Mouse fetal hemoglobin.

Using isoelectric focusing, a fetal hemoglobin was found in the peripheral blood of C57BL/6 fetal mouse during the 14 to 20 days gestational period. In acid-urea polyacrylamide gel the pattern of this fetal hemoglobin was different from that of the adult hemoglobin. The mouse fetal hemoglobin was differentiated from the mouse adult hemoglobin by immunodiffusion reaction. It suggests that there is a transient fetal hemoglobin in the C57BL/6 mouse during gestational age.     

On the kinetics of erythroid cell differentiation in fetal mice. II. DNA and hemoglobin measurements of individual erythroblasts during gestation

Microspectrophotometric absorption measurements were used to determine the hemoglobin content of erythroid cells derived from the yolk sac during gestation of fetal C3H mice, from day 9 to day 15. Using the DNA content as a marker for the mitotic state between 2C and 4C phase, five successive cell generations and their mean hemoglobin contents were distinguished: 12 pg (pg, picogram = 10^?12 gm). 22.2 pg, 37 pg, 50 pg and 56 pg. In the final state, nucleated erythrocytes contained 98 ± 22 pg hemoglobin. Erythroid cells derived from the liver were measured on day 15 of fetal gestation. The hemoglobin content of proerythroblasts was below 0.3 pg. The two cell generations in the basophilic state had 0.6 pg and 1.7 pg respectively. Polychromatic erythroblasts yielded a hemoglobin content of 5.1 pg in the first cell generation and 7.5 pg in the second one. Orthochromatic erythroblasts contained 8 pg, reticulocytes 12 pg and mature erythrocytes 28 ± 7 pg hemoglobin. Calculations based on these data suggest that the rate of total hemoglobin synthesis is similar in both yolk sac and liver erythropoiesis. The difference between the final hemoglobin content in nucleated erythrocytes of yolk sac origin and that in hepatic erythrocytes can be explained by the different cell generation times.     

Carbohydrate metabolism in the fetal pig during late gestation.

In acute experiments on pregnant sows under sodium pentobarbitone anaesthesia, acid base balance, oxygenation and plasma metabolite concentrations were well maintained in the dam and all fetuses which remained undisturbed in utero, irrespective of the duration of the experiment. Fetal liver glycogen concentrations were also unaffected by the time of removal of the fetus. By contrast, intravascular catheterization and withdrawal of blood led to fetal hyperglycaemia and depletion of hepatic glycogen although blood gas and pH values were not changed by these procedures. In the 1 1/2--2 h sampling period following catheterization the normal positive umbilical venous-arterial differences in plasma glucose and lactate generally became reversed. These changes were prevented by the administration of hexamethonium (10--15 mg . kg-1 i.v.) but the drug did not block the fall in hepatic glycogen in catheterized fetuses. Both adrenaline and noradrenaline, which were each infused intravenously at 2.7--3.9 or 0.6--0.9 microgram . kg-1 . min-1, resulted in fetal hyperglycaemia and lacticacidemia together with a fall in arterial blood pH; hepatic glycogen concentrations in these fetuses were also reduced. The apparent sensitivity of the glycogenolytic mechanism to surgical trauma and haemorrhage in the fetal piglet is discussed in relation to findings in other species.     

On the kinetics of erythroid cell differentiation in fetal mice. I. Microspectrophotometric determination of the hemoglobin content in erythroid cells during gestation

In a microspectrophotometric study, photographic emulsions and a computer are used for measuring the hemoglobin content of a large number (about 50,000) of erythroid cells in fetal mice. Histograms of the hemoglobin content in erythroid cells illustrate the kinetics of erythropoiesis in yolk sac derived nucleated cells in the fetal peripheral blood, in fetal liver, and in fetal spleen. After the occasional extrusion of their nucleus, yolk sac derived erythrocytes remain as “macrocytes” in fetal circulation two or three days longer than the nucleated yolk sac derived erythrocytes do. Erythrocytes in fetal liver have a constant hemoglobin content of 28 pg ² until day 17 of gestation. During further erythropoiesis in liver and then in the spleen, this amount is gradually adapted to the normal hemoglobin content in red blood cells of 16 pg.     

