Determining the Effect of Birth Weight on Therapeutic Hypothermia in Neonates with Hypoxic-Ischemic Encephalopathy

OBJECTIVE

 We examine the effect of birth weight (BW) for gestational age (GA) on the temperatures reached during the treatment of neonatal hypoxic-ischemic encephalopathy (HIE) with therapeutic hypothermia (TH).

STUDY DESIGN

 Retrospective data of 1,736 neonates with HIE who received TH were extracted from the Canadian Neonatal Network database for neonates admitted from 2010 to 2017. Neonates were stratified into three BW groups: small for GA < 10th centile, large for GA > 90th centile, and according to GA 10th to 89th centile at a given gestation using Canadian population data norms.

RESULTS

 There was no significant difference in the lowest temperature reached, the likelihood of overshooting temperatures < 32.5°C during TH, or the change of encephalopathy stages among the three groups.

CONCLUSION

 BW for GA did not appear to influence the temperatures neonates reached during hypothermia or encephalopathy stage following TH.

KEY POINT

· Therapeutic hypothermia is well tolerated irrespective of weight for age. · SGA infants achieved and maintained target temperature similar to AGA and LGA babies. · Change in the Sarnat stage after hypothermia was similar across all birth weight groups.

CPAP Versus NIPPV Postextubation in Preterm Neonates: A Comparative-Effectiveness Study

BACKGROUND AND OBJECTIVES

Nasal intermittent positive pressure ventilation (NIPPV) has been shown to be superior to nasal continuous positive airway pressure (CPAP) postextubation in preterm neonates. However, studies have not permitted high CPAP pressures or rescue with other modes. We hypothesized that if CPAP pressures >8 cmH2O and rescue with other modes were permitted, CPAP would be noninferior to NIPPV.

METHODS

We conducted a pragmatic, comparative-effectiveness, noninferiority study utilizing network-based real-world data from 22 Canadian NICUs. Centers self-selected CPAP or NIPPV as their standard postextubation mode for preterm neonates <29 weeks' gestation. The primary outcome was failure of the initial mode ≤72 hours. Secondary outcomes included failure ≤7 days, and reintubation ≤72 hours and ≤7 days. Groups were compared using a noninferiority adjusted risk-difference (aRD) margin of 0.05, and margin of no difference.

RESULTS

A total of 843 infants extubated to CPAP and 974 extubated to NIPPV were included. CPAP was not noninferior (and inferior) to NIPPV for failure of the initial mode ≤72 hours (33.0% vs 26.3%; aRD 0.07 [0.03 to 0.12], Pnoninferiority(NI) = .86), and ≤7 days (40.7% vs 35.8%; aRD 0.09 [0.05 to 0.13], PNI = 0.97). However, CPAP was noninferior (and equivalent) to NIPPV for reintubation ≤72 hours (13.2% vs 16.1%; aRD 0.01 [-0.05 to 0.02], PNI < .01), and noninferior (and superior) for reintubation ≤7 days (16.4% vs 22.8%; aRD -0.04 [-0.07 to -0.001], PNI < .01).

CONCLUSIONS

CPAP was not noninferior to NIPPV for failure ≤72 hours postextubation; however, it was noninferior to NIPPV for reintubation ≤72 hours and ≤7 days. This suggests CPAP may be a reasonable initial postextubation mode if alternate rescue strategies are available.

Neurodevelopmental outcomes of preterm neonates receiving rescue inhaled nitric oxide in the first week of age: a cohort study

OBJECTIVE

To assess the neurodevelopmental outcomes of preterm neonates who received inhaled nitric oxide (iNO) in the first week of age for hypoxaemic respiratory failure (HRF).

METHODS

In this retrospective cohort study, we included neonates born at <29 weeks gestational age (GA) between January 2010 and December 2018 who had a neurodevelopmental assessment at 18-24 months corrected age (CA) at one of the Canadian Neonatal Follow-Up Network clinics. The primary outcome was neurodevelopmental impairment (NDI). We performed propensity score-matched analysis to compare the outcomes of those who received and did not receive iNO.

