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1.
The population energetics of a temporary and a permanent pond population of Musculium partumeium in Southwest Ohio were studied. In the permanent pond (surface area = 396 m2, maximum depth = 0.7 m) the population was bivoltine and iteroparous whereas in the temporary pond (surface area = 1042 m2, maximum depth = 0.9 m) the population was usually univoltine and semelparous.Growth and biomass were assessed as total organic carbon and total nitrogen to provide estimates of productivity and seasonal changes in C:N for each generation. Productivity (non-respired assimilation = growth + reproduction; N-R.A. = G + R) was 6939 mgC·m–2·a–1 (3858 and 3353 mgC·m–2·a–1 for each generation) and 1661 mgC·m–2·a–1 for the permanent and temporary pond populations respectively. The average standing crop biomass (B) was 606.8 mgC·m–2 (357.5 and 249.3 mgC·m–2 for each generation) and 231.9 mgC·m–2 with overall productivity: biomass ratios of 11.4 and 7.2 for the permanent pond and temporary pond populations respectively.Respiration rates were converted to carbon equivalents (respired assimilation = R.A.) and used to evaluate the components of total assimilation (T.A. = R.A. + N-R.A.) and the efficiency of partitioning this energy to N-R.A. for G and R. When expressed as a percentage, the production efficiencies (100 × N-R.A.:T.A.) were 50.4 and 62%, and the reproductive efficiencies (100 × R:N-R.A.) were 26.4 and 18% for the permanent and temporary pond populations respectively. The reproductive efficiencies for populations of these viviparous clams are greater than those for most oviparous molluscs.The comparative information on the energetics of these populations does not completely fit any theoretical consideration of reproductive effort or life-history strategy. These data are discussed in relation to selection for population success in temporary ponds.Funded in part by grants to Albert J. Burky from the Ohio Biological Survey and the University of Dayton Research CouncilFunded in part by grants to Albert J. Burky from the Ohio Biological Survey and the University of Dayton Research Council 相似文献
2.
The effects of particle concentration and season on the filtration rates of the freshwater clamSphaerium striatinum Lamarck were assessed by measuring clearance rates of small (2.02 μm) latex beads from dilute suspensions. Filtration rates
decreased as particle concentration increased over a range of 2–64 mg 1−1, with rates decreasing in similar proportion for clams of all sizes. For a 1-mg clam, rates decreased from approximately
8.4 to 0.57 ml clam−1 h−1. Seasonal filtration rates for adult clams peaked during periods of greatest reproduction. The patterns for smaller clams
are similar, though proportional changes in filtration rates differ for various sizes of clams.
It is estimated that clams occupying 1 m2 of stream substrate removed about 3.67 gCa−1. This is equivalent to 0.0004% of the carbon that flows past them annually. Filter-feeding provided only 24% of the calculated
energy needs of the population, suggesting that another mode of feeding (e.g. deposit-feeding) may provide an important energy
source for these forms.
Funded in part by a grant-in-aid to D. J. Hornbach from Sigma-Xi, The Research Society.
Funded in part by a grant-in-aid to D. J. Hornbach from Sigma-Xi, The Research Society. 相似文献
3.
Dennis Way Mary Hendrix Marlys Witte Charles Witte Ray Nagle John Davis 《In vitro cellular & developmental biology. Plant》1987,23(9):647-652
Summary An endothelial cell line derived from a massive recurrent chyle-containing retroperitoneal lymphangioma was isolated in monolayer
culture. Scanning and transmission electron microscopy and immunohistochemistry confirmed a close resemblance to blood vascular
endothelium with typical cobblestone morphology, positive immunofluorescence staining for endothelial marker Factor VIII-associated
antigen and fibronectin, and prominent Weibel-Palade bodies. The endothelial cells also exhibited other ultrastructural features
characteristic of lymphatic endothelium, including sparse microvillous surface projections, overlapping intercellular junctions,
and abundant intermediate filaments. This endothelial cell line represents a new source of proliferating lymphatic endothelium
for future study, including structural and functional comparison to blood vascular endothelium.
Supported in part by Arizona Disease Control Research Commission contracts 8277-000000-1-1-AT-6625 and ZB-7492. Presented
in part at the 10th International Congress of Lymphology in Adelaide, Australia, August 1985. 相似文献
4.
5.
