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1.
J Dermatolog Treat ; 33(3): 1329-1338, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-32900254

RESUMO

BACKGROUND: Methotrexate (MTX) is frequently used in the treatment of moderate-to-severe psoriasis, however, there is limited data on health-related quality-of-life (HRQoL), psoriasis clinical outcomes and hepatic fibrosis in MTX-treated patients in routine clinical practice. OBJECTIVES: To investigate the impact of moderate-to-severe psoriasis in MTX-treated patients in Spain regarding to HRQoL, psoriasis clinical data and risk of hepatic fibrosis. METHODS: Observational, non-interventional, cross-sectional, retrospective, multicentre study, performed in Spain in moderate-to-severe plaque psoriasis patients treated with MTX > 16 weeks prior to inclusion. RESULTS: Despite ongoing treatment, 17.1% of 457 evaluable patients reported moderate-to-extreme impact on HRQoL (DLQI > 5); 21.4% BSA > 5 and 35.2% moderate-to-severe pruritus (VAS ≥ 4). Persistent severe psoriasis (PASI ≥ 10 and/or DLQI ≥ 10) was observed in 10.7%. Hepatic steatosis was identified in 64.1% of patients (HSI ≥ 36) and 37.2% of the patients were at-risk of advanced fibrosis which was associated to the MTX treatment duration. CONCLUSIONS: The study identified unmet needs in moderate-to-severe plaque psoriasis patients treated with MTX, revealing a significant proportion of sub-optimally controlled patients in terms of HRQoL and different domains of the disease. This study also found patients at-risk of advanced fibrosis, with evidence suggesting a correlation between longer exposures to MTX and higher risk of advanced fibrosis.


Assuntos
Fármacos Dermatológicos , Psoríase , Estudos Transversais , Fármacos Dermatológicos/efeitos adversos , Humanos , Cirrose Hepática , Metotrexato/uso terapêutico , Psoríase/induzido quimicamente , Psoríase/tratamento farmacológico , Qualidade de Vida , Estudos Retrospectivos , Índice de Gravidade de Doença , Resultado do Tratamento
2.
Actas dermo-sifiliogr. (Ed. impr.) ; 111(8): 655-664, oct. 2020. tab
Artigo em Espanhol | IBECS | ID: ibc-197151

RESUMO

ANTECEDENTES Y OBJETIVO: El cuestionario 4-item Psoriatic arthritis UnclutteRed screening Evaluation (PURE-4) puede considerarse una herramienta útil para identificar pacientes con posible artritis psoriásica y derivarlos al servicio de reumatología para confirmar el diagnóstico. La versión original en inglés presenta alta validez discriminatoria (85,7% de sensibilidad, 83,6% de especificidad). El objetivo de este trabajo es adaptarlo para población española como paso previo a su validación. MATERIAL Y MÉTODO: Se aplicó la metodología recomendada por la International Society Pharmacoeconomic and Outcome Research (ISPOR) para adaptaciones culturales de medidas centradas en el paciente. Fases: preparación, traducción, reconciliación, retrotraducción/revisión, armonización, test de comprensión/revisión, corrección de pruebas. RESULTADOS: En la preparación se obtuvo el permiso del autor del cuestionario original. Dos traductores nativos realizaron la traducción del cuestionario original al español. En la reconciliación se realizaron pequeñas modificaciones, principalmente en el enunciado de los ítems. Se realizó retrotraducción al inglés, logrando una versión equivalente al cuestionario original. La versión española derivada se administró en el test de comprensión a 7 pacientes, obteniéndose la versión final en español. Durante las traducciones, el responsable del proyecto y un comité científico formado por un dermatólogo y un reumatólogo revisaron las diferentes versiones. Los intercambios de información entre el equipo durante todo el proceso integraron la fase de armonización, siendo un control de calidad continuo que garantizó la equivalencia conceptual de las traducciones. CONCLUSIONES: La adaptación del cuestionario PURE-4 para población española constituye la primera etapa para su uso en práctica clínica habitual. La metodología estandarizada garantiza la equivalencia entre la versión española y la original


