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Biomedical subjects

N Torres

Publications and source records attributed to N Torres.

At least 37 records · Page 2Linked to original sources
PubMed1998

Histidase expression is regulated by dietary protein at the pretranslational level in rat liver.

The effect of dietary protein on the expression of histidase (Hal) was investigated to understand the mechanism of induction of histidase by a high protein diet. In this study, we examined the following: 1) the effect of 0, 6, 18, 35 and 50% casein diets on hepatic and epidermal Hal activity, amount of the enzyme and Hal-mRNA; 2) the effect of a high histidine diet (1.25%) on Hal expression; 3) the response of Hal expression in rats fed a 10% casein diet and injected with glucagon (0.6 mg /(100 g body wt.d); and 4) the half-lives of the enzyme and Hal-mRNA in rats fed an 80% casein diet for 7 d followed by a protein-free diet. Hal activity increased as the protein content in the diet increased (r = 0.986, P < 0.001) and was associated with a significant increase in Vmax without a change in Km. The dietary regulation was liver specific because skin Hal was unresponsive. Increments in hepatic Hal activity were accompanied by concomitant significant increases in the amount of histidase and its mRNA. The response was more pronounced in rats fed diets containing >18% casein. Rats fed a 12% casein diet containing 1.25% histidine did not have different Hal activity and mRNA levels compared with rats fed a 12% casein diet, indicating that Hal expression is not modified by its substrate. Injection of glucagon into rats fed the 10% casein diet increased Hal activity threefold and Hal- mRNA expression fivefold compared with uninjected rats fed the same diet. The apparent half-life of hepatic histidase in protein-depleted rats previously fed an 80% casein diet was 2.8 d, whereas the half-life of Hal-mRNA was 17 h. In summary, these data support the hypothesis that Hal expression is regulated by dietary protein at the pretranslational level in rat liver, and that glucagon is one of the hormones involved in the induction of Hal.

Animals↗
PubMed1998

Regulation of branched-chain amino acid metabolism in the lactating rat.

There is evidence that during lactation, uptake of the essential branched-chain amino acids (BCAA) by mammary glands exceeds their output in milk protein. In this study, we have measured the potential of lactating rats to catabolize BCAA. The activity, relative protein and specific mRNA levels of the first two enzymes in the BCAA catabolic pathway, branched-chain aminotransferase (BCAT) and branched-chain alpha-keto acid dehydrogenase (BCKD), were measured in mammary gland, liver and skeletal muscle obtained from rat dams at peak lactation (12 d), from rat dams 24 h after weaning at peak lactation and from age-matched virgin controls. Western analysis showed that the mitochondrial BCATm isoenzyme was found in mammary gland. Comparison of lactating and control rats revealed that tissue BCATm activity, protein and mRNA were at least 10-fold higher in mammary tissue during lactation. Values were 1.3- to 1. 9-fold higher after 24 h of weaning. In mammary gland of lactating rats, the BCKD complex was fully active. In virgin controls and weaning dams, only about 20% of the complex was in the active state. Hypertrophy of the liver and mammary gland during lactation resulted in a 73% increase in total oxidative capacity in lactating rats. The results are consistent with increased expression of the BCATm gene in the mammary gland during lactation, whereas oxidation appears to be regulated primarily by changes in activity state (phosphorylation state) of BCKD.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1998

Dietary protein level regulates expression of the mitochondrial branched-chain aminotransferase in rats.

The first step in the degradation of branched-chain amino acids (BCAA) is transamination catalyzed by the branched-chain aminotransferase (BCAT), which is located in extrahepatic tissues. Studies of the effect of dietary protein on BCAT activity have given contradictory results. Therefore, we established the levels of BCAT activity and mitochondrial BCAT (BCATm) mRNA expression in different organs and tissues of rats. We then determined the effect of different levels of dietary protein in well-nourished rats, the effect of feeding a 0.5% casein diet for 5 wk (protein-malnourished rats) and nutritional rehabilitation of these rats with different levels of dietary protein on BCAT activity and BCATm mRNA expression in selected tissues. Finally, the response of tissue BCAT activity and BCATm mRNA levels in rats fed a 10% casein diet and injected with glucagon (4 d) or hydrocortisone (7 d) was determined. The highest concentration of BCATm mRNA was found in stomach, followed by kidney, heart, muscle, brain, skin and lung. Low levels were found in intestine, and no BCATm mRNA was detectable in liver. Although BCAT activity was significantly higher in muscle, kidney and brain from rats adapted to consume a 50% casein diet for 7 h/d for 10 d than in rats fed 6, 18 or 35% casein diets, only muscle had significantly higher levels of BCATm mRNA. In protein-malnourished rats, BCAT activity and BCATm mRNA expression in kidney, muscle and heart were not different from those of rats with free access to an 18% casein diet. Nutritional rehabilitation of the protein-malnourished rats with 50% casein for 21 d significantly increased the BCAT activity and BCATm mRNA expression in muscle. Neither hydrocortisone nor glucagon injection affected BCAT activity or BCATm mRNA concentrations in rat kidney, muscle or heart. We conclude that the nutritional regulation of BCATm is extrahepatic, tissue specific and may involve transcriptional and post-translational mechanisms.

