Showing papers in "Pediatric Research in 1998"

Microstructural development of human newborn cerebral white matter assessed in vivo by diffusion tensor magnetic resonance imaging.

Abstract: Alterations of the architecture of cerebral white matter in the developing human brain can affect cortical development and result in functional disabilities. A line scan diffusion-weighted magnetic resonance imaging (MRI) sequence with diffusion tensor analysis was applied to measure the apparent diffusion coefficient, to calculate relative anisotropy, and to delineate three-dimensional fiber architecture in cerebral white matter in preterm (n = 17) and full-term infants (n = 7). To assess effects of prematurity on cerebral white matter development, early gestation preterm infants (n = 10) were studied a second time at term. In the central white matter the mean apparent diffusion coefficient at 28 wk was high, 1.8 microm2/ms, and decreased toward term to 1.2 microm2/ms. In the posterior limb of the internal capsule, the mean apparent diffusion coefficients at both times were similar (1.2 versus 1.1 microm2/ms). Relative anisotropy was higher the closer birth was to term with greater absolute values in the internal capsule than in the central white matter. Preterm infants at term showed higher mean diffusion coefficients in the central white matter (1.4 +/- 0.24 versus 1.15 +/- 0.09 microm2/ms, p = 0.016) and lower relative anisotropy in both areas compared with full-term infants (white matter, 10.9 +/- 0.6 versus 22.9 +/- 3.0%, p = 0.001; internal capsule, 24.0 +/- 4.44 versus 33.1 +/- 0.6% p = 0.006). Nonmyelinated fibers in the corpus callosum were visible by diffusion tensor MRI as early as 28 wk; full-term and preterm infants at term showed marked differences in white matter fiber organization. The data indicate that quantitative assessment of water diffusion by diffusion tensor MRI provides insight into microstructural development in cerebral white matter in living infants.

Visual Acuity and the Essentiality of Docosahexaenoic Acid and Arachidonic Acid in the Diet of Term Infants

Abstract: The need for a dietary supply of docosahexaenoic acid (DHA) and arachidonic aid (AA) in term infants was evaluated in a double-masked randomized clinical trial of the effects of supplementation of term infant formula with DHA (0.35% of total fatty acids) or with DHA (0.36%) and AA (0.72%) on visual acuity development. One hundred and eight healthy term infants were enrolled in the study; 79 were exclusively formula-fed from birth (randomized group) and 29 were exclusively breast-fed (gold standard group). Infants were evaluated at four time points during the first 12 mo of life for blood fatty acid composition, growth, sweep visual evoked potential (VEP) acuity, and forced choice preferential looking acuity. Supplementation of term infant formula with DHA or with DHA and AA during the first 4 mo of life yields clear differences in total red blood cell (RBC) lipid composition. Supplementation of term infant formula with DHA or with DHA and AA also yields better sweep VEP acuity at 6, 17, and 52 wk of age but not at 26 wk of age, when acuity development reaches a plateau. The RBC lipid composition and sweep VEP acuity of supplemented infants was similar to that of human milk-fed infants, whereas the RBC lipid composition and sweep VEP acuity of unsupplemented infants was significantly different from human milk-fed infants. Differences in acuity among diet groups were too subtle to be detected by the forced choice preferential looking protocol. Infants in all diet groups had similar rates of growth and tolerated all diets well. Thus, early dietary intake of preformed DHA and AA appears necessary for optimal development of the brain and eye of the human infant.

Erythropoietin and erythropoietin receptor in the developing human central nervous system.

Abstract: We have previously shown the presence of erythropoietin (Epo) within the spinal fluid of normal preterm and term infants, and the presence of Epo receptor (Epo-R) in the spinal cords of human fetuses. It is not known, however: 1) whether cells within the fetal central nervous system(CNS) express Epo; 2) if so, whether this expression changes with development; 3) which cells within the CNS express Epo-R;4) whether Epo-R expression within the CNS changes with development; and 5) whether Epo-R within the fetal CNS are functional. Expression of mRNA for Epo and Epo-R was sought by reverse transcription-PCR in mixed primary cultures of fetal spinal cords as well as NT2 and hNT cells, human cell lines of neuronal precursors and mature neurons, respectively. Epo was measured by ELISA in spent media from primary cell culture, and immunohistochemistry was used to identify Epo-R on neurons and glia in cell culture, and in brain sections. Developmental changes in Epo and Epo-R expression were sought in spinal cords and brains from fetuses of 7-24 wk postconception by semiquantitative PCR. To assess Epo-R function, NT2 cells were exposed to conditions which stimulate programmed cell death, and rescue from apoptosis by the addition of recombinant Epo was evaluated by nuclear matrix protein ELISA, cell counts, and by Klenow labeling of DNA fragments. Epo and Epo-R mRNA were expressed in mixed primary cultures of neural tissues and NT2 and hNT cells. Epo was detected by ELISA in media removed from mixed cell cultures, and immunohistochemical staining confirmed the presence of Epo-R on neurons and their supporting cells. Semiquantitative PCR revealed no significant change in expression of either Epo or Epo-R in spinal cords between 7 and 16 wk of gestation, with increased expression of Epo and Epo-R in brains from 8 to 24 wk of gestation. Epo mRNA expression from neurons doubled under conditions of hypoxia. Recombinant Epo decreased apoptotic cell death of neurons under conditions of hypoxia. Protein and mRNA for Epo and its receptor are expressed by human neurons and glial cells in spinal cord and brain during fetal development. These receptors appear to have a neuroprotective effect in conditions of hypoxia.

