Probiotics and the prevention of necrotizing enterocolitis in preterm infants: A systematic review of the literature

Necrotizing enterocolitis is a common gastrointestinal disease associated with high mortality and morbidity among preterm infants. This was a systematic literature review that evaluated whether the administration of probiotic supplements is of benefit in the prevention of NEC. The search was narrowed to randomized clinical trials identified through The Cochrane Central Register of Controlled Trials, U.S. National Institute of Health clinical trials registry database, Pub Med and OVID MEDLINE databases. Inclusion criteria were: prospective, randomized clinical trials that administered probiotics as a preventive measure against NEC for infants of early gestational age (<35 wks) and/or low birth weight (<1500g), maintained NEC as the primary measured outcome, used Bell’s classification for NEC diagnosis with reports of stage 2 NEC or higher, and began probiotic administration within 10 days of life. Trials were excluded if participant enrollment was fewer than 100 infants, published before the year 2000, or probiotic supplementation was discontinued after less than seven consecutive days. Based on specific study characteristics, each resulting article was then judged by two authors for study quality. The search was further narrowed to studies of either high or moderate quality, which were then summarized in a set of tables based on study characteristics and results. From an initial set of 20 identified studies, five clinical trials met all criteria; each was discussed thoroughly based on trial limitations, strengths and comparisons to other included publications. Based on this review, the weight of evidence appears to support the use of probiotic supplementation in preterm infants as a preventive measure against NEC. Recommendations for future research were also provided.^

Congenital diaphragmatic hernia in the preterm infant.

BACKGROUND: Congenital diaphragmatic hernia (CDH) remains a significant cause of death in newborns. With advances in neonatal critical care and ventilation strategies, survival in the term infant now exceeds 80% in some centers. Although prematurity is a significant risk factor for morbidity and mortality in most neonatal diseases, its associated risk with infants with CDH has been described poorly. We sought to determine the impact of prematurity on survival using data from the Congenital Diaphragmatic Hernia Registry (CDHR). METHODS: Prospectively collected data from live-born infants with CDH were analyzed from the CDHR from January 1995 to July 2009. Preterm infants were defined as <37 weeks estimated gestational age at birth. Univariate and multivariate logistic regression analysis were>performed. RESULTS: During the study period, 5,069 infants with CDH were entered in the registry. Of the 5,022 infants with gestational age data, there were 3,895 term infants (77.6%) and 1,127 preterm infants (22.4%). Overall survival was 68.7%. A higher percentage of term infants were treated with extracorporeal membrane oxygenation (ECMO) (33% term vs 25.6% preterm). Preterm infants had a greater percentage of chromosomal abnormalities (4% term vs 8.1% preterm) and major cardiac anomalies (6.1% term vs 11.8% preterm). Also, a significantly higher percentage of term infants had repair of the hernia (86.3% term vs 69.4% preterm). Survival for infants that underwent repair was high in both groups (84.6% term vs 77.2% preterm). Survival decreased with decreasing gestational age (73.1% term vs 53.5% preterm). The odds ratio (OR) for death among preterm infants adjusted for patch repair, ECMO, chromosomal abnormalities, and major cardiac anomalies was OR 1.68 (95% confidence interval [CI], 1.34-2.11). CONCLUSION: Although outcomes for preterm infants are clearly worse than in the term infant, more than 50% of preterm infants still survived. Preterm infants with CDH remain a high-risk group. Although ECMO may be of limited value in the extremely premature infant with CDH, most preterm infants that live to undergo repair will survive. Prematurity should not be an independent factor in the treatment strategies of infants with CDH.

Neonatal outcomes of extremely preterm infants from the NICHD Neonatal Research Network.

OBJECTIVE: This report presents data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network on care of and morbidity and mortality rates for very low birth weight infants, according to gestational age (GA). METHODS: Perinatal/neonatal data were collected for 9575 infants of extremely low GA (22-28 weeks) and very low birth weight (401-1500 g) who were born at network centers between January 1, 2003, and December 31, 2007. RESULTS: Rates of survival to discharge increased with increasing GA (6% at 22 weeks and 92% at 28 weeks); 1060 infants died at CONCLUSION: Although the majority of infants with GAs of >or=24 weeks survive, high rates of morbidity among survivors continue to be observed.

