Impact of membrane lipid polyunsaturation on dopamine D2 receptor ligand binding and signaling

Increasing evidence supports a relationship between lipid metabolism and mental health. In particular, the biostatus of polyunsaturated fatty acids (PUFAs) correlates with some symptoms of psychiatric disorders, as well as the efficacy of pharmacological treatments. Recent findings highlight a direct association between brain PUFA levels and dopamine transmission, a major neuromodulatory system implicated in the etiology of psychiatric symptoms. However, the mechanisms underlying this relationship are still unknown. Here we demonstrate that membrane enrichment in the n-3 PUFA docosahexaenoic acid (DHA), potentiates ligand binding to the dopamine D2 receptor (D2R), suggesting that DHA acts as an allosteric modulator of this receptor. Molecular dynamics simulations confirm that DHA has a high preference for interaction with the D2R and show that membrane unsaturation selectively enhances the conformational dynamics of the receptor around its second intracellular loop. We find that membrane unsaturation spares G protein activity but potentiates the recruitment of β-arrestin in cells. Furthermore, in vivo n-3 PUFA deficiency blunts the behavioral effects of two D2R ligands, quinpirole and aripiprazole. These results highlight the importance of membrane unsaturation for D2R activity and provide a putative mechanism for the ability of PUFAs to enhance antipsychotic efficacy.

The impact of lipid polyunsaturation on the physical and mechanical properties of lipid membranes

The lipid composition of cellular membranes and the balance between the different lipid components can be impacted by aging, certain pathologies, specific diets and other factors. This is the case in a subgroup of individuals with psychiatric disorders, such as schizophrenia, where cell membranes of patients have been shown to be deprived in polyunsaturated fatty acids (PUFAs), not only in brain areas where the target receptors are expressed but also in peripheral tissues. This PUFA deprivation thus represents a biomarker of such disorders that might impact not only the interaction of antipsychotic medications with these membranes but also the activation and signaling of the targeted receptors embedded in the lipid membrane. Therefore, it is crucial to understand how PUFAs levels alterations modulate the different physical properties of membranes. In this paper, several biophysical approaches were combined (Laurdan fluorescence spectroscopy, atomic force microscopy, differential scanning calorimetry, molecular modeling) to characterize membrane properties such as fluidity, elasticity and thickness in PUFA-enriched cell membranes and lipid model systems reflecting the PUFA imbalance observed in some diseases. The impact of both the number of unsaturations and their position along the chain on the above properties was investigated. Briefly, data revealed that PUFA presence in membranes increases membrane fluidity, elasticity and flexibility and decreases its thickness and order parameter. Both the level of unsaturation and their position affect these membrane properties.

Stranded in the high tide line: Spatial and temporal variability of beached microplastics in a semi-enclosed embayment (Arcachon, France)

Coastal environments are a predominant ultimate destination of marine debris, becoming a key focus of studies assessing microplastic (MP) contamination. Here, we described the visible fraction of MP (from 0.5 to 5 mm) that washed up during the high tide at different sites of a semi-enclosed mesotidal bay and investigated the main abiotic factors driving MP beaching. Three contrasted beaches of the Arcachon Bay (SW France) were monitored on a monthly basis during 2019. Samplings were made along a 100 m longitudinal transect at the high-water strandline (4 quadrats of 0.25m²) and at an intermediate tidal range. Each sampled particle was characterized by morphometric data (e.g. size, shape, color, roughness) and polymer identification was performed by ATR-FTIR technique. Results show that MP concentration was higher on the beach located at the mouth of the bay (36.0 ± 39.2 MP.m^-2) than at the back and the outside of the bay (respectively 2.7 ± 4.4 and 1.7 ± 2.4 MP.m^-2). This may be related to the strong currents at the entry of the embayment and the beach orientation, exposed to predominant winds. Beached MP were mainly pre-production pellets and fragments as they represented respectively 49% and 39% of all analyzed shapes. Polymers with low density were particularly abundant. Polyethylene represented 69% of all the particles while polypropylene accounted for 17% and polystyrene for 10%. We also observed that MP were mostly washed up when wind, waves and river flow were more intense. Analysis suggest that wind direction and speed are key factors influencing beaching as strong onshore wind enhance this process.

