Stable planar mesoscopic photonic crystal cavities.

Mesoscopic self-collimation (MSC) in mesoscopic photonic crystals with high reflectivity is exploited to realize a novel high Q-factor cavity by means of mesoscopic PhC planar mirrors. These mirrors efficiently confine a mode inside a planar Fabry-Perot-like cavity, that results from a beam focusing effect that stabilizes the cavity even for small beam sizes, resembling the focusing behavior of curved mirrors. Moreover, they show an improved reflectivity with respect to their standard distributed Bragg reflector counterparts that allows higher compactness. A Q-factor higher than 104 has been achieved for an optimized 5-period-long mirror cavity. The optimization of the Q-factor and the performances in terms of energy storage, field enhancement, and confinement are detailed.

High angular tolerance and reflectivity with narrow bandwidth cavity-resonator-integrated guided-mode resonance filter.

Guided mode resonance filters (GMRFs) are a promising new generation of reflective narrow band filters, that combine structural simplicity with high efficiency. However their intrinsic poor angular tolerance and huge area limit their use in real life applications. Cavity-resonator-integrated guided-mode resonance filters (CRIGFs) are a new class of reflective narrow band filters. They offer in theory narrow-band high-reflectivity with a much smaller footprint than GMRF. Here we demonstrate that for tightly focused incident beams adapted to the CRIGF size, we can obtain simultaneously high spectral selecitivity, high reflectivity, high angular acceptance with large alignment tolerances. We demonstrate experimentally reflectivity above 74%, angular acceptance greater than ±4.2° for a narrow-band (1.4 nm wide at 847 nm) CRIGF.

Measurement and modeling of 2D hexagonal resonant-grating filter performance.

We report the measurement of a polarization-independent guided-mode resonant filter with a Q factor of approximately 2200 functioning near normal incidence in the near infrared (850 nm). Besides this remarkable performance, we provide a detailed optical and structural characterization of the component, which points out the origins of the limitation of the experimental performance. We conclude that the defaults in question can be corrected by improving the lithography process, and we are confident that even greater performance will be obtained in future realizations.

Interaction of cysteine and its derivatives with monolayers of dipalmitoylphosphatidylcholine.

Molecular interactions between l-cysteine (Cys) and its ester derivatives (Cysx); l-cysteine ethyl ester (CE), l-cysteine methyl ester (CM) and N-acetyl l-cysteine (NAC) with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers were investigated using Langmuir film balance technique. The effect of charge on monolayers made of cysteine and three ester derivatives with DPPC was investigated by working with un-buffered and buffered subphases. Also, the effects of cysteine derivatives interaction with DPPC monolayers were studied measuring the change in the surface tension upon aminoacid injection in the subphase whilst keeping lipid molecular density and lateral packing controlled. Cysteine and its ester derivatives showed interfacial activity reducing the air/water surface tension (πi) by 4 mN m-1. However, ester derivatives were able to insert into preformed DPPC monolayers at much higher surface pressures (Δπ), indicating a preferential interaction of Cysx with DPPC. The results indicate that, although the different derivatives of cysteine presented low surface activity, they were able to favourably interact with DPPC monolayers. Also, compression isotherms experiments in binary mixtures indicate that the more surface active compounds stabilized the gel phase of DPPC. The charge on cysteine and its derivatives did not increase the observed effects.

The case for class II bacteriocins: A biophysical approach using "suicide probes" in receptor-free hosts to study their mechanism of action.

Class II bacteriocins are unmodified membrane-active peptides that act over a narrow spectrum of target bacteria. They bind a specific receptor protein on the membrane to form a pore, leading to membrane permeabilization and cell death. However, little is known about the molecular events triggering the pore formation after the bacteriocin recognizes the receptor. It is not clear yet if the pore is the same receptor forced into an open conformation or if the pore results from the bacteriocin insertion and oligomeric assembly in the lipid bilayer. In order to reveal which model is more suitable to explain the toxicity mechanism, in this work we use chimeric peptides, resulting from the fusion of the bitopic membrane protein EtpM with different class II bacteriocins: enterocin CRL35, pediocin PA-1 and microcin V. E. coli strains lacking the specific receptors for these bacteriocins were chosen as expression hosts. As these constructs display a lethal effect when they are heterologously expressed, they are called "suicide probes". The results suggest that, indeed, the specific receptor would act as a docking molecule more than as a structural piece of the pore, as long as the bacteriocin is somehow anchored to the membrane. These set of chimeric peptides also represent an in vivo system that allows to study the interaction of the bacteriocins with real bacterial membranes, instead of model membranes. Hence, the effects of these suicide probes in membrane fluidity and transmembrane potential were also assessed, using fluorescence spectroscopy. The data show that the different suicide probes are able to increase phospholipid order and depolarize the membranes of receptor-free bacterial cells.