Protective Effects of Moderate Hypothermia after Neonatal Hypoxia-Ischemia: Short- and Long-Term Outcome

Abstract: We have previously shown that mild hypothermia applied after hypoxia-ischemia in newborn piglets and rats reduces brain injury evaluated 3-7 d after the insult. The aim of the present study was to assess the neuroprotective efficacy of hypothermia with respect to short- (neuropathology) and long-term (neuropathology and sensorimotor function) outcome after hypoxia-ischemia in 7-d-old rats. One hundred fourteen animals from 13 litters survived either 1 or 6 wk after a hypoxic-ischemic insult. The animals were randomized to either 1) normothermic recovery for the whole 1- or 6-wk period or 2) cooling to a rectal temperature of 32.0 degrees C for the first 6 h followed by normothermic recovery with the dam. Hypothermia offered a uniform protection of 27, 35, 28, and 25% in cerebral cortex, hippocampus, basal ganglia, and thalamus, respectively, in the 1-wk survivors (n = 32). The corresponding values for the 6-wk survivors (n = 61) were 22, 28, 37, and 35%. There was a significant correlation between sensorimotor performance and infarct volume (r = 0.66; p < 0.001). However, the sensorimotor function was not significantly improved by hypothermia if all animals were included, but in female pups the total functional score was higher in the hypothermia group (150 +/- 35 versus 100 +/- 34, p < 0.0007) which corresponded to a marked (51%) reduction of the neuropathology score in this subgroup. This is the first neonatal study to show a long-term histopathologic protection of the brain after posthypoxic hypothermia.

Regional Hemodynamic Responses to Visual Stimulation in Awake Infants

Abstract: This study presents the first measurements using near infrared spectroscopy of changes in regional hemodynamics as a response to a visual stimulus in awake infants. Ten infants aged 3 d to 14 wk viewed a checkerboard with a 5-Hz pattern reversal. The emitter and detector (optodes) of a near infrared spectrophotometer were placed over the occipital region of the head. Changes in concentration of oxy- and deoxyhemoglobin (Hbo2 and Hb) were measured and compared during 10-s epochs of stimulus on and off. A control group of 10 infants aged 18 d to 13 wk were examined with the same setup, but with the optodes over the frontoparietal region. In the test group the total hemoglobin concentration (Hbo2 + Hb) increased while the stimulus was on by a mean (+/-SD) of 2.51 (+/-1.48) micromol x L(-1). Nine out of 10 infants showed an Hbo2 increase, and 9 out of 10 an Hb increase related to the stimulus. There was no significant change in any of these parameters in the control group. The results imply that there is increased cerebral blood flow due to stimulation that is specific to the visual cortex and that infants, unlike adults, show increased cerebral oxygen utilization during activation that outstrips this hemodynamic effect. The study demonstrates that near infrared spectroscopy can be used as a practical and noninvasive method of measuring visual functional activation and its hemodynamic correlates in the awake infant.

Effects of environmental exposure to polychlorinated biphenyls and dioxins on birth size and growth in Dutch children

Abstract: Lower birth weight and growth retardation has been found in studies with laboratory animals, in children born of mothers exposed to accidental high levels of polychlorinated biphenyls (PCBs) and related compounds, and in children born of mothers who consumed PCB-contaminated fish. The effect of background exposure to PCBs and dioxins on birth size and growth in human newborns, however, is still unknown. This study examined birth size and postnatal growth of term newborns in relation to their background PCB and dioxin exposure. Birth weight and weight, length, and head circumference were measured at 10 d and 3, 7, 18, and 42 mo of age in 207 children, of whom 105 were breast-fed and 102 were formula-fed during infancy. The effect of in utero exposure to PCBs on birth size, assessed by cord and maternal plasma PCB levels, was investigated in the whole group. The effect of prenatal PCB exposure on postnatal growth was studied in the formula-fed group, whereas the effect of prenatal as well as lactational exposure to PCBs and dioxins on postnatal growth was studied in the breast-fed group. After adjustment for covariates, cord and maternal plasma PCB levels where both negatively associated with birth weight. Infants with high cord plasma PCB levels (P90 = 0.80 microL) weighed 165 g less compared with infants with low cord plasma PCB levels (P10 = 0.20 microg/L). Cord and maternal plasma PCB levels where both significantly associated with lower growth rate, defined as change in SD score (SDS) of weight, length, and head circumference from birth to 3 mo in the formula-fed group (all p values <0.05). No negative effects of prenatal PCB exposure on growth rate were found from 3 to 42 months of age. Postnatal PCB and dioxin exposure was not negatively associated with growth rate in the breast-fed group. In utero exposure to environmental levels of PCBs is negatively associated with birth weight and postnatal growth until 3 mo of age. Although this growth delay was described in healthy term born infants, intrauterine and postnatal growth retardation are potentially harmful to the developing human and should be avoided by reducing maternal PCB and dioxin body burden, and consequently fetal exposure to these pollutants.

Prenatal Dexamethasone Causes Oligonephronia, Sodium Retention, and Higher Blood Pressure in the Offspring

Abstract: Recent reports have shown that low birth weight infants have a higher incidence of adult hypertension. These observations have stimulated a number of studies designed to evaluate the mechanisms of this phenomenon. In this study, fetal growth retardation was induced by treating pregnant rats with dexamethasone. After birth, pups whose mothers were treated with dexamethasone had a lower body and kidney weight and a lower number of glomeruli than control pups. Immunohistochemistry on treated kidneys demonstrated a marked reduction in the number of cells undergoing mitosis in the cortical nephrogenic zone. In the treated group, body and kidney weight normalized by 60 d of age, but blood pressure was significantly higher compared with controls (130 ± 4 versus 107 ± 1 mm Hg). In addition, GFR was significantly lower, albuminuria was higher, urinary sodium excretion rate and fractional sodium excretion were lower, and sodium tissue content was higher. In contrast, when pregnant rats were treated with a natural glucocorticoid (hydrocortisone) which is metabolized by the placenta, fetal development and adult blood pressure were normal. In conclusion, we found that high levels of maternal glucocorticoids impair renal development and lead to arterial hypertension in offspring. Even though renal mass eventually normalizes, glomerular damage as well as sodium retention occur and these factors may contribute to the development of hypertension.

