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C Matos

Publications and source records attributed to C Matos.

At least 19 recordsLinked to original sources
PubMed2001

Effect of liposomes on the rate of alkaline hydrolysis of indomethacin and acemetacin.

The anti-inflammatory, analgesic, and antipyretic drugs indomethacin (INDO) and acemetacin (ACE), extensively used for the treatment of diseases of degenerative or inflammatory character, exhibit marked gastric irritant action, have low water solubility at neutral pH, and decompose in alkali. Alternative formulations are being investigated to obtain products with lower toxicity and higher stability. Here we examine the effect of liposome charge on the rate of alkaline decomposition of INDO and ACE using micelles as reference. Binding of ACE and INDO to zwitterionic hexadecylphosphocholine (HDPC) micelles and phosphatidylcholine (PC) liposomes was analyzed using a two-phase separation model to quantify the effect of these aggregates on the rate of alkaline degradation. The substrate association constants to HDPC micelles were 1335 and 2192 M(-1) for INDO and ACE, respectively, whereas the corresponding values for PC vesicles were 612 and 3050 M(-1). The difference was attributed to the additional hydrophobicity of ACE. The inhibitory effect of HDPC micelles and PC vesicles was quantified by calculating the ratio between the rate constants in water (k(w)) and in the aggregate (k(m)). The values of the k(w)/k(m) ratios for INDO and ACE in HDPC micelles were, respectively, 80 and 42, and in PC liposomes these ratios were 21 and 3.7, respectively. Positively charged micelles of hexadecyltrimethylammonium chloride (CTAC) and vesicles containing varying proportions of dioctadecyldimethylammonium chloride (DODAC) and PC increase the rate of INDO and ACE alkaline decomposition. Vesicle effects were very sensitive to the DODAC/PC ratio, with rates increasing with the proportion of DODAC. The data were analyzed quantitatively using a pseudophase model with explicit consideration of ion exchange. The calculated second-order rate constants in micelles and vesicles were lower than that in water. The charge density in the liposome necessary to increase the entrapment efficiency and decrease drug decomposition can be modulated, by judicious choice of pH and ionic strength. These manipulations can lead to more stable formulation with increased efficiency in drug entrapment and controlled effects on drug stability.

Hydrogen-Ion Concentration↗
PubMed2001

The role of MR imaging for the assessment of complicated duplex kidneys in children: preliminary report.

OBJECTIVE: To determine whether MR imaging, including MR urography, is able to assess complicated duplex kidneys and to determine the possible role of MRI compared to other imaging techniques in such uropathies. MATERIAL AND METHODS: Twenty consecutive patients (age 1 month-11 years) presenting with a suspicion of a complicated duplex kidney were prospectively studied with MRI and MR urography. The examinations were performed on a 0.5-T machine using routinely available sequences that were optimised to the patient's age and size. MR images were reviewed separately by two observers blinded to the patient history. They were asked to assess the presence of a duplex kidney, the presence of an abnormality that may require surgery and to indicate the type of the inferior ureteric insertion. A qualitative gradation of these results was performed on the basis of the final diagnosis provided at endoscopy (n = 6) or surgery (n = 14). MR results were compared to those provided by US examinations and excretory urography, when available, and a non-parametric statistical analysis was performed. RESULTS: MRI differentiated well between the upper and the lower poles of the kidneys and correctly answered the three questions in all 20 patients. The two observers agreed completely in all the 20 patients. MR was statistically superior to both US and excretory urography in the evaluation of the distal ureter (P < 0.05). CONCLUSIONS: MRI provides a precise assessment of the complications associated with duplex kidneys. Its optimal role seems to be the assessment of ectopic extra-vesical ureteric insertions and whenever an occult upper pole is suspected.

Child↗
PubMed2001

A fast and reliable spectroscopic method for the determination of membrane--water partition coefficients of organic compounds.

