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Biomedical subjects

B Robertson

Publications and source records attributed to B Robertson.

At least 343 records · Page 19Linked to original sources
PubMed1981

Lung compliance and alveolar expansion in the artificially ventilated premature newborn rabbit after maternal treatment with ambroxol.

Premature newborn rabbits were delivered on day 27 of gestation, with or without antenatal treatment with ambroxol (50 mg/kg/day in maternal injections, on days 24-26). The animals were tracheostomized, kept in body plethysmographs at 35 degrees C, and ventilated artificially for 10 min with 100% oxygen, insufflation pressure 30 cm H2O, frequency 40/min, and varying inspiration time (20, 40, 60, or 80%). Lung-thorax compliance increased with inspiration time in both ambroxol-treated animals and controls, but there was no difference in compliance between treated and non-treated litters. Alveolar expansion, evaluated morphometrically in histological sections, was enhanced in ambroxol-treated animals ventilated with prolonged inspiration phase (60 or 80%); such a difference was not found in the on-treated group. This suggests that antenatal treatment with ambroxol might have a stimulating effect on the synthesis and/or release of factors improving alveolar stability in the premature lung.

Ambroxol↗
PubMed1981

Surfactant treatment in experimental hyaline membrane disease.

Premature newborn rabbits obtained by hysterotomy on day 27 of gestation were ventilated artificially under standardized conditions, serving as experimental model of neonatal hyaline membrane disease. Natural surfactant with a phospholipid concentration of approximately 8 mg/ml was administered as 50-microliter doses after 10 min of ventilation and at subsequent 30-min intervals. Initial values for lung-thorax compliance were significantly improved following two doses of surfactant, whereas compliance levels of non-treated littermates remained unchanged. Treatment with surfactant resulted in increased alveolar air expansion. Bronchiolar epithelial lesions were present in both surfactant-treated animals and controls, but the severity of these lesions was clearly reduced after surfactant treatment. We conclude that surfactant substitution is an effective treatment in experimental hyaline membrane disease, even when given after an initial period of artificial ventilation.

Animals↗
PubMed1981

Lung-thorax compliance in the artificially ventilated premature rabbit neonate in relation to variations in inspiration:expiration ratio.

Surfactant-deficient premature newborn rabbits obtained by hysterotomy on day 27 of gestation were tracheostomized at birth, kept in a multichambered pressure-constant body plethysmograph, and subjected to intermittent positive pressure ventilation using a standardized insufflation pressure (30 cm H2O). A sequence of various frequencies (20, 40, and 60/min) and inspiration:expiration (I:E) ratios (1:4, 1:2, 1:1, 2:1, and 4:1) were applied, and the effect of these various respirator settings on tidal volume (VT) and flow was evaluated by means of a Fleisch tube connected to the body plethysmograph. Irrespective of respirator frequency, increasing I:E ratio from the basic setting of 1:1 resulted in increased VT; decreasing I:E ratio had the opposite effect. There was a nearly linear relation between variations in I:E ratio and VT, but the slope of the regression line was steeper at frequencies 40 and 60/min than at 20/min. At a frequency of 20/min, values (X +/- S.D.) for lung-thorax compliance at I:E ratios of 1:4 and 4:1 were 0.50 +/- 0.26 and 0.99 +/- 0.42 ml/cm H2O.kg, respectively. Corresponding figures for frequency of 60/min were 0.21 +/- 0.10 and 0.73 +/- 0.36 ml/cm H2O.kg. At the two higher frequencies and low I:E ratios (less than or equal to 1:1), the duration of the inspiration phase was not sufficient to provide the maximal degree of lung expansion attainable with this insufflation pressure under static conditions. At frequency of 60/min and I:E ratio of 4:1, the expiration was short enough to prevent zero flow before onset of inspiration.

Animals↗
PubMed1981

A coupled NAD+-peroxidase spectrophotometric assay for cholesterol.

We describe a modified enzymic reagent for determination of cholesterol and cholesterol ester in serum and in high-density lipoprotein. In this new procedure, the hydrogen peroxide produced by the action of cholesterol oxidase is used as a substrate for NAD+ peroxidase. Spectrophotometric determination of the NADH consumed in this coupled reaction provides a direct and absolute measure of the cholesterol originally present in free form and that liberated by the action of cholesterol ester hydrolase.

Cholesterol↗
PubMed1980

The effect of cytidine diphosphate choline on in vivo lung mechanics in premature newborn rabbits.

