Exogenous porcine surfactant (Curosurf) is inactivated by monoclonal antibody to the surfactant-associated hydrophobic protein SP-B

A monoclonal antibody to the surfactant-associated hydrophobic protein SP-B was added at various concentrations to a standard preparation of porcine surfactant (Curosurf 10 mg/ml), and surface properties were evaluated with pulsating bubble. Retarded adsorption of surfactant was observed at antibody concentrations > or = 0.5 mg/ml and significantly increased values for minimum surface tension were observed at antibody concentrations > or = 1 mg/ml. In vivo effects of the antibody were tested in immature newborn rabbits ventilated with a standardized sequence of insufflation pressures. Animals receiving 0.1 ml surfactant (80 mg/ml) mixed with antibody at concentrations > or = 4 mg/ml had low tidal volumes, poor lung stability in pressure-volume recordings, poor alveolar expansion in histological sections and widespread epithelial necrosis in peripheral airways. Admixtures of IgG had no such effects. We conclude that this monoclonal antibody inactivates exogenous porcine surfactant, probably by preventing fast adsorption of surfactant lipids to the alveolar air-liquid interfaces.

[The pattern of the clinical use of digitalis. The need for a reassessment]

PURPOSE

To evaluate the pattern of utilization of digitalis in an academic hospital.

METHODS

Clinical files of all patients admitted in medical wards at the Hospital de Clínicas de Porto Alegre were studied. Data were collected during five different days, three in the winter and two in the summer, keeping an interval of at least two weeks between each data collection. Heart failure diagnosis was evaluated objectively by means of a score proposed by Carlson et al.

RESULTS

From a total number of 881 patients, 114 (13%) were receiving digoxin. Mean age was 66 +/- 13 years and 47% were males. Considering the patients who were taking digoxin, 32% presented scores compatible with definite or possible heart failure; 26% had atrial flutter or fibrillation; 18% had heart failure and supraventricular tachyarrhythmias; and in 24% no clear indications were found according to our criteria. Previous use of digoxin was found in 85% of the patients and 32% were withdrawn during the hospitalization. Considering just the patients who had no reason for using digoxin, only 44% had the drug withdrawn.

CONCLUSION

According to current criteria, many hospitalized patients receive digoxin without a definite indication. These data suggest that reassessment of the use of digitalis should be incorporated into clinical practice.

Direct current application: easy induction of ventricular fibrillation for the determination of the defibrillation threshold in patients with implantable cardioverter defibrillators

For the determination of the defibrillation threshold, the induction of ventricular fibrillation is mandatory. However, in severely damaged hearts it is sometimes difficult to induce ventricular fibrillation by rapid stimulation or alternating current. Only rapid nonclinical ventricular tachycardias may result, and their cardioversion threshold may be different from the defibrillation threshold. Therefore, it was the purpose of this study to test the potential of direct current (DC) application to rapidly induce ventricular fibrillation in patients with an implanted cardioverter defibrillator. The defibrillation threshold had to be determined in 13 patients (9 with coronary heart disease, 4 with dilative cardiomyopathy, ejection fraction 35%) during and 2 weeks after the implantation of a cardioverter defibrillator. DC was applied 37 times by a commercially available 9-V DC battery via a bipolar catheter for about 3 seconds. Ventricular fibrillation was induced 23 times (62%) and rapid nonclinical ventricular tachycardias were induced six times (16%). In one patient clinical ventricular tachycardia was observed. In seven instances (19%) sinus rhythm remained. In 12 of the 13 patients, ventricular fibrillation could be induced by DC. Thus, the induction of ventricular fibrillation by DC application may serve as an additional tool to induce ventricular fibrillation, determining the defibrillation threshold in implantable cardioverter defibrillator patients.

Lung protein leakage in respiratory failure induced by a hybridoma making monoclonal antibody to the hydrophobic surfactant-associated polypeptide SP-B

Adult mice were inoculated intraperitoneally with a hybridoma (8B5E) making monoclonal antibody to the porcine surfactant-associated polypeptide SP-B; this antibody cross-reacts with the corresponding polypeptide in the mouse surfactant system. Respiratory failure, developing 7-9 days after inoculation, was associated with a decrease in lung-thorax compliance determined during artificial ventilation, and an increase in the amount of protein including the specific antibody in lung lavage fluid. There was a statistically significant negative correlation between the compliance and the amount of protein as well as antibody recovered by lung lavage: r (log scale) = -0.69 and -0.82, respectively (P less than 0.01, both), but no decrease in the amount of phospholipids in lung lavage from animals inoculated with the hybridoma. Treatment with a large dose of porcine surfactant (about 320 mg phospholipids/kg body weight) had no positive effect on lung-thorax compliance during artificial ventilation; on the contrary, surfactant-treated animals showed a decrease in compliance similar to that seen in control animals after instillation of a similar volume of saline into the airways. We conclude that respiratory failure developing after inoculation with this hybridoma is probably at least in part mediated by flooding of the airspaces with antibody interfering with surfactant function.

