bluuebunny/crossref_metadata_2025 huggingface dataset:
Harnessing the potential of communication-mediating domains for the biocombinatorial synthesis of nonribosomal peptides
Authors: Hahn Martin , Stachelhaus Torsten
Published: January 2006

The interaction between enzymes of a nonribosomal peptide synthetase (NRPS) complex relies on the interplay of compatible sets of donor and acceptor communication-mediating (COM) domains. Hence, these domains are essential for the formation of a defined biosynthetic template, thereby directing the synthesis of a specific peptide product. Without the selectivity provided by different sets of COM domains, NRPSs should form random biosynthetic templates, which would ultimately lead to combinatorial peptide synthesis. This study aimed to exploit this inherent combinatorial potential of COM domains. Based on sequence alignments between COM domains, the crosstalk between different biosynthetic systems was predicted and experimentally proven. Furthermore, key residues important for maintaining (or preventing) NRPS interaction were identified. Point mutation of one of these key residues within the acceptor COM domain of TycC1 was sufficient to shift its selectivity from the cognate donor COM of TycB3 toward the noncognate donor COM domain of TycB1. Finally, an artificial NRPS complex was constructed, constituted of enzymes derived from three different biosynthetic systems. By virtue of domain fusions, the interactions between all enzymes were established by the same set of COM domains. Because of the abrogated selectivity, this universal communication system was able to simultaneously form two biosynthetic complexes that catalyzed the combinatorial synthesis of different peptide products.
Stable isotopes in elephant hair document migration patterns and diet changes
Authors: Cerling Thure E. , Wittemyer George , Rasmussen Henrik B. , Vollrath Fritz , Cerling Claire E. , Robinson Todd J. , Douglas-Hamilton Iain
Published: January 2006

We use chronologies of stable isotopes measured from elephant (Loxodonta africana) hair to determine migration patterns and seasonal diet changes in elephants in and near Samburu National Reserve in northern Kenya. Stable carbon isotopes record diet changes, principally enabling differentiation between browse and tropical grasses, which use the C3and C4photosynthetic pathways, respectively; stable nitrogen isotopes record regional patterns related to aridity, offering insight into localized ranging behavior. Isotopically identified range shifts were corroborated by global positioning system radio tracking data of the studied individuals. Comparison of the stable isotope record in the hair of one migrant individual with that of a resident population shows important differences in feeding and ranging behavior over time. Our analysis indicates that differences are the result of excursions into mesic environments coupled with intermittent crop raiding by the migrant individual. Variation in diet, quantified by using stable isotopes, can offer insight into diet-related wildlife behavior.
A Novel Three‐Dimensional Computer‐Assisted Method for a Quantitative Study of Microvascular Networks of the Human Cerebral Cortex
Authors: CASSOT FRANCIS , LAUWERS FREDERIC , FOUARD CÉLINE , PROHASKA STEFFEN , LAUWERS‐CANCES VALERIE
Published: January 2006

Objective: Detailed information on microvascular network anatomy is a requirement for understanding several aspects of microcirculation, including oxygen transport, distributions of pressure, and wall shear stress in microvessels, regulation of blood flow, and interpretation of hemodynamically based functional imaging methods, but very few quantitative data on the human brain microcirculation are available. The main objective of this study is to propose a new method to analyze this microcirculation.

Methods: From thick sections of india ink‐injected human brain, using confocal laser microscopy, the authors developed algorithms adapted to very large data sets to automatically extract and analyze center lines together with diameters of thousands of brain microvessels within a large cortex area.

Results: Direct comparison between the original data and the processed vascular skeletons demonstrated the high reliability of this method and its capability to manage a large amount of data, from which morphometry and topology of the cerebral microcirculation could be derived.

Conclusions: Among the many parameters that can be analyzed by this method, the capillary size, the frequency distributions of diameters and lengths, the fractal nature of these networks, and the depth‐related density of vessels are all vital features for an adequate model of cerebral microcirculation.
Dietary Steatotic Liver Attenuates Acetaminophen Hepatotoxicity in Mice
Authors: ITO YOSHIYA , ABRIL EDWARD R. , BETHEA NANCY W. , MCCUSKEY MARGARET K. , MCCUSKEY ROBERT S.
Published: January 2006

Objective: To determine whether hepatic steatosis is susceptible to acetaminophen (APAP) hepatotoxicity.

Methods: Male C57Bl/6 mice were fed a “Western‐style” diet (high fat and high carbohydrate) for 4 months to develop severe hepatic steatosis with mild increases in alanine aminotransferase (ALT) levels. These were compared to mice fed a standard chow diet.

Results: Treatment with APAP (300 mg/kg, orally) to mice fed a regular chow increased ALT levels (519‐fold) and caused hepatic centrilobular injury at 6 h. APAP increased hepatic cytochrome‐P (CYP)‐2E1 mRNA levels (17‐fold). In vivo microscopic studies showed that APAP caused a 30% decrease in sinusoidal perfusion and the infiltration of red blood cells into the space of Disse. Electron microscopy demonstrated that numerous gaps were formed in sinusoidal endothelial cells. Mice fed the “Western‐style” diet were protected from APAP hepatotoxicity as evidenced by 89% decrease in ALT levels and less centrilobular injury, which was associated with 42% decrease in CYP2E1 mRNA levels. The APAP‐induced liver microcirculatory dysfunction was minimized in mice fed the “Western‐style” diet.

