[Need for a coordinated pediatric intensive care].
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Child↗
Biomedical subjects
M Lindroth
Publications and source records attributed to M Lindroth.
Pulmonary complications of umbilical venous catheters.
Umbilical venous catheters that are pushed in too far will usually cross the atrial septum and may dislodge in a pulmonary vein. The authors report eight neonates with radiographic documentation of this catheter malposition together with either a localized pulmonary opacification or an autopsy report of a pulmonary hemorrhage or infarction corresponding to the catheter position. The lung injury ranged from a transient edema to hemorrhagic pulmonary infarction and hydrothorax. In two cases autopsy demonstrated localized infarction without previous radiographic signs of catheter-related injury.
Catheterization, Peripheral↗
Low risk of seizure recurrence after early withdrawal of antiepileptic treatment in the neonatal period.
The risk of seizure recurrence within the first year of life was evaluated in infants with neonatal seizures diagnosed with a combination of clinical signs, amplitude-integrated electroencephalogram (EEG) monitoring, and standard EEG. Fifty eight of 283 (4.5%) neonates in tertiary level neonatal intensive care had seizures. The mortality in the infants with neonatal seizures was 36.2%. In 31 surviving infants antiepileptic treatment was discontinued after one to 65 days (median 4.5 days). Three infants received no antiepileptic treatment, two continued with prophylactic antiepileptic treatment. Seizure recurrence was present in only three cases (8.3%)--one infant receiving prophylaxis, one treated for 65 days, and in one infant treated for six days. Owing to the small number of infants with seizure recurrence, no clinical features could be specifically related to an increased risk of subsequent seizures. When administering antiepileptic treatment, one aim was to abolish both clinical and electrographical seizures. Another goal was to minimise the duration of treatment and to keep the treatment as short as possible. It is suggested that treating neonatal seizures in this way may not only reduce the risk of subsequent seizure recurrence, but may also minimise unnecessary non-specific prophylactic treatment for epilepsy.
Anticonvulsants↗
Propofol induces changes in the cytosolic free calcium concentration and the cytoskeletal organization of cultured human glial cells and primary embryonic rat brain cells.
BACKGROUND: The site of action of the intravenous anesthetic drug propofol is uncertain. Therefore, we examined the effects of propofol on the cytosolic free calcium levels of cultured primary embryonic rat brain cells (80-85% neurons), and on the organization of the cytoskeleton in these rat cells and in a model system of cultured human glial cells (astrocytes). METHODS: Propofol was added to the cells as the clinically available solution Diprivan. Cytosolic free calcium changes in neurons were studied using Fura2 and a single-cell microfluorometric method. Fluorescence microscopy was used to study the organization of actin filaments and tubulin in detergent-extracted cells. RESULTS: An increase in the cytosolic free calcium concentration of 116 +/- 39 nM was seen shortly after the addition of 0.3 microgram.ml-1 propofol, and a propofol concentration of 0.03 microgram.ml-1 resulted in an increase in cytosolic free calcium concentration of the same magnitude, 119 +/- 42 nM. Most of the calcium (60-75%) came from the extracellular environment, and the rest was from intracellular stores. When neurons were depleted of intracellular calcium by 1,2-bis-5-methyl-amino-phenoxylethane-N,N'-tetra-acetoxymethyla cetate (MAPT/AM), no changes were seen in the actin organization of the cytoskeleton. Actin organization was affected by all concentrations of propofol, 0.3-50 micrograms.ml-1 (1.7-280 microM), when exposure to the drug was achieved by a 30-min incubation. After the incubation, the exposed cells were more rounded and exhibited increased ruffling activity, both at the periphery and on the cellular surface, and ring-shaped actin structures were also seen. These effects were concentration dependent and reversible, and reached a maximum after 20 min of incubation. Propofol had no apparent effect on the organization of tubulin. CONCLUSIONS: Propofol induced changes in the cytoskeletal organization of actin in cultured rat neurons and human glial cells. These changes must have been due to the increase in intracellular calcium seen shortly after the addition of propofol, since no effects on actin organization were seen when intracellular calcium was depleted.
Actins↗
[High competence is required in neonatal intensive care].
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Clinical Competence↗
PDGF and neomycin induce similar changes in the actin cytoskeleton in human fibroblasts.
