bluuebunny/crossref_metadata_2025 huggingface dataset:
Vesicular glutamate filling and AMPA receptor occupancy at the calyx of Held synapse of immature rats
Authors: Yamashita Takayuki , Kanda Takeshi , Eguchi Kohgaku , Takahashi Tomoyuki
Published: March 2009

At central glutamatergic synapses, neurotransmitter often saturates postsynaptic AMPA receptors (AMPARs), thereby restricting the dynamic range of synaptic efficacy. Here, using simultaneous pre‐ and postsynaptic whole‐cell recordings, at the calyx of Held synapse of immature rats, we have investigated the mechanism by which transmitter glutamate saturates postsynaptic AMPARs. When we loaded l‐glutamate (1–100 mm) into presynaptic terminals, the quantal EPSC (qEPSC) amplitude changed in a concentration‐dependent manner. At physiological temperature (36–37°C), the qEPSC amplitude increased when intraterminal l‐glutamate concentration was elevated from 1 mm to 10 mm, but it reached a plateau at 10 mm. This plateau persisted after bath‐application of the low affinity AMPAR antagonist kynurenate, suggesting that it was caused by saturation of vesicular filling with glutamate rather than by saturation of postsynaptic AMPARs. In contrast to qEPSCs, action potential‐evoked EPSCs remained unchanged by increasing intraterminal l‐glutamate from 1 mm to 100 mm, even at room temperature, indicating that multi‐quantal glutamate saturated postsynaptic AMPARs. This saturation could be relieved by blocking AMPAR desensitization using cyclothiazide (100 μm). The concentration of ambient glutamate in the slice, estimated from NMDA receptor current fluctuations, was 55 nm; this was far below the concentration required for AMPAR desensitization. We conclude that rapid AMPAR desensitization, caused by glutamate released from multiple vesicles during synaptic transmission, underlies postsynaptic AMPAR saturation at this immature calyceal synapse before the onset of hearing.
Prolonged illumination up‐regulates arrestin and two guanylate cyclase activating proteins: a novel mechanism for light adaptation
Authors: Codega Paolo , Santina Luca Della , Gargini Claudia , Bedolla Diana E. , Subkhankulova Tatiana , Livesey Frederick J. , Cervetto Luigi , Torre Vincent
Published: March 2009

Light adaptation in vertebrate photoreceptors is mediated by multiple mechanisms, one of which could involve nuclear feedback and changes in gene expression. Therefore, we have investigated light adaptation‐associated changes in gene expression using microarrays and real‐time PCR in isolated photoreceptors, in cultured isolated retinas and in acutely isolated retinas. In all three preparations after 2 h of an exposure to a bright light, we observed an up‐regulation of almost 100% of three genes, Sag, Guca1a and Guca1b, coding for proteins known to play a major role in phototransduction: arrestin, GCAP1 and GCAP2. No detectable up‐regulation occurred for light exposures of less than 1 h. Functional in vivo electroretinographic tests show that a partial recovery of the dark current occurred 1–2 h after prolonged illumination with a steady light that initially caused a substantial suppression of the photoresponse. These observations demonstrate that prolonged illumination results in the up‐regulation of genes coding for proteins involved in the phototransduction signalling cascade, possibly underlying a novel component of light adaptation occurring 1–2 h after the onset of a steady bright light.
Long‐term facilitation of upper airway muscle activity induced by episodic upper airway negative pressure and hypoxia in spontaneously breathing anaesthetized rats
Authors: Ryan Stephen , Nolan Philip
Published: March 2009

Obstruction of the upper airway (UA) is associated with episodes of hypoxia and upper airway negative pressure (UANP). In the companion paper it is shown that episodic hypoxia elicits long‐term facilitation (LTF) of tongue protrudor, retractor and respiratory pump muscle activity. However, whether repeated exposure to UANP also induces LTF is unknown. We hypothesized that repetitive exposure to UANP would induce LTF of UA and respiratory pump muscle activity and when coupled with hypoxia, as occurs when the UA obstructs, would lead to an even greater facilitation of muscle activity and the response to UANP. Experiments were performed in 24 anaesthetized, spontaneously breathing rats with intact vagi. To induce LTF, UANP stimuli (−10 cmH2O) of 5 s duration were delivered every 30 s for 3 min (± hypoxia). This was repeated eight times over 1 h, each 3 min episode separated by 5 min of normoxia. Genioglossus (GG), hyoglossus (HG) and diaphragm (Dia) muscle activity was recorded before, during and for 1 h following the last exposure to episodic UANP alone (n= 8), UANP and hypoxia together (n= 8) or normoxia alone (n= 8). During the final hour, single pulses of UANP were applied at 1 min and every 10 min thereafter to determine whether LTF of the response to UANP had been induced. Our results show that LTF of GG muscle activity and its response to UANP was induced following exposure to episodic UANP stimuli alone and UANP applied during hypoxia. However, there was no significant difference between these responses. Episodic UANP alone also induced LTF of HG muscle activity but this effect did not manifest until 40 min following the last episode of repeated UANP stimulation. In the presence of hypoxia, no LTF of HG muscle response to UANP was found. In conclusion, episodic UANP stimulation induces LTF of UA dilator and retractor tongue muscles, but no further facilitation occurs when coupled with hypoxia. This response may serve as an important protective mechanism of respiratory homeostasis during sleep, particularly in patients who suffer from obstructive sleep apnoea.
Left ventricular torsion and untwisting during exercise in heart transplant recipients
Authors: Esch Ben T. , Scott Jessica M. , Warburton Darren E.R. , Thompson Richard , Taylor Dylan , Baron June Cheng , Paterson Ian , Haykowsky Mark J.
Published: March 2009

