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1.
Rev Sci Instrum ; 93(8): 083706, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-36050051

RESUMO

Sub-resonance tapping (SRT) mode of atomic force microscopy (AFM) enables researchers to image surfaces with well-controlled load forces and to collect maps of multiple physical properties of samples. The major bottleneck of this mode is a relatively low scan speed compared to other scanning modes. This paper presents a novel control algorithm that substantially improves the scanning speed over the standard SRT. We propose naming the new modality Trajectory Tracking SRT (TT-SRT). In contrast with the standard SRT control, TT-SRT uses the feedback within every single touch of the sample by the AFM probe. To demonstrate the advantage of TT-SRT, we conduct scans on a variety of samples with differing topologies, roughnesses, and mechanical properties. Each sample region is scanned with both standard SRT and TT-SRT at the same set of speeds. The control gains are tuned before each scan for maximum performance in each mode. Performance is evaluated by selecting a given level of image quality and finding the maximum speed that can be achieved by each algorithm. We find that with increased demand for data quality, the utility of TT-SRT becomes more apparent; for example, the speed of TT-SRT can be ten times faster or more than standard SRT for a reasonable expectation of data quality.


Assuntos
Algoritmos , Vibração , Aceleração , Retroalimentação , Microscopia de Força Atômica/métodos
2.
Rheumatol Adv Pract ; 6(2): rkac058, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35855108

RESUMO

Objective: The incidence of first-time venous thromboembolic events (VTEs) is high in granulomatosis with polyangiitis (GPA). The incidence of recurrent VTEs is unknown. We aimed to describe the recurrence rate of second VTEs in patients with GPA. Methods: Retrospective chart review was performed in patients with GPA and at least one VTE at a single centre from 2002 to 2016. Inclusion criteria were 1990 ACR criteria or 2012 Revised International Chapel Hill nomenclature for GPA, at least two follow-up visits, at least one VTE during the study period, and VTE occurrence after or within 3 months before GPA diagnosis. Second VTE event-free survival rates were estimated. Results: Out of 147 patients initially screened for GPA and with at least one VTE, 84 met inclusion criteria. Median age at first VTE was 57 years. Incidence rate for second VTE was 8.4 events per 100 patient-years (95% CI: 5.7, 12.3). Eighty-three point three per cent of first VTEs and 57.7% of second VTEs occurred when disease was active (P < 0.001). Renal involvement and constitutional symptoms at the time of first VTE were associated with VTE recurrence. Conclusion: GPA has a high rate of VTE recurrence compared with the reported data in the general population with unprovoked VTE. Our results suggest that VTE in GPA is a recurrent co-morbidity, not always during active vasculitis, and more so in those with renal involvement and constitutional symptoms at the time of first VTE.

3.
Clin Exp Rheumatol ; 38 Suppl 124(2): 135-138, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31928590

RESUMO

OBJECTIVES: Neurosarcoidosis (NS) and primary angiitis of central nervous system (PACNS) are inflammatory diseases affecting central nervous system, with overlapping clinical and pathological characteristics. Distinguishing these diseases is important given distinct therapeutic implications. In this study, we aimed to compare demographic, CSF and MRI characteristics between these two conditions. METHODS: All the clinical, CSF and laboratory characteristics at the time of presentation were retrieved from electronic medical records. Brain and/or spinal cord MRI performed near the time of presentation were blindly evaluated by two neuroradiologists. Data regarding involvement of pachy- and leptomeninges, basal meninges, cranial nerves, cerebral grey and white matter, and spinal cord were recorded for each patient. RESULTS: 78 patients with PACNS and 25 patients with NS were included in the study. Mean age of patients was 43.7 (±16.7) and 43.6 (±12.5) in PACNS and NS, respectively. African-American race was found to be associated with the diagnosis of NS rather than PACNS. Patients with PACNS had higher frequency of cerebral involvement, while patients with NS demonstrated more frequent spinal cord, basal meningeal and cranial nerve involvements. CONCLUSIONS: These findings suggest that MRI can be an efficient tool in distinguishing PACNS from NS. A follow-up study with a larger sample size would be required to validate our results.


