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P D Klein

Publications and source records attributed to P D Klein.

At least 37 records · Page 2Linked to original sources
PubMed1996

Twenty-minute fasting version of the US 13C-urea breath test for the diagnosis of H. pylori infection.

BACKGROUND: In large-scale multi-center clinical trials, the US 13C-urea breath test (UBT) has proven to have a sensitivity and specificity of approximately 95%. Ingestion of a meal to delay gastric emptying has advantages of increasing the level of signal as well as prolonging the duration of significantly increased 13C excretion, at the expense of requiring 40 to 60 minutes to complete the test. Our aim was to explore the utility of the 13C-UBT with a total duration of 30 minutes or less. METHODS: After a baseline breath sample was obtained, 125 mg of 13C-urea was given in 100 ml of water, and additional breath samples were taken after 20 and 30 minutes. The results of the UBT were compared to histological assessment, culture, and the rapid urease test. 13C-UBTs were carried out on normal volunteers who underwent gastroscopy during which six mucosal biopsies were taken. Three biopsies were for histological evaluation (Genta stain), two for culture, and one was for agar gel rapid urease testing. The UBT was conducted 2 to 3 days either before or after the endoscopic procedure. RESULTS: The cutoff value for a positive UBT was enrichment of 2.4 delta/1000 (delta over baseline). Of the 66 tests, 51/1000 were Helicobacter pylori-positive. There were no false positive UBTs and only two false negative UBTs at 20 minutes (sensitivity, 96%; specificity, 100%). At 30 minutes, one other UBT was false negative (gray zone of 2.36/1000) (sensitivity, 94%; specificity, 100%). CONCLUSION: These results suggest that omission of the meal and shortening the duration of the US 13C-UBT to 20 minutes still may maintain excellent specificity and sensitivity of the test.

Adult↗
PubMed1996

Low point prevalence of peptic ulcer in normal individuals with Helicobacter pylori infection.

OBJECTIVE: A recent study from Italy reported a high prevalence of ulcer disease in asymptomatic Helicobacter pylori infection. Such results are at variance with previous endoscopy screening studies. Our study was performed to obtain data on ulcer prevalence in normal H. pylori-infected subjects in the United States. METHODS: One hundred and ninety healthy individuals of either gender, over the age of 18, were studied. After completion of a detailed questionnaire and a urea breath test for H. pylori status, endoscopy was performed. Ulcer was defined as a mucosal ulceration > 5 mm in diameter and with apparent depth. RESULTS: There were 108 (57%) women and 82 (43%) men. The mean (+/-SD) age was 38.9 (+/-10.7) yr, range 21-79 yr. Careful history obtained after enrollment revealed presence of dyspeptic symptoms in 35 subjects (18%); the remaining 155 individuals were completely symptom-free. Infection with H. pylori was present in 102 subjects (54%). The infection rate was highest in Hispanics (70%), followed by African-Americans (58%), Caucasians (38%), and Asians (17%). The prevalence increased with age. Only two (1%) of 190 subjects, both with H.pylori infection, had peptic ulcer. In the H. pylori-infected group, the prevalence of peptic ulcer was 2%. CONCLUSION: In the United States, significant unrecognized and asymptomatic gastroduodenal disease is uncommon in H. pylori-infected individuals. These findings do not support the need for a mass screening program for H. pylori infection or for the use of antimicrobial treatment of asymptomatic subjects with this infection.

Adult↗
PubMed1996

Noninvasive detection of Helicobacter pylori infection in clinical practice: the 13C urea breath test.

