Biomedical subjects
Publications and source records attributed to M S Medow.
A 15-month-old girl with celiac disease presented with microcephaly and developmental delay. Head growth resumed during a gluten-free diet. Subsequent gluten ingestion resulted in no head growth, areflexia, and increased celiac antibodies. All resolved with gluten elimination. Poor head growth may precede other clinical manifestations of celiac disease.
Stimulation of the local renin-angiotensin system and apoptosis characterize the diabetic heart. Because IGF-1 reduces angiotensin (Ang) II and apoptosis, we tested whether streptozotocin-induced diabetic cardiomyopathy was attenuated in IGF-1 transgenic mice (TGM). Diabetes progressively depressed ventricular performance in wild-type mice (WTM) but had no hemodynamic effect on TGM. Myocyte apoptosis measured at 7 and 30 days after the onset of diabetes was twofold higher in WTM than in TGM. Myocyte necrosis was apparent only at 30 days and was more severe in WTM. Diabetic nontransgenic mice lost 24% of their ventricular myocytes and showed a 28% myocyte hypertrophy; both phenomena were prevented by IGF-1. In diabetic WTM, p53 was increased in myocytes, and this activation of p53 was characterized by upregulation of Bax, angiotensinogen, Ang type 1 (AT(1)) receptors, and Ang II. IGF-1 overexpression decreased these biochemical responses. In vivo accumulation of the reactive O(2) product nitrotyrosine and the in vitro formation of H(2)O(2)-(.)OH in myocytes were higher in diabetic WTM than TGM. Apoptosis in vitro was detected in myocytes exhibiting high H(2)O(2)-(.)OH fluorescence, and apoptosis in vivo was linked to the presence of nitrotyrosine. H(2)O(2)-(.)OH generation and myocyte apoptosis in vitro were inhibited by the AT(1) blocker losartan and the O(2) scavenger TIRON: In conclusion, IGF-1 interferes with the development of diabetic myopathy by attenuating p53 function and Ang II production and thus AT(1) activation. This latter event might be responsible for the decrease in oxidative stress and myocyte death by IGF-1.
The present study investigated the effects of sustained hydrostatic pressure (SHP; up to 4 cm H2O) on human umbilical vein endothelial cell (HUVEC) proliferation, focal adhesion plaque (FAP) organization, and integrin expression. Exposure of HUVECs to SHP stimulated cell proliferation and a selective increase in the expression of integrin subunit alphaV. The increase in alphaV was observed as early as 4 hours after exposure to pressure and preceded detectable increases in the bromodeoxyuridine labeling index. Laser confocal microscopy studies demonstrated colocalization of the alphaV integrin to FAPs. The individual FAPs in pressure-treated cells demonstrated a reduced area and increased aspect ratio and were localized to both peripheral and more central regions of the cells, in contrast to the predilection for the cell periphery in cells maintained under control pressure conditions. The pressure-induced changes in alphaV distribution had functional consequences on the cells: adhesivity of the cells to vitronectin was increased, and alphaV antagonists blocked the pressure-induced proliferative response. Thus, the present study suggests a role for alphaV integrins in the mechanotransduction of pressure by endothelial cells.
BACKGROUND: Nonspecific esophageal motility disorders (NEMDs) have been identified in up to 50% of adults with noncardiac chest pain or dysphagia. This study sought to determine the incidence of NEMDs in children with upper gastrointestinal tract symptoms and to evaluate the clinical course of pediatric patients with these manometric abnormalities. METHODS: The study involved 154 children aged 4 to 18 years (mean age, 11.6+/-2.6 years [SE]) who had upper gastrointestinal, swallowing-related symptoms. The children were evaluated by 24-hour intraesophageal pH monitoring, esophageal manometry, and esophagogastroduodenoscopy. RESULTS: Gastroesophageal reflux (GER) was diagnosed by pH study in 109 (71%) of 154 patients, and examination of biopsy specimens demonstrated esophagitis in 70 children with GER. Results of esophageal manometry were abnormal in 30 (67%) of 45 children without GER. A variety of motility disorders were diagnosed in 17 of the patients without GER, whereas NEMDs were diagnosed in the remaining 13 children (mean age, 10.6+/-2.7 years; 10 boys, 3 girls). Patients with GER showed normal esophageal wave propagation; however, mean lower esophageal sphincter pressure was significantly lower in patients with GER than in children with NEMDs. The children with NEMDs exhibited a diverse array of symptoms, including esophageal food impaction in 4 of the 13 patients. During a 36.2+/-4.3-month follow-up period, no correlation was found between therapeutic intervention and clinical course in the 13 patients with NEMDs. Symptomatic improvement occurred in 6 of 13 patients, including 3 children for whom no pharmacologic therapy was prescribed. CONCLUSIONS: These data indicate that NEMDs represent a common group of esophageal manometric abnormalities in children with upper gastrointestinal tract symptoms and without GER. Food impaction appears to be a relatively frequent complication, and NEMDs should be considered in children who have this finding.
