Differential expression and distribution of placental glutathione peroxidases 1, 3 and 4 in normal and preeclamptic pregnancy.

Preeclampsia is a pregnancy-specific condition affecting 2-7% of women and a leading cause of perinatal and maternal morbidity and mortality; it may also predispose the mother and fetus to increased risks of adult cardiovascular disease. The selenoprotein glutathione peroxidases (GPxs) have critical roles in regulating antioxidant status. OBJECTIVES, STUDY DESIGN AND MAIN OUTCOME MEASURES: Immunohistochemical measurements of GPx1, GPx3 and GPx4 protein expression were performed on samples taken from three standardised sampling sites between the cord insertion and the periphery of the placenta from 12 normotensive, and 12 preeclamptic women to establish if their expression differed between sampling sites. Total GPx activities were also examined from the three sampling sites of these placentae. RESULTS: There were highly significant reductions in overall immunohistochemical staining of all 3 GPxs in the preeclampsia compared to normotensive placentae (GPx1: P=0.016; GPx3: P=0.003; GPx4: P<0.001). Furthermore, graded differences in expression between the standardised placental sampling sites were also found for GPx3 (higher in the inner region, P=0.05) and GPx4 (higher in the periphery, P=0.02) but not GPx1. Placental GPx enzyme activity was also significantly reduced in tissue from preeclamptic women as compared to normotensive women (P=0.007; the difference was more pronounced nearest the cord insertion). CONCLUSIONS: We have shown highly significant reductions in expression of all three major classes of GPx in placentae from women with preeclampsia, and distribution gradients in activity, which may relate to the differential oxygenation of regions of the placenta.

Formation of specialized propagules resistant to desiccation and cryopreservation in the threatened moss Ditrichum plumbicola (Ditrichales, Bryopsida).

BACKGROUND AND AIMS: Successful cryopreservation of bryophytes is linked to intrinsic desiccation tolerance and survival can be enhanced by pre-treatment with abscisic acid (ABA) and sucrose. The pioneer moss Ditrichum plumbicola is naturally subjected to desiccation in the field but showed unexpectedly low survival of cryopreservation, as well as a poor response to pre-treatment. The effects of the cryopreservation protocol on protonemata of D. plumbicola were investigated in order to explore possible relationships between the production in vitro of cryopreservation-tolerant asexual propagules and the reproductive biology of D. plumbicola in nature. METHODS: Protonemata were prepared for cryopreservation using a four-step protocol involving encapsulation in sodium alginate, pre-treatment for 2 weeks with ABA and sucrose, desiccation for 6 h and rapid freezing in liquid nitrogen. After each stage, protonemata were prepared for light and electron microscopy and growth on standard medium was monitored. Further samples were prepared for light and electron microscopy at intervals over a 24-h period following removal from liquid nitrogen and re-hydration. KEY RESULTS: Pre-treatment with ABA and sucrose caused dramatic changes to the protonemata. Growth was arrested and propagules induced with pronounced morphological and cytological changes. Most cells died, but those that survived were characterized by thick, deeply pigmented walls, numerous small vacuoles and lipid droplets in their cytoplasm. Desiccation and cryopreservation elicited no dramatic cytological changes. Cells returned to their pre-dehydration and cryopreservation state within 2 h of re-hydration and/or removal from liquid nitrogen. Regeneration was normal once the ABA/sucrose stimulus was removed. CONCLUSIONS: The ABA/sucrose pre-treatment induced the formation of highly desiccation- and cryopreservation-tolerant propagules from the protonemata of D. plumbicola. This parallels behaviour in the wild, where highly desiccation-tolerant rhizoids function as perennating organs allowing the moss to endure extreme environmental conditions. An involvement of endogenous ABA in the desiccation tolerance of D. plumbicola is suggested.

Evaluation of the sensitivity of a rapid polymerase chain reaction for detection of group B streptococcus.

