Role of pH in production of hydrogen from carbohydrates by colonic bacterial flora. Studies in vivo and in vitro.

Hydrogen produced by colonic bacteria and excreted in breath is a useful index of carbohydrate malabsorption. Since colonic contents are often acidic in individuals with carbohydrate malabsorption and in normal newborns, we determined the effect of colonic acidification on H2 production. Acidification of colonic contents by dietary means significantly reduced excess breath H2 excretion from 55.4 +/- 11.1 (SEM) to 12.2 +/- 3.1 ml/4 h (P less than 0.05) after administration of 0.3 g/kg of the nonabsorbable sugar lactulose to five normal adult subjects. Similarly, the breath H2 response to lactose was reduced or eliminated in two proven lactose malabsorbers after acidification. The correlation between pH and H2 production from carbohydrate was further investigated in adults and neonates, using an in vitro fecal incubation system. Glucose disappearance and H2 production were pH dependent and highly correlated (r = 0.94) in the pH range 5.5-7.6. Maximal production of H2 from glucose by fecal incubates occurred at pH 7.0-7.45. Inhibition of H2 production from carbohydrate occurred at acid pH. H2 per hour from glucose at pH 6.2 and 5.5 averaged 60.2% and 24.2%, respectively, of that produced at neutral pH. Rapid reversal of pH-induced inhibition by neutralization indicated a metabolic, rather than a bactericidal process. The observations indicate that the breath H2 response to malabsorbed carbohydrate is affected by colonic pH. It appears that the efficiency of bacterial carbohydrate metabolism in the colon is pH dependent.

Nonabsorbed carbohydrate: effect on fecal pH in methane-excreting and nonexcreting individuals.

To determine whether the acidifying effect of malabsorbed carbohydrate on fecal pH differed between methane-excreting and nonexcreting individuals, we administered the poorly absorbed disaccharide lactulose to five CH4 excretors and six CH4 nonexcretors. Lactulose, 20 g twice daily for 1 wk, significantly lowered fecal pH among CH4 nonexcretors as compared with CH4-excreting individuals (5.38 +/- 0.66 vs 6.90 +/- 0.61, p less than 0.01). To determine whether this observation was due to differences in acid production from bacterial carbohydrate fermentation, feces from each subject were incubated with lactulose. There were no differences in in vitro acid or hydrogen production between groups. We conclude that malabsorbed carbohydrate fails to induce in vivo colonic acidification in CH4 excretors. In contrast, in vitro fecal carbohydrate fermentation is similar among CH4 excretors and nonexcretors. These results suggest differences between these two groups in the colonic absorption of fermentation products.

Influence of frequent and long-term bean consumption on colonic function and fermentation.

The objective of this study was to determine the influence of frequent and long-term consumption of legume seeds on colonic function. Two groups of subjects were studied--one group habitually consumed legume seeds as part of their normal diet, a second group only infrequently consumed legumes. No differences between these groups could be detected for fecal output and frequency, intestinal transit time, VFA excretion or fecal pH during 23-day study periods in which subjects consumed either their usual diet or 100 g red kidney beans, daily. However, the addition of beans to the diets of both groups provided significantly more dietary fiber, and produced greater fecal output and a higher concentration of VFA in feces. Fecal output appeared to be determined by two independent parameters--dietary fiber intake and VFA excretion. Beans provided a physiologically useful source of dietary fiber and favorably influenced colonic function.

Effect of yogurt on symptoms and kinetics of hydrogen production in lactose-malabsorbing children.

Lactase-deficient adults demonstrate improved lactose absorption and fewer symptoms when consuming yogurt than when consuming milk containing equivalent amounts of lactose. To examine this effect and its mechanisms in children, we compared symptoms and hydrogen production as an index of lactose malabsorption after typical servings of milk, pasteurized yogurt, and yogurt containing active live culture in 14 lactose-malabsorbing children (mean age 9.5 y). Symptoms and interval breath-hydrogen concentrations were recorded for 8 h after ingestion of 12 g lactose served as milk and yogurts. Lactose-malabsorbing children experienced significantly fewer symptoms after consuming yogurt containing active cultures than after consuming milk (P < 0.005). Pasteurized yogurt showed an intermediate effect. Lactose from yogurt was not better absorbed than was lactose from milk, as indicated by similar areas under the hydrogen curve; however, yogurt was associated with a delayed time to rise and lower rate of rise of the hydrogen curve. The rate of hydrogen rise correlated with the degree of symptoms. In children, mechanisms other than enhanced lactose absorption from yogurt may lead to changes in the kinetics of hydrogen production, which in turn are associated with improved tolerance.

