69 research outputs found
Time scale and dimension analysis of a budding yeast cell cycle model
The progress through the eukaryotic cell division cycle is driven by an underlying molecular regulatory network. Cell cycle progression can be considered as a series of irreversible transitions from one steady state to another in the correct order. Although this view has been put forward some time ago, it has not been quantitatively proven yet. Bifurcation analysis of a model for the budding yeast cell cycle has identified only two different steady states (one for G1 and one for mitosis) using cell mass as a bifurcation parameter. By analyzing the same model, using different methods of dynamical systems theory, we provide evidence for transitions among several different steady states during the budding yeast cell cycle. By calculating the eigenvalues of the Jacobian of kinetic differential equations we have determined the stability of the cell cycle trajectories of the Chen model. Based on the sign of the real part of the eigenvalues, the cell cycle can be divided into excitation and relaxation periods. During an excitation period, the cell cycle control system leaves a formerly stable steady state and, accordingly, excitation periods can be associated with irreversible cell cycle transitions like START, entry into mitosis and exit from mitosis. During relaxation periods, the control system asymptotically approaches the new steady state. We also show that the dynamical dimension of the Chen’s model fluctuates by increasing during excitation periods followed by decrease during relaxation periods. In each relaxation period the dynamical dimension of the model drops to one, indicating a period where kinetic processes are in steady state and all concentration changes are driven by the increase of cytoplasmic growth.We apply two numerical methods, which have not been used to analyze biological control systems. These methods are more sensitive than the bifurcation analysis used before because they identify those transitions between steady states that are not controlled by a bifurcation parameter (e.g. cell mass). Therefore by applying these tools for a cell cycle control model, we provide a deeper understanding of the dynamical transitions in the underlying molecular network
Alteration of sarcoplasmic reticulum Ca<sup>2+</sup> ATPase expression in lower limb ischemia caused by atherosclerosis obliterans
Atherosclerosis is a disease caused by a build-up of fatty plaques and cholesterol in the arteries. The lumen of the vessels is obliterated resulting in restricted blood supply to tissues. In ischemic conditions, the cytosolic Ca2+ level of skeletal muscle may increase, indicating the alteration of Ca2+ removal mechanisms. Ca2+ is transported from cytosol into the sarcoplasmic reticulum by Ca2+ ATPase (SERCA), with its 1a isoform expressed in adult, while its 1b isoform in neonatal and regenerating fast-twitch skeletal muscle. To investigate the role of these isoforms in ischemic skeletal muscle, biopsies from musculus biceps femoris of patients who underwent amputation due to atherosclerosis were examined. Samples were removed from the visibly healthy and hypoxia-affected tissue. Significantly increased SERCA1a expression was detected under the ischemic conditions (246 ± 69%; p  0.05), whereas SERCA2a did not change. In addition, in primary cultures derived from hypoxia-affected tissue, the diameter and fusion index of myotubes were significantly increased (30 ± 1.6 µm vs. 41 ± 2.4 µm and 31 ± 4% vs. 45 ± 3%; p < 0.05). We propose that the increased SERCA1a expression indicates the existence and location of compensating mechanisms in ischemic muscle
Uncertainty of the rate parameters of several important elementary reactions of the H2 and syngas combustion systems
Kinetics of the hydrogen abstraction ·C2H5 + alkane → C2H6 + alkyl reaction class: an application of the reaction class transition state theory
This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions at alkane by the C2H5 radical on-the-fly. The linear energy relationship (LER), developed for acyclic alkanes, was also proven to hold for cyclic alkanes. We have derived all RCTST
parameters from rate constants of 19 representative
reactions, coupling with LER and the barrier height
grouping (BHG) approach. Both the RC-TST/LER, where
