739
plastic cannula of a 20-gauge ’Abbocath-T’ intravenous needle to connect the giving set to the fine-bore tubing. This cannula is less likely to perforate the tubing wall at the point of contact if flexion occurs there. As Mr Crow points out (Sept. 23, p. 690) a set comprising guide-wire and fine bore tubing with an attached Luer connection is now commercially available. Patient acceptability has been good, and one man has been inserting his own tube when necessary. An important point in the acceptability of these fine tubes seems to be their ability to allow normal deglutition of ordinary food. We have not found a.constant-rate infusion pump necessary; the limitation of flow-rate provided by the fine diameter of the tubing, as pointed out by Metz et al., is an important factor in the prevention of complications. Severe diarrhoea or gastric stasis can often be overcome by decreasing the dilution of the feeding solutions over a period of 8-10 days. During this time supplementation may be necessary. parenteral This method of feeding is cheaper and safer than parenteral nutrition. Our experience and that of Metz et al. suggests that it should be considered in all patients with an intact gastrointestinal tract who require nutritional supplementation. Department of Surgery, Royal Victoria Infirmary, Newcastle upon Tyne NE 1
A. J. RICH M. E. WHITEHOUSE P. D. WRIGHT
4LI
CONGENITAL INSENSITIVITY TO PAIN AND NALOXONE
Yanagida (Sept. 2, p. 520) is conattempt explain the syndrome of congenital insensitivity to pain by invoking a permanent hyperactivity of an endogenous morphine-like system. However, the naloxone injections should have been done double-blind with placebo control. Moreover, the doses of naloxone (2 and 10 mg) were SIR,-The report from
sistent with
our
Dr
to
large, and we need to know if such doses affect tooth pulp evoked potentials of normal subjects. We used 0.8 mg and sometimes 1.2mg naloxone2after checking that there was no significant effect (on the threshold of the nociceptive flexion reflex of a flexor muscle of the lower limb3) in normal subjects. Our two patients had a classical congenital insensitivity to pain:4 they had lacked pain sensation from birth, the entire body was affected, and all other sensations, particularly thermal sensations, were perceived normally. They could discriminate accurately between hot and cold. Neuropathological examinations failed to reveal any abnormality in the peripheral and central nervous systems.4 In contrast Yanagida’s patient failed to perceive thermal sensations (hot and cold) and had had numerous skeletal fractures resulting in "multiple joint deformities of the Charcot type", as in the cases described by Swansons and by Chatrian et al. This syndrome is called "congenital insensitivity to pain with anhydrosis". In these cases the neuropathologist finds absence of small neurons in the dorsal-root ganglia, lack of small fibres in the dorsal roots, absence of Lissauer tract at all levels in the spinal cord, and reduction in size of the descending tract of the trigeminal nerve in the medulla and cord, with great decrease of small fibres of this tract. "These histologic findings suggest that these patients’ defects in pain and temperature were related to absence, probably due to defective development of small primary sensory neurons, classically believed to subserve these sensations".6 Histologically, therefore, congenital insensitivity to pain and congenital insensitivity to pain with anhydrosis 1. Dehen, H., Willer, J. C., Boureau, F., Cambier, J. Lancet, 1977, ii, 293. 2. Dehen, H., Willer, J C., Cambier, J. Paper presented at the 2nd World Congress on Pain, held m Montreal, in August, 1978. 3. Boureau, F., Willer,J.C., Dauther, C. J. Neuropharmac. 1978, 17, 565. 4. Thrush, D.C. Brain, 1973, 96, 369. 5. Swanson, A. G. ArchsNeurol. 1963, 8, 299. 6. Chatrian, G. E., Farrell, D. F., Canfield, R. C., Reegt, E. L. ibid. 1975, 32, 141 7. Swanson, A. G., Buchan, G. C., Alvord, E. C. ibid. 1965, 12, 12.
Nevertheless, if naloxone does enhance nocievoked potentials in cases such as Yanagida’s this would prompt questions about the relations between the endogenous opiates and the small afferent fibres and the small priare
very different.
ceptive
mary sensory
neurons.
