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Resumen Presentar la experiencia en el diagnóstico clínico-radiológico y tratamiento de vólvulo sigmoideo. Se incluyeron casos con clínica sugestiva de obstrucción intestinal secundaria a vólvulo de sigmoides. Los factores de riesgo fueron: sexo masculino, mayor estancia hospitalaria, edad mayor a 70 años y la tríada clásica. Los estudios de imagen resultaron concluyentes, siendo la radiografía de abdomen y la tomografía simple de abdomen, los de elección para el abordaje diagnóstico. El vólvulo de sigmoides tiene un patrón clínico-radiológico predecible, un examen físico minucioso y estudios de gabinete de primera línea pueden ser concluyentes. La opción terapéutica para estos pacientes fue la cirugía.
Abstract To present the experience in clinical/radiological diagnosis and treatment of sigmoid volvulus. Cases with symptoms suggestive of intestinal obstruction secondary to sigmoid volvulus were included. The risk factors were: male sex, longer hospital stay, age over 70 years and the classic triad. Imaging studies were conclusive, with abdominal radiography and simple abdominal tomography being the tests of choice for the diagnostic approach. Sigmoid volvulus has a predictable clinical-radiological pattern, a thorough physical examination and first-line cabinet studies can be conclusive. The therapeutic option for these patients was surgery.
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BACKGROUND/OBJECTIVES: Factors associated with chronic heart failure (CHF) in patients with systemic lupus erythematosus (SLE) have received little attention. Recent data on the use of hydroxychloroquine in the treatment of SARS-CoV-2 infection have cast doubt on its cardiac safety. The factors associated with CHF, including therapy with antimalarials, were analyzed in a large multicenter SLE cohort. METHODS: Cross-sectional study including all patients with SLE (ACR-1997 criteria) included in the Spanish Society of Rheumatology Lupus Register (RELESSER), based on historically gathered data. Patients with CHF prior to diagnosis of SLE were excluded. A multivariable analysis exploring factors associated with CHF was conducted. RESULTS: The study population comprised 117 patients with SLE (ACR-97 criteria) and CHF and 3,506 SLE controls. Ninety percent were women. Patients with CHF were older and presented greater SLE severity, organ damage, and mortality than those without CHF. The multivariable model revealed the factors associated with CHF to be ischemic heart disease (7.96 [4.01-15.48], p < 0.0001), cardiac arrhythmia (7.38 [4.00-13.42], p < 0.0001), pulmonary hypertension (3.71 [1.84-7.25], p < 0.0002), valvulopathy (6.33 [3.41-11.62], p < 0.0001), non-cardiovascular damage (1.29 [1.16-1.44], p < 0.000) and calcium/vitamin D treatment (5.29 [2.07-16.86], p = 0.0015). Female sex (0.46 [0.25-0.88], p = 0.0147) and antimalarials (0.28 [0.17-0.45], p < 0.000) proved to be protective factors. CONCLUSIONS: Patients with SLE and CHF experience more severe SLE. Treatment with antimalarials appears to confer a cardioprotective effect.
