Greater physical fitness ( VO 2 max ) in healthy older adults associated with increased integrity of the locus coeruleus-noradrenergic system.

AIM: Physical activity (PA) is a key component for brain health and Reserve, and it is among the main dementia protective factors. However, the neurobiological mechanisms underpinning Reserve are not fully understood. In this regard, a noradrenergic (NA) theory of cognitive reserve (Robertson, 2013) has proposed that the upregulation of NA system might be a key factor for building reserve and resilience to neurodegeneration because of the neuroprotective role of NA across the brain. PA elicits an enhanced catecholamine response, in particular for NA. By increasing physical commitment, a greater amount of NA is synthetised in response to higher oxygen demand. More physically trained individuals show greater capabilities to carry oxygen resulting in greater Vo 2 max - a measure of oxygen uptake and physical fitness (PF). METHODS: We hypothesized that greater Vo 2 max would be related to greater Locus Coeruleus (LC) MRI signal intensity. In a sample of 41 healthy subjects, we performed Voxel-Based Morphometry analyses, then repeated for the other neuromodulators as a control procedure (Serotonin, Dopamine and Acetylcholine). RESULTS: As hypothesized, greater Vo 2 max related to greater LC signal intensity, and weaker associations emerged for the other neuromodulators. CONCLUSION: This newly established link between Vo 2 max and LC-NA system offers further understanding of the neurobiology underpinning Reserve in relationship to PA. While this study supports Robertson's theory proposing the upregulation of the NA system as a possible key factor building Reserve, it also provides ground for increasing LC-NA system resilience to neurodegeneration via Vo 2 max enhancement.

Early Superimposed NMES Training is Effective to Improve Strength and Function Following ACL Reconstruction with Hamstring Graft regardless of Tendon Regeneration.

The study aimed at investigating the effects of neuromuscular electrical stimulation superimposed on functional exercises (NMES+) early after anterior cruciate ligament reconstruction (ACLr) with hamstring graft, on muscle strength, knee function, and morphology of thigh muscles and harvested tendons. Thirty-four participants were randomly allocated to either NMES+ group, who received standard rehabilitation with additional NMES of knee flexor and extensor muscles, superimposed on functional movements, or to a control group, who received no additional training (NAT) to traditional rehabilitation. Participants were assessed 15 (T1), 30 (T2), 60 (T3), 90 (T4) and at a mean of 380 days (T5) after ACLr. Knee strength of flexors and extensors was measured at T3, T4 and T5. Lower limb loading asymmetry was measured during a sit-to-stand-to-sit movement at T1, T2, T3, T4 and T5, and a countermovement-jump at T4 and T5. An MRI was performed at T5 to assess morphology of thigh muscles and regeneration of the harvested tendons. NMES+ showed higher muscle strength for the hamstrings (T4, T5) and the quadriceps (T3, T4, T5), higher loading symmetry during stand-to-sit (T2, T3, T4, T5), sit-to-stand (T3, T4) and countermovement-jump (T5) than NAT. No differences were found between-groups for morphology of muscles and tendons, nor in regeneration of harvested tendons. NMES+ early after ACLr with hamstring graft improves muscle strength and knee function in the short- and long-term after surgery, regardless of tendon regeneration.

A Bridge between the Breath and the Brain: Synchronization of Respiration, a Pupillometric Marker of the Locus Coeruleus, and an EEG Marker of Attentional Control State.

Yogic and meditative traditions have long held that the fluctuations of the breath and the mind are intimately related. While respiratory modulation of cortical activity and attentional switching are established, the extent to which electrophysiological markers of attention exhibit synchronization with respiration is unknown. To this end, we examined (1) frontal midline theta-beta ratio (TBR), an indicator of attentional control state known to correlate with mind wandering episodes and functional connectivity of the executive control network; (2) pupil diameter (PD), a known proxy measure of locus coeruleus (LC) noradrenergic activity; and (3) respiration for evidence of phase synchronization and information transfer (multivariate Granger causality) during quiet restful breathing. Our results indicate that both TBR and PD are simultaneously synchronized with the breath, suggesting an underlying oscillation of an attentionally relevant electrophysiological index that is phase-locked to the respiratory cycle which could have the potential to bias the attentional system into switching states. We highlight the LC's pivotal role as a coupling mechanism between respiration and TBR, and elaborate on its dual functions as both a chemosensitive respiratory nucleus and a pacemaker of the attentional system. We further suggest that an appreciation of the dynamics of this weakly coupled oscillatory system could help deepen our understanding of the traditional claim of a relationship between breathing and attention.

