- Email: [email protected]
CORNEAL AUTOPSY
838
phenformin3related directly to those which had been described for debrisoquine.2Blood lactate levels are significantly greater in subjects given phenformin who show limited ability to metabolise the drug than in those who metabolise phenformin extensively.4 These results, together with the study of these two patients, strongly suggest that, in the absence of other predisposing factors, a genetic impairment of phenformin metabolism and consequent accumulation of the drug may be of importance in the development of lacticacidosis. The wider implications of polymorphic drug oxidation for other adverse drug reactions depends upon further studies of the type described for nortriptyline and phenformin. It may prove possible by a simple non-invasive test such as that for debrisoquine,to identify individuals most at risk of untoward and occasionally fatal effects and to modify therapy accordingly. N. S. OATES Department of Biochemical R. R. SHAH and Experimental Pharmacology, St Mary’s Hospital Medical School, London W2 1PG
J. R.
lymphoblasts. This work was partly supported by CNR grant CT 80.00539.04 and progetto finalizzato CNR "controllo della crescita neoplastica" contract no 78.02847.96.
Medical Clinic I,
University of Milan, 20122 Milan, Italy; Comitato Nazionale per l’Energia Nucleate, Rome; Istituto Medico e di Ricerca Scientifica, Rome, and Consiglio Nazionale delle Ricerche, Rome
SIR,-Cyclosporin A (CyA) is thought to prevent cell proliferation in T cell subpopulations undergoing immunological stimulation. The data reported by Dr Crawford and her colleagues (Jan. 3, p. 10) accord with this view. To see if CyA displays similar activity on spontaneously proliferating T cells, such as leukaemia cells, we have studied the human T lymphoblastic leukaemia cell line 8402.5 We first investigated CyA’s effect on the doubling time of 8402 cells. As the table shows, there was a dose-dependent inhibition of the target cells’ growth rate. CyA was active at concentrations somewhat higher than those reported when treating non-leukaemic lymphocytes.6 Next, we studied CyA’s activity on the tritiated thymidine uptake as assessed by liquid scintillation counting. A marked decrease of isotope incorporation was observed which could not be explained in terms of changes in cell number of cell viability. A redistribution of the 8402 cells in the cell cycle phases had therefore to be assumed. To clarify the mode of action at the cell cycle level, the DNA content of both control and treated cells was measured by means of a Phywe ICP-22 flow system apparatus. Analysis of the DNA histograms showed a marked increase of the Gl phase of treated cells. CyA was also assayed for antiproliferative activity on the human promyelocytic leukaemia cell line HL60. No relevant effect on the growth rate of myeloid cells was recorded (table), nor was there any effect on the distribution of these cells in the cell cycle phases. Our data show that CyA is strongly active in vitro on the T
Mahgoub A, Idle JR, Dring LG. et al. Polymorphic hydroxylation of debrisoquine in
man. Lancet 1977; ii: 584-86. 3. Shah RR, Oates NS, Idle JR, Smith RL. Genetic impairment of phenformin metabolism. Lancet 1980; 1: 1147. 4. Oates NS, Shah RR, Idle JR, Smith RL. Is there a genetic predisposition to phenformin induced lactic acidosis? Br J Clin Pharmacol (in the press). 5. Huang CC, Hou Y, Woods LK et al. Cytogenetic study of human lymphoid T cell lines derived from lymphocytic leukaemia. J Nail Cancer Inst 1974; 53: 655-60. 6. Gordon MY, Singer JW. Selective effect of cyclosporin A on colony forming lymphoid and myeloid cells in man. Nature 1979; 279: 433-34. 7. Collins SJ, Gallo RC, Gallagher RE. Continuous growth and differentiation of human myeloid leukaemic cells in suspension culture. Nature 1977; 270: 347-51.
IN VITRO CYCLOSPORIN A ACTIVITY ON DOUBLING-TIME OF TWO
HUMAN LEUKAEMIA CONTINUOUS CELL LINES
P. FOA A. T. MAIOLO L. BALDINI A. MAISTO M. SPANÒ G. STARACE F. QUARTO DI PALO E. E. POLLI
IDLE
R. L. SMITH
ANTIPROLIFERATIVE ACTIVITY OF CYCLOSPORIN A ON HUMAN T-LYMPHOBLASTIC LEUKAEMIA CELL LINE
2.
