bluuebunny/crossref_metadata_2025 huggingface dataset:
An integrated 6 MV linear accelerator model from electron gun to dose in a water tank
Authors: St. Aubin J. , Steciw S. , Kirkby C. , Fallone B. G.
Published: April 2010

Purpose: The details of a full simulation of an inline side‐coupled 6 MV linear accelerator (linac) from the electron gun to the target are presented. Commissioning of the above simulation was performed by using the derived electron phase space at the target as an input into Monte Carlo studies of dose distributions within a water tank and matching the simulation results to measurement data. This work is motivated by linac‐MR studies, where a validated full linac simulation is first required in order to perform future studies on linac performance in the presence of an external magnetic field.

Methods: An electron gun was initially designed and optimized with a 2D finite difference program using Child's law. The electron gun simulation served as an input to a 6 MV linac waveguide simulation, which consisted of a 3D finite element radio‐frequency field solution within the waveguide and electron trajectories determined from particle dynamics modeling. The electron gun design was constrained to match the cathode potential and electron gun current of a Varian 600C, while the linac waveguide was optimized to match the measured target current. Commissioning of the full simulation was performed by matching the simulated Monte Carlo dose distributions in a water tank to measured distributions.

Results: The full linac simulation matched all the electrical measurements taken from a Varian 600C and the commissioning process lead to excellent agreements in the dose profile measurements. Greater than 99% of all points met a 1%/1mm acceptance criterion for all field sizes analyzed, with the exception of the largest field for which 98% of all points met the 1%/1mm acceptance criterion and the depth dose curves matched measurement to within 1% deeper than 1.5 cm depth. The optimized energy and spatial intensity distributions, as given by the commissioning process, were determined to be non‐Gaussian in form for the inline side‐coupled 6 MV linac simulated.

Conclusions: An integrated simulation of an inline side‐coupled 6 MV linac has been completed and benchmarked matching all electrical and dosimetric measurements to high accuracy. The results showed non‐Gaussian spatial intensity and energy distributions for the linac modeled.
Patient doses and projection angle in cone beam CT
Authors: He Wenjun , Huda Walter , Magill Dennise , Tavrides Emily , Yao Hai
Published: April 2010

Purpose: To investigate how x‐ray tube projection angle affects organ and effective doses to patients undergoing a CT examination on a cone beam scanner.

Methods: The authors investigated two cone beam CT systems that use a flat panel detector to capture the x‐ray pattern transmitted through patients. One system had the flat panel detector and x‐ray tube mounted on a conventional CT gantry (gantry CT), whereas the other CT scanner had the x‐ray tube and flat panel detector mounted on a C‐arm apparatus (C‐arm CT). PCXMC software package (version 2.0.1) was used to compute absorbed doses at a constant x‐ray beam output as a function of the x‐ray tube projection angle. This software uses a mathematical hermaphroditic phantom with a weight of 73.2 kg and a height of 178.6 cm. Average absorbed doses were generated and recorded for five radiosensitive organs (i.e., breast, colon, lung, red bone marrow, and stomach), as well as the corresponding effective dose. Doses for both CT gantries were obtained every 15° of the x‐ray tube projection angle, at each of six locations in 10 cm increments along the patient long axis. The authors also investigated the effect on patient dose of filtrations ranging from 2.5 to 9.5 mm Al, with x‐ray tube voltages ranging from 80 to 140 kV.

Results: There were substantial differences in organ doses as a function of the projection angle, with higher organ doses for anteroposterior projection and lower doses for lateral projections. The maximum to minimum ratios of organ dose as a function of the x‐ray tube angle were for the lungs, for the colon, for the red bone marrow, for the breast, and for the stomach. At the same x‐ray tube voltage (kV) and intensity (mA s), the ratio of dose maxima for the two cone beam CT geometries for the five organs investigated was , which is mainly attributed to differences in source to isocenter distances. Effective doses varied with x‐ray tube angle by a factor of for chest CT examinations and by a factor of for abdomen/pelvis examinations. Changes in the x‐ray tube voltage and beam filtration showed the expected changes in absolute organ doses, but had little effect on relative doses.

Conclusions: There are major differences in organ and effective dose as the x‐ray tube rotates around the patient. The results suggest that the use of x‐ray tube current modulation could produce substantial reductions in organ and effective dose for body imaging with cone beam CT.
Simultaneous segmentation and reconstruction: A level set method approach for limited view computed tomography
Authors: Yoon Sungwon , Pineda Angel R. , Fahrig Rebecca
Published: April 2010

Purpose:

An iterative tomographic reconstruction algorithm that simultaneously segments and reconstructs the reconstruction domain is proposed and applied to tomographic reconstructions from a sparse number of projection images.

Methods:

The proposed algorithm uses a two‐phase level set method segmentation in conjunction with an iterative tomographic reconstruction to achieve simultaneous segmentation and reconstruction. The simultaneous segmentation and reconstruction is achieved by alternating between level set function evolutions and per‐region intensity value updates. To deal with the limited number of projections,a prioriinformation about the reconstruction is enforced via penalized likelihood function. Specifically, smooth function within each region (piecewise smooth function) and bounded function intensity values for each region are assumed. Sucha prioriinformation is formulated into a quadratic objective function with linear bound constraints. The level set function evolutions are achieved by artificially time evolving the level set function in the negative gradient direction; the intensity value updates are achieved by using the gradient projection conjugate gradient algorithm.

