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Biomedical subjects

A Torrado

Publications and source records attributed to A Torrado.

At least 19 recordsLinked to original sources
PubMed2003

The effect of resin particle size on the rate of ion release: interactions in mixed bed systems.

The aim of the present study is to evaluate the influence of resin particle sizes on the rate of ions release from a mixture of ion-exchange resins (named NMTD) which supplies calcium, fluoride, and phosphate ions as the main mineral content, and to elucidate the different phenomena taking place through the related ion-exchange process. The final goal of the study, related to dental application (enamel restoration), is to limit the particle size range, since the rate of ion release is a key parameter in the successful achievement of such objective. Weak-type ion-exchange resins, loaded with the appropriate ions, were ground and sieved into granulometric fractions of bead diameters of 0.1-0.075, 0.075-0.063, and 0.063-0.05 mm. Particle size was controlled by a laser diffraction particle distribution analyzer. The experiments on the kinetics of ions release were carried out under batch conditions in artificial saliva desorption solution thermostatized at 37 degrees C. The release of Ca(2+) and F(-) was determined by corresponding ion-selective electrodes automatically controlled, whereas H(2)PO(4)(-) was measured spectrophotometrically by the inductively coupled plasma-optical emission technique (ICP-OES). The results of this study show that the process of ion-exchange for the different particle size fractions of resins is critical for the study of the kinetics release of the ions immobilized in the corresponding mixed bed polymeric matrices. In fact, despite the apparent narrow range of particle sizes of the mixed bed systems studied, appreciable differences in the rate of ions release are obtained. Since the ion release rate is depending on the contact surface, an increase of factor of 2 in particle size represents an increase of an order of magnitude of the resin contact surface due to the resin porosity. In this concern, it has been observed that the rate of ions release increases when particle size decreases. The interactions occurring during the ion release from the mixed bed resins (containing calcium-, fluoride-, and phosphate-loaded resins) can be interpreted by the following phenomena: H(2)PO(4)(-), which hardly modifies its rate of release in the presence of Ca(2+) and F(-) in the mixture, promotes a considerable increase in the rate of Ca(2+) release due to the formation of a calcium dihydrogen phosphate soluble complex. F(-) also produces an acceleration in the rate of Ca(2+) release due to the formation of solid CaF(2 )on the surface of cationic resin particles, which in contrast leads to a decrease in the rate of F(-) release.

Journal Article↗
PubMed2000

A pericyclic cascade to the stereocontrolled synthesis of 9-cis-retinoids

A domino reaction that is pericyclic in nature is thought to be triggered upon treatment of alkenynol 10 with arylsulfenyl chlorides. The process comprises an ordered sequence of sigmatropic rearrangements: a reversible [2,3]-allyl sulfenate to allyl sulfoxide shift, followed by a [2,3]-propargyl sulfenate to allenyl sulfoxide rearrangement, and last a stereodifferentiating [1,5]-sigmatropic hydrogen migration leading to polyene 13. The occurrence of the C7 to C11 hydrogen migration has been demonstrated by labeling experiments. The double diastereoselection of the [1,5]-sigmatropic hydrogen shift to afford a single isomer of the final polyene 13 is thought to arise from a combination of the electronic effect of the sulfoxide at one terminus, and the steric effect imparted by the bulky trimethylcyclohexenyl substituent at the other terminus. The overall process thus constitutes a stereoselective synthesis of an E,Z,Z-triene fragment from an alkenynol and, in particular, a retinoid with the 7E,9Z,11Z,13E configuration on the conjugated polyenic side chain. Application of this method to the synthesis of retinoids, including labeled analogues, is straightforward.

Journal Article↗
PubMed1988

Osteoglophonic dysplasia: a new case.

A new case of osteoglophonic dysplasia is described in a Portuguese boy. The clinical and radiographic features are similar to the five previously described cases. The boy died suddenly at 10 months of age.

Abnormalities, Multiple↗
PubMed1988

Renal effects of d-tubocurarine and pancuronium in the newborn rabbit.

