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A M Torres

Publications and source records attributed to A M Torres.

At least 55 records · Page 3Linked to original sources
PubMed1997

Patterns of intra-familiar distribution of undernutrition: methods and applications for developing societies.

OBJECTIVE: To propose a method to assess patterns of intra-familiar distribution of undernutrition and apply it to different socioeconomic strata of the Brazilian population. DESIGN: A large nationally representative cross-sectional anthropometric survey undertaken in 1989 is the primary source of information. Undernutrition was defined as body mass index (adults) and weight-for-age (children) below the 5th percentile of a healthy and non-malnourished reference population. Log-linear models were used to assess patterns of intra-familiar distribution of nutritional status in four income strata. SUBJECTS: Two thousand, one hundred and seventy-four families composed by at least one child 6-36 month-old and his/her father and mother. SETTING: All regions in Brazil. RESULTS: Undernutrition was significantly associated among household members only for the 25% poorest families (P < 0.0001). In this group, the presence of undernutrition in the mother or the father increased 1.6-1.9 times the risk of undernutrition in the child and the presence of undernutrition in the father made it 2.7 times more frequent in the mother. The relatively small prevalence ratios suggest that even in extremely poor families only a small proportion of undernutrition could be attributed to common household determinants. CONCLUSION: Our results are consistent with the hypothesis that in transitional societies undernutrition would appear as a global family problem only for those at the earlier stages of the nutrition transition. Policies and strategies to overcome undernutrition should take this fact into account.

Adolescent↗
PubMed1996

Gender-differential liver plasma membrane affinities in hepatic tetrabromosulfonephthalein (TBS) uptake.

The sex difference in the hepatic uptake of tetrabromosulfonephthalein (TBS) was investigated in male and female rats in two different experimental models. In the intact animal, the initial plasma disappearance constant rate, the initial velocity of uptake, and the plasma clearance of TBS were significantly higher in females than in males. In sinusoidal liver plasma membrane vesicles, kinetic parameters of TBS uptake were investigated in both sexes. The Km was lower in females than in males (5.5 +/- 0.4 vs 17 +/- 4 microM, P < 0.05), whereas Vmax showed comparable values (544 +/- 15 vs 581 +/- 60 nmol TBS/min/mg protein, mean +/- SD, NS, females and males, respectively). Collectively, these data indicate that the sex difference in hepatic uptake of TBS is located at the sinusoidal liver plasma membrane and is due to a greater affinity of the electrogenic transport system(s) in females.

Animals↗
PubMed1996

ATP modulates sulfobromophthalein uptake in rat liver plasma membrane vesicles.

The hepatic uptake of the bilirubin-bilirubin-sulfobromophthalein (BSP) group of organic anions is a carrier-mediated process and is accounted for by at least four distinct plasma membrane proteins (bilitranslocase, BSP/bilirubin-binding protein, organic anion-binding protein and the organic anion transport protein). In order to investigate the regulation of basolateral organic anion uptake, BSP transport was measured in rat basolateral liver plasma membrane vesicles in the presence of ATP. ATP significantly stimulated the electroneutral uptake of BSP with an increment in Vmax compared with control (1.57 +/- 0.14 vs 0.73 +/- 0.06 nmol BSP/mg protein per 15 s, respectively; P < 0.001) while the apparent K(m) was not changed significantly (12 +/- 1 vs 12 +/- 2 mumol/L). The stimulatory effect was dose-dependent for ATP (K(m) 1.01 +/- 0.37 mmol/L). ATP had no detectable effect on the electrogenic component of BSP transport. Other nucleotides (ADP, AMP, GTP) and non-hydrolysable ATP did not enhance BSP uptake, suggesting that ATP hydrolysis was necessary for the effect. This was supported by the lack of effect on BSP uptake when ATP was added in the presence of vanadate. The addition of phorbol-12-myristate 13-acetate, an activator of protein kinase C (PKC), increased BSP uptake in a dose-dependent manner in the presence, but not in the absence, of ATP. Incubation of vesicles with staurosporine, an inhibitor of PKC activity, resulted in a dose-dependent inhibition of ATP-sensitive BSP transport. These data indicate that electroneutral BSP hepatic uptake is modulated by ATP. The effect is related to ATP hydrolysis and involves the activity of PKC.

Adenosine Triphosphate↗
PubMed1995

Solution structure of human insulin-like growth factor II. Relationship to receptor and binding protein interactions.

