Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.197
Filtrar
1.
J Alzheimers Dis ; 81(3): 1039-1052, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33935071

RESUMO

BACKGROUND: Previous research has identified a small subgroup of older adults that maintain a high level of cognitive functioning well into advanced age. Investigation of those with superior cognitive performance (SCP) for their age is important, as age-related decline has previously been thought to be inevitable. OBJECTIVE: Preservation of cortical thickness and volume was evaluated in 76 older adults with SCP and 100 typical older adults (TOAs) assessed up to five times over six years. METHODS: Regions of interest (ROIs) found to have been associated with super-aging status (a construct similar to SCP status) in previous literature were investigated, followed by a discovery phase analyses of additional regions. SCPs were aged 70 + at baseline, scoring at/above normative memory (CVLT-II) levels for demographically similar individuals aged 30-44 years old, and in the unimpaired range for all other cognitive domains over the course of the study. RESULTS: In linear mixed models, following adjustment for multiple comparisons, there were no significant differences between rates of thinning or volume atrophy between SCPs and TOAs in previously identified ROIs, or the discovery phase analyses. With only amyloid-ß negative individuals in the analyses, again there were no significant differences between SCPs and TOAs. CONCLUSION: The increased methodological rigor in classifying groups, together with the influence of cognitive reserve, are discussed as potential factors accounting for our findings as compared to the extant literature on those with superior cognitive performance for their age.


Assuntos
Envelhecimento/patologia , Atrofia/patologia , Espessura Cortical do Cérebro , Córtex Cerebral/patologia , Cognição/fisiologia , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/psicologia , Atrofia/diagnóstico por imagem , Atrofia/psicologia , Córtex Cerebral/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Testes Neuropsicológicos , Tamanho do Órgão/fisiologia
2.
J Alzheimers Dis ; 81(1): 413-426, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33814443

RESUMO

BACKGROUND: Identifying modifiable risk factors for cognitive decline can reduce burden of dementia. OBJECTIVE: We examined whether homocysteine was associated with memory performance, mediated by entorhinal volume, hippocampal volume, total gray matter volume, or white matter lesions, and moderated by APOE ɛ4 allele, B vitamins, creatinine, total cholesterol, or triglycerides. METHODS: All 204 members of the Czech Brain Aging Study with subjective cognitive decline (SCD; n = 60) or amnestic mild cognitive impairment (aMCI; n = 144) who had valid data were included. Linear regression was used, followed by conditional process modeling to examine mediation and moderation. RESULTS: Controlling for age, sex, and education, higher homocysteine was related to poorer memory performance overall (b = -0.03, SE = 0.01, p = 0.017) and in participants with SCD (b = -0.06, SE = 0.03, p = 0.029), but less so in aMCI (b = -0.03, SE = 0.02, p = 0.074); though sensitivity analyses revealed a significant association when sample was reduced to aMCI patients with more complete cognitive data (who were also better functioning; b = -0.04, SE = 0.02, p = 0.022). Results were unchanged in fully adjusted models. Neither mediation by markers of brain integrity nor moderation by APOE ɛ4, B vitamins, creatinine, and cardiovascular factors were significant. Memory sub-analyses revealed that results for SCD were likely driven by non-verbal memory. The homocysteine-memory relationship was significant when hippocampal volume was below the median (b = -0.04, SE = 0.02, p = 0.046), but not at/above the median (p = 0.247). CONCLUSION: Higher homocysteine levels may adversely influence memory performance, which appears particularly apparent in those without cognitive impairment. Results appear to be independent of brain health, suggesting that homocysteine may represent a good target for intervention.