BACKGROUND AND OBJECTIVE: The 4-item Psoriatic arthritis UnclutteRed screening Evaluation (PURE-4) questionnaire is a useful tool for identifying patients with suspected psoriatic arthritis before referring them to a rheumatology department for confirmation. The original English version has good discriminant validity (sensitivity, 85.7%; specificity, 83.6%). We aimed to produce an adapted Spanish version of the PURE-4 for validation and use in Spain. MATERIAL AND METHOD: We applied the method recommended by the International Society for Pharmacoeconomic and Outcome Research for the cultural adaptation of patient-centered measurement tools. The phases in the processes involved forward translation, reconciliation, back translation review, harmonization, cognitive debriefing and review, and proofreading. RESULTS: We obtained the permission of the author of the original questionnaire. Two native-speaking translators translated the questionnaire into Spanish. Small changes, mainly in the way the items were expressed, were then made in order to reconcile the 2 translations. The questionnaire was then back translated to English and revised to achieve a version equivalent to the original. A Spanish translation derived from the revision was tested for understandability in 7 patients, and the final Spanish version was then produced. During the translation phases, the project manager and a scientific committee made up of a dermatologist and a rheumatologist reviewed the different versions. Team members exchanged information throughout the process, providing for harmonization and the quality control that guaranteed conceptual equivalence. CONCLUSIONS: This adaptation of the PURE-4 questionnaire for use in Spain has been the first step toward using it in routine clinical practice. The standardized method we used ensures that the Spanish and the original versions are equivalent


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Artrite Psoriásica/diagnóstico , Inquéritos e Questionários/normas , Traduções , Comparação Transcultural , Sensibilidade e Especificidade , Fatores Socioeconômicos , Reprodutibilidade dos Testes , Espanha
3.
Actas Dermosifiliogr (Engl Ed) ; 111(8): 655-664, 2020 Oct.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-32401721

RESUMO

BACKGROUND AND OBJECTIVE: The 4-item Psoriatic arthritis UnclutteRed screening Evaluation (PURE-4) questionnaire is a useful tool for identifying patients with suspected psoriatic arthritis before referring them to a rheumatology department for confirmation. The original English version has good discriminant validity (sensitivity, 85.7%; specificity, 83.6%). We aimed to produce an adapted Spanish version of the PURE-4 for validation and use in Spain. MATERIAL AND METHOD: We applied the method recommended by the International Society for Pharmacoeconomic and Outcome Research for the cultural adaptation of patient-centered measurement tools. The phases in the processes involved forward translation, reconciliation, back translation review, harmonization, cognitive debriefing and review, and proofreading. RESULTS: We obtained the permission of the author of the original questionnaire. Two native-speaking translators translated the questionnaire into Spanish. Small changes, mainly in the way the items were expressed, were then made in order to reconcile the 2 translations. The questionnaire was then back translated to English and revised to achieve a version equivalent to the original. A Spanish translation derived from the revision was tested for understandability in 7 patients, and the final Spanish version was then produced. During the translation phases, the project manager and a scientific committee made up of a dermatologist and a rheumatologist reviewed the different versions. Team members exchanged information throughout the process, providing for harmonization and the quality control that guaranteed conceptual equivalence. CONCLUSIONS: This adaptation of the PURE-4 questionnaire for use in Spain has been the first step toward using it in routine clinical practice. The standardized method we used ensures that the Spanish and the original versions are equivalent.


Assuntos
Artrite Psoriásica , Artrite Psoriásica/diagnóstico , Humanos , Linguística , Espanha , Inquéritos e Questionários , Traduções
4.
Sci Rep ; 5: 14820, 2015 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-26438975

RESUMO

The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers.


Assuntos
Seda/química , Seda/ultraestrutura , Aranhas , Animais , Evolução Biológica , Filogenia , Resistência à Tração , Difração de Raios X
5.
Phys Rev E Stat Nonlin Soft Matter Phys ; 90(5-1): 052715, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25493824

RESUMO

Mechanical deformability of cells is a key property that influences their ability to migrate and their contribution to tissue development and regeneration. We analyze here the possibility of characterizing the overall deformability of cells by their apparent viscosity, using a simplified method to estimate that parameter. The proposed method simplifies the quantitative analysis of micropipette-aspiration experiments. We have studied by this procedure the overall apparent viscosity of cardiac stem cells, which are considered a promising tool to regenerate damaged cardiac tissue. Comparison with the apparent viscosity of low-viscosity cells such as immune-system cells suggests that treatments to reduce the viscosity of these cells could enhance their ability to repair damaged cardiac tissue.