Hexagonal phase with ordered acyl chains formed by a short chain asymmetric ceramide.

Ceramides constitute a group of lipids with usually high melting temperature that also favor negative curvature in membranes when mixed with other lipids. The short chain C10:0 ceramide is an asymmetric lipid which consists of an 18 carbon sphingosine base N-acylated with decanoic acid. According to high sensitivity differential scanning calorimetry, it shows a minor exothermic peak at 61°C and a main endothermic transition at 75°C. By small angle X-ray scattering and polarized light microscopy we found that, at temperatures below the main transition, the fully hydrated lipid dispersions are arranged in a tridimensional structure corresponding to an inverted hexagonal phase. Infrared spectroscopy and wide angle X-ray diffraction indicated that the acyl chains of ceramides exhibit a relatively high order in the hexagonal phase. As far as we know, this is the first report of a lipid hexagonal phase having highly ordered acyl chains. Molecular asymmetry due to the different length of the sphingosine and the N-acyl chains of C10:0 ceramide may explain why this novel phase is formed.

Single-mode in-gap emission of medium-width photonic crystal waveguides on InP substrate.

In this paper, we present a numerical and experimental study of W3-4 photonic crystal (PhC) waveguide lasers fabricated on InP substrate. In such a PhC waveguide, the dispersion curve of the fundamental mode folds in the two-dimensional gap of the triangular lattice. Folding occurs at the Brillouin zone edge as in the case of genuine distributed feedback (DFB) lasers. Single-mode emission is presently observed in both electrical and optical pumping configurations. This behavior is attributed to the different levels of out-of-plane losses experienced by the two DFB mode components. Three-dimensional finite-difference-time-domain calculations are used to finely quantify the quality factors of the waveguide modes. The modal discrimination is shown to be reinforced when lasing occurs far from the conduction band edge. This trend is also predicted for other canonical waveguides in triangular PhCs as for instance W2-3 waveguides.

The antimicrobial peptide microcin J25 stabilizes the gel phase of bacterial model membranes.

The bacterial membrane interaction of the antimicrobial peptide microcin J25 was studied with the probe-free techniques Langmuir monolayers and infrared spectroscopy. Membrane model systems composed by phosphatidylethanolamine:phosphatidylglycerol 7:3, which mimic the cytoplasmic membrane of Gram negative bacteria, were used in both monolayer and bilayer approaches. The peptide reduced the transition surface pressure of the expanded-to-condensed lipid monolayer states, as well as increased the gel-to-liquid crystalline transition temperature in bilayers, indicating a stabilization of membrane ordered state. In addition, a reduction of the surface pressure at which condensed domains appeared was observed upon mixed monolayers compression after microcin J25 adsorption. The results indicate a favorable interaction of microcin J25 with bacterial membrane model systems. Also, the effects on the ordered phases stabilization are discussed in terms of the biological effects observed in membranes of sensitive cells.

Evidence for the presence of several phosphodiesterase isoforms in brown adipose tissue of Zucker rats: modulation of PDE2 by the fa gene expression.

The present study was undertaken to characterise the phosphodiesterases (PDEs) present in brown adipose tissue (BAT) of Zucker rat pups and to determine whether the capacity for degradation of cyclic nucleotides was affected by the fatty genotype. Regardless of the genotype, PDE2-4 contributed to total PDE activity, the PDE3 activity equalling the sum of PDE2 and 4 activities. In fa/fa compared to Fa/fa rats, (a) PDE2 activity was significantly increased, (b) Western blot analysis of PDE2 revealed two signals at 71 and 105 kDa, with changes in protein being in good parallelism with changes in activity, (c) the PDE2 mRNA concentration was also significantly increased. In good agreement, the cGMP concentration was decreased in BAT from fa/fa pups.