Plasmon Waveguide Resonance: Principles, Applications and Historical Perspectives on Instrument Development

Plasmon waveguide resonance (PWR) is a variant of surface plasmon resonance (SPR) that was invented about two decades ago at the University of Arizona. In addition to the characterization of the kinetics and affinity of molecular interactions, PWR possesses several advantages relative to SPR, namely, the ability to monitor both mass and structural changes. PWR allows anisotropy information to be obtained and is ideal for the investigation of molecular interactions occurring in anisotropic-oriented thin films. In this review, we will revisit main PWR applications, aiming at characterizing molecular interactions occurring (1) at lipid membranes deposited in the sensor and (2) in chemically modified sensors. Among the most widely used applications is the investigation of G-protein coupled receptor (GPCR) ligand activation and the study of the lipid environment’s impact on this process. Pioneering PWR studies on GPCRs were carried out thanks to the strong and effective collaboration between two laboratories in the University of Arizona leaded by Dr. Gordon Tollin and Dr. Victor J. Hruby. This review provides an overview of the main applications of PWR and provides a historical perspective on the development of instruments since the first prototype and continuous technological improvements to ongoing and future developments, aiming at broadening the information obtained and expanding the application portfolio.

Microfluidic diffusional sizing probes lipid nanodiscs formation

The biophysical characterisation of membrane proteins and their interactions with lipids in native membrane habitat remains a major challenge. Indeed, traditional solubilisation procedures with detergents often causes the loss of native lipids surrounding membrane proteins, which ultimately impacts structural and functional properties. Recently, copolymer-based nanodiscs have emerged as a highly promising tool, thanks to their unique ability of solubilising membrane proteins directly from native membranes, in the shape of discoidal patches of lipid bilayers. While this methodology finally set us free from the use of detergents, some limitations are however associated with the use of such copolymers. Among them, one can cite the tedious control of the nanodiscs size, their instability in basic pH and in the presence of divalent cations. In this respect, many variants of the widely used Styrene Maleic Acid (SMA) copolymer have been developed to specifically address those limitations. With the multiplication of new SMA copolymer variants and the growing interest in copolymer-based nanodiscs for the characterisation of membrane proteins, there is a need to better understand and control their formation. Among the techniques used to characterise the solubilisation of lipid bilayer by amphipathic molecules, cryo-TEM, ³¹P NMR, DLS, ITC and fluorescence spectroscopy are the most widely used, with a consensus made in the sense that a combination of these techniques is required. In this work, we propose to evaluate the capacity of Microfluidic Diffusional Sizing (MDS) as a new method to follow copolymer nanodiscs formation. Originally designed to determine protein size through laminar flow diffusion, we present a novel application along with a protocol development to observe nanodiscs formation by MDS. We show that MDS allows to precisely measure the size of nanodiscs, and to determine the copolymer/lipid ratio at the onset of solubilisation. Finally, we use MDS to characterise peptide/nanodisc interaction. The technique shows a promising ability to highlight the pivotal role of lipids in promoting interactions through a case study with an aggregating peptide. This confirmed the relevance of using the MDS and nanodiscs as biomimetic models for such investigations.

