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1.
J Biomech ; 119: 110259, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-33618329

RESUMO

Natural modes and frequencies of three-dimensional (3D) deformation of the human brain were identified from in vivo tagged magnetic resonance images (MRI) acquired dynamically during transient mild acceleration of the head. Twenty 3D strain fields, estimated from tagged MRI image volumes in 19 adult subjects, were analyzed using dynamic mode decomposition (DMD). These strain fields represented dynamic, 3D brain deformations during constrained head accelerations, either involving rotation about the vertical axis of the neck or neck extension. DMD results reveal fundamental oscillatory modes of deformation at damped frequencies near 7 Hz (in neck rotation) and 11 Hz (in neck extension). Modes at these frequencies were found consistently among all subjects. These characteristic features of 3D human brain deformation are important for understanding the response of the brain in head impacts and provide valuable quantitative criteria for the evaluation and use of computer models of brain mechanics.


Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Aceleração , Adulto , Encéfalo/diagnóstico por imagem , Cabeça/diagnóstico por imagem , Humanos , Rotação
2.
Osteoporos Int ; 31(9): 1807-1815, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32383065

RESUMO

This study evaluated the peri-implant bone repair in orchiectomized rats receiving intermittently PTH 1-34. The treatment returned the bone quality and quantity of the animals to normal in the computerized microtomography, laser confocal microscopy, and histological analysis. The PTH 1-34 promoted marked bone formation with increased volume, improved quality, and greater bone turnover. INTRODUCTION: Osteoporosis can be a problem in implant osseointegration. So this study aimed to evaluate the quantity and quality of peri-implant bone repair in orchiectomized Wistar rats receiving intermittently administered PTH 1-34. METHODS: Animals (n = 24) were divided into 3 groups: healthy control (SHAM), orchiectomized (ORQ), and orchiectomized and treated with 0.5 µg/kg/day PTH 1-34 (TERI), and each received an implant in the right and left tibial metaphysis, which was allowed to repair for 60 days. The resultant bone formation was evaluated through computerized microtomography (micro-CT) to compare the percent bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular number and separation (Tb.N, Tb.Sp), and bone implant contact (BIC) through the intersection surface (i.S) between groups. Laser confocal microscopy was used to evaluate fluorochrome areas for mineral apposition rate (MAR) and neoformed bone area (NBA). In addition, histological evaluation of calcified tissues with Stevenel blue and alizarin red staining was performed. RESULTS: Treatment with PTH 1-34 returned the bone quality and quantity of the osteoporotic animal to normal, as the TERI group presented statistically significant higher values for BV/TV, Tb.Th, and BIC parameters compared with ORQ (p < 0.05), but when compared with SHAM (p > 0.05), no statistical difference was noted. In addition, in the bone turnover analysis (MAR, NBA) for TERI, the highest results are presented, followed by SHAM, and then ORQ (TERI × ORQ: p < 0.05). CONCLUSIONS: Intermittent treatment with PTH 1-34 on orchiectomized animals promoted marked bone formation with increased volume, improved quality, and greater bone turnover in the peri-implant space, returning the bone quality and quantity to the present standard in healthy animals.


Assuntos
Osteoporose , Teriparatida , Animais , Densidade Óssea , Osso e Ossos , Feminino , Humanos , Osseointegração , Osteoporose/tratamento farmacológico , Ovariectomia , Ratos , Ratos Wistar , Microtomografia por Raio-X
4.
NMR Biomed ; 31(10): e3918, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29727498

