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Biomedical subjects

Michael Obladen

Publications and source records attributed to Michael Obladen.

At least 19 recordsLinked to original sources
PubMed2006

Maturation-dependent oligodendrocyte apoptosis caused by hyperoxia.

In the immature human brain, periventricular leukomalacia (PVL) is the predominant white matter injury underlying the development of cerebral palsy. PVL has its peak incidence during a well-defined period in human brain development (23-32 weeks postconceptional age) characterized by extensive oligodendrocyte migration and maturation. We hypothesized that the dramatic rise of oxygen tissue tension associated with mammalian birth and additional oxygen exposure of the preterm infant during intensive care may be harmful to immature oligodendrocytes (OLs). We therefore investigated the effects of hyperoxia on rat oligodendroglia cells in vitro and in vivo. Immature OLs (OLN-93), their progenitors [preoligodendrocytes (pre-OL)], and mature OLs were subjected to 80% hyperoxia (24-96 hr). Flow cytometry was used to assess cell death. Cell viability was measured by metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT). In addition, 6-day-old rat pups were subjected to 80% oxygen (24 hr) and then sacrificed, and their brains were processed for immunfluorescence staining. Apoptosis was detected at various stages (annexin-V, activated caspase-3) after 24-48 hr of incubation in 80% oxygen in pre- and immature OLs. Mature OLs were resistant to oxygen exposure. These results were confirmed by MTT assay. This cell death was blocked by administration of the pan-caspase inhibitor zVAD-fmk. Degeneration of OLs was confirmed in 7-day-old rat brains by positive staining for activated caspase-3. Hyperoxia triggers maturation-dependent apoptosis in immature and pre-OLs and involves caspase activation. This mechanism may be relevant to the white matter injury observed in infants born preterm.

Animals↗
PubMed2006

Genetic deafness in a preterm infant with a critical postnatal course.

OBJECTIVE: We present a case of deafness in a preterm infant with several predisposing factors of an acquired hearing impairment that, however, turned out to have a genetic cause. We describe the severe postnatal course and review the relevant literature. DESIGN: Case report. SETTING: University-based tertiary neonatal intensive care unit. PATIENT: Preterm infant (gestational age, 26/37; wks). MEASUREMENTS AND MAIN RESULTS: A preterm infant exhibited hearing impairment after a complicated clinical course with pneumothoraces, a hemodynamically relevant patent ductus arteriosus, treatment with potentially ototoxic drugs, intraventricular hemorrhage, and periventricular leukomalacia. Despite the absence of a family history for deafness, genetic testing was performed. Surprisingly, genetic analysis revealed the presence of two compound heterozygous mutations in the patient's GJB2 gene as the cause for his early-onset nonsyndromic deafness. CONCLUSION: To elucidate the nature of a hearing disorder, it is worthwhile to consider a genetic cause, despite the fact that it may seem unlikely in a severely sick preterm infant with numerous risk factors for a postnatally acquired hearing impairment and without a positive family history.

Connexin 26↗
PubMed2005

Urinary S-100B concentrations in term and preterm infants at risk for brain damage.

BACKGROUND: Elevated serum concentrations of S-100B, a 21-kDa protein expressed in astroglial cells, has been used to assess cerebral damage after head trauma, infection, ischemia, and perinatal asphyxia. OBJECTIVE: As S-100B is eliminated by the kidneys, we investigated the feasibility of measuring S-100B in urine of newborns with severe perinatal asphyxia, and in very low birth weight (VLBW) preterm infants at risk for neurodevelopmental impairment. METHODS: We first analyzed urine samples of 8 term or near-term newborns without major medical problems, followed by urine samples of 2 term newborns with severe birth asphyxia, and finally urine samples of 8 VLBW (gestational age 24-28 weeks) infants collected every 4 h for up to 10 days. RESULTS: Urinary S-100B concentrations in 8 term or near-term newborns without major medical problems were consistently <1 microg/l. In 2 term newborns with severe asphyxia (Apgar 0/0/0 and 0/2/4) who subsequently had widespread cerebral damage on magnetic resonance imaging, peak urinary S-100B concentrations on the first day of life were 28.1 and 28.4 microg/l, respectively. In 5/8 VLBW infants, urinary S-100B was> microg/l in samples obtained on the first day of life (range 1.2-44.9 microg/l, median 6.8 microg/l). Peak S-100B in urine samples collected during the first 12 h of life were negatively related to gestational age (R(s)=-0.882, p=0.009). Three of the 8 preterm infants had peak urinary concentrations>0 microg/l but neither ultrasound signs of brain damage nor neurodevelopmental delay at 1 year corrected age. CONCLUSIONS: The determination of urinary S-100B concentrations might be helpful in term infants with severe asphyxia, while high urinary S-100B concentrations in preterm infants are to be attributed to immaturity.

