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Reproduction is a remarkably intricate process involving the interaction of multiple cell types and organ systems unfolding over long periods of time and that culminates with the production of gametes. The initiation of germ cell development takes place during embryogenesis but only completes decades later in humans. The complexity inherent to reproduction and its study has long hampered our ability to decipher how environmental agents disrupt this process. Single-cell approaches provide an opportunity for a deeper understanding of the action of toxicants on germline function and analyze how the response to their exposure is differentially distributed across tissues and cell types. In addition to single-cell RNA sequencing, other single-cell or nucleus level approaches such as ATAC-sequencing and multi-omics have expanded the strategies that can be implemented in reproductive toxicological studies to include epigenomic and the nuclear transcriptomic data. Here we will discuss the current state of single-cell technologies and how they can best be utilized to advance reproductive toxicological studies. We will then discuss case studies in two model organisms (Caenorhabditis elegansand mouse) studying different environmental exposures (alcohol and e-cigarettes respectively) to highlight the value of single-cell and single-nucleus approaches for reproductive biology and reproductive toxicology.

Objective: To describe the clinical approach used by neonatologists for diagnosis of congenital/perinatal infections (CPI); no such data currently exist. Study design: A national survey regarding the diagnosis of toxoplasma, syphilis, rubella, cytomegalovirus, and herpes simplex virus (HSV) infection in neonates. Result: We received 553 (11%) responses. Central nervous system calcification or hydrocephalus was the commonest trigger to pursue a CPI diagnosis (98%); maternal history was the least frequent (67%). Four hundred twenty-two (76%) used general screening such as “TORCH titer screen” (57%) or total IgG or IgM (39%). Further evaluation targeted known clinical sequelae; but cerebrospinal fluid testing was used in only 65% of those suspected of having HSV or syphilis. Fifty-six percent chose a treponemal instead of a non-treponemal test for syphilis. Multivariable analyses did not identify factors associated with the clinical diagnostic approach. Conclusion: We observed clinically important deviations from CPI diagnostic test recommendations in a national cohort of neonatologists.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe clinical disorders that mainly develop from viral respiratory infections, sepsis, and chest injury. Antigen-presenting cells play a pivotal role in propagating uncontrolled inflammation and injury through the excess secretion of pro-inflammatory cytokines and recruitment of immune cells. Autophagy, a homeostatic process that involves the degradation of cellular components, is involved in many processes including lung inflammation. Here, we use a polyinosinic-polycytidylic acid (poly(I:C))-induced lung injury mouse model to mimic viral-induced ALI/ARDS and show that disruption of autophagy in macrophages exacerbates lung inflammation and injury, whereas autophagy induction attenuates this process. Therefore, induction of autophagy in macrophages can be a promising therapeutic strategy in ALI/ARDS.

To compare the effects of electroacupuncture (EA) and moxibustion at Zusanli(ST 36) on the lung phenotype of rat offspring exposed to nicotine during the perinatal period.

Background:By stimulating lipofibroblast maturation, parenterally administered peroxisome proliferator-activated receptor ? (PPAR?) agonists promote lung homeostasis and injury repair in the neonatal lung. In this study, we determined whether PPAR? agonists could be delivered effectively via nebulization to neonates, and whether this approach would also protect against hyperoxia-induced lung injury.Methods:One-day old Sprague-Dawley rat pups were administered PPAR? agonists rosiglitazone (RGZ, 3?mg/kg), pioglitazone (PGZ, 3?mg/kg), or the diluent, via nebulization every 24?h; animals were exposed to 21% or 95% O2for up to 72?h. Twenty-four and 72?h following initial nebulization, the pups were sacrificed for lung tissue and blood collection to determine markers of lung maturation, injury repair, and RGZ and PGZ plasma levels.Results:Nebulized RGZ and PGZ enhanced lung maturation in both males and females, as evidenced by the increased expression of markers of alveolar epithelial and mesenchymal maturation. This approach also protected against hyperoxia-induced lung injury, since hyperoxia-induced changes in bronchoalveolar lavage cell and protein contents and lung injury markers were all blocked by nebulized PGZ.Conclusion:Nebulized PPAR? agonist administration promotes lung maturation and prevents neonatal hyperoxia-induced lung injury in both males and females.