Putative interaction site for membrane phospholipids controls activation of TRPA1 channel at physiological membrane potentials

The transient receptor potential ankyrin 1 (TRPA1) channel is a polymodal sensor of environmental irritant compounds, endogenous proalgesic agents, and cold. Upon activation, TRPA1 channels increase cellular calcium levels via direct permeation and trigger signaling pathways that hydrolyze phosphatidylinositol-4,5-bisphosphate (PIP₂ ) in the inner membrane leaflet. Our objective was to determine the extent to which a putative PIP₂ -interaction site (Y1006-Q1031) is involved in TRPA1 regulation. The interactions of two specific peptides (L992-N1008 and T1003-P1034) with model lipid membranes were characterized by biophysical approaches to obtain information about affinity, peptide secondary structure, and peptide effect in the lipid organization. The results indicate that the two peptides interact with lipid membranes only if PIP₂ is present and their affinities depend on the presence of calcium. Using whole-cell electrophysiology, we demonstrate that mutation at F1020 produced channels with faster activation kinetics and with a rightward shifted voltage-dependent activation curve by altering the allosteric constant that couples voltage sensing to pore opening. We assert that the presence of PIP₂ is essential for the interaction of the two peptide sequences with the lipid membrane. The putative phosphoinositide-interacting domain comprising the highly conserved F1020 contributes to the stabilization of the TRPA1 channel gate.

Alanine screening mutagenesis establishes the critical inactivating damage of irradiated E. coli lactose repressor

The function of the E. coli lactose operon requires the binding of lactose repressor to operator DNA. We have previously shown that γ rradiation destabilizes the repressor-operator complex because the repressor loses its DNA-binding ability. It was suggested that the observed oxidation of the four tyrosines (Y7, Y12, Y17, Y47) and the concomitant structural changes of the irradiated DNA-binding domains (headpieces) could be responsible for the inactivation. To pinpoint the tyrosine whose oxidation has the strongest effect, four headpieces containing the product of tyrosine oxidation, 3,4-dihydroxyphenylalanine (DOPA), were simulated by molecular dynamics. We have observed that replacing Y47 by DOPA triggers the largest change of structure and stability of the headpiece and have concluded that Y47 oxidation is the greatest contributor to the decrease of repressor binding to DNA. To experimentally verify this conclusion, we applied the alanine screening mutagenesis approach. Tetrameric mutated repressors bearing an alanine instead of each one of the tyrosines were prepared and their binding to operator DNA was checked. Their binding ability is quite similar to that of the wild-type repressor, except for the Y47A mutant whose binding is strongly reduced. Circular dichroism determinations revealed small reductions of the proportion of α helices and of the melting temperature for Y7A, Y12A and Y17A headpieces, but much larger ones were revealed for Y47A headpiece. These results established the critical role of Y47 oxidation in modifying the structure and stability of the headpiece, and in reduction of the binding ability of the whole lactose repressor.

Isoquinoline-based lanthanide complexes: bright NIR optical probes and efficient MRI agents

