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Experiments were conducted to determine effects of the synthetic glucocorticoid, dexamethasone, on the lipid fluidity of cultured rabbit cardiac muscle microvessel endothelial cells and the possible role(s) for altered fluidity in the steroid inhibition of cellular eicosanoid production. Following a sixteen hour exposure to 10(-7) M dexamethasone, membranes prepared from treated cells exhibited a decreased fluidity compared to their control counterparts, as assessed by steady-state fluorescence polarization techniques using 1,6-diphenyl-1,3,5-hexatriene (DPH). Examination of the effects of temperature on the anisotropy values of DPH using Arrhenius plots revealed consistent differences in the steroid treated cells over the entire temperature range (40-5 degrees C). These dexamethasone-dependent fluidity changes were associated with increases in the cholesterol/phospholipid ratio of membrane lipids. Restoration of membrane fluidity to control values with the fluidizing agent, 2-(2-methoxyethoxy)ethyl-8-(cis- 2-n-octylcyclopropyl)octanoate (A2C), partially reversed dexamethasone induced inhibition of A23187-stimulated eicosanoid release. These observations suggest that at least part of dexamethasone's inhibitory actions on eicosanoid generation in microvessel endothelial cells are mediated by alterations in membrane composition and fluidity.

To determine the effects of prolonged low-density lipoprotein (LDL) exposure in vitro on cultured endothelial cell (EC) lipid dynamics and cellular function, human umbilical vein ECs were incubated in LDL concentrations [cholesterol (Chol) = 240 mg/dl] associated with the premature development of atherosclerosis. After 4 days of incubation, cells were examined for changes in cellular lipid composition and for membrane fluidity. Results indicate that LDL-EC have increased Chol content (control EC vs. LDL-EC = 22.4 +/- 5.26 vs. 38.9 +/- 0.24 nmol/10(6) cells, P less than 0.05) and cellular Chol-to-phospholipid ratio (0.61 +/- 0.10 vs. 1.21 +/- 0.10 mol/mol, P less than 0.05). Augmentation of EC Chol content was accompanied by a marked decrease in EC cellular membrane fluidity as assessed by fluorescence polarization (anisotropy, r values, 0.172 +/- 0.019 vs. 0.226 +/- 0.014, P less than 0.0001). LDL-induced changes in EC lipid dynamics were associated with enhanced EC binding of monocytes (P less than 0.05) and U937 cells (P less than 0.01). Both LDL-induced decreases in membrane fluidity and enhanced attachment of mononuclear cells were reversed to control levels following a 2-min incubation of LDL-EC with the membrane mobility agent, A2C. These data therefore suggest that LDL-induced modulations in lipid dynamics play an important role in perturbation of EC function.

Lactose-intolerant children manifest diminished or nonexistent intestinal lactase activity, resulting in flatulence, abdominal pain, and diarrhea. To assess the hydrolytic capability of lactase-containing tablets taken immediately before oral lactose challenge, we studied 18 children previously identified as being lactose intolerant and having no underlying organic gastrointestinal disease. Subjects had a mean (+/- SEM) age of 11.4 +/- 3.4 years; 72% were male. At time of the study, lactase-containing tablets or placebo tablets were ingested (double-blind) immediately before drinking a solution of lactose. Breath samples were obtained for hydrogen analysis at 30-minute intervals during a 2-hour period, and clinical symptoms were monitored. In lactose-intolerant patients, hydrogen production was significantly greater following placebo (maximum hydrogen excretion, approximately 60 ppm) compared with lactase-containing tablets (maximum hydrogen excretion, 7 ppm). Increased hydrogen production was associated with clinical symptoms including abdominal pain (89% of subjects following placebo ingestion), bloating (83%), diarrhea (61%), and flatulence (44%). These results indicate, therefore, that coingestion of lactose and lactase-containing tablets significantly reduces both breath hydrogen excretion and clinical symptoms associated with lactose intolerance.

