Latest Articles Include:
- Editorial & Author biographies
- Bioscience Horizons 2(1):iii (2009)
- Outer membrane proteomics of Pasteurella multocida isolates to identify putative host-specificity determinants
- Bioscience Horizons 2(1):1-12 (2009)
Pasteurella multocida is a Gram-negative bacterium responsible for diseases affecting a broad range of farm-reared animals. Although there is an association between capsular serotype and disease, the molecular basis of host specificity is poorly understood. Outer membrane proteins (OMPs) are at the interface of bacterium and host and are likely to play important roles in host specificity and disease. Two classes are of particular importance--adhesins that are adapted for colonization of specific host niches and iron-acquisition proteins that allow pathogens to acquire iron from host-specific iron complexes. A comparative analysis of the outer membrane (OM) proteome of eight P. multocida isolates associated with disease of avian, bovine, ovine and porcine species was performed to identify putative host-specificity determinants. Isolates were cultured in iron-replete media, and also in iron-limited conditions to mimic the iron-limited host environment, and induce express! ion of iron-regulated OMPs expressed in vivo. The OMP-rich sarcosyl-insoluble cell fraction was isolated and the OMPs were separated by SDS-PAGE and identified by matrix-assisted light desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The expressed proteome was compared with the in silico predicted proteome from the genome sequence of P. multocida strain Pm70, using PSORTb and Proteome Analyst subcellular localization software. In iron-rich conditions isolates were clustered into three groups based on high molecular weight (HMW) OMP similarity. Isolates responsible for invasive disease were clustered into a single group. Putative colonization OMPs were present in isolates recovered from different host species, but showed molecular weight heterogeneity. Such proteins are good candidates for further study as disease or host-specificity determinants, as variation between these proteins may be a consequence of adaptation to different host niches. HMW OMPs w! ere identified as being involved in iron-uptake. However, isol! ates associated with different diseases and host species expressed different iron-uptake proteins, or regulated expression differently, suggesting adaptation to specific host niches. - ERp57 is involved in the oxidative folding of the low-density lipoprotein receptor in the endoplasmic reticulum
- Bioscience Horizons 2(1):13-21 (2009)
This work explores the role of the thiol-oxidoreductase ERp57 in the post-translational oxidative folding of the low-density lipoprotein receptor (LDL-R), a cell-surface glycoprotein responsible for the uptake of cholesterol from plasma. The LDL-R provides a general model to analyse oxidative folding of multi-domain proteins in the endoplasmic reticulum; yet its folding pathway is also of specific interest as a high proportion of mutations in disulphide-rich domains of the protein are evident in familial hypercholesterolemia. Previous studies have suggested that the LDL-R forms a set of distinct non-native disulphide intermediates during folding, which are extensively isomerized prior to secretion of the native conformer. In addition, ERp57 has been suggested to be predominantly reduced in vivo and to form a mixed disulphide with the LDL-R. In this study, the LDL-R was expressed in both wild-type cells and those lacking the thiol-oxidoreductase ERp57 under conditions t! hat prevent disulphide formation. The protein was then allowed to fold under oxidizing conditions, and samples taken at various timepoints. The electrophoretic mobility of folding intermediates from knock-out cells was compared with that of wild-type cells. The results show that dissimilar disulphide intermediates form between the two cell types, particularly during early stages of folding. A mutant form of ERp57, able to form but unable to resolve mixed disulphides, was also found to form mixed disulphides with the LDL-R. The results signify the requirement for ERp57 in oxidative folding of the LDL-R and also suggest that non-native disulphide intermediates may be central to the process of multi-domain protein folding. - Enhancer of split-related-2 mRNA shows cyclic expression during somitogenesis in Xenopus laevis
- Bioscience Horizons 2(1):22-31 (2009)
Somitogenesis is responsible for production of the segmented body plan typical of vertebrate embryos. The somites are blocks of mesoderm, produced by this process, that give rise to the vertebrae and ribs, the dermis of the skin and all the skeletal muscle of the body. Many genes that regulate somitogenesis have been identified in chick and mouse, whereas considerably fewer are known in Xenopus laevis. The expression of Hairy/Enhancer of split-related genes is known to cycle during somitogenesis and provides a mechanism for the regular formation of somites. In this project, in situ hybridizations were carried out on bowline, Thylacine1, Enhancer of split-related-1 (ESR1), ESR2 and ESR-5 in order to study their expression in relation to somitogenesis. All genes were found to be expressed during somitogenesis, even as early on as late gastrula stages in some cases. In addition, the expression of ESR2 is shown to be oscillating in the presegmented mesoderm of neurula and ! early-tailbud embryos. This study has identified ESR2 as the second known gene (after esr9) to show periodic oscillations of gene expression which can be considered as cycling during somitogenesis in X. laevis. - The application of social network theory to animal behaviour
- Bioscience Horizons 2(1):32-43 (2009)