In the objective of developing ligands that simultaneously satisfy the requirements for MRI contrast agents and near-infrared emitting optical probes that are suitable for imaging, three isoquinoline-based polyaminocarboxylate ligands, L1, L2 and L3, have been synthesized and the corresponding Gd(3+), Nd(3+) and Yb(3+) complexes investigated. The specific challenge of the present work was to create NIR emitting agents which (i) have excitation wavelengths compatible with biological applications and (ii) are able to emit a sufficient number of photons to ensure sensitive NIR detection for microscopic imaging. Here we report the first observation of a NIR signal arising from a Ln(3+) complex in aqueous solution in a microscopy setup. The lanthanide complexes have high thermodynamic stability (log K(LnL) =17.7-18.7) and good selectivity for lanthanide ions versus the endogenous cations Zn(2+), Cu(2+), and Ca(2+) thus preventing transmetalation. A variable temperature and pressure (17)O NMR study combined with nuclear magnetic relaxation dispersion measurements yielded the microscopic parameters characterizing water exchange and rotation. Bishydration of the lanthanide cation in the complexes, an important advantage to obtain high relaxivity for the Gd(3+) chelates, has been demonstrated by (17)O chemical shifts for the Gd(3+) complexes and by luminescence lifetime measurements for the Yb(3+) analogues. The water exchange on the three Gd(3+) complexes is considerably faster (k(ex)(298) = (13.9-15.4) × 10(6) s(-1)) than on commercial Gd(3+)-based contrast agents and proceeds via a dissociative mechanism, as evidenced by the large positive activation volumes for GdL1 and GdL2 (+10.3 ± 0.9 and +10.6 ± 0.9 cm(3) mol(-1), respectively). The relaxivity of GdL1 is doubled at 40 MHz and 298 K in fetal bovine serum (r(1) = 16.1 vs 8.5 mM(-1) s(-1) in HEPES buffer), due to hydrophobic interactions between the chelate and serum proteins. The isoquinoline core allows for the optimization of the optical properties of the luminescent lanthanide complexes in comparison to the pyridinic analogues and provides significant shifts of the excitation energies toward lower values which therefore become more adapted for biological applications. L2 and L3 bear two methoxy substituents on the aromatic core in ortho and para positions, respectively, that further modulate their electronic structure. The Nd(3+) and Yb(3+) complexes of the ligand L3, which incorporates the p-dimethoxyisoquinoline moiety, can be excited up to 420 nm. This wavelength is shifted over 100 nm toward lower energy in comparison to the pyridine-based analogue. The luminescence quantum yields of the Nd(3+) (0.013-0.016%) and Yb(3+) chelates (0.028-0.040%) are in the range of the best nonhydrated complexes, despite the presence of two inner sphere water molecules. More importantly, the 980 nm NIR emission band of YbL3 was detected with a good sensitivity in a proof of concept microscopy experiment at a concentration of 10 μM in fetal bovine serum. Our results demonstrate that even bishydrated NIR lanthanide complexes can emit a sufficient number of photons to ensure sensitive detection in practical applications. In particular, these ligands containing an aromatic core with coordinating pyridine nitrogen can be easily modified to tune the optical properties of the NIR luminescent lanthanide complexes while retaining good complex stability and MRI characteristics for the Gd(3+) analogues. They constitute a highly versatile platform for the development of bimodal MR and optical imaging probes based on a simple mixture of Gd(3+) and Yb(3+)/Nd(3+) complexes using an identical chelator. Given the presence of two inner sphere water molecules, important for MRI applications of the corresponding Gd(3+) analogues, this result is particularly exciting and opens wide perspectives not only for NIR imaging based on Ln(3+) ions but also for the design of combined NIR optical and MRI probes.

Diffusion of ofloxacin in the endocarditis vegetation assessed with synchrotron radiation UV fluorescence microspectroscopy

The diffusion of antibiotics in endocarditis vegetation bacterial masses has not been described, although it may influence the efficacy of antibiotic therapy in endocarditis. The objective of this work was to assess the diffusion of ofloxacin in experimental endocarditis vegetation bacterial masses using synchrotron-radiation UV fluorescence microspectroscopy. Streptococcal endocarditis was induced in 5 rabbits. Three animals received an unique IV injection of 150 mg/kg ofloxacin, and 2 control rabbits were left untreated. Two fluorescence microscopes were coupled to a synchrotron beam for excitation at 275 nm. A spectral microscope collected fluorescence spectra between 285 and 550 nm. A second, full field microscope was used with bandpass filters at 510–560 nm. Spectra of ofloxacin-treated vegetations presented higher fluorescence between 390 and 540 nm than control. Full field imaging showed that ofloxacin increased fluorescence between 510 and 560 nm. Ofloxacin diffused into vegetation bacterial masses, although it accumulated in their immediate neighborhood. Fluorescence images additionally suggested an ofloxacin concentration gradient between the vegetation peripheral and central areas. In conclusion, ofloxacin diffuses into vegetation bacterial masses, but it accumulates in their immediate neighborhood. Synchrotron radiation UV fluorescence microscopy is a new tool for assessment of antibiotic diffusion in the endocarditis vegetation bacterial masses.

