Acid and Moisture Uptake into Red Beets during in Vitro Gastric Digestion as Influenced by Gastric pH

Food Biophysics - Acid and moisture diffusion into foods during digestion influence food breakdown and nutrient release. As these mass transport processes can be affected by gastric pH and initial...     

Denaturation and in Vitro Gastric Digestion of Heat-Treated Quinoa Protein Isolates Obtained at Various Extraction pH

The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components.     

A Tracer Bolus Method for Investigating Glutamine Kinetics in Humans

Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-¹³C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoR_a) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoR_a of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoR_a showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoR_a in healthy volunteers, which was not attributable to the alanine part of the dipeptide.     

Digestion of Raw and Roasted Almonds in Simulated Gastric Environment

Knowledge of digestion kinetics of solid foods in human stomach, as affected by food processing methods, is critical in establishing processing conditions at the manufacturing stage to achieve desirable release of nutrients in the gastrointestinal tract. The objective of this study was to investigate how roasting affected disintegration and solid release properties of almond in simulated gastric environment. In vitro trials were performed for raw and roasted almonds by using static soaking method and a model stomach system. The changes in sample weight, dry mass, and moisture during the trials were determined. Both compression and penetration tests were used to investigate the texture of almonds with a focus on the influence of absorption of gastric juice. Light microscopy and transmission electronic microscopy were used to study the change in microstructure of the raw and roasted almonds after simulated digestion. The results suggested that the slow disintegration rate and the high amount of swelling of the almonds in the stomach may contribute to their high satiety property. Roasting significantly improved the disintegration rates of almonds and increased loss of solids during simulated digestion, which is well correlated with the decrease in the rigidity of almond samples after absorbing gastric juice. Microstructure of digested almonds showed breakage and breach of cell walls due to acid hydrolysis. Intercellular and intracellular channels formed in almonds during roasting are important for penetration of gastric juice that may facilitate an effective digestion.     

Kinetics of Acetate Metabolism during Sludge Digestion

The quantitative contribution of acetic acid to methane production was studied by use of C(14)-labeled acetic acid. Samples of domestic sewage sludge were incubated anaerobically in Warburg vessels. The rate of methane production in the vessels was 0.033 mumoles per ml per min. C(14)-labeled acetic acid was added, and the turnover rate was calculated. The pool size of acetic acid in the sludge was 4.7 mumoles/ml. The turnover rate was 0.0052 min(-1), giving a rate of formation of acetic acid of 0.024 mumoles per ml per min. Under these conditions, acetic acid would account for approximately 73% of the methane produced by the sludge. Acetic acid was found to exist primarily in an extracellular pool. The turnover rate of the extracellular pool was rapid, and it was concluded that most of the acetic acid must be metabolized to methane by a specialized microflora not involved in the formation of acetic acid.     

In Vitro Digestion of caseinate and Tween 20 Emulsions

Food Biophysics - In vitro digestion experiments are set-up with emulsions stabilized either with sodium caseinate and/or Tween 20, in the presence of mucin in the simulated GI fluids. The progress...     

Solid Loss of Carrots During Simulated Gastric Digestion

The knowledge of solid loss kinetics of foods during digestion is crucial for understanding the factors that constrain the release of nutrients from the food matrix and their fate of digestion. The objective of this study was to investigate the solid loss of carrots during simulated gastric digestion as affected by pH, temperature, viscosity of gastric fluids, mechanical force present in stomach, and cooking. Cylindrical carrot samples were tested by static soaking method and using a model stomach system. The weight retention, moisture, and loss of dry mass were determined. The results indicated that acid hydrolysis is critical for an efficient mass transfer and carrot digestion. Internal resistance rather than external resistance is dominant in the transfer of soluble solids from carrot to gastric fluid. Increase in viscosity of gastric fluid by adding 0.5% gum (w/w) significantly increased the external resistance and decreased mass transfer rate of carrots in static soaking. When mechanical force was not present, 61% of the solids in the raw carrot samples were released into gastric fluid after 4 h of static soaking in simulated gastric juice. Mechanical force significantly increased solid loss by causing surface erosion. Boiling increased the disintegration of carrot during digestion that may favor the loss of solids meanwhile reducing the amount of solids available for loss in gastric juice. Weibull function was successfully used to describe the solid loss of carrot during simulated digestion. The effective diffusion coefficients of solids were calculated using the Fick’s second law of diffusion for an infinite cylinder, which are between 0.75 × 10⁻¹¹ and 8.72 × 10⁻¹¹ m²/s, depending on the pH of the gastric fluid.     

