Population Pharmacokinetic Modeling of Total and Free Ceftriaxone in Critically Ill Children and Young Adults and Monte Carlo Simulations Support Twice Daily Dosing for Target Attainment

Critical illness, including sepsis, causes significant pathophysiologic changes that alter the pharmacokinetics (PK) of antibiotics. Ceftriaxone is one of the most prescribed antibiotics in patients admitted to the pediatric intensive care unit (PICU). We sought to develop population PK models of both total ceftriaxone and free ceftriaxone in children admitted to a single-center PICU using a scavenged opportunistic sampling approach. We tested if the presence of sepsis and phase of illness (before or after 48 h of antibiotic treatment) altered ceftriaxone PK parameters. We performed Monte Carlo simulations to evaluate whether dosing regimens commonly used in PICUs in the United States (50 mg/kg of body weight every 12 h versus 24 h) resulted in adequate antimicrobial coverage. We found that a two-compartment model best described both total and free ceftriaxone concentrations. For free concentrations, the population clearance value is 6.54 L/h/70 kg, central volume is 25.4 L/70 kg, and peripheral volume is 19.6 L/70 kg. For both models, we found that allometric weight scaling, postmenstrual age, creatinine clearance, and daily highest temperature had significant effects on clearance. The presence of sepsis or phase of illness did not have a significant effect on clearance or volume of distribution. Monte Carlo simulations demonstrated that to achieve free concentrations above 1 mu g/ml for 100% of the dosing intervals, a dosing regimen of 50 mg/kg every 12 h is recommended for most patients. A continuous infusion could be considered if the target is to maintain free concentrations four times above the MICs (4 mu g/ml)

Comparison of the α and β isomeric forms of the detergent n-dodecyl-D-maltoside for solubilizing photosynthetic complexes from pea thylakoid membranes

AbstractMild non-ionic detergents are indispensable in the isolation of intact integral membrane proteins and protein-complexes from biological membranes. Dodecylmaltoside (DM) belongs to this class of detergents being a glucoside-based surfactant with a bulky hydrophilic head group composed of two sugar rings and a non-charged alkyl glycoside chain. Two isomers of this molecule exist, differing only in the configuration of the alkyl chain around the anomeric center of the carbohydrate head group, axial in α-DM and equatorial in β-DM. In this paper, we have investigated the solubilizing properties of α-DM and β-DM on the isolation of photosynthetic complexes from pea thylakoids membranes maintaining their native architecture of stacked grana and stroma lamellae. Exposure of these stacked thylakoids to a single step treatment with increasing concentrations (5–100mM) of α-DM or β-DM resulted in a quick partial or complete solubilization of the membranes. Regardless of the isomeric form used: 1) at the lowest DM concentrations only a partial solubilization of thylakoids was achieved, giving rise to the release of mainly small protein complexes mixed with membrane fragments enriched in PSI from stroma lamellae; 2) at concentrations above 30mM a complete solubilization occurred with the further release of high molecular weight protein complexes identified as dimeric PSII, PSI-LHCI and PSII–LHCII supercomplexes. However, at concentrations of detergent which fully solubilized the thylakoids, the α and β isomeric forms of DM exerted a somewhat different solubilizing effect on the membranes: higher abundance of larger sized PSII–LHCII supercomplexes retaining a higher proportion of LHCII and lower amounts of PSI–LHCI intermediates were observed in α-DM treated membranes, reflecting the mildness of α-DM compared with its isomer. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial

Notch signaling inhibits hepatocellular carcinoma following inactivation of the RB pathway

Mice lacking all three Rb genes in the liver develop tumors resembling specific subgroups of human hepatocellular carcinomas, and Notch activity appears to suppress the growth and progression of these tumors

Generating a neutralizing antibody against IL13R1? [abstract]

Abstract only availableFaculty Mentor: Habib Zaghouani, Molecular MicrobiologyEach year approximately 1.44 million deaths result from neonatal infection. Initial insights into the differences between the adult and neonatal immune systems were revealed by Sir Peter Medawar during his studies of organ transplantation. He discovered that skin grafts between different strains of mice, which normally result in a rejection of the graft between adult mice, could be successful if the recipient was initially transferred with splenic cells from the donor mouse during its neonatal stage of development. The phenomenon of neonatal tolerance has gone largely unexplained for nearly 50 years. Recent data from our lab supports a theoretical model for neonatal tolerance in which apoptosis of CD4+ T helper type I cells precludes rejection of the transplant. More specifically, we have demonstrated the involvement of the type II IL4 cytokine receptor in initiating this apoptotic signal. The IL13Rα1 cytokine receptor subunit is one component of this heterodimeric receptor, creation of an antibody that functionally inactivates this subunit would therefore provide a useful reagent to carry out more articulate studies of the neonatal immune system. Utilizing a baculovirus vector encoding the extracellular domain of IL13Rα1, we have expressed and purified recombinant IL13Rα1 and have further immunized Armenian hamsters to initiate an antibody response. Soon, we will fuse the B cells derived from these animals with immortalized myeloma cells to generate a permanent cell line expressing an antibody specific for IL13Rα1

