Biomedical subjects
Publications and source records attributed to J Bonnar.
In discussing the possible vascular complications of oral contraception, one must differentiate between venous and arterial effects. Different estrogen-progestogen combinations have different effects on the hemostatic system.
Levels of vitamin A, beta-carotene and vitamin E in peripheral venous blood of women in abruptio placentae and in normal pregnancy have been compared. Chemical methods were used for the estimation of these compounds. The results show that levels of all three compounds in abruptio placentae are lower than those found in the normal pregnancy. We have earlier shown that levels of ascorbic acid in these subjects are low while other studies have indicated that levels of folic acid in them are also low. Based on our present and earlier published work it is suggested that abruptio placentae is a condition with multiple vitamin deficiency. Whether this is its cause or effect is however not clear.
Explore the source record for details and available documents.
Concentrations of histamine and total ascorbic acid (L-ascorbic acid plus dehydroascorbic acid) in the antecubital vein blood of women in abruptio placentae (normally situated placentae) and placenta praevia have been measured. The results show that blood ascorbic acid in abruptio placentae is significantly (P less than 0.05) lower than the values found in placenta praevia. This may reflect impaired absorption and/or increased breakdown of ascorbic acid in abruptio placentae. Histamine levels in the two conditions are similar to one another.
Levels of histamine and total ascorbic acid (L-ascorbic acid plus dehydroascorbic acid) in the peripheral blood of women in pre-eclampsia have been measured. The results show that blood histamine is increased both in the moderate and severe form of pre-eclampsia. Blood ascorbic acid on the other hand is increased only in the severe form of pre-eclampsia. The rise in histamine values may be in response to the rising blood pressure in pre-eclampsia. The rise in ascorbic acid values may reflect the reduced maternal blood volume and/or restricted transport of ascorbic acid from maternal to fetal tissues.
The effects of inert (Lippes Loop D and Dalkon Shields) and medicated (copper 7, copper T, and Progestasert) intrauterine contraceptive devices (IUDs) on the ultrastructure of the endometrium were studied in intact human uteri. The most striking morphologic changes induced by the inert and copper-bearing devices were erosion of the surface epithelium and extensive microthrombosis in stromal capillaries of the endometrium in contact with the device. These abnormalities were associated with extravascular thrombi, erythrocytes, and fibrin deposition in the adjacent stroma. Capillary microthrombosis and leukocyte infiltration into the uterine cavity were most extensive around the active part of the copper-bearing devices. With the Progestasert erosion of surface epithelium was rarely seen, but the intact epithelial lining had fewer ciliated cells with flattened and shortened cilia. Large dilated venules were a common finding below the surface epithelium adjacent to the active part of the Progestasert; capillary microthrombosis was found only below the inert arms of the Progestasert. The vascular response of the endometrium to IUDs appears, therefore, to be directly related to the type and proximity of the device. The morphologic changes induced in both surface epithelium and the microvasculature of the endometrium are the likely explanation of the uterine bleeding problems associated with IUDs but are probably intrinsic to the mode of action of the IUD in interfering with implantation.
Explore the source record for details and available documents.
Menstrual fluid was obtained from the uterine cavity and vagina in 20 women within the first 48 h of menstruation. Ten of the women had normal menstrual cycles and blood loss and ten were patients with dysfunctional uterine bleeding. The menstrual samples were examined by electron microscopy for the presence of fibrin and platelets and nearly all were found to contain both fibrin and aggregating platelets. By a simple quantitative system no differences in fibrin and platelet content were found between samples collected from the uterine cavity or the vagina. Likewise no difference was found in the morphology of fibrin and platelets between women with normal menstrual loss and patients with dysfunctional uterine bleeding.
Three oral contraceptive preparations were compared for effects on blood coagulation, fibrinolysis and platelet function in a total of 86 healthy young women. Two of the preparations contained 30 micrograms ethinyl estradiol combined with levonorgestrel or norethindrone acetate, and the third contained 50 micrograms mestranol and norethindrone. Tests were conducted before use of the agents, at intervals over 48 weeks' use and after discontinuation. This study showed that the changes in coagulation activity and fibrinolysis were largely related to the dose of estrogen in the contraceptive preparation; the smallest changes occurred with the low-dose (30 micrograms) preparations. This study also showed that changes occurring in certain coagulation factors and inhibitors were significantly smaller in the preparation containing 30 micrograms of ethinyl estradiol combined with levonorgestrel, suggesting that the progestogen used in these combination oral contraceptives modifies the estrogen effects.
