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CYANIDE AND THIOCYANATE STUDIES
231 variable appears
to
be differences in the strain of E.
gracilis.
Laboratories using this organism have maintained it by serial transfer in liquid media often for many years, and the strains differ significantly in their metabolism nrnmaxine. This ooint needs further investigation.
mas now
Department of Hæmatology, Royal Perth Hospital, Western Australia.
of chlor-
tom in
R. E. DAVIS D. J. NICOL.
COLONY-COUNTS FROM URINE SIR,-Dr. Butler1 has drawn attention to possible errors of diagnosis that have not been mentioned in many recent articles abour urinary infection. One error to which she refers is certainly easy to make: it is the failure to recognise slow-growing dwarf-colony forms of Escherichia coli. Infections by these strains are uncommon, and nearly always occur in patients with underlying disease of the urinary tract. Several years ago I showed that dwarf-colony coliform strains are nutritionally deficient and that many will grow rapidly to colonies of normal size if a suitable sulphur compound such as cysteine is added to the medium.2 Cysteine-dependent dwarf-colony strains of Esch. coli, type 055, have caused Mstrnenteritis in infants.3 Department of Pathology, Bristol Royal Hospital, Royal Infirmary Branch, Bristol
2.
W. A. GILLESPIE.
CYANIDE AND THIOCYANATE STUDIES SIR,-The letter of Dr. Wokes and Dr. Ellis (July 2) contains a fascinating miscellany of metabolic observations, most of which can be explained in terms of the large size of the body metabolic pool of thiocyanate,4 and the very low renal clearancerate from the plasma.5 If it is assumed that thiocyanate is uniformly distributed throughout an extracellular space containing 14 litres of fluid in a 70 kg. man, then in non-smokers with a mean thiocyanate concentration of 5-3 umoles per 100 ml. the thiocyanate pool must contain about 750 jimoles of thiocyanate. The mean daily urinary excretion of thiocyanate is 114 umoles 6 in such a subject-i.e., 15% of the total body pool. Because of the equilibration delay it is therefore not surprising that variations in thiocyanate (or cyanide) intake are not immediately and exactly paralleled in the urine. Thiocyanate is, however, rapidly absorbed from the gut with corresponding and predictable changes in plasma concentration. Moreover, renal excretionrates of thiocyanate are strikingly influenced by the rate of urine production, and diuresis causes a rapid increase. Thus conclusions about cyanide and thiocyanate metabolism based on short-term measurement of thiocyanate excretion are likely to be misleading. It is considerations such as these, as much as the difficulties of collecting urine for 24 hours from Nigerian villagers, that led us to use plasma determinations of thiocyanate 9 as a much better estimate of the thiocyanate pool. It seems likely that Wokes" et al. have seriously underestimated the contribution of dietary thiocyanate to the body pool, especially in subjects on a European diet. Thiocyanate is present in many vegetables,6 11 as well as milk,12 in quantities which could in our view account for most if not all of the thiocyanate present in healthy European non-smokers. In panents with anorexia nervosa,5 and in subjects on a diet lacking m milk and vegetables (but not deficient in vitamin B12), Butler, H. M. Lancet, 1966, i, 1219. 2 Gillespie, W. A.J. Path. Bact. 1952, 64, 551. 3 Lane, W. F., Marshall, J., Wading, J. Mon. Bull. 1
Min.
plasma-thiocyanate concentrations are very low, and this may also be the explanation for the relatively low plasma-thiocyanate concentrations in patients with untreated, uncomplicated pernicious anaemia,13 since anorexia is often a prominent symp-
Hlth, 1955, 14,
174
4 Boxer, G. E., Rickards, J. C. Archs Biochem. 1952, 39, 7. 5 Stza, K. F Medical Yearbook of the University of Bergen: no. 2. 1957. 6 Wilson, J. Ph.D. Thesis, London, 1965. 7 Langman, M. J. S., Doll, R., Wilson, J. Gut (in the press). 8 Wilson, J. Unpublished. 9 Monekosso, G. L., Wilson, J. Lancet, 1966, i, 1062. 10kes, F , Badenoch, J., Sinclair, H. M. Am. J. clin. Nutr. 1955, 3, 375. 11 Gemeinhardt, K. Ber. dt. bot. Ges. 1938, 56, 275. 12 Wokes, F, Wedgwood, P., Wyatt, J. Biochem. J. 1952, 50, xix.
