斜脉蝠蛾幼虫分类特征研究

本文研究报道了冬虫夏草主要寄主之一斜脉蝠蛾Hipialus oblifurcus Chu et Wang幼虫头、胸、腹各部分的形态特征、颜色、毛序及各龄幼虫的头宽和体长,可作为鉴别种类的依据。     

The tRNA discriminator base defines the mutual orthogonality of two distinct pyrrolysyl-tRNA synthetase/tRNAPyl pairs in the same organism

Site-specific incorporation of distinct non-canonical amino acids into proteins via genetic code expansion requires mutually orthogonal aminoacyl-tRNA synthetase/tRNA pairs. Pyrrolysyl-tRNA synthetase (PylRS)/tRNA^Pyl pairs are ideal for genetic code expansion and have been extensively engineered for developing mutually orthogonal pairs. Here, we identify two novel wild-type PylRS/tRNA^Pyl pairs simultaneously present in the deep-rooted extremely halophilic euryarchaeal methanogen Candidatus Methanohalarchaeum thermophilum HMET1, and show that both pairs are functional in the model halophilic archaeon Haloferax volcanii. These pairs consist of two different PylRS enzymes and two distinct tRNAs with dissimilar discriminator bases. Surprisingly, these two PylRS/tRNA^Pyl pairs display mutual orthogonality enabled by two unique features, the A73 discriminator base of tRNA^Pyl2 and a shorter motif 2 loop in PylRS2. In vivo translation experiments show that tRNA^Pyl2 charging by PylRS2 is defined by the enzyme''s shortened motif 2 loop. Finally, we demonstrate that the two HMET1 PylRS/tRNA^Pyl pairs can simultaneously decode UAG and UAA codons for incorporation of two distinct noncanonical amino acids into protein. This example of a single base change in a tRNA leading to additional coding capacity suggests that the growth of the genetic code is not yet limited by the number of identity elements fitting into the tRNA structure.     

Microstructure of the silk apparatus in the coelotine spider Paracoelotes spinivulva (Araneae: Amaurobiidae)

The microstructural characteristics of the silk‐spinning apparatus and its ecological significance in the coelotine spider Paracoelotes spinivulva were examined by field emission scanning electron microscopy, with the goal of understanding the properties and the evolutionary origins of these silk constructs. The silk apparatuses of this spider were composed of four basic types of silk‐spinning spigot (ampullate, pyriform, aciniform and tubuliform), which connected with typical silk glands in the abdominal cavity. Of the three pairs of spinnerets, the posterior pairs were highly elongated along the body axis. Anterior spinnerets comprised two pairs of ampullate glands and approximately 70–80 pairs of pyriform glands in both sexes. Middle spinnerets had one to two pairs of ampullate spigots, three pairs of tubuliform spigots in females, and 50–60 (female) or 80–90 (male) pairs of aciniform spigots. An additional two pairs of tubuliform spigots in females and 70–80 (female) or 100–120 (male) pairs of aciniform spigots were counted on the spinning surfaces of the posterior spinnerets in both sexes. Although the coelotine spiders use their silk to catch prey, P. spinivulva characteristically do not have a typical “triad” spigot, including a flagelliform and two aggregate spigots, for capture thread production.     

Pattern discrimination by the honeybee (Apis mellifera): training on two pairs of patterns alternately

Pattern discrimination in the honeybee was studied by training alternately with two different pairs of patterns. Individually marked bees made a forced choice from a fixed distance in a standard Y-choice maze for a reward of sugar solution. Bees were trained, first on one pair of patterns for 10min then on a second pair, and so on, alternately between the two pairs. The pairs of patterns were selected to test the hypothesis that bees have a limited number of parallel mechanisms for the detection and discrimination of certain generalized global features. If this is so, it might be expected that each channel could process one pair of patterns simultaneously, but two pairs of patterns that are processed by the same channel would interfere with each other during the learning process. Features tested were: average orientation of edges, radial and tangential edges based on a symmetry of three or six, the position of a black spot, and the exchange of black and white. The bees fail to learn when the two alternated pairs of patterns offer the same feature, and they discriminate when the pairs offer two different features.     