Brain↗
PubMed2005

Arthrogryposis multiplex with deafness, inguinal hernias, and early death: a family report of a probably autosomal recessive trait.

We report on three male newborn infants of a highly inbred Lebanese family presenting with a characteristic phenotype: arthrogryposis multiplex, deafness, large inguinal hernia, hiccup-like diaphragmatic contractions, and inability to suck, requiring nasogastric gavage feeding. All three boys died from respiratory failure during the first 3 months of life. Intra vitam or post mortem examinations revealed myopathic changes and elevated glycogen content of muscle tissue. This new syndrome is probably transmitted in an autosomal recessive mode, although X-linked inheritance cannot be excluded.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2005

Neuronal damage after moderate hypoxia and erythropoietin.

Both mild hypoxia and exogenous erythropoietin may protect the brain against subsequent severe hypoxia, and the conditioning effect of transient hypoxia is partly mediated by hypoxia-induced endogenous erythropoietin. We now observed in several experimental models that combining transient hypoxia and exogenous erythropoietin may cause neuronal damage. High-dose erythropoietin (40 IU/ml) profoundly impeded synaptic transmission of rat hippocampal slice cultures when used in conjunction with moderate hypoxia (10% O2 for two 8-h periods). Addition of erythropoietin increased viability of cultured rat embryonic cortical neurons at 21% O2 but decreased viability under hypoxic conditions (2% O2) in a dose-dependent fashion. Death of human neuronal precursor cells challenged by oxygen and glucose deprivation was increased by erythropoietin when cells were cultured under hypoxic but not under normoxic conditions. In neonatal rats exposed to moderate hypoxia plus erythropoietin, numbers of degenerating cerebral neurons were increased, as compared to controls or rats subjected to either hypoxia or erythropoietin alone. Thus, erythropoietin may aggravate rather than ameliorate neuronal damage when administered during transient hypoxia.

Age Factors↗
PubMed2005

History of surfactant up to 1980.

Remarkable insight into disturbed lung mechanics of preterm infants was gained in the 18th and 19th century by the founders of obstetrics and neonatology who not only observed respiratory failure but also designed devices to treat it. Surfactant research followed a splendid and largely logical growth curve. Pathological changes in the immature lung were characterized in Germany by Virchow in 1854 and by Hochheim in 1903. The Swiss physiologist von Neergard fully understood surfactant function in 1929, but his paper was ignored for 25 years. The physical properties of surfactant were recognized in the early 1950s from research on warfare chemicals by Pattle in Britain and by Radford and Clements in the United States. The causal relationship of respiratory distress syndrome (RDS) and surfactant deficiency was established in the USA by Avery and Mead in 1959. The Australian obstetrician Liggins induced lung maturity with glucocorticoids in 1972, but his discovery was not fully believed for another 20 years. A century of basic research was rewarded when Fujiwara introduced surfactant substitution in Japan in 1980 for treatment and prevention of RDS.

Animals↗
PubMed2005

Glutaric acid and its metabolites cause apoptosis in immature oligodendrocytes: a novel mechanism of white matter degeneration in glutaryl-CoA dehydrogenase deficiency.

