老挝北部宾夕法尼亚纪的一个新(筳)类动物群

作者报道了一个小型■类动物群,包括Eostaffella? sp., Pseudoendothyra sp., Staffella pseudosphae-roidea Dutkevich, Neostaffella ( N.)sp ., Profusulinella bona Grozdilova et Lebedeva以及P.cf .prisca (Depart) ,此动物群是在老挝北部琅勃拉邦省西南部的Thong Phiang Vilay村附近的石灰岩山中发现的。根据Profusulinella bona和P.cf. prisca的出现,该动物群的时代可归到晚石炭世宾夕法尼亚纪巴什基尔期或莫斯科期最早期。这是在老挝北部对该时代■类动物群的首次报道。当前■类动物群证明琅勃拉邦地区和泰国北部的黎地区在地质上有重要的关系,表明老挝北部地区从地质构造上属于印度支那板块的边缘。     

Isolation and characterization of microsatellite markers in Japanese pear (Pyrus pyrifolia Nakai)

Fourteen microsatellite markers were developed from an enriched genomic library of Japanese pear (Pyrus pyrifolia) by selective hybridization. They were characterized using 17 Japanese pear cultivars. The expected heterozygosity and observed heterozygosity ranged from 0.21 to 0.74 and from 0 to 0.88, respectively. Two to 11 alleles were detected per locus, with IPPN09 and IPPN15 judged to amplify multiple loci. IPPN17 was the most informative locus with the lowest probability of identity (0.19). These primers exhibited a high cross‐species transferability between species and genera.     

Genetic and Epigenetic Control of the Proliferation and Differentiation of Mouse Epidermal Melanocytes in Culture

Serum-free culture of epidermal cell suspensions from neonatal skin of mice of strain C57BL/10JHir (B10) showed that α-melanocyte-stimulating hormone (α-MSH) was involved in regulating the differentiation of melanocytes by inducing tyrosinase activity, melanosome formation, and dendritogenesis. Dibutyryl adenosine 3′:5′-cyclic monophosphate (DB-cAMP) similarly induced the differentiation of melanocytes. On the other hand, DBcAMP induced the proliferation of epidermal melanocytes in culture in the presence of keratinocytes. Basic fibroblast growth factor (bFGF) was also shown to stimulate the sustained proliferation of undifferentiated melanoblasts in the presence of DBcAMP and keratinocytes. These results suggest that the proliferation and differentiation of mouse epidermal melanoblasts and melanocytes in culture are regulated by the three factors; namely, cAMP, bFGF, and keratinocyte-derived factors. Moreover, serum-free primary culture of mouse epidermal melanocytes derived from B10 congenic mice, which carry various coat color genes, showed that the coat color genes were involved in regulating the proliferation and differentiation of mouse epidermal melanocytes by controlling the proliferative rate, melanosome formation and maturation, and melanosome distribution.     

Fitness minimization and dynamic instability as a consequence of predator–prey coevolution

We analyse dynamic models of the coevolution of continuous traits that determine the capture rate of a prey species by a predator. The goal of the analysis is to determine conditions when the coevolutionary dynamics will be unstable and will generate population cycles. We use a simplified model of the evolutionary dynamics of quantitative traits in which the rate of change of the mean trait value is proportional to the rate of increase of individual fitness with trait value. Traits that increase ability in the predatory interaction are assumed to have negative effects on another component of fitness. We concentrate on the role of equilibrial fitness minima in producing cycles. In this case, the mean trait of a rapidly evolving species minimizes its fitness and it is chased around this equilibrium by adaptive evolution in the other species. Such cases appear to be most likely if the capture rate of prey by predators is maximal when predator and prey phenotypes match each other. They are possible, but less likely when traits in each species determine a one-dimensional axis of ability related to the interaction. Population dynamics often increase the range of parameter values for which cycles occur, relative to purely evolutionary models, although strong prey self-regulation may stabilize an evolutionarily unstable subsystem.     

