Structure of S-lectin, a developmentally regulated vertebrate beta-galactoside-binding protein

The crystal structure of a 14-kDa bovine spleen S-lectin complexed with the disaccharide N-acetyllactosamine at 1.9-A resolution reveals a surprising structural relationship to legume lectins, despite the lack of sequence homology. Two monomers associate to form an extended beta-sandwich, each with the same jelly roll topology typical of legume lectins but with dramatically trimmed loops and with different dimer association. Each monomer binds one N-acetyllactosamine molecule in a topologically and spatially different site than that of legume lectins. The carbohydrate-binding site provides an unprecedented paradigm for carbohydrate binding, with a unique network of salt bridges. The specificity for beta-galactose arises from intricate interactions that constrain the position of the O4 atom.

C-type lectins and galectins mediate innate and adaptive immune functions: their roles in the complement activation pathway

In recent years, a 'new' pathway for complement activation mediated by the mannose-binding lectin (MBL) has been described as a key mechanism for the mammalian acute phase response to infection. This complement activation pathway is initiated by a non-self recognition step: the binding of a humoral C-type lectin [mannose-binding lectin (MBL)] to microbial surfaces bearing 'foreign' carbohydrate determinants. The recognition factor, MBL, is associated with a serine protease [MBL-associated serine protease (MASP)] which, upon MBL binding to the microbial ligand, activates the complement component C3, leading to either (a) phagocytosis of the opsonized target via the complement receptor, or (b) humoral cell killing via assembly of the membrane attack complex. Galectins (formerly known as S-type lectins) modulate activity of the complement receptor 3 (CR3), the macrophage membrane receptor for complement components C3b and iC3b, downstream products of the MBL pathway which are covalently bound to 'target cells. Galectins also mediate macrophage- and dendrocyte-adhesion to lymphocytes activated by signaling through another C-type lectin, the L-selectin, leading to immunoglobulin-mediated responses. Thus, the functional interplay of MBL, galectins and L-selectin in the acute phase response neutralizes the microbial challenge, and lead to further adaptive immunity. Although the observation of various components of the lectin pathway in different invertebrate species demonstrates the high conservation and ancient roots of the components of innate immunity, there has previously been no evidence supporting the possibility that the integral lectin-mediated complement activation pathway is present in invertebrates. We now have evidence for the coexistence of homologs of all the pathway's key components (MBL, MASP, C3, and galectin) in the protochordate Clavelina picta, suggesting the lectin-mediated pathway of complement activation preceded the immunoglobulin pathway in evolution. Therefore, despite being 'new' to the textbooks, experimental evidence indicates that this pathway is ancient, and has been conserved intact throughout its evolution.

Focal therapy in prostate cancer-report from a consensus panel

PURPOSE

To establish a consensus in relation to case selection, conduct of therapy, and outcomes that are associated with focal therapy for men with localized prostate cancer.

MATERIAL AND METHODS

Urologic surgeons, radiation oncologists, radiologists, and histopathologists from North America and Europe participated in a consensus workshop on focal therapy for prostate cancer. The consensus process was face to face within a structured meeting, in which pertinent clinical issues were raised, discussed, and agreement sought. Where no agreement was possible, this was acknowledged, and the nature of the disagreement noted.

RESULTS

Candidates for focal treatment should have unilateral low- to intermediate-risk disease with clinical stage <or=cT(2a). Prostate size and both tumor volume and tumor topography are important case selection criteria that depend on the ablative technology used. Currently, the best method to ascertain the key characteristics for men who are considering focal therapy is exposure to transperineal template mapping biopsies. MRI of the prostate using novel techniques such as dynamic contrast enhancement and diffusion weighed imaging are increasingly being used to diagnose and stage primary prostate cancer with excellent results. For general use, however, these new techniques require validation in prospective clinical trials. Until such are performed, MRI will, in most centers, continue to be an investigative tool in assessing eligibility of patients for focal therapy.

CONCLUSIONS

Consensus was derived for most of the key aspects of case selection, conduct of treatment, and outcome measures for men who are undergoing focal therapy for localized prostate cancer. The level of agreement achieved will pave the way for future collaborative trials.

