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991.
Christian E. W. Steinberg Sebastian Hss Rainer Brüggemann 《International Review of Hydrobiology》2002,87(1):121-133
Humic isolates have previously been shown to modulate the reproduction of the nematode, Caenorhabditis elegans Maupas . The aim of this study was to find out if a hormone‐like effect is an intrinsic feature of humic substances. Therefore, the same nematode bioassay was used with ten humic substances (XAD and/or reverse osmosis isolates). The results confirmed the hormone‐like effect of humic substances, nine isolates significantly increased the numbers of offspring per worm, one isolate did not modulate the reproduction of C. elegans. This effect occurred with XAD isolates and with reverse osmosis isolates as well. Thus, this effect is an intrinsic feature of humic substances. This reproduction modulating potential of humic substances may be due to alkylaromatics that are major structural and photo stable structural components, rather than to sterols that are only minor structural components. This is a new view about the direct interactions of humic with aquatic organisms. The effects haven been mathematically modeled by a simple approach, considering a hormone‐like effect (β) and a non‐hormone like effect, such as nutrient effect (α) on growth. The different effects observed can be interpreted in terms of trade‐offs between these two competing mode of actions. 相似文献
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This study focuses on the cytotoxic effects of fumonisin B1 (FB1) on both immortalised and immortalised and subsequently transfected normal human bronchial epithelial (NHBE) cells of human
origin using four bioassays. While the MTT, Neutral Red and hexosaminidase colorimetric assays showed little difference between
the toxic effects on the two related cell lines, the clonogenic assay, measuring cell survival and proliferation, indicated
that FB1 had a more toxic effect on the nontransfected cells. This kind ofin vitro approach using cells which retain many characteristics of normal cell growth and differentiation can go some way to developing
evaluation models for food safety in the case of mycotoxin contamination without resorting totally to whole animal testing.
Nevertheless, one or two cytotoxicity tests may be inadequate for a complete appraisal of toxic potential: rather, as wide
a range of methodologies as feasible should be employed initially before meaningful conclusions may be drawn. 相似文献
995.
Mary W. Marzke N. Toth K. Schick S. Reece B. Steinberg K. Hunt R. L. Linscheid K-N. An 《American journal of physical anthropology》1998,105(3):315-332
The activity of 17 hand muscles was monitored by electromyography (EMG) in three subjects during hard hammer percussion manufacture of Oldowan tools. Two of the subjects were archaeologists experienced in the replication of prehistoric stone tools. Simultaneous videotapes recorded grips associated with the muscle activities. The purpose of the study was to identify the muscles most likely to have been strongly and repeatedly recruited by early hominids during stone tool-making. This information is fundamental to the identification of skeletal features that may reliably predict tool-making capabilities in early hominids. The muscles most frequently recruited at high force levels for strong precision pinch grips required to control the hammerstone and core are the intrinsic muscles of the fifth finger and the thumb/index finger regions. A productive search for skeletal evidence of habitual Oldowan tool-making behavior will therefore be in the regions of the hand stressed by these intrinsic muscles and in the joint configurations affecting the relative lengths of their moment arms. Am J Phys Anthropol 105:315–332, 1998. © 1998 Wiley-Liss, Inc. 相似文献
996.
Moshe Shemesh Avshalom Tam Miriam Kott-Gutkowski Mark Feldman Doron Steinberg 《BMC microbiology》2008,8(1):236
Background
A biofilm is a complex community of microorganisms that develop on surfaces in diverse environments. The thickness of the biofilm plays a crucial role in the physiology of the immobilized bacteria. The most cariogenic bacteria, mutans streptococci, are common inhabitants of a dental biofilm community. In this study, DNA-microarray analysis was used to identify differentially expressed genes associated with the thickness of S. mutans biofilms. 相似文献997.
Melinda A. Coleman Gaynor Dolman Brendan P. Kelaher Peter D. Steinberg 《Conservation Genetics》2008,9(4):1015-1017
Habitat-forming macroalgae play a central role in the ecology of temperate reefs worldwide but there exists a critical lack
of knowledge about important processes such as dispersal and gene flow. Understanding dispersal and gene flow of habitat-forming
seaweeds is particularly pertinent given that loss of habitat-forming algae is an increasingly prevalent problem worldwide.
Here, we develop 10 microsatellite markers for the monotypic Phyllospora comosa, an important habitat-forming macroalga that has undergone massive declines on urbanised coastlines of Sydney, Australia.
We characterise population genetic diversity and structure and estimate levels of dispersal and gene flow between the geographically
isolated northern and southern populations in this subtidal macroalga. 相似文献
998.
Azevedo AL Nascimento CS Steinberg RS Carvalho MR Peixoto MG Teodoro RL Verneque RS Guimarães SE Machado MA 《Genetics and molecular research : GMR》2008,7(3):623-630
Frequencies of kappa-casein gene alleles were determined in 1316 animals from the Brazilian Bos indicus genetic groups (Sindhi cows, Gyr sires, Gyr cows, Guzerat sires, Guzerat cows, Nellore sires, and Gyr x Holstein crossbreds) by means of polymerase chain reaction-restriction fragment length polymorphism analysis using two independent restriction nucleases (Hinf I and HaeIII). The genotyping of kappa-casein alleles (A and B) is of practical importance, since the B allele is found to correlate with commercially valuable parameters of cheese yielding efficiency. The frequencies of the B allele of kappa-casein among breeds ranged from 0.01 to 0.30. The Sindhi breed had the highest frequency for the B allele (0.30), while the frequencies of this allele in other breeds ranged from 0.01 to 0.18. A wide variation in the B allele frequency among B. indicus breeds was found suggesting that molecular selection for animals carrying the B allele could impact breeding programs for dairy production. 相似文献
999.
Role of vascular endothelial growth factor in the stimulation of cellular invasion and signaling of breast cancer cells. 总被引:25,自引:0,他引:25
The expression of vascular endothelial growth factor (VEGF) by breast tumors has been previously correlated with a poor prognosis in the pathogenesis of breast cancer. Furthermore, VEGF secretion is a prerequisite for tumor development. Although most of the effects of VEGF have been shown to be attributable to the stimulation of endothelial cells, we present evidence here that breast tumor cells are capable of responding to VEGF. We show that VEGF stimulation of T-47D breast cancer cells leads to changes in cellular signaling and invasion. VEGF increases the cellular invasion of T-47D breast cancer cells on Matrigel/ fibronectin-coated transwell membranes by a factor of two. Northern analysis for the expression of the known VEGF receptors shows the presence of moderate levels of Flt-1 and low levels of Flk-1/KDR mRNAs in a variety of breast cancer cell lines. T-47D breast cancer cells bind 125I-labeled VEGF with a Kd of 13 x 10(-9) M. VEGF induces the activation of the extracellular regulated kinases 1,2 as well as activation of phosphatidylinositol 3'-kinase, Akt, and Forkhead receptor L1. These findings in T-47D breast cancer cells strongly suggest an autocrine role for VEGF contributing to the tumorigenic phenotype. 相似文献
1000.