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AGGRESSION AND ATHEROMA
1308 this relative reduction is similar to the effect reported by Dr. Barth and his colleagues. While statistically significant this depression was considered negligible when compared with the potent depression of the cellular immune response brought about by A.L.S. or A.T.S. If A.L.s.-affected cells were crucial to interferon production, a much greateI decrease in interferon levels should have been seen. In a previous study in this laboratory, the pathogenicity of vaccinia in mice was found to be considerably potentiated by A.T.S. Interferon levels, measured at a time when peak response was expected, were not affected by A.T.S. treatment. Functioning cellular immunity was clearly the crux of host defence. The pathogenetic significance of a lowering of interferon level on the progression of oncogenic-virus infections has not been examined, nor has a model system for protracted suppression of endogenous interferon synthesis been described. However, in an additive rather than subtractive experiment, Gresser et al. showed that exogenous interferon retards the progression of Friend-virus leukaemia in mice. This effect was only observed when a potent interferon preparation was given throughout the four-week duration of the experiment. Others have noted a similar requirement for continuing interferon treatment for protection from oncogenic-virus disease. 8, The limited protective effect of interferon on viral oncogensis can only be contrasted with the dramatic potentiating action of A.L.S. in an indirect way, since an experiment dissecting the relative roles in a common model has not been reported. The effect of A.L.S. upon viral infections, whether cytopathic or oncogenic, is mediated via a significant depression of cellular immune responsiveness. 10 In experimental viral tumours, host defence is directed against virus and the neoantigens of transformed cells; the potentiation of oncogenicity by A.L.S. probably supresses effective host defences directed against both antigenic specificities. In organtransplant patients receiving A.L.S. (and other immunosuppressants), transformed cells are the only known new antigens presented to surveillance-defence mechanisms. Depressed interferon levels may play an important role in enhancing the oncogenicity of the yet-to-be-discovered human cancer virus(es); however, this hypothesis must’be set in perspective. Available evidence demands re-emphasis of the known direct suppressive effect of A.L.s. upon cellular immune mechanisms which function toward rejection of the new antieenicitv of a tumour cell. Viropathology Laboratory, ERNEST C. BORDEN National Communicable Disease Center,
Atlanta, Georgia 30333.
FREDERICK A. MURPHY.
AGGRESSION AND ATHEROMA SIR,-Dr. Carruthers’ mechanism (Nov. 29, p. 1170) of atheroma-potentiation-by increase of free fatty acids in the blood due to lipolysis of adipose tissue by increased adrenaline and noradrenaline secretion in emotional states-could be aided by the hyperpietic effect of these hormones, which, as I suggested," might help to block the cylindrical Buchner filter (pores 2[L) of the fenestrated elastic membranes. Devonport Pathological Laboratory, Greenwich, London S.E.10.
S., Hahmias, A. J., Murphy, F. A., Kramer, J. H. J. 1968, 128, 121. 7. Gresser, I., Coppey, J., Fontaine-Brouty-Boye, D., Falcoff, E., Falcoff, R., Zajdela, F., Bourali, C., Thomas, M. in Interferon CIBA Symposium (edited by G. Wolstenholme and M. O’Connor); p. 240. Boston, 1967. 8. Merigan, T. C. ibid. p. 250. 9. Rhim, J. S., Greenawalt, C., Huebner, R. J. Nature, Lond. 1969, 222, 1166. 10. Hirsch, M. S., Murphy, F. A. Lancet, 1968, ii, 37. 11. Robinson, G. L. Br. Heart J. 1963, 25, 270. 6.
M. exp. Med.
G. L. ROBINSON.
Hirsch,
INDUCTION OF IN-VIVO RESISTANCE OF TRICHOMONAS VAGINALIS TO METRONIDAZOLE
SIR,-It seems possible to some workers1 that the spread of strains of Trichomonas vaginalis resistant to metronidazole may gradually undo the progress made in the past dozen years in the treatment of the widespread disease, trichomonas vaginitis. (Chloroquine-resistance in human malaria first became evident after the drug had been used for many years.) There is, however, no immediate danger: such strains of the parasite as are resistant to metronidazole appear to remain partially sensitive to other nitroimidazole
derivatives-e.g., nitrimidazine.2 So far there have not been many reports of strains of vaginalis resistant to metronidazole in clinical practice,3-6 and even the existence of such strains has been questioned. 7,8I In veterinary practice resistant strains of T. faetus have been reported.9 Nevertheless, some workers have obtained strains of T. vaginalis resistant to the drug in vitro,lo-12 by serial in-vitro passages in the presence of increasing but suboptimal concentrations of the drug. One of these strains eventually turned out to be resistant also in vivo in subcutaneously infected mice." More recently, Actor et aU have described a strain of T. fcetus that became resistant to metronidazole both in vitro and in vivo after a vaginal passage in hamsters treated with subcurative doses of metronidazole. We have recently obtained strains of T. vaginalis resistant in vivo by two distinct methods, one of which is in vitro and the other in vivo.
