Lipid selectivity in novel antimicrobial peptides: Implication on antimicrobial and hemolytic activity.

Antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against a wide range of bacteria, fungi and viruses. For an AMP to be considered as a therapeutic option, it must have not only potent antibacterial properties but also low hemolytic and cytotoxic activities [1]. Even though many studies have been conducted in order to correlate the antimicrobial activity with affinity toward model lipid membranes, the use of these membranes to explain cytotoxic effects (especially hemolysis) has been less explored. In this context, we studied lipid selectivity in two related novel AMPs, peptide 6 (P6) and peptide 6.2 (P6.2). Each peptide was designed from a previously reported AMP, and specific amino acid replacements were performed in an attempt to shift their hydrophobic moment or net charge. P6 showed no antimicrobial activity and high hemolytic activity, and P6.2 exhibited good antibacterial and low hemolytic activity. Using both peptides as a model we correlated the affinity toward membranes of different lipid composition and the antimicrobial and hemolytic activities. Our results from surface pressure and zeta potential assays showed that P6.2 exhibited a higher affinity and faster binding kinetic toward PG-containing membranes, while P6 showed this behavior for pure PC membranes. The final position and structure of P6.2 into the membrane showed an alpha-helix conversion, resulting in a parallel alignment with the Trps inserted into the membrane. On the other hand, the inability of P6 to adopt an amphipathic structure, plus its lower affinity toward PG-containing membranes seem to explain its poor antimicrobial activity. Regarding erythrocyte interactions, P6 showed the highest affinity toward erythrocyte membranes, resulting in an increased hemolytic activity. Overall, our data led us to conclude that affinity toward negatively charged lipids instead of zwitterionic ones seems to be a key factor that drives from hemolytic to antimicrobial activity.

Phenylalanine interaction with lipid monolayers at different pHs.

The influence of Phe on the surface pressure of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers at the air-water interface was studied at different initial surface pressures (26 and 40 mN/m) and two pHs (5.0 and 7.3) at constant temperature (20 °C). Changes produced by the aminoacid added to the subphase on the surface pressure and on the dipole potential of lipid monolayers were measured at a fixed area. Compressibility properties of the monolayers at different pHs were studied by (π-A) isotherms. The results suggest that Phe intercalates into a DPPC film at the air-water interface at pH 5 and forms a different arrangement at pH 7.3. The possible relevance of these results of the effect of Phe in physiological conditions is discussed.

Prevalencia de patología oftalmológica en prematuros menores de un año de edad / Prevalence of ocular pathology in premature children under one year of age

Objetivo: Reportar hallazgos oftalmológicos en niños prematuros examinados antes del año de edad gestacional corregida (EGC). Pacientes y Método: Revisión retrospectiva de fichas clínicas de una serie de prematuros ([peso nacimiento (PN) < 1 500 g y/o < 32 sem edad gestacional (EG)] nacidos en CAS entre 2006-2009, examinados antes del año de EGC. Se consignó EG, PN, antecedente de retinopatía del prematuro (ROP), EGC al examen, refracción, anisometropia y estrabismo. Resultados: De 149 prematuros nacidos en el período, 100 tuvieron examen oftalmológico antes del año de edad (67,14 por ciento); el promedio de EG y PN fue 29,3 (rango 2336) semanas y 1217 (343-2190) g, respectivamente. El 29 por ciento presentó ROP, requiriendo tratamiento el 4 por ciento. La EGC promedio al examen oftalmológico fue 6,4 (3-11,5) meses. El equivalente esférico fue +1,34D (-1,75 a +5,75), presentando anisometropia >1D el 2,2 por ciento(95 por ciento IC, -0,82-5,26). El 3,3 por ciento (95 por ciento IC, -0,38-7,04) presentaba indicación de lentes según recomendaciones internacionales y el 4 por ciento (95 por ciento IC, 0,16-7,84) presentó estrabismo. Conclusiones: La baja prevalencia de factores de riesgo para ambliopia detectada en esta cohorte comparada con la reportada para prematuros con ROP severa podria explicarse por la baja prevalencia de ésta última en la presente serie.

