Intestinal bowel disease and PPARγ;Le récepteur gamma activé par les proliférateurs de péroxysomes et les maladies inflammatoires chroniques de l'intestin (MICI et PPARγ)

Journal de la Societe de Biologie

Volumn 200, Issue 2, 2006, Pages 121-131

  Rousseaux, Christel ^a   Desreumaux, Pierre ^a  

^a Physiopathologie des Maladies Osseuses Inflammatoires   (France)

Author keywords

[No Author keywords available]

Indexed keywords

BACTERIA (MICROORGANISMS);

EID: 33751362282     PISSN: 12950661     EISSN: None     Source Type: Journal    
DOI: 10.1051/jbio:2006015     Document Type: Conference Paper

References (85)

1. Beamer B. A., Negri C., Yen C. J., Gavrilova O., Rumberger J. M., Durcan M. J., Yarnall D. P., Hawkins A. L., Griffm C. A., Burus D. K., Roth J., Reitman M. & Shuldiner A. R., Chromosomal localization and partial genomic structure of the human peroxisome proliferator activated receptor-γ (hPPARγ gene. Biochem. Biophys. Res. Commun., 1997, 233, 756-759.
2. Bordji K., Grillasca J. P., Gouze J. N., Magdalou J., Schohn H., Keller J. M., Bianchi A., Dauca M., Netter P. & Terlain, B., Evidence for the presence of peroxisome proliferator-activated receptor (PPAR) α and γ and retinoid Z receptor in cartilage. PPARγ activation modulates the effects of interleukin-1β on rat chondrocytes. J. Biol. Chem., 2000, 275, 12243-12250.
3. Burant C. F., Sreenan S., Hirano K., Tai T. A., Lohmiller J., Lukens J., Davidson N. O., Ross S. & Graves R. A., Troglitazone action is independent of adipose tissue. J. Clin. Invest., 1997, 100, 2900-2908.
4. Cario E., Rosenberg I. M., Brandwein S. B., Beck P. L., Reinecker H. C. & Podolsky D. K., Lipopolysaccharide activates distinct signaling pathways in intestinal epithelial cell lines expressing Toll-like receptors. J. Immunol., 2000, 164, 966-972.
5. Clark R. B., Bishop-Bailey D., Estrada-Hernandez T., Hla T., Puddington L. & Padula S. J., The nuclear receptor PPAR γ and immunoregulation: PPAR γ-mediates inhibition of helper T cell responses. J. Immunol., 2000, 164, 1364-1371.
6. Colville-Nash P. R., Qureshi S. S., Willis D. & Willoughby D. A., Inhibition of inducible nitric oxide synthase by peroxisome proliferator- activated receptor agonists: correlation with induction of heme oxygenase 1. J. Immunol., 1998, 161, 978-984.
7. Combs C. K., Johnson D. E., Karlo, J. C., Cannady S. B. & Landreth G. E., Inflammatory mechanisms in Alzheimer's disease: inhibition of β-amyloid-stimulated proinflammatory responses and neurotoxicity by PPARγ agonists. J. Neurosci., 2000, 20, 558-567.
8. Darfeuille-Michaud A., Neut C., Barnich N., Lederman E., Di Martino P., Desreumaux P., Gambiez L., Joly B., Cortot A. & Colombel J. F., Presence of adherent Escherichia coli strains in ileal mucosa of patients with Crohn's disease. Gastroenterology, 1998, 115, 1405-1413.
9. De Vos P., Lefebvre A. M., Miller S. G., Guerre-Millo M., Wong K., Saladin R., Hamann L. G., Staels B., Briggs M. R. & Auwerx J. Thiazolidinediones repress gene expression in rodents via activation of peroxisome proliferator-activated receptor γ. J. Clin. Invest., 1996, 98, 1004-1009.
10. Debril M. B., Renaud J. P., Fajas L. & Auwerx J., The pleiotropic functions of peroxisome proliferator-activated receptor γ. J. Mol. Med., 2001, 79, 30-47.
11. Desreumaux P., Brandt E., Gambiez L., Emilie D., Geboes K., Klein O., Ectors N., Cortot A., Capron M. & Colombel J. F., Distinct cytokine patterns in early and chronic ileal lesions of Crohn's disease. Gastroenterology, 1997, 113, 118-126.
