Days Of Intrauterine Life Research Articles

Intracellular signalling of epinephrine in rat hepatocytes during fetal development and hepatic regeneration

The changes in intracellular calcium concentration and IP3 production after the addition of epinephrine were analysed in adult, fetal (20th-22nd day of intrauterine life), and regenerating rat hepatocytes (4 h-24 h after partial hepatectomy) to determine whether the signal transduction is the same in quiescent proliferating and differentiating cells. The epinephrine treatment causes a significative cytosolic calcium transient in hepatocytes isolated in the last day of fetal life (22-day old) and in the early stage of regeneration (4 h). This effect is not significant in the previous stage of fetal life (20-day old) and at the onset of M phase of cell cycle after partial hepatectomy (24 h). [3H]myo inositol incorporation into IP3 and IP4 is higher in 20 day fetal and regenerating hepatocytes with respect to the control. In these cells the epinephrine does not affect basal level of IP3 and IP4, while it causes a substantial increase of these inositol phosphates in adult hepatocytes. [3H]myo inositol incorporation into PIP2 is very low at the 20th day of fetal life. Epinephrine has no effect on this parameter in fetal and regenerating hepatocytes. Our results show that the epinephrine signal is mediated differently in proliferating and in quiescent hepatocytes.

Corticotropin-releasing factor-like immunoreactivity, arginine vasopressin-like immunoreactivity and ACTH-releasing bioactivity in hypothalamic tissue from fetal and neonatal sheep.

Corticotropin-releasing factor-like immunoreactivity (CRF-LI), arginine vasopressin-like immunoreactivity (AVP-LI) and ACTH-releasing bioactivity of hypothalamic tissue from 63- to 143-day-old ovine fetuses and from 7- and 150-day-old lambs have been assessed. CRF-LI and AVP-LI contents and concentrations increased steadily between 63 and 138 days of gestation, decreased at day 143 then rose again in postpartum animals. In terms of concentration, the AVP-LI/CRF-LI ratio remained close to 5 between 63 and 123 days of intrauterine life, decreased steadily in late gestation down to 1.2 at day 143 increased again in lambs. The total hypothalamic ACTH-releasing bioactivity increased 26-fold between 63 and 138 days of gestation and remained constant until day 143. The highest values were observed in 150-day-old-lambs. These data support the view that AVP and oCRF1-41 might be important hypothalamic factors involved in the regulation of ACTH release by the pituitary gland of the sheep fetus. In addition, they suggest that AVP is more important in young fetuses and lambs than in prepartum animals.

Changes in the cAMP synthesis by fetal thyroid during the 5 last days of the intrauterine life in the rat.

The cAMP synthesis by fetal rat thyroids is stimulated in vitro by thyrotropin (TSH) or forskolin during the 5 last days of intrauterine life. The effects are TSH- or forskolin-dose-dependent with equal responses to 20 mIU.ml-1 TSH or to 1 microM forskolin. The magnitude of the responses to TSH or to forskolin decreases significantly as the fetus is ageing. Since forskolin effects bypass hormone receptors, the adenylate cyclase activity can be concluded to decrease during the end of gestation probably in relation with thyroid iodine accumulation. The responses to TSH and forskolin becoming synergic between 19 1/2 and 21 1/2 days indicate modifications of adenylate cyclase properties probably related to some maturation of the enzyme.

Development of erythroid colony-forming cells in rat fetal spleen: apparent lack of sensitivity to an in vivo corticosteroid excess as compared to fetal liver.

The development of splenic erythroid colony-forming cells from rat embryos in the last 4 days of intrauterine life was examined after 2 and 7 days in a methylcellulose culture system. The number of 2- and 7-day erythroid colonies decreased sharply between, respectively, days 20 and 21 of gestation and days 19 and 20. Concomitantly, a maturation of proerythroblasts and basophilic erythroblasts to mature erythroblasts was detected on smears of splenic cellular suspensions. The effect of a corticosteroid excess induced by a maternal laparotomy was tested on spleen and liver cultures from the same control or experimental fetuses. The ratio of the number of 2-day to the number of 7-day erythroid colonies did not differ in experimental and control splenic cultures, but in liver cultures was significantly lower at days 19 and 20 in experimental than in control cultures.