Objective: To report ocular abnormalities in premature infants examined before one year of Corrected Gestational Age (CGA). Patients and Methods: Retrospective review of medical records of a number of premature infants ([birth weight (BW) < 1 500 g and/or < 32 week gestational age (GA)] born between 2006 and 2009 and examined before one year of CGA. GA, BW, retinopathy of prematurity (RQP), CGA examination, refraction, anisometropia and strabismus information were recorded. results: Out of the 149 premature infants born during the period, 100 had eye exam before one year of age (67.14 percent), the mean GA and BW was 29.3 (range 23-36) weeks and 1217 (343-2190) g, respectively. 29 percent had ROP, 4 percent required treatment. The mean CGA at the time of ophthalmologic examination was 6.4 (3 to 11.5) months. The spherical equivalent was +1.34 D (-1.75 to +5.75), 2.2 percent presented anisometropia > 1D (95 percent CI, -0.82 to 5.26). 3.3 percent (95 percent CI, -0.38 to 7.04) were in need of glasses according to international recommendations and 4 percent (95 percent CI, 0.16 to 7.84) had strabismus. Conclusions: The low prevalence of risk factors for amblyopia detected in this population compared with that reported for premature infants with severe RQP could be explained by the low prevalence of the latter in this study.

Evaluación de riesgos y gestión en desastres: 10 preguntas para la década actual / Risk assessment and disaster management: 10 questions for the present decade

La sociedad humana está siendo tensionada por crecientes eventos destructivos o alteradores de su calidad de vida, ya sea por causas de origen natural o creadas por la acción humana. Frente a estos retos, distintas iniciativas han pretendido en las Décadas 1990-1999 y 2000-2010, corregirlas con éxito. Desafortunadamente, la mayoría de ellas, originadas en el mundo de la Ciencia y Tecnología, no parecen generar igual compromiso y entusiasmo en los niveles políticos y de toma de decisión, expresándose en Políticas Públicas, Leyes, Reglamentos y Presupuestos para una Gestión Integral del Riesgo mucho más Preventiva y permanente en la Agenda Pública. El autor ha seleccionado 10 frecuentes preguntas de su quehacer académico y que nos ayudan a entender mejor este complejo proceso. La Globalización de algunos de estos eventos, como es el caso del Cambio Climático Global, hacen necesario políticas integradoras y un despertar de la comunidad organizada.

Human society is being stressed by increasing destructive events, natural or man-made or those that can alter their quality of life. Facing this challenge, different initiatives on two Decades (1990-1999 and 2000-2010) have attemted to make useful corrections. Unfortunately, most of them born in the world of Sciences and Technology, do not seem to generate equal commitment and enthusiasm at the political and decision-making levels expressed in Public Policies, Laws, Rules and Budgets oriented to Integral Risk Management much more Preventive and Permanent on the Public Agenda. The author has selected 10 frequent questions coming from his academic duties and helping us to better understand this complex process. World-wide events as the case of Global Climatic Change, make necessary integral policies and an awakening of the organized community.

Bombas de infusión continua de jeringa en unidades neonatales / Continuous infusion pumps at neonatal intensive care units

Introduction: Continuous Infusion pumps (CIP) are frequently used at neonatal intensive care units (NICUs), to administer medications at flow rates lower than 1 ml/H. Various factors have been shown to alter their performance. No studies have been completed in Chile in this area. Objectives: To describe frequent clinical practices to administer medications through CIP at NICUs in Chile, and suggest recommendations about it. Methods: Four professionals at NICUs in 19 centers were surveyed regarding syringe size, flow rate and precautions. Results: When starting countinuous infusion, 81.9 percent of surveyed professionals use 50 cc syringes, and 66.7 percent of them use flow rates under 1 ml/h. Main precautions include elimination of bubbles in the circuit (51.4 percent), review of conections (38.9 percent) and precise fit between the syringe and the CIP (36.1 percent). Conclusions: In surveyed NICUs, low flow rates and 50cc syringes are frequently used to infuse medications. NICU staff must consider factors that affect the performance of CIP, prefer smaller syringes and flow rate over 1 ml/h for continuous infusion of drugs.