Placental transport of leucine and lysine is reduced in intrauterine growth restriction.

Abstract: Intrauterine growth restriction (IUGR) is characterized by a reduction in fetal plasma concentrations of a number of essential amino acids. Whether this is caused by impaired placental transport is unknown. We studied transport of leucine and lysine in syncytiotrophoblast microvillous (MVM) and basal membrane (BM) vesicles isolated from uncomplicated (control) and IUGR pregnancies. In addition, we investigated the possibility that leucine uptake is stimulated by an outwardly directed glycine gradient. Uptake of 3H-L-lysine (0.1 microM) and 3H-L-leucine (0.25 microM) was studied at 37 degrees C using rapid filtration techniques. In IUGR, mediated uptake of lysine was reduced by 44% (p < 0.05) in BM and uptake of leucine was lower in both MVM (-46%, p < 0.05) and BM (-38%, p < 0.05) compared with control vesicles. Intravesicular glycine (2 mM) increased the uptake of leucine by 98% in MVM (p < 0.05). These data suggest that the activity of placental transporters for cationic and neutral amino acids is reduced in IUGR. We speculate that a reduced glycine gradient in the placenta in IUGR, due to reduction in system A activity, will impair leucine transport to the fetus, providing an additional mechanism for reduced placental transport of leucine in IUGR.

Plasma Levels and Gene Expression of Granulocyte Colony-Stimulating Factor, Tumor Necrosis Factor-α, Interleukin (IL)-1β, IL-6, IL-8, and Soluble Intercellular Adhesion Molecule-1 in Neonatal Early Onset Sepsis

Abstract: Bacterial sepsis is still a leading cause of neonatal morbidity and mortality. Early onset sepsis in particular, presents with a different clinical course and involves other pathogens than sepsis later in life. In this study, plasma concentrations and mRNA expression of granulocyte colony-stimulating factor (G-CSF), tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-6, IL-8, and soluble intercellular adhesion molecule-1 (sICAM-1) of neonates with early onset sepsis were evaluated in cord blood and during the first days of life. Irrespective of prematurity, plasma levels of G-CSF, TNF-alpha, IL-1beta, IL-6, and IL-8, but not sICAM-1, were excessively elevated in septic neonates when compared with both healthy infants and infants with clinically suspected but not confirmed sepsis. Compared with the corresponding maternal levels, neonatal cytokine cord plasma levels were likewise highly elevated, indicating the endogenous cytokine production by the neonate. With the exception of TNF-alpha, mRNA expression in blood cells from septic infants was, however, not more frequently detectable than in those from nonseptic patients. Cytokine levels decreased significantly within the first days of life, whereas levels of sICAM-1 and C-reactive protein increased during the same time period. In summary, in contrast to C-reactive protein and sICAM-1, cord blood plasma levels, but not the presence of mRNA, of G-CSF, TNF-alpha, IL-1beta, IL-6, and IL-8 can predict neonatal early onset sepsis with a high sensitivity and specificity. Cell types other than blood cells are likely to contribute considerably to the high cytokine production in septic newborns.

Proton Magnetic Resonance Spectroscopy: An Emerging Technology in Pediatric Neurology Research

Abstract: Proton magnetic resonance spectroscopy (MRS) is an emerging technology that allows for the quantitative noninvasive assessment of regional brain biochemistry. The capacity to carry out MRS studies requires existing magnetic resonance imaging (MRI) technology platforms and the purchase of commercially available software modifications. In this review, the physical basis for MRS will be presented leading to an understanding of its potential applications and limitations within the clinical research milieu. Thus far, within pediatric neurology, proton MRS studies have been used to assist in the prediction of outcome in a variety of settings of acquired brain injuries (perinatal asphyxia, near drowning). In addition, proton MRS has been used to document disturbances in oxidative metabolism in neurometabolic disorders, assisting in defining phenotype and the response to therapeutic interventions. In epilepsy, spectroscopic studies have been useful in localizing the epileptogenic zone in intractable focal epilepsies. Future applications of proton MRS will also be highlighted. These include its use as a means of observing the transport and metabolism of various compounds in the brain, its concurrent application with other nuclear magnetic resonance techniques such as MRI and functional MRI, and finally its potential as a means of assessing the short-term effects of any CNS targeted pharmacologic interventions.

Intrauterine Growth Restriction Is Associated with a Reduced Activity of Placental Taurine Transporters

Abstract: Taurine is an essential amino acid during fetal life and appears to be vital for the growth of the fetus and for the development of the CNS. In intrauterine growth restriction (IUGR), fetal plasma concentrations of taurine are reduced, and we tested the hypothesis that this is caused by altered placental transport of taurine. Syncytiotrophoblast microvillous membrane (MVM) and basal membrane (BM) vesicles were isolated from control (fetal weight, 3068+/-191 g; gestational age, 37.0+/-0.7 wk; n=13) and IUGR pregnancies (fetal weight, 1724+/-118 g; gestational age, 35.8+/-0.7 wk; n=11). Uptake of [3H]taurine (0.5 microM) was studied at 22 degrees C using rapid filtration techniques. Sodium stimulated taurine uptake 35-fold in MVM, confirming Na+-dependent transport in this membrane. A Na+-dependent taurine transport could also be demonstrated in BM; however, the activity was only 6% of that in MVM. Na+-independent transport activities were similar in MVM and BM. In IUGR, MVM Na+-dependent taurine transport was reduced by 34% (p < 0.05), whereas Na+-independent uptake was unaltered. In contrast to MVM, Na+-dependent taurine uptake in BM was unaffected by IUGR, whereas Na+-independent transport was decreased by 33% (p < 0.05). The highly polarized distribution of the Na+/taurine cotransporter to the MVM in conjunction with similar Na+-independent transport rates for taurine in MVM and BM provides the basis for net taurine flux from the mother to the fetus. These data suggest that the low plasma concentrations of taurine in IUGR fetuses are caused by a reduced activity of placental taurine transporters.

