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41.
Polypterids, the most basal actinopterygians, are a group of fish long-considered living fossils and holding a key position for understanding fish and tetrapod evolution. Knowledge of the natural history of Polypterus is limited, their having been studied in little detail since the early 1900s. The locomotory habits of wild Polypterus senegalus from Lake Albert, Uganda, were investigated in 2014. High-speed videography demonstrated the capability of large Polypterus to move overland successfully. Contrary to previous evidence, field observations found that terrestrial locomotion in Polypterus is not inherently restricted by body size. Evidence that Polypterus exhibit this behaviour as part of their natural life history can be found in the existence of environmental challenges and the presence of adaptations for amphibious life. 相似文献
42.
43.
Nerve growth factor (NGF) induces sprouting of specific neurons of the snail, Lymnaea stagnalis 总被引:2,自引:0,他引:2
Nerve growth factor (NGF) was examined for its ability to elicit sprouting by adult molluscan neurons. Motoneurons and interneurons (but not neurosecretory cells) from Lymnaea exhibited a sprouting response to murine 2.5S NGF in defined medium with a half-maximal response at about 150 ng/mL. Furthermore, an NGF antiserum blocked sprouting by all normally responsive neurons. We tested whether an NGF-like molecule is a component of conditioned medium (CM) by attempting to preabsorb its sprout-inducing activity with NGF antiserum. Treatment of CM with immune (but not nonimmune) serum largely blocked the response of motoneurons, but not that of neurosecretory cells, to CM. We conclude that NGF exerts neurotrophic activity on specific adult Lymnaea neurons, and suggest the possibility that an NGF-like molecule may exist in the molluscan nervous system. 相似文献
44.
Jellinck PH Kaufmann M Gottfried-Blackmore A Croft G Byford V McEwen BS Jones G Bulloch K 《The Journal of steroid biochemistry and molecular biology》2006,98(1):41-47
Studies to elucidate the role of dehydroepiandrosterone (DHEA) metabolism in neuroprotection have compared its relative 7-hydroxylation against estrogen formation by way of 4-androstenedione (AD) in various rodent brain cell lines. In all cases, the 7alpha- and 7beta-hydroxy epimers of DHEA were found to be the dominant products with one notable exception. BV2 mouse microglia were virtually unable to hydroxylate DHEA at C-7 and converted AD to a major unknown metabolite not observed with mouse BHc hippocampal cells. In this paper, we describe the identification of this compound based on its physical properties and analysis by TLC and HPLC. Its identity as 3beta-hydroxy-4-androstene-17-one, the Delta(4)-isomer of DHEA, was confirmed by mass spectrometry (LC/MS), as well as by reverse isotope dilution analysis involving co-crystallization with the synthetic steroid. Possible mechanisms for the formation of this isomer of DHEA by BV2 microglia are proposed, together with that of other C-19 steroids detected which include testosterone (T), 5alpha-dihydrotestosterone and 5alpha-androstanedione. 相似文献
45.
Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: II. Cloning and expression in Escherichia coli 总被引:7,自引:0,他引:7
Crawford IP; Wilde A; Yelverton EM; Figurski D; Hedges RW 《Molecular biology and evolution》1986,3(5):449-458
The genes for the large and small subunits of anthranilate synthase (trpE
and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174
into E. coli by R-prime formation with the broad-host- range plasmid
R68.44. Sequential subcloning into plasmid vectors reduced the active
Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that
this region contains the promoter for its own expression and retains a
vestigial regulatory response to tryptophan scarcity or excess.
相似文献
46.
EM Armstrong 《BMJ (Clinical research ed.)》1996,312(7042):1320.2
47.
Gottfried-Blackmore A Sierra A Jellinck PH McEwen BS Bulloch K 《The Journal of steroid biochemistry and molecular biology》2008,109(1-2):96-107
In the CNS, steroid hormones play a major role in the maintenance of brain homeostasis and it's response to injury. Since activated microglia are the pivotal immune cell involved in neurodegeneration, we investigated the possibility that microglia provide a discrete source for the metabolism of active steroid hormones. Using RT-PCR, our results showed that mouse microglia expressed mRNA for 17β-hydroxysteroid dehydrogenase type 1 and steroid 5-reductase type 1, which are involved in the metabolism of androgens and estrogens. Microglia also expressed the peripheral benzodiazepine receptor and steroid acute regulatory protein; however, the enzymes required for de novo formation of progesterone and DHEA from cholesterol were not expressed. To test the function of these enzymes, primary microglia cultures were incubated with steroid precursors, DHEA and AD. Microglia preferentially produced delta-5 androgens (Adiol) from DHEA and 5-reduced androgens from AD. Adiol behaved as an effective estrogen receptor agonist in neuronal cells. Activation of microglia with pro-inflammatory factors, LPS and INFγ did not affect the enzymatic properties of these proteins. However, PBR ligands reduced TNF production signifying an immunomodulatory role for PBR. Collectively, our results suggest that microglia utilize steroid-converting enzymes and related proteins to influence inflammation and neurodegeneration within microenvironments of the brain. 相似文献
48.
