Context evaluation: a profile of irrigator climate knowledge, needs and practices in the northern Murray - Darling Basin to aid development of climate-based decision support tools and information and dissemination of research

Understanding client needs, knowledge and practices offers a means of ensuring research outputs match intended audience requirements. This paper shows the initial impact of context evaluation on the development of a suite of decision support tools and information to help irrigators better manage their water resources under different climatic conditions. The context evaluation study involved a survey of ~170 irrigators in the northern Murray�Darling Basin in Australia. It sought to clarify how they make cropping area and water management decisions and their levels of understanding and use of climate information. We found irrigators consult widely on cropping decisions and those with large areas commonly apply the Southern Oscillation Index to property decisions. Respondents demonstrated a reasonably good understanding of climate phenomena in an Southern Oscillation Index knowledge test. Two-thirds use seasonal climate outlook information, but only 20% are very confident to apply climate information to decisions. More than half would find a decision support system (comprising tools and information) useful for cropping decisions. Almost 75% would change their crop area, and 43% their crop type, if given advance information about water availability up to 4 months ahead of irrigation season. About 70% have access to a computer and half to the internet, but two-thirds consider their personal computing skill is only nil or basic. Twenty-three percent of respondents expressed interest in working directly with the research team to interact regarding their requirements, indicating the potential for future participative research activities such as collaborative, on-farm research. The context evaluation facilitated formation of a focus group that cooperated to assess research findings and incorporate improvements to the project�s set of decision support tools. The evaluation was a new experience for the researchers and, albeit an arms-length consultation process, it has broadened our knowledge about our target audience and their preferred ways to access research findings.

Mechanisms of glutamine transport in rat adipocytes and acute regulation by cell swelling

Adipose tissue is a major site for whole-body glutamine synthesis and we are investigating mechanisms and regulation of glutamine transport across the adipocyte membrane. Glutamine transport in adipocytes includes both high- and low-affinity Na+-dependent components (consistent with observed expression of ASCT2 and ATA2/SAT2 transporter mRNAs respectively) and a Na+-independent transport component (consistent with observed expression of LAT1/2 transporter mRNAs). Hypo-osmotic (235 mosmol/kg) swelling of adipocytes transiently stimulated glutamine uptake (180% increase at 0.05 mM glutamine) within 5 mins. Stimulation was blocked by the tyrosine kinase inhibitor genistein and the MAP kinase pathway inhibitors PD98059 and SB203580, but not by wortmannin (PI 3-kinase inhibitor) or rapamycin (mTOR pathway inhibitor). Cell-swelling also stimulated uptake of glucose but not MeAIB (indicating that ASCT2 rather than ATA2 was stimulated by swelling). Insulin (66 nM) treatment for up to 1 h stimulated Na+-dependent glutamine transport and increased adipocyte water space. Activation of the ERK1-2 MAP kinase pathway by cell swelling or insulin may be important for rapid activation of the ASCT2 glutamine transporter in adipocytes. Insulin may also exert a minor additional stimulatory effect on adipocyte glutamine transport indirectly via cell swelling. The mechanisms regulating glutamine transport in adipose tissue are distinct from those in other major sites of glutamine turnover in the body (notably liver and skeletal muscle).

Role of the System L permease LAT1 in amino acid and iodothyronine transport in placenta

The feto-placental unit relies on a maternal supply of indispensable amino acids and iodothyronines for early development and normal growth. We examined the role of the System L transporter in placental uptake of these substances, using the human placental choriocarcinoma cell line BeWo as a model experimental system. BeWo cells express both heavy (4F2hc) and light (LAT1, LAT2) chains of the System L holotransporter. Saturable transport of both L-[(3)H]tryptophan and [(125)I]tri-iodo-L-thyronine in BeWo cells includes components sensitive to inhibition by the System-L-specific substrate 2-endoamino-bicycloheptane-2-carboxylic acid; kinetic properties of these components indicate that the 4F2hc-LAT1 transporter isoform is likely to predominate for the carriage of both substances at physiologically relevant concentrations. Both 4F2hc and LAT1 proteins are also expressed in human placental membranes and LAT1 at least is localized largely to the syncytiotrophoblast layer of the term human placenta. The 4F2hc-LAT1 transporter might therefore serve a vital role in supplying the developing fetus and the placenta with both thyroid hormones and indispensable amino acids from the maternal circulation.

Effect of hypothyroidism on pathways for iodothyronine and tryptophan uptake into rat adipocytes

Adipocytes are an important target tissue for thyroid hormone action, but little is known of the mechanisms of thyroid hormone entry into the cells. The present results show a strong interaction between transport of iodothyronines [L-thyroxine (T4), L-triiodothyronine (T3), reverse T3 (rT3)], aromatic amino acids, and the System L amino acid transport inhibitor 2-amino[2,2,1]heptane-2-carboxylic acid (BCH) in white adipocytes. System L appears to be a major pathway of iodothyronine and large neutral amino acid entry into these cells in the euthyroid state. We also demonstrate expression of the CD98hc peptide subunit of the System L transporter in adipocyte cell membranes. Experimental hypothyroidism (28-day propylthiouracil treatment) has no significant effect on System L-like transport of the amino acid tryptophan in adipocytes. In contrast, uptake of T3 and especially T4 is substantially reduced in adipocytes from hypothyroid rats, partly due to reduction of the BCH-sensitive transport component. Transport of iodothyronines and amino acids in adipocytes therefore becomes decoupled in the hypothyroid state, as occurs similarly in liver cells. This may be due to downregulation or dissociation of iodothyronine receptors from the System L transporter complex. Regulation of iodothyronine turnover in fat cells by this type of mechanism could contribute significantly to modulation of T4-T3/rT3 metabolism in the hypothyroid state.

