Ineffective morphine treatment regimen for the control of Neonatal Abstinence Syndrome in buprenorphine- and methadone-exposed infants.

This study aimed to determine if morphine is effective in ameliorating Neonatal Abstinence Syndrome (NAS) symptoms to non-opioid-exposed control levels in methadone- and buprenorphine-exposed infants. A prospective, non-randomized comparison study with flexible dosing was undertaken in a large teaching maternity hospital in Australia. Twenty-five infants in the groups of buprenorphine-, methadone- and control non-opioid-exposed infants were compared (total n = 75 infants). Oral morphine sulphate (1 mg/ml) was administered every 4 h to opioid agonist-exposed infants. Modified Finnegan Withdrawal Scale (MFWS) scores determined dosing: score of 8-10: 0.5 mg/kg/day, 11-13: 0.7 mg/kg/day and 14+: 0.9 mg/kg/day. Withdrawal score, amount of morphine administered and length of hospital stay, were used to assess NAS over a 4-week follow-up period. No controls achieved a score higher than 7 on the MFWS. There was no significant difference in the percentage of infants requiring treatment between methadone (60%) and buprenorphine (48%) infants. For treated infants, significantly (P < 0.01) more morphine was administered to methadone (40.07 ± 3.95 mg) compared with buprenorphine infants (22.77 ± 4.29 mg) to attempt to control NAS. Following treatment initiation, significantly more (P < 0.01) methadone (87%) compared with buprenorphine infants (42%) continued to exceed scoring thresholds for morphine treatment requirement, and non-opioid-exposed control infant scores. For treated infants, there was no significant difference in length of hospital stay between methadone and buprenorphine infants. Morphine treatment was not entirely effective in ameliorating NAS to non-opioid-exposed control symptom levels in methadone or buprenorphine infants. The regimen may be less effective in methadone compared with buprenorphine infants.

Antioxidant enzymes in the developing lungs of egg-laying and metamorphosing vertebrates.

The activities of the pulmonary antioxidant enzymes (AOE), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase, increase in the final 10-20 % of gestation in the mammalian lung, to protect the lung from attack by increasing levels of reactive oxygen species at birth. Whether the increase occurs as a normal 'preparation for birth', i.e. by a genetically determined mechanism, or in response to increased levels of oxygen, i.e. in response to the environment, is not completely understood. We examined the activities of catalase, SOD and GPx in the developing lungs of two oviparous vertebrate species, the chicken (Gallus gallus) and an agamid lizard (Pogona vitticeps), and in a metamorphosing vertebrate, the anuran Limnodynastes terraereginae. During in ovo development embryos come into contact with higher levels of environmental oxygen, and at a much earlier stage of development, compared with the intrauterine development of mammals. Furthermore, in metamorphosing frogs, the lungs are inflated at an early stage to aid in buoyancy, although the gas-exchange function only develops much later upon final metamorphosis. Here, we hypothesise that the activity of the AOE will be elevated relatively much earlier during development in both oviparous and metamorphosing vertebrates. We also examined the effect of mild hypoxia (17 % oxygen) on the development of the pulmonary AOE in the chicken, to test the hypothesis that these enzymes are responsive to environmental oxygen. In the normoxic lung of both Gallus gallus and Pogona vitticeps, catalase and GPx activities were significantly increased in late incubation, whereas SOD activity decreased in late incubation. Catalase and SOD activities were virtually identical in hypoxic and normoxic embryos of the chicken, but GPx activity was significantly affected by hypoxia. In the developing frog, the activities of all enzymes were high at stage 30, demonstrating that the system is active before the lung displays any significant gas-exchange function. SOD and GPx activity did not increase further with development. Catalase activity increased after stage 40, presumably correlating with an increase in air-breathing. In summary, catalase expression in the two oviparous vertebrates appears to be completely under genetic control as the activity of this enzyme does not change in response to changes in oxygen tension. However, in tadpoles, catalase may be responsive to environmental oxygen. SOD also appears to follow a largely genetically determined program in all species. Under normoxic conditions, GPx appears to follow a genetically determined developmental pattern, but this enzyme demonstrated the largest capacity to respond to environmental oxygen fluctuations. In conclusion, it appears that the AOE are differentially regulated. Furthermore, the AOE in the different species appear to have evolved different levels of dependency on environmental variables. Finally, the late developmental increase in AOE activity seen in mammals is not as pronounced in oviparous and metamorphosing vertebrates.

Control of pulmonary surfactant secretion: an evolutionary perspective.

Pulmonary surfactant, a mixture consisting of phospholipids (PL) and proteins, is secreted by type II cells in the lungs of all air-breathing vertebrates. Virtually nothing is known about the factors that control the secretion of pulmonary surfactant in nonmammalian vertebrates. With the use of type II cell cultures from Australian lungfish, North American bullfrogs, and fat-tailed dunnarts, we describe the autonomic regulation of surfactant secretion among the vertebrates. ACh, but not epinephrine (Epi), stimulated total PL and disaturated PL (DSP) secretion from type II cells isolated from Australian lungfish. Both Epi and ACh stimulated PL and DSP secretion from type II cells of bullfrogs and fat-tailed dunnarts. Neither Epi nor ACh affected the secretion of cholesterol from type II cell cultures of bullfrogs or dunnarts. Pulmonary surfactant secretion may be predominantly controlled by the autonomic nervous system in nonmammalian vertebrates. The parasympathetic nervous system may predominate at lower body temperatures, stimulating surfactant secretion without elevating metabolic rate. Adrenergic influences on the surfactant system may have developed subsequent to the radiation of the tetrapods. Furthermore, ventilatory influences on the surfactant system may have arisen at the time of the evolution of the mammalian bronchoalveolar lung. Further studies using other carefully chosen species from each of the vertebrate groups are required to confirm this hypothesis.

Development of the pulmonary surfactant system in two oviparous vertebrates.

In birds and oviparous reptiles, hatching is often a lengthy and exhausting process, which commences with pipping followed by lung clearance and pulmonary ventilation. We examined the composition of pulmonary surfactant in the developing lungs of the chicken, Gallus gallus, and of the bearded dragon, Pogona vitticeps. Lung tissue was collected from chicken embryos at days 14, 16, 18 (prepipped), and 20 (postpipped) of incubation and from 1 day and 3 wk posthatch and adult animals. In chickens, surfactant protein A mRNA was detected using Northern blot analysis in lung tissue at all stages sampled, appearing relatively earlier in development compared with placental mammals. Chickens were lavaged at days 16, 18, and 20 of incubation and 1 day posthatch, whereas bearded dragons were lavaged at day 55, days 57-60 (postpipped), and days 58-61 (posthatched). In both species, total phospholipid (PL) from the lavage increased throughout incubation. Disaturated PL (DSP) was not measurable before 16 days of incubation in the chick embryo nor before 55 days in bearded dragons. However, the percentage of DSP/PL increased markedly throughout late development in both species. Because cholesterol (Chol) remained unchanged, the Chol/PL and Chol/DSP ratios decreased in both species. Thus the Chol and PL components are differentially regulated. The lizard surfactant system develops and matures over a relatively shorter time than that of birds and mammals. This probably reflects the highly precocial nature of hatchling reptiles.

Control of pulmonary surfactant secretion from type II pneumocytes isolated from the lizard Pogona vitticeps.

Pulmonary surfactant, a mixture consisting of lipids and proteins and secreted by type II cells, functions to reduce the surface tension of the fluid lining of the lung, and thereby decreases the work of breathing. In mammals, surfactant secretion appears to be influenced primarily by the sympathetic nervous system and changes in ventilatory pattern. The parasympathetic nervous system is not believed to affect surfactant secretion in mammals. Very little is known about the factors that control surfactant secretion in nonmammalian vertebrates. Here, a new methodology for the isolation and culture of type II pneumocytes from the lizard Pogona vitticeps is presented. We examined the effects of the major autonomic neurotransmitters, epinephrine (Epi) and ACh, on total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) secretion. At 37 degrees C, only Epi stimulated secretion of total PL and DSP from primary cultures of lizard type II cells, and secretion was blocked by the beta-adrenoreceptor antagonist propranolol. Neither of the agonists affected Chol secretion. At 18 degrees C, Epi and ACh both stimulated DSP and PL secretion but not Chol secretion. The secretion of surfactant Chol does not appear to be under autonomic control. It appears that the secretion of surfactant PL is predominantly controlled by the autonomic nervous system in lizards. The sympathetic nervous system may control surfactant secretion at high temperatures, whereas the parasympathetic nervous system may predominate at lower body temperatures, stimulating surfactant secretion without elevating metabolic rate.

Alterations in pulmonary surfactant after rapid arousal from torpor in the marsupial Sminthopsis crassicaudata.

Torpor in the dunnart, Sminthopsis crassicaudata, alters surfactant lipid composition and surface activity. Here we investigated changes in surfactant composition and surface activity over 1 h after rapid arousal from torpor (15-30 degrees C at 1 degrees C/min). We measured total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) content of surfactant lavage and surface activity (measured at both 15 and 37 degrees C in the captive bubble surfactometer). Immediately after arousal, Chol decreased (from 4.1 +/- 0.05 to 2.8 +/- 0.3 mg/g dry lung) and reached warm-active levels by 60 min after arousal. The Chol/DSP and Chol/PL ratios both decreased to warm-active levels 5 min after arousal because PL, DSP, and the DSP/PL ratio remained elevated over the 60 min after arousal. Minimal surface tension and film compressibility at 17 mN/m at 37 degrees C both decreased 5 min after arousal, correlating with rapid changes in surfactant Chol. Therefore, changes in lipids matched changes in surface activity during the postarousal period.