Left ventricular (LV) rotation is the dominant deformation during relaxation and links systole with early diastolic recoil. LV torsion and untwisting rates during submaximal exercise were compared between heart transplant recipients (HTRs), young adults and healthy older individuals to better understand impaired diastolic function in HTRs. Two dimensional and colour M‐mode echocardiography with speckle‐tracking analysis were completed in eight HTRs (age: 61 ± 9 years), six recipient age‐matched (RM, age: 60 ± 11 years), and five donor age‐matched (DM, age: 35 ± 8 years) individuals (all males) at rest and during submaximal cycle exercise. LV peak torsion, peak rate of untwisting and peak intraventricular pressure gradients (IVPGs) were examined. LV torsion increased with exercise in DMs (6.5 ± 5.6 deg, P < 0.05), but not in RMs (−2.6 ± 7.0 deg) or HTRs (−0.9 ± 4.4 deg). The change from rest to exercise in the peak rate of untwisting was significantly greater for DMs (−2.1 ± 0.5 rads s−1, P < 0.05) compared to RMs (−0.7 ± 1.3 rads s−1) and HTRs (−0.2 ± 0.9 rads s−1). The amount of untwisting occurring prior to mitral valve opening substantially declined with exercise in RMs and HTRs only. The change in IVPGs was 1.3‐fold greater in DMs versus HTRs or RMs (P > 0.05). Peak LV torsion and untwisting are blunted during exercise in HTRs and RMs compared to DMs. These factors may contribute to the impaired diastolic filling found in HTRs during exercise. Similarities between HTRs and RMs during exercise suggest functional accelerated ageing of the cardiac allograft.
Studies on Resonant Water Motion Between a Ship and a Fixed Terminal in Shallow Water
Authors: Kristiansen Trygve , Faltinsen Odd M.
Published: March 2009

This work focuses on the hydrodynamical problem of a Liquid Natural Gas (LNG) carrier near a Gravity Based Structure (GBS) -type offshore terminal subject to incoming waves in medium deep to shallow water conditions. The work is restricted to 2D, and the ship is restrained from moving. The resonant behavior of the fluid in the gap between the ship and the terminal is investigated. The problem is investigated by means of a numerical model and model tests. Potential theory is assumed, and a linear as well as a nonlinear time-domain numerical wavetank based on a boundary element method with a mixed Eulerian–Lagrangian approach is implemented for this purpose. Model tests (near 2D) of a midship section near a vertical wall are carried out in a 26.5m long and 0.595m wide wave flume in model scale 1:70. In full scale the ship beam is 45m and the ship draft is 12m. The ship model is constructed in such a way as to avoid flow separation, i.e., no sharp corners. Several parameters are varied: water depth, wave period, and wave steepness. Wave elevation is measured at 12 locations.
Comparison of two commercial whole body PET systems based on LSO and BGO crystals respectively for brain imaging
Authors: Trébossen Régine , Comtat Claude , Brulon Vincent , Bailly Pascal , Meyer Marc‐Etienne
Published: March 2009

The prevalence of neurodegenerative diseases is growing in western countries and PET imaging is increasingly frequently used for clinical and research purposes. However, few PET cameras are dedicated to cerebral imaging. The Biograph™ 6 (Biograph6) (Siemens Medical Solutions) is a PET/CT dedicated to high throughput whole body studies. Its performance for cerebral imaging has not yet been assessed. The aims of this study were to compare the quantification and detectability of the Biograph for cerebral imaging with those of a well‐validated PET camera, the ECAT EXACT () (Siemens Medical Solutions). A phantom measuring long and in diameter was filled with a ‐fluorodeoxyglucose solution. Two 5.7 and spheres filled with water (cold‐spots), three spheres (sphere‐to‐background: 3, 6, and 12), one sphere (sphere‐to‐background: 3), and one sphere (sphere‐to‐background: 2) filled with a radioactive solution were inserted into the phantom. The activity concentration was chosen so that the count rates for the phantom measurements matched those of typical brain studies on both cameras. Images were reconstructed using FORE and OSEM algorithms. The reconstruction parameters were adjusted to obtain a similar signal‐to‐noise ratio in images acquired with the two cameras. The contrast recovery (CR) coefficients were similar on the two scanners for the 5.7 and spheres (cold spheres) and the 1.14 and spheres (hot spheres). For the spheres, the CR values were 35% higher for the sphere‐to‐background ratio of 12 and 39% higher for the sphere‐to‐background ratio of 6 on the Biograph6 for the scan. The variability of measurements was lower on the Biograph6 than on the . The detectability for the smallest spheres on the Biograph6 was close to that on the . The Biograph has similar performances as the reference tomograph for the detection and quantification of small hot spots and cold spots.
Adapting liver motion models using a navigator channel technique
Authors: Nguyen T‐N. , Moseley J. L. , Dawson L. A. , Jaffray D. A. , Brock K. K.
Published: March 2009

