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101.
102.
Tsou CH 《American journal of botany》1998,85(11):1531-1547
The early floral development of Camellioideae was studied. Two major evolutionary lineages were recognized for this subfamily. The earlier evolved lineage (Camellia, Polyspora, and Pyrenaria) has normally 11-14 perianth members, which are initiated in a continuous spiral and are differentiated into sepals and petals at late floral development, and numerous stamens initiated individually and centrifugally on the whole androecial region. The later derived lineage (Franklinia, Hartia, Schima, and Stewartia) has five sepals and five petals arranged in two whorls, and numerous individual stamens originating centrifugally from the five petal-opposed zones. Hartia-Stewartia and Franklinia-Schima further diverged as two branches - the former is characterized by having androecial fascicles and axile-basal placentation. The androecial fascicle is considered to be derived within this subfamily. The latter exhibits a higher degree of carpellary congenital fusion and axile-central placentaion, and as a whole, is concluded to be the most advanced group in the Camellioideae. A taxonomic treatment of the Camellioideae at the tribal level is also proposed. 相似文献
103.
The translocation profiles of 11C-photoassimilates from eithertendrils or leaflets of the compound leaf of Pisum sativum weresimilar in shape, speed and susceptibility to blockage by chillingand heat girdling. When the feed leaf component was exposedto an anaerobic gas stream consisting of N2 gas supplementedwith 40 Pa CO2, the export of previously-fixed 11C-photoassimilatesfrom both leaflets and tendrils continued in the light, butstopped in the dark. However, in the light, translocation of11C-assimilates from the leaflet was rapidly blocked by a flowof pure N2 (i.e. anoxia). Movement of 11C-assimilates from theleaf of another C3 plant, sunflower, was similar to that fromthe pea leaflet. In contrast to both laminar leaf components,export from the tendrils was stopped under pure N2 only in thedark. Taken together the data suggest that photosynthetic O2production facilitated the movement of 11C-assimilates in theabsence of exogenous O2. The differences observed between thetendrils and the leaflets exposed to pure N2 could be attributedto the greater capacity of tendrils to produce and recycle CO2to support photosynthetic O2 production in the light. Key words: Pea, 11C-translocation, anoxia, tendril, leaflet 相似文献
104.
Unfolding and refolding of dimeric creatine kinase equilibrium and kinetic studies. 总被引:2,自引:0,他引:2 下载免费PDF全文
Y. X. Fan J. M. Zhou H. Kihara C. L. Tsou 《Protein science : a publication of the Protein Society》1998,7(12):2631-2641
Equilibrium and kinetic studies of the guanidine hydrochloride induced unfolding-refolding of dimeric cytoplasmic creatine kinase have been monitored by intrinsic fluorescence, far ultraviolet circular dichroism, and 1-anilinonaphthalene-8-sulfonate binding. The GuHCl induced equilibrium-unfolding curve shows two transitions, indicating the presence of at least one stable equilibrium intermediate in GuHCl solutions of moderate concentrations. This intermediate is an inactive monomer with all of the thiol groups exposed. The thermodynamic parameters obtained by analysis using a three-state model indicate that this intermediate is similar in energy to the fully unfolded state. There is a burst phase in the refolding kinetics due to formation of an intermediate within the dead time of mixing (15 ms) in the stopped-flow apparatus. Further refolding to the native state after the burst phase follows biphasic kinetics. The properties of the burst phase and equilibrium intermediates were studied and compared. The results indicate that these intermediates are similar in some respects, but different in others. Both are characterized by pronounced secondary structure, compact globularity, exposed hydrophobic surface area, and the absence of rigid side-chain packing, resembling the "molten globule" state. However, the burst phase intermediate shows more secondary structure, more exposed hydrophobic surface area, and more flexible side-chain packing than the equilibrium intermediate. Following the burst phase, there is a fast phase corresponding to folding of the monomer to a compact conformation. This is followed by rapid assembly to form the dimer. Neither of the equilibrium unfolding transitions are protein concentration dependent. The refolding kinetics are also not concentration dependent. This suggests that association of the subunits is not rate limiting for refolding, and that under equilibrium conditions, dissociation occurs in the region between the two unfolding transitions. Based upon the above results, schemes of unfolding and refolding of creatine kinase are proposed. 相似文献
105.