There is a large body of literature suggesting that the recent increase in the incidence of childhood asthma might be associated with vitamin D deficiency during lung development. There are also strong experimental animal data showing that vitamin D is one of the local alveolar paracrine factors that spatiotemporally modulates perinatal pulmonary maturation. However, the mechanistic link between vitamin D deficiency during pregnancy and childhood asthma is not known. In this review, we demonstrate how perinatal vitamin D deficiency could mechanistically drive both the proximal and distal airways to a myogenic phenotype, molecularly and structurally, predisposing the offspring to asthma. More specifically, we will review how perinatal vitamin D deficiency results in an increased abundance of mesenchymal myofibroblasts, a feature that is highly consistent with the pathophysiology of asthma. We also provide evolutionary insights as to how vitamin D deficiency might (re)activate the atavistic host defense mechanisms that could precipitate a lung phenotype consistent with asthma. Since vitamin D deficiency seems to alter the normal homeostatic epithelialmesenchymal signaling pathways in the developing lung, it offers a distinct translational opportunity to prevent this process through targeted molecular manipulations. While we wait for the results of on-going trials of vitamin D supplementation during pregnancy to get some definitive answers on its role in the pathogenesis of childhood asthma, we advocate studies to discover new vitamin D analogs and/or metabolites with optimal respiratory effects and without any significant side effects.

The mechanism underlying the potentially beneficial effects of the “gentler” modes of ventilation on chronic lung disease (CLD) of the premature infant is not known. We have previously demonstrated that alveolar parathyroid hormone-related protein-peroxisome proliferator-activated receptor (PTHrP-PPAR) signaling is critically important in alveolar formation, and this signaling pathway is disrupted in hyperoxia- and/or volutrauma-induced neonatal rat lung injury. Whether the same paradigm is also applicable to CLD, resulting from prolonged intermittent mandatory ventilation (IMV), and whether differential effects of the mode of ventilation on the PTHrP-PPAR signaling pathway explain the potential benefits of the “gentler” modes of ventilation are not known. Using a well-established preterm lamb model of neonatal CLD, we tested the hypothesis that ventilatory support using high-frequency nasal ventilation (HFNV) promotes alveolar PTHrP-PPAR signaling, whereas IMV inhibits it. Preterm lambs managed by HFNV or IMV for 21 d following preterm delivery at 132-d gestation were studied by Western hybridization and immunofluorescence labeling for key markers of alveolar homeostasis and injury/repair. In lambs managed by IMV, the abundance of key homeostatic alveolar epithelial-mesenchymal markers was reduced, whereas it was significantly increased in the HFNV group, providing a potential molecular mechanism by which “gentler” modes of ventilation reduce neonatal CLD.

The mechanism underlying the potentially beneficial effects of the “gentler” modes of ventilation on chronic lung disease (CLD) of the premature infant is not known. We have previously demonstrated that alveolar parathyroid hormone-related protein-peroxisome proliferator-activated receptor? (PTHrP-PPAR?) signaling is critically important in alveolar formation, and this signaling pathway is disrupted in hyperoxia- and/or volutrauma-induced neonatal rat lung injury. Whether the same paradigm is also applicable to CLD, resulting from prolonged intermittent mandatory ventilation (IMV), and whether differential effects of the mode of ventilation on the PTHrP-PPAR? signaling pathway explain the potential benefits of the “gentler” modes of ventilation are not known. Using a well-established preterm lamb model of neonatal CLD, we tested the hypothesis that ventilatory support using high-frequency nasal ventilation (HFNV) promotes alveolar PTHrP-PPAR? signaling, whereas IMV inhibits it. Preterm lambs managed by HFNV or IMV for 21 d following preterm delivery at 132-d gestation were studied by Western hybridization and immunofluorescence labeling for key markers of alveolar homeostasis and injury/repair. In lambs managed by IMV, the abundance of key homeostatic alveolar epithelial-mesenchymal markers was reduced, whereas it was significantly increased in the HFNV group, providing a potential molecular mechanism by which “gentler” modes of ventilation reduce neonatal CLD.

