350 research outputs found

    3D Imaging and Mechanical Modeling of Helical Buckling in Medicago truncatula Plant Roots

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    We study the primary root growth of wild-type Medicago truncatula plants in heterogeneous environments using 3D time-lapse imaging. The growth medium is a transparent hydrogel consisting of a stiff lower layer and a compliant upper layer. We find that the roots deform into a helical shape just above the gel layer interface before penetrating into the lower layer. This geometry is interpreted as a combination of growth-induced mechanical buckling modulated by the growth medium and a simultaneous twisting near the root tip. We study the helical morphology as the modulus of the upper gel layer is varied and demonstrate that the size of the deformation varies with gel stiffness as expected by a mathematical model based on the theory of buckled rods. Moreover, we show that plant-to-plant variations can be accounted for by biomechanically plausible values of the model parameters

    3D Imaging and Mechanical Modeling of Helical Buckling in Medicago truncatula Plant Roots

    Get PDF
    We study the primary root growth of wild-type Medicago truncatula plants in heterogeneous environments using 3D time-lapse imaging. The growth medium is a transparent hydrogel consisting of a stiff lower layer and a compliant upper layer. We find that the roots deform into a helical shape just above the gel layer interface before penetrating into the lower layer. This geometry is interpreted as a combination of growth-induced mechanical buckling modulated by the growth medium and a simultaneous twisting near the root tip. We study the helical morphology as the modulus of the upper gel layer is varied and demonstrate that the size of the deformation varies with gel stiffness as expected by a mathematical model based on the theory of buckled rods. Moreover, we show that plant-to-plant variations can be accounted for by biomechanically plausible values of the model parameters

    Rest and treatment/rehabilitation following sport-related concussion: a systematic review

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    AIM OR OBJECTIVE: The objective of this systematic review was to evaluate the evidence regarding rest and active treatment/rehabilitation following sport-related concussion (SRC). DESIGN: Systematic review. DATA SOURCES: MEDLINE (OVID), CINAHL (EbscoHost), PsycInfo (OVID), Cochrane Central Register of Controlled Trials (OVID), SPORTDiscus (EbscoHost), EMBASE (OVID) and Proquest DissertationsandTheses Global (Proquest) were searched systematically. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies were included if they met the following criteria: (1) original research; (2) reported SRC as the diagnosis; and (3) evaluated the effect of rest or active treatment/rehabilitation. Review articles were excluded. RESULTS: Twenty-eight studies met the inclusion criteria (9 regarding the effects of rest and 19 evaluating active treatment). The methodological quality of the literature was limited; only five randomised controlled trials (RCTs) met the eligibility criteria. Those RCTs included rest, cervical and vestibular rehabilitation, subsymptom threshold aerobic exercise and multifaceted collaborative care. SUMMARY/CONCLUSIONS: A brief period (24-48‚ÄČhours) of cognitive and physical rest is appropriate for most patients. Following this, patients should be encouraged to gradually increase activity. The exact amount and duration of rest are not yet well defined and require further investigation. The data support interventions including cervical and vestibular rehabilitation and multifaceted collaborative care. Closely monitored subsymptom threshold, submaximal exercise may be of benefit. SYSTEMATIC REVIEW REGISTRATION: PROSPERO 2016:CRD42016039570

    Smoking Enhances Risk for New External Genital Warts in Men

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    Repeat episodes of HPV-related external genital warts reflect recurring or new infections. No study before has been sufficiently powered to delineate how tobacco use, prior history of EGWs and HIV infection affect the risk for new EGWs. Behavioral, laboratory and examination data for 2,835 Multicenter AIDS Cohort Study participants examined at 21,519 semi-annual visits were evaluated. Fourteen percent (391/2835) of men reported or were diagnosed with EGWs at 3% (675/21,519) of study visits. Multivariate analyses showed smoking, prior episodes of EGWs, HIV infection and CD4+ T-lymphocyte count among the infected, each differentially influenced the risk for new EGWs

