Acquisition and transmission of potato mop-to furovirus by a culture of Spongospora subterranea f.sp. subterranea derived from a single cystosorus

Potato mop-top virus (PMTV) was detected by ELISA in primary zoospores from four out of six isolates of Spongospora subterranea f.sp. subterranea. One virus-free isolate (N) of S. subterranea was used to acquire PMTV from potato roots and to transmit the virus to healthy plants. A mono-fungal culture of S. subterranea (isolate N) was derived by infecting tomato plant roots with a single cystosorus. The culture was used successfully to acquire PMTV from the roots of infected Nicotiana debneyi plants that had been manually inoculated with virus isolates, and subsequently to transmit the virus to healthy bait plants. These experiments confirm that S. subterranea is a vector of PMTV. Two PMTV isolates that had been maintained by manual inoculation for 19 and 21 passages were also acquired and transmitted by the fungus culture.     

云贵鹅耳枥群落演替中乔木树种间协变的研究

采用Ｓｐｅａｒｍａｎ秩相关系数探讨了贵阳喀斯特山地云贵鹅耳枥群落演替中１６种常见乔木树种间的协变,并对这些乔木树种间的协变关系及其对群落的性质、结构和动态的影响进行了分析。     

水对生物驻极体猪骨压电系数d_（33）测量影响的研究

研究了水在生物驻极体的压电过程中的作用,通过测量猪肩胛骨和软骨组织的纵向压电系数ｄ３３得出的结论是：水不仅能影响压电系数的测量,而且对压电效应的产生也起很大作用。水的含量及存在状态不同,压电系数也不同。     

Measuring protein self-association using pulsed-field-gradient NMR spectroscopy: Application to myosin light chain 2

Summary At the millimolar concentrations required for structural studies, NMR spectra of the calcium-binding protein myosin light chain 2 (MLC2) showed resonance line widths indicative of extensive self-association. Pulsed-field-gradient (PFG) NMR spectroscopy was used to examine whether MLC2 aggregation could be prevented by the zwitterionic bile salt derivative 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). PFG NMR measurements indicated that CHAPS was capable of preventing MLC2 self-association, but only at concentrations well above the critical micelle concentration of 7.5 mM. CHAPS was most effective at a concentration of 22.5 mM, where the apparent molecular mass of MLC2 correponded to a protein monomer plus seven molecules of bound detergent. The resolution and sensitivity of 2D ¹⁵N-¹H HSQC spectra of MLC2 were markedly improved by the addition of 25 mM CHAPS, consistent with a reduction in aggregation following addition of the detergent. The average amide nitrogen T₂ value for MLC2 increased from 30 ms in the absence of CHAPS to 56 ms in the presence of 25 mM CHAPS. The results of this study lead us to propose that PFG NMR spectroscopy can be used as a facile alternative to conventional techniques such as analytical ultracentrifugation for examining the self-association of biological macromolecules.     

Partition coefficients of the iron(III) complexes of pyridoxal isonicotinoyl hydrazone and its analogs and the correlation to iron chelation efficacy

Pyridoxal isonicotinoyl hydrazone and its analogs are orally effective Fe(III) chelators which show potential as drugs to treat iron overload disease. The present investigation describes the measurement of the partition coefficient of the apochelator and Fe(III) complex of 20 of these ligands. These measurements have been done to investigate the relationship between lipophilicity and the efficacy of iron chelation in rabbit reticulocytes loaded with non-heme ⁵⁹Fe. The results demonstrate a linear relationship between the partition coefficient (P) of the apochelator and its Fe(III) complex, and a simple equation has been derived relating these two parameters. Experimental data in the literature are in agreement with the equation. The relationship of the partition coefficients of the iron chelators and of their Fe(III) complexes to the effectiveness of the ligands in mobilizing iron in vitro and in vivo is also discussed.     

