Intensity statistics of Friedel opposites.

A previous analysis of the average intensity and mean-square intensity difference of Friedel opposites, confined to the space group P1 [Flack & Shmueli (2007). Acta Cryst. A63, 257-265], is here extended to all the non-centrosymmetric space groups. The present analysis presumes purely non-centrosymmetric content of the unit cell. An important result of this study is that the average intensity and mean-square intensity difference of Friedel opposites have the same values for all the non-centrosymmetric space groups as those previously obtained for the triclinic space group P1. The ratios of average intensity and root-mean-square intensity difference to their triclinic equivalents were derived and exemplified for general as well as for special reflections. For the latter, enhancements were obtained which are shown to be due to those of average intensity and not to a mechanism related to Friedel opposites being explicitly considered.

Using X-ray absorption spectra to monitor specific radiation damage to anomalously scattering atoms in macromolecular crystallography.

Radiation damage in macromolecular crystals is not suppressed even at 90 K. This is particularly true for covalent bonds involving an anomalous scatterer (such as bromine) at the 'peak wavelength'. It is shown that a series of absorption spectra recorded on a brominated RNA faithfully monitor the extent of cleavage. The continuous spectral changes during irradiation preserve an 'isosbestic point', each spectrum being a linear combination of 'zero' and 'infinite' dose spectra. This easily yields a good estimate of the partial occupancy of bromine at any intermediate dose. The considerable effect on the near-edge features in the spectra of the crystal orientation versus the beam polarization has also been examined and found to be in good agreement with a previous study. Any significant influence of the (C-Br bond/beam polarization) angle on the cleavage kinetics of bromine was also searched for, but was not detected. These results will be useful for standard SAD/MAD experiments and for the emerging 'radiation-damage-induced phasing' method exploiting both the anomalous signal of an anomalous scatterer and the 'isomorphous' signal resulting from its cleavage.

Modelling and refining site-specific radiation damage in SAD/MAD phasing.

Site-specific radiation damage on anomalously scattering sites can be used to generate additional phase information in standard single- or multi-wavelength anomalous diffraction (SAD or MAD) experiments. In this approach the data are kept unmerged, down to the Harker construction, and the evolution of site-specific radiation damage as a function of X-ray irradiation is explicitly modelled and refined in real space. Phasing power is generated through the intensity differences of symmetry-related reflections or repeated measurements of the same reflection recorded at different X-ray doses. In the present communication the fundamentals of this approach are reviewed and different models for the description of site-specific radiation damage are presented. It is shown that, in more difficult situations, overall radiation damage may unfold on a time scale that is similar to the evolution of site-specific radiation damage or to the total time that is required to record a complete data set. In such cases the quality of the phases will ultimately be limited by the effects of overall radiation damage.

Laparoscopic Roux-en-Y gastric bypass versus laparoscopic vertical banded gastroplasty: results of a 2-year follow-up study.

BACKGROUND: The world's epidemic of obesity is responsible for the development of bariatric surgery in recent decades. The number of gastrointestinal surgeries performed annually for severe obesity (BMI > 40 kg/m2) in the United States has increased from about 16,000 in the early 1990s to about 103,000 in 2003. The surgical techniques can be classified as restrictive, malabsorptive, or mixed procedures. This article presents the results for 2 years of bariatric surgery in the authors' minimally invasive center and analyzes the results of the most used surgical techniques with regard to eating habits. METHODS: Between January 2002 and January 2004, the authors attempted operations for morbid obesity in 110 consecutive patients adequately selected by a multidisciplinary obesity unit. This represented 43% of all consultations for morbidly obese patients. The patients were classified as sweet eaters or non-sweet eaters. All sweet eaters underwent gastric bypass. The procedures included 70 Roux-en-Y gastric bypasses, 39 Mason's vertical banded gastroplasties, and 1 combination of vertical gastroplasty with an antireflux procedure. Revision procedures were excluded. RESULTS: The mean age of the patients was 41.36 years (range, 23-67 years), and 72.3% were female. The mean preoperative body mass index was 44.78 kg/m2 (range, 34.75-70.16 kg/m2). The mean operating time was longer for gastric bypass than for the Mason procedure. Three patients required conversion to an open procedure (2.7%). The two operative techniques had the same efficacy in weight reduction. Early complications developed in 11 patients (10%), and late complications occurred in 9 patients (8.1%). The postoperative length of hospital stay averaged 4.4 days (range, 1-47 days; median, 4 days), and was longer in the gastric bypass group. The mortality rate was zero. Data were available 2 years after surgery for 101 of the 110 patients (91%). Most comorbid conditions resolved by 1 year after surgery regardless of the type of operation used. CONCLUSION: With zero mortality and low morbidity, bariatric surgery performed for adequately selected patients is the most effective therapeutic intervention for weight loss and subsequent amelioration or resolution of comorbidities. The patient's eating habits before surgery play an important role in the choice of the operative technique used.

