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1.
In C4 plants phosphoenolpyruvate (PEP) of the C4 cycle may betransported on a chloroplast transporter which also transports3-phosphoglycerate (3-PGA) and triosephosphates. In C3 plantsPEP is not considered to be effectively transported on the chloroplastphosphate translocator. The influences of certain organic phosphates,having a similar structure to either PEP or triose-phosphates,on 3-PGA dependent O2 evolution by C4 (Digitaria sanquinalisL. Scop.) and C3 (Hordeum vulgare L.) mesophyll chloroplastswere investigated. In the C4 mesophyll chloroplasts phosphoglycolatewas a competitive inhibitor (Ki = 2.1 mM) of 3-PGA dependentO2 evolution, and was as effective as previously reported forPEP. 2-Phosphoglycerate was also a competitive inhibitor (Kt= 8.6 mM) of O2 evolution in the C4 mesophyll chloroplasts with3-PGA as substrate, while phospholactate was a weak inhibitorand glyphosate had no effect. Neither PEP, phosphoglycolatenor 2-phosphoglycerate were effective inhibitors of 3- PGA dependentO2 evolution in the C3 chloroplasts. Phosphohydroxypyruvatewas a competitive inhibitor of 3-PGA dependent O22 evolutionin both chloroplast types. The selectivity in inhibition ofO2 evolution with 3-PGA as substrate suggests that the C4 mesophyllchloroplasts can recognize certain organic phosphates with thephosphate in the C-2 or C-3 position but that the C4 mesophyllchloroplasts can only effectively recognize certain organicphosphates with the phosphate in the C-3 position. The resultsalso support the view that 3-PGA and PEP are transported onthe same phosphate translocator in C4 mesophyll chloroplasts.
1 Current address: Department of Horticulture, 2001 Fyffe Court,The Ohio State University, Columbus, Ohio 43210-1096. (Received March 24, 1987; Accepted April 16, 1987) 相似文献
2.
Gerald Rosen 《Bulletin of mathematical biology》1980,42(1):95-106
For precise boundary conditions of biological relevance, it is proved that the steadily propagating plane-wave solution to
the Fisher equation requires the unique (eigenvalue) velocity of advance 2(Df)1/2, whereD is the diffusivity of the mutant species andf is the frequency of selection in favor of the mutant. This rigorous result shows that a so-called “wrong equation”, i.e.
one which differs from Fisher's by a term that is seemingly inconsequential for certain initial conditions, cannot be employed
readily to obtain approximate solutions to Fisher's, for the two equations will often have qualitatively different manifolds
of exact solutions. It is noted that the Fisher equation itself may be inappropriate in certain biological contexts owing
to the manifest instability of the lowerconcentration uniform equilibrium state (UES). Depicting the persistence of a mutantdeficient
spatial pocket, an exact steady-state solution to the Fisher equation is presented. As an alternative and perhaps more faithful
model equation for the propagation of certain species properties through a homogeneous population, we consider a reaction-diffusion
equation that features a cubic-polynomial rate expression in the species concentration, with two stable UES and one intermediate
unstable UES. This equation admits a remarkably simple exact analytical solution to the steadily propagating plane-wave eigenvalue
problem. In the latter solution, the sign of the eigenvelocity is such that the wave propagates to yield the “preferred” stable
UES (namely, the one further removed from the unstable intermediate UES) at all spatial points ast→∞. The cubic-polynomial equation also admits an exact steady-state solution for a mutant-deficient or mutant-isolated spatial
pocket. Finally, the perpetuating growth of a mutant population from an arbitrary localized initial distribution, a mathematical
problem analogous to that for ignition in laminar flame theory, is studied by applying differential inequality analysis, and
rigorous sufficient conditions for extinction are derived here. 相似文献
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Daniel A. Vardy Csaba Kari Gerald S. Lazarus Pamela J. Jensen Asher Zilberstein Gregory D. Plowman Ulrich Rodeck 《Journal of cellular physiology》1995,163(2):257-265
