Insights into the Structure of Dot@Rod and Dot@Octapod CdSe@CdS Heterostructures

CdSe@CdS dot@rods with diameter around 6 nm and length of either 20, 27, or 30 nm and dot@octapods with pod diameters of ?15 nm and lengths of ?50 nm were investigated by X-ray absorption spectroscopy. These heterostructures are prepared by seed-mediated routes, where the structure, composition, and morphology of the CdSe nanocrystals used as a seed play key roles in directing the growth of the second semiconducting domain. The local structural environment of all the elements in the CdSe@CdS heterostructures was investigated at the Cd, S, and Se K-edges by taking advantage of the selectivity of X-ray absorption spectroscopy, and was compared to pure reference compounds. We found that the structural features of dot@rods are independent of the size of the rods. These structures can be described as made of a CdSe dot and a CdS rod, both in the wurtzite phase with a high crystallinity of both the core and the rod. This result supports the effectiveness of high temperature colloidal synthesis in promoting the formation of core@shell nanocrystals with very low defectivity. On the other hand, data on the CdSe@CdS with octapod morphology suggest the occurrence of a core composed of a CdSe cubic sphalerite phase with eight pods made of CdS wurtzite phase. Our findings are compared to current models proposed for the design of functional heterostructures with controlled nanoarchitecture

Environmental risk assessment of antibacterial agents using an in vitro test

Algal toxicity of antibacterial agents used in intensive farming was investigated. The growth-inhibiting effects of oxytetracycline (OTC), sulphametazine (SMZ) and tylosin (TYL) were investigated by a modified test procedure based on the procedure described in the ISO 8692 (1989) protocol on the freshwater green alga Selenastrum capricornutum. Algal growth was measured as increased chlorophyll concentration. The chlorophyll was extracted with ethanol and fluorometrically determined. Results were quantified in terms of growth rates using Weibull equation to describe the concentration response relationship. The toxicity (EC50 value, mg/l) were: OTC, 4,17; SMZ, 10,7;TYL, 0,949, respectively

Synthesis of a ditopic cyclophane based on the cyclobutane ring by chalcone photocycloaddition

The intramolecular photocycloaddition of chalcones to give cyclobutanes has proven to be a fast and simple method to shrink a cyclophane ring to a tricyclic system, in order to prepare potential ditopic receptors. In particular, the chalcone 1, having dioxyethylene chains as spacers, is converted in high yield to the cyclobutane 2. NOESY spectroscopy indicates that the formation of 2 occurs by a head-to-head syn ring closure. (C) 2003 Elsevier Science Ltd. All rights reserved

In vitro hydroxylation of testosterone in rabbits: influence of age and sex*

Introduction Hydroxylated metabolites of testosterone (T) have been proposed as useful markers of specific isoform P450 activity in rats (1). Only few studies have been devoted to characterisation of P450 biotransformation activity in food producing species thus the aim of this study was to define the influence of sex and age in rabbits on the metabolic profile of hydroxylated testosterone (OHT) metabolites using an HPLC method able to separate nine metabolites. The role played by CYP3A was also studied in Rifampicin (RIF) induced rabbits. Material and methods Liver microsomes were obtained (2) from rabbits. five male (3\ub10.4 kg), five female (3\ub10.2 kg), five young male (1,5\ub10,3 kg), and two male induced with RIF (50 mg/kg, 4 days, ip). Microsomes (0.2 mg/ml) were incubated for 10 min, at 37\ub0C with 250 \ub5M T. Hydroxylated metabolites were extracted with methylene chloride and separated according to Purdon (3) with HPLC using a C18column and ternary phase gradient elution. Elution times were compared with those of pure standards (Steraloids). Discussion Main differences are: the absence in males of 16alfa-OHT; the greater production (*P<0,001) of 6beta-OHT, 11alfa-OHT, 16beta-OHT and 2beta-OHT compared to females; the decreased production (#P<0.001) of 6beta-OHT and 16alfa-OHT in young rabbits versus adult ones. Based on data reported for other species (1, 4) apparently, the isoforms involved in rabbits are CYP3A for 6beta-OHT, and 2beta-OHT; and CYP2B for 16alfa-OHT, and 16beta-OHT. RIF induced microsomes gave a significantly (\ub0P<0,001) greater quantities of 6beta-OHT, 2beta-OHT supporting, also in rabbits, the CYP3A role played in the production of these hydroxyl-derivatives