Epithelial Tight Junction Structure in the Jejunum of Children with Acute and Treated Celiac Sprue

Abstract: Tight junction morphology was analyzed in freeze fracture electron micrographs from biopsies at two locations along the surface-crypt axis in the jejunum of children with treated and untreated sprue and in control subjects. In control jejunum, strand number, meshwork depth, and total depth of the tight junction decreased from surface to crypt, consistent with the concept of the crypt being more permeable than the surface epithelium. In acute sprue, strand number was reduced in all regions along the surface-crypt axis, from 5.5 ± 0.2 to 3.4 ± 0.3 (surface) and from 4.7 ± 0.2 to 3.6 ± 0.1 (crypt). Meshwork depth was also reduced at all regions along the surface-crypt axis. Strand discontinuities were more frequent in acute sprue. Aberrant strands appeared below the main meshwork of crypt tight junctions in acute sprue. In asymptomatic children treated with the gluten-free diet, jejunal tight junctional structure only partially recovered. Strand number was restored to normal at the surface, but was still decreased in the crypts, from 4.7 ± 0.2 to 3.9 ± 0.3. We conclude that the epithelial barrier function of the small intestine is seriously disturbed by structural modifications of the tight junction in acute symptomatic celiac disease, thereby accounting for increased ionic permeability noted in a parallel study on identical specimens. This epithelial barrier defect may contribute to diarrhea in celiac disease by a “leak flux mechanism.” In children with sprue treated with a gluten-free diet, barrier dysfunction was only partly recovered, suggesting a level of“minimal damage.”

Near infrared spectroscopy detects cerebral ischemia during hypotension in piglets.

Abstract: We have previously reported concordant changes in cerebral intravascular oxygenation measured by near infrared spectroscopy (NIRS) and mean arterial blood pressure (MAP) in premature infants. We hypothesized that the cerebral oxygenation changes are caused by MAP-induced alterations in cerebral blood flow (CBF) and studied these parameters in neonatal piglets (n = 6). Changes in cerebral intravascular oxygenation were measured by NIRS from the hemoglobin difference (HbD) signal (oxyhemoglobin-deoxyhemoglobin). CBF was measured by the radioactive microsphere technique. The cerebral circulation was also monitored by Doppler determinations of CBF velocity (time average mean velocity) in the anterior cerebral artery. Hypotension to <50% of baseline MAP was achieved by a ligature around the ascending aorta. Arterial oxygenation was maintained constant by mechanical ventilation. As observed in our studies of premature infants, cerebral HbD and MAP showed concordant changes. Hypotension was accompanied by significant decreases both in CBF (42.8 ± 12.5% of baseline p < 0.01) and HbD (-65.0 ± 22.0 µmol/L·dpf, p < 0.01). HbD was significantly correlated with MAP (p < 0.05) and time average mean velocity (p = 0.01). Importantly, decreases in cerebral total hemoglobin (HbT), a measure of cerebral blood volume, did not correlate significantly with decreases in MAP. We conclude that 1) decreases in cerebral intravascular oxygenation, as assessed by NIRS, observed with decreases in MAP reflect a decline in CBF, and hence oxygen delivery, 2) the HbD signal is more sensitive to changes in CBF than the HbT signal, and 3) NIRS recordings may have clinical utility in detecting cerebral ischemia.

Neonatal cord blood leptin : Its relationship to birth weight, body mass index, maternal diabetes, and steroids

Abstract: Neonatal Cord Blood Leptin: Its Relationship to Birth Weight, Body Mass Index, Maternal Diabetes, and Steroids

Cytokine Response in Cerebrospinal Fluid after Birth Asphyxia

Abstract: Experimental studies suggest that cytokine-mediated inflammatory reactions are important in the cascade leading to hypoxicischemic brain injury. The purpose was to study the content of pro- and antiinflammatory cytokines in cerebrospinal fluid (CSF) of asphyxiated and control infants. Samples of CSF were obtained from 20 infants who fulfilled the criteria of birth asphyxia and from seven newborn control subjects. The concentrations of IL-1β, IL-8, IL-10, tumor necrosis factor (TNF)-α, and granulocyte/monocyte colony-stimulating factor (GM-CSF) were determined with ELISA and of IL-6 using a bioassay. The concentration of IL-6 (pg/mL) was higher in asphyxiated(250, 35-543; median, interquartile range) than in control (0, 0-18) infants(p = 0.001). There was also a significant relationship between IL-6 and the degree of HIE, and between IL-6 and outcome. In addition, the content of IL-8 (pg/mL) was higher (p = 0.009) in the asphyxia group (170, 70-1440), than in the the control group (10, 0-30) and there was an association between IL-8 and degree of HIE. The levels of IL-10, TNF-α, GM-CSF, and IL-1β did not differ between groups. In conclusion, the proinflammatory cytokines IL-6 and IL-8 were markedly elevated in CSF of asphyxiated infants, and the intrathecal levels of these cytokines corresponded to the degree of HIE.

