Corrosion Cast Technique Applied in Lymphatic Pathways

The paper deals with methods and results of the microcorrosion cast technique in lymph angiology. For the representation of the special organization of the lymph vascular system including the initial vascular structures, intranodal pathways, bigger collectors, and lymph trunks, the application of various injection techniques is necessary. The interstitial injection of Mercox proves to be suitable to show the initial lymphatics and prelymphatic spaces. Similarly, the intranodal injection makes visible the system of the lymph sinuses and the spaces of the reticular tissue in this organ. Casts of bigger collecting vessels, lymph trunks, and thoracic duct can be obtained by direct injection of the resin into the vascular lumen. Thus, these techniques enable to make visible the structural details of the cast preparations of all parts of the lymphatic system

The Endothelium of Initial Lymphatics During Postnatal Development of the Rat Tongue

The luminal surface of the subepithelial lymphatic plexus in the tongue of rats was investigated with SEM at different stages of postnatal development. In newborn and infant animals prominent and branched endothelial cells exhibit a conspicuous phenomenon producing a very irregular inner profile of the vascular wall. Among these cells the spindle-shaped type proves to be an essential component of the valve structures already found in few-day-old animals. There are also prominent cells with a polygonal appearance resembling histioblasts which form with their manifold processes, that partly extend into the lumen, an interlacing cellular pattern. The special morphological characteristics of the endothelium of the initial lymphatics already occurring in early postnatal development point to several particular functional activities such as controlled permeability, contractility, phagocytotic property, and demonstrate the exceptional position of this kind of vessel among the structures of the lymph- and blood-draining system

Examination of Injected Specimens by Confocal Laser Scanning Microscopy and Scanning Electron Microscopy

Although corrosion casts commonly examined by scanning electron microscopy (SEM) offer good insights into the general arrangement of the microvasculature of certain organs, no information can be obtained from such specimens on special morphological data or dynamic events. Thus, most investigators are obliged to make their interpretations of cast structures only on the basis of indirect criteria. A synopsis, which considers the most important data in that respect, is given for the blood and lymphatic microvessels. Moreover, a methodological approach is introduced, based on the application of fluorescent resin, which allows the examination of cast structures in uncorroded specimens together with the surrounding tissue by confocal laser scanning microscopy (CLSM). When two differently stained resins are injected at different sites, e.g., Mercox-fluorescent yellow into an artery and Mercox-rhodamine into the interstice, blood vessels and lymphatics can be well distinguished. In lymph nodes, the system of lymphoid spaces and that of intranodal sinuses can be separately represented with the same technique. Applications and advantages of the CLSM method, which is a useful tool for an extended interpretation of corrosion casts in SEM, are shown in cast specimens from tongue, skin, and liver in rats. In this study, both corroded and uncorroded specimens were considered. In addition, a new approach is demonstrated which combines casting technique and fluorescence microscopy with investigations carried out under experimental conditions. This allows the examination of microvascular casts together with labelled cells in liver and spleen in a state of phagocytosis

Interpretation of Structural Patterns Appearing on Corrosion Casts of Small Blood and Initial Lymphatic Vessels

Structures imprinted on the corrosion casts of blood and lymphatic microvessels are examined by correlative scanning electron microscopy of corroded casts and fixed tissue. Replicas of the endothelial nuclear portions and cell boundaries and the plastic bands surrounding the casts of terminal blood vessels are demonstrated. In small lymphatics the replication of valve structures, interendothelial open junctions and direct prelymphatic connections is shown. The different imprint patterns are examined in regard to their morphological significance and under methodical aspects

Phylogeography of the thermophilic Cyanobacterium Mastigocladus Laminosus

We have taken a phylogeographic approach to investigate the demographic and evolutionary processes that have shaped the geographic patterns of genetic diversity for a sample of isolates of the cosmopolitan thermophillic cyanobacterial Mastigocladus laminosus morphotype collected from throughout most of its range. Although M. laminosus is found in thermal areas throughout the world, our observation that populations are typically genetically differentiated on local geographic scales suggests the existence of dispersal barriers, a conclusion corroborated by evidence for genetic isolation by distance. Genealogies inferred using nitrogen metabolism gene sequence data suggest that a significant amount of the extant global diversity of M. laminosus can be traced back to a common ancestor associated with the western North American hot spot currently located below Yellowstone National Park. Estimated intragenic recombination rates are comparable to those of pathogenic bacteria known for their capacity to exchange DNA, indicating that genetic exchange has played an important role in generating novel variation during M. laminosus diversification. Selection has constrained protein changes at loci involved in the assimilation of both dinitrogen and nitrate, suggesting the historic use of both nitrogen sources in this heterocystous cyanobacterium. Lineage-specific differences in thermal performance were also observed

CyanoClust: comparative genome resources of cyanobacteria and plastids

Cyanobacteria, which perform oxygen-evolving photosynthesis as do chloroplasts of plants and algae, are one of the best-studied prokaryotic phyla and one from which many representative genomes have been sequenced. Lack of a suitable comparative genomic database has been a problem in cyanobacterial genomics because many proteins involved in physiological functions such as photosynthesis and nitrogen fixation are not catalogued in commonly used databases, such as Clusters of Orthologous Proteins (COG). CyanoClust is a database of homolog groups in cyanobacteria and plastids that are produced by the program Gclust. We have developed a web-server system for the protein homology database featuring cyanobacteria and plastids. Database URL: http://cyanoclust.c.u-tokyo.ac.jp/