Biomedical subjects

M Mañas

Publications and source records attributed to M Mañas.

At least 19 recordsLinked to original sources

PubMed2002

Effect of extracellular magnesium on nerve-mediated and acetylcholine-evoked in vitro amylase release in rat parotid gland tissue.

In this study the effects of changes in extracellular magnesium ([Mg(2+)](o)) and calcium ([Ca(2+)](o)) concentrations on basal and on nerve-mediated and acetylcholine (ACh)-evoked in vitro amylase release and calcium mobilization were investigated in rat parotid gland tissue. In the presence of a normal (2.56 mM) [Ca(2+)](o), both zero (0 mM) and an elevated (10 mM) [Mg(2+)](o) significantly attenuated basal and ACh-evoked amylase release compared to the response obtained in normal (1.1 mM) [Mg(2+)](o). During electrical field stimulation (EFS) of parotid tissues, only elevated [Mg(2+)](o) reduced amylase release. In a Ca(2+)-free medium, both basal and ACh-evoked amylase output were markedly reduced compared to the responses obtained under similar conditions in normal [Ca(2+)](o). Again, the ACh-induced amylase release in a Ca(2+)-free solution was larger in normal [Mg(2+)](o) than when the [Mg(2+)](o) was either zero or was elevated to 10 mM. Perturbation of [Mg(2+)](o) had no significant effect on basal intracellular free calcium concentration ([Ca(2+)](i)) in parotid acinar cells loaded with the fluorescent Ca(2+) indicator fura-2. Both zero Mg(2+) and an elevated [Mg(2+)](o) significantly reduced the ACh-induced rise in the peak and the plateau phase of the Ca(2+) transient that was seen in normal [Mg(2+)](o). In parotid acinar cells loaded with the fluorescent Mg(2+) indicator magfura-2, ACh elicited a gradual decrease in intracellular free Mg(2+) concentration ([Mg(2+)](i)) to below the basal level. The results indicate that both hypo- and hypermagnesaemia may reduce both basal and ACh-evoked amylase secretion from the salivary gland. As far as the ACh-evoked response is concerned, the effect may be exerted by a decrease in cellular Ca(2+) transport.

Acetylcholine↗

PubMed2001

Dietary fat type and regular exercise affect mitochondrial composition and function depending on specific tissue in the rat.

Physical exercise and fatty acids have been studied in relation to mitochondrial composition and function in rat liver, heart, and skeletal muscle. Male rats were divided into two groups according to dietary fat type (virgin olive and sunflower oils). One-half of the animals from each group were subjected to a submaximal exercise for 8 weeks; the other half acted as sedentary controls. Coenzyme Q, cytochromes b, c + c1, a + a3 concentrations, and the activity of cytochrome c oxidase were determined. Regular exercise increased (P < 0.05) the concentration of the above-mentioned elements and the activity of the cytochrome c oxidase by roughly 50% in liver and skeletal muscle. In contrast, physical exercise decreased (P < 0.05) cytochrome c oxidase activity in the heart (in micromol/min/g, from 8.4+/-0.1 to 4.9+/-0.1 in virgin olive oil group and from 9.7+/-0.1 to 6.7+/-0.2 in sunflower oil animals). Dietary fat type raised the levels of coenzyme Q, cytochromes, and cytochrome c oxidase activity in skeletal muscle (P < 0.05) among the rats fed sunflower oil. In conclusion, dietary fat type, regular exercise, and the specific tissue modulate composition and function of rat mitochondria.

Animals↗

PubMed2001

Nitric oxide and the pancreas: morphological base and role in the control of the exocrine pancreatic secretion.

The distribution of nitric oxide synthase in both neuronal and non-neuronal pancreatic tissues and the role of nitric oxide in the control of exocrine pancreatic secretion are reviewed in this article. Earlier reports based on in vivo studies suggested that nitric oxide can affect the secretory activity of the exocrine pancreas through changes in pancreatic blood flow. More recently, the employment of either nitric oxide synthase inhibitors or nitric oxide donors in in vitro preparations has provided evidence that nitric oxide can exert a direct action on this gland independently on its vascular effects. Most research in this area seems to indicate that modulation of exocrine pancreatic function by nitric oxide is exerted via activation of guanylate cyclase and generation of cGMP, although other pathways cannot be excluded. Experiments performed over the last year in our laboratory reveal a novel and interesting mechanism based on the ability of nitric oxide to control the release of endogenous neurotransmitter in the pancreas and, subsequently, the nerve-mediated enzyme secretion.