Deformable registration can improve the accuracy of tumor targeting; however for online applications, efficiency as well as accuracy is important. A navigator channel technique has been developed to combine a biomechanical model‐based deformable registration algorithm with a population motion model and patient specific motion information to perform fast deformable registration for application in image‐guided radiation therapy. A respiratory population‐based liver motion model was generated from breath‐hold CT data sets of ten patients using a finite element model as a framework. The population model provides a biomechanical reference template of the average liver motions, which were found to be (absolute ) , , and in the left‐right (LR), anterior‐posterior (AP), and superior‐inferior (SI) directions, respectively. The population motion model was then adapted to the specific liver motion of 13 patients based on their exhale and inhale CT images. The patient motion was calculated using a navigator channel (a narrow region of interest window) on liver boundaries in the images. The absolute average accuracy of the navigator channel to predict the 1D SI and AP motions of the liver was less than 0.11, which is less than the out‐of‐plane image voxel size, 0.25 cm. This 1D information was then used to adapt the 4D population motion model in the SI and AP directions to predict the patient specific liver motion. The absolute average residual error of the navigator channel technique to adapt the population motion to the patients’ specific motion was verified using three verification methods: (1) vessel bifurcation, (2) tumor center of mass, and (3) MORFEUS deformable algorithm. All three verification methods showed statistically similar results where the technique's accuracy was approximately on the order of the voxel image sizes. This method has potential applications in online assessment of motion at the time of treatment to improve image‐guided radiotherapy and monitoring of intrafraction motion.
Intracranial CT angiography obtained from a cerebral CT perfusion examination
Authors: Gratama van Andel H. A. F. , Venema H. W. , Majoie C. B. , Den Heeten G. J. , Grimbergen C. A. , Streekstra G. J.
Published: March 2009

CT perfusion (CTP) examinations of the brain are performed increasingly for the evaluation of cerebral blood flow in patients with stroke and vasospasm after subarachnoid hemorrhage. Of the same patient often also a CT angiography (CTA) examination is performed. This study investigates the possibility to obtain CTA images from the CTP examination, thereby possibly obviating the CTA examination. This would save the patient exposure to radiation, contrast, and time. Each CTP frame is a CTA image with a varying amount of contrast enhancement and with high noise. To improve the contrast‐to‐noise ratio (CNR) we combined all 3D images into one 3D image after registration to correct for patient motion between time frames. Image combination consists of weighted averaging in which the weighting factor of each frame is proportional to the arterial contrast. It can be shown that the arterial CNR is maximized in this procedure. An additional advantage of the use of the time series of CTP images is that automatic differentiation between arteries and veins is possible. This feature was used to mask veins in the resulting 3D images to enhance visibility of arteries in maximum intensity projection (MIP) images. With a Philips Brilliance 64 CT scanner CTP examinations of eight patients were performed on of brain using the toggling table technique. The CTP examination consisted of a time series of 15 3D images (; ; each) with an interval of . The authors measured the CNR in images obtained with weighted averaging, images obtained with plain averaging, and images with maximal arterial enhancement. The authors also compared CNR and quality of the images with that of regular CTA examinations and examined the effectiveness of automatic vein masking in MIP images. The CNR of the weighted averaged images is, on the average, 1.73 times the CNR of an image at maximal arterial enhancement in the CTP series, where the use of plain averaging increases the CNR only with a factor of 1.49. The quality of the weighted averaged images approaches that of CTA images, although in the present study the image quality of CTA was not quite reached. The automatic masking of veins is effective and only small remnants of veins were sometimes present in the masked images. Weighted averaging makes it possible to create CTA images from a CTP examination with a CNR considerably higher than that of images with maximal arterial enhancement. The quality of the resulting images approaches that of CTA images and offers the additional advantages to automatically differentiate between arteries and veins.
Region‐of‐interest image reconstruction with intensity weighting in circular cone‐beam CT for image‐guided radiation therapy
Authors: Cho Seungryong , Pearson Erik , Pelizzari Charles A. , Pan Xiaochuan
Published: March 2009

Imaging plays a vital role in radiation therapy and with recent advances in technology considerable emphasis has been placed on cone‐beam CT (CBCT). Attaching a kV x‐ray source and a flat panel detector directly to the linear accelerator gantry has enabled progress in target localization techniques, which can include daily CBCT setup scans for some treatments. However, with an increasing number of CT scans there is also an increasing concern for patient exposure. An intensity‐weighted region‐of‐interest (IWROI) technique, which has the potential to greatly reduce CBCT dose, in conjunction with the chord‐based backprojection‐filtration (BPF) reconstruction algorithm, has been developed and its feasibility in clinical use is demonstrated in this article. A nonuniform filter is placed in the x‐ray beam to create regions of two different beam intensities. In this manner, regions outside the target area can be given a reduced dose but still visualized with a lower contrast to noise ratio. Image artifacts due to transverse data truncation, which would have occurred in conventional reconstruction algorithms, are avoided and image noise levels of the low‐ and high‐intensity regions are well controlled by use of the chord‐based BPF reconstruction algorithm. The proposed IWROI technique can play an important role in image‐guided radiation therapy.
Accuracy of two simple methods for estimation of thyroidal kinetics for dosimetry‐based treatment of Graves’ disease
Authors: Traino A. C. , Xhafa B.
Published: March 2009