this condition. Vitamin B12 is not necessary for the conversion of cyanide to thiocyanate through the action of rhodanase or mercaptopyruvate trans-sulphurase, and Dr. Wokes and Dr. Ellis have not substantiated their claims for an alternative route of formation of thiocyanate, involving cyanocobalamin. We prefer to accept the suggestion that the ready combination of cyanide with hydroxocobalamin results in its rapid incorporation into the 1-C metabolic pool.4 It is this pathway which may be significantly impaired in vitamin-B12 deficiency.14 M.R.C. Clinical Genetics Research Unit, Institute of Neurology, The National Hospital, Queen Square, London W.C.1.
G. L. MONEKOSSO JOHN WILSON.
ANTICOAGULANTS DURING DENTAL SURGERY SIR,-Dr. McIntyre (July 9) raises several points which
require
comment.
The mode of action of heparin is more complex than is stated, and there is little evidence that it interferes in the prothrombin-to-thrombin reaction. The " indirect " anticoagulants have no recorded action on factor xi-presumably this is a misprint for factor x. While the action of the indirect anticoagulants may " be reversed in a matter of hours by the use of vitamin K ", this is a variable result. Most authorities agree that vitamin Kl is more reliable than other vitamin-K preparations, which also are inferior in antidotal activity to Kl’ Vitamin Ki must be stored in the dark; when used in patients taking phenprocoumon there is a significantly slowed reversal of anticoagulant action (measured by the Quick one-stage test) compared with phenindione reversal-which may take up to 12 hours even in normal individuals,15 With warfarin the prothrombin-time may lengthen again after an initial reversal phase. The oral or intravenous routes are more rapidly effective than the intramuscular for vitamin K1; larger does are required when the
heart, liver,
kidneys are failing. McIntyre states: " The patients attended the anticoagulant clinic two days before operation so that the prothrombin-time could be adjusted to the upper level of the therapeutic range using the thrombotest as described by Owren (1959)." Most laboratories recognise that it is not possible to compare the results of these two different tests-the Quick one-stage prothrombin-time and Owren’s ’Thombotest’. The prothrombin-time " was adjusted to the range 7-15°thrombotest, but no indication of the actual prothrombin-time is given, nor is there any indication of the levels at which these patients were controlled before the dental episode. After dental treatment requirements for anticoagulant drugs fall substantially in some patients-an effect which has been attributed to stress,16 and which may be magnified by other drugs such as aspirin, corticotrophin, cincophen, phenylbutazone, and liquid paraffin. It is difficult to assess the haemostatic state of these patients-" the prothrombin-time was rechecked on the day of operation ", but it is not made clear that this was by Owren’s thrombotest, and it is not surprising to find that in the one patient who bled, the level recorded (5%) was well below " the upper level of the therapeutic range ". As Dr. McIntyre hinted the real problem is whether to alter the therapeutic regimen at all, and there is little guidance in the published reports. In two cases detailed by Ziffer et al.17 no special precautions were taken; the first developed a massive facial hxmatoma which interferred with vision (prothrombinor
Dr.
"
13. Langman, M. J. S., Wilson, J. Unpublished. 14. Wilson, J., Langman, M. J. S. Nature, Lond. (in the press). 15. Chalmers, J. N. M., Nixon, M. F., Polack, W. Br. med.J. 1954, ii, 956. 16. Mullertz, S., Storm, O. Circulation, 1954, 10, 213. 17. Ziffer, A. M., Scopp, I. W., Beck, J., Baum, J., Berger, A. R. New Engl. J. Med. 1957, 256, 351.
to
be differences in the strain of E.
gracilis.