Glutaryl-CoA dehydrogenase deficiency is an inherited metabolic disease characterized by elevated concentrations of glutaric acid (GA) and its metabolites glutaconic acid (GC) and 3-hydroxy-glutaric acid (3-OH-GA). Its hallmarks are striatal and cortical degeneration, which have been linked to excitotoxic neuronal cell death. However, magnetic resonance imaging studies have also revealed widespread white matter disease. Correspondingly, we decided to investigate the effects of GA, GC, and 3-OH-GA on the rat immature oligodendroglia cell line, OLN-93. For comparison, we also exposed the neuroblastoma line SH-SY5Y and the microglia line BV-2 to GA, GC, and 3-OH-GA. Cell viability was measured by metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium. Flow cytometry was used to assess apoptosis via annexin-V, anti-active caspase-3 antibody, and propidium iodide staining. GA, GC, and 3-OH-GA reduced OLN-93 oligodendroglia cell viability in a dose-dependent manner. Toxicity of GA, GC, and 3-OH-GA was abrogated by preincubation with the pan-caspase inhibitor z-VAD-fmk. Apoptosis but not necrosis was detected at various stages (early: annexin-V; effector: caspase-3) after 24-48 h of incubation with GA, GC, or 3-OH-GA in OLN-93 but not in neuroblastoma or microglia cells. OLN-93 lacked expression of N-methyl-d-aspartate receptors, making classical glutamatergic excitotoxicity an unlikely explanation for the selective toxicity of GA, GC, and 3-OH-GA for OLN-93 cells. GA, GC, and 3-OH-GA directly initiate the apoptotic cascade in oligodendroglia cells. This mechanism may contribute to the white matter damage observed in glutaryl-CoA dehydrogenase deficiency.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Caspase-1-processed interleukins in hyperoxia-induced cell death in the developing brain.

Infants born prematurely may develop neurocognitive deficits without an obvious cause. Oxygen, which is widely used in neonatal medicine, constitutes one possible contributing neurotoxic factor, because it can trigger neuronal apoptosis in the developing brain of rodents. We hypothesized that two caspase-1-processed cytokines, interleukin (IL)-1beta and IL-18, are involved in oxygen-induced neuronal cell death. Six-day-old Wistar rats or C57/BL6 mice were exposed to 80% oxygen for various time periods (2, 6, 12, 24, and 48 hours). Neuronal cell death in the brain, as assessed by Fluoro-Jade B and silver staining, peaked at 12 to 24 hours and was preceded by a marked increase in mRNA and protein levels of caspase 1, IL-1beta, IL-18, and IL-18 receptor alpha (IL-18Ralpha). Intraperitoneal injection of recombinant human IL-18-binding protein, a specific inhibitor of IL-18, attenuated hyperoxic brain injury. Mice deficient in IL-1 receptor-associated kinase 4 (IRAK-4), which is pivotal for both IL-1beta and IL-18 signal transduction, were protected against oxygen-mediated neurotoxicity. These findings causally link IL-1beta and IL-18 to hyperoxia-induced cell death in the immature brain. These cytokines might serve as useful targets for therapeutic approaches aimed at preserving neuronal function in the immature brain, which is exquisitely sensitive to a variety of iatrogenic measures including oxygen.

Animals↗
PubMed2004

Vascular endothelial growth factor and transforming growth factor-beta1 are highly expressed in the cerebrospinal fluid of premature infants with posthemorrhagic hydrocephalus.

The expression of specific growth factors such as vascular endothelial growth factor (VEGF) and transforming growth factor-beta1 (TGF-beta1) is of importance during brain development and in the pathogenesis of neurodegenerative disorders. VEGF and TGF-beta1 was studied in the cerebrospinal fluid (CSF) of neonates with posthemorrhagic hydrocephalus (PHHC) and nonhemorrhagic hydrocephalus. For determining the interference of inflammatory cytokine interaction with the expression of VEGF and TGF-beta1, IL-6 and IL-10 CSF concentrations were measured. Eighteen neonates who had PHHC and underwent serial reservoir puncture and nine neonates who had congenital nonhemorrhagic hydrocephalus (CHC) and underwent first shunt surgery were included in the study. CSF samples of 11 neonates with lumbar puncture for the exclusion of meningitis served as control subjects. VEGF, TGF-beta1, IL-6, and IL-10 concentrations in the CSF were measured by ELISA technique. VEGF concentrations in the CSF of patients with PHHC were significantly higher (median: 377 pg/mL; range: 101-1301 pg/mL) when compared with patients with CHC (median: 66 pg/mL; range: 3-1991; p < 0.001) and control subjects (median: 2 pg/mL; range: 0-12 pg/mL; p < 0.0001). TGF-beta1 CSF concentrations did not differ from control infants in all groups. Median IL-6 and IL-10 concentrations in the CSF were found to be low in all patient groups. Increased release of VEGF in the CSF of neonates with PHHC and nonhemorrhagic hydrocephalus may serve as an indicator of brain injury from progressive ventricular dilation. TGF-beta1 CSF concentrations are not elevated in the phase of acute fibroproliferative reactions in patients with PHHC.

