Stressful animal housing conditions and their potential effect on sympathetic neurotransmission in mice

Although the sympathetic nervous system (SNS) plays a major role in mediating the peripheral stress response, due consideration is not usually given to the effects of prolonged stress on the SNS. The present study examined changes in neurotransmission in the SNS after exposure of mice (BALB/c) to stressful housing conditions. Focal extracellular recording of excitatory junction currents (EJCs) was used as a relative measure of neurotransmitter release from different regions of large surface areas of the mouse vas deferens. Mice were either group housed (control), isolation housed (social deprivation), group housed in a room containing rats (rat odor stress), or isolation housed in a room containing rats (concurrent stress). Social deprivation and concurrent stressors induced an increase of 30 and 335% in EJC amplitude, respectively. The success rate of recording EJCs from sets of varicosities in the concurrent stressor group was greater compared with all other groups. The present study has shown that some common animal housing conditions act as stressors and induce significant changes in sympathetic neurotransmission.

Habitat-predator association and avoidance in rainbowfish (Melanotaenia spp.)

The ability to recall the location of a predator and later avoid it was tested in nine populations of rainbowfish (Melanotaenia spp.), representing three species from a variety of environments. Following the introduction of a model predator into a particular microhabitat, the model was removed, the arena rotated and the distribution of the fish recorded again. In this manner it could be determined what cues the fish relied on in order to recall the previous location of the predator model. Fish from all populations but one (Dirran Creek) were capable of avoiding the predator by remembering either the location and/or the microhabitat in which the predator was recently observed. Reliance on different types of visual cues appears to vary between populations but the reason for this variation remains elusive. Of the ecological variables tested (flow variability, predator density and habitat complexity), only the level of predation appeared to be correlated with the orientation technique employed by each population. There was no effect of species identity, which suggests that the habitat that each population occupies plays a strong role in the development of both predator avoidance responses and the cues used to track predators in the wild.

One-dimensional quantum walk with unitary noise

The effect of unitary noise on the discrete one-dimensional quantum walk is studied using computer simulations. For the noiseless quantum walk, starting at the origin (n=0) at time t=0, the position distribution P-t(n) at time t is very different from the Gaussian distribution obtained for the classical random walk. Furthermore, its standard deviation, sigma(t) scales as sigma(t)similar tot, unlike the classical random walk for which sigma(t)similar toroott. It is shown that when the quantum walk is exposed to unitary noise, it exhibits a crossover from quantum behavior for short times to classical-like behavior for long times. The crossover time is found to be Tsimilar toalpha(-2), where alpha is the standard deviation of the noise.

Genetics of melanoma predisposition

Predisposition to melanoma is genetically heterogeneous. Two high penetrance susceptibility genes, CDKN2A and CDK4, have so far been identified and mapping is ongoing to localize and identify others. With the advent of a catalogue of millions of potential DNA polymorphisms, attention is now also being focused on identification of genes that confer a more modest contribution to melanoma risk, such as those encoding proteins involved in pigmentation, DNA repair, cell growth and differentiation or detoxification of metabolites. One such pigmentation gene, MC1R, has not only been found to be a low penetrance melanoma gene but has also been shown to act as a genetic modifier of melanoma risk in individuals carrying CDKN2A mutations. Most recently, an environmental agent, ultraviolet radiation, has also been established as a modifier of melanoma risk in CDKN2A mutation carriers. Hence, melanoma is turning out to be an excellent paradigm for studying gene-gene and gene-environment interactions.

The trans-membrane protein p25 forms highly specialized domains that regulate membrane composition and dynamics

