全身纤维结缔组织网络中的界面流体传输现象

纤维结缔组织在身体中的作用是支撑、连接和分隔不同的组织和器官。最近,人体断肢解剖研究证实,一种定向纤维结缔组织组成了一种长程液体传输通路。其解剖位置有两种:皮肤传输通路(包括真皮、皮下组织和脂肪小叶间隔)和血管周围传输通路(静脉和动脉周围纤维结缔组织)。这种纤维通路的三维空间内部结构是一种纵向分布、相互连接的纤维丝,在每一根纤维丝及其周围水凝胶之间形成了一种固液界面区;纤维结缔组织中的液体能够通过这种界面区传输,命名为"生物界面流体传输通路";存在于各种组织和器官纤维基质中的液体,很可能并没有被束缚在"组织凝胶"中,而是在尚未明确的某种物理机制的作用下,朝向一定的方向传输。这些研究结果为理解纤维结缔组织的功能提供了一个新的视角。     

Kleptoparasitism and complexity in a multi-trophic web

In this work the effects of kleptoparitism in a multi-trophic food-web, in which an omnivorous species scavenges the kills of a top predator, are investigated. Scavengers are assumed to be able to steal predators’ kills by direct interference and aggression. The amount of prey shared depends on the relative competitive abilities of omnivores and predators and on their abundances. To make the proposed model consistent, scavenging is accompanied by other features. First, the predator can prey only on the juvenile life stage of scavengers (i.e. not on adult individuals) as well as on a different species of herbivores. Hence, an age structure is enforced within scavengers, so that they belong to the guild of preys when they are young and vulnerable. Second, predators can switch between prey species selecting the most abundant one. This condition grants the competitive exclusion of the two vegetation eaters, allowing them to co-exist: the omnivore and the herbivore compete for the same vegetation pool but pure herbivores are indeed assumed to be more efficient in its exploitation. The omnivorous species is not able to kill the herbivores, but nonetheless it may exploit their carcasses after they have been killed by predators. Finally, the juvenile/adult ratio of omnivores varies depending on the available resources and predators’ amount. In such a scenario it is shown that kleptoparasitism can modify to a large extent the stability of the system, leading either to a regularization or to chaos, depending both on the scavenger's and the predator's functional response. Moreover, an excess of kleptoparasitism is shown to compromise the whole trophic web, making extinct both predators and scavengers. As far as the authors are aware of, this paper is the first one to explicitly introduce kleptoparasitism in trophic web models.     

小麦异交结实特性的研究

本文研究了不同成分的授粉液与小麦品种绵阳 31 1异交结实的关系 .试验结果表明 :以含硼、钙、镁与赤霉素的组合液较好 ,能促进花粉的活力增强 ,提高异交结实率 .以该品种的柱头和花药提取液作为授粉液 ,也有类似的良好效果     

Structured population on two patches: modeling dispersal and delay

We derive from the age-structured model a system of delay differential equations to describe the interaction of spatial dispersal (over two patches) and time delay (arising from the maturation period). Our model analysis shows that varying the immature death rate can alter the behavior of the homogeneous equilibria, leading to transient oscillations around an intermediate equilibrium and complicated dynamics (in the form of the coexistence of possibly stable synchronized periodic oscillations and unstable phase-locked oscillations) near the largest equilibrium.     

Feasibility of communication in binary signaling games

In signaling games the replicator dynamics does not almost always converge to states of perfect communication. A significant portion of the state space converges to components of Nash equilibria that characterize states of partial communication. Since these components consist of non-hyperbolic rest points, the significance of this result will depend on the dynamic behavior of specific perturbations of the replicator equations. In this paper we study selection-mutation dynamics of signaling games, which may be considered as one plausible perturbation of the replicator dynamics. We find that the long term behavior of the dynamics depends on the mutation rates of senders and receivers and on the relevance of communication.     

