Thomas W. Boutton

Epidemiology of Campylobacter pylori Infection: Ethnic Considerations

A proper perspective of the association of Campylobacter pylori with various diseases can be achieved only when the incidence of C. pylori infection in the normal population is known. We used the 13C urea breath test (a simple, specific, noninvasive, safe, and reproducible method to assess the presence of active C. pylori infection) to compare the frequency of C. pylori infection in healthy young adults from three areas of the world. We studied 26 women and 32 men (ages 20 to 29): 29 from the United States, 10 from China, 6 from Mexico, and 13 from India. All foreign nationals had been in the United States 5 years or less. The frequency of C. pylori infection was 21%, 67%, 33% and 46%, for those from the U.S., China, Mexico and India, respectively. Although, we found no difference in the frequency of C. pylori infection among ethnic groups from North America (U.S. citizens compared with citizens of Mexico), all individuals studied were of middle to upper class socioeconomic status. Subsequent studies will investigate whether the prevalence of C. pylori infection is different in economically disadvantaged populations. Our results suggest that there may be major differences in the age-related frequency of C. pylori infection in individuals from different parts of the world.

The use of stable carbon isotope analysis in rooting studies

SummaryStable carbon isotope analysis was evaluated as a means of predicting the relative proportions of C3 and C4 root phytomass in species mixtures. The following mixtures of C3 and C4 species were used: 1) big bluestem (Andropogon gerardii)/cheatgrass (Bromus tectorum), 2) little bluestem (Schizachyrium scoparium)/cheatgrass, and 3) sorghum (Sorghum bicolor)/sunflower (Helianthus annuus). There was a significant correlation (P<0.01) between % C4 phytomass and stable carbon isotope values for each of the three combinations (r2>0.98). Root length per mass varied among the five species studied (10.1–94.3 m/g), which resulted in different conclusions depending on whether root values are expressed as length or mass. For example, field samples from a tallgrass prairie site were estimated to contain about 20% cheatgrass on a mass basis, whereas the figure was 68% when expressed in terms of length. The combination of stable carbon isotope analysis with length-for-mass measurements promises to be a useful means of studying root competition between C3 and C4 plants.

Characterization of HCO3−/CO2 Pool Sizes and Kinetics in Infants

The first bicarbonate pool sizes and kinetic data necessary for the interpretation of substrate oxidation studies have been determined in six fed, nonacidotic infants, ages 2.5 to 5 months. Following an intravenous bolus of NaH13CO3 (50 mumol/kg), breath samples were collected over 240 min for the analysis of breath 13CO2. Each breath 13CO2 disappearance curve was fitted to a multicompartmental bicarbonate model previously derived in adults. The mean sizes of the three bicarbonate pools were: 7.4 +/- 0.8 mmol/kg (central pool), 15.1 +/- 4.8 mmol/kg (rapidly exchanging peripheral pool), and 8.8 +/- 3.5 mmol/kg (slowly exchanging peripheral pool). The mean percentage dose recovery was 57 +/- 10%. The pool sizes suggested that extensive metabolic exchange of carbon between HCO3- and organic metabolites occurred in the infant.

Absorption and Oxidation of Glucose Polymers of Different Lengths in Young Infants

ABSTRACT. Because mucosal glucoamylase is most active against glucose polymers less than 10 glucose units in length, longer chain polymers may not be completely absorbed by young infants. In order to investigate this possibility, the absorption and oxidation of I3C-rich glucose, short-chain (3 to 8 glucose units in length) and long-chain (average length 43 units) glucose polymers (GP) were compared in 12 healthy, 1-month-old infants. Recovery of the GP and glucose in stool was measured by determining the I3C enrichment of stool. The oxidation of the GP was measured by tracing the increase in breath 13CO2 after GP were fed. Carbohydrate malabsorbed in the small bowel was assessed by measurement of breath H2, a gas formed from the fermentation of carbohydrate in the colon. Analysis of the infants stools revealed that one infant excreted 9.7% of the dose of glucose, another 6.7% of the dose of short-chain GP, and five infants excreted 2.6 to 18.5% (mean 8.4%) of the dose of long-chain GP. The percent of the administered dose recovered in breath was similar among substrates (mean=28.7% of the dose fed). A rise in breath H2 greater than 20 ppm was found in four of the 12 infants after the feeding of glucose, in five of 12 after the short-chain GP, and in six of 12 after the long-chain GP. None of the infants developed diarrhea. The results suggest that healthy young infants do not absorb long-chain GP as completely as they absorb short-chain GP. In the absence of pancreatic amylase, salivary amylase and mucosal glucoamylase are sufficient in some young infants to allow for complete digestion of long-chain GP.

A Carbon-13 Breath Test to Characterize Glucose Absorption and Utilization in Children

After the administration of a 5% glucose-water solution that contained tracer amounts of the stable nonradioactive isotope 13C, breath samples were collected from five children with congenital glucose-galactose malabsorption and five with severe small bowel villous atrophy and chronic diarrhea. The 13CO2 breath test curves of the children with the congenital malabsorption and chronic diarrhea were compared with each other and with those from three healthy children and four infants with severe malnutrition but no diarrhea. The breath test curves from the children with glucose-galactose malabsorption and from those with diarrhea were significantly different from those of the other two groups, a finding consistent with impairment of glucose absorption. The [13C]glucose breath test clearly identified the children with severe glucose malabsorption. Further studies are required to determine whether less severe cases of carbohydrate malabsorption also can be identified using the parameters described in our study.

Effect of infant age on aminopyrine breath test results.

