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1.
The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, branched and randomly distributed protrusionswhich are derived largely from the preexistingmembrane,and a lower part,a band with microvilli.During 4-and 8-cel1 stages,the strip is almost vanishedand microvilli in the band is shortened.The nascentmembrane is smooth at the 180°stage,then a rough areaappears below the smooth region and quickly expands.Wheat germ agglutinin which can bind to preexistingmembrane interrupts the development of the regionbetween the preexisting and nascent membranes.Detergent,Brij,having the property to increase the areaof nascent membrane,does not interrupt the developmentof the region between the preexisting and nascentmembranes.  相似文献   

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<正>Unveiling the structure and function of all the proteins a human body produces is undoubtedly a key task for us to better understand ourselves.Although a mission difficult to achieve,this apparently becomes more feasible upon the determination of the DNA sequence of the whole human genome,which was predicted to encode a total of20,000–25,000 proteins[1].Recent efforts of direct(de no-  相似文献   

5.
Questions concerning the functional role of the hollow region of the butterfly Pyrameis atalanta (L.) scale are experimentally investigated. Attention was initially directed to this problem by observation of the complex microstrucmre of the butterfly scale as well as other studies indicating higher lift on butterfly wings covered with scale. The aerodynamic forces were measured for two oscillating scale models. Results indicated that the air cavity of an oscillating model of the Pyrameis atalanta (L.) scale increased the lift by a factor of 1.15 and reduced the damping coefficients by a factor of 1.38. The modification of the aerodynamic effects on the model of butterfly scale was due to an increase of the virtual air mass, which influenced the body. The hollow region of the scale increased the virtual air mass by a factor of 1.2. The virtual mass of the butterfly scale with the hollow region was represented as the sum of air mass of two imaginary geometrical figures: a circular cylinder around the scale and a right-angled parallelepiped within the hollow region. The interaction mechanism of the butterfly Pyrameis atalanta (L.) scale with a flow was described. This novel interaction mechanism explained most geometrical features of the airpermeable butterfly scale (inverted V-profile of the ridges, nozzle of the tip edge, hollow region, and openings of the upper lamina) and their arrangement.  相似文献   

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Morphological structure and optical properties of the wings of Morphidae   总被引:2,自引:0,他引:2  
The morphological structure and optical properties of the wings of 14 species of Morphidae have been investigated. Most of the scales of the iridescent species of Morphidae (Lepidoptera) present a very particular structure. The ground scales, responsible for the major part of the optical properties, are covered by a very regular set of longitudinal ridges. The ridges themselves are constituted by a superposition of lamellae that act locally as a multilayered structure. This very specific morphology leads to both interferences and diffraction effects. The first one is responsible of the brilliant blue coloration of the males, while the second one diffracts this colored light at a very large angle. These two phenomena give to the butterfly a very effective long-range communication system. The morphological characteristics of the scales of the various species are presented in detail. Two types of optical measurement were performed on the iridescent wings of 14 different species of Morphidae: spectroscopic measurements under various incidences and gonioscopic measurements for a given incidence angle and wavelength. The first allows a determination of the index of refraction of the cuticular material. The second leads to the drawing of spatial diffraction maps. It shows that most of the reflected light is diffracted laterally over a very large angle (90° 〈 0 〈 120°, according to the different species) and that this repartition depends of the polarization of incident light. As predicted by previous calculations, the dissymmetric structure of the ridge is responsible for the separation of the polarization modes in the various diffraction orders.  相似文献   

