Distinct proliferative and differentiated stages of murine MC3T3-E1 cells in culture: an in vitro model of osteoblast development.

We examine clonal murine calvarial MC3T3-E1 cells to determine if they exhibit a developmental sequence similar to osteoblasts in bone tissue, namely, proliferation of undifferentiated osteoblast precursors followed by postmitotic expression of differentiated osteoblast phenotype. During the initial phase of developmental (days 1-9 of culture), MC3T3-E1 cells actively replicate, as evidenced by the high rates of DNA synthesis and progressive increase in cell number, but maintain a fusiform appearance, fail to express alkaline phosphatase, and do not accumulate mineralized extracellular collagenous matrix, consistent with immature osteoblasts. By day 9 the cultures display cuboidal morphology, attain confluence, and undergo growth arrest. Downregulation of replication is associated with expression of osteoblast functions, including production of alkaline phosphatase, processing of procollagens to collagens, and incremental deposition of a collagenous extracellular matrix. Mineralization of extracellular matrix, which begins approximately 16 days after culture, marks the final phase of osteoblast phenotypic development. Expression of alkaline phosphatase and mineralization is time but not density dependent. Type I collagen synthesis and collagen accumulation are uncoupled in the developing osteoblast. Although collagen synthesis and message expression peaks at day 3 in immature cells, extracellular matrix accumulation is minimal. Instead, matrix accumulates maximally after 7 days of culture as collagen biosynthesis is diminishing. Thus, extracellular matrix formation is a function of mature osteoblasts. Ascorbate and beta-glycerol phosphate are both essential for the expression of osteoblast phenotype as assessed by alkaline phosphatase and mineralization of extracellular matrix. Ascorbate does not stimulate type I collagen gene expression in MC3T3-E1 cells, but it is absolutely required for deposition of collagen in the extracellular matrix. Ascorbate also induces alkaline phosphatase activity in mature cells but not in immature cells. beta-glycerol phosphate displays synergistic actions with ascorbate to further stimulate collagen accumulation and alkaline phosphatase activity in postmitotic, differentiated osteoblast-like cells. Mineralization of mature cultures requires the presence of beta-glycerol phosphate. Thus, MC3T3-E1 cells display a time-dependent and sequential expression of osteoblast characteristics analogous to in vivo bone formation. The developmental sequence associated with MC3T3-E1 differentiation should provide a useful model to study the signals that mediate the switch between proliferation and differentiation in bone cells, as well as provide a renewable culture system to examine the molecular mechanism of osteoblast maturation and the formation of bone-like extracellular matrix.

Cefazolin versus cefamandole for prophylaxis during total joint arthroplasty.

A prospective, randomized, double-blind comparison of cefazolin versus cefamandole was carried out to evaluate safety and efficacy and to determine bone and serum antibiotic concentrations in patients undergoing total joint arthroplasty. Dosages were 1 g of cefazolin before surgery followed by 500 mg every eight hours for six doses, versus 2 g of cefamandole before surgery followed by 1 g every eight hours for six doses. Intraoperative doses were given during prolonged procedures. No significant adverse drug reactions were clearly attributable to either drug. Among 48 patients receiving cefazolin there was one postoperative wound infection and one distant site infection. Among 49 patients receiving cefamandole, there were two postoperative wound infections and two distant site infections. No deep wound infections occurred in either group during at least 48 months of follow-up study. In hip specimens removed at surgery, the mean antibiotic concentrations were 1.6 +/- 1.4 micrograms/g for cefazolin recipients, compared with 5.7 +/- 5.9 micrograms/g for cefamandole recipients (p less than .001). In knee specimens, the mean antibiotic concentrations were 0.64 +/- 0.57 microgram/g for cefazolin recipients compared to 3.8 +/- 3.4 micrograms/g for cefamandole recipients (p = .004). Cefazolin given at one-half the dose of cefamandole appeared to be equally safe and effective but resulted in lower bone concentrations of antibiotic.

Dendritic bundles: occurrence and regeneration in the forebrain of the Japanese carp, Cyprinus carpio.

Dendritic bundles were observed in the striatum and cerebellum of the Japanese carp. The striatal bundles were found to regenerate following telencephalic removal. This finding in conjunction with incoming axonal budding suggests that formation of the bundles are under the control of dynamic biological factors and not simple mechanical distortions.

Regeneration of the forebrain of the Japanese carp, Cyprinus carpio: a Golgi analysis.

The regeneration of the forebrain of the Japanese carp, Cyprinus carpio was examined with the rapid Golgi method. Characteristic of both 40 and 70 day regenerated forebrains was a proliferation of the spine processes of ependymal cells. Concomitant with this spinous augmentation was the appearance of swellings in many of the processes. Adjacent to the ependyma were cells that appeared to bud-off the ependyma and become migrating neuroblasts. The examination of the neurons in both normal and regenerated forebrains revealed no obvious and consistent differences between the configurations in both cases. In contrast to this finding, examination of the incoming axons showed numerous swellings and enlargements which were presumed to be immature synapses. The signifiance of these findings to the regeneration of the forebrain is discussed.

Technique for bonding gold and silver metals on sapphire.

A technique is described for bonding gold and silver metals onto sapphire. This technique has been successfully used in ac calorimetry for heat capacity of films.

Abnormal fatty acid composition and impaired oxygen supply in cystic fibrosis patients.

Impaired oxygen supply and deteriorating health, in cystic fibrosis patients, correlates with abnormal changes in the fatty acid composition of blood lipids. As the proportion of oleates increases and that of linoleates decreases, erythrocyte membrane interference with the formation of intracellular oxyhemoglobin increases and arterial oxygen pressure decreases. The physical-chemical basis for these changes seems to be that oleic and linoleic acid differ in their ability to undergo reversible oxygenation in response to changes in oxygen pressure. The oxygen complex of linoleic acid dissociates at relatively high pressures, whereas that of oleic dissociates only at low pressures. Accordingly, excessive substitution of oleic for linoleic acid in membrane lipids would be expected to decrease the intracellular oxygen pressure to a level where hemoglobin oxygenation and any other oxygen-requiring processes would be impaired.

Non-physician development of problem lists from office records.

It has been argued that conversion of office records to the problem-oriented medical record entails a prohibitive cost in money and physician time. This study reports an evaluation of the cost of preparing problem lists from existing ambulatory patient records by non-physician personnel. The problem lists constructed by non-physician personnel were judged by physicians to be accurate, and the cost was much less than that required when physicians reviewed charts and prepared problem lists themselves. The method described here is an accurate and cost-effective way to begin conversion of outpatient records to P.O.M.R.