Social network analysis (SNA) is a mathematical technique for analysing social relationships and the patterns and implications of these relationships (Wasserman S, Faust K (1994) Social Network Analysis: Methods and Applications. Cambridge: Cambridge University Press). It has only recently been discovered by behavioural biologists as a useful tool in the study of animal behaviour (Wey T, Blumstein DT, Shen W et al. (2008) Social network analysis of animal behaviour: a promising tool for the study of sociality. Anim Behav 75: 333-344). Video recording over a 2 month period was used to record the behaviour of the elephant group at Chester Zoo. SNA was applied in an investigation of the group structure and interactions of the group. Observations of individual and group behaviour were based upon 40 h of playback of the social interactions were recorded and analysed using AGNA (2003) and Pajek (2005) packages. The analysis showed that the many facets of individual behaviour! could be understood in terms of social structure of the group. This study has demonstrated that SNA is a powerful approach to understanding group dynamics and is particularly applicable to the study of obligate social species. In conclusion, it is suggested that SNA is potentially a useful tool in the management of captive animal populations. - The impact of stream support on the hydrology and macrophytes of the upper Bristol Avon
- Bioscience Horizons 2(1):44-54 (2009)
Low river flow due to water abstraction has impacted the macrophyte communities on several rivers in England. Stream Support is a method of alleviating low flows by augmenting water supply to the headwater channels of rivers when flow falls below a trigger level. This project has studied that the effect Stream Support has had on the hydrology of the upper Bristol Avon, and the consequent impact these changes have had on the macrophyte communities of the river. The Winterbourne classification methodology was used to investigate hydrological effects on macrophyte communities since the early 1990s. Stream Support was found to have successfully targeted low flow conditions with the annual Q95 measure of low flow closely associated with augmentation (Tetbury: R2 = 71%, p < 0.001; Sherston: R2 = 78%, p < 0.001). Decade long Q95 (discharge exceeded 95% of the time) measures of low flow on the river were shown to have risen in 1998-2007 by 60% above measures for 1978-1987 and ! 1988-1997. Aquatic species such as Ranunculus penicillatus pseudofluitans had increased coverage since the 1990s by as much as 40%, but wetland species such as Myosotis scorpioides and Mentha aquatica had marginally lower coverage. These changes may be partly attributable to a reduction in low flow conditions. Stream Support may not be sustainable if global warming leads to annually occurring prolonged periods of summer drought. - An electrophysiological analysis of deep cerebellar nuclei, with particular focus on Kv3 channels
- Bioscience Horizons 2(1):55-63 (2009)
Deep cerebellar nuclei (DCN) form three symmetrical, bilateral nuclei, deep within the white matter of the cerebellum and represent the sole output of the cerebellum to the central nervous system. Although innervated by spontaneously active inhibitory Purkinje cells, DCN neurons also fire action potentials spontaneously at a relatively high frequency, a property attributed to Kv3 channels. In the present study, an electrophysiological approach was carried out on DCN neurons, the purpose of which was to investigate the properties and elucidate the involvement of Kv3 channels. Using whole-cell patch clamp techniques, electrophysiological recordings from the dentate nucleus were obtained from coronal cerebellar slices of Wistar rats (P [~] 12) in both current and voltage clamp modes. Kv3-mediated currents were investigated in the presence of tetrodotoxin (1 {micro}M), by applying low concentration tetraethyl ammonium (TEA) (100 {micro}M). Current-clamp recordings revealed! a population of tonically firing neurons, exhibiting a maximum action potential firing frequency of 18.1 {+/-} 6.9 Hz and a steady firing frequency of 14.2 {+/-} 4.8 Hz (n = 6). These neurons were also shown to exhibit a mean action potential amplitude of 48.7 {+/-} 9.5 mV, mean half-width of 2.9 {+/-} 1 ms and mean afterhyperpolarization amplitude of 19.6 {+/-} 7.5 mV. Depolarizing sag (indicative of the Ih current), followed by rebound depolarization, was observed in all neurons. Voltage-clamped neurons revealed a voltage-dependent slowly inactivating outward current with a peak amplitude of 1538.5 {+/-} 1096.6 pA (n = 10). Application of low concentration TEA (100 {micro}M) reduced the current by a statistically significant 19.4 {+/-} 13.4% (P < 0.05; paired t-test) and this effect was reversible. Application of a Boltzmann function yielded a V1/2 value of 9.9 mV for the TEA-sensitive current. As Kv3 channels have been previously localized in DCN, the results suggest th! at the TEA-sensitive current ([~]20% of the total outward curr! ent exhibited) is mediated by Kv3 channels. - Cell-penetrating peptides and their therapeutic applications
- Bioscience Horizons 2(1):64-72 (2009)
