452
immunological explanation since leucocyteantibodies to fetal antigens can be demondependent strated in older women who have been pregnant (unpublished results). The above hypothesis appears to be important in relation to recent questions about the validity of the immune surveillance theory. 10 The relative incidence of melanoma in males and females in this study was approximately equal ( 1 13/1 00), although other investigations have shown a slight female preponderance.* This implies that the immune response to fetal antigens on melanoma cells does not prevent the occurrence of tumours since the incidence would then be expected to be lower in females with previous pregnancies than in males. Our results may therefore indicate that the immune response to tumours is important not in preventing their occurrence, as proposed in the immune surveillance theory, 11 but in preventing dissemination of melanoma cells and death from the tumour. may have
an
This work was supported by the Bill White Melanoma Fund and the New South Wales State Cancer Council. We thank Sister P. Dilworth for assistance in research of the melanoma files.
Requests for reprints should be addressed to P. H. REFERENCES
2--Cumulative survival-rates of women presenting with melanoma according to whether they had pregnancies prior to melanoma developing and their age on presenation.
Fig.
both groups was much better for those under 50 than in those over 50. In those under 50 the 5-year survival-rate was 83% in those with previous pregnancy and 73% in those without previous pregnancy compared with 73% and 53%, respectively, for those over 50. The effect of the stage of melanoma at presentation was also assessed. Differences between women with previous pregnancies and no previous pregnancies were apparent irrespective of the stage, although the differences were not statistically significant by the x2 test. The 5-year survival-rates for women with stage-1 melanoma with previous pregnancies was- 84% compared with 75% for those with no previous pregnancies. Comparable 5-year survival-rates for patients presenting with stage 2 or 3 melanoma were 38% and 29%, respectively. Discussion Women with melanoma have a much better survivalthan men with melanoma.89 Our results indicate that there is also a difference in survival-rates among women according to whether or not they had ever been pregnant before melanoma developed. The better survival in those who had been pregnant could not be explained in terms of a disparity in the age distribution of patients or stage of the disease at presentation, and presumably reflects a biological difference between the two groups of women. Although the reason for this difference in survivalrates is not known, the previous demonstration of both fetal antigens on melanoma cellsl-4 and the presence of an immune response to fetal antigens in pregnant women offers a possible explanation. The response of women who have already been exposed to fetal antigens could be expected to be more rapid and more vigorous on re-exposure to fetal antigens on melanoma cells. The reason for the more pronounced disparity in older women between the two groups is not clear, but again rate
1.
Hersey, P., Honeyman, M., Edwards, A., Adams, E., McCarthy, W. H. Int. J. Cancer (in the press). 2. Lewis, M. G., Sheikh, K. M. A. Behring Inst. Mitt. 1975, 56, 78. 3. Macher, E., Muller, C. H. R., Sorg, G., Gassen, A., Sorg, C. ibid. p. 86. 4. Viza, D., Phillips, J. and Trejdosiewicz, L. K. ibid. p. 83. 5. Cutler, S. J., Ederer, F. J. chron. Dis. 1958, 8, 699. 6. Peto, R., Peto, J. J. R. statist. Soc. A, 1972, 135, 185. 7. Pike, M. C. Rec. Res. Cancer Res. 1973, 43, 126. 8. McLeod, G. R., Beardmore, G. L., Little, J. H., Quinn, R L., Davis, N. C. Med. J. Aust. 1971, i, 1211. 9. Nathanson, L., Hall, T. C., Farber, S. Cancer, 1967, 20, 650. 10. Schwartz, R. S. New Engl. J. Med. 1975, 293, 181. 11. Burnet, F. M. Prog. exp. Tumor Res. 1970, 13, i.
Preliminary Communication RADIOLABELLED ANTI-HUMAN FIBRIN ANTIBODY: A NEW THROMBUS-DETECTING AGENT VLADIMIR B.
