Tachykinin NK-1 receptor probed with constrained analogues of substance P

The action of rotameric probes introduced either in position 7 or 8 in the sequence of substance P (SP) was investigated, i.e. -tetrahydroisoquinoleic acid (Tic), -fluorenylglycine (Flg), -diphenylalanine (Dip), the diastereoisomers of -1-indanylglycine (Ing) and -benz[ƒ]indanylglycine (Bfi), the Z- and E-isomers of dehydrophenylalanine and dehydronaphthylalanine (Δ^ZPhe, Δ^EPhe, Δ^ZNal, Δ^ENal) and (Dmp). The aim of this study was the topographical characterization of the binding subsites of human NK-1 receptor expressed in CHO cells, especially the S₇ and S₈ subsites, corresponding to residues Phe⁷ and Phe⁸ of substance P. According to the binding potencies of these substituted-SP analogues, the S₇ binding subsite is smaller than the S₈ subsite: the S₇ subsite accepts only one aromatic nucleus, while the S₈ can accommodate three coplanar nuclei altogether. These findings are compatible with the idea that the S₈ binding subsite may reside in the extracellular loops of the hNK-1 receptor. NK-1 agonists bind to human NK-1 receptor and activate the production of both inositol phosphates and cyclic AMP. As already quoted for septide, [pGlu⁶, Pro⁹]SP(6–11), discrepancies are observed between affinity (K_i) and activity (EC₅₀) values for IPs production. While a weak correlation between K_i and EC₅₀ values for IPs production could be found (r = 0.70), an excellent correlation could be demonstrated between their affinities (K_i) and their potencies (EC₅₀) for cAMP production (r = 0.97). The high potency (EC₅₀) observed for ‘septide-like’ molecules on PI hydrolysis, compared to their affinity is not an artefact related to the high level of NK-1 receptors expressed on CHO cells since a good correlation was found between EC₅₀ values obtained for PI hydrolysis and those measured for spasmogenic activity in guinea pig ileum bioassay (r = 0.94).

According to the binding potencies of constrained analogues of phenylalanine, the S₇ binding subsite of human NK-1 receptor is small, whereas the S₈, which can accommodate three coplanar nuclei, might probably reside in the extracellular loop. The discrepancies observed between affinity (K_i) and activity (EC₅₀) values for IPs production are not an artefact of CHO cells since a good correlation was found between EC₅₀ for PI hydrolysis and those measured in guinea pig ileum bioassay.     

苦楝果实活性物质研究

本文报道苦楝果实中的生物活性物质。发现果实的抽提物和单体化合物不仅具有防治作物害虫的作用,而且,还对植物有生长调节作用。通过生物活性鉴定结果表明:果实种仁的水抽提物对水稻早期萌动、发芽与秧苗的生长均有促进作用。其中,处理稻种第2天(48h),其发芽率比对照高出24.67％～42.86％;第4天秧苗的根长在1cm以上占56.5％～65.0％,而对照组只有15.5％。尤其是抽提液浓度在6000ppm时处理的稻种,测得生长10d的秧苗总长为对照的120.27％,胚根长为对照的121.54％;以及叶片中的叶绿素总含量比对照高8.5％。还证明了从果实中提取分离的几种三萜类化合物和在果实中发现的一种新化合物对苯二甲酸二甲酯,均对菜青虫有拒食和胃毒活性。     

人类口腔小生境微生物的多样性

本文论述了人类口腔中微生物的物种多样性,口腔小生境的复杂性与微生物多样性的关系,以及口腔中微生物变化与人类疾病和健康的关系。     

Impact of grazing and atmospheric nitrogen deposition on the vegetation of dry coastal dune grasslands

Abstract. A five-year experimental study was carried out to examine the combined effects of grazing and atmospheric nitrogen deposition on the vegetation of three dry dune grasslands: one short species-rich, one short species-poor, and one predominated by tall graminoids. Additional fertilization with nitrogen had no significant effect, neither in grazed nor in non-grazed plots. Exclusion of grazing by rabbits resulted in an increase in the frequency of perennial graminoids and a decrease in the frequency of annual graminoids and herbs. Nevertheless, species diversity remained the same in the species-rich grassland. During the experiment, the above-ground biomass increased in all nongrazed plots and the amount of bare soil and mosses decreased. The vegetation changes occurred mainly within one year after the exclusion of grazing. An exception is the grass-dominated site where the amount of Calamagrostis epigejos increased gradually from ca. 20 % in the first two years to about 50 % in the fourth and fifth year. Grazing by rabbits seems essential to prevent graminoids to become predominant in the dry dunes. If graminoids are dominant, grazing by horses can be an appropriate method to restore the original grassland vegetation. After six months of grazing by horses the grass-dominated site showed a decrease of the frequency of perennial graminoids, from 95 % to 80 %, and an increase of the frequency of perennial herbs, from 2.5 % to between 13 and 20 %.     

