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141.
p38 mitogen-activated protein kinase is the central regulator of cyclic AMP-dependent transcription of the brown fat uncoupling protein 1 gene 总被引:5,自引:0,他引:5 下载免费PDF全文
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The mammalian retina contains numerous morphological and physiological subtypes of amacrine cells necessary for integrating and modulating visual signals presented to the output neurons. Among subtypes of amacrine cells grouped by neurotransmitter phenotypes, the glycinergic and gamma-aminobutyric acid (GABA)ergic amacrine cells constitute two major subpopulations. To date, the molecular mechanisms governing the specification of subtype identity of amacrine cells remain elusive. We report here that during mouse development, the Barhl2 homeobox gene displays an expression pattern in the nervous system that is distinct from that of its homologue Barhl1. In the developing retina, Barhl2 expression is found in postmitotic amacrine, horizontal and ganglion cells, while Barhl1 expression is absent. Forced expression of Barhl2 in retinal progenitors promotes the differentiation of glycinergic amacrine cells, whereas a dominant-negative form of Barhl2 has the opposite effect. By contrast, they exert no effect on the formation of GABAergic neurons. Moreover, misexpressed Barhl2 inhibits the formation of bipolar and Müller glial cells, indicating that Barhl2 is able to function both as a positive and negative regulator, depending on different types of cells. Taken together, our data suggest that Barhl2 may function to specify the identity of glycinergic amacrine cells from competent progenitors during retinogenesis. 相似文献
145.
Young?Sik?Kim Chong?Ho?Lee Phillip?C.?Wankat Yoon?Mo?KooEmail author 《Biotechnology and Bioprocess Engineering》2004,9(5):362-368
A new one-column chromatography process, analogous to a four-zone simulated moving bed (SMB), was presented. The basic principle
of the process was identical to that of a four-zone SMB. The process consisted of one chromatographic column and four tanks,
instead of the four columns in the four-zone SMB (1-1-1-1), and has been used for the separation of two amino acids, phenylalanine
and tryptophan, using an ion exchange resin. The operating parameters for the one-column process and four-zone SMB were obtained
from equilibrium theory. Computer simulations were used to compare the performances of the new one column process to that
of the general four-zone SMB, using Aspen Chromatography™ v 11.1. The differences between the one-column and SMB processes in terms of the purities and yields of phenylalanine and
tryptophan were less than 4 and about 6%, respectively. The lower purities of the one-column process were due to the loss
of the developed concentration profiles in the column when the liquid was stored in tanks. The one-column process gave great
flexibility, and would be useful for reconstructing an existing conventional chromatography process to one of a SMB. 相似文献
146.
In?Seop?KimEmail author Yong?Woon?Choi Sung?Rae?Lee Hark?Mo?Sung 《Biotechnology and Bioprocess Engineering》2004,9(1):65-68
The purpose of the present study was to examine the efficacy and mechanism of fraction IV cold ethanol fractionation and pasteurization
(60°C heat treatment for 10h), involved in the manufacture of albumin from human plasma, in the removal and/or inactivation
of the hepatitis A virus (HAV). Samples from the relevant stages of the production process were spiked with HAV and the amount
of virus in each fraction then quantified using a 50% tissue culture infectious dose (TCID50). HAV was effectively partitioned from albumin during the fraction IV cold ethanol fractionation with a log reduction factor
of 3.43. Pasteurization was also found to be a robust and effective step in inactivating HAV, where the titers were reduced
from an initial titer of 7.60 log TCID50 to undetectable levels within 5 h of treatment. The log reduction factor achieved during pasteurization was≽4.76. Therefore,
the current results indicate that the production process for albumin has sufficient HAV reducing capacity to achieve a high
margin of virus safety. 相似文献
147.
Increasing terrestrial vegetation activity in China, 1982—1999 总被引:16,自引:0,他引:16
FANG Jingyun PIAO Shilong HE Jinsheng MA Wenhong 《中国科学:生命科学英文版》2004,47(3):229-240
Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982 to 1999. In order to eliminate the effects of non-vegetation factors, we characterized areas with NDVI < 0.1 as “sparsely vegetated areas” and areas with NDVI ≥ 0.1 as “vegetated areas”. The results showed that increasing NDVI trends were evident, to varying extents, in almost all regions in China in the 18 years, indicating that vegetation activity has been rising in recent years in these regions. Compared to the early 1980s, the vegetated area increased by 3.5% by the late 1990s, while the sparsely vegetated area declined by 18.1% in the same period. The national total mean annual NDVI increased by 7.4% during the study period. Extended growing seasons and increased plant growth rates accounted for the bulk of these increases, while increases in temperature and summer rainfall, and strengthening agricultural activity were also likely important factors. NDVI changes in China exhibited relatively large spatial heterogeneity; the eastern coastal regions experienced declining or indiscernibly rising trends, while agricultural regions and western China experienced marked increases. Such a pattern was due primarily to urbanization, agricultural activity, regional climate characteristics, and different vegetation responses to regional climate changes. 相似文献
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149.
Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982 to 1999. In order to eliminate the effects of non-vegetation factors, we characterized areas with NDVI < 0.1 as “sparsely vegetated areas” and areas with NDVI ≥0.1 as “vegetated areas”. The results showed that increasing NDVI trends were evident, to varying extents, in almost all regions in China in the 18 years, indicating that vegetation activity has been rising in recent years in these regions. Compared to the early 1980s, the vegetated area increased by 3.5% by the late 1990s, while the sparsely vegetated area declined by 18.1% in the same period. The national total mean annual NDVI increased by 7.4% during the study period. Extended growing seasons and increased plant growth rates accounted for the bulk of these increases, while increases in temperature and summer rainfall, and strengthening agricultural activity were also likely important factors. NDVI changes in China exhibited relatively large spatial heterogeneity; the eastern coastal regions experienced declining or indiscernibly rising trends, while agricultural regions and western China experienced marked increases. Such a pattern was due primarily to urbanization, agricultural activity, regional climate characteristics, and different vegetation responses to regional climate changes. 相似文献
150.
Koo BC Kwon MS Choi BR Lee HT Choi HJ Kim JH Kim NH Jeon I Chang W Kim T 《Molecular reproduction and development》2004,68(4):429-434
Here, we successfully demonstrate expression of the EGFP (enhanced green fluorescence protein) gene in chickens using replication-defective MLV (murine leukemia virus)-based retrovirus vectors encapsidated with VSV-G (vesicular stomatitis virus G glycoprotein). The recombinant retrovirus was injected beneath the blastoderm of non-incubated chicken embryos (stage X). After 12 days incubation, all of the eight living embryos assayed were found to express this vector-encoded EGFP gene, which was under the control of the RSV (Rous Sarcoma Virus) promoter, in diverse organ tissues, including head, beak, neck, wing, hock, tail, toes, heart, amnion, and yolk sac. Surprisingly, despite the presumed cytotoxicity of EGFP, some embryos hatched and survived and these had prominent green fluorescent spots, both in internal organs and externally. 相似文献