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J Muñiz

Publications and source records attributed to J Muñiz.

At least 19 recordsLinked to original sources
PubMed2005

Fast-activating channel controls cation fluxes across the native chloroplast envelope.

A prerequisite for photosynthetic CO(2) fixation is the maintenance of alkaline pH in the stroma. This is achieved by H(+) pumping from the stroma to the cytosol, electrically balanced by an influx of cations through some unidentified non-selective envelope channels. In this study, the patch-clamp technique was applied to isolated Pisum sativum L. (pea) chloroplasts, and a fast-activating chloroplast cation (FACC) channel was discovered in the native envelope. This channel opens within a few milliseconds upon voltage steps to large positive or negative potentials. Remarkably, the single-channel conductance increased fivefold, from approximately 40 pS to approximately 200 pS (symmetric 250 mM KCl), upon a potential change from zero to +/- 200 mV. The FACC channel conducts all physiologically essential inorganic cations (K(+), Na(+), Ca(2+), Mg(2+)) with little preference. An increase of stromal pH from 7.3 to 8.0, mimicking dark-light transition, caused about a 2-fold decrease of the FACC channel activity within a physiologically relevant potential range. The FACC channel was completely and irreversibly blocked by Gd(3+). Based on the estimated transport capacity of the whole chloroplast population of FACC channels together with the envelope H(+)-ATPases, these channels can mediate electroneutral K(+)/H(+) exchange across the envelope, enabling stroma alkalinization, thereby allowing an optimal photosynthetic performance.

Antiporters↗
PubMed2005

Regulation of the slow vacuolar channel by luminal potassium: role of surface charge.

Voltage-dependent activation of slow vacuolar (SV) channels has been studied on isolated patches from red beet (Beta vulgaris L.) vacuoles. Isoosmotic variation of vacuolar K(+) from 10 to 400 mM in Ca(2+)-free solutions at the vacuolar side shifted the SV channel activation threshold to more positive voltages. The effect of K(+) could be mimicked by additions of choline or N-methyl D-glucamine and could be explained by unspecific screening of the negative surface charge. Fitting the dependence of voltage shift on K(+) concentration to the Gouy-Chapman model yields a surface charge density of 0.36 +/- 0.05 e(-)/nm(2). Negative surface potential also tended to increase the local concentration of permeable ions (K(+)), resulting in anomalously high single-channel conductance, approximately 200 pS in 10 mM KCl. An increase of ionic strength due to addition of impermeable cations greatly reduced the unitary conductance. Large positive shift of the SV channel voltage dependence, caused by physiological (0.5 mM) free vacuolar Ca(2+), was partly ameliorated by increasing luminal K(+). We interpreted these results as follows: K(+)induced a reduction of surface potential, hence i) causing a positive shift of the voltage dependence and ii) a dilution of Ca(2+) in the membrane vicinity, thus reducing the inhibitory effect of vacuolar Ca(2+) and causing a negative shift of the SV channel voltage dependence, with a sum of the two shifts being negative.

Beta vulgaris↗
PubMed2005

Independent predictors of renal dysfunction after heart transplantation in patients with normal pretransplant renal function.

BACKGROUND: Renal dysfunction (RD) is a common complication after heart transplantation (HT), but predictors of post-HT RD have not been clearly identified. METHODS: We studied 262 HT patients (mean age 54 years, 221 men) with normal baseline renal function. Potential risk factors examined were age, sex, pre-HT ischemic cardiomyopathy, pre- and post-HT diabetes mellitus, pre- and post-HT arterial hypertension, initial immunosuppressive protocol (before 1998 [high cyclosporine, azathioprine, and prednisone] vs after 1998 [low cyclosporine, mycophenolate mofetil, and prednisone]), occurrence of rejection episodes > or =ISHLT Grade 3A, and creatinine level 1 month after HT. RD was considered mild if creatinine level was 1.5 to 2.5 mg/dl, moderate if creatinine level was >2.5 mg/dl, and severe if dialysis or kidney transplant was required. RESULTS: The cumulative incidence of RD (creatinine >1.5 mg/dl) was 35% at 12 months, 42% at 24 months, and 47% at 60 months (mean follow-up 59 +/- 31 months). Only 1% of patients had severe RD 60 months after HT. Independent predictors of RD 24 months after HT were older age (odds ratio [OR] 1.1 [95% confidence interval (95% CI) 1.0-1.1]; p = 0.001), male sex (OR 3.3 [95% CI 1.3-8.1]; p = 0.008), pre-1998 immunosuppressive protocol (OR 2.8 [95% CI 1.4-5.4]; p = 0.003), and creatinine level 1 month after HT (OR 3.2 [95% CI 1.0-5.4]; p < 0.0001). CONCLUSIONS: The cumulative incidence of RD in HT patients treated with calcineurin inhibitors increased with time after HT. Age, male sex, an immunosuppressive protocol with relatively high cyclosporine levels and creatinine level 1 month after HT were independent predictors of the presence of RD 24 months after HT.

