2D self-assembly of oligo(p-phenylene vinylene) derivatives: from dimers to chiral rosettes

Enantiomerically pure oligo(p-phenylene vinylene) diaminotriazine derivatives and a short structurally related achiral diaminotriazine derivative, all having a rigid backbone in common, are studied to self-assemble at the solution-graphite interface by scanning tunneling microscopy. As a function of the length of the backbone, different two-dimensional motifs are formed (dimers and rosettes) that are rationalized in terms of the balance between different intermolecular interactions, in this case, intermolecular hydrogen bonding and the packing requirements of the alkyl chains on a graphite surface. In addition, the effect of molecular chirality on monolayer chirality is investigated, revealing molecular size-dependent expressions of the monolayer chirality.     

Inter-comparison of laser photoacoustic spectroscopy and gas chromatography techniques for measurements of ethene in the atmosphere

Laser photoacoustic spectroscopy (LPAS) is highly suitable for the detection of ethene in air due to the overlap between its strongest absorption lines and the wavelengths accessible by high-powered CO2 lasers. Here, we test the ability of LPAS to measure ethene in ambient air by comparing the measurements in urban air with those from a gas chromatography flame-ionization detection (GC-FID) instrument. Over the course of several days, we obtained quantitative agreement between the two measurements. Over this period, the LPAS instrument had a positive offset of 330 +/- 140 pptv (parts-per-trillion by volume) relative to the GC-FID instrument, possibly caused by interference from other species. The detection limit of the LPAS instrument is currently estimated around 1 ppbv and is limited by this offset and the statistical noise in the data. We conclude that LPAS has the potential to provide fast-response measurements of ethene in the atmosphere, with significant advantages over existing techniques when measuring from moving platforms and in the vicinity of emission sources.     

Sediment dilution method to determine sorption coefficients of hydrophobic organic chemicals

Sorption coefficients of hydrophobic organic chemicals (HOC) to sediments and soils can easily be underestimated in traditional batch experiments, especially because analysis of the aqueous concentration often includes compounds sorbed to colloidal organic matter. In this work, a "sediment dilution approach" has been combined with measurements of freely dissolved concentrations to determine sorption coefficients of five chlorobenzenes and two chloroanilines in spiked sediment and of two unknown chemicals in field-contaminated sediment. A range of sediment suspensions with different sediment-water ratios was made. Freely dissolved concentrations in these suspensions were measured by negligible depletion solid-phase microextraction (nd-SPME). Sediment-water sorption coefficients (KD) were derived from the decrease of the freely dissolved concentrations as a function of the "dilution factor" (DF = volume water/mass sediment). The determined sorption coefficients were very similar to literature values. The experimental setup provides sorption coefficients without the need for total extractions, and the negligible depletion SPME technique does not require phase separation. The proposed method might be an alternative for batch equilibrium experiments to determine sorption coefficients.     

Community assessment of availability, consumption, and cultural acceptability of food sources of (pro)vitamin A: toward the development of a dietary intervention among preschool children in rural Burkina Faso

BACKGROUND: Vitamin A deficiency remains a public health problem in Burkina Faso and elsewhere in the developing world. Dietary diversification is a promising strategy that needs to be explored to strengthen the country's ongoing supplementation program. OBJECTIVE: The purpose of this study was to identify locally available and acceptable (pro)vitamin A-rich foods to be included in a dietary intervention addressing vitamin A deficiency in children aged six months to three years. METHODS: A food ethnographic study combining recall methods, observation, and focused group discussion was conducted in the dry and rainy seasons. Thirty-five mother-child pairs were randomly selected and included in the study. RESULTS: The dietary pattern of children was characterized by low diversity with extremely low energy and vitamin A intake in both seasons. The study identified the availability of numerous (pro)vitamin A-rich foods, but these foods are either not consumed or consumed by few in low amounts and/or in low frequencies. The main constraining factors identified are related to financial accessibility (for liver), seasonal availability (for egg, milk, mango, papaya, and green leafy vegetables), and beliefs related to consumption and preparation (for green leafy vegetables). However, the study also revealed that the study population associated all identified (pro)vitamin A-rich foods with positive attributes such as health, strength, and vitamin richness, which might offer an entry point for designing and implementing dietary interventions. CONCLUSIONS: Based on the findings of this formative research, intervention strategies with mango and liver are proposed to improve the vitamin A intake and status of children in the rural areas of Burkina Faso.     

Lead and zinc contents of food and diets in the Netherlands

Summary The lead and zinc contents of foodstuffs sampled in Dutch retail shops were determined by means of atomic absorption spectrophotometry. Extremely high contents of these metals were not found. The daily intakes through food and beverages calculated on the basis ofper caput consumption data for the Netherlands were 105 microgrammes of lead and 16.8 milligrammes of zinc. Calculations based on diet studies of selected population groups (farmers, inhabitants of a city, families in a northern province and students) provided intakes of lead and zinc of the same order, namely 63 to 161 microgrammes of lead and 15.4 to 24.6 milligrammes of zinc per person per day. The intakes by toddlers were assessed at 42 g and 8.0 mg respectively. These results are compared with those calculated for three other countries. A toxicological evaluation of these levels is given.