BOŠNJAKOVIĆ
Radioisotope Laboratory, Faculty of Medicine, Belgrade, Yugoslavia BRANISLAV D.
JANKOVIĆ
JOZEF HORVAT
Immunology Research Centre, Belgrade, Yugoslavia
JELISAVKA ČVORIC Institute Boris
Kidrič, Vinča, Belgrade, Yugoslavia
Rabbit anti-human fibrin globulin (A.F.G.) was labelled with iodine (131I) and used as a thrombus-detecting agent. 131I-A.F.G. labelled thrombi were displayed by means of a gamma scintillation camera. Normal subjects and patients with thrombophlebitis of legs, acute fibrin depositions other than thrombi, and chronic varicosities were examined. The 131I-A.F.G. technique detected both formed thrombi and those that were forming and could discriminate between
Summary
thrombosis and chronic varicosities. Thromboand extravascular fibrin depositions were best demonstrated between 24 and 72 hours of 131I-A.F.G. inacute
phlebitis
453
jection. Radiolabelled A.F.G. in normal veins and chronic varicosities was best displayed within 6 hours of injection. INTRODUCTION
ALTHOUGH many radiopharmaceuticals have been used to detect thrombi,I-7 none has proved to be more advantageous than any other. Since thrombi contain substantial amounts of fibrin, we used radiolabelled anti-human fibrin antibody as a specific agent for localising thrombi. We describe the preparation of radiolabelled rabbit anti-human fibrin antibody and the initial clinical diagnostic trials. MATERIALS AND METHODS
Preparation and Radiolabelling of Anti-human Fibrin Globulin (A.F.G.) 30 mg of human fibrin particles which could easily be passed a no. 26 needle were suspended in saline solution, emulsified with complete Freund adjuvant, and injected intramuscularly and subcutaneously into a rabbit. Further injections of 30 mg of fibrin without adjuvant were given intraperitoneally and subcutaneously at monthly intervals. Serum samples were collected 10 days after each challenge and heatinactivated. Since rabbit antisera thus prepared cross-reacted with human fibrinogen,8 they were absorbed first with 1 ml of packed human erythrocytes per 10 ml of antiserum, then with 100 mg of insolubilised9 human fibrinogen per ml of antiserum, and finally with 10 mg of insolubilised9 human serum proteins per ml of antiserum. Incubation with each immunoabsorbent lasted 1 hour at 37°C, 2 hours at 22°C, and overnight at 8°C. Normal rabbit sera were adsorbed in an identical manner. The globulin fraction was precipitated by ammonium sulphate and protein concentrations were determined by a
through
a sterile Millipore (0.25 p.m) filter the 13’1-A.F.G. contained 1.5-2.0 mCi/ml of 13’I and about 6 mg/ml of protein. Electrophoretic and immunodiffusion analyses showed that A.F.G. was not denaturated by radioiodination. The presence of anti-human fibrin antibody in non-radioiodinated and radioiodinated A.F.G. was detected by Ouchterlony double diffusion
through
in 0.8% agarose.