Sujet(s)
Antipaludiques , COVID-19 , Défaillance cardiaque , Lupus érythémateux disséminé , Rhumatologie , Antipaludiques/usage thérapeutique , Études transversales , Femelle , Défaillance cardiaque/traitement médicamenteux , Défaillance cardiaque/épidémiologie , Humains , Lupus érythémateux disséminé/complications , Lupus érythémateux disséminé/traitement médicamenteux , Enregistrements , SARS-CoV-2RÉSUMÉ
OBJECTIVE: Interstitial lung disease (ILD) is one of the most serious complications of rheumatoid arthritis (RA). In the present study, we aimed to assess the efficacy of abatacept (ABA) in patients with ILD associated to RA. METHODS: National multicenter, non-controlled, open-label registry study of RA patients with ILD treated with ABA. RESULTS: 63 patients (36 women) with RA-associated ILD undergoing ABA therapy were studied. The mean ± standard deviation age at the time of the study was 63.2 ± 9.8 years. The median duration of RA and ILD from diagnosis were 6.8 and 1 year, respectively. RA was seropositive in 55 patients (87.3%). In 15 (23.8%) of 63 patients the development of ILD was closely related to the administration of synthetic or biologic disease modifying anti-rheumatic drugs. After a follow-up of 9.4 ± 3.2 months, two-thirds of patients remained stable whereas one-quarter experienced improvement in the Modified Medical Research Council scale. At that time forced vital capacity remained stable in almost two-thirds of patents and improved in one out of five patients assessed. Also, diffusing capacity of the lung for carbon monoxide remained stable in almost two-thirds and showed improvement in a quarter of the patients assessed. At 12 months, 50% of the 22 patients in whom chest HRCT scan was performed due persistence of respiratory symptoms showed stabilization, 8 (36.4%) improvement and 3 worsening of the HRCT scan pattern. Eleven of 63 patients had to discontinue ABA, mainly due to adverse events. CONCLUSION: ABA appears to be an effective in RA-associated ILD.
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Abatacept/usage thérapeutique , Antirhumatismaux/usage thérapeutique , Polyarthrite rhumatoïde/traitement médicamenteux , Pneumopathies interstitielles/traitement médicamenteux , Sujet âgé , Polyarthrite rhumatoïde/complications , Femelle , Humains , Pneumopathies interstitielles/étiologie , Mâle , Adulte d'âge moyen , Résultat thérapeutiqueRÉSUMÉ
BACKGROUND: Tumour necrosis factor (TNF)-alpha inhibitors are beneficial for the treatment of rheumatoid arthritis (RA) for reducing the risk of joint damage, improving physical function and improving the quality of life. This review is an update of the 2014 Cochrane Review of the treatment of RA with certolizumab pegol. OBJECTIVES: To assess the clinical benefits and harms of certolizumab pegol (CZP) in people with RA who have not responded well to conventional disease-modifying anti-rheumatic drugs (DMARDs). SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL: Cochrane Library 2016, Issue 9), MEDLINE, Embase, Web of Knowledge, reference lists of articles, clinicaltrials.gov and ICTRP of WHO. The searches were updated from 2014 (date of the last search for the previous version) to 26 September 2016. SELECTION CRITERIA: Randomised controlled trials that compared certolizumab pegol with any other agent, including placebo or methotrexate (MTX), in adults with active RA, regardless of current or prior treatment with conventional disease-modifying anti-rheumatic drugs (DMARDs), such as MTX. DATA COLLECTION AND ANALYSIS: Two review authors independently checked search results, extracted data and assessed trial quality. We resolved disagreements by discussion or referral to a third review author. MAIN RESULTS: We included 14 trials in this update, three more than previously. Twelve trials (5422 participants) included measures of benefit. We pooled 11 of them, two more than previously. Thirteen trials included information on harms, (5273 participants). The duration of follow-up varied from 12 to 52 weeks and the range of doses of certolizumab pegol varied from 50 to 400 mg given subcutaneously. In Phase III trials, the comparator was placebo plus MTX in seven trials and placebo in five. In the two Phase II trials the comparator was only placebo.The approved dose of certolizumab pegol, 200 mg every other week, produced clinically important improvements at 24 weeks for the following outcomes:- American College of Rheumatology (ACR) 50% improvement (pain, function and other symptoms of RA): 25% absolute improvement (95% confidence interval (CI) 20% to 33%); number need to treat for an additional beneficial outcome (NNTB) of 4 (95% CI 3 to 5); risk ratio (RR) 3.80 (95% CI 2.42 to 5.95), 1445 participants, 5 studies.