RESULTS

Of the 5612 eligible neonates, 460 (8.2%) received iNO in the first week of age. Maternal age, receipt of antenatal corticosteroids, GA and birth weight were lower in the iNO group compared with the no-iNO group. Neonates in the iNO group had higher illness severity scores and higher rates of preterm prolonged rupture of membranes and were small for GA. Severe brain injury, bronchopulmonary dysplasia and mortality were higher in the iNO group. Of the 4889 survivors, 3754 (77%) neonates had follow-up data at 18-24 months CA. After propensity score matching, surviving infants who received rescue iNO were not associated with higher odds of NDI (adjusted OR 1.34; 95% CI 0.85 to 2.12).

CONCLUSIONS

In preterm neonates <29 weeks GA with HRF, rescue iNO use was not associated with worse neurodevelopmental outcomes among survivors who were assessed at 18-24 months CA.

Relative effectiveness and safety of pharmacotherapeutic agents for patent ductus arteriosus (PDA) in preterm infants: a protocol for a multicentre comparative effectiveness study (CANRxPDA)

INTRODUCTION

Patent ductus arteriosus (PDA) is the most common cardiovascular problem that develops in preterm infants and evidence regarding the best treatment approach is lacking. Currently available medical options to treat a PDA include indomethacin, ibuprofen or acetaminophen. Wide variation exists in PDA treatment practices across Canada. In view of this large practice variation across Canadian neonatal intensive care units (NICUs), we plan to conduct a comparative effectiveness study of the different pharmacotherapeutic agents used to treat the PDA in preterm infants.

METHODS AND ANALYSIS

A multicentre prospective observational comparative-effectiveness research study of extremely preterm infants born <29 weeks gestational age with an echocardiography confirmed PDA will be conducted. All participating sites will self-select and adhere to one of the following primary pharmacotherapy protocols for all preterm babies who are deemed to require treatment.Standard dose ibuprofen (10 mg/kg followed by two doses of 5 mg/kg at 24 hours intervals) irrespective of postnatal age (oral/intravenous).Adjustable dose ibuprofen (oral/intravenous) (10 mg/kg followed by two doses of 5 mg/kg at 24 hours intervals if treated within the first 7 days after birth. Higher doses of ibuprofen up to 20 mg/kg followed by two doses of 10 mg/kg at 24 hours intervals if treated after the postnatal age cut-off for lower dose as per the local centre policy).Acetaminophen (oral/intravenous) (15 mg/kg every 6 hours) for 3-7 days.Intravenous indomethacin (0.1-0.3 mg/kg intravenous every 12-24 hours for a total of three doses).

OUTCOMES

The primary outcome is failure of primary pharmacotherapy (defined as need for further medical and/or surgical/interventional treatment following an initial course of pharmacotherapy). The secondary outcomes include components of the primary outcome as well as clinical outcomes related to response to treatment or adverse effects of treatment.

SITES AND SAMPLE SIZE

The study will be conducted in 22 NICUs across Canada with an anticipated enrollment of 1350 extremely preterm infants over 3 years.

ANALYSIS

To examine the relative effectiveness of the four treatment strategies, the primary outcome will be compared pairwise between the treatment groups using χ² test. Secondary outcomes will be compared pairwise between the treatment groups using χ² test, Student's t-test or Wilcoxon rank sum test as appropriate. To further examine differences in the primary and secondary outcomes between the four groups, multiple logistic or linear regression models will be applied for each outcome on the treatment groups, adjusted for potential confounders using generalised estimating equations to account for within-unit-clustering. As a sensitivity analysis, the difference in the primary and secondary outcomes between the treatment groups will also be examined using propensity score method with inverse probability weighting approach.

ETHICS AND DISSEMINATION

The study has been approved by the IWK Research Ethics Board (#1025627) as well as the respective institutional review boards of the participating centres.

TRIAL REGISTRATION NUMBER

NCT04347720.

Central Line-Associated Blood Stream Infections and Non-Central Line-Associated Blood Stream Infections Surveillance in Canadian Tertiary Care Neonatal Intensive Care Units

OBJECTIVE

To determine if the reported reduction in hospital-acquired infections is due to reduced central line-associated blood stream infections (CLABSI) or non-CLABSIs.

