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1.
The sheep immunoglobulin heavy chain Igh-J locus has been characterized in order to determine the genomic organization of JH segments and their contribution to heavy chain diversity. The locus contains six segments, of which two are functional and
four are apparently pseudogenes. These segments span a 1.8 kilobase (kb) region. The distance between JH-ps4 (the 3′-most segment) and the first domain of the μ-chain encoding constant gene is about 5 kb. The two functional JH segments have a standard upstream recombination signal sequence, including heptamer and nonamer sequences separated by a
22–23 nucleotide spacer, and end with a RNA donor splice site. These two segments possess all the characteristic JH invariant residues and are found in expressed μ heavy chain variable regions. The 5′ functional JH1 segment is used in more than 90% of the cDNAs sequenced to date. The contribution of JH segment germline multiplicity to variable regions diversity appears therefore to be minimal. Comparison with other mammalian
JH segments shows that all loci are very closely related and probably have evolved from a common ancestral locus.
Received: 19 November 1996 / Revised: 17 March 1997 相似文献
2.
M. E. Manetti M. Rossi M. Nakabashi M. A. Grandbastien Marie Anne Van Sluys 《Molecular genetics and genomics : MGG》2009,281(3):261-271
Eukaryotic genome expansion/retraction caused by LTR-retrotransposon activity is dependent on the expression of full length
copies to trigger efficient transposition and recombination-driven events. The Tnt1 family of retrotransposons has served
as a model to evaluate the diversity among closely related elements within Solanaceae species and found that members of the
family vary mainly in their U3 region of the long terminal repeats (LTRs). Recovery of a full length genomic copy of Retrosol
was performed through a PCR-based approach from wild potato, Solanum oplocense. Further characterization focusing on both LTR sequences of the amplified copy allowed estimating an approximate insertion
time at 2 million years ago thus supporting the occurrence of transposition cycles after genus divergence. Copy number of
Tnt1-like elements in Solanum species were determined through genomic quantitative PCR whereby results sustain that Retrosol in Solanum species is a low copy number retrotransposon (1–4 copies) while Retrolyc1 has an intermediate copy number (38 copies) in
S. peruvianum. Comparative analysis of retrotransposon content revealed no correlation between genome size or ploidy level and Retrosol
copy number. The tetraploid cultivated potato with a cellular genome size of 1,715 Mbp harbours similar copy number per monoploid
genome than other diploid Solanum species (613–884 Mbp). Conversely, S. peruvianum genome (1,125 Mbp) has a higher copy number. These results point towards a lineage specific dynamic flux regarding the history
of amplification/activity of Tnt1-like elements in the genome of Solanum species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Suchánková P Kubaláková M Kovárová P Bartos J Cíhalíková J Molnár-Láng M Endo TR Dolezel J 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,113(4):651-659
Isolation of mitotic chromosomes using flow cytometry is an attractive way to dissect nuclear genomes into their individual chromosomal components or portions of them. This approach is especially useful in plants with complex genomes, where it offers a targeted and hence economical approach to genome analysis and gene cloning. In several plant species, DNA of flow-sorted chromosomes has been used for isolation of molecular markers from specific genome regions, for physical mapping using polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH), for integration of genetic and physical maps and for construction of chromosome-specific DNA libraries, including those cloned in bacterial artificial chromosome vectors. Until now, chromosome analysis and sorting using flow cytometry (flow cytogenetics) has found little application in barley (2n = 14, 1C ∼ 5,100 Mbp) because of the impossibility of discriminating and sorting individual chromosomes, except for the smallest chromosome 1H and some translocation chromosomes with DNA content significantly different from the remaining chromosomes. In this work, we demonstrate that wheat–barley ditelosomic addition lines can be used to sort any arm of barley chromosomes 2H–7H. Thus, the barley genome can be dissected into fractions representing only about 6–12% of the total genome. This advance makes the flow cytogenetics an attractive tool, which may greatly facilitate genome analysis and gene cloning in barley. 相似文献
4.
