Tin oxide nanocluster hydrogen and ammonia sensors

We have prepared sensitive hydrogen and ammonia sensors from thin films of tin nanoclusters with diameters between 3 and 10 nm. By baking the samples at 200 °C in ambient air the clusters were oxidized, resulting in very stable films of tin oxide clusters with similar diameters to the original Sn clusters. By monitoring the electrical resistance, it is shown that the cluster films are highly responsive to hydrogen and ammonia at relatively low temperatures, thereby making them attractive for commercial applications in which low power consumption is required. Doping of the films by depositing Pd on top of the clusters resulted in much improved sensor response and response times. It is shown that optimal sensor properties are achieved for very thin cluster films (a few monolayers of clusters).

Early factor VIII exposure and subsequent inhibitor development in children with severe haemophilia A

Recent reports have suggested that the incidence of inhibitors in haemophilia is the highest in those first exposed to factor VIII under 6 months of age. In this study, we investigated inhibitor development in children first exposed to FVIII as neonates and also examined the effect of other genetic and environmental variables. Three hundred and forty-eight children with severe haemophilia A were investigated. Inhibitors developed in 68 of 348 (20%), with 34 of 348 (10%) high titre inhibitors. The incidence in relation to initial FVIII exposure was: <1 month nine of 35 (26%), 1-6 months 13 of 51 (25%), 6-12 months 27 of 130 (21%), 12-18 months 13 of 66 (20%) and >18 months six of 66 (9%). While we observed a significant difference in inhibitor development and age at first exposure across all age groups (P = 0.018), no significant difference was observed in children treated at different time points during the first year of life (P = 0.44). Similar results were obtained for high titre inhibitors. There was also no difference in the incidence of inhibitors in relation to initial FVIII exposure in a subgroup of 144 children with the intron 22 mutation. Inhibitors developed more frequently in those initially treated with recombinant when compared with plasma-derived FVIII (P = 0.006) and in those with a major molecular defect (P = 0.009). In this study, exposure to FVIII during the neonatal period was not associated with a higher incidence of inhibitors than those treated later during the first year of life. Initial treatment with recombinant FVIII and the presence of a major molecular defect were the most important variables affecting inhibitor development.

The comparative plasma pharmacokinetics of intravenous cefpodoxime sodium and oral cefpodoxime proxetil in beagle dogs

The pharmacokinetic properties of cefpodoxime, and its prodrug, cefpodoxime proxetil, were evaluated in two separate studies, one following intravenous (i.v.) administration of cefpodoxime sodium and the second after oral (p.o.) administration of cefpodoxime proxetil to healthy dogs. After cefpodoxime administration, serial blood samples were collected and plasma concentrations were determined by high performance liquid chromatography (HPLC). A single i.v. administration of cefpodoxime sodium at a dose of 10 mg cefpodoxime/kg body weight resulted in a cefpodoxime average maximum plasma concentration (Cmax) of 91 (+/-17.7) microg/mL, measured at 0.5 h after drug administration, an average half-life (t1/2) of 4.67 (+/-0.680) h, an average AUC(0-infinity) of 454 (+/-83.1) h.microg/mL, an average V(d(ss)) of 151 (+/-27) mL/kg, an average Cl(B) of 22.7 (+/-4.2) mL/h/kg and an average MRT(0-infinity) of 5.97 (+/-0.573) h. When dose normalized to 10 mg cefpodoxime/kg body weight, cefpodoxime proxetil administered orally resulted in Cmax of 17.8 +/- 11.4 microg/mL for the tablet formulation and 20.1 +/- 6.20 microg/mL for the suspension formulation and an average AUC(0-LOQ) of 156 (+/-76.1) h.microg/mL for the tablet formulation and 162 (+/-48.6) h.microg/mL for the suspension formulation. Relative bioavailability of the two oral formulations was 1.04 (suspension compared with tablet), whereas the absolute bioavailability of both oral formulations was estimated to be approximately 35-36% in the cross-study comparison with the i.v. pharmacokinetics. Combined with previous studies, these results suggest that a single daily oral dose of 5-10 mg cefpodoxime/kg body weight as cefpodoxime proxetil maintains plasma concentrations effective for treatment of specified skin infections in dogs.