Glucose metabolism is elevated and vascular resistance and maternofetal transfer is normal in perfused placental cotyledons from severely growth-restricted fetuses

We hypothesized that placental resistance was elevated and transfer reduced in cotyledons from intrauterine growth-restricted (IUGR) fetuses. We perfused 10 cotyledons from term, normally grown fetuses, six from preterm, normally grown fetuses with normal umbilical arterial end-diastolic velocities (EDV), and six from preterm IUGR fetuses (<3rd centile) with absent or reversed umbilical arterial EDV. Perfused cotyledons were pressure-fixed, and villi were observed by scanning electron microscopy. The groups did not differ in fetoplacental resistance at baseline; neither did they differ in the change in resistance that followed the administration of nitroglycerin or angiotensin II. The increase in resistance during hypoxia was similar in the two preterm groups but greater in the term than in the preterm normally grown group (p < 0.05). Groups did not differ in net maternofetal transfer of oxygen or glucose, or in clearance of aminoisobutyric acid or antipyrine. However, glucose consumption was doubled in cotyledons of preterm IUGR versus preterm normally grown fetuses (p < 0.05). Terminal villi of perfused cotyledons from preterm IUGR fetuses displayed less terminal villous branching and budding than preterm controls, as anticipated from previous work. IUGR fetuses with absent or reversed umbilical arterial EDV in vivo may have high placental resistance due to a vasoconstrictive rather than anatomic abnormality and an elevated placental glucose consumption that may impair glucose transfer.

Thyroid hormone transport by 4F2hc-IU12 heterodimers expressed in Xenopus oocytes

Thyroid hormone (TH) action and metabolism require hormone transport across cell membranes. We have investigated the possibility that TH are substrates of amino acid transport (System L) mediated by heterodimers of 4F2 heavy-chain (hc) and the light-chain (lc) permease IU12. Co-expression of 4F2hc and IU12 cDNAs injected into Xenopus oocytes induces saturable, Na(+) -independent transport of tri-iodothyronine (T(3)), thyroxine (T(4)) (K(m) of 1.8 and 6.3 microM respectively), tryptophan and phenylalanine. Induced TH and tryptophan uptakes are inhibited by excess BCH (synthetic System L substrate). Induced TH uptake is also inhibited by excess reverse tri-iodothyronine (rT(3)), but not by triodothyroacetic acid (TRIAC) (TH analogue lacking anamino acid moiety). T(3) and tryptophan exhibit reciprocal inhibition of their 4F2hc-IU12 induced uptake. Transport pathways produced by 4F2hc-lc permease complexes may therefore be important routes for movement and exchange of TH (as well as amino acids) across vertebrate cell membranes, with a potential role in modulating TH action.

Maternal neutrophil apoptosis in normal pregnancy, preeclampsia, and normotensive intrauterine growth restriction

OBJECTIVE

In normal pregnancy there is both a neutrophilia and a mild neutrophil activation. In preeclampsia both direct and indirect evidence supports further marked neutrophil activation. In the pathogenesis of preeclampsia peripheral blood neutrophils may play a vital role in communicating between the preeclamptic placenta and the maternal vascular endothelium and contribute to the endothelial cell dysfunction that characterizes the maternal syndrome of preeclampsia. Preeclampsia shares many elements with the systemic inflammatory response syndrome. Neutrophils, key effectors of the systemic inflammatory response syndrome, are associated with hepatic necrosis and adult respiratory distress syndrome, both of which most commonly kill women with preeclampsia. We hypothesized that delayed neutrophil apoptosis could explain (1) the neutrophilia of normal pregnancy and (2) the differential maternal responses to the shared placental abnormality of preeclampsia and normotensive intrauterine growth restriction.

STUDY DESIGN

Neutrophils were isolated (dextran 500, Ficoll [Amersham Pharmacia Biotech AB, Uppsala, Sweden], and erythrocyte lysis) from (1) case patients with preeclampsia at </=34 weeks' gestation, (2) healthy pregnant control subjects, (3) case patients with normotensive intrauterine growth restriction at </=34 weeks' gestation, and (4) nonpregnant female control subjects. Apoptosis was determined after 18 hours of incubation (with or without endotoxin or anti-Fas monoclonal antibody) by deoxyribonucleic acid profile (propidium iodide study), annexin V binding, and CD16 expression.

RESULTS

Compared with propidium iodide profile values in nonpregnant women (median, 25%; range, 14%-40%) neutrophil apoptosis was significantly delayed in normal pregnancy (median, 9.5%; range, 7.6%-15%) and normotensive pregnancy with intrauterine growth restriction (median, 11%; range. 9.3%-19%) and was further delayed in preeclampsia (median, 6.9%; range, 4.1%-8. 2%; P </=.005 vs normal pregnancy and normotensive intrauterine growth restriction). All neutrophils remained sensitive to endotoxin inhibition but were resistant to anti-Fas induction of apoptosis. Spontaneous neutrophil apoptosis decreased as gestational age increased (r (2) = 0.48).

CONCLUSIONS

Impaired neutrophil apoptosis may explain the neutrophilia associated with normal pregnancy. In women with preeclampsia activated neutrophils remain in the circulation, perhaps contributing to the persistence of preeclampsia after delivery. Neutrophils appear to modulate the variation in maternal response between preeclampsia and normotensive intrauterine growth restriction.

Umbilical artery blood flow velocity in pregnancies complicated by systemic lupus erythematosus

PURPOSE

We evaluated the role of umbilical artery Doppler velocimetry in the surveillance of pregnancies complicated by systemic lupus erythematosus (SLE).

METHODS

We retrospectively studied 56 women with SLE whose pregnancies were managed at our perinatal center between 1988 and 1995.

RESULTS

Absent or reversed end-diastolic flow velocity was detected in 6 (11%) of 56 patients. This sub-group of patients had an increased risk of pre-eclampsia, intrauterine growth restriction, cesarean section, and preterm delivery.

CONCLUSIONS

A high incidence (11%) of abnormal umbilical artery waveforms was detected. This finding was associated with an increased risk of maternal and fetal complications.

Elevated high-density lipoprotein cholesterol and dietary fat intake in women with cyclic mastopathy

OBJECTIVE

This study was designed to examine the contribution of plasma lipids to the pathophysiology of cyclic mastopathy, before and after consideration of diet and sex hormones.

STUDY DESIGN

Thirty-four women with severe cyclic mastopathy (case patients) and 29 women without cyclic mastopathy (control subjects) recorded their breast symptoms daily during 1 menstrual cycle. During each menstrual phase (follicular, early luteal, late luteal, and menstrual) they prospectively completed 2 24-hour dietary diaries, provided blood for lipid and hormone assays, and underwent anthropometric measurements.