Effect of amiloride and surfactant on lung liquid clearance in newborn rabbits

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.

[Quantification of tricuspid insufficiency--comparison of Doppler echocardiography and radionuclide ventriculography]

In 40 patients (pts) (ages 34-83 years) the severity of tricuspid regurgitation (TR) was graded by pulsed Doppler echocardiographic determination of regurgitant jet extension. Mild TR was assessed in seven pts (group I), mode-rate TR in 20 pts (group II), and severe TR in 13 pts (group III). The enddiastolic diameter of the left ventricle as measured by M-mode-echocardiography was 55 +/- 16 mm in group I, 48 +/- 6 mm in group II, and 50 +/- 10 mm in group III. The regurgitant index (RI), i.e., the ratio of left-to-right-ventricular stroke counts (normal range 0.89-1.97) and the time-activity curve over the liver area were measured by equilibrium radionuclide ventriculography (RNV). The RI differed significantly between group I (1.6 +/- 0.5), II (1.0 +/- 0.3), and III (0.8 +/- 0.3) (p less than 0.01). An RI-value below 0.89 as an index of right-ventricular volume overload was found in 14% (group I), 45%, (group II) and 77% (group III). The time-activity curve over the liver area, as graded by count variation in phase with the right atrium from 1 (no count variation) to 4 (typical count variation) showed all grades in groups I and II, but only grade 2 to 4 in group III. The RI resp. the time-activity curve over the liver is a sensitive parameter for the detection of moderate to severe TR. If TR is ascertained, severe regurgitation can be differentiated from mild regurgitation by RNV-derived RI as an index of right-ventricular volume overload.

Experimental neonatal respiratory failure induced by a monoclonal antibody to the hydrophobic surfactant-associated protein SP-B

The present experiments were designed to test whether selective blocking of the surfactant-associated hydrophobic polypeptide SP-B (8.7 kD) would interfere with lung function during neonatal adaptation. A MAb to porcine SP-B was produced by hybridoma cell line (8B5E); this antibody cross-reacts with rabbit SP-B. Six mg of MAb to SP-B, dissolved in 0.2 mL of saline, was instilled into the airways of near-term newborn rabbits (gestational age 29 d), before the onset of ventilation. Control animals received the same amount of nonspecific rabbit IgG in saline, or were untreated. The animals were ventilated for 120 min with a standardized tidal volume (10 mL/kg). The specific antibody caused a prominent, immediate decrease in lung-thorax compliance, associated with acute inflammatory and exudative lung lesions including hyaline membranes. IgG alone had no such effects. Our data suggest that the MAb to SP-B inhibits surfactant function in the neonatal period by blocking one of the mechanisms responsible for fast adsorption of the surfactant phospholipids to the alveolar air-liquid interface. In addition, an acute inflammatory reaction is probably triggered in the lung parenchyma by the immune reaction.

Left ventricular function and wall thickness in long-term insulin-dependent diabetes mellitus: an echocardiographic study

Left ventricular function and wall thickness were evaluated in 111 type I diabetic subjects (mean age 25.5 +/- 9 years, mean duration of diabetes 13.4 +/- 6.2 years), using 2-D-derived M-mode echocardiography. Patients were carefully selected for the absence of major coronary risk factors or manifest cardiac disorders, and compared with 91 age- and sex-matched control subjects. Fractional shortening and the maximal velocity of cirumferential fibre shortening did not differ significantly between the two groups. Furthermore, no differences were found in the diastolic functional parameter of velocity of circumferential fibre extension. Posterior wall thickness was significantly increased in the diabetic patients compared to the controls (9.5 +/- 1.8 mm vs. 8.4 +/- 1.3 mm. P less than 0.01). As the thickness of the interventricular septum was also moderately increased (9.2 +/- 2.2 mm vs. 8.9 +/- 1.7 mm, NS), these findings provide evidence for an early structural change of the myocardium in young diabetic patients without clinically relevant functional consequences.