12. Desreumaux P., Dubuquoy L., Nutten S., Peuchmaur M., Englaro W., Schoonjans K., Derijard B., Desvergne B., Wahli W., Chambon P., Leibowitz M. D., Colombel J. F. & Auwerx J., Attenuation of colon inflammation through activators of the retinoid X receptor (RXR)/peroxisome proliferator-activated receptor γ (PPARγ) heterodimer. A basis for new therapeutic strategies. J. Exp Med., 2001, 193, 827-838.
13. Desvergne B. & Wahli W., Peroxisome proliferator-activated receptors: nuclear control of metabolism. Endocr. Rev., 1999, 20, 649-688.
14. Dubuquoy L., Jansson E. A., Deeb S., Rakotobe S., Karoui M., Colombel J. F., Auwerx J., Pettersson S. & Desreumaux P., Impaired expression of peroxisome proliferator-activated receptor γ in ulcerative colitis. Gastroenterology, 2003, 124, 1265-1276.
15. Ellis C. N., Varani J., Fisher G. J., Zeigler M. E., Pershadsingh H. A., Benson S. C., Chi Y. & Kurtz T. W., Troglitazone improves psoriasis and normalizes models of proliferative skin disease: ligands for peroxisome proliferator-activated receptor-γ inhibit keratinocyte proliferation. Arch. Dermatol., 2000, 136, 609-616.
16. Fajas L., Auboeuf D., Raspe E., Schoonjans K., Lefebvre A. M., Saladin R., Najib J., Laville M., Fruchart J. C., Deeb S., Vidal-Puig A., Flier J., Briggs M. R., Staels B., Vidal H. & Auwerx J., The organization, promoter analysis, and expression of the human PPARγ gene. J. Biol. Chem., 1997, 272, 18779-18789.
17. Fajas L., Fruchart J. C. & Auwerx J., PPARγ3 mRNA: a distinct PPARγ mRNA subtype transcribed from an independent promoter. FEBS Lett., 1998, 438, 55-60.
18. Forman B. M., Tontonoz P., Chen J., Brun R. P., Spiegelman B. M. & Evans R. M., 15-Deoxy-δ12, 14-prostaglandin J2 is a ligand for the adipocyte determination factor PPARγ. Cell, 1995, 83, 803-812.
19. Frohnert B. I., Hui T. Y. & Bernlohr D. A., Identification of a functional peroxisome proliferator-responsive element in the murine fatty acid transport protein gene. J. Biol. Chem., 1999, 274, 3970-3977.
20. Gower-Rousseau C., Salomez J. L., Dupas J. L., Marti R., Nuttens M. C., Votte A., Lemahieu M., Lemaire B., Colombel J. F. & Cortot A., Incidence of inflammatory bowel disease in northern France (1988-1990). Gut, 1994, 35, 1433-1438.
21. Guha M. & Mackman N., LPS induction of gene expression in human monocytes. Cell Signal, 2001, 13, 85-94.
22. Gupta R. A., Brockman J. A., Sarraf P., Willson T. M. & DuBois R. N., Target genes of peroxisome proliferator-activated receptor γ in colorectal cancer cells. J. Biol. Chem., 2001, 276, 29681-29687.
23. Harris P. K. & Kletzien R. F., Localization of a pioglitazone response element in the adipocyte fatty acid-binding protein gene. Mol. Pharmacol., 1994, 45, 439-445.
24. Heneka M. T., Klockgether T. & Felustein D. L., Peroxisome proliferator-activated receptor-γ ligands reduce neuronal inducible nitric oxide synthase expression and cell death in vivo. J. Neurosci., 2000, 20, 6862-6867.
25. Hill M. R., Young M. D., McCurdy C. M. & Gimble J. M., Decreased expression of murine PPARγ in adipose tissue during endotoxemia. Endocrinology, 1997, 138, 3073-3076.
26. Huang J. T., Welch J. S., Ricote M., Binder C. J., Willson T. M., Kelly C., Witztum J. L., Funk C. D., Conrad D. & Glass C. K. Interleukin-4- dependent production of PPAR-γ ligands in macrophages by 12/15-lipoxygenase. Nature, 1999, 400, 378-382.
