Effect of indomethacin on the regulation of cerebral blood flow during respiratory alkalosis in newborn piglets

The effect of cyclooxygenase inhibition by indomethacin on regional cerebral blood flow (CBF) during hypocapnia induced by hyperventilation and during hypercapnia induced by CO2 inhalation was examined. CBF was measured in 27 anesthetized, ventilated piglets (2-8 d) using microspheres in control and indomethacin treated animals (5 mg/kg) after hyperventilation or inhalation of 6% CO2. In the control group (n = 6), CBF decreased significantly (p less than 0.05) to all regions of the brain after hyperventilation with a 32% decrease in the cerebral cortex. In the indomethacin-treated group (n = 6), blood flow significantly decreased by 35 to 49% in all regions of the brain, except the cerebral white matter, during normocapnia with no further decrease in flow during subsequent hypocapnia. Although CBF increased significantly after indomethacin treatment during hypercapnia the response was markedly attenuated with blood flow to the cerebral gray matter, hippocampus and pons rising only 42, 25, and 42% in contrast to 108, 75, and 225% in the control group. Since indomethacin decreased resting CBF, unilateral sympathetic nerve stimulation at 15 Hz was used to test the specificity of indomethacin on hypocapnic vasoconstriction (n = 5). Unilateral sympathetic nerve stimulation caused a further statistically significant decrease in CBF on the stimulated side after hyperventilation with indomethacin (12%), which was comparable to that which occurred during normocapnia (16%). The data demonstrate that indomethacin attenuates the cerebrovascular sensitivity to both increases and decreases in CO2/H+ and implicate a possible role for vasoactive prostanoids in mediating the response of CBF to fluctuations in CO2 in newborn piglets.

Lipid peroxidation as the mechanism of modification of the affinity of the Na+, K+-ATPase active sites for ATP, K+, Na+, and strophanthidin in vitro

The effect of lipid peroxidation on the affinity of specific active sites of Na+,K+-ATPase for ATP (substrate), K+ and Na+ (activators), and strophanthidin (a specific inhibitor) was investigated. Brain cell membranes were peroxidized in vitro in the presence of 100 microM ascorbate and 25 microM FeCl2 at 37 degrees C for time intervals from 0-20 min. The level of thiobarbituric acid reactive substances and the activity of Na+, K+-ATPase were determined. The enzyme activity decreased by 80% in the first min. from 42.0 +/- 3.8 to 8.8 +/- 0.9 mumol Pi/mg protein/hr and remained unchanged thereafter. Lipid peroxidation products increased to a steady state level from 0.2 +/- 0.1 to 16.5 +/- 1.5 nmol malonaldehyde/mg protein by 3 min. In peroxidized membranes, the affinity for ATP and strophanthidin was increased (two and seven fold, respectively), whereas affinity for K+ and Na+ was decreased (to one tenth and one seventh of control values, respectively). Changes in the affinity of active sites will affect the phosphorylation and dephosphorylation mechanisms of Na+, K+-ATPase reaction. The increased affinity for ATP favors the phosphorylation of the enzyme at low ATP concentrations whereas, the decreased affinity for K+ will not favor the dephosphorylation of the enzyme-P complex resulting in unavailability of energy for transmembrane transport processes. The results demonstrate that lipid peroxidation alters Na+, K+-ATPase function by modification at specific active sites in a selective manner, rather than through a non-specific destructive process.

Regional cerebral blood flow response during and after acute asphyxia in newborn piglets

The hemodynamic response during and after acute asphyxia was studied in 14 newborn piglets. An apnea-like asphyxial insult was produced in paralyzed mechanically ventilated piglets by discontinuing ventilation until the piglets became bradycardic (heart rate less than 80 beats/min). Seven piglets had organ blood flow measured by microspheres at control, during asphyxia (PO2 = 16 +/- 11 Torr, pH = 7.31 +/- 0.07, PCO2 = 47 +/- 9 Torr), and during recovery from asphyxia. During acute asphyxia, rapid organ blood flow redistribution occurred, producing decreased renal and skeletal muscle blood flow, while coronary blood flow increased. Although total brain blood flow changed little during asphyxia, regional cerebral blood flow (rCBF) analysis revealed significant nonhomogeneous blood flow distribution within the brain during asphyxia, with decreases to the cerebral gray and white matter and the choroid plexus, whereas brain stem structures had increased flow. During recovery with reventilation, total brain blood flow increased 24% above control, with a more uniform distribution and increased flow to all brain regions. The time course of rCBF changes during acute asphyxia was then determined in seven additional piglets with CBF measurements made sequentially at 30-60 s, 60-120 s, and 120-180 s of asphyxia. The vasoconstriction seen in cortical structures, concurrent with the reduction in skeletal and kidney blood flow, known to be sympathetically mediated, suggest a selective reflex effect in this brain region. The more gradual and progressive vasodilation in brain stem regions during asphyxia is consistent with chemical control. These findings demonstrate significant regional heterogeneity in CBF regulation in newborn piglets.

Effect of sustained pharmacologic vitamin E levels on incidence and severity of retinopathy of prematurity: a controlled clinical trial

The incidence and severity of retinopathy of prematurity (ROP) as affected by vitamin E prophylaxis at pharmacologic serum levels (5 mg/dl) were evaluated in a double-masked clinical trial of infants with a birth weight less than or equal to 2000 gm or a gestational age less than or equal to 36 weeks. The infants were enrolled by age 5 days and randomly assigned to receive parenterally administered, and later orally administered, free alpha-tocopherol (vitamin E) or its placebo. Study medication was continued until retinal vascularization was complete or active ROP had subsided, except in infants with a diagnosis of severe disease, in whom vitamin E was substituted for study medication. Acute ROP data were collected on 755 infants. Logistic regression analysis, with control for immaturity, oxygen exposure, and other illness risk factors, showed a decrease in incidence of ROP in vitamin E-treated infants (p = 0.003, all infants; p = 0.035, infants weighing less than or equal to 1500 gm at birth). Among the 424 infants weighing less than or equal to 1500 gm at birth, the age at enrollment influenced treatment effect (age day 0 to 1, p = 0.006 (n = 288) vs age day 2 to 5, p greater than 0.1 (n = 136]. Overall, 77.6% of infants with ROP had mild disease. Moderate to severe ROP was confined to infants weighing greater than or equal to 1500 gm at birth (25 given placebo, 25 given vitamin E), with progression to severe disease in nine placebo-treated versus three vitamin E-treated infants (p = 0.048). The incidence of severe ROP per se was not significantly decreased (all birth weights, p = 0.086; less than or equal to 1500 gm birth weight, p = 0.080); the sample size was too small, however, to assess this end point adequately. An increased incidence of sepsis and late-onset necrotizing enterocolitis was found among vitamin E-treated infants weighing less than or equal to 1500 gm at birth who received study medication for greater than or equal to 8 days (p = 0.006). Because most ROP is mild in degree and regresses completely, the risk/benefit ratio of pharmacologic prophylaxis for ROP is unfavorable. Treatment of moderate and severe ROP with vitamin E above physiologic serum levels (greater than 3 mg/dl) appears promising and should be further investigated. The interpretation of cicatricial outcome was confounded by the small number of patients involved and by subsequent treatment of severe ROP in placebo-treated infants with vitamin E.

