295 research outputs found

    A study of the effects of size-dependent processes on survival and growth of Atlantic cod (Gadus morhua) larvae

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    Fish year-class strength can be established at early life stages, such as the egg and larval stage. A small variation in growth and survival during these early life periods can result in a substantial variation in fish recruitment. Therefore, a better understanding of factors influencing growth and survival of fish eggs and larvae can help fisheries scientists better understand the variations in fish population sizes. Based on a literature review and laboratory experiments, this study investigated the size-dependent effects on early life stages (egg and larvae) of Atlantic cod (Gadus morhua). -- Egg size can be influenced by many factors including female size (age, length or weight), fecundity and seasonal temperature. Larval size at hatching is often related to egg size and incubation temperature. Size (stage)-dependent survival has been observed for larvae in many studies. Growth rate, which may be influenced by many factors including temperature and food supply, is one of the key factors determining larval size and mortality rate. -- For Atlantic cod, my study showed that larger eggs yielded larger larvae at hatching, but took longer to hatch. Larval size at hatching and incubation time were negatively correlated with incubation temperature. Although neither egg size nor incubation temperature was found to affect yolk size at hatching, higher accumulated incubation temperature significantly decreased the yolk size at hatching, but increased larval size at hatching. -- The larval survival and growth experiment showed that feeding conditions and larval size at hatching significantly influenced larval survival. Better feeding resulted in higher survival. The study found that the survival rate for small larvae was higher than that for large larvae, which might result from the absence of predators in this study. Higher temperature reduced the time of yolk utilization and thus caused the cod larvae to start exogenous feeding earlier. The growth rate of cod larvae during the exogenous feeding period is higher than that during endogenous feeding period. The first few days of growth mainly resulted in a significant increase in larval weight. Delayed first feeding significantly decreased the growth rate in cod larvae. However, the large larvae showed a higher growth rate compared with small larvae under the delayed first feeding condition. After a 10 to 13-day acclimatization, the larvae under delayed first feeding exhibited the compensatory growth. -- The size effect on cod larval growth was only significant in the delayed feeding condition, which implies that the bigger the better is more evident in cod larvae under unfavourable conditions, such as delayed initial feeding in this study

    Recent Results on Balanced Symmetric Boolean Functions

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    In this paper we prove all balanced symmetric Boolean functions of fixed degree are trivial when the number of variables grows large enough. We also present the nonexistence of trivial balanced elementary symmetric Boolean functions except for n=l⋅2t+1−1n=l\cdot2^{t+1}-1 and d=2td=2^t, where tt and ll are any positive integers, which shows Cusick\u27s conjecture for balanced elementary symmetric Boolean functions is exactly the conjecture that all balanced elementary symmetric Boolean functions are trivial balanced. In additional, we obtain an integer n0n_0, which depends only on dd, that Cusick\u27s conjecture holds for any n>n0n>n_0

    An Improved Transplantation Strategy for Mouse Mesenchymal Stem Cells in an Acute Myocardial Infarction Model

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    To develop an effective therapeutic strategy for cardiac regeneration using bone marrow mesenchymal stem cells (BM-MSCs), the primary mouse BM-MSCs (1st BM-MSCs) and 5th passage BM-MSCs from β-galactosidase transgenic mice were respectively intramyocardially transplanted into the acute myocardial infarction (AMI) model of wild type mice. At the 6th week, animals/tissues from the 1st BM-MSCs group, the 5th passage BM-MSCs group, control group were examined. Our results revealed that, compared to the 5th passage BM-MSCs, the 1st BM-MSCs had better therapeutic effects in the mouse MI model. The 1st BM-MSCs maintained greater differentiation potentials towards cardiomocytes or vascular endothelial cells in vitro. This is indicated by higher expressions of cardiomyocyte and vascular endothelial cell mature markers in vitro. Furthermore, we identified that 24 proteins were down-regulated and 3 proteins were up-regulated in the 5th BM-MSCs in comparison to the 1st BM-MSCs, using mass spectrometry following two-dimensional electrophoresis. Our data suggest that transplantation of the 1st BM-MSCs may be an effective therapeutic strategy for cardiac tissue regeneration following AMI, and altered protein expression profiles between the 1st BM-MSCs and 5th passage BM-MSCs may account for the difference in their maintenance of stemness and their therapeutic effects following AMI

    Increased serum lysyl oxidase-like 2 levels correlate with the degree of left atrial fibrosis in patients with atrial fibrillation

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    Atrial fibrillation (AF) progression is generally accompanied by increased atrial fibrosis and atrial structural remodeling. Lysyl oxidase-like 2 (LOXL2) is known to play an important role in many fibrotic conditions, including cardiac fibrosis. The present study aimed to explore the relationship between serum LOXL2 levels and AF. Fifty-four AF patients and 32 control subjects were enrolled in the study. High-density three-dimensional electroanatomic mapping was performed, and mean bipolar voltage was assessed in AF patients. LOXL2 levels were measured by enzyme-linked immunosorbent assay. All patients underwent echocardiography to assess left atrium size and left ventricle function. Serum LOXL2 levels were significantly elevated in AF patients compared with the control group (526.81 ± 316.82 vs 240.94 ± 92.51 pg/ml, P<0.01). In addition, serum LOXL2 level was significantly correlated with the size of the left atrium (LAD) (r2 = 0.38, P<0.01). Furthermore, the serum LOXL2 levels were significantly higher in AF patients with LAD ≥ 40 mm compared with those with LAD < 40 mm (664.34 ± 346.50 vs 354.90 ± 156.23 pg/ml, P<0.01). And the Spearman’s correlation analysis further revealed that the mean bipolar left atrial voltage was inversely correlated with the LOXL2 (r2 = −0.49, P<0.01) in AF patients. Multivariate regression analysis further demonstrated that serum LOXL2 [odds ratio (OR) 1.013, 95% confidence interval (CI) 1.002–1.024, P<0.05] and LAD (OR 1.704, 95% CI 1.131–2.568, P<0.01) were independent predictors of AF. In conclusion, serum LOXL2 levels were significantly elevated and were correlated with the degree of left atrial fibrosis in AF patients

    SnapShot: Histone Modifications

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    Histone proteins are decorated by a variety of protein posttranslational modifications called histone marks that modulate chromatin structure and function, contributing to the cellular gene expression program. This SnapShot summarizes the reported human, mouse, and rat histone marks, including recently identified lysine acylation marks

    Phosphorylation-Dependent 14-3-3 Binding to LRRK2 Is Impaired by Common Mutations of Familial Parkinson's Disease

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    ) are the cause of the most common inherited and some sporadic forms of Parkinson's disease (PD). The molecular mechanism underlying the pathogenic role of LRRK2 mutations in PD remains unknown. and in cell culture, suggesting that PKA is a potential upstream kinase that regulates LRRK2 function. Finally, our study indicates that the common PD-related mutations of LRRK2, R1441G, Y1699C and G2019S, decrease homeostatic phosphorylation levels of S935 and impair 14-3-3 binding of LRRK2., and the phosphorylation of specific sites (e.g. S935) determines 14-3-3 binding of LRRK2. We propose that 14-3-3 is an important regulator of LRRK2-mediated cellular functions. Our study suggests that PKA, a cAMP-dependent kinase involved in regulating dopamine physiology, is a potential upstream kinase that phosphorylates LRRK2 at S935. Furthermore, the reduction of phosphorylation/14-3-3 binding of LRRK2 due to the common familial PD-related mutations provides novel insight into the pathogenic mechanism of LRRK2-linked PD
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