Inactivation of exogenous surfactant by pulmonary edema fluid

Modified natural porcine surfactant was mixed with edema fluid sampled from the airways of hyperoxia-exposed adult rabbits. By varying the concentration of surfactant lipids (10, 25, and 50 mg/mL) and edema fluid proteins (0-280 mg/mL), we obtained a series of preparations with protein to surfactant lipid weight ratios ranging from 0 to 11.2. The surfactant activity of these various mixtures was analyzed with a pulsating bubble (at a lipid concentration of 10 mg/mL) or in experiments on immature newborn rabbits (at lipid concentrations of 25 or 50 mg/mL). For the latter purpose, animals were delivered at a gestational age of 27 d and ventilated with a standardized sequence of insufflation pressures after receiving 0.1 mL of the surfactant-edema sample into the airways at birth. Nearly complete in vitro inhibition of surfactant (markedly delayed film adsorption and a minimum surface tension of 23 mN/m during pulsation) was observed at a protein to surfactant lipid ratio of 4.5. Under in vivo conditions, nearly complete surfactant inhibition (tidal volumes reduced to less than 20% of the values for littermates ventilated with the same pressure after receiving surfactant without admixture of edema fluid) was documented at a protein to surfactant lipid ratio of 11.2. Our data suggest that the functional properties of an immature neonatal lung, in which serum proteins tend to leak into the airspaces after the onset of ventilation, depend on the stoichiometric relation between surfactant lipids and inhibitory proteins in the lung liquid.

Diastolic ventricular function in type 1 diabetic patients: a study using Doppler echocardiography

The transmitral flow velocity pattern of 28 Type 1 diabetic patients and 39 age-matched healthy control subjects was studied for determination of left ventricular diastolic function. No patient had systemic hypertension, congestive heart failure, or ischaemic heart disease by clinical or electrocardiographic criteria. Echocardiographic measures of systolic ventricular function were within normal range in all subjects. The ratio of early to late transmitral peak flow velocity (ve/va) was significantly decreased in the diabetic patients (1.3 +/- 0.1 (+/- SE) vs 1.6 +/- 0.1, p less than 0.05), while other Doppler derived variables did not show any significant difference. No correlation of ve/va with duration of diabetes was found (r = -0.27), but it correlated with age in both groups (both r = -0.40, p less than 0.05). Furthermore, a significant correlation was found between ve/va and heart rate (r = -0.55 for diabetic patients, p less than 0.01; r = -0.58 for control subjects, p less than 0.01). After matching for heart rate (24 diabetic patients and 24 control subjects) no significant decrease of ve/va was observed in the diabetic group.

Application of a new ventilator-multi-plethysmograph system for testing efficacy of surfactant replacement in newborn rabbits

We applied a new ventilator-multi-plethysmograph system to evaluate the effect of surfactant replacement in newborn rabbits under well controlled, nearly physiological conditions characterized by normal ECG and adequate PCO2 in right ventricular heart blood obtained at the end of the experiment. Up to 10 animals were ventilated in parallel with a pressure-constant common respirator system. Using a working pressure of 4.9 kPa (50 cmH2O), we could adjust the pressure delivered to each animal within the range of 0.49-4.4 kPa (5-45 cmH2O), by changing the length of an open high-resistance tube constituting the outflow limb of the connection between the common ventilator tube and the tracheal cannula. Immature newborn animals obtained after 27.5 days gestation and ventilated for 30 min with a tidal volume of 8-10 ml.kg-1 had a mean +/- SD lung-thorax compliance of 4.2 +/- 1.1 ml.kPa-1.kg-1 (0.41 +/- 0.11 ml.cmH2O-1.kg-1) and PCO2 of 8.5 +/- 1.9 kPa. In littermates treated at birth with a large dose of natural surfactant (Curosurf, 200 mg.kg-1, compliance increased to 6.0 +/- 1.0 ml.kPa-1.kg-1 (0.68 +/- 0.10 ml.cmH2O-1.kg-1) (p less than 0.01) and PCO2 decreased to 6.9 +/- 1.2 kPa (p less than 0.01). Near-term animals, obtained at 30 days gestation and ventilated under similar conditions had a compliance of 7.2 +/- 0.9 ml.kPa-1.kg-1 (0.71 +/- 0.09 ml.cmH2O-1.kg-1) and PCO2 of 6.4 (1.2) kPa. Administration of surfactant (same dose as above) to these mature animals at birth had no adverse effects.

Application of a new ventilator-multi-plethysmograph system for testing efficacy of surfactant replacement in newborn rabbits

We applied a new ventilator-multi-plethysmograph system to evaluate the effect of surfactant replacement in newborn rabbits under well controlled, nearly physiological conditions characterized by normal ECG and adequate PCO2 in right ventricular heart blood obtained at the end of the experiment. Up to 10 animals were ventilated in parallel with a pressure-constant common respirator system. Using a working pressure of 4.9 kPa (50 cmH2O), we could adjust the pressure delivered to each animal within the range of 0.49-4.4 kPa (5-45 cmH2O), by changing the length of an open high-resistance tube constituting the outflow limb of the connection between the common ventilator tube and the tracheal cannula. Immature newborn animals obtained after 27.5 days gestation and ventilated for 30 min with a tidal volume of 8-10 ml.kg-1 had a mean +/- SD lung-thorax compliance of 4.2 +/- 1.1 ml.kPa-1.kg-1 (0.41 +/- 0.11 ml.cmH2O-1.kg-1) and PCO2 of 8.5 +/- 1.9 kPa. In littermates treated at birth with a large dose of natural surfactant (Curosurf, 200 mg.kg-1, compliance increased to 6.0 +/- 1.0 ml.kPa-1.kg-1 (0.68 +/- 0.10 ml.cmH2O-1.kg-1) (p less than 0.01) and PCO2 decreased to 6.9 +/- 1.2 kPa (p less than 0.01). Near-term animals, obtained at 30 days gestation and ventilated under similar conditions had a compliance of 7.2 +/- 0.9 ml.kPa-1.kg-1 (0.71 +/- 0.09 ml.cmH2O-1.kg-1) and PCO2 of 6.4 (1.2) kPa. Administration of surfactant (same dose as above) to these mature animals at birth had no adverse effects.

