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F Segura

Publications and source records attributed to F Segura.

At least 37 records · Page 2Linked to original sources
PubMed2000

Automatic analysis for amperometrical recordings of exocytosis.

Amperometry is a widely used technique for monitoring the secretion of catecholamines (CA) by exocytosis. The use of carbon fibre microelectrodes allows the on-line recording of CA released from a single secretory vesicle. Amperometric signals are generated by oxidation of the quantally released CA close to the electrode tip. Each event of exocytosis is called a secretory spike. Here we describe a program written for IGOR (Wavemetrics, Lake Oswego, OR, USA), which may be used to analyze amperometric signals off-line. The procedures allow, (i) digital filtering and analysis of the current noise, spike identification and calculation of spike kinetic parameters; (ii) spike review; (iii) pooling spikes and data to create galleries, tables and histograms of measured parameters which can be exported to a graphic format or files for further analysis.

Action Potentials↗
PubMed2000

Comparison of twice-daily stavudine plus once- or twice-daily didanosine and nevirapine in early stages of HIV infection: the scan study.

OBJECTIVES: To evaluate the safety and effectiveness of once-daily didanosine and nevirapine plus twice-daily stavudine versus twice-daily administration of all three drugs. METHODS: This open-label, randomized, multicentre study enrolled 94 antiretroviral-naive patients with chronic HIV infection, CD4+ cell counts > 500 x 10(6) cells/l, and viral loads > 5000 copies/ml. Patients were treated with either 40 mg stavudine (twice daily) plus 400 mg didanosine (once daily) and 400 mg nevirapine (once daily) or 40 mg stavudine (twice daily) plus 200 mg didanosine (twice daily) and 200 mg nevirapine (twice daily). RESULTS: After 12 months, 68% of patients who received twice-daily didanosine and nevirapine had viral loads < 200 copies/ml in the intention-to-treat and 79% in the on-treatment analysis, respectively. The corresponding values for patients treated with didanosine and nevirapine, taken once-daily, were 73 and 85%. The percentages of patients in each group with viral loads < 5 copies/ml at 12 months were 40% (once daily ) and 45% (twice daily) for the intention-to-treat analysis. Five of 11 patients (45%) with plasma viral loads < 5 copies/ml at 12 months had detectable virus in tonsillar tissue. Genotypic resistance to nevirapine was noted in seven of the 14 patients with detectable viral load at month 12. Mean changes in CD4+ cell counts for patients treated with stavudine plus once- or twice-daily didanosine and nevirapine were 154 and 132 x 10(6) cells/l, respectively. Treatment was interrupted due to adverse events in seven patients (8%) (four who received once-daily didanosine and nevirapine and three treated with twice-daily doses). CONCLUSIONS: The combination of twice-daily stavudine plus once-daily didanosine and nevirapine was as safe and well tolerated as twice-daily administration of all three agents. Both regimens were equally effective in reducing viral loads and in increasing CD4+ cell counts.

Anti-HIV Agents↗
PubMed2000

Comparison of immunologic restoration and virologic response in plasma, tonsillar tissue, and cerebrospinal fluid in HIV-1-infected patients treated with double versus triple antiretroviral therapy in very early stages: The Spanish EARTH-2 Study. Early Anti-Retroviral Therapy Study.

The objective of antiretroviral therapy is to obtain an almost complete and durable suppression of viral replication in all compartments to facilitate recovery of the immune system. We assessed the virologic effect in plasma, tonsillar tissue, and cerebrospinal fluid (CSF) in 94 HIV-1-infected patients with CD4 counts >500 x 106 cells per liter and viral load >5000 copies/ml randomly assigned to triple antiretroviral therapy (two nucleoside reverse transcriptase inhibitors (NRTIs) plus one protease inhibitor) versus double therapy (two NRTIs). We also analyzed the immunologic recovery in this cohort of patients. Lymphoid tissue and cerebrospinal fluid viral load, development of genotypic resistance, proliferative responses to HIV-1 specific antigens, and other immunophenotypic markers were analyzed. The proportion of patients who achieved a decrease in HIV RNA levels to <200 copies/ml was significantly greater in the triple therapy group than in the two drug groups (p =.0002 for each pair-wise difference). At week 52, tonsillar tissue HIV RNA from 5 patients treated with triple therapy was lower than the limit of detection, whereas the mean +/- standard error in patients with double therapy (n = 5) was 5.03 +/- 0.34 copies/mg/tissue. In all 10 patients, CSF viral load (VL) was <20 HIV-1 RNA copies/ml at week 52. CSF cell counts and protein levels tended to decrease after 52 weeks of antiretroviral therapy. After 1 year of therapy, 13 of 21 patients (62%) in the double-therapy groups (zidovudine plus lamivudine [n = 9] and stavudine plus lamivudine [n = 12]) had evidence of M184V mutation. None of the 10 samples of patients receiving triple therapy could be amplified because of low HIV RNA levels. The mean increase in CD4 cells at week 52 was greater in the stavudine and lamivudine and indinavir group than in the double-treatment arms (186 versus 67 and 102, respectively; p =.03). In patients treated with triple therapy, the increase in naive T cells (CD4 and CD8) was greater than in patients treated with double therapy. Markers of activation decreased further in patients treated with the regimen that included protease inhibitors. Proliferative responses to HIV-1 p24 antigen were never recovered after double or triple therapy. Our study suggests that even in very early stages of HIV-1 disease only therapy with two NRTIs and one protease inhibitor reduces plasma, lymphoid tissue, and CSF VL to undetectable levels. HIV-1-related immune system abnormalities improved but were still defective after 1 year of antiretroviral therapy.