The process of introducing drugs into cells has always proved a major challenge for research scientists and for the pharmaceutical industry. The cell membrane is selectively permeable and supports no generic mechanism for their uptake. A drug must be either highly lipophilic or very small to stand a chance of cellular internalization. These restrictions mean that the repertoire of possible drug molecules is limited. Similarly, novel therapeutic approaches such as gene and protein therapy also have limited potential due to the cell-impermeable nature of peptides and oligonucleotides. The existing methods for delivery of macromolecules, such as viral vectors and membrane perturbation techniques, can result in high toxicity, immunogenicity and low delivery yield. However, in 1988 the remarkable ability of a peptide to traverse a cell's plasma membrane independent of a membrane receptor was revealed. Known as Tat, the transcription activator of the human immunodeficiency v! irus type 1 (HIV-1) viral genome was shown to enter cells in a non-toxic and highly efficient manner. In light of such properties Tat became known as the first cell-penetrating peptide' (CPP). CPPs have demonstrated themselves to be capable of delivering biologically active cargo to the cell interior and the vehicular capabilities of CPPs have already been harnessed for use as laboratory tools. However, it is believed that their true potential lies within the field of therapeutics. Attached to a CPP, therapeutic cargo could be delivered to an intracellular target, thus overcoming the entry restrictions set by the plasma membrane. Since the discovery of Tat, the number of known peptides with cell-penetrating capabilities has grown and in 2003, the first CPP-based drug reached phase II clinical trials. This review discusses the controversial mechanism of entry employed by CPPs, their potential applications in vitro and in vivo, and the ways in which CPP properties have been ! optimized to maximize their potential as future therapeutics. - Leishmania vaccines: from leishmanization to the era of DNA technology
- Bioscience Horizons 2(1):73-82 (2009)
Leishmania are obligate intracellular vector-borne parasites that cause significant morbidity and mortality in many countries worldwide. There are several species of the parasite which vary according to geographical location and cause a variety of clinical syndromes ranging from self-limiting cutaneous lesions to potentially fatal infection of the viscera. The disease manifested is dependent on both the species of the parasite and the immune response of the host. Depending on the species of the parasite, resistance to infection is generally associated with a T-helper-1 immune response that activates macrophages to kill intracellular Leishmania in a nitric oxide-dependent manner. Conversely, disease progression is generally associated with a T-helper-2 response that activates humoral immunity. Chemotherapeutic treatments for leishmaniasis exist but are expensive, toxic and ineffective against resistant strains. A vaccine against leishmaniasis is feasible since most indi! viduals that were once infected become resistant to clinical infection when later exposed. However, despite the wealth of information regarding the genetics of the parasite and the experimental immunology of the disease, there is currently no vaccine against Leishmania. A multitude of vaccine strategies have been pursued including the use of killed and genetically modified parasites. Immunization with naked plasmid DNA encoding Leishmania antigens represents a new approach to a Leishmania vaccine and confers several advantages over the more traditional vaccination methods. In order to develop an effective vaccine against leishmaniasis, it is important to understand the mechanisms of the immune response to Leishmania infection. This review discusses such immune mechanisms in detail and also explores several of the Leishmania vaccination strategies employed to date, with particular emphasis on DNA vaccines. - Molecular mechanisms involved in intervertebral disc degeneration and potential new treatment strategies
- Bioscience Horizons 2(1):83-89 (2009)
Lower back pain (LBP) is a major cause of pain and disability. However, current treatment strategies are focused primarily on relieving its symptoms and have varying degrees of success. For future treatments to be proactive, they must target the underlying pathogenic alterations in cellular biology. Intervertebral disc degeneration (IVDD) has been linked to a high percentage of LBP cases, therefore, inhibition of the processes contributing to IVDD and, regeneration of the intervertebral disc (IVD) matrix lost during IVDD are the primary focuses of current research. Therapies aimed at the inhibition of the cytokine interleukin-1 that is increased during IVDD have been investigated as potential treatments aimed at inhibiting the pathogenic processes of IVDD. In addition, the application of growth factors, such as insulin-like growth factor, transforming growth factor and bone morphogenetic protein or alternatively replacement of abnormal IVD cells, either by injection of! mesenchymal stem cells or autologous disc cell transplantation, has been investigated as potential therapeutic agents aimed at regeneration of the IVD matrix. However, for research into these therapeutic techniques to progress, a more detailed knowledge of the complex cellular biology of the IVD is required. - Insights into the development of online plant identification keys based on literature review: an exemplar electronic key to Australian Drosera
- Bioscience Horizons 2(1):90-96 (2009)
Keys are traditionally created from data gathered from real observations, which can be a complex and time-consuming process. With a large number of texts containing written descriptions of species, data needed for the creation of a key are already available. A number of published works on Drosera were chosen and the data in these were used to create an interactive, web-based key. The types of data used were evaluated for ease of use and accuracy and the effectiveness of purely literature-based data was tested. The resulting key highlighted a number of problems of using characters and states which have not been observed, as well as showing that literature-based research can lead to a workable key. - Author biographies
- Bioscience Horizons 2(1):97 (2009)
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