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1.
Nat Commun ; 12(1): 543, 2021 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-33483488

RESUMEN

The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here, we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG's electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high responsivity (>4 kV/W) and low-noise (0.2 pW/[Formula: see text]) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors' responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor.

2.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 32(5): 498-501, 2020 Jul 29.
Artículo en Chino | MEDLINE | ID: mdl-33185061

RESUMEN

OBJECTIVE: To investigate the prevalence of Schistosoma japonicum infections in Elaphurus davidianus released to Poyang Lake areas and evaluate the impact of the project of "E. davidianus released to wild environments for natural reproduction and growth" "(E. davidianus return home project") on the transmission of schistosomiasis in Poyang Lake areas. METHODS: During the period from April 2018 to December 2019, the population distribution, inhabiting activity and natural reproduction of E. davidianus released to Poyang Lake areas were investigated by means of GPS and artificial observations. The S. japonicum infection was identified in animal feces in E. davidianus inhabitats using a hatching test, and snail distribution was surveyed in E. davidianus inhabiting grass islands using a systematic sampling method. RESULTS: A total of 51 E. davidianus were released to the Poyang Lake areas in 2018, which subsequently produced 5 E. davidianus habitats in Yinlong Lake, Longkou, Nanchi Lake, Lianzi Lake and Zhu Lake. E. davidianus was found to predominantly inhibit in grass islands, farmlands and forest lands in hilly regions around the Poyang Lake areas. The natural reproduction rate of E. davidianus was 25% in the habitats in 2019, and the mean density of snails was 0.009 to 0.039 snails/0.1 m2 in E. davidianus inhabitats; however, no S. japonicum infection was identified in snails. In addition, the mean densities of wild E. davidianus and bovine feces were 4.6 samples/hm2 and 2.1 samples/hm2, Conclusions The E. davidianus released to Poyang Lake areas may get infections with S. japonicum, and cause schistosomiasis transmission through fecal contamination in grass islands. The impact on and the prevalence of S. japonicum infection was 4.35% and 13.16% (P = 0.236), respectively; however, the intensities of S. japonicum infections were "+++" and "+", respectively. CONCLUSIONS: The E. davidianus released to Poyang Lake areas may get infections with S. japonicum, and cause schistosomiasis transmission through fecal contamination in grass islands. The impact on local schistosomiasis transmission and the response strategy requires to be investigated following the release of E. davidianus to lake regions, to ensure the achievement of the goal of schistosomiasis elimination and the successful implementation of the "E. davidianus return home project" in Poyang Lake areas.


Asunto(s)
Lagos , Servicios Preventivos de Salud , Esquistosomiasis Japónica , Animales , Bovinos , China/epidemiología , Ecosistema , Heces/parasitología , Pradera , Prevalencia , Servicios Preventivos de Salud/normas , Esquistosomiasis Japónica/epidemiología , Esquistosomiasis Japónica/prevención & control , Esquistosomiasis Japónica/transmisión
3.
Nat Commun ; 11(1): 3054, 2020 Jun 11.
Artículo en Inglés | MEDLINE | ID: mdl-32528007

RESUMEN

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

4.
Sci Adv ; 6(16): eaay7838, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32494602

RESUMEN

Magnetic fields force ballistic electrons injected from a narrow contact to move along skipping orbits and form caustics. This leads to pronounced resistance peaks at nearby voltage probes as electrons are effectively focused inside them, a phenomenon known as magnetic focusing. This can be used not only for the demonstration of ballistic transport but also to study the electronic structure of metals. Here, we use magnetic focusing to probe narrowbands in graphene bilayers twisted at ~2°. Their minibands are found to support long-range ballistic transport limited at low temperatures by intrinsic electron-electron scattering. A voltage bias between the layers causes strong minivalley splitting and allows selective focusing for different minivalleys, which is of interest for using this degree of freedom in frequently discussed valleytronics.

