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Biomedical subjects

C Webster

Publications and source records attributed to C Webster.

At least 91 records · Page 5Linked to original sources
PubMed1983

Differentiation properties of pure populations of human dystrophic muscle cells.

The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation.

Cell Differentiation↗
PubMed1983

Cytoplasmic activation of human nuclear genes in stable heterocaryons.

We have induced the stable expression of muscle-specific genes in human nonmuscle cells. Normal diploid human amniocytes were fused with differentiated mouse muscle cells by using polyethylene glycol. The fusion product, a stable heterocaryon in which the parental cell nuclei remained distinct, did not undergo division and retained a full complement of chromosomes. This is in contrast with typical interspecific hybrids (syncaryons), in which the parental nuclei are combined and chromosomes are progressively lost during cell division. The human muscle proteins, myosin light chains 1 and 2, MB and MM creatine kinase and a functional mouse-human hybrid MM enzyme molecule were detected in the heterocaryons. Synthesis of these proteins was evident 24 hr after fusion and increased in a time-dependent manner thereafter. Our results indicate that differentiated mouse muscle nuclei can activate human muscle genes in the nuclei of a cell type in which they are not normally expressed, and that this activation occurs via the cytoplasm. The activators are still present in cells which have already initiated differentiation, are recognized by nuclei of another species, and do not diffuse between unfused cells. The reprogrammed amniocyte nuclei of stable heterocaryons provide a unique system in which to study the mechanisms regulating gene expression during cell specialization.

Amniotic Fluid↗
PubMed1983

Defective myoblasts identified in Duchenne muscular dystrophy.

A defect in the proliferative capacity of satellite cells, mononucleated precursors of mature muscle fibers, was found in clonal analyses of cells cultured from Duchenne muscular dystrophy (DMD) patients. The total yield of myoblasts per gram of muscle biopsy was decreased to 5% of normal. Of the DMD myoblast clones obtained, a large proportion contained a morphological class of flat distended cells that had an increased generation time and ceased to proliferate beyond 100-1,000 cells but could be induced to fuse and form myotubes. The altered muscle phenotype was detected in all cultures from DMD patients but was rarely found among myoblasts of controls. By age 14 yr, it comprised as man as 90% of DMD myoblasts. The remaining DMD myoblast clones, which initially grew well, had severely impaired proliferative capacity upon passage and further cultivation. Eventually all myoblasts from DMD muscle tissue exhibited defective growth potential. In contrast, the fibroblast yield and proliferative capacity from DMD samples did not differ from normal. Based on these findings, we propose a hypothesis for the etiology of DMD: Dividing myoblasts are required for muscle growth and maintenance, and the limited capacity of DMD myoblasts to grow is directly related to the progressive muscle degeneration characteristic of the disease.

Adolescent↗
PubMed1981

Isolation and characterization of human muscle cells.

We have developed an in vitro system for the study of postnatal human muscle under standardized conditions. The technique utilizes cloning to isolate pure populations of muscle cells. By manipulating culture conditions we can maximize either proliferation or differentiation of individual clones or of clones pooled to yield mass cultures of muscle cells. The muscle phenotype is stable; cells can be stored in liquid nitrogen for long-term use without loss of proliferative or differentiative potential. We have determined proliferative capacity of muscle cells from an analysis of clonal growth kinetics; we determined differentiative capacity from morphological evidence (cell fusion, striations, contractions, and the appearance of acetylcholine receptors) and biochemical analysis of muscle protein synthesis (creatine kinase, alpha-actin, tropomyosin, and myosin light chains). Our approach eliminates the variability in cellular composition that has complicated studies of primary muscle to date. We can now study in a controlled fashion the interactions and contributions of different cell types to the development of normal and genetically dystrophic human muscle.

Actins↗
PubMed1981

Failure of bacterial filters to reduce the incidence of pneumonia after inhalation anesthesia.

The authors prospectively studied 520 patients undergoing inhalation anesthesia to evaluate the efficacy of low resistance 0.22-micron bacterial filters in preventing postoperative pneumonias. Patients undergoing elective thoracic, upper abdominal and lower abdominal surgeries were randomly assigned preoperatively to filtered and nonfiltered anesthesia circuits by a study nurse. A second study nurse, who was unaware of patient assignments, followed each patient for five postoperative days to identify possible pulmonary complications. Both groups of patients were similar in age, sex distribution, smoking history, prior pulmonary disease, types and duration of surgery, ASA physical status classification, and receipt of intraoperative antibiotics. No differences in rates of postoperative pneumonia were observed between patients assigned to filtered and nonfiltered circuits (16.7 per cent vs. 18.3 per cent, respectively, P = 0.73). Also no differences were observed when the incidences of other outcome criteria such as postoperative fever, abnormal chest x-ray, sputum production, or abnormal pulmonary physical exam findings were evaluated. The results suggest that bacterial gas filters do not influence the incidence of postoperative pneumonias and that routine use of these devices for this purpose is not cost-effective.

Anesthesia, Inhalation↗