Co-translational targeting of secretory and integral membrane proteins to the endoplasmic reticulum (ER) requires two key mediators, the signal recognition particle (SRP) and its receptor. The SRP receptor is composed of two tightly associated subunits termed SRα and SRβ. Very little is known about the mechanism of membrane assembly of these two subunits of the SRP receptor. Therefore, it is the aim of this thesis to study the interactions between SRα and SRβ on the ER membrane as well as the role of SRα and SRβ in membrane assembly of functional SRP receptor. Unlike typical endoplasmic reticulum (ER) integral membrane proteins, both subunits of the SRP receptor were extracted from the ER membrane with 0.08% deoxycholate; 0.2M Tris pH 9.0. Nevertheless, SRβ could be targeted to the ER only when the SRP dependent pathway of translocation was functional, similar to other integral membrane proteins of the ER. Urea resistant anchoring of SRa on the ER membrane was sensitive to limited digestion of the membranes with trypsin (Andrews eta/., 1989). However, anchoring of SRα was restored by incorporating exogenous SRβ into trypsin treated membranes, confirming that one function of SRβ is anchoring of SRα. Consistent with this is the observation that, SRβ could be immunoprecipitated in a complex with SRα but not with SRα mutants containing deletions in the anchoring domain. Finally, an antiserum to the GTP binding domain of SRβ inhibited translocation of the secretory protein preprolactin suggesting that SRβ also has a direct role in translocation. / Thesis / Master of Science (MSc)

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Salmonella continues to threaten public health as well as negatively impact dairy producers on multiple levels. Efficacious solutions to control Salmonella among dairy cattle have long been sought to alleviate these problems. A novel vaccine technology has been developed based on purified siderophore receptors and porin proteins (SRP®) derived from Salmonella Newport. When vaccinated with these SRP® cattle are stimulated to produce antibodies which act in concert with host defenses to disrupt iron acquisition of pathogenic bacteria. To evaluate the effectiveness of this technology, a prospective cohort study was designed utilizing herds (n = 11) that practiced whole herd vaccination with the SRP® vaccine (vaccinated cohort) and herds (n = 11) that had not used the SRP® vaccine. Samples were collected during four rounds at approximately six week intervals from June through October 2009. Samples were transported to the laboratory at West Texas A&M University and cultured for the prevalence of Salmonella using selective enrichment methods. Salmonella isolates were evaluated for antimicrobial susceptibility and serotype. Data was analyzed using commercially available software to evaluate the herd-level effects of vaccination. Salmonella was ubiquitous throughout the Texas Panhandle and Eastern New Mexico, within-herd animal level estimates of prevalence ranged from 0.0 – 92%, over the length of the study period. Overall all rounds vaccinated herds had decreased (P = 0.012) Salmonella prevalence (15.3 vs. 27.5%). Vaccinated herds had numerically fewer Salmonella isolates belonging to the Newport serotype. Salmonella Typhimurium isolates were recovered approximately equally from vaccinated and non-vaccinated herds. Isolates from vaccinated herds were resistant to fewer antimicrobials throughout the study period. The ACSSuT(resistant to ampicillin, chloramphenicol, streptomycin, sulphisoxazole, and tetracycline) and MDR-AmpC (ACSSuT resistance plus resistance to ceftiofur and amoxicillin/clavulanate) resistant phenotypes were more frequently observed among non-vaccinated herds and none of the isolates from vaccinated or non-vaccinated herds were resistant to nalidixic acid, gentamicin, ciprofloxacin, or amikacin. These findings indicate vaccine efficacy for the reduction of Salmonella prevalence. Dairy operators along with herd veterinarians are encouraged to utilize this data with other herd specific factors in determining whether to use this specific vaccine.