In vivo developmental modifications of the expression of genes encoding muscle-specific enzymes in rat.

cDNA clones for rat muscle-type creatine kinase and glycogen phosphorylase and aldolase A were isolated from a rat muscle cDNA library. An additional clone recognizing an unidentified 2.7-kilobase pair mRNA species was also isolated. These cDNA clones were used as probes to investigate the expression of the corresponding mRNAs during muscle development. Two aldolase A mRNA species were detected, one of 1650 bases expressed in non-muscle tissues, fetal muscle, and adult slow-twitch muscle, the other of 1550 bases was highly specific of adult fast-twitch skeletal muscle differentiation. These aldolase A mRNAs were shown by primer extension to differ by their 5' ends. The accumulation of muscle-type phosphorylase and creatine kinase and muscle-specific aldolase A mRNA accumulation during muscle development seems to be a coordinate process occurring progressively from the 17th day of intrauterine life up to the 30th day after birth. In contrast, the 2.7-kilobase pair RNA species is maximally expressed at the 1st week after birth as is the neonatal form of myosin heavy chain mRNA.

Plasma growth hormone concentration in the chronically catheterized ovine fetus during spontaneous term delivery and premature delivery induced by continuous intravascular infusion of low doses of adrenocorticotropin or cortisol to the fetus

Fetal plasma growth hormone concentrations were measured in 15 pregnant ewes over the last 5 days before delivery. In five chronically catheterized pregnant ewes that underwent spontaneous vaginal delivery 146 ± 2 days (mean ± SD) of gestation, fetal plasma growth hormone concentrations fell from 124.6 ± 44.1 ng · ml−1 5 days before delivery to 35.2 ± 31.3 ng · ml−1 at delivery. In three fetuses in which premature delivery was induced by the infusion of cortisol to the fetus at 128 days of gestation, fetal plasma growth hormone levels fell from 195 ± 19.1 ng · ml−1 to 70.7 ± 25.5 ng · ml−1 over the last 5 days of intrauterine life. In seven fetuses in which premature delivery was induced with infusion of synthetic adrenocorticotropin to the fetus beginning at 120 or 130 days of gestation, the fetal plasma growth hormone level did not fall (175.6 ± 75.7 to 158.9 ± 60.1 ng · ml−1). Fetal plasma cortisol concentrations at delivery were significantly higher in the cortisol-infused fetuses (214 ± 38.4 ng · ml−1) than in both control (94.4 ± 33.7 ng · ml−1) and adrenocorticotropic hormone-infused fetuses (94.5 ± 31.9 ng · ml−1). The fall in the fetal plasma growth hormone level in cortisol-induced fetuses may be due to the higher fetal plasma cortisol concentrations achieved in the cortisol-infused compared with the adrenocorticotropic hormone-infused fetuses in which no comparable decrease in growth hormone was observed. These findings suggest that there are significant differences in the fetal response to various experimental regimens used for the induction of premature labor in the sheep.

Developmental changes of proteoglycan synthesis in rat liver and isolated hepatocytes

The synthesis of sulfated proteoglycans in late fetal (19th to 22nd day of intrauterine life), early postnatal, and adult liver tissue as well as in hepatocytes and their distribution in plasma membranes were studied. Overall proteoglycan production is enhanced two-fold in fetal as compared with adult liver tissue. In contrast to slices from adult liver, in which the synthesis of heparan [ 35S]-sulfate comprises more than 80% and chondroitin sulfate less than 5% of total glycosaminoglycans, chondroitin [ 35S]sulfate is the major type of glycosaminoglycans synthesized in fetal liver representing about 50% of total sulfated glycosaminoglycans. Thus, the synthesis of chondroitin sulfate is elevated nearly 30-fold in fetal liver as compared with the adult counterpart. Immediately after birth chondroitin sulfate formation decreases rapidly reaching adult levels between the 10th and 15th day of postnatal life. The production of heparan sulfate is almost unchanged during perinatal liver development due to a relatively low fractional synthesis of heparan [ 35S]sulfate in fetal liver. Hepatocytes were identified as the cell type responsible for elevated chondroitin sulfate production in fetal liver. Erythroblasts, which synthesize chondroitin sulfate, contribute less than 10% to total glycosaminoglycan synthesis in embryonic liver. Plasma membranes of adult liver contain exclusively heparan sulfate whereas in neonatal liver cell membranes 25% of labeled glycosaminoglycans is represented by chondroitin sulfate, a fraction which decreases rapidly after birth. In parallel to the postnatal shut down of chondroitin sulfate synthesis the activity of the UDPxylose:coreprotein xylosyltransferase (EC. 2.4.2.26) decreases from 4.8±0.5 dpm/h per μg protein to 0.3±0.1 dpm/h per μg protein suggesting a regulatory function of the enzyme for proteochondroitin sulfate synthesis in developing liver. The formation of both heparan sulfate and chondroitin sulfate is dependent on functioning protein synthesis, which indicates, together with double labeling experiments using [ 3H]serine and [ 14C]glucosamine as isotopic precursors, their synthesis as proteoglycans. The positive correlation ( r − 0.949) between the incorporation of [ 3H]thymidine into DNA and chondroitin [ 35S]sulfate production supports the assumption of a cell growth promoting activity of chondroitin sulfate and points to a significant role of the glycosaminoglycan in the process of cellular proliferation and tissue differentiation.

