Shear Testing of Topologically Optimised Web Cover Plates in Splice Connections-Experiment Design and Results

Testing shear-resisting plates in steel connections is one of the most challenging laboratory undertakings in steel construction, as the most common experimental layout design includes simulating the connection with its adjoining members. This significant hindrance gained particular magnitude as the need to test prototypes of topologically optimised shear cover plates became more pressing. Indeed, new code-compliant topology optimisation approaches for steel construction have recently been offered, and physically non-linear analyses have been demonstrated to be vital for assessing these elements. Hence, a rapid and reliable experimental process has become a fundamental necessity. To answer this need, a novel layout is herein proposed, in which topologically optimised and previously numerically examined bolted shear plates of a well-known steel joint were tested. The results allowed for the definition of the material trilinear model for use in subsequent numerical analysis, as well as the validation of the numerical simulation results. The discrepancy between the previously mathematically anticipated and empirically determined ultimate resistance did not exceed 1.7%.

A method for a column-by-column EELS quantification of barium lanthanum ferrate

High-resolution STEM-EELS provides information about the composition of crystalline materials at the atomic scale, though a reliable quantitative chemical analysis is often hampered by zone axis conditions, where neighbouring atomic column intensities contribute to the signal at the probe position. In this work, we present a procedure to determine the concentration of two elements within equivalent atomic columns from EELS elemental maps - in our case barium and lanthanum within the A-sites of Ba1.1La1.9Fe2O7, a second order Ruddlesden-Popper phase. We took advantage of the large changes in the elemental distribution from column to column and introduced a technique, which substitutes inelastic scattering cross sections during the quantification step by using parameters obtained from the actual experiment. We considered channelling / de-channelling effects via inelastic multislice simulations and were thereby able to count occupancies in each atomic column. The EELS quantification results were then used as prior information during the Rietveld refinement in XRD measurements in order to differentiate between barium and lanthanum.

Intensive monitoring of adverse drug events associated with the use of new glucose-lowering drugs: results from an inception cohort study in Portugal

AIMS

To determine the frequency and the time-course profile of adverse drug events associated with new glucose-lowering drugs in daily practice and to explore factors potentially associated to these events.

METHODS

An inception cohort study was implemented. Adults with type 2 diabetes mellitus initiating a dipeptidyl peptidase-4 inhibitor, a glucagon-like peptide-1 receptor agonist or a sodium-glucose co-transporter-2 inhibitor were eligible for inclusion. Data were collected through baseline and follow-up telephone questionnaires, administered at 2 weeks, 3 months and 6 months. Kaplan-Meier curves and log-rank were computed to compare the time to adverse drug event onset. Cox models were used to explore potential factors associated with adverse drug events.

RESULTS

A total of 1328 participants were recruited to the study. In all, 1118 adverse drug events were reported (of which 36% were not listed in the summary of product characteristics) by 41% of participants. The median latency time of adverse drug events reported in ≥1% of participants ranged from 0 to 2 days. Glucagon-like peptide-1 receptor agonist and sodium-glucose co-transporter-2 inhibitor subgroups were associated with an increased likelihood of adverse drug event reporting when compared with the dipeptidyl peptidase-4 inhibitor subgroup. A total of 328 glucose-lowering drugs were withdrawn, more than half as a result of an adverse drug event.

CONCLUSIONS

More than two-fifths of participants reported an adverse drug event; dipeptidyl peptidase-4 inhibitors led to the highest proportion of unlabelled adverse drug events. Adverse drug event latency time data show that counselling and adverse drug event management should be proactively addressed from treatment initiation. There should be greater focus on prevalent new users of glucose-lowering drugs, who were more complex participants in this study in terms of type 2 diabetes disease, as they were more likely to report an adverse drug event than the incident new users.

Synthesis and high-resolution structural and chemical analysis of iron-manganese-oxide core-shell nanocubes

We have investigated the structure and chemical composition of nanoparticles synthesized by thermal decomposition of a mixture of iron oleate and manganese oleate in a high-boiling solvent in the presence of Na-oleate and oleic acid as surfactants by analytical transmission electron microscopy (TEM). The particles appear core-shell like in bright field TEM images. Higher spatial resolution TEM (HRTEM) analysis reveals a FeO/MnO like structure in the core and a spinel like structure in the shell. With high-resolution analytical methods like energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), the distribution of the metals Mn and Fe was investigated. Differences in the oxidation state of these metals were found between the core and the shell region. The presence of sodium from the used surfactant (Na-oleate) on the surface of the particles has been proved.