Structure of oxidized bismuth nanoclusters

Synchrotron X-ray diffraction has determined that β-Bi2O3 is the dominant oxide phase covering hexagonal bismuth nanoclusters produced in an inert gas aggregation source. Simulated Debye–Scherrer patterns have indicated that the oxide is 20 ± 5 Å thick on average, at the surface of 320 ± 40 Å diameter clusters. A Williamson–Hall analysis of the peak broadening was used to measure the non-uniform strain in clusters. The oxidized clusters were in −0.11 ± 0.06% uniform compressive strain compared with other clusters without oxides detectable by X-ray diffraction which only have a small tensile uniform strain. High-resolution transmission electron microscopy (HRTEM) and multislice image simulations indicated a β-Bi2O3 thickness of 20–50 Å. The HRTEM micrographs show the relative orientation between the oxide and the cluster core.

Angiotensin-converting enzyme inhibitors in veterinary medicine

Angiotensin-converting enzyme (ACE) inhibitors represent one of the most commonly used categories of drugs in canine and feline medicine. ACE inhibitors currently approved for use in veterinary medicine are benazepril, enalapril, imidapril and ramipril. They are all pro-drugs administered by oral route. A physiologically based model taking into account the saturable binding to ACE has been developed for pharmacokinetic analysis. The bioavailability of the active compounds from their respective pro-drug is low. The active metabolites are eliminated by renal, hepatorenal or biliary excretion, according to the drug. The elimination half-life of the free fraction of the active compounds is very short (ranging from approximately 10 min to 2 h). ACE inhibitors are generally well tolerated. Benazepril, enalapril, imidapril and ramipril are approved for dogs with chronic heart failure (CHF). The efficacy of ACE inhibitors has been convincingly demonstrated in dogs with CHF, especially in those with chronic valvular disease. In such clinical settings, ACE inhibitors improve hemodynamics and clinical signs, and increase survival time. In cats with cardiovascular disease, little information is available except for reports of some benefit in cats with hypertrophic cardiomyopathy in two non-controlled investigations. ACE inhibitors have also a mild to moderate hypotensive effect. There is also evidence to recommend ACE inhibitors in dogs and cats with chronic renal failure (CRF). They decrease the glomerular capillary pressure, have antiproteinuric effects, tend to delay the progression of CRF and to limit the extent of renal lesions.

Metabolic effects of interventions to increase exercise in adults with type 2 diabetes

AIMS/HYPOTHESIS

The aim of this meta-analysis was to integrate the results of primary research testing the effect of diabetes self-management interventions that included recommendations to increase exercise on metabolic outcomes among adults with type 2 diabetes.

MATERIALS AND METHODS

Extensive literature searching strategies were used to identify published and unpublished intervention studies that measured glycated haemoglobin outcomes. Primary study results were coded. Fixed- and random-effects meta-analytic procedures included moderator analyses.

RESULTS

Data were synthesised across 10,455 subjects from 103 research reports. The overall mean weighted effect size for two-group comparisons was 0.29 (higher mean for treatment than control). This effect size is consistent with a difference in HbA1c means of 0.45% (e.g. 7.38% for treatment subjects vs 7.83% for control subjects). For single-group studies, the overall mean weighted effect size was 0.32-0.34. Control group subjects experienced no improvement in metabolic control during participation in the studies. Interventions that targeted multiple health behaviours resulted in smaller effect size estimates (0.22) than interventions that focused only on exercise behaviours (0.45). Funded studies reported greater improvements in metabolic controls. Studies with a greater proportion of female subjects reported lower effect sizes. Baseline HbA1c and BMI were unrelated to metabolic outcomes.

CONCLUSIONS/INTERPRETATION

These findings suggest that self-management interventions that include exercise recommendations improve metabolic control, despite considerable heterogeneity in the magnitude of the intervention effect. Interventions that emphasise exercise may be especially effective in improving metabolic control. Primary research testing interventions in randomised trials to confirm causal relationships would be constructive.

Experimental and simulational study of the operation conditions for a high transmission mass filter

The operation conditions of a double pulsed field mass filter were studied using both experiment and simulation. The mass filter consists of two pairs of parallel plates and operates on the time-of-flight principle. The study showed that the ions' beam deflection angle is a critical factor in optimizing the mass filter transmission efficiency. This angle is dependent on the accelerating voltage, ion mass, and horizontal velocity of the ions. The optimum operating conditions for the mass filter were found and used to study the mass distribution of palladium ions produced by a magnetron sputtering source. The study shows that this mass filter is suitable for technological applications because of its high transmission and wide mass range.

