Ethanol Tolerance in the Rat Neurohypophysis: a Dissertation

One of the main components underlying drug addiction is the emergence of tolerance. Although its development is a complex issue, and is believed to have both psychological and physiological connotations, it is clear that some physiological change must occur that would enable an organism to withstand drug concentrations lethal to a naïve system. The purpose of this thesis was to identify and study a physiological mechanism, whose characteristics were altered due to chronic exposure to ethanol. Vasopressin (AVP), whose primary function is to control water balance, release from the neurohypophysis is suppressed by an acute ethanol challenge. Therefore, I hypothesized; 1) that chronic ethanol exposure would reduce the normal suppression of AVP release during an acute ethanol challenge and 2) that the ion channels that are acutely sensitive to ethanol, involved in the control of AVP release, would exhibit a change in their ethanol sensitivity and characteristics. To study the hypothesis, I utilized the neurohypophysis from rats chronically exposed to ethanol and yoked controls to determine whether chronic exposure would modify the acute ethanol sensitivity of the neurohypophysial vasopressin release mechanism. I examined whether the long-term ethanol exposure affected the suppression of vasopressin release from either or both the intact neurohypophysis and the isolated neurohypophysial terminals. In addition, I investigated how chronic exposure affected two types of potassium channels, the ethanol sensitive large conductance Ca+2-activated (BK) channel and the fast inactivating (IA) channel known to be insensitive to physiologically relevant concentrations of ethanol. I was able to establish that chronic ethanol exposure reduced the suppression of vasopressin release by an acute ethanol challenge from both the intact neurohypophysis and the isolated neurohypophysial terminals. In addition, I discovered that oxytocin release was affected similarly. I concluded from this data that chronic exposure to ethanol affected a general mechanism, which controlled hormone release from the neurohypophysis, and that this mechanism could be isolated to the neurohypophysial terminals. I also used electrophysiological techniques to study ion channel characteristics of both the BK and IA potassium channels. I found that in naïve rats, BK channels were potentiated and IA channels insensitive to physiological relevant concentrations of ethanol. But in chronic ethanol-exposed rats the BK channels exhibited a reduced sensitivity to ethanol while IA channels were inhibited. In addition, the current density of the BK channel was significantly reduced. These results show that at least one characteristic of each potassium channel has been modified. This suggests that chronic exposure can not only modify the ethanol sensitivity of ion channels known to be ethanol-sensitive, but also those believed to be relatively insensitive. Therefore, since modifications in these channels have previously been shown to alter the duration and frequency of action potentials, I conclude that these ethanol-induced modifications play a role in the modified hormone release patterns observed in the chronically exposed rats

{beta}3GnT2 Maintains Adenylyl Cyclase-3 Signaling and Axon Guidance Molecule Expression in the Olfactory Epithelium

In the olfactory epithelium (OE), odorant receptor stimulation generates cAMP signals that function in both odor detection and the regulation of axon guidance molecule expression. The enzyme that synthesizes cAMP, adenylyl cyclase 3 (AC3), is coexpressed in olfactory sensory neurons (OSNs) with poly-N-acetyllactosamine (PLN) oligosaccharides determined by the glycosyltransferase beta3GnT2. The loss of either enzyme results in similar defects in olfactory bulb (OB) innervation and OSN survival, suggesting that glycosylation may be important for AC3 function. We show here that AC3 is extensively modified with N-linked PLN, which is essential for AC3 activity and localization. On Western blots, AC3 from the wild-type OE migrates diffusely as a heavily glycosylated 200 kDa band that interacts with the PLN-binding lectin LEA. AC3 from the beta3GnT2(-/-) OE loses these PLN modifications, migrating instead as a 140 kDa glycoprotein. Furthermore, basal and forskolin-stimulated cAMP production is reduced 80-90% in the beta3GnT2(-/-) OE. Although AC3 traffics normally to null OSN cilia, it is absent from axon projections that aberrantly target the OB. The cAMP-dependent guidance receptor neuropilin-1 is also lost from beta3GnT2(-/-) OSNs and axons, while semaphorin-3A ligand expression is upregulated. In addition, kirrel2, a mosaically expressed adhesion molecule that functions in axon sorting, is absent from beta3GnT2(-/-) OB projections. These results demonstrate that PLN glycans are essential in OSNs for proper AC3 localization and function. We propose that the loss of cAMP-dependent guidance cues is also a critical factor in the severe axon guidance defects observed in beta3GnT2(-/-) mice

Olfactory discrimination largely persists in mice with defects in odorant receptor expression and axon guidance

<p>Abstract</p> <p>Background</p> <p>The defining feature of the main olfactory system in mice is that each olfactory sensory neuron expresses only one of more than a thousand different odorant receptor genes. Axons expressing the same odorant receptor converge onto a small number of targets in the olfactory bulb such that each glomerulus is made up of axon terminals expressing just one odorant receptor. It is thought that this precision in axon targeting is required to maintain highly refined odor discrimination. We previously showed that β3GnT2^−/− mice have severe developmental and axon guidance defects. The phenotype of these mice is similar to adenylyl cyclase 3 (AC3) knockout mice largely due to the significant down-regulation of AC3 activity in β3GnT2^−/− neurons.</p> <p>Results</p> <p>Microarray analysis reveals that nearly one quarter of all odorant receptor genes are down regulated in β3GnT2^−/− mice compared to controls. Analysis of OR expression by quantitative PCR and <it>in situ</it> hybridization demonstrates that the number of neurons expressing some odorant receptors, such as mOR256-17, is increased by nearly 60% whereas for others such as mOR28 the number of neurons is decreased by more than 75% in β3GnT2^−/− olfactory epithelia. Analysis of axon trajectories confirms that many axons track to inappropriate targets in β3GnT2^−/− mice, and some glomeruli are populated by axons expressing more than one odorant receptor. Results show that mutant mice perform nearly as well as control mice in an odor discrimination task. In addition, <it>in situ</it> hybridization studies indicate that the expression of several activity dependent genes is unaffected in β3GnT2^−/− olfactory neurons.</p> <p>Conclusions</p> <p>Results presented here show that many odorant receptors are under-expressed in β3GnT2^−/− mice and further demonstrate that additional axon subsets grow into inappropriate targets or minimally innervate glomeruli in the olfactory bulb. Odor evoked gene expression is unchanged and β3GnT2^−/− mice exhibit a relatively small deficit in their ability to discriminate divergent odors. Results suggest that despite the fact that β3GnT2^−/− mice have decreased AC3 activity, decreased expression of many ORs, and display many axon growth and guidance errors, odor-evoked activity in cilia of mutant olfactory neurons remains largely intact.</p

Discovery of two new super-eruptions from the Yellowstone hotspot track (USA): is the Yellowstone hotspot waning?

Super-eruptions are amongst the most extreme events to affect Earth’s surface, but too few examples are known to assess their global role in crustal processes and environmental impact. We demonstrate a robust approach to recognize them at one of the best-preserved intraplate large igneous provinces, leading to the discovery of two new super-eruptions. Each generated huge and unusually hot pyroclastic density currents that sterilized extensive tracts of Idaho and Nevada in the United States. The ca. 8.99 Ma McMullen Creek eruption was magnitude 8.6, larger than the last two major eruptions at Yellowstone (Wyoming). Its volume exceeds 1700 km3, covering ≥12,000 km2. The ca. 8.72 Ma Grey’s Landing eruption was even larger, at magnitude of 8.8 and volume of ≥2800 km3. It covers ≥23,000 km2 and is the largest and hottest documented eruption from the Yellowstone hotspot. The discoveries show the effectiveness of distinguishing and tracing vast deposit sheets by combining trace-element chemistry and mineral compositions with field and paleomagnetic characterization. This approach should lead to more discoveries and size estimates, here and at other provinces. It has increased the number of known super-eruptions from the Yellowstone hotspot, shows that the temporal framework of the magmatic province needs revision, and suggests that the hotspot may be waning

