SummaryTo determine if some specific "preparation for birth" occurs in the developing lung to help assure its successful adaptation to a comparatively 02-rich world at birth, we measured the activities of the antioxidant enzymes in the developing lungs of rabbit fetuses from 10 d before parturition to several days after birth. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GP) activities showed similar maturational patterns with significant increases id activity, compared with earlier gestational levels, during the last 3-5 d before birth. During the final days in utero, SOD and CAT activities increased by -110% and lung GP activity by -200%. There were no parallel changes in lung Oz consumption demonstrable over this same prenatal period. High concentrations of 0 2 are toxic to the lungs of all species, including man. The principal biochemical defense against 02-induced lung damage is generally accepted to be the antioxidant enzymes-SOD, CAT, and the GP system-and the lipid membrane constituent, Vitamin E (8,15,17,41). Studies from our own and other laboratories have established positive correlations between relative resistance to hyperoxia and increased levels of some or all of the pulmonary antioxidant enzymes (4,8,(15)(16)(17)41). It was noted a few years ago that SOD, CAT, and GP activities were all higher in the lungs of newborn rats than in the lungs of 2-d premature rat fetuses (43). In another study, SOD activity in the lungs from a small sampling of premature infants (26-32 wk gestation) ( n = 3) was found to be substantially lower than the SOD activity in the lungs of full-term newborns (n = 4) (1). These findings, combined with the fact that at birth the newborn leaves a hypoxic uterine environment (fetal arterial Poz -20-25 mm Hg) (7, 29) to enter a relatively hyperoxic 21% Oz environment, have made us wonder if some specific "preparation for birth" occurs in the developing lung to help assure its successful adaptation to a comparatively 02-rich world at birth. To examine the question, we have measured the activities of the antioxidant enzymes in the developing lungs of rabbit fetuses at intervals from 10 d before parturition (gestation period = 31.5 d) to several days after birth. We report here the changes in these protective enzymes that occur over this extended developmental period. Abbreviations MATERIALS AND METHODSAnimals. Pregnant California-strain rabbits were obtained from K-W Farms, Tice, FL. The exact breeding times (2 1 h) were provided by the supplier.All the fetuses used were delivered on the same day by hysterotomy under ketamine:xylazine anesthesia (90 mg/kg: 10 mg/kg) (Ketalar, Parke-Davis, Moms Plains, NJ; Rompun, Payvet Division-Cutter Labs, Shawnee, KS). All the pups used were sacrificed by an overdose of sodium pentobarbital administered intraperitoneally. The timed-gestations were interrupted at 2 1, 22, 26, 28, and 30 d. The pups used were <1-h old, 3-4-d-old, and 5-6-d-old. Adult does used for lung enzyme studies were sacrificed by pentobarbital over...

Undernutrition was found to compromise the tolerance of newborn rat pups to hyperoxia (greater than 95% O2 for 7 days). Survival rate for the normally nourished pups (11 pups/dam) was 56 of 77 (73%) but only 47 of 108 (44%) for the undernourished (18 pups/dam) group (P less than 0.005). Body growth, lung growth, and lung DNA content were significantly reduced by undernutrition. Hyperoxia inhibited these same parameters in both groups of pups. The growth inhibitory effects of O2 and undernutrition were additive, with an especially marked depression of lung DNA content (decreases 65%). Lung maturation was also markedly inhibited by O2 but to a similar extent in both nutrition groups. Despite the disparity in their O2 tolerance, 18/litter and 11/litter pups in O2 responded with equivalent increases in lung antioxidant enzymes. We suggest that the additive depressive effects of neonatal undernutrition and hyperoxia on lung DNA may compromise repair of ongoing O2-induced lung damage and help account for the compromised O2-tolerance we consistently observed even in the presence of significantly elevated antioxidant enzyme defenses.