Conclusions: These results suggest that hepatic steatosis elicited by the “Western‐style” diet attenuated APAP‐induced hepatotoxicity by inhibiting CYP2E1 induction and by minimizing sinusoidal endothelial cell injury, leading to protection of liver microcirculation.
Transient Osmotic Absorption of Fluid in Microvessels Exposed to Low Concentrations of Dimethyl Sulfoxide
Authors: GLASS CATHERINE A. , PERRIN RACHEL M. , POCOCK TRISTAN M. , BATES DAVID O.
Published: January 2006

Dimethyl Sulfoxide (DMSO) is a common solvent for pharmacological agents. It is a small, lipophilic molecule thought to be relatively highly permeable through the cell membrane. While measuring the effect of low concentrations of DMSO (0.05–0.5% v/v) on capillary hydraulic conductivity as a vehicle control for pharmacological agents, the authors noticed what appeared to be an unusual transient absorption of fluid across the vessel wall. This absorption occurred during occlusion of the vessel, but dissipated quickly (1.7–8.6 s). The transient reabsorption reappeared upon each successive occlusion. To determine the nature of this transient absorption, the authors have measured the effect of increasing the pressure of the perfusing solution, of the concentration and time of perfusion of DMSO, and of superfusing the DMSO. They found that the absorption rate, but not the filtration rate, was concentration dependent, and was significantly correlated with the osmotic pressure of the DMSO. Moreover, the time taken for completion of the transient, i.e., time to reversal of flow, was inversely proportional to the hydraulic conductivity of the vessel. Furthermore, the transient absorption could be reduced and eventually abolished by increasing the hydrostatic pressure. These results strongly suggested that perfusion with low concentrations of DMSO could set up a significant osmotic pressure gradient across the vessel wall. This proposed mechanism for the absorption was confirmed by the measurement of a significant osmotic reflection coefficient of the vessel wall to DMSO (0.11 ± 0.01). Relatively low concentrations (0.05–0.5%) of DMSO were therefore able to stimulate a significant osmotic transient across the blood vessel walls.
High‐Resolution Intravital NADH Fluorescence Microscopy Allows Measurements of Tissue Bioenergetics in Rat Ileal Mucosa
Authors: ROSE JIM , MARTIN CLAUDIO , MACDONALD TAMMY , ELLIS CHRIS
Published: January 2006

Objectives: NADH fluorescence microscopy has been used as an index of the metabolic state of tissue but is associated with various obstacles such as low spatial resolution and quenching effects of blood pigments that prevent reliable monitoring of tissue bioenergetics. The objective of this study was to develop a system to monitor tissue bioenergetics in vivo using NADH fluorescence microscopy in the rat ileal mucosa.

Materials and Methods: Using an inverted microscope with an epifluorescence unit and an intensified charge‐coupled device camera, NADH fluorescence images were visualized. Fluorescence intensity was measured of β ‐NADH solutions at varying concentration (n = 6) and pH (n = 3) and in ex vivo (n = 6) and in vivo (n = 6) preparations of ileal mucosa of Sprague‐Dawley rats anesthetized with isoflurane.

Results: Intravital fluorescence microscopy reveals a map of the microcirculation that permits visualization of NADH fluorescence and intercapillary areas. The system was adjusted so a linear relationship between physiological concentrations of β ‐NADH and fluorescence was achieved (r2 = 0.98, p < .0001). Decreasing the pH of the solution had no effect on fluorescence intensity and fluorescence intensity in an anoxic ex vivo ileal segment was similar to that of the in vivo ileum after ischemia. Ischemia also resulted in spatial heterogeneity that was abolished by the addition of a 550‐nm LP filter.

Conclusions: With this system, intravital NADH fluorescence microscopy provides the high resolution necessary to reliably monitor tissue bioenergetics in the rat ileal mucosa.
Basal Ganglia Accumulation and Motor Assessment Following Manganese Chloride Exposure in the C57BL/6 Mouse
Authors: Dodd Celia A. , Ward Daniel L. , Klein Bradley G.
Published: January 2006

Equivocal clinical evidence for involvement of manganese in development of Parkinson’s disease necessitates experimental studies on this issue. The aged, 1-methyl-4-phenyl-1,2,3,6-tetrahyropyridine–treated C57BL/6 mouse is one of the most common models for Parkinson’s disease. However, there is little information on brain bioaccumulation of manganese, and little or no information on clinical/behavioral manifestations of manganese neurotoxicity, in this strain. Male C57BL/6 retired breeder mice were given a single subcutaneous injection of either 0, 50, or 100 mg/kg of MnCl2 (single-dose regimen) or three injections of either of these doses over 7 days (multiple-dose regimen). Behavioral assessment was performed 24 h after final injection, followed by sacrifice, and body weight was recorded each day. There was a 105% increase in striatal manganese concentration 1 day after a single 100 mg/kg injection, and 421% and 647% increases, respectively, 1 day after multiple doses of 50 or 100 mg/kg of MnCl2. One day after a single injection, there were respective 30.9% and 38.9% decreases in horizontal movement (grid crossing) for the 50 and 100 mg/kg doses and a 43.2% decrease for the multiple dose of 100 mg/kg. There was no significant main effect of dose level on rearing, swimming, grip strength, or grip fatigue. Unlike previous work with the C57BL/6 strain using smaller intraperitoneal doses, this study established dosing regimens that produced significant increases in basal ganglia manganese concentration reminiscent of brain increases in the CD-1 mouse following subcutaneous doses close to our lowest. A decrease in locomotor behavior, significant but not severe in this study, has been reported following manganese exposure in other mouse strains. These data, particularly the significant increase in basal ganglia manganese concentration, provide guidance for designing studies of the potential role of manganese in Parkinson’s disease using the most common animal model for the disorder.
Bispyridinium Oximes As Antidotal Treatment of Cyclosarin Poisoning—In Vitro and In Vivo Testing
Authors: Bartosova Lucie , Kuca Kamil , Jun Daniel , Kunesova Gabriela
Published: January 2006

