Understanding the origins of metal-organic framework/polymer compatibility.

The microscopic interfacial structures for a series of metal-organic framework/polymer composites consisting of the Zr-based UiO-66 coupled with different polymers are systematically explored by applying a computational methodology that integrates density functional theory calculations and force field-based molecular dynamics simulations. These predictions are correlated with experimental findings to unravel the structure-compatibility relationship of the MOF/polymer pairs. The relative contributions of the intermolecular MOF/polymer interactions and the flexibility/rigidity of the polymer with respect to the microscopic structure of the interface are rationalized, and their impact on the compatibility of the two components in the resulting composite is discussed. The most compatible pairs among those investigated involve more flexible polymers, i.e. polyvinylidene fluoride (PVDF) and polyethylene glycol (PEG). These polymers exhibit an enhanced contact surface, due to a better adaptation of their configuration to the MOF surface. In these cases, the irregularities at the MOF surface are filled by the polymer, and even some penetration of the terminal groups of the polymer into the pores of the MOF can be observed. As a result, the affinity between the MOF and the polymer is very high; however, the pores of the MOF may be sterically blocked due to the strong MOF/polymer interactions, as evidenced by UiO-66/PEG composites. In contrast, composites involving polymers that exhibit higher rigidity, such as the polymer of intrinsic microporosity-1 (PIM-1) or polystyrene (PS), present interfacial microvoids that contribute to a decrease in the contact surface between the two components, thus reducing the MOF/polymer affinity.

Identification of stable reference genes for quantitative PCR in koalas.

To better understand host and immune response to diseases, gene expression studies require identification of reference genes with stable expression for accurate normalisation. This study describes the identification and testing of reference genes with stable expression profiles in koala lymph node tissues across two genetically distinct koala populations. From the 25 most stable genes identified in transcriptome analysis, 11 genes were selected for verification using reverse transcription quantitative PCR, in addition to the commonly used ACTB and GAPDH genes. The expression data were analysed using stable genes statistical software - geNorm, BestKeeper, NormFinder, the comparative ΔCt method and RefFinder. All 13 genes showed relative stability in expression in koala lymph node tissues, however Tmem97 and Hmg20a were identified as the most stable genes across the two koala populations.

HFE genotype modifies the influence of heme iron intake on iron status.

BACKGROUND: Public health policy to prevent iron deficiency through food fortification or other measures may be disadvantageous to people with hereditary hemochromatosis. METHODS: From a cohort of U.K. women, 2531 women were typed for C282Y and H63D mutations in the hemochromatosis gene. These women completed food frequency questionnaires and provided blood for iron status. RESULTS: C282Y homozygotes (n=31) had serum ferritin concentrations 2.4 times higher (95% confidence interval=1.9-3.1) than wild types (n=1774), but heterozygotes (n=726) were not different from wild types. H63D genotype had no effect on its own. The effect of heme iron intake (from meat, fish, and poultry) was 2.0 times greater (1.2-3.2) on C282Y homozygotes than other groups. Nonheme iron had little effect. CONCLUSIONS: There may be scope for dietary intervention in women homozygous for the C282Y mutation. C282Y heterozygotes and H63D homozygotes and heterozygotes have similar serum ferritin concentrations to wild type and need not reduce their meat intake other than as part of a normal healthy diet.

Antiepileptic drug treatment of nonconvulsive seizures induced by experimental focal brain ischemia.

Nonconvulsive seizures (NCSs) after traumatic and ischemic brain injury are often refractory to antiepileptic drug therapy and are associated with a decline in patient outcome. We recently characterized an in vivo rat model of focal brain ischemia-induced NCS and here sought to evaluate potential pharmacological treatments. Electroencephalographic activity was recorded continuously for 24 h in freely behaving rats subjected to permanent middle cerebral artery occlusion (MCAo). Rats were treated with an antiepileptic drug from one of seven different drug classes at ED(50) and 2x ED(50) doses (as reported in other rat seizure models), delivered as a single i.v. injection 20 min post-MCAo. Vehicle-treated rats (n = 9) had an 89% incidence of NCS with an average number of NCS of 8.6 +/- 1.9. The latency to onset of NCS was 32.5 +/- 3.4 min post-MCAo with an average duration of 49.1 +/- 8.2 s/event. The high doses of ethosuximide, gabapentin, fos-phenytoin, and valproate significantly reduced the incidence of NCS (11, 14, 14, and 38%, respectively), whereas midazolam, phenobarbital, and dextromethorphan had no significant effect at either dose. Across treatment groups, there was a low but significant correlation between the number of NCS events per animal and volume of brain infarction (r = 0.352). Antiepileptic drug therapy that prevented the occurrence of NCS also reduced mortality from 26 to 7%. Based on combined effects on NCS, infarction, neurological recovery, and mortality, ethosuximide and gabapentin were identified as having the best therapeutic profile.

