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At least 19 recordsLinked to original sources
PubMed1992

Influence of plasma proteinase inhibitors and the secretory leucocyte proteinase inhibitor on pancreatic elastase-induced degradation of some plasma proteins.

Pancreatic elastase-induced degradation of some plasma proteins was studied in an in vitro model. The digestion was correlated with the degree of saturation of the alpha 1-proteinase inhibitor (alpha 1PI) and also with varying amounts of secretory leucocyte proteinase inhibitor (SLPI). SLPI was found to inhibit pancreatic elastase showing a Ki of about 10(-7) M for the complex. On the addition of human pancreatic elastase to plasma cleavage of C3, kininogen, fibrinogen and fibronectin was observed when the alpha 1PI approached saturation. In the present in vitro model it was possible to block the cleavage of the four plasma proteins, mentioned above completely with SLPI. Addition of the inhibitor also decreased the consumption of alpha 1PI.

Blood Proteins↗
PubMed2026

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↗
PubMed2026

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↗
PubMedDate not supplied

[Food protein quality. III Enzymatic ultrafiltrate digest (EUD) aminoacid index (author's transl)].

An aminoacid index for protein quality evaluation is presented, using a new model of enzymatic digestion of proteins in vitro. The EUD index is obtained determining on the ultrafiltrate the available aminoacids after digestion with pepsin, trypsin, pancretin and erepsin in an Amicon ultrafiltration cell. A very high correlation is obtained between EUD index and the biological values of 10 protein or food protein samples. The experimental validity of this in vitro method allow his utilization for direct evaluation of protein quality instead of the more complicated and time consuming biological tests.

Amino Acids↗
PubMed1978

[Digestant effects of a new digestive enzyme capsule, Excelase, on jejunectomized and pancreato-jejunectomized Beagle dogs (author's transl)].

The digestant effects of a new digestive capsule, excelase containing sanactase, proctase, meicelase, olipase-2S and pancreatic digestive enzyme TA, were investigated in vivo. Jejunectomy and pancreato-jejunectomy were performed to cause an artificial disturbance of gastro-intestinal digestion and absorption in Beagle dogs. Absorption of protein and fat was measured using chromic oxide as an indicator. Excelase (3 capsules/dog/day) was given orally to Beagle dogs 1 week after each operation for 7 weeks. Changes in body weight and absorption of protein and fat were observed during the administration. The decrease in body weight of dogs treated with excelase fully recovered, however, that of controls remained even 8 weeks after the surgery. Absorption of protein and fat in the groups of dogs treated with excelase was greatly improved as compared with controls. The digestant effects of excelase on percent absorption of protein and fat were more manifest in pancreato-jejunectomized dogs than in jejunectomized dogs. These results indicate that excelase is effective for gastro-intestinal disturbances of digestion and absorption. The digestant effects of excelase on starch, protein and cellulose were also investigated in vitro using a gastro-intestinal model.

Animals↗
PubMed1989

[Rusitec--fermentation equipment for the study of digestive processes in ruminants].

The fermentation equipment RUSITEC (Rumen Simulation Technique) is a simplified model of the rumen which stimulates the conditions inside the rumen, enables to keep the normal microbial population of the rumen for a long time under strictly controllable conditions, and enables a permanent monitoring of fermentation processes. Trials were conducted to see whether this model of "artificial rumen" can be used to determine the nutritive value of untreated beech sawdust and beech sawdust treated hydrobarothermically at the pressure of 1.4 MPa and impregnated with 1% H2SO4. The digestibility of the dry matter and fibre components was higher in the treated beech sawdust than in the untreated sawdust. In both reaction vessels, the amounts of acetic, propionic and butyric acids as well as the total VFA, were higher during the fermentation of treated beech sawdust, as compared with the diet with raw beech sawdust. The increased output of VFA, especially the acetic and butyric acids, resulted in a proportional increase in the output of gases, especially carbon dioxide and methane, as compared with the production of gases in rumens digesting untreated beech sawdust. In comparison with other in-vitro methods, this model of fermentation equipment characterizes the nutritive values of various kinds of feed in a more thorough way: using this equipment, the simulation technique has proceeded much closer to reality.

Animals↗
PubMed1987

cAMP elevation modulates physiological activity of pyloric neurons in the lobster stomatogastric ganglion.

