Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 34.286
Filtrar
1.
Adv Exp Med Biol ; 1146: 13-29, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31612451

RESUMO

The development of traction-force microscopy, in the past two decades, has created the unprecedented opportunity of performing direct mechanical measurements on living cells as they adhere or crawl on uniform or micro-patterned substrates. Simultaneously, this has created the demand for a theoretical framework able to decipher the experimental observations, shed light on the complex biomechanical processes that govern the interaction between the cell and the extracellular matrix and offer testable predictions. Contour models of cellular adhesion, represent one of the simplest and yet most insightful approach in this problem. Rooted in the paradigm of active matter, these models allow to explicitly determine the shape of the cell edge and calculate the traction forces experienced by the substrate, starting from the internal and peripheral contractile stresses as well as the passive restoring forces and bending moments arising within the actin cortex and the plasma membrane. In this chapter I provide a general overview of contour models of cellular adhesion and review the specific cases of cells equipped with isotropic and anisotropic actin cytoskeleton as well as the role of bending elasticity.


Assuntos
Adesão Celular , Modelos Biológicos , Citoesqueleto de Actina , Animais , Elasticidade
2.
Handchir Mikrochir Plast Chir ; 51(5): 384-393, 2019 Sep.
Artigo em Alemão | MEDLINE | ID: mdl-31574553

RESUMO

BACKGROUND: Burn scars are a serious psychological and physiological problem for affected individuals. Clinical studies and scientific research have shown that Medical Needling improves scar quality in terms of skin elasticity, moisture, transepidermal water loss and erythema. At the same time, patients are confronted with a comparatively low-risk therapy without any postoperative complications. OBJECTIVE: The goal of our study was to examine the influence of Medical Needling on mature hypertrophic scars with regard to skin elasticity and tension. A total of 20 patients with an average age of 34.6 years and second or third-degree burn scars were treated. Scars that were at least 2 years old and had healed by secondary intention met the criteria for inclusion in the study. METHODS: Medical Needling is performed using a roller covered with needles of 3 mm length. The needling device is rolled over the scar in three directions: vertically, horizontally and diagonally. The procedure of puncture leads to multiple micro wounds and intradermal bleeding, which induces the post needling regeneration cascade. The patients were followed up for 12 months postoperatively. The results were evaluated by means of objective and subjective measurement methods. RESULTS: Objective measurements show that Medical Needling improves pathological values of skin tension and elasticity. Depending on the scarring, a reduction in tension or an increased tightness of overstrained and lax skin was recorded. Rigid scars gained vital features and profited from a physiological degree of elasticity. CONCLUSION: Medical Needling proves to be a promising approach for the treatment of mature hypertrophic scars with pathological changes of skin elasticity and tension.


Assuntos
Queimaduras , Cicatriz Hipertrófica , Adulto , Queimaduras/terapia , Cicatriz , Cicatriz Hipertrófica/terapia , Elasticidade , Feminino , Humanos , Masculino , Agulhas , Pele
3.
Soft Matter ; 15(33): 6630-6641, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31403143

RESUMO

The mechanics of blister delamination and growth plays a major role in a diversity of areas including medicine (skin pathology and mechanics of cell membranes), materials (adhesive and fracture) or soft robotics (actuation and morphing). The behavior of a blister in this context is typically difficult to grasp as it arises from the interplay of two highly nonlinear and time-dependent processes: membrane attachment and decohesion from a substrate. In the present work, we device a simplified approach, based on experimental systems, to predict the deformation path of a blister under various conditions. For this, we consider the problem of a growing blister made of a rubber-like membrane adhered on a rigid substrate, and develop a theoretical and experimental framework to study its stability and growth. We start by constructing a theoretical model of viscoelastic blister growth which we later validate with an experimental setup. We show that blister growth is controlled by the competition between two instabilities: one inherent to the rubber, and a second one pertaining to the adhesion with the substrate. Using these concepts, we show that a "targeted" stable blister shape can be achieved by controlling two parameters: the thickness of the film and the inflation rate.