Partial ureteric obstruction in the pubescent rat. II. Long-term effects on the renal morphology

Partial obstruction of one ureter was created in pubescent rats (6 weeks of age) and its effects were studied after 1-15 weeks. Within 1 week, a considerable hydronephrosis and a moderate decrease in the number of glomeruli had developed. These changes did not progress with time. The renal parenchymal weight never became affected and the microstructure was only slightly influenced. Thus, the effects of a partial ureteric obstruction on renal morphology seem to be comparatively mild in this age group, and even less prominent than the modest changes previously observed in rats obstructed since the neonatal period. The reasons for this age difference and for the reduction in glomerular number are discussed.

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.

[Relationship of the left ventricular wall thickness to the degree of late microvascular complications in diabetes mellitus type I]

Left-ventricular wall thickness, measured by echocardiography, was determined in 111 normotensive diabetics (63 men and 48 women; mean age 26 +/- 9 years; diabetes duration 13.5 +/- 6.2 years) and 91 comparable control subjects. The interventricular septum was significantly thicker in diabetics than in controls: systolic 13.3 +/- 2.3 mm, diastolic 9.2 +/- 2.2 mm vs. systolic 12.5 +/- 2.1 mm and diastolic 8.9 +/- 1.7 mm (P less than 0.05). Posterior wall thickness measurements were: systolic 15.8 +/- 2.2 mm vs 14.6 +/- 2.0 mm (P less than 0.001), diastolic 9.5 +/- 1.8 mm vs 8.4 +/- 1.3 mm (P less than 0.01). Left-ventricular wall thickness increased stepwise with increasing severity of microvascular complications (retinopathy, nephropathy, neuropathy). There was a moderately close correlation between blood pressure values and the degree of microvascular complications (r = 0.49, P less than 0.01). These correlations indicate that increases in wall thickness are diabetes specific, but may be influenced by the level of blood pressure.

[New aspects of the traffic noise problem in the inner city area]

As a result of a sociological-oriented noise study in the city of Erfurt specific intracity noise problems are analysed via their effects. The authors deal with the expectation of calm of people living in different areas of the city, with the relevance of effect of the two usual evaluation levels Leq and Lmax for noise by running traffic, with noise decrease by sound attenuation improvements, and with the subjective and objective evaluation of an industrial front ventilation element. Moreover, the effects of traffic noise on inhabitants before and after significant traffic reduction are shown.

[Street traffic noise and stress experience]

Interpreting a sociological study in the city of Erfurt the results of a written interrogation of noise annoyance of a representative random sample of inhabitants are shown and selected characteristics both of the annoyed and the nonannoyed inhabitants are compared. From noise level measurements a proposal for a traffic noise threshold limit has been derived that corresponds to the requirement for calm. Moreover, moderators have been investigated which interfere with the degree of annoyance; health complaints of both groups of the interrogated individuals were compared. It could be shown, that a written interrogation of inhabitants of a territory is able to deliver sufficiently exact information concerning noise annoyance.

Passive expiratory flow-volume recordings in immature newborn rabbits. Effect of surfactant replacement on the time constant of the respiratory system

Immature newborn rabbits with a gestational age of 27 days were paralyzed and kept in body plethysmographs. They were ventilated for 10 min with a tidal volume of approximately 10 ml/kg, with or without previous surfactant treatment via the airways. Tidal volumes and flow were recorded with a pneumotachograph connected to the body plethysmograph, and the expiratory time constant of the respiratory system (trs) was determined from flow-volume diagrams. The values of trs after 10 min were significantly higher in surfactant-treated animals than in controls (50 +/- 7 vs. 23 +/- 4 ms; p less than 0.002), indicating stabilization of the alveoli. There was also a close correlation between trs and the compliance values calculated from tidal volumes and ventilator pressure (r = 0.80; p less than 0.001), as well as between trs and the alveolar volume density in histological lung sections, determined by automated image analysis (r = 0.71; p less than 0.001).

