Abstract
The cellular responses to ras and nuclear oncogenes were investigated in purified populations of rat Schwann cells. v-Ha-ras and SV40 large T cooperate to transform Schwann cells, inducing growth in soft agar and allowing proliferation in the absence of added mitogens. Expression of large T alone reduces their growth factor requirements but is insufficient to induce full transformation. In contrast, expression of v-Ha-ras leads to proliferation arrest in Schwann cells expressing a temperature-sensitive mutant of large T at the restrictive temperature. Cells arrest in either the G1 or G2/M phases of the cell cycle, and can re-enter cell division at the permissive temperature even after prolonged periods at the restrictive conditions. Oncogenic ras proteins also inhibit DNA synthesis when microinjected into Schwann cells. Adenovirus E1a and c-myc oncogenes behave similarly to SV40 large T. They cooperate with Ha-ras oncogenes to transform Schwann cells, and prevent ras-induced growth arrest. Thus nuclear oncogenes fundamentally alter the response of Schwann cells to a ras oncogene from cell cycle arrest to transformation.
Full text
PDF










Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Armelin H. A., Armelin M. C., Kelly K., Stewart T., Leder P., Cochran B. H., Stiles C. D. Functional role for c-myc in mitogenic response to platelet-derived growth factor. Nature. 1984 Aug 23;310(5979):655–660. doi: 10.1038/310655a0. [DOI] [PubMed] [Google Scholar]
- Bar-Sagi D., Feramisco J. R. Microinjection of the ras oncogene protein into PC12 cells induces morphological differentiation. Cell. 1985 Oct;42(3):841–848. doi: 10.1016/0092-8674(85)90280-6. [DOI] [PubMed] [Google Scholar]
- Barbacid M. ras genes. Annu Rev Biochem. 1987;56:779–827. doi: 10.1146/annurev.bi.56.070187.004023. [DOI] [PubMed] [Google Scholar]
- Berridge M. J., Irvine R. F. Inositol trisphosphate, a novel second messenger in cellular signal transduction. Nature. 1984 Nov 22;312(5992):315–321. doi: 10.1038/312315a0. [DOI] [PubMed] [Google Scholar]
- Bishop J. M. The molecular genetics of cancer. Science. 1987 Jan 16;235(4786):305–311. doi: 10.1126/science.3541204. [DOI] [PubMed] [Google Scholar]
- Bishop J. M. Viral oncogenes. Cell. 1985 Aug;42(1):23–38. doi: 10.1016/s0092-8674(85)80098-2. [DOI] [PubMed] [Google Scholar]
- Bregnard A., Knüsel A., Kuenzle C. C. Are all the neuronal nuclei polyploid? Histochemistry. 1975;43(1):59–61. doi: 10.1007/BF00490154. [DOI] [PubMed] [Google Scholar]
- Brockes J. P., Fields K. L., Raff M. C. Studies on cultured rat Schwann cells. I. Establishment of purified populations from cultures of peripheral nerve. Brain Res. 1979 Apr 6;165(1):105–118. doi: 10.1016/0006-8993(79)90048-9. [DOI] [PubMed] [Google Scholar]
- Brockes J. P., Raff M. C., Nishiguchi D. J., Winter J. Studies on cultured rat Schwann cells. III. Assays for peripheral myelin proteins. J Neurocytol. 1980 Feb;9(1):67–77. doi: 10.1007/BF01205227. [DOI] [PubMed] [Google Scholar]
- Brockman W. W. Transformation of BALB/c-3T3 cells by tsA mutants of simian virus 40: temperature sensitivity of the transformed phenotype and retransofrmation by wild-type virus. J Virol. 1978 Mar;25(3):860–870. doi: 10.1128/jvi.25.3.860-870.1978. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brooks R. F., Riddle P. N., Richmond F. N., Marsden J. The G1 distribution of "G1-less" V79 Chinese hamster cells. Exp Cell Res. 1983 Oct;148(1):127–142. doi: 10.1016/0014-4827(83)90193-3. [DOI] [PubMed] [Google Scholar]
