Morphogenesis in an asymmetric medium

Some key experiments of artificial production ofsitus inversus viscerum are briefly reviewed and a two-step mechanism for the explanation of the systematic asymmetric visceral arrangement in vertebrates is proposed. A two-variable reaction-diffusion system displaying a symmetry-breaking bifurcation is considered, and it is demonstrated that a slight asymmetry of the boundary conditions can give rise to a marked asymmetry in the resulting dissipative structure in both one-and three-dimensional systems. A criterion is formulated allowing classification of reaction-diffusion systems operating in a three-dimensional space with regard to their ability to incorporate slight asymmetries at the boundaries in the form of a chiral dissipative structure.     

Morphogenesis of floral buds of cucumber cultured in vitro

Young floral buds of cucumber plants were cultured aseptically on media containing mineral salts, sugar and various organic metabolites and the development of anthers and pistil in these buds was studied. Three types of buds were used: potentially male, potentially female, and potentially hermaphrodite, removed from seedlings of monoecious, gynoecious and hermaphrodite plants, respectively, but at the time of inoculation all buds were at the bisexual stage.Auxin (3-indoleacetic acid) added to the culture medium promoted ovary development in potentially male buds; gibberellic acid counteracted this IAA effect but seemed to have no constructive effect of its own, whether alone or in combination with IAA. Very young potentially male buds tended to form ovaries even without addition of IAA. Isolated potentially female and potentially hermaphrodite buds continued in isolation their normal development and were little affected by IAA as well as GA₃, although GA₃ at high concentrations seemed to have a deforming effect on the bud (mainly on the ovary tissue).The bearing of these results on the understanding of normal morphogenesis of cucumber flower buds is discussed.     

Morphogenesis as a macroscopic self-organizing process

We start from reviewing different epistemological constructions used for explaining morphogenesis. Among them, we explore the explanatory power of a law-centered approach which includes top-down causation and the basic concepts of a self-organization theory. Within such a framework, we discuss the morphomechanical models based upon the presumption of feedbacks between mechanical stresses imposed onto a given embryo part from outside and those generated within the latter as a kind of active response. A number of elementary morphogenetic events demonstrating that these feedbacks are directed towards hyper-restoration (restoration with an overshoot) of the initial state of mechanical stresses are described. Moreover, we show that these reactions are bound together into the larger scale feedbacks. That permits to suggest a reconstruction of morphogenetic successions in early Metazoan development concentrated around two main archetypes distinguished by the blastopores geometry. The perspectives of applying the same approach to cell differentiation are outlined. By discussing the problem of positional information we suggest that the developmental pathway of a given embryo part depends upon its preceded deformations and the corresponding mechanical stresses rather than upon its static position at any moment of development.     

SARS病毒的形态结构及其在体外培养细胞中的感染装配

Morphological characterization of purified SARS-associated virus(SARS-CoV) from Hubei patient was carried out by negative stain and ultrathin section electronmicroscopy. The spike of isolated SARS-CoV virus is shorter and smaller than Human coronavirus. A large quantity of SARS-CoV particles could be observed in the infected Vero cells. The process of infection, assembly and morphogenesis was observed.     

Features of Morphogenesis of Iris ensata Thunb. in vitro Culture

Russian Journal of Plant Physiology - This paper presents a protocol for in vitro culture of Iris ensata Thunb. and the results of a histological analysis of subsequent morphogenesis stages. To...     

Saponin Glycosylation in Cereals

Triterpene saponins are glycosylated plant secondary metabolites that are common in dicotyledonous species but rare in monocots. These compounds are antimicrobial and are important for plant defence. They also have a variety of pharmaceutical and industrial applications. Oat (Avena spp.) produces triterpene saponins called avenacins, specialised metabolites that are not represented in other cereals. The avenacins are synthesised and stored in roots and provide protection against soil-borne fungal pathogens. Glycosylation is often critical for bioactivity of saponins. We are using a combination of mutant analysis, database mining, expression profiling and functional characterisation to identify glycosyltransferases required for addition of sugar units to avenacins. By identifying the molecular machinery required for avenacin biosynthesis we hope to understand the broader elements of the evolution of specialised metabolic pathways.     

SARS病毒的形态结构及其在体外培养细胞中的感染装配

人冠状病毒1965年由Tyrrell等从人胎儿器官培养(HET-OC)中最初分离.其后Hamre和Kapikian等从组织培养中分离了病毒[4].     