Intensive care for extreme prematurity--moving beyond gestational age.

BACKGROUND: Decisions regarding whether to administer intensive care to extremely premature infants are often based on gestational age alone. However, other factors also affect the prognosis for these patients. METHODS: We prospectively studied a cohort of 4446 infants born at 22 to 25 weeks' gestation (determined on the basis of the best obstetrical estimate) in the Neonatal Research Network of the National Institute of Child Health and Human Development to relate risk factors assessable at or before birth to the likelihood of survival, survival without profound neurodevelopmental impairment, and survival without neurodevelopmental impairment at a corrected age of 18 to 22 months. RESULTS: Among study infants, 3702 (83%) received intensive care in the form of mechanical ventilation. Among the 4192 study infants (94%) for whom outcomes were determined at 18 to 22 months, 49% died, 61% died or had profound impairment, and 73% died or had impairment. In multivariable analyses of infants who received intensive care, exposure to antenatal corticosteroids, female sex, singleton birth, and higher birth weight (per each 100-g increment) were each associated with reductions in the risk of death and the risk of death or profound or any neurodevelopmental impairment; these reductions were similar to those associated with a 1-week increase in gestational age. At the same estimated likelihood of a favorable outcome, girls were less likely than boys to receive intensive care. The outcomes for infants who underwent ventilation were better predicted with the use of the above factors than with use of gestational age alone. CONCLUSIONS: The likelihood of a favorable outcome with intensive care can be better estimated by consideration of four factors in addition to gestational age: sex, exposure or nonexposure to antenatal corticosteroids, whether single or multiple birth, and birth weight. (ClinicalTrials.gov numbers, NCT00063063 [ClinicalTrials.gov] and NCT00009633 [ClinicalTrials.gov].).

Redistribution of plasma membrane phosphatidylserine during erythroid development

Phosphatidylserine (PS) is not only one of the structural components of the plasma membrane, it also plays an important role in blood coagulation, and cell-cell interactions during aging and apoptosis.^ Here we studied some alterations that occur in membrane phosphatidylserine asymmetry during erythroid differentiation-associated apoptosis and erythrocyte aging and characterized some aspects in the regulation of PS asymmetry.^ Erythroleukemia cells, frequently used to study erythroid development, undergo apoptosis when induced to differentiate along the erythroid lineage. In the case of K562 cells induced to differentiate with hemin, this event is characterized by DNA fragmentation that correlates with downregulation of the survival protein BCL-xL and ultimately the result is cell death. We showed here that reorientation of PS from the inner-to-outer plasma membrane leaflet and inhibition of the aminophospholipid translocase are also events observed upon hemin treatment. We observed that constitutive expression of BCL-2 did not inhibit the alterations caused by hemin in membrane lipid asymmetry and only slightly prevented hemin-induced DNA fragmentation. On the other hand, BCL-2 effectively inhibited actinomycin D and staurosporine-induced DNA fragmentation and the appearance of PS at the outer leaflet of these cells. z.VAD.fmk, a widely used caspases inhibitor, blocked DNA fragmentation induced by both hemin and actinomycin D but only inhibited PS externalization in cells treated with actinomycin D.^ These results showed that PS externalization occurs during differentiation-related apoptosis. Unlike the pharmacologically-induced event, however, hemin-induced PS redistribution seems to be regulated by a mechanism independent of BCL-2 and caspases.^ Membrane PS is externalized not only during apoptosis but also during red blood cell senescence. To study this event, we artificially induced cellular aging by in vitro storage or vesiculation in the presence of the amphipathic lipid dilauroylphosphatidylcholine. These cells were monitored for age-dependent changes in cell density by Percoll gradient centrifugation and assessed for alterations in membrane lipid asymmetry and their ability to be cleared in vivo. These experiments demonstrated a progressive increase in red cell density upon vesiculation and in vitro aging. The clearance rate of cells obtained after vesiculation, was biphasic in nature, showing a very rapid component together with a second component consistent with the clearance rates of control populations. Quantitation of PS in the outer leaflet of red cells revealed that membrane redistribution of PS occurred upon in vitro storage and vesiculation. Inhibition of the aminophospholipid translocase with the sulfhydryl-oxidant reagent pyridyldithioethylamine resulted in higher PS externalization and enhanced clearance of vesiculated RBC.^ These observations not only suggest that vesiculation may be the mechanism responsible for some of the characteristic changes in cell density and PS asymmetry that occur upon cell aging, but also confirm the role of PS in the recognition and clearance of senescent cells. ^

