共查询到20条相似文献,搜索用时 31 毫秒
1.
《International Journal of Insect Morphology and Embryology》1997,26(2):139-147
The present work reports on a neuroanatomical study of the butterfly Pararge aegeria (Lepidoptera : Satyridae) focusing on the lamina ganglionaris underlying two different regions of the retina of the compound eye: the dorsal rim area and the large dorsal region. No differences between both lamina regions, concerning the structure of the cartridges and the morphology of the identified neurons, could be detected. After passing the basement membrane, the visual cell axons are organized in retinotopic bundles (pseudocartridges), in which the axons of the 9 visual cells (V1 and 5, D2, 4, 6, 8, H3 and 7, B9) are arranged in the same way as in the retina. In the pseudocartridge there are no synaptic contacts. Before entering the lamina cartridge, the bundles rotate 90 °. The cartridges are joined by the fibres of 4 monopolar cells (L1, L2, L3 and L4), which could be identified and located inside the lamina cartridges in serial EM-sections. Golgi impregnations revealed the morphology of these fibres. Thus, the regional specialization of the retina (dorsal rim area and large dorsal region) does not seem to be reflected at the level of the first visual neuropil. Additionally, the cartridges of both lamina regions were investigated qualitatively for synaptic contacts among fibres. In addition to monadic chemical synapses and multiple contact synapses with presynaptic ribbons, cell contacts are also facilitated by invaginations and bridges. These cellular interactions and their functional implications are discussed. 相似文献
2.
Gitte Petersen Ole Seberg Argelia Cuenca Dennis W. Stevenson Marcela Thadeo Jerrold I. Davis Sean Graham T. Gregory Ross 《Cladistics : the international journal of the Willi Hennig Society》2016,32(2):141-159
A phylogenetic analysis of the early branching lineages of the monocotyledons is performed using data from two plastid genes (rbcL and matK), five mitochondrial genes (atp1, ccmB, cob, mttB and nad5) and morphology. The complete matrix includes 93 terminals representing Acorus, the 14 families currently recognized within Alismatales, and numerous lineages of monocotyledons and other angiosperms. Total evidence analysis results in an almost completely resolved strict consensus tree, but all data partitions, genomic as well as morphological, are incongruent. The effects of RNA editing and potentially processed paralogous sequences are explored and discussed. Despite a decrease in incongruence length differences after exclusion of edited sites, the major data partitions remain significantly incongruent. The 14 families of Alismatales are all found to be monophyletic, but Acorus is found to be included in Alismatales rather than being the sister group to all other monocotyledons. The placement is strongly supported by the mitochondrial data, atp1 in particular, but it cannot be explained as an artifact caused by patterns of editing or by sampling of processed paralogues. 相似文献
3.
Airoldi M Gennaro G Giomini M Giuliani AM Giustini M 《Journal of biomolecular structure & dynamics》2011,29(3):585-594
When the model polynucleotide poly(dG-dC)?poly(dG-dC) [polyGC] is titrated with a strong acid (HCl) in unbuffered aqueous solutions containing the chlorides of the alkali metals in the concentration range 0.010?M-0.600?M, two transitions in the absorbance vs. pH plots are evidenced, characterized by the constants pK(a(?)) and pK(a(?)). The limiting values at infinite saline concentrations of these two constants, namely pK(∞)(a(?)) and pK(∞)(a(?)) obtained making use of the "one site saturation constant" equation or, in turn, of the double logarithmic plot: pK(a) vs. log([salt]?1), exhibit a clear dependence on the nature of the cations. The effects of the different alkali cations on the pK(∞)(a) values follow the Hofmeister series. In fact, the pK(∞)(a(?)) and the pK(∞)(a(?)) values are smaller for Li+ and Na+ than for Rb+ and Cs+, with K+ at the border between the two, showing that the transitions require higher concentrations of protons to occur in the presence of high concentrations of the cosmotropic ions. 相似文献
4.
