The population's aging: a challenge, an obligation, and an opportunity in Latin America.
Explore the source record for details and available documents.
Aged↗
Biomedical subjects
A F Rodriguez
Publications and source records attributed to A F Rodriguez.
Artificial neural network Radon inversion for image reconstruction.
Image reconstruction techniques are essential to computer tomography. Algorithms such as filtered backprojection (FBP) or algebraic techniques are most frequently used. This paper presents an attempt to apply a feed-forward back-propagation supervised artificial neural network (BPN) to tomographic image reconstruction, specifically to positron emission tomography (PET). The main result is that the network trained with Gaussian test images proved to be successful at reconstructing images from projection sets derived from arbitrary objects. Additional results relate to the design of the network and the full width at half maximum (FWHM) of the Gaussians in the training sets. First, the optimal number of nodes in the middle layer is about an order of magnitude less than the number of input or output nodes. Second, the number of iterations required to achieve a required training set tolerance appeared to decrease exponentially with the number of nodes in the middle layer. Finally, for training sets containing Gaussians of a single width, the optimal accuracy of reconstructing the control set is obtained with a FWHM of three pixels. Intended to explore feasibility, the BPN presented in the following does not provide reconstruction accuracy adequate for immediate application to PET. However, the trained network does reconstruct general images independent of the data with which it was trained. Proposed in the concluding section are several possible refinements that should permit the development of a network capable of fast reconstruction of three-dimensional images from the discrete, noisy projection data characteristic of PET.
Algorithms↗
An open study to compare azithromycin with cefaclor in the treatment of children with acute otitis media.
An open, multicentre study involving 259 children between 6 months and 13 years of age was performed to assess the efficacy and safety of azithromycin and to compare it with cefaclor as treatment of acute otitis media. Patients were randomized to receive either azithromycin 10 mg/kg once daily for 3 days or cefaclor 40 mg/kg daily in divided doses every 8 h for 10 days. Cure or improvement in signs and symptoms was observed in 112/114 (98%) evaluable azithromycin-treated patients and 116/120 (97%) evaluable cefaclor-treated patients on days 11-15. In contrast to cefaclor, however, azithromycin was associated with a significantly (P = 0.033) higher cure rate 1 month after completion of treatment. In those patients who were followed up to days 25-30, the response was satisfactory (cure or improvement) in 31/32 (97%) patients who had received azithromycin and in 31/36 (86%) to whom cefaclor had been administered. Patients tolerated both treatments well and no severe adverse events related to therapy were recorded in either group. The results of this study show that a 3-day, once-daily regimen of azithromycin has comparable clinical efficacy and tolerability to a thrice-daily course of cefaclor administered for 10 days, but the azithromycin is associated with a lower incidence of relapse.
Acute Disease↗
Comparison of derivatization procedures for the determination of diuretics in urine by gas chromatography-mass spectrometry.
Three different GC-MS screening procedures, which use different ways of derivatization (methylation), are compared. In the first one, derivatization with iodomethane in acetone and a previous solid-liquid extraction is used; the second one is based on an extractive alkylation method using iodomethane in toluene (liquid-liquid extraction); and the last one is flash methylation by pyrolysis of tetraalkylammonium salts in the injector of the gas chromatograph using trimethylanilinium as the derivatization agent. The speed of the extraction, reproducibility and accuracy have been compared for 20 diuretics including the ones most often used in sports, such as bumetanide, ethacrynic acid, acetazolamide, dichlorphenamide, furosemide, hydroflumethiazide, hydrochlorothiazide and chlorthalidone; they have also been applied to the two uricosuric agents probenecid and benzbromarone.
Diuretics↗
Determination of ephedrines in urine by high-performance liquid chromatography.
An improved high-performance liquid chromatographic method with ultraviolet detection for the simultaneous determination of norephedrine, norpseudoephedrine, ephedrine, pseudoephedrine, methylephedrine and ethylephedrine in urine is described. The six substances were separated on a reversed-phase column with phosphate buffer-triethylamine (pH 5.5) as the mobile phase. The linearity and reproducibility were satisfactory for the levels usually found in urine (1-30 micrograms/ml).
Chromatography, High Pressure Liquid↗
Hematogenous pneumococcal meningitis in the infant rat: description of a model.