Examining the Role of the Noradrenergic Locus Coeruleus for Predicting Attention and Brain Maintenance in Healthy Old Age and Disease: An MRI Structural Study for the Alzheimer's Disease Neuroimaging Initiative.

The noradrenergic theory of Cognitive Reserve (Robertson, 2013-2014) postulates that the upregulation of the locus coeruleus-noradrenergic system (LC-NA) originating in the brainstem might facilitate cortical networks involved in attention, and protracted activation of this system throughout the lifespan may enhance cognitive stimulation contributing to reserve. To test the above-mentioned theory, a study was conducted on a sample of 686 participants (395 controls, 156 mild cognitive impairment, 135 Alzheimer's disease) investigating the relationship between LC volume, attentional performance and a biological index of brain maintenance (BrainPAD-an objective measure, which compares an individual's structural brain health, reflected by their voxel-wise grey matter density, to the state typically expected at that individual's age). Further analyses were carried out on reserve indices including education and occupational attainment. Volumetric variation across groups was also explored along with gender differences. Control analyses on the serotoninergic (5-HT), dopaminergic (DA) and cholinergic (Ach) systems were contrasted with the noradrenergic (NA) hypothesis. The antithetic relationships were also tested across the neuromodulatory subcortical systems. Results supported by Bayesian modelling showed that LC volume disproportionately predicted higher attentional performance as well as biological brain maintenance across the three groups. These findings lend support to the role of the noradrenergic system as a key mediator underpinning the neuropsychology of reserve, and they suggest that early prevention strategies focused on the noradrenergic system (e.g., cognitive-attentive training, physical exercise, pharmacological and dietary interventions) may yield important clinical benefits to mitigate cognitive impairment with age and disease.

Sex differences in clinical phenotype and transitions of care among individuals dying of COVID-19 in Italy.

BACKGROUND: Among the unknowns posed by the coronavirus disease 2019 (COVID-19) outbreak, the role of biological sex to explain disease susceptibility and progression is still a matter of debate, with limited sex-disaggregated data available. METHODS: A retrospective analysis was performed to assess if sex differences exist in the clinical manifestations and transitions of care among hospitalized individuals dying with laboratory-confirmed SARS-CoV-2 infection in Italy (February 27-June 11, 2020). Clinical characteristics and the times from symptoms' onset to admission, nasopharyngeal swab, and death were compared between sexes. Adjusted multivariate analysis was performed to identify the clinical features associated with male sex. RESULTS: Of the 32,938 COVID-19-related deaths that occurred in Italy, 3517 hospitalized and deceased individuals with COVID-19 (mean 78 ± 12 years, 33% women) were analyzed. At admission, men had a higher prevalence of ischemic heart disease (adj-OR = 1.76, 95% CI 1.39-2.23), chronic obstructive pulmonary disease (adj-OR = 1.7, 95% CI 1.29-2.27), and chronic kidney disease (adj-OR = 1.48, 95% CI 1.13-1.96), while women were older and more likely to have dementia (adj-OR = 0.73, 95% CI 0.55-0.95) and autoimmune diseases (adj-OR = 0.40, 95% CI 0.25-0.63), yet both sexes had a high level of multimorbidity. The times from symptoms' onset to admission and nasopharyngeal swab were slightly longer in men despite a typical acute respiratory illness with more frequent fever at the onset. Men received more often experimental therapy (adj-OR = 2.89, 95% CI 1.45-5.74) and experienced more likely acute kidney injury (adj-OR = 1.47, 95% CI 1.13-1.90). CONCLUSIONS: Men and women dying with COVID-19 had different clinical manifestations and transitions of care. Identifying sex-specific features in individuals with COVID-19 and fatal outcome might inform preventive strategies.

Deprescribing in Nursing Home Residents on Polypharmacy: Incidence and Associated Factors.

OBJECTIVES: To assess 1-year incidence and factors related to deprescribing in nursing home (NH) residents in Europe. DESIGN: Longitudinal multicenter cohort study based on data from the Services and Health for Elderly in Long TERm care (SHELTER) study. SETTING: NHs in Europe and Israel. PARTICIPANTS: 1843 NH residents on polypharmacy. METHODS: Polypharmacy was defined as the concurrent use of 5 or more medications. Deprescribing was defined as a reduction in the number of medications used over the study period. Residents were followed for 12 months. RESULTS: Residents in the study sample were using a mean number of 8.6 (standard deviation 2.9) medications at the baseline assessment. Deprescribing was observed in 658 residents (35.7%). Cognitive impairment (mild/moderate impairment vs intact, odds ratio [OR] 1.41, 95% confidence interval [CI] 1.11-1.79; severe impairment vs intact, OR 1.60, 95% CI 1.23-2.09), presence of the geriatrician within the facility staff (OR 1.41, 95% CI 1.15-1.72), and number of medications used at baseline (OR 1.10, 95% CI 1.06-1.14) were associated with higher probabilities of deprescribing. In contrast, female gender (OR 0.76, 95% CI 0.61-0.96), heart failure (OR 0.69, 95% CI 0.53-0.89), and cancer (OR 0.64, 95% CI 0.45-0.90) were associated with a lower probability of deprescribing. CONCLUSIONS AND IMPLICATIONS: Deprescribing is common in NH residents on polypharmacy, and it is associated with individual and organizational factors. More evidence is needed on deprescribing, and clear strategies on how to withdraw medications should be defined in the future.

Association of polypharmacy and hyperpolypharmacy with frailty states: a systematic review and meta-analysis.

PURPOSE: To investigate: (1) the cross-sectional association between polypharmacy, hyperpolypharmacy and presence of prefrailty or frailty; (2) the risk of incident prefrailty or frailty in persons with polypharmacy, and vice versa. METHODS: A systematic review and meta-analysis was performed according to PRISMA guidelines. We searched PubMed, Web of Science, and Embase from 01/01/1998 to 5/2/2018. Pooled estimates were obtained through random effect models and Mantel-Haenszel weighting. Homogeneity was assessed with the I2 statistic and publication bias with Egger's and Begg's tests. RESULTS: Thirty-seven studies were included. The pooled proportion of polypharmacy in persons with prefrailty and frailty was 47% (95% CI 33-61) and 59% (95% CI 42-76), respectively. Increased odds ratio of polypharmacy were seen for prefrail (pooled OR = 1.52; 95% CI 1.32-1.79) and frail persons (pooled OR = 2.62, 95% CI 1.81-3.79). Hyperpolypharmacy was also increased in prefrail (OR = 1.95; 95% CI 1.41-2.70) and frail (OR = 6.57; 95% CI 9.57-10.48) persons compared to robust persons. Only seven longitudinal studies reported data on the risk of either incident prefrailty or frailty in persons with baseline polypharmacy. A significant higher odds of developing prefrailty was found in robust persons with polypharmacy (pooled OR = 1.30; 95% CI 1.12-1.51). We found no papers investigating polypharmacy incidence in persons with prefrailty/frailty. CONCLUSIONS: Polypharmacy is common in prefrail and frail persons, and these individuals are also more likely to be on extreme drug regimens, i.e. hyperpolypharmacy, than robust older persons. More research is needed to investigate the causal relationship between polypharmacy and frailty syndromes, thereby identifying ways to jointly reduce drug burden and prefrailty/frailty in these individuals. PROSPERO REGISTRATION NUMBER: CRD42018104756.

