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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 5 (1971), S. 215-224 
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A dextran-polythylene glycol aqueous two-phase system has been used to separate cell surface membranes from other cellular organelles. The surface membranes have been identified on the basis of morphology, content of Na+, K+-ATPase, and presence of surface antigen as detected by a51Cr release method. Contamination of the surface membrane preparations by smooth endoplasmic reticulum, mitochondria, and nuclei has been found to be minimal. An average of 6.5% of the total protein was found in the membrane fraction. Less than two hours is required to isolate the membrane fraction after preparation of a Dounce homogenate. Fractionation by aqueous two-phase polymer systems appears to be a rapid and effective method for the isolation of surface membranes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 16 (1981), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The premolar teeth were extracted from eight dogs, and cells from their periodontal ligaments and from attached gingiva were cultured in vitro. The lateral incisors were extracted later, the periodontal ligaments and pulps removed and the root canals filled. The roots were demineralized for 48 h in 0.5M EDTA, pH 7.4, and then divided into three groups. Cultured gingival cells were attached to those in the first group, psriodontal ligament cells to those in the second and no cells to those in the third which acted as controls. The roots were transplanted to holes drilled in the edentulous premolar region of the mandibular alveolar process and completely covered by a gingival flap, the roots and cells always being returned to the same dog from which they were removed. Because of infection, only 20 of the roots were recovered and, of these, only 4 bore periodontal ligament cells. All of the roots exhibited ankylosis and resorption. Only the roots bearing cultured periodontal ligament cells were associated with fragments of new fibrous tissue which was identified as periodontal ligament on the basis of the orientation of its fibres, the presence of Sharpey's fibres in bone and tooth, and cells located in positions normally occupied by osteoblasts and cementoblasts.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 15 (1980), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Connective tissue cells responding to wounding of the periodontal ligament of the lower first molar in mice were studied using the techniques of radioautography and grain counting. Animals were given an intraperitoneal injection of 2 uCi 1g 3H-Tdr 1 hr before being killed at either 30, 72 or 120 hr after wounding. The ligament in 1 um plastic sections was divided into compartments on the basis of distance from the wound, and the relative number of labelled cells in each compartment was assessed at 30, 72 and 120 hours after wounding. The distance of each labelled cell from the closest blood vessel was also measured at each time to detect relative movement of labelled cells away from blood vessels. In a Parallel experiment, haematogenous progenitors of macrophages were depleted by irradiating the animals with 800rads prior to woundilng to determine if mistakes in identification between fibroblasts and marophages could significantly affect the results. The ultrastructural characteristics of 150 of the 3H-Tdr labelled cells was examined in thin sections of wounded periodontal ligament prepared for elctron microcope radioautography, The majority of cells lebelled 30 hours after wounding were confirmed to be paravascular, and most of them were found to be located within 200 μ of the wound margin. Some of these cells appreared to have divided a number of times between 30 and 72 hours after wounding, and to have migrated into the wound between 70 and 120 hours after wounding. Examination of the irradiated material and the electron microscope radio-autographs suggested that significant numbers of macrophages had not been included in the counts of labelled cells. The elctron microscope radioautographs also suggested that cells which exhibited different degrees of cytodifferentiation had incorporated 3H-Tdr.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 18 (1983), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The use of tritiated thymidine labelling given by continuous delivery over long periods by means of an implanted osmotic minipump is a convenient method of accurately determining the rate of cellular proliferation in various tissues, but is especially advantageous for the periodontal ligament (PDL), the fibroblasts of which turn over at an extremely low rate. This technique was used to examine the hypothesis that differences exist between cell turnover in normal hamsters (N.D.) and those which had been placed on a periodontal disease inducing diet (S.S.D.). Turnover rates were then calculated for PDL and epithelial attachment (EA) for N.D and S.S.D animals before and after disease had been induced. No effect of disease was noted for either PDT or EA. However, the technique was sufficiently sensitive to demonstrate a significant effect of age on the turnover of cells in the epithelial attachment.