Segregate families from the Euphorbiaceae

Segregate families from the Euphorbiaceae. Several families have been segregated from the Euphorbiaceae. Some of these are of long-standing, and are now generally accepted. Others are more recent, and somewhat controversial. Five such have recently been recognized at Kew, and are discussed here, as are two others which have not been so recognized.     

Butterflyfish social behaviour,with special reference to the incidence of territoriality: a review

Synopsis Butterflyfishes (Chaetodontidae) are among the best studied of coral reef fishes. Feeding ecology and some aspects of behaviour have been firmly established. However, spacing behaviour remains controversial. Two major studies made in the 1970s concluded that the majority of species were not territorial. We suggest that these and other studies which have concluded that territories are not held have generally suffered from short observation periods, and have not mapped the ranges occupied by individuals. Further, low frequencies of agonistic behaviour have been interpreted as evidence of non-territoriality. By contrast, studies which have proven territoriality have had long observation periods and have mapped ranges. These have shown that territories are usually maintained with very little overt aggression. Spacing behaviour and feeding behaviour are clearly linked, with territoriality common among benthic-feeding species, especially obligate corallivores. Species with broad dietary flexibility tend to have flexible social systems, while plankton feeders are usually gregarious. The widespread occurrence of monogamy in butterflyfishes appears linked to territoriality, the majority of territorial species identified to date occurring predominantly as pairs. Data currently available suggest that this is because pair defence of the territory is more efficient than by individuals. However, several alternative hypotheses for the evolution of monogamy based on spawning constraints and predation risk cannot yet be ruled out.     

针对留学生的教学特点提高全英文教学质量

针对留学生英语基础好,思维活跃,爱记笔记但有少数学生学习积极性不高、旷课和迟到等特点,在教学过程中通过选拔英语基础好、教学能力强、教学经验丰富的教师,采用灵活多样的教学方法和加强学生教学过程的管理等途径有效的提高全英文教学质量。     

Genome evolution of allopolyploids: a process of cytological and genetic diploidization

Allopolyploidy is a prominent mode of speciation in higher plants. Due to the coexistence of closely related genomes, a successful allopolyploid must have the ability to invoke and maintain diploid-like behavior, both cytologically and genetically. Recent studies on natural and synthetic allopolyploids have raised many discrepancies. Most species have displayed non-Mendelian behavior in the allopolyploids, but others have not. Some species have demonstrated rapid genome changes following allopolyploid formation, while others have conserved progenitor genomes. Some have displayed directed, non-random genome changes, whereas others have shown random changes. Some of the genomic changes have appeared in the F1 hybrids, which have been attributed to the union of gametes from different progenitors, while other changes have occurred during or after genome doubling. Although these observations provide significant novel insights into the evolution of allopolyploids, the overall mechanisms of the event are still elusive. It appears that both genetic and epigenetic operations are involved in the diploidization process of allopolyploids. Overall, genetic and epigenetic variations are often associated with the activities of repetitive sequences and transposon elements. Specifically, genomic sequence elimination and chromosome rearrangement are probably the major forces guiding cytological diploidization. Gene non-functionalization, sub-functionalization, neo-functionalization, as well as other kinds of epigenetic modifications, are likely the leading factors promoting genetic diploidization.     

Functional restraints on the patterns of amino acid substitutions: application to sequence-structure homology recognition

Amino acid residues that are involved in functional interactions in proteins have strong evolutionary pressure to remain unchanged and consequently their substitution patterns are different from those that are noninteracting. To characterize and quantify the differences between amino acid substitution patterns due to structural restraints and those under functional restraints, we have made a comparative analysis of families of homologous proteins. Residues classified as having the same amino acid type, secondary structure, accessibility, and side-chain hydrogen bonds are shown to be better conserved if they are close to the active site. We have focused on enzyme families for this analysis since they have functional sites that are easily defined by their catalytic residues. We have derived new sets of environment-specific substitution tables, which we term function-dependent environment-specific substitution tables, where amino acid residues are classified according to their distance from the functional sites. The residues that are within a distance of 9 A from the active site have distinct amino acid substitution patterns when compared to the other sites. The function-dependent environment-specific substitution tables have been tested using the sequence-structure homology recognition program FUGUE and the results compared with the recognition performance obtained using the standard environment-specific substitution tables. Significant improvements are obtained in both recognition performance and alignment accuracy using the function-dependent environment-specific substitution tables (P-value = 0.02, according to the Wilcoxon signed rank test for alignment accuracy). The alignments near the active site are greatly improved with pronounced improvements at lower percentage identities (less than 30%).     