Assuntos
Substância Cinzenta/diagnóstico por imagem , Homocisteína/sangue , Memória/fisiologia , Substância Branca/diagnóstico por imagem , Idoso , Idoso de 80 Anos ou mais , Feminino , Hipocampo/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Tamanho do Órgão/fisiologia
3.
Eur J Histochem ; 65(2)2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33764018

RESUMO

As a vital male accessory reproductive gonad, the prostate requires vascular endothelial growth factors for promoting its growth and development. In this study, we investigated the localizations and expressions of vascular endothelial growth factor (VEGF) and its receptors including VEGF-receptor1 (VEFGR1) and VEGF-receptor2 (VEGFR2) in the prostate of the wild ground squirrels during the breeding and the non-breeding seasons. The values of total prostate weight and volume in the breeding season were higher than those in the non-breeding season. Histological observations showed that the exocrine lumens of the prostate expanded in the breeding season and contracted in the non-breeding season. The mRNA expression levels of VEGF and VEGFR2 in the prostate were higher in the breeding season than those in the non-breeding season, but the mRNA expression level of VEGFR1 had no significant change between the breeding and non-breeding seasons. Immunohistochemical results revealed that VEGF, VEGFR1 and VEGFR2 were presented in epithelial and stromal cells during the breeding and non-breeding seasons. In addition, the microvessels of the prostate were widely distributed and the number of microvessels increased obviously in the breeding season, while decreased sharply in the non-breeding season. These results suggested that expression levels of VEGF and VEGFR2 might be correlated with seasonal changes in morphology and functions of the prostate, and VEGF might serve as pivotal regulators to affect seasonal changes in the prostate functions of the wild male ground squirrels via an autocrine/paracrine pathway.


Assuntos
Próstata/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Animais , Imuno-Histoquímica , Masculino , Densidade Microvascular/fisiologia , Tamanho do Órgão/fisiologia , Próstata/citologia , Sciuridae , Estações do Ano
5.
Nat Commun ; 12(1): 721, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33526780

RESUMO

Aging and Alzheimer's disease (AD) are associated with progressive brain disorganization. Although structural asymmetry is an organizing feature of the cerebral cortex it is unknown whether continuous age- and AD-related cortical degradation alters cortical asymmetry. Here, in multiple longitudinal adult lifespan cohorts we show that higher-order cortical regions exhibiting pronounced asymmetry at age ~20 also show progressive asymmetry-loss across the adult lifespan. Hence, accelerated thinning of the (previously) thicker homotopic hemisphere is a feature of aging. This organizational principle showed high consistency across cohorts in the Lifebrain consortium, and both the topological patterns and temporal dynamics of asymmetry-loss were markedly similar across replicating samples. Asymmetry-change was further accelerated in AD. Results suggest a system-wide dedifferentiation of the adaptive asymmetric organization of heteromodal cortex in aging and AD.


Assuntos
Envelhecimento/fisiologia , Doença de Alzheimer/patologia , Córtex Cerebral/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Córtex Cerebral/diagnóstico por imagem , Feminino , Voluntários Saudáveis , Humanos , Estudos Longitudinais , Imageamento por Ressonância Magnética/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão/fisiologia , Fatores de Tempo , Adulto Jovem
6.
Int J Sports Med ; 42(6): 494-496, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33506444

RESUMO

Specialized resistance training techniques (e.g., drop-set, rest-pause) are commonly used by well-trained subjects for maximizing muscle hypertrophy. Most of these techniques were designed to allow a greater training volume (i.e., total repetitions×load), due to the supposition that it elicits greater muscle mass gains. However, many studies that compared the traditional resistance training configuration with specialized techniques seek to equalize the volume between groups, making it difficult to determine the inherent hypertrophic potential of these advanced strategies, as well as, this equalization restricts part of the practical extrapolation on these findings. In this scenario, the objectives of this manuscript were 1) to present the nuance of the evidence that deals with the effectiveness of these specialized resistance training techniques and - primarily - to 2) propose possible ways to explore the hypertrophic potential of such strategies with greater ecological validity without losing the methodological rigor of controlling possible intervening variables; and thus, contributing to increasing the applicability of the findings and improving the effectiveness of hypertrophy-oriented resistance training programs.


