Adsorption of potassium on Cr₂O₃(0001) at ionic and metallic coverages and uv-laser-induced desorption

Translational energy distributions of neutral potassium atoms are reported as a function of potassium coverage after uv-laser-induced desorption from well-characterized adsorption sites on an epitaxial film of Cr2O3(0001)/Cr(110). Measurements using x-ray photoelectron spectroscopy, low-energy electron diffraction, and work-function measurements revealed that potassium adsorbs in a nonmetallic phase for deposition temperatures around 280–300 K allowing only a maximal saturation coverage to be grown for moderate growth rates. Aggregates are observed after deposition at 90 K; at this temperature any layer thickness is obtainable. The uv-laser-induced desorption for these two different phases was studied using excitation energies of 3.5 eV, 5.0 eV, and 6.4 eV and (1+1)-resonantly enhanced multiphonon ionization via the 6p2P state for detection. Desorption of potassium atoms from the nonmetallic phase proves to be ten times [σ(6.4eV)=(2±1)×10−19cm2] more efficient than desorption from metallic potassium aggregates. The mechanism of desorption from the nonmetallic phase appears to be the inverse harpooning process starting with an ion pair followed by a transfer of hot electrons from the substrate to unoccupied potassium states to neutralize the initially positively charged potassium. The maximum of the translational energy distribution (starting at 0.65 eV for low coverages) decreases with increasing potassium coverage and is by a factor of approximately 4 smaller for desorption from large potassium aggregates (0.16 eV). The decrease of the translational energy with increasing coverages for isolated atoms is ascribed to an increasing lateral interaction between the adsorbates and a concomittant smooth change of the ionicity of the atoms from partially ionic to neutral

Plasma cholesterol levels and brain development in preterm newborns.

BackgroundTo assess whether postnatal plasma cholesterol levels are associated with microstructural and macrostructural regional brain development in preterm newborns.MethodsSixty preterm newborns (born 24-32 weeks gestational age) were assessed using MRI studies soon after birth and again at term-equivalent age. Blood samples were obtained within 7 days of each MRI scan to analyze for plasma cholesterol and lathosterol (a marker of endogenous cholesterol synthesis) levels. Outcomes were assessed at 3 years using the Bayley Scales of Infant Development, Third Edition.ResultsEarly plasma lathosterol levels were associated with increased axial and radial diffusivities and increased volume of the subcortical white matter. Early plasma cholesterol levels were associated with increased volume of the cerebellum. Early plasma lathosterol levels were associated with a 2-point decrease in motor scores at 3 years.ConclusionsHigher early endogenous cholesterol synthesis is associated with worse microstructural measures and larger volumes in the subcortical white matter that may signify regional edema and worse motor outcomes. Higher early cholesterol is associated with improved cerebellar volumes. Further work is needed to better understand how the balance of cholesterol supply and endogenous synthesis impacts preterm brain development, especially if these may be modifiable factors to improve outcomes

Nutrient Intake in the First Two Weeks of Life and Brain Growth in Preterm Neonates.

BACKGROUND: Optimizing early nutritional intake in preterm neonates may promote brain health and neurodevelopment through enhanced brain maturation. Our objectives were (1) to determine the association of energy and macronutrient intake in the first 2 weeks of life with regional and total brain growth and white matter (WM) maturation, assessed by 3 serial MRI scans in preterm neonates; (2) to examine how critical illness modifies this association; and (3) to investigate the relationship with neurodevelopmental outcomes. METHODS: Forty-nine preterm neonates (21 boys, median [interquartile range] gestational age: 27.6 [2.3] weeks) were scanned serially at the following median postmenstrual weeks: 29.4, 31.7, and 41. The total brain, basal nuclei, and cerebellum were semiautomatically segmented. Fractional anisotropy was extracted from diffusion tensor imaging data. Nutritional intake from day of life 1 to 14 was monitored and clinical factors were collected. RESULTS: Greater energy and lipid intake predicted increased total brain and basal nuclei volumes over the course of neonatal care to term-equivalent age. Similarly, energy and lipid intake were significantly associated with fractional anisotropy values in selected WM tracts. The association of ventilation duration with smaller brain volumes was attenuated by higher energy intake. Brain growth predicted psychomotor outcome at 18 months\u27 corrected age. CONCLUSIONS: In preterm neonates, greater energy and enteral feeding during the first 2 weeks of life predicted more robust brain growth and accelerated WM maturation. The long-lasting effect of early nutrition on neurodevelopment may be mediated by enhanced brain growth. Optimizing nutrition in preterm neonates may represent a potential avenue to mitigate the adverse brain health consequences of critical illness

Temporal Progression of Fatty Acids in Preterm and Term Human Milk of Mothers from Switzerland.

