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Biomedical subjects

J R Coleman

Publications and source records attributed to J R Coleman.

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

Age-dependent effects of acoustic deprivation on spherical cells of the rat anteroventral cochlear nucleus.

The effects of monaural deprivation by ligation of the external auditory meatus on spherical cells in the anteroventral cochlear nucleus of the rat were examined. Sound deprivation from postnatal days 10, 16, 24, and 36 resulted in a reduction in spherical cell size, with the most dramatic reduction produced by deprivation at 10 and 16 days after birth. The anteroventral cochlear nucleus was subdivided into dorsal, middle, and ventral zones which generally correspond to different frequency representations, and the effects of deprivation on cells in these regions were examined. Cells in the dorsal zone of the anteroventral cochlear nucleus were significantly smaller than cells in the middle or ventral zones, thus indicating a position-dependent effect of acoustic deprivation. Our results suggest a sensitive period during which alterations in normal acoustic input can significantly and differentially affect the development of cells in the anteroventral cochlear nucleus.

Age Factors↗
PubMed1983

Analysis of muscle protein expression in polyethylene glycol-induced chicken: rat myoblast heterokaryons.

Heterokaryons derived from polyethylene glycol-mediated fusion of myoblasts at different stages of development were used to investigate the transition of cells in the skeletal muscle lineage from the determined to the differentiated state. Heterokaryons were analyzed by immunofluorescence, using rabbit antibodies against the skeletal muscle isoforms of chicken creatine kinase and myosin, and a mouse monoclonal antibody that cross-reacts with chicken and rat skeletal muscle myosin. When cytochalasin B-treated rat L8(E63) myocytes (Konieczny S.F., J. McKay, and J. R. Coleman, 1982, Dev. Biol., 91:11-26) served as the differentiated parental component and chicken limb myoblasts from stage 23-26 or 10-12-d embryos were used as the determined, undifferentiated parental cell, heterokaryons exhibited a progressive extinction of rat skeletal muscle myosin during a 4-6-d culture period, and no precocious expression of chicken differentiated gene products was detected. In the reciprocal experiment, 85-97% of rat myoblast X chicken myocyte heterokaryons ceased expression of chicken skeletal muscle myosin and the M subunit of chicken creatine kinase within 7 d of culture. Extinction was not observed in heterokaryons produced by fusion of differentiated chicken and differentiated rat myocytes and thus is not due to species incompatibility or to the polyethylene glycol treatment itself. The results suggest that, when confronted in a common cytoplasm, the regulatory factors that maintain myoblasts in a proliferating, undifferentiated state are dominant over those that govern expression of differentiated gene products.

Animals↗
PubMed1983

Metrizamide--a potential in vivo inhibitor of glucose metabolism.

Metrizamide used as a contrast medium for examination of the subarachnoid space and its contents may produce adverse reactions, but the mechanism for these reactions is not certain. The present study demonstrated a depression of glucose metabolism in rat neural tissue by metrizamide. Sixteen paired experiments using hippocampal tissue from rats showed a depression of glucose metabolism of 24.4 +/- 4.78%. This depression was significant (p less than 0.001) and was not related to a dilutional or hypertonic effect. The depression occurred at about the same time that adverse reactions are seen in patients, suggesting that the adverse reactions may be related to inhibition of glucose metabolism in the central nervous system.

Animals↗
PubMed1982

Measurement of photorespiration in algae.

The rates of true and apparent photosynthesis of two unicellular green algae, one diatom and four blue-green algae were measured in buffer at pH 8.0 at subsaturating concentrations of dissolved inorganic carbon (13-27 micromolar). Initial rates of depletion from the medium of inorganic carbon and (14)C activity caused by the algae in a closed system were measured by gas chromatography and by liquid scintillation counting, respectively. The rate of photorespiration was calculated as the difference between the rates of apparent and true photosynthesis. The three eucaryotic algae and two blue-green algae had photorespiratory rates of 10 to 28% that of true photosynthesis at air levels of O(2). Reduction of the O(2) level to 2% caused a 52 to 91% reduction in photorespiratory rate. Two other blue-green algae displayed low photorespiratory rates, 2.4 to 6.2% that of true photosynthesis at air levels of O(2), and reduction of the O(2) concentration had no effect on these rates.

Journal Article↗
PubMed1981

Inorganic Carbon Accumulation and Photosynthesis in a Blue-green Alga as a Function of External pH.

