Maternal n-6 and n-3 fatty acid status during pregnancy is related to infant heart rate and heart rate variability: An exploratory study.

Early life heart rate (HR) and heart rate variability (HRV) reflect autonomic system maturation. Intervention with n-3 long chain polyunsaturated fatty acids (LCPUFAs) during pregnancy favorably affects fetal HR and HRV, complementing previous observations for n-3 LCPUFA intervention during infancy. The relationship between maternal fatty acid status during pregnancy and infant HR/HRV has not previously been assessed. The aim of this study was to explore associations between maternal n-6 and n-3 fatty acid status during pregnancy and infant HR and HRV at 2 weeks, 4 months, and 6 months of age using linear regression models. Maternal n-3 fatty acids were inversely related to infant HR and positively related to HRV. Conversely, maternal n-6 fatty acids were positively related to infant HR and inversely related to HRV. These data build on existing literature evidencing a role for n-3 fatty acids in accelerating autonomic development and link n-6 fatty acids to HR/HRV.

Technical and methodologic considerations for performance of indirect calorimetry in ventilated and nonventilated preterm infants.

OBJECTIVE: To evaluate and refine indirect calorimetry measurement techniques so that accurate metabolic measurements can be performed in mechanically ventilated and convalescing preterm infants who require supplemental oxygen. DESIGN: Laboratory validation of an indirect calorimeter; clinical and laboratory assessments of technical problems in performing metabolic measurements; and clinical indirect calorimetry studies in mechanically ventilated and nonventilated preterm infants. SETTING: Neonatal intensive care unit (ICU) in a tertiary care university hospital. PATIENTS: Level II and level III mechanically ventilated (n = 10) and nonventilated (n = 14) neonatal ICU patients who required FIO2 levels ranging from 0.21 to 0.42. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: System calibration was assessed by combustion of 100% ethanol; the mean respiratory quotient was 0.667 +/- 0.001 (SEM). In addition, oxygen consumption (Vo2) and CO2 production (Vco2) were simulated by CO2/nitrogen infusions within the range expected for 0.5- to 7-kg infants. Mean relative errors were 0.6 +/- 0.3% and 1.8 +/- 0.3% for expected Vo2 and Vco2 values, respectively. In 27 mechanically ventilated patients with no audible endotracheal tube leak, measured endotracheal tube leak ranged from 0.0% to 7.5%. Fluctuations in FIO2 during mechanical ventilation were monitored in 30-min studies, using wall-source (n = 27) or tank-source (n = 11) supplemental oxygen. Mean FIO2 variation was 0.00075 +/- 0.00013 vs. 0.00011 +/- 0.00001 using wall-source and tank-source oxygen, respectively. Some of the difficulties of obtaining accurate measurements in supplemental hood oxygen studies were overcome by using tank-source vs. wall-source oxygen and a unique hood design. CONCLUSIONS: Accurate indirect calorimetry studies can be performed in both ventilated and nonventilated infants weighing as little as 500 g, providing that sufficient attention is paid to technical and methodologic measurement details.

Hepatic metabolism of glucose, galactose, and lactate after milk feeding in newborn lambs.

The purpose of this study was to test the ability of the liver to efficiently clear substrates absorbed from the gastrointestinal tract after a feeding before entry into the systemic circulation. We placed a hepatic vein (HV) catheter in utero at 135-140 days gestation. The lamb was then allowed to deliver spontaneously, and additional catheters were placed in the portal vein (PV) and femoral artery (FA) at 1-3 days postnatal age. After at least 2 days recovery, lambs were fasted overnight at 4-10 days of age and then allowed to nurse ad libitum. There was significant hepatic glucose release during fasting and after 80 min postprandially. No net hepatic uptake of glucose was observed before or after feeding. PV galactose was significantly greater than FA and HV from 40 to 160 min after feeding (P less than 0.005). Hepatic glucose extraction was negligible in the fasted state (1 +/- 3%) and increased after feeding to 75 +/- 2% when PV galactose was less than 1.0 mM. There was a significant hepatic arteriovenous concentration difference of lactate (0.23 +/- 0.03 mM) and of oxygen (0.27 +/- 0.01 mM), which did not change significantly after feeding. The metabolic quotient for galactose increased significantly after feeding, such that galactose was the largest carbon contributor for postprandial hepatic carbon accretion. After a milk feeding, the newborn liver efficiently extracts galactose, lactate, and oxygen, but not glucose.

Relationship of human milk pH during course of lactation to concentrations of citrate and fatty acids.

Human milk pH was measured in 309 samples obtained from 52 women who had delivered at term and lactated for as long as 10 months thereafter. The mean pH decreased from 7.45 for colostrum to a nadir of 7.04 during the second week of lactation. Thereafter, the pH of milk remained between 7.0 and 7.1 until 3 months postpartum and then increased gradually to 7.4 by 10 months. The change in hydrogen ion concentration in milk was associated with corresponding changes throughout lactation in the concentration of citrate but not with the concentration of lactose. Lactose concentration increased gradually for 3 weeks; the concentration of saturated medium-chain fatty acids increased more rapidly. One interpretation of these findings is that the hydrogen ions and citrate generated by mammary secretory cell metabolism are used after the second week of lactation for de novo synthesis of fatty acids more rapidly than they are synthesized. Milk samples from ruminants were found to have concentrations of hydrogen ions and citrate that are greater than and pH that is less than the respective measurements in human milk. The significance for the recipient infant of the predictable changes in human milk pH during lactation and of the higher pH of human milk throughout lactation relative to bovine milk is unknown. However, drug excretion into milk, milk enzyme activity, milk leukocyte function, and neonatal gastrointestinal function are affected by ambient pH and may be influenced by the pH of milk.

Ontogenic studies of gastrointestinal function. II. Lower esophageal sphincter maturation in neonatal beagle puppies.

The purpose of the present study was to investigate the postnatal development of lower esophageal sphincter (LES) competence in the beagle and to determine the role of gastrin in LES functional ontogeny. Eleven beagle puppies taken from two litters were studied. All puppies were allowed to suckle during the first 3 postnatal wk. In the 4th wk, all puppies were weaned, and by the 5th wk only solid chow was offered. Intraluminal manometric pressure determinations were obtained in unanesthetized, unsedated puppies using twin-lumen, 1.7 mm OD, 1 mm ID polyvinyl catheters. A 12-15 min baseline period of intraluminal pressure was monitored, after which the puppies received successive doses of 0.03, 0.1, 1.0, and 8.0 micrograms/kg pentagastrin (PG) SC spaced at 45-min intervals. Progressive increases in LES pressure both during basal periods and during gastric contractions and in gastric fundus (GF) pressures during gastric contractions occurred during the 1st 5 weeks of life. An increase in pressure gradient between the LES and GF during gastric contraction occurred from birth through 5 wk of age. There was no response to 0.1-8.0 micrograms/kg PG until postnatal days 5-6 when the LES pressure gradient in the basal state increased in response to each of these doses. There was also no significant response by the LES to PG during gastric contraction until days 11-12 when all doses of PG evoked enhancement of LES pressure. These studies suggest that an increase in LES-GF intraluminal pressure gradient develops during the initial 2 postnatal wk in this species and that this development does not involve the hormone gastrin. Later, however, the pressure gradient may depend upon both age and gastrin since a two-way analysis of variance indicated that not only is LES pressure affected by postnatal age and by PG dose, but that there is an interaction between postnatal age and PG dose which is significant. By the fifth wk, there was an apparent dose-response effect in which the lower two doses produced increased LES pressure and the larger two doses produced decreased LES pressures.