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1.
The expression of p21ras proteins was investigated by immunocytochemistry in permanent cell lines and in fresh human leukaemic cells. While high and low levels of p21ras could be detected in most of the cell lines, no significant p21ras immunoreactivity was noted in cells of ten human acute and chronic leukaemias. Thus, notwithstanding its possible role in the initial transformation process in human leukaemias, p21ras expression appears not to be an irrevocable requirement for the maintenance of the transformed state. 相似文献
2.
Karl J. Siegert 《Archives of insect biochemistry and physiology》1992,21(2):129-143
Activation and inactivation of fat body glycogen phosphorylase was investigated in ligated abdomens of larval Manduca sexta and in vitro. After maximal activation through Manduca adipokinetic hormone (AKH) or chilling, inactivation of glycogen phosphorylase commenced as soon as the stimulus for the activation was removed indicating that the enzyme system in the fat body is fine-tuned to low phosphorylase activities which is necessary to allow glycogen synthesis. In intact ligated abdomens phosphorylase can be activated repeatedly by either stimulus showing that the fat body system does not lose its responsiveness. It was impossible to achieve complete conversion of the inactive form of phosphorylase into the active form even after administration of AKH and simultaneous chilling. © 1992 Wiley-Liss, Inc. 相似文献
3.
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
4.
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
5.
Ronny Martinez Felix Jakob Ran Tu Petra Siegert Karl‐Heinz Maurer Ulrich Schwaneberg 《Biotechnology and bioengineering》2013,110(3):711-720
Bacillus gibsonii Alkaline Protease (BgAP) is a recently reported subtilisin protease exhibiting activity and stability properties suitable for applications in laundry and dish washing detergents. However, BgAP suffers from a significant decrease of activity at low temperatures. In order to increase BgAP activity at 15°C, a directed evolution campaign based on the SeSaM random mutagenesis method was performed. An optimized microtiter plate expression system in B. subtilis was established and classical proteolytic detection methods were adapted for high throughput screening. In parallel, the libraries were screened for increased residual proteolytic activity after incubation at 58°C. Three iterative rounds of directed BgAP evolution yielded a set of BgAP variants with increased specific activity (Kcat) at 15°C and increased thermal resistance. Recombination of both sets of amino acid substitutions resulted finally in variant MF1 with a 1.5‐fold increased specific activity (15°C) and over 100 times prolonged half‐life at 60°C (224 min compared to 2 min of the WT BgAP). None of the introduced amino acid substitutions were close to the active site of BgAP. Activity‐altering amino acid substitutions were from non‐charged to non‐charged or from sterically demanding to less demanding. Thermal stability improvements were achieved by substitutions to negatively charged amino acids in loop areas of the BgAP surface which probably fostered ionic and hydrogen bonds interactions. Biotechnol. Bioeng. 2013; 110: 711–720. © 2012 Wiley Periodicals, Inc. 相似文献
6.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
7.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase 下载免费PDF全文
Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
8.
M.J. Siegert A. Behar M. Bentley D. Blake S. Bowden P. Christoffersen C. Cockell H. Corr D. C. Cullen H. Edwards A. Ellery C. Ellis-Evans G. Griffiths R. Hindmarsh D. A. Hodgson E. King H. Lamb L. Lane K. Makinson M. Mowlem J. Parnell D. A. Pearce J. Priscu A. Rivera M. A. Sephton M. R. Sims A . M. Smith M. Tranter J. L. Wadham G. Wilson J. Woodward 《Reviews in Environmental Science and Biotechnology》2007,6(1-3):161-179
Antarctic subglacial lakes have, over the past few years, been hypothesised to house unique forms of life and hold detailed
sedimentary records of past climate change. Testing this hypothesis requires in situ examinations. The direct measurement
of subglacial lakes has been considered ever since the largest and best-known lake, named Lake Vostok, was identified as having
a deep water-column. The Subglacial Antarctic Lake Environments (SALE) programme, set up by the Scientific Committee on Antarctic
Research (SCAR) to oversee subglacial lakes research, state that prior exploration of smaller lakes would be a “prudent way
forward”. Over 145 subglacial lakes are known to exist in Antarctica, but one lake in West Antarctica, officially named Ellsworth
Subglacial Lake (referred to hereafter as Lake Ellsworth), stands out as a candidate for early exploration. A consortium of
over 20 scientists from seven countries and 14 institutions has been assembled to plan the exploration of Lake Ellsworth.