STUDY DESIGN

A retrospective cohort study design was used to describe the change in organism pattern and incidence of hospital-acquired infections (CLABSIs and non-CLABSIs) in neonates <33 weeks of gestation admitted to tertiary neonatal intensive care units in the Canadian Neonatal Network between January 1, 2010, and December 31, 2016. Hospital-acquired infection was diagnosed when a pathogenic organism was isolated from blood or cerebrospinal fluid in a neonate with suspected sepsis. CLABSI was diagnosed when a central venous catheter was present at the time or removed in the 2 days before a hospital-acquired infection diagnosis. Cochran-Armitage and Mann-Kendall trend tests and linear regression models were used for statistical analyses.

RESULTS

Of 28 144 eligible neonates from 30 Canadian Neonatal Network neonatal intensive care units, 3306 (11.7%) developed hospital-acquired infections. There was a significant decrease in the rate of hospital-acquired infections (14.2% in 2010 and 9.2% in 2016; P < .01), and the rate of both CLABSIs and non-CLABSIs (P < .01) over the study period concomitant with a significant decrease in the duration of central line use (P = .01). The rates of meningitis also decreased during the study period (1.2% in 2010 and 0.9% in 2016; P < .01). Infections owing to gram-positive cocci significantly decreased, but infections owing to gram-negative organisms remained unchanged.

CONCLUSION

Although there was a significant decrease in CLABSIs and non-CLABSIs, hospital-acquired infections in preterm neonates remained high. Infections owing to gram-negative organisms remained unchanged and are a target for future preventative efforts.

Notch and Cdk5 in Zebrafish Mindbomb Mutant: Co-regulation or Coincidence?

Notch signalling is critical for the development of the nervous system. In the zebrafish mindbomb mutants, disruption of E3 ubiquitin ligase activity inhibits Notch signalling. In these mutant embryos, precocious development of primary neurons leading to depletion of neural progenitor cells results in a neurogenic phenotype characterized by defects in neural patterning and brain development. Cyclin-dependent kinase 5 (Cdk5), a predominant neuronal kinase, is involved in a variety of essential functions of the nervous system. Most recently, mammalian studies on Notch and Cdk5 regulating each other's function have been emerging. The status of Cdk5 in the mindbomb mutant embryos with excessive primary neurons is not known. In situ hybridization of the zebrafish mindbomb mutant embryos uncovered a robust upregulation in Cdk5 expression but with a reduced Cdk5 activity. The implications of these findings in both the mammalian system and zebrafish are discussed in this mini-review to provide a glimpse into the relationship between Notch and Cdk5 that may explain certain neurodevelopmental defects associated with either mutations in ubiquitin ligase or altered expression of Cdk5.

Gradual loss of DNA-PK activity from the cytoplasm is coincident with the nuclear translocation of its activator Ku during early development of Xenopus laevis

DNA-dependent protein kinase is a serine/ threonine kinase consisting of a catalytic subunit, p460, and a regulatory subunit called Ku (p80/p70). DNA-dependent protein kinase plays a role in transcription, non-homologous recombination, and DNA repair. Previous data have shown the presence of DNA-dependent protein kinase in Xenopus oocytes and changes in its activity during vitellogenesis. Metabolic labelling studies have shown that the increased enzyme activity in vitellogenic oocytes correlates with increased levels of Ku protein, and compared to the pre- and early-vitellogenic oocytes, vitellogenic and post-vitellogenic oocytes show an increased level of DNA-dependent protein kinase activity. Whether DNA-dependent protein kinase activity is altered during early embryogenesis in Xenopus is not known. The present study demonstrates that DNA-dependent protein kinase activity is gradually lost from the cytoplasm in the early embryonic cells of blastulae and gastrulae. The gradual loss of DNA-dependent protein kinase activity during post-fertilization early embryogenesis in Xenopus is consistent with the reports on Arbacia punctulata. Immunohistochemistry of the oocytes at various stages and early embryos (gastrulae) shows that Ku70, a regulatory subunit of DNA-dependent protein kinase, is present both in the cytoplasm and nucleus in the pre-vitellogenic oocytes, full-grown post-vitellogenic oocytes and in the gastrula cells. However, Ku70 appears to accumulate in higher concentrations in the nuclei of gastrula cells. These results suggest that gradual loss of DNA-dependent protein kinase activity from the cytoplasm of the early embryos could be the consequence of Ku translocating to the nuclei that may be necessary for post-zygotic transcription followed by cellular differentiation.

