- Email: [email protected]
BRAIN DEATH AS DETERMINED BY CEREBRAL ARTERIOGRAPHY
Unlike the experience of Dr Dalen and Dr not observe any aggravation of parkinsonian symptoms by lithium carbonate. Since lithium-carbonate therapy is technically difficult to regulate and potentially toxic, we caution against its routine use in levodopa-induced involuntary movements until further controlled investigations determine its overall efficacy.
sleepiness). Steg,
we
did
Departments of Internal Medicine and Pharmacology, Yale University School of Medicine MELVIN H. VAN WOERT New Haven, Connecticut, U.S.A. LALIT M. AMBANI.
SUSTAINED-RELEASE LEVODOPA
SIR,-Our clinical observations with a sustainedrelease form of levodopa (’ Brocadopa Temtabs ’) agree with those already reported,!.2 although we question the conclusion that such preparations have no practical value. It now appears that the " on/off " response to levodopa occurs with increasing frequency and severity as the duration of treatment lengthens. If this brittle response is mainly due to the fluctuations in circulating dopa levels which attend the oral administration of standard levodopa preparations, then sustained-release formulations might prove helpful. We studied 3 parkinsonian patients who manifested the " on/off " response to levodopa. Each was observed over 6-9 hours while kept fasting and supine in bed. Levodopa was given orally at optimum therapeutic dose levels every 2t hours in combination with a peripheral decarboxylase inhibitor (MK 486, ’Carbidopa’) 25 mg. every 5 hours. Plasma-dopa levels rose sharply after each dose of levodopa (see figure). Peak circulating levels of the aminoacid were generally followed by periods of maximum suppression of parkinsonism and the appearance of dyskinesias, while low plasma-dopa values presaged the return of severe parkinsonian signs and the disappearance of dyskinesias. When these patients were studied under the same conditions but received levodopa by means of a 1. 2.
Eckstein, B., Shaw, K., Sten, G. Lancet, Feb. 24, 1973, p. 431. Curzon, G., Friedel, J., Grier, L., Marsden, C. D., Parker, J. D., Shipley, M., Zilkhak, J. ibid. April 7, 1973, p. 781.
HOURS
Effect of oral or intravenous levodopa on plasma-dopa concentrations (0----0), overall parkinsonian severity (8-8), and degree of
Oral
dyskinesias (A-A). every 2! hours
levodopa given
severity scored
Dyskinesias
( ).
scale of 0 (absent) to 12 rated between 0 (absent) and 4 (very on
a
Parkinsonian
(very severe). severe).
constant intravenous infusion, relatively steady plasma levels of the aminoacid were associated with a notably stable clinical response (see figure). From these observations we conclude that the on/off response to orally administered levodopa under the above conditions is largely due to fluctuations in circulating dopa levels rather than to some centrally mediated mechanism. As shown by Curzon et al.,2the irregular response to the available sustained-release levodopa preparation reflects the failure of this compound to maintain clinically effective plasma-dopa concentrations for significantly longer periods than the standard form of levodopa. An effective sustainedrelease preparation which substantially reduced these fluctuations in blood levels should benefit parkinsonian patients. Therefore, additional efforts directed towards development of such a preparation should be profitable.
Neurology Unit, National Institute of Mental
Health, Bethesda, Maryland 20014, U.S.A.
ANNE C. WOODS GEORGE A. GLAUBIGER THOMAS N. CHASE.
