风速变化对草原生态系统的影响研究进展

在全球风速呈下降趋势的大背景下,研究风速变化对生态系统的影响具有重要意义,尤其是其重要组成部分——草原生态系统。近年来大量学者开始研究风速变化对草原生态系统的影响,主要集中在以下几个方面并得出相关的结论,(1)风速变化会影响植物的生长速率和叶片形态,适当的风速能够促进植物生长发育、提高植被初级生产力,而强风或持续大风不仅会对植物产生破坏作用,还会影响其生长发育;(2)风会最先带走地表细小颗粒,从而导致土壤质地变粗、水分下降、营养成分重新分配;(3)风引起地表边界层和大气边界层物质和能量的转移和交换,热量和水汽的交换导致地表微气候发生变化,如风速降低会导致地表温度升高;(4)风力作用使得土壤水分亏缺、营养成分变化,导致草原生态系统结构变化、草地覆盖度降低、物种生活型复杂化、耐旱植物增加;(5)大气稳定性、CO2交换速率和碳排放都会随着风速的增加而增加,碳吸收则相反,碳通量也因此发生变化。综上,风速降低对于草原生态系统的影响复杂且利弊相当,未来的发展趋势会更加侧重于以下几个方面的发展:研究对象的多样化、加强控制实验的定量化研究、综合多要素的相互作用机理研究、整体结构和功能性的研究。     

Myokine IL-15 regulates the crosstalk of co-cultured porcine skeletal muscle satellite cells and preadipocytes

The present study was carried out to preliminarily reveal the underlying mechanisms of the co-culture system between porcine muscle satellite cells (SCs) and stromal-vascular cells (SVs). The two cell types were co-cultured to assess both proliferation and differentiation. Desmin and Pref-1 immunofluorescence staining technique were taken to identify the two types of isolated cells. The expression of specific marker genes Myogenin was up-regulated in SCs (P < 0.05) and the differentiation of SCs could be promoted when co-cultured with preadipocytes compared with the single-cultured control, while expression of c/EBPβ in SVs was down-regulated (P < 0.05) and the differentiation of preadipocytes could be inhibited. Furthermore, secretion of myokine IL-15 was markedly increased, as well as its gene and protein expression levels in co-culture supernatants. However, the secretion of adipokine leptin was significantly decreased. These findings demonstrate that myokines like IL-15 could facilitate the SCs’ differentiation while inhibit the SVs differentiation, and act as an important regulator of co-culture between muscle cells and adipocytes.     

MiR‐155 promotes interleukin‐1β‐induced chondrocyte apoptosis and catabolic activity by targeting PIK3R1‐mediated PI3K/Akt pathway

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation, in which elevated chondrocyte apoptosis and catabolic activity play an important role. MicroRNA‐155 (miR‐155) has recently been shown to regulate apoptosis and catabolic activity in some pathological circumstances, yet, whether and how miR‐155 is associated with OA pathology remain unexplored. We report here that miR‐155 level is significantly up‐regulated in human OA cartilage biopsies and also in primary chondrocytes stimulated by interleukin‐1β (IL‐1β), a pivotal pro‐catabolic factor promoting cartilage degradation. Moreover, miR‐155 inhibition attenuates and its overexpression promotes IL‐1β‐induced apoptosis and catabolic activity in chondrocytes in vitro. We also demonstrate that the PIK3R1 (p85α regulatory subunit of phosphoinositide 3‐kinase (PI3K)) is a target of miR‐155 in chondrocytes, and more importantly, PIK3R1 restoration abrogates miR‐155 effects on chondrocyte apoptosis and catabolic activity. Mechanistically, PIK3R1 positively regulates the transduction of PI3K/Akt pathway, and a specific Akt inhibitor reverses miR‐155 effects on promoting chondrocyte apoptosis and catabolic activity, phenocopying the results obtained via PIK3R1 knockdown, hence establishing that miR‐155 promotes chondrocyte apoptosis and catabolic activity through targeting PIK3R1‐mediated PI3K/Akt pathway activation. Altogether, our study discovers novel roles and mechanisms of miR‐155 in regulating chondrocyte apoptosis and catabolic activity, providing an implication for therapeutically intervening cartilage degradation and OA progression.     

How competitive intransitivity and niche overlap affect spatial coexistence

Competitive intransitivity is mostly considered outside the main body of coexistence theories that rely primarily on the role of niche overlap and differentiation. How the interplay of competitive intransitivity and niche overlap jointly affects species coexistence has received little attention. Here, we consider a rock–paper–scissors competition system where interactions between species can represent the full spectra of transitive–intransitive continuum and niche overlap/differentiation under different levels of competition asymmetry. By comparing results from pair approximation that only considers interference competition between neighbouring cells in spatial lattices, with those under the mean-field assumption, we show that 1) species coexistence under transitive competition is only possible at high niche differentiation; 2) in communities with partial or pure intransitive interactions, high levels of niche overlap are not necessary to beget species extinction; and 3) strong spatial clustering can widen the condition for intransitive loops to facilitate species coexistence. The two mechanisms, competitive intransitivity and niche differentiation, can support species persistence and coexistence, either separately or in combination. Finally, the contribution of intransitive loops to species coexistence can be enhanced by strong local spatial correlations, modulated and maximised by moderate competition asymmetry. Our study, therefore, provides a bridge to link intransitive competition to other generic ecological theories of species coexistence.     

Polymorphisms of LAP3 gene and their association with the growth traits in the razor clam Sinonovacula constricta

Molecular Biology Reports - Leucine aminopeptidase 3 (LAP3) is an important proteolytic enzyme that catalyzes the hydrolysis of leucine residues from the amino termini of protein or peptide...     

The razor clam Sinonovacula constricta uses the strategy of conversion of toxic ammonia to glutamine in response to high environmental ammonia exposure

Molecular Biology Reports - High ammonia can inhibit the survival and growth, and even cause mortality of razor clam (S. constricta). The accumulation of ammonia to lethal concentrations in some...     

Immune responses induced in HHD mice by multiepitope HIV vaccine based on cryptic epitope modification

CD8+ T cells play an important role in early HIV infection. However, HIV has the capacity to avoid specific CTL responses due to a high rate of mutation under selection pressure. Although the HIV proteins, gag and pol, are relatively conserved, these sequences generate low-affinity MHC-associated epitopes that are poorly immunogenic. Here, we applied an approach that enhanced the immunogenicity of low-affinity HLA-A2.1-binding peptides. The first position with tyrosine (P1Y) substitution enhanced the affinity of HLA-A2.1-associated peptides without altering their antigenic specificity. More importantly, P1Y variants efficiently stimulated in vivo native peptide-specific CTL that also recognized the corresponding naturally processed epitope. The potential to generate CTL against any low-affinity HLA-A2.1-associated peptide provides us with the necessary technique for identification of virus cryptic epitopes for development of peptide-based immunotherapy. Therefore, identification and modification of the cryptic epitopes of gal and pol provides promising candidates for HIV immunotherapy dependent upon efficient presentation by virus cells. Furthermore, this may be a breakthrough that overcomes the obstacle of immune escape caused by high rates of mutation. In this study, bioinformatics analysis was used to predict six low-affinity cryptic HIV gag and pol epitopes presented by HLA-A*0201. A HIV compound multi-CTL epitope gene was constructed comprising the gene encoding the modified cryptic epitope and the HIV p24 antigen, which induced a strong CD8+ T cell immune response regardless of the mutation. This approach represents a novel strategy for the development of safe and effective HIV prophylactic and therapeutic vaccines.