27. Hugot J. P., PPAR and Crohn's disease: another piece of the puzzle? Gastroenterology, 2005, 128, 500-503.
28. Hugot J. P., Chamaillard M., Zouali H., Lesage S., Cezard J. P., Belaiche J., Almer S., Tysk C., O'Morain C. A., Gassull M., Binder V., Finkel Y., Cortot A., Modigliani R., Laurent-Puig P., Gower-Rousseau C., Macry J., Colombel J. F., Sahbatou M. & Thomas G. Association of NOD2 leucine-rich repeat variants with susceptibility to Crohn's disease. Nature, 2001, 411, 599-603.
29. Hugot J. P., Laurent-Puig P., Gower-Rousseau C., Olson J. M., Lee J. C., Beaugerie L., Naom I., Dupas J. L., Van Gossum A., Orholm M., Bonaiti-Pellie C., Weissenbach J., Mathew C. G., Lennard-Jones J. E., Cortot A., Colombel J. F. & Thomas G. Mapping of a susceptibility locus for Crohn's disease on chromosome 16. Nature, 1996, 379, 821-823.
30. Issemann I. & Green S., Activation of a member of the steroid hormone receptor superfamily by peroxisome proliferators. Nature, 1990, 347, 645-650.
31. Jiang C., Ting A. T. & Seed B., PPAR-γ agonists inhibit production of monocyte inflammatory cytokines. Nature, 1998, 391, 82-86.
32. Kaisho T. & Akira S., Toll-like receptors as adjuvant receptors. Biochim. Biophys. Acta, 2002, 1589, 1-13.
33. Kallen C. B. & Lazar M. A., Antidiabetic thiazolidinediones inhibit leptin (ob) gene expression in 3T3-L1 adipocytes. Proc. Natl. Acad. Sci. USA, 1996, 93, 5793-5796.
34. Kawahito Y., Kondo M., Tsubouchi Y., Hashiramoto A., Bishop-Bailey D., Inoue K., Kohno M., Yamada R, Hla T. & Sano H., 15-deoxy-δ(12,14)- PGJ(2) induces synoviocyte apoptosis and suppresses adjuvant-induced arthritis in rats. J. Clin. Invest., 2000, 106, 189-197.
35. Kelly D., Campbell J. I., King T. P., Grant G., Jansson E. A., Coutts A. G., Pettersson S. & Conway S., Commensal anaerobic gut bacteria attenuate inflammation by regulating nuclear-cytoplasmic shuttling of PPAR-γ and RelA. Nat. Immunol., 2004, 5, 104-112.
36. Kitamura Y., Shimohama S., Koike H., Kakimura J., Matsuoka Y., Nomura Y., Gebicke-Haerter P. J. & Taniguchi T., Increased expression of cyclooxygenases and peroxisome proliferator-activated receptor-γ in Alzheimer's disease brains. Biochem. Biophys. Res. Commun., 1999, 254, 582-586.
37. Kliewer S. A., Lenhard J. M., Willson T. M., Patel I., Morris D. C. & Lehmann J. M., A prostaglandin J2 metabolite binds peroxisome proliferator-activated receptor-γ and promotes adipocyte differentiation. Cell, 1995, 83, 813-819.
38. Kliewer S. A., Umesono K., Noonan D. J., Heyman R. A. & Evans R. M., Convergence of 9-cis retinoic acid and peroxisome proliferator signalling pathways through heterodimer formation of their receptors. Nature, 1992, 358, 771-774.
39. Kota B. P., Huang T. H. & Roufogalis B. D., An overview on biological mechanisms of PPARS. Pharmacol. Res., 2005, 51, 85-94.
40. Lefebvre M., Paulweber B., Fajas L., Woods J., McCrary C., Colombel J. F., Najib J., Fruchart J. C., Datz C., Vidal H., Desreumaux P. & Auwerx J., Peroxisome proliferator-activated receptor γ is induced during differentiation of colon epithelium cells. J. Endocrinol., 1999, 162, 331-340.
41. Lehmann J. M., Lenhard, J. M., Oliver B. B., Ringold G. M. & Kliewer S. A., Peroxisome proliferator-activated receptors α and γ are activated by indomethacin and other non-steroidal anti-inflammatory drugs. J. Biol. Chem., 1997, 272, 3406-3410.
42. Lehmann J. M., Moore L. B., Smith-Oliver T. A., Wilkison W. O., Willson T. M. & Kliewer S. A., An antidiabetic thiazolidinedione is a high affinity ligand for peroxisome proliferator-activated receptor γ (PPARγ). J. Biol. Chem., 1995, 270, 12953-12956.
