Three‐dimensional reconstruction and comparison of vacuolar membranes in response to viral infection

The vacuole is a unique plant organelle that plays an important role in maintaining cellular homeostasis under various environmental stress conditions. However, the effects of biotic stress on vacuole structure has not been examined using three‐dimensional (3D) visualization. Here, we performed 3D electron tomography to compare the ultrastructural changes in the vacuole during infection with different viruses. The 3D models revealed that vacuoles are remodeled in cells infected with cucumber mosaic virus (CMV) or tobacco necrosis virus A Chinese isolate (TNV‐A^C), resulting in the formation of spherules at the periphery of the vacuole. These spherules contain neck‐like channels that connect their interior with the cytosol. Confocal microscopy of CMV replication proteins 1a and 2a and TNV‐A^C auxiliary replication protein p23 showed that all of these proteins localize to the tonoplast. Electron microscopy revealed that the expression of these replication proteins alone is sufficient to induce spherule formation on the tonoplast, suggesting that these proteins play prominent roles in inducing vacuolar membrane remodeling. This is the first report of the 3D structures of viral replication factories built on the tonoplasts. These findings contribute to our understanding of vacuole biogenesis under normal conditions and during assembly of plant (+) RNA virus replication complexes.     

Standardized xeno- and serum-free culture platform enables large-scale expansion of high-quality mesenchymal stem/stromal cells from perinatal and adult tissue sources

Background aimsMesenchymal stem/stromal cells (MSCs) are of interest for the treatment of graft-versus-host disease, autoimmune diseases, osteoarthritis and neurological and cardiovascular diseases. Increasing numbers of clinical trials emphasize the need for standardized manufacturing of these cells. However, many challenges related to diverse isolation and expansion protocols and differences in cell tissue sources exist. As a result, the cell products used in numerous trials vary greatly in characteristics and potency.MethodsThe authors have established a standardized culture platform using xeno- and serum-free commercial media for expansion of MSCs derived from umbilical cord (UC), bone marrow and adipose-derived (AD) and examined their functional characteristics.ResultsMSCs from the tested sources stably expanded in vitro and retained their biomarker expression and normal karyotype at early and later passages and after cryopreservation. MSCs were capable of colony formation and successfully differentiated into osteogenic, adipogenic and chondrogenic lineages. Pilot expansion of UC-MSCs and AD-MSCs to clinical scale revealed that the cells met the required quality standard for therapeutic applications.ConclusionsThe authors’ data suggest that xeno- and serum-free culture conditions are suitable for large-scale expansion and enable comparative study of MSCs of different origins. This is of importance for therapeutic purposes, especially because of the numerous variations in pre-clinical and clinical protocols for MSC-based products.     

Numerical Study of an Ultra-Broadband and Wide-Angle Insensitive Perfect Metamaterial Absorber in the UV–NIR Region

Plasmonics - Developing a simple structure using low-cost material that enables both large-scale fabrication and broadband absorption response is highly desirable but very challenging for achieving...     

Enhanced skeletal muscle glycogen repletion after endurance exercise is associated with higher plasma insulin and skeletal muscle hexokinase 2 protein levels in mice: comparison of level running and downhill running model

Journal of Physiology and Biochemistry - To identify factors that influence post-exercise muscle glycogen repletion, we compared the glycogen recovery after level running with downhill running, an...     

Functional activity of RLIM/Rnf12 is regulated by phosphorylation-dependent nucleocytoplasmic shuttling

The X-linked gene Rnf12 encodes the ubiquitin ligase really interesting new gene (RING) finger LIM domain–interacting protein (RLIM)/RING finger protein 12 (Rnf12), which serves as a major sex-specific epigenetic regulator of female mouse nurturing tissues. Early during embryogenesis, RLIM/Rnf12 expressed from the maternal allele is crucial for the development of extraembryonic trophoblast cells. In contrast, in mammary glands of pregnant and lactating adult females RLIM/Rnf12 expressed from the paternal allele functions as a critical survival factor for milk-producing alveolar cells. Although RLIM/Rnf12 is detected mostly in the nucleus, little is known about how and in which cellular compartment(s) RLIM/Rnf12 mediates its biological functions. Here we demonstrate that RLIM/Rnf12 protein shuttles between nucleus and cytoplasm and this is regulated by phosphorylation of serine S214 located within its nuclear localization sequence. We show that shuttling is important for RLIM to exert its biological functions, as alveolar cell survival activity is inhibited in cells expressing shuttling-deficient nuclear or cytoplasmic RLIM/Rnf12. Thus regulated nucleocytoplasmic shuttling of RLIM/Rnf12 coordinates cellular compartments during mammary alveolar cell survival.     

