The eyes of deep-sea fish I: Lens pigmentation, tapeta and visual pigments

Deep-sea fish, defined as those living below 200 m, inhabit a most unusual photic environment, being exposed to two sources of visible radiation: very dim downwelling sunlight and bioluminescence, both of which are, in most cases. maximal at wavelengths around 450-500 nm. This paper summarises the reflective properties of the ocular tapeta often found in these animals the pigmentation of their lenses and the absorption characteristics of their visual pigments. Deepsea tapeta usually appear blue to the human observer. reflecting mainly shortwave radiation. However, reflection in other parts of the spectrum is not uncommon and uneven tapetal distribution across the retina is widespread. Perhaps surprisingly, given the fact that they live in a photon limited environment, the lenses of some deep-sea teleosts are bright yellow, absorbing much of the shortwave part of the spectrum. Such lenses contain a variety of biochemically distinct pigments which most likely serve to enhance the visibility of bioluminescent signals. Of the 195 different visual pigments characterised by either detergent extract or microspectrophotometry in the retinae of deep-sea fishes, cn. 87% have peak absorbances within the range 468-494 nm. Modelling shows that this is most likely an adaptation for the detection of bioluminescence. Around 13% of deep-sea fish have retinae containing more than one visual pigment. Of these, we highlight three genera of stomiid dragonfishes, which uniquely produce far red bioluminescence from suborbital photophores. Using a combination of longwave-shifted visual pigments and in one species (Malacosteus niger) a chlorophyll-related photosensitizer. these fish have evolved extreme red sensitivity enabling them to see their own bioluminescence and giving them a private spectral waveband invisible to other inhabitants of the deep-ocean. (C) 1998 Elsevier Science Ltd. All rights reserved.

Reducing the toll of opioid overdose deaths in Australia

Opioid overdose mortality among young adults in Australia has increased consistently over the past several decades. Among Australian adults aged 15-44 years, the number of these deaths has increased from six in 1964 to 600 in 1997. The rate (per million adults in this age group) increased 55-fold, from 1.3 in 1964 to 71.5 in 1997, The proportion of all deaths in adults in this age group caused by opioid overdose increased from 0.1% in 1964 to 7.3% in 1997, The magnitude of the increase makes it unlikely to be an artefact of changes in diagnosis, especially as similar increases have also been observed in other countries. These trends are also consistent,vith historical information which indicates that illicit heroin use first came to police attention in Sydney and Melbourne in the late 1960s, There is an urgent need to implement and evaluate a variety of measures to reduce the unacceptable toll of opioid overdose deaths among young Australians. These include: peer education about the risks of polydrug use and overdose after resuming opioid use after periods of abstinence, and attracting more dependent users into opioid maintenance treatment. Measures are also needed to improve responses to overdose by encouraging witnesses to call ambulances, training drug users in CPR, and trialling distribution of the opiate antagonist naloxone to users at high risk of overdose.

Analysis of the substrate specificity of human sulfotransferases SULT1A1 and SULT1A3: Site-directed mutagenesis and kinetic studies

Sulfonation is an important metabolic process involved in the excretion and in some cases activation of various endogenous compounds and xenobiotics. This reaction is catalyzed by a family of enzymes named sulfotransferases. The cytosolic human sulfotransferases SULT1A1 and SULT1A3 have overlapping yet distinct substrate specificities. SULT1A1 favors simple phenolic substrates such as p-nitrophenol, whereas SULT1A3 prefers monoamine substrates such as dopamine. In this study we have used a variety of phenolic substrates to functionally characterize the role of the amino acid at position 146 in SULT1A1 and SULT1A3. First, the mutation A146E in SULT1A1 yielded a SULT1A3-like protein with respect to the Michaelis constant for simple phenols. The mutation E146A in SULT1A3 resulted in a SULT1A1-like protein with respect to the Michaelis constant for both simple phenols and monoamine compounds. When comparing the specificity of SULT1A3 toward tyramine with that for p-ethylphenol (which differs from tyramine in having no amine group on the carbon side chain), we saw a 200-fold preference for tyramine. The kinetic data obtained with the E146A mutant of SULT1A3 for these two substrates clearly showed that this protein preferred substrates without an amine group attached. Second, changing the glutamic acid at position 146 of SULT1A3 to a glutamine, thereby neutralizing the negative charge at this position, resulted in a 360-fold decrease in the specificity constant for dopamine. The results provide strong evidence that residue 146 is crucial in determining the substrate specificity of both SULT1A1 and SULT1A3 and suggest that there is a direct interaction between glutamic acid 146 in SULT1A3 and monoamine substrates.

