Graphene oxide and chitosan are promising materials for tissue regeneration. The present study explores a novel biomimetic mineralization route employing a graphene oxide (GO)-chitosan (CS) conjugate as a template material for the biomineralization of hydroxyapatite (HAP). Structural and morphological studies involving X-ray diffraction, Fourier transform infrared spectroscopy, and electron microscopy indicated that extensive mineralization occurred in the CS-GO conjugate system because of strong electrostatic interactions between the functional groups (carboxyl groups of GO and amino groups of CS) and calcium ions in the simulated body fluid (SBF). The combination of chitosan-graphene oxide conjugate and biomineralization was advantageous in favorably modulating cellular activity (osteoblast functions: cell attachment, proliferation, actin, vinculin and fibronectin expression). It is concluded that biomineralized hydroxyapatite in the HAP-CS-GO system induced homogeneous spatial osteoblastic cell growth and quantitatively (e.g. area) and qualitatively (e.g. mineral-to-matrix ratio) increased mineralization in relation to the HAP-GO system. The data underscore that covalent linkage of HAP to chitosan influences osteoblastic cell differentiation, mineralization, and cell growth. The proposed system and the revelation of fundamental insights merit consideration in tissue engineering.

Sapwood and juvenile wood of Sapium sebiferum (Euphorbiaceae) was collected during 2000 –2002. In air-dried vessel elements, the surface of pit membranes (PMs) in the outermost growth ring was coated with plaque-like or interstitial material that was 2–5 nm thick. This coating was phase dark and overlaid a phase bright layer of globules and reticulately arranged microfibrils (MFs) that was 25–50 nm thick. Beneath the reticulate layer there was another surface exposed during sectioning/fracturing. It had parallel MFs which appeared to be continuous with the middle lamella, and were also coated. The total thickness of the dried PM appeared to be in the range of 50–100 nm. Overwintering and heartwood PMs were encrusted with a non-microfibrillar layer that differed from the above mentioned coating. Prior to chemical treatment, specific dried, untreated PMs were located and then the sample was dismounted, treated with acidic H2O2, and observed after treatment so that before and after images could be compared. Treatment with acidic H2O2 removed some of the coating and greatly modified the fibrillar nature of the surface layer, but did not reduce its overall thickness. The native structure of sapwood PMs was observed in water. Non-dried PMs displayed two layers, each with a different type of surface. The outer layer was non-microfibrillar and covered the entire surface of the PM. The non-microfibrillar layer was extremely sensitive to mechanical perturbation by the AFM tip, and had phase characteristics similar to the coating of dried PMs. The underlying layer was thick and microfibrillar. The MFs in non-dried PMs were, like the dried MFs, phase bright but they were much more loosely intermeshed compared with those seen in dried materials. The measurable thickness (which does not represent the total thickness) of non-dried PMs frequently ranged from 90–225 nm, although a few 500 nm vertical features were measured.

Abstract. The distribution of alpha-spectrin in Drosophila embryos was determined by immunofluorescence using affinity-purified polyclonal or monoclonal antibodies. During early development, spectrin is concentrated near the inner surface of the plasma membrane, in cytoplasmic islands around the syncytial nuclei, and, at lower concentrations, throughout the remainder of the cytoplasm of preblastoderm embryos. As embryogenesis proceeds, the distribution of spectrin shifts with the migrating nuclei toward the embryo surface so that, by nuclear cycle 9, a larger proportion of the spectrin is concentrated near the plasma membrane. During nuclear cycles 9 and 10, as the nuclei reach the cell surface, the plasma membrane-associated spectrin becomes concentrated into caps above the somatic nuclei. Concurrent with the mitotic events of the syncytial blastoderm period, the spectrin caps elongate at interphase and prophase, and divide as metaphase and anaphase progress. During cellularization, the regions of spectrin concentration appear to shift: spectrin increases near the growing furrow canal and concomitantly decreases at the embryo surface. In the final phase of furrow growth, the shift in spectrin concentration is reversed: spectrin decreases near the furrow canal and concomitantly increases at the embryo surface. In gastrulae, spectrin accumulates near the embryo surface, especially at the forming amnioproctodeal invagination and cephalic furrow. During the germband elongation stage, the total amount of spectrin in the embryo increases significantly and becomes uniformly distributed at the plasma membrane of almost all cell types. The highest levels of spectrin are in the respiratory tract cells; the lowest levels are in parts of the forming gut. The spatial and temporal changes in spectrin localization suggest that this protein plays a role in stabilizing rather than initiating changes in structural organization in the embryo.

No abstract

The role and regulation of specific plant myosins in cyclosis is not well understood. In the present report, an affinity-purified antibody generated against a conserved tail region of some class XI plant myosin isoforms was used for biochemical and immunofluorescence studies of Zea mays. Myosin XI co-localized with plastids and mitochondria but not with nuclei, the Golgi apparatus, endoplasmic reticulum, or peroxisomes. This suggests that myosin XI is involved in the motility of specific organelles. Myosin XI was more than 50% co-localized with tailless complex polypeptide-1alpha (TCP-1alpha) in tissue sections of mature tissues located more than 1.0 mm from the apex, and the two proteins co-eluted from gel filtration and ion exchange columns. On Western blots, TCP-1alpha isoforms showed a developmental shift from the youngest 5.0 mm of the root to more mature regions that were more than 10.0 mm from the apex. This developmental shift coincided with a higher percentage of myosin XI /TCP-1alpha co-localization, and faster degradation of myosin XI by serine protease. Our results suggest that class XI plant myosin requires TCP-1alpha for regulating folding or providing protection against denaturation.