Lack of tolerance after chronic administration of controlled-release isosorbide-5-mononitrate. Interaction of nitrate and gallopamil

The effect of a controlled-release formulation of isosorbide-5-mononitrate (IS-5-MN) was studied in patients with coronary heart disease (CHD), with the aim of comparing the acute effect with that after chronic administration on parameters of ischemia. To determine whether any tolerance developed, several aspects of ischemia were observed: ECG signs, clinical parameters, and left ventricular function. Fifteen patients with angiographically proven CHD were examined with 12-lead exercise ECG before, 2 h and 4 h after the first dose and after 10 days of therapy with 60 mg IS-5-MN (Coleb-Duriles) once daily. After 7 days, three radionuclide ventriculographies were performed: control, 2 h after nitrate and 2 h after 75 mg gallopamil. Plasma concentrations of IS-5-MN were measured before every exercise test. The results showed a reduction of total ST-segment depression from 0.59 mV to 0.29 mV after 2 h (NS) and 4 h (P less than 0.05) on the 1st day and from 0.48 mV to 0.32 mV (P less than 0.05) and 0.31 mV (NS) after 10 days. The severity of angina pectoris was diminished by about 50%. The effect on exercise duration and time to ST-segment depression by more than 0.1 mV remained unchanged after 10 days, whereas the effect on blood pressure, heart rate and time to onset of angina was attenuated. The mean decrease in ejection fraction (EF) from rest to exercise was reduced from--5.9% to -1.9% (P less than 0.05) after nitrate, while an increase of +1.4% was seen after gallopamil (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Genomic footprinting in mammalian cells with ultraviolet light

A simple and accurate genomic primer extension method has been developed to detect ultraviolet footprinting patterns of regulatory protein-DNA interactions in mammalian genomic DNA. The technique can also detect footprinting or sequencing patterns introduced into genomic DNA by other methods. Purified genomic DNA, containing either damaged bases or strand breaks introduced by footprinting or sequencing reactions, is first cut with a convenient restriction enzyme to reduce its molecular weight. A highly radioactive single-stranded DNA primer that is complementary to a region of genomic DNA whose sequence or footprint one wishes to examine is then mixed with 50 micrograms of restriction enzyme-cut genomic DNA. The primer is approximately 100 bases long and contains 85 radioactive phosphates, each of specific activity 3000 Ci/mmol (1 Ci = 37 GBq). A simple and fast method for preparing such primers is described. Following brief heat denaturation at 100 degrees C, the solution of genomic DNA and primer is cooled to 74 degrees C and a second solution containing Taq polymerase (Thermus aquaticus DNA polymerase) and the four deoxynucleotide triphosphates is added to initiate primer extension of genomic DNA. Taq polymerase extends genomic hybridized primer until its polymerization reaction is terminated either by a damaged base or strand break in genomic DNA or by the addition of dideoxynucleotide triphosphates in the polymerization reaction. The concurrent primer hybridization-extension reaction is terminated after 5 hr and unhybridized primer is digested away by mung bean nuclease. Primer-extended genomic DNA is then denatured and electrophoresed on a polyacrylamide sequencing gel, and radioactive primer extension products are revealed by autoradiography. By using this method we demonstrate that it is possible to footprint with ultraviolet light, in intact monkey cells, regulatory protein--DNA interactions along a single copy of a simian virus 40 viral genome integrated into the monkey genome.

[Stress testing of long-term type I diabetic patients with radionuclide ventriculography]

Left ventricular function was assessed by means of radionuclide ventriculography in 42 patients with long-standing (13 +/- 5 yrs) insulin-dependent diabetes mellitus and in eleven healthy age matched control subjects. Only diabetics were included in the study without diabetes related cardiac risk factors such as hypertension and CAD in order to evaluate diabetes specific changes of cardiac function. No differences were seen between diabetics and controls concerning heart rate and functional parameters of left ventricle in systole and diastole. The rapid filling period was not prolonged. According to our radionuclide data there is no evidence of diabetes related impairment of ventricular function in young patients with long-standing type-1-diabetes mellitus.

Inhibition of exogenous surfactant in ventilated immature newborn rabbits

Immature newborn rabbits were treated at birth by tracheal instillation of porcine surfactant (100 microliters, phospholipid concentration 80 mg.ml-1), to which [14C]dipalmitoylphosphatidylcholine had been added as a marker. They were kept in a body plethysmograph/pneumotachygraph system at 37 degrees C. During a 120 min period of artificial ventilation with a peak insufflation pressure of 20 cm H2O, there was a gradual decrease in tidal volumes (36%.h-1). This decrease was correlated to an elevation of minimum surface tension (r = 0.81; P less than 0.01) and to a prolongation of the adsorption rate (r = 0.80; P less than 0.01) of surfactant recovered by lung lavage from the same animals. There was also correlations between duration of ventilation and minimum surface tension (r = 0.56; P less than 0.01), and between duration of ventilation and adsorption rate (r = 0.73; P less than 0.01). The surface properties of phospholipids extracted from the lavage fluid were similar to those of the original surfactant preparation. Our data suggest that, in immature newborn rabbits subjected to artificial ventilation, exogenous surfactant may become inactivated, probably due to protein leakage into the airspaces.