Partition coefficients (Kp) between egg yolk phosphatidylcholine multilamellar vesicles and water were determined for two nonsteroidal anti-inflammatory drugs (indomethacin and acemetacin) using two independent methodologies: derivative spectrophotometry and variation of the experimental acidity constant in the presence of increasing vesicle concentration. Second-derivative spectrophotometry allowed for total elimination of background signal effects arising from lipid vesicles, without the need for separation techniques that may disturb equilibrium states. By using a model based on a simple partition, the values of K(T)p can be obtained directly; furthermore, by performing determinations at two different pH values it is possible to calculate partition coefficients for the neutral and negatively charged forms of the drugs (K(AH)p and K(A)p). In the other methodology, values of apparent acidity constants (K(app)) were determined by spectrophotometry at different pH values and different lipid concentrations, and an increase in K(app) with decreasing lipid concentration was observed for both drugs, and from this dependence it was possible to calculate K(AH)p and K(A-)p for each drug. These values were used as a check for those obtained by derivative spectroscopy, which has proven to be a reliable and more expeditious method to obtain K(AH)p and K(A-)p .

Animals↗
PubMed2001

Pancreas divisum: evaluation with secretin-enhanced magnetic resonance cholangiopancreatography.

BACKGROUND: The clinical significance of pancreas divisum (PD) remains controversial. Secretin-enhanced magnetic resonance cholangiopancreatography (S-MRCP) is a noninvasive diagnostic procedure that relies on the dynamic response of the main pancreatic duct (MPD) to secretin stimulation. The aim of this study was to determine the frequency of PD and to analyze the dynamic changes of the MPD by using S-MRCP in patients referred for suspected pancreatic diseases before ERCP. METHODS: MRCP was obtained before and at 30-second intervals over 10 minutes after secretin stimulation in consecutive patients with idiopathic acute pancreatitis (n = 67), persistent hydrolasemia (n = 42), recurrent abdominal pain thought to be of pancreatic origin (n = 48), severe chronic pancreatitis (n = 68), and in a control group (n = 54). RESULTS: Thirty patients (10.8%) had a PD at S-MRCP. Secretin stimulation improved the detection of PD in 23% (7/30). The frequency of PD was not significantly different (p > 0.2) between these groups. The occurrence of an abnormal response at S-MRCP (persistent dilatation of the MPD) did not significantly differ in patients with or without PD (p > 0.4). CONCLUSION: The frequency of PD did not differ between groups, and the dynamic changes of the MPD during S-MRCP were similar in patients with and without PD.

Adolescent↗
PubMed2000

Prevalence and clinical evolution of isolated ventral pancreatitis in alcoholic chronic pancreatitis.

BACKGROUND: The role of pancreas divisum in chronic pancreatitis is controversial. Ductal changes limited to the pancreatic ventral duct (isolated ventral pancreatitis) have only been described as isolated case reports. METHODS: In a cohort of 542 patients with chronic pancreatitis we determined the frequency of ventral chronic pancreatitis among patients with pancreas divisum and analyzed the clinical presentation of 10 patients with isolated ventral alcohol-induced pancreatitis compared with 10 patients with isolated dorsal alcohol-induced pancreatitis and 30 patients with chronic pancreatitis and without pancreas divisum. Magnetic resonance pancreatography under secretin stimulation was used to evaluate the status of the dorsal pancreatic duct in some patients during follow-up. RESULTS: We identified 62 (11.4%) patients with pancreas divisum and 16 (2.9%) patients with incomplete pancreas divisum. The ventral duct was affected by chronic pancreatitis in 74% of these patients. Isolated ventral or dorsal duct alterations were identified in 14% and 26%, respectively, of patients with pancreas divisum. Patients with isolated ventral pancreatitis had pain symptoms similar to those of the two other groups but had no endocrine or exocrine insufficiency on initial presentation. After a mean follow-up of 44 months, 83% of patients studied with isolated ventral pancreatitis developed alterations of the dorsal ductal part of the gland. CONCLUSION: We conclude that isolated ventral alcohol-induced pancreatitis is one of the first manifestations of generalized pancreatic disease where the anatomic factor of pancreas divisum plays only a marginal role.