Chromosomes of the liver fluke, Clonorchis sinensis

A karyological study was carried out in order to compared the chromosome numbers, chromosome morphologies and karyotypes of the oriental liver fluke, Clonorchis sinensis (Trematoda: Opisthorchiidae), collected from Korea and China. Chromosome preparations were made by means of air-drying method. The chromosome number was 2n = 56 in both Korean and Chinese flukes, and chromosomes were divided into two groups based on this size; consisting of 8 pairs of large and 20 pairs of small chromosomes. However, the karyotypes showed some differences between Korean and Chinese flukes. The karyotype of liver flukes from Korea consisted of three metacentric pairs, one meta-/submetacentric pair, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes. On the other hand, liver flukes from China consisted of two metacentric pairs, two meta-/submetacentric pairs, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes.     

HLA and genomewide allele sharing in dizygotic twins

Gametic selection during fertilization or the effects of specific genotypes on the viability of embryos may cause a skewed transmission of chromosomes to surviving offspring. A recent analysis of transmission distortion in humans reported significant excess sharing among full siblings. Dizygotic (DZ) twin pairs are a special case of the simultaneous survival of two genotypes, and there have been reports of DZ pairs with excess allele sharing around the HLA locus, a candidate locus for embryo survival. We performed an allele-sharing study of 1,592 DZ twin pairs from two independent Australian cohorts, of which 1,561 pairs were informative for linkage on chromosome 6. We also analyzed allele sharing in 336 DZ twin pairs from The Netherlands. We found no evidence of excess allele sharing, either at the HLA locus or in the rest of the genome. In contrast, we found evidence of a small but significant (P=.003 for the Australian sample) genomewide deficit in the proportion of two alleles shared identical by descent among DZ twin pairs. We reconciled conflicting evidence in the literature for excess genomewide allele sharing by performing a simulation study that shows how undetected genotyping errors can lead to an apparent deficit or excess of allele sharing among sibling pairs, dependent on whether parental genotypes are known. Our results imply that gene-mapping studies based on affected sibling pairs that include DZ pairs will not suffer from false-positive results due to loci involved in embryo survival.     

Aromatic side-chain interactions in proteins. I. Main structural features

In a data set of 593 nonhomologous proteins from the PDB, we have analyzed the pairing of phenylalanine, tyrosine, tryptophan, and histidine residues with their closest aromatic partner. The frequency distribution of the shortest interatomic distance of partners is bimodal with a sharp peak at approximately 3.8 A and a wider one at a longer distance. Only the 3.8 A peak corresponds to direct ring-ring interactions thus aromatic pairs. The aromatic pairs were separated into two classes, near-sequence pairs and far-sequence pairs. Near sequence pairs stabilize local structure, and far-sequence pairs stabilize tertiary structure. Far-sequence pairs (74% of all pairs) mainly bridge two beta-strands, followed by pairs that bridge a beta-strand and a helix, and pairs that bridge a beta-strand and a random coil structure. Pairs that bridge helices are rare. The secondary structure of the near-sequence pairs depends on the partner distance in the sequence. When the partners are 1, 3, or 4 residues apart in the sequence, pairs are mostly found in helical structures. When the partners are two apart, pairs are mostly found in the same beta-strand. Analysis of the frequency of near sequence pairs supports the hypothesis that aromatic pairing occurs after, rather than before, the formation of secondary structures.     

The use of double fluorescence in situ hybridization to physically map the positions of 5S rDNA genes in relation to the chromosomal location of 18S-5.8S-26S rDNA and a C genome specific DNA sequence in the genus Avena.