The mechanism of intoxication with organophosphorus compounds, including highly toxic nerve agents and less toxic pesticides, is based on the formation of irreversibly inhibited acetylcholinesterase, which causes cumulation of neuromediator acetylcholine in synaptic clefts and subsequent overstimulation of cholinergic receptors, that is followed by a generalized cholinergic crisis. Nerve agent poisoning is conventionally treated using a combination of a cholinolytic (atropine mostly) to counteract the accumulation of acetylcholine and acetylcholinesterase reactivators (pralidoxime or obidoxime) to reactivate inhibited acetylcholinesterase. In this study of cyclosarin poisoning treatment, oximes of different chemical structures (obidoxime, HI-6, BI-6, and HS-6) were tested in vitro on rat brain acetylcholinesterase (enzyme source: rat brain homogenate), and afterwards, they were tested in vivo in equimolar doses, in mice and rats. The HI-6 oxime appeared to be the most effective oxime in vitro and in vivo.
Evaluation of Triamcinolone Acetonide Following Intravitreal Injection in New Zealand White Rabbits
Authors: McGee David H. , Dembinska Olga , Gruebbel Margarita M.
Published: January 2006

The safety of intravitreally injected triamcinolone acetonide suspension (TA) was evaluated in rabbits. Each animal received 0.1 ml (1) balanced salt solution (BSS) vehicle, (2) formulation vehicle, (3) 4% TA (4-mg dose), (4) 16% TrAc (16-mg dose) or (5) 25% TA (25-mg dose) as a single intravitreal injection into the right eye. The left eyes served as untreated controls. All animals were observed for 1 month following treatment. In-life evaluations included clinical signs, body weights, slit-lamp biomicroscopic and indirect ophthalmoscopic examinations, intraocular pressure and corneal thickness measurements, and electroretinograms (ERGs). Ocular tissues were harvested following a 1-month post-treatment observation period, fixed, processed, and evaluated by light microscopy. No significant or treatment-related clinical signs were observed for any animals during the study. The opaque white test article was clearly visible in the eye for all TrAc-treated groups, and remained so throughout the study. No statistically significant differences in mean body weights were present between the control and treatment groups, though changes in body weight varied. Corneal thickness was slightly reduced for some treated groups. Intraocular pressures were not statistically significantly different from controls for any treatment group. No significant changes in ERG were evident between treatment groups or from baseline readings. Microscopically, basophilic material (presumed to be drug) was seen in the vitreous of all or most treated eyes, with accumulations in the vitreous or in clumps adjacent to the retinal surface. No pathological changes were observed in the retina or other ocular structures. Triamcinolone acetonide suspension was safe and well tolerated following intravitreal injection in New Zealand white rabbits.
Refining the Effects Observed in a Developmental Neurobehavioral Study of Ammonium Perchlorate Administered Orally in Drinking Water to Rats. II. Behavioral and Neurodevelopment Effects
Authors: York Raymond G. , Barnett John , Girard Michael F. , Mattie David R. , Bekkedal Marni V. K. , Garman Robert H. , Strawson Joan S.
Published: January 2006

A developmental neurotoxicity study was conducted to generate additional data on the potential functional and morphological hazard to the central nervous system caused by ammonium perchlorate in offspring from in utero and lactation exposure. Female Sprague-Dawley rats (23 to 25/group) were given continuous access to 0 (carrier), 0.1, 1.0, 3.0, and 10.0 mg/kg-day perchlorate in the drinking water beginning 2 weeks prior to mating and continuing through day 10 of lactation for the behavioral function assessment or given continuous access to 0 (carrier), 0.1, 1.0, 3.0, and 30.0 mg/kg-day beginning on gestation day 0 and continuing through day 10 of lactation for neurodevelopment assessments. Motor activity was conducted on postpartum days 14, 18, and 22 and juvenile brain weights, neurohistopathological examinations, and regional brain morphometry were conducted on postpartum days 10 and 22. This research revealed a sexually dimorphic response, with some brain regions being larger in perchlorate-treated male rats than in comparable controls. Even so, there was no evidence of any obvious exposure-related effects on male rat brain weights or neuropathology. The most consistent exposure-related effect in the male pups was on the thickness of the corpus callosum, with both the right- and left-sided measures of the thickness of this white matter tract being significantly greater for the male pups in the 0.1 and 1.0 mg/kg-day exposure groups. The behavioral testing suggests prenatal exposure to ammonium perchlorate does not affect the development of gross motor movements in the pups.
Toxicity Assessment of Thiodiglycol
Authors: Reddy Gunda , Major Michael A. , Leach Glenn J.
Published: January 2006

