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Cord blood levels of transferrin (Tf) and insulin-like growth factor I (IGF-1) were measured in 33 normal and 12 preterm infants. Tf was measured by the single radial immunodiffusion technique, while IGF-1 was measured by specific RIA. Tf levels in normal term infants (195 +/- 27 mg/dl) were significantly below normal adult levels (261 +/- 12 mg/dl). Tf levels in preterm infants (159 +/- 30 mg/dl) were lower than those in normal term infants. Tf levels showed a positive correlation with birth length, weight, gestational age and albumin levels in all infants. There was no correlation between Tf and IGF-1 levels in term and preterm infants.  相似文献   

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The coevolutionary dynamics between European bitterling Rhodeus amarus and freshwater unionid mussels, which the former parasitize by laying eggs on their gills, were tested. In a series of experiments fish preferences and mussel responses were compared in parasites and hosts of recent (Europe) and ancient (Asia) sympatry. Rhodeus amarus readily oviposited on the gills of all mussel species tested. Fish that laid their eggs on the gills of Asian Anodonta woodiana, however, suffered a dramatic reduction in reproductive success compared to fish that oviposited on the gills of European mussels: Unio pictorum , Unio tumidus , Anodonta anatina and Anodonta cygnea . This difference was the result of egg ejection behaviour by mussels rather than the unsuitability of the internal gill environment for European bitterling embryo development. The ejection response of mussels with a long sympatry with European bitterling was considerably more pronounced than that of mussels with a substantially shorter sympatry. The data support a coevolutionary arms race between bitterling and mussels and point to an evolutionary lag in the relationship between R. amarus and its European mussel hosts.  相似文献   

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《Phytochemistry》1987,26(4):975-978
A 10-day time-course study on the production of 2,7-dihydroxycadalene, 2-hydroxy-7-methoxycadalene, lacinilene C and lacinilene C 7-methyl ether in cotton leaves induced by cell-free mycelial extracts of Aspergillus flavus showed that the cadalenes and the lacinilenes accumulate in a cyclic fashion. The initial increase at 2 days is followed by a greater increase at 6 days after treatment. The location of these compounds was found predominately either in a 6 mm wounded, treated area or in a 3 mm area immediately surrounding the 6 mm treated area of the leaf. Lacinilene C and lacinilene C 7-methyl ether were both phytotoxic in a Lemna minor bioassay. Endogenous constituents produced by plant cell damage could have triggered the production of the cadalenes and lacinilenes observed.  相似文献   

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Synopsis Certain components of dentition — teeth on the third basibranchial in the Centrarchidae and on the parasphenoid in the anabantoids (sensu lato) — are very rare elsewhere in higher teleostean fishes. Though these basibranchial and parasphenoid teeth in the two fish groups are on opposite sides of the oral cavity, it is hypothesized that they both developed as adaptations for gripping a particular category of food items, namely strong-clawed, hard-shelled, active animals that, once within the oral cavity, would try to crawl out again. A corollary to this hypothesis is that higher teleosts with extensive dentition in the central part of the oral cavity have a grasping jaw bite, which, unlike a piercing, shearing, or crushing jaw bite, does not necessarily kill the prey that is taken into the oral cavity.  相似文献   

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The intracellular invertase ofSaccharomyces cerevisiae is mainly found in a soluble form (91–95%), while only minor amounts are found bound to the internal (4–8%) and plasma membranes (less than 1%). In the processes of derepression or repression, inhibition of RNA or protein synthesis, or in the presence of 2-deoxy-d-glucose, the levels of the membrane-bound and external activities are modified in a way in which their relation is clear, while the soluble enzyme does not change at all. These results, together with the fact that the membrane-bound and the external enzymes are glycoproteins, suggest a precursor-product relationship between the enzymic forms.  相似文献   

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Winthout close phylogenetic ties to any of the other algae, the Euglenophyta are a taxonomic enigma. The argument is made here that the euglenophytes have extensive morphological homology with the zooflagellte trypanosomatids, bodonids, andIsonema. A phylogenetic sequence is postulated linking these group; the available data suggest that the euglenophytes had their origin in these zooflagellates and that the introduction of the chloroplast and a phototrophic mode of nutrition was a relatively late step in this evolutionary process.  相似文献   

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Background peptide chemistry, and the known 49-amino acid sequence of thymopoietin and the known 9-amino acid sequence of the facteur thymique serique (FTS) allowed the concept that Arg49 of thymopoietin might be linked to Gln1 of FTS in a new 58-amino acid peptide in tissue. Cleavage between Arg49 and Gln50 adjacent to the unique Lys48-Arg49 moiety could liberate thymopoietin and the [H-Gln1]-FTS which could cyclize to FTS by the known reaction. In support of, rather than negating, this concept, synthetic FTS and the new dodecapeptide consisting of Val-Lys-Arg linked to the N-terminal of [H-Gln1]-FTS showed comparable immune stimulating activity, in vivo; both peptides appeared more active than synthetic thymopoietin II.  相似文献   

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