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1.
Clin Physiol Funct Imaging ; 41(6): 514-522, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34549507

RESUMO

The present study examined cross-sectional and longitudinal relationships between total and segmental subcutaneous tissue thicknesses from ultrasonography (US) and total and segmental fat mass (FM) estimates from dual-energy X-ray absorptiometry (DXA). Traditional US FM estimates were also examined. Twenty resistance-trained males (mean ± SD; age: 22.0 ± 2.6 years; body mass: 74.8 ± 11.5 kg; DXA fat: 17.5 ± 4.5%) completed a 6-week supervised resistance training programme while consuming a hypercaloric diet. Pre- and post-intervention body composition was assessed by DXA and B-mode US. Data were analysed using Pearson's correlation (r), Lin's correlation coefficient (CCC), paired t-tests, Wilcoxon signed-rank tests and Bland-Altman analysis, as appropriate. Cross-sectionally, correlations were observed between total DXA FM and total subcutaneous tissue thickness (r = 0.88). Longitudinally, a correlation was observed between total DXA FM changes and total subcutaneous tissue changes (r = 0.49, CCC = 0.38). Correlations of similar magnitudes were observed for the upper body and trunk estimates, but DXA FM changes were unrelated to subcutaneous tissue changes for the lower body and arms. Cross-sectionally, US 2-compartment FM and DXA FM were correlated (r = 0.91, CCC = 0.83). Longitudinally, a weaker correlation was observed (r = 0.47, CCC = 0.33). In summary, longitudinal associations between US and DXA are weaker than cross-sectional relationships; additionally, correlations between US subcutaneous tissue and whole-body DXA FM appear to be driven by the trunk region rather than appendages. Reporting raw skinfold thicknesses rather than FM estimates alone may improve the utility of techniques based on subcutaneous tissue thickness, such as US and skinfolds.

2.
J Int Soc Sports Nutr ; 18(1): 60, 2021 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-34503541

RESUMO

BACKGROUND: Numerous studies have demonstrated the efficacy of creatine supplementation for improvements in exercise performance. Few studies, however, have examined the effects of phosphocreatine supplementation on exercise performance. Furthermore, while polyphenols have antioxidant and anti-inflammatory properties, little is known regarding the influence of polyphenol supplementation on muscular strength, power, and endurance. Thus, the purpose of the present study was to compare the effects of 28 days of supplementation with phosphocreatine disodium salts plus blueberry extract (PCDSB), creatine monohydrate (CM), and placebo on measures of muscular strength, power, and endurance. METHODS: Thirty-three men were randomly assigned to consume either PCDSB, CM, or placebo for 28 days. Peak torque (PT), average power (AP), and percent decline for peak torque (PT%) and average power (AP%) were assessed from a fatigue test consisting of 50 maximal, unilateral, isokinetic leg extensions at 180°·s- 1 before and after the 28 days of supplementation. Individual responses were assessed to examine the proportion of subjects that exceeded a minimal important difference (MID). RESULTS: The results demonstrated significant (p < 0.05) improvements in PT for the PCDSB and CM groups from pre- (99.90 ± 22.47 N·m and 99.95 ± 22.50 N·m, respectively) to post-supplementation (119.22 ± 29.87 N·m and 111.97 ± 24.50 N·m, respectively), but no significant (p = 0.112) change for the placebo group. The PCDSB and CM groups also exhibited significant improvements in AP from pre- (140.18 ± 32.08 W and 143.42 ± 33.84 W, respectively) to post-supplementation (170.12 ± 42.68 W and 159.78 ± 31.20 W, respectively), but no significant (p = 0.279) change for the placebo group. A significantly (p < 0.05) greater proportion of subjects in the PCDSB group exceeded the MID for PT compared to the placebo group, but there were no significant (p > 0.05) differences in the proportion of subjects exceeding the MID between the CM and placebo groups or between the CM and PCDSB groups. CONCLUSIONS: These findings indicated that for the group mean responses, 28 days of supplementation with both PCDSB and CM resulted in increases in PT and AP. The PCDSB, however, may have an advantage over CM when compared to the placebo group for the proportion of individuals that respond favorably to supplementation with meaningful increases in muscular strength.