Vascular to alveolar leak of iron dextran (120 kD) in the immature ventilated rabbit lung

Rabbit fetuses were delivered by hysterotomy on day 27 or 28 of gestation. Immediately after birth, the animals were tracheotomized and received by intravenous injection 0.2 mu Ci radiolabeled albumin and 11 mg iron dextran in 0.2 ml saline. The newborn rabbits then were ventilated artificially with a tidal vol of 12 ml/kg for 5-20 min. One group of nonventilated animals served as controls. At the end of the experiment, one lung was lavaged via the airways and the other was fixed for histologic examination. The recovery of labeled albumin and iron dextran in the lavage fluid was quantified. Iron dextran complexes were easily identified in the lung sections by staining with Prussian blue. Iron dextran accumulated in the airspaces of animals delivered on day 27 (about 4% of the injected dose during 10-20 min of ventilation). The albumin leakage was slightly higher than that of the dextran, a result consistent with different mol wt of the markers. The vol density of leaking alveoli in histologic sections increased with time, from 0 at birth to a mean value of 0.36 after 20 min of ventilation. The leakage starts as a focal event, gradually involving more and more terminal airspaces. In the histologic sections, there was no indication of a significant leakage at the bronchiolar level, although the epithelium of terminal and preterminal airways was clearly injured in all ventilated animals.

Respiratory failure in mice caused by a hybridoma making antibodies to the 15 kDa surfactant apoprotein

Hybridoma cells were obtained by fusing spleen cells from mice, immunized against the 15 kDa porcine surfactant apoprotein, with a myeloma cell line. Adult mice were inoculated intraperitoneally with this hybridoma; mice that were not inoculated or were inoculated with myeloma cells served as controls. Lung-thorax compliance was measured at various intervals after inoculation. The animals were then killed for histologic-morphometric evaluation of alveolar air expansion, inflammatory reaction in the pulmonary parenchyma, and intraalveolar edema. In the hybridoma group, the mice developed respiratory failure 9 days after inoculation, with markedly reduced lung-thorax compliance, lung congestion, alveolar collapse, hemorrhagic pulmonary edema, and hyaline membranes. Morphometric data from the same animals showed reduced volume density of alveolar air, and increased volume densities of intraalveolar "fluid" (edema) and tissue components. These lung lesions are similar to those in the adult respiratory distress syndrome.

Prolonged ventilation of the premature newborn rabbit after treatment with natural or apoprotein-based artificial surfactant

Premature rabbit neonates (gestational age 27 days) were treated at birth with natural surfactant purified from chloroform extracts of porcine lung lipids either by acetone precipitation (Surfactant CK, n = 10) or liquid gel chromatography (Curosurf, n = 22). Another group of animals received artificial surfactant "reconstituted" from isolated low molecular weight (less than or equal to 15 K) apoproteins and synthetic dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) (Aposurf, n = 10). The phospholipid concentrations of the preparations were adjusted to provide the same individual dose of DPPC for each group of treated animals (3 or 4 mg). In comparison with untreated controls from the same litters, there was a 4-7-fold enhancement of lung-thorax compliance in all groups of surfactant-treated animals during a 3-h period of artificial ventilation. The average initial (20 min) compliance value was lower in the Aposurf-treated group than in animals receiving natural surfactant preparations, but the difference between the groups gradually diminished and was no longer statistically significant during the 2nd and 3rd h of artificial ventilation. Judged from the fall in tidal volume during ventilation with a short expiration phase (0.17 instead of 0.75 s), the apoprotein-based artificial surfactant was also less effective in stabilizing the lungs. A similar conclusion could be drawn from data on alveolar expansion in histological sections, evaluated by automated image analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of antenatal hydrocortisone on tidal volumes in spontaneously breathing preterm newborn rabbits. Possible mediation by adrenal catecholamines

Rabbit fetuses were injected on day 26 of gestation with hydrocortisone (2 mg) and delivered by hysterotomy 2 days later. The animals were tracheotomized at birth, and tidal volumes and esophageal pressures were recorded during spontaneous ventilation at standardized intervals from the first breath to the age of 2 h. In a subgroup of animals, the catecholamine content was measured in the adrenal glands. In comparison with littermate controls, tidal volumes were enlarged in hydrocortisone-treated neonates at the first breath and 60 min after birth; however, this effect was associated with an increased incidence of intra-alveolar hemorrhage. Hydrocortisone-treated animals also had a significantly increased adrenal content of adrenaline. Our data confirm a modest beneficial effect of antenatal hydrocortisone treatment on the fetal lung and suggest that this might in part be mediated by adrenal catecholamines. Stimulation of beta-adrenergic receptors could thus potentiate the effect induced by direct influence of glucocorticoids on fetal lung maturation.