The Dialectics of Identity of the Modern and Postmodern Art

Ako pojam identiteta shvatimo u hegelijanskom smislu kao iskustvo što ga svijest stječe o sebi, onda se taj pojam nameće kao ključan u razmatranju (vizualne) umjetnosti XX. stoljeća. Prema Hegelu, moderna umjetnost transcendira mogućnost adekvatnog izražavanja svoga duhovnog sadržaja pukom osjetilnom reprezentacijom (koja je kao takvu određuje) te stoga zahtijeva pojmovnu refleksiju. Budući da je umjetnost uvijek i dio stvarnosti i o stvarnosti, propitivanje njezina vlastita pojma ide ruku pod ruku s ontološkom problematikom. Epistemološke promjene koje konstituiraju i modernu i postmodernu odražavaju se tako u dijalektici pojma moderne i postmoderne umjetnosti. Prema nekim autorima ta je dijalektika određena značajnim promjenama u teoriji subjekta, kulturalnim razlikama i tehnologiji.If the notion of identity is considered in the Hegelian sense as the experience of the consciousness about itself, then this notion becomes of key importance in reflecting upon the 20th-century (visual) art. Modern art, in Hegel’s view, transcends the possibility of an adequate expression of its spiritual content by its merely sensuous representation (that defines it as such) and hence calls for a reflection on its notion. Since art has always been both part of and about reality, the questioning of its own notion goes hand in hand with the ontological problematics. The epistemological changes that constitute both Modernism and Postmodernism thus reflect themselves in the dialectics of the notion of modern and postmodern art. According to some authors, such dialectics is determined by important changes which took place in the theory of the subject, in cultural differences as well as in technology

The utilisation of health research in policy-making: Concepts, examples and methods of assessment

The importance of health research utilisation in policy-making, and of understanding the mechanisms involved, is increasingly recognised. Recent reports calling for more resources to improve health in developing countries, and global pressures for accountability, draw greater attention to research-informed policy-making. Key utilisation issues have been described for at least twenty years, but the growing focus on health research systems creates additional dimensions. The utilisation of health research in policy-making should contribute to policies that may eventually lead to desired outcomes, including health gains. In this article, exploration of these issues is combined with a review of various forms of policy-making. When this is linked to analysis of different types of health research, it assists in building a comprehensive account of the diverse meanings of research utilisation. Previous studies report methods and conceptual frameworks that have been applied, if with varying degrees of success, to record utilisation in policy-making. These studies reveal various examples of research impact within a general picture of underutilisation. Factors potentially enhancing utilisation can be identified by exploration of: priority setting; activities of the health research system at the interface between research and policy-making; and the role of the recipients, or 'receptors', of health research. An interfaces and receptors model provides a framework for analysis. Recommendations about possible methods for assessing health research utilisation follow identification of the purposes of such assessments. Our conclusion is that research utilisation can be better understood, and enhanced, by developing assessment methods informed by conceptual analysis and review of previous studies

No Origin, No Problem for Yeast DNA Replication

Eukaryotic DNA replication initiates from multiple sites on each chromosome called replication origins (origins). In the budding yeast Saccharomyces cerevisiae, origins are defined at discrete sites. Regular spacing and diverse firing characteristics of origins are thought to be required for efficient completion of replication, especially in the presence of replication stress. However, a S. cerevisiae chromosome III harboring multiple origin deletions has been reported to replicate relatively normally, and yet how an origin-deficient chromosome could accomplish successful replication remains unknown. To address this issue, we deleted seven well-characterized origins from chromosome VI, and found that these deletions do not cause gross growth defects even in the presence of replication inhibitors. We demonstrated that the origin deletions do cause a strong decrease in the binding of the origin recognition complex. Unexpectedly, replication profiling of this chromosome showed that DNA replication initiates from non-canonical loci around deleted origins in yeast. These results suggest that replication initiation can be unexpectedly flexible in this organism

