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Biomedical subjects

R Nilsson

Publications and source records attributed to R Nilsson.

At least 127 records · Page 7Linked to original sources
PubMed1980

Artificial surfactant and natural surfactant. Comparative study of the effects on premature rabbit lungs.

Premature newborn rabbits, delivered on day 27 of gestation, were treated with tracheal deposition of dry artificial surfactant containing dipalmitoyl phosphatidylcholine and unsaturated phosphatidylglycerol (7:3), or crude natural surfactant prepared by centrifugation of lung wash from adult rabbits. Before receiving surfactant, the animals were allowed to breathe for 7--27 min; they were then subjected to artificial ventilation under standardised conditions. In comparison with littermate controls, both groups of surfactant-treated animals showed statistically significant improvement in lung-compliance 30 and 60 min after onset of ventilation. However, necrosis of bronchiolar epithelium and hyaline membranes was present in nearly all animals, even in those treated with natural surfactant; this suggests that in order to prevent epithelial lesions, surfactant should be given as soon as possible and preferably at birth. Our findings confirm earlier observations that treatment with supplementary surfactant has a beneficial effect on lung mechanics in the premature neonate. The fact that this effect can be obtained not only with natural surfactant but also with dry artificial surfactant should increase the possibility of clinical application.

Animals↗
PubMed1980

Pathogenesis of neonatal lung lesions induced by artificial ventilation: evidence against the role of barotrauma.

Premature newborn rabbits, delivered on day 27 of gestation, were ventilated for 10 min with a standardized peak pressure of 35 cm H2O, with or without previous instillation of natural surfactant into the airways. Lung-thorax compliance and stability were significantly enhanced in surfactant-treated fetuses. Although these fetuses were greatly overventilated, their tendency to develop bronchiolar epithelial lesions was significantly reduced in comparison with controls; this was verified by light as well as electron microscopy. Our findings argue against barotrauma as the cause of bronchiolar epithelial lesions during artificial ventilation, and favor the concept that these lesions reflect an abnormal expansion pattern due to surfactant deficiency.

Animals↗
PubMed1979

Lung mechanics during spontaneous ventilation in premature and fullterm rabbit neonates.

Rabbit neonates were tracheotomized on day 27--30 of gestation, and lung mechanics during spontaneous ventilation was registered with a fluid-filled esophagus catheter for pressure recording and a pneumotachograph connected to the tracheal cannula via a Fleisch tube. The first breath of all neonates had a very long inspiratory phase (less than or equal to 1.12 sec), with insufflation pressures amounting to 42 cm H2O in the mature animals. The expiration phase of the first breath was usually 'passive', i.e. there was no positive expiratory esophagus pressure. In animals delivered on day 27--28 there was, as a rule, no difference between inspiratory and expiratory tidal volume during the first few breaths, whereas such difference was regularly registered in mature animals; this phenomenon probably corresponds to the establishment of FRC. Dynamic lung compliance increased with both gestational and postnatal age, up to 60 min after delivery. Shortly after birth, pulmonary resistance was higher in immature animals than in fullterm ones, but at later intervals, there was no difference between survivors of various gestational age.

Animals↗
PubMed1979

Fatigue and recovery of the human acoustic stapedius reflex in industrial noise.

The fatiguability of the acoustic stapedius muscle reflex in an actual noisy industrial environment was investigated in normal-hearing subjects. In a laboratory situation a small depression was found with a considerable individual variability. The stapedius reflex recovered slowly, approximately as a linear function of time. In a field study on an entire day of exposure in a ship-building yard the reflex depression was on the average 4 dB in response to a stimulation of 2000 Hz 10 min after the end of the workday. This corresponds to less than 8 dB immediately at the end of the exposure.

Acoustic Impedance Tests↗
PubMed1979

Lung compliance and lung morphology following artificial ventilation in the premature and full-term rabbit neonate.

Rabbit neonates delivered on day 27--30 of gestation were subjected to intermittent positive pressure ventilation (IPPV) for 60 min. Tidal volume was standardized to 10 ml/kg, and the insufflation pressure required to maintain this tidal volume was recorded. The quasistatic compliance of the lung-thorax system, corrected for variations in body weight, was significantly lower in animals delivered on day 27--28 than in those delivered on day 29--30. Immature animals with low lung-thorax compliance (less than 0.40 ml/cm H2O.kg) regularly developed widespread necrosis of bronchiolar epithelium following IPPV, whereas no such lesions were observed in mature animals. It seems probable that these lesions are secondary to overdistension of bronchioles during IPPV and that this abnormal expansion pattern is related to a deficiency of surfactant in the lungs of immature newborn animals.

Animals↗
PubMed1973

Permeability of microsomal membranes isolated from rat liver.

Water compartments, permeability, and the possible active translocation of various substances in rat liver microsomes were studied by using radioactive compounds and ultracentrifugation. The total water of the microsomal pellet, 3.4 microl/mg dry weight, is the sum of water in the extramicrosomal and intramicrosomal spaces, or 56 and 44%, respectively. Sucrose space accounts for 77% of the intramicrosomal water and the hydration water approximately 14%, leaving almost no sucrose-impermeable space when using the ultracentrifugation approach. With increasing sucrose concentration, microsomes do not show an osmotic response. The intramicrosomal water decreases greatly in the presence of Cs(+) and Mg(++) in rough but not in smooth microsomes. Uncharged substances of molecular weight of up to at least 600 freely penetrate microsomal membranes, which already become impermeable to charged substances at a molecular weight of 90. These substances also induce an osmotic response. The vesicles can be made permeable to charged substances after water treatment and cooling, which, however, does not increase glucose-6-phosphatase and inosine diphosphatase (IDPase) activities, and these enzymes can still be activated by deoxycholate. IDPase, reduced nicotinamide adenine dinucleotide-cytochrome c reductase, and reduced nicotinamide adenine dinucleotide phosphate-dependent hydroxylation reactions, performed in vitro, also disproved the hypothesis of an accumulation of charged substances inside of vesicles of being a major pathway. The products of the enzymic reactions as well as the glucuronidated form of a hydroxylated product can be recovered on the cytoplasmic side of membranes, and little accumulation occurs in the intravesicular compartment.

Animals↗