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2.
Opt Express ; 28(15): 22144-22150, 2020 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-32752481

RESUMO

We introduce the concept of a liquid compound refractive X-ray zoom lens. The lens is generated by pumping a suitable liquid lens material like water, alcohol or heated lithium through a line of nozzles each forming a jet with the cross section of lens elements. The system is housed, so there is a liquid-circulation. This lens can be used in white beam at high brilliance synchrotron sources, as radiation damages are cured by the continuous reformation of the lens. The focal length can be varied by closing nozzles, thus reducing the number of lens elements in the beam.

3.
Nanoscale ; 8(5): 2974-81, 2016 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-26781940

RESUMO

An experimental three dimensional characterization of the local refractive index sensitivity of plasmonic gold nanorods is performed by controlled apposition of lithographic nanostructures. We show up to seven times higher sensitivity values to local changes in the refractive index at the particle tip than center. In addition, successive deposition of defined nm-thin dielectric layers on nanorods covered with stripe masks allows us to study the sensitivity decrease normal to the particle surface separately for different particle sites. Clear trends to a stronger sensitivity decay at sites of higher local sensitivity are demonstrated experimentally and theoretically. Our sensitivity characterization provides an important tool to find the most suitable particle type and particle site for specific bio-sensing applications.


Assuntos
Nanotubos/química , Técnicas Biossensoriais , Ouro/química , Nanopartículas Metálicas/química , Microscopia Eletrônica de Varredura , Polimetil Metacrilato/química , Técnicas de Microbalança de Cristal de Quartzo , Dióxido de Silício/química , Ressonância de Plasmônio de Superfície
4.
Klin Monbl Augenheilkd ; 231(12): 1174-82, 2014 Dec.
Artigo em Alemão | MEDLINE | ID: mdl-25519504

RESUMO

In case of presbyopia or cataract the "artificial accommodation system" represents one future possibility to durably restore the ability to accommodate. The work presented describes recent progress in the development of the artificial accommodation system. Major advances were achieved in the fields of the actuator system for the active optics, the pupil near reflex sensor, the communication system, the power supply system as well as in system integration. Beside the technical advances, first trials were performed to implant the artificial accommodation system into animals. These trials showed that the new lens shaped design and the C-shaped haptics are beneficial for implantation and secure fixation of the implant inside the capsular bag.


Assuntos
Acomodação Ocular , Lentes Intraoculares , Sistemas Microeletromecânicos/instrumentação , Erros de Refração/terapia , Terapia Assistida por Computador/instrumentação , Próteses Visuais , Análise de Falha de Equipamento , Humanos , Desenho de Prótese
6.
Artigo em Inglês | MEDLINE | ID: mdl-22254948

RESUMO

Age-related ailments like presbyopia and cataract are increasing concerns in the aging society. Both go along with a loss of ability to accommodate. A new approach to restore the patients' ability to accommodate is the Artificial Accommodation System. This micro mechatronic system will be implanted into the capsular bag to replace the human crystalline lens. Depending on the patients' actual need for accommodation, the Artificial Accommodation System autonomously adapts the refractive power of its integrated optical element in a way that the projection on the patients' retina results in a sharp image. As the Artificial Accommodation System is an active implant, its subsystems have to be supplied with electrical energy. Evolving technologies, like energy harvesting, which can potentially be used to power an implant like the Artificial Accommodation System are at the current state of art not sufficient to power the Artificial Accommodation System autonomously [1]. In the near future, therefore an inductive power supply system will be developed which includes an energy storage to power the Artificial Accommodation System autonomously over a period of 24 h and can be recharged wirelessly. This Paper describes a new possibility to optimize the secondary coil design in a solely analytical way, based on a new figure of merit. Within this paper the developed figure of merit is applied to optimize the secondary coil design for the Artificial Accommodation System.


Assuntos
Acomodação Ocular , Desenho de Equipamento , Humanos , Cristalino/fisiopatologia
7.
Phys Rev Lett ; 105(25): 253001, 2010 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-21231585

RESUMO

We experimentally demonstrate a detection scheme suitable for state analysis of single optically trapped atoms in less than 1 µs with an overall detection efficiency η exceeding 98%. The method is based on hyperfine-state-selective photoionization and subsequent registration of the correlated photoion-electron pairs by coincidence counting via two opposing channel electron multipliers. The scheme enables the calibration of absolute detection efficiencies and might be a key ingredient for future quantum information applications or precision spectroscopy of ultracold atoms.