5.
Nat Commun ; 11(1): 2339, 2020 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-32393747

RESUMEN

Electron-electron interactions play a critical role in many condensed matter phenomena, and it is tempting to find a way to control them by changing the interactions' strength. One possible approach is to place a studied system in proximity of a metal, which induces additional screening and hence suppresses electron interactions. Here, using devices with atomically-thin gate dielectrics and atomically-flat metallic gates, we measure the electron-electron scattering length in graphene and report qualitative deviations from the standard behavior. The changes induced by screening become important only at gate dielectric thicknesses of a few nm, much smaller than a typical separation between electrons. Our theoretical analysis agrees well with the scattering rates extracted from measurements of electron viscosity in monolayer graphene and of umklapp electron-electron scattering in graphene superlattices. The results provide a guidance for future attempts to achieve proximity screening of many-body phenomena in two-dimensional systems.

6.
Nat Commun ; 10(1): 4008, 2019 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-31488842

RESUMEN

At very small twist angles of ∼0.1°, bilayer graphene exhibits a strain-accompanied lattice reconstruction that results in submicron-size triangular domains with the standard, Bernal stacking. If the interlayer bias is applied to open an energy gap inside the domain regions making them insulating, such marginally twisted bilayer graphene is expected to remain conductive due to a triangular network of chiral one-dimensional states hosted by domain boundaries. Here we study electron transport through this helical network and report giant Aharonov-Bohm oscillations that reach in amplitude up to 50% of resistivity and persist to temperatures above 100 K. At liquid helium temperatures, the network exhibits another kind of oscillations that appear as a function of carrier density and are accompanied by a sign-changing Hall effect. The latter are attributed to consecutive population of the narrow minibands formed by the network of one-dimensional states inside the gap.

7.
Science ; 364(6436): 162-165, 2019 04 12.
Artículo en Inglés | MEDLINE | ID: mdl-30819929

RESUMEN

An electrical conductor subjected to a magnetic field exhibits the Hall effect in the presence of current flow. Here, we report a qualitative deviation from the standard behavior in electron systems with high viscosity. We found that the viscous electron fluid in graphene responds to nonquantizing magnetic fields by producing an electric field opposite to that generated by the ordinary Hall effect. The viscous contribution is substantial and identified by studying local voltages that arise in the vicinity of current-injecting contacts. We analyzed the anomaly over a wide range of temperatures and carrier densities and extracted the Hall viscosity, a dissipationless transport coefficient that was long identified theoretically but remained elusive in experiments.

9.
Ann R Coll Surg Engl ; 100(5): e114-e117, 2018 May.
Artículo en Inglés | MEDLINE | ID: mdl-29607721

RESUMEN

Trauma with foreign objects retained within the human body has become a common surgical emergency condition. Traditional surgical methods often involve creating large incisions in soft tissue and may lead to additional complications during wound healing. We have developed a new method of removing foreign bodies from patients' abdomens by using laparoscopy with the help of a novel navigation system that provides accurate positioning. This approach is minimally invasive and simple. This is the first combination of both technologies in this field.


Asunto(s)
Cuerpos Extraños/cirugía , Laparoscopía/métodos , Espacio Retroperitoneal/cirugía , Cirugía Asistida por Computador/métodos , Adulto , Humanos , Masculino , Metales
10.
Phys Chem Chem Phys ; 19(32): 21862-21868, 2017 Aug 16.
Artículo en Inglés | MEDLINE | ID: mdl-28787056

RESUMEN

A N and Fe codoped monoclinic BiVO4 (N-Fe-BVO) photocatalyst was prepared via a conventional sol-gel method and was evaluated for the photocatalytic reduction of CO2 with H2O under visible-light irradiation (>400 nm). As revealed by the structural and photoelectric characterization, the doped N and Fe species can enter the lattice of BiVO4 and induce the codopant levels in the forbidden region of BiVO4, which helps in increasing visible-light absorption, suppressing charge recombination and promoting charge migration. Compared to pure or single-doped BiVO4, the N-Fe-BVO photocatalyst exhibited substantially improved visible-light photocatalytic activity for CO2 reduction, with the highest hydrocarbon generation rate of 27 µmol h-1 gcat-1 and the corresponding quantum efficiency of 1.86% being obtained. The enhanced photocatalytic activity of N-Fe-BVO can be attributed to the synergistic effect of the simultaneous presence of the Fe and N dopants, and the possible photocatalytic mechanism was also proposed based on the characterization results.

