During implantation the embryo attaches to the endometrial surface and trophoblast traverses the uterine epithelium, anchoring in the uterine connective tissue. To determine whether trophoblast can facilitate invasion of the uterus by degrading components of normal uterine extracellular matrix, mouse blastocysts were cultured on a radio-labeled extracellular matrix that contained glycoproteins, elastin, and collagen. The embryos attached to the matrix, and trophoblast spread over the surface. Starting on day 5 of culture there was a release of labeled peptides into the medium. The radioactive peptides released from the matrix by the embryos had molecular weights ranging from more than 25,000 to more than 200. By day 7 there were areas where individual trophoblast cells had separated from one another, revealing the underlying substratum that was cleared of matrix. When trophoblast cells were lysed with NH(4)OH on day 8, it was apparent that the area underneath the trophoblast outgrowth had been cleared of matrix. Scanning electron microscopy and time-lapse cinemicrography confirmed that the digestion of matrix was highly localized, taking place only underneath the trophoblast, with no evidence of digestion of the matrix beyond the periphery of the trophoblast outgrowth. The sharp boundaries of degredation observed may be due to localized proteinase secretion by trophoblast, to membrane proteinases on the surface of trophoblast, or to endocytosis. Digestion of the matrix was not dependent on plasminogen, thus ruling out a role for plasminogen activator. Digestion was not inhibited by a variety of hormones and inhibitors, including progesterone, 17β-estradiol, leupeptin, EDTA, colchicine, NH(4)Cl, or ε-aminocaproic acid. This system of culturing embryos on extracellular matrix may be useful in determining the processes that regulate trophoblast migration and invasion into the maternal tissues during implantation.0 相似文献
The phytochrome nuclear gene family encodes photoreceptor proteins that
mediate developmental responses to red and far red light throughout the
life of the plant. From studies of the dicot flowering plant Arabidopsis,
the family has been modeled as comprising five loci, PHYA- PHYE. However,
it has been shown recently that the Arabidopsis model may not completely
represent some flowering plant groups because additional PHY loci related
to PHYA and PHYB of Arabidopsis apparently have evolved independently
several times in dicots, and monocot flowering plants may lack orthologs of
PHYD and PHYE of Arabidopsis. Nonetheless, the phytochrome nucleotide data
were informative in a study of organismal evolution because the loci occur
as single copy sequences and appear to be evolving independently. We have
continued our investigation of the phytochrome gene family in flowering
plants by sampling extensively in the grass family. The phytochrome nuclear
DNA data were cladistically analyzed to address the following questions:
(1) Are the data consistent with a pattern of differential distribution of
phytochrome genes among monocots and higher dicots, with homologs of PHYA,
B, C, D, and E present in higher dicots, but of just PHYA, B, and C in
monocots, and (2) what phylogenetic pattern within Poaceae do they reveal?
Results of these analyses, and of Southern blot experiments, are consistent
with the observation that the phytochrome gene family in grasses comprises
the same subset of loci detected in other monocots. Furthermore, for
studies of organismal phylogeny in the grass family, the data are shown to
provide significant support for relationships that are just weakly resolved
by other data sets.
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Camarodont sea urchins possess a rapidly evolving actin gene family whose
members are expressed in distinct cell lineages in a developmentally
regulated fashion. Evolutionary changes in the actin gene family of
echinoids include alterations in number of family members, site of
expression, and gene linkage, and a dichotomy between rapidly and slowly
evolving isoform-specific 3' untranslated regions. We present sequence
comparisons and an analysis of the actin gene family in two congeneric sea
urchins that develop in radically different modes, Heliocidaris
erythrogramma and H. tuberculata. The sequences of several actin genes from
the related species Lytechinus variegatus are also presented. We compare
the features of the Heliocidaris and Lytechinus actin genes to those of the
the actin gene families of other closely related sea urchins and discuss
the nature of the evolutionary changes among sea urchin actins and their
relationship to developmental mode.
