Characterization of swimming motility in a marine unicellular cyanobacterium

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution April 1988The structural mechanism, behavior, energetics and functional significance of the unique swimming motility displayed by some oceanic isolates of the cyanobacterium Synechococcus was investigated. A variety of analytical techniques confirmed that these strains swam through liquids without flagella or flagellar-like appendages. No extracellular structures were observed in a broad range of cell preparations examined by transmission electron microscopy (TEM), or by high-intensity dark field microscopy. The possibility that a structure might be present that eluded visualization was eliminated by the lack of motility-dependent amplitude spectra, the absence of discrete circulation of microspheres around the cell body and the inability of shearing forces to arrest motility. TEM and gel electrophoretic analysis of spheroplasts, cell wall-enriched fractions from motile and nonmotile strains, and cell material collected following the application of a flagellar hook-basal body complex isolation technique to a motile Synechococcus strain provided no further evidence of a structure or protein unique to motile strains. The motile Synechococcus strains represent the only cyanobacterium reported to date capable of swimming rather than gliding motility. Swimming behavior was characterized by several features: between 50 - 80% of cells were actively motile during loyarithmic phase of growth, with speeds that ranged from 5 - 40 um s-1 the average speed was 13 um s-1. Swimming patterns were entirely random, consistent with the absence of bacterial flagella. Synechococcus motility resembled flagellar-mediated motility in that thrust (forward motion) was accompanied by torque (cell rotation) as demonstrated by i) dividing cells which swam with the daughter cells at an angle, ii) individual cells that were sometimes seen to rotate end over end at a rate of 3 to 5 rev s-1, iii) polystyrene beads attached to the cell body served as a point of reference as the cell rotated concomitant with translocation and iv) cells attached to the coverslip or slide spun about one pole at an average rate of 1 rev s-1. When observed in the same plane of focus, 50% of the cells spun clockwise and 50% spun counterclockwise, but unlike flagellated cells, Synechococcus was never seen to change direction of rotation, as would be predicted if the cell body were rotating as a single unit and the motility apparatus were incapable of reversing direction of rotation. This motility apparatus appeared to operate at a constant torque, as indicated by the relationship between swimming speeds and the fluidity of the surrounding medium. Investigation of the energetics of motility in Synechococcus WH8ll3 demonstrated that swimming was sodium coupled. There was a specific sodium requirement such that cells were immotile at external sodium concentrations below 10 mM, with speeds increasing with increasing sodium to a maximum speed at 150 to 250mM sodium, pH 8.0 to 8.5. The sodium motive force increased similarly, but other energetic parameters including proton motive force, electrical potential, and the proton and sodium diffusion gradients lacked correlation to levels of motility. When components of the sodium motive force were diminished by monensin or carbonyl cyanide m-chlorophenyl-hydrazone, motility was arrested. Motility was independent of the magnitude of internal ATP pools, which were depleted to 2% of control values without affecting cell motility. These results suggest that the direct source of energy for Synechococcus motility is a sodium motive force, and that the devise driving motility is located in the cytoplasmic membrane, as is the case for flagellated bacteria. The ecological role of Synechococcus motility was explored and several lines of evidence indicated that cells lacked behavioral photoresponses but were able to detect and respond to very low concentrations of simple nitrogenous compounds. When 23 compounds were tested in spatial gradients established in blind well chemotaxis chambers, cells displayed positive chemoresponses only when placed in gradients of NH4Cl, NaN03, urea, glycine and alanine. Cells also failed to respond in chambers which lacked gradients due to the presence of only seawater or an equal distribution of chemoeffector, demonstrating that a gradient was required to elicit a response. The apparent threshold levels of 10-10 M - 10-9 M for Synechococcus chemoresponses are 4 to 5 orders of magnitude lower than those for most other bacteria and place them in the range of ecological significance. The presence of chemotaxis in this oceanic cyanobacterium may help support the notion that nutrient enriched microaggregates may play an important role in picoplankton nutrient dynamics

Impact of the ASCO 2007 Presentation of HOG Lun 01-24/USO-023 on the Prescribing Plans of American Medical Oncologists for Patients with Stage IIIB Non-small Cell Lung Cancer