Present state of the Mini-Invasive Surgery (MIS) in esophageal and gastric cancer.

The purpose of this review is to stress the role of the Mini-Invasive Surgery (MIS) in the treatment of the esophagogastric malignant illnesses, supporting ourselves on the most relevant publications of the literature as well as on our own experience in this subject. In short, although no randomised prospective study has proven the MIS advantages in relation to the traditional surgery in the esophagectomy due to cancer, some authors preferently indicate this approach to selected and informed enough patients, who present the following: - High grade dysplasia, preferently choosing from laparoscopic transhiatal esophagectomy (LTE). - Carcinoma in situ, preferently choosing the LTE vs thoracoscopy. - Esophageal tumour locally advanced, in resectable patients with contraindication for a thoracotomy or, in initially non-resectable patients with tumoral reduction after neo-adjuvant chemo-radiotherapy. The arguments given by the authors are the postoperative spectacular improvement in relation to the comfort and quality of life and, the absence of oncological negative effects in the long-term followup. Concerning gastric cancer, the MIS, as exeresis surgical tool in the so-called <> gastric forms, is such a definite and oncological approach as the traditional approach, and superior to this as far as quality of life is concerned. When the MIS is used for treating locally advanced forms of gastric cancer, it is as safe as the laparotomic way and it seems to obtain the same oncological outcomes in the long-term.

Present state of the Mini-Invasive Surgery (MIS) in esophageal and gastric cancer

No disponible

The purpose of this review is to stress the role of theMini-Invasive Surgery (MIS) in the treatment of theesophagogastric malignant illnesses, supporting ourselveson the most relevant publications of the literatureas well as on our own experience in this subject.In short, although no randomised prospective studyhas proven the MIS advantages in relation to thetraditional surgery in the esophagectomy due tocancer, some authors preferently indicate this approachto selected and informed enough patients,who present the following:− High grade dysplasia, preferently choosing fromlaparoscopic transhiatal esophagectomy (LTE).− Carcinoma in situ, preferently choosing the LTEvs thoracoscopy.− Esophageal tumour locally advanced, in resectablepatients with contraindication for a thoracotomyor, in initially non-resectable patients withtumoral reduction after neo-adjuvant chemo-radiotherapy.The arguments given by the authors are the postoperativespectacular improvement in relation to thecomfort and quality of life and, the absence of oncologicalnegative effects in the long-term followup.Concerning gastric cancer, the MIS, as exeresis surgicaltool in the so-called «advanced» gastric forms,is such a definite and oncological approach as thetraditional approach, and superior to this as far asquality of life is concerned.When the MIS is used for treating locally advancedforms of gastric cancer, it is as safe as the laparotomicway and it seems to obtain the same oncologicaloutcomes in the long-term

Vulnerability, unsafe sex and non-adherence to HAART: evidence from a large sample of French HIV/AIDS outpatients.

Current socio-behavioural research in HIV-infected people has tried to identify patients with "high-risk" profiles, i.e. who simultaneously exhibit non-adherence to highly active anti-retroviral therapy (HAART) and unsafe sex with serodiscordant partners. We challenged this approach by investigating the correlates of both behaviours, for homosexual men, heterosexual men and heterosexual women separately, among a representative sample of 4963 HIV-infected people in France. Variables introduced in the analysis dealt with patients' background and daily life, with a focus on situations of economic, social and personal vulnerability. Overall, 2932 patients agreed to participate, and 1809 were both receiving HAART and sexually active. Among heterosexual women, non-adherence and unsafe sex appeared as joint outcomes of similar situations of vulnerability. Among heterosexual men, these behaviours were weakly correlated and shared some predictors related to situations of vulnerability. Among homosexual men, non-adherence and unsafe sex were not correlated and had distinct determinants. Situations of vulnerability, the context and the motives of unsafe sex, as well as factors associated with non-adherence and unsafe sex varied greatly with gender and sexual preference. Theoretical models used for designing behavioural interventions should take into account this diversity.

