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1.
J Endocrinol Invest ; 46(10): 2115-2124, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36966469

RESUMO

PURPOSE: To investigate the accuracy of cutoff values of the morning serum cortisol (MSC) using the cortisol stimulus test (CST) insulin tolerance test (ITT) and 250 mcg short Synacthen test (SST) as the reference standard tests, to better define its clinical role as a tool in the diagnostic investigation of adrenal insufficiency (AI) AI. METHODS: An observational study was conducted with a retrospective analysis of MSC in adult patients who had been submitted to a CST to investigate AI between January 2014 and December 2020. The normal cortisol response (NR) to stimulation was defined based on the cortisol assay. RESULTS: 371 patients underwent CST for suspected AI, 121/371 patients (32.6%) were diagnosed with AI. ROC curve analysis showed an area under the curve (AUC) for MSC of 0.75 (95% CI 0.69 - 0.80). The best MSC cutoff values to confirm AI were < 3.65, < 2.35 and < 1.5 mcg/dL with specificity of 98%, 99%, and 100%, respectively. MSC > 12.35, > 14.2 and > 14.5 mcg/dL had sensitivity of 98%, 99%, and 100%, respectively, being the best cutoff values to exclude AI. Almost 25% of patients undergoing CST for possible AI had MSC values between < 3.65 mcg/dL (6.7% of patients) and > 12.35 mcg/dL (17.5% of patients), making the formal CST testing unnecessary if we consider these cutoff values. CONCLUSION: With the most modern cortisol assays, MSC could be used as a diagnostic tool, with high accuracy to confirm or exclude AI, avoiding unnecessary CST; thus, reducing expenses and safety risks during AI investigation.


Assuntos
Insuficiência Adrenal , Hidrocortisona , Adulto , Humanos , Estudos Retrospectivos , Insuficiência Adrenal/diagnóstico , Curva ROC , Fatores de Tempo
3.
Mar Pollut Bull ; 74(1): 156-64, 2013 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-23896407

RESUMO

The growth of maritime transport and oil exploitation activities may increase the risk of oil spills. Thus, plans and actions to prevent or mitigate impacts are needed to minimize the effects caused by oil. However, tools used worldwide to support contingency plans have not been integrated, thus leading to failure in establishing priority areas. This investigation aimed to develop indices of environmental vulnerability to oil (IEVO), by combining information about environmental sensibility to oil and results of numerical modeling of spilled oil. To achieve that, a case study concerning to oil spills scenarios in a subtropical coastal area was designed, and IEVOs were calculated and presented in maps, in order to make the information about the areas' vulnerability more easily visualized. For summer, the extension of coastline potentially affected by oil was approximately 150 km, and most of the coastline presented medium to high vulnerability. For winter, 230 km coastline would be affected, from which 75% were classified as medium to high vulnerability. Thus, IEVO maps allowed a rapid and clearer interpretation of the vulnerability of the mapped region, facilitating the planning process and the actions in response to an oil spill.


Assuntos
Conservação dos Recursos Naturais/métodos , Poluição por Petróleo/prevenção & controle , Gestão de Riscos/métodos , Poluição Química da Água/prevenção & controle , Brasil , Planejamento em Desastres , Monitoramento Ambiental , Poluição por Petróleo/estatística & dados numéricos , Poluição Química da Água/estatística & dados numéricos
4.
Ultrasound Obstet Gynecol ; 41(1): 90-4, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22461324

RESUMO

We report on four cases of fetal cervical tumor, comprising three lymphangiomas and one teratoma, evaluated by ultrasound and magnetic resonance imaging (MRI) between 26 and 37 weeks' gestation. The aim was to investigate the use of virtual bronchoscopy to evaluate fetal airway patency in each case. A three-dimensional (3D) model of the airway was created from overlapping image layers generated by MRI. The files obtained were manipulated using 3D modeling software, allowing the virtual positioning of observation cameras, adjustment of lighting parameters and creation of simulated 3D movies for analysis of a virtual path through the model. In all fetuses, fetal airway patency was clearly demonstrated by virtual bronchoscopy and this was confirmed postnatally. MRI with virtual bronchoscopy could become a useful tool for studying fetal airway patency in cases of cervical tumor.


