Effect of tolerance to paternal antigens on placental and fetal weight in the mouse

Placental and fetal weight was measured on the 16th day of pregnancy in normal and tolerant mice. Placental weight was increased in A mice tolerant to C57BL/10 mice only when donor cells from males were used. Fetal weight was unaffected.     

Assay of a placental protein to determine fetal risk.

Plasma concentrations and total amounts of pregnancy associated plasma protein A were determined in 272 patients at 34 weeks'' gestation by immunoelectrophoretic assay. The mean plasma concentration and mean total amount of this protein were closely related (r = 0.9643) and were significantly raised in patients who subsequently developed pre-eclampsia (28 patients), went into premature labour (12), or suffered from antepartum haemorrhage (10). Mean values in all patients delivering growth-retarded babies were also raised, but when the results for such patients who also had other complications were excluded there were no differences between the sets of means. The assays were easily performed, and they may be a useful technique for screening pregnant women to detect those at risk of developing pre-eclamptic toxaemia, although the full potential of these assays cannot be realised until the protein''s function is known.     

Bioactivation of procarcinogens to mutagens in human fetal and placental tissues.

Enzyme systems in homogenates of human fetal hepatic, pulmonary, adrenal, renal and placental tissues catalyzed the conversion of benzo(a)pyrene, 7, 12-dimethylbenz(a)anthracene and N-2-fluorenyl-acetamide to intermediary metabolites that produced mutations in $\text{Salmonella typhimurium}$. The mutagenic metabolites generated from the three procarcinogen/promutagens displayed specificity with respect to the auxotrophic strains, chemicals and tissues investigated.     

Birth weight and placental proximity in like-sexed twins.

In addition to zygosity, the type of placentation has proven to be an important variable in twin studies. A number of quantitative traits in human twins have been found to be influenced by chorion type. Our study confirms an earlier finding that there is larger within-pair birth weight variability in dichorionic twins with fused placentas than in those with separate placentas. This finding emphasizes the importance of detailed twin placental examinations to help identify traits that may be influenced by prenatal environmental influences.     

Maternal nutrition in early and late pregnancy in relation to placental and fetal growth.

OBJECTIVE: To assess how nutrient intakes of mothers in early and late pregnancy influence placental and fetal growth. DESIGN: Prospective observational study. SETTING: Princess Anne Maternity Hospital, Southampton. SUBJECTS: 538 mothers who delivered at term. MAIN OUTCOME MEASURES: Placental and birth weights adjusted for the infant''s sex and duration of gestation. RESULTS: Mothers who had high carbohydrate intakes in early pregnancy had babies with lower placental and birth weights. Low maternal intakes of dairy and meat protein in late pregnancy were also associated with lower placental and birth weights. Placental weight fell by 49 g(95% confidence interval 16 g to 81 g; P=0.002) for each log g increase in intake of carbohydrate in early pregnancy and by 1.4 g (0.4 g to 2.4 g; P=0.005) for each g decrease in intake of dairy protein in late pregnancy. Birth weight fell by 165 g (49 g to 282 g; P=0.005) for each log g increase in carbohydrate intake in early pregnancy and by 3.1 g (0.3 g to 6.0 g; P=0.03) for each g decrease in meat protein intake in late pregnancy. These associations were independent of the mother''s height and body mass index and of strong relations between the mother''s birth weight and the placental and birth weights of her offspring. CONCLUSION: These findings suggest that a high carbohydrate intake in early pregnancy suppresses placental growth, especially if combined with a low dairy protein intake in late pregnancy. Such an effect could have long term consequences for the offspring''s risk of cardiovascular disease.     

Estimation of fetal weight by ultrasound.

Estimation of fetal size by ultrasound has supported two recent concepts of fetal growth. Firstly, the normal weight gain is constant from 28 weeks of gestation until several weeks after term; about 27 g/day. Secondly, the average weight of fetuses born preterm is lower than the average weight of fetuses of the same gestational age who remain in utero. This means that up to 40% of infants born at 28-30 weeks of gestation are small-for-gestational age, when related to the biological optimum. Unfortunately, the test-retest variation of fetal weight estimation is as much as 50% of the standard deviation of the gestational-age-specific fetal weight distribution. This means that fetal growth has to be followed for many weeks to document statistically significant deviations. No study has, as yet, demonstrated the value of this approach to distinguish between intrauterine growth retardation and growth along low centiles by fetuses of reduced growth potential.     