The present study set out to elucidate the structure and function of the large subcuticular air sacs encountered in the gaster
of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). Gastral segments I, II, III, together with the anterior portion of segment IV, comprise the greater
volume of the gaster, and inside them, beneath the cuticle, are contained not only structures that extend throughout their
entire length, like the alimentary canal, and the nerve cord with its paired abdominal ganglia, situated near the cuticle
in the ventral side, but also the heart, which is actually a muscular and dorsally located blood vessel that pumps blood anteriorly,
toward the head of the hornet. The mentioned structures take up only a small volume of the gaster, while the rest is occupied
by air sacs and tracheal ducts that also extend longitudinally. Interposed between the two air sacs, there is a hard partition
and above it, at the center – a paired tracheal duct that extends the entire length of the air sacs. The endothelium of the
air sacs is very anfractuous, thereby enlarging and strengthening the surface area. In each gastral segment there is an aperture
for the entry of air, namely, a spiracle. Additionally, in each segment, in the antero-lateral aspect of its tergum and situated between two successive
segments, there is an intersegmental conjunctive bearing parallel slits of 1–2 microM in width and 10–30 microM in length.
The latter are arranged concentrically around bundles of tracheae that traverse the cuticle from segment to segment. From
the upper rims of the slits are suspended downward fringe-like structures or "shutters" ranging between 3–10 microM in length.
We discuss the possibility that the Oriental hornet resorts to internal circulation of air, along with a thermoelectric heat
pump mechanism, in order to achieve cooling and thermoregulation of its body. 相似文献
5.
The complementary fragments of human Hb α, α1–30, and α31–141 are spliced together by V8 protease in the presence of 30%n-propanol to generate the full-length molecule (Hb α-semisynthetic reaction). Unlike the other protease-catalyzed protein/peptide
splicing reactions of fragment complementing systems, the enzymic condensation of nonassociating segments of Hb α is facilitated
by the organic cosolvent induced α-helical conformation of product acting as the “molecular trap” of the splicing reaction.
The segments α24–30 and α31–40 are the shortest complementary segments that can be spliced by V8 protease. In the present study, the chemistry of the contiguous
segment (product) α24–40 has been manipulated by engineering the amino acid replacements to the positions α27 and α31 to delineate the structural basis of the molecular trap. The location of Glu27 and Arg31 residues in the contiguous segment α24–40 (as well as in other larger segments) is ideal to generate (i, i+4) side-chain carboxylate-guanidino interaction in its α-helical conformation. The amino acid residue replacement studies
have confirmed that the side chains at α27 and α31 facilitate the semisynthetic reaction. The relative influence of the substitute at these sites on the splicing reaction depends
on the chemical nature of the side chain and the location. The γ-carboxylate guanidino side-chain interaction appears to contribute
up to a maximum of 85% of the thermodynamic stability of the molecular trap. The studies also demonstrate that the thermodynamic
stability of the molecular trap is determined by two interdependent conformational aspects of the peptide. One is an amino
acid-sequence-specific event that facilitates the induction of an α-helical conformation to the contiguous segment in the
presence of organic cosolvent that imparts some amount of protease resistance to Glu30-Arg31 peptide bond. The second structural aspect is a site-specific event, ani, i+4 side-chain interaction in the α-helical conformation of the peptide which imparts an additional thermodynamic stability
to the molecular trap. The results suggest that conformationally driven “molecular traps” of protease-mediated ligation reactions
of peptides could be designed into products to facilitate the modular assembly of peptides/proteins. 相似文献
6.
The complementary fragments of human Hb α, α1–30, and α31–141 are spliced together by V8 protease in the presence of 30%n-propanol to generate the full-length molecule (Hb α-semisynthetic reaction). Unlike the other protease-catalyzed protein/peptide
splicing reactions of fragment complementing systems, the enzymic condensation of nonassociating segments of Hb α is facilitated
by the organic cosolvent induced α-helical conformation of product acting as the “molecular trap” of the splicing reaction.