Assuntos
Broncoscopia/métodos , Feto/patologia , Neoplasias de Cabeça e Pescoço/complicações , Imageamento Tridimensional/métodos , Imageamento por Ressonância Magnética/métodos , Sistema Respiratório/patologia , Feminino , Doenças Fetais/patologia , Humanos , Linfangioma/complicações , Masculino , Gravidez , Segundo Trimestre da Gravidez , Terceiro Trimestre da Gravidez , Teratoma/complicações
5.
Braz. j. morphol. sci ; 30(1): 33-42, 2013. ilus, tab
Artigo em Inglês | LILACS | ID: lil-699327

RESUMO

Protein malnutrition is particularly deleterious in young individuals. An immunodeficient state is a well‑known functional consequence but alterations in thymic morphology remain unknown. Our aim is to analyze morphological characteristics of the rat thymus in a perinatal undernutrition and renutrition model – we hypothesize these morphological alterations are reversible with early refeeding. Ninety-day-old Wistar rats were allowed to mate and divided into three groups: nourished (N – normal 20% protein diet), undernourished (UN – pre- and postnatal 5% protein diet until post-natal day 60 – PND 60) and renourished (RN – as UN but normal diet from PND 21 to 60). The thymi of 10 pups/group were submitted to macroscopic, histology, morphometry and scanning electron microscopy analyses. Body weight was highest in N and lowest in UN animals as expected but the thymic/body weight ratio remained similar in N and UN; this ratio was significantly higher in the RN group. UN thymi had a prevalence of type I collagen fibers, atrophic lobules and absence of a clear corticomedullary boundary. Thymic cortical component was decreased in UN. Apoptotic thymocytes were more frequently visualized in the UN thymi. N and RN thymi exhibited very similar morphology. Perinatal protein malnutrition induces drastic morphological alterations in rat thymi but these could be largely reversed with early renutrition. Functional studies are needed to assess if organ function mimics morphology in its recovery.


Assuntos
Animais , Masculino , Feminino , Ratos , Timo/citologia , Fenômenos Fisiológicos da Nutrição Animal , Microscopia Eletrônica de Varredura , Estudos de Avaliação como Assunto , Estudos de Avaliação como Assunto , Ratos Wistar
7.
Arq. bras. med. vet. zootec ; 62(3): 504-510, June 2010. graf, tab
Artigo em Português | LILACS | ID: lil-554916

RESUMO

Avaliou-se o efeito do ibuprofeno administrado uma hora antes da inovulação de embriões bovinos, com o objetivo de melhorar a taxa de prenhez. Após a avaliação da resposta ao protocolo de sincronização do estro, 76 fêmeas selecionadas como receptoras de embriões foram distribuídas em três grupos (G) experimentais: G1 (n=25) receptoras usadas como controle, G2 (n=30) receptoras que receberam ibuprofeno 5mg/kg, I.M, uma hora antes da inovulação dos embriões, e G3 (n=21) receptoras que receberam uma matriz polimérica de liberação controlada de ibuprofeno administrado por via subcutânea. As taxas de prenhez foram de 16 por cento (4/25), 43,3 por cento (13/30) e 14,2 por cento (3/21), para G1, G2 e G3, respectivamente. Observou-se diferença (P<0,024) na taxa de prenhez do G2 quando comparado ao G1 e ao G3. A administração do ibuprofeno por via intramuscular uma hora antes da inovulação dos embriões resultou em melhor taxa de prenhez em receptoras da raça Nelore.