Assuntos
Força Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Fosfocreatina/farmacologia , Resistência Física/efeitos dos fármacos , Extratos Vegetais/farmacologia , Mirtilos Azuis (Planta)/química , Creatina , Suplementos Nutricionais , Método Duplo-Cego , Humanos , Masculino , Torque , Adulto Jovem
3.
Br J Nutr ; : 1-19, 2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34325758

RESUMO

The present study reports the validity of multiple assessment methods for tracking changes in body composition over time and quantifies the influence of unstandardised pre-assessment procedures. Resistance-trained males underwent 6 weeks of structured resistance training alongside a hyperenergetic diet, with four total body composition evaluations. Pre-intervention, body composition was estimated in standardised (i.e. overnight fasted and rested) and unstandardised (i.e. no control over pre-assessment activities) conditions within a single day. The same assessments were repeated post-intervention, and body composition changes were estimated from all possible combinations of pre-intervention and post-intervention data. Assessment methods included dual-energy X-ray absorptiometry (DXA), air displacement plethysmography, three-dimensional optical imaging, single- and multi-frequency bioelectrical impedance analysis, bioimpedance spectroscopy and multi-component models. Data were analysed using equivalence testing, Bland-Altman analysis, Friedman tests and validity metrics. Most methods demonstrated meaningful errors when unstandardised conditions were present pre- and/or post-intervention, resulting in blunted or exaggerated changes relative to true body composition changes. However, some methods - particularly DXA and select digital anthropometry techniques - were more robust to a lack of standardisation. In standardised conditions, methods exhibiting the highest overall agreement with the four-component model were other multi-component models, select bioimpedance technologies, DXA and select digital anthropometry techniques. Although specific methods varied, the present study broadly demonstrates the importance of controlling and documenting standardisation procedures prior to body composition assessments across distinct assessment technologies, particularly for longitudinal investigations. Additionally, there are meaningful differences in the ability of common methods to track longitudinal body composition changes.

4.
J Strength Cond Res ; 2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34172636

RESUMO

ABSTRACT: Rodriguez, C, Harty, PS, Stratton, MT, Siedler, MR, Smith, RW, Johnson, BA, Dellinger, JR, Williams, AD, White, SJ, Benavides, ML, and Tinsley, GM. Comparison of indirect calorimetry and common prediction equations for evaluating changes in resting metabolic rate induced by resistance training and a hypercaloric diet. J Strength Cond Res XX(X): 000-000, 2021-The ability to accurately identify resting metabolic rate (RMR) changes over time allows practitioners to prescribe appropriate adjustments to nutritional intake. However, there is a lack of data concerning the longitudinal utility of commonly used RMR prediction equations. The purpose of this study was to evaluate the validity of several commonly used prediction equations to track RMR changes during a hypercaloric nutritional intervention and supervised resistance exercise training program. Twenty resistance-trained men completed the study. The protocol lasted 6 weeks, and subjects underwent RMR assessments by indirect calorimetry (IC) preintervention and postintervention to obtain reference values. Existing RMR prediction equations based on body mass (BM) or dual-energy X-ray absorptiometry fat-free mass (FFM) were also evaluated. Equivalence testing was used to evaluate whether each prediction equation demonstrated equivalence with IC. Null hypothesis significance testing was also performed, and Bland-Altman analysis was used alongside linear regression to assess the degree of proportional bias. Body mass and FFM increased by 3.6 ± 1.7 kg and 2.4 ± 1.6 kg, respectively. Indirect calorimetry RMR increased by 165 ± 97 kcal·d-1, and RMR:FFM increased by 5.6 ± 5.2%. All prediction equations underestimated mean RMR changes relative to IC, with magnitudes ranging from 75 to 155 kcal·d-1, while also displaying unacceptable levels of negative proportional bias. In addition, no equation demonstrated equivalence with IC. Common RMR prediction equations based on BM or FFM did not fully detect the increase in RMR observed with resistance training plus a hypercaloric diet. Overall, the evaluated prediction equations are unsuitable for estimating RMR changes in the context of this study.