It has been shown in a previous paper (8) that the prime product of reassociation of related DNA sequences under open experimental conditions are mismatched duplexes which undergo maturation upon further incubation. Due to this feature, the Tm value of the duplexes of a large number of DNAs is strongly dependent on the Cot value. Here we present data showing that the Tm of the duplexes of such type of DNAs depends also on the concentration of DNA in the range of one and the same Cot value. The significance of this finding in studying the taxonomic relationship by DNA-DNA hybridisation is discussed.Abbreviations Co =
initial concentration of single-stranded DNA in moles of nucleotides per liter
- t =
time of incubation in seconds
- Cot =
the product of Co and t (mol. sec. 11)
- PB =
an equimolar mixture of NaH2PO4 and Na2HPO4, pH 6.8
- HAP =
hydroxyapatite
- Ti =
incubation temperature
- Tm =
melting temperature
- Te =
elution temperature, i.e. the temperature at which one half of the DNA is eluted as single strands by HAP-thermal chromatography 相似文献
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6.
A A Ne?fakh 《Ontogenez》1985,16(1):15-25
Two closely related controversial problems are discussed: whether the developmental processes can be reduced to the synthesis of polypeptides encoded in DNA, and whether the information in DNA is equivalent to that in the adult organism. Critically considered are the ideas that DNA is only responsible for the protein synthesis, whereas morphogenesis proceeds independently and according to epigenetic regularities of its own. It is stated that development is the realization of genetic information in which more elementary (molecular) processes unambiguously determine a more complex cellular level which in its turn determines morphogenesis of tissues and organs. Various mechanisms of the appearance of new information in the course of development are considered. The statement is made that new information concerns only some individual characters of the organism, whereas most of information that determines the process of development and the structure of the adult organism is created in the course of evolution, is stored in DNA and inherited. 相似文献
7.
Benthic surveys carried out in 1989 (literature data), 1995, and 2001 (original data) revealed changes in the structure of soft bottom communities of Wrangel Bay (Peter the Great Bay, Sea of Japan), where a deep-water port of Vostochnyi is situated. The functioning of the port has caused no significant environmental pollution by heavy metals, hydrocarbons, and other pollutants. Bottom dredging and the siltation induced by it have drastically lowered the benthos biomass, changed benthic communities, and altered their trophic structure. Sestonophages have disappeared nearly altogether being replaced by detrivores. The ecological state of the benthos is characterized as unstable. 相似文献
8.
Jere Kahanp?? 《ZooKeys》2014,(441):183-207
An updated checklist of the Atelestidae, Brachystomatidae, Dolichopodidae, Empididae and Hybotidae (Diptera) recorded from Finland is presented. The genera with uncertain placement within superfamily Empidoidea (= the Iteaphila group) are also included in this paper. 相似文献
9.
《Gene》1998,211(1):159-167
Genomic sequences of the self-incompatibility genes, the S-RNase genes, from two rosaceous species, Japanese pear and apple, were characterized. Genomic Southern blot and sequencing of a 4.5-kb genomic clone showed that the S4-RNase gene of Japanese pear is surrounded by repetitive sequences as in the case of the S-RNase genes of solanaceous species. The flanking regions of the S2- and Sf-RNase genes of apple were also cloned and sequenced. The 5′ flanking regions of the three alleles bore no similarity with those of the solanaceous S-RNase genes, although the position and sequence of the putative TATA box were conserved. The putative promoter regions of the Japanese pear S4- and apple Sf-RNase genes shared a stretch of about 200 bp with 80% sequence identity. However, this sequence was not present in the S2-RNase gene of apple, and thus it may reflect a close relationship between the S4- and Sf-RNase genes rather than a cis-element important in regulating gene expression. Despite the uniform pattern of expression of the rosaceous S-RNase genes, sequence motifs conserved in the 5′ flanking regions of the three alleles were not found, implying that the cis-element controlling pistil specific gene expression also locates at the intragenic region or upstream of the analyzed promoter region. 相似文献
10.
Ghalebani L Wahlström A Danielsson J Wärmländer SK Gräslund A 《Biochemical and biophysical research communications》2012,421(3):554-560
Metal ions like Cu(II) and Zn(II) are accumulated in Alzheimer's disease amyloid plaques. The amyloid-β (Aβ) peptide involved in the disease interacts with these metal ions at neutral pH via ligands provided by the N-terminal histidines and the N-terminus. The present study uses high-resolution NMR spectroscopy to monitor the residue-specific interactions of Cu(II) and Zn(II) with (15)N- and (13)C,(15)N-labeled Aβ(1-40) peptides at varying pH levels. At pH 7.4 both ions bind to the specific ligands, competing with one another. At pH 5.5 Cu(II) retains its specific histidine ligands, while Zn(II) seems to lack residue-specific interactions. The low pH mimics acidosis which is linked to inflammatory processes in vivo. The results suggest that the cell toxic effects of redox active Cu(II) binding to Aβ may be reversed by the protective activity of non-redox active Zn(II) binding to the same major binding site under non-acidic conditions. Under acidic conditions, the protective effect of Zn(II) may be decreased or changed, since Zn(II) is less able to compete with Cu(II) for the specific binding site on the Aβ peptide under these conditions. 相似文献
11.
