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The digestion of bacterial macromolecules by phagocytic cells: the effect of mepacrine and ethanol.

The digestion of radiolabelled DNA, RNA and protein from two species of bacteria was measured after their ingestion by neutrophils and monocytes. The Escherichia coli (W3110T-) strain was more susceptible to digestion than Staphylococcus aureus. Monocytes solubilized the majority of bacterial DNA to trichloroacetic acid (TCA)-soluble oligonucleotides, which were released rapidly from the cell, whereas neutrophils digested little DNA and retained most as a high molecular weight residue. Both monocytes and neutrophils released about 30% of DNA as large TCA-insoluble fragments. However, neutrophils were more proficient than monocytes at degrading bacterial RNA. Monocytes and neutrophils digested bacterial protein equally well. The drug mepacrine hydrochloride inhibited phagocytosis of bacteria by both neutrophils and monocytes, although monocytes were more sensitive to the drug. Mepacrine specifically inhibited the terminal digestion of DNA by monocytes to TCA-soluble molecules, whereas digestion to large molecular weight fragments apparently was not affected. Ethanol also inhibited the breakdown of DNA by phagocytic cells.

Bacterial Proteins↗

Suppression of DNA synthesis in mitogen stimulated leukocytes with partial trypsin digests of Staphylococcus aureus protein A.

Staphylococcus aureus protein A (SPA) acts as a mitogen stimulating DNA synthesis and is not antagonistic to the mitogenic activity of other mitogens. The mitogenicity of SPA is due to the protein's multivalent Fc antibody receptors. Partial trypsin digestion of SPA yields monovalent Fc antibody receptors which are not mitogenic. Using a thymidine incorporation assay, results indicated that tryptic digests of SPA added to mouse splenic leukocytes 12 hours after stimulation with either concanavalin A, lipopolysaccaride or SPA suppressed the DNA synthesis normally elicited by these mitogens. SPA was digested with 1% trypsin at pH 8 for varying periods of time. As the digestion time increased from 0 to 60 minutes the mitogenicity of the SPA-trypsin digests decreased indicating cleavage from multivalent to monovalent SPA Fc antibody receptors. The decrease in mitogenicity of the SPA digests was directly associated with increased ability to inhibit DNA synthesis in mitogen stimulated leukocytes. A proposed mechanism for the inhibition of DNA synthesis suggests that SPA-monovalent Fc antibody receptors mimic cellular Fc receptor function thereby influencing cellular gene expression.

Animals↗

Purification and separation of subsets of human Ia molecules by papain digestion.

Papain digestion of human Ia(-like) molecules was performed under various conditions using 125I-labelled preparation of non-ionic-detergent-solubilized Ia antigens of Daudi cells. The products were examined for their allospecificities by a direct binding reaction with human Ia alloantisera. The Daudi Ia preparation is known to contain Ia molecules of DRw6 specificity, an HLA-DR specificity and also Ia molecules of DC1 specificity, a putative non-HLA-DR specificity. Limited papain digestion cleaved off the hydrophobic portion of human Ia molecules and gave smaller sized Ia products. The cleavage did not affect the Ia alloantigenic determinants and occurred much more readily with molecules of DC1 specificity than with molecules of DRw6 specificity. As a consequence, limited papain digestion of the Daudi Ia pool yielded an Ia preparation with DRw6 specificity but lacking DC1 specificity and another Ia preparation which was enriched in DC1 specificity. The limited papain digestion of the Daudi Ia pool followed by gel filtration and LcH affinity chromatography also produced Ia REPARATIONS OF HIGH PURITY. Extensive papain digestion damaged the Ia alloantigenic determinants but the DC1 determinant was much more resistant than the DRw6 determinant. Thus extensive papain digestion yielded an Ia preparation which was relatively rich in DC1 specificity and essentially devoid of DRw6 specificity.

Antigen-Antibody Reactions↗

Endoglycosidase H digestion of neuronal intracellular lectin-binding sites.