Comparing G matrices: are common principal components informative?

Common principal components (CPC) analysis is a technique for assessing whether variance-covariance matrices from different populations have similar structure. One potential application is to compare additive genetic variance-covariance matrices, G. In this article, the conditions under which G matrices are expected to have common PCs are derived for a two-locus, two-allele model and the model of constrained pleiotropy. The theory demonstrates that whether G matrices are expected to have common PCs is largely determined by whether pleiotropic effects have a modular organization. If two (or more) populations have modules and these modules have the same direction, the G matrices have a common PC, regardless of allele frequencies. In the absence of modules, common PCs exist only for very restricted combinations of allele frequencies. Together, these two results imply that, when populations are evolving, common PCs are expected only when the populations have modules in common. These results have two implications: (1) In general, G matrices will not have common PCs, and (2) when they do, these PCs indicate common modular organization. The interpretation of common PCs identified for estimates of G matrices is discussed in light of these results.     

Some Bacteriophages Active Against Rhizobium trifolii Strain W19

Fourteen soil bacteriophages active against Rhizobium trifolii W19 have been studied which fall into four structural groups. Group 1 phages have contractile tails. Some particles show double base plates to which at least three spikes are attached, and fibers are attached to the base plates. Group 2 phages also have contractile tails. At least five spikes are attached to the base plate, and there are spherical bodies adjacent to the tail, at the ends of fibers attached to the tail base. Group 3 phages have contractile tails, but are larger than phages of groups 1 and 2. The end of the tail has a complex structure. Group 4 phages have long, noncontractile tails.     

新疆四种补血草属植物叶片的解剖学研究

利用叶片离析法和石蜡切片法研究了补血草属4种植物叶片的形态结构。结果表明:(1)4种植物的叶片有许多共同的结构适应特征,表皮细胞排列紧密,表面有厚的角质层;气孔类型均为不等型,气孔位置为平置或略微下陷;上下表皮还具有多细胞构成的盐腺;栅栏组织发达,多为等面叶;存在粘液细胞和单宁细胞;机械组织和维管组织都不发达等。(2)不同种间有不同的结构适应特征,如表皮细胞的形状、大小、垂周壁饰样,气孔密度,盐腺密度,叶片厚度和栅栏组织厚度等。通过叶的结构特征反映出盐生植物与旱生植物的不同。     

Flagella in prokaryotes and lower eukaryotes.

During the past year, significant advances have been made in the understanding of both prokaryotic and eukaryotic flagella. About 50 genes are dedicated to the assembly and operation of bacterial flagella. Recent discoveries have advanced our understanding of how these genes are regulated and how their products assemble into a functional, rotating organelle. The dynein arms of eukaryotic flagella are now also better understood. Several genes that are found in the mechanochemical macroassemblies have been cloned, and other loci have been identified, suggesting that there is even greater complexity than first expected.     

Defining selection criteria to improve yield under drought

The many selection criteria that have been proposed to increase drought resistance of our crops have had little, if any, impact on improving crop yields in dry environments. There are several likely reasons for this lack of success. Some of these are: (i) criteria proposed have been related more to survival mechanisms under drought than to productivity, (ii) criteria are inappropriate to the target environment, and (iii) criteria are temporal and are therefore likely to have minimal impact on growth and yield over the entire lifecycle. Another important reason is that breeders have not been convinced the proposed criteria will be successful as they are too difficult to measure. On the other hand, empirical breeding programmes to improve yield under drought have been successful. Surprisingly, some of the greatest successes have been achieved by breeding in environments where water is non-limiting. This paper reviews breeding approaches to improve yield under drought. It focuses on critical factors that must be considered to identify likely plant attributes that can be targeted. These factors, their link with yield, the nature of the target environment, the level of organisation where the trait is expressed are discussed. Three quite different examples are given to emphasize the above considerations and which show substantial promise in targeting traits to improve yield under drought. They are drought at flowering, improving transpiration efficiency and improving early leaf area development.     