Synchrotron UV fluorescence microscopy uncovers new probes in cells and tissues

Use of deep ultraviolet (DUV, below 350 nm) fluorescence opens up new possibilities in biology because it does not need external specific probes or labeling but instead allows use of the intrinsic fluorescence that exists for many biomolecules when excited in this wavelength range. Indeed, observation of label free biomolecules or active drugs ensures that the label will not modify the biolocalization or any of its properties. In the past, it has not been easy to accomplish DUV fluorescence imaging due to limited sources and to microscope optics. Two worlds were coexisting: the spectrofluorometric measurements with full spectrum information with DUV excitation, which lacked high-resolution localization, and the microscopic world with very good spatial resolution but poor spectral resolution for which the wavelength range was limited to 350 nm. To combine the advantages of both worlds, we have developed a DUV fluorescence microscope for cell biology coupled to a synchrotron beamline, providing fine tunable excitation from 180 to 600 nm and full spectrum acquired on each point of the image, to study DUV excited fluorescence emitted from nanovolumes directly inside live cells or tissue biopsies.

Locally advanced breast cancer patients with negative pathological lymph node status after neoadjuvant chemotherapy and conservative surgery: Is lymph node irradiation necessary?

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Background: The increased use of neoadjuvant chemotherapy (CT) in breast cancer (BC) management has raised new questions regarding the optimal locoregional treatment. The aim of this retrospective study was to compare the outcomes of BC patients (pts) with pathological N0 status (pN0) following primary CT and conservative surgery who received breast radiotherapy with or without lymph node irradiation. Methods: Between 1990 and 2004, 1054 patients received preoperative CT for locally advanced BC. Data from 248 pts (23.5%) with clinical N0 (164 pts) or N1-N2 (84 pts) lymph node status at diagnosis and pN0 status after primary CT were studied. Among them, 93 pts (37.5%) received breast irradiation alone and 155 pts (62.5%) underwent locoregional irradiation. Outcome was assessed in relation to lymph node recurrence, disease-free survival (DFS) and overall survival (OS). Results: Both groups were comparable in terms of baseline characteristics. With a median follow-up of 88 months, 3 pts experienced nodal recurrence in the breast irradiation alone group compared with 2 pts in the locoregional irradiation group (p>.05). Among the 164 N0 pN0 pts, the 5-year DFS and OS rates were respectively 84% and 89% vs 84% and 95%, according to whether they received (n=87) or not (n=77) lymph node irradiation(p>.05). Among the 84 N1-N2 pN0 pts, same outcome values did not show any significant difference according to group of treatment: 72% and 88% in 68 pts treated with locoregional irradiation vs 81% and 81% in 16 pts treated with breast irradiation alone (p>.05). Conclusions: Our results suggest that breast irradiation alone is not associated with a higher risk of regional recurrence in locally advanced BC pts with pN0 status after neoadjuvant chemotherapy. Whether this allows the omission of lymph node irradiation for such strategy should be addressed prospectively.

No significant financial relationships to disclose.

Use of ruthenium dyes for subnanosecond detector fidelity testing in real time transient absorption

Transient absorption spectroscopy is a powerful tool for the study of photoreactions on time scales from femtoseconds to seconds. Typically, reactions slower than approximately 1 ns are recorded by the "classical" technique; the reaction is triggered by an excitation flash, and absorption changes accompanying the reaction are recorded in real time using a continuous monitoring light beam and a detection system with sufficiently fast response. The pico- and femtosecond region can be accessed by the more recent "pump-probe" technique, which circumvents the difficulties of real time detection on a subnanosecond time scale. This is paid for by accumulation of an excessively large number of shots to sample the reaction kinetics. Hence, it is of interest to extend the classical real time technique as far as possible to the subnanosecond range. In order to identify and minimize detection artifacts common on a subnanosecond scale, like overshoot, ringing, and signal reflections, rigorous testing is required of how the detection system responds to fast changes of the monitoring light intensity. Here, we introduce a novel method to create standard signals for detector fidelity testing on a time scale from a few picoseconds to tens of nanoseconds. The signals result from polarized measurements of absorption changes upon excitation of ruthenium complexes {[Ru(bpy)(3)](2+) and a less symmetric derivative} by a short laser flash. Two types of signals can be created depending on the polarization of the monitoring light with respect to that of the excitation flash: a fast steplike bleaching at magic angle and a monoexponentially decaying bleaching for parallel polarizations. The lifetime of the decay can be easily varied via temperature and viscosity of the solvent. The method is applied to test the performance of a newly developed real time transient absorption setup with 300 ps time resolution and high sensitivity.