Assuntos
Doenças do Sistema Nervoso Central/diagnóstico por imagem , Sarcoidose/diagnóstico por imagem , Vasculite do Sistema Nervoso Central/diagnóstico por imagem , Adulto , Doenças do Sistema Nervoso Central/líquido cefalorraquidiano , Demografia , Diagnóstico Diferencial , Seguimentos , Humanos , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Sarcoidose/líquido cefalorraquidiano , Vasculite do Sistema Nervoso Central/líquido cefalorraquidiano
4.
Span J Psychol ; 22: E57, 2019 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-31868154

RESUMO

We investigated whether older adults are more likely than younger adults to violate a foundational property of rational decision making, the axiom of transitive preference. Our experiment consisted of two groups, older (ages 60-75; 21 participants) and younger (ages 18-30; 20 participants) adults. We used Bayesian model selection to investigate whether individuals were better described via (transitive) weak order-based decision strategies or (possibly intransitive) lexicographic semiorder decision strategies. We found weak evidence for the hypothesis that older adults violate transitivity at a higher rate than younger adults. At the same time, a hierarchical Bayesian analysis suggests that, in this study, the distribution of decision strategies across individuals is similar for both older and younger adults.


Assuntos
Envelhecimento Cognitivo/fisiologia , Tomada de Decisões/fisiologia , Adolescente , Adulto , Fatores Etários , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
5.
Clin Exp Rheumatol ; 37 Suppl 117(2): 45-51, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30789149

RESUMO

OBJECTIVES: Primary angiitis of the central nervous system (PACNS) is a vasculitis confined to the brain and spinal cord, which often presents with severe cognitive and functional deficits. Despite progress in diagnosis, little is still known about long-term outcomes. Our aim was to evaluate long-term functional capabilities, quality of life, and depression, and to determine the effect of treatment duration on patient outcomes. METHODS: We identified patients by ICD-9 codes for cerebral angiitis, and included them if they met two of the three following criteria: inflammatory cerebrospinal fluid (CSF), cerebral angiogram typical of vasculitis, or findings of vasculitis on pathologic examination of brain tissue. Disability was assessed by the Barthel Index, quality of life was assessed by EuroQol, and depression was assessed with Patient Health Questionnaire. RESULTS: Seventy-eight patients met the inclusion criteria, of which 27 responded to the questionnaire (34.6%). Mean follow-up of those who responded was 5.5 years (± 4.7). Nineteen of 27 patients (70.4%) had mild disability; meanwhile, 5 (18.5%) had severe disability. Fourteen of 27 patients (51.9%) had no mobility problem, 18 (66.7%) had no problems with self-care, 15 (55.6%) had no problems with usual activities, 14 (51.9%) had no pain, and 8 (29.6%) had no anxiety. Approximately 70% of patients had minimal or no depression. CONCLUSIONS: This is the longest reported follow-up of patients with PACNS described in the literature to date. Most patients had mild long-term disability and minimal to no depression, which may be reflective of treatment advances.


Assuntos
Transtornos Cognitivos/diagnóstico , Transtorno Depressivo/diagnóstico , Vasculite do Sistema Nervoso Central , Angiografia Cerebral , Transtornos Cognitivos/etiologia , Transtorno Depressivo/etiologia , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Exame Neurológico , Qualidade de Vida , Vasculite do Sistema Nervoso Central/líquido cefalorraquidiano , Vasculite do Sistema Nervoso Central/complicações , Vasculite do Sistema Nervoso Central/diagnóstico
6.
Span. j. psychol ; 22: e57.1-e57.14, 2019. tab, graf
Artigo em Inglês | IBECS | ID: ibc-190208