To determine an effective nutritional regimen for management of growth failure in infants with congenital heart disease and congestive heart failure, the authors studied 19 infants with cardiac anomalies who were not candidates for early corrective surgery. Patients were randomly assigned to one of three feeding groups: group 1 (n = 7) received continuous, 24-hour nasogastric alimentation; group 2 (n = 5) received overnight, 12-hour nasogastric infusions plus daytime oral feedings as tolerated; and group 3 (n = 7) received oral feedings alone. For all patients, commercial infant formula (cow's milk or soy protein) was supplemented to a calorie density of approximately 1 kcal/mL. During a 5.25 +/- 0.45 month study period, only group 1 infants achieved intakes greater than 140 kcal/kg per day (mean = 147 kcal). Serial anthropometric measurements demonstrated that only 24-hour infusions (group 1) were associated with significantly improved nutritional status, when assessed by z scores for weight (P less than .01) and length (P less than .05). Group 1 infants also showed marked increases in midarm muscle circumference and triceps and subscapular skinfold thicknesses (P less than .01, compared with groups 2 and 3). These data suggest that infants with congenital cardiac defects complicated by malnutrition manifest increased nutrient requirements for growth and weight gain. Continuous, 24-hour, nasogastric alimentation is a safe and effective method for achieving both increased nutrient intake and improved overall nutritional status in these infants.

To examine the ontogenesis of bile acid transport in the rabbit ileum, brush-border membrane vesicles (12- to 20-fold purified) were prepared from 14- to 49-day-old animals. Taurocholate uptake was characterized by the emergence of secondary active, Na(+)-dependent transport at the start of weaning (21 days). Transient intravesicular accumulation (overshoot) of taurocholate occurred at 5-10 s of incubation, and the overshoot maximum increased significantly from 21 days (349.2 +/- 22.4 nmol/mg protein) to 35 days (569.0 +/- 84.3 nmol/mg protein; p less than 0.001), without further increase at maturity (49 days, not equal to 607.6 +/- 136.7 nmol/mg protein). No significant taurocholate active uptake component was noted at 14 days; however, ileal vesicles from sucklings showed carrier-mediated, Na+ D-glucose cotransport. In greater than or equal to 35-day-old rabbits, osmolarity studies at 20 s of incubation showed that only approximately 12% of [14C]taurocholate uptake was secondary to bile acid-to-membrane binding. Conversely, at 20 min, greater than 95% of radiolabel incorporation represented solute bound to the external and/or internal membrane surface. Arrhenius plots establish brush-border membrane taurocholate uptake as an intrinsic, lipid-dependent process, with a slope discontinuity between 24 and 28 degrees C, similar to the membrane lipid thermotropic transition region. Steady-state fluorescence polarization studies (1,6-diphenyl-1,3,5-hexatriene) demonstrate a temporal association between the maturation of taurocholate uptake and age-related decreases in ileal brush-border membrane fluidity. These data indicate that maturation of bile acid secondary active transport in the rabbit ileum may be regulated, at least in part, by changes in brush-border membrane lipid dynamics.

To evaluate relationships between gastroesophageal reflux (GER) and the development and onset of apparent life-threatening event(s) (ALTE), 16 infants presenting with ALTE and 6 control subjects manifesting clinical GER alone were studied using prolonged, esophageal pH monitoring in conjunction with simultaneous pulse oximetry and transthoracic impedance pneumocardiography. Despite the absence of a clinical vomiting history in 14 of 16 patients with ALTE, the incidence of GER was similar in both groups (patients with ALTE vs control subjects, 95% vs 100%). Significant arterial oxygen desaturation (less than 90% for greater than 3 minutes) was monitored during 60 episodes in 14 of 16 infants with ALTE, compared with no episodes of reduced arterial oxygen saturation in control subjects. Fifty-four of 60 of these desaturation events commenced within 3.9 +/- 0.4 minutes (mean +/- SD) of onset of a drop in esophageal pH to less than 4.0. Linear regression analysis indicates a significant correlation between duration of esophageal acidification and length of individual hypoxemic episodes (r = .39). Pneumocardiograms were normal in all patients. These data suggest that unsuspected GER is common in infants presenting with ALTE and, in these patients, GER may be directly associated with reflex hypoxemic episodes. Prolonged intraesophageal pH monitoring, performed simultaneously with evaluation for apnea, should be considered in all infants presenting with ALTE.