Cerebral metabolic response and mitochondrial activity following insulin-induced hypoglycemia in newborn lambs

We evaluated the newborn lamb's cerebral cellular activity and metabolism following acute insulin-induced hypoglycemia. Eleven animals received an insulin bolus followed by a continuous infusion to maintain a plasma glucose of 1 mM/l for 2 h, while 8 other animals received an equivalent dose of saline. Following the induction of hypoglycemia, the animals became quiet and transient seizures were observed in 3 animals. A significant increase in heart rate (p less than 0.01), and a decrease in arterial PaCO2 at 30 min (p less than 0.01), and pH at 2 h (p = 0.02), following hypoglycemia, were observed in the experimental group. Hypoglycemia did not significantly alter the cerebral blood flow, mitochondrial respiratory control ratio or the state-3 activity. The cerebral arteriovenous difference (CAVD) for oxygen did not change, while the glucose CAVD was significantly reduced from 0.47 +/- 0.21 to 0.24 +/- 0.16 mM/l (p less than 0.05) at the end of the hypoglycemia period, suggesting consumption of alternate substrates of energy by the brain. Insulin-induced hypoglycemia was associated with a significant increase in arterial lactate (p less than 0.01), and a significant correlation (p less than 0.01) between arterial and CAVD for lactate and beta-hydroxybutyrate (BOB) was observed. Cerebral consumption of alternate substrates of energy was inconsistent, and only observed for lactate in 5 and for BOB in 3 experimental animals following hypoglycemia. These data indicate that the newborn lamb's cerebral cellular activity is not affected by the degree of hypoglycemia achieved in these studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid peroxidation in developing fetal guinea pig brain during normoxia and hypoxia

Lipid peroxidation in the fetal guinea pig brain was studied at 30, 35, 40, 45, 50, and 60 days of gestation. Conjugated dienes and fluorescent compounds, indices of lipid peroxidation, peaked at 35 days of gestation, decreased by 45 days, and remained at that level until birth. The higher levels of peroxidation products in early gestational periods (30-40 days) suggest that either the anti-oxidant mechanisms for scavenging oxygen free-radicals and further metabolizing oxidation products are underdeveloped, or the rate of peroxidation is higher than periods near term. Prenatal hypoxia increased the levels of conjugated dienes and fluorescent products in the brains of preterm (50 days) and term (60 days) fetuses. Brain homogenates incubated in air at 37 degrees C underwent rapid lipid peroxidation as measured by the level of thiobarbituric acid (TBA)-reactive substances. However, term brain showed a higher rate of peroxidation and attained higher steady state levels of TBA-reactive substances than preterm brain. This may be due to the higher levels and degrees of unsaturation in fatty acids in term brain. Following hypoxia, term brain showed 5 times the rate of lipid peroxidation and a 3-fold increase in total TBA-reactive substances over controls. These studies show that a significant degree of lipid peroxidation is occurring in the fetal brain during gestation and that the developing brain is more susceptible to lipid peroxidation near term. Furthermore, prenatal hypoxic stress further increases the susceptibility of the brain to peroxidative reactions.

5'-Nucleotidase and adenosine deaminase in developing fetal guinea pig brain and the effect of maternal hypoxia

The activity of key enzymes of adenosine metabolism was studied in the developing fetal guinea pig brain. The activities of 5'-nucleotidase and adenosine deaminase were determined in the brains of fetal guinea pigs at 30, 35, 40, 45, 50, 55, and 60 days of gestation. The level of 5'-nucleotidase activity was extremely low at 30 and 35 days of gestation but increased rapidly during the 40 to 60 day period. The enzyme activity increased in the presence of Mg2+ with the Mg2+ - dependent activation increasing with the age of gestation. This Mg2+ - dependent activity was primarily associated with the membrane fraction. Prenatal hypoxia significantly increased the fetal brain M2+ - independent 5'-nucleotidase activity at 45 days of gestational age and beyond. Prior to this age, no effect was evident. Furthermore, following hypoxia, the Mg2+ - dependent activation of 5'-nucleotidase activity was lost. The activity of adenosine deaminase was present at 30 days of gestation and, unlike 5'-nucleotidase, it remained at the same level until 60 days. The results indicate that the term fetal guinea pig brain has the enzymatic mechanisms of adenosine metabolism and thus the potential for adenosine-mediated regulation of cerebrovasculature during hypoxia.

In vivo 31P nuclear magnetic resonance measurement of chronic changes in cerebral metabolites following neonatal intraventricular hemorrhage

The purpose of this study was to determine whether cerebral metabolic changes occur after intraventricular hemorrhage in the newborn. Five babies with bilateral grade 3 to 4 intraventricular hemorrhage were compared with 15 preterm infants without intraventricular hemorrhage. Cerebral high-energy phosphorus metabolites and intracellular pH were measured with in vivo 31P nuclear magnetic resonance spectroscopy. Spectra were collected initially within the first 2 weeks of life, and then every other week until discharged from the hospital. The phosphocreatine to inorganic phosphate ratio and the phosphocreatine to adenosine triphosphate ratio were significantly lower in the group with intraventricular hemorrhage, but differences in intracellular pH were not significant. Differences between babies with and without intraventricular hemorrhage varied with postconceptional age: in those with intraventricular hemorrhage, the phosphocreatine to adenosine triphosphate ratio was decreased at all postconceptional ages, and the phosphocreatine to inorganic phosphate ratio was lower in babies with intraventricular hemorrhage and younger than 30 weeks. Results of this study confirm the presence of chronic metabolic changes following intraventricular hemorrhage which may exacerbate neurologic damage after intraventricular hemorrhage in the newborn.