1. We analyzed the physiological effects of the adenylate cyclase activator forskolin, and other adenosine 3',5'-cyclic monophosphate (cAMP)-elevating agents, on neurons of the pyloric circuit from the stomatogastric ganglion of the lobster Panulirus interruptus. Agents were bath applied to pyloric neurons either in the synaptically intact pyloric circuit or following isolation from all known synaptic input. 2. Several cAMP-elevating agents, including forskolin, 3-isobutyl-1-methylxanthine, Ro20-1724, and 8-bromo-cAMP, generated similar motor patterns from the pyloric circuit. The motor patterns exhibited an increased cycle frequency and enhanced spike activity from all classes of pyloric neurons. Since these agents differ both in structure and site of action in the cAMP pathway, their physiological effects on the motor pattern probably result from increased cAMP levels in pyloric neurons. 3. When forskolin was applied to synaptically isolated neurons, it caused a strong activation or enhancement of activity of all pyloric cells. However, it induced different types of activity in different cells, including the induction of bursting pacemaker potentials in one cell type, activation of plateau potentials in another, and depolarization with activation or enhancement of tonic spike activity in the remaining cells. Thus there is no single physiological response to cAMP elevation in the pyloric circuit; its effects can be quite diverse, mediating several activity states, in different cells. 4. Radioimmunoassays were performed on whole stomatogastric ganglia to determine whether known neuromodulators can affect cAMP concentrations. Both forskolin and octopamine increased cAMP levels, whereas dopamine, serotonin, proctolin, and FMRFamide did not appreciably affect cAMP levels. The physiological effects of octopamine and forskolin are similar in most, but not all, pyloric cells. Octopamine is thus a candidate neuromodulator whose actions may be mediated, at least in part, by increased cAMP in some pyloric cells; however, forskolin does not completely mimic the physiological effects of octopamine on all pyloric neurons, suggesting that octopamine can also act by other biochemical mechanisms.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Blood-brain barrier alterations in bacterial meningitis: development of an in vitro model and observations on the effects of lipopolysaccharide.

To further examine the effects of purified Haemophilus influenzae type b lipopolysaccharide (LPS) on blood-brain barrier permeability, we have developed an in vitro model of the BBB. Microvascular endothelial cells were isolated from rat cerebral cortices by enzymatic digestion, dextran centrifugation, and separation on percoll gradients. The cells were determined to be endothelial in origin by positive fluorescent staining for Factor VIII-related antigen and the ability to take up acetylated low density lipoproteins, and their cerebral origin by the formation of junctional complexes in vitro. Cells were seeded onto semipermeable polycarbonate filters and permeability assessed by measuring traversal of radioactive albumin across the monolayer. Treatment of the cells with LPS at concentrations of 1.0 microgram/ml and 0.1 microgram/ml for 4 h led to statistically significant increases in albumin permeability of 4.6% (P = 0.001) and 5.6% (P less than 0.001), respectively, without evidence of cell death as assessed by release of lactate dehydrogenase into the media. These results indicate that LPS significantly increases albumin permeability across a monolayer of cerebral microvascular endothelial cells in the absence of host inflammatory cells. Future studies on the effects of LPS on intracellular regulation will determine the mechanisms responsible for these alterations.

Albumins↗
PubMed1990

Intestinal hydrolysis of pyridoxal 5'-phosphate in vitro and in vivo in the rat. Effect of amino acids and oligopeptides.

The first step in the intestinal absorption of phosphorylated forms of vitamin B6 is intraluminal hydrolysis mediated by alkaline phosphatase. The present studies were performed to evaluate the effect of amino acids and oligopeptides, the products of protein digestion, on the hydrolysis of pyridoxal 5'-phosphate. Models utilized rats and included a cell-free in vitro system and the in vivo, single-pass, perfused jejunal segment. In vitro all amino acids and oligopeptides tested significantly inhibited pyridoxal 5'-phosphate decay (hydrolysis). The degree of inhibition of decay was dependent on the particular compound used, the concentration of that compound, and the pH of the medium. Similar effects for L-lysine concentration and perfusate pH were demonstrated in perfused segments in vivo; by contrast, L-lysine had no effect on pyridoxine uptake. These studies demonstrate that intraluminal hydrolysis of phosphorylated vitamin B6 may be modulated by yet other intraluminal constituents and conditions.