Some epidemiological models with nonlinear incidence

Epidemiological models with nonlinear incidence rates can have very different dynamic behaviors than those with the usual bilinear incidence rate. The first model considered here includes vital dynamics and a disease process where susceptibles become exposed, then infectious, then removed with temporary immunity and then susceptible again. When the equilibria and stability are investigated, it is found that multiple equilibria exist for some parameter values and periodic solutions can arise by Hopf bifurcation from the larger endemic equilibrium. Many results analogous to those in the first model are obtained for the second model which has a delay in the removed class but no exposed class.Research supported in part by Centers for Disease Control Contract 200-87-0515. Support services provided at University House Research Center at the University of IowaResearch supported in part by NSERC A-8965 and the University of Victoria President's Committee on Faculty Research and Travel     

In vivo vitiligo induction and therapy model: double-blind, randomized clinical trial

In this study, we developed an in vivo vitiligo induction model to explore the underlying mechanisms leading to Koebner's phenomenon and to evaluate the efficacy of therapeutic strategies. The model consisted of 12 pigmented test regions on the back of generalized vitiligo patients that were exposed to three Koebner induction methods: cryotherapy, 755 nm laser therapy, and epidermal abrasion. In addition, four cream treatments (pimecrolimus, tacrolimus, steroid and placebo) were randomly applied. Koebnerization was efficiently induced by all three induction methods. In general, cryotherapy was the best method of Koebner induction, followed by 755 nm laser therapy and epidermal abrasion. Reproducible results were obtained, which showed enhanced depigmented surface areas and higher amounts of T lymphocytes in placebo-treated test zones compared to active treated areas. Tacrolimus and local steroids were better inhibitors of Koebner's process (P < 0.05) compared to pimecrolimus. Our in vivo vitiligo induction model is very informative to investigate vitiligo induction and to determine the efficacy of topical treatments in vitiligo. This proof of concept confirms the efficient comparison of head-to-head therapeutic strategies intra-individually in a standardized, specific and better timed way.     

Inactivation of glycogen synthase kinase 3β (GSK-3β) enhances mitochondrial biogenesis during myogenesis

Background

Mitochondrial biogenesis is crucial for myogenic differentiation and regeneration of skeletal muscle tissue and is tightly controlled by the peroxisome proliferator-activated receptor-γ co-activator 1 (PGC-1) signaling network. In the present study, we hypothesized that inactivation of glycogen synthase kinase (GSK)-3β, previously suggested to interfere with PGC-1 in non-muscle cells, potentiates PGC-1 signaling and the development of mitochondrial biogenesis during myogenesis, ultimately resulting in an enhanced myotube oxidative capacity.

Differences in reactivity of confluent and nonconfluent cultures of human endothelial cells toward thrombin-stimulated platelets or heparinized salt solution

Summary This study examined whether nonconfluent endothelial cell cultures reacted differently than confluent ones toward thrombin-stimulated platelets or a heparinized salt solution. The adherence to the endothelial cell cultures of⁵¹Cr-labeled human platelets stimulated at different thrombin concentrations was studied. There was significantly higher adherence of stimulated platelets to nonconfluent cultures compared with confluent ones. This was confirmed by scanning electron microscopy, which also revealed a tendency for the platelets to adhere at the cell periphery. Electron microscopy also showed that thrombin-stimulated platelets induced endothelial cell contraction. Part of the peripheral endothelial cell surface toward the bottom of the culture dish was inverted, facing the lumen of the dish. This phenomenon was particularly seen in nonconfluent cultures. When⁵¹Cr-labeled endothelial cultures were incubated with a mildly injurious fluid as heparinized sodium acetate and 20% serum, at 20° C for 30 min, the nonconfluent cultures showed significantly more cell detachment and release of⁵¹Cr than the confluent ones. We conclude that under the conditions of the present experiments there are differences in the reactivity of confluent and nonconfluent endothelial cell cultures. These differences probably reflect biological dissimilarities. In experiments where properties of cultured endothelium are studied, care should be taken that the degree of confluency is standardized.