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Biomedical subjects

O Pineda

Publications and source records attributed to O Pineda.

At least 19 recordsLinked to original sources
PubMed2001

Bocdene and mocdene derivatives of catechols and catecholamines.

[reaction in text] Catechols react chemoselectively, in the presence of either alcohols, 1,2-diols, or simple phenols, with tert-butyl propynoate and with methyl propynoate to give 2-Boc-ethylidene (Bocdene) and 2-Moc-ethylidene (Mocdene) acetals, respectively, in 96-100% yields within 30 min at room temperature, provided that 150 mol % of DMAP is added. Cleavage of these acetals with pyrrolidine readily takes place (at room temperature!) in 95-100% yields. By taking advantage of the features of Bocdene acetals, novel catecholamine-related phosphate mimetics have been prepared.

Acetals↗
PubMed2001

Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate.

Forty infants, 6 to 36 mo old, with iron-deficiency anemia (hemoglobin < 11 g/dL) were matched and assigned to two groups. One group received FeS0(4) and the other received ferrous bis-glycinate chelate at a dose of 5 mg of Fe daily per kilogram of body weight for 28 d. Both groups had significant hemoglobin increases (P < 0.001), but only the group treated with ferrous bis-glycinate chelate had significant increases (P < 0.005) in plasma ferritin. Apparent iron bioavailabilities were calculated at 26.7% for FeS0(4) and 90.9% for ferrous bis-glycinate chelate. Regression analysis indicated that absorption of both sources of iron were similarly regulated by the body according to changes in hemoglobin. We concluded that ferrous bis-glycinate chelate is the iron of choice for the treatment of infants with iron-deficiency anemia because of its high bioavailability and good regulation.

Anemia, Iron-Deficiency↗
PubMed2000

Arabidopsis transcription factors: genome-wide comparative analysis among eukaryotes.

The completion of the Arabidopsis thaliana genome sequence allows a comparative analysis of transcriptional regulators across the three eukaryotic kingdoms. Arabidopsis dedicates over 5% of its genome to code for more than 1500 transcription factors, about 45% of which are from families specific to plants. Arabidopsis transcription factors that belong to families common to all eukaryotes do not share significant similarity with those of the other kingdoms beyond the conserved DNA binding domains, many of which have been arranged in combinations specific to each lineage. The genome-wide comparison reveals the evolutionary generation of diversity in the regulation of transcription.

Amino Acid Motifs↗
PubMed2000

New protecting groups for 1,2-diols (boc- and moc-ethylidene). Cleavage of acetals with bases.

[reaction: see text] 1,2-Diols react at rt with alkyl propynoates, in the presence of 4-dimethylaminopyridine, to give cyclic acetals which are quite stable to acid-catalyzed hydrolysis or methanolysis. 1,3-Diols and 1, 4-diols do not form acetals with alkyl propynoates under the same conditions. Deprotection is accomplished with bases (via elimination and addition/elimination steps).

Journal Article↗
PubMed1999

Mammary type I deiodinase is dependent on the suckling stimulus: differential role of norepinephrine and prolactin.

Mammary deiodinase type I (M-D1) is present only during lactation and exhibits a clear direct correlation with lactation intensity (size of litters). The present work shows that M-D1 is suckling dependent and that intervals between suckling periods no longer than 12 h are essential to maintain this activity. Moreover, we find that with only 15 min of resuckling in 12-h nonsuckled mothers, the 50% decrease in both M-D1 messenger RNA and enzymatic activity could be restored to control values. This restorative effect by suckling may involve pre- and posttranscriptional mechanisms in which norepinephrine and PRL play important roles. Norepinephrine elicits a potent stimulatory effect on M-D1 messenger RNA and enzyme activities, whereas PRL only increases M-D 1 activity and may modulate the enzyme response to norepinephrine. Oxytocin and GH had no effect. These data suggest that the adrenergic nervous system and PRL could directly participate in mammary energetic expenditure, regulating the local T3 supply.

Animals↗
PubMed1997

Milk inhibits and ascorbic acid favors ferrous bis-glycine chelate bioavailability in humans.

