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Biomedical subjects

R Nilsson

Publications and source records attributed to R Nilsson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Lung expansion in premature newborn rabbits treated with emulsified synthetic surfactant; principles for experimental evaluation of synthetic substitutes for pulmonary surfactant.

This paper presents a sequence of tests for experimental evaluation of potential substitutes for pulmonary surfactant. Differential thermal analysis and the pulsating bubble technique were applied to identify an emulsified mixture of synthetic lipids with properties similar to those of natural surfactant. Instilled into the airways of premature newborn rabbits, this emulsion improved pulmonary pressure-volume characteristics and enhanced lung-thorax compliance during artificial ventilation. However, the in vivo effect was inferior to that of natural surfactant, especially as the emulsion failed to prevent the development of bronchiolar epithelial lesions.

Animals↗
PubMed1983

Different protein A immunosorbents may have different binding specificity for rat immunoglobulins.

Purified polyclonal immunoglobulin preparations representing the 4 rat IgG subclasses were tested for binding to Staphylococcus aureus protein A attached to 3 different solid phases (Staphylococcus aureus Cowan I bacteria, Sepharose CL4B and Sepharose 6MB). Protein A Sepharose CL4B showed higher reactivity with IgG1 and IgG2b than the staphylococci, whereas protein A Sepharose 6MB showed a lower uptake of these subclasses. No differences were seen for IgG2a and IgG2c. Protein A on different solid phases cannot be used interchangeably without confirmation of binding specificity.

Animals↗
PubMed1983

The acoustic reflex threshold in relation to noise-induced hearing loss.

In 100 consecutive cases with severe noise-induced hearing loss, pure-tone threshold measurements revealed symmetric hearing losses with maximum shifts at 4000 and 6000 Hz. Acoustic reflex measurements showed that few patients had an elevated pathologic reflex threshold. In contrast, we found a depressed acoustic reflex sensation level (i.e., the difference, in decibels, between pure-tone threshold and acoustic reflex threshold) suggesting a cochlear localization of the injury. Consequently, the probability of retro-cochlear involvement was small, or the cochlear component dominated the retro-cochlear one. The relation between the absence of the acoustic reflex and the degree of hearing loss showed that even at a pure-tone threshold of 80 dB HL, 50% of the ears still had an elicitable acoustic reflex. Statistical analysis yielded a significant correlation between acoustic reflex sensation level and speech discrimination, but no such correlation between acoustic reflex threshold and speech discrimination. We suggest that acoustic reflex sensation level should be a complement to the acoustic reflex threshold in order to distinguish between different localizations of sensorineural hearing losses.

Adult↗
PubMed1983

Noise-induced hearing loss in shipyard workers with unilateral conductive hearing loss.

In a study of 6500 workers in the shipbuilding industry, 8 subjects were found to have unilateral conductive hearing impairment established before the noise exposure period and without recurrent attacks of acute or chronic infection or clinical diagnosis of otosclerosis. All subjects demonstrated a more pronounced sensorineural hearing loss at 4.0 kHz in the ear with normal middle ear function. The results show the value of even a small permanent conductive hearing loss for protection against noise-induced hearing loss. The observations are discussed in relation to the role of individual variations in sound transmission, the value of the acoustic reflex in noise-induced hearing loss and the efficiency of continuous use of hearing protectors.

Auditory Threshold↗
PubMed1982

Fractionation of rat IgG subclasses and screening for IgG Fc-binding to bacteria.

The four IgG subclasses of the rat, IgGl, IgG2a, IgG2b and IgG2c, were purified from normal serum by a combination of protein A-affinity chromatography and DEAE-cellulose chromatography. Purified, radiolabelled preparations of IgG were tested for binding to Gram-positive bacteria representing five different Fc-receptor (FcR) types. Distinct rat subclass-specific Fc-binding was noted to bacterial species belonging to different Fc-receptor types. Staphylococcus aureus (FcR I) strains bind IgGl and IgG2c as shown by others. Group C and G Streptococci (FcR III) bind all four subclasses of rat IgG. Streptococcus zooepidemicus strains (FcR V) also bind all four subclases but only to a lower degree. Human group A Streptococci (FcR II) and bovine group G Streptococci (FcR IV) do not bind any of the rat IgG subclasses. Elution studies on two strains. Staphylococcus aureus, Cowan I, and human group G Streptococcus, G 148, showed that both thiocyanate and pH-elution might be useful for the fractionation of IgG subclasses bound to bacterial cells. The present work indicates the possible use of bacterial cells as solid-phase absorbents in immunological studies of rat IgG.

Animals↗
PubMed1982

The artificially ventilated preterm rabbit neonate as experimental model of hyaline membrane disease.

Bronchiolar epithelial lesions, similar to those in human hyaline membrane disease (HMD), can be induced by artificial ventilation of newborn rabbits, delivered on day 27 of gestation. As verified by electron microscopy, these epithelial lesions develop within only 1-5 min of artificial ventilation. Tracheal instillation of natural surfactant at birth improves lung-thorax compliance in these animals, enhances the aeration of the alveolar compartment, and prevents the development of bronchiolar epithelial lesions. This prophylactic effect is obtained even when the compliant lungs of the surfactant-treated animals are greatly overventilated, i.e. when the ventilator is set at standardized high insufflation pressure. The application of a low positive end-expiratory pressure (5 cmH2O) also results in increased lung-thorax compliance, and reduces the extent of bronchiolar epithelial lesions. These findings suggest that the epithelial lesions are secondary to an abnormal expansion pattern. In a premature neonate with surfactant deficiency, overdistension of airways and irregular aeration of the alveolar compartment might produce shear stress in the airway mucosa leading to disruption of the epithelium and formation of hyaline membranes. The same mechanism is probably also involved in the pathogenesis of the epithelial lesions in human neonatal HMD.

Adult↗
PubMed1981

Effect of supplementary surfactant on in vivo lung mechanics in the premature rabbit neonate.

Premature newborn rabbits, delivered on day 27 of gestation, were subjected to positive-pressure ventilation, with or without treatment with natural surfactant. The surfactant, obtained by centrifugation of lung wash from adult rabbits, was deposited in the tracheal cannula before the onset of ventilation. Parameters of lung mechanisms, recorded during spontaneous ventilation after 1 h, were significantly improved in animals receiving surfactant. In comparison with littermate controls, surfactant-treated animals also had less prominent bronchiolar epithelial lesions. We conclude that treatment with supplementary surfactant facilitates functional adaptation of the premature lung and prevents the development of epithelial lung lesions during artificial ventilation.

Animals↗
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↗
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

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↗