A PHARMACOLOGICAL EVALUATION OF THE MECHANISM OF CYTOTOXICITY OF 9-BETA-D- XYLOFURANOSYLADENINE IN CHINESE HAMSTER OVARY CELLS

The biochemical determinants of cytotoxicity of the purine nucleoside analog, 9-(beta)-D-xylofuranosyladenine (xyl-A) were studied in wild-type Chinese hamster ovary cells and in nucleoside kinase deficient mutants. It was found that {('3)H}xyl-A was readily phosphorylated to the triphosphate level in both the wild-type and deoxycytidine kinase deficient mutant, but not by the adenosine kinase deficient cells. Values for the apparent Km and Vmax of this uptake process were 43.9 (mu)M and 118.7 nmol/min/10('9) cells, respectively. Cloning procedures indicated that the viability of CHO cells was decreased 90 per cent by a 5-hr incubation with 10 (mu)M xyl-A. However, the toxicity of xyl-A was increased 100-fold by the addition of a nontoxic concentration (10 (mu)M) of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) to the medium. High-pressure liquid chromatographic analysis indicated that after 5 hr, the concentration of 9-(beta)-D-xylofuranosyladenine 5'-triphosphate (xyl-ATP) in cells incubated with xyl-A plus EHNA was 2.0 mM, four times greater than in those cells incubated with xyl-A alone. Incubation with xyl-A plus EHNA had no significant effect on the cellular concentrations of 5-phosphoribosyl-1-pyrophosphate after 1 hr whereas, treatment with 3'-dexoyadenosine (cordycepin) decreased the concentration of this metabolite. Determinations of the cellular nucleoside triphosphates indicated that under conditions that resulted in an intracellular accumulation of 500 (mu)M xyl-ATP, the endogenous concentrations of neither the ribonucleoside triphosphates nor deoxyribonucleoside triphosphates were significantly different from those of control cells. The ID(,50) for {('3)H}thymidine incorporation into DNA, 105 (mu)M xyl-ATP, was four-fold less than the ID(,50) for {('3)H}uridine incorporation into RNA suggesting that the process of DNA synthesis is more sensitive to the presence of xyl-ATP. When removed from exogenous xyl-A, CHO cells failed to recover their ability to synthesize RNA and DNA, although the intracellular xyl-ATP concentration decreased to less than 35 (mu)M. The selective inhibition of RNA synthesis by 6-azauridine did not prevent the expression of toxicity by xyl-ATP. However, the selective inhibition of DNA synthesis by ara-C significantly spared toxicity in cells that had accumulated an otherwise lethal concentration of xyl-ATP. It is shown that in cells which had accumulated 1.27 mM {('3)H}xyl-ATP, {('3)H}xyl-A was found to terminate cellular RNA chains at a frequency of 1.42 (mu)mol of {('3)H}xyl-A 3' termini per mol of mononucleotide. These results indicate that a general mechanism for the toxicity of xyl-A to CHO cells includes the cellular accumulation of xyl-ATP, which serves as a substrate for RNA synthesizing enzymes and subsequently is incorporated into nascent RNA transcripts as a chain terminator. A specific mechanism involving the premature termination of RNA primers required for the initiation of DNA synthesis is proposed to account for the inhibitory action of xyl-ATP on DNA synthesis. ^