Results:

The proposed simultaneous segmentation and reconstruction results were compared to “conventional” iterative reconstruction (with no segmentation), iterative reconstruction followed by segmentation, and filtered backprojection. Improvements of 6%–13% in the normalized root mean square error were observed when the proposed algorithm was applied to simulated projections of a numerical phantom and to real fan‐beam projections of the Catphan phantom, both of which did not satisfy thea prioriassumptions.

Conclusions:

The proposed simultaneous segmentation and reconstruction resulted in improved reconstruction image quality. The algorithm correctly segments the reconstruction space into regions, preserves sharp edges between different regions, and smoothes the noise within each region. The proposed algorithm framework has the flexibility to be adapted to differenta prioriconstraints while maintaining the benefits achieved by the simultaneous segmentation and reconstruction.
Uncertainty analysis of a Compton camera imaging system for radiation therapy dose reconstruction
Authors: Mundy Daniel W. , Herman Michael G.
Published: April 2010

Purpose:

Improved radiotherapy dose delivery techniques over the past decade have increased the necessity for accurate, independent verification of delivered dose. Compton camera imaging (CCI) systems may have the potential to quantitatively reconstruct three‐dimensional dose delivered to the patient with little or noa priori information.

Methods:

In this work, the adequacy of a Compton camera imaging system for application to radiotherapy dose reconstruction is explored using analytical models of system spatial and dosimetric resolution. The effects of scatter and absorption detector energy resolution, initial photon energy, and detector separation distance on system performance were calculated with the goal of determining whether current detector technology is adequate for such an application.

Results:

Results indicate that the energy and spatial resolutions associated with current Si and Ge double‐sided strip detectors in a planar configuration is sufficient to determine dose deposition to within an average of 1.9 mm and 2.5%. Minimum values of less than 0.5 mm and 1% are achievable under certain conditions. As the energy of the photon incident on the patient increases from 1.0 to 10 MeV, system performance improves at the expense of the range of patient and detector scattering angles over which the system is capable of reconstructing dose deposition to within the acceptable upper limits of 5 mm and 5%. System performance also improves with increasing distance between the scatter and absorption detectors, but is acceptable throughout the range of values likely to be associated with a gantry‐mounted system (2–20 cm).

Conclusions:

The results indicate that Compton camera imaging systems based on current solid‐state detector technology have the potential to provide independent verification of dose delivered to a patient during radiation therapy. Further consideration must be given to detector efficiency and image reconstruction algorithms for this application of CCI systems.
Image‐based modeling of tumor shrinkage in head and neck radiation therapya)
Authors: Chao Ming , Xie Yaoqin , Moros Eduardo G. , Le Quynh‐Thu , Xing Lei
Published: April 2010

Purpose:

Understanding the kinetics of tumor growth/shrinkage represents a critical step in quantitative assessment of therapeutics and realization of adaptive radiation therapy. This article presents a novel framework for image‐based modeling of tumor change and demonstrates its performance with synthetic images and clinical cases.

Methods:

Due to significant tumor tissue content changes, similarity‐based models are not suitable for describing the process of tumor volume changes. Under the hypothesis that tissue features in a tumor volume or at the boundary region are partially preserved, the kinetic change was modeled in two steps: (1) Autodetection of homologous tissue features shared by two input images using the scale invariance feature transformation (SIFT) method; and (2) establishment of a voxel‐to‐voxel correspondence between the images for the remaining spatial points by interpolation. The correctness of the tissue feature correspondence was assured by a bidirectional association procedure, where SIFT features were mapped from template to target images and reversely. A series of digital phantom experiments and five head and neck clinical cases were used to assess the performance of the proposed technique.

Results:

The proposed technique can faithfully identify the known changes introduced when constructing the digital phantoms. The subsequent feature‐guided thin plate spline calculation reproduced the “ground truth” with accuracy better than 1.5 mm. For the clinical cases, the new algorithm worked reliably for a volume change as large as 30%.

Conclusions:

An image‐based tumor kinetic algorithm was developed to model the tumor response to radiation therapy. The technique provides a practical framework for future application in adaptive radiation therapy.
Diaphragm motion quantification in megavoltage cone‐beam CT projection images
Authors: Chen Mingqing , Siochi R. Alfredo
Published: April 2010

Purpose:

To quantify diaphragm motion in megavoltage (MV) cone‐beam computed tomography (CBCT) projections.

Methods:

User identified ipsilateral hemidiaphragm apex (IHDA) positions in two full exhale and inhale frames were used to create bounding rectangles in all other frames of a CBCT scan. The bounding rectangle was enlarged to create a region of interest (ROI). ROI pixels were associated with a cost function: The product of image gradients and a gradient direction matching function for an ideal hemidiaphragm determined from 40 training sets. A dynamic Hough transform (DHT) models a hemidiaphragm as a contour made of two parabola segments with a common vertex (the IHDA). The images within the ROIs are transformed into Hough space where a contour's Hough value is the sum of the cost function over all contour pixels. Dynamic programming finds the optimal trajectory of the common vertex in Hough space subject to motion constraints between frames, and an active contour model further refines the result. Interpolated ray tracing converts the positions to room coordinates. Root‐mean‐square (RMS) distances between these positions and those resulting from an expert's identification of the IHDA were determined for 21 Siemens MV CBCT scans.

Results:

Computation time on a 2.66 GHz CPU was 30 s. The average craniocaudal RMS error was. While much larger errors occurred in a few near‐sagittal frames on one patient's scans, adjustments to algorithm constraints corrected them.