8.
Phys Rev Lett ; 101(26): 260403, 2008 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-19437626

RESUMO

We report the observation of entanglement between a single trapped atom and a single photon at remote locations. The degree of coherence of the entangled atom-photon pair is verified via appropriate local correlation measurements, after communicating the photon via an optical fiber link of 300 m length to a receiver 3.5 m apart. In addition, we measured the temporal evolution of the atomic density matrix after projecting the atom via a state measurement of the photon onto several well-defined spin states. We find that the state of the single atom dephases on a time scale of 150 micros, which represents an important step towards long-distance quantum networking with individual neutral atoms.

9.
J. venom. anim. toxins incl. trop. dis ; 13(3): 664-676, 2007. ilus, graf
Artigo em Inglês | LILACS, VETINDEX | ID: lil-461651

RESUMO

Snake venom is characterized by hemorrhagic, coagulant, proteolytic and myotoxic activities which in Bothrops jaracussu venom are related to intraspecific variations. In the present study, female Swiss mice were divided into two groups: treated with 25æg or 50æg venom. These were subdivided into three groups of six animals each, according to blood collection: 2, 4 or 24h after venom injection. Animals were anesthetized using diethyl-ether inhalation and 1ml of blood was collected by heart puncture. Then, the following organs were removed: spleen, skeletal muscle, kidneys, liver and lungs; histological sections were obtained and stained with hematoxylin-eosin (HE). The following biochemical parameters were analyzed: aspartate aminotransferase (AST/GOT), alanine aminotransferase (ALT/GPT), total lactate dehydrogenase (LDH), glucose, creatinine and urea levels, and total protein content. Results showed significant alterations in AST, LDH, glucose and urea levels, and total protein content, as well as important tissue alterations in the liver, kidneys and lungs. It could be concluded that, even using sublethal doses of venom, there were significant changes in almost all the tested biochemical parameters as well as tissue alterations in the kidneys and lungs.(AU)


Assuntos
Animais , Camundongos , Venenos de Serpentes , Fenômenos Bioquímicos , Técnicas Histológicas , Bothrops
10.
Hautarzt ; 55(3): 301-15; quiz 316, 2004 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-15029439

RESUMO

Consumption of tobacco is hazardous to the health. It leads to cardiovascular diseases, and increases the incidence of numerous neoplasms. The adverse effects on the skin are less well-known and often ignored. Changes in the rheologic characteristics of the blood, increased vasoconstriction and damage to the epithelial layer of the vessel play an important pathogenic role in impaired wound healing, thromboangiitis obliterans and peripheral arterial obstructive diseases. Interactions with collagen metabolism are of special significance in wound healing and skin aging. The immunological effects, such as the induction of an inflammation reaction play a role in palmoplantar pustulosis, psoriasis, atopic dermatitis, acne vulgaris, acne inversa, thromboangiitis obliterans and lupus erythematodes. In addition, immunosuppression caused by nicotine consumption may contribute to the pathogenesis of human papilloma-virus infections, malignant melanoma and epithelial tumors of the skin and neighboring mucous membranes.


Assuntos
Dermatopatias/etiologia , Fumar/efeitos adversos , Tabagismo/complicações , Estrogênios/deficiência , Feminino , Humanos , Isquemia/etiologia , Masculino , Melanoma/etiologia , Nicotina/toxicidade , Fatores de Risco , Pele/irrigação sanguínea , Envelhecimento da Pele/efeitos dos fármacos , Neoplasias Cutâneas/etiologia , Poluição por Fumaça de Tabaco/efeitos adversos , Vasoconstrição/fisiologia , Cicatrização/efeitos dos fármacos
11.
Mol Cell Neurosci ; 24(4): 939-50, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14697660

RESUMO

Activity-dependent changes in expression and localization of the largest major isoform of the neural cell adhesion molecule NCAM180 and three subtypes of glutamate receptors predominantly expressed in the outer part of the molecular layer of the dentate gyrus of adult rats-the NMDA receptor NR2A, the AMPA receptor GluR2/3, and the metabotropic glutamate receptor mGluR1 - were investigated using postembedding immunogold labeling, and electron microscopy. In synaptic membranes of nonstimulated spine synapses, NCAM180 and NR2A accumulated in the center of the postsynaptic density, whereas GluR2/3 and mGluR1 were distributed evenly. Twenty-four hours following induction of long-term potentiation in vivo, NCAM180 and NR2A accumulated at the edges of postsynaptic densities, whereas GluR2/3 was localized more centrally. Also, the distribution of gold particles per synapse significantly changed for NCAM180, NR2A, and mGluR1. Thus, changes in synaptic strength are associated with concomitant changes in the expression and distribution of NCAM180 and glutamate receptors, particularly of the NR2A subtype.