OBJECTIVES: To validate the 13C urea breath test for the detection of Helicobacter pylori infection both before and after treatment. METHODS: 13C urea breath tests with 125-mg and 250-mg doses were carried out on each of 60 infected and 60 noninfected subjects. Results were compared with histological examination of gastric biopsies to establish detection limits. The best cut-off point was used in a clinical trial of the efficacy of the breath test in duodenal ulcer patients before and after antimicrobial therapy. The incremental increase (percentage, delta over baseline in U of delta/mil) in respiratory 13CO2 abundance was associated with histological evidence of H.pylori. Outpatient, tertiary care medical center, and secondary and primary care facilities were included. One hundred twenty healthy asymptomatic subjects and 465 patients with duodenal ulcer disease were studied. The test kit assessed repeatability of breath sample collection and storage and stability of stored samples. Test performance was analyzed by comparison of 125-mg and 250-mg 13C urea with measurements at 30 and 40 min postdose. The test was used to diagnose active H.pylori infection and gauge success of antimicrobial therapy. RESULTS: The test kit results were highly reproducible. The cut-off values were higher with 250-mg compared with 125-mg doses of 13C urea and 40 min compared with 30 min. Using a 125-mg 13C urea and test detection limit of 2.4% at 30 min, the accuracy was 94.8 (95% confidence interval = 92-97%) before antimicrobial therapy and 95.4% (95% confidence interval = 91-98%) after. An increase of 2.4% in the abundance of breath 13CO2 measured 30 min after a 125-mg dose of 13C urea reliably indicated the presence of active H.pylori infection either before or after antimicrobial therapy. The 13C urea breath test provides a simple and reliable and noninvasive method of assessing H.pylori status.

Anti-Bacterial Agents↗
PubMed1995

Evidence for incorporation of intact dietary pyrimidine (but not purine) nucleosides into hepatic RNA.

The absorption and metabolism of dietary nucleic acids have received less attention than those of other organic nutrients, largely because of methodological difficulties. We supplemented the rations of poultry and mice with the edible alga Spirulina platensis, which had been uniformly labeled with 13C by hydroponic culture in 13CO2. The rations were ingested by a hen for 4 wk and by four mice for 6 days; two mice were fed a normal diet and two were fed a nucleic acid-deficient diet. The animals were killed and nucleosides were isolated from hepatic RNA. The isotopic enrichment of all mass isotopomers of the nucleosides was analyzed by selected ion monitoring of the negative chemical ionization mass spectrum and the labeling pattern was deconvoluted by reference to the enrichment pattern of the tracer material. We found a distinct difference in the 13C enrichment pattern between pyrimidine and purine nucleosides; the isotopic enrichment of uniformly labeled [M + 9] isotopomers of pyrimidines exceeded that of purines [M + 10] by > 2 orders of magnitude in the avian nucleic acids and by 7- and 14-fold in the murine nucleic acids. The purines were more enriched in lower mass isotopomers, those less than [M + 3], than the pyrimidines. Our results suggest that large quantities of dietary pyrimidine nucleosides and almost no dietary purine nucleosides are incorporated into hepatic nucleic acids without hydrolytic removal of the ribose moiety. In addition, our results support a potential nutritional role for nucleosides and suggest that pyrimidines are conditionally essential organic nutrients.

Adenosine↗
PubMed1995

In vivo oxidation of [13C]galactose in patients with galactose-1-phosphate uridyltransferase deficiency.

We developed an intravenous and oral [13C]galactose breath test for the in vivo study of galactose metabolism. Following an intravenous bolus of 7 mg/kg of [1-13C]galactose in the fasting state, normal children and adults eliminated 3-6% and 21-47% of the bolus as 13CO2 in expired air collected over 1 and 5 h, respectively. Comparable fractional elimination was seen when the dose was given orally. Patients with galactosemia who have barely detectable or absent galactose-1-phosphate uridyltransferase (GALT) activity in erythrocytes and are homoallelic for the Q188R gene mutation, when given a 7 mg/kg intravenous bolus had barely detectable 13CO2 in air samples in the first hour, but eventually eliminated as much as 3.6% of the dose in 5 h. A galactosemia/Duarte (Q188R/N314D) compound heterozygote and a homozygous Duarte subject, as well as a subject with one normal allele and one Q188R allele, showed normal in vivo oxidation. An assessment of whole body galactose metabolism can be made with this procedure. Further use of this in vivo modality in patients with different genetic backgrounds should increase our understanding of genotype-phenotype relationships in hereditary galactosemia.

Adolescent↗
PubMed1995

[13C]Aminopyrine breath test detects altered liver metabolism caused by low-dose oral contraceptives.

