First Days Of Extrauterine Life Research Articles

Meeting the nutritional needs of premature babies: their future is in our hands.

The goals of early nutrition in preterm infants are to provide all the necessary vital nutrients, achieve extra-uterine growth rates similar to fetuses of the same gestational age, and support functional neurodevelopmental outcomes that are comparable to those of infants born at term. It is vital to provide nutrition that will maximally support brain growth and development, but over-feeding with accelerated growth, fat accumulation and long-term metabolic consequences should also be avoided. Because the morbidity associated with prematurity increases nutritional and energetic demands, the basic approach is of providing early intensive nutrition. Protein is the main driving force for growth and brain development. Since deficits in protein occur from the first day of extra-uterine life, sufficient quantities of parenteral amino acids should be provided from the first hours of life. With protein and carbohydrates, enough energy should also be provided, via concomitant early administration of intravenous lipid emulsions. Early initiation of enteral feeding with advancement to full enteral nutrition is associated with better maturation of the gut and better neuro-developmental outcomes. Human milk is the best food for preterm babies, although enrichment may be needed.

Meconium lactoferrin levels in neonates: can we predefine normal values?

Background and aims: In recent years, Lactoferrin (LF) has become an object of interest to neonatologists. To date, there have been no studies on the presence of LF in neonatal meconium. The aim of the study was to assess LF concentrations in successive portions of meconium passed in the first days of extrauterine life and to calculate the total amount of LF accumulated in the fetal intestine in utero.Methods: The LF concentrations were determined using the ELISA Kit in meconium samples (n = 81), collected serially from neonates (n = 20). The sum of LF amounts in all portions of meconium passed by a neonate was considered to represent the total accumulation of this protein in the fetal intestine in utero.Results: The LF concentration in a single meconium portion was [μg/g]: mean ± SD = 45.07 ± 78.53, median = 18.98, range = 1.69–511.43. The total LF accumulation in the fetal intestine was [μg]: mean ± SD = 757.23 ± 745.41, median = 514.73, range = 20.48–2749.55. LF concentrations increased in the last meconium portions compared with the first portions passed immediately after birth (p = 0.017).Conclusions: Very large differences in LF concentrations between meconium portions and in the total LF accumulation between the neonates suggest the influence of intrauterine factors on the variations in fetal intestinal LF concentrations.

Neuromuscular state of children of different gestational ages during transition from intrauterine immersion to earth’s gravity

This study describes the neuromuscular state of premature babies in the context of the ontogenetic gravity and zero gravity model using the results of superficial interference electromyography (IEMG). During six postnatal weeks, the IEMG of premature babies is similar to the EMG of a full-term baby during the first days of extrauterine life; it is characterized by a “simplified” temporal structure, as well as low amplitude and frequency. The IEMG dynamics of a premature baby is slow, in contrast to that one in a full-term baby. This is, probably, due to the fact that the locomotion system of the latter is better prepared and more mature after spending as much time as possible in an intrauterine state. On the other hand, complexity and high amplitude of the IEMG in a premature baby, compared to a full-term baby of the same postconceptual age, are associated with the inevitable sensory stimulation after birth. Abilitation procedures provided to a premature baby could be adapted to the purposes of post-flight rehabilitation of astronauts.

Transcriptomics of the late gestation ovine fetal brain: modeling the co-expression of immune marker genes.

BackgroundMajor changes in gene expression occur in the fetal brain to modulate the function of this organ postnatally. Thus, factors can alter the genomics of the fetal brain, predisposing to neurological disorders later in life. We hypothesized that the physiological dynamics of the immune system transcriptome of the fetal brain during the last stage of gestation will reveal patterns of immune function and development in the developing brain. In this study we applied weighted gene co-expression analysis of microarrays performed on ovine fetal brain samples, to model the changes in gene expression throughout the second half of gestation.ResultsClusters of co-expressed genes that strongly increase in expression toward the first day of extra-uterine life are related to the hematopoietic lineage, while activation of immune pathways is induced after birth. Moreover, the pattern of gene expression suggests induction of tolerance mechanisms, probably necessary to protect highly produced proteins –such as myelin basic protein- from an autoimmune attack.ConclusionsThis study provides insight into the dramatic changes in gene expression that take place in the brain during the fetal life, especially during the last stage of gestation, and suggests that the immune system may have an important role in maturation of the fetal brain, which if disrupted or altered, could have negative consequences in postnatal life.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1001) contains supplementary material, which is available to authorized users.