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 17 (1982), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous methods of determining the labelling index (LI) of periodontal ligament (PDL) over an extended period of time have required multiple injections of isotope or addition of isotope to the animal's drinking water. Problems with these techniques are overcome to a great extent by the use of osmotic minipumps. Male Syrian hamsters had minipumps which had been filled with 2μCiH3-TdR implanted intraperitoneally. Animals were killed at 2,4,7,21. and 42 days. Specimens were embedded in plastic and 1 μm sections prepared forradioautography. Results show that the LI rose from less than 1% to reach over 50% by the end of the experiment. It is concluded that cells of the PDL are a slowly renewing population.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 16 (1981), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It has previously been difficult to examine the nature of the attachment between tissues and metal implants. To resolve this problem, a technique has been developed in which oral epithelial cells are grown on very thin films of titanium on epoxy resin. Discs of epon/araldite were formed by polymerizing the liquid resin in 60 mm tissue culture dishes. Discs were then placed in a vacuum deposition chamber and titanium wire vaporized onto the surface to a final thickness of about 300Å. Discs were cleaned in acetone and 70 % alcohol before being placed in plastic culture dishes and plated with epithelial cells cultured from porcine periodontal ligament in MEM plus 15 % calf serum and antibiotics for fourteen days. Cultures were fixed in situ in 2.5 % glutaraldehyde, post-fixed in OsO4 and epon/ araldite polymerized on the surface of the discs. Thin sections were cut perpendicular to the surface and examined in the electron microscope. Results show that the epithelial cells attach to the titanium surface by means of basal lamina and hemidesmosomes, in much the same manner in which the epithelial attachment is applied to the surface of a tooth.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 18 (1983), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In the present study we have investigated the effect of factors released by cells derived from porcine epithelial rests of Malassez (ERM) on bone resorption in vitro. The osteolytic effect of these cells was tested by co-culturing them with fetal rat calvariae and then measuring the cumulative change in calcium concentration of the culture medium. When ERM cells were cultured with calvariae for 4 days, there was a significant increase in calcium release from the bones compared with bones cultured without ERM. ERM cells alone did not change the calcium concentration of the culture medium. When calvariae there cultured in medium that had been collected from ERM cultures, significant bone resorption could also be obtained. Indomethacin (200 ng/ml), an inhibitor of prostaglandin synthesis, inhibited calcium release from control calvariae and from calvariae cultured with ERM. However, calvariae cultured in the presence of ERM and indomethacin released significantly more calcium than those cultured in the presence of indomethacin alone. Thus, factors other than PG account for the osteolytic effect of ERM. Other cells cultured from oral tissues, such as gingival fibroblasts and fibroblasts from periodontal ligament as well as rat osteosarcoma cells also stimulated calcium release from calvariae. These results show that many cell types have the capacity to release bone resorbing factors in vitro and support the belief that under suitable conditions in vivo breakdown of alveolar bone may be stimulated by tissues proximal to it.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 16 (1981), S. 0 
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Porcine gingival explants maintained in culture produced collagenase and non-specific gelatinase. These enzymes were detected in both latent and active forms in explant culture medium. The latent enzymes could be activated by limited proteolysis with trypsin or by treatment with organomercurials (4-hydroxy mercuribenzoate, PCMB and 4-aminophenylmercuric acetate, APMA). The explants also produced protein capable of inhibiting the collagenase and non-specific gelatinase activities. Treatment of inhibitor with trypsin or organomercurials under latent enzyme activation conditions blocked the inhibitory activity against both enzymes suggesting that the latent enzymes are enzyme-inhibitor complexes. A specific gelatinase was also detected in the culture medium in an active form which was not inhibited by other macromolecules in the medium. The addition of endotoxin (30 μg/ml) to the gingival explant medium increased the synthesis of the collagenase and non-specific gelatinase activities but had no apparent effect on the production of the inhibitor activity nor the specific gelatinase activity.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 50 (1975), S. 301-312 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The locations of chromosomal bands in the muntjac,(Muntiacus muntjak, Zimmerman) are shown to be constant, that is the bands occupy the same relative position regardless of the state of contraction of the chromosome. Each band can thus be assigned a precise location. Different banding techniques produce bands at identical locations and thus precisely similar patterns, with one notable exception in which certain bands disappear. It is proposed that this more exact procedure be used to identify chromosomal bands, especially in cases of chromosomal rearrangement. It may be of particular use in computer analyses of karyotypes.
    Type of Medium: Electronic Resource
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