Marco Antônio Condé de Oliveira

Organic Hydroperoxide Resistance Gene Encodes a Thiol-dependent Peroxidase*

ohr (organic hydroperoxide resistance gene) is present in several species of bacteria, and its deletion renders cells specifically sensitive to organic peroxides. The goal of this work was to determine the biochemical function of Ohr fromXylella fastidiosa. All of the Ohr homologues possess two cysteine residues, one of them located in a VCP motif, which is also present in all of the proteins from the peroxiredoxin family. Therefore, we have investigated whether Ohr possesses thiol-dependent peroxidase activity. The ohrgene from X. fastidiosa was expressed in Escherichia coli, and the recombinant Ohr decomposed hydroperoxides in a dithiothreitol-dependent manner. Ohr was about twenty times more efficient to remove organic hydroperoxides than to remove H2O2. This result is consistent with the organic hydroperoxide sensitivity of Δohr strains. The dependence of Ohr on thiol compounds was ascertained by glutamine synthetase protection assays. Approximately two thiol equivalents were consumed per peroxide removed indicating that Ohr catalyzes the following reaction: 2RSH + ROOH → RSSR + ROH + H2O. Pretreatment of Ohr with N-ethyl maleimide and substitution of cysteine residues by serines inhibited this peroxidase activity indicating that both of the Ohr cysteines are important to the decomposition of peroxides. C125S still had a residual enzymatic activity indicating that Cys-61 is directly involved in peroxide removal. Monothiol compounds do not support the peroxidase activity of Ohr as well as thioredoxin from Saccharomyces cerevisiaeand from Spirulina. Interestingly, dithiothreitol and dyhydrolipoic acid, which possess two sulfhydryl groups, do support the peroxidase activity of Ohr. Taken together our results unequivocally demonstrated that Ohr is a thiol-dependent peroxidase.

Associação entre fatores de risco para doença arterial coronariana e coronariopatia em pacientes submetidos a cintilografia de perfusão do miocárdio

OBJECTIVES: To establish the degree of association between cardiovascular risk factors and the presence of coronary artery disease (CAD) in a group of patients undergoing myocardial perfusion scintigraphy (MPS). METHODS: The study included 7183 patients who had undergone MPS. Using logistic regression analysis the odds ratios for the following risk factors were evaluated: age, gender, family history, body mass index, smoking, dyslipidemia, diabetes mellitus (DM) and systemic hypertension. Indicators for the presence of CAD were defined as: myocardial infarction, revascularization, angioplasty or an altered MPS. Analysis was based on the whole the group as well as on male and female subgroups. The impact of the risk factors in relation to age was also analyzed. RESULTS: A statistically significant association was observed between patient age and gender and the presence of CAD. For females, it was demonstrated that DM is the main modifiable risk factor for CAD. For males various modifiable risk factors were associated with the presence of CAD, particularly DM and dyslipidemia. In the analysis by age groups some risk factors showed a more expressive association. CONCLUSION: The main risk factors for CAD were aging and male gender. In relation to modifiable risk factors and the presence of CAD, the greatest associations for males were DM and dyslipidemia and for females DM. The most relevant factors for specific age groups were smoking for young men and DM and smoking for women between the ages of 40 and 50.

Discordant results in Tc-99m tetrofosmin and Tc-99m sestamibi parathyroid scintigraphies

Parathyroid scintigraphies have been used to detect pathological parathyroid glands either before as well as after the parathyroid resection surgery in patients with hyperparathyroidism. One of the most utilized techniques to perform the studies is the double-phase images with Tc-99m sestamibi, which has been shown to be very accurate in the localization of enlarged parathyroid glands. Similar to Tc-99m sestamibi, Tc-99m tetrofosmin is a radiopharmaceutical initially developed to perform myocardial perfusion study that has been used to perform parathyroid scintigraphies. Although most of the papers suggest that the overall sensitivities of both radiopharmaceuticals are similar, there are some papers questioning the accuracy of Tc-99m tetrofosmin to detect abnormal parathyroid glands. In the present article, we report a case with discordant results by both methods.

Importância da complementação com SPECT e 99mTc na cintilografia das paratiroides e da correlação clínica, laboratorial, ultrassonográfica e citológica na localização pré-operatória do adenoma de paratiroide - ensaio pictórico

OBJECTIVE In patients with primary hyperparathyroidism, candidates for surgical intervention, the parathyroid pre-operative localization is of fundamental importance in planning the appropriate surgical approach. MATERIALS AND METHODS The additional acquisition of SPECT and Technetium-99m images, during parathyroid scintigraphy with Sestamibi, is not common practice. Usually, only planar image acquisition, 15 minutes prior and 2 hours after radiopharmaceutical administration, is performed. RESULTS In our experience, the complete protocol in parathyroid scintigraphy increases the accuracy of pre-operative parathyroid localization. CONCLUSION The complete utilization of all available nuclear medicine methods (SPECT e 99mTc) and image interpretation in a multidisciplinary context can improve the accuracy of parathyroid scintigraphy.

