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  • Life and Medical Sciences  (47)
  • Wiley-Blackwell  (47)
  • American Institute of Physics
  • 1980-1984  (47)
  • 1
    Electronic Resource
    Electronic Resource
    An electromyographic study of the function of the jaw adducting muscles in Varanus exanthematicus (varanidae) (1982)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 173 (1982), S. 137-158 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The function of major features of the skull of Varanus exanthematicus during feeding was examined using cineradiography and electromyography. During the initial stages of feeding, Varanus grabs and orients a prey item in the mouth with no mastication, tearing of the prey, or killing bite. Ingestion is through a highly stereotyped movement, inertial feeding. The tongue plays no role in food transport. Once the prey is in the pharyngeal region, the hyoid apparatus squeezes the prey into the esophagus and stomach. Activity of jaw adducting muscles during prey orientation and inertial feeding is strikingly different. In prey orientation, the adductor musculature is active over long periods, and intermuscular differentiation and unilateral activity are common. During these phases the musculature is producing force against the resistance of the prey item held between the teeth. In inertial feeding, the jaw musculature functions to close the jaws rapidly against little resistance. A consistent pattern of intramuscular differentiation is present, with some portions of the musculature being active during both jaw opening and closing. Activity of the Mm. adductor mandibulae externus and pterygoideus is indistinguishable. Neither meso- nor metakinetic movement was observed during inertial feeding; resolution of interacranial movement was less certain during power phases. The quadrate moved during jaw opening and closing in inertial feeding. However, its movement was not linked with that of the palatomaxillary segment. These data are discussed in three contexts: cranial kinesis, intramuscular differentiation, and the mechanics of whole muscles.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051730203
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  • 2
    Electronic Resource
    Electronic Resource
    Size and shape of the mandibular condyle in primates (1983)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 177 (1983), S. 59-68 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The relationships between the size of the articular surface of the mandibular condyle and masticatory muscle size, tooth size, diet, and biomechanical variables associated with mastication were studied by taking 12 measurements on skulls of 253 adult female anthropoid primates, including three to ten specimens from each of 32 species.In regressions of condylar length, width, or area against body weight, logarithmic transformations substantially improve the fit of the equations compared with untransformed data. There is a strong relationship betwden condylar measurements and body weight, with all correlations being .94 or higher. The slopes of the allometric regressions of length, width, and area of the condylar head indicate slight positive allometry with body size.Folivorous primates have smaller condyles than frugivorous primates, and colobines have smaller condyles than cebids, cercopithecines, or hominoids. When colobines are eliminated, the differences between frugivores and folivores are not significant. However, the two species with the relatively largest condyles are Pongo pygmaeus and Cercocebus torquatus, suggesting that there may be a relationship between unusually large condylar dimensions and the ability to crak hard nuts between the teeth.Cranial features having strong positive correlations with condylar dimensions include facial prognathism, maxillary incisor size, maxillar postcanine area, mandibular ramus breadth, and temporal fossa area. These data are interpreted as indicating that relatively large condyles are associated with relatively large masticatory muscles, relatively inefficient mandibular biomechanics, and a large dentition. These relationships support the growing evidence that the temporomandibular joint is a stress-bearing joint in normal function.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051770106
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  • 3
    Electronic Resource
    Electronic Resource
    The larval nephridia of the brackish-water polychaete, Nereis diversicolor (1984)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 179 (1984), S. 273-289 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The larval nephridia of the brackish-water polychaete Nereis diversicolor are described for the first time, and have been studied to determine if their times of development and structural characteristics are consistent with a role in the osmotic regulation of the larva. As shown in serial paraffin sections and by interference-contrast optics, the nephridia of the three-setiger larva consist of a single pair of very large metanephridia, arising in the 3rd larval setiger, but with their elongated terminal ducts and coiled ciliated tubules pushed forward into the 2nd setiger; their open metanephrostomes and anterior anchoring filaments lie dorsal to the 2nd set of setae. In contrast, the definitive or juvenile metanephridia, arising in the 4th and subsequently formed setigerous segments, have short terminal ducts and coiled