SEARCH

SEARCH BY CITATION

References

  • 1
    Ridpath JF. Classification and molecular biology. In: GoyalSM, RidpathJF, eds. Bovine Viral Diarrhea Virus: Diagnosis, Management and Control. Ames, IA: Blackwell Publishing; 2005:6580.
  • 2
    Harding MJ, Cao X, Shams H, et al. Role of bovine viral diarrhea virus biotype in the establishment of fetal infections. Am J Vet Res 2002;63:14551463.
  • 3
    Fulton RW, Ridpath JF, Ore S, et al. Bovine viral diarrhoea virus (BVDV) subgenotypes in diagnostic laboratory accessions: Distribution of BVDV1a, 1b, and 2a subgenotypes. Vet Microbiol 2005;111:3540.
  • 4
    Ridpath JF, Bendfeldt S, Neill JD, et al. Lymphocytopathogenic activity in vitro correlates with high virulence in vivo for BVDV type 2 strains: Criteria for a third biotype of BVDV. Virus Res 2006;118:6269.
  • 5
    Ridpath JF, Bolin SR. The genomic sequence of a virulent bovine viral diarrhea virus (BVDV) from the type 2 genotype: Detection of a large genomic insertion in a noncytopathic BVDV. Virology 1995;212:3946.
  • 6
    De Mia GM, Greiser-Wilke I, Feliziani F, et al. Genetic characterization of a caprine pestivirus as the first member of a putative novel pestivirus subgroup. J Vet Med B Infect Dis Vet Public Health 2005;52:206210.
  • 7
    Vilcek S, Paton DJ, Durkovic B, et al. Bovine viral diarrhoea virus genotype 1 can be separated into at least eleven genetic groups. Arch Virol 2001;146:99115.
  • 8
    Flores EF, Ridpath JF, Weiblen R, et al. Phylogenetic analysis of Brazilian bovine viral diarrhea virus type 2 (BVDV-2) isolates: Evidence for a subgenotype within BVDV-2. Virus Res 2002;87:5160.
  • 9
    Ridpath JF, Neill JD, Frey M, et al. Phylogenetic, antigenic and clinical characterization of type 2 BVDV from North America. Vet Microbiol 2000;77:145155.
  • 10
    Fulton RW, Hessman B, Johnson BJ, et al. Evaluation of diagnostic tests used for detection of bovine viral diarrhea virus and prevalence of subtypes 1a, 1b, and 2a in persistently infected cattle entering a feedlot. J Am Vet Med Assoc 2006;228:578584.
  • 11
    Durham PJ, Hassard LE. Prevalence of antibodies to infectious bovine rhinotracheitis, parainfluenza 3, bovine respiratory syncytial, and bovine viral diarrhea viruses in cattle in Saskatchewan and Alberta. Can Vet J 1990;31:815820.
  • 12
    Bolin SR, McClurkin AW, Coria MF. Frequency of persistent bovine viral diarrhea virus infection in selected cattle herds. Am J Vet Res 1985;46:23852387.
  • 13
    Scott HM, Sorensen O, Wu JT, et al. Seroprevalence of Mycobacterium avium subspecies paratuberculosis, Neospora caninum, bovine leukemia virus, and bovine viral diarrhea virus infection among dairy cattle and herds in Alberta and agroecological risk factors associated with seropositivity. Can Vet J 2006;47:981991.
  • 14
    VanLeeuwen JA, Forsythe L, Tiwari A, et al. Seroprevalence of antibodies against bovine leukemia virus, bovine viral diarrhea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum in dairy cattle in Saskatchewan. Can Vet J 2005;46:5658.
  • 15
    VanLeeuwen JA, Tiwari A, Plaizier JC, et al. Seroprevalences of antibodies against bovine leukemia virus, bovine viral diarrhea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum in beef and dairy cattle in Manitoba. Can Vet J 2006;47:783786.
  • 16
    Wittum TE, Grotelueschen DM, Brock KV, et al. Persistent bovine viral diarrhoea virus infection in US beef herds. Prev Vet Med 2001;49:8394.
  • 17
    O'Connor AM, Sorden SD, Apley MD. Association between the existence of calves persistently infected with bovine viral diarrhea virus and commingling on pen morbidity in feedlot cattle. Am J Vet Res 2005;66:21302134.