Laboratory of Clinical Neurophysiology, Hôpital Saint-Antoine, 75012 Paris, France; and Department of Clinical Neurology,
Hôpital Beaujon, Clichy
J. C. WILLER H. DEHEN F. BOUREAU J. CAMBIER
ELEVATED METABOLIC RATES IN OBESITY
SIR,-Dr James and his colleagues (Aug. 26, p. 472) confirm the decrease in resting metabolic rate (R.M.R.) upon slimming and comment on the discrepancy between the observed decrease in R.M.R. and that expected from changes in metabolic size. In their original article! they suggest that "energy-dissipating mechanisms appear to be involved". I and my colleagues have studied the thermal responses of five obese females undergoing weight reduction.2 The women were studied in a thermoneutral environment before and during a dietary intake of approximately 4-2 MJ (1000 kcal)/24 h. Over a sixty-day period a mean weight loss of 4.6% was achieved. Finger blood-flow (ml/100 ml/min) measured by occlusion plethysmography showed a fall from venous 38.8:t0.9 (mean :tS.E.M.) to 18.7 :t4.3.
Changes in peripheral blood-flow represent an important physiological thermoregulatory mechanism. The decreased finger blood-flow, observed in a thermoneutral environment, could represent an attempt by the body to conserve heat, and therefore energy, in response to energy deprivation. This increased energy conservation would therefore be a contributory factor to the greater than predicted decrease in R.M.R. upon slimming, and would suggest that changes in energy-dissipating mechanisms do indeed occur. Department of Physiology Trinity College, Dublin 2
J. F. JACKSON
ROUTINE MEASUREMENT OF GLYCOSYLATED HÆMOGLOBIN
SIR,-Our experience of chromatographic separation of gly-
cosylated haemoglobins may help others. The difference between glycosylated and non-glycosylated haemoglobins is very small. The attachment of two glucose molecules to the beta-chains does not significantly alter the structure of hoemoglobin but merely neutralises two out of some two hundred titratable groups. The isoelectric point changes by 0.01 pH units. This is the extent of the difference on which the separation of these hemoglobins must be based. It is not surprising, therefore, that a clean separation on minicolumns is difficult. The method is very sensitive to minor variations in technique. We have found that:
(1) Separation on the cation-exchange resins ’Amberlite-IRC 50’ (B.D.H), ’Bio-Rex-70’ (BioRad), and CM-52 cellulose (Whatman) was grossly affected by minor changes in the ionic strength of the eluting buffer, more so than by changes in pH. Most sensitive was CM-52 cellulose, where increasing the ionic strength from 20 mmol/1 phosphate buffer pH 6.70 to 25 mmol/I was the difference between elution of no hoemoglobin and the elution of all hemoglobins. Bio-rex-70 columns behaved similarly, and we found that the "percentage glycosylated ha:moglobin" increased with increasing ionic strength of the eluting buffer. (2) Because proteins can contribute significantly to the ionic 1. James, W. P. T., Davies, H. L., Bailes,
J., Dauncey, P. L. D. Lancet, 1978, i, 1122. 2. Jackson, J. F., Moore, R. E., Tomkin, G. H. IrishJ. med. Sci. 1978, 147, 217.
740
strength of buffers we also observed that the percentage glycosylated haemoglobins increased with increasing hxmolysate concentrations in the range 0-5—3 g/dl within the same sample. In all cases we could see an apparently clean banding of the eluting hmmoglobins. However, on measurement, more fast-fraction ha:moglobins were eluted with higher lysate concentrations for a given specimen. (3) The rate of elution was also critical, percentage glycosylated hxmoglobins and elution-rate being directly related. Using similar quantities of resin and haemolysate as Dr Davis and Mr Nichol (Aug. 12, p.350) we found that the elution-time had to be at least 10 min if consistent results were to be obtained; shorter elution-times gave higher values for glycosylated haemoglobins.
These three factors
least must be rigorously checked if results is to be maintained. Neither Davis and Nichol nor Kynoch and Lehmann’ provide qualitycontrol data in their papers. Within-run and between-run variation of results, particularly over several batches of resin, would be valuable data (we have found great variation in results when changing batches of bio-rex resin). Some indication of normal range and clinical values would have been helpful, as well as data relating to comparison of their method with others. The correlation of their’ results with the clinical assessment of patients would have allowed readers to assess the validity of the method. Perhaps these workers could state more clearly the limits within which buffer concentrations, haemolysate concentrations, and elution-times must fall to produce an acceptably controlled assay.