Early Feeding, Antenatal Glucocorticoids, and Human Milk Decrease Intestinal Permeability in Preterm Infants

Abstract: To determine the effects of age, feeding regimen, and antenatal glucocorticoids on intestinal permeability, preterm infants (n = 132) were stratified by gestational age and by diet (mothers' own milk versus preterm formula), and assigned randomly to one of four feeding regimens: early-continuous, early-bolus, standard-continuous, and standard-bolus. At 10, 28, and 50 d of age permeability was determined by measuring the ratio of lactulose/ mannitol in the urine after the two sugars were administered enterally for 30 h. The mean (+/-SE) birth weight and gestational age of the infants were 1044 +/- 13 g and 27 +/- 0.1 wk, respectively. Permeability changed as a function of age (p = 0.003). Early feeding was associated with a reduction in permeability at 10 d of age (p = 0.01). Antenatal steroid administration was associated with decreased permeability at 28 d of age (p = 0.017). The feeding of human milk (versus formula) was associated with decreased permeability at 28 d of age (p = 0.02). Continuous versus bolus feeding did not affect permeability.

Effects of Chronic Placental Insufficiency on Brain Development in Fetal Sheep

Abstract: Clinical evidence has linked intrauterine compromise such as fetal hypoxemia to poor neurologic outcome in the newborn. In this study we examined the effects of inducing chronic fetal hypoxemia by impairment of placental function on brain development in fetal sheep. Placental insufficiency was induced from 120 to 140 d of gestation (term = 145-148 d) by injection of microspheres into the umbilical circulation in five fetal sheep. Fetal partial pressure of oxygen, PaO2, was reduced from 24.1 +/- 0.5 mm Hg before embolization to 14.8 +/- 0.4 mm Hg after embolization (p < 0.05). In another three fetuses a similar level of hypoxemia (PaO2, 13.8 +/- 0.4 mm Hg) occurred spontaneously. At 140 d of gestation the fetal brains were perfused with fixatives and compared with five control fetuses for the assessment of structural and immunohistochemical alterations. Hypoxemic fetuses demonstrated severe gliosis in the cerebral cortex and reduced myelination of subcortical white matter as visualized by glial fibrillary acidic protein and myelin basic protein staining, respectively (p < 0.05). White matter lesions were observed in two fetuses. The diameter of cerebral capillaries was increased in hypoxemic fetuses (p < 0.05), but there was no change in the number of nitric oxide synthase immunoreactive cells. Growth of neuronal processes was affected in the cerebellum, where there was also a reduction in the number of Purkinje neurons (p < 0.05). These results show that a prolonged period of placental insufficiency, resulting in moderate fetal hypoxemia during the last third of gestation, can affect neurodevelopmental processes that occur late in gestation such as myelination and growth of the cerebellum. This prenatal damage could affect neural connectivity and have functional consequences after birth.

Daily energy expenditure and physical activity in survivors of childhood malignancy.

Abstract: Changes in body composition, in particular the onset of obesity, may result from reductions in total daily energy expenditure (TDEE) as a consequence of relative physical inactivity. Children previously treated for acute lymphoblastic leukemia (ALL) become obese, yet the mechanism remains undefined. TDEE and physical activity levels [PAL = TDEE/basal metabolic rate (BMR)] were measured in 34 long-term survivors of ALL and compared with results from 21 survivors of other malignancies and 32 healthy sibling control subjects using the flex-heart rate technique. Body composition was measured by dual energy x-ray absorptiometry. The median TDEE was reduced in the ALL group (150 kJ x kg d(-1)) compared with other malignancies and controls (207 and 185 kJ x kg d(-1), respectively, p < 0.01). This reduction was accounted for mainly by a relative decrease in the PAL of the ALL group (1.24) compared with both other malignancies and controls (1.58 and 1.47, respectively, p < 0.01). TDEE and PAL were correlated with percentage body fat (r = -0.39, p < 0.001 and r = -0.24, p < 0.05, respectively). Obesity in survivors of ALL may, in part, be explained by a reduction in TDEE as a consequence of reduced PAL. The cause of such reduction is uncertain.

Visual activation in infants and young children studied by functional magnetic resonance imaging

Abstract: The purpose of this study was to determine whether visual stimulation in sleeping infants and young children can be examined by functional magnetic resonance imaging. We studied 17 children, aged 3 d to 48 mo, and three healthy adults. Visual stimulation was performed with 8-Hz flickering light through the sleeping childs' closed eyelids. Functional magnetic resonance imaging was performed with a gradient echoplanar sequence in a 1.5-T magnetic resonance scanner. Six subjects were excluded because of movement artifacts; the youngest infant showed no response. In 10 children, we could demonstrate areas of signal decrease during visual stimulation in the occipital cortex (mean decrease 2.21%), contrary to the signal increase observed in the adult controls (mean increase 2.82%). This decrease may be due to a higher proportional increase in oxygen extraction compared with increase in cerebral blood flow during activation. The different response patterns in young children and adults can reflect developmental or behavioral differences. Localization of the activation seemed to be age-dependent. In the older children and the adults, it encompassed the whole length of the calcarine sulcus, whereas it was restricted to the anterior and medial part of the calcarine sulcus in the younger infants. This may reflect a different functional organization of the young child's visual cortex or the on-going retinal development.

