Modulation of Neuropeptide FF Receptors by Guanine Nucleotides and Cations in Membranes of Rat Brain and Spinal Cord

Abstract: Using a radioligand binding assay, we examined ionic modulation and G protein coupling of neuropeptide FF(NPFF) receptors in membranes of rat brain and spinal cord. We found that NaCl (but not KCl or LiCl) and MgCl₂ increased specific ¹²⁵I-YLFQPQRFamide (¹²⁵I-Y⁸Fa) binding to NPFF receptors in both tissues in a dose-dependent manner, with optimal conditions being 60 m M NaCl and 1 m M MgCl₂. Guanine nucleotides dose-dependently inhibited specific ¹²⁵I-Y⁸Fa binding to rat brain and spinal cord membranes with maximal effects of 64 ± 6 and 71 ± 2%, respectively. The order of potency was nonhydrolyzable GTP analogues > GTP GDP > GMP, ATP. The guanine nucleotide inhibition was observed in the absence and presence of NaCl and MgCl₂. The mechanism of inhibition in spinal cord membranes appeared to be a reduction in the number of NPFF receptors; in one experiment, control K_D and B_max values were 0.068 n M and 7.2 fmol/mg of protein, respectively, and with 0.1 μ M guanylylimidodiphosphate the respective values were 0.081 n M and 4.9 fmol/mg, a 32% reduction in receptor number. Similar results were obtained with guanosine 5'-0-(3-thiotriphosphate). Our data suggest that ¹²⁵I-Y8Fa binding sites in rat CNS are G protein-coupled NPFF receptors regulated by GTP and cations.     

Changes of Membrane Stability in Potassium Stressed Plants

The maintenance of membrane function is critical to the ability of plants to resist environmental stresses; specifically, the stability and appropriate fluidity of membranes are crucial to their normal function. We previously demonstrated that plants adapt to long term potassium (K+) deficiency by accumulation of membrane lipids in leaves and maintenance of the lipid composition in roots. In this study, which involved Arabidopsis thaliana and its K+ deficiency tolerant relative Crucihimalaya himalaica, we first calculated the double bond index (DBI) as an indicator of membrane fluidity. After exposure to long term K+ deficiency stress, the DBI of the total lipids in leaves of Athaliana and Chimalaica showed no significant changes, whereas the DBI of the total lipids in the roots of these species showed slight increases. Changes in lysophospholipids (lysoPLs) levels, and digalactosyldiacylglycerol/monogalactosyldiacylglycerol (DGDG/MGDG) and phosphatidylcholine/phosphatidylethanolamine (PC/PE) ratios, all of which strongly reflect membrane stability, were also studied in K+ stressed Athaliana and Chimalaica. After long term K+ deficiency, total lysoPLs levels increased in Athaliana and Chimalaica leaves, but showed no significant changes in roots. DGDG/MGDG and PC/PE ratios were higher in Chimalaica leaves and roots than in those of Athaliana. These results indicate that Chimalaica exhibits superior membrane stability compared with Athaliana. This may explain its superior growth and tolerance under K+ deficient conditions.     

The value of simulating herbivory in selecting effective weed biological control agents

Invasive species have a significant economic and ecological cost and biological control can be a powerful tool in their management. Classical biological control practice involves the re-establishment of trophic links between specialist insect and fungal agents to regulate populations of invasive species. However, the permanent nature of biological control agent introductions raises concerns about the unintended consequences of such introductions on non-target organisms, particularly when such agents are ineffective on their target organisms. In this paper, we explore the current debate in the selection of agents for weed classical biological control. We then propose an alternate approach, based on studying plant response to simulated herbivory, that could minimize the chances of release of ineffective agents. Simulating herbivory could yield insights into the vulnerability of plants to certain types of damage. Selection of agents within guilds that are likely to have a significant influence on the plant can improve the chances of achieving biological control sooner and reduce the likelihood of releasing ineffective agents that may have non-target impacts. We propose a method by which simulated herbivory could be integrated into the agent selection process and discuss its strengths and shortcomings. We present case studies of two Neotropical weeds illustrating how this method could be applied.     