- The Health Assessment Questionnaire (HAQ): -12% absolute improvement (95% CI -9% to -14%); NNTB of 8 (95% CI 7 to 11); mean difference (MD) - 0.35 (95% CI -0.43 to -0.26; 1268 participants, 4 studies) (scale 0 to 3; lower scores mean better function).- Proportion of participants achieving remission (Disease Activity Score (DAS) < 2.6) absolute improvement 10% (95% CI 8% to 16%); NNTB of 8 (95% CI 6 to 12); risk ratio (RR) 2.94 (95% CI 1.64 to 5.28), 2420 participants, six studies.- Radiological changes: erosion score (ES) absolute improvement -0.29% (95% CI -0.42% to -0.17%); NNTB of 6 (95% CI 4 to 10); MD -0.67 (95% CI -0.96 to -0.38); 714 participants, two studies (scale 0 to 230), but not a clinically important difference.-Serious adverse events (SAEs) were statistically but not clinically significantly more frequent for certolizumab pegol (200 mg every other week) with an absolute rate difference of 3% (95% CI 1% to 4%); number needed to treat for an additional harmful outcome (NNTH) of 33 (95% CI 25 to 100); Peto odds ratio (OR) 1.47 (95% CI 1.13 to 1.91); 3927 participants, nine studies.There was a clinically significant increase in all withdrawals in the placebo groups (for all doses and at all follow-ups) with an absolute rate difference of -29% (95% CI -16% to -42%), NNTH of 3 (95% CI 2 to 6), RR 0.47 (95% CI 0.39 to 0.56); and there was a clinically significant increase in withdrawals due to adverse events in the certolizumab groups (for all doses and at all follow-ups) with an absolute rate difference of 2% (95% CI 0% to 3%); NNTH of 58 (95% CI 28 to 329); Peto OR 1.45 (95% CI 1.09 to 1.94) 5236 participants Twelve studies.We judged the quality of evidence to be high for ACR50, DAS remission, SAEs and withdrawals due to adverse events, and moderate for HAQ and radiological changes, due to concerns about attrition bias. For all withdrawals we judged the quality of evidence to be moderate, due to inconsistency. AUTHORS' CONCLUSIONS: The results and conclusions did not change from the previous review. There is a moderate to high certainty of evidence from randomised controlled trials that certolizumab pegol, alone or combined with methotrexate, is beneficial in the treatment of RA for improved ACR50 and health-related quality of life, an increased chance of remission of RA, and reduced joint damage as seen on x-ray. Fewer people stopped taking their treatment, but most of these who did stopped due to serious adverse events. Adverse events were more frequent with active treatment. We found a clinically but not statistically significant risk of serious adverse events.
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Antirhumatismaux/usage thérapeutique , Polyarthrite rhumatoïde/traitement médicamenteux , Certolizumab pégol/usage thérapeutique , Fragments Fab d'immunoglobuline/usage thérapeutique , Adulte , Antirhumatismaux/effets indésirables , Certolizumab pégol/effets indésirables , Humains , Méthotrexate/usage thérapeutique , Essais contrôlés randomisés comme sujet , Abstention thérapeutique/statistiques et données numériquesRÉSUMÉ
We describe our process for quality improvement (QI) for a 3-year accreditation cycle in echocardiography by the Intersocietal Accreditation Commission (IAC) for a large group practice. Echocardiographic laboratory accreditation by the IAC was introduced in 1996, which is not required but could impact reimbursement. To ensure high-quality patient care and community recognition as a facility committed to providing high-quality echocardiographic services, we applied for IAC accreditation in 2010. Currently, there is little published data regarding the IAC process to meet echocardiography standards. We describe our approach for developing a multicampus QI process for echocardiographic laboratory accreditation during the 3-year cycle of accreditation by the IAC. We developed a quarterly review assessing (1) the variability of the interpretations, (2) the quality of the examinations, (3) a correlation of echocardiographic studies with other imaging modalities, (4) the timely completion of reports, (5) procedure volume, (6) maintenance of Continuing Medical Education credits by faculty, and (7) meeting Appropriate Use Criteria. We developed and implemented a multicampus process for QI during the 3-year accreditation cycle by the IAC for Echocardiography. We documented both the process and the achievement of those metrics by the Echocardiography Laboratories at the Ochsner Medical Institutions. We found the QI process using IAC standards to be a continuous educational experience for our Echocardiography Laboratory physicians and staff. We offer our process as an example and guide for other echocardiography laboratories who wish to apply for such accreditation or reaccreditation.