RESULTS

Mean age was 34 years. Premenstrual breast swelling and tenderness were significantly more severe in case patients (P < .0001). Cyclic change (late luteal vs follicular) of high-density lipoprotein cholesterol differed between case patients and control subjects, with case patients having a relative excess of high-density lipoprotein cholesterol in the premenstrual phase (P = .01). Dietary fat intake was greater throughout the cycle in case patients (37.5 vs 33.7% of calories, P = .02), and case patients reported increased appetite in the premenstrual phase (P = .01). In multivariate analyses the contributions of mean dietary fat intake and of cyclic change in high-density lipoprotein cholesterol were independently significant, with odds ratios for upper versus lower quintiles being slightly >5.

CONCLUSIONS

Women with cyclic mastopathy had a relative excess of high-density lipoprotein cholesterol during the symptomatic late luteal phase of the menstrual cycle and a higher fat intake throughout the cycle than did control subjects. These observations support the hypothesis that lipids (notably high-density lipoprotein cholesterol) and a high-fat diet play a role in the pathophysiologic characteristics of cyclic mastopathy.

The Toronto Tri-Hospital Gestational Diabetes Project. A preliminary review

In this study, we assessed maternal-fetal outcomes in untreated patients with increasing carbohydrate intolerance not meeting the current criteria for the diagnosis of gestational diabetes mellitus (GDM), examined the relationship between birth weight and mode of delivery among women with untreated borderline GDM, treated overt GDM, and normoglycemia, and established more efficient screening strategies for detection of GDM. This was a prospective analytic cohort study in which nondiabetic women aged > or = 24 years were eligible for enrollment. A 50-g glucose challenge test (GCT) and a 100-g oral glucose tolerance test (OGTT) were administered at 26 and 28 weeks gestational age, respectively. Risk factors for unfavorable maternal-fetal outcomes were recorded. Time since the last meal prior to the screening test was recorded, as well. Caregivers and patients were blinded to glucose values except when test results met the National Diabetes Data Group criteria for GDM. Maternal and fetal outcomes, including the mode of the delivery, were recorded in the postpartum period. Of 4,274 patients screened, 3,836 (90%) continued to the diagnostic oral glucose tolerance test. GDM was seen in 145 women. Increasing carbohydrate intolerance in women without overt gestational diabetes was associated with a significantly increased incidence of cesarean section, preeclampsia, macrosomia, and need for phototherapy, as well as an increased length of maternal and neonatal hospital stay. Multivariate analysis showed that increasing carbohydrate intolerance remained an independent predictor for various unfavorable outcomes, but the strength of the associations was diminished. Compared with normoglycemic control subjects, the untreated borderline GDM group had increased rates of macrosomia (28.7 vs. 13.7%, P < 0.001) and cesarean delivery (29.6 vs. 20.2%, P = 0.03). Usual care of known GDM patients normalized birth weights, but the cesarean delivery rate was about 33%, whether macrosomia was present or absent. An increased risk of cesarean delivery among treated patients compared with normoglycemic control subjects persisted after adjustment for multiple maternal risk factors. As for the screening tests, time since the last meal had a marked effect on mean plasma glucose. Receiver operating characteristic curve analysis allowed the selection of the most efficient cut points for the GCT based on the time since the last meal. These cut points were 8.2, 7.9, and 8.3 mmol/l (1 mmol/l = 18.015 mg/dl) for elapsed postprandial time of < 2, 2-3, and > 3 h, respectively. With this change from the current threshold of 7.8 mmol/l, the number of patients with a positive screening test dropped from 18.5 to 13.7%. There was an increase in positive predictive value from 14.4 to 18.7%. The overall rate of patient misclassification fell from 18.0 to 13.1%. In conclusion, increasing maternal carbohydrate intolerance in pregnant women without GDM is associated with a graded increase in adverse maternal and fetal outcomes. Infant macrosomia is an important factor in high cesarean delivery rates for women with untreated borderline GDM. Although detection and treatment of GDM normalizes birth weights, rates of cesarean delivery remain inexplicably high. Recognition of GDM may lead to a lower threshold for surgical delivery. The efficiency of screening for GDM can be enhanced by adjusting the current GCT threshold of 7.8 mmol/l to new values related to time since the last meal before screening. Further analyses are underway to elucidate whether maternal risk factors can be used to achieve additional efficiency gains in screening.

Endoglin regulates trophoblast differentiation along the invasive pathway in human placental villous explants

Successful invasion of the maternal vascular system by trophoblast cells is a prerequisite for the establishment of a normal hemochorial placenta. Transforming growth factor-beta (TGFbeta) has been implicated in the regulation of trophoblast invasiveness into the uterus. Endoglin is a component of the TGFbeta receptor complex that binds beta1 and beta3 isoforms and is expressed at high levels on syncytiotrophoblast throughout pregnancy and is also transiently up-regulated on extravillous trophoblasts differentiating along the invasive pathway. We investigated the role of endoglin in a serum-free human villous explant culture system that allows the study of trophoblast outgrowth, migration, and invasion and mimics events occurring in anchoring villi during the first trimester of gestation. Addition to explant cultures from 5-8 weeks gestation of a monoclonal antibody to endoglin or of antisense endoglin oligonucleotides significantly stimulated trophoblast outgrowth and migration. These responses were specific, as incubation of explants with nonimmune IgG or sense and scrambled oligonucleotides had no effect. Antisense endoglin-induced trophoblast outgrowth and migration were accompanied by cell division of villous-associated trophoblasts within the proximal region of the forming column and by the characteristic switch in integrins observed in anchoring villi in situ. Treatment of villous explants with antibody and antisense oligonucleotides to endoglin also resulted in an increased fibronectin release into the culture medium. The stimulatory effect of antisense endoglin on fibronectin production was overcome by the addition of exogenous TGFbeta2, but not TGFbeta1 and -beta3. These findings suggest that endoglin expression in the transition from polarized to nonpolarized trophoblasts in anchoring villi is necessary for mediation of the inhibitory effect of TGFbeta1 and/or TGFbeta3 on trophoblast differentiation along the invasive pathway.