The [13C]aminopyrine breath test measures hepatic mixed function oxidase activity. The cumulative percent dose recovered over 2 hr is a sensitive indicator of hepatic dysfunction; values < or = 7.0% have been shown to indicate severe liver disease. Previous studies have suggested that the test results may be influenced by the use of oral contraceptives steroids. We compared the results from five non-oral contraceptive-using women with those from 31 women whose duration of oral contraceptive steroid usage ranged from 4 to 204 months. The women were taking one of four oral contraceptive formulations that differed in the amounts of estrogen (20, 35, or 50 micrograms with 1 mg progesterone) and progesterone (35 micrograms estrogen with stepped levels of progesterone of 0.5, 0.75, and 1.0 mg). The [13C]aminopyrine breath test was performed on days 21 and 28 of the menstrual cycle. Cumulative percent dose recovery values among the normal menstrual cycle of non-oral contraceptive steroid-using women were 12.1 +/- 1.6 and 11.8 +/- 1.5% (mean +/- SD). In contrast, oral contraceptive steroid users showed a marked reduction in cumulative percent dose recovery at 21 days, averaging 6.1 +/- 2.3% (P < 0.001), and returned to normal values (10.2 +/- 3.5%) at 28 days in most women(seven days after oral contraceptive steroid usage was paused). The adverse impact on hepatic mixed function oxidase by oral contraceptive formulations did not differ on the basis of estrogen or progesterone content. The adverse impact of oral contraceptive usage on the mixed function oxidase activity measured by the [13C]aminopyrine breath test must be considered for women of childbearing potential.

Adult↗
PubMed1995

Determination of Helicobacter pylori status by reverse transcription-polymerase chain reaction. Comparison with urea breath test.

We previously reported the development and the possible application of reverse transcription-polymerase chain reaction (RT-PCR) assay for the detection of H. pylori in gastric mucosal biopsy specimens. In this communication, the application of this assay was assessed by comparing its results from 79 gastric biopsy specimens obtained from 68 patients with the more traditional [13C]urea breath test. When the amplified products were examined, the specificity and sensitivity of this RT-PCR assay were 100% and 47% on agarose gels and 80% and 91% by Southern hybridization, respectively. The specificity and sensitivity of urea breath test were 91% and 96% and were generally superior to RT-PCR (negative predictive value of 94% for UBT and 59-76% for RT-PCR). Although our RT-PCR results compare favorably with other PCR assays applied to gastric biopsy specimens for the detection of H. pylori, the use of this method did not add significantly to currently available noninvasive diagnostic methods.

Adult↗
PubMed1995

Isotopic evidence for the differential regulation of arginine and proline synthesis in man.

Arginine and proline derive from the metabolism of delta 1-pyrolline-5-carboxylate, a product of intestinal glutamic acid metabolism. We studied the extent of glutamate, arginine, and proline synthesis in four adult fed and fasted women. The subjects ingested a single dose of a mixture of uniformly (U)-13C-labeled amino acids and carbohydrate of algal origin. Frequent blood samples were taken for 24 hours. All the mass isotopomers of plasma lysine, glutamate + glutamine (GLX), arginine, and proline were measured using negative chemical ionization, selected-ion monitoring gas chromatography-mass spectrometry. In this isotopic approach, the appearance of U-13C-amino acid in the plasma reflects entry of the dietary amino acids, and the appearance of 13C in lower mass isotopomers demonstrates synthesis of the respective amino acids by the subject. All the mass isotopomers (including [M + 4]) of GLX became enriched with 13C. We suggest that the [M + 4] isotopomer of GLX reflects synthesis of the amino acid from alpha-ketoglutarate derived from the metabolism of U-13C-carbohydrate by the bacterial flora. Arginine labeling showed two patterns. The [M + 5] isotopomer of plasma arginine was labeled as rapidly as [M + 6] (ie, tracer) arginine, and we propose that the appearance of the [M + 5] isotopomer reflects the synthesis of citrulline from dietary [M + 5]-glutamate in first pass. The [M + 1] to [M + 3] isotopomers of arginine were also labeled for a prolonged period of time, suggesting that systemic glutamate was also a precursor for arginine synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Estimates of the effect of feeding on whole-body protein degradation in women vary with the amino acid used as tracer.

