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Biomedical subjects

B Stoll

Publications and source records attributed to B Stoll.

At least 19 recordsLinked to original sources
PubMed2006

Measuring splanchnic amino acid metabolism in vivo using stable isotopic tracers.

The splanchnic bed comprises the liver and the portal-drained viscera (PDV). The PDV, which include the stomach, intestines, pancreas, and spleen, represent 4 to 6% of BW, yet they account for 20 to 35% of whole-body protein turnover and energy expenditure. Because the PDV are the first to be exposed to the diet, their nutrient needs are met first. Consequently, the extraction of dietary nutrients, especially AA, by the intestine will have a critical influence on their availability to peripheral tissues and therefore, on whole body requirements. Moreover, the systemic availability of dietary AA is a key determinant of lean body growth rate. A complicating factor in the measurement of intestinal nutrient use is that the intestinal epithelial cells receive nutrients from 2 sources: the diet and the arterial circulation. However, combining measurements of the net portal balance with those of isotopic enrichments from enterally and intravenously administered stable isotope-labeled AA provides an in vivo model that can be used to determine the proportion of AA extracted by the intestine from either source. Using this technique in fed animals demonstrated that the PDV contribute significantly to the use of essential (>60% of threonine) and nonessential (>90% of glutamate) AA provided by the diet. The relative use by the PDV of individual AA from the diet and arterial inputs varies widely, and dietary AA are the preferred fuel over dietary glucose. Stable isotope-labeled AA also enable the determination of the metabolic fate of individual AA. Using this technique, studies have shown that an insufficient protein supply or the mode of feeding affects AA use by the PDV, and consequently, may affect whole-body growth.

Amino Acids↗
PubMed2005

Glucagon-like peptide-2 protects against TPN-induced intestinal hexose malabsorption in enterally refed piglets.

Premature infants receiving chronic total parenteral nutrition (TPN) due to feeding intolerance develop intestinal atrophy and reduced nutrient absorption. Although providing the intestinal trophic hormone glucagon-like peptide-2 (GLP-2) during chronic TPN improves intestinal growth and morphology, it is uncertain whether GLP-2 enhances absorptive function. We placed catheters in the carotid artery, jugular and portal veins, duodenum, and a portal vein flow probe in piglets before providing either enteral formula (ENT), TPN or a coinfusion of TPN plus GLP-2 for 6 days. On postoperative day 7, all piglets were fed enterally and digestive functions were evaluated in vivo using dual infusion of enteral ((13)C) and intravenous ((2)H) glucose, in vitro by measuring mucosal lactase activity and rates of apical glucose transport, and by assessing the abundances of sodium glucose transporter-1 (SGLT-1) and glucose transporter-2 (GLUT2). Both ENT and GLP-2 pigs had larger intestine weights, longer villi, and higher lactose digestive capacity and in vivo net glucose and galactose absorption compared with TPN alone. These endpoints were similar in ENT and GLP-2 pigs except for a lower intestinal weight and net glucose absorption in GLP-2 compared with ENT pigs. The enhanced hexose absorption in GLP-2 compared with TPN pigs corresponded with higher lactose digestive and apical glucose transport capacities, increased abundance of SGLT-1, but not GLUT-2, and lower intestinal metabolism of [(13)C]glucose to [(13)C]lactate. Our findings indicate that GLP-2 treatment during chronic TPN maintains intestinal structure and lactose digestive and hexose absorptive capacities, reduces intestinal hexose metabolism, and may facilitate the transition to enteral feeding in TPN-fed infants.

Algorithms↗
PubMed2003

Validation of multi-element isotope dilution ICPMS for the analysis of basalts.