Changes in permeability of fetal guinea pig skin during gestation

Permeability of fetal skin to tritiated water was measured in vitro using samples taken from the back and flanks of 21 guinea pig fetuses whose gestational age ranged from 30 to 67 days (term = 68 days). From 30 to 45 days, fetal skin was relatively permeable to water, with a permeability coefficient for unidirectional, diffusional transfer of labelled water that averaged 0.372 +/- 0.041 (SEM) X 10(-4) cm/s. Then during a 5-10 day interval, the measured permeability coefficient decreased abruptly to very low and barely detectable levels. These changes took place at the time during gestation when others have shown the skin becomes keratinized and growth of new hair follicles is completed. Thus these findings are consistent with a relatively free exchange of water between amniotic fluid and fetal interstitium across the skin during the first two-thirds of gestation and then with further maturation an abrupt functional separation between these fluid compartments during the last third of gestation.     

Morphological observations of the fetal rat spleen during prolonged gestation

The ultrastructure of splenic cells and frequency of cell types were examined in fetal rats during progesterone-induced (P23, 24, 25) and surgically-induced (S23, 24, 25) prolonged gestation, and compared to term (T) fetuses and newborn animals (N1, N2, N3). Statistical analysis revealed an increase in numbers of erythroblasts and a decrease in numbers of neutrophils in post-term fetuses distinct from that seen in term and newborn animals. However, there were also significant differences between the post-term groups: the frequency of erythrocytes and total number of cells were higher in the drug-treated group, despite similar splenic weights in the two. The results are interpreted as a response by the spleen (increased erythropoiesis) to fetal hypoxia, which is known to exist during prolonged gestation.     

The initiation of fetal hemoglobin biosynthesis.

Biosynthesis of the alpha and beta chains of rabbit and human adult hemoglobin is initiated with a methionyl residue, which is removed during elongation of the peptide chain. To study the initiation of biosynthesis of the delta chain of human fetal hemoglobin, fresh placental blood was used for labeling experiments with radioactive amino acids. Labeled nascent peptide chains were purified from the polysomal fraction of placental blood reticulocytes. The number of amino acid residues in nascent gamma chain at the time of removal of its N-terminal methionine was estimated to be 40--60 from the relative yields of labeled tryptic peptides.     

Transferrin in fetal sheep cerebrospinal fluid and plasma during gestation

1. Transferrin concentrations in fetal sheep CSF and plasma have been estimated between 31 and 125 days gestation and in the adult, using a radial immunodiffusion assay. 2. The plasma concentration was lowest (183 +/- 35 mg/100 ml) in the earliest fetuses examined (31 days). It increased to over 350 mg/100 ml by 35 days; thereafter it was around the adult value (580 mg/100 ml). 3. In CSF the transferrin concentration increased from 43 +/- 10 mg/100 ml at 31 days to a maximum of 163 +/- 14 mg/100 ml at 40 days gestation after which it decreased considerably to 6.1 +/- 0.7 mg/100 ml at 125 days and was even lower in the adult (1.1 +/- 0.2 mg/100 ml). 4. CSF: plasma ratios for transferrin especially when compared with those of other plasma proteins, are not compatible with passive leakage of protein from blood to CSF in the developing brain. The results may be explained by specific transfer of proteins into CSF but synthesis by the choroid plexus or brain has not been excluded.     

Maternal and fetal prostaglandin concentrations during late gestation in dairy cattle

A study was conducted to measure the blood plasma concentrations of prostaglandin F_2α (PGF_2α), 13,14-dihydro-15-keto-prostaglandin F_2α (PGFM), prostaglandin E₂ (PGE₂) and 13,14-dihydro-15-keto-prostaglandin E₂ (PGEM) in the jugular vein, umbilical vein and artery and uterine vein of 18 Holstein Friesian cows during late gestation. A caesarean section was performed on all cows before term in order to obtain blood samples from the different sources. Plasma PG concentrations in the uterine or fetal circulation were significantly higher than in jugular vein plasma. Correlations between peripheral PG metabolite concentrations and primary PG concentrations in the various sources of the uterus or fetus were not significant (r = .17 − .47) and demonstrated that prostaglandin values based upon peripheral blood alone are of limited value.     

