Immature and nearly mature fetal rabbits (gestational age 27.5 and 29.5 days, respectively) were obtained by hysterotomy and tracheotomized at birth. Immature rabbits received, via the tracheal cannula, 2.5 ml/kg of either normal saline, porcine surfactant (60 mg/ml), 1 mM amiloride in normal saline, or a mixture of surfactant and amiloride; nearly mature rabbits received either normal saline, or 1 mM amiloride in saline. The neonates were ventilated with a tidal volume of approximately 10 ml/kg for 0-60 min (immature animals) or 0-120 min (nearly mature animals). The lungs were then excised for determination of wet lung weight/body weight ratio (LW/BW). The right lung was further processed for quantification of extravascular lung water (EVLW) per unit dry lung weight, and the left lung fixed for measuring the size of perivascular 'cuffs' (adventitial tissue including lymphatics) in histological sections, using vascular lumen as reference volume. Immature animals receiving surfactant had improved compliance and smaller perivascular cuffs in comparison with the other groups. In immature animals amiloride had no effect on compliance, LW/BW, and EVLW, but reduced perivascular cuff size at 15 min. Nearly mature animals receiving amiloride had higher values for LW/BW and EVLW at 120 min, and lower perivascular cuff size at 15, 60, and 120 min, in comparison with saline-treated litter-mates. We conclude that surfactant improves lung-thorax compliance and reduces perivascular fluid accumulation in immature newborn animals without influencing total lung water content, and that amiloride retards fetal lung liquid resorption in nearly mature newborn animals without affecting lung-thorax compliance during artificial ventilation.

Absorption↗

PubMedDate not supplied

Immunochemical and immunohistochemical evaluation of lung permeability in ventilated newborn rabbits.

These experiments were designed to quantify the vascular-to-alveolar leakage albumin in the neonatal lung and to analyze the distribution of leaking airspaces in the lung parenchyma. Immediately after delivery, newborn rabbits with gestational age 27-29 days received an intravenous injection of human albumin as a marker and were ventilated for 15 min with standardized tidal volume (10 ml/kg). After the period of ventilation the lungs were either lavaged via the airways or fixed for histological studies. The median amount of albumin in lung lavage fluid, determined by immunodiffusion, was 4.8% of the injected dose after 27 days, 1.3% after 28 days, and 0.4% after 29 days of gestation; it was inversely correlated with the compliance of the respiratory system (r = -0.78; p less than .001). Immunohistochemical examination of lung section revealed that the leak was not diffuse; even in animals with gestational age 27 days it involved only a median of 48% of total alveoli. The median amount of alveoli containing the label fell to 6% after 28 days and to 0% after 29 days gestation, correlating inversely with the compliance of the respiratory system (r = -0.53; p less than 0.01). We suggest that our experimental model is useful for histological demonstration of serum proteins leaking into the airpaces under experimental conditions and for evaluating the effect of therapeutic regiments on neonatal lung permeability.

Animals↗

PubMedDate not supplied

[Pedagogic and psychologic aspects of intelligence diagnosis in brain damaged children and its significance in therapy and prognosis].

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Brain Damage, Chronic↗