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81.
S. J. Tzartos M. T. Cung P. Demange H. Loutrari A. Mamalaki M. Marraud I. Papadouli C. Sakarellos V. Tsikaris 《Molecular neurobiology》1991,5(1):1-29
Myasthenia gravis (MG) is caused by autoantibodies against the nicotinic acetylcholine receptor (AChR) of the neuromuscular junction. The anti-AChR antibodies are heterogeneous. However, a small region on the extracellular part of the AChR alpha subunit, called the main immunogenic region (MIR), seems to be the major target of the anti-AChR antibodies, but not of the specific T-cells, in experimental animals and possibly in MG patients. The major loop of the overlapping epitopes for all testable anti-MIR monoclonal antibodies (MAbs) was localized within residues 67-76 (WNPADYGGIK for Torpedo and WNPDDYGGVK for human AChR) of the alpha subunit. The N-terminal half of alpha 67-76 is the most critical, Asn68 and Asp71 being indispensable for binding. Yet anti-MIR antibodies are functionally and structurally quite heterogeneous. Anti-MIR MAbs do not affect channel gating, but they are very potent in mediating acceleration of AChR degradation (antigenic modulation) in cell cultures and in transferring experimental MG in animals. Fab fragments of anti-MIR MAbs bound to the AChR prevent the majority of the MG patients' antibodies from binding to and causing loss of the AChR. Whether this inhibition means that most MG antibodies bind on the same small region or is a result of broad steric/allosteric effects is under current investigation. 相似文献
82.
D.H. Wong C.F. Runham L. C. DenHollander J.E. Kinnear 《Letters in applied microbiology》1991,12(5):161-163
A new, inexpensive, simple and rapid bioassay for sodium monofluoroacetate (compound 1080) was developed using bacteria. Two 1080-sensitive isolates ( Bacillus sp. DHW and Acinetobacter sp. DHW) from local aquatic environments were tested on different agar media using the disc diffusion technique. Both bacteria exhibited zones of growth inhibition surrounding the 1080 discs that were linearly proportional to the concentrations (log10 ) of 1080. Preliminary studies indicate that this technique can be used for assaying 1080 in environmental and biological samples. 相似文献
83.
84.
A test of root growth inhibition of spruce and beech roots, according to Lynch's procedure (1977), shows the inhibitory effects of soil solution extracted from the holorganic layers (Of2-Oh) under beech and spruce. Molecular gel filtration of soil solutions shows that the molecular weights vary over a wide range, from less than 100 to over 40,000 daltons. Chemical analysis, using CGC, HPLC and sometimes MS shows only negligible concentrations of simple aliphatic (C1-C5) and aromatic acids in the free state. Using the fraction scheme of Forsyth (1977) and the carbazole procedure, it is shown that uronic acids represent only a small percentage of the carboxylic acids, and have no inhibitory effects on root growth. By analogy with results of other authors, the presence of polycarboxylic acids in the soil solution are considered to be the main cause of root growth inhibition. 相似文献
85.
Haplotype analysis of the human apolipoprotein B mutation associated with familial defective apolipoprotein B100. 总被引:8,自引:2,他引:6 下载免费PDF全文
Haplotype analysis was conducted on the mutant allele of 14 unrelated subjects heterozygous for a mutation in the codon for amino acid 3500 of human apolipoprotein B100. This mutation is associated with defective binding of low-density lipoprotein to the low-density lipoprotein receptor and with moderate hypercholesterolemia. Ten markers were used for haplotyping: eight diallelic markers within the structural gene and two hypervariable loci flanking the gene. Seven of eight unequivocally deduced haplotypes were identical, and one revealed only a minor difference at one of the hypervariable loci. The genotypes of the six other affected subjects were consistent with this same assigned haplotype. These data are consistent with a common ancestral chromosome and provide no evidence for a recurrent mutation at this potentially hypermutable CG dinucleotide, despite the fact that this mutation is not rare. 相似文献
86.
87.
T. H. Lanthorn 《Amino acids》1994,6(3):247-260
Summary D-Cycloserine can enhance activation of the NMDA receptor complex and could enhance the induction of long-term potentiation (LTP). In animals and humans, D-cycloserine can enhance performance in learning and memory tasks. This enhancing effect can disappear during repeated administration. The enhancing effects are also lost when higher doses are used, and replaced by behavioral and biochemical effects like those produced by NMDA antagonists. It has been reported that NMDA agonists, applied before or after tetanic stimulation, can block the induction of LTP. This may be the result of feedback inhibition of second messenger pathways stimulated by receptor activation. This may explain the antagonist-like effects of glycine partial agonists like D-cycloserine. In clinical trials of D-cycloserine in age-associated memory impairment (AAMI) and Alzheimer's disease, chronic treatment provided few positive effects on learning and memory. This may be due to inhibition of second messenger pathways following chronic stimulation of the receptor complex. 相似文献
88.
Only a limited number of phenotypic tests are available for the differentiation of all 13 known hybridization groups (HG) of Aeromonas spp. These organisms have a wide spectrum of warm-blooded and cold-blooded hosts. In the present study, the maximum growth temperatures (tmax) of the most common HGs of Aeromonas spp. originating from human fecal samples, food, water, and healthy and diseased fish were determined with a plate-type continuous temperature-gradient incubator. We observed that determination of the tmax can be applied for differentiation of HG 1 from HG 2 and 3 (phenospecies A. hydrophila); HG 6 from HG 4, 5A, and 5B (phenospecies A. caviae); HG 7 from HG 8/10 (phenospecies A. sobria); and HG 11 from HG 8/10 (phenospecies A. veronii). HG 1, 4, 8/10, and 13 strains occurring also in human clinical samples had a high tmax, about 40°C or higher. Hybridization group 2, 3, 5A, and 5B strains, which in most cases originated from water or food, had tmax values in the range of about 36–39°C, while HG 6, 7, and 11 had tmax values in the range of about 33–37°C. Fish pathogenic strains of A. salmonicida subsp. salmonicida and subsp. achromogenes had the lowest tmax values from about 30 to 35°C.
Correspondence to: M.-L. Hdnninen 相似文献
89.
A new instrument for environmental monitoring, called at 1-Hz fluorometer, provides two modes of application. First, it enables
a quantitative determination of algal concentrations down to 20 ng/l. Second, it can be used as a biosensor for changes in
environmental conditions. The distinction between the signals from living chlorophyll-containing algae and other fluorescent
material is achieved by using two modulated light-sources resulting in a mean fluence rate of 200 μE. The measuring light
induces changes in chlorophyll fluorescence (yield) with a frequency of 1 kHz, and the actinic light modulates the redox state
of the quenchers of PS II with a frequency of 1 Hz. This leads to a modulation of the yield which is detected by two phase-sensitive
rectifiers (double correlation). Measurements from different sites in a river, and in the Baltic and North Seas, show that
correction by the built-in simultaneously-measured attenuation is necessary in order to obtain values which are identical
with those determined by a photometric analysis (Uvikon 860). This applies if the transmission becomes less than about 95%.
Suspensions ofDunaliella salina exposed to ammonia and phosphate were used for illustrating the usage for environmental monitoring. It is shown that this
system can measure changes in the chlorophyll fluorescence of living algae caused by changes in concentration of ammonia down
to 1 μg/l and of phosphate down to 10 μg/l. 相似文献
90.