Reference Values for Plasma B-Type Natriuretic Peptide in the First Days of Life

The clinical relevance of B-type natriuretic peptide (BNP)1 and the amino terminal fragment of its prohormone (NT-proBNP) as biomarkers in pediatric heart disease have recently been shown (1)(2). BNP and NT-proBNP concentrations are dependent on age and sex, at least in adults(3). Because commercial methods are affected differently by the presence in plasma of several peptides derived from the degradation of intact prohormone and BNP(3), little if any agreement exists among reported reference intervals, especially those used for infants during the first days of extrauterine life(1). Data are scarce regarding the reference values for BNP and NT-proBNP in infancy (1)(2)(4). Recently, Nir et al.(2) summarized NT-proBNP concentrations measured with an electrochemiluminescence immunoassay method in 690 healthy individuals (47% males) with ages ranging from birth to 18 years, including 127 newborns in the first week of life (43 in the first 2 days). The NT-proBNP concentrations were highest in the first days of life, and then showed a marked decline. Concentrations in males and females differed only for children age 10–14 years. Large reference value studies for BNP for newborns and infants have …

Alpha-1-Antitrypsin and IgA in Serial Meconium and Faeces of Healthy Breast-Fed Newborns

Background: Meconium is a series of layers formed in the foetal intestine from the 12th week of gestation. High content of meconial alpha-1-antitrypsin (AAT), decreasing within the first several days of extrauterine life appears to reflect the meconium clearance of the gut. At birth, IgA is not present in the meconium and breast-fed infants receive this antibody postnatally with human milk. The aim of the study was to determine changes in AAT concentrations, functional activity of that inhibitor expressed as trypsin inhibitory capacity (TIC) and IgA concentration in serial meconium and faeces, as endogenous biochemical markers discriminating between faeces portions formed in intrauterine and extrauterine life periods of healthy breast-fed newborns. Methods: A group of 24 healthy breast-fed newborns delivered by spontaneous labour were studied prospectively during the first 4 days of postnatal life. AAT and IgA concentrations in the newborn‘s meconial and faecal samples and IgA concentration in mother’s milk samples taken on the third day after delivery, were determined by radial immunodiffusion. TIC was assessed using BAPNA (N-benzoyl-DL-arginine-p-nitroanilide). Results: The medians (range) of AAT concentrations in milligrams per gram of dry meconium or faeces were: 68.8(29.2–138.4) (day 1), 56.9 (30.8–112.8) (day 2), 26.2 (6.8–80.7) (day 3), and 6.6 (1.4–27.1) (day 4). The medians (range) of TIC in milligrams of trypsin/g dry mass of meconium or faeces were: 0.76 (0.33–1.79) (day 1), 0.44 (0.17–1.08) (day 2), 0.16 (0.03–0.56) (day 3), and 0.03 (0–0.11) (day 4). The median (range) of IgA concentration in mothers’ milk was 715 mg/dl (420–890). IgA was absent in meconium portions from the first day of life while on the successive days the medians (range) of IgA concentration in mg/g dry mass of meconium and faeces were as follows: 0 (0–2.90) (day 2), 2.50 (1.10–9.60) (day 3), 7.05 (4.10–30.60) (day 4). On day 4 of extrauterine life a negative correlation was found between AAT and IgA concentrations in faeces of the newborns (r = –0.46) and a positive correlation was seen between IgA concentrations in faeces and milk (r = 0.93). Conclusions: Analyses of the systematic decrease in AAT and increase of IgA concentration in serial portions of meconium and faeces over the first days of extrauterine life of breast-fed newborns can date newborn’s faeces portions formed during intrauterine and extrauterine maturation. AAT deposited in foetal intestine is an active antiprotease.

Postnatal maturation of phosphodiesterase 5 (PDE5) in piglet pulmonary arteries: activity, expression, effects of PDE5 inhibitors, and role of the nitric oxide/cyclic GMP pathway.