空间分析方法在微生物生态学研究中的应用

微生物生态正在受到越来越多的关注,对其研究也渐趋深入。然而由于微生物个体微小的特点及研究手段的限制,多数研究还停留在探索阶段,研究方法也在不断完善当中。近年来,较多的研究开始探讨空间因素在微生物多样性和分布中的影响,对空间分布的探讨有助于更好地认识生态过程,是一种有力的研究手段。微生物空间分析方法已经成为微生物生态学领域中重要的研究方向之一,我国空间方法在微生物生态研究中的应用还没有得到普遍的重视。从不同研究角度出发,结合空间统计的作用,对空间统计方法在微生物生态研究中的应用的必要性及现状做了评述。介绍了空间自相关性的检验,方差图,Mantel检验,Kriging插值等方法在微生物生态研究中的应用,并论述了微生物研究中的尺度问题。这一梳理,对丰富微生物生态学研究中的新方法、新手段具有一定价值。     

Agents that target telomerase and telomeres

Telomeres are guanine-rich regions that are located at the ends of chromosomes and are essential for preventing aberrant recombination and protecting against exonucleolytic DNA degradation. Telomeres are maintained by telomerase, an RNA-dependent DNA polymerase. Because telomerase is known to be expressed in tumor cells, which concurrently have short telomeres, and not in most somatic cells, which usually have long telomeres, telomerase and telomere structures have been recently proposed as attractive targets for the discovery of new anticancer agents. The most exciting current strategies are aimed at specifically designing new drugs that target telomerase or telomeres and new models have been formulated to study the biological effects of inhibitors of telomerase and telomeres both in vitro and in vivo.     

Peptides and neurotransmission in the central nervous system

Radioimmunoassays of brain extracts have shown that several peptides occur in high concentrations in the CNS. The releasing-factor peptides TRF, LRF, somatostatin, CRF and GRF have the highest concentration in the hypothalamic extracts. High levels of somatostatin, CCK octapeptide, neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) are found in cortical extracts. Substance P, CCK, NPY, and enkephalins are present in high concentrations in basal ganglia and mesolimbic areas. Pharmacological doses of these peptides result in several behavioural and vegetative effects. Immunocytochemical studies show that the CNS peptides are localised in neurones and in synaptic vesicles. In vitro studies with brain tissues show that peptides are capable of modifying the ongoing classical neurotransmission. In depressive patients several neuropeptides (CCK, CRF and NPY) have been shown to have low CSF levels. Patients dying of senile dementia have low cortical levels of somatostatin, CRF and substance P. In schizophrenic patients CCK peptides have shown to improve some symptoms. At present the therapeutic potentials of peptides are poorly known. More studies are required to understand their role in neurotransmission and related pathological states.     

黄杨花蜜腺的形态解剖学研究

黄杨花单性,雌雄同株,雄花花蜜腺４枚,乳头状,着生于退化雌蕊子房顶部;雌花花蜜腺３枚,短柱状,位于３枚花柱之间。雌、雄花蜜腺均由分泌表皮、产蜜组织和维管束构成,在发育过程中产蜜组织细胞的液泡都发生有规律的变化。雌花蜜腺大,属非淀粉型蜜腺,泌蜜量大,蜜汁含糖分多,维管束中仅含韧皮部;雄花蜜腺小,属淀粉型蜜腺,泌蜜量小．蜜汁含糖量小,维管束由木质部和韧皮部构成。     

Comparative anatomy and systematics of the orchid tribe Vanilleae excluding Vanilla