BRAIN DEATH AS DETERMINED BY CEREBRAL ARTERIOGRAPHY
SIR,-The accepted definition of brain death in patients with cardiac function includes complete unreceptivity and unresponsivity to intense stimulation, lack of spontaneous respirations or movement, areflexia, and two flat electroencephalograms (E.E.G.S) at least 24 hours apart3 in the This absence of hypothermia or depressant drugs.3 definition of brain death was a major breakthrough, but many potential donor organs are lost during the 24-hour waiting-period, because cardiac function and/or renal perfusion cannot be adequately maintained. I should like to propose the substitution of complete absence of intracranial circulation for the two flat E.E.G.S in determining brain death. Retrograde four-vessel cerebral arteriography by the Seldinger method would be the quickest and perhaps the easiest method to assess the absence of intracranial bloodA left carotid arteriogram and a right brachial flow. arteriogram, however, would also suffice. A unilateral carotid arteriogram would not be sufficient, because in unilateral intracranial lesions the pressure in the right and left anterior and middle fossa and that in the posterior fossa are not necessarily equal. 4,5 If the contrast material puddled in the major neck vessels and none entered the intracranial circulation over a 5-minute period, then, with the other criteria being met (excluding two E.E.G.S 24 hours apart), brain death could be declared. Riishede and Ethelberg 6 in 1953 reported non-filling of the intracranial portion of the internal carotid artery in 5 patients with space-occupying intracranial lesions, and they attributed it to tentorial herniation. Horowitz and Dunsmorethought non-filling to be secondary to diencephalic reflexes, and Newton and Couch 11 suggested it might be due to arterial spasm. Pribram9 first proposed that nonfilling of the internal carotid above the siphon is due to increased intracranial pressure, and Mitchell et al. 10 experimentally confirmed that, when the intracranial pressure exceeds the systolic blood-pressure, intracranial blood-flow ceases. Mitchell et al. presented 5 cases of non-filling and 3. J. Am. med. Ass. 1968, 205, 337. 4. Cantu, R. C. Int. Surg. 1972, 57, 668. 5. Langfitt, T. W., Weinstein, J. D., Cassell, N. F., Gagliardi, L. J. J. Neurosurg. 1964, 21, 998. 6. Riishede, J., Ethelberg, S. Archs Neurol. Psychiat. 1953, 70, 399. 7. Horowitz, N. H., Dunsmore, R. H. J. Neurosurg. 1956, 13, 155. 8. Newton, T. H., Couch, R. S. C. Radiology, 1960, 75, 766. 9. Pribram, H. F. W. Neurology, Minneap. 1960, 11, 10. 10. Mitchell, O. C., Torre, E., Alexander, E., Davis, C. H. J. Neurosurg. 1962, 19, 766.
, JUNE 16 out that none had a demonstrable pressure cone when the brain was removed at necropsy. They also discussed a case of an infant in opisthotonos in which a left vertebral arteriogram showed vertebral filling but no filling of the basilar artery, illustrating that the intracranial posterior circulation can be arrested when the pressure within the posterior fossa exceeds the systolic bloodThis confirms that, in cases pressure. They concluded, of acutely raised intracranial pressure, the cerebral circulation is slowed to such an extreme that death is inevitable." Today, many potential donor organs are lost from patients with irreversible brain damage because of the required waiting-period of at least 24 hours to obtain two flat E.E.G.s. The waiting-period is often longer than 24 hours if E.E.G.s are not readily available. The importance of this loss is brought into perspective when we realise that there are now 70 people on dialysis awaiting cadaverkidney transplantation at one major Boston hospital alone.
pointed
"
Neurosurgical Service, Emerson Hospital, Concord, Massachusetts 01742, U.S.A.
ROBERT C. CANTU.
REORGANISATION—RATES FOR THE
JOBS
SIR,-Your editorial (June 2, p. 1228) might have gone further and remarked that no salary scales for medical administrators have yet been published or posts advertised notwithstanding. There may be more bitter pills to be swallowed. 47
Corstorphine Bank Drive, Edinburgh EH12 8RH.
G. G. SAVAGE.
The lymphocytes can be easily pipetted off and collected. The viability of the lymphocytes after washing and resuspension in phosphate-buffered saline or tissue-culture medium approaches 98%(as measured by trypan-blue exclusion). The lymphocytes were shown to react in various tests measuring blastogenesis and cytotoxicity. The recovery-rate of lymphocytes from normal blood with this technique exceeds 70%. University of Texas at Houston, M. D. Anderson Hospital and Tumor Institute, Houston, Texas, U.S.A.
