Ocular findings in cystic fibrosis patients receiving vitamin A supplementation.

BACKGROUND: Vitamin A deficiency with eye symptoms has been reported in patients with cystic fibrosis who received the recommended daily intake of vitamin A. METHODS: We measured serum retinol, dark adaptation, contrast sensitivity, and dry eye status in 35 adult cystic fibrosis patients to ascertain whether they had ocular signs or symptoms. RESULTS: Median serum retinol concentration was 1.95 mumol/l, range 1.08-4.01 mumol/l, with no values indicating vitamin A deficiency. Retinal light sensitivity was normal. Nineteen patients had reduced contrast sensitivity. Conjunctival imprints all showed plenty of goblet cells, but were characteristic of dry eye in 42% of patients (n = 14). Decreased tear film stability was found in 49% (n = 17), tear production was low in 31% (n = 11), and 23% (n = 8) showed an increased amount of dying epithelial cells. Nine patients (26%) had keratoconjunctivitis sicca according to the Copenhagen criteria. CONCLUSION: Our patients had no biochemical or clinical signs of vitamin A deficiency. We speculate that the high incidence of dry eye could be a primary manifestation of cystic fibrosis.

Beta-adrenergic receptor-mediated functions in porcine adipose tissue are not affected differently by saturated vs. unsaturated dietary fats.

Young postweaning pigs were fed a high fat diet containing beef tallow (saturated fat) or corn oil (unsaturated fat). Adipose tissue was used to measure adipocyte size and number of cells per gram of tissue, ligand binding by beta-adrenergic receptors and lipolytic and palmitate esterification rates. Pigs fed the saturated fat diet had more saturated and monounsaturated fatty acids and less polyunsaturated fatty acid in the crude membrane fraction. Adipocytes were larger in pigs fed the saturated fat diet. There was no difference in the binding affinities of the receptors; more binding sites were expressed on a protein or cell basis and fewer sites were expressed per unit surface area in adipocyte ghosts isolated from pigs fed the saturated fat diet. Fatty acid esterification was greater in pigs fed saturated fat diets. Isoproterenol inhibition was marginal in both groups but tended to be greater in pigs fed saturated fat diets. The beta-adrenergic receptor-mediated lipolytic rates were not different; only the theophylline-stimulated rates tended to be greater in the saturated fat-fed group. Thus, a large increase in saturated fatty acid concentration of porcine adipose tissue membranes caused an increase in beta-adrenergic receptor number without any change in receptor affinity. These receptor changes were at best only marginally reflected in beta-adrenergic agonist-mediated functions.

Extracellular volume estimation from ratios of bromide to chloride in urine or saliva.

Use of either urine or saliva samples to estimate extracellular water volume was investigated in 10 men using nonradioactive bromide (Br) and in seven newborn piglets using radioactive Br (82Br) and chloride (36Cl). The relation to Br to Cl concentrations in urine enabled an estimation of Br dilution volume from human urine (267 +/- 42 ml/kg, mean +/- SD) that was not significantly different (P = 1.0) from the Br dilution volume calculated from plasma Br concentration (268 +/- 20 ml/kg). Although the Br dilution volume estimated from saliva was not different from that of plasma, the error in the estimates of Br dilution volume from saliva was too large (mean difference, -36 +/- 64 ml/kg) to make its use practical. The data from piglets showed good agreement between 82Br and 36Cl dilution volumes calculated from 4-hr plasma samples (356 +/- 14 ml/kg and 347 +2- 12 ml/kg; P greater than 0.1) and between 82Br dilution volumes calculated from urine 82Br:36Cl and plasma 82Br (360 +/- 31 ml/kg and 356 +/- 14 ml/kg; P greater than 0.1). Extracellular water volume can be estimated in both adult and young animals using the Br dilution volume calculated from urine samples. It requires (i) two urine collections: one before and one 4 to 8 hr after administration of Br; (ii) a measurement or estimate of plasma Cl concentration; and (iii) a correction factor that describes the relationship of the ratio of Br to Cl in urine to that ratio in plasma.

A comparison of chloride, bromide, and sucrose dilution volumes in neonatal pigs.

Use of 36Cl, 82Br, and [3H]sucrose to estimate extracellular water volume was evaluated in 14 piglets (7-14 days old). 36Cl and 82Br were distributed in approximately the same volume, but a period of 5-6 hr after injection was required to reach equilibrium in the neonatal pig. Dilution volumes calculated before equilibration (2-5 hr) for 36Cl (326 +/- 11 ml/kg) and 82Br (328 +/- 13 ml/kg) were different from equilibration (6-8 hr) phase volumes (356 +/- 13 ml/kg and 355 +/- 13 ml/kg, respectively; P less than 0.001). A 3-hr sample estimated the same volume distribution calculated by extrapolation of the 6- to 8-hr period because of the relationship between the two slopes of the plasma clearance curves. After the 82Br and 36Cl had achieved equilibration, each was distributed in a volume equivalent to total body chloride space (362 +/- 29 ml/kg) measured by neutron activation; no statistical differences were found (P = 0.6). The early equilibration phase measured a 10% smaller, faster exchangeable fraction of total body Cl. Sucrose dilution volume (332 +/- 19 ml/kg) required multiple plasma samples for extrapolation and measured a dilution volume 7% smaller (P less than 0.05) than total body chloride space.

Measurement of extracellular water volume by bromide ion chromatography.

Extracellular body water can be determined from plasma bromide dilution. Plasma Br is separated from other anions by ion chromatography and is detected at an ultraviolet wavelength of 210 nm. Plasma proteins are removed by ultrafiltration, and interference by plasma chloride is minimized by dilution and the use of 5 mmol NaCl/L as the eluant. Human plasma samples were spiked with known quantities of Br (between 37.54 and 125.14 mumol/L) and were measured by ion chromatography. The results were reproducible to within 0.72 mumol/L (SD) and differed from the gravimetric values by -1.88 +/- 4.27 mumol/L (mean +/- SD). The difference, however, was not significantly different from 0 (p = 0.19). Extracellular water volumes of 10 newborn minipigs measured by Br dilution by using the chromatographic technique (400 +/- 63 mL/kg) were comparable with literature values reported for premature infants.