Fullerene-like boron nitride cages BxNy (x + y = 28): stabilities and electronic properties from density functional theory computation.

Computations based on density functional theory (DFT) were performed to get insights into the structural stability, electronic, and magnetic properties of fullerene-like boron nitride cages (f-like BNCs) for different BxNy chemical stoichiometry (x + y = 28). The results reveal at least metastable nanostructures for anionic charge (Q = -1) and doublet state (M = 2); furthermore, a magnetic moment of 1.0 bohr magneton is associated with them. These systems, in general, have high chemical stability due to their large values of cohesion energy, and the structural stability was corroborated by means of vibrational calculations. According to quantum descriptors, they exhibit high polarity (except to B27N and B28 systems), low average chemical reactivity and average work function, and electronic behavior like semiconductors. Therefore, the properties of these systems are improved compared to the B28 system, and thus the nonstoichiometry fullerenes can be used for more applications than the pristine one.

Interactions of B12N12 fullerenes on graphene and boron nitride nanosheets: A DFT study.

In the search of nanomaterials to be used in drug delivery applications, Density Functional Theory calculations were implemented to study the interaction between graphene (G) and hexagonal boron nitride nanosheet (hBNN) with octahedral B12N12 fullerenes. These B12N12 fullerenes were considered in two cases: pristine and the modified one with boron-boron, nitrogen-nitrogen (tetragon) and boron-boron-boron (hexagon) homo-nuclear bonds. The whole systems were analyzed in the gas and aqueous phases. The results reveal for all these systems that the interaction is in the range of physisorption (Eads = from -0.03 to -0.37 eV) for both phases, limiting its functions as a vehicle. However, for the nano-composite: B12N12 fullerene modified and hBNNs, the values of average chemical reactivity and HOMO-LUMO gap decreased whereas the polarity was improved, thereby this combination of quantum descriptors lead them to be considered as potential vehicle for drug delivery.

Theoretical analysis of C-F bond cleavage mediated by cob[I]alamin-based structures.

In the present work, C-F bond cleavage mediated by the super-reduced form of cobalamin (i.e., CoICbl) was theoretically studied at the ONIOM(BP86/6-311++G(d,p):PM6) + SMD level of theory. Dispersion effects were introduced by employing Grimme's empirical dispersion at the ONIOM(BP86-D/6-311++G(d,p):PM6) + SMD level. In the first stage of the study, cobalamin was characterized in terms of the coordination number of the central cobalt atom. The ONIOM(BP86/6-311++G(d,p):PM6) results showed that the base-off form of the system is slightly more stable than its base-on counterpart (ΔE = E base-off - E base-on ~ -2 kcal/mol). The inclusion of dispersive forces in the description of the system stabilizes the base-on form, which becomes as stable as its base-off counterpart. Moreover, in the latter case, the energy barrier separating both structures was found to be negligible, with a computed value of 1.02 kcal/mol. In the second stage of the work, the reaction CoICbl + CH3F → MeCbl + F- was studied considering the base-off and the base-on forms of CoICbl. The reaction that occurs in the presence of the base-on form of CoICbl was found to be kinetically more favorable (ΔE ≠ = 13.7 kcal/mol) than that occurring in the presence of the base-off form (ΔE ≠ = 41.2 kcal/mol). Further reaction-force analyses of the processes showed that the energy barrier to C-F bond cleavage arises largely due to structural rearrangements when the reaction occurs on the base-on form of the CoICbl complex, but is mainly due to electronic rearrangements when the reaction takes place on the base-off form of the complex. The latter behavior emerges from differences in the synchronicity of the bond strengthening/weakening processes along the reaction path; the base-on mode of CoICbl is able to decrease the synchronicity of the chemical events. This work gives new molecular-level insights into the role of Cbl-based systems in the cleavage of C-F bonds. These insights have potential implications for research into processes for degrading fluorine-containing pollutants.