The objective of this study was to compare detection of group B streptococcal (GBS) carriage using 'real-time' polymerase chain reaction (PCR) and microbiological standard culture. The study design was a test accuracy study comparing a novel molecular technique against the standard microbiological cultural technique in normal pregnant women. The setting and population consisted of 143 pregnant women with pre-labour rupture of the membranes, recruited from two large teaching hospitals in the UK. The study examined the efficacy of a polymerase chain reaction (PCR) assay for screening pregnant women who presented with term rupture of the membranes. Low vaginal specimens were obtained from the women. The specimens were tested for GBS by conventional culture and with a GBS-specific real-time PCR assay. The main outcome measure was the sensitivity and specificity of the PCR assay with 95% confidence intervals (CI) compared with the standard culture. The length of time to obtain a result was also reported for both methods. Among the 143 women, the results of the culture were positive (at least one colony) for GBS in 20 women (14%). The PCR assay detected GBS carriage in 10 women (7%). As compared with the culture method, the sensitivity and specificity of the PCR assay were 45% and 99%, respectively. The positive and negative predictive values of the PCR assay were 90% and 92%, respectively. The length of time required to obtain results for the majority of women (94%) was <2.5 h for the PCR assay and at least 24 h for culture. While a rapid result (within 3 h) of carriage of GBS can be obtained by the PCR assay, at present, it cannot replace conventional culture without further optimisation of the DNA extraction method. The sensitivity may further be improved by testing both low vaginal and rectal specimens.

Influence of maternal pre-pregnancy body composition and diet during early-mid pregnancy on cardiovascular function and nephron number in juvenile sheep.

The prenatal diet can program an individual's cardiovascular system towards later higher resting blood pressure and kidney dysfunction, but the extent to which these programmed responses are directly determined by the timing of maternal nutritional manipulation is unknown. In the present study we examined whether maternal nutrient restriction targeted over the period of maximal placental growth, i.e. days 28-80 of gestation, resulted in altered blood pressure or kidney development in the juvenile offspring. This was undertaken in 6-month-old sheep born to mothers fed control (100-150 % of the recommended metabolisable energy (ME) intake for that stage of gestation) or nutrient-restricted (NR; 50 % ME; n 6) diets between days 28 and 80 of gestation. Controls were additionally grouped according to normal (>3, n 7) or low body condition score (LBCS; <2, n 6), thereby enabling us to examine the effect of maternal body composition on later cardiovascular function. From day 80 to term (approximately 147 d) all sheep were fed to 100 % ME. Offspring were weaned at 12 weeks and pasture-reared until 6 months of age when cardiovascular function was determined. Both LBCS and NR sheep tended to have lower resting systolic (control, 85 (se 2); LBCS, 77 (se 3); NR, 77 (se 3) mmHg) and diastolic blood pressure relative to controls. Total nephron count was markedly lower in both LBCS and NR relative to controls (LBCS, 59 (se 6); NR, 56 (se 12) %). Our data suggest that maternal body composition around conception is as important as the level of nutrient intake during early pregnancy in programming later cardiovascular health.

Description of a technique for anaesthetizing pregnant ewes for fetal surgery.

General anaesthesia in 12 pregnant ewes undergoing surgery for fetal physiological research was supplemented with an intravenous infusion of remifentanil. This allowed us to employ a lighter plane of surgical anaesthesia and to use intermittent positive pressure ventilation. Our aim was to improve fetomaternal outcome. We monitored maternal pulse, blood pressure, transcutaneous oxygen saturation and end-tidal carbon dioxide levels. Remifentanil doses of 0.75-2.0 microg/kg/min were needed and typically this allowed halothane concentrations of 1-1.5% to be used for maintenance of anaesthesia. Surgery lasted up to 2.5 h. All 12 ewes and their singleton fetuses survived the peri- and postoperative period in good condition.

Programming of adult cardiovascular function after early maternal undernutrition in sheep.