We measured how feeding status affects the kinetics of multiple indispensable amino acids in four adult female subjects studied both in fed and fasted state. The subjects ingested one dose of uniformly 13C-labeled algae (Spirulina platensis). The isotopic enrichments (measured with negative chemical ionization gas chromatography-mass spectrometry) of the branched chain amino acids, phenylalanine, lysine and threonine were followed for 24 h in both the plasma and in VLDL-apolipoprotein B-100 (apoB-100). Fasting lowered body protein degradation when measured with the branched chain amino acids, increased it when measured with phenylalanine and had no statistically significant effect when determined from the kinetics of lysine and threonine. These apparent differences challenge the adequacy of current models of whole-body protein turnover. The ratio of the peak labeling of amino acids in plasma and apoB-100 was used as an estimate of the isotopic dilution in the hepatic pool. In contrast to our earlier observations during intravenous tracer amino acid administration, in the present study fasting lowered the ratio of the peak isotopic enrichments of apoB-100 and plasma amino acids. This supports our contention that feeding increases the use of hepatic portal amino acids for hepatic secretory protein synthesis.

Adult↗
PubMed1995

In vivo study of colonic fermentation of carbohydrate in infants.

Dietary carbohydrate in the colon is fermented and converted into short-chain fatty acids. We studied the fate of carbohydrate that arrives in the colon under circumstances similar to those that occur during an episode of diarrhea and determined whether a quantitative correlation exists among certain indicators of colonic fermentation of carbohydrate arriving in the large bowel. A stable-isotope method was used to estimate carbon scavenging by the colon. Fourteen infants with severe malnutrition and history of watery stools and/or increased numbers of stools in the preceding 20 days were studied. Infants underwent nasocecal intubation and a 60-min infusion of 0.5 g/kg glucose containing 5 mg/kg of 13C-glucose. Stools were assessed for carbohydrate-fermenting bacteria, acetate, glucose, and 13C abundance; blood was assessed for acetate; and breath was assessed for hydrogen. Some of the infants eliminated the infusate per anus within 30 min of the infusion (group I; n = 5), while others did so 120 min or more after the infusion (Group II; n = 9). The volume of fecal output after the intracecal infusion differed significantly between group I and group II (57 +/- 13 vs. 24 +/- 4 ml; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1995

A novel stable isotope breath test: 13C-labeled glycosyl ureides used as noninvasive markers of intestinal transit time.

OBJECTIVES: Breath tests are widely used for diagnosis and control of treatment efficacy. There is a need for breath test substrates that reflect intestinal transit times under various conditions. METHODS: We synthesized a new class of breath test substrates, 13C-labeled glycosyl ureides, which are specific markers for the action of colonic microbial flora. We then investigated their usefulness as markers of intestinal transit time. RESULTS: Bolus ingestion of 1 g lactose or cellobiose 13C-ureide resulted in bacterial cleavage of the N-glycosyl bond and subsequent urea hydrolysis. 13CO2 appeared in breath and was determined by gas-isotope-ratio-mass spectrometry. Label first appeared after 5-6 h, peak excretion occurred between 8-14 h, and the signal returned to baseline after 18-24 h. Metoclopramide (10 mg) administered 1 h before the substrate advanced the onset of the signal by 2.4 +/- 1.95 h (mean +/- SD; n = 7; p < 0.05) and the time of peak response by 0.8 +/- 1.44 h. Loperamide (16 mg) broadened the peak and delayed the time of breath signal onset by 1.0 +/- 2.78 h and peak excretion by 4.0 +/- 3.7 h (p < 0.05). CONCLUSIONS: The glycosyl ureide breath test reflected intestinal transit time and rapid changes in gastrointestinal motility. This test should be useful in the diagnosis of a variety of gastrointestinal motility disorders and in the development of drugs that affect gastrointestinal motility.

Adolescent↗
PubMed1994

Leucine oxidation changes rapidly after dietary protein intake is altered in adult women but lysine flux is unchanged as is lysine incorporation into VLDL-apolipoprotein B-100.