Sensorineural deafness occurs in 20%-30% of children after Streptococcus pneumoniae meningitis. An infant rat model of S. pneumoniae meningitis was developed to study the pathogenesis of inner ear invasion by S. pneumoniae. S. pneumoniae type 6 was administered intraperitoneally (inoculum: 1-10 x 10(8) cfu) every 24 h for 3 days to 5-day-old rats. Bacteremia (12 [50%] of 24) and meningitis (11 [46%] of 24) were detected most frequently 4 days after the three doses. The mean cerebrospinal fluid (CSF) white blood count for rats with positive CSF cultures was 7271/mm3 (range, 81-20,475). Hematoxylin-eosin-stained brain tissue from the 11 rats with positive CSF cultures showed inflammation in the meninges and scala tympani in 9 each (82%), and scala vestibuli in 6 (55%), but none in the scala media. Gram's-stained brain and inner ear sections from the same 11 rats showed organisms in the meninges in 5 (45%) and scala tympani or vestibuli in 2 (18%). Perilymphatic inflammation occurred significantly (P less than .001) more than did endolymphatic inflammation.
Animals↗
Effect of dexamethasone or HWA-138 in combination with antibiotics in experimental Haemophilus influenzae type b infection.
Modulation of the host's inflammatory response in bacterial meningitis may be beneficial. In this study, the effects of dexamethasone and HWA-138, an analog of pentoxifylline, on CSF cultures and cochlear inflammation in an infant rat model of Haemophilus influenzae type b were studied. Five-day-old infant rats were inoculated once intraperitoneally with 1 x 10(4) to 10 x 10(4) CFU of H. influenzae type b (strain 1406). Twenty-four hours later, infant rats were treated intraperitoneally with one dose of ampicillin (0.1 mg/g of body weight), cefotaxime (0.05 mg/g), or cefuroxime (0.05 mg/g) alone or in combination with one dose of dexamethasone (0.00015 mg/g) or HWA-138 (0.005 mg/g). Twenty-four hours after treatment with cefuroxime plus dexamethasone, animals had a significantly (P less than or equal to 0.04) greater incidence of bacteremia and meningitis (eight of nine animals) than that in animals of the other treatment groups. Overall, dexamethasone was associated with less inflammation (P less than 0.04) of the cochlear nerve compared with that from antibiotic treatment alone. In this model, when suboptimal antimicrobial therapy is administered, anti-inflammatory agents may be beneficial with respect to reducing cochlear inflammation. However, dexamethasone and cefuroxime lead to a higher rate of positive blood and cerebral spinal fluid cultures than cefuroxime alone.
Ampicillin↗
Cerebrospinal fluid values in the very low birth weight infant.
The cerebrospinal fluid values obtained in the first 12 weeks of life from 43 infants with birth weights of 1500 gm or less were analyzed to determine the ranges for leukocyte count and chemistry values. All these neonates had birth weights appropriate for gestational age, negative cerebrospinal fluid culture for bacteria, and no evidence of intracranial bleeding by head ultrasound examination. The mean birth weight was 1002 gm (range 550 to 1500 gm), and mean gestational age was 27 weeks (range 24 to 33 weeks). The mean cerebrospinal fluid leukocyte count was 5 cells/mm3 (range 0 to 44 cells/mm3); leukocyte differential was 7% polymorphonuclear leukocytes (range up to 66%) and 85% mononuclear leukocytes (range 13% to 100%). Additional values included protein concentration, 142 mg/dl (range 45 to 370 mg/dl); and glucose, 60 mg/dl (range 29 to 217 mg/dl). Knowledge of these measurements should help in the interpretation of the cerebrospinal fluid values of the very low birth weight infant undergoing examination of a central nervous system disorder.
Birth Weight↗
Evaluation of the Technicon H-1 hematology analyzer in febrile children.
Explore the source record for details and available documents.
Child, Preschool↗
Characterization of laminin-stimulated adherence and motility in tumor cells.
Laminin was shown to stimulate attachment, spreading and motility in a line of murine tumor cells. The stimulated cells began to attach and spread within 1 h and remained attached and spread throughout a 48-hour observation period. Pretreatment of the cells with laminin for 24 h beforehand did not interfere with their ability to bind laminin in a second treatment. Laminin-stimulated attachment and spreading occurred in the absence of extracellular Ca2+ or Mg2+, but not in the absence of both divalent cations. A number of cell function inhibitors blocked the adherence response, but were only partially effective even at high concentrations. These characteristics of laminin-stimulated adherence are different from those of the adherence response stimulated by peptide chemotactic factors and phorbol esters.
Animals↗