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Blei- und Zinkgehalt der Lebensmittel und der Kost in den Niederlanden

Zusammenfassung Die Blei- und Zinkgehalte von Lebensmitteln aus niederländischen Läden wurden durch Atomabsorptionsspektrophotometrie ermittelt. Außerordentlich hohe Gehalte wurden nicht gefunden. Berechnungen auf Grund der täglichen Aufnahme durch Nahrung und Getränke (aus Produktions-, Import- und Exportwerten ermittelt) ergaben pro Kopf der Bevölkerung 105 g Blei und 16,8 mg Zink. Weitere Berechnungen stützten sich auf den täglichen Lebensmittelverbrauch von Sondergruppen (Bauern, Stadtbewohnern, Familien in einer nördlichen Provinz und Studenten); sie ergaben Blei- und Zinkaufnahmen in ähnlichen Mengen, nämlich 63 bis 161 g Blei und 15,4 bis 24,6 mg Zink pro Tag. Für die Aufnahme durch Kleinkinder wurden 42 g Blei und 8,0 mg Zink pro Tag berechnet. Die Ergebnisse wurden mit Daten aus drei anderen Ländern verglichen. Eine toxikologische Beurteilung der Befunde wurde versucht.

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Authors wish to thank Mr. P. W. J. de Graaf and Mr. W. van der Schee for their zinc and lead determinations.     

Radiation-activated prodrugs as hypoxia-selective cytotoxins: model studies with nitroarylmethyl quaternary salts

Bioreductive drugs are designed to be activated by enzymatic reduction in hypoxic regions of tumours, but activation of these drugs is not always fully suppressed by oxygen in normal tissues. A further limitation is that bioreductive drug activation depends on suitable reductases being expressed in the hypoxic zone. This essay proposes an alternative approach in which prodrugs are reduced, and thereby activated, in hypoxic regions by ionizing radiation rather than by enzymes. This strategy is theoretically attractive, but design requirements for such radiation-activated cytotoxins are challenging. In particular, the reducing capacity of radiation at clinically relevant doses is small, which necessitates the development of prodrugs capable of releasing very potent cytotoxins efficiently in hypoxic tissue. It is shown that nitroarylmethyl quaternary (NMQ) salts possess many of the features required of a radiation-activated prodrug. In some heterocyclic NMQ compounds the cytotoxicity of the latent cytotoxic amine effector is suppressed by > 100-fold in the prodrug form, and the effector is released rapidly by fragmentation following reduction by a single electron. Appreciable cytotoxic activation of NMQ prodrugs can be achieved by irradiation at clinically relevant doses in anoxic plasma. Some of the further drug design challenges required to develop a clinical agent based on this approach are outlined.     

Experimental hepatitis E: pathogenesis in cynomolgus macaques (Macaca fascicularis)

Children with acute lymphoblastic leukemia (ALL) who have completed 2.5 to 3 years of initial chemotherapy have an off-therapy relapse rate of approximately 20%. In an attempt to improve the survival of children with a late bone marrow (BM) relapse (ie, occurring greater than 6 months after cessation of primary therapy), the Pediatric Oncology Group designed a randomized study to compare the efficacy of doxorubicin/prednisone and cytarabine/teniposide in a multidrug retreatment chemotherapy program. Treatment consisted of remission reinduction with vincristine, prednisone, and doxorubicin, central nervous system prophylaxis with triple intrathecal chemotherapy, and continuation therapy (for 132 weeks) with alternating cycles of oral 6-mercaptopurine/methotrexate and intravenous vincristine/cyclophosphamide. Patients received intermittent courses of either prednisone/doxorubicin (regimen 1) or teniposide/cytarabine (regimen 2) during continuation therapy and a late intensification phase with either vincristine, prednisone, and doxorubicin (regimen 1) or teniposide and cytarabine (regimen 2). One hundred two of 105 evaluable patients (97%) achieved a second complete remission. Twenty-eight of 50 patients on regimen 1 have failed compared with 28 or 52 patients on regimen 2 (log-rank analysis, P = .68), indicating that this trial was inconclusive as to which treatment regimen was superior. The overall 4-year event-free survival for children with a late BM relapse was 37% +/- 6%. Age less than 10 years at initial diagnosis (P < or = .001), white blood cell count less than 5,000/microL at relapse (P = .036) and duration of first remission greater than 54 months (P = .039) were independently associated with a more favorable outcome. While the randomized trial was inconclusive, prolonged second complete remissions were secured in more than one-third of children with a late BM relapse of ALL. The prognostic factors identified may help select children with a late BM relapse who can be successfully retreated with chemotherapy alone.     

Continuous spinal anaesthesia

CD59 is a cell membrane-bound complement regulatory protein on glomerular cells that inhibits C5b-9 assembly and insertion. This report describes a recently developed model of immune thrombotic microangiopathy (TMA) induced by the renal artery perfusion of anti-glomerular endothelial cell (anti-GEN) antibody. To examine the role of CD59 in protecting the GEN from immune-mediated injury, rats underwent selective renal artery perfusion with F(ab')2 fragments of anti-CD59 monoclonal antibody to block CD59 activity or control mouse IgG followed by anti-GEN antibody or control goat IgG. Neutralization of CD59 in normal rats did not result in any significant functional or histologic changes. Perfusion with anti-CD59 did not change deposition of the pathogenic anti-GEN IgG used to induce the TMA model. However, neutralization of CD59 in the TMA model resulted in more C5b-9 formation in glomeruli, accompanied by increased platelet and fibrin deposition, more severe endothelial injury, and reduced renal function compared with the animals perfused with control F(ab')2 fragments. These results demonstrate directly that CD59 serves a protective role for GEN in this TMA model of rats, and confirm that C5b-9 formation has a critical pathogenic role in the mediation of the disease. CD59 may play an important role in protecting glomerular endothelium from other complement-mediated types of injury.