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21.
Alexey Fedorov Larisa Fedorova Valery Starshenko Vadim Filatov Eugeni Grigor'ev 《Journal of molecular evolution》1998,46(3):263-271
Nonrandomness in the intron and exon phase distributions in a sample of 305 human genes has been found and analyzed. It was
shown that exon duplications had a significant effect on the exon phase nonrandomness. All of the nonrandomness is probably
due to both the processes of exon duplication and shuffling. A quantitative estimation of exon duplications in the human genome
and their influence on the intron and exon phase distributions has been analyzed. According to our estimation, the proportion
of duplicated exons in the human genome constitutes at least 6% of the total. Generalizing the particular case of exon duplication
to the more common event of exon shuffling, we modeled and analyzed the influence of exon shuffling on intron phase distribution.
Received: 28 March 1997 / Accepted: 9 July 1997 相似文献
22.
Ahmad Golaraei Kamdin Mirsanaye Yeji Ro Serguei Krouglov Margarete K. Akens Brian C. Wilson Virginijus Barzda 《Journal of biophotonics》2019,12(1)
Polarization‐dependent second‐harmonic generation (P‐SHG) microscopy is used to characterize molecular nonlinear optical properties of collagen and determine a three‐dimensional (3D) orientation map of collagen fibers within a pig tendon. C6 symmetry is used to determine the nonlinear susceptibility tensor components ratios in the molecular frame of reference and , where the latter is a newly extracted parameter from the P‐SHG images and is related to the chiral structure of collagen. The is observed for collagen fibers tilted out of the image plane, and can have positive or negative values, revealing the relative polarity of collagen fibers within the tissue. The P‐SHG imaging was performed using a linear polarization‐in polarization‐out (PIPO) method on thin sections of pig tendon cut at different angles. The nonlinear chiral properties of collagen can be used to construct the 3D organization of collagen in the tissue and determine the orientation‐independent molecular susceptibility ratios of collagen fibers in the molecular frame of reference. 相似文献
23.
Mayumi YOSHIMURA 《Entomological Science》2012,15(2):145-154
Natural and human‐made disasters such as floods and logging occur in and around rivers. Stream‐dwelling aquatic insects respond to these disturbances in various ways. Primary consumers among them rely greatly on algae and leaf litter from riparian vegetation as food. Therefore, once a disturbance such as a flood has occurred, insects may find it difficult to find food in a stream, and the aquatic insect assemblage can be impacted greatly as a result. Disturbances in riparian areas also increase fine sediment loads into streams, damaging habitat and altering the aquatic insect assemblage. Deforestation impacts not only terrestrial but also aquatic animals. In this review paper, aquatic insect assemblages are assessed according to alterations in land use in and around streams. Following this paper, it is expected that clarification of aquatic insect fauna and their life cycles will progress and that the distribution and habitat use of aquatic insects will be afforded greater attention in forest management. 相似文献
24.
Larvae of the caddisfly, Diplectrona modesta (Hydropsychidae), were found to be permanent inhabitants of a small, intermittent, headwater stream in southern Ontario. They survived desiccation for at least four weeks in summer. A laboratory experiment gave a mean survivorship of 50% after 30 days without water in stream gravel and stones after the larvae had been permitted to construct their shelters. Survivors were those that constructed their tubes deep in the substrate. 相似文献
25.
Here we report the development of 10 microsatellite loci for the alpine caddisfly, Allogamus uncatus. Polymorphism as detected in 24 individuals ranged from three to 17 alleles per locus, and observed heterozygosity ranged from 0.087 to 0.864. These primers will enable research on the genetic population structure of this species, the extent of gene flow among alpine permanent and temporary streams, and the genetic consequences of extinction/recolonization events. 相似文献
26.