6.
Transplant Proc ; 46(10): 3629-36, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25498101

RESUMO

A significant proportion of transplant patients undergoing immunosuppressant therapy experience gastrointestinal (GI) symptoms. The SIGIT-QoL is a brief instrument developed to measure adverse gastrointestinal effects on patients' health-related quality of life (HRQoL). The goal of this study was to analyze the psychometric properties of the SIGIT-QoL that are required for its use in clinical research and practice, especially its value for detecting changes in the impact of gastrointestinal symptoms on HRQoL of solid organ transplant (SOT) recipients. To this end, an observational, multicenter, prospective study was conducted. SOT patients aged ≥18 years who had received the graft 3 to 24 months before and were experiencing gastrointestinal symptoms were evaluated at baseline, 1 to 2 weeks later, and 3 months after baseline. Sociodemographic and clinical data recorded included: age, sex, SOT type (lung, kidney, liver, or heart), acute allograft rejection, gastrointestinal etiology, Clinical Global Impressions (CGI) and Patient Global Impression (PGI) Severity of Illness (SI) and Global Improvement (GI) scores, and the SIGIT-QoL (scores range from 0 [maximum impact] to 68 [minimum disruption]). Intraclass correlation coefficients, differences between baseline and last visit (Wilcoxon test), effect size (Cohen's d), the minimal important differences (using CGI and PGI scores as anchors in General Linear Models), and the cutoff score (receiver-operating characteristic analysis) were calculated. In total, 277 SOT patients (61.4% male) were included. Mean ± SD age was 52.69 ± 11.65 years, time since transplantation was 12.31 ± 6.74 months, and 22.4% experienced an acute allograft rejection. At baseline, total SIGIT-QoL mean scores (51.21 ± 11.25) showed an impact on patients' HRQoL that was diminished 3 months later (57.40 ± 8.38; P < .001). SIGIT-QoL test-retest reliability was adequate (intraclass correlation coefficient, 0.740-0.895). A moderate effect size (d = -0.550) was found. Moreover, a minimal important difference of 4.2 points in total scores was found (F4,223 = 16.917 [P < .001] and F4,224 = 25.138 [P < .001]). Finally, a cutoff point (55.00 points) was estimated (area under the concentration-time curve, 0.846 [95% confidence interval, 0.798-0.894], P < .001; sensitivity, 0.793; specificity, 0.713; negative likelihood ratio, 0.290; positive likelihood ratio, 2.762). We concluded that the SIGIT-QoL is a feasible (average completion time, <6.5 minutes), reliable, and valid instrument for assessing the impact of gastrointestinal symptoms on the HRQoL of SOT patients.


Assuntos
Gastroenteropatias/psicologia , Transplante de Órgãos/efeitos adversos , Qualidade de Vida , Transplantados , Idoso , Feminino , Gastroenteropatias/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Psicometria , Reprodutibilidade dos Testes , Inquéritos e Questionários
7.
Transplant Proc ; 46(1): 14-20, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24507019

RESUMO

Chronic renal dysfunction (CRD) is a major complication after heart transplantation. We sought to describe the renal function over time, to assess the risk factors associated with CRD development, and to evaluate the clinical attitudes on diagnosis and treatment of CRD. A retrospective, cross-sectional, multicenter study was conducted in 13 outpatient clinics in Spain. A total of 244 heart recipients who survived more than 2 years after transplantation were included. Post-transplantation follow-up was 7.7 years (range: 2-22 years). CRD was diagnosed in 32.4% of patients at a mean of 3.3 years after transplantation. Serum creatinine increased 0.1 ± 0.2 mg/dL per year in CRD group compared with 0.0 ± 0.2 mg/dL per year in non-CRD group (P = .003) and glomerular filtration rate decreased -1.5 ± 4.3 mL/min/1.73 m(2) per year in CRD group versus -0.1 ± 4.8 mL/min/1.73 m(2) per year in non-CRD group (P = .027). After CRD diagnosis, major changes in immunosuppression based on calcineurin inhibitors reduction were instituted in 46.8% of patients. Multivariate model identified recipient age (P < .0001), female sex (P = .0398), and time since transplant (P < .0001) as predictors of CRD. In conclusion, the prevalence of CRD in long-term heart recipient survivors was quite high. CRD was associated with nonmodifiable factors (age, gender, and time since transplant).