Autocrine activation of the epidermal growth factor (EGF) receptor on keratinocytes has been recognized as an important growth regulatory mechanism involved in epithelial homeostasis, and, possibly, hyperproliferative diseases. Insulin-like growth factor (IGF)-1 and insulin have been shown to be paracrine keratinocyte mitogens that bind to the type I IGF receptor which is expressed on actively proliferating keratinocytes in situ. In this report, we demonstrate that IGF-1/insulin induced production of keratinocyte-derived autocrine growth factors that bind to the EGF receptor. Increased steady-state mRNA levels for transforming growth factor alpha (TGF-α) and for amphiregulin (AR) were observed upon incubation of keratinocytes with mitogenic concentrations of IGF-1. IGF-1 also induced production and secretion of TGF-α and AR proteins as detected by immunoassays. An EGF receptor antagonistic monoclonal antibody abolished the mitogenic effect of IGF-1 on cultured keratinocytes. These results suggest that stimulation of keratinocyte growth by IGF-1 requires activation of an EGF receptor-mediated autocrine loop. © 1995 Wiley-Liss, Inc. 相似文献
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A previous experiment(Herzfeld & Taub, 1977) demonstrated that slide projections and explicit suggestions relating to thermal experiences can significantly augment temperature self-regulations training(.5° F,p<.05). However, the experimental design was thought to result in an underestimate of the magnitude of the effect, since each subject served as his own control and could therefore make use on nonsuggestion training days of material provided on training days. In this experiment, separate groups of subjects either were given feedback combined with the suggestion procedure on each of 8 training days or were given feedback alone. The mean temperature self-regulation of the suggestion group(2.01° F) was significantly better than the self-regulation(.73) of the nonsuggestion group(t test,p<.01).a difference of 1.28° F. 相似文献
9.
Summary Osteogenesis imperfecta (OI) is a phenotype with clinical and biochemical heterogeneity. We report here that expression of the OI phenotype extends to the level of dermal fibroblast morphology in vitro. Growth characteristics and morphology of control (n=6) and OI cell strains (n=10, representing the four major OI categories, Sillence classification) were compared by measuring the following: (i) days required in culture to reach confluence after plating at uniform density; (ii) cell density at confluence; (iii) width and length of cells (measured on phase contrast micrographs at 300xmagnification). Our results show that: (i) OI fibroblasts take longer (11–27 days, mean 20 days) than control cells (10–19 days, mean 16 days) to reach stationary phase; (ii) all OI phenotypes achieve a lower cell density (0.87x106 cells/P60, range 0.3–1.6x106) at stationary phase relative to control cells (2.2x106 cells/P60, range 1.7–2.6x106; F4,77=56.1, p<0.01, indicating that OI cells are larger than normal). Cell shape (expressed as the width: length ratio) was also abnormal in OI cells. (F4,730=37.6, p<0.01), types I and II OI cells have significantly increased ratios (p<0.01) relative to control, type III, and type IV cells. Intra-group phenotypic heterogeneity was also apparent in the OI categories and also within the control population. These findings confirm deviant morphologic phenotypes in OI dermal fibroblasts and further demonstrate interindividual heterogeneity in the expression of genes that determine size and shape of dermal fibroblasts in both OI and normal donors.Publication No. 84013 from the Montreal Children's Hospital Research Institute 相似文献
10.
Dennis W. Jung Gerald P. Brierley 《Biochemical and biophysical research communications》1982,106(4):1372-1377
Heart mitochondria respiring in the presence of Pi release endogenous K+ to a sucrose medium when an uncoupler is added. The uncoupled mitochondria retain K+, however, if the oxidation of NAD(P)H is prevented by the addition of rotenone or antimycin. Addition of rotenone, once the uncoupler-dependent K+-efflux has been initiated, results in a rapid reduction of NAD(P) and a simultaneous decrease in permeability to K+. These changes are independent of respiration. The results suggest that a latent pathway for K+-permeability is present in the membrane, that it can be opened and closed reversibly, and that it reflects, either directly or indirectly, the redox status of mitochondrial pyridine nucleotides. The possible relationship of this putative pathway to those available for Ca2+ uptake and release is considered. 相似文献