43. Li A. C., Brown K. K., Silvestre M. J., Willson T. M., Palinski W. & Glass C. K. Peroxisome proliferator-activated receptor γ ligands inhibit development of atherosclerosis in LDL receptor-deficient mice. J. Clin. Invest., 2000, 106, 523-531.
44. Loviscach M., Rehman N., Carter L., Mudaliar S., Mohadeen P., Ciaraldi, T. P., Veerkamp J. H. & Henry R. R., Distribution of peroxisome proliferator-activated receptors (PPARs) in human skeletal muscle and adipose tissue: relation to insulin action. Diabetologia, 2000, 43, 304-311.
45. Martin G., Schoonjans K., Lefebvre A. M., Staels B. & Auwerx J., Coordinate regulation of the expression of the fatty acid transport protein and acyl-CoA synthetase genes by PPARα and PPARγ activators. J. Biol. Chem., 1997, 272, 28210-28217.
46. Marx N., Kehrle B., Kohlhammer K., Grub M., Koenig W., Hombach V., Libby P. & Plutzky J., PPAR activators as antiinflammatory mediators in human T lymphocytes: implications for atherosclerosis and transplantation-associated arteriosclerosis. Circ. Res., 2002, 90, 703-710.
47. Marx N., Schonbeck U., Lazar M. A., Libby P. & Plutzky J. Peroxisome proliferator-activated receptor γ activators inhibit gene expression and migration in human vascular smooth muscle cells. Circ. Res., 1998, 83, 1097-1103.
48. Medzhitov R., Preston-Hurlburt P. & Janeway C. A. Jr., A human homologue of the Drosophila Toll protein signals activation of adaptive immunity. Nature, 1997, 388, 394-397.
49. Molinie F., Gower-Rousseau C., Yzet T., Merle V., Grandbastien B., Marti R., Lerebours E., Dupas J. L., Colombel J. F., Salomez J. L. & Cortot A., Opposite evolution in incidence of Crohn's disease and ulcerative colitis in Northern France (1988-1999. Gut, 2004, 53, 843-848.
50. Munkholm P., Review article: the incidence and prevalence of colorectal cancer in inflammatory bowel disease. Aliment. Pharmacol. Ther., 2003, 18 (Suppl. 2), 1-5.
51. Nagy L., Tontonoz P., Alvarez J. G., Chen H. & Evans R. M., Oxidized LDL regulates macrophage gene expression through ligand activation of PPAR4γ. Cell, 1998, 93, 229-240.
52. Nolan J. J., Ludvik B., Beerdsen P., Joyce M. & Olefsky J. Improvement in glucose tolerance and insulin resistance in obese subjects treated with troglitazone. N. Engl. J. Med., 1994, 331, 1188-1193.
53. Ogura Y., Bonen D. K., Inohara N., Nicolae D. L., Chen F. F., Ramos R., Britton H., Moran T., Karaliuskas R., Duerr R. H., Achkar J. P., Brant S. R., Bayless T. M., Kirschner B. S., Hanauer S. B., Nunez G. & Cho J. H., A frameshift mutation in NOD2 associated with susceptibility to Crohn's disease. Nature, 2001, 411, 603-606.
54. Ohmen J. D., Yang H. Y., Yamamoto K. K., Zhao H. Y., Ma Y., Bentley L. G., Huang Z., Gerwehr S., Pressman S., McElree C., Targan S., Rotter J. I. & Fischel-Ghodsian N., Susceptibility locus for inflammatory bowel disease on chromosome 16 has a role in Crohn's disease, but not in ulcerative colitis. Hum. Mol. Genet., 1996, 5, 1679-1683.
55. Okuno A., Tamemoto H., Tobe K., Ueki K., Mori Y., Iwamoto K., Umesono K., Akanuma Y., Fujiwara T., Horikoshi H., Yazaki Y. & Kadowaki T., Troglitazone increases the number of small adipocytes without the change of white adipose tissue mass in obese Zucker rats. J. Clin. Invest., 1998, 101, 1354-1361.