Treatment with the fibrinolytic inhibitor tranexamic acid was investigated in 12 women with vaginal bleeding in the second half of pregnancy. The aim of the therapy was to accelerate haemostasis in the uteroplacental circulation and to prevent further bleeding at the placental site. Tranexamic acid 1 g 8-hourly was given for 7 days. Serial investigations of coagulation and fibrinolysis were carried out. Plasma fibrinolytic activity, plasminogen, antiplasmin and platelet count significantly decreased during treatment, while antithrombin III and factor VIII related antigen showed a significant increase. Plasma tranexamic acid levels ranged from 5 mg/l to 17 mg/l. Two patients on treatment at the time of delivery had plasma tranexamic acid levels of 9 mg/l and 12 mg/l detected in the umbilical cord venous blood. No adverse effects were detected in any of the mothers and all 12 were delivered of live born infants. Tranexamic acid may have a therapeutic role in accelerating haemostasis in the uteroplacental circulation and thereby reducing the adverse effects of bleeding at the placental site.
A scanning and transmission electron microscopy study was undertaken of the effect of the progesterone releasing intrauterine device (Progestasert, Alza Corporation, USA) on the uterine endometrium and fallopian tube epithelium. Small erosions of surface epithelium and microthrombosis of stromal capillaries were found in the endometrium below the inert part of the device. A reduction of ciliated cells and shortened cilia were seen in the endometrium below the active part of the device and large dilated venules were present in the underlying stroma. Fallopian tubes from IUD patients contained fewer ciliated cells than those of the controls. The morphological changes described are likely to be major factors responsible for the irregular bleeding which occurs with Progestasert IUDs and the possible increase in tubal pregnancy.
Concentrations of Prostaglandins E2 and F2 alpha in the peripheral venous blood of women during the third trimester of normal pregnancy have been estimated using radioimmunoassay techniques. These values have been related to the levels of total ascorbic acid in the blood. It appears that AA acts to control the ratio between PGE2 and PGF2 alphja in the body. This effect may in turn be mediated via its actions on histamine levels. We have already suggested that AA acts as a modulator to control the synthesis, release and/or breakdown of histamine in the body.
Explore the source record for details and available documents.
Uteroplacental spiral arteries in placental bed biopsies and placentas form 80 pregnancies were studied by light and electron microscopy; of these 30 were complicated by fatal growth retardation(less than 10th centile) and 45 by hypertension during pregnancy. The physiological changes of the spiral arteries and the vascular pathology present in hypertensive pregnancy and fetal growth retardation were investigated. In normotensive pregnancies complicated by fetal growth retardation, the physiological changes of pregnancy frequently did not extend beyond the decidual segments of the utero-placental arteries. In pregnancies complicated by pre-eclampsia, the physiological changes of pregnancy were not always restricted to the decidual segments of the utero-placental arteries. Atheromatous-like lesions of similar morphology were found in spiral arteries from both normotensive and hypertensive pregnancies complicated by fetal growth retardation. No arteriopathy was found which was specific for pre-eclampsia.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Levels of total ascorbic acid and histamine in the peripheral venous blood of women during the third trimester of normal pregnancy have been estimated. The results suggest that ascorbic acid acts as a modulator to control the synthesis and/or release of histamine in the body. Low levels of ascorbic acid may be essential to stimulate the synthesis and/or release of histamine while in high concentrations it may function to inhibit the release and/or to enhance the breakdown of excessive quantities of histamine in the body. Substantial evidence is now available that histamine, perhaps its nascent variety, is essential for growth and repair processes in the body. It is possible that ascorbic acid in low concentrations acts to stimulate this variety of histamine while its high concentrations act to control the levels of histamine released from storage sites which contain preformed histamine.