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Partial 18S rRNA sequences of five chelicerate arthropods plus a
crustacean, myriapod, insect, chordate, echinoderm, annelid, and
platyhelminth were compared. The sequence data were used to infer phylogeny
by using a maximum-parsimony method, an evolutionary-distance method, and
the evolutionary-parsimony method. The phylogenetic inferences generated by
maximum-parsimony and distance methods support both monophyly of the
Arthropoda and monophyly of the Chelicerata within the Arthropoda. These
results are congruent with phylogenies based on rigorous cladistic analyses
of morphological characters. Results support the inclusion of the
Arthropoda within a spiralian or protostome coelomate clade that is the
sister group of a deuterostome clade, refuting the hypothesis that the
arthropods represent the "primitive" sister group of a protostome coelomate
clade. Bootstrap analyses and consideration of all trees within 1% of the
length of the most parsimonious tree suggest that relationships between the
nonchelicerate arthropods and relationships within the chelicerate clade
cannot be reliably inferred with the partial 18S rRNA sequence data. With
the evolutionary-parsimony method, support for monophyly of the Arthropoda
is found in the majority of the combinations analyzed if the coelomates are
used as "outgroups." Monophyly of the Chelicerata is supported in most
combinations assessed. Our analyses also indicate that the
evolutionary-parsimony method, like distance and parsimony, may be biased
by taxa with long branches. We suggest that a previous study's inference of
the Arthropoda as paraphyletic may be the result of (a) having two few
arthropod taxa available for analysis and (b) including long-branched taxa.
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Complete coding regions of the 18S rRNA gene of an enteropneust
hemichordate and an echinoid and ophiuroid echinoderm were obtained and
aligned with 18S rRNA gene sequences of all major chordate clades and four
outgroups. Gene sequences were analyzed to test morphological character
phylogenies and to assess the strength of the signal. Maximum- parsimony
analysis of the sequences fails to support a monophyletic Chordata; the
urochordates form the sister taxon to the hemichordates, and together this
clade plus the echinoderms forms the sister taxon to the cephalochordates
plus craniates. Decay, bootstrap, and tree-length distribution analyses
suggest that the signal for inference of dueterostome phylogeny is weak in
this molecule. Parsimony analysis of morphological plus molecular
characters supports both monophyly of echinoderms plus enteropneust
hemichordates and a sister group relationship of this clade to chordates.
Evolutionary parsimony does not support chordate monophyly.
Neighbor-joining, Fitch-Margoliash, and maximum-likelihood analyses support
a chordate lineage that is the sister group to an
echinoderm-plus-hemichordate lineage. The results illustrate both the
limitations of the 18S rRNA molecule alone for high- level phylogeny
inference and the importance of considering both molecular and
morphological data in phylogeny reconstruction.
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Effects of culturing medium on production and emission of volatiles by Pantoea agglomerans (Beijerinck 1888) Gavini et al. 1989 preparations and on attractiveness of the preparations to the Mexican fruit fly, Anastrepha ludens Loew, were investigated. Bacterial cultures in each of four biochemically different types of liquid media emitted different volatiles. Cultures in a medium containing uric acid as its primary nitrogen source emitted more ammonia and 2‐nonanone than the other media. We postulate that the high production of ammonia was because of uricase activity by this uricase (+) strain. Regardless of media type, supernatants emitted more volatiles than preparations containing cells that had been removed from whole cultures and put into distilled water. Attractiveness varied little with biochemical make‐up of the culturing medium although the uric acid and carbohydrate preparations were as a group more attractive than preparations made from the other two media. Supernatants and whole cultures generally were more attractive than cell preparations and non‐inoculated media. Bacteria grown in aqueous uric acid‐based media emitted volatiles similar but not identical to those emitted by bacteria grown on gel (agar or solid) uric acid‐based media in Petri plates. 相似文献