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The snowdrop lectin GNA (Galanthus nivalis agglutinin) has been shown to possess insecticidal activity to a range of economically important insect pests. However, the precise mechanism of insecticidal action of GNA against insects remains unknown. In this investigation, we attempted to purify and identify receptor(s) responsible for binding of GNA in the larval midgut of a major lepidopteran pest (the cotton leafworm, Spodoptera littoralis) to better understand its mode of action. Therefore, cytoplasmic as well as membrane proteins from 800 larval midguts were chromatographed on a column with immobilized GNA. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the proteins eluted from the GNA column followed by sequencing of the GNA-binding proteins and BLAST analyses revealed that the N-terminal sequences of a 24 kDa polypeptide purified from the cytoplasmic and membrane protein fraction revealed sequence similarity to sequences encoding heavy chain homologs of ferritin from Manduca sexta (76% sequence identity), Calpodes ethlius (80% sequence identity) and Bombyx mori (61% sequence identity). Furthermore, the N-terminal sequence of a 31 kDa polypeptide from the membrane protein fraction showed sequence similarity to a light chain homolog of ferritin from Manduca sexta (88% sequence identity).  相似文献   

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Photoperiod-sensitive genic male sterile (PSGMS) rice is a very useful germplasm for hybrid rice development. It was first found as a spontaneous mutant in a japonica cultivar 'Nongken 58'. pms3 on chromosome 12 was determined to be the locus where the original PSGMS mutation occurred, changing the normal cultivar Nongken 58 to PSGMS Nongken 58S. Large amounts of RAPD and AFLP analyses were also conducted for the fine mapping of the pms3 genomic region, which resulted in 4 molecular markers linked to pms3. Although these markers somewhat increased the marker density of this region, the pms3 locus is still located in a marker-sparse region.  相似文献   

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Boldness is defined as the tendency of an individual to take risks when exposed to novel objects or situations. The main aim of this work was to dilucidate if boldness was related to the development of the secondary sexual traits (SSTs) in the male of the fiver blenny Salariafluviatilis, a freshwater fish which takes care of eggs. As a second objective SSTs effect on pa rental status adoption was also be explored. Wild young fish were caught in the Segre River (Ebro basin) in November 2010. Fish were kept in five aquaria in groups of eight males and eight females with artificial nests. Boldness (boldness score and hesitancy) of males (initially with little SSTs development) was tested as the time required to exit a refuge when exposed to a new environ ment. Fish were mantained in the same aquaria for several months, and males' SSTs development and reproductive behaviour were monitored. Boldness score was negatively associated to cephalic crest development. Hesitancy was negatively related to male length and was also influenced by the interaction between male length and cephalic crest. Parental status acquisition was positively related to the male's length, marginally related to anal gland development, and nonrelated to cephalic crest. These re sults suggest an intrasexual role of the crest as an informative trait of boldness (honest signal) which might not necessarily be chosen by the females. It is also discussed that correlational selection could be responsible for linking boldness and growth rate in this species. Sexual selection, in addition to having directed the evolution of secondary sexual traits, might have favored certain personality traits (e.g. boldness) associated with the achievement of a larger body length .  相似文献   

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Advancement has recently been made on the techniques for separating and maintaining colonies of red imported fire ants, Solenopsis invicta Buren. A new brood rescue method significantly improved the efficiency in separating colony from mound soil. Furthermore, a new method was developed to separate brood from the colony using fire ant repellants. Finally, a cost-effective method was developed to coat containers with diluted Fluon (AGC Chemicals America, Inc, Moorestown, NJ, USA), an aqueous polytetrafluoroethylene, to prevent housed ants from escaping a container. Usually the original Fluon solution is directly applied to the wall of the containers. Reduced concentrations of Fhion were found to be equally effective in preventing ant escape. The use of diluted Fluon solutions to coat the containers was recommended because of environmental and cost-saving benefits. Application of these new techniques can significantly reduce labor, cost and environmental contamination. This review paper collates all the new techniques in one reference which readers can use as a manual.  相似文献   