    Oral leukoplakia and risk of progression to oral cancer: A population-based cohort study

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    BACKGROUND: The optimal clinical management of oral precancer remains uncertain. We investigated the natural history of oral leukoplakia, the most common oral precancerous lesion, to estimate the relative and absolute risks of progression to cancer, the predictive accuracy of a clinician\u27s decision to biopsy a leukoplakia vis-√†-vis progression, and histopathologic predictors of progression. METHODS: We conducted a retrospective cohort study (1996-2012) of patients with oral leukoplakia (n‚ÄČ=‚ÄČ4886), identified using electronic medical records within Kaiser Permanente Northern California. Among patients with leukoplakia who received a biopsy (n‚ÄČ=‚ÄČ1888), we conducted a case-cohort study to investigate histopathologic predictors of progression. Analyses included indirect standardization and unweighted or weighted Cox regression. RESULTS: Compared with the overall Kaiser Permanente Northern California population, oral cancer incidence was substantially elevated in oral leukoplakia patients (standardized incidence ratio = 40.8, 95% confidence interval [CI]‚ÄČ=‚ÄČ34.8 to 47.6; n‚ÄČ=‚ÄČ161 cancers over 22‚ÄČ582 person-years). Biopsied leukoplakias had a higher oral cancer risk compared with those that were not biopsied (adjusted hazard ratio = 2.38, 95% CI‚ÄČ=‚ÄČ1.73 to 3.28). However, to identify a prevalent or incident oral cancer, the biopsy decision had low sensitivity (59.6%), low specificity (62.1%), and moderate positive-predictive value (5.1%). Risk of progression to oral cancer statistically significantly increased with the grade of dysplasia; 5-year competing risk-adjusted absolute risks were: leukoplakia overall‚ÄČ=‚ÄČ3.3%, 95% CI‚ÄČ=‚ÄČ2.7% to 3.9%; no dysplasia‚ÄČ=‚ÄČ2.2%, 95% CI‚ÄČ=‚ÄČ1.5% to 3.1%; mild-dysplasia‚ÄČ=‚ÄČ11.9%, 95% CI‚ÄČ=‚ÄČ7.1% to 18.1%; moderate-dysplasia‚ÄČ=‚ÄČ8.7%, 95% CI‚ÄČ=‚ÄČ3.2% to 17.9%; and severe dysplasia‚ÄČ=‚ÄČ32.2%, 95% CI‚ÄČ=‚ÄČ8.1%-60.0%. Yet 39.6% of cancers arose from biopsied leukoplakias without dysplasia. CONCLUSIONS: The modest accuracy of the decision to biopsy a leukoplakia vis-√†-vis presence or eventual development of oral cancer highlights the need for routine biopsy of all leukoplakias regardless of visual or clinical impression. Leukoplakia patients, particularly those with dysplasia, need to be closely monitored for signs of early cancer

    HMG-CoA reductase inhibitors (statins) use and risk of non-Hodgkin lymphoma in HIV-positive persons

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    Objective: Experimental studies suggested that HMG-CoA reductase inhibitors ('statins') may have antilymphoma properties. We investigated whether statin use is associated with reduced risk of non-Hodgkin lymphoma (NHL) in HIV-positive persons. Design: A nested case-control study was conducted among HIV-positive members of Kaiser Permanente California, a large managed care organization. Methods: Cases were incident HIV√ĺ NHL diagnosed from 1996 to 2008. Controls were HIV-positive members without NHL matched 5 : 1 to cases by age, sex, race, index year and known duration of HIV infection. Data were collected from Kaiser Permanente's electronic medical records. Conditional logistic regression was used to examine the effect of statin use on HIV √ĺ NHL risk, adjusting for potential confounders (matching factors, prior clinical AIDS diagnosis, antiretroviral use, baseline CD4 cell count, and history of selected co-morbidity) and use of nonstatin lipid-lowering therapy (LLT). Results: A total of 259 cases and 1295 controls were included. Eight percent of the cases and 14% of the controls had a history of statin use. Statin use was associated with lower risk of HIV √ĺ NHL; hazard ratio and 95% confidence intervals for ever use, less than 12, and at least 12 months cumulative use was 0.55 (0.31-0.95), 0.64 (0.31-1.28), and 0.50 (0.23-1.10), respectively. P value for trend for duration of statin use was 0.08. No association between nonstatin LLT use and risk of NHL was observed