Alkaline Phosphatase↗
PubMedDate not supplied

Spatial light distribution in tumors: phantom measurements.

The optical characteristics of 39 excised human tumors are determined. Then liquid phantoms, representative of these tumors, are used to measure the space irradiance in a plane containing the optical axis for two irradiation geometries (external and interstitial) and two wavelengths (514 and 630 nm); a rotating miniature probe allows a spatial resolution of 0.1 mm. It is found that, on the optical axis, the space irradiance at the surface of a phantom is higher than the irradiance applied externally and exhibits a maximum prior to reaching an exponential decrease. A zone where green light is expected to provide better photochemical efficiency than red light is determined and the space irradiance obtained with external and interstitial irradiation are compared quantitatively. The clinical usefulness of the results is limited by the fact that individual samples belonging to the same type of tumor differ considerably in their optical characteristics, at least unless a more detailed classification (based on a greater number of tumor samples) is available.

Digestive System Neoplasms↗
PubMed1991

A laboratory model to quantitate the resistance of collagen vascular grafts to biodegradation.

Recent reports have shown that despite extensive preclinical testing, vascular grafts of biological origin undergo severe biodegradation and aneurysm formation after two or more years of implantation in man. The purpose of this study was to develop a laboratory model to quantitate and correlate the stability of crosslinked collagen grafts in vitro and in vivo. This resistance to biodegradation was assessed by measuring changes in suture pullout force and sample weight in response to controlled digestion with bacterial collagenase, in 0.5-cm-long cylindrical graft segments (chemically processed bovine carotid artery and human umbilical cord vein) that were implanted in the rat subcutis for 2 to 12 weeks. Scar tissue was removed from the explants by brief enzymatic digestion, a process that was inhibited when graft segments had become infected. Changes in dry weight were more consistent than were changes in wet weight; drying the graft segments had no effect on their degradation in vivo or in vitro. Intact cylindrical rings suffered somewhat less damage than did opened, flattened cylinders. Graft degradation increased markedly with implantation time, and was detected after only 3 weeks. We conclude that the rat subcutis model, when combined with controlled enzymatic digestion, first to remove scar tissue and then to challenge structural integrity, provides an accelerated assay by which to predict the stability of collagen vascular grafts.

Animals↗
PubMed1992

High density barium sulfate suspension for MRI: optimization of concentration for bowel opacification.

In this in vitro study of a potential oral MRI contrast agent, barium sulfate suspension (BSS), the object was to examine the effect of varying barium sulfate concentration on signal intensity while keeping suspension additives the same; and to optimize the concentration of a specific preparation of BSS. A phantom was used to test suspensions with concentrations of barium sulfate ranging from 90% to 220% w/v. T1-weighted, T2-weighted, and gradient echo sequences all showed a decrease in signal as concentration was increased to 170%. Between 170% and 220%, the signal intensity was constant on the T1-weighted and T2-weighted sequences. With the proton density and gradient echo sequences, there was a slower rate of decline in the signal intensity in the 170 to 220% range of BSS concentrations. We conclude that BSS with a concentration in the range of 170% to 220% w/v is optimum for the specific preparation used. We speculate that the behavior of the signal-to-noise ratio with changing concentration is explained by factors including proton density, T1 relaxation enhancement, diffusion effects, and magnetic field inhomogeneity, depending on the particular pulse sequence used.

Administration, Oral↗
PubMed1990

In vitro migration of lymphocytes through collagen matrix: arrested locomotion in tumor-infiltrating lymphocytes.

Antitumor immunity requires (a) extravasation of lymphocytes from the blood stream to interstitium, (b) locomotion through extracellular matrix to the site of the tumor, (c) effector cell recognition of the tumor target with cell/cell contact and binding of adhesion receptors, (d) T-cell receptor binding to histocompatibility and tumor antigens, and (e) tumor cell lysis. We hypothesize that the tumor microenvironment inhibits lymphocyte locomotion through extracellular matrix as one mechanism by which tumors may avert host defense. Lymphocyte locomotion was investigated in vitro using a three-dimensional collagen gel model. Fresh tumor-infiltrating lymphocytes (TIL) were obtained by enzymatic digestion of melanomas and renal cell carcinoma, and mononuclear cells were isolated by discontinuous Ficoll-Hypaque gradient. The lymphocytes were analyzed for motility from a point of origin between basal and overlay layers of collagen gel. Results showed that TIL migration was almost completely inhibited, compared with migration of normal and cancer patient peripheral blood leukocytes and lymphocytes from lymph nodes. Short-term (24-h) exposure of lymphocytes to cytokines during the assay in the collagen gel matrix had no effect on locomotor ability. Long-term (19, 30, or 35 days) culture of TIL in 200 units/ml of interleukin 2 reinstated locomotor ability. Short-term exposure of any of the lymphocyte populations to interleukin 1-alpha, interleukin 1-beta, interleukin 2, interleukin 3, interleukin 4, alpha-interferon, or gamma-interferon had no effect on migration. Thus, TIL display a uniquely arrested ability to locomote through collagen gel. Inhibition of the locomotion of infiltrating effector cells is possibly a mechanism by which the tumor evades the host immune system.