Evaluating a possible pharmacokinetic interaction between remifentanil and esmolol in the rat.

Remifentanil (Ultiva) is a novel, ultra-short-acting opioid which has recently been approved for use as an analgesic during induction and maintenance of general anesthesia. Esmolol is a short-acting beta-blocker used during surgical procedures to reduce heart rate and blood pressure. Both drugs are metabolized by nonspecific esterases in the blood and other tissues and may be administered concomitantly during surgery. The goal of this study was to determine if coadministration of esmolol significantly alters the pharmacokinetics of remifentanil in the rat. Two groups of rats were dosed with remifentanil [25 micrograms/kg/min (n = 8)] and remifentanil plus esmolol [25 and 200 mg/kg/min (n = 7)] for 20 min. Cardiovascular measurements were collected continuously over the course of the study. Serial blood samples (12) were collected over 25 min into test tubes containing 0.5 mL of acetonitrile. Blood samples were extracted (liquid-liquid) with methylene chloride and then analyzed by a validated GC-MS assay. Compartmental data analysis was performed using PCNONLIN. The mean(+/- SD) for Cl and t1/2 observed in treatment I were 390(+/- 98) mL/min/kg and 0.69(+/- 0.27) min and in treatment II were 421(+/- 164) mL/min/kg and 0.56(+/- 0.22) min, respectively. Comparison of clearance, volume of distribution, and terminal half-life between the two groups showed that coadministration of esmolol had no significant (p < 0.05) effect on the pharmacokinetics of remifentanil in the rat.

EEG spectral analysis of the neuroprotective kappa opioids enadoline and PD117302.

The present study characterized the electroencephalographic (EEG) effects of the neuroprotective kappa opioids enadoline and PD117302 in conscious, freely moving rats with the use of computer-assisted spectral analysis (CASA). Enadoline (25-100 microg/kg) or PD117302 (1.25-5.0 mg/kg) was administered intravenously to rats implanted with cortical EEG electrodes. Although both drugs produced an immediate, mild sedation, there were no signs of head-weaving or ataxia, and there was little visual evidence of opioid-like EEG slow-wave bursts or seizures. Both drugs produced only modest increases in total EEG power that were not dose dependent. In contrast, CASA revealed significant dose-dependent frequency shifts in relative power distributions, thereby identifying distinct kappa opioid alterations in awake EEG activity; EEG power decreased in the 0- to 4-Hz frequency band with concomitant increases in power measured in the 4- to 8-Hz frequency range. The kappa opioids produced a dose-dependent consolidation of the EEG waveform centered about a peak frequency of 5.0 Hz (for enadoline) or 4.8 Hz (for PD117302) and a significant shift in the mean EEG frequency from 6.6 Hz (predrug) to 6.2 Hz (postdrug). Further CASA revealed significant postdrug decreases in the edge frequency, mobility and complexity of the EEG. Both drugs produced moderate increases in the latency to slow-wave sleep (SWS). Overall, enadoline (ED50 = 18 microg/kg) was approximately 94 times more potent than PD117302 (ED50 = 1690 microg/kg) in producing the kappa EEG profile. Because the kappa-induced EEG changes were stereospecific for the (-)-enantiomers and inhibited by norbinaltorphimine (nor-BNI), the EEG "fingerprint" described in this study could be attributed to specific activation of brain kappa opioid receptors.

Neuroprotective sigma ligands attenuate NMDA and trans-ACPD-induced calcium signaling in rat primary neurons.