Introduction:Nonoperative treatment of stage III non-small cell lung cancer has evolved over the past 30 years. The current approach in the Unites States most often includes concurrent chemoradiotherapy.Methods:We have used live, case-based research events to document prescribing plans among American medical oncologists for first-line therapy in patients with N3 stage IIIB non-small cell lung cancer. Changes in prescribing plans documented before and after the 2007 American Society of Clinical Oncology (ASCO) presentation of a Hoosier Oncology Group trial testing the role of consolidation docetaxel chemotherapy in this setting are presented.Results:Data from 2007 show a post-ASCO shift away from plans for docetaxel consolidation, increased use of concurrent chemoradiotherapy alone, and stable to increased plans for concurrent chemoradiation followed by additional cycles of the chemotherapy used during concurrent management (20%). Preliminary data from 2008 confirm the durability of these changes.Conclusions:The findings of the Hoosier Oncology Group trial support a transition away from docetaxel consolidation. A trend in this direction among American medical oncologists is clear from our data. However, nearly 20% of oncologists studied in 2008 still plan to use docetaxel consolidation. Furthermore, a majority of those studied after ASCO 2007 continue to report plans to use more than two cycles of chemotherapy as part of their preferred treatment recommendation despite no level I evidence to support this approach

Design and Development of an In-Space Deployable Sun Shield for the Atlas Centaur

The Centaur, by virtue of its use of high specific-impulse (Isp) LO2/LH2 propellants, has initial mass-to-orbit launch requirements less than half of those upper stages using storable propellants. That is, for Earth escape or GSO missions the Centaur is half the launch weight of a storable propellant upper stage. A drawback to the use of Liquid oxygen and liquid hydrogen, at 90 K and 20 K respectively, over storable propellants is the necessity of efficient cryogen storage techniques that minimize boil-off from thermal radiation in space. Thermal blankets have been used successfully to shield both the Atlas Centaur and Titan Centaur. These blankets are protected from atmospheric air loads during launch by virtue of the fact that the Centaur is enclosed within the payload fairing. The smaller Atlas V vehicle, the Atlas 400, has the Centaur exposed to the atmosphere during launch, and therefore, to date has not flown with thermal blankets shielding the Centaur. A design and development effort is underway to fly a thermal shield on the Atlas V 400 vehicle that is not put in place until after the payload fairing jettisons. This can be accomplished by the use of an inflatable and deployable thermal blanket referred to as the Centaur Sun Shield (CSS). The CSS design is also scalable for use on a Delta upper stage, and the technology potentially could be used for telescope shades, re-entry shields, solar sails and propellant depots. A Phase I effort took place during 2007 in a partnership between ULA and ILC Dover which resulted in a deployable proof-of-concept Sun Shield being demonstrated at a test facility in Denver. A Phase H effort is underway during 2008 with a partnership between ULA, ILC, NASA Glenn Research Center (GRC) and NASA Kennedy Space Center (KSC) to define requirements, determine materials and fabrication techniques, and to test components in a vacuum chamber at cold temperatures. This paper describes the Sun Shield development work to date, and the future plans leading up to a flight test in the 2011 time frame

Management of hepatocellular carcinoma from diagnosis in routine clinical practice

AIM: To assess real-world management of patients diagnosed with hepatocellular carcinoma (HCC) within an integrated delivery network. MATERIALS & METHODS: A retrospective cohort analysis of adults newly diagnosed with HCC from January 2014 to March 2019. Overall survival and treatment journey were assessed over the entire available follow-up period per patient. RESULTS: Of the 462 patients, 85% had ≥1 treatment. The 24-month overall survival rate (95% CI) from first treatment was 77% (72-82%). Majority of Child-Pugh class A (71%) and B (60%) patients received locoregional therapy first. Half (53.6%) of the patients with liver transplantation first were Child-Pugh class C patients. Sorafenib was the predominant systemic therapy. CONCLUSION: This integrated delivery network data analysis offers a comprehensive insight into the real-world management of HCC

National and regional estimates of term and preterm babies born small for gestational age in 138 low-income and middle-income countries in 2010.