Acute Disease↗
PubMed2000

Phenolic acids and derivatives: studies on the relationship among structure, radical scavenging activity, and physicochemical parameters.

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.

Antioxidants↗
PubMed2000

Chronic pancreatitis: evaluation of pancreatic exocrine function with MR pancreatography after secretin stimulation.

PURPOSE: To compare duodenal filling seen at magnetic resonance (MR) pancreatography after secretin stimulation and biochemical parameters determined with the intraductal secretin test (IDST) for evaluation of pancreatic exocrine function. MATERIALS AND METHODS: MR pancreatography after secretin stimulation and IDST were performed in 41 patients with chronic pancreatitis (group 1) and eight patients with other pancreatic disease (group 2). A control group (group 3, n = 28) underwent MR pancreatography after secretin stimulation only. MR pancreatograms were acquired before and every 30 seconds for 10 minutes after secretin injection. Duodenal filling was graded from least amount of filling (grade 1) to normal filling (grade 3) on the last MR pancreatogram. Pancreatic exocrine function was determined at IDST. Main pancreatic ductal diameter was compared between groups 1 and 3. RESULTS: All ductal diameters were significantly larger in group 1 (P <.001). The maximal diameter variation after secretin stimulation was significantly higher in the control group (P =.001). Pancreatic exocrine function parameters determined at IDST were significantly lower in patients with grade 1 duodenal filling than in those with grade 2 or 3 (P <.05). Maximal bicarbonate concentration alone was independently associated with all grades of duodenal filling (P =.007). The sensitivity and specificity of reduced duodenal filling for assessment of reduced pancreatic exocrine function were 72% and 87%, respectively. CONCLUSION: Duodenal filling grade determined at MR pancreatography after secretin stimulation allows specific estimation of pancreatic exocrine function.

Adolescent↗
PubMed2000

[New diagnostic strategies in biliary-pancreatic diseases].

The indication for ERCP have dramatically changed over the last few years, this technique becoming mainly therapeutic and loosing its indication as a diagnostic tool for imaging the biliopancreatic area. The two major less or non invasive techniques which have replaced ERCP in its diagnostic indications are the endoscopic ultrasound (EUS) and the magnetic resonance cholangiopancreatography (MRCP). The present paper reviews the current indications of these two techniques, as well as their impact on the practice of ERCP in 2000.

Biliary Tract Diseases↗
PubMed1999

Secretin-enhanced MR pancreatography.

MR cholangiopancreatography has now emerged as a noninvasive diagnostic technique that can replace diagnostic endoscopic retrograde cholangiopancreatography in many instances. Recent technical issues include the use of fast single-shot T2-weighted single-slice projections in combination with a negative oral contrast agent and secretin stimulation for assessment of pancreatic flow dynamics and duodenal filling. Potential clinical applications include the evaluation of patients with recurrent pancreatitis and inconclusive CT examination as well as the evaluation of chronic pancreatitis complications whenever endoscopic treatment is suggested. In combination with cross-sectional MR sequences, secretin-enhanced MR pancreatography offers the possibility of a comprehensive examination of the pancreas that provides parenchymal, ductal, and functional information within a single diagnostic modality.

Humans↗
PubMed1999

[Imaging of cartilage. Current status and prospects].

This work describes the composition, organisation, metabolism, biomechanical and physiologic properties of normal cartilage. The initial involution process, of biochemical nature, preceding by far the morphological changes is described as well as the degenerative, inflammatory and traumatic pathogenesis. The modern cartilage imaging techniques are described with emphasis on MRI.

Cartilage Diseases↗
PubMed1999

[Magnetic resonance angiography of the renal arteries].