Mucosal function and breath hydrogen excretion: comparative studies in the clinical evaluation of children with nonspecific abdominal complaints.

To evaluate the role of the lactose breath hydrogen test for the detection of lactose malabsorption in children with chronic nonspecific abdominal complaints, breath hydrogen excretion was measured in 131 children with recurrent abdominal pain (n = 75) or chronic nonspecific diarrhea (n = 56) following a lactose load (2 gm/kg; maximum 50 gm). The data were compared to those obtained from lactose tolerance tests (n = 113) and symptom response following a lactose load (n = 109) performed simultaneously with the lactose breath hydrogen test, and with results from small bowel biopsies obtained in 31 children to determine dissacharidase activity and mucosal histology. The results indicate that an increase in breath hydrogen of greater than 10 ppm above base line values (delta ppm) by 120 minutes ("early increase" response) completely discriminates between biopsy-proven isolated lactase-insufficient and lactase-sufficient children. A similar increase after 120 minutes ("late increase" response) is consistent both with normal mucosal function and partial lactase insufficiency due to mucosal injury. Breath hydrogen responses predicted assayed lactase activity in all patients with isolated lactase insufficiency, but were "falsely negative" in four of ten children whose lactase insufficiency was secondary to mucosal injury. In both clinical groups, lactose malabsorbers report significantly more symptoms than absorbers (P less than .001), but neither symptom reports nor tolerance tests are accurate methods for distinguishing lactose malabsorbers from absorbers. Although the lactose breath hydrogen test provides objective documentation of lactose malabsorption, it is equally predictive of assayed lactase activity in all clinical groups.

Chronic nonspecific inflammatory bowel disease of the cecum and proximal colon in children with grossly normal-appearing colonic mucosa: diagnosis by colonoscopic biopsies.

The diagnosis of inflammatory bowel disease rests on radiologic, endoscopic, and histologic criteria. Five patients, 2 to 17 years of age, sought medical attention because of chronic abdominal pain, diarrhea, and heme-positive stools. Rectal biopsies, visual inspection of colonic mucosa through the colonoscope, and contrast radiographs of the large and small intestine yielded nonspecific results. Serial endoscopic biopsies demonstrated a gradient of inflammatory changes diminishing in severity distally from the ileocecal valve and cecum. The disease process was most evident in specimens from the cecum, whereas biopsies distal to the transverse colon had a normal histologic appearance in all five patients. Biopsies from the proximal colon may provide evidence of inflammatory bowel disease not detectable using standard techniques. The combination of chronic abdominal pain, diarrhea, and heme-positive stools associated with inflammatory changes in biopsy specimens obtained from the proximal colon, but normal findings on radiologic, colonoscopic, and rectal biopsy examinations, may represent an early stage in the evolution of chronic nonspecific inflammatory bowel disease, including ulcerative colitis or regional enteritis (Crohn disease).

Diagnostic dilemmas of Wilson's disease: diagnosis and treatment.

Wilson's disease, an autosomal recessive disorder of copper metabolism, may defy diagnosis in children. The classical triad of Kayser-Fleischer rings, neurologic dysfunction, and hypoceruloplasminemia may be absent. Patients may be seen initially with acute or chronic hepatitis, hemolytic anemia, or neurologic dysfunction. Guidelines are presented for diagnosis of Wilson's disease based on a review of 25 pediatric and adolescent patients. A high index of suspicion in necessary so that therapy with penicillamine may be begun before irreversible liver or neurologic damage occurs. The prognosis is excellent when diagnosis and treatment are established early.

Longitudinal assessment of growth in children born to mothers with human immunodeficiency virus infection.