Animals↗
PubMed1998

Primary progressive aphasia with glial cytoplasmic inclusions.

We report a 80-year-old woman who suffered from primary progressive aphasia for 3 years. Cranial CT and MRI studies showed moderate cerebral atrophy, more marked in the left frontal and temporal lobes, and SPECT brain scans revealed marked hypometabolism in the left frontal and temporal lobes. Neuropathologic examination of a temporal lobe biopsy demonstrated Gallyas-positive intracytoplasmic inclusions looking like fibrillary tangles and of Gallyas-positive cell processes, probably from glial cells. Glial intracytoplasmic inclusions were immunolabelled with antibodies to ubiquitin and with phosphorylion-dependent antitau antibodies, indicating the presence of hyperphosphorylated tau in the inclusions. There was only mild pathology of cortical neurons consisting in rare perikarya diffusely stained with antitau antibodies. There were no senile plaques, neurofibrillary tangles, 'achromatic' neurons, ballooned cells, Pick or Lewy bodies, nor microvacuoles or spongiform changes of the neuropil. The glial intracytoplasmic inclusions found in this case were similar to those found in multiple system atrophy, and differ from the cortical changes hitherto reported in primary progressive aphasia.

Aged↗
PubMed1998

Leucine catabolism in mammary tissue, liver and skeletal muscle of dam rat during lactation and weaning.

BACKGROUND: This study was designed to determine the effect of lactation and weaning on the catabolism of branched-chain amino acids (BCAA). METHODS: Rates of transamination and oxidation of leucine and branched chain alpha-ketoacid dehydrogenase (BCKD) activity were measured in homogenates of mammary gland, skeletal muscle and liver on day 12 of lactation and 24 h after separation of dams from the litter (weaning). RESULTS: Lactating dams consumed 250% more protein than control rats, extra protein is required for protein synthesis by the mammary gland, the extent to which the excess of amino acids consumed during lactation is utilized or oxidized by different tissues is not known. The rate of transamination of [1-14C] leucine by mammary tissue of lactating dams was sixfold higher than in virgin rats. The rate of transamination remained elevated fourfold in postweaning dams. Rates of transamination were three times higher in mammary tissue than in muscle of lactating dams. Rate of oxidation [1-14C] leucine by lactating mammary tissue was tenfold higher than in control tissue. CONCLUSIONS: The capacity of mammary tissue for transamination and oxidation of leucine increased greatly during lactation, suggesting that the mammary gland may play an important role in the catabolism of BCAA during lactation.

Animals↗
PubMed1997

Reduced kidney branched chain aminotransferase expression in puromycin aminonucleoside-induced nephrotic syndrome.

Injection of puromycin aminonucleoside to rats induces nephrotic syndrome characterized by hypoalbuminemia, proteinuria and hypercholesterolemia. In these rats, a low protein diet (6% casein diet) increased serum albumin by 26.3%, decreased proteinuria by 39% and reduced total cholesterol by 32%. Branched chain aminotransferase activity in kidney mitochondria of nephrotic rats fed 20 or 6% casein diet decreased by 30 and 24% with respect to their pair-fed groups and it was not modified by the protein content of the diet. Mitochondrial branched chain aminotransferase mRNA expression decreased by 67.3 and 72.5% in nephrotic rats fed 20 and 6% casein diet in comparison to their pair-fed groups. Total serum branched chain amino acids concentration (leucine, isoleucine, valine) in nephrotic rats was 30% higher than their pair-fed groups and it was associated with a decrease in the branched chain aminotransferase activity and mRNA expression suggesting that the catabolism of branched chain amino acid is reduced to conserve body nitrogen.

Animals↗
PubMed1996

Neutral and basic amino acid concentrations in plasma during the day in subjects fed with two model rural and two model urban Mexican diets.

