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INTERPRETATION OF RADIO-ISOTOPE TURNOVER DATA
198 oxidase inhibitor, and that any patient about to receive an anxsthetic, especially if under treatment for his " nerves ", should be questioned specifically about these drugs in the same wAy as a history of cortisone therapy is sought. Department of Anaesthetics, St. Thomas’s Hospital, London, S.E.1.
A. J. CLEMENT DAVID BENAZON.
INTERPRETATION OF RADIO-ISOTOPE TURNOVER DATA SiR,—In a recent preliminary communication, Anderson et al.1 have laid considerable stress upon the observation that the fall in plasma specific activity after intravenous administration of a bone-seeking isotope can be represented as a power function for the first 100 hours or so. They state that exponential functions are inadequate to describe processes which involve active cellular transport and claim that analysis of the data assuming a power-law function facilitates differentiation between various bone
disorders. It is perfectly true that the disappearance of radiocalcium and radiostrontium from plasma is not a mono-exponential function -at least during the first few weeks after administration of the isotope. Although various workers have attempted to interpret their data as though this were the case 2-6 it has become increasingly clear that when plasma specific activities are
an arbitrary double exponential equation as illustrated in figure 1. The upper curve shows such an equation plotted on semi-logarithmic paper, looking not unlike the curves obtained
with
plotted on semi-logarithmic paper the resulting line is not straight. We have previously drawn attention to this fact 78 and have suggested that the explanation is to be sought in slow exchange processes between extracellular fluid and bone mineral which produce a net transfer of isotope into bone. We suggest that after an equilibration period of about 24 hours the system is essentially a two compartment one in which the immediately exchangeable calcium pool represents the first compartment and some additional mineral in the bone represents the second compartment. Mathematical analysis of such a model yields a complex exponential function not unlike the observed plasma-specific-activity/time curves in man. We agree that a straight line can be obtained by plotting the data for the first 7 days or so on log-log paper but consider this may be fortuitous. Thus the same result can easily be obtained Anderson, J., Tomlinson, R. W. S., Osborn, S. B. Lancet, 1962, i, 949. Nordin, B. E. C. Proc. R. Soc. Med. 1959, 52, 351. Fraser, R., Harrison, M., Ibbertson, K. Quart. J. Med. 1960, 29, 85. Heaney, R. P., Whedon, G. D. J. clin. Endocrinol. 1958, 18, 1246. Aubert, J. P., Milhaud, G. Biochim. biophys. Acta, 1960, 39, 122. Eisenberg, E., Gordan, G. S. J. clin. Invest. 1961, 40, 1809. Bluhm, M., MacGregor, J., Nordin, B. E. C. in Radioaktive Isotope, Klinik und Forschung; Band IV. Berlin, 1960. 8. Nordin, B. E. C., Bluhm, M., MacGregor, J. in Radioisotopes and Bone. (Edited by P. Lacroix and A. M. Budy). Oxford, 1962.
1. 2. 3. 4. 5. 6. 7.
from kinetic studies in man. The lower curve shows the same data plotted on log-log paper, demonstrating that straight lines can now be drawn through the data and that the general appearance is very similar to that of fig. 1 of Anderson et al. In fact, unless some curve-fitting criterion such as least squares is applied, it is not readily apparent whether a multi-exponential or a power-law curve best fits the data. Fig. 2 makes the same point with some of our in-vitro data,’ The upper curve (2a) illustrates an experiment in which radioactive strontium was added to buffer in which a slice of dead human bone was immersed. In order to simulate the excretion processes in the living organism, a certain fixed proportion (12%) of the fluid in the system was discarded each day and replaced by unlabelled buffer of the same chemical composition. The falling specific activity observed is due to loss of activity into the bone by exchange processes and to the simulated excretion. It is clear that these data form a curve on semilogarithmic paper not unlike the disappearance curves obtained from studies in Man. In fig. 2b, the same data have been plotted on log-log paper and it can be seen that they now appear to obey a power-law function. Again the appearance is very similar to that of fig. 1 of Anderson et al, and yet it is impossible in this case to invoke active transport mechanisms since only dead bone is present in the system. From the study of the behaviour of bone-seeking isotopes in Man, we have concluded that it can best be described in terms of some relatively complex exponential function. We believe that it may be misleading to adapt an arbitrary line-fitting procedure, and we cannot in any case understand why the postulated power function is taken to imply an active transport mechanism. On the
199
contrary, our experience leads us to believe that during the first few weeks after administration of a bone-seeking isotope most of the activity which finds its way into the skeleton does so by purely physical processes. Department of Medicine, Gardiner Institute, Western Infirmary, Glasgow.