Sulfur mustard (HD) undergoes hydrolysis to form various products such as thiodiglycol (TG) in biological and environmental systems. TG is a precursor in the production of HD and it is also considered as a “Schedule 2” compound (dual-use chemicals with low to moderate commercial use and high-risk precursors). Several toxicological studies on TG were conducted to assess environmental and health effects. The oral LD50 values were >5000 mg/kg in rats. It was a mild skin and moderate ocular irritant and was not a skin sensitizer in animals. It was not mutagenic in Ames Salmonella, Escherichia coli, mouse lymphoma, and in vivo mouse micronucleus assays, but it induced chromosomal aberrations in Chinese hamster ovarian (CHO) cells. A 90-day oral subchronic toxicity study with neat TG at doses of 0, 50, 500, and 5000 mg/kg/day (5 days/week) in Sprague-Dawley rats results show that there are no treatment-related changes in food consumption, hematology, and clinical chemistry in rats of either sex. The body weights of both sexes were significantly lower than controls at 5000 mg/kg/day. Significant changes were also noted in both sexes in absolute weights of kidneys, kidney to body weight ratios, and kidney to brain weight ratios, in the high-dose group. The no-observed-adverse-effect level (NOAEL) for oral toxicity was 500 mg/kg/day. The developmental toxicity conducted at 0, 430, 1290, and 3870 mg/kg by oral gavage showed maternal toxicity in dams receiving 3870 mg/kg. TG was not a developmental toxicant. The NOAEL for the developmental toxicity in rats was 1290 mg/kg. The provisional oral reference dose (RfD) of 0.4 mg/kg/day was calculated for health risk assessments. The fate of TG in the environment and soil showed biological formation of thiodiglycalic acid with formation of an intermediate ((2-hydroxyethyl)thio)acetic acid. It was slowly biodegraded under anaerobic conditions. It was not toxic to bluegill sunfish at 1000 mg/L and its metabolism and environmental and biochemical effects are summarized.
Ototoxicity of Carboplatin Delivered Locally in a Monkey Brainstem
Authors: Carey J. P. , Cooper T. , Jallo G. I. , Carson B. S. , Guarnieri M.
Published: January 2006

Ototoxicity is a common side effect of platinum-based chemotherapy. Intratumoral drug delivery theoretically could reduce the ototoxic effects of systemic drug infusions. However, local delivery to central nervous system (CNS) tumors might promote ototoxicity through drug release into cerebrospinal fluid (CSF). This report describes an examination of the cytoarchitecture of vestibular cells of cynomolgus monkeys that had chronic brainstem infusions with the maximum tolerated dose (MTD) of carboplatin. The brainstems of adult monkeys were infused for 30 days at 0.42 μl/h with 0.025 to 0.25 mg/kg (MTD) of carboplatin. The vestibular sensory epithelia of eight drug-treated animals were isolated for microscopic examination of vestibular hair cells and support cells. Local infusions produced chronic elevated CSF levels of platinum, neurological symptoms, and radiographic evidence of pontine injury. Histology revealed significant cell damage at the infusion sites. Microscopic examinations of vestibular support cells and hair cells demonstrate a small reduction in cell counts in the drug-treated monkeys compared to a noninfused control animal. Parametric and nonparametric tests show no effect of dose in predicting the vestibular cell counts. In this single study of eight monkeys, a dose-dependent reduction of vestibular hair cells or support cells was not observed in animals infused with brainstem infusions of 0.025 to 0.25 mg/kg of carboplatin.
Role of mitochondrial glucocorticoid receptor in glucocorticoid-induced apoptosis
Authors: Sionov Ronit Vogt , Cohen Orly , Kfir Shlomit , Zilberman Yael , Yefenof Eitan
Published: January 2006

The mechanisms by which glucocorticoid receptor (GR) mediates glucocorticoid (GC)-induced apoptosis are unknown. We studied the role of mitochondrial GR in this process. Dexamethasone induces GR translocation to the mitochondria in GC-sensitive, but not in GC-resistant, T cell lines. In contrast, nuclear GR translocation occurs in all cell types. Thymic epithelial cells, which cause apoptosis of the PD1.6 T cell line in a GR-dependent manner, induce GR translocation to the mitochondria, but not to the nucleus, suggesting a role for mitochondrial GR in eliciting apoptosis. This hypothesis is corroborated by the finding that a GR variant exclusively expressed in the mitochondria elicits apoptosis of several cancer cell lines. A putative mitochondrial localization signal was defined to amino acids 558–580 of human GR, which lies within the NH2-terminal part of the ligand-binding domain. Altogether, our data show that mitochondrial and nuclear translocations of GR are differentially regulated, and that mitochondrial GR translocation correlates with susceptibility to GC-induced apoptosis.
Disparate roles of ATR and ATM in immunoglobulin class switch recombination and somatic hypermutation
Authors: Pan-Hammarström Qiang , Lähdesmäki Aleksi , Zhao Yaofeng , Du Likun , Zhao Zhihui , Wen Sicheng , Ruiz-Perez Victor L. , Dunn-Walters Deborah K. , Goodship Judith A. , Hammarström Lennart
Published: January 2006

