bluuebunny/crossref_metadata_2025_split huggingface dataset:
FERTILIZATION IN OEDOGONIUM. II. POLYSPERMY1
Authors: Hoffman Larry R. 
Published: August 2007

SUMMARYThis paper presents the first description of polyspermy in Oedogonium. It has been observed twice, in living material; in each, case it occurred when a pair of haploid spermatozoids initiated plasmogamy in rapid succession with, a single haploid egg. Supportive evidence for polyspermy has also been obtained ultrastructurally. Polyspermy in Oedogonium is anomalous; ordinarily it appears to be prevented by some mechanism initiated at the time of gametic fusion. The present study not only supports the existence of such a mechanism, but calls attention to the fact that further knowledge of its operation may only be possible through experimental studies designed to selectively impair the mechanism.
MODIFICATIONS IN FILTRATION METHODS FOR THE MEASUREMENT OF INORGANIC 14C UPTAKE BY PHOTOSYNTHESIZING ALGAE1
Authors: Berman Thomas 
Published: August 2007

SUMMARYIn the course, of routine primary productivity experiments with phytoplankton, the filtration step may introduce errors into the determination of inorganic 14C uptake into particulate and filtrate organic fractions. However, when ultrafine glass fiber filters, low filtration pressures, and fuming over HC1 were used, and corrections made for nonbiological adsorption of radioactivity on filters, no significant changes of cpm retained on filters per milliliter of filtration volume were found in tests with various algal populations. Cultures of Lauderia sp. and Gonyaulax polyedra, when photosynthesizing in 1 compartment of a 2‐chambered diffusion apparatus, released similar amounts of radioactive dissolved organic compounds measured after diffusion or upon filtration. Under our conditions, only negligible amounts of dissolved organic compounds were retained by fillers. For many natural waters, therefore, these filtration techniques permit adequate accuracy for primary productivity measurements.
WATER STATUS AND THE DISTRIBUTION OF CYANIDIUM CALDARIUM IN SOIL1
Authors: Smith David W. , Brock Thomas D. 
Published: August 2007

SUMMARYThe size and photosynthetic ability of Cyanidium caldarium populations in soil were related to the water status of the soil, welter soil, areas having larger populations and more extensive photosynthesis. The application of the direct methods used to the study of other soil algae, mosses, and lichens is discussed.
THE EFFECTS OF BACTERIA ON THE GROWTH AND REPRODUCTION OF OEDOGONIUM CARDIACUM1
Authors: Machlis Leonard 
Published: August 2007

SUMMARYIsolates of male and female Oedogonium cardiacum for which defined media had been established were subsequently found to be contaminated with a species of Corynebacterium which failed to grow in the nutrient broth used, to test for contamination. After the cultures were rendered, axenic through treatment with, penicillin G, they failed to develop oogonia or sperm except occasionally at a very low level. The addition of small amounts of the bacterium increased the development of the reproductive structures; however a much more striking increase was obtained by constantly infecting the algal cultures with Pseudomonas putida. Neither of the bacteria increased growth as measured by dry weight; however the P. putida resulted, in the growth of very long filaments in contrast to the short filaments characteristic of both the axenic cultures and those infected with Corynebacterium sp.
Early Nineteenth‐Century Readers of Jane Austen
Authors: Bautz Annika 
Published: August 2007

AbstractStudies of the reception of a literary work have traditionally relied mainly on the evidence of printed reviews. However, reviewing is a public activity, and does not represent readers’ private opinions, especially in the case of novels because of their low status. Also, reviewing was a male‐dominated field, so that it does not give conclusions to women's reactions to Austen's novels. This survey of informal comments made by early nineteenth‐century male and female readers in diaries and letters reveals ways in which readers responded to Austen's texts. Among the social classes that could comment in writing, the remarks are by those readers who were driven to record their thoughts. Whether a passing observation, sincere criticism, a recommendation to get hold of and read a novel, a request to a publisher to send another Austen novel as soon as possible or instructions as to where to send it to, these comments show the active nature of private readers’ physical and textual engagement with Austen's novels.
Buddhism, Politics, and Nationalism in the Twentieth and Twenty‐first Centuries
Authors: Borchert Thomas 
Published: August 2007

AbstractBuddhism is widely understood as a religion with a global scope. Particularly from the end of the twentieth century, the widespread growth of Buddhism internationally, and the extensive ties between Buddhists institutions, leave the impression of unity within contemporary Buddhism. Nevertheless, in this article, I argue that Buddhism cannot be understood outside of a national context. Although international ties between Buddhists are real and important, Sanghas generally remain under the governance by national governments and monks and nuns remain citizens of particular nation‐states. As a result, contemporary Buddhism is marked by a tension between the transnational and the national.
A precision translation stage for reproducing measured target volume motions
Authors: Litzenberg Dale W. , Hadley Scott W. , Lam Kwok L. , Balter James M. 
Published: August 2007