Stabilization of a monolayer tellurene phase at CdTe interfaces

Two-dimensional (2D) materials provide a plethora of novel condensed matter physics and are the new playground in materials science, offering potentially vast applications. One of the critical hurdles for many 2D systems is the synthesis of these low-dimensional systems as well as the prediction and identification of new candidates. Herein, a self-assembly of a monolayer tellurene by bonding CdTe wafers is demonstrated for the first time. The conventional applications of wafer-bonding range from the production of microelectromechanical systems to the synthesis of lattice-mismatched multi-junction photovoltaics. Due to the heterogeneous materials that are typically employed, the bond-interface usually contains a thin amorphous layer or arrays of dislocations. Such an interface is thus itself inactive and in many cases has detrimental effects on the device. The new material phase stabilized in this work consists of an undulating monolayer of tellurium atoms covalently bonded to {111} Cd-terminated CdTe wafer surfaces. First-principles calculations and experimentally observed changes in the localized plasmon excitation energy indicate the clear rearrangement of the underlying band-structure suggesting a metallic character, bands showing linear dispersion, and a significant asymmetric spin-band splitting. The I-V characteristics show the presence of a highly conductive pathway that lowers the resistivity by three orders of magnitude, as compared to bulk CdTe, which can be attributed to the tellurium monolayer. The findings indicate that suitably chosen crystallographic wafer surfaces can act as structural templates allowing the production of exotic phases. The presently stabilized monolayer is an addition to the family of tellurene variants, providing new insights into the fundamental properties of this and other emerging 2D materials, while attracting attention to the unusual side of the wafer-bonding technology exemplified in this study.

Unique Structural Characteristics of Catalytic Palladium/Gold Nanoparticles on Graphene

Adding Au to Pd nanoparticles (NPs) can impart high catalytic activity with respect to hydrogenation of a wide range of substances. These materials are often synthesized by reducing metallic precursors; hence, sonochemical and solvothermal processes are commonly used to anchor these bimetals onto thin supports, including graphene. Although similar NPs have been studied reasonably well, a clear understanding of structural characteristics relative to their synthesis parameters is lacking, due to limitations in characterization techniques, which may prevent optimization of this very promising catalyst. In this report, a strategic approach has been used to identify this structural and material synthesis correlation, starting with controlled sample preparation and followed by detailed characterization. This includes advanced scanning transmission electron microscopy and electron energy loss spectroscopy; the latter using a state-of-the-art instrumentation to map the distribution of Pd and Au, and to identify chemical state of the Pd NPs, which has not been previously reported. Results show that catalytic bimetal NP clusters were made of small zero-valent Pd NPs aggregating to form a shell around an Au core. Not only can the described characterization approach be applied to similar material systems, but the results can guide the optimization of the synthesis procedures.

Corrigendum to: Phosphonium Salt Displays Cytotoxic Effects Against Human Cancer Cell Lines

Due to an oversight one of the author’s name was published wrong in the article entitled “Phosphonium Salt Displays Cytotoxic Effects Against Human Cancer Cell Lines” in “Anti-Cancer Agents in Medicinal Chemistry, 2015, Vol. 17, No. 13. pp. 1796.”

The correct names of all authors are given below:

Dhanyalayam D, Palma G, Cappello AR, Mariconda A, Sinicropi MS, Giordano F, Del Vecchio V, Ramunno A, Arra C, Longo P, Saturnino C.

Structure and chemistry of interfaces between ceria and yttria-stabilized zirconia studied by analytical STEM

Epitaxial undoped and Gd₂O₃-doped ceria films were grown by pulsed laser deposition on (1 1 1) faced Y₂O₃-stabilized zirconia (YSZ). Highly localized cerium reduction at the film-substrate interfaces is revealed by atomically resolved valence EELS mapping using C_s aberration-corrected scanning transmission electron microscopy. The chemical profiles reveal interdiffusion of Ce, (Gd), Y, Zr, forming an intermixing zone at the interface 7-9 (1 1 1) lattice planes wide. In its vicinity, the fraction of Ce³⁺ raises gradually over 6-8 lattice planes from zero in the bulk ceria to ≈100% in one single plane at the interface. Beyond this plane the Ce³⁺ fraction drops sharply within the YSZ substrate. In the vicinity of the interface systematic scan deflections are observed during EELS line scans. The advancing electron probe experiences a retarding force at the ceria side, and an accelerating force at the YSZ side, irrespective of the scan direction. This behavior is suggestive of coulombic interactions between the electron probe and a charged interface. This is interpreted as an indication of the presence of a space-charge situation at the YSZ/ceria interface, resulting from an excess negative charge at the ceria side (due to Ce³⁺cations) and an excess positive charge at the YSZ side (due to oxygen vacancies).

Confined Metastable 2-Line Ferrihydrite for Affordable Point-of-Use Arsenic-Free Drinking Water

Arsenic-free drinking water, independent of electrical power and piped water supply, is possible only through advanced and affordable materials with large uptake capacities. Confined metastable 2-line ferrihydrite, stable at ambient temperature, shows continuous arsenic uptake in the presence of other complex species in natural drinking water and an affordable water-purification device is made using the same.