An eight-year programme is envisaged: 3 years for a geophysical survey, 2 years for equipment development and testing, 1 year
for field planning and operation, and 2 years for sample analysis and data interpretation. The science experiment is simple
in concept but complex in execution. Lake Ellsworth will be accessed using hot water drilling. Once lake access is achieved,
a probe will be lowered down the borehole and into the lake. The probe will contain a series of instruments to measure biological,
chemical and physical characteristics of the lake water and sediments, and will utilise a tether to the ice surface through
which power, communication and data will be transmitted. The probe will pass through the water column to the lake floor. The
probe will then be pulled up and out of the lake, measuring its environment continually as this is done. Once at the ice surface,
any water samples collected will be taken from the probe for laboratory analysis (to take place over subsequent years). The
duration of the science mission, from deployment of the probe to its retrieval, is likely to take between 24 and 36 h. Measurements
to be taken by the probe will provide data about the following: depth, pressure, conductivity and temperature; pH levels;
biomolecules (using life marker chips); anions (using a chemical analyzer); visualisation of the environment (using cameras
and light sources); dissolved gases (using chromatography); and morphology of the lake floor and sediment structures (using
sonar). After the probe has been retrieved, a sediment corer may be dropped into the lake to recover material from the lake
floor. Finally, if time permits, a thermistor string may be left in the lake water to take time-dependent measurements of
the lake’s water column over subsequent years. Given that the comprehensive geophysical survey of the lake will take place
in two seasons during 2007–2009, a two-year instrument and logistic development phase from 2008 (after the lake’s bathymetry
has been assessed) makes it possible that the exploration of Lake Ellsworth could take place at the beginning of the next
decade. 相似文献
9.
Siegert KJ 《FEBS letters》1999,447(2-3):237-240
A neuropeptide from the migratory locust, Locusta migratoria, has been identified as a novel member of the family of adipokinetic hormones (AKHs). The peptide is probably synthesised in the brain because it is the first AKH found in the storage lobe, whilst the three 'classic' Locusta AKHs are present in the glandular lobe of the corpora cardiaca. In locusts, the peptide has no biological activity usually associated with AKHs. There is only 36-56% sequence identity with the three Lom-AKHs, but 78% identity with the Drosophila melanogaster AKH, Drm-HrTH. The new peptide is active in the American cockroach, Periplaneta americana, and was provisionally named 'L. migratoria hypertrehalosaemic hormone', Lom-HrTH; its biological role in locusts remains to be established. The high degree of identity with Drm-HrTH suggests that Lom-HrTH is an ancient molecule. 相似文献
10.
Shift of aberrant antigen expression at relapse or at treatment failure in acute leukemia 总被引:1,自引:0,他引:1
Oelschlägel U Nowak R Schaub A Köppel C Herbst R Mohr B Löffler C Range U Günther H Assmann M Siegert E Wendt E Huhn R Bräutigam E Ehninger G 《Cytometry》2000,42(4):247-253
The flow cytometric detection of aberrant antigen expression is one method proposed for the quantification of minimal residual disease (MRD) in acute leukemias. The present study was designed to investigate the stability of the aberrant antigen expression at relapse or at treatment failure of initial chemotherapy. For this purpose, multiparameter immunophenotyping with a panel of 15 monoclonal antibodies was used at diagnosis as well as at relapse (43 patients with overall 65 aberrations) and at treatment failure (35 patients with overall 66 aberrations). There was a significant decrease in the percentage of the initially described aberrant antigen expression on leukemia blasts at relapse (P = 0.001; n = 65) as well as at treatment failure (P = 0.0001; n = 66) considering all aberrations in the whole leukemia population. Concerning only patients with acute myelogenous leukemia (AML), significant decreases in the aberrant expression could be detected at relapse (P = 0.031; n = 42) and at treatment failure (P = 0.0001; n = 52). The changes in patients with acute lymphoblastic leukemia (ALL) were significant only at relapse (P = 0.006; n = 23). Initially, the most informative aberration was not detectable in four patients at relapse and in seven patients at treatment failure. A decrease of under 50% of the initial value was observed in another 8 patients at relapse and in 10 patients at treatment failure. In further studies assessing the detection of aberrant antigen expression for MRD, quantification of the relapses should be explicitly analyzed regarding the persistence of the initially described aberrant antigen expression. 相似文献