Structure–function relationships of four compression wood types: micromechanical properties at the tissue and fibre level

The mechanisms behind compressive stress generation in gymnosperms are not yet fully understood. Investigating the structure–function relationships at the tissue and cell level, however, can provide new insights. Severe compression wood of all species lacks a S3 layer, has a high microfibril angle in the S2 layer and a high lignin content. Additionally, special features like helical cavities or spiral thickenings appear, which are not well understood in terms of their mechanical relevance, but need to be examined with regard to evolutionary trends in compression wood development. Thin compression wood foils and isolated tracheids of four gymnosperm species [Ginkgo biloba L., Taxus baccata L., Juniperus virginiana L., Picea abies (L.) Karst.] were investigated. The tracheids were isolated mechanically by peeling them out of the solid wood using fine tweezers. In contrast to chemical macerations, the cell wall components remained in their original condition. Tensile properties of tissue foils and tracheids were measured in a microtensile apparatus under wet conditions. Our results clearly show an evolutionary trend to a much more flexible compression wood. An interpretation with respect to compressive stress generation is discussed.     

Gibberellin mediates the development of gelatinous fibres in the tension wood of inclined Acacia mangium seedlings

Background and Aims

Gibberellin stimulates negative gravitropism and the formation of tension wood in tilted Acacia mangium seedlings, while inhibitors of gibberellin synthesis strongly inhibit the return to vertical growth and suppress the formation of tension wood. To characterize the role of gibberellin in tension wood formation and gravitropism, this study investigated the role of gibberellin in the development of gelatinous fibres and in the changes in anatomical characteristics of woody elements in Acacia mangium seedlings exposed to a gravitational stimulus.

Methods

Gibberellin, paclobutrazol and uniconazole-P were applied to the soil in which seedlings were growing, using distilled water as the control. Three days after the start of treatment, seedlings were inclined at 45 ° to the vertical and samples were harvested 2 months later. The effects of the treatments on wood fibres, vessel elements and ray parenchyma cells were analysed in tension wood in the upper part of inclined stems and in the opposite wood on the lower side of inclined stems.

Key Results

Application of paclobutrazol or uniconazole-P inhibited the increase in the thickness of gelatinous layers and prevented the elongation of gelatinous fibres in the tension wood of inclined stems. By contrast, gibberellin stimulated the elongation of these fibres. Application of gibberellin and inhibitors of gibberellin biosynthesis had only minor effects on the anatomical characteristics of vessel and ray parenchyma cells.

Conclusions

The results suggest that gibberellin is important for the development of gelatinous fibres in the tension wood of A. mangium seedlings and therefore in gravitropism.     

Comparison of the subcellular distribution of G-proteins in hepatocytes in situ and in primary cultures

The subcellular localization of the heterotrimeric G-proteins in hepatocytes in situ was compared to that in hepatocytes in primary culture. The ability of various ligands to activate adenylyl cyclase (AC) in membrane preparations was also investigated. In hepatocytes in situ the G proteins were mainly localized at the plasma membrane while in hepatocytes in culture they were predominantly cytoplasmic. The localization of the G-proteins in hepatocytes in situ correlates with their role in signal transduction. In homogenates prepared from the cultured cells, ligands which stimulate AC via G_sα were without effect, which was consistent with the localization of G_sα in the cytoplasmic and nuclear compartments. The “relocalization” of the G proteins to the cytoplasm when cells are cultured suggests that transmembrane signalling may be regulated by cell differentiation and cell-cell and cell-extracellular matrix interactions. © 1996 Wiley-Liss, Inc.     

Use of negative staining technique and electron microscopy for the study of structural anomalies of outer dense fibres of human flagellum

Motility disorders due to tail defects are often seen in clinical andrology. Sperm motility should be assessed with regard to the morphology of the flagellum. Since suitable longitudinal sections are rarely obtained by routine transmission electron microscopy (TEM) and in view of the importance of dense fibres in modulating sperm motility and providing tensile strength, a detailed, study of human sperm flagellum by negative staining andTEM was attempted. The study was undertaken in two groups of men (I) fertile and (II) asthenozoospermic. The study revealed that outer dense fibres extend to 50–60% of the principal piece. Normal dense fibres were seen in 83% sperms and 23% sperms in groupsI andII respectively. The characteristics seen were variation in diameter, breakage or degradation with lacking or extended endpiece. The negative staining method provides an easy and useful analytical tool for identifying the defects of dense fibres and quantifying them.     