Patients and Scintigrams Twelve subjects in whom A.F.G. did not produce positive skin reactions were studied. Three young normal volunteers and two patients, one with a fresh hand wound and one with a gangrenous foot, were investigated to determine the accumulation of A.F.G. in fibrin deposits other than thrombi. Three patients with varicosities of the legs but without clinical signs of thrombosis were investigated to determine the effect of dilated bloodvessels and venous stasis on "’1-A.F.G. uptake. Four patients with acute thromboses of the legs were examined at various times after the onset of thrombophlebitis. The patients studied were given Lugol’s solution before intravenous injection of 10-15 Ci of 13’I_n.F.G./kg body-weight into the forearm. A series of scintigrams was obtained with an Anger gamma scintillation camera (Searle, Pho-Gamma HP) by means of a diverging 410 keV collimator and a 35% window with a 364 keV photopeak. 13 ’I-A.F.G. distribution was studied in bloodvessels of pelvic area and lower extremities, and in the heart, liver, and bladder. Scintigrams were taken at 1-hour intervals
biuret reaction. A.F.G. was
method’O in
radioiodinated with 13’I a
by a modified electrolytic platinum electrolytic cell. After being passed
Fig. I-Ouchterlony
double diffusion in
gel
of
globulin
fraction
of A.F.G. Centre well
contains
"’1-A.F.G. absorbed with human
erythrocytes,
fibrinogen, and serum proteins. Other wells contain: (1) human fibrin (30 mg/ml of saline); (2) human fibrin (15 mg/ml); (3) human fibrinogen (30 mg/ml of saline); (4) human fibrinogen (15 mg/ml); (5) normal human serum diluted 1/2; and (6) "’1-A.F.G. absorbed with human erythrocytes, fibrinogen,. serum proteins, and fibrin (20 mg of fibnn/ml OfA.F.G.); incubation at room temperature for 2 h and overnight at 4°C, and centrifuged at 15 000 r.p.m. for 30 mm). Note the reaction of identity between ’-"1-A.F.G. in centre well and fibrin in wells 1 and 2. Human fibrmogen and normal serum did not produce precipitmlines with A.F.G. Absence of precipitin band between wells 1 and 6 demonstrates that absorption of A.F.G. with human fibrin removed anti-human fibrin antibodies from
A.F.G.
Fig. 2-Scintigrams obtained 48 hour§ after 13II-A.F.G. injection in a patient with varicosities of both legs and thrombophlebitis of the left leg (top). Uptake of ’3’I-a.F.. was greater in the thrombophlebitic veins of the left (L) thigh and calf than m the varicosities of the right (R) thigh and calf (bottom).
454 on the first day and then at 72 hours after the injection of 13’1-A.F.G.
up to 6 hours to
daily
intervals up
Hypothesis
RESULTS
In immunodiffusion tests "1-A.F.G. reacted only with human fibrin (fig. 1). The average biological half-life of 1-A.F.G. in three normal subjects was 2.7 days, and in a patient with acute thrombophlebitis of both legs it was. 1.88 days. The investigation to determine the normal distribution of labelled A.F.G. in controls found an increased accumulation during first few hours in the heart and liver and in the iliac and femoral blood-vessels; this was followed by a gradual decrease. Uptake of ’1-A.F.G. by
thrombi reached a maximum 48 hours after injection, as judged by the intensity of the scintigram. The difference in "’1-A.F.G. uptake by thrombi and varicosities was also greatest 48 hours after injection. The uptake ratio was highest in those patients with thrombi, intermediate in those with varicosities, and lowest in those with normal veins. In a woman in her sixties with recurrent thromboses, thrombophlebitis had started in the left leg 7 days before the injection of 13l!-A.F.G. The scintigram obtained 48 hours after injection accorded well with the clinical changes, in that an increased uptake of 13 ’I-A.F.G. and a well-defined outline of the thrombophlebitic areas of the enlarged varicosities of the left thigh and calf were demonstrated. The non-mnamed varicosities of the right leg were less well defined (fig. 2). Extravascular deposits of 131!-A.F.G. in fibrin were found in the patient who had a gangrenous foot, and the one with a fresh hand injury, the uptake of labelled A.F.G. being highest 48 hours after the injection. DISCUSSION
Various
