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EL TOR VIBRIO IN CHLORAMPHENICOL ESTIMATION
691 different urines and to seven sputa, we found that heating at 100°C did not affect the quantity of the antibiotic. By rendering the vibrio resistant to penicillin (100 units per ml.) and to streptomycin (100 y per ml.), it could be used to test the sera of patients undergoing simultaneous treatment with these antibiotics, especially for the presence of
When I wrote that immunisation should be considered here for the whole population in the event of war (rather than reserved for the 10% or so in the Armed Forces), it seemed to me that I was stating an obvious case-and one, furthermore, which committees responsible for advising the Government would have already very fully ffmsiflered.
London, W.
chloramphenicol.
’
Our conclusion is that quantitative estimation of chloramphenicol by the use of El Tor vibrio (Doorenbos) is of practical importance. The strain of El Tor vibrio can be obtained from the laboratory of the Academisch
PATRICK CLARKSON.
1.
INTRAVENOUS IRON
SIR,-We would like to thank Dr. Klopper for his letter published in your issue of March 3. We would point out, however, that we make no claim regarding the existence of a renal threshold of iron, nor do we stress the significance of the iron lost in the urine. We merely report our findings and suggest that such hypotheses are worth considering in future investigations. As regards the delayed cases, Dr. Klopper appears to have misunderstood us. It is perhaps unfortunate that the two paragraphs relating to delayed cases and hsemodilution were in juxtaposition. The finding of hsemodilution was common to all cases whether the
Ziekenhuis, Leiden, or from the National Collection of Type Cultures, Colindale Avenue, London, N.W.9. Laboratory, University Hospital, Leiden ; and Antibiotics Research Laboratory, Gistfabriek, Delft, Holland.
VERATRUM IN HYPERTENSION
SiR,-Your leading article of March 10 gives
difference between these and, for instance, the methonium compounds is that whereas the latter cause a fall of bloodpressure by interfering with the transmission of impulses on the efferent side of the cardiovascular reflex systems, the veratrum alkaloids have their principal effect on the circulation by exciting receptors on’the afferent side of the reflex arc. As long ago as 1868 von Bezold and Hirtdescribed the fall of blood-pressure and heart-rate which follows the intravenous injection of crude veratrum preparations and came to the conclusion that this must be due to a reflex action initiated by the stimulation of receptors, probably in the heart itself. Interest in the subject was revived by Jarisch and his colleagues,2 who confirmed Bezold’s original observation that the circulatory response to the intravenous injection of veratrine was abolished by cutting both vagi, and came to similar conclusions as to the location of the receptors. By this time much more was known about the reflex control of the circulation, and Jarisch pointed out that the anatomical and physiological basis for the Bezold reflex had still to be dis-3 covered. A few years later Krayer and his colleagues took up the story. They showed that if large doses of the pure alkaloids were used these had a direct action on the central nervous system ; but that in considerably smaller doses-and this is most probably the case in man-the whole fall of blood-pressure and heart-rate could be explained by the Bezold reflex. The receptors for the reflex are located in the area of distribution of the coronary arteries, probably in the left ventricle.4 They have not yet been positively identified with any physiological mechanism, though the suggestion has been made 25 that they serve the purpose of limiting the pressure rise in the left ventricle. The further elucidation of the Bezold reflex mechanism has therefore considerable physiological interest. Another feature of the actions of these alkaloids which interested physiologists for many years was the veratrine contracture," which was eventually traced to excitation of repetitive discharges in muscle and in nerve.6 Tlie ability of veratrine and of the pure alkaloids to cause repetitive discharges in nerves and stretch receptors 57
occurrence.