After birth and during the first days of extrauterine life, pulmonary arterial pressure is progressively reduced to reach the adult values. We hypothesized that changes in PDE5 activity might be involved in the pulmonary postnatal maturation of the nitric oxide (NO)/cGMP pathway. The PDE5 inhibitor sildenafil produced vasorelaxant responses in isolated pulmonary arteries. These effects were similar in newborn (3-18 h) and 2-wk-old piglets, unchanged by endothelium removal, and markedly inhibited by the soluble guanylyl cyclase inhibitor ODQ. The peak of the transient vasorelaxant response to NO gas increased with postnatal age but was unaffected by PDE inhibition. However, the duration of the response to NO was significantly increased. The vasorelaxant response to sodium nitroprusside was potentiated by sildenafil in both age groups. The PDE5 inhibitors dipyridamole and zaprinast, produced qualitatively similar effects but with lower potency. Both total and PDE5-dependent cGMP hydrolytic activity and PDE5 protein expression increased with postnatal age. All these results suggest that PDE5 is a key regulator of NO-induced vasodilation in the postnatal pulmonary arteries. PDE5 inhibition is able to produce pulmonary vasodilation even in the absence of a functional endothelium and potentiates the vasorelaxant response to exogenous NO and nitroprusside. However, PDE5 is not responsible for the maturational increase of NO bioactivity during the first days of extrauterine life.

Twenty-one years of developmental nephrology: the kidney then and now.

Developmental renal physiology was guided for a long time by the notion that the "immature" kidney is characterized by glomerular-tubular imbalance, with glomerular preponderance. In accordance with this concept, the filtering capacity of the developing kidney exceeds the ability of the renal tubules to handle the filtrate, resulting in the urinary loss of substances such as amino acids and bicarbonate. Estimates of age-related changes in glomerular volume, based on measurements of glomerular diameter, and of proximal tubular volume, based on measurements of tubular length and tubular diameter, appeared to support this contention. The experimental approach that led to these conclusions was based on the assumptions that the increase in glomerular size is distributed evenly between the vascular and nonvascular elements and that tubular volume increases pari passu with the luminal surface area. Both assumptions were proved wrong. Moreover, micropuncture studies performed in guinea pigs and rats revealed that the proportionality between glomerular filtration and proximal reabsorption of fluid (i.e., glomerulo-tubular balance) is maintained throughout development. Subsequent studies showed that several transport mechanisms function quite adequately from the first days of extrauterine life. Sodium is avidly reabsorbed in distal nephron segments, under the stimulus of the high levels of aldosterone present during infancy. The increase in the secretion of potassium that would occur in the adult under these circumstances is mitigated by the low expression of potassium channels. In the case of phosphate, there is enhanced reabsorption, particularly at the level of the proximal tubule, due in part to a growth-specific NaPi type II transporter. These different adaptive mechanisms converge towards the maintenance of a positive external balance for substances that are essential to growth. The emergence of cellular and molecular biology has also encouraged research in the field of renal morphology. The genes that control mesenchymal-epithelial interactions and the signaling factors that mediate their effect have been described. Progress is being made in the identification of genes involved in certain forms of renal malformations. Novel methods of investigation, such as DNA arrays, are likely to lead to an even fuller, dynamic portrayal of gene expression during nephrogenesis. Characterizing the functional correlates of these genes will require investigators who are not only proficient in molecular biology, but who are also masters of physiological methods.

Postnatal maturation in nitric oxide-induced pulmonary artery relaxation involving cyclooxygenase-1 activity.

The maturation in the vasodilator response to nitric oxide (NO) in isolated intrapulmonary arteries was analyzed in newborns and 15- to 20-day-old piglets. The vasodilator responses to NO gas but not to the NO donor sodium nitroprusside increased with age. The inhibitory effects of the superoxide dismutase inhibitor diethyldithiocarbamate and xanthine oxidase plus hypoxanthine and the potentiation induced by superoxide dismutase and MnCl(2) of NO-induced vasodilatation were similar in the two age groups. Diphenyleneiodonium (NADPH oxidase inhibitor) potentiated the response to NO, and this effect was more pronounced in the older animals. The nonselective cyclooxygenase inhibitors indomethacin and meclofenamate and the preferential cyclooxygenase-1 inhibitor aspirin augmented NO-induced relaxation specifically in newborns, whereas the selective cycloxygenase-2 inhibitor NS-398 had no effect. The expressions of alpha-actin, cycloxygenase-1, and cycloxygenase-2 proteins were similar, whereas Cu,Zn-superoxide dismutase decreased with age. Therefore, the present data suggest that the maturational increase in the vasodilatation of NO in the pulmonary arteries during the first days of extrauterine life involves a cycloxygenase-dependent inhibition of neonatal NO activity.