Conclusions:

The DHT based algorithm can compute IHDA trajectories immediately prior to radiation therapy on a daily basis using localization MVCBCT projection data. This has potential for calibrating external motion surrogates against diaphragm motion.
Freshwater Outburst from Lake Superior as a Trigger for the Cold Event 9300 Years Ago
Authors: Yu Shi-Yong , Colman Steven M. , Lowell Thomas V. , Milne Glenn A. , Fisher Timothy G. , Breckenridge Andy , Boyd Matthew , Teller James T.
Published: April 2010

Down the Drain

A pervasive cooling event affected much of the Northern Hemisphere approximately 9300 years ago. This event was accompanied by changes in ocean circulation in the North Atlantic, forced presumably by a large injection of fresh water produced by melting of the Laurentide Ice Sheet, but the source, magnitude, and routing of the meltwater remain unknown.

Yu
et al.

(p.
1262
, published online 29 April) present evidence that the trigger for this cooling episode was an outburst flood from Lake Superior. Reconstructing lake-level changes in the Superior basin suggests that a rapid fall of lake level of about 45 meters occurred 9300 years ago, possibly due to the sudden failure of a drift dam. Rapid drainage through the North Bay–Ottawa River–St. Lawrence River valleys into the North Atlantic should have been sufficient to disturb ocean circulation in line with the geologic record.
Lysosomal Pathology and Osteopetrosis upon Loss of H
+
-Driven Lysosomal Cl
–
Accumulation
Authors: Weinert Stefanie , Jabs Sabrina , Supanchart Chayarop , Schweizer Michaela , Gimber Niclas , Richter Martin , Rademann Jörg , Stauber Tobias , Kornak Uwe , Jentsch Thomas J.
Published: April 2010

Chloride Balancing Act

The ionic composition of the cytosol and intracellular organelles must be regulated in the face of ongoing membrane traffic into and out of the cell. Now, two papers address the consequences of a change in the transport phenotype of an intracellular Cl
−
transport protein from a coupled exchanger to a passive Cl
−
conductor (see the Perspective by

Smith and Schwappach

).

Novarino
et al.

(p.
1398
, published online 29 April) investigated the consequence of a knock-in of the uncoupled ClC-5 transporter into mouse. The knock-out mouse of this endosomal kidney transporter has a severe endocytic phenotype believed to be due to a defect in vesicular acidification. The current study shows a similarly impaired endocytic phenotype for the uncoupled mutant, but the acidification of endosomes was unaffected.

Weinert
et al.

(p.
1401
, published online 29 April) used a similar strategy to investigate the consequence of the equivalent mutation in the lysosomal transporter ClC-7, which is highly expressed in the resorption lacuna of osteoclasts and whose knock-out in mice produces lysosomal storage disease and severe osteopetrosis. A similar (though less severe) phenotype was observed in the knock-in mice containing the uncoupled ClC-7, indicating that coupled transport plays a critical role in lysosomes.
Exploring the population dynamics of winter skate (Leucoraja ocellata) in the Georges Bank region using a statistical catch-at-age model incorporating length, migration, and recruitment process errors
Authors: Frisk M. G. , Martell S. J.D. , Miller T. J. , Sosebee K.
Published: April 2010

Winter skate ( Leucoraja ocellata ) of all length classes increased dramatically in abundance on Georges Bank in the 1980s following the decline of many groundfish species. We present a full population model of winter skate to better understand the population dynamics of the species and elucidate the mechanisms underlying their increase in abundance in the 1980s. Specifically, we developed four statistical catch-at-age models incorporating length-frequency data with the following model structures: (i) observation error only (base model R1); (ii) observation and recruitment process errors (model R2); (iii) adult migration modeled as a random walk in adult mortality (model R3); and (iv) observation and recruitment process errors and adult migration (model R4). Akaike’s information criterion values indicated that models R3 and R4, which both included adult migration, were the most parsimonious models. This finding strongly suggests that the winter skate population increase on Georges Bank in the 1980s was not solely a result of increases in recruitment but likely involved adult migration (i.e., it is an open population). Finally, recent predicted fishing mortalities exceeded FMSY for all models.
Can changes in length-at-age and maturation timing in Scotian Shelf haddock (Melanogrammus aeglefinus) be explained by fishing?
Authors: Neuheimer Anna B. , Taggart Christopher T.
Published: April 2010

Factors affecting size-at-age in fish populations include temperature and fishing where the latter can represent a strong selective force on size-at-age variation through changes in population growth and maturation. Over the past three decades, Scotian Shelf haddock ( Melanogrammus aeglefinus ) exhibited declines in maturation timing and mature fish length-at-age. Here, we examine these declines with respect to temperature, stock biomass, and fishing. We employ the thermal integral (growing degree-day, GDD, °C·day) to examine the variation in length-at-age (length-at-day, LaD, cm) and maturity (age-at-50%-maturity) that is attributable to temperature. Unexplained variation in LaD and age-at-50%-maturity remains and is characterized by declines in the LaD-at-GDD regression parameters and the thermal constant for maturity with increasing year-class. We find no significant correlation between the temperature-independent declines in LaD and stock biomass. The combination of high fishing mortality (favouring early maturation) and sustained harvesting of large fish (fast-growing, late-maturing individuals) offers the simplest explanation for the systematic decline in inferred growth and age-at-maturity for Scotian Shelf haddock. These results are consistent with other exploited populations and recent laboratory experiments quantifying the effects of fishing on size-at-age and age-at-maturity.
Model averaging and probable status of North Pacific striped marlin, Tetrapturus audax
Authors: Brodziak Jon , Piner Kevin
Published: April 2010