In this study we have validated a newly developed multi-element isotope dilution (ID) ICPMS method for the simultaneous analysis of up to 12 trace elements in geological samples. By evaluating the analytical uncertainty of individual components using certified reference materials we have quantified the overall analytical uncertainty of the multi-element ID ICPMS method at 1-2%. Individual components include sampling/weighing, purity of reagents, purity of spike solutions, calibration of spikes, determination of isotopic ratios, instrumental sources of error, correction of mass discrimination effect, values of constants, and operator bias. We have used the ID-determined trace elements for internal standardization to improve indirectly the analysis of 14 other (mainly mono-isotopic trace elements) by external calibration. The overall analytical uncertainty for those data is about 2-3%. In addition, we have analyzed USGS and MPI-DING geological reference materials (BHVO-1, BHVO-2, KL2-G, ML3B-G) to quantify the overall bias of the measurement procedure. Trace element analysis of geological reference materials yielded results that agree mostly within about 2-3% relative to the reference values. Since these results match the conclusions obtained by the investigation of the overall analytical uncertainty, we take this as a measure for the validity of multi-element ID ICPMS.

Journal Article↗
PubMed2003

Glucagon-like peptide 2 function in domestic animals.

Glucagon-like peptide 2 (GLP-2) is a member of family of peptides derived from the proglucagon gene expressed in the intestines, pancreas and brain. Tissue-specific posttranslational processing of proglucagon leads to GLP-2 and GLP-1 secretion from the intestine and glucagon secretion from the pancreas. GLP-2 and GLP-1 are co-secreted from the enteroendocrine L-cells located in distal intestine in response to enteral nutrient ingestion, especially carbohydrate and fat. GLP-2 secretion is mediated by direct nutrient stimulation of the L-cells and indirect action from enteroendocrine and neural inputs, including GIP, gastrin-releasing peptide (GRP) and the vagus nerve. GLP-2 is secreted as a 33-amino acid peptide and is rapidly cleaved by dipeptidylpeptidase IV (DPP-IV) to a truncated peptide which acts as a weak agonist with competitive antagonistic properties. GLP-2 acts to enhance nutrient absorption by inhibiting gastric motility and secretion and stimulating nutrient transport. GLP-2 also suppresses food intake when infused centrally. The trophic actions of GLP-2 are specific for the intestine and occur via stimulation of crypt cell proliferation and suppression of apoptosis in mucosal epithelial cells. GLP-2 reduces gut permeability, bacterial translocation and proinflammatory cytokine expression under conditions of intestinal inflammation and injury. The effects of GLP-2 are mediated by a G-protein-linked receptor that is localized to the intestinal mucosa and hypothalamus. The intestinal localization of the GLP-2R to neural and endocrine cells, but not enterocytes, suggests that its actions are mediated indirectly via a secondary signaling mechanism. The implications of GLP-2 in domestic animal production are largely unexplored. However, GLP-2 may have therapeutic application in treatment of gastrointestinal injury and diarrheal diseases that occur in developing neonatal and weanling animals.

Amino Acid Sequence↗
PubMed2001

Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples.

Spark source mass spectrometry (SSMS) has experienced important and significant improvements in nearly all analytical features by the use of a multiple ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necessary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the development of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international reference materials, are presented using the improved MIC-SSMS technique. The data set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor of 3 better than that of conventional SSMS, as demonstrated by analyses of Hawaiian samples. Total uncertainties of MIC-SSMS concentration data including all sources of error are generally between 2 and 5% for concentrations higher than about 0.3 microg/g and about 10% for trace element abundances in the ng/g range.

Journal Article↗
PubMed2001

The pattern of intestinal substrate oxidation is altered by protein restriction in pigs.

BACKGROUND & AIMS: Previous studies indicate that amino acids and glucose are the major oxidative substrates for intestinal energy generation. We hypothesized that low protein feeding would lower the contribution of amino acids to energy metabolism, thereby increasing the contribution of glucose. METHODS: Piglets, implanted with portal, arterial, and duodenal catheters and a portal flow probe, were fed isocaloric diets of either a high protein (0.9 g/[kg/h] protein, 1.8 g/[kg/h] carbohydrate, and 0.4 g/[kg/h] lipid) or a low protein (0.4 g/[kg/h] protein, 2.2 g/[kg/h] carbohydrate, and 0.5 g/[kg/h] lipid) content. They received enteral or intravenous infusions of [1-13C]leucine (n = 17), [U-13C]glucose (n = 15), or enteral [U-13C]glutamate (n = 8). RESULTS: CO2 production by the splanchnic bed was not affected by the diet. The oxidation of leucine, glutamate, and glucose accounted for 82% of the total CO2 production in high protein-fed pigs. Visceral amino acid oxidation was substantially suppressed during a low protein intake. Although glucose oxidation increased to 50% of the total visceral CO2 production during a low protein diet, this increase did not compensate entirely for the fall in amino acid oxidation. CONCLUSIONS: Although low protein feeding increases the contribution of enteral glucose oxidation to total CO2 production, this adaptation is insufficient. To compensate for the fall in amino acid oxidation, other substrates become increasingly important to intestinal energy generation.