Electron microscopic evidence for the presence of an asialoglycoprotein receptor on isolated foetal rat hepatocyte surface

The ontogeny of asialoglycoprotein receptor was investigated by electron microscopic cytochemistry in hepatocytes isolated from foetal and adult rat. The binding capacity for asialofetuin coupled to horseradish peroxidase was lacking before the 18th day of intrauterine life; it arises at this time and increases with developmental age. The ligand-receptor complexes form small patches. The distribution pattern of positivity is very similar in pre and postnatal age, covering the entire cell surface. These results indicate a rather late appearance of the galactose-binding capacity related to the asialoglycoprotein clearance function, which is typical of adult mammalian liver.

Chemical Composition of Bodies and Organs of Pig Fetuses in the Last Forty Days of Intrauterine Life

Padalikova Drahomira, Jdkova Dagmar: Chemical Composition of Bodies and Organs of Pig Fetuses in the Last Forty Days of Intrauterine Life. Acta Vet. Brno, 53, 1984: 19-30. Proteins are the main organic component of pig fetal bodies. Their relative amount increases from 5.03 ± 0.16 % in fetuses 74 days old to 9.13 ± 0.25 % in 114-day old fetuses. The steepest increase of both relative and actual amounts of proteins in fetal body is seen until the 94th day of gestation. On the 114th day of gestation the significant positive relation between fetal mass and protein per cent in their bodies can be demonstrated. The relative fat amount in fetal bodies increases between 74th and 84th day from 0.72 ± 0.03 to 1.11 ± 0.02 % and between 94th and 104th gestation day from 1.13 ± 0.02 to 1.53 ± 0.03 %. In the last 10 days prior to birth the relative fat content in fetal bodies statistically significantly decreases from 1.53 ± 0.03 to 1.37 ± 0.05 %. The relative ash content in fetal bodies rises during the whole followed period and in ll4-day old fetuses reaches the value of 3.95 ± ± 0.03 %. The amount of all the three followed components of fetal bodies protein, fat and ash was found to be quantitatively sevenfold higher at the 114th day of gestation when compared with the 74th day of their age. The body mass of fetuses increases four times during the last 40 days of intrauterine life. Further the development of mass and chemical composition of the heart, lungs and liver, and changes in the mass of the kidney were followed. The most pronounced changes occurred in the chemical composition of the liver the relative protein content of which decreased from 12.11 ± 0.20 to 7.55 ± 0.20 % in the last twenty days prior to birth. Pig fetuses, body mass, organ mass, protein, fat, ash and dry matter content. Although data concerning the chemical composition of fetal bodies are encountered in literature (Svecin et al. 1967, Pomeroy 1960, Curtis et al. 1969) the detailed information concetning especially the last 40 days of intrauterine life is very scarce. Svecin et al. (1967) reports e. g. on chemical composition of fetal bodies at 88th and 113th gestation day, Pomeroy (1960) reports on fetuses 51, 74, 95 and 114 days old stating that heavier fetuses of the same age group have higher relative content of protein. Curtis at al. (1969) when prolonging the gestation period of sows found that the biochemical composition of 114-day old fetuses was not changed by the prolonged gestation by 1 week. In our previous work (Padalikova et al. 1972; J dkova et al. 1971) we followed the changes of weight and hydration of pig fetuses that occur during the last 40 days of intrauterine life. We have decided to expand this knowledge by an analysis of changes in chemical composition of pig fetal bodies and organs.

