Fetal magnetic resonance imaging in prenatal diagnosis of central nervous system abnormalities: 3-year experience.

OBJECTIVE: To evaluate the comparative merits of ultrasound and fetal magnetic resonance imaging (MRI) in the correct antenatal diagnosis of suspected central nervous system abnormalities. METHODS: A retrospective review of 27 consecutive pregnancies referred for fetal MRI for suspected central nervous system abnormalities between July 1998 and July 2001. Women were referred for the MRI examination when further anatomical and/or pathological clarification of the ultrasound scan findings was needed. Antenatal ultrasound scan and MRI were reviewed in relation to the findings on postpartum investigations. RESULTS: Data were complete for 26 pregnancies. The median gestational age at the time of the ultrasound examination was 26 weeks (95% CI 24 weeks 2 days to 28 weeks 1 day). The median gestational age at the time of magnetic resonance imaging was 27 weeks' gestation (95% Cl 26 weeks 1 day to 29 weeks 2 days). Eight fetuses had associated skeletal, renal and/or cardiac abnormalities previously noted on ultrasound examination. MRI confirmed the ultrasound diagnosis in 15/26 cases (58%). It changed the diagnosis to the correct one in 7/26 (27%) and misdiagnosed four cases (15%). Three of the four cases that were misdiagnosed on MRI occurred in the first 18 months of our 36-month experience. CONCLUSION: Ultrasound remains the primary imaging modality for prenatal diagnosis. Fetal MRI appears to be a useful adjunct to ultrasound to confirm or exclude certain abnormalities; this will consequently help in the counselling of parents and assist in planning further management. However, like any imaging technique, the sensitivity and specificity of the test are likely to improve with experience.

Relationship of cell adhesion molecule expression to endothelium-dependent relaxation in normal pregnancy and pregnancies complicated with preeclampsia or fetal growth restriction.

OBJECTIVES: To determine the degree of endothelium-dependent relaxation in myometrial and omental resistance arteries from normal pregnancies and pregnancies complicated with preeclampsia or fetal growth restriction (FGR) (compromised pregnancy group), and to correlate the results with the endothelial surface expression of cell adhesion molecules (CAMs) in the same vessels. METHODS: Parallel wire myography was used to assess the relaxation of omentum or myometrial vessels obtained from nonpregnant women (n = 3), women with normal pregnancies (n = 11), and women with pregnancies complicated by preeclampsia or fetal growth restriction (n = 10). These resistance vessels were constricted with incremental concentrations of vasopressin (10(-10) mol/L to 3.3 x 10(-8) mol/L) prior to the addition of incremental concentrations of bradykinin (10(-10) mol/L to 3.3 x 10(-6) mol/L). Immunohistochemistry was used to assess the endothelial expression of the CAMs E-selectin, ICAM-1, VCAM-1, and PECAM. RESULTS: A significant reduction in endothelium-dependent relaxation of myometrial vessels was found in the compromised pregnancy group when compared with both the normotensive pregnant group and the nonpregnant group. This reduction was not noted with omental vessels. All vessels in the nonpregnant group, normal pregnant group, and compromised pregnancy group expressed PECAM and ICAM-1 on the endothelium. There was no difference in intensity of immunostaining between the groups. None of the vessels in any of the groups expressed VCAM-1 or E-selectin. CONCLUSIONS: We found no evidence that impaired relaxation responses to bradykinin are linked to altered expression of CAMs in preeclampsia and FGR. These results suggest that increased CAM expression occurs in a vascular bed separate from those investigated in the present study. Possible sites for this would be in the microcirculation of organs such as the kidney.

Mechanisms of endothelium-dependent relaxation in myometrial resistance vessels and their alteration in preeclampsia.

OBJECTIVE: To investigate the importance of prostacyclin and nitric oxide synthesis in endothelium-dependent relaxation in myometrial resistance vessels, and to test the hypothesis that a deficiency in nitric oxide synthesis contributes to the known alterations in endothelial function in preeclampsia. METHODS: Thirty-six women with normal pregnancies and 14 with preeclampsia had the myometrium biopsied at cesarean section. Resistance arteries were dissected and mounted on a wire myograph. After preconstriction with vasopressin, vessels were treated cumulatively with bradykinin. The process was repeated in the presence of indomethacin and then indomethacin and NG-monomethyl-L-arginine (L-NMMA). RESULTS: The vessels from women with normal pregnancies showed endothelium-dependent relaxation to bradykinin which was not significantly altered by the presence of indomethacin. The addition of L-NMMA significantly, but only partially, reduced the relaxation to bradykinin in the presence of indomethacin (p = 0.03). The vessels from women with preeclampsia showed markedly reduced relaxation to bradykinin (p < 0.0001), as compared to vessels from normal pregnant women. Relaxation of vessels from women with preeclampsia was increased by the addition of indomethacin (p = 0.03) but was virtually eradicated by the presence of L-NMMA. CONCLUSIONS: Eicosanoid synthesis plays little part in the relaxation of normal pregnant myometrial vessels to bradykinin. Nitric oxide synthesis mediates part but not all of the endothelium-dependent relaxation. In preeclampsia, relaxation to bradykinin is reduced; inhibition of eicosanoid synthesis allows increased relaxation, and nitric oxide synthesis appears to mediate a greater proportion of the relaxation than in normal pregnant women.