Late preterm births have been on the increase. Though the reasons for the increase in late preterm births are unclear, non-medically indicated inductions and cesarean sections seem to be the significant preventable contributors. Late preterm infants are typically healthier than very preterm infants, but compared to term infants they are at significantly increased risk of both short and long term morbidity and mortality. In the short term they have increased rates of feeding difficulties, hypoglycemia, jaundice, temperature instability, apnea, respiratory distress and sepsis evaluation compared to term infants. Emerging data also suggest a higher rate of long-term neurodevelopmental, social, and medical morbidity. Therefore, if elective induction of labor or cesarean section at late preterm gestation (34–36 weeks of gestational age) is considered for either maternal or fetal indications, the risk and benefits should be carefully examined. The family and physician should discuss that elective delivery of late preterm infants is not recommended unless absolutely indicated. Due to a considerably higher risk of morbidity and mortality, developing and testing new paradigms of obstetric and fetal management for pregnancies with potential for late preterm delivery are a logical objective. For example, strategies to enhance fetal physiologic maturation when late preterm delivery is unavoidable need to be explored.

The nuclear transcription factor peroxisome proliferator-activated receptor (PPAR) plays a central role in normal lung development. However, the effects of modulating PPAR expression by exogenously administered PPAR agonists on lung development and basic blood biochemical and metabolic profiles in a developing animal are not known. To determine these effects, newborn Sprague-Dawley rat pups were administered either diluent or rosiglitazone (RGZ), a potent PPAR agonist, for either 1 or 7 d. Then the pups were killed and the lungs were examined for specific markers of alveolar epithelial, mesenchymal, and vascular maturation, and lung morphometry. The effect of RGZ on a limited number of blood biochemical and metabolic parameters was also determined. Overall, systemically administered RGZ significantly enhanced lung maturation without affecting serum electrolytes, blood glucose, blood gases, plasma cholesterol, triglycerides, and serum cardiac troponin levels. The lung maturation effect of PPAR agonists was also confirmed by another PPAR agonist, the naturally occurring PPAR ligand prostaglandin J2. We conclude that systemically administered RGZ significantly enhances lung maturation without significantly affecting the acute blood biochemical and metabolic profiles, providing rationale for further studying PPAR agonists for enhancing lung maturation, and for promoting lung injury/repair in neonates.

The nuclear transcription factor peroxisome proliferator-activated receptor (PPAR) ? plays a central role in normal lung development. However, the effects of modulating PPAR? expression by exogenously administered PPAR? agonists on lung development and basic blood biochemical and metabolic profiles in a developing animal are not known. To determine these effects, newborn Sprague-Dawley rat pups were administered either diluent or rosiglitazone (RGZ), a potent PPAR? agonist, for either 1 or 7 d. Then the pups were killed and the lungs were examined for specific markers of alveolar epithelial, mesenchymal, and vascular maturation, and lung morphometry. The effect of RGZ on a limited number of blood biochemical and metabolic parameters was also determined. Overall, systemically administered RGZ significantly enhanced lung maturation without affecting serum electrolytes, blood glucose, blood gases, plasma cholesterol, triglycerides, and serum cardiac troponin levels. The lung maturation effect of PPAR? agonists was also confirmed by another PPAR? agonist, the naturally occurring PPAR? ligand prostaglandin J2. We conclude that systemically administered RGZ significantly enhances lung maturation without significantly affecting the acute blood biochemical and metabolic profiles, providing rationale for further studying PPAR? agonists for enhancing lung maturation, and for promoting lung injury/repair in neonates.