Cerebellar Purkinje cells contain intracellular membrane systems that are highly enriched in concanavalin A (Con A)-binding sites and which may be involved in axonal and dendritic transport. We have attempted to characterize these Con A-binding sites in fixed slices of cerebellum by their susceptibility to endoglycosidase H (Endo H) digestion. Tissue slices labeled with Con A-peroxidase without prior Endo H digestion had moderately dense label in the molecular and granular layers with the heaviest label occurring in Purkinje cell somata. Endo H digestion of tissue slices produced little change in the pattern of Con A label in the molecular and granular layers, but the Con A label in Purkinje cell somata was removed except for small discrete patches. Electron microscopic examination of Purkinje cells from tissue slices not digested with Endo H showed Con A label in cisternal elements of the endoplasmic reticulum (ER), nuclear envelope, hypolemmal cisternae, and the Golgi complex. Presynaptic terminal smooth membrane cisternae and dendritic hypolemmal cisternae of Purkinje cells were also labeled with Con A-peroxidase. Endo H digestion removed Con A-binding sites in cisternae of the ER, somal and dendritic hypolemmal membrane system, and presynaptic terminal smooth membrane profiles. Con A-binding sites in the nuclear envelope and Golgi complexes of Purkinje cells were not removed by Endo H digestion. These results present ultrastructural evidence in support of biochemical studies which report the rough ER as the site of polymannose oligosaccharide addition to nascent polypeptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Effects of dimethyldioctadecylammonium bromide on phagocytosis and digestion of Listeria monocytogenes by mouse peritoneal macrophages.

Listeria monocytogenes was labelled with [3H]-thymidine and phagocytosis in vivo, measured after the intraperitoneal injection of killed or viable listeria. The loss of intracellular radioactivity after incubation in vitro was used as a measure for digestion. Killing was assessed by counting the numbers of viable listeria before and after in vitro incubation. Peritoneal macrophages from mice immunized with viable listeria showed better phagocytosis and digestion of both killed and viable listeria than macrophages from normal mice. Viable listeria were digested to a lesser degree than killed ones by both normal and immune macrophages. The simultaneous injection of the surfactant dimethyldioctadecylammonium bromide (DDA) with killed or viable listeria greatly depressed the digestion of listeria. Phagocytosis of viable listeria was not affected whereas that of killed listeria was slightly enhanced. The injection of 10(8) killed listeria mixed with DDA greatly impaired the digestion of viable listeria 7 days but not 1 day after injection. The impairment of digestion was accompanied by an increase in the number of intracellular viable listeria.

Animals↗

[Effect of Maillard protein modification on protein resistance to hydrolysis by digestive proteinases].

A study was made of the influence of the Maillard reaction in proteins on their digestibility by pepsin, trypsin, and chymotrypsin. The model substrates were obtained by heating bovine serum albumin (BSA) and beta-lactoglobulin (BLG) with glucose for the preset period of time at 50 degree C. The rate of proteolysis by alkaline proteolytic enzymes was measured by the autotitration technique, whereas pepsin activity was determined by fluorometry. An evidence was obtained that digestibility by trypsin and chymotrypsin of BLG-glycose decreased, while the amount of protein bound carbohydrate increased. In the case of BSA, the incubation with glucose led at first to an insignificant lowering of digestibility by these two enzymes whereupon the protein resistance decreased. Thermal processing of both BLG and BSA in the absence of glucose led to a distinct growth of digestibility as compared to the native forms of proteins. As to pepsin, the authors failed to find any decrease in the digestibility of the Maillard compounds. It was revealed that the Maillard reaction in proteins had different effects on digestibility of different protein substrates by different proteolytic enzymes.

Allergens↗

Active pancreatic digestive enzymes show striking differences in their potential to damage isolated rat pancreatic acinar cells.