Evolution of surface activity related functions of vertebrate pulmonary surfactant.

1. Pulmonary surfactant is a mixture of lipids and proteins that lines the air-liquid interface of the lungs of all vertebrates. In mammals, it functions to reduce and vary surface tension, which helps to decrease the work of breathing, provide alveolar stability and prevent alveolar oedema. The present review examines the evolution and relative importance of these surface activity related functions in the lungs of vertebrates. 2. The surface activity of surfactant from fish, amphibians, birds and most reptiles is generally very low, correlating with a low body temperature and a low disaturated phosholipid content of their surfactant. In contrast, the surfactant of those reptiles with a higher preferred body temperature, as well as that of birds and mammals, has a much higher surface activity. 3. The two main functions of surfactant in mammals are to provide alveolar stability and to increase compliance of the relatively stiff bronchoalveolar lung. As the respiratory units of most non-mammalian vertebrates are up to 1000-fold larger and up to 100-fold more compliant, surfactant is not required for these functions. 4. In non-mammals, surfactant appears to act as an anti-glue preventing the adhesion of respiratory surfaces that may occur when the lungs collapse (e.g. during diving, swallowing of prey or on expiration). Surfactant also controls lung fluid balance. These functions can be fulfilled by a surfactant with relatively low surface activity and may represent the primitive functions of surface active material in vertebrate lungs.

Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata.

Torpor changes the composition of pulmonary surfactant (PS) in the dunnart Sminthopsis crassicaudata [C. Langman, S. Orgeig, and C. B. Daniels. Am. J. Physiol. 271 (Regulatory Integrative Comp. Physiol, 40): R437-R445, 1996]. Here we investigated the surface activity of PS in vitro. Five micrograms of phospholipid per centimeter squared surface area of whole lavage (from mice or from warm-active, 4-, or 8-h torpid dunnarts) were applied dropwise onto the sub-phase of a Wilhelmy-Langmuir balance at 20 degrees C and stabilized for 20 min. After 4 h of torpor, the adsorption rate increased, and equilibrium surface tension (STeq), minimal surface tension (STmin), and the %area compression required to achieve STmin decreased, compared with the warm-active group. After 8 h of torpor, STmin decreased [from 5.2 +/- 0.3 to 4.1 +/- 0.3 (SE) mN/m]; %area compression required to achieve STmin decreased (from 43.4 +/- 1.0 to 27.4 +/- 0.8); the rate of adsorption decreased; and STeq increased (from 26.3 +/- 0.5 to 38.6 +/- 1.3 mN/m). ST-area isotherms of warm-active dunnarts and mice at 20 degrees C had a shoulder on compression and a plateau on expansion. These disappeared on the isotherms of torpid dunnarts. Samples of whole lavage (from warm-active and 8-h torpor groups) containing 100 micrograms phospholipid/ml were studied by using a captive-bubble surfactometer at 37 degrees C. After 8 h of torpor, STmin increased (from 6.4 +/- 0.3 to 9.1 +/- 0.3 mN/m) and %area compression decreased in the 2nd (from 88.6 +/- 1.7 to 82.1 +/- 2.0) and 3rd (from 89.1 +/- 0.8 to 84.9 +/- 1.8) compression-expansion cycles, compared with warm-active dunnarts. ST-area isotherms of warm-active dunnarts at 37 degrees C did not have a shoulder on compression. This shoulder appeared on the isotherms of torpid dunnarts. In conclusion, there is a strong correlation between in vitro changes in surface activity and in vivo changes in lipid composition of PS during torpor, although static lung compliance remained unchanged (see Langman et al. cited above). Surfactant from torpid animals is more active at 20 degrees C and less active at 37 degrees C than that of warm-active animals, which may represent a respiratory adaptation to low body temperatures of torpid dunnarts.

[A comparative study of the antenatal action of inducers of the mono-oxygenase system and of dexamethasone on the body indices of full-term newborn rat pups]. / Sravnitel'noe izuchenie antenatal'nogo deistviia induktorov monooksigenaznoi sistemy i deksametazona na nekotorye pokazateli organizma donoshennykh novorozhdennykh krysiat.

Experiments on newborn rats demonstrated that hepatic monooxygenase system inductors, such as phenobarbital, benzonal, zixorin, increased their body weight, absolute and relative mass of newborn lungs when applied antenatally in contrast to dexamethasone which decreased the above parameters. The inductors increased pulmonary and hepatic phospholipid levels, which suggests that they are superior to dexamethasone in this respect.