We agree with Dr. Fench (March 17) that haemodilution is responsible for many of the mathematical aberrations noted in anaemia of pregnancy, but we are not convinced that it is the only factor of importance. Even allowing for hsemodilution, we find in our cases that the utilisation of iron does not reach the theoretical level. We are of the opinion that more important factors are the storage of iron in early pregnancy and f obtal demands in the last trimester. It is also relevant to point out that the haemoglobin mass increases considerably in normal pregnancy (by as much as 20% of the total according to Smallwood,’ and 12% per sq. m. according to Roscoe and Donaldson 2). Much of his argument is therefore negatived. JEAN M. SCOTT Glasgow Royal Maternity A. D. T. GOVAN. and Women’s Hospital. EL TOR VIBRIO IN CHLORAMPHENICOL
ESTIMATION our method for the quantitative estimation of antibiotics is to bring together different
SiR,-The principle of
dilutions of blood-serum or other substances with a micro-organism sensitive to the antibiotic, and to note the dilutions in which growth of the organism is inhibited, using the micro-method of Goslings.3 A strain of El Tor vibrio proved very sensitive to chloramphenicol, its growth being completely inhibited in the presence of 0-5 y per ml. In tests on fifty sera, we found that inactivating them at 56°C for 30 minutes abolished their natural bactericidal effect, which may otherwise cause a false or pseudo titre. The El Tor vibrio used
was
isolated
"
"
twenty years
ago from
pilgrims in El Tor quarantine camp (Doorenbos) and has kept its capacity to produce active exohsemolysins in liquid media. It grows well in peptone water of pH 7-2 to which 5% defibrinated sheep’s blood has been added; after incubation at 37°C for 18 hours the pH of the medium increases to 7-4. The optimum pH for the activity of chloramphenicol being 7’2, the conditions are satisfactory for its quantitative estimation, using haemolysis as an indicator. The inhibitory effect of urine on the vibrio can be abolished by keeping it for 15 minutes at 100°C. After adding a known quantity of chloramphenicol-e.g., 5 y per ml.-to sixty 1. Smallwood, W. C. Brit. med. J. 1936, ii, 573. 2. Roscoe, M. H., Donaldson, G. M. M. J. Obstet. Gynœc. 1946, 53, 527. 3. Goslings, W. R. O. Ned. Tijdsschr. Geneesk. 1947, 91, 1542.
an
altogether misleading account of what is known of the mode of action of the veratrum alkaloids. The essential’
improvement was immediate or delayed, and was not specially related to the delay in response to treatment. The delay appeared to be related more to a protein Dr. deficiency than any change in blood-volume. of the of Klopper’s hypothesis displacement copper from the protein molecule by iron is also attractive and ingenious, but as yet he has supplied no proof of its
"
W. DOORENBOS J. KOP.
1. 2.
3. ,
4. 5. 6. 7.
Bezold, A., Hirt, L. Unters. physiol. Lab. Würzburg, 1867, 1, 73. Jarisch, A., Richter, H. Klin. Wschr. 1939, 18, 185. Jarisch, A., Richter, H. Arch. exp. Path. Pharmak. 1939, 193, 347, 355. Jarisch, A. Arch. Kreislaufforsch. 1940, 7, 260 ; Ibid, 1941, 9, 1. Amann, A., Jarisch, A. Arch. exp. Path. Pharmak. 1943, 201, 46. Krayer, O. Wood, E. H., Montes, G. J. Pharmacol. 1943, 79, 215. Krayer, O., Moe, G. K., Mendez, R. Ibid, 1944, 82, 167. Dawes, G. S. Ibid, 1947, 89, 325. Aviado, D. M., Pontius, R. G., Schmidt, C. F. Ibid, 1949, 97, 420. Jarisch, A., Zotterman, Y. Acta physiol. scand. 1948, 16, 31. Schaefer, H. Ergebn. Physiol. 1950, 46, 71. Krayer, O., Acheson, G. H. Physiol. Rev. 1946, 26, 383. Amann, A., Schaefer, H. Pflüg. Arch. ges. Physiol. 1943, 246, 757. Acheson, G. H., Rosenblueth, A. Amer. J. Physiol. 1941, 133, 736. Meier, R., Bein, H. J., Helmich, H. Experientia, 1949, 5, 484. Dawes, G. S. Acta physiol. scand. 1951, 22, 73.
von
When I wrote that immunisation should be considered here for the whole population in the event of war (rather than reserved for the 10% or so in the Armed Forces), it seemed to me that I was stating an obvious case-and one, furthermore, which committees responsible for advising the Government would have already very fully ffmsiflered.
