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排序方式: 共有419条查询结果,搜索用时 15 毫秒
81.
82.
Effects of medium growth regulator composition and embryo size on shoot organogenesis of callus derived from globular- to torpedo-shaped zygotic embryos of five sunflower (Helianthus annuus L.) genotypes were examined. Forty growth regulator combinations composed of 0 to 5 mgl-1 naphthaleneacetic acid (NAA) and 0 to 1 mgl-1 6-benzylaminopurine (BA) were tested. The frequency of zygotic embryos forming shoot-regenerating callus was analysed according to categorical data modelling using a maximum-likelihood approach. Both NAA and BA must be present to induce the formation of morphogenic callus from zygotic embryos, but each growth regulator effect varied with the genotype. For four genotypes, NAA and BA effects were neither linear nor quadratic; whereas, they were linear for the fifth one. Most effective concentrations across genotypes were 0.1 mgl-1 NAA and 0.5 mgl-1 or 0.2 mgl-1 BA. However, the optimal growth regulator combination depended on the genotype and an interaction between the two growth regulators. The frequency of shoot-regenerating callus also varied with the size of the embryo explant. For all five genotypes, 0.4 to 1.2 mm long heart-shaped zygotic embryos formed morphogenic callus more frequently than smaller less-developed ones. 相似文献
83.
Ganapathy Sivakumar Daniel R. Vail Vipin Nair Fabricio Medina-Bolivar Jackson O. Lay Jr. 《Biotechnology journal》2009,4(12):1704-1711
Diabetes is one of the nation's most prevalent, debilitating and costly diseases. For diabetes, frequent insulin treatment is very expensive and may increase anti-insulin antibody production, which may cause unwanted side effects. Corosolic acid may also have some efficacy in the treatment of diabetes, but without induction of anti-insulin antibodies. Recently, corosolic acid from Lagerstroemia speciosa L. leaf extracts has been reported to act via an indirect mechanism (unlike insulin) in animal experiments. The insulin-complementary anti-diabetic therapeutic value observed in these Japanese preliminary clinical trials has led to renewed interest in the biosynthesis of this compound. So far, there has been no clear evidence for a corosolic acid biosynthetic pathway in plants. This article provides possible roles of corosolic acid and hypothetical information on the biosynthetic pathway in plants. 相似文献
84.
Markus Anton Michael Passreiter Dorothee Lay Thanh-Phuong Thai Karin Gorgas Wilhelm W. Just 《Cell biochemistry and biophysics》2000,32(1-3):27-36
The authors characterized on a molecular level the clofibrate-inducible 26-kDa integral peroxisomal membrane protein (Pmp26p,
Pex11-1p) of rat liver. By screening cDNA databases with the obtained Pex11-1p-cDNA, a second homologous cDNA was identified
that codes for a polypeptide with slightly larger molecular mass than Pex11-1p. The authors call this polypeptide Pex11-2p.
Studies on the topology of Pex11-1p revealed two transmembrane domains with the N- and C-terminus facing the cytoplasm. The
C-terminal tail of Pex11-1p ends in a consensus dilysine motif of the type-KXKXX-COOH, which is known to be involved in the
ADP-ribosylation factor (ARF)1-coat protein (COP) I coat (ARF)1-dependent membrane recruitment to Golgi membranes. Studies
with isolated peroxisomes incubated in the presence of cytosol, adenosine triphosphate and GTPγS, indeed, provided evidence
for specific binding of ARF and coatomer to peroxisomes. Expression of Pex11-1p in Chinese hamster ovary (CHO) wild-type cells
led to a twofold increase in the number of peroxisomes, but expression in a temperature-sensitive CHO mutant, defective in
coatomer, induced elongation and tubulation of peroxisomal structures, rather than numerical proliferation. The obtained results
for the first time offer a mechanism explaining Pex11-1p-, as well as ARF- and coatomer-mediated peroxisomal vesiculation.
Two models are presented that may explain how these observations fit in with peroxisome biogenesis. 相似文献
85.
Ca++-dependent binding of antigen-19 S antibody complexes to macrophages 总被引:28,自引:0,他引:28
86.
87.