The chemical properties of ferrous bis-glycine chelate allow for its use as a fortificant in fluid, high fat vehicles. This chemical form may also protect iron from the inhibitory or enhancing effects of the diet on iron absorption. Alternatively, iron bis-glycine chelate may be absorbed by a mechanism independent of an individual's iron stores. To test these hypotheses, the bioavailability of iron bis-glycine chelate added to water and milk was studied using a double-isotopic method in two groups of 14 women. Iron absorption from aqueous solutions of 0.27 mmol/L (15 mg/L) of elemental iron as either iron bis-glycine or ferrous ascorbate was not significantly different (34.6 and 29.9%, respectively). There were significant correlations between (log) iron absorption of iron bis-glycine with (log) serum ferritin (r = -0.60, P < 0.03) and with (log) iron absorption from ferrous ascorbate (r = 0.71, P < 0.006), suggesting that iron bis-glycine chelate bioavailability is indeed affected by iron stores. Iron absorption of iron bis-glycine given in milk was significantly lower (P < 0.002) than when given in water, with values of 11.1 and 46.3%, respectively (standardized to 40% absorption of the reference dose). With the addition of 0.57 mmol/L ascorbic acid (100 mg/L), iron absorption of iron bis-glycine given in milk increased significantly from 11.1 to 15.4% (P < 0.05). These findings show that milk and ascorbic acid affect iron bis-glycine chelate bioavailability and also demonstrate that iron stores may influence its bioavailability as well. The good bioavailability of iron bis-glycine makes this compound a suitable alternative to be considered in iron fortification programs.

Adult↗
PubMed1995

Fortification of sugar with iron sodium ethylenediaminotetraacetate (FeNaEDTA) improves iron status in semirural Guatemalan populations.

A 32-mo-long, double-blind field study involving one highland control community receiving only vitamin A-fortified sugar and three vitamin A- and FeNaEDTA-sugar-fortified communities, two in the lowlands and one in the highlands of Guatemala, was undertaken to test the effectiveness of this approach in controlling iron deficiency. The communities' population ranged between 1200 and 17000. Sugar fortified with 1 g FeNaEDTA and 15 mg retinol as retinyl palmitate/kg was stable, did not segregate, and was well accepted by the communities. The impact of fortification on iron nutrition was estimated at 8, 20, and 32 mo of intervention. All pregnant women and subjects with severe anemia received supplements or treatment and were excluded from the analysis. Iron stores in the fortified communities increased significantly except for women 18-48 y of age in one lowland community and > 49 y in the highland community. Iron stores in the control community remained unchanged except for a rise among adult males.

Adolescent↗
PubMed1991

Minor and trace elements in human milk from Guatemala, Hungary, Nigeria, Philippines, Sweden, and Zaire. Results from a WHO/IAEA joint project.

Concentrations of As, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Sn, V, and Zn were determined in human whole milk samples from Guatemala, Hungary, Nigeria, Philippines, Sweden, and Zaire; in most of these countries, three groups of subjects representing different socioeconomic conditions were studied. Analytical quality control was a primary consideration throughout. The analytical techniques used were atomic absorption spectrophotometry, atomic emission spectrometry with an inductively coupled plasma, colorimetry, electrochemistry, using an ion-selective electrode and neutron activation analysis. The differences between median concentrations of Ca, Cl, Mg, K, Na, and P (minor elements) were lower than 20% among the six countries. Among trace elements, concentrations observed in Filipino milk for As, Cd, Co, Cr, Cu, F, Fe, Mn, Mo, Ni, Pb, Sb, Se, and V were higher than for milk samples from other countries. The remaining five countries showed a mixed picture of high and low values. In the case of at least some elements, such as, F, I, Hg, Mn, Pb, and Se, the environment appears to play a major role in determining their concentrations in human milk. The nutritional status of the mother, as reflected by her socioeconomic status, does not appear to influence significantly the breast milk concentrations of minor and trace elements. Significant differences exist between the actual daily intakes observed in this study and current dietary recommendations made by, for example, WHO and the US National Academy of Sciences. These differences are particularly large (an order of magnitude or more!) for Cr, F, Fe, Mn, and Mo; for other elements, such as, Ca, Cu, Mg, P, and Zn, they amount to at least a factor 2. In the opinion of the present authors, these findings point to the need for a possible reassessment of the dietary requirements of young infants with respect to minor and trace elements, particularly for the elements Ca, Cr, Cu, F, Fe, Mg, Mn, Mo, P, and Zn.

Democratic Republic of the Congo↗
PubMed1990

Effect of temperature on the lactose hydrolytic capacity of a lactase derived from Kluyveromyces lactis.