Properties of the vertebrate skeletal muscle tubular system as a sealed compartment

Confocal imaging of impermeant fluorescent dyes trapped in the tubular (t-) system of skeletal muscle fibres of rat and cane toad was used to examine changes in the morphology of the t-system upon mechanical skinning, the time course of dye loss from the sealed t-system in mechanically skinned fibres and the influence of rapid application and removal of glycerol on the morphology of the sealed t-system. In contrast to intact fibres, which have a t-system open to the outside, the sealed t-system of toad mechanically skinned fibres consistently displayed local swellings (vesicles). The occurrence of vesicles in the sealed t-system of rat-skinned fibres was infrequent. Application and removal of 200-400 mM glycerol to the sealed t-system did not produce any obvious changes in its morphology. The dyes fluo-3, fura-2 and Oregon green 488 were lost from the sealed t-system of toad fibres at different rates suggesting that the mechanism of organic anion transport across the tubular wall was not by indiscriminate bulk transport. The rate of fluo-3 and fura-2 loss from the sealed t-system of rat fibres was greater in rat than in toad fibres and could be explained by differences in surface area: volume ratio of the t-system in the two fibre types. Based on the results presented here and on other results from this laboratory, an explanation is given for the formation of numerous vesicles in toad-skinned fibres and lack of vesicle formation in rat-skinned fibres. This explanation can also help with better understanding the mechanism responsible for vacuole formation in intact fibres.     

Über die Struktur der Pilzkörper des Insektenhirns

Zusammenfassung Die Organisation der Corpora pedunculata im Gehirn von Acheta domesticus L. (Orthoptera, Insecta) wurde mit Hilfe von Golgi-Imprägnierungen lichtmikroskopisch untersucht. Die Corpora pedunculata sind aus pilzkörpereigenen, systembegrenzten (intrinsischen) und pilzkörperfremden (extrinsischen) Neuronentypen aufgebaut. Nach ihrer Gestalt lassen sich mindestens 3 intrinsische und 16 extrinsische Fasertypen unterscheiden. Die Zahl der intrinsischen Neuronen (insgesamt 50000 in einem Corpus pedunculatum) ist wesentlich größer als die der extrinsischen Elemente. Das Neuropil der Corpora pedunculata ist in festgelegte Untereinheiten verschiedener Größenordnung zu untergliedern, in denen die Fasertypen spezifisch angeordnet sind. Vergleichende Gestaltbetrachtungen der Fasertypen in den Corpora pedunculata verschiedener Insektenarten lassen gemeinsame Bauprinzipien erkennen. Die Gestaltspezialisierungen der Nervenfasern (blebs, spines, boutons) werden im Hinblick auf elektronenmikroskopische Befunde über synaptische Verknüpfungen diskutiert.

---

Structure of the mushroom-bodies in the brain of insects

Summary The organization of the corpora pedunculata (CP) in the brain of Acheta domesticus L. (Orthoptera, Insecta) was investigated by means of light microscopical techniques (Golgi impregnations). The CP contain intrinsic neurones (globule cells) with fibres restricted to the CP-system and extrinsic fibres (endings and collaterals), which form connexions whith other parts of the brain and nervous system. At least 3 intrinsic and 16 extrinsic types of neurones are distinguished by their shape and size. The number of intrinsic neurones (about 50000 in one Corpus pedunculatum) greatly exceeds that of the extrinsic elements. The neuropile of the CP is subdivided into areas which show a characteristic arrangement of fibre types. Fibre types in the CP of different species exhibit striking similarities in their special structure. Specializations of nerve fibres (blebs, spines, boutons) are discussed with respect to synaptic contacts demonstrated by electron microscopy.

     

Morphometrische Befunde zum submikroskopischen Aufbau des Sehnerven der Ratte

Zusammenfassung An 10 normalen Sehnerven (Länge: 10 mm; Durchmesser: 0,5 mm) erwachsener Albino-Ratten wurden morphometrische licht- und elektronenmikroskopische Untersuchungen mit der Treffermethode an 3 Stellen durchgeführt: 1 mm vor dem Bulbus oculi (Meßort A); Mitte zwischen Bulbus und Chiasma (Meßort B); 1 mm vor dem Chiasma opticum (Meßort C). Die statistisch signifikanten Ergebnisse der Untersuchung sind: 1. die Gesamtzahl der markhaltigen Fasern im Sehnerven der erwachsenen Ratte beträgt in elektronenmikroskopischen Aufnahmen 107152±6780. 2. Der relative Volumenanteil der Markfasern (Axone und Markscheiden) nimmt von A über B nach C um 13,3 Vol.- % zu, der relative Volumenanteil des Interstitiums (Glia, Gefäßmesenchym und extracellulärer Raum) um den gleichen Betrag ab. 3. Mit der Volumenabnahme des Interstitiums korreliert eine Abnahme der Gliakernzahl pro mm³ von A über B nach C um 46,2% und eine Abnahme der Dichte des Capillarnetzes gemessen an der Zahl der Endothel- und Pericytenkerne. 4. Die Größe der Querschnittsflächen durch den Sehnerven ist am Meßort B (Mittelabschnitt) kleiner als bei A und C. 5. Die Berechnung der absoluten Volumina aus den relativen Volumenwerten und der Querschnittsflächengröße ergibt, daß das Volumen des Interstitiums zwischen A und B um 34,8% abnimmt, während das Markfaservolumen hier fast unverändert bleibt. Dagegen nimmt zwischen B und C das Markfaservolumen um 11,8% zu, während das Volumen des Interstitiums weiter, aber nur geringfügig abnimmt. Die Ergebnisse zeigen, daß die Umfang. zunahme des Sehnerven vom Mittelabschnitt (Durchtritt durch den Canalis opticus) gegen beide Endabschnitte durch Volumenvermehrung jeweils verschiedener Gewebskomponenten bedingt ist.