Assuntos
Potenciação de Longa Duração/fisiologia , Microscopia Imunoeletrônica/métodos , Moléculas de Adesão de Célula Nervosa/análise , Receptores de Glutamato/análise , Sinapses/química , Animais , Giro Denteado/química , Giro Denteado/fisiologia , Giro Denteado/ultraestrutura , Imuno-Histoquímica , Masculino , Moléculas de Adesão de Célula Nervosa/fisiologia , Moléculas de Adesão de Célula Nervosa/ultraestrutura , Isoformas de Proteínas/análise , Isoformas de Proteínas/fisiologia , Isoformas de Proteínas/ultraestrutura , Ratos , Ratos Wistar , Receptores de AMPA/análise , Receptores de AMPA/fisiologia , Receptores de AMPA/ultraestrutura , Receptores de Glutamato/fisiologia , Receptores de Glutamato/ultraestrutura , Receptores de Glutamato Metabotrópico/análise , Receptores de Glutamato Metabotrópico/fisiologia , Receptores de Glutamato Metabotrópico/ultraestrutura , Receptores de N-Metil-D-Aspartato , Sinapses/fisiologia , Sinapses/ultraestrutura
12.
Brain Res ; 922(1): 153-7, 2001 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-11730715

RESUMO

In transverse hippocampus slices a short period of hypoxia/hypoglycemia induced by perfusion with an O(2)/glucose-free medium caused early loss and incomplete restoration of evoked field potentials in the CA(1) region. In the present study a search was made for whether the formation of free oxoradicals immediately after starting the hypoxic phase could be part of the breakdown and incomplete restoration of the excitatory potentials (EPs). It was shown that preincubation and postischemic incubation with the radical scavenger PBN did not prevent the potential breakdown but significantly enhances potential restoration, even when PBN was added to the perfusion medium 40 min after hypoxia. Thus, free oxoradicals may damage membrane constituents such as receptors or channel proteins at a very early phase, before neuronal death is pronounced. The results also show that treatment with radical scavengers has a beneficial effect on early hypoxic damage.


Assuntos
Potenciais Evocados/fisiologia , Sequestradores de Radicais Livres/farmacologia , Hipocampo/fisiologia , Hipoglicemia/fisiopatologia , Hipóxia Encefálica/fisiopatologia , Fármacos Neuroprotetores/farmacologia , Óxidos de Nitrogênio/farmacologia , Animais , Óxidos N-Cíclicos , Maleato de Dizocilpina/farmacologia , Potenciais Evocados/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Radicais Livres/metabolismo , Hipocampo/efeitos dos fármacos , Técnicas In Vitro , Masculino , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores
13.
J Neurobiol ; 49(2): 142-58, 2001 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-11598921

RESUMO

We have investigated the possibility that morphologically different excitatory glutamatergic synapses of the "trisynaptic circuit" in the adult rodent hippocampus, which display different types of long-term potentiation (LTP), may express the immunoglobulin superfamily recognition molecules L1 and NCAM, the extracellular matrix molecule tenascin-R, and the extracellular matrix receptor constituent beta1 integrin in a differential manner. The neural cell adhesion molecules L1, NCAM (all three major isoforms), NCAM180 (the largest major isoform with the longest cytoplasmic domain), beta1 integrin, polysialic acid (PSA) associated with NCAM, and tenascin-R were localized by pre-embedding immunostaining procedures in the CA3/CA4 region (mossy fiber synapses) and in the dentate gyrus (spine synapses) of the adult rat hippocampus. Synaptic membranes of mossy fiber synapses where LTP is expressed presynaptically did not show detectable levels of immunoreactivity for any of the molecules/epitopes studied. L1, NCAM, and PSA, but not NCAM180 or beta1 integrin, were detectable on axonal membranes of fasciculating mossy fibers. In contrast to mossy fiber synapses, spine synapses in the outer third of the molecular layer of the dentate gyrus, which display postsynaptic expression mechanisms of LTP, were both immunopositive and immunonegative for NCAM, NCAM180, beta1 integrin, and PSA. Those spine synapses postsynaptically immunoreactive for NCAM or PSA also showed immunoreactivity on their presynaptic membranes. NCAM180 was not detectable presynaptically in spine synapses. L1 could not be found in spine synapses either pre- or postsynaptically. Also, the extracellular matrix molecule tenascin-R was not detectable in synaptic clefts of all synapses tested, but was amply present between fasciculating axons, axon-astrocyte contact areas, and astrocytic gap junctions. Differences in expression of the membrane-bound adhesion molecules at both types of synapses may reflect the different mechanisms for induction and/or maintenance of synaptic plasticity.


