Extinction of Cocaine Self-Administration Induces Metaplasticity in Nucleus Accumbens

Cocaine addiction remains a significant problem and is thought to be a disorder of pathologically strong associations between environmental stimuli, motivated action, and drug reward. Behavioral exposure therapies that repeatedly present the addicted patient with cues but not drug could theoretically break this pathological association and enable addicts to refrain from drug seeking. The neurobiological basis for the learned association between environmental stimuli and drug seeking has been well characterized, especially regarding its involvement of glutamatergic synaptic plasticity in the nucleus accumbens. The learning that ultimately countermands the motivational value of the learned drug associations and leads to patients refraining from drug seeking may likewise rely on glutamatergic synaptic plasticity in nucleus accumbens. This therapeutic learning to inhibit drug seeking can be modeled in animals by extinction training, in which an operant response (e.g. lever press) that previously delivered drug fails to deliver a drug reinforcement, and animals gradually learn to refrain from emitting the operant response. In the experiments contained in this thesis, I demonstrate that extinction training induces a form of metaplasticity in D2 dopamine receptor-­‐expressing medium spiny neurons (D2-­‐MSNs). This enables D2-­‐MSNs to undergo transient synaptic potentiation (tSP) when an animal is given the opportunity to seek drug, and the D2-­‐MSN potentiation suppresses drug seeking. In contrast, D1-­‐MSN tSP underlies drug seeking and is not altered by extinction training. Finally, tSP during refraining is distinct from tSP during reinstatement in its cellular expression profile, anatomical locus, and signaling mechanisms. Overall, these findings suggest that mechanisms supporting synaptic potentiation of D2-­‐MSNs may present therapeutic targets for the treatment of cocaine addiction

Data remanence in New Zealand: 2011

This paper presents findings from a study of computer data remanence in New Zealand and considers three research questions. Those questions are “What is the level of data remanence in New Zealand?”, “How does it compare with other countries?”, and “Are there industries in New Zealand that are more likely to have data remanence issues?” Computer data remanence is data that remains on a hard disk drive after that hard drive has been prepared for disposal. Typically data remanence research involves purchasing second hand hard drives without knowing the original source and then a variety of tools and techniques are used to determine what if any data remains. That data can range from the mundane such as holiday snapshots, to data of concern such as the credit card details used to book the holiday. This research uses a very similar methodology to the research of an Australian-British led consortium into computer data remanence that has been conducted since 2005 (Jones et al., 2005). For this research, 100 hard drives were sourced from companies based in New Zealand that deal in second hand hard drives. A total of 24 hard drives were found to have identifying information on them and this is consistent with the results of the consortium. When examining “Are there industries in New Zealand that are more likely to have data remanence issues?” there was an effective sample size of 14 hard drives which was not considered to be a large enough sample size to adequately draw conclusions. The data does suggest that schools are likely to be of concern however

On the detectability of HI 21-cm in MgII absorption system

We investigate the effect of two important, but oft neglected, factors which can affect the detectability of HI 21-cm absorption in MgII absorption systems: The effect of line-of-sight geometry of the coverage of the background radio flux and any possible correlation between the 21-cm line strength and the rest frame equivalent width of the MgII line. Regarding the former, while the observed detection rate at small angular diameter distance ratios is a near certainty, for an unbiased sample, where either a detection or a non-detection are equally likely, at ratios > 0.8 the observed detection rate has an 8 sigma significance, suggesting that the mix of ratios values at z < 1 is correlated with the mix of detections and non-detections at low redshift, while the exclusively high values of the ratio at z > 1 contribute to the low detection rates at high redshift. In DLAs, the correlation between the 21-cm line strength and the MgII equivalent width is dominated by the velocity spread of the 21-cm line. This has recently been shown not to hold for MgII systems in general. However, we do find the significance of the correlation to increase when the MgII absorbers with MgI equivalent widths of >0.5 A are added to the DLA sample. Large values of the angular diameter distance ratio may explain why the absorbers which have similar equivalent widths to the detections remain undetected. We do, however, also find the neutral hydrogen column densities of the non-detections to be significantly lower. Applying the 21-cm line strength/equivalent width correlation to yield column densities for the MgII absorbers in which this is unmeasured, we find no evidence of a cosmological evolution in the neutral hydrogen column density.Comment: 9 pages, accepted by MNRA

Quantitative relationships between benthic diatom assemblages and water chemistry in Macquarie Island lakes and their potential for reconstructing past environmental changes