H. I. GLASS J. MACGREGOR B. E. C. NORDIN.
RECRUITMENT FOR DERMATOLOGY SIR,-It is surprising and rather serious that advertisements for registrars in dermatology should provoke only a poor response. It is serious because there will not be the trained men to fill the many consultant posts that will arise in the near future. It is surprising because of the abundant and important opportunities and facilities offered in dermatology to the able clinician and to those interested in research and experimental medicine. If both these interests are combined in the one candidate, so much the better. You have emphasised in a recent annotationthat dermatology, unlike some specialties, has, in its advances since the war, become more broad based. It enters into every facet of medical practice. I doubt if the young man entering the field of training for a higher post in medicine realises the scope offered by a period spent in dermatological work or the facilities available for clinical and scientific study. It is to be hoped that the excitement and enthusiasm shown for this field in other countries, and particularly in America, will soon invade this country. Department of Dermatology, Royal Victoria Infirmary, Newcastle upon Tyne.
JOHN T. INGRAM.
A LOCAL ANTIBACTERIAL AGENT
SIR,-Professor Howie (June 2) is to be congratulated on a very clear exposition on the prevention and treatment of infection. He has drawn attention to many very simple ways in which cross-infection can arise and be prevented, which would escape the notice of most physicians and surgeons because so apparently obvious. Among the agents confined to local use he singles out colistin and polymyxin as being of special importance because of their activity against Pseudomonas pyocyanea. I should like to draw attention to polynoxylin (’ Anaflex ’), a local antibacterial agent, which I have used considerably for the past two years.2 simple compound, which is said by the manufacturers condensation product of formaldehyde and urea, has a very wide antibacterial spectrum.3 It is particularly effective against Staphylococcus aureus, and I have yet to encounter a strain of this organism which is resistant to it. This is in striking contrast to the older penicillins, to which, in my experience, over 50% of strains of Staph. aureus are resistant. The incidence of strains resistant to chloramphenicol and the tetracyclines is also rising steadily. 2 Polynoxylin is also effective both in vitro and in vivo against proteus and Ps. pyocyanea. In five instances of leg ulcers infected with Ps. pyocyanea all were quickly cleared by polynoxylin. This drug has also proved to be clinically efficacious against local infections with Clostridium welchii and Candida albicans. Although it is strongly inhibitory of streptococci in vitro I have not found it so effective in vivo against this organism. This, I think, is because the powdered preparation I used was unsuitable for eruptions with profuse serous discharge and crust formation. As
or pus. Apart from the removal of these before treatthe choice of preparation in which the agent is presented ment, is often veiy important. Since evidence of- polynoxylin-resistant strains of Staph. aureus is not yet forthcoming, it appears that this antibacterial agent has a definite place not only in dermatology but also This is especially as a prophylactic measure in surgery. important in view of the fact that because of its insolubility, the drug is not yet given internally. It should be a valuable preparation in surgical situations where infections with proteus, Ps. pyocyanea, and Cand. albicans are likely to appear (e.g., aural and rectal surgery and in bedsores). There is also evidence8 that as a nasal spray it is of value in the control of staphylococcal carriers.
sloughs
Skin Department, Glasgow Royal Infirmary.
J. O’D. ALEXANDER.
VISITING CHILDREN SIR,-It was pleasing to see5 that unrestricted visiting to children in hospitals is now widely accepted. It is probably not generally appreciated that many local authorities still restrict visits to children in their care to one a month. This seems to be a harmful practice, even if the parents have been guilty of cruelty to the children; and surely it should not be tolerated when a child has been
admitted for purely social reasons. Perhaps an exchange of ideas between the Ministry of Health and the Home Office would produce beneficial results. " NODDY." DEHYDROGENASE ISOENZYMES SIR,-The letter from Dr. Hawkins and Mr. Whyley (May 26) prompts me to report a technique for the demonstration of lactic dehydrogenase isoenzymes (L.D.H.) using cellulose acetate. This method has the advantage of great simplicity, and it can be adopted for diagnostic use in a routine laboratory.