We measured the 13C enrichments of expired CO2 and deuterium enrichments of plasma free lysine and VLDL-apolipoprotein B-100 in five nulliparous women who received an oral bolus dose of [1-13C]leucine and a primed, constant infusion of [2H4]lysine on d 2 and 6 while consuming protein diets of 1.5, 1.0 and 0.4 g.kg-1 x d-1. Peak enrichments and cumulative percent recoveries of 13C in expired CO2 increased during the high, and decreased during the low protein periods within 24 h of altered intakes; these changes averaged 89% of that on d 6 of the high and low protein diets. The early changes in leucine oxidation showed significant relationships with urinary nitrogen excretion on d 6 of the dietary periods. The ratio of the isotopic enrichment of lysine in VLDL-apolipoprotein B-100 to that in plasma was unaltered by the level of protein intake. Thus, amino acid oxidation adapts rapidly to altered protein intakes in adult women and is useful to determine protein needs during rapidly changing physiologic conditions. However, 6-d periods of protein intake over the range of 1.5 to 0.4 g.kg-1 x d-1 do not affect the proportional use of dietary amino acids for hepatic secretory protein synthesis.

Administration, Oral↗
PubMed1994

Dietary cholesterol supplementation improves growth and behavioral response of pigs selected for genetically high and low serum cholesterol.

We hypothesized that, in pigs selected for low (L) or high (H) serum cholesterol for four generations, neonatal endogenous cholesterol synthesis would be sufficient to meet requirements for brain and body growth. In Experiment 1, eight 16-wk-old L pigs received a diet with or without 200 mg cholesterol/100 g diet for 35 d. Supplemented pigs grew approximately 25% faster and had a significantly greater concentration of free cholesterol in the cerebrum. In Experiment 2, 16 H and 16 L newborn pigs were fed a milk replacer with or without 200 mg cholesterol/100 g diet for 28 d. Pigs fed cholesterol had greater average daily gain (P < or = 0.09), significantly reduced liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity, and significantly increased cerebral cholesterol content than pigs not fed cholesterol. One of three indices of exploratory behavior was significantly greater in the L pigs that received cholesterol compared with L pigs that did not receive cholesterol. These data suggest that these neonatal pigs are unable to produce sufficient cholesterol to meet requirements for normal growth and brain development and are dependent on dietary cholesterol in milk.

Animal Feed↗
PubMed1994

Dietary cholesterol inhibits whole-body but not cerebrum cholesterol synthesis in young pigs.

We studied the effect of dietary cholesterol on tissue cholesterol synthesis in 10 genetically lean pigs using the 2H2O incorporation method. Five pigs were fed a diet containing 0% cholesterol (controls) and five were fed a diet containing 0.5% cholesterol (cholesterol-fed) from d 1 to d 54 of age. From d 30 to d 54, they received 2H2O and cholesterol synthesis was determined by measuring deuterium enrichment in erythrocyte cholesterol. All pigs were killed on d 54 and liver, ileum, jejunum, kidney, adipose tissue, muscle, and cerebrum were collected for measurement of free and esterified cholesterol and of the deuterium content of tissue free cholesterol. In vivo cholesterol synthesis was inhibited by dietary cholesterol as reflected by a decrease in fractional synthesis rate from 16.8 +/- 1.7%/d in controls to 2.3 +/- 1.1%/d in cholesterol-fed pigs. Cholesterol feeding raised cholesterol ester concentration in plasma, liver, and other tissues. Deuterium enrichment of free cholesterol in tissues, such as liver, was reduced from 11.98 +/- 2.82 milli atom percent excess in controls to 1.83 +/- 1.14 in cholesterol-fed pigs. Greater cholesterol intake did not inhibit cholesterol synthesis in the cerebrum. Deuterium enrichment levels of cholesterol in plasma and liver were similar to those in other tissues except for brain, suggesting an equilibration of cholesterol between the liver and most extrahepatic tissues. The control of cholesterol synthesis in brain appears to be independent of that in liver and other tissues of the body.

Animals↗
PubMed1994

Insulin, cortisol and thyroid hormones modulate maternal protein status and milk production and composition in humans.

