Perinatal adaptation in mammals: the impact of metabolic rate

Mammalian birth is accompanied by profound changes in metabolic rate that can be described in terms of body size relationship (Kleiber's rule). Whereas the fetus, probably as an adaptation to the low intrauterine pO2, exhibits an "inappropriately" low, adult-like specific metabolic rate, the term neonate undergoes a rapid metabolic increase up to the level to be expected from body size. A similar, albeit slowed, "switching-on" of metabolic size allometry is found in human preterm neonates whereas animals that are normally born in a very immature state are able to retard or even suppress the postnatal metabolic increase in favor of weight gain and O2 supply. Moreover, small immature mammalian neonates exhibit a temporary oxyconforming behavior which enhances their hypoxia tolerance, yet is lost to the extent by which the size-adjusted metabolic rate is "locked" by increasing mitochondrial density. Beyond the perinatal period, there are no other deviations from metabolic size allometry among mammals except in hibernation where the temporary "switching-off" of Kleiber's rule is accompanied by a deep reduction in tissue pO2. This gives support to the hypothesis that the postnatal metabolic increase represents an "escape from oxygen" similar to the evolutionary roots of mitochondrial respiration, and that the overall increase in specific metabolic rate with decreasing size might contribute to prevent tissues from O2 toxicity.

Evidence and structural mechanism for late lung alveolarization

According to the current view, the formation of new alveolar septa from preexisting ones ceases due to the reduction of a double- to a single-layered capillaries network inside the alveolar septa (microvasculature maturation postnatal days 14-21 in rats). We challenged this view by measuring stereologically the appearance of new alveolar septa and by studying the alveolar capillary network in three-dimensional (3-D) visualizations obtained by high-resolution synchrotron radiation X-ray tomographic microscopy. We observed that new septa are formed at least until young adulthood (rats, days 4-60) and that roughly half of the new septa are lifted off of mature septa containing single-layered capillary networks. At the basis of newly forming septa, we detected a local duplication of the capillary network. We conclude that new alveoli may be formed in principle at any time and at any location inside the lung parenchyma and that lung development continues into young adulthood. We define two phases during developmental alveolarization. Phase one (days 4-21), lifting off of new septa from immature preexisting septa, and phase two (day 14 through young adulthood), formation of septa from mature preexisting septa. Clinically, our results ask for precautions using drugs influencing structural lung development during both phases of alveolarization.

Differential distribution of stem cells in the auditory and vestibular organs of the inner ear

The adult mammalian cochlea lacks regenerative capacity, which is the main reason for the permanence of hearing loss. Vestibular organs, in contrast, replace a small number of lost hair cells. The reason for this difference is unknown. In this work we show isolation of sphere-forming stem cells from the early postnatal organ of Corti, vestibular sensory epithelia, the spiral ganglion, and the stria vascularis. Organ of Corti and vestibular sensory epithelial stem cells give rise to cells that express multiple hair cell markers and express functional ion channels reminiscent of nascent hair cells. Spiral ganglion stem cells display features of neural stem cells and can give rise to neurons and glial cell types. We found that the ability for sphere formation in the mouse cochlea decreases about 100-fold during the second and third postnatal weeks; this decrease is substantially faster than the reduction of stem cells in vestibular organs, which maintain their stem cell population also at older ages. Coincidentally, the relative expression of developmental and progenitor cell markers in the cochlea decreases during the first 3 postnatal weeks, which is in sharp contrast to the vestibular system, where expression of progenitor cell markers remains constant or even increases during this period. Our findings indicate that the lack of regenerative capacity in the adult mammalian cochlea is either a result of an early postnatal loss of stem cells or diminishment of stem cell features of maturing cochlear cells.