Problems and needs for improving primary care of osteoarthritis patients: the views of patients, general practitioners and practice nurses

BACKGROUND: Osteoarthritis (OA) is highly prevalent and has substantial impact on quality of life as well as on healthcare costs. The general practitioner (GP) often is the first care provider for patients with this chronic disease. The aim of this study was to identify health care needs of patients with OA and to reveal possible obstacles for improvements in primary care management of OA patients. METHODS: We performed semi-structured interviews with a stratified sample of 20 patients, 20 GPs and 20 practice nurses. RESULTS: Diagnosing OA posed no major problem, but during the course of OA, GPs found it difficult to distinguish between complaints resulting from the affection of the joints and complaints related to a concomitant depression. Patients felt to be well informed about the degenerative nature of the disease and possible side effects of medications, but they lacked information on individual consequences of the disease. Therefore, the most important concerns of many patients were pain and fear of disability which they felt to be addressed by GPs only marginally. Regarding pain treatment, physicians and patients had an ambivalent attitude towards NSAIDs and opiates. Therefore, pain treatment was not performed according to prevailing guidelines. GPs felt frustrated about the impact of counselling regarding life style changes but on the other hand admitted to have no systematic approach to it. Patients stated to be aware of the impact of life style on OA but lacked detailed information e.g. on how to exercise. Several suggestions were made concerning improvement. CONCLUSION: GPs should focus more on disability and pain and on giving information about treatment since these topics are inadequately addressed. Advanced approaches are needed to increase GPs impact on patients' life style. Being aware of the problem of labelling patients as chronically ill, a more proactive, patient-centred care is needed

Mapping of quantitative trait loci for flesh colour and growth traits in Atlantic salmon (Salmo salar)

<p>Abstract</p> <p>Background</p> <p>Flesh colour and growth related traits in salmonids are both commercially important and of great interest from a physiological and evolutionary perspective. The aim of this study was to identify quantitative trait loci (QTL) affecting flesh colour and growth related traits in an F2 population derived from an isolated, landlocked wild population in Norway (Byglands Bleke) and a commercial production population.</p> <p>Methods</p> <p>One hundred and twenty-eight informative microsatellite loci distributed across all 29 linkage groups in Atlantic salmon were genotyped in individuals from four F2 families that were selected from the ends of the flesh colour distribution. Genotyping of 23 additional loci and two additional families was performed on a number of linkage groups harbouring putative QTL. QTL analysis was performed using a line-cross model assuming fixation of alternate QTL alleles and a half-sib model with no assumptions about the number and frequency of QTL alleles in the founder populations.</p> <p>Results</p> <p>A moderate to strong phenotypic correlation was found between colour, length and weight traits. In total, 13 genome-wide significant QTL were detected for all traits using the line-cross model, including three genome-wide significant QTL for flesh colour (Chr 6, Chr 26 and Chr 4). In addition, 32 suggestive QTL were detected (chromosome-wide P < 0.05). Using the half-sib model, six genome-wide significant QTL were detected for all traits, including two for flesh colour (Chr 26 and Chr 4) and 41 suggestive QTL were detected (chromosome-wide P < 0.05). Based on the half-sib analysis, these two genome-wide significant QTL for flesh colour explained 24% of the phenotypic variance for this trait.</p> <p>Conclusions</p> <p>A large number of significant and suggestive QTL for flesh colour and growth traits were found in an F2 population of Atlantic salmon. Chr 26 and Chr 4 presented the strongest evidence for significant QTL affecting flesh colour, while Chr 10, Chr 5, and Chr 4 presented the strongest evidence for significant QTL affecting growth traits (length and weight). These QTL could be strong candidates for use in marker-assisted selection and provide a starting point for further characterisation of the genetic components underlying flesh colour and growth.</p