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  • Life and Medical Sciences  (8)
  • 1
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fluid shear stress can stimulate secretion of tissue plasminogen activator (tPA) by cultured human endothelial cells, while plasminogen activator inhibitor type-1 secretion remains unstimulated. To determine whether hemodynamically induced changes in tPA messenger RNA (mRNA) levels also occur, primary cultures from the same harvst of primary human umbilical vein endothelial cells were either maintained in stationary culture or exposed to arterial levels of shear stress (25 dynes/cm2) for 24 hours. Total cellular RNA was isolated from the shear stressed and stationary cultures and the relative levels of tPA mRNA and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA were determined using a coupled reverse transcriptase/polymerase chain reaction method. As indicated by the amount of amplification product, tPA mRNA levels were many fold higher (〉 10) in endothelial cells subjected to shear stress for 24 hours than in stationary controls. In contrast, mRNA levels for GAPDH were similar in control and shear stressed cells. The constancy of the measured GAPDH signal indicated that the tPA response was a selective effect of fluid shear stress. When a similar polymerase chain reaction method was used, the mRNA levels of basic fibroblast growth factor (bFGF) were found not to vary in comparison to GAPDH mRNA after 24 hours of shear stress. These results indicate that enhancement of the fibrinolytic potential of endothelial cells in response to hemodynamic forces could involve transcriptional events.
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  • 2
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of polycyclic hydrocarbons on rodent and primate cells in vitro was studied using dimethyl sulfoxide as the initial solvent for the hydrocarbons prior to their addition to the cell cultures. Because the dimethyl sulfoxide was not toxic to the cells at a final concentration in which relatively high concentrations of the hydrocarbons remained in solution in the medium, the effects of the compounds could be measured quantitatively.The carcinogenic hydrocarbons, benzpyrene and methylcholanthrene, but not the non-carcinogenic hydrocarbon, pyrene, inhibited the multiplication of normal embryonic cells from several rodent species. However, concentrations of the carcinogens as high as 10 μg/ml did not affect the growth of virus-transformed or malignant cells from these species.In contrast to the differential cytotoxic response of normal and malignant rodent cells to the carcinogenic hydrocarbons, the multiplication of normal, as well as transformed, monkey and human cells was not inhibited by benzpyrene or methylcholanthrene at concentrations of 10 to 20 μg/ml. Organ cultures of human embryonic skin initiated and maintained for ten weeks in medium containing 5 μg benzpyrene/ml showed no abnormalities in the growth rate or morphology of the fibroblasts that grew out of the explants.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 200 (1989), S. 71-86 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In primitive eutherians, the stapedial artery is the primary supplier of blood to the nonneural tissues of the head. Beyond a certain body size, the stapedial artery can no longer function as the sole supplier to its original territory because the diameter of its stem is limited by the size of the intercrural foramen of the stapes, which exhibits strong negative allometry. Some eutherians have extended the upper limit that the diameter of the stapedial stem can attain by developing a coarctation (narrowing) at the transcrural portion of the vessel. In the Norway rat (Rattus norvegicus) and the golden hamster (Mesocricetus auratus) the coarctation develops in postnatal life and is evidently caused by a retardation in growth that keeps the diameter of the vessel at infantile dimensions. In the rat, additional reduction in the external diameter is produced by a thinning of the tunica media of the arterial wall. A comfortable gap between the wall of the artery and the sides of the intercrural foramen is maintained that most likely facilitates the attenuation of potentially disruptive low-frequency vibrations produced by the arterial pressure pulse. The only negative side effect of a coarctation in rat-sized animals is that resistance to flow is increased and volume flow rate is concomitantly diminished. The coarctation does not create flow disturbances downstream of the constriction. One possible additional benefit of the coarctation is a flattening out of the arterial pressure pulse. It is speculated that the capacity to develop a coarctation once a certain body size is reached is an ancient trait that dates at least as far back as the Early Cretaceous.