Sympathetic regulation of cerebral blood flow during seizures in newborn lambs

We examined cerebral blood flow (CBF) regulation by the sympathetic nerves in 12 newborn lambs (3-11 days old) during seizures, a potent reflex stimulator of the sympathetic nervous system. CBF was measured with microspheres, and seizures were induced with bicuculline. In six of these lambs, one hemibrain was denervated (D) chronically by interrupting the ipsilateral cervical sympathetic trunk; the other hemibrain remained innervated (I). Before and after 10, 35, and 70 min of seizures, cerebral gray matter blood flow (mean +/- SE ml.min-1.100 g-1) was, respectively, 12 +/- 3 (9%), 71 +/- 12 (21%), 120 +/- 15 (38%), and 54 +/- 5 (14%) greater (P less than 0.05) in the D than in the I hemibrain. In the cerebral white matter, hippocampus, caudate, and thalamus blood flows to the D and I hemibrains were similar before seizures but during seizures they were 10-39% greater (P less than 0.05) in the D than in the I hemibrain. Midbrain, brainstem, and cerebellum D and I blood flows were always similar. In the other six lambs, acute denervation during seizures increased ipsilateral cerebral gray and hippocampus blood flow by 10-31%, but unilateral electrical stimulation decreased ipsilateral cerebral gray, cerebral white, hippocampus, thalamus, and caudate blood flow by 17-27%. The data demonstrate that, during seizures, sympathetic nerve activity modifies regional CBF and the effect is sustained, suggesting a role for the sympathetic nervous system in newborn CBF regulation.

Blood-brain barrier to hydrogen ion during acute metabolic acidosis in piglets

The present study investigates the integrity of the blood-brain barrier to H+ or HCO3- during acute plasma acidosis in 35 newborn piglets anesthetized with pentobarbital sodium. Cerebrospinal fluid acid-base balance, cerebral blood flow (CBF), and cerebral oxygenation were measured after infusion of HCl (0.6 N, 0.191-0.388 ml/min) for a period of 1 h at a constant arterial PCO2 of 35-40 Torr. HCl infusion resulted in decreased arterial pH from 7.38 +/- 0.01 to 7.00 +/- 0.02 (P less than 0.01). CBF measured by the tracer microsphere technique was decreased by 12% from 69 +/- 6 to 61 +/- 4 ml.min-1.100 g-1 (P less than 0.05). Infusion of 0.6 N NaCl as a hypertonic control had no effect on CBF. Cerebral metabolic rate for O2 and O2 extraction was not significantly changed from control (3.83 +/- 0.20 ml.min-1.100 g-1 and 5.7 +/- 0.6 ml/100 ml, respectively) during acid infusion. Cerebral venous PO2 was increased from 41.6 +/- 2.1 to 53.8 +/- 4.0 Torr by HCl infusion (P less than 0.02) associated with a shift in O2-hemoglobin affinity of blood in vivo from 38 +/- 2 to 50 +/- 1 Torr. Cisternal cerebrospinal fluid pH decreased from 7.336 +/- 0.014 to 7.226 +/- 0.027 (P less than 0.005), but cerebrospinal fluid HCO3- concentration was not changed from control (25.4 +/- 1.0 meq/l). These data suggest that there is a functional blood-brain barrier in newborn piglets, that is relatively impermeable to HCO3- or H+ and maintains cerebral perivascular pH constant in the face of acute severe arterial acidosis. (ABSTRACT TRUNCATED AT 250 WORDS)

Na+,K+-ATPase in developing fetal guinea pig brain and the effect of maternal hypoxia

Na+,K+-ATPase activity was determined in fetal guinea pig brain at 35, 40, 45, 50, 55, and 60 days of gestation. The activity remained at a constant level during the early periods (35-45 days) of gestation and increased significantly during 45-60 days. Following maternal hypoxia, the activity of Na+,K+-ATPase in the term (60 days) fetal brain was reduced by 50% whereas the preterm (50 days) brain activity was unaffected. Under identical hypoxic conditions, the enzymatic activity of adult brain was significantly reduced by 20%. Na+,K+-ATPase obtained from fetal brain (50 days of gestation) has both a low and a high affinity for ATP (Km values = 0.50 and 0.053 mM and corresponding Vmax values = 10.77 and 2.82 mumoles Pi/mg protein/hr), whereas the enzyme in the adult brain has only a low affinity (Km = 1.67 mM and Vmax = 20.32 mumoles Pi/mg protein/hr). The high and low affinity sites for ATP in the fetal brain suggests a mechanism essential for the maintenance of cellular ionic gradients at low concentrations of ATP and which would provide the fetal brain with a greater tolerance to hypoxia. The high sensitivity of Na+,K+-ATPase activity to hypoxia in guinea pig brain at term suggests that the cell membrane functions of the fetal brain may be more susceptible to hypoxia at term than it is earlier in gestation.

Anti-oxidant enzymes in fetal guinea pig brain during development and the effect of maternal hypoxia

The development of the anti-oxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase was studied in the fetal guinea pig brain at 30, 35, 40, 45, 50, 55, and 60 days of gestation. The activities of these enzymes remained constant during 30-45 days of gestation and increased significantly during the 45-60 day period, with the exception of superoxide dismutase, which remained unchanged throughout the gestational period. The enzyme activities in fetal brain tissue at every gestational age were unaffected by maternal hypoxia (inspired oxygen, 7% for 40 min). The concurrent development of glucose-6-phosphate dehydrogenase, glutathione reductase, and glutathione peroxidase during 45-60 days of gestation indicates an increased ability of the fetal brain to detoxify lipid peroxidation products by reinforcing the glutathione system. The results of this study indicate that the anti-oxidant enzymatic defense mechanisms in the guinea pig brain are fairly mature at birth. However, these mechanisms are underdeveloped during the early stages of gestation and, therefore, during this period the brain might be at potential risk for lipid peroxidative damage under conditions leading to increased formation of oxygen free radicals.

Regional variations in human newborn cerebral blood flow

Regional differences in the local cerebral metabolic rate of glucose have been reported in newborn infants. This study was performed to determine if comparable differences exist in neonatal regional cerebral blood flow (rCBF). In 21 infants, rCBF was measured with a modified xenon 133 (133Xe) clearance technique by means of eight extracranial detectors positioned over four homologous regions (frontal, parietal, temporal, and occipital). The rCBF was lowest in the frontal region, higher in the parietal region, and highest in the temporal and occipital regions. Regional differences in rCBF may be caused by regional differences in brain development and function.