RESUMO

Aging and degeneration are associated with changes in mechanical properties in the intervertebral disc, generating interest in the establishment of mechanical properties as early biomarkers for the degenerative cascade. Magnetic resonance elastography (MRE) of the intervertebral disc is usually limited to the nucleus pulposus, as the annulus fibrosus is stiffer and less hydrated. The objective of this work was to adapt high-frequency needle MRE to the characterization of the shear modulus of both the nucleus pulposus and annulus fibrosus. Bovine intervertebral discs were removed from fresh oxtails and characterized by needle MRE. The needle was inserted in the center of the disc and vibrations were generated by an amplified piezoelectric actuator. MRE acquisitions were performed on a 4.7-T small-animal MR scanner using a spin echo sequence with sinusoidal motion encoding gradients. Acquisitions were repeated over a frequency range of 1000-1800 Hz. The local frequency estimation inversion algorithm was used to compute the shear modulus. Stiffness maps allowed the visualization of the soft nucleus pulposus surrounded by the stiffer annulus fibrosus surrounded by the homogeneous gel. A significant difference in shear modulus between the nucleus pulposus and annulus fibrosus, and an increase in the shear modulus with excitation frequency, were observed, in agreement with the literature. This study demonstrates that global characterization of both the nucleus pulposus and annulus fibrosus of the intervertebral disc is possible with needle MRE using a preclinical magnetic resonance imaging (MRI) scanner. MRE can be a powerful method for the mapping of the complex properties of the intervertebral disc. The developed method could be adapted for in situ use by preserving adjacent vertebrae and puncturing the side of the intervertebral disc, thereby allowing an assessment of the contribution of osmotic pressure to the mechanical behavior of the intervertebral disc.


Assuntos
Anel Fibroso/fisiologia , Técnicas de Imagem por Elasticidade , Imageamento por Ressonância Magnética , Núcleo Pulposo/fisiologia , Animais , Fenômenos Biomecânicos , Bovinos , Humanos , Análise de Regressão , Resistência ao Cisalhamento
5.
Int J Oral Maxillofac Surg ; 47(5): 665-671, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29246424

RESUMO

The aim of this study was to compare the volumetric changes and the new bone microarchitecture in human maxillary sinuses augmented with bioactive glass (Biogran) alone, bioactive glass combined with autogenous bone graft (1:1), or autogenous bone graft alone. Twelve maxillary sinuses were grafted with bioactive glass (group 1), nine with bioactive glass mixed with autogenous bone graft 1:1 (group 2), and 12 with autogenous bone graft (group 3). Patients underwent cone beam computed tomography 15days after the procedure to determine the initial volume of the graft (T1) and again 6 months later (T2). Biopsies were obtained at the time of dental implant placement and were subjected to micro-computed tomography. The volumetric change was 44.2% in group 1, 37.9% in group 2, and 45.7% in group 3 (P>0.05). The trabecular microarchitecture results showed that the materials used in groups 1 and 2 were good bone substitutes. However, the addition of 50% bioactive glass to autogenous bone graft improved the microarchitecture of the graft. Furthermore, the results for volumetric changes indicated that bioactive glass, its association with autogenous bone graft in a 1:1 ratio, and autogenous bone graft alone have similar resorption.


Assuntos
Materiais Biocompatíveis/uso terapêutico , Transplante Ósseo/métodos , Implantação Dentária Endo-Óssea/métodos , Implantes Dentários , Vidro , Levantamento do Assoalho do Seio Maxilar/métodos , Adulto , Biópsia , Tomografia Computadorizada de Feixe Cônico , Feminino , Humanos , Masculino , Maxila/diagnóstico por imagem , Maxila/cirurgia , Estudos Prospectivos , Resultado do Tratamento , Microtomografia por Raio-X
6.
J Mech Behav Biomed Mater ; 79: 30-37, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29253729