Phasing in the presence of severe site-specific radiation damage through dose-dependent modelling of heavy atoms.

The case of a brominated RNA crystal structure determination in which standard three-wavelength MAD phasing was unsuccessful because of fast X-ray-induced debromination was reinvestigated [Ennifar et al. (2002), Acta Cryst. D58, 1262-1268]. It was found that if the data are kept unmerged and if a dose-stamp is associated with each reflection measurement, dose-dependent occupancies can be refined for the Br atoms. Such a parametrization has been implemented in the macromolecular phasing program SHARP. Refining such dose-dependent occupancies on an unmerged data set gave a dramatic improvement, even for SAD phases from only the first wavelength (peak), and resulted in a good electron-density map after solvent flattening. The adverse effect of radiation damage has been turned into a beneficial one. The crucial difference is made by the use of unmerged data: phasing power is generated through the intensity differences of symmetry-related reflections recorded at different doses, i.e. corresponding to different states of the X-ray-induced debromination. This approach should prove useful in all situations of experimental phasing where site-specific radiation damage occurs unavoidably and undesirably and not only in cases in which radiation damage is purposely being created in order to demonstrate its potential usefulness.

Generation, representation and flow of phase information in structure determination: recent developments in and around SHARP 2.0.

The methods for treating experimental data in the isomorphous replacement and anomalous scattering methods of macromolecular phase determination have undergone considerable evolution since their inception 50 years ago. The successive formulations used are reviewed, from the most simplistic viewpoint to the most advanced, including the exploration of some blind alleys. A new treatment is proposed and demonstrated for the improved encoding and subsequent exploitation of phase information in the complex plane. It is concluded that there is still considerable scope for further improvements in the statistical analysis of phase information, which touch upon numerous fundamental issues related to data processing and experimental design.

Dose-dependent differences in the profile of mutations induced by carcinogenic (R,S,S,R) bay- and fjord-region diol epoxides of polycyclic aromatic hydrocarbons.

Chinese hamster V79 cells were exposed to a high or low concentration of the highly carcinogenic (R,S,S,R) or the less active (S,R,R,S) bay- or fjord-region diol epoxides of benzo[a]pyrene, benzo[c]phenanthrene or dibenz[c,h]acridine. Independent 8-azaguanine-resistant clones were isolated, and base substitutions at the hypoxanthine (guanine) phosphoribosyltransferase (hprt) locus were determined. For the three (R,S,S,R) diol epoxides studied, the proportion of mutations at AT base pairs increased as the concentration of diol epoxide decreased. Concentration-dependent differences in the mutational profile were not observed, however, for the three (S,R,R,S) diol epoxides. In studies, with V-H1 cells (a DNA repair deficient variant of V79 cells), a concentration-dependent difference in the profile of mutations for the (R,S,S,R) diol epoxide of benzo[a]pyrene was not observed. These results suggest that concentration-dependent differences in the mutational profile are dependent on an intact DNA repair system. In additional studies, we initiated mouse skin with a high or low dose of benzo[a]pyrene and promoted the mice for 26 weeks with 12-O-tetradecanoylphorbol-13-acetate. Papillomas were examined for mutations in the c-Ha-ras proto-oncogene. Dose-dependent differences in the profile of c-Ha-ras mutations in the tumors were observed. In summary, (i) dose-dependent differences in mutational profiles at the hprt locus were observed in Chinese hamster V79 cells treated with several highly mutagenic and carcinogenic (R,S,S,R) bay- or fjord-region diol epoxides but not with their less active (S,R,R,S) diol epoxide enantiomers, (ii) a dose-dependent difference in the mutational profile was not observed for the (R,S,S,R) diol epoxide of benzo[a]pyrene in a DNA-repair defective V79 cell line, and (iii) a dose-dependent difference in the mutational profile in the c-Ha-ras proto-oncogene was observed in tumors from mice treated with a high or low dose of benzo[a]pyrene.