Adult↗
PubMed2000

Nitric oxide modulates a late step of exocytosis.

The effects of nitric oxide (NO) on the late phase of exocytosis have been studied, by amperometry, on Ba(2+)-stimulated chromaffin cells. Acute incubation with NO or NO donors (sodium nitroprusside, spermine-NO, S-nitrosoglutathione) produced a drastic slowdown of the granule emptying. Conversely, cell treatment with N(omega)-nitro-l-arginine methyl ester (a NO synthase inhibitor) or with NO scavengers (methylene blue, 2-(4-carboxyphenyl)-4,4,5, 5-tetramethyl-imidazoline-1-oxyl-3-oxide potassium) accelerated the extrusion of catecholamines from chromaffin granules, suggesting the presence of a NO modulatory tone. The incubation with phosphodiesterase inhibitors (3-isobutyl-1-methylxanthine or zaprinast) or with the cell-permeant cGMP analog 8-bromo-cGMP, mimicked the effects of NO, suggesting the involvement of the guanylate cyclase cascade. NO effects were not related to changes in intracellular Ba(2+). NO did not modify the duration of feet. Effects were evident even on pre-fusioned granules, observed under hypertonic conditions, suggesting that the fusion pore is not the target for NO, which probably acts by modifying the affinity of catecholamines for the intragranular matrix. NO could modify the synaptic transmitter efficacy through a novel mechanism, which involves the regulation of the emptying of secretory vesicles.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Neoplasia of plasma cells with atypical presentation and infection by the human immunodeficiency virus. A presentation of two cases.

Neoplasia of plasma cells acquires special clinical characteristics in patients infected by human immunodeficiency virus (HIV). These patients are much younger at the time of diagnosis, and when they are compared with the general population they show an atypical clinical evolution, with a greater frequency of solitary plasmacytomas, less evidence of a monoclonal plasmatic component, or greater aggressiveness of the neoplastic process. This paper provides the most significant data on two patients infected by HIV and diagnosed for plasma cell neoplasia. Recent pathogenetic hypotheses for plasma cell neoplasias that include immune alterations, chronic viral infections, and hyperexpression of cytokines exist in patients infected by HIV, and this could suggest that this type of neoplasia is another malignant haematological process associated with AIDS.

Adult↗
PubMed2000

Short report: isolation and identification of two spotted fever group rickettsial strains from patients in Catalonia, Spain.

Two rickettsial strains, 16B (previously isolated) and FB1, were isolated from blood from patients with Mediterranean spotted fever in Catalonia, Spain. These are the only 2 human rickettsial isolates of the spotted fever group obtained so far in Spain. These strains were identified by the polymerase chain reaction and sequence analysis of a fragment of the outer membrane protein A (ompA) gene. The partial ompA sequence was found to be 100% identical with that of Rickettsia conorii (Malish 7 strain) for both strains. These results confirm the presence of R. conorii in Catalonia, despite the fact that in a previous study, no R. conorii were isolated, but a new rickettsial strain of the spotted fever group (Bar29) was isolated from dog ticks (Rhipicephalus sanguineus) in Catalonia. Further studies are necessary to get a better knowledge of the epidemiology of rickettsiae in Catalonia.

Bacterial Outer Membrane Proteins↗
PubMed1999

[Tuberculosis in a social health care center: epidemiologic study and prevention activities].

