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排序方式: 共有685条查询结果,搜索用时 15 毫秒
1.
F. A. Braeu A. Seitz R. C. Aydin C. J. Cyron 《Biomechanics and modeling in mechanobiology》2017,16(3):889-906
Constrained mixture models for soft tissue growth and remodeling have attracted increasing attention over the last decade. They can capture the effects of the simultaneous presence of multiple constituents that are continuously deposited and degraded at in general different rates, which is important to understand essential features of living soft tissues that cannot be captured by simple kinematic growth models. Recently the novel concept of homogenized constrained mixture models was introduced. It was shown that these models produce results which are very similar (and in certain limit cases even identical) to the ones of constrained mixture models based on multi-network theory. At the same time, the computational cost and complexity of homogenized constrained mixture models are much lower. This paper discusses the theory and implementation of homogenized constrained mixture models for anisotropic volumetric growth and remodeling in three dimensions. Previous constrained mixture models of volumetric growth in three dimensions were limited to the special case of isotropic growth. By numerical examples, comparison with experimental data and a theoretical discussion, we demonstrate that there is some evidence raising doubts whether isotropic growth models are appropriate to represent growth and remodeling of soft tissue in the vasculature. Anisotropic constrained mixture models, as introduced in this paper for the first time, may be required to avoid unphysiological results in simulations of vascular growth and remodeling. 相似文献
2.
Hervé Seitz 《Current biology : CB》2010,20(3):R108-R110
3.
A. E. Melchinger H. H. Geiger G. Seitz G. A. Schmidt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(3):339-345
Summary Three-way cross means were predicted with formulae involving linear functions of general (GCA) and specific combining ability (SCA) effects estimated from single-cross factorials between genetically divergent populations. Data from an experiment with 66 single-cross and 66 three-way cross forage maize (Zea mays L.) hybrids was used for comparing the prediction formulae. The genotypic correlation (r) between observed and predicted three-way crosses increased with increasing , the weighting factor of SCA effects, for plant height and ear dry matter (DM) content. It displayed slightly convex curves for total and stover DM yield, ear percentage, and metabolizable energy content of stover. For Jenkins' method B, r was considerably less than 1.0 for all traits, indicating the presence of epistasis. The square root of heritability (h) of the predicted means decreased with increasing , the reduction being small with a greater number of test environments. Using the product r·h as a criterion of efficiency, none of the prediction methods was consistently superior and the differences among them were rather small (< 7.5%) for all traits, irrespective of the number of test environments. We recommend evaluating the GCA of a greater number of lines from each parent population in testcrosses with a small number of elite lines from the opposite population. All possible three-way or double crosses between both sets of lines should be predicted by Jenkins's method C. This procedure allows one to select with a higher intensity among the predicted hybrids and thus should increase the genetic gain.Extended version of a paper (Geiger et al. 1986) read at the sixth meeting of the EUCARPIA Section Biometrics in Plant Breeding held at Birmingham, UK, July 28–August 1, 1986 相似文献
4.
The ethanol-oxidizing, proton-reducing Pelobacter acetylenicus was grown in chemostat cocultures with either Acetobacterium woodii, Methanobacterium bryantii, or Desulfovibrio desulfuricans. Stable steady state conditions with tightly coupled growth were reached at various dilution rates between 0.02 and 0.14 h-1. Both ethanol and H2 steady state concentrations increased with growth rate and were lower in cocultures with the sulfate reducer < methanogen < homoacetogen. Due to the higher affinity for H2, D. desulfuricans outcompeted M. bryantii, and this one A. woodii when inoculated in cocultures with P. acetylenicus. Cocultures with A. woodii had lower H2 steady state concentrations when bicarbonate reduction was replaced by the energetically more favourable caffeate reduction. Similarly, cocultures with D. desulfuricans had lower H2 concentrations with nitrate than with sulfate as electron acceptor. The Gibbs free energy (G) available to the H2-producing P. acetylenicus was independent of growth rate and the H2-utilizing partner, whereas the G available to the latter increased with growth rate and the energy yielding potential of the H2 oxidation reaction. The critical Gibbs free energy (Gc), i.e. the minimum energy required for H2 production and H2 oxidation, was-5.5 to-8.0 kJ mol-1 H2 for P. acetylenicus,-5.1 to-6.3 kJ mol-1 H2 for A. woodii,-7.5 to-9.1 kJ mol-1 H2 for M. bryantii, and-10.3 to-12.3 kJ mol-1 H2 for D. desulfuricans. Obviously, the potentially available energy was used more efficiently by homoacetogens > methanogens > sulfate reducers. 相似文献
5.