HIV-positive people, risk and sexual behaviour.

For a long time, the sexual behaviour of HIV-infected persons did not receive any serious attention for a variety of reasons. Initially, diagnosis of HIV-infection appeared to imply a death sentence. In this context, the sex life of those infected seemed a secondary issue making prevention focused on sexual behaviour hard to imagine. Furthermore, the conviction that stigmatisation should be avoided also precluded an interest in the sexual behaviour of HIV-infected persons. From an epidemiological perspective and in the context of the developments in the medical treatment of AIDS it is important to address the sexuality of HIV-infected people. The scarce research done until now shows that there are various ways in which an HIV-infection affects people's sexuality. It seems that the sexuality of HIV-infected people can be compromised by their infection, inducing various sexual problems. Research also shows that there are HIV-infected people who do engage in unprotected sex, just as there are HIV-negative people or people with unknown serostatus who do so. Studies into the determinants of unsafe sex in HIV-infected people suggest that to some extent the same determinants are operative as among people in general. These include intention and self-efficacy regarding safe sex. Recreational drug use also affects safe sex regardless of serostatus. However, safe sex as well as sex in general is different for seropositive persons than for people who are seronegative or have an unknown serostatus. Among seropositive people, sex is also related to dilemma's involving disclosing their serostatus to potential sex partners, and their motivation to protect their partners as well as themselves against surinfection and STD. Furthermore, having to cope with a serious disease induces negative mood states (particularly depression) and may compromise sexual functioning. Comprehensive prevention aimed at HIV infected persons should address these various issues and should be an integrated part of general HIV-prevention.

Characterization of the mutational profile of (+)-7R,8S-dihydroxy-9S, 10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene at the hypoxanthine (guanine) phosphoribosyltransferase gene in repair-deficient Chinese hamster V-H1 cells.

Earlier studies have shown that the profile of mutations induced by (+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (+)-BPDE at the hypoxanthine (guanine) phosphoribosyltransferase (hprt) gene of Chinese hamster V79 cells was dependent on the concentration of (+)-BPDE. In the present study, we examined the effect of the concentration of (+)-BPDE on its mutational profile at the hprt gene in repair-deficient V-H1 cells (a derivative of V79 cells) to explore the role of DNA repair in the dose-dependent mutational profile of (+)-BPDE. Independent hprt mutant clones were isolated after exposing V-H1 cells to dimethylsulfoxide (DMSO) or to low (4-6 nM; 95% cell survival) or high (40-48 nM; 31% cell survival) concentrations of (+)-BPDE in DMSO. The mutation frequencies for the DMSO control and for the low and high concentration groups were 0.1, 2.1 and 32.9 mutant colonies/10(5) survivors, respectively. The profile of mutations at the hprt gene was characterized for 148 (+)-BPDE-induced mutant clones and the results from the present study were compared with those obtained earlier with V79 cells. The data indicated that: (i) V-H1 cells were approximately 9-fold more sensitive to the cytotoxic effects of (+)-BPDE than V79 cells; (ii) the mutation frequency in V-H1 cells was similar to that observed in V79 cells following exposure to similar concentrations of (+)-BPDE; (iii) (+)-BPDE-induced mutations at guanine on the transcribed strand of the hprt gene were common in V-H1 cells but were extraordinarily rare in V79 cells; (iv) (+)-BPDE-induced mutations at adenine on the transcribed strand of the hprt gene were common in both V-H1 and V79 cells; (v) although exposure of V79 cells to different doses of (+)-BPDE resulted in a dose-dependent mutational profile at the hprt gene, this was not observed in V-H1 cells. Our observations indicate a defect in the transcription-coupled repair of (+)-BPDE-DNA adducts in V-H1 cells and that the repair activity deficient in V-H1 cells is essential for the dose-dependent mutational profile observed with (+)-BPDE in V79 cells.

Exploring hydrophobic sites in proteins with xenon or krypton.