Acetylcholine↗

PubMed2000

Adaptation of the exocrine pancreas to dietary fats.

This article reviews studies on the adaptation of the exocrine pancreas to dietary fat. We include all the latest information about the mechanisms that underlie the adaptation of the secretory mechanism of the exocrine pancreas to the amount and the type of dietary fat. We review the kinetics of pancreatic adaptation and the mediators of the adaptive response of the pancreas including cellular and molecular mechanisms (modulation of intracellular messengers and gene expression of the different enzymes and secretagogues involved in the adaptation process). At the same time we include our results in this field in dogs and humans.

Adaptation, Physiological↗

PubMed1999

Oxidative stress induced by exercise and dietary fat modulates the coenzyme Q and vitamin A balance between plasma and mitochondria.

Physical exercise induces oxidative stress. Dietary fat modulates lipid composition of plasma and fatty acid profile of mitochondrial membranes. Over 8 wk, two groups of rats were fed virgin olive oil or sunflower oil as the only fat sources. Both groups were divided into 4 subgroups according to exercise: one of sedentary rats and the other three of rats subjected to different exercises on a treadmill. There was a lower concentration of vitamin A and coenzyme Q in the plasma of animals subjected to exercise compared to the sedentary animals. The concentrations of these molecules in liver and skeletal muscle mitochondria of animals exercised until exhaustion were higher than in sedentary animals. This can suggest the existence of a balance between plasma and mitochondrial membrane for these antioxidants as a response to an oxidative attack.

Animals↗

PubMed1999

Physical exercise affects the lipid profile of mitochondrial membranes in rats fed with virgin olive oil or sunflower oil.

The effects of physical exercise on the lipid profile in mitochondrial membranes of liver and skeletal muscle were examined in rats fed with virgin olive oil or sunflower oil. Thirty male Wistar rats, 21 d old, were randomly assigned to four groups according to fat ingestion and physical activity over an 8-week period. For each type of oil, one group acted as a control group while rats from the other were trained to run for 40 min daily on a horizontal treadmill, at a speed of 35 m/min. The results show that diet affected the fatty acid profile of the mitochondrial membranes from skeletal muscle and liver. Physical exercise also modified the fatty acid profile of the mitochondrial membranes. Total monounsaturated fatty acids decreased (P < 0.001) in liver mitochondria of exercised animals. Total polyunsaturated fatty acids in mitochondrial membranes of liver increased (P < 0.005) after exercise but those in mitochondrial membranes of skeletal muscle decreased (P < 0.05). These changes due to the exercise may arise via several mechanisms, e.g. fluidity regulation; changes in the eicosanoid metabolism; differences in the availability or oxidation rate of the different fatty acids.

Analysis of Variance↗

PubMed1998

Tissue specific interactions of exercise, dietary fatty acids, and vitamin E in lipid peroxidation.

Both physical exercise and ingestion of polyunsaturated fatty acids that play an essential role in free radical-mediated damages cause lipid peroxidation. The intake of specific fatty acids can modulate the membrane susceptibility to lipid peroxidation. Data confirmed that liver, skeletal muscle, and heart have different capabilities to adapt their membrane composition to dietary fatty acids, the heart being the most resistant to changes. Such specificity affects membrane hydroperoxide levels that depend on the type of dietary fats and the rate of fatty acid incorporation into the membrane. Sedentary rats fed a monounsaturated fatty acid-rich diet (virgin olive oil) showed a higher protection of their mitochondrial membranes against peroxidation than sedentary rats fed a polyunsaturated fatty acid-rich diet (sunflower oil). Rats subjected to training showed higher hydroperoxide contents than sedentary animals, and exhaustive effort enhanced the aforementioned results as well as in vitro peroxidation with a free radical inducer. This study suggests that peroxide levels first depend on tissue, then on diet and lastly on exercise, both in liver and muscle but not in heart. Finally, it appears that alpha-tocopherol is a less relevant protective agent against lipid peroxidation than monounsaturated fatty acids.

Adaptation, Physiological↗

PubMed1998

Plasma antioxidants are strongly affected by iron-induced lipid peroxidation in rats subjected to physical exercise and different dietary fats.