RESUMO

We investigated whether older adults are more likely than younger adults to violate a foundational property of rational decision making, the axiom of transitive preference. Our experiment consisted of two groups, older (ages 60-75; 21 participants) and younger (ages 18-30; 20 participants) adults. We used Bayesian model selection to investigate whether individuals were better described via (transitive) weak order-based decision strategies or (possibly intransitive) lexicographic semiorder decision strategies. We found weak evidence for the hypothesis that older adults violate transitivity at a higher rate than younger adults. At the same time, a hierarchical Bayesian analysis suggests that, in this study, the distribution of decision strategies across individuals is similar for both older and younger adults


No disponible


Assuntos
Humanos , Masculino , Feminino , Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Idoso , Envelhecimento Cognitivo/psicologia , Tomada de Decisões , Fatores Etários
7.
J Clin Orthop Trauma ; 9(4): 285-288, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30449971

RESUMO

OBJECTIVE: The optimal reconstructive method for advanced degenerative hip disease in young adults is a topic of ongoing discussion. The purpose of this study is to report the largest single institution experience from the United States on the outcomes of Birmingham hip resurfacing (BHR) vs. cementless total hip arthroplasty (THA) in patients 55 years or younger at a minimum follow-up of five years. Currently, BHR is the only FDA-approved hip resurfacing implant available in the US. METHODS: A cohort of 505 patients representing all BHR cases performed at our institution between 2006 and 2010 was compared with an identical size cohort of consecutive patients who underwent primary cementless THA. Exclusion criteria were age greater than 55 years, non-elective cases, revision procedures, and those performed for fractures, tumors, or by low-volume arthroplasty surgeons. THAs with metal on metal articulation were also excluded. OUTCOMES: assessed were all-cause reoperations, complications, patient satisfaction, and mortality. After exclusions, 442 patients with BHR and 327 with THA were included. RESULTS: Mean follow-up was 73.2 months. After controlling for potential confounding factors, multivariate analyses showed significant increase in the rates of revision surgery (p < 0.001), overall complications (p < 0.001), all-cause reoperations (p = 0.014), and mortality (p < 0.001) in the THA cohort. Component loosening was the most common cause for revision in the THA group. Patients with THA were also less likely to be satisfied (p = 0.046). CONCLUSIONS: This is largest US study to report on the midterm outcomes of BHR vs. THA. The results demonstrate favorable results for BHR in patients 55 years or younger. Long-term multicenter studies are needed to better understand the optimal patient characteristics when deciding between THA versus BHR.

8.
Orthopedics ; 41(5): e695-e700, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-30092109

RESUMO

Although total hip arthroplasty and total knee arthroplasty commonly overlap, there are concerns about the safety and quality of this scenario. The objectives of this study were to (1) compare the operative time and the incidence of 90-day complications between overlapping and nonoverlapping total joint arthroplasties; and (2) evaluate the effect of the duration of overlap on operative time and the incidence of 90-day complications. A total of 9192 patients who underwent primary total hip arthroplasty or total knee arthroplasty at a large academic hospital from 2005 to 2014 were identified. A surgery was defined as overlapping if it had an incision to closure overlap time of at least 1 minute with any other surgery performed by the same surgeon. A total of 2669 (29%) patient procedures were classified as overlapping. Operative times and 90-day complications were compared between overlapping and nonoverlapping surgeries. Mixed effects regression models were used to assess the independent effects of overlapping surgeries. After adjusting for baseline characteristics, operative times were longer for the overlapping surgery group (P<.001). Overlapping surgeries had fewer thromboembolic events (P=.003) and periprosthetic joint infections (P=.039). Wound dehiscence (P=.662), superficial infection (P=.161), and wound hematoma (P=.511) were similar between the 2 groups. Operative times increased with increasing duration of overlap (P<.001); however, there was no association between duration of overlap and 90-day complications (P>.05 for all). Although overlapping surgeries had increased operative times, they did not appear to increase the risk of perioperative complications. This information may be helpful for scheduling overlapping procedures and counseling patients. [Orthopedics. 2018; 41(5):e695-e700.].