Animals↗
PubMed2001

Glucagon-like peptide 2: a nutrient-responsive gut growth factor.

Glucagon-like peptide 2 (GLP-2) is a 33-amino acid peptide derived from the tissue-specific, post-translational processing of the proglucagon gene expressed in the intestinal enteroendocrine L-cell. The primary stimulus for GLP-2 secretion is nutrient intake, and involves direct luminal stimulation of the L-cell as well as indirect enteroendocrine and neural mechanisms. The biological activity of GLP-2 in circulation is regulated by the proteolytic cleavage of the N-terminus by dipeptidylpeptidase IV. Several studies have shown that GLP-2 has specific trophic effects on the small and large intestine, which are mediated by stimulation of cell proliferation and inhibition of apoptosis and proteolysis. GLP-2 also has been shown to suppress gastric motility and acid secretion, increase hexose transport activity and suppress food intake, specifically when infused centrally. The actions of GLP-2 are mediated by a G-protein-linked, membrane receptor (GLP-2R) that is localized largely to the gastrointestinal tract, but also is found in the brain. The secretion of GLP-2 and expression of the GLP-2R are present in the late gestation fetus. However, the developing intestine does not become responsive to the trophic effect of GLP-2 until after birth. Based on its efficacy in preventing atrophy and stimulating growth in the neonatal gut, GLP-2 may be a promising therapeutic adjuvant for treatment of infants with compromised gut function.

Cell Division↗
PubMed2001

Secretion of trophic gut peptides is not different in bolus- and continuously fed piglets.

In neonates, bolus feeding is associated with greater rates of intestinal growth than is continuous feeding. We tested whether the concentrations and secretion rates of trophic gut peptides are higher in bolus-fed than in continuously fed piglets. Five 21-d-old piglets were surgically implanted with gastric, arterial and portal catheters and a portal blood flow probe. At postnatal d 30 and 31, pigs received an equal amount of primed continuous or bolus feeding of a cow's milk formula in a randomized, crossover design. During a 6-h period, portal blood flow and arterial and portal concentrations of glucagon-like peptide-2 (GLP-2), peptide YY (PYY) and gastric inhibitory polypeptide (GIP) were measured. All hormone levels were significantly increased within 1 h of the start of the experiment, independent of the feeding modality. There were no differences between bolus and continuous feeding in either the arterial concentrations or secretion rates of GLP-2, PYY and GIP. In both treatment groups, the increases in the plasma concentrations of GLP-2 and GIP after feeding were substantially greater than those for PYY. We conclude that the production or circulating concentrations of GLP-2, PYY and GIP are not significantly different in bolus- and primed continuously fed piglets.

Animals↗
PubMed2001

Oral IGF-I alters the posttranslational processing but not the activity of lactase-phlorizin hydrolase in formula-fed neonatal pigs.

