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SUCROSE INTAKE AND CORONARY HEART-DISEASE
1249 ask ourselves is: is it in the baby’s interest to use sac as a culture ground for its mother’s or is it not time to revise our views on Credé’s
we
have
its
conjunctival
to
pathogens, prophylaxis ? Rochdale, Lancashire.
B. KALCEV.
PROPRANOLOL AND DIAZEPAM FOR IMIPRAMINE POISONING SiR,-The cardiac irregularities that sometimes occur with large overdoses of imipramine are difficult to manage. Our experience with imipramine (’ Tofranil ’) intoxication in children led us to use a p-adrenergic blocking agent (propranolol) in one patient. This treatment was successful and we are now carrying out animal studies in an attempt to document our clinical observation. Further, we have used parenteral diazepam (’Valium’) instead of barbiturates for the control of the convulsions ; it does not add to the complications of the intoxication, and it provides adequate control of the seizures. Toxicology Service, LARRY J. MARSHALL The Children’s Mercy Hospital, VERNON A. GREEN. Kansas City, Missouri 64106.
PHENOLIC SUBSTANCES IN DRINKING-WATER to note that in random samples of are concerned SIR,-We drinking-water taken by this laboratory from 11 hospitals, 4 petrol-filling stations, 4 police stations, 3 private houses, 1 public convenience, and 1 university department covering 24 towns or county boroughs in the United Kingdom and representing a population of 7,000,000, all contained more than 0.032 mg. per litre of phenolic substances, or greater than 16 times the World Health Organisation maximum allowable limit.1 These results appear to call for a further investigation of all water supplies and for action, unless the W.H.O. limits are unrealistic. Municipal Laboratory, C. D. REED University Department of Civil Engineering, J. A. TOLLEY. Liverpool 3.
SUCROSE INTAKE AND CORONARY HEART-DISEASE SIR,-Surgeon Captain Cleave (Nov. 30, p. 1187) makes an important point. Rapid changes in the environment, such as a rapid change in sugar consumption, may affect the general level of health in a community, but this effect is masked by other changes. It is genetic susceptibility which almost invariably determines the particular individuals who are affected. Hence the environmental cause is easily missed. The best illustrations of this are possibly in the history of vitamindeficiency diseases. Experienced physicians who were no fools repeatedly refused to believe that rickets and scurvy could be the result of a deficiency; they had seen too many cases where affected individuals were on a similar or better diet than unaffected. Another illustration is the sigmoid dose-response curve which the pharmacologist uses in standardising a drug. Even with a highly inbred strain of rats and a molecule quite new to biology, the graded susceptibility of multifactorial inheritance results in one rat surviving several times the dose which kills another. One of the scandals of our rough and ready health statistics is that it takes many years to detect harmful molecules in the environment even when they are limited to particular occupations. To detect the effect of sugar, we must compare whole populations on a low-sugar diet with populations on a highsugar one. If everyone smoked 30-60 cigarettes a day, I doubt 1. International Standards for Drinking-Water, World Health tion, Geneva, 1963; section 3. 1. 4., p. 39.
Organisa-
if
Dr. Doll would have had the patience to compile the statistics which would be needed to show that 50-60 cigarettes were more dangerous than 30-40. Even if it were possible to show the greatc danger, the difference would be so slight that the discoverer would be scorned as a crank. Budleigh Salterton, DENYS JENNINGS. Devon. even
enormous
BIRTH CONTROL AND HUMAN EVOLUTION
SIR,-According to a generally accepted concept, family planning is a safe and useful method for solving some medical, social, and economic problems in undeveloped populations. But, lately, eminent American demographers 12 have discussed the possibility of encouraging compulsory national policies for reducing reproduction towards a zero growth-rate. This proposal seems to ignore some reasonable questions posed in two recent symposia on the genetic implications in the new demographic trends.34 Is the genetic quality of the human population being severely eroded by economic and medical advances ? By concentrating on environmental approaches is society neglecting promising genetic possibilities ? How great a genetic load can a population tolerate ? A year ago your Round the World correspondent warned5 that, before pursuing a population policy too enthusiastically, it would be well to try to assess some of the hazards. It must be remembered that the evolution of the human population is controlled by powerful cosmic forces operating at large on our planet. In 1930 Fisher 6 was able to propose a fundamental hypothesis of evolution; unifying the ideas of Darwin and Mendel, he compared natural selection to the entropy law in thermodynamics. Turnerhas extended this hypothesis by
considering as a fundamental law a theorem relating increasing biological energy to the efficient use of limiting resources in an ecosystem. Canning and Edwardshave shown that the forces of natural selection are controlled by the classical equation of conics, the same mathematical law which governs the dynamics of our solar system. The relationships between darwinian fitness, genetic load, and contraception are under study. Turner7 considers contraception as a population-density regulator factor which controls absolute fitness or population growth. When contraception is practised the rate of increase declines until population maintains a constant size; if we consider a mathematical model, with overlapping generations mean fitness will decrease to zero and the population will develop a constant age-structure. But a lower mean fitness means a higher genetic load. If we define fitness as the probability of survival, then the genetic load is the proportion of deaths which arise from variation in fitness.99 If genetic load is large a population may be in danger of extinction.9 This possibility is denied by Turner,44 who argues a protection from ecological flexibility. But, in any case, findings by Kirk,1O Crow," Matsunaga,12 and myself 13 suggest that genetic load is increasing in " civilised " populations, because total opportunities for selection are getting smaller as the family size approaches uniformity. More cautiously, Schull 14 prefers to explain the genetic component of reproduction before evaluating the consequences of population control. Department of Medical Genetics, J. J. Aguirre Hospital, Santiago, Chile. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
