Biologic Material (biologic + material)

Distribution by Scientific Domains
Medical Sciences75%

Selected Abstracts

Surface Elastic Properties of Human Retinal Pigment Epithelium Melanosomes,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2008
Senli Guo
Atomic force microscope (AFM) imaging and nanoindentation measurements in water were used to probe the mechanical properties of retinal pigment epithelium melanosomes isolated from 14-year-old and 76-year-old donors. Topographic imaging reveals surface roughness similar to previous measurements on dry melanosomes. Force-indentation measurements show different types of responses that were catalogued into four different categories. In these measurements no permanent surface damage of melanosomes was observed as revealed by imaging before and after indentation measurements. The indentation measurements that exhibited nearly elastic responses were used to determine the Young's modulus of melanosomes. The average Young's modulus values are similar for 14-year-old and 76-year-old melanosomes with a somewhat narrower distribution for the 14-year-old sample. These elastic modulus values are considerably higher than the modulus of organelles with cytoplasm (<1 MPa) and approaching values of the modulus of protein crystals (,100 MPa) indicating rather high packing density of biologic material in melanosomes. The width of the Young's modulus distributions is considerable spanning from few megapascals to few tens of megapascals indicating large heterogeneity in the structure. A fraction of the force curves cannot be described by the homogeneous elastic sample model; these force curves are consistent with ,10 nm structural heterogeneity in melanosomes. The approach-withdraw hysteresis indicates a significant viscoelasticity, particularly in the samples from the 14-year-old sample. Adhesion of the AFM probe was detected on ,3% and ,20% of the surface of 14-year-old and 76-year-old samples, respectively. In light of previous studies on these same melanosomes using photoelectron emission microscopy, this adhesion is attributed to the presence of lipofuscin on the surface of the melanosomes. This suggestion indicates that part of the difference in photochemical properties between the old and young melanosomes originates from surface lipofuscin. [source]

Alternative Methods for Developmental Toxicity Testing

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 5 2006
Aldert H. Piersma
The aims of these investigations have been to reduce animal experimentation, to refine effect assessment and mechanistic studies, and to accelerate and simplify safety testing in an area of toxicology that uses relatively many animals. Many alternatives have been developed over the years with different compexities, using biologic material ranging from continuous cell lines to complete embryos. The validation of alternatives and their application in testing strategies is still in its infancy, although significant steps towards these aims are currently being made. The introduction of the genomics technology is a promising emerging area in developmental toxicity testing in vitro. Future application of alternatives in testing strategies for developmental toxicity may significantly gain from the inclusion of gene expression studies, given the unique programme of gene expression changes in embryonic and foetal development. [source]

2333: Cultivation of limbal stem cells-derived corneal epithelium on different biologic materials for clinical transplantation

ACTA OPHTHALMOLOGICA, Issue 2010
G PETROVSKI
Purpose To develop simple, reproducible, animal-materials free method for cultivating limbal stem-cells and differentiating them into corneal epithelium on different human biologic materials for clinical transplantation. Methods The limbal tissues (2x2mm) were harvested from cadavers not more than 8 hours after death and proliferated in vitro on cell culture tissue plates, human amniotic membranes (HAM) or human lens capsules in medium containing human AB serum. Cell viability was tested using the MTT assay and annexin-FITC/Propidium Iodide positivity methods. Molecular gene and immunofluorescent marker studies for stemness, proliferation and differentiation were used for the analysis. Results Over a period of one year, 50 limbal tissue explants were cultivated. Emergence of cells at one edge of the explants occurred within 24 hours from culturing and formed monolayer within 14 days. Although the speed of cell growth varied among donors and types of media for growth, inadequate growth at two weeks was never recorded. The viability of the cells at 7 and 14 days of cultivation was higher than 96% except in case of HAM use where viability was below 80%. The growing cells were characterized for their positivity for stemness (P63, ABCG2), proliferation (ki67) and epithelial cell markers CK 3, 8, 12, 14, 18 and 19. Conclusion We demonstrate a simple, animal-materials free technique for generating corneal epithelium from cadavers or alternatively from autologous donors for viable cell growth on different biologic materials for transplantation. The growth of corneal epithelium on lens capsules proved to be superior compared to the other cultivation techiques. [source]