quality control
at
over test
Departments of Hæmatology and Medicine, Flinders Medical Centre, Bedford Park, South Australia 5042
R. G. RYALL J. J. GRAHAM
MATERNAL/FETAL TRANSMISSION OF HBSAg NEGATIVE HEPATITIS be transmitted from mother to to mothers who had acute offspring.2-4 viral hepatitis B during pregnancy had hepatitis B antigen (HBsAg) in their blood.35 Though Stokes et awl. hypothesise transplacental transmission of virus, others suggest that the virus is transmitted around the time of labour and delivery. 34 There is no evidence for such transmission with hepatitis A virus. A 28-year-old gravida 3 had hepatitis in the ninth month of pregnancy. Her husband had had hepatitis immediately before his wife’s illness. She was brought to hospital on March 20, 1978 in the second stage of labour and with fulminant hepatic failure. Fetal heart sounds were absent. She delivered spontaneously a fresh stillborn male fetus weighing 2.5 kg (maturity approximately 36 weeks) with no obvious congenital malformation. Investigations of the mother showed Hb 13 g/dl, normal total and differential leucocyte-count, and low prothrombin index (20-30%). Bilirubin ranged from 17 to 25-55 mg/dl (conjugated 9.5-15 mg/dl), serum glutamic-oxaloacetic transaminase 258 l.u., alkaline phosphatase 300 King-Armstrong units. HBsAg was negative by cotintercurrent immunoelectrophoresis. The patient died on March 24, 1978. Complete necropsies were done on both mother and fetus. The maternal liver showed fulminant hepatitis with massive hepatic necrosis. The fetal liver also showed massive hepatic necrosis (see figure). Autolysis was ruled out because no other
SIR,-Hepatitis
B virus
can
40-50% of babies born
1. 2.
3. 4. 5.
Kynoch, P. A. M., Lehmann, H. Lancet, 1977, ii, 16. Stokes, J., Wolman, I, J., Blanchord, M. C., Farquhar, J. D Am. J. Dis. Child. 1951, 82, 213. Schweitzer, I. L., Wing, A., McPeak, C., Spears, R. L. L.J. Am. med. Ass. 1972, 220, 1092. Stevens, C. E., Beasley, R. P., Tsin, J., Lee, W. C. New Eng J. Med. 1975, 292, 771. Schweitzer, I. L., Dunn, A. E. G., Peters, R. L., Spears, R. L. Am. J. Med. 1973, 55, 762.
Photomicrograph of fetal liver showing extensive hepatocytic damage characterised by swelling, vacuolation of cytoplasm, and necrosis. There are foci of haemorrhage with dilatation of sinusoids. Hepatocytes in the immediate vicinity of the central vein are much less affected. (Hasmaioxytin and eosin; x about 350.)
organ showed autolysis and because the histological picture of liver-cell damage with areas of haemorrhage is unlike that seen in autolysis. Cord blood was negative for HBsAg, and so were the post-mortem blood samples and liver tissues of both mother
and baby. A hepatitis virus was transmitted to the fetus in utero, possibly via the transplacental route, leading to massive hepatic necrosis. Since serum and hepatic tissue of both mother and baby were negative for HBsAg, (which is positive in 80-90% of cases of acute viral hepatitis B in the icteric phase) it seems that the hepatitis in mother and baby was not due to hepatitis B virus. However, because of lack of tests of hepatitis A antigen, we cannot say whether this was hepatitis A or acute
hepatitis non-A, non-B. Departments of Obstetrics and Gynæcology and Pathology
Postgraduate Institute of
Medical Education and Research,
Chandigarh, India
BIPIN GUPTA
SHARDA AGARWAL
V. V. JOSHI
NITROUS OXIDE AND BONE-MARROW to correct that part of your editorial which was concerned with our paper, published in your issue of Aug. 12. First, in the deoxyuridine suppression test 3H-thymidine is used, not 3H-deoxyuridine. Secondly, in this test the uptake of 3H-thymidine by normal bone-marrow cells, but not by cells deficient in vitamin B12 or folate, is almost completely suppressed by preincubation with deoxyuridine. Thirdly, our results were typical of those seen with vitamin-B12 deficiency (i.e., the incorporation of deoxyuridine into D.N.A. in vitro was partially corrected by adding cyanocobalamin or pteroylglutamic acid whereas in folate deficiency the addition of cyanocobalamin has no effect). Fourthly, your editorial may give the impression that this abnormality could be reversed by the invivo administration of hsematinics. The pretreatment of one patient with large doses of parenteral vitamin B12 did not alter the morphological or biochemical effect produced by the administration of 50% nitrous oxide and 50% oxygen mixture.
SIR,-We would like
(Sept. 16,
p.
