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The current structural models of the cellulose microfibril as well as its mechanical and thermal properties are reviewed. The cellulose microfibril can be considered as a single thin and long crystalline entity with highly anisotropic physical properties. The contribution and limit of different methods employed such as electron microscopy, infrared spectroscopy, X-ray scattering and diffraction, solid state nuclear magnetic resonance spectroscopy, and molecular modeling are also discussed.

Physical, chemical, and biological properties of wood depend largely on the properties of cellulose, noncellulosic polysaccharides, and lignin, and their assembly mode in the cell wall. Information on the assembly mode in the main part of the ginkgo tracheid wall (middle layer of secondary wall, S2) was drawn from the combined results obtained by physical and chemical analyses of the mechanically isolated S2 and by observation under scanning electron microscopy. A schematic model was tentatively proposed as a basic assembly mode of cell wall polymers in the softwood tracheid as follows: a bundle of cellulose microfibrils (CMFs) consisting of about 430 cellulose chains is surrounded by bead-like tubular hemicellulose-lignin modules (HLM), which keep the CMF bundles equidistant from each other. The length of one tubular module along the CMF bundle is about 16 +- 2 nm, and the thickness at its side is about 3 - 4 nm. In S2, hemicelluloses are distributed in a longitudinal direction along the CMF bundle and in tangential and radial directions perpendicular to the CMF bundle so that they are aligned in the lamellae of tangential and radial directions with regard to the cell wall. One HLM contains about 7000 Csub(6)-Csub(3) units of lignin, and 4000 hexose and 2000 pentose units of hemicellulose.

We examined ultrastructural changes of the cell organelles of Arabidopsis stems in response to gamma irradiation. Seedlings treated with 0 to 5 Gy developed normally, while height growth in plants exposed to 50 Gy was significantly inhibited. Based on TEM observations, the chloroplasts were extremely sensitive to such irradiation. In particular, the thylakoids were heavily swollen, some portions of the mitochondria and endoplasmic reticulum were structurally altered, and the plasmalemma had pulled away from the cell wall in places.

Human adipose-derived mesenchymal stem cells (hADMSCs) are a potential cell source for autologous cell therapy due to their regenerative ability. However, detailed cytological or phenotypic characteristics of these cells are still unclear. Therefore, we determined and compared cell size, morphology, ultrastructure, and immunohistochemical (IHC) expression profiles of isolated hADMSCs and cells located in human adipose tissues. We also characterized the localization of these cells in vivo. Light microscopy examination at low power revealed that hADMSCs acquired a spindle- shaped morphology after four passages. Additionally, high power views showed that these cells had various sizes, nuclear contours, and cytoplasmic textures. To further evaluate cell morphology, transmission electron microscopy was performed. hADMSCs typically had ultrastructural characteristics similar to those of primitive mesenchymal cells including a relatively high nuclear/cytosol ratio, prominent nucleoli, immature cytoplasmic organelles, and numerous filipodia. Some cells contained various numbers of lamellar bodies and lipid droplets. IHC staining demonstrated that PDGFR and CD10 were constitutively expressed in most hADMSCs regardless of passage number but expression levels of α-SMA, CD68, Oct4 and c-kit varied. IHC staining of adipose tissue showed that cells with immunophenotypic characteristics identical to those of hADMSCs were located mainly in the perivascular adventitia not in smooth muscle area. In summary, hADMSCs were found to represent a heterogeneous cell population with primitive mesenchymal cells that were mainly found in the perivascular adventitia. Furthermore, the cell surface markers would be CD10/PDGFR. To obtain defined cell populations for therapeutic purposes, further studies will be required to establish more specific isolation methods.

The antimicrobial activity of fatty acids (C8 to C14), monolaurin, citric, succinic, fumaric, malic and lactic acids was determined in cultures of 2 strains of Escherichia coli, 3 strains of Salmonella sp. and 2 strains of Clostridium perfringens. Caprylic acid was the only acid inhibiting glucose utilization in all cultures. Strains CCM 3954 and CCM 4225 of E. coli were inhibited also by capric acid at 5 mg/mL. Strains CCM 4435T and CNCTC 5459 of C. perfringens were inhibited by fatty acids, oleic acid and one strain also by linoleic acid. Growth of C. perfringens was inhibited also by monoglyceride of lauric acid and by citric acid. The separation of inner and outer cell membranes was apparent in C. perfringens CCM 4435T treated with lauric acid at 1 mg/mL, or with its monoglyceride at 5 mg/mL. Medium-chain fatty acids were more efficient antimicrobials than the other, more polar, organic acids tested.

