bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractal Characteristics of Tumor Vascular Architecture During Tumor Growth and Regression
Authors: Gazit Yuval , Baish James W. , Safabakhsh Nina , Leunig Michael , Baxter Laurence T. , Jain Rakesh K. 
Published: April 2008

ABSTRACTObjective: Tumor vascular networks are different from normal vascular networks, but the mechanisms underlying these differences are not known. Understanding these mechanisms may be the key to improving the efficacy of treatment of solid tumors.Methods: We studied the fractal characteristics of two‐dimensional normal and tumor vascular networks grown in a murine dorsal chamber preparation and imaged with an intravital microscopy station.Results: During tumor growth and regression, the vasculature in the tumor has scaling characteristics that reflect the changing state of the tissue. Growing tumors show vascular networks that progressively deviate from their normal pattern, in which they seem to follow diffusion‐limited aggregation to a pathological condition in which they display scaling similar to percolation clusters near the percolation threshold. The percolation‐like scaling indicates that the key determinants of tumor vascular architecture are local substrate properties rather than gradients of a diffusing substance, such as an angiogenic growth factor. During tumor regression, the fractal characteristics of the vasculature return to an intermediate between those of growing tumors and those of healthy tissues. Previous studies have shown that percolation‐like scaling generally inhibits transport.Conclusions: In the present context, the percolation‐like nature of tumor vasculature implies that tumor vascular networks possess inherent architectural obstacles to the delivery of diffusible substances such as oxygen and drugs.
Imaging of Oxygen Saturation and Distribution of Erythrocytes in Microvessels
Authors: Tateishi Norihiko , Suzuki Yoji , Tanaka Junya , Maeda Nobuji 
Published: April 2008

ABSTRACTObjective: To construct images of oxygen saturation and the distribution of erythrocytes in a network of microvessels.Methods: The image of a small group of microvessels under an inverted microscope was incorporated into an image processor through a video camera and was digitized. Based on the information obtained through six visible interference filters of different wavelengths, oxygen saturation and the amount of erythrocytes in microvessels were calculated with a computer. The system was applied to a microvascular bed of isolated rabbit mesentery perfused with a suspension of human erythrocytes.Results: In a steady flow, with lowering of tissue oxygen tension by superfusion with nitrogen‐bubbled isotonic saline containing 20 mmol/L sodium dithionite, the decrease of oxygen saturation of erythrocytes from arterioles to venules was imaged. Simultaneously, the distribution of erythrocytes in the microvessels was imaged and the marginal cell‐free layer was profiled under high magnification. No significant alteration of the erythrocyte distribution on the deoxygenation of erythrocytes was observed. The exposure of erythrocytes to acidic pH and the decrease of the flow velocity of erythrocytes increased the release of oxygen from the erythrocytes in microvessels.Conclusions: The present method will be useful for the comprehensive analysis of oxygen transfer in the microvascular network, on the basis of both changes of the oxygen saturation and the flow behavior of erythrocytes.
Resistance to Blood Flow in Nonuniform Capillaries
Authors: Secomb T. W. , Hsu R. 
Published: April 2008

ABSTRACTObjective: Microvessels in living tissues are not uniform cylinders, and red blood cells (RBCs) are continually deformed when traversing them. This may contribute to higher resistance to blood flow observed in microvessels compared with that in corresponding uniform glass tubes. Here, a theoretical model was used to estimate flow resistance in nonuniform capillaries and its dependence on hematocrit, flow rate, and mechanical properties of RBCs.Methods: Single‐file motion of RBCs through capillaries with sinusoidally varying cross‐sections was simulated, assuming axisymmetrical geometry. Effects of cell membrane shear viscosity and elasticity were included. Lubrication theory was used to describe the plasma flow.Results: Predicted resistance to blood flow in capillaries with variable cross‐sections was substantially higher than in uniform vessels with the same mean diameters. Resistance depended on vessel geometry, flow rate, and hematocrit. At tube hematocrit 30%, the increase in resistance was 40%–58% when diameter varied between 4.5 and 6 μm with wavelength 20 μm and 58%–77% for variations between 4 and 5 μm with wavelength 10 μm. Larger relative increases in resistance were predicted for RBCs with increased membrane shear viscosity.Conclusions: Effects of transient RBC deformations in irregular capillaries contribute significantly to blood flow resistance in capillaries. However, this effect is not sufficient to account for the flow resistance observed in living tissues.
Structural Changes in the Cardiac Microvasculature of the Rat in Response to Acute High Glucose Levels: A Comparison With Diabetes
Authors: Ward B. J. , Al‐haboubi H. A. 
Published: April 2008

