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Biomedical subjects

C Ramírez

Publications and source records attributed to C Ramírez.

At least 19 recordsLinked to original sources
PubMed2006

Influence of degree of hepatic steatosis on graft function and postoperative complications of liver transplantation.

The aim of this study was to evaluate the impact on initial graft function of the degree of steatosis detected in the back-table biopsy, and its repercussion on the clinical results of the transplant (early posttransplant mortality and morbidity). We undertook a retrospective analysis of 300 liver transplants performed at our center from 1997 to 2004. A wedge liver biopsy was done routinely during back-table surgery (available in 294 transplants). The degree of steatosis was classified as: S0-no steatosis, 201 transplants; S1-mild steatosis (<30%), 58 transplants; S2-moderate steatosis (30% to 60%), 18 transplants; and S3-severe steatosis (>60%), 17 transplants. The ischemia-reperfusion (I/R) injury, based on the maximum mean peak aspartate transferase in the first 72 posttransplant hours, tended to be greater as the degree of graft steatosis increased: S0, 1316; S1, 1985; S2, 2446; and S3, 2955 (P < .005 between S0 and S3). This greater initial hepatic dysfunction was correlated in the group with severe steatosis with a higher rate of severe renal failure requiring hemofiltration/hemodialysis: S0, 9%; S1, 15%; S2, 11%; and S3, 41% (P < .001); as well as with a higher early mortality (90 days): S0, 10%; S1, 21%; S2, 11%; and S3, 41% (P < .001). The Kaplan-Meier survival curve showed a significant difference (log-rank and Breslow) between the group with severe steatosis and the group with no steatosis (P = .002). We conclude that the degree of liver graft steatosis is an important determinant of I/R injury, although this progressive increase in the I/R injury with the degree of steatosis only had clinical repercussions in the case of severe steatosis.

Fatty Liver↗
PubMed2005

Liver transplant results for hepatocellular carcinoma applying strict preoperative selection criteria.

INTRODUCTION: Liver transplantation is currently the best therapeutic option for small hepatocellular carcinoma (HC) in selected cirrhotic patients. The main aim of this study was to analyze the results of a recent series of liver transplant cirrhotic patients with small HC applying strict preoperative selection criteria. PATIENTS AND METHODS: During a period of 6 years we performed 53 liver transplants with a final diagnosis of HC on cirrhosis. The selection criteria for liver transplantation (LT) by modern imaging techniques were the Milan criteria (TNM I and II of the modified classification). RESULTS: Of the 53 patients, 44 (83%) were transplanted with preoperatively known HC, and 9 (17%) with incidental HC. The mean time on the waiting list was 74 +/- 62 days. Despite using strict selection criteria, 23 patients (43%) exceeded the Milan criteria in the specimen and 17 (32%) even exceeded the extended criteria of the UCSF. With a mean follow-up of 2 years, only two patients have developed recurrences. The overall survival at 1, 3, and 5 years was 80%, 70%, and 70%, respectively. The survival of patients that exceeded the Milan or USF criteria at 1, 3, and 5 years was 72% and 76%; 67% and 69%; 67% and 69%, respectively. CONCLUSIONS: The results of liver transplantation for HC are excellent when applying strict preoperative selection criteria. The current imaging methods lead to a considerable infrastaging percentage (30% to 40%), extending the indications for liver transplant due to HC beyond the scope that clinical reports would justify.

Carcinoma, Hepatocellular↗
PubMed2004

Severe cardiac allograft dysfunction without endomyocardial biopsy signs of cellular rejection: incidence and management.

