bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infection Dynamics and Response to Chemotherapy in a Rabbit Model of Tuberculosis using [
18
F]2-Fluoro-Deoxy-
d
-Glucose Positron Emission Tomography and Computed Tomography
Authors: Via Laura E. , Schimel Dan , Weiner Danielle M. , Dartois Veronique , Dayao Emmanuel , Cai Ying , Yoon Young-Soon , Dreher Matthew R. , Kastenmayer Robin J. , Laymon Charles M. , Carny J. Eoin , Flynn JoAnne L. , Herscovitch Peter , Barry Clifton E. 
Published: June 2012

ABSTRACT

With a host of new antitubercular chemotherapeutics in development, methods to assess the activity of these agents beyond mouse efficacy are needed to prioritize combinations for clinical trials. Lesions in
Mycobacterium tuberculosis
-infected rabbits are hypoxic, with histopathologic features that closely resemble those of human tuberculous lesions. Using [
18
F]2-fluoro-deoxy-
d
-glucose ([
18
F]FDG) positron emission tomography–computed tomography (PET-CT) imaging, we studied the dynamics of tuberculosis infection in rabbits, revealing an initial inflammatory response followed by a consolidative chronic disease. Five weeks after infection, as much as 23% of total lung volume was abnormal, but this was contained and to some extent reversed naturally by 9 weeks. During development of this chronic state, individual lesions in the same animal had very different fates, ranging from complete resolution to significant progression. Lesions that remained through the initial stage showed an increase in volume and tissue density over time by CT. Initiation of chemotherapy using either isoniazid (INH) or rifampin (RIF) during chronic infection reduced bacterial load with quantitative changes in [
18
F]FDG uptake, lesion density and total lesion volume measured by CT. The [
18
F]FDG PET uptake in lesions was significantly reduced with as little as 1 week of treatment, while the volume and density of lesions changed more slowly. The results from this study suggest that rabbits may be a useful surrogate species for evaluating novel chemotherapies and understanding changes in both PET and CT scans in human clinical trials.
Bifunctional CD4–DC-SIGN Fusion Proteins Demonstrate Enhanced Avidity to gp120 and Inhibit HIV-1 Infection and Dissemination
Authors: Du Tao , Hu Kai , Yang Jun , Jin Jing , Li Chang , Stieh Daniel , Griffin George E. , Shattock Robin J. , Hu Qinxue 
Published: June 2012

ABSTRACT

Early stages of mucosal infection are potential targets for HIV-1 prevention. CD4 is the primary receptor in HIV-1 infection whereas DC-SIGN likely plays an important role in HIV-1 dissemination, particularly during sexual transmission. To test the hypothesis that an inhibitor simultaneously targeting both CD4 and DC-SIGN binding sites on gp120 may provide a potent anti-HIV strategy, we designed constructs by fusing the extracellular CD4 and DC-SIGN domains together with varied arrangements of the lengths of CD4, DC-SIGN and the linker. We expressed, purified and characterized a series of soluble CD4-linker–DC-SIGN (CLD) fusion proteins. Several CLDs, composed of a longer linker and an extra neck domain of DC-SIGN, had enhanced affinity for gp120 as evidenced by molecular-interaction analysis. Furthermore, such CLDs exhibited significantly enhanced neutralization activity against both laboratory-adapted and primary HIV-1 isolates. Moreover, CLDs efficiently inhibited HIV-1 infection in
trans
via a DC-SIGN-expressing cell line and primary human dendritic cells. This was further strengthened by the results from the human cervical explant model, showing that CLDs potently prevented both localized and disseminated infections. This is the first time that soluble DC-SIGN-based bifunctional proteins have demonstrated anti-HIV potency. Our study provides proof of the concept that targeting both CD4 and DC-SIGN binding sites on gp120 represents a novel antiviral strategy. Given that DC-SIGN binding to gp120 increases exposure of the CD4 binding site and that the soluble forms of CD4 and DC-SIGN occur
in vivo
, further improvement of CLDs may render them potentially useful in prophylaxis or therapeutics.
Understanding the Molecular Determinants of Substrate and Inhibitor Specificities in the Carbapenemase KPC-2: Exploring the Roles of Arg220 and Glu276
Authors: Papp-Wallace Krisztina M. , Taracila Magdalena A. , Smith Kerri M. , Xu Yan , Bonomo Robert A. 
Published: June 2012