KAMRAN TEBBI.*
RADIOIMMUNOASSAY OF PLASMA-RENIN ACTIVITY
SIR,-In a comparison of the Schwarz-Mann and Squibb commercial kits for the measurement of plasmarenin activity by radioimmunoassay of angiotensin-I production, Chervu et aLl used 10 1. of dimercaprol (8 mM) as inhibitor in each case, although only 2 jjj. of dimercaprol (1-6 mM) is recommended in the SchwarzMann kit. Chervu et al. did not mention any reason for this alteration, but there is considerable variation, from 1-6 2-4 to 8-0 mM,l in the amount of dimercaprol used by various investigators of angiotensin-I activity, the main differences being typified by the low concentration recommended in the Schwarz-Mann kit, and the high concentrations used in the Squibb kit. Ryan et al.,5,6 who originally recommended the use of dimercaprol to inhibit angiotensinases, used a concentration of 10 mM before
bioassay. PURIFICATION OF LYMPHOCYTES
SiR,-Several methods for the separation of lymphocytes from other cellular elements of the blood are available.1-3 The ’Ficoll ’-’ Hypaque ’ method1 is probably the easiest and most useful. With this technique, however, some contamination with granulocytes and monocytes is unavoidable in 5-10% of specimens. In addition, some of the monocytes that contaminate the lymphocyte preparation become " activated " during this procedure; thus, nonspecific reactions can occur. The following technique has proved very successful in eliminating contamination of the lymphocyte preparation with granulocytes and monocytes. It is based on phagocytosis of colloidal iron particles by blood leucocytes before centrifugation in ficoll-hypaque gradient. Simple laboratory facilities In
are
required.
clean 100 x 16 mm. glass tube, 2 ml. buffy-coat leucocytes separated from heparinised blood are mixed with 1 ml. 10% carbonyl iron (G.A.F. Corporation, New York, N.Y.) suspended in 10% acacia solution. The mixture is incubated for 30 minutes at 37 °C on a rocker at 30 revolutions per minute (Ames Co., Indiana). After adding 2 ml. normal saline, the contents are carefully laid over 3 ml. separating fluid " in another 100 x 16 mm. glass tube. The " separating fluid " consists of 9% ficoll (Farmacetica, Uppsala, Sweden) and 34% hypaque (Winthrop Laboratories, New York, N.Y.) in ratio of 2-4/1 to give a specific gravity of 1-076-1-078. The tube is centrifuged for 30 minutes at 20°C at 1300 r.p.m. Four distinct layers separate in the centrifuged tube. The upper layer consists of the plasma and saline. The next layer is that of the purified lymphocytes. Repeated studies indicate contamination with granulocytes or monocytes to be less than 0-5%. The third layer consists of the clear ficollhypaque mixture. The fourth layer is the sediment containing all the red cells and the iron-laden granulocytes and monocytes a
"
We are using a kit manufactured by Societa Ricerche Nucleari (SORIN) which, like the Schwarz-Mann kit, is based on the method of Haber et al.,2 who used 1-60 mM dimercaprol. These authors did not mention the reason for choosing this low concentration and hence it may not be optimal. This problem is emphasised by our own results. In June, 1972, SORIN changed the recommended amount of dimercaprol from 2 ,1. (1-6 mM) to 6 1. (4-8 mM). Since no explanation for the change was offered we compared estimations using the two concentrations, and found a substantial increase in the measured plasma-renin activity when using the higher concentration of inhibitor. Ten samples of normal plasma, collected after one hour’s rest, gave mean results (s.D.) of 0-33:0-16 ng. angiotensin I per ml. per hour using 1-6 mM dimercaprol and 0-740-36 ng. per ml. per hour using 4-8 mM dimercaprol, an increase of x 2-2. The most probable explanation for the difference is that the lower concentration of dimercaprol does not completely inhibit the enzymic degradation of
Impianti
angiotensin
*
Present address: St. Louis Children’s Hospital, St. Louis, Missouri 63110, U.S.A. 1.