The effect of neuroprotective sigma ligands possessing a range of relative selectivity for sigma and phencyclidine (PCP) binding sites on N-methyl-D-aspartate (NMDA) and (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD)-stimulated calcium flux was studied in 12-15-day-old primary cultures of rat cortical neurons. In approximately 80% of the neurons tested, NMDA (80 microM) caused a sustained increase in intracellular calcium ([Ca2+]i). With the exception of R-(+)-3-(3-hydroxyphenyl)-N-propylpiperidine hydrochloride ((+)-3-PPP) (previously shown not to be neuroprotective) all of the sigma ligands studied significantly altered NMDA-induced calcium dynamics. The primary effect of dextromethorphan, (+)-pentazocine, (+)-cyclazocine, (+)-SKF10047, carbetapentane, 1,3-di(2-tolyl) guanidine (DTG), and haloperidol was to shift the NMDA response from a sustained, to either a biphasic or a transient, calcium event. In contrast to NMDA, the primary response observed in 62% of the neurons treated with trans-ACPD (100 microM) was a transient elevation in [Ca2+]i. Here, however, only the highly selective neuroprotective sigma ligands (i.e., those lacking substantial PCP binding affinity) significantly decreased the number of transient responses elicited by trans-ACPD whereas the PCP-related sigma ligands such as dextromethorphan, (+)-SKF10047 and (+)-cyclazocine were ineffective. Unexpectedly, (+)-3-PPP potentiated trans-ACPD activity. These results demonstrating attenuating effects of sigma ligands on NMDA-stimulated neuronal calcium responses agree with earlier studies using glutamate and KCl and identify a sigma receptor modulation of functional NMDA responsiveness. Furthermore, the ability of sigma ligands to attenuate NMDA-, trans-ACPD- and KCl-evoked neuronal calcium dynamics indicates that the receptor mechanisms mediating sigma neuroprotection comprise complex interactions involving ionotropic, metabotropic, and even voltage-gated calcium signaling processes.

The pharmacokinetics and electroencephalogram response of remifentanil alone and in combination with esmolol in the rat.

PURPOSE: The goal of this study was to determine if the co-administration of esmolol (ES), a short acting cardioselective beta-blocker, significantly alters the pharmacokinetics and/or pharmacodynamics of remifentanil (REMI), an ultra short-acting opioid, in the rat. METHODS: Sprague-Dawley rats (N = 8, Wt. = 325 +/- 15 g) were surgically implanted with stainless steel cerebrocortical EEG electrodes three days before the study. Each rat was dosed with REMI (15 micrograms/kg/min), and REMI & ES (15 micrograms/kg/min and 600 micrograms/kg/min) for 21 minutes in a random crossover design. Six serial blood samples were collected over 25 minutes into test-tubes containing 0.5 ml acetonitrile. Blood samples were extracted with methylene chloride and analyzed by a validated GC-MS assay. EEG was captured and subjected to power spectral analysis (0.1-50 Hz) for spectral edge (97%). RESULTS: No significant differences (p < 0.05) were found in clearance (REMI = 287 + 73 ml/min/leg vs. REMI & ES = 289 +/- 148 ml/min kg) or Vd (REMI = 286 +/- 49 ml/kg vs REMI & ES = 248 + 40 ml/kg). A linked sigmoid Emax PK-PD model was used and the pharmacodynamic parameters were not statistically different. Mean Emax and EC50 after REMI were 18.0 +/- 6.0 Hz and 32 +/- 12 ng/ml; and after REMI + ES were 19 + 4.8 Hz and 26 + 8.6 ng/ml. CONCLUSIONS: At the doses tested, there is no pharmacokinetic or pharmacodynamic interaction between remifentanil and esmolol in the rat.

Role of calcium in sigma-mediated neuroprotection in rat primary cortical neurons.

Since unique calcium dynamics have been reported for toxic (40-80 M) and non-toxic (5-10 microM) concentrations of glutamate, we evaluated the effect of neuroprotective sigma ligands on glutamate and potassium chloride (KCl)-stimulated changes in [Ca2+]i using 12-15 day old primary rat neuronal cortical cultures. In approximately 80% of the neurons tested, 80 microM glutamate caused a sustained calcium flux previously shown to be associated with neurotoxicity. The majority of sigma ligands that were evaluated altered glutamate-induced calcium flux. For example, the primary effect of maximally neuroprotective concentrations of the sigma ligands dextromethorphan, (+)-pentazocine, (+)-cyclazocine, (+)-SKF 10047, carbetapentane and haloperidol was a shift from a sustained, to either a biphasic or a monophasic transient calcium response indicative of neuroprotection. (+)-3-PPP, previously shown not to be neuroprotective in this model system, failed to alter glutamate-induced calcium flux. In contrast to glutamate, KCl (50 mM) produced changes in [Ca2+]i which were not neurotoxic to the neurons as measured by LDH release. The primary response observed in 59% of the neurons treated with 50 mM KCl alone was an initial spike in [Ca2+]i which abruptly declined then plateaued above basal levels throughout the 12 min of analysis (modified sustained response). The highly selective sigma ligands produced a shift from the modified sustained response to a monophasic transient calcium response. Again, (+)-3-PPP had no effect on KCl-induced calcium dynamics. Of the PCP-related sigma ligands only (+)-SKF-10047 consistently attenuated the KCl-induced calcium flux. Collectively, these results indicate that modulation of [Ca2+]i through receptor and voltage-gated calcium channels contributes significantly to sigma mediated neuroprotection.