radiolabelled agents, 1-1, including antifibrinogen antibody,7 have been used to localise thrombi. However, the use of anti-fibrinogen antibody was restricted by its cross-reactivity with fibrin. The anti-fibrin antibody tested in the present study has the advantages of pronounced specificity for fibrin and the ability to detect both forming and formed thrombi. Our results suggest that 131I-A.F.G. can also discriminate between acute thrombosis and chronic varicosities. The most discriminant thrombus-to-normal or thrombus-to-varices ’1-A.F.G. ratios in the veins of lower extremities were found 24 and 48 hours after the injection, thus indicating that this was the best time to scan for thrombi. Compared with the low rate of uptake in the heart cavities at 24 hours such an accumulation-rate in the blood-vessels implies that coronary thrombosis might be displayed by this method. Further, the observation that the 24-hour period after injection of A.F.G. is sufficient for the display of thrombi indicates that iodine-123, with its 13-hour physical half-life, could also be used as a radiotracer with A.F.G. The risk of sensitisation to rabbit immunoglobulins is a disadvantage of
SILICON, FIBRE, AND ATHEROSCLEROSIS KLAUS SCHWARZ
Laboratory of Experimental Metabolic Diseases, Hospital, Long Beach, California,
Veterans Administration
U.S.A. and
Department of Biological Chemistry, School of Medicine, University of California, Los Angeles, California
logical argument can be made for the hypothesis that lack of silicon may be an important ætiological factor in atherosclerosis. As silicic acid or its derivatives, silicon is essential for growth. It is found mainly in connective tissue, where it functions as a cross-linking agent. Unusually high amounts of bound silicon are present in the arterial wall, especially in the intima. Various kinds of dietary fibre have been reported to be effective in preventing experimental models of atherosclerosis, reducing cholesterol and blood-lipid levels, and binding bile acids in vitro. Exceptionally large amounts of silicon (1000 to 25 000 p.p.m.) were found in fibre products of greatly varying origin and chemical composition which were active in these tests. Inactive materials, such as different types of purified cellulose, contained only negligible quantities of the element. It is concluded that silicate-silicon may be the active agent in dietary fibre which affects the development of atherosclerosis. Two out of three samples of bran also had relatively low levels, which could explain why bran does not lower serum-cholesterol. The fact that atherosclerosis has a low incidence in less developed countries may be related to the availability of dietary silicon. Two instances are presented where silicon is reduced by industrial treatment: white flour and refined soy products were much lower in silicon than—their respective crude natural products. The chemical nature of Summary
silicon in different types of fibre is not known. It could exist as orthosilicic acid, polymeric silicic acid, colloidal silica (opal), dense silica concretions, or in the form of organically bound derivatives of silicic acid (silanolates). Possible mechanisms of action are discussed. INTRODUCTION
IN 1972 we demonstrated, by means of a plastic traceelement-sterile isolator system and highly purified DR
4. 5.
Siegel,
620.
6.
by grants from the Republic Research
Requests for reprints should be addressed to V.B.B.
BOŠNJAKOVIĆ AND OTHERS: REFERENCES
Atkins, P., Hawkins, L. A. Lancet, 1965, ii, 1217. Kakkar, V. V. Archs Surg. 1972, 104, 152. Charkes, N. D., Dugan, M. A., Maier, W. P., Soulen, R., Escovitz, E., Learner, N., Dubin, R., Kozer, J. J. nucl. Med. 1974, 15, 1163. Webber, M. M., Bennett, L. R., Cragin, M., Webb, R. Radiology, 1969, 92,
1. 2. 3.
A.F.G.
This work was supported Fund of Serbia, Belgrade.
A
7.
8. 9. 10.
M. E., Malmud, L. S., Rhodes, B. A., Bell, W. S., Wagner, H. N., Jr. ibid. 1972, 103, 695. Coleman, R. E., Harwing, S. S. L., Harwing, J. F., Sherman, L. A., Welch, M. J. Circulation Res. 1975,17, 542. Spar, I. L., Varen, M. I., Goodland, R. L., Schwartz, S. I. Archs Surg. 1966. 92, 752. Gitlin, D., Landing, B. H., Whipple, A. J. exp. Med. 1953, 97, 163. Avrameas, S., Ternynck, T. Immunochemistry, 1969, 6, 53. Jovanovic, V., Nemoda, Dj., Lwin, K. Int. J. appl. Radiat. Isotopes, 1972.