EEG and electrodermal activity in girls with Attention-Deficit/Hyperactivity Disorder.

OBJECTIVE: This study investigated the Hypoarousal Model of Attention-Deficit/Hyperactivity Disorder (AD/HD) in girls. METHODS: 40 girls with AD/HD and 40 girl controls (aged 7-12 years) had an eyes-closed resting EEG recorded from 19 electrodes and Fourier transformed. Estimates for total power, absolute and relative power in the delta, theta, alpha, beta and gamma frequency bands, and theta/beta ratio were analysed in nine cortical regions. Skin conductance level (SCL) was simultaneously recorded. Regression analyses explored relationships between symptoms and physiology. RESULTS: Compared with controls, girls with AD/HD had globally elevated relative delta, globally reduced absolute beta, and globally reduced absolute and relative gamma activity. Girls with AD/HD also had lower mean SCL. Inattentive symptoms were predicted by elevated frontal relative delta, reduced SCL, and reduced temporal relative gamma activity, while elevated hyperactive-impulsive symptoms correlated with elevated frontal relative delta activity in both the patient and control groups. CONCLUSIONS: These EEG results are comparable with the limited female AD/HD literature. Girls with AD/HD are hypoaroused, indicated by reduced SCL, and appear to have an anomalous arousal mechanism. Absolute and relative gamma results are similar to previous findings in AD/HD children. Symptom correlations with physiology offer intriguing insights for future research. SIGNIFICANCE: This is the first study to examine CNS arousal exclusively in girls with AD/HD.

Does hyperflex total knee design improve postoperative active flexion?

INTRODUCTION: The rotating platform flexion (RPF) Sigma total knee prosthesis (DePuy; Warsaw, Indiana) was designed for maintaining the contact of the condyles with their corresponding tibial plateau throughout the high-flexion range. However, this requires an additional 3-mm bone cut of the posterior condyles. Compared to the conventional design, this modification is intended to improve the flexion range. This hypothesis was tested by studying the increase in flexion (flexion gain, range of motion [ROM], active flexion) of 59 consecutive patients who had received the hyperflex design implant (RPF), whose preoperative mobility values were retrospectively compared to these same values in another 59 consecutive matched patients who had received an implant with the conventional design of the same implant (rotating platform [RP]) between June 2005 and June 2006. Postoperative mobility was measured visually with a goniometer. PATIENTS AND METHODS: Only osteoarthritic knees were eligible to be included. Knees with more than 20 degrees flexion contracture or less than 90 degrees flexion, and patients with a body mass index (BMI) greater than 30 were excluded. Both groups were comparable with regard to age, preoperative mobility values, and BMI. The sex ratio differed significantly, but preoperative mobility did not differ significantly in male and female patients in the RP and in the RPF groups. The difference in sex ratio did not appear to be a bias influencing preoperative mobility. RESULTS: Overall, the flexion gain was correlated to preoperative flexion (r=-0.75, p<0.001). The flexion gain in the RPF group was significantly greater than in the RP group (13+-20 versus 6+-13; p=0.02) as was the ROM gain (10+/-17 degrees versus 4+/-12 degrees; p=0.02). However, the one-year active mean flexions were not significantly different (118+/-14 degrees versus 116+/-6 degrees; p=0.47). In patients whose preoperative flexion was less than 120 degrees (18 and 27 RPF prostheses), the flexion and ROM gains were significantly greater in the RPF group (23+/-16 degrees versus 14+/-16 degrees; p=0.03 and 26+/-18 degrees versus 17+/-9 degrees; p=0.05), and the mean one-year active flexion was also greater in the RPF group (124+/-13 degrees versus 116+/-8 degrees, p=0.02). In patients with more than 120 degrees of preoperative flexion, the flexion and ROM gains and the final mean flexions in both groups were comparable. In particular, there were nine patients in the RP group and ten patients in the RPF group whose flexion decreased. CONCLUSION: Thus, the Sigma RPF prosthesis provided a significant additional flexion gain in patients with 90-120 degrees preoperative flexion, and less than 20 degrees flexion contracture. Patients with a preoperative flexion greater than 120 degrees were exposed to a decrease in flexion range whichever implant was used, RP or RPF. LEVEL OF EVIDENCE: Level 3, therapeutic study.

