Effects of acute and prolonged opiate abstinence on extinction behaviour in rats.

We examined the role of withdrawal in relapse to drug-seeking and drug-taking by testing the effects of opiate abstinence on extinction behaviour in rats trained to self-administer heroin. Male Long-Evans rats responded for IV heroin under a heterogeneous chain (VI 120 s; FR 1) schedule in which "seeking" responses preceded a "taking" response which produced a drug infusion. Responding was then measured in extinction during acute (6, 12, and 24 hr) and prolonged (3, 6, 12, and 25 day) abstinence. Sucrose consumption and somatic withdrawal were assessed at each testing period. During acute abstinence, responses on the "drug-seeking" manipulandum increased at 24 hr, whereas responses on the "drug-taking" manipulandum increased at 6 hr. Both responses were elevated during the 12-day abstinence test. Sucrose consumption was reduced and somatic withdrawal scores were increased in opiate-experienced rats at each test period. Results suggest that heroin abstinence has different effects on drug-seeking and drug-taking and that these effects do not temporally coincide with somatic measures of opioid withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning probe microscopy of biological samples and other surfaces

Scanning probe microscopes derived from the scanning tunnelling microscope (STM) offer new ways to examine surfaces of biological samples and technologically important materials. The surfaces of conductive and semiconductive samples can readily be imaged with the STM. Unfortunately, most surfaces are not conductive. Three alternative approaches were used in our laboratory to image such surfaces. 1. Crystals of an amino acid were imaged with the atomic force microscope (AFM) to molecular resolution with a force of order 10^?8 N. However, it appears that for most biological systems to be imaged, the atomic force microscope should be able to operate at forces at least one and perhaps several orders of magnitude smaller. The substitution of optical detection of the cantilever bending for the measurement by electron tunnelling improved the reliability of the instrument considerably. 2. Conductive replicas of non-conductive surfaces enabled the imaging of biological surfaces with an STM with a lateral resolution comparable to that of the transmission electron microscope. Unlike the transmission electron microscope, the STM also measures the heights of the features. 3. The scanning ion conductance microscope scans a micropipette with an opening diameter of 0·04-0·1 μm at constant ionic conductance over a surface covered with a conducting solution (e.g., the surface of plant leaves in saline solution).     

Imaging red blood cells with the atomic force microscope

A novel technique for the reproduction of ultramorphological images and details of the surface of normal and pathological red blood cells (RBC) was investigated. The atomic force microscope (AFM) provided high-resolution images of cell surfaces. The RBC dimensions obtained by this technique revealed differences between native red cells in smears and glutaraldehyde-fixed red cells. It was shown that fixed red blood cells were best suited for the ultramorphological imaging of the cell surface.     

A multilevel framework for the attribute description of telecommunication services

Telecommunication services are traditionally described from the terminal viewpoint, including the user interaction with the service, as well as the specific terminal characteristics to the network that it is meant for. Also traditionally the instance of the telecommunication service was a call and a connection as a one-to-one couple. Nowadays networks with powerful multimedia/multiconnection/multiparty capabilities require that a telecommunication service should not be described any more as a conglomerate, but by its main service elements, which in turn are supported by other service elements, so that a service may be built up by building blocks in a levelled model. The criteria to be considered to find these elements are the user viewpoint, the information coding (or terminal) viewpoint and the network access viewpoint. This leads to the telecommunication service, party, party edge, user service module and abstract service module as pure user-dependent service elements, the service module for the terminal aspect, and the access connection element for transfer of the information over the network. All these basic service elements are ordered in a levelled structure called a multilevel framework. Each level or co-level represents a service element type which may be instantiated as a service object, and which is described statically by a table of attributes. Attributes for each level are listed and clarified. An example describing a well-known service is given to illustrate the use of the framework. The views expressed in this document have been developed by the RACE 2044 MAGIC.

1 RACE: Research into Advanced Communication Technologies for Europe. MAGIC: Multi-service Applications Governing Integrated Control.

