PubMed Health⌕ Search

Biomedical subjects

J A Delgado

Publications and source records attributed to J A Delgado.

18 recordsLinked to original sources
PubMed2004

Fabrication of low temperature macroporous hydroxyapatite scaffolds by foaming and hydrolysis of an alpha-TCP paste.

The development of the new technologies of bone tissue engineering requires the production of bioresorbable macroporous scaffolds. Calcium phosphate cements are good candidate materials for the development of these scaffolds, as an alternative to the traditional porous sintered ceramics. In this work a novel two-step method, based in the foaming of an alpha-tricalcium phosphate (alpha-TCP) cement paste and its subsequent hydrolysis to a calcium deficient hydroxyapatite (CDHA) is presented. The foaming agent was a hydrogen peroxide (H2O2) solution, which decomposes in water and oxygen gas. CDHA foams, which combined an interconnected macroporosity with a high microporosity were obtained. The apatitic phase obtained by the hydrolysis reaction was more similar to the biologic one, in terms of chemical composition, crystallinity and specific surface than the hydroxyapatites obtained by sintering. The percentage of porosity in the foams reached a 66%. It was shown that it was possible to control the porosity, and pore size and shape by different processing parameters such as the liquid-to-powder ratio, the concentration of the H2O2 solution and the particle size of the powder.

Biocompatible Materials↗
PubMed2004

Propagation of fatigue cracks in acrylic bone cements containing different radiopaque agents.

In this work three iodine-containing monomers were proposed as new radiopaque agents for acrylic bone cements. In previous studies the addition of iodine-containing methacrylate monomers provided a statistically significant increase in tensile stress, fracture toughness and ductility, with respect to the barium sulphate (BaSO4)-containing cement. However, since fatigue resistance is one of the main properties required to ensure a good long-term performance of permanent prostheses, it is important to compare the fatigue properties of these new bone cement formulations with the radiolucent and BaSO4-containing bone cements. Because the acrylic cements have initial cracks, fatigue crack propagation studies were performed. It can be observed that these acrylic cements followed the Paris-Erdogan model. The results showed that the addition of some organic radiopacifiers (DISMA, TIBMA) increased the fatigue crack propagation resistance as compared to the radiolucent cement, being similar to the BaSO4-containing cement. The radiolucent cement showed a low crack propagation resistance.

Complex Mixtures↗
PubMed2002

Comparison of adsorption equilibrium and kinetics of four chlorinated organics from water onto GAC.

This study deals with the adsorption of four chlorinated pollutants onto GAC (F-400); two pesticides (lindane and alachlor) and two PCB congeners: 2-PCB (MPCB) and 2,2',5,5'-PCB (TPCB). Equilibrium and kinetic parameters have been obtained for the adsorption of alachlor and each PCB. whereas the kinetic results for lindane presented elsewhere (Proc. First World Water Congr. Int. Water Assoc., Texts of Posters, CD-ROM, AGHTM, Paris, 2000) are reanalyzed in this work. A model assuming a bidisperse structure (macro- and micropores). each region having a different adsorption isotherm, is used to study the adsorption kinetics in a batch system in the period dominated by macropore diffusion. Both the saturation capacity and the rate of internal transport of TPCB are much lower than those of the other solutes. This difference is attributed to a chemisorption mechanism for this compound, which is favored by its very low solubility.

Acetamides↗
PubMed2002

Subclinical pain and thermal sensory dysfunction in children and adolescents with Type 1 diabetes mellitus.