The segments α24–30 and α31–40 are the shortest complementary segments that can be spliced by V8 protease. In the present study, the chemistry of the contiguous
segment (product) α24–40 has been manipulated by engineering the amino acid replacements to the positions α27 and α31 to delineate the structural basis of the molecular trap. The location of Glu27 and Arg31 residues in the contiguous segment α24–40 (as well as in other larger segments) is ideal to generate (i, i+4) side-chain carboxylate-guanidino interaction in its α-helical conformation. The amino acid residue replacement studies
have confirmed that the side chains at α27 and α31 facilitate the semisynthetic reaction. The relative influence of the substitute at these sites on the splicing reaction depends
on the chemical nature of the side chain and the location. The γ-carboxylate guanidino side-chain interaction appears to contribute
up to a maximum of 85% of the thermodynamic stability of the molecular trap. The studies also demonstrate that the thermodynamic
stability of the molecular trap is determined by two interdependent conformational aspects of the peptide. One is an amino
acid-sequence-specific event that facilitates the induction of an α-helical conformation to the contiguous segment in the
presence of organic cosolvent that imparts some amount of protease resistance to Glu30-Arg31 peptide bond. The second structural aspect is a site-specific event, ani, i+4 side-chain interaction in the α-helical conformation of the peptide which imparts an additional thermodynamic stability
to the molecular trap. The results suggest that conformationally driven “molecular traps” of protease-mediated ligation reactions
of peptides could be designed into products to facilitate the modular assembly of peptides/proteins. 相似文献
7.
Yukihiro Chiba 《Ecological Research》1991,6(1):21-28
Ramification in tree structure was investigated by the main axis cutting method, which differs from the ordinary stratified
clipping method. An axis running from the arbitrary terminal leader of the shoot to the stem base was termed the “main axis”.
Cutting the main axis into pieces of constant length gives the “segment layer”, which consists of segments of the main axis
and all branches and leaves diverging from the respective segments. There was a linear relationship between the weight of
a main axis segment (in the range where leaves exist) of constant length and that of all the parts above the segment. Since
plant form is determined by branches diverging regularly from the mother branch or stem, this linear relationship is considered
to support the concept of the pipe model theory. It is also suggested that the proportionality constant of the linear relationship
may specify the branching structure or ramifications of plant form. 相似文献
8.
V. B. Meyer-Rochow W. A. Reid 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(5):319-324
Fifty randomly selected publications dealing with aspects of crustacean vision had their Materials and methods sections examined. In half of the articles gleaned, only the name of the animal under study was given; the other half mentioned
“adult” or “mature” animals; twelve papers provided information on size or age of the experimental animal and six gave the
sex. In Petrolisthes elongatus, rhabdom microvilli not only become more regular in outline as the animal grows, but also decrease in diameter from 90.4±21.2 nm
in crabs of 5.0–8.9 mm carapace length via 86.6±13 nm in crabs of 9.0–12.9 mm carapace length to 79.7±7 nm in crabs of 13.0–16.9 mm
carapace length. Approximately 400 cross sectional diameters of microvilli from identical regions in four eyes of each size
class were measured and provided the basis for Anova-, Levene-, and t-tests. The three size classes possess microvilli of significantly different diameters and standard deviations. Our observations
show that investigators of the crustacean photoreceptor have frequently neglected to consider the size of their experimental
animals, but that this practice should not be continued as the now documented changes in microvillus diameters may influence
the amount of visual pigment present and, thus, the photoreceptor’s sensitivity to light.
Accepted: 7 May 1996 相似文献
9.