Molecular evolution of protein O-fucosyltransferase genes and splice variants.

O-Fucose has been described on both epidermal growth factor-like (EGF-like) repeats and Thrombospondin type 1 repeats (TSRs). The enzyme adding fucose to EGF-like repeats, protein O-fucosyltransferase 1 (Pofut1), is a soluble protein located in the lumen of endoplasmic reticulum (ER). A second protein O-fucosyltransferase, Pofut2, quite divergent from its homolog Pofut1, has recently been shown to O-fucosylate TSRs but not EGF-like repeats. To date, Pofut1 genes have only been characterized in human, mouse, and fly, and Pofut2 in mouse, fly, and partially in the nematode Caenorhabditis elegans. Here, we report cDNA sequences and genomic structures of bovine Pofut1 and Pofut2 genes and describe for the first time five alternative spliced transcripts for each gene. Only one transcript for both Pofut1 and Pofut2 encodes an active bovine O-fucosyltransferase. Variant transcript distribution was examined in 13 bovine tissues. Transcripts encoding active forms are ubiquitous, whereas other forms possess a more restricted tissue-expression profile. Sequence comparison and phylogenetic analyses revealed that both Pofut genes are present as a single copy in animal genomes, and their exon-intron organizations are conserved among vertebrates. The last common ancestor of all analyzed bilaterian species would be predicted to possess polyexonic Pofut genes in their genome.

Development of thyroxine type II deiodinase activity in brains of Zucker rats.

The present study was undertaken to determine whether the capacity for 3,5,3',5'-tetraiodothyronine (T4) conversion into 3,5,3'-tri-iodothyronine (T3), as measured by the activity of thyroxine type II 5'-monodeiodinase (T4-5'D), was altered in the brains of young Zucker fa/fa rats during the period of intense maturation of the central nervous system (i.e. from 10 to 20 days of life). From 7 to 14 days of age, no difference in brain T4-5'D activity could be detected between lean and pre-obese rats; serum free T4 was not affected by the fa gene. During the suckling to weaning transition, T4-5'D reached a plateau in brains of lean rats, while it increased by 50% in brains of pre-obese rats; concurrently, serum free T4 increased in Fa/fa rats, whereas it did not change in fa/fa rats. The increased capacity for conversion of T4 into T3 observed in brains of pre-obese compared with lean rats could not be ascribed to a variation in the amount of T4-5'D, since Vmax. did not differ between the two genotypes; however, it could be totally accounted for by an increased affinity of the enzyme for T4. This change may represent an adaptive response to low serum free T4 in order to maintain the cerebral T3 concentration in pre-obese rats. These results show that the alteration in T4 metabolism in brains of fa/fa rats is not an early event and thus cannot interfere with maturation of the central nervous system. However, the decreased serum free T4 which was observed in pre-obese rats after suckling might play a secondary role in development of this genetic obesity.

Acute injection of beta-adrenoceptor agonist BRL 35135 corrects both impaired uncoupling protein and lipoprotein lipase gene expression but not hypercapacity of lipogenesis in brown adipose tissue of suckling fa/fa rats.

This study was undertaken to determine whether acute injection of the beta-adrenoceptor BRL 35135, which is known to activate thermogenesis, could correct the earliest detectable metabolic abnormalities that characterize brown (BAT) and white (WAT) adipose tissues of pre-obese Zucker rats. In 14-day-old pups, a single intraperitoneal injection of BRL (10 micrograms/g, 3 h before sacrifice) had no effect on uncoupling protein mRNA content in BAT of lean pups, whereas the low level of this mRNA was restored to normal in pre-obese rats. Both lipoprotein lipase (LPL) activity and mRNA content, which were decreased in BAT of pre-obese compared to lean pups (-60%), were stimulated after BRL injection. However, this effect was more pronounced in fa/fa than in Fa/fa rats (+100% and +50%, respectively). In BAT, the increase in fatty acid synthetase (FAS) activity observed in fa/fa rats compared to their lean Fa/fa littermates was not reduced. In WAT, the stimulation of beta-adrenergic receptors had no effect on lipid storage capacity, since FAS and LPL activities remained unchanged. In conclusion, pre-obese Zucker fa/fa rats are responsive to BRL 35135 treatment: acute administration of this drug was able to improve impaired thermogenesis and to correct temporarily other abnormalities of early emergence in BAT. This treatment had no effect in WAT. Taken together, our data reinforce the hypothesis that reduced sympathetic activity in BAT is one of the primary lesions of the obese rat which may play a key role in the development of this genetic obesity.

