Retinopathy of prematurity: Risk factors and variability in Canadian neonatal intensive care units.

OBJECTIVE: To identify predictors of severe retinopathy of prematurity (ROP) in a large population-based cohort and to examine risk-adjusted variations across units. STUDY DESIGN: Retrospective analysis of Canadian Neonatal Network data on neonates with birth weight <1500 g who were screened for ROP between 2003 and 2010. Characteristics of infants with and without ROP were compared and a risk-adjusted model for severe ROP was developed. Rates of severe ROP were compared between sites. RESULTS: 1163 of 9187 (12.7%) infants developed severe ROP. Lower gestational age, male sex, small for gestational age, patent ductus arteriosus, late onset sepsis, more than two blood transfusions, inotrope use, and outborn status were associated with an increased risk of severe ROP. Severe ROP rates varied significantly between units. CONCLUSION: Younger, smaller and sicker male infants had higher adjusted risks of severe ROP and rates varied significantly among sites.

Corticotropin releasing hormone modulates endotoxin-induced inflammatory cytokine expression in human trophoblast cells.

Recent studies have suggested a significant increase in corticotropin releasing hormone (CRH) in maternal plasma and placenta during the course of maternal infection. The aim of this study was to examine the possible role of CRH in lipopolysaccharide (LPS)-induced pro-inflammatory cytokine expression using the well-established human extravillous trophoblast cell line HTR-8/SVneo. Exposure of the HTR-8/SVneo cells to LPS resulted in increased secretion of tumour necrosis factor alpha (TNF-alpha) and interleukin (IL)-8. Pre-treatment of the cells with CRH prior to LPS exposure significantly enhanced LPS induced TNF-alpha and IL-8 secretion. This effect was inhibited by the CRH antagonist astressin. Stimulation of the cells with CRH caused a rapid and transient phosphorylation of p38/MAPK while CRH had no effect on ERK1/2 activation. The effect of CRH on p38/MAPK activation was suppressed by astressin and by the p38/MAPK inhibitor SB203580. Exposure of the cells to CRH resulted in increased expression of TLR-4 and this effect was also inhibited by astressin. Taken together, these findings suggest that CRH augments LPS induced cytokine secretion in human trophoblast cells. Modulation of LPS induced immune responses by CRH may be mediated through regulation of TLR-4 and selective activation of the p38/MAPK signalling pathway.

Zinc and copper inhibit nerve growth factor-mediated protection from oxidative stress-induced apoptosis.

We have previously provided evidence that two transition metal cations, Zn2+ and Cu2+, can alter the conformation of nerve growth factor (NGF), rendering it unable to bind to its receptors or to activate signal transduction pathways. In the present study, we have assessed the influence of Zn2+ and Cu2+ on NGF-mediated protection from an oxidative insult. Exposure of rat pheochromocytoma (PC12) cells to hydrogen peroxide resulted in an increase in cell death via apoptosis, which was inhibited by NGF. Zn2+ and Cu2+, when added to cultures at a concentration of 100 microM, prevented NGF-mediated survival-promoting effects. Neither of these ions had an effect on basal cell viability (in the absence of NGF) after an oxidative insult. These results demonstrate that Zn2+ and Cu2+ can selectively inhibit NGF-mediated resistance to an oxidative stress, and have significant implications for neuronal function under both physiological and pathological (e.g. cerebral ischemia) conditions.

Effects of a peptide analogue of the amphiphilic domain of the common neurotrophin receptor on nerve growth factor-mediated motility of human neuroblastoma cells.

Exposure of human neuroblastoma cells (IMR-32) to a peptide mimic of the cytoplasmic amphiphilic domain of the common neurotrophin receptor (p75NTR 367-379) resulted in enhanced nerve growth factor (NGF)-mediated inhibition of cell invasion in vitro. The peptide also enhanced NGF-mediated neurite extension and GAP-43 gene expression but had no effect on NGF-mediated cell survival. These latter functional effects mimicked influences on NGF-mediated neurite growth in other trkA-positive cells as reported previously. NGF-dependent trkA phosphorylation was significantly enhanced by the presence of the peptide, whereas high-affinity binding of 125I-NGF, both NGF receptors mRNA and protein expression, and trkA dimer/monomer ratios were not influenced. The studies suggest that ligand-mediated trkA activation has differential effects on cell motility phenomena and that the amphiphilic domain of p75NTR has a role in this differential signaling.

Collaborative and reciprocal effects of ciliary neurotrophic factor and nerve growth factor on the neuronal phenotype of human neuroblastoma cells.