Pyridine-based lanthanide complexes: towards bimodal agents operating as near infrared luminescent and MRI reporters

We report two prototype Ln(3+) complexes that address requirements for both MRI and luminescence imaging and we demonstrate that the presence of two H(2)O molecules bound to the Ln(3+), beneficial for MRI applications of the Gd(3+) analogue, is not a major limitation for the development of NIR luminescent agents.

[Accelerated partial breast irradiation: a concept to individualize treatment in breast cancer]

Whole breast irradiation delivering an equivalent dose of 50 Gy in 5 weeks, followed by a 10 to 16 Gy-boost to the tumor bed is the standard of care after breast-conserving surgery for early-breast cancer. Accelerated partial breast irradiation (APBI) is currently under investigations in large multi-institutional, prospective, randomized trials to objectively address the critical endpoints of treatment efficacy, toxicity and cosmesis. Patient's selection for this new approach is crucial to individualise treatments and define the subgroups of patients who will really benefit from APBI in terms of quality of life without decreasing long-term results of the disease control and cosmesis. In this review, we will discuss the patients' profiles selection for APBI regarding their general and tumor criteria. The differences between APBI techniques either performed intra or post operatively will be also discussed.

Role of the middle residue in the triple tryptophan electron transfer chain of DNA photolyase: ultrafast spectroscopy of a Trp-->Phe mutant

Photoreduction of the semi-reduced flavin adenine dinucleotide cofactor FADH* in DNA photolyase from Escherichia coli into FADH- involves three tryptophan (W) residues that form a closely spaced electron-transfer chain FADH*-W382-W359-W306. To investigate this process, we have constructed a mutant photolyase in which W359 is replaced by phenylalanine (F). Monitoring its photoproducts by femtosecond spectroscopy, the excited-state FADH* was found to decay in approximately 30 ps, similar as in wild type (WT) photolyase. In contrast to WT, however, in W359F mutant photolyase the ground-state FADH* fully recovered virtually concomitantly with the decay of its excited state and, despite the presence of the primary electron donor W382, no measurable flavin reduction was observed at any time. Thus, W359F photolyase appears to behave like many other flavoproteins, where flavin excited states are quenched by very short-lived oxidation of aromatic residues. Our analysis indicates that both charge recombination of the primary charge separation state FADH-W382*+ and (in WT) electron transfer from W359 to W382*+ occur with time constants <4 ps, considerably faster than the initial W382-->FADH* electron-transfer step. Our results provide a first experimental indication that electron transfer between aromatic residues can take place on the time scale of approximately 10(-12) s.

Observation of an intermediate tryptophanyl radical in W306F mutant DNA photolyase from Escherichia coli supports electron hopping along the triple tryptophan chain