Class switch recombination (CSR) and somatic hypermutation (SHM) are mechanistically related processes initiated by activation-induced cytidine deaminase. Here, we have studied the role of ataxia telangiectasia and Rad3-related protein (ATR) in CSR by analyzing the recombinational junctions, resulting from in vivo switching, in cells from patients with mutations in the ATR gene. The proportion of cells that have switched to immunoglobulin (Ig)A and IgG in the peripheral blood seems to be normal in ATR-deficient (ATRD) patients and the recombined S regions show a normal “blunt end-joining,” but impaired end joining with partially complementary (1–3 bp) DNA ends. There was also an increased usage of microhomology at the μ-α switch junctions, but only up to 9 bp, suggesting that the end-joining pathway requiring longer microhomologies (≥10 bp) may be ATR dependent. The SHM pattern in the Ig variable heavy chain genes is altered, with fewer mutations occurring at A and more mutations at T residues and thus a loss of strand bias in targeting A/T pairs within certain hotspots. These data suggest that the role of ATR is partially overlapping with that of ataxia telangiectasia–mutated protein, but that the former is also endowed with unique functional properties in the repair processes during CSR and SHM.
The fate of human Langerhans cells in hematopoietic stem cell transplantation
Authors: Collin Matthew P. , Hart Derek N.J. , Jackson Graham H. , Cook Gordon , Cavet James , Mackinnon Stephen , Middleton Peter G. , Dickinson Anne M.
Published: January 2006

Langerhans cells (LC) and other antigen-presenting cells are believed to be critical in initiating graft versus host responses that influence the outcome of allogeneic hematopoietic stem cell transplantation. However, their fate in humans is poorly understood. We have sought to define the effect of conditioning regimes and graft versus host disease (GVHD) on the survival of recipient LC and reconstitution of donor cells after transplant. Confocal microscopy of epidermal sheets shows that full intensity transplant (FIT) depletes LC more rapidly than reduced intensity transplant (RIT) at day 0, although the nadir is similar in both at 14–21 d. Recovery occurs rapidly within 40 d in the absence of acute GVHD, but is delayed beyond 100 d when GVHD is active. LC chimerism was determined in sex-mismatched transplants using a two-step Giemsa/fluorescence in situ hybridization assay on isolated cells. Acquisition of donor chimerism at 40 d is more rapid after FIT (97%) than RIT (36.5%), irrespective of blood myeloid engraftment. At 100 d, all transplants achieve at least 90% LC donor chimerism and over half achieve 100%. Complete donor chimerism is associated with prior acute cutaneous GVHD, suggesting a role for allogeneic T cells in promoting LC engraftment.
Cytokine signal transduction is suppressed in preselection double-positive thymocytes and restored by positive selection
Authors: Yu Qing , Park Jung-Hyun , Doan Loretta L. , Erman Batu , Feigenbaum Lionel , Singer Alfred
Published: January 2006

Death by neglect requires that CD4+8+ double-positive (DP) thymocytes avoid cytokine-mediated survival signals, which is presumably why DP thymocytes normally extinguish IL-7R gene expression. We report that DP thymocytes before positive selection (preselection DP thymocytes) fail to transduce IL-7 signals even when they express high levels of transgenic IL-7R on their surface, because IL-7R signal transduction is actively suppressed in preselection DP thymocytes by suppressor of cytokine signaling (SOCS)–1. SOCS-1 is highly expressed in preselection DP thymocytes, but it is down-regulated by T cell receptor–mediated positive selection signals. Interestingly, we found that the uniquely small cell volume of DP thymocytes is largely the result of absent IL-7 signaling in preselection DP thymocytes. We also report that, contrary to current concepts, preselection DP thymocytes express high levels of endogenously encoded IL-4Rs. However, their ability to transduce cytokine signals is similarly suppressed by SOCS-1. Thus, despite high surface expression of transgenic or endogenous cytokine receptors, cytokine signal transduction is actively suppressed in preselection DP thymocytes until it is restored by positive selection.
Innate secretory antibodies protect against natural Salmonella typhimurium infection
Authors: Wijburg Odilia L.C. , Uren Tania K. , Simpfendorfer Kim , Johansen Finn-Eirik , Brandtzaeg Per , Strugnell Richard A.
Published: January 2006

The production of IgA is induced in an antigen-unspecific manner by commensal flora. These secretory antibodies (SAbs) may bind multiple antigens and are thought to eliminate commensal bacteria and self-antigens to avoid systemic recognition. In this study, we addressed the role of “innate” SAbs, i.e., those that are continuously produced in normal individuals, in protection against infection of the gastrointestinal tract. We used polymeric immunoglobulin receptor (pIgR−/−) knock-out mice, which are unable to bind and actively transport dimeric IgA and pentameric IgM to the mucosae, and examined the role of innate SAbs in protection against the invasive pathogen Salmonella typhimurium. In vitro experiments suggested that innate IgA in pIgR−/− serum bound S. typhimurium in a cross-reactive manner which inhibited epithelial cell invasion. Using a “natural” infection model, we demonstrated that pIgR−/− mice are profoundly sensitive to infection with S. typhimurium via the fecal-oral route and, moreover, shed more bacteria that readily infected other animals. These results imply an important evolutionary role for innate SAbs in protecting both the individual and the herd against infections, and suggest that the major role of SAbs may be to prevent the spread of microbial pathogens throughout the population, rather than protection of local mucosal surfaces.
Vesicoureteric reflux and renal malformations: a developmental problem
Authors: Murawski IJ , Gupta IR
Published: January 2006

