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Biomedical subjects

E A Greene

Publications and source records attributed to E A Greene.

30 records · Page 2Linked to original sources
PubMed1991

Desmin is present in proliferating rat muscle satellite cells but not in bovine muscle satellite cells.

The presence of desmin was characterized in cultured rat and bovine satellite cells and its potential usefulness as a marker for identifying satellite cells in vitro was evaluated. In primary cultures, positive immunohistochemical staining for desmin and skeletal muscle myosin was observed in rat and bovine myotubes. A small number of mononucleated cells (20% of rat satellite cells and 5% of bovine satellite cells) were myosin-positive, indicative of post-mitotic differentiated myocytes. In bovine satellite cell cultures 13% of the mononucleated cells were desmin-positive, while 84% of the mononucleated cells in rat satellite cell cultures were desmin-positive. Rat satellite cell mass cultures and bovine satellite cell clonal density cultures were pulsed with 3H-thymidine, and autoradiographic data revealed that greater than 94% of dividing rat cells were desmin-positive, suggesting that desmin is synthesized in proliferating rat satellite cells. However, no desmin was seen in cells that incorporated labeled thymidine in bovine satellite cell clones. Analysis of clonal density cultures revealed that only 14% of the mononucleated cells in bovine satellite cell colonies were desmin-positive, whereas 98% of the cells in rat satellite cell colonies were desmin-positive. Fibroblast colonies from both species were desmin-negative. In order to further examine the relationship between satellite cell differentiation and desmin expression, 5-bromo-2'-deoxyuridine (BrdU) was added to culture medium at the time of plating to inhibit differentiation. Fusion was inhibited in rat and bovine cultures, and cells continued to divide. Very few desmin-positive cells were found in bovine cultures, but greater than 90% of the cells in rat cultures stained positive for desmin. The presence of desmin and sarcomeric myosin was also evaluated in regenerating rat tibialis anterior five days after bupivacaine injection. In regenerating areas of the muscle many desmin-positive cells were present, and only a few cells stained positive for skeletal muscle myosin. Application of desmin staining to rat satellite cell growth assays indicated that rat satellite cells cultured in serum-containing medium were contaminated with fibroblasts at levels that ranged from approximately 5% in 24 hr cultures to 15% in mature cultures. In defined medium 4 day cultures contain approximately 95% to 98% desmin-positive satellite cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Growth factor regulation of bovine satellite cell growth in vitro.

This study examined the effects of basic fibroblast growth factor (bFGF), insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF-beta) on the proliferation and differentiation of primary bovine satellite cells (BSC) in vitro. Individually, these three factors had the following effects on satellite cells: bFGF stimulated proliferation (P less than .01) but inhibited differentiation (P less than .05); IGF-I had no effect on proliferation but stimulated differentiation (P less than .01); and TGF-beta inhibited both proliferation and differentiation (P less than .01). When combined, the following effects were observed: maximum stimulation of proliferation (P less than .01) occurred in the presence of bFGF and IGF-I and differentiation was not stimulated; TGF-beta and bFGF continued to inhibit differentiation (P less than .01), but in the presence of bFGF, TGF-beta stimulated proliferation (P less than .01). No stimulation was observed in the presence of TGF-beta and IGF-I. Bovine satellite cells respond to these three growth factors that have been shown to regulate the activity of other myogenic cells, and in most instances, the responses among cells from various species are similar. These experiments indicate that the interactions of growth factors may be critical in regulating bovine satellite cell activity.

Animals↗
PubMed1983

A covalently cross-linked matrix in skeletal muscle fibers.

When skeletal, cardiac, and smooth muscle is exhaustively extracted with a protein-unfolding reagent such as 6 M guanidine HCl and a disulfide-reducing reagent such as 5% beta-mercaptoethanol, a tissue ghost remains intact and retains the characteristic shape and dimensions of the tissue before extraction. In the case of chicken pectoral muscle, the tissue ghost contains 1% of the original muscle proteins. Guanidine HCl extraction followed by collagenase treatment of glycerol-extracted chicken pectoral muscle releases a clean preparation of elongated structures containing 0.2% of the original protein and representing the covalently cross-linked remnants of the muscle fibers. The material of these muscle fiber ghosts extends throughout the interior of the cell. Antibodies raised against the tissue ghosts of smooth muscle cross-react with glycerol extracted skeletal myofibrils, forming a banding pattern which coincides with the banding pattern observed when myofibrils are reacted with antibodies against titin. Titin, a large and soluble protein found in skeletal muscle, cross-reacts with our antigizzard antibody. However, amino acid analysis of the muscle fiber ghosts indicates that titin cannot be the only subunit of the insoluble polymer, but that one or more proteins with a very high glycine and alanine content and a very low basic and acidic amino acid content must also form part of the covalently cross-linked matrix. The possibility is presented that this matrix may be the basis of the superthin 2-3-nm filaments which have been observed in a variety of cell types.

Amino Acids↗
PubMed1975

Potassium influx in the frog atrium during the cardiac cycle.

A method for measuring inwardly directed transmembrane tracer flow during the cardiac cycle was developed and applied to a study of 42K influx in frog atrial trabeculae. A fine frog atrial fiber was suspended in a stream of nonisotopic perfusate into which a smaller tracer-containing bolus could be injected, subjecting the fiber to a brief, controlled exposure to the tracer at any desired point in the cardiac cycle. In an experiment, the tissue was exposed to a fixed number of radioactive pulses at a selected point in the cardiac cycle; a brief flush with nonradioactive perfusate removed ambient and extracellular label and an extended wash and removed the remaining intracellular tracer for radioassay. The same procedure was repeated at different points in the cycle, and the resulting tracer uptake at each point measured the relative influx of the particular ion. In this way, a characteristic and reproducible 42K influx profile was demonstrated which exhibited a marked drop below diastolic values during the first 500 msec or so of the action potential followed by a rise and an overshoot above resting values. The time of return to the resting level was somewhat uncertain but was tentatively placed in the vicinity of rapid repolarization. We suggest that the rise and the overshoot reflect the activity of the membrane Na+, K+-adenosinetriphosphatase.

Animals↗
PubMedDate not supplied

Sulfolane degradation by mixed cultures and a bacterial isolate identified as a Variovorax sp.

Sulfolane (tetrahydrothiophene-1,1-dioxide) is used in the Sulfinol process for natural gas sweetening. At many sour-gas processing plants spills, landfills and leakage from unlined surface storage ponds have contaminated groundwaters with sulfolane. Due to its high water solubility and mobility in aquifers, sulfolane poses a risk for off-site contamination. This study investigated the aerobic biodegradation of sulfolane by two mixed microbial enrichment cultures and by three bacterial isolates. Sulfolane served as the sole C, S and energy source for these cultures. In the two mixed cultures, 60% and 80% of the sulfolane C was recovered as CO2, whereas in cultures of the three isolates only 40-42% of the substrate C was recovered as CO,. In the mixed cultures, 81% and 97% of the sulfolane S was converted to sulfate, and in the pure isolates, 55-90% of the substrate S was converted to sulfate. Thus, the mixed cultures were capable of greater mineralization than the pure isolates. One isolate, strain WP1, was identified using a combination of 16S rRNA gene sequencing, physiological traits and cell morphology. WP1 was determined to be most similar to Varioivorax paradoxus.

Aerobiosis↗