DNA photolyases repair UV-induced cyclobutane pyrimidine dimers in DNA by photoinduced electron transfer. The redox-active cofactor is FAD in its doubly reduced state FADH-. Typically, during enzyme purification, the flavin is oxidized to its singly reduced semiquinone state FADH degrees . The catalytically potent state FADH- can be reestablished by so-called photoactivation. Upon photoexcitation, the FADH degrees is reduced by an intrinsic amino acid, the tryptophan W306 in Escherichia coli photolyase, which is 15 A distant. Initially, it has been believed that the electron passes directly from W306 to excited FADH degrees , in line with a report that replacement of W306 with redox-inactive phenylalanine (W306F mutant) suppressed the electron transfer to the flavin [Li, Y. F., et al. (1991) Biochemistry 30, 6322-6329]. Later it was realized that two more tryptophans (W382 and W359) are located between the flavin and W306; they may mediate the electron transfer from W306 to the flavin either by the superexchange mechanism (where they would enhance the electronic coupling between the flavin and W306 without being oxidized at any time) or as real redox intermediates in a three-step electron hopping process (FADH degrees * <-- W382 <-- W359 <-- W306). Here we reinvestigate the W306F mutant photolyase by transient absorption spectroscopy. We demonstrate that electron transfer does occur upon excitation of FADH degrees and leads to the formation of FADH- and a deprotonated tryptophanyl radical, most likely W359 degrees. These photoproducts are formed in less than 10 ns and recombine to the dark state in approximately 1 micros. These results support the electron hopping mechanism.

MammoSite brachytherapy for low-risk breast carcinoma: Toxicity, cosmetic evaluation and quality-of-life results of a phase II study

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Background: The MammoSite is a device that was developed with the goal of making breast-conserving surgery more widely available. Our objective was to evaluate the MammoSite device performances after an open cavity placement procedure and quality of life in highly selected patients with early-stage breast cancer. Methods: From March 2003 to March 2005, 43 patients with T1 breast cancer were enrolled in a phase II prospective study. Twenty-five (58%) patients were qualified for HDR brachytherapy delivery. The median age was 72 years (range: 60–75). Twenty-five (58%) were treated with high-dose rate brachytherapy using the MammoSite applicator to deliver 34 Gy prescribed at 1 cm from the balloon surface in 10 fractions over 5 to 8 days. Results: The main disqualifying factor was pathologic sentinel node involvement. After a median follow-up of 13 months, there were no local recurrences. Seventeen (68%), 13 (52%), 7 (28%), 5 (20%) and 4 (16%) patients had erythema, seroma, inflammation, hematoma and infection, respectively. Only 2 patients developed telangiectasia. At 3 months breast erythema grade ≥ 2 was significantly correlated to cosmetic results (12.5% in the ‘good to excellent‘ versus 57% in the ‘poor to fair‘ group; p = 0.045). The strongest trend of excellent cosmetic outcome was observed in patients with skin spacing ≥ 19 mm (50%) compared to patients with < 19 mm (11%; p = 0.087). At 1 year the rate of ‘good to excellent‘ cosmetic results was 84%. Significant changes in QoL were observed for emotional and social well-being between 3 and 12 months. At 24 months only emotional well-being subscore changes were statistically significant (p = 0.015). Param Conclusions: To our knowledge, this is the first study since the initial FDA clinical study showing the feasibility of MammoSite brachytherapy procedure as a sole therapy in highly selected patients older than 60 years. This is also the first report on QoL during and after APBI using HDR brachytherapy with a MammoSite device. The toxicity and cosmetic results are in the range of other series. Higher range of skin spacing allowed a significant reduction of the risk of telangiectasia. QoL evaluation indicate that baseline scores were satisfactory. Changes concerned mainly emotional and social well-being.

No significant financial relationships to disclose.

Ultraviolet-induced autofluorescence characterization of normal and tumoral esophageal epithelium cells with quantitation of NAD(P)H

Cellular autofluorescence was characterized in normal human esophageal cells and in malignant esophageal epithelial cells. The study was performed under excitation at 351 nm where the cell fluorescence is mainly due to the reduced pyridine nucleotides (NAD(P)H) with a very small contribution from the oxidized flavins (FMN, FAD) or lipopigments. The autofluorescence emission of squamous cell carcinoma, adenocarcinoma on Barrett's mucosa and normal cells was characterized by microspectrofluorimetry on monolayers and by spectrofluorimetry on cell suspensions. The relative contribution of each fluorophore to the fluorescence emission of the different cell types was evaluated by a curve-fitting analysis. A statistically highly significant difference was observed between the average intensity of the raw spectra of the different cell types. Tumoral cells had a fluorescence intensity approximately twice as high as that of normal cells. The results of the NAD(P)H quantitation analyzed by microspectrofluorimetry on single living cells and spectrofluorimetry on cell suspensions were consistent with those obtained by biochemical cycling assays, showing that the amount of intracellular NAD(P)H is higher in tumoral cells than in normal cells. Bound NAD(P)H concentration was found to be quite stable whatever the cell type while the amount of free NAD(P)H showed a very important increase in tumoral cells.