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We describe a pediatric patient with dyskeratosis congenita, whose symptoms included abdominal pain, vomiting, dysphagia, and hematochezia. Gastrointestinal symptom are prominent in this rare genetic disorder.
OBJECTIVE: To determine the importance of acid reflux-induced dysmotility in the genesis of noncardiac chest pain in children. METHOD: We performed esophageal manometries during intraesophageal perfusion with 0.9% NaCl or 0.1 N HCl in 19 children (age, 14.5 +/- 0.5 yr) with gastroesophageal reflux, biopsy-proven esophagitis, and complaints of at least one episode of chest pain per day. RESULTS: Baseline esophageal motilities were normal in all patients. Eight of 19 children (42%) complained of chest pain during intraesophageal acid perfusion. In three of these eight patients, complaints of chest pain during acid perfusion were temporally associated with "conversion" of previously normal motility patterns to manometric tracings, indicating esophageal dysmotility. Compared with findings during saline perfusion, esophageal acid exposure in these three children resulted in significant increases in both the duration (13.6 +/- 4.0 vs 3.2 +/- 0.2 s, p < 0.05) and amplitude (105.2 +/- 7.8 vs 61.2 +/- 2.1 mm Hg, p < 0.05) of esophageal contractions during wet swallows. Symptoms of chest pain resolved in all patients after therapy with H2-receptor antagonists. CONCLUSIONS: These data represent the first demonstration of acid-induced esophageal dysmotility in children with chest pain and suggest that reflux-induced motor abnormalities contribute to the onset and/or exacerbation of chest pain in pediatric patients with gastroesophageal reflux and esophagitis.
Taurine, a product of sulfur amino acid metabolism, is important in cerebral osmoregulation. To understand the adaptive changes in transport which accompany different hyperosmolal states, we determined lipid composition and fluorescence anisotropy of synaptosomal liposomes from rats with chronic hypernatremic dehydration (CHD), streptozocin-induced (STZ) diabetes, and insulin treated diabetes. Induction of CHD increased serum osmolality, and enhanced in vitro synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Fluorescence anisotropy studies showed that the fluidity of lipids from CHD synaptosomes was higher than control (P < 0.05, n = 3). STZ-diabetes resulted in hyperglycemia, increased serum osmolality, and stimulated synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Insulin treatment of diabetic rats restored serum osmolality and taurine transport to control values. The fluidity of diabetic rat brain synaptosomal lipids was significantly higher than control (P < 0.05, n = 3); fluidity was normalized by insulin administration to diabetic rats. Total fatty acid, cholesterol, and cholesterol/phospholipid molar ratio of CHD, STZ, and insulin treated diabetic rats were similar to control. However, the ratio of saturated to unsaturated fatty acids was decreased in hyperosmolal states. This suggests that adaptive increases in cerebral taurine transport during hyperosmolality may result from a direct effect on membrane composition that alters fluidity and permits enhanced transmembrane flux of osmoprotective molecules.