One of the major challenges to the more widespread use of individualized, dosimetry‐based radioiodine treatment of Graves’ disease is the development of a reasonably fast, simple, and cost‐effective method to measure thyroidal kinetics in patients. Even though the fixed activity administration method does not optimize the therapy, giving often too high or too low a dose to the gland, it provides effective treatment for almost 80% of patients without consuming excessive time and resources. In this article two simple methods for the evaluation of the kinetics of in the thyroid gland are presented and discussed. The first is based on two measurements 4 and 24 h after a diagnostic administration and the second on one measurement 4 h after such an administration and a linear correlation between this measurement and the maximum uptake in the thyroid. The thyroid absorbed dose calculated by each of the two methods is compared to that calculated by a more complete kinetics evaluation, based on seven thyroid uptake measurements for 35 patients at various times after the therapy administration. There are differences in the thyroid absorbed doses between those derived by each of the two simpler methods and the “reference” value (derived by more complete uptake measurements following the therapeutic administration), with 20% median and 40% 90‐percentile differences for the first method (i.e., based on two thyroid uptake measurements at 4 and 24 h after administration) and 25% median and 45% 90‐percentile differences for the second method (i.e., based on one measurement at 4 h post‐administration). Predictably, although relatively fast and convenient, neither of these simpler methods appears to be as accurate as thyroid dose estimates based on more complete kinetic data.
Automated versus manual detection of left ventricular wall motion abnormalities by gated blood pool SPECT
Authors: Nichols Kenneth J. , Van Tosh Andrew , Wang Yi , Palestro Christopher J. , Reichek Nathaniel
Published: March 2009

The purpose of this investigation was to describe the rationale and implementation of new totally automated algorithms to compute global and regional left ventricular (LV) function measurements from blood pool (BP) gated SPECT data and to test the hypothesis that automated calculations are as accurate as manual calculations for detecting global and regional LV wall motion abnormalities when compared to independent cardiac magnetic resonance (CMR) measurements. From an Institutional Review Board approved retrospective review of data for 43 patients (age ; 82% males; 59% with CHF; 59% with prior MI) evaluated for cardiac disease, CMR data were analyzed along with automated and manual calculations of BP data. There was no difference among global LV EF values (ANOVA ) and strong correlation between automated and manual global LV EFs versus CMR, with no significant trends or biases. There was “very good agreement” of automated and manual discriminations of cases with LV EF versus CMR. Detection of LV segments with abnormal regional wall motion was equally accurate for automated and manual processings of BP data [ROC versus ]. The authors conclude that automated and manual computations were equivalent to each other and accurate at identifying both global and regional LV wall motion abnormalities.
Assessment of trabecular bone microarchitecture by two different x‐ray microcomputed tomographs: A comparative study of the rat distal tibia using Skyscan and Scanco devices
Authors: Bonnet N. , Laroche N. , Vico L. , Dolleans E. , Courteix D. , Benhamou C. L.
Published: March 2009

Important aspects of modern skeletal research depend on the phenotypical characterization of trabecular bone microarchitecture as assessed by microcomputed tomography (micro‐CT). Until now, however, there have been no studies which compare the two most commonly utilized micro‐CT devices, namely, Skyscan and Scanco. The purpose of the current study was to examine the reproducibility and accuracy of these two micro‐CT devices in comparison to traditional histomorphometry in ovariectomized rats treated with either propranolol, salbutamol, or vehicle. 6 month old female Wistar rats were ovariectomized () or sham operated . OVX rats were divided into four groups and then subcutaneously injected with propranolol 0.1 mg/kg/day, propranolol 20 mg/kg/day, salbutamol 3 mg/kg/day, or vehicle for 10 weeks. At sacrifice, the left tibial trabecular bone microarchitecture was analyzed using both the micro‐CT Skyscan 1072 (ex vivo) and Scanco vivaCT40 (in vivo). Histomorphometric analysis was performed on the right proximal tibia. Comparisons between the different methods were performed using regression analysis, Bland‐Altman, Passing‐Bablock, and Mountain plots. Correlations were highly significant for all parameters measured between the two micro‐CT instruments and were less significant between histomorphometry and micro‐CT measurements taken from either the Skyscan or Scanco apparatus. Micro‐CT overestimated bone volume compared to histomorphometry. In the ovariectomized rat model, the two micro‐CT instruments revealed the same difference between groups whereas histomorphometry revealed only the difference which displayed the largest disparity between groups. In regards to the comparison between the two micro‐CT devices, Mountain plot methods indicated that BV/TV, BS/BV, and TbSp were equivalent, whereas a systematic bias was observed for TbN and TbTh. The authors were also able to describe the routine method used to determine the threshold between the two micro‐CT devices, which may help explain these differences. While some minor differences in the absolute values of the morphometry parameters exist between the micro‐CT measurements from the Skyscan and Scanco instruments, both of these devices display a high degree of accuracy and reproducibility.
Antibiotic Resistance in
Pseudomonas aeruginosa
Strains with Increased Mutation Frequency Due to Inactivation of the DNA Oxidative Repair System
Authors: Mandsberg L. F. , Ciofu O. , Kirkby N. , Christiansen L. E. , Poulsen H. E. , Høiby N.
Published: March 2009

