Exposure to supplemental oxygen and its effects on oxidative stress and antioxidant enzyme activity in term newborn lambs.

The optimal oxygen concentration for the resuscitation of term infants remains controversial. We studied the effects of 21 versus 100% oxygen immediately after birth, and also exposure for 24 h to 100% oxygen, on oxidant lung injury and lung antioxidant enzyme (AOE) activities in term newborn lambs. Lambs at 139 d gestation were delivered and ventilated with 21% (RAR) or 100% (OXR) for 30 min. A third group of newborn lambs were ventilated with 100% O2 for 24 h (OX24). Oxidized glutathione levels in whole blood were significantly different among the groups with lower values in the RAR group, and these values correlated highly with partial pressure of arterial oxygen (Pao2). The reduced to oxidized glutathione ratio was significantly different among the groups, the ratio decreasing with increasing oxygen exposure. Lipid hydroperoxide (LPO) activity was significantly higher in the OXR and OX24 groups. AOE activity was higher in the whole lung and in red cell lysate in the OX24 group. Increased myeloperoxidase (MPO) activity, percent neutrophils, and proteins in lung lavage suggested inflammation in the OX24 group after maximal oxygen exposure. We conclude that even relatively brief exposure of the lung to 100% oxygen increases systemic oxidative stress and lung oxidant injury in ventilated term newborn lambs.

Exposure to supplemental oxygen downregulates antioxidant enzymes and increases pulmonary arterial contractility in premature lambs.

BACKGROUND: The optimal oxygen concentration for the resuscitation of premature infants remains controversial. OBJECTIVES: We studied the effects of 21 versus 100% oxygen at initial resuscitation and also the effects of 24-hour exposure to 100% oxygen on arterial blood gases, oxidant lung injury, activities of lung antioxidant enzymes (AOEs) and isolated pulmonary artery (PA) contractility in preterm newborn lambs. METHODS: Preterm lambs at 128 days' gestation (term = 145 days) were delivered and ventilated with 21 (RAR; n = 5) or 100% oxygen (OXR; n = 5) for the first 30 min of life. Subsequently, FiO2 was adjusted to maintain an arterial PO2 (PaO2) between 45 and 70 mm Hg for 24 h. A third group of lambs was mechanically ventilated with 100% oxygen for 24 h (OX24; n = 5). RESULTS: Oxidized glutathione levels in whole blood correlated highly with PaO2. Reduced to oxidized glutathione ratio was significantly different between the groups, the ratio increasing with decreasing oxygen exposure. The OX24 group had significantly higher activities of lipid hydroperoxide and myeloperoxidase and significantly lower activities of superoxide dismutase, catalase and glutathione peroxidase in the lung at 24 h. Activities of AOEs correlated inversely with alveolar PO2. PA contractility to norepinephrine and KCl was greater with increasing oxygen exposure. Pretreatment with superoxide dismutase and catalase significantly reduced PA contractility in the OXR and OX24 groups, but not in the RAR group. CONCLUSIONS: We conclude that ventilated premature lambs are unable to appropriately increase AOE activity in response to hyperoxia and that increasing exposure to oxygen aggravates systemic oxidant stress, oxidant lung injury and pulmonary arterial contractility in these lambs.

Multivalent glycomimetics: synthesis of nonavalent mannoside clusters with variation of spacer properties.

Oligosaccharide mimetics are important tools in the glycosciences. In this work, we have employed spaced glycodendrons for the synthesis of oligomannoside mimetics. Starting from a number of trivalent, branched molecular wedges, the preparation of nonavalent cluster mannosides was accomplished, which were varied with regard to the chemical characteristics of their spacer moieties and spacer lengths. For ligation of the various trivalent dendrons to the nonavalent target molecules peptide coupling was employed.

Fluorescent labelled thiourea-bridged glycodendrons.

GlcNAc-coated glycodendrimers, which are polyvalent glycomimetics, display strong in vitro affinity for the rat natural killer cell protein-1A (NKR-P1A), a C-type lectin-like receptor of natural killer (NK) cells in rats, humans and some strains of mice. Administration of these compounds in vivo results in a substantial increase in the antitumour activity with involvement of the natural cell immunity. To clarify the in vitro and in vivo fate of these molecules, we synthesized labelled glycodendron analogues of the previously studied glycodendrimers. Labelling with fluorescent tags enabled the localization of the glycodendrons in white blood cells, tumours and other tissues by using different imaging techniques such as fluorescence and confocal microscopy. These studies are useful for probing the mechanism of action and fate of artificial ligands and the cell receptors involved.

Efficient synthesis of isotopically pure isotope-coded affinity tagging reagents.

Synthesis of an isotopically pure d8-ICAT linker, N-[(5,5,6,6,8,8,9,9-2H)-13-biotinamido-4,7,10-trioxatridecanyl] tert-butyloxy carbamide (12), has been achieved in seven steps with an overall yield of 33%. Conjugation of exchange-inert d4-starting materials by classic etherification reaction yielded a pure synthon, carrying eight deuteriums that remained exchange-inert throughout subsequent reactions. This modified synthesis constitutes a significant improvement to the reported syntheses of "heavy" ICAT reagent in terms of expense, yield, and isotopic retention. This synthesis is easily adapted to incorporate additional deuterium atoms and is equally applicable for incorporation of either 13C and/or 18O. In addition, this synthesis allows for the introduction of different orthogonal functionalities and provides for a high yielding series of differentially encoded ICAT tags.