- Brown K., Quintanilla M., Ramsden M., Kerr I. B., Young S., Balmain A. v-ras genes from Harvey and BALB murine sarcoma viruses can act as initiators of two-stage mouse skin carcinogenesis. Cell. 1986 Aug 1;46(3):447–456. doi: 10.1016/0092-8674(86)90665-3. [DOI] [PubMed] [Google Scholar]
- Brugge J. S., Butel J. S. Role of simian virus 40 gene A function in maintenance of transformation. J Virol. 1975 Mar;15(3):619–635. doi: 10.1128/jvi.15.3.619-635.1975. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Böhm N., Kröner B., Kaiser E. Cytophotometric evidence of non-S-phase extra-DNA in human neuronal nuclei. Cell Tissue Kinet. 1981 Jul;14(4):433–444. doi: 10.1111/j.1365-2184.1981.tb00550.x. [DOI] [PubMed] [Google Scholar]
- Carey D. J., Eldridge C. F., Cornbrooks C. J., Timpl R., Bunge R. P. Biosynthesis of type IV collagen by cultured rat Schwann cells. J Cell Biol. 1983 Aug;97(2):473–479. doi: 10.1083/jcb.97.2.473. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cepko C. L., Roberts B. E., Mulligan R. C. Construction and applications of a highly transmissible murine retrovirus shuttle vector. Cell. 1984 Jul;37(3):1053–1062. doi: 10.1016/0092-8674(84)90440-9. [DOI] [PubMed] [Google Scholar]
- Colamonici O. R., Trepel J. B., Neckers L. M. Phorbol ester enhances deoxynucleoside incorporation while inhibiting proliferation of K-562 cells. Cytometry. 1985 Nov;6(6):591–596. doi: 10.1002/cyto.990060614. [DOI] [PubMed] [Google Scholar]
- Cone R. D., Mulligan R. C. High-efficiency gene transfer into mammalian cells: generation of helper-free recombinant retrovirus with broad mammalian host range. Proc Natl Acad Sci U S A. 1984 Oct;81(20):6349–6353. doi: 10.1073/pnas.81.20.6349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Coppola J. A., Cole M. D. Constitutive c-myc oncogene expression blocks mouse erythroleukaemia cell differentiation but not commitment. Nature. 1986 Apr 24;320(6064):760–763. doi: 10.1038/320760a0. [DOI] [PubMed] [Google Scholar]
- Cornbrooks C. J., Carey D. J., McDonald J. A., Timpl R., Bunge R. P. In vivo and in vitro observations on laminin production by Schwann cells. Proc Natl Acad Sci U S A. 1983 Jun;80(12):3850–3854. doi: 10.1073/pnas.80.12.3850. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dotto G. P., Parada L. F., Weinberg R. A. Specific growth response of ras-transformed embryo fibroblasts to tumour promoters. Nature. 1985 Dec 5;318(6045):472–475. doi: 10.1038/318472a0. [DOI] [PubMed] [Google Scholar]
- Falcone G., Tatò F., Alemà S. Distinctive effects of the viral oncogenes myc, erb, fps, and src on the differentiation program of quail myogenic cells. Proc Natl Acad Sci U S A. 1985 Jan;82(2):426–430. doi: 10.1073/pnas.82.2.426. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Feramisco J. R., Gross M., Kamata T., Rosenberg M., Sweet R. W. Microinjection of the oncogene form of the human H-ras (T-24) protein results in rapid proliferation of quiescent cells. Cell. 1984 Aug;38(1):109–117. doi: 10.1016/0092-8674(84)90531-2. [DOI] [PubMed] [Google Scholar]
