Biomedical subjects

D Tomé

Publications and source records attributed to D Tomé.

84 records · Page 5Linked to original sources

PubMed1992

Putrescine uptake by rabbit intestinal brush-border membrane vesicles.

The transport of putrescine in rabbit intestinal brush-border membrane vesicles is a time-dependent, Na+ and H+ gradient-independent slow process, reaching a high equilibrium level from 1 hr onwards. An approximately 12-fold concentration gradient of 5.4 microM putrescine was generated in the vesicles after 3 h of incubation at 25 degrees C, suggesting a substantial binding of the polyamine to membrane components. Putrescine uptake did not appear to occur via a polyamine-H+ exchange pathway, but the activity of transport was strongly reduced when the medium pH was lowered from 7.5 to 6.0. Although it was inhibited in the presence of SCN-, putrescine uptake was found neither to involve a preferred anion nor to be sensitive to changes in the membrane potential. Putrescine accumulation was substantially stimulated in the presence of a 10 mM concentration of the divalent cations Ca2+, Mg2+ or Ba2+, unlike the monovalent cations K+, Na+ or Li+. Despite the presence of a Ca(2+)-dependent transglutaminase activity, vesicular accumulation does not appear to result from covalent binding of putrescine to membrane peptides. Inhibition of the uptake by polyamines, unlike choline and dibasic amino acids, shows that putrescine may bind noncovalently to other specific anionic sites.

Animals↗

PubMed1991

Digestion of bovine milk proteins in patients with a high jejunostomy.

Digestion of milk proteins was studied in short-bowel patients. After ingestion of water, purified beta-lactoglobulin (beta-Ig), or skim milk, effluents were collected at the stoma. The flow rate of the effluent peaked in the first 30-min period after ingestion and returned to the basal value within the first 60 min. After milk ingestion 1) the nitrogen concentration of effluents peaked in the first 30 min, 2) SDS-polyacrylamide gel electrophoresis and Western blot indicated the presence of beta-Ig and alpha-lactalbumin (alpha-lac) in jejunal effluents but only during the first 30 min whereas caseins were detected during the initial 1-2 h effluents, and 3) immunoenzymo metric assay indicated that 64% and 44% of the beta-Ig and alpha-lac, respectively, were recovered in an intact antigenic form. Results indicate that the digestion of milk proteins in humans differs quantitatively. Digestion appeared partially incomplete in the upper jejunum, suggesting the importance of the ileum for completion of digestion.

Blotting, Western↗

PubMed1991

Effect of chronic antigen exposure on growth and intestinal histamine content of sensitized rats.

The effects of chronic antigen feeding on systemically sensitized rats were investigated. Findings include a reduction of water and antigen intake in egg albumin (EA), sensitized rats receiving EA in their drinking water for an 8 day period, compared to that of sensitized rats fed bovine serum albumin and of naive rats. Feeding EA to sensitized animals also induced a decrease in daily weight gain. This decline did not seem to be a consequence of a decreased food intake, but might rather reflect a decreased water consumption and an alteration of nutrient absorption in the gut. Indeed, sensitized rats fed EA exhibited a significant increase in jejunal and ileal histamine content compared to control rats, which may indicate the development of an inflammatory reaction in the small intestinal mucosa. Intestinal troubles experienced because of this inflammatory reaction might explain the reduction of antigen and water intake observed in sensitized rats.

Animals↗

PubMed1990

In vitro transport of beta-lactoglobulin across the jejunum of lactose-fed rats.

Changes in protein absorption through the intestinal mucosa occur with aging and might reflect modifications in enterocyte membrane characteristics. We have observed that bovine beta-lactoglobulin (beta-LG) was efficiently transported across the small intestine of adult rats in vitro and that 12-16% of the absorbed protein was recovered intact or as large hydrophobic peptides. Ten percent lactose-feeding resulted in decreased tissue conductance and significantly reduced (-58%, P less than 0.05) beta-LG transport across rat small intestinal mucosa. The amounts of beta-LG absorbed, either as amino acids and peptides or as intact protein, were reduced to the same extent. Therefore, the effect of lactose feeding might be related to a decrease in protein endocytosis at the brush-border level, rather than to reduced protein transport across tight junctions.