RESUMO

The mechanical properties of brain tissue, particularly those of white matter (WM), need to be characterized accurately for use in finite element (FE) models of brain biomechanics and traumatic brain injury (TBI). Magnetic resonance elastography (MRE) is a powerful tool for non-invasive estimation of the mechanical properties of soft tissues. While several studies involving direct mechanical tests of brain tissue have shown mechanical anisotropy, most MRE studies of brain tissue assume an isotropic model. In this study, an incompressible transversely isotropic (TI) material model parameterized by minimum shear modulus (µ2), shear anisotropy parameter (ϕ), and tensile anisotropy parameter (ζ) is applied to analyze MRE measurements of ex vivo porcine white matter (WM) brain tissue. To characterize shear anisotropy, "slow" (pure transverse) shear waves were propagated at 100, 200 and 300Hz through sections of ex vivo brain tissue including both WM and gray matter (GM). Shear waves were found to propagate with elliptical fronts, consistent with TI material behavior. Shear wave fields were also analyzed within regions of interest (ROI) to find local shear wavelengths parallel and perpendicular to fiber orientation. FE simulations of a TI material with a range of plausible shear modulus (µ2) and shear anisotropy parameters (ϕ) were run and the results were analyzed in the same fashion as the experimental case. Parameters of the FE simulations which most closely matched each experiment were taken to represent the mechanical properties of that particular sample. Using this approach, WM in the ex vivo porcine brain was found to be mildly anisotropic in shear with estimates of minimum shear modulus (actuation frequencies listed in parenthesis): µ2= 1.04 ± 0.12 kPa (at 100Hz), µ2= 1.94 ± 0.29 kPa (at 200Hz), and µ2= 2.88 ± 0.34 kPa (at 300Hz) and corresponding shear anisotropy factors of ϕ= 0.27 ± 0.09 (at 100Hz), ϕ= 0.29 ± 0.14 (at 200Hz) and ϕ= 0.34 ± 0.13 (at 300Hz). Future MRE studies will focus on tensile anisotropy, which will require both slow and fast shear waves for accurate estimation.


Assuntos
Encéfalo/diagnóstico por imagem , Técnicas de Imagem por Elasticidade , Imageamento por Ressonância Magnética , Substância Branca/diagnóstico por imagem , Animais , Anisotropia , Modelos Teóricos , Suínos
7.
Int J Oral Maxillofac Surg ; 46(4): 503-510, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28185708

RESUMO

The aim of this study was to compare the use of beta-tricalcium phosphate (ß-TCP) (chronOS) with autogenous bone grafts alone in maxillary sinus elevation surgery. The test samples were ß-TCP alone, ß-TCP mixed with autogenous bone grafts (1:1), and autogenous bone grafts alone. Twelve maxillary sinuses were grafted with ß-TCP (group 1), nine with ß-TCP+autogenous bone graft (group 2), and 12 with autogenous bone graft (group 3). After 6 months, biopsies were obtained concurrent to the placement of dental implants; these were subjected to histomorphometric analysis and immunohistochemical analysis for runt-related transcription factor 2 (RUNX2) and vascular endothelial growth factor (VEGF). The average bone formation in group 1 was 46.3±11.6% in the pristine bone region, 47.6±9.9% in the intermediate region, and 44.8±22.1% in the apical region; in group 2, values were 35.0±15.8%, 32.5±13.7%, and 32.8±16.0%, respectively; in group 3, values were 43.1±16.0%, 31.0±13.0%, and 46.1±16.3%, respectively. Immunostaining of samples in group 2 showed high cellular activity and immature bone; this differed from groups 1 and 3, in which mature bone was demonstrated. Thus, this study showed that ß-TCP presents the same behaviour as autogenous bone graft, which makes it a good bone substitute.


Assuntos
Substitutos Ósseos/uso terapêutico , Transplante Ósseo/métodos , Fosfatos de Cálcio/uso terapêutico , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Osteogênese/fisiologia , Levantamento do Assoalho do Seio Maxilar/métodos , Fator A de Crescimento do Endotélio Vascular/metabolismo , Feminino , Humanos , Imuno-Histoquímica , Masculino , Estudos Prospectivos , Resultado do Tratamento
8.
Magn Reson Med ; 78(6): 2360-2372, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28097687