London, W.
chloramphenicol.
’
Our conclusion is that quantitative estimation of chloramphenicol by the use of El Tor vibrio (Doorenbos) is of practical importance. The strain of El Tor vibrio can be obtained from the laboratory of the Academisch
PATRICK CLARKSON.
1.
INTRAVENOUS IRON
SIR,-We would like to thank Dr. Klopper for his letter published in your issue of March 3. We would point out, however, that we make no claim regarding the existence of a renal threshold of iron, nor do we stress the significance of the iron lost in the urine. We merely report our findings and suggest that such hypotheses are worth considering in future investigations. As regards the delayed cases, Dr. Klopper appears to have misunderstood us. It is perhaps unfortunate that the two paragraphs relating to delayed cases and hsemodilution were in juxtaposition. The finding of hsemodilution was common to all cases whether the
Ziekenhuis, Leiden, or from the National Collection of Type Cultures, Colindale Avenue, London, N.W.9. Laboratory, University Hospital, Leiden ; and Antibiotics Research Laboratory, Gistfabriek, Delft, Holland.
VERATRUM IN HYPERTENSION
SiR,-Your leading article of March 10 gives
difference between these and, for instance, the methonium compounds is that whereas the latter cause a fall of bloodpressure by interfering with the transmission of impulses on the efferent side of the cardiovascular reflex systems, the veratrum alkaloids have their principal effect on the circulation by exciting receptors on’the afferent side of the reflex arc. As long ago as 1868 von Bezold and Hirtdescribed the fall of blood-pressure and heart-rate which follows the intravenous injection of crude veratrum preparations and came to the conclusion that this must be due to a reflex action initiated by the stimulation of receptors, probably in the heart itself. Interest in the subject was revived by Jarisch and his colleagues,2 who confirmed Bezold’s original observation that the circulatory response to the intravenous injection of veratrine was abolished by cutting both vagi, and came to similar conclusions as to the location of the receptors. By this time much more was known about the reflex control of the circulation, and Jarisch pointed out that the anatomical and physiological basis for the Bezold reflex had still to be dis-3 covered. A few years later Krayer and his colleagues took up the story. They showed that if large doses of the pure alkaloids were used these had a direct action on the central nervous system ; but that in considerably smaller doses-and this is most probably the case in man-the whole fall of blood-pressure and heart-rate could be explained by the Bezold reflex. The receptors for the reflex are located in the area of distribution of the coronary arteries, probably in the left ventricle.4 They have not yet been positively identified with any physiological mechanism, though the suggestion has been made 25 that they serve the purpose of limiting the pressure rise in the left ventricle. The further elucidation of the Bezold reflex mechanism has therefore considerable physiological interest. Another feature of the actions of these alkaloids which interested physiologists for many years was the veratrine contracture," which was eventually traced to excitation of repetitive discharges in muscle and in nerve.6 Tlie ability of veratrine and of the pure alkaloids to cause repetitive discharges in nerves and stretch receptors 57
occurrence.