ABSTRACT

β-Lactamases are important antibiotic resistance determinants expressed by bacteria. By studying the mechanistic properties of β-lactamases, we can identify opportunities to circumvent resistance through the design of novel inhibitors. Comparative amino acid sequence analysis of class A β-lactamases reveals that many enzymes possess a localized positively charged residue (e.g., R220, R244, or R276) that is critical for interactions with β-lactams and β-lactamase inhibitors. To better understand the contribution of these residues to the catalytic process, we explored the roles of R220 and E276 in KPC-2, a class A β-lactamase that inactivates carbapenems and β-lactamase inhibitors. Our study reveals that substitutions at R220 of KPC-2 selectively impact catalytic activity toward substrates (50% or greater reduction in
k
cat
/

K
m

). In addition, we find that residue 220 is central to the mechanism of β-lactamase inhibition/inactivation. Among the variants tested at Ambler position 220, the R220K enzyme is relatively “inhibitor susceptible” (

K
i

of 14 ± 1 μM for clavulanic acid versus

K
i

of 25 ± 2 μM for KPC-2). Specifically, the R220K enzyme is impaired in its ability to hydrolyze clavulanic acid compared to KPC-2. In contrast, the R220M substitution enzyme demonstrates increased

K
m

values for β-lactamase inhibitors (>100 μM for clavulanic acid versus 25 ± 3 μM for the wild type [WT]), which results in inhibitor resistance. Unlike other class A β-lactamases (i.e., SHV-1 and TEM-1), the amino acid present at residue 276 plays a structural rather than kinetic role with substrates or inhibitors. To rationalize these findings, we constructed molecular models of clavulanic acid docked into the active sites of KPC-2 and the “relatively” clavulanic acid-susceptible R220K variant. These models suggest that a major 3.5-Å shift occurs of residue E276 in the R220K variant toward the active S70 site. We anticipate that this shift alters the shape of the active site and the positions of two key water molecules. Modeling also suggests that residue 276 may assist with the positioning of the substrate and inhibitor in the active site. These biochemical and molecular modeling insights bring us one step closer to understanding important structure-activity relationships that define the catalytic and inhibitor-resistant profile of KPC-2 and can assist the design of novel compounds.
Identification of Signaling Pathways Mediating Cell Cycle Arrest and Apoptosis Induced by Porphyromonas gingivalis in Human Trophoblasts
Authors: Inaba Hiroaki , Kuboniwa Masae , Sugita Hideyuki , Lamont Richard J. , Amano Atsuo 
Published: June 2012

ABSTRACT

Epidemiological and interventional studies of humans have revealed a close association between periodontal diseases and preterm delivery of low-birth-weight infants.
Porphyromonas gingivalis
, a periodontal pathogen, can translocate to gestational tissues following oral-hematogenous spread. We previously reported that
P. gingivalis
invades extravillous trophoblast cells (HTR-8) derived from the human placenta and inhibits proliferation through induction of arrest in the G
1
phase of the cell cycle. The purpose of the present study was to identify signaling pathways mediating cellular impairment caused by
P. gingivalis
. Following
P. gingivalis
infection, the expression of Fas was induced and p53 accumulated, responses consistent with response to DNA damage. Ataxia telangiectasia- and Rad3-related kinase (ATR), an essential regulator of DNA damage checkpoints, was shown to be activated together with its downstream signaling molecule Chk2, while the p53 degradation-related protein MDM2 was not induced. The inhibition of ATR prevented both G
1
arrest and apoptosis caused by
P. gingivalis
in HTR-8 cells. In addition, small interfering RNA (siRNA) knockdown of p53 abrogated both G
1
arrest and apoptosis. The regulation of apoptosis was associated with Ets1 activation. HTR-8 cells infected with
P. gingivalis
exhibited activation of Ets1, and knockdown of Ets1 with siRNA diminished both G
1
arrest and apoptosis. These results suggest that
P. gingivalis
activates cellular DNA damage signaling pathways that lead to G
1
arrest and apoptosis in trophoblasts.
Role of Lipid Rafts and Flagellin in Invasion of Colonic Epithelial Cells by Shiga-Toxigenic Escherichia coli O113:H21
Authors: Rogers Trisha J. , Thorpe Cheleste M. , Paton Adrienne W. , Paton James C. 
Published: June 2012