The blue-green alga Coccochloris peniocystis photosynthesizes optimally over the pH range of 7.0 to 10.0, but the O(2)-evolution rate is inhibited below pH 7.0 and ceases below pH 5.25. Measurement of the inorganic carbon pool in this alga in the light, using the silicone-fluid filtration technique demonstrated that the rate of accumulation of dissolved inorganic carbon remained relatively constant over a wide pH range. At external dissolved inorganic carbon concentrations of 0.56 to 0.89 millimolar the internal concentration after 30 seconds illumination was greater than 3.5 millimolar over the entire pH range. Intracellular pH measured in the light using [(14)C]5,5-dimethyloxazolidine-2,4-dione and [(14)C]methylamine dropped from pH 7.6 at an external pH of 7.0 to pH 6.6 at an external pH of 5.25. Above an external pH of 7.0 the intracellular pH rose gradually to pH 7.9 at an external pH 10.0. Ribulose-1,5-bisphosphate carboxylase activity of cell-free algal extracts exhibited optimal activity at pH 7.5 to 7.8 but was inactive below pH 6.5. It is suggested that the inability of Coccochloris to maintain its intracellular pH when in an acidic environment restricts its photosynthetic capacity by a direct pH effect on the principal CO(2) fixing enzyme.

Journal Article↗
PubMed1981

Induction by butyrate of differentiated properties in cloned murine rhabdomyosarcoma cells.

A cell line derived from the murine rhabdomyosarcoma BW10139 (Dexter, Cancer Res. 37: 3136, 1977) was subcloned and examined with respect to growth and myogenic characteristics in the presence and absence of 1 mM butyrate. Without butyrate, these cells behave as typical transformed cells: they grow rapidly and chaotically, do not form multinucleated muscle fibers and have little or no creatine kinase activity. In the presence of 1 mM sodium butyrate or butyric acid, growth slows, cells become arranged in whorl patterns, and creatine kinase activities increase to levels comparable to those found in normal chick myoblasts immediately prior to cell fusion. The increase in creatine kinase activity is detectable within 2 h exposure to butyrate, reaches a maximum by 24 h, and the elevated level can be maintained for at least six weeks. The induction is reversible upon sequential addition, deletion, and readdition of butyrate to the culture medium. Isoenzyme analyses demonstrated that only the BB form of creatine kinase is induced; MM creatine kinase was not detected. Although formation of multinucleated cells increases after exposure to butyrate, no typical myotubes form. The results suggest that this rhabdomyosarcoma cell line can, under appropriate conditions, re-express some properties characteristic of skeletal muscle, but not the complete muscle phenotype.

Animals↗
PubMed1981

Mithramycin- and 4'-6-diamidino-2-phenylindole (DAPI)-DNA staining for fluorescence microspectrophotometric measurement of DNA in nuclei, plastids, and virus particles.

The properties of two DNA-specific fluorochromes, 4'-6-diamidino-2-phenylindole (DAPI) and mithramycin, have been analyzed as reagents to quantitate cellular DNA by fluorescence microspectrophotometry. Optimal staining conditions and concentrations, and the effects of other cellular materials to which the dyes bind, have been evaluated in measurements of the DNA of rat, chick, and yeast nuclei, Gonyostomum chloroplasts, and T4 particles. Use of either fluorochrome permits a high degree of resolution of different DNA quantities in nuclei and in cell organelles, and the DAPI-DNA complex is sufficiently fluorescent to permit quantitation of the DNA content in genomes as small as those of individual T4 bacteriophage particles. Fluorescence of mithramycin- or DAPI-stained DNA is proportional to DNA quantity when DNA of the same has composition is compared. Quantitation does not appear to be affected discernably by the state of the DNA, whether in different stages of the cell cycle, in condensed chromosomes, or in noncycling, differentiated nuclei. The use of chicken red blood cells is recommended as an internal monitor for variations in staining conditions.

Amidines↗
PubMed1980

Characterization of the methylxanthine-induced propagated wave phenomenon in striated muscle.

Escalation is a propagated wave phenomenon readily observable in chick skeletal muscle fibers growing in culture. It occurs in fibers bathed in methylxanthines, halothane, or quinine, at concentrations associated with twitch potentiation. From the results of a variety of experiments, an explanation of the phenomenon is proposed. Cation requirements suggest that a wave may be initiated in conjunction with a spontaneous calcium influx or calcium spike; and drug concentration, temperature, and extracellular potassium effects support the theory that wave propagation occurs by calcium-induced calcium release from the sarcoplasmic reticulum. The optical effect may then reflect osmotic changes associated with the transient calcium release. Escalation is not restricted to cultured muscle, nor to chick. At appropriate temperatures and in the presence of methylxanthines, escalation has been observed in chick, frog, and rat skeletal muscle. This suggests that it is a subthreshold event, related to contraction, capable of providing further insight into excitation-contraction coupling. The superior visibility conditions and accessibility to experimental manipulation make cultured chick skeletal muscle fibers suitable subjects for such study.