Acute dysfunction of cardiac allograft without evidence of cellular rejection is a potentially fatal complication of heart transplantation that suggests a humoral origin. In clinical practice, humoral rejection (HR) is suspected when there is evidence of severe allograft dysfunction but endomyocardial biopsy (EMB) shows no evidence of cellular rejection. Between April 1991 and August 2003, 12 patients (2.74%) among 438 heart transplants displayed this condition. Time post-heart transplant (HT) was 21.3 +/- 24.7 months (range 2 to 72 months). Immunofluorescence studies using classic markers were negative. All patients were treated with methylprednisolone "bolus" and plasmapheresis until clinical recovery, after which their immunosuppressive regimens were modified. Eleven of the 12 patients recovered satisfactory allograft function. In this series the incidence of suspected HR was low. Unlike other studies, we observed HR not only soon but also even years after HT. Plasmapheresis seems to be an effective treatment.

Adult↗
PubMed2004

Methylene blue-photoinactivated plasma vs. fresh-frozen plasma as replacement fluid for plasma exchange in thrombotic thrombocytopenic purpura.

BACKGROUND AND OBJECTIVES: Plasma exchange with fresh-frozen plasma (FFP) is the treatment of choice in thrombotic thrombocytopenic purpura (TTP). Methylene blue-photoinactivated plasma (MBPIP) has been proposed as a safer alternative to FFP, but its effectiveness in the treatment of TTP is not well established. The purpose of this study was to investigate whether MBPIP is as effective as FFP in the treatment of TTP by plasma exchange. MATERIALS AND METHODS: A retrospective analysis was carried out of 56 TTP episodes, occurring between 1990 and 2003, which had been treated by plasma exchange. MBPIP was used for fluid replacement in 27 episodes and FFP in 29. The effect of plasma (MBPIP or FFP) on treatment outcomes was analysed by multivariate logistic regression. RESULTS: Compared to patients treated with FFP, those receiving MBPIP had an increased risk of dying from progressive TTP [adjusted odds ratio (OR) = 31; 95% confidence interval (CI): 1.2 to > 100], a greater number of recurrences while on plasma exchange therapy (OR = 4.6; 95% CI: 1.2-17), and a lower probability of attaining a sustained remission within 9 days of starting plasma exchange (OR = 5.2; 95% CI: 1.3-20). CONCLUSIONS: MBPIP seems to be less effective than FFP in the treatment of TTP. It is therefore prudent to avoid MBPIP until therapeutic equivalency to FFP has been established by randomized, controlled trials.

Adult↗
PubMed2003

Application of CFD modelling to study the hydrodynamics of various anaerobic pond configurations.

The simulation of hydrodynamics and transport phenomena in waste stabilization ponds is a developing tool worth studying in order to understand their internal processes and interactions. Pond design involves several physical, hydrological, geometric and dynamic variables so as to provide high hydrodynamic efficiency and maximum substrate utilization rates. CFD modelling allows the combination of these factors to predict the behaviour of ponds having different configurations. The two-dimensional depth-integrated model MIKE 21 was used in this study to simulate hydrodynamic and advection-dispersion processes in a full-scale anaerobic pond (AP) located in southwest Colombia. A set of 12 configurations including sludge contents, inlet-outlet positioning, baffling and pond geometry were modelled. Results showed that a crosswise (diagonally opposite) inlet-outlet layout, a length-to-breadth ratio of 2:1, plus provision of two cross baffles at 1/3 L and 2/3 L were the most effective measures to improve overall AP hydrodynamics and dispersion patterns.

Bacteria, Anaerobic↗
PubMed2002

Noncommutative quantum cosmology.

We propose a model for noncommutative quantum cosmology by means of a deformation of minisuperspace. For the Kantowski-Sachs metric we are able to find the exact wave function. We construct wave packets and show that new quantum states that "compete" to be the most probable state appear, in clear contrast with the commutative case. A tunneling process could be possible among these states.

Journal Article↗
PubMed2002

Influence of reagents formulation on real-time PCR parameters.