Trans-membrane proteins of the p24 family are abundant, oligomeric proteins predominantly found in cis-Golgi membranes. They are not easily studied in vivo and their functions are controversial. We found that p25 can be targeted to the plasma membrane after inactivation of its canonical KKXX motif (KK to SS, p25SS), and that p25SS causes the co-transport of other p24 proteins beyond the Golgi complex, indicating that wild-type p25 plays a crucial role in retaining p24 proteins in cis-Golgi membranes. We then made use of these observations to study the intrinsic properties of these proteins, when present in a different membrane context. At the cell surface, the p25SS mutant segregates away from both the transferrin receptor and markers of lipid rafts, which are enriched in cholesterol and glycosphingolipids. This suggests that p25SS localizes to, or contributes to form, specialized membrane domains, presumably corresponding to oligomers of p25SS and other p24 proteins. Once at the cell surface, p25SS is endocytosed, together with other p24 proteins, and eventually accumulates in late endosomes, where it remains confined to well-defined membrane regions visible by electron microscopy. We find that this p25SS accumulation causes a concomitant accumulation of cholesterol in late endosomes, and an inhibition of their motility - two processes that are functionally linked. Yet, the p25SS-rich regions themselves seem to-exclude not only Lamp1 but also accumulated cholesterol. One may envision that p25SS accumulation, by excluding cholesterol from oligomers, eventually overloads neighboring late endosomal membranes with cholesterol beyond their capacity (see Discussion). In any case, our data show that p25 and presumably other p24 proteins are endowed with the intrinsic capacity to form highly specialized domains that control membrane composition and dynamics. We propose that p25 and other p24 proteins control the fidelity of membrane transport by maintaining cholesterol-poor membranes in the Golgi complex.

Link invariants associated with gauge equivalent solutions of the Yang-Baxter equation: The one-parameter family of minimal typical representations of Uq[gl(2|1)]

In this paper we investigate the construction of state models for link invariants using representations of the braid group obtained from various gauge choices for a solution of the trigonometric Yang-Baxter equation. Our results show that it is possible to obtain invariants of regular isotopy (as defined by Kauffman) which may not be ambient isotopic. We illustrate our results with explicit computations using solutions of the trigonometric Yang-Baxter equation associated with the one-parameter family of minimal typical representations of the quantum superalgebra U-q,[gl(2/1)]. We have implemented MATHEMATICA code to evaluate the invariants for all prime knots up to 10 crossings.

A coupled knowledge-based expert system for design of liquid-retaining structures

This paper describes a coupled knowledge-based system (KBS) for the design of liquid-retaining structures, which can handle both the symbolic knowledge processing based on engineering heuristics in the preliminary synthesis stage and the extensive numerical crunching involved in the detailed analysis stage. The prototype system is developed by employing blackboard architecture and a commercial shell VISUAL RULE STUDIO. Its present scope covers design of three types of liquid-retaining structures, namely, a rectangular shape with one compartment, a rectangular shape with two compartments and a circular shape. Through custom-built interactive graphical user interfaces, the user is directed throughout the design process, which includes preliminary design, load specification, model generation, finite element analysis, code compliance checking and member sizing optimization. It is also integrated with various relational databases that provide the system with sectional properties, moment and shear coefficients and final member details. This system can act as a consultant to assist novice designers in the design of liquid-retaining structures with increase in efficiency and optimization of design output and automated record keeping. The design of a typical example of the liquid-retaining structure is also illustrated. (C) 2003 Elsevier B.V All rights reserved.

A Sco homologue plays a role in defence against oxidative stress in pathogenic Neisseria

Sco proteins are found in mitochondria and in a variety of oxidase positive bacteria. Although Sco is required for the formation of the Cu-A centre in a cytochrome oxidase of the aa(3) type, it was observed that oxidases with a Cu-A centre are not present in many bacteria that contain a Sco homologue. Two bacteria of this type are the pathogens Neisseria meningitidis and Neisseria gonorrhoeae. The sco genes of N. gonorrhoeae strain 1291 and N. meningitidis strain MC58 were cloned, inactivated by inserting a kanamycin resistance cassette and used to make knockout mutants by allelic exchange. Both N. gonorrhoeae and N. meningitidis sco mutants were highly sensitive to oxidative killing by paraquat, indicating that Sco is involved in protection against oxidative stress in these bacteria. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

The synthesis and X-ray crystal structure of 9-carboxyhexahydro-7-methoxy-4a,7-ethano-benzopyran-5-en-1-one

9-Carboxyhexahydro-7-methoxy-4a,7-ethano-benzopyran-5-en-1-one (1) was prepared and examined by X-ray crystallography to probe its potential as a new peptide scaffold/template. The crystal structure of the anhydride precursor 7-(2-acetoxyethyl)-4-methoxy-3a,4,7,7a-tetrahydro-4,7-ethanoisobenzofuran-1,3-dione (6) is also reported.