Pharmacokinetics of cefovecin in cats

The pharmacokinetics of the novel cephalosporin cefovecin were investigated in a series of in vivo, ex vivo and in vitro studies following administration to adult cats at 8 mg/kg bodyweight. Bioavailability and pharmacokinetic parameters were determined in a cross-over study after intravenous (i.v.) and subcutaneous (s.c.) injections. [14C]cefovecin was used to evaluate excretion for 21 days after s.c. administration. Protein binding was determined in vitro in feline plasma and ex vivo in transudate from cats surgically implanted with tissue chambers. After s.c. administration, cefovecin was characterized by rapid absorption with mean peak plasma concentrations of 141+/-12 microg/mL being achieved within 2 h of s.c. injection with full bioavailability (99%). The mean elimination half-life was 166+/-18 h. After i.v. administration, volume of distribution was 0.09+/-0.01 L/kg and mean plasma clearance was 0.35+/-0.04 mL/h/kg. Approximately 50% of the administered radiolabelled dose was eliminated over the 21-day postdose period via urinary excretion and up to approximately 25% in faeces. In vitro and ex vivo plasma protein binding ranged from 99.8% to 99.5% over the plasma concentration range 10-100 microg/mL. Ex vivo protein binding in transudate was as low as 90.7%. From 8 h postdose, concentrations of unbound (free) cefovecin in transudate were consistently higher than in plasma, with mean unbound cefovecin concentrations being maintained above 0.06 microg/mL (MIC90 of Pasteurella multocida) in transudate for at least 14 days postdose. The slow elimination and long-lasting free concentrations in extracellular fluid are desirable pharmacokinetic attributes for an antimicrobial with a 14-day dosing interval.

Peripheral clocks: keeping up with the master clock

Circadian clocks influence most aspects of physiology and behavior, so perhaps it is not surprising that circadian oscillators exist in nearly all mammalian cells. These cells remain synchronized to the outside world in hierarchical fashion, with a "master clock" tissue in the suprachiasmatic nucleus of the hypothalamus receiving light input from the retina and then conveying timing information to "slave" clocks in peripheral tissues. Recent research has highlighted both the similarities and differences between central and peripheral clocks and provided new insight into their communication. Above all, however, this parallelism of clockwork has provided a unique opportunity to study at the cellular level a regulatory mechanism that affects complex behaviors.

Reentrant adhesion behavior in nanocluster deposition

We simulate the collision of atomic clusters with a weakly attractive surface using molecular dynamics in a regime between soft landing and fragmentation, where the cluster undergoes large deformation but remains intact. As a function of incident kinetic energy, we find a transition from adhesion to reflection at low kinetic energies. We also identify a second adhesive regime at intermediate kinetic energies, where strong deformation of the cluster leads to an increase in contact area and adhesive energy.

Effect of chloroquine on the bioavailability of ciprofloxacin in humans

Chloroquine, a front-line drug in the treatment of malaria, has developed widespread resistance, especially to the Plasmodium falciparum strains. Ciprofloxacin is a second-generation quinolone used as a broad-spectrum fluoroquinolone antibacterial agent. The possibility of using ciprofloxacin as an antimalarial, especially in chloroquine-resistant strains, is very promising. They concluded from in vitro studies however that the anti-malarial effect occur at high dose level of ciprofloxacin to achieve the required serum concentrations. Studies have shown that there is little interstrain variability in the in vitro susceptibility of P. falciparum to fluoroquinolones. There is also no cross-resistance between them. Another study stated that 50% inhibition of parasite growth in vitro required 6.6 microg/mL after a high dose of ciprofloxacin was used. They thus concluded that ciprofloxacin should not be used alone. There is need for in vivo studies to ascertain the achievable serum concentration of ciprofloxacin when given alone and when given in combination with chloroquine. The serum concentration of ciprofloxacin was studied when ciprofloxacin was given alone and in combination with chloroquine in humans. Five healthy male volunteers aged (19-31) years who were not taking any of the prescribed medications and had no sensitivity to either ciprofloxacin or chloroquine, each received 500 mg ciprofloxacin orally with 250 mL of water, and after a 2-week wash-out period, 500 mg ciprofloxacin plus 600 mg of chloroquine was administered orally with 250 mL of water after informed consent. A blood sample (2.5 mL) was collected just before taking the drug at 8:00 AM representing 0 hours and continued afterward at 1, 2, 4, 8, 12, and 24 hours the following day. Serum samples were stored at -20 degrees C until analyzed. The minimal inhibitory concentrations (MIC) by diffusion through agar technique was used for the assay of serum ciprofloxacin. The following bioavailability parameters: Cmax, tmax, and AUC 0-24, AUC 0-infinity were calculated. The peak serum concentration Cmax of ciprofloxacin was 3.42 +/- 0.32 microg/mL, which dropped to 2.8 +/- 0.18 microg/mL when chloroquine was taken together with ciprofloxacin. These values were less than the in vitro 12.5 microg/mL concentrations required to inhibit P. falciparum. Though the effect of parasitemia was not ascertained, the in vivo use of ciprofloxacin alone or in combination is doubtful because increasing the dose that will reach the in vitro level will lead to toxicity in vivo.