We longitudinally compared fatty acids (FA) from human milk (HM) of mothers delivering term and preterm infants. HM was collected for 4 months postpartum at 12 time points for preterm and for 2 months postpartum at 8 time points for term group. Samples were collected from the first feed of the morning, and single breast was fully expressed. FA were analyzed by gas chromatography coupled with flame ionization detector. Oleic, palmitic and linoleic acids were the most abundant FA across lactation and in both groups. Preterm colostrum contained significantly (p < 0.05) higher 8:0, 10:0, 12:0, sum medium chain fatty acids (MCFA), 18:3 n-3 FA compared to term counterparts. Preterm mature milk contained significantly higher 12:0, 14:0, 18:2 n-6, sum saturated fatty acids (SFA), and sum MCFA. We did not observe any significant differences between the preterm and term groups for docosahexaenoic acid, arachidonic acid and eicosapentaenoic acid at any stage of lactation. Overall, preterm milk was higher for SFA with a major contribution from MCFA and higher in 18:2 n-6. These observational differences needs to be studied further for their implications on preterm developmental outcomes and on fortification strategies of either mothers' own milk or donor human milk

Longitudinal Analysis of Macronutrient Composition in Preterm and Term Human Milk: A Prospective Cohort Study.

Mother's own milk is the optimal source of nutrients and provides numerous health advantages for mothers and infants. As they have supplementary nutritional needs, very preterm infants may require fortification of human milk (HM). Addressing HM composition and variations is essential to optimize HM fortification strategies for these vulnerable infants. To analyze and compare macronutrient composition in HM of mothers lactating very preterm (PT) (28 0/7 to 32 6/7 weeks of gestational age, GA) and term (T) infants (37 0/7 to 41 6/7 weeks of GA) over time, both at similar postnatal and postmenstrual ages, and to investigate other potential factors of variations. Milk samples from 27 mothers of the PT infants and 34 mothers of the T infants were collected longitudinally at 12 points in time during four months for the PT HM and eight points in time during two months for the T HM. Macronutrient composition (proteins, fat, and lactose) and energy were measured using a mid-infrared milk analyzer, corrected by bicinchoninic acid (BCA) assay for total protein content. Analysis of 500 HM samples revealed large inter- and intra-subject variations in both groups. Proteins decreased from birth to four months in the PT and the T HM without significant differences at any postnatal time point, while it was lower around term equivalent age in PT HM. Lactose content remained stable and comparable over time. The PT HM contained significantly more fat and tended to be more caloric in the first two weeks of lactation, while the T HM revealed higher fat and higher energy content later during lactation (three to eight weeks). In both groups, male gender was associated with more fat and energy content. The gender association was stronger in the PT group, and it remained significant after adjustments. Longitudinal measurements of macronutrients compositions of the PT and the T HM showed only small differences at similar postnatal stages in our population. However, numerous differences exist at similar postmenstrual ages. Male gender seems to be associated with a higher content in fat, especially in the PT HM. This study provides original information on macronutrient composition and variations of HM, which is important to consider for the optimization of nutrition and growth of PT infants

Human Milk Oligosaccharides in the Milk of Mothers Delivering Term versus Preterm Infants.

Human milk oligosaccharides (HMOs) are a major component of human milk, and play an important role in protecting the infant from infections. Preterm infants are particularly vulnerable, but have improved outcomes if fed with human milk. This study aimed to determine if the HMO composition of preterm milk differed from that of term milk at equivalent stage of lactation and equivalent postmenstrual age. In all, 22 HMOs were analyzed in 500 samples of milk from 25 mothers breastfeeding very preterm infants (< 32 weeks of gestational age, < 1500g of birthweight) and 28 mothers breastfeeding term infants. The concentrations of most HMOs were comparable at equivalent postpartum age. However, HMOs containing α-1,2-linked fucose were reduced in concentration in preterm milk during the first month of lactation. The concentrations of a number of sialylated oligosaccharides were also different in preterm milk, in particular 3'-sialyllactose concentrations were elevated. At equivalent postmenstrual age, the concentrations of a number of HMOs were significantly different in preterm compared to term milk. The largest differences manifest around 40 weeks of postmenstrual age, when the milk of term infants contains the highest concentrations of HMOs. The observed differences warrant further investigation in view of their potential clinical impact

Longitudinal Changes of Mineral Concentrations in Preterm and Term Human Milk from Lactating Swiss Women.