Assuntos
Músculo Esquelético/anatomia & histologia , Treinamento de Força/métodos , Humanos , Músculo Esquelético/crescimento & desenvolvimento , Tamanho do Órgão/fisiologia
7.
Sci Rep ; 11(1): 1762, 2021 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-33469140

RESUMO

The threshold size for enlarged abdominal lymph nodes (E-ALNs), a common pediatric disorder, has yet to be standardized. According to the maximum short-axis diameter, this study divided ALNs into Grade A (≥ 10 mm), Grade B (8-10 mm), Grade C (5-8 mm), and Grade D (< 5 mm, normal). To identify the threshold size for E-ALNs, the prevalence of each grade was compared between asymptomatic individuals and symptomatic (e.g., abdominal pain) individuals without other diseases (e.g., appendicitis) that could explain the symptoms for different ages using data from > 200,000 individuals. The results showed the following: (1) For ages 1-3 years, the recommended threshold size is 8 mm, as the differences in the prevalence between the two groups were nonsignificant for Grade C but significant (p < 0.05) for both Grades A and B. (2) For ages 3-14 years, the recommended threshold size is 5 mm, as the differences between the two groups were significant (p < 0.05) for Grades A, B, and C. (3) The prevalence of Grades A, B, and C was very low for ages 0-1 years and high for ages 1-6 years. (4) The prevalence for males was generally higher than that for females for Grades A and B.


Assuntos
Linfonodos/patologia , Linfadenopatia/patologia , Linfadenite Mesentérica/patologia , Abdome/fisiologia , Dor Abdominal/patologia , Adolescente , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Tamanho do Órgão/fisiologia
8.
Trop Anim Health Prod ; 53(1): 91, 2021 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-33415493

RESUMO

Body size and testicular measurements were found to be important parameters for the evaluation of the breeding quality. A study was therefore carried out on Arabia bucks (n = 180) to record normal testicular characteristics and to evaluate the effect of age on body (BCS, BW, WH, CG, AC, CS, and BL) and testicular (SC, TW, EW, TL, TD, and TL) measurements. Animals were classified into three age classes (less than or equal to 12 months, from 12 to 24 months, and over 24 months). The BW, BCS, testicular, and body measurements of the 3rd age group were significantly higher than those of age groups 1 and 2 (p < 0.01). Male age had a significant effect (p < 0.01) on BW, BCS, and body measurements. Indeed, the parameters of the 3rd age group were significantly higher than those of the 1st and 2nd age groups (p < 0.01). The same was true for testicular measurements (SC, TL, TW, EW, and EL) except for testicular diameter (TD) where the results of the first two age groups had no significant difference. The highest correlation coefficients were recorded between BW and all body (r = 0.7-0.9) and testicular traits (r = 0.72-0.85), BCS and body measurements (r = 0.73-0.89), and scrotal circumference and testicular measurements (r = 0.77-0.85). In conclusion, it was found that the use of BCS is readily measurable in live animals and is expected to be the best indicator of testicular and epididymal measurements. These results, particularly the predictive models developed, could be useful in the selection of males for reproduction.


Assuntos
Tamanho Corporal , Peso Corporal , Cabras/fisiologia , Testículo/fisiologia , Fatores Etários , Argélia , Animais , Masculino , Tamanho do Órgão/fisiologia
9.
Neurology ; 96(7): e964-e974, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33408144

RESUMO

OBJECTIVE: To test the hypothesis that greater levels of leisure-time moderate to vigorous intensity physical activity (MVPA) in midlife or late life are associated with larger gray matter volumes, less white matter disease, and fewer cerebrovascular lesions measured in late life, we utilized data from 1,604 participants enrolled in the Atherosclerosis Risk in Communities study. METHODS: Leisure-time MVPA was quantified using a past-year recall, interviewer-administered questionnaire at baseline and 25 years later and classified as none, low, middle, and high at each time point. The presence of cerebrovascular lesions, white matter hyperintensities (WMH), white matter integrity (mean fractional anisotropy [FA] and mean diffusivity [MD]), and gray matter volumes were quantified with 3T MRI in late life. The odds of cerebrovascular lesions were estimated with logistic regression. Linear regression estimated the mean differences in WMH, mean FA and MD, and gray matter volumes. RESULTS: Among 1,604 participants (mean age 53 years, 61% female, 27% Black), 550 (34%), 176 (11%), 250 (16%), and 628 (39%) reported no, low, middle, and high MVPA in midlife, respectively. Compared to no MVPA in midlife, high MVPA was associated with more intact white matter integrity in late life (mean FA difference 0.13 per SD [95% confidence interval (CI) 0.004, 0.26]; mean MD difference -0.11 per SD [95% CI -0.21, -0.004]). High MVPA in midlife was also associated with a lower odds of lacunar infarcts (odds ratio 0.68, 95% CI 0.46, 0.99). High MVPA was not associated with gray matter volumes. High MVPA compared to no MVPA in late life was associated with most brain measures. CONCLUSION: Greater levels of physical activity in midlife may protect against cerebrovascular sequelae in late life.