Organogenesis of the venous structures of the human liver: A hemodynamic theory

Reconstruction of human embryonic livers (Streeter's developmental horizons XVI, XIX and XX) showed that hepatic segmentation arises between the 35th and 45th day of intrauterine life and that the vena umbilicalis sinistra plays an important role in this developmental phenomenon. Conversely, the results of this study demonstrated the regressive and non functional nature of the vena umbilicalis dextra and vitelline vessels. Furthermore, our observations allowed to identify the embryonic period during which umbilical blood flow begins to invest the mass of hepatic cells and runs about the sinusoids. The flow pattern described in this report induces special fluid currents which are reflected by a progressive increase in the variability of the venous structures lying more and more distally to the point of entry of the vena umbilicalis sinistra in the liver. These hemodynamic phenomena could thus account for the constancy of the left part and the variability of the right part of the liver, as well as the variability of the site of origin of the right paramedian vein with respect to the bifurcation of the vena portae.

Fetal and postnatal development of cyclic GMP phosphodiesterase activity in the rat brain

Cyclic GMP concentration and cyclic GMP phosphodiesterase activity were studied in rat mothers and fetuses at 17, 19 and 21 days of intrauterine life and 0, 1, 4, 10, 15,20, 30 and 45 days after birth. During this developmental period, the increase in cyclic GMP concentration was discrete and the value in 15-day-old rats was already similar to the adult level. Cyclic GMP phosphodiesterase activity increased from 17- to 19-day fetuses and was significantly reduced in 21-day fetuses, neonates, and 1-day-old rats. This reduction may be a result of fetal endocrine preparation for parturition. During postnatal development, cyclic GMP phosphodiesterase activity increased in a parallel way in the limbic system, corpora striata, cerebral hemispheres, and diencephalon, reaching maximal level between 20 and 30 days after birth, and then decreasing to the adult value. The highest activity was found in corpora striata and the lowest in diencephalon. Cerebellar cyclic GMP phosphodiesterase activity was very high in the 4-day-old rat (257% of adult value) and diminished significantly in the 10-day-old rat with no subsequent changes. Kinetic analysis of the enzyme during postnatal forebrain development showed an increase in both the V max and the apparent K m. A decrease in the enzyme's V max was observed only in the cerebellum. The importance of cyclic GMP phosphodiesterase regulation of cyclic GMP concentrations in the brain during development is discussed.

Fetal and Early postnatal development of adenylate cyclase and cyclic AMP phosphodiesterase activities in rat brain.

Brain cyclic AMP metabolism was studied in rat offspring at 17, 19 and 21 days of intrauterine life and 0, 1 and 4 postnatal days. Wet weight and protein and DNA and RNA concentrations in brain increased in parallel with body weight until the 4th postnatal day although during the perinatal phase some of these parameters suffered a manifest temporal retardation. In the brain, similar qualitative changes were observed in both adenylate cyclase and high Km cyclic AMP phosphodiesterase activity while the low Km enzyme showed a rise from 17-day fetuses to those of 19 days with no further changes. The increase in cyclic AMP concentration was very mild and the values found in the 21-day fetuses were already similar to those in adults. In the mother's brain a significant reduction in adenylate cyclase activity appeared at 19 and 21 days of gestation. The retardation in the ontogenic development of cyclic AMP metabolism during the perinatal phase in offspring is probably a consequence of their specific metabolic situation while in the mother it may be the result of its endocrine preparation for parturition.

Insulin receptors in the live rat fetus. Differential effects of maturation according to cellular type

Purified carrier-free monoiodinated insulin (Ins*) alone or mixed with an excess of native insulin was injected into the vitelline vein of 17, 19 or 21 day-post coitum (d.p.c.) rat fetuses in utero. Several organs concentrated Ins* among which liver, kidneys, heart, jejuno-ileum and lungs. Their radioactivity was analyzed by gel chromatography and autohistoradiography. In the 3 age groups, the liver had the highest specific activity: binding was saturable, partly reversible, associated with the hepatocytes and to a lower extent with the liver hematopoietic cells. Liver maturation was essentially characterized by a progressively increasing rate of hormone internalization and degradation. In the lungs, high affinity and saturable binding was associated with the glycogen-laden cells of the bronchial tubes (pseudoglandular stage: 17 d.p.c. fetuses). Ins* binding was no longer observed in more mature surfactant synthetizing cells (canalicular, 19 d.p.c. and alveolar, 21 d.p.c. stages).In conclusion: 1. Insulin receptors ontogenesis occurs early in gestation. 2. During the last 5 days of intra-uterine life, cytodifferentiation differently affects insulin metabolism at the cellular level, inducing loss of insulin receptors (lungs) or maturation of post receptor steps (hepatocytes).