Initially, the clinical use of magnetic resonance angiography (MRA) in the abdomen has been restricted because of motion and flow related artifacts. The advent of high performance gradient systems made possible the development of 3D gadolinium-enhanced MRA techniques and expanded the clinical applications of MRA into the abdominal area, particularly for the investigation of renal arteries. This technique is safe, because the administered contrast agent (gadolinium) is free of clinically detectable nephrotoxicity and has a low incidence of allergic reactions. Moreover, contrast MRA also eliminates the risks of ionizing radiation which allows repeating the examination without the accumulation of radiation exposure. The main disadvantages of the technique are its low availability and the fact that the use of contrast agents for this procedure is still not reimbursed by the social security. Many studies demonstrated that contrast MRA allows for the reliable assessment of renal artery morphology and pathologic states. Furthermore, within a single MR examination a comprehensive approach including renal artery morphology, hemodynamic significance of any stenosis and kidney perfusion is available. In this paper, we provide a review of the literature concerning the clinical performance of contrast MRA for the renal arteries and suggest its rationale for the investigation of patients suspected of renovascular disease in our specific environment.

Artifacts↗
PubMed1999

An Outbreak of Nosocomial Infection Caused by ESBLs Producing Serratia marcescens in a Brazilian Neonatal Unit.

Serratia marcescens has been reported as an organism which can cause rapidly spreading, antibiotic resistant nosocomial colonization and disease. We report here an outbreak of colonization and disease due to S.marcescens involving 53 infants admitted to the Neonatal Intensive Care Unit (NICU) of the Uberlandia Federal University Hospital, Brazil, between December, 1997, and April, 1998. Thirty-eight infants were colonized without clinical signs of infection and 15 infants had clinical disease. Five infants developed septicemia (4 cases were fatal, including the presumed index case). Seven infants developed conjunctivitis, 1 developed both sepsis and conjunctivitis, 1 infant developed otitis, and 1 infant had a urinary tract infection. On univariate analysis, independent risk factors for S. marcescens clinical disease were: low birth weight (<1.500g), incubator care, use of carbapenems, duration of hospitalization (>/=7days), low Apgar score, and prematurity. All the isolates of S.marcescens showed the same antimicrobial susceptibility profile. The causative strains were resistant to oxyimino-cephalosporins due to their production of extended-spectrum beta-lactamases. Cultures from the hands of 12 NICU health care professionals (HCWs), soap samples, ventilator reservoirs, and work and incubator surfaces failed to identify a reservoir of S.marcescens, but positive cultures were found in half of the sink drains. Containment of the outbreak was achieved by closure of the NICU new admissions, employment of strict hygienic measures, and careful nursing care of the infected and colonized infants. Rapid organism identification and initiation of control measures are important in containing such an epidemic at an early stage.

Journal Article↗
PubMed1998

Magnetic resonance cholangiopancreatography: interest of IV secretin administration in the evaluation of pancreatic ducts.

The aim of this study was to investigate whether IV secretin administration is useful to enhance the delineation of the main pancreatic duct (MPD) and its side branches, and if it provides additional information concerning signal voids and strictures. Twenty-seven patients referred for abdominal pain or laboratory abnormalities (group 1, n = 13) or for the follow-up of chronic pancreatitis (CP; group 2, n = 14) were studied. Magnetic resonance cholangiopancreatography was acquired at 1.5 T before and after IV secretin by a coronal 3D TSE T2-weighted sequence with maximum intensity projection postprocessing. In group 1 secretin provided a better visualization of MPD in 9 patients. In a patient with pancreas divisum, it allowed suggestion of stenosis of the accessory papilla, confirmed at endoscopic retrograde cholangiopancreatography (ERCP). In group 2 secretin provided a better visualization of MPD only in the 3 patients with mild disease. A mild dilation upstream a stricture occurred in 2 cases and a marked dilation appeared upstream a wallstent which was non-patent at ERCP. Few changes were noticed concerning side branches. These preliminary results indicate that in patients without CP, secretin improves MPD delineation avoiding invasive diagnostic ERCP. In patients with mild CP secretin does not improve the characterization of signal voids, but it may be useful to appreciate their significance and to follow-up stenosis.