The effect of the administered ibuprofen was evaluated one hour before the embryo transfer of bovine embryos in order to improve pregnancy rates. After evaluating the response to protocol synchronization of estrus, 76 Females selected as the recipients of embryos were distributed into three experimental groups: G1 (n = 25) surrogate cows used as control, G2 (n = 30) surrogate cows that received 5mg/kg ibuprofen, IM, one hour before the embryo transfer, and G3 (n = 20) surrogate cows that received an array polymeric release of controlled ibuprofen subcutaneously administered. The pregnancy rates were 16 percent (4/25), 43.3 percent (13/30), and 14.2 percent (3/21) for G1, G2, and G3, respectively. There was statistical difference (P<0.024) on pregnancy rate of G2, in comparison with those of G1 and G3. The administration of ibuprofen intramuscularly one hour before the embryo transfer resulted in better pregnancy rate in Nellore surrogate cows.


Assuntos
Animais , Ibuprofeno/uso terapêutico , Prenhez , Sincronização do Estro , Inseminação Artificial
8.
Ultrasound Obstet Gynecol ; 36(3): 355-61, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20205157

RESUMO

OBJECTIVE: To generate physical fetal models using images obtained by three-dimensional ultrasonography (3DUS), magnetic resonance imaging (MRI) and computed tomography (CT) to guide additive manufacturing technology. METHODS: Images from 33 fetuses, including three sets of twins, were used. Fifteen fetuses were normal and evaluated only by 3DUS. Eighteen cases had abnormalities such as conjoined twins, tumors, aneuploidy, skeletal abnormalities, central nervous system abnormalities and facial or thoracic defects. Scans were performed using high-resolution 3DUS. In cases of abnormalities, MRI and CT were performed on the same day as 3DUS. The images obtained with 3DUS, CT or MRI were exported to a workstation in DICOM format. A single observer performed slice-by-slice manual segmentation using a digital high-definition screen. Software that converts medical images into numerical models was used to construct virtual 3D models, which were physically realized using additive manufacturing technologies. RESULTS: Physical models based on 3DUS, MRI and CT images either separately or combined were successfully generated. They were remarkably similar to the postnatal appearance of the aborted fetus or newborn baby, especially in cases with pathology. CONCLUSION: The use of 3DUS, MRI and CT may improve our understanding of fetal anatomical characteristics, and these technologies can be used for educational purposes and as a method for parents to visualize their unborn baby. The images can be segmented and applied separately or combined to construct 3D virtual and physical models.


Assuntos
Feto/anatomia & histologia , Processamento de Imagem Assistida por Computador/métodos , Modelos Anatômicos , Feminino , Humanos , Imageamento Tridimensional/métodos , Imageamento por Ressonância Magnética/métodos , Gravidez , Tomografia Computadorizada por Raios X/métodos
10.
J Endocrinol Invest ; 31(11): 985-90, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19169054

RESUMO

OBJECTIVE: (a) To evaluate body fat in men with prolactinoma and healthy controls, using whole body dual energy x-ray absorptiometry (DXA), and (b) to correlate DXA results with anthropometry and clinical aspects of male prolactinomas. MATERIAL AND METHODS: A cross-sectional study was performed in two University referral centers. Eleven newly-diagnosed men with prolactinoma and 9 with normal PRL levels due to dopamine agonist treatment were submitted to DXA and blood analysis (PRL, testosterone, dihydrotestosterone, estradiol, and SHBG) by the time of their clinical evaluation. They were compared with 14 control men of similar age and body mass index distribution. RESULTS: Newly-diagnosed men with prolactinoma had higher fat percentage in the arms and the total body, when compared with patients treated with dopamine agonists and controls. The former group also presented higher fat percentage in the legs than the controls. Truncal fat percentage of the newly-diagnosed patients was lower than the dopamine agonist treated group. The 3 groups had similar android and gynoid fat contents. Fat percentage of the 6 sites correlated with PRL, testosterone, and dihydrotestosterone levels. CONCLUSION: Newly-diagnosed men with prolactinomas had higher body fat content. Body fat was linked to disease control, especially to the PRL and androgen levels. Consequently, adequate control of hyperprolactinemia should be pursued in order to reduce the risk of obesity and its metabolic complications in men with prolactinoma.