Kinetics of Cellulose Digestion by Fibrobacter succinogenes S85

Growing cultures of Fibrobacter succinogenes S85 digested cellulose at a rapid rate, but nongrowing cells and cell extracts did not have detectable crystalline cellulase activity. Cells that had been growing exponentially on cellobiose initiated cellulose digestion and succinate production immediately, and cellulose-dependent succinate production could be used as an index of enzyme activity against crystalline cellulose. Cells incubated with cellulose never produced detectable cellobiose, and cells that were preincubated for a short time with thiocellobiose lost their ability to digest cellulose (competitive inhibition [K(infi)] of only 0.2 mg/ml or 0.56 mM). Based on these results, the crystalline cellulases of F. succinogenes were very sensitive to feedback inhibition. Different cellulose sources bound different amounts of Congo red, and the binding capacity was HCl-regenerated cellulose > ball-milled cellulose > Sigmacel > Avicel > filter paper. Congo red binding capacity was highly correlated with the maximum rates of metabolism of cellulose digestion and inversely related to K(infm). Congo red (250 (mu)g/ml) did not inhibit the growth of F. succinogenes S85 on cellobiose, but this concentration of Congo red inhibited the rate of ball-milled cellulose digestion. A Lineweaver-Burk plot of ball-milled cellulose digestion rate versus the amount of cellulose indicated that Congo red was a competitive inhibitor of cellulose digestion (K(infi) was 250 (mu)g/ml).     

Partial In Vitro Digestion of Active Gliadin-Related Peptides in Celiac Disease

Peptides corresponding to residues 75–86 (RPQQPYPQPQPQ) and 75–85 of the A-gliadin structure, which were shown to be active in an animal model of celiac disease, were digested in vitro with small intestinal mucosa from children with celiac disease in remission and with mucosa from normal children. The products of digestion were separated into two fractions by gel permeation chromatography. Undigested residues (M _r > 400 fraction) from both peptides contained mainly glutamine, proline, and tyrosine, while the digested materials (M _r < 400 fraction) contained mainly proline, glutamine and arginine. Much larger amounts of undigested peptides were obtained from digestion with celiac mucosa than from normal mucosa. The results with peptide 75–86 indicated that the octapeptide 77–84 (QQPYPQPQ) was the main residual component and this peptide was shown to be active in the assay. Peptide 77–84 was also obtained as a residue from digestion of peptide 75–85, together with heptapeptide 77–83. The results lend further support for a primary mucosal defect in celiac disease and indicate that residual peptides in the small intestine of patients with the disease still retain appreciable toxicity.     

Ran 在胃癌中的表达及其临床意义

目的:利用免疫组织化学的方法探讨小G蛋白Ran在胃癌中的表达及临床意义。方法:利用免疫组织化学染色法研究74例胃癌组织标本(其中高分化25例,中分化24例,低分化25例)及其毗邻正常组织中Ran的表达情况,并分析该蛋白表达水平与临床病理参数之间的关联。结果:(1)Ran在胃癌组织中的染色强度明显高于正常组织。(2)在癌组织中Ran表达于胞核和胞浆,其中又以胞核为主,在正常组织中Ran主要表达于胞浆。(3)Ran的表达与患者年龄、性别无相关性(0.464、0.912),与肿瘤分化、TNM分期和转移与否有显著相关性(0.001、<0.001、<0.001)。结论:与正常组织相比,Ran在胃癌组织中的表达显著增高,并且与肿瘤分化和病理分期存在显著正相关,其可能作为胃癌新的分子标志物,在肿瘤的发生发展中发挥重要作用。     

NMR of Microencapsulated Fish Oil Samples During In Vitro Digestion

The use of nuclear magnetic resonance (NMR) spectroscopy for characterising microencapsulated tuna oil powders (25% and 50% w/w oil) and assessing the behaviour of the microcapsules on their exposure to water, simulated gastric fluid or to sequential exposure of simulated gastric and intestinal fluids was examined. The matrices used for encapsulation were physical mixtures of casein or whey protein in combination with carbohydrates (dextrose monohydrate with either dried glucose syrup or a physically modified resistant starch) or heated mixtures of these matrices. Solid-state ¹³C cross-polarised magic angle spinning NMR and dipolar de-coupled magic angle spinning NMR record the ¹³C NMR signals of the encapsulant material and that of the encapsulated oil, respectively. ¹H and ¹³C solution NMR were used to investigate the relative increase in mobility of the various encapsulant matrices due to their dissolution on exposure to gastrointestinal fluids. The results suggested that the dissolution characteristics of matrices of microencapsulated oil powders were dependent on the type of milk protein and carbohydrate used and whether the protein–carbohydrate matrices were heat-treated prior to encapsulation of the oil.     