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Effects on skin blood perfusion of permanent ceramic magnets [0.1 T (1000 G) surface field], individually (disk shaped, 4 cm diameter x 1 cm thick) or in the form of a 11 x 7 in pad ( approximately 28 x 17.8 cm) with an array of 16 rectangular magnets (4.5 x 2.2 cm), were investigated in 16 female volunteers (27.4 +/- 1.7 years, range 21-48 years) using three separate protocols. In protocol A, a disk magnet was placed on the palmar surface of the hand in contact with the thenar eminence (n = 5). In protocol B, the magnet was placed on the hand dorsum overlying the thenar eminence (n = 5). In protocol C, the entire palm and fingers rested on the magnetic pad (n = 6). Magnets were in place for 36 min on one hand, and a sham was in place on the other hand. Blood perfusion was measured on the middle finger dorsum by laser Doppler flowmetry (LDF) and on the index finger by laser Doppler imaging (LDI). Perfusion measurements were simultaneously taken in sham and magnet exposed hands, before and during the entire magnet exposure interval. Magnetic field effects were tested by comparing skin blood perfusion sequences in magnet and sham exposed regions. Results showed no significant changes in either LDF or LDI perfusion at magnet or sham sites during exposure, nor were there any significant differences between sham and magnet sites for any protocol. Measurements of skin temperature at the LDF measurement sites also showed no significant change. It is concluded that in the healthy subjects studied with normal, unstressed circulation, magnets of the type and for the duration used, showed no detectible effect on skin blood perfusion in the anatomical area studied.

Although no effects of permanent magnets on resting skin blood flow (SBF) in humans have yet been demonstrated, the possibility that magnet related effects might modify dynamic SBF changes has not been previously studied. We hypothesized that magnets may alter local neurovascular mechanisms to cause changes in normal SBF vasoactive responses. To test this, we studied the effects of a magnet on SBF reductions induced by sympathetic reflexes associated with deep inspirations. SBF was continuously monitored by a dual channel laser-Doppler flowmeter with probes on the middle finger dorsum of both hands of 24 healthy subjects. In the first of two successive intervals, each of the fingers rested on sham ceramic magnets (control interval). Subsequently, one finger rested on an active magnet and the other finger on a sham (experimental interval). Skin temperatures were also measured. The magnet was a 37 mm diameter  14 mm thick ceramic magnet with a surface field strength of 85 mT measured in the geometrical center of the magnet. Field strength at the finger dorsum, 13 mm above magnet, was 31.5 mT. During each interval, three deep breaths were used to elicit SBF reductions. Responses were calculated as the percent reduction in SBF from its prior 20 s average. Breaths in each interval were spaced 3 min apart to permit full recovery between responses. The experimental interval started after an active magnet was in place for 20 min. Results showed no significant difference in either vasoconstrictive responses or skin temperature due to the magnet. We conclude that magnets of the type, strength and duration used, have no significant effect on vasoconstrictive processes associated with this sympathetic reflex in this group of healthy subjects.

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Effects on skin blood perfusion of permanent ceramic magnets [0.1 T (1000 G) surface field], individually (disk shaped, 4 cm diameter x 1 cm thick) or in the form of a 11 x 7 in pad ( approximately 28 x 17.8 cm) with an array of 16 rectangular magnets (4.5 x 2.2 cm), were investigated in 16 female volunteers (27.4 +/- 1.7 years, range 21-48 years) using three separate protocols. In protocol A, a disk magnet was placed on the palmar surface of the hand in contact with the thenar eminence (n = 5). In protocol B, the magnet was placed on the hand dorsum overlying the thenar eminence (n = 5). In protocol C, the entire palm and fingers rested on the magnetic pad (n = 6). Magnets were in place for 36 min on one hand, and a sham was in place on the other hand. Blood perfusion was measured on the middle finger dorsum by laser Doppler flowmetry (LDF) and on the index finger by laser Doppler imaging (LDI). Perfusion measurements were simultaneously taken in sham and magnet exposed hands, before and during the entire magnet exposure interval. Magnetic field effects were tested by comparing skin blood perfusion sequences in magnet and sham exposed regions. Results showed no significant changes in either LDF or LDI perfusion at magnet or sham sites during exposure, nor were there any significant differences between sham and magnet sites for any protocol. Measurements of skin temperature at the LDF measurement sites also showed no significant change. It is concluded that in the healthy subjects studied with normal, unstressed circulation, magnets of the type and for the duration used, showed no detectible effect on skin blood perfusion in the anatomical area studied.