Effects of training frequency on the dynamics of performance response to a single training bout.

The aim of this study was to analyze the effect of an increase in training frequency on exercise-induced fatigue by using a systems model with parameters free to vary over time. Six previously untrained subjects undertook a 15-wk training experiment composed of 1) an 8-wk training period with three sessions per week (low-frequency training), 2) 1 wk without training, 3) a 4-wk training period with five sessions per week [high frequency training (HFT)], and 4) 2 wk without training. The systems input ascribed to training loads was computed from interval exercises and expressed in arbitrary units. The systems output ascribed to performance was evaluated three times each week using maximal power sustained over 5 min. The time-varying parameters of the model were estimated by fitting modeled performances to the measured ones using a recursive least squares method. The variations over time in the model parameters showed an increase in magnitude and duration of fatigue induced by a single training bout. The time needed to recover performance after a training session increased from 0.9 +/- 2.1 days at the end of low-frequency training to 3.6 +/- 2.0 days at the end of HFT. The maximal gain in performance for a given training load decreased during HFT. This study showed that shortening recovery time between training sessions progressively yielded a more persistent fatigue induced by each training.     

Revisiting spatial distribution and biochemical composition of calcium-containing crystals in human osteoarthritic articular cartilage

Introduction

Calcium-containing (CaC) crystals, including basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPP), are associated with destructive forms of osteoarthritis (OA). We assessed their distribution and biochemical and morphologic features in human knee OA cartilage.

Methods

We prospectively included 20 patients who underwent total knee replacement (TKR) for primary OA. CaC crystal characterization and identification involved Fourier-transform infra-red spectrometry and scanning electron microscopy of 8 to 10 cartilage zones of each knee, including medial and lateral femoral condyles and tibial plateaux and the intercondyle zone. Differential expression of genes involved in the mineralization process between cartilage with and without calcification was assessed in samples from 8 different patients by RT-PCR. Immunohistochemistry and histology studies were performed in 6 different patients.

Results

Mean (SEM) age and body mass index of patients at the time of TKR was 74.6 (1.7) years and 28.1 (1.6) kg/m², respectively. Preoperative X-rays showed joint calcifications (chondrocalcinosis) in 4 cases only. The medial femoro-tibial compartment was the most severely affected in all cases, and mean (SEM) Kellgren-Lawrence score was 3.8 (0.1). All 20 OA cartilages showed CaC crystals. The mineral content represented 7.7% (8.1%) of the cartilage weight. All patients showed BCP crystals, which were associated with CPP crystals for 8 joints. CaC crystals were present in all knee joint compartments and in a mean of 4.6 (1.7) of the 8 studied areas. Crystal content was similar between superficial and deep layers and between medial and femoral compartments. BCP samples showed spherical structures, typical of biological apatite, and CPP samples showed rod-shaped or cubic structures. The expression of several genes involved in mineralization, including human homolog of progressive ankylosis, plasma-cell-membrane glycoprotein 1 and tissue-nonspecific alkaline phosphatase, was upregulated in OA chondrocytes isolated from CaC crystal-containing cartilages.

Conclusions

CaC crystal deposition is a widespread phenomenon in human OA articular cartilage involving the entire knee cartilage including macroscopically normal and less weight-bearing zones. Cartilage calcification is associated with altered expression of genes involved in the mineralisation process.     

The Spatial-Temporal Heterogeneity of Understory Light Availability in a Temperate Forest of North China

The spatial-temporal variation of understory light availability has important influences on species diversity and community assembly. However, the distribution characteristics and influencing factors of understory light availability have not been fully elucidated, especially in temperate deciduous, broad-leaved forests. In this study, the understory light availability was monitored monthly (May–October) in a temperate deciduous, broad-leaved forest in Henan Province, China. Differences in the light availability among different months and habitat types were statistically analyzed using Kruskal–Wallis method, respectively. Partial least squares path modeling (PLS-PM) was used to explore the direct and/or indirect effects of stand structure, dominant species and topographic factors on the light environment. Results showed that there were differences in light environments among the four habitat types and during the studied six months. The PLS-PM results showed that the stand structure and the dominant species were negatively correlated with the light environment, and the path coefficient values were −0.089 (P = 0.042) and −0.130 (P = 0.004), respectively. Our result indicated that the understory light availability exhibit a distinct spatial and temporal heterogeneity in temperate deciduous, broad-leaved forest of north China. The characteristics of woody plant community, especially the abundance of one of the dominant plant species, were the important factors affecting the understory light availability.     