Current authentication methods for wireless networks are difficult to maintain. They often rely on globally shared secrets or heavyweight public-key infrastructure. Wireless Authentication using Remote Passwords (WARP) mitigates authentication woes by providing usable mechanisms for both administrators and end-users. Administrators grant access by simply adding users' personal messaging identifiers (e.g., email addresses, IM handles, cell phone numbers) to an access control list. There is no need to store passwords or other account information. Users simply prove ownership of their authorized identifier to obtain wireless access.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18834号 / 理博第4092号 / 新制||理||1588(附属図書館) / 31785 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 大野 睦人, 教授 阿形 清和, 教授 森 和俊 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Abstract This research investigated the distribution of Trichodesmium in the South China Sea and the ecological factors that affect it. The survey periods were from August 1999 to October 2000. A total of 5 cruises were conducted, mostly in summer and autumn, including cruise 559 (August 18~25, 1999), cruise 629 (May 22~27, 2000), cruise 588 (July 3~14, 2000), cruise 597 (October 4-13, 2000), and cruise 657 (October 16-21, 2000). The sampling stations were located on the continental shelves, the slope zones, and the basin in the South China Sea between 13~22∘N and 114~120∘E. The density of Trichodesmium in the South China Sea varied greatly among the continental shelves, the slope zones, and the basin zones. Trichodesmium density in the continental shelf and the slope was high, with an average density of 150¡Ó297¡Ñ103 trichomes/m3 (4~1008¡Ñ103 trichomes/m3) in the surface water and 151¡Ó322¡Ñ103 trichomes/m3 (13~1114¡Ñ103 trichomes/m3) in 2-60m water depth. This could be caused by the influence of the mixing of the Kuroshio water and the substances of terrestrial origin. In the basin, Trichodesmium density was low, with an average density of 5¡Ó7¡Ñ103 trichomes/m3 (0~22¡Ñ103 trichomes/m3) in the surface water and an average density of 6¡Ó7¡Ñ103 trichomes/m3(0~22¡Ñ103 trichomes/m3) in 2~60m water depth. The Trichodesmium communities are mainly composed of T. thiebautii and T. erythraeum, with T. thiebautii being more abundant than T. erythraeum. Their relative importance at the continental shelf and the slope zones was 58% and 36% respectively, and 64% and 31% in the basin respectively. Trichodesmium appeared commonly as a single trichome, rarely in colony. The vertical distribution of Trichodesmium concentrated at 0-100m. The highest density was near the surface, varying between 4~1008¡Ñ103 trichomes/m3. In summer, the Trichodesmium in the continental shelf and the slope zone of the South China Sea was slightly higher than that in the East China Sea. The influences of temperature, nutrient abundance and wind speed on the distribution of Trichodesmium are not obvious. Trichodesmium in shallow water became abundant after the passage of a typhoon. The maximum density of Trichodesmium was observed in shallow water and average number of trichome per colony decreased. The influences of the typhoon on Trichodesmium species composition and colony density were not obvious. High density of Trichodesmium occurred at shallow waters and the water column with low stratification index (SI) which repressed the properties of waters in the continental shelf and the slope zones. The regions in which high-density Trichodesmium appeared, were the continental shelves and slope which showed water properties similar to those of the Kuroshio water, indicating possible intrusion of the Kuroshio water in summer into the continental shelves and slope of the northern South China Sea.