Genetics of the quantitative Lp(a) lipoprotein trait 总被引:13,自引:1,他引:12
Gerd Utermann Hans Georg Kraft Hans Jürgen Menzel Thomas Hopferwieser Christoph Seitz 《Human genetics》1988,78(1):41-46
The Lp(a) lipoprotein is a complex particle composed of a low density lipoprotein (LDL)-like lipoprotein and the disulfide bonded Lp(a) glycoprotein. The complex represents a quantitative genetic trait. SDS gel electrophoresis under reducing conditions of sera followed by immunoblotting with affinity-purified polyclonal anti-Lp(a) demonstrated inter- and intra-individual size heterogeneity of the glycoprotein with apparent Mr in the range 400-700kDa. According to their relative mobilities compared to apo B-100 the Lp(a) patterns were categorized into phenotypes F, B, S1, S2, S3 und S4 and into the respective double-band phenotypes. This size heterogeneity seems to be controlled by multiple alleles designated LpF, LpB, LpS1, LpS2, LpS3, LpS4 and a null allele (LpO) at a single locus. Phenotype frequencies observed in 441 unrelated subjects were in good agreement with those expected from the genetic hypothesis. Comparison of Lp(a) lipoprotein concentrations in the different phenotypes revealed a highly significant association of phenotypes B, S1 and S2 with high, and phenotypes S3 und S4 with intermediate Lp(a) concentrations. A third mode is represented by the null phenotype were no Lp(a) band is detected upon immunoblotting and Lp(a) lipoprotein is low or absent. We conclude that the same gene locus is involved in determining Lp(a) glycoprotein phenotype and Lp(a) lipoprotein concentrations in plasma. This major gene seems to be the Lp(a) glycoprotein structural gene locus. 相似文献
6.
Cryopreservation of Digitalis lanata Ehrh. cell cultures: Preculture and freeze tolerance 总被引:4,自引:0,他引:4
Cryopreservation experiments were performed with Digitalis lanata cell cultures. The main stress was laid on the behaviour of the cells during the preculture period and the capacity of various preculture additives to induce freeze tolerance. The following compounds were used as preculture additives: trehalose, mannitol, sucrose, melibiose, proline, and sorbitol. They are listed in the order of their respective efficiency. Using trehalose, high post-thaw viability rates were achieved and the cells resumed growth after a short lag period. Melibiose was used as a preculture additive for the first time. Its suitability was in the range of that of sucrose. Proline and sorbitol were not able to induce freeze tolerance in Digitalis cells. Cell viability showed a considerable decrease at the beginning of the preculture period. This reduction was found to be transient in the presence of trehalose, mannitol, sucrose, and melibiose. The damaging effects of proline and sorbitol were too severe to be compensated for by the cells. The PAL activity increased markedly in the presence of proline, whereas the trehalose-treated and the control cells behaved nearly identical to one another. 相似文献
7.