We agree with Dr. Fench (March 17) that haemodilution is responsible for many of the mathematical aberrations noted in anaemia of pregnancy, but we are not convinced that it is the only factor of importance. Even allowing for hsemodilution, we find in our cases that the utilisation of iron does not reach the theoretical level. We are of the opinion that more important factors are the storage of iron in early pregnancy and f obtal demands in the last trimester. It is also relevant to point out that the haemoglobin mass increases considerably in normal pregnancy (by as much as 20% of the total according to Smallwood,’ and 12% per sq. m. according to Roscoe and Donaldson 2). Much of his argument is therefore negatived. JEAN M. SCOTT Glasgow Royal Maternity A. D. T. GOVAN. and Women’s Hospital. EL TOR VIBRIO IN CHLORAMPHENICOL
ESTIMATION our method for the quantitative estimation of antibiotics is to bring together different
SiR,-The principle of
dilutions of blood-serum or other substances with a micro-organism sensitive to the antibiotic, and to note the dilutions in which growth of the organism is inhibited, using the micro-method of Goslings.3 A strain of El Tor vibrio proved very sensitive to chloramphenicol, its growth being completely inhibited in the presence of 0-5 y per ml. In tests on fifty sera, we found that inactivating them at 56°C for 30 minutes abolished their natural bactericidal effect, which may otherwise cause a false or pseudo titre. The El Tor vibrio used
was
isolated
"
"
twenty years
ago from
pilgrims in El Tor quarantine camp (Doorenbos) and has kept its capacity to produce active exohsemolysins in liquid media. It grows well in peptone water of pH 7-2 to which 5% defibrinated sheep’s blood has been added; after incubation at 37°C for 18 hours the pH of the medium increases to 7-4. The optimum pH for the activity of chloramphenicol being 7’2, the conditions are satisfactory for its quantitative estimation, using haemolysis as an indicator. The inhibitory effect of urine on the vibrio can be abolished by keeping it for 15 minutes at 100°C. After adding a known quantity of chloramphenicol-e.g., 5 y per ml.-to sixty 1. Smallwood, W. C. Brit. med. J. 1936, ii, 573. 2. Roscoe, M. H., Donaldson, G. M. M. J. Obstet. Gynœc. 1946, 53, 527. 3. Goslings, W. R. O. Ned. Tijdsschr. Geneesk. 1947, 91, 1542.
an
altogether misleading account of what is known of the mode of action of the veratrum alkaloids. The essential’
improvement was immediate or delayed, and was not specially related to the delay in response to treatment. The delay appeared to be related more to a protein Dr. deficiency than any change in blood-volume. of the of Klopper’s hypothesis displacement copper from the protein molecule by iron is also attractive and ingenious, but as yet he has supplied no proof of its
"
W. DOORENBOS J. KOP.
1. 2.
3. ,
4. 5. 6. 7.
Bezold, A., Hirt, L. Unters. physiol. Lab. Würzburg, 1867, 1, 73. Jarisch, A., Richter, H. Klin. Wschr. 1939, 18, 185. Jarisch, A., Richter, H. Arch. exp. Path. Pharmak. 1939, 193, 347, 355. Jarisch, A. Arch. Kreislaufforsch. 1940, 7, 260 ; Ibid, 1941, 9, 1. Amann, A., Jarisch, A. Arch. exp. Path. Pharmak. 1943, 201, 46. Krayer, O. Wood, E. H., Montes, G. J. Pharmacol. 1943, 79, 215. Krayer, O., Moe, G. K., Mendez, R. Ibid, 1944, 82, 167. Dawes, G. S. Ibid, 1947, 89, 325. Aviado, D. M., Pontius, R. G., Schmidt, C. F. Ibid, 1949, 97, 420. Jarisch, A., Zotterman, Y. Acta physiol. scand. 1948, 16, 31. Schaefer, H. Ergebn. Physiol. 1950, 46, 71. Krayer, O., Acheson, G. H. Physiol. Rev. 1946, 26, 383. Amann, A., Schaefer, H. Pflüg. Arch. ges. Physiol. 1943, 246, 757. Acheson, G. H., Rosenblueth, A. Amer. J. Physiol. 1941, 133, 736. Meier, R., Bein, H. J., Helmich, H. Experientia, 1949, 5, 484. Dawes, G. S. Acta physiol. scand. 1951, 22, 73.
von