RESUMO

PURPOSE: To establish the essential requirements for characterization of a transversely isotropic material by magnetic resonance elastography (MRE). THEORY AND METHODS: Three methods for characterizing nearly incompressible, transversely isotropic (ITI) materials were used to analyze data from closed-form expressions for traveling waves, finite-element (FE) simulations of waves in homogeneous ITI material, and FE simulations of waves in heterogeneous material. Key properties are the complex shear modulus µ2 , shear anisotropy ϕ=µ1/µ2-1, and tensile anisotropy ζ=E1/E2-1. RESULTS: Each method provided good estimates of ITI parameters when both slow and fast shear waves with multiple propagation directions were present. No method gave accurate estimates when the displacement field contained only slow shear waves, only fast shear waves, or waves with only a single propagation direction. Methods based on directional filtering are robust to noise and include explicit checks of propagation and polarization. Curl-based methods led to more accurate estimates in low noise conditions. Parameter estimation in heterogeneous materials is challenging for all methods. CONCLUSIONS: Multiple shear waves, both slow and fast, with different propagation directions, must be present in the displacement field for accurate parameter estimates in ITI materials. Experimental design and data analysis can ensure that these requirements are met. Magn Reson Med 78:2360-2372, 2017. © 2017 International Society for Magnetic Resonance in Medicine.


Assuntos
Anisotropia , Encéfalo/diagnóstico por imagem , Técnicas de Imagem por Elasticidade , Imageamento por Ressonância Magnética , Algoritmos , Simulação por Computador , Análise de Elementos Finitos , Humanos , Processamento de Imagem Assistida por Computador , Resistência ao Cisalhamento , Razão Sinal-Ruído , Resistência à Tração
9.
Int J Oral Maxillofac Surg ; 46(2): 151-156, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27876532

RESUMO

This systematic review evaluated the efficacy of the morning fasting serum C-terminal telopeptide (CTX) test in predicting the development of bisphosphonate-related osteonecrosis of the jaw (BRONJ). A comprehensive search of studies published up to March 2016, and listed in the PubMed/MEDLINE, Web of Science, and Cochrane Library databases, was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. This review has been registered in the PROSPERO international prospective register of systematic reviews (CRD42016036717). The search identified 542 publications; eight studies were finally deemed eligible for inclusion according to the study criteria. These studies included a total 1442 patients (mean age 66.7 years). The most prescribed drug was alendronate, with osteoporosis being the most frequent indication for the prescription of bisphosphonates. Tooth extraction was the most common trigger for BRONJ. Of all patients evaluated after bisphosphonate treatment, only 24 (1.7%) developed BRONJ. All eight of the selected studies found that CTX levels were not predictive of the development of BRONJ. In conclusion, this systematic review indicates that the CTX test has no predictive value in determining the risk of osteonecrosis in patients taking bisphosphonates.


Assuntos
Osteonecrose da Arcada Osseodentária Associada a Difosfonatos/sangue , Colágeno Tipo I/sangue , Peptídeos/sangue , Humanos , Valor Preditivo dos Testes , Fatores de Risco , Extração Dentária/efeitos adversos
10.
Int J Oral Maxillofac Surg ; 45(12): 1570-1576, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27765427

RESUMO

The purpose of this systematic review was to perform a comparative analysis of the use or not of graft material in maxillary sinus lift surgery. Relevant studies published in the last 10 years were identified through a search of the PubMed/MEDLINE, ScienceDirect, and Cochrane Library databases and were assessed against the study inclusion and exclusion criteria. The initial search resulted in 1037 articles. After applying the inclusion and exclusion criteria, 16 articles remained. Four hundred and thirty-six patients were followed up over a postoperative period ranging from 6 months to 11 years. In total, 868 implants were installed in 397 maxillary sinuses. The implant survival rate was 96.00% for surgeries performed without graft material and 99.60% for those in which biomaterial was used, within a follow-up period of 48 to 60 months. In conclusion, maxillary sinus lift surgery, with or without graft material, is a safe procedure with a low complication rate and predictable results.