Assuntos
Artroplastia de Quadril/efeitos adversos , Artroplastia do Joelho/efeitos adversos , Complicações Pós-Operatórias/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Duração da Cirurgia , Estudos Retrospectivos , Risco
9.
J Clin Orthop Trauma ; 9(2): 103-106, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29896009

RESUMO

BACKGROUND: Total hip arthroplasty (THA) is increasingly performed in younger patients. The purpose of this study is to report on the midterm outcomes of primary cementless THA in patients 55 years and younger; and specifically to examine the risk factors for aseptic failure, all-cause revision, and mortality in this patient population. METHODS: Four hundred and twenty-six consecutive patients with minimum 5-year follow-up were retrospectively reviewed. Multivariate analyses were conducted to control for potential confounding factors identified by univariate analyses. RESULTS: Mean follow-up was 92.12 ± 30.9 months. The overall 5-year implant survival rate was 90.8% and the aseptic survival rate was 92.6%. Among the potential risk factors, only bearing surface had a significant relationship with aseptic revision (P = 0.041). Aseptic revisions occurred more frequently with metal-on-polyethylene articulation (P = 0.012). Higher Charlson comorbidity index (CCI) was a significant risk factor for all-cause complications (P = 0.04) while higher CCI and lower body mass index were significant risk factors for mortality (P = 0.001 and 0.006 respectively). CONCLUSION: Bearing type was the only risk factor for revision surgery, particularly metal-on-polyethylene bearing. Patients with higher comorbidities were at increased risk for postoperative complications and mortality, while higher body weight appeared to have a protective effect against mortality. These findings should be considered before surgery for risk modification and management of patient expectations. While it appears that bearing couples other than metal-on-polyethylene are especially suitable for young patients, more studies are needed to determine the best bearing couple and to reduce the rates of postoperative complications in this patient population.

10.
J Arthroplasty ; 33(6): 1675-1680, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29478678

RESUMO

BACKGROUND: Standardized care pathways are evidence-based algorithms for optimizing an episode of care. Despite the theoretical promise of care pathways, there is an inconsistent literature demonstrating improvements in patient care. The authors hypothesized that implementing a care pathway, across 11 hospitals, would decrease hospital length of stay (LOS), decrease postoperative complications at 90 days, and increase discharges to home. METHODS: A multidisciplinary team developed an evidence-based care pathway for total hip arthroplasty (THA) perioperative care. All patients receiving THA in 2013 (pre-protocol, historical control), 2014 (transition), and 2015 (full protocol implementation) were included in the analysis. Multivariable regression assessed the relationship of the care pathway to 90-day postoperative complications, LOS, and discharge disposition. Cost savings were estimated using previously published postarthroplasty episode and per diem hospital costs. RESULTS: A total of 6090 primary THAs were conducted during the study period. After adjusting for the covariates, the full protocol implementation was associated with a decrease in LOS (mean ratio, 0.747; 95% confidence interval [CI; 0.727, 0.767]) and an increase in discharges to home (odds ratio, 2.079; 95% CI [1.762, 2.456]). The full protocol implementation was not associated with a change in 90-day complications (odds ratio, 1.023; 95% CI [0.841, 1.245]). Payer-perspective-calculated theoretical cost savings, including both index admission and postdischarge costs, were $2533 per patient. CONCLUSION: The THA care pathway implementation was successful in reducing LOS and increasing discharges to home. The care pathway was not associated with a change in 90-day complications; further targeted interventions in this area are needed. Despite care standardization efforts, high-volume hospitals and surgeons had higher performance. Extrapolation of theoretical cost savings indicates that widespread THA care pathway adoption could lead to national healthcare savings of $1.2 billion annually.