11.
Eur Rev Med Pharmacol Sci ; 18(2): 217-28, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24488911

RESUMEN

OBJECTIVE: We aim to explore the expression difference between lung cancer cells and normal lung cells, and to investigate the mechanism of lung cancer development. Besides, we predicted the potential target site of transcriptional factors and microRNAs for differentially expressed genes (DEGs), which may help to regulate expression of DEGs. Small molecules were also identified to cure lung cancer. MATERIALS AND METHODS: Gene expression profiles we used were downloaded from Gene Expression Omnibus (GEO) using accession number of GSE2378. Firstly, we identified differential genes between lung cancer cells and normal lung cells by using R package limma. Then, we detected the processes and pathways that changed in lung cancer cells by Gene Ontology (GO) and KEGG pathway enrichment analysis. Potential target sites of transcriptional factors and microRNAs were also detected based on gene annotation data in MSigDB. Finally, small molecule drugs were screened via querying Connectivity Map database. RESULTS: We obtained 2961 differentially expressed genes between lung cancer cells and normal lung cells. Besides changes in cell cycle, metabolic processes and proteasome were also dramatically disordered. Some DEGs shared target sites of the transcription factor such as E2F, ETS and CEBPB. Target sites of hsa-miR-196a and hsa-miR-200c were also significantly enriched by DEGs. Iloprost simulated the state of normal cells, while MS-275 might be potential pathogenic substances. CONCLUSIONS: We investigate the lung cancer from Gene Ontology, pathway, transcription factors and microRNAs based on gene expression profiles. All these results may facilitate lung cancer treatment with a new breakthrough.


Asunto(s)
Regulación Neoplásica de la Expresión Génica/genética , Neoplasias Pulmonares/genética , Transcriptoma/genética , Ciclo Celular/genética , Línea Celular , Línea Celular Tumoral , Perfilación de la Expresión Génica/métodos , Humanos , MicroARNs/genética
12.
Plant Dis ; 98(5): 692, 2014 May.
Artículo en Inglés | MEDLINE | ID: mdl-30708513

RESUMEN

Amorphophallus muelleri is a perennial tuberous plant in the family Araceae. The name konjac is commonly used for the species of genus Amorphophallus that produce a polysaccharide, glucomannan. The latter, called konjac glucomannan, is extracted from the tubers of these species. Glucomannan is an excellent gelling agent used in food, pharmaceutical and chemical industry, a specialty crop grown as a source of glucomannan for industrial use. It is an important cash crop and thus contributes to poverty alleviation in southwest China. Its planting area is about 150 million mu (10 million ha). In July 2012, symptoms of an unknown blight were observed on 5 to 10% of A. muelleri flowers and seeds being grown for commercial seed production. Greenhouses temperatures ranged from 20 to 34°C (avg. 26°C). A light grey mycelium was observed on symptomatic tissues, especially flowers. Severely infected flowers and stems eventually rotted, then dried out. Diseased tissue was excised from affected flowers and surfaces and disinfected with 1% sodium hypochlorite, followed by 70% alcohol. The tissue was then rinsed in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 26°C. Mycelial growth on PDA was initially whitish and turned gray with age. Dark appearing conidiophores bore botryose heads of hyaline, ellipsoid, unicellular conidia, grey in mass, measuring 7.2 (6.2 to 9.5) × 5.3 (4.5 to 6.0) µm. Black, irregular sclerotia formed at random in the culture. These morphological features were typical of those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced (1). BLAST analysis of a 557-bp segment had a 99% similarity with the sequence of Botryotinia fuckeliana (anamorph = B. cinerea). The representative nucleotide sequence has been assigned the GenBank Accession No. KC999986. On the basis of morphological and molecular results, the fungus isolated from diseased konjac flowers and flower tissue was confirmed to be B. cinerea. Pathogenicity tests: Inoculum was prepared from 7-day-old cultures on PDA. Six flowering A. muelleri in 1-liter pots were spray inoculated with a 1.0 × 106 conidia/ml suspension from 7-day-old PDA cultures. As a control, six healthy plants were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 3 days and maintained in a greenhouse at temperatures between 20 and 26°C. After 8 days, small, round to irregular brown spots developed on both flowers and stems, which finally blighted. Water-treated plants remained symptomless. Koch's postulates were fulfilled when the pathogen was re-isolated from the diseased organs. Blight on common calla lily (calla lily and Amorphophallus are in the same family, different genera) flower attributed to B. cinerea was previously reported in Argentina (3). To our knowledge, this is the first report of the presence of B. cinerea on A. muelleri in China. References: (1) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (3) M. C. Rivera and S. E. Lopez. Plant Dis. 90:970, 2006.