<b></b> An adequate mineral supply to preterm infants is essential for normal growth and development. This study aimed to compare the mineral contents of human milk (HM) from healthy mothers of preterm (28-32 weeks) and full term (>37 weeks) infants. Samples were collected weekly for eight weeks for the term group (n = 34) and, biweekly up to 16 weeks for the preterm group (n = 27). Iron, zinc, selenium, copper, iodine, calcium, magnesium, phosphorus, potassium, and sodium were quantitatively analyzed by Inductively Coupled Plasma-Mass Spectrometry. The mineral contents of both HM showed parallel compositional changes over the period of lactation, with occasional significant differences when compared at the same postpartum age. However, when the comparisons were performed at an equivalent postmenstrual age, preterm HM contained less zinc and copper from week 39 to 48 (p < 0.002) and less selenium from week 39 to 44 (p < 0.002) than term HM. This translates into ranges of differences (min-max) of 53% to 78%, 30% to 72%, and 11% to 33% lower for zinc, copper, and selenium, respectively. These data provide comprehensive information on the temporal changes of ten minerals in preterm HM and may help to increase the accuracy of the mineral fortification of milk for preterm consumption

Impact of Early Nutritional Intake on Preterm Brain: a Magnetic Résonance Imaging Study

Investigateurs : Lydie Beauport, Juliane Schneider, Mohamed Faouzi, Patric Hagmann, Petra Hüppi, Jean-François Tolsa, Anita C Truttmann, Céline J Fischer Fumeaux Contexte : Plusieurs études ont montré un bénéfice de l’optimisation du soutien nutritionnel précoce sur le développement neurologique et cognitif des enfants nés prématurément. Cependant l’impact de la nutrition sur la maturation et les lésions cérébrales reste peu compris. Objectifs: Cette étude a pour objectif d’évaluer l’impact des apports nutritionnels, lipidiques et énergétiques pendant les 14 premiers jours de vie sur le développement cérébral évalué par IRM cérébrale à l’âge du terme chez des nouveau-nés grand prématurés. Méthode : Il s’agit d’une étude ancillaire d’une cohorte prospective (1) incluant des prématurés de <30 semaines d’âge gestationnel nés dans un niveau 3 sans malformation majeure. Les données cliniques et nutritionnelles étaient collectées à partir des dossiers informatisés. Les apports cumulatifs entéraux et parentéraux en protéines, lipides et énergie étaient calculés de J1 à 14. L’IRM cérébrale (Trio3Tesla Siemens) était effectuée à terme et comprenaient les séquences conventionnelles T1 et T2. Le degré de sévérité des lésions de la substance blanche et grise ainsi que le niveau de maturation étaient évalués selon le score de Kidokoro (2), résultant en un score global. Les patients étaient alors divisés en un premier groupe avec un score normal ou légèrement anormal (score < 75ème percentile) et en un 2ème groupe avec un score modérément à sévèrement anormal (score > 75ème percentile). L’association entre les apports nutritionnels et le degré de sévérité du score IRM était analysée par régression uni-et multivariée. Résultats : 42 patients avec un âge gestationnel médian [Q1, Q3] de 27.4 [26.4-28.4] semaines et un poids de naissance médian de 890 g [763-1045] ont été inclus. La médiane du score IRM était à 4 et le 75ème percentile à 6, séparant le groupe 1 avec un score normal ou légèrement anormal (score 0-5, n= 27), du groupe 2 présentant un score modérément à sévèrement anormal (score 6-12, n=15). En analyse univariée, le sepsis, le CRIB score et les apports nutritionnels faibles étaient significativement associés à un risque plus élevé d’avoir un score IRM ≥ 6 (OR [95%CI] énergie : 0.99 [0.99-0.99], lipides : 0.89 [0.83-0.97], hydrates de carbone : 0.95 [0.91-0.99]). Dans des modèles bivariés, après ajustements pour le sepsis, le CRIB score, l’âge gestationnel, les stéroïdes postnataux et la dysplasie bronchopulmonaire, l’association avec les apports énergétiques et lipidiques totaux restait significative. L’association était plus forte pour la composante de la substance grise du score IRM. Conclusions : Cette étude montre que des apports énergétiques et lipidiques plus élevés durant les 2 premières semaines de vie sont associés à un risque plus faible de lésions et de troubles de maturation cérébraux à terme corrigé chez les nouveau-nés grands prématurés. Optimiser la nutrition durant cette période vulnérable pourrait même réduire l’impact négatif de certains facteurs comme le sepsis. L’impact sur le devenir neuro-développemental à long terme doit cependant encore être confirmé