56. Orholm M., Munkholm P., Langholz E., Nielsen O. H., Sorensen I. A. & Binder V., Familial occurrence of inflammatory bowel disease. N. Engl. J. Med., 1991, 324, 84-88.
57. Parkes M., Satsangi J., Lathrop G. M., Bell J. I. & Jewell D. P., Susceptibility loci in inflammatory bowel disease. Lancet, 1996, 348, 1588.
58. Pasceri V., Wu H. D., Willerson J. T. & Yeh E. T., Modulation of vascular inflammation in vitro and in vivo by peroxisome proliferator-activated receptor-γ activators. Circulation, 2000, 101, 235-238.
59. Peraldi P., Xu M. & Spiegelman B. M., Thiazolidinediones block tumor necrosis factor-α-induced inhibition of insulin signaling. J. Clin. Invest., 1997, 100, 1863-1869.
60. Poltorak A., He X., Smirnova I., Liu M. Y., Huffel C. V., Du X., Birdwell D., Alejos E., Silva M., Galanos C., Freudenberg M., Ricciardi-Castagnoli P., Layton B. & Beutler B., Defective LPS signaling in C3H/HeJ and C57BL/10ScCr mice: mutations in Tlr4 gene. Science, 1998, 282, 2085-2088.
61. Qureshi S. T., Lariviere L., Leveque G., Clermont S., Moore K. J., Gros P. & Malo D., Endotoxin-tolerant mice have mutations in Toll-like receptor 4 (Tlr4). J. Exp. Med., 1999, 189, 615-625.
62. Reimund J. M., Wittersheim C., Dumont S., Muller C. D., Kenney J. S., Baumann R., Poindron P. & Duclos B., Increased production of tumour necrosis factor-α interleukin-1 β and interleukin-6 by morphologically normal intestinal biopsies from patients with Crohn's disease. Gut, 1996, 39, 684-689.
63. Ricote M., Li A. C., Willson T. M., Kelly C. J. & Glass C. K., The peroxisome proliferator-activated receptor-γ is a negative regulator of macrophage activation. Nature, 1998, 391, 79-82.
64. Rieusset J., Auwerx J. & Vidal H., Regulation of gene expression by activation of the peroxisome proliferator-activated receptor γ with rosiglitazone (BRL 49653) in human adipocytes. Biochem. Biophys. Res. Commun., 1999, 265, 265-271.
65. Rocchi S., Picard F., Vamecq J., Gelman L., Potier N., Zeyer D., Dubuquoy L., Bac P., Champy M. F., Plunket K. D., Leesnitzer L. M., Blanchard S. G., Desreumaux P., Moras D., Renaud J. P. & Auwerx J., A unique PPARγ ligand with potent insulin-sensitizing yet weak adipogenic activity. Mol. Cell., 2001, 8, 737-747.
66. Ron D., Brasier A. R., McGehee R. E. Jr. & Habenen J. F., Tumor necrosis factor-induced reversal of adipocytic phenotype of 3T3-L1 cells is preceded by a loss of nuclear CCAAT/enhancer binding protein (C/EBP). J. Clin. Invest., 1992, 89, 223-233.
67. Rousseaux C., Lefebvre B., Dubuquoy L., Lefebvre P., Romano O., Auwerx J., Metzger D., Walter W., Desvengne B., Naccari G. C., Chavatte P., Farce A., Bulois P., Cortot A., Colombel J. F. & Desreumaux P., Intestinal anti-inflammatory effect of 5-aminosalicylic acid is dependent on PPARγ. Journal of Experimental Medicine, 2005, in press.
68. Schoonjans K., Staels B. & Auwerx J., The peroxisome proliferator-activated receptors (PPARS) and their effects on lipid metabolism and adipocyte differentiation. Biochim. Biophys. Acta, 1996, 1302, 93-109.
69. Schoonjans K., Staels B., Grimaldi P. & Auwerx J., Acyl-CoA synthetase mRNA expression is controlled by fibric-acid derivatives, feeding and liver proliferation. Eur. J. Biochem., 1993, 216, 615-622.
70. Schoonjans K., Watanabe M., Suzuki H., Mahfoudi A., Krey G., Wahli W., Grimaldi P., Staels B., Yamamoto T. & Auwerx J., Induction of the acyl-coenzyme A synthetase gene by fibrates and fatty acids is mediated by a peroxisome proliferator response element in the C promoter. J. Biol. Chem., 1995, 270, 19269-19276.