Assuntos
Transplante Ósseo , Implantação Dentária Endo-Óssea , Implantes Dentários , Seio Maxilar/cirurgia , Levantamento do Assoalho do Seio Maxilar/métodos , Seguimentos , Humanos
11.
Phys Med Biol ; 61(16): 6121-31, 2016 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-27461395

RESUMO

An accurate and noninvasive method for assessing treatment response following radiotherapy is needed for both treatment monitoring and planning. Measurement of solid tumor volume alone is not sufficient for reliable early detection of therapeutic response, since changes in physiological and/or biomechanical properties can precede tumor volume change following therapy. In this study, we use magnetic resonance elastography to evaluate the treatment effect after radiotherapy in a murine brain tumor model. Shear modulus was calculated and compared between the delineated tumor region of interest (ROI) and its contralateral, mirrored counterpart. We also compared the shear modulus from both the irradiated and non-irradiated tumor and mirror ROIs longitudinally, sampling four time points spanning 9-19 d post tumor implant. Results showed that the tumor ROI had a lower shear modulus than that of the mirror ROI, independent of radiation. The shear modulus of the tumor ROI decreased over time for both the treated and untreated groups. By contrast, the shear modulus of the mirror ROI appeared to be relatively constant for the treated group, while an increasing trend was observed for the untreated group. The results provide insights into the tumor properties after radiation treatment and demonstrate the potential of using the mechanical properties of the tumor as a biomarker. In future studies, more closely spaced time points will be employed for detailed analysis of the radiation effect.


Assuntos
Neoplasias Encefálicas/patologia , Técnicas de Imagem por Elasticidade/métodos , Glioblastoma/patologia , Processamento de Imagem Assistida por Computador/métodos , Animais , Neoplasias Encefálicas/radioterapia , Feminino , Glioblastoma/radioterapia , Camundongos , Camundongos Endogâmicos BALB C , Carga Tumoral
12.
J Biomech ; 49(7): 1042-1049, 2016 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-26920505

RESUMO

Mechanical anisotropy is an important property of fibrous tissues; for example, the anisotropic mechanical properties of brain white matter may play a key role in the mechanics of traumatic brain injury (TBI). The simplest anisotropic material model for small deformations of soft tissue is a nearly incompressible, transversely isotropic (ITI) material characterized by three parameters: minimum shear modulus (µ), shear anisotropy (ϕ=µ1µ-1) and tensile anisotropy (ζ=E1E2-1). These parameters can be determined using magnetic resonance elastography (MRE) to visualize shear waves, if the angle between the shear-wave propagation direction and fiber direction is known. Most MRE studies assume isotropic material models with a single shear (µ) or tensile (E) modulus. In this study, two types of shear waves, "fast" and "slow", were analyzed for a given propagation direction to estimate anisotropic parameters µ, ϕ, and ζ in two fibrous soft materials: turkey breast ex vivo and aligned fibrin gels. As expected, the speed of slow shear waves depended on the angle between fiber direction and propagation direction. Fast shear waves were observed when the deformations due to wave motion induced stretch in the fiber direction. Finally, MRE estimates of anisotropic mechanical properties in turkey breast were compared to estimates from direct mechanical tests.


Assuntos
Técnicas de Imagem por Elasticidade , Modelos Teóricos , Animais , Anisotropia , Elasticidade , Feminino , Fibrina/fisiologia , Géis , Glândulas Mamárias Animais/fisiologia , Fenômenos Mecânicos , Perus
13.
Int J Oral Maxillofac Surg ; 44(6): 798-805, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25813087

RESUMO

The aim of this study was to evaluate bone healing at the bone-implant interface in rats with induced osteoporosis. The rats underwent a bilateral ovariectomy (OVX) and were fed a low calcium and phosphate diet. The OVX rats were divided into three groups: one was treated with raloxifene (OVX-RAL), one with alendronate (OVX-ALE), and one received no medication (OVX-NT). The control group rats (SHAM-DN) underwent sham surgery and were fed a normal diet. Each animal received one implant in each tibia: a machined surface implant in the right tibia and an implant with surface etching in the left tibia. All animals were euthanized after 42 days. Analysis of variance (ANOVA) and Tukey post hoc tests were applied to the biomechanics (reverse torque) and bone-implant contact (BIC) data (P<0.05). The RAL and ALE groups showed improved peri-implant bone healing. However, the ALE group showed no significant difference from the OVX-NT group. Surface treatment promoted higher corticalization at the bone-implant interface, but showed the same characteristics of mature bone and bone neoformation in concentric laminations as the machined implant. There were no statistically significant differences in reverse torque (P=0.861) or BIC (P=0.745) between the OVX-RAL and SHAM-DN groups. Therefore, the use of raloxifene resulted in good biomechanical, BIC, and histological findings in the treatment of induced osteoporosis in rats.