5.
Eur J Clin Nutr ; 75(7): 1060-1068, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33727706

RESUMO

BACKGROUND: Due to inherent errors involved in the transformation of raw bioelectrical variables to body fluids or composition estimates, the sole use of resistance (R), reactance (Xc), and phase angle (φ) has been advocated when quantifying longitudinal changes. The aim of this investigation was to assess the ability of four bioimpedance analyzers to detect raw bioimpedance changes induced by purposeful weight gain with resistance training. METHODS: Twenty-one resistance trained males completed a 6-week lifestyle intervention with the aim of purposeful weight gain. Bioimpedance analysis was performed before and after the intervention using four different analyzers (MFBIAInBody: InBody 770; MFBIASECA: Seca mBCA 515/514; BIS: ImpediMed SFB7; SFBIA: RJL Quantum V) for the quantification of R, Xc, and φ at the 50-kHz frequency. Repeated measures ANOVA and follow up tests were performed. RESULTS: Analysis revealed main effects of time and method for R, Xc, and φ (p ≤ 0.02), without significant time x method interactions (p ≥ 0.07). Follow up for time main effects indicated that, on average, R decreased by 4.5-5.8%, Xc decreased by 2.3-4.0%, and φ increased by 1.8-2.6% across time for all analyzers combined. However, varying levels of disagreement in absolute values were observed for each bioelectrical variable. CONCLUSIONS: The differences in absolute bioelectrical values suggests that analyzers should not be used interchangeably, which holds particular importance when reference values are utilized. Despite absolute differences, analyzers with varying characteristics demonstrated similar abilities to detect changes in R, Xc, and φ over time.


Assuntos
Treinamento de Força , Composição Corporal , Impedância Elétrica , Humanos , Masculino , Projetos de Pesquisa , Ganho de Peso
6.
Lancet Public Health ; 6(4): e232-e239, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33662329

RESUMO

BACKGROUND: Social isolation has been associated with increased risk of coronary heart disease and stroke. However, it is unclear whether the associations differ between fatal and non-fatal events or by the type of isolation (living alone or having few social contacts). We aimed to examine these associations in two large UK prospective cohorts. METHODS: Million Women Study and UK Biobank participants without previous coronary heart disease or stroke who provided data in median year 2010 (IQR 2009-2011) on social contacts were included in this prospective analysis. Participants were followed up to median year 2017 (2017-2017) by electronic linkage to national hospital and death records. Risk ratios (RRs) were calculated using Cox regression for first coronary heart disease and stroke event (overall, and separately for hospital admission as the first event and for death without an associated hospital admission as the first event) by three levels of social isolation (based on living alone, contact with family or friends, and group participation) adjusted for age, sex, study, region, deprivation, smoking, alcohol intake, body-mass index, physical activity, and self-rated health. FINDINGS: 938 558 participants were included in our analyses (mean age 63 years [SD 9]): 481 946 participants from the Million Women Study (mean age 68 years [5]) and 456 612 participants (mean age 57 years [8]) from UK Biobank. During a mean follow-up period of 7 years (2), 42 402 first coronary heart disease events (of which 1834 were fatal without an associated hospital admission) and 19 999 first stroke events (of which 529 were fatal without an associated hospital admission) occurred. Little, if any, association was found between social isolation and hospital admission for a first coronary heart disease or stroke event (combined RR for both studies 1·01 [95% CI 0·98-1·04] for coronary heart disease and 1·13 [1·08-1·18] for stroke, when comparing the most isolated group with the least isolated group). However, the risk of death without an associated hospital admission was substantially higher in the most isolated group than the least isolated group for coronary heart disease (1·86 [1·63-2·12]) and stroke (1·91 [1·48-2·46]). For coronary heart disease or stroke death as the first event, RRs were substantially higher (test for heterogeneity, p=0·002) for participants living alone versus those not living alone (1·60 [1·46-1·75]) than for those with fewer versus more contact with family, friends, or groups (1·27 [1·16-1·38]). These findings did not differ greatly between studies, or by self-rated health. INTERPRETATION: Social isolation seems to have little direct effect on the risk of developing a first coronary heart disease or stroke. By contrast, social isolation substantially increases the risk that the first such event is fatal before reaching hospital, particularly among people who live alone, perhaps because of the absence of immediate help in responding to an acute heart attack or stroke. FUNDING: UK Medical Research Council, Cancer Research UK.


