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71.
The human voluntary force:velocity relationship frequently fails to demonstrate the expected high eccentric forces. Possible
explanations include unique activation strategies which might be affected by neural learning mechanisms. We investigated the
effect of practicing eccentric contractions on (1) the force: velocity relationship of the human knee extensor muscles and
(2) the extent of agonist and antagonist muscle activity. Eight healthy adults [seven women, group mean age 31 (SEM 5) years ± ]
practised twice a week for 4 weeks using their non-dominant legs. Each session comprised three isokinetic concentric and eccentric
maximal voluntary contractions (MVC) at randomised angular velocities of 100, 200 and 300° · s−1. Before and after, the force:velocity relationship was determined bilaterally (angular velocities 0–300° · s−1). There were no significant differences in the forces generated or relative electromyogram (EMG) activity after practice,
although there was a trend for dynamic forces to increase. Beforehand, the bilateral eccentric MVC forces were lower than
isometric (P < 0.0025); afterwards they were broadly similar. The agonist EMG was similar during isometric and eccentric contractions, but
lower during concentric (P < 0.03). Antagonist EMG activity showed considerable individual variation, was similar during all contraction types and tended
to be greater during dynamic contractions. These data indicate that neither central learning mechanisms nor total muscle activation
strategies underlie the human failure to produce the expected high eccentric voluntary forces in humans.
Accepted: 19 September 2000 相似文献
72.
Origin and primary dispersal of the Mycobacterium tuberculosis Beijing genotype: clues from human phylogeography 总被引:2,自引:0,他引:2 下载免费PDF全文
Mokrousov I Ly HM Otten T Lan NN Vyshnevskyi B Hoffner S Narvskaya O 《Genome research》2005,15(10):1357-1364
We suggest that the evolution of the population structure of microbial pathogens is influenced by that of modern humans. Consequently, the timing of hallmark changes in bacterial genomes within the last 100,000 yr may be attempted by comparison with relevant human migrations. Here, we used a lineage within Mycobacterium tuberculosis, a Beijing genotype, as a model and compared its phylogeography with human demography and Y chromosome-based phylogeography. We hypothesize that two key events shaped the early history of the Beijing genotype: (1) its Upper Palaeolithic origin in the Homo sapiens sapiens K-M9 cluster in Central Asia, and (2) primary Neolithic dispersal of the secondary Beijing NTF::IS6110 lineage by Proto-Sino-Tibetan farmers within east Asia (human O-M214/M122 haplogroup). The independent introductions of the Beijing strains from east Asia to northern Eurasia and South Africa were likely historically recent, whereas their differential dissemination within these areas has been influenced by demographic and climatic factors. 相似文献
73.
Deniz Eyice Karabacak Semra Demir Osman Ozan Yeğit Ali Can Kadriye Terzioğlu Derya Ünal Müge Olgaç Raif Coşkun Bahauddin Çolakoğlu Suna Büyüköztürk Aslı Gelincik 《Allergy》2021,76(8):2535-2543
Background
Hereditary angioedema (HAE) attacks can be provoked with psychological factors. The aim of this study was to assess the effects of anxiety, depression and stress related to COVID-19 pandemic on disease activity of HAE patients during the quarantine period (QP) and the return to normal period (RTNP).Methods
This study was conducted between March 2020 and September 2020 in four allergy centres. Demographic, clinical features and mental health status were evaluated in QP (from March to the beginning of June) and RTNP (from June to the beginning of September) applied by the government. The 10-point visual analogue scale (VAS10) was used to define the severity of HAE attacks. Depression, Anxiety and Stress Scales-21 (DASS-21) and Fear of COVID-19 (FC-19) scale were performed to assess mental health status.Results
139 HAE patients were included in the study. In QP, median attack numbers and median VAS10 scores were 5 (min-max: 0–45) and 6 (min-max: 0–10), respectively. HAE attack numbers, DASS-21 stress, anxiety, depression and total DASS-21 scores, and FC-19 scores were higher in QP than RTNP (p = 0.001, p < 0.001, p = 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). However, there was no difference in attack severity scores between the two periods (p > 0.05).Conclusions
This study revealed that the restriction measures during COVID-19 outbreak cause an increase in the number of HAE attacks in relation to anxiety, depression, stress and fear of COVID-19 pandemic. Therefore, it is important to provide psychological support to HAE patients during the pandemic.74.