Active digestive enzymes are involved in the pathophysiology of acute pancreatitis. Previous studies have mainly focused on the role of trypsin in the autodigestive process. The present study compares the noxious potential of different pancreatic enzymes to damage acinar cells. Acinar cells were isolated from rat pancreas by collagenase digestion. Cell viability was studied by (1) exclusion of trypan blue, (2) release of lactate dehydrogenase, and (3) release of newly synthesized proteins identified with methionine labeled with sulfur 35. Cells were then incubated in oxygenated N-2-hydroxyethylpiperazine-N-'-2-ethanesulfonic acid-Ringer solution containing different concentrations of various active digestive enzymes. Uptake of trypan blue was the most sensitive and reliable test of cell damage when compared with release of lactate dehydrogenase or radiolabeled newly synthesized proteins. All active digestive enzymes studied caused dose-dependent cell damage. The noxious potential, however, was strikingly different for the various enzymes. Pancreatic elastase in nanomolar concentrations caused marked cell damage after 45 to 90 minutes of incubation. Lipase and chymotrypsin caused a similar damage only at micromolar concentrations, whereas even millimolar concentrations of trypsin failed to cause significant damage. The present results confirmed recent work showing that lipase and phospholipase A2 probably cause cell damage through release of free fatty acids and lysolecithin. Although activation of trypsin might be the trigger to start the activation cascade in acute pancreatitis, trypsin itself is markedly less noxious to acinar cells when compared with other digestive enzymes. Elastase by far had the greatest noxious potential of all enzymes evaluated. Studies analyzing therapeutic effects of protease inhibitors should evaluate not only the inhibitory potential against trypsin but also that against other digestive enzymes, particularly elastase.

Acute Disease↗

Insoluble dietary fiber of grain food legumes and protein digestibility.

The present work aimed to verify the digestibility of cooked whole food grain legumes. Samples of beans (Phaseolus vulgaris and Vigna sinensis), chickpeas (Cicer arietinum) and lentils (Lens culinaris) were used in the experiment. The interrelationship between the insoluble dietary fiber presented in the food grain legumes and the low protein digestibility was studied. The insoluble dietary fiber and the proteic nitrogen presented in the neutral detergent fiber (NDF) were determined. "In vivo" digestibility was performed in rats fed with diets containing cooked grain legumes, casein and protein free diet. The experiments were performed on rats over a period of 21 days. High excretion of nitrogen was observed by rats fed with cooked food grain legumes compared to casein diet. "In vitro" digestibility was performed by enzymatic hydrolysis with pepsin and trypsin. No significant differences was found between "in vivo" and "in vitro" digestibility. The heat treatment caused increased in the values of insoluble dietary fiber by the complexation of its components with protein and aminoacids. The results obtained showed the increased of the insoluble dietary fiber, in the cooked samples compared with raw samples. Significant values of protein nitrogen were found in the NDF, suggested that it was originated by complexation with proteins and aminoacids. This fact contributed to become proteic nitrogen nonavailability decreasing consequently the digestibility of the proteins.

Animals↗

Upper digestive tract dyspepsia and early gastric cancer.

AIM: The study of the frequency and evolution of upper digestive tract dyspepsia in a group of patients operated for early gastric cancer (EGC) and to perform a strategy of diagnosis for the patients with long term upper digestive tract dyspepsia. METHODS: Clinical data of 35 patients operated for EGC were retrospectively evaluated. The frequency, characteristics and evolution time of upper digestive tract dyspepsia, main when it began more than 6 months before surgery, were analyzed. Radiologic and endoscopic exams carried out for diagnosis were also evaluated. Histological diagnosis of surgical specimens were considered, looking for the presence of chronic atrophic gastritis, intestinal metaplasia, and peptic gastric ulcer. RESULTS: Long-term upper digestive tract dyspepsia was present in 27 patients (mean evolution time of 43.4 months). Clinical changes of previous symptoms that suggested gastric carcinoma were not found in 15 patients. Concurrent peptic gastric carcinoma were not found in 15 patients. Concurrent peptic gastric ulcer along with EGC was diagnosed by histology in 11 patients, and chronic atrophic gastritis and intestinal metaplasia were both present in the non-tumoral gastric mucosa in all cases. CONCLUSIONS: 1) Unspecific upper digestive tract dyspepsia is frequently found in patients with EGC. 2) Endoscopy should be the first exam performed in patients with upper digestive tract dyspepsia. 3) The patients with gastric ulcer, chronic atrophic gastritis or intestinal metaplasia must be submitted to sequential endoscopic follow-up.

Dyspepsia↗

Digestive stimulant action of three Indian spice mixes in experimental rats.

