9 resultados para Repeat breeders

em Brock University, Canada


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This descriptive-exploratory study examined factors which were perceived by students at a College of Applied Arts and Technology (CAAT) campus as influencing them in choosing to come or not to come for personal counselling and why they would or would not retum. A total of 250 students selected through a sample of convenience were surveyed. A questionnaire survey was conducted with quantitative data collected using a 4-point, forced-choice Likert scale and yes/no questions and qualitative data collected using open-ended questions and invited comments. The responses were analyzed using means and modes for the Likert responses and percentages for the yes/no and check-off questions. The narrative responses were subjected to content analysis to identify themes. The mean score findings on factors influencing students to come for personal counselling were at or close to the mid- point of 2.5. Personal distress was the only variable found to have a negative response, meaning students would not come to counselling if they were in personal distress. On factors that would keep them from choosing to come to counselling, students seemed to trust counsellors and feel accepted by them and rejected the notion that peer pressure or the first session being unhelpful would keep them away from counselling. The counsellor's relationship with the student is the major determinant for repeat sessions. When asked what factors would influence students to not retum for personal counselling, students rejected the variables of peer pressure, the extra time needed for counselling, and not getting what they wanted in a session, but, in one instance, indicated that variables regarding the counselling relationship would keep them from returning.

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It is well accepted that structural studies with model membranes are of considerable value in understanding the structure of biological membranes. Many studies with models of pure phospholipids have been done; but the effects of divalent cations and protein on these models would make these studies more applicable to intact membrane. The present study, performed with above view, is a structural analysis of divalent io~cardio1ipin complexes using the technique of x-ray diffraction. Cardiolipin, precipitated from dilute solution by divalent ionscalcium, magnesium and barium, contains little water and the structure formed is similar to the structure of pure cardiolipin with low water content. The calcium-cardiolipin complex forms a pure hexagonal type II phase that exists from 40 to 400 C. The molar ratio of calcium and cardiolipin in the complex is 1 : 1. Cardiolipin, precipitated with magnesium and barium forms two co-existing phases, lamellar and hexagonal, the relative quantity of the two phases being dependent on temperature. The hexagonal phase type II consisting of water filled channels formed by adding calcium to cardiolipin may have a remarkable permeability property in intact membrane. Pure cardiolipin and insulin at pH 3.0 and 4.0 precipitate but form no organised structure. Lecithin/cardiolipin and insulin precipitated at pH 3.0 give a pure lamellar phase. As the lecithin/cardiolipin molar ratio changes from 93/7 to SO/50, (a) the repeat distance of the lamellar changes from 72.8 X to 68.2 A; (b) the amount of protein bound increases in such a way that cardiolipin/insulin molar ratio in the complex reaches a maximum constant value at lecithin/cardiolipin molar ratio 70/30. A structural model based on these data shows that the molecular arrangement of lipid and protein is a lipid bilayer coated with protein molecules. The lipid-protein interaction is chiefly electrostatic and little, if any, hydrophobic bonding occurs in this particular system. So, the proposed model is essentially the same as Davson-Daniellifs model of biological membrane.