2. 3. 4. 5. 6. 7.
(macrophages). 8. 1. 2.
3.
Harris, R., Ukaejiofo, E. O. Lancet, 1969, ii, 327. Thorsby, E., Bratlie, A. in Histocompatibility Testing (edited by P. I. Terasaki); p. 665. Copenhagen, 1970. Gelsthorpe, K., Doughty, W., Fox, M. Br. J. Surg. 1970, 57, 358.
i.
Further work is required to establish the optimum inhibitor effect, but several workers 7-10 have already
9. 10.
Chervu, L. R., Lory, M., Liang, T., Lee, H. B., Blaufox, M. D. J. nucl. Med. 1972, 13, 806. Haber, E., Koerner, T., Page, L. B., Kliman, B., Purnode, A. J. clin. Endocr. 1969, 29, 1349. Kritzinger, E. C., Kanengoni, E., Jones, J. J. Lancet, 1972, i, 412. Craswell, P. W., Hird, V. M., Judd, P. A., Baillod, R. A., Varghese, Z., Moorhead, J. F. Br. med. J. 1972, iv, 749. Ryan, J. W., McKenzie, J. K., Lee, M. R. Third International Congress of Nephrology, abstract 265. Washington, 1966. Ryan, J. W., McKenzie, J. K., Lee, M. R. Biochem. J. 1968, 108, 679. Stockigt, J. R., Collins, R. D., Biglieri, E. G. Circulation Res. 1971, 28/29, suppl. 2, p. 175. Stockigt, J. R., Collins, R. D., Noakes, C. A., Schambelan, M., Biglieri, E. G. Lancet, 1972, i, 1194. Vallotton, M. B. Horm. metab. Res. 1971, suppl. 3, p. 94. Boyd, G. W., Adamson, A. R., Fitz, A. E., Peart, W. S. Lancet, 1969, i, 213.
sleepiness). Steg,
we
did
Departments of Internal Medicine and Pharmacology, Yale University School of Medicine MELVIN H. VAN WOERT New Haven, Connecticut, U.S.A. LALIT M. AMBANI.
SUSTAINED-RELEASE LEVODOPA
SIR,-Our clinical observations with a sustainedrelease form of levodopa (’ Brocadopa Temtabs ’) agree with those already reported,!.2 although we question the conclusion that such preparations have no practical value. It now appears that the " on/off " response to levodopa occurs with increasing frequency and severity as the duration of treatment lengthens. If this brittle response is mainly due to the fluctuations in circulating dopa levels which attend the oral administration of standard levodopa preparations, then sustained-release formulations might prove helpful. We studied 3 parkinsonian patients who manifested the " on/off " response to levodopa. Each was observed over 6-9 hours while kept fasting and supine in bed. Levodopa was given orally at optimum therapeutic dose levels every 2t hours in combination with a peripheral decarboxylase inhibitor (MK 486, ’Carbidopa’) 25 mg. every 5 hours. Plasma-dopa levels rose sharply after each dose of levodopa (see figure). Peak circulating levels of the aminoacid were generally followed by periods of maximum suppression of parkinsonism and the appearance of dyskinesias, while low plasma-dopa values presaged the return of severe parkinsonian signs and the disappearance of dyskinesias. When these patients were studied under the same conditions but received levodopa by means of a 1. 2.
Eckstein, B., Shaw, K., Sten, G. Lancet, Feb. 24, 1973, p. 431. Curzon, G., Friedel, J., Grier, L., Marsden, C. D., Parker, J. D., Shipley, M., Zilkhak, J. ibid. April 7, 1973, p. 781.