Sequential pulmonary function measurements in very low-birth weight infants during the first week of life

Sequential lung function was measured in 12 very low-birth weight infants (less than or equal to 1,250 g) within 14 hours of birth, and at daily intervals thereafter for the first week of life, using an esophageal balloon and pneumotachograph system. All infants were clinically free of respiratory distress syndrome and radiographically showed no evidence of atelectasis or pulmonary edema. The alveolar-arterial oxygen tension gradient was high at birth and remained elevated over the period during which arterial blood gases were monitored. Increases of lung compliance and tidal volume between the first day and the end of the first week of life were not significant. Day-to-day determinations of lung compliance revealed an individual and group variability without a definite pattern. Lung resistance measurements indicated no clear trend for the group as a whole, but inspiratory resistance was generally lower than expiratory resistance. Possible causes, in addition to technical factors, that may account for the variability in the pulmonary mechanics of these small infants include an instability of lung volume and uneven distribution of pleural pressure due to chest wall distortion, differences in sleep-state, and alteration in the distribution of body fluids, resulting in a change in lung water. Any or all of these mechanisms may result in an unstable lung, even in an apparently clinically stable very low-birth weight infant.

Brain oxidative phosphorylation following alteration in head position in preterm and term neonates

An alteration in head position, which effects cerebral blood flow, may increase the risk for intraventricular hemorrhage in the critically ill infant. The purpose of this study was to evaluate in vivo cerebral oxidative metabolism as an index of tissue oxygen delivery reflecting brain blood flow, in healthy preterm and term infants following a change in head position. Cerebral phosphoenergetics using 31 phosphorus nuclear magnetic resonance spectroscopy were measured in 10 preterm and eight term infants following three different head positions: neutral, prone, and supine. All infants were clinically stable at the time of study. The phosphocreatine to inorganic phosphate ratio, an indicator of bioenergetic reserve, was determined. The mean +/- SD for phosphocreatine to inorganic phosphate ratio in the neutral position in preterm and term infants was 1.08 +/- 0.15 and 1.12 +/- 0.21, respectively, and did not change significantly following head turning. These data suggest that any alteration in cerebral blood flow as a result of a change in head position in the healthy neonate may be compensated by physiological and biochemical regulations so that no changes in brain oxidative phosphorylation are measurable.

Alpha-adrenergic receptor subtypes in the cerebral circulation of newborn piglets

The purpose of this study was to identify the alpha-adrenergic receptor subtype mediating cerebral vasoconstriction during sympathetic nerve stimulation in the newborn piglet. The effect of alpha 1- and alpha 2- antagonists prazosin and yohimbine on the cerebrovascular response to unilateral electrical stimulation (15 Hz, 15 V) of the superior cervical sympathetic trunk was studied in 25 newborn piglets. Regional cerebral blood flow was measured with tracer microspheres (15 +/- 1 micron). Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum hippocampus, choroid plexus, and masseter muscle by 15 +/- 2, 10 +/- 2, 51 +/- 5, and 94 +/- 5%, respectively. alpha 1-Adrenergic receptor blockade with prazosin (0.5 mg/kg, n = 10) inhibited the sympathetic vasoconstriction in the cerebrum, hippocampus, and masseter muscle (7 +/- 2, 4 +/- 3, and 55 +/- 9%, respectively) and abolished it in the choroid plexus. alpha 2-Adrenergic receptor blockade with yohimbine (0.5 mg/kg, n = 6 and 1.0 mg/kg, n = 5) had no effect. Following the higher dose of yohimbine, however, blood flow to all brain regions was increased by approximately two-fold, possibly due to enhanced cerebral metabolism. These data demonstrate that vascular alpha 1-adrenergic receptors mediate vasoconstriction to neuroadrenergic stimulation in cerebral resistance vessels in the newborn piglet.

The effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants

The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (133Xe) clearance technique, which uses an intravenous bolus of 133Xe, an external chest detector to estimate arterial 133Xe concentration, eight external cranial detectors to measure cephalic 133Xe clearance curves, and a two-compartmental analysis of the cephalic 133Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.

31P-NMR studies of cerebral metabolic changes during graded hypoxia in newborn lambs

We measured cerebral phosphocreatine (PCr), inorganic phosphate (Pi), ATP, and intracellular pH (pHi) with in vivo phosphorus nuclear magnetic resonance (NMR) during 10- to 15-min periods of reversible hypoxic hypoxia in 20 newborn lambs (1-11 days). There was a significant correlation between arterial O2 partial pressure (PaO2) and the PCr/Pi ratio or pHi; however, between PaO2 130-33 mmHg, metabolite changes were not significant. PCr/Pi and pHi decreased significantly when PaO2 was lowered below 33 and 28 mmHg, respectively. After recovery, metabolite ratios and pHi returned to base-line values within 5 min. During the early phases of hypoxia and recovery, there were large fluctuations in metabolites and pHi, indicating that mitochondrial reactions were not in a steady state. After several minutes of hypoxia or recovery, PCr/Pi and pHi stabilized, suggesting steady state kinetics for mitochondrial respiration. NMR is extremely sensitive to changes in mitochondrial oxygenation, and stable PCr/Pi and pHi indicate that O2 tension in cerebral mitochondria of the newborn lamb is constant between PaO2 of 30 and 140 mmHg.

A randomized clinical trial of early hospital discharge and home follow-up of very-low-birth-weight infants

To determine the safety, efficacy, and cost savings of early hospital discharge of very-low-birth-weight infants (less than or equal to 1500 g), we randomly assigned infants to one of two groups. Infants in the control group (n = 40) were discharged according to routine nursery criteria, which included a weight of about 2200 g. Those in the early-discharge group (n = 39) were discharged before they reached this weight if they met a standard set of conditions. For families of infants in the early-discharge group, instruction, counseling, home visits, and daily on-call availability of a hospital-based nurse specialist for 18 months were provided. Infants in the early-discharge group were discharged a mean of 11 days earlier, weighed 200 g less, and were two weeks younger at discharge than control infants. The mean hospital charge for the early-discharge group was 27 percent less than that for the control group ($47,520 vs. $64,940; P less than 0.01), and the mean physician's charge was 22 percent less ($5,933 vs. $7,649; P less than 0.01). The mean cost of the home follow-up care in the early-discharge group was $576, yielding a net saving of $18,560 for each infant. The two groups did not differ in the numbers of rehospitalizations and acute care visits, or in measures of physical and mental growth. We conclude that early discharge of very-low-birth-weight infants, with follow-up care in the home by a nurse specialist, is safe and cost effective.

