Document OjMmJ5Vg93v678egQb2jRN7e

NATURE VOL. 232 AUGUST 27 1971 #41 tlons, whidj uc stimulated to synthesize DNA by contact with antigen, deter a resting |>haae until stimulated to re-enter division by secondary exposure to tbe same antigen. By definition these would ba memory cells. They apparently correspond to Mitchell and Miner's "educated T lympho cytes''1, for they were only observed at a time when the mitotic response of thymus-derived lymphocytes is maximal1. We are currently seeking direct experimental proof of their identity. Previous attempts to establish this point11 have failed, perhaps because of the use of Salmonella antigens, which are poor stimulators of thymus-derived cells11. Our finding implies ,i Miller, J. J. HI, J. Immunol., 92,673 (1964). Miller, J. J. Ill, and Cole, L. J., J. Exp. Med.. 124, 109 (1967). Miller, J. J. Ill, and Cole, L. J., J. Immunol., 99 982 (1967). * i* Bosnian, C.. and Feldman, J. D.,J. Exp. Med., 129, 293 (1968). Ford. C F-, in Tissue Grafting taut Padiatlon (edit, by Micklm, H. S., and Loutit, J. F.), 197 (Academic Press, New York, I1 1966). Miller. J. J. III, and Cole. L. J., J. Immunol., 101, 133 (1968). IS Carter. R. L., Davies, A. i. S., Leuchars, E., Wallis, V. J., and Qerehon, R. K., in Lymphatic Tissue and Germinal Centers In II Inornate Pesponse, 143 (Plenum Press, New York, 1969). Katz, D. H., nut, W. ., GoidL E. A., and Bbnacenaf, B., Science, 170,462 (1970). that cell replication may sprve as a means of enlarging and/or altering the pool of thymus-derived cells capable of reacting with certain antigens. Replication may not, however, be essential to tbe helper function of thuse celts11. At the peak of the secondary response to SRC 30-40^ of the cells in mitosis in the spleen ate thymus-derived1. Thus we were initially- surprised to find only 8-9% of the Spleen Polychlorinated Biphenyls: Photolysis of 2.4,^2 ',4 ',6 Hexachlorobiphenyl cells responding mitoticany to a second ir\jection of antigen which showed evidence of having responded in the earlier Many aromatic organochlorine compounds are readily utilized or otherwise decomposed by a number of specific micro primary responss. It is important to remember that the work organisms. In the environment, however, these compounds delineating the time and magnitude of the response of thymusfierived cells to antigen was carried out in irradiated, thymus- are relatively stable and resistant to general microbial break down. For many of these compounds photochemical degra grafted mice. Thus it Is possible that there may be some differences in normal mice. If there should be any significant dation, induced by the ultraviolet content of the Sun's light, may be a major pathway of decomposition. differences, however, there would probably be an increase of Because a huge number of pesticides contain a chloroaro- thymus-derived cells responding in normal mice. Davies et al. have shown that increasing the number of reconstituting matic moisty re a primary structural feature, considerable attention has been paid to the photolysis of these com thymus grafts up to a point increases the number of peripheral pounds* ~T. Photochemical decomposition of chiorobiphenyls thymus-derived cells1. This Increase does not, however, alter the percentage of thymus-derived cells responding to antigen may be a significant process in the environment because they absorb in that region of the ultraviolet (ref. 8 and our unpub in lymph nodes nor does it change thy timing of their response. lished demonstrations) which is available in natural conditions It is possible that some thymus-derived memory cells lost their (compare ref. 1) from sunlight. label through division after the period of labelling. We are Commercially available polychlorinated biphenyls (PCB) investigating the possibility of recruitment of thymus-derived for example 'Arodor*. consist of a complex mixture of chlor cells by other thymus-derived cells responding specifically. inated biphenyls which can be resolved into more than fifty s The small number (0-1 %) of labelled cells found In control peaks by gu chromatography on `Scot columns' (private animals may be due. at least in part, to the emergence and communication from D. S. Sissons and G. M. Telling). 