human T lymphoblastic leukaemia cell line, while it is not on human myeloid leukaemia cells. These findings might be relevant in view of a possible use of CyA as an antileukaemic agent specific to T
CORNEAL AUTOPSY
SIR,—It is well known that one can get a blurred image of the "floaters" in one’s own anterior chamber by gazing intently at a small, bright, point source of light, such as a pinhole in front of a reading lamp. What seems to be less well known is that one can visualise structures on the surface of one’s own cornea in a similar fashion. In February last year, when on a sabbatical in Paris, I was gazing down the spout of a tube of cyanoacrylate adhesive to discover the source of frustrating blockage. Shortly afterwards I was seeking advice at the emergency ophthalmology clinic of a local hospital for gummed lids and what was there diagnosed as a small corneal abrasion of the left eye. I was given atropine and chloramphenicol drops and sent home. Since I am amblyopic on the right I had little to do but try to make sense of a world reduced to 20/60, where reading was impossible. It was in these circumstances, some twelve hours after my accident, that I became aware of the fact that the reflection from the highly polished stainless-steel type-guide of my typewriter as viewed close-up with my cycloplegic better eye had a curiously structured quality. A few experimental blinks convinced me that this vague, circular spot was a sharp, inverted image of the anterior surface of my own cornea, with the abrasion appearing as a small, irregular dark area, clearly delineated and trailing threads of mucoid secretions. This dark object was noticeably smaller six hours later and had disappeared entirely within a further eighteen. Further experimentation has shown me that another fairly satisfactory way of observing the phenomenon is to use a pinhole of about 01mm diameter and a bright light. On gazing through the pinhole, with the eye focussed for distance vision, a little practice will enable one to see a circular field containing a grainy, reticulated pattern with a number of prominent, lacy objects floating around within it. Most of these objects are floaters in the anterior chamber, but an occasional brighter or darker object with a more deliberate pattern of vertical movement, and some horizontal banding will also be seen. These are droplets and threads of mucus on the anterior surface of the cornea which will, as expected, disappear on blinking. On squinting slightly, one will also see, in the lower part of the field, an enormously enlarged image of the upper lashes, proving that the image is an inverted one. My tentative explanation borrows from photographic theory, in that the depth of field of any imaging system is increased as the aperture is decreased. A 0 1 1 mm pinhole in front of a human eye focused on infinity (f= 24 mm) gives an aperture off/240. Evidently at this minute aperture, everything from the anterior chamber to the light source itself is in sharp focus and all these images are seen superimposed upon one another. Although the pinhole method works well, and is easier to use than the reflected light method, the latter, when properly performed, seems to give much sharper images of the cornea, with less contamination by floaters. Any highly polished convex surface with a radius of curvature of 055 -mm is satisfactory. Medical Centre, 1175 Denman Street, Vancouver, British Columbia, Canada
MICHAEL SCOTT
phenformin3related directly to those which had been described for debrisoquine.2Blood lactate levels are significantly greater in subjects given phenformin who show limited ability to metabolise the drug than in those who metabolise phenformin extensively.4 These results, together with the study of these two patients, strongly suggest that, in the absence of other predisposing factors, a genetic impairment of phenformin metabolism and consequent accumulation of the drug may be of importance in the development of lacticacidosis. The wider implications of polymorphic drug oxidation for other adverse drug reactions depends upon further studies of the type described for nortriptyline and phenformin. It may prove possible by a simple non-invasive test such as that for debrisoquine,to identify individuals most at risk of untoward and occasionally fatal effects and to modify therapy accordingly. N. S. OATES Department of Biochemical R. R. SHAH and Experimental Pharmacology, St Mary’s Hospital Medical School, London W2 1PG
J. R.
lymphoblasts. This work was partly supported by CNR grant CT 80.00539.04 and progetto finalizzato CNR "controllo della crescita neoplastica" contract no 78.02847.96.