The development of four‐dimensional (4D) imaging, treatment planning, and treatment delivery methods for radiation therapy requires a quality assurance device that can reproduce clinical motions. Here, we present a high‐precision translation stage for testing and validating 4D techniques. These techniques may require spatial resolutions of 1 mm and temporal resolutions of 2 – 30 Hz for computed tomography imaging, electromagnetic tracking, and fluoroscopic imaging. A one‐dimensional programmable translation stage capable of reproducing idealized and measured anatomic motions common to the thorax and providing support for phantoms weighing up to 27 kg was designed and built to meet the foregoing spatial and temporal resolution requirements. The stage consists of a polycarbonate base and table, driven by an ac servo motor with encoder feedback by means of a belt‐coupled precision screw. Complex motions are made possible by a programmable motion controller that can run multiple independent control and monitoring programs concurrently on independent motion axes. Programmable input and output ports allow motion to be synchronized with beam delivery and other imaging and treatment delivery devices to within 2.0 ms. Average deviations from the programmed positions are typically 0.2 mm or less, and the average maximum positional errors are typically 0.5 mm for an indefinite number of parameterized breathing motion cycles during reproduction of measured target volume motions for several minutes.PACS number: 87.66.Xa
Quantitative assessment of four‐dimensional computed tomography image acquisition quality
Authors: Starkschall George , Desai Neil , Balter Peter , Prado Karl , Luo Dershan , Cody Dianna , Pan Tinsu 
Published: August 2007

The purpose of the present work was to describe the development and validation of a series of tests to assess the quality of four‐dimensional (4D) computed‐tomography (CT) imaging as it is applied to radiation treatment planning. Using a commercial respiratory motion phantom and a programmable moving platform with a CT phantom, we acquired 4D CT datasets on two commercial multislice helical CT scanners that use different approaches to 4D CT image reconstruction. Datasets were obtained as the platform moved in various patterns designed to simulate breathing. Known inserts in the phantom were contoured, and statistics were generated to evaluate properties important to radiation therapy—namely, accuracy of phase‐binning, shape, volume, and CT number. Phase‐binning accuracy varied by as much as 5% for a 4D procedure in which images were reconstructed and then binned, but exhibited no variation for a 4D procedure in which projections were binned before reconstruction. The magnitude of geometric distortion was found to be small for both approaches, as was the magnitude of volume error. Partial‐volume effects in the direction perpendicular to the transverse planes of reconstruction affected volume accuracy, however. Computed tomography numbers were reproduced accurately, but 4D images exhibited more variation in CT number than static CT images did. Characterization of such properties can be used to better understand and optimize the various parameters that affect 4D CT image quality.PACS numbers: 87.53.‐j, 87.59.Fm
Commissioning and acceptance testing of a CyberKnife linear accelerator
Authors: Sharma Subhash C. , Ott Joseph T. , Williams Jamone B. , Dickow Danny 
Published: August 2007

Acceptance testing and commissioning of a CyberKnife robotic stereotactic radiosurgery system was performed in April 2006. The CyberKnife linear accelerator produces a photon beam of 6 MV nominal energy, without the use of a flattening filter. Clinically measured tissue–phantom ratios, off‐center ratios, and output factors are presented and compared with similar data from other CyberKnife sites throughout the United States. In general, these values agreed to within 2%.PACS number: 87.53.Dq
Lag correction model and ghosting analysis for an indirect‐conversion flat‐panel imager
Authors: Mail Noor , O'Brien Peter , Pang Geordi 
Published: August 2007

Cone‐beam digital tomosynthesis (CBDT) is a new approach that was recently proposed for rapid tomographic imaging of soft‐tissue targets in the radiotherapy treatment room. One of the potential problems in implementing CBDT using, for example, megavoltage (MV) X rays is the possibility of artifacts caused by image lag and ghosting of the X‐ray detector used. In the present work, we developed a model to correct for image lag with indirect‐conversion flat‐panel imagers (FPIs) used for MV‐CBDT. This model is based on measurement and analysis of image lag in an indirect‐conversion FPI irradiated with a 6‐MV X‐ray beam. Our results demonstrated that image lag is amenable to correction. In addition, we measured the ghosting effect for an indirect‐conversion FPI and found it to be insignificant.PACS numbers: 87.53.Oq, 87.57.Ce
Dietary Inclusion of Colicin E1 Is Effective in Preventing Postweaning Diarrhea Caused by F18-Positive
Escherichia coli
in Pigs
Authors: Cutler S. A. , Lonergan S. M. , Cornick N. , Johnson A. K. , Stahl C. H. 
Published: August 2007