Characteristics of small intestinal microvillus membrane lipid composition and associated lipid fluidity were studied throughout postnatal development in the rabbit. Microvillus membranes from jejunal and ileal epithelia were isolated in high purity from 14 days to adulthood. Significant jejunal-ileal differences in microvillus membrane cholesterol to phospholipid molar ratios were observed at all ages. Despite a relatively constant cholesterol content (as percentage of total lipids) both regionally and at all ages, marked increases in the microvillus membrane cholesterol to phospholipid ratio were observed after weaning in both jejunum (14 days = 0.56, adult = 0.83) and ileum (14 days = 0.66, adult = 0.98). Further age-related changes in microvillus membrane lipid composition were characterized by a significant reduction in the weight ratio of saturated to unsaturated fatty acids in jejunum and ileum and by the emergence, in the mature animal, of a jejunal-ileal difference in total lipid content (jejunum = 1.21 mg/mg protein, ileum = 1.01 mg/mg protein). Changes in microvillus membrane lipid fluidity estimated by fluorescence polarization spectrometry directly paralleled changes in the cholesterol to phospholipid molar ratio. Fluorescence anisotropy of jejunal and ileal microvillus membranes increased during the weaning period, suggesting decreased membrane fluidity. At all ages, ileal membranes were relatively less fluid than jejunal microvillus membrane. Studies of protein-free microvillus membrane liposomes, prepared from extracted membrane lipid, confirmed a major lipid-dependent thermotropic transition point at approximately 23 degrees C in adult jejunal and approximately 25 degrees C in adult ileal enterocyte membranes, although no clear transition point was observed in suckling microvillus membrane. These combined data suggested that significant alterations in the microvillus membrane lipid composition and its physical-chemical properties occur during postnatal development in both jejunal and ileal rabbit small intestinal microvillus membrane. It is proposed that membrane lipid-dependent structural characteristics may be directly related to the maturation of enterocyte transport function.

Frank clinical selenium deficiency has been described in cystic fibrosis (CF), and a relative deficiency has been proposed as contributing to the pathogenesis of the disease. Because of these possibilities, we investigated the relationship between overall nutritional status in CF with measures of selenium nutriture. Fifteen stable outpatients with CF (group I) were compared to 13 age-matched controls (group II) and 27 healthy adults (group III). Whole blood, plasma, and red blood cell selenium levels were reduced by 31%, 29%, and 33%, respectively, in CF patients vs controls (all p less than 0.001). In addition, both groups I and II showed significantly lower blood selenium levels than healthy adults (p less than 0.005). Nutritional assessment revealed CF patients to be undernourished, with significant decreases in serum albumin (p less than 0.025), weight-for-height deficit (p less than 0.01), and weight-for-age (p less than 0.025) vs controls. However, only the triceps skinfold (TSF) measurement correlated significantly with selenium status (r = 0.56: p less than 0.05 for whole blood selenium vs TSF). We conclude, based on the magnitude of decrement in blood selenium, that it is unlikely that selenium plays a significant primary pathogenic role in cystic fibrosis. However, these patients are at high risk for developing clinical selenium deficiencies. The measurement of blood selenium levels using appropriate age-matched normal standards should be mandatory in all CF patients with malnutrition, or in those requiring parenteral nutritional support.

