Stephen E. Harding

Effects of Naltrexone and Fluoxetine on Alcohol Self-Administration and Reinstatement of Alcohol Seeking Induced by Priming Injections of Alcohol and Exposure to Stress

We have recently shown that priming injections of alcohol and footshock stress reinstate alcohol seeking in drug-free rats. Here we tested whether naltrexone and fluoxetine, two drugs used in the treatment of alcohol dependence, would affect reinstatement of alcohol seeking induced by these events. We also determined the effects of these drugs on alcohol self-administration during the maintenance phase. Rats were trained to press a lever for a 12% w/v alcohol solution. After stable drug-taking behavior was obtained, lever pressing for alcohol was extinguished. Reinstatement of drug seeking was then determined after priming injections of alcohol (0.24–0.96 g/kg) or exposure to intermittent footshock (5 and 15 min). Rats were pretreated with naltrexone (0.2–0.4 mg/kg) or fluoxetine (2.5–5 mg/kg) during maintenance or during tests for reinstatement. Both naltrexone and fluoxetine decreased lever presses for alcohol during the maintenance phase. Naltrexone blocked alcohol-induced, but not stress-induced reinstatement. In contrast, fluoxetine blocked stress-induced reinstatement, while its effect on alcohol-induced reinstatement was less consistent. The implications of these data to the understanding of relapse to alcohol are discussed.

Dynamic light scattering as a relative tool for assessing the molecular integrity and stability of monoclonal antibodies

Abbreviations used: AUC: analytical ultracentrifugation, DLS: dynamic light scattering, HPLC: high performance liquid chromatography, PCS: photon correlation spectroscopy, QELS: quasi elastic light scattering, PDI: polydispersity index, kDa: kiloDalton, SLS: static light scattering, M W : weight average molar mass, S: Svedbergs, IgG4: immunoglobulin G subclass 4, Fab: fragment antigen binding, T M : melting point temperature. Biotechnology and Genetic Engineering Reviews Vol. 24, 117-128 (2007)

Polysaccharide drug delivery systems based on pectin and chitosan.

Abstract Chitosans and pectins are natural polysaccharides which show great potential in drug delivery systems. Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-D-glucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). Other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds. Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the “smooth” and “hairy” regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (LM) pectins have a DM < 50%. Low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca2 +) which has potential applications especially in nasal formulations.

The effect of the degree of esterification on the hydrodynamic properties of citrus pectin

Estimation of the influence of the degree of esterification on the hydrodynamic properties of citrus pectins provides a simple demonstration of how chemical variation can influence structural properties of polysaccharides. Five citrus pectins with average degree of esterification 77.8, 65.0, 53.9, 37.8 and 27.9%, respectively were studied using capillary viscometry, sedimentation velocity, sedimentation equilibrium and size exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLS). Molecular weights (weight average) for all five pectin samples were within the range 190 000^ 30 000 g/mol as confirmed by theindependent techniques of sedimentation equilibrium and SEC-MALLS. Estimates for the conformation dependent Wales‐van HoldeOks=âhaU and frictionalO f=f0U ratios from the hydrodynamic data clearly indicates increasing chain stiffness with decreasing degree of esterification. It appears that both steric and electrostatic interactions are important in these conformational changes. q 2000 Elsevier Science Ltd. All rights reserved.

Transmission electron microscopy studies on pig gastric mucin and its interactions with chitosan

Transmission electron microscopy has been employed to visualize the molecular structure and organization of a highly purified preparation of pig gastric mucin (molar mass M~9 × 106g/mol, as determined by low speed sedimentation equilibrium), prepared for microscopy by two completely independent methods. Samples were prepared for imaging by air drying on mica (in the presence of 50% glycerol) as well as critical point drying in acetone/CO2. The data appear consistent with the accepted linear model for mucins, and are consistent with regions of variable degrees of glycosylation along the polypeptide backbone chain, with the overall conformation that of a loose or random coil. The behaviour of this mucin in a dilute solution mixture with the potential mucoadhesive polymer chitosan (M~1 60,000 g/mol) was then explored, and a clear interaction was demonstrated, consistent with dilute solution measurements using sedimentation velocity analysis in the analytical ultracentrifuge.

Simultaneous determinations of the molecular weight distributions of amyloses and the fine structures of amylopectins of native starches

Abstract Native A (wheat and waxy rice), B (potato), and C (cassava and sweet potato) types of starches were each debranched with isoamylase, and separated into amylose and amylopectin fractions by HPLC on size exclusion columns coupled on-line to multi-angle-laser-light-scattering and differential refractometer detectors. The absolute molecular weights of amyloses and chain length distributions of amylopectins were determined simultaneously, and pre-isolation of the amylopectin was not necessary. The molecular weights of debranched amylose from starches that have not been fractionated to separate amylose and amylopectin are significantly higher than published values for the undebranched fractionated amylose. The polymodal profiles of the refractive index chromatograms showed the complexity of the amylopectin structure of starches. The chain length distribution of amylopectin depends critically on the method for analysing the broad chromatogram when determined by either noting the minima/inflections or deconvoluting the overlapping amylopectin fraction into numerous normal/Gaussian distributions. Although the results from the former (conventional) method of analysis were comparable with the literature values, they did not appear to be as sensitive a technique for detecting differences as the multiple Gaussian approach. Overall, the study suggested that the amylopectin chain units might be more complex than originally envisaged and that different degrees of chain packing for the molecules can be inferred from this multiple component analysis.