Adult↗
PubMed2005

Long-term results of heart transplant in recipients older and younger than 65 years: a comparative study of mortality, rejections, and neoplasia in a cohort of 445 patients.

BACKGROUND: Whether being older than 65 years should be considered an absolute counterindication to heart transplant (HT), as it is in some centers, is controversial. In our centre, patients older than 65 years are accepted for HT if they satisfy stringent conditions. The aim of this study was to examine whether heart recipients older than 65 years have a greater risk of rejection, neoplasia, or mortality than younger ones. METHODS: We studied 445 patients who underwent HT between April 1991 and December 2003, 42 of whom were older than 65 years and 403 who were 65 years or younger. The parameters evaluated were the cumulative incidences of neoplasias and rejections (ISHLT grade > or = 3A), and the survival rates 1 month, 1 year, and 5 years post-HT. RESULTS: The two groups had similar percentages of patients with at least one rejection episode (< or =65 years 56.9%, >65 years 51.3%; P > .05), and although there were proportionally almost twice as many tumors in the older group (14.2%) as in the younger (7.9%), this difference was not statistically significant either. Nor were there any significant differences in survival, the 1-month, 1-year, and 5-year rates being 87.8%, 82.1%, and 68.8%, respectively, in the younger group and 85.7%, 78.6%, and 73.4%, respectively, in the older. CONCLUSIONS: Among carefully selected patients aged more than 65 years, HT can be performed without incurring greater risk of rejection, malignancy, or death than is found among recipients younger than 65 years.

Age Factors↗
PubMed2005

Cytotoxin and pyrogenic toxin superantigen gene profiles of Staphylococcus aureus associated with subclinical mastitis in dairy cows and relationships with macrorestriction genomic profiles.

A set of 84 Staphylococcus aureus isolates collected from the milk of cows with subclinical mastitis in Asturias (a cattle region of Spain) and six control strains were tested for sequences of genes encoding hemolysins (hla, hlb, hld, hlg, and hlg-2), leukotoxins (lukPV, lukM, and lukED), toxic shock syndrome toxin (tst), and enterotoxins (sea to see, seg to ser, and seu) by conventional and multiplex PCR. It was found that 84, 83, 11, and 39 isolates carried some type of hl, luk, tst, or se gene, respectively, which were arranged in 14 exotoxin genotypes. All of the isolates were negative for lukPV, hlg, sea, sed, see, sej, sek, sep, seq, and ser. Two gene groupings could be related with pathogenicity islands-[lukED, seg, sei, sem, sen, seo +/- seu] with Sabeta-1 and [tst, sec, sel] with SaPIbov, present in 45 and 13.1% of the isolates, respectively-while 11.9% of them carried both islands. Only one contained seb (together with upsilonSabeta-1), and another contained seh (together with lukED). The isolates were also analyzed by pulsed-field gel electrophoresis performed with SmaI. Thirty-nine SmaI profiles (similarity coefficient [S] = 0.94 to 0.21) were differentiated; 12, 1, and 10 of these, respectively, were generated by isolates presumptively carrying Sabeta-1, SaPIbov, or both. Five SmaI profiles (S > or = 0.8) formed a cluster, which contained 20 and 10 isolates carrying one (upsilonSabeta-1) or both islands. These data show the high frequency of genes encoding cytotoxins and pyrogenic toxin superantigens, their relationship with pathogenicity islands, and their distribution among a diversity of genetic types of S. aureus related to subclinical mastitis.

Animals↗
PubMed2003

Folding-unfolding of FN-III domains in tenascin: an elastically coupled two-state system.