Structure/function studies of S100A8/A9

The functional importance of members of the S100 Ca2+-binding protein family is recently emerging. A variety of activities, several of which are apparently opposing, are attributed to S100A8, a protein implicated in embryogenesis, growth, differentiation, and immune and inflammatory processes. Murine (m) S100A8 was initially described as a chemoattractant (CP-10) for myeloid cells. It is coordinately expressed with mS100A9 (MRP14) in neutrophils and the non-covalent heterodimer is presumed to be the functional intracellular species. The extracellular chemotactic activity of mS100A8, however, is not dependent on mS100A9 and occurs at concentrations (10(-13)-10(-11) M) at which the non-covalent heterodimer would probably dissociate. This review focuses on the structure and post-translational modifications of mS100A8/A9 and their effects on function, particularly chemotaxis.

Chemical synthesis, characterization and activity of RK-1, a novel alpha-defensin-related peptide

The 32-residue peptide, RK-1, a novel kidney-derived three disulfide-bonded member of the antimicrobial alpha-defensin family, was synthesized by the continuous now Fmoc-solid phase method. The crude, cleaved and S-reduced Linear peptide was both efficiently folded and oxidized in an acidic solution of aqueous dimethyl sulfoxide. Following purification of the resulting product, it was shown by a variety of analytical techniques, including matrix assisted laser desorption time of flight mass spectrometry, to possess a very high degree of purity. The disulfide bond pairing of the synthetic peptide was determined by H-1-NMR spectroscopy and confirmed to be a Cys(1)-Cys(6), Cys(2)-Cys(4), Cys(3)-Cys(5) arrangement similar to other mammalian alpha-defensin peptides. The synthetic RK-1 was also shown to inhibit the growth of Escherichia coli type strain NCTC 10418, Copyright (C) 2000 European Peptide Society and John Wiley & Sons, Ltd.

Optimal release strategies for biological control agents: an application of stochastic dynamic programming to population management

1. Establishing biological control agents in the field is a major step in any classical biocontrol programme, yet there are few general guidelines to help the practitioner decide what factors might enhance the establishment of such agents. 2. A stochastic dynamic programming (SDP) approach, linked to a metapopulation model, was used to find optimal release strategies (number and size of releases), given constraints on time and the number of biocontrol agents available. By modelling within a decision-making framework we derived rules of thumb that will enable biocontrol workers to choose between management options, depending on the current state of the system. 3. When there are few well-established sites, making a few large releases is the optimal strategy. For other states of the system, the optimal strategy ranges from a few large releases, through a mixed strategy (a variety of release sizes), to many small releases, as the probability of establishment of smaller inocula increases. 4. Given that the probability of establishment is rarely a known entity, we also strongly recommend a mixed strategy in the early stages of a release programme, to accelerate learning and improve the chances of finding the optimal approach.

Adhesion of microbes using 3-aminopropyl triethoxy silane and specimen stabilisation techniques for analytical transmission electron microscopy

A variety of adhesive support-films were tested for their ability to adhere various biological specimens for transmission electron microscopy. Support films primed with 3-amino-propyl triethoxy silane (APTES), poly-L-lysine, carbon and ultraviolet-B (UV-B)-irradiated carbon were tested for their ability to adhere a variety of biological specimens including axenic cultures of Bacillus subtilis and Escherichia coli and wild-type magnetotactic bacteria. The effects of UV-B irradiation on the support film in the presence of air and electrostatic charge on primer deposition were tested and the stability of adhered specimens on various surfaces was also compared. APTES-primed UV-B-irradiated Pioloform(TM) was consistently the best adhesive, especially for large cells, and when adhered specimens were UV-B irradiated they became remarkably stable under an electron beam. This assisted the acquisition of in situ phase-contrast lattice images from a variety of biominerals in magnetotactic bacteria, in particular metastable greigite magnetosomes. Washing tests indicated that specimens adhering to APTES-primed UV-B-irradiated Pioloform(TM) were covalently coupled. The electron beam stability was hypothesised to be the result of mechanical strengthening of the specimen and support film and the reduced electrical resistance in the specimen and support film due to their polymerization and covalent coupling.