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 104 (1980), S. 375-389 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cells of confluent cultures of the established pig renal epithelial line, LLC-PK1, accumulate α-methyl-D-glucoside against a concentration gradient. This transport system is strongly inhibited by phlorizin and 6-deoxy-D-glucose, moderately inhibited by phloretin, and only weakly inhibited by 3-0-methyl-D-glucose, paralleling the situation in mammalian kidney. The time course for the uptake of α-methyl-D-glucoside and for the carrier-mediated but passive uptake of 3-0-methyl-D-glucose are identical to those seen in mammalian kidney. Subconfluent cultures of LLC-PK1 cells are unable to accumulate α-methyl-D-glucoside, and their transport of this glucose analog is less sensitive to phlorizin inhibition than is the transport system in confluent cultures. Transmission electron micrographs show that cells from subconfluent cultures lack the microvillous surface seen in cells from confluent cultures. Cell density is thus a factor in the occurrence of structural and functional differentiated properties related to transport in these cells.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 105 (1980), S. 1-6 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Uptake of α-methyl-D-glucoside (AMG) by LLC-PK1 cells is inhibited by the uncoupler p-trifluoro-methoxyphenyl-hydrazone (FCCP) and by the absence of extracellular Na+, indicating that the transport system is energy- and Na+ -dependent. We have previously demonstrated that transport of AMG by LLC-PK1 cells proceeds against a concentration gradient and is phlorizin-sensitive (Mullin et al., '80). Uptake of AMG was also inhibited by ouabain (OUA) but not by ortho-vanadate (VAN). Rubidium uptake also was affected by OUA but not by VAN. VAN, however, caused collapse of the three-dimensional domes of confluent LLC-PK1 monolayers much more rapidly and thoroughly than OUA. Since domes are presumably dependent upon the Na+ pump, yet VAN is not acting on transport-related functions of the OUA-sensitive (Na+ + K+)-ATPase, we hypothesize a direct effect of VAN on the water permeability of these cells. We also suggest that OUA does not act on these cells until domes collapse in normal course, and access of the OUA to the extracellular surface of antiluminal membranes is then achieved.
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  • 6
    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 incubation temperature on cell multiplication and on the efficiency of benzpyrene (BP) metabolism to water-soluble derivatives was compared in cell cultures derived from three poikilothermic and three homeo-thermic vertebrate species. The fish cells grew optimally at about 20°C and the amphibian and reptilian cells at about 30°C, and in general, these cells multiplied over broader ranges of temperature than the mouse, hamster or chick cells. In each cell system, the maximum temperature supporting efficient BP metabolism exceeded the maximum temperature supporting cell growth by 4 to 8°, but the range of temperatures supporting near-maximal BP metabolism was also considerably broader in the poikilothermic than in the homeothermic vertebrate cultures.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 104 (1980), S. 83-96 
    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 bromodeoxyuridine (BrdUrd) on the growth, morphology, and tumorigenicity of the spontaneously transformed rat liver cell line R72/3 were studied. These cells grow either in suspension or in a monolayer and are tumorigenic. In monolayer cultures, cells treated with low concentrations (2.5 μg/ml) of BrdUrd were larger, more spread out, and more firmly attached to the substratum than were untreated controls. Treated cells failed to grow in suspension or on confluent monolayers of 3T3 cells and did not form colonies in soft agar. Scanning electron microscopy revealed extensive flattening of treated cells and a dramatic reduction in the number of microvilli on the cell surface. Transmission electron microscopy showed an increase in polyribosomes and rough endoplasmic reticulum, as well as an enlargement of endoplasmic reticulum cisternae and a complete absence of the bundles of intermediate size filaments that were conspicuous in untreated cells. The persistence of these changes required the continuous presence of BrdUrd in the medium. The effects of BrdUrd were readily reversed by withdrawal of BrdUrd and were not expressed in the presence of excess thymidine.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 121 (1984), S. 193-198 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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