Stearoyl-coenzyme A desaturase 1 (SCD1) catalyzes the conversion of stearate (18:0) to oleate (18:1n-9) and of palmitate (16:0) to palmitoleate (16:1), which are key steps in triglyceride synthesis in the fatty acid metabolic network. This study investigated the role of SCD1 in fatty acid metabolism in HepG2 cells using SCD1 inhibitors and stable isotope tracers. HepG2 cells were cultured with [U-13C]stearate, [U-13C]palmitate, or [1,2-13C]acetate and (1) DMSO, (2) compound CGX0168 or CGX0290, or (3) trans-10,cis-12 conjugated linoleic acid (CLA). 13C incorporation into fatty acids was determined by GC-MS and desaturation indices calculated from the respective ion chromatograms. FAS, SCD1, peroxisome proliferator-activated receptor α, and peroxisome proliferator-activated receptor γ mRNA levels were assessed by semiquantitative RT-PCR. The addition of CGX0168 and CGX0290 decreased the stearate and palmitate desaturation indices in HepG2 cells. CLA led to a decrease in the desaturation of stearate only, but not palmitate. Comparison of desaturation indices based on isotope enrichment ratios differed, depending on the origin of saturated fatty acid. SCD1 gene expression was not affected in any group. In conclusion, the differential effects of SCD1 inhibitors and CLA on SCD1 activity combined with the dependence of desaturation indices on the source of saturated fatty acid strongly support the compartmentalization of desaturation systems. The effects of SCD1 inhibition on fatty acid composition in HepG2 cells occurred through changes in the dynamics of the fatty acid metabolic network and not through transcriptional regulatory mechanisms.

Stearoyl-coenzyme A desaturase 1 (SCD1) catalyzes the conversion of stearate (18:0) to oleate (18:1n-9) and of palmitate (16:0) to palmitoleate (16:1), which are key steps in triglyceride synthesis in the fatty acid metabolic network. This study investigated the role of SCD1 in fatty acid metabolism in HepG2 cells using SCD1 inhibitors and stable isotope tracers. HepG2 cells were cultured with [U-13C]stearate, [U-13C]palmitate, or [1,2-13C]acetate and (1) DMSO, (2) compound CGX0168 or CGX0290, or (3) trans-10,cis-12 conjugated linoleic acid (CLA). 13C incorporation into fatty acids was determined by GC-MS and desaturation indices calculated from the respective ion chromatograms. FAS, SCD1, peroxisome proliferator-activated receptor α, and peroxisome proliferator-activated receptor γ mRNA levels were assessed by semiquantitative RT-PCR. The addition of CGX0168 and CGX0290 decreased the stearate and palmitate desaturation indices in HepG2 cells. CLA led to a decrease in the desaturation of stearate only, but not palmitate. Comparison of desaturation indices based on isotope enrichment ratios differed, depending on the origin of saturated fatty acid. SCD1 gene expression was not affected in any group. In conclusion, the differential effects of SCD1 inhibitors and CLA on SCD1 activity combined with the dependence of desaturation indices on the source of saturated fatty acid strongly support the compartmentalization of desaturation systems. The effects of SCD1 inhibition on fatty acid composition in HepG2 cells occurred through changes in the dynamics of the fatty acid metabolic network and not through transcriptional regulatory mechanisms.