Assuntos
Simulação por Computador , Membranas Artificiais , Modelos Teóricos , Adsorção , Elasticidade , Cinética , Propriedades de Superfície , Termodinâmica , Viscosidade
4.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(4): 613-618, 2019 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-31441262

RESUMO

Study of the mechanical properties of in vivo corneal materials is an important basis for further study of corneal physiological and pathological phenomena by means of finite element method. In this paper, the elastic coefficient ( E) and viscous coefficient ( η) of normal cornea and keratoconus under pulse pressure are calculated by using standard linear solid model with the data provided by corneal visualization scheimpflug technology. The results showed that there was a significant difference of E and η between normal cornea and keratoconus cornea ( P < 0.05). Receiver operating characteristic curve analysis showed that the area under curve (AUC) for E, η and their combined indicators were 0.776, 0.895 and 0.948, respectively, which indicated that keratoconus could be predicted by E and η. The results of this study may provide a reference for the early diagnosis of keratoconus and avoid the occurrence of keratoconus after operation, so it has a certain clinical value.


Assuntos
Córnea/fisiologia , Elasticidade , Ceratocone/patologia , Viscosidade , Área Sob a Curva , Humanos , Curva ROC
5.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(4): 619-626, 2019 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-31441263

RESUMO

Aiming at the problem of the influence of preloading force on its mechanical response in soft tissue compression experiments, an elimination method of preloading force based on linear loading region is proposed. Unconfined compression experiments under a variety of different preloading forces are performed. The influence of the preloading force on the parameters of constitutive model is analyzed. In the preload phase, the mechanical response of the soft tissue is taken as a linear model. The preloading force is eliminated by taking the preloading phase into account throughout the response process. According to five different preloading forces of the unconfined compression experiments, the elimination method is validated with two different constitutive models of soft tissue, and the error between the models obtained by the preloading force elimination method and the traditional method with the experimental results is compared. The results show that the error obtained by preloading force elimination method is significantly smaller than the traditional method. The preloading force elimination method can eliminate the influence of preloading force on mechanical response to a certain extent, and constitutive model parameters which are closer to the true properties of soft tissue can be obtained.


Assuntos
Modelos Biológicos , Pressão , Elasticidade , Modelos Lineares , Estresse Mecânico
6.
BMC Ophthalmol ; 19(1): 172, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31391006

RESUMO

BACKGROUND: To evaluate corneal biomechanical properties by the Ocular Response Analyzer (ORA) in non keratoconic patients underwent penetrating keratoplasty (PK). METHODS: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann- correlated intraocular pressure (IOPg), cornea-compensated IOP (IOPcc) using the ORA, and central graft thickness (CGT) were measured in 30 eyes at least two years after penetrating keratoplasty for non keratoconic indications. IOP using the Goldmann applanation tonometer (GAT) was also obtained after compensation for graft thickness and astigmatism. RESULTS: The mean age of patients was 33.1 ± 10.13 years; indications for PK were herpetic corneal scar (53.3%), corneal stromal dystrophy (23.3%), traumatic corneal opacity (10%), chemical corneal opacity (6.7%), and Fuchs endothelial dystrophy (6.7%). Mean CH and CRF were 8.52 ± 1.81 mmHg, and 8.56 ± 1.59 mmHg, respectively. Mean CGT was 532.43 ± 30 µm. Mean IOP GAT, IOPg, and IOPcc were 11.88 ± 3.66, 14.64 ± 4.08, and 17.27 ± 4.60 mmHg, respectively (P < 0.001). No significant association was found between CGT and IOP readings obtained using either the ORA or GAT. There were significant negative association between CH with both IOP GAT and IOPcc, while CRF had significant positive association with IOPg. CONCLUSION: After penetrating keratoplasty for non keratoconic patients, graft biomechanics does not return to average values even 2 years after the operation; moreover, intraocular pressure measurement with ORA gives higher values than thickness compensated GAT.


Assuntos
Córnea/fisiopatologia , Opacidade da Córnea/cirurgia , Distrofia Endotelial de Fuchs/cirurgia , Pressão Intraocular/fisiologia , Ceratoplastia Penetrante/métodos , Adulto , Idoso , Córnea/cirurgia , Opacidade da Córnea/fisiopatologia , Estudos Transversais , Elasticidade , Feminino , Seguimentos , Distrofia Endotelial de Fuchs/fisiopatologia , Humanos , Ceratocone , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Tempo , Tonometria Ocular/métodos , Acuidade Visual , Adulto Jovem
7.
Cesk Slov Oftalmol ; 75(1): 14-24, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31382752