ABSTRACT

Shiga-toxigenic
Escherichia coli
(STEC) O113:H21 strains that lack the locus of enterocyte effacement (LEE) efficiently invade eukaryotic cells
in vitro
, unlike LEE-positive O157:H7 strains. We used a
fliC
deletion mutant of the O113:H21 STEC strain 98NK2 (98NK2Δ
fliC
) to show that invasion of colonic epithelial (HCT-8) cells is heavily dependent on production of flagellin, even though adherence to the cells was actually enhanced in the mutant. Flagellin binds and signals through Toll-like receptor 5 (TLR5), but there was no evidence that either TLR5, the adaptor protein myeloid differentiation primary response gene 88 (MyD88), or the serine kinase interleukin-1 receptor-associated kinase (IRAK) were required for invasion of HCT-8 cells by strain 98NK2, as judged by transfection, RNA knockdown, or inhibitor studies. However, pretreatment of cells with anti-asialo-GM1 significantly decreased 98NK2 invasion (by 40.8%), while neuraminidase treatment (which cleaves terminal sialic acid residues, thus converting GM1 into asialo-GM1) significantly increased invasion (by 70.7%). Pretreatment of HCT-8 cells with either the cholesterol-depleting agent methyl-β-cyclodextrin (MβCD) or the tyrosine kinase inhibitor genistein significantly decreased invasion by 98NK2, indicating a potential role for lipid rafts in the invasion mechanism. Confocal microscopy also showed invading 98NK2 colocalized with lipid raft markers caveolin-1 and GM1. Interestingly, anti-asialo-GM1, neuraminidase, MβCD, and genistein have similar effects on the vestigial level of STEC invasion seen for STEC strain 98NK2Δ
fliC
, indicating that lipid rafts mediate a common step in flagellin-dependent and flagellin-independent cellular invasion.
Confirmation of hybridity using GISH and determination of 18S rDNA copy number using FISH in interspecific F1hybrids ofTecoma(Bignoniaceae)
Authors: Contreras Ryan N. , Ruter John M. , Conner Joann , Zeng Yajuan , Ozias-Akins Peggy 
Published: June 2012

Interspecific hybridization in Tecoma Juss. was conducted to develop novel forms for the nursery industry. We report fertile hybrids from the cross T. garrocha Hieron. (pistillate parent) × T. stans (L.) Juss. ex Kunth. Leaf morphology of the F1hybrids of T. garrocha × T. stans was intermediate between the parents. GISH also confirmed hybridity. The F1hybrids were successfully backcrossed to both parents and self-pollinated to produce BC and F2progeny. Tecoma garrocha , T. stans, and T. guarume A. DC. ‘Tangelo’ were self-fertile. The F1hybrids also were crossed with T. capensis (Thunb.) Lindl. and T. guarume ‘Tangelo’, resulting in three-species hybrids. FISH conducted on F1hybrids identified four copies of the 18S internal transcribed spacer region. Further analysis using FISH has the potential to provide information on the evolution of Bignoniaceae and the potential role of polyploidy.
Integrated cytogenetic, ecological, and DNA barcode study reveals cryptic diversity inSimulium(Gomphostilbia)angulistylum(Diptera: Simuliidae)
Authors: Pramual Pairot , Kuvangkadilok Chaliow 
Published: June 2012

An integrated approach based on cytogenetics, molecular genetics, and ecology was used to examine diversity in the black fly Simulium angulistylum Takaoka & Davies in Thailand. Cytological analysis revealed three cytoforms (A, B, and C) of S. angulistylum differentiated by fixed chromosome inversions. Distributions of these cytoforms were associated with ecology. Cytoforms A and B were found in low-altitude habitats (<600 m above sea level), whereas cytoform C occurred at high altitudes (>1000 m above sea level). Mitochondrial DNA sequences of the cytochrome oxidase subunit I barcoding region revealed significant genetic differentiation among the cytoforms. The mitochondrial DNA haplotype network revealed divergent lineages within cytoforms, indicating additional hidden diversity. Therefore, integrated approaches are necessary for fully understanding black fly biodiversity. Population genetic analysis revealed high genetic structuring that could be due to the habitat preferences of S. angulistylum. Phylogeographic analyses indicated population demographic expansion at the mid-Pleistocene (900 000 years ago), which is older than for other black flies and insects in the Southeast Asian mainland. The high level of genetic structure and diversity, therefore, could also be due to the long demographic history of S. angulistylum.
Platelets selectively enhance lymphocyte adhesion on subendothelial matrix under arterial flow conditions
Authors: Ersoy Maria , Hjemdahl Paul , Savion Naphtali , Varon David , Spectre Galia , Zhu Linjing , Li Nailin 
Published: June 2012