Elemental electron energy loss mapping of a precipitate in a multi-component aluminium alloy

The elemental distribution of a precipitate cross section, situated in a lean Al-Mg-Si-Cu-Ag-Ge alloy, has been investigated in detail by electron energy loss spectroscopy (EELS) and aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). A correlative analysis of the EELS data is connected to the results and discussed in detail. The energy loss maps for all relevant elements were recorded simultaneously. The good spatial resolution allows elemental distribution to be evaluated, such as by correlation functions, in addition to being compared with the HAADF image. The fcc-Al lattice and the hexagonal Si-network within the precipitates were resolved by EELS. The combination of EELS and HAADF-STEM demonstrated that some atomic columns consist of mixed elements, a result that would be very uncertain based on one of the techniques alone. EELS elemental mapping combined with a correlative analysis have great potential for identification and quantification of small amounts of elements at the atomic scale.

Tailoring superradiance to design artificial quantum systems

Cooperative phenomena arising due to the coupling of individual atoms via the radiation field are a cornerstone of modern quantum and optical physics. Recent experiments on x-ray quantum optics added a new twist to this line of research by exploiting superradiance in order to construct artificial quantum systems. However, so far, systematic approaches to deliberately design superradiance properties are lacking, impeding the desired implementation of more advanced quantum optical schemes. Here, we develop an analytical framework for the engineering of single-photon superradiance in extended media applicable across the entire electromagnetic spectrum, and show how it can be used to tailor the properties of an artificial quantum system. This “reverse engineering” of superradiance not only provides an avenue towards non-linear and quantum mechanical phenomena at x-ray energies, but also leads to a unified view on and a better understanding of superradiance across different physical systems.

Cu₂Se and Cu Nanocrystals as Local Sources of Copper in Thermally Activated In Situ Cation Exchange

Among the different synthesis approaches to colloidal nanocrystals, a recently developed toolkit is represented by cation exchange reactions, where the use of template nanocrystals gives access to materials that would be hardly attainable via direct synthesis. Besides, postsynthetic treatments, such as thermally activated solid-state reactions, represent a further flourishing route to promote finely controlled cation exchange. Here, we report that, upon in situ heating in a transmission electron microscope, Cu2Se or Cu nanocrystals deposited on an amorphous solid substrate undergo partial loss of Cu atoms, which are then engaged in local cation exchange reactions with Cu "acceptor" phases represented by rod- and wire-shaped CdSe nanocrystals. This thermal treatment slowly transforms the initial CdSe nanocrystals into Cu(2-x)Se nanocrystals, through the complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu "donor" and "acceptor" particles were not always in direct contact with each other; hence, the gradual transfer of Cu species from Cu2Se or metallic Cu to CdSe nanocrystals was mediated by the substrate and depended on the distance between the donor and acceptor nanostructures. Differently from what happens in the comparably faster cation exchange reactions performed in liquid solution, this study shows that slow cation exchange reactions can be performed at the solid state and helps to shed light on the intermediate steps involved in such reactions.

Effect of incorporation of POSS compounds and phosphorous hardeners on thermal and fire resistance of nanofilled aeronautic resins

The aim of this work is the identification of the best strategy for improving thermal, fire resistance and electrical conductivity of an epoxy resin for aeronautic applications.

Probing the chemical structure in diamond-based materials using combined low-loss and core-loss electron energy-loss spectroscopy

We report the analysis of the changes in local carbon structure and chemistry caused by the self-implantation of carbon into diamond via electron energy-loss spectroscopy (EELS) plasmon energy shifts and core-edge fine structure fingerprinting. These two very different EELS energy and intensity ranges of the spectrum can be acquired under identical experimental conditions and nearly simultaneously using specially designed deflectors and energy offset devices known as "DualEELS." In this way, it is possible to take full advantage of the unique and complementary information that is present in the low- and core-loss regions of the EELS spectrum. We find that self-implanted carbon under the implantation conditions used for the material investigated in this paper creates an amorphous region with significant sp 2 content that varies across the interface.

Far-field signatures of a two-body bound state in collective emission from interacting two-level atoms on a lattice

The collective emission from a one-dimensional chain of interacting two-level atoms is investigated. We calculate the light scattered by dissipative few-excitation eigenstates in the far field, and, in particular, focus on signatures of a lattice two-body bound state. We present analytical results for the angle-resolved, temporal decay of the scattered light intensity. Moreover, we find that the steady-state emission spectrum that emerges when the system is probed by a weak, incoherent driving field exhibits a distinct signature for the existence of a bound state, and allows us to determine the momentum distribution of the two-body relative wave function. Intriguingly, our study does not rely on single-atom addressability and/or manipulation techniques.

Facility implementation and comparative performance evaluation of probe-corrected TEM/STEM with Schottky and cold field emission illumination

We report the installation and performance evaluation of a probe aberration-corrected high-resolution JEOL JEM-ARM200F transmission electron microscope (TEM). We provide details on construction of the room that enables us to obtain scanning transmission electron microscope (STEM) data without any evident distortions/noise from the external environment. The microscope routinely delivers expected performance. We show that the highest STEM spatial resolution and energy resolution achieved with this microscope are 0.078 nm and 0.34 eV, respectively. We report a direct comparative evaluation of the performance of this microscope with a Schottky thermal field-emission gun versus a cold field-emission gun. Cold field-emission illumination improves spatial resolution of the high current probe for analytical spectroscopy, the TEM information limit, and the electron energy resolution compared to the Schottky thermal field-emission source.

Pulse propagation of photon-added coherent states in waveguides with side-coupled nonlinear cavities

We present a theoretical analysis of pulse propagation in a waveguide with a side-coupled Kerr nonlinear cavity. As a specific application, we demonstrate how the nonlinearity has a profound influence on transport properties of a photon-added coherent state. We find that the fields provided by the coherent states facilitate a tunable nonlinearity on the few-photon level, allowing for a robust gating of single photons.

The Hong-Ou-Mandel effect in the context of few-photon scattering

The Hong-Ou-Mandel effect is studied in the context of two-photon transport in a one-dimensional waveguide with a single scatterer. We numerically investigate the scattering problem within a time-dependent, wave-function-based framework. Depending on the realization of the scatterer and its properties, we calculate the joint probability of finding both photons on either side of the waveguide after scattering. We specifically point out how Hong-Ou-Mandel interferometry techniques could be exploited to identify effective photon-photon interactions which are mediated by the scatterer. The Hong-Ou-Mandel dip is discussed in detail for the case of a single two-level atom embedded in the waveguide, and dissipation and dephasing are taken into account by means of a quantum jump approach.

Few-photon transport in low-dimensional systems: interaction-induced radiation trapping

We present a detailed analysis of the dynamics of photon transport in waveguiding systems in the presence of a two-level system. In these systems, quantum interference effects generate a strong effective optical nonlinearity on the few-photon level. We clarify the relevant physical mechanisms through an appropriate quantum many-body approach. Based on this, we demonstrate that a single-particle photon-atom bound state with an energy outside the band can be excited via multiparticle scattering processes. We further show that these trapping effects are robust and, therefore, will be useful for the control of photon entanglement in solid-state based quantum-optical systems.

[Smoking cessation and weight gain]

Cigarette smoking is the single most important preventable cause of death and illness. Smoking cessation is associated with substantial health benefits, but weight gain after smoking cessation is perceived to be a barrier against quitting smoking. The aim of the study was to analyse predictors of weight gain after smoking cessation. The sample included 1067 residents, aged 18-70 years, in a health district of Rome who answered to an anonymous postal questionnaire. Among them 482 were former smokers; 398 provided lifetime histories of both body weight and smoking and were considered in the analysis. 52.5% (49.3% M; 60.5% F) reported weight gain after smoking cessation; among these 25.4% reported a weight gain > or =5 kg. The multivariate logistic regression analysis showed a direct association between female gender (OR 1.9, CI 95% 1.1-3.2), age - 45 years (45-65 years: OR 2.5, CI 95% 1.4-4.4; > 64 years OR 2.1, CI 95% 1.0-4.0), number of cigarettes per day >20/day (OR 3.8, CI 95% 1.3-11.5) and weight gain after smoking cessation. The relevance of weight gain following smoking cessation suggests that health benefits associated with smoking cessation may to some extent be negated by the detrimental effects on health of associated weight gain. Smoking cessation programmes should therefore consider incorporating follow-up support to prevent weight gain; regular measurements of body weight together with dietary indications and increase of physical activity are basic factors to implement in the intervention of smoking cessation.

Kidney vending: opinions of the medical school students on this controversial issue

BACKGROUND

In this era of globalization, in which different cultural and economic barriers are progressively abated, in the context of the development of rapid information networks such as the Internet, physicians are increasingly challenged by clinical and ethical questions. Kidney vending, banned in some countries, legal or tolerated in others, may be the prototype of the ethical aspects of health-care globalization.

METHODS

To test the interest and the opinions of medical school students, a simulated case was proposed to students attending a seminar within the nephrology course fourth year of the Medical School of Torino, san Luigi): an Italian patient comes to the nephrologist's office asking for advice on the possibility to legally buy a kidney in a foreign country. The 43 students attending the lesson answered a semistructured questionnaire (15 boys, 28 girls, of median age 23 years). Attendance was within the usual standards (50 students inscribed per year). From the clinical point of view, 11.6% were favorable to kidney vending, 51.2% were contrary, 37.2% were uncertain. From the ethical point of view, no student was pro, 81.4% were contrary, and 18.6% were uncertain. The open comments underline the importance of patient self-determination and of informed consent. Similar opinions were recorded in a nonstructured question: "What should physician's attitude be, in the face of a choice he/she doesn't share?"