Assuntos
Encéfalo/diagnóstico por imagem , Exercício Físico/fisiologia , Substância Cinzenta/diagnóstico por imagem , Atividades de Lazer , Substância Branca/diagnóstico por imagem , Feminino , Humanos , Leucoencefalopatias/diagnóstico por imagem , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neuroimagem , Tamanho do Órgão/fisiologia
10.
Am J Phys Med Rehabil ; 100(5): 473-482, 2021 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32889861

RESUMO

OBJECTIVE: The aims of this study were to investigate changes in regional brain volume after concussion (mild traumatic brain injury) and to examine the relationship between change in brain volume and cognitive deficits. DESIGN: Twenty-eight patients with mild traumatic brain injury and 27 age-matched controls were included in this study. Magnetic resonance imaging (3 T) data were obtained from the participants. Structural brain volume changes were examined using tensor-based morphometry, which identifies regional structural differences in the whole brain, including cerebrospinal fluid, gray matter, and white matter. Volume contraction and expansion were compared between groups using a two-sample t test. The association between time post-injury or neurocognitive function and volumetric changes was examined using regression analysis. RESULTS: Individuals with mild traumatic brain injury exhibited volume reduction in the brainstem, including the pontine reticular formation. Regional cerebral volume changes were not associated with time post-injury but were significantly associated with neurocognitive function, especially with executive card sorting test, forward digit span test, and performance on verbal learning test. The greater regional cerebral volume was associated with better cognitive performance after mild traumatic brain injury. CONCLUSION: Decreased brainstem volume may indicate its vulnerability to traumatic injury, and cerebral volume in specific regions was positively associated with patients' cognitive function after injury.


Assuntos
Concussão Encefálica/fisiopatologia , Tronco Encefálico/fisiopatologia , Disfunção Cognitiva/fisiopatologia , Tamanho do Órgão/fisiologia , Adulto , Concussão Encefálica/diagnóstico por imagem , Tronco Encefálico/diagnóstico por imagem , Disfunção Cognitiva/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Inquéritos e Questionários , Adulto Jovem
11.
Neuroimage ; 224: 117395, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-32979525

RESUMO

The structure of the adult brain is the result of complex physical mechanisms acting in three-dimensional space through development. Consequently, the brain's spatial embedding plays a key role in its organization, including the gradient-like patterning of gene expression that encodes the molecular underpinning of functional specialization. However, we do not yet understand how changes in brain shape and size that occur across development influence the brain's transcriptional architecture. Here we investigate the spatial embedding of transcriptional patterns of over 1800 genes across seven time points through mouse-brain development using data from the Allen Developing Mouse Brain Atlas. We find that transcriptional similarity decreases exponentially with separation distance across all developmental time points, with a correlation length scale that follows a power-law scaling relationship with a linear dimension of brain size. This scaling suggests that the mouse brain achieves a characteristic balance between local molecular similarity (homogeneous gene expression within a specialized brain area) and longer-range diversity (between functionally specialized brain areas) throughout its development. Extrapolating this mouse developmental scaling relationship to the human cortex yields a prediction consistent with the value measured from microarray data. We introduce a simple model of brain growth as spatially autocorrelated gene-expression gradients that expand through development, which captures key features of the mouse developmental data. Complementing the well-known exponential distance rule for structural connectivity, our findings characterize an analogous exponential distance rule for transcriptional gradients that scales across mouse brain development, providing new understanding of spatial constraints on the brain's molecular patterning.


