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The Function of the Small Acid-Soluble Proteins in Clostridioides difficile Spores
No full textClostridioides difficile (C. difficile) is a major cause of antibiotic associated diarrhea with over 200,000 cases of infection annually and a resultant 12,000 deaths. A major issue with C. difficile infection (CDI) is recurrence, with 1 in 4 infected individuals experiencing relapse post-infection. This is due to the ability of C. difficile to produce metabolically dormant endospores. Spores are highly resistant dormant forms of the bacteria that can survive UV light, chemical and antibiotic treatment. Spores are important in the infection cycle of C. difficile as they can survive in the aerobic environment outside of the host while vegetative cells cannot, and thus serve as the transmissible form of disease. Sporulation is controlled through a signal cascade of sporulation-specific RNA sigma factors. These factors drive the process of sporulation where the cell is divided into asymmetric compartments, the larger mother cell compartment, and the smaller forespore compartment. The forespore becomes engulfed within the mother cell and completes maturation before the mother cell lyses and releases the spore into the environment. A major component of the spore, that aids in many resistance properties in B. subtilis, is the small acid-soluble proteins (SASPs). In B. subtilis and in C. difficile, these SASPs protect the spore from UV light and aid in outgrowth of the vegetative cell from spores. Unlike B. subtilis SASPs, C. difficile SASPs do not contribute to chemical resistance but instead, a novel phenotype was discovered. A C. difficile ��sspA ��sspB strain, which lacks the major SASPs, produced immature spores that were phase gray, lacked the cortex layer, and were trapped in the mother cell. Through an EMS mutagenesis selection strategy, we identified alleles of spoIVB2 that suppressed the sporulation phenotype of the C. difficile double SASP mutant. We have found that C. difficile SASPs and SpoIVB2 are necessary for the proper formation of spores and likely regulate sporulation through and as of yet unknown mechanism. One possible mechanism is through SpoIVB2-mediated cleavage of SpoIIP, an amidase and endopeptidase involved in peptidoglycan remodeling during engulfment of the forespore. The novel C. difficile SASP phenotype gives insight for therapeutics that could target sporulating cells and prevent formation of dormant spores, thus preventing transmission of disease
Medical Device to Continuously Monitor Core Body Temperature
Get PDFMonitoring core body temperature has been shown to be essential in operating rooms and in intensive care units as it would provide insight on the patient���s overall health. If their core body temperature becomes abnormal, disruptions in normal cell functioning would closely follow. However, many methods that are able to accurately read core body temperature are invasive and only limited in operating rooms. As a result, a new device is needed that can non-invasively measure a patient���s core body temperature while still maintaining high accuracy. While there are a couple of different non-invasive devices, such as the 3M SpotOn and Draeger TCoreTM, that have been developed to monitor core body temperature, these devices have been clinically shown to have its own limitations. For example, the SpotOn device is limited to the presence of an external power source and its use of the zero-heat-flux technology contains a bandwidth parameter that affects its accuracy in different clinical settings. While the TCoreTM device addresses these limitations and utilizes a temperature gradient, clinical testing is still required to determine if its measurements are as accurate as invasive measures. As a result of these, the Maxim temperature sensing patch was created that utilizes the presence of a temperature gradient from the surface of the skin to the environment in order to accurately and continuously calculate a patient���s core body temperature. To address the limitations found from the other non-invasive solutions, the Maxim patches would be created from materials that can be commercially purchased from third-party vendors, runs on a primary cell rather than requiring an external power source and would contain four different temperature sensors displaced throughout the patch to determine the total power loss of the system for a higher accuracy reading. From being delivered circuit boards from Maxim containing the temperature sensors, ten patches would be created and characterized in order to calculate the correction factor needed to accurately output a patient���s core body temperature. A test system was created to characterize the assembled patches, and with it, would help determine the patch accuracy. From having a hot plate to simulate core body temperature, the patches are adhered to an assembled skin phantom to determine how it would clinically perform. From running the tests from 35-39��C to represent the range of temperatures from hypothermia to hyperthermia, the fudge factor of the Maxim patches were calculated to be approximately 0.93, which would result in a core body temperature reading accuracy within 0.4��C. While this doesn���t have as high of an accuracy compared to the SpotOn device, small changes to the assembly or instruction on how to apply the patch so that it fully conforms to the skin would be provided to allow for the patch to pass Federal Communications Commission class II certification
Analyzing External Memory Politeness Control for Web Crawling Applications
Get PDFOne of the key components of many problems in computer science is organizing and querying large volumes of data in an efficient manner. Specifically, such problems arise in the domain of web crawling. In this work, we are concerned with the task of efficiently observing a per-host politeness policy in web crawling, which is an anti-spam mechanism using request limits published by individual hosts. Past methods to observe such constraints require a priority queue structure that maintains information about when a host was last visited and the next available host to be crawled. However, once a crawl scales to hundreds of millions of unique hosts, maintaining such a structure in-memory can become infeasible on many workstations and other limited resource settings. Past work conducted in our lab has shown dramatic performance losses in the web crawler BuBING due to excessive RAM consumption, partly due to its politeness control scheme. In this work, we investigate methods of offloading politeness control to external memory. We first describe the history and specific applications, challenges, and considerations of developing external memory algorithms. We then present two external memory solutions that can be used for politeness control: A priority queue implementation from STXXL, a popular C++ library of external memory algorithms/data structures, and a customized solution, which we name a rolling priority queue, which exploits specific properties of the politeness control problem for a simpler approach. We then discuss specific methods for applying these solutions for politeness control, their theoretical performance and measured benchmarks, and limitations/open questions that motivate future work in this area
Using the Bronfenbrenner Model to Explore Risk and Protective Factors Associated With Anxious-Depressive Symptoms Among Adolescents With High Body Weights
No full textAdolescent anxiety and depression are prevalent during adolescence; however, Black adolescents with high body weights are especially susceptible to anxious-depressive symptoms due to systemic oppression. Previous researchers have examined the independent associations of sleep problems, parent-child communication, and community stressors on anxious-depressive symptoms in youth. Limited research has explored how these multilevel risk and protective factors collectively relate to mental health in Black-identified adolescents with high body weights. The current study explored associations between anxious-depressive symptoms and factors across the bioecology of individual (sleep problems), microsystem (parent-child communication), and ecosystem (community cohesion and community disorder) in Black adolescents with high body weights. Participants were 95 Black adolescents aged 11���17 (Mage = 14.01, SD = 1.85; 62.1% female; MBMI z-score = 2.47, SD = 0.40) seeking treatment in a Mid-South U.S. pediatric obesity clinic. A hierarchical multiple linear regression was conducted to examine associations between anxious-depressive symptoms and sleep problems (Model 1), parent-child communication problems, open parent-child communication (Model 2), community cohesion, and community disorder (Model 3). The final model was significant, F (5, 89) =7.86, p<.001. More sleep problems (b= .33, p <.001) and less caregiver-adolescent problematic communication (b= -.37, p <.001) were associated with greater anxious-depressive symptoms. Findings suggest person and microsystem factors contribute to anxious-depressive symptoms in Black adolescents with high body weights. Given that this study was cross-sectional, future research should utilize a longitudinal design to assess these variables across multiple time points, and specifically examine directionality