Assuntos
Cardiopatias/epidemiologia , Isolamento Social , Acidente Vascular Cerebral/epidemiologia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Medição de Risco , Reino Unido/epidemiologia
7.
Med Sci Sports Exerc ; 53(3): 658-667, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-32804903

RESUMO

PURPOSE: The purpose of this study was to assess the agreement between a field-based three-compartment (3CFIELD) model and a laboratory-based three-compartment (3CLAB) model for tracking body composition changes over time. METHODS: Resistance-trained males completed a supervised nutrition and resistance training intervention. Before and after the intervention, assessments were performed via air displacement plethysmography (ADP), bioimpedance spectroscopy (BIS), portable ultrasonography (US), and bioelectrical impedance analysis (BIA). ADP body density and BIS body water were used within the reference 3CLAB model, whereas US-derived body density and BIA body water were used within the 3CFIELD model. Two-compartment model body composition estimates provided by US and BIA were also examined. Changes in fat-free mass and fat mass were analyzed using repeated-measures ANOVA, equivalence testing, Bland-Altman analysis, linear regression, and related validity analyses. RESULTS: Significant increases in fat-free mass (3CLAB, 4.0 ± 4.5 kg; 3CFIELD, 3.9 ± 4.2 kg; US, 3.2 ± 4.3 kg; BIA, 3.9 ± 4.2 kg) and fat mass (3CLAB, 1.3 ± 2.2 kg; 3CFIELD, 1.4 ± 2.2 kg; US, 2.1 ± 2.6 kg; BIA, 1.4 ± 2.9 kg) were detected by all methods. However, only the 3CFIELD model demonstrated equivalence with the 3CLAB model. In addition, the 3CFIELD model exhibited superior performance to US and BIA individually, as indicated by the total error (3CFIELD, 1.0 kg; US, 1.8 kg; BIA, 1.6 kg), 95% limits of agreement (3CFIELD, ±2.1 kg; US, ±3.3 kg; BIA, ±3.1 kg), correlation coefficients (3CFIELD, 0.79-0.82; US, 0.49-0.55; BIA, 0.61-0.72), and additional metrics. CONCLUSIONS: The present study demonstrated the potential usefulness of a 3CFIELD model incorporating US and BIA data for tracking body composition changes over time, as well as its superiority to US or BIA individually. As such, this accessible multicompartment model may be suitable for implementation in field or limited-resource settings.


Assuntos
Tecido Adiposo/fisiologia , Composição Corporal/fisiologia , Treinamento de Força , Tecido Adiposo/diagnóstico por imagem , Adulto , Análise de Variância , Água Corporal , Carboidratos da Dieta/administração & dosagem , Proteínas na Dieta/administração & dosagem , Impedância Elétrica , Humanos , Modelos Lineares , Masculino , Avaliação Nutricional , Pletismografia/métodos , Reprodutibilidade dos Testes , Fatores de Tempo , Ultrassonografia , Adulto Jovem
8.
Bull World Health Organ ; 98(11): 754-765B, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-33177772

RESUMO

Objective: To explore how primary care organizations assess and subsequently act upon the social determinants of noncommunicable diseases in their local populations. Methods: For this systematic review we searched the online databases of PubMed®, MEDLINE®, Embase® and the Health Management Information Consortium from inception to 28 June 2019, along with hand-searching of references. Studies of any design that examined a primary care organization assessing social determinants of noncommunicable diseases were included. For quality assessment we used Cochrane's tool for assessing risk of bias in non-randomized studies of interventions. We used narrative data synthesis to appraise the extent to which the assessments gathered data on the domains of the World Health Organization social determinants of health framework. Findings: We identified 666 studies of which 17 were included in the review. All studies used descriptive study designs. Clinic-based and household surveys and interviews were more commonly used to assess local social determinants than population-level data. We found no examples of organizations that assessed sociopolitical drivers of noncommunicable diseases; all focused on sociodemographic factors or circumstances of daily living. Nevertheless, the resulting actions to address social determinants ranged from individual-level interventions to population-wide measures and introducing representation of primary care organizations on system-level policy and planning committees. Conclusion: Our findings may help policy-makers to consider suitable approaches for assessing and addressing social determinants of health in their domestic context. More rigorous observational and experimental evidence is needed to ascertain whether measuring social determinants leads to interventions which mitigate unmet social needs and reduce health disparities.