23, 242.
i
immunological explanation since leucocyteantibodies to fetal antigens can be demondependent strated in older women who have been pregnant (unpublished results). The above hypothesis appears to be important in relation to recent questions about the validity of the immune surveillance theory. 10 The relative incidence of melanoma in males and females in this study was approximately equal ( 1 13/1 00), although other investigations have shown a slight female preponderance.* This implies that the immune response to fetal antigens on melanoma cells does not prevent the occurrence of tumours since the incidence would then be expected to be lower in females with previous pregnancies than in males. Our results may therefore indicate that the immune response to tumours is important not in preventing their occurrence, as proposed in the immune surveillance theory, 11 but in preventing dissemination of melanoma cells and death from the tumour. may have
an
This work was supported by the Bill White Melanoma Fund and the New South Wales State Cancer Council. We thank Sister P. Dilworth for assistance in research of the melanoma files.
Requests for reprints should be addressed to P. H. REFERENCES
2--Cumulative survival-rates of women presenting with melanoma according to whether they had pregnancies prior to melanoma developing and their age on presenation.
Fig.
both groups was much better for those under 50 than in those over 50. In those under 50 the 5-year survival-rate was 83% in those with previous pregnancy and 73% in those without previous pregnancy compared with 73% and 53%, respectively, for those over 50. The effect of the stage of melanoma at presentation was also assessed. Differences between women with previous pregnancies and no previous pregnancies were apparent irrespective of the stage, although the differences were not statistically significant by the x2 test. The 5-year survival-rates for women with stage-1 melanoma with previous pregnancies was- 84% compared with 75% for those with no previous pregnancies. Comparable 5-year survival-rates for patients presenting with stage 2 or 3 melanoma were 38% and 29%, respectively. Discussion Women with melanoma have a much better survivalthan men with melanoma.89 Our results indicate that there is also a difference in survival-rates among women according to whether or not they had ever been pregnant before melanoma developed. The better survival in those who had been pregnant could not be explained in terms of a disparity in the age distribution of patients or stage of the disease at presentation, and presumably reflects a biological difference between the two groups of women. Although the reason for this difference in survivalrates is not known, the previous demonstration of both fetal antigens on melanoma cellsl-4 and the presence of an immune response to fetal antigens in pregnant women offers a possible explanation. The response of women who have already been exposed to fetal antigens could be expected to be more rapid and more vigorous on re-exposure to fetal antigens on melanoma cells. The reason for the more pronounced disparity in older women between the two groups is not clear, but again rate
1.
Hersey, P., Honeyman, M., Edwards, A., Adams, E., McCarthy, W. H. Int. J. Cancer (in the press). 2. Lewis, M. G., Sheikh, K. M. A. Behring Inst. Mitt. 1975, 56, 78. 3. Macher, E., Muller, C. H. R., Sorg, G., Gassen, A., Sorg, C. ibid. p. 86. 4. Viza, D., Phillips, J. and Trejdosiewicz, L. K. ibid. p. 83. 5. Cutler, S. J., Ederer, F. J. chron. Dis. 1958, 8, 699. 6. Peto, R., Peto, J. J. R. statist. Soc. A, 1972, 135, 185. 7. Pike, M. C. Rec. Res. Cancer Res. 1973, 43, 126. 8. McLeod, G. R., Beardmore, G. L., Little, J. H., Quinn, R L., Davis, N. C. Med. J. Aust. 1971, i, 1211. 9. Nathanson, L., Hall, T. C., Farber, S. Cancer, 1967, 20, 650. 10. Schwartz, R. S. New Engl. J. Med. 1975, 293, 181. 11. Burnet, F. M. Prog. exp. Tumor Res. 1970, 13, i.
Preliminary Communication RADIOLABELLED ANTI-HUMAN FIBRIN ANTIBODY: A NEW THROMBUS-DETECTING AGENT VLADIMIR B.