Assuntos
Encéfalo , Córtex Cerebral/fisiologia , Expressão Gênica/fisiologia , Tamanho do Órgão/fisiologia , Animais , Encéfalo/crescimento & desenvolvimento , Encéfalo/fisiologia , Mapeamento Encefálico/métodos , Processamento de Imagem Assistida por Computador/métodos , Camundongos Endogâmicos C57BL
12.
Acta Obstet Gynecol Scand ; 100(6): 1040-1050, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-32865812

RESUMO

INTRODUCTION: Infection and inflammation have been implicated in the etiology and subsequent morbidity associated with preterm birth. At present, there are no tests to assess for fetal compartment infection. The thymus, a gland integral in the fetal immune system, has been shown to involute in animal models of antenatal infection, but its response in human fetuses has not been studied. This study aims: (a) to generate magnetic resonance imaging (MRI) -derived fetal thymus volumes standardized for fetal weight; (b) to compare standardized thymus volumes from fetuses that delivered before 32 weeks of gestation with fetuses that subsequently deliver at term; (c) to assess thymus size as a predictor of preterm birth; and (d) to correlate the presence of chorioamnionitis and funisitis at delivery with thymic volumes in utero in fetuses that subsequently deliver preterm. MATERIAL AND METHODS: Women at high-risk of preterm birth at 20-32 weeks of gestation were recruited. A control group was obtained from existing data sets acquired as part of three research studies. A fetal MRI was performed on a 1.5T or 3T MRI scanner: T2 weighted images were obtained of the entire uterine content and specifically the fetal thorax. A slice-to-volume registration method was used for reconstruction of three-dimensional images of the thorax. Thymus segmentations were performed manually. Body volumes were calculated by manual segmentation and thymus:body volume ratios were generated. Comparison of groups was performed using multiple regression analysis. Normal ranges were created for thymus volume and thymus:body volume ratios using the control data. Receiver operating curves (ROC) curves were generated for thymus:body volume ratio and gestation-adjusted thymus volume centiles as predictors of preterm birth. Placental histology was analyzed where available from pregnancies that delivered very preterm and the presence of chorioamnionitis/funisitis was noted. RESULTS: Normative ranges were created for thymus volume, and thymus volume was standardized for fetal size from fetuses that subsequently delivered at term, but were imaged at 20-32 weeks of gestation. Image data sets from 16 women that delivered <32 weeks of gestation (ten with ruptured membranes and six with intact membranes) and 80 control women that delivered >37 weeks were included. Mean gestation at MRI of the study group was 28+4  weeks (SD 3.2) and for the control group was 25+5  weeks (SD 2.4). Both absolute fetal thymus volumes and thymus:body volume ratios were smaller in fetuses that delivered preterm (P < .001). Of the 16 fetuses that delivered preterm, 13 had placental histology, 11 had chorioamnionitis, and 9 had funisitis. The strongest predictors of prematurity were the thymus volume Z-score and thymus:body volume ratio Z-score (ROC areas 0.915 and 0.870, respectively). CONCLUSIONS: We have produced MRI-derived normal ranges for fetal thymus and thymus:body volume ratios between 20 and 32 weeks of gestation. Fetuses that deliver very preterm had reduced thymus volumes when standardized for fetal size. A reduced thymus volume was also a predictor of spontaneous preterm delivery. Thymus volume may be a suitable marker of the fetal inflammatory response, although further work is needed to assess this, increasing the sample size to correlate the extent of chorioamnionitis with thymus size.