10.
J Int Soc Sports Nutr ; 17(1): 45, 2020 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-32831109

RESUMO

BACKGROUND: Energy drinks are often consumed by the general population, as well as by active individuals seeking to enhance exercise performance and augment training adaptations. However, limited information is available regarding the efficacy of these products. Thus, the purpose of this study was to determine the effects of a commercially available caffeine- and protein-containing energy drink on metabolism and muscular performance. METHODS: Sixteen resistance-trained males (n = 8; mean ± SD; age: 22.4 ± 4.9 years; body mass: 78.8 ± 14.0 kg; body fat: 15.3 ± 6.4%) and females (n = 8; age: 24.5 ± 4.8 years; body mass: 67.5 ± 11.9 kg; body fat: 26.6 ± 7.1%) participated in this randomized, double-blind, placebo-controlled, crossover study. Following a familiarization visit, participants completed two identical visits to the laboratory separated by 5-10 days, each of which consisted of indirect calorimetry energy expenditure (EE) assessments before and after consumption of the beverage (Bang® Keto Coffee; 130 kcal, 300 mg caffeine, 20 g protein) or placebo (30 kcal, 11 mg caffeine, 1 g protein) as well as after exercise testing. In addition, participants' subjective feelings of energy, fatigue, and focus as well as muscular performance (leg press one-repetition maximum and repetitions to fatigue, maximal isometric and isokinetic squat testing) were assessed. Multiple repeated measures ANOVAs with Tukey post-hoc tests were used to analyze data. Estimates of effect size were quantified via partial eta squared (ηP2) and Hedge's g. RESULTS: A significant interaction effect was identified for EE (p < 0.001, ηP2 = 0.52) but not respiratory exchange ratio (p = 0.17, ηP2 = 0.11). Following consumption of the beverage, EE was 0.18 [corrected] kcal·min- 1 greater than placebo at the post-beverage time point (p < 0.001) and 0.08 [corrected] kcal·min- 1 greater than placebo at the post-exercise time point (p = 0.011). However, no between-condition differences were detected for any subjective or muscular performance outcomes. CONCLUSIONS: The results of this study suggest that consumption of the energy drink had minimal effects on lower-body muscular performance and subjective factors in the context of a laboratory setting. However, the beverage was found to significantly increase energy expenditure compared to placebo immediately following ingestion as well as during the recovery period after an exercise bout, suggesting that active individuals may improve acute metabolic outcomes via consumption of a caffeine- and protein-containing energy drink. TRIAL REGISTRATION: This trial was prospectively registered at ClinicalTrials.gov (Identifier: NCT04180787 ; Registered 29 November 2019).


Assuntos
Café , Bebidas Energéticas , Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Músculo Esquelético/fisiologia , Treinamento de Força , Adolescente , Adulto , Cafeína/farmacologia , Calorimetria Indireta , Estudos Cross-Over , Método Duplo-Cego , Metabolismo Energético/efeitos dos fármacos , Teste de Esforço/métodos , Feminino , Humanos , Perna (Membro)/fisiologia , Masculino , Músculo Esquelético/efeitos dos fármacos , Substâncias para Melhoria do Desempenho/farmacologia , Troca Gasosa Pulmonar/efeitos dos fármacos , Treinamento de Força/métodos , Levantamento de Peso/fisiologia , Adulto Jovem
11.
Methods Mol Biol ; 2026: 121-133, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31317407

RESUMO

Mathematical models are important tools in helping us to understand complex biological systems. Models of phytochrome-regulated systems in Arabidopsis thaliana have shown the importance of dimerization, nuclear transport, and thermal/dark reversion in mediating phytochrome activity and plant development. Here we go through the steps required to calculate the steady-state amounts of phytochrome subspecies relative to the total phytochrome molecule population. Starting from a simplified two-state system we expand and apply the technique to the extended phytochrome dimer model. Additionally, we provide a Python package that can automatically calculate the proportion of phytochrome B in a particular state given specific experimental conditions.