We show how model averaging can be applied to estimate the probable status of a fishery resource under assessment scenario uncertainty. This approach is applied to North Pacific striped marlin ( Tetrapturus audax ), an apex predator that may be vulnerable to recruitment overfishing in pelagic longline fisheries targeting tunas. In the current striped marlin assessment, two assessment scenarios were used to account for different hypotheses about the steepness of the stock–recruitment dynamics. Estimates of spawning stock and recruitment from these scenarios are used post hoc to fit age-structured production models that represent alternative hypotheses about the degree of compensation in stock–recruitment dynamics and the degree of serial correlation of environmental forcing. Model-averaged estimates of target spawning biomass to produce maximum sustainable yield (SMSY) and the associated limit fishing mortality (FMSY) characterize relative stock status (S/SMSY and F/FMSY) under each scenario. Scenario-weighted averages of relative status determine probable stock status, with weightings reflecting the credibility of each scenario. Estimates of the variance of probable status account for both model selection and assessment scenario uncertainty in risk analyses. Using model averaging to estimate probable stock status from multiple assessment scenarios is analogous to using ensemble averages from multiple predictive models to make weather forecasts.
Pleiotropy of cytoplasmically and nuclearly inherited resistance to inhibitors of mitochondrial function in Saccharomyces cerevisiae
Authors: Rank G. H.
Published: April 2010

Strains with cytoplasmically and nuclearly inherited antibiotic-resistant markers were tested for cross resistance to diverse inhibitors of mitochondrial function. Five independently isolated nuclear markers were observed to result in resistance to chloramphenicol, tetracycline, oligomycin, antimycin A, carbonylcyanide-m-chlorophenylhydrazone, and triphenylmethylphosphonium bromide; these same strains were sensitive to erythromycin, neomycin, and ethidium bromide. In contrast, 11 strains carrying cytoplasmically inherited resistance markers were not cross resistant to any unrelated chemical inhibitors. It is suggested that the nuclear mutations are expressed as general membrane mutants whereas mitochondrial DNA codes for more specific mitochondrial functions.
Formation of tetrachloroazobenzene in some Canadian soils treated with propanil and 3,4-dichloroaniline
Authors: Hughes A. F. , Corke C. T.
Published: April 2010

The formation of 3,3′,4,4′-tetrachloroazobenzene from the herbicide propanil (N-(3,4-dichlorophenyl)propionamide), and from 3,4-dichloroaniline was studied in nine soils which varied in pH, percentage of organic matter, clay, and sand. Marked differences were observed in these soils in the amounts of azobenzene formed. In five soils whose pH values fell within a range of pH 4.5 to 5.5, azobenzene was produced from both substrates, while in two soils (Guelph loam and Wendigo loamy sand), azobenzene was only detected from 3,4-dichloroaniline. No azobenzene was detected from either substrate in two additional soils (Belleisle marsh soil (site 22, pH 3.4) and Biz silt loam (pH 6.4)). Air-drying soils, as well as extended periods of storage of freshly collected soils at 4 °C, reduced the formation of azobenzene.
Rhizosphère du sapin (Abies religiosa). II. Mycorhizes : isolement et culture
Authors: Peña-Cabriales J. J. , Valdés-Hgo María
Published: April 2010

Morphological study of several ectotrophic mycorrhizae of fir (Abies religiosa) showed that they are dichotomic or corralloid, simple or ramified. Four symbiotic fungi were isolated from the mycorrhizae, and judging from the type of infection, they were active and of medium virulence. The macro- and micro-scopic descriptions of each fungal strain show different cultural characteristics as well as different stimulations to the development of the plant.
Stability of different viruses in a newly developed transport medium
Authors: Bishai F. R. , Labzoffsky N. A.
Published: April 2010

Two media for preserving the viability of different viruses in clinical material during transit at ambient temperature have been developed. One was designed for transporting stool specimens and autopsy material, while the other was designed for such specimens as throat washings, swabs, and cerebrospinal fluid. The essential ingredient in both media was bentonite either uncoated or coated with serum proteins. Preparation of both media is given in detail.Experimental results presented indicate that coxsackie A9, B5, echo 11, adeno 5, influenza A2, parainfluenza, rubella, and herpes simplex viruses could sustain their infectivity without loss of titer in bentonite transport medium for prolonged time, from 3 to 21 days, depending on the virus type.The bentonite transport medium was found to be superior to commonly used charcoal viral transport medium.
Effects of concentration of volatile metabolites from bacteria and germinating seeds on fungi in the presence of selective absorbents
Authors: Moore-Landecker Elizabeth , Stotzky G.
Published: April 2010

Fusarium oxysporum f. conglutinans, Gelasinospora cerealis, Penicillium viridicatum, Trichoderma viride, and Zygorhynchus vuilleminii were grown on slide cultures supported above cultures of seven bacteria and one actinomycete. Except with Escherichia coli and Nocardia corallina, heavy bacterial growth always inhibited growth and sporulation of the fungi, whereas lighter growth either inhibited, did not alter, or stimulated growth and (or) sporulation, depending on the fungus–bacterium combination. Differential absorption of the volatiles by KOH, KMnO4, charcoal, or soil indicated that different volatiles were produced, that some were inhibitory and others stimulatory, and that at least some of the volatiles were organic. Volatiles emitted by germinating seeds reduced spore formation only in G. cerealis, Penicillium vermiculatum, and Z. vuilleminii, but otherwise had no effect on growth, sporulation, or morphology of the above fungi nor on Aspergillus flavipes or Cunninghamella elegans.
Cell-mediated immunity during the infection of CBA mice with Trypanosoma musculi
Authors: Viens Pierre , Pouliot Pierre , Targett G. A. T.
Published: April 2010