NuMA phosphorylation by CDK1 couples mitotic progression with cortical dynein function

Spindle positioning and spindle elongation are critical for proper cell division. In human cells, an evolutionary conserved ternary complex (NuMA/LGN/Gαi) anchors dynein at the cortex during metaphase, thus ensuring correct spindle positioning. Whether this complex contributes to anaphase spindle elongation is not known. More generally, the mechanisms coupling mitotic progression with spindle behaviour remain elusive. Here, we uncover that levels of cortical dynein markedly increase during anaphase in a NuMA‐dependent manner. We demonstrate that during metaphase, CDK1‐mediated phosphorylation at T2055 negatively regulates NuMA cortical localization and that this phosphorylation is counteracted by PPP2CA phosphatase activity. We establish that this tug of war is essential for proper levels of cortical dynein and thus spindle positioning during metaphase. Moreover, we find that upon CDK1 inactivation in anaphase, the rise in dephosphorylated NuMA at the cell cortex leads to cortical dynein enrichment, and thus to robust spindle elongation. Our findings uncover a mechanism whereby the status of NuMA phosphorylation coordinates mitotic progression with proper spindle function.     

Light and soil moisture effects on biomass and its allocation in Osmorhiza depauperata Philippi (Apiaceae)

Changes in forest openings affect light quality and quantity, and the magnitude of rainfall that reaches the soil surface. Osmorhiza depauperata, a geophyte, acclimates to changes imposed because of forest openings. We studied which changes in biomass allocation allow acclimation of O. depauperata to the various environments that this species inhabits, and where it develops better. Three light intensities (I4 = 4 %, I26 = 26 %, I64 = 64 % of ambient sunlight) and two moisture levels (M40 = 40–60 %, M80 = 80–100 % field capacity) were evaluated on O. depauperata under greenhouse conditions. Plant biomasses per pot were 0.81, 0.56 and 0.48 g at I26, I4 and I64 light intensities, respectively, after one growing season. The biomass allocation to aboveground tissues and leaf area decreased as light intensity increased. Soil moisture modified only belowground biomass and weight of fine roots. The interaction between soil moisture content and light intensity was consistent. This was because of a significant reduction in total plant biomass under high both soil moisture content and high light intensity. Osmorhiza depauperata growth was favored most at medium light intensities. Changes in biomass allocation among various organs allow this species to inhabit forest habitats with different light intensities.     

Basic calcium phosphate crystals induce monocyte/macrophage IL-1β secretion through the NLRP3 inflammasome in vitro

Basic calcium phosphate (BCP) crystals are associated with severe osteoarthritis and acute periarticular inflammation. Three main forms of BCP crystals have been identified from pathological tissues: octacalcium phosphate, carbonate-substituted apatite, and hydroxyapatite. We investigated the proinflammatory effects of these BCP crystals in vitro with special regard to the involvement of the NLRP3-inflammasome in THP-1 cells, primary human monocytes and macrophages, and mouse bone marrow-derived macrophages (BMDM). THP-1 cells stimulated with BCP crystals produced IL-1β in a dose-dependent manner. Similarly, primary human cells and BMDM from wild-type mice also produced high concentrations of IL-1β after crystal stimulation. THP-1 cells transfected with short hairpin RNA against the components of the NLRP3 inflammasome and mouse BMDM from mice deficient for NLRP3, apoptosis-associated speck-like protein, or caspase-1 did not produce IL-1β after BCP crystal stimulation. BCP crystals induced macrophage apoptosis/necrosis as demonstrated by MTT and flow cytometric analysis. Collectively, these results demonstrate that BCP crystals induce IL-1β secretion through activating the NLRP3 inflammasome. Furthermore, we speculate that IL-1 blockade could be a novel strategy to inhibit BCP-induced inflammation in human disease.     

Evidence for the involvement of testicular protein CRISP2 in mouse sperm-egg fusion

