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251.
252.
A Robust Structural PGN Model for Control of Cell-Cycle Progression Stabilized by Negative Feedbacks
Nestor Walter Trepode Hugo Aguirre Armelin Michael Bittner Junior Barrera Marco Dimas Gubitoso Ronaldo Fumio Hashimoto 《EURASIP Journal on Bioinformatics and Systems Biology》2007,2007(1):73109
The cell division cycle comprises a sequence of phenomena controlled by a stable and robust genetic network. We applied a probabilistic genetic network (PGN) to construct a hypothetical model with a dynamical behavior displaying the degree of robustness typical of the biological cell cycle. The structure of our PGN model was inspired in well-established biological facts such as the existence of integrator subsystems, negative and positive feedback loops, and redundant signaling pathways. Our model represents genes interactions as stochastic processes and presents strong robustness in the presence of moderate noise and parameters fluctuations. A recently published deterministic yeast cell-cycle model does not perform as well as our PGN model, even upon moderate noise conditions. In addition, self stimulatory mechanisms can give our PGN model the possibility of having a pacemaker activity similar to the observed in the oscillatory embryonic cell cycle. 相似文献
253.
Davídková M Juha L Bittner M Koptyaev S Hájková V Krása J Pfeifer M Stísová V Bartnik A Fiedorowicz H Mikolajczyk J Ryc L Pína L Horváth M Babánková D Cihelka J Civis S 《Radiation research》2007,168(3):382-387
A large-scale, double-stream gas puff target has been illuminated by sub-kJ, near-infrared (NIR) focused laser pulses at the PALS facility (Prague Asterix Laser System) to produce high-energy pulses of soft X rays from hot, dense plasma. The double-puff arrangement ensures high gas density and conversion efficiency from NIR to X rays approaching that typical for solid targets. In addition, its major advantage over solid targets is that it is free of debris and has substantially suppressed charged-particle emission. The X-ray emission characteristics of the source were determined for a range of gases that included krypton, xenon, N(2), CO and N(2)-CO. A demonstrated application of the xenon-based source is a single-shot damage induction to plasmid DNA. The yields of single-strand breaks (SSBs) and double-strand breaks (DSBs) were determined as a function of energy fluence adjusted by varying distance of sample from the source and thickness of aluminum filters. 相似文献
254.
Summary. The five regioisomeric bromotryptophans (BrTrps) play an important role in the life of sponges and lower marine invertebrates.
These bromo-amino acids, which are formed by post-translational modifications, are not found in nature in their free state,
but rather are involved in more complex structures. Any of the BrTrps can be part of a peptide, a cyclic peptide, an indole
alkaloid, an ergot alkaloid, a macrocycle and others. The present review covers the synthesis, physical and spectroscopic
properties of the five BrTrps. It also describes the many exiting pharmacological and biological activities played by the
BrTrps and by various secondary metabolites containing brominated tryptophan moieties. Of special interest are cyclic peptides
containing the 2-BrTrp unit, which were isolated from marine sponges e.g. konbamide, orbiculamide A, the various keramamides,
jaspamide eusynstyelamide and more. Important families of non-cyclic peptides containing the 6-BrTrp, include the styelins,
the conotoxins, the cathelicidins and several constrained macrocyclic peptides. Many marine secondary BrTrp-containing, non-peptidic
metabolites also display a remarkable spectrum of bioactivities, which can be harnessed for therapeutic and other purposes.
Examples are: barettin, bromotryptanthrin, tetraacetyl clionamide, cyclocinamide A, clavicipitic acid, various brominated
β-carbolines. In this review we have presented the various synthetic routes leading to the preparation of the five BrTrps
and many of its derivatives. Also, we have introduced the reader to many synthetic routes leading to BrTrp-containing non-peptidic
natural products. Although the functional role of the various compounds in the human body is only poorly understood, its effects
were extensively studied. Almost all of these compounds exhibit important therapeutic properties e.g. antifungal, antimicrobial,
antihelmintic, insecticidal ichthyotoxic and anticancer activity. In the present review attempts have been made to provide
synopsis, synthesis and symbiosis of chemical and biological actions, which may provide future guidance and facilitate further
research in this area. 相似文献
255.
Barten MJ Tarnok A Garbade J Bittner HB Dhein S Mohr FW Gummert JF 《Cell proliferation》2007,40(1):50-63
OBJECTIVES: Recent studies show that measuring pharmacodynamic (PD) effects offers a unique possibility to predict immunosuppression. Thus, in this study we have monitored the PD properties of immunosuppressants on diverse T-cell functions in heart transplant (HTx) recipients. MATERIALS: PDs and blood concentrations (PK) of three different basis-immunosuppressive drugs were studied: cyclosporin A (CsA); tacrolimus (TRL) and sirolimus (SRL). T-cell function was analysed by expression of proliferating cell nuclear antigen (PCNA) labelling, expression of cytokines (IL-2, IFN-gamma) and surface antigen (for example, CD25) by FACS analysis. RESULTS: In group I, at time points C0 and C2, increased CsA-PK significantly inhibited expression of IL-2, IFN-gamma, PCNA and CD25 (P < 0.05). Correlations (r(2)) at C2 between inhibition of T-cell functions (PD) with PK and with drug doses were: CsA-PK: 0.71-0.91 and CsA-dose: 0.73-0.87. In group II, increased TRL-PK over time did not further inhibit expression of CD25, but inhibited PCNA expression more on day 3, and IL-2 and IFN-gamma expression was significantly higher on days 2 and 3 compared to PD effects of CsA (P < 0.05). Blood SRL concentrations in C0 group III, increased on day 1 and remained stable at days 3 and 4. Expression of PCNA was not altered in the SRL-PK category, whereas expression of CD25 was higher and expression of cytokines was lower than PD effects of CsA. CONCLUSIONS: Our results show that PD effects on T-cell function can be used to monitor immunosuppression bringing potential to increase the efficacy and safety of immunosuppressive therapy after HTx. 相似文献
256.
MOTIVATION: The formal representation of mereological aspects of canonical anatomy (parthood relations) is relatively well understood. The formal representation of other aspects of canonical anatomy, such as connectedness and adjacency relations between anatomical parts, their shape and size as well as the spatial arrangement of anatomical parts within larger anatomical structures are, however, much less well understood and represented in existing computational anatomical and bio-medical ontologies only insufficiently. RESULTS: In this article, we provide a methodology of how to incorporate this kind of information into anatomical and bio-medical ontologies by applying techniques of representing qualitative spatial information from Artificial Intelligence. In particular, we focus on how to explicitly take into account the qualitative and time-dependent character of these relations. As a running example, we use the human temporomandibular joint (TMJ). AVAILABILITY: Using the presented methodology, a formal ontology was developed which is accessible on http://www.ifomis.org/bfo/fol. This ontology may help to improve the logical and ontological rigor of bio-medical ontologies such as the OBO relation ontology. 相似文献
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