Intracellular cyclic AMP concentration responds specifically to growth regulation by serum

Intracellular concentrations of cyclic AMP increase when cells are deprived of serum. Studies with the mouse fibroblast line 3T3, an SV40-transformed subline of 3T3, and six different revertant lines derived from this clone show that a marked increase in cyclic AMP occurs only when the serum concentration is reduced below the minimum necessary for growth of a given line. Conversely, density-dependent inhibition of growth is not accompanied by an increase in cyclic AMP concentration in any line.

Synthesis of infective poliovirus in BSC-1 monkey cells enucleated with cytochalasin B

BSC-1 monkey kidney cells were enucleated by two cycles of centrifugation in the presence of cytochalasin B. The resulting populations contained 99.5 percent enucleated cells. After infection, newly synthesized poliovirus was recovered from the enucleated populations. Final virus yield per enucleated cell was about one-fifth the yield per infected untreated cell

Preservation of normal behavior by enucleated cells in culture

BHK-21 fibroblasts and BSC-1 epithelial cells were enucleated with cytochalasin B. The enucleated cells were trypsinized and replated; their subsequent behavior was monitored by light optical techniques. The results demonstrate that the information necessary for attachment, spreading, shape formation, pinocytosis, contact inhibition, and cell locomotion is present in enucleated cytoplasm.

Human-mouse hybrid cell lines and susceptibility to polio virus. II. Polio sensitivity and the chromosome constitution of the hybrids

A number of human-mouse hybrid cell lines with partial human chromosome complements were sensitive to poliovirus because the cells contained the viral receptor substance of human origin. Infection of the lines with one type of poliovirus regularly led to the survival of a few cells, whose progeny were found to be resistant to all types of poliovirus. Comparison of the chromosomes of sensitive hybrids and their resistant sublines showed no consistent difference in the number of biarmed human chromosomes of any group. The number of acrocentrics was always lower in the resistant hybrids than in the corresponding sensitive lines. It is suggested that the human chromosome bearing the polio receptor gene is an acrocentric.

Human-mouse hybrid cell lines and susceptibility to poliovirus. I. Conversion from polio sensitivity to polio resistance accompanying loss of human gene-dependent polio receptors

A number of human-mouse somatic hybrid cell lines have been prepared, containing from 3 to 12 human biarmed chromosomes. These lines were susceptible to poliovirus type 1, producing viral yields comparable to those of the human parental cells. A small proportion of the cells of these lines survived the polio infection, and their progeny were solidly resistant to reinfection with the virus. Both sensitive and resistant hybrids produced virus following infection with viral ribonucleic acid, indicating that the cytoplasm of the resistant hybrids was able to support viral multiplication. Viral adsorption studies carried out at 4 C showed that the resistant sublines had negligible ability to adsorb the virus. It was concluded that the hybrid cells became resistant to polio through loss of the human chromosome bearing the gene for the receptor substance.

Risk of complications of first metatarsal head osteotomies with biodegradable pin fixation: Biofix versus Orthosorb

Bioabsorbable materials for fracture repair have recently become available in the United States. These products have been especially attractive to surgeons that perform elective foot surgeries because an additional surgery is not required to remove internal fixation, and exposed pins and their complications can be avoided. The aim of this study was to compare complications in distal first metatarsal head osteotomies fixed with Biofix, polyglycolide pins and Orthosorb, polydioxanon pins. The authors identified nine patients with 11 distal first metatarsal osteotomies repaired with Biofix and 28 patients with 34 osteotomies repaired with Orthosorb from surgery logs for a 2-year period. The authors abstracted medical records and radiographs to identify sterile sinus formation, non-unions, malunions, and osteolytic lesions. The age and gender of patients in the Orthosorb and Biofix groups were similar. Six osteotomies in five patients in the Biofix group demonstrated bone resorption and osteolytic changes involving the osteotomy. Two of these patients also had a dorsally subluxed malunion of the first metatarsal head. There was one dorsally subluxed malunion in the Orthosorb group. No sterile sinus tracts were identified in either group. Complications were more common in distal first metatarsal osteotomies fixed with Biofix compared with Orthosorb (Biofix 55%, Orthosorb 3%, p < 0.001, odds ratio: 39.6, confidence interval (CI) = 3.9-401.6). Complications in the Biofix group were significantly more common in patients 50 years of age and older (p < 0.05).