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Agrément/normes , Échocardiographie/normes , Laboratoires hospitaliers/normes , /normes , Assurance de la qualité des soins de santé/normes , Amélioration de la qualité/normes , LouisianeRÉSUMÉ
Adult-onset Still's disease (AOSD) is often refractory to standard therapy. Anakinra (ANK), an interleukin-1 receptor antagonist, has demonstrated efficacy in single cases and small series of AOSD. We assessed the efficacy of ANK in a series of AOSD patients. Multicenter retrospective open-label study. ANK was used due to lack of efficacy to standard synthetic immunosuppressive drugs and in some cases also to at least 1 biologic agent. Forty-one patients (26 women/15 men) were recruited. They had a mean age of 34.4 ± 14 years and a median [interquartile range (IQR)] AOSD duration of 3.5 [2-6] years before ANK onset. At that time the most common clinical features were joint manifestations 87.8%, fever 78%, and cutaneous rash 58.5%. ANK yielded rapid and maintained clinical and laboratory improvement. After 1 year of therapy, the frequency of joint and cutaneous manifestations had decreased to 41.5% and to 7.3% respectively, fever from 78% to 14.6%, anemia from 56.1% to 9.8%, and lymphadenopathy from 26.8% to 4.9%. A dramatic improvement of laboratory parameters was also achieved. The median [IQR] prednisone dose was also reduced from 20 [11.3-47.5] mg/day at ANK onset to 5 [0-10] at 12 months. After a median [IQR] follow-up of 16 [5-50] months, the most important side effects were cutaneous manifestations (n = 8), mild leukopenia (n = 3), myopathy (n = 1), and infections (n = 5). ANK is associated with rapid and maintained clinical and laboratory improvement, even in nonresponders to other biologic agents. However, joint manifestations are more refractory than the systemic manifestations.
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Immunosuppresseurs/usage thérapeutique , Antagoniste du récepteur à l'interleukine-1/usage thérapeutique , Maladie de Still débutant à l'âge adulte/traitement médicamenteux , Adulte , Association de médicaments , Femelle , Humains , Immunosuppresseurs/administration et posologie , Antagoniste du récepteur à l'interleukine-1/administration et posologie , Mâle , Adulte d'âge moyen , Prednisone/administration et posologie , Études rétrospectivesRÉSUMÉ
BACKGROUND: The effect of treatment with ß-blockers on the prognosis of patients newly diagnosed with heart failure with preserved systolic function (HF-PSF) is unknown. OBJECTIVES: To analyze the relationship of commencing treatment with the ß-blockers bisoprolol or carvedilol (CT-ßB) with the mortality and the morbidity of newly diagnosed HF-PSF. METHODS: Prospective propensity-adjusted cohort study over 5 years on 1085 adults diagnosed with HF-PSF for the first time, in an integrated university-based health organization in Spain. The independent relationship between CT-ßB and mortality and morbidity was analyzed, stratifying patients for comorbidity, after a multivariable adjustment for potential confounders. RESULTS: The 378 patients (34.8%) who CT-ßB were more frequently older women, with more cardiovascular comorbidity. Of the total patients 554 (51.0%) died, and 711 (65.5%) were hospitalized. Using an intent-to-treat approach, CT-ßB was associated with a lower risk of mortality (all-cause: RR [CI 95%] 0.37 [0.21 to 0.50], and cardiovascular: 0.31 [0.18 to 0.45]), and a lower age- and sex-adjusted hospitalization rate (per 100 persons/year), 13.6 vs. 19.2, (P<0.001 in all cases), even after adjustment for the propensity to take ß-blockers, or other medications, comorbidities, and other potential confounders. CONCLUSIONS: In this observational study, commencing treatment with the ß-blockers bisoprolol or carvedilol is associated with a reduced mortality and morbidity of patients with newly diagnosed heart failure with preserved systolic function.