ABSTRACTObjective: Isolated rat hearts were used to determine whether structural changes in the coronary microcirculation caused by diabetes mellitus occur soon after the onset of hyperglycemia and whether early changes might be reversed by return to normoglycemic conditions.Methods: Three experimental groups of hearts were used. The perfusate was Krebs‐Henseleit medium with the addition of (a) 25 mmol/L glucose for 60 minutes, (b) as (a) followed by 5 mmol/L glucose for 30 minutes, and (c) hearts from diabetic rats perfused for 15 minutes. All the hearts were fixed and processed for electron microscopy. Measurements were made of various capillary dimensions and basal lamina thickness.Results: The high glucose concentration caused an overall reduction in capillary dimensions which was partly reversed by reperfusion with 5 mmol/L glucose. Diabetic hearts showed enlarged whole capillary and luminal area and thinning of the endothelial cells without any change in cross‐sectional area. Endothelial gaps, consistent with increased permeability, were observed in the high glucose group but not in diabetic hearts. The basal lamina was thickened in all three experimental groups compared with controls.Conclusions: The results show that morphological changes in the microcirculation occur much earlier than was previously thought and, with the possible exception of the basal lamina thickening, may be reversible.
The Resistance to Flow of Individual Human Neutrophils in Glass Capillary Tubes with Diameters between 4.65 and 7.75 μm
Authors: Shao Jin‐Yu , Hochmuth Robert M. 
Published: April 2008

ABSTRACTObjective: The resistance to flow of individual human neutrophils flowing through smooth‐walled glass capillary tubes at velocities ranging between 0 and 30 μm/s is measured for six different capillary tube diameters between 4.65 and 7.75 μm.Methods: The experiments were performed with a micropipet manipulation system. The velocity of individual human neutrophils was measured under different constant pressures and compared to the velocity of the cell‐free fluid in the same tube. With the aid of a theory that describes the motion of a concentric, smooth‐walled, sausage‐shaped body in a tube, the experimental measurements are used to calculate an apparent gap width between the cell and the capillary wall.Results: The maximum calculated gap width in the larger capillary tubes was on the order of 0.1 μm, whereas the minimum gap width in the smaller capillaries was about 0.015 μm. These small gap widths mean that even one neutrophil can cause a significant increase in the apparent viscosity when a cell flows through 100‐ to 200‐μm‐long capillary tubes. The neutrophils often exhibited a small static friction that tended to increase as the capillary diameter decreased. Maximum values for the adhesive force caused by the static friction were on the order of 80 pN.Conclusions: Even a single white cell entirely within a capillary can cause a significant increase in the resistance of flow.
Can atmospheric input of nitrogen affect seed bank dynamics in habitats of conservation interest? The case of dune slacks
Authors: Plassmann Katharina , Brown Nigel , Jones M. Laurence M. , Edwards‐Jones Gareth 
Published: April 2008

Abstract.Questions: Does the increased atmospheric deposition of nitrogen, which can have major effects on the established vegetation of nutrient‐poor habitats, also impact germination from the soil seed bank?Location: Coastal dune slacks at Newborough Warren, Wales, UK.Methods: The effects of nitrogen addition (15 kg.ha‐1.a‐1) on seed germination from the soil seed bank were investigated using the seedling emergence method between September 2004 and February 2005.Results: More seedlings emerged from fertilised samples than unfertilised controls. Most species showed enhanced germination after fertilisation with nitrogen, with seedling numbers statistically significantly greater in nitrogen addition samples in a quarter of species abundant enough for analysis. Species that responded positively to fertilisation were species with low Ellenberg indicator values indicative of infertile sites.Conclusions: Most species showed increased germination after fertilisation with nitrogen, including early successional species normally growing in nutrient‐poor conditions. This suggests that the increased atmospheric deposition of nitrogen probably not only impacts on established vegetation, but also has the potential to alter seed bank dynamics.
Para-[123I]iodo-L-phenylalanine in patients with pancreatic adenocarcinoma
Authors: Gouverneur E. , Schaefer A. , Raedle J. , Menges M. , Kirsch C.-M. , Samnick S. , Hellwig D. 
Published: April 2008