Intra-epithelial lipids in the dorsoposterior area of the tongue in new-born rats

The mucosa covering the posterior surface of the tongue in new-born rats was studied by scanning and transmission electron microscopy. The results demonstrated that in the first days of extra-uterine life in the epithelium of this mucosa there is an accumulation of lipidic material, which appeared as round or oval droplets with a mean diameter of about 0.8–1.0 μm. Their density was homogeneously low and they did not contain fibrillar or granular material. In the first day of extra-uterine life, the droplets were scarce and mainly localized in the dorsal surface of the vallate papilla. In the following days, the lipid deposit was present in large areas of the posterior surface of the tongue. At the end of the first week of extra-uterine life, as well as in adult animals, the lipids were rather scarce. A multilocular lipid deposit was also visible in superficial cells detaching from the mucosa. With magnetic resonance spectroscopy, lipids extracted from the posterior mucosa of the tongue appeared mainly saturated. Small amounts of unsaturated and polyunsaturated lipid were also detectable. These findings suggest that in the first week of extra-uterine life, specialized areas of the oral epithelium store lipid.

Changes in leptin concentration during the early postnatal period: adjustment to extrauterine life?

There are substantial alterations in fuel homeostasis immediately after birth. Leptin is a putative regulator of energy metabolism. Consequently, the aim of this study was to examine whether there are changes in circulating leptin concentrations during the early postnatal period. Umbilical cord mixed blood samples were taken at delivery, and a venous blood sample was obtained at 3 d of age from 38 healthy newborn infants (20 male, 18 female; gestational age 36.3 to 41.9 wk) for analysis of leptin concentration with radioimmunoassay. Cord plasma leptin concentration was 9.7+/-5.2 microg/L (mean+/-SD), with no gender difference between male (8.6+/-4.6 microg/L) and female (10.9+/-5.6 microg/L) infants. In male newborns, cord plasma leptin concentration correlated with arm circumference (r = 0.48, p < 0.05), and in female newborns with body mass index (r = 0.62, p < 0.01), thickness of the s.c. fat (r = 0.54, p < 0.05), and arm circumference (r = 0.72, p < 0.01). By the third postnatal day, plasma leptin decreased similarly in male (to 1.8+/-0.4 microg/L, p < 0.001) and female (to 2.3+/-0.8 microg/L, p < 0.001) infants, when there was a significant gender difference in leptin levels (p = 0.01). At 3 d of age, plasma leptin correlated with weight (r = 0.49, p < 0.05) and arm circumference (r = 0.49, p < 0.05) in female but not in male newborns. In conclusion, 1) circulating leptin already correlates with adiposity at birth in female but not in male newborn infants and 2) leptin decreases markedly in both genders by the third postnatal day, and the gender difference with higher leptin levels in females develops by that time. Thus, the postnatal decrease in plasma leptin concentration may be a physiologically feasible adaptation to profound alterations in fuel homeostasis during the first days of extrauterine life.

Development and Maturation of the Autonomic Nervous System in Premature and Full-Term Infants Using Spectral Analysis of Heart Rate Fluctuations

The changes in the power spectra of heart rate (HR) fluctuations, in particular the total power (within 0.02-2.0 Hz) and the power in the low- (0.02-0.2 Hz) and high- (0.2-2.0 Hz) frequency ranges, were computed from the ECG and respiratory signals of 59 premature and full-term infants. The objective of the study was to investigate the development and maturation of the autonomic nervous system from the first day of extrauterine life to several weeks of postnatal age. The study population was divided into four age groups. Group A: seven 1-d-old premature infants with gestational age of 34-35 wk. Group B: 28 premature infants 7-49 d old with a conceptional age of 34-35 wk. Group C: seven 1-d-old full-term infants of 39-41 wk gestation. Group D: six premature infants 35-97 d old with a conceptional age of 39-40 wk. Mean HR (+/- SEM) of groups C and D combined, i.e. 135 +/- 2 bpm, was significantly lower compared with groups A and B, i.e. 152 +/- 2 (p < 0.01). The mean (+/- SEM) of the low- to high-frequency power ratio obtained from the HR power spectrum decreased progressively from 71 +/- 31 in group A to 34 +/- 8 in group B, 16 +/- 3 in group C, and 17 +/- 2 in group D. The mean low to high ratio for the combined groups C and D, 17 +/- 1, was significantly lower compared with the combined group A and B, i.e. 44 +/- 9 (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