Abstract 1. The influence of infestation of the larval host plant Gentiana cruciata on the egg‐laying preferences of the xerophilous ecotype of Alcon Blue butterfly (Maculinea alcon) was studied in a semi‐dry grassland area (Aggtelek Karst Region, Northern Hungary). 2. We examined whether oviposition patterns of females differed when G. cruciata stems were uninfested compared with when they were infested by an aphid (Aphis gentianae) or a rust (Puccinia gentianae) species. 3. Females laid more than 90% of their eggs on fertile, uninfested G. cruciata stems, although these stems comprised only ~ 50% of the total stems available. Stems infested by aphids were similar to uninfested ones in properties that had a strong correlation with egg numbers, and yet there were significantly fewer eggs on infested stems than on intact ones. 4. Females never laid eggs on parts of Gentiana stems infested by aphids, and the presence of Lasius paralienus ants, which have a mutualistic interaction with Aphis gentianae, did not increase the repulsive effect of aphids. Infection of Gentiana by Puccinia did not influence the egg‐laying behaviour of females, even though the flowers and buds of infested stems exhibited a delayed development. 5. Aphid infestation can influence butterfly oviposition patterns through both direct and indirect effects. The presence of aphids directly excluded oviposition, but our data also indicated the possibility of an indirect effect of aphid infestation. Stems that had no aphids at the last egg counting, but were infested prior to it, had significantly fewer eggs than those that were never infested. 相似文献
The soils of the Pampas are thought to be generally non-contaminated but there is growing evidence of trace element accumulation at some specific sites. The goal of this study was to measure the current levels of the main Potentially Toxic Elements (PTE) in the top horizon and in specific soil profiles so that we would establish the baseline concentrations of these elements. Eighty-eight top soils and three soil profiles were sampled. The samples were acid digested. Arsenic, boron, barium, cadmium, cobalt, chromium, copper, lead, manganese, mercury, molybdenum, nickel, silver, selenium and zinc were determined with inductively coupled argon plasma emission spectrometry (ICPES).
All of the values found are within the normal range for uncontaminated soils as reported from several continents. Elements with high environmental risk potential are lower than the admissible range of the European Union and some of them are orders of magnitude lower than those of the United States Environmental Protection Agency (US-EPA) 501 levels. Potentially Toxic Elements contents increased with depth or showed a maximum concentration at the B2 horizon. This is related to the parent material and the pedogenetic processes but not to recent contamination. Soil profiles showed higher concentrations of PTE in clayey horizons. However, these relationships did not appear in top soil samples in any soil Great Group studied. The shown data establishes a baseline for PTE concentrations for Pampas soils. 相似文献
We report on the identification, molecular cloning, and characterization of
an alpha1,3 fucosyltransferase (alpha1,3FT) expressed by the nematode,
Caenorhabditis elegans . Although C. elegans glycoconjugates do not express
the Lewis x antigen Galbeta1-- >4[Fucalpha1-->3]GlcNAcbeta-->R,
detergent extracts of adult C.elegans contain an alpha1,3FT that can
fucosylate both nonsialylated and sialylated acceptor glycans to generate
the Lexand sialyl Lexantigens, as well as the lacdiNAc-containing acceptor
GalNAcbeta1-->4GlcNAcbeta1-- >R to generate GalNAcbeta1-->4
[Fucalpha1-->3]GlcNAcbeta1-->R. A search of the C.elegans genome
database revealed the existence of a gene with 20-23% overall identity to
all five cloned human alpha1,3FTs. The putative cDNA for the C.elegans
alpha1,3FT (CEFT-1) was amplified by PCR from a cDNA lambdaZAP library,
cloned, and sequenced. COS7 cells transiently transfected with cDNA
encoding CEFT-1 express the Lex, but not sLexantigen. The CEFT-1 in the
transfected cell extracts can synthesize Lex, but not sialyl Lex, using
exogenous acceptors. A second fucosyltransferase activity was detected in
extracts of C. elegans that transfers Fuc in alpha1,2 linkage to Gal
specifically on type-1 chains. The discovery of alpha-fucosyltransferases
in C. elegans opens the possibility of using this well-characterized
nematode as a model system for studying the role of fucosylated glycans in
the development and survival of C.elegans and possibly other helminths.
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