Ajuba, a cytosolic LIM protein, shuttles into the nucleus and affects embryonal cell proliferation and fate decisions

Cellular adhesive events affect cell proliferation and differentiation decisions. How cell surface events mediating adhesion transduce signals to the nucleus is not well understood. After cell-cell or cell-substratum contact, cytosolic proteins are recruited to clustered adhesion receptor complexes. One such family of cytosolic proteins found at sites of cell adhesion is the Zyxin family of LIM proteins. Here we demonstrate that the family member Ajuba was recruited to the cell surface of embryonal cells, upon aggregate formation, at sites of cell-cell contact. Ajuba contained a functional nuclear export signal and shuttled into the nucleus. Importantly, accumulation of the LIM domains of Ajuba in the nucleus of P19 embryonal cells resulted in growth inhibition and spontaneous endodermal differentiation. The differentiating effect of Ajuba mapped to the third LIM domain, whereas regulation of proliferation mapped to the first and second LIM domains. Ajuba-induced endodermal differentiation of these cells correlated with the capacity to activate c-Jun kinase and required c-Jun kinase activation. These results suggest that the cytosolic LIM protein Ajuba may provide a new mechanism to transduce signals from sites of cell adhesion to the nucleus, regulating cell growth and differentiation decisions during early development.

MEKK4 mediates differentiation in response to retinoic acid via activation of c-Jun N-terminal kinase in rat embryonal carcinoma P19 cells

Differentiation of P19 embryonal carcinoma cells in response to the morphogen retinoic acid is regulated by Galpha(12/13) and is associated with activation of c-Jun N-terminal kinase. The role of MEKK1 and MEKK4 upstream of the c-Jun N-terminal kinase was investigated in P19 cells. P19 clones stably expressing constitutively active and dominant negative mutants of MEKK1 and MEKK4 were created and characterized. Expression of the constitutively active form of either MEKK1 or MEKK4 mimicked the action of retinoic acid, inducing these embryonal carcinoma cells to primitive endoderm. Expression of the dominant negative form of MEKK1 had no influence on the ability of retinoic acid to induce either JNK activation or primitive endoderm formation in P19 stem cells. Expression of the dominant negative form of MEKK4, in contrast, effectively blocks both morphogen-induced activation of JNK and cellular differentiation. These data identify MEKK4 as upstream of c-Jun N-terminal kinase in the pathway mediating differentiation of P19 stem cells to primitive endoderm.

Microinjection of an antibody to the Ku protein arrests development in sea urchin embryos

Ku is the regulatory subunit of the DNA-dependent protein kinase (DNA-PK). This enzyme plays a role in DNA repair, recombination, and transcription. It is composed of a large catalytic subunit (p460), and a regulatory heterodimer, the Ku protein, which consists of 86-kDa and 70-kDa subunits. These various components of the enzyme have been found in both eggs and embryos of the sea urchin. When variable amounts of a specific monoclonal antibody to the Ku protein (Ku 162) were injected into one cell of a 2-cell embryo of Lytechinus pictus, they caused a dose-dependent developmental arrest of the injected cell. The non-injected cell continued to develop normally. In contrast, injection of an antibody (N3H10) raised against the 70-kDa subunit of the Ku protein had no effect on development when injected into 2-cell-stage embryos. Co-injection of purified DNA-PK with the antibody reversed the antibody-mediated inhibition of development. In the fertilized egg and during the early stages of development, the DNA-PK was localized largely in the cytoplasm, but in later developmental stages, it assumed a nuclear location. On the basis of these results, we postulate that the injection of the Ku antibody either prevents the translocation of the DNA-PK into the nucleus or interferes with its enzymatic activity either in the nucleus or in the cytoplasm. In either case, the results suggest that DNA-PK plays an important role in regulating the early stages of embryogenesis in this primitive organism.