HOURS
Effect of oral or intravenous levodopa on plasma-dopa concentrations (0----0), overall parkinsonian severity (8-8), and degree of
Oral
dyskinesias (A-A). every 2! hours
levodopa given
severity scored
Dyskinesias
( ).
scale of 0 (absent) to 12 rated between 0 (absent) and 4 (very on
a
Parkinsonian
(very severe). severe).
constant intravenous infusion, relatively steady plasma levels of the aminoacid were associated with a notably stable clinical response (see figure). From these observations we conclude that the on/off response to orally administered levodopa under the above conditions is largely due to fluctuations in circulating dopa levels rather than to some centrally mediated mechanism. As shown by Curzon et al.,2the irregular response to the available sustained-release levodopa preparation reflects the failure of this compound to maintain clinically effective plasma-dopa concentrations for significantly longer periods than the standard form of levodopa. An effective sustainedrelease preparation which substantially reduced these fluctuations in blood levels should benefit parkinsonian patients. Therefore, additional efforts directed towards development of such a preparation should be profitable.
Neurology Unit, National Institute of Mental
Health, Bethesda, Maryland 20014, U.S.A.
ANNE C. WOODS GEORGE A. GLAUBIGER THOMAS N. CHASE.
BRAIN DEATH AS DETERMINED BY CEREBRAL ARTERIOGRAPHY
SIR,-The accepted definition of brain death in patients with cardiac function includes complete unreceptivity and unresponsivity to intense stimulation, lack of spontaneous respirations or movement, areflexia, and two flat electroencephalograms (E.E.G.S) at least 24 hours apart3 in the This absence of hypothermia or depressant drugs.3 definition of brain death was a major breakthrough, but many potential donor organs are lost during the 24-hour waiting-period, because cardiac function and/or renal perfusion cannot be adequately maintained. I should like to propose the substitution of complete absence of intracranial circulation for the two flat E.E.G.S in determining brain death. Retrograde four-vessel cerebral arteriography by the Seldinger method would be the quickest and perhaps the easiest method to assess the absence of intracranial bloodA left carotid arteriogram and a right brachial flow. arteriogram, however, would also suffice. A unilateral carotid arteriogram would not be sufficient, because in unilateral intracranial lesions the pressure in the right and left anterior and middle fossa and that in the posterior fossa are not necessarily equal. 4,5 If the contrast material puddled in the major neck vessels and none entered the intracranial circulation over a 5-minute period, then, with the other criteria being met (excluding two E.E.G.S 24 hours apart), brain death could be declared. Riishede and Ethelberg 6 in 1953 reported non-filling of the intracranial portion of the internal carotid artery in 5 patients with space-occupying intracranial lesions, and they attributed it to tentorial herniation. Horowitz and Dunsmorethought non-filling to be secondary to diencephalic reflexes, and Newton and Couch 11 suggested it might be due to arterial spasm. Pribram9 first proposed that nonfilling of the internal carotid above the siphon is due to increased intracranial pressure, and Mitchell et al. 10 experimentally confirmed that, when the intracranial pressure exceeds the systolic blood-pressure, intracranial blood-flow ceases. Mitchell et al. presented 5 cases of non-filling and 3. J. Am. med. Ass. 1968, 205, 337. 4. Cantu, R. C. Int. Surg. 1972, 57, 668. 5. Langfitt, T. W., Weinstein, J. D., Cassell, N. F., Gagliardi, L. J. J. Neurosurg. 1964, 21, 998. 6. Riishede, J., Ethelberg, S. Archs Neurol. Psychiat. 1953, 70, 399. 7. Horowitz, N. H., Dunsmore, R. H. J. Neurosurg. 1956, 13, 155. 8. Newton, T. H., Couch, R. S. C. Radiology, 1960, 75, 766. 9. Pribram, H. F. W. Neurology, Minneap. 1960, 11, 10. 10. Mitchell, O. C., Torre, E., Alexander, E., Davis, C. H. J. Neurosurg. 1962, 19, 766.