Plasma is an important vehicle through which antioxidant molecules are conveyed and in which they may show different behaviors, either acting as a protective factor for oxidative damage to different blood elements or using it as a vehicle through which dietary antioxidant factors would be distributed to the body. The aim of the study was to determine the plasma level of vitamin E, coenzyme Q, uric acid and vitamin A and their relation with the cellular oxidative damage mediated by physical training and the ingestion of different fat (virgin olive and sunflower oils). Male Wistar rats were divided into 8 subgroups based on the dietary fat intake and their physical activity. Results show that both dietary fat and physical training affect susceptibility to iron-induced lipid peroxidation in plasma and the tissues that were studied. The increase of this lipid peroxidation parallels a decrease of the level of all the plasma antioxidants that were studied.

Animals↗

PubMed1997

Coenzyme Q content depends upon oxidative stress and dietary fat unsaturation.

The presence of Coenzyme Q (CoQ) in food, its role in cellular bioenergetics and antioxidant protection and the key role played by dietary fatty acids on membrane structure support the interest for a wide research concerning the relationship between dietary fats, CoQ content and biochemical behaviour. Several models of peroxidative stress 'in vivo' have been extensively investigated in our laboratory, with particular regards to the influence of dietary fat upon mitochondrial CoQ levels. First studies showed that the unsaturation degree of dietary fat leads to different CoQ9 and CoQ10 mitochondrial contents. The highest levels were found using polyunsaturated fat. A significant CoQ9 decrease after adriamycin peroxidative induction was found when dietary fat was polyunsaturated; on the contrary, a light increase was found in the case of monounsaturated fat. Another example of oxidative stress is that produced by food frying. The results obtained were in some cases similar to those of the previous experimental design: in fact monounsaturated dietary fats increased CoQ mitochondrial contents, whereas the polyunsaturated ones decreased CoQ levels. Finally, the combined effect of physical exercise and dietary fats on tissue and plasma CoQ levels has been studied. CoQ levels did not change during aerobic performances when dietary fat was monounsaturated whereas light increases were detected in the case of polyunsaturated fats. On the contrary, in anaerobic conditions, CoQ levels clearly increased with monounsaturated fats and no alterations were found in the case of polyunsaturated ones.

Aerobiosis↗

PubMed1997

Influence of type of dietary fat (olive and sunflower oil) upon gastric acid secretion and release of gastrin, somatostatin, and peptide YY in man.

The effects of adaptation to two diets differing in the type of dietary fat on the gastric acid secretory response to food and on the circulating levels of gastrin, somatostatin and peptide YY (PYY) were examined in humans. The study involved 18 cholecystectomized subjects previously submitted to a 30-day adaptation period to diets containing olive (group O) or sunflower oil (group S) as the fat source. During the experiments, physiological stimulation was achieved by ingestion of 200 ml of oleic acid- (group O) or linoleic acid-enriched (group S) liquid mixed meals. These resulted in an immediate rise in gastric pH. In group S, the return to the premeal value was completed within 60 min, and a further decline to values significantly lower than the basal ones was observed at the end of the study period. In contrast, ingestion of the meal containing olive oil attenuated and prolonged the pH decrease after the meal, this being associated with the suppression of postprandial gastrin response. Food ingestion induced no significant changes in plasma somatostatin concentration in either group, and no significant differences were revealed between them during the basal or postprandial situations. Plasma PYY levels were consistently higher in group O throughout the entire study period, although significance was reached only at resting. In conclusion, our results show that a 30-day adaptation period to diets containing olive oil as the main source of dietary fat results, compared with those containing sunflower oil, in an attenuated gastric secretory function in response to a liquid meal in humans. The effects of olive oil were associated with a suppression of serum gastrin and higher levels of PYY.

Adult↗

PubMed1997

Effects of the amount and type of dietary fat on exocrine pancreatic secretion in dogs after different periods of adaptation.

Mongrel dogs were fed, from weaning to 6 months of age, on one of two 9% lipid diets that differed only in the type of fat content (sunflower oil or virgin olive oil) to study their effects on exocrine pancreatic secretion, in the basal period and in response to food. In addition, the results were compared with those obtained in a previous work performed by us on dogs adapted for 8 months to diets containing a higher (15%) amount of the same dietary fats to further evaluate the influence of the amount of dietary fat and the length of the adaptation period. The results from the present study show that both the volume and bicarbonate secreted in the absence of stimuli are unaffected by the quality of dietary fat. In contrast, in response to food, the pancreatic juice flow and the bicarbonate output were significantly higher in the group of animals given the sunflower oil diet. The differences seem to be related with the oleic acid content in the diets and the effectiveness of this fatty acid in triggering the release of inhibitory peptides such as pancreatic polypeptide and peptide YY. The comparison between the results from our present and previous studies supports the afore-mentioned hypothesis and confirms the existence of a clear influence of the amount and type of dietary fat, especially the oleic acid content, upon the pancreatic response to food, without ruling out a role for the duration of the adaptation period.