Diahann TSL Jansen Hanane el Bannoudi Ramon Arens Kim LL Habets Marjolijn Hameetman Tom WJ Huizinga Jeroen N. Stoop René EM Toes 《Arthritis research & therapy》2015,17(1)
IntroductionAbatacept is a fusion protein of human cytotoxic T-lymphocyte–associated protein (CTLA)-4 and the Fc portion of human immunoglobulin G1 (IgG1). It is believed to be effective in the treatment of rheumatoid arthritis by inhibiting costimulation of T cells via blocking CD28–B7 interactions as CTLA-4 binds to both B7.1 (CD80) and B7.2 (CD86). However, the interaction of CD28 with B7 molecules is crucial for activation of naive cells, whereas it is unclear whether the action of already activated CD4+ T cells, which are readily present in established disease, also depends on this interaction. The aim of this study was to determine whether the mode of action of abatacept depends solely on its ability to halt T cell activation in established disease.MethodsArthritis was induced in thymectomized male DBA/1 mice by immunisation with bovine collagen type II. The mice were subsequently depleted for CD4+ T cells. Abatacept or control treatment was started when 80 % of the mice showed signs of arthritis. Arthritis severity was monitored by clinical scoring of the paws, and anti-collagen antibody levels over time were determined by enzyme-linked immunosorbent assay.ResultsTreatment with abatacept in the absence of CD4+ T cells resulted in lower disease activity. This was associated with decreasing levels of collagen-specific IgG1 and IgG2a antibodies, whereas the antibody levels in control or CD4+ T cell–depleted mice increased over time.ConclusionsThese results show that abatacept decreased disease activity in the absence of CD4+ T cells, indicating that the mode of action of abatacept in established arthritis does not depend entirely on its effects on CD4+ T cell activation. 相似文献
49.
Irene EM Bultink D?rte Hamann Marc A Seelen Margreet H Hart Ben AC Dijkmans Mohamed R Daha Alexandre E Voskuyl 《Arthritis research & therapy》2007,8(6):R183
Infection imposes a serious burden on patients with systemic lupus erythematosus (SLE). The increased infection rate in SLE
patients has been attributed in part to defects of immune defence. Recently, the lectin pathway of complement activation has
also been suggested to play a role in the occurrence of infections in SLE. In previous studies, SLE patients homozygous for
mannose-binding lectin (MBL) variant alleles were at an increased risk of acquiring serious infections in comparison with
patients who were heterozygous or homozygous for the normal allele. This association suggests a correlation between functional
MBL level and occurrence of infections in SLE patients. We therefore investigated the biological activity of MBL and its relationship
with the occurrence of infections in patients with SLE. Demographic and clinical data were collected in 103 patients with
SLE. Functional MBL serum levels and MBL-induced C4 deposition were measured by enzyme-linked immunosorbent assay using mannan
as coat and an MBL- or C4b-specific monoclonal antibody. The complete MBL-dependent pathway activity was determined by using
an assay that measures the complete MBL pathway activity in serum, starting with binding of MBL to mannan, and was detected
with a specific monoclonal antibody against C5b-9. Charts were systematically reviewed to obtain information on documented
infections since diagnosis of SLE. Major infections were defined as infections requiring hospital admission and intravenous
administration of antibiotics. In total, 115 infections since diagnosis of lupus, including 42 major infections, were documented
in the 103 SLE patients (mean age 41 ± 13 years, mean disease duration 7 ± 4 years). The percentage of SLE patients with severe
MBL deficiency was similar to that in 100 healthy controls: 13% versus 14%, respectively. Although deposition of C4 to mannan
and MBL pathway activity were reduced in 21% and 43% of 103 SLE patients, respectively, neither functional MBL serum levels
nor MBL pathway activity was associated with infections or major infections in regression analyses. In conclusion, SLE patients
frequently suffer from infections, but deficiency of functional MBL does not confer additional risk. 相似文献
50.
WalterDuartedeAraujo Filho Fábio Kurt Schneider Rigoberto EM Morales 《Biomedical engineering online》2012,11(1):1-14