116
[SD 4-6] years, range 28-44; number of previously attempts 2-5 [1-5], 1--6; number of previously transferred embryos 7-2 ,1-19), which amounts to a clinical pregnancy rate of 67% and an implantation rate of 29%. Tadir and colleagues’ pioneering work was based on experimental research, whereas the erbium-YAG laser has already repeatedly proved its qualities in clinical appliance.
mean
age 35-5
failed IVF
Institute of Sterility Treatment, A-1130 Vienna, Austria
WILFRIED FEICHTINGER HEINZ STROHMER KARL M. RADNER
Kaufmann R, Hibst R. Pulsed Er:YAG- and 308 nm UV-excimer laser: an in vitro and in vivo study of skin-ablative effects. Lasers Surg Med 1989; 9: 132-40. 2. Rasmussen RE, Hammer-Wilson M, Berns MW. Mutation and sister chromatid exchange induction in Chinese hamster ovary (CHO) cells by pulsed excimer laser 1.
radiation at 193 nm and 308 nm and continuous UV radiation at 254 nm. Photochem Photobiol 1989; 49: 413-18. 3. Strohmer H, Feichtinger W. Successful clinical application of laser for micromanipulation in an in vitro fertilization program. Fertil Steril (in press).
Cryopreservation of embryos and
pregnancy
rates after IVF
SIR,-Dr Tan and colleagues (June 6, p 1390) demonstrate that the cumulative pregnancy rate after repeated IVF treatment declines after the female partner reaches the age of 34 years. The cryopreservation of embryos after IVF is a safe and cost-effective 1 way to increase cumulative pregnancy rates per oocyte recovery, do not include this in their results. yet they PREGNANCY RATES PER TRANSFER OF CRYOPRESERVED EMBRYOS IN NATURAL CYCLES (NC) OR CYCLES WITH HORMONE REPLACEMENT THERAPY (HRT).
colleagues in the University of Kansas School of Medicine in the 1920s, and they showed that a bolus injection of 30-50 mg/kg methylguanidine sulphate resulted in a large (greater than 100 mm Hg) sustained rise in blood pressure, similar to that seen with inhibitors of NO synthase.4 The results were consistent in over 200 experiments. These experiments were done to explain why patients with renal disease developed hypertension, the theory being that a pressor product of metabolism may be retained in these patients. Such studies influenced Goldblatt and colleagues,’ who believed that retention of guanidine compounds was one explanation for their observation that renal ischaemia causes hypertension. Since the dose Taylor and colleagues used was only slightly lower than that used by Major it seems that there may be inter-species differences in sensitivity of the endothelial constitutive NO synthase to this substance. Furthermore, the demonstration that aminoguanidine is an effective inhibitor of the inducible NO synthase6 invalidates the presumption that the full aminoacid structure is needed to inhibit NO synthase. Despite the thoughts of Taylor and colleagues, it seems that small molecules that resemble the guanidino end of the arginine molecule may in fact be important modulators of NO synthesis and deserve further study. Departement of Medicine and Therapeutics, University of Aberdeen,
NIGEL BENJAMIN
Foresterhill, Aberdeen AB9 2ZD, UK
Major RH. Relationship between certain products of metabolism and arterial hypertension. JAMA 1924; 83: 81-84. 2. Major RH. The possible relationship between guanidine and high blood pressure. Am J Med Sci 1925; 170: 228-32. 3. Major RH, Weber CJ. The effect of methylguanidine upon the blood pressure of adrenalectomized dogs. J Pharmacol Exp Ther 1929; 35: 351-54. 4. Aisaka K, Gross SS, Steinberg C, Griffith OW, Levi R. NG methylarginine, an inhibitor of endothelium-derived nitric oxide synthesis, is a potent pressor agent m the guinea pig: does nitric oxide regulate blood pressure in vivo? Biochem Biophys 1.
Res Comm 1989; 160: 881 5. Goldblatt H, Lynch J, Hanzal RF, Summerville WW. The production of persistent elevation of systolic blood pressure by means of renal ischaemia. J Exp Med 1934; 59: 347-78. 6. Corbett JA, Tilton RG, Chang K, et al. Aminoguanidine, a novel inhibitor of nitric oxide formation, prevents diabetic vascular dysfunction. Diabetes 1992; 41: 552-56.