Vesicoureteric reflux (VUR) is a congenital urinary tract defect caused by the failure of the ureter to insert correctly into the bladder. It occurs in up to 1% of the general population and is associated with recurrent urinary tract infections and renal failure. Despite treatment of affected children for the past 40 years, the incidence of end‐stage renal disease secondary to VUR has not decreased. Twin and family studies reveal that VUR has a genetic basis. Some of the gene candidates that have been identified regulate the position of ureteric budding, a critical step in both kidney and urinary tract development. Analysis of data from humans and mice suggests that some of the renal damage associated with VUR is congenital and is due to a kidney malformation. Therefore, in these cases, the association of VUR and renal failure may be caused by a genetic defect affecting the formation of the kidney and the urinary tract.
Prevalence of HFE C282Y and H63D in Jewish populations and clinical implications of H63D homozygosity
Authors: Matas M , Guix P , Castro JA , Parera M , Ramon MM , Obrador A , Picornell A
Published: January 2006

The frequencies of C282Y and H63D mutations of the HFE gene vary between different populations. A previous study showed an unexpectedly high H63D frequency in Chuetas (a population of Jewish descent). The present study addressed the question of the distribution of these mutations in Jewish populations from different origins and studied the possible causes of the high H63D frequency in Chuetas. Moreover, to improve the understanding of the controversial relationship between H63D homozygosity and iron overload, a group of patients with altered iron metabolism were studied. The high frequency of H63D mutation in Chuetas is not due to a high prevalence of this mutation in Sephardic Jews. Jewish populations have low C282Y and moderate H63D frequencies, suggesting slight gene flow from their surrounding populations. In accordance with historical and demographic data, genetic drift is the most probable cause for the singular H63D frequency in Chuetas. Clinically, this study of H63D homozygotes supports the conclusion that this genotype must be taken into account, because it confers an increased risk of iron overload and therefore genetic susceptibility to developing hereditary hemochromatosis or to aggravating other diseases.
Quantification of all fetal nucleated cells in maternal blood in different cases of aneuploidies
Authors: Krabchi K , Gadji M , Forest J‐C , Drouin R
Published: January 2006

We quantified all fetal nucleated cells (FNCs) per unit volume of maternal blood in different aneuploid pregnancies using molecular cytogenetic techniques. Seven cases of male trisomy 18, two triploidies (69,XXX), two 47,XXX, one 47,XXY, one 47,XYY, one male trisomy 13, and one case of 47,XY,r(22),+r(22) were analyzed. Whole blood samples were obtained from 15 women between 17 and 29 gestational weeks and harvested without using fetal cell enrichment procedures. Fluorescence in situ hybridization and primed in situ labeling were performed to identify the FNCs. All slides were manually scanned to quantify those cells. We have identified 4–20 FNCs/ml of maternal blood in the cases of trisomy 18; 10 and 25 FNCs/ml in the two cases of triploidy; 16 and 14 FNCs/ml, respectively, in the two X trisomies; 19 FNCs/ml in the 47,XXY; 26 FNCs/ml in the 47,XYY; nine FNCs/ml in the trisomy 13; and 10 FNCs/ml in the case of r(22). To detect all FNCs in all aneuploid pregnancies, we have used a very simple method that minimizes the manipulation steps to avoid losing fetal cells. The number of FNCs identified in aneuploid pregnancies was 2–5 times higher than in normal pregnancies. This higher number of FNCs will favor the design of a non‐invasive pre‐natal test.
Prescription Drug Expenditures and Population Demographics
Authors: Morgan Steven G.
Published: January 2006

Objective. To provide detailed demographic profiles of prescription drug utilization and expenditures in order to isolate the impact of demographic change from other factors that affect drug expenditure trends.

Data Sources/Study Setting. Demographic information and drug utilization data were extracted for virtually the entire British Columbia (BC) population of 1996 and 2002. All residents had public medical and hospital insurance; however their drug coverage resembled the mix of private and public insurance in the United States.

Study Design. A series of research variables were constructed to illustrate profiles of drug expenditures and drug utilization across 96 age/sex strata.

Data Collection/Extraction Methods. Drug use and expenditure information was extracted from the BC PharmaNet, a computer network connecting all pharmacies in the province.

Principal Findings. Per capita drug expenditures increased at an average annual rate of 10.8 percent between 1996 and 2002. Population aging explained 1.0 points of this annual rate of expenditure growth; the balance was attributable to rising age/sex‐specific drug expenditures.

Conclusions. Relatively little of the observed increase in drug expenditures in BC could be attributed to demographic change. Most of the expenditure increase stemmed from the age/sex‐specific quantity and type of drugs purchased. The sustainability of drug spending therefore depends not on outside forces but on decisions made by policy makers, prescribers, and patients.
The Effect of Rural Hospital Closures on Community Economic Health
Authors: Holmes George M. , Slifkin Rebecca T. , Randolph Randy K. , Poley Stephanie
Published: January 2006

Objective. To examine the effect of rural hospital closures on the local economy.

Data Sources. U.S. Census Bureau, OSCAR, Medicare Cost Reports, and surveys of individuals knowledgeable about local hospital closures.