We have probed the molecular basis of functional effects of ciliary neurotrophic factor (CNTF) and nerve growth factor (NGF) on aspects of the neuronal differentiation of LA-N-2 neuroblastoma cells. The influence of CNTF on the cholinergic phenotype can be accounted for by transcriptional/translational effects without implicating posttranslational mechanisms. Although both NGF receptors are expressed constitutively by LA-N-2 cells, CNTF has a marked stimulatory effect on trkA mRNA and protein. The NGF receptors are functional in serum-free conditions where they mitigate CNTF effects on cell adhesion but do not support process extension. Following priming by CNTF, NGF and CNTF have synergistic influences on process formation but not on choline acetyltransferase-specific activity.

Congenital erythroleukemia in a neonate with severe hypoxic ischemic encephalopathy.

We report a case of a neonate who presented with hypoxic ischemic encephalopathy, persistent hypoglycemia and hypotension, intractable metabolic acidosis, renal failure and a coagulopathy but who, at autopsy, was found to have massive infiltration of nonhematopoietic tissues with blasts. The diagnosis of congenital erythroleukemia was confirmed by the detection of glycophorin A, a major erythrocyte membrane protein, on the surface of the blasts. The clinical presentation and course of the case described here have not previously been reported for this extremely rare condition.

Differentiation effects of ciliary neurotrophic factor on human neuroblastoma cells.

In the human neuroblastoma cell line LA-N-2, recombinant rat ciliary neurotrophic factor (CNTF) induced neurite growth and cholinergic differentiation that were both half-maximally saturated at < 100 pM of the neurokine, but was not required for cell survival in serum-free conditions over a 13-day period. CNTF markedly stimulated choline acetyltransferase activity and acetylcholine synthesis, whereas high-affinity choline transport was only slightly enhanced and acetylcholinesterase activity was unchanged. Leukemia inhibitory factor had effects identical to CNTF on neurite growth and choline acetyltransferase activity, but interleukin 6 had no effect. Radioiodinated CNTF binding and affinity cross-linking studies were consistent with tripartite receptor activation as a mediator of the observed biological effects.

Modulation of neurite promoting proteoglycans by neuronal differentiation.

A human cell line committed to neuronal lineage was used to examine the influence of differentiation on proteoglycan synthesis and function. Where the LA-N-2 cells were stimulated to differentiate towards a phenotype of cholinergic neurons, proteoglycans of the heparan sulphate class increased relative to chondroitin sulphate proteoglycans and displayed more homogeneously shorter glycosaminoglycan chains with increasing degrees of sulphation. The changes were accompanied by increasing potency of the heparan sulphate proteoglycans in neurite growth-promoting activity when immobilized on a laminin substrate. These studies begin to address the role of activity-independent growth and differentiation on the synthesis and release by neurons of neurite growth-promoting proteoglycans. The observations have implications for understanding the role of proteoglycan overexpression and the production of dystrophic neurites in Alzheimer disease.

Neurite growth modulation associated with astrocyte proteoglycans: influence of activators of inflammation.

Of the three classes of sulphated proteoglycans produced by type 1 astrocytes in vitro and released into conditioned medium, only heparan sulphate (HS) was associated with enhanced neurite growth by sensory neurons following pretreatment of a laminin substratum. Astrocyte-conditioned medium (ACM) produced in the presence of certain inflammatory mediators had reduced titers of neurite-promoting activity. The low activity ACM contained inhibitors of neurite growth. Heparan sulphate proteoglycans may modulate neurite growth when complexed to constituents of the extracellular milieu either directly or by interacting with other growth-promoting or growth-inhibitory factors.

Synergistic effect of triiodothyronine and dexamethasone on male and female fetal rat lung surfactant synthesis.

It has previously been reported that morphologic and functional indices of fetal lung maturation are delayed in male rabbit fetuses, and these differences cannot be overcome by glucocorticoid treatment. Since thyroid hormone also stimulates surfactant production we have studied the effects of triiodothyronine (T3) and dexamethasone on saturated phosphatidylcholine (SPC) synthesis by day 20 male and female rat lung. Control male lung slices incorporated significantly less 3H-choline into SPC than females; surgery on day 17 markedly stimulated 3H-choline incorporation into SPC by both sexes, but the sex difference persisted. The optimal dose of T3 inhibited SPC synthesis by both sexes while dexamethasone was stimulatory. When T3 and dexamethasone were given together they had a greater effect than that of dexamethasone or T3 alone. Based on these results we conclude that the male deficit in pulmonary surfactant production may be overcome by the synergistic effects of T3 and dexamethasone.