CBA/J mice were infected with Trypanosoma musculi. On the 10th day of infection, when the parasitemia had become stabilized and parasites consisted only of adult (non-dividing) trypomastigotes, non-adherent spleen cells from immune donors were injected intravenously, with or without simultaneous subcutaneous administration of immune serum. The immune spleen cells accelerated the termination of infection whilst immune serum transfer had no effect on the course of the parasitemia.
Metabolism during differentiation in the slime mold Physarum polycephalum
Authors: Goodman E. M. , Beck T.
Published: April 2010

The introduction of growing microplasmodia into a balanced salt solution induces the formation of hard-walled units (spherules) within 24 h to 36 h. The respiration rate was followed throughout differentiation and was found to decrease from a starting value of 62 μl O2/mg protein per hour to 17.5 μl O2/mg protein per hour after 40 h in the salt solution. The use of exogenous glucose and protein catabolism was also studied, and the results indicate that proteins are a major energy source during spherulation. On the basis of the data from this study and the results of other investigators, the process of spherulation has been divided into three developmental periods.
A quantitative bioassay for determining low numbers of microsclerotia of Verticillium dahliae in field soils
Authors: Evans G. , McKeen C. D. , Gleeson A. C.
Published: April 2010

The relationship between inoculum density and the number of colonies of Verticillium dahliae Kleb./unit length of root from plants growing in naturally infested soils is shown to be linear. The evidence supports the contention that the propagules giving rise to these colonies are microsclerotia or small groups of microsclerotia embedded in fragments of plant tissue. Thus the colonies growing on plant roots are a quantitative measure of the number of these propagules in soil. The data show that plant roots are an extremely sensitive trap and can be used to measure low numbers of microsclerotia.
The photosensitizing action of carcinogens. I. The action of 2-naphthylamine on Escherichia coli K-12 and Paramecium caudatum
Authors: Ellis S. P. , Smith Robert C. , Neely W. C.
Published: April 2010

Cultures of Paramecium caudatum incubated with 7 × 10−7 M 2-naphthylamine were rapidly killed when exposed to light of 366 nm. Cultures not exposed to the amine were unaffected by the light; cultures kept in the dark were unaffected by the amine. Escherichia coli K-12 populations were markedly reduced after irradiation of suspensions in water containing 3 × 10−4 M 2-naphthylamine with light simulating natural sunlight in intensity and wavelength distribution. Suspensions of E. coli in deionized water were unaffected by the light and E. coli suspended in solutions of the amine but kept in the dark were also unaffected. Since 2-naphthylamine is a known water pollutant these results may be of ecological importance.
Xanthacin. A bacteriocin of Myxococcus xanthus f b
Authors: McCurdy Jr. Howard D. , MacRae Thomas H.
Published: April 2010

An extremely stable, particulate, bacteriocin, namely xanthacin, has been found in Myxococcus xanthus f b after mitomycin C induction. Xanthacin is resistant to trypsin, protease type VI, RNase, DNase, sodium dodecyl sulfate (SDS), acetone, ether, ultraviolet irradiation, and autoclaving. A high-titer preparation was obtained after partial purification by pervaporative concentration, differential centrifugation, molecular sieve chromatography, and density gradient centrifugation. Electron microscopy of platinum-shadowed and uranyl acetate stained preparations revealed the presence of circular bodies of varied size which resembled membrane fragments.
Oxidation of metal sulfides by Thiobacillus ferrooxidans grown on different substrates
Authors: Silver Marvin , Torma Arpad E.
Published: April 2010

Thiobacillus ferrooxidans, grown on either ferrous sulfate, lead sulfide concentrate, or chalcopyrite concentrate demonstrated oxygen uptake and CO2 fixation in the presence of ferrous sulfate, chalcopyrite ore, pyrite ore, and red antimony trisulfide. Lead suifide-grown cells could oxidize lead sulfide ore and galena, using the energy obtained for CO2 fixation. All three cell types could oxidize nickel sulfide, but could not fix CO2 in the presence of this substrate. The solubilization of metals from the substrates and the crystallographic changes in the insoluble residues are reported.
Morphological variation in isolates of Verticillium albo-atrum R. & B.
Authors: Campbell W. P. , Griffiths D. A.
Published: April 2010

The morphology of resting mycelium in isolates of Verticillium albo-atrum varied according to cultural conditions; on natural media hyphae were modified to form unbranched, swollen, pigmented, resting mycelium whereas on artificial media the hyphae became highly segmented, torulose, and intertwined to form mycelial knots. In one isolate, aerial hyphae sometimes developed external bands, or 'blisters,' of electron-dense material deposited in discrete regions along the length of the hyphae. The function of these modified aerial hyphae is probably different from that of resting mycelium and might represent an early stage in the formation of some hitherto undescribed structure.
The metabolism of acetate by rumen microorganisms
Authors: Emmanuel B. , Milligan L. P. , Turner B. V.
Published: April 2010

Rumen contents were incubated in vitro with acetate-1-14C. Significant amounts of 14C were incorporated into rumen microbial proteins, nucleic acids, and lipids. Serine, glutamic acid, methionine, and cystine were highly labeled, whereas less, or insignificant radioactivity was found in other amino acids. Acetate was incorporated into a wide range of microbial fatty acids. The quantitative significance of acetate metabolism is discussed.
Inhibition of colicin production by fermentable sugars
Authors: Lavoie M. , Mathieu L. G. , Charron-Allie L.
Published: April 2010

Several fermentable sugars (glucose, lactose, arabinose, and to a lesser extent sucrose) were found to reduce colicin production in a strain of Shigella sonnei P9 (colicins E2 and I) and in a strain of Escherichia coli CA31 (colicin A). Inositol and adonitol, which are apparently not fermented by these colicinogenic strains, did not seem to affect colicin production under our experimental conditions. The results indicated that the production of colicins E2 and A, like the formation of certain R-factor-coded enzymes, may be subject to catabolite repression. A system of mixed cultivation in nutrient broth, of colicinogenic and sensitive strains, was also used; under these conditions, the number of viable units of the sensitive indicator strain decreased more rapidly in the absence than in the presence of added glucose.
Biodégradation et humification. IV. Microorganismes intervenant dans la décomposition des cellules d'Aureobasidium pullulans (De Bary) Arnaud
Authors: Reisinger Otto , Kilbertus Gérard
Published: April 2010

We have studied the biodegradation of melanized cells of Aureobasidium pullulans by electron microscopy. There is no difference after 6 months and 1 year of incubation.This study provides evidence for the removal of cell components, enzymatic lysis of cell wall, and the production of black granula. The appearance of subunits as part of granula was also observed surrounding the bacteria.At the earliest stage of cell decomposition of Aureobasidium pullulans (utilization of gum), fungi are active. After 6 months, micromycetes stop their activity and the bacteria degrade the wall structures and, probably, some of these bacteria also degrade the granula.The value of various techniques used to demonstrate the decomposition stages and the role of surrounding microorganisms is discussed. [Translated by the journal]
Radiobiological properties of Acholeplasma laidlawii B
Authors: Chelack W. S. , Forsyth M. P. , Petkau A.
Published: April 2010

Survival data were obtained on Acholeplasma laidlawii B after exposure to ionizing radiation at various ages, pH, temperature, and supplements to the medium. The D0 value varied slightly with pH in air but much more after irradiations in N2 or N2O. Replacement of the growth medium with fresh broth resulted in an increase in D0 while dilution of the growth medium with Tris-NaCl 1:100 caused a decrease in D0 both in air and N2. The D0 varied with the age of the culture and the temperature at the time of irradiation. In air the ratio of increment in D0 (ΔD0) over the increment in temperature (ΔT) had positive values as a function of age of the cells while under N2 this ratio was always negative. In N2 the D0 decreased in a smoothly non-linear fashion with an increase in temperature while in air it remained constant below 12° and increased linearly above that temperature at a rate equivalent to 1.65 kcal/mol. ATP was found to radioprotect the cells in N2 at pH 6.3 but radiosensitize them both in air and N2 at pH 7.5. The adenine nucleotides ATP, ADP, and AMP eliminated radiation-induced division delay in the cells in air. Cyclic AMP had no effect on the division delay in air but was found to synchronize cell growth.
Growth of vesicular stomatitis virus in mosquito cell lines
Authors: Artsob Harvey , Spence Leslie
Published: April 2010

Cocal strain of vesicular stomatitis virus was propagated in Aedes albopictus and Aedes aegypti cell lines. Infection of the cell lines at 30 °C resulted in a low-titered virus infection involving only a small proportion of the cell population with no cytopathic effects. Virus titers in A. albopictus were increased by adsorption with DEAE-dextran or by increasing the temperature of incubation. Use of a high-input multiplicity of virus and incubation of cells at 37 °C resulted in 100% infection of cells, allowing an electron-microscopic study of virus development. These studies indicated that virus maturation in A. albopictus cells occurred primarily at intracytoplasmic vesicles.
Biosynthesis of chloramphenicol in Streptomyces species 3022a. Isotope incorporation experiments with [G-14C] chorismic, [G-14C] prephenic, and [G-14C, 6-3H] shikimic acids
Authors: Emes A. , Floss H.-G. , Lowe D. A. , Westlake D. W. S. , Vining L. C.
Published: April 2010

When chloramphenicol-producing cultures of Streptomyces species 3022a were administered [G-14C] chorismic, [G-14C] prephenic, and [G-14C, 6-3H] shikimic acids, radiochemical yields in the antibiotic were very low (0.01–0.1%). [G-14C] chorismic and prephenic acids labeled chloramphenicol to about the same specific activity as tyrosine, aspartic acid, and glutamic acid from mycelial protein, whereas protein phenylalanine was 100 times more active. We conclude that these two substrates are unable to penetrate the cell membrane and the radioactivity incorporated enters as [G-14C] phenylpyruvic acid. Labeled shikimic acid, on the other hand, was directly incorporated into the cells. The 14C: 3H ratio in chloramphenicol isolated after feeding the [G-14C, 6R-3H] and [G-14C, 6S-3H] labeled forms indicated that the pro-6R-hydrogen was eliminated during ring aromatization. Antibiotic labeled from [G-14C, 6S-3H] shikimic acid was chemically degraded to 2,4,6-tribromoaniline without change in the 14C: 3H ratio thus establishing the specific incorporation of shikimic acid into the phenyl ring, and locating the tritium at positions ortho to the propanoid substituent.
Production of spore spheroplasts of Clostridium botulinum and DNA extraction for density gradient centrifugation
Authors: Durban Egon , Durban Elisa M. , Grecz Nicholas
Published: April 2010

