ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 45-58 
    ISSN: 0886-1544
    Keywords: colcemid ; kinesin ; actin ; topographic guidance ; micromachined substrata ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fibroblats cultured on grooved substrata align themselves and migrate in the direction of the grooves, a phenomenon called contact guidance. Microtubules have been deemed important for cell polarization, directed locomotion, and contact guidance. Because microtubules were the first cytoskeletal element to align with the grooves when fibroblasts spread on grooved substrata, we investigated the consequences of eliminating the influence of microtubules by seeding fibro-blasts onto smooth and grooved micromachined substrata in the presence of colcemid. Fibroblasts were examined by time-lapse cinematography and epifluorescence or confocal microscopy to determine cell shape and orientation and the distribution of cytoskeletal or associated elements including actin filaments, vinculin, intermediate filaments, microtubules, and kinesin.As expected, cells spreading on smooth surfaces in the presence of colcemid did not polarize or locomote. Surprisingly however, by 24 hours, cells spread on grooves in the presence of colcemid were morphologically indistinguishable from controls spread on grooves. Both groups were aligned and polarized with the direction of the grooves and demonstrated directional locomotion along the grooves. In the absence of microtubules, kinesin localized to some of the aligned stress fibers and to leading edges of cells spreading on grooves. The grooved substratum compensated for the microtubule deficiency by organizing and maintaining an aligned actin filament framework. Thus, microtubules are not required to establish or maintain stable, polarized cell shapes or directed locomotion, provided an alternate oriented cytoskeletal component is available.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 493-515 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ideally, the surface of epithelium-pene- trating implants should impede apical epithelial migration. Previous studies have shown that micromachined grooved surfaces can produce connective-tissue ingrowth, which inhibits epithelial downgrowth on percutaneous implants [Chehroudi et al., J. Biomed. Mater. Res., 24, 9, (1990)]. However, in those studies, connective tissue and epithelium interacted with the same surface so that the effects of the surfaces on each population could not be determined separately. The objectives of this study were (a) to examine cell behavior on implants in which connective tissue contacted surfaces of various topographies and epithelium encountered only a smooth surface, and (b) to compare one- stage and two-stage surgical techniques. Implants had a base component (BC) which was either smooth or had a surface with 19-pm- or 30-pm-deep grooves or 120-pm- deep tapered pits, and a skin-penetrating component (SPC) which was smooth. In the two-stage technique, the BC was implanted subcutaneously for 8 weeks, which permitted the healing of the periimplant connective tissue. In the second stage the SPC was connected to the BC. For one-stage implants, BC & SPC were connected and implanted percutaneously. Implants (BC & SPC) were removed 1, 2, or 3 weeks after percutaneous implantation and histological sections were measured for recession, connective tissue and epithelial attachment as well as capsule thickness. Light microscopy indicated that both grooved and tapered pitted surfaces encouraged connective tissue ingrowth. On the grooved surfaces, the orientation of fibroblasts changed from an oblique to a more complex pattern which included cells having round nuclei within the grooves, as well as cells oriented oblique or perpendicular to the grooves. In the tapered pits a hammock-like arrangement of fibroblasts was observed. In some cases, foci of mineralization and formation of bonelike tissue were found on the grooved and pitted surfaces. The apical migration of the epithelium was significantly (p 〈 0.05) inhibited by those micromachined surfaces which produced connective tissue ingrowth to the BC. This study found that placing the implants in two stages improved the performance of percutaneous devices, and that a further improvement was achieved if the implant had a surface promoting connective tissue ingrowth.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 1067-1085 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of a grooved titanium-coated substratum on epithelial (E) cell behavior were studied in vitro and in vivo. V-shaped grooves, 10 m̈m deep, were produced in silicon wafers by micromachining, a process which was developed for the fabrication of microelectornic components. The grooved substrata were replicated in epoxy resin and coated with 50 nm of titanium. More E cells were found attached to the grooved titanium surfaces than to adjacent smooth surfaces. In comparison to the smooth surfaces where clusters of E cells were randomly oriented, on the grooved surfaces, clusters of E cells were markedly oriented along the long axis of grooves. Grooved and smooth titanium-coated epoxy implants were placed percutaneously in the parietal area of rats. Electron and light microscopic obsrvations indicated that E cells were tightly attached to the implant surfaces and this attachment is through basal lamina-like and hemidesmosome-like structures. In the grooved portion of the implant, E cells interdigitated into the grooves and had rounded nuclei. Histomorphometric measurements indicated that there was a shorter length of epithelial attachment, longer length of connective tissue attachment, and less recession in the grooved, compared to the smooth portion of implants after 7 and 10 days. These results indicate that horizontal grooves produced by micro-machining can significantly impede epithelial downgrowth on titanium-coated epoxy implants.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 387-405 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous studies using light microscopy have demonstrated that micromachined grooved surfaces inhibit epithelial (E) downgrowth and affect cell orientation at the tissue/implant interface. This study investigates the ultrastructure of the epithelial and connective-tissue attachment to titanium-coated micromachined grooved, as well as smooth control, implant surfaces. V-shaped grooves, 3, 10, or 22 μm deep, were produced in silicon wafers by micromachining, replicated in epoxy resin, and coated with 50-nm titanium. These grooved, as well as smooth, titanium-coated surfaces were implanted percutaneously in the parietal area of rats and after 7 days processed for electron microscopy. The tissue preparation technique used in this study enabled us to obtain ultrathin sections with few artifacts from the area of epithelial and connective-tissue attachment. The histological observations demonstrated that E cells closely attached to, and interdigitated with, the 3-μm and 10-μm grooves. In contrast, E cells were not found inside the 22-μm-deep grooves and made contact only with the flat ridges between the grooves. As a general rule, fibroblasts (F) were oriented parallel to the long axis of the implants and produced a connective tissue capsule with 3-μm and 10-μm-deep grooved surfaces as well as smooth surfaces. On the 22-μm-deep grooved surfaces, however, F inserted obliquely into the implant. The attachment of F to the titanium surface was mediated by two zones; a thin (≍20 nm), amorphous, electron dense zone immediately contacting the titanium surface, and a fine fibrillar zone extending from the amorphous zone to the cell membrane. As oblique orientation of F has been associated with the inhibition of epithelial downgrowth, micromachined grooved surfaces of appropriate dimensions have the potential to improve the performance of percutaneous devices.