Assuntos
Modelos Teóricos , Fitocromo B/química , Arabidopsis/metabolismo , Proteínas de Arabidopsis/análise
12.
Phys Rev E ; 99(5-1): 052417, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31212540

RESUMO

It is well known that the kinetics of an intracellular biochemical network is stochastic. This is due to intrinsic noise arising from the random timing of biochemical reactions in the network as well as due to extrinsic noise stemming from the interaction of unknown molecular components with the network and from the cell's changing environment. While there are many methods to study the effect of intrinsic noise on the system dynamics, few exist to study the influence of both types of noise. Here we show how one can extend the conventional linear-noise approximation to allow for the rapid evaluation of the molecule numbers statistics of a biochemical network influenced by intrinsic noise and by slow lognormally distributed extrinsic noise. The theory is applied to simple models of gene regulatory networks and its validity confirmed by comparison with exact stochastic simulations. In particular, we consider three important biological examples. First, we investigate how extrinsic noise modifies the dependence of the variance of the molecule number fluctuations on the rate constants. Second, we show how the mutual information between input and output of a network motif is affected by extrinsic noise. And third, we study the robustness of the ubiquitously found feed-forward loop motifs when subjected to extrinsic noise.

13.
Elife ; 82019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30947807

RESUMO

The immune system distinguishes between self and foreign antigens. The kinetic proofreading (KPR) model proposes that T cells discriminate self from foreign ligands by the different ligand binding half-lives to the T cell receptor (TCR). It is challenging to test KPR as the available experimental systems fall short of only altering the binding half-lives and keeping other parameters of the interaction unchanged. We engineered an optogenetic system using the plant photoreceptor phytochrome B (PhyB) as a ligand to selectively control the dynamics of ligand binding to the TCR by light. This opto-ligand-TCR system was combined with the unique property of PhyB to continuously cycle between the binding and non-binding states under red light, with the light intensity determining the cycling rate and thus the binding duration. Mathematical modeling of our experimental datasets showed that indeed the ligand-TCR interaction half-life is the decisive factor for activating downstream TCR signaling, substantiating KPR.


Assuntos
Antígenos/metabolismo , Fitocromo B/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais , Linfócitos T/imunologia , Humanos , Células Jurkat , Cinética , Luz , Modelos Teóricos , Optogenética/métodos , Ligação Proteica
14.
Mol Cell ; 73(4): 763-774.e10, 2019 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-30661980

RESUMO

The biosynthesis of coenzyme Q presents a paradigm for how cells surmount hydrophobic barriers in lipid biology. In eukaryotes, CoQ precursors-among nature's most hydrophobic molecules-must somehow be presented to a series of enzymes peripherally associated with the mitochondrial inner membrane. Here, we reveal that this process relies on custom lipid-binding properties of COQ9. We show that COQ9 repurposes the bacterial TetR fold to bind aromatic isoprenes with high specificity, including CoQ intermediates that likely reside entirely within the bilayer. We reveal a process by which COQ9 associates with cardiolipin-rich membranes and warps the membrane surface to access this cargo. Finally, we identify a molecular interface between COQ9 and the hydroxylase COQ7, motivating a model whereby COQ9 presents intermediates directly to CoQ enzymes. Overall, our results provide a mechanism for how a lipid-binding protein might access, select, and deliver specific cargo from a membrane to promote biosynthesis.


Assuntos
Lipídeos de Membrana/metabolismo , Membranas Mitocondriais/enzimologia , Proteínas Mitocondriais/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Ubiquinona/biossíntese , Sítios de Ligação , Cardiolipinas/metabolismo , Cristalografia , Proteínas Mitocondriais/química , Proteínas Mitocondriais/genética , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica em alfa-Hélice , Transporte Proteico , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Relação Estrutura-Atividade , Triptofano , Ubiquinona/química , Ubiquinona/genética
15.
Plant Cell Environ ; 42(2): 606-617, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30216475

RESUMO

Vegetation shade is characterized by marked decreases in the red/far-red ratio and photosynthetic irradiance. The activity of phytochrome in the field has typically been described by its photoequilibrium, defined by the photochemical properties of the pigment in combination with the spectral distribution of the light. This approach represents an oversimplification because phytochrome B (phyB) activity depends not only on its photochemical reactions but also on its rates of synthesis, degradation, translocation to the nucleus, and thermal reversion. To account for these complex cellular reactions, we used a model to simulate phyB activity under a range of field conditions. The model provided values of phyB activity that in turn predicted hypocotyl growth in the field with reasonable accuracy. On the basis of these observations, we define two scenarios, one is under shade, in cloudy weather, at the extremes of the photoperiod or in the presence of rapid fluctuations of the light environment caused by wind-induced movements of the foliage, where phyB activity departs from photoequilibrium and becomes affected by irradiance and temperature in addition to the spectral distribution. The other scenario is under full sunlight, where phyB activity responds mainly to the spectral distribution of the light.