RESUMO

BACKGROUND: Shear wave elastography (SWE) is an imaging modality using advantage of ultrasound to detect differences of elastic properties (mechanical rigidity) of tissues. SWE increasingly develops across medical specialities and is already used in hematology, urology and oncology. In the field of ophthalmology using SWE to evaluate corneal mechanical properties, peripapillary biomechanical qualities in glaucoma patients several papers were published Also SWE ultrasound mechanical specificity safety studies were published. Aim of this work is to review SWE technique and its potentional using during examination in patients with endocrine orbitopathy (EO). In practical part of this work is evaluated the elasticity of oculomotor rectus muscles in healthy population, in patients with EO in early stage of disease (oculomotor muscles oedema) and in patients with EO in terminal stage of this disease (oculomotor muscles fibrosis) is determinate. Also possibility of using SWE (in comparison with standard ultrasound examination) for measuring thickness of oculomotor muscles is evaluated. METHODS: There were 60 eyes in 30 patients with EO examined and the elasticity of oculomotor muscles was determined. Results were compared with values of elasticity in 40 eyes in healthy population of 20 people. All measurements were performed with ultrasonic system Aixplorer of SuperSonic manufacturer in standardized terms and been undertaken by the same performer. Each value was measured several times to reduce measurement errors. RESULTS: Oculomotor rectus muscle elasticity values in healthy population measured by using SWE were as follows: musculus rectus superior (MRS) 19.7 ± 3.2 kPa, musculus rectus medialis (MRM) 20.5 ± 3.6 kPa, musculus rectus inferior (MRI) 20.4 ± 3.1 kPa and musculus rectus temporalis (MRT) 20.2 ± 1.7 kPa. As statistical analysis shows, there is no significant difference between muscles (ANOVA test p > 0.05); overall elasticity of oculomotor muscles in healthy population is 20.3 ± 3.0 kPa. Elasticity of muscles in group of EO patients in oedema stage and EO patients in fibrosis stage is 18.4 ± 3.2 kPa and 34.6 ± 7.5 kPa respectively. Both values show statistical significance in the comparison with healthy population (p.


Assuntos
Técnicas de Imagem por Elasticidade , Músculos Oculomotores , Elasticidade , Humanos , Músculos Oculomotores/diagnóstico por imagem , Músculos Oculomotores/fisiopatologia , Ultrassonografia
8.
Am J Dent ; 32(4): 165-168, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31436935

RESUMO

PURPOSE: To evaluate the biomechanical behavior of monolithic ceramic crowns with functional elasticity gradient. METHODS: Using a CAD software, a lower molar received a full-crown preparation (1.5 mm occlusal and axial reduction). The monolithic crown was modeled with a resin cement layer of 0.1 mm. Four groups were distributed according to the full crown elastic modulus (E) :(a) Bioinspired crown with decreasing elastic modulus (from 90 to 30GPa); (b) Crown with increasing elastic modulus (from 30 to 90 GPa); (c) Rigid crown (90 GPa) and (d) Flexible crown (30 GPa). The model was exported to the analysis software and meshed into 385.240 tetrahedral elements and 696.310 nodes. Materials were considered isotropic, linearly elastic, and homogeneous, with ideal contacts. A 300-N load was applied at the occlusal surface and the base of the model was fixed in all directions. The results were required in maximum principal stress criterion. RESULTS: Crowns consisting of layers with increasing elastic modulus presented intermediate results between the rigid and flexible crowns. Compared to the flexible crown, the bioinspired crown showed acceptable stress distribution across the structure with lower stress concentration in the tooth. In dental crowns the multilayer structure with functional elasticity gradient modifies the stress distribution in the restoration, with promising results for bioinspired design. CLINICAL SIGNIFICANCE: The manufacturing of posterior crowns with functional elasticity gradient should be considered due to its promising results on the stress concentration behavior.


Assuntos
Coroas , Cimentos de Resina , Porcelana Dentária , Planejamento de Prótese Dentária , Análise do Estresse Dentário , Módulo de Elasticidade , Elasticidade , Teste de Materiais , Dente Molar , Estresse Mecânico
9.
Phys Chem Chem Phys ; 21(34): 18422-18457, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31410425

