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11.
This paper reports on the mycorrhizal status of 82 plant species growing in traditionally managed grasslands in three different locations in the boreal and boreo-nemoral vegetation zone in the eastern part of Norway. Seventy-four species were found to have arbuscular mycorrhiza (AM). To our knowledge, we report AM for the first time in Achillea ptarmica, Ajuga pyramidalis, Alchemilla glaucescens, Carex brunnescens, Carex pallescens, Crepis praemorsa, Hieracium lactucella, Rumex longifolius, Scorzonera humilis, Trifolium aureum and Trifolium spadiceum. The rare and threatened species Arnica montana, S. humilis, C. praemorsa, Gentianella campestris, Parnassia palustris, T. aureum and T. spadiceum, all confined to grasslands, were found to possess AM fungi. 相似文献
12.
It is well accepted that neo-vascular formation can be divided into three main stages (which may be overlapping): (1) changes
within the existing vessel, (2) formation of a new channel, (3) maturation of the new vessel.
In this paper we present a new approach to angiogenesis, based on the theory of reinforced random walks, coupled with a Michaelis-Menten
type mechanism which views the endothelial cell receptors as the catalyst for transforming angiogenic factor into proteolytic
enzyme in order to model the first stage. In this model, a single layer of endothelial cells is separated by a vascular wall
from an extracellular tissue matrix. A coupled system of ordinary and partial differential equations is derived which, in
the presence of an angiogenic agent, predicts the aggregation of the endothelial cells and the collapse of the vascular lamina,
opening a passage into the extracellular matrix. We refer to this as the onset of vascular sprouting. Some biological evidence
for the correctness of our model is indicated by the formation of teats in utero. Further evidence for the correctness of
the model is given by its prediction that endothelial cells will line the nascent capillary at the onset of capillary angiogenesis.
Received: 27 May 1999 / Revised version: 28 December 1999 / Published online: 16 February 2001 相似文献
13.
Summary We have determined the DNA sequence of a BALB/cTla region class I gene from the major histocompatibility complex (MHC) that had been identified previously as encoding a murine antigen by DNA-mediated gene transfer. Analysis of the DNA sequence shows, however, that this gene, the T1c gene from theTla
c genotype, could not encode a TL antigen or any other functional class I molecule due to the presence of numerous stop codons and frameshift mutations in the coding regions. This result suggests that the earlier transformation data may have been incorrect or perhaps that the clone containing the T1c gene contains sequences that induced expression of a serologically reactiveTla gene in the genome of the recipient L cell. The T1c gene is structurally related to the previously sequenced T13c gene that encodes a serologically defined TL antigen. The 3 half of the T1c gene including exons 4, 5, 6, and the 3 untranslated region has about 85% nucleotide similarity (including introns) with the corresponding parts of the T13c gene; however, the 5 half of the T1c gene has little homology with the T13c gene. There is a sharp line of demarcation between the homologous and nonhomologous regions, and this border occurs precisely at a B2 Alu repeat sequence present in the T13c gene. This suggests that a recombination event took place here and that an Alu repeat sequence that is known to have characteristics of transposable elements played some role in a recombination or gene conversion event. 相似文献
14.
15.
Peters GJ Adema AD Bijnsdorp IV Sandvold ML 《Nucleosides, nucleotides & nucleic acids》2011,30(12):1168-1180
Many drugs that are currently used for the treatment of cancer have limitations, such as induction of resistance and/or poor biological half-life, which reduce their clinical efficacy. To overcome these limitations, several strategies have been explored. Chemical modification by the attachment of lipophilic moieties to (deoxy)nucleoside analogs should enhance the plasma half-life, change the biodistribution, and improve cellular uptake of the drug. Attachment of a lipophilic moiety to a phosphorylated (deoxy)nucleoside analog will improve the activity of the drugs by circumventing the rate-limiting activation step of (deoxy)nucleoside analogs. Encapsulating drugs in nanoparticles or liposomes protects the drug against enzymatic breakdown in the plasma and makes it possible to get lipophilic compounds to the tumor site. In this review, we discuss the considerable progress that has been made in increasing the efficacy of classic (deoxy)nucleoside and fluoropyrimidine compounds by chemical modifications and alternative delivery systems. 相似文献
16.