The addition of platelet-derived growth factor (PDGF) to serum-starved fibroblasts induces increased motility, formation of lamellipodia, increased ruffling activity, and actin ring structures associated with dorsal ruffles. Involvement of the phosphatidylinositol cycle (PI-cycle) in these morphological changes was investigated by observing the effects of neomycin, an inhibitor of the PI-cycle, on cultured human foreskin fibroblasts. The role of actin in the changes was investigated by using cytochalasin D (CD). Actin in detergent-extracted cells was labelled with TRITC-phalloidin and examined with fluorescence microscopy. Using PDGF and neomycin simultaneously potentiated lamellipodia formation, ruffling activity, as well as the number of cells with actin rings. Furthermore, neomycin by itself induced morphological changes similar to those induced by PDGF. Quantitation of actin rings showed dose and time dependency for PDGF and neomycin respectively, with a maximal number of cells containing rings after 15 min of exposure to either 3.5 mM neomycin or 10 ng PDGF/ml. Comparing the two substances, PDGF induced ring formation in a greater number of cells. These processes were inhibited by the presence of CD. PDGF- and neomycin-induced changes in the actin cytoskeleton were also observed in human embryonic lung fibroblasts, human glial cells, and embryonic mouse fibroblasts, all of which are known to express PDGF-receptors. In conclusion, the present study indicates that an increased turnover of the PI-cycle is not essential for the changes in actin organization induced by PDGF.
3T3 Cells↗
Preservation and visualization of molecular structure in detergent-extracted whole mounts of cultured cells.
Today's electron microscopes have a resolution sufficient to resolve supramolecular structures. However, the methods used to prepare biological samples for electron microscopy often limit our ability to achieve the resolution that is theoretically possible. We use whole mounts of detergent-extracted cells grown on Formvar-coated gold grids as a model system to evaluate various steps in the preparation of biological samples for high resolution scanning electron microscopy (SEM). Factors that are important in determining the structure and composition of detergent-extracted cells include the nature of the detergent and the composition of the extraction vehicle. Chelation of calcium is extremely important to stabilize and preserve the cytoskeletal filaments. We have also demonstrated both morphologically and by gel electrophoresis that treatment of cells with bifunctional protein crosslinkers before or during extraction with detergent can significantly enhance the preservation of both proteins and supramolecular structures. The methods used to dry samples are a major determinant of the quality of structural preservation. For cytoskeletons freeze-drying (FD) is superior to critical point-drying (CPD), one reason being that CPD samples have to be dehydrated, thereby causing more shrinkage as compared to FD samples. The high pressures to which samples are exposed during CPD may also cause increased shrinkage, and water contamination during CPD causes severe structural damage. We have obtained the best structural preservation of detergent-extracted and fixed cells by manually plunging them into liquid propane and drying over night in a freeze-dryer. The factor that most limits achievement of high resolution in SEM is the metal coat, which has to be very thin, uniform, and free of grain in order not to hide structures or to create artifactual ones. We have found that sputter-coating with 1-3 nm of tungsten (W) or niobium (Nb) gives extremely fine-grained films as well as satisfactory emission of secondary electrons. These samples can also be examined at high resolution by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The best preservation and visualization of supramolecular structures have been obtained using cryosputtering, in which the samples are freeze-dried and then sputter-coated within the freeze-dryer while still frozen.
Animals↗
Cryosputtering--a combined freeze-drying and sputtering method for high-resolution electron microscopy.
Preparing cellular structures for visualization by high-resolution scanning electron microscopy (SEM) is a multi-step process which includes fixation, dehydration, drying and metal coating. Drying and metal coating are limiting for high-resolution work. Commonly, the dried samples are exposed to the air before they are inserted into a metal coating apparatus, thereby exposing them to moisture and the accompanying risk of rehydration, which may cause changes in the supramolecular structure. We have modified a freeze-dryer to accommodate a magnetron sputtering head, in order to sputter-coat the frozen-dried samples while still in the drying chamber in the cold, a process we call cryosputtering. A layer of 1.5 nm of tungsten was cryosputtered onto whole mounts of cytoskeletons from detergent-extracted human glioma cells or fibroblasts and the specimens were examined by high-resolution SEM and transmission electron microscopy (TEM). To reduce the effects of backstreaming oil from the vacuum system, a turbomolecular pump backed by a two-stage rotary vane pump was connected to the drying-coating chamber. This pump system provides a high vacuum, making it possible to dry the specimens at -90 degrees C/183 K, thus reducing the risk for recrystallization of water. Furthermore, the high vacuum minimizes the negative effects of contaminants, which can be deposited onto the specimen surface and affect the quality of the metal coat formed during sputtering.
Cell Line↗
[Diagnostic equipments owned by neonatal departments make their use more efficient].
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Blood Chemical Analysis↗
[The kangaroo method is a good complement to traditional incubator care].
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Humans↗
Spontaneous pneumopericardium in an otherwise healthy full-term newborn.
Neonatal pneumopericardium is usually a complication of mechanical ventilation in premature infants with respiratory distress syndrome. We report a full-term neonate who developed pneumopericardium after forceps delivery and mild asphyxia. The child was never ventilated and had no signs of parenchymal lung disease. The pneumopericardium resolved spontaneously. Although drainage of pneumopericardium is usually recommended, this may not always be necessary when there are no signs of cardiac tamponade.
