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  • Life and Medical Sciences  (7)
  • Polymer and Materials Science  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Morphological identification of functional capillaries in the myocardium (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 208 (1984), S. 283-289 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This study used acrylic resin as an intravascular marker to demonstrate functional myocardial capillaries after fixation by perfusion. Eight rat hearts were excised and allowed to function as isolated organs perfused with oxygenated Krebs-Henseleit buffer (37o 10 kPa) for 10 min. Four were fixed by perfusion (4 min) with 2.5% glutaraldehyde at the same temperature and pressure and then immersion fixed (24 hr). The other four hearts were perfused with 0.2% procaine HCl for 30 sec just prior to similar fixation. Polymerizing low viscosity acrylic resin was injected at 10 kPa pressure into the fixed vascular beds and allowed to cure, then transmural blocks of left ventricular myocardium were prepared for scanning electron microscopy. Total initial coronary flow of fixative after procaine treatment was significantly increased, while in untreated hearts the initial fixative flow rate was closely similar to that of oxygenated buffer. The pattern of capillary perfusion was assessed, and the percentage of capillary profiles filled by acrylic resin were calculated. Following procaine treatment, 95.2% of capillaries appeared functional, whereas without procaine arrest, only 62.0% of capillaries allowed the passage of resin. This study indicates that perfusion fixation with glutaraldehyde stabilizes myocardial structure so that the proportion of functional capillary pathways remains closely similar to that in the beating heart and so that such functional capillaries can be identified in morphological preparations by using a low viscosity intraluminal resin marker.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092080216
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  • 2
    Electronic Resource
    Electronic Resource
    Catalase activity in human spermatozoa and seminal plasma (1989)
    New York, NY : Wiley-Blackwell
    Gamete Research 24 (1989), S. 185-196 
    Details
    ISSN: 0148-7280
    Keywords: free radicals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Catalase activity was determined in human semen by measuring the oxygen burst with a Clark electrode, after H2O2 addition. Significant catalase activities (mean ± SD) were found in migrated, motile spermatozoa (44 ± 17 nmoles O2/min/108 cells) and in seminal plasma of normozoospermic men (129 ± 59 nmoles O2/min/ml). It has been demonstrated that seminal catalase originated from prostate; however, its activity was not correlated with the usual prostatic markers (such as citric acid and zinc). Our data suggest a multiglandular function secreted by this organ. The catalase activities measured in seminal samples from asthenozo-ospermic, infertile men were found lower than those from normozoospermic subjects. The understanding of the relative contribution of the different enzyme systems against O2 toxicity (superoxide dismutase, catalase, glutathione peroxidase) seem to be a priority area of research to understand disturbances of sperm function.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120240206
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  • 3
    Electronic Resource
    Electronic Resource
    Fatigue fracture of reaction injection molded (RIM) nylon composites (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 3029-3056 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study was undertaken to determine how milled glass fibers affect the fatigue resistance of reaction injection molded (RIM) nylon 6. Specifically the effects of glass content, fiber length, orientation, and surface treatment were investigated. The fatigue crack growth rates for unfilled and glass-filled samples were observed to follow the well-known Paris equation in terms of dependence on cyclic stress intensity factor. For the unfilled nylon a line shaped zone was observed in advance of the crack tip. Fractography results suggest that the zone was the projection of the actual crack tip profile through the thickness of the sample rather than a distinct plastic or deformation zone. The fatigue fracture surface exhibited a patchy type structure with features 50-150 μm in size, suggesting a void coalescence type of mechanism as has been reported for injection molded nylons. A diffuse damage zone, several millimeters in size, was observed at the crack tip for the glass-filled RIM nylon 6. The zone was observed to pulsate with the applied oscillating load. The growth of the damage zone volume with increasing crack length (and thus increasing stress intensity factor range) followed the Paris law, as did the crack growth rate data. The damage mechanism is attributed to void formation and microcracking at the fiber-matrix interface. The results of this study show that, for milled glass-reinforced RIM nylon 6, the crack growth rates were much more rapid than observed for injection-molded nylon 6 containing chopped glass fibers. This difference is attributed to the greatly reduced glass fiber lengths for the milled glasses.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070371019
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  • 4
    Electronic Resource
    Electronic Resource