Rapid diagnosis of experimental meningitis by bacterial heat production in cerebrospinal fluid

BACKGROUND: Calorimetry is a nonspecific technique which allows direct measurement of heat generated by biological processes in the living cell. We evaluated the potential of calorimetry for rapid detection of bacterial growth in cerebrospinal fluid (CSF) in a rat model of bacterial meningitis. METHODS: Infant rats were infected on postnatal day 11 by direct intracisternal injection with either Streptococcus pneumoniae, Neisseria meningitidis or Listeria monocytogenes. Control animals were injected with sterile saline or heat-inactivated S. pneumoniae. CSF was obtained at 18 hours after infection for quantitative cultures and heat flow measurement. For calorimetry, 10 microl and 1 microl CSF were inoculated in calorimetry ampoules containing 3 ml trypticase soy broth (TSB). RESULTS: The mean bacterial titer (+/- SD) in CSF was 1.5 +/- 0.6 x 108 for S. pneumoniae, 1.3 +/- 0.3 x 106 for N. meningitidis and 3.5 +/- 2.2 x 104 for L. monocytogenes. Calorimetric detection time was defined as the time until heat flow signal exceeded 10 microW. Heat signal was detected in 10-microl CSF samples from all infected animals with a mean (+/- SD) detection time of 1.5 +/- 0.2 hours for S. pneumoniae, 3.9 +/- 0.7 hours for N. meningitidis and 9.1 +/- 0.5 hours for L. monocytogenes. CSF samples from non-infected animals generated no increasing heat flow (<10 microW). The total heat was the highest in S. pneumoniae ranging from 6.7 to 7.5 Joules, followed by L. monocytogenes (5.6 to 6.1 Joules) and N. meningitidis (3.5 to 4.4 Joules). The lowest detectable bacterial titer by calorimetry was 2 cfu for S. pneumoniae, 4 cfu for N. meningitidis and 7 cfu for L. monocytogenes. CONCLUSION: By means of calorimetry, detection times of <4 hours for S. pneumoniae and N. meningitidis and <10 hours for Listeria monocytogenes using as little as 10 microl CSF were achieved. Calorimetry is a new diagnostic method allowing rapid and accurate diagnosis of bacterial meningitis from a small volume of CSF.

Regulation of fetal growth: consequences and impact of being born small

The first trimester of pregnancy is the time during which organogenesis takes place and tissue patterns and organ systems are established. In the second trimester the fetus undergoes major cellular adaptation and an increase in body size, and in the third trimester organ systems mature ready for extrauterine life. In addition, during that very last period of intrauterine life there is a significant increase in body weight. In contrast to the postnatal endocrine control of growth, where the principal hormones directly influencing growth are growth hormone (GH) and the insulin-like growth factors (IGFs) via the GH-IGF axis, fetal growth throughout gestation is constrained by maternal factors and placental function and is coordinated by growth factors. In general, growth disorders only become apparent postnatally, but they may well be related to fetal life. Thus, fetal growth always needs to be considered in the overall picture of human growth as well as in its metabolic development.

Neonatological and pulmonological management of bilateral pulmonary sequestration in a neonate

BACKGROUND: Bronchopulmonary sequestration is a lung malformation characterized by nonfunctioning lung tissue without primary communication with the tracheobronchial tree. Intrauterine complications such as mediastinal shift, pleural effusion or fetal hydrothorax can be present. We present the case of a newborn with bilateral intralobar pulmonary sequestration. METHODS: Prenatal ultrasonography in a primigravida at 20 weeks of gestation revealed echogenic masses in the right fetal hemithorax with mediastinal shift towards the left side. Serial ultrasound confirmed persistence of the lesion with otherwise appropriate fetal development. Delivery was uneventful and physical examination revealed an isolated intermittent tachypnea. Chest CT scan and CT angiography showed a bilateral intrathoracic lesion with arterial supply from the aorta. Baby lung function testing suggested possible multiple functional compartments. RESULTS: Right and left thoracotomy was performed at the age of 7 months. A bilateral intralobar sequestration with vascularisation from the aorta was resected. Pathological and histological examination of the resected tissue confirmed the surgical diagnosis. At the age of 24 months, the child was doing well without pulmonary complications. CONCLUSIONS: Bilateral pulmonary sequestration requires intensive prenatal and postnatal surveillance. Though given the fact of a bilateral pulmonary sequestration, postnatal outcome showed similar favourable characteristics to an unilateral presentation. Baby lung function testing could provide additional information for optimal postnatal management and timing of surgical intervention.