Synthesis of 8-geranyloxypsoralen analogues and their evaluation as inhibitors of CYP3A4

Furanocoumarins have been shown to inhibit CYP3A4 in vitro with varying degrees of potency. In this study, we report the effects of a series of novel furanocoumarins based on the naturally occurring derivative 8-geranylepoxypsoralen which has been shown to be a more potent inhibitor of CYP3A4 than its 5-position-substituted counterpart bergamottin. Compounds were designed, synthesised and tested for their ability to inhibit CYP3A4 activity in human liver microsomes using testosterone as the marker substrate. Both the saturated and unsaturated phenolic furanocoumarin derivatives were found to be inactive. However, the 8-alkyloxy-furanocoumarin analogues were shown to inhibit CYP3A4 activity in a dose dependent manner, with IC(50) values ranging from 0.78+/-0.11 to 3.93+/-0.53 microM. The reduced furan derivative dihydro-8-geranyloxypsoralen showed a 4-fold decrease in inhibitory potency, suggesting that the furan moiety plays a role in the interaction between these compounds and CYP3A4.

Design, synthesis and evaluation of furanocoumarin monomers as inhibitors of CYP3A4

A number of furanocoumarins isolated from grapefruit juice have been found to inhibit CYP3A4 activity in vitro. In this study, we have designed and synthesised a range of analogues based on bergamottin to investigate the relationship between chemical structure and inhibition of CYP3A4 activity. Studies were performed using human liver microsomes and human intestinal S9 fraction, with testosterone as the marker substrate. With the exception of the coumarin and phenolic furanocoumarin derivatives, which were inactive, the alkyloxy-furanocoumarin analogues were found to inhibit CYP3A4 activity in a dose dependent manner, with observed IC50 values ranging from 0.13 +/- 0.03 to 49.3 +/- 1.9 microM. The unsaturated furan derivatives were found to exhibit time-dependent inhibition, showing a 2-, 4- and 14-fold increase in potency for 6',7'-epoxybergamottin, 6',7'-dihydroxybergamottin and bergamottin, respectively after a preincubation period of ten minutes. Reduction of the furan moiety resulted in an 11-fold decrease in inhibitory potency, suggesting that this functional group is key to the interaction between these compounds and CYP3A4.

Individual HIV type 1 envelope-specific T cell responses and epitopes do not segregate by virus subtype

HIV-1 vaccines are often designed to target one or several virus subtype(s). They therefore include antigens (e.g., env or env/gag/pol) from each targeted subtype to elicit subtype-directed immunity. To determine if individual T cells respond to HIV-1 antigens in a subtype-directed manner, we selected four T cell hybridomas, each representative of a different immunodominant response toward a subtype B envelope. Hybridomas were tested for responses toward 20 subtype B envelope proteins and one protein each from subtypes A, C, and D. None of the hybridomas cross-reacted with all subtype B envelopes, yet three responded to a non-B protein. Core epitopes and flanking regions affected responsiveness. This lack of subtype-directed activity was corroborated by analyses of the Los Alamos database; like immune responses, epitope distributions were not dictated by subtype. Results highlight the difficulty of predicting immune responses based on subtype alone and encourage considerations of antigenic disparity in addition to subtype disparity during HIV-1 vaccine design.