ciliated tubules confined to the segments on which their external nephropores open; their nephrostomes are ventrally located and open into the rear of the next anterior segment. These findings are in contrast to the claims of Edouard Meyer (1887), who described two pairs of closed protonephridia in the 2nd and 3rd larval setigers of Perinereis cultrifera. Although it is not excluded that the single larval pair of metanephridia of N. diversicolor may arise as protonephridia, Meyer's claim of two pairs of larval protonephridia was an observational error. The larval nephridia of the marine Platynereis dumerilii resemble in form, but are considerably smaller than, those of N. diversicolor. It is concluded that the hypertrophied pair of larval metanephridia of N. diversicolor is an evolutionary adaptation to existence in habitats of low and unpredictably varying salinity. Their development occurs irrespective of the prevailing salinity; hence, it must be genetically determined.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051790306
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of amino acid transport in chicken embryo fibroblasts by purified multiplication-stimulating activity (MSA) (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 102 (1980), S. 55-62 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Enhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication-stimulating activity (MSA). This increase in amino acid transport is an early event occuring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by α-aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na+-dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly+ upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while Km remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041020109
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  • 5
    Electronic Resource
    Electronic Resource
    In vitro proliferation and lifespan of bovine aorta endothelial cells: Effect of culture conditions and fibroblast growth factor (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 103 (1980), S. 385-392 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of culture conditions on calf dorsal aorta endothelial cells was studied. Population doubling time varied as a function of the cell seeding density, growth medium, serum supplement, and concentration of fibroblast growth factor (FGF). The shortest population doubling time was found for cells (population doubling level 0-30) grown in Eagle's Minimal Essential Medium (MEM) supplemented with 10% fetal bovine serum (FBS) and 100 ng/ml FGF. The stimulatory effect of FGF on bovine endothelial cell proliferation was dependent on cell inoculation density. FGF significantly increased cell division rate at cell inocula less than 1 ± 104 cells/cm2 but not at higher densities. The population doubling time and cell size increased as the mass culture population doubling level increased. The replicative lifespans of bovine endothelial cells grown in medium supplemented with 20% FBS were 10-15% greater than parallel cultures supplemented with 10% FBS. Cultures grown in medium supplemented with 10% FBS and 50 ng/ml FGF showed a 50% increase in replicative lifespan compared to cultures grown in medium supplemented with 10% FBS alone. When FGF was used the increase in the number of doublings was a function of the length of time the cells were grown in the presence of FGF. This report extends comparable observations on the in vitro aging of human diploid fibroblasts to bovine endothelial cells.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041030303
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  • 6
    Electronic Resource
    Electronic Resource
    Intracellular concentration of elements in normal and dystrophic skeletal muscles of the chicken (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 103 (1980), S. 193-200 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X-ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 ± 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 ± 16.5 in normal controls. The concentration of chlorine was 90.5 ± 27.5 and 54.1 ± 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041030204
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  • 7
    Electronic Resource
    Electronic Resource
    Variable coupling of active NA+ + K+ transport in Ehrlich ascites tumor cells: Regulation by external NA+ and K+ (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 106 (1981), S. 407-418 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of altered external sodium and potassium concentrations on steady state, active Na+ + K+ transport in Ehrlich ascites tumor cells have been investigated. Membrane permeability to Na+ and K+, intracellular [Na+] and [K+], and membrane potential were measured. Active cation fluxes were calculated as equal and membrane potential were measured. Active cation fluxes were calculated as equal and opposite to the net, diffusional leak fluxes. Elevation of external K+ (6-60 Mm)by equivalent replacement of Na+ (154-91 mM) inhibits both active Na+ and K+ fluxes, but not proportionally. This results in a decrease of the coupling ratio (rp = -Jkp/JpNa) as external K+ is increased. Elevation of external K+ (3-68 mM) at constant Na+ (92mM) inbibits Jpk, but is without effect on JpNa. The coupling ratio declines from 1.01 ± 0.14 to 0.07 ± 0.05, a 14-fold alteration. Reduction of external Na+ (154-25 mM) at constant K+ (6mM) depresses JpNa, but is without effect on Jpk. The coupling ratio increases from 0.63 ± 0.04 at 154 mM Na+ to 4.5 ± 2.04 at 25 mM Na+. The results of this investigation are consistent with the independent regulation of active cation fluxes by the transported species. Kinetic analysis of the data indicates that elevation of external sodium stimulates active sodium efflux by interacting at “modifier sites” at the outer cell surface. Similarly, external potassium inhibits active potassium influx by interaction at separate modifier sites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041060310