Cerebral metabolic effects of neonatal seizures measured with in vivo 31P NMR spectroscopy

In vivo phosphorus 31 nuclear magnetic resonance (31P NMR) spectroscopy was used to evaluate changes in cerebral high-energy phosphate compounds in 8 infants with seizures. During the study 4 babies had seizures that caused a 50% decrease in the phosphocreatine to inorganic phosphate (PCr/Pi) ratio. Focal seizures caused lateralized decreases in the PCr/Pi ratio; generalized seizures caused bilateral decreases. Postictal spectra had increased PCr/Pi ratios, presumably due to postictal inhibition. Interictal 31P NMR spectra were normal. One patient's seizures were successfully treated with intravenously administered phenobarbital during NMR data acquisition, causing an immediate increase in the PCr/Pi ratio from 0.7 to 1.2. These studies indicate that cerebral PCr concentration decreases by approximately 33% and that oxidative metabolism increases by approximately 45% during neonatal seizures. Five babies had PCr/Pi ratios of less than 0.8 during seizures and subsequently developed long-term neurological sequelae, which suggests that neonatal seizures may cause or exacerbate cerebral injury by increasing cerebral metabolic demands above energy supply.

Principles in cellular oxygenation: fetal and neonatal intestines

Complex biochemical consequences are the result of a series of secondary biochemical changes caused by oxygen depletion. Hypoxia in the fetus and neonate results in decreased GI blood flow, especially to the GI mucosa. Although severe O2 deprivation cannot be entirely compensated for, an increase in tissue O2 extraction does occur in cases of moderate hypoxemia. In the neonate increased demands for O2 during feedings result in increased blood flow. The occurrence of hypoxia during feedings causes a decrease in intestinal motility, suggesting a clinical correlate to feeding intolerance and increased vulnerability to necrotizing enterocolitis.

Effect of sympathetic nerve stimulation on cerebral blood flow in newborn piglets

The purpose of this study was to determine the effect of sympathetic nerve stimulation on regional cerebral blood flow during the first 3 wk of postnatal development in piglets. Forty-one piglets ranging in age from 2 to 24 days were studied while anesthetized with 30% N2O, paralyzed and mechanically ventilated (PaCO2 = 35-40 mm Hg). Regional cerebral blood flow was measured with tracer microspheres (15 +/- micron) during electrical stimulation (15 Hz, 15 V, 3 ms) of the right cervical sympathetic trunk. Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum (gray and white matter) (-15 +/- 2%), hippocampus (-9 +/- 2%), choroid plexus (-50 +/- 5%), and masseter muscle (-93 +/- 2%) compared to the contralateral side where blood flow to these regions was 74 +/- 4, 45 +/- 2, 258 +/- 26, and 24 +/- 4 ml/min/100 g, respectively (mean +/- SEM; p less than or equal to 0.05). The magnitude of the reduction in cerebral blood flow was not dependent on postnatal age as no significant differences were noted when the piglets were grouped according to age. Hypercapnia (PaCO2 = 64 +/- 5 mm Hg) increased blood flow 2- to 4-fold above control in all brain regions except the choroid plexus. The effect of sympathetic nerve stimulation was augmented during hypercapnia where blood flow to the ipsilateral cerebrum, hippocampus, and caudate nucleus was decreased by -34 +/- 4, -23 +/- 5, and -16 +/- 3%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Infections in newborn infants in a special care unit. A changing pattern of infection

An analysis of infections in the intensive and intermediate care nurseries (special care unit) of the Hospital of the University of Pennsylvania was made over a three year period. From January 1982 to September 1984, 98 bacteremias were identified in 2571 infants, giving an overall incidence of 3.8 per 100 infants admitted to the special care unit and 11.8 per 1000 hospital births; 7 of 98 infants died, all from early onset disease. Fifty-eight percent of bacteremias were nosocomial. Gram positive organisms accounted for 89 percent of all bacteremias, with coagulase negative staphylococcus and beta hemolytic streptococcus Group B (GBS) being the most frequently identified organisms. Coagulase negative staphylococcus was responsible for 42 percent of bacteremias and 75 percent of all nosocomial infections during this period. Streptococcus Group B was responsible for 78 percent of early onset infection; mortality rate from GBS was 11 percent. In view of the changing pattern of infection and the predominance of coagulase negative staphylococcus, the therapy for nosocomial infection should include antibiotics effective against this organism.

Physiology of the placenta--gas exchange

The placenta serves as the fetus' organ of gas exchange throughout intra-uterine life. While the dependence of fetal well-being on an intact maternal-placental unit has been recognized for centuries, it is only in the last several decades that research with fetal animals has begun to unravel the mechanisms by which it regulates blood supply and oxygen, as well as its role in the maternal-to-fetal transfer of carbohydrates, proteins, fats, water, and inorganic salts. The anatomy and physiology of the placenta are presented here as they relate specifically to gas exchange. In addition, compensatory adaptations of the fetus and placenta to acute asphyxial events will be discussed.

Nuclear magnetic resonance: an overview of its spectroscopic and imaging applications in pediatric patients

Magnetic resonance (MR) is a technique that permits the noninvasive evaluation of morphologic features and function based on the distribution of protons and other selected elements. We present a basic description of MR and illustrate both 31P-MR spectroscopy and proton imaging applications in pediatric patients. The applications of these techniques are diverse, and are presented concisely in an attempt to give pediatricians an overview of this new technology and its potential role in patient management.

Relationship of prolonged pharmacologic serum levels of vitamin E to incidence of sepsis and necrotizing enterocolitis in infants with birth weight 1,500 grams or less

The incidence of culture-proven neonatal sepsis and necrotizing enterocolitis (NEC) in preterm infants maintained at pharmacologic (mean 5.1 mg/dL +/- 1.45 SD) serum vitamin E levels for long periods was prospectively studied as part of a double-masked clinical trial of the effect of prophylactic vitamin E v placebo treatment on the development and course of retinopathy of prematurity (ROP). Within a few days of birth, 914 preterm infants were enrolled in the study; 545 (275 placebo-treated infants, 270 vitamin E-treated infants had birth weight of 1,500 g or less. A significant difference in incidence of neonatal sepsis (17 placebo-treated infants, 37 vitamin E-treated infants) and NEC (18 placebo-treated infants, 32 vitamin E-treated infants) was observed among infants who had been treated for eight or more days and who had developed neither sepsis nor NEC before that time. The association of vitamin E treatment with increased incidence of disease was much higher with sepsis than with NEC. The most likely reason for these observations is a pharmacologic serum vitamin E-related decrease in oxygen-dependent intracellular killing ability which results in a decreased resistance to infection in preterm infants. The data suggest that, if this occurs, it is clinically significant only in the more immature infants. In view of the known variability of absorption of oral vitamin E and the association between high serum vitamin E levels and increased incidence of sepsis and late-onset NEC reported here, it can be concluded that serum vitamin E levels must be monitored when supplemental vitamin E is administered to premature infants, especially those with birth weight 1,500 g or less. The risk-benefit ratio of long-term treatment using vitamin E at high serum levels should be clearly assessed.