We have taken a basic biologic approach to elucidate the pathophysiology of bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, based on cell/molecular mechanisms of physiologic lung development. Stretch coordinates parathyroid hormone-related protein (PTHrP) signaling between the alveolar type II cell and the mesoderm to coordinately up-regulate key genes for the homeostatic fibroblast phenotype- including peroxisome proliferator activated receptor gamma (PPAR), adipocyte differentiation related protein (ADRP), and leptin- and the retrograde stimulation of type II cell surfactant synthesis by leptin. Each of these paracrine interactions requires cell-specific receptors on adjacent cells derived from the mesoderm or endoderm, respectively, to serially up-regulate the signaling pathways between and within each cell-type. It is this functional compartmentation that is key to understanding how specific agonists and antagonists can predictably affect this mechanism of alveolar homeostasis. Using a wide variety of pathophysiologic insults associated with BPD- barotrauma, oxotrauma, and infection, we have found that there are type II cell and/or fibroblast cell/molecular effects generated by these insults, which can lead to the BPD phenotype. We have exploited these cell-specific mechanisms to effectively prevent and treat lung injuries using PPAR agonists to sustain this signaling pathway. It is critically important to judiciously select physiologically and developmentally relevant interventions when treating the preterm neonate.

We have taken a basic biologic approach to elucidate the pathophysiology of bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, based on cell/molecular mechanisms of physiologic lung development. Stretch coordinates parathyroid hormone-related protein (PTHrP) signaling between the alveolar type II cell and the mesoderm to coordinately up-regulate key genes for the homeostatic fibroblast phenotype- including peroxisome proliferator activated receptor gamma (PPAR?), adipocyte differentiation related protein (ADRP), and leptin- and the retrograde stimulation of type II cell surfactant synthesis by leptin. Each of these paracrine interactions requires cell-specific receptors on adjacent cells derived from the mesoderm or endoderm, respectively, to serially up-regulate the signaling pathways between and within each cell-type. It is this functional compartmentation that is key to understanding how specific agonists and antagonists can predictably affect this mechanism of alveolar homeostasis. Using a wide variety of pathophysiologic insults associated with BPD- barotrauma, oxotrauma, and infection, we have found that there are type II cell and/or fibroblast cell/molecular effects generated by these insults, which can lead to the BPD phenotype. We have exploited these cell-specific mechanisms to effectively prevent and treat lung injuries using PPAR? agonists to sustain this signaling pathway. It is critically important to judiciously select physiologically and developmentally relevant interventions when treating the preterm neonate.

Intrauterine meconium (MEC) passage and aspiration may result in significant newborn morbidity, though there is little understanding of the physiologic mechanisms for MEC passage. We hypothesized that stress induces fetal MEC passage via corticotrophin releasing factor (CRF), a known mediator of colonic motility in adult rats. Pregnant rats at e22 were subjected to acute hypoxia or normoxia for 35 min, after which rats were anesthetized and fetuses operatively delivered. Amniotic fluid bilirubin and intestinal alkaline phosphatase were measured as markers for MEC passage, and fetal and maternal plasma CRF and corticosterone levels determined. Hypoxic stress induced defecation in all dams and provoked visible MEC passage in all fetuses. Amniotic fluid bilirubin content was significantly higher in hypoxic fetuses versus controls (1.064 ± 0.101 versus 0.103 ± 0.003 O.D. at 410 nm) and intestinal alkaline phosphatase was consistently elevated in MEC stained amniotic fluid. Hypoxia significantly increased plasma CRF (maternal, 82 ± 5 to 196 ± 14 pg/mL; fetal, 284 ± 15 to 1523 ± 185 pg/mL) and corticosterone (maternal, 417 ± 50 to 1150 ± 50 ng/mL; fetal, 96 ± 5 to 182 ± 10 ng/mL) compared with controls. In view of the known action of CRF in adult colonic motility, these results suggest that hypoxic stress-mediated MEC passage in term fetal rats is mediated by a CRF dependent pathway.