In a single-molecule atomic force microscopy (AFM) experiment, the tenascin molecule is stretched by an external force causing an elongation which is due to the unfolding of the FN-III modules. The features of the force-extension curves depend on the pulling speed and show a saw-tooth pattern (lower speeds) or a smooth pattern (higher speeds). In any case, the unfolded domains are elastically coupled to the unfolded modules, acting as transmitters of the external force. In this communication, the folding-unfolding process of the FN-III domains in tenascin is studied using reaction rate theory and a simple two-state model. The main hypothesis of the study is that, at microscopic level, the force needed to unfold a domain and the unfolding rate (unfolding velocity) can mimic the macroscopic process of measurement by AFM. As the external force is applied, the probability of unfolding increases as dictated by the reaction rate theory. Within this context, a relationship between the unfolding force and the unfolding velocity is obtained. The latter relation will describe microscopically the process in a phenomenological fashion. Moreover, while relating the results of this study with other experimental (AFM measurements) and theoretical (Monte Carlo simulations) data, we found that the graph of unfolding force-unfolding velocity is similar to that of external force-pulling velocity. The refolding process can also be studied within this model and the results show similar trends. The latter suggests a generic and universal behavior of such kind of molecular domains at least in the light of the proposed model.

Computer Simulation↗
PubMed2003

Neither acute rejection nor immunosuppressant drug therapy (cyclosporine or tacrolimus) correlates with expression of either CD40 or CD154 on peripheral blood cells among human cardiac transplant patients.

Acute allograft rejection (AAR) is an important cause of graft loss following heart transplantation (HT). Increasing evidence shows that CD40-CD154 interactions play a central role in the immune processes leading to AAR. In this study we investigated the expression of CD40 and CD154 on peripheral blood cells from HT patients so as to determine possible association with AAR. Using two-color flow cytometry, we determined the expression of CD40 and CD154 in 102 samples of peripheral blood taken from 53 adult HT patients and in 17 samples from healthy adult volunteers. Samples from patients were obtained at the same time as endomyocardial biopsy was performed. We analyzed the relationships between the expression of these molecules and the following parameters: immunosuppressive treatment (cyclosporine vs tacrolimus), gender, age, time post-HT, and AAR (indicated by an ISHLT rating > or =3A). The percentages of HT patients' blood samples showing above-normal CD40 or CD154 expression did not differ significantly from those of controls. The percentage of patients' samples showing above-normal CD40 expression decreased with time after HT. Expression of these molecules was not above normal during rejection episodes, and for neither was there any statistically significant correlation between expression level and the immunosuppressor drug.

Adult↗
PubMed2003

Renal dysfunction after orthotopic heart transplantation: incidence, natural history, and risk factors.

BACKGROUND: Renal dysfunction is a common complication after orthotopic heart transplantation (HT). The importance of factors other than exposure to immunosuppressive drugs is unclear. The purpose of this study was to determine the incidence and natural history of renal dysfunction following heart transplantation, and to evaluate a number of variables as risk factors for this condition. METHODS: We examined the creatinine levels at 1, 6, 12, 24, and 60 months in 262 consecutive heart transplant patients who survived at least 1 year. The potential risk factors included pre- and posttransplantation diabetes mellitus, arterial hypertension, and drugs used to control arterial hypertension. RESULTS: 17.2% of patients showed mild renal dysfunction (creatinine 1.5-2.5 mg/dL) and 1.9% moderate dysfunction (creatinine >2.5 mg/dL) at 1 month; 29.8% showed mild and 1.1% moderate dysfunction at 6 months; 33.2% showed mild and 1.9% moderate dysfunction at 1 year; 40% showed mild, 0.9% moderate and 0.4% severe dysfunction (requiring dialysis or renal transplantation) at 2 years; and 43.6% showed mild, 1.7% moderate and 0.9% severe dysfunction at 5 years. None of the conditions analyzed as possible risk factors showed a significant association with renal dysfunction except the use of diuretics. CONCLUSION: The incidence of renal dysfunction after orthotopic heart transplantation was 33.6% within the first year after transplant and 44% within the first five years, although more than 95% of cases were mild. The incidence increased with time after transplantation. Renal dysfunction seems likely to be multifactorial in origin, but no individual risk factors were identified.

Creatinine↗
PubMed2003

Hypotension, acidosis and vasodilation syndrome after heart transplant: incidence, risk factors, and prognosis.