- Fleischman L. F., Chahwala S. B., Cantley L. ras-transformed cells: altered levels of phosphatidylinositol-4,5-bisphosphate and catabolites. Science. 1986 Jan 24;231(4736):407–410. doi: 10.1126/science.3001936. [DOI] [PubMed] [Google Scholar]
- Franza B. R., Jr, Maruyama K., Garrels J. I., Ruley H. E. In vitro establishment is not a sufficient prerequisite for transformation by activated ras oncogenes. Cell. 1986 Feb 14;44(3):409–418. doi: 10.1016/0092-8674(86)90462-9. [DOI] [PubMed] [Google Scholar]
- Furth M. E., Davis L. J., Fleurdelys B., Scolnick E. M. Monoclonal antibodies to the p21 products of the transforming gene of Harvey murine sarcoma virus and of the cellular ras gene family. J Virol. 1982 Jul;43(1):294–304. doi: 10.1128/jvi.43.1.294-304.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gibbs J. B., Sigal I. S., Poe M., Scolnick E. M. Intrinsic GTPase activity distinguishes normal and oncogenic ras p21 molecules. Proc Natl Acad Sci U S A. 1984 Sep;81(18):5704–5708. doi: 10.1073/pnas.81.18.5704. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gilman A. G. G proteins and dual control of adenylate cyclase. Cell. 1984 Mar;36(3):577–579. doi: 10.1016/0092-8674(84)90336-2. [DOI] [PubMed] [Google Scholar]
- Goustin A. S., Leof E. B., Shipley G. D., Moses H. L. Growth factors and cancer. Cancer Res. 1986 Mar;46(3):1015–1029. [PubMed] [Google Scholar]
- Graessmann M., Graessmann A. Microinjection of tissue culture cells. Methods Enzymol. 1983;101:482–492. doi: 10.1016/0076-6879(83)01033-2. [DOI] [PubMed] [Google Scholar]
- Graham F. L., van der Eb A. J. A new technique for the assay of infectivity of human adenovirus 5 DNA. Virology. 1973 Apr;52(2):456–467. doi: 10.1016/0042-6822(73)90341-3. [DOI] [PubMed] [Google Scholar]
- Ignatius M. J., Chandler C. R., Shooter E. M. Nerve growth factor-treated, neurite-bearing PC12 cells continue to synthesize DNA. J Neurosci. 1985 Feb;5(2):343–351. doi: 10.1523/JNEUROSCI.05-02-00343.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jat P. S., Cepko C. L., Mulligan R. C., Sharp P. A. Recombinant retroviruses encoding simian virus 40 large T antigen and polyomavirus large and middle T antigens. Mol Cell Biol. 1986 Apr;6(4):1204–1217. doi: 10.1128/mcb.6.4.1204. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jessen K. R., Mirsky R. Nonmyelin-forming Schwann cells coexpress surface proteins and intermediate filaments not found in myelin-forming cells: a study of Ran-2, A5E3 antigen and glial fibrillary acidic protein. J Neurocytol. 1984 Dec;13(6):923–934. doi: 10.1007/BF01148594. [DOI] [PubMed] [Google Scholar]
- Kahn P., Frykberg L., Brady C., Stanley I., Beug H., Vennström B., Graf T. v-erbA cooperates with sarcoma oncogenes in leukemic cell transformation. Cell. 1986 May 9;45(3):349–356. doi: 10.1016/0092-8674(86)90320-x. [DOI] [PubMed] [Google Scholar]
- Kalderon D., Oostra B. A., Ely B. K., Smith A. E. Deletion loop mutagenesis: a novel method for the construction of point mutations using deletion mutants. Nucleic Acids Res. 1982 Sep 11;10(17):5161–5171. doi: 10.1093/nar/10.17.5161. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kelekar A., Cole M. D. Immortalization by c-myc, H-ras, and Ela oncogenes induces differential cellular gene expression and growth factor responses. Mol Cell Biol. 1987 Nov;7(11):3899–3907. doi: 10.1128/mcb.7.11.3899. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Korman A. J., Frantz J. D., Strominger J. L., Mulligan R. C. Expression of human class II major histocompatibility complex antigens using retrovirus vectors. Proc Natl Acad Sci U S A. 1987 Apr;84(8):2150–2154. doi: 10.1073/pnas.84.8.2150. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lacal J. C., Fleming T. P., Warren B. S., Blumberg P. M., Aaronson S. A. Involvement of functional protein kinase C in the mitogenic response to the H-ras oncogene product. Mol Cell Biol. 1987 Nov;7(11):4146–4149. doi: 10.1128/mcb.7.11.4146. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Lake P., Clark E. A., Khorshidi M., Sunshine G. H. Production and characterization of cytotoxic Thy-1 antibody-secreting hybrid cell lines. Detection of T cell subsets. Eur J Immunol. 1979 Nov;9(11):875–886. doi: 10.1002/eji.1830091109. [DOI] [PubMed] [Google Scholar]
- Land H., Chen A. C., Morgenstern J. P., Parada L. F., Weinberg R. A. Behavior of myc and ras oncogenes in transformation of rat embryo fibroblasts. Mol Cell Biol. 1986 Jun;6(6):1917–1925. doi: 10.1128/mcb.6.6.1917. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Land H., Parada L. F., Weinberg R. A. Cellular oncogenes and multistep carcinogenesis. Science. 1983 Nov 18;222(4625):771–778. doi: 10.1126/science.6356358. [DOI] [PubMed] [Google Scholar]
- Land H., Parada L. F., Weinberg R. A. Tumorigenic conversion of primary embryo fibroblasts requires at least two cooperating oncogenes. Nature. 1983 Aug 18;304(5927):596–602. doi: 10.1038/304596a0. [DOI] [PubMed] [Google Scholar]
- Lapham L. W. Tetraploid DNA content of Purkinje neurons of human cerebellar cortex. Science. 1968 Jan 19;159(3812):310–312. doi: 10.1126/science.159.3812.310. [DOI] [PubMed] [Google Scholar]
- Lemke G. E., Brockes J. P. Identification and purification of glial growth factor. J Neurosci. 1984 Jan;4(1):75–83. doi: 10.1523/JNEUROSCI.04-01-00075.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mann R., Mulligan R. C., Baltimore D. Construction of a retrovirus packaging mutant and its use to produce helper-free defective retrovirus. Cell. 1983 May;33(1):153–159. doi: 10.1016/0092-8674(83)90344-6. [DOI] [PubMed] [Google Scholar]
- Melchers F., Lernhardt W. Three restriction points in the cell cycle of activated murine B lymphocytes. Proc Natl Acad Sci U S A. 1985 Nov;82(22):7681–7685. doi: 10.1073/pnas.82.22.7681. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mougneau E., Lemieux L., Rassoulzadegan M., Cuzin F. Biological activities of v-myc and rearranged c-myc oncogenes in rat fibroblast cells in culture. Proc Natl Acad Sci U S A. 1984 Sep;81(18):5758–5762. doi: 10.1073/pnas.81.18.5758. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mulcahy L. S., Smith M. R., Stacey D. W. Requirement for ras proto-oncogene function during serum-stimulated growth of NIH 3T3 cells. Nature. 1985 Jan 17;313(5999):241–243. doi: 10.1038/313241a0. [DOI] [PubMed] [Google Scholar]
- Noble M., Albrechtsen M., Møller C., Lyles J., Bock E., Goridis C., Watanabe M., Rutishauser U. Glial cells express N-CAM/D2-CAM-like polypeptides in vitro. Nature. 1985 Aug 22;316(6030):725–728. doi: 10.1038/316725a0. [DOI] [PubMed] [Google Scholar]
- Ozanne B., Fulton R. J., Kaplan P. L. Kirsten murine sarcoma virus transformed cell lines and a spontaneously transformed rat cell-line produce transforming factors. J Cell Physiol. 1980 Oct;105(1):163–180. doi: 10.1002/jcp.1041050118. [DOI] [PubMed] [Google Scholar]