4 subsequent response of a few thymus-derived cells which were As it is difficult to correlate data from such a complex mixture i- undergoing division in the thymus at the time of thymidine administration. , The chief conclusion we should like to drew from this we have synthesized a series of isomeric di, tri, tetra, penta, hexa, octa and decachlorobiphenyls to facilitate fundamental studies on analytical, biological and chemical aspects of | experiment is that one result of the DNA synthesis which PCB (manuscript In preparation). We have also shown that all c follows primary antigenic stimulation is the generatiqn of these compounds give strong molecular ions on electron j rrtemory cells. The ability to identify these cells should be of value in characterizing them further. R. K. O. is a recipient of a US Public Health Service Career TaMa 1 OLC and Man Spectral Data for Hexachlorobiphenyl Development Award. The work was supports^ by JUS Public rnOVOVyWS rTOOUCre Health Service grants from the National Cancer Institute, the National Institute of Allergy and Infectious Diseases and Retention time* (min) mfe of M* Chlorine t content an American Cane# Society sub-graht. We thank Kazunari Koodo and Anne Shapiro for technical assistance. Note added in proof: Since we submitted tfiis rriaruncript, another report in which roepiory cells were identified by autoradiography, has appeared. Bosmann, C., and Fridman, J. D., Ctln. Exp. Immmol., 7, 965; 1970. . 'll! i k. K. GritawN 1. KaOoaa > 1. D. NxYiMmi TLC band I Peak 1 Peak 2 Peak 3 Peak 4 Peak 5 Peak 6 Peak 7 . Peak 8 5.6 8.2 9.9 13.5 14.1 19.0 29.7 36.9 -t -t 222 256 290(256) 324 (290) 358 304 0 0 2 3 4, (3") S. (4) 6 2 t - . ,B- H Departments of Pathology and Microbiology, Yak Untrerslty School of Medicine, New Horen, Connecticut 06510 . Waoman TLC band 11 Peak 1 Peak 2 Peak 1 19.6 26.8 33.2* 290 324 358 4 00 5 lO 6 CO CO Received November 11,1970; rev^td Match ML 197l. ' 1 Gowant, J. 1, and UKr, J. W., 1 . Med., 124,1017 (1966). 1 Miller, J. F. A. P , and Mitchell, O. P., Transplant. Per., 1, 3 (1969). ' Davie*, A. I. S., Transplant. Per., 1,43 (1949). 1 Raff. M. C. Nature. 224, 1257 (1970). * Davtea, A. J. S., Leuchars, E., Wallis, V., and Roller, P. C., Transplantation, 4, 438 (19661. * Conditions: inurnment, Hewlett-Packard 5750; column, 6% QF-1+4% SE30 on `Chromosorb' (AW) 60-80 mesh 5`, 1/4* outside diameter, gtan; injection port temperature, 220" C; column temperature, 175" C. flame ionization detector temperature and collection port temperature, 240* C; helium flow rate, 40 ml./min. t From isotope peak distribution; tr, trace. J Hydrocarbon peaks, M ` not identifled. | Corresponding to starting material. '2 t STLCOPCB4079154 442 - NATURE VOL 232 AUGUST 27 1t71 IMlClp) i Pig. 1 70 eV mu spectrum (Dul mt/CEC 21-1108 instrument). The temperature of thesample. controlled independently from the source , mmm C The intensity of ions correuwodinc to the oom. ponentj (Q(aC|}H40^t OiaCuHiO|t end so on) ui the mixture varies with sample tcpiperatuie. Each boater shows an M+-70 ion as the most important fragment. These ions are indicated as C3-70, 0,-70, and so on. 5 i i i impact, followed by lea intense ions resulting from successive low of a and/or HC1 (manuscript in preparation). As the general formula for PCB is CuHte-.Q. the molecular ions of individual isomers are thus readily recognized in a mass spectrum of a mixture of these compounds (compare ref. 9). We now wish to report the photochemical behaviour of 2.4,6,2',4,,6'-hexachiorobiphenyl/ A sample of 25 mg of this compound in 2.0 ml. of hexane was irradiated at 3100 A for 100 min. Thin-layer chromatography, using `Merck Silica Gel F-254' and hexane, revealed the presence of two major bends; band I (R, 0.40) and band Q (It, 0.65, corresponding to starting material). The mass spectrum of band 1 (Fig. 1) indicated molecular ions corresponding to di, tri, tetra, penta and