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The purpose of the study was to investigate the effect of skate blade radius of hollow (ROH) on anaerobic performance, specifically during the acceleration and stopping phases of an on-ice skating test. Fifteen, male Junior B hockey players (mean age 19 y ± 1.46) were recruited to participate. On-icc testing required each participant to complete an on-ice anaerobic performance test [Reed Repeat Skate (RRS)) on three separate days. During each on-ice test, the participant's skate blades were sharpened to one of three, randomly assigned, ROH values (0.63 cm, 1.27 cm, 1.90 cm). Performance times were recorded during each RRS and used to calculate anaerobic variables [anaerobic power (W), anaerobic capacity (W), and fatigue index (s, %)). Each RRS was video recorded for the purpose of motion analysis. Video footage was imported into Peak Motus™ to measure kinematic variables of the acceleration and stopping phases. The specific variables calculated from the acceleration phase were: average velocity over 6 m (m/s), average stride length (m), and mean stride rate (strides/s). The specific variables calculated from the stopping phase were: velocity at initiation of stopping (rn/s), stopping distance (m), stopping time (s). A repeated measures ANOV A was used to assess differences in mean performance and kinematic variables across the three selected hollows. Further analysis was conducted to assess differences in trial by trial performance and kinematic variables for all hollows. The primary findings of the study suggested that skate blade ROH can have a significant effect on kinematic variables, namely stride length and stride rate during the acceleration phase and stopping distance and stopping time during the stopping phase of an on-ice anaerobic performance test. During the acceleration phase, no significant difdifferences were found in SR and SL across the three selected hollows. Mean SR on the 1.27 cm hollow was significantly slower than both the 0.63 cm and 1.90 cm hollows and SL was significantly longer when skating on the 1.27 cm hollow in comparison to the 1.90 cm hollow. During the stopping phase, stopping distance on the 0.63 cm hollow (4.12 m ± 0.14) was significantly shorter than both the 1.27 cm hollow (4.43 m ± 0.08) (p < 0.05) and the 1.90 cm ho])ow (4.35 m ± 0.12) (p < 0.05). Mean ST was also significantly shorter when stopping on the 0.63 cm hollow then both the 1.27 cm and 1.90 cm hollows. Trial by trial results clearly illustrated the affect of fatigue on kinematic variables; AV, SR, IV decreased from trial 1 to 6. There was no significant effect on anaerobic performance variables during the RRS. Altering the skate blade ROH has a significant and practical affect on accelerating and stopping performance will be discussed in this paper.

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Gramicidin is an antibiotic peptide that can be incorporated into the monolayers of cell membranes. Dimerization through hydrogen bonding between gramicidin monomers in opposing leaflets of the membrane results in the formation of an iontophoretic channel. Surrounding phospholipids, with various associated mechanical properties, have been shown to influence the gating properties of this channel. Conversely, gramicidin incorporation has been shown to affect the structure of spontaneously formed lipid assemblies. Using small-angle x-ray diffraction and model systems composed of phospholipids and gramicidin, the physical effects incurred by gramicidin incorporation were measured. The reverse hexagonal (H^) phase composed of dioleoylphosphatidylethanolamine (DOPE) monolayers decreased in lattice dimension with increasing incorporation of gramicidin. This indicated that gramicidin was adding negative curvature to the monolayers. In this system, gramicidin was measured to have an apparent intrinsic radius of curvature (Rop*™") of -7. 1 A. The addition of up to 4 mol% gramicidin in mixtures with DOPE did not result in the monolayers becoming stiffer, as indicated by unaltered bending moduli for each composition. Dioleoylphosphatidylcholine (DOPC) alone forms the lamellar (LJ phase when hydrated, but undergoes a transition into the H^ phase when mixed with gramicidin. The lattice repeat dimension decreases systematically with increased gramicidin content. Again, this indicated that gramicidin was adding negative curvature to the monolayers. At 12 mol% gramicidin in mixtures with DOPC, the apparent radius of intrinsic curvature of gramicidin (Rop*"^) was measured to be -7.4 A. This mixture formed monolayers that were very resistant to bending under osmotic pressure, with a measured bending modulus of 1 15 kT. The measurements made in this study demonstrate that peptides are able to modulate the spontaneous curvature and other mechanical properties of phospholipid assemblies.

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Surface proteinaceous fibrils, termed fimbriae, were first identified on gram negative bacteria in the 1940s. Fungal fimbriae, discovered some 25 years later, are found on members of all fungal classes. In the present study, polyclonal antiserum raised against the fimbrial proteins of U. vio/acea were used in order to identify antigenically related proteins from Coprinus cinereus and Schizophy//um commune. Two polypeptides with molecular masses of 37 and 39 kDa from C. cinereus were observed and confirm earlier results. A single previously unidentified 50 kDa polypeptide in S. commune crossreacted with the antiserum. The 50 kDa protein was found to consist of 3 isoforms with isoelectric points ranging from 5.6 to 5.8. A fimbrial cDNA derived from U. vio/acea was used to identify DNA restriction fragments from C. cinereus and S. commune showing homology to the fimbrial transcript of U. vio/acea. Heterologous hybridization with this cDNA was used in order to screen a C. cinereus genomic DNA library. A single clone, A2-3A, with a 14 kbp insert showed strong homology to the pfim3-1 cDNA. The region of homology, a 700 bp Xba I fragment, was subcloned into pUG19. This plasmid was refered to as pXX8. DNA sequence determinations of pXX8 and adjacent fragments from A2-3A suggested that the cloned DNA was a portion of the rONA repeat encoding the small subunit rRNA. DNA sequence analysis of pfim3-1 yielded an incomplete open reading frame. The predicted amino acid sequence codes for a 206 amino acid, 22 kDa polypeptide which contains a domain similar to a transmembrane domain from rat leukocyte antigen, GDS3. As well, an untranslated 576 nucleotide domain showed 81 % homology to pXX8 and 830/0 homology to the 188 rRNA sequence of Ustilago maydis. This sequence was found adjacent to a region of adenine-thymine base pairs presumed to represent the polyadenylation sequence of the fimbrial transcript. The size and extent of homology is sufficient to account for the hybridization of pfim3-1 to rDNA. It is suggested that this domain represents a completely novel regulatory domain within eukaryotes that may enable the observed rapid regeneration of fimbriae in U. violacea.