Assuntos
Conservadores da Densidade Óssea/farmacologia , Implantes Dentários , Implantes Experimentais , Osteoporose/tratamento farmacológico , Cloridrato de Raloxifeno/farmacologia , Tíbia/cirurgia , Alendronato/farmacologia , Animais , Densidade Óssea/efeitos dos fármacos , Feminino , Microscopia Confocal , Ovariectomia , Ratos , Ratos Wistar
14.
Phys Biol ; 10(1): 016005, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23357794

RESUMO

In humans and many other mammals, the cortex (the outer layer of the brain) folds during development. The mechanics of folding are not well understood; leading explanations are either incomplete or at odds with physical measurements. We propose a mathematical model in which (i) folding is driven by tangential expansion of the cortex and (ii) deeper layers grow in response to the resulting stress. In this model the wavelength of cortical folds depends predictably on the rate of cortical growth relative to the rate of stress-induced growth. We show analytically and in simulations that faster cortical expansion leads to shorter gyral wavelengths; slower cortical expansion leads to long wavelengths or even smooth (lissencephalic) surfaces. No inner or outer (skull) constraint is needed to produce folding, but initial shape and mechanical heterogeneity influence the final shape. The proposed model predicts patterns of stress in the tissue that are consistent with experimental observations.


Assuntos
Córtex Cerebral/fisiologia , Animais , Córtex Cerebral/crescimento & desenvolvimento , Módulo de Elasticidade , Furões , Modelos Neurológicos
15.
J Biomech ; 46(5): 863-70, 2013 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-23352648

RESUMO

Characterization of the dynamic mechanical behavior of brain tissue is essential for understanding and simulating the mechanisms of traumatic brain injury (TBI). Changes in mechanical properties may also reflect changes in the brain due to aging or disease. In this study, we used magnetic resonance elastography (MRE) to measure the viscoelastic properties of ferret brain tissue in vivo. Three-dimensional (3D) displacement fields were acquired during wave propagation in the brain induced by harmonic excitation of the skull at 400 Hz, 600 Hz and 800 Hz. Shear waves with wavelengths in the order of millimeters were clearly visible in the displacement field, in strain fields, and in the curl of displacement field (which contains no contributions from longitudinal waves). Viscoelastic parameters (storage and loss moduli) governing dynamic shear deformation were estimated in gray and white matter for these excitation frequencies. To characterize the reproducibility of measurements, two ferrets were studied on three different dates each. Estimated viscoelastic properties of white matter in the ferret brain were generally similar to those of gray matter and consistent between animals and scan dates. In both tissue types G' increased from approximately 3 kPa at 400 Hz to 7 kPa at 800 Hz and G″ increased from approximately 1 kPa at 400 Hz to 2 kPa at 800 Hz. These measurements of shear wave propagation in the ferret brain can be used to both parameterize and validate finite element models of brain biomechanics.


Assuntos
Envelhecimento , Lesões Encefálicas , Encéfalo , Imageamento por Ressonância Magnética , Modelos Biológicos , Animais , Fenômenos Biomecânicos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiopatologia , Lesões Encefálicas/diagnóstico por imagem , Lesões Encefálicas/fisiopatologia , Elasticidade , Feminino , Furões , Radiografia
16.
Arzneimittelforschung ; 62(11): 537-44, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22972470

