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Biomedical subjects

M Navarro

Publications and source records attributed to M Navarro.

At least 91 records · Page 5Linked to original sources
PubMed2001

Effectiveness of the ProFile.04 Taper Series 29 files in removal of gutta-percha root fillings during curved root canal retreatment.

The purpose of this in vitro study was to evaluate the capacity of ProFile.04 Taper Series 29 files to remove gutta-percha during curved root canal retreatment. Forty-four mandibular molars whose mesial roots presented between 26 and 40 degrees of curvature, determined by Schneider's method, were selected. The root canals were enlarged to ISO size 35 and obturated with laterally condensed gutta-percha using Sealer 26. The teeth were randomly divided into three groups for gutta-percha removal: GI: size 2 Gates Glidden drills; GII: size 6 ProFile.04 Taper Series 29 files; GIII: size 7 ProFile.04 Taper Series 29 files. The penetration of the instruments was measured with millimetered x-rays and clinical observation. The ProFile.04 Taper Series 29 files removed the endodontic filling material better than the Gates Glidden files.

Analysis of Variance↗
PubMed2001

Usefulness of saliva for measurement of 3,4-methylenedioxymethamphetamine and its metabolites: correlation with plasma drug concentrations and effect of salivary pH.

BACKGROUND: Saliva is an alternative biologic matrix for drugs-of-abuse testing that offers the advantages of noninvasive, rapid, and easy sampling. We studied the excretion profile of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolites in both saliva and plasma, as well the effect of the drug on salivary pH. METHODS: Saliva and plasma samples were obtained from eight healthy MDMA consumers after ingestion of a single 100-mg dose of the drug. Concentrations of MDMA and its main metabolites, 3,4-methylenedioxyamphetamine (MDA) and 4-hydroxy-3-methoxymethamphetamine (HMMA), in saliva and plasma were measured by gas chromatography-mass spectrometry. Apparent pharmacokinetic parameters for MDMA in saliva were estimated, and the saliva-to-plasma ratio at each time interval was calculated and correlated with salivary pH. RESULTS: MDMA, MDA, and HMMA were detected in saliva. Salivary concentrations of MDMA were 1728.9-6510.6 microg/L and peaked at 1.5 h after drug intake. This was followed by a progressive decrease, with a mean concentration of 126.2 microg/L at 24 h. The saliva-to-plasma ratio was 32.3-1.2, with a peak of 18.1 at 1.5 h after drug administration. Salivary pH seemed to be affected by MDMA administration; pH values decreased by 0.6 units (mean pH values of 6.9 and 6.8 at 1.5 and 4 h after drug administration vs predose pH of 7.4). CONCLUSIONS: Measurement of MDMA in saliva is a valuable alternative to determination of plasma drug concentrations in both clinical and toxicologic studies. On-site testing is also facilitated by noninvasive and rapid collection of salivary specimens.

3,4-Methylenedioxyamphetamine↗
PubMed2001

Calcium fluoride uptake by human enamel after use of fluoridated mouthrinses.

The aim of this study was to evaluate, using scanning electron microscopy (SEM), the calcium fluoride uptake by human enamel in situ after topical application using three fluoridated mouthrinses: a neutral pH solution (Fluordent), an acidulated solution (Fluorgard) and a solution associated with chlorhexidine (Duplak). Twenty-four samples from 6 third sound human molars were divided into two groups: 5-min treatment and 10-min treatment. In both the 5-min and 10-min treatment samples, those treated with the chlorhexidine-associated solution showed higher formation of CaF2-like material. In the 10-min treatment group, the samples treated with the neutral solution showed higher formation of CaF2. These results indicated that the products used deposited CaF2 on the enamel surface and may be recommended to aid the prevention and control of dental caries.

Adsorption↗
PubMed2001

[Remifentanil or propofol for sedation in subarachnoid anesthesia. Effects on ventilation, hemodynamic stability and bispectral index].

OBJECTIVES: To compare depth of sedation, hemodynamic and respiratory effects, and bispectral index (BIS) in surgical patients under subarachnoid anesthesia with intravenous perfusion of 1 mg/kg/h of propofol or 3 microgram/kg/h of remifentanil or placebo. PATIENTS AND METHOD: Fifty-one elective surgery patients were randomly assigned to one of 3 groups: propofol (n = 17), remifentanil (n = 17) or placebo (n = 17). We monitored ECG, blood pressure (BP), respiratory frequency (RF), oxygen saturation by pulse oximetry (SpO2), nasal end tidal carbon dioxide pressure (PETCO2), BIS and sedation on the Observer's Assessment of Alertness/Sedation scale (OAA/S). Five minutes after starting subarachnoid anesthesia, we initiated the assigned intravenous perfusion. Measurement of hemodynamic variables, BIS, PETCO2, RF and OAA/S score occurred at baseline, every 5 minutes during surgery and after withdrawal of sedation at intervals until recovery of baseline values. RESULTS: Patient data and SpO2 were similar in the 3 groups. PETCO2, FR and OAA/S did not change significantly from baseline in the placebo group but were significantly different in the other groups. BIS was significantly lower in the propofol group than in either the remifentanil or the control group. Times to recovery were similar in the two sedation groups. Slight complications were observed in 35.3% patients in the propofol group, 53.3% in the remifentanil group and 7.7% in the placebo group; complications were mainly nausea, pruritus and hypoventilation in the remifentanil group and venous pain in the propofol group. CONCLUSIONS: The sedation regimens used were safe and adequate. Propofol is associated with fewer complications than remifentanil.

Anesthesia, Spinal↗
PubMed2000

cFos induction during conditioned taste aversion expression varies with aversion strength.

Fos-like immunoreactivity (FLI) can indicate the location of neurons activated following expression of conditioned taste aversion (CTA). After one conditioning trial FLI has been identified in the intermediate nucleus of the solitary tract (iNTS) with little expression in other brain regions. The present study assessed the effect of increasing aversion strength on the magnitude and anatomical distribution of FLI during CTA expression. When animals received three rather than one conditioning trial, significant FLI was seen not only in the iNTS but also in the parabrachial nucleus (PBN), and the central nucleus of the amygdala (CNA), regions thought to be important in taste aversion learning.

Amygdala↗
PubMed2000

Insulin receptor substrate-1, p70S6K, and cell size in transformation and differentiation of hemopoietic cells.

After an initial burst of cell proliferation, the type 1 insulin-like growth factor receptor (IGF-IR) induces granulocytic differentiation of 32D IGF-IR cells, an interleukin-3-dependent murine hemopoietic cell line devoid of insulin receptor substrate-1 (IRS-1). The combined expression of the IGF-IR and IRS-1 (32D IGF-IR/IRS-1 cells) inhibits IGF-I-mediated differentiation, and causes malignant transformation of 32D cells. Because of the role of IRS-1 in changing the fate of 32D IGF-IR cells from differentiation (and subsequent cell death) to malignant transformation, we have looked for differences in IGF-IR signaling between 32D IGF-IR and 32D IGF-IR/IRS-1 cells. In this report, we have focused on p70(S6K), which is activated by the IRS-1 pathway. We find that the ectopic expression of IRS-1 and the inhibition of differentiation correlated with a sustained activation of p70(S6K) and an increase in cell size. Phosphorylation in vivo of threonine 389 and, to a lesser extent, of threonine 421/serine 424 of p70(S6K) seemed to be a requirement for inhibition of differentiation. A role of IRS-1 and p70(S6K) in the alternative between transformation or differentiation of 32D IGF-IR cells was confirmed by findings that inhibition of p70(S6K) activation or IRS-1 signaling, by rapamycin or okadaic acid, induced differentiation of 32D IGF-IR/IRS-1 cells. We have also found that the expression of myeloperoxidase mRNA (a marker of differentiation, which sharply increases in 32D IGF-IR cells), does not increase in 32D IGF-IR/IRS-1 cells, suggesting that the expression of IRS-1 in 32D IGF-IR cells causes the extinction of the differentiation program initiated by the IGF-IR, while leaving intact its proliferation program.

Animals↗
PubMed2000

Reversal of dopamine D(2) receptor responses by an anandamide transport inhibitor.

We characterized the pharmacological properties of the anandamide transport inhibitor N-(4-hydroxyphenyl)-arachidonamide (AM404) in rats and investigated the effects of this drug on behavioral responses associated with activation of dopamine D(2) family receptors. Rat brain slices accumulated [(3)H]anandamide via a high-affinity transport mechanism that was blocked by AM404. When administered alone in vivo, AM404 caused a mild and slow-developing hypokinesia that was significant 60 min after intracerebroventricular injection of the drug and was reversed by the CB1 cannabinoid receptor antagonist SR141716A. AM404 produced no significant catalepsy or analgesia, two typical effects of direct-acting cannabinoid agonists. However, AM404 prevented the stereotypic yawning produced by systemic administration of a low dose of apomorphine, an effect that was dose-dependent and blocked by SR141716A. Furthermore, AM404 reduced the stimulation of motor behaviors elicited by the selective D(2) family receptor agonist quinpirole. Finally, AM404 reduced hyperactivity in juvenile spontaneously hypertensive rats, a putative model of attention deficit hyperactivity disorder. The results support a primary role of the endocannabinoid system in the regulation of psychomotor activity and point to anandamide transport as a potential target for neuropsychiatric medicines.

Animals↗
PubMed2000

Insulin-like growth factor I receptor signaling in differentiation of neuronal H19-7 cells.

The type I insulin-like growth factor receptor (IGF-IR) is known to send two seemingly contradictory signals inducing either cell proliferation or cell differentiation, depending on cell type and/or conditions. H19-7 cells are rat hippocampal neuronal cells immortalized by a temperature-sensitive SV40 large T antigen that grow at 34 degrees C in epidermal growth factor or serum but differentiate at 39 degrees C when induced by basic fibroblast growth factor. At 39 degrees C, expression of the human IGF-IR in H19-7 cells induces an insulin-like growth factor (IGF) I-dependent differentiation. We have investigated the domains of the IGF-IR required for differentiation of H19-7 cells. The tyrosine 950 residue and serines 1280-1283 in the COOH terminus of the receptor are required for IGF-I-induced differentiation at 39 degrees C, although they are dispensable for IGF-I-mediated growth at 34 degrees C. Both domains have to be mutated to inactivate the differentiating function. The inability of these mutant receptors to induce differentiation correlates with mitogen-activated protein kinase activation. In contrast, inhibitors of phosphatidylinositol 3'-kinase have no effect on IGF-I-mediated differentiation of H19-7 cells, although they do inhibit the mitogenic response.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Standardized approach for microsatellite instability detection in colorectal carcinomas.

BACKGROUND: Ubiquitous mutations in microsatellite DNA sequences define a specific type of genetic instability, termed microsatellite instability (MSI). Various approaches have been used to identify the presence and degree of MSI. To define standard diagnostic criteria for MSI, we developed and tested a mathematical model. METHODS: We designed an algorithm for the efficient characterization of MSI and used it to analyze data on six microsatellite markers in colorectal carcinoma and normal tissues from 415 patients. Theoretical models considering one, two, or three populations were tested against the data collected. RESULTS: The observed frequencies of MSI in our series of samples best fit a two-population model, stable and unstable, defined by instability in two or more of four to six markers analyzed. MSI was observed in 7.5% of the tumors. The misclassification rate was less than 5% when any four loci were analyzed and less than 1% when the six markers were used. A stepwise strategy, consisting first of a bulk screening of two loci and then a second screening of two to four additional markers, provided excellent sensitivity (>/=97%) and specificity (100%). Tumors with MSI had distinctive genetic and clinicopathologic features, including better patient survival. CONCLUSION: To assess the presence of MSI in colorectal cancer, we have developed a simple, sensitive, and specific approach based on the apparent good fit of the data to a two-population model. Its application to a prospective series of patients with colorectal carcinomas demonstrates that the presence of MSI characterizes a subset of less aggressive tumors.

Adult↗
PubMed2000

Irinotecan combined with fluorouracil compared with fluorouracil alone as first-line treatment for metastatic colorectal cancer: a multicentre randomised trial.

BACKGROUND: Irinotecan is active against colorectal cancer in patients whose disease is refractory to fluorouracil. We investigated the efficacy of these two agents combined for first-line treatment of metastatic colorectal cancer. METHODS: 387 patients previously untreated with chemotherapy (other than adjuvant) for advanced colorectal cancer were randomly assigned open-label irinotecan plus fluorouracil and calcium folinate (irinotecan group, n=199) or fluorouracil and calcium folinate alone (no-irinotecan group, n=188). Infusion schedules were once weekly or every 2 weeks, and were chosen by each centre. We assessed response rates and time to progression, and also response duration, survival, and quality of life. Analyses were done on the intention-to-treat population and on evaluable patients. FINDINGS: The response rate was significantly higher in patients in the irinotecan group than in those in the no-irinotecan group (49 vs 31%, p<0.001 for evaluable patients, 35 vs 22%, p<0.005 by intention to treat). Time to progression was significantly longer in the irinotecan group than in the no-irinotecan group (median 6.7 vs 4.4 months, p<0.001), and overall survival was higher (median 17.4 vs 14.1 months, p=0.031). Some grade 3 and 4 toxic effects were significantly more frequent in the irinotecan group than in the no-irinotecan group, but effects were predictible, reversible, non-cumulative, and manageable. INTERPRETATION: Irinotecan combined with fluorouracil and calcium folinate was well-tolerated and increased response rate, time to progression, and survival, with a later deterioration in quality of life. This combination should be considered as a reference first-line treatment for metastatic colorectal cancer.

Adenocarcinoma↗
PubMed2000

Antihepatotoxic activity of Rosmarinus tomentosus in a model of acute hepatic damage induced by thioacetamide.

R. tomentosus is a vegetal species closely related to the culinary rosemary (R. officinalis), a plant reported to contain antihepatotoxic agents. A dried ethanol extract of the aerial parts of Rosmarinus tomentosus (Lamiaceae) and its major fraction separated by column chromatography (fraction F19) were evaluated for antihepatotoxic activity in rats with acute liver damage induced by a single oral dose of thioacetamide. Silymarin was used as a reference antihepatotoxic substance. Pre-treatment with R. tomentosus ethanol extract, fraction F19 or silymarin significantly reduced the impact of thioacetamide toxicity on plasma protein and urea levels as well as on plasma aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase and gamma-glutamyl transpeptidase activities compared with thioacetamide-treated animals (group T). Pre-treatment with R. tomentosus ethanol extract significantly reduced the impact of thioacetamide damage on alkaline phosphatase and gamma-glutamyl transpeptidase activities compared with group T. Silymarin administration significantly reduced alkaline phosphatase and gamma-glutamyl transpeptidase activities compared with group T. Fraction F19 administration reduced only alkaline phosphatase activity compared with group T. According to these data, R. tomentosus extract shows promising antihepatotoxic activity, suggesting the need to isolate the chemical principles responsible for this activity and to study this activity in a model of thioacetamide-induced cirrhosis.

Animals↗
PubMed2000

Analysis of chromosome 6p in Spanish families with recessive polycystic kidney disease.

Several previous reports have suggested that autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in a single gene (the PKDH1 gene). Linkage analysis showed a positive linkage for polymorphic markers at the short arm of chromosome 6 (6p) in all families. PKHD1 has not been cloned. Recombinants in the critical region would permit the narrowing of the 6p interval containing the PKHD1 gene, thus facilitating the final identification (cloning) of this gene. Our study included 30 Spanish families. Each family consisted of both parents and at least two children, with at least one diagnosed with ARPKD by clinical and pathological parameters. DNA was obtained and 6p microsatellite markers were used to establish haplotypes for each family. A positive linkage to chromosome 6p was found for all families. In 2 cases, recombinants in the region containing the PKHD1 gene were found. These families will help narrow the size of the 6p region, facilitating the efforts to position and clone the PKHD1 gene. In conclusion, our analysis of Spanish ARPKD families confirms the lack of linkage heterogeneity. This suggests that mutations at a single locus on chromosome 6p21.1-p12 are responsible for the broad clinical spectrum of variable phenotypes.

Adolescent↗
PubMed2000

Towards guidelines for dialysis in children with end-stage renal disease.

There are few data describing the current practices of treatment selection for children with end-stage renal disease (ESRD). In an effort to establish a consensus among Spanish pediatric nephrologists for inclusion and exclusion criteria for renal replacement therapy in children with ESRD, in 1995 we surveyed members of the Spanish Pediatric Nephrology Association. Although only 43% of members responded, pediatric nephrologists and bioethicists studied the results and compiled a list of ten guidelines for treatment of children with ESRD. The proposed guidelines are meant to be a starting point for further discussion. An emphasis on flexibility, individual case assessment, and consideration of the best interests of the patient must remain central to any treatment plan. Decision making should ideally be shared by parents, professionals, the child, when appropriate, and ethics committees, as necessary.

Child↗
PubMed2000

The molecular karyotype of the megabase chromosomes of Trypanosoma brucei stock 427.

We present the molecular karyotype of the megabase chromosomes of Trypanosoma brucei stock 427, clone 221a. This cloned stock is most commonly used in research laboratories in genetic manipulation experiments and in studies of antigenic variation. Using 116 previously characterised chromosome-specific markers, we identify 11 diploid pairs of megabase chromosomes and detect no loss of synteny in EST and gene marker distribution between this stock and the genome project reference stock TREU 927/4. Nevertheless, the chromosomes of 427 are all larger than their homologues in 927, except chromosomes IIa and IXa. The greatest size variation is seen in chromosome I, the smallest of which is 1.1 Mb (927-Ia) and the largest 3.6 Mb (427-Ib). The total nuclear DNA content of both stocks has been estimated by comparison of the mobility of T. brucei and yeast chromosomes. Trypanosomes of stock 427 contain approximately 16.5 Mb more megabase chromosomal DNA than those of stock 927. We have detected the presence of bloodstream-form expression-site-associated sequences on eight or more megabase chromosomes. These sequences are not found on the same chromosomes in each stock. We have determined the chromosomal band location of nine characterised variant surface glycoprotein genes, including the currently expressed VSG 221. Our results demonstrate both the stability of the T. brucei genome, as illustrated by the conservation of syntenic groups of genes in the two stocks, and the polymorphic nature of the genomic regions involved in antigenic variation. We propose that the chromosomes of stock 427 be numbered to correspond to their homologues in the genome project reference stock TREU 927/4.

Animals↗
PubMed2000

Lessons learned from enrollment in the BEST study--a multicenter, randomized trial of group psychosocial support in metastatic breast cancer.

The BEST study, a multicenter randomized trial of group psychosocial support in metastatic breast cancer, had several unusual features that may have influenced recruitment, notably the group nature of the intervention and the need for close collaboration between medical and psychosocial investigators. The recruitment process was examined in light of these features. Establishment of study centers was facilitated by involvement of experienced medical investigators who had successfully collaborated in previous research projects. Systematic evaluation of potential subjects or direct recruitment by psychosocial investigators optimized recruitment; however, the group nature of the intervention prolonged recruitment. Overall, 652 women were approached and 237 (43.3% of those medically eligible) randomized. Using population-based estimates, 24.3% of women with metastatic breast cancer were assessed for the study and 8.7% randomized. A randomization ratio of 2:1 was required to form and maintain groups. Competing clinical trials were the greatest barrier to recruitment. Five lessons were learned during recruitment for this trial: (1) multicenter randomized trials of psychosocial interventions are feasible, even in very ill patients, (2) the use of a group intervention effectively increased the required sample size by 50%, (3) similarity of randomization rates suggests that generalizability of study results will probably be comparable to that of other randomized cancer trials, (4) multidisciplinary collaborations and involvement of experienced researchers facilitated enrollment, and (5) most challenges encountered in recruitment were similar to those seen in all clinical trials.

Breast Neoplasms↗