Doppler evaluation of maternal and fetal vessels during normal gestation in rabbits

The aim of this work was to evaluate the hemodynamic changes in the utero-placental arterial vessels in rabbits (Orictolagus cuniculus) throughout pregnancy as well as those in the umbilical cord, aorta, and caudal vena cava of fetuses to establish their normal reference ranges for systolic peak velocity (SPV), end diastolic velocity (EDV), pulsatility index (PI), and resistance index (RI). The blood flow waveforms were monitored every 4 d in 10 rabbits from Day 10 of pregnancy onward by means of color and pulsed wave Doppler ultrasonography using a 5.5-7.5 MHz microconvex transabdominal probe. The utero-placental blood flow was characterized by steep increases and decrease in the SPV with a slow diastolic wave and relatively high EDV, whereas that of the umbilical artery was discontinuous until Day 22 of pregnancy, when a diastolic waveform was also detectable. From Day 10 to 22 of pregnancy, the fetal aorta blood flow was discontinuous, but thereafter a diastolic peak was measurable. The blood flow of the fetal caudal vena cava was characterized by a systolic peak followed by a small diastolic peak. Throughout the gestation, the SPV and the EDV of maternal and fetal vessels increased (α < 0.05), whereas the PI and the RI decreased (α < 0.05), except for the utero-placental vessels. This work confirms that the rabbit could also be a valid experimental animal model to study, by Doppler ultrasonography, functional hemodynamic changes of the fetuses and placenta vessels in both normal and pathophysiologic conditions.     

Variations of chromosome radiation sensitivity in fetal and adult mice during gestation

Mice were exposed to 2 Gy of γ-rays at various days of pregnancy, and just before and after gestation. Chromosomes were analyzed 4 h after irradiation in spontaneously dividing hematopoietic cells from liver for fetuses and bone marrow for mothers. On average, there was significantly less chromosome damage in fetuses than in mothers. A very strong increase of chromosome breakage was observed in mothers at days 16–19 of gestation. This increase parallels that of gestation hormones, suggesting a direct relationship. The differences between fetuses and mothers in relation to gestation age result from the increase in the rate of chromatid and chromosome breaks but not of chromatid exchanges, which remained stable. This suggests that a DNA repair step involved in joining broken extremities is the cause. More experiments are needed to understand the origin of these variations of radiation sensitivity and the possible extrapolation of these observations to other species.     

Repeated ethanol exposure during late gestation decreases nephron endowment in fetal sheep

Maternal alcohol consumption during pregnancy can affect fetal development, but little is known about the effects on the developing kidney. Our objectives were to determine the effects of repeated ethanol exposure during the latter half of gestation on glomerular (nephron) number and expression of key genes involved in renal development or function in the ovine fetal kidney. Pregnant ewes received daily intravenous infusion of ethanol (0.75 g/kg, n=5) or saline (control, n=5) over 1 h from 95 to 133 days of gestational age (DGA; term is approximately 147 DGA). Maternal and fetal arterial blood samples were taken before and after the start of the daily ethanol infusions for determination of blood ethanol concentration (BEC). Necropsy was performed at 134 DGA, and fetal kidneys were collected for determination of total glomerular number using the physical disector/fractionator technique; at this gestational age nephrogenesis is completed in sheep. Maximal maternal and fetal BECs of 0.12+/-0.01 g/dl (mean+/-SE) and 0.11+/-0.01 g/dl, respectively, were reached 1 h after starting maternal ethanol infusions. Ethanol exposure had no effect on fetal body weight, kidney weight, or the gene expression of members of the renin-angiotensin system, insulin-like growth factors, and sodium channels. However, fetal glomerular number was lower after ethanol exposure (377,585+/-8,325) than in controls (423,177+/-17,178, P<0.001). The data demonstrate that our regimen of fetal ethanol exposure during the latter half of gestation results in an 11% reduction in nephron endowment without affecting the overall growth of the kidney or fetus or the expression of key genes involved in renal development or function. A reduced nephron endowment of this magnitude could have important implications for the cardiovascular health of offspring during postnatal life.     

Lack of change in the composition of fetal lamb lung surfactant during gestation

Fetal surfactant from lamb lung fluids collected daily from day 114 to day 146 of gestation, was isolated by centrifugation (pellet material) and further purified by sucrose density gradient centrifugation. The concentration of the pellet material from lung fluid (crude surfactant) increased from day 125 till day 135 and fluctuated strongly from that period onwards, whereas lung fluid secretion increased linearly until a few days before parturition. The pellet phospholipid composition changed with gestational age, suggesting biochemical maturation of the surfactant-producing system. The purified surfactant fraction, of which approximately 85% was phosphatidylcholine, did not change however from day 122 onwards except for a small increase in the percentage of phosphatidylglycerol. Alveolar wash surfactant or the lamellar body material, isolated from fetal lungs at different gestational ages had the same composition as surfactant from lung fluids. Only the composition of lamellar bodies of '125 day' lungs differed slightly from that of the lung fluid surfactant. The similar characteristics of all purified surfactant fractions throughout gestation indicate that, in the fetal lamb, lung maturation is associated with an increase in surfactant production no significant changes in phospholipid composition.     

