Rhodnius prolixus and Rhodnius robustus–like (Hemiptera, Reduviidae) wing asymmetry under controlled conditions of population density and feeding frequency

Habitat change in Rhodnius spp may represent an environmental challenge for the development of the species, particularly when feeding frequency and population density vary in nature. To estimate the effect of these variables in stability on development, the degree of directional asymmetry (DA) and fluctuating asymmetry (FA) in the wing size and shape of R. prolixus and R. robustus–like were measured under laboratory controlled conditions. DA and FA in wing size and shape were significant in both species, but their variation patterns showed both inter-specific and sexual dimorphic differences in FA of wing size and shape induced by nutrition stress. These results suggest different abilities of the genotypes and sexes of two sylvatic and domestic genotypes of Rhodnius to buffer these stress conditions. However, both species showed non-significant differences in the levels of FA between treatments that simulated sylvan vs domestic conditions, indicating that the developmental noise did not explain the variation in wing size and shape found in previous studies. Thus, this result confirm that the variation in wing size and shape in response to treatments constitute a plastic response of these genotypes to population density and feeding frequency.     

Polyhydroxyalkanoate accumulation in Streptomyces coelicolor affected by SCO7613 gene region

Polyhydroxyalkanoate (PHA) is stored as an important carbon and energy source in bacterial cells. For biomedical applications, gram-positive bacteria can be better sources of PHAs, since they lack outer membrane lipopolysaccharide. Although gram-positive Streptomyces coelicolor A3(2) has been indicated as a high potential PHA producer, pha C gene that encodes the key enzyme PHA synthase in the metabolic pathway is not determined in its genome. BLAST search results of the GenBank database argued that SCO7613 could specify a putative polyhydroxyalkanoate synthase (PhaC) responsible for PHA biosynthesis. Deduced amino acid sequence of SCO7613 showed the presence of conserved lipase box like sequence, ⁵⁵⁵GASAG⁵⁵⁹, in which serine residue was present as the active nucleophile. Present study describes deletion of putative S. coelicolor pha C gene via PCR dependent method. We showed that SCO7613 is not an essential gene in S. coelicolor and its deletion affected PHA accumulation negatively although it is not ceased. Transcomplementation abolished the mutant phenotype, demonstrating that the decrease in PHA resulted from the deletion of SCO7613.     

In Vitro Evidence for Increased Facilitation of Striatal Acetylcholine Release via Pre- and Postsynaptic NMDA Receptotors in Hemiparkinsonian Rats

Abstract : The NMDA-evoked acetylcholine release from striatal slices and synaptosomes was investigated in rats subjected to unilateral injection of 6-hydroxydopamine into the substantia nigra. In slices prepared from the striatum contralateral to the lesion, the NMDA-evoked endogenous acetylcholine release was not significant at 10 μ M NMDA and maximal at 100 μ M NMDA (124 ± 19%). Conversely, in slices taken from the dopamine-depleted striatum, NMDA was effective even at 10 μ M (41 ± 4%), and at 100 μ M (196 ± 24%) efficacy was nearly doubled. In synaptosomes prepared from the contralateral striatum, NMDA maximally stimulated 20 m M KCl-induced endogenous acetylcholine release at 1 μ M (66 ± 5.1%), with lower concentrations (0.01-0.1 μ M ) being ineffective. Conversely, in synaptosomes prepared from the dopamine-depleted striatum, NMDA maximally enhanced the K⁺-evoked acetylcholine release at 0.1 μ M (118 ± 12.4%). Concentration-response curves of NMDA-evoked acetylcholine release in sham-operated rats could be superimposed on those observed in the contralateral striatum of the 6-hydroxydopamine-lesioned animals. The present data support the view of an increased glutamatergic regulation of striatal acetylcholine release via pre- and postsynaptic NMDA receptors during Parkinson's disease.     

Differential effect of NR2A and NR2B subunit selective NMDA receptor antagonists on striato-pallidal neurons: relationship to motor response in the 6-hydroxydopamine model of parkinsonism

We previously demonstrated that NMDA receptors containing the NR2A or NR2B subunits differentially regulate striatal output pathways. We now investigate whether such a differential control is altered under parkinsonian conditions and whether subunit selective antagonists have different abilities to attenuate parkinsonian-like motor deficits. Three microdialysis probes were simultaneously implanted in the dopamine-depleted striatum, globus pallidus and substantia nigra reticulata of 6-hydroxydopamine hemilesioned rats. The NR2A antagonist NVP-AAM077 perfused in the striatum reduced pallidal GABA, but not glutamate, levels whereas the NR2B antagonist Ro 25-6981 was ineffective. Neither antagonist affected striatal or nigral amino acid levels. To investigate whether these neurochemical responses were predictive of different antiparkinsonian activities, antagonists were administered systemically and motor activity evaluated in different motor tasks. Neither antagonist attenuated akinesia/bradykinesia in the bar and drag test. However, NVP-AAM077 dually modulated rotarod performance (low doses being facilitatory and higher ones inhibitory) while Ro 25-6981 monotonically improved it. Microdialysis revealed that motor facilitating doses reduced pallidal GABA levels while motor inhibiting doses increased them. We conclude that, under parkinsonian conditions, the striato-pallidal pathway is driven by striatal NR2A subunits. Motor improvement induced by NVP-AAM077 and Ro 25-6981 is accomplished by blockade of striatal NR2A and extrastriatal NR2B subunits, respectively.     