The prenatal nutritional environment influences the subsequent risk of hypertension in adulthood. Animal studies have used, generally, the rat as a model species to illustrate the association between maternal nutrient intake and blood pressure in the resulting adult offspring. No study to date has shown programming of adult cardiovascular function in the sheep through maternal dietary intervention. We therefore fed pregnant sheep to either 100% recommended intake from day 0 of gestation to term [ approximately 147 days gestational age (dGA); controls n = 8] or to 50% recommended intake from day 0 to 95 dGA and thereafter to 100% intake (NR; n = 9). Sheep lambed naturally, offspring were weaned at 16 wk, and the male offspring were reared on pasture until 3 yr of age. At this time, cardiovascular catheters were inserted under halothane anesthesia and sheep were allowed 2-4 days recovery. Basal cardiovascular status and pressor responses to infusion of norepinephrine, angiotensin II, and captopril were then assessed alongside basal plasma concentrations of glucose, cortisol, and leptin. NR sheep were of similar birth weight to controls but at 3 yr of age had higher blood pressure before, but not after, feeding. Peripheral sensitivity to vasoconstrictor infusion was similar between dietary groups, although a reflex bradycardia was not apparent in NR sheep during norepinephrine infusion. Circulating leptin correlated well with fat mass and increased more after vasoconstrictor infusion in NR sheep. In conclusion, early NR has been shown to program aspects of cardiovascular control and adipocyte function in adult sheep.

Maternal nutrient restriction during placental growth, programming of fetal adiposity and juvenile blood pressure control.

Epidemiological and experimental studies have demonstrated that maternal undernutrition during pregnancy is associated with abnormal placental growth. In sheep, maternal nutrient restriction over the period of rapid placental growth (30-80 days) restricts placentome growth. Then following adequate nutrition up to term (147 days), placental mass is greater in association with a higher total abundance of the predominant placental glucose transporter-1. The resulting lambs are larger at birth, have heavier kidneys with an increased expression of the glucocorticoid-responsive type 1 angiotensin II receptor. Near to term, these fetuses possess more adipose tissue, the endocrine sensitivity of which is markedly enhanced. For example, the abundance of mRNA for 11beta-hydroxysteroid dehydrogenase type 1, which catalyses the conversion of cortisone to bio-active cortisol is increased. This is associated with a higher abundance of both leptin and glucocorticoid receptor mRNA. At 6 months of age, the juvenile offspring of nutrient restricted ewes have lower resting blood pressure that was positively correlated with plasma cortisol concentration, suggesting their blood pressure could be more strongly driven by circulating cortisol. These offspring also exhibited a greater pressor response to vasoconstrictor challenges, but showed no difference in vasodilatory response. At this age, the kidney weight was similar between groups, but the abundance of cytochrome c in kidney mitochondria was enhanced in lambs born to nutrient restricted ewes that could indicate increased mitochondrial activity. Reduced maternal nutrition during the period of rapid placental growth may therefore contribute to hypertension in later life through physiological and vascular adaptations during fetal life.

The effects of pregnancy and maternal nutrition on the maternal renin-angiotensin system in sheep.