Pavlov G Finet S Tatarenko K Korneeva E Ebel C 《European biophysics journal : EBJ》2003,32(5):437-449
The hydrodynamic characteristics of heparin fractions in a 0.2 M NaCl solution have been determined. Experimental values varied over the following ranges: the sedimentation coefficient (at 20.0 °C), 1.3<s0×1013<3.2 s; the Gralen coefficient (sedimentation concentration-dependence parameter), 10<ks<70 cm3 g–1; the translational diffusion coefficient, 3.9<D0×107<15.4 cm2 s–1; the intrinsic viscosity, 7.9<[]<40 cm3 g–1. Combination of
s0 with D0 using the Svedberg equation yielded molecular weights in the range 3.9<M×10–3<37 g mol–1. The value of the mass per unit length of the heparin molecule,
ML, was determined using the theory of hydrodynamic properties of a weakly bending rod, giving
ML=570±50 g nm–1 mol–1. The equilibrium rigidity, Kuhn segment length (A=9±2 nm) and hydrodynamic diameter (d=0.9±0.1 nm) of heparin were evaluated on the basis of the worm-like coil theory without the excluded volume effect, using the combination of hydrodynamic data obtained from fractions of different sizes. Small-angle X-ray scattering for three heparin fractions allowed an estimate for the cross-sectional radius of gyration as 0.43 nm; from the evolution with the macromolecule contour length of the radius of gyration, a value for the Kuhn segment length of 9±1 nm was obtained. A good correlation is thus observed for the conformational parameters of heparin from hydrodynamic and X-ray scattering data. These values describe heparin as a semi-rigid polymer, with an equilibrium rigidity that is essentially determined by a structural component, the electrostatic contribution being negligible in 0.2 M NaCl.Presented at the conference for Advances in Analytical Ultracentrifugation and Hydrodynamics, 8–11 June 2002, Grenoble, France 相似文献
10.
J. B. Wickham J. M. M. Brown 《European journal of applied physiology and occupational physiology》1998,78(3):219-225
The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within
the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of
the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical
segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a
cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder
joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic
(EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned
over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were
then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint
in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric
force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude
of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion
force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction.
Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed
the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that
segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid
can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications
normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at
least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task.
Accepted: 15 December 1997 相似文献
11.
W. H. Rimawi An. A. Ogrel J. Raap V. I. Shvets 《Russian Journal of Bioorganic Chemistry》2000,26(8):725-733
Analogues of 16-membered peptide antibiotic zervamicin IIB with the Gln3 and Gln11 residues15N-labeled at the Cα-atoms were synthesized by coupling the antibiotic segments (1–4), (5–9), and (10–16). In turn, these were
prepared by a stepwise chain elongation in solution starting from theirC-termini using benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP) as an activating agent. The sterically
hindered 2-aminoisobutyric acid was introduced by the BOP-dimethylaminopyridine system with the preactivation of the carboxyl
component. The segment condensation was performed with the use of the 6-trifluoromethylbenzotriazol-1-yloxy-tris(pyrrolidino)phosphonium
hexafluorophosphate activating reagent. The homogeneity of the resulting zervamicin analogues was confirmed by HPLC, and their
structures were proved by NMR spectroscopy and FAB mass spectrometry. 相似文献
12.
High Gradient Magnetic Separation (HGMS) is a rapid and straightforward technique that has previously been proven effective
in extracting erythrocytes from a flowing cell suspension if the red cell hemoglobin is in a paramagnetic state. In this work
it was applied to the enrichment of the small population (<2%) of splenocytes from an immune mouse that bound sheep red cells
to form rosettes. Samples flowed through the HGMS column in a strong magnetic field where rosettes and free sheep cells were
selectively retained. These were subsequently eluted by simply removing the magnetic field. The process required 20–30 min
per mouse spleen.
Rosettes in the initial sample and in the fractions that passed through, or were retained by, the column were enumerated under
the microscope. Under the conditions used here, the retained and eluted cells typically showed a 20–50-fold increase in the
frequency of rosetted cells, and the cells that passed through the magnet showed 90–100% depletion of rosettes. The recovery
of intact rosettes and the overall cell recovery were generally both in the range of 80–90%. 相似文献
13.