CONCLUSION

Students' uncertainties and doubts underline the need to discuss ethical scenarios in the clinical teachings of the medical school.

How many organs should one patient receive? the ethics of transplantation in the medical school

BACKGROUND

Interest in the humanities in the medical school is growing; while several medical schools, mainly of Anglo-Saxon background, have developed dedicated courses, the experience in Italy is limited.

METHODS

Since the academic year 2000 to 2001, a discussion of ethical problems was implemented in the nephrology course (fourth year of the Medical School of Torino, Italy; overall 6 years). In 2002 to 2003, a case entitled "Retransplantation of Multiple Organs (Prog Transplant 2002)" was discussed in 2 hours of small-group tutorial teaching: a boy received a renal graft at age 5, failed at age 7 due to recurrent glomerulonephritis, required a heart-kidney graft at age 11, and a second heart-kidney graft at 17. Student opinions were gathered by anonymous semistructured questionnaires at the beginning of the lessons as a basis for discussion.

RESULTS

Following the lessons all students returned the questionnaires (n = 104). In the absence of competition for allocation, retransplantation was approved by 76.2%, unacceptable for 1% (22.9% uncertain-blank). With a waiting list of 10 patients, the opinions changed: 32.4% approved transplantation, 6.7% didn't approve it, 60.9% were uncertain. A theoretical categorization into deontological or utilitaristic approaches favored the first (41.9% vs 26.7%), with a high prevalence of blank-uncertain (31.5%); 21.9% of the students would change their opinion was that study head of the Transplant Department.

CONCLUSION

Ethical aspects of the medical profession have been discussed with interest by medical school students; the high prevalence of uncertain answers and requests to develop specific tools underline the importance of this educational approach.

To give or to receive? opinions of teenagers on kidney donation

BACKGROUND

The attitude toward living donation varies widely in the world, for economic and cultural reasons. In Italy, as in other Mediterranean settings, the role of living kidney donation is minor.

AIM

To analyze the reasons for this attitude, we gathered data in a general population sample of high school students in a large northern Italian industrial city (Torino, about 900,000 inhabitants).

METHODS

Semistructured questionnaires (n = 1676), gathered in 2001 to 2002 in 14 high schools, in the context of an educational program on dialysis, renal transplantation, and organ donation, were analyzed presumably reflecting opinions gathered before the educational intervention.

RESULTS

Most students, in the case of a close relative or partner needing dialysis, answer that they would donate a kidney (yes: 78.2%, no: 2.9%, uncertain-blank: 18.9%); receiving a living donor kidney is felt as disturbing: only 57.5% of the students would accept it (no: 5.9%, uncertain-blank: 36.6%), mainly because of fear of long-term problems for the donor. Donation from an older to a younger person is seen more positively than vice versa.

CONCLUSION

In our settings, the attitude of the teenagers on living donation is positive; however, while "giving" is positively seen, the presence of unresolved fears is witnessed by the lower acceptance of the idea of "taking." These data suggest to focus on the risks of kidney donation in educational campaigns and in patient-physician information. The positive attitude shared by the teenagers supports the working hypothesis that lack of information is one of the determinants of the low living donor transplantation rate in our area.

Efficacy of an educational program on dialysis, renal transplantation, and organ donation on the opinions of high school students: a randomized controlled trial

AIM

Organ shortage is a rate-limiting factor for transplantation. The aim of this study was to evaluate the impact of an educational program targeted to high school students on opinions concerning organ donation.

METHODS

Sixteen public high schools in Torino, Italy, were randomized (2001 to 2002) as interventions (n = 8) or controls (n = 8). Intervention was composed of first questionnaire, first lesson (one to two classes; 2 hours, by a trained nephrology fellow); second lesson (all classes together; coordinated by a nephrologist, with patients and trainees); second questionnaire. Control included questionnaires. Statistical analysis compared the opinions in the questionnaires after stratification for age, sex, and type of school.

RESULTS

Fourteen schools completed the program (seven interventions: 937 first and 808 second questionnaires; controls: 739 and 659). Television (82.5%) and newspapers (43.2%) were the main sources of information; knowledge on renal transplantation (grafts feasible per patient, average duration) was low; only 12.2% of the students gave correct answers. The opinions on living donation were highly positive (76.8%) with no difference in control, intervention schools, first and second questionnaires, according to sex, age, or type of school. The opinions on cadaveric transplantation were affected by the educational intervention with a drop in negative answers (from 33.7% to 16%), with an increase in positive (from 31.5% to 42.9%) and in uncertain ones (from 34.8% to 41.1%) among the intervention schools; 98% of the students appreciated the program.