Prediction factors in the determination of final height in subjects born small for gestational age

Abstract: The aim of this study was to identify factors predictive of individual final height (FH) in subjects born small for gestational age (SGA). All full-term singleton subjects born SGA (birth weight and/or length <3rd percentile) during the period 1971-1978, matched with appropriate birth weight for gestational age (AGA) subjects (birth weight between 25th and 75th percentile) were followed from birth to FH and evaluated before puberty at a mean age +/- SD of 6.1 +/- 0.7 y and after puberty at a mean age of 20.8 +/- 2.0 y (subjects born SGA, n = 213; born AGA, n = 272). When adjusted for target height, a significant deficit in final height (p < 0.0001) was found in SGA as compared with AGA subjects for both male subjects (-3.99 cm with 95% confidence interval from -5.6 to -2.4) and female subjects (-3.64 cm with 95% confidence interval from -5.0 to -2.3), with 13.6% of subjects in the SGA population presenting short final stature. In a multiple regression analysis, target height and studied group (SGA or AGA) were found to be the strongest predictors of individual FH (p < 0.0001, r2 = 0.35 for male subjects, p < 0.0001, r = 0.40 for female subjects). For SGA subjects and according to a multiple stepwise linear regression model, 31% of the variability of individual FH [SD score (SDS)] and 58% of the variability of individual height gain SDS could be explained at birth from mother's height, father's height, and birth length SDS. No other variables were found to be predictive such as sex, gestational age (from 37 to 42 wk), birth weight SDS, ponderal index at birth, or risk factors during pregnancy associated with intrauterine growth retardation such as pregnancy-induced hypertension, smoking, or a history of SGA in offspring. Although a significant increase of body mass index SDS was documented before and after puberty in SGA subjects, puberty was not found to have any influence on growth outcome.

Lower Incidence of Necrotizing Enterocolitis in Infants Fed a Preterm Formula with Egg Phospholipids

Abstract: Necrotizing enterocolitis (NEC) causes approximately 4000 deaths/y and significant morbidity among U.S.-born preterm infants alone. Various combinations of inadequate tissue oxygenation, bacterial overgrowth, and enteral feeding with immaturity may cause the initial damage to intestinal mucosa that culminates in necrosis. Presently, there is not a way to predict the onset of the disease or to prevent its occurrence. As part of risk-benefit assessment, we compared disease in hospitalized preterm infants fed a commercial (control) preterm formula or an experimental formula with egg phospholipids for a randomized, double-masked, clinical study of diet and infant neurodevelopment. Infants fed the experimental formula developed significantly less stage II and III NEC compared with infants fed the control formula (2.9 versus 17.6%, p < 0.05), but had similar rates of bronchopulmonary dysplasia (23.4 versus 23.5%), septicemia (26 versus 31%), and retinopathy of prematurity (38 versus 40%). Compared with the control formula, the experimental formula provided 7-fold more esterified choline, arachidonic acid (AA, 0.4% of total fatty acids), and docosahexaenoic acid (0.13%). Phospholipids are constituents of mucosal membranes and intestinal surfactant, and their components, AA and choline, are substrates for intestinal vasodilatory and cytoprotective eicosanoids (AA) and the vasodilatory neurotransmitter, acetylcholine (choline), respectively. One or more of these components of egg phospholipids may have enhanced one or more immature intestinal functions to lower the incidence of NEC in this study. Regardless of the potential mechanism, a larger randomized trial designed to test the effect of this egg phospholipid-containing formula on NEC seems warranted.

Enteric defensin expression in necrotizing enterocolitis.

Abstract: Immaturity of local innate defenses has been suggested as a factor involved in the pathophysiology of necrotizing enterocolitis (NEC). The mRNA of enteric human defensins 5 (HD5) and 6 (HD6), antibiotic peptides expressed in Paneth cells of the small intestine, have significantly lower levels of expression in fetal life compared with the term newborn and adult. In the current study, intracellular HD5 was demonstrated by immunohistochemistry at 24 wk of gestation, but at low levels, consistent with findings at the mRNA level. These data suggest that the low level enteric defensin expression, characteristic of normal intestinal development, may contribute to the immaturity of local defense, which predisposes the premature infant to NEC. To test if levels of defensin expression are altered in NEC, specimens from six cases of patients with NEC and five control subjects (four patients with atresia and one with meconium ileus) were analyzed to determine HD5 and HD6 mRNA levels by in situ hybridization. Compared with the control group, the level of enteric defensin expression per Paneth cell assessed by image analysis was increased 3-fold in cases of NEC (p = 0.02, analysis of variance and covariance). In addition, the number of Paneth cells was increased 2-fold in the small intestinal crypts of NEC specimens compared with those of control subjects (p < 0.01, covariance analysis). In healthy tissue, peptide levels within Paneth cells paralleled mRNA levels through development. In tissue from infants with NEC, the steady state level of intracellular peptide was not increased in conjunction with the observed rise in defensin mRNA. A straightforward interpretation of this finding is that HD5 is actively secreted in this setting and the Paneth cells maintain a constant steady state level of intracellular peptide, but the possibility of translational regulation of peptide expression is also consistent with these data. The associations between NEC and enteric defensin expression reported here offer support for future studies to address the role of these endogenous host defense factors in the pathophysiology of this disease.

Evolution of Immunologic Functions of the Mammary Gland and the Postnatal Development of Immunity

Abstract: Physiologic delays in production of immune factors occur in mammals including Homo sapiens. This finding is counter to a basic tenet of biologic evolution, because such delays increase the risk of infections. The disadvantage is, however, offset by defense factors in milk of the species in whom the developmental delay occurs. Reciprocal relationships between the production of immune factors by the lactating mammary gland and the production of those defense agents during early infancy are found in all investigated mammalian species. Thus, the evolution of these processes is closely related. Certain immunologic components of milk are highly conserved, whereas others vary according to the species. The variations most likely evolved by genetic mutations and natural selection. In addition, the immune composition of mammalian milks is associated with developmental delays in the same immunologic agents. Furthermore, most closely related mammals, such as humans and chimpanzees, are most similar in the defense agents in their milks and the corresponding developmental delays in their immune systems. Defense factors in human milk include antimicrobial agents (secretory IgA, lactoferrin, lysozyme, glycoconjugates, oligosaccharides, and digestive products of milk lipids), antiinflammatory factors (antioxidants, epithelial growth factors, cellular protective agents, and enzymes that degrade mediators of inflammation), immunomodulators (nucleotides, cytokines, and antiidiotypic antibodies), and leukocytes (neutrophils, macrophages, and lymphocytes). Because of a lack of geographic/ethnic variation in the immunologic composition of human milk and corresponding immunologic delays in infants, these evolutionary processes seem stable. This is supported by investigations of diverse populations that indicate that this evolutionary outcome is highly beneficial to human infants.