The three-dimensional structure of human insulin-like growth factor (IGF) II in aqueous solution at pH 3.1 and 300 K has been determined from nuclear magnetic resonance data and restrained molecular dynamics calculations. Structural constraints consisting of 502 NOE-derived distance constraints, 11 dihedral angle restraints, and three disulfide bridges were used as input for distance geometry calculations in DIANA and X-PLOR, followed by simulated annealing refinement and energy minimization in X-PLOR. The resulting family of 20 structures was well defined in the regions of residues 5 to 28 and 41 to 62, with an average pairwise root-mean-square deviation of 1.24 A for the backbone heavy-atoms (N, C2, C) and 1.90 A for all heavy atoms. The poorly defined regions consist of the N and C termini, part of the B-domain, and the C-domain loop. Resonances from these regions of the protein gave stronger cross peaks in two dimensional NMR spectra, consistent with significant motional averaging. The main secondary structure elements in IGF-II are alpha-helices encompassing residues 11 to 21, 42 to 49 and 53 to 59. A small anti-parallel beta-sheet is formed by residues 59 to 61 and 25 to 27, while residues 26 to 28 appear to participate in intermolecular beta-sheet formation. The structure of IGF-II in the well-defined regions is very similar to those of the corresponding regions of insulin and IGF-I. Significant differences between IGF-II and IGF-I occur near the start of the third helix, in a region known to modulate affinity for the type 2 IGF receptor, and at the C terminus. The IGF II structure is discussed in relation to its binding sites for the insulin and IGF receptors and the IGF binding proteins.

Amino Acid Sequence↗
PubMed1994

Competition of bile acids on the sulfobromophthalein uptake in basolateral rat liver plasma membrane vesicles.

The effect of different bile acids (BA) on the hepatic uptake of sulfobromophthalein (BSP) was investigated in liver plasma membrane vesicles enriched in basolateral fraction. BSP uptake was measured either in the absence (electroneutral component) or in the presence of a membrane potential (electrogenic component) induced by the addition of valinomycin in the presence of an inwardly-directed potassium gradient. BSP uptake was also measured in the presence of different BA [cholate (C), taurocholate (TC), ursodeoxycholate (UDC) and tauroursodeoxycholate (TUDC)]. Electrogenic BSP uptake was not affected by BA. Conversely, the electroneutral portion of the BSP uptake was inhibited with an inhibition constant (Ki, microM) of 230 +/- 40 for C, 103 +/- 33 for TC, 99 +/- 34 for UDC and 120 +/- 39 for TUDC, respectively (means +/- SD, N = 4). The Dixon and Cornish-Bowden plot of the data revealed an uncompetitive type of inhibition for each BA. These data indicate that the electroneutral, but not the electrogenic, BSP transport system is modulated by BA.

Animals↗
PubMed1994

Role of BSP/bilirubin binding protein and bilitranslocase in glutathione uptake in rat basolateral liver plasma membrane vesicles.

Glutathione (GSH) efflux in the liver is mediated by carrier proteins sensitive to membrane potential (electrogenic), and it is inhibited by organic anions. The hepatic uptake of tetrabromosulfophthalein (BSP) is also a carrier-mediated function accomplished at least by two different transport mechanisms, bilitranslocase (BTL) and BSP/Bilirubin Binding Protein (BBBP). The two proteins operate in parallel, the former operating electro-genically, the latter being insensitive to membrane potential (electroneutral). To investigate the relationship between transport mechanisms for GSH and organic anions, the initial uptake rate of 35S-labelled BSP into basolateral rat liver plasma membranes was measured in the presence of external or intravesicular GSH. Electrogenic and electroneutral BSP uptake were neither cis-inhibited nor trans-stimulated by GSH. 3H glycine-GSH uptake in LPMV was not modified by pre-incubating LPMV with anti-BTL or anti-BBBP antibodies. These data indicate that GSH hepatic uptake is mediated neither by BBBP nor BTL.

Animals↗
PubMed1994

[Hypothermic preservation of the liver. Evaluation of Eurocollins solution using rats liver slices].

In the present work, we analyze the effects produced by cold ischemia on the liver using Eurocollins solution (EC). This evaluates the function of slices obtained from preserved livers in EC (livers from adult female Wistar rats were used), which were perfused with Krebs-Henseleit solution (KH) for 10 min. and then with cold EC. These livers were stored at 4 degrees C in EC for 7, 24 and 48 hours. At the end of each period of preservation, the livers were sliced and they were incubated 1 hour at 37 degrees C in KH. The following parameters were determined: tissular water distribution and electrolytes content (K+ and Na+), LDH release at the incubation medium, thiobarbituric acid reactive substances (TBARS) and urea synthesis. The slices obtained from preserved livers (7 hours), showed an increase of tissular water, expressed by the expansion of the extracellular space, a progressive diminution of tissular K+ content and an increase in TBARS and the LDH release with the increment of the preservation time. No changes in ureogenesis rate were observed. These results suggest that the cold ischemia in EC, in periods that exceed 5 hours, cause, changes in the membrane permeability and severely affects the mechanism of regulation of the tissular volume and may compromise the functional viability of the organ to be transplanted.