The influence of CDP-choline on neonatal lung adaptation was studied in premature rabbit neonates, delivered on day 28 of gestation. We found that the administration of CDP-choline (200 mg/kg body wt) at birth has a moderately beneficial effect on the respiratory frequency, dynamic lung compliance, and expiratory lung resistance. Since this effect was obtained within 60 min, and since the phospholipid content of the alveolar wash was similar on experimental and control animals, we concluded that the observed improvement in lung mechanics was probably not mediated by increased synthesis or release of surfactant phospholipids.

Animals↗
PubMed1980

In vivo lung lavage as an experimental model of the respiratory distress syndrome.

Using adult guinea-pigs, we have developed an experimental model in which alveolar surfactant phospholipids are removed by repeated lung lavage in vivo, and in which the short-term survival of the animals is ensured by artificial ventilation. Blood gases, parameters of lung mechanics, and histologic and electron microscopic findings indicate that the lavage procedure induces a condition similar to the adult respiratory distress syndrome. We propose that our technique might be used for evaluation of pharmacological agents and various forms of artificial ventilation which have been suggested for treatment of this disease.

Animals↗
PubMed1980

Artificial ventilation of premature newborn rabbits: effects of positive end-expiratory pressure on lung mechanics and lung morphology.

44 premature newborn rabbits, removed by hysterotomy on day 27 of gestation, were ventilated with positive pressure under differing standardized conditions, with or without application of positive end-expiratory pressure (PEEP; 5 cm H2O). After 10 min ventilation, compliance of the lung-thorax system was significantly higher in fetuses ventilated with PEEP than in controls. The application of PEEP also resulted in a significantly lower maximal expiratory air flow compared to controls in groups ventilated with standardized tidal volume. Morphometric evaluation revealed bronchiolar epithelial lesions to be less prominent in fetuses treated with PEEP. Our findings show that application of PEEP has a beneficial effect on lung mechanics during artificial ventilation and that it reduces the risk of epithelial damage to the airways, presumably by promoting uniform expansion of the lung parenchyma.

Animals↗
PubMed1980

Bronchiolar epithelial lesions induced in the premature rabbit neonate by short periods of artificial ventilation.

Premature newborn rabbits were ventilated with standardized tidal volume (10 ml/kg) or standardized insufflation pressure (35 cm H2O) for 1--30 min. The lungs of the experimental fetuses were fixed by perfusion of the pulmonary artery and examined by light and electron microscopy, with particular reference to the prevalence and ultrastructure of bronchiolar epithelial lesions. Necrosis and desquamation of bronchiolar epithelium were constant findings in fetuses ventilated for 5 min. or more, and were also present in some of the fetuses ventilated for only 1 min. Since the light microscopic and ultrastructural appearance of these bronchiolar lesions is similar to early stages of human neonatal hyaline membrane disease, we conclude that artificially ventilated pre-term newborn rabbits might serve as a useful model of this disease.

Animals↗
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↗
PubMed1980

Basic morphology of the pulmonary defence system.

Bronchoalveolar clearance is based on the coordination of multiple mechanisms, including surface flux from alveolus to bronchiole (owing to a surface-pressure gradient at end-expiration), adequate composition of the mucous blanket covering the larger airways, and proper ciliary function. The alveolar macrophages, the scavenger cells of the lungs, reside in the acellular lining of the terminal airspaces and eventually leave the lungs via the conducting airways. These cells are probably also involved in the turnover and removal of worn-out fragments of the surface film. There is evidence that the alevolar macrophages utilize this material as substrate for biochemical processes involved in the intracellular killing of bacteria. Lymphatic tissue is normally absent at the alveolar level but present in the mucosa of larger and medium-sized airways, especially at sites of bifurcation--i.e., where larger particles tend to impact on the bronchial surface during inspiration.

Animals↗
PubMed1980

Experimental obstructive hydronephrosis in newborn rats. I. Surgical technique and long-term morphologic effects.

Partial obstruction of one ureter was created in newborn rats and its effects were studied in the adult rat. The obstructed renal pelvis was found to be enlarged 10x. The parenchymal weight of this kidney was reduced by 8 per cent, primarily because of destruction of the papilla, and was completely compensated for by hypertrophy of the contralateral kidney. A high correlation was found between true volumes and areas on urography. The turnover time for urine in the hydronephrotic pelvis ranged from 47 to 473 min. The implications of this measurement for clearance values are discussed.

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↗