Assuntos
Artroplastia de Quadril/estatística & dados numéricos , Procedimentos Clínicos/estatística & dados numéricos , Tempo de Internação/estatística & dados numéricos , Alta do Paciente/estatística & dados numéricos , Complicações Pós-Operatórias/epidemiologia , Idoso , Artroplastia de Quadril/efeitos adversos , Artroplastia de Quadril/economia , Redução de Custos , Procedimentos Clínicos/economia , Cuidado Periódico , Feminino , Custos Hospitalares , Hospitalização , Hospitais com Alto Volume de Atendimentos , Humanos , Masculino , Pessoa de Meia-Idade , Razão de Chances , Ohio/epidemiologia , Assistência Perioperatória/normas , Complicações Pós-Operatórias/etiologia , Estudos Retrospectivos , Fatores de Risco , Fatores de Tempo
11.
Orthop J Sports Med ; 5(9): 2325967117726521, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28944250

RESUMO

BACKGROUND: Validated patient-reported outcome measures (PROMs) of hip pain and function at the time of arthroscopy could be predictors of the final outcome. Little is known about how patient factors or pathologic intra-articular findings relate to hip pain or function at the time of surgery for those presenting with femoroacetabular impingement (FAI). PURPOSE: To evaluate all patient and operative factors that contribute to hip pain and dysfunction in patients with FAI. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A prospective cohort of patients undergoing hip arthroscopy for FAI were electronically enrolled between February 2015 and September 2016. Baseline PROMs were collected, including Hip disability and Osteoarthritis Outcome Score (HOOS) for pain, HOOS-Physical Function Shortform (HOOS-PS), Veterans RAND 12-Item Health Survey (VR-12), and University of California-Los Angeles (UCLA) Activity Score. Surgeons documented intra-articular operative findings and treatment. Multivariable linear regression models were created for continuous scores of HOOS pain, HOOS-PS, and VR-12 Physical Component Score as outcome measures. Risk factors included patient characteristics and intraoperative anatomic and pathologic findings. RESULTS: During the study period, 396 patients underwent arthroscopic hip procedures, and 373 (94%) completed preoperative PROMs; 331 patients were undergoing arthroscopic surgery for FAI. The mean patient age was 32.91 ± 12.49 years, mean body mass index was 26.22 ± 4.92 kg/m2, and 71% were female. Multivariate analyses demonstrated female sex, lower education levels, smoking, lower mental health scores, and lower activity-level scores predicted HOOS pain preoperatively. According to multivariate analysis, patient factors associated with worse baseline HOOS-PS include smoking, additional years of education, lower mental health, and activity scores. Lower baseline VR-12 functional scores were predicted by female sex, elevated body mass index, smoking, and lower activity levels. For all baseline PROMs, there was no instance where an arthroscopic variable or pathologic finding proved statistically significant after the important patient covariates were controlled for. CONCLUSION: Patient factors, including mental health, activity level, sex, and smoking, are more predictive of baseline hip pain (as measured by HOOS) and function than are intra-articular findings (eg, status of the labrum or articular cartilage) during hip arthroscopy for FAI. Future studies evaluating patient outcomes after surgery for FAI should consider adjusting for these identified patient factors to accurately interpret the effect of treatment on patient-reported outcomes after surgery.

12.
J Arthroplasty ; 32(6): 1880-1883, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28108170

RESUMO

BACKGROUND: Birmingham hip resurfacing (BHR) is the only Food and Drug Administration-approved hip resurfacing system available in the United States and is used as an alternative to conventional total hip arthroplasty in younger patients. The purpose of this study is to report on the midterm outcomes of BHR in patients 55 years and younger, and specifically to examine the risk factors for aseptic failure, all-cause revision, and complications in this patient population. METHODS: Four hundred forty-two consecutive patients with 5-year follow-up were retrospectively reviewed. Multivariate analyses were conducted to control for potential confounding factors identified by univariate analyses. RESULTS: Mean follow-up was 71.68 ± 10.24 months. Among the potential risk factors, only female gender and smaller head sizes had a significant univariate relationship with aseptic revision, all-cause revision, and all-cause complications. When both risk factors were included in a multivariable logistic regression model, analyses showed both variables were closely related, with female gender a better predictor of adverse outcomes than head size (ie, small head size can be thought of as a proxy for female gender). The 5-year implant survival is 95.1% females compared to 99.0% in males. CONCLUSION: Hip resurfacing with BHR has excellent survival rates in young patients with degenerative hip disease. Although this study suggests that females with small templated head sizes may not be suitable candidates for BHR, further studies are needed to better understand the underlying differences in gender.


