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Biomedical subjects

A Cifuentes

Publications and source records attributed to A Cifuentes.

At least 37 records · Page 2Linked to original sources
PubMed1998

Quantitation of active ingredients and excipients in nasal sprays by high-performance liquid chromatography, capillary electrophoresis and UV spectroscopy.

A study on the use of different analytical methodologies to determine active ingredients and excipients found in commercial nasal sprays is presented. Two of the developed methodologies consisted of separation techniques, i.e. high-performance liquid chromatography and capillary electrophoresis, and the third one involved a UV-spectroscopic multicomponent procedure. The samples studied are characterized by a high viscosity and the existence of a large number of particles in suspension; therefore, special emphasis is paid on the sample preparation required by each methodology. Advantages and drawbacks of each analytical technique are also discussed in terms of speed of analysis, sensitivity and reproducibility. From this work it is observed that although the UV method needs the most laborious sample preparation, the total time required per analysis is the shortest one. The best reproducibility in terms of analysis time and quantitation of the analyzed compounds is obtained using HPLC. CE allows the determination of more components in the same sample.

Administration, Intranasal↗
PubMed1998

Liver conditioning after cardiac arrest: the use of normothermic recirculation in an experimental animal model.

The aim of this study was to compare the possible role of normothermic recirculation with the role of liver transplants from non-heart-beating donor pigs after 20 min of cardiac arrest. Three groups were studied, of which two were control groups: group 1, in which the liver was harvested from a heart-beating donor; group 2, in which the liver was harvested after a period of cardiac arrest followed by total body cooling; and group 3, in which the liver was procured as in group 2, but including a period of 30 min of cardiopulmonary bypass and tissue oxygenation at 37 degrees C before total body cooling. Survival at 5 days; endothelial (hyaluronic acid) and hepatocellular damage (AST, ALT, and alpha-GST); adenine nucleotides (energy charge), and histological changes were evaluated. Normothermic recirculation during 30 min showed a significant effect on survival (p = .03), endothelial damage (p < .05), and histological changes after reperfusion (p = .04). Cardiopulmonary bypass significantly increased the energy charge during the normothermic recirculation period (p = .001). Moreover, this study shows that a significant survival (100%) can be achieved with a liver allograft after 20 min of cardiac arrest. Although the liver suffers a major insult in terms of endothelial damage and hepatocellular damage, lesions caused by the ischemic injury are reversible. Histological changes also indicate lesion reversibility, since they almost disappear after 5 days.

Adenine Nucleotides↗
PubMed1997

Separation and quantitation of debrisoquine and 4-hydroxydebrisoquine in human urine by capillary electrophoresis and high-performance liquid chromatography.

A comparative study on the use of reversed-phase high-performance liquid chromatography (RP-HPLC) and capillary electrophoresis (CE) for the determination of debrisoquine (D) and its metabolite, 4-hydroxydebrisoquine (4-HD), in human urine is presented. Four different urine pre-treatments are compared for purification of samples prior to their injection in HPLC and CE. The use of a solid-phase extraction with a C18 cartridge provides the best results for the urine sample treatment, with good recoveries, i.e., 94.5% for D and 93.4% for 4-HD, and high reproducibility, i.e., R.S.D. N = 10 values of 1.7% and 1.2%, respectively. Under our separation conditions it is shown that CE is twice as fast and provides slightly better analysis time reproducibility than HPLC for this type of sample. Both the sensitivity and peak area reproducibility are better when HPLC is used. The two techniques show good agreement when employed for determination of phenotypes for hydroxylation, which seems to corroborate the usefulness of CE for this type of study.

Antihypertensive Agents↗
PubMed1997

Multiple peaks in high-performance liquid chromatography of proteins. beta-Lactoglobulins eluted in a hydrophobic interaction chromatography system.

The chromatographic behavior of beta-lactoglobulins when eluted in hydrophobic interaction chromatography systems is studied. By modifying some factors, such as pH and temperature, the relationship between shape of the chromatographic peak and protein structure is shown. At pH 4.5 and low temperature multiple peaks for beta-LG A and beta-LG B are observed and assigned to aggregates. The effects of other parameters, besides pH and temperature, such as volume and concentration of injected sample, contact time between protein and stationary and/or mobile phases, and nature and concentration of mobile phase upon aggregation are studied. Comparison of the chromatographic behavior of both variants of beta-lactoglobulin is made.