    Temporal pattern of C1q deposition after transient focal cerebral ischemia

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    Recent studies have focused on elucidating the contribution of individual complement proteins to post-ischemic cellular injury. As the timing of complement activation and deposition after cerebral ischemia is not well understood, our study investigates the temporal pattern of C1q accumulation after experimental murine stroke. Brains were harvested from mice subjected to transient focal cerebral ischemia at 3, 6, 12, and 24 hr post reperfusion. Western blotting and light microscopy were employed to determine the temporal course of C1q protein accumulation and correlate this sequence with infarct evolution observed with TTC staining. Confocal microscopy was utilized to further characterize the cellular localization and characteristics of C1q deposition. Western Blot analysis showed that C1q protein begins to accumulate in the ischemic hemisphere between 3 and 6 hr post-ischemia. Light microscopy confirmed these findings, showing concurrent C1q protein staining of neurons. Confocal microscopy demonstrated co-localization of C1q protein with neuronal cell bodies as well as necrotic cellular debris. These experiments demonstrate the accumulation of C1q protein on neurons during the period of greatest infarct evolution. This data provides information regarding the optimal time window during which a potentially neuroprotective anti-C1q strategy is most likely to achieve therapeutic success. © 2006 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50651/1/20775_ftp.pd

    Management of aneurysms involving branches of the celiac and superior mesenteric arteries: A comparison of surgical and endovascular therapy

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    ObjectiveAneurysms involving branches of the superior mesenteric and celiac arteries are uncommon and require proper management to prevent rupture and death. This study compares surgical and endovascular treatment of these aneurysms and analyzes outcome.MethodsPatients at the Mount Sinai Medical Center in New York who were treated for aneurysms in the branches of the celiac artery and superior mesenteric artery were identified through a search of the institution‚Äôs medical records and endovascular database. Patient demographics, history, clinical presentation, aneurysm characteristics, treatments, and follow-up outcome were retrospectively recorded. Significant differences between patients treated by surgical or endovascular therapy were determined by using Student‚Äôs t test and Ōá 2 analysis.ResultsBetween January 1, 1991, and July 1, 2005, 59 patients with 61 aneurysms were treated at a single institution. Twenty-four patients had surgical repair, and 35 underwent endovascular treatment, which included coil embolization and stent-graft therapy. Splenic (28) and hepatic (22) artery aneurysms predominated. Eighty-nine percent of splenic artery aneurysms were true aneurysms and were treated by endovascular and surgical procedures in near equal numbers (14 and 11, respectively). Pseudoaneurysms were significantly more likely to be treated by endovascular means (P < .01). The technical success rate of endovascular treatment for aneurysms was 89%, and failures were successfully treated by repeat coil embolization in all patients who presented for retreatment. Patients treated by endovascular techniques had a significantly higher incidence of malignancy than patients treated with open surgical techniques (P = .03). Furthermore, patients treated by endovascular means had a shorter in-hospital length of stay (2.4 vs 6.6 days, P < .001).ConclusionEndovascular management of visceral aneurysms is an effective means of treating aneurysms involving branches of the celiac and superior mesenteric arteries and is particularly useful in patients with comorbidities, including cancer. It is associated with a decreased length of stay in the elective setting, and failure of primary treatment can often be successfully managed percutaneously
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