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NAM SO GREGORY E. MAES FILIP A. M. VOLCKAERT 《Biological journal of the Linnean Society. Linnean Society of London》2006,89(4):719-728
Larvae of the sutchi catfish Pangasianodon hypophthalmus were collected during peak downstream drift in the Lower Mekong river on four occasions over an 8-week period during the 2003 spawning season, and genotyped using seven microsatellite loci. We provide evidence for several heterogeneous groups within and among the temporally discrete larval peak samples. Strong evidence for a significant deficit of heterozygotes was observed for each larval sample and the pooled sample, possibly due to population admixture. Although individual-based assignment tests suggested that each larval peak sample was admixed, significant but low genetic differentiation was observed among larval samples ( F ST = 0.0052, P < 0.01). The lack of significant relatedness confirms the multifamily composition of each larval group, excluding family bias to explain the observed genetic heterogeneity. Both the entire larval peak and each temporally separated larval peak originated from spawning groups with heterogeneous allelic composition involving several distinct spawning events. We propose three explanations to account for our findings: (1) the ecological match/mismatch hypothesis; (2) the genetic 'sweepstakes' selection hypothesis; and (3) life-history-specific characteristics of the spawning populations. Finally, an intra-annual shift in the contribution of the spawning populations to the larval drift was detected on successive occasions. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 719–728. 相似文献
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The potential of Pseudomonas aeruginosa expressing the Vitreoscilla hemoglobin gene (vgb) for rhamnolipid production was studied. P. aeruginosa (NRRL B-771) and its transposon mediated vgb transferred recombinant strain, PaJC, were used in the research. The optimization of rhamnolipid production was carried out
in the different conditions of cultivation (agitation rate, the composition of culture medium and temperature) in a time-course
manner. The nutrient source, especially the carbon type, had a dramatic effect on rhamnolipid production. The PaJC strain
and the wild type cells of P. aeruginosa started producing biosurfactant at the stationary phase and its concentration reached maximum at 24 h (838 mg/l−1) and at 72 h (751 mg l−1) of the incubation respectively. Rhamnolipid production was optimal in batch cultures when the temperature and agitation
rate were controlled at 30°C and 100 rpm. It reached 8373 mg l−1 when the PaJC cells were grown in 1.0% glucose supplemented minimal media. Genetic engineering of biosurfactant producing
strains with vgb may be an effective method to increase its production. 相似文献
4.
Sang‐Sup SO Tae‐Hwan HWANG Waseem AKRAM Jhong‐Kyung CHOI Jong‐Jin LEE 《Entomological Research》2012,42(3):158-162
The present study relates to a methanol extract of the seed coat of Ginkgo biloba, and tested particularly on the third instar larvae of Spodoptera exigua. The extract was found to have an inhibitory effect on the growth of the larvae besides bringing a change in the nutrient reserves in the body of the insect. Topical application of five different doses of the methanol extract resulted in a mortal effect to third instar larvae of S. exigua that is very much dependent on the dose as well as duration of exposure. Lower doses revealed lower mortality after 24 h of application. At doses of 1.00, 2.00, 4.00, 8.00 and 16.00 ng/larva, mortalities were 9.25, 26.07, 50.32, 56.28 and 92.44%, respectively. The dose for 50% mortality (LD50) of methanol extracts by applied by a topical method with 1 µL of acetone solution was 1.92 ng/larva. Nutrient reserves like protein, glycogen and lipid are known to regulate pupation and adult emergence. These reserves have been found to be lower in treated larvae, indicating the insecticidal role of methanol extracts from G. biloba against third instar larvae of S. exigua. 相似文献
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RICLEF GROLLE MAY LING SO 《Botanical journal of the Linnean Society. Linnean Society of London》2003,142(2):229-235
Riccia fruticulosa O.F.Müll., 1782 from Norway is a valid name, referring to Riccardia palmata (Hedw.) Carruth. In 1785 Dickson misidentified British plants of a blue Metzgeria as R. fruticulosa . The European blue species of Metzgeria is conspecific with M. violacea (Ach.) Dumort., which replaces M. fruticulosa auct. The true origin of the type of Jungermannia violacea Ach., 1805 is probably Tierra del Fuego (rather than Dusky Bay, New Zealand), where the species is widespread. Reports from Australasia, Asia and Africa are all erroneous. The blue colour of Jungermanniales is found only in living plants and is derived from the oil-bodies. In contrast, that of Metzgeria appears only after death; its biological function is unknown. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142 , 229−235. 相似文献
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Abstract. 1. Larval rearing densities of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae) in standardized carrion were manipulated in order to investigate changes in life-history parameters in response to larval competition for food.