Automated image analysis of alveolar expansion patterns in immature newborn rabbits treated with natural or artificial surfactant

Automated image analysis of histological lung sections was used to compare the efficacy of an artificial surfactant (dipalmitoylphosphatidylcholine + high-density lipoprotein, 10:1) and a natural surfactant (the phospholipid fraction of porcine surfactant, isolated by liquid-gel chromatography in ventilated immature newborn rabbits delivered after 27 days' gestation. Tidal volumes were significantly improved in each group treated with surfactant when compared with controls, but natural surfactant-treated rabbits had significantly higher tidal volumes than those receiving artificial surfactant. There were no statistically significant differences in alveolar expansion between the artificial surfactant group and the controls, but alveolar volume density and a shape factor (assessing the 'circularity' of terminal airspaces) were significantly higher in animals receiving natural surfactant. These animals also had a lower coefficient of variation of alveolar volume density and a lower alveolar average integral mean surface curvature, indicating a uniform pattern of alveoli with a smooth profile. We conclude that automated image analysis is useful for the quantitation of alveolar expansion patterns in immature neonatal lungs and that natural surfactant is superior to the artificial surfactant tested in the present study.

Severe neonatal respiratory distress syndrome treated with the isolated phospholipid fraction of natural surfactant

Ten newborn infants (795-1680 g) with severe respiratory distress syndrome (RDS) were treated with the isolated phospholipid fraction of bovine or porcine surfactant, which was administered via the airways (dose 200 mg/kg), at a median age of 10.5 h. Before receiving surfactant, all the infants were on artificial ventilation (FiO2 0.6-1.0). Within 2 h after surfactant replacement, the arterial-to-alveolar PO2 ratio increased from 0.1 to 0.35. There was a concomitant improvement in lung aeration on the chest roentgenograms and a significant reduction in the right-to-left shunt. Four patients died of cerebral hemorrhage; two of them also had a patent ductus arteriosus. One surviving infant developed bronchopulmonary dysplasia, and another succumbed 8 months later to the sudden infant death syndrome. No antibodies against surfactant were detected in the sera of the survivors. Since our results show a significant improvement in lung function after replacement therapy, the efficacy of this new surfactant preparation should be further tested in randomized clinical trials.

The role of the low-molecular weight (less than or equal to 15,000 daltons) apoproteins of pulmonary surfactant

An artificial surfactant was prepared by combining synthetic dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol and the low-molecular weight (less than or equal to 15,000 daltons) surfactant apoproteins in the proportions 80:20:5. In the Wilhelmy balance, this surfactant formed a film with an equilibrium surface tension of 29 mN/m; surface tension was reduced to nearly zero during cyclic film compression, with effective respreadability during multiple compression-expansion cycles; similar surface properties were recorded with a pulsating bubble. When instilled into the airways of artificially ventilated immature newborn rabbits, the apoprotein-based artificial surfactant produced a five-fold increase in tidal volumes at insufflation pressure 25 cm H2O; this effect is similar to that obtained in previous experiments with natural surfactant phospholipids, administered in equal concentration (5 mg/ml). Higher concentration of the apoprotein-based surfactant could not be evaluated in vivo due to the high viscosity of the material. Systematic studies should be undertaken to find out whether an even more effective artificial surfactant could be prepared from the low-molecular weight apoproteins and other combinations of synthetic phospholipids.

Correlations between physical and physiological properties of various preparations of lung surfactant

The physical and physiological properties of natural surfactant were investigated after the addition of various synthetic lipids. Three types of surfactant were studied: 1. Bovine surfactant with rapid spreading (1.6 s) and a relatively high minimal surface tension during surface compression (16 mN/m). 2. The same surfactant enriched with dipalmitoylphosphatidylcholine (DPPC), tripalmitin, and palmitic acid showing slow spreading (55 s) and low minimal surface tension (5 mN/m). 3. The same surfactant enriched with DPPC and dipalmitin, showing rapid spreading (1.8 s) and low minimal surface tension (6 mN/m). The physiological properties of these surfactants were evaluated in immature newborn rabbits. All three preparations effectively improved lung expansion and stability in pressure-volume recordings, increased tidal volumes during artificial ventilation, and enhanced alveolar volume density in histological sections. The magnitude of the therapeutic effects was similar for non-enriched and enriched materials. Thus, wide variations in in vitro surface properties do not seem to influence the in vivo activity of the surfactant preparations.

