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排序方式: 共有197条查询结果,搜索用时 203 毫秒
1.
Anabaena sp., isolated from a rice paddy, was investigated for its nitrogen fixation as measured by acetylene reduction activity (ARA)
in P-limited continuous and light-limited semi-continuous cultures. Growth rate (μ) under P limitation was a function of cell
P content (q
p). Both the photosynthetic capacity (Pmax) and photosynthetic efficiency (α) increased with μ when expressed per cell, but not per unit chla. The ARA of steady-state cells under P limitation increased with μ and was linearly related to C-fixation rate. This was
apparently a consequence of the control of C-fixation by P limitation. In light-limited cells, steady state ARA, both at the
culture light intensity and in the dark, increased asymptotically with μ, but the activity in the dark was only about 51%
of that in the light. When the light level of steady-state cells grown at a high in intensity was switched to a low level,
ARA decreased exponentially with time. Dark ARA activity also showed a similar decline, but at much lower levels. Thus, ARA
depended not only on light history, but also immediate photosynthesis. Steady-state ARA at the ambient intensity or in the
dark showed a strong correlation with14C-fixation rate. ARA of light-limited cells showed the same light-saturation characteristics as their14C-fixation, with the same initial saturation intensity,I
k. The ratios of Pmax to the maximum ARA (ARAmax), and α to the slope of ARA (αara) were identical. A comparison of gross to net photosynthesis and N2 fixation suggested that there was little leakage or excretion of fixed C or N. 相似文献
2.
Priyanka Kushwaha Soohyun Kim Gabrielle E. Foxa Megan N. Michalski Bart O. Williams Ryan E. Tomlinson Ryan C. Riddle 《Journal of cellular physiology》2020,235(10):6673-6683
The activation of the Wnt/β-catenin signaling pathway is critical for skeletal development but surprisingly little is known about the requirements for the specific frizzled (Fzd) receptors that recognize Wnt ligands. To define the contributions of individual Fzd proteins to osteoblast function, we profiled the expression of all 10 mammalian receptors during calvarial osteoblast differentiation. Expression of Fzd4 was highly upregulated during in vitro differentiation and therefore targeted for further study. Mice lacking Fzd4 in mature osteoblasts had normal cortical bone structure but reduced cortical tissue mineral density and also exhibited an impairment in the femoral trabecular bone acquisition that was secondary to a defect in the mineralization process. Consistent with this observation, matrix mineralization, markers of osteoblastic differentiation, and the ability of Wnt3a to stimulate the accumulation of β-catenin were reduced in cultures of calvarial osteoblasts deficient for Fzd4. Interestingly, Fzd4-deficient osteoblasts exhibited an increase in the expression of Fzd8 both in vitro and in vivo, which suggests that the two receptors may exhibit overlapping functions. Indeed, ablating a single Fzd8 allele in osteoblast-specific Fzd4 mutants produced a more severe effect on bone acquisition. Taken together, our data indicate that Fzd4 is required for normal bone development and mineralization despite compensation from Fzd8. 相似文献
3.
Seong Rim Byeon Hyunjin Vincent Kim Mijin Jeon Young Gil Ahn Maeng Sup Kim Jae Yang Kong Hye Yun Kim Young Soo Kim Dong Jin Kim 《Bioorganic & medicinal chemistry letters》2013,23(11):3467-3469
Alzheimer’s disease drug discovery regarding exploration into the molecules and processes has focused on the intrinsic causes of the brain disorder correlated with the accumulation of amyloid-β. An anti-amyloidogenic bis-styrylbenzene derivative, KMS80013, showed excellent oral bioavailability (F = 46.2%), facilitated brain penetration (26%, iv) in mouse and target specific in vivo efficacy in acute AD mouse model attenuating the cognitive deficiency in Y-maze test. Acute toxicity (LD50 >2000 mg/kg) and hERG channel inhibition (14% at 10 μM) results indicated safety of KMS80013. 相似文献
4.
Hyun‐Joo Lee MinSeok Chang Jong‐Mook Kim HyeJin Hong KiEun Maeng Jane Koo ShinJae Chang Myung‐Sam Cho 《Biotechnology progress》2013,29(2):432-440
Host cell lines developed by genetic engineering sometimes show instabilities in maintaining their genetically acquired phenotypes. Previously, a hybrid host cell line, designated as hybrid of kidney and B cells (HKB), capable of retaining selected phenotypes originally existing in the parental cells was developed via fusion of 293 cells and HH514‐16 cells. Although HKB did indeed successfully preserve several favorable phenotypes, the expression of Epstein‐Barr virus (EBV) specific nuclear antigen 1 (EBNA1), which should be constitutively expressed for host cells to utilize oriP expression vector in transient production of therapeutic proteins, was observed to be unstable. Here, in an attempt to obtain stable expression of EBNA1, a cell type that contains an integrated EBV genome, rather than HH514‐16 cells, which harbor an episomal EBV genome, was applied for fusion with 293 cells. Fusion of 293 cells with Namalwa cells led to the creation of a new type of hybrid, F2N, which was able to stably express EBNA1 while not producing EBV particles. One of the F2N clones, F2N78, was observed to maintain EBNA1 expression for more than 1 year under serum‐free suspension culture conditions along with human specific glycosyl phenotypes observed previously in HKB. In addition, F2N78 was demonstrated to be an appropriate host cell line for both the transient and stable production of recombinant therapeutics with the features of safety expected of production cell lines for human use. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 432–440, 2013 相似文献
5.
Gaeul Han Junhyuk Choi Seung-Yun Cha Byung Il Kim Hee Kyung Kho Maeng-Jin Jang Mi Ae Kim Sungho Maeng Heeok Hong 《Current issues in molecular biology》2021,43(3):1669
Postmenopausal syndrome refers to symptoms caused by the gradual decrease in female hormones after mid-40 years. As a target organ of estrogen, decrease in estrogen causes various changes in brain function such as a decrease in choline acetyltransferase and brain-derived neurotrophic factor; thus, postmenopausal women experience cognitive decline and more depressive symptoms than age-matched men. Radix Polygalae has been used for memory boosting and as a mood stabilizer and its components have shown neuroprotective, antidepressant, and stress relief properties. In a mouse model of estrogen depletion induced by 4-vinylcyclohexene diepoxide, Radix Polygalae was orally administered for 3 weeks. In these animals, cognitive and depression-related behaviors and molecular changes related to these behaviors were measured in the prefrontal cortex and hippocampus. Radix Polygalae improved working memory and contextual memory and despair-related behaviors in 4-vinylcyclohexene diepoxide-treated mice without increasing serum estradiol levels in this model. In relation to these behaviors, choline acetyltransferase and brain-derived neurotrophic factor in the prefrontal cortex and hippocampus and bcl-2-associated athanogene expression increased in the hippocampus. These results implicate the possible benefit of Radix Polygalae in use as a supplement of estrogen to prevent conditions such as postmenopausal depression and cognitive decline. 相似文献
6.
The most abundant root proteins of ginseng (Panax ginseng) have been detected and identified by comparative proteome analysis with cultured hairy root of ginseng. Four abundant proteins (28, 26, 21 and 20 kDa) of P. ginseng had isoforms with different pl values on two-dimensional gel electrophoresis (2DE). The results of N-terminal and internal amino acid sequencing, however, showed that all of them originate from a 28 kDa protein, known as ginseng major protein (GMP). The GMP gene was searched for in the expressed sequence tag database of P. ginseng and found to encode a 27.3 kDa protein having 238 amino acid residues. Analysis of the amino acid sequences indicates that GMP exhibits high sequence homology with plant RNases and RNase-like proteins. However, purified GMP had no RNase activity even though it has conserved amino acid residues known to be essential for active sites of RNase. The GMPs present in ginseng main root were not expressed in cultured hairy roots of ginseng. 2DE analysis showed that the amounts of GMPs in main roots change according to seasonal fluctuation. These results suggest that the GMPs are root-specific RNase-like proteins, which function as vegetative storage proteins of ginseng for survival in the natural environment. 相似文献
7.
8.
Use of microorganism-immobilized polyurethane foams to absorb and degrade oil on water surface 总被引:6,自引:0,他引:6
Highly oil-absorbent polyurethane foam (PUF) materials were obtained by polymerizing polyether polyol mixture and carbodiimide-modified
d-methyl diisocyanate in a weight ratio of 10:2. The foam materials were prepared to contain inorganic nutrients (slow-release
fertilizer; SRF) and oil-degrading yeast cells, Yarrowia lipolytica 180, to be applied for removal of oil films on surface waters through absorption and biodegradation after oil spills. PUFs
absorbed 7–9 times their own weight of Arabian light crude oil and the oil absorbency appeared to improve as the ratio of
surface area to foam weight increased. PUFs showed excellent floatability which was maintained for more than 6 months in sea
water, and less than 5% of the absorbed oil was released when the foams were left on water for more than 10 days. For immobilization
of yeast cells into PUFs, various immobilization techniques were tested to compare their oil degrading ability and the maintenance
thereof. All immobilized cells showed oil degrading abilities as good as those of free cells immediately after the preparation
of PUFs, however, the activity of chitin-immobilized cells remained at a high level for the longest period of preservation.
The high efficiency of oil absorption and oil degradation by PUF-immobilized yeast cells suggested that PUF-immobilized cells
have a high potential as a bioremediation technique for the treatment of oil films on surface waters.
Received: 27 September 1999 / Received revision: 6 March 2000 / Accepted: 17 March 2000 相似文献
9.
Saccharomyces cerevisiae has three distinct citrate synthases, two located in mitochondria (mature Cit1p and Cit3p) and one in peroxisomes (mature Cit2p). While the precursor of the major mitochondrial enzyme, Cit1p, has a signal for mitochondrial targeting at its N-terminus (MTS), Cit2p has one for peroxisomal targeting (PTS1) at its C-terminus. We have previously shown that the N-terminal segment of Cit2p is removed during import into peroxisomes [Lee, H.S. et al. (1994) Kor. J. Microbiol. 32, 558-564], which implied the presence of an additional N-terminal sorting signal. To analyze the function of the N-terminal region of Cit2p in protein trafficking, we constructed the N-terminal domain-swapped versions of Cit1p and Cit2p. Both fusions, Cit1::Cit2 and Cit2::Cit1, complemented the glutamate auxotrophy caused by the double-disruption of the CIT1 and CIT2 genes. In addition, part of the Cit2::Cit1 fusion protein, as well as Cit1::Cit2, was shown to be transported into both mitochondria and peroxisomes. The subcellular localization of the recombinant fusion proteins containing various N-terminal segments of Cit2p fused to a mutant version of green fluorescent protein (GFP2) was also examined. As a result, we found that the 20-amino acid N-terminal segment of Cit2p contains a cryptic cleavable targeting signal for both peroxisomes and mitochondria. In addition, we show that the peroxisomal import process mediated by the N-terminal segment of Cit2p was not affected by the disruption of either PEX5 (encoding PTS1 receptor) or PEX7 (encoding PTS2 receptor). 相似文献
10.