Per Wallgren Inger Marit Brunborg Gunilla Blomqvist Gunnar Bergström Frida Wikström Gordon Allan Caroline Fossum Christine Monceyron Jonassen 《Acta veterinaria Scandinavica》2009,51(1):13
Background
Postweaning Multisystemic Wasting Syndrome (PMWS) is an emerging disease in pigs of multifactorial origin, but associated to porcine circovirus type 2 (PCV2) infection. PMWS was first diagnosed in Sweden at a progeny test station that received pigs aged five weeks from 19 different nucleus herds on the day after weaning. The objective of this study was to examine, for the first time in an index outbreak of PMWS, the relationship between PCV2 virus, antibodies to PCV2 and serum amyloid a (SAA) in sequentially collected serum samples from pigs with and without signs of PMWS. 相似文献17.
18.
Tania Kjellerup Lind Hanna Wacklin Jürgen Schiller Martine Moulin Michael Haertlein Thomas Günther Pomorski Marité Cárdenas 《PloS one》2015,10(12)
Supported lipid bilayers are widely used for sensing and deciphering biomolecular interactions with model cell membranes. In this paper, we present a method to form supported lipid bilayers from total lipid extracts of Escherichia coli by vesicle fusion. We show the validity of this method for different types of extracts including those from deuterated biomass using a combination of complementary surface sensitive techniques; quartz crystal microbalance, neutron reflection and atomic force microscopy. We find that the head group composition of the deuterated and the hydrogenated lipid extracts is similar (approximately 75% phosphatidylethanolamine, 13% phosphatidylglycerol and 12% cardiolipin) and that both samples can be used to reconstitute high-coverage supported lipid bilayers with a total thickness of 41 ± 3 Å, common for fluid membranes. The formation of supported lipid bilayers composed of natural extracts of Escherichia coli allow for following biomolecular interactions, thus advancing the field towards bacterial-specific membrane biomimics. 相似文献
19.
Marit Espe Raja Mansingh Rathore Zhen-Yu Du Bjørn Liaset Adel El-Mowafi 《Amino acids》2010,39(2):449-460
The current experiment aimed to study whether interactions with lipid metabolism possibly might explain the relative increased
liver weight obtained in fish fed sub-optimal methionine levels. A basal diet based on a blend of plant proteins which is
low in methionine (1.6 g Met/16 g N) was compared to a methionine adequate diet (2.2 g Met/16 g N) prepared by adding dl-methionine (2.4 g/kg) to the basal diet in the expense of wheat grain. Fish oil was used as the lipid source. The diets were
balanced in all nutrients except methionine. The diets were fed to Atlantic salmon (500 g BW) for a period of 3 months. Feed
intake did not differ, rendering the intake of all nutrients except methionine equal. Fish fed the low methionine diet had
an increased liver size relative to body weight, indicating fat deposition in the liver. Fish given the sub-optimal methionine
diet showed about six times higher fatty acid synthase (FAS) activity as compared to the fish fed the adequate methionine
diet, indicating a higher de novo lipogenesis. A significant rise in the liver 18:1 to 18:0 fatty acid ratios also supported
storage of lipids over fatty acid oxidation. Indeed, methionine limitation resulted in significantly higher TAG concentrations
in the liver. Sub-optimal dietary methionine also resulted in lower hepatic taurine concentrations and the total bile acids
concentrations were reduced in faeces and tended to be reduced in plasma. Taken together, our data show that salmon fed sub-optimal
methionine levels had increased relative liver weight and developed signs commonly described in the early stage of non-alcoholic
fatty liver disease in rodent models (increased FAS activity, changed fatty acid ratios and TAG accumulation). 相似文献
20.
Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm−2 , the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed. 相似文献