DEVELOPMENT OF NOVEL FURANOCOUMARIN DIMERS AS POTENT AND SELECTIVE INHIBITORS OF CYP3A4

Grapefruit juice has been found to cause an increase in the oral bioavailability of many therapeutic agents. Such interactions are believed to result from the mechanism-based inhibition of CYP3A4 activity in the intestine. Furanocoumarin dimers present in the juice have been found to be extremely potent inhibitors of CYP3A4 activity. The aim of this work was to synthesize and test a series of dimers with a view to defining the relationship between structure and inhibitory activity and establish whether they might make suitable probes of CYP3A4 activity. Eleven furanocoumarin dimers were synthesized and evaluated as inhibitors of CYP3A4 using human liver microsomes, with testosterone as the marker substrate. Four of the most potent dimers were also investigated for their effects on CYP3A4 activity in the human intestine and on five additional hepatic cytochrome P450 isoforms. The dimers showed potent dose-dependent inhibition of CYP3A4 activity in both liver and intestine; IC50 values ranged from 0.021 +/- 0.002 to 0.146 +/- 0.041 microM (mean +/- S.D. n = 3). Of the four dimers evaluated further, all showed time-dependent inhibition of CYP3A4 activity. 88Prop showed moderate inhibition of both CYP2C19 and CYP1A2 with IC50 values of 4.42 +/- 0.01 and 1.98 +/- 0.34 microM, 88Octa was found to inhibit CYP2C19 (IC50 = 3.16 +/- 0.01 microM) and 58Prop to inhibit CYP1A2 (IC50 = 2.39 +/- 0.77 microM). Minimal inhibition of CYP2D6 and CYP2C9 was observed (IC50 > 10 microM). In conclusion, all the dimers tested were extremely potent inhibitors of CYP3A4 activity. In particular, dimer 55EE was highly selective toward the enzyme, suggesting that this compound is a suitable probe for determining the contribution of CYP3A4 to drug metabolism.

Enlightening the adrenal gland

The secretion of glucocorticoid hormones is tightly regulated by the circadian clock and by negative humoral feedback loops, both acting on the hypothalamic-pituitary gland-adrenal axis. However, a new study Ishida et al., 2005 [this issue of Cell Metabolism) shows that light can influence the adrenal's glucocorticoid output by a more direct pathway.

The period length of fibroblast circadian gene expression varies widely among human individuals

Mammalian circadian behavior is governed by a central clock in the suprachiasmatic nucleus of the brain hypothalamus, and its intrinsic period length is believed to affect the phase of daily activities. Measurement of this period length, normally accomplished by prolonged subject observation, is difficult and costly in humans. Because a circadian clock similar to that of the suprachiasmatic nucleus is present in most cell types, we were able to engineer a lentiviral circadian reporter that permits characterization of circadian rhythms in single skin biopsies. Using it, we have determined the period lengths of 19 human individuals. The average value from all subjects, 24.5 h, closely matches average values for human circadian physiology obtained in studies in which circadian period was assessed in the absence of the confounding effects of light input and sleep–wake cycle feedback. Nevertheless, the distribution of period lengths measured from biopsies from different individuals was wider than those reported for circadian physiology. A similar trend was observed when comparing wheel-running behavior with fibroblast period length in mouse strains containing circadian gene disruptions. In mice, inter-individual differences in fibroblast period length correlated with the period of running-wheel activity; in humans, fibroblasts from different individuals showed widely variant circadian periods. Given its robustness, the presented procedure should permit quantitative trait mapping of human period length.

A novel method permits characterization of circadian rhythms in humans and mice using single skin biopsies.

PERIOD1-associated proteins modulate the negative limb of the mammalian circadian oscillator

The clock proteins PERIOD1 (PER1) and PERIOD2 (PER2) play essential roles in a negative transcriptional feedback loop that generates circadian rhythms in mammalian cells. We identified two PER1-associated factors, NONO and WDR5, that modulate PER activity. The reduction of NONO expression by RNA interference (RNAi) attenuated circadian rhythms in mammalian cells, and fruit flies carrying a hypomorphic allele were nearly arrhythmic. WDR5, a subunit of histone methyltransferase complexes, augmented PER-mediated transcriptional repression, and its reduction by RNAi diminished circadian histone methylations at the promoter of a clock gene.