Medical Clinic I,
University of Milan, 20122 Milan, Italy; Comitato Nazionale per l’Energia Nucleate, Rome; Istituto Medico e di Ricerca Scientifica, Rome, and Consiglio Nazionale delle Ricerche, Rome
SIR,-Cyclosporin A (CyA) is thought to prevent cell proliferation in T cell subpopulations undergoing immunological stimulation. The data reported by Dr Crawford and her colleagues (Jan. 3, p. 10) accord with this view. To see if CyA displays similar activity on spontaneously proliferating T cells, such as leukaemia cells, we have studied the human T lymphoblastic leukaemia cell line 8402.5 We first investigated CyA’s effect on the doubling time of 8402 cells. As the table shows, there was a dose-dependent inhibition of the target cells’ growth rate. CyA was active at concentrations somewhat higher than those reported when treating non-leukaemic lymphocytes.6 Next, we studied CyA’s activity on the tritiated thymidine uptake as assessed by liquid scintillation counting. A marked decrease of isotope incorporation was observed which could not be explained in terms of changes in cell number of cell viability. A redistribution of the 8402 cells in the cell cycle phases had therefore to be assumed. To clarify the mode of action at the cell cycle level, the DNA content of both control and treated cells was measured by means of a Phywe ICP-22 flow system apparatus. Analysis of the DNA histograms showed a marked increase of the Gl phase of treated cells. CyA was also assayed for antiproliferative activity on the human promyelocytic leukaemia cell line HL60. No relevant effect on the growth rate of myeloid cells was recorded (table), nor was there any effect on the distribution of these cells in the cell cycle phases. Our data show that CyA is strongly active in vitro on the T
Mahgoub A, Idle JR, Dring LG. et al. Polymorphic hydroxylation of debrisoquine in
man. Lancet 1977; ii: 584-86. 3. Shah RR, Oates NS, Idle JR, Smith RL. Genetic impairment of phenformin metabolism. Lancet 1980; 1: 1147. 4. Oates NS, Shah RR, Idle JR, Smith RL. Is there a genetic predisposition to phenformin induced lactic acidosis? Br J Clin Pharmacol (in the press). 5. Huang CC, Hou Y, Woods LK et al. Cytogenetic study of human lymphoid T cell lines derived from lymphocytic leukaemia. J Nail Cancer Inst 1974; 53: 655-60. 6. Gordon MY, Singer JW. Selective effect of cyclosporin A on colony forming lymphoid and myeloid cells in man. Nature 1979; 279: 433-34. 7. Collins SJ, Gallo RC, Gallagher RE. Continuous growth and differentiation of human myeloid leukaemic cells in suspension culture. Nature 1977; 270: 347-51.
IN VITRO CYCLOSPORIN A ACTIVITY ON DOUBLING-TIME OF TWO
HUMAN LEUKAEMIA CONTINUOUS CELL LINES
P. FOA A. T. MAIOLO L. BALDINI A. MAISTO M. SPANÒ G. STARACE F. QUARTO DI PALO E. E. POLLI
IDLE
R. L. SMITH
ANTIPROLIFERATIVE ACTIVITY OF CYCLOSPORIN A ON HUMAN T-LYMPHOBLASTIC LEUKAEMIA CELL LINE
2.
human T lymphoblastic leukaemia cell line, while it is not on human myeloid leukaemia cells. These findings might be relevant in view of a possible use of CyA as an antileukaemic agent specific to T
CORNEAL AUTOPSY
SIR,—It is well known that one can get a blurred image of the "floaters" in one’s own anterior chamber by gazing intently at a small, bright, point source of light, such as a pinhole in front of a reading lamp. What seems to be less well known is that one can visualise structures on the surface of one’s own cornea in a similar fashion. In February last year, when on a sabbatical in Paris, I was gazing down the spout of a tube of cyanoacrylate adhesive to discover the source of frustrating blockage. Shortly afterwards I was seeking advice at the emergency ophthalmology clinic of a local hospital for gummed lids and what was there diagnosed as a small corneal abrasion of the left eye. I was given atropine and chloramphenicol drops and sent home. Since I am amblyopic on the right I had little to do but try to make sense of a world reduced to 20/60, where reading was impossible. It was in these circumstances, some twelve hours after my accident, that I became aware of the fact that the reflection from the highly polished stainless-steel type-guide of my typewriter as viewed close-up with my cycloplegic better eye had a curiously structured quality. A few experimental blinks convinced me that this vague, circular spot was a sharp, inverted image of the anterior surface of my own cornea, with the abrasion appearing as a small, irregular dark area, clearly delineated and trailing threads of mucoid secretions. This dark object was noticeably smaller six hours later and had disappeared entirely within a further eighteen. Further experimentation has shown me that another fairly satisfactory way of observing the phenomenon is to use a pinhole of about 01mm diameter and a bright light. On gazing through the pinhole, with the eye focussed for distance vision, a little practice will enable one to see a circular field containing a grainy, reticulated pattern with a number of prominent, lacy objects floating around within it. Most of these objects are floaters in the anterior chamber, but an occasional brighter or darker object with a more deliberate pattern of vertical movement, and some horizontal banding will also be seen. These are droplets and threads of mucus on the anterior surface of the cornea which will, as expected, disappear on blinking. On squinting slightly, one will also see, in the lower part of the field, an enormously enlarged image of the upper lashes, proving that the image is an inverted one. My tentative explanation borrows from photographic theory, in that the depth of field of any imaging system is increased as the aperture is decreased. A 0 1 1 mm pinhole in front of a human eye focused on infinity (f= 24 mm) gives an aperture off/240. Evidently at this minute aperture, everything from the anterior chamber to the light source itself is in sharp focus and all these images are seen superimposed upon one another. Although the pinhole method works well, and is easier to use than the reflected light method, the latter, when properly performed, seems to give much sharper images of the cornea, with less contamination by floaters. Any highly polished convex surface with a radius of curvature of 055 -mm is satisfactory. Medical Centre, 1175 Denman Street, Vancouver, British Columbia, Canada
MICHAEL SCOTT