Target height as predicted by parental heights in a population-based study

Abstract: The corrected midparental height method was introduced by Tanner in 1970 (Tanner method) and is commonly used to estimate target height in children to evaluate the effectiveness of growth-promoting therapies. It has not been established if the equation used to compute target height should be the same for children with short, normal, or tall parents. In this study, we examined the predicted target height values by parental heights in a large population-based study (n = 2402). A simple linear function of midparental height (x) was proposed to estimate target height (y): y = 45.99 + 0.78x (boys), y = 37.85+0.75x (girls), with a 95% predicted interval of about +/-10 cm. The prediction model was similar for boys and girls in SD scores (SDS), and was not affected by assortative mating or difference in parental heights. The model may underestimate the potential stature by about 2 cm for children with midparental height below -2 SDS, or 163 cm. In comparison, the Tanner method may lead to a 6-cm error in underestimating target height for these children. The function would be a better choice than the Tanner method for estimating target height in the clinical evaluation of growth promotion treatments because it is common that short children also have short parents. Children with very short parents will usually be much taller than their parents in adult stature, and we believe that a different function should be developed. The results support the proposed nondominant, non-sex-linked, polygenic inheritance in stature. The estimated heritability values were 0.75-0.78 in cm or 0.55-0.60 in SDS.

Defective Natural Killer Cell Function in Patients with Hemophagocytic Lymphohistiocytosis and in First Degree Relatives

Abstract: Hemophagocytic lymphohistiocytosis (HLH), also referred to as familial erythrophagocytic lymphohistiocytosis, is a rare disorder of infancy associated with proliferation of activated histiocytes and T cells, anemia, thrombocytopenia, and fevers. This disorder appears to be due to the uncontrolled activation of T cells producing IL-2, tumor necrosis factor-alpha, and interferon-gamma. Untreated, the disorder is universally fatal. Various deficits in immune function have been described during acute disease activity including impaired T cell function, impaired monocyte-mediated antibody-dependent cytotoxicity, impaired natural killer cell function, and impaired IL-1 production. We examined natural killer cell function in familial HLH patients to determine whether this finding was consistently associated with the disease. We also examined natural killer cell function in asymptomatic parents and siblings of patients. Impaired natural killer cell function was identified in all patients and in some family members, including obligate carrier parents. This implies that one potential genetic defect in HLH may result in depressed natural killer function, but that this may not be sufficient to reliably predict eventual progression to disease.

Influence of Restricted Maternal Nutrition in Early to Mid Gestation on Placental and Fetal Development at Term in Sheep

Abstract: We investigated the influence of restricted maternal nutrition between 28 and 77 d of gestation on placental weight and appearance, and on fetal weight and conformation. Single-bearing ewes were fed either twice [i.e. controls (n = 19)] or half [i.e. nutrient-restricted (n = 28)] their energy requirements from 28 to 77 d of gestation, after which all ewes were fed to fully meet the energy requirements for maintenance and pregnancy. Close to term (145 ± 1 d) placental weight was higher in the nutrient-restricted group [nutrient-restricted, 416.3 ± 12.6 g; controls, 347.4 ± 17.6 g (p < 0.01)], as was the abundance of everted placentomes. There was no significant difference in total fetal weight, or weights of individual organs between groups, but crown-rump length was significantly greater in lambs born to nutrient-restricted ewes [nutrient-restricted, 50.4 ± 0.4 cm; controls, 48.2 ± 0.6, cm (p < 0.01)]. Fetal to placental weight ratio was lower in the nutrient-restricted group [nutrient-restricted, 9.51 ± 0.23; controls, 10.81 ± 0.39 (p < 0.01)]. A stronger relationship between the total weight of the fetal component of the placental and fetal weight was observed in controls (r2 = 0.50) than in nutrient-restricted ewes (r2 = 0.18). In conclusion, maternal nutrient restriction over the period of rapid placental growth results in a larger placenta and altered placental to fetal weight ratio if ewes are subsequently fed to requirements for the remainder of gestation.

Regulation of ductus arteriosus patency by nitric oxide in fetal lambs: the role of gestation, oxygen tension, and vasa vasorum.

Abstract: We hypothesized that nitric oxide (NO) production by the fetal ductus arteriosus is limited because of low fetal PO2, but that at neonatal PO2, NO might be an important regulator of ductus arteriosus tone. We exposed isolated rings of fetal lamb ductus arteriosus to elevated PO2. L-NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), and methylene blue and 6-anilino-5,8-quinolinedione (LY83583), inhibitors of guanylate cyclase, produced constriction of the ductus arteriosus. When ductus arteriosus rings were exposed to low PO2, L-NAME had no effect, and methylene blue and LY83583 had only a small effect on ductus arteriosus tone. Sodium nitroprusside and calcium ionophore A23187 relaxed ductus arteriosus rings more than aortic rings, and relaxed ductus arteriosus rings from immature fetuses more than those from late gestation fetuses. In contrast, ductus arteriosus rings from both early and late gestation were equally sensitive to 8-bromo-cGMP. By both reverse transcriptase-polymerase chain reaction and immunohistochemistry, endothelial cell NOS and inducible calcium-independent NOS, but not nerve cell NOS, were detected in the ductus arteriosus. Inducible NOS was expressed only by endothelial cells lining the ductus arteriosus lumen; in contrast, endothelial cell NOS was expressed by both luminal and vasa vasorum endothelial cells. The role of inducible NOS in the ductus arteriosus is uncertain because the potency of a specific inducible NOS inhibitor in constricting the ductus arteriosus was negligible compared with that of an endothelial cell NOS inhibitor. We speculate that NO may be an important regulator of ductus arteriosus tone at high but not low PO2. The endothelial cell NOS isoform found in vasa vasorum may be an important source of NO because removal of ductus arteriosus luminal endothelium only partially blocks the effects of L-NAME, methylene blue, and LY83583.