Humans↗
Potential of early chest roentgen examination in ventilator treated newborn infants to predict future lung function and disease.
The potentially of early chest X-ray to predict the risk of lung function abnormalities was studied prospectively in 40 preterm ventilator treated infants in a 8-10-year follow-up investigation. According to the findings at chest X-ray 3 to 10 days after completed ventilator treatment the infants were divided into 3 groups considered to represent increasing risk and severity of lung damage: 1) normal findings, 2) interstitial parenchymal abnormalities exclusively or 3) in combination with local or general hyperinflation. Lung function tests and chest x-ray were performed at the age of 8 to 10 years. A correlation was found between the findings at the early chest roentgen examination and the risk of abnormal lung function at the follow-up. Occurrence of focal or general hyperinflation or both were associated with a greater risk of airway obstruction. Infants with only interstitial abnormalities were, however, at a higher risk than those with normal chest examination to develop general hyperinflation and increased air way obstruction.
Bronchopulmonary Dysplasia↗
Association of ligand-receptor complexes with actin filaments in human neutrophils: a possible regulatory role for a G-protein.
Most ligand-receptor interactions result in an immediate generation of various second messengers and a subsequent association of the ligand-receptor complex to the cytoskeleton. Depending on the receptor involved, this linkage to the cytoskeleton has been suggested to play a role in the termination of second messenger generation and/or the endocytic process whereby the ligand-receptor complex is internalized. We have studied how the binding of chemotactic peptide-receptor complexes to the cytoskeleton of human neutrophils is accomplished. As much as 76% of the tritiated formylmethionyl-leucyl-phenylalanine (fMet-Leu-[3H]Phe) specifically bound to intact cells, obtained by a 30-s stimulation with 20 nM fMet-Leu-[3H]Phe, still remained after Triton X-100 extraction. Preincubating intact cells with dihydrocytochalasin B (dhCB) or washing the cytoskeletal preparation with a high concentration of potassium, reduced the binding of ligand-receptor complexes to the cytoskeleton by 46% or more. Inhibition of fMet-Leu-Phe-induced generation of second messengers by ADP-ribosylating the alpha-subunit of the receptor-coupled G-protein with pertussis toxin, did not reduce the binding of ligand-receptor complexes to the cytoskeleton. However, using guanosine-5'-O-(2-thiodiphosphate) (GDP beta S) to prevent the dissociation of the fMet-Leu-Phe-associated G-protein within electrically permeabilized cells, led to a pronounced reduction (62%) of the binding between ligand-receptor complexes and the cytoskeleton. In summary, in human neutrophils the rapid association between chemotactic peptide-receptor complexes and the cytoskeleton is dependent on filamentous actin. This association is most likely regulated by the activation and dissociation of the fMet-Leu-Phe-associated G-protein.
Actins↗
Measurement of ventilation and respiratory mechanics during continuous positive airway pressure (CPAP) treatment in infants.
A new method has been evaluated for measuring ventilation and lung mechanics in spontaneously breathing infants by means of a face chamber. Airway flow is measured with a pneumotachograph inserted between the face chamber and a stable pressure source. Oesophageal pressure is measured via a water-filled oesophageal catheter. The method is suitable for use in conjunction with continuous positive airway pressure (CPAP) treatment in neonatal intensive care. A flat frequency response curve up to 15 Hz for the two measuring systems (i.e., airway flow and oesophageal pressure), and a time shift between the two respective signals of less than 2 msec are prerequisites for correct evaluation of respiratory mechanics. In preterm infants with chest distortion, the inhomogeneity of pleural pressure affects the significance of resistance and compliance values, as calculated from oesophageal pressure. Supra-diaphragmatic pressure variations reflect the resistive and elastic load on the diaphragm exerted by the lungs and thorax. Thus, oesophageal pressure is still useful in studies of respiratory mechanics in preterm infants.
Apnea↗
Lung function eight years after neonatal ventilation.
Forty children who had had artificial ventilation during the neonatal period were studied at the age of 8-10 years with spirometry, the nitrogen washout test, bicycle exercise test, pulse oximetry, electrocardiogram, vectorcardiogram, and chest radiography. The median gestational age at birth was 29 weeks, and the median birth weight was 1310 g. Hyaline membrane disease was the indication for neonatal ventilation in 25 children. Bronchopulmonary dysplasia was diagnosed from radiographs in 11 infants (27%). Airway obstruction was observed in 10 of 11 children who had had bronchopulmonary dysplasia and in nine of 29 children who had not. After inhalation of terbutaline, the forced expiratory volume in one second (FEV1) was significantly increased. General hyperinflation was found in 16 of 17 children with abnormal chest radiographs (eight who had had bronchopulmonary dysplasia and nine who had not). Functional residual capacity was significantly higher in children with abnormal radiographs. Each child had a normal maximum working capacity and a normal electrocardiogram, and all but two had normal vectorcardiograms. Oxygen saturation at maximum work load decreased significantly in both groups of children. The risk of future respiratory problems calls for further follow up of lung function and chest radiography.