Evidence for an excess of B→D*τ(-)ν(τ) decays

Based on the full BABAR data sample, we report improved measurements of the ratios R(D(*))=B(B[over ¯]→D(*)τ(-)ν[over ¯](τ))/B(B[over ¯]→D(*)ℓ(ℓ)(-)ν[over ¯](ℓ)), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D(*))=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.

Soluble beta-galactosyl-binding lectin (galectin) from toad ovary: crystallographic studies of two protein-sugar complexes

Galectin-1, S-type beta-galactosyl-binding lectins present in vertebrate and invertebrate species, are dimeric proteins that participate in cellular adhesion, activation, growth regulation, and apoptosis. Two high-resolution crystal structures of B. arenarum galectin-1 in complex with two related carbohydrates, LacNAc and TDG, show that the topologically equivalent hydroxyl groups in the two disaccharides exhibit identical patterns of interaction with the protein. Groups that are not equivalent between the two sugars present in the second moiety of the disaccharide, interact differently with the protein, but use the same number and quality of interactions. The structures show additional protein-carbohydrate interactions not present in previously reported lectin-lactose complexes. These contacts provide an explanation for the enhanced affinity of galectin-1 for TDG and LacNAc relative to lactose. Galectins are in dimer-monomer equilibrium at physiological protein concentrations, suggesting that this equilibrium may be involved in organ-specific regulation of activity. Comparison of B. arenarum with other galectin-1 structures shows that among different galectins there are significant changes in accessible surface area buried upon dimer formation, providing a rationale for the variations observed in the free-energies of dimerization. The structure of the B. arenarum galectin-1 has a large cleft with a strong negative potential that connects the two binding sites at the surface of the protein. Such a striking characteristic suggests that this cleft is probably involved in interactions of the galectin with other intra or extra-cellular proteins. Proteins 2000;40:378-388.

The role of different protein components from the Haemophilus ducreyi cytolethal distending toxin in the generation of cell toxicity

Cytolethal distending toxin of Haemophilus ducreyi (HdCDT) is a multicomponent toxin, encoded by an operon consisting of three genes, cdtABC. To investigate the role of the individual products in generation of toxicity, recombinant plasmids were constructed allowing expression of each of the genes individually or in different combinations in Escherichia coli and Vibrio cholerae. Expression of all three genes (cdtABC) was necessary to generate toxicity on cells, and no activity was obtained using combinations in which only one or two of the genes were expressed. Of the individual gene products, the CdtA was shown to exist in two forms with an MW of 23 and 17 kDa, respectively. The CdtB protein alone resulted in DNase activity. CdtC purified from both toxic and non-toxic extracts (from strains expressing cdtCAB and cdtC, respectively) had a molecular weight of about 20 kDa and reacted with a CdtC-specific monoclonal antibody. However, the protein isoelectric point (pI) of CdtC from toxic preparations was about 1.5 pH units more basic than from non-toxic ones. Both forms were immunogenic giving rise to toxin-neutralizing antibodies. Toxicity was reconstructed by combining non-toxic cell sonicates from E. coli, expressing CdtA, CdtB and CdtC proteins individually. Only combinations including all three products gave toxicity, indicating that all are actively involved in the generation of toxic activity on cells. The reconstruction resulted in a 1.5 pH unit shift in the PI of CdtC, making it identical to that of the protein isolated from bacteria expressing cdtABC. The results showed that the CdtB component produces DNase activity, but cell toxicity depends on the involvement of the other two components of CDT and is associated with absorption of all three proteins by HEp-2 cells.

Animal lectins as self/non-self recognition molecules. Biochemical and genetic approaches to understanding their biological roles and evolution

In recent years, the significant contributions from molecular research studies on animal lectins have elucidated structural aspects and provided clues not only to their evolution but also to their multiple biological functions. The experimental evidence has suggested that distinct, and probably unrelated, groups of molecules are included under the term "lectin." Within the invertebrate taxa, major groups of lectins can be identified: One group would include lectins that show significant homology to membrane-integrated or soluble vertebrate C-type lectins. The second would include those beta-galactosyl-specific lectins homologous to the S-type vertebrate lectins. The third group would be constituted by lectins that show homology to vertebrate pentraxins that exhibit lectin-like properties, such as C-reactive protein and serum amyloid P. Finally, there are examples that do not exhibit similarities to any of the aforementioned categories. Moreover, the vast majority of invertebrate lectins described so far cannot yet be placed in one or another group because of the lack of information regarding their primary structure. (See Table 1.) Animal lectins do not express a recombinatorial diversity like that of antibodies, but a limited diversity in recognition capabilities would be accomplished by the occurrence of multiple lectins with distinct specificities, the presence of more than one binding site, specific for different carbohydrates in a single molecule, and by certain "flexibility" of the binding sites that would allow the recognition of a range of structurally related carbohydrates. In order to identify the lectins' "natural" ligands, we have investigated the interactions between those proteins and the putative endogenous or exogenous glycosylated substances or cells that may be relevant to their biological function. Results from these studies, together with information on the biochemical properties of invertebrate and vertebrate lectins, including their structural relationships with other vertebrate recognition molecules, are discussed.

