Effects of Progestogen Oral Contraception with Norethisterone on Blood Clotting and Platelets

The effects on clotting tests and platelet function of six months'' continuous administration of the 19-norsteroid, progestogen-only contraceptive, norethisterone, have been studied in four groups of women. In a group of women who have not previously taken oral contraceptive no acceleration of clotting or platelet factors was found, but in contrast a tendency to reduced coagulability was observed. Women who had previously been taking combined oestrogen-progestogen preparations showed reduced clotting and platelet parameters when norethisterone was substituted. No changes in clotting or platelets were found in women who changed from 17-acetoxysteroid progestogen chloramadinone acetate or in a group of women started postpartum.     

Oestrogen/Progestogen Oral Contraception and Blood Clotting: A Long-term Follow-up

In a long-term study of women taking the combined oestrogen/progestogen oral contraceptives Ortho-Novin and Norinyl-1 the follow-up has been continued for three years and four years respectively.Acceleration of both “intrinsic” and “extrinsic” clotting tests and of specific factor VII and X assays, reported previously at the nine-month stage, persisted throughout the period of study. Acceleration of Chandler''s tube platelet aggregation and hypercoagulable thrombelastographic patterns were recorded. There was, however, no evidence of a cumulative effect after the first nine months.     

Blood Clotting and Platelet Aggregation during Oral Progestogen Contraception: A Follow-up Study

A two-year follow-up study of progestogen-only contraception with chlormadinone acetate indicates no increase of the level of factors VII and X, as found after three cycles with all oestrogen-progestogen oral contraceptives. Clotting factors which were raised with combined preparations became normal after the sixth monthly cycle of progestogen and remained normal during the two-year period of study.From 12 months onwards significant changes in the thromboelastograph pattern were recorded, but not to the same extent as with combined preparations. At two years platelet aggregation was significantly accelerated with chlormadinone acetate but was not as rapid as with combined preparations.     

Selective Light-Triggered Release of DNA from Gold Nanorods Switches Blood Clotting On and Off

Blood clotting is a precise cascade engineered to form a clot with temporal and spatial control. Current control of blood clotting is achieved predominantly by anticoagulants and thus inherently one-sided. Here we use a pair of nanorods (NRs) to provide a two-way switch for the blood clotting cascade by utilizing their ability to selectively release species on their surface under two different laser excitations. We selectively trigger release of a thrombin binding aptamer from one nanorod, inhibiting blood clotting and resulting in increased clotting time. We then release the complementary DNA as an antidote from the other NR, reversing the effect of the aptamer and restoring blood clotting. Thus, the nanorod pair acts as an on/off switch. One challenge for nanobiotechnology is the bio-nano interface, where coronas of weakly adsorbed proteins can obscure biomolecular function. We exploit these adsorbed proteins to increase aptamer and antidote loading on the nanorods.     

Clotting Problems with the Teflon-Silastic Arteriovenous Shunt in Patients on Regular Haemodialysis

Episodes of clotting that occurred in 22 patients on regular haemodialysis were studied over a six-month period. The venous pressure during dialysis and the radiology of the Teflon-Silastic arteriovenous shunt were found to be satisfactory guides for the management of the shunt. The failure of the shunt during the early stage was mainly due to technical reasons. Histological study of the excised vessels in removed long-term shunts showed that these had failed because of rigidity and thickening of the vessel wall due to calcium and iron deposits or chronic inflammation, or both.