McGill Science undergraduate research journal : MSURJ最新文献

{"title":"High UV Excitation Intensity Induces Photoconversion of DAPI During Wide-Field Microscopy","authors":"C. Brown","doi":"10.26443/msurj.v9i1.158","DOIUrl":"https://doi.org/10.26443/msurj.v9i1.158","url":null,"abstract":"Background: Multi-color fluorescence microscopy is dependent on the spectral specificity of the dyes and probes used for localization. One of the most commonly used fluorescent DNA dyes is DAPI, which is usually excited by UV light to emit in the blue visible light range. Herein, we describe a pattern of decreasing DAPI fluorescence upon extended UV exposure, closely followed by an increase in emission maxima in the green range. \u0000Methods: UV-induced photo-conversion of DAPI to green-fluorescing photoproducts was studied on Chinese hamster ovary cells using wide-field fluorescence microscopy, at different UV exposure times and intensities. Imaging was done in repetitive cycles, by alternating between a DAPI and FITC filter cube and following this with a 1 second UV excitation time. The effect of differing UV light intensities on the photo- conversion process was not previously described in the literature. \u0000Results: Upon image analysis from a large sample of cells, the rate of photo-conversion was shown to be dependent on both the duration of UV excitation and the intensity of the UV light source. Both the process of DAPI depletion and photo-product growth showed biphasic exponential patterns of change. Furthermore, the level of DAPI fluorescence intensity was found to be negatively correlated with the green fluorescence of the photo-product. \u0000Limitations: This study did not examine the effect of differing mounting media or a variation in DAPI concentration on the rate of DAPI photo-conversion. Also, the exact light dosage to the system was not measured from the 100W Hg bulb. Photo-bleaching of green fluorescence in cells not stained with DAPI was not measured to control for bleaching of endogenous cell molecules. \u0000Conclusion: Based on our findings, a set of recommendations was formulated in order to help reduce the effects of UV-induced DAPI photo-conversion.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microstimulation to the Middle Temporal Area and its Effect on the Generation of Microsaccades","authors":"Haider Riaz, A. Golzar","doi":"10.26443/msurj.v9i1.157","DOIUrl":"https://doi.org/10.26443/msurj.v9i1.157","url":null,"abstract":"It has been repeatedly shown that neural activity in different brain structures can be correlated with perceptual and cognitive functions using electrical microstimulation. Currently, microstimulation is the only method that can demonstrate causal links between neural activity and specific cognitive functions. This study investigates the effects of microstimulation to the MT area of the visual cortex on the production of microsaccades for several seconds. Microsaccades are a type of fixational eye movement characterized by their quickness and low amplitude. The preliminary findings in this paper suggest that microstimulation to the MT area causes an increase in frequency and peak velocity of microsaccades. However, a more in-depth analysis to establish a correlation between the two was unsuccessful. These results suggest further investigation into the effects of microstimulation on microsaccades – using more sophisticated and reliable data collecting and analyzing techniques – is necessary.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parrotfish Body Size As An Indicator of Diurnal Fish Species Richness On Fringing Coral Reefs in Barbados","authors":"A. Eger, Catherine Pigeon-Dubeau, Lauriane Sibileau","doi":"10.26443/msurj.v9i1.155","DOIUrl":"https://doi.org/10.26443/msurj.v9i1.155","url":null,"abstract":"Background: Coral reefs around the world are host to some of the most condensed and varied ecosystems. However, over the past decades, their biodiversity has alarmingly decreased. A rapid and reliable way of assessing their status is urgently needed to monitor and prevent their decline. The purpose of this study is to assess whether or not family Scaridae (common name: parrotfish) body size can be used as an index to evaluate the diurnal fish diversity on coral reefs. \u0000Methods: We selected 6 accessible reefs on the West coast of Barbados and measured the size of parrotfish we encountered, as well as the number of fish species present on the reef; this data was then plotted and statistically analyzed to establish a possible correlation. \u0000Results: Our results show that reef fish species richness is strongly correlated to both the ratio of large to small parrotfish and the average parrotfish size. It is however the large to small ratio that exhibited the strongest relationship. Further analysis revealed that the population size of large parrotfish correlates with reef biodiversity with a Pearson’s r coefficient of 0.97. \u0000Conclusion: This relationship could be due to the fact that large parrotfish (greater than or equal to 20 cm) have increased grazing rates compared to smaller ones, this increased grazing promotes coral polyp recruitment, thereby benefiting the diversity observed on coral reefs. Further research is needed to elucidate whether these results can be extended to other areas of the Caribbean and provide conservation efforts with an easy tool to survey and protect coral reef ecosystems.