Animals↗
PubMed1997

Behavior of peptides in capillary electrophoresis: effect of peptide charge, mass and structure.

In the last decade the large potential of capillary electrophoresis as a technique for separation and characterization of peptides has been demonstrated extensively. In this field, a large number of chemical structures has to be taken into consideration, for which very often no data or even standards are available. As a result, there has been a strong desire to relate electrophoretic behavior to molecular properties and structure of the compounds. The activities in that direction, in the area of capillary zone electrophoresis, are critically reviewed. Special attention is paid to peptide charge, mass, hydrophobicity and structure, and their influence on the selectivity of the separation. Also, some complexation phenomena are discussed.

Computer Simulation↗
PubMed1997

Liver transplantation for alcoholic cirrhosis with anti-HCV antibodies.

The results of orthotopic liver transplantation (OLT) in patients with alcoholic liver cirrhosis (ALC) are currently similar to those obtained in patients with other indications. However, the frequent association of ALC with hepatitis C virus (HCV) infection may impair these results. We retrospectively studied the consequences of HCV infection on survival and graft function in 59 patients with ALC undergoing OLT. Patients were classified into two groups depending on their HCV serology before transplantation: group 1 comprised 24 anti-HCV-positive patients, and group 2, 35 anti-HCV-negative patients. Patient and graft survival were similar in both groups. Liver function tests 1 and 4 years after OLT showed AST and ALT values that were significantly higher in group 1 patients and post-transplant histologically proven chronic hepatitis was found in 45% and 61% of these patients at 1 and 4 years, respectively. We conclude that pretransplant HCV infection in patients with ALC does not affect survival after OLT. However, one must bear in mind the high incidence of post-transplant chronic hepatitis secondary to recurrence of HCV infection and be cautious when drawing this conclusion.

Adult↗
PubMed1997

Postoperative complications of laparoscopic-assisted colectomy.

BACKGROUND: This study was performed to prospectively assess the complications of 118 consecutive patients who underwent laparoscopic assisted colorectal resections. METHODS: The variables included were: indication for surgery, type of resection, duration of operation, duration of postoperative ileus, length of hospital stay, port-site recurrence, and complications in relation to the laparoscopic technique. RESULTS: 118 Laparoscopic-assisted procedures were performed between July 1992 and October 1995. Surgical indications were: 106 patients for colonic malignancy, six for diverticulitis, two for Crohn's disease, two for benign polyps, one for endometriosis, and one for ischemic colitis. Fifteen patients required conversion to open techniques for completion of the operations (12.7%). The mean operating time was 168.8 min. The amount of operative blood loss was 98 ml. The mean time for passing flatus was 36 +/- 16 h. Mean postoperative stay was 5.4 (range 3-13) days. Eight patients (6.8%) sustained complications: four unrelated to laparoscopy (three wound infection, one anastomotic leak); and four complications related to the laparoscopic approach: one small-bowel obstruction, one trocar injury, one rotation of the anastomosis, and one misdiagnosed synchronous adenocarcinoma. CONCLUSIONS: We suggest that with the development of improved technical devices and more experience, the indications for laparoscopic colectomy should continue to expand. The low incidence of infectious complications suggests an important role for the laparoscopic approach to colorectal surgery.

Adult↗
PubMed1996

Selectivity change in the separation of proteins and peptides by capillary electrophoresis using high-molecular-mass polyethyleneimine.

A study of the capillary electrophoretic separations of proteins and peptides using high-molecular-mass polyethyleneimine (PEI) is presented. Experiments were performed in the PEI-coated capillaries together with the use of this polymer as a buffer additive under different separation conditions. The effects of pH and the concentration of PEI in the buffer on the electroosmotic flow and the migration orders of biopolymers were investigated. The use of the cationic polymer offers an alternative for the modification of the separation selectivity and resolution of biopolymers.

Amino Acid Sequence↗
PubMed1996

Effect of venovenous bypass on perioperative renal function in liver transplantation: results of a randomized, controlled trial.