Frailty and atrial fibrillation: A systematic review.

Atrial fibrillation (AF) is a common cardiac arrhythmia and its prevalence increases with age. There is a significant correlation between frailty, morbidity and mortality in elderly patients with cardiovascular disease, but the relation between AF and frailty is still under debate. The aim of this study is to systematically review evidence on the association between AF and frailty. A systematic review of articles published between 02/01/2002 and 09/28/2017 according to PRISMA recommendations was carried out. PubMed, Web of Science, and Embase were searched for relevant articles. 11 studies were included; one longitudinal, 10 cross-sectional. Only 4 studies assessed the association of frailty with AF, while 7 studies were performed in a sample of participants with AF and did not provide any measure of association between these two conditions. The prevalence of frailty in AF patients ranged from 4.4%-75.4% while AF prevalence in the frail population ranged from 48.2%-75.4%. Selected studies enrolled an overall sample of 9420 participants. Among them, 2803 participants were diagnosed with AF and of these 1517 (54%) were frail and 1286 (46%) were pre-frail or robust. The four studies assessing the association of AF and frailty provided conflicting results. Evidence suggests that frailty is common in persons with AF. More research is needed to better assess the association of these conditions and to identify the optimal therapeutic approach to AF in persons with frailty.

A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties: The NNPDF Collaboration.

We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a fitting framework designed to provide a statistically sound representation of FF uncertainties and to minimise any procedural bias. We discuss novel aspects of the methodology used in this analysis, namely an optimised parametrisation of FFs and a more efficient [Formula: see text] minimisation strategy, and validate the FF fitting procedure by means of closure tests. We then present the NNFF1.0 sets, and discuss their fit quality, their perturbative convergence, and their stability upon variations of the kinematic cuts and the fitted dataset. We find that the systematic inclusion of higher-order QCD corrections significantly improves the description of the data, especially in the small-z region. We compare the NNFF1.0 sets to other recent sets of FFs, finding in general a reasonable agreement, but also important differences. Together with existing sets of unpolarised and polarised parton distribution functions (PDFs), FFs and PDFs are now available from a common fitting framework for the first time.

The purified vepoloxamer prevents haemolysis in 42-day stored, DEHP/PVC-free red blood cell units.

BACKGROUND: Use of the plasticiser di(2-ethylhexyl) phthalate (DEHP) in polyvinyl chloride (PVC) blood bags poses a potential dilemma. The presence of DEHP in blood bags has been shown to be beneficial to red blood cells during storage by diminishing haemolysis. However, DEHP use in PVC may be carcinogenic or estrogenising. Vepoloxamer is a poloxamer with rheological and cytoprotective rheological properties and a favourable toxicity profile in clinical trials. We hypothesised that vepoloxamer may be sufficient to replace the plasticiser DEHP to prevent elevated haemolysis while conserving the biochemical and redox potential++ in RBCs stored for up to 42 days. MATERIALS AND METHODS: Paired analyses of aliquots from pooled RBC suspensions of ABO identical donors were aseptically split into test storage containers (DEHP/PVC or DEHP-free/ethylene vinyl acetate [EVA]) supplemented with or without vepoloxamer (at concentrations of 0.1, 1, 5 or 7.89 mg/mL) and cold stored for up to 42 days. RESULTS: Vepoloxamer significantly prevented the increased haemolysis induced by the absence of DEHP in EVA bags in a dose-dependent manner by days 28 and 42 of storage (approx. 50% reduction of the maximum concentration of vepoloxamer; p<0.001). There was an inverse correlation between the concentration of vepoloxamer used and the haemolysis rate (r2=0.27, p<0.001) and a direct correlation between haemolysis and phosphatidylserine (PS) exposure (r2=0.42; p<0.01). Increased osmotic fragility and shear induced deformability of 42-day stored RBC in EVA bags was significantly corrected by the addition of vepoloxamer. DISCUSSION: Vepoloxamer, in a concentration-dependent fashion, is able to partly rescue the increased haemolysis and PS exposure induced by the absence of the commonly used plasticiser DEHP. These results provide initial but strong evidence to support vepoloxamer use to replace DEHP in long-term storage of RBC.