T.
In the first experiment we induced in-vitro resistance in an initially moderately resistant strain of T. vaginalis (6 lAg. per ml.) which had become more sensitive (up to 0-23 {ig. per ml.) after being cultured for several years. The in-vivo sensitivity of this strain was tested in subcutaneously infected mice.13 Metronidazole was given orally 6, 24, and 48 hours after infection in 5 scalar doses, in 10 mice for each dose-level; therapeutic effects were evaluated 6 days after infection according to the presence or absence of live trichomonas organisms in the lesions by direct microscopical examination; and, from the lesions, we also made subcultures, which were incubated for up to 5 days at 37°C, and read daily. Statistical calculation of the median effective dose and potency-ratio was carried out by the method of Litchfield.14 The E.D.5o was 1-15 mg. per kg., with confidence-limits of 0-76 to 1-73 for p-005. After one year of passages in C.P.L.M. medium containing increasing concentrations of metronidazole, the minimum trichomonacidal concentration of metronidazole for the original strain had risen from 0-23 .g. per ml. to 80 ,g. per ml., as determined by the method of scalar 1/1-5 dilutions in C.P.L.M. medium with horse-serum 15; microscopical readings were taken at 72 hours of incubation at 37°C; and subcultures in the same medium were always made for confirmation. Concurrently, the H.D’5o for this branch of the strain was 90-0 mg. per kg. with confidencelimits of 70-3 to 115-2. In a parallel test the H.D.5o for the initial (sensitive) strain was 1-27 mg. per kg. (0-96 to 1-67). The potencyratio between the two branches was 70-86, with confidence-limits of 48-2 to 104-1. In a second experiment we obtained a strain resistant in vivo by 1. Actor, P., Ziv, D. S., Pagano, J. F. Science, N.Y. 1969, 2. de Carneri, I., Cantone, A., Emanueli, A., Giraldi, P. N.,
164, 439. Logemann, W., Meinardi, G., Monti, G., Nannini, G., Tosolini, G., Vita, G. Proc. VI Int. Congr. Chemother. Tokyo, p. A1. 1969. 3. Robinson, S. C. Can. med. Ass. J. 1962, 86, 665. 4. de Carneri, I., Baldi, G. F., Giannone, R., Passalia, S. Archs Ostet. Ginec. 1963, 48, 422. 5. Robinson, S. C., Mirchandani, G. Am. J. Obstet. Gynec. 1965, 93, 502.
6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
de
Carneri, I. Lancet, 1966, i, 1042. Squires, S., McFadzean, J. A. Br. J. vener. Dis. 1962, 38, 218. Nicol, C. S., McFadzean, J. A., Squires, S. L. Lancet, 1966, i, 1100. McLoughlin, D. K. J. Parasit. 1967, 53, 646. Samuels, R. J. Protozool. 1961, 8 (suppl.), 5. de Carneri, I. Proc. I Int. Congr. Parasit. p. 366. Oxford, 1966. Honigberg, B. M., Livingston, M. C. ibid. p. 365. Lynch, J. E., Holley, E. C., Margison, J. E. Antibiotics Chemother. 1955, 5, 508. Litchfield, J. T., Wilcoxon, F. J. Pharmac. exp. Ther. 1949, 96, 99. de Carneri, I. Am. J. trop. Med. Hyg. 1956, 5, 677.
Atlanta, Georgia 30333.
FREDERICK A. MURPHY.
AGGRESSION AND ATHEROMA SIR,-Dr. Carruthers’ mechanism (Nov. 29, p. 1170) of atheroma-potentiation-by increase of free fatty acids in the blood due to lipolysis of adipose tissue by increased adrenaline and noradrenaline secretion in emotional states-could be aided by the hyperpietic effect of these hormones, which, as I suggested," might help to block the cylindrical Buchner filter (pores 2[L) of the fenestrated elastic membranes. Devonport Pathological Laboratory, Greenwich, London S.E.10.
S., Hahmias, A. J., Murphy, F. A., Kramer, J. H. J. 1968, 128, 121. 7. Gresser, I., Coppey, J., Fontaine-Brouty-Boye, D., Falcoff, E., Falcoff, R., Zajdela, F., Bourali, C., Thomas, M. in Interferon CIBA Symposium (edited by G. Wolstenholme and M. O’Connor); p. 240. Boston, 1967. 8. Merigan, T. C. ibid. p. 250. 9. Rhim, J. S., Greenawalt, C., Huebner, R. J. Nature, Lond. 1969, 222, 1166. 10. Hirsch, M. S., Murphy, F. A. Lancet, 1968, ii, 37. 11. Robinson, G. L. Br. Heart J. 1963, 25, 270. 6.