Exercise during pregnancy--potential fetal and placental metabolic effects

Exercise during pregnancy has become an important topic with the recent popularity of physical fitness programs among the non-pregnant population. Various physiological effects of exercise have been reported in several animal species, and there are some reports of physiological effects in pregnant women which will be reviewed.

Sequential changes in red cell glycolytic enzymes and intermediates and possible control mechanisms in the first two months of postnatal life in lambs

The sequential changes in several glycolytic enzymes, glucose-6-phosphate dehydrogenase, glycolytic intermediates, and adenosine triphosphate, as well as intracellular pH and plasma inorganic phosphorus were followed simultaneously in eight lambs from birth to 2 months of age. The activities of all glycolytic enzymes and glucose-6-phosphate dehydrogenase were elevated at birth. The 2,3-diphosphoglycerate concentration increased markedly postnatally and was associated with a simultaneous increase in the concentrations of red cell glucose-6-phosphate and total triose phosphate and a decrease in intracellular pH. Inorganic phosphorus also increased and correlated with the 2,3-diphosphoglycerate concentration in the first 10 days of postnatal life. The content of red cell 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate, and ATP increased slightly. These results suggested increased glycolytic flux through the diphosphoglycerate mutase reaction which resulted in net synthesis of 2,3-diphosphoglycerate. The red cell total triose phosphate peaked and fell initially, followed by glucose-6-phosphate and 2,3-diphosphoglycerate suggesting inhibition of phosphofructokinase activity and a decrease in glycolysis secondary to decreased red cell intracellular pH. After 10 days of postnatal life all glycolytic intermediates fell simultaneously, which correlated with a decrease in activity of the glycolytic enzymes.

Red cell glycolytic intermediates and adenosine triphosphate in preterm infants on the first day of life

Red cell glycolytic intermediates and ATP were evaluated in 47 appropriate for gestational age preterm infants on the 1st day of life who were divided into three groups on the basis of gestational age: 28-30, 31-33, and 34-36 wk. The results were compared to those previously obtained in term infants. The concentrations of glucose-6-phosphate, total triose phosphates, and ATP were significantly higher than in term infants but appeared to be appropriately elevated for the young mean age of the red cell population. The concentration of red cell 2,3-diphosphoglycerate (2,3-DPG) was significantly decreased when compared to term infants and was lowest at 28-30 wk gestation. The content of red cell 3-phosphoglycerate was increased in term infants and was inappropriately elevated for the age of the red cell population at 28-30 wk gestation. This pattern of glycolytic intermediates was suggestive of a young red cell population metabolizing at an increased glycolytic rate with increased flow through the phosphoglycerate kinase step rather than the 2,3-DPG bypass in "normal" preterm infants. Two preterm infants of 28-30 wk gestation with low red cell intracellular pH were also evaluated and had markedly decreased concentrations of red cell 2,3-DPG and ATP and all phosphorylated intermediates distal to the phosphofructokinase reaction, indicative of a cross-over at the phosphofructokinase step secondary to acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitochondrial respiration following acute hypoxia in the perfused rat heart

Mitochondria isolated from tissues of hypoxic animals have increased respiratory capacity (State 3 respiration) when assayed in vitro at ambient oxygen tensions. The present study utilized the isolated perfused rat heart to determine whether or not this change could be produced in the absence of the neural and hormonal changes that accompany hypoxia in vivo. Following 10-min single pass retrograde perfusion with normoxic Krebs-Henseleit buffer (PO2 greater than or equal to 600 mmHg), perfusion was continued for up to 15 min with either normoxic or hypoxic buffer (PO2 less than or equal to 150 mmHg). After 10 min of hypoxic perfusion State 3 respiration of the mitochondria from the hypoxic hearts was 13 to 15% higher (P less than or equal to 0.05) than that of normoxic hearts when assayed with either glutamate/malate or succinate as substrate but was unchanged when TMPD and ascorbate was the substrate. Succinate-supported State 4 respiration of the hypoxic mitochondria also showed a small (10%) but significant (P less than or equal to 0.05) increase. These changes were not abolished by preperfusing the heart with propranolol (10(-7), 10(-6), or 10(-5) M) indicating that the response was not attributable to release of local stores of catecholamines. Respiratory control and ADP/O ratios as well as contents of cytochrome c and aa3 of the mitochondria from the hypoxic hearts were similar to those of normoxic hearts indicating that the mitochondria remained intact and tightly coupled. We concluded that the hypoxia-induced increase in mitochondrial State 3 respiration, while independent of neural and hormonal influences from the body requires an intracellular event, since they cannot be reproduced by subjecting isolated mitochondria to hypoxia in vitro.

Cerebral blood flow and metabolism following pancuronium bromide in newborn lambs

The purpose of this study was to evaluate cerebral blood flow and metabolism following pancuronium bromide paralysis in healthy newborn lambs. Cerebral blood flow and cerebral metabolic rate for O2 and glucose were measured along with blood pressure and blood gases before and again at 15 and 60 min following pancuronium paralysis in seven newborn lambs. Pancuronium bromide paralysis had no effect on any of these parameters either at 15 or 60 min of paralysis. Total cerebral blood flow, cerebral metabolic rate for O2, and cerebral metabolic rate for glucose were 87 +/- 6 ml/min/100 g, 258 +/- 10 mumol O2/min/100 g, and 53 +/- 10 mmol glucose/min/100 g, respectively. Neither was any change in regional cerebral blood flow noted. In spite of being connected immediately to the ventilator, however, some animals experienced a transient increase (average = 32%) in blood pressure, that was not associated with an increase in end tidal CO2. The data suggest that pancuronium paralysis in healthy awake newborn lambs does not lead to any alteration in cerebral blood flow or metabolism.