R. CRUZ-COKE.
Davis, K. Science, N.Y. 1968, 159, 828. McElroy, W. D. ibid. p. 827. Seitz, F. Proc. natn. Acad. Sci. U.S.A. 1967, 59, 650. Turner, J. R. G., Williamson, M. H. Nature, Lond. 1968, 218, 700. See Lancet, 1967, i, 43. Fisher, R. A. Genetical Theory of Natural Selection. Oxford, 1930. Turner, J. R. G. Proc. R. Soc. B, 1967, 169, 31. Cannings, C., Edwards, A. W. F. Ann. hum. Genet. 1968, 31, 421. O’Donald, P. Nature, Lond 1967, 216, 1348. Kirk, D. Proc. natn. Acad. Sci. U.S.A. 1968, 59, 662. Crow, J. F. ibid. p. 655. Matsunaga, E. J. Am. med. Ass. 1966, 198, 533. Cruz-Coke, R. Revta med. Chile, 1966, 94, 667. Schull, W. J. Proc. natn. Acad. Sci. U.S.A. 1968, 59, 670.
we
have
its
conjunctival
to
pathogens, prophylaxis ? Rochdale, Lancashire.
B. KALCEV.
PROPRANOLOL AND DIAZEPAM FOR IMIPRAMINE POISONING SiR,-The cardiac irregularities that sometimes occur with large overdoses of imipramine are difficult to manage. Our experience with imipramine (’ Tofranil ’) intoxication in children led us to use a p-adrenergic blocking agent (propranolol) in one patient. This treatment was successful and we are now carrying out animal studies in an attempt to document our clinical observation. Further, we have used parenteral diazepam (’Valium’) instead of barbiturates for the control of the convulsions ; it does not add to the complications of the intoxication, and it provides adequate control of the seizures. Toxicology Service, LARRY J. MARSHALL The Children’s Mercy Hospital, VERNON A. GREEN. Kansas City, Missouri 64106.
PHENOLIC SUBSTANCES IN DRINKING-WATER to note that in random samples of are concerned SIR,-We drinking-water taken by this laboratory from 11 hospitals, 4 petrol-filling stations, 4 police stations, 3 private houses, 1 public convenience, and 1 university department covering 24 towns or county boroughs in the United Kingdom and representing a population of 7,000,000, all contained more than 0.032 mg. per litre of phenolic substances, or greater than 16 times the World Health Organisation maximum allowable limit.1 These results appear to call for a further investigation of all water supplies and for action, unless the W.H.O. limits are unrealistic. Municipal Laboratory, C. D. REED University Department of Civil Engineering, J. A. TOLLEY. Liverpool 3.