RESUMO

Our review addresses how material properties emerge from atomistic-level interactions in the case of lipid membrane nanostructures. We summarize advances in solid-state nuclear magnetic resonance (NMR) spectroscopy in conjunction with alternative small-angle X-ray and neutron scattering methods for investigating lipid flexibility and dynamics. Solid-state 2H NMR is advantageous in that it provides atomistically resolved information about the order parameters and mobility of phospholipids within liquid-crystalline membranes. Bilayer deformation in response to external perturbations occurs over a range of length scales and allows one to disentangle how the bulk material properties emerge from atomistic forces. Examples include structural parameters such as the area per lipid and volumetric thickness together with the moduli for elastic deformation. Membranes under osmotic stress allow one to further distinguish collective undulations and quasielastic contributions from short-range noncollective effects. Our approach reveals how membrane elasticity involves length scales ranging from the bilayer dimensions on down to the size of the flexible lipid segments. Collective lipid interactions of the order of the bilayer thickness and less occur in the liquid-crystalline state. Emergence of lipid material properties is significant for models of lipid-protein forces acting on the mesoscopic length scale that play key roles in biomembrane functions.


Assuntos
Bicamadas Lipídicas/química , Espectroscopia de Ressonância Magnética/métodos , Nanoestruturas/química , Fosfolipídeos/química , Membrana Celular/química , Elasticidade , Cristais Líquidos/química , Proteínas de Membrana/química , Modelos Químicos , Nêutrons , Pressão Osmótica , Espalhamento de Radiação , Termodinâmica , Raios X
10.
Braz J Cardiovasc Surg ; 34(4): 451-457, 2019 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-31454199

RESUMO

OBJECTIVE: To evaluate the aortic wall elasticity using the maximal rate of systolic distension (MRSD) and maximal rate of diastolic recoil (MRDR) and their correlation with the aortic size index (ASI). METHODS: Forty-eight patients with thoracic aortic aneurysm were enrolled in this study. A standard magnetic resonance imaging (MRI) protocol was used to calculate MRSD and MRDR. Both MRSD and MRDR were expressed as percentile of maximal area/10-3 sec. ASI (maximal aortic diameter/body surface area) was calculated. A correlation between MRSD, MRDR, ASI, and the patient's age was performed using regression plot. RESULTS: A significant correlation between MRSD (t=-4,36; r2=0.29; P≤0.0001), MRDR (t=3.92; r2=0.25; P=0.0003), and ASI (25±4.33 mm/m2; range 15,48-35,14 mm/m2) is observed. As ASI increases, aortic MRSD and MRDR decrease. Such inverse correlation between MRSD, MRDR, and ASI indicates increased stiffness of the ascending aorta. A significant correlation between the patient's age and the decrease in MRSD and MRDR is observed. CONCLUSION: MRSD and MRDR are significantly correlated with ASI and the patient's age. They seem to describe properly the increasing stiffness of aortas. These two new indexes provide a promising, accessible, and reproducible approach to evaluate the biomechanical property of the aorta.


Assuntos
Aneurisma Dissecante/diagnóstico por imagem , Aorta/fisiopatologia , Aneurisma da Aorta Torácica/diagnóstico por imagem , Imagem por Ressonância Magnética , Adulto , Idoso , Diástole/fisiologia , Dilatação Patológica , Elasticidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sístole/fisiologia
11.
J Chem Theory Comput ; 15(8): 4660-4672, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31282669

RESUMO

DNA cyclization is a powerful technique to gain insight into the nature of DNA bending. While the wormlike chain model provides a good description of small to moderate bending fluctuations, it is expected to break down for large bending. Recent cyclization experiments on strongly bent shorter molecules indeed suggest enhanced flexibility over and above that expected from the wormlike chain. Here, we use a coarse-grained model of DNA to investigate the subtle thermodynamics of DNA cyclization for molecules ranging from 30 to 210 base pairs. As the molecules get shorter, we find increasing deviations between our computed equilibrium j-factor and the classic wormlike chain predictions of Shimada and Yamakawa for a torsionally aligned looped molecule. These deviations are due to sharp kinking, first at nicks, and only subsequently in the body of the duplex. At the shortest lengths, substantial fraying at the ends of duplex domains is the dominant method of relaxation. We also estimate the dynamic j-factor measured in recent FRET experiments. We find that the dynamic j-factor is systematically larger than its equilibrium counterpart-with the deviation larger for shorter molecules-because not all the stress present in the fully cyclized state is present in the transition state. These observations are important for the interpretation of recent cyclization experiments, suggesting that measured anomalously high j-factors may not necessarily indicate non-WLC behavior in the body of duplexes.


