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排序方式: 共有299条查询结果,搜索用时 15 毫秒
1.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
2.
The influence of several factors on the chemiluminescence (CL) activity of haemocytes from the Mediterranean mussel (Mytilus galloprovincialis) was studied. Haemocytes were stimulated in vitro with different concentrations of zymosan, phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS) (adding superoxide dismutase, SOD, to the zymosan-stimulated haemocytes in order to test the specificity of the reaction). The in vitro effect of the clam pathogens Vibrio tapetis (bacteria) and a Perkinsus atlanticus-like protozoan tentatively named Pseudoperkinsus taapetis on the mussel haemocytes CL response was also assessed. To study the in vivo stimulation of haemocytes, mussels were inoculated with zymosan and the CL response of their haemocytes was subsequently measured. Zymosan added in vitro produced the highest CL response, although PMA also enhanced the CL emission and, in addition, increased the zymosan-stimulated CL. LPS and V. tapetis did not activate haemocytes. SOD significantly decreased the CL emission in zymosan-stimulated haemocytes. P. tapetis cells, as well as their extracellular products, inhibited the CL response to zymosan. Haemocytes from mussels injected with zymosan showed lower levels of stimulation than in vitro treated cells, and CL increased with time after injection. 相似文献
3.
Park TS Oh SH Lee EY Lee TK Park KH Figueras MJ Chang CL 《Letters in applied microbiology》2003,37(4):349-353
AIMS: To find the cause of misidentification of aeromonads when using the Vitek system. METHODS AND RESULTS: Two Aeromonas veronii biovar sobria isolates were misidentified as Vibrio alginolyticus by the Vitek system. Both strains' identification was confirmed by biochemical testing, API 20E/20NE kits and/or 16S RFLP analysis. Thirty-one known Aeromonas species were tested by the Vitek system using 0.45 and 0.85% saline in the suspension medium. It was not clear whether low salinity causes misidentification of Aeromonas species more frequently. CONCLUSIONS: The specified reaction time may be inappropriately short for some critical biochemical tests of some strains. An ingenious reading strategy regarding incubation time is necessary to improve identification of Aeromonas species by the Vitek system. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of misidentification of A. veronii biovar sobria as V. alginolyticus in the Vitek system. 相似文献
4.
Miquel Marc David S. Brown Teresa Capell Xavier Figueras Antonio F. Tiburcio 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1995,666(2)
A rapid high-performance liquid chromatographic method for the separation of polyamines as their dansyl derivative has been developed. The chromatographic system used consisted of a reversed-phase column and a mobile phase of acetonitrile and water. The separation of 1,3-diaminopropane, putrescine, cadaverine, spermidine and spermine takes only 9 min. This method provides a good resolution between 1,3-diaminopropane and putrescine. It has been applied to quantify polyamines from seeds of wheat, petals of Phalaenopsis hybrids and various rat tissues. 相似文献
5.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
6.
Jason A Roberts Michael S Roberts Andrew Semark Andrew A Udy Carl MJ Kirkpatrick David L Paterson Matthew J Roberts Peter Kruger Jeffrey Lipman 《BMC anesthesiology》2011,11(1):1-7
Background
Critical illness, mediated by trauma or sepsis, can lead to physiological changes that alter the pharmacokinetics of antibiotics and may result in sub-therapeutic concentrations at the sites of infection. The first aim of this project is to identify the clinical characteristics of critically ill patients with significant trauma that have been recently admitted to ICU that may predict the dosing requirements for the antibiotic, cefazolin. The second aim of this is to identify the clinical characteristics of critically ill patients with sepsis that may predict the dosing requirements for the combination antibiotic, piperacillin-tazobactam.Methods/Design
This is an observational pharmacokinetic study of patients with trauma (cefazolin) or with sepsis (piperacillin-tazobactam). Participants will have samples from blood and urine, collected at different intervals. Patients will also have a microdialysis catheter inserted into subcutaneous tissue to measure interstitial fluid penetration of the antibiotic. Participants will be administered sinistrin, indocyanine green and sodium bromide as well as have cardiac output monitoring performed and tetrapolar bioimpedance to determine physiological changes resulting from pathology. Analysis of samples will be performed using validated liquid chromatography tandem mass-spectrometry. Pharmacokinetic analysis will be performed using non-linear mixed effects modeling to determine individual and population pharmacokinetic parameters of antibiotics.Discussion
The study will describe cefazolin and piperacillin-tazobactam concentrations in plasma and the interstitial fluid of tissues in trauma and sepsis patients respectively. The results of this study will guide clinicians to effectively dose these antibiotics in order to maximize the concentration of antibiotics in the interstitial fluid of tissues. 相似文献7.
Drought signal transduction in plants 总被引:5,自引:0,他引:5
Anders B. Jensen Peter K. Busk Mercé Figueras M. Mar Albà Giovanna Peracchia Ramon Messeguer Adela Goday Montserrat Pagès 《Plant Growth Regulation》1996,20(2):105-110
Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis. 相似文献
8.
9.
M Alonso N Alonso Rodriguez C Garzelli M Martínez Lirola M Herranz S Samper MJ Ruiz Serrano E Bouza D García de Viedma 《BMC microbiology》2010,10(1):151
Background
The Beijing lineage of Mycobacterium tuberculosis is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases. 相似文献10.
Recent advances in the understanding of polyamine functions during plant development 总被引:15,自引:0,他引:15
Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- ADC
arginine decarboxylase
- Chl
chlorophyll
- DAP
diaminopropane
- DFMA
DL--difluoromethylarginine
- DFMO
DL--difluoromethylornithine
- PAs
polyamines
- Put
putrescine
- SAM
S-adenosylmethionine
- Spd
spermidine
- Spm
spermine 相似文献