OBJECTIVES: To describe and to evaluate the longitudinal growth of children born to mothers with human immunodeficiency virus (HIV) infection. DESIGN: Measurements of weight, length (measured in infants in a recumbent position) and height (measured in older children in an upright position), and head circumference were documented and evaluated longitudinally using generalized estimating equations in a group of children born to HIV-infected mothers. Children infected with HIV were compared with uninfected children and with National Center for Health Statistics standards. SETTING: Primary care clinic in an urban hospital devoted to the medical care of children born to HIV-infected mothers. PATIENTS: One hundred nine children born to HIV-infected mothers, 59 HIV-infected and 50 uninfected, between birth and 70 months of age. RESULTS: The mean birth weights of both groups were below the 50th percentile. While the mean weight-for-age curve of uninfected children attained the 50th percentile by age 24 months, the mean birth weight-for-age curve of HIV-infected children remained below the 50th percentile. Weight gain became significantly different between the two groups by age 36 months. The mean birth length-for-age curves of HIV-infected and uninfected children was also below the 50th percentile. The mean height-for-age curve of uninfected children attained the 50th percentile by age 40 months, while that of HIV-infected children remained well below the 50th percentile. Linear growth between HIV-infected and uninfected children diverged earlier than weight, becoming significantly different by age 15 months. CONCLUSIONS: Although children born to HIV-infected mothers are born with weight and length below the 50th percentile, uninfected children catch up, while HIV-infected children remain below the 50th percentile and experience an earlier and more pronounced decrease in linear growth (height-for-age) than in weight-for-age.

Behavioral assessment and treatment of pediatric feeding disorders.

Pediatric feeding disorders are estimated to occur in as many as one in every four infants and children, and when serious can require numerous, costly and sustained interventions. For over a decade research has cumulated evidence on the contributions of Behavior Analysis in understanding and remediating some types of pediatric feeding disorders. The systematic use of this body of evidence in conjunction with other approaches (medical, nutrition, occupational therapy, physical therapy, and so forth) is being carried out on an inpatient treatment unit at the Kennedy Krieger Institute. Key aspects are described here, including direct observation behavior assessment, approaches for increasing and decreasing feeding behavior, skill acquisition, transfer of treatment gains, and parent training. The results based on case studies and overall program evaluation indicate that medically complicated, severe feeding disorders can be treated successfully in a few months with a multidisciplinary approach which incorporates behavioral procedures.

Effect of breastfeeding support from different sources on mothers' decisions to breastfeed.

A cross-sectional study compared 100 breastfeeding and 100 non-breastfeeding new mothers in order to investigate the relationship between mothers' choice of breastfeeding and support from health professionals and lay people, taking into account potentially confounding sociodemographic influences. The importance of the male partners' opinion about breastfeeding was also examined. A favorable attitude of partners towards breastfeeding was the most important factor associated with breastfeeding (odds ratio = 32.8). Prenatal class attendance and breastfeeding support from lay people increased the odds of breastfeeding 2.7 and 3.3 times, respectively. Breastfeeding orientation provided by doctors, nurses, and nutritionists was not associated with the maternal decision to breastfeed. The results point toward the need for reevaluation of prenatal care interventions, inclusion of fathers in breastfeeding educational programs, and emphasis on community-based programs.

Acute and chronic hepatitis in children.

Discrimination between hepatitis A and B is becoming easier as the serologic and clinical characteristics of each type become better known. Hepatitis A is generally a benign pediatric illness with few sequelae. In contrast, hepatitis B is more often associated with complications and may progress to chronic liver disease in as many as 10% of cases. Chronic persistent hepatitis appears to be a benign disorder not requiring therapy. Occasionally related etiologically to virus B, chronic active hepatitis is often associated with severe clinical illness. However, it generally responds to steroid therapy, at least initially, and may be arrested or cured.

Lactose intolerance. Pinpointing the source of nonspecific gastrointestinal symptoms.

Lactose intolerance is a common condition that can cause nonspecific gastrointestinal symptoms. A reliable diagnosis cannot be made on the basis of the patient's history. The breath hydrogen test is simple, noninvasive, accurate, and inexpensive and is the diagnostic method of choice. In addition to traditional dietary restriction of lactose, treatment may consist of alterations in dietary fat content or caloric density to reduce symptoms and use of dairy products or additives that provide lactase activity.

NZVI modified magnetic filter paper with high redox and catalytic activities for advanced water treatment technologies.

The in situ synthesis of air-stable zero-valent iron nanoparticles (NZVI) embedded in cellulose fibers leads to the assembly of highly reactive magnetic filter papers. These engineered materials display a wide range of applications in the treatment of wastewater and drinking water, including chromium removal, phenol degradation, environmental bioremediation, and catalysis.