Developmental alveolarization of the mouse lung

Postnatal lung development is not well characterized in mice, especially the time point when alveolarization is completed. Using the total length and the length density of the free septal edge as measured for the formation of new septa, we followed alveolarization throughout postnatal lung development (days 2-125). Furthermore, the alveolar surface area was estimated. The formation of new septa was observed until day 36. Approximately 10% of the septa present in adult mice were formed prenatally by branching morphogenesis, approximately 50% were generated postnatally before and approximately 40% after maturation of the alveolar microvasculature. Approximately 5% of the alveolar surface area present during adulthood was present before alveolarization started, approximately 55% was formed during alveolarization (days 4-36) and approximately 40% afterward due to growth processes. We conclude that alveolarization continues until young adulthood and that the maturation of the alveolar microvasculature does not preclude further alveolarization.

Impairment of gastric acid secretion and increase of embryonic lethality in Foxq1-deficient mice

The mouse Foxq1 gene, also known as Hfh1, encodes a winged helix/forkhead transcription factor. In adult mice, Foxq1 is highly expressed in kidney and stomach. Here, we report that Foxq1 is expressed during prenatal and postnatal stomach development and the transcripts are restricted to acid secreting parietal cells. Mice homozygous for a deletion of the Foxq1 locus on a 129/Sv x C57BL/6J hybrid genetic background display variable phenotypes consistent with requirement of the gene during embryogenesis. Approximately 50% of Foxq1-/- embryos die in utero. Surviving homozygous mutants are normal and fertile, and have a silky shiny coat. Although the parietal cell development is not affected in the absence of Foxq1, there is a lack of gastric acid secretion in response to various secretagogue stimuli. Ultrastructural analysis suggests that the gastric acid secretion defect in Foxq1-deficient mice might be due to impairment in the fusion of cytoplasmic tubulovesicles to the apical membrane of secretory canaliculi.

Perinatal stem-cell and gene therapy for hemoglobinopathies

Most genetic diseases of the lymphohematopoietic system, including hemoglobinopathies, can now be diagnosed early in gestation. However, as yet, prenatal treatment is not available. Postnatal therapy by hematopoietic stem cell (HSC) transplantation from bone marrow, mobilized peripheral blood, or umbilical cord blood is possible for several of these diseases, in particular for the hemoglobinopathies, but is often limited by a lack of histocompatible donors, severe treatment-associated morbidity, and preexisting organ damage that developed before birth. In-utero transplantation of allogeneic HSC has been performed successfully in various animal models and recently in humans. However, the clinical success of this novel treatment is limited to diseases in which the fetus is affected by severe immunodeficiency. The lack of donor cell engraftment in nonimmunocompromised hosts is thought to be due to immunologic barriers, as well as to competitive fetal marrow population by host HSCs. Among the possible strategies to circumvent allogeneic HLA barriers, the use of gene therapy by genetically corrected autologous HSCs in the fetus is one of the most promising approaches. The recent development of strategies to overcome failure of efficient transduction of quiescent hematopoietic cells using new vector constructs and transduction protocols opens new perspectives for gene therapy in general, as well as for prenatal gene transfer in particular. The fetus might be especially susceptible for successful gene therapy approaches because of the developing, expanding hematopoietic system during gestation and the immunologic naiveté early in gestation, precluding immune reaction towards the transgene by inducing tolerance. Ethical issues, in particular regarding treatment safety, must be addressed more closely before clinical trials with fetal gene therapy in human pregnancies can be initiated.

Levoatrial cardinal vein in mitral atresia and closed foramen ovale: prenatal diagnosis and perinatal management

A levoatrial cardinal vein is a rare cardiovascular anomaly that may be present in malformed hearts with severe left heart obstruction and restrictive interatrial communication. We report the prenatal diagnosis at 23 weeks of a fetus with mitral atresia, double-outlet right ventricle, premature closure of the foramen ovale and a levoatrial cardinal vein draining into the innominate vein. In a prior examination performed elsewhere the levoatrial cardinal vein had been interpreted as an aortic arch perfused retrogradely, and hypoplastic left heart syndrome with aortic atresia had been diagnosed. Prenatal management, induction at 38 weeks and postnatal examinations and treatment are reported. To the best of our knowledge, this is the first reported prenatal diagnosis of this embryological vessel, presenting a potential pitfall for prenatal echocardiography.