Assuntos
Insuficiência Cardíaca/complicações , Transplante de Coração/efeitos adversos , Falência Renal Crônica/etiologia , Adulto , Idoso , Creatinina/sangue , Estudos Transversais , Feminino , Insuficiência Cardíaca/cirurgia , Humanos , Rim/fisiologia , Falência Renal Crônica/terapia , Masculino , Pessoa de Meia-Idade , Pacientes Ambulatoriais , Prevalência , Estudos Retrospectivos , Espanha , Fatores de Tempo , Resultado do Tratamento
8.
Sci Rep ; 3: 3061, 2013 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-24162473

RESUMO

Spider silks combine a significant number of desirable characteristics in one material, including large tensile strength and strain at breaking, biocompatibility, and the possibility of tailoring their properties. Major ampullate gland silk (MAS) is the most studied silk and their properties are explained by a double lattice of hydrogen bonds and elastomeric protein chains linked to polyalanine ß-nanocrystals. However, many basic details regarding the relationship between composition, microstructure and properties in silks are still lacking. Here we show that this relationship can be traced in flagelliform silk (Flag) spun by Argiope trifasciata spiders after identifying a phase consisting of polyglycine II nanocrystals. The presence of this phase is consistent with the dominant presence of the -GGX- and -GPG- motifs in its sequence. In contrast to the passive role assigned to polyalanine nanocrystals in MAS, polyglycine II nanocrystals can undergo growing/collapse processes that contribute to increase toughness and justify the ability of Flag to supercontract.


Assuntos
Nanopartículas/química , Peptídeos/química , Proteínas/química , Seda/química , Aranhas/metabolismo , Motivos de Aminoácidos , Animais , Ligação de Hidrogênio , Microscopia de Força Atômica , Proteínas/metabolismo , Seda/metabolismo
9.
Biomacromolecules ; 13(7): 2087-98, 2012 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-22668322

RESUMO

The mechanical behavior and microstructure of minor ampullate gland silk (miS) of two orb-web spinning species, Argiope trifasciata and Nephila inaurata, were extensively characterized, enabling detailed comparison with other silks. The similarities and differences exhibited by miS when compared with the intensively studied major ampullate gland silk (MAS) and silkworm (Bombyx mori) silk offer a genuine opportunity for testing some of the hypotheses proposed to correlate microstructure and tensile properties in silk. In this work, we show that miSs of different species show similar properties, even when fibers spun by spiders that diverged over 100 million years are compared. The tensile properties of miS are comparable to those of MAS when tested in air, significantly in terms of work to fracture, but differ considerably when tested in water. In particular, miS does not show a supercontraction effect and an associated ground state. In this regard, the behavior of miS in water is similar to that of B. mori silk, and it is shown that the initial elastic modulus of both fibers can be explained using a common model. Intriguingly, the microstructural parameters measured in miS are comparable to those of MAS and considerably different from those found in B. mori. This fact suggests that some critical microstructural information is still missing in our description of silks, and our results suggest that the hydrophilicity of the lateral groups or the large scale organization of the sequences might be routes worth exploring.