Adaptation, Physiological↗

PubMed1997

Effect of age on the exocrine pancreatic secretion of the preruminant milk-fed goat.

The effect of age on the exocrine pancreatic function was studied in fifteen Granadina goat kids during the second, third and fourth postnatal week. The animals, chronically catheterized, were bottle-fed on goat milk twice a day. Pure pancreatic juice was collected from 1 hour before and throughout 8 hours after milk ingestion. Pancreatic flow rate, bicarbonate and chloride concentrations, total protein content and enzyme activities were determined. In resting conditions, pancreatic flow rate augmented with age, probably reflecting an increase in body and pancreas weight. Resting amylase and lipase activities recorded significant increases during the fourth week of life. That may be associated, respectively, to the immediate change to a high-starch diet and to a simultaneous decrease in the salivary lipase levels. Our results also showed age-related differences after ingestion of milk, mainly concerning the volume response and the lipase output. The latter can be explained in the same way as regarding resting conditions. With respect to the volume response, several factors could be implicated, such as the circulating levels of gastrointestinal hormones, the sensitivity of the pancreas to such stimuli, the maturation degree in the secretory mechanisms of the gland or the development of the digestive tract.

Aging↗

PubMed1997

Exocrine pancreatic secretion in suckling goats. Adaptative effects of maternal milk and a milk substitute.

Suckling goats were fed ad libitum during the first month of their life by goat milk or by a milk replacer. These diets differed in the amount of fat and the type of protein. The composition of the exocrine pancreatic secretion in the basal period and in response to food were compared in both conditions. Pancreatic juice was collected one hour before meal intake up to the 8th postprandial hour. Pancreatic flow rate, bicarbonate and chloride levels, total protein and enzyme activities were measured. In resting conditions and in response to food, the lipase activity was found to be significantly lower in the group fed with milk replacer, which was poorer in fat. These results indicate an adaptation of the enzyme output to the available quantity of its substrate, similar to that described in the rat. Postprandial differences in the pancreatic flow rate, electrolytes and total protein were found between both groups. Their origin can be attributed to the protein used (soyabean) in the milk substitute. Such soya protein alters the normal clot formation in the abomasum and allows an accelerated abomasal digesta outflow and duodenal pH alkalinisation.

Adaptation, Physiological↗

PubMed1997

Postnatal development of the exocrine pancreas in suckling goat kids.

A total of 25 preruminant Granadina breed goats were used. They were bottle-fed goat milk ad libitum from postnatal day 3 to 28. Until the age of 3 d, kids were fed colostrum. Body weight, pancreas weight, total protein concentration, enzyme activities in pancreatic tissue and hormone concentrations (cortisol, gastrin, T3 and T4) were determined at 3, 7, 14, 21 and 28 d of age. Our results show that the rates of pancreatic synthesis and secretion of chymotrypsin are well developed at birth in the kid, and may compensate for possible deficiencies in gastric and/or enterocytes intracellular proteolysis. In week 4, there was a marked increase in amylase activity, change that can be attributed to the beginning of the transitional period known as weaning. The significant increase in circulating concentration of cortisol during week 4 suggests the involvement of corticosteroid as a mediator of pancreatic development at weaning. Changes in blood levels of this hormone are believed to be important in the expression of amylase in the neonatal period. However, T3-T4 blood levels remained unchanged from d 3 to 28, suggesting that, in the kid, these hormones appear to have no clear influence upon the postnatal development of the exocrine pancreas.

Animals↗

PubMed1997

Regulation by diet of the pancreas enzyme content of suckling goats.

To study pancreas enzyme content regulation when the diet was modified in suckling goats, a comparison was made between kids fed a milk replacer and ones fed maternal milk. A total of 25 preruminant Granadina breed goats were bottle-fed a milk replacer ad libitum from postnatal days 3 to 28 (until the age of 3 days kids had been fed colostrum). Body weight, pancreas weight, total protein concentration, and enzyme activities in pancreatic tissue were determined at 3, 7, 14, 21 and 28 days of age, and the results were compared to those previously obtained in kids fed maternal milk for the same period. Lipase activity was significantly lower in the group fed milk replacer, which was poorer in fat. Amylase activity was higher in this group, perhaps due to the starch products present in the milk substitute. However, the postnatal evolution of chymotrypsin activity followed a similar pattern regardless of diet. Our results seem to confirm that in preruminant kids there is a nutritional regulation of pancreatic amylase and lipase activities, depending on the amounts of their respective substrates in the diet, similar to that described in nonruminants.