Study Design. Economic data at the county level for 1990–2000 were combined with information on hospital closures. The study sample was restricted to rural counties experiencing a closure during the sample period. Longitudinal regression methods were used to estimate the effect of hospital closure on per‐capita income, unemployment rate, and other community economic measures. Models included both leading and lagged closure terms allowing a preclosure economic downturn as well as time for the closure to be fully realized by the community.

Data Collection. Information on closures was collected by contacting every state hospital association, reconciling information gathered with that contained in the American Hospital Association file and OIG reports.

Principal Findings. Results indicate that the closure of the sole hospital in the community reduces per‐capita income by $703 (p<0.05) or 4 percent (p<0.05) and increases the unemployment rate by 1.6 percentage points (p<0.01). Closures in communities with alternative sources of hospital care had no long‐term economic impact, although income decreased for 2 years following the closure.

Conclusions. The local economic effects of a hospital closure should be considered when regulations that affect hospitals' financial well‐being are designed or changed.
Disparities in Primary Care for Vulnerable Children: The Influence of Multiple Risk Factors
Authors: Stevens Gregory D. , Seid Michael , Mistry Ritesh , Halfon Neal
Published: January 2006

Objectives.To analyze vulnerability as aprofileof multiple risk factors for poor pediatric care based on race/ethnicity, poverty status, parent education, insurance, and language. Profiles are used to examine disparities in child/adolescent health status and primary care experience.

Data Sources.Cross‐sectional data on 19,485 children/adolescents 0–19 years of age from the 2001 California Health Interview Survey.

Study Design.Multiple logistic regression models are used to examine risk profiles in relation to health status and three aspects of primary care:access(physician and dental visit; access surety),continuity(regular source of care), andcomprehensiveness(i.e., health promotion counseling).

Principal Findings.About 43 percent of (or 4.4 million) children in California have two or more risk factors (RF). Controlling for age and gender, more RFs is associated with poorer health status (i.e. percent reporting “excellent/very good” health: no RFs=81 percent, 1=71 percent, 2=57 percent, 3=45 percent, 4=35 percent, 5=28 percent, allp<.001). Controlling for health status, higher risk profiles is associated with poorer primary care access and continuity, butgreatercomprehensiveness of care. For example, higher risk profile children are less likely to have a regular source of care: one RF (prevalence ratio [PR]=0.92, confidence interval [CI]: 0.86–0.98), two (PR=0.77, CI: 0.69–0.84), three (PR=0.55, CI: 0.46–0.65), and four or more (PR=0.31, CI: 0.22–0.44), allp<.001.

Conclusions.This study demonstrates a dose–response relationship of higher risk profiles with poorer child health status, access to, and continuity of primary care. Having gained access, however, adolescents with higher risk profiles are more likely to receive health promotion counseling. Higher profiles appear to be associated with greater barriers to accessing primary care for children in “fair or poor” health, suggesting that vulnerable children who have the greatest health care needs also have the greatest difficulty obtaining primary care.
AAPM Task Group 108: PET and PET/CT Shielding Requirements
Authors: Madsen Mark T. , Anderson Jon A. , Halama James R. , Kleck Jeff , Simpkin Douglas J. , Votaw John R. , Wendt Richard E. , Williams Lawrence E. , Yester Michael V.
Published: January 2006

The shielding of positron emission tomography (PET) and PET/CT (computed tomography) facilities presents special challenges. The annihilation photons associated with positron decay are much higher energy than other diagnostic radiations. As a result, barrier shielding may be required in floors and ceilings as well as adjacent walls. Since the patient becomes the radioactive source after the radiopharmaceutical has been administered, one has to consider the entire time that the subject remains in the clinic. In this report we present methods for estimating the shielding requirements for PET and PET/CT facilities. Information about the physical properties of the most commonly used clinical PET radionuclides is summarized, although the report primarily refers to fluorine‐18. Typical PET imaging protocols are reviewed and exposure rates from patients are estimated including self‐attenuation by body tissues and physical decay of the radionuclide. Examples of barrier calculations are presented for controlled and noncontrolled areas. Shielding for adjacent rooms with scintillation cameras is also discussed. Tables and graphs of estimated transmission factors for lead, steel, and concrete at are also included. Meeting the regulatory limits for uncontrolled areas can be an expensive proposition. Careful planning with the equipment vendor, facility architect, and a qualified medical physicist is necessary to produce a cost effective design while maintaining radiation safety standards
Iterative reconstruction method for light emitting sources based on the diffusion equation
Authors: Slavine Nikolai V. , Lewis Matthew A. , Richer Edmond , Antich Peter P.
Published: January 2006

Bioluminescent imaging (BLI) of luciferase‐expressing cells in live small animals is a powerful technique for investigating tumor growth, metastasis, and specific biological molecular events. Three‐dimensional imaging would greatly enhance applications in biomedicine since light emitting cell populations could be unambiguously associated with specific organs or tissues. Any imaging approach must account for the main optical properties of biological tissue because light emission from a distribution of sources at depth is strongly attenuated due to optical absorption and scattering in tissue. Our image reconstruction method for interior sources is based on the deblurring expectation maximization method and takes into account both of these effects. To determine the boundary of the object we use the standard iterative algorithm—maximum likelihood reconstruction method with an external source of diffuse light. Depth‐dependent corrections were included in the reconstruction procedure to obtain a quantitative measure of light intensity by using the diffusion equation for light transport in semi‐infinite turbid media with extrapolated boundary conditions.
A method to implement full six‐degree target shift corrections for rigid body in image‐guided radiotherapy
Authors: Yue Ning J. , Knisely Jonathan P. S. , Song Haijun , Nath Ravinder
Published: January 2006