Assuntos
Seda/química , Aranhas , Resistência à Tração , Animais , Módulo de Elasticidade , Feminino , Microscopia de Força Atômica , Seda/ultraestrutura , Análise Espectral Raman , Água/química , Difração de Raios X
10.
Transplant Proc ; 44(5): 1281-6, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22664001

RESUMO

BACKGROUND: Transplant patients receiving immunosuppressant treatment suffer gastrointestinal symptoms (GIS) limiting their health-related quality of life (HRQOL) and causing dose redíuctions and discontinuations. METHODS: This observational, multicenter, cross-sectional study aims to develop and validate a questionnaire for detecting and quantifying the impact of GIS on the HRQOL of patients with functioning organ transplants. We developed a pilot version of the questionnaire SIGIT-QOL (Impact of Gastrointestinal Symptoms on Quality Of Life) and then evaluated the feasibility, validity, and reliability. We consecutively recruited 274 solid organ transplant patients from 20 hospitals. Sociodemographic and clinical data were collected. Patients completed the SIGIT-QOL and Gastrointestinal Quality of Life Index-GIQLI- questionnaires. RESULTS: Mean age was 52.7 (SD, 7.59) and 181 were male; 43.4% showed an episode of GIS since transplantation (3-12 months before). Of all patients, 95.3% completed the SIGIT-QOL. Mean time of completion was 6.49 minutes. Exploratory factorial analysis identified a 1-dimensional structure (42% of total variance). Internal consistency was high (Cronbach's alpha, 0.889). A significant association was found between the SGITI-QOL and the presence of GIS (P < .01). Finally, correlation coefficients between SIGIT-QOL and GIQLI were moderate-high except for Social Function. CONCLUSION: The brief SIGIT-QOL questionnaire can detect and quantify the GIS and their impact on the HRQOL of solid organ transplant patients.


Assuntos
Gastroenteropatias/psicologia , Imunossupressores/efeitos adversos , Transplante de Rim/efeitos adversos , Qualidade de Vida , Perfil de Impacto da Doença , Inquéritos e Questionários , Efeitos Psicossociais da Doença , Estudos Transversais , Feminino , Gastroenteropatias/induzido quimicamente , Humanos , Transplante de Rim/imunologia , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Psicometria , Reprodutibilidade dos Testes , Espanha , Resultado do Tratamento
11.
Med Biol Eng Comput ; 50(6): 559-66, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22391945

RESUMO

The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship with age and pathologies. Fresh ascending aortic specimens harvested from 23 healthy donors, 12 patients with bicuspid aortic valve (BAV) and 14 with aneurysm were tensile-tested in vitro under physiological conditions. Tensile strength, stretch at failure and elbow stress were measured. The obtained results showed that age causes a major reduction in the mechanical parameters of healthy ascending aortic tissue, and that no significant differences are found between the mechanical strength of aneurysmal or BAV aortic specimens and the corresponding age-matched control group. The physiological level of the stress in the circumferential direction was also computed to assess the physiological operation range of healthy and diseased ascending aortas. The mean physiological wall stress acting on pathologic aortas was found to be far from rupture, with factors of safety (defined as the ratio of tensile strength to the mean wall stress) larger than six. In contrast, the physiological operation of pathologic vessels lays in the stiff part of the response curve, losing part of its function of damping the pressure waves from the heart.


Assuntos
Aorta/fisiologia , Aneurisma Aórtico/fisiopatologia , Adolescente , Adulto , Aorta/fisiopatologia , Valva Aórtica/anormalidades , Valva Aórtica/fisiopatologia , Elasticidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estresse Mecânico , Resistência à Tração , Adulto Jovem
12.
Artigo em Inglês | MEDLINE | ID: mdl-21096878

RESUMO

The lack of reliable mechanical data on coronary arteries and, more specifically, on their wall strength hampers the application of numerical models and simulations to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. Studies of the mechanical properties of coronary arteries have been carried out almost exclusively on animals. Only a few studies have tried to characterize the in vivo behavior of human coronaries through tests under physiological conditions. In this work, the mechanical properties of human coronary arteries have been characterized. Whole samples from human right (RC) and left anterior descending (LAD) coronary arteries aged between 23 and 83 years have been studied by means of in-vitro tensile testing up to failure.


Assuntos
Artérias/fisiologia , Vasos Coronários/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Humanos , Pessoa de Meia-Idade , Resistência à Tração
13.
Int J Biol Macromol ; 46(5): 555-7, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20359492

RESUMO

Supercontraction is commonly considered as a functional adaptation of major ampullate gland (MA) silk to its role as the main structural material in orb-webs. However, the observation of supercontraction in the dragline silk of a lynx spider species, as it is shown in this work, offers a strong support to the hypothesis that the appearance of supercontraction preceded the advent of capture webs. Moreover, the absence of proline in the sequence of dragline silk spidroin in Oxyopidae and related spiders indicates that the presence of this amino acid may not be required for the existence of supercontraction. In this regard, the presence of particular subrepeats--in orb-web and non-orb-web building spiders--adds new clues for the understanding of supercontraction and associated effects.