Biomarkers↗
PubMed2004

Intrauterine onset of acute neuropathic type 2 Gaucher disease: identification of a novel insertion sequence.

A subset of patients with type 2 Gaucher disease is characterized by intrauterine onset of rapidly progressive neuropathic disease, arthrogryposis, hydrops fetalis and in some cases restrictive dermopathy. beta-Glucocerebrosidase (beta-glucosidase) activity is usually low or undetectable. In most cases death ensues either in-utero or within hours or days after birth. We report on an infant born to non-consanguineous parents of Caucasian origin presenting at birth with hydrops, arthrogryposis, severe respiratory distress, hepatosplenomegaly, and liver failure. Death occurred within several hours after delivery and autopsy revealed typical Gaucher cells in multiple organs in combination with severe apoptotic neurodegeneration throughout the brain. beta-Glucocerebrosidase activity was 1% of the norm in fibroblasts and a novel heterozygous insertion c.1515_1516insAGTGAGGGCAAT was identified by genomic sequencing and an insertion-specific seminested PCR. In addition, molecular studies revealed a previously described in type 1 Gaucher disease missense mutation c.476G --> A which results in a heterozygous substitution of R120Q. Our observations confirm considerable genotypic heterogeneity in patients with type 2 Gaucher disease. The transheterozygous combination of a mutation, previously described in type 1 Gaucher disease, together with a newly identified insertion may result in this severe phenotype.

Age of Onset↗
PubMed2004

Nutrition of very low birth weight infants fed human milk with or without supplemental trace elements: a randomized controlled trial.

BACKGROUND: Very low birth weight infants (<1500 g) have high nutritional needs. Deficiencies of minerals, trace elements (especially zinc) may develop as a result of rapid growth, low body stores and low content of these substances in human milk We hypothesized that fortification of human milk might prevent deficiencies. METHODS: Prospective, randomized trial to evaluate mineral, trace element, thyroid status and growth of infants fed human milk fortified with different amounts of calcium, phosphorus and protein, with (BMF) or without (FM 85) trace elements. Sixty-two infants, 1000 to 1499 g birth weight, were randomized. Minerals and trace elements in serum, red blood cells and human milk and alkaline phosphatase activity, TSH, T4 and FT4 in serum were measured once until the fifth day and at 3 and 6 weeks of life. Clinical course and anthropometric measurements were recorded. RESULTS: Intake of zinc, copper, manganese, calcium, phosphorus and magnesium was higher in the BMF group (P < 0.001). Serum zinc concentrations <0.49 mg/L occurred in 12% of the FM 85 group and 7% of the BMF group at 6 weeks (not significant). Median alkaline phosphatase activity was 436/379 IU/L in the FM 85/BMF group at 6 weeks (P < 0.01). The FM 85 group showed a higher weight gain (P < 0.05), possibly because of higher caloric (P < 0.01) and protein intake (P < 0.05) at 3 weeks. CONCLUSIONS: Zinc deficiency was rare. Elevated intake of calcium, phosphorus and zinc was associated with lower serum alkaline phosphatase activity but did not influence serum zinc concentration.

Alkaline Phosphatase↗
PubMed2003

Soluble Fas (CD95/Apo-1), soluble Fas ligand, and activated caspase 3 in the cerebrospinal fluid of infants with posthemorrhagic and nonhemorrhagic hydrocephalus.