Summary An improved protocol for shoot regeneration from hypocotyl segments of seedlings from open-pollinated seeds of lingonberry
(Vaccinium vitis-idaea L.) cultivars, ‘Ida’, ‘Splendor’, and ‘Erntesegen’, and a native clone from Newfoundland was developed. The effect of thidiazuron
(TDZ) on adventitious bud and shoot formation from apical, central, and basal segments of the hypocotyl was tested. Highly
regenerative callus was obtained from hypocotyl segments on modified Murashige and Skoog (MMS) medium containing 5–10 μM TDZ. A maximum of 10 buds and 12 shoots per apical segment for seedlings of cultivar ‘Ida’ regenerated on MMS containing
10 μM TDZ. Callus and bud regeneration frequency, callus growth, and number of buds and shoots per regenerating explant depended
not only on the specific segment of the hypocotyl, but also on parental genotype. Inhibition of shoot elongation by TDZ was
overcome by transferring shoot cultures to a shoot proliferation medium containing 1–2 μM zeatin. The optimal concentration of sucrose for shoot elongation was 20 gl−1. Shoots were rooted ex vitro on a 2 peat: 1 perlite (v/v) medium after dipping in 0.8% indole-3-butyric acid, and rooted plants acclimatized readily under
greenhouse conditions. 相似文献
14.
A method for micropropagation ofDalbergia sissoo has been developed. Single node segments obtained from coppice shoots of a mature tree (20 – 25 year old) produced 3–4 shoots
per explant on Murashige and Skoog (MS) medium containing 4.4 x 10−6 M benzylaminopurine (BAP) and 4.4 × 10−7 M of Β-naphthoxy acetic acid (NOA) (shoot multiplication medium) within 4 weeks. Thein vitro regenerated shoots were 3 – 4 cm in length and provided 2 to 3 culturable nodal segments which on shoot multiplication medium
again produced 3–4 shoots. Following this procedure 18–24 shoots were produced from single nodal segment within 60 d. 80 %
of the shoots directly produced five roots when they were firstly treated with MS medium supplemented with 10−5 M indole-3-butyric acid (IBA) and subsequently transferred to half strength liquid MS medium containing 1 % activated charcoal
followed by half strength liquid MS free hormones, vitamins and activated charcoal. Thein vitro raised plants were hardened for survival after transplantation to soil by exposing them to various humidity conditions, gradually
from higher to low, with nearly 100 % transplant success.
Acknowledgement: Authors are grateful to CSIR and DST, New Delhi for financial assistance. 相似文献
15.
We have previously computed the structures of three loops, residues 591–596, 654–675 and 742–751, in the ras-p21 protein-binding
domain (residues 568–1044) of the guanine nucleotide-exchange-promoting SOS protein that were crystallographically undefined
when one molecule of ras-p21 (unbound to nucleotide) binds to SOS. Based on our computational results, we synthesized three
peptides corresponding to sequences of each of these three loops and found that all three peptides strongly inhibit ras-p21
signaling. More recently, a new crystal structure of SOS has been determined in which this protein binds to two molecules
of ras-p21, one unbound to GTP and one bound to GTP. In this structure, the 654–675 loop and residues 742–743 and 750–751
are now crystallographically defined. We have superimposed our energy-minimized structure of the ras-binding domain of SOS
bound to one molecule of ras-p21 on the X-ray structure for SOS bound to two molecules of ras-p21. We find that, while the
two structures are superimposable, there are large deviations of the residues 673 and 676 and 741 and 752, flanking the two
loop segments. This suggests that the binding of the extra ras-p21 molecule, which is far from each of the three loops, induces conformational changes
in these domains and further supports their role in signal transduction. In spite of these differences, we have superimposed our computed structures for the loop
residues on those from the more recent X-ray structure. Our structure for the 654–675 segment is an anti-parallel beta-sheet
with a reverse turn at residues 663–665; in the X-ray structure residues 655–662 adopt an alpha-helical conformation; on the
other hand, our computed structure for residues 663–675 superimpose on the X-ray structure for these residues. We further
find that our computed structures for residues 742–743 and 750–751 are superimposable on the X-ray structure for these residues. 相似文献
16.