The present study examined the favourable influence of three spice mixes derived from a few commonly consumed spices of known digestive stimulant action on digestive enzymes of pancreas and small intestine, and on bile secretion and composition in experimental rats. The common ingredients of these mixes were coriander, turmeric, red chilli, black pepper and cumin, while the spice mix II additionally had ginger, and spice mix III contained onion. All the three spice mixes favourably enhanced the activities of pancreatic lipase, chymotrypsin and amylase when consumed during the diet. In addition, these spice mixes brought about a pronounced stimulation of bile flow and of bile acid secretion. Among the three spice mixes examined, spice mix III which is customized so as to include spices that are desirable from the point of view of stimulation of digestion, had the highest stimulatory influence particularly on bile secretion, bile acid output and the activities of pancreatic enzymes. While activities of pancreatic lipase, amylase and chymotrypsin were elevated by 40, 16 and 77%, respectively, the bile volume as well as the bile acid secretion were almost doubled in spice mix III treatment. The higher secretion of bile especially with an elevated level of bile acids and a beneficial stimulation of pancreatic digestive enzymes, particularly of lipase could probably be the two mechanisms by which these combinations of spices aid in digestion.

Amylases↗

Responses of the digestive tract of the omnivorous northern brown bandicoot, Isoodon macrourus (Marsupialia: Peramelidae), to plant- and insect-containing diets.

The gastrointestinal tract of omnivores such as bandicoots (Marsupialia: Peramelidae) must be able to process foods as different as invertebrates, fungi and plant material. We studied the mechanisms involved in the utilisation by captive northern brown bandicoots (Isoodon macrourus) of insect larvae and milled lucerne (Medicago sativa) hay incorporated into a basal diet of a commercial small carnivore mix. Animals on the plant-basal mix digested less dry matter, energy, lipid, fibre and total nitrogen, but consumed 79% more dry matter than those on the insect-basal mix. Consequently intake of digestible energy (i.e. energy absorbed) was not significantly different between diets. Mean retention time (MRT, the mean time a marker remains in the tract) of a large particle marker was shorter on the plant-basal mix, reflecting its higher intake, but MRT of a solute marker was not significantly different between diets. Consequently the solute marker was retained longer than the particle marker on the plant-basal mix, indicating selective retention of solutes and very small particles in the caecum on this diet. This was confirmed by a higher proportion of small particles in the caecum than the distal colon of road-killed I. macrourus. Thus the main responses by I. macrourus to the plant-basal mix appeared to be an increase in gastrointestinal tract capacity (from radiographic evidence), selective retention of solutes and very small particles in the caecum, and facilitated passage of less tractable large particles through the colon. As a consequence, food intake was higher on the plant-basal mix, which compensated for its lower digestibility, and intake of digestible energy was similar to that on the insect-basal mix. This considerable flexibility of the morphologically rather simple digestive tract of northern brown bandicoots helps to explain their ability to cope with naturally variable diets consisting of mainly invertebrates in summer to much more plant and fungal material in winter, and to survive in nutritionally dynamic environments such as heathlands where there can be dramatic changes in food type and availability following periodic wildfires.

Animals↗

Gastrointestinal digestion governs insect protein hydrolysis and predicted bioactive peptide release: Species-dependent implications for functional food applications.

This study investigates the digestion of insect proteins and the release of predicted bioactive peptides during human gastrointestinal digestion. Using the Infogest in vitro model, mealworm, cricket, and black soldier fly larvae (BSFL) proteins were digested and analyzed through discovery proteomics and bioinformatics to identify predicted bioactive peptides. Sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) quantified insect proteins including predicted bioactive peptide precursor proteins, the precursors of predicted bioactive peptides. Results indicated that gastrointestinal digestion strongly influences peptide release, with the gastric phase exhibiting a richer predicted bioactive peptide profile than the small intestinal phase. Many predicted bioactive peptides were rapidly hydrolysed under small intestine conditions, which may lead to reduced stability or diminished activity in vivo, potentially explaining why certain peptides show strong bioactivity in vitro but limited effects in vivo. Additionally, predicted bioactive peptide release varied by insect species, influenced by genetic factors and peptide abundance. These findings highlight the importance of species selection and consideration of proteolytic digestion patterns in optimizing insect-derived bioactive peptides for functional foods and nutraceutical applications.