Assuntos
DNA Circular/química , Pareamento de Bases , Ciclização , Elasticidade , Modelos Moleculares , Método de Monte Carlo , Conformação de Ácido Nucleico , Termodinâmica
12.
J Forensic Leg Med ; 66: 120-128, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31299484

RESUMO

PURPOSE: A series of studies suggest that non-Hispanic White women have significantly more injuries than non-Hispanic Black women after sexual assault and consensual sexual intercourse. One explanation for this difference is that the degree of skin protection may vary as skin mechanics and skin pigmentation vary. The aim of the study was to determine the association among genital-anal injury, skin color, skin viscoelasticity and skin hydration in women following consensual sexual intercourse when controlling for age, smoking history, body mass index (BMI), sun exposure, and health status. PROCEDURES: We employed a prospective cohort study design to enroll women 21 years of age or older at two study sites. They underwent two data collection sessions, baseline and follow-up after consensual sexual intercourse. Baseline genital-anal injury identification occurred with a standard forensic examination (direct visualization, nuclear staining with toluidine blue contrast, and colposcopy examination) and measurements of other variables (skin color, skin viscoelasticity, skin hydration, age, smoking history, body mass index [BMI], sun exposure, and health status). Participants were then asked to have consensual sexual intercourse with a male partner of their choice and to return for a second forensic examination for injury detection. Genital-anal injury was regressed on skin color, skin viscoelasticity, skin hydration, age, smoking history, BMI, sun exposure, and health status. FINDINGS: We enrolled 341 participants, 88 non-Hispanic White (25.8%), 54 non-Hispanic Black (15.8%), 190 Hispanic/Latina (55.7), and 9 Other Identities (2.6%). At baseline the genital-anal injury prevalence was 57.77% and at follow-up after consensual sexual intercourse, injury prevalence was 72.73%. External genital injury prevalence was associated with increased L* (lightness) values (Adjusted Odds Ratio [AOR] = 1.98, 95% Confidence Interval [CI] = 1.03, 4.04) and decreased skin elasticity (AOR = 0.96, 95% CI = 0.93, 0.99) at baseline. Increased skin hydration was associated with a significantly higher frequency of external, internal, anal, and total genital-anal injuries (Adjusted Rate Ratio [ARR] > 1.27) at follow-up. Also at the follow-up examination, Hispanic/Latina participants had significantly lower external genital and total genital-anal injury prevalence and frequency as compared to non-Hispanic White participants (AOR < 0.40). CONCLUSIONS: Our findings provide qualified support for the importance of skin color during the forensic examination. Women with lighter skin tones may have skin that is more easily injured than women with darker tones. In contrast, external genital injuries may be more easily identified in women with light as compared to dark skin, a situation that is important in both the health care and criminal justice systems. Additionally, women with decreased viscoelasticity and increased hydration may be more easily injured. These findings support the need to develop forensic procedures that are effective in people across the range of skin colors and to interpret forensic findings considering the innate properties of the skin.


Assuntos
Canal Anal/lesões , Coito , Elasticidade/fisiologia , Genitália Feminina/lesões , Fenômenos Fisiológicos da Pele , Pigmentação da Pele/fisiologia , Adulto , Canal Anal/fisiopatologia , Fenômenos Biomecânicos/fisiologia , Estudos de Coortes , Colposcopia , Grupos de Populações Continentais , Feminino , Medicina Legal , Genitália Feminina/fisiopatologia , Nível de Saúde , Humanos
13.
Medicine (Baltimore) ; 98(28): e16464, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31305479

RESUMO

Atherosclerosis is the primary etiological factor associated with acute coronary syndrome (ACS). Kidneys have a highly arterial vascular structure and are therefore commonly affected by atherosclerosis, including those affecting the coronary arteries. Renal shear wave elastography (SWE) is an ultrasonographic method, which provides reliable information regarding the condition of the renal parenchyma.We investigated the relationship between SWE findings and the severity of coronary atherosclerosis.We calculated the following: the renal cortical stiffness (rCS) evaluated via SWE, the renal resistive index, the renal pulsatility index, the acceleration time, and the mean Syntax score (SS). Patients with a mean SS <12 were categorized into a low-risk (LR) and those with a mean SS ≥12 were categorized into the high-risk (HR) group.Our study included 132 patients-76 in the LR and 56 in the HR group. Creatinine, high-sensitivity C-reactive protein (hs-CRP), and rCS were significantly higher, but the glomerular filtration rate (GFR) was significantly lower in the HR group. The Hs-CRP (odds ratio [OR] 1.220), GFR (OR 0.967), and rCS (OR 1.316) were observed to be independent predictors for the HR group. The cutoff value of rCS using receiver-operating characteristic curve analysis was 4.43 for the prediction of HR patients and showed 60.7% sensitivity and 57.9% specificity (area under the curve 0.642).SWE which shows renal parenchymal injury and atherosclerosis in renal vessels may give an idea about the severity of coronary atherosclerosis.