Prednisone and aspirin in women with autoantibodies and unexplained recurrent fetal loss

BACKGROUND

Recurrent fetal loss has been well described in women with antiphospholipid antibodies. Such women also often have other autoantibodies commonly found in patients with systemic lupus erythematosus. Treating them with prednisone and aspirin may reduce the risk of fetal loss.

METHODS

We screened 773 nonpregnant women who had the unexplained loss of at least two fetuses for antinuclear, anti-DNA, antilymphocyte, and anticardiolipin antibodies and for the lupus anticoagulant. Of 385 women with at least one autoantibody, 202 who later became pregnant were randomly assigned in equal numbers to receive either prednisone (0.5 to 0.8 mg per kilogram of body weight per day) and aspirin (100 mg per day) or placebo for the duration of the pregnancy. The women were stratified according to age (18 to 34 years or 35 to 39 years) and the week of gestation at which the previous fetal losses had occurred (< or = 12 or > 12 weeks). The primary outcome measure was a successful pregnancy.

RESULTS

Live infants were born to 66 women in the treatment group (65 percent) and 57 women in the placebo group (56 percent, P=0.19). More infants were born prematurely in the treatment group than in the placebo group (62 percent vs. 12 percent, P<0.001). The major side effects of therapy in the mothers were hypertension (treatment group, 13 percent; placebo group, 5 percent; P=0.05) and diabetes mellitus (15 percent and 5 percent, P=0.02).

CONCLUSIONS

Treating women who have autoantibodies and recurrent fetal loss with prednisone and aspirin is not effective in promoting live birth, and it increases the risk of prematurity.

Impact of increasing carbohydrate intolerance on maternal-fetal outcomes in 3637 women without gestational diabetes. The Toronto Tri-Hospital Gestational Diabetes Project

OBJECTIVE

Our purpose was to assess maternal-fetal outcomes in patients with increasing carbohydrate intolerance not meeting the current criteria for the diagnosis of gestational diabetes.

STUDY DESIGN

We conducted a prospective analytic cohort study in which nondiabetic women aged > or = 24 years, receiving prenatal care in three Toronto teaching hospitals, were eligible for enrollment. A glucose challenge test and an oral glucose tolerance test were administered at 26 and 28 weeks' gestation, respectively; risk factors for unfavorable maternal-fetal outcomes were recorded. Caregivers and patients were blinded to glucose values except when test results met the current criteria for gestational diabetes.

RESULTS

Of 4274 patients screened, 3836 (90%) continued to the diagnostic oral glucose tolerance test. The study cohort was formed by the 3637 (95%) patients without gestational diabetes, carrying singleton fetuses. Increasing carbohydrate intolerance in women without overt gestational diabetes was associated with a significantly increased incidence of cesarean sections, preeclampsia, macrosomia, and need for phototherapy, as well as an increased length of maternal and neonatal hospital stay. Multivariate analysis showed that increasing carbohydrate intolerance is an independent predictor for various unfavorable outcomes.

CONCLUSION

Increasing maternal carbohydrate intolerance in pregnant women without gestational diabetes is associated with a graded increase in adverse maternal-fetal outcomes.

The effects of maternal aerobic exercise on human placental development: placental volumetric composition and surface areas

The histomorphometry of term placentae from women who exercised regularly throughout either the first half or all of pregnancy was compared to that of placentae from matched controls to determine if regular exercise during pregnancy produced histomorphometric evidence of altered development and transport capacity. Conventional stereological techniques were used to estimate placental volumetric composition, surface areas, and villous and vascular configurations in the three groups. Exercise confined to early pregnancy increased the parenchymal component of the placenta, total vascular volume and site-specific capillary volume and surface area. Exercise throughout pregnancy increased these and multiple other histomorphometric parameters associated with the rate of placental perfusion and transfer function. However, significant changes were confined to villi > 80 microns in diameter. The localization of both the timing of the stimulus and the anatomical sites affected indicates that regular, sustained exercise modifies placental development primarily in early and mid-pregnancy. We speculate that the lack of significant changes in the structure and configuration of the smaller villi indicates that other adaptive mechanisms, such as increased rates of placental blood flow, must be well developed by the latter portion of the mid-trimester and adequately maintain fetal oxygenation and substrate delivery throughout the third trimester.

Reduced placental villous tree elaboration in small-for-gestational-age pregnancies: relationship with umbilical artery Doppler waveforms

OBJECTIVE

Our purpose was to investigate the three-dimensional architecture of placental villi from normal and growth-restricted fetuses and relate findings to umbilical artery blood flow velocity waveforms.

STUDY DESIGN

Placentas from term (n = 15) and preterm (n = 5) appropriately grown and term (n = 9) and preterm (n = 7) growth-restricted fetuses (birth weight < 10th percentile) were examined to determine the number of arteries per stem villus and the three-dimensional configuration of the villous trees and their vessels. Umbilical blood flow before delivery was assessed by Doppler ultrasonography. The effects of age and growth restriction were determined by two-way analyses of variance.

RESULTS

Growth restriction was associated with reduced large vessel wall thickness (p < or = 0.05) but no reduction in the number of these vessels per stem villus. The volumes and surface areas of intermediate and terminal villi were reduced (p < or = 0.001), especially in preterm growth-restricted cases, where a marked reduction in diastolic blood flow velocity was observed in the umbilical artery.

CONCLUSIONS

Reduced villous development may contribute to abnormal umbilical artery blood flood flow, as assessed by Doppler ultrasonography, in some cases of intrauterine growth restriction.

Impact of time since last meal on the gestational glucose challenge test. The Toronto Tri-Hospital Gestational Diabetes Project

OBJECTIVE

The purpose of the study was to evaluate the impact of time since the last meal on the glucose challenge test and to find cut points that are most likely to predict the outcome of the oral glucose tolerance test in patients screened for gestational diabetes.

STUDY DESIGN

This prospective analytic cohort study was carried out at the University of Toronto Perinatal Complex. A 50 gm glucose load was given at 26 weeks' gestation and the time since previous meal ingestion was recorded. At 28 weeks' gestation a 100 gm oral glucose tolerance test was administered. A total of 4274 eligible patients were screened.