Assuntos
Fibroínas/química , Fenômenos Mecânicos , Aranhas/química , Animais , Teste de Materiais , Resistência à Tração
14.
Artigo em Inglês | MEDLINE | ID: mdl-19965024

RESUMO

Biomechanical and functional properties of tissue engineered vascular grafts must be similar to those observed in native vessels. This supposes a complete mechanical and structural characterization of the blood vessels. To this end, static and dynamic mechanical tests performed in the sheep thoracic and abdominal aorta and the cava vein were contrasted with histological quantification of their main constituents: elastin, collagen and muscle cells. Our results demonstrate that in order to obtain adequate engineered vascular grafts, the absolute amount of collagen fibers, the collagen/elastin ratio, the amount of muscle cells and the muscle cells/elastic fibers ratio are necessary to be determined in order to ensure adequate elastic modulus capable of resisting high stretches, an adequate elastic modulus at low and normal stretch values, the correct viscous energy dissipation, and a good dissipation factor and buffering function, respectively.


Assuntos
Artérias/patologia , Prótese Vascular , Veias/patologia , Animais , Aorta Abdominal/patologia , Aorta Torácica/patologia , Fenômenos Biomecânicos , Soluções Tampão , Colágeno/química , Módulo de Elasticidade , Elastina/química , Masculino , Ovinos , Estresse Mecânico , Resistência à Tração , Engenharia Tecidual/métodos , Veias Cavas/patologia
15.
Int J Biol Macromol ; 44(2): 195-202, 2009 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-19133291

RESUMO

The microstructures of N-methylmorpholine-N-oxide (NMMO) regenerated silk fibers have been characterized by atomic force microscopy from the micrometer to the nanometer scale and compared with those previously found from natural silks. Regenerated fibers show poor tensile properties and a brittle behavior, but their mechanical properties improve if subjected to post-spinning drawing. Consequently, it was hypothesized that post-spinning drawing would lead to a microstructure more similar to that of the natural material. Here we show that the microstructure of the samples not subjected to post-spinning drawing is composed of nanoglobules that differ from those found in natural silkworm silk both in size and orientation with respect to the macroscopic axis of the fiber. The microstructure of samples subjected to post-spinning drawing evolves in the sense of decreasing the size but increasing the orientation of the nanoglobules, but these effects are only observed in some regions of the fibers.


Assuntos
Bombyx/química , Fibroínas/química , Seda/química , Animais , Fibroínas/ultraestrutura , Microscopia de Força Atômica , Seda/ultraestrutura , Resistência à Tração
16.
Int J Cardiol ; 132(3): 444-6, 2009 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-18164083

RESUMO

Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary syndromes seem to be triggered by bacterial and viral infections, being fever the common symptom. The thermo-mechanical behavior of thoracic aortas of New Zealand White rabbits with different degrees of atherosclerosis was measured by means of pressure-diameter tests at different temperatures. Specific measurements of the thermal dilatation coefficient of atheroma plaques were performed by means of tensile tests. Results show a different thermo-mechanical behavior, the dilatation coefficient of atheroma plaque being at least twice that of the arterial wall. Temperature-induced mechanical stress at the plaque-vessel interface could be enough to promote plaque rupture. Therefore, increases of corporal temperature, either local or systemic, can play a role in increasing the risk of acute coronary syndromes and deserve a more comprehensive study.