147 TRANSIENT FORAMEN OVALE INCOMPETENCE IN NORMAL NEWBORNS

In contrast with the generally accepted mechanism of functional closure of the foramen ovale at birth, echocardiography studies in sick newborns revealed the presence of transient interatrial left to right shunts (IALRS) in several patients without structural heart disease. The aim of this study was to assess incidence and natural history of IALRS in healthy newborns. 20 healthy term newborns underwent an echocardiography and Doppler study daily during the first week after birth. Left atrial and aortic root dimensions were measured, as well as duration and direction of ductal and interatrial shunting. In 11 of these infants a predominant IALRS was detected on the first day of extrauterine life. In one infant IALRS persisted for as long as 6 weeks. Median persistance of IALRS in the remaining 10 infants was 3 days. Ductal left to right shunts were present in 3 infants with and in 2 without IALRS. There was no significant difference between infants with or without IARLS in respect to ductal patency, birthweight or sex. There was a statistically significant relation between lower gestational age and presence and duration of IALRS. We conclude that transient IALRS is common in normal newborns during the first week of extrauterine life. We suggest that this transient foramen ovale incompetence results from a relatively short foramen ovale flap in combination with the relative large extracellular volume as is present in the first days of life.

Expression of liver carnitine palmitoyltransferase I and II genes during development in the rat

The enzyme activity and the expression (protein and mRNA concentrations) of genes encoding for hepatic carnitine palmitoyl-transferases (CPT) I and II were studied during neonatal development, in response to nutritional state at weaning and during the fed-starved transition in adult rats. The activity, the protein concentration and the level of mRNA encoding CPT I are low in foetal-rat liver and increase 5-fold during the first day of extra-uterine life. The activity and gene expression of CPT I are high during the entire suckling period, in the liver of 30-day-old rats weaned at 20 days on to a high-fat diet and in the liver of 48 h-starved adult rats. The activity and CPT I gene expression are markedly decreased in the liver of rats weaned on to a high-carbohydrate diet. By contrast, the activity, the protein concentration and the level of mRNA encoding CPT II are already high in the liver of term foetuses and remain at this level throughout the suckling period, irrespective of the nutritional state of the animals either at weaning or in the adult.

Permanent abnormal response to a glucose load after prenatal ethanol exposure in rats

Postnatal development of the glucose and insulin balance in offspring of ethanol-treated and control rats has been studied. Newborn rats were separated from their mothers and placed with normal lactating, nonethanol-treated dams. Prenatal exposure to ethanol led to hypoglycemia on the first day of extrauterine life and a general tendency to hyperinsulinemia during the entire postnatal period studied. The glucose-tolerance test in weaned rats (30 days old) gave a greater and faster increase than controls in levels of both glucose and plasma insulin. At adult age (90 days) the response of blood glucose to an oral glucose load in offspring from ethanol-treated mothers was not different from that in offspring from controls, but the insulin response was higher. This abnormal insulin response, such a long time after the end of ethanol exposure, suggests either a permanent alteration in the pancreatic response, or a peripheral insulin resistance and/or differences in the rate of insulin degradation in these animals.

Glucocorticoids increase the fluidity of the fetal-rat liver microsomal membrane in the perinatal period.

Dexamethasone, a synthetic glucocorticoid, was administered to pregnant rats during the last week of pregnancy in order to examine its effects on the fluidity of the developing fetal-rat liver microsomal membrane. This early prenatal exposure to dexamethasone, which preceded the natural appearance of fetal corticosteroids, markedly accelerated the normal perinatal course of fluidization of this membrane. The lipid apparent microviscosity, which was determined by measurement of fluorescence polarization, decreased in 21-days-old treated fetuses to values that were indistinguishable from those of untreated newborn rats. This dexamethasone-mediated acceleration of membrane fluidization was associated with an increase in the index of unsaturation of the fatty acyl moiety of microsomal lipids. Dexamethasone caused a significant increase in the microsomal content of polyunsaturated fatty acids (arachidonic and linoleic acid), which was accompanied by a decrease in content of monoenoic fatty acids (oleic and palmitoleic acid). This early exposure in utero to dexamethasone precociously induced the changes in fatty acid composition of fetal-rat liver microsomal lipids that normally occur between the last day of pregnancy and the first day of extra-uterine life. These results suggest that endogenous glucocorticoids play a major role in the perinatal fluidization of the rat liver microsomal membrane.