Real-time polymerase chain reaction (PCR) techniques are increasingly used to quantify target sequences for diagnostic and research purposes. Due to its 'quantitative' character, it is very important to determine the variability of this technique correlating with several experimental conditions. The objective of this study was to analyse the effect of manufacturing lots of PCR reagents on two main PCR parameters, specificity and sensitivity. For this study, we used four different amplicons, using either mouse genomic DNA or viral DNA. Although a PCR product could be obtained in any of the conditions, we observed that there are relevant variations in sensitivity depending on the reagents formulation. We conclude that different lots of reagents may determine the analytical performance of PCR assays indicating that reagents testing are of special importance when the PCR protocol is used for quantitative purposes.

Actins↗
PubMed2001

The effect of BCG vaccination on tuberculin reactivity and the booster effect among hospital employees.

BACKGROUND: We estimated the effect of remote BCG vaccination on tuberculin reactivity and the booster effect among hospital employees. METHODS: Cross-sectional survey at a university hospital. All personnel employed during a 24-month period were included in the study. Employees were administered 2-step tuberculin testing, and BCG vaccination scars were verified. RESULTS: Of 665 hospital employees studied, 239 (36%) had been vaccinated with BCG in childhood. Significant tuberculin reactions (> or =5 mm) were more frequent among BCG-vaccinated (60%) than among nonvaccinated (29%) employees (odds ratio [OR], 3.6; 95% confidence interval [CI], 2.6-5.2). The predictive value of tuberculosis infection increased with increasing reaction size and greater age (from 37% in subjects 30 years or younger with indurations > or =5 mm to 100% in subjects 50 years or older with indurations > or =15 mm). Among 374 employees with a negative tuberculin test reaction who underwent a second test, 39 (43%) of 91 vaccinated subjects had a positive booster reaction in contrast to 51 (22%) of 232 nonvaccinated subjects (OR, 3.4; 95% CI, 2-5.7). Neither different size criteria nor different definitions of the booster effect had an impact on the predictive value of tuberculosis infection. CONCLUSIONS: Remote BCG vaccination largely influences the tuberculin reaction and the boosting phenomenon among hospital employees. The interpretation of the results of 2-step tuberculin testing in a BCG-vaccinated subject must take into account age, size of the reaction, and local prevalence of tuberculosis infection. No single criterion, however, can accurately separate reactions caused by true infection from those caused by BCG vaccination.

Adult↗
PubMed2001

Tuning dimensionality by nanowire adsorption on layered materials.

The dimensionality of electronic states determines a number of physical phenomena such as phase transitions, transport, or superconductivity. Employing scanning tunneling microscopy combined with angle-resolved photoemission spectroscopy we demonstrate how the dimensionality of electronic states can be continuously tuned from three to two dimensions. This is achieved by adsorption of nanowires on surfaces of layered crystals without changing the chemical composition of the material. Exemplary results for Rb nanowires on TiTe2 are discussed with the help of electronic structure calculations.

Journal Article↗
PubMed2001

Synthesis of analogues of Eunicea gamma-cembranolides containing cyclic ethers via saponification.

A method for the synthesis of derivatives of the lead structures euniolide (1), 12,13-bisepieupalmerin (2), and eupalmerin acetate (3) containing tetrahydrofuran and tetrahydropyran ring systems was developed on the basis of alkali-induced intramolecular oxacyclizations. Representatives of the new analogues were submitted to the in vitro antitumor cell-line-screening program of the National Cancer Institute (NCI). While it was shown that a variety of structural modifications are possible, these transformations led typically to nontoxic synthetic cembranoids.

Animals↗
PubMed2001

Acute nutritional and intestinal changes after pelvic radiation.