Fatores biológicos e superestimação da fração de ejeção do ventrículo esquerdo no gated SPECT

BACKGROUND Some patients present an overestimated left ventricular ejection fraction (LVEF) on electrocardiogram-gated myocardial scintigraphy (gated SPECT). OBJECTIVE To establish the relationship between biological factors and overestimated LVEF. METHODS We selected 3838 patients who underwent gated SPECT between May 20, 2000 and September 16, 2005 with normal perfusion images and LVEF > or =50%. The following variables were analyzed: gender (29.4% females and 70.6% males), age (from 20 to 94 years - mean: 56 years), weight (from 33.5 to 150 kg - mean: 79.6 kg), height (from 138 to 220 cm - mean: 171 cm) and BMI (from 13.9 to 54 - mean: 27.2). In a subgroup of 1002 patients who underwent echocardiogram, the diastolic diameter (from 36 to 68 mm - mean 47.5 mm) and systolic diameter (from 22 to 41 mm - mean 29.8 mm) variables were included. The patients were divided into two groups: normal LVEF (< or =80%) and overestimated LVEF (>80%). The odds ratio (OR) for presenting an overestimated LVEF was calculated for each variable using logistic regression. RESULTS The following odds ratios were found (p < 0.005): female gender OR = 3.585 (95%CI: 2.745 to 4.683), age in years OR = 1.020 (95%CI: 1.011 to 1.029) and height in cm OR = 0.893 (95%CI: 0.829 to 0.962). Weight and BMI were not significantly associated with LVEF (p>0.2). In the subgroup of 1002 patients, a statistically significant influence was found in overestimated LVEF values for the systolic diameter, gender and height variables. CONCLUSION Although systolic diameter influences the overestimation of LVEF, the gender and height variables have an independent influence on LVEF overestimation by gated SPECT.

Tumor marrom em esterno: uma causa potencial de resultado falso-positivo na cintilografia das paratireóides com sestamibi-99mTc

Parathyroid scintigraphies have been used to detect pathological parathyroid glands either before as well as after the parathyroid resection surgery in patients with hyperparathyroidism. Although this test presents high specificity for detection of increased parathyroid glands, there exist causes of false positive results. In the present article, we report a case of a renal transplanted patient, with multiple lytic lesions on pelvic bones reported as brown tumors, who presented a focal uptake in the anterior portion of the superior mediastinum on Tc-99m sestamibi scintigraphy. This focal uptake, initially thought to be an ectopic parathyroid gland, after a more detailed analysis and the performance of other imaging diagnostic tests was demonstrated to be a brown tumor of the sternum.

Estratégia para Individualizar uma Dose Eficiente de Betabloqueador em Pacientes Idosos com Isquemia Miocárdica e Função Ventricular Esquerda Preservada

OBJECTIVE: To assess the strategy of titration for prescribing an efficient dosage of propranolol to reduce myocardial ischemia in the elderly. METHODS: The study comprised 14 elderly men (73.6 ± 5.3 years) with stable coronary heart disease documented on coronary cineangiography, ischemic response to exercise testing, and preserved left ventricular function. Titration was performed to identify the dosage of propranolol that would cause a 15% reduction in heart rate at the end of a 50 W load (corresponding to normal daily activities in the elderly) in weekly exercise tests. Synchronous scintigraphic study of the cardiac chambers was performed at rest and during exercise prior to and after propranolol use. RESULTS: The reductions in heart rate with the 50 W load and at rest were similar (21% vs 20%; P=0.5100). Propranolol improved the duration of exercise (12.2 ± 2.0 min vs 13.1 ± 1.8 min; P=0.0313) and abolished the changes in the ST segment induced by exercise in 8 (57%) patients. At rest, the ejection fraction was not modified by the beta-blocker. During maximum exercise, propranolol reduced the end-systolic volume index and increased ejection fraction. CONCLUSION: The strategy of using beta-blockers to reduce heart rate by 15% with a 50 W load is safe and beneficial in the elderly patient with myocardial ischemia and preserved ventricular function. The dose of beta-blocker used reduced myocardial ischemia and improved tolerance to exercise without hampering ventricular performance during maximum exercise.

Directional analysis of cardiac motion field from gated fluorodeoxyglucose PET images using the Discrete Helmholtz Hodge Decomposition

OBJECTIVES Extract directional information related to left ventricular (LV) rotation and torsion from a 4D PET motion field using the Discrete Helmholtz Hodge Decomposition (DHHD). MATERIALS AND METHODS Synthetic motion fields were created using superposition of rotational and radial field components and cardiac fields produced using optical flow from a control and patient image. These were decomposed into curl-free (CF) and divergence-free (DF) components using the DHHD. RESULTS Synthetic radial components were present in the CF field and synthetic rotational components in the DF field, with each retaining its center position, direction of motion and diameter after decomposition. Direction of rotation at apex and base for the control field were in opposite directions during systole, reversing during diastole. The patient DF field had little overall rotation with several small rotators. CONCLUSIONS The decomposition of the LV motion field into directional components could assist quantification of LV torsion, but further processing stages seem necessary.

Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.