Spindle burst like spike discharge oscillations in organotypic cultures of neonatal rat cortex

Early network oscillations and spindle bursts are typical patterns of spontaneous rhythmic activity in cortical networks of neonatal rodents in vivo and in vitro. The latter can also be triggered in vivo by stimulation of afferent inputs. The mechanisms underlying such oscillations undergo profound developmental changes in the first postnatal weeks. Their possible role in cortical development is postulated but not known in detail. We have studied spontaneous and evoked patterns of activity in organotypic cultures of slices from neonatal rat cortex grown on multielectrode arrays (MEAs) for extracellular single- and multi-unit recording. Episodes of spontaneous spike discharge oscillations at 7 - 25 Hz lasting for 0.6 - 3 seconds appeared in about half of these cultures spontaneously and could be triggered by electrical stimulation of few distinct electrodes. These oscillations usually covered only restricted areas of the slices. Besides oscillations, single population bursts that spread in a wavelike manner over the whole slice also appeared spontaneously and were triggered by electrical stimulation. In most but not all cultures, population bursts preceded the oscillations. Both population bursts and spike discharge oscillations required intact glutamatergic synaptic transmission since they were suppressed by the AMPA/kainate glutamate receptor antagonist CNQX. The NMDA antagonist d-APV suppressed the oscillations but not the population bursts, suggesting an involvement of NMDA receptors in the oscillations. These findings show that spindle burst like cortical rhythms are reproduced in organotypic cultures of neonatal cortex. The culture model thus allows investigating the role of such rhythms in cortical circuit formation. Supported by SNF grant No. 3100A0-107641/1.

Prenatal diagnosis and treatment planning of congenital heart defects-possibilities and limits

BACKGROUND: Newborns with hypoplastic left heart syndrome (HLHS) or right heart syndrome or other malformations with a single ventricle physiology and associated hypoplasia of the great arteries continue to be a challenge in terms of survival. The vast majority of these forms of congenital heart defects relate to abnormal morphogenesis during early intrauterine development and can be diagnosed accurately by fetal echocardiography. Early knowledge of these conditions not only permits a better understanding of the progression of these malformations but encourages some researchers to explore new minimally invasive therapeutic options with a view to early pre- and postnatal cardiac palliation. DATA SOURCES: PubMed database was searched with terms of "congenital heart defects", "fetal echocardiography" and "neonatal cardiac surgery". RESULTS: At present, early prenatal detection has been applied for monitoring pregnancy to avoid intrauterine cardiac decompensation. In principle, the majority of congenital heart defects can be diagnosed by prenatal echocardiography and the detection rate is 85%-95% at tertiary perinatal centers. The majority, particularly of complex congenital lesions, show a steadily progressive course including subsequent secondary phenomena such as arrhythmias or myocardial insufficiency. So prenatal treatment of an abnormal fetus is an area of perinatal medicine that is undergoing a very dynamic development. Early postnatal treatment is established for some time, and prenatal intervention or palliation is at its best experimental stage in individual cases. CONCLUSION: The upcoming expansion of fetal cardiac intervention to ameliorate critically progressive fetal lesions intensifies the need to address issues about the adequacy of technological assessment and patient selection as well as the morbidity of those who undergo these procedures.

