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171.
Field observations in sublittoral Prince Edward Island, Canada, indicated that on a friable sandstone substratum Chondrus crispus was more commonly associated with Phymatolithon sp. than with bare rock. Thus, a substantial proportion of the population of Irish moss along the coast of Prince Edward Island occurs on this encrusting coralline. These observation may be explained on the basis of the relative stability of the substratum in contrast to other studies in which sloughing of epithallial cells by species of both Phymatolithon and Lithothamnium has been reported to limit epiphytism by fleshy macrophytes.Issued as NRCC 31426. 相似文献
172.
173.
Roscoe W Veitch GI Gong XQ Pellegrino E Bai D McLachlan E Shao Q Kidder GM Laird DW 《The Journal of biological chemistry》2005,280(12):11458-11466
Oculodentodigital dysplasia, a rare condition displaying congenital craniofacial deformities and limb abnormalities, has been associated with over 20 known human connexin43 (Cx43) mutations. The localization of two of these mutants, G21R and G138R, was examined in Cx43-positive normal rat kidney cells (NRK) and Cx43-negative gap junctional intercellular communication-deficient HeLa cells. Green fluorescent protein-tagged and untagged Cx43 G21R and G138R mutants were transported to the plasma membrane and formed punctate structures reminiscent of gap junction plaques in both NRK and HeLa cells. Further localization studies revealed no significant trafficking defects as subpopulations of Cx43 mutants were found in both the Golgi apparatus and lysosomes, not unlike wild-type Cx43. Dual patch clamp functional analysis of the mutants expressed in gap junctional intercellular communication-deficient N2A cells revealed that neither G21R nor G138R formed functional gap junction channels, although they successfully reached cell-cell interfaces between cell pairs. Importantly, when either mutant was expressed in NRK cells, dye coupling experiments revealed that both mutants inhibited endogenous Cx43 function. These studies suggest that, although patients suffering from oculodentodigital dysplasia possess one wild-type Cx43 allele, it is likely that Cx43-mediated gap junctional intercellular communication is reduced below 50% because of a dominant-negative effect of mutant Cx43 on wild-type Cx43. 相似文献
174.
175.
McLachlan E Manias JL Gong XQ Lounsbury CS Shao Q Bernier SM Bai D Laird DW 《Cell communication & adhesion》2005,12(5-6):279-292
Oculodentodigital dysplasia (ODDD) is associated with at least 28 connexin43 (Cx43) mutations. We characterized four of these mutants; Q49K, L90V, R202H, and V216L. Populations of these GFP-tagged mutants were transported to the cell surface in Cx43-negative HeLa cells and Cx43-positive NRK cells. Dual patch-clamp functional analysis in N2A cells demonstrated that channels formed by each mutant have dramatically reduced conductance. Dye-coupling analysis revealed that each mutant exhibits a dominant-negative effect on wild-type Cx43. Since ODDD patients display skeletal abnormalities, we examined the effect of three other Cx43 mutants previously shown to exert dominant-negative effects on wild-type Cx43 (G21R, G138R, and G60S) in neonatal calvarial osteoblasts. Differentiation was unaltered by expression of these mutants as alkaline phosphatase activity and extent of culture mineralization were unchanged. This suggests that loss-of-function Cx43 mutants are insufficient to deter committed osteoblasts from their normal function in vitro. Thus, we hypothesize that the bone phenotype of ODDD patients may result from disrupted gap junctional intercellular communication earlier in development or during bone remodeling. 相似文献
176.
A. J. McLachlan 《Hydrobiologia》1969,33(2):237-249
Summary A series of experiments were carried out to determine whether substrate selection could be demonstrated in the case of chironomid larvae of the species Nilodorum brevibucca Freeman in the absence of competition for food. Definite substrate preferences were exhibited. In particular, coarse sand was avoided, and this could be related to the suitability of the particles as a tube building material. In addition, the substrate affected the rate of migration and settlement of larvae. The application of these results to field distribution patterns of chironomid larvae has been considered.