Early erythropoiesis in foetal rat bone marrow: evidence for a liver-to-bone marrow relay

Erythropoietic activity of foetal rat femoral marrow was examined during the last four days of intra-uterine life. Insignificant at day 18, it develops slowly thereafter until birth. In the non-suckled neonate (not older than two hours), it appears notably enhanced. In order to test the potential of the foetal marrow to develop precocious or increased erythropoiesis, the activity of the erythropoietic organ predominant at this time, the liver, was altered by modifying the level of circulating corticosteroids, which govern its function. Maturation and involution of the hepatic erythron wee prevented by corticosteroid deprivation of the foetus (maternal adrenalectomy and foetal hypophysectomy). Precocious maturation and exhaustion of the hepatic erythron was induced by submitting foetuses to corticosteroids excess from day 14. Both corticosteroid deprivation and excess increase the erythropoietic activity of the femoral marrow. This activity can reach and even exceed by day 20 of intrauterine life that in neonatal marrow. Foetal hepatic erythron misfunction can therefore initiate and stimulate bone marrow erythropoiesis. The study of circulating red blood cells demonstrates that : (1) anaemia initiates medullary erythropoietic activity; (2) this anaemia is largely corrected by the bone marrow. The regulatory mechanism is presumably erythropoietin mediated.

Placental transfer of aldosterone in the guinea-pig during late pregnancy

The rates of foeto-maternal exchange and metabolism of aldosterone were calculated from experiments in which the labeled hormone was infused at a constant rate into the maternal and foetal circulations of the guinea-pig during the last few days of intrauterine life. It was found that d-[1,2,6,7- 3H]-aldosterone crossed the placenta from the mother to the foetus and in the reverse direction. The maternal to foetal, as well as the foetal to maternal ratios of the tracer, increased between 60 and 67 days of gestation. The maternal contribution to the concentration of aldosterone in the plasma of the foetus was of 23.8 % at 64 days and 35.7% at 67 days. At least 60% of the aldosterone in the foetal plasma was of foetal origin. The foetus contributed very little to the concentration of aldosterone in the plasma of the mother.

Skeletal development of an orang-utan premature Newborn: A comparative study with man

The state of skeletal ossification of a premature newborn of Pongo pygmaeus has been studied radiologically. it is described comparatively to a human foetus of the same age (210–230 days of intrauterine life). Correlations may be established between the degree of development of some skeletal districts (mainly skull and foot) and the different speicalizations of the two evolutionary lines.

Dominant and recessive effects of induced lethals in female mice by exposure to gamma-irradiation during the 10th to 14th day of intrauterine life

The frequency of (dominant and) recessive lethal mutations induced by 160-rad chronic gamma-irradiation given with a dose rate of 0.03 rad/min during the 10th to 14th day of gestation has been studied in female CBA-mice. An increased rate of recessive lethal equivalents by about 10% has been noted. This increase corresponds to a mutation rate of 6.3 × 10 −4 mutation/rad/ genome. There were not found any dominant mutations, nor any dominance effects from the induced recessive lethal equivalents. The hazards after irradiation during foetal development are discussed.

Histologische und biochemische Untersuchungen zur postnatalen Entwicklung der Leber beim Meerschweinchen