2. Competition was of the typical scramble type. Survivorship remained high at densities up to 32 larvae g liver-1 but decreased rapidly as larval density increased further.
3. Emergent adults were undersized with reduced fecundity and longevity. Variations in adult body size apparently reduced the effects of competition on larval mortality.
4. Females of dry weight corresponding to only 10.4% of the potential maximum emerged at the highest rearing densities of 128 larvae g liver-1. However, these females had a nearly four-fold increase in reproductive investment (per unit weight) when compared to the largest individuals.
5. The duration of larval development declined when competition was intense (i.e. at high larval densities).
6. The short adult life of H.ligurriens, combined with the unpredictability of larval habitat availability, may reduce the value of long-range dispersal so that females 'do better' by maintaining reproductive investment despite a concomitant decline in dispersal ability. 相似文献
2. Competition was of the typical scramble type. Survivorship remained high at densities up to 32 larvae g liver
3. Emergent adults were undersized with reduced fecundity and longevity. Variations in adult body size apparently reduced the effects of competition on larval mortality.
4. Females of dry weight corresponding to only 10.4% of the potential maximum emerged at the highest rearing densities of 128 larvae g liver-1. However, these females had a nearly four-fold increase in reproductive investment (per unit weight) when compared to the largest individuals.
5. The duration of larval development declined when competition was intense (i.e. at high larval densities).
6. The short adult life of H.ligurriens, combined with the unpredictability of larval habitat availability, may reduce the value of long-range dispersal so that females 'do better' by maintaining reproductive investment despite a concomitant decline in dispersal ability. 相似文献
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Sebnem O. Erenler Salih Gencer Hikmet Geckil Benjamin C. Stark Dale A. Webster 《Applied Biochemistry and Microbiology》2004,40(3):241-248
The hemoglobins found in unicellular organisms show a great deal of chemical reactivity, protecting cells against oxidative stress, and hence have been implicated in a wider variety of potential functions than those traditionally associated with animal and plant hemoglobins. There are well-documented studies showing that bacteria expressing Vitreoscilla hemoglobin (VHb), the first prokaryotic hemoglobin characterized, have better growth and oxygen uptake rates than their VHb counterparts. Here, the expression of VHb, its effect on the growth and antioxidant enzyme status of cells under different culture conditions was studied by cloning the complete regulatory and coding sequences (vgb) for VHb in Enterobacter aerogenes. Contrary to what has been reported for Escherichia coli, the expression of vgb in E.aerogenes decreased several fold under 10% of atmospheric oxygen (2% oxygen) and its growth was not greatly improved by the presence of VHb. Measured either as viable cells or total cell mass, untransformed E. aerogenes grew better than the recombinant strains. At the late exponential phase, however, the vgb-bearing strain was determined to have a higher cell number and total cell mass than the strain bearing only the plasmid vector with no vgb insert. The VHb expressing strain also had an oxygen uptake rate several fold higher than its counterparts. Given that oxidative stress may occur upon elevated oxygen exposure and be balanced by the action of antioxi-dative compounds, the level of antioxidative response of E. aerogenes expressing VHb was also studied. The VHb expressing strain had substantially (1.5–2.6-fold) higher catalase activity than strains not expressing VHb. Both VHb+ and VHb- strains, however, showed similar levels of superoxide dismutase activity. The activity of both enzymes was also growth phase dependent. Stationary phase cells of all strains showed 2–5-fold higher activity for these enzymes than cells at the exponential phase. 相似文献
8.