SUCROSE INTAKE AND CORONARY HEART-DISEASE SIR,-Surgeon Captain Cleave (Nov. 30, p. 1187) makes an important point. Rapid changes in the environment, such as a rapid change in sugar consumption, may affect the general level of health in a community, but this effect is masked by other changes. It is genetic susceptibility which almost invariably determines the particular individuals who are affected. Hence the environmental cause is easily missed. The best illustrations of this are possibly in the history of vitamindeficiency diseases. Experienced physicians who were no fools repeatedly refused to believe that rickets and scurvy could be the result of a deficiency; they had seen too many cases where affected individuals were on a similar or better diet than unaffected. Another illustration is the sigmoid dose-response curve which the pharmacologist uses in standardising a drug. Even with a highly inbred strain of rats and a molecule quite new to biology, the graded susceptibility of multifactorial inheritance results in one rat surviving several times the dose which kills another. One of the scandals of our rough and ready health statistics is that it takes many years to detect harmful molecules in the environment even when they are limited to particular occupations. To detect the effect of sugar, we must compare whole populations on a low-sugar diet with populations on a highsugar one. If everyone smoked 30-60 cigarettes a day, I doubt 1. International Standards for Drinking-Water, World Health tion, Geneva, 1963; section 3. 1. 4., p. 39.
Organisa-
if
Dr. Doll would have had the patience to compile the statistics which would be needed to show that 50-60 cigarettes were more dangerous than 30-40. Even if it were possible to show the greatc danger, the difference would be so slight that the discoverer would be scorned as a crank. Budleigh Salterton, DENYS JENNINGS. Devon. even
enormous
BIRTH CONTROL AND HUMAN EVOLUTION
SIR,-According to a generally accepted concept, family planning is a safe and useful method for solving some medical, social, and economic problems in undeveloped populations. But, lately, eminent American demographers 12 have discussed the possibility of encouraging compulsory national policies for reducing reproduction towards a zero growth-rate. This proposal seems to ignore some reasonable questions posed in two recent symposia on the genetic implications in the new demographic trends.34 Is the genetic quality of the human population being severely eroded by economic and medical advances ? By concentrating on environmental approaches is society neglecting promising genetic possibilities ? How great a genetic load can a population tolerate ? A year ago your Round the World correspondent warned5 that, before pursuing a population policy too enthusiastically, it would be well to try to assess some of the hazards. It must be remembered that the evolution of the human population is controlled by powerful cosmic forces operating at large on our planet. In 1930 Fisher 6 was able to propose a fundamental hypothesis of evolution; unifying the ideas of Darwin and Mendel, he compared natural selection to the entropy law in thermodynamics. Turnerhas extended this hypothesis by
considering as a fundamental law a theorem relating increasing biological energy to the efficient use of limiting resources in an ecosystem. Canning and Edwardshave shown that the forces of natural selection are controlled by the classical equation of conics, the same mathematical law which governs the dynamics of our solar system. The relationships between darwinian fitness, genetic load, and contraception are under study. Turner7 considers contraception as a population-density regulator factor which controls absolute fitness or population growth. When contraception is practised the rate of increase declines until population maintains a constant size; if we consider a mathematical model, with overlapping generations mean fitness will decrease to zero and the population will develop a constant age-structure. But a lower mean fitness means a higher genetic load. If we define fitness as the probability of survival, then the genetic load is the proportion of deaths which arise from variation in fitness.99 If genetic load is large a population may be in danger of extinction.9 This possibility is denied by Turner,44 who argues a protection from ecological flexibility. But, in any case, findings by Kirk,1O Crow," Matsunaga,12 and myself 13 suggest that genetic load is increasing in " civilised " populations, because total opportunities for selection are getting smaller as the family size approaches uniformity. More cautiously, Schull 14 prefers to explain the genetic component of reproduction before evaluating the consequences of population control. Department of Medical Genetics, J. J. Aguirre Hospital, Santiago, Chile. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
R. CRUZ-COKE.
Davis, K. Science, N.Y. 1968, 159, 828. McElroy, W. D. ibid. p. 827. Seitz, F. Proc. natn. Acad. Sci. U.S.A. 1967, 59, 650. Turner, J. R. G., Williamson, M. H. Nature, Lond. 1968, 218, 700. See Lancet, 1967, i, 43. Fisher, R. A. Genetical Theory of Natural Selection. Oxford, 1930. Turner, J. R. G. Proc. R. Soc. B, 1967, 169, 31. Cannings, C., Edwards, A. W. F. Ann. hum. Genet. 1968, 31, 421. O’Donald, P. Nature, Lond 1967, 216, 1348. Kirk, D. Proc. natn. Acad. Sci. U.S.A. 1968, 59, 662. Crow, J. F. ibid. p. 655. Matsunaga, E. J. Am. med. Ass. 1966, 198, 533. Cruz-Coke, R. Revta med. Chile, 1966, 94, 667. Schull, W. J. Proc. natn. Acad. Sci. U.S.A. 1968, 59, 670.