Engineering of bone using bone marrow stromal cells and a silicon-stabilized tricalcium phosphate bioceramic: evidence for a coupling between bone formation and scaffold resorption.

Resorbable porous ceramic constructs, based on silicon-stabilized tricalcium phosphate, were implanted in critical-size defects of sheep tibias, either alone or after seeding with bone marrow stromal cells (BMSC). Only BMSC-loaded ceramics displayed a progressive scaffold resorption, coincident with new bone deposition. To investigate the coupled mechanisms of bone formation and scaffold resorption, X-ray computed microtomography (muCT) with synchrotron radiation was performed on BMSC-seeded ceramic cubes. These were analyzed before and after implantation in immunodeficient mice for 2 or 6 months. With increasing implantation time, scaffold thickness significantly decreased while bone thickness increased. The muCT data evidenced that all scaffolds showed a uniform density distribution before implantation. Areas of different segregated densities were instead observed, in the same scaffolds, once seeded with cells and implanted in vivo. A detailed muX-ray diffraction analysis revealed that only in the contact areas between deposited bone and scaffold, the TCP component of the biomaterial decreased much faster than the HA component. This event did not occur at areas away from the bone surface, highlighting coupling and cell-dependency of the resorption and matrix deposition mechanisms. Moreover, in scaffolds implanted without cells, both the ceramic density and the TCP:HA ratio remained unchanged with respect to the pre-implantation analysis.

Polyglucosan body axonal enlargement increases myelin spiral length but not lamellar number.

The area of the unrolled myelin sheet of internodes of myelinated fibers (MF) of peripheral nerve is thought to be determined by axonal caliber and internodal length. We studied the effect of a focal increase of axonal caliber due to the deposition of polyglucosan bodies (PGB), amylopectin-like glucose polymers, on number of myelin lamellae (NL), interlamellar distance (periodicity), and myelin spiral length (MSL) from a sural nerve biopsy specimen of a patient with chronic inflammatory demyelinating polyneuropathy. Axonal area, NL, periodicity, and MSL were estimated within internodes of MF above, at, and below PGB. The axon caliber at the level of the PGB was significantly (P less than 0.002) increased when the PGB was included. At the PGB, NL and their periodicity were not significantly different from those above or below the PGB. The MSL was significantly longer overlying the PGB than it was in the same internode above or below the PGB. Because slippage or stretching of the myelin sheath as well as movement of molecular constituents of myelin is not likely over large distances, localized biosynthesis and assembly of new myelin may explain this increase of MSL.

Prenatal education for the Spanish speaking: an evaluation.

A Spanish-language prenatal health-education program of classes in four topic areas was conducted for randomly selected pregnant women. The topics included newborn care, labor and delivery, family planning, and dental health care. A questionnaire was administered to the participants after they had attended all four sessions and at the end of their 36th week of gestation. A matched group of control women received the same questions soon after entering the program and before attending any classes. Women attending the health-education classes demonstrated significantly greater knowledge of the subjects covered than did those not taking the classes. Insights gained from the study suggest potential approaches for working with such a population with respect to cultural considerations, evaluation question construction, and question selection.