Mola hidatidiforme completa con preeclampsia e hipertiroidismo: presentación clásica / Complete hydatidiform mole with preeclampsia and hyperthyroidism: classic presentation

Introducción: La enfermedad trofoblástica gestacional es un espectro de enfermedades de la placenta, existiendo entre ellas algunas con potencial de invasión y metástasis, dentro de las cuales se incluye la mola invasiva, coriocarcinoma, tumores del sitio de inserción de la placenta y mola hidatidiforme. Esta última a su vez se divide en mola completa y parcial, diferenciándose en histopatología, morfología, cariotipo, malignización y comportamiento clínico, que es el punto al cual nos referiremos en este caso. Caso clínico: mujer de 46 años ingresa por hemoptisis, metrorragia, disnea a pequeños esfuerzos, ortopnea y disnea paroxística nocturna, asociado a hipertensión, taquicardia, masa hipogástrica firme e inmóvil y edema de extremidades. Se realiza ecografía abdominal compatible con MH y bhCG elevada. Evoluciona con crisis hipertensivas, insuficiencia cardiaca congestiva y tirotoxicosis. Inicia trabajo de parto expulsando 665 grs de mola, presentando posteriormente a legrado uterino anemia severa y shock hipovolémico, requiriendo transfusiones y drogas vasoactivas. Se recupera progresivamente con posterior control al alta de bhCG indetectable a los 6 meses. Discusión: Es infrecuenta en la actualidad la presentación clínica clásica de la mola hidatidiforme completa debido al diagnóstico y control precoz del embarazo asociado al uso masivo de la ecografía. Sin embargo es relevante tener un alto grado de sospecha de esta patología debido a sus graves consecuencias, y así realizar una derivación y manejo precoz.

Background: Gestational trophoblastic disease is a spectrum of diseases of the placenta, existing some with potential for invasion and metastasis, among which include invasive mole, choriocarcinoma, tumors of the insertion site of the placenta and hydatidiform mole. The last one is divided into complete and partial mole, differing in histopathology, morphology, karyotype, and clinical malignant behavior, witch is the point we refer to in this case. Case report: 46 year old woman admitted for hemoptysis, metrorrhagia, dyspnea on slight exertion, orthopnea and paroxysmal nocturnal dyspnea associated with hypertension, tachycardia, firm and immovable hypogastric mass and limb edema. Abdominal ultrasound compatible with MH and high BhCG is performed. Evolve with hypertensive crisis, congestive heart failure and thyrotoxicosis. Labor starts driving out 665 grams of mole, after the curettage present hypovolemic shock and severe anemia requiring transfusions and vasoactive drugs. It gradually recovers further control the discharge of BhCG undetectable at 6 months. Discussion: It is currently infrequent classical clinical presentation of complete hydatidiform mole due to early diagnosis and management of pregnancy associated with the widespread use of ultrasound. However it is important to have a high degree of suspicion of this disease because of its serious consequences, and thus make a referral and early management.

[Clinical epidemiologic study of patients admitted to the intensive care unit, according to age]. / Estudio clínico epidemiológico de los pacientes ingresados a UCI, según grupo etáreo.

BACKGROUND: Lately, we have observed an increase in the admission to intensive care units of patients over 65 years old, probably due to the increase in life expectancy that is occurring in Chile. AIM: To compare the frequency of admissions to intensive care units in patients over 65 years old, their diagnoses, their severity and hospital course, with those of younger patients. PATIENTS AND METHODS: The charts of all patients admitted to an intensive care unit of a University Hospital, during one year, were reviewed. The diagnosis that caused the admission was considered the main disease. Severity at the moment of admission was assessed using the Apache score. RESULTS: A total of 777 patients were admitted during the study period. Twenty had to be excluded due to lack of reliable data. Four hundred thirty two (57%) were over 65 years old. Cardiovascular diseases were the main cause of admission in young and old patients. Mortality was 14.8% of patients over 65 years old and 18.7% in younger patients. Main causes of death were cardiac arrest, cardiogenic shock, sepsis and cerebrovascular disease. No differences in causes of death were observed between young and old patients. CONCLUSIONS: Patients older than 65 years old admitted to intensive care units are very similar to their younger counterparts in their prognosis and causes of admission.

[Patients with acute adult respiratory distress syndrome: effects of inhaled nitric oxide on gas exchange and hemodynamics]. / Pacientes con síndrome de distress respiratorio agudo del adulto: efectos del óxido nítrico inhalado sobre el intercambio gaseoso y la hemodinamia.