环境因子对豆科共生固氮影响的研究进展

环境因子的限制一直是豆科植物一根瘤菌共生固氮体系没有在农业生产中充分发挥作用的重要原因之一。目前,研究涉及的环境因子主要行水分、矿质营养元素、温度、重金属、钠盐、CO2、土壤类型以及pH等。水分胁迫会导致豆科植物根瘤减少和固氮效率低下;矿质元素方面,除氮磷钾外,微量死素对固氮影响也很明显;不适的温度会对豆科植物的结瘤固氮产生一定的限制;重金属能从不同方面直接和间接地影响共生同氮,寻找适合作尾矿先锋植物的豆科植物是当前的一个研究热点。本文除详细阐述了这方面开展的研究以外,还浅析了这方而研究目前国内外存在的一些主要问题和发展趋势。     

Stability criterion for controlling standing in able-bodied subjects

A new stability criterion that can be used to assess the standing condition of a subject from center of pressure (CoP) measurements is presented. This criterion can be applied, for example, to control a standing prosthesis, which should allow a paraplegic subject to stand up, sit down and stand safely without using hands for support. Experiments conducted with able-bodied subjects enabled us to establish a relationship between its stability and the subject's CoP position. Four CoP stability zones were identified: high preference, low preference, undesirable and unstable zones. The high preference zone is defined as the area where the CoP is found 99% of the time during quiet standing. The area where the CoP is found during the remaining 1% of the time is called the low preference zone. The undesirable zone is defined as the CoP area where the subject is forced to change posture in order to maintain balance, and the unstable zone is defined as the CoP area in which the subject is forced to step forward, backward or sideways to maintain stability. A general model of the proposed four stability zones was derived, which can be used to compute stability zones a priori for any subject and thus allows one to assess the subject's stability condition from the CoP measurements.     

Generation of potent mouse monoclonal antibodies to self-proteins using T-cell epitope “tags”

Immunization of mice or rats with a "non-self" protein is a commonly used method to obtain monoclonal antibodies, and relies on the immune system''s ability to recognize the immunogen as foreign. Immunization of an antigen with 100% identity to the endogenous protein, however, will not elicit a robust immune response. To develop antibodies to mouse proteins, we focused on the potential for breaking such immune tolerance by genetically fusing two independent T-cell epitope-containing sequences (from tetanus toxin (TT) and diphtheria toxin fragment A (DTA)) to a mouse protein, mouse ST2 (mST2). Wild-type CD1 mice were immunized with three mST2 tagged proteins (Fc, TT and DTA) and the specific serum response was determined. Only in mice immunized with the T-cell epitope-containing antigens were specific mST2 serum responses detected; hybridomas generated from these mice secreted highly sequence-diverse IgGs that were capable of binding mST2 and inhibiting the interaction of mST2 with its ligand, mouse interleukin (IL)-33 (mIL-33). Of the hundreds of antibodies profiled, we identified five potent antibodies that were able to inhibit IL-33 induced IL-6 release in a mast cell assay; notably one such antibody was sufficiently potent to suppress IL-5 release and eosinophilia infiltration in an Alternaria alternata challenge mouse model of asthma. This study demonstrated, for the first time, that T-cell epitope-containing tags have the ability to break tolerance in wild-type mice to 100% conserved proteins, and it provides a compelling argument for the broader use of this approach to generate antibodies against any mouse protein or conserved ortholog.     

水分胁迫和氮肥对花生根系形态发育及叶片生理活性的影响

以"花育22号"花生为试验材料,在中度干旱胁迫和充足灌水两个水分条件下,分别设置不施氮肥(N0)、中氮(N1,90 kg·hm-2)、高氮(N2,180 kg·hm-2)3个施氮水平,研究不同土壤水分和氮肥条件对花生叶片生理活性及根系形态发育特征的影响.结果表明:与不施氮肥处理相比,两个水分条件下中氮处理均显著增加花生产量,但对收获指数无显著影响.干旱胁迫条件下,中氮处理对总根系生物量和总根长无显著影响,但显著增加花生总根系表面积;中氮和高氮处理均显著增加20~40 cm土层内根长和根系表面积,且高氮处理显著增加40 cm以下土层内根系生物量和根系表面积;施用氮肥显著提高叶片过氧化氢酶(CAT)和过氧化物酶(POD)活性,而丙二醛(MDA)含量随施氮量的增加而降低.正常供水条件下,施用氮肥显著降低了花生根系表面积和40 cm以下土层内根系生物量、根长和根系表面积,中氮处理可提高叶片保护酶活性.相关性分析表明,20~40 cm土层内根长和叶片超氧化物歧化酶(SOD)、CAT、POD活性与产量呈显著相关.