Ajuba, a novel LIM protein, interacts with Grb2, augments mitogen-activated protein kinase activity in fibroblasts, and promotes meiotic maturation of Xenopus oocytes in a Grb2- and Ras-dependent manner

LIM domain-containing proteins contribute to cell fate determination, the regulation of cell proliferation and differentiation, and remodeling of the cell cytoskeleton. These proteins can be found in the cell nucleus, cytoplasm, or both. Whether and how cytoplasmic LIM proteins contribute to the cellular response to extracellular stimuli is an area of active investigation. We have identified and characterized a new LIM protein, Ajuba. Although predominantly a cytosolic protein, in contrast to other like proteins, it did not localize to sites of cellular adhesion to extracellular matrix or interact with the actin cytoskeleton. Removal of the pre-LIM domain of Ajuba, including a putative nuclear export signal, led to an accumulation of the LIM domains in the cell nucleus. The pre-LIM domain contains two putative proline-rich SH3 recognition motifs. Ajuba specifically associated with Grb2 in vitro and in vivo. The interaction between these proteins was mediated by either SH3 domain of Grb2 and the N-terminal proline-rich pre-LIM domain of Ajuba. In fibroblasts expressing Ajuba mitogen-activated protein kinase activity persisted despite serum starvation and upon serum stimulation generated levels fivefold higher than that seen in control cells. Finally, when Ajuba was expressed in fully developed Xenopus oocytes, it promoted meiotic maturation in a Grb2- and Ras-dependent manner.

DNA-dependent protein phosphorylation activity in Xenopus is coupled to a Ku-like protein

DNA-dependent protein kinase (DNA-PK) is a nuclear enzyme and functions as a serine/threonine kinase that has been well characterized in both the human and the mouse. The regulatory subunit of DNA-PK is the Ku autoantigen. To demonstrate that a Ku-like protein is present in Xenopus oocytes, we used immunoprecipitation analysis with a monoclonal antibody raised against human Ku antigen and autoimmune serum containing anti-Ku antibodies. Metabolic labeling studies indicate that the Ku-like protein is synthesized mainly in late vitellogenic oocytes. By using a specific peptide substrate for DNA-PK, we demonstrate the activity of a DNA-dependent protein kinase in oocyte extracts. The kinase activity requires the Ku-like protein, since extracts depleted of Ku protein by immunoadsorption with human anti-Ku antibodies fail to demonstrate the DNA-dependent phosphorylation activity. The increased enzyme activity in vitellogenic oocytes may be correlated to the increased levels of Ku protein observed in these oocytes compared to the pre- and early vitellogenic oocytes.

Autoimmunity to RNA polymerase II is focused at the carboxyl terminal domain of the large subunit

OBJECTIVE

Previous studies have demonstrated antibodies to the large (220 kd) polypeptide subunit of RNA polymerase II (Pol II) in sera from certain patients with scleroderma. In the present study, we sought to identify the autoantigenic region on this polypeptide.

METHODS

A recombinant fusion protein, corresponding to the 52-heptapeptide repeat found in the carboxyl terminal domain (CTD) of the large Pol II subunit, was used to identify 15 patient sera that contained autoantibodies. Synthetic peptides CTD7 (representing a single heptapeptide) and CTD18 (representing 2 1/2 heptapeptide repeats) were used in a competitive inhibition assay to define the specificity of these sera and the importance of the CTD as an autoantigen.

RESULTS

All 15 sera immunoprecipitated the Pol II subunit from radiolabeled cell extracts, and 11 of them bound the CTD fusion protein in immunoblots. Immunoprecipitation of Pol II was completely inhibited by CTD18 in 5 sera and partially inhibited in 4 additional sera.

CONCLUSION

These results indicate that the CTD heptapeptide repeat is a focal point for autoimmune responses in scleroderma. It is likely that the repetitive sequence and high content of charged residues of this structure contribute to its role as an autoantigen.