Assuntos
Síndrome Coronariana Aguda/diagnóstico , Aterosclerose/diagnóstico , Doença da Artéria Coronariana/diagnóstico , Técnicas de Imagem por Elasticidade , Córtex Renal/diagnóstico por imagem , Biomarcadores/sangue , Proteína C-Reativa/metabolismo , Angiografia Coronária , Creatinina/sangue , Elasticidade , Feminino , Taxa de Filtração Glomerular , Humanos , Córtex Renal/irrigação sanguínea , Masculino , Pessoa de Meia-Idade , Tecido Parenquimatoso/diagnóstico por imagem , Sensibilidade e Especificidade , Índice de Gravidade de Doença
14.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao ; 41(3): 383-387, 2019 Jun 30.
Artigo em Chinês | MEDLINE | ID: mdl-31282334

RESUMO

Objective To compare the values of elasticity imaging(EI)and Virtual Touch TM tissue imaging and quantification(VTIQ)in diagnosing thyroid nodules and explore the factors influencing the accuracy of these two techniques.Methods Totally 62 patients who were planned to receive surgery for thyroid nodules underwent conventional ultrasound,EI,and VTIQ examinations.EI patterns were scored according to the degree and distribution of strain,the strain of nodule and surrounding normal reference tissue were measured,and then strain index was calculated.Shear wave velocity in nodules were obtained under VTIQ mode.Results The nodules were malignant in 40 patients and benign in 22 patients.When the strain score of 3 was regarded as malignant,the diagnostic sensitivity,specificity,and accuracy of EI in detecting thyroid nodules were 90.00%,31.82%,and 69.32%,respectively.Receiver operating characteristic curve results showed that the area under curves of EI-SI and VTIQ methods for diagnosing thyroid nodules was 77.8%(95%CI:0.64-0.91)(P=0.000)and 74.3%(95%CI:0.62-0.87)(P=0.002),respectively.Thyroid nodules' characteristics location(P=0.04)and size(P=0.02)were correlated with the diagnostic accuracy of EI.The accuracy of SI and VTIQ were not affected by thyroid nodules' characteristics(P>0.05).Conclusions The diagnostic accuracy of EI for thyroid nodules is related to nodules' characteristics.EI combined with semi-quantitative SI and quantitative VTIQ can effectively improve the diagnostic capability for thyroid nodules.


Assuntos
Técnicas de Imagem por Elasticidade , Nódulo da Glândula Tireoide/diagnóstico por imagem , Realidade Virtual , Diagnóstico Diferencial , Elasticidade , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Ultrassonografia
15.
Nat Commun ; 10(1): 3056, 2019 07 11.
Artigo em Inglês | MEDLINE | ID: mdl-31296869

RESUMO

Lamin A is a nuclear intermediate filament protein critical for nuclear architecture and mechanics and mutated in a wide range of human diseases. Yet little is known about the molecular architecture of lamins and mechanisms of their assembly. Here we use SILAC cross-linking mass spectrometry to determine interactions within lamin dimers and between dimers in higher-order polymers. We find evidence for a compression mechanism where coiled coils in the lamin A rod can slide onto each other to contract rod length, likely driven by a wide range of electrostatic interactions with the flexible linkers between coiled coils. Similar interactions occur with unstructured regions flanking the rod domain during oligomeric assembly. Mutations linked to human disease block these interactions, suggesting that this spring-like contraction can explain in part the dynamic mechanical stretch and flexibility properties of the lamin polymer and other intermediate filament networks.