The chronic
Pseudomonas aeruginosa
infection of the lungs of cystic fibrosis (CF) patients is characterized by the biofilm mode of growth and chronic inflammation dominated by polymorphonuclear leukocytes (PMNs). A high percentage of
P. aeruginosa
strains show high frequencies of mutations (hypermutators [HP]).
P. aeruginosa
is exposed to oxygen radicals, both those generated by its own metabolism and especially those released by a large number of PMNs in response to the chronic CF lung infection. Our work therefore focused on the role of the DNA oxidative repair system in the development of HP and antibiotic resistance. We have constructed and characterized
mutT
,
mutY
, and
mutM
mutants in
P. aeruginosa
strain PAO1. The
mutT
and
mutY
mutants showed 28- and 7.5-fold increases in mutation frequencies, respectively, over that for PAO1. These mutators had more oxidative DNA damage (higher levels of 7,8-dihydro-8-oxodeoxyguanosine) than PAO1 after exposure to PMNs, and they developed resistance to antibiotics more frequently. The mechanisms of resistance were increased β-lactamase production and overexpression of the MexCD-OprJ efflux-pump. Mutations in either the
mutT
or the
mutY
gene were found in resistant HP clinical isolates from patients with CF, and complementation with wild-type genes reverted the phenotype. In conclusion, oxidative stress might be involved in the development of resistance to antibiotics. We therefore suggest the possible use of antioxidants for CF patients to prevent the development of antibiotic resistance.
Antimicrobial Susceptibility and Mechanisms of Resistance in
Shigella
and
Salmonella
Isolates from Children under Five Years of Age with Diarrhea in Rural Mozambique
Authors: Mandomando Inácio , Jaintilal Dinis , Pons Maria J. , Vallès Xavier , Espasa Mateu , Mensa Laura , Sigaúque Betuel , Sanz Sergi , Sacarlal Jahit , Macete Eusébio , Abacassamo Fátima , Alonso Pedro L. , Ruiz Joaquim
Published: March 2009

The antimicrobial susceptibility and mechanisms of resistance of 109
Shigella
and 40
Salmonella
isolates from children with diarrhea in southern Mozambique were assessed. The susceptibility to seven antimicrobial agents was tested by disk diffusion, and mechanisms of resistance were searched by PCR or colorimetric method. A high proportion of
Shigella
isolates were resistant to chloramphenicol (Chl) (52%), ampicillin (Amp) (56%), tetracycline (Tet) (66%), and trimethoprim-sulfamethoxazole (Sxt) (84%). Sixty-five percent of the isolates were multidrug resistant.
Shigella flexneri
isolates were more resistant than those of
Shigella sonnei
to Amp (66% versus 0.0%,
P
< 0.001) and Chl (61% versus 0.0%,
P
< 0.001), whereas
S. sonnei
isolates presented higher resistance to Tet than
S. flexneri
isolates (93% versus 64%,
P
= 0.02). Resistance among
Salmonella
isolates was as follows: Tet and Chl, 15% each; Sxt, 18%; and Amp, 25%. Only 3% of
Salmonella
isolates were resistant to nalidixic acid (Nal), and none to ciprofloxacin or ceftriaxone (Cro). Among
Salmonella
isolates, multiresistance was found in 23%. Among
Shigella
isolates, antibiotic resistance was related mainly to the presence of
oxa-1
-like β-lactamases for Amp,
dfrA1
genes for Sxt,
tetB
genes for Tet, and Chl acetyltransferase (CAT) activity for Chl. Among
Salmonella
isolates, resistance was conferred by
tem-
like β-lactamases for Amp,
floR
genes and CAT activity for Chl,
tetA
genes for Tet, and
dfrA1
genes for Sxt. Our data show that
Shigella
isolates are resistant mostly to the most available, inexpensive antibiotics by various molecular mechanisms but remain susceptible to ciprofloxacin, Cro, and Nal, which is the first line for empirical treatment of shigellosis in the country.
High Rate of Reduced Susceptibility to Ciprofloxacin and Ceftriaxone among Nontyphoid
Salmonella
Clinical Isolates in Asia
Authors: Lee Hao-Yuan , Su Lin-Hui , Tsai Ming-Han , Kim Shin-Woo , Chang Hyun-Ha , Jung Sook-In , Park Kyung-Hwa , Perera Jennifer , Carlos Celia , Tan Ban Hock , Kumarasinghe Gamini , So Thomas , Chongthaleong Anan , Hsueh Po-Ren , Liu Jien-Wei , Song Jae-Hoon , Chiu Cheng-Hsun
Published: March 2009

This multinational study from Asia revealed that reduced susceptibility to ciprofloxacin (MIC, 0.125 to 1 μg/ml) in nontyphoid
Salmonella
isolates was common in Taiwan (48.1%) and Thailand (46.2%) and in
S. enterica
serotype Choleraesuis (68.8%) and
S
. Virchow (75.0%) from all countries. Reduced susceptibility to ceftriaxone (MIC, 2 to 8 μg/ml) remained uncommon in Asia, except in Taiwan (38.0%) or in
S
. Typhimurium (25.0%) from all countries.
Topoisomerase I Gene Mutations at F270 in the Large Subunit and N184 in the Small Subunit Contribute to the Resistance Mechanism of the Unicellular ParasiteLeishmania donovanitowards 3,3′-Diindolylmethane
Authors: Roy Amit , BoseDasgupta Somdeb , Ganguly Agneyo , Jaisankar Parasuraman , Majumder Hemanta K.
Published: March 2009