only reaction energy is needed, and the RC-TST/BHG,
where no other information is needed, can predict rate
constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 50% systematic errors on the average exist in the predicted rate constants using either
the RC-TST/LER or RC-TST/BHG method, while in comparison with explicit rate calculations, the differences
are within a factor of 2 on the average. The results also
show that the RC-TST method is not sensitive to the choice
of density functional theory used
Abcg2 labels multiple cell types in skeletal muscle and participates in muscle regeneration
Abcg2-expressing cells proliferate after muscle injury and are required for effective regeneration of multiple muscle cell lineages
Molecular structure and developmental expression of zebrafish atp2a genes
[[abstract]]We isolated two atp2a genes, atp2a1 and atp2a2a, from embryonic zebrafish. Amino acid sequences deduced from zebrafish atp2a genes are aligned with orthologue proteins from other species, the results showed that they share high percentage of identities (82%–94%) and acidic pIs (5.03–5.33). Whole mount in situ hybridization experiments showed that atp2a1 and atp2a2a are maternal inherited genes which can be detected at 1-cell stage embryos and express in the entire animal pole from 6 hours post-fertilization (hpf) to 12 hpf. At the later stages (48–96 hpf), expression of atp2a1 was restricted in head and trunk muscles as well as in some neurons. In contrast to the strongly expression of atp2a1 in head muscle, expression of atp2a2a was detected in head muscle in a fainter manner. In addition, transcripts of atp2a2a were observed in the developing heart during early cardiogenesis. The present studies not only help us to comparatively analyze atp2a genes across species, but also provide useful information about expressions during early embryogenesis that will help in further investigations of functional studies of Atp2a in the future.[[incitationindex]]SCI[[booktype]]紙
Kinetics of 1,6-hydrogen migration in alkyl radical reaction class
The kinetics of the 1,6-intramolecular hydrogen migration in the alkyl
radical reaction class has been studied using the reaction class transition state theory
(RC-TST) combined with the linear energy relationship (LER) and the barrier height
grouping (BHG) approach. The RC-TST/LER, where only reaction energy is needed,
and RC-TST/BHG, where no other information is needed, are found to be promising
methods for predicting rate constants for any reaction in the 1,6-intramolecular H
migration in alkyl radicals reaction class. Direct comparison with available experimental
data indicates that the RC-TST/LER, where only reaction energy is needed, can
predict rate constants for any reaction in this reaction class with satisfactory accuracy
Zur Analyse der Meskalin-Wirkung am Normalen (Zugleich allgemeiner und einleitender Teil fĂĽr die beiden folgenden Abhandlungen.)
Silencing SERCA1b in a few fibers stimulates growth in the entire regenerating soleus muscle
The neonatal isoform of the sarcoplasmic/endoplasmic
reticulum Ca2+ ATPase 1 (SERCA1b) is a dominant
Ca2+ pump in the young Wbers of regenerating muscle.
In vivo transfection of about 1% of the Wbers with
SERCA1b RNAi plasmid resulted in no apparent change in
the transfected Wbers, but enhanced the increase of fresh
weight and Wber size in the whole regenerating rat soleus
muscle, until the normal size was reached. Co-transfection
of calcineurin inhibitor cain/cabin-1 with SERCA1b RNAi
was suYcient to cut down the widespread growth stimulation,
but the subsequent transfection of cain into the
SERCA1b RNAi transfected muscle did not inhibit muscle
growth. The SERCA1b RNAi preferably upregulated the expression of the NFAT reporter lacZ compared to controls
when co-transfected into the Wbers. Notably, perimuscular
injection of interleukin-4 (IL-4) antibody but not that of an
unrelevant antibody completely abolished the growth-promoting
eVect of SERCA1b RNAi. This indicates that
silencing SERCA1b in a few Wbers stimulates the calcineurin-
NFAT-IL-4 pathway and Wber growth in the whole
regenerating soleus. These results suggest the presence of
an autocrine–paracrine coordination of growing muscle
Wbers, and put forward a new method to stimulate skeletal
muscle regeneration
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