Physiological changes occurring in the mother during pregnancy can determine the outcome of pregnancy in terms of birthweight and neonatal viability. Maternal adaptations include plasma volume expansion linked to enhanced activity of the renin-angiotensin system (RAS). The present study was designed to determine whether these changes occur very early in gestation, and the extent to which maternal nutrient restriction may compromise the maternal RAS. Using sheep, we have investigated the effects of pregnancy per se, maternal nutrient restriction and later restoration of maternal diet on maternal body weight, plasma volume and plasma renin concentration (PRC), and angiotensinogen (Aogen) and arginine vasopressin (AVP) concentration. During the period of placental growth (i.e. 28-80 days gestation) ewes were fed either a nutrient-restricted (NR) diet or were well fed (WF). NR ewes consumed between 3.2 and 3.8 MJ day(-1) of metabolisable energy (ME) which is close to 60 % of requirements taking into account the ME required for both ewe maintenance and growth of the conceptus in order to produce a 4.5 kg lamb at term. WF ewes consumed 150 % of ME requirements. Restoration of maternal diet between 80 and 140 days gestation (i.e. fed to satiety and consuming between 8 and 10.9 MJ day(-1), which is close to 150 % of ME requirements) followed previous nutrient restriction. Between pre-conception and 28 days gestation, plasma volume increased in conjunction with a decline in PRC and Aogen concentration. During the period of nutrient restriction ewe body weight did not increase and plasma volume was lower in NR than WF ewes. During this time there was no effect of maternal nutrition on PRC; however, Aogen concentration was lower in the NR group. From 80 days gestation following the rise in food intake for previously NR ewes, greater increases in ewe body weight, plasma volume and PRC occurred up to term compared with ewes that were well fed throughout gestation. Plasma AVP concentration was not significantly affected by either maternal nutrition or gestational age. In conclusion, the stimulus of moderately severe maternal nutrient restriction evoked smaller rises in maternal weight, plasma volume and Aogen concentration than occurred in ewes that were well fed throughout gestation. Following the restoration of maternal diet after 80 days gestation, PRC gradually rose to peak at term. These adaptations in the maternal RAS during the critical period of placental growth may have long-term effects on fetal development.

The maternal cerebral circulation in pre-eclampsia: investigations using Laplace transform analysis of Doppler waveforms.

OBJECTIVE: To compare the maternal cerebral circulation in pre-eclampsia and normal pregnancy using an alternative method of Doppler waveform analysis called the Laplace transform analysis, which provides haemodynamic data additional to standard Doppler indices. DESIGN: A prospective cross-sectional study. SETTING: Department of Obstetrics and Gynaecology, Nottingham University Hospital. SAMPLE: The study involved 17 women in the third trimester of a normal pregnancy, 11 with pregnancy-induced hypertension and 26 with pre-eclampsia. METHODS: Doppler recordings were obtained from the internal and external carotid and middle cerebral arteries, with the measurements in hypertensive women being carried out before any treatment was given. The waveforms were then subjected to Laplace transform analysis which provides information on vessel wall stiffness and upstream and downstream flow conditions. MAIN OUTCOME MEASURES: The determination of the Laplace transform analysis parameters, including alpha, the natural frequency of oscillation and real pole, and pulsatility index. RESULTS: Laplace transform analysis demonstrated a significant increase in vessel wall stiffness in all the arteries in hypertensive pregnancies, but this was more marked in pre-eclampsia. The data were also consistent with, but do not prove, increased downstream resistance in the middle cerebral artery in women with pre-eclampsia but not in those with pregnancy-induced hypertension. CONCLUSIONS: The Laplace transform analysis of Doppler waveforms yields important physiological information concerning the cerebral circulation in pre-eclampsia, not detected using conventional Doppler indices. The results suggest that both pre-eclampsia and pregnancy-induced hypertension are associated with increased cerebral arterial wall stiffness and that, in addition, there may be cerebral vasoconstriction in pre-eclampsia.

Intravenous infusion of magnesium sulfate and regional redistribution of fetal blood flow during maternal hemorrhage in late-gestation gravid ewes.