3,3′-Diindolylmethane (DIM), a novel poison targetingLeishmania donovanitopoisomerase I (LdTOP1LS), induces programmed cell death inLeishmaniaparasites. The development of resistant parasites by adaptation with increasing concentrations of DIM generates random mutations in LdTOP1LS. Single-nucleotide mutations result in the amino acid substitutions F270L and K430N in the large subunit and N184S in the small subunit of the enzyme. DIM failed to inhibit the catalytic activity of the recombinant mutant enzyme (LdTOP1DRLS). Transfection studies of the mutant genes showed that the mutated topoisomerase I confers DIM resistance on wild-typeLeishmaniaparasites. Site-directed mutagenesis studies revealed that a substantial level of resistance is conferred by the F270L mutation alone; however, all three mutations (F270L, K430N, and N184S) together are required to reach a higher-resistance phenotype. DIM fails to stabilize the topoisomerase I-DNA covalent complexes in the F270 mutant. Moreover, DIM cannot interfere with the religation step in the catalytic cycle of the recombinant F270L mutant enzyme. Taken together, these findings identify novel mutations in topoisomerase I that hinder its interaction with DNA, thereby modulating enzyme catalysis and conferring resistance to DIM. These studies advance our understanding of the mechanism of cell poisoning by DIM and suggest a specific modification of the drug that may improve its efficacy.
Articulated laticifers in the vegetative organs of Mandevilla atroviolacea (Apocynaceae, Apocynoideae)
Authors: Lopes Karina Lucas Barbosa , Thadeo Marcela , Azevedo Aristéa Alves , Soares Arlete Aparecida , Meira Renata Maria Strozi Alves
Published: March 2009

The occurrence of nonarticulated laticifers has been recorded in the literature for Apocynaceae, but little information is available on their structure and the chemical compounds in their latex. The objective of this study was to describe, anatomically and histochemically, the laticifers and latex found in the roots, stems, and leaves of Mandevilla atroviolacea (Stadelm) Woodson, a genus in the Apocynaceae. Laticifer anatomy was examined by light microscopy, and the chemical nature of the exuded latex was studied using cytochemistry. Articulated laticifers were present in M. atroviolacea. The lactiferous system in stems and leaves originated from both procambium and ground meristem, and it was determined to be functional, as indicated by changes in the cytoplasm immediately subsequent to its formation. However, in tuberous roots, laticifers originated from the vascular cambium, phellogen, and parenchymatous cortical cells. The primary wall of laticifers consists of pectins and cellulose and is thicker than that of adjacent cells. The laticifer secretion contained an emulsion of lipophilic substances rich in neutral lipids, resin oils, and possibly rubber. The presence of articulated laticifers is reported for the first time for Apocynoideae, contributing to the knowledge and understanding of these structures in the family Apocynaceae.
A new computer program for estimating the statistical significance of cross-dating positions for "floating" tree-ring series
Authors: Yamaguchi David K. , Allen George L.
Published: March 2009

CORREL is a FORTRAN program that employs cross correlation to (i) determine potential cross-dating (matching) positions for "floating" (undated) ring series; (ii) detect missing or false rings; and (iii) estimate the statistical significance of potential dating positions. To work properly, CORREL input data must be detrended and modeled using the autoregressive moving average procedure. To guard against spurious dating, the output's best date should be checked for dating consistency. The significance level of the best date is obtained by adjusting its single-dating-trial significance for multiplicity (repeated dating trials). Ideally, COREL should be used with the detrending tree-ring programs ARSTAN or INDEX, and with the data quality-control program COFECHA.
Modelling regeneration and recruitment in a tropical rain forest
Authors: Vanclay Jerome K.
Published: March 2009

A two-stage model predicts the recruitment (i.e., the number of stems reaching or exceeding 10 cm DBH) of the 100 species that account for 97% of all the recruitment observed on 217 permanent sample plots in the tropical rain forest of north Queensland. The first stage predicts the probability of the occurrence of any recruitment from stand basal area and the presence of that species in the existing stand. These probabilities can be implemented stochastically, or deterministically by summing the probabilities and initiating recruitment on unity. The second stage indicates the expected amount of recruitment, given that it is known to occur, and employs stand basal area, the relative number of trees of that species in the stand, and site quality. This approach is easily implemented in growth models and planning systems.
Tree-ring width and maximum latewood density at the North American tree line: parameters of climatic change
Authors: D'Arrigo Rosanne D. , Jacoby Gordon C. , Free Rosemary M.
Published: March 2009

In remote subarctic North America, instrumental records are very short and sparsely distributed. Yet a long-term understanding of subarctic climate is critical to studies of global change. Annual tree-ring width and maximum latewood density are complementary, high-resolution parameters with different environmental and physiological controls that can be used to assess recent centuries of climatic change. In this paper we present a comparison of the different temperature information inferred from these parameters for white spruce (Piceaglauca (Moench) Voss), a dominant North American latitudinal tree line species. Ring-width and maximum latewood density chronologies (with a common period from 1720–1977) are shown for five sites along a widely spaced transect of the forest–tundra transition in northern Canada. The positive temperature response of maximum latewood density to year to year local temperatures is more consistent and covers a longer portion of the growing season than does that of ring width. Unlike density, the ring-width data show a preference for cold spring conditions. Some, but not all, of the ring-width and density series display increases during the recent century's large-scale climatic warming trend. It is concluded that both types of parameters are necessary for understanding changes in climate and forest dynamics at the northern tree line.
Allelopathic effects by Empetrumhermaphroditum on seed germination of two boreal tree species
Authors: Zackrisson Olle , Nilsson Marie-Charlotte
Published: March 2009