BACKGROUND: HAV syndrome, the combination of hypotension, acidosis and vasodilation (HAV), is a serious postoperative complication after heart transplantation (HT). Its etiology and prognosis are poorly understood. AIM: To determine the incidence and prognosis of post-HT HAV syndrome and examine possible risk factors. METHODS: Retrospective examination of the records of 85 consecutive patients who underwent HT between December 1999 and June 2002 sought the HAV criteria: systolic BP <85 mm Hg plus HCO3 <19 mEq/l whole excluding cardiogenic, hypovolemic and septic shock. Donor variables included sex, age, weight, height, cause of death, time in ICU, and ischemic time; while recipient variables, sex, age, weight, height, etiology of cardiopathy, previous cardiopulmonary bypass surgery, preoperative amiodarone, beta-blockers, catecholamines, mechanical ventilation or intra aortic balloon pump (IABP), RVP, time on waiting list, pump time, reoperations, polytransfusion, preoperative creatinine, GOT, GPT and GGT, induction with OKT3 or anti-CD25, bypass-to-HAV time, duration of catecholamine treatment, and 1 month survival after HT. RESULTS: The 11 HAV cases (13%) appeared between 1 and 72 h after HT (75% in the first hour). Catecholamines were used for 1 to 6 days; control was achieved within 48 h in 58% of cases. Two HAV patients (18%) died within the first month versus six non-HAV patients (8.1%) (P=.275). Only polytransfusion showed more than a borderline value to predict HAV syndrome. CONCLUSIONS: HAV syndrome has an incidence of 13% and a mortality of 18% within 1 month post-HT. The only likely risk factor is polytransfusion.

Acidosis↗
PubMed2001

Conduction of monovalent and divalent cations in the slow vacuolar channel.

The conduction properties of individual physiologically important cations Na+, K+, Mg2+, and Ca2+ were determined in the slowly activating (SV) channel of sugar beet vacuoles. Current-voltage relationships of the open channel were measured on excised tonoplast patches in a continuous manner by applying a +/-140 mV ramp-wave protocol. Applying KCl gradients of either direction across the patch we have determined that the relative Cl- to K+ permeability was < or =1%. Symmetrical increase of the concentration of tested cation caused an increase of the single channel conductance followed by saturation. Fitting of binding isotherms at zero voltage to the Michaelis-Menten equation resulted in values of maximal conductance of 300, 385, 18, and 13 pS, and of apparent dissociation constants of 64, 103, 0.04, and 0.08 mm for Na+, K+, Mg2+, and Ca2+, respectively. Deviations from the single-ion occupancy mechanism are documented, and alternative models of permeation are discussed. The magnitude of currents carried by divalent cations at low concentrations can be explained by an unrealistically wide (approximately 140 A) radius of the pore entrance. We propose instead a fixed negative charge in the pore vestibules, which concentrates the cations in their proximity. The conduction properties of the SV channel are compared with reported characteristics of voltage-dependent Ca2+-permeable channels, and consequences for a possible reduction of postulated multiplicity of Ca2+ pathways across the tonoplast are drawn.

Calcium↗
PubMed2001

Effect of exogenous melatonin on hepatic energetic status during ischemia/reperfusion: possible role of tumor necrosis factor-alpha and nitric oxide.

BACKGROUND: This study was designed to determine if the very potent antioxidant melatonin is able to reduce organ damage and improve energetic status in an in situ liver ischemia/reperfusion model. MATERIALS AND METHODS: Total hepatic ischemia was induced in rats by occlusion of the hepatic artery, portal vein, and bile duct. A portojugular shunt was inserted. After 60 min of ischemia, reperfusion was established for a period of 120 min. Rats were assigned to one group receiving systemic melatonin administration or to another receiving only normal saline. Variables were observed at preischemia, after 60 min of ischemia, and at 30, 60, and 120 min of reperfusion. RESULTS: Energy charge, measured as the arterial ketone body ratio, showed higher values in the melatonin group during the first 60 min of reperfusion. Rises in plasma nitrite, tumor necrosis factor (TNF)-alpha, aspartate aminotransferase, alanine aminotransferase, lipid peroxidation products, and inducible nitric oxide synthase (iNOS) expression were less severe with melatonin. Linear regression analysis demonstrated a significant correlation between nitrites and arterial ketone body ratio (R(2) = 0.2454). Bile production was higher with melatonin. Seven-day survival rates were 52% for control, 80% for melatonin, and 100% for sham groups. CONCLUSIONS: Exogenous melatonin is capable of preserving the functional and energetic status during ischemia/reperfusion which is associated with reduced concentrations of TNF-alpha and inhibited expression of iNOS and NO production. This improvement may be due to an adequate preservation of the hepatic mitochondrial redox status.

3-Hydroxybutyric Acid↗
PubMed2001

[Variability in the in-hospital management of acute myocardial infarction in Spain. IBERICA Study (Investigación, Búsqueda Específica y Registro de Isquemia Coronaria Aguda)].

