F-actin rearrangements and analysis of physical environment of invasive hyphal growth.

Invasive growth through a substrate requires a massive amount of penetrative force, and this is generated in the space of a few microns in a growing tip. This process is known to be critical in the root hair, pollen tube, rhizoids, and the topic of this thesis, hyphal growth. However defining the mechanisms underlying the tip growth remains a contentious issue. Shortcomings in control of direction and regulation of growth began to undermine early turgor-based theories, and the cytoskeletal protein actin, ubiquitous in nature and with crucial roles in structure and motility became a target for investigation. A major breakthrough came with the discovery that a characteristic actin depleted zone (ADZ) occurs at the growing tip of hyphae during invasive but not non-invasive hyphal growth. The ADZ is likely to have an important role in generating the greater protrusive force required for invasive growth. However, since its discovery, little has been determined about the characteristics of the ADZ. Uncertainty in the description of the physical environment the hyphae face adds a layer of complexity to interpretation of results. This thesis aims to address this issue, studying the impact of increasing agarose substrate concentration on the presence and dimensions of the ADZ in the oomycete A. bisexualis. Furthermore, agarose is examined by compression and imaging to compare the physical characteristics of the agar samples over the range of concentrations, and determine whether increasing agarose concentration influences agarose gel structure. Results suggest a difference in the number of ADZ observed in non-invasive compared with invasive samples, however no significant differences in the number or dimensions of ADZ were found amongst the 1-4% w/v agarose concentrations. The 0% sample showed 20.7 percent of hyphae exhibited depleted zones, while 1, 2, 3 and 4% samples showed 56.9%, 48.8%, 40.9% and 54.2% respectively. ADZ dimensions did not correlate with agarose concentration. The average ADZ area:hyphal diameter ratio was 0.634, 0.526, 0.430, 1.09, and 0.65 for 0-4% agarose concentrations respectively. Additionally, investigation of gel compression forces revealed gel strength increases with agarose concentration. The force required to compress the agarose increased from 1.85 Psi in 1% agarose to 4.85, 7.09 and 12.22 Psi in 2, 3 and 4% agarose concentrations respectively. SEM imaging, however, suggests heterogeneity of the fibrous interconnected network of agarose gels at a microscopic scale with variable porous structure at all agarose concentrations. This scale is relevant to hyphal tip growth. In combination, these results suggest F-actin depletion may be a response mechanism to provide greater force for invasive growth. Additionally, this response is not dependent on the concentration of the agarose media, possibly due to the variability encountered within the media. These results contribute another important step forward in unraveling the elusive mechanism of tip growth

Методика развития умений аудирования студентов неязыкового вуза в условиях смешанного обучения (английский язык).

Научно-квалификационная работа посвящена проблеме развития умений аудирования студентов неязыкового вуза в условиях смешанного обучения. Представлен процесс разработки методики развития умений аудирования, предложен алгоритм ее реализации, охарактеризован специально созданный комплекс упражнений в электронной обучаюшей среде LMS Moodle.The qualifying research paper considers the issue of developing students’ listening skills in a non-linguistic university within a blended learning environment. Methodology for developing listening skills is presented and algorithm of its implementation is proposed. The paper describes a complex of special tasks developed for LMS Moodle e-learning platform

A longitudinal study on the occurrence of Cryptosporidium and Giardia in dogs during their first year of life

<p>Abstract</p> <p>Background</p> <p>The primary aim of this study was to obtain more knowledge about the occurrence of <it>Cryptosporidium </it>and <it>Giardia </it>in young dogs in Norway.</p> <p>The occurrence of these parasites was investigated in a longitudinal study by repeated faecal sampling of dogs between 1 and 12 months of age (litter samples and individual samples). The dogs were privately owned and from four large breeds. Individual faecal samples were collected from 290 dogs from 57 litters when the dogs were approximately 3, 4, 6, and 12 months old. In addition, pooled samples were collected from 43 of the litters, and from 42 of the mother bitches, when the puppies were approximately 1 and/or 2 months old.</p> <p>Methods</p> <p>The samples were purified by sucrose gradient flotation concentration and examined by immunofluorescent staining.</p> <p>Results</p> <p>128 (44.1%) of the young dogs had one or more <it>Cryptosporidium </it>positive samples, whilst 60 (20.7%) dogs had one or more <it>Giardia </it>positive samples. The prevalence of the parasites varied with age. For <it>Cryptosporidium</it>, the individual prevalence was between 5.1% and 22.5%, with the highest level in dogs < 6 months old, and declining with age. For <it>Giardia</it>, the individual prevalence was between 6.0% and 11.4%, with the highest level in dogs > 6 months old, but the differences between age groups were not statistically significant. Significant differences in prevalences were found in relation to geographic location of the dogs. Both parasites occurred at low prevalences in Northern Norway.</p> <p>Conclusion</p> <p>Both <it>Cryptosporidium </it>and <it>Giardia </it>are common in Norwegian dogs, with <it>Cryptosporidium </it>more prevalent than <it>Giardia</it>. Prevalences of the parasites were found to be influenced by age, geographical location, and infection status before weaning.</p