Cyclic-GMP-Binding, Cyclic-GMP-Specific Phosphodiesterase (PDE5) Gene Expression Is Regulated during Rat Pulmonary Development

Abstract: Increased nitric oxide (NO) production plays a critical role in the mammalian pulmonary vascular adaptation to extrauterine life. NO activates soluble guanylate cyclase, increasing intracellular cGMP concentrations, thereby inducing relaxation of vascular smooth muscle. cGMP is inactivated by cyclic nucleotide phosphodiesterases (PDEs). One PDE isozyme, PDE5, specifically hydrolyzes cGMP, is abundant in lung tissues, and modifies the pulmonary vasodilatory response to exogenous NO. To investigate the regulation of PDE5 gene expression during pulmonary development, PDE5 mRNA levels, as well as cGMP-metabolizing PDE enzyme activity, were measured in the lungs of perinatal and adult rats. RNA blot hybridization revealed that PDE5 mRNA was detectable in fetal lung tissue as early as 18.5 d of the 22-d term gestation and reached maximal levels in neonatal lungs. mRNA levels in adult rat lungs were 3-4-fold less than the levels measured in lungs of 1- and 8-d-old rats. Pulmonary cGMP hydrolytic activity in 1-d-old animals was 30-fold greater than the cGMP hydrolytic activity of adult rat lungs. Zaprinast, a specific PDE5 antagonist, inhibited 52 and 56% of cGMP hydrolytic activity in lungs of 1- and 8-d-old rats, respectively, but only 18% of the activity in adult lungs. In situ hybridization revealed that PDE5 mRNA transcripts were present in the vascular smooth muscle cells of neonatal and adult lungs. PDE5 mRNA was also detected in the alveolar walls of neonatal rat lungs. These results demonstrate that the gene encoding PDE5 is abundantly expressed in the lungs of perinatal rats, and is available to participate in the mammalian pulmonary vascular transition to extrauterine life. Extravascular PDE5 gene expression in neonatal lungs suggests a potentially important nonvascular role for this enzyme during pulmonary development.

Ontogeny of Apoptosis during Lung Development

Abstract: Apoptosis has been shown to be involved in several processes during embryogenesis, but the ontogeny of apoptosis during lung development has not been studied. The goals of the current study were to determine if apoptosis occurs during lung development, and to determine the ontogeny of the changes in apoptosis that occur. We studied the ontogeny of apoptosis in vivo using lungs from 14-18-d gestation fetal rats, newborn rats, and 1-d-, 2-d-, 5-d-, and 10-d-old rat pups. Apoptosis was assessed by electron microscopy and the terminal deoxyribonucleotidyl transferase dUTP nick end-labeling assay. We compared the in vivo results with explants of 14-d gestation fetal rat lung placed in culture for 1-4 d because the biochemical development of the lung in organ culture has been shown to closely parallel the development of the lung in vivo. We found apoptosis of mesenchymal cells at the periphery of distal lung buds in early fetal lung(14-16-d gestation). Apoptosis of both mesenchyme and epithelium was present in later fetal lung (18-d gestation). There were no qualitative differences in apoptosis between in vivo fetal lung and explant cultures of fetal lung. There was a 14-fold increase in apoptosis at birth and in the first postnatal day of life (9-12% of cells) compared with fetal lung (0.6-1% of cells). This was followed by a rapid decline in the percentage of apoptotic cells to fetal levels at postnatal d 2-10. We conclude that apoptosis occurs in a spatially, temporally, and cell-specific manner during lung development. The number of cells undergoing apoptosis increases dramatically in the first day after birth.

Measurement of cerebral blood flow in newborn infants using near infrared spectroscopy with indocyanine green.

Abstract: Cerebral blood flow (CBF) measurement by near infrared spectroscopy (NIRS) using oxyhemoglobin (HbO2) as a tracer (CBF-HbO2) needs rapid changes in arterial oxygen saturation (SaO2) which often cannot be achieved in many sick infants. An alternative method based on the same adaptation of the Fick principle using i.v. injection of the dye indocyanine green (ICG) is described (CBF-ICG). Six mechanically ventilated infants (age 26-38 wk, birth weight 0.885-3.730 kg) requiring supplementary oxygen therapy were studied within 72 h of birth. For CBF-ICG measurements, ICG (0.1 mg x kg-1 was injected via an umbilical venous catheter, and blood ICG concentration was measured by an optical umbilical artery catheter and brain ICG concentration was measured by NIRS. For CBF-HbO2 measurements the inspired oxygen concentration was rapidly increased, blood HbO2 concentration was calculated from SaO2 measured by pulse oximetry, and brain HbO2 concentration was measured by NIRS. A series of CBF measurements were performed using each method before and after altering the arterial carbon dioxide tension (PaCO2). Mean CBF values from repeated measurements by each method at any given PaCO2 were used to compare the methods. The SD of single measurements within an individual subject by CBF-ICG was 15%, and by CBF-HbO2, 24%. The relationship between the methods was mean CBF-ICG = (1.13 x mean CBF-HbO2) - 2.76 mL x 100 g-1 x min-1 HbO2 (r = 0.93, p < 0.001). The mean difference between the methods (CBF-ICG - CBF-HbO2) was -0.25 mL x 100 g-1 x min-1 (95% confidence interval 6.30 to -6.80). The methods were in good agreement, and the use of i.v. ICG permitted rapid and repeated CBF measurements in the sickest infants at greatest risk of cerebral injury.