Guimarães ET Domingos M Alves ES Caldini N Lobo DJ Lichtenfels AJ Saldiva PH 《Environmental and Experimental Botany》2000,44(1):1-8
Tradescantia pallida cv. purpurea, a popular garden plant in Brazil, was used for the Tradescantia micronucleus (Trad-MCN) assay. In situ monitoring of the genotoxicity of air pollutants was carried out by sentinel approach, using the plant grown in the field or using the plants in pots which were carried to the monitoring sites. Two highly polluted sites, in S?o Paulo city (Cerqueira Cesar and Congonhas) and two rural sites (the cities of Pirassununga, 200 km and Caucaia do Alto, 50 km from S?o Paulo, respectively) were chosen for this study, in order to determine the gradient difference of the air pollution levels. Sentinel plants in Congonhas site presented the highest frequency of micronuclei (4.4%), in comparison with 2.2 and 2.3% found in plants from Pirassununga and Cerqueira Cesar sites, respectively (Kruskal-Wallis; P<0.020). Significant increases (F test; P<0.0001) in the frequency of micronuclei were observed in plants exposed in the polluted urban sites (Cerqueira Cesar: 5.7%; Congonhas: 7.1% and Caucaia do Alto: 2.3%). The increase in the frequency of micronuclei observed indicates the potential risk of mutagenicity in presence of high concentrations of pollutants. 相似文献
12.
Summary The ultrastructure of the paracervical (Frankenhäuser) ganglion in the rat was studied after immersion or perfusion fixation with glutaraldehyde followed by post-osmification. This ganglion is located at the uterovaginal junction in the vicinity of arteria uterina and contains three neuronal cell types. (1) Principal neurons have a fine structure mainly similar to the ganglion cells of other autonomic ganglia. (2) Small granule-containing cells occur in clusters often close to fenestrated capillaries. They are divided into two subgroups according to the size of their cytoplasmic granules; those containing only small granulated vesicles of 800 to 1400 Å in diameter and those having also large granulated vesicles of 2000 to 3000 Å in diameter. (3) Vacuolated nerve cells are large cells that resemble the principal neurons in their cytoplasmic components, except that they contain one to ten vacuoles with corpuscles of different size and shape. The possible physiological significance of the small, granule-containing cells in the uterine function is discussed. 相似文献
13.
The structure of the plankton community of the Öregrundsgrepen (southwest Bothnian Sea) 总被引:1,自引:0,他引:1
Taxonomic composition and variations in density and biomass of the plankton community in the Öregrundsgrepen, a shallow coastal area, were investigated from June 1972 to November 1973. The phytoplankton biomass was large in spring but small during the rest of the year. The spring bloom was dominated by diatoms and dinoflagellates, especially byThalassiosira spp. which were also important during other seasons. Small forms, such asCryptomonas spp.,Rhodomonas spp. and monads, dominated during summer. Blue-green algae were never of any major importance. During the summer, the trophogenic layer exceeded 10 m in thickness. The metazoan fauna was of lower diversity than the plankton flora. The dominating species, the copepodsAcartia bifilosa andEurytemora affinis, constituted on the average 83% of the standing crop. The low salinities, 5–6 S, were regarded as the principal pertinent limiting factor. The metazoan fauna reached large biomass values from July to October. The protozoan fauna (in the case of ciliates), obtained biomass maxima during the spring bloom. It is suggested that the Öregrundsgrepen represents an area of elevated productivity within a region of low overall production, presumably due to local upwelling. From June 1972 to May 1973, the average biomasses were: phytoplankton 0.464 g C m–2, ciliates 0.040 g C m–2, copepod nauplii 0.010 g C m–2, micro-rotifers 0.004 g C m–2, and mesozooplankton (larger than 0.2 mm) 0.312 g C m–2. It is estimated that about than 60% of the phytoplankton production is consumed by the microzooplankton (<0.2 mm). 相似文献
14.
