Cellulase Induction and Wall Extension in the Water Mold Achlya ambisexualis

Branching of the coenocytic hyphae in the water mold Achlya ambisexualis Raper is always accompanied by a rise in cellulase activity. Branching and the cellulase response can be induced either by the sexual hormone atheridiol or by casein hydro-lysate. Only those strains which branch in response to the inducer show a concomitant rise in cellulase. The peak of induced mycelial cellulase corresponds in time with the appearance of branch primordia.     

Meristem growth dynamics and branching patterns in the Cladoniaceae

Branching patterns in the lichen family Cladoniaceae are varied and taxonomically important. Branching occurs on the podetium, the erect secondary thallus that characterizes most species in the Cladoniaceae, and is influenced by growth dynamics of the fungal meristem tissue at the apex of the podetium. Branching is primarily the result of meristem divisions, and branching patterns are modified by meristem enlargement, deformation, and torsion. Branching processes are conserved, and early branch ontogeny provides information from which to determine relationships in the Cladoniaceae. Branching is characterized by two major patterns. In one pattern, branches arise from the relatively late divisions of a large meristem (≥100 μm in diameter), whose shape changes during ontogeny. In a second pattern, branches arise from small meristems (<100 μm in diameter), which split early in ontogeny but whose shape does not change. The trend toward reduced meristems that split early in ontogeny is seen as an evolutionary advance in the Cladoniaceae. Some "small meristem" species retain aspects of the "large meristem" habit in early ontogeny, and this provides a clue to their relationships. Patterns of meristem growth dynamics provide a basis for interpreting phylogeny in mycobionts of the Cladoniaceae. Meristem activities in four genera of the Cladoniaceae were compared in order to determine trends in growth dynamics within the family.     

The evolutionary relationships among known life forms

Summary Sequences of small subunit (SSU) and large subunit (LSU) ribosomal RNA genes from archaebacteria, eubacteria, and the nucleus, chloroplasts, and mitochondria of eukaryotes have been compared in order to identify the most conservative positions. Aligned sets of these positions for both SSU and LSU rRNA have been used to generate tree diagrams relating the source organisms/organelles. Branching patterns were evaluated using the statistical bootstrapping technique. The resulting SSU and LSU trees are remarkably congruent and show a high degree of similarity with those based on alternative data sets and/or generated by different techniques. In addition to providing insights into the evolution of prokaryotic and eukaryotic (nuclear) lineages, the analysis reported here provides, for the first time, an extensive phylogeny of the mitochondrial lineage.     

Localization of Branching Enzyme in Potato Tuber Cells with the Use of Immunoelectron Microscopy

Potato branching enzyme, a key enzyme in the biosynthesis of starch, was localized in amyloplasts in starch-storage cells of potato (Solanum tuberosum L.) with the use of immunogold electron microscopy. Branching enzyme was found in the amyloplast stroma, concentrated at the interface of the stroma and the surface of the starch granule. ADP-glucose pyrophosphorylase, a key regulatory enzyme in starch synthesis, was localized for comparison to exclude possible artifacts. ADP-glucose pyrophosphorylase, in contrast with branching enzyme, proved to be evenly distributed throughout the stroma. Branching enzyme also appears to be present in a membrane-bounded inclusion body in the stroma, whereas ADP-glucose pyrophosphorylase is not. The presence of branching enzyme predominantly at the surface of the starch granule indicates that branching takes place at that surface and not throughout the amyloplast stroma.     

PI3K signaling in the regulation of branching morphogenesis

Branching morphogenesis drives the formation of epithelial organs including the mammary gland, lung, kidney, salivary gland and prostate. Branching at the cellular level also drives development of the nervous and vascular systems. A variety of signaling pathways are orchestrated together to establish the pattern of these branched organs. The phosphoinositide 3-kinase (PI3K) signaling network is of particular interest because of the diverse outcomes it generates, including proliferation, motility, growth, survival and cell death. Here, we focus on the role of the PI3K pathway in the development of branched tissues. Cultured cells, explants and transgenic mice have revealed that the PI3K pathway is critical for the regulation of cell proliferation, apoptosis and motility during branching of tissues.     

Structural studies of mannans from the cell walls of the pathogenic yeasts Candida albicans serotypes A and B and Candida parapsilosis

A comparative study of three cell-wall mannans, of Candida albicans serotypes A and B and Candida parapsilosis, by means of methylation analysis supports a model of yeast mannans as having an alpha-(1----6)-linked backbone with some units (depending on the origin of the mannan) being substituted at O-2 with oligosaccharides joined by alpha-(1---2) and, to a lesser extent, by alpha-(1----3) glycosidic bonds. Branching points in the side chains of Candida albicans mannans were found in substantial proportions for the first time, and the corresponding branched hexasaccharides were isolated by means of acetolysis and subsequent gel filtration. 13C-N.m.r. spectroscopy of the mannans, as well as a 1H-n.m.r. spectroscopic study of the oligosaccharides obtained on acetolysis of the mannans, led to results that agreed with those of methylation analysis.     