RESULTS

Time since the last meal had a marked effect on mean plasma glucose. Receiver-operator characteristic curve analysis with National Diabetes Data Group criteria to interpret the oral glucose tolerance allowed the selection of the most efficient cut points for the glucose challenge test on the basis of time since the last meal. These cut points were 8.2, 7.9, and 8.3 mmol/L for elapsed postprandial times of < 2, 2 to 3, and > 3 hours, respectively. With this change from the current threshold of 7.8 mmol/L the number of patients with a positive screening test dropped from 18.5% to 13.7%. There was an increase in positive predictive value from 14.4% to 18.7%. The rate of patient misclassification fell from 18.0% to 13.1%.

CONCLUSION

We suggest that screening strategies for detection of gestational diabetes be reconsidered, to account for the impact of variable postprandial status on the test results.

Determinants of increased left ventricular output during in utero ventilation in fetal sheep

A model of in utero ventilation was used to elucidate the mechanisms by which left ventricular (LV) output increases with the transition from a fetal to a neonatal circulation. Using a conductance catheter, LV volumes were measured in seven anesthetized, near-term fetal sheep. Pressure-volume data was recorded before and with oxygen ventilation and again after occlusion of the umbilical cord. Ventilation caused increases in LV end-diastolic volume measured in seven anesthetized, near-term fetal sheep. Pressure-volume data was recorded before and with oxygen ventilation and again after occlusion of the umbilical cord. Ventilation caused increases in LV end-diastolic volume (2.3 +/- 0.9 to 2.9 +/- 0.6 mL/kg; p < 0.05), stroke volume (1.2 +/- 0.3 to 1.9 +2- 0.2 mL/kg; p < 0.001), and ejection fraction (52.8 +/- 11.1 to 66.4 +/- 8.8%; p < 0.001). Contractile state, as assessed by end-systolic elastance, did not change during the transition. Heart rate also remained constant. Afterload, as assessed by effective arterial elastance, decreased from 1.80 +/- 0.37 to 1.04 +/- 0.33 kPa/mL (p < 0.01). Occlusion of the umbilical cord did not result in any further change in hemodynamic parameters. Pressure-volume analysis revealed that a decrease in effective LV afterload and an increased LV end-diastolic volume are the major determinants of, and contribute comparably to, the profound increase in LV output with in utero ventilation. Enhanced contractility is not required for the increase in LV output to occur.

Localization of two angiogenic growth factors (PDECGF and VEGF) in human placentae throughout gestation

The spatiotemporal distribution of two angiogenic growth factors, platelet-derived endothelial cell growth factor (PDECGF) and vascular endothelial growth factor (VEGF) were determined using immunohistochemistry on sections of human placentae from each trimester of pregnancy. In the first trimester PDECGF was detected in trophoblast and in a band in the centre of the villous core. During gestation staining spread throughout the stroma but began to weaken in trophoblast until, by term, it was found only in stroma and in some endothelial cells. VEGF was detected exclusively in cytotrophoblast during the first trimester and then in syncytiotrophoblast throughout the remainder of pregnancy. Western blot analysis revealed that PDECGF antisera bound to three bands approximately 27, 47 and 94 kDa. The lowest band was not detected in platelet lysate and may represent an alternatively processed form of this peptide in placenta. VEGF antisera bound strongly to bands approximately 36, 46, 54, 56 and 64 kDa. The intensity of most bands increased between the first and second trimesters, consistent with an increased level of angiogenesis as the placenta develops. The presence of both factors in trophoblast in early pregnancy may be indicative of the trophoblast playing an active role in influencing the development of the villous vascular network.

The effects of hypoxic acidemia on left ventricular end-systolic elastance in fetal sheep

Using the conductance catheter technique, we measured the effects of hypoxic acidemia on left ventricular end-systolic elastance in anesthetized, 133-d gestation, in utero fetal sheep (n = 7). Conductance and Millar catheters were introduced into the left ventricle through a carotid artery cutdown. Fetuses were rendered progressively hypoxic and acidemic by placental embolization with repeated injections of 5 x 10(5) 50-microns plastic spheres every 15 min via a catheter placed in the fetal abdominal aorta. We recorded pressure-volume data and arterial blood gases at 15-min intervals. End-systolic elastance was computed using a single-beat method of extrapolating maximum isovolumic pressure. A mean of five boluses was required to cause fetal death. Placental embolization caused progressive fetal acidemia. Mean baseline fetal arterial pH was 7.32 +/- 0.06 (mean +/- SD) and gradually decreased with embolization (p < 0.0001). A linear relationship was found to exist between elastance and pH with a mean decrease of 0.46 kPa/mL per 0.1-unit drop in pH (r = 0.96; p < 0.0001). Despite the decrease in end-systolic elastance, stroke volume and left-ventricular output were maintained due to a parallel decrease in afterload. The decrease in end-systolic elastance was gradual and extended over the entire clinically important range of pH, rather than being a terminal event. This study, which, to our knowledge, is the first to use the conductance catheter to measure fetal left ventricular function demonstrates that hypoxic acidemia adversely affects myocardial contractility assessed by end-systolic elastance.

Absent end-diastolic flow velocity waveforms in the umbilical artery--the subsequent pregnancy

OBJECTIVE

Our purpose was to assess the recurrence risk, course, and outcome of subsequent pregnancies in women with absent umbilical end-diastolic velocity.

STUDY DESIGN

Absent umbilical end-diastolic velocity was detected in 88 women. Sixteen of them were prospectively followed up in their 19 subsequent pregnancies. These pregnancies were compared with their index pregnancies.

RESULTS

The index pregnancy was invariably complicated with a perinatal mortality of 56%, growth restriction in 94% (15/16), and prematurity in 100% (75% < 32 weeks' gestation). In contrast, the outcome of the subsequent pregnancies was much better, and 74% (14/19) were uncomplicated. No perinatal deaths occurred, and none were delivered before 32 weeks' gestation. Absent umbilical end-diastolic velocity recurred in only two pregnancies, both of which were complicated. Six women had autoantibodies; these accounted for 80% (4/5) of subsequent complicated pregnancies.