Renal brush-border membrane vesicles (BBMV) show an age-dependent increase in height of the Na(+)-gradient driven overshoot for glucose and proline uptake. Conversely, early uptake of 22Na+ is more rapid in BBMV from kidney of 7-day-old vs. adult rats. To understand the mechanisms responsible for these observations, ionic permeability characteristics of BBMV from different aged animals were determined using an electrical potential sensitive fluorescent dye, diS-C3(5). Absolute and relative ionic permeabilities were determined after a 3-h incubation in 100 mM KCl. Intravesicular K+ ([K+]in), a measure of absolute K+ permeability, was calculated from the extravesicular K+ at which valinomycin produced no potential difference (PD). [K+]in was significantly lower in vesicles from 7-day, compared to adult (P < 0.01). While Cl- permeability, relative to that of K+ was similar, PNa+/PK+ decreased significantly with age (P < 0.05, 7 day vs. adult). In the presence of an inwardly directed NaCl gradient, the lower PNa+ relative to PCl- of the adult vesicles would result in a less positive intravesicular charge, which would therefore augment Na(+)-solute co-transport. Fluorescence polarization studies also show that lipids from BBM vesicles of 7-day-old rats are more fluid than those from adult. These differences are likely due to developmental lipid compositional changes, which influence membrane transport and permeability characteristics. These findings would explain, in part, the age-dependent alterations of renal BBMV solute transport.
To evaluate the relationship between colonic methane production and carbohydrate malabsorption, we measured end-expiratory methane levels in 70 normal and 40 lactose-intolerant children. Time-dependent excretion of hydrogen and methane was determined every 30 min for 120 min following a fasting oral lactose challenge (2 g/kg). Mean breath hydrogen levels in normals (lactose-tolerant) equaled 3.7 parts per million (ppm) throughout the study, but increased to > 10 ppm by 60 min and remained elevated in lactose-intolerant subjects. Breath methane in normal children averaged 1.6 ppm from 0 to 120 min. In contrast, CH4 excretion by lactose-intolerant children averaged 5.1 ppm at 90 min; and, by 120 min levels increased significantly compared with control. Breath methane levels in lactose-intolerant subjects following a lactose load continued to increase, however, despite the coingestion of exogenous lactase in amounts calculated to result in complete hydrolysis of the disaccharide. These data demonstrate that lactase-deficient children manifest significant increases in breath methane excretion following lactose ingestion and that enhanced methane production may be a consequence of several factors, including altered fecal pH and increased methanogenic substrates provided by colonic lactose fermentation. Further studies are required to determine the clinical significance of elevated methane production in lactose intolerance.
To determine the effect of altered membrane fluidity on platelet aggregation/agglutination, fresh, washed human platelets were treated with A2C, a cyclopropyl fatty acid ester which is known to enhance mobility of intrinsic membrane bilayer constituents and increase membrane fluidity. Fluorescence polarization studies demonstrated A2C incubation time- and concentration-dependent increases in platelet membrane fluidity (decreased fluorescence anisotropy). Preincubation with A2C was associated with diminished collagen, thrombin and ristocetin-induced platelet aggregation/agglutination. Aggregation/agglutination was diminished by 93 +/- 5% for collagen (0.2 mg/ml), 53 +/- 3% for thrombin (1.0 U/ml) and 85 +/- 9% for ristocetin (1.1 mg/ml). These data suggest that membrane fluidity is involved in the regulation of platelet function.
Esophageal motility was studied in 31 patients with mild to moderate esophagitis and in 48 patients without esophagitis to determine the effect of esophageal inflammation on lower esophageal sphincter pressure, and the amplitude, duration, and velocity of esophageal contractions. There were no significant differences in any of these parameters associated with esophageal inflammation. We conclude that mild to moderate esophagitis does not cause serious esophageal dysfunction in children.