BACKGROUND: Adult respiratory distress syndrome is highly prevalent in intensive care units and has a high mortality. Lately, nitric oxide has been used as adjuvant therapy. AIM: To study the effects of nitric oxide inhalation in patients with adult respiratory distress syndrome. PATIENTS AND METHODS: Twelve patients with adult respiratory distress syndrome, were subjected to nitric oxide inhalation at a concentration of 10 parts per million, during 30 minutes. RESULTS: At the end of the nitric oxide inhalation period, there was an improvement of PaO2/FIO2 ratio from 89 +/- 32 to 111 +/- 43 mm Hg and a 16% reduction of lung shunting (Qs/Qt). CONCLUSIONS: Nitric oxide inhalation at a concentration of 10 parts per million improved arterial oxygenation and reduced pulmonary shunting in patients with adult respiratory distress syndrome.

[Pulmonary thromboendarterectomy: a case of surgical treatment of chronic pulmonary thromboembolism under circulatory arrest with deep hypothermia]. / Tromboendarterectomía pulmonar. Tratamiento quirúrgico del tromboembolismo pulmonar crónico bajo paro circulatorio con hipotermia profounda en un caso.

Pulmonary thromboendarterectomy under circulatory arrest and deep hypothermia is presently a curative treatment for pulmonary hypertension secondary to chronic pulmonary artery thromboembolic occlusion, but is still not frequently performed around the world. We report here the first successful pulmonary thromboendarterectomy under circulatory arrest performed in Chile. The patient was a 37 year old white man, high school teacher, with a 5 months history of effort dyspnea and cough. Pulmonary hypertension secondary to chronic pulmonary thromboembolism was confirmed by angiography and echocardiography. The patient was operated on April 27, 1995. After the operation the patient had an immediate and maintained normalization of his pulmonary hemodynamics. He presented periods of delirium that postponed mechanical ventilation disconnection until the 7th postoperative day, after which he had an uneventful neurological recovery. Before hospital discharge a control angiography showed complete patency of the pulmonary artery system with no evidence of residual thrombi. Presently he is enjoying a normal life and back to his teaching activities.

[Vital prognosis in severe acute hepatic failure. Value of the quantitative indexes of evaluation]. / Pronóstico vital en insuficiencia hepática aguda grave. Valor de los índices cuantitativos de evaluación.

The aim of this study was to assess the predictive value for mortality of admission and daily APACHE II score, mortality due to multiple organ failure and the Organ Failure Score in patients with acute hepatic failure. We retrospectively studied 15 such patients admitted to an intensive care unit. Thirteen patients died (87%) and their admission APACHE II score was 22 +/- 7.5 compared to 21 +/- 8.5 in survivors. Daily APACHE II score, mortality due to multiple organ failure and multiple organ failure score had a 100% sensitivity to predict mortality and a 69.2, 76.9 and 76.9% specificity respectively. The predictive accuracies of multiple organ failure and multiple organ failure score were 80% and significantly better than the accuracy of admission APACHE II score (53%). We conclude that these prognostic scores can be useful in the assessment of patients with acute hepatic failure.

[Multidisciplinary study of cerebrovascular disorders. II. Cardiovascular profile of occlusive vascular disorders]. / Estudio multidisciplinario de los accidentes vasculares encefálicos. II--Perfil cardiovascular de los accidentes vasculares oclusivos.

Ischemic stroke constitute a mayor cause of morbidity and mortality in the adult population, particularly in the elderly. Heart disease may predispose to ischemic stroke, especially in the presence of transient or permanent precipitating factors such as atrial fibrillation. To elucidate the role of heart disease in predisposing to ischemic stroke we studied the clinical and non invasive cardiac profile (EKG, 2D-Echo, Holter) of 186 consecutive patients, 91 of them embolic (GI) and 96 non embolic (lacunar, atherothrombotic, others) (GII), as determined by brain CT scan and thorough clinical evaluation. Age and male/female ratio were significantly different (71 + 13 vs 65 + 12 years, 40/60 vs 65/35, p < 0.003). Hypertension was equally common in both groups (38 and 40%). Patients in GI had higher prevalence of valvular heart disease (23 vs 1%), atrial fibrillation (67 vs 10%), 2D Echo left atrial enlargement (45 vs 16%) and supraventricular ectopy in Holter (59 vs 32%) p < 0,001. By contrast absence of heart disease (45 vs 19%), ST-T changes in EKG (28 vs 14%), left ventricular hypertrophy in 2D Echo (28 vs 9%) and ventricular ectopy in Holter (54 vs 23%) were more prevalent in GII patients, p < 0.001. Multiple stepwise logistic regression analysis showed age > 70 years (relative risk (RR) 1.67), valvular heart disease (RR 2.25), chronic AF (RR 2.44) and paroxysmal AF (RR 1.89) were significant independent predictors of embolic stroke, whereas the presence of left ventricular hypertrophy in 2D-Echo (RR 0.76) and frequent ventricular premature beats in Holter (RR 0.47) were predictors of occlusive non embolic stroke. Thus, the clinical and non invasive cardiac profile of embolic and non embolic ischemic stroke is significantly different, which is relevant to preventive strategies.