A physical map of the locations of the 5S rDNA genes and their relative positions with respect to 18S-5.8S-26S rDNA genes and a C genome specific repetitive DNA sequence was produced for the chromosomes of diploid, tetraploid, and hexaploid oat species using in situ hybridization. The A genome diploid species showed two pairs of rDNA loci and two pairs of 5S loci located on both arms of one pair of satellited chromosomes. The C genome diploid species showed two major pairs and one minor pair of rDNA loci. One pair of subtelocentric chromosomes carried rDNA and 5S loci physically separated on the long arm. The tetraploid species (AACC genomes) arising from these diploid ancestors showed two pairs of rDNA loci and three pairs of 5S loci. Two pairs of rDNA loci and 2 pairs of 5S loci were arranged as in the A genome diploid species. The third pair of 5S loci was located on one pair of A-C translocated chromosomes using simultaneous in situ hybridization with 5S rDNA genes and a C genome specific repetitive DNA sequence. The hexaploid species (AACCDD genomes) showed three pairs of rDNA loci and six pairs of 5S loci. One pair of 5S loci was located on each of two pairs of C-A/D translocated chromosomes. Comparative studies of the physical arrangement of rDNA and 5S loci in polyploid oats and the putative A and C genome progenitor species suggests that A genome diploid species could be the donor of both A and D genomes of polyploid oats. Key words : oats, 5S rDNA genes, 18S-5.8S-26S rDNA genes, C genome specific repetitive DNA sequence, in situ hybridization, genome evolution.     

A Note on Interval Estimation of the Simple Difference in Data with Correlated Matched Pairs

When we employ cluster sampling to collect data with matched pairs, the assumption of independence between all matched pairs is not likely true. This paper notes that applying interval estimators, that do not account for the intraclass correlation between matched pairs, to estimate the simple difference between two proportions of response can be quite misleading, especially when both the number of matched pairs per cluster and the intraclass correlation between matched pairs within clusters are large. This paper develops two asymptotic interval estimators of the simple difference, that accommodate the data of cluster sampling with correlated matched pairs. This paper further applies Monte Carlo simulation to compare the finite sample performance of these estimators and demonstrates that the interval estimator, derived from a quadratic equation proposed here, can actually perform quite well in a variety of situations.     

Karyotype study of Rana camerani and comparisons with the other 26-chromosome European brown frog species (Amphibia, Anura).

The results of a detailed morphological and morphometrical chromosome analysis of Rana camerani (2n = 26) are described. It was established that the karyotype of this species consisted of three homologous pairs of large metacentrics, two homologous pairs of large submetacentrics, three homologous pairs of small metacentrics, two homologous pairs of small submetacentrics, and three homologous pairs of small subtelocentrics. Morphologically discernible sex chromosomes were not found. The similarity and peculiarities in the R. camerani karyotype and those of R. temporaria, R. dalmatina and R. graeca are discussed. This comparative karyotype analysis has suggested the possibility for developing a general chromosomal formula, by means of which these 26-chromosome species could be characterized.     

Stoichiometry of lac repressor binding to nonspecific DNA: three different complexes form

The stoichiometry of lac repressor binding to nonspecific DNA was investigated by three different techniques. Four molecules of the fluorescent probe 5,5'-bis(8-anilino-1-naphthalenesulfonate) [bis(ANS)] bind to each repressor subunit with an average dissociation constant of 20 microM. Nonspecific DNA displaces most of this bound bis(ANS), reducing the fluorescence. Titrations of repressor with nonspecific DNA monitored with high [bis(ANS)] (5-15 microM) had end points at 8 base pairs per repressor. Lower [bis(ANS)] (0.1-1 microM) resulted in end points at either 15 or 26 base pairs per repressor, depending on the ionic strength. These end points correspond to complexes containing approximately one, two, or four repressors per 28 base pairs. Boundary sedimentation velocity experiments with saturating amounts of repressor revealed that five repressors can bind to 28 base pairs. By monitoring the circular dichroism as DNA was added to repressor, the sequential appearance of complexes containing approximately four, two, and one repressors per 28 base pairs was observed. The inability of repressor cores or iodinated repressor to bind to complexes containing one or two repressors per 28 base pairs implies that all of the repressors directly contact the DNA in the complex containing four repressors per 28 base pairs. It is proposed that while two subunits of each repressor contact the DNA in complexes containing one or two repressors per 28 base pairs, only one subunit of each repressor contacts the DNA in the complex with four repressors per 28 base pairs. These results suggest a novel mechanism for the one-dimensional diffusion of repressor along DNA.     