Assuntos
Nascimento Prematuro/diagnóstico por imagem , Timo/diagnóstico por imagem , Timo/fisiologia , Ultrassonografia Pré-Natal/métodos , Adulto , Estudos de Casos e Controles , Feminino , Ruptura Prematura de Membranas Fetais/diagnóstico por imagem , Idade Gestacional , Humanos , Recém-Nascido , Imageamento por Ressonância Magnética , Tamanho do Órgão/fisiologia , Projetos Piloto , Gravidez , Gravidez de Alto Risco , Timo/embriologia , Timo/patologia
13.
Neuroinformatics ; 19(2): 347-366, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-32856237

RESUMO

Accurate knowledge of adult human brain volume (BV) is critical for studies of aging- and disease-related brain alterations, and for monitoring the trajectories of neural and cognitive functions in conditions like Alzheimer's disease and traumatic brain injury. This scoping meta-analysis aggregates normative reference values for BV and three related volumetrics-gray matter volume (GMV), white matter volume (WMV) and cerebrospinal fluid volume (CSFV)-from typically-aging adults studied cross-sectionally using magnetic resonance imaging (MRI). Drawing from an aggregate sample of 9473 adults, this study provides (A) regression coefficients ß describing the age-dependent trajectories of volumetric measures by sex within the range from 20 to 70 years based on both linear and quadratic models, and (B) average values for BV, GMV, WMV and CSFV at the representative ages of 20 (young age), 45 (middle age) and 70 (old age). The results provided synthesize ~20 years of brain volumetrics research and allow one to estimate BV at any age between 20 and 70. Importantly, however, such estimates should be used and interpreted with caution because they depend on MRI hardware specifications (e.g. scanner manufacturer, magnetic field strength), data acquisition parameters (e.g. spatial resolution, weighting), and brain segmentation algorithms. Guidelines are proposed to facilitate future meta- and mega-analyses of brain volumetrics.


Assuntos
Envelhecimento , Encéfalo/diagnóstico por imagem , Líquido Cefalorraquidiano/diagnóstico por imagem , Substância Cinzenta/diagnóstico por imagem , Imageamento por Ressonância Magnética/tendências , Substância Branca/diagnóstico por imagem , Idoso , Envelhecimento/fisiologia , Algoritmos , Encéfalo/fisiologia , Líquido Cefalorraquidiano/fisiologia , Cognição/fisiologia , Feminino , Substância Cinzenta/fisiologia , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão/fisiologia , Substância Branca/fisiologia , Adulto Jovem
14.
Br J Sports Med ; 55(3): 169-174, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32917671

RESUMO

OBJECTIVES: To determine the acute and early long-term associations of sport-related concussion (SRC) and subcortical and cortical structures in collegiate contact sport athletes. METHODS: Athletes with a recent SRC (n=99) and matched contact (n=91) and non-contact sport controls (n=95) completed up to four neuroimaging sessions from 24 to 48 hours to 6 months postinjury. Subcortical volumes (amygdala, hippocampus, thalamus and dorsal striatum) and vertex-wise measurements of cortical thickness/volume were computed using FreeSurfer. Linear mixed-effects models examined the acute and longitudinal associations between concussion and structural metrics, controlling for intracranial volume (or mean thickness) and demographic variables (including prior concussions and sport exposure). RESULTS: There were significant group-dependent changes in amygdala volumes across visits (p=0.041); this effect was driven by a trend for increased amygdala volume at 6 months relative to subacute visits in contact controls, with no differences in athletes with SRC. No differences were observed in any cortical metric (ie, thickness or volume) for primary or secondary analyses. CONCLUSION: A single SRC had minimal associations with grey matter structure across a 6-month time frame.


Assuntos
Traumatismos em Atletas/diagnóstico por imagem , Traumatismos em Atletas/fisiopatologia , Concussão Encefálica/diagnóstico por imagem , Concussão Encefálica/fisiopatologia , Tamanho do Órgão/fisiologia , Adolescente , Adulto , Feminino , Humanos , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Masculino , Estudos Prospectivos , Universidades , Adulto Jovem
15.
Eur J Sport Sci ; 21(1): 45-52, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32172673