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In order to fully understand an organism's behaviours the interactions between multiple enemies or selective pressures need to be considered, as these interactions are usually far more complex than the simple addition of their effects in isolation. In this thesis, I consider the impact of multiple enemies (fish predators and parasites) on the behaviour of three larval anurans (Lithobates sylvaticus, L. clamitans and L. catesbeianus). I also determine whether species that differ in life-histories and habitat preferences possess different antipredator mechanisms and how this affects species responses to multiple enemies. I show that the three Ranid larvae respond differently to the trade-off imposed by the presence of both fish predators and trematode parasites within the environment. The two more permanent pond breeders (L. clamitans and L. catesbeianus) increased activity when in the combined presence of predators and parasites. In contrast, the temporary pond breeder (L. sylvaticus) decreased activity in the combined presence of predator and parasites, in the same manner as they responded to fish alone. Further, the presence of fish along with parasites increased the susceptibility of both L. sylvaticus and L. clamitans to trematode infection, whereas parasite infection in L. catesbeianus was unaffected by the presence of fish. A second experiment to assess palatability of the three anuran species to fish, revealed a range of palatabilities, with L. catesbeianus being least palatable, L. clamitans being somewhat unpalatable, and L. sylvaticus being highly palatable. This result helps to explain the species differences in tthe observed behaviour to the combined presence of fish and parasites. In conclusion, the results from this study highlight the importance of considering multiple selective pressures faced by organisms and how this shapes their behaviour.

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Transcript (spelling and grammar retained): Chippawa [Chippewa] 28th August 1860 My Dear Sir I duly received your very kind letter of the 24th [June] asking me to communicate such facts of general interest connected with my career during the War with the United States. I have no objection to afford you such information as came under my own observation; nevertheless I do so, with the understanding, I have no desire to be my own trumpeter. With respect to your circular wherein you state you have been for several years collecting materials for a History of the late War between the United States & Great Britain, for which you are now gathering further materials to add to your collection, concerning the Second War for Independence. I am rather at a loss to know, what is meant by the second war; If you allude to the petty Rebellion, it could not be called a War, Those that caused the outbreak were very soon put down, by the Loyal people of the Province without the aid of Regular Troops being satisfied with the Independence they enjoyed. With respect to the several questions names in your circular: To the 1st I would say, this locality is made memorable by the battle of Chippawa [Chippewa] which took place about a mile above the village on the ground I pointed out to you, when I had the pleasure of seeing you a few days ago, with Mr Porter of the Niagara Falls, of which I believe you took sketches at the time. 2nd I have no historical documents of any value; so many years having gone past, the most of my old papers have either been lost or destroyed, I however came across two letters, one dated Queenston 9th July 1812 from Lt. Col. Nicholl Quarter Master General of Militia, the other from Lt. Col Myers Deputy Quarter Master General of the Regular Army date Fort George 23rd same month, directed to me in the hand writing of each of those officers as Deputy Quarter Master General of Militia, which letters I shall be obliged you would return at as early a day possible, as I wish to place them with tome others in the case, I have had made to hold the cocked hat & feather I wore during that eventful period, which I am sorry I did not exhibit when you was at my house; with reference to it I now enclose a letter from Lt. Col. Clark, residing at Port Dalhousie he was Captain & Adjutant of Militia in the War of 1812__ I send the letter in proof of the cock’d hat it is a lengthy one, but you may find time to turn over it, as I shall also place it in the hat case__ 3rd Where are [but] [for] traditionary [sic] witnesses residing in this vicinity – Col Clark above named Mr Merritt of St. Catharines, & Mr Kerby of Brantford are the only ones I now recollect, who could offord [sic] you any statistical information. 4th I have no pictorial sketches of any Military Movements or fortifications. As regards my own career, which you appear [ ? ] of knowing__ I was first a Lieutenant in a volunteer flank company stationed on the river side opposite [Navy] Island not far from the battle ground of Chippawa [Chippewa], I got promotion as Lieutenant of Cavalry before I got my Cavalry dress completed in three days more, I was called by General Brock to Fort George, was appointed Deputy Quarter Master General of Militia with the rank of Captain s the accompanying letters will show. I was at the battle of Stony Creek, several skirmishes at the Cross Roads, when the American army [ ? ] Fort George, at the taking of Col. Boerstler at the Beaver Dam, & had the honor of receiving Colonel Chapens sword at the surrender, who commanded a company of volunteer Horse Men was at the taking of 15 regulars & two officers at Fort Schlosser—was with Col. Bishop at the taking of Black Rock, near him when he fell, three men of the 8th Reg. more killed in the Boat I was in – I was at Chippawa battle, and the last, not the least in Lundy’s lane battle, which the Americans call the battle of Bridge [Waters]. I had forgot; there was another small affair at Corks Mill where I was. I could write a little history of events, but have not the time to do so. If what I have stated will be of any service for the purpose you require I shall feel happy. The history of the late War was published at Toronto in the Anglo American Magazine. Did you ever see it, I have the Books, there were however several errors which came under my notice, which I could have corrected. If my time would permit I could give you a more detailed statement of events. I trust however you may succeed with your publication , and I shall be most happy to hear from you at all times—I related many little occurances verbally to you when here, which I thought not necessary to repeat again as you would have a perfect recollection of them. Be pleased to return the letters for the purpose I require them. I am My Dear Sir Your respectful friend James Cummings

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Human endogenous retroviruses (HERVs) are the result of ancient germ cell infections of human germ cells by exogenous retroviruses. HERVs belong to the long terminal repeat (LTR) group of retrotransposons that comprise ~8% of the human genome. The majority of the HERVs documented have been truncated and/or incurred lethal mutations and no longer encode functional genes; however a very small number of HERVs seem to maintain functional in making new copies by retrotranspositon as suggested by the identification of a handful of polymorphic HERV insertions in human populations. The objectives of this study were to identify novel insertion of HERVs via analysis of personal genomic data and survey the polymorphism levels of new and known HERV insertions in the human genome. Specifically, this study involves the experimental validation of polymorphic HERV insertion candidates predicted by personal genome-based computation prediction and survey the polymorphism level within the human population based on a set of 30 diverse human DNA samples. Based on computational analysis of a limited number of personal genome sequences, PCR genotyping aided in the identification of 15 dimorphic, 2 trimorphic and 5 fixed full-length HERV-K insertions not previously investigated. These results suggest that the proliferation rate of HERVKs, perhaps also other ERVs, in the human genome may be much higher than we previously appreciated and the recently inserted HERVs exhibit a high level of instability. Throughout this study we have observed the frequent presence of additional forms of genotypes for these HERV insertions, and we propose for the first time the establishment of new genotype reporting nomenclature to reflect all possible combinations of the pre-integration site, solo-LTR and full-length HERV alleles.

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Sequence repeats are an important phenomenon in the human genome, playing important roles in genomic alteration often with phenotypic consequences. The two major types of repeat elements in the human genome are tandem repeats (TRs) including microsatellites, minisatellites, and satellites and transposable elements (TEs). So far, very little has been known about the relationship between these two types of repeats. In this study, we identified TRs that are derived from TEs either based on sequence similarity or overlapping genomic positions. We then analyzed the distribution of these TRs among TE families/subfamilies. Our study shows that at least 7,276 TRs or 23% of all minisatellites/satellites is derived from TEs, contributing ∼0.32% of the human genome. TRs seem to be generated more likely from younger/more active TEs, and once initiated they are expanded with time via local duplication of the repeat units. The currently postulated mechanisms for origin of TRs can explain only 6% of all TE-derived TRs, indicating the presence of one or more yet to be identified mechanisms for the initiation of such repeats. Our result suggests that TEs are contributing to genome expansion and alteration not only by transposition but also by generating tandem repeats.