BACKGROUND: National estimates for the numbers of babies born small for gestational age and the comorbidity with preterm birth are unavailable. We aimed to estimate the prevalence of term and preterm babies born small for gestational age (term-SGA and preterm-SGA), and the relation to low birthweight (<2500 g), in 138 countries of low and middle income in 2010. METHODS: Small for gestational age was defined as lower than the 10th centile for fetal growth from the 1991 US national reference population. Data from 22 birth cohort studies (14 low-income and middle-income countries) and from the WHO Global Survey on Maternal and Perinatal Health (23 countries) were used to model the prevalence of term-SGA births. Prevalence of preterm-SGA infants was calculated from meta-analyses. FINDINGS: In 2010, an estimated 32·4 million infants were born small for gestational age in low-income and middle-income countries (27% of livebirths), of whom 10·6 million infants were born at term and low birthweight. The prevalence of term-SGA babies ranged from 5·3% of livebirths in east Asia to 41·5% in south Asia, and the prevalence of preterm-SGA infants ranged from 1·2% in north Africa to 3·0% in southeast Asia. Of 18 million low-birthweight babies, 59% were term-SGA and 41% were preterm-SGA. Two-thirds of small-for-gestational-age infants were born in Asia (17·4 million in south Asia). Preterm-SGA babies totalled 2·8 million births in low-income and middle-income countries. Most small-for-gestational-age infants were born in India, Pakistan, Nigeria, and Bangladesh. INTERPRETATION: The burden of small-for-gestational-age births is very high in countries of low and middle income and is concentrated in south Asia. Implementation of effective interventions for babies born too small or too soon is an urgent priority to increase survival and reduce disability, stunting, and non-communicable diseases. FUNDING: Bill & Melinda Gates Foundation by a grant to the US Fund for UNICEF to support the activities of the Child Health Epidemiology Reference Group (CHERG)

Estimates of Burden and Consequences of Infants Born Small for Gestational Age in Low and Middle Income Countries with INTERGROWTH-21(st) Standard: Analysis of CHERG Datasets.

Objectives To estimate small for gestational age birth prevalence and attributable neonatal mortality in low and middle income countries with the INTERGROWTH-21st birth weight standard. Design Secondary analysis of data from the Child Health Epidemiology Reference Group (CHERG), including 14 birth cohorts with gestational age, birth weight, and neonatal follow-up. Small for gestational age was defined as infants weighing less than the 10th centile birth weight for gestational age and sex with the multiethnic, INTERGROWTH-21st birth weight standard. Prevalence of small for gestational age and neonatal mortality risk ratios were calculated and pooled among these datasets at the regional level. With available national level data, prevalence of small for gestational age and population attributable fractions of neonatal mortality attributable to small for gestational age were estimated. Setting CHERG birth cohorts from 14 population based sites in low and middle income countries. Main outcome measures In low and middle income countries in the year 2012, the number and proportion of infants born small for gestational age; number and proportion of neonatal deaths attributable to small for gestational age; the number and proportion of neonatal deaths that could be prevented by reducing the prevalence of small for gestational age to 10%. Results In 2012, an estimated 23.3 million infants (uncertainty range 17.6 to 31.9; 19.3% of live births) were born small for gestational age in low and middle income countries. Among these, 11.2 million (0.8 to 15.8) were term and not low birth weight (≥2500 g), 10.7 million (7.6 to 15.0) were term and low birth weight (\u3c2500 g) and 1.5 million (0.9 to 2.6) were preterm. In low and middle income countries, an estimated 606 500 (495 000 to 773 000) neonatal deaths were attributable to infants born small for gestational age, 21.9% of all neonatal deaths. The largest burden was in South Asia, where the prevalence was the highest (34%); about 26% of neonatal deaths were attributable to infants born small for gestational age. Reduction of the prevalence of small for gestational age from 19.3% to 10.0% in these countries could reduce neonatal deaths by 9.2% (254 600 neonatal deaths; 164 800 to 449 700). Conclusions In low and middle income countries, about one in five infants are born small for gestational age, and one in four neonatal deaths are among such infants. Increased efforts are required to improve the quality of care for and survival of these high risk infants in low and middle income countrie

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Minimum Information about a Biosynthetic Gene cluster

A wide variety of enzymatic pathways that produce specialized metabolites in bacteria, fungi and plants are known to be encoded in biosynthetic gene clusters. Information about these clusters, pathways and metabolites is currently dispersed throughout the literature, making it difficult to exploit. To facilitate consistent and systematic deposition and retrieval of data on biosynthetic gene clusters, we propose the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard.Chemistry and Chemical Biolog

Prescott, harley, and klein s microbiology, 7th ed./ Willey

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