Luisa Costessi Fabiola Porro Alessandra Iaconcig Mirjana Nedeljkovic Andrés Fernando Muro 《PloS one》2013,8(3)
Most genes have multiple polyadenylation sites (PAS), which are often selected in a tissue-specific manner, altering protein products and affecting mRNA stability, subcellular localization and/or translability. Here we studied the polyadenylation mechanisms associated to the beta-adducin gene (Add2). We have previously shown that the Add2 gene has a very tight regulation of alternative polyadenylation, using proximal PAS in erythroid tissues, and a distal one in brain. Using chimeric minigenes and cell transfections we identified the core elements responsible for polyadenylation at the distal PAS. Deletion of either the hexanucleotide motif (Hm) or the downstream element (DSE) resulted in reduction of mature mRNA levels and activation of cryptic PAS, suggesting an important role for the DSE in polyadenylation of the distal Add2 PAS. Point mutation of the UG repeats present in the DSE, located immediately after the cleavage site, resulted in a reduction of processed mRNA and in the activation of the same cryptic site. RNA-EMSA showed that this region is active in forming RNA-protein complexes. Competition experiments showed that RNA lacking the DSE was not able to compete the RNA-protein complexes, supporting the hypothesis of an essential important role for the DSE. Next, using a RNA-pull down approach we identified some of the proteins bound to the DSE. Among these proteins we found PTB, TDP-43, FBP1 and FBP2, nucleolin, RNA helicase A and vigilin. All these proteins have a role in RNA metabolism, but only PTB has a reported function in polyadenylation. Additional experiments are needed to determine the precise functional role of these proteins in Add2 polyadenylation. 相似文献
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16.
The phosphorus retention capacity was established for two predams having the same water supply and the same seasonality but with contrasting hydraulic retention times and phosphorus loads. The annual retention of total phosphorus of the shallow Misère predam amounted to about 60%, whereas the deeper Bavigne predam retained about 82%; for soluble reactive phosphorus (SRP) the annual retention rates were 4 and 54%, respectively. The different behaviour of the predams is probably due to their different flow regimes and morphology. The highest retention rates were observed during summer, when up to 90% of SRP could be retained in the Bavigne predam. The comparison of the measured removal rates of SRP with those calculated on the basis of the model proposed by Benndorf & Pütz (Wat. Res. 1987 21: 829–838) shows a rather good agreement for the thermally stratified Bavigne predam. For the shallow Misère predam, the model adequately predicts the annual trends of SRP removal, but a great discrepancy is observed for the absolute values. This is probably due to the phytoplankton composition and to the release of phosphorus from the sediments in the summer period. 相似文献
17.
The dependence of the efficacy of the influence of a kava-pyrone (±)-kavain (330 µM) on the frequency of activation of Na+ channels and voltage dependence of the effects of (±)-kavain on the rate of inactivation of these channels were studied in experiments on isolated neurons from the rat hippocampus. In all series of experiments, the holding potential equalled –100 mV. The efficacy of (±)-kavain-induced blockade of Na+ channels was independent of the frequency of stimulation within the range up to 10/sec. In the control experiments, the rate of inactivation increased with the rise of depolarization from –40 mV to +30 mV, and then the saturation effect was observed. At the membrane potential of –40 mV, the rate of (±)-kavain-evoked inactivation increased approximately by a factor of 2.5. At the more positive shifts of the membrane potential, the efficacy of the effects of (±)-kavain on the rate of inactivation became noticeably reduced, and at +30 mV (±)-kavain exerted no distinct influence on this parameter.Neirofiziologiya/Neurophysiology, Vol. 28, No. 6, pp. 312–315, November–December, 1996. 相似文献
18.
19.
Jere Kahanp?? 《ZooKeys》2014,(441):291-303
A checklist of the Agromyzidae (Diptera) recorded from Finland is presented. 279 (or 280) species are currently known from the country. Phytomyza
linguae Lundqvist, 1947 is recorded as new to Finland. 相似文献
20.
Pharyngodon medinae García-Calvente, 1948 (Nematoda: Pharyngodonidae) is redescribed from Podarcis pityusensis (Bosca, 1883) (Sauria: Lacertidae) of the Balearic Islands (Spain) and confirmed as a member of the genus Skrjabinodon Inglis, 1968. A systematic review of S. medinae and closely related species is also given. Parathelandros canariensis is referred to Skrjabinodon as a new combination and Parathelandros Magzoub et al., 1980 is dismissed as a junior homonym of Parathelandros Baylis, 1930. 相似文献