Over a one-year period, 95 children and adolescents presenting with epigastric pain and/or vomiting, and without associated risk factors for development of peptide disease, underwent endoscopic antral biopsies for pathologic diagnosis and to detect presence of Campylobacter ss. pylori (C. pylori). Additional biopsies of the esophagus, stomach, and duodenum were obtained for histologic evaluation. C. pylori was identified in 16 patients (16.8%), all of whom had evidence of acute and/or chronic gastritis. Significant discriminating factors between C. pylori-positive and -negative subjects included age at presentation (positive vs negative = 14.6 vs 9.9 years, P less than 0.01), biopsy-confirmed gastritis (100% vs 30.4%, P less than 0.001), and diagnosis of duodenitis alone (0% vs 46.8%, P less than 0.001). Risk for bacterial colonization was significantly higher in the presence of endoscopic gastritis (P less than 0.001). Among C. pylori-positive patients, none responded to standard antiulcer therapy (H2-receptor antagonists, antacids). Symptomatic and histologic remission was achieved utilizing combined therapy with bismuth subsalicylate and antibiotics. Seven of 79 C. pylori-negative patients with biopsy-proven gastritis who responded poorly to antisecretory therapy had the organism identified in follow-up antral biopsies; these patients improved clinically following treatment for C. pylori. These data suggest that C. pylori is a significant factor in the etiology of upper gastrointestinal tract inflammatory disease in pediatrics, and presence of the organism should be evaluated, particularly in children with evidence of acute and/or chronic gastritis.

The incidence and temporal patterns of gastroesophageal reflux (GER) in infants presenting with an apparent life-threatening event (ALTE) was compared with GER characteristics of infants evaluated for persistent emesis, utilizing continuous 24 h intraesophageal pH monitoring. These data indicate that the incidence of significant GER was similar in both groups, despite the absence of a clinical vomiting history in 46% of ALTE patients. Furthermore, infants with ALTE demonstrate a significantly higher incidence of sleep reflux when compared with control infants presenting with vomiting alone (27 vs. 0%, p less than 0.001). Awake GER beyond the first two postprandial hours was not observed in either study group. Monitoring results, therefore, indicate that significant GER is common in infants with ALTE; and these infants manifest an apparently unique pattern of GER distinct from that observed in age-matched controls with GER alone. Possible relationships between GER in ALTE patients and the development/onset of apneic episodes are discussed.

We evaluated five children with severe psychomotor retardation who developed frequent vomiting and poor weight gain after surgical placement of a feeding gastrostomy tube. Prolonged pH probe testing before surgery did not reveal notable gastroesophageal reflux (GER). Treatment with 12-hour gastrostomy tube feeding resulted in a marked reduction in vomiting; after one year of continuous feeding, all patients had achieved significant weight gain (mean, 44.0%). Esophageal manometrics and 24-hour pH probe testing before and at the end of the 12-month continuous-feeding period demonstrated low pressures of the lower esophageal sphincter and significant GER in the five children studied. These results indicate that children may develop symptomatic GER after gastrostomy tube placement. In such patients continuous gastrostomy tube feeding may result in a cessation of vomiting and achievement of significant weight gain. Definitive antireflux surgery can then be performed with the patient in an improved nutritional state.

To evaluate physicochemical properties of the small intestinal basolateral cell surface during postnatal development, membranes were isolated from suckling (14-17 days) and weanling-mature (35-49 days) rabbit jejunal and ileal enterocytes at 30- to 40-fold purification (based on Na+-K+-ATPase specific activity) and with limited contamination from coisolated cellular elements. Membrane lipid analysis demonstrated age-dependent reductions and proximal to distal increases in total lipid (per milligram protein). Postnatal increases in membrane total cholesterol of jejunum (suckling vs. mature, 0.18 vs. 0.26 mumol/mg protein; P less than 0.01) and ileum (0.18 vs. 0.31 mumol/mg protein; P less than 0.01) resulted in markedly higher cholesterol-to-phospholipid molar ratios (jejunum, 0.43 vs. 0.73; ileum, 0.43 vs. 0.72 mumol/mg protein; P less than 0.01). Membranes from mature animals had higher relative sphingomeylin and phosphatidylcholine content and, in both age groups, fatty acyl saturation was increased in ileum compared with jejunum. By utilization of the fluorophores 1,6-diphenyl-1,3,5-hexatriene and DL-12-(9-anthroyl)stearic acid, the fluidity of basolateral membranes and liposomes prepared from extracted membrane lipid decreased markedly in mature rabbits. Arrhenius plots demonstrated higher apparent thermotropic transition temperatures of mature membrane lipid. These data therefore demonstrate significant changes in small intestinal basolateral membrane lipid composition and fluidity that occur during the weaning period. Possible relationships to ontogenesis of membrane protein function are discussed.