Assuntos
Tecido Adiposo/patologia , Prolactinoma/patologia , Absorciometria de Fóton , Adulto , Cabergolina , Estudos Transversais , Agonistas de Dopamina/uso terapêutico , Ergolinas/uso terapêutico , Humanos , Masculino , Prolactinoma/tratamento farmacológico
11.
Bioresour Technol ; 98(15): 2800-13, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17400444

RESUMO

The removal of Cu, Ni and Zn from electroplating effluents by adsorption in cattle manure vermicompost has been discussed. A glass column 38 cm long and 7 cm i.d. was loaded with cattle manure vermicompost and effluents were passed through it. The metal concentrations were measured in the elutant. The experiments on adding effluent aliquots into the columns were continued until the metal concentrations in the elutant reached the maximum values established for effluent discharges in water courses by the Brazilian quality criteria, i.e., Cu=1.0 mg L(-1), Ni=2.0 mg L(-1), and Zn=5.0 mg L(-1). The amount of Cu retention by the vermicompost was determined at the natural effluent pH (2.0). The Zn and Ni retentions were evaluated at the natural effluent pH (6.9 and 7.4, respectively) as well pH 2.0. Vermicompost residues obtained from this process were used for lettuce cultivation. The vermicompost was found to be efficient in removing metals from the electroplating wastes, as well as in the increase of its pH values. Metal retention values were close to 100%. The Cu concentrations in lettuce leaves from the treatment with vermicompost enriched with this metal were below the range of critical toxicity level to plants, i.e., from 20 to 100 mg L(-1). However, the estimated Cu concentrations in the roots from the treatment with vermicompost enriched with Cu were much larger than that of the treatment with the natural vermicompost, reaching 246.3 mg L(-1). The Ni and Zn concentrations in lettuce leaves from the treatments, with vermicomposts enriched with the respective metals, were above the range of critical toxicity levels to plants, i.e., from 10 to 50 mg kg(-1) and from 15 to 30 mg kg(-1), respectively. However, no symptom of toxicity was found visually. Larger accumulations of Cu, Ni and Zn were found in the lettuce leaves than in the roots after the treatments with the uncontaminated vermicompost. A greater absorption of Cu and Ni by roots was found in treatments with vermicompost enriched with these elements, whereas Zn was found preferentially in the leaves. The statistical analysis was done by analyses of variance and regression.


Assuntos
Lactuca/crescimento & desenvolvimento , Metais Pesados/isolamento & purificação , Solo , Folhas de Planta/química , Raízes de Plantas/química , Espectrofotometria Infravermelho , Difração de Raios X
12.
Environ Monit Assess ; 127(1-3): 315-26, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17058005

RESUMO

A study was performed to evaluate the environmental contamination in the Turvo Limpo River basin which receives effluent discharges from domestic (residential and commercial) activities. The watercourses examined were the São Bartolomeu Stream, Turvo Sujo River, and Turvo Limpo River, located in the Minas Gerais State, Brazil. Water samples were collected at the river-side and analyzed for evaluation of pollutant inputs. The pH, temperature, electrical conductivity, redox potential (Eh), dissolved oxygen (DO), total and settleable solids, visual color, hardness, chemical oxygen demand (COD), biochemical oxygen demand (BOD), chloride, total phosphate, total nitrogen, ammonia nitrogen, nitrate, total coliforms and E. coli, as well as the Cd, Pb, Cu, and Zn speciation were determined in the watercourses. The data obtained were compared with those of the Brazilian Environmental Standards and with data from non-contaminated areas. River water characteristics in some sites were far from the limit values established for superficial waters with satisfactory quality. For instance, the BOD values reached 411 mg L(-1) for a maximum limit of 10.0 mg L(-1), while the ammonia nitrogen concentration reached 28 mg L(-1) for a maximum limit of 13.3 mg L(-1). Some sites showed E. coli values above those of non-contaminated regions. Besides the effects of sewage discharges into the water-courses, agriculture activities and the use of the area for cattle husbandry influenced the quality of the river waters, for instance, the pH of a spring-water sample reached the value of 4.3. The São Bartolomeu Stream has been contributing to the deterioration of the water quality of the Turvo Sujo River, while the Turvo Limpo River has also been affected by anthropogenic discharges in the Turvo Sujo River. The speciation of Cd, Cu and Pb showed that these metals were mainly found in the particulate fraction (i. e., associated with the suspended material). Fifty five percent of the water samples showed labile Zn concentrations greater than that of the nonlabile Zn.