BACKGROUND: The high prevalence of infection and the often atipic presentation of tuberculosis in older people constitute an important risk factor for the nosocomial spread of the infection in the long-term care hospitals. PATIENTS AND METHOD: After a tuberculosis case, in a patient with positive sputum smears, in a long-term care hospital with 220 beds, we established a preventive programme that was based on: a) the determination, by the tuberculin test, of the prevalence of tuberculosis infection; b) the early detection of new cases of the disease, and c) the evaluation of the indications of the chemoprophylaxis. RESULTS: The global prevalence of the tuberculosis infection was 44%. 16% of the patients with a significant reaction to tuberculin showed lung fibrosis in the X-ray of the thorax and 27% of them were diagnosed as active tuberculosis. During the first year of the study, the rate of illness between the infected cases was 6.45%. After 2 years the conversion rate of the tuberculin test was 6.25%. CONCLUSIONS: Tuberculosis is an endemic infection in our long-term care hospital and the diagnostic delay of the active illness is an important risk factor for its dissemination. The difficulty of the interpretation of the response to the tuberculin test in old people, the evidence of the hidden illness in patients with lung fibrosis and some physic-psychological conditions of those patients, make the application of the chemoprophylaxis difficult.

Aged↗
PubMed1999

A new way for the analysis of the exocytosis.

Exocytosis is the most common way for cells to secrete substances. This is a wide distributed phenomenon that involves all cell types and all animal species from yeast to human. Catecholamine (CA) release from adrenal chromaffin cells occurs by the exocytosis of secretory vesicles also called chromaffin granules. Individual secretory events can be easily monitored by the use of carbon fibers encased in glass microelectrodes. Catecholamines oxidized at the electrode tip produce a transient electrical current wave called secretory spike. The typical secretory spike consists in a sharp elevation of current followed by a rapid exponential decrease to the basal level. A 35-50% of the spikes showed a pre-spike wave called "foot" which represents the CA release through the fusion pore. The time course of secretory spikes observed is altered by extracellular phenomena's like diffusion. It has been suggested that amperometric spikes can be described by the convolution of a Gaussian with a decreasing exponential. The exponential function is partially governed by the diffusion of the secreted substances towards the electrode. In this article a method to deconvolve both functions is proposed. This mathematical approach allows the observation of the original secretory profile--the Gaussian--without the distortion caused by the diffusional broadening of catecholamines.

Adrenal Medulla↗
PubMed1996

[Prevalence of nosocomial urinary infection. Alternatives to bladder catheterization].

BACKGROUND: The detection of a high percentage of nosocomial urinary infection (NUI) associated with vesical catheterization (VC) and the frequent use of VC in patients with urinary incontinence, led us to implant a prevention programme which included the introduction of absorbent diapers as a alternative to vesical catheterization in incontinent patients. MATERIAL AND METHODS: After actualization and introduction of VC preventive measures and the introduction of absorbent diapers, regular determinations were made of the prevalence of NUI with analysis of the variations using the chi 2 test for trends. The prevalence of urinary incontinence and the efficacy of the diapers were also measured. RESULTS: The prevalence of NUI associated with VC showed a significant decrease, from 27.5% to 3% (p = 0.004). Between 6% and 11% of the patients admitted to the medical service had urinary incontinence. After introduction of the diapers as part of health care assistance programme, the use of VC in patients with urinary incontinence is rare. CONCLUSIONS: 1) The prevention programme allowed a significant reduction in the prevalence of NUI associated with VC. 2) The use of absorbent diapers to care for patients with urinary incontinence probably contributed to reducing the prevalence of NUI. It was well accepted by the nursing staff and iatrogeny associated with their use was scarce.

Aged↗
PubMed1996

Antimicrobial use in patients with positive intravascular catheter cultures: a six-month prospective survey in a teaching hospital.

Review of medical records revealed that, of 190 intravascular catheters sent for culture during the study period, 50 were positive. Of these 50, 11 (22%) were sent for culture as a routine procedure without special clinical indications. Of the remaining 39 cultures, only 11 (28%) had clinical impact in the patient's management. Ten of the 50 therapeutic interventions were inappropriate. Restricting cultures to patients who may have catheter-related infection is likely to lead to significant cost savings.

Anti-Bacterial Agents↗
PubMed1993

Antibodies to Rickettsia conorii in dogs: seasonal differences.

Eight dogs, having showed positivity to Rickettsia conorii in serum samples obtained during the spring and summer, were studied again by means of a second determination during the next winter, 4-10 months later. Serum titer became negative in six dogs, persisted high in one, and fell from 1:640 to 1:40 in another dog. This seasonal difference suggests a short persistence of antibodies in dogs after contact with R. conorii in the Mediterranean area.

Animals↗
PubMed1990

Randomized trial of doxycycline versus josamycin for Mediterranean spotted fever.

We undertook a randomized clinical trial comparing therapeutic efficacy of the 1-day doxycycline regimen with the 5-day josamycin regimen for Mediterranean spotted fever. All 59 patients recovered uneventfully, and results did not significantly differ between the two schedules. One-day doxycycline therapy is an effective, easy, and inexpensive treatment. Josamycin is a useful therapeutic alternative that may be particularly convenient for pregnant women and patients with a history of allergy to tetracyclines.

Adolescent↗