/terapia , Humanos , Lactante , Recién Nacido , Obstrucción Intestinal/etiología , Obstrucción Intestinal/cirugía , Divertículo Ileal/complicaciones , Divertículo Ileal/cirugía , Fotograbar
18.
Brain ; 132(Pt 11): 3152-64, 2009 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19805493

RESUMEN

Cannabinoid-derived drugs are promising agents for the development of novel neuroprotective strategies. Activation of neuronal CB(1) cannabinoid receptors attenuates excitotoxic glutamatergic neurotransmission, triggers prosurvival signalling pathways and palliates motor symptoms in animal models of neurodegenerative disorders. However, in Huntington's disease there is a very early downregulation of CB(1) receptors in striatal neurons that, together with the undesirable psychoactive effects triggered by CB(1) receptor activation, foster the search for alternative pharmacological treatments. Here, we show that CB(2) cannabinoid receptor expression increases in striatal microglia of Huntington's disease transgenic mouse models and patients. Genetic ablation of CB(2) receptors in R6/2 mice, that express human mutant huntingtin exon 1, enhanced microglial activation, aggravated disease symptomatology and reduced mice lifespan. Likewise, induction of striatal excitotoxicity in CB(2) receptor-deficient mice by quinolinic acid administration exacerbated brain oedema, microglial activation, proinflammatory-mediator state and medium-sized spiny neuron degeneration. Moreover, administration of CB(2) receptor-selective agonists to wild-type mice subjected to excitotoxicity reduced neuroinflammation, brain oedema, striatal neuronal loss and motor symptoms. Studies on ganciclovir-induced depletion of astroglial proliferation in transgenic mice expressing thymidine kinase under the control of the glial fibrillary acidic protein promoter excluded the participation of proliferating astroglia in CB(2) receptor-mediated actions. These findings support a pivotal role for CB(2) receptors in attenuating microglial activation and preventing neurodegeneration that may pave the way to new therapeutic strategies for neuroprotection in Huntington's disease as well as in other neurodegenerative disorders with a significant excitotoxic component.


Asunto(s)
Enfermedad de Huntington , Microglía/metabolismo , Fármacos Neuroprotectores/metabolismo , Receptor Cannabinoide CB2/metabolismo , Animales , Antibacterianos/farmacología , Biomarcadores/metabolismo , Cuerpo Estriado/citología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Cuerpo Estriado/patología , Humanos , Proteína Huntingtina , Enfermedad de Huntington/metabolismo , Enfermedad de Huntington/patología , Enfermedad de Huntington/fisiopatología , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Minociclina/farmacología , Degeneración Nerviosa/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Ácido Quinolínico/farmacología , Receptor Cannabinoide CB2/genética , Prueba de Desempeño de Rotación con Aceleración Constante , Convulsiones/fisiopatología
19.
Medwave ; 20(9): e8053, 2020 Nov 02.
Artículo en Español | MEDLINE | ID: mdl-33231574

RESUMEN

Alopecia areata is a common type of non-scarring alo¬pecia. Although the exact pathogenesis remains elusive, alopecia areata is thought to have a multifactorial etiology described as an interplay of genetic predisposition and environmental exposures. In patients with genetic susceptibility, stress, infection, and microtrauma have been documented to decrease immunosuppressive cytokines that generally maintain the hair follicle's immune privilege. There is currently no curative therapy for alopecia areata, although some treatments can induce hair growth in a percentage of patients. It has been postulated that simvastatin reestablishes the immune privilege, and ezetimibe would provide an immunomodulatory and anti-inflammatory effect. We report a case of a 23 years-old woman with alopecia areata successfully treated with simvastatin/ezetimibe.


La alopecia areata es un tipo común de alopecia no cicatricial. Aunque la patogénesis exacta permanece sin dilucidar, se piensa que la alopecia areata tiene una etiología multifactorial en donde se interrelacionan predisposición genética y factores ambientales. En pacientes susceptibles, se han documentado que el estrés, infecciones y microtraumas disminuyen las citoquinas inmunosupresoras que normalmente mantienen el privilegio inmune del folículo piloso. Actualmente no hay terapia curativa para la alopecia areata, aunque ciertos tratamientos pueden inducir el crecimiento del cabello en un porcentaje de pacientes. Se postula que la simvastatina restablece el privilegio inmune y ezetimibe aportaría un efecto inmunomodulador y antiinflamatorio. Se presenta el caso de una mujer de 23 años con alopecia areata, exitosamente tratada con simvastatina y ezetimibe.


Asunto(s)
Alopecia Areata , Ezetimiba , Inmunosupresores , Simvastatina , Adulto , Alopecia Areata/tratamiento farmacológico , Alopecia Areata/genética , Ezetimiba/uso terapéutico , Femenino , Predisposición Genética a la Enfermedad , Humanos , Inmunosupresores/uso terapéutico , Simvastatina/uso terapéutico , Adulto Joven
20.
Animals (Basel) ; 10(11)2020 Nov 11.
Artículo en Inglés | MEDLINE | ID: mdl-33187104

RESUMEN

Kennelled dogs are at risk of suffering chronic stress due to long-term spatial, social and feeding restrictions. Chronic stress may decrease the dogs' capacity to feel pleasure when facing hedonic experiences, modifying their perception for palatable ingredients. However, different abilities to cope with environmental stressors could prevent the onset of anhedonia. Fourteen kennelled Beagle dogs were used to study the acceptability and preference for different dilute sucrose and monosodium glutamate (MSG) solutions. Coping style of animals was previously evaluated through a human approach test (HAT) and classified as close dogs (CD; proactive) or distant dogs (DD; reactive) according to whether or not they approached an unfamiliar human when a feeding opportunity was presented. Consumption results were analysed taking into account the sucrose/MSG concentrations, HAT (CD or DD), age, and weight of the animals. DD presented a lower intake of sucrose (p = 0.041) and MSG (p = 0.069) solutions compared with CD. However, DD exhibited a higher consumption of MSG than CD at its highest concentrations, supporting that their intake depends on solution palatability. Finally, DD did not prefer sucrose or MSG solutions over water at any dilute solution offered. Together, these results suggest that dogs that are categorized as reactive animals could diminish their ability to perceive dilute palatable solutions, reflecting depressive-like behaviours as anhedonia.

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