1. The use of morphological gill abnormalities of hydropsychid larvae was assessed in Hydropsyche siltalai larvae exposed to cadmium in the laboratory and Cheumatopsyche lepida and H. pellucidula larvae collected from a polluted river. Two biomarkers were evaluated: (1) Hydropsychid abnormality incidence (HAI), referring to the proportion of individuals with at least some abnormalities, and (2) Hydropsychid gill abnormality indice (HYI), referring to the average number of abnormal gill tufts for all individuals. 2. Abnormality–contaminant relations for both biomarkers were established by studying gill responses along gradients of increasing cadmium and organochlorine concentrations. A cadmium gradient was verified in laboratory exposures, whereas the concentrations of polychlorinated dibenzo‐p‐dioxin (PCDD), dibenzofuran (PCDF) and diphenyl ether (PCDE) of the aquatic moss Fontinalis antipyretica were used as measures of an organochlorine gradient in the field. 3. Morphological abnormalities were easily distinguished as heavy darkening, malformation and/or reduction of single gill tufts. Darkening of the gills appeared to start either at the basal or distal ends. 4. A marked increase of HYI values with increasing Cd concentration reflected a clear abnormality‐contaminant relation, whereas the mere dicotomic classification of larvae as normal or abnormal (HAI) was less informative. High values of both HAI and HYI were associated with high contamination. A significant positive correlation was found between organochlorine concentration in mosses and biomarker values for H. pellucidula, but not for C. lepida. 5. We conclude that HAI indicates deleterious effects, but fails to quantify the severity of degradation. Use of individual gill tufts, as response units in deriving HYI, revealed a simple solution to the quantification problem. Further research into the ecological meaning, physiological background and patterns of gill abnormality is recommended for assessing the applicability and relevance of hydropsychid gill biomarkers. 相似文献
27.
Carl M. Way Albert J. Burky Juliana M. Harding Skippy Hau William K.L.C. Puleloa 《Environmental Biology of Fishes》1998,51(1):53-65
Constant pressure in Hawai'i to use limited freshwater resources has resulted in increasing concern for the future of the
native stream fauna. Hawaiian freshwater gobies have an amphidromous life cycle with a marine larva period and require streams
which flow continuously to the ocean for the critical reproductive periods and during recruitment. As such, the stream fauna
is particularly sensitive to any anthropogenic perturbations which disrupt the continuity of stream flows. The objective of
this 2-year study was to compare the life cycles of the goby, Lentipes concolor, from a heavily diverted stream on Moloka'i
and a relatively undisturbed stream on Maui. In Makamaka'ole Stream, Maui, the population of L. concolor was reproductively
active all year with females potentially spawning 2–3 times annually. The timing of spawning did not occur consistently during
the wet or dry season but coincided with high stream flow conditions regardless of time-of-year. In Waikolu Stream, Moloka'i,
the reproductive pattern was more variable with the number of reproductively active females ranging from 0% to 100%. In general
the number of eggs was greater and egg size smaller for female L. concolor in Waikolu Stream than in Makamaka'ole Stream.
However, female reproductive condition of L. concolor from Maui was consistently higher than from fish on Moloka'i. Reproduction
of L. concolor in Makamaka'ole Stream was correlated with the seasonal pattern of flow rates with peaks in female reproductive
condition associated with periods of elevated discharge. No correlation between reproduction and discharge occurred in Waikolu
Stream. There were considerable differences between the magnitude of discharge in the two streams. Waikolu Stream experienced
prolonged periods of extremely low flows which have become common since the Moloka'i Irrigation System began diverting water
from the stream in 1960. In Makamaka'ole Stream, L. concolor was capable of reproducing throughout the year and adjusting
fecundity in response to stream flow conditions. In contrast, the population in Waikolu Stream appeared to have a ‘boom or
bust’ reproductive pattern; the population had reduced or no reproduction when stream flow conditions reached extreme low
levels, but the population succesfully reproduced during higher flow months. The diversion structure in Waikolu Stream has
dampened the natural seasonal discharge cycle, exacerbated natural low flow conditions, and increased the likelihood of prolonged
periods of extremely low flow. Stream management practices in the Hawaiian Islands must take into account the complex life
cycles and sensitivity to variable stream flow conditions of the native fauna.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
The species composition of aquatic insects in theboreal stream, Skiftesåa, was investigated usingemergence traps, Malaise traps and kick samples. Atleast 13 Ephemeroptera, 16 Plecoptera, 25 Trichopteraand 120 Chironomidae species were recorded. This faunais representative for non-polluted, northern streams.The production of macrobenthos was estimated to beonly about 1 g dry weight per year and m2,possibly due to the fluctuating flow of water. 相似文献
29.
