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ABSTRACT. We used [3H]nitrendipine to characterize dihydropyridine sensitive calcium channels on cells isolated from neonatal (1 d) and weanling (11 wk) rabbit gastric fundic and antral smooth muscle. Incubating with and without nifedipine 20 pM, specific binding was 56 + 4% of total binding at 0.1 nM [3H]nitrendipine. Specific binding was saturable, reversible, achieved equilibrium by 10 min at 4"C, and was linearly related to cell concentration. The affinity constant for [3H]nitrendipine was higher in weanling fundus (kd = 243 f 121 pM) versus antrum (kd = 771 + 190 pM), p < 0.05. There were no age-related changes in affinity. In the antrum, the number of binding sites (B,,,) increased from 6 000 + 266/cell in neonates to 27 500 f 8 440/cell in weanlings (p < 0.05). In the fundus B, , , was 7 750 + 2 100/cell in neonates, and there was no age-related change. To assess function, we compared isometric stress in full thickness muscle strips oriented to the circular layer. Bethanechol stimulated dose-dependent tonic contractions in the fundus and phasic contractions in the antrum. Maximal stress increased with age from 305 + 54 mN/cm2 to 1140 + 73 mN/cmZ (p < 0.05) in the fundus and from 72 f 20 mN/cm2 to 154 f 30 mN/cm2 (p < 0.05) in the antrum. Preincubation and incubation without calcium resulted in reversible inhibition of contraction at both ages. Nifedipine 10-pM inhibited 100% of bethanechol-stimulated contraction in the antrum, but only 25% in the fundus at both ages. In summary, in rabbit gastric smooth muscle: 1 ) 13H]nitrendipine identified functional calcium channels in neonates and weanlings, 2) there are age-related increases in calcium channels on antral, but not on fundic cells, 3) there are age-related increases in stress in strips from antrum and fundus, 4) the fundus utilizes intracellular calcium stores for bethanechol-stimulated contraction, whereas the antrum requires extracellular calcium. Age-related increases in dihydropyridine sensitive calcium channels are consistent with the requirement of the antrum for extracellular calcium to support contraction. (Pediatr Res 25:600-604, 1989) In muscle strips from rabbit stomach, maximal contraction was greater in adult compared to newborn animals (1). These data were compatible with studies in humans, showing that the intraluminal pressures achieved in the stomach are greater in adults compared to neonates (2). The age-related changes in gastric smooth muscle physiology that are responsible for increasing contraction have not been examined.

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Background: We sought to examine the influence of various marginal donor criteria on pediatric heart transplantation outcome. Methods: We reviewed the medical records of 191 pediatric heart transplants performed in 174 patients from 1984 through 2003 at our institution. Recipients were grouped into four (0, 1, 2, and ≥ 3 marginal factors) based on number of donor marginal criteria. A marginal donor allograft was defined by at least one of the following criteria: hx of cardiac arrest, LVEF≤50%, positive hepatitis B or C serology, dopamine ≥ 10 mcg/kg/min, gender mismatch (female donor), age ≥ 34 yr, allograft ischemia time ≥ 6 hours and donor-recipient weight ratio ≤ 0.8 ≥ 2. Study endpoints were actuarial survival and freedom from rejection. A Cox proportional hazards model was used for statistical analysis. Results: