Efficacy of artemisinin and mefloquine combinations against Plasmodium falciparum. In vitro simulation of in vivo pharmacokinetics

The activity of artemisinin in combination with mefloquine was tested in vitro against a chloroquine‐sensitive (F32) strain of Plasmodium falciparum . A method of repetitive dosing and extending the culture observation period to 28–30 days was used to mimic the in vivo pharmacokinetic situation. Plasmodium falciparum was exposed to artemisinin from 10⁻⁸ to 10⁻⁵  m , mefloquine from 3×10⁻⁹ to 10⁻⁵  m and their combinations. The exposure time for artemisinin was 3 hours twice daily and for mefloquine 24 hours. The drug‐dosing duration was 3 days.
Neither artemisinin nor mefloquine alone provided radical clearance of P. falciparum , even when maximum concentrations (10⁻⁵  m ) were applied. The antiparasitic activity of artemisinin and mefloquine were significantly higher when dosed alone. Effective concentrations for different degrees of inhibition (EC 50, 90 and 99) of both artemisinin and mefloquine respectively were significantly lower when used in combination. At concentrations normally reached in vivo , this effect was clearly synergistic ( P =0.016)
Our in vitro model of intermittent dosing of artemisinin and mefloquine combinations for 3 days provides significant evidence of positive interaction between the two compounds. Lower combination concentrations around the MIC‐values for the individual compounds showed synergistic effect, and high concentrations showed additive effect. This indicates that such drug combinations may provide radical clearance at concentrations lower than those required for single‐drug treatment.     

Surfactant replacement for ventilator-associated pneumonia: a preliminary report

BACKGROUND: Surfactant abnormalities have been described in bacterial pneumonia. OBJECTIVE: To determine the safety and effect of exogenous surfactant replacement in patients with ventilator-associated pneumonia (VAP). METHODS: Patients with VAP were randomized in a double-blind study to receive either an artificial surfactant (Exosurf) consisting mostly of disaturated phospholipids (DSPL) or saline via a continuous nebulizer system for 5 days. Patients underwent bronchoscopy and bronchoalveolar lavage (BAL) prior to and after 4 days of therapy. RESULTS: Twenty-two patients were randomized, with 8 receiving Exosurf. There was no detected difference in outcome between the saline- and Exosurf-treated patients in terms of days on ventilator, 30-day or hospital mortality. At the follow-up lavage, the patients treated with Exosurf had a significant rise in the level of DSPL (p < 0.05), while the saline group did not, suggesting delivery of drug. Also at the follow-up lavage, the percentage of neutrophils in the BAL fell in the Exosurf patients (p < 0.01), but not in the saline group. CONCLUSION: Exogenous surfactant replacement given to patients with VAP increased the amount of DSPL retrieved by BAL. This treatment was associated with a fall in the neutrophil response to pneumonia.     

Review of epidemiological studies on drinking water hardness and cardiovascular diseases.

BACKGROUND: Major risk factors do not entirely explain the worldwide variability of morbidity and mortality due to cardiovascular disease. Environmental exposures, including drinking water minerals may affect cardiovascular disease risks. METHOD: We conducted a qualitative review of the epidemiological studies of cardiovascular disease and drinking water hardness and calcium and magnesium levels. RESULTS: Many but not all ecological studies found an inverse (i.e., protective) association between cardiovascular disease mortality and water hardness, calcium, or magnesium levels; but results are not consistent. Some case-control studies and one cohort study found either a reduced cardiovascular disease mortality risk with increased drinking water magnesium levels or an increased risk with low magnesium levels. However, the analytical studies provide little evidence that cardiovascular risks are associated with drinking water hardness or calcium levels. CONCLUSION: Information from epidemiological and other studies supports the hypothesis that a low intake of magnesium may increase the risk of dying from, and possibly developing, cardiovascular disease or stroke. Thus, not removing magnesium from drinking water, or in certain situations increasing the magnesium intake from water, may be beneficial, especially for populations with an insufficient dietary intake of the mineral.     

Experimental evolution as an efficient tool to dissect adaptive paths to antibiotic resistance

Antibiotic treatments increasingly fail due to rapid dissemination of drug resistance. Comparative genomics of clinical isolates highlights the role of de novo adaptive mutations and horizontal gene transfer (HGT) in the acquisition of resistance. Yet it cannot fully describe the selective pressures and evolutionary trajectories that yielded today's problematic strains. Experimental evolution offers a compelling addition to such studies because the combination of replicated experiments under tightly controlled conditions with genomics of intermediate time points allows real-time reconstruction of evolutionary trajectories. Recent studies thus established causal links between antibiotic deployment therapies and the course and timing of mutations, the cost of resistance and the likelihood of compensating mutations. They particularly underscored the importance of long-term effects. Similar investigations incorporating horizontal gene transfer (HGT) are wanting, likely because of difficulties associated with its integration into experiments. In this review, we describe current advances in experimental evolution of antibiotic resistance and reflect on ways to incorporate horizontal gene transfer into the approach. We contend it provides a powerful tool for systematic and highly controlled dissection of evolutionary paths to antibiotic resistance that needs to be taken into account for the development of sustainable anti-bacterial treatment strategies.     