*p < 0 05 both
[SD 4-6] years, range 28-44; number of previously attempts 2-5 [1-5], 1--6; number of previously transferred embryos 7-2 ,1-19), which amounts to a clinical pregnancy rate of 67% and an implantation rate of 29%. Tadir and colleagues’ pioneering work was based on experimental research, whereas the erbium-YAG laser has already repeatedly proved its qualities in clinical appliance.
mean
age 35-5
failed IVF
Institute of Sterility Treatment, A-1130 Vienna, Austria
WILFRIED FEICHTINGER HEINZ STROHMER KARL M. RADNER
Kaufmann R, Hibst R. Pulsed Er:YAG- and 308 nm UV-excimer laser: an in vitro and in vivo study of skin-ablative effects. Lasers Surg Med 1989; 9: 132-40. 2. Rasmussen RE, Hammer-Wilson M, Berns MW. Mutation and sister chromatid exchange induction in Chinese hamster ovary (CHO) cells by pulsed excimer laser 1.
radiation at 193 nm and 308 nm and continuous UV radiation at 254 nm. Photochem Photobiol 1989; 49: 413-18. 3. Strohmer H, Feichtinger W. Successful clinical application of laser for micromanipulation in an in vitro fertilization program. Fertil Steril (in press).
Cryopreservation of embryos and
pregnancy
rates after IVF
SIR,-Dr Tan and colleagues (June 6, p 1390) demonstrate that the cumulative pregnancy rate after repeated IVF treatment declines after the female partner reaches the age of 34 years. The cryopreservation of embryos after IVF is a safe and cost-effective 1 way to increase cumulative pregnancy rates per oocyte recovery, do not include this in their results. yet they PREGNANCY RATES PER TRANSFER OF CRYOPRESERVED EMBRYOS IN NATURAL CYCLES (NC) OR CYCLES WITH HORMONE REPLACEMENT THERAPY (HRT).
colleagues in the University of Kansas School of Medicine in the 1920s, and they showed that a bolus injection of 30-50 mg/kg methylguanidine sulphate resulted in a large (greater than 100 mm Hg) sustained rise in blood pressure, similar to that seen with inhibitors of NO synthase.4 The results were consistent in over 200 experiments. These experiments were done to explain why patients with renal disease developed hypertension, the theory being that a pressor product of metabolism may be retained in these patients. Such studies influenced Goldblatt and colleagues,’ who believed that retention of guanidine compounds was one explanation for their observation that renal ischaemia causes hypertension. Since the dose Taylor and colleagues used was only slightly lower than that used by Major it seems that there may be inter-species differences in sensitivity of the endothelial constitutive NO synthase to this substance. Furthermore, the demonstration that aminoguanidine is an effective inhibitor of the inducible NO synthase6 invalidates the presumption that the full aminoacid structure is needed to inhibit NO synthase. Despite the thoughts of Taylor and colleagues, it seems that small molecules that resemble the guanidino end of the arginine molecule may in fact be important modulators of NO synthesis and deserve further study. Departement of Medicine and Therapeutics, University of Aberdeen,
NIGEL BENJAMIN
Foresterhill, Aberdeen AB9 2ZD, UK
Major RH. Relationship between certain products of metabolism and arterial hypertension. JAMA 1924; 83: 81-84. 2. Major RH. The possible relationship between guanidine and high blood pressure. Am J Med Sci 1925; 170: 228-32. 3. Major RH, Weber CJ. The effect of methylguanidine upon the blood pressure of adrenalectomized dogs. J Pharmacol Exp Ther 1929; 35: 351-54. 4. Aisaka K, Gross SS, Steinberg C, Griffith OW, Levi R. NG methylarginine, an inhibitor of endothelium-derived nitric oxide synthesis, is a potent pressor agent m the guinea pig: does nitric oxide regulate blood pressure in vivo? Biochem Biophys 1.
Res Comm 1989; 160: 881 5. Goldblatt H, Lynch J, Hanzal RF, Summerville WW. The production of persistent elevation of systolic blood pressure by means of renal ischaemia. J Exp Med 1934; 59: 347-78. 6. Corbett JA, Tilton RG, Chang K, et al. Aminoguanidine, a novel inhibitor of nitric oxide formation, prevents diabetic vascular dysfunction. Diabetes 1992; 41: 552-56.
*p < 0 05 both