Animals↗
PubMed1980

Effect of oxygen and temperature on the efficiency of photosynthetic carbon assimilation in two microscopic algae.

The CO(2) compensation points of Coccochloris peniocystis, a blue-green alga and Chlamydomonas reinhardtii, a green alga, were determined at pH 8.0 in a closed system by a gas chromatographic technique. The compensation point of Chlamydomonas increased markedly with temperature, rising from 0.79 microliter per liter CO(2) at 15 C to 2.5 microliters per liter CO(2) at 35 C. In contrast, the compensation point of Coccochloris at 20 C was 0.71 microliter per liter CO(2) and rose to only 0.95 microliter per liter CO(2) at 40 C.The compensation point of the green alga was significantly reduced at low O(2) concentrations (1 to 2%) when measured over the temperature range of 15 to 35 C. The compensation point of the blue-green alga, over the temperature range of 20 to 40 C, was unaffected by lowering the O(2) concentration.The whole cell CO(2) affinity of Chlamydomonas decreased substantially with increasing temperature at 21% O(2) whereas little change was observed over the same temperature regime when the CO(2) affinity was determined at O(2) concentrations of 1 to 2%. The CO(2) affinity of Coccochloris did not decrease significantly with either increasing temperature or O(2) concentration.These results suggest that while photorespiration is undetectable in Coccochloris some photorespiratory CO(2) release occurs in Chlamydomonas.

Journal Article↗
PubMed1980

Health care expenditures in nine industrialized countries, 1960-76.

This article reports the findings of a study developed to compare health care costs in the United States with those of eight other industrially advanced countries over the period 1960-76. All of the countries studied were found to share with the United States the problem of increased health care spending that has outpaced inflation in other sectors of the economy and continues to consume a growing share of national resources. The American growth rate in these expenditures has, in fact, been lower than that of all other coutries. Though U.S. health care expenditures have traditionally been relatively high when measured as a share of gross national product, Canada outspent the United States in this respect during the 1960's. In most recent years, West Germany, the Netherlands, and Sweden have devoted a larger share of GNP to health care than has the United States.

Australia↗
PubMed1979

Sizing free-standing ambulatory care facilities.

This guide, written by an administrator and an industrial engineer, identifies and discusses the factors that should be considered when planning space requirements for ambulatory care facilities. The authors view sizing the ambulatory care facility as a complicated sequential task where trade-offs are made with regard to several factors: philosophy of patient care; cost; expansion requirements; patient comfort and waiting time; patient privacy; staff preferences; utilization patterns; and scurity of the faculty. It is suggested that the weight assigned to each factor when making trade-offs will be largely affected by the philosophy of patient care. The authors divide ambulatory care facilities into five functional groups: (1) basic medical services; (2) supporting medical services; (3) administrations; (4) support and service facilities; and (5) community and secondary support facilities. There are tables summarizing recommended space requirements for each of the functional groups based on mathematical models of the number and type of people using them (i.e., a typical physician is expected to see 24 patients per day). Space requirements for the whole clinic can be determined by adding together those required for each functional component. Provisions for growth and technological advances are discussed. An extensive bibliography is included.

Ambulatory Care Facilities↗
PubMed1979

Metal binding by intestinal mucus.

Electron probe microanalysis offers distinct advantages for the study of intestinal mucus. This technique permits analysis of metal binding in situ, requires only a small amount of tissue, allows several experiments to be performed with one animal, and can resolve variations in binding that may occur in different portions of the intestine. We have used electron probe microanalysis to examine the metal binding capacity of intestinal mucus in situ. We have exposed portions of excised intestine to various concentrations of several metals, rapidly frozen the tissue and freeze dried it. After anhydrous embedding, thick sections were cut and analyzed on silicon discs or carbon coated copper grids. Qualitative analysis shows two distinctive patterns of distribution. The results of this work show clearly that at least three divalent cations are bound by mucus, that mucus exhibits different affinities for different metals, and that binding of metals is not uniform throughout mucus.

Animals↗