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Mechanical Protection (mechanical + protection)
Selected AbstractsWet-Spun Biodegradable Fibers on Conducting Platforms: Novel Architectures for Muscle RegenerationADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Joselito M. Razal Abstract Novel biosynthetic platforms supporting ex vivo growth of partially differentiated muscle cells in an aligned linear orientation that is consistent with the structural requirements of muscle tissue are described. These platforms consist of biodegradable polymer fibers spatially aligned on a conducting polymer substrate. Long multinucleated myotubes are formed from differentiation of adherent myoblasts, which align longitudinally to the fiber axis to form linear cell-seeded biosynthetic fiber constructs. The biodegradable polymer fibers bearing undifferentiated myoblasts can be detached from the substrate following culture. The ability to remove the muscle cell-seeded polymer fibers when required provides the means to use the biodegradable fibers as linear muscle-seeded scaffold components suitable for in vivo implantation into muscle. These fibers are shown to promote differentiation of muscle cells in a highly organized linear unbranched format in vitro and thereby potentially facilitate more stable integration into recipient tissue, providing structural support and mechanical protection for the donor cells. In addition, the conducting substrate on which the fibers are placed provides the potential to develop electrical stimulation paradigms for optimizing the ex vivo growth and synchronization of muscle cells on the biodegradable fibers prior to implantation into diseased or damaged muscle tissue. [source] Opisthonotal glands in the Camisiidae (Acari, Oribatida): evidence for a regressive evolutionary trendJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2009G. Raspotnig Abstract Paired, sac-like and typically large opisthonotal glands (syn. oil glands), mainly considered for chemical protection and communication, characterize the so-called ,glandulate Oribatida' which include the Parhyposomata, Mixonomata, Desmonomata and Brachypylina but also the Astigmata. Among these groups distinct evolutionary trends affect the morphology of glands and their secretion profiles, thereby rendering them highly informative characters with phylogenetic significance. One striking tendency, convergently occurring in a few glandulate groups, leads to the degeneration or even complete regression of opisthonotal glands. In this study, a first example of coherent evolutionary steps towards opisthonotal gland degeneration is described by using desmonomatan Camisiidae as a model: Opisthonotal glands in representatives of genus Platynothrus still show morphologically and chemically ancient conditions with fairly-well developed glandular reservoirs. Secretion patterns mainly consist of a characteristic set of terpenes and aromatics (,astigmatid compounds') as found in outgroups such as desmonomatan Trhypochthoniidae. Progressive states of regression of opisthonotal glands, along with a reduction of component-richness and amounts of secretions, occur in representatives of Heminothrus and, more conspicuously, in species of Camisia, most likely indicating a consistent evolutionary trend. This trend towards opisthonotal gland atrophy may be due to novel alternative and cheap strategies of passive defense in more-derivative camisiids , such as mechanical protection by encrustation of the cuticle , that possibly compensate for the lack of chemical defenses. Zusammenfassung Paarige, sackförmige und typischerweise große opisthosomatische Drüsen (syn. Öldrüsen), deren Sekrete hauptsächlich zum chemischen Schutz und zur Kommunikation dienen sollen, kennzeichnen die sogenannten glandulaten Hornmilben. Innerhalb dieser Hornmilbengruppe, die die Parhyposomata, Mixonomata, Desmonomata, Brachypylina, aber auch die astigmaten Milben umfasst, waren die Öldrüsen offensichtlich in morphologischer und chemischer Hinsicht deutlich unterschiedlichen evolutiven Trends unterworfen; damit sind Öldrüsen ein phylogenetisch außerordentlich wichtiger Merkmalskomplex in der Oribatiden-Systematik geworden. Eine auffällige Tendenz allerdings, die offensichtlich mehrmals konvergent auftritt, führt zur Rückbildung der Drüsen in bestimmten glandulaten Gruppen. In der vorliegenden Arbeit wird zum ersten Mal eine zusammenhängende Linie solcher Rückbildungsstadien am Beispiel der Camisiidae (Desmonomata) beschrieben: die weitgehend noch gut ausgebildeten Öldrüsen von Vertretern der Gattung Platynothrus zeigen morphologisch und chemisch ursprüngliche Merkmale. Sekretprofile bestehen hauptsächlich aus einem charakteristischen Set von Terpenen und Aromaten ("astigmatid compounds'), das auch in Außengruppen wie z.B. bei Trhypochthoniiden auftritt. Fortschreitende Stadien der Rückbildung von Öldrüsen, verbunden mit einer Verarmung der Sekretprofile und