13.
Eur Rev Med Pharmacol Sci ; 17(14): 1951-7, 2013 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-23877861

RESUMEN

BACKGROUND: Iliac bone graft harvesting is a common procedure in spinal surgery and trauma center for spinal fusion and nonunion of the extremities. AIM, PATIENTS AND METHODS: To compare the pain and cosmetic outcomes of patients undergoing iliac crest anatomical reconstruction using equivalent iliac crest allograft (R group) with those of patients without reconstruction of the iliac crest defect (NR group), a prospective nonrandomized controlled study was conducted. RESULTS: In R group, the intensity and prevalence of pain were significantly lower than those in NR group. Cosmetic outcome and satisfaction score were also significantly improved in R group. One patient of R group suffered from lipolysis and superficial infection which healed by regular dressing change for two weeks. There were no cases of allograft displacement, implant loosening, internal fixation breakage or immunological rejection. Seven patients in NR group had significant pain related to the tenting of skin over the defect. Radiologic incorporation of pelvis was documented in all patients except four having partial re-sorption of the allograft. Early fibrous healing and the late creeping substitution were noted in all patients of R group. CONCLUSIONS: Equivalent iliac crest allograft provides an effective alternative for iliac crest anatomical reconstruction, leading to reduced donor site pain and better cosmesis.


Asunto(s)
Ilion/anatomía & histología , Ilion/trasplante , Sitio Donante de Trasplante/anatomía & histología , Adolescente , Adulto , Trasplante Óseo/efectos adversos , Evaluación de la Discapacidad , Femenino , Humanos , Ilion/diagnóstico por imagen , Masculino , Persona de Mediana Edad , Dimensión del Dolor , Dolor Postoperatorio/epidemiología , Estudios Prospectivos , Radiografía , Fusión Vertebral , Sitio Donante de Trasplante/diagnóstico por imagen , Resultado del Tratamiento
14.
Water Sci Technol ; 67(8): 1859-66, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23579843

RESUMEN

The efficacy and capacity of vertical-flow wetland filters on molybdenum (Mo) removal from wastewater was examined, employing reed (Phragmites australis) and cattail (Typha latifolia) as well as different adsorption granular media. Humus, cinder, modified cinder, as well as pyrite were used as filter media. A synthetic effluent with different concentrations of Mo(VI) at different hydraulic retention times was used for simulating Mo leached mine wastewater. Laboratory experiments showed that the equilibrium adsorption data were in agreement with the Langmuir isotherm model, and the maximum Mo(VI) adsorption capacities of modified cinder and pyrite were 10.01 and 6.25 mg/g, respectively. Mo(VI) removal in F5 (combination substrates of pyrite and cinder) was found to be more stable and effective than that of F1 (conventional gravel and soil filter media) during the 14-week experiment. Most of the Mo(VI) was retained in the 10-20 cm of the substrate, and adsorbed by the modified cinder and pyrite. The largest fraction of Mo(VI) retained was the water-soluble fraction on the surface of the pyrite. Cattail was more suitable for Mo(VI) absorption than reed, but the bioaccumulation accounted for a very small portion of the total removal.