    Biconstituent fibers from segmented polyurethanes and nylon 6 (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 1387-1401 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The characteristics of Monvelle, a new biconstituent fiber from nylon 6 and a segmented polyurethane, are reviewed briefly, and some of the technical problems inherent in producing such a fiber are discussed. The characterization of two series of polyurethanes which can be melt spun is given in detail. The chemical composition of the hard segment was maintained constant, being derived from 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol, in all polymers. In one series using poly(butylene adipate) of MW 2000 as the soft segment, the average hard segment content was varied from 33% to 54%. In the other series, the hard segment content was held at 43%, and three additional soft segments, each at MW 2000, were used: poly(ethylene adipate), polycaprolactone and poly-1,4-oxybutylene glycol (PBG). Characterizations include molecular weight distributions, thermal analysis, rheological studies, and selected small-angle and wide-angle x-ray diffraction and polarized light microscopy. Crystallinity, melt viscosity, and activation energy of flow increased with increasing hardsegment content. Changes in the polyester soft segments had little effect on the properties studied, but with PBG the crystalline melting point of the polymer, without annealing, was higher and the melt viscosity was slightly higher than corresponding polyester-based samples, in agreement with previous reports of sharper phase separation in polyether urethanes, compared to polyester urethanes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1975.070190519
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  • 5
    Electronic Resource
    Electronic Resource
    A scanning tunneling microscope study of single crystal polyethylene (1990)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 28 (1990), S. 399-410 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The scanning tunneling microscope has been used to image single crystal polyethylene lamellae coated with thin Au or Cr overlayers. The images show a variety of different morphologies ranging from single crystal lamella resting on atomically flat, highly oriented pyrolitic graphite substrates to large pyramidal structures formed by a multilayer growth process. Small outgrowth structures were observed on the top surface of many individual lamellae and were found to be in registry with the edge of the underlying “seed” lamella. The STM studies show evidence for sectorization of the single crystal lamella as well as plastic deformation of overlapping lamellae involving c-axis slip.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1990.140281302
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of a macroporous biodegradable polylactide implant for neuronal transplantation (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 1349-1362 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This article reports the production of a surgical implant meeting several specific requirements such as biocompatibility, biodegradability, macroporosity, and flexibility. Porosity was controlled by an original method consisting of the aggregation of calibrated poly-D,L-lactide microparticles. The size of the interstices between the aggregated microspheres was in a direct relationship to the microsphere diameter. A first approach was based on coating the microspheres with poly(vinyl alcohol) followed by chemically crosslinking the coating layers that were in mutual contact. This method was disregarded because of the acute cytotoxicity of glutaraldehyde used as the crosslinking agent, the absence of macroporosity, and the complete lack of flexibility. A physical technique of aggregation was then tested, which relied on the plasticization of poly-D,L-lactide microspheres with triethylcitrate to the point where microspheres strongly adhered to each other when they were in contact. This method has proved to be straightforward and definitely superior to the chemical approach, particularly with respect to cytotoxicity, control of macroporosity, and flexibility. A polymer support was thus successfully produced which was biodegradable, macroporous (interconnected pores of 10-100 μm in diameter), and flexible. This potential medical device is presently being used for neuronal transplantation in the central nervous system. © 1995 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820291106
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  • 7
    Electronic Resource
    Electronic Resource
    Abnormal regulation of de novo purine synthesis and purine salvage in a cultured mouse T-cell lymphoma mutant partially deficient in adenylosuccinate synthetase (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 99 (1979), S. 139-151 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The isolation and characterization of a mutant murine T-cell lymphoma (S49) with altered purine metabolism is described. This mutant, AU-100, was isolated from a mutagenized populatio of S49 cells by virtue of its resistance to 0.1 mM 6-azauridine in semisolid agarose. The AU-100 cells are resistant to adenosine mediated cytotoxicity but are extraordinarily sensitive to killing by guanosine.High performance liquid chromatography of AU-100 cells extracts has demonstrated that intracellular levels of GTP, IMP, and GMP are all elevated about 3-fold over those levels found in wild type cells. The AU-100 cells also contain an elevated intracellular level of pyrophosphoribosylphosphate (PPriboseP), which as in wild type cells is diminished by incubation of AU-100 cells with adenosine. However AU-100 cells synthesize purines de novo at a rate less than 35% of that found in wild type cells.In other growth rate experiments, the AU-100 cell line was shown to be resistant to 6-thioguanine and 6-mercaptopurine. Levels of hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) measured in AU-100 cell extracts, however, are 50-66% greater than those levels of HGPRTase found in wild type cell extracts. Nevertheless this mutant S49 cell line cannot efficiently incorporate labeled hypoxanthine into nucleotides since the salvage enzyme HGPRTase is inhibited in vivo.The AU-100 cell line was found to be 80% deficient in adenylosuccinate synthetase, but these cells are not auxotrophic for adenosine or other purines. The significant alterations in the control of purine de novo and salvage metabolism caused by the defect in adenylosuccinate synthetase are mediated by the resulting increased levels of guanosine necleotides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040990115