CONCLUSION

After an index pregnancy with absent umbilical end-diastolic velocity, subsequent pregnancies had favorable outcomes. Recurrence of absent umbilical end-diastolic velocity was low. The absence of autoantibodies and normal Doppler studies were associated with improved outcome.

Cardiac electromechanical dissociation in the hypoxic fetal sheep may have clinical implications

OBJECTIVES

Our purpose was to determine the sequence of fetal cardiac electrical and mechanical events associated with acute hypoxic acidemia and to correlate those events with terminal fetal heart rate patterns preceding fetal death.

STUDY DESIGN

Eight acutely catheterized fetal sheep were rendered hypoxic by placental embolization with microspheres until fetal death occurred. The fetal electrocardiogram, Doppler cardiogram, left ventricular and aortic pressures, and fetal heart rate were continuously recorded.

RESULTS

All eight fetuses showed a terminal bradycardia consisting of two phases: an initial phase of falling ventricular pressures, culminating in mechanical asystole, and a subsequent phase after asystole during which the electrocardiographic signal persisted for an average duration of 15.2 +/- 8.7 minutes (range 3.1 to 32.4) and triggered a Hewlett-Packard 8040A monitor to show a heart rate pattern.

CONCLUSIONS

The phenomenon of cardiac electromechanical dissociation may be occurring during similar terminal bradycardias that are observed in human labor and explains the delivery of a fresh stillbirth in spite of the recording of an electrocardiographic signal from a scalp electrode.

What is a low-lying placenta?

Transvaginal ultrasonography was performed in 127 women thought to have placenta previa. In all cases of complete previa, placental location was confirmed at cesarean section. Where the placenta was situated in the lower segment of the uterus but did not cover the cervical os the distance from the placental edge to the internal cervical os was measured. This distance was analyzed in relation to the route of delivery. No patient with a placental edge greater than 2 cm from the internal cervical os required cesarean section for the indication of placenta previa, whereas seven of eight patients with a distance of less than or equal to 2 cm underwent cesarean section because of bleeding characteristic of a placenta previa. These preliminary results suggest that transvaginal ultrasonography measurement may indicate the optimal delivery route and make the traditional classification of placenta previa obsolete.

Transvaginal Doppler assessment of the fetal cerebral circulation

Blood flow velocity waveforms were recorded by pulsed Doppler examination of the fetal internal carotid and middle cerebral arteries using the established transabdominal route as well as a new transvaginal approach. Fourteen normal controls and 11 pregnancies complicated by intrauterine growth retardation were studied. Satisfactory recordings were obtained in all 25 cases. There was a good correlation (R2 = 0.98) between pulsatility index (PI) values obtained transabdominally and transvaginally. The PI in the middle cerebral artery was significantly higher than in the internal carotid artery in both normal and growth-retarded fetuses. Pulsatility in both cerebral vessels was significantly decreased in growth-retarded fetuses when compared with normal controls. The transvaginal route, which produces a coronal section of the fetal brain, allows better distinction between the internal carotid and middle cerebral arteries. Furthermore, signals of equal quality are obtained from vessels in both cerebral hemispheres. Transvaginal scanning of the fetal cerebral arteries is a feasible technique offering an alternative to transabdominal scanning when the latter is hampered by technical difficulties.

Epidural anesthesia, episiotomy, and obstetric laceration

The relationships among epidural anesthesia, forceps use, parity, episiotomy, and laceration were studied in 9493 uncomplicated vertex deliveries of spontaneous onset and normal course. The use of epidural anesthesia was not associated with an increased incidence or severity of birth-canal trauma. Episiotomy was associated with a decreased rate of perineal laceration, but an overall increase in the rate of perineal trauma. The trauma that did occur with episiotomies was four times more likely to be major than that when no episiotomy was performed.

Hypoxic acidemia, hyperviscosity, and maternal hypertension do not affect the umbilical arterial velocity waveform in fetal sheep

The effect of hypoxic acidemia, hyperviscosity, and maternal hypertension on the umbilical arterial velocity waveform was studied in 23 chronically catheterized fetal sheep. Fetal hypoxic acidemia induced by lowering the maternal inspired oxygen concentration (n = 7) caused no change in the ratio of systolic/diastolic blood velocity even when fetal arterial pH was as low as 6.8. Fetal blood hyperviscosity (n = 7) induced by exchange transfusion with packed maternal blood cells increased placental vascular resistance by greater than or equal to 50% but had no significant effect on the systolic/diastolic ratio. Similarly, maternal hypertension induced by intravenous infusion of angiotensin II to the ewe (n = 9) did not affect the systolic/diastolic ratio despite a 50% increase in maternal arterial blood pressure. We conclude that umbilical arterial velocity waveform abnormalities observed in growth-restricted human fetuses are probably not a direct result of fetal hypoxemia or hyperviscosity or maternal hypertension.

Acute hypoxemia does not affect the umbilical artery flow velocity waveform in fetal sheep

The present study in sheep was undertaken to test whether acute fetal hypoxemia causes abnormalities in the umbilical artery velocity waveform. A 1-hour period of hypoxemia was induced in six chronically catheterized fetal sheep by reducing the inspired oxygen content of the ewe. During hypoxemia, the ratio of the systolic to diastolic velocity did not change significantly compared with controls. From this experimental evidence, we conclude that normal Doppler waveforms in the umbilical artery do not necessarily imply fetal normoxemia in sheep and that, because a direct cause-effect relationship has not been established, fetuses that have abnormal waveforms are not necessarily hypoxemic. Whether this is also true in humans remains to be shown.

Effect of placental embolization on the umbilical arterial velocity waveform in fetal sheep

Absent diastolic velocity and reversed diastolic velocity have been observed in the umbilical artery of growth-retarded human fetuses by means of Doppler ultrasonography. Because the physiologic mechanism is unknown, the purpose of this study was to determine whether such waveform changes could be induced in sheep fetuses by embolization of the resistance vessels of the placenta. Seven chronically catheterized sheep fetuses were instrumented with Doppler crystals mounted on one umbilical artery. The placenta was progressively embolized from the fetal side with plastic microspheres. In all cases the umbilical arterial waveform showed a progression from normal to zero diastolic velocity with embolization. In six of seven animals diastolic velocity eventually reversed in direction before fetal death. We conclude that occlusion of placental arteries and arterioles in fetal sheep recreates the waveform changes observed in severely growth-retarded human fetuses.