OBJECTIVES: Even though magnesium sulfate is commonly prescribed for women with preeclampsia as prophylaxis against seizure and for women with preterm labor as a tocolytic agent there is limited information about its effects on the fetus. It is of particular concern that women with preeclampsia or in premature labor are at high risk for abruptio placentae with consequent compromise of fetal oxygenation. Magnesium sulfate is a vasodilator and thus may exert cardiovascular effects on the fetus. The goal of this study was to evaluate the effects of magnesium sulfate on fetal organ blood flow, especially regional cerebral blood flow, during the stressful condition of maternal hemorrhage. STUDY DESIGN: Studies were performed with 11 long-term instrumented pregnant ewes and their fetuses at 121 to 128 days' gestation (term, 147 days' gestation). Animals were randomly allocated to either the experimental (n = 5) or the control (n = 6) group. After a 60-minute baseline period, experimental fetuses received intravenous magnesium sulfate diluted in 0.9% sodium chloride (0.3 g loading dose, then 0.3 g/h at a rate of 3 mL/h) and control fetuses were infused with an equivalent volume of intravenous 0.9% sodium chloride. After 60 minutes of this infusion-only period, the infusions were continued and ewes were intermittently bled 4 times at a rate of 5 mL/kg for 10 minutes with 5 minutes between hemorrhages. The total blood lost at the end of the hemorrhage-plus-infusion hour was 20 mL/kg. The infusions were continued and the sheep were observed for 1 hour after this period (posthemorrhage period). At the end of baseline, infusion-only, and hemorrhage-plus-infusion periods, fetal and maternal blood pressures and blood gas values were measured and fetal organ blood flows were determined through a fluorescent microsphere technique. Repeated-measures analysis of variance and Wilcoxon tests were used to determine the significance of changes in hemodynamic, blood gas, and organ blood flow parameters between different time points within each group. Comparisons between groups were made with rank sum tests (Mann-Whitney tests). RESULTS: There were no significant differences between groups or within groups for baseline and infusion-only measurements in any measured hemodynamic or hematologic factor. Mean maternal blood pressure decreased significantly (P <.05) after hemorrhage, with similar median decrements in both control and experimental groups of 41 mm Hg (interquartile range, 24-57 mm Hg) and 41 mm Hg (interquartile range, 12-43 mm Hg), respectively. There were no significant differences between groups in fetal blood gas values or hemodynamic parameters. Fetal arterial PO(2) decreased significantly after hemorrhage plus infusion, with similar mean (+/-SEM) decreases in control and experimental groups of 5.9 +/- 1.4 mm Hg and 4.5 +/- 1.5 mm Hg, respectively. Fetal pH also decreased significantly in both groups. After hemorrhage plus infusion there were significant increases in fetal regional cerebral and myocardial blood flows in both groups. Adrenal blood flow increased significantly from baseline (214%, 183%-294%) in the control group after hemorrhage plus infusion but not in the experimental group. No other difference in organ blood flow between control and experimental groups was observed. Significant regional variations in cerebral blood flow were not observed in either group at any time. CONCLUSIONS: In these initially healthy, late-gestation fetal lambs magnesium sulfate exposure did not impair cardiac output redistribution, nor did it cause fetal death in response to maternal hemorrhage.

The effect of the menstrual cycle on human cerebral blood flow: studies using Doppler ultrasound.

OBJECTIVE: Previous studies have demonstrated hemodynamic changes at different phases in the menstrual cycle, but the cerebral circulation has not been investigated. Our aim was to study carotid and cerebral blood flow during the menstrual cycle using Doppler ultrasound. Two different techniques of Doppler waveform analysis were used: standard Doppler indices and Laplace transform analysis (LTA), which may provide additional hemodynamic information. DESIGN: This was a prospective study of healthy volunteers who were providing pre-conception data for a subsequent longitudinal study set in the Department of Obstetrics and Gynaecology, Nottingham University Hospital. Nineteen women were studied in the mid-follicular and mid-luteal phases of 27 ovulatory menstrual cycles. Doppler recordings were obtained from the internal and external carotid and middle cerebral arteries. The standard Doppler indices (systolic/diastolic ratio, pulsatility index and resistance index) and LTA parameters were calculated. RESULTS: The standard Doppler indices were all significantly higher in the luteal compared to the follicular phase in the right middle cerebral artery (p < 0.05). However, no changes were seen in the standard indices in the carotid arteries or in any of the LTA parameters in any artery. Using the LTA, vessel wall stiffness was greater and absolute velocity of flow lower in the middle cerebral compared to the carotid arteries. CONCLUSIONS: Increased ventilation and a subsequent lowering of alveolar CO2 pressure secondary to a raised progesterone level in the mid-luteal phase could account for the observed changes within the middle cerebral artery. Under the conditions of this study the LTA appears less sensitive at detecting alterations in downstream resistance compared to the standard Doppler indices.