Assuntos
Monitoramento Ambiental/métodos , Rios/química , Poluição da Água/análise , Brasil , Metais Pesados , Esgotos
13.
J Oral Rehabil ; 33(10): 722-8, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16938100

RESUMO

Meniscectomy of the temporomandibular joint (TMJ) was frequently performed until a few years ago but now is seldom employed. This procedure induces important articular modifications but the complete extent of ultrastructural changes is still unknown. Twenty-one Wistar rats were submitted to unilateral meniscectomy. Animals were randomly divided into three groups and followed for 15, 35 or 60 days. After killing both meniscectomized and contralateral TMJ specimens were sectioned sagittally and prepared for light and scanning electron microscopy studies. Normal TMJs are characterized by glenoid fossa and condylar process with distinct conjunctive layers in which regularly arranged type 1 collagen fibres predominate. Meniscectomized animals initially exhibit a different tissue covering the eroded articular surface of the condyle with the prevalence of type 3 collagen fibres but type 1 fibres predominate in the late postoperative period. Subchondral cysts are clearly visible. A complex remodelling process of the TMJ after meniscectomy is evident with important ultrastructural modifications that may correlate to unsatisfactory clinical results. The dynamic nature of this process is also observed when specimens from different postoperative periods are compared. Surgeons should always bear in mind these alterations when indicating this procedure.


Assuntos
Articulação Temporomandibular/ultraestrutura , Animais , Masculino , Côndilo Mandibular/ultraestrutura , Microscopia Eletrônica de Varredura/métodos , Ratos , Ratos Wistar , Articulação Temporomandibular/cirurgia , Disco da Articulação Temporomandibular/cirurgia , Disco da Articulação Temporomandibular/ultraestrutura
14.
Environ Monit Assess ; 112(1-3): 309-26, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16404548

RESUMO

A study was performed to evaluate the pH and the availability of Zn, Cu, Mn, Pb, and Ni in soil amended with increasing doses of composted solid wastes, collected in Rio de Janeiro, Rio de Janeiro State and in Coimbra, Minas Gerais State, Brazil. The influence of the time elapsed between compost application to the soil and the sampling of the plant growth substrate (soil + compost) for pH and metal availability analyses was also examined. The availability of heavy metals in the soil, in the compost and in the substrate was evaluated using DTPA solution for metal extraction. The increase of the compost doses added to the soil resulted in the increase of the pH in the substrate. The addition of the compost from the bigger city, Rio de Janeiro, resulted in higher increase in soil pH and available Zn, Cu, Pb, and Ni levels as compared to the addition of the compost from the smaller city, Coimbra. Increasing the time elapsed between the compost application to the soil and the sampling of the mixture resulted in higher available Zn, Cu, Mn, and Pb levels. The addition of the compost from Rio de Janeiro resulted in substrate metal concentrations in the order Zn > Pb > Ni > Cu > Mn and for the Coimbra compost the metal concentrations in the substrate was Zn > Pb > Cu > Ni > Mn. The higher values of pH and available metals obtained for the bigger city were attributed to the greatest metal contamination of its compost.