Electrocardiography↗
Problems associated with the preparation of whole mounts of cytoskeletons for high resolution electron microscopy.
The resolution currently available in both transmission and scanning electron microscopes is theoretically adequate to visualize the organization of the cytoskeleton at the supramolecular and macromolecular levels. However, achieving this resolution in practice requires that the methods used to prepare the specimens both preserve the structures of interest and render them visible for observation in the microscope without obscuring or altering them. In this paper we discuss our own and others efforts to develop methods to overcome several problems associated with preparing whole mounts of cytoskeletons for observation by electron microscopy. These problems include: controlling the degree to which cellular components are extracted; the effects of osmium tetroxide on the cytoskeleton; controlling and recognizing shrinkage and drying artifacts; the choice of a method of visualization; deposition of grain-free ultrathin films of metal; and interpreting the results. The standard procedure which we currently use consists of the following steps: growing cells on carbon-stabilized Formvar-coated gold electron microscope grids; extracting in 0.5% Triton X-100 detergent in a microtubule stabilizing buffer; postfixing in 2.5% glutaraldehyde in stabilizing buffer; freeze-drying; magnetron sputter-coating with 1.5 nm of tungsten; and observation by TEM, SEM, or STEM. Cytoskeletons prepared in this manner contain over 100 polypeptides and are composed of a complex three dimensional meshwork of clean, uniform filaments, the smallest of which are 7 nm in diameter. A structure resembling the microtrabecular lattice is present only if the cells are prefixed with a relatively long bifunctional protein crosslinking reagent prior to extraction with detergent.
Animals↗
Effects on respiration of CPAP immediately after extubation in the very preterm infant.
The effects of continuous positive airway pressure (CPAP) on pulmonary function during weaning from ventilator treatment were examined immediately after extubation in 17 very preterm infants, who had been ventilator-treated because of hyaline membrane disease (15 infants) and chronic pulmonary insufficiency of prematurity (two infants). Seven infants had bronchopulmonary dysplasia. Median birthweight was 920 g and median gestational age 26 completed weeks. The median duration of ventilator treatment was 10 days. Application of CPAP by means of a face chamber device after endotracheal extubation significantly lowered the frequency of apnea (P = 0.02) and enhanced oxygenation (P = 0.001). The respiratory mechanical indices derived from flow rate and juxta-diaphragmatic esophageal pressure measurements showed a reduced elastic (P = 0.03) and resistive (P = 0.02) load on the diaphragm. Even if the measured values do not accurately represent absolute resistances and compliances, the relative values of end-inspiratory and end-expiratory pressures differed significantly with and without CPAP (P = 0.001 and 0.002, respectively). We found CPAP applied via the face chamber technique immediately after extubation to be beneficial and to facilitate weaning from ventilator treatment in very preterm infants.
Female↗
Transforming growth factor (TGF beta) decreases the proliferation of human bone marrow fibroblasts by inhibiting the platelet-derived growth factor (PDGF) binding.
Human bone marrow fibroblasts were cultivated and characterized by immunofluorescent staining and electron microscopy. Their interactions with PDGF and TGF beta were studied. While a positive intracellular antifibronectin staining was observed, the cultured cells were not labeled with specific antibodies toward factor VIII von Willebrand factor (F VIII/vWF), desmin, and macrophage antigen. Moreover, electron microscopy excluded the presence of endothelial cells by the absence of Weibel-Palade bodies. The binding of pure human PDGF to the cultured bone marrow fibroblasts was investigated. Addition of an excess of unlabeled PDGF decreased the binding to 75 and 80%, which means that the nonspecific binding represented 20-25% of total binding, whereas epidermal growth factor (EGF) had no effect. Two classes of sites were detected by Scatchard analysis with respectively 21,000 and 37,000 sites per cell, with a KD of 0.3 x 10(-10) M and KD of 0.5 x 10(-9) M. The stimulation of DNA synthesis by PDGF was quantified by [3H]thymidine incorporation. When PDGF was added alone at a concentration of 15 ng/ml, it induced a maximal DNA synthesis of 400%, which increased up to 900%, in the presence of platelet-poor plasma (PPP). On the other hand, PDGF-induced fibroblast proliferation was inhibited in a dose-dependent manner by TGF beta. This inhibition was related to a significantly decreased binding of 125I-labeled PDGF observed in the presence of TGF beta. Our results suggested that PDGF and TGF beta could modulate the growth of bone marrow fibroblasts.
Bone Marrow↗