[Multidisciplinary study of cerebrovascular accidents: I. Definition, design, and general results]. / Estudio multidisciplinario del accidente vascular encefálico: I.- Definición, diseño y resultados generales.

Cerebrovascular accidents (CVA) constitute a major cause of adult cardiac cardiovascular mortality in Chile. From July 87 to August 89 we prospectively studied 300 patients with CVA utilizing a multidisciplinary approach. Besides clinical evaluation this included brain CT scan (48 hrs), glucidic and lipid profile. Occlusive CVA were additionally studied with 2D-Echocardiogram, 24 hr Holter, Cerebral Angiography and/or carotid Duplex Echotomograph, and a second brain CT scan was performed within the first week. We found a 62.3% incidence of cerebral infarcts, 28.3% of cerebral hemorrhages and 9.3% of transient ischemic attacks. Cerebral infarcts were found to be cardiac related in 33.5% of cases, whereas 13.2% were lacunar, 4.4% were atherothrombotic and 14% had no precise etiology. Hypertension was associated to cerebral hemorrhages in 76% of cases, 26% of which were intracranial. At 2 months of follow-up 16.3% of patients were severely handicapped and mortality was 19.3%. We have confirmed that cerebral infarcts constitute the most common cause of CVA and most of them are cardiac related. Hypertension appears to be the most important cause of cerebral hemorrhage. A multidisciplinary approach to cerebrovascular accidents allowed a more precise diagnosis and contributed to implement appropriate therapeutic and preventive strategies. Proper identification of high risk patients could contribute to decrease the high incidence and mortality of CVA in our community.

Risk factors for systemic embolism in patients with paroxysmal atrial fibrillation.

The purpose of this study was to define the risk factors for systemic embolism in patients with recently diagnosed paroxysmal atrial fibrillation. We therefore studied 63 consecutive patients with symptomatic nonvalvular paroxysmal atrial fibrillation and performed a clinical and noninvasive cardiac, peripheral vascular, and neurologic evaluation that included two-dimensional echocardiography, 24-hour Holter monitoring, and computed tomographic brain scan. Patients with predisposing clinical conditions for systemic embolism (valvular heart or coronary artery disease) or paroxysmal atrial fibrillation (sick sinus disease, preexcitation, or thyroid dysfunction) were excluded. At entry 34 patients had idiopathic paroxysmal atrial fibrillation and 29 had hypertension. Fourteen patients had a recent systemic embolic complication: nine had a recent occlusive nonlacunar cerebrovascular accident, two had transient ischemic attacks, and three had peripheral systemic emboli that required surgery. In addition, five patients had evidence of old cerebrovascular accident on the computed tomographic scan (group 1). Forty-four patients had no systemic embolism (group 2). Results of univariate analysis showed that patients in group 1 were older (72 +/- 9 vs 63 +/- 13 years, p less than 0.05), had a higher incidence of hypertension (70% vs 35%, p less than 0.01), and had an increased left atrial diameter (4.1 +/- 0.7 vs 3.6 +/- 0.5 cm, p less than 0.05). Multiple stepwise logistic regression analysis showed that a history of hypertension and left atrial enlargement on two-dimensional echocardiography were significant independent risk factors for systemic embolism in patients with symptomatic nonvalvular paroxysmal atrial fibrillation.

[Severity evaluation system: APACHE II, SAPS. National experience in a unit of medical intensive therapy]. / Sistemas de evaluación de gravedad: APACHE II SAPS. Experiencia nacional en una unidad de terapia intensiva médica.