The MRN-CtIP Pathway Is Required for Metaphase Chromosome Alignment

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Highlights? The MRN-CtIP pathway is required for metaphase chromosome alignment in egg extracts ? MRN inhibition interferes with spindle assembly around DNA-coated beads ? MRN inhibition in cells causes a metaphase delay and disrupts the RanGTP gradient ? The MRN complex regulates the stable association of RCC1 to chromatin     

Note: A Convenient Method for the Preparation of N2, N2-Dimethylguanosine

Abstract

The preparation of N², N²-dimethylguanosine is described. The use of the 2-(p-nitrophenyl)ethyl group instead of the benzyl protecting group for the O⁶ position of the guanine ring resulted in better yields and shorter protocols.     

Cyclin B1 is an efficacy-predicting biomarker for Chk1 inhibitors

Chk1 is the major mediator of cell-cycle checkpoints in response to various forms of genotoxic stress. Although it was previously speculated that checkpoint abrogation due to Chk1 inhibition may potentiate the efficacy of DNA-damaging agents through induction of mitotic catastrophe, there has not been direct evidence proving this process. Here, through both molecular marker and morphological analysis, we directly demonstrate that specific downregulation of Chk1 expression by Chk1 siRNA potentiates the cytotoxicities of topoisomerase inhibitors through the induction of premature chromosomal condensation and mitotic catastrophe. More importantly, we discovered that the cellular cyclin B1 level is the major determinant of the potentiation. We show that downregulation of cyclin B1 leads to impairment of the induction of mitotic catastrophe and correspondingly a reduction of the potentiation ability of either Chk1 siRNA or a small molecule Chk1 inhibitor. More significantly, we have extended the study by examining a panel of 10 cancer cell-lines with different tissue origins for their endogenous levels of cyclin B1 and the ability of a Chk1 inhibitor to sensitize the cells to DNA-damaging agents. The cellular levels of cyclin B1 positively correlate with the degrees of potentiation achieved. Of additional interest, we observed that the various colon cancer cell lines in general appear to express higher levels of cyclin B1 and also display higher sensitivity to Chk1 inhibitors, implying that Chk1 inhibitor may be more efficacious in treating colon cancers. In summary, we propose that cyclin B1 is a biomarker predictive of the efficacy of Chk1 inhibitors across different types of cancers. Unlike previously established efficacy-predictive biomarkers that are usually the direct targets of the therapeutic agents, cyclin B1 represents a non-drug-target biomarker that is based on the mechanism of action of the target inhibitor. This finding may be potentially very useful for the stratification of patients for Chk1 inhibitor clinical trials and hence, maximize its chance of success.     

Diabetes Inhibits Cerebral Ischemia-Induced Astrocyte Activation - an Observation in the Cingulate Cortex

The objective of this study was to study the effect of diabetic hyperglycemia on astrocytes after forebrain ischemia. Streptozotocin (STZ)-injected hyperglycemic and vehicle-injected normoglycemic rats were subjected to 15 minutes of forebrain ischemia. The brains were harvested in sham-operated controls and in animals with 1 and 6 h of recirculation following ischemia. Brain damage was accessed by haematoxylin and eosin (H&E) staining, cleaved caspase-3 immunohistochemistry and TdT-mediated-dUTP nick end labeling (TUNEL). Anti-GFAP antibody was employed to study astrocytes. The results showed that the 15-minute ischemia caused neuronal death after 1 and 6 h of reperfusion as revealed by increased numbers of karyopyknotic cells, edema, TUNEL-positive and active caspase-3-positive cells. Ischemia also activated astrocytes in the cingulated cortex as reflected by astrocyte stomata hypertrophy, elongated dendrites and increases in the number of dendrites, and immunoreactivity of GFAP. Diabetic hyperglycemia further enhanced neuronal death and suppressed ischemia-induced astrocyte activation. Further, diabetes-damaged astrocytes have increased withdrawal of the astrocyte end-foot from the cerebral blood vessel wall. It is concluded that diabetes-induced suppression and damages to astrocytes may contribute to its detrimental effects on recovery from cerebral ischemia.