Rapid thyroid-hormone effect on mitochondrial and cytosolic ATP/ADP ratios in the intact liver cell. 总被引:2,自引:2,他引:0
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The effect of thyroid-hormone application on cytosolic and mitochondrial ATP/ADP ratio was investigated in rat liver in vivo and in the isolated perfused organ. In vivo the ATP/ADP ratio in livers from hypothyroid rats was 0.84 +/- 0.08 in the mitochondrial matrix and 5.6 +/- 0.9 in the cytosol, as was observed in euthyroid controls. In contrast, hyperthyroidism was followed by a significant decrease in the mitochondrial and by an increase in the cytosolic ATP/ADP ratio (to 0.34 +/- 0.06 and 11.3 +/- 2.8 respectively). In the perfused liver from hypothyroid animals, addition of L-3,3',5-tri-iodothyronine in the perfusate also provoked, within 2 h, a significant decrease in the mitochondrial ATP/ADP ratio, whereas the cytosolic ratio was unaffected. From these and previous data in the isolated perfused liver and in isolated mitochondria from hypothyroid and tri-iodothyronine-treated rats it is concluded that thyroid hormones increase mitochondrial respiration and ATP regeneration, which is associated with an acceleration of mitochondrial adenine nucleotide transport and significant alterations in the mitochondrial and cytosolic ATP/ADP ratios. 相似文献
8.
Histological effects of the microbial metabolite and chitin synthesis inhibitor complex Nikkomycin (AMS 0896 Bayer Leverkusen) on osmoregulatory organs of all developmental stages of Tetranychus urticae are described. The metabolite, in a concentration of 100 ppm, was applied via the nutritive plant. Mites fed for 2 to 14 days, and then were collected and immediately fixed. Two osmoregulatory organs occur in T. urticae. The Malpighian complex, differentiated only in females, shows an increased number of apical microvilli in the epithelium of the distal regions after metabolite application, thus resulting in an enlargement of the surface area. Changes in the second osmoregulatory organ, the coxal organ, after Nikkomycin application include depositions of membranous bodies in the lumen as well as in cytoplasmic vacuoles of the proximal tubule. Additionally, an increase in the luminal diameter occurs. Numerous vacuoles of different contents are observed in the cytoplasm of the distal tubule. Consequences of histological alterations in osmoregulatory organs after Nikkomycin application are discussed with special reference to the composition of salivary secretions. 相似文献
9.
Physical properties and function of phallolysin 总被引:3,自引:0,他引:3
Phallolysin, a mixture of two to three cytolytic proteins (all of Mr 34 000), has been isolated from Amanita phalloides mushrooms and purified to homogeneity (specific activity 24 000 hemolytic units/mg of protein). After separation by isoelectric focusing, the amino acid composition of two of these proteins has been determined. They are rich in water-soluble amino acids and contain one tryptophan residue each, but no cysteine or methionine. Mr was determined to be 34 000 in the native form as well as under denaturing conditions, indicating that the native proteins exist as monomers. Many of the physical properties of phallolysin are strikingly similar to those of staphylococcal alpha-toxin, e.g., molecular weight, existence of multiple forms, pI values, amino acid composition, and thermolability (60 degrees C). Pure phallolysin allowed us to prepare a radioactively labeled toxin. Labeling was achieved by reaction with formaldehyde, followed by reduction with sodium [3H]borohydride. With the labeled toxin (specific activity 7-14 Ci/mmol, ca. 60% biological activity), we investigated its binding to human A2 erythrocytes. We determined the number of receptors on these cells (2 X 10(4) per cell) as well as their affinity to the toxin (KD = 4 X 10(-9) M). In studies on the mechanism of cytolytic activity, we were able to distinguish at least three sequential events: binding of the toxin to human erythrocytes, K+ release, and membrane rupture (hemoglobulin release). These steps could be characterized by different kinetics as well as by different temperature dependencies. Again, the kinetic data for phallolysin are very closely related to those obtained for staphylococcal alpha-toxin.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)
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Wieland B. Huttner Wilhelm Krone Hans J. Seitz Wolfgang Tarnowski 《The Biochemical journal》1974,142(3):691-693
Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ. 相似文献