CONCLUSION

The positive effect on student opinions suggests the need to develop educational approaches as a part of our routine clinical work.

Incidence of nosocomial rotavirus infections, symptomatic and asymptomatic, in breast-fed and non-breast-fed infants

Rotavirus is one of the most important aetiological agents of nosocomial infections in childhood. We studied the incidence of nosocomial rotavirus infections in 420 patients (age range 1-18 months) consecutively admitted from 1 December 1999 to 31 May 2000 to the infant ward of the Department of Paediatrics, University of Turin. We also evaluated the protective effect of breast feeding. Faecal specimens were collected from every child (whether developing diarrhoeic symptoms or not) and tested for rotavirus during hospitalization and 72 h after discharge. The incidence of rotavirus nosocomial infections was 27.7%. The incidence of symptomatic nosocomial infections was 16.8%, and the incidence of asymptomatic infections was 10.9%. The attack rate of the infections that occurred during hospitalization was 11.8%, while for those occurring after discharge, it was 15.9%. Rotavirus infection, on average, prolonged hospital stay from 5.2 to 6.4 days. 10.6% of breast-fed infants and 32.4% of non-breast-fed infants contracted rotavirus infection (P<0.005). None of the breast-fed infants who contracted rotavirus infection developed diarrhoeic symptoms.

A mammalian expression vector for expression and purification of secreted proteins for structural studies

A mammalian expression vector with features optimized for simple expression and purification of secreted proteins has been developed. This vector was constructed to facilitate X-ray crystallographic studies of cysteine-rich glycoproteins that are difficult to express by other means. Proteins expressed with this vector possess an N-terminal human growth hormone domain and an octahistidine tag separated from the desired polypeptide sequences by a tobacco etch virus protease recognition site. Advantages of this vector are high levels of expression, simple detection and purification of expressed proteins, and reliable cleavage of the fusion protein. Cotransfection of this vector with a dihydrofolate reductase gene allows amplification of expression levels with methotrexate. Over one dozen cysteine-rich secreted proteins have been expressed in sufficient quantity for structural studies using this vector; the structure of at least one of these proteins has been determined.

Accumulated clonal genetic alterations in familial and sporadic colorectal carcinomas with widespread instability in microsatellite sequences

A subset of hereditary and sporadic colorectal carcinomas is defined by microsatellite instability (MSI), but the spectra of gene mutations have not been characterized extensively. Thirty-nine hereditary nonpolyposis colorectal cancer syndrome carcinomas (HNPCCa) and 57 sporadic right-sided colonic carcinomas (SRSCCa) were evaluated. Of HNPCCa, 95% (37/39) were MSI-positive as contrasted with 31% (18/57) of SRSCCa (P < 0.000001), but instability tended to be more widespread in SRSCCa (P = 0.08). Absence of nuclear hMSH2 mismatch repair gene product by immunohistochemistry was associated with germline hMSH2 mutation (P = 0.0007). The prevalence of K-ras proto-oncogene mutations was similar in HNPCCa and SRSCCa (30% (11/37) and 30% (16/54)), but no HNPCCa from patients with germline hMSH2 mutation had codon 13 mutation (P = 0.02), and two other HNPCCa had multiple K-ras mutations attributable to subclones. 18q allelic deletion and p53 gene product overexpression were inversely related to MSI (P = 0.0004 and P = 0.0001, respectively). Frameshift mutation of the transforming growth factor beta type II receptor gene was frequent in all MSI-positive cancers (85%, 46/54), but mutation of the E2F-4 transcription factor gene was more common in HNPCCa of patients with germline hMSH2 mutation than in those with germline bMLH1 mutation (100% (8/8) versus 40% (2/5), P = 0.04), and mutation of the Bax proapoptotic gene was more frequent in HNPCCa than in MSI-positive SRSCCa (55% (17/31) versus 13% (2/15), P = 0.01). The most common combination of mutations occurred in only 23% (8/35) of evaluable MSI-positive cancers. Our findings suggest that the accumulation of specific genetic alterations in MSI-positive colorectal cancers is markedly heterogeneous, because the occurrence of some mutations (eg, ras, E2F-4, and Bax genes), but not others (eg, transforming growth factor beta type II receptor gene), depends on the underlying basis of the mismatch repair deficiency. This genetic heterogeneity may contribute to the heterogeneous clinical and pathological features of MSI-positive cancers.