ABSTRACT

With worldwide concern over the use of antibiotics in animal agriculture and their contribution to the spread of antibiotic resistance, alternatives to conventional antibiotics are needed. Previous research in our laboratories has shown that colicin E1 is effective against some
Escherichia coli
strains responsible for postweaning diarrhea (PWD) in vitro. In this study we examined the efficacy of the dietary inclusion of colicin E1 in preventing experimentally induced PWD caused by F18-positive enterotoxigenic
E. coli
in young pigs. Twenty-four weaned pigs (23 days of age), identified by genotyping to be susceptible to F18-positive
E. coli
infections, were individually housed and fed diets containing 0, 11, or 16.5 mg colicin E1/kg diet. Two days after the start of the trial, all animals were orally inoculated with 1 × 10
9
CFU of each of two F18-positive
E. coli
strains isolated from pigs with PWD. The dietary inclusion of colicin E1 decreased the incidence and severity of PWD caused by F18-positive enterotoxigenic
E. coli
and improved the growth performance of the piglets. Additionally, the reduced incidence of PWD due to dietary colicin E1, lowered the levels of expression of the genes for interleukin 1β and tumor necrosis factor beta in ileal tissues from these animals. The dietary inclusion of colicin E1 may be an effective alternative to conventional antibiotics in the diets of weaning pigs for the prevention of PWD caused by F18-positive enterotoxigenic
E. coli
.
Prevalence and Expression of the Plasmid-Mediated Quinolone Resistance Determinant
qnrA1
Authors: Xu Xiaogang , Wu Shi , Ye Xinyu , Liu Yang , Shi Wanliang , Zhang Yingyuan , Wang Minggui 
Published: August 2007

ABSTRACT

Since its discovery,
qnrA
has been found in most common
Enterobacteriaceae
. Ciprofloxacin MICs conferred by different
qnrA
-positive plasmids could range from 0.1 μg/ml to 2 μg/ml in
Escherichia coli
J53. The reasons for different ciprofloxacin MICs conferred by
qnrA
have not been fully clarified. Five hundred forty-one consecutive gram-negative clinical strains that were resistant or intermediate to ciprofloxacin and that were isolated in Shanghai in 2005 were screened for
qnrA
by PCR. For
qnrA
-positive isolates, the transferability of quinolone resistance was determined by conjugation and mutations within the quinolone resistance-determining region (QRDR) of
gyrA
and
parC. aac
(
6
′)-
Ib-cr
was detected and
qnrA
RNA expression was determined using real-time reverse transcription-PCR for transconjugants with different ciprofloxacin MICs. The
qnrA
gene was detected in 7 of the 541 clinical isolates. Quinolone resistance was transferred in four strains by conjugation. Mutations in the QRDR of
gyrA
and
parC
were detected in five
qnrA
-positive clinical strains with higher ciprofloxacin MICs. Of four
qnrA
-bearing plasmids in
E. coli
J53, pHS4 and pHS5 conferred ciprofloxacin MICs of 0.094 to 0.125 μg/ml; pHS3, which harbored the
aac
(
6
′)-
Ib-cr
gene as well, conferred a ciprofloxacin MIC of 0.25 μg/ml, and pHS6, which had both the
aac
(
6
′)-
Ib-cr
gene and a high expression level of
qnrA
, had a ciprofloxacin MIC of 1.0 μg/ml. The prevalence of
qnrA
appeared to be higher in
Enterobacter cloacae
than in other
Enterobacteriaceae
. The coexistence of
qnrA
and
aac
(
6
′)-
Ib-cr
in a single plasmid and increased
qnrA
expression can account for the different levels of ciprofloxacin resistance seen in transconjugants.
Variations in Reverse Transcriptase and RNase H Domain Mutations in Human Immunodeficiency Virus Type 1 Clinical Isolates Are Associated with Divergent Phenotypic Resistance to Zidovudine
Authors: Ntemgwa Michel , Wainberg Mark A. , Oliveira Maureen , Moisi Daniela , Lalonde Richard , Micheli Valeria , Brenner Bluma G. 
Published: August 2007