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development and Characterization of a Directional Gamma-ray Detector","authors":"Felix Cormier, Marcel P. Georgin, Stephen Koelbl, R. Oda","doi":"10.26443/msurj.v9i1.156","DOIUrl":"https://doi.org/10.26443/msurj.v9i1.156","url":null,"abstract":"Background: This work characterizes the first generation of detectors from the Hanna Laboratory to implement Silicon Photomultipliers and a heptagonal scintillator conguration. The purpose of the device is to determine the angle at which a radioactive source is located. \u0000Methods: The development of the detector consisted of three phases: construction(September 2012- December 2012), simulation and characterization (April 2013). The experimental portion of the work consisted of placing a 137 Cs source at an arbitrary location, measuring the count rates in each scintillator panel and analysing the results. \u0000Results: The detector’s function was validated by confirming the inverse square law with a radioactive source moving away from the detector. Furthermore, with a x2 summation method of analysis the angular position of a source was determined with an accuracy of 10˚ and a precision of 12˚. With a normalisation method of analysis the angular position of a source was found with an accuracy of 2˚ and a corresponding precision of 2˚. \u0000Limitations: The quality of the electronics handling the signal from the silicon photomultipliers limited our resolution. Occasional double counts occur when a large amount of energy is imparted to the scintillator. Furthermore, the custom-built circuitry lowered the signal-to-noise ratio such that large distances were not feasible due to electronic noise constraints. Finally, simulation data analysis showed that the break of one circuit only had a small effect on the x2 method of analysis. \u0000Conclusions: In conclusion, the design of the detector and the analysis techniques were shown to be suitable for short range angular resolution of a gamma-ray source. Both distance trials and a simulation of the detector prototype confirmed the validity of our design and of the analysis methods used. These promising results at short distances motivate further work in electronic circuit design to improve the range while maintaining both accuracy and precision.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neuroplasticity and Post-Synaptic Rebound-Induced Spiking at Purkinje Cell-Deep Cerebellar Nuclei Synapses","authors":"Jenna Hotton","doi":"10.26443/msurj.v9i1.160","DOIUrl":"https://doi.org/10.26443/msurj.v9i1.160","url":null,"abstract":"Background: Within the cerebellum white matter are located four pairs of nuclei, collectively known as the deep cerebellar nuclei (DCN) (1). In the cerebellum, signal integration from pre-cerebellar structures via excitatory parallel fibers and climbing fibers in the cerebellar cortex occurs in GABAergic Purkinje cells (PC) (2). The main target of these PC cells is the DCN (2) and approximately 85% of GABAergic input on the DCN is from PCs (3). Furthermore, PCs outnumber DCN neurons (26:1) (2). Therefore, despite receiving substantial inhibition from Purkinje cells, DCN neurons are still active at rest showing regular spiking or spontaneous bursts (4). DCN neurons fire spontaneously at approximately 10-50 Hz (5). Given this unique anatomy of PC-DCN synapses, characterization of this synaptic circuit is important in understanding the overall role of the DCN in the brain. \u0000Methods: The findings of 28 studies, including a few reviews, are reported in this paper. Studies selected focused principally on characterization of DCN circuitry properties and the role these properties have in the functioning of the DCN. Most studies employed in vivo and/or in vitro cellular recordings in rodents, among other models. Studies ranged from 1984 to 2013. \u0000Summary: This review outlines current findings on the forms of plasticity found in the DCN, the function of the DCN and the connections between the DCN and other brain regions. In short, neurons in the DCN demonstrate both synaptic and non-synaptic plasticity. Cerebellar involvement in motor activity has been extensively studied therefore, not surprisingly; DCN neurons form connections with the motor cortex but also the prefrontal cortex. PC input on the DCN influences spike rate and timing through fluctuations in PC synchrony, and rebound depolarization.