Stuart G. Fisher Nancy B. Grimm Eugènia Martí Robert M. Holmes Jeremy B. Jones Jr. 《Ecosystems》1998,1(1):19-34
Stream ecosystems consist of several subsystems that are spatially distributed concentrically, analogous to the elements
of a simple telescope. Subsystems include the central surface stream, vertically and laterally arrayed saturated sediments
(hyporheic and parafluvial zones), and the most distal element, the riparian zone. These zones are hydrologically connected;
thus water and its dissolved and suspended load move through all of these subsystems as it flows downstream. In any given
subsystem, chemical transformations result in a change in the quantity of materials in transport. Processing length is the length of subsystem required to “process” an amount of substrate equal to advective input. Long processing lengths
reflect low rates of material cycling. Processing length provides the length dimension of each cylindrical element of the
telescope and is specific to subsystem (for example, the surface stream), substrate (for instance, nitrate), and process (denitrification,
for example). Disturbance causes processing length to increase. Processing length decreases during succession following disturbance.
The whole stream-corridor ecosystem consists of several nested cylindrical elements that extend and retract, much as would
a telescope, in response to disturbance regime. This telescoping ecosystem model (TEM) can improve understanding of material
retention in running water systems; that is, their “nutrient filtration” capacity. We hypothesize that disturbance by flooding
alters this capacity in proportion to both intensity of disturbance and to the relative effect of disturbance on each subsystem.
We would expect more distal subsystems (for example, the riparian zone) to show the highest resistance to floods. In contrast,
we predict that postflood recovery of functions such as material processing (that is, resilience) will be highest in central
elements and decrease laterally. Resistance and resilience of subsystems are thus both inversely correlated and spatially
separated. We further hypothesize that cross-linkages between adjacent subsystems will enhance resilience of the system as
a whole. Whole-ecosystem retention, transformation, and transport are thus viewed as a function of subsystem extent, lateral
and vertical linkage, and disturbance regime.
Received 15 April 1997; accepted 1 September 1997. 相似文献
30.
Camilla Fonseca Silva Luciana Guimarães Keyller Bastos Borges Clebio Soares Nascimento Jr. 《Chirality》2020,32(1):53-63
Dinotefuran is a low-cost agrochemical considered a highly toxic product. In this sense, there is a need for its constant environmental, biological, and food control, aiming to ensure its use to humans as well as to preserve biodiversity and ecosystems. In the present work, we developed an experimental and theoretical method for dinotefuran chiral discrimination. According to the main results, the dinotefuran enantioselective separation was efficiently optimized by high-performance liquid chromatography evaluating the influence of different percentage compositions in the mobile phase to improve the resolution of the peaks in the chromatogram. The novelty of this work was the proposition of a reduced molecular model for the chiral selector amylose-Tris-(3,5-dimethylphenylcarbamate) polysaccharide that was able to adequately describe at the molecular level its interaction with the dinotefuran enantiomers. Besides, the thermodynamic and structural parameters obtained via density functional theory calculations pointed out the chiral discrimination as well as the enantiomeric elution order of the analyte studied, confirming the experimental data, thus validating our proposed method. Finally, hydrogen bonds and repulsive interactions played a key role in the discrimination between the diastereomeric complexes, and consequently, for the dinotefuran enantioselective separation. 相似文献