On Branching Processes and the Early Stages of the Spread of an Epidemic

Branchingprocess(BP)isusedtomodeltheearlystagesofthespreadofasexuallytransmitteddisease.TheearlystagesofAIDSspreadwhichistransmittedbothhomosexuallyandheterosexuallyarestudiedasaBP.     

Wnt/PCP proteins regulate stereotyped axon branch extension in Drosophila

Branching morphology is a hallmark feature of axons and dendrites and is essential for neuronal connectivity. To understand how this develops, I analyzed the stereotyped pattern of Drosophila mushroom body (MB) neurons, which have single axons branches that extend dorsally and medially. I found that components of the Wnt/Planar Cell Polarity (PCP) pathway control MB axon branching. frizzled mutant animals showed a predominant loss of dorsal branch extension, whereas strabismus (also known as Van Gogh) mutants preferentially lost medial branches. Further results suggest that Frizzled and Strabismus act independently. Nonetheless, branching fates are determined by complex Wnt/PCP interactions, including interactions with Dishevelled and Prickle that function in a context-dependent manner. Branching decisions are MB-autonomous but non-cell-autonomous as mutant and non-mutant neurons regulate these decisions collectively. I found that Wnt/PCP components do not need to be asymmetrically localized to distinct branches to execute branching functions. However, Prickle axonal localization depends on Frizzled and Strabismus.     

Mechanics of mesenchymal contribution to clefting force in branching morphogenesis

Branching morphogenesis is ubiquitous and may involve several different mechanisms. Glandular morphogenesis is affected by growth, cell rearrangements, changes in the basal lamina, changes in the stromal ECM, changes in cell-cell and cell-ECM adhesions, mesenchymal contractility, and possibly other mechanisms. We have developed a 3D model of the mechanics of clefting, focusing in this paper solely on the potential role of mesenchyme-generated traction forces. The tissue mechanics are assumed to be those of fluids, and the hypothesized traction forces are modeled as advected by the deformations which they generate. We find that mesenchymal traction forces are sufficient to generate a cleft of the correct size and morphology, in the correct time frame. We find that viscosity of the tissues affects the time course of morphogenesis, and also affects the resulting form of the organ. Morphology is also strongly dependent on the initial distribution of contractility. We suggest an in vitro method of examining the role of mesenchyme in branching morphogenesis.     

DNA synthesis in relation to hyphal branching and wall composition in Allomyces macrogynus

In A. macrogynus the first replication of DNA occurred after germination, at the time of the first branching of rhizoids. Before the second replication galactan in the wall exceeded the glucan content and was not firmly attached. After the second DNA replication hyphal lengthening commenced with an increase in the content of glucan but the walls lacked rigidity. At the time of the third replication walls underwent a change which commenced at the hyphal tip and worked back to the rhizoids, converting the hyphae to a rigid, cylindrical shape. Branching commenced after the fourth replication of DNA. Multiple branching occurred when mature plants were transferred to glucose-histidine-methionine solution without further DNA synthesis. Hyphal branching was used to show that A. macrogynus was able to use methionine, methionine sulfoxide, methionine sulfone, sodium sulfide, cysteine, cystathionine and homocysteine but not cystine. Thioacetamide supported growth through many subcultures showing that A. macrogynus can synthesize its sulfur amino acids.     

Scatter factor-dependent branching morphogenesis: structural and histological features

Branching morphogenesis is a multi-step process that controls the formation of polarised tubules starting from hollow cysts. Its execution entails a series of rate-limiting events which include reversible disruption of cell polarity, dismantling of intercellular contacts, acquisition of a motile phenotype, stimulation of cell proliferation, and final re-establishment of cell polarity for creation of the definitive structures. Branching morphogenesis takes place physiologically during development, accounting for the establishment of organs endowed with a ramified architecture such as glands, the respiratory tract and the vasculartree. In cancer, aberrant implementation of branching morphogenesis leads to deregulated proliferation, protection from apoptosis and enhanced migratory/invasive properties, which together exacerbate the aggressive features of neoplastic cells. Under both physiological and pathological conditions, branching morphogenesis is mainly accomplished by a family of growth factors known as scatter factors. In this review, we will summarise the current knowledge on the biological and functional roles of scatter factors during branching morphogenesis, with a special emphasis on the phenotypic (structural and histological) consequences of scatter factor activity in different tissues.     

Tube or not tube: remodeling epithelial tissues by branching morphogenesis

Branching morphogenesis involves the restructuring of epithelial tissues into complex and organized ramified tubular networks. Early rounds of branching are controlled genetically in a hardwired fashion in many organs, whereas later, branching is stochastic, responding to environmental cues. We discuss this sequential process from formation of an organ anlage and invagination of the epithelium to branch initiation and outgrowth in several model systems including Drosophila trachea and mammalian lung, mammary gland, and kidney.     