Epidural anaesthesia and blood flow velocity in mother and fetus

Doppler ultrasound has recently been used to assess changes in blood velocity in the uterine and umbilical arteries. Alterations in the ratio of systolic to diastolic velocity (S/D ratio) are believed to reflect changes in placental vascular resistance. We have used this technique to assess potential beneficial or detrimental effects of epidural anaesthesia on blood flow to the placenta. Continuous wave Doppler ultrasound was used to measure the S/D ratio in the uterine and umbilical arteries of 12 patients undergoing epidural anaesthesia prior to elective caesarean section. Anaesthesia was achieved using lidocaine and epinephrine. The S/D ratio in both the uterine and umbilical arteries remained unaltered either by the fluid preload or by the epidural anaesthesia. It is concluded that epidural anaesthesia using this technique has neither a beneficial nor detrimental effect on uterine or umbilical blood velocity in the uncomplicated pregnancy.

The influence of spontaneous accelerations of fetal heart rate on umbilical artery velocity waveforms

For clinical interpretation of Doppler waveforms, it is important to establish the extent to which fetal heart rate changes affect the umbilical artery velocity waveform. Umbilical artery waveforms were measured with continuous wave ultrasonography during spontaneous accelerations of the fetal heart rate in 20 uncomplicated, near-term pregnancies. On average, an acceleration of 20 beats/min of fetal heart rate within an individual was associated with a reduction in the systolic/diastolic velocity ratio of 0.25. There was, however, considerable variability in the response, and in six patients the systolic/diastolic ratio actually increased with heart rate. We conclude that fetal heart accelerations within the normal range cause only small and variable changes in the systolic/diastolic ratio.

Fetal and maternal hemodynamic responses to exercise in pregnancy assessed by Doppler ultrasonography

It is common for women to undertake vigorous exercise in the late phase of pregnancy. This may have detrimental effects on the blood flow to the uterus and placenta or from the fetus to the placenta. Fifteen pregnant women with no obstetric or medical complications were subjected to a 5-minute exercise period. The maternal heart rate and blood pressure were elevated after exercise. The uteroplacental and umbilical circulations were assessed with Doppler ultrasonography. The ratio of the systolic/diastolic velocity in the uterine artery was elevated, which suggests that uteroplacental vascular resistance increased. The fetal heart rate was elevated after exercise, whereas the systolic/diastolic velocity ratio in the umbilical artery was unaltered. We conclude that moderate maternal exercise causes increased resistance to blood flow in the uterine circulation, whereas the umbilical circulation remains unaltered.

Maternal cigarette smoking: the effects on umbilical and uterine blood flow velocity

Maternal and fetal effects of smoking one cigarette were assessed in 15 healthy women at 36 to 41 weeks' gestation with no obstetric complications. It was found that smoking was associated with increases in maternal heart rate and blood pressure, but there was no significant change in the uterine artery vascular resistance as measured by means of the systolic/diastolic velocity ratio. There also was an increase in the fetal heart rate as well as a highly significant rise in the systolic/diastolic velocity ratio of the umbilical artery. The responses suggest that smoking causes a direct increase in the vascular resistance of the placenta from the fetal side. This resistance may impair oxygen exchange across the placenta and contribute to the increased perinatal morbidity associated with smoking.

Antenatal diagnosis of placental anastomosis in a twin pregnancy using Doppler ultrasound

Qualitative analysis of blood velocity in the umbilical arteries of twin fetuses detected by pulsed Doppler ultrasound revealed discordant patterns which permitted an accurate antenatal diagnosis of an artery-to-artery anastomosis. One twin was consistently larger than the other, had a normal umbilical artery impedance and survived; the other fetus was consistently smaller, had persistently high umbilical artery impedance and died in utero. The death of one fetus did not affect the blood flow patterns within the umbilical artery of the other up to delivery 24 h later. The case demonstrates that intrauterine morbidity due to vascular anastomoses is not confined to the transfusion of significant amounts of blood from one fetus to another.

Failure of nonstress test and Doppler-assessed umbilical arterial blood flow to detect imminent intrauterine death

An unexplained intrauterine death occurred within 12 hours of a normal reactive nonstress test. Furthermore the umbilical arterial impedance measured by pulsed Doppler ultrasound was also normal.

The effect of maternal consumption of alcohol on human umbilical artery blood flow

A Doppler ultrasound technique was used to measure the effect on human umbilical artery impedance of a single moderate dose of alcohol consumed by mothers compared to a control solution in six normal third-trimester pregnancies. No significant difference in impedance was detected between the alcohol and the control solutions during the subsequent 90 minutes. The results suggest that the known toxicity of maternally ingested alcohol is probably mediated by some mechanism other than a significant acute alteration in fetoplacental blood flow characteristics.

Quantitative measurement of fetal blood flow using Doppler ultrasound

Blood flow in the descending human fetal aorta and in the intra-abdominal portion of the umbilical vein was quantified using pulsed Doppler ultrasound in a longitudinal series of normal pregnancies, the accuracy of the method having been verified in vitro. The results obtained are in keeping with previous studies but indicate that, although the method is relatively simple, determination of absolute blood flow in these vessels has little clinical potential because of inherent measurement inaccuracies.

Umbilical artery blood flow characteristics in normal and growth-retarded fetuses

Time-velocity waveforms or sonograms obtained by pulsed Doppler ultrasound from the umbilical artery were analysed in a longitudinal study of 15 normal pregnancies. The sonograms from nine fetuses with intrauterine growth retardation were compared qualitatively and had quite different characteristics implying a high distal impedance to blood flow. Methods of analysis capable of differentiating between the normal and abnormal sonograms are described and discussed.