Asunto(s)
Molibdeno/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua , Humedales , Adsorción , Concentración de Iones de Hidrógeno , Hierro/química , Molibdeno/metabolismo , Nitrógeno/química , Fósforo/química , Sulfuros/química , Ácidos Sulfúricos/química , Termodinámica , Typhaceae/metabolismo , Aguas Residuales/química
15.
Plant Dis ; 96(12): 1821, 2012 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30727268

RESUMEN

Helwingia chinensis Batal is distributed in the western and southern regions of China. The aerial part of this plant has long been used to treat dysentery, hematochezia, and swelling. An outbreak of cankers and dieback was observed for the first time on H. chinensis in China during June of 2010. Disease symptoms included dieback of shoots and branches, lesions, and canker formation on the stems. In order to identify the causal agent(s) of this canker disease, samples composed of inner bark and woody tissues were collected from the junction of healthy and diseased tissues of declining trees from Kunming and Wenshan districts of China during July to October of 2010. Pieces of surface-sterilized tissue samples were plated on potato dextrose agar (PDA) and incubated at 26°C. Fungal colonies developed copious, white, aerial mycelium that became dark green with age. Pycnidia started to develop after 20 days. Macroconidia, which were 20 to 29 × 4 to 6 µm, were hyaline, aseptate, and fusiform. No fungus was isolated from water-inoculated tissues of control plants and healthy trees. Identity was confirmed by analysis of the rDNA internal transcribed spacer region (ITS1-5.8S-ITS2) with primers ITS1 and ITS4. BLAST searches showed 99% identity with Botryosphaeria dothidea isolates from GenBank (Accession Nos. HQ660454 and FJ790846). Representative sequences of B. dothidea from H. chinensis from China have been deposited in GenBank (Accession No. JQ766122). On the basis of morphological and molecular results, the fungus isolated from diseased H. chinensis was confirmed to be B. dothidea. Pathogenicity tests were conducted by stem inoculation of 1-year-old H. chinensis seedlings. Mycelial plugs (3 to 4 mm in diameter) of B. dothidea from actively growing colonies were applied to same-sized bark wounds on the middle point of the stems. Control seedlings were inoculated with sterile PDA plugs. Inoculated and control seedlings (three each) were kept in a greenhouse and watered as needed. After 4 weeks, all H. chinensis seedlings developed vascular tissue discoloration and leaf wilting; no such symptoms were manifested by seedlings in the control treatment. B. dothidea was reisolated from all B. dothidea-inoculated, symptomatic tissues, fulfilling Koch's postulates. In China, B. dothidea has previously been reported to cause canker and dieback disease of Eucalyptus grandis (2) and gummosis of peach (1); however, to our knowledge, this is the first report of B. dothidea causing canker and dieback on H. chinensis. References: (1) Y. Ko et al. Plant Pathol. Bull. 1:70, 1992. (2) L. Yu et al. Plant Dis. 93:764, 2009.

16.
Plant Dis ; 96(11): 1697, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30727480

RESUMEN

Blueberry (Vaccinium spp.) production in southwest and northeast China has grown to over 100,000 ha in the last 20 years thanks to the fruit's high nutritional and economic value. As blueberry acreage increases, the diversity of diseases and challenges for control are gaining more attention. In August 2010, stem and branch blight occurred on Highbush Blueberries (Vaccinium corymbosum L.) at commercial farms in Lijiang and Zongdian, Yunnan Province (southwestern China), with crop damage ranging from 10 to 15%. Typical symptoms of the disease were blight and dieback on the stems with lesions extending along entire branches. Diseased samples (phloem and xylem sectors in the wood) were washed with running tap water, disinfected with 2% sodium hypochlorite, then 70% alcohol, rinsed in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 28°C. Fungal isolates developed copious, white aerial mycelium that became dark gray after 4 to 5 days and formed black pycnidia after 18 days. Conidia were hyaline, aseptate, thin walled, fusiform, and measured 21 to 27 × 4 to 6 µm. Identity was confirmed by analysis of the ribosomal DNA internal transcribed spacer region ITSI-5.8S -ITS2 with primers ITS1 and ITS4. BLAST searches showed 99% identity with Botryosphaeria dothidea isolates from GenBank (Accession Nos. AB693904 and JF800139). Representative sequences of B. dothidea from Highbush Blueberries from China were deposited into GenBank (Accession No. JX096631). On the basis of morphological and molecular results, the fungus isolated from diseased Highbush Blueberries stem was confirmed to be B. dothidea. Pathogenicity tests were conducted on 2-year-old blueberry seedlings (Highbush Blueberries). Mycelial plugs (2 to 3 mm in diameter) of B. dothidea from actively growing colonies (PDA) were applied to same-size bark wounds in the center of the stems. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (five each) were kept in a greenhouse and watered as needed. After 12 days, all of the inoculated but none of the control blueberry seedlings showed dark vascular stem tissue. B. dothidea was reisolated from symptomatic tissues, thus fulfilling Koch's postulates. No symptoms were visible in the control seedlings. B. dothidea has been reported as a pathogen of sycamore (3), olives (1), and peach (2). However, no research has been conducted on stem blight of blueberry caused by B. dothidea in southwest or mainland China. To our knowledge, this is the first report of B. dothidea on blueberry in southwest China. References: (1) M. Chattaoui, et al. Plant Dis. 95:770, 2011. (2) Y. Ko et al. Plant Pathol. Bull. 1:70, 1992. (3) E. Turco, et al. Plant Dis. 90:1106, 2006.