The acute renal effects of d-tubocurarine and pancuronium were assessed in 14 anesthetized newborn rabbits. Glomerular filtration rate (GFR) and renal blood flow (RBF) were calculated from the inulin and p-aminohippuric acid clearances, respectively. Each animal acted as its own control. At doses used in human neonates, d-tubocurarine administration (0.80 mg/kg) produced a marked increase in renal vascular resistance (+123 +/- 62%) with a concomitant significant decrease in GFR (-35.4 +/- 12%) and RBF (-39 +/- 13%). Pancuronium administration (0.25 mg/kg) was associated with a nonsignificant decrease in GFR (-19 +/- 17%) and RBF (-20 +/- 12%) and an increase in renal vascular resistance (+66 +/- 52%). These results stress the need for careful monitoring of renal function in neonates receiving nondepolarizing muscle-relaxant agents.

Animals↗
PubMed1987

[Evolution of acute transitory renal insufficiency in severe hypernatremic dehydration].

In this study the authors analysed the evolution of blood urea nitrogen in 14 infants during treatment of hypernatremic dehydration. BUN values decreased at a low rate comparing with usual standard limits: a) a correlation between initial BUN and natremia was observed, b) in 9 out of 14 infants there was a transient elevation of BUN, between 5 to 24 hours after the beginning of rehydration, and c) renal function was normal in 8 children who were reevaluated 3 to 28 months after the episode of dehydration.

Acute Kidney Injury↗
PubMed1980

Assessment of glomerular filtration rate in children.

Five different methods of assessment of glomerular filtration rate (GFR) were compared in 500 children older than one year of age. Results of each method were compared with standard inulin clearance values: 1. An evaluation of glomerular function may be inferred from plasma creatinine levels; the validity of this inference is, however, limited because of the wide range of normal values; 2. creatinine clearance values calculated over 3 hours significantly overestimate inulin clearance values; 3. clearance values derived from plasma creatinine concentration ahd height show a poor correlation with traditionally calculated inulin clearances; 4. clearance values calculated as the sum of twice the creatinine clearance and once the urea clearance, divided by three, better predict inulin clearance than either C-creatinine or C-urea alone; 5 inulin clearance values calculated by dividing the quantity of inulin perfused by its plasma concentration, once it has become stable, differ significantly from the values obtained by the standard inulin clearance.--Of all the methods studied, none was found to be an ideal alternative to the traditional inulin clearance when a precise assessment of GFR is warranted. It is concluded that in most clinical conditions derived clearance values do not have significant advantages over the simple determination of plasma creatinine, a valuable but not infallible index of glomerular function.

Adolescent↗
PubMed1979

Single injection clearance in the neonate.

The single injection clearance of inulin was compared to the standard clearance in neonates aged 1--20 days. In the first 3 days of life, the single injection method overestimated glomerular filtration rate by approximately 30%. From the 2nd week of life, values obtained by the two techniques were not significantly different. We conclude that caution should be paid when interpreting results obtained by the single injection technique during the very first days of life.

Age Factors↗
PubMed1979

Maturation of renal function in full-term and premature neonates.

The development of renal function was studied in neonates with gestational ages ranging from 28 to 43 weeks. The effect of gestational age on the maturation of renal function was assessed in newborn infants studied during the first 72 h of life. Postnatal maturation was examined during the first 3 weeks of life. None of these neonates presented any cardiopulmonary or renal disturbances. Inulin and PAH were used as markers of glomerular filtration rate and effective renal plasma flow, respectively. From the 28th to the 35th week of gestation, there is a progressive increase in inulin and PAH clearances (r = 0.93; p less than 0.001 and r = 0.81; p less than 0.005, respectively), which then level off up to the end of gestation. A linear increase in systemic blood pressure is observed during the last 12 weeks of gestation (r = 0.88; p less than 0.001). There is a positive significant correlation between the rise in blood pressure and inulin or PAH clearance (p less than 0.005). Postnatal maturation of renal function is similar in preterm and term neonates. In both groups birth is followed by a sharp rise in inulin and PAH clearances, a twofold increase of these parameters being observed during the first two weeks of life.

Gestational Age↗
PubMed1978

Urinary tract infection in high-risk newborn infants.

