Browsing by Author "Ramirez, Marcelo"

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    Migration of coccinellids to alfalfa fields with varying adjacent vegetation in Central Chile
    (2010) Grez, Audrey A.; Torres, Constanza; Zaviezo, Tania; Lavandero, Blas; Ramirez, Marcelo
    A. A. Grez, C. Torres, T. Zaviezo, B. Lavandero, and M. Ramirez. Migration of coccinellids to alfalfa fields with varying adjacent vegetation in Central Chile. 2010. Cien. Inv. Agr. 37(2): 111-121. Permanent and permeable edges, where natural enemies can feed, overwinter or easily cross over, should enhance the early arrival of these predators to crops. We evaluated the abundance and species richness of coccinellids migrating to alfalfa fields adjacent to Eucalyptus, a mix of false acacia, blackberries and poplar (F-B-P), vineyards, corn and annual vegetables. From September 2007 to May 2008, we captured coccinellids in three sticky traps (2.64 m(2)) placed at the borders between alfalfa fields and adjacent vegetation. We also estimated the abundance of aphid populations in the alfalfa fields, by counting the number of individuals per alfalfa stem in spring, summer and autumn. We collected 90,396 coccinellids from 14 species. Neither total abundance nor species richness of coccinellids was significantly affected by adjacent vegetation, but Adalia deficiens, Psyllobora picta and Cycloneda sanguinea were more abundant in alfalfa adjacent to Eucalyptus and F-B-P, meanwhile Olla v-nigrum next to annual crops and Hyperaspis sphaeridioides next to vineyards. Edge height and orientation explained 94% of the variance in species abundance. Particularly, P picta and O. v-nigrum were positively and negatively influenced by border height, respectively. Hyperaspis sphaeridioides was negatively affected by northern exposure and none of the species was affected by edge permeability. Aphids were less abundant in alfalfa fields adjacent to F-B-P, especially in spring. These results show that most species of coccinellids were not affected by the composition of crop edges, although tall permanent edges may enhance the arrival of particular coccinellid species to alfalfa fields.
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    Population pharmacokinetics of amikacin in suspected cases of neonatal sepsis
    (Wiley, 2023) Severino Cuevas, Nicolás Felipe; Urzúa Baquedano, Maria Soledad; Ibacache Figueroa, Mauricio Enrique; Paulos Arenas, Claudio; Cortinez Fernandez, Luis Ignacio; Toso Milos, Alberto Antonio; Leguizamon Marino, Liliana Marcela; Inojosa Mackenzie, Fernanda; Maccioni Romero, Andrea Ana; Meza Cañas, Sebastián Jaime; Garcia, Andres; Ramirez, Marcelo; Von Mentlen Gutierrez, Catalina Paz; Ceballos Jorquera Javiera Nicol; Paredes Galvez, Noemi Saray
    Aims:This study aimed to characterize the population pharmacokinetic parameters of intravenously administered amikacin in newborns and assess the effect of sepsis in amikacin exposure. Methods: Newborns aged >= 3 days who received at least 1 dose of amikacin during their hospitalization period were eligible for the study. Amikacin was administered intravenously during a 60-min infusion period. Three venous blood samples were taken from each patient during the first 48 h. Population pharmacokinetic parameter estimates were obtained using a population approach with the programme NONMEM. ResultsData from 329 drug assay samples were obtained from 116 newborn patients (postmenstrual age [PMA] 38.3, range 32-42.4 weeks; weight 2.8, range 1.6-3.8 kg). Measured amikacin concentrations ranged from 0.8 to 56.4 mg/L. A 2-compartment model with linear elimination produced a good fit of the data. Estimated parameters for a typical subject (2.8 kg, 38.3 weeks) were clearance (Cl = 0.16 L/h), intercompartmental clearance (Q = 0.15 L/h), volume of distribution of the central compartment (Vc = 0.98 L) and peripheral volume of distribution (Vp = 1.23 L). Total bodyweight, PMA and the presence of sepsis positively influenced Cl. Plasma creatinine concentration and circulatory instability (shock) negatively influenced Cl. ConclusionOur main results confirm previous findings showing that weight, PMA and renal function are relevant factors influencing newborn amikacin pharmacokinetics. In addition, current results showed that pathophysiological states of critically ill neonates, such as sepsis and shock, were associated with opposite effects in amikacin clearance and should be considered in dose adjustments.