The partitioning of dietary and endogenous nutrients during lactation is not well understood. To examine associations between plasma hormone and substrate profiles and indices of either maternal body protein metabolism or lactational performance, we measured plasma insulin, cortisol, prolactin, thyroxine, triiodothyronine, individual amino acid, blood urea nitrogen, and prealbumin concentrations in lactating and nulliparous women in the postabsorptive state. We related these measurements to the subjects' nitrogen balance, urinary 3-methylhistidine excretion, [1-13C]leucine metabolism and milk production. Insulin concentrations showed significant positive relationships with nitrogen balance and prealbumin concentrations; cortisol levels showed a significant negative relationship with nitrogen balance and a significant positive relationship with leucine incorporation into protein. Thyroid hormone concentrations showed significant positive relationships with urinary 3-methylhistidine excretion, leucine incorporation into protein, and milk production. Proline concentrations were associated positively with nitrogen balance and negatively with leucine incorporation into protein, whereas glutamate-glutamine concentrations showed positive associations with leucine oxidation and milk nitrogen concentrations. We propose that insulin and cortisol modulate the channeling of nutrients between anabolic and anti-anabolic aspects of maternal body protein metabolism, whereas thyroid hormones and cortisol modulate nutrient partitioning toward milk production and visceral protein synthesis. We suggest that some nonessential amino acids (proline, glutamate-glutamine) may become limiting during lactation because of their unique contributions to milk protein synthesis.

Adult↗
PubMed1994

Effects of infant nutrition on cholesterol synthesis rates.

Nutrient effects on cholesterol fractional synthesis rates (FSR) in infancy by stable isotope determination have not been studied. We hypothesized that FSR is significantly reduced with high dietary cholesterol and phytoestrogen intake and increased with low dietary cholesterol and phytoestrogen intake. We prospectively studied 33 term male infants exclusively fed human milk (high cholesterol, low phytoestrogen, n = 12), cow milk-based formula (low cholesterol, low phytoestrogen, n = 8), soy milk-based formula (zero cholesterol, high phytoestrogen, n = 7), or soy milk-based formula modified to contain cholesterol (low cholesterol, high phytoestrogen, n = 6) during the first 4 mo of life. Cholesterol FSR was determined from rate of incorporation of deuterium into erythrocyte membrane cholesterol, and urinary isoflavone excretion (an index of dietary phytoestrogen exposure) was measured by gas chromatography-mass spectrometry. Significant differences in cholesterol FSR were found. FSR (%/d) was lowest in human milk (2.62 +/- 0.38), highest in soy milk-based formula (9.40 +/- 0.51), and intermediate in cow milk-based and modified soy milk-based formula (6.90 +/- 0.48 and 8.03 +/- 0.28, respectively), p < 0.0001. Cholesterol FSR was significantly lower in modified soy milk-based compared with soy milk-based formula, p < 0.05. We also show for the first time that dietary phytoestrogens are absorbed and excreted by the infant fed soy protein-based formula. Urinary isoflavone excretion was inversely related to cholesterol FSR, but it was not significantly related to serum cholesterol concentration. We conclude that the type of infant nutrition and dietary cholesterol are major factors influencing cholesterol fractional synthesis rates in infancy.

Adaptation, Physiological↗
PubMed1994

The epidemiology of Helicobacter pylori in Peruvian children between 6 and 30 months of age.

OBJECTIVES: Cross-sectional studies of children in developing countries show a high prevalence of Helicobacter pylori infection at 6 months of age, but a decrease in the prevalence of infection between 1 and 5 yr of age. The decrease suggests a loss or clearance of infection, an uncommon finding in adults. Our objective in this study was to determine the longitudinal persistence of H. pylori infection in young children. METHODS: We tested an initial cohort of 105 6-month-old infants at 6-month intervals with the 13C-urea breath test; 56 subjects were successfully studied for 2 yr or until 30 months of age. RESULTS: Overall prevalence decreased from 71.4% to 47.9% when children were between 6 and 18 months of age, and we found a significant gender difference (males 63.6-55.0%, females 80.0-38.7%, p = 0.03). Of the 56 subjects, six had negative breath tests at all 6-month intervals, 10 were consistently positive, and 36 subjects had one or more negative tests after a positive test. The overall probability of acquiring H. pylori in a given 6-month period ranged between 0.28 and 0.38; the probability of clearing the infection was between 0.22 and 0.45. During the first 18 months after birth, male infants were more likely to acquire H. pylori and less likely to clear the infection than female infants. CONCLUSION: We conclude that H. pylori colonization in infants may be a reversible process.

Breath Tests↗