613)
of Hæmatology, St. Bartholomew’s Hospital, London EC1A 7BE
Department
J. A. L. AMESS J. F. BURMAN D. L. MOLLIN
plastic cannula of a 20-gauge ’Abbocath-T’ intravenous needle to connect the giving set to the fine-bore tubing. This cannula is less likely to perforate the tubing wall at the point of contact if flexion occurs there. As Mr Crow points out (Sept. 23, p. 690) a set comprising guide-wire and fine bore tubing with an attached Luer connection is now commercially available. Patient acceptability has been good, and one man has been inserting his own tube when necessary. An important point in the acceptability of these fine tubes seems to be their ability to allow normal deglutition of ordinary food. We have not found a.constant-rate infusion pump necessary; the limitation of flow-rate provided by the fine diameter of the tubing, as pointed out by Metz et al., is an important factor in the prevention of complications. Severe diarrhoea or gastric stasis can often be overcome by decreasing the dilution of the feeding solutions over a period of 8-10 days. During this time supplementation may be necessary. parenteral This method of feeding is cheaper and safer than parenteral nutrition. Our experience and that of Metz et al. suggests that it should be considered in all patients with an intact gastrointestinal tract who require nutritional supplementation. Department of Surgery, Royal Victoria Infirmary, Newcastle upon Tyne NE 1
A. J. RICH M. E. WHITEHOUSE P. D. WRIGHT
4LI
CONGENITAL INSENSITIVITY TO PAIN AND NALOXONE
Yanagida (Sept. 2, p. 520) is conattempt explain the syndrome of congenital insensitivity to pain by invoking a permanent hyperactivity of an endogenous morphine-like system. However, the naloxone injections should have been done double-blind with placebo control. Moreover, the doses of naloxone (2 and 10 mg) were SIR,-The report from
sistent with
our
Dr
to
large, and we need to know if such doses affect tooth pulp evoked potentials of normal subjects. We used 0.8 mg and sometimes 1.2mg naloxone2after checking that there was no significant effect (on the threshold of the nociceptive flexion reflex of a flexor muscle of the lower limb3) in normal subjects. Our two patients had a classical congenital insensitivity to pain:4 they had lacked pain sensation from birth, the entire body was affected, and all other sensations, particularly thermal sensations, were perceived normally. They could discriminate accurately between hot and cold. Neuropathological examinations failed to reveal any abnormality in the peripheral and central nervous systems.4 In contrast Yanagida’s patient failed to perceive thermal sensations (hot and cold) and had had numerous skeletal fractures resulting in "multiple joint deformities of the Charcot type", as in the cases described by Swansons and by Chatrian et al. This syndrome is called "congenital insensitivity to pain with anhydrosis". In these cases the neuropathologist finds absence of small neurons in the dorsal-root ganglia, lack of small fibres in the dorsal roots, absence of Lissauer tract at all levels in the spinal cord, and reduction in size of the descending tract of the trigeminal nerve in the medulla and cord, with great decrease of small fibres of this tract. "These histologic findings suggest that these patients’ defects in pain and temperature were related to absence, probably due to defective development of small primary sensory neurons, classically believed to subserve these sensations".6 Histologically, therefore, congenital insensitivity to pain and congenital insensitivity to pain with anhydrosis 1. Dehen, H., Willer, J. C., Boureau, F., Cambier, J. Lancet, 1977, ii, 293. 2. Dehen, H., Willer, J C., Cambier, J. Paper presented at the 2nd World Congress on Pain, held m Montreal, in August, 1978. 3. Boureau, F., Willer,J.C., Dauther, C. J. Neuropharmac. 1978, 17, 565. 4. Thrush, D.C. Brain, 1973, 96, 369. 5. Swanson, A. G. ArchsNeurol. 1963, 8, 299. 6. Chatrian, G. E., Farrell, D. F., Canfield, R. C., Reegt, E. L. ibid. 1975, 32, 141 7. Swanson, A. G., Buchan, G. C., Alvord, E. C. ibid. 1965, 12, 12.
Nevertheless, if naloxone does enhance nocievoked potentials in cases such as Yanagida’s this would prompt questions about the relations between the endogenous opiates and the small afferent fibres and the small priare
very different.
ceptive
mary sensory
neurons.