Clinical application of breath hydrogen measurements.

Breath hydrogen (H2) measurements are applied in clinical medicine for the detection of carbohydrate malabsorption. H2 in expired air results when dietary sugars escape absorption in the small intestine, thereby becoming available for bacterial fermentation. H2 produced by bacterial metabolism of the carbohydrate is absorbed into the portal circulation and excreted in breath. Relatively simple collection, storage, and analysis methodologies have been developed in recent years. They permit convenient and noninvasive testing of patients in most age groups for common clinical disorders of digestion and absorption, including lactase deficiency and other disorders of di- and mono-saccharide malabsorption, starch malabsorption, and small bowel bacterial overgrowth. Limitations of breath hydrogen testing are few. Developmental considerations constrain the ease of interpretation of breath H2 measurements in early infancy, and factors affecting intraluminal H2 production by the intestinal flora may occasionally affect the H2 signal. Despite these factors, breath H2 testing has repeatedly been demonstrated to be the most accurate indirect indicator of lactase deficiency, and breath H2 measurements have been widely applied in studying digestion of the entire spectrum of dietary carbohydrates.

Digestion and absorption of fruit juice carbohydrates.

As consumption of dietary fructose and sorbitol increases, the association between consumption of these sugars and gastrointestinal symptoms has been recognized. As a result, studies of fructose and sorbitol absorption and malabsorption have emerged with investigations relying largely on the use of breath hydrogen (H2) measurements. Since these sugars are prevalent in fruit juices, a major dietary staple in the first 5 years of life, an understanding of fructose and sorbitol absorption is particularly important to pediatric health care providers. This review examines fructose and sorbitol absorption in humans, reviewing as well the breath H2 method upon which studies of fructose and sorbitol absorption largely depend.

Gastroduodenal disorders in children.

Studies within the past year examining the mechanisms underlying infantile hypertrophic stenosis at the cellular and molecular level are reviewed. A number of new modalities, including electrogastrography, and the 13C octanoid acid breath test have been used in the study of normal and abnormal gastrointestinal motility, as well as for the characterization of patterns of development of gastric motility in early infancy. Several studies pertaining to the natural outcome, the mode of transmission, and the associated symptomatology of Helicobacter pylori were published, attesting that, despite the tremendous progress achieved in our understanding of H. pylori, important gaps remain in our knowledge of this microorganism. Newly described clinical presentations of eosinophilic gastroenteritis and food allergy will also be of interest to the reader.

Glycoproteins as substrates for production of hydrogen and methane by colonic bacterial flora.

Hydrogen and methane in human breath derive entirely from bacterial fermentation in the intestinal lumen. The sources of substrates utilized for these reactions have not been completely determined. Basal excretion of both gases occurs in the fasted state, while malabsorbed carbohydrate commonly results in increased hydrogen but not methane production. Using an in vitro fecal incubation system, we have studied hydrogen and methane production from glycoproteins of endogenous as well as dietary origin. All glycoproteins tested yielded hydrogen when incubated with fecal homogenates. Mean hydrogen production from substrates containing less than 3% sugar (human serum albumin, bovine serum albumin, and alpha-casein) averaged 2.2 +/- 0.9% of hydrogen production from equivalent amounts of glucose, while carbohydrate-rich mucin yielded 46.0 +/- 6.7% of hydrogen production from glucose. Glycoproteins of intermediate carbohydrate content, including transferrin and egg white, yielded intermediate values. Methane production from glycoproteins was optimal from carbohydrate-poor protein substrates in fecal homogenates which accumulated hydrogen and became rapidly acidic when incubated with pure carbohydrate. In contrast, methane production was comparable for essentially sugar-free proteins, glycoproteins, and glucose when hydrogen did not accumulate and neutral pH was maintained. We conclude that glycoproteins are substrates for hydrogen and methane production by colonic bacteria from healthy adults. In individuals with bacterial overgrowth syndromes and in protein-losing enteropathy, bacterial catabolism of endogenous glycoproteins may cause increased basal hydrogen and methane excretion. These findings also raise the possibility that measurement of hydrogen or methane after oral administration of dietary glycoproteins may be useful in detection of protein malabsorption.