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Studying a poxvirus gene capture model through recombination and reactivation","authors":"K. Johnson, D. Evans","doi":"10.26443/msurj.v8i1.106","DOIUrl":"https://doi.org/10.26443/msurj.v8i1.106","url":null,"abstract":"\u0000 \u0000 \u0000Introduction: Vaccinia poxvirus (VACV) is a double stranded DNA virus that replicates in the cytoplasm of infected cells. Some VACV genes resemble homologs of host genes and appear to have been captured from the cell; however, since poxviruses are confined to the cytoplasm, researchers are unclear as to how these viruses acquire this homology (1). If a cellular mRNA was accidentally reverse transcribed into cDNA, which could occur during retrovirus co-infection, a poxvirus might be able to incorporate this sequence into its own genome through rare non-homologous (homology-independent) recombination. \u0000Methods: We modeled this process using two different recombination systems and substituted a DNA encoding mycophenolic acid (MPA), a selectable marker, for the hypothetical non-homologous host cDNA. We prepared DNA constructs containing this marker along with 20 base pairs homologous to the 5’ and 3’ flanking regions of the VACV-encoded NotI restriction site. A construct without this flanking homology was also prepared. The “passive” recombination system used a helper poxvirus to reactivate VACV DNA; in contrast, VACV infected BSC40 cells were transfected with the construct in the “active” recombination system. \u0000Results: The “passive” recombination system generated 105 PFU/mL of reactivated VACV; however, no recombinants containing the selectable marker were detected. The “active recombination” method generated 106 PFU/mL of total VACV and approximately 10 PFU/mL of recombinant virus for both homology containing and non-homology containing constructs. \u0000Discussions: We were unable to determine the recombination frequency of the “passive system” because recombinant virus was not detected. Based on virus titers determined from plaque assays, we approximated the recombination frequency of the “active system” to be ≤ 10-5. We are currently cloning and sequencing viruses resulting from non-homologous recombination to determine where the MPA marker is located. Preliminary analysis of these types of clones (data not shown in this paper) suggests that the transfected DNAs are being incorporated into a diversity of sites, some located near the boundary of the VACV genome where the right terminal inverted repeat begins. In summary, our findings suggest that the recombination frequencies in both methods are very low and better methods of selection are needed to observe these rare events. Future studies of recombinant clones are needed to gain a better understanding of this non- homologous gene capture process. \u0000 \u0000 \u0000","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69324898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stress reactivity during evaluation by the opposite sex: comparison of responses induced by different psychosocial stress tests","authors":"L. Goff, N. Ali, J. Pruessner","doi":"10.26443/msurj.v8i1.105","DOIUrl":"https://doi.org/10.26443/msurj.v8i1.105","url":null,"abstract":"\u0000 \u0000 \u0000It is becoming increasingly difficult for researchers to continue their high rates of publication when funding budgets are running tighter than ever. It is therefore in a researcher’s best interest to utilize more economical tests whenever possible. This project aims to compare various stress tests in order to determine whether the new, cost-efficient Maastricht Acute Stress Test (MAST) activates a physiological and subjective stress response with the same effectiveness as pre-existing, more resource-intensive tests. This study demonstrated that the MAST produces a response similar to that of the previously predominant Trier Social Stress Test (TSST). Meanwhile, database data shows that the purely physiological Cold Pressor Task (CPT) lags behind in terms of response elicited. These findings may allow for a more cost-efficient yet highly effective stress task to become available to researchers. \u0000 \u0000 \u0000","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69324885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Operational transformation in cooperative software systems","authors":"C. Leung","doi":"10.26443/msurj.v8i1.113","DOIUrl":"https://doi.org/10.26443/msurj.v8i1.113","url":null,"abstract":"\u0000 \u0000 \u0000Modern cooperative software systems involve multiple concurrent users undertaking a common task in a real-time distributed environment, such as editing a shared text document. Maintaining data consistency, transaction causality, and replication convergence in such an environment, while providing fast client responsiveness, is a substantial challenge for classical distributed computing techniques. Operational transformation (OT) is a class of concurrency algorithms and data models that supports these functionalities, which has drawn significant research attention in the past decade. In this review, we discuss the basic components of operational transformation models, the algorithms involved, and their actual implementations in real-world networked systems. We compare several existing OT