Search for a dark photon in e(+)e(-) collisions at BABAR

Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A^{'}), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e^{+}e^{-}→γA^{'}, A^{'}→e^{+}e^{-}, μ^{+}μ^{-} using 514  fb^{-1} of data collected with the BABAR detector. We observe no statistically significant deviations from the standard model predictions, and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^{-4}-10^{-3} for dark photon masses in the range 0.02-10.2  GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon.

Human splenic galaptin: carbohydrate-binding specificity and characterization of the combining site

A galactose-binding lectin (galaptin) from human spleen has been purified to homogeneity by affinity chromatography on asialofetuin-Sepharose. The carbohydrate-binding specificity of galaptin has been investigated by analyzing the binding of galaptin to asialofetuin in the presence of putative inhibitors. An enzyme-linked immunosorbent assay (ELISA) was developed that involved adsorption of asialofetuin to microtiter plates. Galaptin bound to asialofetuin was detected with polyclonal rabbit anti-galaptin serum followed by goat anti-rabbit IgG-peroxidase conjugate. The concentrations of inhibitors giving 50% inhibition of galaptin binding relative to controls were graphically determined and normalized relative to galactose or lactose. These analyses revealed that galaptin has a combining site at least as large as a disaccharide. The disaccharides having non-reducing-terminal beta-galactosyl residues linked (1,3), (1,4), and (1,6) to Glc or GlcNAc are better inhibitors than free Gal. GalNAc, either free or glycosidically linked, appears to have no affinity for the lectin. The nitrophenyl galactosides are better inhibitors than methyl galactosides, indicating the occurrence of hydrophobic interactions. The data indicate that OH groups at C-4 and C-6 of Gal and the OH at C-3 of GlcNAc in Gal beta(1,4)GlcNAc are important for lectin sugar interaction. Our data support the hypothesis that endogenous receptors for galaptin are most likely lactosaminoglycan moieties.

Multicentre prospective cohort study of body mass index and postoperative complications following gastrointestinal surgery

BACKGROUND

There is currently conflicting evidence surrounding the effects of obesity on postoperative outcomes. Previous studies have found obesity to be associated with adverse events, but others have found no association. The aim of this study was to determine whether increasing body mass index (BMI) is an independent risk factor for development of major postoperative complications.

METHODS

This was a multicentre prospective cohort study across the UK and Republic of Ireland. Consecutive patients undergoing elective or emergency gastrointestinal surgery over a 4-month interval (October-December 2014) were eligible for inclusion. The primary outcome was the 30-day major complication rate (Clavien-Dindo grade III-V). BMI was grouped according to the World Health Organization classification. Multilevel logistic regression models were used to adjust for patient, operative and hospital-level effects, creating odds ratios (ORs) and 95 per cent confidence intervals (c.i.).

RESULTS

Of 7965 patients, 2545 (32·0 per cent) were of normal weight, 2673 (33·6 per cent) were overweight and 2747 (34·5 per cent) were obese. Overall, 4925 (61·8 per cent) underwent elective and 3038 (38·1 per cent) emergency operations. The 30-day major complication rate was 11·4 per cent (908 of 7965). In adjusted models, a significant interaction was found between BMI and diagnosis, with an association seen between BMI and major complications for patients with malignancy (overweight: OR 1·59, 95 per cent c.i. 1·12 to 2·29, P = 0·008; obese: OR 1·91, 1·31 to 2·83, P = 0·002; compared with normal weight) but not benign disease (overweight: OR 0·89, 0·71 to 1·12, P = 0·329; obese: OR 0·84, 0·66 to 1·06, P = 0·147).