Formation of biliary thrombi in protoporphyrin-induced cholestasis in perfused rat liver

The effect of bile acids on the formation of biliary thrombi in protoporphyrin-induced cholestasis was determined by perfusing isolated rat livers with taurocholate, chenodeoxycholate and ursodeoxycholate with and without protoporphyrin. Protoporphyrin-induced reduction of bile flow was similar in the presence of each bile acid. The cholestasis was greater at high doses (2,000 to 10,885 nmol) than at low doses (1,500 nmol) of protoporphyrin, unrelated to the amount of lactate dehydrogenase released into the perfusate, and it was not altered by increasing bile acid infusions. Bile acid excretion was inhibited by high protoporphyrin doses. Periportal birefringent pigment deposits were seen in canaliculi and ductules when the biliary protoporphyrin concentration exceeded 161 nmol/ml, 345 nmol/ml and 1,036 nmol/ml for ursodeoxycholate, chenodeoxycholate and taurocholate, respectively; or, when the protoporphyrin (nanomole) to bile acid (micromole) ratio exceeded 3.23, 7.03 and 23.43, respectively. The maximal ratio of ductular deposits to portal tract deposits examined was 0.9. Electron microscopy showed these deposits were associated with canalicular thrombi. Thus, biliary thrombi were produced by infusion of bile acids and protoporphyrin. The occurrence of thrombi varied with bile acid structure. Explanations for this finding are speculative. The presence of periportal thrombi, however, did not influence the degree of functional cholestasis.     

αCaMKII Autophosphorylation Controls the Establishment of Alcohol Drinking Behavior

The α-Ca²⁺/calmodulin-dependent protein kinase II (αCaMKII) is a crucial enzyme controlling plasticity in the brain. The autophosphorylation of αCaMKII works as a ‘molecular memory'' for a transient calcium activation, thereby accelerating learning. We investigated the role of αCaMKII autophosphorylation in the establishment of alcohol drinking as an addiction-related behavior in mice. We found that alcohol drinking was initially diminished in αCaMKII autophosphorylation-deficient αCaMKII^T286A mice, but could be established at wild-type level after repeated withdrawals. The locomotor activating effects of a low-dose alcohol (2 g/kg) were absent in αCaMKII^T286A mice, whereas the sedating effects of high-dose (3.5 g/kg) were preserved after acute and subchronic administration. The in vivo microdialysis revealed that αCaMKII^T286A mice showed no dopamine (DA) response in the nucleus accumbens to acute or subchronic alcohol administration, but enhanced serotonin (5-HT) responses in the prefrontal cortex. The attenuated DA response in αCaMKII^T286A mice was in line with altered c-Fos activation in the ventral tegmental area after acute and subchronic alcohol administration. In order to compare findings in mice with the human condition, we tested 23 single-nucleotide polymorphisms (SNPs) in the CAMK2A gene for their association with alcohol dependence in a population of 1333 male patients with severe alcohol dependence and 939 controls. We found seven significant associations between CAMK2A SNPs and alcohol dependence, one of which in an autophosphorylation-related area of the gene. Together, our data suggest αCaMKII autophosphorylation as a facilitating mechanism in the establishment of alcohol drinking behavior with changing the DA–5-HT balance as a putative mechanism.     

VKORC1-dependent pharmacokinetics of intravenous and oral phylloquinone (vitamin K1) mixed micelles formulation

Objective

The pharmacokinetics of phylloquinone (vitamin K1) were evaluated in healthy human adult volunteers (15 male and 15 female) following oral and intravenous administration of a mixed micelles formulation (Konakion® MM 2 mg) in an open label study design. The subjects were allocated to one of three genotype-specific groups (n?=?10 in each group) in terms of VKORC1 promoter polymorphism c.-1639 G?>?A to explore the relationship between genotype and pharmacokinetic parameters.

Methods

Blood samples were collected for up to 24 h after administration. Phylloquinone serum levels were determined by reversed phase HPLC with fluorometric detection after post-column zinc reduction. Pharmacokinetic evaluation was performed using non-compartmental analysis.

Results

Pharmacokinetic analysis of serum phylloquinone concentration versus time profiles revealed significant differences in the main pharmacokinetic parameters between groups. Upon oral administration, VKORC1 AG carriers showed 41 % higher mean bioavailability (p?=?0.01) compared with homozygous AA individuals. Furthermore, AG subjects exhibited 30 % (p?=?0.042) and 36 % (p?=?0.021) higher mean AUC compared with GG and AA respectively. Terminal half-life was 32 % and 27 % longer for AG carriers in comparison to GG (p?=?0.004) and AA (p?=?0.015) genotypes respectively.