Antigens, CD↗
PubMed1990

Isolation and structural elucidation of biotransformation products from acarbose.

Following oral administration the a-glucosidase inhibitor acarbose (O-4,6-dideoxy-4-[[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl) -2-cyclohexen-1-yl]amino]-a-D-glucopyranosyl-(1----4)-O-a-D-glu copyranosyl-(1----4)-D-glucopyranose, Bay g 5421) is degraded by digestive enzymes and/or intestinal microorganism. The effect of anaerobic intestinal bacteria can be studied in an in vitro model which involves the incubation of acarbose with human or animal intestinal flora. Acarbose and nine biotransformation products can be isolated from the incubation mixture. These products were identified by nuclear magnetic resonance and mass spectrometry as so-called component 2 (loss of the terminal glucose), component 1 (loss of both glucose rings), hexose homologues of acarbose and component 2, methyl homologues of acarbose, butyric acid ester of component 2, basic disaccharide (loss of the cyclitol ring of component 2), delta-aminovaleric acid and gamma-aminobutyric acid. Following oral administration of [14C]-acarbose to healthy volunteers, 35% of the radioactivity was excreted in the form of at least 13 metabolites in the urine. Three of the metabolites were isolated by Craig countercurrent distribution and ion-pair HPLC and characterized by virtue of their nuclear magnetic resonance and mass spectra as derivatives of 4-methylpyrogallol. Two were shown to be monomethylether-monosulphates while the third was a monosulphate-monoglucuronide. The synthesis of ten reference substances and the comparison of HPLC and UV data clearly indicated that the majority of the non-isolated metabolites were also 4-methylpyrogallol derivatives. The peculiarities of the nuclear magnetic resonance and mass spectra of this type of compound are discussed.

Acarbose↗
PubMed1988

Long-term culture of hamster duodenal explants and cells.

Explants from adult Syrian hamster duodenum have been maintained in organ culture on gelatin sponges using CMRL 1066 serum supplemented media for 30 days. There was necrosis of the tall villi architecture during the 1st week in culture while columnar and mucous cells survived, migrated, and replicated along portions of the explant basement membrane and in the gelatin sponge matrix. Cells in the sponge multiplied and formed epithelial sheets which showed villus projections and cyst configurations. The cells in these epithelial structures were attached to one another by junctional complexes. Epithelial cells were isolated from the sponge matrix by collagenase digestion and were successfully grown in culture. These duodenal explants and cells show potential for use as in vitro models for experimental studies, involving acute and chronic response of cells to injury or carcinogen-induced transformation.

Animals↗
PubMedDate not supplied

[A study of hydrolysis of various synthetic peptides with gastrointestinal enzymes using thin-layer chromatography].

Hydrolysis in vitro of alpha- and epsilon-peptide bonds of synthetic amino acids and peptide substrates,--models of protein fragments, with digestive enzymes was studied. The kinetics of hydrolysis was studied by quantitative thin-layer chromatography followed by densitometric analysis of the chromatographic patterns. The rate constants of hydrolysis of Phe-Lys, Gly-Lys dipeptides and their epsilon-acetyl and epsilon-succinyl derivatives with leucine aminopeptidase and pancreatic enzymes were calculated. epsilon-Acyl residues of the substrates failed to split off under these conditions. The digestive enzymes hydrolysed the alpha-peptide bonds adjacent to the acylated lysine. Hydrolysis of epsilon-acetyl substrates proceeded faster as compared to epsilon-succinyl derivatives.

Amino Acids↗