Microstructure of the silk apparatus of the comb-footed spider, Achaearanea tepidariorum (Araneae: Theridiidae)

The microstructural organization of the silk‐spinning apparatus of the comb‐footed spider, Achaearanea tepidariorum, was observed by using a field emission scanning electron microscope. The silk glands of the spider were classified into six groups: ampullate, tubuliform, flagelliform, aggregate, aciniform and pyriform glands. Among these, three types of silk glands, the ampullate, pyriform and aciniform glands, occur only in female spiders. One (adult) or two (subadult) pairs of major ampullate glands send secretory ductules to the anterior spinnerets, and another pair of minor ampullate glands supply the median spinnerets. Three pairs of tubuliform glands in female spiders send secretory ductules to the median (one pair) and posterior (two pairs) spinnerets. Furthermore, one pair of flagelliform glands and two pairs of aggregate glands together supply the posterior spinnerets, and form a characteristic spinning structure known as a “triad” spigot. In male spiders, this combined apparatus of the flagelliform and the aggregate spigots for capture thread production is not apparent, instead only a non‐functional remnant of this triad spigot is present. In addition, the aciniform glands send ductules to the median (two pairs) and the posterior spinnerets (12–16 pairs), and the pyriform glands feed silk into the anterior spinnerets (90–100 pairs in females and 45–50 pairs in males).     

Cognitive association formation in human memory revealed by spatiotemporal brain imaging

Cognitive theory posits association by juxtaposition or by fusion. We employed the measurement of event-related brain potentials (ERPs) to a concept fusion task in order to explore memory encoding of these two types of associations between word pairs, followed by a memory test for original pair order. Encoding processes were isolated by subtracting fusion task ERPs corresponding to pairs later retrieved quickly from ERPs corresponding to pairs later retrieved slowly, separately for pairs fused successfully and unsuccessfully (i.e., juxtaposed). Analyses revealed that the encoding of these two types of associations yields different ERP voltage polarities, scalp topographies, and brain sources extending over the entire time course of processing.     

The karyotype of Eubothrium rugosum (Cestoda: Pseudophyllidea)

The diploid chromosome set of Eubothrium rugosum contains 16 elements. The karyotype consists of three pairs of metacentric, three pairs of acrocentric and two pairs of submeta-metacentric chromosomes. Their mean absolute length ranges from 2.20 to 8.80 microns. The first two pairs of large metacentric chromosomes comprise over 45% of the total complement length.     

Fine-scale analysis of synchronous breathing in wild Indo-Pacific bottlenose dolphins (Tursiops aduncus)

We quantitatively analysed synchronous breathing for dyads in Indo-Pacific bottlenose dolphins at Mikura Island, Tokyo, Japan. For most cases, we observed dyads swimming in the same direction (97%), in close proximity (i.e., less than 1.5 m) and with their body axes parallel as they breathed synchronously. Moreover, the pairs engaged in identical behaviour before and after the synchronous breathing episodes. These results suggest that the dolphins synchronize their movements, and that synchronous breathing is a component of “pair-swimming”, an affiliative social behaviour. Same sex pairs of the same age class frequently engaged in synchronous breathing for adults and subadults, as well as mother-calf and escort-calf pairs. The distance between individuals during synchronous breathing for mother-calf pairs was less than for other pairs. The distance observed between individuals for female pairs was less than for male pairs. The time differences between each exhale for each of the two dolphins involved in synchronous breathing episodes for female pairs were smaller than for male pairs, and time differences for adult pairs were smaller than subadult pairs. These results suggest that age and sex class influenced the characteristics of this behaviour.     