Basolateral membranes from rabbit proximal colon were prepared from isolated colonocytes throughout postnatal maturation, using a modification of published techniques. In suckling (14-20 day) and post-weaning/mature (35-49 day) animals, membranes were purified approx. 10-fold, based upon the enrichment of ouabain-sensitive, sodium-potassium dependent adenosine triphosphatase activity. Membrane lipid analyses demonstrated age-dependent increases in total cholesterol and the cholesterol/phospholipid molar ratio, as well as decreases in phosphatidylethanolamine content and the fatty acid unsaturation index. Fluidity of basolateral membranes and membrane liposomes, determined from fluorescence anisotropy measurements using the lipid probes 1,6-diphenyl-1,3,5-hexatriene and DL-12-(9-anthroyl)stearic acid, demonstrated significant, ontogenic decreases in fluidity; and, additional studies showed that fluidity changes occurred early in the weaning period (by day 24 postnatally). Arrhenius plots of liposome anisotropies suggested a bilayer lipid thermotropic transition temperature of 22 degrees C in sucklings 26 degrees C in mature rabbits. These findings demonstrate that ontogeny of colonic basolateral membranes is associated with significant modulations in lipid composition and fluidity.
The charts of 83 children with chest pain who underwent esophageal manometry followed by esophagogastroscopy were reviewed. Forty-seven (57%) had normal esophageal histology and normal motility (group I). Esophagitis and normal motility were demonstrated in 15 children (group II), normal esophageal histology and esophageal dysmotility in 13 (group III), and both esophagitis and abnormal motility in 8 (group IV). Diffuse esophageal spasm and achalasia were the most common motility disorders identified (in seven and four patients, respectively). The presence and duration of symptoms, the age, and the gender were not different among the four patient groups. After six months of H2-receptor blockade, 12 of 15 group II patients were asymptomatic, whereas a significantly smaller percentage (five of 18) of patients with abnormal esophageal motility responded to esophageal dilation or treatment with calcium channel blockade, H2-receptor antagonist, and/or prokinetic agents (P less than 0.01). These data suggest that the evaluation of children with chest pain should include esophageal motility testing and esophagoscopy, even in the absence of other gastrointestinal-associated symptoms, and that while treatment of esophagitis results in resolution of symptoms, motility disorders were relatively refractory to therapy.
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.
Chest pain in adolescents and children is usually not of cardiac origin. Of cardiac conditions commonly linked to chest pain in childhood, mitral valve prolapse (MVP) is the most prevalent, but this association has recently been questioned. In light of recent reports of gastroesophageal sources of chest pain in adults with MVP, we performed a comprehensive gastroesophageal evaluation of 17 preadolescents and adolescents with mitral valve prolapse who had chest pain as their presenting symptom. Evaluation consisted of esophageal manometry, Bernstein test, esophageal pH probe, and/or esophagogastroscopy. Fourteen of the 17 patients had at least one abnormal finding. Five patients had esophagitis, five had gastritis, one had high-amplitude esophageal contractions, one had abnormal esophageal manometry with positive Bernstein test, one had esophageal reflux and positive Bernstein test, and one had abnormal manometry with esophageal reflux. The 13 patients with esophagitis, gastritis, reflux, or positive Bernstein test were treated with antacid, with resolution of chest pain in 12 patients. Two of these patients underwent follow-up endoscopy with documentation of improvement. The patient with high-amplitude esophageal contractions was treated with dicyclomine, which resulted in resolution of chest pain. The observation that the chest pain was not related to mitral valve prolapse is important in clinical practice and raises further questions as to whether mitral valve prolapse causes chest pain.
Sixteen patients with asthma and chest pain of greater than 2 months duration underwent gastroenterological evaluation utilizing fiber-optic esophagogastroduodenoscopy (EGD), esophageal manometry, and Bernstein testing. Eleven of 16 patients (75%) had endoscopic and histologic evidence of esophagitis. One patient with esophagitis exhibited high-amplitude peristaltic contractions during motility testing. Four of these 11 patients (36%) had a positive Bernstein test. Extended intraesophageal pH monitoring of seven patients with esophagitis revealed significant gastroesophageal reflux (GER) in all of these patients. Chest pain was associated with an episode of GER in three patients (43%). Nine of 11 patients (82%) with esophagitis responded to medical therapy, resulting in resolution of esophageal inflammation and chest pain. One patient required Nissen fundoplication surgery after failure of medical therapy, and one patient who refused surgery progressively developed more severe esophagitis during 9 months of medical therapy. Children with asthma may have chest pain due to gastroesophageal reflux-associated esophagitis that usually responds to medical therapy.