Laboratory of Clinical Neurophysiology, Hôpital Saint-Antoine, 75012 Paris, France; and Department of Clinical Neurology,
Hôpital Beaujon, Clichy
J. C. WILLER H. DEHEN F. BOUREAU J. CAMBIER
ELEVATED METABOLIC RATES IN OBESITY
SIR,-Dr James and his colleagues (Aug. 26, p. 472) confirm the decrease in resting metabolic rate (R.M.R.) upon slimming and comment on the discrepancy between the observed decrease in R.M.R. and that expected from changes in metabolic size. In their original article! they suggest that "energy-dissipating mechanisms appear to be involved". I and my colleagues have studied the thermal responses of five obese females undergoing weight reduction.2 The women were studied in a thermoneutral environment before and during a dietary intake of approximately 4-2 MJ (1000 kcal)/24 h. Over a sixty-day period a mean weight loss of 4.6% was achieved. Finger blood-flow (ml/100 ml/min) measured by occlusion plethysmography showed a fall from venous 38.8:t0.9 (mean :tS.E.M.) to 18.7 :t4.3.
Changes in peripheral blood-flow represent an important physiological thermoregulatory mechanism. The decreased finger blood-flow, observed in a thermoneutral environment, could represent an attempt by the body to conserve heat, and therefore energy, in response to energy deprivation. This increased energy conservation would therefore be a contributory factor to the greater than predicted decrease in R.M.R. upon slimming, and would suggest that changes in energy-dissipating mechanisms do indeed occur. Department of Physiology Trinity College, Dublin 2
J. F. JACKSON
ROUTINE MEASUREMENT OF GLYCOSYLATED HÆMOGLOBIN
SIR,-Our experience of chromatographic separation of gly-
cosylated haemoglobins may help others. The difference between glycosylated and non-glycosylated haemoglobins is very small. The attachment of two glucose molecules to the beta-chains does not significantly alter the structure of hoemoglobin but merely neutralises two out of some two hundred titratable groups. The isoelectric point changes by 0.01 pH units. This is the extent of the difference on which the separation of these hemoglobins must be based. It is not surprising, therefore, that a clean separation on minicolumns is difficult. The method is very sensitive to minor variations in technique. We have found that:
(1) Separation on the cation-exchange resins ’Amberlite-IRC 50’ (B.D.H), ’Bio-Rex-70’ (BioRad), and CM-52 cellulose (Whatman) was grossly affected by minor changes in the ionic strength of the eluting buffer, more so than by changes in pH. Most sensitive was CM-52 cellulose, where increasing the ionic strength from 20 mmol/1 phosphate buffer pH 6.70 to 25 mmol/I was the difference between elution of no hoemoglobin and the elution of all hemoglobins. Bio-rex-70 columns behaved similarly, and we found that the "percentage glycosylated ha:moglobin" increased with increasing ionic strength of the eluting buffer. (2) Because proteins can contribute significantly to the ionic 1. James, W. P. T., Davies, H. L., Bailes,
J., Dauncey, P. L. D. Lancet, 1978, i, 1122. 2. Jackson, J. F., Moore, R. E., Tomkin, G. H. IrishJ. med. Sci. 1978, 147, 217.
740
strength of buffers we also observed that the percentage glycosylated haemoglobins increased with increasing hxmolysate concentrations in the range 0-5—3 g/dl within the same sample. In all cases we could see an apparently clean banding of the eluting hmmoglobins. However, on measurement, more fast-fraction ha:moglobins were eluted with higher lysate concentrations for a given specimen. (3) The rate of elution was also critical, percentage glycosylated hxmoglobins and elution-rate being directly related. Using similar quantities of resin and haemolysate as Dr Davis and Mr Nichol (Aug. 12, p.350) we found that the elution-time had to be at least 10 min if consistent results were to be obtained; shorter elution-times gave higher values for glycosylated haemoglobins.
These three factors
least must be rigorously checked if results is to be maintained. Neither Davis and Nichol nor Kynoch and Lehmann’ provide qualitycontrol data in their papers. Within-run and between-run variation of results, particularly over several batches of resin, would be valuable data (we have found great variation in results when changing batches of bio-rex resin). Some indication of normal range and clinical values would have been helpful, as well as data relating to comparison of their method with others. The correlation of their’ results with the clinical assessment of patients would have allowed readers to assess the validity of the method. Perhaps these workers could state more clearly the limits within which buffer concentrations, haemolysate concentrations, and elution-times must fall to produce an acceptably controlled assay.
