Physico-chemical characterization of the native and mutant protein cochlin, and its role in adult-onset hearing and balance loss

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Includes bibliographical references (p. 39-40).This thesis investigates the role of the protein cochlin and its isoforms in DFNA9 autosomal dominant late onset senorineural loss and vestibular disorder by quantifying the concentration of cochlin in the inner fluid called perilymph. Through the use of affinity chromatography, high performance liquid chromatography, the Bradford assay, western blot analysis, and proteomics analysis by mass spectroscopy, I acquired data which suggests that the concentration of cochlin in the perilymph of bovine calf ears is at most on the order of 10- mg/ml. I also determined the total protein concentration of native bovine perilymph to be 2.1+0.2 mg/ml. Additionally, I discuss the theory of quasielastic light scattering along with its relevance to understanding the role of cochlin in DFNA9.by Benjamin L. Grannan.S.B

Optical Communication with Semiconductor Laser Diode

Theoretical and experimental performance limits of a free-space direct detection optical communication system were studied using a semiconductor laser diode as the optical transmitter and a silicon avalanche photodiode (APD) as the receiver photodetector. Optical systems using these components are under consideration as replacements for microwave satellite communication links. Optical pulse position modulation (PPM) was chosen as the signal format. An experimental system was constructed that used an aluminum gallium arsenide semiconductor laser diode as the transmitter and a silicon avalanche photodiode photodetector. The system used Q=4 PPM signaling at a source data rate of 25 megabits per second. The PPM signal format requires regeneration of PPM slot clock and word clock waveforms in the receiver. A nearly exact computational procedure was developed to compute receiver bit error rate without using the Gaussion approximation. A transition detector slot clock recovery system using a phase lock loop was developed and implemented. A novel word clock recovery system was also developed. It was found that the results of the nearly exact computational procedure agreed well with actual measurements of receiver performance. The receiver sensitivity achieved was the closest to the quantum limit yet reported for an optical communication system of this type

COX-2 selective inhibition reverses the trophic properties of gastrin in colorectal cancer

Gastrin is a gastrointestinal peptide that possesses potent trophic properties on both normal and neoplastic cells of gastrointestinal origin. Previous studies have indicated that chronic hypergastrinaemia increases the risk of colorectal cancer and cancer growth and that interruption of the effects of gastrin could be a potential target in the treatment of colorectal cancer. Here we demonstrate that gastrin leads to a dose-dependent increase in colon cancer cell proliferation and tumour growth in vitro and in vivo, and that this increment is progressively reversed by pretreatment with the cyclo-oxygenase-2 inhibitor NS-398. Gastrin was able to induce cyclo-oxygenase-2 protein expression, as well as the synthesis of prostaglandin E2, the major product of cyclo-oxygenase. Moreover, gastrin leads to approximately a two-fold induction of cyclo-oxygenase-2 promoter activity in transiently transfected cells. The results of these studies demonstrate that cyclo-oxygenase-2 appears to represent one of the downstream targets of gastrin and that selective cyclo-oxygenase-2 inhibition is capable of reversing the trophic properties of gastrin and presumably might prevent the growth of colorectal cancer induced by hypergastrinaemia

Interaction of influenza virus NS1 protein with growth arrest-specific protein 8

NS1 protein is the only non-structural protein encoded by the influenza A virus, and it contributes significantly to disease pathogenesis by modulating many virus and host cell processes. A two-hybrid screen for proteins that interact with NS1 from influenza A yielded growth arrest-specific protein 8. Gas8 associated with NS1 in vitro and in vivo. Deletion analysis revealed that the N-terminal 260 amino acids of Gas8 were able to interact with NS1, and neither the RNA-binding domain nor the effector domain of NS1 was sufficient for the NS1 interaction. We also found that actin, myosin, and drebrin interact with Gas8. NS1 and β-actin proteins could be co-immunoprecipitated from extracts of transfected cells. Furthermore, actin and Gas8 co-localized at the plasma membrane. These results are discussed in relation to the possible functions of Gas8 protein and their relevance in influenza virus release