Studio mediante sistemi in vitro e HPLC delle differenze specie specifiche dei metaboliti idrossilati del Testosterone

SUMMARY - A preliminary study was performed to investigate by HPLC analyses the metabolism of testosterone to various hydroxylated metabolites by using liver microsomal preaparation obtained from different veterinary species. The analytical method was able to identify and quantify the various TST-metabolites produced. Different production of the metabolites was observed among the different veterinary species considered

In Vitro Test Of Antibacterial Agents Used in Intensive Farming

Antibacterial agents may be considered environmental micropollutants because of they are developed with the intention of performing a biological effect and have many of the necessary properties to bioaccumulate and provoke effects in the ecosystem. The antibacterial agents are greatly used in intensive farming for therapeutic and prophylactic purpose and the manure used as fertiliser directly applied on fields may contain these pharmaceutical substances that will end up first in the terrestrial ecosystem and then in the aquatic one. The antibacterial agents commonly used in Italy are oxitetracycline (OT), sulphametazine (SM) and tylosin (TY). The toxic effect data (EC50) of antibacterial agents on various aquatic species found in the literature (Macri et al., 1988; Wollenberger et al., 2000) shows values in the mg/l range and the investigations have primarily been done on crustaceans and fish rather than algal species. The few tests carried out using as test organisms algal species show on the other hand that algae are very sensitive to antibacterial agents (Holten Lutzhoft et al., 1999) Aim of this study was to perform acute toxicity test using as sensible model a freshwater green alga. The growth-inhibiting effects of OT, SM and TY were investigated by a modified test procedure based on the procedure described in the ISO 8692 (1989) protocol on the freshwater green alga Selenastrum capricornutum. The compounds were tested at 8 concentration levels without replicates in a range of 1-25 mg/l for SM, 0,1-5 mg/l for TY and 1-10 mg/l for OT, whereas the controls were grown in six replicates. The number of tests was at least three. Algal growth was measured as increased chlorophyll concentration by extraction with ethanol followed by measurement of fluorescence (excitation wavelength = 430 nm, emission wavelength = 671 nm). Results were quantified in terms of growth rates using Weibull equation (Nyholm et al., 1992) to describe the concentration response relationship. The toxicity (EC50 value, mg/l) were: OT, 4,17; SM, 10,7;TY, 0,949. Although tylosin is the most toxic agent (EC50 = 0,949 mg/l) experimental data shows that it is the one with the shortest DT50 among those assayed. References H-C. Holten Lutzhoft et al.: Arch. Environ. Contam. Toxicol. (1999) 36, 1-6. ISO 8692 (1989). A. Macri et al.: Ecotoxicol. Environ. Safety (1998) 8, 101-105. N. Nyholm et al.: Environ. Toxicol. Chem. (1992) 11, 157-167. L. Wollenberger et al.: Chemosphere (2000) 40, 723-730

In vivo hormone treatments in calves: effects on in vitro hydroxylation of testosterone

Introduction Stereospecific hydroxylation of testosterone has been related to the activity of specific isoforms of P450 (1) and, in cattle, CYP3A has been reported to be involved in the production of 2beta-hydroxytestosterone (2beta-OHT), 6beta hydroxytestosterone (6beta-OHT) and androstenedione (2,3). The aim of this study was to evaluate the pattern of hydroxylation of testosterone in calves treated with hormones at dosages schedules usually adopted in illegal treatment. Material and methods Calves were randomly organised in 6 groups as follow, control (C), and treated with estradiol (E, 25 mg), testosterone (T, 100 mg), nortestosterone (NT, 100 mg), E+T (25 mg + 100 mg), E+NT (25 mg + 100 mg). Single or combined hormones im administrations were at day 0 and after 14, 28 and 42 days. All the animals were slaughtered 14 days after the last treatment (day 58) and liver lobes collected for microsome preparations. Microsomes (0.2 mg/ml) were incubated for 10 min, at 37\ub0C with 250 \ub5M TST. Metabolites were extracted with methylene chloride and hydroxy-TST metabolites (OHT) were separated according to Purdon (1) with a Jasco HPLC using a C18column and ternary (water, acetonitrile, methanol) gradient elution. Elution times were compared with those of pure standards (Steraloids). Conclusions Liver microsomes from NT treated calves produced significantly (*P<0.001) lower amount of 6beta-OHT, 16beta-OHT, and 2beta-OHT, and detectable quantities of two other metabolites: 11alfa-OHT and 7alfa-OHT, never found in the incubation extracts obtained with the other groups of treatment. The lacking of significant effects on OHT metabolites production in animal treated with E, T, E+NT and E+T it is likely due to the too long interval time (14 days) between the last hormone administration and the animal slaughtering. Nevertheless at that time the inhibitory effect related to the NT treatment was still evident