  • 18
    Loneragan GH, Thomson DU, Montgomery DL, et al. Prevalence, outcome, and health consequences associated with persistent infection with bovine viral diarrhea virus in feedlot cattle. J Am Vet Med Assoc 2005;226:595601.
  • 19
    Hessman BE, Fulton RW, Sjeklocha DB, et al. Evaluation of economic effects and the health and performance of the general cattle population after exposure to cattle persistently infected with bovine viral diarrhea virus in a starter feedlot. Am J Vet Res 2009;70:7385.
  • 20
    Grondahl C, Uttenthal , Houe H, et al. Characterisation of a pestivirus isolated from persistently infected mousedeer (Tragulus javanicus). Archives Virol 2003;148:14551463.
  • 21
    Nettleton PF. Pestivirus infections in ruminants other than cattle. Rev Sci Tech 1990;9:131150.
  • 22
    Van Campen H, Ridpath J, Williams E, et al. Isolation of bovine viral diarrhea virus from a free-ranging mule deer in Wyoming. J Wildl Dis 2001;37:306311.
  • 23
    Evermann JF. Pestiviral infection of llamas and alpacas. Small Ruminant Res 2006;61:201206.
  • 24
    Celedon M, Sandoval A, Drougett J, et al. Survey for antibodies to pestivirus and herpesvirus in sheep, goats, alpacas (Lama pacos), llamas (Lama glama), guanacos (Lama guanicoe) and vicuna (Vicugna vicugna) from Chile. Archivos De Medicina Veterinaria 2001;33:165172.
  • 25
    Wentz PA, Belknap EB, Brock KV, et al. Evaluation of bovine viral diarrhea virus in New World camelids. J Am Vet Med Assoc 2003;223:223228.
  • 26
    Shimeld LA. Seroprevalence to BVDV of alpacas in Southern California. In: 4th US BVDV Symposium, Phoenix, AZ, 2009.
  • 27
    Topliff CL, Smith DR, Clowser SL, et al. Prevalence of bovine viral diarrhea virus infections in alpacas in the United States. J Am Vet Med Assoc 2009;234:519529.
  • 28
    Byers SR, Snekvik KR, Righter DJ, et al. Disseminated bovine viral diarrhea virus in a persistently infected alpaca (Vicugna pacos) cria. J Vet Diagn Invest 2009;21:145148.
  • 29
    Carman S, Carr N, DeLay J, et al. Bovine viral diarrhea virus in alpaca: Abortion and persistent infection. J Vet Diagn Invest 2005;17:589593.
  • 30
    Foster AP, Houlihan MG, Holmes JP, et al. Bovine viral diarrhoea virus infection of alpacas (Vicugna pacos) in the UK. Vet Rec 2007;161:9499.
  • 31
    Kim SG, Anderson RR, Yu JZ, et al. Genotyping and phylogenetic analysis of bovine viral diarrhea virus isolates from BVDV infected alpacas in North America. Vet Microbiol 2009;136:209216.
  • 32
    Mattson DE, Baker RJ, Catania JE, et al. Persistent infection with bovine viral diarrhea virus in an alpaca. J Am Vet Med Assoc 2006;228:17621765.
  • 33
    Edmondson MA, Walz PH, Johnson JW, et al. Experimental exposure of pregnant alpacas to different genotypes of bovine viral diarrhea virus. In: 4th US BVDV Symposium, Phoenix, AZ, 2009.
  • 34
    Celedon MO, Osorio J, Pizarro J. Isolation and identification of pestiviruses in alpacas (Lama pacos) and llamas (Lama glama) introduced to the Region Metropolitana, Chile. Archivos De Medicina Veterinaria 2006;38:247252.
  • 35
    Johnson JW, Edmonson MA, Walz PH, et al. Experimental exposure of naive alpacas to different genotypes of bovine viral diarrhea virus isolated from cattle and alpacas. In: 4th US BVDV Symposium, Phoenix, AZ, 2009.
  • 36
    Duncan C, Van Campen H, Soto S, et al. Persistent bovine viral diarrhea virus infection in wild cervids of Colorado. J Vet Diagn Invest 2008;20:650653.