Assuntos
Hipocampo/química , Microscopia Imunoeletrônica , Proteínas do Tecido Nervoso/análise , Isoformas de Proteínas/análise , Sinapses/química , Animais , Anticorpos Monoclonais/imunologia , Astrócitos/ultraestrutura , Axônios/ultraestrutura , Giro Denteado/química , Giro Denteado/ultraestrutura , Proteínas da Matriz Extracelular/análise , Técnica Indireta de Fluorescência para Anticorpo , Junções Comunicantes/química , Junções Comunicantes/ultraestrutura , Hipocampo/citologia , Integrina beta1/análise , Complexo Antígeno L1 Leucocitário , Masculino , Glicoproteínas de Membrana/análise , Camundongos , Camundongos Endogâmicos C57BL , Fibras Musgosas Hipocampais/química , Fibras Musgosas Hipocampais/ultraestrutura , Família Multigênica , Terminações Nervosas/química , Terminações Nervosas/ultraestrutura , Moléculas de Adesão de Célula Nervosa/análise , Moléculas de Adesão de Célula Nervosa/química , Plasticidade Neuronal , Via Perfurante/química , Via Perfurante/ultraestrutura , Células Piramidais/química , Células Piramidais/ultraestrutura , Ratos , Ratos Wistar , Ácidos Siálicos/análise , Manejo de Espécimes , Sinapses/ultraestrutura , Tenascina/análise
14.
Brain Res ; 913(1): 68-77, 2001 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-11532248

RESUMO

Recent investigations indicate monosynaptic activation by the perforant pathway (pp) of the dentate gyrus and the CA3 region. While short-term potentiation and long-term potentiation (LTP) and its opioid modulation are frequently described for the dentate gyrus, data for the CA3 region are rare. Therefore, evoked potentials and opioid modulation of LTP were directly compared in both target regions of the pp. Male Wistar rats were chronically implanted with a bipolar stimulation electrode in the pp (angular bundle) and two recording electrodes in the dorsal dentate gyrus and the CA3 region. Stimulation of the pp in the freely behaving animals induced short-latency evoked potentials in both target structures which were compared with respect to waveform, latency, amplitude and signs of short- and long-term neuronal plasticity. The short-latency potential in the CA3 region seemed to be a monosynaptic potential which displayed LTP sensitive to the N-methyl-D-aspartate receptor antagonist, MK 801, and depotentiating stimulation. After application of specific opioid antagonists at the mu-, delta- and kappa-opioid receptor subtypes, naloxone, funaltrexamine, naltrindole and binaltorphimine, different effects on induction and maintenance of LTP of the population spike were found both within the dentate gyrus and between the dentate gyrus and the CA3 region. The results show marked diminution of LTP in the dentate gyrus only for naloxone and naltrindole and only small, if any, effects of naloxone on LTP in the CA3 region. Thus, neuronal plasticity in the direct perforant pathway input to the CA3 region seems not to be under such substantial opioidergic control. LTP would be inducible in that region even when LTP in the input formation, the dentate gyrus, and transsynaptic LTP via the mossy fibres are blocked.