Materials for Encapsulation

A multitude of substances are known which can be used to entrap, coat, or encapsulate solids, liquids, or gases of different types, origins, and properties. However, only a limited number thereof have been certified for food applications as “generally recognized as safe” (GRAS) materials. It is worth mentioning that the regulations for food additives are much stricter than for pharmaceuticals or cosmetics. Consequently, some compounds, which are widely accepted for drug encapsulation, have not been approved for use in the food industry. Moreover, different regulations can exist for different continents, economies, or countries, a problem which has to be addressed by food producers who wish to export their products or who intend expanding their markets.

Polyuronide solubilization during ripening of normal and mutant tomato fruit

Abstract The amount and molecular size of soluble polyuronide extractable from ripening tomatoes is markedly affected by residual enzyme activity. The efficacy of phenol-acetic acid-water treatment to remove this residual activity is demonstrated. Data obtained using treated wall preparations confirms that there is an increase in soluble polyuronide during normal ripening and that this also occurs in the ‘Never-ripe’ mutant, and to a lesser degree in the ‘ripening-inhibitor’ mutant. However, changes in the molecular size of this polyuronide during normal ripening were not as extensive as previously reported and few changes were apparent in either of the mutants. Measurements were also made of polygalacturonase (EC 3.2.1.15) and pectinesterase (EC 3.1.1.11) activity during ripening. The level of polygalacturonase activity does not appear to correlate with the amount of soluble polyuronide released, but may be related to the extent of depolymerisation. No relationship was apparent between the level of pectinesterase and either soluble polyuronide released or depolymerization.

Effects of unconditioned and conditioned social defeat on alcohol self-administration and reinstatement of alcohol seeking in rats

Rationale and objectivesWe and others have shown that a stressor commonly used in laboratory studies, intermittent footshock, reinstates alcohol seeking in a rat relapse model. The effects of more ethologically relevant stressors on reinstatement have not been examined. Here, we characterized the effects of social defeat (a naturalistic stressor) or a cue associated with the defeat experience on reinstatement of alcohol seeking. We also examined the effect of unconditioned and conditioned social defeat on alcohol self-administration.MethodsRats were trained to self-administer alcohol (12% w/v, 1 h day−1), and after stable responding, one group of animals received five exposures to social defeat paired with peppermint odor prior to daily self-administration sessions. After three more self-administration sessions, these rats were tested for the effects of the peppermint odor cue on self-administration. In another group of rats, the effects of three daily exposures to social defeat paired with peppermint odor on extinction of responding were examined. After further extinction sessions, the effect of the odor cue on reinstatement was tested in these animals. The acute effect of social defeat on reinstatement was examined in another group of animals.ResultsAcute exposure to social defeat decreased alcohol self-administration, reduced rates of responding during extinction, and did not reinstate alcohol seeking. Exposure to a discrete odor cue previously paired with social defeat decreased alcohol self-administration but induced modest reinstatement of alcohol seeking.ConclusionsResults provide the first demonstration of reinstatement of alcohol seeking by a cue paired with social defeat and are also in agreement with previous findings on the suppressive effect of social defeat stress on alcohol self-administration.

MSTARA and MSTARI: interactive PC algorithms for simple, model independent evaluation of sedimentation equilibrium data

Abstract This paper describes a program available for PCs for the evaluation of molecular weights from sedimentation equilibrium. This program, in its two forms – MSTARA for absorption optical records and MSTARI for interference optical records – requires no prior assumption of the nature of the system (ideal, non-ideal, monodisperse, polydisperse, self-associating etc.) and takes into consideration the whole solute distribution (i.e. from solution meniscus to cell base) in the ultracentrifuge cell rather than just a selected data-set. MSTARA or MSTARI are therefore recommended as a first analysis programme of sedimentation equilibrium data coming off an absorption or interference based analytical ultracentrifuge. These programmes are therefore particularly well suited if heterogeneity (polydispersity or interaction phenomena) or non-ideality is suspected. Their use is demonstrated for a series of data-set types (ideal, non-ideal, polydisperse and self-associating). Although MSTARA and MSTARI are model independent, they provide the basis for more detailed analysis of interactions, polydisperse distributions or non-ideality via easy export of ASCII datafiles to model dependent routines.