Preservation and High Sequence Conservation of Satellite DNAs Suggest Functional Constraints

Due to a high evolutionary turnover many satellite DNAs are restricted to a group of closely related species. Here we demonstrate that the satellite DNA family PSUB, abundant in the beetle Palorus subdepressus, is distributed in a low number of copies among diverse taxa of Coleoptera (Insecta), some of them separated for an evolutionary period of up to 60 Myr. Comparison of PSUB cloned from the species Tribolium brevicornis with the PSUB family previously characterized in Palorus subdepressus revealed high sequence conservation and absence of fixed species-specific mutations. The most polymorphic sites are those with ancestral mutations shared among clones of both species. Since the ancestral mutations contribute significantly to overall diversity, it could be proposed that a similar mutational profile already existed in an ancestral species. The pattern of variability along the satellite monomer is characterized by the presence of conserved and variable regions. The nonrandom pattern of variability as well as the absence of sequence divergence is also discerned for PRAT satellite DNA, cloned previously from two Palorus species and a distantly related Pimelia elevata. Since PRAT and PSUB are present in parallel in diverse taxa of Coleoptera, we propose that their long evolutionary preservation suggests a possible functional significance. This indication is additionally supported not only by the high evolutionary conservation of the sequences, but also by the presence of significantly conserved and variable regions along the monomers. [Reviewing Editor: Dr. Jerzy Jurka]     

On the dynamics of flying insects populations controlled by large scale information

We present a diffusion model adapted to an operational control of flying insects. The operational objective entails working with non-homogeneous regions and the corresponding non-uniform diffusion tensors. It the becomes necessary to study the problem of scale in order to justify the diffusion equation. We show that in typical cases, the spatial resolution must be coarser than 20 m and we have specified the appropriated time scales. We propose a method for computing the tensors at the given resolution, in relation to the landscape and the insects' species and a method for the numerical solution of the equations and present two applications.     

不同CMV分离物侵染寄主的超微结构变化

应用电镜观察了黄瓜花叶病毒ＣＭＶ不同分离物侵染寄主的细胞超微结构变化。来自一患红（Ｓａｌｖｉａｓｐｌｅｎｄｅｎｓ）的不含卫星ＲＮＡ分离物Ｍ－２２侵染心叶烟,病毒粒子散布于细胞质,在液泡中形成大片病毒粒子结果,液泡膜边缘产生小泡结构,完整的病毒粒子穿过胞间连丝在细胞间运转,胞间连丝中央部分有扩张现象。     

Observations of satellite cells in rat skeletal muscle incubated in vitro

Summary Satellite cells were studied in the peripheral fibres from isolated rat muscles, which had been incubated for various periods of time. The cells were in an activated state with prominent organelles and increased cytoplasm visible. Mitosis of some satellite cells was occasionally observed. It is suggested that when incubated muscle preparations are used as models for physiological systems in vivo, the state of the satellite cell population should be taken into consideration.     

Structural Property of DNA That Migrates Faster in Gel Electrophoresis,as Deduced by CD Spectroscopy

Bent DNAs are known to migrate slower than ordinary DNA in non-denaturing polyacrylamide gel electrophoresis. In contrast, several satellite DNAs have been shown to migrate fast. The structural property that causes the fast migration, however, is not clarified so far on molecular basis. We have investigated the structural property of a satellite DNA, which contains consecutive purine sequences and migrates faster in gel, by CD spectroscopy. Partial formation of an A-form–like structure has been suggested. Reduction in DNA length due to the formation of the A-form–like structure may be responsible for the fast migration. The pronounced rigidity of DNA may also contribute to the behavior.     

Cell–cell contact and signaling in the muscle stem cell niche

Muscle stem cells (also called satellite cells or SCs) rely on their local niche for regulatory signals during homeostasis and regeneration. While a number of cell types communicate indirectly through secreted factors, here we focus on the significance of direct contact between SCs and their neighbors. During quiescence, SCs reside under a basal lamina and receive quiescence-promoting signals from their adjacent skeletal myofibers. Upon injury, the composition of the niche changes substantially, enabling the formation of new contacts that mediate proliferation, self-renewal, and differentiation. In this review, we summarize the latest work in understanding cell–cell contact within the satellite cell niche and highlight areas of open questions for future studies.     

星状神经节阻滞对非体外循环冠脉移植术病人ACTH、AT-Ⅱ及GL的影响

目的：比较单纯全麻和星状神经节阻滞术复合全麻对非体外循环冠状动脉旁路移植术（OPCABG）中应激反应的影响。方法：选择拟行OPCABG病人40例,根据实验设计随机分为星状神经节阻滞组（S组）和对照组（N组）各20例,S组在入室完成各项监测麻醉诱导前行右侧星状神经节阻滞术,两组麻醉及手术方式相同。分别于入室（T0,S组在行星状神经节阻滞前）、插气管导管（T1）、劈胸骨（T2）、和吻合前降支（T3）时记录患者的血压、脉搏并采中心静脉血测血糖,集中以放免法测促肾上腺皮质激素、血管紧张素Ⅱ和胰高血糖素。结果：与N组比较,S组患者各时点血流动力学变化更趋平稳;促肾上腺皮质激素和胰高血糖素的升高幅度明显较小（P〈0.01）。结论：星状神经节阻滞术可有效减轻OPCABG中麻醉与手术所致的过强应激反应。     