Introducción: En las unidades de cuidado intensivo neonatal (UCIN) se utilizan frecuentemente bombas de infusión continua (BIC) a flujos menores de 1 ml/h para administrar medicamentos. Está demostrado que distintos factores alteran el funcionamiento de las BIC a flujos bajos. En Chile, no existen estudios que describan prácticas relacionadas al uso de BIC. Objetivo: Describir prácticas clínicas frecuentes al administrar medicamentos en BIC en UCIN de Chile y proponer recomendaciones respecto a su uso. Método: Se encuestaron 4 profesionales de UCIN en 19 centros. Los principales aspectos evaluados fueron: tamaño de jeringa usado en las BIC, flujos de infusión continua utilizados y precauciones al instalar una BIC. Resultados: Al instalar una infusión continua, el 81,9 por ciento de los profesionales encuestados usa jeringas de 50 ml y el 66,7 por ciento utiliza flujos menores de 1 ml/h. Las principales precauciones fueron la eliminación de burbujas del circuito (51,4 por ciento), la revisión de las conexiones del sistema (38,9 por ciento) y el ajuste preciso entre jeringa y BIC (36,1 por ciento). Conclusiones: En las UCIN estudiadas se utilizan frecuentemente flujos bajos y jeringas de 50 ml para infundir medicamentos. Las UCIN deben considerar los factores que alteran el funcionamiento de las BIC y preferir el uso de jeringas de menor tamaño y flujos mayores de 1 ml/h para la infusión continua de medicamentos.

Enterocolitis necrótica y sífilis congénita en un recién nacido / Congenital syphilis and necrotizing enterocolitis in a newborn infant

Un recién nacido por cesárea a las 36 semanas de edad gestacional (hijo de una pareja promiscua cuya madre no cumplió controles prenatales) evolucionó con hipoclicemia, hiperbilirrubinemia y distensión abdominal progresiva, títulos de VDRL en sangre del cordón umbilical de 1/l28, FTA-ABS, hemoglutinación y ELISA IgM para treponemas positivos. Las imágenes de ultrasonografía y radiología mostraron gas en lo vía biliar y neumatosis intestinal. Los cultivos bacterianos dieron resultados negativos. En la laparotomía se encontraron extensos signos de enteritis necrótica. Falleció al tercer dia de vida en falla circulatoria. En la necropsia se encontraron alteraciones histológicas características de sífilis en los tejidos pulmonar (neumonía alba), pancreático e intestinal, junto con extensa neumatosis que afectaba todo el intestino delgado, el colon y el recto

Enfermedades crónicas en pacientes pediátricos hospitalizados: frecuencia y tipo de enfermedad / Chronic diseases among hospitalized pediatric patients: frequency and type of disease

Se estudió la frecuencia y tipo de enfermedades crónicas en menores de 15 años que egresaron de las unidades de lactantes, infecciosos, cirugía infantil, cuidado intensivo y niños mayores de un servicio de pediatría en un hospital docente de Santiago metropolitano, entre el 1 de abril y 30 de septiembre de 1992. No se incluyeron casos oncohematológicos de pacientes politraumatizados o de urgencia y se consideró enfermedades crónicas cualquiera que durase mas de seis meses. Los casos se clasificaron según la seguridad con que se formuló el diagnóstico, en certeza y sospecha. La proporción de afecciones crónicas fue 35,2 por ciento entre los egresos y 32,9 por ciento entre los niños, aumentando gradulamente con la edad, hasta 47,1 por ciento en los mayores de 10 años. Entre los 137 niños con enfermedades crónicas, 13,1 por ciento (n=18) tenían sólo diagnóstico de sospecha, siendo mayor la incertidumbre en los menores de seis meses (25 por ciento). La mediana de la edad de los casos crónicos fue 19 meses y sólo 10 meses en los agudos. Las afecciones respiratorias conformaron el grupo de diagnósticos mas frecuente, seguidas de las anomalías congénitas y las afecciones génitourinarias

In vitro studies of natural killer cell activity in post traumatic stress disorder patients. Response to methionine-enkephalin challenge.