Microaerophilic/anaerobic bacteria as a cause of urinary tract infection in pregnancy

The involvement of microaerophilic/anaerobic bacteria as a cause of urinary tract infection was investigated by appropriate culture of urine samples obtained after periurethral toilet from 48 pregnant women admitted to hospital with urinary tract symptoms. Significant bacterial counts were demonstrated in 28 of these patients; 24 were due to microaerophilic/anaerobic organisms, and the remaining four were due to established urinary pathogens. In 25 pregnant women admitted without urinary tract symptoms, who were used as controls, four had significant bacterial counts, all of which were due to microaerophilic/anaerobic organisms. It is concluded that these organisms may be responsible for urinary tract symptoms in pregnant women when no significant growth is demonstrated on urinary culture by conventional methods.

A continuing use for Kielland's forceps?

A retrospective study over a 5-year period compared neonatal outcomes after birth by Kielland's forceps with those after caesarean section in the second stage of labour. The 253 babies born by these two modes of delivery showed no difference in Apgar score, the need for active resuscitation, incidence of jaundice or abnormal neurological behaviour. The neonatal outcome was no worse in the small number of patients where Kielland's forceps delivery was attempted but failed. This study offers support for the continuing role of Kielland's forceps in modern obstetrical practice.

Fetal breathing movements and lung maturation in the congenitally abnormal human fetus

Fetal breathing movements have been studied in conjunction with features of anatomical and biochemical development of the lung at birth in fetuses with congenital abnormalities affecting the respiratory system. Total absence of fetal breathing movements or abnormal fetal breathing movements were associated with lung hypoplasia and failure of normal surfactant release into saline extracts of lung fluid. Surfactant synthesis was demonstrated regardless of the presence or absence of fetal breathing movements. The study supports the hypothesis that normal fetal breathing movements are important for fetal lung development and suggests that surfactant synthesis and its release are independent. The latter process may be dependent upon fetal breathing movements while the former is not.

Induction of labor using high-dose or low-dose prostaglandin vaginal pessaries

Two hundred women were studied in a randomized controlled trial of induction of labor using high-dose (3 mg) or low-dose (0.5 mg) prostaglandin E2 vaginal pessaries. Induction using 3-mg pessaries was more successful, with a shorter overall induction-delivery interval and less requirement for analgesia, although uterine hyperstimulation occurred in two patients. In contrast, the low-dose regimen did not cause hypertonus and, though less successful in inducing labor, the total dose of prostaglandin E2 used was considerably less than in the 3-mg group. The cesarean section rate when the cervix was initially unfavorable was high in both groups (high dose 18.2%, low dose 16.7%). The response to prostaglandin E2 did not relate closely to the initial cervical state.

The rate and regularity of breathing movements in the normal and growth-retarded fetus

The rate and regularity of fetal breathing movements (FBM) were determined in 14 women with uncomplicated singleton pregnancies, eight of whom were between 30 and 33 weeks gestation and six between 37 and 40 weeks gestation. Similar observations were made in 19 women with pregnancies complicated by severe intrauterine growth retardation, 11 of whom were between 30 and 33 weeks and eight between 37 and 40 weeks. In normal pregnancy recordings of breath-to-breath intervals showed that FBM became more regular with advancing gestational age, and the rate [breaths/min, mean (SEM)] slowed from 57.2 (1.3) at 30-33 weeks to 47.9 (0.8) at 37-40 weeks. FBM in the growth-retarded group were regular at each gestation studied and the rate was even slower than in the normal group at term, being 41.9 (1.2) at 30-33 weeks and 41.1 (1.0) at 37-40 weeks. Hyperoxia and hypercapnia appeared to have no consistent effect on fetal breathing rate. Fasting for greater than 12 h considerably reduced the rate of FBM in the normal fetus but only marginally so in those with growth retardation. It is concluded that the pattern of FBM provides more information about the fetus than the amount of time spent breathing, particularly when growth is retarded.

The effects of hypoxia on glucose turnover in the fetal sheep

The origin of the hypoxia-induced rise in fetal blood glucose concentration in fetal sheep of 124-135 days was investigated. Hypoxia was induced in pregnant sheep and fetuses with chronically implanted vascular catheters by causing the ewes to breathe 9% O2 and 3% CO2 in N2 for 60 min. The rise in fetal plasma glucose caused by a 60% reduction in maternal PaO2 was associated with a 50% fall in plasma insulin concentration. The fall in insulin and rise in glucose was prevented by the alpha-adrenergic blocking agent phentolamine but not by the beta-antagonist propranolol. Turnover of glucose in the fetus under these conditions was measured with [6-3H] and [U-14C] glucose. Hypoxia reduced fetal glucose consumption despite the hyperglycaemia. After 30 min of hypoxia there was no evidence of fetal production of glucose but by 60 min substantial production was evident. The reduced fetal consumption and increased production of glucose was inhibited by phentolamine but not by propranolol. It is concluded that in the fetal sheep hypoxia induced hyperglycaemia is first caused by reduced consumption of glucose and thus fetal glycogen stores are not depleted. If the hypoxia persists fetal blood glucose is elevated further by fetal production of glucose.

The effects of adrenergic blockade on fetal response to hypoxia

The actions of the adrenergic blocking agents propranolol and phentolamine upon the responses of 124-135 days fetal sheep to hypoxia induced by causing pregnant ewes to breathe 9% O2 and 3% CO2 in N2 have been studied. During hypoxia fetal heart rate fell and any tendency for this to return was prevented by propranolol and stimulated by phentolamine. The ability of the fetal heart rate to return during hypoxia appears to be related to the rise in plasma catecholamines. Hypoxia induced increases in plasma ACTH and cortisol and in plasma metabolites appear to have the same characteristics as those changes induced by catecholamine infusion; the former being largely an alpha-receptor effect and the latter being beta-receptor mediated. The results indicate but do not prove that many of the fetal responses to hypoxia could be caused by the rise in plasma catecholamines.

Fetal breathing movements and maternal hyperoxia in the growth retarded fetus

The effect of fetal breathing movements (FBM) of maternal breathing of 50% oxygen was examined. The procedure caused a two-fold rise in maternal arterial Po2 and did not alter FBM in normal pregnancy. In pregnancy complicated by intrauterine growth retardation (IUGR) a substantial increase in the incidence of FBM was recorded during hyperoxia (control 29.8 +/- 3.9%, hyperoxia 68.2 +/- 3.6). No such change was observed in pregnancies where IUGR was suspected but not proven at delivery.