A longitudinal study of maternal bloodflow in normal pregnancy and the puerperium: analysis of Doppler waveforms using Laplace transform techniques.

OBJECTIVE: To describe changes in the maternal cerebral circulation and the external iliac arteries throughout pregnancy and the puerperium using the Laplace transform analysis of Doppler waveforms. DESIGN: A prospective longitudinal study. SETTING: Department of Obstetrics and Gynaecology, Nottingham University Hospital. SAMPLE: A cohort of 17 healthy women studied every four weeks from early pregnancy until term and up to three months postpartum. Pre-conception data were available for 10 subjects. METHODS: Doppler signals were recorded from the internal carotid, middle cerebral and external iliac arteries. The waveforms were analysed using two different techniques: standard indices (systolic:diastolic ratio, pulsatility and resistance indices) and Laplace transform analysis, an alternative method of waveform shape analysis which may provide additional haemodynamic information. RESULTS: Vessel wall tone decreased at an early stage in pregnancy in the cerebral circulation and in the external iliac artery, but this rose again following delivery. The Laplace transform analysis techniques suggest dramatic eight-fold increases in downstream resistance within the external iliac artery in the second half of pregnancy. An increase in downstream resistance to flow also occurred in the internal carotid artery whereas more stable conditions were noted in the middle cerebral artery. CONCLUSIONS: Having a preliminary idea of the normal ranges for the Laplace transform analysis variables during pregnancy in a variety of maternal vessels, haemodynamic changes in pregnancies complicated by conditions, such as pre-eclampsia, can now be studied.

A longitudinal study of umbilical artery Doppler waveforms in normal pregnancy: analysis using Laplace transform techniques.

OBJECTIVE: To analyse umbilical artery Doppler waveforms using the Laplace transform analysis technique, an alternative method of waveform shape analysis, and to determine the normal ranges for the variables of this technique throughout normal pregnancy. DESIGN: A prospective longitudinal study. SETTING: Department of Obstetrics and Gynaecology, Nottingham University Hospital. SAMPLE: A cohort of 17 healthy women investigated every four weeks from the end of the first trimester until term. METHODS: Umbilical artery Doppler signals were recorded and analysed using the Laplace transform analysis technique. The median and interquartile ranges for each variable were determined and serial changes during pregnancy described. RESULTS: Vessel wall tone decreases in the umbilical artery at the beginning of the second trimester. Alpha, the variable related to upstream flow conditions, also decreases at this stage of pregnancy but values are then comparatively stable from 24 weeks of gestation until term. A fall in downstream resistance within the fetoplacental circulation during pregnancy is detected using the C-coefficient. Real pole appears to be of no value in the assessment of downstream resistance to flow in the fetus. CONCLUSIONS: The normal ranges for the Laplace transform analysis variables have been established for the umbilical artery longitudinally through normal pregnancy. Changes in fetal blood flow during complicated pregnancy can now be investigated using this technique.

Proteinuric hypertension in a pregnant baboon: was this pre-eclampsia?

We report the results of investigating a pregnant baboon that developed hypertension, proteinuria, and oedema in late gestation. Although the clinical presentation suggested a diagnosis of pre-eclampsia, the evolution of her clinical signs and results of a renal biopsy performed 3 weeks after delivery suggested that glomerulonephritis was the underlying disease.

Waveform shape analysis: extraction of physiologically relevant information from Doppler recordings.

