PubMed Health⌕ Search

Biomedical subjects

A Palacios

Publications and source records attributed to A Palacios.

At least 19 recordsLinked to original sources
PubMed2006

Enhancement and control of H2 dissociative ionization by femtosecond VUV laser pulses.

We report ab initio calculations of H2 ionization by VUV/fs 10(12) W/cm2 laser pulses including correlation and all electronic and vibrational degrees of freedom (DOF). Inclusion of the nuclear DOF leads to a substantial increase of resonance enhanced multiphoton ionization. By varying pulse duration, it is possible to control the ratio of dissociative to nondissociative ionization as well as the final H+(2) vibrational distribution. For pulses longer than 10 fs and proportional to omega>0.46 a.u., dissociative ionization entirely dominates, which is a very unusual situation in photoionization studies.

Journal Article↗
PubMed2006

[Multiple schwannoma of the penis].

Schwannoma or neurilemmoma designate a tumour that originates in the Schwann cells of peripheral nerves, therefore occurring anywhere in the body. They are very rare in the penis. In the literature are reported twenty seven cases of penile schwannoma. We report a case of multiple schwannoma of the penis and make a brief literature revision about this rare pathology.

Humans↗
PubMed2005

Analysis of the expression of some stress induced genes in several commercial wine yeast strains at the beginning of vinification.

AIMS: During fermentation yeast cells should cope with stress conditions. We pursue a better understanding of the stress response in wine yeasts at the beginning of vinification. METHODS AND RESULTS: We analyse by means of quantitative PCR the expression of several stress induced genes in 24 efficient commercial wine yeast strains at the beginning of vinifications performed under standard conditions or with small variations in pH and temperature. In all cases, high levels (with differences among strains) of GPD1 mRNA but quite low expression of other stress genes (TRX2, HSP104 and SSA3) were found. For all these genes, mRNA levels increase as temperature decreases or pH increases. CONCLUSIONS: Important levels of expression of GPD1 (but not of other stress genes) are required during the first hours of vinification, because of the need for glycerol production to counteract the hyperosmotic stress at this point. The differences among strains suggest that certain level of expression is enough to ensure the continuity of the process. Variations in the pH and temperature of the vinification can affect gene expression. SIGNIFICANCE AND IMPACT OF THE STUDY: A common pattern of stress response between efficient wine strains exists, which could be used as a criterion for selection. Studies of this kind can allow the establishment of connections between gene expression and physiological traits.

Fermentation↗
PubMed2003

Infrastructure of radiotherapy in Spain: a minimal standard of radiotherapy resources.

PURPOSE: To assess the state of our specialty, the Spanish Society of Radiotherapy and Oncology ordered a survey of all Spanish services of radiation oncology. METHODS AND MATERIALS: In June 1999, the Society ordered an analysis of the state of radiation oncology. It created a survey that was sent to all radiotherapy units in Spain. A database was created in which 230 variables were analyzed. RESULTS: Eighty-four centers were analyzed, and 157 external beam irradiation, megavoltage units were counted, of which 67 were cobalt units and 90 were linear accelerators. The cobalt units worked an average of 11.4 h daily and the linear accelerators 11.6 h. The number of patients/unit/y was 472 for the cobalt units and 442 for the linear accelerators. The number of patients by physician and year was 179. Each center received a mean of 958 new patients annually. The average between the reception and start of treatment was 25.52 days (maximum 60), and it was estimated that only 38.1% of cancers were irradiated. The number of radiation oncologists working was 392. Spain has a deficit of 297 radiation oncologists. CONCLUSION: There is a need for 44 MV units and for the replacement of 67 cobalt units. The present lack of units has had an impact on palliative treatment, which has resulted in pharmacy costs. As long as these instrumental deficiencies are not solved, waiting lists will continue to be inherent to the system. There are also important staff deficiencies, in that about 297 radiation oncologists would be needed to cover the needs.

Health Services Needs and Demand↗
PubMed2002

Environmental factors as determinants of malaria risk. A descriptive study on the northern coast of Peru.

We conducted a series of studies on the northern Pacific coast of Peru to determine environmental risk factors for malaria. We report in this paper the results of both a descriptive study of incidence and a prevalence survey of malaria. Both studies showed that the area was at low risk for malaria. The malaria incidence rate was 40/1000 p.a. during the study period, and the prevalence of infection was 0.9% (95% CI: 0.4-1.7) before and 1.4% (95% CI: 0.8-2.2) after the high incidence period. However, the risk of malaria varied according to season, village and even house within a single village. Incidence rates increased from February (2.6/1000 p.a.) to May (12.9/1000 p.a.) and decreased during the second part of the year. Most of the cases were clustered in four villages that constituted only 21% of the total population of the area. Houses where multiple cases were recorded were often located near a source of water. Our observations suggested that environmental factors, and particularly the presence of water for irrigation around villages and houses, played a major role in determining the risk of malaria. These observations were extended through an entomological study and a case-control study, to be published elsewhere.

Adolescent↗
PubMed2002

Genomic and antigenomic chains of hepatitis C virus and hepatitis G virus in serum, liver and peripheral blood mononuclear cells.

OBJECTIVE: To determine HCV and HGV replication sites in patients with chronic hepatitis C and to study interaction between these two viruses. PATIENTS: HGV RNA was studied in 272 patients with chronic hepatitis C. Of these, 35 were positive (group I). Twenty-three patients with chronic hepatitis C not co-infected with HGV were selected (group II). RESULTS: Genomic and antigenomic chains of HCV were studied in both groups and those of HGV in group I in serum samples, peripheral blood mononuclear cells and liver tissue. In group I genomic chains of HCV and HGV were observed in 86 and 100%, respectively (ns), in serum samples (n = 35), and antigenomic chains in 17 and 23%, respectively (ns). In mononuclear cell samples (n = 15) 100% presented the genomic chain of HCV and 60% presented that of HGV (p < 0.05). Antigenomic chains were detected in 13 and 33%, respectively (ns). In liver tissue (n = 25) genomic chains were observed in 100 and 12%, respectively (p < 0.001); the antigenomic chain of HCV was detected in 76% while that of HGV was not present (p < 0.001). In group II genomic chains of HCV were found to be present in a very high percentage in all samples, while antigenomic chains appeared in 13% of serum and mononuclear cell samples and 89% of liver samples. CONCLUSIONS: HCV and HGV have different sites of replication: whereas HCV replicates mainly in the liver, HGV is not hepatotropic. Mononuclear cells could represent a replication site for HGV but they are less important for HCV. Lastly, HGV does not modify the viral replication of HCV.

Adult↗
PubMed2001

Comparative studies on lipid peroxidation of microsomes and mitochondria obtained from different rat tissues: effect of retinyl palmitate.

The effect of retinyl palmitate on the polyunsaturated fatty-acid composition, chemiluminescence and peroxidizability index of microsomes and mitochondria obtained from rat liver, kidney, brain, lung and heart, was studied. After incubation of microsomes and mitochondria in an ascorbate Fe++ system (120 min at 37 degrees C) it was observed that the total cpm/mg protein originated from light emission: chemiluminescence was lower in liver microsomes, mitochondria and kidney microsomes in the vitamin A group than in the control group. In mitochondria obtained from control rats, the most sensitive fatty acids for peroxidation were arachidonic acid C20:4 n6 in liver and docosahexaenoic acid C22:6 n3 in kidney and brain. In microsomes obtained from control rats, the most sensitive fatty acids for peroxidation were linoleic acid C18:2 n6 and C20:4 n6 in liver and C22:6 n3 in kidney. Changes in the most polyunsaturated fatty acids were not observed in organelles obtained from lung and heart. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of fatty acids, showed significant changes in liver, kidney and brain mitochondria, while in microsomes changes were significant in liver and kidney. These changes were less pronounced in membranes derived from rats receiving vitamin A. Our results confirm and extend previous observations that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.

Animals↗
PubMed2000

[Coinfection with hepatitis G virus in chronic hepatitis C. Response to treatment with interferon alpha].

BACKGROUND: It is thought that the cytopathic effect of HGV is not important. Nevertheless, the cytopathic effect on liver is less known in the cases of co-infection with HCV. The aim was to study the prevalence of co-infection in patients with chronic hepatitis C (CHC) and to analyse the clinical-epidemiological and histological data and the interferon (IFN) response. PATIENTS AND METHODS: We included 180 patients with CHC and the HGV-RNA was determined. RESULTS: The prevalence of co-infection was 12.2% (n = 22). No statistical differences were observed between the non co-infected and co-infected groups with regard to the age, sex, mechanism of transmission and alcohol abuse. Also, there were no differences in the hepatic biochemical, no organ-specific antibodies, histological lesions and Knodell index. The HCV biochemical response (BR) and virological response (VR) after 6 months post-IFN were the same in both groups (HGV negative: BR = 29%, VR = 12%; HGV positive: BR = 22%, VR = 18%). HGV was determined after 6 months posttreatment in the co-infected group (first cycle of IFN, n = 22; second cycle of IFN, n = 9): 12 (55%) were HGV-RNA negative and 5 (23%) HCV-RNA negative, (p = 0.021). When we compared the BR vs VR in this group, there were 12 HGV-RNA negative but only two had BR (NS). On the contrary, the BR was related to HCV-RNA negative (p = 0.023). CONCLUSION: The prevalence of HGV co-infection is important in our area (12.8%). The HGV does not increase the pathogenicity of HCV and does not change the IFN response, although the HGV is more IFN sensible than HCV. The determination of HGV is not necessary in patients with HCV.

Adolescent↗
PubMed2000

Multiple endocrine abnormalities in a child with Blackfan-Diamond anemia and hemochromatosis. Significant improvement of growth velocity and predicted adult height following growth hormone treatment despite liver damage.

We evaluated a short, prepubertal 13.9 year-old boy with Blackfan-Diamond anemia and significant liver iron stores due to multiple blood transfusions and found him to have several endocrine abnormalities, including hypothyroidism, hypoparathyroidism, primary and secondary hypogonadism and IGF-I insufficiency. Growth velocity was poor despite treatment with levothyroxine, calcitriol, calcium and aggressive therapy with chelating agents. After 25 months of treatment with rhGH his growth velocity, height for age and PAH increased significantly, suggesting a degree of sensitivity to GH despite his liver damage.

Adolescent↗
PubMed2000

Multicenter retrospective study of response to interferon in chronic hepatitis B.

AIM: The only agent known to have a lasting beneficial effect in chronic hepatitis B is interferon alpha, which achieves long-term remission in 25-40% of the patients. The goals of treatment are to induce clearance of HBV DNA from serum, to return serum aminotransferases to normal, and to improve histological findings in the liver. The most important factors predictive of response to treatment are high serum aminotranferases levels, low serum HBV DNA concentrations, and active histologic changes on liver biopsy. The aim of this study was to assess the response to interferon alpha in patients with chronic hepatitis B and to analyze the factors predictive of response. METHODS: We conducted a multicenter retrospective study to investigate the effect of interferon treatment in 132 patients with chronic hepatitis B in overall terms and based on HBeAg, and factors predictive of response. RESULTS: A overall sustained response was noted in 59 of 132 interferon-treated patients (45%) and 61 patients were nonresponders (46%). 12 patients relapsed (9%). None of the patients had negative HBsAg. No difference was observed in the response rate between the two treatment groups (HBeAg-positive and HBeAg-negative patients). Overall, high initial levels of serum AST and ALT predicted a good response. Age and liver biopsy findings were factors predictive of response in HBeAg-positive and HBeAg-negative patients respectively. Sex, epidemiological factors, treatment and type of virus did not correlate with the response to interferon. CONCLUSIONS: A sustained response to interferon alpha was observed in 45% of the patients with chronic hepatitis B. HBeAg seroconversion was found in up to 50% of HBeAg-positive patients. None of the patients had negative HBsAg. Overall, the response rate was higher in patients with high pretreatment serum aminotransferase levels. Age was the predictive factor in HBeAg-positive patients, and histological features were predictive in the HBeAg-negative group. However, further studies in a larger patient population are necessary to obtain well-substantiated conclusions.

Adolescent↗
PubMed1999

Development of low cost peptide-based anti-hepatitis C virus screening and confirmatory assays: comparison with commercially available tests.

Screening and confirmatory low cost reagent tests have been developed for detection of anti-hepatitis C virus (HCV). Assays are based on the use of specific synthetic peptides from several structural and non-structural viral proteins. The efficacy of the screening anti-HCV EIA-Spep assay was compared with both Abbott EIA 2.0 (Abbott Laboratories, North Chicago, IL) and Ortho EIA 2.0 (Ortho Diagnostic Systems, Raritan, NJ) anti-HCV detection kits and the confirmatory EIA-Cpep assay was compared with the Abbott Matrix anti-HCV confirmation test. In the EIA-Spep, a pool of 3 peptides was added to each well of a microtiter plate. In EIA-Cpep, each well was separately coated with 1 of 4 peptides and 1 recombinant protein. A total of 867 blood donor samples from Costa Rica tested simultaneously with the 3 screening assays yielded the same specificity and negative predictive values of > or =99.9% and 100%, respectively. A comparative study on voluntary blood donor samples from Honduras, Nicaragua, and El Salvador using the 2 anti-HCV confirmatory assays revealed different patterns that are 46% positive, 24% indeterminate, and 30% negative with the EIA-Cpep assay vs. 31% positive, 48% indeterminate, and 21% negative with the Matrix assay. A study of 71 patient samples from Costa Rica showed a higher correlation between initially reactive samples when analyzed by the Abbott and Ortho kits, than when the assay results were compared between the Abbott and EIA-Spep kits; the latter detected 7 and 15 non-reactive samples, respectively. These results could reflect the use of a similar antigen source for the 2 commercial assays. The presence of HCV RNA in a group of 29 samples analyzed was related to the simultaneous reactivity in all 3 screening assays. None of the discordant samples had detectable levels of HCV RNA. Economic difficulties for health care services in the developing countries of Central America have prevented implementation of routine anti-HCV blood donor screening tests. This is likely to be the primary reason for uncontrolled dissemination of HCV, and the lack of identification of potential high risk groups. Alternative low cost reagents developed locally as described in this article could be a useful tool in the control of HCV spread throughout the developing world.

Amino Acid Sequence↗
PubMed1999

Inhibition of lipid peroxidation of microsomes and mitochondria by cytosolic proteins from rat liver: effect of vitamin A.

Studies were carried out to determine the effect of rat liver cytosolic protein enriched in fatty acid binding protein on the microsomal and mitochondrial ascorbate-Fe+2 lipid peroxidation and to determine how vitamin A influences the inhibitory effect of this protein in the peroxidation process. The inhibition of light emission (maximal induced chemiluminescence) by the fatty acid binding protein containing fraction was protein concentration dependent. The inhibition of chemiluminescence produced by the addition of cytosolic protein on rat liver microsomes or mitochondria was more evident when the soluble protein obtained from the vitamin A treated group was used. The results indicated that vitamin A plays a role in protecting rat liver microsomes and mitochondria against the harmful effect of lipid peroxidation.

Animals↗
PubMed1999

Integrating the Kuramoto-Sivashinsky equation in polar coordinates: application of the distributed approximating functional approach.

An algorithm is presented to integrate nonlinear partial differential equations, which is particularly useful when accurate estimation of spatial derivatives is required. It is based on an analytic approximation method, referred to as distributed approximating functionals (DAF's), which can be used to estimate a function and a finite number of derivatives with a specified accuracy. As an application, the Kuramoto-Sivashinsky (KS) equation is integrated in polar coordinates. Its integration requires accurate estimation of spatial derivatives, particularly close to the origin. Several stationary and nonstationary solutions of the KS equation are presented, and compared with analogous states observed in the combustion front of a circular burner. A two-ring, nonuniform counter-rotating state has been obtained in a KS model simulation of such a burner.

Journal Article↗
PubMed1999

Interferon versus ribavirin plus interferon in chronic hepatitis C previously resistant to interferon: a randomized trial.

BACKGROUND: More than 70% of patients with chronic hepatitis C are resistant to interferon therapy. Ribavirin, in association with interferon, has been demonstrated as effective, at a dose of 800-1200 mg/day, but the efficacy of a lower dose has not been established. METHODS: We assessed the effectiveness of the combination of 600 mg/day of ribavirin plus 3 MU of interferon over a period of 6 months, in a group of patients previously resistant to interferon. Sixty-two patients with chronic hepatitis C with serum and hepatic HCV RNA relapsers or non-responders to interferon, were randomly divided into two groups: group A received 3 MU of interferon alpha-2b, three times a week for 6 months; group B was given the same dose plus 600 mg per day of ribavirin for 6 months. Two patients from each group dropped from therapy. One patient from group A and two from group B withdrew from treatment because of adverse effects. RESULTS: Mean alanine aminotransferase levels were similar in both groups throughout the study. A sustained response was observed in 7% and 7.4% of groups A and B with short-term response in 39% and 59%, and no response in 54% and 34% from both groups respectively (non-significant). At 12 months, 4 and 7 patients from groups A and B respectively, cleared serum HCV RNA however, only one sustained responder from each group cleared HCV RNA from peripheral blood mononuclear cells. At 18 months, 3 patients remained serum HCV RNA negative. Adverse effects were similar. Only haemoglobin values were lower in group B in the first month of therapy (p<0.05). CONCLUSION: In conclusion, the combination of 3 MU of interferon plus 600 mg of ribavirin is not effective in chronic hepatitis C resistant to interferon.

Adult↗
PubMed1999

Interferon-alpha in patients with chronic hepatitis C and normal transaminase levels.

OBJECTIVE: to assess the response to interferon-alpha therapy in patients with chronic hepatitis C and normal alanine transferase levels. METHODS: 16 patients with normal transaminases (group A) and 36 patients with elevated ALT levels (group B) were treated with interferon-alpha-2b at a dose of 3 MU for 6 months. The biochemical, virological (HCV RNA in serum, liver and peripheral blood mononuclear cells) and histological responses were analyzed. RESULTS: no significant differences were observed between the two groups in age, sex, parenteral or sporadic transmission, hepatic lesion, Knodell index or HCV genotype, except for the higher proportion of women in group A. We found no significant differences between the groups in rates of patients with normal ALT in the follow-up period (6 months post-interferon, group A 44%, group B 17%) or in post-therapy negativization of HCV RNA levels (group A 31%, group B 17%). In 7 patients (44%) in group A, ALT remained normal throughout the study, whereas in the rest of the patients we observed some elevation during or after interferon treatment. Post-therapy mean Knodell index was 6 +/- 3 in group A versus 9 +/- 4 in group B (p < 0.05). CONCLUSIONS: the response to interferon was similar in patients with normal or elevated transaminases.

Adult↗