Assuntos
Doença da Artéria Coronariana/fisiopatologia , Vasos Coronários/fisiopatologia , Infarto do Miocárdio/fisiopatologia , Animais , Aorta Torácica/fisiopatologia , Fenômenos Biomecânicos , Modelos Animais de Doenças , Elasticidade , Masculino , Modelos Cardiovasculares , Coelhos , Ruptura Espontânea , Estresse Mecânico , Temperatura
17.
Artigo em Inglês | MEDLINE | ID: mdl-19163487

RESUMO

There is a pressing need to obtain adequate vascular substitutes for arterial by-pass or reconstruction. Since the performance of venous and commercially prosthetic grafts is not ideal and the availability of autologous arteries is limited, the use of cryopreserved arteries has emerged as a very attractive alternative. In this sense, the development of an inter-continental network for cryopreserved tissue exchange would improve international cooperation increasing the possibilities of obtaining the requested materials. In this work, the effects of an inter-continental shipment, which includes cryopreservation, on the biomechanical properties of sheep aortas were evaluated by means of the arterial complex elastic modulus. It is shown that these properties were preserved after the shipment. The actual possibilities of establishing a network for arterial exchange for the international cooperation are discussed.


Assuntos
Aorta/patologia , Fenômenos Biomecânicos , Artérias Carótidas/anatomia & histologia , Artérias Carótidas/citologia , Criopreservação/métodos , Algoritmos , Animais , Artérias/patologia , Prótese Vascular , Sobrevivência Celular , Elasticidade , Eletrofisiologia/métodos , Modelos Estatísticos , Pressão , Ovinos , Estresse Mecânico
18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 76(4 Pt 1): 041903, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17995022

RESUMO

A great number of biological structures are composed of fibers (elastin, collagen, etc.) dispersed on an aqueous matrix in such a complex way that a detailed mechanical analysis based on microconstituents is, for practical purposes, out of reach. Consequently, the preferred approach to the mechanical behavior of these materials is based on setting up of constitutive equations that homogenize the behavior while capturing their main microstructural features. This work presents a simple macroscopic model for fiber-reinforced materials with deformable matrices, especially suited to many biological structural tissues. The constitutive equation is derived by imposing equivalence between the virtual works of both the fiber-reinforced and the equivalent continuum media, showing that it is independent of the control volume used for such equivalence. The model is particularized to incompressible materials, and an extension to orthotropic biological fibers is shown. Numerical simulations of uniaxial tests on silk fibers demonstrate the model's ability to capture the progressive alignment of the microconstituents under large deformations.


Assuntos
Biofísica/métodos , Algoritmos , Colágeno/química , Cristalização , Elastina/química , Ligação de Hidrogênio , Modelos Estatísticos , Modelos Teóricos , Física/métodos , Seda , Estresse Mecânico
19.
Biomacromolecules ; 7(7): 2173-7, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16827584

RESUMO

The characterization of silk properties requires a reliable measurement of stress-strain curves from tensile tests, which calls for a detailed analysis of what is considered the cross section of the sample and how it varies during the experiments. Here, spider silk fibers from the major ampullate gland (MAS) of Argiope trifasciata spiders are tensile tested, and the cross-sectional area is measured under different strained configurations. It has been found that the fiber volume remains practically constant during stretching, and deformation proceeds homogeneously in all the fibers. The conservation of volume is validated independently of the type of fiber and the strain level. This result, applied to compute true stress-strain curves for different MAS fibers, shows that the description of their properties depends noticeably on which set of tensile parameters is chosen (true or engineering), and that engineering values could lead to misinterpretation of experiments that combine results from different strain ranges.


Assuntos
Seda/química , Aranhas/química , Animais , Microscopia Eletrônica de Varredura , Seda/ultraestrutura , Aranhas/classificação , Resistência à Tração
20.
J Exp Biol ; 209(Pt 2): 320-6, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16391354

RESUMO

In this study of the effect of anaesthesia on both the forced silking process and on the properties of the retrieved silk fibres, a monitored forced silking process enables the silking force to be measured during the whole process. Silk samples were tensile-tested and their diameters measured. Force-displacement curves and stress-strain curves were drawn. The evolution of the silking process of anaesthetized spiders is found to be complex, but it sheds light on the details of the spinning mechanism of spider silk.


Assuntos
Anestésicos/farmacologia , Secreções Corporais/efeitos dos fármacos , Secreções Corporais/metabolismo , Dióxido de Carbono/farmacologia , Seda/efeitos dos fármacos , Aranhas/fisiologia , Animais , Secreções Corporais/fisiologia , Teste de Materiais , Seda/química
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