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Antagonistes bêta-adrénergiques/usage thérapeutique , Défaillance cardiaque/traitement médicamenteux , Défaillance cardiaque/mortalité , Score de propension , Systole/effets des médicaments et des substances chimiques , Antagonistes bêta-adrénergiques/pharmacologie , Sujet âgé , Études cas-témoins , Études de cohortes , Femelle , Études de suivi , Défaillance cardiaque/épidémiologie , Humains , Mâle , Adulte d'âge moyen , Morbidité , Études prospectives , Systole/physiologie , Résultat thérapeutiqueRÉSUMÉ
BACKGROUND: The effect of treatment with angiotensin-converting enzyme inhibitors (ACEIs) on the prognosis of patients newly diagnosed with heart failure with preserved systolic function (HF-PSF) is unclear. We evaluate the relationship of commencing ACEI therapy (C-ACEI-T) with the morbidity and mortality of patients with HF-PSF. METHODS: Prospective propensity-adjusted cohort study over 5 years on 1120 adults diagnosed with HF-PSF for the first time, within an integrated health organization in Spain. We analyzed the independent relationship between C-ACEI-T and mortality, and morbidity, stratifying patients according to comorbidity, after a multivariable adjustment for potential confounders. RESULTS: The 865 patients (77.2%) who C-ACEI-T were younger, with more cardiovascular comorbidity. During the median follow-up of 908.3 days (interquartile range 558.6-1302.0) 580 patients (51.8%) died, and 727 (64.9%) were hospitalized. Using an intention-to-treat analysis, C-ACEI-T was associated with a lower risk of all-cause (RR [CI 95%] 0.34 [0.23 to 0.46]), and cardiovascular (RR 0.28 [0.20 to 0.36]) mortality, and a lower age- and sex-adjusted rate of hospitalization (per 100 persons-year), 12.3 vs. 19.4, (P<0.001 in all cases), even after adjustment for the propensity to take ACEIs, or other medications, comorbidities, and other potential confounders. CONCLUSION: In this prospective observational study the establishment of ACEI therapy is associated with a reduced mortality and morbidity of patients with newly diagnosed non-systolic heart failure.
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Inhibiteurs de l'enzyme de conversion de l'angiotensine/usage thérapeutique , Défaillance cardiaque/traitement médicamenteux , Défaillance cardiaque/mortalité , Score de propension , Sujet âgé , Études cas-témoins , Études de cohortes , Femelle , Études de suivi , Humains , Mâle , Adulte d'âge moyen , Morbidité , Études prospectives , Systole/effets des médicaments et des substances chimiques , Systole/physiologie , Résultat thérapeutiqueRÉSUMÉ
BACKGROUND: The effect of treatment with statins on the prognosis of newly diagnosed heart failure (ndHF) is not established. We evaluate the relationship of commencing treatment with statins (CTS) with the mortality and the morbidity of ndHF, systolic (HF-DSF) and non-systolic (HF-PSF). METHODS: Prospective propensity-adjusted cohort study over 5 years on 2573 patients with ndHF. The main outcomes were all-cause and cardiovascular mortality, hospitalizations and visits. We analyze the independent relationship of CTS with the mortality and the morbidity, stratifying patients for cardiovascular co-morbidity, after adjusting for potential confounders. RESULTS: 1343 patients (52.2%) CTS, 1071 (39.5%) died, and 1729 (67.2%) were hospitalized. CTS was associated not only with a lower mortality: RR for HF-overall (CI 95%) 0.23 (0.10 to 0.36), RR for HF-PSF 0.34 (0.21 to 0.47), and RR for HF-DSF 0.20 (0.09 to 0.31), but with dose-dependency (statin>20 mg/day vs. statin<=20 mg/day): RR for HF-overall 0.49 (0.33 to 0.67), RR for HF-PSF 0.53 (0.39 to 0.70), and RR for HF-DSF 0.37 (0.26 to 0.52), and with a lower rate of hospitalization (per 100 persons-year): HF-overall (13.3 vs. 18.2), HF-PSF (13.9 vs. 19.7), and HF-DSF (12.7 vs. 16.6), (P<0.001 in all cases), even after adjustment for the propensity to take statins, or other medications, and other potential confounders. CONCLUSION: The commencement of treatment with statins is associated with a dose-dependent reduction of the mortality and of the morbidity of patients with ndHF (systolic or non-systolic).