RESUMO

G protein-coupled receptor 119 (GPCR 119 (GPR119)) agonists have received considerable attention as a promising therapeutic option for treatment of type 2 diabetes mellitus. GPR119 is one of the GPCRs expressed in pancreatic islet ß-cells and its activation enhances stimulation of insulin secretion in a glucose-dependent manner. We have recently described a series of 6-amino-1H-indan-1-ones as potent, selective, and orally bioavailable GPR119 agonists with an amino group that plays important roles not only in their drug-like properties, such as high aqueous solubility, but also in their potent agonistic activity. However, many of these compounds displayed strong to moderate inhibition of human ether-à-go-go related gene channel. Attenuation of the basicity of the amino group by replacing the adjacent benzene ring with electron-deficient heteroaromatic rings provided several heterocyclic cores among which 6-aminofuro[3,2-c]pyridin-3(2H)-one was selected as a promising scaffold. Further optimization around the side chain moiety led to the discovery of 17i, which showed not only strong human GPR119 agonistic activity (EC50=14 nM), but also beneficial effects on gastric emptying and plasma total glucagon-like peptide-1 levels in mice.


Assuntos
Hipoglicemiantes/síntese química , Piridonas/síntese química , Receptores Acoplados a Proteínas G/agonistas , Animais , Esvaziamento Gástrico/efeitos dos fármacos , Peptídeo 1 Semelhante ao Glucagon/sangue , Hipoglicemiantes/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Piridonas/farmacologia , Relação Estrutura-Atividade
17.
J Biomech Eng ; 134(6): 061004, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22757501

RESUMO

The mechanical characterization of soft anisotropic materials is a fundamental challenge because of difficulties in applying mechanical loads to soft matter and the need to combine information from multiple tests. A method to characterize the linear elastic properties of transversely isotropic soft materials is proposed, based on the combination of dynamic shear testing (DST) and asymmetric indentation. The procedure was demonstrated by characterizing a nearly incompressible transversely isotropic soft material. A soft gel with controlled anisotropy was obtained by polymerizing a mixture of fibrinogen and thrombin solutions in a high field magnet (B = 11.7 T); fibrils in the resulting gel were predominantly aligned parallel to the magnetic field. Aligned fibrin gels were subject to dynamic (20-40 Hz) shear deformation in two orthogonal directions. The shear storage modulus was 1.08 ± 0. 42 kPa (mean ± std. dev.) for shear in a plane parallel to the dominant fiber direction, and 0.58 ± 0.21 kPa for shear in the plane of isotropy. Gels were indented by a rectangular tip of a large aspect ratio, aligned either parallel or perpendicular to the normal to the plane of transverse isotropy. Aligned fibrin gels appeared stiffer when indented with the long axis of a rectangular tip perpendicular to the dominant fiber direction. Three-dimensional numerical simulations of asymmetric indentation were used to determine the relationship between direction-dependent differences in indentation stiffness and material parameters. This approach enables the estimation of a complete set of parameters for an incompressible, transversely isotropic, linear elastic material.


Assuntos
Elasticidade , Fibrina , Teste de Materiais/métodos , Resistência ao Cisalhamento , Anisotropia , Análise de Elementos Finitos , Géis , Humanos , Modelos Lineares , Rotação
18.
Oncol Lett ; 3(4): 807-815, 2012 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-22740998

RESUMO

Tyrosine kinase inhibitors (TKIs) have emerged as a promising class of agents against thyroid cancer. The aim of the present study was to investigate the in vitro and in vivo activity of dasatinib against a panel of thyroid cancer cell lines and explore possible mechanisms of action, using various assays and western blotting. Our results showed that dasatinib exhibits prominent cytostatic activity both in vitro and in vivo against thyroid cancer cell lines with RET/PTC rearrangement (BHP2-7) and KRAS mutation (Cal62). Although dasatinib has primarily been described as an ABL/SRCfamily kinase inhibitor, the cytostatic activity observed in the present study is mediated by several off-target effects of dasatinib, some of which have not previously been reported. These effects include a reduction in phospho-FAK, FAK, RAS, Caveolin and SYK protein levels and an increase in ß-catenin protein expression, which leads to the induction of senescence, an increase in the adhesiveness of the cells, a decrease in reactive oxygen species level, and changes in the expression profile of molecules involved in cellular adhesion such as integrins. Therefore, we propose that dasatinib is an effective therapeutic agent for certain patients with thyroid cancer, and these candidate patients may be identifiable on the basis of standard genotypic analyses.