Study on the Correlation of Chemial Structure and Ovicidal Activities of 2-Bromoethylthiobenzenes

Ovicidal and chemical properties of many analogs of 2-bromoethylthiobenzenes were investigated. Replacement of the sulfur atom of 2-bromoethylthiobenzenes by an oxygen atom or a sulfone group, and that of the ethylene group by a trimethylene or a tetramethylene group lowered both the ovicidal activity and the chemical reactivities. Branching of methyl group(s) in the ethylene chain of a certain substituted 2-bromoethylthiobenzenes extremely enhanced the chemical reactivities, but lowered the ovicidal activity of the parent compound.     

Multiple forms of starch branching enzyme of maize: Evidence for independent genetic control

Purification of starch branching enzymes from kernels of two nonlinked mutants of maize, $\text{sugary}$ and $\text{amylose-extender}$, showed the basis of the two mutations to be associated with branching enzymes I and IIb, respectively. Branching enzyme I from $\text{sugary}$ kernels purified as nonmutant branching enzyme I, but had an altered pattern of activity when amylose was used as a substrate. In addition to the typical fall in absorbance at high wavelengths (550–700 nm) of the amylose-iodine complex, branching of amylose by $\text{sugary}$ branching enzyme I caused an increase in absorbance at low wavelengths (400–550 nm). Branching enzyme IIb was undetected in extracts of $\text{amylose-extender}$ kernels, while branching enzymes I and IIa appeared unaltered. Low umprimed starch synthase activity was also observed in DEAE-cellulose fractions of $\text{amylose-extender}$ maize, but this activity was regenerated by the addition of any branching enzyme.     

An investigation of the effects of Ca²+ channel inhibitors on branching and chemotropism in the oomycete Achlya bisexualis: Support for a role for Ca²+ in apical dominance

In an attempt to better understand branching and chemotropism, we describe the effects of Ca2+ channel inhibitors on these processes in Achlya bisexualis, using a branch induction technique and whole plate assays. Branching appears to be a two step process with the initial formation of a bump from which a branch emerges. Verapamil increased numbers of branches in whole plate assays and decreased the distance from the first branch to the tip. In induction assays verapamil increased the number of bumps formed, although in some hyphae it inhibited the transition from an initial bump to a branch. When a branch formed it did not affect the time taken to branch. It had no effect on chemotropism. Lanthanum (La3+) and gadolinium (Gd3+) also increased branching in whole plate assays but their effect was much less marked and they had no effect on bump/branch number in induction assays. Gd3+ decreased the time taken to branch. Both La3+ and Gd3+ increased chemotropism. These data suggest firstly that the respective inhibitors may affect different parts of the branching process and secondly that Ca2+ influx through channels may not be a requirement for branching, indeed such movements may suppress branching. This would fit with elevated Ca2+ at the tip playing a role in apical dominance.     

FKBP52对小鼠前列腺发育的影响

目的通过FKBP52基因敲除小鼠模型探索FKBP52在小鼠前列腺发育过程中的作用。方法分别对胚胎第17．5天、新生的和出生后3周的野生型和FKBP52基因敲除小鼠的前列腺进行切片HE染色,观察不同发育时期里野生型和FKBP52基因敲除小鼠前列腺发育的异同。结果（1）小鼠前列腺发育的起始不依赖于FKBP52基因的参与;（2）随着胚胎的发育,FKBP52在雄鼠前列腺发育中的作用逐渐显现出来,即FKBP52的缺失会导致前列腺叶发育受阻,最终不能形成成熟的前列腺。结论FKBP52在小鼠前列腺的发育过程中具有重要作用,它不参与前列腺的发育起始过程,但其缺失会导致前列腺发育受阻,即不能形成成熟的前列腺。     

Reconstruction of cell population dynamics using CFSE

Background  

Quantifying cell division and death is central to many studies in the biological sciences. The fluorescent dye CFSE allows the tracking of cell division in vitro and in vivo and provides a rich source of information with which to test models of cell kinetics. Cell division and death have a stochastic component at the single-cell level, and the probabilities of these occurring in any given time interval may also undergo systematic variation at a population level. This gives rise to heterogeneity in proliferating cell populations. Branching processes provide a natural means of describing this behaviour.     

Epithelial branching: the power of self-loathing

Branching morphogenesis of epithelia is an important mechanism in mammalian development. The last decade has seen the identification of many signalling pathways and intracellular mechanisms that control epithelial branching. Tissue-level mechanisms that space new branches out have, however, remained an unsolved problem. A recent publication by Nelson et al.1 suggests--if extrapolation from their novel and abstract culture system is valid--that branches may be spaced out by a system of mutual inhibition based on diffusion of TGFbeta. Such a system would allow a developing tree to arrange itself, without detailed genetic specification, by adaptive self-organization.