High-elevation rock outcrop vegetation of the Southern Appalachian Mountains

Abstract. Species composition patterns and vegetation-environment relationships were quantified for high-elevation rock outcrops of the Southern Appalachian Mountains, an infrequent and insular habitat in a forested landscape. Outcrops occur over a wide geographic range encompassing extensive variation in both geology and climate. Geographic-scale factors interact with site-scale factors to produce variation in vegetation among outcrops. Similarly, site-scale factors interact with micro-scale factors to produce variation in vegetation within outcrops. To provide a quantitatively-based classification of outcrop vegetation we used a TWINSPAN analysis of 154 100-m² plots. We recognized nine communities that primarily correspond to different combinations of elevation, bedrock type, geography, and moisture. Within outcrops of a single bedrock type, vegetation composition of 100-m² plots was consistently correlated with elevation and solar radiation, but relationships to soil nutrients varied with bedrock type. Both site-scale (100 m²) factors (e.g. elevation, slope, aspect, and bedrock type) and plot-scale (1-m²) microsite factors (e.g. soil depth, vegetation height, soil nutrients) were strongly correlated with species composition at the 1-m² level. Environment can be used to predict composition more effectively for 100-m² plots on a single bedrock type than either across bedrock types or at a 1-m² scale. Composition-environment relationships resemble those described for outcrop systems from other regions with pronounced topographic relief more than they do those described for the nearby but flatter and lower-elevation outcrops of the Southeastern Piedmont. There is strong spatial autocorrelation in this community, perhaps owing to dispersal limitation. Consequently, a comprehensive conservation strategy must include reservation of both a range of geologic types and a range of geographic locations.     

Analysis of the genetic effects for several traits in oil palm (Elaeis guineensis Jacq.) populations. I. Population means

An oil palm experiment was set up in the Ivory Coast to compare the effects of crossing and selfing within two origins, Deli and La Mé, on the mean and the variability of Deli x Mé between-origin hybrids. The originality of the experiment lay in the crossing plan, which provided access to genetic parameters related to additivity, dominance and different components of epistasis. This first part covers the analysis of the components of the mean. The parents used were obtained from four palms, two from each origin. Those of La Mé origin were half-sibs. The common parent came from a wild stand in the Ivory Coast. Those of Deli origin were from two different populations bred in Southeast Asia for several generations from a narrow genetic base. These four parents gave rise to nine Deli x La Mé hybrid populations with double-cousintype links. The additive component is more important within the Deli origin than within the La Mé origin. This may be explained by the large genetic divergence between the two Deli parent palms. On the other hand, the additive^* additive epistasis is more substantial within the La Mé origin, probably because of inbreeding. The discussion concentrates on how this information should be used when choosing parents to be crossed and tested and to produce improved populations. The crossing plan proposed can be of general use and is suitable for other species in a reciprocal recurrent selection programme.     

Synonymous substitution rates in Drosophila: Mitochondrial versus nuclear genes

Synonymous substitution rates in mitochondrial and nuclear genes of Drosophila were compared. To make accurate comparisons, we considered the following: (1) relative synonymous rates, which do not require divergence time estimates, should be used; (2) methods estimating divergence should take into account base composition; (3) only very closely related species should be used to avoid effects of saturation; (4) the heterogeneity of rates should be examined. We modified the methods estimating synonymous substitution numbers to account for base composition bias. By using these methods, we found that mitochondrial genes have 1.7–3.4 times higher synonymous substitution rates than the fastest nuclear genes or 4.5–9.0 times higher rates than the average nuclear genes. The average rate of synonymous transversions was 2.7 (estimated from the melanogaster species subgroup) or 2.9 (estimated from the obscura group) times higher in mitochondrial genes than in nuclear genes. Synonymous transversions in mitochondrial genes occurred at an approximately equivalent rate to those in the fastest nuclear genes. This last result is not consistent with the hypothesis that the difference in turnover rates between mitochondrial and nuclear genomes is the major factor determining higher synonymous substitution rates in mtDNA. We conclude that the difference in synonymous substitution rates is due to a combination of two factors: a higher transitional mutation rate in mtDNA and constraints on nuclear genes due to selection for codon usage. Received: 27 November 1996 / Accepted: 8 May 1997     