Assuntos
Proteínas de Filamentos Intermediários/metabolismo , Lamina Tipo A/metabolismo , Matriz Nuclear/metabolismo , Multimerização Proteica/fisiologia , Sequência de Aminoácidos/fisiologia , Animais , Cardiomiopatia Dilatada/genética , Reagentes para Ligações Cruzadas/química , Elasticidade , Humanos , Proteínas de Filamentos Intermediários/química , Proteínas de Filamentos Intermediários/genética , Proteínas de Filamentos Intermediários/isolamento & purificação , Lamina Tipo A/química , Lamina Tipo A/genética , Lamina Tipo A/isolamento & purificação , Espectrometria de Massas/métodos , Distrofias Musculares/genética , Mutação , Membrana Nuclear/metabolismo , Domínios Proteicos/genética , Estrutura Secundária de Proteína/fisiologia , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo
16.
Carbohydr Polym ; 219: 181-190, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31151515

RESUMO

Water-soluble fraction (WSF), CDTA-soluble fraction (CSF), sodium carbonate-soluble fraction (SSF), loosely-bonding KOH-soluble fractions (LKF) and tightly-bonding KOH-soluble fractions (TKF) were sequentially extracted from tomato cell wall polysaccharides. Physicochemical properties and functional bioactivities of these different bonding state tomato fruit polysaccharides (DBTP) were investigated. WSF, CSF and SSF were identified as pectic polysaccharides, while LKF and TKF were identified as hemicellulose. WSF, possessing plenty of galacturonic acids, was considered as an aggregative of linear homogalacturonan with extremely high molecular weight. CSF and SSF, rich in neutral sugars side chains, contained abundant rhamnogalacturonan regions. These polysaccharides exhibited distinct surface morphology and special FTIR spectrums. Thermal analysis manifested that LKF and TKF exhibited higher thermal stability. WSF and SSF showed higher apparent viscosity and elasticity. Assays for functional bioactivities suggested that CSF and SSF displayed stronger antioxidant activities, while CSF, SSF and TKF exhibited higher hypolipidemic activities.


Assuntos
Parede Celular/química , Frutas , Lycopersicon esculentum , Polissacarídeos , Antioxidantes/farmacologia , Elasticidade , Frutas/citologia , Frutas/metabolismo , Hipolipemiantes/farmacologia , Lycopersicon esculentum/citologia , Lycopersicon esculentum/metabolismo , Pectinas/química , Polissacarídeos/química , Polissacarídeos/isolamento & purificação , Polissacarídeos/farmacologia , Solubilidade , Viscosidade
17.
Soft Matter ; 15(27): 5511-5520, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31241632

RESUMO

Red blood cells in shear flow show a variety of different shapes due to the complex interplay between hydrodynamics and membrane elasticity. Malaria-infected red blood cells become generally adhesive and less deformable. Adhesion to a substrate leads to a reduction in shape variability and to a flipping motion of the non-spherical shapes during the mid-stage of infection. Here, we present a complete state diagram for wall adhesion of red blood cells in shear flow obtained by simulations, using a particle-based mesoscale hydrodynamics approach, multiparticle collision dynamics. We find that cell flipping at a substrate is replaced by crawling beyond a critical shear rate, which increases with both membrane stiffness and viscosity contrast between the cytosol and suspending medium. This change in cell dynamics resembles the transition between tumbling and tank-treading for red blood cells in free shear flow. In the context of malaria infections, the flipping-crawling transition would strongly increase the adhesive interactions with the vascular endothelium, but might be suppressed by the combined effect of increased elasticity and viscosity contrast.


Assuntos
Eritrócitos/citologia , Eritrócitos/fisiologia , Adesão Celular , Movimento Celular , Forma Celular , Simulação por Computador , Elasticidade , Membrana Eritrocítica/fisiologia , Cinética , Fenômenos Físicos , Resistência ao Cisalhamento , Estresse Mecânico , Propriedades de Superfície , Viscosidade
18.
Forensic Sci Int ; 301: 254-262, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31181409