Problem: In newborn guinea pigs the structural development of the liver was studied with emphasis on changes in the lipid content as related to biochemical parameters. Material and methods: The livers of 149 guinea, pigs (strain Pirbright) up to an age of 21 days were examined. The mothers were grouped in cages and kept as usual (room temperature 22 °C, air humidity 60–70 %, natural light-dark rhythm and commercial standard diet ad libitum, sawdust and straw as bedding). Pregnant animals were placed in individual cages being left there together with their offspring until weaning or sacrification. In this period additional uptake of solid diet was allowed to the young guinea pigs. The animals were bleeded to death in anesthesia (by head stroke). For histological examination tissue samples from the Lobes sinister lateralis were fixed in Barker’s formol or absolute alcohol. The following staining reactions were applied (paraffin embedding or frozen sections): haemalumeosin stain ; PAS-reaction; Sudan III; Sudan black; Best’s carmine (for details on the techniques see Romeis 1968). In biochemical analysis the total lipids of the liver were determined by the isolation methods reported by Folch et 301. (1957). Moreover, in modification of the analytical procedures earlier described (Sallmann 1972 a, b) several fractions of the liver total lipids could be isolated. By dialysis against a rubber membrane a dialysable lipid component (hydrocarbons, triglycerides, incomplete glycerides, cholesterol and free lipid acids) was isolated from the phosphatide fractions. Further separation of the “dialysable” lipids on Florisil columns yielded purified glyceride fractions. The total lipids as well as all components isolated from these were determined gra,vimetrically after removal of the solvents concerned. In biochemical analysis the livers of fetuses 10–12 days an te partum and of young animals up to 53 days were included. Results (see also table 1): The relative liver weight — related to the body weight reduced for that of the gastrointestinal tract — is highest at birth. It is lowered independent of the development of the gastrointestinal tract within a short period, then it remains fairly constant during the rest of the time of observation. On the 1st day abundant lipids are regularly distributed throughout the whole liver lobule (fig. 1). Beginning with the 3rd day the central parts of the lobules are nearly free from lipids, only in the peripheral zones of the lobules lipid augmentation was still observed. Consequently the marked decrease in liver weight is due to the rapid reduction of lipids within the first 3 days of life. These observations are in accordance with the biochemical findings: about 10 days ante partum noticeable storage of lipids occurs in the liver reaching its peak 2 to 3 days after birth (physiological fatty infiltration of the liver during the last days of intrauterine life). In fetal liver tissue predominantly tryglycerides are augmented. In addition to de-novo-synthesis especially the intense transplacental influx of the maternal free fatty acids into the fetal tissue of guinea pigs is suggested to contribute to the enhancement of lipid and lipoproteid synthesis (very low density lipoproteins = VLDL). With respect to their energy metabolism the newborn guinea pigs are obviously dependent on these immediately available lipid stores in the liver during the first few days after birth. This mainly meets with the guinea, pig as it is of high motility already on the 1st postnatal day after a, relatively long period of intrauterine development. The observations concerning liver glycogen can be interpreted in similar way: Within the first few postnatal days the glycogen estimations show strongly positive results throughout the whole liver lobule. On the 3rd and the 4th day the glycogen is predominantly localized mainly in the centrolobular area, however, it still extends fairly deep into the peripheral zones. This pattern of distribution with marked decrease of glycogen in the peripheral zone of the lobule persists until the end of the experimental period.

Testosterone in the fetal rat testis.

Testes of fetal rats possess the enzymes necessary for converting radioactive acetate to radioactive testosterone as early as 15.5 days of intrauterine life. The fetal testis is, therefore, capable of formation do novo of testosterone through the period of sexual differentiation of the internal genitalia. Testosterone was measured in testicular tissue of fetal rats. Values ranged from as low as 0.09 ng/mg at 15.5 days of gestation to 2.76 ng/mg at 18.5 days of gestation. The sharp rise at 18.5 days of fetal age coincides with morphological evidence that relatively large amounts of testosterone are necessary for Wolifian duct stabilization at this time. Fetal testes were also incubated with [‘4C] acetate or [‘H] pregnenolone. Whereas conversion of both substrates to radioactive testosterone occurred at 15.5 and 16.5 days of gestation, no such conversion was evident at 14.5 days of fetal age with either substrate. Nonradioactive testosterone was, however, measurable in incubation from all three time periods. Neither radioactive nor nonradioactive testosterone was detectable in incubations of fetal ovaries with radioactive acetate or pregnenolone at 15 to 20 days of gestation. The influence of steroid androgens on

Development of the adrenal gland in pigs during the perinatal period. Growth rate and ascorbic acid content of the adrenal.

The rate of adrenal growth in fetal pigs during the last third of gestation showed an abrupt rise in the last 20 days of intrauterine life. After birth the ratio of adrenal weight to body weight decreased with age. The ascorbic acid concentration of the adrenal gland rose abruptly during a few days before and after birth and showed no substantial changes thereafter. The ascorbic acid concentration of the liver, on the other hand, showed a rapid decline after reaching a maximum at 2–4 days after birth. It is suggested that the high activity of the pig adrenal cortex at birth is a result of intense progressive developnent in about the last sixth of fetal life.