17.
Neuroscience ; 89(1): 191-207, 1999 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-10051229

RESUMEN

Neurons exhibiting D2 receptor-like immunoreactivity were investigated in the substantia nigra pars compacta of weaver mice at the light and electron microscope levels using immunocytochemical techniques. At the light microscope level, there was significant loss of D2-like immunoreactive cells in weaver mice and the remaining labeled cells exhibited less intense immunoreactivity. At the ultrastructural level, there was a decrease in the number of immunoreactive profiles and fewer synapses were observed abutting labeled dendritic profiles. In addition, degenerative changes were noted in some of the D2 receptor-like immunoreactive profiles. Double labeling with D2 and tyrosine hydroxylase indicated that the majority of the labeled profiles were double labeled. Eight-week-old homozygous weavers were paired with wild-type littermates as controls and perfused with a buffered solution of acrolein/paraformadehyde. Midbrain sections were reacted immunocytochemically either with an antiserum to D2 or with antisera to D2 and tyrosine hydroxylase, using a double-labeling technique. Sections were processed for light and electron microscopy by standard methods. The results of this study confirm the autoreceptor-like activity of D2 receptors on nigral dopamine neurons. The cell degeneration, down-regulation of D2 receptors, and decreased dendritic and synaptic components in the neuropil suggest that the synaptic integrity of the substantia nigra has been compromised, which in turn would affect the functional efficacy of the basal ganglia circuitry. This altered circuity is expressed in the Parkinson-like symptoms displayed by this mutant mouse.


Asunto(s)
Neuronas/química , Receptores de Dopamina D2/análisis , Sustancia Negra/citología , Animales , Muerte Celular/fisiología , Dendritas/química , Dendritas/enzimología , Dendritas/ultraestructura , Ratones , Ratones Mutantes Neurológicos , Microscopía Electrónica , Neuronas/enzimología , Neuronas/ultraestructura , Enfermedad de Parkinson/metabolismo , Terminales Presinápticos/química , Terminales Presinápticos/enzimología , Terminales Presinápticos/ultraestructura , Receptores de Dopamina D2/inmunología , Sinapsis/química , Sinapsis/enzimología , Tirosina 3-Monooxigenasa/análisis
18.
Epilepsia ; 36(10): 960-5, 1995 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-7555959

RESUMEN

GABAergic transmission in the substantia nigra pars reticulata (SNR) has an important role in the control of experimental seizures. In the flurothyl seizure model, SNR microinjection of the selective GABAA receptor agonist muscimol results in a biphasic dose-response curve in adults: Intermediate doses are anticonvulsant, but high doses have proconvulsant effects. Another GABAA agonist, THIP (4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridin-3-ol), also produces anticonvulsant effects at lower doses, whereas higher doses tend to produce a proconvulsant effect. In 16-day-old rat pups, no anticonvulsant but only proconvulsant effects of muscimol occur, and at lower doses than in adults. These data suggest that the immature SNR is significantly more sensitive to the proconvulsant effects of GABAA receptor agonists than is the SNR of adults. We hypothesize that the age-related differences in nigral GABAergic response may be due to ontogenic changes in GABAA-sensitive neuronal circuits in the SNR.