X-ray diffraction is used to study the binding of xenon and krypton to a variety of crystallised proteins: porcine pancreatic elastase; subtilisin Carlsberg from Bacillus licheniformis; cutinase from Fusarium solani; collagenase from Hypoderma lineatum; hen egg lysozyme, the lipoamide dehydrogenase domain from the outer membrane protein P64k from Neisseria meningitidis; urate-oxidase from Aspergillus flavus, mosquitocidal delta-endotoxin CytB from Bacillus thuringiensis and the ligand-binding domain of the human nuclear retinoid-X receptor RXR-alpha. Under gas pressures ranging from 8 to 20 bar, xenon is able to bind to discrete sites in hydrophobic cavities, ligand and substrate binding pockets, and into the pore of channel-like structures. These xenon complexes can be used to map hydrophobic sites in proteins, or as heavy-atom derivatives in the isomorphous replacement method of structure determination.

Young homosexual itineraries in the context of HIV: establishing lifestyles.

PIP: "This article analyses the itineraries of young male homo/bisexuals based on a survey conducted in the gay press [in France] in 1995.... Young homosexuals have to face the double problem of finding a place in a circle of tolerant relations and creating a way of life which will allow a full development of their sexual orientation. To this there is now added a dramatic epidemiological context, in the form of the very high incidence of HIV in this group.... General population studies are used to examine whether the process whereby young homosexuals become autonomous is similar to that of other young people and to what extent their trajectory is influenced by their marginal sexuality." (EXCERPT)^ieng

Crystal structure of the protein drug urate oxidase-inhibitor complex at 2.05 A resolution.

The gene coding for urate oxidase, an enzyme that catalyzes the oxidation of uric acid to allantoin, is inactivated in humans. Consequently, urate oxidase is used as a protein drug to overcome severe disorders induced by uric acid accumulation. The structure of the active homotetrameric enzyme reveals the existence of a small architectural domain that we call T-fold (for tunnelling-fold) domain. It assembles to form a perfect unusual dimeric alpha 8 beta 16 barrel. Urate oxidase may be the archetype of an expanding new family of tunnel-shaped proteins that now has three members; tetrahydropterin synthase, GTP cyclohydrolase I and urate oxidase. The structure of the active site of urate oxidase around the 8-azaxanthine inhibitor reveals an original mechanism of oxidation that does not require any ions or prosthetic groups.

Molecular structure of the lipoamide dehydrogenase domain of a surface antigen from Neisseria meningitidis.

The protein p64k from the surface of the Neisseria meningitidis bacteria has been characterized as a two-domain protein. It contains a dihydrolipoamide dehydrogenase domain of 482 residues, involving a FAD prosthetic group as a cofactor, and a smaller lipoic acid binding domain of 86 residues. The two domains are joined by a flexible segment rich in alanine and proline residues. The structure of the dihydrolipoamide dehydrogenase domain was determined by X-ray diffraction. It was solved by a combination of molecular replacement and multiple isomorphous replacement techniques and refined to 2.7 A resolution. In the crystal, the recombinant p64k mimics the functional homo-dimer by using one of the crystallographic 2-fold axes. The reactive disulphide bridge Cys161-Cys166 is in the oxidised state and the FAD is bound in an extended conformation. This main domain contains the major antigenic determinant of the protein, an extended loop of 32 residues at the surface of the protein. A mis-attribution at residue 553 in the sequence has been detected by inspection of electron density maps and the geometry. However, when compared to the other dihydrolipoamide dehydrogenases, there are some significant differences: (1) an unusual number of cis-proline residues and (2) a new motif built around a 2-fold axis by the sulphur atoms of residues Met558, Cys560 and their symmetry related equivalents.

High-pressure krypton gas and statistical heavy-atom refinement: a successful combination of tools for macromolecular structure determination.