ABSTRACT: The aminopyrine breath test has been used in adults as a measure of hepatic N-demethylase activity. In order to study maturational changes in enzyme function, 13C aminopyrine (2 mg/kg) was administered orally to infants (n = 16) between the ages of 1 and 38 wk. Breath samples were collected for 6 h after administration of the labeled aminopyrine for the measurement of 13CO2 enrichment. Using a number of different scoring methods to quantitate 13CO2 elimination of breath, demethylation of aminopyrine was found to be positively correlated to age. By 20 wk of age, some infants had rates of elimination similar to those measured in adults. Absorption was excluded as a limiting variable, because no improvement in oxidation rates was found when the aminopyrine was readministered as an intravenous bolus. Changes in nutritional status and route of feeding (enteral versus parenteral) did not prevent the effect of maturation on aminopyrine elimination. Conclusions: 1) maturational differences are seen in the metabolism of aminopyrine; 2) these differences may reflect immaturity of N-demethylase activity or diversion of the liberated formaldehyde into biosynthetic rather than oxidative pathways.

Absorption of carbon 13-labeled rice in milk by infants during acute gastroenteritis

To determine whether rice cereal could be used to complement a cow milk-based diet in the nutritional management of infants with acute diarrhea, we assessed its digestion and absorption in eight affected male infants, 69 to 131 days of age. They received cow milk formula with 5.4% lactose (diluted 1:1 with water and precooked rice cereal) 5 to 22 hours after admission and rehydration. The first feeding consisted of milk diluted with carbon 13-enriched rice cereal. A 48-hour fecal collection and balance study was performed. Rice cereal was reasonably well absorbed (84.0% to 95.8%) by seven of the eight infants. The study was repeated in seven of the infants after they had recovered. Our results indicated that rice cereal is well absorbed by young infants with acute diarrhea and that it is an adequate nutrient supplement for this patient population.

Rooting dynamics of Medicago sativa seedlings growing in association with Bothriochloa caucasica

SummaryMedicago sativa was seeded into an established sward of Bothriochloa caucasica. Two frequencies of sward defoliation were compared to a nondefoliated control. Although 84 to 92% of the root mass at 0–20 cm belonged to B. caucasica during the spring and summer samplings, defoliation generally reduced the root mass of B. caucasica. During the summer, aboverground mass of B. caucasica ranged from 735 to 1220 g m-2 and 295 to 410 g m-2 for control and defoliation treatments, respectively. Defoliation apparently reduced the competitive effects of B. caucasica on M. sativa, as taproot and lateral root mass of M. sativa was much higher in defoliated than in control plots by the end of the growing season. Predawn xylem potential of M. sativa was 0.4 to 0.8 MPa more negative in control than in defoliated plots from mid-summer to fall. Thus, we suggest that the transpirational demand of undefoliated B. caucasica reduced soil moisture available to M. sativa, thereby reducing its growth and survival during late summer and fall, compared to defoliated treatments.

Background levels of carbon-13 reduced in breath and stool by new infant formula

Studies of the absorption and bioavailability of nutrients naturally enriched with 13C require accurate measurements of small increases of 13C in respiratory CO2 and stool carbon. The sensitivity of these measurements would be increased if the natural background of 13C in these excreta were reduced. We have developed a 13C-depleted infant formula based on lactose, whey, and casein from New Zealand cows that consume only C3 vegetation naturally low in 13C. This formula, designated CNRC3, was produced by a commercial infant formula manufacturer and was comparable with a 60:40 whey/casein product. To test the ability of the formula to reduce baseline levels of 13C in infant excreta, 10 formula-fed infants 28-60 days old and free of metabolic disorders were enrolled in the 9-day study. Two stool samples were collected daily. Infants received their usual formula on days 1 and 2 and were switched to CNRC3 formula for days 3-9. On days 2 and 9, seven breath samples were collected at 30-min intervals with a face mask. Breath and stool samples were analyzed for 13C content by gas isotope ratio mass spectrometry. Infants consuming their commercial formula had breath delta 13C values of -21.1 +/- 0.6% over the 3-h collection period; stool values were -22.9 +/- 0.4%. After 7 days on the CNRC3 formula, delta 13C values of breath declined by 5.6% to -26.7 +/- 0.7%; stool values declined by 3.0% to -25.6 +/- 0.5%. The reduced background of 13C achieved by the CNRC3 formula can improve resolution of excess 13C from naturally enriched substrates in infant breath by approximately 50% and in stool by approximately 30%.

[13C]Acetate Oxidation in Infants After Oral Versus Rectal Administration: A Kinetic Model

Summary: To study the fate of volatile fatty acids (VFA) in the large bowel, we compared the rate of oxidation of 13C-labeled VFA administered rectally with that of the orally administered substrate. On two different days, 1-[13C]acetate was administered rectally or orally to five infants recovering from diarrhea. Breath samples were collected over 4 h and analyzed for 13C enrichment of breath CO2 by gas isotope ratio mass spectrometry. The percent dose recoveries of 13C in breath were fitted to multicom-partmental models using the SAAM-27 program. Following model development procedures, the oral acetate breath test curves could be accounted for only by a compartmental model in which labeled acetate underwent absorption into and mixed with a systemic pool before oxidation took place. The rectal acetate breath test curves could be accounted for by a simpler model in which oxidation occurred directly in the compartment in which the rectal acetate was administered, and required no rate-limiting absorptive process. Our results indicate that the labeled acetate was oxidized more rapidly when the substrate was administered rectally than orally. This observation points to the direct utilization of volatile fatty acids within the colon.