The prevalence of neonatal urinary tract infection (UTI) was studied in 1,762 high-risk neonates. Symptomatic bacteriuria was found in 1.9% and asymptomatic bacteriuria in 0.5% of these neonates. Male preponderance was 5:1. Clinical manifestations were extremely variable--vomiting, weight loss, and diarrhea being the prominent symptoms. Bacteremia was associated with UTI in six infants. The organisms identified in the urine obtained by suprapubic aspiration were Escherichia coli, Klebsiella, and Proteus. A mixed infection was found in four patients. Roentgenographic examination of the urinary tract showed abnormalities in 44% of the symptomatic patients. It is conclued that symptomatic high-risk newborn infants should be screened for bacteriuria, and that radiological investigations be preformed in those with proven infection.

Bacteriuria↗
PubMed1976

Renal function in respiratory distress syndrome.

Renal function wa assessed in 20 newborn infants with idiopathic respiratory distress syndrome and compared to that of 10 neonates without respiratory distress or renal disease. Inulin and PAH clearances were markedly depressed in neonates with RDS as compared to controls (5.9 +/- 0.6 vs 9.3 +/- 0.8 ml/min/m2 (p less than 0.01) and 13.5 +/- 2.0 vs 23.2 +/- 1.2 ml/min/m2 ( p less than 0.01), respectively). The impairment of inulin and PAH clearances correlated with the severity of the pulmonary disease. Improvement of the respiratory distress was followed by a progressive rise of inulin and PAH clearances toward normal values. Intravenous administration of hypertonic mannitol in three patients resulted in an immediate increase in urine flow and inulin and PAH clearances. It is concluded that a state of acute, reversible, renal insufficiency can occur in the acute phase of idiopathic respiratory distress syndrome.

Body Weight↗
PubMed1975

Effect of intravenous diazepam on renal function.

The effect of intravenous diazepam on glomerular filtration rate (inulin clearance) and effective renal plasma flow (PAH clearance) was investigated in 6 children and 12 anesthetized rabbits. A transient decrease in inulin and PAH clearances was observed in 6 children given 4 mg of diazepam intravenously, without measurable change in blood pressure. A similar renal effect was observed in anesthetized rabbits, together with a transient drop in systemic arterial pressure. Continuous infusion of diazepam (5 mg/kg/hr) did not affect renal function in rabbits. We suggest that this effect of diazepam should be borne in mind when the drug is administered to patients undergoing renal clearance studies or to patients with preexistent renal insufficiency.

Aminohippuric Acids↗
PubMed1975

Glomerular filtration rate in the first three weeks of life.

Clearances of inulin and para-aminohippuric acid were performed in 22 newborn infants without renal disease. Ages varied from 12 hours to 25 days. The mean values of inulin and PAH clearances during the first four days of life were 10.8 +/- 1.0 ml/min/m2 and 30.8 +/- ml/min/m2, respectively. A twofold increase in glomerular filtration rate was observed during the first 14 days of life. A similar increase in PAH clearance occurred during this period. No correlation was found between gestational age (range: 32 to 39 weeks) and GFR in ten neonates studied during the first four days after birth.

Age Factors↗
PubMed1975

Renal function in obstructive nephropathy: long-term effect of reconstructive surgery.

Renal function was studied in 24 children with chronic hydronephrosis and renal insufficiency. The follow-up period after reconstructive surgery was 1 to 12 years. Glomerular filtration rate (GFR) was assessed by the clearance of endogenous creatinine or inulin. Effective renal plasma flow was assessed by the clearance of PAH. Reconstructive surgery was performed during the first year of life in 12 out of 24 patients, between one and two years of life in 6 patients, and after two years of life in 6 patients. Three different patterns of evolution could be observed after relief of obstruction: (1) An improvement or a normalization of renal function only occurred in patients operated upon before one year of life. (2) A stabilization of renal function without normalization was observed in patients operated upon between one and two years of life. (3) A progressive deterioration of renal function towards terminal renal failure was observed in five out of six patients operated upon after two years of age. This deterioration could not be explained by recurrence of detectable urinary tract infection or urinary stasis. The changes in GRF in four patients with a solitary kidney followed the same pattern. We conclude that it is essential to correct severe chronic hydronephrosis associated with renal insufficiency before one year of age if a lasting improvement of renal function is to be expected.

Child, Preschool↗