Now at Biology Department, Chancellor College, University of Malawi. 相似文献
Zusammenfassung Eine Series von Experimenten wurde ausgeführt, um festzustellen, ob eine Auswahl von Substraten in Abwesenheit eines Wettstreits um Nahrung im Falle der Species Nilodorum brevibucca Freeman demonstreit werden kann. Es zeigte sich eindeutige Bevorzugung von Substraten. Grober Sand wurde besonders vermieden, was durch die Eignung der Partikel als Baumaterial für die Röhren bedingt sein könnte. Außerdem wurde die Wanderungsrate und die Ansiedlung von Larven durch das Substrat beeinträchtigt. Die Anwendung dieser Resultate auf das Verteilungsschema von Chironomiden-Larven im Feld wurde erwogen.
Now at Biology Department, Chancellor College, University of Malawi. 相似文献
177.
The synthesis of phosvitin in vitro by slices of liver from the laying hen 总被引:2,自引:1,他引:1
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1. Slices of liver from laying hens incorporated Na214CO3 and NaH232PO4 into phosvitin. Slices of liver from immature birds did not do so to any appreciable extent. The 32P was incorporated into O-phosphorylserine in the phosvitin molecule. 2. Kidney, spleen, muscle, large and small intestine, ovary and oviduct from laying birds did not incorporate Na214CO3 into phosvitin. 3. Slices of liver from laying hens carried out a net synthesis of phosphoprotein under the standard conditions of incubation. Slices from the livers of immature pullets did not do so. 4. Liver from the laying hen incorporated [2-14C]glycine, [3-14C]serine and [2-14C]glutamic acid into phosvitin. Part of the glycine was shown to be present as serine in the final product. 5. Slices of liver from immature birds treated with oestradiol synthesized phosvitin from [2-14C]glycine, but the addition of oestrogens in vitro to slices from untreated immature birds did not promote synthesis during a 3 hr. incubation period. 相似文献
178.
LILIAN JÄRVEKÜLG JÜRI SõBER RIIVO SINIJÄRV INDREK TOOTS MART SAARMA 《The Annals of applied biology》1989,114(2):279-291
Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double-antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots. MAbs against PVM were used as capture antibodies and europium-labelled MAbs as conjugates in time-resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10--4 with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double-label TRFIA using europium-labelled MAbs to PVM and samarium-labelled MAbs to PVX. 相似文献
179.
180.
Generation and characterization of novel antibodies highly selective for phosphorylated linked histone H1 in Tetrahymena and HeLa cells 总被引:4,自引:0,他引:4
M. Janice Lu Christopher A. Dadd Craig A. Mizzen Carolyn A. Perry Donald R. McLachlan Anthony T. Annunziato C. David Allis 《Chromosoma》1994,103(2):111-121
Phosphorylated forms of Tetrahymena macronuclear histone H1 were separated from each other and from dephosphorylated H1 by cation-exchange HPLC. A homogeneous
fraction of hyperphosphorylated macronuclear H1 was then used to generate novel polyclonal antibodies highly selective for
phosphorylated H1 in Tetrahymena and in human cells. These antibodies fail to recognize dephosphorylated forms of H1 in both organisms and are not reactive
with most other nuclear or cytoplasmic phosphoproteins including those induced during mitosis. The selectivity of these antibodies
for phosphorylated forms of H1 in Tetrahymena and in HeLa argues strongly that these antibodies recognize highly conserved phosphorylated epitopes found in most H1s and
from this standpoint Tetrahymena H1 is not atypical. Using these antibodies in indirect immunofluorescence analyses, we find that a significant fraction of
interphase mammalian cells display a strikingly punctate pattern of nuclear fluorescence. As cells enter S-phase, nuclear
staining becomes more diffuse, increases significantly, and continues to increase as cells enter mitosis. As cells exit from
mitosis, staining with the anti-phosphorylated H1 antibodies is rapidly lost presumably owing to the dephosphorylation of
H1. These immunofluorescent data document precisely the cell cycle changes in the level of H1 phosphorylation determined by
earlier biochemical studies and suggest that these antibodies represent a powerful new tool to probe the function(s) of H1
phosphorylation in a wide variety of eukaryotic systems.
Received: 3 August 1993; in revised form: 9 November 1993 / Accepted: 23 November 1993 相似文献