Animals↗
PubMed1993

Difference in hepatic uptake of tetra- and di-bromosulfophthalein in rat. Role of hydrophobicity, binding to plasma proteins and affinity for plasma membrane carrier protein.

The relative role of hydrophobicity, binding to plasma proteins and affinity for one of the plasma membrane transport proteins in the hepatic uptake of 3,4,5,6-tetra- (BSP) and 3,6-di- (DBSP) bromosulfophthalein was investigated in the rat. In terms of physicochemical characteristics, the two molecules show different pKa values and degrees of hydrophobicity, as determined from the n-octanol:water partition coefficient. In the intact animal, the plasma clearance and the plasma removal rate after a dose of 1.5 mumol/kg i.v. were significantly (P < 0.001) faster for BSP than DBSP, while no difference was found in the plasma distribution volume. The dissociation constant (Kd) of the high affinity binding sites of plasma proteins also differed for the two anions, being significantly lower for BSP than DBSP (0.95 +/- 0.02 vs 1.44 +/- 0.14 microM, P < 0.001). [35S]BSP uptake by liver plasma membrane vesicles was saturable with an apparent Km of 5.20 +/- 0.80 microM, and was competitively inhibited by DBSP (Ki 18.2 +/- 1.2 microM) indicating a common uptake system. The Kd value for binding of the organic anions to purified bilitranslocase, a plasma membrane protein involved in the electrogenic transport of pthaleins, was also significantly lower for BSP than DBSP (1.10 +/- 0.12 vs 3.02 +/- 0.27 microM, N = 3, P < 0.001), indicating a higher affinity of the former ligand for the carrier protein. No difference was observed in the capacity of the high affinity binding sites (32 +/- 3 vs 33 +/- 3 nmol/mg protein, BSP and DBSP, respectively). These data indicate that BSP and DBSP are two different cholephilic organic anions which share a common uptake mechanism, at least partly mediated by bilitranslocase. The greater affinity of BSP than DBSP for the carrier protein may account for the faster plasma disappearance rate of BSP observed in vivo, in spite of the higher plasma protein binding.

Animals↗
PubMed1993

Bilitranslocase and sulfobromophthalein/bilirubin-binding protein are both involved in the hepatic uptake of organic anions.

The hepatic uptake of cholephilic organic anions is a carrier-mediated process. Three distinct proteins [bilitranslocase (BTL), sulfobromophthalein (BSP)/bilirubin-binding protein (BBBP), and organic anion-binding protein] have been isolated from the basolateral plasma-membrane domain of the hepatocyte. To investigate the relative role of the first two of them in accounting for the hepatic uptake of organic anions, we measured the initial rates of uptake of 35S-labeled BSP into rat liver plasma-membrane vesicles. Because transport by BTL is electrogenic but transport by BBBP is electroneutral, studies were done either with or without a positive-inside membrane potential produced by adding valinomycin in the presence of an inwardly directed K+ gradient (outside K+ > inside K+). Both electrogenic and electroneutral transport systems followed saturation kinetics. Electroneutral uptake showed an apparent Km of 20 +/- 3 microM (mean +/- SD) and a Vmax of 1.0 +/- 0.13 nmol.(mg of prot)-1.15 sec-1, whereas the electrogenic portion of BSP uptake exhibited a Km of 5.2 +/- 0.8 microM and a Vmax of 1.1 +/- 0.1 nmol.(mg of prot)-1.15 sec-1. In this case, an overshoot was observed 15 sec after valinomycin addition. Electroneutral BSP uptake was inhibited by incubation with anti-BBBP antibody, whereas anti-BTL antibody did not show any inhibitory effect. Conversely, the electrogenic uptake was inhibited by anti-BTL antibody at a BSP concentration of 5 microM; no inhibition was seen either at 20 microM BSP or upon addition of anti-BBBP antibody. From these data we conclude that the hepatic uptake of organic ions occurs via two immunologically distinct carrier proteins (BTL and BBBP) operating in parallel. BTL is a higher affinity electrogenic transporting system of organic ions, whereas BBBP is a lower affinity electroneutral transporter.

Animals↗
PubMed1993

Renal transport of glycine during glutathione replenishment in rats.