Intestinal wall-adhesive hydrogel to study therapeutic treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is defined as pathogenesis in the intestine in a form of ulcerative colitis, Crohn's disease, etc. The number of IBD patients has recently increased rapidly majorly due to western diet and lifestyle. Because current treatment methods of IBD in the field are limited in targeting specific location and accompanying side effects such as vomiting, burping and chest pain occur. Hence, an unmet need remains in suggesting new perspective of drug delivery system to overcome these problems. Here, as an effort to develop an intestinal wall-adhesive, target specific peptide-conjugated hydrogel as a means of drug delivery, we synthesize mPEG-PCL (methoxy poly (ethylene glycol)-block-poly(ε-caprolactone)). The mPEG-PCL exhibits molecule weight of 3,200-3,500 g/mol, and its sol-gel transition occurs within the molecular weight range. This sol-gel makes the mPEG-PCL appropriate to load and deliver the drug to the inflamed area. Next, its binding affinity is increased to the colon epithelium by conjugating flagellin-derived peptide to the mPEG-PCL, which binds to TLR5 (Toll-like receptor 5) of colon epithelium. When loaded to the peptide-conjugated hydrogel, dug is released in a controllable fashion depending on the concentration of mPEG-PCL. Also, the hydrogel shows the binding specificity to intestinal cells in vitro. The results indicate several advantages of the peptide-conjugated mPEG-PCL as a drug delivery means: First, the sol-gel transition of hydrogel serves as a minimally invasive means of vehicle injection, an on-site depot of drug, and a concentration-dependent platform for controlled drug release. Second, the conjugation of flagellin-derived peptide enables drug targeting to inflamed areas when applied to the intestine, thereby reducing the drug amount compared to systemic delivery means such as oral intake or intraperitoneal injection. Lastly, the nano-scale micelle property facilitates not only drug delivery to inflamed areas but also drug invasion into the intestinal wall underneath epithelium. In conclusion, further optimization and examination of these functional advantages would enable a promising potential to address the unmet need by serving as a tunable platform for user-friendly, disease area -specific drug delivery to the intestine. 염증성 장 질환(IBD)는 크론병과 궤양성대장염의 한 형태로 장내 염증성 병인으로 정의된다. 근대화, 서양식 식단 등의 원인으로 인해 IBD 환자 수가 급격히 증가하고 있으며 대증적 치료수단을 이용한 증상완화에 초점을 맞추고 있다. 현재 IBD 치료약인 항염증제와 면역억제제는 구강 섭취로 소장과 대장에 전달된다. 위 약물은 설사, 혈변, 면역력 감소등의 부작용을 동반하는데 이는 염증 부위로의 표적 약물 전달이 불가능하기 때문이다. 이를 극복하기 위해 효율적인 장벽 특이적 약물전달 치료수단이 필요하다. 여기서, 우리는 mPEG-PCL를 기본 모체로 장벽 염증부위 특이적 약물 전달 하이드로겔을 개발하였다. 약물전달체의 장벽부착능력을 증가시키기 위해 편모 유래 펩타이드를 하이드로겔에 부착하였다. 편모는 장외벽에 발현하는 TLR5와 상호작용을 하는 펩타이드이다. 우리가 개발한 약물전달체는 상온에서 졸 상태로 존재하다 체온에서 젤상태가 된다. 이러한 졸 젤 전이는 약물을 담지하고 염증부위에 전달하는데 유용하다. 또한, 약물전달체의 농도를 조절함에 따라 약물의 방출 속도 조절이 가능하다. 표적 특이적 약물전달체의 개발은 몇 가지 이점을 지닌다. 첫째, 표적 특정 약물 전달을 통해 염증 부위에만 약물을 전달할 수 있다. 따라서, 필요한 약물의 양은 경구 투여로 인해 섭취하는 양에 비해 현저히 감소한다. 둘째, 약물을 지속적으로 방출하며, 약물의 효과가 더 오래 지속된다. 마지막으로, 염증부위로의 특이적 약물 전달은 다른 질병에 사용함에 있어 확장성이 있다. 결론적으로, 장 외벽 접착, 표적 특이적 약물전달 시스템으로 인해 사용해야하는 약물의 양을 줄이고 표적 특이전달 및 지속방출을 증가시켜 약물의 부작용을 줄일 수 있다.open석

Novel optical transmitters for high speed optical networks

The objective of this thesis is to investigate the performance of novel optical transmitter lasers for use in high speed optical networks. The laser technology considered is the discrete mode laser diode (DMLD) which is designed to achieve single wavelength operation by etching features on the surface of the ridge waveguide. This leads to a simplified manufacturing process by eliminating the regrowth step used in conventional approaches, presenting an economic approach to high volume manufacture of semiconductor lasers. Two application areas are investigated in this work. The bit rate in next generation access networks is moving to 10 Gbit/s. This work characterises the performance of DMLDs designed for high speed operation with the objective of identifying the limitations and improving performance to meet the specifications for uncooled operation at 10 Gbit/s. With the deployment of advanced modulation formats the phase noise of the laser source has become an important parameter, particularly for higher order formats. DMLDs were developed for narrow linewidth operation. The linewidth of these devices was characterised and a value as low as 70 kHz was demonstrated. Transmission experiments were also carried out using a coherent transmission test bed and the performance achieve is compared with that of an external cavity laser

On the Low False Positive Probabilities of Kepler Planet Candidates

We present a framework to conservatively estimate the probability that any particular planet-like transit signal observed by the Kepler mission is in fact a planet, prior to any ground-based follow-up efforts. We use Monte Carlo methods based on stellar population synthesis and Galactic structure models, and report a priori false positive probabilities for every Kepler Object of Interest in tabular form, assuming a 20% intrinsic occurrence rate of close-in planets in the radius range 0.5 Rearth < Rp < 20 Rearth. Almost every candidate has FPP <10%, and over half have FPP <5%. This probability varies most strongly with the magnitude and Galactic latitude of the Kepler target star, and more weakly with transit depth. We establish that a single deep high-resolution image will be an extremely effective follow-up tool for the shallowest (Earth-sized) transits, providing the quickest route towards probabilistically "validating" the smallest candidates by potentially decreasing the false positive probability of an earth-sized transit around a faint star from >10% to <1%. On the other hand, we show that the most useful follow-up observations for moderate-depth (super-Earth and Neptune-sized) candidates are shallower AO imaging and high S/N spectroscopy. Since Kepler has detected many more planetary signals than can be positively confirmed with ground-based follow-up efforts in the near term, these calculations will be crucial to using the ensemble of Kepler data to determine population characteristics of planetary systems. We also describe how our analysis complements the Kepler team's more detailed BLENDER false positive analysis for planet validation.Comment: Revision including results of calculations of individual FPPs for all KOIs as well as an additional discussion section regarding the relationship of our calculations to BLENDER. ApJ in pres