- Pardee A. B., Dubrow R., Hamlin J. L., Kletzien R. F. Animal cell cycle. Annu Rev Biochem. 1978;47:715–750. doi: 10.1146/annurev.bi.47.070178.003435. [DOI] [PubMed] [Google Scholar]
- Pierce J. H., Aaronson S. A. Myeloid cell transformation by ras-containing murine sarcoma viruses. Mol Cell Biol. 1985 Apr;5(4):667–674. doi: 10.1128/mcb.5.4.667. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Porter S., Clark M. B., Glaser L., Bunge R. P. Schwann cells stimulated to proliferate in the absence of neurons retain full functional capability. J Neurosci. 1986 Oct;6(10):3070–3078. doi: 10.1523/JNEUROSCI.06-10-03070.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raff M. C., Abney E., Brockes J. P., Hornby-Smith A. Schwann cell growth factors. Cell. 1978 Nov;15(3):813–822. doi: 10.1016/0092-8674(78)90266-0. [DOI] [PubMed] [Google Scholar]
- Raff M. C., Fields K. L., Hakomori S. I., Mirsky R., Pruss R. M., Winter J. Cell-type-specific markers for distinguishing and studying neurons and the major classes of glial cells in culture. Brain Res. 1979 Oct 5;174(2):283–308. doi: 10.1016/0006-8993(79)90851-5. [DOI] [PubMed] [Google Scholar]
- Raff M. C., Miller R. H., Noble M. A glial progenitor cell that develops in vitro into an astrocyte or an oligodendrocyte depending on culture medium. Nature. 1983 Jun 2;303(5916):390–396. doi: 10.1038/303390a0. [DOI] [PubMed] [Google Scholar]
- Ratner N., Bunge R. P., Glaser L. A neuronal cell surface heparan sulfate proteoglycan is required for dorsal root ganglion neuron stimulation of Schwann cell proliferation. J Cell Biol. 1985 Sep;101(3):744–754. doi: 10.1083/jcb.101.3.744. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rein A., Keller J., Schultz A. M., Holmes K. L., Medicus R., Ihle J. N. Infection of immune mast cells by Harvey sarcoma virus: immortalization without loss of requirement for interleukin-3. Mol Cell Biol. 1985 Sep;5(9):2257–2264. doi: 10.1128/mcb.5.9.2257. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roberts B. E., Miller J. S., Kimelman D., Cepko C. L., Lemischka I. R., Mulligan R. C. Individual adenovirus type 5 early region 1A gene products elicit distinct alterations of cellular morphology and gene expression. J Virol. 1985 Nov;56(2):404–413. doi: 10.1128/jvi.56.2.404-413.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Royer-Pokora B., Beug H., Claviez M., Winkhardt H. J., Friis R. R., Graf T. Transformation parameters in chicken fibroblasts transformed by AEV and MC29 avian leukemia viruses. Cell. 1978 Apr;13(4):751–760. doi: 10.1016/0092-8674(78)90225-8. [DOI] [PubMed] [Google Scholar]
- Rozengurt E. Early signals in the mitogenic response. Science. 1986 Oct 10;234(4773):161–166. doi: 10.1126/science.3018928. [DOI] [PubMed] [Google Scholar]
- Ruley H. E. Adenovirus early region 1A enables viral and cellular transforming genes to transform primary cells in culture. Nature. 1983 Aug 18;304(5927):602–606. doi: 10.1038/304602a0. [DOI] [PubMed] [Google Scholar]
- Schneider J. F., Fisher F., Goding C. R., Jones N. C. Mutational analysis of the adenovirus E1a gene: the role of transcriptional regulation in transformation. EMBO J. 1987 Jul;6(7):2053–2060. doi: 10.1002/j.1460-2075.1987.tb02470.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shih C., Weinberg R. A. Isolation of a transforming sequence from a human bladder carcinoma cell line. Cell. 1982 May;29(1):161–169. doi: 10.1016/0092-8674(82)90100-3. [DOI] [PubMed] [Google Scholar]