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 371-379 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It is generally accepted that cell shape plays a pivotal role in many aspects of cell behavior including proliferation, differentiation, and gene expression. Although previous reports have shown that implant-surface topography can alter cell shape in vitro, in vivo evidence for such an effect is largely based on intuitive interpretation of two-dimensional histological sections. The objective of this in vivo, study was to develop a method to reconstruct in three dimensions the shape of epithelial cells attached to smooth and micromachined implant surfaces. Titanium-coated epoxy replicas of smooth and 10-μm-deep micromachined grooved surfaces were implanted percutaneously in the parietal of region of rats. After 7 days the implants and attached tissue were removed and processed for light and electron microscopy. One-micrometer-thick serial histological sections were used to trace and digitize cells and their nuclei into a Hewlett Packard computer. Three-dimensional images were reconstructed and rotated to measure length, width, height, area, orientation index and the angle cells or nuclei formed with the long axis of the grooves (XY angle), and the angle cells or nuclei formed with the long axis of the implant (XZ angle). Epithelial cells attached to the smooth surfaces were found to be significantly (P, 〈 .05) flatter and more spread than were the cells attached to the grooved surfaces. Cells on the smooth surfaces were aligned parallel with the long axis of the implant, whereas on the grooved surfaces cells were oriented obliquely with the implant. There was a strong correlation (r = 0.9) between measurements of parameters of cells and those of nuclei on the smooth surfaces, but little correlation was found for the cells and their nuclei on grooved surfaces. These measurements indicated that cell shape is altered by the topography of the implant surface in vivo, but that one cannot necessarily predict the shape of a cell from the shape of its nucleus. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 459-473 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of grooved epoxy substrata on epithelial (E) cell behavior were studied in vitro and in vivo. V-shaped grooves, 10 μm deep, were produced in silicon wafers by micromachining, a process which was developed for the fabrication of microelectronic components. The grooved substrata were replicated in epoxy resin. More E cells attached to grooved surfaces than to adjacent smooth surfaces. Clusters of E cells were markedly oriented by the grooved surfaces in comparison to the adjacent smooth surfaces where the orientation was random. Grooved and smooth epoxy implants were placed percutaneously in the parietal area of rats. One week after implantation E cells were found to adhere tightly to the implant surfaces. In the grooved portion of the implant E cells interdigitated into the grooves and had rounded nuclei. Histomorphometric measurements indicated that there was a shorter length of epithelial attachment and a longer length of connective tissue attachment in the grooved, compared to the smooth, portion of implants. After 10 days the epithelial attachment had migrated down the length of the protruding smooth portion of the implant and was located on the base of the implant. However, epithelium remained attached to the grooved portion of the implant. These observations indicate that grooved surfaces have the potential to impede epithelial downgrowth on percutaneous devices.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 1203-1219 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A desirable feature of an implant surface which penetrates epithelium would be that the surface impedes epithelial downgrowth. Previous experiments have shown that the micromachined, horizontally oriented grooves on the percutaneous implant surface can impede epithelial downgrowth (Chehroudi et al., J. Biomed. Mater. Res., 22, 459 (1988) and 23, 1067 (1989)). However, little is known of the effect of varying groove parameters such as depth, spacing, and orientation on epithelial downgrowth and attachment of epithelial (E)-cells and fibroblasts (F) to percutaneous implants in vivo. Grooves were produced with a 30-μm pitch and depths of 22 μm, 10 μm, or 3 μm. In addition, 10-μm- and 3-μm-deep grooves were made with pitches of 39 μm and 7 μm, respectively. Implants with grooves oriented either horizontally or vertically to the long axis of the implant as well as smooth control surfaces were coated with 50 nm of titanium and placed in the parietal area of rats for a period of 7 days. Close attachment of E-cells was found on the smooth, 10-μm- and 3-μm-deep, horizontally or vertically aligned grooved surfaces; in contrast, E-cells bridged over the 22-μm-deep, horizontally oriented grooves. F formed a capsule on the smooth surface as well as the 10-μm- and 3-μm-deep horizontally oriented grooves, but F inserted obliquely into the 22-μm-deep, horizontally aligned grooved surface. Histomorphometric measurements indicated that the epithelial downgrowth was greatest on the vertically oriented grooved and smooth surfaces and was shortest on the 22-μm-deep and 10-μm-deep horizontally aligned grooved surfaces. These differences indicate that epithelial downgrowth was accelerated on the vertically oriented grooved surfaces and inhibited on the horizontally oriented grooved surfaces. Moreover, the mechanism of inhibition of the epithelial downgrowth may differ among these surfaces. E-cells bridged over the 22-μm-deep grooves and their migration appeared to be inhibited by the F that inserted into the implant surface. In the shallower horizontal grooves, however, epithelial downgrowth was probably inhibited by contact guidance because there was no evidence of F inserting obliquely into the implant surface.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...