Chopper, a new death domain of the p75 neurotrophin receptor that mediates rapid neuronal cell death

The cytoplasmic juxtamembrane region of the p75 neurotrophin receptor (p75(NTR)) has been found to be necessary and sufficient to initiate neural cell death. The region was named Chopper to distinguish it from CD95-like death domains. A 29-amino acid peptide corresponding to the Chopper region induced caspase- and calpain-mediated death in a variety of neural and nonneural cell types and was not inhibited by signaling through Trk (unlike killing by full-length p75(NTR)). Chopper triggered cell death only when bound to the plasma membrane by a lipid anchor, whereas non-anchored Chopper acted in a dominant-negative manner, blocking p75(NTR)-mediated death both in vitro and in vivo. Removal of the ectodomain of p75(NTR) increased the potency of Chopper activity, suggesting that it regulates the association of Chopper with downstream signaling proteins.

Transmission of ocular media in labrid fishes

Wrasses (Labridae) are the second largest family of fishes on the: Great Barrier Reef (after the Gobiidae) and, in terms of morphology and lifestyle, one of the most diverse. They occupy all zones of the reef from the very shadow reef flats to deep slopes, feeding on a variety of fauna. Many wrasses also have elaborately patterned bodies and reflect a range of colours from ultraviolet (UV) to far red. As a first step to investigating the visual system of these fishes we measured the transmission properties of the ocular media of 36 species from the Great Barrier Reef, Australia, and Hawaii, California and the Florida Keys, USA. Transmission measurements were made of whole eyes with a window cut into the back, and also of isolated lenses and corneas. Based on the transmission properties of the corneas the species could be split into two distinct groups within which the exact wavelength of the cut-off was variable. One group had visibly yellow corneas, while the corneas of the other group appeared clear to human observers. Five species had ocular media that transmitted wavelengths below 400 nm, making a perception of UV wavelengths for those species possible. Possible functional roles for the different filler types are discussed.

Spectral tuning and the visual ecology of mantis shrimps

The compound eyes of mantis shrimps (stomatopod crustaceans) include an unparalleled diversity of visual pigments and spectral receptor classes in retinas of each species. We compared the visual pigment and spectral receptor classes of 12 species of gonodactyloid stomatopods from a variety of photo environments, from intertidal to deep water ( > 50 m), to learn how spectral tuning in the different photoreceptor types is modified within different photic environments. Results show that receptors of the peripheral photoreceptors, those outside the midband which are responsible for standard visual tasks such as spatial vision and motion detection, reveal the well-known pattern of decreasing lambda(max) with increasing depth. Receptors of midband rows 5 and 6, which are specialized for polarization vision, are similar in all species, having visual lambda(max)-values near 500 nm, independent of depth. Finally the spectral receptors of midband rows 1 to 4 are tuned for maximum coverage of the spectrum of irradiance available in the habitat of each species. The quality of the visual worlds experienced by each species we studied must vary considerably, but all appear to exploit the full capabilities offered by their complex visual systems.

The anti-tumor activity of IL-12: Mechanisms of innate immunity that are model and dose dependent

IL-12 has been demonstrated to have potent anti-tumor activities in a variety of mouse tumor models, but the relative roles of NK, NKT, and T cells and their effector mechanisms in these responses have not been fully addressed. Using a spectrum of gene-targeted or Ab-treated mice we have shown that for any particular tumor model the effector mechanisms downstream of IL-12 often mimic the natural immune response to that tumor. For example, metastasis of the MHC class I-deficient lymphoma, EL4-S3, was strictly controlled by NK cells using perforin either naturally or following therapy with high-dose IL-12. Intriguingly, in B16F10 and RM-1 tumor models both NK and NKT cells contribute to natural protection from tumor metastasis, In these models, a lower dose of IL-12 or delayed administration of IL-12 dictated a greater relative role of NKT cells in immune protection from tumor metastasis. Overall, both NK and NKT cells can contribute to natural and IL-12-induced immunity against tumors, and the relative role of each population is turner and therapy dependent.