Animals↗

Insights into the fate and dynamics of antibiotic resistance in multidrug-resistant Bacillus cereus during in vitro simulated gastrointestinal digestion.

Bacillus cereus, an important pathogen responsible for causing foodborne diseases worldwide, releases pore-forming enterotoxins, which target host epithelial cells, leading to osmotic lysis and ultimately manifesting as diarrheal syndrome. Moreover, some B. cereus strains carry antimicrobial resistance genes that confer multidrug resistance against a spectrum of antibiotics. Characterizing the survival traits of multidrug-resistant (MDR) B. cereus strains in the intestinal microenvironment is essential for developing targeted strategies to effectively manage diarrheal foodborne diseases caused by this pathogen. This study used whole-genome sequencing (WGS) to evaluate the pre- and post-digestion toxigenic potential, antimicrobial resistance profiles, and genetic diversity of MDR B. cereus strains isolated from food samples in Guangdong Province, China. The four B. cereus isolates investigated in this study exhibited a genetic diversity, as determined by multilocus sequence typing analysis of WGS data. All four isolates produced the diarrheal toxins Hbl, Nhe, and CytK to varying levels, indicative of their potential to cause outbreaks of foodborne diseases. Each of the four isolates exhibited resistance to more than three classes of antibiotics, fulfilling the criterion for multidrug resistance. At an initial concentration of 9 log colony-forming units (CFU)/mL, the intestinal concentration of these four isolates crossed the threshold required to induce widespread diarrhea in the general population. Under rice slurry protection, all tested isolates maintained intestinal concentration beyond the threshold when the initial concentration was increased to ≥8 log CFU/mL. Moreover, the upregulations of genes associated with acid tolerance, bile tolerance and stress response were observed in the surviving MDR B. cereus isolates. Digestion markedly altered the antibiotic resistance profiles of the MDR B. cereus isolates. In the absence of a food matrix, the MDR isolates lost their resistance to imipenem, meropenem, amoxicillin-clavulanic acid, and trimethoprim-sulfamethoxazole post-digestion and was influenced by the initial concentration of the strains. In the presence of food matrix rice slurry, the effects of digestion on the antibiotic resistance of MDR B. cereus isolates can be mitigated, enabling them to maintain their antibiotic resistance to the greatest extent. Most remarkably, after digestion, the isolates Bce055 and Bce166 exhibited newly emergent resistance to cefotetan and trimethoprim-sulfamethoxazole, respectively. Our findings clarify the fate of MDR B. cereus isolates in the gastrointestinal tract and inform the development of prevention and control strategies for foodborne diseases caused by this pathogen.

Drug Resistance, Multiple, Bacterial↗

Development of the gastrointestinal tract and digestibility of dietary fibre and amino acids in young chickens, ducks and geese fed diets with high amounts of barley.

The experiment comprised of 50 chickens, 40 ducks and 30 geese fed a diet containing 40% barley. Birds were kept in metabolic cages from 1 to 42 days of age. A balance trial was carried out during the last week of the bird's life and the apparent digestibility of nutrients was determined. At 21 and 42 days of age 12 animals per species were killed. The absolute length of intestines followed the live weight (LW) of the animals. In relation to metabolic LW (kg(0.67)), the total length was significantly higher in chickens and geese than in ducks at 21 days of age, but identical in the three species at 42 days of age. The absolute and relative weights of intestines were smaller in ducks than in chickens and geese both at 21 and 42 days of age. Dietary fibre was digested better by chickens than by ducks and geese (P<0.01). Ileal digestibility of total amino acids amounted to 76% in chickens, 69% in ducks (P>0.05) and only 56% in geese (P<0.01) with relatively low digestibility of methionine (70, 44 and 52%) and lysine (72, 57 and 41%), respectively. The overall tract-faecal digestibility of total amino acids was evaluated on the level of 86% for all three species and indicates a substantial hind gut synthesis of amino acids.

Amino Acids↗

Release of angiotensin I converting enzyme (ACE) inhibitory activity during in vitro gastrointestinal digestion: from batch experiment to semicontinuous model.

