Christian P. Speer

Recombinant human tumor necrosis factor α constricts pial arterioles and increases blood-brain barrier permeability in newborn piglets

Tumor necrosis factor alpha (TNF alpha) plays a significant role in the pathogenesis of central nervous system infections. We investigated the effect of intracisternal injection of recombinant human TNF alpha (50-50,000 IU) on pial vasoreactivity and blood-brain barrier permeability in newborn piglets. The cytokine administration resulted in arterial vasoconstrictions, blood-brain barrier opening for Na-fluorescein (mol. wt. 376 Da) and increased Na-fluorescein uptake in brain regions examined (parietal and occipital cortex, cerebellum, pons/medulla, periventricular white matter) in a dose-dependent manner. TNF alpha may be involved in the pathophysiology of neonatal brain injuries.

Effects of dexamethasone on chemotactic activity and inflammatory mediators in tracheobronchial aspirates of preterm infants at risk for chronic lung disease

To evaluate the effects of dexamethasone on pulmonary inflammation and permeability in preterm infants at high risk for chronic lung disease (birth weight < 1200 gm), we assessed tracheobronchial aspirate fluid for chemotactic activity and concentrations of mediators of inflammation. In a prospective study, 21 infants still undergoing mechanical ventilation at day 10 of postnatal age who required a fraction of inspired oxygen > or = 0.3, a peak inspiratory pressure > or = 16 cm H2O, or both were randomly assigned to treatment with dexamethasone at day 10 (early treatment group, n = 10) or day 16 (late treatment group, n = 11). The groups were compared with respect to all measurements on day 15; the late treatment group served as a control group. Additionally, the effects of dexamethasone within both groups were evaluated. In the early treatment group, the chemotactic response of peripheral blood neutrophils exposed to tracheobronchial aspirate fluid was significantly reduced 5 days after initiation of dexamethasone treatment compared with pretreatment values of the late treatment group (median (25th to 75th percentile): migratory distance before dexamethasone, 149 microns (140 to 173 microns); after dexamethasone, 81 microns (68 to 114 microns); p < 0.01). In addition, the following values were decreased after dexamethasone therapy in the early treatment group: number of neutrophils in tracheobronchial aspirate fluid (p < 0.05), and concentrations of leukotriene B4 (p < 0.01), interleukin-1 (p < 0.01), elastase-alpha 1-proteinase inhibitor (p < 0.01), and albumin (p < 0.01). Free elastase activity was found in only two infants; detectable activity of protective alpha 1-proteinase inhibitor was present in the others. Analysis of dexamethasone effects within the groups showed that all measurements were significantly decreased after both the early and the late treatment regimens, with the exception of leukotriene B4 and interleukin-1, which declined only after early dexamethasone treatment. Our results indicate that the pulmonary inflammatory response and microvascular permeability are decreased by dexamethasone, which affects the release of inflammatory mediators and neutrophil influx into the airways of preterm infants who require mechanical ventilation.

Elastase-α1-proteinase inhibitor in early diagnosis of neonatal septicemia

predominant increase in tHb suggest a respiratory origin. Thus we hypothesize that with straining, as during a Valsalva maneuver, the increase in intrathoracic pressure compresses veins and impedes cerebral venous return. Increased pressure within the cerebral venous circulation then could lead to microcirculatory congestion and altered blood flow patterns. The marked increase in cerebral blood volume, demonstrated here in preterm infants with hypertensive peaks, provides a possible explanation for the increased incidence of intraventricular hemorrhage in this population. 8 The associated repeated shifts to greater cyt aa3 reduction raises an additional concern about the adequacy and constancy of cellular oxygenation during these periods of blood pressure instability.

Elastase-α1-proteinase inhibitor: An early indicator of septicemia and bacterial meningitis in children

In 26 infants and children with septicemia or bacterial meningitis, significantly elevated plasma levels of elastase-α 1 -proteinase inhibitor (E-α 1 -Pl) were present at time of recognition of infection, even in those patients with neutropenia (range of reference values: 25 to 190 μg/L, n=142; patients: 444 to 2049 μg/L, n=26). After initiation of therapy, normalization of E-α 1 -Pl levels was observed in all patients who recovered from infection. In addition, 18 of 19 children with bacterial meningitis had increased cerebrospinal fluid concentrations of E-α 1 -Pl above the range of normal (range of reference values: 0 to 39 μg/L, n=62; patients: 30 to 3490 μg/L, n=19); concentrations of E-α 1 -Pl in bacterial meningitis were significantly increased when compared with those in aseptic meningitis (range 25 to 194 μg/L; n=15). In 30 patients with local bacterial infections (pneumonia, urinary tract infections, etc.), E-α 1 -Pl was also elevated. These data suggest that E-α 1 -Pl is a sensitive indicator of systemic and local bacterial infection in childhood.