The purpose of the study was to measure the variation in concentrations of plasma neutral and basic amino acids during the day in subjects fed two Mexican model rural diets, one containing 55% (R55) and the other 70% (R70) of energy as carbohydrates, and two model urban diets with the same two proportions of carbohydrates (U55 and U70). The R55 and R70 diets contained 1.35- and 1.69-fold more fiber than the U55 and U70 diets, respectively. Eight female volunteers were adapted to each of the four diets for 3 d before the day of blood sampling. Protein and energy intakes were adjusted to each subject for a consumption of 1 g protein/kg body wt and 150.7 kJ/kg body wt. Blood samples were withdrawn at 0700, 0930, 1100, 1500, 1900, 2300, and 0300. Only plasma concentrations of alanine changed during the day, dropping significantly (P<0.05) at 2300 and 0300 with the U70 diet. Urban diets produced significantly higher plasma isoleucine and valine values than did the rural diets at some sampling times. Plasma phenylalanine was significantly higher with the U70 diet at 2300 than with the other three diets. Alanine plasma concentrations were significantly higher with the U55 diet at 1900 and significantly lower with the R55 diet at 0930 with respect to the other diets. Lysine was significantly higher at 0700 with the U70 diet than with the other three diets. No other significant changes were observed. These results show the stability of the plasma amino acid profile despite the consumption of different diets in physiologic proportions. Possibly, some of the changes observed in the plasma amino acids can be explained by the high proportion of dietary fiber in the Mexican rural diets.

Adult↗
PubMed1996

Riboflavin and pyridoxine status in a group of pregnant Mexican women.

In order to assess the nutritional status of riboflavin and pyridoxine during pregnancy, 24 Mexican women were studied during the second trimester and 17 during the third trimester of gestation. The biochemical evaluation of the riboflavin and pyridoxine status was performed by measuring the activation coefficients (AC) of the erythrocyte glutathione reductase (eGR) and aspartate aminotransferase (eAAT), respectively. Dietary protein, riboflavin, thiamin, and calcium intake decreased significantly in the last trimester of gestation. The women presented biochemical deficiency of pyridoxine in the second and third trimester of pregnancy, but they developed biochemical deficiency of riboflavin and pyridoxine deficiency. None showed clinical signs of vitamin deficiency. No significant correlation was found between individual serum concentrations of estradiol or progesterone and eGR-AC or eAAT-AC in both trimesters of pregnancy. Six newborns studied showed normal eGR-AC and eAAT-AC.

Adult↗
PubMed1996

[Regulation of gene expression by nutrients].

Nutrients can regulate, directly or indirectly, the pathway of expression of genes coding for enzymes involved in metabolic pathways related to the utilization of carbohydrates, lipids and amino acids. On the other hand, nutrients such as carbohydrates, lipids or amino acids can generate an specific hormonal state in the organism, and hormones are the mediators throughout which some genes are activated. The objective of the present review is to show some specific examples of dietary and hormonal regulation of enzyme genes involved in the metabolism of carbohydrates (phosphoenol pyruvate carboxykinase), lipids (malic enzyme) and amino acids (serine dehydratase).

Enzymes↗
PubMed1995

Evolution of immunoglobulin A nephropathy into Henoch-Schönlein purpura in an adult patient.

We report the first case of the evolution of immunoglobulin A (IgA) nephropathy into Henoch-Schönlein purpura in an adult patient. A 28-year-old man presented with an episode of gross hematuria and acute renal failure. The serum IgA level was increased and renal biopsy findings were diagnostic of IgA nephropathy. In addition, many renal tubuli were filled by red blood cell casts and presented a marked tubular necrosis. Coincidental with the disappearance of gross hematuria, renal function progressively improved. The patient continued to have microhematuria, normal renal function, and isolated bouts of macroscopic hematuria. Ten years later, the patient developed arthralgias, a purpuric rash in the legs, gross hematuria, and an elevated serum creatinine level. A skin biopsy showed leukocytoclastic vasculitis with IgA deposits. The renal biopsy showed histologic lesions very similar to those observed in the first biopsy 10 years before: mesangial proliferation with mesangial deposition of IgA and tubular necrosis with obstruction of renal tubuli by red blood cell casts. The serum creatinine level returned to normal. Recurrent episodes of purpura associated with macroscopic hematuria persisted during the follow-up, but without worsening of renal function. An interesting feature of our patient was the development of reversible renal failure associated with macroscopic hematuria on two different occasions. Although this complication has been described in IgA nephropathy, it has been rarely reported in Henoch-Schönlein purpura. It is possible that IgA nephropathy and Henoch-Schönlein purpura are different clinical manifestations of the same disease and probably share a common pathogenesis. Our case is a demonstrative example of this hypothesis.