Introduction and objective. Although some in-hospital studies have described the management of acute myocardial infarction (MI) patients in Spain, none has been able to guarantee the exhaustiveness of patient registry. This study sought to determine the clinical characteristics and in-hospital management of patients with MI in eight Spanish population registries.Methods. The IBERICA study is a population-based MI registry carried out in the 25 to 74 year-old population, in eight Spanish regions in 1997. A standardized methodology was used to register and investigate all MI arriving alive to a hospital. Clinical characteristics, cardiovascular risk factors prevalence, pharmacological treatment, invasive and non-invasive procedures performed and complications at 28 days of evolution were recorded. A descriptive analysis was performed and the variation coefficient (VC) was calculated.Results. In 1997, 4,041 MI patients were registered, 79.9% were men with a mean age of 61.1 years. Although 10.9% (95% CI: 9.9-11.9%) were not admitted to the coronary care unit, a large variability existed among different areas (VC = 53%). There was a high variability in the utilization and performance of non-invasive and invasive procedures among regions, as well as in the use of pharmacological treatment. Only the use of antiaggregants (91.5%) and thrombolytic therapy (41.8%) showed a low variability (VC < 10%). Twenty-eight day mortality was 16.2% (95% CI: 15.1-17.4%) with a high variability being observed among the different regions (VC = 20.6%).Conclusion. Patient characteristics vary among the different Spanish regions. The differences in management and prognosis suggest a lack of equality in the health care provided to MI patients in the different regions in Spain.

Adult↗
PubMed2001

Processing and representation of meta-data for sleep apnea diagnosis with an artificial intelligence approach.

In this article, we revise and try to resolve some of the problems inherent in questionnaire screening of sleep apnea cases and apnea diagnosis based on attributes which are relevant and reliable. We present a way of learning information about the relevance of the data, comparing this with the definition of the information by the medical expert. We generate a predictive data model using a data aggregation operator which takes relevance and reliability information about the data into account to produce a diagnosis for each case. We also introduce a grade of membership for each question response which allows the patient to indicate a level of confidence or doubt in their own judgement. The method is tested with data collected from patients in a Sleep Clinic using questionnaires specially designed for the study. Other artificial intelligence predictive modeling algorithms are also tested on the same data and their predictive accuracy compared to that of the aggregation operator.

Adult↗
PubMed2001

Effects of sprint and endurance training on passive stress-strain relation of fast- and slow-twitch skeletal muscle in Wistar rat.

We investigated the effects of endurance and sprint training on the passive mechanical properties of fast-twitch (FT) and slow-twitch (ST) skeletal muscles. Eight-week-old male Wistar rats (n=18) were divided into three groups: control (C), sprint-trained (S) and endurance-trained (E). The trained animals exercised for 10 weeks on a treadmill. Under anaesthesia, Plantaris and Soleus muscles were deformed cyclically in vivo at 0.33 mm x s(-1) with length increments of 1 mm in successive cycles until rupture. The rupture of muscle occurs at belly. Stress-strain relation were constructed using the maximum stress and maximum strain in each cycle. The data were fitted to an S-shaped curve. The curve-fitting parameters for trained and untrained muscles showed significant statistical differences. Stress and strain at rupture and maximum deformation energy were statistically greater for trained ST muscles (both groups) than for the controls. The changes induced by the present training protocols were not significant in Plantaris. The above results suggest the plasticity of passive structure caused by activity-demands.

Animals↗
PubMed2000

[Dermatologic complications after heart transplantation: incidence and prognosis].

BACKGROUND: This study was conducted to analyze the type, incidence, predisposing factors and prognosis of cutaneous complications (CC) occurring in heart transplant recipients (HTR). PATIENTS AND METHODS: A retrospective study was carried out among 192 HTR with a survival > 1 month. The following variables were recorded: age, sex, place of residence, post-transplant diabetes, glucocorticoid dose, prophylaxis with acyclovir/itraconazole and CC. RESULTS: One hundred sixty three CC were diagnosed in 93 patients. The major types were infectious complications (n = 115; 70.5%) and tumors (n = 20; 12.3%). The most common infections were viral (herpes zoster; n = 22) and fungal (pityriasis versicolor; n = 53). Out the 20 tumors, 3 were malignant: 2 squamous cell carcinomas (SCC) and 1 Kaposi sarcoma. None of the CC caused mortality or prolonged hospital stay. No relationship was found between CC and the variables studied. CONCLUSIONS: Skin infections were the most common CC in this cohort of HTR. The incidence of SCC was very low and its prognosis was good due to early diagnosis and surgical excision.

Aged↗