19.
Phys Med Biol ; 56(19): 6379-400, 2011 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-21908903

RESUMO

Magnetic resonance elastography (MRE) is used to quantify the viscoelastic shear modulus, G*, of human and animal tissues. Previously, values of G* determined by MRE have been compared to values from mechanical tests performed at lower frequencies. In this study, a novel dynamic shear test (DST) was used to measure G* of a tissue-mimicking material at higher frequencies for direct comparison to MRE. A closed-form solution, including inertial effects, was used to extract G* values from DST data obtained between 20 and 200 Hz. MRE was performed using cylindrical 'phantoms' of the same material in an overlapping frequency range of 100-400 Hz. Axial vibrations of a central rod caused radially propagating shear waves in the phantom. Displacement fields were fit to a viscoelastic form of Navier's equation using a total least-squares approach to obtain local estimates of G*. DST estimates of the storage G' (Re[G*]) and loss modulus G″ (Im[G*]) for the tissue-mimicking material increased with frequency from 0.86 to 0.97 kPa (20-200 Hz, n = 16), while MRE estimates of G' increased from 1.06 to 1.15 kPa (100-400 Hz, n = 6). The loss factor (Im[G*]/Re[G*]) also increased with frequency for both test methods: 0.06-0.14 (20-200 Hz, DST) and 0.11-0.23 (100-400 Hz, MRE). Close agreement between MRE and DST results at overlapping frequencies indicates that G* can be locally estimated with MRE over a wide frequency range. Low signal-to-noise ratio, long shear wavelengths and boundary effects were found to increase residual fitting error, reinforcing the use of an error metric to assess confidence in local parameter estimates obtained by MRE.


Assuntos
Técnicas de Imagem por Elasticidade/métodos , Modelos Teóricos , Animais , Elasticidade , Técnicas de Imagem por Elasticidade/instrumentação , Gelatina/química , Glicerol/química , Humanos , Análise dos Mínimos Quadrados , Imagens de Fantasmas , Distribuição de Poisson , Resistência ao Cisalhamento , Razão Sinal-Ruído , Estresse Mecânico , Vibração , Viscosidade
20.
Biophys J ; 100(11): 2716-25, 2011 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-21641317

RESUMO

The distributed propulsive forces exerted on the flagellum of the swimming alga Chlamydomonas reinhardtii by surrounding fluid were estimated from experimental image data. Images of uniflagellate mutant Chlamydomonas cells were obtained at 350 frames/s with 125-nm spatial resolution, and the motion of the cell body and the flagellum were analyzed in the context of low-Reynolds-number fluid mechanics. Wild-type uniflagellate cells, as well as uniflagellate cells lacking inner dynein arms (ida3) or outer dynein arms (oda2) were studied. Ida3 cells exhibit stunted flagellar waveforms, whereas oda2 cells beat with lower frequency. Image registration and sorting algorithms provided high-resolution estimates of the motion of the cell body, as well as detailed kinematics of the flagellum. The swimming cell was modeled as an ellipsoid in Stokes flow, propelled by viscous forces on the flagellum. The normal and tangential components of force on the flagellum (f(N) and f(T)) were related by resistive coefficients (C(N) and C(T)) to the corresponding components of velocity (V(N) and V(T)).The values of these coefficients were estimated by satisfying equilibrium requirements for force and torque on the cell. The estimated values of the resistive coefficients are consistent among all three genotypes and similar to theoretical predictions.


Assuntos
Chlamydomonas reinhardtii/citologia , Flagelos/metabolismo , Fenômenos Mecânicos , Movimento , Algoritmos , Proteínas de Bactérias/metabolismo , Fenômenos Biomecânicos , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/metabolismo , Dineínas/metabolismo , Genótipo , Hidrodinâmica , Cinética , Mutação
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