To determine the cellular mechanism whereby oral insulin-like growth factor I (IGF-I) increases intestinal lactase-phlorizin hydrolase (LPH) activity, we studied 2-d-old pigs fed cow's milk formula (control, n = 5), formula + low IGF-I (0.5 mg/L; n = 6) or formula + high IGF-I (12.0 mg/L, n = 6) for 15 d. On d 15, intestinal protein synthesis and lactase processing were measured in vivo in fed pigs using a 6-h intravenous, overlapping infusion of multiple stable isotopes (2H(3)-Leu, 13C(1)-Leu, 13C(1)-Phe, 2H(5)-Phe, 13C(6)-Phe and 13C(9)-Phe). Morphometry and cell proliferation also were measured in the jejunum and ileum. Neither dose of IGF-I affected the masses of wet tissue, protein or DNA, or the villus height, cell proliferation or LPH-specific activity. Oral IGF-I decreased the synthesis and abundance of prolactase-phlorizin hydrolase (pro-LPH), but increased brush-border (BB)-LPH synthesis in the ileum. The BB-LPH processing efficiency was twofold to threefold greater in IGF-fed than in control pigs. In all pigs, villus height and the total mucosal and specific activity of LPH activity were greater in the ileum than in the jejunum, yet the synthesis of BB-LPH were significantly lower in the ileum than in the jejunum. We conclude that oral IGF-I increases the processing efficiency of pro-LPH to BB-LPH but does not affect LPH activity. Moreover, the posttranslational processing of BB-LPH is markedly lower in the ileum than in the jejunum.

Administration, Oral↗
PubMed2001

Enterocyte digestive enzyme activity along the crypt-villus and longitudinal axes in the neonatal pig small intestine.

Our objective was to examine the distribution of enterocyte digestive enzyme activity along the crypt-villus and longitudinal axes of the small intestine in formula-fed neonatal pigs between the ages of 14 and 18 d. The distended intestinal sac method was used to isolate 12 sequential fractions (F1 through F12) of epithelial cells. Enterocyte migration rate was measured in the proximal and distal intestine using in vivo bromodeoxyuridine labeling. Specific activities of representative villus cell marker enzymes of alkaline phosphatase, aminopeptidase N, sucrase, and lactase increased 6- to 17-fold from F12 (crypt cells) to F1 (villus cells), whereas the crypt cell marker [3H]thymidine incorporation increased 8- to 18-fold from F1 (villus cells) to F12 (crypt cells). Enterocyte migration rate was similar (3.2 vs 3.0 microm/h), whereas the villus height (547.4 vs 908.5 microm) and enterocyte life span (4.7 vs 10.2 d) were markedly lower (P < 0.05) in the proximal than in the distal segments, respectively. In general, the specific activities of all enzymes were lowest in the crypt fractions (F9 through F12) but increased markedly (ranging from 8- to 17-fold) from F12 to F1. The activity of aminopeptidase N was higher and that of sucrase was lower in the distal than in the proximal segment. The activities of the remaining enzymes were similar in the proximal and the distal segments. Our results suggest that the enterocyte life span in the distal small intestine is approximately twice as long as in the proximal small intestine. However, despite the difference in life span, the patterns of enzyme activities along the crypt-villus axis were generally similar in the proximal and the distal regions.

Adenosine Triphosphatases↗
PubMed2001

Critical Incident Stress Management with inmates: an atypical application.

In March 2001, Centerstone Community Mental Health Centers, Inc.'s CISM Team was asked to debrief 14 inmates after a murder in a rural county jail. We had no specific experience providing CISM in this particular setting, so we contacted ICISF and local law enforcement personnel for their input. We found that neither had a significant amount of experience with this population. In general, although our Team found significant differences related to the restrictions inherent in the environmental setting and the overall group dynamic, we also found similarities in the general manner in which the CISM model was utilized.

Adult↗
PubMed2000

Adaptive regulation of intestinal lysine metabolism.