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of hypertonic and sodium-free medium on transport of a membrane glycoprotein along the secretory pathway in cultured mammalian cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 146 (1991), S. 34-42 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Incubation of cultured cells in hypertonic medium and sodium-free medium have been shown to block transport at two different stages along the endocytic pathway. To determine the effects of these treatments on the exocytic pathway, we studied the transport of the membrane glycoprotein of vesicular stomatitis virus (VSV-G) in cells infected with tsO45 mutant virus. This mutant synthesizes a VSV-G that accumulates in the endoplasmic reticulum (ER) when cells are incubated at 39.5°C. In addition, VSV-G accumulates in the post-ER pre-Golgi compartment when cells are incubated at 15°C and in the trans-Golgi network (TGN) when cells are incubated at 18°C. Upon transfer of cells to 32°C in control medium, VSV-G exits each of these compartments and is transported to the cell surface. Incubation in sodium-free medium at 32°C did not block transport from any of these three compartments. In contrast, incubation in hypertonic medium blocked export from the ER, transport from the pre-Golgi compartment to the Golgi complex, and transport from the TGN to the cell surface. Our results, in combination with previous studies, suggest that hypertonic medium blocks at least five distinct transport steps: the three exocytic steps described here, endocytosis from the cell surface, and transport of cell surface proteins into the Golgi complex. This raises the possibility that vesicular transport in different parts of the cell shares common elements that are inhibited by this treatment.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041460106
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  • 9
    Electronic Resource
    Electronic Resource
    Regulation of insulin-like growth factor-II expression and its role in autocrine growth of human neuroblastoma cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 290-300 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Insulin-like growth factor-II (IGF-II) is highly expressed in fetal tissues and may act as an autocrine growth factor during early embryogenesis. The SH-SY5Y human neuroblastoma cell line also expresses IGF-II and its receptors and responds to exogenous IGF-II with increased DNA synthesis, cell division, and neuritic outgrowth. For this study, we tested the hypothesis that IGF-II mediates autocrine growth of SH-SY5Y cells in serum-free media. SH-SY5Y cells plated at high densities proliferated in serum-free media, whereas sparsely plated cells did not. IGF-II mRNA levels increased within 24 hours of serum deprivation and were associated with increased immunoreactive IGF-II protein. Exogenous addition of IGF-II increased 3H-TdR incorporation and cell number in a dose- and time-dependent fashion. By nuclear labelling experiments using 5-Bromo-2′ deoxyuridine (BrdU), we detected a twofold higher percentage of S phase nuclei after a 24-hour incubation in IGF-II. Treatment of SH-SY5Y cells with anti-IGF-II antibodies in serum-free media inhibited cell proliferation, and this inhibition was partially overcome by the addition of increasing concentrations of IGF-II. Collectively, our results indicate that IGF-II mediates an autocrine growth mechanism in SH-SY5Y cells that is associated with increased IGF-II expression. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041550210
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  • 10
    Electronic Resource
    Electronic Resource
    The H+/site ratio of mitochondrial electron transport (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 89 (1976), S. 595-602 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The number of H+ ejected during passage of 2e- through each energy-conserving site of the mitochondrial respiratory chain (the H+/site ratio) was measured in three ways. In each case transmembrane movements of endogenous phosphate were minimized. (1) Measurement of the uptake of weak acids during loading of mitochondria with Ca2+ demonstrated that 2.0 weak acid anions were accumulated per Ca2+ ion. Since 1.7 to 2.0 Ca2+ ions were taken up per site, these data correspond to an H+/site ratio of 3.5 to 4.0. (2) More direct measurement of H+ ejection using the oxygen pulse technique demonstrated that the H+/site ratio was 3.0. In these experiments phosphate movements were prevented by addition of N-ethylmaleimide to inhibit phosphate-hydroxide antiport, by washing the mitochondria to remove endogenous phosphate, or by working at 5°C to reduce the rate of phosphate transport. When phosphate movements were allowed, H+/site ratios of 2.0 were observed. (3) Measurement of the initial steady rates of oxygen consumption and H+ ejection following addition of substrate to aerobic, substrate-limited mitochondria yielded H+/site ratios of 2.0, which were elevated to 4.0 when phosphate transport was prevented as described above.Previous determinations of the H+/site ratio were thus underestimates due to the unrecognized movements of endogenous phosphate; our results show that the H+/site ratio is at least 3.0 and may be as high as 4.0.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040890415
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