This study is the first published survey of diatom-environment relationships Oil sub-Antarctic Macquarie Island. Fifty-eight sites in 50 coastal and inland lakes were sampled for benthic diatoms and water chemistry. 208 diatom species from 34 genera were identified. Multivariate analyses indicated that the lakes were distributed along nutrient and conductivity gradients. Conductivity, pH, phosphate (SRP), silicate and temperature all explained independent portions of the variance in the diatom data. Transfer functions provide a quantitative basis for palaeolimnological studies of past climate change and human impacts, and can be used to establish baseline conditions for assessing the impacts of recent climate change and the introduction of non-native plants and animals. Statistically robust diatom transfer functions for conductivity, phosphate and silicate were developed, while pH and temperature transfer functions performed less well. The lower predictive abilities of the pH and temperature transfer functions probably reflect the broad pH tolerance range of diatoms on Macquarie Island and uneven distribution of lakes along the temperature gradient. This study contributes to understanding the current ecological distribution of Macquarie Island diatoms and provides transfer functions that will be applied in studies of diatoms in lake sediment cores to quantitatively reconstruct past environmental changes

A deep search for 21cm absorption in high redshift damped Lyman-α\alpha systems

We present deep GMRT 21cm absorption spectra of 10 damped Lyman-$\alpha$ systems (DLAs), of which 8 are at redshifts z \ga 1.3. HI absorption was detected in only one DLA, the $z = 0.5318$ absorber toward PKS 1629+12, which has been identified with a luminous spiral galaxy; the spin temperature limit ($T_s \le 310$ K) derived from our observations continues the trend of DLAs associated with bright spirals having low spin temperatures. In 7 of the remaining 9 systems, the observations place strong lower limits on the spin temperature of the HI gas. The sample of DLAs searched for 21cm absorption now consists of 31 systems, with $T_s$ estimates available in 24 cases; of these, 16 are at $z < 2$ and 8 at $z > 2$, with 11 (all at $z < 1$) having optical IDs. For the latter 11 systems, we find that all low $T_s$ DLAs have been identified with luminous galaxies, while all high $T_s$ (T_s \ga 1000 K) DLAs have been identified with either LSBs or dwarfs. DLA spin temperatures thus appear to correlate with galaxy type, with no correlation seen between $T_s$ and impact parameter. The trend that low $z$ DLAs exhibit both high and low $T_s$ values while high redshift (z \ga 3) DLAs only show high spin temperatures is present in this expanded data set. Based on this difference in spin temperatures, the Gehan test rules out the hypothesis that DLAs at $z > 2$ and DLAs at $z < 2$ are drawn from the same parent population at ~ 99 % confidence level. Finally, we estimate upper limits on the fraction of cold HI, $f_{CNM}$, in the z \ga 3 DLAs. In local spirals, $f_{CNM} \sim 0.5$; in contrast, we find that $f_{CNM} < 0.3$ in all 7 high $z$ DLAs, with $f_{CNM} < 0.1$ in 5 of the 7 cases. (abridged)Comment: 13 pages, 5 figures. Accepted for publication in Astronomy & Astrophysic

Influence of Graft Type on Outcomes After Pediatric Liver Transplantation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74904/1/j.1600-6143.2004.00359.x.pd

Organ donation and utilization in the USA

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75486/1/j.1600-6135.2004.00396.x.pd

Transplanting Kidneys Without Points for HLA‐B Matching: Consequences of the Policy Change

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87103/1/j.1600-6143.2011.03606.x.pd

The Clp1/Cdc14 phosphatase contributes to the robustness of cytokinesis by association with anillin-related Mid1

Cdc14 phosphatases antagonize cyclin-dependent kinase–directed phosphorylation events and are involved in several facets of cell cycle control. We investigate the role of the fission yeast Cdc14 homologue Clp1/Flp1 in cytokinesis. We find that Clp1/Flp1 is tethered at the contractile ring (CR) through its association with anillin-related Mid1. Fluorescent recovery after photobleaching analyses indicate that Mid1, unlike other tested CR components, is anchored at the cell midzone, and this physical property is likely to account for its scaffolding role. By generating a mutation in mid1 that selectively disrupts Clp1/Flp1 tethering, we reveal the specific functional consequences of Clp1/Flp1 activity at the CR, including dephosphorylation of the essential CR component Cdc15, reductions in CR protein mobility, and CR resistance to mild perturbation. Our evidence indicates that Clp1/Flp1 must interact with the Mid1 scaffold to ensure the fidelity of Schizosaccharomyces pombe cytokinesis