To evaluate the role of artificial feeding and natural feeding in early growth of enteric mucosa, we determined enteric mucosal mass, protein and DNA content, and disaccharidase activities in beagle puppies at birth, and after 24 h of either natural or artificial feeding. Despite similar increases in body weight over the first 24 h of life, neither mucosal mass, DNA content, nor protein content of the artificially fed animals was different from that of newborn animals. In contrast, mucosal mass of the suckled animals was 75% greater, DNA content was 56% greater, and protein content was 93% greater than that of newborn animals. The mucosal protein/DNA ratio of the suckled animals was greater than that of newborn, but not artificially fed animals. The greater DNA, protein, and protein/DNA ratio in this group suggest that the greater mucosal mass is a result of both cellular hyperplasia and hypertrophy. Sucrase specific activity of the suckled animals was less than that of the artificially fed but not the newborn animals. Other disaccharidase activities were not different among the three groups. These data extend the findings of Widdowson et al.(25) to another species and demonstrate that this rapid enteric growth over the first day of life results only from natural feeding. They strongly suggest, therefore, that rapid early enteric growth, mediated perhaps by a factor in natural milk that stimulates enteric mucosal growth, is an important heretofore unappreciated phase of intestinal development.

A severe infantile form of nemaline myopathy has a high mortality rate when untreated because of subsequent malnutrition and respiratory failure. Three infants with this condition demonstrated persistent vomiting, poor weight gain, and recurrent pneumonias. Esophageal manometry demonstrated decreased lower esophageal sphincter pressures and low amplitude peristalsis; 24-hour esophageal pH monitoring revealed significant gastroesophageal reflux. Medical therapy was ineffective in relieving symptoms. After antireflux surgery, vomiting and respiratory symptoms ceased, and there was no longer significant gastroesophageal reflux during pH monitoring. Our experience indicates that in some infants with nemaline myopathy a severe form of gastroesophageal reflux develops that is not responsive to medical therapy. Early surgical intervention may decrease life-threatening complications associated with gastroesophageal reflux in these infants.

During a period of 30 months, cow's milk- or soy protein-induced colitis was diagnosed in 22 infants. All patients presented with hematochezia. Only three patients had substantial diarrhea. Colonoscopic evaluations demonstrated a characteristic mucosal appearance, manifested by aphthoid ulcerations with intervening, normal-appearing mucosa. Histologic findings included surface ulcerations and associated inflammation of the lamina propria and submucosa, marked by substantial eosinophilic infiltration. Both clinical symptoms and colonoscopic abnormalities rapidly resolved in all patients after the elimination of cow's milk and/or soy protein from the diet. These data indicate that hematochezia may be the predominant symptom of cow's milk protein and soy protein intolerance in many affected infants, and that colonoscopy is the most effective means of establishing a definitive diagnosis in this patient population.

A new 24-h ambulatory esophageal pH monitoring system (AMBI 24) was evaluated in 72 pediatric patients with suspected gastroesophageal reflux (GER). Forty-seven of these patients were monitored at home and the other 25 in our hospital. This system was employed without complication in infants and a full range of pediatric patients, as well as in older children with severe psychomotor delay. The data obtained were consistent with those reported utilizing standard monitoring equipment, and the results served as the basis for subsequent medical management. The results of this study, therefore, suggest that this method of esophageal pH monitoring is a safe and effective means of evaluating GER while allowing for patient mobility.