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The paradigm, still around in textbooks, that 'in insects sex is strictly genetic, thus that they do not have sex hormones', is mainly based on a wrong interpretation of the 'gynandromorph argument'. It is no longer tenable. Given the fact that vertebrates and invertebrates probably had a common, sexually reproducing ancestor, there is no reason to assume that only vertebrates need sex hormones. The major function of sex hormones is to inform the somatoplasm about developmental changes that take place in the gonads. In contrast to juvenile hormone and neuropeptides, ecdysteroids meet all criteria to act as sex hormones, which was probably their ancient role. Their much better documented role in moulting and metamorphosis was a secondary acquisition that enabled arthropods to cope with growth problems, imposed by a rigid cuticle. Female insects use 20-hydroxyecdysone (20E), secreted by the follicle cells of the ovary, in a similar way as females of egg-laying vertebrates use estrogens. For a variety of reasons, the possibility that ecdysteroids, in particular ecdysone (E), might also act as sex hormones in male insects, thus as the counterpart of testosterone of vertebrates, has been very much overlooked. Thanks to the recent discovery of the molecular basis of the haploid-diploid system of sex determination in the honeybee, the characterization of Halloween genes, proteomics, RNAi and so on, it now becomes possible to verify whether in insects, as with vertebrates, males are the endocrinologically default gender form.  相似文献   

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In the present study, the karyotypes of 34 populations belonging to 11 species and one variety of Heracleum from the Hengduan Mountains in China were examined. Chromosome numbers and the karyotypes of three species (H. souliei, H. la'ngdoni, and H. wenchuanense) are reported for the first time, as are the karyotypes of H. moellendorffii and H. henryi (tetraploid). Populations of H. candicans, H. franchetii, and H. kingdoni in the Hengduan Mountains were found to consist of a mixture of diploid and tetraploid plants. Except for four species of Heracleum, namely H. candicans, H. franchetii, H. henryi, and H.kingdoni, which have both diploid and tetraploid karyotypes, all other species of Heracleum are were found to be diploid. All karyotypes were found to belong to the 2A type of Stebbins, with the exception ofH. candicans var. obtusifolium, which belongs to 2B, and H. hemsleyanum and H. franchetii (Mt. Dujuan, Daocheng, Sichuan, China), which belong to 1A. There was only a slight difference in the karyotype asymmetry index, which suggests a close kinship for species of Heracleum and that the entire phylogenetic development of Heracleum is relatively primitive. Species that exhibited advanced morphological features were also more advanced in karyotype structure, with the order ofkaryotype evolution being 1A→2A→2B. This phenomenon indicates that the species distributed in the Hengduan Mountains have not diverged completely and that the Hengduan Mountains are a relatively young and active area for the evolution of Heracleum. Polyploidization in Heracleum may be an important evolutionary mechanisms for some species, generating diversity. The biological attributes, distribution range, and the geological history of the genus have all played a part in accelerating the evolution through polyploidization or aneuploidization. It is known that as the distribution latitude of Heracleum decreases from north to south, the chromosome number, ploidy level, and asymmetry structure appear to increase. In the Hengd  相似文献   

15.
XIEYONG  ZUMEINI 《Cell research》1997,7(1):13-19
Recently the antichromosome antisera from several sclerogerma patients have been found to recognize the pellicle of metaphase and anaphase chromosomes.In order to identify the pellicle components,we used these antichromosome antisera to screen a human embryonic cDNA library.The sequences of the positive clones are identical to the cDNA gene sequence of CENP-C (centromere protein C),a human centromere autoantigen.This result suggusts that CENP-C is a component of the pellicle of human metaphase and anaphase chromosomes.  相似文献   

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In this issue of the Journal of Bionics Engineering we start something which is novel in academic publication but which is not at all uncommon in other serial publications. We present, in a series of seven chapters, a book on the interrelations between biology and engineering. It is not a handbook of bionics ( though that might follow) but a series of essays that will bridge the gap between biology and engineering. We hope you will find them entertaining and informative, and that they will reinforce and revise areas of your knowledge,no matter what your entry point into this subject.  相似文献   