Ioulia?Kobliakova Olga?Zatsepina Vera?Stefanova Vladimir?Polyakov Igor?KireevEmail author 《Chromosome research》2005,13(2):169-181
In this study we used a novel technique to reveal both longitudinal and transverse differentiation within mammalian mitotic
chromosomes. Structural changes in chromosomes that we term ‘differential decondensation’ were produced in cells that were
first incubated in hypotonic medium (15% Hanks’ solution), then adapted to normotonic conditions and thereafter exposed to
a second short hypotonic shock. Such a double hypotonic treatment (DHT) is not critical for cell viability, but considerably
elongates the G2 phase of the cell cycle. Giemsa staining of differentially decondensed chromosomes corresponds to standard
G-banding, but does not need the standard post-fixation treatment. Using ‘dynamic’ BrdU banding, we show that such ‘differential’
staining is a result of differential resistance of the R- and G-bands to DHT. Thus, early-replicating foci, markers of R-bands,
are localized in the peripheral chromatin halo, whereas late-replicating foci, corresponding to G-bands, remain associated
with the axial regions of chromatids. Remarkably, despite these major changes in the structure of the chromosomal bands, the
replication foci still preserve their discrete structure. 相似文献
75.
Alexander Yu. Bilibin Olga S. Sokolova Anatoly J. Grigorjev 《Macromolecular chemistry and physics.》1996,197(3):1021-1029
Two series of fluorine-containing liquid crystalline polyesters were synthesized from fluorinated alkylene diols and mesogenic acid dichlorides. The thermal behaviour of the polymers differs considerably from that of their hydrocarbon analogues. Formation of a nematic phase was observed only for melts of polymers with fluorinated spacers whereas polymers with alkylene spacers form mainly smectic phases. The most interesting feature is the unusual dependence of the polymer melting temperature on the spacer length — it increases with increasing number of CF2 groups in the spacer. 相似文献
76.
Smooth muscle myosin filament assembly under control of a kinase-related protein (KRP) and caldesmon
Kudryashov DS Vorotnikov AV Dudnakova TV Stepanova OV Lukas TJ Sellers JR Watterson DM Shirinsky VP 《Journal of muscle research and cell motility》2002,23(4):341-351
Kinase-related protein (KRP) and caldesmon are abundant myosin-binding proteins of smooth muscle. KRP induces the assembly
of unphosphorylated smooth muscle myosin filaments in the presence of ATP by promoting the unfolded state of myosin. Based
upon electron microscopy data, it was suggested that caldesmon also possessed a KRP-like activity (Katayama et al., 1995, J Biol Chem 270: 3919–3925). However, the nature of its activity remains obscure since caldesmon does not affect the equilibrium between
the folded and unfolded state of myosin. Therefore, to gain some insight into this problem we compared the effects of KRP
and caldesmon, separately, and together on myosin filaments using turbidity measurements, protein sedimentation and electron
microscopy. Turbidity assays demonstrated that KRP reduced myosin filament aggregation, while caldesmon had no effect. Additionally,
neither caldesmon nor its N-terminal myosin binding domain (N152) induced myosin polymerization at subthreshold Mg2+ concentrations in the presence of ATP, whereas the filament promoting action of KRP was enhanced by Mg2+. Moreover, the amino-terminal myosin binding fragment of caldesmon, like the whole protein, antagonizes Mg2+-induced myosin filament formation. In electron microscopy experiments, caldesmon shortened myosin filaments in the presence
of Mg2+ and KRP, but N152 failed to change their appearance from control. Therefore, the primary distinction between caldesmon and
KRP appears to be that caldesmon interacts with myosin to limit filament extension, while KRP induces filament propagation
into defined polymers. Transfection of tagged-KRP into fibroblasts and overlay of fibroblast cytoskeletons with Cy3KRP demonstrated
that KRP colocalizes with myosin structures in vivo. We propose a new model that through their independent binding to myosin and differential effects on myosin dynamics, caldesmon
and KRP can, in concert, control the length and polymerization state of myosin filaments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
We examined changes in ionic and gating currents in CaV 1.2 channels when extracellular Ca2+ was reduced from 10 m m to 0.1 μ m . Saturating gating currents decreased by two-thirds ( K D ≈ 40 μ m ) and ionic currents increased 5-fold ( K D ≈ 0.5 μ m ) due to increasing Na+ conductance. A biphasic time dependence for the activation of ionic currents was observed at low [Ca2+ ], which appeared to reflect the rapid activation of channels that were not blocked by Ca2+ and a slower reversal of Ca2+ blockade of the remaining channels. Removal of Ca2+ following inactivation of Ca2+ currents showed that Na+ currents were not affected by Ca2+ -dependent inactivation. Ca2+ -dependent inactivation also induced a negative shift of the reversal potential for ionic currents suggesting that inactivation alters channel selectivity. Our findings suggest that activation of Ca2+ conductance and Ca2+ -dependent inactivation depend on extracellular Ca2+ and are linked to changes in selectivity. 相似文献
78.