Assuntos
Proteínas de Arabidopsis/metabolismo , Fitocromo B/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Hipocótilo/crescimento & desenvolvimento , Luz , Modelos Biológicos , Fotoperíodo , Luz Solar
16.
Pers Soc Psychol Bull ; 45(1): 67-80, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29911504

RESUMO

People commonly lament the inability to re-experience familiar things as they were first experienced. Four experiments suggest that consuming familiar things in new ways can disrupt adaptation and revitalize enjoyment. Participants better enjoyed the same familiar food (Experiment 1), drink (Experiment 2), and video (Experiments 3a-3b) simply when re-experiencing the entity via unusual means (e.g., eating popcorn using chopsticks vs. hands). This occurs because unconventional methods invite an immersive "first-time" perspective on the consumption object: boosts in enjoyment were mediated by revitalized immersion into the consumption experience and were moderated by time such that they were strongest when using unconventional methods for the first time (Experiments 1-2); likewise, unconventional methods that actively disrupted immersion did not elicit the boost, despite being novel (Experiments 3a-3b). Before abandoning once-enjoyable entities, knowing to consume old things in new ways (vs. attaining new things altogether) might temporarily restore enjoyment and postpone wasteful replacement.


Assuntos
Comportamento do Consumidor , Satisfação Pessoal , Reconhecimento Psicológico , Adolescente , Adulto , Comportamento Exploratório , Feminino , Humanos , Masculino , Adulto Jovem
17.
J Acoust Soc Am ; 144(4): 2334, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30404487

RESUMO

This paper presents the results of an experimental investigation of the parametric stabilization of Rayleigh-Bénard convection through the imposition of sinusoidal vibration. The ability to dynamically stabilize Rayleigh-Bénard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines as the introduction of parasitic convection can have deleterious effects on the desired operation and thermodynamic efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and cryogenic pulse tube chillers. This paper reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration with comparison to the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135, 654-668 (2014)]. Measurements are obtained using a large-displacement kinematic shaker of an original design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. These experiments are believed to be the first demonstrating the suppression of convection through vibration in rectangular containers.

18.
BMC Syst Biol ; 12(1): 72, 2018 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-29914475

RESUMO

BACKGROUND: Models of metabolism are often used in biotechnology and pharmaceutical research to identify drug targets or increase the direct production of valuable compounds. Due to the complexity of large metabolic systems, a number of conclusions have been drawn using mathematical methods with simplifying assumptions. For example, constraint-based models describe changes of internal concentrations that occur much quicker than alterations in cell physiology. Thus, metabolite concentrations and reaction fluxes are fixed to constant values. This greatly reduces the mathematical complexity, while providing a reasonably good description of the system in steady state. However, without a large number of constraints, many different flux sets can describe the optimal model and we obtain no information on how metabolite levels dynamically change. Thus, to accurately determine what is taking place within the cell, finer quality data and more detailed models need to be constructed. RESULTS: In this paper we present a computational framework, DMPy, that uses a network scheme as input to automatically search for kinetic rates and produce a mathematical model that describes temporal changes of metabolite fluxes. The parameter search utilises several online databases to find measured reaction parameters. From this, we take advantage of previous modelling efforts, such as Parameter Balancing, to produce an initial mathematical model of a metabolic pathway. We analyse the effect of parameter uncertainty on model dynamics and test how recent flux-based model reduction techniques alter system properties. To our knowledge this is the first time such analysis has been performed on large models of metabolism. Our results highlight that good estimates of at least 80% of the reaction rates are required to accurately model metabolic systems. Furthermore, reducing the size of the model by grouping reactions together based on fluxes alters the resulting system dynamics. CONCLUSION: The presented pipeline automates the modelling process for large metabolic networks. From this, users can simulate their pathway of interest and obtain a better understanding of how altering conditions influences cellular dynamics. By testing the effects of different parameterisations we are also able to provide suggestions to help construct more accurate models of complete metabolic systems in the future.