The noble gas krypton is shown to bind to crystallized proteins in a similar way to xenon [Schiltz, Prangé & Fourme (1994). J. Appl. Cryst. 27, 950-960]. Preliminary tests show that the major krypton binding sites are essentially identical to those of xenon. Noticeable substitution is achieved only at substantially higher pressures (above 50 x 10(5) Pa). As is the case for xenon, the protein complexes with krypton are highly isomorphous with the native structure so that these complexes can be used for phase determination in protein crystallography. Krypton is not as heavy as xenon, but its K-absorption edge is situated at a wavelength (0.86 A) that is readily accessible on synchrotron radiation sources. As a test case, X-ray diffraction data at the high-energy side of the K edge were collected on a crystal of porcine pancreatic elastase (molecular weight of 25.9 kDa) put under a krypton gas pressure of 56 x 10(5) Pa. The occupancy of the single Kr atom is approximately 0.5, giving isomorphous and anomalous scattering strengths of 15.2 and 1.9 e, respectively. This derivative could be used successfully for phase determination with the SIRAS method (single isomorphous replacement with anomalous scattering). After phase improvement by solvent flattening, the resulting electron-density map is of exceptionally high quality, and has a correlation coefficient of 0.85 with a map calculated from the refined native structure. Careful data collection and processing, as well as the correct statistical treatment of isomorphous and anomalous signals have proven to be crucial in the determination of this electron-density map. Heavy-atom refinement and phasing were carried out with the program SHARP, which is a fully fledged implementation of the maximum-likelihood theory for heavy-atom refinement [Bricogne (1991). Crystallographic Computing 5, edited by D. Moras, A. D. Podjarny & J. C. Thierry, pp. 257-297. Oxford: Clarendon Press]. It is concluded that the use of xenon and krypton derivatives, when they can be obtained, associated with statistical heavy-atom refinement will allow one to overcome the two major limitations of the isomorphous replacement method i.e. non-isomorphism and the problem of optimal estimation of heavy-atom parameters.

Protein Crystallography at Ultra-Short Wavelengths: Feasibility Study of Anomalous-Dispersion Experiments at the Xenon K-edge.

A protein crystallography experiment at the xenon K-edge (lambda = 0.358 A) has been successfully carried out at the materials science beamline (BL2/ID11) of the ESRF. The samples used in this methodological study were crystals of porcine pancreatic elastase, a 26 kDa protein of known structure. The diffraction data are of excellent quality. The combination of isomorphous replacement and anomalous dispersion of a single xenon heavy-atom derivative allowed accurate phase determination and the computation of a high-quality electron density map of the protein molecule. This is the first fully documented report on a complete protein crystallography experiment, from data collection up to phase determination and calculation of an electron density map, carried out with data obtained at ultra-short wavelengths. Experimental considerations as well as possible advantages and drawbacks of protein crystallography at very short and ultra-short wavelengths are discussed.

The catalytic site of serine proteinases as a specific binding cavity for xenon.

BACKGROUND: Under moderate pressure, xenon can bind to proteins and form weak but specific interactions. Such protein-xenon complexes can be used as isomorphous derivatives for phase determination in X-ray crystallography. RESULTS: Investigation of the serine proteinase class of enzymes shows that the catalytic triad, the common hydrolytic motif of these enzymes, is a specific binding site for one xenon atom and shows high occupancy at pressures below 12 bar. Complexes of xenon with two different serine proteinases, elastase and collagenase, were analyzed and refined to 2.2 A and 2.5 A resolution, respectively. In both cases, a single xenon atom with a low temperature factor is located in the active site at identical positions. Weak interactions exist with several side chains of conserved amino acids at the active site. Xenon binding does not induce any major changes in the protein structure and, as a consequence, crystals of the xenon complexes are highly isomorphous with the native protein structures. Xenon is also found to bind to the active site of subtilisin Carlsberg, a bacterial serine proteinase, that also has a catalytic triad motif. CONCLUSIONS: As the region around the active site shows conserved structural homology in all serine proteinases, it is anticipated that xenon binding will prove to be a general feature of this class of proteins.

[Male homosexuals faced with the AIDS epidemic]. / Les homosexuels face à l'épidémie du SIDA.

This survey among 1 000 french male homosexuals and bisexuals (July-August 1985) shows the reactions to AIDS in the still largest risk group. The survey reveals the diversity of social and sexual lifestyles. Gays perceive AIDS as a health threat, but also as a social threat eventually leading to discrimination. Ambivalence also prevails in their relationships with medical authorities. This survey allows to draw some conclusions concerning preventive strategies in the gay community.