Assuntos
Metais Pesados/análise , Poluentes do Solo/análise , Poluentes Químicos da Água/análise , Disponibilidade Biológica , Brasil , Concentração de Íons de Hidrogênio , Metais Pesados/farmacocinética , Eliminação de Resíduos/métodos , Esgotos , Urbanização
15.
Prosthet Orthot Int ; 26(3): 195-205, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12562066

RESUMO

This study compares the strength of the flexor and extensor muscles of the knee in a group (A) of 25 patients with unilateral trans-tibial amputation, regardless of cause, and a group (B) of 27 normal volunteers. Measured parameters were peak bending moment, total work, maximum power and flexor/extensor relation. The dynamometer used was a Cybex model 6000, set at velocities of 60 degrees/s and 180 degrees/s (4 and 20 repetitions). Exercise type was concentric, both for flexion and extension of the knee joint. Patients were grouped according to stump size, age and time since amputation. These patients were tested with their prosthesis. Mean age in group A was 35.9 +/- 13 years (age range: 12-59 years). Mean age in group B was 34 +/- 8 years (age range: 19-56 years). Comparison according to subject sex was similar. Data analysis between the amputated and the sound limb reveals strength deficit (bigger deficit at 180 degrees/s), which relates to age but not to stump size. When compared to non-amputated subjects in the measured parameters, negative relations both in the amputated side and the non-amputated side were found. The authors' conclusion is that revision of the parameters used until then for rehabilitation of the patients subjected to trans-tibial amputation is needed.


Assuntos
Amputados , Joelho/fisiologia , Músculo Esquelético/fisiologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
16.
Clin Exp Rheumatol ; 19(4): 425-30, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11491498

RESUMO

OBJECTIVE: Reports have shown that anticardiolipin (aCL) antibodies present in patients with autoimmune diseases are dependent on the cofactor,beta2 glycoprotein I (beta2 GPI), as opposed to aCL antibodies seen in infectious diseases such as syphilis, HIV hepatitis C, etc. The assay for anti-beta2GPI antibodies has been reported to be more specific for antiphospholipid syndrome (APS). However, the prevalence of these antibodies in diseases such as leishmaniasis and leptospirosis remains unknown. The aim of the present study was determine the prevalence of antibodies to cardiolipin and to beta2GPI in patients with different infectious diseases, including leptospirosis, syphilis and leishmaniasis. METHODS: Samples from patients with Kala-azar (visceral leishmaniasis), syphilis or leptospirosis were tested for IgG and IgM anticardiolipin and IgG anti-beta2GPI antibodies by ELISA. RESULTS: In patients with Kala-azar the prevalence of IgG aCL, IgM aCL and anti-beta2GPI was 6% (2/30), 3% (1/30) and 53% (16/30), respectively. In syphilis the prevalence was 18% (14/74), 13% (10/74) and 10% (8/70), respectively. In leptospirosis the frequency of these antibodies was 23% (9/39), 10% (4/39) and 17% (6/34), respectively. There was no statistical correlation between aCL and anti-beta2GPI antibodies in these diseases. DISCUSSION: This study clearly shows a significant prevalence of anti-beta2GPI antibodies in leptospirosis and leishmaniasis and syphilis. This indicates that the assay for antibeta2GPI antibodies should be thoroughly validated before it is introduced as a definitive tool for the diagnosis of APS, testing a larger number of sera from patients with a wider range of clinical conditions.