Acute Kidney Injury↗
PubMed1995

Leucine affects the metabolism of valine by isolated perfused rat hearts: relation to branched-chain amino acid antagonism.

This study was conducted to determine the effects of different concentrations of leucine on the transport, transamination and oxidation of valine and on incorporation of valine into heart proteins in the isolated perfused rat heart. Valine metabolism was studied in rat hearts perfused with medium containing glucose and graded levels of L-leucine. In transport studies L-phenylalanine was also tested. Uptake of L-[1-14C]valine (0.2 mmol/L) was significantly reduced (-50%) by inclusion of 0.2 mmol/L phenylalanine or leucine, and by -70% by inclusion of 1.0 mmol/L phenylalanine or leucine in the perfusate. Transamination of valine decreased by 37 and 48%, and oxidation of valine by 53 and 71%, respectively, when 0.2 or 1.0 mmol/L leucine was included in the perfusate. Tissue concentrations of valine decreased by 43, 48 and 62% in the presence of 0.2, 0.5 and 1.0 mmol/L leucine, respectively; tissue concentrations of leucine, glutamate and alanine increased approximately 11-fold, 1.2-fold and 0.5-fold, respectively, when 1.0 mmol/L leucine was present in the perfusate. Addition of 0.2-1.0 mmol/L leucine did not affect incorporation of valine into heart proteins. We conclude that 1) competition among large neutral amino acids for transport into heart occurs at physiological concentrations of these amino acids in plasma; 2) inhibition of valine uptake by leucine can limit the rate of valine catabolism in heart; and 3) depletion of tissue valine concentration by an excess of leucine did not affect the rate of protein synthesis.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1994

[Vasculitis associated with a myelodysplastic syndrome: a report of 5 cases].

In a study of 94 patients with myelodysplastic syndrome (MDS) associated vasculitis was observed in 5, which preceded hematologic diagnosis in 4. Leukocytoclastic vasculitis was observed in 5 cases being associated to lobular panniculitis in one. Three patients had refractory anemia, one sideroblastic anemia (SA) and another refractory anemia with excess blasts (RAEB). In the latter case lymphomatoid papulosis was also observed which, to date, has not been previously described in association with MDS. Another case presented seronegative polyarthritis and renal disease coinciding with vasculitis. Polyarteritis nodosa was diagnosed in a third patient in agreement with the criteria of the American College of Rheumatology, the association of which with MDS is exceptional. In the same case medullary cytogenetic study showed 46, XY,t (12;20), an abnormally which has not been described to date in cases of MDS. All the cases were treated with glucocorticoids in addition to cyclophosphamide in the patient with polyarteritis nodosa, with an improvement in the vasculitis being observed in all the patients. Two patients died, one (SA) due to pneumonia and the other (RAEB) due to subdural hematoma following transformation to acute myeloblastic leukemia. With 5% of the MDS studied presenting vasculitis, this syndrome should be included in the differential diagnosis of vasculitis observed in patients with cytopenia.

Aged↗
PubMed1992

Brain amines in glucocorticoid-induced hypertension in the rat.

A two week administration of the glucocorticoid betametasone to male Wistar rats produced a mild hypertensive state. The brain of these rats showed some significant changes in amine and metabolite content with respect to normotensive controls. Epinephrine and metanephrine were increased in the rostral ventrolateral medulla and in the preoptic area. Epinephrine also increased in the septal area. Normetanephrine decreased in the rostral ventrolateral medulla. Dopamine and homovanillic acid increased in septal and preoptic areas. Dopamine alone increased in rostral ventrolateral medulla. Serotonin and 5-hydroxyindole-3-acetic acid increased in the septal area and dorsal medulla. These changes suggest significant alterations in the aminergic activity of the brain circuitry known to regulate cardiovascular functions; the changes may play a basic role in the development and maintenance of glucocorticoid-induced hypertension.

Animals↗
PubMed1992

Aqueous humor hydrogen peroxide analysis with dichlorophenol-indophenol.