control algorithms, the transformation functions and properties supported by each of the algorithms, and the trade-offs that are made with respect to each one. The data and operational models used in OT are well suited for high- latency environments such as the Internet, making them more frequently used in modern web services. Although many different OT control algorithms exist, choosing the most effective one often depends on the particular operations that an application must support. \u0000 \u0000 \u0000","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS): a once obscure neurodegenerative disease with increasing significance for neurological research","authors":"Xinlu Li","doi":"10.26443/msurj.v8i1.114","DOIUrl":"https://doi.org/10.26443/msurj.v8i1.114","url":null,"abstract":"\u0000 \u0000 \u0000Background: Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a rare cerebellar ataxia occurring in the Charlevoix-Saguenay population in Quebec with high incidence as a result of founder effects. Following the discovery of the gene responsible for the disease, many other patient groups have been identified worldwide and the characterization of the gene product, sacsin, has unveiled similarities between the pathogenic mechanism of ARSACS and those of other major neurodegenerative disease. \u0000Summary: The core symptoms of ARSACS consist of a triad of early-onset cerebellar ataxia, peripheral neuropathy and spasticity, which is accounted by degeneration of Purkinje neurons. The gene responsible for the disease is located on chromosome 13q11 and encodes for the chaperone sacsin. Drp-1, a GTPase crucial for regulating mitochondrial fission/fusion dynamics, has been identified as a potential substrate of sacsin, suggesting a link between the pathogenic mechanisms of ARSACS and prevalent neurodegenerative diseases such as Alzheimer’s, Parkinson’s and Huntington’s diseases. \u0000 \u0000 \u0000","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Selecting for multicellularity in the unicellular alga Chlamydomonas reinhardtii","authors":"Tyler Moulton, Dr. Graham Bell","doi":"10.26443/msurj.v8i1.108","DOIUrl":"https://doi.org/10.26443/msurj.v8i1.108","url":null,"abstract":"\u0000 \u0000 \u0000Background: Researchers have recently begun experimentally exploring the origins of multicellularity (4-6). Their studies have found that the transition to a multicellular state may have been surprisingly simple, considering its profound implications for the history of life (3). This study experimentally selected for multicellularity in the unicellular biflagellated alga Chlamydomonas reinhardtii. This organism is especially interesting because it is basal to the Volvocaceae—a family of biflagellates whose evolutionary transition from unicellular organisms to complex forms have been meticulously characterized (2). The present study aimed to recreate the early stages of this transition, starting from incomplete cytokinesis after cell division. \u0000Methods: The procedure was modeled loosely on the experiment performed by Ratcliff et al. (4) in which the authors successfully selected for multicellular Saccharomyces Cerevisiae—unicellular baker’s yeast. Three experimental replicates and one control for nine strains of C. reinhardtii were cultured in round-bottom vials in shaking incubators. Prior to each transfer (every 3-4 days), each culture was slowly mixed, and selection lines were then gently and briefly centrifuged. This applied a selection pressure which rendered heavier (clustered) cells more fit. The very bottom ~2% of the tubes’ contents was transferred, and cell cultures were examined for multicellularity. \u0000Results: Six of nine lines of C. reinhardtii demonstrated an increased frequency of C. reinhardtii existing in a two- to four-celled state (the paired cell state accounted for 88% of these clusters)—consistent with the first step toward multicellularity as outlined by Kirk (2). A close study of cell division in the line which exhibited the strongest shift towards the multicellular phenotype suggests that true multicellularity began to evolve in this experiment. A multicellular phenotype did not become fixed in any population. \u0000Conclusion: Our findings suggest that an artificial selection pressure is capable of inducing the evolution of multicellularity. Expanding upon this study could help us understand the mechanisms underlying the evolution of multicellularity. \u0000Limitations: Sporadic data, possibly the result of difficulties in the procedure, prevented us from rigorously examining the effect of selection through time, limiting our ability to describe the evolutionary response. In addition, the study of individual cells, due to its time-consuming nature, was limited to one replicate of one line exhibiting a pronounced multicellular response. Thorough replication would be required before drawing a strong conclusion from this assay. \u0000 \u0000 \u0000","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69325035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}