Assuntos
Metabolismo , Modelos Biológicos , Software , Automação , Lactococcus lactis/metabolismo
19.
Phys Biol ; 15(5): 056003, 2018 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-29714708

RESUMO

Spatial relocalization of proteins is crucial for the correct functioning of living cells. An interesting example of spatial ordering is the light-induced clustering of plant photoreceptor proteins. Upon irradiation by white or red light, the red light-active phytochrome, phytochrome B, enters the nucleus and accumulates in large nuclear bodies (NBs). The underlying physical process of nuclear body formation remains unclear, but phytochrome B is thought to coagulate via a simple protein-protein binding process. We measure, for the first time, the distribution of the number of phytochrome B-containing NBs as well as their volume distribution. We show that the experimental data cannot be explained by a stochastic model of nuclear body formation via simple protein-protein binding processes using physically meaningful parameter values. Rather modelling suggests that the data is consistent with a two step process: a fast nucleation step leading to macroparticles followed by a subsequent slow step in which the macroparticles bind to form the nuclear body. An alternative explanation for the observed nuclear body distribution is that the phytochromes bind to a so far unknown molecular structure. We believe it is likely this result holds more generally for other nuclear body-forming plant photoreceptors and proteins.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Fitocromo B/metabolismo , Transporte Ativo do Núcleo Celular/efeitos da radiação , Arabidopsis/citologia , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/análise , Núcleo Celular/efeitos da radiação , Simulação por Computador , Luz , Modelos Biológicos , Fitocromo B/análise , Ligação Proteica/efeitos da radiação , Processos Estocásticos
20.
J Biol Chem ; 293(14): 4955-4968, 2018 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-29449375

RESUMO

As a major component of plant cell walls, lignin is a potential renewable source of valuable chemicals. Several sphingomonad bacteria have been identified that can break the ß-aryl ether bond connecting most phenylpropanoid units of the lignin heteropolymer. Here, we tested three sphingomonads predicted to be capable of breaking the ß-aryl ether bond of the dimeric aromatic compound guaiacylglycerol-ß-guaiacyl ether (GGE) and found that Novosphingobium aromaticivorans metabolizes GGE at one of the fastest rates thus far reported. After the ether bond of racemic GGE is broken by replacement with a thioether bond involving glutathione, the glutathione moiety must be removed from the resulting two stereoisomers of the phenylpropanoid conjugate ß-glutathionyl-γ-hydroxypropiovanillone (GS-HPV). We found that the Nu-class glutathione S-transferase NaGSTNu is the only enzyme needed to remove glutathione from both (R)- and (S)-GS-HPV in N. aromaticivorans We solved the crystal structure of NaGSTNu and used molecular modeling to propose a mechanism for the glutathione lyase (deglutathionylation) reaction in which an enzyme-stabilized glutathione thiolate attacks the thioether bond of GS-HPV, and the reaction proceeds through an enzyme-stabilized enolate intermediate. Three residues implicated in the proposed mechanism (Thr51, Tyr166, and Tyr224) were found to be critical for the lyase reaction. We also found that Nu-class GSTs from Sphingobium sp. SYK-6 (which can also break the ß-aryl ether bond) and Escherichia coli (which cannot break the ß-aryl ether bond) can also cleave (R)- and (S)-GS-HPV, suggesting that glutathione lyase activity may be common throughout this widespread but largely uncharacterized class of glutathione S-transferases.


Assuntos
Glutationa Transferase/metabolismo , Lignina/metabolismo , Sphingomonadaceae/enzimologia , Substituição de Aminoácidos , Domínio Catalítico , Cristalografia por Raios X , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Glutationa Transferase/química , Glutationa Transferase/genética , Lignina/química , Modelos Moleculares , Conformação Proteica , Multimerização Proteica , Sphingomonadaceae/química , Sphingomonadaceae/genética , Sphingomonadaceae/metabolismo , Estereoisomerismo , Especificidade por Substrato , Transcriptoma
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