Escherichia coli 0111 B4 Lipopolysaccharide Given Intracisternally Induces Blood-Brain Barrier Opening during Experimental Neonatal Meningitis in Piglets

ABSTRACT: Neonatal bacterial meningitis remains a life-threatening infection, and severe neurologic sequelae may be left in survivors as well. The goal of the study was to develop and characterize a porcine model of the disease with intravital observation of the permeability changes in cerebral microvessels. Eighteen newborn piglets were given doses of 0 ng (group 1), 20 ng (group 2), and 200 ng (group 3) of Escherichia coli 0111 B4 endotoxin (LPS) intracisternally (n = 6 in each group). Cardiovascular parameters were without changes, but a compensated metabolic acidosis occurred in group 3 4 h after LPS injection. Using the open cranial window technique combined with fluorescence excitation, there was no blood-brain barrier leakage in pial-arachnoid microvessels for sodium fluorescein during the 4 h of experiments in group 1 piglets, whereas spotty extravasations occurred in group 2 and in group 3 after the LPS injections (70.5 ± 10.5 and 55.2 ± 4.1 min, respectively, mean ± SEM). A dose-dependent increase in sodium fluorescein uptake in brain regions examined (parietal and occipital cortex, cerebellum, and periventricular white matter) was also found by fluorescence spectropho-tometry. LPS-treated piglets had developed pleocytosis. Four h after the challenge, the white blood cell counts in cerebrospinal fluid were (mean ± SD): group 1, 8.2 ± 7.6 μL-1; group 2, 453 ± 703 μL-1; and group 3, 1027 ± 620 μL-1; respectively, whereas there was no change in white blood cell count of peripheral blood samples. Sixty min after the intracisternal injection, LPS content measured by Limulus amebocytes lysate assay was mildly elevated in cerebrospinal fluid in group 2 and group 3, whereas it was unchanged in sera in either group. We conclude that our model may be appropriate for further in vivo examination of the pathogenesis and treatment of neonatal bacterial meningitis.

Surfactant therapy in the newborn

In 1959 Avery and Mead demonstrated that surfactant deficiency was a key feature in the pathogenesis of respiratory distress syndrome (RDS).’ Pulmonary surfactant is a complex mixture of phospholipids, neutral lipids and specific proteins which spread as a monolayer at the air-liquid interfaces of the lung and lower surface tension at end-expiration thus preventing alveolar collapse. Phosphatidylcholine is the major component, constituting about 60% of total phospholipids and dipalmitoylphosphatidylcholine (DPPC) is the primary surface-tension lowering phospholipid. The physical effects of surfactant depend on the interaction between phospholipids and surfactant-associated proteins, for which at least four have been identified SP-A, SP-B, SP-C and SP-D. These apoproteins are synthesized and secreted by type II alveolar cells. The hydrophilic protein SP-A (MW 28-36 kDa) improves surface properties and regulates secretion and recycling of surfactant constituents by alveolar cells. The hydrophobic proteins SP-B and SP-C (3.5-8.4 kDa) facilitate the adsorption and spreading of lipids.2 In addition SP-A and SP-D seem to play a role in host defence mechanisms of the lung. The pool size of endogenous alveolar surfactant lipids in healthy neonates is at least 100 mg/kg; in preterm infants with RDS, however, it is usually less than about 10 mg/kg.3 Surfactant deficiency causes alveolar collapse, increased work of breathing and progressive respiratory failure in babies with RDS. As a consequence of lung injury during the course of the disease or its treatment, serum proteins leak into the air spaces and inhibit the surfactant function.

Early versus late surfactant replacement therapy in severe respiratory distress syndrome

Abstract26 preterm infants with severe respiratory distress syndrome (RDS) have been treated at different ages with a single dose of natural porcine surfactant (Curosurf, 200 mg/kg). Criteria for treatment included clinical and radiological signs of severe RDS (grade III–IV), requirement of artificial ventilation and an FiO2 ≥0.6. Nineteen neonates have been subjected to early treatment (2–15 h of age, mean birth weight SD: 1201 ± 387 g) and 7 patients to late treatment (> 15 h to 48 h of age, birth weight SD 1624 ± 649 g). Average FiO2 before treatment was 0.88 in early-treated patients and 0.8 in late-treated patients, age at treatment was 4.6 h and 36 h, respectively (median). Both early- and late-treated infants exhibited an improvement in oxygenation (more than twofold increase of the PaO2/FiO2 ratio) within 5 minutes after initiation of therapy. Average duration of intermittent pressure ventilation was 15 days in the early treatment group and 19 days in the late treatment group. Total exposition to >21% oxygen was 21 days in early-treated and 48 days in late-treated infants. Pneumothorax occurred in none of the patients. All early treated infants survived without signs of severe bronchopulmonary dysplasia (BPD>21%O2, >90 days plus radiological changes). However, two out of seven late-treated infants developed severe BPD; one patient died as a consequence of cardiopulmonary deterioration. Two patients in the early treatment group died of nonpulmonary complications. We conclude that surfactant replacement therapy should probably be initiated as soon as possible after manifestation of severe RDS.

Elastase Given Intracisternally Opens Blood-Brain Barrier in Newborn Piglets

The effect of elastase on the blood-brain barrier (BBB) permeability was intravitally studied by fluorescence photomacroscope using the open cranial window technique in newborn piglets. Eleven animals (group 1) were given intracisternal injection of porcine elastase (1.0 micrograms), while 7 piglets served as controls (group 2). Elastase administration resulted in spotty sodium fluorescein (MW 376 daltons) extravasations in pial venules in all animals of group 1 78 +/- 4 min (mean +/- SEM) after the challenge, and in a 2-fold increase (p < 0.05) in brain sodium fluorescein uptake both in occipital cortex and white matter. The concentration of elastase-alpha 1-proteinase inhibitor complex increased significantly (p < 0.05) in cerebrospinal fluid samples in group 1, 2 and 4 h after the injection, while it did not change in sera. A significant pleocytosis and leukocytosis was also seen in group 1, while there was no change in laboratory data and BBB remained tight in group 2. BBB permeability changes during neonatal meningitis may be caused, at least partially, by elastase.