Animals↗

PubMed1989

Indirect effect of casein phosphopeptides on calcium absorption in rat ileum in vitro.

Casein phosphopeptides (CPP) are the phosphorylated fragments of bovine milk casein. They are believed to enhance intestinal absorption of calcium by their ability to form soluble complexes with calcium thereby inhibiting the precipitation of phosphate-calcium salts. In order to evaluate whether they also act in an additional direct manner on the intestinal mucosa, these peptides were added in a phosphate-free medium at a concentration of 1, 2, or 4 mg/ml on the mucosal side of rat ileum mounted in an Ussing chamber in vitro. No effect on the electrical parameters of the tissue was observed. The unidirectional mucosal-to-serosal flux of calcium was significantly reduced in the presence of the peptides, without alteration in the serosal-to-mucosal flux. Jms was 51.71 +/- 2.67 microEq/h.cm2 for control vs. 19.23 +/- 3.95 in the presence of 4 mg/ml CPP. This effect was associated with a reduction in free calcium in the mucosal reservoir of the Ussing chamber, without modification of mucosal total calcium or of serosal total and free calcium. These results indicate that CPP did not directly act on rat ileum to enhance calcium absorption. These peptides bind calcium, and the CPP--calcium complex which was not efficiently absorbed remained on the mucosal side of the tissue. In these conditions, the physiological role of CPP on intestinal calcium absorption could be only an indirect luminal inhibition of the precipitation of phosphate-calcium salts. This effect remains to be clearly established.

Animals↗

PubMed1989

Permeability of milk protein antigens across the intestinal epithelium in vitro.

Degradations by proteolytic enzymes and intestinal epithelial permeability represent two major drawbacks to the transfer of food protein antigens to blood. These steps were studied in vitro for the milk protein antigens beta-lactoglobulin (beta-Lg), alpha-Lactalbumin (alpha-La) and beta-casein (beta-cas). Pepsin-trypsin hydrolysis and permeability in isolated rabbit ileum in Ussing chamber were suited by ELISA and radiolabelled-protein measurement. Pepsin-trypsin hydrolysis showed an increasing resistance in the order beta-cas less than alpha-La less than beta-Lg. The rate of absorption of the antigenic proteins by isolated rabbit ileum was in the same order, and the rate of absorption of the whole proteins (degraded and antigenic forms) was significantly higher for beta-Lg than for alpha-La and beta-cas. These results suggest a selective intestinal permeability for milk protein antigens. This selectivity is probably important in the mechanism of food protein sensitization via the oral route.

Animals↗

PubMed1989

Effect of systemic and orally administered iota-carrageenan on ovalbumin-specific antibody response in the rat.

Iota-carrageenans are high molecular weight polygalactans commonly used in the food industry. Their immunomodulating effects were examined on the reaginic and IgG ovalbumin-specific responses after systemic or oral administration to Brown Norway rats. Intraperitoneal injection of ovalbumin with either iota-carrageenan or alum induced both a reaginic and IgG response. Reaginic antibodies were detected in the primary response with alum, but only in the secondary response with iota-carrageenan. Oral tolerance to ovalbumin was similarly induced whether the protein was given alone or admixed in solution with iota-carrageenan. These results confirmed the systemic adjuvant action of iota-carrageenan described earlier, and showed that this effect did not take place when orally administered.

Adjuvants, Immunologic↗

PubMed1988

Neuromediated action of beta-casomorphins on ion transport in rabbit ileum.

beta-casomorphins (beta-CMs) are opioid peptides derived from milk beta-casein. The beta-casomorphin analog beta-[DAla2,4, Tyr5] CM-5-NH2 reduced short-circuit current (lsc) and stimulated electrolyte absorption by an opioid effect in rabbit ileum in vitro. This effect was inhibited by 10(-7) M tetrodotoxin, 10(-6) M epinephrine and 10(-5) M naloxone. Atropine in the 10(-7)-10(-5) M range and 10(-5) M hexamethonium did not inhibit the action of the peptide on lsc. In comparison the muscarinic effect of 10(-3) M carbachol was inhibited by atropine in the 10(-8)-10(-5) M range. These results indicate that the action of the beta-casomorphin analog was neuromediated and suggest that this peptide acted on the submucosal plexus located on the blood side of the intestinal epithelium. A physiological role of the food-derived beta-CMs peptides implies the passage of the active sequences from the lumen to the blood side of the intestine.