Laboratories using this organism have maintained it by serial transfer in liquid media often for many years, and the strains differ significantly in their metabolism nrnmaxine. This ooint needs further investigation.
mas now
Department of Hæmatology, Royal Perth Hospital, Western Australia.
of chlor-
tom in
R. E. DAVIS D. J. NICOL.
COLONY-COUNTS FROM URINE SIR,-Dr. Butler1 has drawn attention to possible errors of diagnosis that have not been mentioned in many recent articles abour urinary infection. One error to which she refers is certainly easy to make: it is the failure to recognise slow-growing dwarf-colony forms of Escherichia coli. Infections by these strains are uncommon, and nearly always occur in patients with underlying disease of the urinary tract. Several years ago I showed that dwarf-colony coliform strains are nutritionally deficient and that many will grow rapidly to colonies of normal size if a suitable sulphur compound such as cysteine is added to the medium.2 Cysteine-dependent dwarf-colony strains of Esch. coli, type 055, have caused Mstrnenteritis in infants.3 Department of Pathology, Bristol Royal Hospital, Royal Infirmary Branch, Bristol
2.
W. A. GILLESPIE.
CYANIDE AND THIOCYANATE STUDIES SIR,-The letter of Dr. Wokes and Dr. Ellis (July 2) contains a fascinating miscellany of metabolic observations, most of which can be explained in terms of the large size of the body metabolic pool of thiocyanate,4 and the very low renal clearancerate from the plasma.5 If it is assumed that thiocyanate is uniformly distributed throughout an extracellular space containing 14 litres of fluid in a 70 kg. man, then in non-smokers with a mean thiocyanate concentration of 5-3 umoles per 100 ml. the thiocyanate pool must contain about 750 jimoles of thiocyanate. The mean daily urinary excretion of thiocyanate is 114 umoles 6 in such a subject-i.e., 15% of the total body pool. Because of the equilibration delay it is therefore not surprising that variations in thiocyanate (or cyanide) intake are not immediately and exactly paralleled in the urine. Thiocyanate is, however, rapidly absorbed from the gut with corresponding and predictable changes in plasma concentration. Moreover, renal excretionrates of thiocyanate are strikingly influenced by the rate of urine production, and diuresis causes a rapid increase. Thus conclusions about cyanide and thiocyanate metabolism based on short-term measurement of thiocyanate excretion are likely to be misleading. It is considerations such as these, as much as the difficulties of collecting urine for 24 hours from Nigerian villagers, that led us to use plasma determinations of thiocyanate 9 as a much better estimate of the thiocyanate pool. It seems likely that Wokes" et al. have seriously underestimated the contribution of dietary thiocyanate to the body pool, especially in subjects on a European diet. Thiocyanate is present in many vegetables,6 11 as well as milk,12 in quantities which could in our view account for most if not all of the thiocyanate present in healthy European non-smokers. In panents with anorexia nervosa,5 and in subjects on a diet lacking m milk and vegetables (but not deficient in vitamin B12), Butler, H. M. Lancet, 1966, i, 1219. 2 Gillespie, W. A.J. Path. Bact. 1952, 64, 551. 3 Lane, W. F., Marshall, J., Wading, J. Mon. Bull. 1
Min.
plasma-thiocyanate concentrations are very low, and this may also be the explanation for the relatively low plasma-thiocyanate concentrations in patients with untreated, uncomplicated pernicious anaemia,13 since anorexia is often a prominent symp-
Hlth, 1955, 14,
174
4 Boxer, G. E., Rickards, J. C. Archs Biochem. 1952, 39, 7. 5 Stza, K. F Medical Yearbook of the University of Bergen: no. 2. 1957. 6 Wilson, J. Ph.D. Thesis, London, 1965. 7 Langman, M. J. S., Doll, R., Wilson, J. Gut (in the press). 8 Wilson, J. Unpublished. 9 Monekosso, G. L., Wilson, J. Lancet, 1966, i, 1062. 10kes, F , Badenoch, J., Sinclair, H. M. Am. J. clin. Nutr. 1955, 3, 375. 11 Gemeinhardt, K. Ber. dt. bot. Ges. 1938, 56, 275. 12 Wokes, F, Wedgwood, P., Wyatt, J. Biochem. J. 1952, 50, xix.