通过整体消化法分离具有集落形成能力的胰腺上皮样细胞

目的:胰腺上皮细胞能诱导成表达胰岛素的细胞,成为细胞替代疗法治疗糖尿病的重要来源。胰腺细胞的分离多采用机械剪切后胶原酶消化,本文在以往研究基础上,探索一种能分离得到更纯净的胰腺上皮样细胞的新方法。方法:本研究采用胰腺整体消化的方法,将成体小鼠整个胰腺取下,摘除系膜及大的血管,置于胶原酶中消化20min,用PBS吹打胰腺组织,得到的细胞悬液,离心后去除上清与细胞碎片,用培养基重悬实质细胞,接种于6 cm培养皿中,培养7-10天后得到单细胞集落。结果:整体消化法不剪碎胰腺组织,从而避免多种胰腺细胞的参与,得到较为纯净的胰腺上皮细胞悬液,细胞总体数量小于部分消化法,但是单细胞比率远远高于部分消化法,得到的细胞集落更纯净,不需要去除成纤维细胞,方便筛选及进一步扩大培养。结论:整体消化法能够分离纯化出一群在离体条件下具有强增殖能力、形成大的上皮样集落的细胞。该分离方法方便、快捷,为今后进一步研究成体胰腺干细胞增殖与分化调控机制等问题奠定基础。     

Oral and Gastric Helicobacter Pylori: Effects and Associations

IntroductionThis study consisted in the comparison of the prevalence of Helicobacter pylori (H. pylori) present in the stomach and in saliva of a sample of Portuguese adolescents and the assessment of the association between H. pylori infection with socio-demographic variables and prevalence of dental caries.ResultsThe prevalence of gastric H. pylori detected by UBT was 35.9%. Within the adolescents with a gastric UBT positive, only 1.9% were positive for oral H. pylori. The presence of gastric H. pylori was found to be associated with age (>15years, Odds ratio (OR)=1.64,95%CI=1.08-2.52), residence area (urban,OR=1.48,95%CI=1.03-2.29) and parents´ professional situation (unemployed,OR=1.22,95%CI=1.02-1.23). Among those with detected dental caries during the intra-oral observation, 37.4% were positive for gastric H. pylori and 40.2% negative for the same bacterial strain (p=0.3).ConclusionsThe oral cavity cannot be considered a reservoir for infection of H. pylori. Gastric H. pylori infection was found to be associated with socio-demographic variables such as age, residence area and socioeconomic status.     

Thiouracil-Forming Bacteria Identified and Characterized upon Porcine In Vitro Digestion of Brassicaceae Feed

In recent years, the frequent detection of the banned thyreostat thiouracil (TU) in livestock urine has been related to endogenous TU formation following digestion of glucosinolate-rich Brassicaceae crops. Recently, it was demonstrated that, upon in vitro digestion of Brassicaceae, fecal bacteria induce TU detection in livestock (porcine livestock > bovines). Therefore, the present study was intended to isolate and identify bacteria involved in this intestinal TU formation upon Brassicaceae digestion and to gain more insight into the underlying mechanism in porcine livestock. Twenty porcine fecal inocula (gilts and multiparous sows) were assessed through static in vitro colonic-digestion simulations with rapeseed. After derivatization and extraction of the fecal suspensions, TU was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS²). On average, lower TU concentrations were observed in fecal colonic simulations in gilts (8.35 ng g⁻¹ rapeseed ± 3.42 [mean ± standard deviation]) than in multiparous sows (52.63 ng g⁻¹ ± 16.17), which correlates with maturation of the gut microbial population with age. Further exploration of the mechanism showed cell-dependent activity of the microbial conversion and sustained TU-forming activity after subjection of the fecal inoculum to moderate heat over a time span of up to 30 min. Finally, nine TU-producing bacterial species were successfully isolated and identified by a combination of biochemical and molecular techniques as Escherichia coli (n = 5), Lactobacillus reuteri (n = 2), Enterococcus faecium (n = 1), and Salmonella enterica subsp. arizonae (n = 1). This report demonstrates that endogenous formation of TU is Brassicaceae induced and occurs under colonic conditions most likely through myrosinase-like enzyme activity expressed by different common intestinal bacterial species.