Interaction of nucleic acid bases with water molecules and formation of mismatched nucleotide pairs

The possibility of the inclusion of water molecules in the formation of mismatched nucleotide pairs was considered in relation to the mechanisms of point errors in template directed biosynthesis. Calculations of the intermolecular interaction energy for systems containing two bases and one water molecule were carried out by the method of atom-atom potential functions. There exist energy minima for each base pair, corresponding to a single N--H...O or N--H...N H-bond between the bases and H-bonding of the water molecule with both bases. The relative positions of glycosyl bonds in some of these minima are closer to those for Watson--Crick pairs, than the positions of minima for these pairs without water. For other minima, the H-bond formation between the water molecule and the two bases additionally stabilizes the relative base position in wobble-pairs with two H-bonds between the bases. The base and water positions in energy minima are compared with the positions in some pairs proposed on the basis of NMR and X-ray data for double helical oligonucleotides.     

Thermodynamic stabilities of internal loops with GU closing pairs in RNA

Many internal loops that form tertiary contacts in natural RNAs have GU closing pairs; examples include the tetraloop receptor and P1 helix docking site in group I introns. Thus, thermodynamic parameters of internal loops with GU closing pairs can contribute to the prediction of both secondary and tertiary structure. Oligoribonucleotide duplexes containing small internal loops with GU closing pairs were studied by optical melting, one-dimensional imino proton NMR, and one-dimensional phosphorus NMR. The thermodynamic stabilities of asymmetric internal loops with GU closing pairs relative to those of loops with GC closing pairs may be explained by hydrogen bonds. In contrast, the free energy increments for symmetric internal loops of two noncanonical pairs with GU closing pairs relative to loops with GC closing pairs show much more sequence dependence. Imino proton and phosphorus NMR spectra suggest that some GA pairs adjacent to GU closing pairs may form an overall thermodynamically stable but non-A-form conformation.     

The influence of pair-status on the breeding behaviour of the Kittiwake Rissa tridactyla before egg-laying

The breeding behaviour of individually marked Kittiwakes Rissa tridactyla that retained mates from the previous year (SAME) was compared, over the period from pair-formation to egg-laying, with those that changed mates (CHANGE). Position of nest-site in colony and breeding experience did not differ in the two groups studied. Hirds in CHANGE pairs attended the nest-site more frequently and as a result probably had less 'off-duty' time during which to forage. Rates of greeting were higher in CHANGE pairs. Differences between the two groups were usually greatest during the first two weeks after pair-formation an decreased toward egg-laying. CHANGE pairs copulated over a longer period before egg- laying, but stopped copulating sooner than SAME pairs. Copulation rates were higher in SAME pairs immediately before egg-laying. The causation of the behavioural differences between the two groups is discussed in terms of mate familiarity. It is suggested that the recorded differences explain the lower reproductive success in CHANGE pairs reported by other workers.     

Proton exchange in DNA-luzopeptin and DNA-echinomycin bisintercalation complexes: rates and processes of base-pair opening.

Imino proton exchange studies are reported on the complexes formed by bisintercalation of luzopeptin around the two central A.T pairs of the d(CCCATGGG) and d(AGCATGCT) duplexes and of echinomycin around the two central C.G pairs of the d(AAACGTTT) and d(CCAAACGTTTGG) duplexes. The depsipeptide backbone of the drugs occupies the minor groove of the complexes at the bisintercalation site. The exchange time of the amide protons of the depsipeptide rings provides a lower estimate of the complex lifetime: 20 min at 15 degrees C for the echinomycin complexes and 4 days at 45 degrees C for the luzopeptin complexes. The exchange time of imino protons is always shorter than the complex lifetime. Hence, base pairs open even within the complexed oligomers. For the two base pairs sandwiched between the aromatic rings of the drug, the base-pair lifetime is strongly increased, and the dissociation constant is correspondingly reduced. Hence, the lifetime of the open state is unchanged. This suggests similar open states in the free duplex and in the complex. In contrast to the sandwiched base pairs, the base pairs flanking the intercalation site are not stabilized in the complex. Thus, the action of the bisintercalating drug may be compared to a vise clamping the inner base pairs. Analysis suggests that base-pair opening may require prior unwinding or bending of the DNA duplex.