The concepts presented are related to Release 2 and 3 for BISDN as defined in ITU-T.     

Motivational control of heroin seeking by conditioned stimuli associated with withdrawal and heroin taking by rats.

The authors investigated the impact of conditioned withdrawal on drug seeking by training rats to work for a heroin infusion on a seeking-taking schedule, which required responding on a seeking lever in order to gain the opportunity to self-administer the drug by a single response on a taking lever. Following the establishment of opiate dependence, a conditioned stimulus (CS) that had been previously paired with naloxone-precipitated withdrawal suppressed heroin seeking in extinction. However, when the rats had prior experience of heroin taking in the presence of the withdrawal CS, drug seeking was elevated in the presence of this stimulus. The authors conclude that the conditioned motivation of drug seeking in withdrawal depends on previous association of the CS with drug taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of glycerol and desmopressin on exercise performance and hydration in triathletes

Previous work from this laboratory has demonstrated an association between the suppression of c-myc expression and the antiproliferative activity of both topoisomerase II inhibitors and ionizing radiation in MCF-7 breast tumor cells. These findings suggested that suppression of c-myc expression could be related to the induction of DNA damage in this cell line. The present studies were designed to determine whether the inhibition of topoisomerase I (and the consequent induction of DNA strand breaks) would also result in the suppression of c-myc expression. At camptothecin concentrations of 1 microM and below, there was no detectable damage (single- or double-strand breaks) in bulk DNA or suppression of c-myc expression. At camptothecin concentrations of 5, 10, and 25 microM, where suppression of c-myc expression was observed, strand breaks in bulk DNA were also detected. These findings are consistent with the idea that suppression of c-myc expression could be a component of the DNA damage response pathway in MCF-7 breast tumor cells. In contrast to the absence of detectable damage to bulk DNA or suppression of c-myc expression at the lower concentrations of camptothecin, DNA synthesis was inhibited over the entire range of drug concentrations and demonstrated a strong correspondence with growth inhibition. These observations support the concept that growth inhibition of MCF-7 cells by camptothecin is closely related to the early suppression of DNA synthesis.     

Use of the synthetic superoxide dismutase/catalase mimetic EUK-134 to compensate for seasonal antioxidant deficiency by reducing pre-existing lipid peroxides at the human skin surface

The generation of reactive oxygen species (ROS) in UV-exposed skin is believed to contribute to the photoaging process. The stratum corneum (SC) contains a variety of enzymatic and non-enzymatic antioxidants to protect against various environmental sources of free radicals. We have previously shown a seasonal variation in SC catalase activity with strong deactivation in sun-exposed skin in the summer, whereas SC superoxide dismutase (SOD) activity remained intact in those conditions. This potentially leads to the local overproduction of H(2)O(2). The oxidized lipid squalene hydroperoxide accumulates at the surface of sun-exposed skin in the summer and upon exposure to ultravoilet A (UVA) doses as low as 0.1 J cm(-2) and adequate protection against excessive lipid peroxidation at times of UV exposure should be aimed for. We have been using the induction of lipid hydroperoxides at the skin surface by a single dose of UVA (1 J cm(-2)) as a model system to evaluate the protective effect of antioxidants in vivo. Topical treatment with the synthetic SOD/catalase mimetic molecule (EUK-134) 1 h before UVA exposure reduced the level of lipid peroxides at the surface of UVA-exposed skin but also baseline peroxide levels on non-irradiated skin were reduced in a dose-dependent fashion. In contrast to alpha-tocopherol, EUK-134 even reduced the level of lipid peroxides at the surface of UVA-exposed skin when it was applied after irradiation. We confirmed that this salen-manganese complex was able to reduce squalene hydroperoxide levels in vitro, suggesting peroxidase-like activity towards organic peroxides. These data support the concept that the synthetic SOD/catalase mimetic EUK-134 might be able to compensate for seasonal deficiencies in antioxidant defense capacity at the skin surface, thereby contributing to an optimal protection of the skin against the accumulation of oxidative damage.