1. Doppler recordings were made from the brachial artery of healthy female subjects during a series of manoeuvres which altered the pressure-flow characteristics of the vessel. 2. Changes were induced in the peripheral circulation of the forearm by the application of heat or ice-packs. A sphygmomanometer cuff was used to create graded occlusion of the vessel above and below the point of measurement. Recordings were also made whilst the subjects performed a standardized Valsalva manoeuvre. 3. The Doppler recordings were analysed both with the standard waveform indices (systolic/diastolic ratio, pulsatility index and resistance index) and by the method of Laplace transform analysis. 4. The waveform parameters obtained by Laplace transform analysis distinguished the different changes in flow conditions; they thus had direct physiological relevance, unlike the standard waveform indices.

Pressor, heart rate and plasma catecholamine responses to noradrenaline in pregnant and nonpregnant women.

OBJECTIVE: To study cardiovascular responses to noradrenaline during early pregnancy. DESIGN: Administration of incremental intravenous infusions of noradrenaline under basal conditions. SETTING: University Hospital, Nottingham. SUBJECTS: Nineteen women admitted for termination of pregnancy in first or second trimester and 18 nonpregnant women as control subjects. INTERVENTIONS: Recordings of blood pressure and heart rate responses during the infusion of noradrenaline. Blood samples taken before, during and after the infusion. MAIN OUTCOME MEASURES: Evoked responses of systolic and diastolic blood pressure and heart rate at steady state during the noradrenaline infusion. Plasma catecholamine concentrations measured by high performance liquid chromatography. RESULTS: There were no significant differences between the evoked pressor responses to noradrenaline in pregnancy compared to the nonpregnant state, but there was a lesser bradycardia in response to a standardised change in blood pressure. Neither basal plasma catecholamine concentrations nor those achieved during infusion of noradrenaline differed between pregnant and nonpregnant women. Thirty minutes after discontinuance of the infusion there was a persistent elevation of heart rate in all women, although plasma catecholamine concentrations had returned to basal levels. In pregnant women, systolic and diastolic blood pressures were also elevated at this time, compared to preinfusion levels. CONCLUSION: Cardiovascular regulatory mechanisms are altered in pregnancy with a diminution in the bradycardic response to a pressor challenge evoked by noradrenaline and a delayed recovery from that challenge.

Endothelial healing following defined injury to rabbit aorta. Depth of injury and mode of repair.

A study has been made of the healing of a narrow deep injury to rabbit aortic endothelium which also involves damage to the media of the vessel. The injury was produced using a nylon catheter containing a wire filament; the injury was approximately 150 micron in width and damaged up to 3 elastic lamellae. Immediately after injury platelet aggregates were observed over the injured areas, several hours later large numbers of leukocytes were also seen to adhere. Two days after injury a non-thrombogenic neointimal surface was observed over deeply injured areas; endothelial cells could be identified covering the injured area at 6 days. The healing process following the injury has been directly compared with the healing of rabbit aortic endothelium following a superficial injury of similar width, where endothelial cells are removed without significant damage to the media of the vessel [1]. The results show that (a) following a narrow injury to the aorta which causes damage to the media platelet aggregation and proliferation of smooth muscle cells occurs, (b) despite the disruption of subendothelial components, endothelium rapidly regenerates over the narrow injured area, although not as quickly as for a superficial injury.

Narrow superficial injury to rabbit aortic endothelium. The healing process as observed by scanning electron microscopy.

A study was made of the healing of aortic endothelium in rabbits following the production of a defined superficial injury. This was induced using a fine nylon filament which removed the endothelial cells without producing significant damage to underlying structures. The morphology of the injury and subsequent repair was observed using light microscopy and scanning and transmission electron microscopy. Two forms of injury were produced (a) a longitudinal injury along the full length of the aorta which was 50-80 microns wide (about 5-8 cell widths), (b) a circumferential injury approximately 80 microns wide (about 2 cell lengths). Thirty minutes after injury the exposed tissue was almost devoid of adherent cells, but after 4 h became covered by a sparse monolayer of platelets. Occasional leukocytes were also present from 7 h after injury. Injury tracks were found to repair very quickly; re-endothelialisation being complete by 48 h and there being no sign of injury by 7 days.