Synthesis and Evaluation of DMPO-Type Spin Traps

The spin traps substituted with some groups at the 4-position of dimethyl-1-pyrroline N-oxide(DMPO) were compared with DMPO itself regarding their abilities as spin traps and their physical properties. 4,5,5-Trimethyl-l-pyroHine N-oxide (4MDMPO) and 5,5-dimethyl- 4-phenyl-l-pyrolline N-oxide (4PDMPO) were synthesized by the Bonnett method, and 5,5-dimethyl-4-hydroxymethyl-l-pyrolline N-oxide (4HMDMPO) was made by a unique method from 2(5H)-furanone. The melting points of 4MDMPO, 4PDMPO and 4HMDMPO were higher than that of DMPO. The magnitude of hydrophilicity was in the order of 4HMDMPO, DMPO, 4MDMPO, and 4PDMPO based on the partition coefficient experiments in a 1-octanol-water system. Several radicals, O₂, HO-, -CH₃, -CH₂OH, -CH(CH₃)OH, (CH₃)₃ CO and H radicals, were trapped with these DMPO derivatives for comparison with the trapping by DMPO itself. Spin adducts of O J with the three DMPO derivatives showed ESR spectra similar to that of DMPO. In spite of the formation of diastereomers arising from spin trapping, the line-width enlargement was very small. The intensities and the decay rates of the spectra of 4MDMPO-O₂^-, 4PDMPO-O₂^- 4HMDMPO-O₂^- and DMPO-O₂^- were almost equal. In the trapping of the OH radical by 4MDMPO, 4PDMPO and 4HMDMPO, the eight-line ESR spectra observed were different from the well-known four-line spectrum of DMPO-OH.     

Regeneration and characterization of plants produced from mature tobacco pollen protoplasts via gametosomatic hybridization

Summary Mature pollen protoplasts (n) isolated from kanamycin resistant plants of Nicotiana tabacum (2n = 4x = 48) were fused with somatic mesophyll protoplasts (2n) of Nicotiana plumbaginifolia (2n = 20) to produce plants. A total of 3.6·10⁶ mature pollen protoplasts were fused with 7·10⁶ mesophyll protoplasts using a PEG/Ca²⁺ method. Mature pollen protoplasts did not divide in our culture conditions, and N. plumbaginifolia protoplasts stopped dividing when the protoplast-derived colonies were transferred to a selection medium containing paromomycine (20 mg·l^-1). A total of 133 actively growing colonies were recovered on the selection medium containing kanamycin (100 mg·l^-1). Plants from twenty resulting cell lines were confirmed as hybrids (17) or cybrids (3) based on leaf and floral morphology and fertility analysis. Isozyme pattern analysis confirmed the nuclear hybrid and cybrid nature, respectively, for 2 and 3 typical gametosomatic selected plants. Root tip squashes of 6 of the gametosomatic hybrid plants revealed chromosome numbers ranging from 44 to 68; the 3 selected cybrid plants had 48 chromosomes. Evidence for organelle transmission from the mesophyll partner in the gametosomatic plants is shown. From the analysis it can be concluded that the gametosomatic fusion involving mature pollen protoplasts (n) carrying a dominant selection marker can be convenient for synthesis of either hybrids or cybrids. Such gametosomatic fusion is therefore considered as a new approach towards the production of androgenetic plants with a choosen cytoplasm.Abbreviations AAT aspartate aminotransferase - BCP bromocresol purple - EST esterase - MES 2-(N-morpholino) ethanesulfonic acid - AP acid phosphatase - PEG polyethyleneglycol - PER peroxydase     

Adverse Effects of Epiphytic Crustose Lichens upon Stem Photosynthesis and Chlorophyll of Populus tremula L.

Dry cork layer (phellem) in stems of Populus tremula transmitted 35–55 percent of incident irradiation, depending upon moisture content. A cover of crustose Lecanora lichens reduced transmission through phellem to 10 percent or less of incident irradiation. The bark contains photosynthetically active cells. Apparent quantum yield for photosynthetic O₂-evolution was 0.017 in bark covered with dry Lecanora compared with 0.070 in naked bark. The capacity for gross photosynthesis in high light (1090 μmol photons m^?2 s^?1) was reduced by 50 percent in Lecanora-covered bark. Lecanora did not reduce the ratio between variable and maximal chlorophyll a fluorescence (F_v/F_m). Chlorophyll content per unit area was similar in leaves and naked bark of Populus tremula. The chlorophyll content in the bark decreased with increasing chlorophyll content in Lecanora. Chlorophyll a/b ratio was 2.5 in the bark compared with 4.0 in leaves and in Lecanora, and the ratio decreased down the stems. The a/b ratio was 2.3 in Lecanora covered bark compared with 2.6 in naked bark. The changes in bark photosynthesis below a Lecanora crust were probably due to acclimation of bark photosynthesis to shade, since the lichen acids in the measured lichens neither suppressed photosynthetic O₂-evolution nor changed the F_v/F_m in bark disks.     