Renal transport of glycine was studied in control and glutathione-depleted rats. Diethylmaleate (4.0 mmol/kg body wt, ip) was used as a glutathione depletor agent and the studies were carried out 6 and 10 h post-diethylmaleate injection. Renal transport was measured in isolated rat kidney preparations by means of clearance techniques and in brush border membrane vesicles by a rapid filtration method. Tubular reabsorption of glycine, when compared to glomerular filtration rate, measured at different substrate tubular loads, was higher in treated kidneys. Tissue 14C accumulation was also higher in kidneys from diethylmaleate-treated animals. Studies with brush border membrane vesicles indicated that glutathione depletion induced higher sodium-dependent glycine uptake in contrast with control preparations. This adaptation was not associated with an increment in either tau-glutamyltransferase activity or in protein concentrations. These results could explain in part the replenishment of GSH cellular levels in glutathione-depleted kidneys by means of higher transport capacity for glycine (a glutathione precursor) which was maintained even when GSH levels were restored.

Animals↗
PubMed1992

Can secular trends in child growth be estimated from a single cross sectional survey?

OBJECTIVE: To formulate and evaluate a new method to measure secular trends in child growth based on the cross sectional collection of heights of children and young adults. DESIGN: Trends in child growth obtained from comparison of two national surveys made with an interval of 15 years were compared with estimates obtained from comparison of height deficits of children and young adults in the more recent survey. SETTING: Brazil. SUBJECTS: Random sample of children (6 and 7 years old) and young adults (21 and 22 years old) living in Brazil in 1974 and 1989 (a total of 23,271 subjects in 1974 and 5479 in 1989). MAIN OUTCOME MEASURES: Increments in average heights of 6 and 7 year old children in a 15 year period. RESULTS: Mean height of 6 year old children increased 4.0 cm (boys) and 3.3 cm (girls) from 1974 to 1989. Similar results were obtained by subtracting, in the 1989 survey, mean height deficits found at ages 21 and 6 (3.8 cm for males and 3.5 cm for females). Positive changes in the mean height of 7 year old children could also be predicted by subtracting, in the 1989 survey, height deficits found at ages 7 and 22. CONCLUSIONS: Findings of this study support the hypothesis that secular trends in child growth can be estimated by comparing height deficits observed in children and young adults.

Adult↗
PubMed1992

Effect of ethinylestradiol and epomediol on bile flow and biliary lipid composition in rat.

Epomediol (1,3,3-trimethyl-2-oxabicyclo(2.2.2.)octan-6,7-endo,endo-diol) (EPO) is a terpenoid compound shown to reverse 17 alpha-ethinylestradiol (EE)-induced cholestasis in rat. The effect is related to the restoration of normal liver plasma membrane fluidity values. To further characterize the effect of EPO, bile flow and biliary lipid composition were measured in rats treated either with EE or EE associated with EPO. EE significantly reduced the bile flow; this reduction was prevented by concomitant treatment with EPO with an increase in the bile salt secretion rate. EPO alone showed a choleretic effect. The biliary secretion rate of cholesterol was also significantly reduced by EE while being comparable to controls in EE-EPO-treated animals. Phospholipid (PL) biliary excretion was significantly (P less than 0.002) increased by EE either alone or combined with EPO. After EE treatment, the biliary PL composition showed a reduction in phosphatidylcholine (PC) concentration with a parallel increase in lyso-phosphatidylcholine (LPC) when compared to control animals (PC:LPC ratio 5.0 +/- 2.5 vs 26.8 +/- 9.9, mean +/- SD, P less than 0.005). EPO administration to EE-treated rats restored the biliary PC:LPC ratio to control values (27.6 +/- 10.6). EPO alone did not show any appreciable effect as compared to both control and EE-EPO treated animals. As increased concentrations of LPC have been reported to induce an alteration in the function of membrane lipids and membrane-associated proteins, such as regulatory enzymes for bile acid, cholesterol and phospholipid metabolism, these results suggest that the protective effect of EPO in EE-induced cholestasis may be related to the reversal of the alterations in membrane lipid composition and function induced by EE.

Animals↗
PubMed1992

Carrier-mediated transport of tetrabromosulfonephthalein by rat liver plasma membrane vesicles.