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Défaillance cardiaque systolique/traitement médicamenteux , Défaillance cardiaque systolique/mortalité , Inhibiteurs de l'hydroxyméthylglutaryl-CoA réductase/administration et posologie , Sujet âgé , Études de cohortes , Relation dose-effet des médicaments , Femelle , Défaillance cardiaque diastolique/traitement médicamenteux , Défaillance cardiaque diastolique/mortalité , Humains , Hypertrophie ventriculaire gauche/traitement médicamenteux , Hypertrophie ventriculaire gauche/mortalité , Estimation de Kaplan-Meier , Mâle , Adulte d'âge moyen , Morbidité , Analyse multifactorielle , Facteurs de risqueRÉSUMÉ
BACKGROUND AND OBJECTIVE: To evaluate if consultation between specialists in Internal Medicine and family doctors (CIMFD) improves the clinical management and prognosis of patients with heart failure (HF). DESIGN: prospective case-control study (5 years of follow-up). SETTING: community-based sample within the area of a university teaching hospital. SUBJECTS: 1857 patients (> or = 14 years) diagnosed for the first time with HF (1stDxHF), in the CIMFD. CONTROL GROUP: 1981 patients (from health centres not covered by the CIMFD), 1stDxHF, in the external consultations of the hospital. MAIN OUTCOME MEASURES: mortality rate (MR). Admissions (HA). Emergency services visits (ESV). Delays in receiving specialist attention (DRSA), and the resolution of the process (DRP). Number (NTP) and delays in reporting (DTP) tests performed. Proportion (PRC) and delay (DRC) in resolving cases. RESULTS: We observed a reduction of: MR (by 10.8%, CI 95%, 8.6-13.0, p < 0.005); HA, per patient per year (ppy) (by 1.8, 1.3-2.3, p < 0.01); ESV, ppy (by 1.9, 1.2-2.6, p < 0.01); DRSA (by 26.5 days, 21.8-31.2, p < 0.001); DRP (by 21.0 days, 18.3-23.7, p < 0.001), and DRC (by 25.8 days, 20.3-31.4, p < 0.01). The PRC (17.2%, CI 95%, 15.5-18.9, p < 0.01) was higher for the CIMFD. CONCLUSION: The CIMFD approach improves prognosis and efficacy in the clinical management of patients with HF because it reduces mortality and morbidity (HA and ESV), shortens the delays in receiving care and in resolving the diagnostic and therapeutic process (DRSA, DRP, DRC), and increases the proportion of diagnosed and treated patients.
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Médecine de famille/statistiques et données numériques , Défaillance cardiaque/mortalité , Défaillance cardiaque/thérapie , Médecine interne/statistiques et données numériques , Orientation vers un spécialiste/statistiques et données numériques , Sujet âgé , Sujet âgé de 80 ans ou plus , Prise en charge personnalisée du patient/statistiques et données numériques , Études cas-témoins , Femelle , Études de suivi , Humains , Mâle , Adulte d'âge moyen , , Pronostic , Études prospectivesRÉSUMÉ
We review data from epidemiologic and population-based studies that demonstrate the impact of abnormal left ventricular geometric patterns, including both concentric remodeling and left ventricular hypertrophy, on major cardiovascular morbidity and mortality. We also review studies from Ochsner Clinic Foundation that assessed the impact of various left ventricular geometric patterns on overall cardiovascular prognosis, especially all-cause mortality.