---

Stereological study on the submicroscopic structure of the rat optic nerve

Summary The normal optic nerves of ten adult albino rats were studied using stereological methods of cell counting in light microscopic preparations and point-hit counting on electron micrographs. The observations were confined to three locations of the nerve: one mm from the eyeball (point A), one mm from the optic chiasm (point C) and midway between these sites corresponding to the canalis opticus (point B). The statistically significant results are: 1. the total number of myelinated nerve fibres in the optic nerve is 107152±6780. 2. The volume of myelinated nerve fibres (axons plus myelin sheaths) increases by 13.3% from point A to C, whereas the volume of interstitium (glial cells, capillaries and extracellular space) decreases concomitantly. 3. The decrease in interstitial tissue corresponds to a 46.2% decrease in glial cells between A and C and of capillaries indicated by the numbers of endothelial cells and pericytes. 4. The surface area of cross sections of the optic nerve at point B is smaller than at point A and point C. 5. The absolute volume of the two structural components in the optic nerve, calculated from percentage volume and cross section surfaces, showed that the volume of interstitial tissue decreases from the eyeball to the intermediate portion by 34.8% whereas the volume of myelinated fibres remains nearly constant. From the intermediate portion to the optic chiasm the volume of myelinated fibres increases by 11.8% whereas the interstitial volume further decreases slightly. Thus the increasing diameter of the optic nerve from the middle part to both ends is caused by increases in volume of different tissue constituents.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Musculature of an illoricate predatory rotifer Asplanchnopus multiceps as revealed by phalloidin fluorescence and confocal microscopy

The pattern of muscles in the actively swimming predatory rotifer Asplanchnopus multiceps is revealed by staining with tetramethyl-rhodamine isothiocyanate (TRITC)-labelled phalloidin and confocal scanning laser microscopy (CSLM). The major components of the musculature are: prominent semicircular muscles of the corona; paired lateral, dorsal and ventral retractors in the trunk; a network of six seemingly complete circular muscles and anastomosing longitudinal muscles in the trunk; two short foot retractors, originating from a transverse muscle in the lower third of the trunk. The sphincter of the corona marks the boundary between the head and the trunk. The muscular patterns in rotifers with different lifestyles differ clearly, therefore, the muscular patterns seem to be determined by the mode of locomotion and feeding behaviour.     

The characterization of Tasmanian devil Sarcophilius harrisii pelage fibres and their associated lipids

The Tasmanian devil (Sarcophilius harrisii) is the largest living marsupial carnivore left on Earth. In this paper we report the results of the first thorough characterization of the keratin fibres comprising the Tasmanian devil pelage. The fibre's morphology, structure, composition and surface have been investigated. The results have been compared with those of a number of other mammalian species including carnivores and herbivores. The fibres structure was found to be consistent with that expected for a keratin fibre. From the results of the bound lipid analysis it can be concluded that the Tasmanian devil is a typical mammal in which the 21‐carbon atom anteiso branched fatty acid is the predominant bound fatty acid. This is consistent with the Tasmanian devil's position in the mammalian phylogenetic tree. The amino acid analysis places the devil in line with other carnivores. The high cystine and proline content may correlate with the Tasmanian devil's diet which is rich in muscle and collagen proteins.     

A phylogenetic and functional perspective on the origin and evolutionary shifts of growth ring anatomical markers in seed plants

We reconstruct the evolutionary changes in different anatomical markers in order to understand the evolution and functional aspects of growth rings during the diversification of seed plants (spermatophytes), one of the largest and most diverse lineages of the tree of life. We carried out a wide revision of the anatomy of secondary xylem in spermatophytes and reconstructed the evolution of the different anatomical markers in a time-calibrated phylogeny. By embodying a functionally and evolutionarily significant concept in growth rings we reveal a new panorama for their frequency and show how common they are in diverse lineages of tropical plants. In this context, the principal anatomical markers of growth rings are identified in the evolutionary history of plants and their association with climate-related ecological characteristics. We discuss the function of these anatomical markers, especially for thick-walled and/or radially flattened latewood fibres, fibre zone and dilated rays. Despite the high evolutionary lability of the anatomical markers evidenced by our analyses, they appear to represent deep homologies.