Reduced beta-cell mass and altered glucose sensing impair insulin-secretory function in betaIRKO mice

Pancreatic beta-cell-restricted knockout of the insulin receptor results in hyperglycemia due to impaired insulin secretion, suggesting that this cell is an important target of insulin action. The present studies were undertaken in beta-cell insulin receptor knockout (betaIRKO) mice to define the mechanisms underlying the defect in insulin secretion. On the basis of responses to intraperitoneal glucose, approximately 7-mo-old betaIRKO mice were either diabetic (25%) or normally glucose tolerant (75%). Total insulin content was profoundly reduced in pancreata of mutant mice compared with controls. Both groups also exhibited reduced beta-cell mass and islet number. However, insulin mRNA and protein were similar in islets of diabetic and normoglycemic betaIRKO mice compared with controls. Insulin secretion in response to insulin secretagogues from the isolated perfused pancreas was markedly reduced in the diabetic betaIRKOs and to a lesser degree in the nondiabetic betaIRKO group. Pancreatic islets of nondiabetic betaIRKO animals also exhibited defects in glyceraldehyde- and KCl-stimulated insulin release that were milder than in the diabetic animals. Gene expression analysis of islets revealed a modest reduction of GLUT2 and glucokinase gene expression in both the nondiabetic and diabetic mutants. Taken together, these data indicate that loss of functional receptors for insulin in beta-cells leads primarily to profound defects in postnatal beta-cell growth. In addition, altered glucose sensing may also contribute to defective insulin secretion in mutant animals that develop diabetes.

Effect of the NMDA-receptor antagonist dextromethorphan in infant rat pneumococcal meningitis

Excitatory amino acids (EAA) and particularly glutamate toxicity have been implicated in the pathogenesis of neuronal injury occurring in bacterial meningitis by activating the N-methyl-d aspartate (NMDA) receptor complex. Here, we evaluated the effect of adjuvant treatment with the antitussive drug dextromethorphan (DM), a non-competitive NMDA receptor antagonist with neuroprotective potential, in an infant rat model of pneumococcal meningitis. The experiments were carried out in postnatal day 6 (P6) and 11 (P11) animals. Pharmacokinetics of DM and its major metabolite dextrorphan (DO) were performed for dose finding. In our study, DM did not alter clinical parameters (clinical score, motor activity, incidence of seizures, spontaneous mortality) and cortical neuronal injury but increased the occurrence of ataxia (P<0.0001). When DM treatment was started at the time of infection (DM i.p. 15 mg/kg at 0, 4, 8 and 16 hours (h) post infection) in P11 animals, an aggravation of apoptotic neuronal death in the hippocampal dentate gyrus was found (P<0.05). When treatment was initiated during acute pneumococcal meningitis (DM i.p. 15 mg/kg at 12 and 15 h and 7.5 mg/kg at 18 and 21 h after infection), DM had no effect on the extent of brain injury but reduced the occurrence of seizures (P<0.03). We conclude that in this infant rat model of pneumococcal meningitis interference of the EEA and NMDA pathway using DM causes ataxia, attenuates epileptic seizures and increases hippocampal apoptosis, but is not effective in protecting the brain from injury.

Postoperative sepsis in infants below 6 months of age

BACKGROUND: Sepsis is a threatening postoperative complication especially in small infants. Regarding the advances in perinatal medicine, its incidence is unknown to date. We aimed to investigate the incidence, risk factors, laboratory findings and outcome of postoperative sepsis in infants younger than 6 months old. METHODS: We examined postoperative sepsis in babies below 6 months of age during a 4-year period at a tertiary pediatric institution. RESULTS: The rate of postoperative sepsis was 6.9%. Laparotomy with enterotomy, thoracotomy and diaphragmatic hernia repair (P<0.05, respectively) as well as low postnatal age and long operation time (P<0.001, respectively) were correlated with the incidence of sepsis. Significant independent predictors for the development of sepsis were the presence of a central venous catheter and perioperative antibiotic treatment (P<0.001, respectively). Coagulase negative Staphylococci were the major infecting organism associated with postoperative sepsis, accounting for 53% of monomicrobial infections. Complete blood counts with differential were not different between infants with sepsis and controls, who had undergone the same surgical procedures. Outcome was favorable in all cases; however, the length of hospital stay was significantly longer in sepsis patients (P<0.05). CONCLUSIONS: Postoperative sepsis syndrome is a frequent complication in infants below 6 months of age and causes significant prolongation of hospital stay. Adequate prevention and therapeutic strategies warrant further prospective investigations.