ALBERT

Notes: Summary The ultrastructural characteristics of fracture surfaces from southern pine and Douglas-fir specimens tested in tension at various angles to grain were examined. The fracture surace morphology was inspected using scanning electron microscopy. Three anatomical failure types were recognized: intercell failure, transwall failure, and intrawall failure. Certain failure characteristics were ascribed as a function of the magnitudes of paralleland perpendicular-tograin tension and parallel-to-grain shear present in the specimen. In specimens tested in paralleland perpendicular-to-grain tension, the thick-walled latewood cells were found to fail in a combination of transwall and intrawall failure. The intrawall failures were usually at the S1–S2 interface. The more thin-walled earlywood cells were more likely to exhibit abrupt, transwall failures. At intermediate angles of load to grain, surfaces indicative of the type found in pure shear tests were predominant. Perpendicularto-grain tension failures resulted in mostly intercell failures. Ray cells consistently exhibited transwall failures. The failure surface frequently changed planes in all loading modes. This path transfer was inevidably associated with material discontinuities in the wood. When the path did transfer, all three failure types were observed. No significant species effect was observed.

Notes: Abstract The use of normal adult liver hepatocytes in cell culture for biochemical, toxicological and pharmacological studies has been greatly limited owing to the loss of replicative capacity and differentiated liver function. This is contrary to the ability of the liver to regenerate following injury in vivo. This suggests that liver “stem” or “transitional” hepatocytes exist that upon proper stimulus divide and differentiate into mature hepatocytes. In this study we report the establishment and culture of hepatocytes from normal human adult liver, which: (1) possess replicative capacity sufficient to subpassage 12–15 times (27–37 cumulative population doublings); (2) can be cryopreserved for subsequent use without loss of replica five capacity; and (3) upon differentiation in culture synthesize albumin and keratin 18 and metabolize benzo[a]pyrene. The ability of these cells to divide or express differentia tedfunctions appears to be due to a number of cellular, biochemical and physical characteristics that are present during the primary establishment and subsequent growth phases of the cell cultures. Disassociation of cells ffom excess liver tissue was best achieved by combining the mechanical action of the Stomacher@ with very low amounts of proteolytic enzymes and EGTA. The cell lines appeared to grow best when established and subpassaged in an rnALPHA medium supplemented with insulin, hydrocortisone, transferrin, epithelial growth factor and fetal bovine serum ® rescreened for human hepatocyte cell growth). The seeding density and cell-cell contact in culture appeared to be important for both cell division and expression of liver function. When cells were seeded at a low density and subpassaged before confluency, the cells continued to divide. Albumin and keratin 18 synthesis occurred primarily in tightly packed cell clusters. When cells were seeded at a high density, near confluency, albumin and keratin 18 synthesis occurred uniformly in all of the cells of the culture and the culture metabolized benzo[a]pyrene to water-soluble metabolites, which covalently bound to cellular DNA. This appearance of liver functions was consistent with the “transition” of hepatocytes to a terminally differentiated state. Nonhepatic markers, i.e., α-fetoprotein, factor VIII and ψ-glutamyl transpeptidase activity were not expressed in cells cultured at either low or high density. Thus, the data presented here indicate that normal human adult liver hepatocytes, once established in culture, can be subpassaged to a high number of population doublings, cryopreserved for later use, and modulated to express differentiated liver functions.bl]References