SummaryRecently, p-[123I]iodo-L-phenylalanine (IPA) was clinically validated for brain tumour imaging. Preclinical studies demonstrated uptake of IPA into pancreatic adenocarcinoma suggesting its diagnostic application in patients with pancreatic tumours. The aim was to study the tumour uptake of IPA in patients with pancreatic adenocarcinoma and to analyse its biodistribution and dosimetry to assess the radiation dose resulting from its diagnostic use. Patients, methods: Seven patients with pancreatic adenocarcinoma underwent whole-body scintigraphies and SPECT up to 24 h after administration of 250 MBq of IPA. Tumour uptake of IPA was assessed visually. Time activity curves and the corresponding residence times were determined for whole-body, kidneys, liver, spleen, lung, heart content, brain, and testes. Mean absorbed doses for various organs and the effective dose were assessed based on the MIRD formalism using OLINDA/EXM. Results: IPA exhibited no accumulation in proven manifestations of pancreatic adenocarcinomas. IPA was exclusively eliminated by the urine and showed a delayed clearance from blood. Residence times were 0.26 ± 0.09 h for kidneys, 0.38 ± 0.19 h for liver, 0.15 ± 0.07 h for spleen, 0.51 ± 0.20 h for lungs, 0.22 ± 0.07 h for heart content, 0.11 ± 0.05 h for brain, 0.014 ± 0.005 h for testes and 6.4 ± 2.2 h for the remainder. The highest absorbed doses were determined in the urinary bladder wall and in the kidneys. According to the ICRP 60 the effective dose resulting from 250 MBq IPA was 3.6 ± 0.7 mSv. Conclusion: Para-[123I]iodo-L-phenylalanine can be used in diagnostic nuclear medicine with acceptable radiation doses. Besides its proven validity for brain tumour imaging, IPA does not appear to be suitable as tracer for pancreatic cancer.
Myocardial perfusion scintigraphy 2006 in Germany
Authors: Burchert W. , Bengel F. M. , Zimmermann R. , vom Dahl J. , Schäfer W. , Schober O. , Kluge R. , Schäfers M. , Lindner O. 
Published: April 2008

SummaryAim: This second survey was to deliver further information on myocardial perfusion scintigraphy (MPS) in Germany in 2006. Method: 351 questionnaires were evaluated: 207 private practices (PP), 117 hospitals (HO), 27 from university hospitals (UH). Results: MPS of 106 331 patients were reported, 85% were investigated with 99mTc-perfusion tracers. 74% [2005=72%] were performed in PP, 17% [2005=15%] in HO and 9% [2005=13%] in UH. PP, which participated in 2005 and 2006, demonstrated an increase by 3,9% (HO 0%, UH –13,0%). The type of stress was pharmacological in 27% [2005=22%]; 54% adenosine (of these 29% with exercise), 37% dipyridamole (of these 56% with exercise), and 9% dobutamine. Gated SPECT was performed in 42% [2005=36%] of all restand in 39% [2005=32%] of all stress MPS. An attenuation correction was used by 69 [2005=78] institutions. 40% of all MPS were performed in patients suspected to have CAD. 24% of all institutions reported changes in the use of MPS by competing methods. Conclusion: There is a small increase of MPS between 2005 and 2006 despite competing methods. Gated SPECT has experienced more acceptance. Suspicion of CAD is an important indication of MPS. In order to tap the full potential of MPS a gated SPECT should be performed routinely.
Biomarkers for detection of prenatal alcohol exposure: A critical review of fatty acid ethyl esters in meconium
Authors: Burd Larry , Hofer Ryan 
Published: April 2008