- Simanis V., Lane D. P. An immunoaffinity purification procedure for SV40 large T antigen. Virology. 1985 Jul 15;144(1):88–100. doi: 10.1016/0042-6822(85)90308-3. [DOI] [PubMed] [Google Scholar]
- Southern P. J., Berg P. Transformation of mammalian cells to antibiotic resistance with a bacterial gene under control of the SV40 early region promoter. J Mol Appl Genet. 1982;1(4):327–341. [PubMed] [Google Scholar]
- Sporn M. B., Todaro G. J. Autocrine secretion and malignant transformation of cells. N Engl J Med. 1980 Oct 9;303(15):878–880. doi: 10.1056/NEJM198010093031511. [DOI] [PubMed] [Google Scholar]
- Stern D. F., Roberts A. B., Roche N. S., Sporn M. B., Weinberg R. A. Differential responsiveness of myc- and ras-transfected cells to growth factors: selective stimulation of myc-transfected cells by epidermal growth factor. Mol Cell Biol. 1986 Mar;6(3):870–877. doi: 10.1128/mcb.6.3.870. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sullivan N. F., Sweet R. W., Rosenberg M., Feramisco J. R. Microinjection of the ras oncogene protein into nonestablished rat embryo fibroblasts. Cancer Res. 1986 Dec;46(12 Pt 1):6427–6432. [PubMed] [Google Scholar]
- Sweet R. W., Yokoyama S., Kamata T., Feramisco J. R., Rosenberg M., Gross M. The product of ras is a GTPase and the T24 oncogenic mutant is deficient in this activity. Nature. 1984 Sep 20;311(5983):273–275. doi: 10.1038/311273a0. [DOI] [PubMed] [Google Scholar]
- Tegtmeyer P., Schwartz M., Collins J. K., Rundell K. Regulation of tumor antigen synthesis by simain virus 40 gene A. J Virol. 1975 Jul;16(1):168–178. doi: 10.1128/jvi.16.1.168-178.1975. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Trahey M., Milley R. J., Cole G. E., Innis M., Paterson H., Marshall C. J., Hall A., McCormick F. Biochemical and biological properties of the human N-ras p21 protein. Mol Cell Biol. 1987 Jan;7(1):541–544. doi: 10.1128/mcb.7.1.541. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Varmus H. E. Oncogenes and transcriptional control. Science. 1987 Dec 4;238(4832):1337–1339. doi: 10.1126/science.2825348. [DOI] [PubMed] [Google Scholar]
- Wakelam M. J., Davies S. A., Houslay M. D., McKay I., Marshall C. J., Hall A. Normal p21N-ras couples bombesin and other growth factor receptors to inositol phosphate production. Nature. 1986 Sep 11;323(6084):173–176. doi: 10.1038/323173a0. [DOI] [PubMed] [Google Scholar]
- Weinberg R. A. The action of oncogenes in the cytoplasm and nucleus. Science. 1985 Nov 15;230(4727):770–776. doi: 10.1126/science.2997917. [DOI] [PubMed] [Google Scholar]
- Willumsen B. M., Norris K., Papageorge A. G., Hubbert N. L., Lowy D. R. Harvey murine sarcoma virus p21 ras protein: biological and biochemical significance of the cysteine nearest the carboxy terminus. EMBO J. 1984 Nov;3(11):2581–2585. doi: 10.1002/j.1460-2075.1984.tb02177.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zetterberg A., Larsson O. Kinetic analysis of regulatory events in G1 leading to proliferation or quiescence of Swiss 3T3 cells. Proc Natl Acad Sci U S A. 1985 Aug;82(16):5365–5369. doi: 10.1073/pnas.82.16.5365. [DOI] [PMC free article] [PubMed] [Google Scholar]