Comparison of inactivation and conformational changes of D-glyceraldehyde-3-phosphate dehydrogenase during thermal denaturation 总被引:2,自引:0,他引:2
Y Z Lin S J Liang J M Zhou C L Tsou P Q Wu Z K Zhou 《Biochimica et biophysica acta》1990,1038(2):247-252
The inactivation of D-glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating) EC 1.2.1.12) (GAPDH) during thermal denaturation has been compared to its dissociation-aggregation measured by light scattering and changes in secondary structure measured by CD in the far ultraviolet. The inactivation at 38.5 degrees C consists of two stages. The rate of the first stage is too fast to be followed by conventional methods. The extent of this fast stage inactivation increases with increasing temperature and, more markedly, with increasing pH. At this stage, the inactivation is reversible and no appreciable dissociation or change in secondary structure can be detected. The secondary structure of the enzyme is relatively heat stable, showing no appreciable change at 38.5 degrees C. At this temperature, the enzyme first dissociates within several minutes probably into dimers and with prolonged heating, it becomes irreversibly aggregated. The above results are in accord with the earlier suggestion, based on results obtained during denaturation of a number of enzymes by guanidine hydrochloride (GdnHCl) and urea, that for some enzymes the active site is situated in a region more susceptible to perturbation than the molecule as a whole (Tsou, C.-L. (1986) Trends Biochem. Sci. 11, 427). 相似文献
106.
Cynthia S. Ricard Janelle M. Jakubowski John W. Verbsky M. Alejandro Barbieri William M. Lewis G. Esteban Fernandez Marion Vogel Christina Tsou Vinoy Prasad Philip D. Stahl Gabriel Waksman Clarissa M. Cheney 《Genesis (New York, N.Y. : 2000)》2001,31(1):17-29
Summary: Rab GTPases are essential for vesicular transport. Rab GDP dissociation inhibitor (GDI) binds to GDP‐bound rabs, removes rabs from acceptor membranes and delivers rabs to donor membranes. We isolated lethal GDI mutations in Drosophila and analyzed their developmental phenotypes. To learn how these mutations affect GDI structure, the crystal structure of Drosophila GDI was determined by molecular replacement to a resolution of 3.0 Å. Two hypomorphic, missense mutations are located in domain II of GDI at highly conserved positions, but not in previously identified sequence conserved regions. The mutant GDIs were tested for ability to extract rabs from membranes and showed wild‐type levels of rab membrane extraction. The two missense alleles showed intragenic complementation, indicating that domain II of GDI may have two separable functions. This study indicates that GDI function is essential for development of a complex, multicellular organism and that puparium formation and pole cell formation are especially dependent on GDI function. genesis 31:17–29, 2001. © 2001 Wiley‐Liss, Inc. 相似文献
107.
Yang CW Su JY Tsou AP Chau GY Liu HL Chen CH Chien CY Chou CK 《Biochemical and biophysical research communications》2005,330(2):489-497
DNA microarray has been widely used to examine gene expression profile of different human tumors. The information generated from microarray analysis usually represents the overall range of cancer-associated abnormality associated with gene regulation. In order to identify key regulatory genes involved in carcinogenesis of human cancer, hypothesis driven data mining of the microarray data plus experimental validation becomes a critical approach in the post-genome era. Here, we present an integrative genomic analysis of published microarray data and homolog gene database. Over 20,000 genes were examined to reveal 16 genes specific to vertebrates, cell cycle G2/M regulated, and overexpressed in human HCC. Using Affymetrix microarray analysis, we found that all 16 genes were up-regulated in human HCC. Among these 16 genes, we experimentally validated the up-regulation of receptor for hyaluronan-mediated motility (RHAMM) in different cell model systems. We first confirmed elevation of RHAMM in the G2/M phase of synchronized HeLa cells. We also found that RHAMM had an elevated level of expression in all the HCC samples we examined and it was induced during the G2/M phase of regenerating mouse hepatocytes after partial hepatectomy. Thus, the expression of RHAMM appears to be tightly regulated during mammalian cell cycle G2/M progression. The ectopic overexpression of RHAMM in 293T cells resulted in the accumulation of cells at G2/M phase. RHAMM-induced mitotic arrest of cells was predominantly in the prophase. Taken together, using an integrated functional genomic approach, we have uncovered a set of genes that may play specific roles in cell cycle progression and in HCC development. To elucidate the function of these genes in cell cycle regulation may shed light on the control mechanism of human HCC in the future. 相似文献
108.