Hydrocephalus may result in loss of tissue associated with neuronal degeneration, axonal damage, and reactive gliosis. The soluble form of the anti-apoptotic regulator Fas (sFas) and the pro-apoptotic factors soluble FasL (sFasL) and activated caspase 3 were studied in the cerebrospinal fluid of infants with hydrocephalus. Fifteen preterm infants with posthemorrhagic hydrocephalus undergoing serial reservoir puncture and seven term or near-term infants with nonhemorrhagic hydrocephalus and shunt surgery were included in the study. Twenty-four age-matched patients with lumbar puncture for the exclusion of meningitis served as controls. Elevated levels of sFas were observed in infants with posthemorrhagic hydrocephalus [median (range), 131 ng/mL (51-279 ng/mL)] and in nonhemorrhagic hydrocephalus [127 ng/mL (35-165 ng/mL)]. sFas concentrations were highest in a subgroup of eight patients with posthemorrhagic hydrocephalus developing periventricular leukomalacia [164 ng/mL (76-227 ng/mL)]. In contrast, in 24 control infants, sFas was low, in 15 cases below detection limit (0.5 ng/mL) and in nine cases, 24 ng/mL (20-43 ng/mL). sFasL and activated caspase 3 did not differ from control infants in all groups of patients. Increased intrathecal release of sFas in the cerebrospinal fluid of infants with hydrocephalus may serve as an indicator of brain injury from progressive ventricular dilatation.

Apoptosis↗
PubMed2003

Hyperoxia causes inducible nitric oxide synthase-mediated cellular damage to the immature rat brain.

Relative hyperoxia is a condition frequently encountered in premature infants, either spontaneously or during treatment in the Neonatal Intensive Care Unit. The effects of high inspiratory oxygen concentrations on immature brain cells and their signaling cascades are largely unknown. The aim of the study was to investigate the effect of hyperoxia on the amount and topographic distribution of iNOS-expression (inducible nitric oxide synthase) in the immature rat brain, and to localize hyperoxia-induced formation of peroxynitrite as a potential marker of cellular damage to immature cerebral structures. Seven-day-old Wistar rat pups were exposed to >80% oxygen for 24 h and were then transcardially perfused. Following paraformaldehyde fixation, brains were paraffin-embedded and immunohistochemically stained for iNOS and nitrotyrosine. iNOS protein was quantified by Western blot; iNOS mRNA expression was studied by RT-PCR. Total brain iNOS mRNA was up-regulated, demonstrating a peak at 6 h following the onset of hyperoxia. Immunohistochemical staining was predominantly observed in microglial cells of hippocampus and frontal cortex with some iNOS reactivity in endothelial and perivascular cells. Nitrotyrosine staining was positive in apical dendrites of neurons in the frontal cortex. There was no positive staining for iNOS or nitrotyrosine in control animals. Hyperoxia causes iNOS mRNA and protein up-regulation in microglial cells of the immature rat brain. Positive neuronal nitrotyrosine staining indicates formation of peroxynitrite with potential deleterious effects for immature cellular structures in the neonatal brain.

Animals↗
PubMed2003

Predictive value of brain-specific proteins in serum for neurodevelopmental outcome after birth asphyxia.

Brain-specific proteins have been used to detect cerebral injury after birth asphyxia. Previous investigations suggest that serum protein S-100beta, brain-specific creatine kinase (CK-BB), and neuron-specific enolase (NSE) are capable of identifying patients with a risk of developing hypoxic-ischemic encephalopathy. Whether detection of elevated serum concentrations of these proteins reflects long-term neurodevelopmental impairment remains to be investigated. We examined serum protein S-100beta, NSE, and CK-BB at 2, 6, 12, and 24 h after birth in 29 asphyxiated infants and 20 control infants. Neurodevelopmental follow-up examinations were performed at 20 mo of age using the German revision of the Griffiths scales for developmental assessment. Elevated concentrations of serum protein S-100beta, NSE, and CK-BB within 24 h after asphyxia did not correlate with long-term neurodevelopmental delay. We conclude that serum protein S-100beta, NSE, and CK-BB, sampled on the first day of life, is of limited value in predicting severe brain damage after birth asphyxia.

Asphyxia Neonatorum↗
PubMed2002

Erythropoietin improves synaptic transmission during and following ischemia in rat hippocampal slice cultures.

Erythropoietin (EPO) prevents neuronal damage following ischemic, metabolic, and excitotoxic stress. In this study evoked extracellular field potentials (FP) were used to investigate the effect of EPO on synaptic transmission in hippocampal slice cultures. EPO treated cultured slices (40 units/ml for 48 h) showed significantly increased FP during and following oxygen and glucose deprivation compared with untreated control slices. The addition of the Jak2 inhibitor AG490 (50 microM for 48 h) blocked the EPO effect. These data suggest that EPO improves synaptic transmission during and following ischemia in hippocampal slice cultures.

Animals↗