ABSTRACTMutations in the RNase H domain of human immunodeficiency virus type 1 RT have been reported to cause resistance to zidovudine (ZDV) in vitro. However, very limited data on the in vivo relevance of these mutations in patients exist to date. This study was designed to determine the relationship between mutations in the RNase H domain and viral susceptibility to nucleoside analogues. Viruses harboring complex thymidine analogue mutation (TAM) and nucleoside analogue mutation (NAM) profiles were evaluated for their phenotypic susceptibilities to ZDV, tenofovir (TNF), and the nonapproved nucleoside reverse transcriptase inhibitors (NRTIs) β-2′,3′-didehydro-2′,3′-dideoxy-5-fluorocytidine (Reverset), β-d-5-fluorodioxolane-cytosine, and apricitabine. As controls, viruses from NRTI-naïve patients were also studied. ThepolRT region (codons 21 to 250) of the viruses were sequenced and evaluated for mutations in the RNase H domain (codons 441 to 560) and the connection domain (codons 289 to 400). The results showed that viruses from patients failing multiple NRTI-containing regimens had distinct TAM and NAM profiles that conferred various degrees of resistance to ZDV (0.9- to >300-fold). Sequencing of the RNase H domain identified five positions (positions 460,468, 483, 512, and 519) at which extensive amino acid polymorphisms common in both wild-type viruses and viruses from treated patients were identified. No mutations were observed at positions 539 and 549, which have previously been associated with ZDV resistance. Mutations in the RNase H domain did not appear to correlate with the levels of phenotypic resistance to ZDV. Although some mutations were also observed in the connection domain, the simultaneous presence of the L74V and M184V mutations was the most significant determinant of phenotypic resistance to ZDV in patients infected with viruses with TAMs.
Crystal Structure of Cefditoren Complexed with
Streptococcus pneumoniae
Penicillin-Binding Protein 2X: Structural Basis for Its High Antimicrobial Activity
Authors: Yamada Mototsugu , Watanabe Takashi , Miyara Takako , Baba Nobuyoshi , Saito Jun , Takeuchi Yasuo , Ohsawa Fukuichi 
Published: August 2007

ABSTRACT

Cefditoren is the active form of cefditoren pivoxil, an oral cephalosporin antibiotic used for the treatment of respiratory tract infections and otitis media caused by bacteria such as
Streptococcus pneumoniae
,
Haemophilus influenzae
,
Streptococcus pyogenes
,
Klebsiella pneumoniae
, and methicillin-susceptible strains of
Staphylococcus aureus
. β-Lactam antibiotics, including cefditoren, target penicillin-binding proteins (PBPs), which are membrane-associated enzymes that play essential roles in the peptidoglycan biosynthetic process. To envision the binding of cefditoren to PBPs, we determined the crystal structure of a trypsin-digested form of PBP 2X from
S. pneumoniae
strain R6 complexed with cefditoren. There are two PBP 2X molecules (designated molecules 1 and 2) per asymmetric unit. The structure reveals that the orientation of Trp374 in each molecule changes in a different way upon the formation of the complex, but each forms a hydrophobic pocket. The methylthiazole group of the C-3 side chain of cefditoren fits into this binding pocket, which consists of residues His394, Trp374, and Thr526 in molecule 1 and residues His394, Asp375, and Thr526 in molecule 2. The formation of the complex is also accompanied by an induced-fit conformational change of the enzyme in the pocket to which the C-7 side chain of cefditoren binds. These features likely play a role in the high level of activity of cefditoren against
S. pneumoniae
.
In Vitro Activity of Human β-Defensin 2 againstPseudomonas aeruginosain the Presence of Tear Fluid
Authors: Huang Ling C. , Redfern Rachel L. , Narayanan Srihari , Reins Rose Y. , McDermott Alison M. 
Published: August 2007