M. exp. Med.
G. L. ROBINSON.
Hirsch,
INDUCTION OF IN-VIVO RESISTANCE OF TRICHOMONAS VAGINALIS TO METRONIDAZOLE
SIR,-It seems possible to some workers1 that the spread of strains of Trichomonas vaginalis resistant to metronidazole may gradually undo the progress made in the past dozen years in the treatment of the widespread disease, trichomonas vaginitis. (Chloroquine-resistance in human malaria first became evident after the drug had been used for many years.) There is, however, no immediate danger: such strains of the parasite as are resistant to metronidazole appear to remain partially sensitive to other nitroimidazole
derivatives-e.g., nitrimidazine.2 So far there have not been many reports of strains of vaginalis resistant to metronidazole in clinical practice,3-6 and even the existence of such strains has been questioned. 7,8I In veterinary practice resistant strains of T. faetus have been reported.9 Nevertheless, some workers have obtained strains of T. vaginalis resistant to the drug in vitro,lo-12 by serial in-vitro passages in the presence of increasing but suboptimal concentrations of the drug. One of these strains eventually turned out to be resistant also in vivo in subcutaneously infected mice." More recently, Actor et aU have described a strain of T. fcetus that became resistant to metronidazole both in vitro and in vivo after a vaginal passage in hamsters treated with subcurative doses of metronidazole. We have recently obtained strains of T. vaginalis resistant in vivo by two distinct methods, one of which is in vitro and the other in vivo.
T.
In the first experiment we induced in-vitro resistance in an initially moderately resistant strain of T. vaginalis (6 lAg. per ml.) which had become more sensitive (up to 0-23 {ig. per ml.) after being cultured for several years. The in-vivo sensitivity of this strain was tested in subcutaneously infected mice.13 Metronidazole was given orally 6, 24, and 48 hours after infection in 5 scalar doses, in 10 mice for each dose-level; therapeutic effects were evaluated 6 days after infection according to the presence or absence of live trichomonas organisms in the lesions by direct microscopical examination; and, from the lesions, we also made subcultures, which were incubated for up to 5 days at 37°C, and read daily. Statistical calculation of the median effective dose and potency-ratio was carried out by the method of Litchfield.14 The E.D.5o was 1-15 mg. per kg., with confidence-limits of 0-76 to 1-73 for p-005. After one year of passages in C.P.L.M. medium containing increasing concentrations of metronidazole, the minimum trichomonacidal concentration of metronidazole for the original strain had risen from 0-23 .g. per ml. to 80 ,g. per ml., as determined by the method of scalar 1/1-5 dilutions in C.P.L.M. medium with horse-serum 15; microscopical readings were taken at 72 hours of incubation at 37°C; and subcultures in the same medium were always made for confirmation. Concurrently, the H.D’5o for this branch of the strain was 90-0 mg. per kg. with confidencelimits of 70-3 to 115-2. In a parallel test the H.D.5o for the initial (sensitive) strain was 1-27 mg. per kg. (0-96 to 1-67). The potencyratio between the two branches was 70-86, with confidence-limits of 48-2 to 104-1. In a second experiment we obtained a strain resistant in vivo by 1. Actor, P., Ziv, D. S., Pagano, J. F. Science, N.Y. 1969, 2. de Carneri, I., Cantone, A., Emanueli, A., Giraldi, P. N.,
164, 439. Logemann, W., Meinardi, G., Monti, G., Nannini, G., Tosolini, G., Vita, G. Proc. VI Int. Congr. Chemother. Tokyo, p. A1. 1969. 3. Robinson, S. C. Can. med. Ass. J. 1962, 86, 665. 4. de Carneri, I., Baldi, G. F., Giannone, R., Passalia, S. Archs Ostet. Ginec. 1963, 48, 422. 5. Robinson, S. C., Mirchandani, G. Am. J. Obstet. Gynec. 1965, 93, 502.
6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
de
Carneri, I. Lancet, 1966, i, 1042. Squires, S., McFadzean, J. A. Br. J. vener. Dis. 1962, 38, 218. Nicol, C. S., McFadzean, J. A., Squires, S. L. Lancet, 1966, i, 1100. McLoughlin, D. K. J. Parasit. 1967, 53, 646. Samuels, R. J. Protozool. 1961, 8 (suppl.), 5. de Carneri, I. Proc. I Int. Congr. Parasit. p. 366. Oxford, 1966. Honigberg, B. M., Livingston, M. C. ibid. p. 365. Lynch, J. E., Holley, E. C., Margison, J. E. Antibiotics Chemother. 1955, 5, 508. Litchfield, J. T., Wilcoxon, F. J. Pharmac. exp. Ther. 1949, 96, 99. de Carneri, I. Am. J. trop. Med. Hyg. 1956, 5, 677.