AIMS: To assess cutaneous thermal and pain thresholds in upper and lower limbs in neurologically asymptomatic children and adolescents, and to study the relationships of clinical parameters and these sensory thresholds in subclinical diabetic neuropathy. METHODS: Thirty-five neurologically asymptomatic patients, aged 8-16 years, diagnosed with Type 1 diabetes mellitus (DM), and a control group of 35 healthy age-matched subjects participated in the study. Warmth, cold, and heat-induced pain thresholds were measured in the dorsum of the right arm and foot, using quantitative sensory testing (QST). Relevant clinical parameters, retrieved from medical records or measured at the QST session, were obtained for each patient. RESULTS: Compared with controls, diabetic patients had increased thresholds for warmth in the hand (P = 0.002), and cold and warmth in the foot (P = 0.015 and P = 0.004, respectively). Of the diabetic patients, 43% showed abnormality of at least one sensory threshold. A significant correlation was observed for duration of diabetes and heat-induced pain threshold in the hand (P = 0.045), but no correlation was found for age, height, weight, pre-test blood glucose, age of onset, current insulin dose, and mean of glycosylated haemoglobin determinations of the previous 18 months. No significant correlation was found for other sensory thresholds. CONCLUSIONS: Using QST, abnormal cutaneous thermal perception is a common finding, in both upper and lower limbs, in neurologically asymptomatic young diabetic patients. Heat-induced pain threshold in the hand was correlated with the duration of the diabetes.

Adolescent↗
PubMed2001

[Cutaneous horn of the penis].

OBJECTIVE: To describe a case of cutaneous horn of the penis and review its clinical and histological features. METHODS: The clinical and histological features of cutaneous horn of the penis are described. RESULTS/CONCLUSIONS: Cutaneous horn of the penis is an uncommon lesion that is diagnosed without difficulty. Treatment is by surgery with sufficient margins due to its possible association with malignant lesions.

Aged↗
PubMed2000

Endothelium-independent relaxation induced by histamine in human dorsal penile artery.

1. In vitro preparations of human dorsal penile arteries were used to evaluate the effect of histamine and to characterize the histamine receptors involved in the response. 2. Cumulative administration of histamine induced a concentration-dependent relaxation in precontracted arteries. The H1 receptor agonist 2-pyridylethylamine induced a biphasic response: contraction followed by dilation. The H2 receptor agonist dimaprit produced a marked relaxation. Mepyramine, a histamine H1 receptor antagonist, led to a slight but statistically significant change in the pD2 value corresponding to the relaxant phase of the H1 receptor agonist and the histamine curve. The H2 receptor antagonist cimetidine induced a marked shift in the dimaprit concentration-response curve without affecting the maximum response. Incubation with cimetidine led to a considerable loss in the sensitivity of the arteries to histamine and in the maximum relaxation. Combined treatment with histamine H1 and H2 receptor antagonists resulted in an additional displacement compared with the effect of each antagonist alone on the histamine response. The effects observed using a histamine H3 receptor agonist and antagonist suggest that the involvement of this receptor is unlikely. 3. Removal of the endothelium was unable to reverse the histamine response. Pretreatment with NG-nitro-L-arginine methyl ester, L-arginine and indomethacin had no effect on the histamine control curve. 4. In conclusion, the vasodilation of human dorsal penile artery induced by histamine seems to be mainly mediated by muscular histamine H2 receptors, without the intervention of key intracellular mediators, such nitric oxide or relaxant prostanoids. A minor population of relaxant histamine H1 receptors cannot be excluded.

Adolescent↗
PubMed1999

Zirconia-toughened hydroxyapatite ceramic obtained by wet sintering.

A toughened hydroxyapatite (HA) ceramic has been obtained through the incorporation of magnesia partially stabilized zirconia (Mg-PSZ) under uniaxial pressing and sintering in wet oxygen at 1250 degrees C for 4 h. The powder X-ray diffraction (XRD) patterns and infrared spectra (FT-IR) show that HA is the only calcium phosphate phase present. The composite (MgPSZ-HA) has a density of 94% the theoretical value. The bending strength and the fracture toughness are around 50% higher for Mg-PSZ reinforced than for HA. The grain size and the fracture surface were studied by scanning electron microscopy (SEM). The influence of the Mg-PSZ particles on the fracture mechanism of the HA ceramic is discussed.

Journal Article↗
PubMed1997

Complex behavior of marine animal tissue extracts in the competitive binding assay of brevetoxins with rat brain synaptosomes.