Although venovenous bypass (VVBP) has been suggested to protect the kidneys during liver transplantation and its systematic use has therefore been recommended, this beneficial effect of VVBP has not been clearly demonstrated. In a prospective, randomized, controlled trial, 77 patients receiving liver transplants for chronic liver disease were allocated to be supported with VVBP (group 1, 38 patients) or not (group 2, 39 patients). Both groups were similar in relation to preoperative clinical and laboratory data and operative transfusion requirements. Inulin clearance and urinary beta(2)-microglobulin and N-acetyl-beta-D-glucosaminidase (NAG) excretion (to determine glomerular filtration rate and tubular damage, respectively) were measured at different perioperative periods (anesthesia induction, hepatectomy, anhepatic phase, biliary anastomosis, and 24 hours after surgery). A significant decrease in inulin clearance and increase in tubular damage markers were observed in the anhepatic phase, which only partly improved in the subsequent phases. No significant differences were observed between groups 1 and 2 at any perioperative phase, except during the anhepatic phase, in which a more marked renal function impairment occurred in group 2 patients. However, renal function on the 7th postoperative day and the need for hemodialysis/ hemofiltration during the 1st week were similar in both groups. Among 40 variables analyzed, only low mean arterial pressure at anesthesia induction was identified as an independent predictor for early postoperative severe renal failure (inulin clearance < 10 mL/min/1.73 m(2) at the 24th postoperative hour), with no significant relationship between this complication and the use of venovenous bypass. Renal function markedly deteriorates during liver transplantation, and renal impairment persists during the early postoperative period. Because VVBP support is not associated with any clear benefit in renal function, its systematic use does not seem to be justified.

Acute Kidney Injury↗
PubMed1995

Capillary electrophoresis of peptides using rectangular and cylindrical geometries: a comparative study.

A study on the use of rectangular columns in capillary zone electrophoresis (CZE) is presented. The equations controlling the hydrodynamic flow and the plate height in rectangular capillaries are deduced. Several experiments were carried out in order to test the validity of these equations. Also, the possibilities of these columns in terms of thermal dissipation, efficiency, analysis speed and sample capacity were studied and compared with those for cylindrical tubing. The results from both rectangular and cylindrical columns are compared to each other, employing the parameters mentioned above, and also with those predicted by theory. The advantages, i.e. better heat dissipation, higher speed and larger sample capacity, and drawbacks, i.e. high fragility and incompatibility with some capillary electrophoresis instruments, of employing rectangular geometries in CZE are discussed.

Electric Conductivity↗
PubMed1995

Effect of pH and ionic strength of running buffer on peptide behavior in capillary electrophoresis: theoretical calculation and experimental evaluation.

The effect of pH and ionic strength of running buffer on peptide behavior in capillary electrophoresis (CE) is studied. A system for predictions of peptide migration in CE (SPPMCE) developed in our laboratory has been tested in a wide range of pH and buffer concentrations. The SPPMCE consists of a computer program for calculating peptide pKa values, an equation which relates peptide structures to their electrophoretic mobilities and a coupled computer program for the prediction of electropherograms. More than 25 different buffers have been employed, covering a pH range of 2-11 and a concentration range of 5-100 mM. Results from experiments are compared with the theoretical predictions. Good agreement is observed, which confirms the utility of the SPPMCE and allows fast and easy optimization of peptide separations in CE, with nothing more than the amino acid sequence of the linear peptide as the input.

Amino Acid Sequence↗
PubMed1995

The spilled stone. A potential danger after laparoscopic cholecystectomy.

The application of laparoscopic techniques in digestive surgery to areas in which there was no previous experience has favored the appearance of new complications and clinical situations that were not observed during the open era. Initial opinion considered that stones left in the abdominal cavity were harmless, and a few clinical and experimental studies supported this opinion. But cumulative reports of cases suggest a potential danger. From 1991 to date, 49 cases of complications related to stones left in the abdominal cavity have been reported with severe complications that required an open surgical procedure. Stone spillage has not always been considered an indication of conversion of laparoscopic cholecystectomy but is now accepted as a source of infrequent but severe complications that may require a reintervention for treatment. Therefore it is recommended that efforts should be made to retrieve all spilled stones; the surgical procedure should be prolonged until this is achieved, in order to reduce one source of unpredictable morbidity. Open retrieval should be considered in selected cases if a large number or large stones are lost.

Animals↗