ABSTRACTPseudomonas aeruginosacauses vision-threatening keratitis and is difficult to treat due to emerging resistance. Human β-defensin 2 (hBD-2) is an antimicrobial peptide expressed by ocular surface epithelia with broad-spectrum activity against various pathogens, includingP. aeruginosa. The activity of hBD-2 againstP. aeruginosain the presence of human tears or NaCl was studied. In some experiments, tears were heat-inactivated, filtered, and separated into cationic/anionic fractions or mucin MUC5AC was removed by immunoprecipitation before use. Immunoprecipitation was performed to study the interaction between hBD-2 and MUC5AC. hBD-2 activity was reduced by 40 to 90% in the presence of 17.5 to 70% (vol/vol) tears. NaCl reduced hBD-2 activity, but at most it could account for only 36% of the inhibitory effect of tears. Heat inactivation and filtration attenuated the ability of tears to inhibit hBD-2 activity by 65 and 68%, respectively. Anionic tear fractions significantly reduced (86%) the activity of hBD-2, whereas only a 22% reduction was observed with the cationic fractions. In the absence of MUC5AC, the activity of hBD-2 was restored by 64%. Immunoprecipitation studies suggested that the loss of hBD-2 activity in tears is due to a direct binding interaction with MUC5AC. Our data showed that the antimicrobial activity of hBD-2 is sensitive to the presence of human tears and that this is partly due to the salt content and also the presence of MUC5AC. These data cast doubt on the effectiveness of hBD-2 as an antimicrobial peptide, and additional studies are required to conclusively elucidate its role in innate immunity at the ocular surface in vivo.
Concentration-Dependent
Mycobacterium tuberculosis
Killing and Prevention of Resistance by Rifampin
Authors: Gumbo Tawanda , Louie Arnold , Deziel Mark R. , Liu Weiguo , Parsons Linda M. , Salfinger Max , Drusano George L. 
Published: August 2007

ABSTRACT

Rifampin is a cornerstone of modern antituberculosis therapy. However, rifampin's half-life of 3 h is believed to limit its utility for intermittent therapy, so new congeners with long half-lives are being developed. Using an in vitro pharmacokinetic-pharmacodynamic model of tuberculosis, we examined the relationships between rifampin exposure, microbial killing of log-phase-growth
Mycobacterium tuberculosis
, and suppression of resistance. Rifampin's microbial killing was linked to the area under the concentration-time curve-to-MIC ratio. The suppression of resistance was associated with the free peak concentration (
C
max
)-to-MIC ratio and not the duration that the rifampin concentration was above MIC. Rifampin prevented resistance to itself at a free
C
max
/MIC ratio of ≥175. The postantibiotic effect duration was ≥5.2 days and was most closely related to the
C
max
/MIC ratio (
r
2
= 0.96). To explain rifampin's concentration-dependent effect, we examined the kinetics of rifampin entry into
M. tuberculosis
. Rifampin achieved concentration-dependent intracellular steady-state concentrations within 15 min. Our results suggest that doses of rifampin higher than those currently employed would optimize the effect of rifampin, if patients could tolerate them. Another major implication is that in the design of new rifampin congeners for intermittent therapy, the important properties may include (i) the efficient entry of the rifamycin into
M. tuberculosis
, (ii) the achievement of a free
C
max
/MIC of >175 that can be tolerated by patients, and (iii) a long postantibiotic effect duration.
Anthrax Protective Antigen Cleavage and Clearance from the Blood of Mice and Rats
Authors: Moayeri Mahtab , Wiggins Jason F. , Leppla Stephen H. 
Published: August 2007

ABSTRACT

Bacillus anthracis
protective antigen (PA) is an 83-kDa (PA83) protein that is cleaved to the 63-kDa protein (PA63) as an essential step in binding and internalizing lethal factor (LF). To assess in vivo receptor saturating PA concentrations, we injected mice with PA variants and measured the PA remaining in the blood at various times using PA83- and PA63-specific enzyme-linked immunosorbent assays. We found that both wild-type PA (WT-PA) and a receptor-binding-defective mutant (Ub-PA) were cleaved to PA63 independent of their ability to bind cells. This suggested a PA-acting protease activity in the blood. The protease cleaved PA at the furin cleavage sequence because furin site-modified PA mutants were not cleaved. Cleavage measured in vitro was leupeptin sensitive and dependent on calcium. Cell surface cleavage was important for toxin clearance, however, as Ub-PA and uncleavable PA mutants were cleared at slower rates than WT-PA. The cell binding-independent cleavage of PA was also verified by using Ub-PA (which is still cleaved) to rescue mice from toxin challenge by competitively binding circulating LF. This mutant was able to rescue mice even when given 12 h before toxin challenge. Its therapeutic ability was comparable to that of dominant-negative PA, which binds cells but does not allow LF translocation, and to the protection afforded through receptor clearance by WT-PA and uncleavable receptor binding-competent mutants. The PA cleavage and clearance observed in mice did not appear to have a role in the differential mouse susceptibility as it occurred similarly in lethal toxin (LT)-resistant DBA/2J and LT-sensitive BALB/cJ mice. Interestingly, PA63 was not found in LT-resistant or -sensitive rats and PA83 clearance was slower in rats than in mice. Finally, to determine the minimum amount of PA required in circulation for LT toxicity in mice, we administered time-separated injections of PA and LF and showed that lethality of LF for mice after PA was no longer measurable in circulation, suggesting active PA sequestration at tissue surfaces.