Brevetoxins are produced by the marine dinoflagellate Ptychodiscus brevis, an organism linked to red tide outbreaks, and the accompanying toxicity to marine animals and to neurotoxic shellfish poisoning in humans. Brevetoxins bind with high affinity to voltage-sensitive sodium channels and cause increased sodium ion conductance and nerve cell depolarization. The brevetoxin competitive binding assay with tritium-labeled brevetoxin 3 (3H-PbTx-3) and rat brain synaptosomes is a sensitive and specific assay for pure brevetoxins. Here we report that extracts of manatee, turtle, fish, and clam tissues contain components that interfere with the assay by cooperative, noncompetitive inhibition of 3H-PbTx-3 specific binding and increased nonspecific binding to synaptosomes. By determining the "apparent" toxin concentration ("[Toxin]") in the extract at several assay concentrations, a reasonable correction for the complex inhibition could be made using a semilog plot to extrapolate [Toxin] to zero extract concentration to obtain [Toxin]0. Spiking 4 extracts with 60 nM PbTx-3 caused [Toxin]0 to increase by 41 +/- 8 nM, indicating that the noncompetitive components did not prevent the assay of toxin but did reduce the accuracy of the result. Fourfold repetition of the assay of 4 samples gave standard deviations of 25 to 60% of the value of [Toxin]0, so the error can be fairly large, especially for samples with little toxin. Purification of an extract with a 1 g sample prep column of C-18 decreased the complex inhibition by about 3-fold but did not eliminate interference in the assay.

Animals↗
PubMed1997

Nitric oxide is involved in the inhibitory neurotransmission and endothelium-dependent relaxations of human small penile arteries.

1. Alteration in the flow of blood to the penis is thought to be the most frequent organic cause of erectile dysfunction or impotence. However, information concerning the penile small arteries (helicine arteries) which control blood flow between the arterial systemic circulation and the cavernous sinusoids is scarce. Therefore, the purpose of the present study was to investigate the involvement of nitric oxide, which is considered to be the main neurotransmitter in corpus cavernosum, in both the non-adrenergic non-cholinergic inhibitory neurotransmission and the endothelium-dependent responses in human penile small arteries. 2. Penile small arteries (lumen diameter 200-700 microns), which were branches of the human deep penile arteries obtained either from patients undergoing penile surgery or from organ donors, were mounted in microvascular myographs for isometric tension recording and electrical field stimulation was performed in the presence of guanethidine and atropine to block adrenergic neurotransmission and muscarinic receptors, respectively. 3. In phenylephrine-contracted penile small arteries, electrical field stimulation (0.5-32 Hz) induced frequency-dependent relaxations of both endothelium-intact and -denuded preparations. The inhibitor of nitric oxide synthase, NG-nitro-L-arginine (3 x 10(-5) mol/l), abolished the relaxations at the lowest frequencies, while slow-developing relaxations were still observed at high frequencies (16 and 32 Hz). The inhibitory effect of NG-nitro-L-arginine was reversed in the presence of L-arginine (3 x 10(-3) mol/l). Tetrodotoxin totally abolished the relaxations to electrical field stimulation. In contracted small penile arteries in the presence of NG-nitro-L-arginine, the nitrovasodilator sodium nitroprusside induced potent relaxations. 4. The endothelium-dependnet vasodilator acetylcholine induced relaxations of penile small arteries, which were only partially reduced in the presence of NG-nitro-L-arginine. In contrast, the relaxations to acetylcholine of trabecular corpus cavernosum preparations were almost abolished in the presence of NG-nitro-L-arginine. 5. The present study suggests that relaxations of human intracavernosal small penile arteries induced by non-adrenergic non-cholinergic nerve stimulation partially involve nitric oxide and also another inhibitory transmitter causing relaxations resistant to nitric oxide synthase blockade. In addition, endothelium-dependnet relaxations in human small penile arteries are mediated by both nitric oxide and a factor resistant to NG-nitro-L-arginine.

Acetylcholine↗
PubMed1996

Headache of recent onset in adults: a prospective population-based study.

One hundred consecutive adult patients with headache of recent onset were prospectively studied. Every patient was examined by craneal CT scan. Their mean age was 46 years (range 17-82). Neurological examination was normal in 80 patients. Organic headache represented 39% of the entire group, and 26% of them had a normal neurological examination. The yield of CT scan in patients with headaches and a normal neurological examination was 22.5% (95% IC: 14%-33%); of which we encountered the following pathologies: intracranial tumors (13), hydrocephalus (2), arachnoid cyst (1), toxoplasmic abscess (1) and parenchymal hemorrhage (1). The clinical characteristics of the headache on their own was insufficient to rule out the possibility of an intracranial tumor. Neuroimaging studies should be performed in all adult patients with non-vascular headache of recent onset, and previously headache-free individuals.

Adolescent↗
PubMed1993

Diagnosis of X-adrenoleucodystrophy phenotypic variants.

We report the radiological and biochemical data of a familial X-adrenoleucodystrophy with an extreme phenotypic variability, in which the diagnosis of several affected members was delayed for several years. The propositus developed a progressive dementia, while two of his brothers were diagnosed of primary Addison's disease several years previously. MRI in two cases with different phenotypes revealed hyperintense diffuse white matter lesions, and the diagnosis was confirmed by increased serum levels of very long chain fatty acids. We conclude that X-adrenoleucodystrophy should be included in the differential diagnosis of adult Addison's disease even though no neurological involvement or family history is recorded, and that MRI is a useful tool for diagnosis and follow-up of neurological involvement in this disease.

Addison Disease↗
PubMed1992

[Carcinoma of the penis. Our experience with 22 cases].

The penis carcinoma is a neoplasia representing 0.7% of all male neoplasias, with an annual incidence between 1 and 2 cases per 100,000 inhabitants/year. The present study compiles the authors' experience in treating 22 patients presenting this neoplasia in the period between 1977-90. The procedures carried out included local resection, partial amputation, radical penectomy with lymphadenectomy plus radiotherapy, and palliative surgery plus radiotherapy all based on staging made following TNM grading. Therapy complications, follow-up, and survival results are explained. There were 5 occasions of spinocellular carcinoma co-existing with other neoplasias: 1 colon adenocarcinoma, 1 prostate carcinoma, 1 cleaved small cell centrocytic diffuse lymphoma, and 2 skin epithelioma in other sites, and relevant literature was reviewed. A background of psoriasis treated with psoralens plus UV was present in 4 cases, and caution was advised towards genital protection in patients undergoing UV radiations whether for therapeutic, recreational or cosmetic reasons.

Adult↗
PubMed1987

[Effectiveness and tolerance of the treatment of infantile bronchial asthma with soluble and delayed-action theophylline].

Twenty-seven asthmatic children have been studied in the phase between crises. According to treatment they have been grouped in treated with soluble theophylline and treated with retard theophylline. Initial oral dose was for both groups of 16 mg/kg/day. Three stages have been considered in every patient: control, at 7 days and at 21 days, performing at each time a clinical (symptoms), functional (spirometry) and analytical evaluation (theophylline blood levels). Following results were obtained: Both frequency and intensity of clinical symptoms are progressively reduced along the study. This reduction is more apparent with retard theophylline, that shows a positive significant correlation (p less than 0.05) between blood level-forced vital capacity after 7 days and blood-level-peak flow after 21 days. Incidence of undesired drug effects is comparable in both groups. The number of children showing no adverse drug effects was greater in group of retard theophylline, however, number of adverse drug effects child was greater in this group. Theophylline mean doses required to attain clinical efficacy are similar in both groups. Neither soluble nor retard theophylline provide a mean blood level in therapeutic range after 7 days, however retard theophylline does so after 21 days.

Asthma↗
PubMed1986

Measurement of body fat in Turner syndrome.

Fourteen individuals with the Turner syndrome (gonadal dysgenesis with X chromosome chromosome abnormalities) were evaluated for obesity using hydrostatic weighing and skinfold measurements. While skinfold estimates of body fat correlated well with clinical impression, hydrostatic weighing appeared to falsely overestimate percent body fat. We suggest that reduced skeletal mass and/or occult lymphedema in Turner syndrome may invalidate the formula used to calculate percent body fat derived from hydrostatic weights. In this population and possibly in other disorders where skeletal mass is reduced from the normal, the use of hydrostatic weighing may be inappropriate.

Adult↗
PubMed1970

A field on Che.

Explore the source record for details and available documents.

Argentina↗