The environmental fate of veterinary drugs: in field assessment

Recent studies have shown that a multitude of drugs are present in the aquatic systems [1]. Due to the spreading of drug-resistance there is concern about the persistence of antibiotic residues in the environment. In past times tetracyclines and macrolides were used as feed additives in food producing animals; now their use has been restricted to therapeutic purposes. A high percentage of the drug is often excreted unchanged in manure and its use as top soil dressing can contaminate water via run-off drainage or through leaching. In 1996 a \u201cNote for guidance for the environmental risk assessment of veterinary drugs\u201d [2] was approved and several information on the environmental persistence and safety of drugs are now requested for registration. In this study the results from an experimental model carried out \u201cin-field\u201d are reported. The environmental fate of tylosin (TYL) and oxytetracycline (OTC) orally administered for five days to 40 calves (20 mg/kg and 60 mg/kg, respectively) was monitored for 6 months in manure, in soil and in surface water. TYL showed a rapid degradation, falling below the limit of quantification after 45 days. For OTC drug half-life in manure was calculated (T1/2el=30 days); only traces (lower than the limit of detection, 10 ppb) were found in soil and ground water. Ten ppb is the Safety Limit recommended by the EMEA [2] for drug residues in soil. The data were fitted to a simple mathematical model to check its suitability to predict environmental concentration in manure, soil, and ground water. Result indicate that the five months period necessary for manure ripening permits an adequate degradation and appears sufficient to minimize the environmental impact of these drugs

Use of oxytetracycline and tylosin in intensive calf farming: evaluation of transfer to manure and soil

Antibiotics may enter soils with manure from treated animals. Because of their biological effects, antibiotics are regarded as potential micropollutants. The levels of oxytetracycline and tylosin over time were followed in faeces, bedding and manure, and then in the soil of a manured field and surrounding drainage courses, after oral treatment of calves. Fifty Simmental calves were treated for 5 days with 60 mg/kg/day of oxytetracycline. After 15 days the animals were treated for 5 days with 20 mg/kg/day of tylosin. Tylosin degraded rapidly, and was no longer detected in manure 45 days after cessation of treatment and no trace of the compound was detected in soil or surrounding water (detection limits 10 microg/l). The half-life of oxytetracycline in manure was 30 days and the compound was still detectable in this matrix (820 microg/kg) after 5 months maturation. In the manured soil oxytetracycline was detected at concentrations at least 10 times lower than the European Agency for the Evaluation of Medicinal Products threshold (100 microg/kg) requiring phase II environmental risk assessment. Oxytetracycline was not detected in the water courses (detection limit 1 microg/l). These results demonstrate that the processes occurring between faeces production and application of manure to the soil are very effective in reducing the load of TYL and OTC in the environment. For both drugs a toxicity test was performed using the alga Selenastrum capricornutum. The EC50 was 4.18 mg/l for oxytetracycline and 0.95 mg/l for tylosin. A worst-case hazard assessment for the aquatic environment was performed comparing the ratio between the measured concentrations (LOD) and effect data from previous work (OTC) or from this work (TYL). This showed ratio between toxicity levels (bacteria) (EC50=0.14 mg/l) and measured concentrations (LOD=1 microg/l) for OTC to be 140. The corresponding value for TYL (LOD=10 microg/l) was 9