A method is described whereby Clostridium botulinum 33A and 51B spore spheroplasts are produced in two sequential steps: (1) by reducing spore coats for 3 h with 50% mercaptoacetic acid – 8 M urea – 0.01 M EDTA, and (2) by lysis of the cortex for 2 h with 500 μg/ml lysozyme in 0.01 M Tris-HCl (pH 8.0) – 0.01 M EDTA – 1 mg/ml dithiothreitol and 25% lactose added as osmotic stabilizing agent.Optical density measurements (absorption spectra) of ultraviolet (UV)-absorbing material released after submitting spheroplasts to osmotic lysis in distilled water showed absorption maxima around 270 nm (dipicolinic acid) and 260 nm (nucleic acids). Radioactivity profiles of 3H-labeled TCA-insoluble material from centrifugation of alkaline sucrose gradients showed that the above schedule for obtaining spore spheroplasts resulted in optimal DNA extraction and did not cause extensive breakage of DNA.Phase-contrast microscopy indicated that spore appearance is not visibly affected by chemical coat reduction; however, spores become phase dark after treatment with lysozyme. Electron microscopy showed that after chemical reduction coat layers are less compact, of less electron density, and dissolved in some areas. Furthermore, lysozyme treatment disintegrates and to a large degree removes the cortex and structural details become visible in the core.
Hydrostatic pressure effects on several stages of protein synthesis in Escherichia coli
Authors: Hardon Michael J. , Albright Lawrence J.
Published: April 2010

Hydrostatic pressure has been shown to inhibit protein synthesis in Escherichia coli by inhibiting amino acid activation and polypeptide synthesis in cell-free systems. Pressure may decrease translational ambiguity by suppressing any non-specific activity of phenylalanyl-tRNA synthetase and by preferentially decreasing the stability of leucyl-tRNA.
Host–phage interaction in Agrobacterium tumefaciens. II. Host strain response to mitomycin C induction
Authors: Pootjes Christine , Stemberger Bridget
Published: April 2010

The growth, DNA synthesis, and cell ultrastructure was compared in lysogenic and "cured" Agrobacterium tumefaciens cultures in the presence and absence of mitomycin C.The lysogenic strain A. tumefaciens LV-1 lysed 4 h after mitomycin C induction and released over 1 × 1011 plaque-forming units/ml after 7 h. Three "cured" strains of A. tumefaciens CV-1, B2AC, and B6-806 were not induced to lyse by mitomycin C and DNA synthesis was blocked; however, electron micrographs revealed phage heads within the cells.
Pleiotropic mutants of the wood-rotting fungus Polyporus adustus lacking cellulase, mannanase, and xylanase
Authors: Eriksson Karl-Erik , Goodell E. W.
Published: April 2010

By screening for mutants which could not degrade cellulose, several cellulase-less mutants were isolated from the wood-rotting fungus Polyporus adustus. Most of the mutants lacked mannanase and xylanase as well. In wild type, the level of cellulase, mannanase, and xylanase was higher when the fungus was grown in a medium containing cellulose than in a medium lacking cellulose. It is proposed that in P. adustus, the induction of this group of enzymes is under the control of a single common regulator gene.
Purification and properties of boticin P produced by Clostridium botulinum
Authors: Lau A. H. S. , Hawirko R. Z. , Chow C. T.
Published: April 2010

A bacteriocin produced spontaneously by a nontoxigenic strain of Clostridium botulinum, type E, PM-15, has been isolated and designated boticin P. It was purified by ammonium sulfate precipitation, gel filtration on Sephadex G-100, sucrose density gradient centrifugation, and cesium chloride equilibrium density gradient centrifugation. Boticin P is composed mainly of proteins (98.8%) with a trace amount of carbohydrates (0.4%), and has an apparent molecular weight in excess of 4 × 106 daltons as estimated by gel filtration on Sepharose 2B. Electron microscopic examination of boticin P reveals a phage tail-like structure of 100 nm in length.Boticin P exerted a static effect on vegetative growth and spore outgrowth but not on the initial events of germination. The boticin was active on 10/12 toxigenic and 3/6 nontoxigenic type E and 2/2 nonproteolytic type B strains of C. botulinum. The activity spectrum on 27 strains supports the proposal that type E and the nonproteolytic type B strains belong to the same taxosubspecies.
Maintenance of primary African green monkey kidney (pAGMK) and Vero cells at room temperature (25°). A system for virus isolation in community practice
Authors: Mingle Julius A. A. , Westwood J. C. N.
Published: April 2010

Primary AGMK cells and Vero cells were maintained at room temperature (25 °C) and their sensitivities tested using echovirus type 9, coxsackie B4 and B5, herpes simplex virus, vaccinia, influenza A2/Hong Kong, and adenovirus type 7. pAGMK maintained for 4 days at room temperature was found to be less sensitive to herpes simplex and coxsackie B4 whilst maintenance of Vero cells at room temperature did not affect the sensitivity. Susceptibility of these two cell cultures to prototype viruses indicated that pAGMK was more susceptible.pAGMK cells were held at room temperature both before and after inoculation with viruses and incubated at 37 °C. Cytopathic effect (CPE) was noticed in these cells earlier after switching them to 37 °C incubation than when refrigerated suspensions of the viruses were inoculated into fresh cultures that had not been subjected to room temperature incubation. The usefulness of such a procedure in field studies of virus infections is discussed.
Selection and in vitro properties of inhibitor-nonsensitive influenza A (H3N2) strains
Authors: Lecomte J. , Boudreault A. , Pavilanis V.
Published: April 2010