RESUMO

Producing a high release speed is important in throwing sports such as baseball and the javelin throw. Athletes in throwing sports might be able to achieve a greater throwing speed by improving the effectiveness of the kinetic chain. In this study a two-dimensional computer simulation model of overarm throwing was used to examine the effect of changes in forearm mass and upper arm mass on the release speed of a lightweight (58 g) projectile. The simulations showed that increasing the mass of the forearm decreases release speed, whereas increasing the mass of the upper arm initially increases release speed. For a given forearm mass there is an optimal upper arm mass that produces the greatest release speed. However, the optimal upper arm mass (5-6 kg) is substantially greater than that of an average adult (2.1 kg). These results suggest that athletes might be able to throw faster if they had a stronger tapering of segment mass along the length of their arm. A stronger taper could be readily achieved by attaching weights to the upper arm or by using hypertrophy training to increase the mass of the upper arm. High-speed overarm throwing is a complex three-dimensional movement and this study was a preliminary investigation into the effect of arm segment mass on throwing performance. Further simulation studies using three-dimensional throwing models are needed to generate more accurate insights, and the predictions of the simulation studies should be compared to data from experimental intervention studies of throwing sports.


Assuntos
Braço/anatomia & histologia , Fenômenos Biomecânicos/fisiologia , Simulação por Computador , Antebraço/anatomia & histologia , Adulto , Braço/fisiologia , Beisebol/fisiologia , Feminino , Antebraço/fisiologia , Humanos , Masculino , Tamanho do Órgão/fisiologia , Fatores Sexuais , Atletismo/fisiologia
16.
J Autism Dev Disord ; 51(2): 405-417, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32472248

RESUMO

We examined whether functional and structural variability in the primary visual area (V1) correlated with autism traits. Twenty-nine participants (16 males; MAge = 26.4 years, SDAge = 4.0 years) completed the autism-spectrum quotient (AQ) questionnaire prior to a magnetic resonance imaging session. The total AQ scores was used to assess the degree of self-reported autism traits. The average functional activation in V1 to visual stimulation and its average grey-matter thickness were calculated. There were no correlations between functional activation in V1 and autism traits. Conversely, grey-matter thickness of the left but not the right V1 correlated with autism traits. We conclude that structural changes in the left V1 could be a marker for the presence of autism traits.


Assuntos
Transtorno Autístico/diagnóstico por imagem , Lateralidade Funcional , Substância Cinzenta/diagnóstico por imagem , Estimulação Luminosa/métodos , Córtex Visual/diagnóstico por imagem , Adulto , Transtorno Autístico/psicologia , Feminino , Lateralidade Funcional/fisiologia , Substância Cinzenta/fisiologia , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Tamanho do Órgão/fisiologia , Autorrelato , Inquéritos e Questionários , Córtex Visual/fisiologia , Adulto Jovem
17.
Res Sports Med ; 29(1): 25-42, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-32482101

RESUMO

This study examined whether the association between hamstring (H) and quadriceps (Q) strength with size depends on the region and the muscle used to examined cross-sectional area (CSA). Maximum isometric contraction knee extension and flexion torque was obtained from 20 young participants while Q and H CSA was recorded using extended field of view ultrasonography at four sections along the thigh. Stepwise linear regression models using the maximum CSA of individual muscles showed a significant association of quadriceps (R2 = 0.793) and hamstring (R2 = 0.275) CSA with MVC torque (p < 0.05). The association was lower when maximum or section-specific muscle group CSAs were used as indices of size. The H:Q CSA ratio showed a significant association (R2 = 0.275, p < 0.05) and a moderate correlation (r = 0.48) with H:Q torque ratio. These results indicated that the association between muscle CSA and strength differs between the knee extensors and flexors. Amongst the various indices of muscle size, the combination of maximum CSA values of each muscle displayed the greatest relationship between strength and CSA. The H:Q CSA ratio can explain a significant but small part of the H:Q isometric strength ratio.