Assuntos
Artroplastia de Quadril/estatística & dados numéricos , Adolescente , Adulto , Artroplastia de Quadril/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Desenho de Prótese , Estudos Retrospectivos , Fatores de Risco , Fatores Sexuais , Resultado do Tratamento , Estados Unidos , United States Food and Drug Administration , Adulto Jovem
13.
Arthritis Res Ther ; 18: 178, 2016 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-27485213

RESUMO

BACKGROUND: Patients with psoriatic arthritis (PsA) are at an increased risk for cardiovascular (CV) disease.  The aim of this study was to identify the frequency of carotid plaque in asymptomatic patients with psoriatic arthritis at baseline and follow-up screening, and to assess for the impact of demonstrating plaque on management of traditional cardiovascular risk factors. METHODS: Eighty-seven PsA patients underwent carotid duplex ultrasound screening. Repeat carotid duplex ultrasound was offered to all patients between 12 and 30 months. Preventive cardiology referrals were generated for all patients through the electronic health record. Traditional cardiovascular risk factors, medication use, and rates of utilization of preventive cardiology services were compared between patients with and without plaque. RESULTS: Carotid plaque was identified in 34/87 (39 %) of PsA patients. Age and triglyceride levels were predictors of plaque presence. Patients with plaque trended toward higher rates of smoking and diabetes, and higher low-density lipoprotein levels. Only 9/87 (10 %) patients completed at least one visit with preventive cardiology after enrollment despite referral. Low use of statin (21 %) and antiplatelet (27 %) medication was observed. Rates of biologic medication use for PsA were higher (75 %) than studies in similar cohorts of patients with carotid plaque. No association was seen between disease duration or activity and the presence of carotid plaque. CONCLUSION: Despite demonstration of high cardiac risk by the presence of carotid plaque, implementation of preventive cardiovascular services and rates of statin and antiplatelet use remained low. Age and triglyceride levels were significant variables in predicting plaque presence. There is no evidence that demonstration of plaque resulted in further evaluation or changes in treatment regimens to address heightened cardiovascular risk.


Assuntos
Artrite Psoriásica/complicações , Doenças das Artérias Carótidas/epidemiologia , Doenças das Artérias Carótidas/etiologia , Placa Aterosclerótica/epidemiologia , Placa Aterosclerótica/etiologia , Adulto , Idoso , Doenças Cardiovasculares/diagnóstico por imagem , Doenças Cardiovasculares/epidemiologia , Doenças Cardiovasculares/etiologia , Doenças das Artérias Carótidas/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Placa Aterosclerótica/diagnóstico por imagem , Fatores de Risco , Ultrassonografia
14.
Lab Chip ; 15(16): 3293-9, 2015 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-26138309

RESUMO

Morphogenesis involves a complex series of cell signaling, migration and differentiation events that are coordinated as tissues self-assemble during embryonic development. Collective cell movements such as those that occur during morphogenesis have typically been studied in 2D with single layers of cultured cells adhering to rigid substrates such as glass or plastic. In vivo, the intricacies of the 3D microenvironment and complex 3D responses are pivotal in the formation of functional tissues. To study such processes as collective cell movements within 3D multilayered tissues, we developed a microfluidic technique capable of producing complex 3D laminar multicellular structures. We call this technique "3D tissue-etching" because it is analogous to techniques used in the microelectromechanics (MEMS) field where complex 3D structures are built by successively removing material from a monolithic solid through subtractive manufacturing. We use a custom-designed microfluidic control system to deliver a range of tissue etching reagents (detergents, chelators, proteases, etc.) to specific regions of multilayered tissues. These tissues were previously isolated by microsurgical excision from embryos of the African claw-toed frog, Xenopus laevis. The ability to shape the 3D form of multicellular tissues and to control 3D stimulation will have a high impact on tissue engineering and regeneration applications in bioengineering and medicine as well as provide significant improvements in the synthesis of highly complex 3D integrated multicellular biosystems.