Scanning electron microscopy of epithelial lesions induced by artificial ventilation of the immature neonatal lung; the prophylactic effect of surfactant replacement

Immature newborn rabbits, delivered on day 27 of gestation were ventilated artificially for 5-10 min with a peak insufflation pressure of about 35 cm H2O, with or without previous treatment with natural surfactant via the airways. The alveolar expansion pattern and the surface structure of the airways were then examined by scanning and transmission electron microscopy. Animals not receiving surfactant had very irregular alveolar expansion and showed prominent desquamation of the bronchiolar epithelium with a strikingly ragged appearance of the mucosa in the scanning electron microscopic images. Litter mates treated with surfactant had improved alveolar expansion and a flattened but otherwise nearly intact bronchiolar epithelium. The findings confirm the beneficial effect of surfactant replacement on the immature neonatal lung.

Gas exchange and lung morphology after surfactant replacement in experimental adult respiratory distress syndrome induced by repeated lung lavage

Severe respiratory insufficiency was induced in adult guinea pigs by repeated lung lavage. The animals were then ventilated for 75 min with 100% O2, insufflation pressure 28/6-8 cmH2O (2.7/0.6-0.8 kPa), frequency 30/min, and 33% inspiration time. One group of animals (I) was treated with protein-depleted porcine surfactant, prepared by a combination of sucrose-gradient centrifugation, heating to 90 degrees C, and chloroform/methanol extraction. Another group (II) received the phospholipid fraction of porcine surfactant, isolated from minced lungs by chloroform/methanol extraction and liquid-gel chromatography. Surfactant was administered in two 1-ml doses (lipid concentration 90 mg/ml) instilled via the tracheal cannula about 15 and 45 min after the lavage procedure. Non-treated, lavaged animals served as controls. After 75 min of ventilation, control values for PaO2 and PaCO2 were 13.3 +/- 6.8 and 6.8 +/- 2.3 kPa (mean +/- s.d.), respectively. The corresponding values in Group I of surfactant-treated animals were 52.9 +/- 7.7 and 4.4 +/- 1.1 kPa, in Group II 53.5 +/- 7.3 and 4.8 +/- 1.3 kPa (P less than 0.02-0.002). The two groups of surfactant-treated animals also had significantly improved alveolar air expansion in histological sections, as reflected by increased alveolar volume density (0.67 +/- 0.05 and 0.62 +/- 0.11 vs 0.45 +/- 0.08 in controls; P less than 0.002). The benefits of surfactant replacement in this experimental model were thus similar to those previously observed in animal models of neonatal surfactant deficiency as well as in babies with respiratory distress syndrome (RDS). Our data suggest that surfactant replacement might have a therapeutic effect also in clinical adult RDS.

Effect of aminophylline on lung maturation in preterm rabbit fetuses

Pregnant rabbit does were treated intravenously with aminophylline (6 mg/kg/day) from the twenty-fifth day after the day of mating, and the fetuses were delivered by hysterotomy on the twenty-eighth day. One group of neonates was breathing air, and another group 100% oxygen. Lung mechanics were evaluated in the newborn animals during spontaneous or artificial ventilation, and the lungs were studied histologically with particular reference to the alveolar volume density. In one series of experiments, the lungs were washed and the lavage fluid was analyzed for phosphatidylcholine and phosphatidylglycerol. Aminophylline-treated litters had greater body weights, an improved survival rate, and an increased amount of phosphatidylglycerol in lung lavage fluid. Respiratory frequency was increased in aminophylline-treated animals breathing air, but data on lung compliance showed no significant difference between treated and control animals. In the present model, the beneficial effect of aminophylline can be attributed largely to a combination of accelerated fetal growth and improved postnatal regulation of breathing and less to a specific influence on the biochemical and functional maturation of the lung.

Leakage of protein in the immature rabbit lung; effect of surfactant replacement

Immature newborn rabbits, delivered on day 27 of gestation, were ventilated artificially for 60 min, with or without previous treatment with natural surfactant. Insufflation pressure was adjusted to maintain an average tidal volume of about 10 ml/kg. All animals received, before the onset of ventilation, 125I-labeled albumin via the airways and 131I-labeled albumin intravenously. At the end of the experiment 3.1 +/- 1.3% (means +/- SD) of the 131I-albumin had permeated into the alveolar compartment of control animals; the corresponding figures for surfactant-treated animals were 1.7 +/- 0.8% (P less than 0.002). In control animals only 18.2 +/- 4.4% of the 125I-albumin could be recovered from the airspaces after 60 min, whereas 69.9 +/- 14.6% of this label was recovered in surfactant-treated animals (P less than 0.002). Alveolar wash samples from control animals also contained significantly increased activity of surfactant inhibitor, as evaluated with pulsating bubble. The bidirectional flux of protein, including surfactant inhibitor, was thus significantly decreased in these immature lungs by surfactant replacement.