BOŠNJAKOVIĆ
Radioisotope Laboratory, Faculty of Medicine, Belgrade, Yugoslavia BRANISLAV D.
JANKOVIĆ
JOZEF HORVAT
Immunology Research Centre, Belgrade, Yugoslavia
JELISAVKA ČVORIC Institute Boris
Kidrič, Vinča, Belgrade, Yugoslavia
Rabbit anti-human fibrin globulin (A.F.G.) was labelled with iodine (131I) and used as a thrombus-detecting agent. 131I-A.F.G. labelled thrombi were displayed by means of a gamma scintillation camera. Normal subjects and patients with thrombophlebitis of legs, acute fibrin depositions other than thrombi, and chronic varicosities were examined. The 131I-A.F.G. technique detected both formed thrombi and those that were forming and could discriminate between
Summary
thrombosis and chronic varicosities. Thromboand extravascular fibrin depositions were best demonstrated between 24 and 72 hours of 131I-A.F.G. inacute
phlebitis
453
jection. Radiolabelled A.F.G. in normal veins and chronic varicosities was best displayed within 6 hours of injection. INTRODUCTION
ALTHOUGH many radiopharmaceuticals have been used to detect thrombi,I-7 none has proved to be more advantageous than any other. Since thrombi contain substantial amounts of fibrin, we used radiolabelled anti-human fibrin antibody as a specific agent for localising thrombi. We describe the preparation of radiolabelled rabbit anti-human fibrin antibody and the initial clinical diagnostic trials. MATERIALS AND METHODS
Preparation and Radiolabelling of Anti-human Fibrin Globulin (A.F.G.) 30 mg of human fibrin particles which could easily be passed a no. 26 needle were suspended in saline solution, emulsified with complete Freund adjuvant, and injected intramuscularly and subcutaneously into a rabbit. Further injections of 30 mg of fibrin without adjuvant were given intraperitoneally and subcutaneously at monthly intervals. Serum samples were collected 10 days after each challenge and heatinactivated. Since rabbit antisera thus prepared cross-reacted with human fibrinogen,8 they were absorbed first with 1 ml of packed human erythrocytes per 10 ml of antiserum, then with 100 mg of insolubilised9 human fibrinogen per ml of antiserum, and finally with 10 mg of insolubilised9 human serum proteins per ml of antiserum. Incubation with each immunoabsorbent lasted 1 hour at 37°C, 2 hours at 22°C, and overnight at 8°C. Normal rabbit sera were adsorbed in an identical manner. The globulin fraction was precipitated by ammonium sulphate and protein concentrations were determined by a
through
a sterile Millipore (0.25 p.m) filter the 13’1-A.F.G. contained 1.5-2.0 mCi/ml of 13’I and about 6 mg/ml of protein. Electrophoretic and immunodiffusion analyses showed that A.F.G. was not denaturated by radioiodination. The presence of anti-human fibrin antibody in non-radioiodinated and radioiodinated A.F.G. was detected by Ouchterlony double diffusion
through
in 0.8% agarose.
