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1.
BMC Neurol ; 21(1): 388, 2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34615473

RESUMO

BACKGROUND: Myasthenia gravis (MG) is an autoimmune disease involving the neuromuscular junction. Myasthenic crisis (MC), which is characterized by respiratory failure and the requirement of mechanical ventilation in patients with MG, is still a medical emergency despite the decrease in mortality with the advances in acute management. Hemogram is a cost-effective test for evaluating hematological complications and systemic inflammation, and hemogram data have been used to predict various clinical outcomes of several diseases. The relationship between hemogram and MG has been discussed, but the role of hemogram data in predicting the prognosis of MC patients has not been established. METHODS: To identify whether hemogram data can predict in-hospital mortality in patients with MC, we retrospectively investigated 188 myasthenic crisis events from the Chang Gung Research Database between April 2001 and March 2019. Demographic and clinical characteristics were collected, as well as hemogram data before intubation and extubation. The endpoints were mortality during mechanical ventilation and mortality after extubation. RESULTS: The overall in-hospital mortality rate was 22%. Multivariate logistic regression analysis for predicting mortality during mechanical ventilation showed that old age at MC onset (OR = 1.039, p = 0.022), moderate-to-severe anemia (OR = 5.851, p = 0.001), and extreme leukocytosis (OR = 5.659, p = 0.022) before intubation were strong predictors of mortality, while acute management with plasma exchange or double-filtration plasmapheresis (PE/DFPP) significantly decreased mortality (OR = 0.236, p = 0.012). For predicting mortality after extubation, moderate-to-severe anemia before extubation (OR = 8.452, p = 0.017) and non-treated with disease-modifying therapy before MC (OR = 5.459, p = 0.031) were crucial predictive factors. CONCLUSION: This study demonstrated that both old age at MC onset and moderate-to-severe anemia are important predictors of in-hospital mortality in patients with MC, and extreme leukocytosis is another crucial predictor of mortality during mechanical ventilation. The suggested mechanism is that anemia-induced hypoxia may enhance the release of proinflammatory cytokines, exacerbate systemic inflammation, and lead to multiple organ dysfunction syndrome and, finally, mortality.


Assuntos
Miastenia Gravis , Insuficiência Respiratória , Mortalidade Hospitalar , Humanos , Miastenia Gravis/complicações , Miastenia Gravis/terapia , Respiração Artificial , Estudos Retrospectivos
2.
Sci Rep ; 11(1): 9610, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33953260

RESUMO

We demonstrated the design of pre-additive manufacturing microalloying elements in tuning the microstructure of iron (Fe)-based alloys for their tunable mechanical properties. We tailored the microalloying stoichiometry of the feedstock to control the grain sizes of the metallic alloy systems. Two specific microalloying stoichiometries were reported, namely biodegradable iron powder with 99.5% purity (BDFe) and that with 98.5% (BDFe-Mo). Compared with the BDFe, the BDFe-Mo powder was found to have lower coefficient of thermal expansion (CTE) value and better oxidation resistance during consecutive heating and cooling cycles. The selective laser melting (SLM)-built BDFe-Mo exhibited high ultimate tensile strength (UTS) of 1200 MPa and fair elongation of 13.5%, while the SLM-built BDFe alloy revealed a much lower UTS of 495 MPa and a relatively better elongation of 17.5%, indicating the strength enhancement compared with the other biodegradable systems. Such an enhanced mechanical behavior in the BDFe-Mo was assigned to the dominant mechanism of ferrite grain refinement coupled with precipitate strengthening. Our findings suggest the tunability of outstanding strength-ductility combination by tailoring the pre-additive manufacturing microalloying elements with their proper concentrations.

3.
Int J Mol Sci ; 21(20)2020 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-33050160

RESUMO

In this study, we optimized the geometry and composition of additive-manufactured pedicle screws. Metal powders of titanium-aluminum-vanadium (Ti-6Al-4V) were mixed with reactive glass-ceramic biomaterials of bioactive glass (BG) powders. To optimize the geometry of pedicle screws, we applied a novel numerical approach to proposing the optimal shape of the healing chamber to promote biological healing. We examined the geometry and composition effects of pedicle screw implants on the interfacial autologous bone attachment and bone graft incorporation through in vivo studies. The addition of an optimal amount of BG to Ti-6Al-4V leads to a lower elastic modulus of the ceramic-metal composite material, effectively reducing the stress-shielding effects. Pedicle screw implants with optimal shape design and made of the composite material of Ti-6Al-4V doped with BG fabricated through additive manufacturing exhibit greater osseointegration and a more rapid bone volume fraction during the fracture healing process 120 days after implantation, per in vivo studies.


