施肥方式对幼龄楸树非结构性碳器官分配和生长季动态的影响

以6年生楸树无性系‘9 1’为试验材料,采用水肥一体化、穴施和不施肥(对照)3种施肥方法,分析施肥对楸树生长、各器官非结构性碳(NSC)含量及时间动态变化的影响,探究楸树NSC分配对施肥的响应机制,为评估楸树单株和林分碳储量提供理论依据。结果表明：(1)连续施肥4年后,与对照相比,穴施处理的树高和胸径分别提高了4.7%和7.1%,水肥一体化处理则分别提高了7.1%和20.5%,水肥一体化的施肥效果更佳。(2)不同施肥方式并未显著改变楸树各器官中可溶性糖含量,但是水肥一体化施肥明显提高了根中淀粉和总NSC的积累;可溶性糖和总NSC在叶和粗根中分布较多,淀粉则在根中含量较高。(3)不同施肥方式并未显著改变楸树各生长时期可溶性糖含量,但水肥一体化施肥明显提高了生长初期和末期淀粉和总NSC含量。研究发现,在整个生长季中,楸树叶中可溶性糖和总NSC一直被消耗,枝中可溶性糖一部分被消耗用于支持叶片生长,一部分以淀粉的形式进行储存,而根系接受源自叶和枝的NSC后转化为淀粉储存起来帮助树木抵抗低温环境;楸树遵循“碳消耗(初期) 碳消耗(中期) 碳积累(末期)”的NSC分配策略;应用水肥一体化技术可显著提高楸树生物量和生产力,在今后林木施肥试验中值得优先考虑。     

Analysis of PDZ domain-ligand interactions using carboxyl-terminal phage display

PDZ domains mediate protein-protein interactions at specialized subcellular sites, such as epithelial cell tight junctions and neuronal post-synaptic densities. Because most PDZ domains bind extreme carboxyl-terminal sequences, the phage display method has not been amenable to the study of PDZ domain binding specificities. For the first time, we demonstrate the functional display of a peptide library fused to the carboxyl terminus of the M13 major coat protein. We used this library to analyze carboxyl-terminal peptide recognition by two PDZ domains. For each PDZ domain, the library provided specific ligands with sub-micromolar binding affinities. Synthetic peptides and homology modeling were used to dissect and rationalize the binding interactions. Our results establish carboxyl-terminal phage display as a powerful new method for mapping PDZ domain binding specificity.     

Linear scan voltammetric indirect determination of Al(III) by the catalytic cathodic response of norepinephrine at the hanging mercury drop electrode

The biological effects of aluminum (Al) have received much attention in recent years. Al is of basic relevance as concern with its reactivity and bioavailability. In this paper, the electrochemical behaviors of norepinephrine (NE) in the absence and presence of Al(III) at the hanging mercury drop electrode have been studied and applied to the practical analysis. Highly selective catalytic cathodic peak of NE is yielded by linear scan voltammetry (LSV) at -1.32 V (vs. SCE). A linear relationship holds between the cathodic peak current and the Al(III) concentration. It has been successfully applied to the determination of Al(III) in real waters and synthetic biological samples with satisfying results, which are in accordance with those obtained by ICP-AES method. The electrochemical properties and the mechanisms of the peaks in the presence and absence of Al(III) have been explored. The results show that they are irreversible adsorptive hydrogen catalytic waves. These studies not only enrich the methods of determining Al, but also lay foundations of further understanding of the mechanisms of neurodementia.     

Effects of gap junction to Ca(2+) and to IP(3) on the synchronization of intercellular calcium oscillations in hepatocytes

The frequency of free cytosolic calcium concentration ([Ca(2+)]) oscillations elicited by a given agonist concentration differs between individual hepatocytes. However, in multicellular systems of rat hepatocytes and even in the intact liver, [Ca(2+)] oscillations are synchronized and highly coordinated. In this paper, we have investigated theoretically the gap junction permeable to calcium and to IP(3) on intercellular synchronization by means of a mathematical model, respectively. It is shown that gap junction permeable to calcium and to IP(3) are effective on synchronizing calcium oscillations in coupled hepatocytes. Our theoretical results are similar either for the case of Ca(2+) acting as coordinating messenger or for the case of IP(3) as coordinating messenger. There exists an optimal coupling strength for a pair of connected hepatocytes. Appropriate coupling strength and IP(3) level can induce various harmonic locking of intercellular [Ca(2+)] oscillations. Furthermore, a phase diagram in two-dimensional parameter space of the coupling strength and IP(3) level (or the velocity of IP(3) synthesis) has been predicted, in which the synchronization region is similar to Arnol'd tongue.     