CONCLUSION

Overweight and obese patients undergoing surgery for gastrointestinal malignancy are at increased risk of major postoperative complications compared with those of normal weight.

Thermodynamics of bovine spleen galectin-1 binding to disaccharides: correlation with structure and its effect on oligomerization at the denaturation temperature

Isothermal titration calorimetry (ITC) measurements of the binding 1-beta carbohydrate-substituted galactopyranoside derivatives to galectin-1 from bovine spleen, a dimer with one binding site per subunit, were performed at 283-285 and 298 K. The disaccharides were lactose, methyl beta-lactoside, lactulose, 4-O-beta-D-galactopyranosyl-D-mannopyranoside, 3-O-beta-D-galactopyranosyl-D-arabinose, 2'-O-methyllactose, lacto-N-biose, N-acetyllactosamine, and thiodigalactopyranoside. The site binding enthalpies, DeltaHb, are the same at both temperatures and range from -42.2 +/- 3.3 kJ mol-1 for thiodigalactopyranoside to -24.5 +/- 0.5 kJ mol-1 for lacto-N-biose, and the site binding constants range from 4.86 +/- 0.78 x 10(3) M-1 for methyl beta-lactoside at 297.8 K to 6.54 +/- 0.97 x 10(4) M-1 for N-acetyllactosamine at 281.3 K. The binding reactions are enthalpically driven, exhibit enthalpy-entropy compensation, and, with the exception of N-acetyllactosamine, follow a van't Hoff dependence of the binding constant on temperature. The number of contacts at distances <4.0 A between the disaccharide and galectin was determined from the energy-minimized conformation of the complex derived from the X-ray crystallographic structure of the galectin-N-acetyllactosamine complex determined by Liao et al. [Liao, D. I., Kapadia, G., Ahmed, H., Vasta, G. R., and Herzberg, O. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 1428-1432]. The binding enthalpies calculated from changes in the solvent-accessible surface areas of the galectin binding site upon binding of the disaccharide were in close agreement with the experimental values for lactose, lactulose, lacto-N-biose, and N-acetyllactosamine, all of which exhibit binding enthalpies >-36 kJ mol-1. Differential scanning calorimetry measurements on solutions of galectin and its disaccharide complexes show that the galectin dimer does not dissociate upon denaturation in contrast to the legume lectins. At the denaturation temperature, the galectin in the absence of sugar exists as a tetramer, and the extent of this association is substantially reduced in the presence of a disaccharide.

Safety and efficacy of non-steroidal anti-inflammatory drugs to reduce ileus after colorectal surgery

BACKGROUND

Ileus is common after elective colorectal surgery, and is associated with increased adverse events and prolonged hospital stay. The aim was to assess the role of non-steroidal anti-inflammatory drugs (NSAIDs) for reducing ileus after surgery.

METHODS

A prospective multicentre cohort study was delivered by an international, student- and trainee-led collaborative group. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The primary outcome was time to gastrointestinal recovery, measured using a composite measure of bowel function and tolerance to oral intake. The impact of NSAIDs was explored using Cox regression analyses, including the results of a centre-specific survey of compliance to enhanced recovery principles. Secondary safety outcomes included anastomotic leak rate and acute kidney injury.

RESULTS

A total of 4164 patients were included, with a median age of 68 (i.q.r. 57-75) years (54·9 per cent men). Some 1153 (27·7 per cent) received NSAIDs on postoperative days 1-3, of whom 1061 (92·0 per cent) received non-selective cyclo-oxygenase inhibitors. After adjustment for baseline differences, the mean time to gastrointestinal recovery did not differ significantly between patients who received NSAIDs and those who did not (4·6 versus 4·8 days; hazard ratio 1·04, 95 per cent c.i. 0·96 to 1·12; P = 0·360). There were no significant differences in anastomotic leak rate (5·4 versus 4·6 per cent; P = 0·349) or acute kidney injury (14·3 versus 13·8 per cent; P = 0·666) between the groups. Significantly fewer patients receiving NSAIDs required strong opioid analgesia (35·3 versus 56·7 per cent; P < 0·001).

CONCLUSION

NSAIDs did not reduce the time for gastrointestinal recovery after colorectal surgery, but they were safe and associated with reduced postoperative opioid requirement.