Selection of stable variants, nonsensitive to horse serum inhibitors, was achieved by growing influenza A (H3N2) strains, originally sensitive, in the allantois-on-shell system with incorporated normal horse serum. Most of these variants, when compared to their respective parental line, showed a greater eluting activity not related to a greater enzymatic activity. Investigation of the ability to agglutinate erythrocytes from different animal species and the thermostability of the hemagglutinin and the neuraminidase did not reveal a complete correlation between these markers and resistance to horse serum inhibitors. When applied to known attenuated strains, also nonsensitive, these same markers could not be linked directly to the attenuation of these viruses for man.
Pseudomonas solanacearum: virulence of biochemical mutants
Authors: Coplin D. L. , Sequeira Luis , Hanson R. S.
Published: April 2010

The virulence of tryptophan auxotrophs (Trp−) of Pseudomonas solanacearum K60 was significantly lower than that of the wild type when inoculated on tobacco (cult. "Bottom Special") and tomato (cult. "Bonny Best"). These auxotrophs persisted at the site of inoculation for several weeks, but did not cause systemic infection. Auxotrophs for methionine (Met−) and leucine (Leu−) biosynthesis, however, were virulent on tobacco and weakly virulent on tomato. In tobacco leaves infiltrated with suspensions of Trp−, Met−, and Leu− mutant strains and strain K60, the population doubling times of each isolate were 16.0, 4.3, 4.2, and 2.3 h respectively. The amino acid requirement of each auxotroph was determined in vitro and compared with levels of these amino acids in xylem sap collected from decapitated plants. Tobacco sap contained sufficient concentrations of required amino acids to support 0, 53, and 54% of maximum growth in vitro of the Trp−, Met−, and Leu− mutant strains, respectively. Tryptophan, methionine, and leucine levels in tomato sap supported 0, 3, and 13% maximum growth of the respective strains in vitro. The relative concentrations of methionine and leucine in xylem sap were sufficiently different to explain the susceptibility of tobacco and resistance of tomato to these auxotrophs. The virulence of tryptophan auxotrophs was restored by genetic transformation to prototrophy and by supplying tryptophan to inoculated tobacco seedlings.
Immunological adjuvants. I. The induction of soluble factor(s) by Freund's complete adjuvant
Authors: Orr K. B. , Paraskevas F.
Published: April 2010

Serum collected from BALB/c mice 6 h after the intraperitoneal injection of Freund's complete adjuvant when mixed with a soluble antigen such as bovine serum albumin or human fibrinogen forms a cytophilic Ig which is taken up by the normal mouse spleen cells. When the serum was absorbed with an aggregated form of antigen, subsequent addition of soluble antigen failed to induce formation of cytophilic Ig, but an eluate recovered from the aggregated antigen did.This property of the serum is most likely non-specific since any antigen thus far tested is effective in inducing formation of cytophilic Ig and furthermore, absorption with one kind of antigen abolished the ability of the serum to form cytophilic Ig upon subsequent addition of any other antigen. Upon fractionation of the serum on Sephadex G-200 the activity was recovered in the 7-S fraction. However, the 4-S fraction (which lacks Ig) contained a factor which in the presence of antigen and normal mouse serum or its 7-S fraction formed a cytophilic Ig. The existing evidence indicated that the cytophilic Ig was taken up by 25 to 35% of the T cells (θ positive). Furthermore, about 15% of Ig carrying cells also took up the cytophilic Ig.The cytophilic Ig belongs to the IgG (IgG2a) class and presumptive evidence suggested that it may represent a complex of Ig and antigen.
Expression of tetracycline resistance mediated by an R-factor in Escherichia coli 15T−
Authors: Braun M. L. , Ferrell D. W. , Ott J. L.
Published: April 2010

Streptomycin and tetracycline resistance were carried on an R-factor in Escherichia coli 15T−R64-11 and 15T−NArR64-11. When growth of these strains was studied in the presence of the antibiotic, tetracycline caused a long lag period before growth occurred. During this lag, cell numbers decreased before cells multiplied. The lag period was eliminated by pretreatment of the inoculum with low levels of the antibiotic. Macromolecular synthesis was measured by incorporation of radioactive precursors into TCA-precipitable material in the absence and presence of tetracycline. In the absence of the antibiotic, RNA and protein synthesis were immediate while DNA synthesis occurred after a 15-min lag. During the lag period caused by tetracycline RNA synthesis was initiated but stopped after 1 h, and then resumed at 4 h. Protein synthesis was evident at 2 h while DNA synthesis occurred simultaneously with cell multiplication. Tetracycline also caused a long lag period when lactose was used as the energy source, but cell numbers did not decrease during this lag.
Cyanogenic compounds in cultures of a psychrophilic basidiomycete (snow mold)
Authors: Tapper B. A. , Macdonald M. A.
Published: April 2010

Glyoxylic acid cyanohydrin was found to be the principal cyanogen accumulating in cultures of snow mold, type B, strain W2, grown on media containing yeast and malt extracts. Small amounts of pyruvic acid cyanohydrin were also present. There was no evidence for presence of linamarin or lotaustralin in the cultures.