this condition. Vitamin B12 is not necessary for the conversion of cyanide to thiocyanate through the action of rhodanase or mercaptopyruvate trans-sulphurase, and Dr. Wokes and Dr. Ellis have not substantiated their claims for an alternative route of formation of thiocyanate, involving cyanocobalamin. We prefer to accept the suggestion that the ready combination of cyanide with hydroxocobalamin results in its rapid incorporation into the 1-C metabolic pool.4 It is this pathway which may be significantly impaired in vitamin-B12 deficiency.14 M.R.C. Clinical Genetics Research Unit, Institute of Neurology, The National Hospital, Queen Square, London W.C.1.
G. L. MONEKOSSO JOHN WILSON.
ANTICOAGULANTS DURING DENTAL SURGERY SIR,-Dr. McIntyre (July 9) raises several points which
require
comment.
The mode of action of heparin is more complex than is stated, and there is little evidence that it interferes in the prothrombin-to-thrombin reaction. The " indirect " anticoagulants have no recorded action on factor xi-presumably this is a misprint for factor x. While the action of the indirect anticoagulants may " be reversed in a matter of hours by the use of vitamin K ", this is a variable result. Most authorities agree that vitamin Kl is more reliable than other vitamin-K preparations, which also are inferior in antidotal activity to Kl’ Vitamin Ki must be stored in the dark; when used in patients taking phenprocoumon there is a significantly slowed reversal of anticoagulant action (measured by the Quick one-stage test) compared with phenindione reversal-which may take up to 12 hours even in normal individuals,15 With warfarin the prothrombin-time may lengthen again after an initial reversal phase. The oral or intravenous routes are more rapidly effective than the intramuscular for vitamin K1; larger does are required when the
heart, liver,
kidneys are failing. McIntyre states: " The patients attended the anticoagulant clinic two days before operation so that the prothrombin-time could be adjusted to the upper level of the therapeutic range using the thrombotest as described by Owren (1959)." Most laboratories recognise that it is not possible to compare the results of these two different tests-the Quick one-stage prothrombin-time and Owren’s ’Thombotest’. The prothrombin-time " was adjusted to the range 7-15°thrombotest, but no indication of the actual prothrombin-time is given, nor is there any indication of the levels at which these patients were controlled before the dental episode. After dental treatment requirements for anticoagulant drugs fall substantially in some patients-an effect which has been attributed to stress,16 and which may be magnified by other drugs such as aspirin, corticotrophin, cincophen, phenylbutazone, and liquid paraffin. It is difficult to assess the haemostatic state of these patients-" the prothrombin-time was rechecked on the day of operation ", but it is not made clear that this was by Owren’s thrombotest, and it is not surprising to find that in the one patient who bled, the level recorded (5%) was well below " the upper level of the therapeutic range ". As Dr. McIntyre hinted the real problem is whether to alter the therapeutic regimen at all, and there is little guidance in the published reports. In two cases detailed by Ziffer et al.17 no special precautions were taken; the first developed a massive facial hxmatoma which interferred with vision (prothrombinor
Dr.
"
13. Langman, M. J. S., Wilson, J. Unpublished. 14. Wilson, J., Langman, M. J. S. Nature, Lond. (in the press). 15. Chalmers, J. N. M., Nixon, M. F., Polack, W. Br. med.J. 1954, ii, 956. 16. Mullertz, S., Storm, O. Circulation, 1954, 10, 213. 17. Ziffer, A. M., Scopp, I. W., Beck, J., Baum, J., Berger, A. R. New Engl. J. Med. 1957, 256, 351.