Necrotizing enterocolitis (NEC) is one of the most common acquired diseases of the gastrointestinal tract in preterm infants. Some randomized, controlled trials (RCTs) have indicated that probiotics may potentially lower the incidence of NEC and mortality. However, debate still remains about the safety of probiotics and their influence on normal infant growth. We performed this meta-analysis to assess the safety and benefits of probiotic supplementation in preterm infants. We searched in PubMed, Embase, and Cochrane databases for English references, and in Wanfang, VIP, and CNKI databases for Chinese references. Ultimately, 27 RCTs (including 9 Chinese articles) were incorporated into this meta-analysis. Relative risk (RR) and weighted mean difference (WMD) were calculated using a random-effects or fixed-effects model, depending on the data type and heterogeneity. A total of 6655 preterm infants, including the probiotic group (n=3298) and the placebo group (n=3357), were eligible for inclusion in this meta-analysis. For Bell stage ≥I and gestational age <37 weeks, risk of NEC incidence was significantly lower in the probiotic group [RR=0.35, 95% confidence interval (CI)=0.27-0.44, P<0.00001]. For Bell stage ≥II or gestational age <34 weeks, there were likewise significant differences between the probiotic and placebo groups concerning NEC incidence (RR=0.34, 95%CI=0.25-0.48, P<0.00001; and RR=0.39, 95%CI=0.27-0.56, P<0.00001). Risk of death was significantly reduced in the probiotic group (RR=0.58, 95%CI=0.46-0.75, P<0.0001). In contrast, there was no significant difference concerning the risk of sepsis (RR=0.94, 95%CI=0.83-1.06, P=0.31). With respect to weight gain and the age at which infants reached full feeds, no significant differences were found between the probiotic and placebo groups (WMD=1.07, 95%CI=−0.21-2.34, P=0.10; and WMD=−1.66, 95%CI=−3.6-0.27, P=0.09). This meta-analysis has shown that, regardless of gestational age and NEC stage, probiotic supplementation could significantly reduce the risk of NEC in preterm infants. Analysis also indicated that such supplementation did not increase the incidence risk of sepsis or of mortality. Finally, the study showed that probiotic supplementation may have no adverse effect on normal feeding and growth.

A B S T R A C TThe cyclic deformation of three structural steels, SS316L stainless steel, 40Cr3MoV bainitic steel and 25CDV4.11 steel, were studied experimentally by uniaxial cyclic straining or stressing tests at room temperature. The cyclic softening/hardening behaviours of the steels were discussed first by cyclic straining tests; and then the effects of cyclic softening/hardening behaviours on the uniaxial ratchetting of the materials were investigated by asymmetrical cyclic stressing tests. It is concluded from the experimental results that the ratchetting greatly depends on the cyclic softening/hardening behaviours of the materials, as well as the loading history. Different ratchetting and failure behaviours are observed for the prescribed steels. It is also stated that the proposed unified visco-plastic constitutive model can provide a fairly reasonable simulation of the uniaxial ratchetting of SS316L stainless steel and 25CDV4.11 steel; but cannot simulate the ratchetting of 40Cr3MoV bainitic steel since the dependence of cyclic softening behaviours on the applied inelastic strain amplitude cannot be reasonably described in the discussed constitutive model. Some significant conclusions are obtained, which are useful to construct constitutive model to describe the ratchetting of the materials with different cyclic softening/hardening behaviours.

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The aim of the present study was to investigate and compare the capacity of fresh-frozen allogeneic bone, nano-hydroxyapatite/collagen/PLA (nHAC/PLA) scaffold, and nHAC/PLA scaffold loaded with bone marrow mesenchymal stem cells (BMSCs) in inducing bone formation. A 10mm segmental rabbit radial defect was surgically created. The animals were divided into four groups in which the defect was either left untreated, or filled with the abovementioned three grafts. The animals were euthanized at 2, 4, 6, 8, 12, and 18 weeks. Radiographic and histologic analyses were performed on the harvested tissue. We show that nHAC/PLA composite combined with mesenchymal stem cells could enhance and accelerate bone formation in segmental defects of rabbits. nHAC/PLA composite is an ideal bone graft; implanting nHAC/PLA composite combined with mesenchymal stem cells is a potential method for surgical treatment of bone defects.