Patients and Scintigrams Twelve subjects in whom A.F.G. did not produce positive skin reactions were studied. Three young normal volunteers and two patients, one with a fresh hand wound and one with a gangrenous foot, were investigated to determine the accumulation of A.F.G. in fibrin deposits other than thrombi. Three patients with varicosities of the legs but without clinical signs of thrombosis were investigated to determine the effect of dilated bloodvessels and venous stasis on "’1-A.F.G. uptake. Four patients with acute thromboses of the legs were examined at various times after the onset of thrombophlebitis. The patients studied were given Lugol’s solution before intravenous injection of 10-15 Ci of 13’I_n.F.G./kg body-weight into the forearm. A series of scintigrams was obtained with an Anger gamma scintillation camera (Searle, Pho-Gamma HP) by means of a diverging 410 keV collimator and a 35% window with a 364 keV photopeak. 13 ’I-A.F.G. distribution was studied in bloodvessels of pelvic area and lower extremities, and in the heart, liver, and bladder. Scintigrams were taken at 1-hour intervals
biuret reaction. A.F.G. was
method’O in
radioiodinated with 13’I a
by a modified electrolytic platinum electrolytic cell. After being passed
Fig. I-Ouchterlony
double diffusion in
gel
of
globulin
fraction
of A.F.G. Centre well
contains
"’1-A.F.G. absorbed with human
erythrocytes,
fibrinogen, and serum proteins. Other wells contain: (1) human fibrin (30 mg/ml of saline); (2) human fibrin (15 mg/ml); (3) human fibrinogen (30 mg/ml of saline); (4) human fibrinogen (15 mg/ml); (5) normal human serum diluted 1/2; and (6) "’1-A.F.G. absorbed with human erythrocytes, fibrinogen,. serum proteins, and fibrin (20 mg of fibnn/ml OfA.F.G.); incubation at room temperature for 2 h and overnight at 4°C, and centrifuged at 15 000 r.p.m. for 30 mm). Note the reaction of identity between ’-"1-A.F.G. in centre well and fibrin in wells 1 and 2. Human fibrmogen and normal serum did not produce precipitmlines with A.F.G. Absence of precipitin band between wells 1 and 6 demonstrates that absorption of A.F.G. with human fibrin removed anti-human fibrin antibodies from
A.F.G.
Fig. 2-Scintigrams obtained 48 hour§ after 13II-A.F.G. injection in a patient with varicosities of both legs and thrombophlebitis of the left leg (top). Uptake of ’3’I-a.F.. was greater in the thrombophlebitic veins of the left (L) thigh and calf than m the varicosities of the right (R) thigh and calf (bottom).
454 on the first day and then at 72 hours after the injection of 13’1-A.F.G.
up to 6 hours to
daily
intervals up
Hypothesis
RESULTS
In immunodiffusion tests "1-A.F.G. reacted only with human fibrin (fig. 1). The average biological half-life of 1-A.F.G. in three normal subjects was 2.7 days, and in a patient with acute thrombophlebitis of both legs it was. 1.88 days. The investigation to determine the normal distribution of labelled A.F.G. in controls found an increased accumulation during first few hours in the heart and liver and in the iliac and femoral blood-vessels; this was followed by a gradual decrease. Uptake of ’1-A.F.G. by
thrombi reached a maximum 48 hours after injection, as judged by the intensity of the scintigram. The difference in "’1-A.F.G. uptake by thrombi and varicosities was also greatest 48 hours after injection. The uptake ratio was highest in those patients with thrombi, intermediate in those with varicosities, and lowest in those with normal veins. In a woman in her sixties with recurrent thromboses, thrombophlebitis had started in the left leg 7 days before the injection of 13l!-A.F.G. The scintigram obtained 48 hours after injection accorded well with the clinical changes, in that an increased uptake of 13 ’I-A.F.G. and a well-defined outline of the thrombophlebitic areas of the enlarged varicosities of the left thigh and calf were demonstrated. The non-mnamed varicosities of the right leg were less well defined (fig. 2). Extravascular deposits of 131!-A.F.G. in fibrin were found in the patient who had a gangrenous foot, and the one with a fresh hand injury, the uptake of labelled A.F.G. being highest 48 hours after the injection. DISCUSSION
Various