AbstractBACKGROUND: The objective of this study was a review of published studies utilizing measurement of fatty acid ethyl esters (FAEE) in meconium as biomarkers for prenatal alcohol exposure. METHODS: We completed a literature search of PubMed using the terms meconium, fatty acid ethyl esters, biomarkers, and prenatal alcohol exposure. We included only peer reviewed studies utilizing analysis of meconium for the presence of FAEE in humans through the year 2007. RESULTS: We found 10 articles reporting on original research examining the relationship of FAEE from meconium and prenatal alcohol exposure (PAE). The 10 articles used six different PAE assessment strategies and four different analytical techniques for determining FAEE endpoints. The articles included 2,221 subjects (range 4 to 725) with 455 (20.5%) subjects identified as exposed using the methods stated in the articles. FAEE levels above the studies' respective cutoffs were reported for 502 (22.6%) subjects. CONCLUSIONS: The accurate identification of alcohol‐exposed pregnancies represents a significant challenge in the development of FAEE detection cutoffs to maximize the sensitivity and specificity of the test. We present several options for the improvement of exposure assessment in future studies of FAEE as biomarkers for PAE. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.
A high‐throughput screen for hyaluronic acid accumulation in recombinant Escherichia coli transformed by libraries of engineered sigma factors
Authors: Yu Huimin , Tyo Keith , Alper Hal , Klein‐Marcuschamer Daniel , Stephanopoulos Gregory 
Published: April 2008

AbstractHyaluronic acid (HA) is an important biomaterial with functional medical and cosmetic applications. As its synthesis has been recently reported in recombinant bacteria, it is of interest to develop a high throughput screening method for the rapid isolation of HA accumulating strains transformed by combinatorial libraries. Here we report a novel two‐step screening strategy to select for better HA‐producing recombinant Escherichia coli strains transformed by mutation libraries of rpoD and rpoS, coding for the σD and σS factors of the RNA polymerase, respectively. The first screen, based on translucent colony morphology identification, was used to qualitatively distinguish HA‐producing strains on agar plates from non‐HA producing strains that exhibit dense colony morphology. The second screen was based on the photometric measurement of an alcian blue staining solution that precipitates with HA, creating an inverse relationship between HA concentration and alcian blue absorbance. The color attenuation fitted a second‐order polynomial between HA concentration and OD540 absorbance. Using the alcian blue absorbance quantification, 74 translucent colonies from the HA‐rpoD library and 78 translucent colonies from the HA‐rpoS library were isolated and cultured for optimal strain selection. Three representative superior recombinants with high, medium and low increase of HA accumulation, respectively, were identified by the screen from the HA‐rpoD and HA‐rpoS mutant library. Further flask culture confirmed that results of the library screen were reliable and the superior recombinant D72 highly accumulated HA of 561.4 mg/L with a productivity of ∼265 mg HA/g dry cell. Sequencing results showed that the mutant rpoD gene in D72 is in a truncated protein that lacks the conserved regions 3 and 4 of the σD. Generally, this two‐step high throughput screen presents a promising strategy for selecting superior HA‐producing strains from large scale mutation libraries. Biotechnol. Bioeng. 2008;101: 788–796. © 2008 Wiley Periodicals, Inc.
High‐efficiency hydrogen production by an anaerobic, thermophilic enrichment culture from an Icelandic hot spring
Authors: Koskinen Perttu E.P. , Lay Chyi‐How , Puhakka Jaakko A. , Lin Ping‐Jei , Wu Shu‐Yii , Örlygsson Jóhann , Lin Chiu‐Yue 
Published: April 2008

AbstractDark fermentative hydrogen production from glucose by a thermophilic culture (33HL), enriched from an Icelandic hot spring sediment sample, was studied in two continuous‐flow, completely stirred tank reactors (CSTR1, CSTR2) and in one semi‐continuous, anaerobic sequencing batch reactor (ASBR) at 58°C. The 33HL produced H2 yield (HY) of up to 3.2 mol‐H2/mol‐glucose along with acetate in batch assay. In the CSTR1 with 33HL inoculum, H2 production was unstable. In the ASBR, maintained with 33HL, the H2 production enhanced after the addition of 6 mg/L of FeSO4 · 7H2O resulting in HY up to 2.51 mol‐H2/mol‐glucose (H2 production rate (HPR) of 7.85 mmol/h/L). The H2 production increase was associated with an increase in butyrate production. In the CSTR2, with ASBR inoculum and FeSO4 supplementation, stable, high‐rate H2 production was obtained with HPR up to 45.8 mmol/h/L (1.1 L/h/L) and HY of 1.54 mol‐H2/mol‐glucose. The 33HL batch enrichment was dominated by bacterial strains closely affiliated with Thermobrachium celere (99.8–100%). T. celere affiliated strains, however, did not thrive in the three open system bioreactors. Instead, Thermoanaerobacterium aotearoense (98.5–99.6%) affiliated strains, producing H2 along with butyrate and acetate, dominated the reactor cultures. This culture had higher H2 production efficiency (HY and specific HPR) than reported for mesophilic mixed cultures. Further, the thermophilic culture readily formed granules in CSTR and ASBR systems. In summary, the thermophilic culture as characterized by high H2 production efficiency and ready granulation is considered very promising for H2 fermentation from carbohydrates. Biotechnol. Bioeng. 2008;101: 665–678. © 2008 Wiley Periodicals, Inc.
NS0 cell damage by high gas velocity sparging in protein‐free and cholesterol‐free cultures
Authors: Zhu Ying , Cuenca James V. , Zhou Weichang , Varma Amit 
Published: April 2008