Huang SY Kuo YH Lee YP Tsou HL Lin EC Ju CC Lee WC 《Animal reproduction science》2000,63(3-4):231-240
This study attempted to clarify the relationship between the levels of 70kDa heat shock protein (HSP70) and semen quality in boars. Semen samples from 29 (13 Duroc, 9 Landrace, and 7 Yorkshire) boars (mean age=25.2+/-2.2 months) were examined. Three to four ejaculates per boar, collected during cool and hot seasons, were evaluated in terms of the sperm concentration, sperm motility, percentage of normal and abnormal sperm, as well as percentage of sperm with proximal and distal plasma droplets. Significant seasonal and breed differences in semen quality were observed. Experimental results indicate that the semen quality of Landrace boars was better than those of Yorkshire and Duroc boars (P<0.05) and semen quality declined significantly during the hot season (P<0.05). One-dimensional SDS-PAGE analysis of spermatozoa proteins indicated that protein profiles did not significantly differ between seasons and among breeds. Both constitutive and stress-inducible form of HSP70 were detected in boar spermatozoa by Western blot analysis. The level of HSP70, which revealed no difference among breeds within a season, was significantly lower during the hot season in all the three breeds (P<0.05). Although there appeared to be low correlation coefficients between the level of HSP70 and semen quality traits, the semen quality tended to decline significantly in samples with a lower level of HSP70. Results in this study suggest that the levels of HSP70 in boar spermatozoa are significantly lower during the hot season and might be associated with semen quality. 相似文献
109.
It is known that denaturation of D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) in low concentrations of GuHCl, around 0.5 M, at 25 degrees C, leads first to a burst phase drop of activity, followed by slow unfolding with further loss of enzyme activity and aggregation. However, GAPDH at higher concentrations does not increase the aggregation in the slow phase as would be expected but decreases both the inactivation and aggregation of the enzyme instead. It seems that GAPDH at high concentrations protects the enzyme against GuHCl-denaturation. This protection is not a general effect of GuHCl binding by increased protein concentration but specific for GAPDH, as either bovine serum albumin or alpha-lactalbumin does not show any protection at similar concentrations. It is proposed that dissociation of tetrameric GAPDH into dimers in the early phase of denaturation in dilute GuHCl is reversible and further unfolding of the dimer to an aggregation prone species is irreversible and rate-limiting for the unfolding process. High concentrations of the enzyme shift the equilibrium towards the tetramer thus decrease the aggregation of GAPDH in dilute GuHCl. 相似文献
110.
We investigated the possible correlation between the leptin concentration and the Zn/Cu ratio in the plasma of women with
thyroid disorder. Forty women with hypothyroidism (n=20) or hypothyroidism (n=20) and 20 euthyroid controls were recruited. The results showed that the women with thyroid disorder (hypothyroidism or
hyperthyroidism) had higher plasma leptin concentrations than the normal controls (p<0.05). Moreover, the plasma leptin concentration had no correlation with plasma thyroid hormone levels in the separate groups,
nor among all the participants considered together. A strong correlation (p<0.005) between leptin and adiposity was only observed in euthyroid women. Plasma values of Zn and Cu and the Zn/Cu ratio
were not markedly different among women with altered thyroid status. However, a weak correlation (r=0.28, p=0.032) between leptin and the Zn/Cu ratio was found from the pooled data of all participants and retained after adjustment
for adiposity. We suggest that there may exist an interaction between the plasma leptin level and thyroid hormone-induced
abnormality for selected minerals. 相似文献