radiolabelled agents, 1-1, including antifibrinogen antibody,7 have been used to localise thrombi. However, the use of anti-fibrinogen antibody was restricted by its cross-reactivity with fibrin. The anti-fibrin antibody tested in the present study has the advantages of pronounced specificity for fibrin and the ability to detect both forming and formed thrombi. Our results suggest that 131I-A.F.G. can also discriminate between acute thrombosis and chronic varicosities. The most discriminant thrombus-to-normal or thrombus-to-varices ’1-A.F.G. ratios in the veins of lower extremities were found 24 and 48 hours after the injection, thus indicating that this was the best time to scan for thrombi. Compared with the low rate of uptake in the heart cavities at 24 hours such an accumulation-rate in the blood-vessels implies that coronary thrombosis might be displayed by this method. Further, the observation that the 24-hour period after injection of A.F.G. is sufficient for the display of thrombi indicates that iodine-123, with its 13-hour physical half-life, could also be used as a radiotracer with A.F.G. The risk of sensitisation to rabbit immunoglobulins is a disadvantage of
SILICON, FIBRE, AND ATHEROSCLEROSIS KLAUS SCHWARZ
Laboratory of Experimental Metabolic Diseases, Hospital, Long Beach, California,
Veterans Administration
U.S.A. and
Department of Biological Chemistry, School of Medicine, University of California, Los Angeles, California
logical argument can be made for the hypothesis that lack of silicon may be an important ætiological factor in atherosclerosis. As silicic acid or its derivatives, silicon is essential for growth. It is found mainly in connective tissue, where it functions as a cross-linking agent. Unusually high amounts of bound silicon are present in the arterial wall, especially in the intima. Various kinds of dietary fibre have been reported to be effective in preventing experimental models of atherosclerosis, reducing cholesterol and blood-lipid levels, and binding bile acids in vitro. Exceptionally large amounts of silicon (1000 to 25 000 p.p.m.) were found in fibre products of greatly varying origin and chemical composition which were active in these tests. Inactive materials, such as different types of purified cellulose, contained only negligible quantities of the element. It is concluded that silicate-silicon may be the active agent in dietary fibre which affects the development of atherosclerosis. Two out of three samples of bran also had relatively low levels, which could explain why bran does not lower serum-cholesterol. The fact that atherosclerosis has a low incidence in less developed countries may be related to the availability of dietary silicon. Two instances are presented where silicon is reduced by industrial treatment: white flour and refined soy products were much lower in silicon than—their respective crude natural products. The chemical nature of Summary
silicon in different types of fibre is not known. It could exist as orthosilicic acid, polymeric silicic acid, colloidal silica (opal), dense silica concretions, or in the form of organically bound derivatives of silicic acid (silanolates). Possible mechanisms of action are discussed. INTRODUCTION
IN 1972 we demonstrated, by means of a plastic traceelement-sterile isolator system and highly purified DR
4. 5.
Siegel,
620.
6.
by grants from the Republic Research
Requests for reprints should be addressed to V.B.B.
BOŠNJAKOVIĆ AND OTHERS: REFERENCES
Atkins, P., Hawkins, L. A. Lancet, 1965, ii, 1217. Kakkar, V. V. Archs Surg. 1972, 104, 152. Charkes, N. D., Dugan, M. A., Maier, W. P., Soulen, R., Escovitz, E., Learner, N., Dubin, R., Kozer, J. J. nucl. Med. 1974, 15, 1163. Webber, M. M., Bennett, L. R., Cragin, M., Webb, R. Radiology, 1969, 92,
1. 2. 3.
A.F.G.
This work was supported Fund of Serbia, Belgrade.
A
7.
8. 9. 10.
M. E., Malmud, L. S., Rhodes, B. A., Bell, W. S., Wagner, H. N., Jr. ibid. 1972, 103, 695. Coleman, R. E., Harwing, S. S. L., Harwing, J. F., Sherman, L. A., Welch, M. J. Circulation Res. 1975,17, 542. Spar, I. L., Varen, M. I., Goodland, R. L., Schwartz, S. I. Archs Surg. 1966. 92, 752. Gitlin, D., Landing, B. H., Whipple, A. J. exp. Med. 1953, 97, 163. Avrameas, S., Ternynck, T. Immunochemistry, 1969, 6, 53. Jovanovic, V., Nemoda, Dj., Lwin, K. Int. J. appl. Radiat. Isotopes, 1972.
23, 242.
i