Methods for prediction of peptide binding to MHC molecules: A comparative study

Background: A variety of methods for prediction of peptide binding to major histocompatibility complex (MHC) have been proposed. These methods are based on binding motifs, binding matrices, hidden Markov models (HMM), or artificial neural networks (ANN). There has been little prior work on the comparative analysis of these methods. Materials and Methods: We performed a comparison of the performance of six methods applied to the prediction of two human MHC class I molecules, including binding matrices and motifs, ANNs, and HMMs. Results: The selection of the optimal prediction method depends on the amount of available data (the number of peptides of known binding affinity to the MHC molecule of interest), the biases in the data set and the intended purpose of the prediction (screening of a single protein versus mass screening). When little or no peptide data are available, binding motifs are the most useful alternative to random guessing or use of a complete overlapping set of peptides for selection of candidate binders. As the number of known peptide binders increases, binding matrices and HMM become more useful predictors. ANN and HMM are the predictive methods of choice for MHC alleles with more than 100 known binding peptides. Conclusion: The ability of bioinformatic methods to reliably predict MHC binding peptides, and thereby potential T-cell epitopes, has major implications for clinical immunology, particularly in the area of vaccine design.

Finite-difference time-domain-based studies of MRI pulsed field gradient-induced eddy currents inside the human body

In modern magnetic resonance imaging (MRI), patients are exposed to strong, rapidly switching magnetic gradient fields that, in extreme cases, may be able to elicit nerve stimulation. This paper presents theoretical investigations into the spatial distribution of induced current inside human tissues caused by pulsed z-gradient fields. A variety of gradient waveforms have been studied. The simulations are based on a new, high-definition, finite-difference time-domain method and a realistic inhomogeneous 10-mm resolution human body model with appropriate tissue parameters. it was found that the eddy current densities are affected not only by the pulse sequences but by many parameters such as the position of the body inside the gradient set, the local biological material properties and the geometry of the body. The discussion contains a comparison of these results with previous results found in the literature. This study and the new methods presented herein will help to further investigate the biological effects caused by the switched gradient fields in a MRI scan. (C) 2002 Wiley Periodicals, Inc.

Conductivity, NMR and crystallographic study of N,N,N,N-tetramethylammonium dicyanamide plastic crystal phases: an archetypal ambient temperature plastic electrolyte material

N,N,N,N-Tetramethylammonium dicyanamide (Me(4)NDCA) has been examined via differential scanning calorimetry (DSC), thermogravimetric analysis, conductivity, single crystal X-ray diffraction and H-1 nuclear magnetic resonance (NMR) analyses, and was found to be highly conductive in the solid state (sigma = 10(-3) S cm(-2) at 420 K) and to also exhibit unusual plastic crystal behaviour. To investigate the correlation between such behaviour and the occurrence of molecular rotations in the crystal, H-1 NMR second moment measurements are compared with calculated values predicted from the crystal structure. While DSC analysis indicates a number of solid-solid transitions at ambient temperatures, subsequent H-1 NMR analysis of the Me4N+ cation shows that a variety of rotational motions become active at low (

Molecular evolution and phylogeny of elapid snake venom three-finger toxins

Animal venom components are of considerable interest to researchers across a wide variety of disciplines, including molecular biology, biochemistry, medicine, and evolutionary genetics. The three-finger family of snake venom peptides is a particularly interesting and biochemically complex group of venom peptides, because they are encoded by a large multigene family and display a diverse array of functional activities. In addition, understanding how this complex and highly varied multigene family evolved is an interesting question to researchers investigating the biochemical diversity of these peptides and their impact on human health. Therefore, the purpose of our study was to investigate the long-term evolutionary patterns exhibited by these snake venom toxins to understand the mechanisms by which they diversified into a large, biochemically diverse, multigene family. Our results show a much greater diversity of family members than was previously known, including a number of subfamilies that did not fall within any previously identified groups with characterized activities. In addition, we found that the long-term evolutionary processes that gave rise to the diversity of three-finger toxins are consistent with the birth-and-death model of multigene family evolution. It is anticipated that this three-finger toxin toolkit will prove to be useful in providing a clearer picture of the diversity of investigational ligands or potential therapeutics available within this important family.