Samples are run in barbitone buffer, pH 8-6, 0-07 M; current 1 mA per 2-5 cm. strip. The sample is applied to the centre of the strip and run for approximately 1 hour 20 minutes. The following reagent mixture is prepared: 1 vol. M lactate, 1 vol. N.A.D. (D.P.N.) 10 mg. per ml., 3 vol. nitro blue-tetrazolium or M.T.T. (1 mg. per ml.), and 0-3 vol. methyl phenazonium metho-sulphate (1 mg. per ml.).6-S A small moist chamber is prepared, and a clean glass slide put at the bottom. When the run is completed, the reagent mixture is applied as a streak to the clean glass plate, a fresh 2-5 cm. wide strip of cellulose acetate is allowed to soak up this mixture. The electrophoresis
This
to be
a
Professor Howie observes, the effectiveness of an antibiotic or chemotherapeutic agent is often impaired by the presence of 1. Lancet, 1962, i, 311. 2. Alexander, J. O’D. Brit. J. Derm, (in the press). 3. Haler, D., Aebi, A. Nature, Lond. 1961, 190, 734. 4. Lamont, I. C. Brit. J. Derm. 1959, 71, 201.
Isoenzymes of lactic dehydrogenase showing five fractions and albumin band (blister fluid).
an
strip is then removed from the tank and immediately superimposed on the blank strip into which the mixture has soaked. The moist chamber is closed and incubated. When enzyme concentration is high, the bands develop within minutes. Sera can be left to incubate for 1 hour if necessary. The strips are then fixed in 10% formalin or alcohol/acetic acid. By this method up to five clearly defined and well-separated bands can be demonstrated in tissue homogenates and in sera (see figure). The relative intensity of the bands varies with the origin of the tissue homogenates, and agrees with findings on agar and starch. Visual inspection of the strip is sufficient to reveal different 5. Lancet, July 14, 1962, p. 105. 6. Van der Helm, H. J. Lancet, 1961, ii, 108. 7. Latner, A. L., Skillen, A. W. ibid. p. 1286. 8. Wieme, R. J. Personal communication.
A. J. CLEMENT DAVID BENAZON.
INTERPRETATION OF RADIO-ISOTOPE TURNOVER DATA SiR,—In a recent preliminary communication, Anderson et al.1 have laid considerable stress upon the observation that the fall in plasma specific activity after intravenous administration of a bone-seeking isotope can be represented as a power function for the first 100 hours or so. They state that exponential functions are inadequate to describe processes which involve active cellular transport and claim that analysis of the data assuming a power-law function facilitates differentiation between various bone
disorders. It is perfectly true that the disappearance of radiocalcium and radiostrontium from plasma is not a mono-exponential function -at least during the first few weeks after administration of the isotope. Although various workers have attempted to interpret their data as though this were the case 2-6 it has become increasingly clear that when plasma specific activities are
an arbitrary double exponential equation as illustrated in figure 1. The upper curve shows such an equation plotted on semi-logarithmic paper, looking not unlike the curves obtained
with
plotted on semi-logarithmic paper the resulting line is not straight. We have previously drawn attention to this fact 78 and have suggested that the explanation is to be sought in slow exchange processes between extracellular fluid and bone mineral which produce a net transfer of isotope into bone. We suggest that after an equilibration period of about 24 hours the system is essentially a two compartment one in which the immediately exchangeable calcium pool represents the first compartment and some additional mineral in the bone represents the second compartment. Mathematical analysis of such a model yields a complex exponential function not unlike the observed plasma-specific-activity/time curves in man. We agree that a straight line can be obtained by plotting the data for the first 7 days or so on log-log paper but consider this may be fortuitous. Thus the same result can easily be obtained Anderson, J., Tomlinson, R. W. S., Osborn, S. B. Lancet, 1962, i, 949. Nordin, B. E. C. Proc. R. Soc. Med. 1959, 52, 351. Fraser, R., Harrison, M., Ibbertson, K. Quart. J. Med. 1960, 29, 85. Heaney, R. P., Whedon, G. D. J. clin. Endocrinol. 1958, 18, 1246. Aubert, J. P., Milhaud, G. Biochim. biophys. Acta, 1960, 39, 122. Eisenberg, E., Gordan, G. S. J. clin. Invest. 1961, 40, 1809. Bluhm, M., MacGregor, J., Nordin, B. E. C. in Radioaktive Isotope, Klinik und Forschung; Band IV. Berlin, 1960. 8. Nordin, B. E. C., Bluhm, M., MacGregor, J. in Radioisotopes and Bone. (Edited by P. Lacroix and A. M. Budy). Oxford, 1962.