On the chromatographic heterogeneity of human fetal hemoglobin.

Minor fetal hemoglobins in red cell hemolysates of newborn and adults with elevated levels of Hb F have been separated and quantitated by Biorex 70 column chromatography. In addition to Hb F1, other minor hemoglobin zones eluting before F1, pre-F1, and after F1, post-f1 have been observed. The relative amounts of the two pre-F1 zones and F1 are higher in the red cells of adults with 97--100% Hb F (homozygous hereditary persistence of fetal hemoglobin, homozygous deltabeta-thalassemia and homozygous beta0-thalassemia) than in the red cells of an adult with homozygous beta+-thalassemia with 66% Hb F, a child with a trisomy-D-13 having 38% Hb F, and in two newborn. Hb F was glycosylated in vitro with [14C]glucose or [14C] glucose 6-phosphate, and was acetylated using chicken reticulocyte lysate or a crude acetyltransferase preparation isolated from the same lysate with [14C]acetyl-CoA as substrate. Chromatographic analyses indicated that the Hb F1 zone can be formed both by glycosylation and acetylation of Hb F, and that pre-F1 zones can be products of the reaction of Hb F with phosphorylated glycolytic intermediates. Biosynthesis of minor hemoglobins in reticulocytes was studied with [14C]leucine in the presence and absence of cycloheximide and by pulse-chase. The resulting data indicate that Hb F1 synthesis is dependent upon Hb F synthesis and that the posttranslational modification may take place at an early stage in Hb F synthesis.     

Caveolin-1 immuno-expression in human fetal tissues during mid and late gestation

Caveolin-1 (Cav-1) is the main protein in caveolae, and serves as a scaffolding protein onto which many classes of signalling molecules are assembled. Through interaction with proto-oncogene products, Cav-1 may suppress cell proliferation; or when phosphorylated, may also stimulate cell growth. The aim of this study was to determine Cav-1 expression in human fetal tissues, tissues composed of cells undergoing growth and differentiation processes which require a nurturing environment provided by transmembrane vesicular transport. By using immunohistochemistry, Cav-1 was detected in several fetal tissues during mid- and late gestation (from 14 to 39 weeks). The protein was present in adipocytes, endothelial cells, smooth muscle fibers and in a number of sites with a pattern of distribution similar to that of the adult. Intriguingly, a positive immunoreaction for Cav-1 was also noticed in tissues, such as the urothelium, which normally do not express this protein in adulthood. This unexpected pattern of Cav-1 in human fetus may predict novel roles for Cav-1 during fetal development.     

Hepatic,placental, and fetal trace elements following molybdenum supplementation during gestation

The effect of dietary Mo (Na2Mo(4)2H2O) added to drinking water at levels of 0, 5, 10, 50, or 100 mg on hepatic (gestating dams), placental, and fetal Mo, Cu, Zn, and Fe contents of Sprague-Dawley rats was studied. These elements were determined by a polarographic catalytic procedure for Mo and by atomic absorption spectrophotometry for Cu, Fe, and Zn. Hepatic Mo increased two to sixfold (5-100 mg Mo). There was a 1.5-fold increase in hepatic Cu, significant only at the 50 to 100 mg Mo/L treatment levels. Although the hepatic Fe content of the gestating rats significantly increased with Mo supplementation, the extent of the increase appeared to be influenced by the litter size, fetal weights, and the degree of fetal resorption. Zinc values did not differ at any of the treatment levels. Placental Mo increased 3-76-fold, Cu one to threefold. No differences were observed in placenta Fe or Zn. Fetal Mo increased two to six-fold (10-100 mg/L) and Cu increased one to fivefold. There were no differences in the Fe and Zn content although both of these elements appeared to decline as the level of supplemental Mo increased. Significant correlations were also observed between hepatic, placental, and fetal Mo, Cu, Fe, and Zn. These results suggest that changes in trace mineral status in gestation, owing to high Mo intake, do occur and such occurrences are also reflected in the fetus.