On the RNA World: Evidence in Favor of an Early Ribonucleopeptide World

A highly complex RNA world, as is sometimes presented in view of the widespread and diversified use of RNA enzymes, would have encountered many difficulties in passing to a world with catalysis mediated by proteins. These difficulties can be overcome by postulating a very early relationship between the nucleotide and the amino acid components. In particular, after asserting that some characteristics expressed by (nucleotide) coenzymes in catalysis are easier to understand if a close and early relationship between these coenzymes and amino acids is hypothesized, a model is presented for the origin of the enzyme–coenzyme complex. This model is essentially based on an intermediate formed by a tRNA-like molecule covalently linked to a polypeptide. The model attributes the majority of the catalytic role in the ribonucleoprotein world to the latter complex and thus it takes into account the birth of the key intermediate in the origin of protein synthesis—namely, peptidyl-tRNA, which would have otherwise been extremely difficult to select. The predictions of the model are discussed along with its robustness, using the data derived from the study of intermediary metabolism and those from molecular biology. Finally, the appearance of the genetic code in the late phase of the ribonucleopeptide world is discussed. Received: 13 January 1997 / Accepted: 25 July 1997     

广西九万山藓类植物区系分析及其对划分热带,亚热带分界线的意义

九万山位于广西北部的中央(25°10’～25°25’N,108°27’E),界于泛北极植物区和古热带植物区的交汇处。其主要植被为亚热带常绿阔叶林。最高海拔为1693m,最低处仅170m。经对1850号标本的鉴定,共计有藓类植物35科、101属和189种。本文分析了九万山的藓类植物区系成分,将其划分为 10种类型。其中东亚成分最为丰富(39.33％),热带、亚热带成分次之(38.20％),而温带成分居第三位(18.54％)。本文选择了九万山临近的五个地区加以比较。其中,金佛山与九万山藓类植物的属和种的相似性系数分别为60.68％和36.87％,神农架为57.29％和33.13％。尖峰岭为48.83％和22.29％,西双版纳为57.29％和29.63％。而我国东部的武夷山则为69.86％和39.57％,其相似性系数在相比较的五个山区中为最高。九万山区有4个特有属并明显受喜马拉雅的影响。特别值得注意的是,在九万山区藓类区系中约有7％的种类是典型的热带成分。根据定量和定性的分析,笔者认为九万山的藓类区系表现出由热带向亚热带过渡的特性,其分界线可能位于九万山的南侧。     

Demonstration of retinal afferents in the RCS rat,with reference to the retinohypothalamic projection and suprachiasmatic nucleus

In the Royal College of Surgeons (RCS) rat, characterized by inherited retinal dystrophy, retinal projections to the brain were studied using anterograde neuronal transport of cholera toxin B subunit upon injection into one eye. The respective immunoreactivity was found predominantly contralateral to the injection site in the lateral geniculate nucleus, superior colliculus, nucleus of the optic tract, medial terminal nucleus of the accessory optic tract, and bilateral hypothalamic suprachiasmatic nuclei. Although terminal density was somewhat reduced in dystrophic rats, the projection patterns in these animals appeared similar to those seen in their congenic controls and were comparable to the visual pathways described for the rat previously. In dystrophic rats, the number of cell bodies exhibiting immunoreactivity to vasoactive intestinal polypeptide, viz. a population of suprachiasmatic neurons receiving major retinohypothalamic input, was reduced by one-third, and some differences were observed in the termination pattern of the geniculohypothalamic tract, as revealed by immunoreactivity to neuropeptide Y in the suprachiasmatic nucleus.This study was supported by grants from the DFG (Re 644/2-1) and the NMFZ, Mainz (to S.R.).