Posterior Coronary Vein as the Substrate for an Epicardial Accessory Pathway

Catheter ablation of Wolff-Parkinson-White syndrome is associated with up to 5% of failure. Coronary sinus (CS) abnormalities or connections between CS myocardial coat and left ventricular epicardium are associated with posteroseptal and left posterior accessory pathways (AP). A 41-year-old patient with WPW syndrome was referred to our hospital after three unsuccessful ablations. The 12-lead ECG suggested a left posteroseptal AP. CT imaging and electro-anatomic mapping showed a relationship between AP electrical course and CS posterior branch. This finding supports the hypothesis CSAPs lie in the myocardial coat around CS and represent an extensive connection between atrial and ventricular epicardial surface.     

病毒攻击泛素蛋白酶体逃逸先天免疫的策略

泛素蛋白酶体水解途径是蛋白质的选择性降解中一种非常重要的机制,它通过选择性地降解蛋白质控制着体内许多重要的生物学过程。病毒侵染宿主细胞后,细胞的泛素蛋白酶体途径与一些重要的病毒蛋白相互作用,参与调节病毒的生命周期。同时,病毒的某些蛋白也会影响泛素蛋白酶体途径,以逃避宿主的防御机制。     

Morphogenesis in vitro in maize inbred lines from the Lancaster heterotic group

The genotypic specificities of morphogenesis and regeneration have been studied in vitro in five maize inbred lines from the breeding-promising Lancaster heterotic group, compared with the representatives of other heterotic groups, that is, PLS61, A188, and Chi31. It has been shown that the ratio between the types of morphogenesis, such as organogenesis and embryoidogenesis, in a callus culture is predetermined by the explant genotype and sucrose concentrations in the medium for callusogenesis. The frequency of embryoidogenesis as the most efficient type of morphogenesis, considering further regeneration, was, on average, 40.0 ± 12.8% for maize inbreds from the Lancaster heterotic group and only 14.0 ± 4.0% from other heterotic groups. A sucrose concentration at a level of 30 g/L in the medium for callusogenesis further supported the process of regeneration through embryoidogenesis in inbreds of the Lancaster heterotic group at a level of 26.5 ± 15.4%, while the sucrose concentration of 60 g/L promoted regeneration up to a level of 57.7 ± 19.8%. Contents of sucrose in the medium for callusogenesis in the inbreds representing other heterotic groups did not affect the process of regeneration, and the level of embryoidogenesis with sucrose at the concentrations of 30 and 60 g/L was, respectively, 11.0 ± 7.0 and 15.0 ± 4.8%.     

Restorative Morphogenesis in vitro in the Annual Medic in the Presence of Benzylaminopurine

Four annual medic species (Medicago orbicularis (L.) All., M. rigidula (L.) Desr., M. scutellata (L.) Miller, and M. rugosa Desr.) were used as model objects for studying the spectrum of morphogenetic reactions in vitro. The seeds were incubated on nutrient media with benzylaminopurine at different concentrations until germination and, thereafter, the explants of seedlings were cultivated in order to obtain primary calluses and morphogenetic structures. Normal and abnormal (with reduced root and/or apex) seedlings were cultivated in the presence of benzylaminopurine. Further cultivation of explants from the seedlings of both types showed a considerable intra- and interspecific polymorphism by the capacity for callusogenesis, frequency of primary restorative reactions, and pattern of microreproduction in vitro. In the control (the seeds were incubated on a hormone-free medium), no cases of microreproduction by way of organogenesis or somatic embryogenesis were observed. In all experimental variants, the restorative reactions preceded microreproduction in vitro.     

Morphogenesis as Influenced by Locally Administered Magnetic Fields

An alteration in morphogenetic development induced in Drosophila melanogaster pupae by exposure to a magnetic probe was shown to persist for more than 30 generations. With succeeding inbred crossings, an initial increase in the time of development through the embryonic and postembryonic stages gradually approached the level found in control cultures. As the development time decreased, a concomitant increase occurred in the yield of progeny. The pattern of morphogenesis suggested a condition of homeostasis operating in an oscillating epigenetic system. The concept of a feedback control mechanism was employed to examine details of the alterations in development time. The data were compatible with this model and rates of recovery from an initial perturbation were determined in several series inbred for a large number of generations. Variations in rate constants and mechanisms involved in the magnetic field inhibition are discussed.