1. 2. 3. 4. 5. 6. 7.
from kinetic studies in man. The lower curve shows the same data plotted on log-log paper, demonstrating that straight lines can now be drawn through the data and that the general appearance is very similar to that of fig. 1 of Anderson et al. In fact, unless some curve-fitting criterion such as least squares is applied, it is not readily apparent whether a multi-exponential or a power-law curve best fits the data. Fig. 2 makes the same point with some of our in-vitro data,’ The upper curve (2a) illustrates an experiment in which radioactive strontium was added to buffer in which a slice of dead human bone was immersed. In order to simulate the excretion processes in the living organism, a certain fixed proportion (12%) of the fluid in the system was discarded each day and replaced by unlabelled buffer of the same chemical composition. The falling specific activity observed is due to loss of activity into the bone by exchange processes and to the simulated excretion. It is clear that these data form a curve on semilogarithmic paper not unlike the disappearance curves obtained from studies in Man. In fig. 2b, the same data have been plotted on log-log paper and it can be seen that they now appear to obey a power-law function. Again the appearance is very similar to that of fig. 1 of Anderson et al, and yet it is impossible in this case to invoke active transport mechanisms since only dead bone is present in the system. From the study of the behaviour of bone-seeking isotopes in Man, we have concluded that it can best be described in terms of some relatively complex exponential function. We believe that it may be misleading to adapt an arbitrary line-fitting procedure, and we cannot in any case understand why the postulated power function is taken to imply an active transport mechanism. On the
199
contrary, our experience leads us to believe that during the first few weeks after administration of a bone-seeking isotope most of the activity which finds its way into the skeleton does so by purely physical processes. Department of Medicine, Gardiner Institute, Western Infirmary, Glasgow.
H. I. GLASS J. MACGREGOR B. E. C. NORDIN.
RECRUITMENT FOR DERMATOLOGY SIR,-It is surprising and rather serious that advertisements for registrars in dermatology should provoke only a poor response. It is serious because there will not be the trained men to fill the many consultant posts that will arise in the near future. It is surprising because of the abundant and important opportunities and facilities offered in dermatology to the able clinician and to those interested in research and experimental medicine. If both these interests are combined in the one candidate, so much the better. You have emphasised in a recent annotationthat dermatology, unlike some specialties, has, in its advances since the war, become more broad based. It enters into every facet of medical practice. I doubt if the young man entering the field of training for a higher post in medicine realises the scope offered by a period spent in dermatological work or the facilities available for clinical and scientific study. It is to be hoped that the excitement and enthusiasm shown for this field in other countries, and particularly in America, will soon invade this country. Department of Dermatology, Royal Victoria Infirmary, Newcastle upon Tyne.
JOHN T. INGRAM.