Assuntos
Giro Denteado/metabolismo , Potenciais Evocados/fisiologia , Potenciação de Longa Duração/fisiologia , Antagonistas de Entorpecentes/farmacologia , Neurônios/metabolismo , Via Perfurante/metabolismo , Receptores Opioides/fisiologia , Animais , Giro Denteado/citologia , Giro Denteado/efeitos dos fármacos , Estimulação Elétrica , Potenciais Evocados/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Neurônios/citologia , Neurônios/efeitos dos fármacos , Peptídeos Opioides/metabolismo , Via Perfurante/citologia , Via Perfurante/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores Opioides/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia
15.
Eur J Neurosci ; 14(4): 595-608, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11556885

RESUMO

A variety of extracellular serine proteases are expressed in the central nervous system or might permeate the blood-brain barrier under pathological conditions. However, their intracerebral targets and physiological functions are largely unknown. Here, we show that four distinct subtypes of protease-activated receptors (PARs) are abundantly expressed in the adult rat brain and in organotypic hippocampal slice cultures. PAR-1 expression was significant in the hippocampus, cortex and amygdala. Highest densities of PAR-2 and PAR-3 were observed in hippocampus, cortex, amygdala, thalamus, hypothalamus and striatum. Apart from the striatum, a similar localization was found for PAR-4. Within the hippocampal formation, each PAR subtype was predominantly localized in the pyramidal cell layers. Additionally, we identified PAR-2 in mossy fibers between dentate gyrus and CA3, PAR-3 in the subiculum and PAR-4 in CA3 and in mossy fibres as well as in the stratum lacunosum moleculare. After exposing hippocampal slice cultures to a severe experimental ischemia (oxygen-glucose deprivation), the expression of PARs 1-3 was up-regulated with subtype-specific kinetics. The localization of PARs in brain regions particularly vulnerable to ischemic insults as well as distinct alterations in the expression pattern after experimental ischemia support the notion of an important role of extracellular serine proteases and PARs in cerebral ischemia.


Assuntos
Isquemia Encefálica/metabolismo , Hipocampo/metabolismo , Receptores de Trombina/metabolismo , Regulação para Cima/fisiologia , Animais , Isquemia Encefálica/fisiopatologia , Expressão Gênica/fisiologia , Hipocampo/fisiopatologia , Imuno-Histoquímica , Masculino , Técnicas de Cultura de Órgãos , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptor PAR-1 , Receptor PAR-2 , Receptores de Trombina/genética
16.
Mol Cell Biol ; 21(17): 5970-8, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11486035

RESUMO

Neurocan is a component of the extracellular matrix in brain. Due to its inhibition of neuronal adhesion and outgrowth in vitro and its expression pattern in vivo it was suggested to play an important role in axon guidance and neurite growth. To study the role of neurocan in brain development we generated neurocan-deficient mice by targeted disruption of the neurocan gene. These mice are viable and fertile and have no obvious deficits in reproduction and general performance. Brain anatomy, morphology, and ultrastructure are similar to those of wild-type mice. Perineuronal nets surrounding neurons appear largely normal. Mild deficits in synaptic plasticity may exist, as maintenance of late-phase hippocampal long-term potentiation is reduced. These data indicate that neurocan has either a redundant or a more subtle function in the development of the brain.


Assuntos
Encéfalo/crescimento & desenvolvimento , Proteoglicanas de Sulfatos de Condroitina/fisiologia , Proteínas da Matriz Extracelular/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Animais , Encéfalo/embriologia , Encéfalo/patologia , Brevicam , Proteoglicanas de Sulfatos de Condroitina/genética , Proteínas da Matriz Extracelular/genética , Regulação da Expressão Gênica no Desenvolvimento , Hipocampo/fisiologia , Lectinas Tipo C , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Neurocam , Plasticidade Neuronal , Sinapses/fisiologia , Tenascina/genética , Regulação para Cima
17.
J Med Chem ; 44(15): 2432-7, 2001 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-11448225

RESUMO

Using the computer system PASS (prediction of activity spectra for substances), which predicts simultaneously several hundreds of biological activities, a training set for discriminating between drugs and nondrugs is created. For the training set, two subsets of databases of drugs and nondrugs (a subset of the World Drug Index, WDI, vs the Available Chemicals Directory, ACD) are used. The high value of prediction accuracy shows that the chemical descriptors and algorithms used in PASS provide highly robust structure-activity relationships and reliable predictions. Compared to other methods applied in this field, the direct benchmark undertaken with this paper showed that the results obtained with PASS are in good accordance with these approaches. In addition, it has been shown that the more specific drug information used in the training set of PASS, the more specific discrimination between drug and nondrug can be obtained.