Substructural specificity and polyvalent carbohydrate recognition by the Entamoeba histolytica and rat hepatic N-acetylgalactosamine/galactose lectins

Both the Entamoeba histolytica lectin, a virulence factor for the causative agent of amebiasis, and the mammalian hepatic lectin bind to N-acetylgalactosamine (GalNAc) and galactose (Gal) nonreducing termini on oligosaccharides, with preference for GalNAc. Polyvalent GalNAc-derivatized neoglycoproteins have >1000-fold enhanced binding affinity for both lectins (Adler,P., Wood,S.J., Lee,Y.C., Lee,R.T., Petri,W.A.,Jr. and Schnaar,R.L.,1995, J. Biol. Chem ., 270, 5164-5171). Substructural specificity studies revealed that the 3-OH and 4-OH groups of GalNAc were required for binding to both lectins, whereas only the E.histolytica lectin required the 6-OH group. Whereas GalNAc binds with 4-fold lower affinity to the E.histolytica lectin than to the mammalian hepatic lectin, galactosamine and N-benzoyl galactosamine bind with higher affinity to the E. histolytica lectin. Therefore, a synthetic scheme for converting polyamine carriers to poly-N-acyl galactosamine derivatives (linked through the galactosamine primary amino group) was developed to test whether such ligands would bind the E.histolytica lectin with high specificity and high affinity. Contrary to expectations, polyvalent derivatives including GalN6lys5, GalN4desmosine, GalN4StarburstTMdendrimer, and GalN8StarburstTMdendrimer demonstrated highly enhanced binding to the mammalian hepatic lectin but little or no enhancement of binding to the E.histolytica lectin. We propose that the mammalian hepatic lectin binds with greatest affinity to GalNAc "miniclusters," which mimic branched termini of N-linked oligosaccharides, whereas the E.histolytica lectin binds most effectively to "maxiclusters," which may mimic more widely spaced GalNAc residues on intestinal mucins.

Phenotypic and genotypic characteristics of aberrant crypt foci in human colorectal mucosa

Aberrant crypt foci (ACF) in colorectal mucosa are proposed to be the earliest morphological lesion in the development of neoplasia, but their characteristics remain controversial. We therefore studied the epithelial phenotype and genotype of ACF from patients with familial adenomatous polyposis (FAP) and of sporadic ACF by evaluating glycoprotein markers associated with neoplasia (lectins Dolichus biflorus agglutinin and peanut agglutinin; monoclonal antibody CA 19-9 against sialyl Lewis-a blood group substance), expression of proliferating cell nuclear antigen, and ras proto-oncogene mutations. The utility of the markers was established by comparing adenomas and hyperplastic polyps. Most FAP ACF resembled adenomas and were found to differ from sporadic ACF in their high frequency of dysplasia, staining with Dolichus biflorus agglutinin, expression of sialyl Lewis-a, proliferation in the epithelium of upper crypts, and low frequency of ras gene mutations (P = .04 to < .0000001). By contrast, sporadic ACF and a subset of FAP ACF had phenotypic characteristics resembling hyperplastic polyps but usually had ras mutations, which were inversely related to dysplasia (P = .00009). Our findings suggest that "aberrant crypt focus" is a generic term analogous to "polyp" and requires further histopathologic, phenotypic, or genotypic classification into dysplastic and heteroplastic (hetero = other, plasia = form) types. Dysplastic ACF represent potential precursors to colorectal adenomas and adenocarcinomas, but heteroplastic ACF appear to be associated, rather than precursor, lesions.

Distinctive ganglioside patterns revealed by anti-ganglioside antibody binding to differentiating CG-4 oligodendrocytes

Oligodendrocytes are central nervous system glial cells responsible for myelination of neuronal axons. During brain development oligodendrocyte progenitor cells progress through a series of morphologically and immunohistochemically distinct differentiation steps leading to mature myelin-producing oligodendrocytes. Much of this same differentiation sequence is expressed in vitro by primary oligodendrocyte progenitor cells, and by the clonal progenitor cell line CG-4. We report the use of highly specific monoclonal antibodies against GM1, GD1a, GD1b, GT1b, and GQ1b to determine major brain ganglioside expression and morphological distribution during CG-4 differentiation in vitro. Prominent anti-GD1b antibody stained defined a highly arborized intermediate stage of oligodendrocyte differentiation. In contrast, anti-GT1b antibody bound to discrete patches on the cell bodies of early progenitor cells and more mature oligodendrocytes, and to sites of progenitor arborization. The other anti-ganglioside antibodies tested did not bind above background levels. Cells with anti-GD1b antibody binding and morphology similar to those in differentiating CG-4 cells were detected in rat brain primary cell cultures enriched in oligodendrocyte precursors. The remarkably distinctive ganglioside immunoreactivity on differentiating oligodendrocytes suggests the possibility of a functional role for their surface expression.