Unique aspects of human newborn cerebral metabolism evaluated with phosphorus nuclear magnetic resonance spectroscopy

In vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was used to evaluate the pattern of phosphate compounds in seven newborn babies (mean gestational age, 32 weeks; birth weight, 1,430 gm; age, 37 days) with a history of perinatal asphyxia. Spectra were collected in a 1.9 Tesla superconductive magnet with surface coil techniques. The spectra had characteristic peaks for phosphorylated monoesters (PME), inorganic phosphate (Pi), phosphodiesters (PD), phosphocreatine (PCr), and ATP. In contrast to cortical spectra from mature animals, these newborn infant 31P NMR spectra were dominated by a large PME peak and had small PCr, Pi, and PD peaks. Intracellular pH, as measured from the chemical shift of the Pi peak relative to the PCr peak, was 7.1 +/- 0.1 (SD). We studied one infant postmortem, and a large PME peak was present in his spectrum. The presence of PME 3 hours after death strongly suggests that it is not a sugar phosphate. In NMR spectroscopy, compounds are identified by their chemical shift relative to a known standard (PCr); the chemical shift of the PME peak was 6.5 ppm, suggesting that it is a mixture of phosphoryl ethanolamine and phosphoryl choline. The PCr/Pi ratio (1.3 +/- 0.7) and the PCr/ATP ratio (0.7 +/- 0.4) were lower in these babies than in mature animals (greater than 2 and greater than 1.4, respectively); the PME/PD ratio (1.2 +/- 0.6), however, was much greater in the infants (mature animals, less than 0.2). These findings suggest that there are unique aspects of human newborn cerebral metabolites and bioenergetic reserve.

Alterations in oxygen transport following WR-2721

The toxicity of radiation and alkylating agent chemotherapy is in part related to free radical formation in DNA and associated proteins, which is enhanced by oxygen and other electron affinic compounds. During the Phase I clinical trials of WR-2721 and alkylating agent chemotherapy, venous blood samples were obtained prior to and immediately following the WR-2721 infusion. We have observed a marked increase in the oxygen saturation of venous blood following WR-2721 (430-910 mg/m2 at a rate of 15 mg/m2/minute). The mean venous PO2 (PvO2) rose from a baseline of 34.0 +/- 13.54 torr to a mean value of 54.60 +/- 12.47 torr (p less than 0.001). The percent venous oxygen saturation increased from 54.52 +/- 21.38% to 82.73 +/- 7.66%. The highest values generally occurred within the first 2 hours after the completion of the WR-2721 infusion. No significant differences were found between the pre and post WR-2721 values for either the venous pH, CO2, or bicarbonate levels. Despite increased PvO2, the patients' heart rates, blood pressures, or respiratory rates did not change pre and post WR-2721. No apparent differences were noted in the effects of WR-2721 or PvO2 when given at doses of 740 or 910 mg/m2. However, when WR-2721 (418-1100 mg/m2) was administered over 15 minutes, the PvO2 increased in only 8/13 courses. We postulated that the marked increase in venous blood oxygen concentration was secondary to one of the following mechanisms: 1) Increased affinity of hemoglobin for oxygen, 2) microcirculatory shunting, or 3) decreased tissue requirements for oxygen. In 12 patients oxygen-hemoglobin dissociation curves and intracellular red cell pH's were obtained before and after 740-910 mg/m2 of WR-2721. Despite the significant increase in oxygenation of venous blood after WR-2721, there were no changes in either oxygen-hemoglobin dissociation or intracellular red cell pH to account for this increase. The oxygen consumption of peripheral blood granulocytes was measured prior to and following 15 courses of WR-2721. A marked decrease in granulocyte oxygen consumption was observed in 6/8 patients who had a significant increase in PvO2 and only 1/7 patients who had either a decrease or no change in PvO2 after WR-2721. Our preliminary investigations suggest that the increased venous blood oxygen content may be secondary to a reduction in normal tissue oxygen consumption. WR-2721 may afford protection by both decreasing oxygen consumption and delivery to normal tissues and increasing intracellular sulfhydryls.

Fibrinogen degradation products in acute renal failure of the newborn

Acute parenchymal renal failure (ARF) in the newborn infant has emerged as a major problem since the advent of neonatal intensive care units. Because intravascular and/or intrarenal coagulation may be important in the development of ARF, a prospective study of coagulation was performed on 20 babies with ARF, with particular emphasis on the measurement of fibrinogen degradation products (FDP) in serum and urine. Thirteen babies with respiratory distress syndrome (RDS) and 40 healthy neonates served as controls. Initial serum FDP levels were significantly higher in ARF than in RDS or normals (P less than 0.001); initial urine FDP levels were higher in ARF than in normals (P less than 0.01). Levels of FDP did not differentiate among the various etiologies of ARF. Since initial urine FDP levels are high in normal newborns, serial urine FDP were compared among patient groups and found to be highest in ARF. Initial serum and urine FDP levels could not differentiate among the 11 survivors and 9 nonsurvivors, but FDP levels declined as the duration of ARF (e.g., survival) increased, often antedating the recovery of renal function. We conclude: (1) serum and urine FDP are significantly elevated in most newborns with ARF; (2) factors other than hypoxia may be involved in the pathogenesis of elevated serum FDP in RDS with ARF newborns, indicating the importance of coagulation; (3) serial measurements of serum and urine FDP may be early indicators of recovery of renal function.

Noninvasive method of estimating human newborn regional cerebral blood flow

A noninvasive method of estimating regional cerebral blood flow (rCBF) in premature and full-term babies has been developed. Based on a modification of the xenon-133 inhalation rCBF technique, this method uses eight extracranial NaI scintillation detectors and an i.v. bolus injection of xenon-133 (approximately 0.5 mCi/kg). Arterial xenon concentration was estimated with an external chest detector. Cerebral blood flow was measured in 15 healthy, neurologically normal premature infants. Using Obrist's method of two-compartment analysis, normal values were calculated for flow in both compartments, relative weight and fractional flow in the first compartment (gray matter), initial slope of gray matter blood flow, mean cerebral blood flow, and initial slope index of mean cerebral blood flow. The application of this technique to newborns, its relative advantages, and its potential uses are discussed.