pp60
c-src
kinase activity can be increased by phosphotyrosine dephosphorylation or growth factor-dependent phosphorylation reactions. Expression of the transmembrane phosphotyrosine phosphatase (PTPase) CD45 has been shown to inhibit growth factor receptor signal transduction (Mooney, RA, Freund, GG, Way, BA and Bordwell, KL (1992) J Biol Chem 267, 23443–23446). Here it is shown that PTPase expression decreased platelet-derived growth factor (PDGF)-dependant activation of pp60
c-src
but failed to increase hormone independent (basal) pp60
c-src
activity. PDGF-dependent tyrosine phosphorylation of its receptor was reduced by approximately 60% in cells expressing the PTPase. In contrast, a change in phosphotyrosine content of pp60
c-src
was not detected in response to PDGF or in PTPase+cells. PDGF increased the intrinsic tyrosine kinase activity of pp60
c-src
in both control and PTPase+cells but the effect was smaller in PTPase+cells. In anin vitro assay, hormone-stimulate pp60
c-src
autophosphorylation from PTPase+ cells was decreased 64±22%, and substrate phosphorylation by pp60
c-src
was reduced 54±16% compared to controls. Hormone-independent pp60
c-src
kinase activity was unchanged by expression of the PTPase. pp60
c-src
was, however, anin vitro substrate for CD45, being dephosphorylated at both the regulatory (Tyr527) and kinase domain (Tyr416) residues. In addition,in vitro dephosphorylation by CD45 increased pp60
c-src
activity. These findings suggest that the PDGF receptor was anin vivo substrate of CD45 but pp60
c-src
was not. The lack of activation of pp60
c-src
in the presence of expressed PTPase may demonstrate the importance of compartmentalization and/or accessory proteins to PTPase-substrate interactions.Abbreviations PTPase
phosphotyrosine phosphatase
- PDGF
platelet-derived growth factor
- PMSF
phenylmethylsulfonyl fluoride
- LCA, CD45
leukocyte common antigen
- PBS
phosphate buffered saline
- SDS
sodium dodecyl sulfate
- PAGE
polyacrylamide gel electrophoresis
- DTT
dithiothreitol
- Na3VO4
sodium orthovanadate
- PV
pervanadate
- -ME
-mercaptoethanol 相似文献
6.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm-
blooded hosts by ixodid ticks. Frequency-dependent selection for variant
outer-surface proteins might be expected to arise in this species, since
rare variants are more likely to avoid immune surveillance in previously
infected hosts. We sequenced the OspA and OspB genes of nine North American
strains and compared them with nine strains previously described. For each
gene, the mean number of synonymous substitutions per synonymous site and
the mean number of nonsynonymous substitutions per nonsynonymous site show
only a twofold excess of silent mutations. Synonymous rates vary widely
along the OspB protein. Some regions show a significant excess of silent
substitutions, while divergence in other regions is constrained by biased
base composition or selection. The presence, in antigenically important
regions of the protein, of significant variation among strains, as well as
evidence for recombination among strains, should be considered in attempts
to develop vaccines against this disease.
相似文献
7.
Rapid detection of SVC virus antigen in infected cell cultures and clinically diseased carp by the enzyme-linked immunosorbent assay (ELISA) 总被引:2,自引:0,他引:2
K. Way 《Zeitschrift fur angewandte Ichthyologie》1991,7(2):95-107
An ELISA was developed using a rabbit antiserum with high levels of binding antibody against SVC virus (SVCV). Modifications were made to the standard assay which increased the sensitivity and resulted in a rapid ELISA (rELISA) which could détéct SVCV antigen in cell cultures and in extracts from infected carp in approximately 1 h. When other cell-grown fish rhabdoviruses were tested, pike fry rhabdovirus (PFRV) antigen cross-reacted in the rELISA but only at a low level. Virus antigen was détécted by the rELISA in clinically and sub-clinically diseased carp during an SVC epizootic but the sensitivity of détéction of subclinical levels of virus was not as great as that of isolation of infectious virus in cell culture. However, antigen was détécted in some fish extracts which failed to yield infectious virus. Fresh extracts of organs from healthy carp were found to give false positive reactions in the rELISA. Kidney and liver extracts from these fish were found to contain a heat labile, non-specific binding factor and further modification of the rapid assay was undertaken which successfully reduced the effect of this factor. 相似文献
8.
Telmatogeton torrenticola Terry is a large endemic chironomid (lastinstar >20 mm) commonly found in high gradient Hawaiian streams on smoothrock surfaces with torrential, shallow flow and in the splash zones ofwaterfalls. We have quantified benthic water flow in larval habitat in a 50m segment of Kinihapai Stream, Maui using a thermistor-based microcurrentmeter. Under base flow conditions at sites suitable for larval attachment,depth was measured and bottom water velocity measurements were made 2 mmabove populations. Larval densities ranged from 386.9–1178m–2, habitat bottom water velocities from 13.4–64.2 cms–1, and water depths from 1.5–50 cm. Bottom velocitiesof sites with zero larvae ranged from 20.8–21.8 cm s–1with depths from 50 to >160 cm. Larval densities were greatest inareas with high bottom water velocities and shallow depths. Stepwisemultiple regression analyses showed that density could be confidentlypredicted best by Froude number (r=0.81; p=0.008). In the absence of Froudenumber as a regression term, the best variable to predict larval density wasbottom velocity ratio: relative depth ratio (r=0.75; p=0.019). In addition,the torrential habitat of the larvae was always characterized by aperiphyton community that appeared to be the primary food resource for thelarvae. These data suggest that torrential flows over appropriate substratesare important factors regulating habitat availability for T. torrenticolaand that reduced discharge (e.g. affected by water diversions) couldsignificantly reduce the amount of available habitat for this organism andother flow sensitive stream fauna. 相似文献
9.
10.