  • 37
    Passler T, Walz PH, Ditchkoff SS, et al. Evaluation of hunter-harvested white-tailed deer for evidence of bovine viral diarrhea virus infection in Alabama. J Vet Diagn Invest 2008;20:7982.
  • 38
    Pogranichniy RM, Raizman E, Thacker HL, et al. Prevalence and characterization of bovine viral diarrhea virus in the white-tailed deer population in Indiana. J Vet Diagn Invest 2008;20:7174.
  • 39
    Frolich K. Bovine virus diarrhea and mucosal disease in free-ranging and captive deer (Cervidae) in Germany. J Wildl Dis 1995;31:247250.
  • 40
    Cantu A, Ortega SJ, Mosqueda J, et al. Prevalence of infectious agents in free-ranging white-tailed deer in northeastern Mexico. J Wildl Dis 2008;44:10021007.
  • 41
    Wolf KN, DePerno CS, Jenks JA, et al. Selenium status and antibodies to selected pathogens in white-tailed deer (Odocoileus virginianus) in southern Minnesota. J Wildl Dis 2008;44:181187.
  • 42
    Elazhary MA, Frechette JL, Silim A, et al. Serological evidence of some bovine viruses in the caribou (Rangifer tarandus caribou) in Quebec. J Wildl Dis 1981;17:609612.
  • 43
    Passler T, Walz PH, Ditchkoff SS, et al. Cohabitation of pregnant white-tailed deer and cattle persistently infected with bovine viral diarrhea virus results in persistently infected fawns. Vet Microbiol 2009;134:362367.
  • 44
    Uttenthal A, Hoyer MJ, Grondahl C, et al. Vertical transmission of bovine viral diarrhoea virus (BVDV) in mousedeer (Tragulus javanicus) and spread to domestic cattle. Arch Virol 2006;151:23772387.
  • 45
    Chase CC, Braun LJ, Leslie-Steen P, et al. Bovine viral diarrhea virus multiorgan infection in two white-tailed deer in southeastern South Dakota. J Wildl Dis 2008;44:753759.
  • 46
    Passler T, Walz PH, Ditchkoff SS, et al. Experimental persistent infection with bovine viral diarrhea virus in white-tailed deer. Vet Microbiol 2007;122:350356.
  • 47
    Ridpath JF, Driskell EA, Chase CC, et al. Reproductive tract disease associated with inoculation of pregnant white-tailed deer with bovine viral diarrhea virus. Am J Vet Res 2008;69:16301636.
  • 48
    Raizman EA, Pogranichniy R, Levy M, et al. Experimental infection of white-tailed deer fawns (Odocoileus virginianus) with bovine viral diarrhea virus type-1 isolated from free-ranging white-tailed deer. J Wildl Dis 2009;45:653660.
  • 49
    Liu L, Xia H, Wahlberg N, et al. Phylogeny, classification and evolutionary insights into pestiviruses. Virology 2009;385:351357.
  • 50
    Giangaspero M, Harasawa R. Numerical taxonomy of the genus pestivirus based on palindromic nucleotide substitutions in the 5′ untranslated region. J Virol Methods 2007;146:375388.
  • 51
    Vilcek S, Ridpath JF, Van Campen H, et al. Characterization of a novel pestivirus originating from a pronghorn antelope. Virus Res 2005;108:187193.
  • 52
    Fernelius AL, Lambert G, Hemness GJ. Bovine viral diarrhea virus-host cell interactions: Adaptation and growth of virus in cell lines. Am J Vet Res 1969;30:15611572.
  • 53
    Buckwold VE, Beer BE, Donis RO. Bovine viral diarrhea virus as a surrogate model of hepatitis C virus for the evaluation of antiviral agents. Antiviral Res 2003;60:115.
  • 54
    Giangaspero M, Vacirca G, Buettner M, et al. Serological and antigenical findings indicating pestivirus in man. Arch Virol Suppl 1993;7:5362.
  • 55
    Giangaspero M, Harasawa R, Verhulst A. Genotypic analysis of the 5′-untranslated region of a pestivirus strain isolated from human leucocytes. Microbiol Immunol 1997;41:829834.
  • 56
    Van Kruiningen HJ, Poulin M, Garmendia AE, et al. Search for evidence of recurring or persistent viruses in Crohn's disease. APMIS 2007;115:962968.