The study of neonatal immunity: Creation of an IL13R[alpha]1 deficient mouse [abstract]

Abstract only availableEach year approximately 1.44 million newborns worldwide die from infections during the first four weeks of life. This is due in part to the inability of the developing neonatal immune systems to mount a Th1 immune response, which is responsible for clearing bacterial and viral infections. Previous studies in our laboratory have shown that expression of the IL-13 receptor alpha 1 subunit (IL13R[alpha]1) is upregulated in neonatal Th1 cells, and this overproduction is hypothesized to signal for their death. Currently, a knockout mouse deficient in expression of IL-13R[alpha]1 is not available and the development of an IL-13R[alpha]1 knockout mouse will allow studies to substantiate this hypothesis and possibly provide new insights into the relationship between IL-13R[alpha]1 signaling and neonatal immunity. If we can better understand the mechanisms that involve IL13R[alpha]1 and the development of Th1 immune responses, then this receptor can be targeted in novel vaccine strategies to protect newborns from infection.Life Sciences Undergraduate Research Opportunity Progra

Induction of human neuronal cells by defined transcription factors,”Nature,

Somatic cell nuclear transfer, cell fusion, or expression of lineagespecific factors have been shown to induce cell-fate changes in diverse somatic cell types Here we show that the same three factors can generate functional neurons from human pluripotent stem cells as early as 6 days after transgene activation. When combined with the basic helix-loophelix transcription factor NeuroD1, these factors could also convert fetal and postnatal human fibroblasts into iN cells showing typical neuronal morphologies and expressing multiple neuronal markers, even after downregulation of the exogenous transcription factors. Importantly, the vast majority of human iN cells were able to generate action potentials and many matured to receive synaptic contacts when co-cultured with primary mouse cortical neurons. Our data demonstrate that non-neural human somatic cells, as well as pluripotent stem cells, can be converted directly into neurons by lineage-determining transcription factors. These methods may facilitate robust generation of patient-specific human neurons for in vitro disease modelling or future applications in regenerative medicine. Encouraged by our recent findings in mouse cells 1

Pharmacokinetic parameters over time during sepsis and the association of target attainment and outcomes in critically ill children and young adults receiving ceftriaxone

Introduction: Early sepsis results in pharmacokinetic (PK) changes due to physiologic alterations. PK changes can lead to suboptimal drug target attainment, risking inadequate coverage from antibiotics like ceftriaxone. Little is known about how ceftriaxone PK and target attainment quantitatively change over time in patients with sepsis or the association between target attainment and outcomes in critically ill children and young adults. Methods: A retrospective analysis of a prospective study was conducted in a single-center pediatric intensive care unit. Septic patients given at least one ceftriaxone dose (commonly as 50 mg/kg every 12 h) and who had blood obtained in both the first 48 h of therapy (early) and afterwards (late) were included. Normalized clearance and central volume were estimated and compared in both sepsis phases. We evaluated target attainment, defined as concentrations above 1× or 4× the minimum inhibitory concentration (MIC) for 100% of dosing intervals, and investigated the association between target attainment and clinical outcomes. Results: Fifty-five septic patients (median age: 7.5 years) were included. Normalized clearance and central volume were similar in both phases (6.18 ± 1.48 L/h/70 kg early vs. 6.10 ± 1.61 L/h/70 kg late, p = 0.60; 26.6 [IQR 22.3, 31.3] L/70 kg early vs. 24.5 [IQR 22.0, 29.4] L/70 kg late, p = 0.18). Individual percent differences in normalized clearance and central volume between sepsis phases ranged from −39% to 276% and −51% to 212% (reference, late sepsis), respectively. Fewer patients attained the 1× MIC target in late sepsis (82% late vs. 96% early, p = 0.013), which was associated with transition to once daily dosing, typically done due to transfer from the pediatric intensive care unit (PICU) to a lower acuity unit. Failure to attain either target in late sepsis was associated with antibiotic broadening. Conclusion: Ceftriaxone PK parameters were similar between early and late sepsis, but there were large individual differences. Fewer patients attained MIC targets in late sepsis and all who did not attain the less stringent target received once daily dosing during this period. The failure to attain targets in late sepsis was associated with antibiotic broadening and could be an area for antibiotic stewardship intervention