Galectin-1 from bovine spleen: biochemical characterization, carbohydrate specificity and tissue-specific isoform profiles

Selected biochemical properties, including the charge heterodispersity profile and carbohydrate specificity, of bovine galectin-1 were determined in detail. The lectin was purified through an improved purification protocol that yielded 35-40 mg/kg of wet tissue with a specific activity of 1.7-2 x 10(4) mg-1.ml. The galectin is a homodimer of approximately 14.5 kDa subunits with E(280)mg/ml of 0.65 ml.mg-1.cm-1. When stored in the presence of its carbohydrate ligand, the lectin's binding activity remained stable in a non-reducing environment even at room temperature. The optimal pH for binding to the ligand was 6.5-8.0. The overall carbohydrate specificity of the bovine galectin-1 isolated from spleen is similar to that of the galectin isolated from heart and to other mammalian galectins that exhibit "conserved" (Type I) carbohydrate recognition domains (CRDs) [Ahmed, H. and Vasta, G.R. (1994) Glycobiology 4, 545-549], but differs from those from Xenopus laevis and rat intestine domain I. The fluorescence of 4-methylumbelliferyl alpha-D-galactopyranoside was quenched on binding to bovine spleen galectin-1. Scatchard plots of data obtained at 5, 15, and 30 degrees C showed that the galectin has two sugar exothermic binding sites with association constants of 3.4 x 10(5), 1.0 x 10(5), and 0.3 x 10(5), respectively. Chemical modification studies indicated that histidine, tryptophan, carboxylic acid, and arginine, but not lysine or tyrosine, are involved in the binding to the carbohydrate ligand. On isoelectric focusing, the spleen galectin-1 appeared as six isoforms ranging from pI4.56-4.88 with main components at pI 4.63 (34.0%), 4.73 (42.6%), and 4.88 (16.6%). The galectin-1 isolated from heart yielded a quali- and quantitatively different profile with four isoforms ranging from pI 4.53-4.73, those with pIs of 4.56, 4.63, and 4.73 being common to the spleen homolog. Edman degradation of selected peptides purified from the spleen galectin-1 digest revealed amino acid sequences identical to those obtained for the heart galectin-1. This suggests that although point mutations in the subunit primary structure may not be the likely source of isolectins, as observed for X. laevis, tissue-specific co- or post-translational modifications may be the possible cause of the differences in the galectin isoform profile between bovine spleen and heart.

Search for Invisible Decays of a Dark Photon Produced in e^{+}e^{-} Collisions at BaBar

We search for single-photon events in 53  fb^{-1} of e^{+}e^{-} collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A^{'} through the process e^{+}e^{-}→γA^{'}; A^{'}→invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A^{'} to e^{+}e^{-} in the mass range m_{A^{'}}≤8  GeV. In particular, our limits exclude the values of the A^{'} coupling suggested by the dark-photon interpretation of the muon (g-2)_{μ} anomaly, as well as a broad range of parameters for the dark-sector models.

Features of a large epidemic of group A meningococcal meningitis in Khartoum, Sudan in 1988

A large epidemic (February-August 1988) of group A sulphonamide resistant, clone III-1 meningococcal meningitis in Khartoum, Sudan is described. A total of 10,099 cases were admitted to treatment centers with 8,397 cases during March and April, corresponding to an annual incidence of 1,679/100,000 inhabitants during this period. The age profile showed a high morbidity in adults (31% of the cases greater than or equal to 20 years). The male dominance was marked especially in the adult cases with a proportion of 3.2:1. The epidemic started during the hot and dry season and declined when the clouds came, humidity rose, temperature fell and a mass vaccination campaign had been implemented together with other epidemic precautions. Vaccination with a combined group A/C polysaccharide vaccine had been given 4 weeks-1 year before hospitalization to 11% of the children, 80% of whom were greater than 18 months of age. The estimated case fatality rate was 6.3%. Since 47% of the cases came from periurban and rural areas, the actual mortality during the epidemic might have been higher when considering those who may have died before reaching any of the treatment centres. Fatal cases had a short history of acute illness and a septic condition. Septicaemia was rare and seen in only 3.7% of the cases, the rest had acute purulent meningitis. Hearing loss/impairment and hemiplegia was diagnosed in 2-3% of the cases. The epidemiology, based on detailed typing/subtyping and restriction enzyme patterns of meningococcal strains, was apparently associated with the Mecca outbreak in August 1987.