Restriction of placental growth in sheep enhances placental metabolism of fetal beta-endorphin-like immunoreactivity

The opioid polypeptide beta-endorphin is present in fetal blood but it is not clear whether its source is the fetus or the placenta. We therefore measured beta-endorphin in extracts of fetal femoral arterial and umbilical venous blood plasma in sheep by radioimmunoassay to determine whether the fetus or the placenta is the major source of beta-endorphin in the fetal circulation. Chromatographic analysis of extracts of fetal arterial plasma showed that beta-lipotropin and other precursors of beta-endorphin made only a minor contribution to the immunoreactivity detected. Concentrations of immunoreactive beta-endorphin were higher in the femoral artery than in the umbilical vein in fetal sheep between 113 and 128 days of pregnancy. Therefore the placenta removes beta-endorphin or a closely related polypeptide of fetal origin from the umbilical circulation in sheep at this stage of gestation. Acute hypoxaemia and hypoglycaemia increase the concentrations of immunoassayable beta-endorphin in blood plasma of adult and fetal sheep, but little is known about the effects of chronic hypoxaemia or hypoglycaemia on the circulating levels of beta-endorphin and related polypeptides in the fetus. Therefore we also measured immunoreactive beta-endorphin in blood plasma from fetal sheep in which growth retardation in association with restricted placental growth was produced by removal of endometrial caruncles before mating. Intra-uterine growth retardation was accompanied by chronic hypoglycaemia and chronic hypoxaemia in the fetuses. This was not associated with higher concentrations of beta-endorphin-like immunoreactivity in fetal arterial or umbilical venous plasma, but was accompanied by significantly increased placental extraction of fetal immunoreactive beta-endorphin from the umbilical circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insignificant response of the fetal placental circulation to arterial hypotension in sheep

Infusion of the angiotensin-converting enzyme inhibitor enalaprilat into fetal sheep caused a profound arterial hypotension within days. Five fetal lambs were infused with enalaprilat for 8 days starting at day 128 of gestation. Total accumulated dose was 0.30 ± 0.11 mg/kg. Arterial pressure decreased from 43.6 to 25.6 mmHg; venous pressure did not change. Biventricular output was not statistically significantly changed; placental blood flow decreased almost in proportion to the decrease in pressure but the increase in somatic flow was not statistically significant. There were no significant changes in pressure 30 min after the initial 50-μg loading dose of enalaprilat. However, the arterial pressure responses to test doses of ANG I were largely abolished. After 1 day, however, there was a significant decrease in somatic vascular resistance, which became stronger with time, but almost no decrease in the placental resistance. We conclude that the fetal somatic circulation exhibits a slow but strong decrease in resistance but that the response to hypotension is weak or absent in the fetal placenta, possibly because it is already fully relaxed.     

The relationships between fetal and maternal placental blood flows.

Individual maternal and fetal flows to 706 placental cotyledons obtained from 9 chronically catheterized pregnant ewes and their fetuses (gestation age 123-141 days) were measured. The larger the cotyledon the greater the maternal and fetal blood flow to it. Both fetal and maternal flows to larger cotyledons, however, tended to be lower when corrected for the weight of the cotyledon perfused. Changes in fetal placental flow (dfgc, ml/min/g) occurring within 15 min of administration of 15 mg i.v. of captopril to the ewe were dependent on changes in fetal placental vascular resistance (dcotfr) and maternal flow (dmgc) according to the equation dfgc = 0.123 + 0.185 dmgc - 0.026 dcotfr. Changes in maternal placental flow occurring within 15 min of administration of 15 mg i.v. of captopril to the ewe were dependent on changes in maternal placental vascular resistance (dcotmr) and changes in fetal flow according to the equation dmgc = 0.483 + 0.496 dfgc - 0.0198 dcotmr. The changes in fetal flow over the next 1.5h of treatment with captopril at 6 mg/h were dependent on neither changes in fetal placental vascular resistance nor maternal placental flow. changes in maternal placental flows over the same time were no longer related to changes in fetal flow and depended only to a minimal extent on changes in maternal placental resistance. These analyses suggest that treatment of the pregnant ewe with captopril may have disturbed the normal relationships between maternal and fetal placental circulations.     

Significance of fresh weight to dry cell weight ratio in plant cell suspension cultures

Summary The ratio of fresh weight to dry cell weight (FW/DCW), an index of cell water content, is important in determining the theoretical maximum cell concentration in high density culture of plant cell suspensions. Theoretical maximum cell density for Thalictrum rugosum was estimated to be as high as 137.2 g/l. The FW/DCW values were found to vary from species to species and it was related to medium osmolarity. When the cells were placed in a high osmolarity environment, decrease of FW/DCW was very rapid, taking place within 24 hours.