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In 1997, we conducted a vegetation survey in three semi-arid natural grasslands (steppes) with different livestock grazing intensities in Southwest Heilongjiang Province, China, The dominant grassland species was the grass Stipa baicalensis Roshev. Grasslands with light, intermediate, and heavy grazing intensities were located 10, 5, and 2 km from a village, respectively. Villagers use the steppe to raise cattle, horses, sheep, and goats. Each of the three grasslands was surveyed by placing 100 quadrats (50 cm×50 cm) along a 50 m line transect. Each quadrat was divided into four equal areas (25 cm×25 cm; S-quadrats) and all plant species occurring in each of these smaller areas were identified and recorded. These data were summarized into frequency distributions and the percentage of S-quadrats containing a given species and the variance of each species were estimated. The power law was applied to these estimates. The power law was used to evaluate the spatial heterogeneity and frequency of occurrence for each species in the grassland community. The lightly grazed grassland exhibited high spatial heterogeneity (caused by large plant size), the highest species diversity, and a high occurrence of S. baicalensis. In contrast, the heavily grazed grassland exhibited high spatial heterogeneity (caused by patchy populations of small plant size), low species diversity, and a low occurrence of S. baicalensis. We judged that the heavily grazed grassland was overgrazed and exclusion of livestock from the degraded areas is necessary for recovery.  相似文献   

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Aphids display life cycles largely determined by the photoperiod.During the warm long-day seasons.most aphid species reproduce by viviparous parthenogenesis.The shortening of the photoperiod in autumn induces a switch to sexual reproduction.Males and sexual females mate to produce overwintering resistant eggs.In addition to this full life cycle(holocycle),there are anholocyelic lineages that do not respond to changes in photoperiod and reproduce continuously by parthenogenesis.The molecular or hormonal events that trigger the scasonal response(i.c,induction of the sexual phenotypes)are still unknown.Although circadian synthesis of melatonin is known to play a key role in vertebrate photoperiodism,the involvement of the circadian clock and/or of the hor-mone melatonin in insect seasonal responses is not so well established.Here we show that melatonin levels in the aphid Acyrthosiphon pisum are significantly higher in holocyclice aphids reared under short days than under long days,while no differences were found between anholoeyelic aphids under the same conditions.We also found that melatonin is localized in the aphid suboesophageal ganglion(SOG)and in the thoracic ganglionic mass(TGM).In analogy to vertcbrates,insect-type arylalkxylamine N-acetyltransferases(i-AANATs)are thought to play a key role in melatonin synthesis.We measured the expression of four I-AANAT genes identified in A.pisum and localized two of them in situ in the insect central nervous systems(CNS).Levels of expression of these genes were compatible with the quantities of melatonin observed.Moreover,like melatonin,expression of these genes was found in the SOG and the TGM.  相似文献   

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The zooplankton, defined a the assemblage of animals and animal-like creatures that lives in the water column of small to big waterbodies, has primarily been studied in the temperate zone, so most "received" concepts about it derive from the temperate, not the tropical belt of this planet. In the present days of biodiversity  相似文献   

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The “oxygen burst” phenomenon that appeared during the light-induction period of intact leaves could be monitored using a photoacoustic technique high time resolution. The relationship between oxygen bursts and dark-adapted time, far-red light pretreatment, photothermal signal, and chlorophyll a (Ch1 a) fluorescence kinetics were investigated in the present study. Using extraneous inhibitors or cofactors of electron transport, a modified vacuum-infiltration method was undertaken to locate directly the site at which oxygen bursts of intact leaves occurred. We found that the photothermal signal showed little evidence of oscillation during the light-induction period. The oxygen burst was resolved into two components if darkadapted time lasted longer than 20 min. Methyl viologen (MV) or far-red light could not eliminate the first component, whereas formate-Na (pH 7.0, 20μmol/L) eliminated the first component but had no effect on the second one. Furthermore, the photochemical quenching, the electron transport rate of Chl a fluorescence,and the first component of the oxygen bursts approached lowest values simultaneously. This evidence indicates that the site at which the first component of oxygen bursts occurred was located between photosystem (PS)I and PSII (i.e. the PQ pool). The formate-Na experiment also showed a linkage between the first component and the S state of oxygen evolution at the donor side of PSII. Furthermore, elimination of the second component by far-red light and absorption of the second component by MV indicated that the site at which the second component of oxygen bursts may be located at the acceptor side of PSII.  相似文献   

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