SummaryPlatelet adhesion at sites of cardiovascular injury may facilitate leukocyte deposition. We asked if and how platelets enhance lymphocyte adhesion on different subendothelial matrix protein (SEMP)-coated surface at arterial shear stress. Hirudinised whole blood was subjected to an arterial shear rate (500 s−1) in a Cone and Plate(let) analyser (CPA) for 5 minutes using plates coated with bovine serum albumin (BSA), collagen, fibrinogen, von Willebrand factor (vWF), or fibronectin. Platelet and lymphocyte adhesion were monitored by CPA and flow cytometry. Exposure of blood to collagen, fibrinogen, and vWF-coated surfaces induced platelet activation. The most marked effect was seen with collagen-coating, which markedly enhanced the adhesion of all lymphocyte subpopulations compared to BSA-coating. Fibrinogen-coating supported both T and NK cell adhesion, while vWF-coated surface only enhanced NK cell deposition. In contrast, fibronectin enhanced neither platelet activation nor lymphocyte adhesion. Moreover, platelets preferentially facilitated adhesion of large CD4+ and CD8+ T cells and NK cells, and of small B cells. Enhanced cell adhesion of larger lymphocytes was associated with elevated platelet conjugation and higher lymphocyte expression of PSGL-1, Mac-1, and CD40L. The enhancement of lymphocyte adhesion was totally platelet-dependent, and was abolished in platelet-depleted blood. Moreover, blockade of the platelet adhesion molecules P-selectin, GPIIb/IIIa, and CD40L attenuated platelet-dependent lymphocyte deposition. In conclusion, platelets support lymphocyte adhesion on SEMP-coated surfaces under arterial shear. The enhancement is selective for large T and NK cells and small B cells.
Arginine restores cholinergic relaxation of hypercholesterolemic rabbit thoracic aorta.
Authors: Cooke J P , Andon N A , Girerd X J , Hirsch A T , Creager M A 
Published: June 2012

BACKGROUND
Reduced synthesis of endothelium-derived relaxing factor (EDRF) may explain impaired endothelium-dependent vasodilation in hypercholesterolemia. Accordingly, we designed studies to determine if endothelium-dependent relaxation in hypercholesterolemic rabbits may be restored by supplying L-arginine, the precursor of EDRF.

METHODS AND RESULTS
Normal or hypercholesterolemic rabbits received intravenous L-arginine (10 mg/kg/min) or vehicle for 70 minutes. Subsequently, animals were killed, thoracic aortas were harvested, and vascular rings were studied in vitro. Rings were contracted by norepinephrine and relaxed by acetylcholine chloride or sodium nitroprusside. Vasorelaxation was quantified by determining the maximal response (expressed as percent relaxation of the contraction) and the ED50 (dose of drug inducing 50% relaxation; expressed as -log M). In vessels from hypercholesterolemic animals receiving vehicle, there was a fivefold rightward shift in sensitivity to acetylcholine compared with normal animals (p = 0.05, n = 5 in each group). In vessels from hypercholesterolemic animals, L-arginine augmented the maximal response to acetylcholine (83 +/- 16% versus 60 +/- 15%, p = 0.04 versus vehicle) and increased the sensitivity to acetylcholine (ED50 value: 6.7 +/- 0.2 versus 6.2 +/- 0.2, p less than 0.05 versus vehicle). Arginine did not affect maximal and EC50 responses to acetylcholine in vessels from normal animals. Arginine did not potentiate endothelium-independent responses in either group.

CONCLUSIONS
We conclude that the endothelium-dependent relaxation is normalized in hypercholesterolemic rabbit thoracic aorta by in vivo exposure to L-arginine, the precursor for EDRF.
What is the best predictor of spontaneous ventricular tachycardia and sudden death after myocardial infarction?
Authors: Richards D A , Byth K , Ross D L , Uther J B 
Published: June 2012

BACKGROUND
Death during the first year after myocardial infarction is most commonly due to spontaneous ventricular tachycardia (VT) or fibrillation (VF). The purpose of this study was to compare, in a single cohort of patients, the values of inducible VT, delayed ventricular activation, low left ventricular ejection fraction, high-grade ventricular ectopy, and ST segment displacement on exercise in predicting electrical events (witnessed instantaneous death and spontaneous VT or VF) during the first year after myocardial infarction.

METHODS AND RESULTS
Three hundred sixty one patients aged less than 71 years underwent electrophysiological study, signal-averaged electrocardiogram, gated blood-pool scan, 24 hour ambulatory electrocardiographic monitoring, and exercise testing 1-2 weeks after myocardial infarction and were then followed up for at least 1 year. There were 34 deaths (eight witnessed instantaneous, 26 other), and nine patients survived one or more episodes of spontaneous VF or VT. Patients with inducible VT were 15.2 times more likely to suffer electrical events than patients without inducible VT. No proportional-hazards model excluding inducible VT was as good a predictor of electrical events as was inducible VT alone.