RESUMO

Bloodstains can provide important information about a criminal act. These biological traces, when analyzed at murder sites, for example, can determine the dynamics of a criminal offense, the identity of a suspect, and the time at which a crime was committed. Determine the time since deposition (TSD) of these blood traces may be the first clue for the police investigators to estimate the time-lapse of a murder. During a criminal attack, the blood spilled from an injury begins the process of degradation and aging from the moment it leaves the human body and comes into contact with the physical environment. The biophysical properties (morphology and elasticity) of red blood cells (RBCs) undergo several changes when outside the human body, which can be analyzed using microscopic techniques such as atomic force microscopy (AFM). Aiming to apply the AFM/force spectroscopy techniques in the analysis of criminal traces, the present study investigated the TSD for blood smears by analyzing possible changes in the RBCs of a group of voluntary donors. Also, we investigated whether there was any difference in TSD analysis after blood smears deposition onto three different surfaces (glass, metal, or ceramic); and finally, we evaluated force×distance curves obtained from deformation of the membrane surface of RBCs as a function of time. The qualitative results apparently showed that there is no perceptible difference in the structure of RBCs when AFM images were analyzed by simple visual comparison over 28 days (T0-T5). Nevertheless, our quantitative results, measured by AFM, demonstrated the increasing trend of the measurements, such as average height (µm), perimeter (µm), area (µm2) and volume (µm3) of these cells during that period. Additionally, the type of surface of bloodstain deposition should be considered during analyses for the TSD, and the results obtained on glass, metal, or ceramic supports showed significant differences. Therefore, the use of force spectroscopy to obtain force×distance curves for the forensic science approach has been shown to have applicability for the calculation of TSD in the RBCs present in the blood smears. In spite of the promising observations obtained, the use of AFM in crime scenes still requires the expansion and development of more studies for a definitive evaluation of the TSD for blood spots.


Assuntos
Manchas de Sangue , Eritrócitos/ultraestrutura , Microscopia de Força Atômica , Adulto , Membrana Celular , Cerâmica , Elasticidade , Feminino , Medicina Legal/métodos , Vidro , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Metais , Software , Propriedades de Superfície , Fatores de Tempo , Adulto Jovem
19.
Cornea ; 38(8): 964-969, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31169608

RESUMO

PURPOSE: To evaluate the course of corneal biomechanical properties (corneal hysteresis and corneal resistance factor) after Descemet membrane endothelial keratoplasty (DMEK) in patients with Fuchs endothelial dystrophy (FECD). METHODS: In this prospective study, we consecutively included 49 patients with FECD with an indication for DMEK. Central corneal thickness, measured using the Oculus Pentacam, and corneal hysteresis (CH) and corneal resistance factor (CRF), both measured using the Reichert Ocular Response Analyzer, were examined preoperatively, 3 months, and 6 months after DMEK. RESULTS: CH was significantly increased 6 months postoperatively (8.66 ± 2.50 mm Hg) compared with preoperative baseline (7.43 ± 1.56 mm Hg). Preoperative CRF (7.89 ± 1.68 mm Hg) increased significantly 6 months after DMEK (8.49 ± 1.71 mm Hg). Preoperative central corneal thickness showed a significant decrease from 629 ± 58 µm to 550 ± 40 µm after 3 months and 535 ± 40 µm after 6 months postoperatively. CONCLUSIONS: DMEK affects both measured corneal biomechanical properties in patients with FECD: CH and CRF. This has to be taken into account for the accuracy of intraocular pressure measurements.


Assuntos
Córnea/fisiopatologia , Ceratoplastia Endotelial com Remoção da Lâmina Limitante Posterior , Elasticidade/fisiologia , Distrofia Endotelial de Fuchs/cirurgia , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos/fisiologia , Feminino , Distrofia Endotelial de Fuchs/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos
20.
Biophys Chem ; 251: 106146, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31158653

RESUMO

Review and analyses of the experimental data indicate that in nearly all cases bending elastic constants of the effective springs between bp of DNA actually undergo a net increase with increasing T from 278 to 315 K. The exceptions to this rule are bending elastic constants obtained from equilibrium topoisomer distributions of a 2686 bp pUC19 DNA by assuming a fixed T-independent value of the torsion elastic constant. When the same data are analyzed using measured T-dependent values of the torsion elastic constant, which decline with increasing T, a modest increase in bending elastic constant with increasing T is obtained. After revising the torsion elastic constants of the previously formulated two-state cooperative transition model to account for additional data, that model is fitted to the bending elastic constants reckoned from the aforementioned topoisomer distributions to determine the best-fit values for each state. The rather good fit implies a strong negative linear correlation between the inverse bending and inverse torsion elastic constants as T is varied. Predictions of the resulting two-state model, wherein each state has fixed bending and torsion elastic constants, agree surprisingly well with single-molecule relative extension and torque data. The same model also yields good agreement with numerous other experimental data. With increasing T the equilibrium is shifted from the (longer, torsionally stiffer, flexurally softer) b-state toward the (shorter, torsionally softer, flexurally stiffer) a-state. This transition is suggested to be the origin of the so-called broad pre-melting transition exhibited by many, but not all, DNAs.


Assuntos
DNA/química , Temperatura Ambiente , Elasticidade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA