PubMed Health⌕ Search

Biomedical subjects

S Pita

Publications and source records attributed to S Pita.

At least 19 recordsLinked to original sources
PubMed2006

HESS observations of the galactic center region and their possible dark matter interpretation.

The detection of gamma rays from the source HESS J1745-290 in the Galactic Center (GC) region with the High Energy Spectroscopic System (HESS) array of Cherenkov telescopes in 2004 is presented. After subtraction of the diffuse gamma-ray emission from the GC ridge, the source is compatible with a point source with spatial extent less than 1.2;{'}(stat) (95% C.L.). The measured energy spectrum above 160 GeV is compatible with a power law with photon index of 2.25+/-0.04(stat)+/-0.10(syst) and no significant flux variation is detected. It is finally found that the bulk of the very high energy emission must have non-dark-matter origin.

Journal Article↗
PubMed2006

Fast variability of tera-electron volt gamma rays from the radio galaxy M87.

The detection of fast variations of the tera-electron volt (TeV) (10(12) eV) gamma-ray flux, on time scales of days, from the nearby radio galaxy M87 is reported. These variations are about 10 times as fast as those observed in any other wave band and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the gamma-ray production. The observations confirm that TeV gamma rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed toward the observer.

Journal Article↗
PubMed2006

A low level of extragalactic background light as revealed by gamma-rays from blazars.

The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the 'first stars', which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the gamma-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of gamma-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources-in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to gamma-rays than previously thought.

Journal Article↗
PubMed2006

Discovery of very-high-energy gamma-rays from the Galactic Centre ridge.

The source of Galactic cosmic rays (with energies up to 10(15) eV) remains unclear, although it is widely believed that they originate in the shock waves of expanding supernova remnants. At present the best way to investigate their acceleration and propagation is by observing the gamma-rays produced when cosmic rays interact with interstellar gas. Here we report observations of an extended region of very-high-energy (> 10(11) eV) gamma-ray emission correlated spatially with a complex of giant molecular clouds in the central 200 parsecs of the Milky Way. The hardness of the gamma-ray spectrum and the conditions in those molecular clouds indicate that the cosmic rays giving rise to the gamma-rays are likely to be protons and nuclei rather than electrons. The energy associated with the cosmic rays could have come from a single supernova explosion around 10(4) years ago.

Journal Article↗
PubMed2006

[Renal transplantation in the northwest of Spain: analysis of the activity in the region of Galicia].

BACKGROUND: Spain is the world leader in organ transplant rates, and the national average is maintained in the northwestern Spanish region of Galicia. However, there is no official registry recording transplantation results in this region. In this paper we report a study of patient and graft survival and risk factors among kidney transplant patients in Galicia between January 1996 and December 2000. METHODS: Patients receiving kidney transplants in Galicia in the above period were monitored up to the end of 2001, deaths and graft losses were recorded and analysed by actuarial and Kaplan-Meier methods, and possible risk factors for death and graft loss were evaluated using Cox's proportional hazards model. RESULTS: In the study period, 672 kidneys were transplanted, all from deceased donors. Graft and patient survival rates were respectively 80% and 94% after 1 year, and 67% and 83%, after 5 years. Two-thirds of graft losses occurred within the first year and the most common cause was vascular thrombosis (44%). Independent risk factors for graft loss were donor asystole (relative risk [RR] = 3.41, 95% confidence interval [CI]: 1.73-6.73), donor age (RR = 1.54, CI: 1.05-2.27 for 40-60-year-olds, RR = 2.59, CI: 1.66-4.07 for over-60s, relative to under-40s), donation from outside the institution in which implant was performed (RR = 1.43, CI: 1.02-2.02), acute rejection (RR = 2.32, CI: 1.63-3.22), and retransplantation (RR = 1.56, CI: 1.03-2.37). The main causes of death were infections (38%), followed by cardiovascular pathologies (30%) and tumours (11%). CONCLUSIONS: The kidney transplant rate varies excessively within Galicia; the global rate is 50 per million inhabitants per year. Patient survival is similar to those recorded in national registers, but graft survival is deficient, apparently due to a high incidence of vascular thrombosis.

Adolescent↗
PubMed2005

Discovery of very high energy gamma rays associated with an x-ray binary.

X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and x-ray observations have led to the presumption that some x-ray binaries called microquasars behave as scaled-down active galactic nuclei. Microquasars have resolved radio emission that is thought to arise from a relativistic outflow akin to active galactic nuclei jets, in which particles can be accelerated to large energies. Very high energy gamma-rays produced by the interactions of these particles have been observed from several active galactic nuclei. Using the High Energy Stereoscopic System, we find evidence for gamma-ray emission of >100 gigaelectron volts from a candidate microquasar, LS 5039, showing that particles are also accelerated to very high energies in these systems.

Journal Article↗
PubMed2005

A new population of very high energy gamma-ray sources in the Milky Way.

Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.

Journal Article↗
PubMed2004

High-energy particle acceleration in the shell of a supernova remnant.

A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate the bulk of Galactic cosmic rays are supernova explosions, and even though the mechanism of particle acceleration in expanding supernova remnant (SNR) shocks is thought to be well understood theoretically, unequivocal evidence for the production of high-energy particles in supernova shells has proven remarkably hard to find. Here we report on observations of the SNR RX J1713.7 - 3946 (G347.3 - 0.5), which was discovered by ROSAT in the X-ray spectrum and later claimed as a source of high-energy gamma-rays of TeV energies (1 TeV = 10(12) eV). We present a TeV gamma-ray image of the SNR: the spatially resolved remnant has a shell morphology similar to that seen in X-rays, which demonstrates that very-high-energy particles are accelerated there. The energy spectrum indicates efficient acceleration of charged particles to energies beyond 100 TeV, consistent with current ideas of particle acceleration in young SNR shocks.

Journal Article↗
PubMed2003

[Lung cancer in the health care area of A Coruña (Spain): incidence, clinical approach and survival].

OBJECTIVE: To determine the incidence, clinical approach, diagnostic delay and survival for bronchogenic carcinoma (BC) in the public health area of A Coruña (Spain). PATIENTS AND METHOD: This was a retrospective study of patients with a diagnosis of BC made in 1995 and 1996 in a health care area with 509,000 inhabitants. For analysis we gathered demographic, clinical and cyto-histologic data and analyzed diagnostic delay, extension of disease and time of death. Crude, age-specific and age-standardized incidences were calculated. RESULTS: BC was diagnosed in 378 patients (95% men and 5% women). The crude incidence was 37 per 100,000 inhabitants (73.7 per 100,000 men and 3 per 100,000 women) and the age-standardized incidence was 21.7 per 100,000. Diagnosis was by cyto-histology in 87% of the cases, and the most frequent biopsy finding was epidermoid carcinoma. Diagnosis was by clinical or radiologic findings for 13.7%, and patients in that group were older and had greater comorbidity. No symptoms were present in 13% and in those patients diagnosis was earlier, with non-small BC predominating and 60% treated surgically. The diagnostic delay (time from the first symptom to histologic confirmation) was 2.5 months (median, 2.1), and length of delay did not affect survival. Surgery was performed in 23% of the patients with non-small BC. The median survival was 7.1 months (5.2 months for patients who were not treated surgically, and 37.6 for those who were). CONCLUSIONS: The incidence of BC in men in our study is consistent with that reported for other Spanish regions, although the incidence we observed for women is much lower. Diagnostic delay did not affect survival. The percentage of patients with surgical-stage disease is very low and survival is very short. These findings support the need for early diagnosis.

Aged↗
PubMed2003

[Prognostic markers determining the start of dialysis].

BACKGROUND: It is widely known that renal disease progresses towards the terminal stage regardless of the cause. The aim of this study is to identify prognostic factors in the progression that determine the start of dialysis. METHODS: From january 1998 until december 1999, 76 patients diagnosed with renal failure were monitored, 52 of whom started dialysis treatments. Clinical and analytical variables were studied. An actuarial analysis was carried out following the methodology of Kaplan-Meier to determine the likelihood of the need for dialysis and the Cox proportional risk analysis was also used. RESULTS: The patients enrolled in this study were between 20 and 78 years of age. 49 (64.5%) of the subjects were men and 27 (35.5%) were women. The most prevalent pathology was nephroangiosclerosis (26.3%), followed by diabetes (25.0%). During the monitoring program, 68.4% of the patients began dialysis treatments (table I). Systolic blood pressure, haemoglobin and the total proteins were univariately identified as prognostic variables. 89.47% and 71.58% of the patients with a systolic blood pressure reading of under 140 mmHg had not begun dialysis after 12 and 24 months respectively. 87.02% and 53.63% of the patients with a systolic blood pressure reading of over 140 mmHg had not begun dialysis after 12 and 24 months respectively (p = 0.025) (fig. 1). With a haemoglobin level higher than 10 gr/dl after 12 months 92.7% had not started dialysis, dropping to 72.33% after 24 months. With a haemoglobin level of under 10 g/dl 78.6% and 37.59% had not started dialysis after 12 and 24 months respectively (p = 0.0008) (fig. 2). Taking into account the mean values of different variables in the two year period prior to starting or not starting dialysis, it was found that haemoglobin significantly affected the risk of the need to start dialysis treatments [RR = 0.729; 95% CI = (0.554;0.959)], while systolic blood pressure was on the borderline of statistical significance (table IV). CONCLUSIONS: Haemoglobin levels significantly affect the risk of the need to start dialysis treatments, while other variables were identified as possible prognostic factors.

Adult↗
PubMed2002

Factors predicting a hospital stay of over 3 days in patients with acute exacerbation of chronic obstructive pulmonary disease.

OBJECTIVE: To investigate the factors predicting a hospital stay of over 3 days in patients who required hospitalization for acute exacerbation of chronic obstructive pulmonary disease (COPD). DESIGN AND SETTING: A cross-sectional study was done at a tertiary hospital serving an area of 500 000 inhabitants. SUBJECTS: A total of 273 patients (alpha=0.05; accuracy=5.94%) who had been admitted consecutively to the Short Stay Medical Unit at the Juan Canalejo Hospital in A Coruña, from February 1998 to March 1999, with a diagnosis focusing on exacerbation of COPD. Methods. Demographic variables, past medical history, symptoms, arterial blood gases, functional tests, treatment and the cause of exacerbation were studied in each patient. The hospital stay was dichotomized into 3 days. The prognostic factors of a hospital stay were determined by log regression. Results. The mean stay was 4.6 +/- 5.1 days (range: 1-64). After monitoring the associated covariables, the following were found to have an independent effect on the prediction of a hospital stay of over 3 days: weekend admissions (OR=4.17; 95% CI: 2.42-7.18), the presence of cor pulmonale (OR=2.19; 95% CI: 1.27-3.78), and the respiratory rate on admission (OR=1.09; 95% CI: 1.03-1.14). Arterial blood gases and functional tests showed no independent effect. Conclusions. The factors having an independent prognostic value in determining the length of hospital stays in patients with COPD are weekend admission, cor pulmonale and respiratory rate. Additional studies are required to validate these findings.

Adult↗
PubMed2002

Factors leading to the removal of the intrauterine implant Gynefix.

OBJECTIVE: The objective of this study was to determine the incidence of expulsion of the Gynefix intrauterine implant, to analyze the variables associated with the above and to examine the efficacy of this intrauterine contraceptive model in users at the Municipal Family Planning Center-SERGAS in A Coruña, Spain. METHODS: A prospective observational study was performed on all women (n = 358) who had a Gynefix implant inserted from March 1998 to September 2000. RESULTS: The accumulated incidence of implant expulsion was 6.7% (95% confidence interval (CI) 4.4-9.9) with a pregnancy rate of 0.6% (95% CI 0.09-2.2). The probability of implant removal decreases with the rise in the number of implants that have been inserted by the professional. A multivariate analysis adjusted for age, number of implants and uterine position showed that the position of the uterus was the variable that independently determined the probability of removal. CONCLUSIONS: It is concluded that retroflexion of the uterus increases the probability of removal.

Adolescent↗
PubMed2001

Operative results and death predictors for nonruptured abdominal aortic aneurysms in the elderly.

Elective repair of abdominal aortic aneurysms (AAA) in the elderly has conventionally been associated with higher mortality rates than in younger patients, although some authors do not agree with this view. The aim of this study is to look into current results of surgical treatment in elderly patients with nonruptured AAA and to define those factors associated with an increased mortality. Over a period of 2 years (1995-1996), 183 patients aged 75 or older were operated on for nonruptured AAA in 21 hospitals. Their medical records were reviewed and those factors that could be related to death were analyzed. Those variables with statistical significance through univariate analysis were entered into a multivariate logistic regression model to predict mortality. The results showed that surgery for nonruptured AAA in the elderly has a greater mortality rate than that in younger patients, but it is not so great as to deny surgical correction to prevent rupture in selected cases, especially if they are unsuitable for endovascular repair. These patients must first undergo thorough cardiac and renal function evaluation. Selective screening must be considered, so earlier detection and treatment in younger patients can be performed.

Age Factors↗
PubMed2001

The importance of the removal of the intrauterine device in genital colonization by actinomyces.

OBJECTIVE: To determine whether, in addition to treatment with antibiotics, it is necessary to remove the intrauterine device (IUD) to eliminate genital colonization by Actinomyces. METHODS: A randomized clinical trial was carried out. Patients were divided into two groups. The intervention group did not have their IUDs removed, while the control group did. Both groups were treated with trimethoprim and sulfamethoxazole. A total of 43 patients were included. RESULTS: The patients from the intervention group and the control group proved to be comparable. The post-intervention cytology smear tested negative for Actinomyces in 100% of the patients whose IUD had been removed and in 66.7% of those whose IUD had not been removed (p = 0.005). The probability that colonization by Actinomyces will continue if the IUD is not removed is greater the longer the patient has been exposed to the IUD. After 24 months, relative risk (RR) = 2, after 36 months RR = 2.16 and after 48 months RR = 2.66. CONCLUSIONS: The removal of the IUD has been effective in genital colonization by Actinomyces. The protective effect exerted by the removal of the IUD was found to be greater in proportion to the length of time the patient had used it.

Actinomyces↗
PubMed1999

Surgical treatment of ruptured abdominal aortic aneurysms in the elderly.

The aims of this study were to investigate current results of surgical treatment for elderly patients with ruptured abdominal aortic aneurysms (AAA) and to define factors associated with mortality. The study included 112 patients aged 75 years or older who were operated on for a ruptured AAA. The surgeries took place from January 1995 to December 1996 in 21 hospitals in Spain. Variables that could be related to death were retrospectively analyzed by entering data into SPSS statistical software. These variables included sex, age, diabetes, hypertension, cardiopathy, pulmonary obstructive disease, renal dysfunction, symptomatic cerebrovascular disease, peripheral occlusive disease, peripheral aneurysms, hematocrit on admission, preoperative hypotension, loss of consciousness, cardiac arrest, AAA location, aneurysm size, type of rupture, place of aortic cross-clamping, type of graft, use of cell saver, technical complications, intraoperative blood loss, and transfusion requirements. Postoperative complications were also considered, including renal failure, sepsis, coagulopathy, cardiac complications, pulmonary complications, colon ischemia, prosthetic graft complications, and need for reoperation. For univariate statistical analysis, the Student's t-test, Mann-Whitney test, and chi-square test were used. Those variables showing statistical significance were entered into a multivariate logistic regression model. The results of these analyses indicate that in elderly patients undergoing surgery for ruptured AAA have a high operative mortality. Comorbid factors, however, were not identified as independent predictors of death. Surgery should not be denied these patients and selective screening should be contemplated.

Aged↗
PubMed1999

Eight years with the same IUD.

The purpose of this study was to determine the efficacy of the TCu380A (GYNET 380 IUD) in long-term users for periods of > 5 years and to obtain the incidence of Actinomyces as related to length of use and reasons for removal. The report is a retrospective descriptive study of all the clinical cases (n = 370 patients) at the Municipal Family Planning Centre-SERGAS A Coruña, Spain, of women who had a TCu380A IUD inserted during the period 1988-1989 with a September 1997 cutoff date for data analysis. A total of 271 (73.5%) patients had been using the TCu380A IUD for > 5 years with 100% efficacy. The accumulated incidence of Actinomyces was 5.9% (CI 95%: 3.8-8.9). The highest incidence was found between the second and third year of use. There was no increase in the incidence of Actinomyces after 5 years of use. The most common reason for removal of the IUD was the duration of use of 8 years with the same device (32.3%).

Actinomycosis↗
PubMed1999

Achalasia: the usefulness of manometry for evaluation of treatment.

Although manometry is used with increasing frequency to evaluate the effectiveness of different treatments for achalasia, the criteria for a successful manometric response have not been well defined. Manometric responses were collected before and after 43 treatments in 35 patients with achalasia in order to determine manometric changes after different clinical outcomes: 15 unsuccessful outcomes and 28 successful outcomes were reported. In the latter, resting pressure of the lower esophageal sphincter decreased to 12.8 mm Hg, whereas in unsuccessful outcomes this was significantly higher (28.2 mm Hg). A decrease of lower esophageal sphincter pressure below 17 mm Hg or more than 40% of the pretreatment level was associated with successful outcomes. Our data suggest that manometry is a good indicator of therapeutic effectiveness and we propose that it be used systematically for objective evaluation of achalasia treatment.

Catheterization↗