Constitutive expression of the cold-regulated COR15a gene of Arabidopsis thaliana results in a significant increase in the survival of isolated protoplasts frozen over the range of -4.5 to -7 degree C. The increased freezing tolerance is the result of a decreased incidence of freeze-induced lamellar-to-hexagonal II phase transitions that occur in regions where the plasma membrane is brought into close apposition with the chloroplast envelope as a result of freeze-induced dehydration. Moreover, the mature polypeptide encoded by this gene. COR15am, increases the lamellar-to-hexagonal II phase transition temperature of dioleoylphosphatidylethanolamine and promotes formation of the lamellar phase in a lipid mixture composed of the major lipid species that comprise the chloroplast envelope. We propose that COR15am, which is located in the chloroplast stroma, defers freeze-induced formation of the hexagonal II phase to lower temperatures (lower hydrations) by altering the intrinsic curvature of the inner membrane of the chloroplast envelope

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is a pest that is rapidly spreading across the globe. Here, the ultrastructure of R. ferrugineus spermatogenesis and sperm are described. The histology of the testis, sperm ultrastructure, and spermiogenesis were investigated using light and transmission electron microscopy. The differentiation of spermatids was observed to occur within spermiogenetic cysts. Inside each cyst, the spermatids were at the same stage of maturation. During early stages, mitochondria aggregated, fused, and elongated beside the growing flagellar axoneme, while the proacrosome transformed into a triple-layered acrosome, with a perforatorium, acrosomal vesicle, and extra-acrosomal layer. The centriolar adjunct was present in early spermatids but was absent from later spermatid stages and sperm. The sperm's tail displayed a typical axoneme with a 9 + 9 + 2 microtubule arrangement, 2 mitochondrial derivatives of unequal size, and 2 accessory bodies. A small number of sperms exhibited twin or multiple tails due to membrane fusion. Our results support systematic relationships within the family Curculionidae.

The Arabidopsis thaliana hypocotyl is widely used to study the effects of light and plant growth factors on cell elongation. To provide a framework for the molecular-genetic analysis of cell elongation in this organ, here we describe, at the cellular level, its morphology and growth and identify a number of characteristic developmental differences between light-grown and dark-grown hypocotyls. First, in the light epidermal cells show a characteristic differentiation that is not observed in the dark. Second, elongation growth of this organ does not involve significant cortical or epidermal cell divisions. However, endoreduplication occurs, as revealed by the presence of 4C and 8C nuclei. In addition, 16C nuclei were found specifically in dark-grown seedlings. Third, in the dark epidermal cells elongate along a steep, acropetal spatial and temporal gradient along the hypocotyl. In contrast, in the light all epidermal cells elongated continuously during the entire growth period. These morphological and physiological differences, in combination with previously reported genetic data (T. Desnos, V. Orbovic, C. Bellini, J. Kronenberger, M. Caboche, J. Traas, H. Hofte [1996] Development 122: 683-693), illustrate that light does not simply inhibit hypocotyl growth in a cell-autonomous fashion, but that the observed growth response to light is a part of an integrated developmental change throughout the elongating organ

The emerging science of bionanotechnology refers to the harnessing of the vast diversity of self-assembling building blocks and processes for the assembly of nano-scaled structures for the manufacture of highly functional nanomaterials. Bionanotechnology is an interdisciplinary field. It combines biological principles with physical and chemical procedures to generate nano-sized building blocks and materials with specific functions and new properties. It involves the development of biologically-based procedures, the use of biological components and systems, the design of biocompatible objects and systems, and the use of nanotechnology to support biotechnological processes. This book provides a survey of the most striking and successful approaches for the production of biogenic nanodevices, considering not only living organisms as manufacturer, but also in vitro processes that utilize the self-assembly of isolated biomolecules. It presents a topical overview of the vast field of bionanotechnology by describing various biological nanostructures, the implied design space, and the enormous potential for applications in medicine and technology. Two chapters describe the microbial production of tailor-made self-assembled nanostructures which can be processed into functional nanoparticles. Additional chapters comprehensively summarize recent developments in the use of protein-based assemblies for nanodevice and nanomaterials production. Topics include: polymer synthesis * self-assembly and display technology * self-assembly and application of cellulosomal components * protein-aided mineralization of inorganic nanostructures * amyloid fibrils as bionanomaterials * self-assembly and applications of bacteriophages and virus-like particles * plant oil bodies and oleosins-structure function and biotechnological applications * visual restoration using microbial rhodopsins * magnetosomes and liposome-nanoparticle assemblies. This is a recommended book for anyone interested in the fields of nanotechnology, biotechnology, metabolic engineering, molecular biology, genetic engineering, and protein design.

Results of transgenetic studies argue that the scrapie isoform of the prion protein (PrPSc) interacts with the substrate cellular PrP (PrPC) during conversion into nascent PrPSc. While PrPSc appears to accumulate primarily in lysosomes, caveolae-like domains (CLDs) have been suggested to be the site where PrPC is converted into PrPSc. We report herein that CLDs isolated from scrapie-infected neuroblastoma (ScN2a) cells contain PrPC and PrPSc. After lysis of ScN2a cells in ice-cold Triton X-100, both PrP isoforms and an N-terminally truncated form of PrPC (PrPC-II) were found concentrated in detergent-insoluble complexes resembling CLDs that were isolated by flotation in sucrose gradients. Similar results were obtained when CLDs were purified from plasma membranes by sonication and gradient centrifugation; with this procedure no detergents are used, which minimizes artifacts that might arise from redistribution of proteins among subcellular fractions. The caveolar markers ganglioside GM1 and H-ras were found concentrated in the CLD fractions. When plasma membrane proteins were labeled with the impermeant reagent sulfo-N-hydroxysuccinimide-biotin, both PrPC and PrPSc were found biotinylated in CLD fractions. Similar results on the colocalization of PrPC and PrPSc were obtained when CLDs were isolated from Syrian hamster brains. Our findings demonstrate that both PrPC and PrPSc are present in CLDs and, thus, support the hypothesis that the PrPSc formation occurs within this subcellular compartment