A LOCAL ANTIBACTERIAL AGENT
SIR,-Professor Howie (June 2) is to be congratulated on a very clear exposition on the prevention and treatment of infection. He has drawn attention to many very simple ways in which cross-infection can arise and be prevented, which would escape the notice of most physicians and surgeons because so apparently obvious. Among the agents confined to local use he singles out colistin and polymyxin as being of special importance because of their activity against Pseudomonas pyocyanea. I should like to draw attention to polynoxylin (’ Anaflex ’), a local antibacterial agent, which I have used considerably for the past two years.2 simple compound, which is said by the manufacturers condensation product of formaldehyde and urea, has a very wide antibacterial spectrum.3 It is particularly effective against Staphylococcus aureus, and I have yet to encounter a strain of this organism which is resistant to it. This is in striking contrast to the older penicillins, to which, in my experience, over 50% of strains of Staph. aureus are resistant. The incidence of strains resistant to chloramphenicol and the tetracyclines is also rising steadily. 2 Polynoxylin is also effective both in vitro and in vivo against proteus and Ps. pyocyanea. In five instances of leg ulcers infected with Ps. pyocyanea all were quickly cleared by polynoxylin. This drug has also proved to be clinically efficacious against local infections with Clostridium welchii and Candida albicans. Although it is strongly inhibitory of streptococci in vitro I have not found it so effective in vivo against this organism. This, I think, is because the powdered preparation I used was unsuitable for eruptions with profuse serous discharge and crust formation. As
or pus. Apart from the removal of these before treatthe choice of preparation in which the agent is presented ment, is often veiy important. Since evidence of- polynoxylin-resistant strains of Staph. aureus is not yet forthcoming, it appears that this antibacterial agent has a definite place not only in dermatology but also This is especially as a prophylactic measure in surgery. important in view of the fact that because of its insolubility, the drug is not yet given internally. It should be a valuable preparation in surgical situations where infections with proteus, Ps. pyocyanea, and Cand. albicans are likely to appear (e.g., aural and rectal surgery and in bedsores). There is also evidence8 that as a nasal spray it is of value in the control of staphylococcal carriers.
sloughs
Skin Department, Glasgow Royal Infirmary.
J. O’D. ALEXANDER.
VISITING CHILDREN SIR,-It was pleasing to see5 that unrestricted visiting to children in hospitals is now widely accepted. It is probably not generally appreciated that many local authorities still restrict visits to children in their care to one a month. This seems to be a harmful practice, even if the parents have been guilty of cruelty to the children; and surely it should not be tolerated when a child has been
admitted for purely social reasons. Perhaps an exchange of ideas between the Ministry of Health and the Home Office would produce beneficial results. " NODDY." DEHYDROGENASE ISOENZYMES SIR,-The letter from Dr. Hawkins and Mr. Whyley (May 26) prompts me to report a technique for the demonstration of lactic dehydrogenase isoenzymes (L.D.H.) using cellulose acetate. This method has the advantage of great simplicity, and it can be adopted for diagnostic use in a routine laboratory.
Samples are run in barbitone buffer, pH 8-6, 0-07 M; current 1 mA per 2-5 cm. strip. The sample is applied to the centre of the strip and run for approximately 1 hour 20 minutes. The following reagent mixture is prepared: 1 vol. M lactate, 1 vol. N.A.D. (D.P.N.) 10 mg. per ml., 3 vol. nitro blue-tetrazolium or M.T.T. (1 mg. per ml.), and 0-3 vol. methyl phenazonium metho-sulphate (1 mg. per ml.).6-S A small moist chamber is prepared, and a clean glass slide put at the bottom. When the run is completed, the reagent mixture is applied as a streak to the clean glass plate, a fresh 2-5 cm. wide strip of cellulose acetate is allowed to soak up this mixture. The electrophoresis
This
to be
a
Professor Howie observes, the effectiveness of an antibiotic or chemotherapeutic agent is often impaired by the presence of 1. Lancet, 1962, i, 311. 2. Alexander, J. O’D. Brit. J. Derm, (in the press). 3. Haler, D., Aebi, A. Nature, Lond. 1961, 190, 734. 4. Lamont, I. C. Brit. J. Derm. 1959, 71, 201.
Isoenzymes of lactic dehydrogenase showing five fractions and albumin band (blister fluid).
an
strip is then removed from the tank and immediately superimposed on the blank strip into which the mixture has soaked. The moist chamber is closed and incubated. When enzyme concentration is high, the bands develop within minutes. Sera can be left to incubate for 1 hour if necessary. The strips are then fixed in 10% formalin or alcohol/acetic acid. By this method up to five clearly defined and well-separated bands can be demonstrated in tissue homogenates and in sera (see figure). The relative intensity of the bands varies with the origin of the tissue homogenates, and agrees with findings on agar and starch. Visual inspection of the strip is sufficient to reveal different 5. Lancet, July 14, 1962, p. 105. 6. Van der Helm, H. J. Lancet, 1961, ii, 108. 7. Latner, A. L., Skillen, A. W. ibid. p. 1286. 8. Wieme, R. J. Personal communication.