Conclusion

Pharmacokinetic differences indicated significant inter-individual variance of vitamin K fate in the human body. The influence of the VKORC1 promoter polymorphism c.-1639 G?>?A on the pharmacokinetic properties of phylloquinone could be demonstrated in humans. To gain deeper insight in other potential genetic determinants of systemic vitamin K exposure, further correlation of the phenotype–genotype relationship of different players in vitamin K turnover has to be gained.     

Synergism of benflumetol and artemether in Plasmodium falciparum.

Using a continuous in vitro culture system, the sensitivity of Plasmodium falciparum to artemether and a new antimalarial drug, benflumetol (lumefantrine), alone and in combination, was investigated with a multiresistant strain (T-996) from Thailand and a chloroquine-resistant strain (LS-21) from India. Both strains showed similar 50% inhibitory concentration (IC50) levels with artemether alone or benflumetol alone, but the IC90 was higher in strain T-996 compared with strain LS-21: for artemether, 34.45 and 7.11 nmol/L (10.28 and 2.12 ng/ml of erythrocyte-medium mixture [EMM]), and for benflumetol, 293.03 and 95.61 nmol/L (154.69 and 50.47 ng/ml of EMM). When tested in association at artemether:benflumetol (mol: mol) ratios between 100:1 and 1:100, substantial synergism was seen in both strains, especially at the IC90 and IC99 levels. This phenomenon resembles the synergistic interaction of artemisinin derivatives and mefloquine, first observed in laboratory models and later confirmed in clinical experience.     

Acromioclavicular and coracoclavicular PDS augmentation for complete AC joint dislocation showed insufficient properties in a cadaver model

Purpose

Optimal surgical treatment of high-grade acromioclavicular joint dislocations is still controversially discussed. The purpose of the present controlled laboratory study was to evaluate whether a polydioxansulfate (PDS^®) cord augmentation with separate reconstruction of the coracoclavicular (CC) ligaments and the acromioclavicular (AC) complex provides sufficient vertical stability in a biomechanical cadaver model.

Methods

Twenty-four shoulders of fresh-frozen cadaveric specimen were tested. Cyclic loading and load to failure protocol was performed in vertical direction on 12 native AC joints and repeated after reconstruction. The reconstruction of the coracoclavicular ligament was performed using two CC PDS cerclages and an additional AC PDS cerclage.

Results

In static load testing for vertical force, the native AC joint complex measured 590.1 N (±95.8 N), elongation 13.4 mm (±2.1 mm) and stiffness 48.7 N/mm (±12.0 N/mm). The mean maximum load to failure in the reconstructed joints was 569.9 N (±97.9 N), elongation 18.8 mm (±4.7 mm) and stiffness 37.9 N/mm (±8.0 N/mm). During dynamic testing of the reconstructed AC joints, all specimens reached the critical elongation of 12.0 mm, defined as clinical failure between 200 and 300 N. The mean amount of repetitions at clinical failure was 305. A plastic deformation of the reconstructed specimens throughout cyclic loading could not be detected.

Conclusion

The AC joint reconstruction with acromioclavicular and coracoclavicular PDS cord cerclages did not provide the aspired vertical stability in a cadaver model.

Level of evidence

Basic Science Study.     

High‐resolution maps of magnetization transfer with inherent correction for RF inhomogeneity and T1 relaxation obtained from 3D FLASH MRI

An empirical equation for the magnetization transfer (MT) FLASH signal is derived by analogy to dual‐excitation FLASH, introducing a novel semiquantitative parameter for MT, the percentage saturation imposed by one MT pulse during TR. This parameter is obtained by a linear transformation of the inverse signal, using two reference experiments of proton density and T₁ weighting. The influence of sequence parameters on the MT saturation was studied. An 8.5‐min protocol for brain imaging at 3 T was based on nonselective sagittal 3D‐FLASH at 1.25 mm isotropic resolution using partial acquisition techniques (TR/TE/α = 25ms/4.9ms/5° or 11ms/4.9ms/15° for the T₁ reference). A 12.8 ms Gaussian MT pulse was applied 2.2 kHz off‐resonance with 540° flip angle. The MT saturation maps showed an excellent contrast in the brain due to clearly separated distributions for white and gray matter and cerebrospinal fluid. Within the limits of the approximation (excitation <15°, TR/T₁ ? 1) the MT term depends mainly on TR, the energy and offset of the MT pulse, but hardly on excitation and T₁ relaxation. It is inherently compensated for inhomogeneities of receive and transmit RF fields. The MT saturation appeared to be a sensitive parameter to depict MS lesions and alterations of normal‐appearing white matter. Magn Reson Med 60:1396–1407, 2008. © 2008 Wiley‐Liss, Inc.