MSM and HIV/AIDS in China

This article profiles current status of spread and control of HIV/AIDS in China. China has a significant population of MSM (men who have sex with men) and they have been becoming very much alive in many ways since 1990s due to recent social changes. Some surveys indicate that great many of MSM are engaged in high-risk behaviors. In addition, majority of MSM have also experienced sexual encounters with women sometimes in their lives, which possibly contribute to spread of HIV to women. Some reports documented that HIV is becoming rampant among MSM since more than 1% of them are now infected. Political, cultural and custom elements could hinder intervention activities against HIV spread among MSM. Fortunately, many cities in China have seen that MSM were in cooperation with responsible institutions carrying out certain intervention measures. The general situation is promising. The authors forecast that the fast HIV spread among MSM of China could possibly be halted within several years when the authorities become more sensible to this issue, health service institutions offer unswerving efforts toward the MSM community and those who involve in MSM undertakes necessary responsibilities.     

Synthesis and anticonvulsant activity of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines

A series of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline derivatives was synthesized using 6-hydroxy-3,4-dihydro-1H-quinolin-2-one as a starting material. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES test) and the subcutaneous (s.c.) pentylenetetrazol test (scMet test), and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). MES and scMet tests show that 7-(4-fluorobenzyloxy)-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4l was found to be the most potent with ED50 value of 11.8 and 6.7 mg kg(-1) and protective index (PI = TD50/ED50) value of 4.6 and 8.1, respectively.     

Peptidomics of Cpe fat/fat mouse hypothalamus: effect of food deprivation and exercise on peptide levels

Carboxypeptidase E is a major enzyme in the biosynthesis of numerous neuroendocrine peptides. Previously, we developed a technique for the isolation of neuropeptide-processing intermediates from mice that lack carboxypeptidase E activity (Cpe fat/fat mice) due to a naturally occurring point mutation. In the present study, we used a differential labeling procedure with stable isotopic tags and mass spectrometry to quantitate the relative changes in a number of hypothalamic peptides in Cpe fat/fat mice in two different paradigms that each cause an approximately 10% decrease in body mass. One paradigm involved a 2-day fast under normal sedentary conditions (i.e. standard mouse cages); the other involved giving mice access to an exercise wheel for 4 weeks with free access to food. Approximately 50 peptides were detected in both studies, and over 80 peptides were detected in at least one of the two studies. Twenty-eight peptides were increased >50% by food deprivation, and some of these were increased by 2- to 3-fold. In contrast, only three peptides were increased >50% in the group with exercise wheels, and many peptides showed a slight 15-30% decrease upon exercise. Approximately one-half of the peptides detected in both studies were identified by tandem mass spectrometry. Peptides found to be elevated by food deprivation but not exercise included a number of fragments of proenkephalin, prothyrotropin-releasing hormone, secretogranin II, chromogranin B, and pro-SAAS. Taken together, the differential regulation of these peptides in the two paradigms suggests that the regulation is not due to the lower body weight but to the manner in which the paradigms achieved this lower body weight.     

Tau phosphorylation in Alzheimer's disease: pathogen or protector?

During the past decade, hypotheses concerning the pathogenesis of most neurodegenerative diseases have been dominated by the notion that the aggregation of specific proteins and subsequent formation of cytoplasmic and extracellular lesions represent a harbinger of neuronal dysfunction and death. As such, in Alzheimer's disease, phosphorylated tau protein, the major component of neurofibrillary tangles, is considered a central mediator of disease pathogenesis. We challenge this classic notion by proposing that tau phosphorylation represents a compensatory response mounted by neurons against oxidative stress and serves a protective function. This novel concept, which can also be applied to protein aggregates in other neurodegenerative diseases, opens a new window of knowledge with broad implications for both the understanding of mechanisms underlying disease pathophysiology and the design of new therapeutic strategies.     

Adjustment of systematic microarray data biases

MOTIVATION: Systematic differences due to experimental features of microarray experiments are present in most large microarray data sets. Many different experimental features can cause biases including different sources of RNA, different production lots of microarrays or different microarray platforms. These systematic effects present a substantial hurdle to the analysis of microarray data. RESULTS: We present here a new method for the identification and adjustment of systematic biases that are present within microarray data sets. Our approach is based on modern statistical discrimination methods and is shown to be very effective in removing systematic biases present in a previously published breast tumor cDNA microarray data set. The new method of 'Distance Weighted Discrimination (DWD)' is shown to be better than Support Vector Machines and Singular Value Decomposition for the adjustment of systematic microarray effects. In addition, it is shown to be of general use as a tool for the discrimination of systematic problems present in microarray data sets, including the merging of two breast tumor data sets completed on different microarray platforms. AVAILABILITY: Matlab software to perform DWD can be retrieved from https://genome.unc.edu/pubsup/dwd/