einer Verringerung an Sekretmengen, treten in Vertretern von Heminothrus und, noch auffälliger, bei verschiedenen Arten von Camisia auf: dieses Phänomen, übereinstimmend mit einem auf morphologischen Daten basierenden Systemvorschlag, wird als evolutiver Trend innerhalb der Camisiidae gedeutet. Dieser Trend zur Öldrüsenrückbildung ist möglicherweise mit einer alternativen Strategie passiver Verteidigung bei weiter abgeleiteten Camisiiden zu erklären, die Krustenbildungen aus Cerotegument und Bodenpartikeln auf der Körperöberfläche als mechanischen Schutz gegen Prädatoren nützen. Diese möglicherweise energetisch billige Variante könnte den Verlust chemischer Verteidigung über Öldrüsensekretion kompensieren. [source] Slow development of leaf photosynthesis in an evergreen broad-leaved tree, Castanopsis sieboldii: relationships between leaf anatomical characteristics and photosynthetic ratePLANT CELL & ENVIRONMENT, Issue 3 2001S.-I. Miyazawa ABSTRACT Changes in net photosynthetic rate on a leaf area basis and anatomical properties during leaf development were studied in an evergreen broad-leaved tree, Castanopsis sieboldii and an annual herb, Phaseolus vulgaris. In C. sieboldii, surface area of mesophyll cells facing the intercellular air spaces on a leaf area basis (Smes) was already considerable at the time of full leaf area expansion (FLE). However, surface area of chloroplasts facing the intercellular air spaces on a leaf area basis (Sc), and chlorophyll and Rubisco contents on a leaf area basis increased to attain their maximal values 15,40 d after FLE. In contrast, in P. vulgaris, chloroplast number on a leaf area basis, Sc and Smes at 10 d before FLE were two to three times greater than the steady-state levels attained at around FLE. In C. sieboldii, the internal CO2 transfer conductance (gi) slightly increased for 10 d after FLE but then decreased toward the later stages. Limitation of photosynthesis by gi was only about 10% at FLE, but then increased to about 30% at around 40 d after FLE. The large limitation after FLE by gi was probably due to the decrease in CO2 concentration in the chloroplast caused by the increases in thickness of mesophyll cell walls and in Rubisco content per chloroplast surface area. These results clearly showed that: (1) in C. sieboldii, chloroplast development proceeded more slowly than mesophyll cell expansion and continued well after FLE, whereas in P. vulgaris these processes proceeded synchronously and were completed by FLE; (2) after FLE, photosynthesis in leaves of C. sieboldii was markedly limited by gi. From these results, it is suggested that, in the evergreen broad-leaved trees, mechanical protection of mesophyll cells has priority over the efficient CO2 transfer and quick construction of the chloroplasts. [source] Functional Morphology of Equine Pre-ovulatory Cumulus-oocyte ComplexesANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005S. Kölle Knowledge of the functional morphology of equine cumulus-oocyte-complexes (COCs) shortly before ovulation is scarce. Therefore the aim of our studies was to characterize COCs matured in vivo by light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and immunohistochemistry (ICC). Pre-ovulatory COCs were obtained by ultrasound-guided transvaginal aspiration of pre-ovulatory follicles of 26 pony mares. The morphology of pre-ovulatory COCs was compared to that of immature COCs obtained by slicing of ovaries from the slaughterhouse. As shown by light microscopy and SEM, immature COCs possess numerous round, densely packed cumulus cells, which contact each other and possess merely single short processes. Contrary, in pre-ovulatory oocytes the cumulus cells are widely separated but send long cytoplasmic processes to the zona pellucida (ZP). All the cumulus cells are embedded in a huge amount of homogenous extracellular matrix. As shown by alcian blue staining and Periodic Acid Schiff Reaction (PAS) with and without amylase digestion, this matrix contains glycoproteins and acidic and sulphated glycosaminoglycans. In pre-ovulatory COCs both the oocyte and the cumulus cells produce glycosaminoglycans, whereas immature COCs are negative for alcian blue. Similarly, glycoproteins are synthesized in pre-ovulatory, but not in immature COCs. As shown by ICC, hyaluronic acid is one of the most abundant mucopolysaccharide in the pre-ovulatory COC. The high synthetic activity of the cumulus cells in the pre-ovulatory COC is confirmed by TEM showing densely packed endoplasmic reticulum (ER) and accumulation of glycogen in the cumulus cells. Our results imply that in the equine in vitro maturation of the oocyte is characterized by the cumulus cells synthesizing an extracellular matrix of glycoproteins and acidic and sulphated glycosaminoglycans. The extensive production of extracellular, water-binding matrix in the pre-ovulatory COC ensures mechanical protection and nutrition of the oocyte. [source] | ||||||||||