Asunto(s)
Flurotilo , Agonistas del GABA/farmacología , Isoxazoles/farmacología , Muscimol/farmacología , Convulsiones/inducido químicamente , Convulsiones/prevención & control , Sustancia Negra/efectos de los fármacos , Sustancia Negra/crecimiento & desarrollo , Factores de Edad , Animales , Animales Recién Nacidos , Relación Dosis-Respuesta a Droga , Agonistas del GABA/administración & dosificación , Isoxazoles/administración & dosificación , Masculino , Microinyecciones , Muscimol/administración & dosificación , Ratas , Ratas Sprague-Dawley , Sustancia Negra/fisiología , Ácido gamma-Aminobutírico/fisiología
19.
Brain Res Dev Brain Res ; 79(2): 297-300, 1994 Jun 17.
Artículo en Inglés | MEDLINE | ID: mdl-7955329

RESUMEN

To determine whether the substantia nigra GABAergic anticonvulsant effects depend on GABAB receptor activation, we tested the effects of intranigral CGP 35,348 (a GABAB receptor antagonist) alone or in combination with gamma-vinyl-GABA (GVG; a GABA-transaminase inhibitor) on flurothyl seizures in rat pups and adult rats. In pups, nigral infusions of CGP 35,348 decreased the thresholds for clonic and tonic seizures and attenuated the anticonvulsant effects of GVG. In adults, nigral infusions of CGP 35,348 did not alter seizure thresholds. The data suggest that, in rat pups, nigral GABAB receptors regulate, in part, flurothyl-induced seizures.


Asunto(s)
Receptores de GABA-B/fisiología , Convulsiones/fisiopatología , Sustancia Negra/fisiología , Animales , Anticonvulsivantes/farmacología , Convulsivantes/farmacología , Flurotilo/farmacología , Antagonistas de Receptores de GABA-B , Masculino , Compuestos Organofosforados/farmacología , Ratas , Ratas Sprague-Dawley , Sustancia Negra/efectos de los fármacos , Sustancia Negra/crecimiento & desarrollo , Vigabatrin , Ácido gamma-Aminobutírico/análogos & derivados , Ácido gamma-Aminobutírico/farmacología
20.
Epilepsy Res ; 15(3): 185-92, 1993 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-8223414

RESUMEN

There is considerable evidence that thalamic nuclei are involved in the propagation and regulation of seizures. In the present study, we investigated the possible role in seizure mechanisms of GABAergic transmission in two thalamic nuclei, the posterior nucleus (PO) and the ventromedial nucleus (VM). Several GABAergic drugs were bilaterally microinfused into PO or VM of adult rats via chronically implanted cannulae, before testing the rats' susceptibility to seizures induced by flurothyl. In PO, infusions of the GABA elevating agent gamma-vinyl-GABA (20 micrograms) or of the GABAA receptor agonist muscimol (100 ng) suppressed both clonic and tonic seizures. Infusions into PO of the GABAA receptor antagonist bicuculline (100 ng) facilitated both these seizure types. Administration of the GABAB receptor agonist baclofen (200 ng) also suppressed clonic seizure susceptibility. Drug infusions into VM, however, did not significantly modify the susceptibility to seizures. These findings lead us to conclude that GABAergic transmission in the vicinity of the PO, but perhaps not in VM, affects flurothyl seizure susceptibility. We hypothesize that GABA synapses in PO may be part of a seizure propagation or control circuit including striatum, substantia nigra, and superior colliculus.


Asunto(s)
Convulsiones/fisiopatología , Transmisión Sináptica/fisiología , Núcleos Talámicos/fisiología , Ácido gamma-Aminobutírico/fisiología , Aminocaproatos/farmacología , Animales , Anticonvulsivantes/farmacología , Baclofeno/farmacología , Conducta Animal/efectos de los fármacos , Bicuculina/farmacología , Flurotilo , Masculino , Microinyecciones , Muscimol/farmacología , Ratas , Ratas Sprague-Dawley , Convulsiones/inducido químicamente , Convulsiones/psicología , Núcleos Talámicos/patología , Vigabatrin
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