Treatment position setup errors often introduce temporal variations in the position of target relative to the planned external radiation beams. The errors can be introduced by the movement of a target relative to external setup marks or to other relevant landmarks that are used to position a patient for radiotherapy. Those variations can cause dose deviations from the planned doses and result in suboptimal treatments where part of the target is not fully irradiated or a critical structure receives more than desired radiation doses. Clinically available technology for image‐guided radiotherapy can detect variations of target position. In this study, a method has been developed to correct for target position variations and restore the original beam geometries relative to the target. The technique involves three matrix transformations: (1) transformation of beams from the machine coordinate system to the patient coordinate system as in the patient geometry in the approved dosimetric plan; (2) transformation of beams from the patient coordinate system in the approved plan to the patient coordinate system that is identified at the time of treatment; (3) transformation of beams from the patient coordinate system at the time of treatment in the treatment patient geometry back to the machine coordinate system. The transformation matrix used for the second transformation is determined through the use of image‐guided radiotherapy technology and image registration. By using these matrix transformations, the isocenter shift, the gantry, couch and collimator angles of the beams for the treatment, adjusted for the target shift, can be derived. With the new beam parameters, the beams will possess the same positions and orientations relative to the target as in the plan for a rigid body. This method was applied to a head phantom study, and it was found that the target shift was fully corrected in treatment and excellent agreement was found in target dose coverage between the plan and the treatment.
Radiotherapy with laser‐plasma accelerators: Monte Carlo simulation of dose deposited by an experimental quasimonoenergetic electron beam
Authors: Glinec Y. , Faure J. , Malka V. , Fuchs T. , Szymanowski H. , Oelfke U.
Published: January 2006

The most recent experimental results obtained with laser‐plasma accelerators are applied to radiotherapy simulations. The narrow electron beam, produced during the interaction of the laser with the gas jet, has a high charge and is quasimonoenergetic . The dose deposition is calculated in a water phantom placed at different distances from the diverging electron source. We show that, using magnetic fields to refocus the electron beam inside the water phantom, the transverse penumbra is improved. This electron beam is well suited for delivering a high dose peaked on the propagation axis, a sharp and narrow tranverse penumbra combined with a deep penetration.
Feasibility of delivering grid therapy using a multileaf collimator
Authors: Ha Jonathan K. , Zhang Guowei , Naqvi Shahid A. , Regine William F. , Yu Cedric X.
Published: January 2006

The feasibility of using a multileaf collimator (MLC) for grid therapy is demonstrated in this study. Grids with the projected field openings of and were created using multiple MLC‐shaped fields. The deposited doses were measured with films at different depths in a solid water phantom and compared to those of Cerrobend grid collimators of similar hole sizes and hole separations. At the depth of maximum dose , the valley‐to‐peak dose ratios of the MLC grids were found to be about 11% and 19% for the respective and grid openings, and those of the corresponding grid blocks were about 15% and 20%. To quantify the dose contributed by transmission in the blocked areas due to the limited leaf thickness, Monte Carlo simulations (based on convolution/superposition method) were performed to calculate the doses in the solid water phantom using an ideal MLC with no leakage and perfect divergence in both the leaf end and side. About 7% reduction in the valley‐to‐peak dose ratio was found for both grid sizes at . The results clearly showed that MLCs can be used to provide grid treatments with at least as good dosimetric properties as those of the Cerrobend grid blocks, though the former would in general require a longer delivery time.
Development and characterization of a tissue equivalent plastic scintillator based dosimetry system
Authors: Petric M. P. , Robar J. L. , Clark B. G.
Published: January 2006

High precision techniques in radiation therapy, such as intensity modulated radiation therapy, offer the potential for improved target coverage and increased normal tissue sparing compared with conformal radiotherapy. The complex fluence maps used in many of these techniques, however, often lead to more challenging quality assurance with dose verification being labor‐intensive and time consuming. A prototype dose verification system has been developed using a tissue equivalent plastic scintillator that provides easy‐to‐acquire, rapid, digital dose measurements in a plane perpendicular to the beam. The system consists of a water‐filled Lucite phantom with a scintillator screen built into the top surface. The phantom contains a silver coated plastic mirror to reflect scintillation light towards a viewing window where it is captured using a charge coupled device camera and a personal computer. Optical photon spread is removed using a microlouvre optical collimator and by deconvolving a glare kernel from the raw images. A characterization of the system was performed that included measurements of linear output response, dose rate dependence, spatial linearity, effective pixel size, signal uniformity and both short‐ and long‐term reproducibility. The average pixel intensity for static, regular shaped fields between and imaged with the system was found to be linear in the dose delivered with linear regression analysis yielding a correlation coefficient . Effective pixel size was determined to be . The system was found to have a signal uniformity of 5.6% and a long‐term reproducibility/stability of 1.7% over a 6 month period. The system's ability to verify a dynamic treatment field was evaluated using dynamic wedged fields and comparing the results to two‐dimensional film dosimetry. Results indicate agreement with two‐dimensional film dosimetry distributions within 8% inside the field edges. With further development, this system promises to provide a fast, directly digital, and tissue equivalent alternative to current dose verification systems.