, JUNE 16 out that none had a demonstrable pressure cone when the brain was removed at necropsy. They also discussed a case of an infant in opisthotonos in which a left vertebral arteriogram showed vertebral filling but no filling of the basilar artery, illustrating that the intracranial posterior circulation can be arrested when the pressure within the posterior fossa exceeds the systolic bloodThis confirms that, in cases pressure. They concluded, of acutely raised intracranial pressure, the cerebral circulation is slowed to such an extreme that death is inevitable." Today, many potential donor organs are lost from patients with irreversible brain damage because of the required waiting-period of at least 24 hours to obtain two flat E.E.G.s. The waiting-period is often longer than 24 hours if E.E.G.s are not readily available. The importance of this loss is brought into perspective when we realise that there are now 70 people on dialysis awaiting cadaverkidney transplantation at one major Boston hospital alone.
pointed
"
Neurosurgical Service, Emerson Hospital, Concord, Massachusetts 01742, U.S.A.
ROBERT C. CANTU.
REORGANISATION—RATES FOR THE
JOBS
SIR,-Your editorial (June 2, p. 1228) might have gone further and remarked that no salary scales for medical administrators have yet been published or posts advertised notwithstanding. There may be more bitter pills to be swallowed. 47
Corstorphine Bank Drive, Edinburgh EH12 8RH.
G. G. SAVAGE.
The lymphocytes can be easily pipetted off and collected. The viability of the lymphocytes after washing and resuspension in phosphate-buffered saline or tissue-culture medium approaches 98%(as measured by trypan-blue exclusion). The lymphocytes were shown to react in various tests measuring blastogenesis and cytotoxicity. The recovery-rate of lymphocytes from normal blood with this technique exceeds 70%. University of Texas at Houston, M. D. Anderson Hospital and Tumor Institute, Houston, Texas, U.S.A.
KAMRAN TEBBI.*
RADIOIMMUNOASSAY OF PLASMA-RENIN ACTIVITY
SIR,-In a comparison of the Schwarz-Mann and Squibb commercial kits for the measurement of plasmarenin activity by radioimmunoassay of angiotensin-I production, Chervu et aLl used 10 1. of dimercaprol (8 mM) as inhibitor in each case, although only 2 jjj. of dimercaprol (1-6 mM) is recommended in the SchwarzMann kit. Chervu et al. did not mention any reason for this alteration, but there is considerable variation, from 1-6 2-4 to 8-0 mM,l in the amount of dimercaprol used by various investigators of angiotensin-I activity, the main differences being typified by the low concentration recommended in the Schwarz-Mann kit, and the high concentrations used in the Squibb kit. Ryan et al.,5,6 who originally recommended the use of dimercaprol to inhibit angiotensinases, used a concentration of 10 mM before
bioassay. PURIFICATION OF LYMPHOCYTES
SiR,-Several methods for the separation of lymphocytes from other cellular elements of the blood are available.1-3 The ’Ficoll ’-’ Hypaque ’ method1 is probably the easiest and most useful. With this technique, however, some contamination with granulocytes and monocytes is unavoidable in 5-10% of specimens. In addition, some of the monocytes that contaminate the lymphocyte preparation become " activated " during this procedure; thus, nonspecific reactions can occur. The following technique has proved very successful in eliminating contamination of the lymphocyte preparation with granulocytes and monocytes. It is based on phagocytosis of colloidal iron particles by blood leucocytes before centrifugation in ficoll-hypaque gradient. Simple laboratory facilities In
are
required.