  • 57
    Yolken R, Dubovi E, Leister F, et al. Infantile gastroenteritis associated with excretion of pestivirus antigens. Lancet 1989;1:517520.
  • 58
    Cherry BR, Reeves MJ, Smith G. Evaluation of bovine viral diarrhea virus control using a mathematical model of infection dynamics. Prev Vet Med 1998;33:91108.
  • 59
    Carman S, Van Dreumel T, Ridpath J, et al. Severe acute bovine viral diarrhea in Ontario, 1993–1995. J Vet Diagn Invest 1998;10:2735.
  • 60
    Rebhun WC, French TW, Perdrizet JA, et al. Thrombocytopenia associated with acute bovine virus diarrhea infection in cattle. J Vet Intern Med 1989;3:4246.
  • 61
    Bolin SR, Ridpath JF. Differences in virulence between two noncytopathic bovine viral diarrhea viruses in calves. Am J Vet Res 1992;53:21572163.
  • 62
    Walz PH, Bell TG, Wells JL, et al. Relationship between degree of viremia and disease manifestation in calves with experimentally induced bovine viral diarrhea virus infection. Am J Vet Res 2001;62:10951103.
  • 63
    Walz PH, Bell TG, Grooms DL, et al. Platelet aggregation responses and virus isolation from platelets in calves experimentally infected with type I or type II bovine viral diarrhea virus. Can J Vet Res 2001;65:241247.
  • 64
    Ellis JA, West KH, Cortese VS, et al. Lesions and distribution of viral antigen following an experimental infection of young seronegative calves with virulent bovine virus diarrhea virus-type II. Can J Vet Res 1998;62:161169.
  • 65
    Liebler-Tenorio EM, Ridpath JF, Neill JD. Lesions and tissue distribution of viral antigen in severe acute versus subclinical acute infection with BVDV2. Biologicals 2003;31:119122.
  • 66
    Kelling CL, Steffen DJ, Topliff CL, et al. Comparative virulence of isolates of bovine viral diarrhea virus type II in experimentally inoculated six- to nine-month-old calves. Am J Vet Res 2002;63:13791384.
  • 67
    Ellis JA, Davis WC, Belden EL, et al. Flow cytofluorimetric analysis of lymphocyte subset alterations in cattle infected with bovine viral diarrhea virus. Vet Pathol 1988;25:231236.
  • 68
    Welsh MD, Adair BM, Foster JC. Effect of BVD virus infection on alveolar macrophage functions. Vet Immunol Immunopathol 1995;46:195210.
  • 69
    Roth JA, Kaeberle ML, Griffith RW. Effects of bovine viral diarrhea virus infection on bovine polymorphonuclear leukocyte function. Am J Vet Res 1981;42:244250.
  • 70
    Roth JA, Kaeberle ML. Suppression of neutrophil and lymphocyte function induced by a vaccinal strain of bovine viral diarrhea virus with and without the administration of ACTH. Am J Vet Res 1983;44:23662372.
  • 71
    Givens MD, Heath AM, Brock KV, et al. Detection of bovine viral diarrhea virus in semen obtained after inoculation of seronegative postpubertal bulls. Am J Vet Res 2003;64:428434.
  • 72
    Kirkland PD, McGowan MR, Mackintosh SG, et al. Insemination of cattle with semen from a bull transiently infected with pestivirus. Vet Rec 1997;140:124127.
  • 73
    Voges H, Horner GW, Rowe S, et al. Persistent bovine pestivirus infection localized in the testes of an immuno-competent, non-viraemic bull. Vet Microbiol 1998;61:165175.
  • 74
    Kirkland PD, Mackintosh SG, Moyle A. The outcome of widespread use of semen from a bull persistently infected with pestivirus. Vet Rec 1994;135:527529.
  • 75
    Niskanen R, Alenius S, Belak K, et al. Insemination of susceptible heifers with semen from a non-viraemic bull with persistent bovine virus diarrhoea virus infection localized in the testes. Reprod Domest Anim 2002;37:171175.
  • 76
    Grooms DL. Reproductive consequences of infection with bovine viral diarrhea virus. Vet Clin North Am Food Anim Pract 2004;20:519.
  • 77
    McGowan MR, Kirkland PD, Richards SG, et al. Increased reproductive losses in cattle infected with bovine pestivirus around the time of insemination. Vet Rec 1993;133:3943.