Assuntos
Anticorpos Anticardiolipina/análise , Glicoproteínas/imunologia , Leishmaniose Visceral/imunologia , Leptospirose/imunologia , Sífilis/imunologia , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Humanos , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Lactente , Masculino , Pessoa de Meia-Idade , beta 2-Glicoproteína I
18.
Ann Thorac Surg ; 70(3): 1066-9, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11016377

RESUMO

BACKGROUND: The objective of this report is to describe our experience using minimally invasive direct coronary artery bypass grafting and to evaluate angiographic patency of anastomoses. METHODS: A total of 120 patients (86 men) were operated on, with ages ranging from 30 to 83 years (mean = 61.2 years). Two access routes were used: for single left anterior descending coronary artery lesions an 8 cm anterior minithoracotomy was performed at the fourth left intercostal space. Extracorporeal circulation was not used. In the last 82 patients a restraining device was used for the regional reduction of heart beats. Coronary cineangiography was carried out between postoperative days 1 and 3 in 84 (70%) patients. Anastomoses were graded: grade A, no blocks; grade B, blocks of more than 50%; grade C, occlusion. This evaluation was performed for two different periods: in the first period a restraining device was not used and in the second period a restraining device was used. RESULTS: In the first study period (38 anastomoses) coronary cineangiography showed grade A, 79%, grade B, 5.2%, and grade C, 15.8%. In the second study period (62 anastomoses), angiography showed grade A, 90.4%, grade B, 6.4%, and grade C, 3.2%. Early mortality was 1.6%. CONCLUSIONS: Minimally invasive coronary artery bypass grafting is a good alternative for some groups of patients. Anastomotic results seem to be better when a restraining device is used.


Assuntos
Angiografia Coronária , Ponte de Artéria Coronária/métodos , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Grau de Desobstrução Vascular , Adulto , Idoso , Idoso de 80 Anos ou mais , Cineangiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Toracotomia/métodos
19.
Acta Biochim Pol ; 47(1): 233-57, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10961698

RESUMO

A combined analysis of enzyme inhibition and activation is presented, based on a rapid equilibrium model assumption in which one molecule of enzyme binds one molecule of substrate (S) and/or one molecule of a modifier X. The modifier acts as activator (essential or non-essential), as inhibitor (total or partial), or has no effect on the reaction rate (v), depending on the values of the equilibrium constants, the rate constants of the limiting velocity steps, and the concentration of substrate ([S]). Different possibilities have been analyzed from an equation written to emphasize that v = f([X]) is, in general and at a fixed [S], a hyperbolic function. Formulas for Su (the value of [S], different from zero, at which v is unaffected by the modifier) and v(su) (v at that particular [S]) were deduced. In Lineweaver-Burk plots, the straight lines related to different [X] generally cross in a point (P) with coordinates (Su, v(su)). In certain cases, point P is located in the first quadrant which implies that X acts as activator, as inhibitor, or has no effect, depending on [S]. Furthermore, we discuss: (1) the apparent Vmax and Km displayed by the enzyme in different situations; (2) the degree of effect (inhibition or activation) observed at different concentrations of substrate and modifier; (3) the concept of Ke, a parameter that depends on the concentration of substrate and helps to evaluate the effect of the modifier: it equals the value of [X] at which the increase or decrease in the reaction rate is half of that achieved at saturating [X]. Equations were deduced for the general case and for particular situations, and used to obtain computer-drawn graphs that are presented and discussed. Formulas for apparent Vmax, Km and Ke have been written in a way making it evident that these parameters can be expressed as pondered means.


Assuntos
Inibidores Enzimáticos/farmacologia , Enzimas/efeitos dos fármacos , Enzimas/metabolismo , Ativação Enzimática , Enzimas/química , Cinética , Modelos Químicos
20.
Acta Biochim Pol ; 47(1): 259-68, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10961699

RESUMO

It is not always clear that some equations affected by complicated factors can, actually, be interpreted as a ratio of two polynomials of first degree and so that they can be, in general, represented by rectangular hyperbolas. In this paper we present an easy procedure to rearrange those equations into Michaelis-Menten-type equations and so to make the aspects of these rectangular hyperbolas more clear, particularly for researchers familiar with general biochemistry. As an example, the method is applied to transform the classical rate equation of the Cleland's Ordered Uni Bi enzyme mechanism.


Assuntos
Enzimas/metabolismo , Cinética , Matemática , Modelos Químicos
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