clean 100 x 16 mm. glass tube, 2 ml. buffy-coat leucocytes separated from heparinised blood are mixed with 1 ml. 10% carbonyl iron (G.A.F. Corporation, New York, N.Y.) suspended in 10% acacia solution. The mixture is incubated for 30 minutes at 37 °C on a rocker at 30 revolutions per minute (Ames Co., Indiana). After adding 2 ml. normal saline, the contents are carefully laid over 3 ml. separating fluid " in another 100 x 16 mm. glass tube. The " separating fluid " consists of 9% ficoll (Farmacetica, Uppsala, Sweden) and 34% hypaque (Winthrop Laboratories, New York, N.Y.) in ratio of 2-4/1 to give a specific gravity of 1-076-1-078. The tube is centrifuged for 30 minutes at 20°C at 1300 r.p.m. Four distinct layers separate in the centrifuged tube. The upper layer consists of the plasma and saline. The next layer is that of the purified lymphocytes. Repeated studies indicate contamination with granulocytes or monocytes to be less than 0-5%. The third layer consists of the clear ficollhypaque mixture. The fourth layer is the sediment containing all the red cells and the iron-laden granulocytes and monocytes a
"
We are using a kit manufactured by Societa Ricerche Nucleari (SORIN) which, like the Schwarz-Mann kit, is based on the method of Haber et al.,2 who used 1-60 mM dimercaprol. These authors did not mention the reason for choosing this low concentration and hence it may not be optimal. This problem is emphasised by our own results. In June, 1972, SORIN changed the recommended amount of dimercaprol from 2 ,1. (1-6 mM) to 6 1. (4-8 mM). Since no explanation for the change was offered we compared estimations using the two concentrations, and found a substantial increase in the measured plasma-renin activity when using the higher concentration of inhibitor. Ten samples of normal plasma, collected after one hour’s rest, gave mean results (s.D.) of 0-33:0-16 ng. angiotensin I per ml. per hour using 1-6 mM dimercaprol and 0-740-36 ng. per ml. per hour using 4-8 mM dimercaprol, an increase of x 2-2. The most probable explanation for the difference is that the lower concentration of dimercaprol does not completely inhibit the enzymic degradation of
Impianti
angiotensin
*
Present address: St. Louis Children’s Hospital, St. Louis, Missouri 63110, U.S.A. 1.
2. 3. 4. 5. 6. 7.
(macrophages). 8. 1. 2.
3.
Harris, R., Ukaejiofo, E. O. Lancet, 1969, ii, 327. Thorsby, E., Bratlie, A. in Histocompatibility Testing (edited by P. I. Terasaki); p. 665. Copenhagen, 1970. Gelsthorpe, K., Doughty, W., Fox, M. Br. J. Surg. 1970, 57, 358.
i.
Further work is required to establish the optimum inhibitor effect, but several workers 7-10 have already
9. 10.
Chervu, L. R., Lory, M., Liang, T., Lee, H. B., Blaufox, M. D. J. nucl. Med. 1972, 13, 806. Haber, E., Koerner, T., Page, L. B., Kliman, B., Purnode, A. J. clin. Endocr. 1969, 29, 1349. Kritzinger, E. C., Kanengoni, E., Jones, J. J. Lancet, 1972, i, 412. Craswell, P. W., Hird, V. M., Judd, P. A., Baillod, R. A., Varghese, Z., Moorhead, J. F. Br. med. J. 1972, iv, 749. Ryan, J. W., McKenzie, J. K., Lee, M. R. Third International Congress of Nephrology, abstract 265. Washington, 1966. Ryan, J. W., McKenzie, J. K., Lee, M. R. Biochem. J. 1968, 108, 679. Stockigt, J. R., Collins, R. D., Biglieri, E. G. Circulation Res. 1971, 28/29, suppl. 2, p. 175. Stockigt, J. R., Collins, R. D., Noakes, C. A., Schambelan, M., Biglieri, E. G. Lancet, 1972, i, 1194. Vallotton, M. B. Horm. metab. Res. 1971, suppl. 3, p. 94. Boyd, G. W., Adamson, A. R., Fitz, A. E., Peart, W. S. Lancet, 1969, i, 213.