Low temperature and defoliation affect fructan-metabolizing enzymes in different regions of the rhizophores of Vernonia herbacea

In addition to the storage function, fructans in Asteraceae from floras with seasonal growth have been associated with drought and freezing tolerance. Vernonia herbacea, native of the Brazilian Cerrado, bears underground reserve organs, rhizophores, accumulating inulin-type fructans. The rhizophore is a cauline branched system with positive geotropic growth, with the apex (distal region) presenting younger tissues; sprouting of new shoots occurs by development of buds located on the opposite end (proximal region). Plants induced to sprouting by excision of the aerial organs present increased 1-fructan exohydrolase (1-FEH) activity in the proximal region, while plants at the vegetative stage present high 1-sucrose:sucrose fructosyltransferase (1-SST) in the distal region. The aim of the present study was to analyze how low temperature (5 °C) could affect fructan-metabolizing enzymes and fructan composition in the different regions of the rhizophores of intact and excised plants. 1-SST and 1-fructan:fructan fructosyltransferase (1-FFT) were higher in the distal region decreasing towards the proximal region in intact plants at the vegetative phase, and were drastically diminished when cold and/or excision were imposed. In contrast, 1-FEH increased in the proximal region of treated plants, mainly in excised plants subjected to cold. The ratio fructo-oligo to fructo-polysaccharides was significantly higher in plants exposed to low temperature (1.17 in intact plants and 1.64 in excised plants) than in plants exposed to natural temperature conditions (0.84 in intact vegetative plants and 0.58 in excised plants), suggesting that oligosaccharides are involved in the tolerance of plants to low temperature via 1-FEH, in addition to 1-FFT. Principal component analysis indicated different response mechanisms in fructan metabolism under defoliation and low temperature, which could be interpreted as part of the strategies to undergo unfavorable environmental conditions prevailing in the Cerrado during winter.     

Structure-activity relationships of bifunctional cyclic disulfide peptides based on overlapping pharmacophores at opioid and cholecystokinin receptors

Prolonged opioid exposure increases the expression of cholecystokinin (CCK) and its receptors in the central nervous system (CNS), where CCK may attenuate the antinociceptive effects of opioids. The complex interactions between opioid and CCK may play a role in the development of opioid tolerance. We designed and synthesized cyclic disulfide peptides and determined their agonist properties at opioid receptors and antagonist properties at CCK receptors. Compound 1 (Tyr-c[d-Cys-Gly-Trp-Cys]-Asp-Phe-NH(2)) showed potent binding and agonist activities at delta and mu opioid receptors but weak binding to CCK receptors. The NMR structure of the lead compound displayed similar conformational features of opioid and CCK ligands.     

The evolution of novel herbicide tolerance in a noxious weed: the geographic mosaic of selection

Understanding how genetic variation is organized over geography has long been of interest to evolutionary biologists given that traits can vary within and among populations, across regions, and at continental or global scales. The pattern of regional variation can have an important impact on trait evolution at the local or population level. Using a common garden, we asked whether a geographically variable mosaic of tolerance to the widely applied herbicide RoundUp^® existed in two closely related co-occurring species of morning glory, Ipomoea purpurea and I. hederacea. We assayed RoundUp tolerance in over 1,700 plants representing 290 families from 29 populations in the southeastern United States. Our findings suggest that the two species of morning glory partition their respective levels of genetic variation for tolerance to glyphosate differently. Variation for tolerance in I. purpurea appears to exist among maternal lines and regions, whereas in I. hederacea, variation in tolerance existed only among populations. In addition, we find a significant hotspot of tolerance or positive spatial aggregation of this trait on a local scale in I. purpurea populations from the Coastal Plain. This suggests that either similar regimes of selection or gene flow between populations can produce a geographic mosaic of tolerance. These results highlight the fact that the genetic variation underlying an adaptive trait can exist at many different scales, whether it be within- or among-populations, among geographical ‘hotspots,’ or among distinct ecological regions. Given these results, the partitioning of genetic variation should be considered before making predictions about an adaptive trait’s evolutionary trajectory.     

Compensation for floral herbivory in <Emphasis Type="Italic">Solanum carolinense</Emphasis>: identifying mechanisms of tolerance

While a plant’s capacity to tolerate damage by herbivores can be studied as a single trait, it is important to recognize that tolerance is generally a result of the combined action of several different traits. Here, we report on a pair of experiments to identify mechanisms for tolerating floral herbivory in Solanum carolinense, an andromonoecious perennial herb that regularly suffers from high levels of florivory. We measured the effect of actual and simulated florivory on host-plant fitness and assessed which plant traits exhibited plasticity in response to florivory. In addition, for each of nine plant genets, we calculated tolerance indices and determined which traits were genetically correlated with tolerance. Traits that served to help S. carolinense tolerate florivory in terms of sexual reproduction included initiating more inflorescences, aborting fewer buds prior to anthesis and fewer ovaries after fertilization, and increasing the ratio of perfect:male flowers. In addition, the greater the levels of florivory, the more the plants allocated to root growth, which may promote tolerance through greater potential future reproduction. The plant population contained significant genetic variation for tolerance itself and for nearly all of the putative tolerance mechanisms, which suggests that S. carolinense has the potential to evolve greater tolerance through a variety of different routes in response to natural selection.     

QTL analysis of tolerance to a German strain of BYDV-PAV in barley (Hordeum vulgare L.)