quality control
at
over test
Departments of Hæmatology and Medicine, Flinders Medical Centre, Bedford Park, South Australia 5042
R. G. RYALL J. J. GRAHAM
MATERNAL/FETAL TRANSMISSION OF HBSAg NEGATIVE HEPATITIS be transmitted from mother to to mothers who had acute offspring.2-4 viral hepatitis B during pregnancy had hepatitis B antigen (HBsAg) in their blood.35 Though Stokes et awl. hypothesise transplacental transmission of virus, others suggest that the virus is transmitted around the time of labour and delivery. 34 There is no evidence for such transmission with hepatitis A virus. A 28-year-old gravida 3 had hepatitis in the ninth month of pregnancy. Her husband had had hepatitis immediately before his wife’s illness. She was brought to hospital on March 20, 1978 in the second stage of labour and with fulminant hepatic failure. Fetal heart sounds were absent. She delivered spontaneously a fresh stillborn male fetus weighing 2.5 kg (maturity approximately 36 weeks) with no obvious congenital malformation. Investigations of the mother showed Hb 13 g/dl, normal total and differential leucocyte-count, and low prothrombin index (20-30%). Bilirubin ranged from 17 to 25-55 mg/dl (conjugated 9.5-15 mg/dl), serum glutamic-oxaloacetic transaminase 258 l.u., alkaline phosphatase 300 King-Armstrong units. HBsAg was negative by cotintercurrent immunoelectrophoresis. The patient died on March 24, 1978. Complete necropsies were done on both mother and fetus. The maternal liver showed fulminant hepatitis with massive hepatic necrosis. The fetal liver also showed massive hepatic necrosis (see figure). Autolysis was ruled out because no other
SIR,-Hepatitis
B virus
can
40-50% of babies born
1. 2.
3. 4. 5.
Kynoch, P. A. M., Lehmann, H. Lancet, 1977, ii, 16. Stokes, J., Wolman, I, J., Blanchord, M. C., Farquhar, J. D Am. J. Dis. Child. 1951, 82, 213. Schweitzer, I. L., Wing, A., McPeak, C., Spears, R. L. L.J. Am. med. Ass. 1972, 220, 1092. Stevens, C. E., Beasley, R. P., Tsin, J., Lee, W. C. New Eng J. Med. 1975, 292, 771. Schweitzer, I. L., Dunn, A. E. G., Peters, R. L., Spears, R. L. Am. J. Med. 1973, 55, 762.
Photomicrograph of fetal liver showing extensive hepatocytic damage characterised by swelling, vacuolation of cytoplasm, and necrosis. There are foci of haemorrhage with dilatation of sinusoids. Hepatocytes in the immediate vicinity of the central vein are much less affected. (Hasmaioxytin and eosin; x about 350.)
organ showed autolysis and because the histological picture of liver-cell damage with areas of haemorrhage is unlike that seen in autolysis. Cord blood was negative for HBsAg, and so were the post-mortem blood samples and liver tissues of both mother
and baby. A hepatitis virus was transmitted to the fetus in utero, possibly via the transplacental route, leading to massive hepatic necrosis. Since serum and hepatic tissue of both mother and baby were negative for HBsAg, (which is positive in 80-90% of cases of acute viral hepatitis B in the icteric phase) it seems that the hepatitis in mother and baby was not due to hepatitis B virus. However, because of lack of tests of hepatitis A antigen, we cannot say whether this was hepatitis A or acute
hepatitis non-A, non-B. Departments of Obstetrics and Gynæcology and Pathology
Postgraduate Institute of
Medical Education and Research,
Chandigarh, India
BIPIN GUPTA
SHARDA AGARWAL
V. V. JOSHI
NITROUS OXIDE AND BONE-MARROW to correct that part of your editorial which was concerned with our paper, published in your issue of Aug. 12. First, in the deoxyuridine suppression test 3H-thymidine is used, not 3H-deoxyuridine. Secondly, in this test the uptake of 3H-thymidine by normal bone-marrow cells, but not by cells deficient in vitamin B12 or folate, is almost completely suppressed by preincubation with deoxyuridine. Thirdly, our results were typical of those seen with vitamin-B12 deficiency (i.e., the incorporation of deoxyuridine into D.N.A. in vitro was partially corrected by adding cyanocobalamin or pteroylglutamic acid whereas in folate deficiency the addition of cyanocobalamin has no effect). Fourthly, your editorial may give the impression that this abnormality could be reversed by the invivo administration of hsematinics. The pretreatment of one patient with large doses of parenteral vitamin B12 did not alter the morphological or biochemical effect produced by the administration of 50% nitrous oxide and 50% oxygen mixture.
SIR,-We would like
(Sept. 16,
p.
613)
of Hæmatology, St. Bartholomew’s Hospital, London EC1A 7BE
Department
J. A. L. AMESS J. F. BURMAN D. L. MOLLIN