In vitro studies of lactose hydrolysis in milk with 20-125 neutral lactase units (NLUs) carried out at 38.0 degrees C for 15 min with a beta-galactosidase derived from Kluyveromyces lactis (Lactaid, Lactaid Inc, Pleasantville, NJ) resulted in 85-95% of the hydrolysis observed with standard incubation conditions (24 h at 4-5 degrees C with 1000 NLU/L). Thirty-three lactose-maldigesting Guatemalan subjects, 16 children and 17 adults, were challenged with oral doses of lactose in milk (children aged less than 12 mo, 2 g/kg body wt; children aged 12-24 mo, 15 g/kg body wt; older children and adults, 18 g/kg body wt) preincubated for 20 min at 38 +/- 0.5 degrees C with 50-125 NLU Lactaid. Under these conditions the subjects consumed milk without presenting any signs of intolerance. Furthermore, their breath-hydrogen excretion showed a 91-93% reduction when compared with a similar load of milk containing nonhydrolyzed lactose.

Adult↗
PubMed1986

[Replacement of peanut oil used for the fortification of sugar with vitamin A for other vegetable oils available in Central America].

The objective of this study was to determine the technical feasibility of replacing the peanut oil used in the preparation of the premix to fortify sugar with vitamin A, for other vegetable oils available in Central America. For this purpose, cottonseed, soybean, corn and African Palm oils were tested. Premixes were prepared using each one of the oils and stored for evaluation during a six-month period. A premix prepared with peanut oil was used as a control. It was found that the stability of vitamin A was similar in all premixes; less than 10% of the original activity was lost through the duration of the study. The physical characteristics of the premixes were also acceptable, with the exception of the one containing soybean oil which became caked and rancid. The peroxide content of the oils contained in the premixes increased throughout the study period. The lowest level of oxidation occurred in the premix made with African Palm oil. Its peroxide content changed only from 1.4 to 8.8 mEq/kg of oil. In contrast, that containing soybean oil showed the greatest change in peroxide from 2.8 to 130.0 mEq/kg of oil. It was concluded that it is indeed technically feasible to substitute the peanut oil by another vegetable oil, which should be low in peroxides and of high stability. Furthermore, it should not alter significantly the stability of the vitamin A contained in the premix during storage. On this basis, the African Palm oil was the most suitable one.

Arachis↗
PubMed1984

Significance of postprandial blood concentrations of retinol, retinol-binding protein, and carotenoids when assessing the vitamin A status of children.

The effect of ingesting a breakfast rich in vitamin A on postprandial blood serum concentration of retinol, retinol-binding protein, and carotenoids has been investigated in children between 5 and 8 yr of age. They were divided by age in two groups (5 to 6 and 7 to 8 yr) and then randomly assigned in three groups to be studied cross-sectionally immediately before and at 2 and 4 h after the ingestion of a meal containing 337 micrograms of retinol equivalents (48% as retinol and 52% as carotenoids). The ingestion of breakfast did not alter significantly (p greater than 0.05) the postprandial serum concentrations of retinol, retinol-binding protein; or carotenoids in any of the age groups. These results indicate that up to 4 h the postprandial blood serum concentrations of these parameters are representative of their corresponding basal concentrations. Therefore, in practice and particularly under field survey conditions, the blood samples required to assess the vitamin A status of children can be obtained either fasting or within 4 h after breakfast without altering the results.

Administration, Oral↗
PubMed1984

The effect of dietary lactose on the early recovery from protein-energy malnutrition. II. Indices of nutrient absorption.

Absorption of dietary energy, nitrogen, carbohydrates and calcium, and retention of nitrogen and calcium were studied in 20 children with protein-energy malnutrition of the edematous type, using metabolic balance techniques and breath H2 analysis, to assess the advisability of using lactose-containing formulas in the rehabilitation of severely malnourished children. Ten patients received for 45 days a diet formula based on cows' milk (intact milk) and 10 similar children received the same formula pretreated with beta-galactosidase to hydrolyze the lactose (hydrolyzed milk). Dietary intakes were gradually increased to reach, on the 8th day, 4 g of protein and 150 kcal/kg. There were no differences between groups with respect to absorption or retention of the index nutrients. Postprandial carbohydrate malabsorption was occasionally observed in two patients with servings of the intact milk formula, and in one with the hydrolyzed milk diet. When the nutritional quality of a diet is assessed, the amount of nutrients that are absorbed and utilized are more important than the small, incompletely absorbed fractions that do not have significant metabolic or clinical implications. Therefore, the use of milk as the protein source for recovery diets is not contraindicated in the routine treatment of PEM.

Animals↗
PubMed1984

The mediating role of the parathyroid gland in the effect of low calcium intake on blood pressure in the rat.