Sunitha Nair Suruchi Arora Jyue Yuan Lim Lay Hoon Lee Lina H.K. Lim 《Cell stress & chaperones》2015,20(4):583-593
Febrile temperatures can induce stress responses which protect cells from damage and can reduce inflammation during infections and sepsis. However, the mechanisms behind the protective functions of heat in response to the bacterial endotoxin LPS are unclear. We have recently shown that Annexin-1 (ANXA1)-deficient macrophages exhibited higher TNFα levels after LPS stimulation. Moreover, we have previously reported that ANXA1 can function as a stress protein. Therefore in this study, we determined if ANXA1 is involved in the protective effects of heat on cytokine levels in macrophages after heat and LPS. Exposure of macrophages to 42 °C for 1 h prior to LPS results in an inhibition of TNFα production, which was not evident in ANXA1−/− macrophages. We show that this regulation involves primarily MYD88-independent pathways. ANXA1 regulates TNFα mRNA stability after heat and LPS, and this is dependent on endogenous ANXA1 expression and not exogenously secreted factors. Further mechanistic studies revealed the possible involvement of the heat shock protein HSP70 and JNK in the heat and inflammatory stress response regulated by ANXA1. This study shows that ANXA1, an immunomodulatory protein, is critical in the heat stress response induced after heat and endotoxin stimulation. 相似文献
88.
Chen MW Kotaka M Vonrhein C Bricogne G Rao F Chuah ML Svergun D Schneider G Liang ZX Lescar J 《Journal of bacteriology》2012,194(18):4837-4846
The nucleotide messenger cyclic di-GMP (c-di-GMP) plays a central role in the regulation of motility, virulence, and biofilm formation in many pathogenic bacteria. EAL domain-containing phosphodiesterases are the major signaling proteins responsible for the degradation of c-di-GMP and maintenance of its cellular level. We determined the crystal structure of a single mutant (R286W) of the response regulator RocR from Pseudomonas aeruginosa to show that RocR exhibits a highly unusual tetrameric structure arranged around a single dyad, with the four subunits adopting two distinctly different conformations. Subunits A and B adopt a conformation with the REC domain located above the c-di-GMP binding pocket, whereas subunits C and D adopt an open conformation with the REC domain swung to the side of the EAL domain. Remarkably, the access to the substrate-binding pockets of the EAL domains of the open subunits C and D are blocked in trans by the REC domains of subunits A and B, indicating that only two of the four active sites are engaged in the degradation of c-di-GMP. In conjunction with biochemical and biophysical data, we propose that the structural changes within the REC domains triggered by the phosphorylation are transmitted to the EAL domain active sites through a pathway that traverses the dimerization interfaces composed of a conserved regulatory loop and the neighboring motifs. This exquisite mechanism reinforces the crucial role of the regulatory loop and suggests that similar regulatory mechanisms may be operational in many EAL domain proteins, considering the preservation of the dimerization interface and the spatial arrangement of the regulatory domains. 相似文献
89.
Aitken JB Lay PA Duong TT Aran R Witting PK Harris HH Lai B Vogt S Giles GI 《Journal of biological inorganic chemistry》2012,17(4):589-598
Synchrotron radiation induced X-ray emission (SRIXE) spectroscopy was used to map the cellular uptake of the organoselenium-based
antioxidant drug ebselen using differentiated ND15 cells as a neuronal model. The cellular SRIXE spectra, acquired using a
hard X-ray microprobe beam (12.8-keV), showed a large enhancement of fluorescence at the Kα line for Se (11.2-keV) following treatment with ebselen (10 μM) at time periods from 60 to 240 min. Drug uptake was quantified
and ebselen was shown to induce time-dependent changes in cellular elemental content that were characteristic of oxidative
stress with the efflux of K, Cl, and Ca species. The SRIXE cellular Se distribution map revealed that ebselen was predominantly
localized to a discreet region of the cell which, by comparison with the K and P elemental maps, is postulated to correspond
to the endoplasmic reticulum. On the basis of these findings, it is hypothesized that a major outcome of ebselen redox catalysis
is the induction of cellular stress. A mechanism of action of ebselen is proposed that involves the cell responding to drug-induced
stress by increasing the expression of antioxidant genes. This hypothesis is supported by the observation that ebselen also
regulated the homeostasis of the transition metals Mn, Cu, Fe, and Zn, with increases in transition metal uptake paralleling
known induction times for the expression of antioxidant metalloenzymes. 相似文献
90.