To investigate the molecular requirements and mechanisms for the hepatic uptake of phthaleins, the transport of tetrabromosulfonephthalein (TBS) was investigated in basolateral rat liver plasma membrane vesicles. TBS uptake was electrogenic as greatly accelerated by the creation of a positive-inside membrane potential by the addition of valinomycin in the presence of an inwardly directed potassium gradient. No effect was observed when the ionophore was added in the presence of a sodium gradient. The transport occurred into an osmotic-sensitive space and was saturable with an apparent Michaelis constant of 5.32 +/- 0.56 microM and a maximal velocity of 9.23 +/- 0.25 nmol.s-1.mg protein-1 (mean +/- SD, n = 3 experiments). TBS uptake was directly related to the extra-vesicular pH, indicating the deprotonated quinoid negative-charged form of the dye as the transported species. In contrast, TBS uptake was inversely related to the intravesicular pH, suggesting that protonation inside the vesicles may act as an efficient trap in transport process. Addition of polyclonal monospecific anti-bilitranslocase antibody to liver vesicles specifically inhibited TBS uptake rate (3.27 +/- 0.17 vs. 5.82 +/- 0.61 nmol.s-1.mg protein-1, n = 3, P less than 0.001). These data indicate that TBS is electrogenically transported across the liver cell plasma membrane by bilitranslocase. They also indicate that the presence of a negative charged group on the benzenic ring of the ligand is important in accounting for the transport.

Absorption↗
PubMed1991

Role of lipid peroxidation on renal dysfunction associated with glutathione depletion. Effects of vitamin E.

This study was designed to investigate the role of lipid peroxidation in the pathogenesis of renal dysfunction in glutathione (GSH)-depleted rats. Renal function parameters and acid-base status were analyzed in diethylmaleate (DEM)-treated rats previously injected with vitamin E (Vit.E). Vit.E was effective in inhibiting the elevation in renal lipid peroxidation found in GSH-depleted rats. Vit.E also ameliorated the renal response to the metabolic acidosis without modification in lactate production induced by DEM administration. The increase in sodium and water urine excretion and the diminution of the urine to plasma osmolalities ratio were not reversed in these animals. These results lead us to conclude that lipid peroxidation is associated with distal acidification impairment observed with GSH-depletion, but it is not related to the sodium reabsorption alteration in the ascending loop of Henle.

Acid-Base Equilibrium↗
PubMed1991

Effect of glutathione depletion on urinary acidification in the rat.

Glutathione (GSH) depletion by diethyl maleate (DEM) administration and its rapid repletion were associated with the development of a moderate acidosis in the rat. The acidosis observed after DEM treatment could be a consequence of an impairment of lactate metabolism. GSH-depleted rats also showed an increased urine pH and a higher bicarbonate fractional excretion compared with control rats. Renal bicarbonate excretion was magnified when blood bicarbonate levels were normalized by means of a bicarbonate infusion in GSH-depleted rats; however, the amount of bicarbonate excreted in the urine was a very small fraction (less than 5%) of the calculated filtered load. GSH-depleted rats failed to elevate the relation urine minus blood (U-B) pCO2 as compared with control rats when they were subjected to a high bicarbonate load to the distal portions of the nephron. All these data were consistent with a distal renal tubular acidosis due to GSH depletion which could participate in the maintenance of the systemic acidosis, although it is unlikely that it is the primary cause of the acidosis.

Acidosis↗
PubMed1989

Rat kidney function related to tissue glutathione levels. Effects of different glutathione depletors.

1. Rat renal function was evaluated during acute depletion of glutathione (GSH) produced by different doses of diethyl-maleate (DEM) or buthionine-sulfoximine (BSO). 2. Similar alterations in renal function were observed when similar GSH levels were obtained independently of the GSH depletor employed. 3. These results confirm the relationship between GSH levels and renal function.

Animals↗
PubMed1989

Vulnerability of the thick ascending limb to glutathione depletion in rat kidney: effects of diuretics and indomethacin.

Previous works supported the idea that the thick ascending limb of Henle was the target structure for glutathione (GSH) depletion effects. In order to obtain more evidence on this hypothesis, we compared GSH depletion effects with those of two loop diuretics: furosemide and ethacrynic acid. The submaximal tubular effects observed with furosemide were magnified when the kidneys were previously GSH depleted, but maximal tubular effects of furosemide were GSH independent. This last observation suggested that furosemide and GSH depletion have common sites or mechanisms of action. On the other hand, ethacrynic acid tubular effects were always magnified when the rats were GSH depleted. As it has been proposed that the renal actions of furosemide and ethacrynic acid are at least in part mediated by prostaglandins, another set of experiments was performed using indomethacin to examine the possible role of renal prostaglandins in GSH depletion effects. It was observed that indomethacin greatly improved tubular functions in GSH-depleted rats suggesting that an increase in prostaglandins levels should be involved in the renal defects observed during GSH depletion. All these data give additional support to the idea that the thick ascending limb cells may have a special sensitivity to the effects of GSH depletion probably mediated by prostaglandins.

Animals↗