Animals↗

PubMed1988

Luminal antisecretory effects of a beta-casomorphin analogue on rabbit ileum treated with cholera toxin.

Because the physiologic significance of the presence of the opioid peptides beta-casomorphins (beta-CMs) in enzymatic digestion of milk proteins is still undetermined, the effect of the nonmetabolized beta-CM analogue beta-[DAla2,4,Tyr5]CM-5-NH2 on water and electrolyte movements was studied in vivo and in vitro in rabbit ileum untreated or treated with cholera toxin (CT). When this analogue was introduced in vivo at a concentration of 10(-3) M into the lumen of rabbit ileal loops, it significantly stimulated net water absorption in untreated loops and reduced net water secretion in CT-treated loops. In vitro addition of this analogue (10(-4) M) to the serosal compartment of untreated ileum in an Ussing chamber reduced Isc (delta Isc = 0.44 +/- 0.05 muEq.h-1/cm2) and stimulated net Na and Cl absorption to the same extent. In CT-treated ileum, both serosal (10(-4) M) and mucosal (5.10(-4) M) addition of the analogue did not further modify the rise in Isc caused by CT but also stimulated net Na and Cl absorption. On the mucosal side, the effect of the analogue was accompanied by its transfer from the luminal to the blood side of the tissue. The transferred analogue was intact as shown by HPLC (Jm----s = 2.4 +/- 0.8 nmol.h-1/cm2). These results demonstrated that the beta-CM analogue stimulates intestinal absorption of electrolytes in rabbit ileum both in the basal state and after its stimulation by CT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Effects of soy protein diet on digestive lumenal polyamines and colonic cell proliferation in pigs.

This study was performed to determine whether erythrocyte and digestive lumenal polyamine concentrations are affected by a soy protein diet when compared to a casein diet. We also determined the effects of these diets on colonic cell proliferation. Sixteen pigs received either a 16% soy protein or casein diet for 25 days. The erythrocyte putrescine was higher in pigs fed the soy protein diet. Significant levels of polyamines were observed in the digestive lumen on both diets. Lumenal putrescine and cadaverine were higher in the proximal colon in the casein group. Lumenal spermidine was higher in the caecum and colon in the soy protein group. No significant differences in the ornithine decarboxylase activity nor in the proliferative cell nuclear antigen labelling index were observed in the colonic mucosa regardless of the regimen. These results indicate that the dietary source of protein induces significant changes in lumenal polyamines in the colon. The physiological effects of these changes need to be further investigated.

Animals↗

PubMedDate not supplied

Formaldehyde content of milk in goats fed formaldehyde-treated soybean oil-meal.

Formaldehyde is used in ruminant feeding for different purposes including the protection of dietary proteins from ruminal degradation. The formaldehyde content of milk of goats fed various levels of formaldehyde-treated soybean oil-meal has been determined by using a sensitive HPLC method. Results showed a significant linear correlation between ingested formaldehyde and formaldehyde concentration in milk. About 0.02% of ingested formaldehyde was excreted in milk, as free formaldehyde.

Animal Feed↗

PubMedDate not supplied

Microsphere entrapped bee-venom phospholipase A2 retains specific IgE binding capacity: a possible use for oral specific immunotherapy.

The only specific treatments of allergy are long and exacting desensitization by subcutaneous injections of the allergens. While oral administration of allergens could greatly facilitate these treatments, effective delivery systems are needed to prevent allergen degradation in the gastrointestinal tract and to enable their uptake by Peyer's patches. The potential for bee-venom phospholipase A2 (PLA2) to be used in such oral immunotherapy was tested. For this purpose, PLA2 potential alterations were analysed when encapsulated into poly(D,L-lactide-co-glycolide) microspheres by double emulsion solvent evaporation. It was shown that microencapsulation had only limited effects on the integrity of the entrapped PLA2, which retained its fully specific murine IgE binding capacity. Thus, PLA2 loaded microspheres could represent a potential delivery system for bee venom allergy-specific oral immunotherapy.

Allergens↗