Adult↗
PubMed1998

Percutaneous transperineal radiofrequency ablation of prostate tumour: safety, feasibility and pathological effects on human prostate cancer.

OBJECTIVE: To evaluate the safety of radiofrequency (RF) energy delivered interstitially in patients with prostate cancer scheduled for radical prostatectomy and to correlate the proposed theoretical lesion size with the pathological findings. PATIENTS AND METHODS: Radiofrequency interstitial tumour ablation (RITA) was performed in 15 patients with localized prostate cancer before radical surgery. RF energy was delivered to the prostate by active needle electrodes (monopolar or bipolar) placed transperineally under transrectal ultrasonography guidance. Needle electrodes were used with different configurations and in some cases were covered by retractable shields to vary the length and circumference of the thermal lesions created. In eight patients, the procedure was performed immediately before radical prostatectomy, in six RITA was performed under spinal anaesthesia 1 week before surgery and in one patient, no surgery was performed but the patient was followed by serial determinations of prostate specific antigen (PSA). At least two lesions were created in each prostate, including both capsule and peripheral zones. NADPH and haematoxylin & eosin (H&E) staining were used to assess the extent of the necrotic lesion in the radical prostatectomy specimen. RESULTS: The mean energy delivered was 10.5 kJ, with central temperatures reaching up to 105 degrees C during 12 min of ablation; rectal temperature remained at < 38 degrees C. There were no complications. Macroscopic examination showed well-demarcated lesions including the prostatic capsule, up to 2.2 x 1.5 x 4.5 cm. With monopolar energy, the observed lesion size was comparable to the predicted 2 x 2 x 2 cm lesion, while with bipolar energy, lesion size was related to interneedle distance and uncovered needle length. Microscopic examination showed clearly delineated lesions both with NADPH (in prostates immediately removed after surgery) and H&E (at 1 week after RITA) staining. The lesion size observed on pathological analysis correlated with the predicted lesion size. In one patient, no residual cancer was found in the specimen. In the patient whose entire prostate was targeted and followed by serial PSA measurements, the latter were undetectable at 3 months of follow-up. CONCLUSION: Transperineally delivered RF energy is capable of safely creating extensive coagulative necrotic lesions in prostate cancer tissue, in a reproducible and controlled manner. The results presented here provide basic information for the potential future application of this form of energy for localized prostate cancer.

Catheter Ablation↗
PubMed1998

Choledochal cysts: comparison of findings at MR cholangiopancreatography and endoscopic retrograde cholangiopancreatography in eight patients.

PURPOSE: To compare prospectively the data provided with endoscopic retrograde cholangiopancreatography (ERCP) and magnetic resonance (MR) cholangiopancreatography (MRCP) in eight patients with symptomatic choledochal cysts. MATERIALS AND METHODS: Eight patients (three children, five adults) with choledochal cyst and abdominal pain underwent sequential single-shot turbo spin-echo T2-weighted MRCP and ERCP. Seven of the eight patients had relapsing pancreatitis. In three patients, a dynamic MR examination was performed after secretin stimulation of exocrine pancreatic function. RESULTS: A complete correlation was observed between ERCP and MRCP for defining the anatomic characteristics of the cyst (seven type I cysts, one type IV cyst) and the presence of an abnormal pancreaticobiliary junction (PBJ) (six patients) with a long common channel. Of the seven patients with acute pancreatitis, six had an abnormal PBJ and one had common bile duct (CBD) stones with a normal ductal union evidenced with both techniques. In two patients, dynamic MRCP demonstrated preferential filling of the gallbladder and the CBD after secretin injection, whereas normal duodenal filling was observed in another patient without a junctional abnormality. CONCLUSION: MRCP provides information equivalent to that provided with ERCP, without potential complications, for the preoperative assessment of choledochal cysts. Dynamic secretin-stimulated MRCP studies might help better understand the pathophysiologic characteristics of this entity.

Adolescent↗