Parton distributions from high-precision collider data: NNPDF Collaboration.

We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and involves both. On the methodological side, we now parametrize and determine the charm PDF alongside the light-quark and gluon ones, thereby increasing from seven to eight the number of independent PDFs. On the data side, we now include the D0 electron and muon W asymmetries from the final Tevatron dataset, the complete LHCb measurements of W and Z production in the forward region at 7 and 8 TeV, and new ATLAS and CMS measurements of inclusive jet and electroweak boson production. We also include for the first time top-quark pair differential distributions and the transverse momentum of the Z bosons from ATLAS and CMS. We investigate the impact of parametrizing charm and provide evidence that the accuracy and stability of the PDFs are thereby improved. We study the impact of the new data by producing a variety of determinations based on reduced datasets. We find that both improvements have a significant impact on the PDFs, with some substantial reductions in uncertainties, but with the new PDFs generally in agreement with the previous set at the one-sigma level. The most significant changes are seen in the light-quark flavor separation, and in increased precision in the determination of the gluon. We explore the implications of NNPDF3.1 for LHC phenomenology at Run II, compare with recent LHC measurements at 13 TeV, provide updated predictions for Higgs production cross-sections and discuss the strangeness and charm content of the proton in light of our improved dataset and methodology. The NNPDF3.1 PDFs are delivered for the first time both as Hessian sets, and as optimized Monte Carlo sets with a compressed number of replicas.

The asymptotic behaviour of parton distributions at small and large x.

It has been argued from the earliest days of quantum chromodynamics that at asymptotically small values of x the parton distribution functions (PDFs) of the proton behave as [Formula: see text], where the values of [Formula: see text] can be deduced from Regge theory, while at asymptotically large values of x the PDFs behave as [Formula: see text], where the values of [Formula: see text] can be deduced from the Brodsky-Farrar quark counting rules. We critically examine these claims by extracting the exponents [Formula: see text] and [Formula: see text] from various global fits of parton distributions, analysing their scale dependence, and comparing their values to the naive expectations. We find that for valence distributions both Regge theory and counting rules are confirmed, at least within uncertainties, while for sea quarks and gluons the results are less conclusive. We also compare results from various PDF fits for the structure function ratio [Formula: see text] at large x, and caution against unrealistic uncertainty estimates due to overconstrained parametrisations.

Distribution, metabolism, and excretion of a novel surface-active agent, purified poloxamer 188, in rats, dogs, and humans.

Purified poloxamer 188 (PP188) is a nonionic, block copolymer surfactant with hemorheologic, antithrombotic, and anti-adhesive properties. PP188 is being studied in phase III clinical trials in sickle cell disease and has been found to be well tolerated and has demonstrated benefit in ameliorating the effects of acute painful vasoocclusive crisis. The disposition of PP188 was studied in rats, dogs, and humans to establish a basis for understanding the safety parameters in support of clinical trials. PP188 was primarily distributed in extracellular water with little or no uptake by red blood cells, and had its highest concentrations in highly perfused tissues such as the kidney, liver, spleen, lymph nodes, and gastrointestinal tract. PP188 had no apparent effect on P450 isozymes in vitro. Metabolism was limited (< 5% of dose) with a higher molecular weight copolymer being the only other material detected in plasma or urine. Renal clearance was the controlling route of clearance for PP188 from the body. The 48-h intravenous infusion doses of PP188 were cleared in all species by approximately 1 week after the cessation of dose administration. PP188's disposition is a model for other nonionic block copolymers with similar physical and chemical properties.

Pharmacokinetics of a novel surface-active agent, purified poloxamer 188, in rat, rabbit, dog and man.