Red cell enzymopathies in the newborn. I. Evaluation of red cell metabolism

In order to evaluate properly red cell metabolic data obtained in newborns with congenital hemolytic disorders, the unique metabolic characteristics and normal developmental changes that occur prenatally and postnatally are presented. The age-dependent red cell glycolytic enzymes (hexokinase, aldolase, pyruvate kinase) and glucose-6-phosphate dehydrogenase and most glycolytic intermediates are elevated at birth and at 11 to 12 months of age, consistent with the presence of a young red cell population the entire first year of life. However, certain red cell enzymes are elevated out of proportion to the age of the red cell population [phosphoglucose isomerase. glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase (PGK), and enolase (ENO)] whereas others are decreased [phosphofructokinase (PFK), glutathione peroxidase, carbonic anhydrase, and others]. These metabolic characteristics are felt to be unique and representative of "fetal erythropoiesis." Activities of PGK and ENO decrease the PFK increases toward normal adult values beginning at eight to nine weeks of age. The concentration of glucose-6-phosphate steadily increases after birth and peaks at three to four weeks of age, at a time when PFK activity remains relatively unchanged, suggesting a relative block in glycolysis at the PFK step secondary to an enzyme with both decreased activity and altered kinetic properties (a "fetal" isozyme). Thus, evaluation of red cell enzyme and glycolytic intermediate data obtained in the first year of life should be related to the knowledge that a young red cell population is present and the characteristic unique metabolic red cell alterations described in cord blood persist beyond the immediate neonatal period.

Retrolental fibroplasia and blood transfusion in very low-birth-weight infants

The relative contribution of transfusions of adult blood to the development of retrolental fibroplasia (RLF) in very low-birth-weight infants was examined. Five years of experience with the expanded use of replacement and exchange transfusions in 90 infants with birth weight less than or equal to 1,250 gm was reviewed. Twenty percent of the infants developed cicatricial RLF. Exchange transfusion was not related to development of cicatricial RLF. The incidence of RLF in infants receiving greater or equal to 130 ml of packed red blood cells per kilogram of birth weight as replacement blood transfusion (RBT) was significantly higher (42.9%) than that in infants receiving 61 to 131 ml of packed red blood cells per kilogram (15.4%) and infants receiving less than or equal to 60 ml of packed red blood cells per kilogram (0%), P less than .001. The need for RBT, however, was strongly correlated (r = .85, P less than .001) with increasing duration of O2 therapy. When O2 therapy was controlled for, the association between RBT and RLF did not achieve statistical significance (P = .07). The association between RBT and RLF remained significant when adjusted for duration of therapy in fractional inspired oxygen (FIO2) greater than 0.4. Further detailed studies of large numbers of susceptible infants are warranted to assess the magnitude of the contribution of transfusions of adult blood to development of RLF.

Red cell metabolic alterations in postnatal life in term infants: possible control mechanisms

Red cell glycolytic intermediates and enzymes in term infants in the first year of life were correlated with the fetal hemoglobin concentration (%F), intra- and extracellular venous pH, plasma inorganic phosphorus (Pi) and pyruvate kinase (PK) activity. Changes in the non-age-dependent enzymes phosphoglycerate kinase, enolase, and phosphofructokinase correlated most significantly with the postnatal decline in %F (P less than 0.001), not the age of the red cell population, as reflected in PK activity. The age-dependent enzymes, hexokinase and glucose-6-phosphate dehydrogenase, however, correlated well with PK activity (P less than 0.001). The concentration of glucose-6-phosphate did not correlate significantly with the postnatal decline in %F (P greater than 0.05) or PK (P greater than 0.10), but correalted significantly with the plasma Pi concentration (P less than 0.001). "Total triose phosphate" and 2,3-diphosphoglycerate did not correlate with Pi. It appears from these studies that an extracellular factor, Pi alters the pattern of glycolytic intermediates in term infants and that the postnatal changes in phosphoglycerate kinase, enolase, and phosphofructokinase are unique to the "fetal" red cell and reflect passage from fetal to "adult" erythropoiesis.

Red cell metabolic alterations in postnatal life in term infants: glycolytic intermediates and adenosine triphosphate

Red cell glycolytic intermediates and adenosinetriphosphate were evaluated in term infants from birth to on year of age and compared to values obtained from normal adults and subjects wit a population of a similar mean cell age. The concentration of glycolytic intermediates, with the exception of phosphoenolypyruvate were elevated at birth when compared to normal subjects, consistent with a young mean red cell population. The mean levels of red cell glucose-6-phosphate, fructose-6-phosphate, and "total triose phosphate" were elevated on days 1 and 4 of life when compared to both red cells from normal adults and subjects with a similar young mean red cell age. Glucose-6-phosphate steadily increased in concentration, peaked at 3 to 4 wk of age, and then progressively decreased in value. Total triose phosphate declined to a mildly elevated concentration by 3 to 4 wk of age. The mean concentrations of 2,3-diphosphoglycerate and adenosine triphosphate were normal on day 1, increased on day 4, and then declined by 3 to 4 wk to normal values, until 5 to 6 months when both increased. The mean phosphoenolpyruvate concentration was decreased on day 1 of age when compared to red cells of a similar mean age, but this decrease was not significant (P greater than 0.05). The mean concentrations of 3-phosphoglycerate increased at 3 to 4 wk of age and remained elevated for cell age at 11 to 12 months but this increase was no statistically significant (P greater than 0.05). 3-Phosphoglycerate levels did not change significantly throughout the first year of life. At one year of age, all red glycolytic intermediates and adenosine triphosphate were elevated when compared to red cells from normal adults, but were comparable to those observed in subjects with a red cell population of a similar mean cell age, consistent with the persistence of a young red cell population throughout the first year of life.

Red cell metabolic alterations in postnatal life in term infants: glycolytic enzymes and glucose-6-phosphate dehydrogenase

The activities of red cell enzymes enolase (ENO), phosphoglycerate kinase (PGK), phosphofructokinase (PFK), glucose-6-phosphate dehydrogenase (G-6-PD), hexokinase (HK), aldolase (ALD), and pyruvate kinase (PK) were followed sequentially in term infants from birth to one year of age. At birth, red cell PGK and ENO activities were disproportionately elevated when compared to both red cells with a similar mean cell age and those with a younger mean cell age; red cell PFK was significantly decreased. There was a progressive full in PGK and ENO activities and rise in PFK levels toward normal values in the first year of life. The most significant changes in PGK, ENO, and PFK appeared to begin at 8 to 9 wk of age. ENO and PFK activities stabilized at approximately 5 to 6 months of age at values compatible with mean cell age; mean PGK levels remained mildly elevated at 11 to 12 months. The age-dependent enzymes G-6-PD, PK, ALD, and HK were all elevated in term newborns. G-6-PD and ALD progressively decreased in activity during the first year of life. PK and HK decreased in activity until 8 to 9 wk when there was a secondary rise in mean activity. Mean red cell G-6-PD, PK, ALD, and HK levels remained mildly to moderately elevated at 11 to 12 months of life, suggesting the persistence of a relatively young red cell population throughout the first year of life.