Amino Acids↗

PubMed1997

Pancreatic enzyme secretion in response to test meals differing in the quality of dietary fat (olive and sunflowerseed oils) in human subjects.

The aim of the present study was to investigate in human subjects whether or not the ingestion of two liquid meals that differed only in their fatty acid composition (due to the addition of olive oil (group O) or sunflowerseed oil (group S) as the source of dietary fat) would lead to differences in the pancreatic enzyme activities secreted into the duodenum. The experiments were performed in eighteen cholecystectomized subjects who, during the 30 d period immediately before surgery, modified their habitual diets in such a way that their fat composition would reflect, as far as possible, that of the experimental meals. Lipase (EC 3.1.1.3), colipase, amylase (EC 3.2.1.1), chymotrypsin (EC 3.4.21.1) and trypsin (EC 3.4.21.4) activities were measured in duodenal contents aspirated before and after the ingestion of the test meals. The plasma levels of secretin and cholecystokinin (CCK) were also examined. Duodenal enzyme activities were similar in resting conditions. No significant differences were revealed in postprandial enzyme activities, except for lipase activity, which was higher in group O, probably in relation to the greater plasma CCK concentrations observed in this group. In the absence of enzyme output data, we should not exclude the possibility that the type of dietary fat will affect human pancreatic enzyme secretion to a greater extent than is evident from the present study, for instance through a flow-mediated effect, as we previously observed in dogs.

Amylases↗

PubMed1996

Taurine- and glycine-conjugated bile acids in the preruminant goat: identification by high performance liquid chromatography.

A reversed-phase high performance liquid chromatography technique has been developed for the identification of taurine- and glycine-conjugated bile acids in the bile of preruminant goats. The mobile phase consisted of two solvents: acetonitrile (A) and 5 mM potassium phosphate buffer (pH 4.5) (B). Samples (10 microliters) were eluted with a linear gradient in which acetonitrile was increased from 25 to 35%, and from 35 to 45%, at 10 min intervals. Flow rate was 1.0 ml min-1, and bile acids were detected at 200 nm. This sample high resolution technique was highly reproducible, involved a minimum of straightforward sample treatment, and required a short chromatographic development time. The technique will be of use in the systematic identifications of bile acids in preruminants.

Acetonitriles↗

PubMed1996

Long-term effects on lipid metabolism in miniature swine (Sus scrofa) of diets enriched in saturated, monounsaturated and polyunsaturated (N-6 and N-3) fatty acids.

In this paper we study the effect of long-term adaptation (twelve months) of lipidic parameters of miniature swine to diets enriched in saturated (lard; L-group), monounsaturated (olive-oil; O-group) and polyunsaturated (sunflower and fish-oil; S- and F-groups respectively). The experimental group with the highest level of total cholesterol, free cholesterol and phospholipids was the S-group. This group had as well levels of HDL-C and LDL-C significantly higher when compared with the remaining groups. The L-group had the lowest value of HDL-C. In spite of that, the index of artherogenicity (HDL/LDL+VLDL) was significantly higher in the L-group, followed by the O-, F- and S-group respectively. On the other hand, after 12 months adaptation we observed that the fatty acid composition of serum lipids clearly reflects the quality of the dietary fats. The O-group had significantly higher serum oleic acid levels than all the other groups, and its content in saturated fatty acids was the lowest. The same happens with red blood cell (Rbcs) membranes fatty acids but the effect is less marked. Membranes of the L-group were found to have the highest saturation index (SI) in Rbcs membranes, while the F-group had the highest unsaturation index (UI), followed by the O-group. Taken together, our findings show that the diet enriched in olive oil produces a lipid pattern intermediate between that obtained with the fish-oil-diet and the sunflower-oil-diet but with the advantage of Rbcs membranes with a lower amount of PUFAS. As it is known, membranes with high percentages of PUFAS are more accessible for peroxidation, and the degree of peroxidation of lipids is directly related with changes in the membranes functionality.

Adaptation, Physiological↗