We evaluated 2 new prognostic indices, APACHE II and SAPS, in 533 consecutive patients admitted to a general hospital clinical care unit. Mortality was 19.5% (13.1% in the ICU). Among non-survivors 80% had a greater than = 20 APACHE II score and 77% a greater than = 13 SAPS score. Only 2% of patients with APACHE score less than 10 or SAPS less than 7 died. A good correlation with previously used indices (APACHE I and TISS) was 0.6. Utilization of these prognostic indices allows comparison of reports from different centers, evaluation of early and long term prognosis and a help in making cost-benefit decisions.

[Intraventricular conduction disorders in acute myocardial infarction: early and late clinical significance]. / Trastornos de conducción intraventricular en infarto agudo del miocardio: significado clínico precoz y tardío.

The prognostic impact of new bundle branch block (BBB) upon the intra hospital course and long-term prognosis of patients with acute myocardial infarction (MI) was studied in 517 consecutive patients with a recent MI: 449 patients did not have BBB (group I) and 69 developed a new BBB (group II). Age and sex were similar in both groups. Incidence of BBB among patients with anterior wall MI was 61% compared to 8% in patients with inferior wall MI (p less than 0.05). The distribution of RBBB, RBBB + left anterior hemiblock and LBBB was 32%, 30% and 38% among 46 patients with anterior wall MI, compared to 28%, 6% and 68% among 18 patients with inferior wall MI (p less than 0.05). The level of peak CK values (2345 vs 1437 IU/l), presence of Killip grade III or IV (56 vs 18%), complete A-V block (24 vs 6%) and mortality (34 vs 9%) were significantly higher in group II (p less than 0.05). Long-term mortality at 1 and 5 years of follow up was 29% and 51% in group II patients, a three fold increase over group I. We conclude that development of new BBB during myocardial infarction is associated with a poor immediate and long term prognosis. This may be related to larger infarcts rather than the conduction defect itself.

[Syncope: general characteristics and its relation to age]. / Síncope: características generales y relación con la edad.

We retrospectively analyzed the clinical data of 146 patients admitted to a general hospital with the diagnosis of syncope. A definite or highly likely cause was identified in 91 patients (62%). These were of cardiovascular origin in 78%: conduction defects (31), sinus node disease (9), obstructive causes (8), ventricular arrhythmia (8), ischemia (5) and miscellaneous (14). A non cardiovascular origin was present in 22% of patients: intoxication (7), hysteria (5), hypoxemia (3), vasovagal (2), gastrointestinal bleeding (2) and 2 others. The final diagnosis in patients with a known cause was established by the history and physical examination in 16, the ECG in 42, Holter 9, ECG monitoring in ICU 8 and echocardiogram 6. No difference in the distribution of causes was present between patients below or above 65 years of age. In hospital mortality was 2%.

[Are there any differences between myocardial infarction with Q and non-Q in ECG]. / Existen diferencias en el infarto del miocardio con o sin onda Q el ECG?

Recent literature provides evidence that Non-Q wave myocardial infarction (Non-Q MI) has a different intrahospital course and prognosis than Q-wave myocardial infarction (Q-MI). We evaluated clinical and laboratory characteristics, complications and therapeutic requirements of 557 consecutive patients, 440 with Q-MI and 117 with Non-Q MI. Risk factors for coronary artery disease did not differ among groups. Non-Q MI patients had a significantly higher incidence of previous cardiac events such as myocardial infarction, angina pectoris and heart failure. Peak CPK enzyme values were significantly lower in Non Q MI patients (952 +/- 753 vs 1,743 +/- 1,425 VI/l p less than 0.05). Early complications were different for both groups: The incidence of heart failure, ventricular arrhythmias and conduction defects was lower in Non-Q MI patients while the incidence of unstable angina pectoris and need for aorto coronary by-pass surgery was higher (18 vs 12%, 17 vs 7% respectively, p less than 0.05). Mortality was not different (8.4% in Non-Q MI vs 12.3% in Q MI). Thus, Non Q MI appears to have a more benign clinical course than Q-MI in terms of less complications such as heart failure, ventricular arrhythmias and conduction defects. However, Non-Q MI is a potentially unstable clinical entity with a higher incidence of early post MI angina pectoris requiring a more aggressive medical and surgical therapy.