Assuntos
Alumínio , Desenvolvimento Ósseo , Vidro , Parafusos Pediculares , Pós , Próteses e Implantes , Titânio , Vanádio , Animais , Fenômenos Biomecânicos , Remodelação Óssea , Processamento de Imagem Assistida por Computador , Osseointegração , Estresse Mecânico , Suínos , Tomografia Computadorizada por Raios X
4.
Addit Manuf ; 35: 101322, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32835025

RESUMO

The deformations of isotropic and anisotropic Ti-6Al-4V columnar structures fabricated by additive manufacturing were extensively examined. The distinct texture and microstructure distributions were characterised. In situ X-ray diffraction measurements show different lattice activities resulting from the different microstructure distributions. Spatially resolved mapping revealed manufacturing-induced crystallite-orientation distributions that determine the deformation mechanisms. We propose a self-consistent model to correlate the multi-scale characteristics, from the anisotropic-texture-distribution microstructure to the bulk mechanical properties. We determined that basal and pyramidal slip activities were activated by tension deformation. The underlying additive-manufacturing-induced crystal plasticity plays a major role. We find that the texture development of the columnar structures and the distribution of crystallite orientation achieved by different processing conditions during additive manufacturing have important effects on the mechanical properties. The dominant deformation mode for the anisotropic Ti-6Al-4V columnar structure is basal slip, and that for the isotropic Ti-6Al-4V columnar structure is pyramidal slip. The difference may be important for determining the fatigue behaviour.

5.
Sci Rep ; 7: 41527, 2017 01 30.
Artigo em Inglês | MEDLINE | ID: mdl-28134347

RESUMO

There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements.

6.
J Biomed Mater Res A ; 100(12): 3490-5, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22829482

RESUMO

Morphologically and chemically modified plano-concave fibers (PCFs) are designed as a unit of guided channels for supporting Schwann cells to facilitate mass transport and promote nerve regeneration. The surface-modified PCFs are imprinted with linearly patterned grooves (LPGs) to guide adherent Schwann cell elongation and axon extension. After being cocultured with PC12 neuron-like cells, Schwann cells differentiate into the myelinated type and interact with PC12 axons. The myelinated axons aggregate as a linear bundle and extend along the direction of LPGs on a PCF. The cross section of a myelin structure is examined using a transmission electron microscope. The PCFs can potentially bridge gaps in injured nerves, improving the therapeutic efficacy of nerve regeneration.


Assuntos
Regeneração Tecidual Guiada/métodos , Fibras Nervosas Mielinizadas/fisiologia , Regeneração Nervosa/fisiologia , Tecidos Suporte/química , Animais , Adesão Celular/efeitos dos fármacos , Técnicas de Cocultura , Corantes Fluorescentes/metabolismo , Ácido Láctico/farmacocinética , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Regeneração Nervosa/efeitos dos fármacos , Células PC12 , Poliésteres , Polímeros/farmacocinética , Ratos , Células de Schwann/citologia , Células de Schwann/efeitos dos fármacos
7.
J Biomed Mater Res A ; 99(2): 158-65, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21976440

RESUMO

A dense poly-L-lactic acid (PLLA) film was employed as the primary material and hot-embossed with the formation of microgrooves (g-PLLA). A thin layer of Au was then deposited on the film to obtain a morphologically modified substrate (Au/g-PLLA). The Au/g-PLLA film surface was then chemically modified by imprinting octadecanethiolate (ODT) self-assembled monolayers on the upper surface (ODT/Au/g-PLLA), followed by Arg-Gly-Asp (RGD) peptide sequences on the microgrooves (RGD_ODT/Au/g-PLLA). The surface chemistry of the as-prepared RGD_ODT/Au/g-PLLA samples was examined. The bioactivity and spreading function of Schwann cells cultured on the morphologically and chemically modified surfaces were assessed. The results demonstrate that Schwann cells adhered to the RGD/Au/g-PLLA surface and proliferated along the microgrooves without crossing over the ODT/Au/PLLA surface. The proposed film surface can be used for manipulating the outgrowth of axons by modifying and arranging a selected region to induce cell growth and to prevent cells from spreading out nondirectionally.


Assuntos
Materiais Biocompatíveis/química , Adesão Celular/fisiologia , Ácido Láctico/química , Polímeros/química , Células de Schwann/fisiologia , Proliferação de Células , Células Cultivadas , Ouro/química , Ácido Láctico/metabolismo , Teste de Materiais , Estrutura Molecular , Oligopeptídeos/química , Espectroscopia Fotoeletrônica , Poliésteres , Polímeros/metabolismo , Células de Schwann/citologia , Propriedades de Superfície
8.
Nanotechnology ; 22(27): 275101, 2011 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-21597149

RESUMO

A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.


Assuntos
Axônios/metabolismo , Bainha de Mielina/metabolismo , Nanotecnologia/métodos , Animais , Axônios/ultraestrutura , Núcleo Celular/metabolismo , Forma Celular , Técnicas de Cocultura , Proteínas da Mielina/metabolismo , Células PC12 , Ratos
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