Interstitial bone stress distributions accompanying ingrowth of a screen-like prosthesis anchorage layer

Recent development of screen-like bonded weaves of titanium wire for orthopaedic implant anchorage affords a unique opportunity for analytic studies of porous ingrowth micromechanics. The regular geometry of individual wires and the periodicity of the mesh weave are exploited in a series of two-dimensional finite element models, mapping interstitial bone stress fields as a function of ingrowth depth and wire size, shape, and spacing.

When the depth of bone ingrowth was less than one wire diameter, peak bone stresses always occurred at the leading (i.e. deepest) edge of bone ingrowth, immediately adjacent to the wire. As ingrowth depth approached a full wire diameter, peak local bone stresses were 2–9 times the nominal applied host bone stress, with greater stresses occurring for lower screen weave densities. Within multiple screen layers, the top layer consistently experienced the peak stress and transmitted most of the applied load, regardless of the number of underlying screen layers surrounded by bone. Neither wire size variations nor partial wire flattening substantially affected general trends in stress predictions.     

Synergism between diacylglycerols and calcium ionophore in the induction of human B cell proliferation mimics the inositol lipid polyphosphate breakdown signals induced by crosslinking surface immunoglobulin

Resting human tonsillar B cells were stimulated to divide by heat killed Staphylococcus aureus Cowan strain 1 which was shown to induce hydrolysis of phosphatidylinositol 4, 5-bisphosphate known to give rise to diacylglycerol and an increase in cytosolic free calcium. Addition of the diacylglycerols, 1-oleoyl-2 acetyl glycerol or sn-1, 2-dioctanoylglycerol, together with the calcium ionophore ionomycin to B cell cultures induced marked cell proliferation whereas these agents were ineffective when used alone. Both diacylglycerols were shown to compete with [3H] phorbol 12,13 dibutyrate in binding to protein kinase C. These data support the hypothesis that synergism between cytosolic calcium and endogenous diacylglycerol, which activates protein kinase C, is involved in signal transduction in the proliferation of human B cells.     

Cat heart acetylcholine: Unilateral vagotomy studies with pyrolysis-mass fragmentography

The distribution of acetylcholine (ACh) in the cat heart was investigated by pyrolysis-gas chromatography (PGC) and pyrolysis-mass fragmentography (PMF) techniques. The hearts were dissected into various regions and homogenized in the presence of butyrycholine (or propionylcholine) as internal standard. The choline esters were isolated and analyzed by PGC or by PMF (at m/e 58). A pattern of distribution for ACh was found to be the same as I have previously described (1,2). Some cats were subjected to either a right or a left unilateral cervical vagotomy 4 weeks before removal and analysis of heart tissue. Hearts from unilateral (right or left) vagotomized cats did not differ from controls in the ACh content of any heart area examined. These results are consistent with the idea that intact parasympathetic neurons may compensate for the denervation following unilateral vagotomy.