W. Tao D. Liu J. Liu Y. Feng P. Chen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(3-4):564-568
Pm6 in bread wheat (Triticum aestivum L.), which was transferred from Triticum. timopheevii L., is a gene conferring resistance to the powdery mildew disease caused by Erysiphe graminis f. sp. tritici. Six near-isogenic lines ( NILs ) of Pm6 in a cultivar ’Prins’ background were analyzed to map this gene using restriction fragment length polymorphism (RFLP). Each
of the six NILs possessed a T. timopheevii-derived segment, varying in length, and associated with powdery mildew resistance. Lines IGV1–465 (FAO163b/ 7*Prins) and
IGV1–467 (Idaed 59B/7*Prins) had the shortest introgressed segments, which were detected only by DNA probes BCD135 and PSR934,
respectively. The polymorphic loci detected by both probes were mapped to the long arm of chromosome 2B. Lines IGV1–458 (CI13250/7*Prins)
and IGV1–456 (CI12559/8*Prins) contained the longest T. timopheevii segments involving both arms of donor chromosome 2G across the centromere. All these introgressed segments had an overlapping
region flanked by the loci xpsr934 and xbcd135 on 2BL. Thus, Pm6 was located in this region since the powdery mildew resistance in all the NILs resulted from the introgressed fragments.
Using the F2 mapping population from a cross of IGV1–463 (PI170914/7*Prins)×Prins, Pm6 was shown to be closely linked to the loci xbcd135 and xbcd266 at a genetic distance of 1.6 cM and 4.8 cM, respectively. BCD135 was successfully used in detecting the presence of Pm6 in different genetic backgrounds.
Received: 29 June 1999 / Accepted: 6 July 1999 相似文献
17.
The voltage-gated Na+ channel of Bacillus halodurans (NaChBac) is composed of six transmembrane segments (S1–S6), with a pore-forming region composed of segments S5 and S6 and
a voltage-sensing domain composed of segments S1–S4. The S4 segment forms the core of the voltage sensor. We explored the
accessibility of four arginine residues on the S4 segment of NaChBac, which are positioned at every third position from each
other. These arginine residues on the S4 segment were replaced with cysteines using site-directed mutagenesis. Na+ currents were recorded using the whole-cell configuration of the patch-clamp technique. We tested the effect of the sulfhydryl
reagents applied from inside and outside the cellular space in the open and closed conformations. Structural models of the
voltage sensor of NaChBac were constructed based on the recently crystallized KvAP and Kv1.2 K+ channels to visualize arginine residue accessibility. Our results suggest that arginine accessibility did not change significantly
between the open and closed conformations, supporting the idea of a small movement of the S4 segment during gating. Molecular
modeling of the closed conformation also supported a small movement of S4, which is mainly characterized by a rotation and
a tilt along the periphery of the pore. Interestingly, the second arginine residue of the S4 segment (R114) was accessible
to sulfhydryl reagents from both sides of the membrane in the closed conformation and, based on our model, seemed to be at
the junction of the intracellular and extracellular water crevices. 相似文献
18.
Michael C. Melnychuk David W. Welch Carl J. Walters Villy Christensen 《Hydrobiologia》2007,582(1):55-65
High mortality (65–73%) occurred in the first month of the smolt migration in a population of wild steelhead trout. We used
acoustic telemetry to monitor the downstream, estuarine, and early ocean migration of tagged smolts and estimate their mortality
rates. After entering the Strait of Georgia most smolts migrated north through Johnstone and Queen Charlotte Straits rather
than south through the Strait of Juan de Fuca. Of 51 smolts tagged in 2004 (49 in 2005), 36–38 (41–42) survived to leave freshwater
and 14–19 (13–14) survived to leave the Strait of Georgia system. Mortality rates in separate segments of the migration were
correlated with segment distances. An additional component of mobile sampling showed that few smolts died during the migration
through Howe Sound. Migration rates averaged 0.7–0.9 body lengths per second (BL s−1) downstream and 1.0–2.6 BL s−1 in ocean waters. Aggregated detection probabilities of 92–96% on lines of ocean receivers suggest that migration routes of
small fishes can be quantified over several hundred kilometres, and survival rates can be estimated for even a modest number
of tagged fish. Quantifying mortality patterns during the smolt migration could help to determine causes of low marine survival
rates observed in recent years. 相似文献
19.