Assuntos
Embrião não Mamífero/citologia , Morfogênese , Animais , Imageamento Tridimensional , Sistemas Microeletromecânicos , Técnicas Analíticas Microfluídicas/instrumentação , Dodecilsulfato de Sódio/química , Engenharia Tecidual , Xenopus laevis/crescimento & desenvolvimento
15.
ISME J ; 9(6): 1399-409, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25478682

RESUMO

Many motile unicellular organisms have evolved specialized behaviors for detecting and responding to environmental cues such as chemical gradients (chemotaxis) and oxygen gradients (aerotaxis). Magnetotaxis is found in magnetotactic bacteria and it is defined as the passive alignment of these cells to the geomagnetic field along with active swimming. Herein we show that Magnetospirillum magneticum (AMB-1) show a unique set of responses that indicates they sense and respond not only to the direction of magnetic fields by aligning and swimming, but also to changes in the magnetic field or magnetic field gradients. We present data showing that AMB-1 cells exhibit sudden motility reversals when we impose them to local magnetic field gradients. Our system employs permalloy (Ni(80)Fe(20)) islands to curve and diverge the magnetic field lines emanating from our custom-designed Helmholtz coils in the vicinity of the islands (creating a drop in the field across the islands). The three distinct movements we have observed as they approach the permalloy islands are: unidirectional, single reverse and double reverse. Our findings indicate that these reverse movements occur in response to magnetic field gradients. In addition, using a permanent magnet we found further evidence that supports this claim. Motile AMB-1 cells swim away from the north and south poles of a permanent magnet when the magnet is positioned less than ∼30 mm from the droplet of cells. All together, these results indicate previously unknown response capabilities arising from the magnetic sensing systems of AMB-1 cells. These responses could enable them to cope with magnetic disturbances that could in turn potentially inhibit their efficient search for nutrients.


Assuntos
Campos Magnéticos , Magnetospirillum/citologia , Quimiotaxia , Magnetismo , Oxigênio/química
16.
Proc Natl Acad Sci U S A ; 111(40): 14366-71, 2014 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-25246549

RESUMO

Spatiotemporal regulation of cell contractility coordinates cell shape change to construct tissue architecture and ultimately directs the morphology and function of the organism. Here we show that contractility responses to spatially and temporally controlled chemical stimuli depend much more strongly on intercellular mechanical connections than on biochemical cues in both stimulated tissues and adjacent cells. We investigate how the cell contractility is triggered within an embryonic epithelial sheet by local ligand stimulation and coordinates a long-range contraction response. Our custom microfluidic control system allows spatiotemporally controlled stimulation with extracellular ATP, which results in locally distinct contractility followed by mechanical strain pattern formation. The stimulation-response circuit exposed here provides a better understanding of how morphogenetic processes integrate responses to stimulation and how intercellular responses are transmitted across multiple cells. These findings may enable one to create a biological actuator that actively drives morphogenesis.


Assuntos
Trifosfato de Adenosina/farmacologia , Forma Celular/efeitos dos fármacos , Mecanotransdução Celular/efeitos dos fármacos , Zigoto/efeitos dos fármacos , Animais , Dextranos/metabolismo , Feminino , Junções Comunicantes/metabolismo , Isoquinolinas/metabolismo , Mecanotransdução Celular/fisiologia , Técnicas Analíticas Microfluídicas , Microscopia Confocal , Rodaminas/metabolismo , Xenopus laevis , Zigoto/metabolismo , Zigoto/fisiologia
17.
Decisions ; 1(1): 2-34, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24999495

RESUMO

The goal of this paper is to make modeling and quantitative testing accessible to behavioral decision researchers interested in substantive questions. We provide a novel, rigorous, yet very general, quantitative diagnostic framework for testing theories of binary choice. This permits the nontechnical scholar to proceed far beyond traditionally rather superficial methods of analysis, and it permits the quantitatively savvy scholar to triage theoretical proposals before investing effort into complex and specialized quantitative analyses. Our theoretical framework links static algebraic decision theory with observed variability in behavioral binary choice data. The paper is supplemented with a custom-designed public-domain statistical analysis package, the QTest software. We illustrate our approach with a quantitative analysis using published laboratory data, including tests of novel versions of "Random Cumulative Prospect Theory." A major asset of the approach is the potential to distinguish decision makers who have a fixed preference and commit errors in observed choices from decision makers who waver in their preferences.