NATURE OF THE INHIBITION OF PROTEIN SYNTHESIS BY ETHIONINE AND AMINO ACID UPTAKE IN EARLY SEA URCHIN EMBRYOS

The inhibition of protein synthesis by ethionine reported previously was found to be apparent, and ethionine inhibited only amino acid uptake like other usual amino acids. Even under such strong inhibition of the uptake, the syntheses of protein and DNA remained almost undiminished. The uptake of amino acid mixture by sea urchin embryos in the early cleavage stage was found to be carried out by active transport, since it was temperature-sensitive and was inhibited by 2,4-dinitrophenol. The uptake of an amino acid mixture or of single amino acids, e.g., valine, leucine and phenylalanine, was inhibited nonspecifically by an excess amount of other single amino acids added exogenously. Reflecting the inhibition of amino acid uptake, in vivo incorporation of amino acids into the protein fraction was apparently inhibited by excess amounts of other amino acids. As far as tested, the inhibition seems to be nonspecific and competitive for all amino acid species. The uptakes of leucine and phenylalanine were inhibited mutually by competition, with almost the same Km and Ki.     

Rice yield enhancement by elevated CO2 is reduced in cool weather

The projected increase of atmospheric CO₂ concentration ([CO₂]) is expected to increase rice yield, but little is known of the effects of [CO₂] at low temperature, which is the major constraint to growing rice in cool climates. We grew rice under two levels of [CO₂] (ambient and elevated by 200 μmol mol^?1) and two nitrogen (N) fertilization regimes in northern Japan in 2003 (cool weather) and 2004 (warm weather) in the field in a free‐air CO₂ enrichment (FACE) system. Elevated [CO₂] significantly increased grain yield in both years in both N regimes, but the magnitude of the increase differed between years: 6% in 2003 vs. 17% in 2004, with a significant interaction between [CO₂] and year. This difference resulted from responses of spikelet number and ripening percentage to elevated [CO₂]. Enhancement of dry matter production and N uptake at heading by elevated [CO₂] was smaller in 2003 than in 2004, although at maturity there was no difference between years. No significant interaction between N regime and [CO₂] was detected in yield and yield components. The results suggest that yield gain due to elevated [CO₂] can be reduced by low temperature.     

Analysis of lichen substances including triterpenoids by high performance liquid chromatography with a differential refractive index detector and a photodiode array detector

A new method for analysis of lichen triterpenoids was established using high performance liquid chromatography with the combination of a differential refractive index detector (RID) and a photodiode array detector (PDA). It is proved that this method was convenient to detect and identify aromatic and aliphatic lichen substances; it enabled quantitative analysis of substances having no or less absorption of ultraviolet rays such as triterpenoids. In addition, they can be measured in high accuracy compared with the TLC method.     

Effects of ramet clipping and nutrient availability on growth and biomass allocation of yellow nutsedge

A glasshouse experiment was conducted to examine how the interactions of nutrient availability and partial ramet clipping affect growth, reproduction and biomass allocation of Cyperus esculentus, an invasive sedge. The plants sprouting from tubers were grown at low and high nutrient levels, and were subject either to no clipping, one, two or three clippings, with each clipping cutting half of the existing ramets at soil level. Our results show that nutrient availability and clipping frequency tended to independently affect most of growth, reproduction and biomass allocation parameters of Cyperus esculentus examined in the present study. Increased supply of nutrients led to an increase in plant productivity and its associated traits. All of the traits, except for the number of ramets, displayed a decreasing pattern with increasing clipping frequency, indicating that Cyperus esculentus had undercompensatory responses to ramet clipping. It is likely that the patterns of plants response to clipping are species specific, and depend on morphological characters of species. Its susceptibility to ramet clipping can offer opportunities for controlling this invasive species through mechanical methods such as mowing. Clipping had little effects on biomass allocation; however, root weight fraction increased with increasing clipping frequency. While nutrient availability and clipping frequency had no influence on leaf carbon concentration at harvest, both of them increased leaf nitrogen concentration, and hence reduced leaf C/N ratio.