Decreased T4-to-T3 conversion in brown adipose tissue of Zucker fa/fa pups before the onset of obesity.

To determine whether the capacity of thyroxine (T4)-to-3,5,3'-triiodothyronine (T3) conversion was altered in Zucker fa/fa pups, we measured thyroxine 5'-monodeiodinase (T(4)5'D) activity in brown adipose tissue (BAT) and liver of suckling and weaned fa/fa and Fa/fa littermates. In suckling fa/fa compared with Fa/fa rats, T(4)5'D was reduced by 30-55% in BAT and slightly increased in liver, while serum free T3 was significantly decreased (-30%). Altered T(4)5'D activity in BAT of fa/fa pups could be corrected by adrenergic stimulation. After weaning, in fa/fa rats, the capacity for T4-to-T3 conversion was totally restored in BAT while it was dramatically reduced in liver. The concentration of serum free T3 remained lower in fa/fa than in Fa/fa rats (-40%). These data confirm that BAT is a very early site of fa gene expression and are consistent with the hypothesis that a defect in the autonomic nervous system may be a primary cause of this genetic obesity. It is also suggested that, during suckling, BAT plays an important role in systemic production of T3.

Increased in vivo glucose utilization in 30-day-old obese Zucker rat: role of white adipose tissue.

In vivo whole-body glucose utilization and uptake in multiple individual tissues were investigated in conscious 30-day-old Zucker rats, which when obese are hyperphagic, hyperinsulinemic, and normoglycemic. Whole-body glucose metabolism (assessed by [3-3H]glucose) was 40% higher in obese (fa/fa) than in lean (Fa/fa) rats, suggesting that obese rats were quite responsive to their hyperinsulinemia (140 vs. 55 microU/ml). In obese compared with lean rats, tissue glucose uptake (assessed by the 2-deoxyglucose technique) was increased by 15, 12, and 6 times in dorsal, inguinal, perigonadal white depots, respectively; multiplied by 2.5 in brown adipose tissue; increased by 50% in skin from inguinal region but not in that from cranial, thoracic, or dorsal area; and increased twofold in diaphragm but similar in heart, in proximal intestine, and in total muscular mass of limbs. Our data establish that in young obese rats the hypertrophied white adipose tissue was a major glucose-utilizing tissue whose capacity for glucose disposal compared with that of half the muscular mass. Adipose tissue could therefore play an important role in the homeostasis of glucose in obese rats in the face of their increased carbohydrate intake.

[Effect of adrenalectomy on the capacity of brown adipose tissue for thermogenesis and the development of obesity in the fa/fa Zucker rat]. / Effet de la surrénalectomie sur la capacité de thermogenèse du tissu adipeux brun et le développement de l'obésité chez le rat Zucker fa/fa.

This study was undertaken to examine whether adrenalectomy performed during the weaning period could correct some of the first metabolic abnormalities to develop in obese fa/fa rats: impaired thermogenesis in brown adipose tissue and hyperlipogenesis in interscapular brown and white (inguinal) adipose tissues. Pups were adrenalectomized or sham-operated at 23 days of age and studied at 30 days of age. Body weight, interscapular brown adipose tissue and inguinal white adipose tissue weight were decreased after adrenalectomy in Fa/fa and fa/fa pups. Adrenalectomy had no effect on the thermogenic capacity of brown adipose tissue (as assessed by GDP binding to mitochondria) which remained significantly lower in fa/fa than in Fa/fa rats. In both Fa/fa and fa/fa rats the lipogenic capacity of brown and white adipose tissues (as assessed by fatty acid synthetase activity) was dramatically reduced by adrenalectomy. However, in adrenalectomized rats, the fatty acid synthetase activity of brown and white adipose tissue remained 2 and 5-fold higher, respectively, in fa/fa than in Fa/fa rats. These results show that adrenalectomy at postweaning, did not affect specifically the rats bearing the fatty genotype but induced large alterations in both groups of rats. Adrenalectomized fa/fa animals remained obese as compared to the appropriate controls.