Differentiation-associated modulation of heparan sulfate structure and function in CaCo-2 colon carcinoma cells 总被引:3,自引:2,他引:1
Salmivirta M; Safaiyan F; Prydz K; Andresen MS; Aryan M; Kolset SO 《Glycobiology》1998,8(10):1029-1036
Heparan sulfate species expressed by different cell and tissue types differ
in their structural and functional properties. Limited information is
available on differences in regulation of heparan sulfate biosynthesis
within a single tissue or cell population under different conditions. We
have approached this question by studying the effect of cell
differentiation on the biosynthesis and function of heparan sulfate in
human colon carcinoma cells (CaCo-2). These cells undergo spontaneous
differentiation in culture when grown on semipermeable supports; the
differentiated cells show phenotypic similarity to small intestine
enterocytes. Metabolically labeled heparan sulfate was isolated from the
apical and basolateral media from cultures of differentiated and
undifferentiated cells. Compositional analysis of disaccharides, derived
from the contiguous N-sulfated regions of heparan sulfate, indicated a
greater proportion of 2-O- sulfated iduronic acid units and a smaller
amount of 6-O-sulfated glucosamine units in differentiated than in
undifferentiated cells. By contrast, the overall degree of sulfation, the
chain length and the size distribution of the N-acetylated regions were
similar regardless the differentiation status of the cells. The structural
changes were found to affect the binding of heparan sulfate to the long
isoform of platelet-derived growth factor A chain but not to fibroblast
growth factor 2. These findings show that heparan sulfate structures change
during cell differentiation and that heparan sulfate-growth factor
interactions may be affected by such changes.
相似文献
9.
Serglycin is the major proteoglycan in most hematopoietic cells, including
monocytes and macrophages. The monoblastic cell line U937-1 was used to
study the expression of serglycin during proliferation and differentiation.
In unstimulated proliferating U937-1 cells serglycin mRNA is
nonconstitutively expressed. The level of serglycin mRNA was found to
correlate with the synthesis of chondroitin sulfate proteoglycan (CSPG).
The U937-1 cells were induced to differentiate into different types of
macrophage-like cells by exposing the cells to PMA, RA, or VitD3. These
inducers of differentiation affected the expression of serglycin mRNA in
three different ways. The initial upregulation seen in the normally
proliferating cells was not observed in PMA treated cells. In contrast, RA
increased the initial upregulation, giving a reproducible six times
increase in serglycin mRNA level from 4 to 24 h of incubation, compared to
a four times increase in the control cells. VitD3 had no effect on the
expression of serglycin mRNA. The incorporation of (35S)sulfate into CSPG
decreased approximately 50% in all three differentiated cell types.
Further, the (35S)CSPGs expressed were of larger size in PMA treated cells
than controls, but smaller after RA treatment. This was due to the
expression of CSPGs, with CS-chains of 25 and 5 kDa in PMA and RA treated
cells, respectively, compared to 11 kDa in the controls. VitD3 had no
significant effect on the size of CSPG produced. PMA treated cells secreted
75% of the (35S)PGs expressed, but the major portion was retained in cells
treated with VitD3 or RA. The differences seen in serglycin mRNA levels,
the macromolecular properties of serglycin and in the PG secretion
patterns, suggest that serglycin may have different functions in different
types of macrophages.
相似文献
10.
Enhanced production of acetoin and butanediol in recombinant Enterobacter aerogenes carrying Vitreoscilla hemoglobin gene 总被引:2,自引:0,他引:2
Geckil H Barak Z Chipman DM Erenler SO Webster DA Stark BC 《Bioprocess and biosystems engineering》2004,26(5):325-330
Microbial production of butanediol and acetoin has received increasing interest because of their diverse potential practical uses. Although both products are fermentative in nature, their optimal production requires a low level of oxygen. In this study, the use of a recombinant oxygen uptake system on production of these metabolites was investigated. Enterobacter aerogenes was transformed with a pUC8-based plasmid carrying the gene (vgb) encoding Vitreoscilla (bacterial) hemoglobin (VHb). The presence of vgb and production of VHb by this strain resulted in an increase in viability from 72 to 96 h in culture, but no overall increase in cell mass. Accumulation of the fermentation products acetoin and butanediol were enhanced (up to 83%) by the presence of vgb/VHb. This vgb/VHb related effect appears to be due to an increase of flux through the acetoin/butanediol pathway, but not at the expense of acid production. 相似文献