Fundulus heteroclitus vitellogenin: the deduced primary structure of a piscine precursor to noncrystalline, liquid-phase yolk protein

We have cloned and sequenced a cDNA encoding a vitellogenin (Vtg) from the mummichog, Fundulus heteroclitus, an estuarine teleost. We constructed a liver cDNA library against RNA from estrogen-treated male mummichogs. Five overlapping cDNA clones totalling 5,197 bp were isolated through a combination of degenerate oligonucleotide probing of the library and PCR. The cDNA sequence contains a 5,112 bp open reading frame. The predicted primary structure of the deduced 1,704-amino-acid protein is 30-40% identical to other documented chordate Vtgs, establishing this Vtg as a member of the ancient Vtg gene family. Of the previously reported chordate Vtg sequences (Xenopus laevis, Gallus domesticus, Ichthyomyzon unicuspis, and Acipenser transmontanus), all four act as precursor proteins to a yolk which is eventually rendered insoluble under physiological conditions, either as crystalline platelets or as noncrystalline granules. The yolk of F. heteroclitus, on the other hand, remains in a soluble state throughout oocyte growth. The putative F. heteroclitus Vtg contains a polyserine region with a relative serine composition that is 10-20% higher than that observed for the other Vtgs. The trinucleotide repeats encoding the characteristic polyserine tracts of the phosvitin region follow a previously reported trend: TCX codons on the 5' end and AGY codons toward the 3' end. Whether the difference in Vtg primary structure between F. heteroclitus and that of other chordates is responsible for the differences in yolk structure remains to be elucidated. As the first complete teleost Vtg to be reported, these data will aid in designing nucleotide and immunological probes for detecting Vtg as a reproductive status indicator in F. heteroclitus and other piscine species.

Expression of extracellular ligand-binding domain of murine guanylate cyclase/atrial natriuretic factor receptor cDNA in Escherichia coli

The membrane-bound form of guanylate cyclase/atrial natriuretic factor receptor (GC/ANF-R) is a 135 kDa transmembrane glycoprotein which binds ANF with high affinity. We have expressed the extracellular ligand-binding domain of murine guanylate cyclase ANF-R (GC/ANFR-LBD) cDNA in Escherichia coli. The cDNA encoding the extracellular ANF-binding domain (nucleotide positions covering from 432-1755 base pair) of GC/ANF-R was amplified by polymerase chain reaction, cloned into BamHI site of pGEX-3X prokaryotic expression vector and was transfected into E. coli, strain JM101. After isopropyl-beta-D-thiogalactopyranoside (IPTG) induction of bacterial cells, the GC/ANFR-LBD was expressed as the glutathione-S-transferase (GST) fusion protein, yielding a molecular mass of 70 kDa. The expressed fusion protein was characterized for binding affinity to both full length and truncated ANF molecules. After expression in E. coli, the binding of 125I-ANF to the extracellular region of GC/ANF-R was similar and corresponded to the pharmacological class of native receptor protein. The 70 kDa fusion product was purified as a predominant single protein band by glutathione-affinity chromatography. These findings establish that E. coli may be utilized as an effective heterologous model system to delineate the structure-function analysis of guanylate cyclase-coupled ANF receptor molecules.

Oogenesis in Fundulus heteroclitus. VI. Establishment and verification of conditions for vitellogenin incorporation by oocytes in vitro

A procedure was developed for studying vitellogenin (VTG) incorporation by vitellogenic oocytes of Fundulus heteroclitus in vitro. Since homologous VTG can be obtained from this animal only with great difficulty, the use of [32P]VTG from Xenopus laevis was explored as an alternative. Vitellogenic as well as maturational-stage oocytes were found to sequester X. laevis [32P]VTG from the medium, and incorporation was found to be linear with time for at least up to 12 hr. Once incorporated into the oocyte, [32P]VTG did not appear to undergo turnover. The effect of different [32P]VTG concentrations on incorporation indicated that the uptake mechanism was saturable. Unlabeled F. heteroclitus VTG and X. laevis VTG were also found to compete effectively with X. laevis [32P]VTG, whereas bovine serum albumin did not. These results represent the first documentation of a successful culture system for receptor-mediated VTG incorporation by teleost oocytes.