Purified poloxamer 188 (PP188) is a non-ionic, block copolymer surfactant that is currently being evaluated clinically in sickle cell disease vaso-occlusive crisis and acute chest syndrome and preclinically in spinal cord injury and muscular dystrophy. This paper describes the pharmacokinetics of PP188 in rats, pregnant rats, pregnant rabbits, dogs and humans. Plasma protein binding interaction studies demonstrated no clinically significant effects on narcotic analgesics, hydroxyurea, warfarin, diazepam or digitoxin, but an increase in free fraction for propranolol. The plasma concentrations increased proportionate with increasing dose in all species tested. Renal clearance accounted for 90% of total plasma clearance in man. A single metabolite was detected and quantified in the plasma from dogs and humans that was cleared more slowly than parent drug. Allometric scaling of plasma clearance and volume of distribution at steady-state (Vss) across species provided good predictions of the pharmacokinetic parameters in humans. Based on the comparative pharmacokinetics of PP188 in rat, rabbit, dog and man, all three animal species were appropriate models for evaluating various aspects of PP188's toxicological profile.

FLOCOR: a new anti-adhesive, rheologic agent.

FLOCOR (purified poloxamer 188) is a surfactant molecule that represents a new class of pharmacological agent. FLOCOR is different in that its activity does not depend on high affinity receptor binding but rather on altering the way cells and molecules interact with water. Extensive preclinical studies in models of vascular occlusive disorders, including circulatory shock, acute stroke, and myocardial infarction (MI), suggest that iv. administration of poloxamer 188 improves microvascular blood flow in ischaemic tissues by inhibiting adhesive interactions, lowering blood viscosity and reducing friction along the vessel wall. In clinical studies, poloxamer 188 demonstrated statistically significant benefits in patients with acute myocardial infarction (AMI) and acute vaso-occlusive crisis of sickle cell disease. However, these studies were conducted with commercial grades of poloxamer 188 that contained nephrotoxic impurities, and elevated creatinine was observed in a small percentage of patients. A new highly purified version of poloxamer 188 free from impurities has been developed. Highly purified poloxamer 188 (trade name FLOCOR) is better tolerated in models of renal failure and is anticipated to have a significantly improved therapeutic index compared to commercial grade poloxamer 188. Clinical studies are now in progress in order to confirm the therapeutic benefits of FLOCOR (purified poloxamer 188).

Inhibition of cytarabine-induced MDR1 (P-glycoprotein) gene activation in human tumor cells by fatty acid-polyethylene glycol-fatty acid diesters, novel inhibitors of P-glycoprotein function.

Fatty acid ester surfactants Cremophor EL and Solutol HS 15 were described earlier as modulators of multidrug resistance mediated by MDR1 P-glycoprotein (Pgp). We have shown that the most active components of these polydisperse surfactants are fatty acid-polyethylene glycol-fatty acid diesters (FA-PEG-FA). A new generation of Pgp-surfactant inhibitors of defined structure was therefore synthesized. In the present study we show that these compounds are also able to inhibit up-regulation of MDR1 gene expression caused by cytarabine (ARA-C) and doxorubicin in human tumor cell lines H9 and KB 3-1, which express minimal levels of MDR1 mRNA. The surfactant inhibitors, however, had no effect on the induction of MDR1 gene expression by protein kinase C agonists. Using a set of FA-PEG-FA diesters with various fatty acids and different lengths of the PEG domain, we demonstrated that the activity of diester preparations as inhibitors of drug-induced MDR1 activation was in proportion to their activity as inhibitors of Pgp function. Oleic and stearic acid diesters with PEG 900 (20 ethylene oxide units) were the most potent. The poloxamer analogs of these diesters demonstrated similar effects. In contrast, the well-known, structurally unrelated inhibitors of Pgp activity, verapamil, cyclosporin A and PSC 833, had no inhibitory effect on drug-induced MDR1 activation. The ability of FA-PEG-FA diesters to inhibit both Pgp function and drug-induced MDR1 activation suggests that these chemomodulators may be uniquely useful for the prophylaxis of Pgp-mediated multidrug resistance in drug-treated tumors.

Reversal of multi-drug resistance in vitro by fatty acid-PEG-fatty acid diesters.