Recent reports suggest an inverse relationship between calcium intake and blood pressure. This effect could be mediated by parathormone (PTH), since a low calcium intake leads to an increase in PTH and this hormone produces an increase in intracellular calcium, raising the excitability of the muscle arteriolar cells. Wistar female rats, 56 days old, were submitted to a parathyroidectomy or to a sham operation. After that, they were placed on a normal or on a calcium-free diet during 10 weeks. Four groups of nine rats were studied: parathyroidectomized animals on a normal calcium diet, parathyroidectomized ones on a calcium-free diet, controls (sham operation) on a normal calcium diet, and controls (sham operation) on a calcium-free diet. The control calcium-free diet showed a significant increase in blood pressure values over the treatment period. The parathyroidectomized calcium-free diet group did not show any increase. The difference between these two groups regarding change in blood pressure was statistically significant. The parathyroidectomized-calcium-free group showed no weight increase during the study, while rats in the other three groups significantly increased their weight. PTH could be the mediator of the blood pressure rise observed in the calcium-deprived rats in spite of the possible confounding effect of the poor weight increase detected in the parathyroidectomized-calcium deprived animals. These results warrant future studies since the role of PTH in the regulation of blood pressure needs to be confirmed. This possibility, therefore, opens a new area of research in the study of the pathophysiology of hypertension.

Animals↗
PubMed1983

Reduction of blood pressure with calcium supplementation in young adults.

Epidemiologic and animal studies have suggested an inverse relationship between calcium intake and BP. Furthermore, calcium intake seems to be inversely correlated with the incidence of eclampsia in pregnancy. In a randomized clinical trial, young adults were allocated to a calcium-supplemented group receiving 1 g/day of elemental calcium (15 men and 15 women) or a placebo group (14 women and 13 men) for a period of 22 weeks. The calcium-supplemented group showed a significant decrease in diastolic BP; this effect was stabilized after nine weeks in women and six weeks in men. The reduction in diastolic BP was 5.6% and 9% from the initial values for women and men, respectively. This study supports epidemiologic and animal evidence of the effect of calcium intake on BP and suggests the need for more research exploring the mechanisms involved in the observed effect.

Adolescent↗
PubMed1983

Studies on the bioavailability of zinc in humans: mechanism of the intestinal interaction of nonheme iron and zinc.

The mechanisms of the previously described competitive zinc:iron interaction were explored in healthy human volunteers, using the increment in plasma zinc concentration after an oral dose of 25 mg of zinc as zinc sulfate as the index of zinc absorption. Ferric iron in a 2:1 Fe/Zn ratio reduced the plasma uptake of zinc, but to a significantly lesser degree than ferrous iron; addition of 1 g of ascorbic acid increased the magnitude of the inhibitory effect of ferric iron to that seen with ferrous iron. An inverse relationship between some indices of iron status in adult women, or of parenteral iron administration in a child, and the magnitude of zinc:iron interaction was observed. Saturation of the intestinal mucosa with consecutive-day doses of therapeutic iron did not influence the uptake of zinc administered alone or in the context of a 2:1 ferrous iron:zinc ratio in solution. The results are most consistent with a combination of an intraluminal competition of the two minerals and an intracellular competition at a site "distal" to the regulatory step by which iron nutriture modulates the entry of iron into the body, but "proximal" to the site at which the daily administration of therapeutic doses of iron blocked the passage of dietary iron.

Adult↗
PubMed1982

The effect of temporary venous occlusion on trace mineral concentrations in plasma.

The effects of short-term venous occlusion on plasma concentration of trace minerals--zinc, iron, and copper--were studied in normal volunteers. In one experiment, antecubital vein blood samples were drawn simultaneously from both arms of 14 subjects while their left arms remained free and their right arms had been occluded from 60 s at 40 mm Hg pressure. Statistical comparison of paired samples showed a significant increase in zinc (p less than 0.05) and iron (p less than 0.001), but not copper concentrations in plasma from the occluded extremity. The mean increase in concentration in the right (ligated) arms with respect to the left (unligated) arms was 3.7 and 24.6%, for zinc and iron, respectively. In a second experiment, simultaneous blood samples were drawn from five subjects with neither arm occluded. No significant difference between right and left was observed. Thus, application of tourniquets during the sampling of venous blood for trace mineral analysis introduces a nonrandom factor. Standardization of sampling techniques is essential to overall reliability of trace mineral determinations.

Adult↗