Hydrogen peroxide is now reported to be a normal aqueous humor component present, in the low microM concentration range, in the animal species which have been studied. This finding was established with the exclusive use of the dichlorophenol-indophenol method of analysis. In this procedure, aqueous humor is added to a blue, oxidized dichlorophenol-indophenol solution. The 605 nm absorbance of this solution immediately decreases in response to the reducing action of ascorbate present in the sample. The extent of reoxidation of the solution upon the addition of peroxidase, as measured by the increase in its 605 nm absorbance, can be quantitatively related to the concentration of H2O2 in the sample. A close examination of this method revealed that reduced dichlorophenol-indophenol spontaneously reoxidizes at a rate of 0.03 nmol min-1 microM-1, with generation of H2O2. H2O2 generation was unequivocally established by analysis of the temporal dependency of the absorbance increase produced by peroxidase in the absence of added H2O2 and by the sensitivity of this phenomenon to catalase. This spontaneous production of H2O2, on the other hand, cannot be attributed to ascorbate auto-oxidation because added ascorbate quantitatively reacts with dichlorophenol-indophenol, provided that an excess of the latter is maintained. This method then has an enormous potential to overestimate H2O2 in any sample. On the other hand, the response of the assay system to a given level of H2O2 depends on the level of reduction previously produced by ascorbate. This results in an artifactual positive correlation between ascorbate and H2O2 levels in samples containing variable amounts of ascorbate. In spite of these serious limitations the method can still be useful to measure H2O2 if appropriate precautions are taken. When using it for the analysis of rabbit aqueous humor H2O2 without correcting for the H2O2 generated during the assay and ignoring differences in the level of ascorbate in the samples, we obtained an average value of 25.3 microM H2O2, which coincides with that reported in the literature for the rabbit, but is obviously incorrect. When analysing aqueous humor there was the additional variable of the aqueous humor itself inhibiting the rate of dichlorophenol-indophenol auto-oxidation and so the final, corrected figure for H2O2 concentration in the aqueous humor became uncertain, since the auto-oxidation of the substrate could not be properly subtracted.(ABSTRACT TRUNCATED AT 400 WORDS)

2,6-Dichloroindophenol↗
PubMed1992

Competition for transport of amino acids into rat heart: effect of competitors on protein synthesis and degradation.

Transport of the neutral amino acids, 2-(methylamino)isobutyrate (MeAIB) and Phe, was examined in isolated rat hearts perfused by the Langendorff method. Hearts were perfused by recirculating for various time periods buffer containing [14C]-MeAIB or [14C]-Phe plus desired additions. Uptake of MeAIB was linear for approximately 30 minutes; Phe uptake was linear for a maximum of 5 minutes, and reached a steady state after 15 minutes. Km and Vmax for MeAIB were 1.1 +/- 0.03 mmol/L and 37.7 +/- 0.4 pmol/microL intracellular fluid (ICF)/min; values for Phe were 1.8 +/- 0.02 mmol/L and 364 +/- 5 pmol/microL ICF/minute. Uptake of MeAIB (0.2 mmol/L) was reduced 95% in the presence of Ser (10 mmol/L), and less severely by large neutral amino acids ([LNAA], 10 mmol/L) such as Phe and Leu (by 46% and 54%, respectively). Uptake of Phe (0.2 mmol/L) was reduced by LNAA such as Val, Leu, and Ile (by 51%, 78%, and 81%, respectively), or by commercial preparations used in parenteral nutrition, eg, Travasol or Travasol plus extra branched-chain amino acids (BCAA) (Branchamin); Ser had little effect (8% reduction). Insulin in the perfusion medium increased the fractional rate of protein synthesis. Individual BCAA at physiological concentrations (0.2 mmol/L) did not alter the rate of protein synthesis. Branchamin or Travasol plus Branchamin also had no effect on the rate of protein synthesis in heart, but did depress the rate of degradation. These studies suggest that amino acid transport into heart may be affected by normal levels of plasma amino acids, whereas protein synthesis is not.

Amino Acids↗
PubMed1992

[Laparoscopy in acute appendicitis].

Our experience shows that laparoscopy is an excellent diagnostic method in cases where acute appendicitis is suspected, but when the clinical picture and tests are equivocal. Laparoscopy can help diagnose other abdominal conditions mimicking acute appendicitis and, in addition, may be used to remove the appendix in most cases, with advantages over open surgery.

Acute Disease↗
PubMed1991

Echocardiographic assessment of doxazosin on left ventricular mass in patients with essential hypertension.

A single daily dose of doxazosin taken during a 12-week period produced a significant reduction in blood pressure and left ventricular mass index in patients with mild or moderate hypertension. The systolic shortening coefficient was also increased and a trend in the improvement of ejection fraction, rate of circumferential fiber shortening, systolic contraction time, and preejective/ejective ratio was observed. No change in heart rate was recorded and no patients had side effects. The serum lipid profile was modified favorably, particularly with regard to the low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio. By producing a reduction in blood pressure and left ventricular mass while favorably modifying the serum lipid profile, doxazosin produced a beneficial change in the overall coronary heart disease risk profile.

Antihypertensive Agents↗