The metabolism of dietary essential amino acids by the gut has a direct effect on their systemic availability and potentially limits growth. We demonstrate that, in neonatal pigs bearing portal and arterial catheters and fed a diet containing 23% protein [high protein (HP) diet], more than half the intake of essential amino acids is metabolized by the portal-drained viscera (PDV). Intraduodenal or i.v. infusions of [U-(13)C]-lysine were used to measure the appearance across and the use of the tracer by the PDV. In HP-fed pigs, lysine use by the PDV was derived almost entirely from the arterial input. In these animals, the small amount of dietary lysine used in first pass was oxidized almost entirely. Even so, intestinal lysine oxidation (24 micromol/kg per h) accounted for one-third of whole-body lysine oxidation (77 micromol/kg per h). Total lysine use by the PDV was not affected by low protein (LP) feeding (HP, 213 micromol/kg per h; LP,186 micromol/kg per h). In LP-fed pigs, the use of lysine by the PDV accounted for more than 75% of its intake. In contrast to HP feeding, both dietary and arterial lysines were used by the PDV of LP-fed pigs in nearly equal amounts. Intestinal lysine oxidation was suppressed completely. We conclude that the PDV are key organs with respect to amino acid metabolism and that the intestines use a disproportionately large amount of the dietary supply of amino acids during protein restriction.

Adaptation, Physiological↗
PubMed2000

Protein nutrition of the neonate.

The period of growth and development between birth and weaning is crucial for the long-term well-being of the organism. Protein deposition is very rapid, is achieved with a high nutritional efficiency, and is accompanied by marked differences in the growth rates of individual tissues and a series of maturational processes. These important aspects of development occur while the neonate is consuming a single and highly-specific food source, milk. Surprisingly, although there is a clear relationship between the nutrient density of milk and the growth rate of its recipient, this relationship does not apply to the overall amino acid composition of mixed milk proteins. Some amino acids, notably glycine and arginine, are supplied in milk in quantities that are much less than the needs of the neonate. The milk-fed neonate is therefore capable of carrying out a tightly-regulated transfer of N from amino acids in excess to those that are deficient. The rapid growth of the neonate is supported by a high rate of tissue protein synthesis. This process appears to be activated by the consumption of the first meals of colostrum. Recent research has identified that skeletal muscle and the brain are specifically responsive to an unidentified factor in colostrum. Following the initial anabolic response the rate of protein synthesis in some tissues, notably muscle, falls from birth to weaning. This decrease reflects a progressively smaller anabolic response to nutrient intake, which not only involves an overall fall in the capacity for protein synthesis, but also in responses to insulin and amino acids. The study of growth and protein metabolism, and their regulation in the neonate is not only important for pediatrics, but may provide important pointers to more general aspects of regulation that could be applied to the nutrition of the mature animal.

Amino Acids↗
PubMed2000

Minimal enteral nutrient requirements for intestinal growth in neonatal piglets: how much is enough?

BACKGROUND: Parenterally nourished preterm infants commonly receive minimal enteral feedings, the aim being to enhance intestinal function. Whether this regimen increases intestinal growth has not been established. OBJECTIVE: Our objective was to determine the minimal enteral nutrient intakes necessary to stimulate and to normalize neonatal intestinal growth. METHODS: Intestinal growth and cell proliferation were quantified in neonatal pigs given equal amounts of an elemental nutrient solution for 7 d. Different groups (n = 5-7 per group) received 0%, 10%, 20%, 40%, 60%, 80%, or 100% of total nutrient intake enterally, with the remainder given parenterally. RESULTS: In the jejunum, wet weight, protein mass, and villus height were significantly greater at enteral intakes >40%. Stimulation of ileal protein mass required a higher enteral intake (60%). In both segments, abrupt increases in DNA mass, crypt depth, ornithine decarboxylase activity, and crypt cells in S-phase occurred between enteral intakes of 40% and 60%. Circulating concentrations of glucagon-like peptide-2 and peptide YY, but not gastrin, increased significantly between enteral intakes of 40% and 60% and closely paralleled indexes of cell proliferation. CONCLUSIONS: The minimal enteral nutrient intake necessary to increase mucosal mass was 40% of total nutrient intake, whereas 60% enteral nutrition was necessary to sustain normal mucosal proliferation and growth. Our results imply that providing <40% of the total nutrient intake enterally does not have significant intestinal trophic effects.

Animals↗
PubMed2000

Dietary plasma protein reduces small intestinal growth and lamina propria cell density in early weaned pigs.