CONCLUSIONS
Inducible VT at electrophysiological study was the single best predictor of spontaneous VT and sudden death after myocardial infarction.
Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure.
Authors: Mancini D M , Eisen H , Kussmaul W , Mull R , Edmunds L H , Wilson J R 
Published: June 2012

BACKGROUND
Optimal timing of cardiac transplantation in ambulatory patients with severe left ventricular dysfunction is often difficult. To determine whether measurement of peak oxygen consumption (VO2) during maximal exercise testing can be used to identify patients in whom transplantation can be safely deferred, we prospectively performed exercise testing on all ambulatory patients referred for transplant between October 1986 and December 1989.

METHODS AND RESULTS
Patients were assigned into one of three groups on the basis of exercise data: Group 1 (n = 35) comprised patients accepted for transplant (VO2 less than or equal to 14 ml/kg/min); group 2 (n = 52) comprised patients considered too well for transplant (VO2 greater than 14 ml/kg/min); and group 3 (n = 27) comprised patients with low VO2 rejected for transplant due to noncardiac problems. All three groups were comparable in New York Heart Association functional class, ejection fraction, and cardiac index (p = NS). Pulmonary capillary wedge pressure was significantly lower in group 2 than in either group 1 or 3 (p less than 0.05), although there was wide overlap. Patients with preserved exercise capacity (group 2) had cumulative 1- and 2-year survival rates of 94% and 84%, which are equal to survival levels after transplantation. In contrast, patients rejected for transplant (group 3) had survival rates of only 47% at 1 year and 32% at 2 years, whereas patients awaiting transplantation (group 1) had a survival rate of 70% at 1 year (both p less than 0.005 versus patients with VO2 greater than 14 ml/kg/min). All deaths in group 2 were sudden. By univariate and multivariate analyses, peak VO2 was the best predictor of survival, with only pulmonary capillary wedge pressure providing additional prognostic information.

CONCLUSIONS
These data suggest that cardiac transplantation can be safely deferred in ambulatory patients with severe left ventricular dysfunction and peak exercise VO2 of more than 14 ml/min/kg.
Thallium reinjection after stress-redistribution imaging. Does 24-hour delayed imaging after reinjection enhance detection of viable myocardium?
Authors: Dilsizian V , Smeltzer W R , Freedman N M , Dextras R , Bonow R O 
Published: June 2012

BACKGROUND
Thallium reinjection immediately after conventional stress-redistribution imaging improves the detection of viable myocardium, as many myocardial regions with apparently "irreversible" thallium defects on standard 3-4-hour redistribution images manifest enhanced thallium uptake after reinjection. Because the 10-minute period between reinjection and imaging may be too short, the present study was designed to determine whether 24-hour imaging after thallium reinjection provides additional information regarding myocardial viability beyond that obtained by imaging shortly after reinjection.

METHODS AND RESULTS
We studied 50 patients with chronic stable coronary artery disease undergoing exercise thallium tomography, radionuclide angiography, and coronary arteriography. Immediately after the 3-4-hour redistribution images were obtained, 1 mCi thallium was injected at rest, and images were reacquired at 10 minutes and 24 hours after reinjection. The stress, redistribution, reinjection, and 24-hour images were then analyzed qualitatively and quantitatively. Of the 127 abnormal myocardial regions on the stress images, 55 had persistent defects on redistribution images by qualitative analysis, of which 25 (45%) demonstrated improved thallium uptake after reinjection. At the 24-hour study, 23 of the 25 regions (92%) with previously improved thallium uptake by reinjection showed no further improvement. Similarly, of the 30 regions determined to have irreversible defects after reinjection, 29 (97%) remained irreversible on 24-hour images. These findings were confirmed by the quantitative analysis. The mean normalized thallium activity in regions with enhanced thallium activity after reinjection increased from 57 +/- 13% on redistribution studies to 70 +/- 14% after reinjection but did not change at 24 hours (71 +/- 14%). In regions with irreversible defects that were unaltered by reinjection, mean regional thallium activity did not differ from the reinjection to the 24-hour studies (57 +/- 17% and 58 +/- 17%, respectively). Twenty-four-hour imaging after reinjection showed improvement in only four of 35 irreversible regions (involving three of the 50 patients).

CONCLUSIONS
These data indicate that thallium reinjection at rest after 3-4 hours of redistribution provides most of the clinically relevant information pertaining to myocardial viability in regions with apparently irreversible thallium defects. Hence, thallium reinjection may be used instead of 24-hour imaging in most patients in whom a persistent thallium defect is observed on conventional redistribution images.