Francesca Snchez-Martínez Silvia Brugueras Gemma Serral Sara Valmayor Olga Jurez María Jos Lpez Carles Ariza 《Nutrients》2021,13(2)
Childhood obesity has increased worldwide over the past four decades. This quasi-experimental study aimed to assess the effectiveness of a multicomponent and multilevel school-based intervention (POIBA) at 3 years of follow-up. The nutrition intervention focused on food groups, food pyramid, nutrients, portions, and balanced menus. In total, 3624 children participated in the study. Anthropometric measurements and information on food frequency and behavior, physical activity, and daily screen use were collected in the intervention (IG) and comparison group (CG). Positive unadjusted changes toward adherence to recommendations were found for water, meat, sweets, and fried potato consumption, proper breakfast, not having dinner in front of the TV, out-of-school physical activity, and daily screen use. Three scores were used to calculate the proportion of children making more than one change to improve healthy habits regarding physical activity (global Activity score), nutrition (global Nutrition score), and both (global score). Students exposed to the intervention had a significantly better global Activity score (16.2% IG vs. 11.9% CG; p = 0.012) and Global score (63.9% IG vs. 58.5% CG; p = 0.025). Intervention effects on obesity incidence at 3-year follow-up lost significance but maintained the positive trend. In conclusion, school-based interventions including a family component could be useful to address the childhood obesity problem. 相似文献
79.
Gabriella Sistilli Veronika Kalendova Tomas Cajka Illaria Irodenko Kristina Bardova Marina Oseeva Petr Zacek Petra Kroupova Olga Horakova Karoline Lackner Amalia Gastaldelli Ondrej Kuda Jan Kopecky Martin Rossmeisl 《Nutrients》2021,13(2)
Preclinical evidence suggests that n-3 fatty acids EPA and DHA (Omega-3) supplemented as phospholipids (PLs) may be more effective than triacylglycerols (TAGs) in reducing hepatic steatosis. To further test the ability of Omega-3 PLs to alleviate liver steatosis, we used a model of exacerbated non-alcoholic fatty liver disease based on high-fat feeding at thermoneutral temperature. Male C57BL/6N mice were fed for 24 weeks a lard-based diet given either alone (LHF) or supplemented with Omega-3 (30 mg/g diet) as PLs (krill oil; ω3PL) or TAGs (Epax 3000TG concentrate; ω3TG), which had a similar total content of EPA and DHA and their ratio. Substantial levels of TAG accumulation (~250 mg/g) but relatively low inflammation/fibrosis levels were achieved in the livers of control LHF mice. Liver steatosis was reduced by >40% in the ω3PL but not ω3TG group, and plasma ALT levels were markedly reduced (by 68%) in ω3PL mice as well. Krill oil administration also improved hepatic insulin sensitivity, and its effects were associated with high plasma adiponectin levels (150% of LHF mice) along with superior bioavailability of EPA, increased content of alkaloids stachydrine and trigonelline, suppression of lipogenic gene expression, and decreased diacylglycerol levels in the liver. This study reveals that in addition to Omega-3 PLs, other constituents of krill oil, such as alkaloids, may contribute to its strong antisteatotic effects in the liver. 相似文献
80.
Dragana Arsenijevic Bojana Stojanovic Jelena Milovanovic Aleksandar Arsenijevic Milos Simic Marija Pergal Igor Kodranov Olga Cvetkovic Danilo Vojvodic Elizabeta Ristanovic Dragan Manojlovic Marija Milovanovic Nebojsa Arsenijevic 《Nutrients》2021,13(3)
The main biologically active components of plants belonging to the genus Allium, responsible for their biological activities, including anti-inflammatory, antioxidant and immunomodulatory, are organosulfur compounds. The aim of this study was to synthetize the mixture of dipropyl polysulfides (DPPS) and to test their biological activity in acute hepatitis. C57BL/6 mice were administered orally with DPPS 6 h before intravenous injection of Concanavalin A (ConA). Liver inflammation, necrosis and hepatocytes apoptosis were determined by histological analyses. Cytokines in liver tissue were determined by ELISA, expression of adhesive molecules and enzymes by RT PCR, while liver mononuclear cells were analyzed by flow cytometry. DPPS pretreatment significantly attenuated liver inflammation and injury, as evidenced by biochemical and histopathological observations. In DPPS-pretreated mice, messenger RNA levels of adhesion molecules and NADPH oxidase complex were significantly reduced, while the expression of SOD enzymes was enhanced. DPPS pretreatment decreased protein level of inflammatory cytokines and increased percentage of T regulatory cells in the livers of ConA mice. DPPS showed hepatoprotective effects in ConA-induced hepatitis, characterized by attenuation of inflammation and affection of Th17/Treg balance in favor of T regulatory cells and implicating potential therapeutic usage of DPPS mixture in inflammatory liver diseases. 相似文献