Assuntos
Músculos Isquiossurais/anatomia & histologia , Músculos Isquiossurais/fisiologia , Contração Isométrica/fisiologia , Força Muscular/fisiologia , Músculo Quadríceps/anatomia & histologia , Músculo Quadríceps/fisiologia , Músculos Isquiossurais/diagnóstico por imagem , Humanos , Masculino , Tamanho do Órgão/fisiologia , Músculo Quadríceps/diagnóstico por imagem , Reprodutibilidade dos Testes , Torque , Ultrassonografia , Adulto Jovem
18.
Proc Natl Acad Sci U S A ; 117(50): 32136-32144, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33257560

RESUMO

Seasonal cycles govern life on earth, from setting the time for the mating season to influencing migrations and governing physiological conditions like hibernation. The effect of such changing conditions on behavior is well-appreciated, but their impact on the brain remains virtually unknown. We investigate long-term seasonal changes in the mammalian brain, known as Dehnel's effect, where animals exhibit plasticity in body and brain sizes to counter metabolic demands in winter. We find large seasonal variation in cellular architecture and neuronal activity in the smallest terrestrial mammal, the Etruscan shrew, Suncus etruscus Their brain, and specifically their neocortex, shrinks in winter. Shrews are tactile hunters, and information from whiskers first reaches the somatosensory cortex layer 4, which exhibits a reduced width (-28%) in winter. Layer 4 width (+29%) and neuron number (+42%) increase the following summer. Activity patterns in the somatosensory cortex show a prominent reduction of touch-suppressed neurons in layer 4 (-55%), the most metabolically active layer. Loss of inhibitory gating occurs with a reduction in parvalbumin-positive interneurons, one of the most active neuronal subtypes and the main regulators of inhibition in layer 4. Thus, a reduction in neurons in layer 4 and particularly parvalbumin-positive interneurons may incur direct metabolic benefits. However, changes in cortical balance can also affect the threshold for detecting sensory stimuli and impact prey choice, as observed in wild shrews. Thus, seasonal neural adaptation can offer synergistic metabolic and behavioral benefits to the organism and offer insights on how neural systems show adaptive plasticity in response to ecological demands.


Assuntos
Hibernação/fisiologia , Plasticidade Neuronal/fisiologia , Musaranhos/fisiologia , Córtex Somatossensorial/fisiologia , Animais , Metabolismo Energético/fisiologia , Feminino , Imageamento por Ressonância Magnética , Masculino , Neurônios/fisiologia , Tamanho do Órgão/fisiologia , Estações do Ano , Córtex Somatossensorial/citologia , Córtex Somatossensorial/diagnóstico por imagem , Percepção do Tato/fisiologia , Vibrissas/fisiologia
19.
PLoS One ; 15(12): e0237552, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33370272

RESUMO

OBJECTIVES: Our previous study showed that long-term practitioners of Sahaja Yoga Meditation (SYM) had around 7% larger grey matter volume (GMV) in the whole brain compared with healthy controls; however, when testing individual regions, only 5 small brain areas were statistically different between groups. Under the hypothesis that those results were statistically conservative, with the same dataset, we investigated in more detail the regional differences in GMV associated with the practice of SYM, with a different statistical approach. DESIGN: Twenty-three experienced practitioners of SYM and 23 healthy non-meditators matched on age, sex and education level, were scanned using structural magnetic resonance imaging (MRI). Their GMV were extracted and compared using Voxel-Based Morphometry (VBM). Using a novel ad-hoc general linear model, statistical comparisons were made to observe if the GMV differences between meditators and controls were statistically significant. RESULTS: In the 16 lobe area subdivisions, GMV was statistically significantly different in 4 out of 16 areas: in right hemispheric temporal and frontal lobes, left frontal lobe and brainstem. In the 116 AAL area subdivisions, GMV difference was statistically significant in 11 areas. The GMV differences were statistically more significant in right hemispheric brain areas. CONCLUSIONS: The study shows that long-term practice of SYM is associated with larger GMV overall, and with significant differences mainly in temporal and frontal areas of the right hemisphere and the brainstem. These neuroplastic changes may reflect emotional and attentional control mechanisms developed with SYM. On the other hand, our statistical ad-hoc method shows that there were more brain areas with statistical significance compared to the traditional methodology which we think is susceptible to conservative Type II errors.


Assuntos
Encéfalo/diagnóstico por imagem , Substância Cinzenta/diagnóstico por imagem , Meditação , Ioga , Adulto , Mapeamento Encefálico , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Plasticidade Neuronal/fisiologia , Tamanho do Órgão/fisiologia , Adulto Jovem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...