18.
Sci Rep ; 4: 4104, 2014 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-24553101

RESUMO

Herein, we demonstrate the control of magnetotactic bacteria through the application of magnetic field gradients with real-time visualization. We accomplish this control by integrating a pair of macroscale Helmholtz coils and lithographically fabricated nanoscale islands composed of permalloy (Ni80Fe20). This system enabled us to guide and steer amphitrichous Magnetospirillum magneticum strain AMB-1 to specific location via magnetic islands. The geometries of the islands allowed us to have control over the specific magnetic field gradients on the bacteria. We estimate that magnetotactic bacteria located less than 1 µm from the edge of a diamond shaped island experience a maximum force of approximately 34 pN, which engages the bacteria without trapping them. Our system could be useful for a variety of applications including magnetic fabrication, self-assembly, and probing the sensing apparatus of magnetotactic bacteria.


Assuntos
Magnetospirillum/fisiologia , Metais/química , Microscopia , Nanoestruturas/química , Análise de Elementos Finitos , Campos Magnéticos , Magnetospirillum/crescimento & desenvolvimento , Nanotecnologia
19.
Annu Rev Biomed Eng ; 13: 369-96, 2011 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-21599491

RESUMO

Control is intrinsic to biological organisms, whose cells are in a constant state of sensing and response to numerous external and self-generated stimuli. Diverse means are used to study the complexity through control-based approaches in these cellular systems, including through chemical and genetic manipulations, input-output methodologies, feedback approaches, and feed-forward approaches. We first discuss what happens in control-based approaches when we are not actively examining or manipulating cells. We then present potential methods to determine what the cell is doing during these times and to reverse-engineer the cellular system. Finally, we discuss how we can control the cell's extracellular and intracellular environments, both to probe the response of the cells using defined experimental engineering-based technologies and to anticipate what might be achieved by applying control-based approaches to affect cellular processes. Much work remains to apply simplified control models and develop new technologies to aid researchers in studying and utilizing cellular and molecular processes.


Assuntos
Fenômenos Fisiológicos Celulares/fisiologia , Células/metabolismo , Técnicas Citológicas/instrumentação , Modelos Biológicos , Biologia de Sistemas , Animais , Retroalimentação Fisiológica/fisiologia , Humanos
20.
Lab Chip ; 11(13): 2182-8, 2011 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-21528131

RESUMO

Dynamic control of three-dimensional (3D) chemical patterns with both high precision and high speed is important in a range of applications from chemical synthesis, flow cytometry, and multi-scale biological manipulation approaches. A central challenge in controlling 3D chemical patterns is the inability to create rapidly tunable 3D profiles with simple and direct approaches that avoid complicated microfabrication. Here, we present the ability to rapidly and precisely create 3D chemical patterns using a single two-dimensional (2D) microfluidic platform. We are not only able to create these 3D patterns, but can rapidly switch from one mode to another (e.g. from a focused to a defocused pattern in less than 1 second) via simple changes in inlet pressures. A feedback control scheme with a pressure modulation mechanism controls the pressure changes. In addition to experiments, we conducted computational simulations for guiding the optimum design of the channels as well as revealing the sensitivity of the patterns to the channel dimensions; these simulations have high experimental correlations. We also show that microvortices play an important role in creating these tunable 3D patterns in this microfluidic platform. We quantitatively determine the degrees of the focused patterns in 2D cross-sections using a focus index with a 2D Gaussian function. Our integrated approach combining feedback control with simple microfluidics will be useful for researchers in diverse disciplines including chemistry, engineering, physics, and biology.


Assuntos
Técnicas Analíticas Microfluídicas/instrumentação , Microtecnologia/instrumentação , Desenho de Equipamento , Retroalimentação , Hidrodinâmica , Pressão , Fatores de Tempo
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