  • 78
    Grooms DL, Brock KV, Pate JL, et al. Changes in ovarian follicles following acute infection with bovine viral diarrhea virus. Theriogenology 1998;49:595605.
  • 79
    Grooms DL, Brock KV, Ward LA. Detection of bovine viral diarrhea virus in the ovaries of cattle acutely infected with bovine viral diarrhea virus. J Vet Diagn Invest 1998;10:125129.
  • 80
    Ellsworth MA, Fairbanks KK, Behan S, et al. Fetal protection following exposure to calves persistently infected with bovine viral diarrhea virus type 2 sixteen months after primary vaccination of the dams. Vet Ther 2006;7:295304.
  • 81
    Collins ME, Desport M, Brownlie J. Bovine viral diarrhea virus quasispecies during persistent infection. Virology 1999;259:8598.
  • 82
    Bolin SR, McClurkin AW, Cutlip RC, et al. Severe clinical disease induced in cattle persistently infected with noncytopathic bovine viral diarrhea virus by superinfection with cytopathic bovine viral diarrhea virus. Am J Vet Res 1985;46:573576.
  • 83
    Brownlie J. Pathogenesis of mucosal disease and molecular aspects of bovine virus diarrhoea virus. Vet Microbiol 1990;23:371382.
  • 84
    Bolin SR. The pathogenesis of mucosal disease. Vet Clin North Am Food Anim Pract 1995;11:489500.
  • 85
    Edmondson MA, Givens MD, Walz PH, et al. Comparison of tests for detection of bovine viral diarrhea virus in diagnostic samples. J Vet Diagn Invest 2007;19:376381.
  • 86
    Brock KV. Diagnosis of bovine viral diarrhea virus infections. Vet Clin North Am Food Anim Pract 1995;11:549561.
  • 87
    Saliki JT, Fulton RW, Hull SR, et al. Microtiter virus isolation and enzyme immunoassays for detection of bovine viral diarrhea virus in cattle serum. J Clin Microbiol 1997;35:803807.
  • 88
    Driskell EA, Ridpath JF. A survey of bovine viral diarrhea virus testing in diagnostic laboratories in the United States from 2004 to 2005. J Vet Diagn Invest 2006;18:600605.
  • 89
    Zimmer GM, Van Maanen C, De Goey I, et al. The effect of maternal antibodies on the detection of bovine virus diarrhoea virus in peripheral blood samples. Vet Microbiol 2004;100:145149.
  • 90
    Ridpath JF, Hietala SK, Sorden S, et al. Evaluation of the reverse transcription-polymerase chain reaction/probe test of serum samples and immunohistochemistry of skin sections for detection of acute bovine viral diarrhea infections. J Vet Diagn Invest 2002;14:303307.
  • 91
    Grooms DL, Keilen ED. Screening of neonatal calves for persistent infection with bovine viral diarrhea virus by immunohistochemistry on skin biopsy samples. Clin Diagn Lab Immunol 2002;9:898900.
  • 92
    Fulton RW, Johnson BJ, Briggs RE, et al. Challenge with bovine viral diarrhea virus by exposure to persistently infected calves: Protection by vaccination and negative results of antigen testing in nonvaccinated acutely infected calves. Can J Vet Res 2006;70:121127.
  • 93
    Cornish TE, Van Olphen AL, Cavender JL, et al. Comparison of ear notch immunohistochemistry, ear notch antigen-capture ELISA, and buffy coat virus isolation for detection of calves persistently infected with bovine viral diarrhea virus. J Vet Diagn Invest 2005;17:110117.
  • 94
    Gripshover EM, Givens MD, Ridpath JF, et al. Variation in E(rns) viral glycoprotein associated with failure of immunohistochemistry and commercial antigen capture ELISA to detect a field strain of bovine viral diarrhea virus. Vet Microbiol 2007;125:1121.
  • 95
    Weinstock D, Bhudevi B, Castro AE. Single-tube single-enzyme reverse transcriptase PCR assay for detection of bovine viral diarrhea virus in pooled bovine serum. J Clin Microbiol 2001;39:343346.
  • 96
    Given MD, Riddell KP, Galik PK, et al. Diagnostic dilemma encountered when detecting bovine viral diarrhea virus in IVF embryo production. Theriogenology 2002;58:13991407.