[Partial breast irradiation: high dose rate peroperative brachytherapy technique using the MammoSite]

In the conservative management of breast cancer, radiation therapy delivering 45 to 50 Gy to the whole breast, in 4.5 to 5 weeks, followed by a booster dose of 10 to 20 Gy is the standard of care. Based on the numerous studies which have reported that the local recurrences occurs within and surrounding the primary tumor site and in order to decrease the treatment duration and its morbidity, partial breast irradiation using several techniques has been developed. Partial irradiation may be considered as an alternative local adjuvant treatment for selected patients with favorable prognostic factors. Using external beam radiation therapy, the 3D-conformal technique is appropriate to deliver the whole dose to a limited volume. In UK, an intraoperative technique using a miniature beam of low energy of x-ray (50 Kv) has been developed (Targit). Milan's team have developed an intraoperative electrons beam radiotherapy using a dedicated linear accelerator in the operative room. In USA and Canada the MammoSite has been advised for clinical use in per-operative brachytherapy of the breast. These two last techniques are currently compared in phase III randomised studies to the standard whole breast irradiation followed by a tumour bed booster dose. In this review we will focus on the MammoSite technique and will describe the per-operative implantation procedure, radiological controls ad dosimetric aspects.

Approximate Solution for the Spreading of a Droplet on a Smooth Solid Surface

The same approach used by Boender, Chesters, and van der Zanden in the context of an advancing liquid-gas meniscus in a capillary tube is extended to the case of spontaneous spreading of a droplet on an ideal solid surface. The result is an ordinary differential equation for the droplet profile which can be solved if the meniscus inclination phi0 is specified at some distance lambda from the solid. As in the capillary-tube case, good agreement is obtained with experimental data obtained by the authors and by others if phi0 is set equal to the static contact angle (zero in cases investigated experimentally), taking lambda of the order of a molecular dimension (1 nm). A comparison of predicted dynamic contact angles in the spreading-drop and capillary-tube cases for given values of the capillary number indicates only a weak dependence of the behavior on the system geometry. De Gennes and co-workers have predicted that during the final stages of spreading the inner length scale lambda should be determined by the effects of disjoining pressure in the thin film adjacent to the contact line rather than by molecular dimensions. The lambda value implied by their model is derived, thereby establishing the regime of spreading in which such effects should be dominant. The observed behavior in this regime is found to correspond somewhat better with a lambda value of the order of a molecular dimension, although the differences are small. Although the explanation probably lies in the nonideality of even the smoothest surfaces, this result suggests that the simplest model, based on a single lambda value of the order of 1 nm, should provide an excellent predictive tool. Copyright 1998 Academic Press.

Thyroid stimulating hormone and selenium supply interact to regulate selenoenzyme gene expression in thyroid cells (FRTL-5) in culture

In the absence of a sodium selenite supplement, FRTL-5 cells showed a reduced activity of cytosolic glutathione peroxidase (cGSH-Px), a marker of selenium status, indicating the cells were Se-deficient. Se-deficient cells showed a 65% reduction in cGSH-Px mRNA abundance but little change in abundance of either phospholipid hydroperoxide glutathione peroxidase or type 1 deiodinase (IDI) mRNA. In Se-replete cells increased thyroid stimulating hormone (TSH) caused a small decrease in IDI abundance but in Se-deficient cells TSH caused a large increase. The results indicate an interaction between TSH and Se status in the regulation of thyroid selenoenzyme synthesis.