Satellite cells isolated from aged or dystrophic muscle exhibit a reduced capacity to promote angiogenesis in vitro

Deficits in skeletal muscle function exist during aging and muscular dystrophy, and suboptimal function has been related to factors such as atrophy, excessive inflammation and fibrosis. Ineffective muscle regeneration underlies each condition and has been attributed to a deficit in myogenic potential of resident stem cells or satellite cells. In addition to reduced myogenic activity, satellite cells may also lose the ability to communicate with vascular cells for coordination of myogenesis and angiogenesis and restoration of proper muscle function. Objectives of the current study were to determine the angiogenic-promoting capacity of satellite cells from two states characterized by dysfunctional skeletal muscle repair, aging and Duchenne muscular dystrophy. An in vitro culture model composed of satellite cells or their conditioned media and rat adipose tissue microvascular fragments (MVF) was used to examine this relationship. Microvascular fragments cultured in the presence of rat satellite cells from adult muscle donors (9–12 month of age) exhibited greater indices of angiogenesis (endothelial cell sprouting, tubule formation and extensive branching) than MVF co-cultured with satellite cells from aged muscle donors (24 month of age). We sought to determine if the differential degree of angiogenesis we observed in the co-culture setting was due to soluble factors produced by each satellite cell age group. Similar to the co-culture experiment, conditioned media produced by adult satellite cells promoted greater angiogenesis than that of aged satellite cells. Next, we examined differences in angiogenesis-stimulating ability of satellite cells from 12 mo old MDX mice or age-matched wild-type mice. A reduction in angiogenesis activity of media conditioned by satellite cells from dystrophic muscle was observed as compared to healthy muscle. Finally, we found reduced gene expression of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in both aged and dystrophic satellite cells compared to their adult and normal counterparts, respectively. These results indicate that functional deficits in satellite cell activities during aging and diseased muscle may extend to their ability to communicate with other cells in their environment, in this case cells involved in angiogenesis.     

Angiotensin II Inhibits Satellite Cell Proliferation and Prevents Skeletal Muscle Regeneration

Cachexia is a serious complication of many chronic diseases, such as congestive heart failure (CHF) and chronic kidney disease (CKD). Although patients with advanced CHF or CKD often have increased angiotensin II (Ang II) levels and cachexia and Ang II causes skeletal muscle wasting in rodents, the potential effects of Ang II on muscle regeneration are unknown. Muscle regeneration is highly dependent on the ability of a pool of muscle stem cells (satellite cells) to proliferate and to repair damaged myofibers or form new myofibers. Here we show that Ang II reduced skeletal muscle regeneration via inhibition of satellite cell (SC) proliferation. Ang II reduced the number of regenerating myofibers and decreased expression of SC proliferation/differentiation markers (MyoD, myogenin, and active-Notch) after cardiotoxin-induced muscle injury in vivo and in SCs cultured in vitro. Ang II depleted the basal pool of SCs, as detected in Myf5^nLacZ/+ mice and by FACS sorting, and this effect was inhibited by Ang II AT1 receptor (AT1R) blockade and in AT1aR-null mice. AT1R was highly expressed in SCs, and Notch activation abrogated the AT1R-mediated antiproliferative effect of Ang II in cultured SCs. In mice that developed CHF postmyocardial infarction, there was skeletal muscle wasting and reduced SC numbers that were inhibited by AT1R blockade. Ang II inhibition of skeletal muscle regeneration via AT1 receptor-dependent suppression of SC Notch and MyoD signaling and proliferation is likely to play an important role in mechanisms leading to cachexia in chronic disease states such as CHF and CKD.     

Viral diseases of the giant fresh water prawn Macrobrachium rosenbergii: a review

The giant freshwater prawn Macrobrachium rosenbergii is cultivated essentially in Southern and South-eastern Asian countries such as continental China, India, Thailand and Taiwan. To date, only two viral agents have been reported from this prawn. The first (HPV-type virus) was observed by chance 25 years ago in hypertrophied nuclei of hepatopancreatic epithelial cells and is closely related to members of the Parvoviridae family. The second, a nodavirus named MrNV, is always associated with a non-autonomous satellite-like virus (XSV), and is the origin of so-called white tail disease (WTD) responsible for mass mortalities and important economic losses in hatcheries and farms for over a decade. After isolation and purification of these two particles, they were physico-chemically characterized and their genome sequenced. The MrNV genome is formed with two single linear ss-RNA molecules, 3202 and 1250 nucleotides long, respectively. Each RNA segment contains only one ORF, ORF1 coding for the RNA-dependant RNA polymerase located on the long segment and ORF2 coding for the structural protein CP-43 located on the small one. The XSV genome (linear ss-RNA), 796 nucleotides long, contains a single ORF coding for the XSV coat protein CP-17. The XSV does not contain any RdRp gene and consequently needs the MrNV polymerase to replicate.