OBJECTIVE: Pelvic radiotherapy induces acute small bowel injury but its effects on nutritional status are unknown. The objective of this study was to prospectively evaluate nutritional, functional and morphologic intestinal changes, after radiotherapy. METHODS: Fifteen patients were studied before and after pelvic irradiation. A clinical, nutritional and routine clinical laboratory assessment was performed. Nutritional parameters included dietary recall, subjective global assessment, anthropometric measurements (body mass index, skinfold thickness at four sites and circumferences of arm, waist and hip), hand grip strength, indirect calorimetry and Dual Energy X-ray absortiometry (DEXA). Intestinal parameters included permeabilty to sugars (assessed by lactulose and mannitol urinary excretion), intestinal transit time (measured by hydrogen breath test after ingestion of lactulose) and jejunal biopsies. RESULTS: Thirteen patients presented diarrhea during radiation therapy. After five weeks, intestinal permeability increased, while intestinal transit time decreased. The second biopsy showed hypertrophy of villae and crypts. Simultaneously, patients lost weight at the expense of fat free mass. Resting energy expenditure was elevated prior to treatment and declined after five weeks. Changes in caloric ingestion were not significant. CONCLUSIONS: Our results indicate that pelvic radiation induces a loss of fat free mass along with intestinal morphologic and functional changes.

Adult↗
PubMed2001

Genotypic characterization of Toxoplasma gondii strains associated with human toxoplasmosis in Spain: direct analysis from clinical samples.

Genetic analysis of the SAG2 locus was performed to determine the prevalence of the different genotypes of Toxoplasma gondii (strain types I, II, and III) associated with human toxoplasmosis in Spain. This determination was made directly from primary clinical samples, obviating the previous process of isolation in mice or cell culture. A total of 34 isolates of T. gondii, collected from immunocompromised patients and congenital infection cases, were analyzed. Restriction fragment length polymorphism in PCR-amplified SAG2 products was used to group strains into one of the three genotypes of T. gondii. Complete characterization of the SAG2 gene was successful in 76.5% of the cases, demonstrating the feasibility of direct genotype analysis from clinical samples of different origins. Strains of T. gondii type II were the most prevalent in immunocompromised patients, with 52% of cases, while strains of type I were present in 75% of the congenital infection cases. These data differ from previous reports that show type II strains to be mostly associated with all kinds of human toxoplasmosis. These differences might be an effect of selection in the process of culture and isolation of the samples performed by other researchers prior to strain characterization.

Animals↗
PubMed2000

The cumbiasins, structurally novel diterpenes possessing intricate carbocyclic skeletons from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer).

From the hexane extract of the West Indian gorgonian Pseudopterogorgia elisabethae, two diterpenes, cumbiasins A (1) and B (2), having a novel tetracyclic carbon skeleton named cumbiane, have been isolated. In addition, we have isolated cumbiasin C (3), a ring cleavage product of cumbiasin B that possesses an unusual carbocyclic framework named seco-cumbiane. The structures and relative configurations of metabolites 1-3 were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS). The carbocyclic skeletons of the cumbiasins are unprecedented and represent new classes of C20 rearranged diterpenes. Cumbiasins A and B display mild in vitro anti-tuberculosis activity.

Animals↗
PubMed2000

Novel terpenoids from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer). Elisapterosins A and B: rearranged diterpenes possessing an unprecedented cagelike framework.

Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocyclic skeletons, were isolated from the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae. The structures and relative configurations of novel metabolites elisabethin D (2), elisabethin D acetate (3), 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyclic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C(20) rearranged diterpenes. Elisapterosin B displays strong in vitro anti-tuberculosis activity.

Animals↗
PubMed2000

A marine diterpene with a novel tetracyclic framework from the West Indian gorgonian octocoral Pseudopterogorgia elisabethae.

[structure: see text] Colombiasin A (1) was isolated from an extract of the West Indian gorgonian octocoral Pseudopterogorgia elisabethae that showed strong inhibitorial activity against Mycobacterium tuberculosis H37Rv. Structure elucidation by interpretation of 2D-NMR spectroscopic data, IR, UV, and accurate mass measurements (HREI-MS) revealed that colombiasin A belongs to a previously undescribed class of C20 rearranged diterpenes possessing an intricate tetracyclic framework.

Animals↗