Gastrointestinal digestion is of major importance in the bioavailability of angiotensin I converting enzyme (ACE) inhibitory peptides, bioactive peptides with possible antihypertensive effects. In this study, the conditions of in vitro gastrointestinal digestion leading to the formation and degradation of ACE inhibitory peptides were investigated for pea and whey protein. In batch experiments, the digestion simulating the physiological conditions sufficed to achieve the highest ACE inhibitory activity, with IC(50) values of 0.076 mg/mL for pea and 0.048 mg/mL for whey protein. The degree of proteolysis did not correlate with the ACE inhibitory activity and was always higher for pea than whey. In a semicontinuous model of gastrointestinal digestion, response surface methodology studied the influence of temperature and incubation time in both the stomach and small intestine phases on the ACE inhibitory activity and degree of proteolysis. For pea protein, a linear model for the degree of proteolysis and a quadratic model for the ACE inhibitory activity could be constituted. Within the model, a maximal degree of proteolysis was observed at the highest temperature and the longest incubation time in the small intestine phase, while maximal ACE inhibitory activity was obtained at the longest incubation times in the stomach and small intestine phase. These results show that ACE inhibitory activity of pea and whey hydrolysates can be controlled by the conditions of in vitro gastrointestinal digestion.

Angiotensin-Converting Enzyme Inhibitors↗

Human milk oligosaccharides are minimally digested in vitro.

In examining the functional aspects of human milk oligosaccharides (HMO), it is not known whether they are digested during the passage through the infant's gastrointestinal tract. HMO were prepared from individual milk samples (n = 6) and separated into neutral and acidic compounds by chromatography. These oligosaccharide fractions were studied for their digestibility by human salivary amylase, porcine pancreatic amylase and brush border membrane vesicles (BBMV) isolated from porcine small intestine; we also examined the effect of low pH on these structures. The characterization of HMO and their digestion products was performed by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) as well as TLC. It was shown that neither salivary amylase nor pancreatic amylase cleaved HMO. Only after a 2-h incubation with BBMV were slight modifications of the HMO observed. HPAEC-PAD analysis revealed two new components within the neutral oligosaccharide fractions; these were characterized by mass spectrometric analysis as lacto-N:-triose and galactose. Only lacto-N:-triose was present within digestion assays of oligosaccharides, which did not contain fucosyl or N:-acetylneuraminic acid residues. These results suggest that <5% of the HMO are digested in the intestinal tract. Hence, HMO may play a role as prebiotics or as factors influencing the local immune system of the intestine in breast-fed infants.

Amylases↗

[Clinical research techniques in functional digestive disorders].

Functional digestive disorders are characterized by symptoms related to the digestive tract for which no pathological causes can be found using routine diagnostic techniques. In the last few years, several methods have been developed to the study digestive function allow relation between in humans functional alterations, mainly motor and sensory and to be related to functional digestive symptoms. As a result of these advances, both motor and sensory alterations have been identified in subgroups of patients with functional digestive disorders. This knowledge should enable current symptom-based classifications of these disorders to be replaced with new classifications based on specific physiopathologic mechanisms. This would allow more effective therapies aimed at the specific mechanism causing the symptoms to be developed.

Diagnostic Techniques, Digestive System↗

Serum sialyl-Tn antigen levels in patients with digestive cancers.

Serum levels of sialyl-Tn antigen (STN) were measured using a one-step radioimmunoassay kit in 257 patients with digestive cancers, 121 patients with benign digestive diseases, and in 64 healthy controls. With 45 U/ml regarded as the cutoff value, the positive rates of serum STN in digestive cancers were as follows: pancreas 40.0%, stomach 28.1, colon and rectum 27.8, biliary tract 25.0, liver 7.1, and esophagus 0%. In benign digestive diseases, the positive rate of STN was low (4.1%). In gastric and colorectal cancers, simultaneous measurements of STN and carcinoembryonic antigen (CEA) revealed that the positive rates of STN, CEA, and STN and/or CEA were 28, 42, and 55%, respectively. There was no significant correlation between STN and CEA in these cancers. STN may be a useful serum marker for digestive cancers, especially gastric and colorectal cancers.

Antigens, Neoplasm↗