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Activation of nicotinic acetylcholine receptors is initiated by binding of agonists, and as a consequence, specific domains transmit the chemical signal to the channel gate through a sequence of conformational changes. Recent high-resolution structural data from a snail acetylcholine binding protein have shown that the side chain of a lysine residue, located in the beta-strand beta7 and strictly conserved in alpha subunits of nicotinic receptors, systematically moves upon agonist binding, suggesting that it might be involved in both binding and gating. To test this hypothesis in neuronal nicotinic receptors, Lys145 was substituted by other amino acids in the alpha7 nicotinic receptor, and expression levels and electrophysiological responses for several nicotinic agonists and antagonists were determined. Substitutions of Lys145 showed a variety of functional effects: 1) strong reductions in the functional responses to acetylcholine, nicotine, and dimethylphenylpiperazinium, the latter becoming an antagonist; 2) increases in the agonist EC50 values (up to 80-fold with acetylcholine); 3) heterogeneous behavior of the different agonists, with epibatidine and cytisine being less affected by the substitutions; 4) decreases of agonist affinities for the desensitized receptors; and 5) small changes in the affinity of nicotinic antagonists. It is concluded that the presence of a polar or positively charged side chain at this position improves the gating function with acetylcholine and nicotine, although the lysine side chain seems to be necessary for retaining the binding properties of acetylcholine. The results are compatible with the involvement of Lys145 in the early steps of channel activation by acetylcholine.
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Mutation faux-sens , Agonistes nicotiniques/pharmacocinétique , Récepteurs nicotiniques/métabolisme , Substitution d'acide aminé , Animaux , Bovins , Séquence conservée , Électrophysiologie , Lysine , Agonistes nicotiniques/pharmacologie , Antagonistes nicotiniques/pharmacologie , Structure tertiaire des protéines , Récepteurs nicotiniques/génétique , Récepteur nicotinique de l'acétylcholine alpha7RÉSUMÉ
Se desarrolló el modelo matemático correspondiente al Coeficiente de Operación (COP) del ciclo de Carnot para una bomba de calor endorreversible, aplicando el criterio de mínima generación de entropía. Este ciclo tiene como características principales ser internamente reversible y externamente irreversible. Las irreversibilidades externas están asociadas a los procesos de transferencia de calor debido a la diferencia de temperaturas entre la fuente térmica y el fluido de trabajo a baja temperatura, y a la diferencia de temperaturas entre el fluido de trabajo y el sumidero térmico a alta temperatura. También son causantes de las irreversibilidades externas los tiempos finitos de duración de los procesos de transferencia de calor y las conductancias térmicas finitas de los equipos de transferencia de calor (evaporador y condensador). Estas causas de irreversibilidades aparecen en el modelo matemático desarrollado y por esto se propone como nuevo modelo de comparación para las bombas de calor, en lugar del modelo clásico de Coeficiente de Operación de Carnot de bomba de calor reversible. Este nuevo modelo marca límites de operación más cercanos a las bombas de calor reales. El modelo obtenido viene a ser una contribución al desarrollo de la termodinámica endorreversible y se puede considerar una generalización, porque cuando se aplican las condiciones de reversibilidades internas y externas, se llega al mismo resultado que el clásico de Carnot.
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Pompes , IngénierieRÉSUMÉ
Transesophageal echocardiography (TEE) is a growing technology that is frequently utilized in the critical care setting by intensivists, surgeons, anesthesiologists as well as specialists in cardiovascular diseases. The clinical application of TEE continues to emerge, and the indications and diagnostic utility of this technology as currently available are summarized in this review.