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  • 8
    Electronic Resource
    Electronic Resource
    Small nuclear RNAs and translation (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 114 (1983), S. 1-6 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The possibility that small nuclear RNA species U1 might be involved in the inhibition of protein synthesis that occurs during mitosis has been explored. Upon exposure of mitotic HeLa cell extracts to 1% sodium deoxycholate, the majority of the rapidly sedimenting U1 RNA shifted to lower sedimentation rates. This suggests that it is associated with heterogeneous nuclear RNA ribonucleoprotein particles, instead of a ribosomal population. Erythrocyte ghost-mediated microinjection of anti-(U1)RNP antibodies into synchronized HeLa cells did not prevent the suppression of protein synthesis that is observed under mitosis. Examination of the published nucleotide sequences of U1 and U2 RNA suggests that these RNA species could potentially code for some short peptides. When purified U1 or U2 RNA were added to cell-free polypeptide synthesizing systems, the synthesis of these peptides was not detected.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041140102
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  • 9
    Electronic Resource
    Electronic Resource
    The membrane potential of Ehrlich ascites tumor cells: An evaluation of the null point method (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 106 (1981), S. 399-406 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of valinomycin (25 pM) on the membrane potential and on initial, passive Na+ and K+ movements have been determined in Ehrlich ascites tumor cells. The membrane potential of steady-state cells in a physiologic environment was - 23.2 mV. Addition of valinomycin induced a small, significant hyperpolarization (Vm = -29.6 mV) when averaged over the population tested. However, analyses of the response of individual cells to valinomycin showed two different potential effects: (1) the majority of cells hyperpolarized after treatment; but (2) a significant fraction depolarized when exposed to valinomycin. The Vm of steady-state cells incubated in saline with K+ at concentrations of 21 mM or 75 mM was - 21.4 mV and -22.0 mV, respectively. Addition of valinomycin to these cells was without effect on Vm, thus establishing the “null point” responses. Only for cells incubated in saline with a K+ of 75 mM was there agreement between Vm and K+ equilibrium potential (Vk). Determinations of cellular Na+ and K+ showed that valinomycin induced net losses of K+ and gains of Na+ by cells incubated in either physiologic saline or saline with a K+ concentration of 21 mM. However, the celular K+ of cells incubated in saline with a K+ concentration of 75 mM was unaltered by valinomycin. There was a two- to threefold increase in K+ permeability of the cell membrane in the presence of valinomycin. These results are consistent with the existence of two null points in the membrane-potential response to valinomycin: One is established when the membrane potential corresponds to Vk; the second occurs when the effects of valinomycin on K+ loss from the cell are exactly offset by its inhibition of active Na+ + K+ transport.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041060309
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of H+ on the kinetics of Na+-dependent amino acid transport in ehrlich ascites tumor cells: Evidence for H+ as an alternative substrate (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 109 (1981), S. 507-516 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of H+ on the kinetics of α-aminoisobutyric acid (AIB) influx in Ehrlich ascites tumor cells have been investigated at different external Na+ concentrations. Elevation of [H+] in the presence of both high (154 mEq/l) and low (10 mEq/l) external Na+ leads to decreases in the maximum influx (Jmaxa) and increases in the apparent Michaleis-Menten constant (Kma) for influx of AIB. In the virtual absence of external Na+ (0.96 ± 0.04 mEq/l), alterations in [H+] are without measurable effect on AIB flux. Furthermore, addition of AIB (10 mM) to cell suspensions (pH 5.90) stimulates H+ uptake by the cells in either the presence or absence of Na+. The data are consistent with two kinetic models for Na+-dependent amino acid transport: an order bireactant (Na+-binding necessary before AIB binding) system or a random bireactant system. Both models require that H+ serve as an alternative substrate for Na+. The consistency of the models was tested by fit to data from the present study (not used to evaluate the kinetic parameters) and by prediction of the pH dependence of Na+-dependent amino acid transport compared to earlier studies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041090317
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