Autism is one of the leading causes of human intellectual disability (ID). More than 1% of the human population has autism spectrum disorders (ASDs), and it has been estimated that over 50% of those with ASDs also have ID. Fragile X syndrome (FXS) is the most common inherited form of mental retardation and is the leading known genetic cause of autism, affecting approximately 1 in 4000 males and 1 in 8000 females. Approximately 30% of boys with FXS will be diagnosed with autism in their later lives. The cause of FXS is through an over-expansion of the CGG trinucleotide repeat located at the 5’ untranslated region of the FMR1 gene, leading to hypermethylation of the surrounding sequence and eventually partially or fully silencing of the gene. Therefore, the protein product of the gene, fragile X mental retardation protein (FMRP), is reduced or missing. As a single-gene disorder, FXS offers a scientifically tractable way to examine the underlying mechanism of the disease and also shed some light on understanding ASD and ID. The mouse model of FXS (Fmr1−/y mice) is widely accepted and used as a good model, offering good structural and face validity. Since a primary deficit of FXS is believed to be altered neuronal communication, in this thesis I examined white matter tract and dendritic spine abnormalities in the mouse model of FXS. Loss of FMRP does not alter the gross morphology of the white matter. However, recent brain imaging studies indicated that loss of FMRP could lead to some minute abnormalities in different major white matter tracts in the human brain. The gross white matter morphology and myelination was unaltered in the Fmr1−/y mice, however, a small but significant increase of axon diameter in the corpus callosum (CC) was found compared to wild-type (WT) controls. Our computation model suggested that the increase of axon diameter in the Fmr1−/y mice could lead to an increase of conduction velocity in these animals. One of the key phenotypes reported previously in the loss of FMRP is the increase of “immature” dendritic spines. The increase of long and thin spines was reported in several brain regions including the somatosensory cortex and visual cortex in both FXS patients and the mouse model of FXS. Although recent studies which employed state-of-the-art microscopy techniques suggested that only minute differences were noticed between the WT and Fmr1−/y mice. In agreement with previous findings, I found an increase of dendritic spine density in the visual cortex in the Fmr1−/y mice, and spine morphology was also different between the two genotypes. We found that the spine head diameter is significantly increased in the CA1 area of the apical dendrites of the Fmr1−/y mice compared to WT controls. Dendritic spine length is also significantly increased in the same region of the Fmr1−/y mice. However, apical spine head size does not alter between the two genotypes in the V1 region of the visual cortex, and spine length is significantly decreased in the Fmr1−/y mice compared to WT animals in this region. Lovastatin, a drug known as one of the 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors, functions as a modulator of the mitogen-activated protein kinases (MAPK) pathway through inhibiting Ras farnesylation, was used in an attempt to rescue the dendritic spine abnormalities in the Fmr1−/y mice. Mice lacking FMRP are susceptible to audiogenic seizure (AGS). Previous work has shown that 48 hr of lovastatin treatment reduced the incidence of AGS in the Fmr1−/y mice. However, chronic lovastatin treatment failed to rescue the spine density and morphology abnormalities in the Fmr1−/y mice. Mouse models are invaluable tools for modelling human diseases. However inter-strain differences have often confounded results between laboratories. In my final Chapter of this thesis, I compared two commonly used C57BL/6 substrains of mice by recording their electrophysiological responses to visual stimuli in vivo. I found a significant increase of high-frequency gamma power in adult C57BL/6JOla mice, and this phenomenon was reduced during the critical period. My results suggested that the C57BL/6JOla substrain has a significant stronger overall inhibitory network activity in the visual cortex than the C57BL/6J substrain. This is in good agreement with previous findings showing a lack of open-eye potentiation to monocular deprivation in the C57BL/6JOla substrain, and highlights the need for appropriate choice of mouse strain when studying neurodevelopmental models. They also give valuable insights into the genetic mechanisms that permit experience-dependent developmental plasticity. In summary, these findings give us a better understanding of the fine structure abnormalities of the Fmr1−/y mice, which in turn can benefit future discoveries of the underlying mechanisms of neurodevelopmental disorders such as ID and ASDs.

The main focus of Master’s thesis is modern methods for user authentication. In the first part are briefly described currently used protocols and pointed out thein advantages and disadvantages. The theoretical introduction analyzes the principles of zero-knowledge authentication, password-based protocols and describes the concept of a new generation hash function. The practical part describes the specific implementation of authentication protocols - Ohta-Okamoto protocol as a representative of the zero knowledge protocols and SRP (Secure Remote Password), which represents password-based protocols. In both cases, the installation procedure is described following the analysis of their implementation (at the source code level) and then compared with the transmitted data captured by Wireshark. The SRP protocol is verified by AVISPA tool. There is summary of both protocols security analysis in the conclusion.

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