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Biomedical subjects

Antonio Navarro

Publications and source records attributed to Antonio Navarro.

9 recordsLinked to original sources
PubMed2003

Hydroxyapatite coating of external fixation pins to decrease axial deformity during tibial lengthening for short stature.

BACKGROUND: Tibial valgus, a known complication of leg lengthening with external fixation techniques, has been related to the stability of the bone-fixator system and, in particular, to pin loosening. A hydroxyapatite coating has been reported to enhance the quality of the bone-pin interface. The aim of this study was to compare the prevalence of axial deformity after tibial lengthening with hydroxyapatite-coated external fixation pins with the prevalence after tibial lengthening with uncoated pins. METHODS: We conducted a prospective study of thirty-four symmetrical tibial lengthening procedures in seventeen pathologically short patients. One limb of each patient was lengthened with use of hydroxyapatite-coated pins and the other, with standard uncoated pins; the sides of the operations were randomly selected. The bone angle in the frontal plane was measured before the operation and at the end of the fixation period, and the difference between these measurements was compared between the lengthening procedures performed with coated pins and those performed with uncoated pins. RESULTS: The mean valgus deviation of the tibia was 6.5 degrees in the group treated with hydroxyapatite-coated pins and 12.5 degrees in the group treated with uncoated pins (p = 0.023). With the numbers available, other factors previously related to the development of valgus deformity did not differ significantly between the two groups. CONCLUSION: Tibiae that are lengthened with the use of hydroxyapatite-coated external fixation pins are less prone to axial deviation in the frontal plane than are those treated with uncoated pins. LEVEL OF EVIDENCE: Therapeutic study, Level I-1a (randomized controlled trial [significant difference]). See Instructions to Authors for a complete description of levels of evidence.

Adolescent↗
PubMed2002

Studies on the mechanism of action of azinomycin B: definition of regioselectivity and sequence selectivity of DNA cross-link formation and clarification of the role of the naphthoate.

Evaluation of the sequence selectivity, noncovalent association, and orientation of the DNA cross-linking agent azinomycin B on its duplex DNA receptor is described. A strong correlation between sequence nucleophilicity and cross-linking yield was observed, and steric effects due to the thymine C5-methyl group were identified. Detailed studies on the role of the azinomycin naphthoate using viscometry, fluorescence contact energy transfer, and DNA unwinding assays point to a nonintercalative binding mode for this group. A kinetic assay for agent regioselectivity was used to determine the orientation of binding and covalent cross-link formation.

Anti-Bacterial Agents↗
PubMed2002

Role of the azinomycin naphthoate and central amide in sequence-dependent DNA alkylation and cytotoxicity of epoxide-bearing substructures.

Studies report a strong correlation between duplex DNA alkylation and in vitro cytotoxicity for a series of azinomycin partial structures 2-6 bearing the biologically relevant epoxide. Compounds lacking the naphthoate ester (e.g., 5 and 6) were poorly reactive toward DNA and were biologically inactive, as were compounds bearing the naphthoate but lacking the terminal carboxamide (e.g., 2). Compounds were evaluated for cytotoxicity against two breast cancer cell lines. [structure: see text]

Alkylation↗
PubMed2002

New strategy for the stereoselective synthesis of fluorinated beta-amino acids.

Racemic and chiral nonracemic alpha-substituted and alpha-unsubstituted beta-fluoroalkyl beta-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained gamma-fluorinated beta-enamino esters 4 by using ZnI(2)/NaBH(4) in a nonchelated aprotic medium (dry CH(2)Cl(2)) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction of chiral beta-enamino esters 4 were provided by the use of (-)-8-phenylmenthol as a chiral auxiliary.

Amino Acids↗
PubMed2002

[Testing a new in-office test for determination of faecal Helicobacter pylori antigen].

BACKGROUND: To date, the search for an in-office reliable test for Helicobacter pylori infection has been unsuccessful. The aim of the present study was to evaluate a new immunocromatographic in-office test using monoclonal antibodies to determine the presence of Helicobacter pylori antigen in faeces (Stick H. pyl, Operon S.A. Zaragoza). We compared its reliability and reproducibility to the currently available test (HpSA, EIA, Premier Platinum HpSA, Meridian Diagnosis Inc, Cincinnati, Ohio). PATIENTS AND METHOD: 71 consecutive dyspeptic patients were enrolled. Helicobacter pylori status was determined by rapid urease test and Giemsa stain of antral biopsy. Patients with a positive result in the two tests were considered as infected and those with a negative result in both tests were regarded as not infected. Faecal Helicobacter pylori antigen was tested twice by means of HpSA. Four consecutive determinations of Stick H. pyl were also performed. We calculated sensitivity, specificity and positive and negative predictive values of each determination. Concordance between determinations was estimated by the kappa statistics. RESULTS: Forty-eight of 68 patients were infected by Helicobacter pylori. Sensitivity, specificity and positive and negative predictive values were 89-96%, 60-70% 85-88% and 74-87%, respectively, for Stick H. pyl and 70-75%, 60-85%, 85-92% and 55-80%, respectively, for HpSA. Correlation coefficients were 0.82-0.93 for Stick H. pyl and 0.57 for HpSA. CONCLUSIONS: The new Stick H. pyl test shows excellent sensitivity and reproducibility for diagnosis of H. pylori infection. Its reliability appears to be far better than that of HpSA.

Adolescent↗
PubMed2002

Studies of piroxicam absorption by oral mucosa.

The present study was undertaken to investigate, if the non-steroidal anti-inflammatory drug (NSAID) piroxicam (CAS 36322-90-4) Fast-Dissolving Dosage Form (FDDF) can be absorbed in the oral mucosa. Piroxicam FDDF was administrated under the tongue to rats with an oesophagus ligation (OL) to prevent the drug entering the stomach and in turn its absorption by the classic way. A group of sham-operated (SO) animals received the same piroxicam FDDF dose. After drug administration, a pharmacokinetic study with serial serum sample extractions at 0, 15, 30, 60 and 120 min was performed. It has been found a prompt increase in serum piroxicam levels in OL-rats, which showed different pharmacokinetics from SO-rats. Areas under curve (AUCs) of OL-rat serum piroxicam levels were higher at 15, 30 and 60 min compared to SO-animals. These results indicate that piroxicam FDDF is absorbed in the rat oral mucosa. Moreover, during the first hour, drug absorption by oral mucosa rendered higher piroxicam levels than gastric absorption.

Absorption↗
PubMed1998

Two Practical and Efficient Approaches to Fluorinated and Nonfluorinated Chiral beta-Imino Sulfoxides.

Reaction of fluorinated and nonfluorinated N-substituted imidoyl chlorides 1 with lithium derivatives of enantiopure methyl p-tolyl sulfoxide 2a (or racemic methyl phenyl sulfoxide 2b) gave a wide variety of chiral N-substituted beta-imino sulfoxides 4 in good to excellent yields. The title compounds (R)-4 were also prepared by aza-Wittig reaction of gamma-fluoro-beta-keto sulfoxides (R)-5 and N-aryl iminophosphoranes 6. The imino-enamino equilibrium was studied, showing, in all instances, the imino form as the predominant tautomer independent of the nature of the N-substituent. The configuration of the C=N double bond was found to be Z for both N-alkyl and N-aryl derivatives on the basis of (1)H NMR NOE difference experiments performed over several compounds. Ab initio calculations (HF/6-31G) carried out on several representative examples of 1 and 4 are, in general, consistent with the experimental results.

Journal Article↗
PubMed1996

An Efficient and Simple Entry to N-Substituted beta-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines.

Reaction of azaenolates of 2-alkyl-oxa(thia)zolines 6 with imidoyl chlorides 7 as electrophiles to furnish masked N-substituted beta-enamino acid derivatives 1-2 in 70-90% yield is described. Alternative routes are discussed. Compounds 1-2 generally appear in one tautomeric form, imino or enamino, depending on the nature of the imidoyl chloride. The configuration of the enamino moiety (Z) and the conformation (s-cis) of compounds 1-2 obtained were established by an NMR study and unequivocally set by nuclear Overhauser effect difference experiments. An X-ray structure of compound 1e is also reported, showing a strong intramolecular NH.N hydrogen bond. Ab initio calculations (HF/3-21G and HF/3-21+G) have been carried out on several representative examples (1e, 1p, and 1l) in an attempt to support and provide the correct geometry of these derivatives. Structural considerations among the possible isomers of compounds 1 are discussed. From these studies it was concluded that the theoretical calculations agree with the experimental results. In addition, a very simple one-pot procedure for the preparation of masked N-substituted alpha-alkylated beta-enamino acid derivatives 2 from 6, 7, and different alkyl halides (R(3)Y) is described.

Journal Article↗