THE ADENINE NUCLEOTIDE (AdN) TRANSLOCASE (T): A ROLE IN DEVELOPMENTAL CHANGES

Although developmental changes occurring during the first days of extrauterine life have been well-characterized in terms of enzymatic activities, little attention has been given to overall cellular energy metabolism. Investigations of energy metabolism in guinea pig liver mitochondria (m) have shown that m from the newborn (N) have membrane pH gradients and membrane electrical potentials similar to those found in adults. During the first 24 hours after birth, State 3 rates of oxygen consumption (OC) increase 3 fold whereas the uncoupled rates of (OC) increase only 30%. The m AdN increases 3 fold with no change in the ATP/ADP ratio. Titrations with carboxyatractyloside (CAT), a stoichiometric inhibitor of the m AdNT show that the N has only 50% of the AdNT activity of the adult. Furthermore, it is possible to evaluate the role of the AdNT on the regulation of respiration using flux control theory (Eur. J. Biochem. 42:97-105). Briefly, the degree of control (control strength) exerted by a particular step in a pathway is defined as the fractional change in pathway flux produced by a fractional change in the activity of the enzyme comprising that step; the sum of all control strengths in a pathway being equal to 1.0. By applying this theory to inhibitor titrations of the AdNT, it has been shown that at any rate of OC the AdNT has greater control strength over respiration in the N than in the adult. At maximal rates of OC the AdNT has a control strength of 0.98 in the N and 0.56 in the adult. Since the AdNT plays a central role in cellular metabolism and the N period is a time of high energy demand, it seems probable that the AdNT plays a critical role in development.

Control of vasopressin secretion in the newborn lamb.

The plasma sodium, osmolality, and arginine vasopressin (AVP) responses to phlebotomy, hypertonic saline, water loading and fluid restriction were studied in 2--49 day old lambs. Phlebotomy of 10 and 20% of the lamb's estimated blood volume produced 37- and 44-fold increments in plasma AVP, without a concomitant change in plasma sodium or osmolality. The infusion of 10 mEq/kg sodium chloride produced a 12% rise in plasma sodium concentration accompanied by a 7-fold rise in plasma AVP. Water loading with 100 ml/kg hypotonic fluid produced a significant fall in plasma sodium concentration (10.7%) and a decrease in plasma AVP. Eighteen hr of water deprivation evoked a 7-fold increase in AVP. These results indicate that the newborn lamb is capable of responding appropriately to known stimuli for AVP secretion. The stimulus response ratio (SRR): (formula: see text) of newborn lambs was nearly identical after hypertonic saline and water loading and was also quite similar to that of the adult ewe after a saline challenge. The SRR of water deprived lambs was greater than that after the other stimuli, presumably reflecting combined volume and osmolar stimuli. We conclude that the neurohypophysis and the volume receptor systems of the newborn lamb are capable of appropriate, mature AVP responsiveness during the first days of extrauterine life.

Effect of the linoleic acid concentration of mother's diet on adenyl cyclase activity of fetal and neonatal rat brown adipose tissue.

An adenyl cyclase activity was measurable in the brown adipose tissue of fetal rat, and could be stimulated in vitro by noradrenaline during the last 3 days of fetal life. The stimulating effect of noradrenaline was maximal at birth and decreased during the first days of extrauterine life. Ingestion by mother of a high lipid diet modified the developmental pattern of fetal adenyl cyclase. The linoleic acid content of mother's diet had no effect on the noradrenaline- or fluoride-stimulated specific activities except on the day 22 of gestation. Relative noradrenaline-stimulated activity, expressed as a fraction of the maximal activity, was significantly increased in fetuses and 1-day-old newborns from mothers fed a high linoleic acid diet, but no effect was observed in suckling newborns.

Noradrenaline appearance in guinea pig brown adipose tissue. Its significance in neonatal nonshivering thermogenesis.

A rapid growth of the guinea pig brown adipose tissue occurred during the last third of fetal life. Endogenous noradrenaline was measurable was measurable from day 55 of gestation and rose until birth. The maximal noradrenaline concentration was achieved on the first day of extrauterine life and remained constant during the postnatal period. So, noradrenaline was present in brown adipose tissue at birth and could mediate the neonatal nonshivering thermogenesis activation as suggested in the discussion.