Plasma from pre-eclamptic women and functional change in myometrial resistance arteries.

This study assesses the ability of plasma from women with pre-eclampsia to induce altered endothelial function in myometrial resistance vessels from normotensive women. Vessels from normotensive pregnant women (n = 7) were incubated with plasma from other pregnant women who were normotensive (n = 6) or had pre-eclampsia (n = 7). A wire myograph was used to test the endothelium-dependent relaxatory response to bradykinin of preconstricted vessels. The relaxation in vessels incubated with plasma from women with pre-eclampsia was markedly less than in vessels incubated with plasma from normotensive pregnant women (P = 0.039). This supports the theory that a plasma-borne factor contributes to the endothelial changes seen in pre-eclampsia.

Loss of endothelium-dependent relaxation in myometrial resistance arteries in pre-eclampsia.

OBJECTIVE: To measure endothelium-dependent relaxation in myometrial resistance arteries and to compare this parameter in nonpregnant and normotensive pregnant women and those with pregnancies complicated by pre-eclampsia. DESIGN: A prospective study. SETTING: Nottingham City Hospital. SAMPLE: Thirty-seven nonpregnant women undergoing hysterectomy and 51 pregnant women undergoing caesarean section, of whom there were 39 normotensive and 12 with pre-eclampsia. METHODS: Resistance arteries, dissected from myometrial biopsies, were mounted on a wire myograph and preconstricted with vasopressin then subjected to incremental doses of bradykinin. RESULTS: Endothelium-dependent relaxation to bradykinin was seen in the vessels of nonpregnant and normotensive pregnant women. Markedly reduced endothelium-dependent relaxation was found in the myometrial arteries from women with pre-eclampsia when compared with both nonpregnant (P < 0.0001) and normotensive pregnant (P < 0.0001) women. CONCLUSION: A significant loss of endothelium-dependent relaxation in myometrial resistance arteries in pre-eclampsia may contribute to the altered vasoreactivity seen in pre-eclampsia, and particularly to the decreased placental perfusion and fetal growth retardation commonly associated with this condition.

A comparison of endothelium-dependent relaxation in omental and myometrial resistance arteries in pregnant and nonpregnant women.

OBJECTIVES: The study aimed to compare endothelium-dependent relaxation in the resistance arteries of the uterine vascular bed by use of a systemic comparison and to investigate the role of the endothelium in adaptation to pregnancy in these vascular beds. STUDY DESIGN: Myometrial and omental resistance arteries were collected from 22 normotensive pregnant women and 27 nonpregnant women of reproductive age. On a wire myograph and preconstricted with vasopressin, the arteries were relaxed with the endothelium-dependent vasodilator bradykinin. RESULTS: The omental arteries showed a consistently greater endothelium-dependent relaxation than the myometrial arteries, both in the nonpregnant state (p < 0.0001) and in pregnancy (p = 0.008); pregnancy did not significantly alter this relaxation in arteries from either the myometrial (p = 0.2075) or omental (p = 0.372) vascular beds. CONCLUSIONS: The endothelium-dependent relaxation to bradykinin is less in myometrial resistance arteries than in omental resistance arteries. There appears to be no intrinsic difference between vessels from nonpregnant and pregnant women in endothelium-dependent response to bradykinin.

Responses of the sheep blowflies Lucilia sericata and L. cuprina to odour and the development of semiochemical baits.

The literature relating to the attraction of the sheep blowflies Lucilia sericata and Lucilia cuprina to their ovine hosts is reviewed. The responses of the two species are similar and different components of the behaviour leading to host location and oviposition appear to involve at least two distinct sets of semiochemical cues. Activation, upwind orientation and landing appear to occur in response to putrefactive sulphur-rich volatiles, originating from bacterial decomposition products. Oviposition is elicited primarily by the presence of decomposition products. Oviposition is elicited primarily by the presence of ammonia-rich compounds; moisture, pheromones and tactile stimuli may also act as oviposition stimuli. There is a pronounced sex difference in the response of Lucilia to semiochemicals with a higher proportion of females attracted than males and a higher proportion of gravid than non-gravid females. While the mechanisms of host location by Lucilia are of intrinsic interest, understanding the responses to semiochemicals is important in the attempt to develop powerful synthetic baits for deployment with the traps or targets used for population sampling or suppression. The literature is discussed with respect to the development of synthetic semiochemical baits.