Fatty acid ester surfactants, e.g., Cremophor EL and Solutol HS 15, that modulate multi-drug resistance (MDR) have been described; however, the drug potential of these preparations is unclear because of the molecular heterogeneity of these and other commercial surfactants. In previous experiments, an active but still polydisperse preparation, designated CRL 1337, was synthesized by reacting purified oleic acid with a 20-fold molar excess of ethylene oxide. We have subjected this preparation to chromatographic separation, and infrared analysis of the active fractions revealed a significant component of diester structures (fatty acid-PEG-fatty acid). A new generation of diester compounds has now been synthesized. Preparations comprised of 99% diesters were significantly more potent than monoester preparations for MDR modification activity in vitro. As previously determined for ethylene oxide-derived preparations similar to CRL 1337, the nature of the fatty acid domains proved to be important for activity, as was the relative length of the polyethylene glycol domain (which determines the hydrophile-lipophile balance). The ester linkage appeared unimportant since homologous diethers and diamides had activity similar to that of diesters. Stearic acid diester was 1.5- to 7-fold more potent than CRL 1337 when tested in cell proliferation inhibition assays. In light of these structural restrictions on drug potentiation, and since these surfactants are active at relatively low concentrations (below 1 microgram/ml), investigations of their mechanism of action were initiated by exploring specific interactions with P-glycoprotein. Both active and inactive diesters inhibited azidopine labeling of P-glycoprotein, suggesting that fatty acid-PEG diesters can interfere with P-glycoprotein substrate binding. Other attributes of these preparations must contribute to their ability to reverse MDR.

Comparison of solutol HS 15, Cremophor EL and novel ethoxylated fatty acid surfactants as multidrug resistance modification agents.

Some well-known fatty acid ester surfactants, e.g., Cremophor EL and Solutol HS 15, are modulators of multidrug resistance in vitro and in vivo. Because they are polydisperse, and their active component(s) have not been identified, the therapeutic potential of such surfactants is unclear. To better define the active components of Solutol HS 15 and to make more potent surfactant multidrug resistance modulators, highly purified C-18 fatty acids were esterified with ethylene oxide at 5-200 molar ratios. Unexpectedly, ethylene oxide esters of pure 12-hydroxy stearic acid, the major components of Solutol HS 15, displayed negligible resistance modification activity compared with Solutol HS 15 itself or to stearic and oleic acid esters synthesized under identical conditions. Since oleic acid esters appeared to have good activity, a series of these compounds was prepared to determine the optimal ethylene oxide/fatty acid ratio. The optimal ratio was found to be 20 mole ethylene oxide: I mole fatty acid, with a steep decline in activity for products made with ratios above and below the optimum. The most active oleic acid ester, designated CRL 1337, was 8.4-fold as potent as Solutol HS 15 and over 19-fold as potent as Cremophor EL in promoting rhodamine 123 accumulation in multidrug-resistant KB 8-5-11 cells in vitro. Our results show that the structure of the hydrophobic domain (fatty acid) of surfactants as well as its hydrophile-lipophile balance are critical in determining the potency of surfactants as reversing agents.

Pharmacokinetics of heparins differing in mean molecular weight using a Xa amidolytic and Heptest clotting method.

The pharmacokinetics of heparins ranging in mean MW from 23,000 to 4,500 were determined using a new clotting test (Heptest) and an anti-Xa, amidolytic method. No significant difference between the two methods was observed in the calculated values for distribution volume (Vd), halflife (t1/2), plasma clearance (Clp) or area under the concentration-time curve (AUC) for heparins of any MW. However, when pharmacokinetic parameters calculated from both methods were compared as a function of MW, significant differences were observed. Values for t1/2 averaged from the two methods increased with decreasing MW. The t1/2 values were 30, 35, and 50 min for the 23,000, 13,300, and 5,100 MW fractions, respectively. Similarly, AUC increased with decreasing MW while Clp decreased. All heparins were observed to have VdS approximating the plasma compartment. A slightly larger Vd was observed with the lowest MW heparin.