Glucocorticoid receptor determinations in leukemia patients using cytosol and whole-cell assays

Parallel determinations of glucocorticoid receptors in the cells of patients with various forms of leukemia were made by two assay methods, one using cell-free cytosolic extracts and the other using whole-cell preparations. Both assays revealed saturable binding of triamcinolone acetonide in all cases. The mean equilibrium dissociation constant for the interaction of triamcinolone acetonide with the cytoplasmic receptor at 2 degrees was 9.45 +/- 6.33 (S.D.) nM while that for the whole-cell binding at 37 degrees was 6.13 +/- 3.25 nM, suggesting an increase in receptor affinity at physiological temperatures. Competition experiments with various unlabeled steroids revealed a higher degree of glucocorticoid specificity at 37 degrees in whole-cell suspensions than at 2 degrees in cytosol. In a comparative analysis of 41 leukemic cell specimens, it was found that determinations carried out by whole-cell assay, calculated as number of sites per cell correlated well with those performed by cytosol assay, calculated as fmol/mg protein, independent of the type of leukemia. However, for cells with low receptor content, the two assay methods were more difficult to compare. In agreement with previous reports, the cytosol assay consistently underestimated the number of receptors with respect to the whole-cell assay, particularly in cases of lymphatic leukemia. Furthermore, the underestimation decreased for increasing levels of total cellular receptor. These results suggest that, in addition to possible defects in the cytoplasm-to-nucleus translocation process, the acceptor-binding capacity of the nucleus may also represent one of the factors which determines the levels of assayable cytoplasmic receptors. Moreover, they indicate that the two assay methods furnish nonequivalent information.

Glucocorticoid receptors and in vitro corticosensitivity of peanut-positive and peanut-negative human thymocyte subpopulations

In 6 human thymus glands, the immature subset of thymocytes was separated from the more mature one, by differential peanut lectin agglutination. These 2 cell subpopulations were analyzed for glucocorticoid receptor content by using a whole cell assay, with (3H)-triamcinolone acetonide as tracer. The unagglutinated thymocytes (peanut negative) contained about 2 times more receptor sites per cell than agglutinated (peanut positive) ones (7650 +/- 1550 S.D. verus 3195 +/- 896 S.D.). The affinity for steroid was similar in both cell subsets, as was the stereospecificity for glucocorticoids, the time-course of steroid-receptor association, and cytoplasmic to nuclear translocation. Despite the greater number of glucocorticoid receptor sites, the peanut-negative thymocyte subpopulation did not differ from the peanut-positive one in its sensitivity to the inhibitory effects of triamcinolone acetonide, as determined by measurements of the incorporation of radiolabeled precursors of protein and DNA. Moreover, the peanut-negative subset appeared more resistant in vitro to the steroid-induced cell lysis as compared to the peanut-positive one. Thus, our data suggest that glucocorticoid receptor density and corticosensitivity are not directly correlated and that the number of glucocorticoid receptor sites may be dependent on the degree of immunologic maturation.

Glucocorticoid receptors and in vitro corticosensitivity of peanut-positive and peanut-negative human thymocyte subpopulations

In 6 human thymus glands, the immature subset of thymocytes was separated from the more mature one, by differential peanut lectin agglutination. These 2 cell subpopulations were analyzed for glucocorticoid receptor content by using a whole cell assay, with (3H)-triamcinolone acetonide as tracer. The unagglutinated thymocytes (peanut negative) contained about 2 times more receptor sites per cell than agglutinated (peanut positive) ones (7650 +/- 1550 S.D. verus 3195 +/- 896 S.D.). The affinity for steroid was similar in both cell subsets, as was the stereospecificity for glucocorticoids, the time-course of steroid-receptor association, and cytoplasmic to nuclear translocation. Despite the greater number of glucocorticoid receptor sites, the peanut-negative thymocyte subpopulation did not differ from the peanut-positive one in its sensitivity to the inhibitory effects of triamcinolone acetonide, as determined by measurements of the incorporation of radiolabeled precursors of protein and DNA. Moreover, the peanut-negative subset appeared more resistant in vitro to the steroid-induced cell lysis as compared to the peanut-positive one. Thus, our data suggest that glucocorticoid receptor density and corticosensitivity are not directly correlated and that the number of glucocorticoid receptor sites may be dependent on the degree of immunologic maturation.

Clinical implications of glucocorticoid receptor studies in childhood acute lymphoblastic leukemia

We have performed in parallel, in 19 children with acute lymphoblastic leukemia, a quantitative determination of glucocorticoid levels, in vitro steroid induced inhibition of nucleic acid precursors, and a short-term clinical trial of corticosteroids alone, before the treatment was given, which included corticosteroids and other drugs. From our results it appears that high glucocorticoid receptor levels in acute lymphoblastic leukemia of children do not guarantee a clinical response to corticosteroids. On the other hand, glucocorticoid receptors may turn out to be of value in predicting a poor response to corticosteroids only if their levels are considerably low.