Indoor and outdoor experiments demonstrated that allelopathy is an important factor explaining seed regeneration failures of Scots pine (Pinussilvestris L.) in forest floor vegetation dominated by the dwarf shrub Empetrumhermaphroditum Hagerup. Scanning electron micrograph views of the leaf surfaces of E. hermaphroditum reveal secretory glands that are shown to be involved in the release of water-soluble phytotoxic substances. Bioassays indicate that low doses and short exposure times of seeds to leachates have strong negative effects on germination and early root development. Activated carbon can eliminate the inhibitory effects of leachates and litter. This technique demonstrates the occurrence of allelopathic interference by E. hermaphroditum on seed germination of both Scots pine and aspen (Populustremula L.). In a field experiment the allelopathic effects by E. hermaphroditum are strong during early spring when germination and growth initiate and ground ice still is present. Extracts passed through soils collected from an E. hermaphroditum site were detoxified, while those passed through sterilized soil were not. Therefore, microorganisms may detoxify the allelochemicals under some environmental conditions.
Conidia of hypovirulent strains of Cryphonectriaparasitica differ in their potential for biocontrol of chestnut blight
Authors: Scibilia K.L. , Hebard F.V. , Shain L.
Published: March 2009

Conidia from eight hypovirulent strains of Cryphonectriaparasitica (Murr.) Barr were suspended in water and applied to the bark of American chestnut (Castaneadentata (Marsh.) Borkh.) trees. Cankers were initiated with mycelium of virulent strains isogenic to the applied conidia. Hypovirulent strains differed significantly in the ability of their conidia to putatively convert isogenic virulent strains in cankers, as indicated by the recovery of cultures with hypovirulent morphology from challenged cankers. A tank mix of conidia from two hypovirulent strains in different conversion groups putatively converted significantly more cankers initiated by isogenic virulent strains than did separate applications of conidia from these strains, particularly when the second application was delayed by 2 weeks. Cankers initiated on excised stems with virulent strain Ep 155 (American Type Culture Collection 38755) yielded cultures with hypovirulent morphology after application of conidia from isogenic hypovirulent strain Ep 780 at densities as low as 50 and 700 conidia/cm2 for inoculations sealed or not sealed with latex caulk, respectively.
Spatial and temporal variation in the prevalence of growth decline in red spruce populations of the northeastern United States
Authors: LeBlanc David C.
Published: March 2009

An analysis of the prevalence of individual-tree growth decline, based on reconstructed annual stemwood volume increment (AVI), was implemented on three data bases that have been used in past dendrochronological analyses of red spruce (Picearubens Sarg.) decline in the northeastern United States. This analysis focused on the proportion of individual trees that exhibited a decrease in periodic mean AVI, a decrease in the linear trend of AVI, and (or) a negative AVI trend during the most recent 20-year period. Various subpopulations within the data bases were identified by site location, elevation, and aspect, and tree size, age, and competitive status, and the proportion of individual trees exhibiting growth decline was compared among these subpopulations. Also, the prevalence of growth decline after 1960 was compared with historical levels of growth decline. Differences in prevalence of growth decline were found among the three data bases and among locations within data bases. The proportion of red spruce that exhibited growth decline after 1960 exceeded historical levels of decline for populations in New York, Vermont, and New Hampshire, but not in the northern Maine population. Weak positive associations were found between prevalence of growth decline and tree size (DBH) and elevation. No consistent relationship was found between growth decline and tree age, competitive status, or stand density. Contrary to a previous report, growth decline was not more common among trees that exhibited evidence of competitive release in the 1940s than among unreleased trees.
INFLATION AND SQUEEZED STATES: LATTICE SCHRÖDINGER PICTURE
Authors: HUANG JUNG-JENG
Published: March 2009

In lattice Schrödinger picture, the wave functionals of the squeezed vacuum states of a free real scalar field in de Sitter space are constructed explicitly in momentum space by using the method of instantaneous Hamiltonian diagonalization. The modified power spectrum and particle production in the general mixed, squeezed initial states are also presented. For the massless minimally coupled scalar field which is relevant to slow roll inflationary models, we recover the power spectrum of scalar fluctuations for the squeezed vacuum states, and show that the evolution of the squeezed vacuum states exhibits an attractor behavior. The case of a massless conformally coupled scalar field is also discussed.
THE ICT-SUPPORTED UNIFIED PROCESS MODEL OF OFFSHORE OUTSOURCING OF SOFTWARE PRODUCTION: EXPLORATORY EXAMINATION AND VALIDATION
Authors: YALAHO ANICET , NAHAR NAZMUN
Published: March 2009

Various important benefits can be achieved through the successful management of offshore outsourcing. Numerous studies exist on outsourcing in general, yet the vast majority of extant literature on offshore outsourcing has dealt with information technology (IT) outsourcing from the client's perspective. Several frameworks, focusing on guiding information systems managers in relation to IT outsourcing, have been developed. However, none of these frameworks attempted to provide a holistic guideline to manage the entire process of offshore outsourcing of software production. There is a significant lack of studies dealing with the management of offshore outsourcing of software production from both the vendor's and client's perspectives. Thus, there is a great need to study such a multifaceted and complex phenomenon more deeply for both scenarios to find out the best practices for managing the unified process. In this study, we utilize the conceptual framework of The ICT-supported Unified Process Model of Offshore Software Production Outsourcing as our research model. We then validate this model by reviewing the vast extant literature, and by conducting multiple case studies from both the vendor's and client's viewpoints, where professionals with extensive experience in managing offshore outsourcing of software production are interviewed. The implications of the findings are discussed for both practical and research purposes.
ASYMPTOTIC EXPANSION FOR DIFFERENCE EQUATIONS WITH INFINITE DELAY
Authors: Cuevas Claudio , del Campo Luis
Published: March 2009

