Myelinisierte Oligodendrozyten in der Wand der Eminentia mediana des Kaninchens

Zusammenfassung In der Wand der Eminentia mediana des erwachsenen Kaninchens kommen myelinisierte Oligodendrozyten vor. Jeder von ihnen ist von einer dünnen Markscheide umgeben. Dieses Myelin unterscheidet sich in folgendem von Axon-Myelin: Stellenweise erscheinen die dieOligodendrozyten umgebenden Lamellen nicht als typische Linien (innere Verbundmembranen), sondern es bleiben zytoplasmatische Umscheidungen der Oligodendrozyten erhalten. Die Lamellen können mit einer zungenförmigen Schleife in verschiedener Länge innerhalb der Markscheide endigen. Das Myelin der Oligodendrozyten ist deshalb unregelmäßg strukturiert.

---

Myelinated oligodendrocytes in the wall of the median eminence in rabbit

Summary In the wall of the median eminence of the adult rabbit myelinated oligodendrocytes occur. Each of them is surrounded by thin myelin sheaths. This myelin differs in the following respects from axonal myelin: In some instances lamellae surrounding oligodendrocytes appear not as typical dense lines (internal compound membranes) but as persisting oligodendrocyte cytoplasm sheaths. Lamellae may terminate in various length within the sheaths forming a tonguelike loop. For this reason irregularities appear in the structure of oligodendrocyte myelin.

Die Untersuchung wurde mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft durchgeführt.     

An Anion‐Tuned Solid Electrolyte Interphase with Fast Ion Transfer Kinetics for Stable Lithium Anodes

The spatial distribution and transport characteristics of lithium ions (Li⁺) in the electrochemical interface region of a lithium anode in a lithium ion battery directly determine Li⁺ deposition behavior. The regulation of the Li⁺ solvation sheath on the solid electrolyte interphase (SEI) by electrolyte chemistry is key but challenging. Here, 1 m lithium trifluoroacetate (LiTFA) is induced to the electrolyte to regulate the Li⁺ solvation sheath, which significantly suppresses Li dendrite formation and enables a high Coulombic efficiency of 98.8% over 500 cycles. With its strong coordination between the carbonyl groups (C?O) and Li⁺, TFA^? modulates the environment of the Li⁺ solvation sheath and facilitates fast desolvation kinetics. In addition, due to relatively smaller lowest unoccupied molecular orbital energy than solvents, TFA^? has a preferential reduction to produce a stable SEI with uniform distribution of LiF and Li₂O. Such stable SEI effectively reduces the energy barrier for Li⁺ diffusion, contributing to low nucleation overpotential, fast ion transfer kinetics, and uniform Li⁺ deposition with high cycling stability. This work provides an alternative insight into the design of interface chemistry in terms of regulating anions in the Li⁺ solvation sheath. It is anticipated that this anion‐tuned strategy will pave the way to construct stable SEIs for other battery systems.     

Geometric relationships between whitefly feeding behavior and vascular bundle arrangements

This study revealed strong evidence that nymphs of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, are obligate feeders on vascular bundles and that there are large differences between different host plants as to the availability of vascular bundles to silverleaf whitefly nymphs. The relationship between nymphs and leaf vascular bundles was studied using 1) leaf sectioning and 2) techniques of leaf clearing of intact leaves. A geometric model is presented of the feeding relationship of vascular bundle-using homopterans. The relative abundance of vascular bundles was examined in six species of host plants that varied from highly preferred to tolerably acceptable. Included in order of acceptance were cantaloupe, cotton, hibiscus, broccoli, lantana and lettuce. The length of vascular bundle per 1.0 mm² of leaf surface ranged from about 10 mm in cantaloupe to 2.8 mm in lettuce. Salivary sheaths were found to connect with vascular bundles in 100% of the intact nymphs examined by the staining and clearing technique. However only 64% of those examined by the sectioning technique appeared to be connected to vascular bundles. This indicates that the sectioning technique leads to a high rate of error, causing an underestimation of the importance of direct contact with vascular bundles. About 50% of epidermal stylet penetrations were through epidermal cells; the remaining 50% went through intercellular junctions. On cotton leaves, the distance between the point of labial contact with the leaf surface and the nearest point of the vascular bundle rarely exceeded 60 m. Our studies show that while 50% of lettuce leaf-surface was beyond 60 m of a vascular bundle, only 10% of cantaloupe leaf surface area was outside of the 60 m range. In cotton, mean distance from labium to the nearest point of the vascular bundle was 40.9 m (SEM=2.66, N=50, range 0–80 m). Over 98% of all salivary sheaths went to minor veins (78% to single-filament vascular bundles, nearly 20% to double filament bundles). Fewer than 2% went to bundles with 3 or more filaments.     

Phylogenetic and taxonomic problems in freshwater Oligochaeta with special emphasis on chitinous structures in Tubificinae

Setae and chitinous penis sheaths are the main characters used to distinguish genera and species of the subfamily Tubificinae. Genital setae and penis sheaths are of functional importance to facilitate copulation. Similar structures in different genera may be homologous or products of parallel evolution (homoiologous). Form and dimensions of the penis sheaths of many tubificine species are very variable. Transspecific overlap of quantitative species characters can make the determination of specimens in the genus Limnodrilus difficult. The configuration of the distal ends of the penis sheaths is an important character to distinguish Limnodrilus species. The definition of the intraspecific variability of this morphological character is problematic.     

Mechanisms of chloride partitioning in the leaves of salt-stressed Sorghum bicolor L.

Chloride transport in sheath and blade tissue and the cellular distribution of Cl^- were investigated in an attempt to determine the physiological basis of the preferential accumulation of Cl^- in sheaths of salt-stressed sorghum ( Sorghum bicolor L.). Import and export of ³⁶Cl^- in leaf sheaths and blades of intact sorghum were followed over a 2 week period. X-ray microanalysis of frozen-hydrated bulk tissue samples was used to determine the accumulation of Cl^- and other elements in the vacuoles of sheath and blade cells.
Sheath tissue accumulated Cl^- despite a relatively high Cl^- turnover rate. Chloride was shown to accumulate in most cell types of the sheath, particularly in adaxial epidermal cells. After an initial increase in the concentration of Cl^-, blade tissue regulated Cl^- levels within certain limits. Chloride levels in blades were greater in the abaxial and adaxial epidermal cells than in other cell types. The epidermal cells of blades accumulated Cl^- to approximately the same concentration as sheath epidermal cells. The Cl^- concentration in the photosynthetically active mesophyll and bundle sheath cells, however, remained low.
Thus, the partitioning of Cl^- previously observed in the leaves of salinized sorghum apparently results from the ability of bundle sheath and mesophyll cells to maintain concentrations of Cl^- at lower levels than do epidermal cells. In addition, the relatively large sheath parenchyma cells tend to serve as reservoirs for the storage of Cl^-.