71. Shao D. & Lazar M. A., Peroxisome proliferator activated receptor γ, CCAAT/enhancer-binding protein α, and ceIl cycle status regulate the commitment to adipocyte differentiation. J. Biol. Chem., 1997, 272, 21473-21478.
72. Shibasaki M., Takahashi K., Itou T., Bujo H. & Saito Y., A PPAR agonist improves TNF-α-induced insulin resistance of adipose tissue in mice. Biochem. Biophys. Res. Commun., 2003, 309, 419-424.
73. Shimaya A., Kurosaki E., Shioduka K., Nakano R., Shibasaki M. & Shikama H., YM268 increases the glucose uptake, cell differentiation, and mRNA expression of glucose transporter in 3T3-L1 adipocytes. Horm. Metab. Res., 1998, 30, 543-548.
74. Spiegelman B. M., PPARγ in monocytes: less pain, any gain? Cell, 1998, 93, 153-155.
75. Sugawara K., Olson T. S., Moskaluk C. A., Stevens B. K., Hoang S., Kozaiwa K., Cominelli F., Ley K. F. & McDuffie M., Linkage to peroxisome proliferator-activated receptor-γ in SAMP1/YitFc mice and in human Crohn's disease. Gastroenterology, 2005, 128, 351-360.
76. Thieringer R., Fenyk-Melody J. E., Le Grand C. B., Shelton B. A., Detmers P. A., Somers E. P., Carbin L., Moller D. E., Wright S. D. & Berger J., Activation of peroxisome proliferator-activated receptor γ does not inhibit IL-6 or TNF-α responses of macrophages to lipopolysaccharide in vitro or in vivo. J. Immunol., 2000, 164, 1046-1054.
77. Tontonoz P., Hu E., Devine J., Beale E. G. & Spiegelman B. M., PPARγ 2 regulates adipose expression of the phosphoenolpyruvate carboxykinase gene. Mol. Cell. Biol., 1995, 15, 351-357.
78. Tontonoz P., Hu E. & Spiegelman B. M., Stimulation of adipogenesis in fibroblasts by PPARγ 2, a lipid-activated transcription factor. Cell, 1994, 79, 1147-1156.
79. Tontonoz P., Nagy L., Alvarez J. G., Thomazy V. A. & Evans R. M., PPARγ promotes monocyte/macrophage differentiation and uptake of oxidized LDL. Cell, 1998, 93, 241-252.
80. Tysk C., Lindberg E., Jarnerot G. & Floderus-Myrhed B., Ulcerative colitis and Crohn's disease in an unselected population of monozygotic and dizygotic twins. A study of heritability and the influence of smoking. Gut, 1988, 29, 990-996.
81. Watanabe T., Kitani A., Murray P. J. & Strober W., NOD2 is a negative regulator of Toll-like receptor 2-mediated T helper type 1 responses. Nat. Immunol., 2004, 5, 800-808.
82. Wu Z., Rosen E. D., Brun R., Hauser S., Adelmant G., Troy A. E., McKeon C., Darlington G. J. & Spiegelman B. M., Crossregulation of C/EBP α and PPARγ controls the transcriptional pathway of adipogenesis and insulin sensitivity. Mol. Cell., 1999, 3, 151-158.
83. Xing H., Northrop J. P., Grove J. R., Kilpatrick K. E., Su J. L. & Ringold G. M. TNFα-mediated inhibition and reversal of adipocyte differentiation is accompanied by suppressed expression of PPARγ without effects on Pref-1 expression. Endocrinology, 1997, 138, 2776-2783.
84. Yang X. Y., Wang L. H., Chen T., Hodge D. R., Resau J. H., DaSilva L. & Farrar W. L., Activation of human T lymphocytes is inhibited by peroxisome proliferator-activated receptor gamma (PPARγ) agonists. PPARγ co-association with transcription factor NFAT. J. Biol. Chem., 2000, 275, 4541-4544.
85. Zhu Y., Qi C., Korenberg J. R., Chen X. N., Noya D., Rao M. S. & Reddy J. K., Structural organization of mouse peroxisome proliferator-activated receptor γ (mPPARγ) gene: alternative promoter use and different splicing yield two mPPARγ isoforms. Proc. Natl. Acad. Sci. USA, 1995, 92, 7921-7925.