Intrauterine meconium (MEC) passage and aspiration may result in significant newborn morbidity, though there is little understanding of the physiologic mechanisms for MEC passage. We hypothesized that stress induces fetal MEC passage viacorticotrophin releasing factor (CRF), a known mediator of colonic motility in adult rats. Pregnant rats at e22 were subjected to acute hypoxia or normoxia for 35 min, after which rats were anesthetized and fetuses operatively delivered. Amniotic fluid bilirubin and intestinal alkaline phosphatase were measured as markers for MEC passage, and fetal and maternal plasma CRF and corticosterone levels determined. Hypoxic stress induced defecation in all dams and provoked visible MEC passage in all fetuses. Amniotic fluid bilirubin content was significantly higher in hypoxic fetuses versuscontrols (1.064 ± 0.101 versus0.103 ± 0.003 O.D. at 410 nm) and intestinal alkaline phosphatase was consistently elevated in MEC stained amniotic fluid. Hypoxia significantly increased plasma CRF (maternal, 82 ± 5 to 196 ± 14 pg/mL; fetal, 284 ± 15 to 1523 ± 185 pg/mL) and corticosterone (maternal, 417 ± 50 to 1150 ± 50 ng/mL; fetal, 96 ± 5 to 182 ± 10 ng/mL) compared with controls. In view of the known action of CRF in adult colonic motility, these results suggest that hypoxic stress-mediated MEC passage in term fetal rats is mediated by a CRF dependent pathway.

Lung development depends on endodermal Sonic Hedgehog (Shh) signaling to mesodermal Wingless/int/beta catenin (Wnt/catenin), followed by parathyroid hormone–related protein (PTHrP) signaling from endoderm to mesoderm. Fluid distension of fetal rat lung explants up-regulates PTHrP signaling and down-regulates Shh/Wnt/catenin signaling, marked by decreases in Patched, Gli, Frizzled, and Dishevelled, inducing fibroblast triglyceride uptake, type II cell saturated phosphatidylcholine, and surfactant protein-B expression. Bumetanide, which inhibits fluid distension, blocked down-regulation of the Shh/Wnt/catenin pathway and up-regulation of the PTHrP pathway, whereas PTHrP (1–34, 5 × 10−7M) treatment overcame bumetanide inhibition, and the PTHrP receptor antagonist PTHrP (7–34) amide (5 × 10−6M) mimicked bumetanide, indicating that PTHrP signaling mediates fluid distension-induced alveolar differentiation. Fetal rat lung explant automaturation was characterized by decreased Wnt/catenin signaling and increased PTHrP/PTHrP receptor signaling, up-regulating fibroblast-specific adipocyte differentiation related protein (ADRP) and peroxisome proliferator–activated receptor gamma. Wnt/catenin agonists (LiCl or SB415268) maintained Shh/Wnt/catenin signaling, blocking spontaneous up-regulation of the PTHrP pathway, whereas PTHrP or cAMP down-regulated Shh/Wnt/catenin signaling and stimulated PTHrP signaling for fibroblast and type II cell differentiation. This is the first evidence that alveolar fluid distension is an organizing principle for PTHrP signaling down-regulation of the Shh/Wnt/catenin pathway.

Lung development depends on endodermal Sonic Hedgehog (Shh) signaling to mesodermal Wingless/int/beta catenin (Wnt/ßcatenin), followed by parathyroid hormone–related protein (PTHrP) signaling from endoderm to mesoderm. Fluid distension of fetal rat lung explants up-regulates PTHrP signaling and down-regulates Shh/Wnt/ßcatenin signaling, marked by decreases in Patched, Gli, Frizzled, and Dishevelled, inducing fibroblast triglyceride uptake, type II cell saturated phosphatidylcholine, and surfactant protein-B expression. Bumetanide, which inhibits fluid distension, blocked down-regulation of the Shh/Wnt/ßcatenin pathway and up-regulation of the PTHrP pathway, whereas PTHrP (1–34, 5 × 10-7M) treatment overcame bumetanide inhibition, and the PTHrP receptor antagonist PTHrP (7–34) amide (5 × 10-6M) mimicked bumetanide, indicating that PTHrP signaling mediates fluid distension-induced alveolar differentiation. Fetal rat lung explant automaturation was characterized by decreased Wnt/ßcatenin signaling and increased PTHrP/PTHrP receptor signaling, up-regulating fibroblast-specific adipocyte differentiation related protein (ADRP) and peroxisome proliferator–activated receptor gamma. Wnt/ßcatenin agonists (LiCl or SB415268) maintained Shh/Wnt/ßcatenin signaling, blocking spontaneous up-regulation of the PTHrP pathway, whereas PTHrP or cAMP down-regulated Shh/Wnt/ßcatenin signaling and stimulated PTHrP signaling for fibroblast and type II cell differentiation. This is the first evidence that alveolar fluid distension is an organizing principle for PTHrP signaling down-regulation of the Shh/Wnt/ßcatenin pathway.