Host density and ectoparasite avoidance in the common lizard (Lacerta vivipara)

Increased transmission of parasites and diseases is generally considered as a major cost of social life. In this study we tested the hypothesis regarding ectoparasites as a cost of living in crowded habitats in the common lizard (Lacerta vivipara). We used two approaches to explore this question. First, we tested if ectoparasite load and prevalence are positively correlated with host density in the field. Second, we experimentally tested if lizards avoid parasitized conspecifics. Contrary to expectation, we found that (1) ectoparasite load is negatively correlated with lizard density; (2) prevalence does not significantly increase with density; (3) unparasitized lizards do not avoid parasitized conspecifics but are attracted by them whatever their parasite load. These findings suggest that ectoparasites cannot be considered as a cost of living at high density in the common lizard, in spite of the potential negative impact mites may have on lizard fitness. Received: 18 August 1996 / Accepted: 7 February 1997     

The function of water channels in Chara: The temperature dependence of water and solute flows provides evidence for composite membrane transport and for a slippage of small organic solutes across water channels

Using the cell pressure probe, the effects of temperature on hydraulic conductivity (Lp; osmotic water permeability), solute permeability (permeability coefficient, P_s), and reflection coefficients (σ_s) were measured on internodes of Chara corallina, Klein ex Willd., em R.D.W.. For the first time, complete sets of transport coefficients were obtained in the range between 10 and 35 °C which provided evidence about pathways of water and solutes as they move across the plasma membrane (water channel and bilayer arrays). Test solutes used to check for the selectivity of water channels were monohydric alcohols of different molecular size and shape (ethanol, n-propanol, iso-propanol, and tert-butanol) and heavy water (HDO). Within the limits of accuracy, Q₁₀ values for Lp and for the diffusive water permeability (P_d) were identical (Q₁₀ for Lp = 1.29 ± 0.17 (± SD; n = 15 cells) and Q₁₀ for P_d = 1.25 ± 0.16 (n = 5 cells)). The Q₁₀ values were equivalent to activation energies of E_a = 16.8 ± 6.4 and 16.6 ± 10.0 kJ · mol⁻¹, respectively, which is similar to that of self-diffusion or of viscous flow of water. The Q₁₀ values and activation energies for P_s of the alcohols were significantly larger (ethanol: Q₁₀ = 1.68 ± 0.16, E_a = 37.1 ± 5.9 kJ · mol⁻¹; n-propanol: Q₁₀ =  1.75 ± 0.40, E_a = 43.1 ± 15.3 kJ · mol⁻¹; iso-propanol: Q₁₀ = 2.12 ± 0.42, E_a =  52.2 ± 14.6 kJ · mol⁻¹; tert-butanol: Q₁₀ = 2.13 ± 0.56, E_a = 51.6 ± 17.1 kJ · mol⁻¹; ±SD; n = 5 to 6 cells). Effects of temperature on reflection coefficients were most pronounced. With increasing temperature, σ_s values of the alcohols decreased and those of HDO increased. The data indicate that water and solutes use different pathways when crossing the membrane. Ordinary and isotopic water use water channels and the other test solutes use the bilayer array (composite transport model of membrane). Changes in σ_s values with temperature were found to be a sensitive measure for the open/closed state of water channels. The decrease of σ_s with temperature was theoretically predicted from the temperature dependence of P_s and Lp. Differences between predicted and measured values of σ_s allowed estimation of the bypass flow (slippage) of solutes through water channels which did not completely exclude test solutes. The permeability of channels depended on the structure and size of test solutes. It is concluded that water channels are much less selective than is usually thought. Since water channels represent single-file or no-pass pores, solutes drag along considerable amounts of water as they diffuse across channels. This results in low overall values of σ_s. The σ_s of HDO was extremely low. Its response to temperature was opposite to that for the σ_s of the alcohols. This suggested a stronger effect of temperature on the hydraulic (osmotic) than on the diffusive water flow across individual water channels, i.e. a differential sensitivity of different mechanisms to temperature. Received: 10 October 1996 / Accepted: 2 December 1996