CRISP2, originally known as Tpx-1, is a cysteine-rich secretory protein specifically expressed in male haploid germ cells. Although likely to be involved in gamete interaction, evidence for a functional role of CRISP2 in fertilization still remains poor. In the present study, we used a mouse model to examine the subcellular localization of CRISP2 in sperm and its involvement in the different stages of fertilization. Results from indirect immunofluorescence and protein extraction experiments indicated that mouse CRISP2 is an intraacrosomal component that remains associated with sperm after capacitation and the acrosome reaction (AR). In vitro fertilization assays using zona pellucida-intact mouse eggs showed that an antibody against the protein significantly decreased the percentage of penetrated eggs, with a coincident accumulation of perivitelline sperm. The failure to inhibit zona pellucida penetration excludes a detrimental effect of the antibody on sperm motility or the AR, supporting a specific participation of CRISP2 at the sperm-egg fusion step. In agreement with this evidence, recombinant mouse CRISP2 (recCRISP2) specifically bound to the fusogenic area of mouse eggs, as previously reported for rat CRISP1, an epididymal protein involved in gamete fusion. In vitro competition investigations showed that incubation of mouse zona-free eggs with a fixed concentration of recCRISP2 and increasing amounts of rat CRISP1 reduced the binding of recCRISP2 to the egg, suggesting that the proteins interact with common complementary sites on the egg surface. Our findings indicate that testicular CRISP2, as observed for epididymal CRISP1, is involved in sperm-egg fusion through its binding to complementary sites on the egg surface, supporting the idea of functional cooperation between homologous molecules to ensure the success of fertilization.     

Oncogenic comparison of human papillomavirus type 58 E7 variants

Human papillomavirus 58 (HPV58) ranks the second or third in East Asian cervical cancers. Current studies on HPV58 are scarce and focus on the prototype. Previously, we identified the three most common circulating HPV58 E7 strains contained amino acid alterations: G41R/G63D (51%), T20I/G63S (22%) and T74A/D76E (14%) respectively. Among them, the T20I/G63S variant (V1) had a stronger epidemiological association with cervical cancer. We therefore suggested that V1 possessed stronger oncogenicity than the other two variants. Here, we performed phenotypic assays to characterize and compare their oncogenicities with HPV58 E7 prototype. Our results showed that overexpression of V1 conferred a higher colony‐forming ability to primary murine epithelial cells than prototype (P < 0.05) and other variants, implicating its higher immortalising potential. Further experiments showed that both V1 and prototype enhanced the anchorage‐independent growth of NIH/3T3 cells (P < 0.001), implicating their stronger transforming power than the two other variants. Moreover, they possessed an increased ability to degrade pRb (P < 0.001), which is a major effector pathway of E7‐driven oncogenesis. Our work represents the first study to compare the oncogenicities of HPV58 E7 prototype and variants. These findings deepened our understanding of HPV58 and might inform clinical screening and follow‐up strategy.     

The nucleoporin Nup205/NPP-3 is lost near centrosomes at mitotic onset and can modulate the timing of this process in Caenorhabditis elegans embryos

Regulation of mitosis in time and space is critical for proper cell division. We conducted an RNA interference-based modifier screen to identify novel regulators of mitosis in Caenorhabditis elegans embryos. Of particular interest, this screen revealed that the Nup205 nucleoporin NPP-3 can negatively modulate the timing of mitotic onset. Furthermore, we discovered that NPP-3 and nucleoporins that are associated with it are lost from the nuclear envelope (NE) in the vicinity of centrosomes at the onset of mitosis. We demonstrate that centrosomes are both necessary and sufficient for NPP-3 local loss, which also requires the activity of the Aurora-A kinase AIR-1. Our findings taken together support a model in which centrosomes and AIR-1 promote timely onset of mitosis by locally removing NPP-3 and associated nucleoporins from the NE.     

TCTP protects from apoptotic cell death by antagonizing bax function

Translationally controlled tumor protein (TCTP) is a potential target for cancer therapy. It functions as a growth regulating protein implicated in the TSC1-TSC2 -mTOR pathway or a guanine nucleotide dissociation inhibitor for the elongation factors EF1A and EF1Bbeta. Accumulating evidence indicates that TCTP also functions as an antiapoptotic protein, through a hitherto unknown mechanism. In keeping with this, we show here that loss of tctp expression in mice leads to increased spontaneous apoptosis during embryogenesis and causes lethality between E6.5 and E9.5. To gain further mechanistic insights into this apoptotic function, we solved and refined the crystal structure of human TCTP at 2.0 A resolution. We found a structural similarity between the H2-H3 helices of TCTP and the H5-H6 helices of Bax, which have been previously implicated in regulating the mitochondrial membrane permeability during apoptosis. By site-directed mutagenesis we establish the relevance of the H2-H3 helices in TCTP's antiapoptotic function. Finally, we show that TCTP antagonizes apoptosis by inserting into the mitochondrial membrane and inhibiting Bax dimerization. Together, these data therefore further confirm the antiapoptotic role of TCTP in vivo and provide new mechanistic insights into this key function of TCTP.