AbstractRecent developments in high cell density and high productivity fed‐batch animal cell cultures have placed a high demand on oxygenation and carbon dioxide removal in bioreactors. The high oxygen demand is often met by increasing agitation and sparging rates of air/O2 in the bioreactors. However, as we demonstrate in this study, an increase of gas sparging can result in cell damage at the sparger site due to high gas entrance velocities. Previous studies have showed that gas bubble breakup at the culture surface was primarily responsible for cell damage in sparged bioreactors. Such cell damage can be reduced by use of surfactants such as Pluronic F‐68 in the culture. In our results, where NS0 cells were grown in a protein‐free and cholesterol‐free medium containing 0.5 g/L Pluronic F‐68, high gas entrance velocity at the sparger site was observed as the second mechanism for cell damage. Experiments were performed in scaled‐down spinners to model the effect of hydrodynamic force resulting from high gas velocities on antibody‐producing NS0 cells. Cell growth and cell death were described by first‐order kinetics. Cell death rate constant increased significantly from 0.04 to 0.18 day−1 with increasing gas entrance velocity from 2.3 to 82.9 m/s at the sparger site. The critical gas entrance velocity for the NS0 cell line studied was found to be ∼30 m/s; velocities greater than 30 m/s caused cell damage which resulted in reduced viability and consequently reduced antibody production. Observations from a second cholesterol‐independent NS0 cell line confirmed the occurrence of cell damage due to high gas velocities. Increasing the concentration of Pluronic F‐68 from 0.5 to 2 g/L had no additional protective effect on cell damage associated with high gas velocity at the sparger. The results of gas velocity analysis for cell damage have been applied in two case studies of large‐scale antibody manufacturing. The first is a troubleshooting study for antibody production carried out in a 600 L bioreactor, and the second is the development of a gas sparger design for a large bioreactor scale (e.g., 10,000 L) for antibody manufacturing. Biotechnol. Bioeng. 2008;101: 751–760. © 2008 Wiley Periodicals, Inc.
Late free atrial wall rupture after percutaneous atrial septal defect closure and transvenous pacemaker implantation
Authors: Huysmans Wim , Budts Werner 
Published: April 2008

AbstractWe report a remarkable case of right atrial rupture, 3 years after transcatheter closure of a secundum atrial septal defect, and 7 months after permanent transvenous two‐chamber pacemaker implantation. The etiology of the rupture remains unclear, but the presence of the two intracardiac devices is probably not coincidental. © 2008 Wiley‐Liss, Inc.
Percutaneous aortic valve replacement in patients with challenging aortoiliofemoral access
Authors: Jilaihawi Hasan , Spyt Tomasz , Chin Derek , Logtens Elaine , Laborde Jean‐Claude , Kovac Jan 
Published: April 2008

AbstractPercutaneous aortic valve replacement (PAVR) offers considerable promise in treating high risk patients with aortic valve disease. Two devices are currently clinically available for transfemoral delivery: the Edwards‐Sapien balloon‐expandable bioprosthesis and the Corevalve self‐expanding bioprosthesis, both of which require careful sizing of the peripheral vasculature. Through a case based discussion, we illustrate that these limits of PAVR technology can be stretched in cases of extraordinary clinical need. We demonstrate that, following a learning curve of “optimal cases,” successful PAVR is also possible in diffusely diseased peripheries of borderline small size or with focal aortoiliofemoral disease amenable to a separate intervention beforehand. © 2008 Wiley‐Liss, Inc.