bexachlorobiphenyls. Gas liquid chromatography (GLQ of bands I and II revealed eight and three major peaks re spectively. Retention times and mass spectra data for all peak components are reported in Table I. When irradiation was carried out in methanol, similar results were obtained, but in addition a third and more polar band appeared, containing oxygenated polychlorinated compounds with structures which have not been investigated further. Two conclusions can be drawn from the results of this study: (i) during photolysis, chlorine is removed rather readily from hcxachlorobiphenyi yielding compounds of lower chlorine content; (ii) photochemical production of new compounds formed by loss of chlorine, rearrangement or condensation may lead to further complications in residue analysis with the possible appearance of chtorobiphenyts ("peaks") in environmental samples that are not present in commercial FCB mixtures. S. San O. HUTZtNOER Atlantic Regional Laboratory, . National'Research Council of Canada, Halifax, Nora Scotia Received March 22, 1971. 1 Crosby. D. G.. and LL M.-Y , in Degradation of Herbicides (edit by Kearney, P7c., and Kaufman, D. D), 321 (IMtkar, New York, 1969). * Crosby. D. G,, Ann. NY Acad. Set., 166, 82 (1969). * Crosby. D. O., and Lcitb, E., J. Agric. Food Chem., 17, 1033 life (I960). 4 Crosby D. G , and Tang, C. S., A Agric. Food Chem., 17, 1041 * Moder, A- L, Gusezi, W. D,, and Miller, L. L, Science, 164, l55 (1969). i 4 PCmmer, J., KfiagebieL U. L, and Hummer, H.,fgTscience, 167, 67 (1970). 1 ' Miller, L. L., and Narang, R. S., Science, 169, 368 (1970). * Friadai, R., and Oichin, M., UV Spectre of Aromatic Compounds (Wilay. New York. 1951). 4 Hutnogar, O., Jamieson, W. D., and Zitfco, V., Nature, 226, 664 " Jamiema. W. D., and Mason, F. G,, Ker. Sci. Inttrum., 41, 778 (1970). Selection for Resistance to Carbamate and Organophosphonis Insecticides in Anopheles atbimanus The development of resistance in anopheline mosquitoes to DDT, HCH, and cydodienes, and the consequent set back in malaria eradication programmes has lent urgency to the search for alternative insecticides to replace the chlorinated hydro carbons. During the past few years, more than 1,300 new insecticides, chiefly organophoephates and carbamates, have been tested under an international collaborative programme of the World Health Organization1. Testing consists of seven sequential stages and only insecticides that satisfy the criteria in all stages are recommended for use on a targe scale. One of the insecticides that satisfied the criteria of stage VI (operational evaluation) and has been found suitable for stage VH (epidemiological evaluation) is the carbamate, propoxurV, It islntrinsically more toxic to adults of many mosquito species than diddrio, malathion, fenthion and fenitrothion, and as a residual spray his been found to be effective for 2 to 4 rhombs againit Anopheles gambiae and A. fmestut in Africa, A. stephtnstnad A. dthali in Iran, and A. atbimanus in Bl Salvador1. No case of resistance to carbamate or organophosphonis insecticides has yfet been reported although tolerance to malathion has been suspected in A. atbimanus in Guatemala and Nicaragua1'4 and subsequently demonstrated in El Salvador14. In this communication we report the development of high degrees of carbamate and organophosphorus resistance in A. atbimamu resulting from intensive selection pressure in the field, and subsequently in the laboratory. Earlier attempt! to induce carbamate resistance in A atbimanus by laboratory selection have been unsuccessful although in Cutex pipiens faiigatu a 30 x level of resistance t< propoxur developed in larvae within twenty-five generation of selection pressure*'*. A strain of A. atbimanus from Panami selected with its-tsopropylphenyl methylcarbemate for fifty generations developed only a 2.8 x increase in the LCo kveP. Another strain from Haiti, containing dieldrin-resistant indivi duals, when subjected to larval selection pressure by propoxur for nineteen generations and to adult pressure during the DSW 332579 i STLCOPCB4079155