Attempts to define biological parameters that may be specifically associated with the pathophysiology of post traumatic stress disorder (PTSD) have met with only limited success, reflecting perhaps the practical limitations resulting from the high frequency of comorbidity of this condition with Axis I, II and III psychiatric diagnoses. We now report our studies on natural killer cell activity (NKCA), and the response of this cellular immune function to an in vitro methionine-enkephalin (MET) challenge in a population of Vietnam veterans with PTSD. Due to the characteristics of our PTSD patients, our protocol included four sex-matched, age-comparable control groups: (1) chronic alcoholics, (2) chronic drug abusers excluding alcohol, (3) chronic users of alcohol and other drugs of abuse and (4) drug-free, healthy volunteers. Although these groups did not significantly differ in their "baseline" NKCA, significant findings emerged from their response to preincubation with MET (10(-10), 10(-8) and 10(-6) M; 40:1 effector-to-target cell ratio). To minimize interindividual variations in the expression of NKCA each subject was used as its own control. Whereas peptide challenge resulted in an increase in NK lytic function in a subpopulation of group four (one or more MET concentrations, 8 out of 22 subjects), it produced mixed results in samples from individuals in group 2, and in general failed to elicit NKCA changes in the samples from participants in groups 1 and 3. Nine of the thirteen PTSD patients responded to MET preincubation with decreases in NKCA, which in five of them reached values below 20% of baseline for the three peptide concentrations tested. These findings may suggest that the "stress factor" in Vietnam veterans with PTSD plays a role in downmodulating NK lytic function in response to an in vitro MET challenge, an effect that appears to be potentiated by the use of drugs of abuse other than alcohol. The possible clinical relevance of these findings, including the identification of a subgroup of PTSD patients on the basis of immunological tests such as the one described in this work, deserves further investigation.

Enhancement of human natural killer cell activity by opioid peptides: similar response to methionine-enkephalin and beta-endorphin.

We studied the effect of methionine-enkephalin (MET) and beta-endorphin upon human peripheral blood lymphocyte natural killer cell (NKC) activity in a group of healthy volunteers (n = 27; 17 male and 10 female, age +/- SD and range of 32 +/- 6, 25-43 years and 36 +/- 11, 22-65 years, respectively). Aliquots from some individual samples were preincubated separately with different concentrations of either peptide (n = 12), while others were tested with only one of these substances (MET, n = 6; beta-endorphin, n = 9). Using each individual as its own control, MET (10(-8) and 10(-6) M) and beta-endorphin (10(-10) and 10(-8) M) significantly increased NKC activity (NKCA) (at least 20% over base value, effector-to-target cell ratio, 40:1) in 7 out of 15 and 7 out of 19 subjects, respectively. Results obtained from the rest of the samples were mixed, e.g., changes observed in NKCA were not significant or showed significance with only one of the peptide concentrations studied. Cells from individuals showing a significant increase in NKC lytic function following preincubation with either MET or beta-endorphin responded similarly to the other peptide (in both cases 5 out of 6 subjects), suggesting that enhancement of NKCA by MET and beta-endorphin may work through a similar mechanism.

[Immunological defects in septic shock. Deficiency of natural Killer cells and T-lymphocytes]. / Defectos inmunológicos en el shock séptico. Deficiencia de células natural killer y de linfócitos T.

It is well known that an immunosuppressive response occurs after acute trauma. Some cellular mediators participate in the pathogenesis of septic shock. However, the exact role of the lymphocyte subsets and natural killer (NK) activity in this condition is not clear. We studied NK cytolytic activity through a 51Cr liberation assay using K-562 target cells in 20 patients with initial septic shock (10 men and 10 females, mean age 41 years old). Lymphocyte subsets CD3 (T3), CD4 (T4), CD8 (T8), CD16 (Leu-11) and CD56 (Leu-19) were also studied by indirect immunofluorescence. Compared to results obtained in 20 healthy volunteers, patient's NK activity was decreased (4.6 +/- 3.9 vs 26.1 +/- 10, p less than 0.025), CD16 was lower (10%/187 vs 15%/280 per ul) and CD56 was also lower (6%/120 vs 12%/224 per ul), p less than 0.05. T lymphocyte subsets were also decreased: CD3 cells (1100 vs 1352 per ul) and CD4 cells (634 vs 873 per ul), p less than 0.05. Thus, a severe decrease in NK cells and NK cell function as well as decreases in CD3 and CD4 lymphocyte subsets are present in the initial stages of septic shock. The predictive value of these findings is currently under study.