The effects of ethinyl estradiol, a synthetic estrogen with cholestatic properties and a propensity to alter hepatocyte and ileal brush-border membrane fluidity, on lipid structure and Na+-K+-ATPase activity of rabbit small intestinal basolateral membranes were determined. Utilizing the fluorophores 1,6-diphenyl-1,3,5-hexatriene and DL-12-(9-anthroyl)stearic acid, increases in fluorescence anisotropy, the reciprocal of fluidity, were found in basolateral membranes and in membrane lipid liposomes isolated from ileum. Fluidity alterations were accompanied by a marked decrease in bilayer phospholipids (0.37 vs. 0.48 mumol/mg protein; P less than 0.01) and an increase in both the cholesterol-to-phospholipid molar ratio (0.85 vs 0.61; P less than 0.02) and membrane saturated fatty acid content. Estrogen-mediated physicochemical changes were associated with a significant reduction in ileal basolateral membrane Na+-K+-ATPase specific activity (100.0 vs. 185.8 nmol Pi.min-1.mg protein-1; P less than 0.02). Control values both for fluorescence anisotropy and for Na+-K+-ATPase specific activity were restored after in vitro membrane fluidization with benzyl alcohol. The data therefore indicate that ethinyl estradiol effects on basolateral membrane lipid dynamics are confined to the ileum and are associated with inhibition of Na+-K+-ATPase activity. These structural and functional changes appear to be related, in part, to specific modifications in the availability of phospholipid after estrogen treatment.

Using succinylacetone (SA), a metabolite of tyrosine excreted in excess by infants and children with hereditary tyrosinemia and the renal Fanconi syndrome (FS), we have investigated developmentally-related membrane transport events leading to emergence of the generalized renal tubular dysfunction seen in human FS. SA was found to impair sugar and amino acid uptake by both newborn renal tubules and 7-day renal brush-border membrane vesicles (BBMV). This impairment by SA was due in part to a slowing of substrate cotransport rate of 22Na+-entry into BBMV. Concentration-dependent uptake studies indicated SA inhibited the newborn high-affinity transport systems for sugars and amino acids. SA also caused an increase in membrane fluidity and a shift in the thermotropic transition temperature. The demonstrated dual nature of SA's effect on membrane fluidity and O2 consumption, together with the relative contribution of each component to SA-induced transport impairment helps to provide a basis for an understanding of the age-related increases in glucosuria, aminoaciduria and natriuria seen in infants with FS.

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.

We have characterized microvillus membrane (MVM) lipid composition and derived estimates of membrane fluidity using fluorescence polarization [with 1,6-diphenyl-1,3,5-hexatriene (DPH) as the probe] in MVM from the jejunum and ileum of suckling (day 14-20) and mature postweaning (day 28-49) rats. The anisotropic values are lower (i.e., increased fluidity) in MVM from jejunum and ileum of suckling rats compared with values from MVM of mature rats, suggesting a more disordered molecular environment in MVMs of suckling animals, although the ileal MVM was relatively less fluid than jejunal membranes in both groups. Anisotropic determinations in protein-free MVM liposomes demonstrate that protein-lipid interactions are major determinants of fluidity estimates. Arrhenius plots of DPH anisotropies in MVM and MVM liposomes indicate a thermotropic lipid-phase transition at 23 degrees C in mature rat jejunum and ileum; however, no clear transition point was observed in 14- to 20-day animals. In addition, both the jejunal and ileal MVM in suckling animals contained greater amounts of total lipid, cholesterol, and phospholipid per milligram protein than did mature MVM preparations. Membrane phospholipid composition changed with age, with a decrease in sphingomyelin and an increase in phosphatidylcholine in the jejunum of the postweaning animal and with similar weight ratios of saturated to unsaturated fatty acids in both age groups. The data demonstrate that the small intestinal MVM manifests both age-dependent and regional proximal-distal differences in lipid composition and biophysical properties.(ABSTRACT TRUNCATED AT 250 WORDS)