Since parathyroid hormone-related protein (PTHrP) secreted by pulmonary alveolar type II cells is a key physiologic paracrine factor in maintaining alveolar homeostasis, we hypothesized that its levels in the tracheal aspirates (TA) of ventilated very low birth weight infants (VLBWI) would correlate with the development of bronchopulmonary dysplasia (BPD). Therefore, we examined whether TA PTHrP content during the first week of life correlates with the later development of BPD. Forty VLBWI birth weight, 943 ± 302 g (mean ± SD); gestational age, 27 ± 2 wk; 21 males and 19 females, who were ventilated for respiratory distress syndrome, were studied. The TA were collected once daily until the infants were extubated and immediately frozen at –70°C for subsequent assays for PTHrP and matrix metalloproteinase-8 (MMP-8), a previously described, nonspecific TA biomarker for BPD. The levels of these proteins were correlated with the later development of BPD. PTHrP in the TA during the first week of life was significantly lower in those infants who developed BPD (12/40) than among those who did not (28/40). The PTHrP levels also correlated with the duration of mechanical ventilation needed in these infants. In contrast, MMP-8 levels did not correlate with BPD. We conclude that lower TA PTHrP content during the first week of life in ventilated VLBWI inversely correlates with prolonged ventilation and the later development of BPD.

Since parathyroid hormone-related protein (PTHrP) secreted by pulmonary alveolar type II cells is a key physiologic paracrine factor in maintaining alveolar homeostasis, we hypothesized that its levels in the tracheal aspirates (TA) of ventilated very low birth weight infants (VLBWI) would correlate with the development of bronchopulmonary dysplasia (BPD). Therefore, we examined whether TA PTHrP content during the first week of life correlates with the later development of BPD. Forty VLBWI [birth weight, 943 ± 302 g (mean ± SD); gestational age, 27 ± 2 wk; 21 males and 19 females], who were ventilated for respiratory distress syndrome, were studied. The TA were collected once daily until the infants were extubated and immediately frozen at –70°C for subsequent assays for PTHrP and matrix metalloproteinase-8 (MMP-8), a previously described, nonspecific TA biomarker for BPD. The levels of these proteins were correlated with the later development of BPD. PTHrP in the TA during the first week of life was significantly lower in those infants who developed BPD (12/40) than among those who did not (28/40). The PTHrP levels also correlated with the duration of mechanical ventilation needed in these infants. In contrast, MMP-8 levels did not correlate with BPD. We conclude that lower TA PTHrP content during the first week of life in ventilated VLBWI inversely correlates with prolonged ventilation and the later development of BPD.

We studied the effects of hypoxia on cerebral cortical and intestinal perfusion and metabolism in normocythemic hyperviscous newborn pigs. Seven pigs were made hyperviscous by an injection of cryoprecipitate, increasing viscosity from 5.8 ± 0.9 to 9.0 ± 1.2 (SD) cycles/s. Six normoviscous pigs received 0.9% NaCl. Reducing the inspired O2decreased the arterial O2content (CaO2) from 9.5 ± 1.6 to 3.6 ± 1.3 ml O2/100 ml. Increases in brain and decreases in gastrointestinal blood flow at the lowerCaO2values were similar between the groups. During hypoxia, blood flow to stomach, distal intestinal mucosa, and large intestines was lower (−50, −23, and −28%, respectively) in the hyperviscous than normoviscous group. At the lower CaO2values, cerebral cortical vascular resistance decreased in both groups and intestinal vascular resistance increased (+257%) in the hyperviscous but not in the normoviscous group. During hypoxia, systemic oxygen delivery decreased, extraction increased, and uptake did not change; cerebral cortical O2delivery, extraction, and uptake did not change; and intestinal O2delivery decreased, extraction increased, and uptake did not change in both groups. Our study demonstrated that 1) during hypoxia, increases in systemic O2extraction compensated for decreases in delivery and systemic uptake did not change; vasodilation sustained cerebral cortical O2delivery and preserved metabolism; increases in intestinal oxygen extraction offset decreases in delivery and uptake was preserved; and 2)nonpolycythemic hyperviscosity did not have a major influence on cardiovascular or metabolic responses to hypoxia, except for modest effects on intestinal resistance and perfusion to certain gastrointestinal regions. We conclude that, under normocythemic conditions, a moderate increase in viscosity does not have a major impact on hemodynamic or metabolic adjustments to hypoxia in newborn pigs.

We evaluated a new method of monitoring cerebral blood flow velocity (CBFV) and described changes in CBFV in relation to central apnea in 17 healthy term infants. The area under the velocity curve during apnea did not change, whereas area under the velocity curve per the waveform showed a significant difference, suggesting that stability is maintained through an increase in CBFV with each heartbeat. The maintenance of cerebral hemodynamics during isolated central apnea supports the assumption that these episodes are benign. (J PEDIATR1995;126:979-82)

To examine the influence of sleep state, respiratory pattern, and ventilation on cyclical fluctuations (CF) in cerebral blood flow (CBF) velocity (CBFV), we studied 21 ‘healthy’ preterm infants: birth weight 1,790 ± 162 g (SEM), study weight 1,960 ± 165 g, gestational age 32 ± 1 weeks, postnatal age 20 ± 4 (range 8–57) days. The CBFV was measured using on-line pulsed Doppler ultrasound by insonating the middle cerebral artery. Breathing was measured using a flow through system. The sleep state was monitored according to conventional criteria. Three hundred and seventy-five epochs of 1 min each were analyzed; 207 during quiet sleep (QS) and 168 during rapid eye movement (REM) sleep. CFs in CBFV were detected in all babies. The frequency of CF ranged from 0.5 to 6 cycles/min. The proportion of epochs showing CF was similar during both sleep states (56% QS vs. 59% REM; p = NS). Although the mean CBFV (cm/s) was similar in these two sleep states, the mean coefficient of variation, a measure of CF amplitude, was significantly higher during REM as compared with QS (6 ± 0.5 vs. 4.3 ± 0.2%; p < 0.05). Similarly, the mean CBFVs were similar with various respiratory patterns, but the coefficient of variation was significantly higher in periodic and apneic patterns as compared with regular and irregular respiratory patterns (5.6 ± 0.6% periodic, 5.6 ± 0.3% apneic, 3.6 ± 0.3% regular, and 4.1 ± 0.5% irregular; p < 0.05). The amplitude of CF was associated with the variability of the heart rate (p < 0.05), but not with the variability of the respiratory measurements. These findings suggest: (1) REM sleep is associated with a greater CBF variability than QS, and (2) periodic and apneic breathing are associated with a greater CBF variability than regular or irregular breathing. We speculate that sleep state and respiratory pattern do not determine but modulate the CBF. Our data suggest that in studies involving interpretation of CBFV data using the Doppler technique, breathing patterns should be taken into account in addition to sleep state.