Assuntos
Bases de Dados Factuais , Desenho de Fármacos , Preparações Farmacêuticas/química , Simulação por Computador , Avaliação Pré-Clínica de Medicamentos , Preparações Farmacêuticas/classificação , Software , Relação Estrutura-Atividade
18.
Int J Dev Neurosci ; 19(3): 247-54, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11337193

RESUMO

In the present study kindling was induced in rats by repeated intraperitoneal injection of pentylenetetrazol (PTZ) once every 48 h. The resulting seizure stages were registered after each PTZ application. The development of PTZ-induced kindling and the time course of possible potentiation effects in the dentate gyrus were examined. The efficacy of perforant pathway transmission to the granule cells was tested in every second kindling session by measuring the monosynaptic evoked field potentials recorded in the dentate gyrus following single test stimuli of the perforant pathway at different times after PTZ injection in freely moving animals. The data suggest that establishment of a PTZ kindling is associated with the development of long-lasting potentiation of the field potentials. After completion of kindling it was demonstrated that kindled rats also show a diminished learning performance. The relationship between the development of potentiation phenomena in hippocampal substructures and learning impairment is discussed.


Assuntos
Convulsivantes/farmacologia , Giro Denteado/fisiologia , Excitação Neurológica/fisiologia , Potenciação de Longa Duração/fisiologia , Pentilenotetrazol/farmacologia , Animais , Aprendizagem da Esquiva/fisiologia , Comportamento Animal/fisiologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Excitação Neurológica/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Via Perfurante/fisiologia , Ratos , Ratos Wistar
19.
Hippocampus ; 11(2): 157-67, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11345122

RESUMO

Rats were chronically implanted with stimulation electrodes in the perforant pathway (pp) bilaterally and a recording electrode in the dentate gyrus (DG) unilaterally. Evoked field potentials (EPs) were recorded upon alternating stimulation of the pp on both sides, and long-term potentiation (LTP) was induced. Besides the EP after ipsilateral stimulation, an EP with a latency of approximately 5.5-6.5 ms was also seen upon stimulation of the contralateral pp. This potential was reversibly abolished during pentobarbital anesthesia and irreversibly after lesioning of the ipsilateral angular bundle. Paired-pulse facilitation and paired-pulse depression, depending on interstimulus interval and intensity, were also observed. Therefore, this long-latency potential could be characterized as polysynaptic and induced perhaps by transsynaptic activation via the ipsilateral entorhinal cortex. Ipsilateral tetanization induced strong E/S potentiation of both the ipsilaterally and contralaterally evoked EP, but with different time courses. Tetanization of the contralateral pp did not induce LTP of the ipsilaterally induced EP in the first 4 h. But afterwards a late and slowly developing potentiation occurred. The contralaterally induced EP also showed potentiation of the population spike, which was not immediately detectable but developed slowly over time. The results can be interpreted such that, after stimulation of the pp, the DG on the opposite side cannot only be activated via the weak crossed entorhinal projection but also transsynaptically via an entorhino/entorhinal connection.


Assuntos
Giro Denteado/fisiologia , Potenciação de Longa Duração/fisiologia , Via Perfurante/fisiologia , Animais , Estimulação Elétrica/métodos , Potenciais Evocados/fisiologia , Masculino , Ratos , Ratos Wistar , Tempo de Reação/fisiologia
20.
J Pediatr Orthop ; 21(2): 162-4, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11242242

RESUMO

This study evaluated the accuracy of plain radiographs and computerized tomography (CT) in assessing juvenile Tillaux fractures of the distal tibia. A simulated Tillaux fracture was made in four cadaver specimens and displaced 0, 1, 2, 3, and 5 mm. Plain radiographs and CT were performed on each specimen at each amount of displacement, and the results were compared with the actual amount of displacement present. Plain radiographs and CT were accurate within 1 mm in depicting the actual fracture displacement about 50% of the time. CT was more sensitive than plain radiographs in detecting fractures with >2 mm of displacement. Fracture displacement of >2 mm is generally considered an indication for fracture reduction. Because of its sensitivity in detecting fractures displaced >2 mm, CT is the preferred imaging modality in the assessment of juvenile Tillaux fractures.


Assuntos
Fraturas da Tíbia/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Cadáver , Criança , Humanos , Técnicas In Vitro
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