ABSTRACT We quantified the effects of a diet containing animal plasma protein on small intestinal growth and mucosal morphology in early weaned pigs. Ninety-six pigs [14 d old, 4 kg body weight (BW)] were assigned in groups of 32 to three dietary treatments as follows: 1) free access to control diet (C), 2) free access to plasma protein diet (P), and 3) plasma protein, pair-fed to C (PPF). Eight pigs from each group were killed at 2, 4, 8 or 16 d. Over a 16-d period, weight gain in the P group was 43% greater (P < 0.05) than that in C pigs; weight gain was similar in C and PPF groups. Protein intake in the P group was 33% higher (P < 0.05) than that in the PPF group; no significant difference was observed between the C and P groups. Dietary protein conversion efficiencies in both the P and PPF groups were approximately 18% greater (P < 0.05) than those in the C group. Intestinal masses in the three groups did not differ at 2, 4 and 8 d. By 16 d, the jejunal and ileal protein and DNA masses (mg/kg BW) in both the P and PPF groups were lower than those in the C group (P < 0.05). Dietary plasma protein did not affect crypt cell proliferation, crypt depth or villous height in either the jejunum or ileum. However, the intravillous lamina propria cell density in the jejunum was significantly lower (P < 0.05) in P and PPF pigs than in C pigs. Plasma urea concentrations were also 40 and 42% lower (P < 0.05) in the P and PPF groups, respectively, than in the C group. Our results indicate that dietary plasma protein reduces the cellularity of the lamina propria, but not epithelial cell surface of the small intestine. Feeding plasma protein also increased the efficiency of dietary protein utilization, in part, by decreasing amino acid catabolism.

Analysis of Variance↗
PubMed2000

Intestinal glutamate metabolism.

Although it is well known that the intestinal tract has a high metabolic rate, the substrates that are used to generate the necessary energy remain poorly established, especially in fed animals. Under fed conditions, the quantification of substrate used by the gut is complicated by the fact that potential oxidative precursors are supplied from both the diet and the arterial circulation. To circumvent this problem, and to approach the question of the compounds used to generate ATP in the gut, we combined measurements of portal nutrient balance with enteral and intravenous infusions of [U-(13)C]substrates. We studied rapidly growing piglets that were consuming diets based on whole-milk proteins. The results revealed that 95% of the dietary glutamate presented to the mucosa was metabolized in first pass and that of this, 50% was metabolized to CO(2). Dietary glucose was oxidized to a very limited extent, and arterial glutamine supplied no >15% of the CO(2) production by the portal-drained viscera. Glutamate was the single largest contributor to intestinal energy generation. The results also suggested that dietary glutamate appeared to be a specific precursor for the biosynthesis of glutathione, arginine and proline by the small intestinal mucosa. These studies imply that dietary glutamate has an important functional role in the gut. Furthermore, these functions are apparently different from those of arterial glutamine, the substrate that has received the most attention.

Animals↗
PubMed2000

Dietary plasma protein is used more efficiently than extruded soy protein for lean tissue growth in early-weaned pigs.

We compared the effects of supplementing either animal plasma or extruded soy protein in the diet based on the efficiency of dietary protein utilization for lean tissue growth in early-weaned pigs. Twenty-four 14-d-old pigs (4 kg body weight) were pair-fed (per kg body weight) either a control diet containing extruded soy protein (C; n = 12) or a diet with 10% animal plasma (P; n = 12) for 24 d. During the 24 days, protein intake was not different, yet mean daily body weight gains (+23%) and food conversion efficiencies (expressed as the ratio of body weight gain to protein intake) (+19%) were greater (P < 0.05) in the P group than in the C group. Lean body mass measured after 24 d, using both dual-energy X-ray absorptiometry and total body potassium analysis, was significantly (P < 0.05) greater (approximately 16%) in P than in C pigs. The circulating urea concentrations were 40% lower (P < 0.05) in P than in C pigs. Our results demonstrate that supplementing early-weaned pig diets with animal plasma rather than extruded soy protein increased the efficiency of dietary protein use for lean tissue growth and that this response is mediated in part by decreased amino acid catabolism.

Animal Feed↗