Using summable dichotomies and Schauder's fixed point theorem, we obtain existence, asymptotic behavior and compactness properties, of convergent solutions for difference equations with infinite delay. Applications on Volterra difference equations with infinite delay are shown.
Chemokine Receptor-5Δ32 Mutation is No Risk Factor for Ischemic-Type Biliary Lesion in Liver Transplantation
Authors: Heidenhain Christoph , Puhl Gero , Moench Christian , Lautem Anja , Neuhaus Peter
Published: March 2009

It has been shown that certain chemokine receptor polymorphisms may correspond to certain complications after organ transplantation. Ischemic-type biliary lesion (ITBL) encounters for major morbidity and mortality in liver transplant recipients. So far, the exact cause for ITBL remains unclear. Certain risk factors for the development of ITBL like donor age and cold ischemic time are well described. In a previous study, a 32-nucleotide deletion of the chemokine receptor-5Δ32 (CCR-5Δ32) was strongly associated with the incidence of ITBL in adult liver transplantation. This study re-evaluates the association of CCR-5Δ32 gene polymorphism and the incidence of ITBL. 169 patients were included into this retrospective analysis. 134 patients were homozygous for wild-type CCR-5, 33 patients heterozygous, and 2 patients were homozygous for CCR-5Δ32 mutation. There were no major differences in donor or recipients demographics. No association was found between CCR-5Δ32 mutation and the development of ITBL. We conclude that CCR-5Δ32 is no risk factor for the development of ITBL in our patient cohort.
Elevated Admission Glucose and Mortality in Elderly Patients Hospitalized With Heart Failure
Authors: Kosiborod Mikhail , Inzucchi Silvio E. , Spertus John A. , Wang Yongfei , Masoudi Frederick A. , Havranek Edward P. , Krumholz Harlan M.
Published: March 2009

Background—

Although some professional societies recommend target-driven glucose control for all hospitalized patients, the association between elevated glucose and adverse outcomes has not been well established in patients hospitalized with heart failure.

Methods and Results—

We evaluated a nationally representative cohort of 50 532 elderly patients hospitalized with heart failure in the United States between April 1998 and June 2001. The association between admission glucose and all-cause mortality at 30 days and 1 year was analyzed with multivariable Cox regression models, both in the entire cohort and in patients with and without diabetes mellitus. After multivariable adjustment, no significant relationship was found between glucose and 30-day mortality (for glucose groups of >110 to 140, >140 to 170, >170 to 200, and >200 mg/dL; hazard ratios for 30-day mortality were 1.09 (95% confidence interval, 0.98 to 1.22), 1.27 (95% confidence interval, 1.11 to 1.45), 1.16 (95% confidence interval, 0.98 to 1.37), and 1.00 (95% confidence interval, 0.87 to 1.15), respectively, versus glucose ≤110 mg/dL;
P
for linear trend=0.53). Results were similar for 1-year mortality and did not differ between patients with and without known diabetes mellitus (for diabetes×glucose interaction,
P
=0.11 and 0.55 for 30-day and 1-year mortality, respectively).

Conclusions—

We found no significant association between admission glucose levels and mortality in a large cohort of patients hospitalized with heart failure. Our findings suggest that the relationship between hyperglycemia and adverse outcomes seen in acute myocardial infarction cannot be automatically extended to patients hospitalized with other cardiovascular conditions.
Reduced Myocardial Creatine Kinase Flux in Human Myocardial Infarction
Authors: Bottomley Paul A. , Wu Katherine C. , Gerstenblith Gary , Schulman Steven P. , Steinberg Angela , Weiss Robert G.
Published: March 2009

Background—

Energy metabolism is essential for myocellular viability. The high-energy phosphates adenosine triphosphate (ATP) and phosphocreatine (PCr) are reduced in human myocardial infarction (MI), reflecting myocyte loss and/or decreased intracellular ATP generation by creatine kinase (CK), the prime energy reserve of the heart. The pseudo–first-order CK rate constant, k, measures intracellular CK reaction kinetics and is independent of myocyte number within sampled tissue. CK flux is defined as the product of [PCr] and k. CK flux and k have never been measured in human MI.

Methods and Results—

Myocardial CK metabolite concentrations, k, and CK flux were measured noninvasively in 15 patients 7 weeks to 16 years after anterior MI using phosphorus magnetic resonance spectroscopy. In patients, mean myocardial [ATP] and [PCr] were 39% to 44% lower than in 15 control subjects (PCr=5.4±1.2 versus 9.6±1.1 μmol/g wet weight in MI versus control subjects, respectively,
P
<0.001; ATP=3.4±1.1 versus 5.5±1.3 μmol/g wet weight,
P
<0.001). The myocardial CK rate constant, k, was normal in MI subjects (0.31±0.08 s
−1
) compared with control subjects (0.33±0.07 s
−1
), as was PCr/ATP (1.74±0.27 in MI versus 1.87±0.45). However, CK flux was halved in MI [to 1.7±0.5 versus 3.3±0.8 μmol(g · s)
−1
;
P
<0.001].

Conclusions—

These first observations of CK kinetics in prior human MI demonstrate that CK ATP supply is significantly reduced as a result of substrate depletion, likely attributable to myocyte loss. That k and PCr/ATP are unchanged in MI is consistent with the preservation of intracellular CK metabolism in surviving myocytes. Importantly, the results support therapies that primarily ameliorate the effects of tissue and substrate loss after MI and those that reduce energy demand rather than those that increase energy transfer or workload in surviving tissue.