The effects of temperature on the polar movement of IAA through6-mm and 12-mm segments of Zea mays roots have been investigatedover the range from 1 to 50°C. At all temperatures an acropetal polar movement of IAA predominated,although at low temperatures and at 50°C the 6-mm segmentsshowed a transient basipetal polarity, before the persistentacropetal polarity developed. At 1°C the differences betweenacropetal and basipetal movement of IAA were less distinct thanat the other temperatures. There is, however, a marked metabolically-dependentacropetal movement of IAA through the tissues at 1°C, becausewhen the segments were deprived of oxygen the acropetal movementwas severely reduced while the basipetal movement was reducedto a smaller extent. At 1°C and at 5°C there was alwaysa persistent basipetal polarity of IAA movement through 6-mmand 12-mm segments under anaerobic conditions. The velocity of acropetal movement (mm h1) was the samethrough the 6-mm and the 12-mm segments and was markedly affectedby temperature. It increased from 1°C to a maximum valueof 8 mm h1 at 31°C and then decreased again at 40and 50°C. The velocity of basipetal movement could be assessedonly at 1 and 5°C at which temperatures it was greater thanthe velocity of acropetal movement, and virtually independentof segment length. The acropetal flux of IAA (cpm h1) was much less through12-mm segments than through 6-mm segments. For both lengthsof segment, however, the flux showed a complex relationshipwith ambient temperature, increasing from 1°C to a maximumat 1015°C, declining to a minimum value at 31°Cand then rising again at 40 and 50°C. The basipetal fluxof IAA could be astimated only at 1 and 5°C at which itwas very much smaller than the acropetal flux. The amount of IAA in the receiver blocks increased linearlywith time at the lower temperatures. At temperatures withinthe range 15°C to about 31°C, however, the amount ofIAA in the receiver blocks began to decline if the transportperiods exceeded a certain length. The time at which this declinein the IAA in the receiver block began was related to the ambienttemperature. Chromatographic analysis indicated one radioactive substancein receiver blocks at the apical end of segments supplied withIAA-1-14C at the basal end after transport periods of 6 h at25°C, and 72 h at 5°C. The Rf of this substance wasclosely similar to that of the radioactive IAA supplied in thedonor blocks. 相似文献
20.
Freeze-fracturing of Funaria hygrometrica caulonema cells leads to a cleavage within the plasma membrane. The extraplasmatic and the plasmatic fracture faces differ in their particle density. The plasmatic fracture face in caulonema tip cells or in tip cells of side branches, but never in other caulonema cells, is further characterized by the occurrence of particle rosettes. The highest density of rosettes is found at the cell apex but decreases steeply toward the cell base. The shape of the rosettes varies remarkably; 20% of them are found in an incomplete, presumably disintegrating or aggregating state. The complete rosette has a diameter of about 25 nm and consists of five to six particles. The size of the single particles varies between 4 nm to 10 nm. The rosettes are thought to posses cellulose-synthase activity. It is assumed that one rosette produces one elementary fibril; rough calculations, considering the number of rosettes and the estimated amount of cellulose produced in the tip region, indicate that an elementary fibrillar length of 900 nm is formed in 1 min by one rosette. The consequence of the kinetics on the life-time of the rosettes and the cellulose-synthase activity are discussed.Abbreviations EF
extraplasmatic fracture face
- PF
plasmatic fracture face 相似文献