  • 97
    Saliki JT, Dubovi EJ. Laboratory diagnosis of bovine viral diarrhea virus infections. Vet Clin North Am Food Anim Pract 2004;20:6983.
  • 98
    Brock KV. The persistence of bovine viral diarrhea virus. Biologicals 2003;31:133135.
  • 99
    Lindberg AL. Bovine viral diarrhoea virus infections and its control. A review. Vet Q 2003;25:116.
  • 100
    Greiser-Wilke I, Grummer B, Moennig V. Bovine viral diarrhoea eradication and control programmes in Europe. Biologicals 2003;31:113118.
  • 101
    Grom J, Barlic-Maganja D. Bovine viral diarrhoea (BVD) infections–control and eradication programme in breeding herds in Slovenia. Vet Microbiol 1999;64:259264.
  • 102
    Sandvik T. Progress of control and prevention programs for bovine viral diarrhea virus in Europe. Vet Clin North Am Food Anim Pract 2004;20:151169.
  • 103
    Van Campen H. Epidemiology and control of BVD in the U.S. Vet Microbiol. 2010;142:9498.
  • 104
    Larson RL. Management systems and control programs. In: GoyalSM, RidpathJF, eds. Bovine Viral Diarrhea Virus: Diagnosis, Management and Control. Ames, IA: Blackwell Publishing; 2005:223238.
  • 105
    Smith DR, Grotelueschen DM. Biosecurity and biocontainment of bovine viral diarrhea virus. Vet Clin North Am Food Anim Pract 2004;20:131149.
  • 106
    Houe H, Meyling A. Prevalence of bovine virus diarrhoea (BVD) in 19 Danish dairy herds and estimation of incidence of infection in early pregnancy. Prev Vet Med 1991;11:916.
  • 107
    Kennedy JA, Mortimer RG, Powers B. Reverse transcription-polymerase chain reaction on pooled samples to detect bovine viral diarrhea virus by using fresh ear-notch-sample supernatants. J Vet Diagn Invest 2006;18:8993.
  • 108
    Munoz-Zanzi CA, Johnson WO, Thurmond MC, et al. Pooled-sample testing as a herd-screening tool for detection of bovine viral diarrhea virus persistently infected cattle. J Vet Diagn Invest 2000;12:195203.
  • 109
    Radwan GS, Brock KV, Hogan JS, et al. Development of a PCR amplification assay as a screening test using bulk milk samples for identifying dairy herds infected with bovine viral diarrhea virus. Vet Microbiol 1995;44:7791.
  • 110
    Drew TW, Yapp F, Paton DJ. The detection of bovine viral diarrhoea virus in bulk milk samples by the use of a single-tube RT-PCR. Vet Microbiol 1999;64:145154.
  • 111
    Fulton RW. Vaccines. In: GoyalSM, RidpathJF, eds. Bovine Viral Diarrhea Virus: Diagnosis, Management and Control. Ames, IA: Blackwell Publishing; 2005:209222.
  • 112
    Rauff Y, Moore DA, Sischo WM. Evaluation of the results of a survey of dairy producers on dairy herd biosecurity and vaccination against bovine viral diarrhea. J Am Vet Med Assoc 1996;209:16181622.
  • 113
    Van Oirschot JT, Bruschke CJ, Van Rijn PA. Vaccination of cattle against bovine viral diarrhoea. Vet Microbiol 1999;64:169183.
  • 114
    Martin SW, Bohac JG. The association between serological titers in infectious bovine rhinotracheitis virus, bovine virus diarrhea virus, parainfluenza-3 virus, respiratory syncytial virus and treatment for respiratory disease in Ontario feedlot calves. Can J Vet Res 1986;50:351358.
  • 115
    Campbell JR. Effect of bovine viral diarrhea virus in the feedlot. Vet Clin North Am Food Anim Pract 2004;20:3950.
  • 116
    Fulton RW, Cook BJ, Step DL, et al. Evaluation of health status of calves and the impact on feedlot performance: Assessment of a retained ownership program for postweaning calves. Can J Vet Res 2002;66:173180.
  • 117
    Lindberg AL, Alenius S. Principles for eradication of bovine viral diarrhoea virus (BVDV) infections in cattle populations. Vet Microbiol 1999;64:197222.