One hundred and forty six barley doubled-haploid lines (DH lines) were tested for variation in grain yield, yield components, plant height, and heading date after artificial infection with a German isolate of barley yellow dwarf virus (BYDV-PAV-Braunschweig). Of these 146 lines 76 were derived from the cross of the barley yellow dwarf virus (BYDV) tolerant cultivar ’Post’ to cv ’Vixen’ (Ryd2) and 70 from the cross of Post to cv ’Nixe’. Phenotypic measurements were gathered on both non-infected plants and plants artificially inoculated with BYDV-PAV by viruliferous aphids in pot and field experiments for three years at two locations. For all traits a continuous variation was observed suggesting a quantitative mode of inheritance for tolerance against BYDV-PAV. Using skeleton maps constructed using SSRs, AFLPs and RAPDs, two QTLs for relative grain yield per plant after BYDV infection, explaining about 47% of the phenotypic variance, were identified in Post × Vixen at the telomeric region of chromosome 2HL and at a region containing the Ryd2 gene on chromosome 3HL. In Post × Nixe, a QTL was found in exactly the same chromosome 2HL marker interval. In this cross, additional QTL were mapped on chromosomes 7H and 4H and together these explained about 40% of the phenotypic variance. QTL for effects of BYDV infection on yield components, plant height, and heading date generally mapped to the same marker intervals, or in the vicinity of the QTL for relative grain yield, on chromosomes 2HL and 3HL, suggesting that these regions are of special importance for tolerance to the Braunschweig isolate of BYDV-PAV. Possible applications of marker-assisted selection for BYDV tolerance based on these results are discussed. Received: 1 December 2000 / Accepted: 9 March 2001     

The Characteristics of Low Temperature Tolerance during Seed Germination of the Ephemeral Plant Lepidium apetalum (Cruciferae)

Lepidium apetalum was used to explore the characteristics and mechanismes of low temperature tolerance during seed germination. The results showed that pre treatment the seeds at 4℃ would improve the seeds viability after stressed by low temperature at -5℃ and -10℃ and the capability of seeds tolerance to cold temperature became weaker along with germination development. Although the growth of radicle was inhibited significantly at 4℃ during germination, the seeds could still survive and grow. With appropriate time of stratified at 4℃, germination pace would be improved and germination rate would not change, while both of which decreased if stratification lasted too long. Moreover, Lapetalum seeds were very sensible to the temperature during germination. It showed no germination at 4℃, while if seeds were stratificated for 48 hours at 4℃ and subsequently treated with 25℃ for more than 6 hours, seeds would germinate at 4℃ and the germination rate increased with the time of 25℃ treatment prolonged. If treatment at 25℃ was less than 5 houes, it showed no germinating. In addition, seeds with stratification for 10 days following 1 h treatment at 25℃ could also germinated at 4℃. The present study indicated that some pivotal genes that related with a key physiological stage before the onset of radicle protrusion might inhibite at 4℃, which resulted in Lapetalum seed could not germinate at 4℃. Except that physiological stage, the Lapetalum seed had a strong tolerance to low temperature at other germination stages. This experiment provided a new way to explore the germination mechanism of ephemerals plants seeds at low temperature.     

酱香型白酒酿造拜耳接合酵母生理代谢特征及其与地衣芽孢杆菌相互作用

【目的】拜耳接合酵母(Zygosaccharomyces bailii)是酱香型白酒酿造过程优势菌株。通过研究拜耳接合酵母酿造相关生理代谢特征及其与酿造环境中其它功能菌株的相互作用,探索其在白酒酿造过程中的贡献。【方法】从酱香酒酿造中筛选一株性能优良的拜耳接合酵母,比较其与模式菌株(Z.bailii,ATCC 58445)的生理代谢特征。通过组合发酵研究其与产酱香特征风味细菌地衣芽孢杆菌的相互作用。【结果】从酱香型酒醅中筛选得到一株性状优良的拜耳接合酵母(Z.bailii 15),可耐受p H 2.0和37°C高温及8%酒精浓度(体积比),较模式株更适应酿造环境,酒精产量(33.58 g/L)也远高于模式株(19.04 g/L),且与酱香型白酒酿酒酵母MT1(34.29 g/L)相当。该菌可产多种风味物质,与模式株相比,独特产生法呢醇、十二醇、2-壬醇、2-乙基己醇、癸酸、月桂酸、辛酸、辛酸乙酯、苯乙酮、4-叔丁基苯酚。共培养体系中,30°C条件下地衣芽孢杆菌对拜耳接合酵母生长影响不大,而在37°C地衣芽孢杆菌抑制拜耳接合酵母生长。此外,地衣芽孢杆菌对拜耳接合酵母乙醇转化率有促进作用,共培养体系风味物质种类及含量也都受到很大影响。【结论】拜耳接合酵母在酱香型白酒酿造体系中产酒精、产风味方面表现优异,对酱香型白酒生产具有重要贡献。