Vanilleae have been divided into three subtribes consisting of ten genera. We had material for study of all except Dictyophyllaria in subtribe Vanillinae. All genera except Vanilla have few species; Clematepistephium and Dictyophyllaria are monospecific. Leafy types have adaxial and abaxial stomata except Clematepistephium, Epistephium , and Eriaxis which have only abaxial tetracytic and anomocytic stomatal apparatuses. Cyrtosia, Erythwrchis, Galeola , and Lecanorchis are leafless. Hypodermis occurs in leaves of Pseudovanilla, Clematepistephium , and Eriaxis; leaves of Epistephium lack a hypodermis. Mesophyll is homogeneous. Stems of Cyrtosia, Galeola , and Eriaxis and rhizomes of Cyrtosia have a hypodermis. A uniseriate velamen occurs in roots of Erythrorchis, Pseudovanilla, Clematepistephium , and Lecanorchis; roots of other genera are bounded by a simple epidermis. Exodermal cell walls are n-thickened; endodermal cell walls are O-thickened. Vascular tissue of roots is variously embedded in sclerenchyma or parenchyma; similarly, pith may be sclerenchymatous or parenchymatous. Cladistic analyses result in two equally parsimonious trees with Epistephium and Eriaxis reversed in placement in each tree. Both trees constitute a paraphyletic complex giving rise to a clade containing the monophyletic Lecanorchidinae and Galeolinae. Vegetative anatomical characters have some phylogenetic value in Vanilleae, but they are not useful in resolving placement of the large and polymorphic genus Vanilla.     

DIVERSITY AND NICHE EVOLUTION ALONG ARIDITY GRADIENTS IN NORTH AMERICAN LIZARDS (PHRYNOSOMATIDAE)

Deserts occupy approximately 12% of the Earth's land surface, and are thought to have species poor but highly specialized biotas. However, few studies have examined the evolutionary origins of desert biotas and of diversity patterns along aridity gradients. Further, it is unclear if species occurring in more extreme conditions on a given niche axis (i.e., precipitation) are more specialized for those conditions (i.e., have narrower niche breadths). We address these questions here using a time‐calibrated phylogeny and climatic data for 117 species of phrynosomatid lizards. Phrynosomatids are the most species‐rich family of lizards in North America, and are found from deserts to rainforests. Surprisingly, we find that phrynosomatids have higher richness in more arid environments. This pattern occurs seemingly because they have been present in more arid habitats longer (～55 million years), and lineages in mesic environments are recently derived from more arid‐dwelling ancestors. We find little support for the hypothesis that species in more extreme environments are more specialized. Instead, many desert‐dwelling species are broadly distributed, and species in the most mesic environments have the broadest niche breadths. In summary, phrynosomatids offer a counterexample to the idea that arid regions are inhabited by a small number of recent and highly specialized lineages.     

滞育和非滞育棉铃虫前胸腺的形态解剖学比较研究

该文用解剖镜和电子显微镜对滞育和非滞育棉铃虫Helicoverpa armigera前胸腺的形态解剖结构进行了比较研究。结果发现滞育棉铃虫的前胸腺细胞及其细胞间隙相对较小,不易着色,细胞核规则,较小,细胞质中几乎见不到光滑内质网和粗面内质网,线粒体极少,这些观察到的现象充分说明滞育棉铃虫的前胸腺活性较低。     

Ablation of renin-expressing juxtaglomerular cells results in a distinct kidney phenotype

Renin-expressing cells are peculiar in that they act as differentiated cells, producing the hormone renin, while they also seem to act as progenitors for other renal cell types. As such, they may have functions independent of their ability to generate renin/angiotensin. To test this hypothesis, we ablated renin-expressing cells during development by placing diphtheria toxin A chain (DTA) under control of the Ren1d mouse renin promoter by homologous recombination in a two-renin gene strain (Ren2 and Ren1d). Renin-expressing cells are essentially absent from kidneys in homozygotes (DTA/DTA) which, unlike wild-type mice, are unable to recruit renin-expressing cells when homeostasis is threatened. In contrast, renin staining in the submandibular gland (SMG), which expresses mainly Ren2, is normal. Homozygous mice survive normally, but the kidneys are small and have morphological abnormalities: 25% of the glomeruli are hyperplastic or atrophic, tubules are dilated and atrophic, and areas of undifferentiated cells exist near the atrophic glomeruli and tubules. However, in contrast to the very abnormal renal vessels found when renin-angiotensin system genes are deleted, the kidney vessels in homozygotes have normal wall thickness and no decrease in lumen size. Homozygotes have severely reduced kidney and plasma renin concentrations and females have reduced blood pressure. Homozygotes have elevated blood urea nitrogen and potassium levels, which are suggestive of altered renal function. We conclude that renin cells per se are necessary for the morphological integrity of the kidney and may have a role in maintenance of normal kidney function.